(For the period October 1, 1995 through September 30, 1996) 

Synchrotron Light Source 

DlSTRlBUTlON OF THIS DOCUMENT IS UNLlMl 

&- United States Department of Energy 

~BtJTlON OF THIS DOCUMENT tS UNLIMm 
BNL 52517 

UC400 

(General Energy Research) 

Front cover: NEXAFS spectromicrograph of an annealed bilayer of polystyrene 

(PS) and poly(methy1 methacrylate) (PMMA) polymer thin film, acquired with the 

Stony Brook X1 A Scanning Transmission X-ray Microscope. The micrograph, acquired at a photon energy most specific to the C=O bond In the PMMA (288.4 

ev), shows the PS to be thick ellipsoidal dispersions within a thin "shell" of 

PMMA and a thin PMMA layer between the PS dispersions, and elucidates the 

spinodal decomposition of this constrained system. Experiments and theoretical 

work on spinodal decomposition of thin films of binary polymer blends 

indicated large changes in phase behavior and dynamics relative to bulk 

behavior. Currently used techniquesare able to sense growingdomain sizes but 

are unable to sense local two and three dimensional variations within domains. 

The common assumption that phase separated domains rapidly reach their 

equilibrium composition and then agglomerate into ever larger domains is not 

likely to hold. Current and planned STXM measurements will allow us to 

address this important issue, particularly for polymer systems where heavy metal staining in a TEM is failing, and will provide a critical test for theories of 

polymer dynamics. Figure courtesy of A. Smith and H. Ade (NCSU) and their coworkers D. Slep (Highlord Chemical), s. Qu, M. Rafailovich, and 1. Sokolov (SUNY 

@I Stony Brook). 

DISCLAIMER 

This report was prepared as an account of work sponsored by an agency of the 

United States Government. Neither the United States Government nor any 

agency thereof, nor any of their employees, nor any of their contractors, 

subcontractors, or their employees, makes any warranty, express or implied, or 

assumes any legal liability or responsibility for the accuracy, completeness, or 

usefulness of any information, apparatus, product, or process disclosed, or 

represents that its use would not infringe privately owned rights. Reference 

herein to any specific commercial product, process, or service by trade name, 

trademark, manufacturer, or otherwise, does not necessarily constitute or imply 

its endorsement, recommendation, or favoring by the United States Government or any agency, contractor, or subcontractor thereof. The views and 

opinions of authors expressed herein do not necessarily state or reflect those of 

the United States Government or any agency, contractor, or subcontractor 

thereof. 

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in electronic image products. Images are 

plpduced hrom the best available original 

dor-?nmeat, 
INTRODUCTION 

INTRODUCTION BY THE CHAIRMAN .............................................................................................................. 2 

ENVIRONMENT. SAFETY AND HEALTH UPDATE ............................................................................................ 5 

Michael Harf 

William Thomlinson 

Eva Z . Rothman 

Pefer W . Stephens 

USER ADMINISTRATION REPORT ................................................................................................................. 7 

USERS' EXECUTIVE COMMITTEE ............................................................................................................... 10 

SCIENCE HIGHLIGHTS 

APPLIED SCIENCE ................................................................................................................................... 16 

BIOLOGICAL SCIENCES ............................................................................................................................ 26 

CHEMICAL SCIENCES ............................................................................................................................... 32 

GEOLOGICAL SCIENCES ........................................................................................................................... 36 

STRUCTURE OF SURFACES AND INTERFACES .............................................................................................. 38 

MATERIAL SCIENCES ............................................................................................................................... 44 

NUCLEAR PHYSICS .................................................................................................................................. 57 

INSTRUMENTATION AND TECHNIQUES ....................................................................................................... 63 

MEETINGS & WORHIHOPS 

THE 1 996 NSLS ANNUAL USERS' MEETING ........................................................................................ 70 

Peter W . Stephens 

Simon R . Bare 

Thomas l? Russell 

Lisa J . Keefe and Stephan L . Ginell 

Alex Darovsky 

Boris Sinkovic 

D . Pefer Siddons and Erik Johnson 

IN SITU APPLICATIONS OF X-RAY ABSORPTION FINE STRUCTURE WORKSHOP ............................................ 73 

OPPORTUNITIESN POLYMER RESEARCH USING SYNCHROTRON RADIATION WORKSHOP .............................. 74 

MULTIPLE WAVELENGTH ANOMALOUS DISPERSION (MAD) IN PROTEIN CRYSTALLOGRAPHY WORKSHOP .... 78 

STRATEGY AND METHODS FOR AREA DETECTOR DATA COLLECTION WORKSHOP ....................................... 79 

THE APPLICATION OF SYNCHROTRONADIATION TO THE STUDY OF MAGNETIC MATERIALS WORKSHOP ..... 80 

HARD X-RAY PRECISION FABRICATION WORKSHOP .................................................................................. 81 

.. 

11 
OPERATIONS 

VUV MACHINE ..................................................................................................................................... 

VUV STORAGE RING PARAMETERS ......................................................................................................... 90 

Stephen Kramer 

BEAMLINE TECHNICAL IMPROVEMENTS ..................................................................................................... 9 1 

Roger Klafiy 

Roger Klaffky 

X-RAY RING ......................................................................................................................................... 94 

X-RAY STORAGE RING PARAMETERS ....................................................................................................... 97 

PROJECTS 

THE NSLS SOURCE DEVELOPMENT LABORATORY .................................................................................. 100 

Erik D. Johnson 

Ilan Ben-Zvi 

Frank Terrano and Mike Kelly 

Peter M. Stefan, Sam Krinsky, and Chi-Chang Kao 

THE ACCELERATOR TEST FACILITY (ATF) .............................................................................................. 1 02 

NSLS FACILITY IMPROVEMENTS ............................................................................................................ 1 05 

INSERTION DEVICE R9D AT X1 3 ........................................................................................................ 1 06 

ORGANIZATION 

NSLS ADVISORY COMMI~EES 112 ............................................................................................................ NSLS STAFF ................................................................................................................... 

........................................................................................................................ X-RAY BEAMLINE GUIDE ...................................................................................................................... 121 I VUV BEAMLINE GUIDE 

~ RESEARCH ANTHOLOGY 

LIGHTING THE WAY TO THE FUTURE ..................................................................................................... 132 

ABSTRACTS & PUBL /CATIONS 

VUV BEAMLINE ABSTRACTS .................................................................................................................. A- 1 

NSLS STAFF PUBLICATIONS ..................................................................................................................D-l I 

X-RAY BEAMLINE ABSTRACTS ................................................................................................................ B-I 

NSLS USER PUBLICATIONS ................................................................................................................... C- 1 

BNL FORMAL AND INFORMAL REPORTS .................................................................................................D-6 

... I 111 
Beamline X12C: The profilin binding site of actin. On the right is a ribbon depiction of actin 

displaying the side chains which contact profilin in the profilin-actin complex. On the left, the 

same contact residues shown in standard atom colors with the outline of the profilin binding 

site shown in yellow. K.S. Thorn, . . . C.E. Schutt,”The Crystal Structure of a Major Allergin from 

Plants”, Sfructure 5, 19-32 (1997). 

Michael Hart 

NSLS Chairman 

The hard work done by the synchrotron radiation 

community, in collaboration with all those using largescale central facilities during 1995, paid off in FY 1996 

through the DOE’S Presidential Scientific Facilities Initiative. In comparison with the other DOE synchrotron 

radiation facilities, the National Synchrotron Light Source 

benefited least in operating budgets because we were 

unable to increase our running time beyond 100%- 

nevertheless, the number ofstation hours was maintained. 

The major thrust at Brookhaven came from a 15% 

increase in budget which allowed the recruitment of seven 

staff in the beamlines support group and permitted a step 

increment in the funding of the extremely long list of 

upgrades; both to the sources and to the beamlines. 

During the December 1995 shutdown, the VW 

Ring quadrant aroundUl0-U12 was totally reconstructed. 

New front ends, enabling apertures up to 90 mrad on U10 

and U12, were installed. During the year new PRTs were 

in formation for the infrared beamlines, encouraged by 

the investment we were able to commit from the initiative 

funds and by awards from the Scientific Facilities Initiative. A new PRT, specifically for small and wide angle 

2 
x-ray scattering from polymers, will start work on X27C 

in FY 1997 and existing PRTs on X26C andX9B working 

on macromolecular crystallography will be joined by new 

members. 

Plans to replace aging radio frequency cavities by an 

improved design, originally a painfully slow six or eight 

year project, were brought forward so that the first pair of 

cavities (half of the project for the X-Ray Ring) will now 

be installed in FY 1997. Current upgrades to 350 mA 

initially and to 438 mA later in the X-Ray Ring were set 

aside due to lack of funds for the necessary thermally 

robust beryllium windows. The Scientific Facilities Initiative allowed us to purchase all 34 windows in FY 1996 

so that the power upgrade will be achieved in FY 1997. 

Half of the windows were installed during the December 

1996 shutdown and the remainder will be installed during 

the May 1997 shutdown. 

The NSLS Phase I11 upgrade, proposed in March 

1994andvalidated by DOEin 1995 showed how $22.5M 

could be used to maximize both the scientific output of 

the facility and the return on DOE'S investment. Sixteen 

beamlines, four on the VUV Ring and twelve on the 

X-Ray Ring, could be made state of the art; improvements 

in beam position monitoring would lead to improved 

beam stability and reliability; replacement radio frequency 

cavities would insure reliability; and new narrow gap 

insertion devices could be developed. In addition 9,400 

square feet of sorely needed laboratory and office space 

could be created on the second floor of the NSLS. 

In the oneyear Scientific Facilities Initiative parts of 

this plan were realized. The results are dramatic; for a tiny 

investment, we will havefor thefirst time a facility-owned 

general user Marr image plate and a CCD area detector 

available to optimize bending magnet and insertion device beamlines. Five x-ray beamlines will benefit from 

new focusing mirrors-impacting on the research of 

almost 200 users. As mentioned above, the first two new 

RF cavities will be available in FY 1997. The instrumentation pool will be almost doubled in value and program 

influence with the addition of a detector and two displex 

refrigerators. 

In addition to the increased facility funding, the 

Scientific Facilities Initiative provided peer reviewed grants 

to users for specific beamline upgrades. Twelve user 

groups secured funds by this mechanism as follows: 

3 
mer such a glorious year it would be a shame to have to end on a down beat. iUext year, however, the r Y I YY/ 

budgets once again seem to be below FY 1990 in real terms for NSLS (see figures). 

Apart from the individual years FY1991, FY1992 

and FYI 996 the NSLS budgets for Operations, Capital 

and Accelerator Repairs Improvements and Maintenance 

have not kept up with inflation. Level or slightly decreasing budgets lead essentially to constant levels of staffing. 

This has been so throughout the 1990s when user numbers and the scientific output of the facility have almost 

doubled. 

Now, at the start of 1997, there is good news once 

again. The political climate is more encouraging for 

science and technology than it was in the recent past. The 

Energy Department in October 1996 announced a review, fundamental and far reaching in scope, of the 

provision by DOE of facilities for synchrotron radiation 

research in the U.S.A. As a third-generation facility 

serving research programs over by far the widest spectral 

range in the world (from 15mm to 3fm wave length), 

providing 75% of the station hours in the country in FY 

1996 and having clear up-grade paths to the future, we 

anticipate making an exceptionally strong case for 

reinvestment. 

4 
ENVIRON H UPDATE 

William Thomlinson 

Associate Chairman 

NSLS 

The ES&H efforts at the NSLS have continued to 

expand both in response to external pressures and to a 

more pro-active approach taken by the members of the 

ES&H group. The result was a year that saw significant 

progress in updating and expansion of our guiding safety 

documentation, full realization of the benefits of a well 

coordinated Tier I safety program, expanded training 

programs, rapid and thorough response to reportable 

incidents, active pursuit of increased radiation safety by 

the ALARA Committee, and expansion of the chemical 

safety and hazcom programs. Each of these efforts has had 

a direct impact on safety at the NSLS. Of course, they are 

all on-going activities which require constant attention. 

The occasional reportable incidents must always be met 

with improvements in our operations, education of users 

and staff in order to avoid recurrences of problems and 

better training programs. For example, we had an incident in which an unlabeled acid bottle exploded in a 

storage shed. Fortunately no one was hurt, but we treated 

the incident with the highest priority and significantly 

increased our efforts in labeling ofchemicals and supplied 

information to the staff and users on proper handling and 

storage of acids. The Tier I inspections which look at 

OSHA and housekeeping types of safety issues are never 

ending. It seems that we are unable to change human 

nature. But now the program has efficient methods of 

following up with cognizant personnel to rectify problems. The shielding of the VW Ring to decrease levels of 

radiation (neutron and gamma) to the experimental floor 

and surrounding offices is well underway. Monitoring of 

the effectiveness of the first sections will determine the 

future course of action for the Wand booster shielding. 

Perhaps the highlight of the year was the NSLS 

participation in a BNL motivated safety stand-down. 

This activity had several primary purposes: clean-up of 

the laboratory grounds and buildings, involvement of the 

entire laboratory staff in maintaining and improving 

safety, and a follow-up Tier I1 self-assessment (to be 

completed in FY 1997). The NSLS management and 

ES&H group took this effort very seriously. Even though 

we had had an NSLS staff meeting in which safety was 

featured, our NSLS safety stand-down consisted of a 

collective staff meeting followed by separate section meetings. At the stand-down meeting, the two most important issues were the results of a BNL safety questionnaire 

and a report on personnel radiation monitoring with the 

new TLD badges. The results of the questionnaire 

indicated that most NSLS staff members are informed 

about safety and feel that the NSLS does a very good job. 

However, it did show that problems exist in certain areas 

and has given guidance to some of our efforts. Doses 

measured with the new TLD badges show increased levels 

being reported above those reported with the old film 

badges. That was expected since there is a significantly 

lower threshold of response for the new badges. This data 

is being used now to improve the general understanding 

of our sources of radiation and to reinforce our efforts to 

make sure that all personnel handle the badges properly. 

The separate meetings of the sections were intended 

to allow any staff member to openly discuss or question 

whatever safety related issues they had. The result was a 

comprehensive compilation of problems and concerns 

important to the staff. They ranged from concerns about 

snow removal, to the desire for more safety training in 

areas such as electrical safety, to radiation issues and to 

traffic safety on and off site. Since the meetings, the 

ES&H staff, with the aidofothers, has reviewed each issue 

and is preparing to answer each question or correct the 

problem. The results will be distributed to the staff. Along 

with issues raised by BNL, we will take our lessons learned 

from the stand-down meetings into account when we 

prepare our Tier I1 self-assessment. For example, two of 

the most common issues raised were safety training of the 

staff and the need to improve the work habits of 

personnel. The feeling of many staff members was that 

safety could be greatly improved if more people had 

training appropriate to their actual work, not determined 

by job title, and if work practice safety could be coupled 

with Tier I inspections. 

5 
The major on-going efforts are thus to continue to 

decrease the small but measurable personnel doses from 

the W and booster operation, education of the staff in 

areas such as use of dose monitors and electrical safety, 

studying behavior in the work place to determine effectiveness of and new directions for training, preparation of 

responses to all ofthe questionnaire and stand down issues 

raised by the staff, improvement of quality of life issues by 

upgrading the working environment, and continued vigilance to maintain our high level of safety. The main thing 

that we were all reminded of this year is that the key to 

safety is the involvement of every staff member and user 

in the safety programs. Coupled with the professional 

puidance and efforts of the NSLS and BNL staff. the 0 

workplace can indeed be safe and productive. 

6 
USE 

Eva Z. Rothman 

User Administrator 

NSLS 

The User Administration Ofice not only deals first-hand with every user that comes through the NSLS’ door, 

we also count them. Based on the numbers of users registering in our office, being trained, getting radiation badges, 

and attending the Annual Users’ Meeting and Workshops, I am happy to say that the NSLS users’ activities at the 

NSLS have been relatively steady and even increasing slightly. During FY 1996, in fact, there was a record number 

of 2261 new or returning users who came to the NSLS to perform research on a beamline! The statistics for the past 

four years are shown in the Table. 

Note that for publications and abstracts, the NSLS relies on the users to volunteer this information to the NSLS. 

Therefore the fluctuations in those columns are usually due to other factors besides actual facility usage e.g. how much 

time the NSLS invested that year in searching for and requesting the information, and how well the users responded 

that year. Unfortunately, these are both items which are scrutinized as indicators of a facility’s productivity - the user 

community should be prepared for renewed efforts on the part of the NSLS to collect this important information. 

Some other interesting facts and analyses emerge from our yearly statistics: 

The NSLS still gets over half of its users from universities. Although there is some proprietary research being 

conducted where the institution is not required to publish or share the data, most ofthe research done at the NSLS 

is published in open literature where anyone who needs it can have access to it. Indeed, the data belongs to the 

people of the U.S. who fund the DOE facilities through tax dollars and the information is out there, available 

to be used in the next invention or new technology. 

Our users are young crowd - over 40% are 30 or under and another 33% are between 30 and 40 years old. 

It seems that a significant population of young scientists is being introduced to the capabilities and usefulness 

of synchrotrons, in many fields of science, at a point in their career where they have many years of research to 

look forward to. 

New York, California, New Jersey, and Pennsylvania, in that order, are the states with the most institutions 

sending users to the NSLS. Illinois and Maryland are tied for fourth place. This illustrates that the NSLS not 

only has a strong regional customer base here in the East, but despite the SSRL and the Advanced Light Source 

in Berkeley there are users with special needs in California who still come to the NSLS. The pattern is likely to 

hold true for the Advanced Photon Source in Illinois - a good fraction of those Illinois users will probably 

continue to use the NSLS, at least in addition to the new APS. 

7 
The industrial institutions with the largest numbers of NSLS users are also local: Dow Chemical Company, 

Exxon, IBM, and Lucent Technologies. 

Users in the field of structural biology have increased each year from 267 in 1993 (12%) to 5 18 in 1996 - now 

23%, or almost a quarter of all NSLS users. The recently completed structural biology addition to the 

experimental floor is providing much-welcomed lab and set-up space for this growing community. 

The User Administration Office meets the varied 

information needs of the NSLS by collecting information 

from users, compiling statistics like those above, and 

producingpublications and pamphlets. Our other equally 

important mission is to support the NSLS user community by administering the General User Program, organizing and running the Annual Users’ Meeting (more on 

that in Section 3 of this Activity Report), and helping the 

users get to their experiments as quickly as possible with 

efficient registration and training procedures. 

The General User Program has seen some major 

changes this year. Up until recently, all the proposal 

information was being data-entered and stored in a large 

WordPerfect file. This worked well for a number ofyears 

but had its limitations. The system constrained the type 

and complexity of reports and statistics we could extract, 

allowed only one person to data-enter the proposals at 

one time (which therefor dictated our processing schedules), and precluded future development of electronic 

methods of submitting and storing proposals. During 

FY 1996, a Proposal Database was designed and implemented by NSLS Administration programmer Liz 

Hicks, with the assistance of 

information systems consultant Peggy Sutherland (now 

with BNL’s Business Information Systems division) and 

Eileen Pinkston (the General 

User Program Coordinator). 

The Proposal Database is actually part of the User Database in which everyone registers when they arrive, so that 

information such as user addresses can be shared instead 

of duplicated. The new database has enabled the User Administration Office to accommodate more complex requests for queries and reports; 

since more than one person 

can use the database at one 

time, it will allow us to shorten 

the proposal processing schedule and become more flexible 

in accepting different types of 

proposals in the future- again, 

without sacrificing turnaround time. Finally, the database opens the possibility 

for electronic submission us8 
ing e-mail or the Web or some combination - this is 

because unlike the WordPerfect file, the database could 

link to or store the 1 to 3 page narratives attached to the 

proposal forms. 

In May of 1996 Lydia Rogers joined the User 

Administration Office, beginning her stay here by helping 

to test the new Proposal Database. She and Eileen have 

already used the new Proposal Database for the May 3 1 

and the September 30 submission deadlines. In addition, 

Lydia has taken a major role in the annual production of 

the Activity Report by taking charge of the abstract 

submissions. 

New technology continues to positively impact the 

User Administration Office. Over the summer of 1996, 

the old Polaroid camera used for taking user ID badge 

photos was replaced by a digital camera attached to a PC. 

The software allows the User Administration Office to 

take the user’s photo, choose the best image from a set of 

nine which the computer automatically generates with 

various contrast settings, and then electronically send it in 

the correct format to the Safeguards and Security Division 

where the BNL ID badges are physically made. In the 

past, the Polaroid snapshots the User Administration 

Office took had to be delivered to Security and rephotographed and digitized for the Security Divisions 

photo database. This Polaroid database stored the images 

in a proprietary format, which means they could not be 

decoded and used for anything else. Now, besides resulting in a much better image quality, the new non-proprietary format allows them to be used with Human Resources personnel files, or at the BNL main gate or HFBR 

where guards could verif>r visitor ID with the computer 

screen. The NSLS for its part will be enhancing the 

electronic NSLS user and staff directory in the lobby to 

display everyone’s photos - if a user needs to locate 

someone for assistance, they will know exactly for whom 

to look! 

9 
us 

Peter W. Stephens 

SUNY @ Stony Brook 

UEC Chair 

The Users‘ Executive Committee exists to facilitate 

communication, in all forms, between the community of 

users and the NSLS administration. Its membership is 

listed in the caption of the accompanying photograph. 

We conduct an annual user meeting and three public 

town meetings each year, followed by discussions with the 

NSLS and Brookhaven Laboratory staff and management 

to discuss relevant issues. I am grateful to all of the 

members of the UEC and the staff and directorate of the 

NSLS and BNL for the time, thoughtfulness, and candor 

which they have brought to this work. The annual user 

meeting drew 368 attendees, 80% ofwhom attended one 

or more of the six workshops. These covered a wide range 

of topics: the application of synchrotron radiation to 

magnetic materials, precision fabrication with hard xrays, strategy and methods for area detector data collection, in situ applications ofx-ray absorption fine structure, 

multiple wavelength anomalous dispersion, and opportunities in polymer research. The keynote speech was given 

by Malcolm Browne, Pulitzer Prize-winning Senior Science Writer of The New York Times, who spoke on 

“Lamplighters and Tool Makers.” The users also heard 

from NSLS Chairman Michael Hart, from William 

Oosterhuis of the Department of Energy, and from seven 

scientists who covered a fraction of the spectrum of 

current research at the NSLS. 

Two ofthe important discussions in which the UEC 

is currently participating are future operating conditions 

and the review of all of the Participating Research Teams. 

In the first case, some of the X-Ray Ring users wish to 

increase the electron energy from 2.584 to 2.8 GeV to 

provide a harder spectrum, particularly for certain gamma 

ray experiments using LEGS. Operation of the storage 

ring at the higher energy has been demonstrated, but it is 

necessary to weigh the impact on the programs of all ofthe 

users. Discussions are also open between the accelerator 

physicists and the users of theVUVRing over the feasibility and desirability of operating in a “top-off mode. The 

NSLS has embarked on the project of renegotiating its 

relationship with all of the PRTs, starting with a review of 

each PRT by the Science Advisory Committee, which 

reports to the NSLS chair. The user community at large 

is represented by the chair of the UEC as an ex-officio 

member of the SAC. I believe that there are very important issues here for the future of the facility, as we seek the 

means to assure access to the large and continuously 

evolving community of users. At the present time, there 

are some existing PRTs which are insufficiently funded 

and staffed to be able to operate full time, while there are 

others which have insufficient beam time to satisfy the 

needs of their members, as well as groups who are interested in forming new PRTs. 

One change in the pattern of usage is reflected in the 

formation of a new Special Interest Group devoted to 

industrial users of the NSLS. Some aspects of the current 

access policy are inappropriate for industrial research, and 

this group is seeking to effect changes which will improve 

the utility of the NSLS to its membership. 

With the continued growth of synchrotron radiation facilities in the world, we see the use of x-rays, 

infrared, and ultraviolet light from such sources becoming 

more of a commodity and less of an independent enterprise. This forces a hard-headed look at cost effectiveness, 

and the NSLS has an enviable record. No other Department of Energy supported synchrotron facility comes 

within a factor of two of our productivity (2268 registered 

users active during FY 1996/ $30.7M annual budget). 

1996 has been another year ofvery strong scientific 

output at the NSLS. Even a casual glance at the abstracts 

and publication lists in this volume will show the reader 

that there is a tremendous variety of interesting work 

going on here. We have become used to the excellent 

operating conditions at the Light Source, and it is worthwhile to reflect on the efforts of the NSLS staff that have 

led to the continuous improvements in beam brightness, 

stability, and reliability over the years. At the same time, 

this is above all a user facility, and it is the scientific 

programs of the users which drive the health of the NSLS. 

I have every reason to look forward to having a 

vital facility here long into the future. 

10 
Users' Executive Committee and 

Special Interest Group Representatives 

(Front, from I@ to right) 

Michael Dudley (SUNY@ Stony Brook), Eva Rothman (BNL-NSLS), Peter Stephens (SUNY@ Stony Brook), Ian 

Robinson (U. of Illinois), and Doon Cibbs (BNL-Physics) 

(Back, from I@ to right, standing) 

Richard Harlow (The DuPont Co 1, Paul Zschack (ORNL), Carl Zimba (Mm, Thomas Russell (U. of Massachusetts), 

Mark Chance (Albert Einstein College of Medicine), Stephen Cinell (ANL), D Peter Siddons (BNL-NSLS), David 

Johnson (BNL-Chemistry), Kim Mohanty (BNL-Physics), Ralf Wehlitz (U. of Tennessee), and Benjamin Ocko (BNLPhysics). 

Absent from photo are Steven Whisnant (U. of South Carolina) and Yves ldzerda (Naval Research Lab). 

11 

SCIENCE HIGHLIGHT

15 
APPLIED SCIENCE 

The research activities categorized as applied science include energy, technology, and the environmental 

sciences. The projects are perhaps more closely geared 

towards solving immediate problems than other kinds of 

fundamental research. 

Environmental Science 

The application of synchrotron techniques to the 

area of environmental science has been one of the key 

areas of development at the NSLS in the last year. 

Particular progress has been made in the study of waste 

metals in soils. EXAFS and XANES are among the core 

techniques applicable towards understanding the typically heterogeneous samples relevant to hazardous waste 

remediation. For example, M. Szulczewski, W.F. Bleam, 

and P.A. Helmke (U. of Wisconsin) examined the structure of metal ions in a number of soil environments using 

the facilities of beamlines X11A and X23B. In one series 

of experiments, XANES spectroscopy was used to identify the oxidation state of chromium (Cr(II1) versus 

Cr(VI)) in contaminated soil samples (Figure 1). Due to 

the significant differences in the pre-edge features of 

various oxidation states of chromium, the presence of the 

notoriously toxic Cr(VI) can be identified (and accurately 

quantified) even when the more benign Cr(II1) predominates. Other studies by this group have examined a range 

of first row transition elements in soil, concluding that the 

elements are bound to humic substances. 

Figure 1 : Cr K-edge spectra of the pre-edge region 

of standard physical mixtures with varying fractions 

of Cr(Vl):Cr(lll). (X23B) 

D.E. Sayers, D. Hesterberg, W. Zhou, W.P. Robarge, 

and G.M. Plummer (North Carolina State U.) have also 

carried out a number of environmental chemistry of soils 

studies on beamline XllA. In one investigation, the 

chemical forms of metals occurring at different depths in 

contaminated soil in a Superfund site were examined, 

with the hypothesis that redox potential and oxygen 

availability would play a significant role in metal speciation. The hypothesis was to some degree confirmed, in 

that analysis of copper EXAFS data showed reduction in 

Cu-oxygen bonding and increases in copper-sulfur bonding with soil depth (Figure 2). Cu-S was determined to 

be the primary mineral species in the sub-surface samples. 

Another example is the collaboration between K. 

Xia, F. Weesner, W.F. Bleam (U. of Wisconsin), P.R. 

Bloom, and U.L. Skyllberg (U. of Minnesota), who 

carried out sulfur K-edge XANES studies on beamline 

XI 9A to characterize the oxidation states of sulfur in both 

soil and aquatic environments. They identified six major 

sulfur containing functional groups in humic material 

and demonstrated the ability to distinguish sulfur oxidation states in aquatic, organic, and mineral soils. 

16 
Trace metals in the environment are important for 

their effects on biological systems, and so these elementspecific techniques are particularly interesting when applied to organisms. The x-ray fluorescence microprobe 

was used to study a number ofproblems ofenvironmental 

importance, including measurements of trace Pb in bone 

byC.S. Fullmer (Cornel1 U.) andK.W. Jones (Brookhaven 

National Laboratory). These studies, on chick tibia, 

investigated how lead affected bone growth by studying 

Ca and Pb distributions in normal and calcium deficient 

bones. Another study of metals in tissue was that undertaken by W.J. Berry, D.J. Borsay (U.S. Environmental 

Protection Agency) and K.W. Jones (BNL) of marine 

organisms living in sediments. In this case, the location of 

absorbed metals could be established for clam worms 

exposed to metals in controlled ways. Additionally, 

samples of dredged material from the NY/NJ harbor were 

studied by K.W. Jones (BNL) and S.-R. Song (BNL and 

Yale U.). By screening for contaminants as a function of 

sample particle size it was possible to check whether a 

simple physical separation method could be useful in 

decontaminating such materials. It was found that contaminants were present for all particle sizes at about the 

same concentration. A somewhat related experiment was 

performed byT.K. Tokunuga, S. Bajt (LawrenceLivermore 

National Laboratory) and G. Shea-McCarthy (U. of 

Chicago) on the oxidation state ofselenium in sediments, 

decomposingplant residue and algae. These studies are of 

interest because the toxicity of selenium is highly related 

to its oxidation state. 

Energy Conversion and Storage 

Environmental systems are interesting not only 

from the life science point ofview, but also as mechanisms 

for efficient energy and chemical conversions. There is 

perhaps no better example than photosynthesis, the natural harvesting and ultimate storage of solar energy. Researchers have been studying a variety of simpler systems, 

such as nanoclusters, for potential applications in photochemistry and electronics. For example, L.X. Chen, 

T. Rajh, D.M. Tiede, P.A. Montano, and M.C. Thurnauer 

(Argonne National Laboratory) studied titanium oxide 

clusters on beamlineX18B. Whenphotoirradiated, these 

semiconductor particles produce charge separation on 

their surfaces. They can thus act as electron donors or 

acceptors in oxidation/reduction reactions with molecules in their surrounding media, making them interesting for environmental remediation applications. The 

researchers studied the titanium k edge EXAFS on clusters ofvarying sizes and found systematicvariations as the 

ratio of surface to bulk atoms changes. They studied the 

photoreduction of Cu” ions on the TiO, colloid surface 

with and without surface derivatization with alanine. 

They were able to confirm the production of Cuo and 

could see complexes between copper ion and alanine as 

seen in Figure 3 along with their time dependence. 

Further studies were also carried out with mercury ions, 

which are environmentally relevant. 

One of the important technological challenges is 

the development of inexpensive and efficient means of 

energy storage. The advent of more and more portable 

electronics, not to mention electricvehicles, is continuing 

to press the development of new battery technologies. 

The central obstacles in these developments are, ofcourse, 

materials questions. T. Thurston, N.M. Jisrawi, 

S. Mukerjee, X.Q. Yang, J. McBreen (Brookhaven National Laboratory), M.L. Daroux, andX.K. King (Gould 

Electronics) have continued to exploit the high energy 

diffraction capabilities of beamline X27A for in situ 

structural characterization of working LixMn,O, batteries. With measurements made through the external case, 

electrolyte, and binding materials, the experimenters 

were still able to collect diffraction patterns at reasonable 

count rates. The researchers found, among other results, 

evidence for coexisting phases over a range of voltages. 

InworkonX23A2 andX23B, P.E. Stallworth (US. 

Naval Academy), M.L. denBoer, S. Kostov, and S. 

Greenbaum (Hunter CUNY) also investigated the properties of lithium based battery cathodes. In systematic 

studies of LiXV6Ol5 {x=0,0.5,1,1.5,2,3,4,5,6} carried out 

with NMR techniques to determine the environment of 

the intercalated lithium and XAS to determine the local 

17 
environment of the vanadium, the researchers found 

several structural regimes as a function of x. Using both 

the near edge quadrupolar peak intensity and the EXAFS 

as measures of the degree of symmetry of VO, octahedra, 

the team found a region of slight increase in the distortion 

from 0, with O<x<l, followed by a region of rapid 

increase in asymmetry for 1<xc3, finally followed by a 

region of only small change. This is illustrated in Figure 

4(a) which shows both the XANES and EXAFS results. 

The NMR evidence suggests that Li enters a single site at 

the lowest concentrations, but a variety of sites at the 

higher ones. The disorder extends beyond the first shell 

[Figure 4(b)], as evidenced by a decline in the outer shell 

amplitudes relative to the first shell. 

Superconductivity 

Superconducting wires and tapes made with highTc cuprates are a prime example. Such wires are typically 

a composite mixture of Bi,Sr2Ca2Cu,0x (Bi-2223) with 

silver, processed to yield a high critical current at a 

particular operating temperature. Like many of the 

cuprates, the superconducting properties of Bi-2223 are 

robust only for transport along the Cu-0 planes, making 

grain orientation a key factor in determining the critical 

current density. For example, T.R. Thurston, W. 

Wildgruber, N.M. Jisrawi, M. Suenaga, Y.L. Wang 

(Brookhaven National Laboratory), and P. Halder (IGC 

Corporation) continued to exploit the high energy powder diffraction capabilities of beamline X27A for in situ 

characterization of Ag-clad Bi-2223 high-temperature 

superconducting wires. In the experiment shown in 

Figure 5, the phase and texture development of Bi-2223 

are monitored as it is generated from precursor materials 

(Bi 2212 + CuO) within its silver sheath. The reaction 

was driven in a series of temperature steps at 600" and 

840°C. The researchers found that the formation of the 

Bi 2223 phase and the overall texturing were decoupled 

processes. 

18 
Electronic Materials 

The rapid developments in the electronics and 

semiconductor industries provide ample motivation for 

materials studies. There are many important problems 

which require diffraction information from areas of a few 

square microns or less within a patterned sample, for 

example a semiconductor device and its interconnections. 

There have been several such microdiffraction experiments performed at the NSLS this year, with significant 

technical applications. E.D. Isaacs, K. Evans-Lutterodt, 

M.A. Marcus, A.A. MacDowell, W. Lenhart, L.J.P. 

Ketelsen, J. Vandenberg, W.T. Tsang, J.E. Johnson, J.A. 

Grenko, and S. Sputz (Bell Laboratories) have produced 

a 5 micron monochromaticspot, and used it for studies of 

patterned InP multi-quantum well (MQW) lasers. The 

variation in MQW period and strain as a function of 

position across the fabricated structure is clearly seen in 

the data of Figure 6. These measurements could only be 

made with x-rays since these structures are buried and thus 

inaccessible to electron diffraction measurements. 

In a somewhat different approach, G.S. Cargill, 

P.-C. Wang (Columbia U.), I.C. Noyan, E.G. Liniger, 

C.-K. Hu, and K.Y. Lee (IBM Research) used a tapered 

capillary to obtain a 10 micron white x-ray beam and 

measured a diffraction pattern with an energy dispersive 

detector at X26C. They applied their setup, the first realtime strain measurements permitting such fine spatial 

resolution, to the study of electromigration and annealing 

in aluminum interconnect lines. Due to the stability and 

reproducibility of the detector in terms of peak shape and 

the use of an in situ tungsten standard, peak positions were 

easily measured to within 1 Yo of the peak width. This was 

sufficient to directly deduce the strain induced from the 

electromigration in the aluminum interconnects under 

study. 

H.Y. Lee (Synchrotron Radiation Research Center), C.H. Lee (Nat. Tsing Hua U., Taiwan), and K.S. 

Liang (Exxon) made in situ measurements of sputterdeposited thin films of LaNiO, on X22A. This material 

is an interesting substrate for integrated ferroelectric capacitors for microelectronic applications. They found 

that the material first deposits as an amorphous film, of 

about 100 A thickness. Another application of x-ray 

analysis to very thin films was made by C. Kim, I.K. 

Robinson, J. Myoung, K.-H. Shim, and K. Kim (U. of 

Illinois) on X1 GC, where they studied the evolution of the 

in-plane and out-of-plane lattice parameters of GaN films 

in the range of 50-10,000 A. 

Metal silicides are potential candidates as contact 

materials in advanced semiconductor applications, but 

many fundamental issues of resistivity and stability 

remain to be investigated. Z. Wang, P.T. Goeller, B.I. 

Boyanov, D.E. Sayers, and R.J. Nemanich (North Carolina State U.) designed, constructed and tested a UHV 

system for in situ studies of structures grown on semiconductor wafers via electron-beam evaporation. In first 

EXAFS measurements on beamline XllA (at the Co k 

edge) on cobalt and silicon codeposited and annealed in 

a 1 :2 stoichiometric ratio on Si,,Ge,,, films, the researchers found evidence for the formation of stable cobalt 

silicide (CoSi,). At annealing temperatures below GOO0 C, 

there was evidence as well for presence of a small amount 

of CoSi. The UHV chamber permits full characterization 

with a variety of techniques in addition to XAS. These 

include AES, XPS, UPS, MEED, andARXPS/UPS, and 

it is again appropriate to point out that well conceived 

XAS science backs up conclusions with corroboration by 

as many methods as possible. 

InP is an important semiconductor material for 

long wavelength optoelectronic devices and high frequency electronic devices. The performance of these 

devices is controlled by the structural and chemical 

19 
uniformity ofthe epitaxial layers, which in turn, is strongly 

dependent on the structural perfection and compositional 

homogeneity of the substrates on which they are grown. 

It is, therefore, imperative to improve the crystalline 

quality and homogeneity of InP substrates. However, the 

relatively low yield stress of InP makes it susceptible to 

deformation by stresses generated during crystal growth, 

making it difficult to produce InP crystals with low 

dislocation density. In addition, temperature fluctuations imposed by turbulent convective flow give rise to 

uncontrolled variations in the local solidification rate and 

in diffusion layer thickness, leading to microscopic and 

macroscopic chemical inhomogeneity. 

In work aimed at studying and improving the 

growth of InP and other semiconductor crystals, V. 

Prasad, H. Zhang, M. Dudley, H. Chung, and W. Si 

. (SUNY @ Stony Brook), D.F. Bliss (Air force Rome 

Laboratories), and A. Maniatty (RPI) have been correlating defect microstructures and interface shapes observed 

using Synchrotron White Beam X-ray Topography 

(SWSXT) with the theoretical predictions ofheat transfer 

and stress generation during the single step, high pressure 

Kyropoulos growth of doped InP boules. This enables a 

correlation between observed defect structures and both 

the growth parameters and modeling predictions. The 

results can provide feedback to the crystal grower to 

enable optimization of these growth parameters. 

Figure 7(a) is a transmission x-ray topograph recorded from a S doped InP crystal. Numerous slip bands 

(S) nucleated from the cylindrical outer surface of the 

boule and propagating into the interior of the crystal were 

revealed. In the growth of indium phosphide, boric oxide 

is used as an encapsulant to prevent the decomposition of 

the melt. The encapsulant also reduces the radiative heat 

loss from the outer surface of the crystal since B,O, acts as 

a heat shield. Detailed heat transfer modeling reveals that 

the maximum heat loss occurs at the point where the hot 

solid material emerges from the encapsulant giving rise to 

maximum temperature gradients in this region. X-ray 

topographs revealed that slip bands are most likely to be 

nucleated at this stage to relieve the large thermal stresses. 

The distribution of excess resolved shear stresses in the 

crystal at various stages in the growth process has been 

calculated using an anisotropic thermo-elastic finite element model for InP single crystals. The result is shown in 

Figure 7(b). It is worth noting that the maximum excess 

resolved shear stresses are generated on the outer surface 

of the crystal at the point where the crystal emerges from 

the encapsulant corresponding to the region with maximum temperature gradients. The calculated result is in 

good accord with the slip band distributions revealed by 

x-ray topography. 

110) 

---t 

Figure 7: (a) Synchrotron White Beam X-ray Topograph (g=004, kO.45A) recorded in transmission 

geometry from a longitudinal cut (1 IO) S doped InP wafer showing the distribution of slip bands (S) 

and (b) the distribution of the total excess resolved shear stress on the (1 10) plane through the center 

of the crystal subject to an intermediate growth stage temperature field. (XI 1 A) 

20 I 
Silicon Carbide (Sic), is avery promising semiconductor material for high temperature, high power, and 

high frequency electronic devices owing to its excellent 

thermal and electrical properties. One key issue for the 

fabrication of these devices is the availability of epitaxial 

layers with high crystalline quality, good dopant homogeneity, and good reproducibility. However, Sic has over 

200 polytypes with different properties. Since these 

polytypes coexist over a wide range of temperatures, 

obtaining single crystals of large size, containing only one 

designated polytype is often difficult. In the case of 4HSic epitaxial growth on (0001) substrates, one ofthe big 

obstacles is the occurrence of triangular inclusions in the 

epilayer. One method of preventing the formation of 

triangular inclusions during epitaxial growth is to use 

substrates misoriented from (000 1). The vicinal surfaces 

of such off-axis substrates provide high densities of surface 

steps. which facilitates epitaxial growth on such surfaces 

proceeding through a step-flow mechanism. However, in 

4H-Sic epitaxy, the occurrence of triangular inclusions 

was still found to persist even when substrates misoriented 

by 3.5" from (0001) were used, although their numbers 

decreased drastically as the misorientation angle approached 8". 

C. Carter, J. Sumakeris, and H.S. Kong (Cree 

Research Inc.), and W. Si and M. Dudley (SUNY @ Stony 

Brook) carried out a detailed study of 4H-Sic epilayers 

grown on 4H-Sic substrates. Synchrotron White Beam 

X-ray Topography (SWBXT) and Nomarski Optical 

Microscopy (NOM) have been used to study the character of triangular inclusions in 4H-Sic epilayers (0001) 

4H-Sic substrates with misorientations ranging from 

3.5" to 8". X-ray diffraction pattern analysis carried out 

on an epilayer grown on a 3.5" misoriented substrate 

reveal that there are two additional phases, 3C(I)-Sic and 

3C(II)-SiC, present in the 4H-Sic epilayer associated 

with the triangular inclusion. The detailed correlation 

between the NOM micrograph and reflection topographs 

is shown in Figure 8 (a) to (d). Evidently, all triangular 

inclusions belong to one or the other of the two 3C-Sic 

structural configurations. Most of the triangular inclusions are single crystal 3C-SiC, although they appear to be 

severely strained. There is only one triangular inclusion 

consisting of both 3C(I) and 3C(II)-Sic, which indicates 

the existence ofa double position boundary (DPB) within 

the inclusion. This research shows unambiguously that 

the triangular defects observed in the 4H-Sic epilayers 

studied are 3C-Sic inclusions. 

It is well known that in 4H-Sic single crystal 

substrates, there exist superscrew dislocations along the 

io00 1 > axis whose Burgers vector magnitudes are equal 

to a multiple of the c lattice constant (c = 10.05 A). 

Figure 9 (see next page) shows (a) a NOM micrograph 

of an epilayer grown on such a substrate and (b) a backreflection topograph. Triangular inclusions (TI), growth 

pits (P), and scratch (S) marks are observed on the 

micrograph. The directions from the apex of the triangle 

to the base are <-I 2 -1 O> directions, which correspond 

to the down-step directions 

Figure 8: 4H-Sic epilayers on 4H-Sic substrates misoriented by 3.5" from (OOOl), 

(a). a NOM micrograph, (b). the reflection topograph from the same region, 4H-SiC, 

g = 1-1 0 6, h = 0.78 A, (c). the reflection topograph of 3C(I)-SiC, g = 202,h = 0.91 

A, and (d). the reflection topograph of 3C(II)-SiC, g = 1 31, h = 0.67 A. (X11 A) 

I 

(direction of lateral step 

growth). The length ofaltitude from base of the triangle to the peak is around 

97 to 120 microns. The 

density of growth hillocks is 

3 - 4 X IO4 /cm2, and the 

diameter is around 1 micron. Superscrew dislocations including micropipes 

(M) and elementary screw 

dislocations (ED) show circular white features on the 

topograph. By comparison, 

it is evident that there is no 

obvious correlation between 

superscrew dislocations and 

3C-Sic triangular inclusions. Also there is no evidence showing that the 

growth hillocks are related to the superscrew 

21 
dislocations since the density of growth hillocks is one 

order of magnitude higher than that of superscrew dislocations (.- 1 03/cm2). 

Magnetic Materials 

Magnetic materials, particularly thin film structures, find immediate application in magnetic recording 

media for computer and entertainment applications. 

Several experiments of technical importance were carried 

out in the past year. Fe-Cr superlattices are of interest 

because of their giant magnetoresistance, but this effect 

depends strongly on the preparation conditions. W. 

Dmowski and T. Egami (U. of Pennsylvania) used 

beamline X7A to study the interfaces of sputtered films, 

and inferred that roughness at relatively short length scales 

increases the magnetoresistance. 

T.R. Thurston, L.H. Lewis, U. Wildgruber, D.O. 

Welch (Brookhaven National Laboratory), and V. 

Panchanathan (Magnequench International) used X27A 

to characterize the texture distribution in 

thermomechanically deformed Nd2Fe,,B magnets. This 

type ofwork is still relatively new at synchrotron sources, 

and is representative of a wealth of potential applications 

which will increasingly appear at the NSLS. L.H. Lewis, 

C.H. Sellers (Idaho National Engineering Laboratory), 

and V. Panchanathan( Magnequench International) have 

also studied Nd2Fe,,B magnets, using X7A to determine 

the phases present in the multiphase samples which result 

from rapid solidification. 

Q. Zhu (Brookhaven National 

Laboratory) used beamline X7A, to 

study the increase in the structural 

order parameter in the soft magnetic 

alloy Fe-Co-V with thermal aging, 

and was able to identify a minority 

phase comprising only 0.3% of the 

sample. The results call into question the widely-accepted belief that a 

fully ordered Fe-Co alloy exhibits the 

optimal magnetic properties. 

Properties of Materials 

X-ray scattering techniques are 

an old and established probe of structural properties of bulk matter. They 

can detect the presence of small 

amounts of a second phase in nominally single phase systems, residual 

strain, the existence of precipitates, 

etc. Thus these techniques remain 

fundamental to understanding details of technologically 

relevant problems in ceramics and alloys, for example. 

The X3A2 beamline was used by Y. Gao, W. Hasz, 

and C.A. Johnson (GE Corporate Research and Development) for a spatially-resolved crystallographic study of 

yttria-stabilized zirconia, oriented toward the development of x-ray diffraction techniques to derive the temperature history of a ceramic sample. A. Sahiner, D. 

Wittmer, and M. Sweeney (S. Illinois U.) used the same 

beamline to study the effects of thermal shock on the 

residual stress of Si3Ni, ceramic composites. They found 

that the compressive stress decreases as the temperature is 

increased above 1 130°C, becoming a tension in the inplane direction at 1400°C. 

The tunability of synchrotron radiation has been 

used to advantage by D. Alexander (APS, Argonne) on 

X6B to study defects in steels used in reactor pressure 

vessels. For example, usinganomalous small angle scattering it was possible to identify CuMn precipitates in a FeCu-Mn alloy. Such precipitates are known to cause 

embrittlement in alloys. 

Polymers and Polymer Composites 

Polymer composites take many forms, depending 

on the application. Structural composites, such as Nextel 

fibers in ceramic matrices and carbon fibers in polyamide, 

are being investigated by R.J. Meilunas and A. Tobin 

(Northrop Grumman) at beamline U2B. Some of these 

Figure 9: 4H-Sic epilayers on the 4H-Sic substrates misoriented by 3.5" 

from (OOOl), (a). a NOM micrograph, and (b) the back-reflection topograph 

recorded from the same region, g = 00024, h = 0.83 A. ( X11 A) 

22 
composites are intended for use in hostile environments 

(elevated temperatures, oxidative atmospheres, etc.) and 

the local chemistry (e.g. at the fiber - host matrix interface) 

controls many of the desired properties. By performing 

IR microspectroscopy on such localized regions, Meilunas 

and coworkers have identified fiber sizings (coatings) that 

inhibit thermo-oxidative degradation of the surrounding 

matrix. 

Another type of polymer composite is in the form of 

laminates. The layers are frequently a few microns to 

several tens of microns in thickness, depending on the 

laminate’s intended purpose e.g. photographic film emulsion or food container. In the latter case, thevarious layers 

provide the proper combination of structural integrity, 

sanitary surfaces, and barriers against penetration by light 

or gases. Much thinner layers are used in photographic 

emulsions. However, in both cases the interdiffusion of 

chemicals between the layers must be understood and 

controlled. Several studies of this nature have been 

conducted, including one study of a laminated polymer 

used for plastic containers. Figure 10 shows such a 

laminate in cross section, and a linear spectroscopic 

absorption map. While the optical image of the 

microtomed section suggests a clear delineation of the 

layered materials, the infrared map provides evidence of 

chemical diffusion. This is especially apparent between 

layers 3 and 4 where the absorption features in the 

“fingerprint region” (below 1500 cm-’) show an overall 

gradient from the interface to a depth of 10 mm or more 

into layer 4. Similar behavior is seen, though to a lesser 

extent, between layers 2 and 3. 

In a collaboration between D.L. Wetzel (Kansas 

State U.) and R.O. Carter (Ford Science Research Center), degradation profiles from photochemical reactions, 

were measured into the surfaces of acrylic polymers with 

and without polyethylene or polypropylene protective 

surface coatings. Cross sections of the exposed acrylic 

were microtomed and measured in transmission. The 

unprotected acrylic materials showed damage that extended from the surface to a depth of about 20 microns. 

In particular, the absorption signatures for the acrylic 

were weak at the surface. Actual photochemical reaction 

products (OH, carbonyl) were detected several microns 

into the surface. Measurements of protected acrylic 

material showed no evidence of damage, even near the 

surface. 

A considerable number ofmeasurements were made 

at XlA by H. Ade, A.P. Smith, T. Coffey (North Carolina 

State U.), and collaborators both on mixtures of copolymers and polymers and on laminate structures, further demonstrating the capability of the technique as an 

analytical tool. The morphology and composition of a 

macro phase separated blend of poly[ (styrene-r-isoprene)’- 

b-(styrene-r-isoprene)” random block copolymer (RBC) 

(20%) with homopolystyrene (PS) (80%) was investigated and micron sized ellipsoidal dispersions of the RBC 

were found within the matrix. Polycarbonate styreneacrylonitrile copolymer blends grafted on to polybutadiene 

and titanium oxide were also studied. In another example, the spinodal decomposition of two polymers PS/ 

PMMA constrained to a surface was imaged and showed 

segregation of the PS into spheroids within the PMMA 

matrix. Studies were also made of polymeric isomers, 

which could be distinguished spectroscopically due to the 

differences in the local chemical environment. Finally, to 

ensure that radiation damage was not a problem in these 

experiments, radiation damage experiments were carried 

out on PET up to 2.7 Mrad. 

Six lavers of commercial 

“Joker” bottle. 

1) polyethylene 

(50 P) 

(30 pm) 

2) polymer adhesive 

3) EVOH polymer 

(air barrier - 50 pm) 

4) polymer adhesive 

(30 pm) 

5) black polyethylene 

(light blocking - 120 pm) 

6) orange polyethylene 

(mech. structure - 120 pm) 

Figure IO: Laminated plastic material 

investigated by scanning IR microspectroscopy. 

(Top) A description of the plastic layers, their 

purpose and respective thicknesses. (Bottom) 

Linear scanned IR absorbance map across a 

6 mm thick microtomed section. Also shown is 

a photographic image of the section, and labels 

for the various layers. (U2B) 

2400 18bO leb0 li3l li00 lW0 

Wavenumber (cm-l) 

23 
Projection Lithography 

A. MacDowell and 0. Wood I1 (Lucent Technologies) continued phase-measuring, lateral shearing interferometry on a multilayer-coated extreme ultraviolet 

(EUV) imaging system using 13.5 nm radiation from the 

U13 undulator. This common-path interferometer addresses one of the major challenges confronting EW 

lithography, namely the lack of wavefront measuring 

metrology at the multilayer coating’s operational wavelength. 

Experimentally a 0.08 NA subaperture of a 1O:l 

reduction Mo/Si multilayer-coated Schwarzschild camera is illuminated by 13.5 nm radiation emerging from a 

4.5 micron pinhole. An open-stencil amplitude grating, 

with period chosen so that the lateral shear between 

diffracted orders is small enough that multiple-beam 

interference can occur in the region of overlap, is positioned in the camera’s image plane. A phase-shifting 

technique, in which a CCD detector is used to record 13 

interferograms produced by shifting the grating in the 

shear direction one twelfth of its period, is used to 

determine the difference in phase between the two 

Figure 11: A two-dimensional phase map of the 

U13 camera‘s wavefront obtained by combining 

phase difference data from the same wavefront 

recorded with shears in orthogonal directions. the 

measured wavefront error over the camera’s 

aperture after piston, tip, tilt, and defocus have 

been removed is 0.098 waves RMS at a wavelength 

of 1 3.5 nm. ( U13) 

interfering wavefronts. Phase difference data from the 

same wavefront recorded with shears in orthogonal directions are combined using amethod involving least squares 

to produce a two-dimensional phase map of the camera’s 

wavefront, as shown in Figure 1 1. The measured wavefront 

error over the camera’s aperture after piston, tip, tilt and 

defocus have been removed is 0.098 waves RMS at a 

wavelength of 13.5 nm. While this value only slightly 

exceeds the Marechal condition (0.071 waves RMS), for 

“diffraction-limited imaging, the wavefront errors in an 

imaging system for production EUV lithography will 

have to be considerably smaller. Since the sensitivity of 

this lateral-shearing interferometer was shown in earlier 

experiments to be better than 0.021 waves RMS at 13.5 

nm wavelength, even in its current state of development 

it can be used to evaluate the image quality and improve 

the alignment of existing EW imaging systems. 

Hard X-Ray Lithography 

To extend lithographic techniques to structures 

thicker than 0.5 mm it has been shown to be beneficial to 

employ a hard x-ray source such as the NSLS X-Ray Ring. 

The NSLS has established a program in this area currently 

located at X27B which is centered on exposure technique 

development. They have succeeded in manufacturing 

precise fully figured 3-dimensional objects on a length 

scale of many millimeters. So far, the material of choice 

as a resist has been polymethyl-methacrylate (PMMA) 

since it is well know in other lithographic applications. In 

the present protocol, x-ray exposed areas are subsequently 

removed in a selective solvent system. To produce a 

pattern on the resist, an x-ray opaque mask is placed in 

front of a resist sample. The mask and sample are scanned 

together vertically through the x-ray beam. Often filtering is employed to tailor the high energy cutoff of the 

beam to the particular application, and parameters such 

as scan rate, total dose, and substrate temperature are 

controlled to manipulate the exposure. The patterning 

masks used to date have included shadow masks assembledfrom thick high 2 materials (tool blocks and rods 

for example), and in collaboration with H. Guckel etal. 

(U. of Wisconsin), 50 micron thick patterned gold absorber on silicon wafers; objects which are themselves 

lithographically produced. Figure 12 (see next page) 

shows an example of the finish provided by hard x-ray 

lithographic exposure (the side walls) as compared with 

conventional diamond machining (the front face of the 

PMMA). It also exhibits faithful reproduction of the 

mask features (crisp corners and defects) and no observable runout from the front of the resist to the wafer 

surface. 

24 
To facilitate prototype hard x-ray exposures, the 

NSLS group developed a controlled aperture system 

which allows objects to be directly written. The 

aperture consists of two pairs of molybdenum rods 

mounted on actuators which compensate for beam 

induced heating. They can be moved under computer 

control to form rectangular apertures of arbitrary 

height and width anywhere within the 40 mm fan of 

beam available from X27B. By placing the sample on 

a rotary stage coupled to avertical scan stage, objects of 

arbitrary shape and orientation can be patterned. Figure 13 shows an SEM image ofaseries oflong channels 

in 1 mm PMMA sheet produced with one axis of the 

writer. An array of 50 channels were machined that are 

40 mm long, 125k 3 mm wide, placed 500 mm apart. 

In order to produce longer channels and multiple 

wafer exposure, a long-throw scanner was built for 

X27B. It has a stroke of over 600 mm, and can scan at 

rates over 250 mm/s. This high speed has proven 

useful for exposure parameter studies, in particular 

fixing not only the total dose, but the dose rate received 

in an exposure. The whole system has been automated 

with a Labview based control system. The scanner has 

proven sufficiently reliable and robust that it is being 

duplicated for the new X14B exposure station. 

Figure 12: Lettering in 1 mm thick PMMA sheet. 

At right is the point of a tailor’s pin. Note the smooth 

sidewalls as compared of the conventionally diamond 

machined surface of the acrylic sheet. (X27B) 

Figure 13: 1 25 micron wide tracks in 1 mm thick 

PMMA sheet. Pitch is 500 microns. (X27B) 

This beamline is being built to provide more user 

access to beam time for prototype production runs. 

The X14B beamline also provides a roughly 100 mm 

wide exposure field which should improve throughput 

over X27B which only has a 40 mm fan of radiation. 

Expansion of this capability will be important, as some 

users have already started moving to the next step of 

device fabrication. For example, J. Song et al. 

(Argonne National Laboratory), used the X26C 

beamline to pattern resist which was ultimately fabricated into mm-Wave Accelerating Cavities. They 

electroplated 99.9% oxygen free copper into cavities 

prepared in PMMA resist by hard x-ray lithography. 

The assembly was then diamond-lapped to provide a 

uniform thickness cavity. They have successfully made 

a 30 cell prototype of a rectangular 108-GHz structure 

using this technique. 

Conclusion 

Synchrotron x-rays are ideal tools for applied 

science. Their penetrating abilities permit in situ 

experiments; their wavelengths are well matched to 

structures at the atomic scale; and the large number of 

available photons enable high precision measurements. 

25 
BIOLOGICAL SCIENCES 

Biological sciences at the NSLS utilize a wide range 

of techniques and have one of the largest user groups with 

a single unifying theme at the NSLS, comprising nearly 

30% ofall registered users at the facility. The experiments 

have as their goal the identification of details of molecular 

chemistry and structure that explain the functions of 

biomolecules and cells. Macromolecular crystallography 

is used to provide detailed structural information, for 

example, about protein-DNA binding or protein-drug 

interactions. In cases where biomolecules cannot be 

crystallized, small-angle scattering can be used to follow 

structure changes. When detailed structure changes of 

protein active site metals are important to the function, 

EXAFS spectroscopy is commonly used to provide structure information. Microscopy techniques, like infrared 

and soft x-ray imaging, extend the range of biological 

investigations from the examination of chemical and 

structural information on biomolecules to the study of 

integrated biological systems, like cells. 

Macromolecular Crystal log rap hy 

A good example of a protein structure determination that relied on complementary features of two different beam lines, was that ofthe Sed translocation ATPase, 

by J. Hunt and J. Deisenhofer (Howard Hughes Medical 

Institute and the U. of Texas Southwestern Medical 

Center), and D. Oliver (Wesleyan U.). This work was 

carried out on beam lines X12B and X4A. SecA is a 

homologue of the family of membrane transport proteins 

known as ATP binding-cassette, or ABC, transporters, 

which couple the hydrolysis ofATP to the active transport 

of ligands across membranes. These proteins are ofstrong 

medical and pharmacological interest, and include, for 

example, the cystic fibrosis transmembrane conductance 

regulator (CFTR) and the P-glycoproteins which mediate 

the multidrug resistance phenotype observed in many 

tumor cells. 

It is quite difficult to undertake high-resolution 

structural studies of integral membrane proteins, but 

insight into their basic structural organization can be 

gained by studying structural and functional homologues 

such as Sed, a soluble enzyme which functions in translocating secretory proteins through the bacterial 

periplasmic membrane. It is believed to function as a 

molecular ratchet in the protein translocation reaction, 

pulling segments of the secretory protein through the 

membrane in conjunction with ATP-driven membrane 

insertion cycles. 

The high-resolution structure (to 2.9 A) of the 

membrane-retracted state of Sed was determined from 

crystallography data collected on X12B. Data were collected on a native crystal and from various derivatives, for 

which the high beam line intensity and wavelength 

tunability (to effect measurements of anomalous differences in the diffraction patterns) allowed for rapid screening. A selenomethionyl derivative data set was measured 

on X4A, taking advantage of the strong anomalous scattering at the Se K absorption edge and the excellent energy 

resolution of that beamline. While the selenomethionyl 

derivative crystals didn’t grow large enough to allow for 

their direct use in multiwavelength anomalous diffraction 

(MAD) phasing, this data set was still useful for pinpointing the methionine locations. The overall preliminary 

structural refinement points to the need to collect further 

data from Sed and its complexes with various physiological ligands at even higher resolution, yet a working model 

for rearrangements of its ATP-binding domains in the 

course of the transport cycle has already been formulated 

on the basis of the data collected. 

A macromolecular crystallography program was 

begun on beam line X9B in 1996 by Albert Einstein 

College ofMedicine. A group from this institution led by 

S. Almo, 2.-Y. Zhang, and D. Lawrence has spearheaded 

an effort to design potential therapeutic agents for and 

understand the structures ofprotein tyrosine phosphatases, 

whose roles in oncogenesis and signal transduction are of 

great significance. The structure of PTPlB (human 

protein tyrosine phosphatase 1 B), complexed with several 

synthetic non-peptide substrates, has been solved to a 

resolution of 1.9 8. Data were collected using Fuji 

imaging plates, which were read out via an off-line scanner. These results have given insight into phosphotyrosine 

binding sites, information that is crucial to the design of 

a new class of tight-binding inhibitors specific to the 

phosphatase. This is becoming of importance as the role 

of PTB 1 B in oncogenesis and non-insulin diabetes mellitus becomes clear. 

The arrest of DNA replication in response to the 

detection of DNA damage is a fundamental mechanism 

by which the cell minimizes the potential transmission of 

lethal mutations. A primary mediator of this response is 

the protein p21WAFl/CIPI, an inhibitor of the cyclin 

dependent protein kinases that also binds to and blocks 

the action of DNA polymerase enzymes directly. An 

elevation of nuclear levels of the tumor suppressor protein 

p53 occurs upon detection ofDNAdamage. This thereby 

stimulates transcription of p21WAFI/CIPl as part of a 
r7 

- - PCNA from S. cerwisiae 

HumanPCNA - p21 peptide 

- PCNAfrom S. cerevisiae - HumanPCNA - p2l peptide 

Figure 14: Ribbon diagram of the PCNA monomer with bound 

p2l peptide. (a) Stereo diagram of the three-dimensional 

structure of one monomer of the PCNA-p2l peptide complex, 

looking directly onto the face of the ring. The peptide (colored 

red) runs alongside the interdomain connecting loop (green). 

The N-terminal domain of PCNA is drawn in yellow and the Cterminal domain in plum, with five residues at the terminus 

shaded blue. 

(b) Superimposition of the C" trace of PCNA from S. Cerevisiue 

(red) onto that of human PCNA (black) with bound p21 peptide 

(green). The orientation is similar to that in (a). (X25) 

p53 signalling pathway, via which the cessation of DNA 

replication is coupled to the stalling of cellular mitosis. 

Using crystallography data measured at the wiggler 

beam line X25, a group led by J. Kuriyan (Howard 

Hughes Medical Institute and Rockefeller U.) determined the structure of the complex of the C-terminal 

region of p21WAFl/CIP1 with the human DNA polymerase delta processivity factor PCNA (proliferating cell 

nuclear antigen), to a resolution of 2.6 A (work to be 

published in CeLLby J. Gulbis, 2. Kelman, 

E. Gibbs, J. Hunvitz, M. O'Donnell, and 

J. Kuriyan). PCNA is a circular protein 

that encircles DNA and allows the polymerase to ride on it without dissociation 

during DNA replication, by forming a 

sliding clamp that tethers the polymerase 

to DNA during strand synthesis. The 

ability of p2 1 WAF 1 /CIPl to inhibit the 

action of PCNA may be due to its masking 

of PCNA elements that are required for 

the binding of components of the polymerase assembly. The derived structure 

(Figure 14) provides a view of a disabled 

PCNA molecule, which maintains a closed 

ring structure but is unable to support 

DNA replication. It also maps regions of 

the PCNA surface that might be important for polymerase attachment, and these 

are potential targets for the design of molecular analogs that would mimic the action of p2 1 WAF 1 /CIP 1. 

Low Angle Scattering 

Small angle scattering was used by 

K. Poole and K. Holmes (Max Planck 

Institute) and collaborators, on beam line 

X9B, to gain insight into structural differences benveen different muscle fiber complexes. Specifically, the motor protein 

myosin was isolated from both chicken 

skeletal and smooth muscles, and then 

introduced and bound to actin filaments 

in rabbit psoas muscle fibers. Small angle 

diffraction patterns were first measured 

from the two types of actomyosin complexes, and found to be different. Subsequent binding of the nucleotide ADP to 

each of these complexes resulted in little 

change to the diffraction pattern of the 

actomyosin complex derived from skeletal 

muscle myosin, but substantial change to - the pattern of the complex derived from smooth muscle 

myosin (Figure 15, see next page), which became similar 

to the pattern associated with skeletal muscle myosin. 

These findings imply that at least some part of the power 

stroke associated with the motor function of these two 

kinds of muscle arises from different configurational 

changes of the actomyosin complex. While the data are 

still being analyzed, this already represents a novel finding 

and will be an intense subject of future study. 

27 
- 

no ADP 1 mM ADP 

Figure 15: The effect 

of ADP on smoothSI decorated skeletal 

muscle action on low 

angle diffraction 

pattern. (X9B) 

Crystal Growth for Macromolecular 

Crystallography 

The growth of crystals that diffract well is the major 

rate limiting step in the collection and analysis of structural data from crystallography. The growth of such 

crystals, despite the improvements provided by mass 

screening procedures, is still an art. Thus it is important 

to try and quantify the results ofagiven growth procedure. 

One technique, used widely in materials science, is x-ray 

topography. Topography provides information specifically about crystalline perfection. 

An experiment performed by V. Stojanoff (European Synchrotron Radiation Facility) and D.P. Siddons 

(National Synchrotron Light Source), E. Snell (National 

Aeroeronautical and Space Agency), and T. Boggon and 

J. Helliwell (U. of Manchester), on beamline X26C, 

addressed the study of crystalline perfection of various 

proteins grown in space (zero gravity conditions) and on 

earth (earth gravity conditions). Triple-axis diffractometry 

and x-ray topography were employed to characterize the 

samples. Using Si( 1 11) monochromator and analyzer 

crystal reflections, the resolution in reciprocal space was 

sufficient to reveal fine structure in some of the Bragg 

peaks that would not have been resolvable using conventional double-axis diffractometry; employing triple-axis 

resolution, Bragg peaks were observed to be split in some 

instances. Fine structure in these peaks could be isolated 

and were further studied with x-ray topography, to provide insight into the spatial nature of crystallite domains 

responsible for the fine structure. From these studies, no 

definitive differences in the aualitv of the two classes of 

protein crystals (grown in zero gravityvs. in earth gravity) 

were revealed. These topography studies demonstrate a 

detailed method of examining crystal quality and may 

lead to a better evaluation of methods of crystal growth. 

M icro-Spectroscopy Techniques 

Synchrotron Radiation is well suited to spectroscopy on the pm scale due to the superior collimation and 

brightness compared to conventional sources. These 

advantages are illustrated in several biological applications, using infrared and x-ray radiation to interrogate a 

number of spectral transitions of interest. Thus, specific 

chemical information is derived associated with specific 

cellular structures. 

Though the infrared absorption features of various 

organic molecules are well-known, very little work exists 

that relates specific infrared signatures with particular 

ultra-structural features in cells and tissues. Much of this 

is due to the small size scale frequently encountered. 

Several groups have begun investigations into biological 

tissues, and a few of the results from beamline U2B are 

described below. 

One application of infrared microspectroscopy is 

for the identification and classification of various diseases 

in tissue samples. In a collaboration between the NRC 

(Canada), U. Manitoba, Kansas State U., and the U. 

Kansas Medical Center, Lin-P'ing Choo and coworkers 

studied microtomed sections from Alzheimer's diseased 

brain tissue. By following the shift of the amide I band 

from 165 1 cm-' to I63 1 cm-' (associated with b-amyloid), 

a maD of diseased locations in a tissue region was obtained. I/ 1 U 
Developing non-destructive techniques is particularly 

important since alternative methods, such as chemical 

staining, can destroy the biochemical integrity of the 

tissue. In related work by the same collaboration, D.L. 

Wetzel (Kansas State U.) examined brain tissues exhibiting multiple sclerosis, and identified spectroscopic features directly associated with diseased regions. 

Measurements on single living cells were conducted 

for the first time by N. Jamine, P. Dumas, and coworkers 

from DIEP-CEA, the Institute Curie and LURE! (all in 

France) as well as the NSLS. A technique was developed 

whereby live cells (mouse hybridoma B) are dispersed 

onto BaF, substrates. The cells, which are about 20 pm 

across, remain alive for several hours. Also there is no 

evidence that the incident synchrotron infrared (+ 10 

mW, or 100mW/mm2) causes damage. Various cells were 

spectroscopically mapped using an effective aperture size 

of 3 pm. In this situation, diffraction limits the spatial 

resolution to a size scale 10 pm. The IR spectra for the 

cells (Figure 16) show absorption features that can be 

attributed to particular chemical species. For example the 

absorption at 2920 cm-' is due to the C-H stretch of 

aliphatic methylene groups associated mostly with lipids 

and proteins. As these lipids and proteins are found to be 

non-uniformly distributed within the cell, the chemical 

maps of the cell shown in Figure 15, and the relationship 

between the lipid distribution and cell division (mitosis) 

is one area of intense interest. 

The soft x-ray microscope on beamline XlA is 

capable of imaging with chemical sensitivity by appropriately combining frames collected at photon energies which 

correspond to maxima and minima in absorption spectra. 

J. Boese, A. Osanna, C. Jacobsen, J. Kirz, E. Tall (SUNY 

@ Stony Brook) andX. Zhang (Harvard U.) are exploring 

the possibilities of protein specific imaging, ie mapping 

the concentrations of selected proteins in biological systems. As first steps, they have collected carbon K-edge 

near edge spectra of pairs of amino acids and compared 

them to the spectra of the corresponding dipeptide (the 

two amino acids bound via a peptide bond). As shown in 

Figure 17 (see next page), the researchers found in the 

case of glycine and tyrosine that the spectrum of the 

dipeptide is very close to a simple sum of the individual 

spectra. The formation of the bond had only a small 

effect,a+0.3 eVshiftintheC ls-~*peakat289 eV. Ifthis 

result holds true for arbitrary combinations of amino 

acids, the absorption spectra of simple 

0.20 , 

0.1 6 

8 

d 

t 

O.I2 

Q 0.08 

0.04 

4000 3500 3000 1500 1000 

Wavenumbers (crn-l) 

2920 em-' (CH-proteins) 1652 cm-I (Amide 1) Visible image 

0 N 

4 c < *4: c 

20 pm 20 pm 20 pm 

Figure 16: Infrared microspectroscopy study of a live cell. 

Top: A typical absorption spectrum for the cell, with various 

absorption modes identified. Bottom: visible and IR images, showing 

distribution of cellular substances. (U2B) 

proteins can be predicted. (However, 

the inverse problem is made more difficult: given a spectrum, there is no 

information regarding the amino acid 

order or whether there are multiple 

molecules.) 

X-Ray Absorption Spectroscopy 

Zinc is ubiquitous in biological 

systems, appearing in countless 

metalloenzymes. It is found, for example, in the active sites of many proteases, metalloproteins which cut other 

proteins in half at sites with specific 

amino acid sequences. One of the 

most interesting fundamental biological questions currently being addressed 

with micro-x-ray absorption spectroscopy concerns the egg. As an essentially closedsystem it must bepreloaded 

with the full complement of metals 

required for complete development. 

In work on beamline X19A, K. Peariso, 

C. van Huis, R. Denver, and J. PennerHahn (U. of Michigan) have been 

studying the structural evolution of 

29 
the 1 mM zinc found in zebrafish and African clawed toad 

(Xenopus) eggs as a function of time after fertilization. 

Due to the mm dimensions and high zinc concentration 

of these eggs, they offer a strong zinc signal on beamline 

XI YA. Transcription factors, called zinc fingers, play 

important roles in early development. The spectra in 

Figure 18 show the large changes in zinc structure that 

occur during development from single cell to late blastula 

phase. This suggests substantial synthesis of new classes of 

zinc proteins during these developmental phases. 

Figure 18 shows Zn k-edge XANES 

difference spectra relative to an unfertilized 

(nondeveloping) egg at various stages in the 

embryo development. Changes are clearly 

evident even in the first few cell divisions. 

The researchers note that the changes indicate the formation of multiple zinc sites in a 

complex process. Planned extensions to this 

work include two and three dimensional 

imaging of metal concentrations. 

The use of EXAFS and XANES to 

examine the metal center structure in 

metalloproteins has been one of the most 

popular applications of synchrotron technology in biology since the initial phases of 

synchrotron development. The ability to 

derive metal-ligand bond length information on dilute and chemically poised samples 

of metalloproteins is extremely valuable in 

understanding mechanisms of protein function. Biological molecules are, of course, 

often large and difficult to study with conventional spectroscopies. The element specificity of XAS techniques make them useful 

for ignoring the background of thousands of 

amino acid residues to focus on the local 

structure around metals or other heavy elements. They complement 2d NMR studies 

and protein crystallography by determining 

oxidation states and precise bond lengths, 

metal properties that are essential for fully 

understanding active site structure function. 

For example, in recent work on X9B, 

H. Anni (Thomas Jefferson Medical College), J. Vanderkooi (U. of Pennsylvania), 

M.R. Chance, and E. Scheuring (Albert 

Einstein College of Medicine) studied the 

structure of zinc I1 substituted cyctochrome 

c. NMR studies had proposed a six coordinate zinc site with five nitrogens and one 

sulfur as ligating atoms. This structure is 

highly unusual, there are no previouslyknown 

six coordinate zinc sites in biological molecules in solution. However, XAS studies followed by refinement 

against theoretical models indeed confirmed the Zn site as 

six coordinate, with bond lengths resolved as Zn-N (porphyrin core) = 2.05 k, Zn-N (histidine) = 2.10-2.20 k, 

and Zn-S = 2.34 A. In denatured protein, the zinc was 

found to have lost the sulfur coordination. The researchers conclude that the unique zinc environment must be 

imposed by the protein structure. 

30 
The study of metalloenzyme chemistry by L. Que 

and co-workers (U. of Minnesota) on beamline X9B has 

been particularly focused on non-heme iron proteins and 

the activation of molecular oxygen to carry out oxygen 

insertion chemistry. For methane monooxygenase, EXAFS 

analysis has shown two Fe-Fe distances of about 3 A and 

3.4 A which may reflect two populations of the enzyme 

with varying diiron (111) core structures. 

L. Powers and co-workers (U. of Utah), using 

beamlineX9B, have continued their examination ofheme 

iron containing enzymes, called peroxidases, which, unlike the diiron proteins, use hydrogen peroxide to oxidize 

iron to the unusual Fe(1V) valence. These hi-valent iron 

species and associated protein radicals then are used to 

oxidize various substrates depending on the peroxidase. 

Site directed mutagenesis studies that varied the basicity 

of the iron coordinating ligands were correlated with 

specific iron-nitrogen bond length changes. As the basicity of the histidine axial ligand was increased by changing 

the hydrogen bonding to the remote nitrogen, the distance from iron to the directly coordinated nitrogen ofthe 

histidine axial ligand decreased by 0.15 A. This definitively demonstrated that changes in hydrogen bonding 3- 

4A from the metal site can control structure and functionality of the iron site through coupling of the iron to the - histidine pi electronic system. 

M. Chance and co-workers (Albert Einstein College of 

Medicine) also carried out studies of heme metalloproteins on 

beamline X9B, in this case the 

oxygen transport protein myoglobin was examined. Synchrotron crystallography experiments 

by I. Schlichting (Max Planck 

Institute), J. Berendzen (Los 

Alamos National Laboratory) 

and co-workers carried out on 

beamline X12C had identified a 

“docking” site for the ligand, essentially identifymg a way station for the ligand on its way to 

its binding site coordinated to 

the heme iron. These results had 

been challenged by other crystallography groups. EXAFS experiments were carried out by 

the Chance group examining the 

same intermediate. In addition, 

ancwglobal mapping procedure, 

where crystallographic coordinates are refined to EXAFS data 

using the ab initio EXAFS code FEFF, (discussed also 

below) was used to show that the Berendzen structure is 

essentially correct. 

The global mapping procedure was also used to 

examine metalloprotein structure in cobalamin enzymes 

by Chance and co-workers (Albert Einstein College of 

Medicine) in collaboration with scientists from U. of 

Michigan and U. of Nebraska, using beamline X9B. 

Cobalamin co-factors are cobalt containing prosthetic 

groups containing cobalt-carbon bonds, and are the only 

known organometallic species in the biological realm. 

Some similarities exist with the hemeproteins, in that an 

axial histidine ligand coordinates the metal perpendicular 

to the planar organic cofactor. The enzymes carry out 

unusual carbon-carbon bond re-arrangements and methylation reactions critical for cell metabolism. Mutant 

forms of the enzyme, methionine synthase, were examined, where the axial histidine is replaced with various 

amino acids. The changes in electronic structure at the 

cobalt ion, and the role of the histidine ligand in controlling enzyme activity were better understood as a result. 

The global mapping technique is illustrated in Figure 19, 

where particular minima based on the FEFF simulations 

can be directly compared to each other in an evenhanded 

manner. 

1 I 

1.94 

.LI & 1.92 

1 

8 g 1.90 

r 

Y II 

% 

rf 

z 1.1111 $ 

U 

1E2 - 1.2m 

9.116 

1.0 2.0 2.1 2.2 2.3 2.4 2.5 2.6 -58 - 74 

Go-N, distance (Ang.) 

Figure 19: A contour plot of the goodness-of-fit versus FEFF 6.01 simulation 

geometry for the Adenosylcobalamin cofactor reconstituted into methyl- malonyl CoA-mutase. (X9B) 

31 
Chemical Crystallography 

Time Resolved Experiments 

The moving image-plate system at X7B has proved 

extremely productive, with a wide variety of reactions and 

phase transitions studied. This system has been developed 

to the point where it routinely provides large quantities of 

high-quality data, too much to be listed here. For details 

the reader is encouraged to browse the relevant abstracts. 

Whereas those experiments relate to the conversion between various crystal structures, there are other important 

structural problems which are interesting when addressed 

in the time domain. Many small angle scattering experiments on polymers made use of time-resolved data sets. 

One other example, with much faster time resolution, is an experiment on the electrodeposition of Cu on 

Pt(l11), performed on X2OA by A. Finnefrock et al. 

(Cornel1 U.). In that work, the Cu is electrodeposited on 

the Pt surface within 0.02 second after a step in the applied 

potential, but the overlayer structure requires from 2 to 5 

seconds to develop long-range order. More detailed 

studies of this phenomena should lead to interesting 

information about the mass-transfer of ions near the 

electrode surface and other aspects of the deposition 

process. 

Single Crystals 

The brightness of 

synchrotron radiation 

can be very favorably 

combined with the use 

of image plate detectors 

for structural studies 

with relatively small 

single crystal samples. 

Mentioned here are a 

few characteristic examples. A. M. Andersen 

etal. (OdenseU.), used 

25 x 25 x 50 pm3 crystals at beamline X7B to 

solve the structure of 

Zr(HPO,),. At thesame 

station, T. Jensen 

et dl. (Odense U.), 

solved the structure of 

aLiZnAsO, from acrystal of 17 x 17 x 60 pm3 

32 

and of GILiZnPO, from a crystal of 39 x 16 x 18 pm3. 

The image plate technique has application to crystallographic problems with normal-sized crystals as well. 

P. Coppens etal. (SUM@ Buffalo), have been working 

on techniques to extract the best-quality intensities from 

image plates, and extending the limits of electron density 

analysis. For example, using a Cr(NH3),Cr(CN), crystal 

of 80 x 30 x 30 micron3 and an x-ray wavelength of 0.394 

A, they have collected and analyzed data out to 0.25 A 

resolution. B. Iversen et al. (U. of California @ Santa 

Barbara), have extracted the electron density (rather than 

only the atomic positions) of the actinide Th(S,P(CH3),)4 

from data taken at X3A1. They avoided the problem of 

dominance of the heavy Th atom by collecting reflections 

for which the Th ion core did not contribute. By this 

means they could determine the charge density, rather 

than merely atom positions quite readily. Other image 

plate based studies on X3A by A. Darovsky (SUNY @ 

Buffalo) include anomalous scattering measurements of 

mixed valence Mn compounds, resolving the Mn2+ -Mn3+ 

thermal equilibrium vs. temperature, and separation of 

Mn3+ and Mn4+ sites in two different mixed valence 

compounds. Both the above studies benefitted from a 

new technique for extracting unbiased integrated intensities from the image plate data (called the seed-skewness 

method, R. Bolotovsky and P. Coppens (SUNY @ 

Buffalo). It relies on the statistical properties of noise to 

Figure 20: Polymeric chain of cyclopentadienylsodium (top) and 

cyclopentadienylpotassium (bottom). (X3B1) 
isolate the data region corresponding to a diffraction spot 

(i.e. a region which is not noise). 

J. Parise et al. (SUN @ Stony Brook), have used 

image plate techniques on beamline X3A1 to solve the 

structures of several new open framework compounds, 

e.g., GeS, and [(CGH,,N,),(H,O)(H,O)l [AgGe,Slol with 

quite small samples, on the order of 30 microns. 

Powder Studies 

For many materials, single crystals are simply not 

available, and one must resort to powder diffraction data 

for whatever structural information is to be gleaned. 

Some of the (conceptually) simplest organic salts, like 

alkali cyclopentadianides AC,H, (A=Li, Na, K, Rb) are 

sufficiently unstable that single crystals cannot be prepared, but they are of particular interest because theoretical calculations are unable to reproduce the observed 

structures of related, but more complicated molecules, 

e.g., M(C5H5)2 (M=Be, Mg, Ca). R. Dinnebier (U. 

Bayreuth) and collaborators have solved anumber of these 

compounds, purely from powder diffraction data at 

beamline X3A1. In one noteworthy example, they solved 

the structures of two polymorphs of RbC,H, present in 

one sample from a single powder pattern. They found 

that the chains buckled to a different degree as a function 

of cation size (Figure 20). 

Electron Spectroscopy 

Valence Electron Excitations 

The gas phase research on Beamline U11 has addressed the thermochemistry and spectroscopy of bromine oxides and chlorine oxides with photoionization 

mass spectrometry. These oxides are not well understood 

because they have low thermal stability and are difficult to 

obtain in a pure state. Br,O has been prepared via the 

reaction of bromine vapor on solid mercuric oxide. Figure 21(a) shows the first direct determination of the 

photoionization efficiency (PIE) spectrum of Br,O. The 

experimental ionization threshold is in good agreement 

with the only published value of 10.23 eV from an ab 

initio calculation. The heat of formation of Br,O can be 

determined using the appearance energy (AE) of BrO 

shown in Figure 21(b), together with the previously 

determined ionization energy of BrO and tabulated heats 

offormationofBrOandBr. TheOKvalueof124.1 k3.5 

kJ mol-' thus determined has been selected and cited in the 

latest NIST-JANAF Thermochemical Tables for the Bromine Oxides. Discharge flow photoionization mass spectrometry has also been used to obtain the PIE spectrum of 

Cl,O, C10 radical, the AE of C10+, and a value for the 

heat of formation of C1,O. 

33 
and bond lengths. Furthermore, the recent grating 

upgrade has enabled the vibrational fine structure in the 

0 Is photoelectron spectrum in CO, to be measured for 

the first time. It is observed that the antisymmetric C-0 

stretch mode ( 307f3 mew is dominant, as predicted for 

the lowering of symmetry and core orbital-vibronic coupling upon 0 Is core ionization. 

On Beamline X24A, polarization-dependent resonant x-ray emission has been studied with excitation at 

the sulfur K absorption threshold in carbonyl sulfide. 

Figure 23 shows the sulfur K-valence emission for different polarizations, at excitation energies for Is transitions 

to the lowest unoccupied molecular orbitals, Rydberg 

states and the continuum. The emission line shape and 

its differences with respect to the post-threshold emission 

spectrum are explained by ab initio calculations of the 

intermediate and final state energies. Variations with 

polarization are explained by a dipole model of absorption and emission. 

Core Electron Excitations 

The interest in atomic-site-selective core-electron 

excitation at Beamline U15 has been extended to 5- 

Oxohexanenitrile isolated in D, matrices. In situ infrared 

spectroscopy is used to monitor the C-0 and the C-N 

stretches at excitation energies corresponding to the C, N 

and 0 resonances and continuum. One of the most 

interesting results from preliminary experiments is that 

’ excitation at resonances, resulting in autoionization 

producing a single valence hole, favors the photodissociation of carbonyl groups while nitrile group photodissociation is favored by continuum excitation resulting in Auger 

decay producing a doubly charged molecular ion. 

As a continuation of the high-resolution studies of 

dynamic effects in core excitation on Beamline XIB, the 

complex vibrational structure in the C 1s photoelectron 

spectrum of ethane has been studied as the prototype for 

the alkanes. Figure 22 shows a least-squares-fit of the 

vibrational structure. The Vibrational energies of the CH stretch and the C-C stretch are found to increase 

significantly upon ionization. The bond lengths are also 

found to be reduced by 0.036 A for C-H and 0.043 A for 

C-C. These and other results on alkenes contribute to the 

discussion on the correlation between shape resonances 

34 I 
Photoemission and Photoabsorption 

from Rare Earth Oxides 

The surface chemistry group at Oak Ridge National 

Laboratory (D. Mullins, D. Huntley and S. Overbury) 

has begun a series of investigations to study the properties 

of metals supported on metal oxides. In the initial 

investigations, the ORNL group has used single crystal 

films of CeO, produced by laser ablation that are 5000 

A thick. CeO, is used to enhance the performance of 

environmental control catalysts such as automotive catalytic converters. The films are highly oriented as indicated 

by x-ray diffraction, transmission electron microscopy 

and low energy ion scattering. Submonolayer amounts of 

Rh were deposited on the oxide films in vacuum and then 

the samples were exposed to NO. The reactivity was then 

studied as a function of Ce oxidation state, Rh coverage 

and temperature. 

Sputtering the oxide with Ar' ions reduces the Ce 

from Ce4+ to Ce3+ and enhances the reactivity of the Rh/ 

CeO, sample. Several highly sensitive indicators of the Ce 

oxidation state were measured using soft x-rayphotoemission (SXPS) and x-ray absorption (XAS). SXPS from the 

Ce 4dand Ce 4flevels andXAS at the 0 kedge are shown 

in Figure 24(a) to (c), respectively. These spectra were 

recorded at beamlines X1B and U4B. The Ce 4dspectra 

are very complex and are characterized by peaks resulting 

from 4f0, 4f' and 4f2 final states. The high binding 

energy peaks near 122 eV are indicative of Ce4+, while 

peaks at lower binding energy, and in particular the 

shoulder at 104 eV, are characteristic of Ce3+. The 

emission from the Ce 4flevel is much easier to interpret. 

The Ce 4flevel lies in the oxide band gap. It is unoccupied in Ce4+ and therefore shows very little intensity from 

a fully oxidized surface. The Ce 4f level is occupied in 

Ce3+ and emission from this level is evident from the 

sputtered surface. Finally, in the 0 1s XAS spectra, 

hybridization between the 0 2p and Ce 4f orbitals 

permits excitation of an 0 Is electron into the Ce 4f. The 

peak at 530 eV results from excitation into the 4f0 initial 

stateofCe4+. The resonanceenergyshifts to ca. 532 eVfor 

excitation into the 4f' initial state of Ce3+ so that the 

decrease in intensity at 530 eV on the sputtered surface 

indicates the reduction of Ce4+ to Ce3+. 

When NO is deposited on Rh on a fully oxidized 

CeO, surface at room temperature, most of the NO 

remains intact as indicated by N Is SXPS andXAS. As the 

sample is heated, most of the NO desorbs while some 

dissociates into atomic N and 0. On a sputtered CeO, 

surface, however, most of the NO dissociates at room 

temperature. 

35 
GEOLOGICAL SCIENCES 

Rheology 

Dynamic processes within the Earth are limited by 

the strength of the minerals at elevated pressure and 

temperature. Deviatoric stresses cause earthquakes and 

mantle flow. Deviatoric stresses in the high pressure 

systems can now be monitored andquantified. Their time 

dependence reveals the relaxation mechanism. Pressure 

and temperature dependencies can relate to depth variations in the Earth. Current x-ray resolution of deviatoric 

stress is about a kilobar, far more than exists in most ofthe 

Earth’s mantle, but comparable to seismic regions. Thus, 

even now we can approach geologically relevant P, T, and 

stress conditions. Within this framework, rheological 

studies for several materials are reported in this volume. 

Earthquakes persist into the Earth’s transition zone. The 

time dependence of strength for the relevant minerals of 

this region are reported by J.-I. Ando et al., Y. Wu et al., 

and J. Chen et al. (SUM @ Stony Brook) Included in 

these studies are the silica rich garnet, majorite, and the 

high pressure phase ofolivine, wadsleyite. Indeed, the role 

of water weakening is also reported. Olivine is a classic 

material in which a small (ppm) amount of water drastically reduces the strength. The high pressure forms of 

olivine (wadsleyite and ringwoodite) can structurally bound 

a considerable amount of water (up to 3 wt %). The 

results of J. Chen etd. andT. Inoue etaL. (SUNYO Stony 

Brook) suggest that these high pressure phases are not 

appreciably weakened by the presence of large amounts of 

water, even though olivine, at these high pressures, is still 

strongly affected by trace amounts ofwater. These studies 

have significant implications concerning the seismic potential of different chemistries within the upper mantle 

and transition zone. All of these studies were carried out 

on X17B1. 

Equation of State 

High temperature equations of state are important 

in extrapolating phase boundaries to higher pressures and 

temperatures than where they are defined. Significant 

work in this area has also been carried out onX17B 1. This 

motivated K. Bose et al. (Princeton U.), to obtain the 

equation of state of antigorite, a hydrous rich low pressure 

phase. The stability field of hydrous minerals help define 

the mass balance of hydrogen into the Earth’s deep 

interior. 

Equations of state of stishovite 0. Liu et aL., SUNY 

O Stony Brook) and Ca(Ti/Si) perovskite (Y. Sinelnikov, 

etd. SUM@ Stony Brook), provide important information concerning the temperature dependence of the bulk 

modulus and are relevant to matching the depth behavior 

in the Earth of the bulk modulus. The equation of state 

and phase equilibria of Fe-Si alloys studied by J. Zhang 

(SUNY O Stony Brook) and F. Guyot (U. of Paris) 

address possible alloying in the Earth’s core. 

Phase Equilibria 

T. Shen et d. (Los Alamos National Laboratory), 

with the double hot plate high pressure high temperature 

system continue the exploration of the iron phase diagram. In the study reported here, they find no evidence 

of the illusive phase transition in the epsilon phase as 

previously reported by suggesting that this phase may be 

created on quench. Surely, this debate has not ended. 

With the expansion of the experimental environmental envelope has come a remarkable expansion in 

types of studies that can be done in conjunction with x-ray 

synchrotron radiation. The most significant breakthrough 

for Earth related studies is the inclusion of acoustic 

velocity measurements at high pressure and temperature 

and simultaneously with x-ray diffraction. This development is discussed in the instrumentation section and has 

already been used on X17B1 to collect acoustic data on 

polycrystalline specimens of majorite, a silica rich garnet 

(G. Gwanmesia etal., Del. State U.) and the high pressure 

form of olivine, wadsleyite (B. Li et d, SUNY @ Stony 

Brook). These two phases are stable at the high pressures 

and temperatures of the Earths transition zone and are 

expected to constitute the bulk of this region of the Earth‘s 

interior. With these new data, we will be able to examine 

various chemical models of this region of the Earth. 

P. Conrad et al. (Carnegie Inst. of Washington), 

use the focusing capability of the X17 system to explore a 

natural high pressure device, that is a natural diamond 

with inclusions as specimens. Presumably, the inclusions 

were emplaced while the entire system was at high pressure. Residual stresses will still exist within the inclusion 

owing to the extremely large bulk modulus of diamond. 

Removal of the inclusion risks back transformation of the 

minerals to low pressure phases. Thus, the structural 

determination with synchrotron x-rays provides a nondestructive probe. 

36 
Microprobe and 

Microspectroscopy 

There were a number of experiments carried out on 

geological samples at X6C, including those by I. Steele 

(U. of Chicago) on Au in sulfides, and Ni, Zn, Ga, Y and 

Zr in garnet. J. Rakovan and R. Reeder (SUNY 0 Stony 

Brook) studied the spatial resolution of trace elements 

such as Y, Sr, Mn, La, Ce and Pr in apatite samples the 

interest being in the relationship between the details of the 

structure of the host material and the amount and distribution of the impurity. Other types of impurity, namely 

fluid inclusions were studied by R. Mayanovic (Southwest 

Missouri State U.), A. Anderson (St. Francis Xavier U., 

Canada) and S. Bajt (LLNL). Here ppm concentrations 

of Zn, Pb and Fe were found in individual inclusions and 

in particular ZnCl dominated and was studied at elevated 

temperatures where its persistence was attributed to a high 

concentration of chloride in the inclusions. Trace elements were also studied in samples of interplanetary dust 

particles (G. Flynn, SUNY @ Plattsburgh), S. Sutton (U. 

of Chicago) and S. Bajt (Lawrence Livermore National 

Laboratory) of two main types and compared to the 

distribution in meteorites. 

G. Cody (Carnegie Institute ofwashington), H. 

Ade (North Carolina State U.), and S. Wirick (SUNY @ 

Stony Brook) at X1A used carbon XANES analysis to 

examine organic rich sedimentary rocks. The lr-~* 

transition of carbon revealed specific chemical signatures 

for particular layers and phases. 

37 
STRUCTURE OF SURFACES AND INTERFACES 

Liquid Surface Studies 

Liquid interfaces are relevant to many disciplines, 

including biology, physics, and chemistry, yet relatively 

little is known about the structure of these interfaces. For 

example, the physical interactions that stabilize the liquid/ 

vapor interface and give rise to surface tension can also 

give rise to interfacial structure which is very different 

from that found in the underlying bulk. Scattering 

experiments that make use of the high brilliance of x-ray 

synchrotron sources are one of the few experimental 

methods - compared to those available at solid interfaces 

- which are capable of investigating the microscopic 

structure of liquid interfaces. Over the last decade a wide 

variety of liquid surfaces and interfaces have been studied 

at NSLS including liquid crystals, simple dielectric liquids, liquid metals, molten chain molecules and organic 

monolayers on both water and liquid metal subphases. 

Many of these studies were scientific “firsts”, and revealed 

new phenomena and novel features for the corresponding 

surfaces. Some of the more important scientific results 

obtained at the NSLS are the quantitative confirmation of 

the in-plane structure of the solute-rich surface layers of 

dilute Bi-Ga and Sn-Ga alloys, and the oxide formation 

on liquid Ga, were also studied recently, and provided 

important insights into fundamental issues of surface 

segregation and surface oxidation, respectively. 

This broad spectrum of liquid surface studies at 

NSLS helped to provide an essential basis for obtaining a 

microscopic understanding of liquid interfaces in general. 

In this short overview, we will concentrate only on the 

more recent findings at NSLS concerning liquid surfaces. 

Earlier results are well documented in the literature. 

Experimental 

Spectrometers for studying liquid surfaces are fundamentally different from standard four-circle 

diffractometers. The free liquid surface is always horizontal, and thus the horizontal beam originating at the ring 

has to be deflected downward to impinge on the surface 

at a given angle. This is usually accomplished by tilting a 

crystal in the Bragg geometry downward as shown in 

Figure 25. Specialized instruments employing this method 

havebeenemployedatX13C,X20,X22B, andX25. This 

long-standing theoretical predictions of the capillary contribution 

to the surface roughness in water, 

ethanol, alkanes, and liquid metals, the roughness and surface correlations of a surfactant monolayer 

at an oil-water interface in equilibrium with a microemulsion, the 

microscopic structural relaxation 

ofcondensed Langmuir monolayer 

phases of fatty acids and esters, the 

nature of the layering transition at 

the surface of isotropic phase of a 

liquid crystal, the adsorption at, 

and structure of polymers at liquid 

surfaces, surface crystallization at 

temperatures above the bulk melting point in normal alkanes and 

alcohols. In addition, measurements resulted in the first unambiguous proof of the long standing 

theoretical predictions of surface 

induced atomic layering along the 

surface normal of liquid Hg, Ga 

and In. The surface induced layering in Ga-In and Ga-Bi alloys and 

38 

//A\ I Crystal 

From 

Synchrotr 

Incident Slit 

To 

Sample 

Figure 25: Steering monochromator for deflecting synchrotron beam 

downward. 
requires precise control of the vertical positions of the 

sample, beam defining slits and detector. General purpose liquid spectrometers employing this method are 

capable of studying the structure within the plane of the 

surface ( by grazing incidence x-ray diffraction, GIXD) as 

well as along the surface normal direction (by x-ray 

reflectivity, XR). While downward deflection ofthe beam 

can also be done using an x-ray mirror, and was implemented in some liquid metal experiments on XlOA, this 

geometry is suitable for GIXD only and can not accommodate reflectivity measurements. 

Environmental chambers for liquid surface measurements depend on the nature of the surfaces studied, 

and range from sophisticated UHV chambers (for studies 

of highly reactive liquid metal surfaces, for example) 

equipped with residual gas analyzers and ion beam sputtering guns for cleaning the sample's surface, through 

Langmuir troughs (for studying monolayers ofamphiphiles 

and polymers on water) equipped with moveable barriers 

for in situ monolayer compression and Wilhelmy plate 

balances of surface tension monitoring, to small and 

simple temperature controlled sealed cells (e.g. for studying surface crystallization of alkanes). A detailed description of these cells is beyond the scope of this brief review, 

and can be found in the literature. Selected examples 

follow: 

Liquid Metals 

An important prediction, central to the theoretical 

understanding of the structure of liquid metals is that of 

atomic layering at the surface. According to this prediction, atoms near the surface will be ordered in layers 

parallel to the surface, and the layering amplitude should 

decay with depth below the surface with a characteristic 

length of several atomic diameters. Although over two 

decades old this prediction was hitherto untested experimentally in spite of substantial efforts by several groups 

worldwide. In a series of experiments by a group from 

Bar-Ilan, Harvard and the Brookhaven Physics Department (BHB) at X22B and X25 this effect has been 

confirmed for both liquid mercury and gallium. The 

surface layering gives rise to a broad quasi-Bragg peak in 

the x-ray reflectivity spectrum at a momentum transfer 

q,=2.2-2.5 A-' corresponding to the layer spacing d=2d 

q,-2.5-2.8 A, which is close to the value for the atomic 

diameter of the metal. The layering is an intrinsic, and 

highly persistent, property of liquid metals, as indicated 

by the nearly identical layering observed for bare and selfassembled thiol monolayer covered mercury surface. The 

studies of the Hg and Ga surface have been extended to 

cover a wide temperature range, and also to various alloys. 

In addition, the effects that varying oxygen exposure has 

on the surface ofliquid Ga have also been studied at room 

and elevated temperatures. The formidable challenge to 

all of measurements on liquid metals is the need to 

measure over a large dynamic range in both qz and 

reflected intensitywhile maintaining an oxide-free surface 

for samples almost all of which are highly reactive. 

In the case of binary liquid metal alloys, surface 

segregation of one of the components often reduces the 

interfacial energy, e.g. the surface tension, and even for 

very dilute alloys, the surface may have a very different 

composition than that of the underlying bulk alloy. 

Studies by Ning Lei, and colleagues at X19C have investigated the structure of gallium alloys with bismuth and 

tin. In the case of the bismuth alloy, grazing angle 

diffraction studies indicate that the bismuth segregates 

into a nearly complete monolayer atop the bulk alloy 

where the bismuth monolayer has the structure of a 

supercooled liquid. The surface tension of the alloy is 

obtained by interpretation of measurements of the diffuse 

scattering around the specular axis in terms of thermally 

excited capillary waves. From reflectivity measurements 

of the gallium-tin alloy, it is found that the tin concentration at the surface is in excess of the bulk concentration 

and that it decreases with increasing temperature, in 

accord with the Gibbs isotherm. X-ray reflectivity measurements ofthe gallium-indium alloyatX25 by the BHB 

group leads to a surface layer with a much higher electron 

density than the underlying liquid. Model fits assign this 

to single indium layer, with subsequent layers at the bulk 

eutectic composition. Ga oxidation studies by the same 

group show that on exposure to -180 Langmuirs of 

oxygen, a thin layer ofgallium oxide forms at the liquid Ga 

surface. As shown in Figure 26 (see next page) this leads 

to modulations in the reflectivity profiles which are well 

described by a uniform 5 A thick oxide layer. The 

reflectivity does not change for exposures up to 1600 

Langmuir, nor for elevated temperatures up to 3OO0C, 

indicating that the oxide layer is solid. The oxide layer is, 

however, most probably amorphous, since first GIXD 

measurements failed to show any dpeaks. Finally, the 

previous x-ray reflectivity measurements on Hg by the 

BHB group have been extended at X22B down to temperatures just above the melting point, -38.9"C. Here it 

is found that the peak in the reflectivity (associated with 

surface layering) increases dramatically in intensity with 

decreasing temperature with no corresponding change in 

the peak width. The latter result demonstrates that the 

intrinsic local decay of the stratified density profile is 

independent of temperature, consistent with similar results obtained for the Ga surface. 

39 
Langmuir Monolayers 

Studies of organic molecules adsorbed on the surface of water, Langmuir monolayers, continue to be one 

of the more active areas of investigation. Ever since 19 17, 

when Langmuir first developed what subsequently became know as the Langmuir film balance, surfactant or 

Langmuir monolayers (LM) have been extensively studied using a variety of techniques. It is only recently that 

the availability of synchrotron radiation sources has allowed grazing incidence diffraction to be used to learn the 

microscopic, molecular structure of these films. Part of 

the reason for the broad current interest in LM is that they 

are one of the few realizable systems in which a film 

exhibiting two dimensional (2D) statistical physics can be 

tuned in a manageable way by varying the molecular 

structure. As a result, the phase diagrams of LM are 

enriched in comparison with those of simpler monatomic 

systems. In addition, many of the properties of LM can 

be related to those of biological membranes and to thin 

organic films that are used for lubrication and other 

purposes Although initial investigations were carried out 

on simple soap like molecules which contain a hydrophobic tail and a hydrophilic headgroup, increasingly more 

complex molecular architectures were investigated over 

the last few years and recent studies addressed such 

systems as fullerene derivatives, gold colloids, discotic and 

nematic liquid crystalline materials and water-soluble 

pigments at lipid interfaces. 

One unfortunate aspect associated with application 

of the GIXD technique to probe the structure of 2D 

phases of LM is the fact that the scattering cross section for 

most of the surfactants that have been studied is not 

sufficient to observe the structure factor of phases with the 

short positional correlation lengths that are typical of 

liquid phases. One exception to this is the study by a 

group from Harvard and Ames Laboratory, at X22B, in 

which they measured the structure factor of an amorphous phase of a LM of a fullerene-propylamine adduct 

(C,,-PA), consisting of a C,, molecule and twelve 

propylamine (NH,(CH,),CH,) chains attached to it. 

This molecule is sufficiently large that the 

structure factor of the LM could readily be 

separated from the diffuse background scattering from the ambient He gas above the 

monolayer and- the bulk liquid water below. 

Figure 27 illustrates GID scans (with background subtracted) for LM of C,,-PA at different surface densities. When the effect of 

the calculated molecular form factor is included the peak position at -0.42 A-' corresponds to the average nearest neighbor distance of + 13.2 A which is close to the diameter 

of the molecule and corresponds to a molecular area of .- 15 1 A2/mol. This is very close to 

the specific area at which the surface pressure 

increases (inset to Figure 27). Although this 

LM was an amorphous solid, the hope is that 

if LM systems can be developed in which the 

fullerenes phase will be fluid it would be 

possible to study 2D melting/solidification. 

A second system in which GIXD studies of a 

disordered phase reveal the broad peak associated with a system having only short range 

order is gold colloid monolayers, studied by 

Clarke and collaborators at X22B. In addition to GIXD studies x-ray reflectivity measurements indicate a monolayer to bilayer 

transition with increasing 2D density. 

Studies of LM systems with smaller 

molecules, for which the in-plane order was 

only observed for phases with relatively 

long range order include the discotic liquid 

40 
crystalline monolayers studied by a group from U. Penn 

at X22B. They studied LM of two different molecules, of 

which only one showed a single GIXD peak. A group 

from Northwestern, working on XI&, carried out similar studies on a LM of an azobenzene containing molecule. Although Brewster angle microscope studies carried out prior to the synchrotron measurement indicated 

the existence of a phase transition from a low density fluid 

phase to a higher density solid phase, the GIXD measurements indicated that both phases have the same degree of 

positional order, implying correlation lengths from 100 A 

to 300 A in each phase. 

The Ames Laboratory/BNL collaboration also carried out a GIXD and reflectivity study at X22B to 

determine the structure of charged water soluble pigments that are adsorbed by charged lipid monolayers at 

the air-water interface. The combination ofpressure/area 

isotherms and x-ray measurements shows that when the 

LM is spread on micro-molar solutions of the pigments 

the LM order is substantially different from that ofthe LM 

spread on pure water. 

Finally the BHB group studied the 

formation of thiol mono- and multilayers 

on liquid mercury. This novel system is 

intermediate between Langmuir films on 

water and self-assembled organic layers on 

crystalline solids. It forms on a disordered 

liquid surface like the former, while its 

structure is dominated by the strong substrate-headgroup interaction like the latter. The monolayers formed were found 

to be well-defined and densely packed, 

with molecules aligned normal to the surface. Surprisingly, however, no long range 

in-plane order was observed for any of the 

chain lengths studied. The multilayers 

were found to have a complex bi-layer 

structure with Hg atoms intercalated in 

the center, and are well-ordered in-plane, 

with a highly oblique unit cell resembling 

that of bulk mercury thiolate. 

Surface Freezing 

A group of researchers from 

Brookhaven, Exxon, Argonne and BarIlan found in measurements carried out at 

NSLS a few years ago that normal-alkanes 

and alcohol exhibit surface freezing, 

i.e. a spontaneous formation of a solid 

layer at the surface of the melt at temperatures of a few degrees above the bulk 

melting temperature. This is a very rare 

phenomenon, since almost all other materials show the 

opposite surface melting effect following a general Statistical Mechanics principle. X-ray measurements at X22B 

showed the surface-frozen layer to be a single monolayer 

in alkanes and single bilayer in alcohols. Their crystalline 

structure was fully characterized as a function of both 

chain length and temperature, resulting in a rich phase 

diagram including rotator and non-rotator phases of 

surface-normal and tilted molecules. More recent studies 

showed the same effect in alkane-alkane and alcoholalcohol mixtures, which also exhibit a novel quasi-2D 

phase diagram for the surface layer, depending on the 

chain length difference of the components. 

In related studies by the same group during this year, 

0. Gang (Bar-Ilan U.) and coworkers have shown that it 

is possible to tune the temperature range of existence as 

well as the surface layer structure of alcohols by judiciously 

chosen molecules added to the bulk at a few percent 

concentration level. Water molecules added to long chain 

alcohols were found to intercalate in between the two 

41 
layers comprising the surface bilayer causing it to swell by 

+2 A. In addition, the bilayer formation and bulk freezing 

temperatures are shifted up, and an increase of 1-2 “C is 

obtained in the range of existence of the bilayer. For 

longer chain alcohols, where tilted phases are observed, 

the intercalating water also reduces the molecular tilt by a 

few degrees, as compared to the dry pure alcohol. Another 

additive, ashort a,w-diol, was found to induce a transition 

from a bilayer to a monolayer in the surface layer, which 

could be affected either through a concentration or a 

temperature variation Reflectivities of the surface-frozen 

layer in the mono- and bilayer phases of the diol-laced C,, 

alcohol are shown in Figure 28, where their characteristically different shapes can be clearly observed. The monolayer phase seems to be stabilized by the adsorption of an 

excess concentration ofdiol molecules at its lower surface, 

probably attracted by the layer of OH groups facing the 

melt. This demonstrate that “engineering” the structure 

of the surface phase by bulk additives is a viable, and 

exciting, possibility. 

Liquid-Liquid Interfaces 

In addition to the liquid vapor interface, x-ray 

reflectivity studies have also been extended to the liquidliquid interface. Following on the earlier work by McLain 

et al. (MIT), on the structure of the oil/water interface in 

equilibrium with a middle-phase microemulsion, M. 

Schlossman et al. (U. of Illinois 0 Chicago), carried out 

a series ofXR and GIXD studies on the oil/micremulsion 

interface of several ternary microemulsions containing a 

straight chain oil, water, and a surfactant from 

the homologous series CiEj (n-alkyl plyglycol 

ether CH,(CH,),_,(OCH, CH,);OH). The 

main interest here is in the interplay between 

the non-monotonic interfacial profiles of the 

two liquids and the large amplitudes of the 

thermally-induced capillary waves, expected 

from the ultra-low, -0.1 mN/m, interfacial 

tension. The challenge for these measurements 

arises from the large absorption losses of the xrays, which must traverse a long path inside the 

oil phase, as well as the very low reflectivity due 

to the high surface roughness. Schlossman’s 

measurements used 15 keVx-rays and a sample 

cell - 35mm wide. Preliminary analysis indicates that the roughness of the surface of the 

mixture containing C,,E4 (s >200 A) is considerably greater than that of mixtures containing 

either C4E, (s = 57a) or C6E, (s = 45 a). All of 

these values are much larger than the corresponding molecular sizes, and indicate strongly 

fluctuating interfaces, as expected. Preliminary 

analysis of the measured diffuse scattering spectra yields a higher surface roughness than the 

reflectivity results, indicating the need for a 

more sophisticated approach then the stepfunction distorted wave Born approximation. 

The application ofsynchrotron radiation 

to the structure of liquid surfaces is currently 

providing atomic level information that is not 

otherwise available. For LM as an example, 

GIXD measurements have revealed rich phase 

diagrams involving multiple two dimensional 

solid-solid phase transitions that correspond 

well with three-dimensional solid-solid phase 

transitions. Similarly XR measurements have 

confirmed the decades old predictions of the 

42 
layered structure ofliquid metal surfaces and revealed new 

features that will continue to be the subject of future 

research for some years. Other technically challenging 

systems, like the liquid/liquid interface, will also continue 

to draw much attention, and will no doubt benefit from 

the high-energy mode of operation currently being explored at the NSLS as well as the higher brilliance and 

intensity available at present insertion-device sources at 

the NSLS. 

Solid Surfaces 

X-ray diffraction continues to be an important 

experimental probe for the determination of the atomic 

structure of single-crystal surfaces, and the problems 

which are tackled by this technique grow successively 

more difficult. For example, the bulk crystal structure of 

gallium consists of dimers tilted slightly away from the 

(00 1) direction, and so it is interesting to know whether 

the surface simply truncates the bulk structure, or if there 

is a more complicated rearrangement. Preliminary results 

by D. Walko etal. (U. of Illinois), on Xl6A indicate that 

the surface is different from the bilayer self-wetted structure proposed theoretically. There has also been work on 

X22C to study whether Ir(O0 1) becomes incommensurate, roughens, or disorders at high temperature, motivated by the behavior ofAu and Pt. G. Watson etal. (U. 

of Maryland), found that it remains commensurate, and 

roughens above 2000 K. Under very different conditions, 

J. Wang and R. Adzic (Brookhaven National Laboratory) 

studied the (I 1 I) surface of Au in contact with a solid 

electrolyte. The experimental conditions guaranteed that 

the observed lifting of the reconstruction with electric 

potential was caused by the surface charge rather than by 

anion adsorption. 

The addition of a monolayer film on a single crystal 

surface opens a rich variety of possibilities, and in-vacuum 

x-ray measurements are well-suited to their study. 

P. Bennett etal. (Arizona State U.), made use of the high 

resolution intrinsic to x-ray scattering techniques to show 

that the monolayer Au on Si(OO1) 5x1 structure is actually 

incommensurate, in contrast to earlier LEED and STM 

results. A different technique, x-ray standing wave analysis, has been used to study the initial stages of adsorption 

of In on GaAs(001) and of Te on Si(OOl), (T.-L. Lee, et 

al., Northwestern U. and P. Lyman, et al. LBNL), on 

X15A. It is also possible to prepare well-defined adsorbed 

phases from solution, and x-ray diffraction is particularly 

useful in penetrating the liquid overlayer to obtain atomicscale information. L. Cheng et al. (Northwestern U.), 

used the x-ray standing wave technique to study the 

adsorption of selenite (SeO, 'e) ions on calcite. J. Wang 

et al. (Brookhaven National Laboratory), used beamline 

X22A to discover that mono- and bi-layers of electrochemically-deposited Ag form an incommensurate phase 

on Pt( 11 1) which is compressed relative to bulk Ag. This 

is quite unexpected, because the reduced coordination at 

the surface usually leads to expanded surface layers. On 

the same beamline, B. Ocko et al. (Brookhaven National 

Laboratory), studied the ordering of Br on Ag(OOl), and 

observed Ising model critical behavior. 

There were two interesting experiments on the 

formation of thin oxide surfaces in aqueous environments. A. Davenport et al. (Brookhaven National Laboratory), have studied thin oxide films on Fe(001) and 

(1 10) on beamline X2OA. They find an epitaxial relationship between oxide and substrate. According to their 

results, the film is not one of the bulk forms of iron oxide, 

but rather is similar to the spinel Fe,O,, with a large 

fraction of oxygen vacancies and some displacement ofthe 

oxygen ions. In relatedwork, Y. Chu andI. Robinson (U. 

of Illinois) have used Xl6C to study the oxidation of 

Cu(l1 I) in perchloric acid. They find epitaxial cubic 

Cu,O grows in two different orientations, in which one 

alignment grows to only a few monolayers, while the other 

can become significantly thicker. 

43 
MATERIALS SCIENCES 

Magnetism 

X-Ray Scattering 

In recent years, synchrotron radiation has become 

an important technique for the study of magnetic properties of thin films and surfaces. Recent examples include 

magnetic diffraction measurements by M. Conover et al. 

(U. of Illinois @ Urbana-Champagne), on X22C studying the influence of monolayer superlattice doping of rare 

earth metal films: Dy in Ho and Y in Er. They found that 

the imposed superlattice produced significant changes in 

the magnetic lock-in structure relative to bulk samples. 

On the same beamline, Helgesen studied the magnetic 

and structural properties of Er films grown epitaxially on 

Lu and Y, producing, respectively, compressed and expanded lattices relative to bulk Er. The depth profile of 

the magnetization was measured directly in a study of the 

magnetic disorder at the surface of a crystal of UO, by G. 

Watson et al. (U. of Maryland), on beamlines X22C and 

X25. UsingX22C,A. Hiess etal. (EITU), found that thin 

films of the heavy fermion superconductor UPd,Al, do 

not develop long range magnetic order, in contrast to bulk 

samples, and attributed that fact to the restricted dimensionality. 

X-ray techniques continue to prove their importance in the determination of magnetic structures. Several 

recent experiments at beamline X22C include a determination of the magnetization of different lattice sites in 

(magnetically incommensurate) Nd by G. Watson et al. 

(U. of Maryland), the use of resonant exchange scattering 

to find the magnetic moment directions in SmNi,B,C 

and NdNi,B,C (C. Detlefs, etal. Iowa State U.), and the 

magnetic structure of TbNi,Ge, by A.H.M. Islam et dl. 

(Iowa State U.). 

Spin- and Angle-Resolved Photoemission 

FY 1996 was a very active year for the spin-resolved 

undulator beamline USUA. Just prior to this replacement, the Magnetic Thin Films group from ANL (D. Li, 

J. Pearson and, S. Bader) joined the NSLS R&D group (E. 

Vescovo) and the BNL Physics Department’s Surface 

Physics group (D.J. Huang, and P.D. Johnson) to perform a very challenging experiment. The goal was to 

elucidate the electronic states responsible for the magnetic 

coupling in the Cr/Fe giant magnetoresistance (GMR) 

materials. 

Over the past few years, spin-resolved photoemission, notably the work done at USUA, has been successful 

in identifying the electronic states which drive the magnetic coupling in the noble-metal based GMR materials. 

In this “simple” case, the long-range magnetic coupling is 

transmitted through the noble-metal spacer material via 

the formation of discrete, sp-derived, quantum-well-states 

(QWS). The spin ofthese states is determined by the spinpolarized boundary conditions at the adjacent ferromagnetic layers. The QW-like thickness dependence of these 

states accounts for the oscillatory behavior observed in the 

magnetic coupling as a function of the separation between 

consecutive magnetic layers. 

The experiment on the atomically flat Cr/Fe( 100) 

44 
whisker was designed to attack the considerably more 

complex situation in which the spacer layer material is not 

anoble-metal: Cr has 3dstates at the Fermi level (EF). The 

QW model is hard pressed to predict the correct magnetic 

coupling in this case. An essential ingredient of this 

picture is the highly delocalized nature of the electronic 

states which characterize the Fermi surface of a noble 

metal. In the Cr case, an analysis of the bulk Cr Fermi 

surface suggests different pieces of the Brillouin zone as 

most likely to be active. Then, using angle-resolved 

photoemission, a careful investigation of the evolution of 

the photoemission spectravs. the thickness of the Cr layer 

deposited on the Fe(001) whisker was conducted at these 

various “hot” k-points. The main result is the unambiguous identification of a 17+ 2 k oscillation period in the 

intensity at E, of the energy distribution curves collected 

at 12” off-normal with 59.7 eV photon energy (Figure 

29). This observed periodicity is in full agreement with 

the long-period magnetic oscillations (1 8 A) found in 

Cr/Fe(OO 1) multilayers. Furthermore, the “hot” k-points 

are in the vicinity of the d-derived “lens” feature of the Cr 

Fermi surface. The observation of QW-like behavior 

there suggests the “lens” region as the k-space origin ofthe 

long period oscillation in Fe/Cr multilayers. 

Near the end of FY 1996, significant new results 

were obtained by a collaboration between the NYU spinresolved group (B. Sinkovic, W. Zhu) and the NSLS 

R&D group (E. Vescovo) on an important magnetic 

materials problem ofboth fundamental and applied interest: half-metallic systems. The novelty of this entirely new 

class of magnetic materials, which was predicted theoretically a few years ago, lies in the 

fact that their spin-dependent electronic structure is metallic in one spin and semiconducting 

- 0.5 eV band gap in the other. Experimental 

evidence has so far been limited, possibly as a 

consequence of the considerable difficulties involved in preparing high quality surfaces of 

these intermetallic samples. Spin-integrated 

photoemission measurements from bulk single 

crystals have been made, which could not address the question of half-metallic character 

owing to lack of spin sensitivity. Recently, J.S. 

Moodera and coworkers from MIT have been 

optical Kerr effect measurements indicate high magnetic 

remanence for these films, the measured spin-polarization 

of the photoemitted electrons has been found to be quite 

modest. In particular, the polarization of the electrons 

close to the Fermi level is found to be only -2OY0, in 

contrast to the prediction ofhalf-metallic behavior (1 00% 

polarization at EF). Encouragingly, however, the spinresolved photoemission measurements (Figure 30) show 

NiMnSb spin-resolved density of states features in good 

agreement with recent linear mufin tin orbital calculations. Considering the very high surface sensitivity of the 

photoemission measurements, these results strongly suggest that the origin of the discrepancy lies in a lowered 

remanent magnetization of the surface region. The next 

step will be to search for surface preparation methods 

which increase the surface remanence. Success would 

have great technological implications for the magnetics 

industry, for which the possibility of using materials with 

large single-spin electric carriers is often seen as anecessary 

prerequisite to engineer a variety of new magnetic devices. 

Structural Studies of 

Novel Materials 

The NSLS has along history ofbeing able to provide 

important characterization of new materials as they are 

produced, and the current year is no exception. 

One newly synthesized material for which synchrotron x-ray diffraction has been important is periodic 

arrays of Au nanocrystals of 50-500 atoms, passivated by 

45 
I 

self-assembled monolayers of alkylthiolate molecules. R. 

Whetten et al. (Georgia Institute of Technology and 

SUNY @ Stony Brook) have developed techniques to 

separate fractions containing controlled shapes and sizes 

of the Au nanocrystals, and these materials show a very 

interesting diffraction pattern (Figure 3 1). 

Another colloidal crystal system, studied by G. 

Beaucage et al. (U. of Cincinnati) on X23A3 this year, 

has a much larger length scale: silica in a polymer matrix 

with lattice parameters in the range of several pm permit 

an interesting opportunity to compare x-ray measurements with optical and scanning electron microscopy. 

This experiment makes use of the Ultra-SAXS BonseHart apparatus at this beamline. 

A completely different technique was applied by T. 

Gog etal. (Argonne National Laboratory) on the wiggler 

beamline X25 to study 50 A GaP clusters imbedded in a 

Si matrix. In this work, they extended their variable 

energy x-ray holography technique to dilute samples, in 

which the lattice match between the clusters and the 

matrix would have made conventional x-ray diffraction 

analysis quite difficult. 

Fullerene materials continue to generate interest, 

and there are several important new results from powder 

diffraction measurements. G. Bendele and co-workers 

(SUNY @ Stony Brook, X3B1) have shown that the 

quenched dimer phase of RbC,, has a different 

interfullerene bonding pattern than the polymeric chains 

found in stable RbC,,; a single bond between one C atom 

on each buckyball instead of a [2+2] cycloaddition. If one 

is sufficiently patient, Na,RbC,, spontaneously transforms from its high-temperature cubic phase to an orthorhombic structure; previously it was thought that this 

transformation required the application of pressure. Incidentally, this work also showed that the orthorhombic 

polymer phase is not a superconductor, in contrast to 

what had been previously thought by some authors. M. 

Stetzer et al. (U. of Pennsylvania), have continued their 

investigations on beamlineX7A offullerenes with handles, 

viz. C,,H, and CG3H6, finding two thermal phase transitions of the former and a likely unit cell for the latter. 

Sliding charge-density waves exist in certain substances, and J. Brockand his colleagues at Cornell U. have 

made measurements using X25 to elucidate both their 

structure and dynamics. They have been able to provide 

strong evidence against recent theoretical models, which 

predict that the equal time phase-phase correlation function should be algebraic at large distances. Similarly, their 

time-resolved measurements of the decay from sliding to 

pinned states contradict the theoretical conclusions. 

I I I llllllll I I I II IIII 

bee: a30.8 A fcc: a=4.08 A 

1.OE+2 I 1 I I I 111 I IIIII I 

1 10 100 

Scattering angle (degrees) 

Highly Correlated Systems 

Far Infrared Ellipsometry 

The technique of far infrared 

ellipsometry is being developed by a group 

from the Max Planck Institute (Stuttgart, 

FRG) at beamline U4IR. Ellipsometry is a 

method for directly extracting a material’s 

optical constants, such as the frequency 

dependent conductivity and dielectric function, from reflectance measurements (as a 

function of polarization angle for non-normal incidence). The high-brightness synchrotron infrared source makes the technique practical, as sample sizes are often 

very small (less than 1 mm by 1 mm) and the 

angle of incidence must be restricted to 

achieve accurate results. R. Henn (Max 

Planck Institute) and coworkers are using 

this technique to investigate the c-axis infrared response of La,-xSrxCu, for various values ofx. They observe that the conductivity 

along this direction changes character as the 

Sr fraction passes through x=0.15 (which 

yields the optimal TC), consistent with dc 

transport measurements. 

46 
X-Ray Scattering 

The recent discovery of colossal magnetoresistance 

behavior in the perovskite-derived manganite system 

La,-xCaxMnO, has stimulated much interest in the structural properties of these materials. A high resolution 

powder diffraction study by P.G. Radaelli et d. (Institut 

Laue Langevin), at X7A in the temperature range 20-300 

K has revealed the presence of weak satellite peaks below 

the antiferromagnetic transition at + 180 K associated 

with a transverse modulation (0.5- ,O,O), corresponding 

to an approximate doubling of the orthorhombic a axis. 

The satellite intensities are consistent with charge-ordering of Mn3+ and Mn4+ ions and orbital ordering of the 

Jahn-Teller-distorted Mn3+0, octahedra, resulting in a 

monoclinic structure in which the Mn4+0, octahedra and 

one-half of the La atoms are shifted by -0.1 and 0.05 A 

respectively as indicated in Figure 32. Since then, D. Cox 

etal. (Brookhaven National Laboratory), have studied the 

pyrochloreT1,Mn,07, and found that it does not have any 

lattice anomaly at the metal-insulator transition. 

v) 

x 

a 

I 

m 

.- 

c-axis 

I, 

X-rays are not merely a passive probe in some 

experiments on GMR materials. V. Kiryukhin et a!. 

(Princeton U.), noted an x-ray photoinduced transition 

from insulating to metallic phases in Pr,,Ca,,MnO, on 

beamline X22B. 

High-Resolution Photoemission 

J.-H. Park (NSLS), S-W. Cheong (Bell Labs.) and 

C.T. Chen (SRRC) have investigated the high temperature metal-insulator transition ofLaCoO, utilizing a high 

resolutionvalence band photoemission spectroscopy (PES) 

at beamline U4B. LaCoO,, which exhibits a diamagnetic 

to paramagnetic transition around 90 K upon heating, 

undergoes a gradual insulator to metal transition around 

500 Kupon heating. Figure 33 shows the high resolution 

valence band PES spectra above (700 K) and below (450 

K) the transition temperature Tr - 500 K. Upon heating 

through T, the insulating band gap disappears [Figure 

33(a)], demonstrating the occurrence of the insulator to 

metal transition. Furthermore, considerable differences 

in spectral lineshape are observed in entire valence band 

[Figure 33(b)] at the two temperatures. These differences 

indicate that the metal-insulator transition is accompanied by a symmetry change, which results in an additional 

spin state change. 

Figure 32: Structural distortions associated with 

the magnetic transition in Lao,,Cao,,MnO,. (X7A) 

47 
X-Ray Spectroscopy 

The impact of EXAFS and XANES in the 

field of superconductors was evidenced by several 

abstracts from beamline U4B and X11 A, using soft 

and hard x-ray spectroscopy respectively. Oxygen 

K-edge NEXAFS was used to understand how 

oxygen orbital structure correlates with the superconductivity of the material. For example, several 

groups examined superconductors of the type: 

(YZREJBa,Cu3Oy. Generally, rare earth substitution has little effect on the superconducting properties, with the notable exception of Pr. Oxygen Is 

NEXAFS of superconductors with increasing concentrations of Pr were examined and showed specific changes in oxygen orbital structure consistent 

with the presence of Fehrenbacher-Rice states. 

In another investigation on beamline X1 lA, 

D. Haskel and E. Stern (U, of Washington) 

investigated the structural consequences of Srt2 

substitution for La+3 in La,xSrxCuO,. Sr+’ in the 

range of 0.075 to 0.25 leads to high Tc superconductivity by inducing hole carriers in the Cu-0 

planes. By examining the Sr-K edge EXAFS of 

oriented powders, it was shown that the Sr-0 

bonding structure is quite different from that of La0 bonding. In particular, the apical oxygen atoms 

are split into 2 sites separated by 0.3 A (Figure 34). 

This implies a fluctuating number of holes at the Cu sites 

near the Sr atoms. The hole-lattice interaction could be 

Surface Dynamics 

involved in the pairing mechanism, leading to high Tc. 

cu 

Sr 

Figure 34: Two site configuration of the 0, 

apical to Sr. (X11A) 

The primary program at beamline U4IR continues 

to be studies of molecular adsorbates on metal surfaces by 

grazing incidence reflectance spectroscopy. Of particular 

interest is the broadband reflectance change of the metallic substrate as a function of the particular adsorbate and 

its coverage. Research groups from Duesseldorf, LURE, 

Tufts, the ALS and the NSLS are studying various aspects 

ofthis behavior. The theoretical model 0fB.N.J. Persson 

explains the reflectance change as due to enhanced scattering of the metal’s electrons from the adsorbate. This 

scattering affects the surface resistance, and the theory 

predicts alinear relationship between the electrical surface 

resistance and the reflectance change. In work by M. 

Hein, P. Dumas, and collaborators (Duesseldorf, LURE 

and the NSLS), both the reflectivity change and resistivity 

were measured for thin Cu( 1 11) films as a function of 

coverage for CO, oxygen, and ethylene adsorbates as 

shown in Figure 35. In accordwith theory, the reflectance 

change for CO and ethylene was found to be linear with 

the resistivity change. However, the behavior for oxygen 

showed some departures from the model predictions. 

Another adsorbate-on-metal system, namely C,, on 

various noble metals [Ag( 1 1 l), Au( 1 lo), Cu( 1 1 l)], was 

48 
investigated by P. Rudolf (LISE-Namur, Belgium) and 

coworkers from LURE (France), Lucent Technologies, 

and the NSLS. C,, readily accepts charge from alkali 

metals (such as potassium) to form a conducting “fulleride”, 

which is accompanied by distinct changes in several of the 

C,, molecule’s IR vibrational modes. In this study of C,, 

deposited on Ag, Au, and Cu, only one absorption mode 

is observed (Figure 36), assigned to the Raman active 

Ag(2) mode. The mode has become IR active due to 

symmetry breaking upon adsorption. The appearance of 

such a mode suggests a strong interaction between the 

metal and the CG0 molecule. However, none of the 

fulleride modes were apparent, indicating that if charge 

transfer (from the metal to the C6, molecule) occurs, it is 

quite different from that associated with alkali metal 

doping. Pre-dosing the noble metal surface with K leads 

to even more interesting behaviors when C,, is deposited. 

For C,, on 1ML of K, theAg(2) mode absorption appears 

as an anti-resonance. This is similar to what is found for 

CO on Cu, indicating that conduction electrons in the 

metal substrate must experience strong scattering from 

the adsorbate. Apparently some charge transfer occurs 

from the Konto the C,,, leading to alarger scattering cross 

section for conduction electrons near the substrate surface. A fulleride does form when C,, is deposited onto 

thicker layers of K, as witnessed by the appearance of an 

absorption mode at 1356 cm-’. The anti-absorption 

mode ar 1450 cm-’ persists. 

High Pressure Research 

The group from the Carnegie Institution of Washington (R. Hemley, A. Goncharov, R. Lu, H.K. Mao et 

al.) continued their investigations of dense hydrogen at 

beamline U2B, while expanding their program to include 

other compounds and minerals at extremely high pressures. Results of IR spectroscopy on hydrogen to pressures above 200 GPa have contributed to our understanding of the phase diagram for the solid. A transition from 

the low pressure, high temperature phase (I) to an intermediate phase (11) occurs for pressures above + 100 GPa 

and T< 100 K. A third phase (111) is observed for pressures 

above 150 GPa. In phases I1 and 111, the absorption 

associated with coupled vibrational modes in the molecular solid (vibrons) shifts in frequency and strength as a 

function of pressure and temperature (Figure 37, on next 

page). The oscillator strength (expressed as an effective 

charge) and frequency shift were found to share a common temperature dependence in both phase I1 and phase 

111. This allowed the Carnegie group to relate both 

quantities to an order parameter that characterizes the 

particular phase. This information, combined with results from Raman studies, have led to a picture where 

phase I1 consists of molecules with ordered angular momentum, and in phase 111 the molecules themselves are 

physically ordered. Thus, the high pressure phases ofsolid 

hydrogen can display quantum mechanical or classical 

ordering. 

49 
The Carnegie group have also investigated mixtures 

ofhydrogen with other simple gases (e.g. CH,, Ar) to high 

pressures. Similar to the situation for pure H, the molecular solids show IR absorption features associated with 

vibrational and rotational modes, but there has been no 

evidence of metallic behavior to the highest pressures 

achieved so far. 

Equation of State 

While P-V-T measurements have become routine 

in synchrotron studies over the past few years, they still 

provide new insights into material properties and a probe 

to bonding characteristics. Peiris and Heinz demonstrate 

the effects ofvacancies in ScS on the bulk modulus. They 

find that the vacancies actually increase the bulk modulus, 

a result which they explain in terms of the changing 

bonding characteristics of the material. Zhang and Reeder 

demonstrate that the bulk modulus-volume systematics 

for calcite-structure carbonates is sensitive to the cation, 

with alkaline earth cations defining a different relationship than transition metals, suggesting differences in 

bonding characteristics. 

Phase Equilibria 

X-ray diffraction patterns serve as fingerprints for 

the phases that exist in the high pressure system. S. Qadri 

etal. (Naval Research Laboratory), document the effect of 

particle size on phase transitions of PbS and E. Skelton et 

al. (Naval Research Laboratory), examine transition rates 

in Pd as affected by electrochemical absorption of deuterium both onX17C. J. Hriljac etal. (U. ofBirmingham), 

explore, on X7A, the phase stability fields of mercurybased superconductors. 

J. Chen etal. (SUNY @ Stony Brook), explore the 

pressure induced amorphization of zironium tungstate, 

the interesting material with a negative thermal expansion, Q. Chen etal. (U. ofWestern Ontario) combinedxray diffraction with electrical conductivity to study silver 

sulfate and various tellurium salts. These studies utilized 

various high pressure systems and share in common the 

goal to use pressure as a thermodynamic variable to map 

out the stability fields of avariety of novel materials. Both 

of these studies were carried out on X17B 1. 

Electronic Structure 

Inelastic X-Ray Scattering 

Inelastic X-Ray Scattering Spectroscopy (IXSS) is 

becoming a routine experimental technique in the study 

of electronic excitations in atomic, molecular, and condensed matter systems. It provides information complementary to photoelectron spectroscopy, optical spectroscopy, electron energy loss spectroscopy, and x-ray absorption spectroscopy. It also allows greater flexibilty in the 

selection of sample environment and experimental conditions. 

The IXSS measurements carried out at NSLS can be 

divided into two categories: non-resonant Raman scattering and resonant Raman scattering. In the case of nonresonant Raman scattering, the energy of the incident xray is far away from that of any absorption edge of the 

sample. The double differential cross section is then 

Absorbance 

frequencyand strength. Left: 

Intermediate (angular 

momentum ordered) phase, 

Right: High pressure 

50 
intrinsic many-body electron-electron correlation effects. They found that the overall 

lineshape is very similar between the liquid and 

the solid; while the fine structure in the linehape 

for the solid phase is significantly reduced in the 

liquid (Figure 39). These findings suggest that 

the overall lineshape of the response is due to 

electron correlations, and that the fine structure 

in the solid phase is not related to many-body 

effects. A similar study was also extended to 

single crystal Na by P. Chow et aL. (University 

of Houston). These and future experimental 

studies in combination with more first principle calculations will certainly contribute to 

our understanding of the many-bodyexchangecorrelation effects in simple metals. 

In the case of resonant Raman scattering, 

the energy of the incident x-ray is tuned near 

that of an absorption edge of the sample. By 

exploiting the resonant condition in the 

X P terms of the electron-photon interaction 

Hamiltonian, the inelastic scattering cross section can be greatly enhanced. The wider 

tuneability of the new X21 monochromator 

was designed so that the Kedges of the late 3dmetals and 

the L edges of all of the rare earth elements can be easily 

A 

related directly to the dielectric response function of the 

system under investigation. Although electron energy loss 

spectroscopy (EELS) also provides the same information, 

it suffers from multiple scattering problem at medium to 

high momentum transfers. As a result, few reliable 

experimental results are available in these momentum 

transfer regimes. Another problem with EELS is that 

samples have to be very thin and vacuum compatible. 

To take special advantage of IXSS, several groups 

have measured the dynamical structure factor, S(q,w), of 

simple metals near q = 2kF, where q is the momentum 

transfer and 4 is the Fermi momentum. The measured 

lineshape shows large discrepancies from the prediction of 

the simplest many-body theory, often referring to as the 

Random PhaseApproximation (RPA). B. Larson (ORNL) 

et al. measured the dynamical structure factor of AI from 

0.7 to 2.57 k,, and compared them with first principle 

dynamical electronic response calculations to extract the 

local-field factors as a function of momentum transfer 

(Figure 38). They found that for q = 2kF and larger the 

experimentally determined local-field factors are nearly 

twice as large as the calculated values; and suggested that 

even in simple metals dynamical electron correlations are 

quite strong. In a closely related experiment, J. Hill etd. 

(Brookhaven National Laboratory), following on from 

their earlier work on liquid Li and Na, measured the 

dynamical structure factors of solid and liquid AI near q = 

2k, to disentangle the effects of long-range order from 

51 
covered to facilitate this class of experiment. Resonant 

Raman experiments conducted near the K edges of Mn, 

Fe, Ni, and Cu were reported this year. 

Continuing their study ofmany electron excitations 

near the Kedge threshold of 3dmetals, M. Deutsch et al. 

(Bar-Ilan U.) studied the near-threshold behavior of the 

Cu K-a,,, emission lines. Three regimes were identified: 

(1) For incident energies below 898 1 eV, the energies of 

K-a,,* emission lines show linear dispersion with incident 

photon energy, and the intensities of the emission lines 

show rapid decrease with decreasing incident photon 

energy. Both are characteristic behavior of resonant 

Raman scattering below an absorption threshold. (2) For 

incident energies between 8981 eV and 8995 eV, the 

lineshape is purely Lorentzian indicating that the 3d 

spectator transitions are still energetically forbidden within 

this energy range. (3) For incident energies above 9000 

eV, 3d spectator transitions become energetically allowed. As shown in Figure 40, the contributions from the 

spectator transitions are most pronounced on the lowenergy side of the K-a, emission line. Lineshape analysis 

is used to extract the evolution of the strength of the 3d 

spectator transitions with incident photon energy, which 

is important in the understanding of electron-electron 

correlation in these systems. 

A common feature in the K edge x-ray absorption 

spectra of 3d transition metal compounds is a weak preedge peak below the absorption threshold. It is typically 

assigned to 1s+3d transition. The strength of the transition depends on the symmetry of the local environment 

around the transition metal. With 0.2 eV incident energy resolution, the splitting of the preedge feature due to the crystal-field can be resolved in some cases. In resonant Raman scattering experiments, one can then selectively excite 

the Is electron to one of the crystal-field split 

states, and monitor the decay of the core hole 

througheither2p+lsernission channelor 3p-h 

emission channel. The final state of the resonant 

Raman process then becomes either 2p53d'+' or 

3p53P1, the same final state configurations 

reached by either L,,3 edge or M2,3 edge soft-x-ray 

absorption processes. As a result, the rich L2,3 

edge many-electron multiplet structure can be 

obtained at the Kedge x-ray energies, a combination that is very important in cases where samples 

are not vacuum compatible. An example was 

given by W. Caliebe etaL (U. of Kiel), in a high 

resolution resonant Raman scattering study of 

Fe203, -hematite at the Fe K edge. Figure 41 

shows the two Raman spectra taken at incident 

x-ray energy tuned to the two crystal-field split 

states. Notice that it is the final state energies 

that are plotted. Also shown in the figure is the Fe L2,3 edge 

absorption spectrum. Clearly, the energies of the two 

3 

52 
main features in the soft-x-ray absorption spectrum 

agree very well with the main peak in the two Raman 

spectra. 

Large resonant enhancement of valence electron excitations was also observed. C.-C. Kao et al. 

(Brookhaven National Laboratory) reported a high 

resolution resonant Raman scattering study of NiO, 

a prototypical Mott-Hubbard system. As the incident photon energy is tuned through the Ni K edge, 

a new loss feature, which is not observed for incident 

energies far from the absorption edge, is observed. 

Figure 42 shows the Ni K absorption spectrum of 

NiO (a), the valence band emission spectrum ofNiO 

(b), and the Raman spectrum takenwith the incident 

energy tuned to the peak of the white line in the 

absorption spectrum (c). The new loss feature can be 

roughly fit with two peaks centered around 5 eV and 

8 eV. These observations were interpreted by using 

a configuration interaction cluster model, and the 

new loss feature is identified as the charge transfer 

excitation in NiO. Subsequently, resonant enhancement of charge transfer excitations near the Kedge of 

Cu have been observed by Hill et al. in Nd,CuO,, 

and by Isaacs et al. in Sr,CuO,Cl,. 

Ar CMA axis 

"K L L" 

In summary, the examples highlighted above are a 

good demonstration of the versatility of IXSS as a probe 

of electronic excitations in a wide range of systems. 

Core Excitation 

An Auger-Auger electron coincidence experimentat 

beamline X24A has been able to detect a large nonisotropic angular correlation between different components of the well-known Auger electron cascade following the Is + 4p resonant excitation of Ar gas. One 

electron detector, a time-of-flight (TOF) spectrometer, 

was set to collect large portions of the LMM Auger 

envelope while the other, a cylindrical mirror analyzer 

(CMA) equippedwith multichannel detection in order t3 

determine the polar and azimuthal angles, was set to 

collect the precursor KL,,,L,,, Auger electrons. The TOF 

spectrometer was oriented along the electric field vector 

of the monochromatized synchrotron radiation and the 

CMA was aligned perpendicular to both the TOF axis 

and the photon beam direction. Operation of the TOF 

spectrometer requires single-bunch operation of the 

X-Ray Ring in order to avoid overlapping signals from 

adjacent electron bunches. 

By dividing the LMM Auger envelope into three 

slices, a large non-isotropic angular correlation was observed for one of these slices (Figure 43), whereas the 

others were isotropic. The large anisotropy observed is 

believed to be an alignment effect rather than a dynamical 

post-collision interaction effect. 

53 
Angle-Resolved Photoemission 

The first results of a program and experimental 

chamber dedicated to high resolution (in angle and electron energy) angle-resolved photoemission were obtained 

at the end of FY 1996 by E. Jensen, T. Balasubramanian 

(Brandeis U.), X. Wu and S. Hulbert (NSLS) at beamline 

U12B. This first experiment was a study of the electronic 

structure of the (0001) surface of beryllium (Be) near the 

Fermi level (E$. The electronic density of states (DOS) 

at the Fermi level of the Be(0001) surface is about four 

54 

times larger than in the bulk. Many properties such as the 

electron-phonon interaction, the resistivity, and the specific heat depend strongly on the DOS at E,. In particular, 

the electron-phonon coupling parameter h is directly 

proportional to the DOS at E,. 

For bulk Be, h is 0.24. Thus one would expect the 

surface h to be about unity. h was measured at the 

Be(000 1) surface using angle resolved photoemission. 

The full width at half maximum (fwhm) of the surface 

state (SS) is interpeted as the inverse hole life time. All of 

the temperature dependence of the lifetime at high temperature comes from the phonon contribution, which is 

given by 2~hkT. Thus by measuring the SS fwhm vs. 

temperature one can determine h. The r - K SS, one of 

three on the Be(0001) surface, was chosen for measurement. This state has a binding energy of 2.8 eV at rand 

disperses parabolically, crossing E, at k,, =0.95 A-'. 

Figure 44(a) shows photoemission from this SS at k ,, 

=0.93 A-' (0.4 eV hole energy) for several temperatures. 

The fwhm of the SS is plotted vs. temperature in Figure 

44(b). Fitting these data to a straight line yields h=0.85 

fO.l. 

Using h=0.85 in the standard formula relating h to 

a superconducting transition temperature Tc, one finds 

that Tc rises to about 50 K (from 0.026 K in the bulk). 

This should be observable in ultra-thin films, and may 

have observable consequences for the surface of a thick 

crystal at low temperatures. 

The success of this experiment was determined in 

large part by the ability to prepare an extremely clean 

Be(0001) surface, an exercise which required more than 

one calendar year ofeffort. During FY 1997, an effort will 

be made to determine the electron-electron and electronimpuritycontributions to the Be(0001) SS lifetime. Also, 

a new high-resolution angle-resolved photoemission analyzer and experimental endstation, funded by the DOE 

Scientific Facilities Initiative, are being fabricated. 

Significant progress has been made recently by S. 

Dhesi, C. Stagarescu, and K. Smith (Boston U.) in the 

study of the electronic structure ofwide band gap nitride 

semiconductors. Such semiconductors (for example, 

GaN) are an important class electronic materials primarily due to potential use in optoelectronic devices operating in the blue to ultraviolet spectral range. Using angleresolved photoemission on beamline U4A, the band 

dispersion of the valence states along all the high symmetry directions in the bulk Brillouin zone has been measured for wurtzite GaN thin films. The n-type wurtzite 

GaN(001) thin films were grown using electron cyclotron resonance assisted molecular beam epitaxy on sapphire substrates at Clean GaN(0001) surfaces were 

prepared by repeated cycles of N,' sputtering and 

-- 
annealing in UHV. Following this procedure Auger 

electron spectroscopy shows minimal contamination, and 

low energy electron diffraction displays a sharp hexagonal 

pattern with no evidence of a surface reconstruction. 

Figure 45 shows a series of normal emission spectra 

taken from atomically clean GaN(0001) surface of a 

wurtzite film. The spectra in Figure 49 reflect the 

dispersion of the states along the rAl? direction of the 

bulk Brillouin zone. By measuring spectra in the offnormal geometry, the dispersion of states along directions 

in the bulk Brillouin zone parallel to the surface were also 

measured. The results of these experiments reveal very 

good agreement with local density approximation calculations for the bulk band structure. One notable result of 

the angle resolved photoemission measurements is the 

observation of a non-dispersive surface state about the 

point in the surface Brillouin zone. This state exists in a 

projected bulk band gap, and is sensitive to oxygen 

adsorption. 

Auger Photoelectron Coincidence 

Spectroscopy (A PECS) 

The Auger Photoelectron Coincidence Spectroscopy endstation continues to utilize its unique capabilities to study interesting surface science phenomena. 

During FY 1996, two APECS experiments were performed at beamline U14A. 

In one of these, the N,,W Auger spectra from the 

Ru(OO0I) surface taken in time coincidence with Ru 

4p,/, or 4~~,~core photoelectrons are compared. As would 

be expected for highly correlated late transition metals 

such as Ru, the measured APECS Auger spectra are not 

well represented by the self-convolution of the Ru(000 1) 

valence band density of states. On the other hand, an 

attempt to model the Auger spectra by multiplets of a d6 

configuration, appropriate if the 4p core hole is fully 

screened prior to Auger decay, has met with some success: 

the differences between the two experimental spectra can 

be explained by a stronger coupling of the high kinetic 

energy 5D multiplet term to the 4p,,, level than the 

4pln level. Calculation of the appropriate matrix elements is underway. This experiment is the result of a 

collaboration between R. Bartynski and R. Gotter (Rutgers 

U.), X. Wu and S. Hulbert (NSLS), and H. Nozoye 

(Japan National Institute of Materials and Chemical 

Research). 

The second APECS experiment of FY 1996, also 

performed at U14A, has put the finishing touches on a set 

of APECS measurements of the lineshape of the Ti 3p 

core level spectrum from stoichiometric (“nearly perfect”) and defective TiO,( 1 10) surfaces, measured in time 

coincidence with M,,W Auger electrons. The selection 

of only those Ti 3p core holes which decay by M,,W 

Auger emission provides a new spectroscopic view of this 

surface. Figure 46 (a),(b), and (c) (see next page) show 

coincidence Ti 3p core Level spectra from the stoichiometric, 900 K vacuum annealed, and ion bombarded (+ lOI4 

Ar+ ions/cm2 at 500eV) surfaces, respectively. Figure 46 

(d), (e), and (f) show non-coincidence (ordinary, or 

“singles”) spectra from the same three surfaces. The 

excess emission in the 68-70eV kinetic energy range in 

Figure 50(a) is attributed to Ti3+ and Ti2+ ions in sites 

55 
adjacent to surface oxygen vacancies. The density of these 

residual surface defects (either point defects or step edges) 

is rather low (+ 1% of a monolayer) on the stoichiometric 

surface, but the associated sub-oxide emission accounts 

for +20% of the total surface Ti 3p emission [Figure 

46(a)]. The enhanced sensitivity in the coincidence 

spectrum is attributed to the extra charge density at the 

reduced Ti sites as compared to Ti4+ sites, which strongly 

affects the M,,,VV Auger decay rate. The assignment of 

this excess emission as defect- related is supported by the 

spectrum [Figure 46(b)] while in the coincidence spectrum [Figure 46(e)] over 50% of the Ti 3p emission is 

associated with reduced Ti oxidation states. Ion bombardment produces a greater fraction of defect-related 

emission in the singles spectrum [Figure 46(f)] than does 

900 K annealing [Figure 46(e)], but results in a very 

similar coincidence spectrum. This shows that this ion 

dose produces a concentration of surface defects similar to 

what 900 K annealing produces, and that a substantial 

fraction of the defect-related emission in the singles 

spectra in Figure 46(b) and (e). 900 K annealing induces 

only a small (+4%) defect-related shoulder in the singles 

spectra arises from subsurface damage. 

56 
NUCLEAR PHYSICS 

LEGS Facility Overview 

The Laser Electron Gamma Source facility (LEGS) 

provides intense, polarized, monochromatic y-ray beams 

by Compton backscattering laser light from relativistic 

electrons circulating in the X-Ray Ring of the National 

Synchrotron Light Source at Brookhaven National Laboratory. Such a beam has a high degree of polarization 

(-90%) with very low background and the energies of the 

photons are well determined by measuring the loss of 

energy of the struck electrons. Photon Energies up to 330 

MeV can be obtained with the present laser shining on 

2.58 GeV electrons. With a new frequency-quadrupled 

laser that is now under development and the possibility of 

2.8 GeVelectrons, photon energies up to 470 MeVcan be 

obtained. 

LEGS has its high degree ofpolarization because the 

interaction of the laser photons with relativistic electrons 

preserves the polarization of the photons. By orienting 

the linear or circular polarization of the laser to give the 

desired polarization for the y-rays, measurements can 

isolate specific contributions to nuclear reaction amplitudes. If the linear polarization (direction of the electric 

fieldvector) is in the plane ofthe reaction, the cross section 

is sensitive to electric multipole moments. This cross 

section is denoted as o,, . If the linear polarization is 

perpendicular to the reaction plane, the cross section is 

sensitive to magnetic multipole moments. This cross 

section is symbolized by aL . The data is usually presented 

in terms of $; or o ,,- oL , or as the asymmetry 

c= (r 'I - " . Comparing these cross sections permits 

Cll+ 01 

the separation of effects due to static charge distributions 

from those due to spin and current distributions. Thus 

this polarization degree offreedom is extremely important 

in the understanding of nucleon and nuclear structure. 

Since 1990, experiments have concentrated on single 

polarization observables (polarized beams on unpolarized 

targets) in nuclear reactions involving the A resonance. 

The A resonance is the first excited state of the nucleon 

with an energy of 294 MeV above the mass of the proton 

and a width of 120 MeV. It decays with a 99.4% branch 

to pion-nucleon (TcN) final states and a 0.6% branch to 

y N. By studying photon induced nuclear reactions in the 

energy region of this excitation, it is possible to measure 

fundamental quantities such as the deformation of the A, 

to test models describing the internal structure of the 

nucleon and the A and the transition between them, and 

to study the effects of As produced inside of nuclei. 

Highlights of the last two years are given below. An 

updated status of LEGS, including recent publications, is 

available on the World Wide Web via http:// 

In 1997 a new phase of operations will begin, 

focusing on double-polarization measurements with circularly polarized photon beams and longitudinally polarized nucleon targets. This work requires the development 

of (i) a new frozen-spin hydrogen-deuteride target that 

provides high polarizations for both nuclear species, and 

(ii) a new large acceptance detector array for measuring 

total reaction cross sections in both neutral and chargedparticle channels. Progress on these instrumentation 

developments is an ongoing effort of the LEGS Spin 

Collaboration (LSC) and is discussed in the last section. 

WWW. LEGS .BNL. GOV/ + LEGS/ . 

The E2 N-ATransition from p(3n) and Compton Scattering 

In constituent quark models, a tensor interaction 

mixing quark spins with their relative motion is needed to 

reproduce the observed baryon spectrum. This necessarily results in a D-wave component in the nucleon wave 

function which breaks spherical symmetry and leads to a 

static deformation for the A. The A is photo-excited 

mainly by M1 radiation. However, the D-state component results in a small E2 transition strength. The 

magnitude and sign of the E2/M1 mixing ratio are quite 

sensitive to the internal structure of the proton. Isolating 

the N + A transition requires a decomposition of the 

multipoles into resonant and background (non-resonant) 

components. This decomposition requires a model, and 

model dependences enter the analysis of n-production 

and Compton scattering in different ways. These two 

final states have different E2 sensitivities and both have 

been studied at LEGS. 

Thep(2~) andp(7, r) reactions were separated by 

detecting photons in a high resolution NaI(T1) spectrometer in coincidence with the recoil protons whose trajectories were tracked through wire (drift) chambers and 

whose energies were measured both by energy deposition 

and by time of flight in an array of plastic scintillators. 

This arrangement is shown in Figure 47. The full data set 

consisted of 3 sets of runs with different NaI and scintillator-bar orientations chosen to provide overlap angles. 

The x"/Compton separation for the full data set centered 

at 90" in the center of momentum (c.m.) is shown in 

57 
Figure 48 where the y-ray energy is plotted against 

the recoil proton energy. Here the y and proton 

recoil energies for Compton scattering, as calculated from the tagged beam energy and the proton 

recoil angles measured in the drift chambers, have 

been subtracted from the measured energies. 

Compton scattering is clearly resolved here, and in 

all other runs. 

In p( ~n), the observable most sensitive to an 

E2 component is the cross section, 'J,, , for no 

production by linearly polarized photons whose 

electric vector is oriented parallel to the reaction 

plane. The corresponding cross section for the 

perpendicular orientation, CT~ , is completely insensitive to E2 excitation at all but extreme angles. 

Thus, the ratio CJ IfoL maximizes E2 sensitivity, 

while dividing out systematic uncertainties. The 

first new measurements of this ratio over a limited 

angular range suggested E2 transition strengths 

significantly larger than expected from previous 

multipole analyses. In our 1994 LEGS Progress 

Report, and at the SPIN'94 Conference, we presented the results of new measurements of this 

KO polarization ratio taken over a large angular 

range. These were compared to the model 

Plastic Scirti ii ator 

Chambers 7% 

Figure 47: The detector arrangement used to separate 

the (y ,x) and (y ,y ) reactions (see text). 

58 

predictions of Davidson, Mukhopadhyay 

and Wittman (DMW). This model contains 

five free parameters, the electric and magnetic coupling constants at the yNA vertex 

(G,and GM), and three constants parameterizing the off-shell behavior. In addition to 

the polarization ratios, cross sections are 

needed to fix these 5 parameters. Since 

absolute cross sections from our experiments 

were not available at the time, our polarization datawas combined with previouslypublished unpolarized results from other laboratories. The results of fitting this composite 

data set to the DMW parameters gave a value 

for GJG, (the N+A part of the E2/M1 

mixing ratio) of - 2.7&0.1%. (The error of 

_+ 0.1% reflected only the variations in the 

methods of unitarizing the pion amplitudes.) 

The analyses of the LEGS experiments 

are now complete. We present here a selection of cross section and polarization data for 

both Compton scattering and no-production 

and examine the consistency of previous E2/ 

M1 determinations in the light of the full 

dataset. The 90" excitation functions for the 
two reactions are shown below in Figures 49 and 50. 

There had been a long standing discrepancy between earlier Compton measurements and dispersion 

calculations that used .n-production as input. The LEGS 

measurement was designed to remove all of the uncertainties associated with separating Compton scattering from 

the no channel by a large overdetermination of kinematic 

parameters. Both reactions are completely specified by 

two kinematic observables. In this experiment, six 

quantities were measured: the beam energy, the scattered 

?-ray energy, the polar and azimuthal angles of the recoil 

proton, and the proton’s time of flight to the detector and 

the energy it deposited in the detector. This large degree 

of over-determination has two important consequences. 

First, it guarantees an accurate separation of the two 

competing channels (Figure 48). Secondly, it enables all 

I/ 

DMW/E2+Born 

220 260 300 340 380 

EY (MeV) II 

detector efficiencies to be evaluated directly from the data 

itself, without resorting to simulations and thus avoiding 

their associated uncertainties. The data shown as solid 

points in Figure 49 reflect all statistical andpolarizationdependent systematic errors. Additional systematic scale 

errors are less than 2%. Near the peak of the A, our results 

are substantially higher than the earlier measurements 

(open squares). Other recently published measurements 

from Mainz (crosses) and from Saskatoon (SAL) (circles) 

are in excellent agreement. Data from earlier experiments 

at Cornel1 (1961), Tokyo (1964), Illinois (1967), and 

Bonn (1 976) at energies higher or lower than the A peak 

are either consistent or slightly lower than these new 

measurements. Why the earlier results are so dramatically 

lower near the resonance energy is not known. 

59 
0 30 60 90 120 150 180 

I L'vov Dispersion Theory: I 

0.5 f --- VPI(FA93) I 

0.4 

0.3 

z 

0.2 

0.1 

0 

0 30 60 90 120 150 180 

e (de@ em. 

Angular distributions of the cross sections and 

linear polarization observables for Compton scattering 

and no-production for energies near the A peak are shown 

as the solid points in Figures 51 and 52. The recent 

Mainz 90" Compton cross section is plotted in the top 

panel of Figure 5 1. For the Compton asymmetry, the 

only previously published datum (from Frascati) is also 

shown. For no production, the results of applying the 

most restrictive cuts to the LEGS data (" Compton-like" 

kinematics), are shown with statistical errors as the 

crosses at 90"and 120"in the top panel ofFigure 56. Also 

plotted are the older Bonn and Lund cross sections and a 

Khar'kov asymmetry measurement. 

Three sets of curves for p(y,no) are plotted in 

Figures 50 and 52. The solid curves are calculations in 

which the parameters of the DMW model were optimized to reproduce a combination of the LEGS no 

polarization ratio results, together with the Bonn unpolarized cross sections. This was the exercise carried out 

with the first new results that yielded the value of -2.7 % 

for GJG, The result of turning off the E2 part of the 

N+A transition in this calculation (i.e setting G,=O) is 

shown as the dotted curve. (Setting the entire E2 

amplitude, including Born contributions, to zero produces dramatic effects but is not terribly informative.) 

For comparison, the predictions of current WI multipole analyses are shown as the dashed curves. Although 

the DMW andVPI predictions are both quite close to the 

no polarization data, the cross section predictions indicate a need for some readjustment of parameters. 

Compton scattering provides an additional constraint on this problem. The imaginary parts of the 

Compton amplitudes can be calculated from (y,~) 

multipoles using s- and u-channel unitarity (s,t, and u are 

the standard Lorentz-invariant Mandelstam variables) 

and dispersion integrals can be written for their real 

parts. The solid, dotted, and dashed curves in Figures 

49 and 5 1 have been calculated by L'vov in this way using 

as input the pion multipoles corresponding to the three 

calculations in Figures 50 and 52. In particular, the 

predictions of the solid and dashed curves started with the 

DMW model (adjusted to give G,=-2.7% of GM) and 

with recent VPI multipole analyses of E-production, 

while the dotted curves were obtained by setting the 

E2j=3'2 Compton multipoles to their s- and u-channel 

Born and t-channel pole values. 

The Compton cross sections at backangles are quite 

sensitive to E2/M 1 interference and these me not reproduced by either the solid or dashed curves. The prediction 

corresponding to the solid curve also gives the poorest 

description of the polarizatiomq asymmetry. The leading 

E2 interference term, fl' corresponding to E2 
0 

0 30 60 90 120 150 180 

0.20 

0 30 60 90 120 150 180 

8 (de$ c.m. 

photoexcitation followed by MI decay, is dominated by 

the N+A transition. Doubling this amplitude results in 

the long-dashed/short-dashed curves in Figure 5 1 which 

seem to describe most of the cross section data although 

the asymmetry calculation remains a little high. 

The new Compton results clearly show the deficiencies in our earlier estimate of GJG,= -2.7% which 

was driven solely by the pion polarization data. A 

complete determination of the E2 component in N+A 

requires a simultaneous fit to both Compton scattering 

and n-production. This is presently underway. 

Deuteron PhotoDisintegration and Coupled NNNN Interactions 

Although the A resonance dominates nuclear reactions from pion threshold to about 1 GeV, its interaction 

with the nucleon is still poorly known. Understanding 

nuclear reactions in this energy region necessarily requires 

a consistent treatment of the NA and NN interactions. 

The NN force can be studied directly using nucleonnucleon reactions but the NA interaction must be inferred from processes with the two nucleon deuteron such 

as ZD + ENN and ED + NN for which the A plays a 

prominent role in the intermediate state. Because of the 

strong coupling of the A to nN, realistic models must 

satisfy three-body unitarity, connecting reactions starting 

from NN, ZD, or YD entrance channels leading to NN, 

nD, or xNN final states. While elastic scattering and 

breakup reactions for the deuteron are reasonably well 

understood because the interaction with a single nucleon 

dominates, pion and photon absorption channels have 

proven to be problematic. Since the effects of the NA 

interaction are the largest near the energy of the A 

resonance and since both the cross section and the polarization observables have been shown to be strongly affected by the NA interaction, the LEGS collaboration 

measured cross sections and asymmetries in the same 

experiment for the first time in order to remove ambiguities in existing data. 

Five independent measurements of the D(y,p)n 

reaction have been carried out at LEGS with three different detector systems, different photon end-point energies 

from different laser wavelengths, different polarizations 

and two different liquid deuterium targets. These measurements overlap in various kinematic regions between 

113 and 325 MeV, and the agreement in the regions of 

overlap is excellent. By taking weighted averages of 

overlapping measurements, a "net" data base has been 

constructed and is available from the LEGS WWW page. 

~ 

+ 

61 
Selections of these data at 300 MeV are compared 

to recent coupled-channel calculations in Figure 53 (note 

with cross sections measured with linear polarization 

parallel to the reaction plane but fail to account for the 

data taken with perpendicular kinematics. The shaded 

band reflects uncertainties in the pion meson exchange 

currents used in the calculations. 

At present, there is no clear explanation for the 

success of the coupled-channel calculations in one polarization kinematics and their failure for the orthogonal 

state. Spin observables provide a considerably more 

sensitive test of the angular momentum modeling than 

do cross sections. Although the model parameters of the 

calculations presented here were fitted to NN phase 

shifts, all assumed static NN potentials, with retardation 

effects included only in the NA and NN-KA-transition 

potentials. The additional use of retarded potentials in 

the NN interaction could significantly alter the angular 

momentum mixing. 

I the suppressed zero).The calculations are in agreement 

i 

=a 

0 30 60 90 120 150 180 

Oc,m. (de@ 

A Figure 53: Angular distributions at 300 f 5 MeV. 

62 
INSTRUMENTATION AND TECHNIQUES 

The development of new techniques and instrumentation goes hand in hand with the continuing scientific advances at any state of the art facility. The NSLS is 

no exception. Because of its unique infrastructure these 

developments are advanced on many fronts by the entire 

community. As in past years significant innovations are 

being made over the entire photon energy spectrum 

covered by the NSLS facility. 

Develo ments in UV and 

Soft X- E ay Instrumentation 

A new area of focus for W photoemission studies is 

in the realm of very high energy and momentum resolution. These techniques have been applied to questions of 

interest in the field of high Tc superconductors over the 

past several years. As part of the push in that direction at 

NSLS, a new high energy resolution angle-resolving photoemission instrument based on the use of a Scienta 

hemispherical analyzer has recently been commissioned 

in the BNL Physics Department. This spectrometer, with 

the capability of multiplexing in both energy and angle, 

has an energy resolution of better than 5 meV and an 

angular resolution of better than 0.2 degrees, resulting in 

an order of magnitude improvement of the momentum 

resolution. It is intended to couple this instrument to the 

new undulator beamline U13UB, which features high 

throughput collection/focusing optics and a high resolution (> 1 O4 resolving power) normal incidence monochromator operating in the 5 to 30 eV photon energy range. 

Imaging science using soft x-rays is now well established. The instrumentation, however, continues to 

develop as experimenters push ever harder toward the 

physical resolution limit of h/2. The XIA scanning x-ray 

microscopes all use Fresnel zone plates as their focusing 

elements. In collaboration with D. Tennant (Lucent 

Technologies Bell Laboratories), S. Spector et al. (SUNY 

@ Stony Brook), have fabricated zone plates by etching 

Ge or, more recently, plating Ni. Outer zone widths of 30 

nm are in use, and 20 nm zones have been fabricated in 

tests; diameters of 80 and 160 microns are in use. 

The Stony Brook team has not only made advances 

in the x-ray optics but have also commissioned a scanning 

transmission x-ray microscope, cryo-STXM, which is 

designed (by J. Maser, et al. SUNY @ Stony Brook,) to 

image frozen hydrated specimens of a few microns in 

thickness at temperatures below -1 65°C. At this temperature, the effects of radiation damage to biological samples 

should be reduced by several orders of magnitude compared to room temperature hydrated specimens. This 

should enable images to be taken at higher resolution and 

even multiple images to be obtained from the same 

sample, a feature which is crucial for elemental and 

chemical mapping and for tomography. In contrast to 

most x-ray microscopes in use, the cryo-STXM has been 

designed to operate at a vacuum of 1 0-7 Torr. This limits 

thermal drifts to around 1 nm per second while also 

helping to reduce contamination of the sample. Samples 

are prepared on EM grids which in turn are mounted on 

a TEM style liquid nitrogen cooled holder. The sample 

temperature can be controlled by a heater. The holder 

itself can tilt by k 80" to allow tomography to be done. 

Sample introduction is done through a JEOL TEM 

airlock, and takes only a few minutes without breaking 

vacuum. Images are obtained by scanning the sample in 

a raster pattern, the x-ray light being focused at a fixed 

point using a Fresnel zone plate. Coarse scans with a 

resolution of 1 micrometer are performed by out-ofvacuum stepping motors with a range of 9 mm by25 mm. 

A piezo driven in-vacuum flexure stage provides finer 

steps of 20 nm and a field of 70 by 70 pm2. Refocusing 

during spectral scans is done using an in-vacuum DC 

motor. Samples can be previewed using an optical microscope with infinity- correctedvisible light lenses in vacuum 

but with the head outside vacuum. The data acquisition 

system has multiple digital and analog channels so that 

several parameters can be recorded. The cryo-STXM is 

now permanently mounted on a separate vibration isolation system at the beamline. 

Scanning transmission x-ray microscopy provides a 

two dimensional image of the sample under study. Holographic techniques hold out the promise of providing information about the third dimension. Previous 

experiments in x-ray holography have yielded high quality 

images of dried specimens at +40 nm resolution. These 

experiments have employed the photoresist PMMA for 

recording the image, a specialized scanning force microscope with a linear scanning stage for hologram readout, 

and computer reconstruction. In 1996, the experimental 

apparatus was completely rebuilt (by S. Lindaas (LBNL), 

and collaborators from Stony Brook) to allow holograms 

to be recorded of frozen hydrated specimens using a cry0 

holder similar to that which is used in cryo-STXM. First 

holograms of frozen hydrated malarial erythrocytes were 

63 
recorded, and reconstructions have been obtained at a 

resolution similar to that of room temperature samples. 

Moreover, iterative twin image elimination algorithms 

have been developed for higher quality image reconstruction. Plans for 1997 include efforts towards holographic 

tomography. 

X-Ray Methods and 

Instrumentation 

High Pressure Research 

The high pressure tools that are used in conjunction 

with the NSLS source have undergone major advances as 

reported in this volume. The variables: magnitude, 

uniformity, and isotropy of pressure, magnitude and 

uniformity of temperature, and sample volume all compete in defining the envelope available to the researcher. 

The diamond anvil cell sets the high pressure limit at the 

price of sample volume, and pressure and temperature 

uniformity. The “double hot plate” system used by T.-D. 

Shen et ul. (Los Alamos National Laboratory), in their 

study of iron defines new boundaries in this experimental 

space. Two multi-mode laser beams are focused on 

opposite faces of the sample through the opposed diamond anvils. By heating both surfaces ofthe sample to the 

same temperature, the normally large temperature gradients within the sample are virtually eliminated. Using 

Kirkpatrick-Baez mirrors, the x-ray beam is focused to a 

diameter of about 10 pm, providing sufficient intensity 

for diffraction spectra to be collected in a few minutes. 

This spot size is much smaller than the laser spot size, thus, 

providing x-ray data for a sample at uniform pressures and 

temperatures. 

“Large volume” high pressure systems define the 

portion of the experimental envelope with sample volumes three orders of magnitude greater than diamond 

anvil cells with a sacrifice in maximum pressure and a gain 

in pressure and temperature homogeneity as well as 

sample volume for x-ray studies. The new anvil geometry 

reported by M. Vaughan et ul. (SUNY @ Stony Brook), 

the Tea-Cup cell [Figure 54(a) and (b)], is beginning to 

compete with diamond anvil cell pressures having broken 

21 GPa with tungsten carbide anvils while maintaining 

large sample volumes. Future plans include using sintered 

diamonds as anvils with the hope of further increasing 

pressure with little loss of other parameters; cost. 

The conventional large volume system used at X17 

is a DIA style multi-anvil apparatus. This workhorse at 

NSLS and the Photon Factory (where it is known as 

MAX-80 and MAX-90) can routinely produce 10 GPa 

with WC anvils with a 4 mm truncation. Wang et al. 

(U. of Chicago) report slight modifications to the anvil 

geometry that have provided a 30% increase in pressure, 

fewer failures, and more productive experimental runs, all 

Btony Brook “Teacup” Press 

. . . . . ... . .. ,,nmr .... ... .. .- .. * 

Figure 54: (a) Stony Brook “Teacup“ Press, a two-stage 

device using eight-cubic anvils to generate high pressure, 

with x-ray access. (X17B1) 

22 

20 

0 

0 100 200 300 400 500 600 700 800 

Oil Pressure, bars 

18 

16 

f 12 

rn 

10 

6 

4 

2 

(b) Pressure performance of Teacup 

apparatus. 

64 
with no cost in sample size or environment. 

With the expansion of the experimental environmental envelope has come a remarkable growth in the 

types of studies that can be done in conjunction with x-ray 

synchrotron radiation. The most significant breakthrough 

for Earth-related studies is the inclusion of acoustic velocity measurements at high pressure and temperature and 

simultaneously with x-ray diffraction. As reported by R. 

Liebermann et al. (SUNY @ Stony Brook), acoustic 

interferometry is used to measure acoustic velocities of 

samples to fractions of a per cent accuracy (see Figure 55 

for diagram of cell assembly). X-rays are essential to 

provide in situ determinations of the pressure using a 

NaCl pressure marker, with thermocouples measuring 

temperature. These experiments are all performed in the 

tapered anvil DIA apparatus, reproducing conditions of 

the transition zone of the Earth. Such measurements at 

simultaneously high pressure and temperature are extremely important in interpreting seismic velocities as a 

function of depth in the Earth. Despite their inherent 

importance, such measurements have been limited to a 

few samples, most notably, MgO, collected a quarter 

century ago. The MgO data reported here by G. Chen 

etal. (SUM @ Stony Brook), using the new technology, 

cover a pressure range one order of magnitude larger than 

the older data with temperatures of twice the previous 

study. 

H.-K. Mao et al. (Carnegie Institute of Washington), have developed a technique to estimate elastic anisotropy and strength at room temperature and megabar 

pressure in a diamond anvil cell. Experimentally, the cell 

geometry must be altered so that the x-rays enter and exit 

through the gasket and not the diamonds. Energy dispersive spectra are collected at varying diffraction directions, 

ranging from nearly parallel to the diamond axis to 

perpendicular to it. With assumptions as to the orientation and homogeneity of the deviatoric stress field, they 

can recover information about the elastic anisotropy and 

material strength. Their new results for iron have exciting 

implications about the elastic anisotropy and evolution of 

the Earth’s inner core. 

Macromolecular Crystallography 

Multilayer monochromators can provide x-ray intensities from NSLS x-ray bending magnet beam lines 

that surpass currently available intensities from NSLS xray wiggler beam lines which use silicon monochromators. Using beam line X25, collaborators S. Burley and J. 

Kuriyan (Howard Hughes Medical Institute and 

Rockefeller U.), and L. Berman, M. Capel, and R. Sweet 

(Brookhaven National Laboratory), employed broad 

bandwidth multilayers (with a relative wavelength spread 

of 1.5%) as monochromating elements instead of 

Platinum Wire 

for Electric CoSpring Loading Devide Acoustic Transducer 

for Acoustic Transducer 

Contact CulPt Foil for / 

Electric Contact 

M 

2 mm 

Figure 55: Diagram of anvil insert and cell assembly for ultrasonic experiments in X17BI. 

65 
conventional narrow bandwidth silicon, in trial 

macromolecular crystallography experiments. The 

multilayers provide an additional two orders of magnitude of flux in the incident x-ray beam. Diffraction data 

were measured from two test specimens: single crystals of 

hen egg-white lysozyme and of TAFIA, a heterodimer of 

two eukaryotic transcription factors (Figure 56). These 

are being analyzed to determine how well the Bragg spots 

can be resolved and indexed, and their structure factors 

extracted, in the presence of the peculiar, highly anisotropic resolution hnction associated with the multilayermonochromated x-ray beam. These tests at X25 were 

performed under single-bunch operation conditions, for 

which the x-ray intensity approximates that available on 

bending magnet stations under normal 25-bunch operation conditions. Nonetheless, exposure times were 

surprisingly short, ranging from one to five seconds for a 

1 O oscillation, and pushed the technical limits of the data 

collection apparatus’ shutter cycle and phi axis rotation. 

Certain classes of crystallography problems should be 

solvable using such an x-ray beam. The major restriction 

is that the ratio of the smallest Brag spacing resolution 

attainable to the longest crystallographic axis repeat is 

limited by the relative bandwidth of the x-ray beam from 

the multilayer monochromator. Within this limitation, 

the dramatic intensity enhancement derived (compared 

with the use of a silicon monochromator) should make 

possible high-resolution studies ofweakly diffracting crystals on NSLS x-ray bending magnet beam lines, that are 

now impossible to execute there. 

Advances have been made in crystallographic data 

collection. J. Skinner and R. Sweet (Brookhaven National Laboratory) have been developing, on beamline 

X12C, beamline-control software that incorporates intelligence and experience into a user-friendly graphical interface to the experimental apparatus. They operate a 

“hybrid instrument that combines a commercial kappaaxis goniometer and interchangeable x-ray area imaging 

detectors. The software provides the user with a simple 

graphical user interface (GUI) to control both the diffraction equipment and the beamline (e.g. wavelength changes 

and alignment). Important features of the software are 

that it allows “one-button” operation of many functions 

that are actually quite complex, and provides automatic 

documentation of the experiment by writing log files to 

describe the operations that are performed, and others 

that contain data about them. 

For example, the software facilitates the measurement of diffraction data for MAD phasing of 

macromolecular structures. Following a simple table set 

Figure 56: Single 

diffraction pattern of 

crystal of hen eggwhite lysozyme 

collected with a 

multilayer 

monochromator. 

W5) 

66 
Figure 57: Beamline control software with a sample of an EXAFS scan. (XI 2C) 

up by the operator to describe the experiment, the 

software will measure the x-ray absorption spectrum of 

the heavy atom incorporated in the crystal, analyze that 

spectrum to locate a particular feature at which data 

should be collected (e.g. the inflection point of the absorption edge), and then collect diffraction data at that wavelength (Figure 57). Numerous “ordinary” MAD structures have been solved with the system. Recently, a 1 OOOresidue protein structure with over a dozen heavy (Se) 

atoms was solved. A small protein structure also was 

solved during single-bunch running, just 54 hours after 

the users commenced data collection and while they were 

still at the beam line collecting data on other problems. 

Diffraction Physics 

A recurrent issue in x-ray diffraction is the phase 

problem. Although it is not generally an obstacle in 

conventional crystallography, there are still areas where 

the answer is not overdetermined and interference 

phenomena can be helpful in retrieving the phase 

Information. An interesting attempt to provide phase 

information in a 2-D diffraction experiment was made by 

Y. Yacoby et al. (Hebrew U.). They were able to use an 

adsorbed gold layer to reflect the diffracted wave back into 

the sample in a surface-diffraction geometry, and to show 

that additional interferences resulted. These interferences 

may prove helpful in assigning reflection phases and 

hence determining structures. 

Techniques for focusing and guiding x-ray continue to be pursued throughout the x-ray scientific community. C. Liu and J. Golovchenko (X15A, Harvard U.) 

have successfully observed the propagation of surfacetrapped x-ray waves along the surface of a curved silicon 

mirror. The wave undergoes successive total external 

reflections on the surface, and its evanescent tail is simultaneously diffracted by the substrate lattice. The phenomenon may have important applications for x-ray __ 

optical elements such as lenses and waveguides. 

67 


Peter W. Stephens 

SUNY @ Stony Brook 

NSLS Users‘ Execuiive Committee Chairman 

The NSLS users held their 1996 Users’ Meeting on 

May 21st, 1996 at Brookhaven National Laboratory, 

where they had an opportunity to celebrate another year 

of scientific and technical achievement, to welcome 

Michael Hart as the new NSLS Chairman, to hear the 

latest news about Department of Energy support for its 

scientific facilities, and to visit once again with old friends. 

Three workshops on various scientific and technical subjects met on May 20, and three more on the 22nd. The 

workshops have continued to grow as an important part 

of the annual get-together; of the 368 people who registered for any part of the meeting, 80% attended a workshop. 

The user community saw the vision for the future 

held by the new NSLS Chairman, Michael Hart. Reminding his audience that the NSLS operates with the 

high-brightness Chasman-Green lattice, he noted that 

the opening of third-generation synchrotron radiation 

sources in Europe (ESRF and Elettra) has not reduced the 

demand nor the productivity of second generation facilities, such as the NSLS. Since many experiments are 

limited by such factors as flux, detector capability, and 

source stability, they will not necessarily be improved by 

the newer accelerators, and the NSLS can expect to play 

an important scientific role in the foreseeable future. 

Many of these points are discussed in the recently released 

white paper, “NSLS Into The 21st Century.” 

Hart also told the users that he has reactivated the 

NSLS Science Advisory Committee, and has instructed it 

to initiate the process of tenure review for each beamline. 

He pointed out that the mission of many of the PRTs has 

changed substantially since they were created, and that 

the PRT system does not necessarily provide the bestsupported access for all users. The NSLS is working to 

broaden the access available to the user community for 

such popular measurement techniques as EXAFS, powder diffraction, and reflectivity. 

William Oosterhuis of the Department of Energy 

described the Scientific Facilities Initiative within the 

Office of Basic Energy Sciences. In the present fiscal year, 

$57 million was made available to the DOE programs at 

twelve facilities. This gave the NSLS a $5 million increase 

in funding, its first real increase in five years. Consequently, the NSLS has increased its beamline support 

staff by 20%, and made significant upgrades to the 

injection system, water supply, computer controls, and 

the accelerators themselves. Oosterhuis congratulated 

the user community in communicating the importance of 

the SFI to Congress. He indicated that the SFI is in the 

President’s FY1997 budget (although 2% less than this 

year) so that we can expect to continue activities started 

this year. 

70 
I 

goal is to develop these techniques to the point 

where they could be economically feasible on a 

production-line basis rather than a technical 

curiosity. 

The next talk moved to a different part of 

the electromagnetic spectrum - the use of 

infrared radiation to elucidate high-temperature superconductivity. Dmitrii Basov of the 

Brookhaven Physics Department spoke about 

three regimes that are observed in layered cuprates 

as a function of oxygen concentration: insulating, “conventional” superconductivity with a 

gap (range of frequencies with zero conductivity), and a pseudo-gap state in which the infrared conductivity is suppressed but nonzero. In 

these materials, the pseudo-gap occurs at rather 

high temperature, and grows deeper as the temperature is lowered, with no abrupt change at 

the superconducting transition. 

Gary Prinz of the Naval Research Laboratory spoke about magnetoelectronic devices, in particular 

about the role of synchrotron radiation in their development. Rapid progress in this field is leading to significant 

applications in sensors, memories, and logic elements. 

These can only be pursued with the detailed understanding of the magnetism of electronic states, especially at 

surfaces and interfaces, which comes from elegant ultraviolet spin-resolved photoemission and magnetic circular 

dichroism experiments. 

The keynote speaker was Malcolm Browne, Pulitzer 

Prize-winning Senior Science Writer of The New York 

Times. His talk, entitled “Lamplighters and Tool Makers,” described two complementary modes of scientific 

progress: the abrupt discovery and the methodical advancement of new knowledge. He drew a number of 

interesting conclusions about the role of science and 

technology in society. 

The talks about scientific topics began with Stephen 

Harrison of Harvard University and the Howard Hughes 

Medical Institute. He spoke about the role of 

protein crystallography in understanding how 

genes are switched on and off in the cell. He 

described his group’s work on the transcription 

factor NF-*B, specifically on the complex of 

one protein dimer with a strand of DNA. This 

work, performed at beamlines X4A and X25, 

used the multiple wavelength anomalous diffraction (MAD) technique for solving the structure. It is also highlighted in a report entitled 

“Structural Biology Research at the NSLS” 

(BNL Informal Report 62916, May 1996). 

Peter Siddons of the NSLS spoke about 

precision machining of plastic (PMMA photoresist) using hard x-rays. The NSLS group 

concentrates on making three-dimensional parts, 

in contrast with the rest of the world’s 

micromachining efforts, which are mostly on 

thin, planar structures. Among other points, he 

described the serendipitous discovery of a technique for making re-entrant cavities, illustrated 

with a tiny hexagonal wine glass. The ultimate 

1’: .’: I ., 

Peter Stephens (SUNY 63 Stony Brook), and D. Peter 

Siddons (Brookhaven National Laboratory, NSLS). 

71 
At the Poster Session: (From left to right) Steven Ehrlich (Purdue 

University), Rachel Eisenhower (University of Illinois @ UrbanaChampagne), and Bill Thomlinson (NSLS Associate Chairman for 

Environment, Safety and HealthNser Programs). 

John Fulton of the Pacific Northwest Laboratories 

discussed recent work on ion solvation in supercritical 

water. This has been suggested as an attractive method for 

cleaning and disposing of hazardous materials, and it is 

important to have a detailed understanding of the fundamental differences between usual solution chemistry and 

solutions in supercritical water. In si& EXAFS experiments are able to reveal such information as the fact that 

Sr2+ is coordinated by half the number ofwater molecules 

in supercritical water than at standard 

temperature and pressure. These experiments also have significant relevance to 

catalysis and to geochemistry. 

Polymer diffraction patterns usually have relatively few, broad peaks, 

whereas one normally associates synchrotron-based powder diffraction with a high 

resolution technique. Nevertheless, 

DuPont scientist Kenn Gardner described 

several significant advantages to the use 

of synchrotron radiation for his work in 

polymer crystallography. Particularly important is the fact that the lineshape is 

accurately known, whereas laboratory 

measurements need good standards 

(which do not exist), e.g., to distinguish 

paracrystalline disorder from finite-size 

broadening for low angle peaks. 

Erik Johnson of the NSLS concluded the series of scientific talks with 

the tantalizing question, “Could you Use 

a Couple of Orders of Magnitude?” He 

proposes to deliver that improvement in 

the intensity of pulsed ultraviolet and 

infrared light at the Source Development 

Laboratory. This is a broadly-based 

project of research and development on 

an ultraviolet free electron laser amplifier 

and on the use of very short electron 

bunches for FEL and coherent synchrotron radiation experiments. 

Two other important features of 

the Users’ Meeting were the scientific 

poster session, with a reception at the 

Brookhaven Center, and the equipment 

show in the Berkner Hall lobby. Both 

were popular opportunities to sniff out 

some of the latest work at the facility, and 

to see the exciting new tools and ideas for 

synchrotron radiation research. 

By way of administrative business, 

the NSLS Users’ Association elected three 

new general members to the Users’ Executive Committee: 

Joel Brock of Cornell University, Ian Robinson of the 

University of Illinois, and Thomas Russell of the University of Massachusetts. It also approved a charter revision 

so that future Special Interest Group elections will be held 

by electronic mail, and approved a new SPIG for industrial users, In executive session, the UEC chose 

Brock to be its Chairman-elect. 

72 
In Situ Applications of X-ray Absorption Fine Structure 

Simon R. Bare 

(Dow Chemical Company) 

The ability ofx-rays to penetrate matter was emphasized in this year's XAFS workshop on studying materials 

under in situ conditions. Eight speakers addressed the 60 

attendees with topics ranging from catalysis to electrochemistry to biology. Jim McBreen (BNL) led off the 

workshop with a presentation on using XAFS to probe the 

electronic and geometric structure of fuel cell catalysts 

under applied voltages. He was able to draw a correlation 

between the Pt-Pt bond length and Pt d-band vacancies 

with reaction rates for several Pt-M alloy catalysts. Mark 

Antonio (ANL) described a novel bulk electrolysis cell for 

probing the structure of species in solution during electrolysis. The focus of the talk was on the Eu2+/Eu3' couple. 

He showed, and explained why, the addition of a single felectron to Eu dramatically changed the Eu L3-edge 

XANES. Simon Bare (Dow Chemical) followed the 

oxidation state of vanadium in a supported vanadium 

phosphate catalyst during the oxidation of butane using 

dispersive XANES with on-line product analysis. He 

showed a direct correlation between the presence of V5+ 

and the formation of maleic anhydride. The ability to 

study surfaces under corrosive conditions usingXAFS was 

illustrated by Inho Song (Case Western Reserve). He 

described a total electron yield detector designed to perform in situ studies of the atmospheric degradation of 

materials. The state of sulfur in gaseous SO, in dry and 

humid environments was determined, together with that 

73 

on the surface of Cu films during exposure to the corrosive 

gas. Following lunch, during which several posters were 

presented, Di-Jia Liu (AlliedSignal) nicely demonstrated 

the need for true in situ experiments to study the form of 

Cu in a ZSM-5 de-NOx catalyst. He showed that there is 

an excellent correlation between the presence ofCu(1) and 

the rate of selective catalytic reduction over this type of 

catalyst. A fascinating presentation on the use of microXANES to follow the uptake and metabolism of metals 

(Cr and Se) in aquatic plants was given by Doug Hunter 

(Savannah River Ecology Lab.). His data indicated that 

there is localized uptake and reduction of both elements. 

For example there is localized reduction of Se in the leaf 

ofthe fern from Se6+ to Se2-. John Fulton (PNL) described 

both a high temperature (500 C), high pressure (1 kbar) 

reaction chamber for studying ion solvation in supercritical 

water, and a quartz capillary reactor for investigating 

metal species in supercritical CO, using EXAFS. He 

showed that there is a difference in solvation of Sr2+ and 

Rb+ ions in supercritical water compared to ambient water 

solutions: there is a reduction in the average coordination 

and a concomitant reduction in metal-oxygen bondlengrh. 

The formal program ended with a presentation by graduate student Mike Nasher (U. of Illinois) on the use of in 

situ EXAFS to monitor the preparation of Re-Ir clusters 

on alumina prepared from novel bimetallic 

carbonyl complexes. 
Research Using Sync K"" rotron Opportunities in Pol 

Radiation 

Thomas P. Russell 

(IBM Almaden Research Center*) 

The use of synchrotron radiation for the investigation of polymers began in the early 1980's with exclusive 

use of small angle scattering methods to elucidate the 

morphological characteristics of bulk polymers. Despite 

the fact that the results from these studies were impressive, 

in quantity and quality, the growth in the application of 

synchrotron radiation for studying polymers was slow. 

Recently, however, there has been a tremendous growth 

in polymer related research. Not only has the number of 

experiments that are performed on polymers grown in 

that time, but the diversity of scientists performing research on polymers has grown. Initially, only those 

scientists whose major research interests were in polymers 

performed work in this field. Now, however, scientists 

with more traditional physics and chemistry backgrounds 

must be included. This growth can be attributed to several 

factors. First, there is the nature of the polymer chain. 

Typically, polymer chains pervade volumes on the tens of 

nanometers size scale. Thus, features characteristic of 

phase transitions are easily observable. Second, due to the 

entangled nature of the polymer chains, relaxation processes are longer. Thus, polymers are ideal candidates for 

the investigation of kinetic phenomena. Third, some of 

the potentials for using the variable wavelengths in the 

hard and soft x-ray region of the spectrum for the study of 

polymers have been realized. Thus, entire new avenues of 

research have been uncovered. Finally, the realization 

that the surfaces of polymers are quite smooth (an rms 

roughness 0f0.6 nm) has permitted the exploitation ofthe 

numerous surface characterization techniques that have 

been developed at synchrotron sources. Both the increase 

in the number of scientists investigating polymers and the 

number of techniques available to pursue polymer re- 

[* Now with the University of Massachusetts] 

search have had significant impact on basic and applied 

research topics. A Workshop on Opportunities in 

Polymer Research Using Synchrotron Radiation was held 

during the 1996 NSLS Users' Meeting. It was designed to 

highlight some of the recent pioneering studies on polymers and to demonstrate areas of potential use of these 

versatile light sources in polymers. 

Professor Benjamin Chu from the State University 

of New York in Stony Brook spoke on small angle x-ray 

scattering studies on polyelectrolyte gellsurfactant complexes. The low contrast between the scatterers, the low 

concentrations and the large size of the chains mandate 

the use of a very high resolution small angle spectrometer 

with high flux. These conditions can only be realized at 

a synchrotron source. The results from the experiments 

described by Chu have provided significant insight into 

the fundamental behavior of polyelectrolyte gels, the 

influence of the pH of the swelling solvent and the testing 

of different theoretical concepts. 

One of the important developments that has occurred with synchrotron sources is the ability to perform 

several different measurements simultaneously, as for 

example small angle scattering and wide angle diffraction. 

Obtaining multiple results on a single sample has tremendous advantages in the case ofpolymers. Due to entanglements, it is ofien difficult to get two different polymer 

samples into precisely the same state and, consequently, 

errors are introduced when multiple samples are used. 

Simultaneously using multiple techniques eliminates this 

error. Dr. Benjamin Hsiao of DuPont discussed a series 

of studies where both small and wide angle x-ray diffraction were used to investigate the crystallization and melting of some semi-rigid polymers, namely poly(etherether-ketone), PEEK. Typical data obtained from such 

studies are shown in Figures la and lb where the time 

resolved small angle x-ray scattering and the wide angle 

diffraction data for a PEEK sample are shown after the 

sample has been cooled from the melt to 290°C. In 

Figure la the small angle scattering data show a growth in 

a peak which is due to the crystallization of the PEEK 

molecules into a lamellar type of morphology. Simultaneously the diffraction data in Figure Ib show the development of the crystal structure in the lamellar morphology. Large anisotropic changes in the unit cell parameters 

occurred in these materials during secondary crystallization processes. By correlating the small and wide angle 

74 
scattering data a model for the crystallization process in 

PEEK was developed. Information of this nature is 

crucial in deriving structure property relationships which 

directly impact the processing and end use of polymers. 

Another areawhere synchrotron radiation has played 

an important role is in the characterization ofsingle fibers 

or small bundles of fibers. Using standard laboratory 

equipment the available flux is simply too small obtain 

acceptable signal to noise ratios. Professor David T. 

Grubb of Cornel1 University described experiments on 

high modulus polyethylene fibers, single fibers of Kevlar 

(about 12 microns in diameter) and bundles of spider 

dragline silk fibers (- 4 pm in diameter) where the fibers 

are placedunder a loadandstretched. Within seconds, full 

4000 

3000 

2000 

1000 

0 

Figure 1 a: Time resolved small angle x-ray scattering of 

a PEEK sample undergoing crystallization. 

Figure 1 b: Time resolved x-ray diffraction for a PEEK 

sample undergoing crystallization. These data were 

collected simultaneously with the small angle data in 

Figure 1 a. 

two dimensional fiber patterns could be obtained which 

permitted the investigation ofdynamic processes and realtime crystal orientation. His lecture focused on deformation mechanisms that were dominated by elastic processes. Dr. N. Sanjeeva Murthy ofAlliedSigna1 Inc. then 

described experiments on the fibrillar and lamellar structures in nylon-6 fibers. Again, with the ability to obtain 

full two dimensional patterns in seconds allowed the 

investigation of structural changes to the fibers during 

drawing and post thermal treatments. However, as pointed 

out by Murthy, since massive amounts of data are collected, much information has been ignored. He then 

described some of the efforts he has been making in the 

utilization of the full pattern. 

The afternoon lectures in the workshop focused on the surface and interfacial behavior of 

polymers. Professor Miriam Rafailovich of the 

State University of New York discussed specular 

reflectivity and off-specular scattering studies on 

Langmuir films of ionic block copolymers at the 

aidwater interface. Block copolymers, which are 

essentially two different polymers covalently bound 

together at one end, can be made such that one 

block is hydrophobic and the other is hydrophilic. 

On a water surface the difference in the 

functionalities of the two blocks cause the formation unique and unusual two dimensional structures. The lateral surface pressure dictates the 

concentration and, consequently, the morphology. These surface structures and the transition 

from one structure to another can be followed by 

use of off-specular scattering where a component 

of the diffraction vector is in the surface plane. 

However, the off-specular scattering is orders of 

magnitude less than the specular reflectivity and, 

consequently, requires the use of a synchrotron 

source to obtain good statistics. Rafailovich then 

demonstrated another area where off-specular scattering was being brought to use. This related to the 

conformality of the polymer films on a rough or 

periodic surface. On the following page, Figure 

2 shows the rocking curve of a substrate that has a 

lpm grating on the surface. This spectacular profile was obtained by rocking the sample by an angle 

h about the specular condition at Q= 0.2 A-‘ 

(where the diffraction vector is oriented normal to 

75 
the surface plane of the sample). The multiple peak results 

from the periodic structure, i.e. the grating, on the surface 

of the sample. Coating this surface with a polymer film 

and then observing the time dependent changes in the offspecular scattering have yielded considerable insight into 

the motions of polymers on surfaces and the ability of 

polymers to planarize the free surface. 

Following this, Dr. Thomas P. Russell of the IBM 

Almaden Research Center described a series of studies 

using Grazing IncidenceX-ray Scattering (G1XS)to probe 

the structure of polymers near a surface. In the particular 

case of an aromatic polyimide, GIXS showed that, in the 

vicinity of a surface, order in the polymer was enhanced. 

Polishing or buffing of the polymer surface, aprocess used 

in the production of flat panel displays, was shown, by 

GIXS, to produce a strong orientation of the polymer 

chains in the vicinity of the surface in the buffing direction. This surface orientation is directly correlated with 

the orientation of liquid crystals in displays. Prefacing the 

next two lectures, Russell also described the use of Near 

Edge X-ray Absorption Fine Structure (NEXAFS), where 

the polarization of the incident x-ray beam was used to 

probe the orientation of the polymer chains at the surface. 

For example, shown in Figure 3 are the NEXAFS results 

for an aromatic polyimide that has been buffed. By 

measuring the Auger and total electron yield as the energy 

of the polarized x-rays is changed where the electric field 

vector of the radiation is either parallel or perpendicular to 

the orientation direction, information concerning the 

surface (first 10 a from the surface) and the near surface 

(about 0.70 A from the surface) orientation of polymer 

chains is found. These results, combined with the GIXS 

results, have led to a detailed understanding of the buffing 

process and the manner - - 

in which information can be 

transferred across a boundary. 

Much emphasis has been 

placed lately on the behavior of 

thin films of multicomponent 

polymer systems. Numerous 

techniques are available for 

depth profiling concentration 

in suchsystems, however, there 

is a paucity of techniques for 

investigating lateral heterogeneities. Professor Harald Ade 

of North Carolina State University described advances that 

he and his collaborators have 

made in the use of x-ray microscopy to this end. The advantage of x-ray microscopy 

over the more traditional techniques, like light microscopy 

and atomic force microscopy 

methods, is that different 

chemical components can be 

seen with alateral resolution of 

0.1 micron. In addition, since 

the x-rays are polarized, lateral 

variations in the orientation of 

76 
the same or different components can be seen. Ade 

described investigations on liquid crystalline polymers, 

ternary polymer mixtures and polyethyleneterephthalate 

where x-ray microscopy has provided key insight into the 

morphology and orientation. X-ray microscopy is relatively new but, as explained, the number of microscopes 

available for study is growing at a rapid rate. In the study 

of the surface and interfacial behavior of polymers it is 

increasingly more important to distinguish the behavior 

of the polymers immediately at the surface or interface 

without having to extract such information from a techniques that averages over the first 5-7 nm. In the case of 

polymers, at a distance of only several monomer diameters 

from the surface, about 1-2 nm, the bulk characteristics of 

the polymer chain are found. Dr. Benjamin Dekoven of 

the Dow research laboratories described studies using 

near edge x-ray absorption spectroscopy on materials 

ranging from self-assembled monolayers to perfluorinated 

polymers where chemical information was obtained on 

the first nanometer from the surface. Such information is 

crucial for developing a quantitative understanding of the surface wetting characteristics of polymers and the transfer 

ofinformation, be this chemical or structural, across an interface. 

Each of the lectures focused on 

specific research problems. However, 

there were several underlying messages 

that became quite clear as the workshop 

progressed. First, synchrotron radiation 

sources offer a tremendous battery of 

techniques for the characterization of 

polymers. The results presented beautifully demonstrated several examples 

where quantitative information was obtained. Second, the number of experiments performed at synchrotron sources 

with polymers as the central research 

theme has increased tremendously over 

the past few years. Finally, there is still 

much that these sources offer for performing polymer related research, a resource that will lead to pioneering developments in the field. 

77 
Multiple Wavelength Anomalous Dispersion (MAD) in Protein 

Crystallography 

Lisa J. Keefe and Stephan 1. Cinell 

(Argonne National Laboratory) 

Multiple wavelength anomalous dispersion (MAD) 

has developed into a powerful crystallographic phasing 

technique for solving macromolecular structures. Synchrotron radiation is essential in order to implement 

MAD phasing, and with the increasing accessibility of 

synchrotron beamlines, the technique is gaining widespread use. The focus ofthis workshop was to present and 

discuss the theoretical approaches to MAD phasing, the 

preparation of selenomethionyl-substituted protein for 

MAD phasing, the strategies of MAD data collection, 

processing and scaling, and examples of the application of 

MAD phasing in solving crystal structures. 

Axel Brunger (Yale University) presented a comparison of algebraic and probabilistic methods applied to 

a MAD data set ofa fragment ofthe carbohydrate binding 

domain of mannose binding protein A. Tom Tenvilliger 

(Los Alamos National Laboratory) discussed a Bayesian 

approach to MAD phasing, as implemented in his program HEAVY (v4.5). In a comparison ofBayesian MAD 

phasing with other methods, namely treatment of MAD 

data as approximate relationships of dispersive and anomalous differences among wavelengths and treatment of 

MAD data as multiple isomorphous replacement, Bayesian MAD phasing gives more accurate phasing, especially 

for incomplete data sets. Alan Friedman (Purdue University) discussed data reduction and scaling for MAD, the 

inherent problems with MAD data and solutions to those 

problems, and MAD phase determination. With MAD 

data, the signal is inherently less than the noise and data 

collation can be problematic. To overcome these two 

obstacles, local scaling with flexible automatic data collation can be performed and robust phase determination 

can be used. 

Robert Sweet (BNL-Biology) presented a talk for 

Venki Ramakrishnan (University of Utah School of 

Medicine) on the use of standard MIR data reduction, 

scaling, and phasing programs to analyze MAD data. Dan 

Leahy (Johns Hopkins School of Medicine) discussed his 

experiences with the use of selenomethionyl-substituted 

protein to solve structures by MAD. He reviewed strategies for substituting selenomethionine for methionine in 

proteins, methods for growing bacteria in media containing selenomethionine and expression ofselenomethioninesubstituted protein, tips on purification and crystallization of selenomethionine- substituted protein, assays for 

selenomethionine in purified proteins, and valuable 

advice on how to prepare for and perform a MAD 

experiment at a synchrotron. Robert Sweet (BNLBiology) discussed issues in data collection for MAD 

phasing, with much emphasis on the integrated and userfriendly beamline-control software used at his beamline 

at NSLS. 

Chi-Hon Lee (Rockefeller U.) presented the crystal 

structure of HIV- 1 Nef complexed with a src-family SH3 

domain. Yee Liu (Columbia U.) discussed a MAD 

experiment at the M4 edge of uranium. This is a very 

difficult and unique experiment due to the low energy 

(3728 eV) of the M4 edge of uranium. The advantage of 

using this heavy atom is that the MAD signal is very strong 

and thus phasing can be accomplished for very large 

molecules or complexes. 

The workshop ended with a lively question and 

discussion session which focussed on the details of solving 

structures using MAD phasing. These included the 

likelihood of solving a structure using MAD phasing. 

This is correlated with the signal to noise ratio, and 

methods for calculating this ratio were reviewed. Also 

discussed was the determination of the anomalous and 

dispersive components, f' and f, respectively, of the 

structure factor and the refinement of these components, 

with and without anisotropy. MAD phasing is rapidly 

becoming the technique of choice for the determination 

of crystal structures and the increasing availability of 

synchrotron radiation beamlines and development of 

cryocrystallographic techniques for performing MAD 

experiments is enabling many otherwise very 

difficult crystal structures to be solved. 

78 
The afternoon session, chaired by Richard Harlow, 

began with a detailed analysis of geometrical conditions 

inherent to the oscillation method presented by Robert 

Sweet (BNL-Biology). The impact of the presentation 

was greatly enhanced by remarkable drawings by coauthor, Zbyszek Dauter (EMBL0,Germany). An advocate of image plate technology, Wladek Minor (U. of 

Virginia) gave an extensive overview of recent developStrate and Methods for 

Area IF etector Data Collection 

Alex Darovsky (Brookhaven National Lab., NSLS) 

The rapid progress in the technology of area detectors (AD) increases their advantages for many scientific 

applications utilizing x-ray diffraction techniques. Being 

primarily oriented to macromolecular studies, AD data 

collection techniques and subsequent reduction and 

interpretation of the data need to be readjusted for the 

new applications, particularly for small molecule crystallography, powder diffraction, and synchrotron crystallography. 

This one day workshop was intended as a forum for 

the discussion and evaluation of methods, procedures, 

and algorithms for AD data collection and processing. 

The morning session was dedicated to in-depth analysis 

of methods for 2D data processing; the afternoon session 

being focused on practical aspects of 2D data collection 

strategy. Following opening remarks by NSLS Chairman 

Michael Hart, Robert Bolotovsky (SUNY @ Buffalo) 

gave a detailed description of a new method for intensity 

integration of 2D diffraction peaks. He emphasized the 

advantage of using the “seed-skewness’’ method for 

integration of weak peaks or some abstinent peaks with 

irregular shapes. 

Joseph Reibenspies (Texas A&M U.) discussed the 

topological property of 2D arrays of data with implication to peaManomaly classification of diffraction pattern 

- another example of generalization of data reduction 

procedures for the AD technique. Finally, analysis of a 

severely delocalized diffraction pattern in terms of its 

crystalline and amorphous components was demonstrated by Peter Moran (SIEMENS). He applied a Fourier filtering technique for estimation of crystallinity of 

partially oriented polycrystalline samples. 

ments in area detector systems and auxiliary x-ray equipment which enhanced the capability of in-lab 

diffractometets making them competitive with the existing synchrotron sources. His talk also focused on the 

practical aspects of data reduction, particularly, on the 

analysis of possible pitfalls and adequate criteria for data 

quality. The first two speakers referring predominantly to 

macromolecular crystallography were complemented by 

aggressive enthusiasts from the small moiety community. 

Patrik Carroll (U.of Pennsylvania) demonstrated a superb performance of the R-AXIS image plate system for 

accurate structure analysis. A vast array of interesting 

molecular structures illustrating his presentation exemplified the effective and professional approach in utilizing 

the commercial hard- and software systems. A competitive, also an expensive so far, utilization of a CCD 

detector for single crystal data collection and processing 

was introduced by James Phillips (SIEMENS). While 

offering a versatile set of sophisticated hardware, he 

stressed the importance of optimization of experimental 

technique in order to obtain the best quality data. A 

detailed description ofoptimizedstrategy and tools implemented in SMART SYSTEM was given and evaluated. 

Finally, Fabienne Adolphe (ESRF,France) reviewed 

the experience accumulated at the BL2 beamline (ESRF) 

with area detectors. The variety of approaches which were 

reported indicates that synchrotron sources, being multiuser facilities with diversified areas of research, provide a 

fertile field for further applications and development of 

area detector techniques as was manifested by the superb 

attendance at the workshop. Comprehensive Workshop 

Notes (partially supported by DuPont de Nemours Co. 

and SIEMENS ) made a valuable addition to the 

educational objective of the workshop. 

79 
The workshop brought together a diverse group of 

researchers involved in the application of a variety of 

synchrotron radiation (UV and x-ray) based techniques 

(scattering, spectroscopy and microscopy) to study of 

magnetic phenomena in magnetic thin films and 

multilayers, interfaces, surfaces, and low dimensional 

magnets. Gary Prinz's (NRL) talk during the NSLS 

Users' Meeting, a day before the workshop, describing 

applications of variety of novel magnetic structures for 

storage, sensors and logic technologies, was an excellent 

introduction to the workshop. The workshop's opening 

remarks by Denis McWhan's (BNL) reiterating the increased interest and activity in studies of magnetism in 

recent years, which were also reflected in larger then 

anticipated workshop participation, resulted in a need to 

move the workshop from Berkner Hall to the NSLS 

Seminar Room. 

The first talk was given by Bernhard Keimer 

(Princeton U.) who discussed x-ray diffraction experiments on compounds undergoing structural transitions 

induced by high magnetic fields. These studies led to the 

discovery ofa novel "soliton lattice" phase in the quantum 

spin-chain compound CuGeO,, which provide an important test for theories of low-dimensional quantum 

magnetism. Gavin Watson (BNL - Physics) reported on 

recent progress in applying resonant x-ray scattering techniques to study the temperature-dependent magnetic 

order near the surface of an antiferromagnet. The studies 

show that within -50 A of the (001) surface of UO,, the 

magnetic scattering intensity decreases continuously as 

the bulk N'eel temperature is approached from below, 

which is in contrast to the bulk transition. Rogerio 

Paniago (U. of Houston) talked about x-ray diffuse scattering study ofinterfacial roughness in metallicmultilayers 

using a novel 2-dimensional Image Plate detector. The 

technique allows the measurement ofthe conformal roughness in the initial stages ofgrowth ofa lattice matched Fe/ 

Au buffer and the height-height correlation function. The 

interfacial cutoff length was shown to be dependent on 

the lattice mismatch, indicating it to be an important 

parameter for the growth of high quality metallic 

multilayers. Stuart Parkin (IBM Almaden) calk gave 

several examples how his work in thin film magnetism has 

benefited by the application of synchrotron radiation 

techniques, in particular EXAFS and MCD. Yves Idzerda 

(NRL) talked about recent development in the absorption 

and reflection of circularly polarized soft x-rays demonstrating the ability to obtain element-specific magnetic 

information for heteroniagnetic thin films, including a 

means to determine the magnetic structure, to measure 

the film thickness with very high accuracy, to identify 

sequence of multilayer switching with applied field, and 

possibly to determine the magnetic roughness of an 

interface. 

In the afternoon session Elio Vescovo (BNL- NSLS) 

showed, through various examples, how a combination of 

spin- and angle-resolved valence-band photoemission 

spectra and ab initio slab calculations can yield a very 

detailed description of the electronic structure of magnetic surfaces, interfaces and thin films. Such studies 

reveal the precise relation between the electronic structure 

and the magnetic properties. Jeahoon Park (BNL-NSLS) 

talked about electronic aspects of the ferromagnetic transition in materials exhibiting colossal magnetoresistance 

(CMR). The high-resolution photoemission data found 

the insulator-metal transition near the Curie temperature 

and suggesting that strong small-polaron effects are responsible for the enigmatic insulating behavior above T,. 

Neville Smith (LBNL) discussed opportunities for magnetic materials research at that high brightness synchrotrons, like ALS, with special emphasize on the microscopic studies. Ulrich Hillebrecht (U. of Duesseldorf) 

talked about element specific magnetic imaging with 

Photoelectron Microscopy using a commercial, Staib 

PEEM-150 microscope. Finally, Andrew Kent (NYU) 

summarized his research on the fabrication and study of 

nanometer scale ferromagnetic structures prepared using 

a scanning tunneling microscope. The work demonstrates that geometrical similar iron nanostructures are 

magnetically distinct, indicative of important contributions to the magnetic anisotropy other than the 

shape. 

The A plication of 

Radia P ion to the 

Magnetic Materials 

Boris Sinkovic 

(New York University) 

80 
Hard X-ray Precision Fabrication 

D. Peter Siddons and Erik Johnson 

(Brookhaven National Lab., NSLS) 

This workshop was intended to be a true workshop 

rather than a mini-conference. It was our intention to 

bring together people who are active in fabricating lithography-based structures in order to stimulate discussion 

around the topic area, and to seek advice on how to 

proceed in our development of the X14B beamline as a 

manufacturing research end-station for hard x-ray fabrication. There were approximately 15 attendees. Judging 

from the level of enthusiasm among the attendees it would 

seem we met with reasonable success in these objectives. 

There were five key areas of concern regarding this program 

0 

0 

0 

0 

0 

which were addressed at the meeting: 

Support Capabilities 

Exposure Station Properties 

Interoperability with Other Facilities 

Qualification of Customer Vendors and Tools 

Beamline Access and Allocation 

The resulting discussion of each of these areas is 

described briefly below. 

Support Capabilities: 

It was felt by many at the workshop that some 

supporting laboratory space be available which would 

provide a clean area to assemble fixtures and package 

samples for shipment. At present we believe this can be 

met by cooperative use of the existing cleanroom in the 

basement of instrumentation, and by allocation of some 

of the X13 Lab space for setup. A measurement 

metrology capability is also regarded as desirable, and in 

this respect, our measurement microscope system (Nikon 

microscope plus the Quadracheck QC-4000 measurement package) was deemed to be adequate to the present 

state of process development. 

Asample development capabilitywas also requested. 

Currently two developer systems are in use, GG and 

MIBK. Although some attendees favored the GG system, 

our research here indicates that for high aspect ratio 

material processing the MIBWEtOH system seems to 

perform as well or better than the GG system. We would 

only consider the GG system if one of the users was 

sufficiently motivated to organize and fund its implementation. 

Exposure Station Properties: 

In our presentation we described the properties of 

our planned scanner. There was general agreement that 

a high linear velocity device was desirable. Our prototype 

hydraulic stage will be capable of scan rates up to 25cm/ 

s with position and speed servo- feedback. One key feature 

which was strongly advocated was interoperability of 

fixturing with other facilities. Since at present, no other 

facility is performing hard x-ray exposures it is largely up 

to us to establish a standard configuration in consultation 

with potential future facilities. Most notable among these 

in the USA is CAMD, who are adding a wiggler to their 

machine for this type of work. The scanner enclosure 

should have a controlled environment which includes 

class 100 particle counts, less than 50% relative humidity, 

electrostatic reduction, and temperature stability the order of ,C. Ideally the scanner should be capable of 

exposing a 15cm by 15cm mask without step and repeat 

motions. The space constraints at X14B are such that we 

can only expose a field about 12 cm wide. This was viewed 

as a satisfactory step in the right direction from our 

present 4cm field at X27B. 

Interoperability with Other Facilities: 

This issue extends beyond fixturing and facilities. 

To make this a viable production technology, it was 

strongly felt that in the long run a pprint shop-capability 

should be created. In essence the idea is that customers 

would take their work to a broker (like MCNC) who 

81 
would then distribute the masks, fixtures, and materials to 

whatever exposure station was suitable and available. 

This implies some dovetailing of scheduling of maintenance and possibly redundancy within facilities. In this 

way if a scanner goes down another is available as backup. 

At the NSLS, beamlineX27B might, for example, serve as 

backup for X14B. In the case of facility maintenance, 

ALS, CAMD and NSLS might coordinate shutdown 

activities. 

Although it seems early these days to be too concerned about this issue, there was a general awareness of 

its longer term impact on the viability of hard x-ray 

machining as a manufacturing technology. It was pointed 

out that this problem is not as acute as it is for the 

specialized analytical work of the type ALS and SSRL are 

undertaking for wafer analysis. In their case full time 

availability is essential to recover from manufacturing line 

problems. In our case, a brief unavailability is part of the 

normally expected contingency in any sound production 

plan. Still it is an issue worth noting. 

Qualification of Customer Vendors 

and Tools: 

If the technology proves both successful and popular, a concern was raised about liability, or at least 

culpability, for production runs that don't work out. If a 

customer provides a mask or fixture that won't work, or 

sub-specification material that cannot be properly processed, establishing responsibility for a failed production 

run could prove both difficult and contentious. This 

should not be a problem with our first users, who will 

essentially be collaborators. If the print shop model takes 

hold we will need to establish standards for acceptable 

material and qualified vendors of masks, fixtures, etc. 

Beamline Access and Allocation: 

Several questions arose which, again, are somewhat 

in the future regarding access to the station currently 

under construction at NSLS. The attendees of the meeting predicted that within a year of establishing the production research line, it will be oversubscribed by as much 

as a factor of 1 O! While NSLS would be pleased with such 

a success, the administrative issues must be established 

well in advance of such a demand. 

seeking advice on these issues from the DOE. 

NSLS is 

82 


OPERATION

7. 
Stephen Kramer 

VUV Ring Manager 

stuc.:s time from that originally scheduled. The planned operating schedule for 

the year was one of the lowest in recent 

years of 62%) this was due to the extendedwintershutdown (November 1995 

through January 1996). This reduced 

schedule provided the necessary break for 

upgrading of the VW beam ports and 

the user’s beamlines. The VW Ring 

returned from this shutdown ahead of 

schedule and with no change in operational properties of the beam, despite a 

somewhat longer vacuum conditioning 

period than originally planned. The entire year of operation was at the higher 

energy of 808 MeV which was commissioned in FY 1995. Consequently the 

integrated current delivered to the user’s 

while not being as great as previous years, 

due to the reduction in the number of 

hours of operation, actually represents 

more than a 30% increase in total energy 

radiated by the beam during the year 

compared to previous years. 

The winter shutdown of the VUV 

Ring was required to replace two of the 

ring eight dipole vacuum chambers ofthe 

with new chambers having larger aperture beam ports for the two new infrared 

beamline UlOIR and U12IR. These 

beamlines will more than double the IR research potential 

of the VW Ring and help alleviate the long list of users 

waiting for access to the present IR beamlines. The U12IR 

beam port is a new beam port similar in design to the world 

leader beamline at U4IR. This port increases the VW 

ring beam ports from 17 to 18, a 12% increase over the 

originally planned 16 beam ports. This beam port extracts 

beam with a 45 degrees mirror at the exit from the dipole 

vacuum chamber, allowing a solid angle of 9O(H) X 90(V) 

mradians to be extracted for the diffraction limited IR 

beamline. The U1 OIR beam port replaces the previous 

small solid angle beam port U10, which provided beam to 

Stephen Kramer, VUV Ring Manager I 

Figure 1 shows the breakdown of the VUV Ring 

operating statistics for the Fiscal Year 1996. The monthly 

breakdown of the most significant operational statistics 

for the year, are shown in Figures 2 through 6. After the 

problems with the booster power supplies in FY1995 

were overcome, the operating reliability of the VW Ring 

improved such that the unscheduled downtime decreased 

by almost a factor of two to l.G%, the lowest level 

achieved to date. Despite this unscheduled loss of user 

beam time, the actual beam time delivered to the users 

was 1 % greater than originally planned,as the result of a 

reduction in maintenance, commissioning, injection and 

86 
UlOA and UlOB beamlines. The new beam port provides 

the largest vertical aperture possible in the standard dipole 

chamber, yielding a solid angle of 100(H)X 48(V) 

mradians. These two beamlines will use the floor space 

previously occupied by the U1O beamlines and therefore 

will not require an elevated platform, with the intrinsic 

vibration issue faced by the U4IR platform. 

The process of replacing these two dipole vacuum 

chambers required taking two of the spare chambers, 

machining and welding the new beam ports onto them 

while maintaining the exacting dimension for the other 

two unchanged beamlines (U9, U11 and Ul2) that share 

the same chambers. Once the new chambers were leak 

checked and ready for installation, the magnets and 

shielding had to be disassembled and the old chambers 

cut-out ofthe ring. The new chambers were then welded 

to the ring in situ and then leak checked. The magnets and 

shielding were re-installed and the alignment checked and 

adjusted to better than 100 microns. After baking and reinstalling the old beamlines, beam was injected and conditioning of the new vacuum chambers began. The old 

vertical betatron tune of the ring proved to be more 

sensitive to the poorer vacuum in the ring. By shifting the 

tune above the quarter integer resonance, good injection 

and greater freedom from ion problems was obtained. 

With the higher injection rate available from the booster, 

conditioning was faster than previous conditiqning periods and the distributed ion pumps showed their ion 

currents leveling off after about 50 Amp-hours, as expected. However, the new ion gauges and the lifetime 

both showed that it took at least 150 Amp-hours for the 

vacuum desorption and lifetime to approach within 10% 

of the old values. The booster performance allowed this 

to be accomplished more than 3 days ahead of schedule. 

Prior to that integrated current level UIO, U9 and UI 3U 

beamlines were able to take beam and verify that the 

photon beam was off from its pre-shutdown vertical 

position by less than 50 microns. This upgrade process 

will be repeated again during the winter 96/97 shutdown, 

when U2IR is planned to get a new larger aperture beam 

port, similar to the UlOIRport. Although only one dipole 

chamber will be replaced at that time, the new chamber 

will go in just ahead of a ceramic vacuum chamber that 

just started to leak in September 1996. Replacement of 

the ceramic chamber was added to the task ofreplacing the 

dipole chamber without requiring a great deal of additional effort. 

87 
88 
Another improvement in the VUV Ring this year 

was the installation of a new coupling loop in the first 

harmonic RF cavity. This loop allowed the RF amplifier 

to be optimized in its coupling to the RF cavity at the 

higher currents. This increases the RF power efficiency of 

the system and will allow future improvements in reducing the affects of higher order modes in the cavity. After 

some initial tuningdifficulties were overcome, this system 

was working as expected, although additional studies will 

be required to more fully utilize this new capability. 

Additional improvements were made in the booster 

system, which had an increase in its repetition rate from 

0.8 Hz to 1 .O Hz for operations and was tested up to 1.2 

Hz for studies. The average injection rate into the VUV 

Ring has shown almost a factor of two increase during this 

year (Figure 2), with injection time to fill the W Ring 

taking only about 3 minutes instead of 5 to 6 minutes. 

The faster injection rate will allow the operators to gradually work on improving the injection efficiency, since 

changes in the rate will appear more instantaneous as 

parameters are tuned, allowing a smoother search for the 

parameters which yield greater efficiency of injection. 

Along these same lines new diagnostics to measure the 

beam motion and current loss after injection were installed and testing started in FY 1996. These improved 

diagnostics already have allowed greater understanding of 

the beam motion and loss during injection. Improved 

radiation monitoring and shielding have been planned 

during this past year for installation in FY 1997. When 

these improvements have been successful in reducing the 

radiation on the VW floor and the second floor offices, 

then additional studies on the testing of the Top-Off 

method of injection will continue, with a goal of demonstrating the improved orbit stability possible with 

that method. 

89 
VUV STORAGE RING PARAMETERS AS OF NOVEMBER 1996 

Normal Operating Energy 

Peak Operating Current (multibunch ops.) 

Circumference 

Number of Beam Ports on Dipoles 

Number of Insertion Devices 

Maximum Length of Insertion Devices 

A@,) 

B(P) 

Electron Orbital Period 

Damping Times 

Lifetime @ 200 mA with 52 MHz 

(with 21 1 MHz Bunch Lengthening) 

Lattice Structure (Chasman-Green) 

Number of Superperiods 

Magnet Complement 

Nominal Tunes (vx, vJ 

Momentum Compaction 

RF Frequency 

Radiated Power 

RF Peak Voltage with 52 MHz (with 211 MHz) 

Design RF Power with 52 MHz (with 211 MHz) 

Synchrotron Tune (vJ 

Natural Energy Spread (o,/E) 

Bunch Length (20) 

(2Irm5 with 21 1 MHz Bunch Lengthening) 

Number of RF Buckets 

Typical Bunch Mode 

Horizontal Damped Emittance (EJ 

Vertical Damped Emittance (EJ 

Power per Horizontal milliradian (1 A) 

0.808 GeV 

0.85 amp (0.9 x 10l2 e-) 

51.0 meters 

8 

2 

- 2.25 meters 

19.9 A (622 eV) 

1.41 Tesla (1.91 meters) 

170.2 nanoseconds 

T~=T~= 13 msec; T~ = 7 msec 

360 min 

(590 min) 

Separated Function, Quad, Doublets 

4 

8 Bending (1.5 meters each) 

24 Quadrupole (0.3 meters each) { 12 Sextupole (0.2 meters each) 

3.14, 1.26 

0.0235 

52.886 MHz 

20.4 kW/amp of Beam 

80 kV (20 kV) 

50 kW (10 kW) 

0.0018 

5.0 x 

9.7 cm (I, < 20 mA) 

(36 cm) 

9 

7 

1.62 x 10" meter-radian * 

2 3.5 x meter-radian (2.8 x in normal ops.) 

3.2 Watts 

I, < 20 mA 

Arc Source Parameters 

Betatron Function (px,pJ 

Dispersion Function (q,, qx,) 

y = (1 +cx~,~)/~~,~ 

Source Size (ox, 0J 

Source Divergence (o,,,oJ 

1.18 to 2.25 m, 10.26 to 14.21 m 

0.500 to 0.062 m, 0.743 to 0.093 m 

0.738 to 0.970 m-l, 1.083 to 0.135 m-' 

536 to 568 pm, >60 to >70 pm (170-200 pm in normal ops.) * 

686 to 373 prad, 19.5 to 6.9 prad (55-20 prad in normal ops.) 

cx = -p' /2 -0.046 to 1.087, 3.18 to -0.96 X.Y X.Y 

X.Y * 

Insertion Device Parameters 

Betatron Function (p, pJ 11.1 m, 5.84 m * 

1240 pm, >45 pm (130 pm in normal ops.) * 

112 krad, >7.7 Frad (22 prad in normal ops.) 

Source Size (ox, OJ 

Source Divergence (ox., oY,) * is adjustable 

90 
Roger Klaffky Beamline Technical Liaison 

VUV BEAMLINES 

There were a number of technical beamline improvements on the W Ring during FY 1996. Beamline 

U3A was in a re-commissioning phase during FY 1996 

after extensive changes during FY 1995. New interlocks 

were installed and the monochromator was interfaced to 

the beamline control computer. In the next few years 

there will be a major upgrade of the U4A beamline from 

a toroidal grating monochromator to a spherical grating 

monochromator (SGM) design. An upgrade of the 

angle-resolved photoemission (ARP) chamber has begun 

with the installation of a cluster of metal evaporators and 

a thin film thickness monitor. A sample transfer and load 

lock system will be installed in the future. A new data 

acquisition computer for the ARP system has been acquired and Labview based software is being upgraded. At 

U4B a new high photon energy resolution SGM-based 

beamline was installed with most of its components 

coming from the U13UA beamline. A magnetic circular 

dichroism end station was constructed, installed and 

commissioned. 

Construction of the new U5UA SGM-based 

beamline took place and commissioning of this line was 

underway. A resolving power of about 10,000 was 

demonstrated at 30 eV photon energy. After commissioning is completed, the U5UA spin-resolved valence 

band photoemission program will resume with a 50 % 

General User allocation. 

There was extensive progress at the new U7A soft 

x-ray photoemission and absorption spectroscopy 

beamline. The SGM monochromator entrance slit was 

rebuilt; and installation of the downstream refocusing 

mirror and the surface chemistry end station with its 

lifting platform and kinematic mounting plate took place. 

The upstream refocusing mirror chamber and end station 

holder were delivered. The initial commissioning and 

debugging of the surface chemistry station began with 

preliminary unfocused beam experiments being performed. 

The U9B fluorescence detection system development was completed with the addition of a polarizer to the 

emission optics and the modification of detection electronics to determine photon polarization as well as wavelength and time of arrival. 

At the U13UB extreme ultraviolet lithography 

(EUVL) beamline, the Offner 1: I Ring Field camera was 

assembled and commissioned. It was used to image 

programmed mask defects down to 75 nm. The 1OX 

Schwarzschild EUV camera installation was also underway in FY 1996. 

Two modified ring vacuum chambers were installed 

during the Spring 1996 shutdown. The chambers incorporate a large IO0 horizontal by 50 vertical milliradian 

port for IR microscopes at UIO, and a 90 milliradian by 

90 milliradian port at U12. Construction and commissioning of IR beamlines at these ports will be underway 

in FY 1997. 

X-RAY BEAMLINES 

At XlA new high resolution zone plates were tested 

and put into operation. Commissioning of a cryogenic 

scanning transmission microscope and holography instrument began. This equipment is designed to study 

radiation sensitive biological specimens near liquid nitrogen temperature where the morphology is “frozen in”. At 

the end of FY 1996, the beamline was shutdown for a 

major upgrade to achieve higher spectral resolution and 

independent wavelength control. 

The X1 B monochromator performance was enhanced after the installation of a new holographically 

recorded laminar grating in May. Above 500 eV the 

photon flux increased by a factor of 5 to 10. As a result, 

high resolution measurements are now possible using first 

order of the grating over the first harmonic range oftheX1 

undulator (200 to 800 eV). 

The X2B microtomography data acquisition speed 

and spatial dynamic range were increased with the upgrade of the detector from a 5 12x5 12 200 kHz CCD to 

a 1024x1024 800 kHz CCD. 

At X5 equipment development continued in preparation for double-polarization measurements with circularly polarized gamma-rays and longitudinally-polarized 

nucleon targets. This equipment included: (i) a new 

91 
frozen-spin hydrogen-deuteride target that provides high 

polarization for both nuclear species, (ii) a new large 

acceptance detector array for measuring total reaction 

cross sections in both neutral and charged-particle channels, and (iii) circularly-polarized gamma-rays extending 

up to 400 MeV (with 2.584 GeVelectrons) and470 MeV 

(with 2.80 GeV electrons) using a new ring-laser system. 

The X9A beamline resumed operation as a white 

beamline. Design work was underway to upgrade X9A 

with the installation of a sagittal focusing monochromator and mirror for MAD crystallography. A new computer system running the NSLS-DAC software was installed onX9B for x-ray absorption spectroscopy. AnX9B 

upgrade planned for 1997 is the installation and testing of 

larger crystals that can accept over 200 mm of beam (12 

horizontal mrad) to increase the flux up to 3 fold. 

The XlOA hutch was extended to allow higher 

resolution and a 2D detector was implemented. A major 

upgrade of the X11A computer system was achieved with 

the installation of two Macintosh 7500 computers, one 

for data acquisition using the NSLS-DAC software, and 

the other for data analysis. 

At X12B a robotic fluid sample changer was implemented which allows for the automatic injection of small 

(100 microliter) liquid samples into a fured observation 

cell and for subsequent recovery. An in-vacuum attenuatodshutter mechanism was installed. The flight paths 

and theta-arm detector mount points were in the process 

ofbeing rebuilt to accommodate aMar scan head. Finally, 

portable visualization and data reduction sobare for 2D 

diffraction images was developed. 

The X13B beamline was modified to allow experiments to be conducted inside a hutch. A new spherical 

grating monochromator for X13A was designed and 

ordered for circular dichroism measurements using the 

elliptically-polarized wiggler (EPW). The EPW began 

100 Hz operation during Summer 1996. 

White beam was brought into theXl6C hutch and 

a pair of Kirkpatrick-Baez mirrors were used to produce a 

4 micron by 25 micron white or monochromatic focal 

spot size. 

At X19A a solid state multi element detector, developed in collaboration with the BNL Instrumentation 

Division, was put into operation. The detector has 250 

-350 eV resolution and is used for spectroscopy and 

scattering applications. Also, plans we made to replace the 

X19A zerodur mirror which was discovered to be damaged by synchrotron radiation. 

At theX19C beamline, new motor control electronics were installed. There were a number of changes and 

upgrades in the x-ray topography hardware. A high precision scanning stage was installed, enabling imaging of six 

92 

inch diameter wafers. A high resolution digital camera 

was purchased to enhance image processing capability. 

Projects that were in progress included the addition of an 

analyzer crystal axis to the goniometer detector arm. The 

analyzer will allow analysis of the diffracted beam harmonic content. Also, the attachment ofa CCD camera to 

the goniometer was underway. There were also upgrades 

in the surface scattering spectrometer. A very high precision, short travel sample stage was installed and the long 

travel stage was upgraded with an optical encoder. New 

motorized Huber slits were installed and motorized fixed 

small gap slits were designed and tested. 

The X21 phase I1 beamline was commissioned 

during FY 1996. The monochromator is tunable from 

5 keV to 10 keV with 0.2 eV energy resolution. On the 

X22A beamline a vertically-focusing mirror was added 

which simplifies many experiments by eliminating harmonic contamination. The X22B computer was upgraded. A gear reducer was added to the spectrometer 

table allowing vertical motion without the loss of steps. 

Also, a new elevator was added to the spectrometer, 

enhancing mercury and Langmuir trough measurements. 

The X23B collimating mirror was replaced providing an 

improved energy resolution of less than 2.6 eV at 6 keV. 

The monochromator bearings were replaced and the 

crystal re-etched, and an additional degree of freedom was 

provided for crystal alignment. 

The X24A beamline was upgraded with the installation of a new first mirror, increasing the flux by a factor 

of two. At X27A a new control system using Labview with 

a graphical user interface was under development. A 

hydraulic powered vertical scan stage was installed to give 

better control of the exposure rate for micromachining 

experiments. 

Just prior to the December 1995 shutdown, a test 

was performed which entailed firing the X24 front end 

fast valve with a 10 mm thick molybdenum blade when 

there was 408 mA of stored beam current. The exposure 

time was 1.93 seconds, to simulate the heating that would 

occur at 500 mA beam current for a 1 second exposure, 

which is the time it takes for the front end mask to close 

after a fast valve is fired. The blade successfully withstood 

the exposure to the x-ray beam, indicating that it will not 

be necessary to dump the X-Ray Ring when a fast valve 

fires after the stainless steel blades are replaced with 

molybdenum blades. During FY 1996 molybdenum 

blades were installed on the X9, X19 andX24 front ends. 

More blade replacements will occur during future shutdowns. There has been a major effort to design and build 

new fast valve sensor boxes and interface boxes. The new 

sensor boxes have been tested and calibrated. They have 

CMOS electronics to provide improved noise rejection 
and they have troubleshooting indicators. The new 

interface boxes have a capacity of 3 sensors per beamline 

and provide for individual lock-out of each sensor. The 

system will be interfaced to the NSLS computer system 

for display on the present X-Ray Beam Line 

Status Channel. 

93 
Roger Klaffky X-Ray Ring Manager 

The X-Ray Ring usage for FY 1996 is broken down 

by categories in Figure 1. There was a 7% increase in 

operations largely resulting from a 25% decrease in downtime and a 9% decrease in the time allocated to maintenance, studies, and conditioning. There were a total of 

1081 Ampere-hours of operations. The monthly integrated Amp-hrs are shown in Figure 2. 

The X-Ray Ring active interlock system certification for all insertion device straight sections was completed in Fall 1995 when the calibration and linearity of 

the last straight section system (X13) was verified up to 

350 dduring 25 bunch operation. The active interlock 

pre-fill test was modified to test the 6 different active 

interlock chains simultaneously so that only one injection 

is required for the test. This reduced the testing time from 

15 minutes to 2 or 3 minutes. The number of pre-fill test 

failures was reduced by accounting for the non-linear 

response of the orbit to the trim strengths. 

To enable operation of the orbit measuring pick-up 

electrodes (PUEs) from 7 mA (for active interlock pre-fill 

1 X-Ray Ring Time Usage I 

1 

Figure 1: The Breakdown of the X-Ray Ring usage 

based on total time (not scheduled time) for FY 1996. 

94 

tests) to 434 mA, the AGC dynamic range was extended 

from 35 dB to 55 dB for all the PUEs. In addition, band 

pass filters were installed before every PUE switch to 

prevent saturation of the PUE receivers in single bunch 

operation. The resolution ofthe PUEs was increased from 

14 to 16 bits, improving the orbit position resolution 

from 2 microns to 0.5 microns. 

During the December 1995 shutdown, a change in 

the RF2 damping antennae configuration successfully 

removed the horizontal and vertical beam size changes 

that had occurred at specific XRF2 tuner positions ( i.e. 

higher order modes) during a fill. Changes in several load 

resistors on the XRF3 anntennae resulted in a several-fold 

decrease in the beam size changes occurring at the resonance position. 

After studies demonstrated that the effects on the 

horizontal and vertical orbit of running the Elliptically 

Polarized Wiggler (EPW) at 100 Hz were compensated, 

100 Hz operation commenced in Summer 1996. At 100 

Hz, there is a significant improvement in the signal-to2 100 

0 

X 

4: e 50 

0 

Oct Dfx Feb Apr Jun Aug I 
noise ratio for magnetic circular dichroism experiments. 

Studies on a lattice with a factor of 2 reduction in 

horizontal emittance continued to progress during FY 

1996. During the midnight studies shifts there were 

several successful trial runs of the digital orbit feedback 

system in either the horizontal or vertical planes, and also 

in both planes simultaneously. This sytem is close to an 

operational state in the vertical plane. In the horizontal 

plane, studies have shown that even though the digital 

feedback system does a better job of keeping the orbit fixed at the PUEs, the horizontal ring chamber motion over each 12 

hour fill may cause the orbit to show greater 

horizontal motion with the digital feedback system. This is not a problem in the 

vertical plane since the chambers show 

little motion vertically. Sensor stands were 

fabricated for installation during the December 1996 shutdown. The chamber 

motion will be mapped out around the ring 

as afunction ofring current. This information will be used to remove the horizontal 

orbit changes caused by the PUEs moving 

with the chamber. 

There were also studies to demonstrate the feasibility of running the X-Ray 

Ring at 2.8 GeV and to determine the 

impact of 2.8 GeV on experimental 

beamlines. In Spring 1996 a ramp from 

744 MeV injection energy to 2.8 GeV was 

established and skew quadrupoles were 

adjusted to maintain the small vertical beam 

size present during 2.584 GeV operation. 

In August it was demonstrated that 250 

mA of beam could be reliably ramped to 

2.8 GeV, as had been previously predicted 

from RF power considerations. In the 

future, studies will be conducted to determine if the dual hybrid RF power amplifier 

installation on RF System 2 in December 

will increase the 250 doperational limit. 

The maximum allowable current at 2.8 

GeV is 320 mA, as determined by ring 

vacuum chamber heating limits. Careful beamline measurements were performed on the XI 9A beamline at 100 

d beam current at both 2.584 GeV and 2.80 GeV. The 

ratio of the third harmonic to fundamental was determined from rocking curves of the X19A second Si(l11) 

monochromator crystal. The factor by which this ratio 

increases at 2.8 GeV was in good agreement with calculated flux ratios at the two energies. A 2.8 GeV Users 

Executive Subcommittee will conduct a survey of users in 

the future as to the desirability of 2.8 GeV operation. 

Beam “drop-out’’ studies indicated the possibility of 

producing substantial levels of high energy gamma ray 

bremsstrahlung radiation in the straight sections during 

single and five bunch operation. In these few bunch 

operational modes, the high peak currents heat the injection septum and other straight section ring components 

causing elevated gas pressures and increased bremsstrahlung radiation. The gamma rays can scatter off beamline 

optical components producing detectable radiation levels 

near these components. Radiation monitors were installed on the straight section beamlines to alert users to 

the presence of radiation. 

In addition, levels from these monitors are displayed 

in the Control Room and are logged on the NSLS 

computer history program. Operators have been instructed to close shutters if the beam lifetime is reduced to 

a few hours. 

95 
In preparation for the December 1996 shutdown, 

water lines have been installed that will bring BNL 

Central Chilled Water Facility (CCWF) water to the 

NSLS experimental water system in Mechanical Equipment Room A. The control valve/controller installation 

for this system in underway with completion expected 

before December. This system will significantly improve 

temperature regulation with the present NSLS system 

providing redundancy in case the CCWF goes down for 

maintenance. Since tuning of the new control system 

requires operational beamlines, there will be variations in 

the experimental water temperature when operations first 

resume in January 1997. 

Since the present Biology cold rooms are cooled by 

the CCWF water, there is a problem on maintaining 

biological samples if there is a CCWF failure since there 

is no automatic backup cooling. Over the past year, there 

have been several instances where samples were lost when 

the CCWF went down. To address this problem, procedures were established so that Operations Coordinators 

can valve off the CCWF water when it is down and open 

valves to provide domestic water for cooling of the cold 

room compressors. In the future this changeover will be 

automated. 

A major effort during the December shutdown will 

be the installation of new beryllium windows to enable 

350 mA operation in January 1997. The design of the 

windows was completed and orders placed for delivery in 

November 1996. 

96 
X-RAY STORAGE RING PARAMETERS AS-OF NOVEMBER 1996 - 11 

Normal Operating Energy 

Maximum Operating Current 

Lifetime 

Circumference 

Number of Beam Ports on Dipoles 

Number of Insertion Devices 

Maximum Length of Insertion Devices 

hJEJ at 1.25 T (B) 

hc(EJ at 5.0 T (W) 

Electron Orbital Period 

Damping Times (2.584 GeV) 

Touschek (2.584 GeV, 0.25A) 

Lattice Structure (Chasman-Green) 

Number of Superperiods 

B(P) 

Magnet Complement 

32 Sextupole 

Nominal Tunes (v, vS 

Momentum Compaction 

R.F. Frequency 

Radiated Power for Bending Magnets 

R.F. Peak Voltage 

Design R.F. Power 

vs (Synchrotron tune) 

Natural Energy Spread (oJE) 

Natural Bunch Length (20) 

Number of RF Buckets 

Typical Bunch Mode 

Horizontal Damped Emittance (EA 

Vertical Damped Emittance (EY) 

Power per Horizontal milliradian (0.25A) 

2.584 GeV 

0.30 amp (10" e) 

-20 hours 

170.1 meters 

30 

5 

< 4.50 meters 

2.23 A (5.6 keV) 

0.56 A (22.2 keV) 

1.25 Tesla (6.875 meters) 

567.2 nanoseconds 

T~ = zy = 6 msec; zE = 3 msec 

227 hrs (vRF = 700 kV) 

Separated Function, Quad Triplets 

8 

16 Bending (2.7 meters each) 

40 Quadrupole (0.45 meters each) { 16 Quadrupole (0.80 meters each) 

(0.20 meters each) 

9.15, 6.20 

0.0056 

52.88 MHz 

144 kW/0.25 amp of Beam 

1000 kV 

400 kW 

0.002 

8.6 x loe4 

10.5 cm 

30 

25 

1.0 x lo7 meter-radian 

1 x meter-radian 

23 watts 

-. Arc Source Parameters 

Betatron function (p,pJ 

Dispersion function (qx,qx,) 

r,, = (1 +~,,Y')/P,, 

Source size (opJ 

Source divergence (ox,,oy) 

1.0 to 3.8 m, Z9 to 26.5 m 

0.47 to -0.1 1, -0.39 to 0.22 

0.952 to 0.962 m-l, 0.81 to 0.52 m-' 

371 to 565 pm, 27 to 49 pm 

439 to 324 prad, 8 to 7 prad 

ax,y = -P.,J2 -0.49 to 1.62, -3.4 to 4.5 

. Insertion Device Parameters 

Betatron function (p,p,) 

Source divergence (ox,,oy.) 

1.60 m, 0.35 m 

260 prad, 35 krad 

97 
Beamline X3B1: Polyhedral representation of the structure of a novel framework comprised 

of [Ge,SJ4- adamantine-clusters (red) linked by trigonal A@,-units (blue). The material was 

synthesized hydrothermally and its structure determined utilizing data collected on a 36 pL 

single crystal using an x-ray synchrotron/imaging plate combination at the X3A1 beamline. 

Each cluster consists of 4-corner linked germanium-centered sulfide tetrahedra. 

J.B. Parise and K. Tan, “Synthesis and structural characterization using synchrotron radiation 

of [(C6H,,N,)2(H,0)(H,0)~[AgCe4S,o] (Dabco-AgGS-SB2): knitting sulfide metal clusters to form 

frameworks, Khem. SOC., Chem. Comm., 1687 (1996). 
PROJECT

z 

x 
LABORATORY: A WORK IN PROGRESS 

Erik D. Johnson 

SDl Project Manager 

The objective of the Source Development Laboratory (SDL) is to facilitate the coordinated development of 

sources and experiments to produce and utilize coherent 

sub-picosecond synchrotron radiation. It is part of the 

fabric of accelerator technology development at 

Brookhaven, and of amplifier based free electron laser 

(FEL) development internationally. The NSLS provides 

much of the intellectual drive for this community, as well 

as support for the SDL experiments. Fundamental theoretical and experimental contributions have been made to 

the field by NSLS physicists. Without this groundwork, 

stretching back over more than a decade, the SDL program, and indeed those of other laboratories, would not 

exist as we now know them. Of particular note are the 

development of high current - high brightness eIectron 

beam technologies at the Accelerator Test Facility, and 

the theoretical framework for high gain FELs and 

subharmonically seeded single-pass FELs. These are the 

BNL "home-grown" cornerstones of the ultra-violet FEL 

experiments to be undertaken at the SDL. 

For the NSLS, the SDL represents a new opportunity for its user community. The ultra-violet FEL (UVFEL) will operate to wavelengths below 100 nm, and will 

produce radiation with substantially shorter pulses than 

are available from the VUV Ring (as brief as 5$!) with 

peak power ranging from hundreds of Megawatts to as 

high as 100 Gigawatts for the shortest pulses. The 

bandwidth of the FEL can to some extent be controlled 

within the constraints of the Fourier 

transform limited nature of the source 

(trading pulse length for bandwidth). In 

terms of peak power, this source will 

open territory completely uncharted by 

existing tunable sources. From the standpoint of average power however, the 

picture is not nearly as exciting. The 

repetition rate available from the SDL 

linac will be at most IO Hz, so for many 

experiments, the SDL will be a site for 

"proof-of-principle" studies. None the 

less, it will provide a new tool for the 

study of nonlinear and ultrafast phenomena. Furthermore, once the principles have been demonstrated, the selection of a different linac or linac technology could increase the repetition rate 

to kiloHertz or higher. One might then 

reasonably askwhy not incorporate these 

capabilities from the outset? The answer 

lies in the costs, the budgets, and the 

obligations of the NSLS. No one reading this annual report will be amazed by 

the statement that budgets have been 

100 
extremely tight in recent years, which makes long range 

planning and investment especially difficult. Nor would 

the statement that NSLS takes its obligations to its user 

community very seriously meet with any surprise, The 

NSLS management and staff continue their commitment 

to attain the highest possible reliability and availability of 

the storage rings, while pushing their performance to the 

greatest extent possible. However, they also recognize 

their responsibility to explore new source technologies, 

and have embarked on a program of source development 

which to the greatest extent possible utilizes existing 

hardware. 

These factors account for the 10 Hz repetition rate 

limit for the facility, since that was the design point for the 

230 MeV linac built as an injector for the SXLS project. 

So while significant modifications to the linac are required 

to make it a suitable driver for an amplifier FEL, it 

provides a huge head start on the SDL accelerator. Similarly, the main undulator for the FEL experiment is 

recovered from an Army program for a high average power 

FEL, which is another major element of the facility. The 

electrical work for control of the 10 meter long NISUS 

undulator was completed this year in collaboration with 

STI Optronics, although the required vacuum modifications are being deferred until the completion of the linac 

installation. An NSLS/ATF designed photocathode gun 

is being built for the SDL in collaboration with SLAC and 

UCLA, and a magnetic pulse compressor will be installed 

to achieve the high brightness-high peak current electron 

beam required for short wavelength FEL amplifier operation. New diagnostics and controls are also in the process 

of being implemented on the linac. Building 729 even 

required some expansion to house the SDL accelerator, 

which was completed last year. Further modifications to 

the building, including the chilled water system and the 

installation of an overhead crane, were completed this 

year. Early in 1997 the machine water system and a class 

1000 cleanroom to house the laser will be installed, 

completing the "infrastructure" modifications required 

for the SDL. The focus of activity in the coming year will 

be the installation and commissioning of the linac. Experiments in non-linear emittance correction and pulse 

compression are planned, as well as studies to examine 

various aspects of emittance degradation, which could 

have a significant impact on the range of FEL operations 

which are possible. Assembly of the machine to undertake 

actual FEL experiments will follow as soon as possible. 

The actual time table for the SDL is very sensitive to the 

available resources. The same can be said of many other 

"fourth generation" source projects hence, where reasonably possible, some aspects of the project are being 

pursued in collaboration with institutions who have programs with technological requirements similar to those of 

the SDL. In addition, the BNLmanagement continues to 

support the effort through significant LDRD contributions, although the availability of NSLS staff and other 

department resources plays a major role in setting the pace 

of the project. So, while maintaining its high standard for 

supporting the operation and utilization of the existing 

storage rings remains the first priority for the department, 

the NSLS remains committed to moving: forward with the " 

SDL, making it very much, a work in progress . . 

101 
llan Ben-Zvi 

ATF Head 

THE ATF - A USERS’ FACILITY 

WITHIN A USERS’ FACILITY 

The Accelerator Test Facility (ATF) is a User’s 

Facility for accelerator and beam physicists, operated by 

the NSLS and the BNL Center for Accelerator Physics. 

There is no other proposal-driven, peer-reviewed facility 

like the ATF that is dedicated for long range R&D in 

accelerator and beam physics. In addition to its singular 

role the ATF has also a unique combination of a highbrightness electron beam, synchronized, high power lasers and a well equipped, 3 beamline experiment hall. The 

high brightness electron beam of the ATF, produced by a 

laser-photocathode RF gun, make it an ideal site for R&D 

on Free-Electron Lasers (FEL). The ATF receives funding from the DOE and the laboratory directorate as well 

as important support from the NSLS. The NSLS has an 

active program in R&D in the production of shortwavelength coherent radiation through its involvement in 

the ATF. Taking advantage ofthe expertise and hardware 

that accumulated at the ATF, the NSLS is pursuing a 

program that touches the most fundamental issues of 

short wavelength FEL R&D today, such as the development of electron sources, single pass FEL experiments and 

more. 

TOWARDS A BRIGHTER SOURCE 

Electron beams with a high density of electrons in 6- 

D phase space are the keystone for future high performance machines such as X-ray Free-Electron Lasers and 

linear colliders, as well as the generation of intense subpicosecond x-ray pulses through the process of Compton 

back-scattering of laser pulses off the electron beam. The 

length of both accelerator and wiggler of any shortwavelength FEL will decrease sharply with improved 

beam brightness. In a remarkable case of parallel evolution, this work is also important to High Energy Physics 

for the construction of future linear colliders. Thus the 

ATF is enjoying considerable support from the DOE 

Office of High Energy Physics. R&D at the ATF on the 

generation of high brightness beams placed the NSLS in 

an international leadership position. The electron gun of 

the ATF generates its high current, low emittance beam 

by irradiating a high-quantum-efficiency metal-cathode 

in the presence ofvery high intensity RF electric fields. A 

new magnesium photocathode has demonstrated an order-of-magnitude increase in quantum efficiency with a 

(so far) unlimited lifetime. The ATF is leading two new 

collaborations for the development of RF guns, one with 

SLAC and UCLA, and the other with Japanese collaborators. The ATF’s gun is now recognized internationally as 

“The BNL Gun” and versions of it are in use in many 

places around the world as well as in BNL’s Center for 

Radiation Chemistry Research and soon at the Source 

Development Laboratory. 

THE USERS OF THE ATF 

Among the fourteen currently approved experiments on the ATF, there is a number of experiments 

dedicated for research into novel radiation generating 

processes, from the IR to x-rays. Among these are some 

FEL experiments and an experiment in the generation of 

Smith-Purcell radiation and Compton back-scattering. A 

few of them are centered about ATF beamline #3, where 

a microundulator oscillator experiment is nearing operation and others are conducted on beamline #2, like the 

High Gain Harmonic Generation FEL, or beamline #1, 

like the Smith-Purcell experiment and the Compton 

back-scattering experiment. A superconducting 68 period micro-undulator (with a period of 0.88 cm and 0.5 

Tesla peak field at a gap of 0.44 cm) has been developed 

at the NSLS. Prototypes of this undulator (up to 23 

periods long) were built and performed extremely well in 

superconducting tests. The field errors of the undulator 

were very low as constructed, making this perhaps the first 

undulator that will require no trimming after manufacture. The FEL experiment makes use of the short period 

of the undulator and the low emittance beam generated by 

the RF photocathode gun to operate at 500 nm with a 50 

MeV electron beam. Since the ATF electron beam energy 

is currently at about 70 MeV, lasing at below 250 nm 

should be possible. The technology developed for this 

102 
undulator will be used to develop a 4 to 5 mm period, 

small gap undulator prototype for the National Synchrotron Light Source X-Ray Ring. 

An MIT group is carrying out a test of a pulsed 

microundulator. This undulator, which is currently installed on the beamline, has parameters that are very 

similar to those of the superferric undulator. Spontaneous 

emission has already been observed from this device and 

preparations are under way to get lasing in the near future. 

A third user group is from Columbia University. They 

will be using the oscillator experiment for studies of 

spiking and optical guiding in FELs. 

The high-gain harmonic-generation experiment will 

be located on beamline #2. This experiment is carried out 

by a NSLS group headed by Li-Hua Yu. In the first stage 

of this experiment, done in collaboration with the Advanced Photon Source, a two meter long undulator (a 

prototype of Undulator-A built by Cornell) will be installed to study single pass FEL gain, start-up from spontaneous emission and saturation. The next step of this 

experiment will be done in collaboration with Northrop 

- Grumman, which is providing many components of the 

undulator for the experiment. This undulator is a derivative of the superconducting micro-undulator of thevisible 

FEL oscillator. It uses the same principle of a continuous 

yoke but has parabolic pole faces for two-axis focusing and 

four distinct regions: a 

prebunching undulator, a dispersive section, an exponential 

growth section and a tapered section. This experiment emulates 

the FEL physics of the NSLS 

approach to VUV FELs. This 

approach is based on single pass, 

seeded FEL amplifiers driven by 

Ti:sapphirelasers. The finalstage 

of harmonic generation is being 

done in the FEL. The principle 

of high-gain harmonic-generation will be tested and characterized in these experiments, as well 

as the superconducting 

undulator, the undulator diagnostics, error and alignment studies and tapering control. Another 

experiment at beamline #2 has 

recently broken the world record 

for Inverse FEL acceleration of 

electrons. This experiment, 

headed by Arie van Steenbergen, 

used the high-power CO, laser 

of the ATF and a special variable 

period wiggler to impart 2% acceleration to a 40 MeV 

beam, using about 0.5 GW of the CO, laser. This 

experiment, which is like an FEL amplifier operated in 

reverse, is motivated by the interest to develop a compact, 

high-gradient electron accelerator. 

ACCELERATOR R&D AND 

GRADUATE EDUCATION AT THE ATF 

Two significant experiments have been recently 

reported by the ATF staff. The first is a measurement of 

the slice-emittance of an electron bunch from the ATF 

electron gun. This newly developed technique makes it 

possible to study in detail the longitudinal dependence of 

the transverse beam-matrix of short slices with 1 picosecond resolution. The slice-emittance measurement enabled us to examine the evolution ofthe beam while it goes 

through the important emittance-compensation process. 

Emittance compensation is a linear correlation-removal 

process that has led to the improvements in photocathode 

RF gun beam brightness and to the recent enhanced 

interest in x-ray FELs. The slice-emittance measurement 

should allow us to do non-linear emittance corrections 

that promise even better x-ray FELs. The second development is the observation of micro-bunching of the ATF’S 

beam. Under certain conditions it is possible to obtain 

103 
and Marcus Ba 

sub-picosecond long bunches with a high charge and 

good emittance. This happens when the photocathode 

laser is adjusted to a small phase, leading to bunch 

compression in the drift space between the gun and the 

linac. One picosecond bunch length have been measured 

(using a variation of the slice emittance set-up). Much 

shorter bunches are predicted theoretically, but await a 

further refinement of Eric Blum’s coherent radiation 

detector. Eric has already observed coherent radiation 

from the ATF’s beam. An installation of a spectrometer 

will allow sub-picosecond bunch length measurement. 

The motivation for this R&D is that sub-picosecond 

bunch length, high brightness electron beams can generate high-intensity, sub-picosecond radiation from the farIR to x-rays. 

As a result of the bunch compression, the bunch 

length of the ATF can be changed easily from about 10 

picoseconds to under one. If this bunch is collided with 

an energetic pulse from the ATF’S synchronized CO, 

laser, a pulse with the same short length of x-rays is 

produced. Compton back-scattering of lasers by electrons 

is a unique x-ray source. Preliminary estimates indicate 

that it should be possible to generate elliptically polarized 

2x108 photon pulses of 8 keV x-rays using the ATF’S 

future 1 Tw CO, laser and its 70 MeV linac. A contract 

for the construction of parts for the ATF’S compact 

picosecond Terawatt laser has been signed last year. 

In a significant contribution to the education of 

future generation of accelerator physicists, eight graduate 

students have finished their thesis at the ATF and six 

others (from Columbia, MIT, Stanford, Stony Brook 

UCLA and the University of New Mexico) are currently 

doing thesis research at this facility. More information on 

the ATF can be found on the World Wide Web, with a 

hyperlink from either the National Synchrotron 

Light Source or BNL Home Pages. 

104 
Frank Tewano 

Mike Kelly 

Although there was no major construction at the NSLS during FY 1996, a number of facility related projects were 

accomplished and initiated. 

BUILDING #725 RAMP TO INNER 

X-RAY RING AREA 

The driveway which provides access to the inner 

courtyard of the x-ray ring was resurfaced and regraded. 

This was done to prevent puddles from occurring and 

eroding the concrete over the X-Ray Ring and x-ray power 

supply areas. 

BUILDING #725 TURNAROUND 

The circular drive at the main entranceway to 

building 8725 was becoming unsightly due to cracks and 

puddles resulting from uneven grading. When combined 

with freezing temperatures, the puddles presented a safety 

hazard as well. The area was resurfaced and graded thus 

eliminating the puddles and improving the overall appearance. 

COOLING TOWER REPLACEMENT 

A jointly funded NSLS/BNL Plant Engineering 

Division project has been implemented for the replacement of the sixteen year old Baltimore Cooling Tower on 

the roof of building #725. This is one of two cooling 

towers which are part of the NSLS “in house” chilled 

water system. This system provides coverage during shutdowns of BNL’s central chilled water facility which is 

becoming our primary source of machine and comfort 

cooling. The tower was purchased during late summer/ 

early fall, with installation completed in December 1996. 

EXPERIMENTAL WATER UPGRADE 

The connection of the experimental water system is 

the final phase of the NSLS hookup to BNL‘s central 

chilled water facility. This project gives the NSLS the 

added reliability and operating flexibility of being able to 

cool the experimental water system from both the central 

chilled water system and the NSLS “in house” chilled 

water system. Installation will be completed during the 

December 1996 shutdown. 

BUILDING #729 TWO TON 

BRIDGE CRANE 

This Project installed an overhead crane to cover 

approximately ninety percent of the floor area in building 

#729, which houses the Source Development Laboratory. 

IMPROVEMENTS TO THE 

EXPERIMENTAL FLOOR AREAS 

Recognizing the concerns expressed in the responses 

to a DOE survey of NSLS users taken in the Spring of 

1996, we have taken steps to remedy three commonly 

repeated themes; seating, sound levels and lighting. 

During the summer months, over two hundred new 

multi-adjustable swivel arm chairs were purchased and 

distributed throughout the X-Ray and W experimental floor areas. These chairs have replaced the worn out 

“old gray chairs”, adding much to the comfort and 

appearance of the facility. 

Sound surveys had been performed around the XRay and VUV Ring areas in 1994 both before and after 

sound insulating panels were installed in the VW area. 

Recently in the summer of I996 soundsurveys were again 

conducted and experts are being consulted in a continuingeffort to minimize noise levels. Results ofthese surveys 

can be found on a poster in the main lobby of building 

#725. Comments or suggestions are invited. 

A 400 Watt mercury vapor lamp fixture was installed over the main entrance area to the VW Ring 

on a trial basis. This fixture has replaced the original 

250 Watt high pressure sodium lamp which is the type 

currently used throughout the experimental areas. The 

mercury vapor lamp is brighter and sheds a whiter “daylight” type oflighting than theyellow and dimmer sodium 

lamp. The feedback from the users in the area has been 

generally favorable and we are currently in the process 

of obtaining estimates for the replacement of all the 

lighting fEtures on the X-Ray and VUV experimental floor. 

105 
Peter M. Stefan 

Sam Chi-Chang Kris% ao 

On the NSLS X-Ray Storage Ring, the XI 3 straight 

section and beamline have been used for insertion-devicerelated R&D since 1990. The development work at X13 

has succeeded in significantly advancing the state-of-theart in important aspects of insertion device design, and the 

light sources produced have the promise of delivering 

significant new capabilities for the NSLS user community. Three important projects will be described below: 

the Prototype Small-Gap Undulator (PSGU), the invacuum undulator (IVUN), and the Time Varying Elliptically Polarized Wiggler (EPW). The PSGU and the 

EPW are presently installed for use at X13. IWN is 

under construction, and in Spring of 1997 it will be 

installed at X13, replacing the PSGU. 

SMALL-GAP UNDULATORS 

The PSGU [ 1,2] combines a short-period (1 6 mm) 

undulator magnet and a variable-aperture vacuum chamber to produce high-brightness undulator light with a 

higher photon energy in the fundamental than would 

otherwise be possible in the X-Ray Ring. The PSGU was 

built in a collaboration between the NSLS and Rockwell 

International Rocketdyne Division. Rocketdyne built 

the permanent magnet arrays. The light produced by the 

PSGU is concentrated in the fundamental and in a few 

higher harmonics, as illustrated in Figure 1 for a magnet 

gap of 7.5 mm. The brightness is between 100 and 1000 

times that of the X-Ray Ring bend magnet sources, while 

the flux in the fundamental is about equal to that from 8 

milliradians of the bend magnet. 

Photons from the PSGU have been used to develop 

a coherent x-ray beam for X-ray Photon Correlation 

Spectroscopy (XPCS). A coherent beam of 3x109 photons/sec at 3 keV (4. IA ) was produced through a IO pm 

pinhole. 

The long straight sections of the NSLS X-Ray Ring 

(such as the X13 straight) are particularly well-suited for 

small-gap insertion devices. The stored electron beam 

focuses to a minimum dimension both in the vertical and 

in the horizontal at the center of the long straight. The 

same strong focussing occurs for an imaginary tube surrounding the electron beam, which represents a “stayclear” aperture. As long as the vacuum chamber stays 

outside the stay-clear region, the beam lifetime is unaffected. Therefore, the PSGU is installed in the center of 

the straight section, and is quite short. The minimumaperture-region of its variable vacuum chamber is 390 

mm long, and the undulator magnet arrays are 320 mm 

long. In the regions closest to the electron beam, the 

PSGU vacuum chamber is thinned to 1 mm. The magnet 

106 
arrays are in air, located just outside the thinned vacuum 

chamber. The magnet gap is always at least 3 mm greater 

than the vertical aperture of the vacuum chamber for the 

electron beam. 

One of the most important studies conducted with 

the PSGU determined the vertical dimension of the stayclear tube mentioned above, and measured the reduction 

in the electron beam lifetime as the variable vacuum 

chamber cut into this tube. The results are illustrated in 

Figure 2. The lifetime was essentially unaffected to a full 

aperture of 4 mm, but then started to decrease. In a 

practical sense, an aperture ofabout 3 mm is operationally 

acceptable, since the overall lifetime reduction is small. 

In order to take full advantage of the ability to run 

with a 3 mm aperture, we are pursuing an in-vacuum 

undulator project (IVUN). This is a logical extension of 

the PSGU, with thevariable vacuum chamber eliminated, 

and the undulator magnet arrays placed directly in the 

storage ring vacuum. For IVUN, the magnet gap and the 

corresponding electron beam aperture are very nearly the 

same dimension. A comparison between the parameters 

of the PSGU and IVUN is presented in Table 1. 

~ ~ ~ ~ 

Table 1: PSGU/IVUN Comparison 

Period Xu 

Nominal Magnet Gap 

Corresponding 

Maximum Beam Aperture 

Peak On-Axis Field 

PSGU 

16mm 

6.0 mm 

3.0 mm 

0.623 T 

2.77 keV, (4.48 A) 

IVUN 

11 mm 

3.3 mm 

3.0 mm 

0.678 T 

4.64 keV, (2.67 A) 

The rVUN design goal is for a photon output at 4.6 

keV (2.7A) in the fundamental, with high flux at the 

second and third harmonics, at a magnet gap of 3.3 mm. 

Experiments spanning the whole spectrum of synchrotron-light applications, from spectroscopy and diffraction 

to microscopy and scattering, can benefit from this highbrightness, high-flux source. In addition the electron 

beam characteristics of the X-Ray Ring allow IVUN to 

produce good second-harmonic intensity on-axis, at just 

over 8 keV, with a half-intensity bandwidth of over 2 

keV. IVUN is being built in a collaboration between the 

NSLS and the Japanese Spring-8 Project. Our collaborators at Spring-8 worked on the first successful in-vacuum 

undulator and are fabricating the 11 mm-period magnet 

arrays for IVUN. When installed in the X13 straight 

section, IWN will replace the PSGU,which is now 

situated at the center of the straight. Studies are planned 

to begin in the Summer of 1997. 

107 
TIME VARYING ELLIPTICALLY 

POLARIZED WIGGLER 

The Time Varying Elliptically Polarized Wiggler 

(EPW) [3] is a very different kind of insertion device, 

comparedwith the PSGU or IVUN. As the name implies, 

it produces elliptically-polarized light on axis, with the 

sense of rotation of the field vectors, i.e. the helicity, 

alternating at up to 100 Hz. The EPW was built in a 

collaboration between the NSLS, the APS at Argonne 

National Lab, and the Budker Institute ofNuclear Physics 

at Novosibirsk. Usable fluxes of photons are available 

from 100 eV to 10 keV, with the measured degree of 

circular polarization exceeding 50%. Such a source is 

extremely useful for circular dichroism studies of both 

magnetic materials and materials with natural optical 

activity. The stable alternation of the helicity, at frequencies up to 100 Hz, is an extremely powerful aspect of the 

source. This allows gating or lock-in techniques to 

separate the responses of the sample to opposite helicities. 

When a lock-in amplifier is used, any steady-state or 

background signals are summarily removed from the 

start, since the lock-in only detects the signals which 

follow the EPW reference signal. Adjustment of the lockin phase selects the sample response to the individual 

helicities. This holds the promise of being a very sensitive 

probe for circular dichroism. 

The concepts [4] behind the EPW are also quite 

interesting, and may be explained as follows: First consider the synchrotron light emitted by a bend magnet 

source in a storage ring. In the NSLS X-Ray Ring, as 

viewed from above, the electron beam enters a bend 

magnet and makes a gentle turn to the right. The light 

emitted into the horizontal plane (which contains the 

electron beam path) is linearly polarized, with the electric 

field vector contained in this same plane. Light directed 

above or below the plane is elliptically polarized, with 

opposite helicity above and below. In a normal wiggler, 

the electron beam makes a bend to the right, then one to 

the left, etc. The polarization of the output light from the 

wiggler is linear everywhere, that is, in the plane of the 

wiggles and above and below. This is due to a cancellation 

of the elliptical nature of the right turns by the kef2 turns. 

In the EPW, a special electromagnet adds vertical deflection to the electron trajectory, as illustrated in Figure 3. 

The right and left turns are twisted out of the horizontal 

plane, but with all the right turns twisted up and the left 

turns twisted down. The photons illustrated in the figure 

were initially directed parallel to the z direction, before 

the twists were applied. As a result, the light which is now 

directed parallel to the z direction comes from below the 

plane of the right turns and above the plane from the left 

turns. Thus, it is elliptically polarized, with the two types 

of turns re-enforcing each other. When the current flow 

in the electromagnet is reversed, the opposite helicity is 

produced on axis. 

The EPW was installed in December 1994, commissioned during Spring 1995 at an operating frequency 

of 2 Hz, and became operational subsequently [5]. Utilizing trim coils at the wiggler ends and the high-precision 

r 

I 

Figure 3: The electron trajectory in the EPW. A special electromagnet adds the vertical deflection to the 

electron trajectory. The right and left turns are twisted out of the horizontal plane; all the right turns are 

twisted upand the left turns twisted down. The photons illustrated in the figure were initially directed parallel 

to the z direction, before the twists were applied. 

108 

I 

Z 
orbit measurement system of the NSLS X-Ray 

Ring, the residual orbit motion was reduced to a 

level below 0.5 pm [6]. No adverse effects on other 

experiments have been observed. The degree of 

circular polarization of the radiation from the wiggler was characterized by making Magnetic Circular 

Dichroism (MCD) measurements using the X13A 

soft-x-ray beamline [7]. For vertical deflection 

parameters, Kx, of 1.2 and 1.6, the MCD effects at 

the Fe L2,3 edges indicated a degree of circular 

polarization 0f60% and 75%, respectively, in good 

agreement with calculated values. Experimental 

programs based on the device, including MCD, 

Natural Circular Dichroism, and Resonant Magnetic Scattering, have also started. As an example, 

very small MCD effects near the Cr L2,3 edges were 

observed in a series of Co-Cr alloys (a promising 

candidate for a high-density perpendicular magnetic recording medium) by a collaboration of the 

Naval Research Laboratory, AT&T, and the NSLS 

[8]. From these results, the Cr in the alloys was 

found to be polarized, and the induced Cr moment 

aligned anti-ferromagnetically with respect to that 

of the neighboring Co. These results also showed 

that MCD effects much smaller than 1% can be 

easily detected with the EPW, as illustrated in 

Figure 4. To fully utilize the EPW, a new soft x-ray 

spherical grating beaniline and a double-crystal xray monochromator are being constructed, and will 

be operational in fiscal year 1997. Studies are now 

underway utilizing the EPW switching at 

100 Hz. 

References: 

[l] P.M. Stefan, L. Solomon, S. Krinsky and G Rakowsky, Proc. 1991 Part. Accel. Conf., San Francisco, CA, 

[2] P.M. Stefan, S. Krinsky, G. Rakowsky and L. Solomon, Proc. 1995 Part. Accel. Conf., Dallas, TX, p. 2435, 

[3] A. Friedman, S. Krinsky and E. Blum, “Polarized Wiggler for NSLS X-Ray Ring: Design Consideration”, 

[4] S. Yamamoto and H. Kitamura,japan/.ofAppl. Phys., 26, p.Ll613, (1987). 

[5] S. Krinsky, and C.-C. Kao, Synchrotron Radiation News, 8, 38, (1995). 

[6] 0. Singh, S. Krinsky, P.M. Ivanov and E.A. Medvedko, Proc. 6th Int. Svnch. Rad. Instrum. Conf., ArEonne, 

IL, October 1995. 

[7] K.J. Randall, 2. Xu, E. Gluskin, I. McNulty, R. Dejus, S. Krinsky, 0. Singh, C.-C. Kao, E.D. Johnson, C.T. 

Chen, and G. Meigs, J. Electron Spectroscopy and Related Phenomena, 80,433, (1996). 

[8] K.M. Kemner, V.G. Harris, V. Chakarian, Y.U. Idzerda, W.T. Elam, C.-C. Kao, Y.C. Feng, D.E. Laughlin, 

and J.C. Woicik,/. Appl. Pbys. 79, 5345, (1996), Proceedings of the 40thAnnual Conference on Mapetism 

and Magnetic Material Nov. 6-9, 1995 Philadelphia. 

p. 2542, (1991). 

(1995). 

Informal Report, BNL 47317, (1992); E.Gluskin, etal., Proc. 1995 Part. Accel. Conf., Dallas, TX, (1995). 

[9] R.P. Walker and B. Diviacco, Rev. Sei. Imtrurn. 63/1, 392, (1992). 

109 


1996-1997 

Users' Executive Committee 

The Users' Executive Committee (UEC) provides for organized 

discussions among the user community, NSLS administration, 

and laboratory directorate. It aims to communicate current and 

future needs, concerns, trends within the user community to 

NSLS staff and management, and to disseminate to the users 

information about NSLS and BNL plans. Members were: 

Chairperson: Peter Stephens, SUNY-Stony Brook 

Vice-Chairperson: Joel D. Brock, Cornell U. 

Past -Chairperson: Paul Zschack, ORNL 

Secretary: Ben Ocko, BNL-Physics 

Doon Cibbs, BNL-Physics 

Kim Mohanty, BNL-Physics 

Ian Robinson, U. of Illinois 

Thomas Russell, IBM 

D. Peter Siddons, NSLS 

Ex-Officio: Eva Rothman, NSLS 

Special Interest Group Representatives 

Special interest groups in areas of common concern communicate with NSLS 

management through the UEC. Group representatives were: 

Biological Scattering, Crystallography 

Energy Dispersive Diffraction 

Imaging 

Industrial Users 

Nuclear Physics 

Students and Post Docs 

Time Resolved Spectroscopy 

Topography 

UV Photoemission, Surface Science 

XAFS 

X-Ray Scattering, Crystallography 

Stephan Ginell, ANL 

No SPlG elected as of this date 

Carl Zimba, MIT 

Richard Harlow, Dupont 

Steven C. Whisnant, U. of S. Carolina 

David Johnson, BNL-Chemistry 

Ralf Wehlitz, U. of Tennessee 

Michael Dudley, SUNY-Stony Brook 

Yves Idzerda, Naval Research Laboratory 

Mark Chance, Albert Einstein Coll. of Med. 

Ben Ocko, BNL-Physics 
Science Advisory Committee 

The Science Advisory Committee (SAC) evaluates the science 

programsat the NSLS and makes recommendations to the Chairman. 

The SAC met in March of 1996 and its members were: 

B. Batterman, CHESS, Cornell U. 

Stephen Harrison, HHMI, Harvard U. 

Franz Himpsel, U. of Wisconsin, Madison 

Jochen Schneider, HASYLAB, DESY 

Albert J. Sievers, Cornell U. 

Paul Sigler, HHMI, Yale U. 

Sunil Sinha, APS, Argonne National Laboratory 

General User Proposal Study Panels 

The Proposal Study Panels met in November 1995, March 1996, and July 1996 to review and rate General 

User research proposals for the FY 1996 cycles. PSP members are drawn from the scientific community and 

usually serve a two year term. Members during FY 1996 were: 

UV Panel 

David Hanson SUNY 

Boris Sinkovic NYU 

David Tanner U. of Florida 

X-Ray Imaging/Other Pane 

Steve Sutton U. of Chicago 

Alastair MacDowell AT8T 

X-Ray Biology 

Thomas Terwilliger LANL 

Howard Einspahr Bristol-Myers Squibb 

X-Ray Spectroscopy Panel 

Chuck Bouldin NIST 

Steven Heald APS 

Linda Powers Utah State U. 

William Orme-Johnson MIT 

Dale Sayers U. of NC 

X-Ray Scattering Panel 

Jerome Cohen NWU 

Simon Moss U. of Houston 

Thomas Russell IBM 

Sunil Sinha AN1 

Ian Robinson U. of Illinois 

Cullie Sparks ORNL 

General User Oversight Committee 

The General User Oversight Committe (GUOC) met in November 1995, March 1996, 

and July 1996 to allocate time on beamlines to each General User proposal for the 

FY 1996 cycles. GUOC members are drawn from the scientific community and usually 

serve a two year term. Members during FY 1996 were: 

UV Members X-Ray Members 

Harold Ade NCSU Malcolm Capel BNL-Biology 

David Heskett U. of R.I. Mark Chance Albert Einstein 

Jan Hrbek BNL-Chemistry Alex Darovsky SUNY-Stony Brook 

Lars Furenlid BNL-NSLS 

James McBreen BNL-DAS 

Gavin Watson BNL-Physics 

113 
II i 

ES&H COORD: Gmur 

OFFICER: Dickinson 

Ackerman, Aloi 

HEALTH PHYSICS S&EP: 

(Seebeck), (Weilandics), 

(Zantopp) 

'1 MEDICAL PROGRAMS: L (LeDuc) 

* 

** 

[I 

0 

IEXPERIMENTAL SUPPORT 

BFAMLINE R&D: 

Siddons 

Berman, Carr, Q. Dong, Dowd, Flaks, Furenlid, 

[Gmur], S. Hulbert, Khalid, Montanez, Park, Shek-Stefan, So, [Thomlinson], Vescovo, Williams, Wu, Yin 

Student: 2. Zhang 

BEAMLINE TCHNICIANS: 

SUPERVISOR: Lenhard 

Carlson, Greene, Ninael, 

USER SHOP: 

van Derlaske 

- LONG-RANGE R&D: 

Hastings 

Johnson, Kao, Milne, Stefan, J.M. Wan 

Student: Ablett, Ealiebe I Visitor: P. Stephens 

Temporary 

Reports to Denis McWhan, 

Assoc. Dir. for Basic Energy Sciences 

NSLS personnel with multiple functions 

PRT personnel or member of non-NSLS division 

Visitor: Jin 

MAGNET GROUP: Rakowsky 

Graves, Solomon, Aspenlieter, Lehecka 

I 

ACCELERATOR TEST FACILIF 

Ben-Zvi 

Babzien, Malone, 

Po orelsky, X Wang, Yakmenko 

STUDENTS: Catravas, 

Fang, Liu, Palmer, Oiu 

TECH. SUPPORT: 

SUPERVISOR: Cahill 

Montemagno, Harrington 

114 
-~- 

CHAIRMAN: Hart** 

DEPUTY CHAIRMAN: Krinsky 

~ 

ASSISTANTTO CHAIRMAN 

Terrano 

ADMINISTRATION: 

r 

General User's Oversight Committee (GUOC) Proposal Study Panels (PSP) 

ADMINISTRATION: 

LEAD: J. Desmond 

DiFilippo, Koebel, LeBrun, White-DePace 

I I 

4-1 ELECTRICAL (Lamb), (Reisig) SYSTEMS: OPERATIONS: I Heese 

MECHANICAL ENGINEERING: 

Woodle 

t SECRETU SUPPORT: 

HEAD: McBrien 

D. Buckley, Ciufo, 

Loverro, Marshall, Messana,Thompson, 

Wrigley 

I ENGINEERING: R Biscardi, I ENGINEERING: H Beauman, Chou, iEncLMortazavi, 1 RING MANAGERS: 

INJECTION: Blum 

W: Kramer 

X-RAY RING MANAGER & 

BEAMLINELIAISON: KlaWcy OPERATIONS: J. Rothman 

MAINTENANCE 

COORDINATOR: [Kemp] 

I I I 

CONTROL ROOM 

SUPERVISOR Church 

OPERATORS: 

Jahnes, Santana, 

Weiner, Zeitler 

COORDINATORS: 

LEADMAN: Kem 

Buckley, Chmief Jew, 

Klu Pharr, Ratzke, 

Warturton 

I Buda, Pietraski, 1 Sheehan, 0. Singh, Towne, M. Thomas, 

COMPLJTER SYSTEMS: 

HEAD: Keane (Acting) Dabrowski, Feng-Berman 

Flannigan,Langenbach, 

Pearson,Ramamoorthy, 

Smith, Tang, Teng 

DATAEME DEVELOPMENT: 

Hicks H MECH. LEADER: Pjerov Checker: Palo 

Amas? Gross, Gugileimino Kim, taicu, Stelmach, Stoeber, Wiseman HEAD: E. Rothman 

Feierabend, Pinkston, 

Rogers, Wright I DIAGNOSTICS: 

HEAD: Nawrocky ~~ ~ 

TRAINING: Klein 

TECH SUPERVISION: 

SR. SUPERVISOR: McKenna 

MECH: Scheuerer 

VACUUM: DeBoer 

UTILITIES: White 

MECHANIW. 

(Pagano, MC), Breck, 

Newburgh, Po 

Radulescu, Fksenberg, Santangelo, 

t 4 BUILDING MANAGER: 

Kelly 

SR. SUP.: Rasmussen 

P/S: Meier 

RF: D'Alsace 

DIAGNOSTICS: Rambo 

ES&H Interlocks: 

Gallagher 

ELECT. DES/DRFT: Neuls I CARPENTERS: 4 (Gildersleeve), (Riddick) 

POWER SUPPLIES: 

Borrelli, Fulkerson, Garrison, McDonald, 

Seda, P. Singh 

Rodriques, Vaughn 

(Custodial Staff) (Bounauito), 

(McPhemn),(O-d ), (Quigley), (Williamsf 

VACUUM: 

Caruso, de Toll, Fruedenberg, Lanni, 

CLEANING SHOP: 

Cernyar 

(Shea) 

CONTROLS & DIAGNOSTICS: I Frisbie, Link, Nielson, Tallent 

(S. Bennett), (Lamble), (Mingino), 

INTERLOCKS: 

Best, Hughes, Poshka I 

I DESIGN: 

CHECKER: L. Hulbert I Bohenek, Rubino 

I SPECIAL PROJECTS: I Romano (signed) Michael Hart, Chairman 

October 1,1996 

ELECTRICIANS: (Didio), 

(HucgSes), yx), (Ro zevik) (T ompson), I 

115 
OCTOBER 1996 

~__________ _______ ~ ~ 

This table lists the abbreviations appearing in the Beamline Guides. 

ARUPS = 

CD 

C-T - 

ERG - 

EXAFS = 

IR - 

LEGS 

MCD - 

MI - 

NEXAFS = 

NIM - 

PGM - 

SEXAFS = 

SGM 

S-N - 

SXES 

TGM - 

TOK 

UPS 

WB - 

WDI 

XPS 

XAS - 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

Angle-Resolved Ultraviolet Photoemission Spectroscopy Circular Diachroism 

Czerney-Turner 

Extended Range Grasshopper Extended X-ray Absorption Fine Structure 

lnfared 

Laser Electron Gamma Source 

Magnetic CD 

Michelson Interferometer 

Near Edge X-ray Absorption Fine Structure 

Normal Incidence Monochromator 

Plane Grating Monochromator 

Surface EXAFS 

Spherical Grating Monochromator 

Seya-Namioka 

Soft X-ray Emission Spectroscopy 

Toroidal Grating Monochromator 

Transverse Opt i ca I Kryst ron 

Ultraviolet Photemission Spectroscopy White Beam 

Wavefront Dividing Interferometer 

X-ray Photoemission Spectroscopy X-ray Absorption Spectroscopy 

116 
Beam Research Mono. Affiliation Local Contact Spokesperson 

line Program 

U1 A 

U1 B 

U2A 

U2B 

USA 

U3B 

u3c 

U4A 

U4B 

SEXAFS, ARUPS, XPS ERG Exxon 

(Conceptual) TGM Exxon 

(Unassigned) 

High pressure, MI 

pump-probe, high Tc 

abs., IR microscopy 

Time-resolved and DC DC/DC 

radiometry; reflectometry 

for optical constants 

(Conceptual) 

Photoelectron sped.; ERG 

exp. system and detector 

calibrations 

ARUPS of solids,surfaces; TGM 

hi res. core level photoemission; total yield 

absorption 

Soft x-ray photoemission SGM 

spectroscopy; NEXAFS; 

SXMCD 

SUNY@SB 

BNL-NSLS 

Northrop Crumman 

Carnegie Inst. Wash 

Los Alamos Natl Lab 

Smiths Astro Obs 

Bechtel Nevada 

Bechtel Nevada 

Sandia Natl Lab 

Los Alamos Natl Lab 

No Carolina St U 

Boston U 

BNL - NSLS 

Naval Res Lab 

BNL-NSLS 

B DeVries 

51 6-344-5206 

51 6-344-5206 

B DeVries 

51 6-344-5206 

51 6-344-5206 

C Williams 

51 6-344-7529 

A Burek 

51 6-344-5503 

W Towell 

51 6-344-7245 

S Dhesi 

51 6-344-5504 

J Chen 

908-730-2738 

J Chen 

908-730-2738 

G Carr 

51 6-344-5502 

51 6-344-2237 

R Blake 

51 6-344-5521 

505-466-0566 

R Bartlett 

51 6-344-5708 

505-667-5923 

K Smith 

61 7-353-61 17 

V Chakarian Y ldzerda 

51 6-344-771 8 51 6-344-771 8 

202-767-4481 

51 6-344-771 8 51 6-344-7290 

51 6-344-4744 

J Freeland 1 Park 

117 
U41R 

u5 

U5UA 

U6 

U7A 

U7B 

U8A 

U8B 

U8C 

U8D 

118 

Vibr. spectr of molecules 

on surfaces; abs of hi Tc 

superconductors; hi res 

gas abs.; fast detectors 

Diagnostics 

Spin polarized angleresolved ultraviolet 

photoemission 

Lithography 

Photoemission; 

SEXAFS; Fluorescence 

yield spectroscopy 

Photoemission; 

SEXAFS 

ARUPS 

NEXAFS 

ARUPS 

NEXAFS 

Zone plate monochr 

evaluation; reflectivity 

measurements of thin 

films and multilayers 

(Conceptual) 

Scanning soft x-ray 

microscopy 

WB 

IBM 

R McFeely R McFeely 

91 4-945-2068 914-945-2068 

K Zhang J Yarmoff 

909-787-5336 

909-787-3537 

R McFeely R McFeely 

91 4-945-2068 91 4-945-2068 

R McFeely R McFeely 

91 4-945-2068 91 4-945-2068 
Beam Research Mono. Affiliation local Contact Spokesperson 

line Program 

U9A (Planned) 

Lithography 

U9B CD; MCD; time-resolved C-T BNL-NSLS 

fluorescence (lifetimes) BNL-Biology 

U1 OA (Unassigned) 

UlOB PSD- WB BNL-NSLS 

general vacuum 

R8D 

U11 Gas phase photo- NIM 

ionization and 

Spectroscopy 

U12 High resolution core TGM 

level Spectroscopy 

ARUPS 

U12A High resolution core TGM 

level spectroscopy 

(construction) 

BNL-NSLS 

BNL-Biology 

Brandeis U 

BNL-DAS 

U of Pennsylvania 

Oak Ridge Natl Lab 

Oak Ridge Natl Lab 

U of Tennessee 

M Strongin 

51 6-344-3763 

J Sutherland J Sutherland 

51 6-344-3406 51 6-344-3406 

51 6-344-3279 51 6-344-3279 

S Kuo 

51 6-344-7003 

51 6-344-4001 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

S Hulbert 

B Klemm 

51 6-344-7570 

51 6-344-4022 

51 6-344-4001 

E Plummer 

D Zehner 

423-974-3055 

51 6-344-551 2 

61 5-574-6291 

E Plummer 

D Zehner 

423-974-3055 

51 6-344-551 2 

61 5-574-6291 

119 
Beam Research Mono. Affiliation Local Contact Spokesperson 

line Program 

U12B Angle-resolved 

photoemission 

U1 SUA High res. VUV/soft 

x-ray abs and electron 

spectroscopy 

(incl. spin-pol 

photoem.) 

U13UB Optical metrology for 

extreme ultraviolet 

projection lithography 

TGM Oak Ridge Natl Lab 

U of Tennessee 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

D Zehner 

51 6-344-551 2 

61 5-574-6291 

423-974-3055 

E Plummer 

SGM BNL-NSLS S Hulbert 

51 6-344-7570 

WB Sandia Natl Lab 

BNL-lnstrum 

A MacDowell 

51 6-344-5334 

S Hulbert 

51 6-344-7570 

A.MacDowel1 

51 6-344-5334 

U14A Solid state PGM 

photoemissions studies 

U14B Detector Research and WB 

Development 

U15 Soft x-ray spectroscopy TGM 

(solids and gases) 

U16A (Unassigned) 

U16B ARUPS; XPS; SEXAFS; ERG 

stimulated desorption; 

NEXAFS 

120 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

SUNY@SB 

SUNY@Buff 

Cornel1 U 

Sandia Natl Lab 

M Shek 

S Hulbert 

51 6-344-5930 

51 6-344-7570 

J Hastings 

51 6-344-3930 

A Wen 

51 6-632-791 8 

Y so0 

51 6-344-2702 

71 6-645-2576 

M Shek 

S Hulbert 

51 6-344-5930 

51 6-344-7570 

J Hastings 

51 6-344-3930 

D Hanson 

Y Kao 

51 6-632-791 7 

71 6-645-2576 

R Merrill 

607-2 5 5-98 5 7 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X1 A 

XI B 

X2A 

X2B 

X3A1 

X3A2 

X3Bl 

Soft x-ray imaging 10-80 A 

Soft x-ray spectroscopy 10-50 A 

Surface scattering 

X-ray microtomography 6.5-30, WB 

Short wavelength 14, 19, 31 

crystallography, 

diffraction and scattering 

Diffractometry; x-ray 3-31 

spectroscopy; scattering; 

crystallography; small 

angle scattering 

X-ray spectroscopy; 4.6-40 

powder diffraction 

BNL-NSLS 

SUNY@SB 

LBNL 

No Carolina St U 

ANL 

BNL-NSLS 

BNL-Physics 

FA - Juelich 

Fritz-Haber-lnst 

Exxon 

ORNL 

U of Tennessee 

Exxon 

SUNY@SB 

SUNY@Buff 

SUNY@SB 

SUNY@Buff 

SUNY@SB 

SUNY@Buff 

X3B2 Surface science 4-20 SUNY@SB 

SUNY @Buff 

S Wirick 

51 6-344-4723 

51 6-632-8095 

P Johnson 

F Loeb 

51 6-344-3705 

51 6-344-2092 

V Jahns 

51 6-344-2823 

51 6-344-5057 

51 6-344-471 9 

S Bennett 

J Dunsmuir 

908-730-2548 

A Darovsky 

51 6-344-3770 

A Darovsky 

51 6-344-3770 

J Kin 

51 6-344-4723 

51 6-632-81 06 

P Johnson 

51 6-344-3705 

K Liang 

908-730-3032 

A Baddord 

423-574-5241 

J Dunsmuir 

908-730-2548 

P Coppens 

ext. 221 7 

71 6-645-6800 

P Coppens 

ext. 221 7 

71 6-645-6800 

P Stephens P Coppens 

51 6-344-5634 ext. 221 7 

51 6-344-31 76 71 6-645-6800 

51 6-632-81 56 

P Stephens P Coppens 

51 6-344-31 76 71 6-645-6800 

51 6-344-5634 

51 6-632-81 56 

ext. 221 7 

121 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X4A 

X4B 

x4c 

X5A 

X5B 

X6A 

X6B 

X7A 

X7B 

X8A 

122 

Multiwavelength 4-30 Howard Hughes Med In 

anomalous diffraction 

analysis of crystalline 

biological macromolecules 

(Conceptual) 

Diffraction measurements 7-20 Howard Hughes Med In 

from biological 

macromolecules 

Laser Electron Gamma 

Source (LEGS); medium 

energy nuclear physics 

80-400 MeV BNL-Physics 

Diagnostic 

Time and space resolved 4-20 ANL 

dispersive x-ray 

spectroscopy 

X-ray scattering 2.4-21.0 ANL 

U of Illinois 

Northwestern U 

BP 

Structural char. through 5-45, WB BNL-NSLS 

powder diffraction BNL-Physics 

Camegie lnst of Was 

E I DuPont 

Mobil 

UOP 

Air Products Corp 

SUNY@SB 

U of Cal @ Santa Barbara 

U of Pennsylvania 

NlST 

Chevron 

Crystallography; 5-21 

wide angle scattering 

Photoionization cross- 0.26. 

sections; photoelectron 

spectr; mirror reflect.; 

detector calib.; spectr. 

BNL-Chemistry 

Swedish Nat Res Coun 

Los Alamos Natl Lab 

Smiths Astro Obs 

C Ogata 

51 6-344-7435 

51 6-344-5466 

C Ogata 

51 6-344-7435 

51 6-344-5466 

C Thorn 

51 6-344-7798 

0 Kistner 

51 6-344-3991 

P Lee 

51 6-344-221 0 

51 6-344-3955 

P Lee 

51 6-344-221 0 

51 6-344-3955 

D Cox 

Q Zhu 

51 6-344-381 8 

51 6-344-381 8 

J Hanson 

51 6-344-4381 

51 6-344-4378 

M Sagurton 

51 6-344-5708 

W Hendrickson 

51 6-344-4938 

21 2-305-3456 

W Hendrickson 

51 6-344-4938 

21 2-305-3456 

A Sandorfi 

B Preedom 

51 6-344-7951 

803-777-6559 

P Montano 

708-2 52-62 39 

P Montano 

708-252-6239 

D Cox 

Q Zhu 

51 6-344-381 8 

51 6-344-381 8 

T Koetzle 

J Larese 

51 6-344-4384 

R Blake 

51 6-344-5521 

505-466-0566 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X8C Diffraction from 5-20 

biological macromolecules 

and detector calibrations 

X9A XAS 

X9B Time resolved 

x-ray spectroscopy; 

scattering; diffraction; 

XAS 

X1 OA Diffraction; small 

angle scattering; 

crystallography; 

scattering 

X1 OB Scattering; 

crystallography 

XlOC EXAFS 

XllA EXAFS 

3.4-1 8.6 

3.2-1 8.8 

6-1 5.2 

8, 12 

3.5-24.7 

Los Alamos Natl Lab 

Sandia Natl Lab 51 6-344-5708 

LLNL 

ANL 

M Sagurton 

Albert Einstein M Sullivan 

51 6-344-3800 

51 6-344-2091 

51 6-344-3800 

L Miller 

Albert Einstein M Sullivan 

51 6-344-3800 

51 6-344-2091 

51 6-344-3800 

L Miller 

Exxon 

Exxon 

Exxon 

4.5-35 No Carolina St U 

U of Connecticut 

Naval Res Lab 

Mobil 

E I DuPont 

Hoechst Celanese 

Naval Surf Warf Center 

Notre Dame U 

U of Washington 

111 lnst of Tech 

Georgia lnst of Tech 

Rice U 

BNL-NSLS 

S Bennett 

51 6-344-471 9 

S Bennett 

51 6-344-471 9 

M Sansone 

51 6-344-5759 

908-730-01 00 

51 6-344-5206 

B DeVries 

C ldzorek 

51 6-344-7245 

505-667-8848 

M Chance 

51 6-344-3800 

71 8-430-2894 

M Chance 

51 6-344-3800 

71 8-430-2894 

E Sirota 

K Liang 

908-730-3407 

908-730-3032 

E Sirota 

K Liang 

908-730-3407 

908-730-3032 

P Stevens 

51 6-344-4828 

908-730-2584 

G Lamble C Lamble 

D Sayers 

51 6-344-7734 51 6-344-7734 

51 6-344-7731 

91 9-51 5-4453 

123 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X11B EXAFS I 1.7-8 No Carolina St U G Lamble G Lamble 

BNL-NSLS D Sayers 

U of Connecticut 51 6-344-7734 51 6-344-7734 

Mobil 51 6-344-7731 I 

E I DuPont 91 9-51 5-4453 I 

Naval Res Lab 

Hoechst Celanese I 

Naval Surf Warf Center 

Notre Dame U 

U of Washington 

Ill lnst of Tech 

Georgia lnst of Tech 

Rice U 

I 

X12A Instrument develoDment BNL-NSLS 

X12B Time-resolved and static 6-1 5 BNL-NSLS 

x-ray diffr. of macromol. BNL-Biology 

systems in both wide and 

small angle regimes 

X12C Protein crystallography 7.8-1 3.6 BNL-Biology 

XI 3 R8D optics development; 

soft x-ray utilization 

BNL-NSLS 

X14A Scattering; 3.5-40 Oak Ridge Natl Lab 

crystallography; U of Illinois 

spectroscopy 

XI 48 (Conceptual) WHITE Oak Ridge Natl Lab 

X-ray microprobe; x-ray micro-focussing; 

micro-diff raction 

X15A X-ray standing waves 3-20, WB ANL 

Northwestern U 

Harvard U 

8 Dowd 

51 6-344-2738 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

M Capel 

51 6-344-571 2

T Langdon 

M Capel 

51 6-344-571 2 

51 6-344-571 2 

R Sweet 

51 6-344-3401 

R Sweet 

51 6-344-3401 

E Johnson 

51 6-344-4603 

J Hastings 

51 6-344-3930 

E Johnson 

51 6-344-4603 

R Eisenhower 

51 6-344-561 4 

G Ice 

423-574-2744 

E Johnson 

J Milne 

51 6-344-4603 

51 6-344-591 0 

E Johnson 

51 6-344-4603 

P Siddons 

51 6-344-5627 

51 6-344-2738 

P Lyman 

51 6-344-561 5

51 6-344-7395 

M Bedzyk 

51 6-344-7395 

708-252-7763 
Beam Research Energy Affiliation local Contact Spokesperson 

line Program MeV) 

X15B SEXAFS 

EXAFS 

NEXAFS 

1.5-1 5 Lucent P Northrup 

A MacDowell 

51 6-344-5334 

51 6-344-5334 

P Citrin 

908-582-5275 

X16A Surface diffraction 4-1 2 Lucent W Lehnert 

U of Illinois 51 6-344-571 5 

51 6-344-5334 

A MacDowell 

K Evans-Lutterodt 

51 6-344-21 25 

908-582-21 54 

51 6-344-7024 

21 7-244-2949 

I Robinson 

XI 6B Diffraction 7.85 Lucent L Flaks 

51 6-344-2738 

P Siddons 

K Evans-Lutterodt 

51 6-344-5627 

51 6-344-21 25 

908-582-21 54 

X16C Novel spectroscopy; 3-1 6 Lucent 

diffraction U of Illinois 

W Lehnert 

A MacDowell 

51 6-344-571 5 

51 6-344-5334 

W Brown 

M Marcus 

908-582-3941 

908-5822749 

X17A (Conceptual) 

X17B1 Chemical crystallography; 10-1 00, WB BNL-NSLS 

hi P physics; tomography; 

x-ray scattering; x-ray 

fluorescence microprobe 

J Hastings 

P Siddons 

51 6-344-3930 

51 6-344-5627 

51 6-344-2738 

J Hastings 

51 6-344-3930 

P Siddons 

51 6-344-5627 

51 6-344-2738 

XI 7B2 Medical research: 33.02,33.3 BNL-NSLS 

Angiography; Stanford U 

computed tomography; Illinois lnst Tech 

radiotherapy SUNY@SB 

LBNL 

BNL-Medical 

N Gmiir 

51 6-344-2490 

W Thomlinson 

51 6-344-3937 

X17C Hi P research; energy 10-1 00, WB Naval Res Lab J Hu H Mao 

dispersive diffraction Carnegie lnst of Was 51 6-344-5343 202-686-241 0 

from microscopic sample LLNL 202-686-241 0 ext. 2467 

volumes U of Chicago E Skelton 

202-767-301 4 

X18A Diffuse and surface 4-20 Purdue U 

scattering Northwestern U 

U of Illinois 

U of Missouri 

Penn State U 

S Ehrlich G Liedl 

J Schwanof S Ehrlich 

51 6-344-7862 31 7-494-41 00 

51 6-344-561 8 51 6-344-7862 

51 6-344-5635 

125 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X18B EXAFS; optics char.; 4-26 BNL-NSLS S Khalid DP Siddons 

reflectivity measurements AlliedSignal 51 6-344-7496 51 6-344-2738 

UOP 51 6-344-5627 

51 6-344-5699 

Chevron L Furenlid 

XI 9A X-ray Absorption Sped.; 2.1 -25.6 BNL-NSLS F Lu L Furenlid 

EXAFS and XANES UCA@Davis 51 6-344-2338 51 6-344-5699 

U of Kentucky 

U of Michigan 

BNL-DAS 

XI 9C Topography; liquid 4-25, WB BNL-NSLS 

surface scattering SUNY@SB 

Johns Hopkins U 

Army Research Lab 

U of Illinois 

U of Chicago 

X2OA Scattering (hi 4-res) 5.6-1 2 MIT 

IBM 

X2OB Scattering at fixed 17.36 IBM 

energy M IT 

X20C Scattering 4-1 1 IBM 

(hi and low Q res) MIT 

X21 High energy resolution > 4 BNL-NSLS 

inelastic scattering 

X22A In-plane diffr. 8 refl. 10 Nom. BNL-Physics 

studies of surfaces under BNL-DAS 

electro-chem. cond., and 

thin films and multilayer 

X22B High resolution x-ray 5-1 0 BNL-Physics 

diffraction Harvard U 

ANL 

126 

M Dudley M Dudley 

51 6-632-8500 51 6-632-8500 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

61 7-253-4937 

R Birgeneau 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

61 7-253-4937 

R Birgeneau 

C Kao 

51 6-344-4494 

R Birgeneau 

61 7-253-4937 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

C Kao 

51 6-344-4494 

B Ocko D Gibbs 

B Ocko 

51 6-344-4299 51 6-344-4608 

B Ocko D Gibbs 

51 6-344-4299 51 6-344-4608 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Promam 

X22C Diffraction studies of 3-1 2 

magnetic and structural 

phase transformations; 

surface scattering 

BNL-Physics 

ANL 

J Hill 

51 6-344-3736 

51 6-344-4730 

D Gibbs 

51 6-344-4608 

X23A2 EXAFS 5.4-30 NlST J Woicik 

51 6-344-5823 

51 6-344-5236 

51 6-344-3923 

301 -975-5975 

S Chu 

J Woicik 

51 6-344-5236 

51 6-344-5823 

X23A3 Topography; smallangle scattering 

X23B EXAFS; scattering; 

crystallography 

5-30, WB NlST 

3-1 1 Naval Res Lab 

D Fischer 

S Chu 

51 6-344-51 77 

51 6-344-3923 

51 6-346-9285 

G Long 

301 -975-5975 

J Kirkland 

51 6-344-2258 

T Elam 

202-767-301 5 

X24A Atomic, molecular, and 1.8-5.0 NIST 

optical physics with ANL 

x-rays 

X24C Photoemission and 2-1 500 eV Naval Res Lab 

reflectance spectroscopy 

X25 High Q-resolution 

elastic scattering 

>3 BNL-NSLS 

X26A Dev. and application of 4-20, WB BNL-DAS 

analytical techniques U of Chicago 

(e.g. microprobe) U of Georgia 

BNL-Biology 

Cold Spring Harb Lab 

X26C Dev. and applic. of x-ray 4-30, WB BNL-DAS 

microscopy techniques; U of Chicago 

Laue diffraction protein BNL-Biology 

crystallography U of Georgia 

Cold Spring Harb Lab 

X27A Instrument development BN L-NSLS 

B Karlin 

51 6-344-7863 

51 6-344-5624 

T Jach 

301 -975-2362 

J Rife 

J Kirkland 

202-767-4654 

51 6-344-2258 

L Berman 

Z Yin 

51 6-344-5333 

51 6-344-5525 

51 6-344-5625 

J Rife 

J Kirkland 

202-767-4654 

51 6-344-2258 

L Berman 

51 6-344-5333 

G Shea-McCarthy S Sutton 

51 6-344-2229 31 2-702-9930 

G Shea-McCarthy S Sutton 

51 6-344-2229 31 2-702-9930 

B Dowd 

51 6-344-2738 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

127 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X27B Instrument development 

X27C Instrument development 

X28A Instrument development; 

Photon-based diagnostics 

and detector development 

X28B Photon-based 

diagnostics and 

detector development 

X28C Photon-based 

diagnostics and 

detector development 

X29A (Unassigned) 

X29B (Unassigned) 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

E Johnson 

51 6-344-4603 

B Dowd 

51 6-344-2738 

E Johnson 

51 6-344-4603 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

P Stefan 

51 6-344-21 17 

P Stefan 

51 6-344-21 17 

P Stefan 

51 6-344-21 17 

P Stefan 

51 6-344-21 17 

P Stefan 

51 6-344-21 17 

P Stefan 

51 6-344-21 17 

X30 Diagnostic 

128 

Beamline X27B: Photograph of the new “mask writer” developed by E. Johnson and C. Milne 

of the NSLS for use on beamline X27B. Through the use of variable apertures, the mask writer 

allows the creation of DXRL (Deep X-Ray Lithography) masks in one step instead of the usual 

three steps, saving not only time but also a large investment in capital equipment. 
RESEARCH ANTHOLOGY 

A 
LIG E: 

An Antholo of Im rovements, Developments, and Researc YR by N S Staff and Collaborators 

Following the commissioning phase of a scientific facility, it is essential to invent, adapt and improve new 

technologies so that the specification and performance of the facility is upgraded over it’s lifetime. It is equally 

important that staffkeep their expertise and research interests at the cutting edge and contribute, based on their unique 

experience, to the present and next generation of experiments at existing facilities and to the specification and R & D 

on which the next generation of facilities will be based. 

A synchrotron radiation facility such as the National Synchrotron Light Source (NSLS) at Brookhaven National 

Laboratory supports a very wide range of science which is dependent on the breadth of the electromagnetic spectrum 

which is generated. Scientists from many disciplines use radiation from the far infra-red (h = 12 mm, Energy = 0.1 

mew through to extreme gamma rays (h = 4 fm, Energy = 300 MeV ). All aspects of the facility need continual 

improvement, development and research including the source itself, the optics of beamlines, experimental concepts 

and the performance of detectors. This collection of papers shows the scope of past work by NSLS staff and their 

collaborators, serves as a reminder of their achievements and as an indicator of the range, quality and quantity ofwork 

which is required to maintain a scientific user facility at the cutting edge. 

Michael Hart 

Chairman, NSLS 

***************** 

132 
SEMINAL PAPERS ON STORAGE RING CONCEPTS 

Coherent Synchrotron Radiation in the SXLS Phase I Electron Storage Ring 

J. B. Murphy, S. Krinsky, and R.L.Gluckstern, “Longitudinal Wakefield for Synchrotron Radiation,” Proc. I995 

Part. Accel. Conf., Dallas, TX (1995). 

J. B. Murphy and S. Krinsky, “Millimeter Wave Coherent Synchrotron Radiation in the SXLS Phase I Electron 

Storage Ring,” Nucl. Instrum. Meth. A 346,571 (I994). 

It is suggested that employing a superconducting RF cavity in the low energy SXLS Phase I storage ring would 

facilitate the generation of coherent synchrotron radiation in the far infrared. This might provide a path to extend 

the infrared program now rapidly growing on the VUV Ring. Also, operation of such a storage ring with electron 

bunch length (0.3mm) an order of magnitude shorter than presently achieved, will explore a new regime of 

accelerator physics, where the beam impedance due to synchrotron radiation is the dominant ring impedance. 

SXLS Phase I Storage Ring 

J. B. Murphy, R. Biscardi, J. Bittner, L.N. Blumberg, E. Bozoki, E. Desmond, H. Halama, R. Heese, H. Hsieh, J. 

Keane, S. Kramer, R. Nawrocky, T. Romano, J. Rothman, J. Schuchman, M. Thomas, J.M. Wang, “Commissioning 

of the Phase I Superconducting X-ray Lithography Source (SXLS) at BNL,” Proc. 1991 IEEE Part. Accel. Conf., 

San Francisco, CA (1991) p. 1 I07. 

R. Heese and T. Romano, “The Ultra-Fast Injection Kicker for SXLS,” Proc. 1991 1EEE PAC, San Francisco, 

CA (1991), p. 993. 

As part of the superconducting x-ray lithography source project funded by DARPA, a 200 MEV electron storage 

ring was built and commissioned to carry out studies of injection into compact storage rings. Currents as high as 

1.3 Amp were stored. The novel injection scheme utilized a single fast kicker magnet. 

Global Orbit Feedback: 1989 R&D 100 Award. 

L.H. Yu, E. Bozoki, J. Galayda, S. Krinsky, G. Vignola, “Real Time Harmonic Closed Orbit Correction,” Nucl. 

Instrum. Meth. A 284,268 (1989). 

The first real time feedback systems to stabilize the entire orbit in a storage ring were developed at the NSLS. These 

systems have improved the orbit stability at the NSLS by an order of magnitude. We are now developing new 

digital global orbit feedback systems as an improvement. over the existing analog systems. A digital design will 

allow more flexibility in the orbit correction algorithm and will provide for the use of an increased number of 

position monitors and correction dipoles. 

Vignola Lattice 

G. Ifignola, “The Use of GradientMagnets in Low Emittance Electron Storage Rings”, Proc. Synch. Rad. Instrum. 

Conf., Stanford, CA (1985). 

Gaetano Vignola developed a triple bend achromatic lattice utilizing gradients in the bending magnets. This 

design was adopted at Lawrence Berkeley National Laboratory for the Advanced Light Source storage ring. 

Chasman-Green Lattice 

R. Chasman, G. K. Green and E. M. Rowe, “Preliminary Design of a Dedicated Synchrotron Radiation Facility,” 

IEEE Trans. Nucl. Sei. NS-22,1765 (1975). 

Proposal for NSLS (1977) BNL 50595, Vol. I and II. 

This lattice was the first designed to optimize brightness of the synchrotron radiation sources and to provide many 

dispersion free straight sections for insertion devices. The design of the third generation hard x-ray sources (ESRF, 

APS, and Spring-8) are all based on the design of Chasman and Green. 

133 
SEMINAL PAPERS ON SCIENCE WITH SYNCHROTRON RADIATION 

X-ray Holography 

S. Lindaas, M. Howells, C. Jacobsen, A. Kalinovsky, “X-ray In-line Holography Sub-50 nm Resolution Imaging 

Using Photoresists and Atomic Force Microscope Examination,” Jour. of the Optical SOC. of America, 1996, in 

press. 

S. Lindaas, M. Howells, C. Jacobsen, and A. Kalinovsky, “X-ray Holographic Microscopy via Photoresist 

Recording and Atomic-force Microscope Readout,” J. Opt. SOC. Am. A 13,1788 (1996). 

C. Jacobson, M. Howells, J. Kirz, S. Rothman, “X-ray Holographic Microscopy Using Photoresists,” Jour. Of 

the Optical SOC. Of America A 7,1847-1861 (1990). 

M. Howells and J. Kirz developed the first successful soft x-ray holographic apparatus at NSLS, initially on 

beamline U15 and subsequently using the X1 undulator beamline. 

High Energy Resolution Resonant Raman Scattering 

M.H. Krisch, C.-C. Kao, F. Sette, W.A. Caliebe, K. Hamalainen, J.B. Hastings, “Evidence for Quadrupolar 

Contribution to the Absorption Cross Section at the LIII Edge of Gadolinium in Gadolinium Gallium Garnet,” 

Phys. Rev. Lett. B 74,4931 (1995). 

X-ray resonant Raman scattering with total energy resolution of 1 eV is achieved. Since x-ray absorption near 

edge structure is the intermediate state in the resonant Raman process, analyzing the energies of the scattered 

photons with high resolution can be used to resolve overlapping features in the absorption spectra if the final states 

of these features can be separated energetically. 

Speckle and Intensity Fluctuation Spectroscopy Using Coherent X-rays 

S.B. Dierker,R. Pindak, R.M. Fleming, I.K. Robinson, andL.E. Berman, ‘X-ray Photon CorrelationSpectroscopy 

Study of Brownian Motion of Gold Colloids in Glycerol,” Phys. Rev. Letts. 75,449 (1995). 

M. Sutton, S.G.J. Mochrie, T. Greytak, S.E. Nagler, L.E. Berman, G.A. Held, and G.B. Stephenson, “Observation 

of Speckle by Diffraction with Coherent X-rays,” Nature 352,608 (1991). 

Analysis of the scattering of coherent x-ray beams from disordered materials can provide a wealth of information 

on their static and dynamic structures, which cannot be had via other methods. In a pioneering experiment on 

beamline X25, the diffuse scatter, of a suitably-prepared coherent x-ray beam, from a disordered copper-gold alloy 

crystal was observed, and studied over time as the crystal was driven thermally into an ordered state, revealing 

the evolution of its ordered crystalline domains. In a later experiment on X25, using a coherent x-ray beam of far 

higher intensity, the diffusion coefficient associated with the Brownian motion of gold colloid particles dispersed 

in a glycerol medium was measured through analysis of the temporal correlations among the scattered x-ray 

photons. The use of x-rays in these experiments, as compared with conventional visible light, has opened the 

possibility to study very short length scale dynamics, down to atomic length scales, in bulk materials (whether or 

not in equilibrium) that are opaque to other probes. 

Soft X-ray Microscopy and Spectromicroscopy: 1991 R&D 100 Award 

J. Kirz, C. Jacobsen, M. Howells, “SoftX-ray Microscopes and their Biological Applications,” Quarterly Reviews 

of Biophysics 28,33 (1995). 

The scanning x-ray microscope was developed by Kirz (SUNY@SB) andRahrback (NSLS). It provided improved 

performance and ease of alignment over the imaging x-ray microscopes popular in Europe. The adaptation of the 

scanning x-ray microscope to provide a microspectroscopic capability was done by Johnson (NSLS) and Ade 

(NCSU) in collaboration with Kirz. This unique capability enables a wide variety of important materials questions 

to be attacked, since even the same chemical species show different spectral features in the near-edge region. Thus, 

for example the different polymers in a polymer mixture can be mapped out using variations in the carbon K-edge 

structure. 

134 
H. Ade, J. Kirz, S. Hulbert, E. Johnson, E. Anderson and D. Kern, “Scanning Photoelectron Microscope with a 

Zone Plate Generated Microprobe,” Nucl. Inst. & Meth. A 291,126 (1990). 

X-ray photoelectron spectroscopy (XPS) is a widely used, technologically important analytical technique for the 

study of surface chemistry and electronic structure. Standard XPS instruments are devoid of spatial resolution, 

and commercial (lab based) microscopes have resolution typically no better that 25-100 pn. This instrument 

takes advantage of the coherence available from an undulator based source to form a microbeam using Fresnel 

zone-plate optics. The sample is scanned through the beam, and the resulting photoelectron signal correlated with 

position. With this instrument, we achieved resolution better than 0.3 pn over an energy range of 400 to 700 eV. 

We also performed some of the first high spatial resolution spectro-microscopy with our first instrument. An 

improved instrument has subsequently been built at the NSLS, and similar instruments are now found at ALS, 

ELETTRA, and under construction at SRRC. 

Medical Applications of Synchrotron Radiation at the NSLS 

W. Thomlinson, “Synchrotron Radiation in the Biosciences,” eds. B. Chance, et al, Oxford University Press, New 

The NSLS is the world leader in breadth of medical research projects and new innovative research programs due 

to the existence of SMERF and our technical developments of the programs. 

York, 674-680 (1 994). 

Soft X-ray Magneto-Optical Kerr Effect 

C.-C. Kao, C.T. Chen, E.D. Johnson, J.B. Hustings, H.J. Lin, G.H. Ho, G. Meigs, J.-M. Brot, S.L. Hulbert, Y.U. 

Idzerda, C. Vettier, “Dichroic Interference Efsects in Circularly Polarized Soft-X-Ray Resonant Magnetic 

Scattering,” Phys. Rev. B 50,9599 (1994). 

C.-C. Kao, J.B. Hastings, E.D. Johnson, D.P. Siddons, G.C. Smith, G.A. Prinz, “Magnetic Resonant Exchange 

Scattering at the Fe LII and LIII Edges,” Phys. Rev. Lett. 65,373 (I990). 

Dramatic enhancement of the magneto-optical Kerr effect was observed near the LII, LUI edges of 3d transition 

elements and the MIV, MV edges of rare earth elements using both linearly and circularly polarized soft-x-rays. 

The element-specific nature of the probe and the enhanced magnetic sensitivity make it an important tool in the 

study of magnetic thin films and rnultilayers. 

Spin-Polarized Photoemission 

P.D. Johnson, N.B. Brookes, S.L. Hulbert, R. Klam, A. Clarke, B. Sinkovic, N.V. Smith, R. Celotta, M.H. Kelly, 

D.T. Pierce, M.R. Scheinfein, B.J. Waclawski, and M.R. Howells, “Spin-Polarized Photoemission Spectroscopy 

of Magnetic Sugaces Using Undulator Radiation,” Rev. Sci. Instrum. 63,1902 (I 992). 

Spin-polarized photoemission, in which the spin of electrons photoemitted from the surface of a wellcharacterized, usually magnetic, solid is measured in addition to their energy and angle, can be further subdivided 

into core-level or valence-band types. Core-level spin-polarized photoemission is practiced at NSLS by two 

groups (P. Johnson, BNL Physics and B. Sinkovic, NYU) at various soft x-ray beamlines, but valence-band spinpolarized photoemission is all performed at the purpose-built USUA beamline. This undulator-based beamline 

is a unique national resource, providing high flux and high photon energy resolution and a dedicated spin-polarized 

photoemission end station based on the NIST compact low-energy spin polarimeter. Both the core-level and 

valence-band programs have produced a wealth of significant results in the area of surface magnetism, including 

especially the discovery and measurement of surface and interface states in thin film magnetic systems which are 

at the heart of the magnetic recording industry. For example, one class of experiment at beamline USUA has 

examined the development of interfacial magnetism when a noble metal is deposited on a ferromagnetic substrate 

and the subsequent evolution of interfacial states into spin-polarized quantum well states as the overlayer films 

become thicker. These studies have provided the first indication that spin polarization effects are present in the 

non-magnetic layer of the associated magnetic multilayers. Indeed, it is these spin-polarized quantum well states 

that are thought to mediate the oscillatory exchange coupling in technologically important magnetic multilayers. 

135 
Nuclear Forward Scattering 

J.B. Hustings, D.P. Siddons, U. van Biirck, R. Hollatz, and U. Bergmann, “Mossbauer Spectroscopy using 

Synchrotron Radiation,” Phys. Rev. Lett. 66, 770 (1991). 

For nearly twenty years prior to this work the idea of using synchrotron radiation for Mossbauer 

spectroscopy had beenproposed. This work was the first demonstration of the technique that is now used 

worldwide to do Mossbauer spectroscopy in the time domain, namely measure the time evolution of the 

delayed nuclear forward scattering. 

The use of high-order Bragg reflections to generate extremely high-resolution beams for various x-ray 

physics experiments was brought to practical utility at NSLS. The optical layouts and principles 

embodied in these instruments have been widely emulated. At the time of OUT NFS experiments (see 

above) the device used for those measurements was the highest resolving power x-ray monochromator 

in the world. 

Infrared Beamline IR4 

G. P. Williams, “The Initial Scientific Program at the NSLS Infrared Beamline,” Nucl. Instrum. Meth. 

A 291,8 (1990). 

The development of the infrared beamline U4IR and its scientific program was a unique contribution 

from the NSLS. The beamline and accelerator scientists worked together to eliminate sources of noise, 

and the global orbit feedback system played an important role in the success of the infrared program. At 

the present time many laboratories around the world are planning the development of infrared beamlines 

based on the success at the NSLS including LURE, France; Daresbury, England; MAX Lab, Sweden; 

SRRC, Taiwan; ALS, Berkeley; ALADDIN, Wisconsin. 

Tunable Linear X-ray Polarimeter 

D. P. Siddons, M. Hart, Y. Amemiya, and J. B. Hastings “X-ray Optical Activity and the Faraday Effect 

in Cobalt and its Compounds,” Phys. Rev. Lett. 64,1967 (1990). 

M. Hart, D.P. Siddons, Y. Amemiya, and V. Stojanoff, “Tunable X-ray Polarimeters for Synchrotron 

Radiation Sources,” Rev. Sci. Instrum. 62,2540 (1 991). 

This instrument was the first to demonstrate the x-ray Faraday effect in amagnetic metal and x-ray optical 

activity in a chiral compound. This instrument was also the first x-ray polarimeter with a spectroscopic 

capability, and was thus able to observe resonance phenomena analogous to those seen in absorption, but 

with higher sensitivity. 

STORAGE RING ENHANCEMENT 

Fourth Harmonic Bunch Lengthening Cavity on VUV Ring 

R. Biscardi, S.L. Kramer, G. Ramirez, “Bunch Length Control in the NSLS VUV Ring,” Nucl. Instrum. 

Meth. A 366,26 (1 995). 

The lifetime of the electron beam in the VUV Ring is limited by intrabunch Coulomb scattering, and 

hence is inversely proportional to the bunch density. For high brightness one wants to keep the transverse 

dimensions of the bunch small, but for most experiments increasing the bunch length is acceptable. The 

lifetime of the beam in the VUV Ring has been doubled by use of a second RF cavity operating at 21 1 

MHZ, which is the fourth harmonic of the fundamental RF cavity. Stable operation of this system 

required the development of a novel approach to the control of the phase of the RF waveform. 

136 
Small Gap Undulator 

P. Stefan, S. Krinsky, G. Rakowsky, and L. Solomon, “Small-Gap Undulator Experiment on the NSLS 

X-Ray Ring,” Proc. 1995 Part. Accel. Conf., Dallas, TX (1995). 

Utilizing the small value of the vertical betafunction at the center of the X-Ray Ring insertions, an 

undulator with a 16cm period has been successfully operated with a vertical electron aperture of only 

3 mm with only slight reduction in the beam lifetime. This provides strong support for the belief that 

small gap undulators will play an important role in the future at synchrotron radiation facilities. 

Presently, a small gap device is being built in collaboration with Spring-8 in Japan, with the permanent 

magnet material in the ring vacuum, so that the magnet gap will only be a few hundred microns larger 

than the beam aperture. This device will be tested in the X-Ray Ring. 

Time-varying Elliptically Polarized Wiggler 

E. Gluskin, D. Frachon, P.M. Ivanov, J. Maines, E.A. Medvedko, E. Trakhtenberg, L.R. Turner, I. 

Vasserman, G.I. Erg, Yu.A. Evtushenko, N.G. Gavrilov, G.N. Kulipanov, AS. Medvedko, S.P. Petrov, 

V.M. Popik, N.A. Vinokurov, A. Friedman, S. Krinsky, G. Rakowsky, and 0. Singh, “The Elliptical 

Multiple Wiggler Project,” Proc. 1995 Part. Accel. Conf , Dallas,TX (1995). 

A. Friedman, S. Krinsky andE. Blum, “Polarized Wigglerforthe NSLSX-Ray Ring” (1 992) BNL-47317. 

In collaboration with Argonne and the BINP, Novosibirsk, Russia, an elliptically polarized wiggler has 

been constructed and operated in the X-Ray Ring with the horizontal wiggler field generated by an 

electromagnet operated AC to produce radiation with a time-varying circular polarized component. The 

AC elliptically polarized wiggler makes it possible to detect the very weak signatures of circular 

dichroism and other effects associated with right versus left handedness of some physical systems. The 

key technical challenge, which was successfully met, was to oscillate the horizontal wiggler field without 

moving the electron beam and disturbing any of the experimenters using other beamlines around the 

X-Ray Ring. At 2 Hz, a residual orbit motion of less than 0.5 micron has been observed, and the device 

has run several months in regular X-Ray operations without complaint from other users. We are now 

working to achieve 100 Hz operation of the wiggler. 

Beam Based Storage Ring Lattice Modeling 

J. Safranek, “Experimental Determination of Linear Optics Including Quadrupole Rotations,” Proc. 

1995 Part. Accel. Con, Dallas,lX (1995). 

This approach uses the very precise orbit measurements now available, to calibrate the mathematical 

model of the storage ring. In the X-Ray this method has been used to reduce the horizontal and vertical 

emittances. It has been employed at the ALS at Berkeley to eliminate a beta-beat caused by variation 

in the strength of the defocusing quadrupoles. There are plans to use this program at MAXLAB, SPEAR, 

ALLADIN and APS. 

137 
THEORETICAL WORK ON PHOTON SOURCES 

Theory of Short Wavelength FEL Amplifiers 

Proposal for the DW Free Electron Laser (1994) BNL 49713. 

L.H. Yu, S. Krinsky, R. L. Gluckstern andJ.B.J. van Zeijts, “The EfSect of Wiggler Errors on FEL Gain,” 

Phys. Rev. A45,1163 (1992). 

L.H. Yu, “Generation oflntense WRadiation by Subharmonically Seeded Single Pass FEL,” Phys. Rev. 

A 44,5178 (1991). 

I. Ben-Zvi, L.F. Di Mauro, S. Krinsky, M.G. White, and L.H. Yu, “Proposed UV-FEL User Facility at 

BNL,” Nucl. Instrum. Meth. A 304,181 (1991). 

L. H. Yu, S. Krinsky and R.L Gluckstern, “Calculation of Universal Scaling Function for FEL Gain,” 

Phys. Rev. Lett. 64,3011 (1990). 

S. Krinsky, “Introduction to the Theory of Free Electron Lasers,” AIP Conf. Proc. 153,1015 (1987). 

J.M. Wang andL.H. Yu, “A TransientAnalysis of a BunchedBeam Free Electron Laser,” Nucl. Instrum. 

Meth. A 250,484 (1986). 

S. Krinsky and L.H. Yu, “Output Power in Guided Modes for Single Pass Free Electron Laser Starting 

from Shot Noise,” Phys. Rev. 35,3406 (1985). 

R. Bonifacio, C. Pelligrini, andL.M. Narducci, “Collective Instabilities and High-gain Regime in a Free 

Electron Laser,” Opt. Commun. 50,373 (1984). 

There has been a continuing effort to develop the theory underlying short wavelength free electron laser 

amplifiers. Above is given a selection of the key publications resulting from the work at the NSLS. 

Subjects covered include: description of the high gain exponential growth regime, self amplified 

spontaneous radiation, effect of electron beam quality on gain, gain reduction due to wiggler errors, 

subharmonically seeded FELs, proposal for a user facility utilizing subharmonically seeded FELs. A 

large scale experiment to study short wavelength FEL amplifiers is under construction at the TESLA 

facility at DESY , Germany. At Brookhaven we are working to carry out experiments on FEL amplifiers 

at the Accelerator Test Facility and the Source Development Laboratory. 

Theory of Undulator Radiation 

S. Krinsky, “Undulators as Sources of Synchrotron Radiation,” IEEE Trans. Nucl. Sci. NS-30,3083 

(1 983). 

M.R. Howells, J. Kirz, and S. Krinsky, “A Beamline for Experiments with Coherent SoftX-rays,” (1982) 

An analysis of undulator radiation was carried out which showed that low-beta insertions were suitable 

locations for these devices. This led to the development of the soft x-ray undulator in the X1 straight 

section of the X-Ray Ring. The relatively large horizontal angular spread does not degrade the 

brightness, but does allow splitting the undulator beam to illuminate three separate experiments. 

BNL-32519. 

138 
X-RAY OPTICS 

X-ray Schlieren Imaging 

D. Chapman, W. Thomlinson, and 2. Zhong (to bepublished). 

A new x-ray technique applied to mammographic imaging. Separation of the absorption image and index of 

refraction image should provide additional information to the mammographers about various tumors. 

Collimating Mirrors for X-ray Beamlines 

J.B. Hustings, “NSLS EXAFS Beamline Design,” BNL Informal Report BNL-30617. 

In general at typical x-ray synchrotron sources the vertical opening angle of the bending magnet radiation is greater 

than the intrinsic width of typical perfect crystal rocking curves. In order to maintain high throughput and improve 

the energy resolution of standard two-crystal instruments the use of an x-ray collimating mirror was proposed 

followed by the monochromator and then a condensing optic to provide a small focus at the sample position. This 

idea was executed at X19 and has proven very successful, reducing the bandwidth of the monochromator by almost 

a factor of three with very little loss in intensity. 

High Resolution Bent-Crystal Analyzers 

K. Hamalainen, M. Krisch, F. Sette, C.-C. Kao, W. Caliebe, J.B. Hustings, “High Resolution X-ray 

Spectrometer Based on a Cylindrically Bent Crystal in Nondispersive Geometry,” Rev. Sci. Instrum. 66, 

1525 (1995). 

V. Stojanofl, K. Hamalainen, D.P. Siddons, J.B. Hustings, L.E. Berman, S. Cramer, G. Smith, “A Highresolution X-ray Fluorescence Spectrometer for Near Edge Absorption Studies,” Rev. Sci. Instrum. 63, 

1125 (1992). 

Spherically and cylindrically bent crystal analyzers with large solid angle acceptance were developed 

for inelastic x-ray scattering experiments. These analyzers can also be used in high resolution 

fluorescence analysis and fluorescence yield x-ray absorption spectroscopy. Multi-element analyzer 

array is being developed at the moment. 

High Resolution Inelastic X-ray Scattering 

C.-C. Kao, W.A. Caliebe, K. Hamalainen, M. Krisch, J.B. Hastings, “The Studies at the Inelastic 

Scattering Beamline at the NSLS,” National Conference on Synchrotron Radiation Instrumentation 

1995, Argonne National Laboratory, October 17-20 1995. Rev. Sci. Instrum. (to be published). 

The inelastic x-ray scattering program is focused on the study of elementary electronic excitations in 

condensed matters. In comparison with other inelastic scattering probes, such as light scattering and 

neutron scattering, inelastic x-ray scattering is unique in providing frequency- and wavevectordependent dielectric responses of materials. 

Optimized Beamline for Low Energy (2-8 keV) Spectroscopy Techniques 

L.R. Furenlid, P.E. Stefan, and J.B. Hustings, 5th International Conference on Synchrotron Radiation 

Instrumentation, Stony Brook, NY, 1994 (unpublished). 

Beamline X19A has been developed through a series of R&D projects to optimize the transport, 

monochromatization, and detection of x-rays in the 2-8 keV domain. Key components include a full 

collimating mirror/focussing mirror arrangement for optimum resolution and intensity; an 8 = pm Be foil 

thin window and associated fast shutter system; a horizontal feedback system to keep beam position 

constant on the sample; triple bounce monochromator crystals for superior rejection of harmonics via 

detuning; a high performance, high stability UHV monochromator with external drive componentry; a 

modular, kwik flange based sample holder and cryostat system for rapid setup of air excluded beam paths, 

and low energy ion-chamber detectors. 

139 
A Single Crystal Bent Laue Monochromator for Coronary Angiography 

P. Suortti, W. Thomlinson, D. Chapman, N. Gmur, D.P. Siddons and C. Schulze, Nucleur Instrument 

Methods, A 336,304 (I 993). 

The development of the bent Laue crystal monochromator increased the available flux for angiography 

by a factor of 6. This allowed greater flexibility in the human imaging program at the NSLS. The concept 

has been used at most major synchrotron medical research centers and for many programs, especially 

on bending magnet beamlinesi, where an increase in flux and bandwidth is useful. 

High Power Diamond Crystal X-ray Monochromator 

L.E. Berman, J.B. Hastings, D.P. Siddons, M. Koike, V. StojanoffandM. Hart, “Diamond Crystal X-ray 

Optics for High-power-density Synchrotron Radiation Beams,” Nuclear Instruments and Methods in 

Physics Research A 329,555 (1 993). 

L.E. Berman andM. Hart, “Preserving the High Finesse ofx-ray Undulator Beams from Perfect Waterjet-cooled Diamond Monochromators,?’ Nuclear Instruments and Methods in Physics Research A 334, 

61 7 (1993). 

Radiated x-ray power densities at present and future synchrotron radiation sources are unprecedented, 

and cannot be tolerated by conventional silicon and germanium crystal monochromators designed to 

diffract x-rays efficiently and simultaneously preserve the ray optics of the primary beam, when used at 

room temperature. Single crystal diamond is an attractive alternative to silicon and germanium as aroom 

temperature x-ray monochromator, because of its substantially superior mechanical and thermal 

properties, foremost among them being an exceptionally high thermal conductivity. Experiments 

performed at X25 have proven the efficacy of diamond as a high-power-density x-ray monochromator 

material, with its implementation as such carried out in a relatively simple and inexpensive manner. This 

bodes well for the highest power beam lines being commissioned at the newer sources such as the APS, 

where plans to use diamond monochromators are being pursued. 

Adaptive Silicon Crystal X-ray Monochromators 

L.E. Berman and J.B. Hastings, “An adaptive Crystal Bender for High Power Synchrotron Radiation 

Beams,” Proc. SPIE 1739,489 (1993). 

L.E. Berman, M. Hart, and S. Sharma, “Adaptive Crystal Optics for Undulator Beamlines,” Nucl. Instr. 

and Meth. A 321,617 (1992). 

L.E. Berman and M. Hart, “Adaptive Crystal Optics for High Power Synchrotron Sources,” Nucl. Inst. 

and Meth. A 302,558 (1991). 

A foremost challenge to proper operation of an x-ray monochromator in a high power x-ray beam, lies 

in eliminating the crystal Bragg plane strains arising from thermal distortion, which reduce the 

diffraction efficiency and spoil the beam brightness. A major research program at beam line X25 has 

been undertaken to study this, with implicit benefits for existing high power beam lines such as X25, as 

well as for future ones such as those under construction at the APS. A solution, which has been adopted 

for the X25 beam line monochromator, involves adaptive mechanical compensation of the thermal strain 

field. This is centered on the use of a bendable triangular silicon wafer that is 

thermally coupled to a cooled heat sink via a liquid metal interface. Tests and use have demonstrated that 

this device faithfully delivers the intrinsic x-ray beam brightness at X25. 

X-ray Optical Delay Line. 

S. Joksch, W. Graeff, J.B. Hastings, and D.P. Siddons, “Performance of an X-ray Optical Delay Line 

with Synchrotron Radiation,” Rev. Sci. Instrum. 63,1114 (1992). 

140 
An optical delay line for x-rays was demonstrated which can deliver a monochromatic beam with a 

variable delay following illumination of the sample with the broad band SR spectrum. This is a technique 

that should find usefulness in a wide variety of pump probe experiments where statistical significance 

can be acquired through cyclic excitation. 

High Energy, High Q-resolution X-ray Scattering 

J.B. Hustings and D.P. Siddons, “The Use of High Energy Synchrotron Radiation forX-ray Scattering,” 

Proc. of 2nd European Con$ on Progress in X-ray Synchrotron Radiation Research, A. Balerna, E. 

Bernieri, and S. Mobilio, Eds., Vol. 25,p. 159, SIF, Bologna (1990). 

The use of high energy x-rays for a broad range of x-ray scattering experiments is summarized. This work 

describes research started in collaboration with Dr. Jochen Schneider from HASYLAB. Both our group 

and a team at HASYLAB have continued to pursue this effort and it has expanded to include beamlines 

at ESRF and SPring-8. 

Mosaic Crystal Two-crystal Monochromator 

D. Hohlwein, D.P. Siddons, and J.B. Hustings, “A Graphite Double Crystal Monochromator for X-ray 

Synchrotron Radiation,” J. Appl. Cryst. 21,91 I (1988). 

A two crystal monochromator utilizing mosaic graphite crystals was constructed. It provides a 

significant increase in bandwidth and intensity when compared with typical perfect crystal instruments. 

Furthermore, in the two crystal arrangement, the mosaic spread only contributes to an increase in the 

divergence in the non-Bragg direction. This idea will be useful in a variety of quasi-monochromatic xray techniques including diffuse scattering and various film techniques applied to shxcture solution. 

Fluorescence Detection for Low-Z X-ray Spectroscopy 

J. Stohr, E.B. Kollin, D.A. Fischer, J.B. Hustings, F. Zaera, and F. Sette, “Surface Extended X-ray 

Absorption Fine Structure of Low ZAdsorbates Studied with Fluorescence Detection,” Phys. Rev. Lett. 

55,1468 (1985). 

This work demonstrated the efficacy of using fluorescence detection for low z x-ray spectroscopy. Prior 

to this work electron detection was thought to be the only viable measure of the variation in absorption 

for low z-materials. Application of fluorescence detection has opened the field of x-ray spectroscopy 

to low z elements in non UHV environments. 

High-Resolution Synchrotron Powder Diffraction 

J.B. Hustings, W. Thomlinson, and D.E. Cox, “Synchrotron X-ray Powder Difraction,” J. Appl. Cryst. 

17, 85 (1 984). 

The use of crystal analyzers for monochromatic SR powder diffraction is presented in detail including 

all the advantages of their use. Also, the detailed analysis of measured peak shapes is 

presented. This contribution has lead to the worldwide use of crystal analyzers for high resolution SR 

powder diffraction. 

Kirkpatrick-Baez Multilayer Optics for an X-ray Microprobe 

M.R. Howells and J.B. Hustings, “Design Considerations for an X-ray Microprobe,” NIM 208, 379 

(I 983). 

Design considerations for an x-ray microprobe were presented and the conclusion drawn that the most 

effective instrument would be a Kirkpatrick-Baez mirror pair where the reflecting optics were coated 

with multilayers. This choice provides the best compromise of large demagnification and quasimonochromaticity. The idea has been executed by several groups including people from LBNL. 

141 
Sagittally Focusing Crystal Monochromators 

C. Sparks, B. Borie, J.B. Hustings. “X-ray Monochromator Geometry for Focusing Synchrotron 

Radiation above 10 KeV,” NIM 172,237 (1980). 

The concept of using crystals to do sagittal focusing was presented. The optimal position of the 

monochromator was discussed giving the 3:l position as that of choice. Detailed calculations of 

collection efficiency were presented. This paper is the basis for all sagittal focusing systems presently 

in use at synchrotron sources. 

ULTRA VIOLET OPTICS 

Economical Upgrade Path for Outdated Toroidal Grating Monochromators. 

N. V. Smith, S. L. Hulbert, P. D. Johnson, and J. L. Erskine, “Spherical-grating Monochromator System 

with Circular-polarization Capability for the U5U Undulator at Brookhaven,” Nucl. Instrum. & 

Methods A 347,119 (1994). 

It has been shown that out-of-date soft x-ray toroidal grating monochromators (TGMs) can be efficiently, 

and therefore cheaply, upgraded to state-of-the-art spherical grating monochromators (SGMs) by 

replacing only the reflecting and diffracting optical elements. In most cases, the collecting and focusing 

functions in these beamlines are provided by a single mirror, usually of toroidal figure. An appropriate 

replacement toroid, near unity magnification, can provide the same throughput as the “standard” 

Kirkpatrick-Baez mirror pair. The new resulting beamline, dubbed TSGM for toroidal-mirror SGM, 

provides photon energy resolution and flux equal to the “standard” SGM configuration, and can fit in 

substantially less floor space since it has no horizontal deflections. 

UHV Compatible Two-Crystal Monochromator. 

P. Cowan, J.B. Hastings, T. Jach, and J. Kirkland, “A UHV Compatible Two-Crystal Monochromator 

for Synchrotron Radiation,” NIM 208,349 (1 983). 

J. Golovchenko and co-workers had developed a mechanical coupling to provide a constant offset wide 

angular range two crystal x-ray monochromator. This mechanical design was adapted to a UHV 

environment. Several innovations were made, including a UHV-compatible long-stroke piezo translator. 

These instruments are used in several locations on the x-ray floor and remain the most functional of all 

designs to date for this application. It is of particular importance for x-ray energies below 4 KeV. 

INFRA RED OPTICS 

Research on the First Infrared Beamlines 

F.M. Hoffmann, B.N.J. Persson, W. Walter, D.A. King, C.J. Hirschmugl, and G.P. Williams, “Antiabsorption Resonances in the InfraredReflectance Spectroscopy ofAlkali-Cu(ll1) Adsorbate Systems,” 

Phys. Rev. Lett. 72,1256 (1994). 

R.J. Hemley, Z.G. Soos, M. Hanfland, and H.-K. Mao, “Charge Transfer States in Dense Hydrogen,” 

Nature 369,384 (1994). 

C. Meade, J.A. Reffner, and E. Ito, “Synchrotron Infrared Absorbency Measurements of Hydrogen in 

MgSiO3 Perovskite,” Science 264,1558 (1 994). 

G.L. Carr, M. Quijada, D.B. Tanner, C.J. Hirschmugl, G.P. Williams, S. Etemad, B. Dutta, F. DeRosa, 

and T. Venkatesan, “Fast Bolometric Response by High Tc Detectors Measured with Subnanosecond 

Synchrotron Radiation,” Appl. Phys. Lett. 57,2725 (1990). 

142 
L. Forro, G.L. Carr, G.P. Williams, D. Mandrus, L. Mihaly, “Far Infrared Transmission Study of Single 

Crystal Bi2Sr2Ca2Cu20x,” Phys. Rev. Lett. 65,1941 (1 990). 

The U4IR beamline was the first infrared beamline developed on the NSLS VUV Ring. The scientific 

program was directed toward far infrared spectroscopy of adsorbates on metal surfaces; a model system 

for exploring the surface physics and chemistry that control catalysis as well as other phenomena. This 

program determined the importance of interactions between adsorbed atoms and conduction electrons. 

Other scientific investigations include the first (and only) far infrared spectra of free-standing high-T, 

cuprate crystals, and demonstrations of time-resolved measurements (such as pump-probe spectroscopy) 

that utilize the synchrotron’s pulse structure. 

The U2B beamline enables high brightness spectroscopy in the mid-infrared. It is used for 

microspectroscopy studies of materials at extremely high pressures (i.e. geo-physical sciences) and for 

micro-analysis of materials such as semiconductors, polymers, ceramic composites, biological cells, and 

even forensics. As a result of a CRADA between the NSLS and the Northop-Grumman Corporation, 

the NSLS was able to initiate construction on two new infrared beamlines (U12IR and UlO), optimized 

for microspectroscopy and very far infrared spectroscopy. 

Lamellar-grating IR Interferometer 

K.D. Moeller, T. Sears, H.T. Liu, C.J. Hirschmugl, and G.P. Williams, “A High Resolution Interferometer 

for use with Synchrotron Radiation,” Nucl. Instr. Meth. Phys. Res. A319,250 (1992). 

K.D. Moeller, D.P. Siddons, C.J. Hirschmugl, D. Scardino, P. Petrone, D. Carlson, and G.P. Williams, 

“Two Mirror Wavefront Dividing Interferometer for Infrared Synchrotron Radiation,” Appl. Optics 30, 

4297 (1991). 

The lamellar grating interferometer is a spectrometer optimized for performance in the very far infrared 

(wavelengths beyond 100 microns); the region where the NSLS VUV Ring outperforms the standard far 

IR spectrometer source (the high pressure mercury arc lamp) in both brightness and flux. This is an 

important spectral range for investigating metals, semiconductors and superconductors, including the 

“bad metals” which are the central theme of the new joint research initiative between the physics 

department and the NSLS. The high degree of transverse coherence to the NSLS source enabled a highly 

efficient, wide-spectral range, wave-front dividing interferometer to be built and demonstrated. The high 

degree of transverse coherence inherent in synchrotron IR radiation permitted a very simple interferometer 

design capable of operation over a very large wavelength range. The coherence properties meant that 

the wavefront could be divided into only two parts (rather than the 20-100 parts used in conventional 

LGI’s). These parts could, therefore, be made of high quality quite easily, thus the coherence could be 

maintained up to quite short wavelengths (a few microns). The long wavelength limit is diffraction 

driven at about 5 mm. Key to the advantages of this instrument is its lack of a beamsplitter; essential if 

such a wide spectral range is to be probed. 

143 
CONSTRUCTION AND OPERATION OF THE BNL ACCELERATOR TEST 

FACILITY A USER FACILITY FOR THE PHYSICS OF BEAMS 

The BNL Accelerator Test Facility (ATF) is this country’s only proposal-driven, peer-reviewed 

user’s-facility for accelerator and beam physics, including studies in the generation of high-brightness 

electron-beams, Free-Electron Laser experiments and many others. Milestone experiments at the ATF 

include: 

Inverse FEL Acceleration of Electrons 

A. van Steenbergen, J. Gallardo, J. Saizdweiss, J.-M. Fang, “Observation of Energy Gain at the BNL 

Inverse Free-Electron Laser,” Phys. Rev. Lett. (to be published). 

Generation of Femtosecond Pulses of High-brightness Electrons 

X.J. Wang, X. Qiu and I. Ben-Zvi, “Experimental Observation of High-Brightness Micro-Bunching in 

a Photocathode RF Gun,” Phys. Rev. Lett. (submitted ). 

Electron beam bunches with an extremely high brightness have been produced by the BNL gun at the 

ATF, from a nanoCoulomb at 10 picosecond FWHM with rms normalized emittance of 4 mm mrad to 

40 picoCoulomb at 0.4 picosecond FW and 0.5 mm mrad. 

Slice Emittance Measurement 

X. Qiu, K. Batchelor, I. Ben-Zvi and X.J. Wang, “Demonstration of Emittance Compensation Through 

the Measurement of the Slice Emittance of a 10 Picosecond Electron Bunch,” Phys. Rev. Lett. 76,3723 

(1996). 

This electron beam diagnostic technique makes it possible to study the phase space of the electron beam 

in 6-D phase space with picosecond resolution. It is an essential element for further improvement of 

electron beam brightness. 

Inverse Cherenkov Acceleration of Electrons 

W.D. Kimura, G.H. Kim, R.D. Romea, L.C. Steinhauer, I.V. Pogorelsky, K.P. Kusche, R.C. Fernow, X.J. 

Wang and Y. Liu, “Inverse Cerenkov Acceleration of Electrons by 3.7 MeV using 580 MW of the ATF’s 

C02 Laser,” Phys. Rev. Lett. 74,546 (1995). 

High-upshift, Forward Angle Smith-Purcell Radiation Measurement 

K.J. Woods, J.E. Walsh, R.E. Stoner, H.G. Kirk, R.C. Fernow, “Forward Directed Smith-Purcell 

Radiation from Relativistic Electrons,” Phys. Rev. Lett. 74,3808 (1 995). 

Development of the High Gain Harmonic Generation FEL 

High-Gain Harmonic-Generation (HGHG) FEL has been developed at BNL’s NSLS as a method to 

achieve UV and x-ray coherent and tunable radiation with a high peak-power, narrow bandwidth, 

high-stability and single pass amplifier approach. 

Chirped-pulse Amplification with HGHG FEL 

L.-H. Yu, E. Johnson, D. Li and D. Umstadter, “Femptosecond Free-electron Laser by Chirped Pulse 

AmpliJi:cation,” Phys. Rev. E 49, No. 5,4480 (1994). 

144 
Development of a Multiple-function Superconducting-undulator 

G. Ingold, I. Ben-Zvi, S. Krinsky, D. Lynch, J. Sheehan, L. Solomon, M. Woodle, L. Yu, X. Zhang, W. 

Sampson, K. Robins, I. Lehrman, R. Heuer, J. Sheehan, D. Weissenburger, “A Superconducting Short 

Period Undulatorfor a Harmonic Generation FEL Experiment,” Proceedings 1993 Particle Accelerator 

Conference, Washington DC, May 17-20, (1 993). 

‘Fresh-Bunch’ Technique 

I. Ben-Zvi, K.M. Yang and L.H. Yu, “The ‘Fresh-Bunch’ Technique in FELs,” Nuclear Instruments & 

Methods in Physics Research A 318, 726 (1992). 

A Proof-of Principle experiment in High Gain Harmonic Generation 

I. Ben-Zvi, A. Friedman, C.M. Hung, G. Ingold, S. Krinsky, L.H. Yu, I. Lehrman and D. Weissenburger, 

“Design of a Harmonic Generation FEL Experiment at BNL,” Nuclear Instruments & Methods in 

Physics Research A 318,208 (1992) 

ACHIEVEMENTS IN TECHNOLOGY AND ENGINEERING 

NSLS-DAC: A Flexible Beamline Control Program 

L.R. Furenlid, A. Mayer, and J. Kirkland, L‘NSLS-DAC: A Flexible Beamline Control PI-ogram,” 

Journal de Physique (submitted). 

Synchrotron beamline control software was developed in the last year and implemented on the 

experimental floor on XAS beamlines U7, XllA, X18B, X19A. and X23B. It is currently being 

implemented on beamline X9B, and in the near future on X23A2. This software presents the novice as 

well as experienced researchers with an intuitive, graphical-user-interface environment for a full 

complement of experimental techniques. Though the software is geared for spectroscopy, a full macro 

capability and the inclusion of calls to user supplied external routines accommodate general purpose data 

collection. The establishment of this software as a standard on the XAS beamlines on the experimental 

floor is already resulting in a significant reduction in the resources spent on user training and enhancing 

experiment quality. 

Very High Aspect Ratio and 3-dimensional Micromachining Using Hard X-rays 

E.D. Johnson, J.C. Milne, D.P. Siddons, H. Guckel, and J.L. Klein, “Precision Machining with HardXrays: Experiments at the NSLS,” Synchrotron Radiation News 9, no. 4,lO (1996). 

D.P. Siddons, E.D. Johnson and H. Guckel, “Precision Machining Using Hard X-rays,” Synchrotron 

Radiation News 7,16, (1994). 

At the NSLS, we initiated a program to explore the features of lithography utilizing hard x-rays with the 

aim of developing methods for the very precise manufacture of macroscopic, three-dimensional 

structures. We have demonstrated lithographic processing of resist materials to the scale of several 

centimeters while maintaining precision at the level of microns. This technology allows complex 

3-dimensional objects to be machined with sub-micron precision. A production beamline is being 

constructed based on this work, and on the substantial interest from companies who want to use hard xray lithography for manufacturing products. 

145 
Multielement Solid State Detector 

A. Pullia, L. Furenlid, H.W. Kraner, G. Bertuccio, P.J. Pietraski, and D.P. Siddons, “Multielement Solid 

State Detector,” Rev. Sci. Instrum. (in press). 

A multielement detector has been developed for x-ray absorption spectroscopy and diffraction applications 

at the NSLS. The front end, developed in collaboration with the Instrumentation Division, comprises 

a silicon wafer based pixel detector and an array of charge sensitive preamplifiers. Powerful NIM-bin 

based modules based on field programmable gate arrays and modular circuit inserts handle all 

subsequent signal processing under complete computer control. A significant scientific and engineering 

effort has lead to outstanding resolution performance. The instrument has been proven in prototype form 

and is now in a manufacturing stage. 

Development of RF Guns, Photocathode Materials and Diagnostic Techniques 

X.J. Wang and I. Ben-Zvi, High-Brightness Electron Beam Diagnostics at the ATF, Proc. Beam 

Instrumentation Workshop, Argonne National Lab., May 68,1996. BNL 63151. 

X.J. Wang, T. Srinivasan-Rao, K. Batchelor, I. Ben-Zvi and J. Fischer, “Measurements on Photoelectrons 

from a Magnesium Cathode in a Microwave Electron Gun,” Nuclear Instruments and Methods in 

Physics Research A 356,159 (1995). 

MacXAFS: An EXAFS Analysis Package for the Macintosh 

C. Bouldin, W.T. Elam, and L.R. Furenlid, “MacXAFS: An EXAFSAnalysis Package for the Macintosh,” 

Physica B 208&209,190 (1995). 

An analysis package for x-ray absorption spectroscopy was developed to permit real-time analysis 

during data acquisition, as well as full, documented work for publication. A front-end application which 

presents a unified interface ties together well tested numerical algorithms for data normalization, 

background subtraction, Fourier analysis, non-linear least squares fitting, and ab-initio modeling. The 

package has a world-wide user base numbering in the hundreds. 

Testing of APS Vacuum Chambers 

C.L. Foerster, C. Lanni, J.R. Noonan and R.A. Rosenberg, “Photon Stimulated Desorption Measurement 

of an Extruded Aluminum Beam Chamber for the Advanced Photon Source,” 42nd National Symposium 

of Amer. Vac. SOC., Oct. 1995. 

PSD measurement on X28A beamline of an extruded aluminum APS storage ring chamber. The data 

was used by ANL to evaluate chamber construction and preparation. 

High Stability, High Power Nd:YAG Laser for Photocathode Illumination 

M. Babzien, I. Ben-Zvi, J. Fischer, AS. Fisher, K. Kusche, I.V. Pogorelsky, T. Srinivasan-Rao, “A High 

Power Picosecond Nd:YAGICO2 Laser System for Electron Guns, Laser Acceleration and FEL,” Proc. 

of Lasers ’94 Conference, Quebec, Canada, Dec. 12-16,1994. BNL 61399. Feb. 1995. 

High Power, Picosecond Pulse C02 Laser 

I. Pogorelsky, W.D. Kimura, C.H. Fisher, F. Kannari, N.A. Kurnit, “Approach to Compact Terawatt 

CO2 Laser System for Particle Acceleration.” Presented at the 6th Workshop on Advanced Accelerator 

Concepts, Lake Geneva, Wisconsin, June 12-18,1994. BNL 60826. 

146 
Non-linear, Non-instantaneous Adaptive Feed-forward Control System for Linac Energy 

R. Zhang, I. Ben-Zvi and J. Xie, “A SelfAdaptive Feed-forward RF Control System for Linacs,” Nuclear 

Instruments and Methods in Physics Research A 324,421 (1993). 

Copper Chamber Desorption Measurements 

CL. Foerster, H. Halama, G. Korn, M. Calderon and W. Barletta, “Desorption Measurements of 

Copper and Copper Alloys For PEP 11,” Vacuum, 44(5-7), 489 (1993). 

PSD measurements of copper and its alloys for PEP 11. Neutral gas, photo electron and scattered photon 

data taken on beamline UlOB. PEP I1 prototype copper chamber was tested on X28A beamline. Work 

supported by LLNL and SLAC. 

Compact UHV Valve with Field Replaceable Windows 

E.D. Johnson, J. Freeman, F. Powell, “Compact UHV Valve with Field Replaceable Windows,” Rev. 

Sci. Instrum. 63,1282 (1992). 

There are many applications in synchrotron radiation research where window valves can be usefully 

employed. Examples include gas cells for monochromator calibration, filters for high-order light 

rejection, and as vacuum isolation elements between machine and experimental vacua. We took 

advantage of a new valve seal geometry developed by VAT corporation to make a simple removable 

window insert in a gate valve sealing plate. The window design was similarly based on a standard 

geometry available from Luxel Corporation. Working together, we developed what has become a very 

popular commercial product for both companies, and a high quality, modest cost device for use at many 

synchrotrons. At present, there are several hundred of these valves in service. 

Bittner-Biscardi Receiver for Beam Position Monitor 

R. Biscardi and J. W. Bittner, “Switched Detector for Beam Position Monitor,” IEEE Proc. 1989 Part. 

Accel. Conf., Chicago, IL,Vol. 111, p. 1516 (1989). 

This high precision receiver forms the basis for orbit measurement and control at the NSLS. Duke 

University FEL Laboratory, ALS at Berkeley, and APS at Argonne plan to use receivers based on this 

design for all of or a subset of their orbit measurements. 

High-Power Ultra-High Vacuum (UHV) Photon Beam Position Monitor 

E.D. Johnson and T. Oversluizen, “Compact High Flux Photon Beam Position Monitor,” Rev. Sci. 

Instrum. 60, I947 (1989). 

In synchrotron radiation sources, from the standpoint of the users, photon beam stability is vital for the 

realization of state of the art research. This is particularly true for undulator beamlines where due to the 

brightness of the source, small shifts in beam position can result in unacceptable intensity and energy 

fluctuations. Reliable measurement of the photon beam position is necessary to apply stabilization 

techniques. Prior to this research, no such device existed. The monitor utilizes electrically isolated 

blades introduced into the edge of the beam. Schemes such as this had been tried before, without success. 

In our case, a geometry was developed which stabilized the positions of the blades, provided electrical 

isolation with significant cooling, and embodied an efficient collection geometry for the photoelectrons 

generated from the blades. This device achieved sub-micron resolution, and has been the acknowledged 

model for similar instruments placed in all of the third generation machines, world wide. 

147 
UHV Synchrotron Radiation Pumped Absorber 

C.L. Foerster, T.S. Chou H. Halama, and C. Lanni, “Measurements of a Prototype Synchrotron 

Radiation Pumped Absorber For Future Light Sources,” AIP Con5 Proc. 171,334 (1988). 

Measurements were made at NSLS UlOB beamline as joint effort of NSLS and LBNL. The concept was 

used for the ALS at LBNL. 

In Situ Reactive Cleaning of X-ray Optics by Glow Discharge 

E.D. Johnson andR.F. Garrett, “ln Situ Reactive Cleaning ofx-ray Optics by Glow Discharge,” Nucl. 

Instrum. & Meth. A 266,381 (1988). 

E.D. Johnson, S.L. Hulbert, R.F. Garrett, G.P. Williams, and M.L. Knotek, “In Situ Reactive Glow 

Discharge Cleaning of X-ray Optical Surfaces,” Rev. Sci. Instrum. 58,1042 (1987). 

In soft x-ray monochromators, particularly at synchrotron radiation facilities, carbon contamination can 

severely limit the throughput and resolution of the instrument, even for wavelengths far away from the 

carbon K edge. We developed a method of in-situ cleaning using RF glow discharges which is capable 

of complete removal of carbon contamination. The various reactors developed at the NSLS are quite 

simple, and have been retrofitted to a variety of instruments. The results achieved are far superior, and 

require significantly less time to obtain than with conventional cleaning methods. This technology, our 

reactor design, and process method have been adopted at essentially every soft x-ray synchrotron facility 

in the world. 

ui 

Demountable UHV Beryllium Window 

T. Oversluizen and P. M. Stefan, “Replaceable Be andAl Windows for X-ray Beamlines,” Nucl. Instrum. 

& Meth. A 266,375 (1988). 

Beryllium windows are essential for a wide range of x-ray apparatus. The standard technology for UHV 

compatible windows was to vacuum-braze the beryllium wafer into a copper or stainless steel assembly. 

This process is expensive and inflexible. T. Oversluizen devised a scheme which used soft metal 

compression seals to capture the beryllium in a stainless steel flange assembly. Thus, the window could 

be easily replaced if damaged, or remounted into a different assembly if the experiment needs changed. 

Such a flange assembly is inexpensive to produce, and the beryllium material can be standard sizes, 

allowing ready production of custom window assemblies. 

A Program for Synchrotron Radiation Dose Calculations 

D. Chapman, N. Gmiir, N. Lazarz and W. Thomlinson,“PHOTON: A Program for Synchrotron 

Radiation Dose Calculations,” Nucl. Instrum. and Meth. A 266,191 (1988). 

A user friendly program to calculate dose from scattered and direct photon beams through arbitrary 

absorbers and storage ring. It has been copied (and much improved) by other labs as well as by our staff. 

Measurement of Photon Stimulated Desorption of NSLS Beam Chamber 

H.J. Halama, C. Foerster, and T. Kobari, “Vacuum Perj4ormance of the UV and X-Ray Rings at the 

NSLS,” J. Vac. Sci. Technol., A 5 (4), 2342 (1987). 

Measurements of PSD in a NSLS aluminum vacuum chamber. The data was used to design new higher 

power beam chambers by the NSLS, BNL and other laboratories worldwide. 

148 
Fast Valve Protection System 

C. Foerster and R. Larson, “Evaluation of NSLS Beamline Fast Valve Protection System,” J. Vac. Sci. 

Technol., A 5 (4), 2401 (1987). 

This valve was designed and built by BNL (T. Oversluizen). Response time, shockwave effects and 

vacuum sealing were tested to establish beamline protection needs and vacuum sensor locations. The 

NSLS design was used by Vacuum Generators Ltd. for their fast valve product line. 

High Flux Photon Beam Monitor 

P. Mortazavi, M.H. Woodle, H. Rarback, D. Shu, and M. Howells, paper SRI Mtg Stanford, CA (1985). 

The device first used heatpipes to transport absorbed heat from detector blades to heat exchanger. 

Eliminated waterflow vibrations at detector and risk of water to UHV leak. 

Fast Vacuum Valve for Vacuum Safety 

T. Oversluizen, “Fast Valve for the National Synchrotron Light Source,” Nucl. Instrum. & Meth. 195, 

399 (1982). 

The need for all-vacuum beamlines with minimal vacuum protection from thick windows prompted this 

design, which extends the time for the shock-wave produced by a vacuum accident at the end-station to 

propagate to the storage ring chamber, thus allowing a fast-acting shutter to close in time to protect the 

ring vacuum. 

Development of In-vacuum Sliding Electrical Contacts 

Work done by P. Mortazavi for 52 MHZ RF Cavity Tuners, (1982). 

The reliability of sliding electrical contacts in vacuum had been a significant problem. A custom spring finger 

design was developed which has reliably operated for years in the NSLS RF cavity tuners. 

Development of Helicoflex Seal for NSLS 52 MHZ RF Cavities 

Work done by P. Mortazavi resulted in a reliable UHV vacuum seal for the RF Cavity cover which allowed 

frequency tuning of the cavity by virtue of seal deflection while maintaining vacuum tightness. 

Optical Metrology: 1993 R&D 100 Award 

The collaboration between P.Z. Takacs and E. Church produced what has become the standard description of 

figure and finish in the optics industry. Previously the standards were extremely qualitative, using ill-defined terms 

such as “scratch” and “dig.” Application of high-resolution optical interferometry and Fourier analysis of the 

results has led to international standards bodies adopting their descriptions of surface figure and finish. The 

industry standard instrument for measuring surface figure in large optics (the Long-trace Profilometer) was 

developed in the BNL Instrumentation Department by P. Takacs and funded by the NSLS. 

149 
HIGH BRIGHTNESS ELECTRON BEAMS 

Development of High Brightness Electron Beams 

X.J. Wang, T. Srinivasan, K. Batchelor, M. Babzien, I. Ben-Zvi, R. Malone, I. Pogorelsky, X. Qiu, J. 

Skaritka and J. Sheehan, “Experimental Characterization of High-Brightness Electron Photoinjector,” 

Nuclear Instruments and Methods in Physics Research A 375,82 (1996). 

Electron beams with a high density of electrons in 6-D phase space are the keystone for future high 

performance machines such as X-ray Free-Electron Lasers and linear colliders. The BNL S-band 

photocathode RF gun has been adopted for use by many laboratories and industries, notably: BNL ATF, 

SDL and CRCR, CERN, Japanese Laboratory for High-Energy Physics, Northrop-Grumman Corporation, 

Rocketdyne Corporation, Stanford Linear Accelerator Center, University of California at Los Angeles. 

The robust metal photocathode for RF guns has been developed at BNL. BNL-developed guns have 

achieved a record peak-surface-electric-field (1 50 MV/m). 

BNL RF Photocathode Electron Gun 

K. Batchelor, H. Kirk, J. Sheehan, M. Woodle, and K. McDonald, “Development of a High Brightness 

Electron Gun for the Accelerator Test Facility,” European Particle Accelerator Conference (1 988). 

Describes the design and testing of the first generation of the BNL design RFPhotocathode Electron Gun. 

Derivative designs used at CERN, SLAC, UCLA , KEK and elsewhere. 

150 

Beamline X25: Solvent-accessible surface of the PCNA trimer. The figure shows the 

molecular surface of the complex, with PCNA colored according to electrostatic potential and 

the peptide shown in white. In the calculation of electrostatic potential, dielectric constants of 

2.0 for the protein interior and 80 for solvent at an ionic strength equivalent to 100 mM KCI 

were used. Side chains of lysine and arginine residues were given a net positive charge and 

aspartate and glutamate negative, with other residues considered neutral. Regions of intense 

positive charge appear blue, and electronegative regions of the surface are red. 

J.M. Gulbis, Z. Kelman, J. Hurwitz, M. ODonnel, and J. Kuriyan, Ce// 87, 297-306 (1996). 
APPENDICE

From the Managing Editor 

This year’s Activity Report abstracts were once again entered by the authors via the Electronic 

Submission System (ESS). The ESS takes information entered through the Forms function on the World 

Wide Web and stores it in a database optimized for document handling. Composition routines then perform 

the integration of text and figures and output our choice of PostScript or PDF file (for the author to view and 

also to go to the printer), SGML file (Standardized Generalized Markup Language) for electronic publishing, 

and HTML (Hyper Text Markup Language) for dissemination on the World Wide Web. Furthermore, the 

ESS allows full storage and retrieval of the abstracts, sorted by beamline and author. 

The ESS was much more user-friendly this year, due to the addition of the PDF file format that the 

authors could view using Adobe Acrobat Reader and some modifications to the Web form and program. 

Judging by the decrease in questions and problems from authors, the system seems to be moving out of 

its development phase and into a real production mode. About 480 abstracts were received for this 1996 

edition, consistent with the previous few years. In addtion, there were another 100 abstracts which authors 

had begun but did not finish in time for the production deadline - these are being ”rolled over” into the 

1997 Activity report and the authors will have opportunity to finish them up as soon as the ESS opens once 

again. Next year, just as in this past year, authors may elect to submit on diskette or via e-mail but for a 

deadline earlier than for the ESS submissions. Please watch the NSLS Newsletter and/or the NSLS Home 

Page for details. 

We thank everyone who used the ESS to report the results of their work at the NSLS. I would especially 

like to thank Lydia Rogers and Linda Feierabend of the User Administration Office, who kept almost 600 

abstracts well organized, worked with lots of new software, and assisted all the authors who called with 

questions. 

You can access the completed abstracts as well as the ESS on the World Wide Web on the NSLS 

Home Page at http://www.nsls.bnl.gov All instructions are provided in both viewable and downloadable 

formats. 

A- 1 
A BSTRA CTS 

VUV Beamlines 

Beamline U1A 

Self-assembled Monolayers of Oligo(p-pheny1ene)s on Gold Investigated with NEXAFS ....... D. Fischer, G. Hahner, N.D. Spencer, S. Brunner, W.R. Caseri, and U.W. Suter (ETH 

Zurich) 

A-07 

Beamline U2B 

Implementation of an Extrinsic Germanium Photoconductive Detector on the U2B Irps Infrared 

Microspectrometer ............................................................................. A-07 

G.L. Carr (NSLS) 

Infrared Microspectrometer and Beamline Optical Analysis ..................................... 

Infrared Microspectroscopy Functional Group Mapping of Normal and Diseased Brain Tissue. ... 

G.L. Carr (NSLS) 

L-P. Choo, M. Jackson, H.H. Mantsch (NRC, Canada), W.C. Halliday (U. Manitoba), 

D.L. Wetzel (Kansas State U.) and S.M. Levine (U. Kansas). 

G.Fuchs, J.J.Barieux, C.Wilhem (ELF-Atochem, France), P.Dumas (LURE and 

LASIR-CNRS, France), G.L.Carr and G.P.Williams (NSLS) 

G.P. Halada (SUNY Stony Brook), C.G. Fountzoulas (USARL), G. Williams and L. Carr (NSLS) 

Fourier Transform Infrared Microspectroscopy of Acetone Wash Induced Pitting in A12024-T3 . . 

G.P. Halada, S.V. Kagwade (SUNY Stony Brook), L. Carr and G. Williams (NSLS) 

Classical and Quantum Mechanical Ordering in Dense Hydrogen: Evidence from Synchrotron 

Infrared Spectroscopy .......................................................................... 

Chemical Profile of a Polymer Composite: The Case of a Commercial Orange Bottle. ........... 

Fourier Transform Microspectroscopy of Defect Structures in Si Diamond-Like Coatings ......... A-09 

A-10 

R. J. Hemley, I. I. Mazin, A. F. Goncharov, M. Li, H. K. Mao (Carnegie Inst. 

of Washington ICHiPR) 

A-08 

A-08 

A-09 

Evidence for Intracellular Structure From IR Microspectroscopy. ................................ 

N.Jamin (DIEP-CEA, France), J.L.Teillaud (Inst. Curie, France), P.Dumas (LURE and 

LASIR,CNRS, France), G.L.Carr and G.P.Williams (NSLS) 

Drug Distribution in Hair Determined by Infrared Microspectroscopy ........................... K.S. Kalasinsky (Armed Forces Inst. Path.), D.G. Cameron (DHC Analysis), 

and D.L. Wetzel (Kansas St. U.) 

Synchrotron Micro-Infrared Spectroscopy of Hydrous (Mg,Fe)zSiOs Phases ..................... R. Lu, R. J. Hemley, H. K. Mao (Carnegie Inst. of Washington / CHiPR), J. H. Chen, 

T. Inoue, and H. Kagi (SUNY Stony Brook, CHiPR) 

R. Lu, R. J. Hemley, H. K. Mao (Carnegie Inst. of Washington / SUNY Stony Brook, CHiPR), 

G. R. Rossman (Caltech) 

High-pressure Synchrotron Infrared Spectroscopy of Hydrogen in Garnets ....................... A-12 

A-11 

A-12 

A-10 

A-11 

A-2 
Synchrotron Based IR Microspectroscopy of Thermal Degradation Mechanisms in Polymer 

Composite Systems ............................................................................ R.J. Meilunas and T. Donnellan (Northrop Grumman Corp) 

Application of Infrared Synchrotron Radiation to Microanalysis of Advanced Ceramic 

Composite Systems ............................................................................ R. J. Meilunas and A. Tobin (Northrop Grumman Corp.) 

D.L. Wetzel (Kansas State U.) and R.O. Carter I11 (Ford Science Res. Ctr.) 

Polymer Depth Profiling with Synchrotron Infrared Microspectroscopy .......................... 

Localized Heterogeneity of Biological Tissues and Textile Surfaces Revealed with Synchrotron 

IR Microspectroscopy .......................................................................... D.L. Wetsel, L. Cho, J. Sweat, (Kansas St. U.), S.M. LeVine (U. Kan. Med. Ctr.), and 

J.A. Reffner (Spectra-Tech, Inc.) 

Carl G. Zimba (MIT) 

Diffraction-Limited Infrared Microspectroscopy of Polymer Laminates .......................... 

Beamline U4A 

The Electronic Structure of GaN Measured Using ARP ...................................... S.S. Dhesi, C.B. Stagarescu, L.-C. Duda and K.E. Smith, R. Singh and T. Moustakas, 

(Boston University) 

E. Goering, M. Schramme, 0. Mller, H. Paulin, M. Klemm, S. Horn (U. Augsburg), 

M. L. denBoer (CUNY Hunter) 

Wei Liu, R.G. Jordan and S.L.Qiu (Florida Atlantic U.) 

C.B. Stagarescu, S.S. Dhesi, and K.E. Smith (Boston U.), R. Haddon (Bell Labs), 

J. S. Brooks, (Florida State U.) 

Angle Resolved Photoemission of of V2O3 and VOz Near the Metal-Insulator Transition ........ 

Photoemission Studies of Ordered and Disordered Cu-Au Alloys ................................ 

Electronic Structure of the Organic Superconductor K-(BEDT-TTF)CU[N(CN)~]B~ ............. 

Beamline U4B 

C Is NEXAFS of LaOCgz .................................................................... J. F. Armbruster, N. Nucker, S. Schuppler, D. Fuchs (Forschungszentrum Karlsruhe, FRG), 

R. H. Michel, M. M. Kappes (U. of Karlsruhe, FRG) 

V. Chakarian and Y. U. Idzerda (NRL), C.T. Chen (Bell Labs) 

Magnetic Circular Dichroism Studies of FeV Alloys ............................................. 

Linearly Polarised Soft X-ray Resonant Magnetic Scattering from Fe,Mnl-,/Ir (001) 

Superlattices ................................................................................... A. DCchelette-Barbara, J.M. Tonnerre, F. Bartolomk, D. Raoux (CNRS, France), H.M. Fischer 

(CNRS, Univ. Nancy I, France), V. Chakarian (NRL), and C.C. Kao (NSLS) 

M. Merz, N. Nucker, E. Pellegrin, S. Schuppler (Forschungszentrum Karlsruhe, FRG), 

M. Kielwein, M. Knupfer, M. S. Golden, J. Fink (IFW Dresden, FRG), C. T. Chen 

(SRRC, Taiwan), V. Chakarian, Y. U. Idserda (NRL), and A. Erb (U Geneve, Switzerland) 

High Temperature Metal-Insulator Transition of Lac003 ...................................... J.-H. Park (NSLS), S-W. Cheong (Bell Labs.), and C. T. Chen (SRRC) 

0 Is NEXAFS of Pr,Y1-,BaZCu3Oy Single Crystals ........................................... 

A-13 

A-13 

A-14 

A-14 

A-15 

A-15 

A-16 

A-16 

A-17 

A-17 

A-18 

A-18 

A-19 

A-19 

A- 3 
Polarization Dependence X-ray Absorption Studies of V2 03 .................................... A-20 

J.-H. Park (NSLS), L. H. Tjeng (U. of Groningen), J. W. Allen (U. of Michigan), 

C. T. Chen (SRRC), and P. Metcalf (Purdue U.) 

E. Pellegrin, L. H. Tjeng, F. M. F. de Groot, R. Hesper, G. A. Sawatzky (RUG), J. 

D. O’Mahony, C. F. J. Flipse (TUE), Y. Moritomo, Y. Tokura (JRCAT), C. T. Chen (SRRC) 

M. Schmidt, N. Niicker, T. R. Cummins, D. H. Lu, S. Schuppler (Forschungszentrum 

Karlsruhe, FRG), F. Lichtenberg (Varta Batterie AG, FRG) 

Soft X-ray Magnetic Circular Dichroism Study of Lal-,Sr,MnO3 ............................... A-20 

Nature of the Unoccupied Electronic States in SrzRu04 ........................................ A-21 

Beamline U4IR 

Pump-probe, Far-infrared Study of Pair Breaking and Recombination in Superconducting b . . A-21 

G.L. Carr and G.P. Williams (NSLS), D.B. Tanner (U. Florida) 

M.R.Chance, A. Xie, B. Sclavi, Q. He, L.M. Miller, M. Sullivan (AECOM) 

R. Henn, A. Wittlin, M. Cardona (Max-Planck Institut) and S. Uchida (U. of Tokyo) 

F.M. Hoffmann (SCI-MED) D.G. Van Campen, G.P. Williams (NSLS), J. Paul 

(Royal Inst. of Tech., Sweden) 

Low-Frequency Modes in Polypeptides and Proteins ............................................ A-22 

Doping Dependence of the IR Response of La2-,SrZCu04 ...................................... A-22 

Carbon Dioxide Activation and Alkali Compound Formation ................................... A-23 

Simultaneous Infrared Spectroscopy and DC Resistivity Measurements on Adsorbate-covered 

Epitaxial Copper Films ........................................................................ A-23 

A. Otto, M. Hein (U. Duesseldorf, Germany), P. Dumas (LURE, U. Paris-Sud, France), 

G.P. Williams (NSLS) 

Infrared Study of Fullerenes and Fullerides on Ag(lll), Au(ll0) and Cu(ll1) ................... 

P.Rudolf (LISE-Namur, Belgique), P.Dumas (LURE and LASIR-CNRS, France), Y.J.Chaba1 

(Lucent Technologies), D.Van Campen and G.P.Williams (NSLS) 

A-24 

Beamline U5UA 

Branch Crossings of Quantum Well States in Cu Films Deposited on Ni(001) ................ A-24 

D.-J. Huang and P. D. Johnson (BNL - Physics) 

The k-Space Origin of the Long Period Oscillation in Fe/Cr Multilayers: A Photoemission 

Study of Epitaxial Cr Grown on an Fe(100) Whisker ........................................... A-25 

J. Pearson, S. D. Bader (ANL), E. Vescovo, D.-J. Huang, P. D. Johnson (BNL), B. 

Heinrich (SFU) 

The U5UA SGM-beamline: First Tests on the Performances ................................... A-25 

E. Vescovo, &.-Y. Dong, G. Nintzel, D. Carlson, and S. Hulbert (NSLS) 

Spin-polarized Electronic Structure of Fe( 100): A New Surface-related State .................... A-26 

E. Vescovo (NSLS), D.-J. Huang, P.D. Johnson (BNL- Physics) 

Beamline U7B 

Photoemission Study of Ni-A1 Alloys .......................................................... A-26 

H. Niu, S.L. Qiu and R.G. Jordan (Florida Atlantic U.) 

A-4 
Beamline U13UB 

Extreme Ultraviolet Lithography . Commissioning of an Offner 1:l Imaging Camera ......... A-27 

A.MacDowel1, O.Wood I1 (Lucent Technologies), K.Fuji (NEC) 

Beamline U14A 

Auger Decay of a Core Level Satellite Feature Observed by Auger Photoelectron 

Coincidence Spectroscopy ..................................................................... A-27 

R. Gotter (Laboratorio TASC-INFM, Italy) , R.A. Bartynski (Rutgers U.), Xu. Wu, 

S.L. Hulbert (NSLS), and H. Nozoye (Natl. Inst. of Materials and Chemical Research, 

Japan) 

Core Hole Decay Mechanisms in Ru Studied by Auger-photoelectron Coincidence 

Spectroscopy .................................................................................. A-28 

R. Gotter, R.A. Bartynski (Rutgers U.), X. Wu, S.L. Hulbert (NSLS), and 

H. Nozoye (Nat. Inst. of Materials and Chemical Research) 

Defects on the TiOz( 110) Surface Observed by Auger-photoelectron Coincidence 

Spectroscopy .................................................................................. A-28 

W.K. Siu, R.A. Bartynski, (Rutgers U.) A. Namgia, A.H. Weiss, (U. of Texas Arlington), X. Wu, 

and S.L. Hulbert (NSLS) 

Beamline U15 

Atomic-Site-Selective Core-Electron Excitation of 5-Oxohexanenitrile Isolated in D2 

Matrices ....................................................................................... A-29 

S. Sambasivan, A. T. Wen and D. M. Hanson (SUNY Stony Brook) 

A- 5 

Self-assembled Monolayers of Oligo(p-pheny1ene)s on Gold Investigated with NEXAFS ~ 

D. Fischer, G. Hahner, N.D. Spencer, S. Brunner, W.R. Caseri, and U.W. Suter 

(ETH Zurich) 

Adsorbing organic molecules by self-assembly on inorganic surfaces is an effective 

way of modifying surface properties. The behavior of ultrathin polymer layers on 

metals is particularly interesting for optimizing those properties, which play an important role in adhesion, sensor technology, tribology and corrosion. 

We have investigated the adsorption of substituted oligo(p-pheny1ene)s of var- ious lengths (Le. different number of phenyl moieties) from solution onto gold 

substrates. The behavior of these model systems is between that of flexible and 

rod-like molecules, and they have been especially synthesized in order to establish 

self-assembled monolayers. NEXAFS was used to study the chain orientation and 

electronic structure of the adsorbed molecules. 

Fig.1 shows NEXAFS spectra taken at the Cls edge for different angles of incidence, 0, for A5C6 (see Figure below), adsorbed from a 1mM solution in toluene 

for 4h. As for all investigated oligomers the thickness of the adsorbed layer is in 

the 5-10A range. On the basis of the spectra it can be concluded that no coordination occurs upon adsorption. The angular dependence of the transition into 

(unoccupied) T* orbitals can be used to determine the average tilt angle of the 

phenyl moieties. However, due to the small number of adsorbed molecules the error limits are large. The determined average tilt angle amounts to 43- 45' relative to 

the surface with error limits of 6-9'. We interpret the measurements as showing 

that the influence of the substrate on the adsorbates is rather weak, regarding both 

electronic structure and orientation, although a slight deviation from a random orientation (corresponding to an average tilt angle of 55') due to the interaction with 

the surface is supported by our data. 

280 295 310 325 

Photon energy [eV] 

Figure 1. 

I U2B I Implementation of an Extrinsic Germanium Photoconductive Detector on the U2B Irps Infrared Microspectrometer 

G.L. Carr (NSLS) 

The standard detector for mid-infrared spectrometers (including microspectrometers is the intrinsic ternary alloy Hg,-,Cd,Te (MCT), operated in a photoconductive ? PC) mode. Such detectors offer the best signal-to-noise commercially available 

for the wavelength range from <4pm to about 15pm. However, in many instances 

these detectors have a non-linear (with intensity) photoresponse, and some applications require performance to beyond 25pm. Photovoltaic (PV) MCT is more linear, 

but the long wavelength response limit is less than for PC MCT. An alternative 

detector for mid-infrared spectroscopy is extrinsic germanium, doped with Cu or 

Zn. The noise level is typically a factor of two higher than for MCT, but response 

extends to 30pm and linearity is very good. To accomodate such a detector, a beam 

exit port, optics, and provision for external signal input were added to the Irps instrument, and comparison tests were conducted. The figures below illustrate the 

relative performance of the two types of detectors. Figure 1 illustrates the noise, 

which is higher for the Ge:Cu detector. Note that the Ge:Cu detector provides data 

down to 400 cm-' (25pm), which is limited by the spectrometer's KBr beamsplitter 

rather than the detector. Figure 2 shows the measured transmission of a lO*l% 

neutral density filter. The Ge:Cu detector provides an accurate measure, whereas 

the MCT detector has an error of -40%! 

1.002 

1.001 ___I <ic:('u 

0 

m 1.000 

LT 

._ - 

0.999 

0.998 I.' ..,. '... 1000 2000 3000 4000 

Frequency [cm-'1 

Figure 1. Signal-to-noise comparisoi 

(100% lines) for the MCT and Ge:Cu de 

tectors. Signal for MCT detector end 

abruptly at 650 cm-' (16pm). 

k&- -&r&--im 

Frequency [cm-'1 

Figure 2. Linearity comparison for 

the MCT and Ge:Cu detectors, showing 

the measured of a neutral density filter 

(1 Ok 1 %). 
1 Infrared Microspectrometer and Beamline Optical Analysis I U2B I 

G.L. Carr (NSLS) 

The present mid-infrared beamline at U2B has a lOxlOmr port and spherical 

mirror optics. In addition, the optical train inside the Irps infrared microspectrometer endstation includes a spherical pre-focusing optic. This optical configuration 

leads a -30 pm spotsize at the sample location, determined by both ray-tracing and 

actual measurements (Fig. 1, top). The ray tracing also reveals that this spotsize 

is determined by aberrations rather than diffraction (Fig.1 bottom). Despite this 

limitation, the signal throughput is 1 to 2 orders of magnitude greater than that 

obtained with a conventional source. A new infrared port with improved optics 

is being constructed at beamline U10. Calculations based on the improved beamline design, and replacing one optic inside the Irps with an off-axis paraboloid, are 

shown in Figure 2. The optics are now diffraction limited, and the combination 

of increased flux (>5x and reduced spotsize should result in a 40-fold increase in 

brightness at the samp Installation of the Irps at UlOB is expected to occur early 

in 1997. 

Calculated profile Measured profile 

"LA 

Radial distance [pnl 

Figure 1. Optical performance fc 

present configuration at U2B. Calci 

lated and measured image (top) an 

calculated encircled energy distributio 

(bottom). 

Calculated profile, 

UlOB With ideal optics '$ff 

Figure 2. Optical performance for improved configuration at UlOB. Calculated image profile (top) and calculated 

encircled energy distribution (bottom). 

Infrared Microspectroscopy Functional Group Mapping of Normal 

and Diseased Brain Tissue. 

L-P. Choo, M. Jackson, H.H. Mantsch (NRC, Canada), W.C. Halliday (U. Manitoba), D.L. Wetzel (Kansas State U.) and S.M. Levine (U. Kansas). 

Multiple frozen sections of human brain tissue, representing Alzheimer's and multiple sclerosis (MS) diseased cases, were prepared for examination by microtoming 

and thaw-mounting on BaFz optical windows. Lesion sites typical of both diseases, 

and also normal tissue, were selected to allow contrast in functional group mapping. 

Synchrotron infrared microspectroscopy provided detailed mappings of 1R absorptions associated with disease-specific functional groups. For each diseased brain, 

the IR functional group features were found coincident with the lesion sites. 

Figure 1 shows a 3-D stacked contour map of MS brain tissue, in which contrast 

is obtained from the peak area of the C-H bending vibration at 1469cm-'. The 

unaffected white matter (center) with the normal amount of lipid is high. The 

affected area where the white matter is destroyed has reduced 1469cm-1 absorption 

(gray matter is shown for comparison). Alzheimer's diseased (AD) brain tissues 

were also mapped. Spectra in figure 2 show the highly localized P-amyloid among 

a series of spectra from 12pm by 12pm apertures collected at 13pm intervals across 

the tissue mapped. This represents the first in situ mapping of @-amyloid in human 

brain tissues. Frequency shifts of the amide I band from 1651cm-' to 1631cmP1 

were used to construct the amide I band position image shown in figure 3. After 

mapping, histological staining of the same tissue confirmed the plaque location. 

x bml 

Figure 1. MS brain 1469cm-1 peak area map, contrasting gray matter (GM), 

normal white matter (WM), and plaque (P). Figure 2: AD brain amide I spectra 

at 13pm intervals showing 1631cm-1 maximum at plaque location. Figure 3: AD 

brain map showing &amyloid frequency shift. 
Chemical Profile of a Polymer Composite: The Case of a Commercial 

Orange Bottle. U2B 

G.Fuchs, J.J.Barieux, C.Wilhem (ELF-Atochem, France), P.Dumas (LURE and 

LASIR-CNRS, France), G.L.Carr and G.P.Williams (NSLS) 

Numerous plastic components are now used in everyday life. One such example 

is an orange juice bottle that is produced as a multi-component, layered polymer. 

As depicted on Fig. 1, this bottle, commercialized in France as "JOKER bottle", is 

composed of six layers. Each layer has a characteristic infrared spectrum. Therefore, 

profile analysis of the frequency and intensity changes through the plastic layers 

allows one to study the different interfaces, and the inter-diffusion of species. 

Such a study was carried out at beamline U2B. A microtome preparation of the 

bottle wall was linearly mapped, with an aperture of 6x6 pm2, and steps of 6 pmm. 

A typical mapping is represented on Fig. 2, in the 1000-2000 cm-I frequency region. 

A visible image of the cross-section is shown to the right. 

From the spectra, two dimensional profiles of each vibrational band, characteristic of a particular chemical function, can be obtained, e.g., such as that associated 

with the OH stretching mode of the alcohol functional group. For the case investigated, there is evidence that material from adhesive layers 2 and 4 has diffused 

into the adjacent material. Control of such diffusion is important for maintaining 

the structural integrity of the plastic. This demonstrates the utility of synchrotron 

IR microspectroscopy interface and interphase analysis of polymer laminate, as the 

useful information is contained mainly within a few microns of the laver interfaces. 

Six layers of commercial 

aker" b.onle. 

I) polyelhyme 

(50 m) 

2) polymer aoherlve 

(30 4 

3) EVOH polymrr 

(alr barr cr . 5u iiiii 

130 .m) 

11rgh1 blochlnp . 120 .tm) 

4) polymer amewe 

5) bldch Po yrlhylene 

6) orange polyelnylene 

(mcch ~lrr~lm I20 m) 

Figure 1. Schematic view of laminated 

plastic ("Joker") bottle material, showing 6 layers. 

I 2000 1800 1000 14W 120Q 1WO 

Wavenumber (cm') 

Figure 2. Linear absorption map across the plastic layers (left), visible image of 

microtomed section, showing the 6 layers 

(right). 

Fourier Transform Microspectroscopy of Defect Structures in Si 

U21R Diamond-Like Coatings 

G.P. Halada (SUNY Stony Brook), C.G. Fountzoulas (USARL), G. Williams and 

L. Carr (NSLS) 

FTIR microspectroscopy at U2IR was used in a preliminary (and ongoing) study 

of the surface o€ a Si-diamondlike carbon coating deposited on Si using an ion 

beam assisted deposition process. This process uses Ar+ ions and tetraphenyltetramethyl-trisiloxane (type 704 Dow-Corning silicone oil) as a precursor material, 

resulting in an average film stoichiometry of CssSi705H26Ar3. In particular, we analyzed areas showing apparent defect structures (pinholes and optically dark or 

speckled surface features as seen in Figure 1) to look for correlations with midinfrared absorbtion data. Figure 2 shows the FTIR line scan (collected along the 

line - from top to bottom - shown on Figure 1). This data was acquired with a 6x6 micron aperature in 5 micron steps. Background infrared absorbtion data from 

a non-coated area of the Si substrate was subtracted from each feature to limit 

the effects of water vapor and carbon dioxide on the observed data. The broad 

absorbtion peak centered at about 2600 wavenumbers has appeared in earlier FTIR 

spectra of Si-DLC films and appears to be associated with C-H (and perhaps some 

Si-H) bond stretching in the film. The small feature at about 1250 wavenumbers 

has been postulated to be evidence of Si-CHs bonding in the coating. Si-H bond 

stretching also results in the absorbtion of frequencies around 800-850 wavenumbers. 

It is of interest to note that the Si-H and Si-CH3 features strengthen slightly for 

darkened regions of the film in which there is a shift of the primary broad peak 

to higher wavenumbers. Additional analyses will be performed to further explain 

these features and results. As noted in the line scan data, the broad feature falls 

off completely in the region of the scan associated with the hole in the coating and seems to build in intensity as the coating thickens at the edge of the hole. As noted, 

the peak shifts slightly to higher wavenumbers as the analysis beam crosses an area 

which shows a dense region of dark inclusions (which appear in a lower density 

scattered across the film). This change may relate to a higher force constant in this 

region, indicating a different H coordination chemistry. In further work, we will 

attempt to find correlations between such shifts in infrared absorbtion features and 

changes in both surface chemistry and mechanical properties (such as hardness). 

Figure 1. Optical micrograph of hole 

(light) and defect-enriched area (dark) 

in diamond-like coating on Si. Line indicates location of line scan (from top to 

bottom) Figure 2. 150 micron FTIR line scan of 

defects in diamond-like coating on Si. 
?- 

U2IR ~ 

Fourier Transform Infrared Microspectroscopy of Acetone Wash Induced Pittine: in A12024-T3 0 

G.P. Halada, S.V. Kagwade (SUNY Stony Brook), L. Carr and G. Williams (NSLS) 

The process of pitting in aluminum alloy A12024-T3 in aqueous NaCl has been a 

subject of numerous investigations due to the alloy’s importance to aircraft structural engineering. Multiple cleaning and surface preparation processes using organic 

solvents such as acetone and isopropanol are commomly used in industry. Ongoing 

electrochemical and X-ray Photoelectron Spectroscopy (XPS) studies of corrosion 

characteristics of A12024-T3 following various surface preparation methods have indicated that an acetone wash prior to introduction to an aqueous NaCl environment 

leads to changes in the alloy surface. Acetone was shown to enhance the formation 

of pits in the presence of aqueous NaC1, and XPS indicated the formation of various 

corrosion products, including acetates, oxides and chlorides, on the sample surface. 

In order to further our understanding of the spatial association of these chemical 

species with visible pits in the alloy surface, a study was undertaken using Fourier 

Transform Infrared microspectroscopy. Figure 1 shows an optical micrograph of a typical pit in an alloy surface washed in acetone and then exposed to an aqueous 

NaCl environment. An FTIR line scan was performed n a 150 micron long path across this region, from left to right, as shown. This data is presented in Figure 

2, in which the origin of the line is to the left. Mid-infrared spectra were taken 

using a 6x6 micron square aperature, moved in 5 micron steps. Background from 

an adjacent clean alloy surface was subtracted from each spectra to limit the effects 

of water vapor and carbon dioxide on the observed data. The data shows that 

the broad hydroxide/bound water peak centered at about 3300 wavenumbers shifts 

slightly to higher frequency as we approach the edge of the pit (at about the dark 

ring about the pit shown in Figure l), probably indicating a higher force constant 

related to increased metal coordination. Strong absorbtion features due to COObonding (about 1550) and CH3 bonding (about 1425) (both features of acetate or 

acetyl-acetone) are also clearly evident in the region surrounding the pit. Within 

the pit, however, these features decrease dramatically, and are partly replaced by 

absorbtion features both in the 500-1000 and 1700-2800 wavenumber region, possibly indicating mixed oxides or metal oxy-chlorides. Ongoing work involving both 

standards and complementary spectroscopies is being pursued to further clarify 

these results. 

I IIIIIIaII, 

m m 2yo %a 1m Im Figure 1. Optical micrograph showing a -I- I‘Sl 

pit on the surface of the alloy. Line on 

figure indicates location of 150 micron 

scan (from left to right) 

~i~~~~ 2. FTIR line profile across the pit 

area 

U2B 

Classical and Quantum Mechanical Ordering in Dense Hydrogen: EVidence from Synchrotron Infrared Spectroscopy 

R. J. Hemley, I. I. Masin, A. F. Goncharov, M. Li, H. K. Mao (Carnegie Inst. of 

Washington /CHiPR) 

High-pressure synchrotron infrared spectroscopy has been instrumental in detailing the rich evolution of the physical properties of solid hydrogen with increasing 

density. Recent work, in particular, has allowed us to identify two fundamentally 

different kinds of pressure-induced orientational ordering transitions at megabar 

pressures. 

As in previous work, synchrotron infrared absorption spectra were measured on 

hydrogen samples contained in modified megabar diamond-anvil cells using the 

high-pressure facility at U2B. Measurements were carried out as a function of temperature to 200 GPa through phase I (the low-pressure, high-temperature phase), 

phase I1 (the low-temperature broken symmetry phase), and phase I11 (the higher 

pressure phase stable above 150 GPa). The intensity of the vibron was carefully 

measured and characterized in terms of effective charges. In phase 111, for example, 

the effective charge of the strong vibron is q*=0.032e at 167 GPa and 85 K; it 

increases with pressure and reaches 0.037e at 230 GPa. In contrast, in phase I1 q* 

is slightly less than 0.004e at 140 GPa and the same temperature, and in phase I, 

there is a broad, weak disorder-induced band instead of a sharp vibron. 

Further understanding can be obtained from analysis of the temperature dependence of the effective charges. The data indicate that the infrared activity, which is 

proportional to (q*)’, is linearly related to Av’, or Avoc q*, over the entire range 

of temperatures and pressures studied. In formal terms, Avocq* can be interpreted as both quantities being linear functions of a scalar order parameter, Avq , and 

q*q. Taken together with previous Raman data, we conclude that phase I11 is 

qualitatively different from the lower-pressure broken-symmetry phase 11. Both are orientationally ordered, but the ordering objects in phase I1 are angular momenta 

of rotating molecules (quantum ordering), and in phase I11 it is the molecules themselves (classical ordering). 

(a) H, 146 GP~ 

0.06 O.D. 83 

c 

[ 

141 K 

157 K 

178 K 

4400 4600 

Wavenumber (cm-’) Wavenumber (em-’) 

4400 4600 

Figure 1. Temp. dependence of infrared vibron spectra. (a) 1-11 transition. (b) 

1-111 transition. 
I Evidence for Intracellular Structure From IR Microspectroscopy. 1 U2B I I Drug Distribution in Hair Determined by Infrared Microspectroscopy I U2B I 

NJamin (DIEP-CEA, France), J.L.Teiaud (Inst. Curie, France), P.Dumas (LURE 

and LASIR,CNRS, France), G.L.Carr and G.P.Williams (NSLS) 

Probing the chemical composition of a living cell is very challenging due to the 

small dimensions (<40pm). Infrared microspectrometers provide chemical specificity, and the average power (at the sample) is too weak to damage living cells. 

But the low brightness of its IR (globar) source restricts its utility to areas ~25pm 

or greater. The IR synchrotron source overcomes this limitation, and we present 

a study demonstrating the successful imaging of a live cell (Mouse hybridoma B) 

using the microspectroscopy system at beamline U2B. 

The cells were dispersed on BaFz using a cytospin technique, and their live character confirmed before and after IR analysis. Infrared spectra were recorded using 

a 3x3pm2 aperture, and a typical spectrum is shown in the top panel. Absorption 

features associated with various cellular chemicals are labelled. Chemical profiling 

of a cell was achieved by collecting spectra at 3pm intervals in a raster-like fashion (-1 min. per spectrum). Two chemical profiles, along with a visible image of 

the cell, are shown in the lower panels of the figure. Of particular interest is the 

stretching mode of aliphatic methylene groups (-CHz), associated mostly with lipids 

and proteins, which shows a lateral separation not apparent in the visible image. 

This demonstrates the great potential of IR synchrotron microspectromscopy for 

investigating the intracellular chemical composition of live cells. 

4 

w 

? - 

CH-Proteins 1652 cm-, 0.16 a, 0 

m 

0 

a 

9 0.12 

a 0.08 

' Amide II 

0.04 ....l....,. ,.,., ., ,..,.... 4000 3500 3000 2500 2000 1500 1000 

Wavenumbers (cm-l) 

visible imaoe 2920 cm-' (CH-proteins) 1652 cm-' (Amine I) 

0 L 0 ss rd i a li I 

4 

20 prn 20 prn 20 prn 

Figure 1. 

~~ 

K.ST Kalasinsky (Armed Forces Inst. Path.), D.G. Cameron (DHC AniyTs), and 

D.L. Wetzel (Kansas St. U.) 

Localization of drug metabolites within human hair is important in determining 

the pharmacokinetics of drug incorporation in hair. This information is critical 

to validate drug testing data from hair. Microspectroscopic probing of small ar- eas (<10pm in diameter) within longitudinally microtomed hair sections provides 

a profile of the drug deposition along a growth line and thus indicates localization 

as a function of time. Probing across individual hairs may reveal the hydrophobic/hydrophilic characteristics of the substance. Hydrophobic drugs tend to bind 

to the central core of the hair medulla, while hydrophilic drugs tend to be spread 

throughout the cortex of the hair, and generally appear in lower concentrations per 

dose. High spatial resolution distribution profiles of hair regions are necessary for 

these determinations. This information is not readily available through conventional 

infrared microspectroscopy. 

Initial work at the NSLS infrared microspectrometer has shown the feasibility 

of resolving the drug incorporation issue. Sample handling has been determined 

and initial work with spiked or doped hairs has shown the presence of drugs in the 

protein profile. Previous data by conventional infrared microscopy has not been 

sensitive enough to show evidence of the drug in the hair without extensive data 

manipulation. The figure below shows NSLS IR microscope protein spectra of spiked 

hairs superimposed on a reference hair spectrum. The indicated band in the spiked 

hairs at 1735 cm-l, which is not present in the reference spectrum, is the carbonyl 

band of 6-monoacetyl morphine (the primary metabolite of heroin). Unfortunately, 

contamination from a sample preparation procedure led to an absorption which 

obscured distribution profiles. Corrective preparation techniques have been devised 

and subsequent data collections at the NSLS are expected to reveal the distribution 

profiles. We also anticipate obtaining high spatial resolution information, which is 

required for determining drug transport and binding in hair, using the synchrotron 

infrared microspectrometer system. 

1x00 1700 1600 1500 

Frequency [ern.'] 

Figure 1. 

showing the shoulder at 1735 cm-I associated with heroine metabolite. 

Spectra from micro-sections of reference (drug-free) and spiked hair, 
? 

r 

U2B Synchrotron Micro-Infrared Spectroscopy of Hydrous (Mg,Fe)zSiO4 

Phases 

R. Lu, R. J. Hemley, H. K. Mao (Carnegie Inst. of Washington / CHiPR), J. H. 

Chen, T. Inoue, and H. Kagi (SUNY Stony Brook, CHiPR) 

Infrared spectroscopy provides detailed information on bonding characteristics of 

crystals, liquids and glasses and it is a useful probe of structural symmetry. It is also 

widely applied to studying structural, thermochemical, and electronic properties of 

materials. 

We have used synchrotron micro-infrared spectroscopy to characterize the effects 

of hydrogen on the phase relations and physical properties of olivine polymorphs E-, 

p:, and y-(Mg,Fe)zSi04. Samples of either San Carlos olivine or forsterite mixed 

with Ha0 were subjected to high temperatures and pressures and quenched to 

ambient conditions. We use the high spatial resolution of the Nicolet microscope as 

a structural probe for phase identification and characterization of the pressure- and 

temperature-quenched material. Grains and structurally zoned areas as small as 

-10 microns were probed and identified in situ by reflectance measurements of the 

polished samples while inside capsules. Absorbance spectra were also measured from 

crystals freed from the capsule. Both sets of measurements are used to determined 

hydroxyl concentrations. 

The presence of structurally bound OH in the Fe-containing olivine system expands the stability field of the ,&phase into both a- and y-phases. This effect is 

not observed in the Mg-end member systems. The advantages of the synchrotron 

micro-IR approach for phase identification include the high-spatial resolution down 

to diffraction limits of the infrared beam) and the non-destructive nature ( 6 ue to 

the weak IR beam) in comparison to XRD and laser-Raman. Both of these advantages are particularly important for such studies because many mantle minerals are both fine grained and metastable at ambient condition. 

so,---. , , , , , , , , , ~ -.--- 8an Carlos 011vlne 

hydrothermally anealed at 14GPa/1200'C10,Shr (from 12 Nrn arey 

4000 3800 3600 3400 3200 3000 2800 

Frequency, cm- ' 

Figure 1. High-frequency infrared spectrum of San Carlos olivine hydrothermally 

annealed at 14 GPa and 1200 C for 0.5 hr. The spectrum was measured under 

ambient conditions. 

U2B High-pressure Synchrotron Infrared Spectroscopy of Hydrogen in 

Garnets 

R. Lu, R. J. Hemley, H. K. Mao (Carnegie Inst. of Washington / SUNY Stony 

Hydrogarnet substitution (Sicj4H is known to be responsible for incorporation 

the infrared spectra of garnets have complex OH bands that suggest alternative 

mechanisms for hydrogen substitution. Study of these mechanisms is important for 

understanding the uptake of hydrogen in mantle minerals in general. We selected 

two garnets, grossular (CasAlaSi3Ol2) and spessartine (Mn3AlzS4012), as models 

for studying hydroxyl substitution. These garnets show respresentative multiple 

OH bands that are expected to originate from both hydrogarnet substitution as 

well as previously undocumented alternative structural sites. We studied these hydroxyl bands at high pressures with a diamond anvil cell by synchrotron infrared 

spectroscopy at beam line U2B. We used custom designed instrumentation based on a Nicolet FTIR spectrometer and microscope consisting of two Cassergrain objectives optically interfaced with a symmetrical diamond anvil cell. Frequencies of 

the OH bands in grossular garnet range from 3534 to 3688 cm-' which corresponds 

to 0-H ... 0 bonds from 2.93 to 3.27 . These bands exhibit both positive and 

negative frequency shifts with pressure ranging widely from -7.7 to 3.0 cm-'/GPa. 

Such large frequency shifts reflect significant changes in 0-H ... 0 bond lengths. By 

contrast, the OH bands in spessartine (ranging from 3582 to 3649 cm-') all have 

positive pressure shifts, and range from 0.23 to 2.91 cm-'/GPa indicating very 

weak hydrogen bonding. Moreover, the frequency shifts for both garnets show a well defined linear dependence on OH frequency, with the slopes (dv/dP)/v of 

0.05 (grossular) and 0.04 (spessartine). These values are systematically higher than 

those for hydrous P-(Mg,Fe)zSi04 and serpentine, for which similar high-pressure 

spectroscopic data are available. Systematics and structural implications of these 

results are under investigation. 

Brook, CHiPR), G. R. Rossman (Caltech) 

of hydrogen in garnets from the Eart 1, 's mantle. It is also known, however, that 

Figure 1. High-pressure infrared spectrum of grossular (South Africa) 
I U2B I Synchrotron Based IR Microspectroscopy of Thermal Degradation 

Mechanisms in Polymer Composite Systems I U2B I Application of Infrared Synchrotron Radiation to Microanalysis of Advanced Ceramic Composite Systems 

R.J. Meilunas and T. Donnellan (Northrop Grumman Corp) 

The enhanced sensitivity of an infrared microscope integrated with a synchrotron 

light source was used to characterize the time dependent thermal degradation in 

several polymer matrix composite systems. For graphite fiber/ polyimide composites, the increased spatial resolution provided by the microscope allows IR characterization of the inter-fiber polymer matrix component of the samples without the 

spectral distortion effects contributed by the broad band absorbance of the graphite 

fibers. This advantage allows for unambiguous determination of local variations in 

chemical structure in the composite materials such as in the surface and interior 

regions of samples exposed to thermo-oxidative environments as well as identifying 

preferential attack between interply and intraply regions. 

In this study the FTIR microscope was used to chemically quantify the effective- ness of different fiber sizing pretreatments on composite thermo-oxidative durability. 

A series of unidirectional, graphite fiber Amoco T650-75 ) / PMR-11-50 polymide 

pretreatments. The samples were heat treated at 370C for up to 700 hrs in air. Polished cross-sections were prepared of samples aged at specific time intervals and IR 

microreflectance measurements taken from select matrix rich regions at the surface, 

center and interply areas of the specimens. The IR spectral features associated 

with the time dependent, diffusion limited, thermo-oxidative degradation of the 

matrix phase were analyzed through the thickness of the composite. Specific fiber 

sizings formulations were identified which significantly reduced the degree of matrix 

degradation in the subsurface regions of the composite specimens. Synchrotron IR 

microspectroscopy is demonstrated as a powerful technique for determining local 

variations in chemical structure in polymer composite materials and for identifying 

degradation mechanisms in these materials and the kinetics of these mechanisms 

under specific exposure conditions. 

composite samples were prepared with di h erent reactive coupling based fiber sizing 

R. J. Meilunas and A. Tobin (Northrop Grumman Corp.) 

The utility of characterizing ceramic matrix composites using the enhanced sensitivity provided by an infrared microscope integrated with a synchrotron light source, was investigated. In this study the influence of pyrolysis process parameters on the 

oxidation stability of a Nextel fiber /silicon carboxide glass ceramic matrix composite system was evaluated. A series of 2D Nextel 312 fiber/ Blackglas 493 ceramic 

matrix composite samples were prepared by several pyrolysis processing conditions. 

The samples were then oxidized at 600C from 100 to 1000 hours in air. Polished 

cross-sections were prepared of samples exposed at specific time intervals and IR 

microreflectance measurements taken from select fiber rich and matrix rich regions 

at the surface and the interior of the specimens. The increased spatial resolution 

provided by the microscope enabled identification of an oxidation induced, interfiber silica phase, whose IR spectral signature would have otherwise been overlapped 

with the Nextel fibers’ silicate spectral band at larger, conventional sampling (aperture) areas. During the initial thermo-oxidative exposure, the inter-fiber Blackglas 

regions throughout the composite were found to convert to a silica phase through 

oxidation via pipe diffusion of oxygen along the fiber matrix interface. By this oxidation mechanism, the carbon stabilized glass matrix eventually is converted to a 

thin shell of silica surrounding all fiber rich regions of the composite. Though little 

variation was found in the IR spectra of the matrix phase as a function of pyrolysis 

conditions, differences were found in the suboxide structure formed during oxida 

tion depending on the pyrolysis treatment. The significance of these observations on the mechanical performance and long term stability of the Blackglas composites 

were assessed. 
Polymer Depth Profiling with Synchrotron Infrared Microspectroscopy 

D.L.Wetze1 (Kansas State U.) and R.O. Carter I11 (Ford Science Res. Ctr.) 

Various polymer specimens, previously subjected to surface treatment, have been 

the objects of surface preferenced IR probing at the laboratories of both investigators. ATR infrared microspectroscopy has been used to compare chemical changes 

at the treated surface with the virgin (back) surface of the same specimen. Photoacoustic infrared spectra of treated surfaces were also recorded prior to the NSLS 

work. The surface IR techniques show dramatic changes in the surface chemistry 

but attempts to establish the depth of the effect proved unsatisfactory. Acrylic 

polypropylene and polyethylene samples were involved. At beamline U2B of the 

NSLS, 6pm thick microtomed cross-sections of polymer laminates were prepared 

and mounted between BaFz windows in a microcompression cell. With a high signal, low noise, narrowly apertured beam of the microspectrometer, infrared transmission spectra were collected in a linear mapping pattern from a 6pm wide 24pm 

long target in a progression of 3pm steps. Even at the high spatial resolution re- quired good quality spectra resulted. Transmission spectra showed reduction in the 

relative intensities of major polymer absorption bands near the surface exposed to 

photochemical attack. At intermediate depth additionally the degregation reaction 

products were in evidence as OH and a new broad band in the fingerprint region. 

Figure 1 shows the beam pattern projected onto the polymer section. Figure 2 shows 

spectra of the changed material compared to the unexposed acrylic film. Acrylic 

film subjected to different photon fluxes and exposures times were interrogated and 

a control was run by mapping corresponding material that was completely protected from photochemical attack. Surface treated polypropylene and polyethylene 

specimen mapping was attempted but no penetration into a 3pm or 6pm depth was 

evident. 

Figure 1. Photomicrograph of mapped 

region. region . Figure 2. IR microspectroscopy map of 

Localized Heterogeneity of Biological Tissues and Textile Surfaces 

Revealed with Synchrotron IR Microspectroscopy 

D.L. Wetzel, L. Cho, J. Sweat, (Kansas St. U.), S.M. LeVine (U. Kan. Med. Ctr.), 

and J.A. Reffner (Spectra-Tech, Inc.) 

Infrared microspectroscopic mapping of biological tissue is routinely done at the 

KSU Microbeam Molecular Spectroscopy Laboratory using an "IRps" with conventional globar (thermal source. The chemical microstructure has been studied in situ 

for plant (wheat kerne 1 slices, etc.) and mammalian (normal and diseased brain) tissues. Additionally, single fibers are analyzed in both ATR and transmission modes. 

Smaller spot sizes are achieved with the same model microspectrometer coupled to 

beamline U2B of the NSLS, producing better spatial resolution and greater detail. 

It has been possible to identify localized heterogeneity using smaller aperture and 

step sizes (6pm or 12pm) that achieve 100% representation of the sampled area. A 

high S/N even at small apertures eliminates excessive scan times and makes high 

definition mapping practical. Tissue samples from mammalian brains and several 

grains that appear visually homogenous have been interrogated by this technique, 

revealling wavelength specific (chemically defined) heterogeneity. Figure 1, a 3-D 

stacked contour plot of a section of corn (Figure 2 shows a visible image), provides 

an example of the detail achieved. Mapping the amide I (protein) band clearly 

resolves the five aluerone cells of the corn, surrounded on one side by pericarp and 

by endosperm on the other. Other wavelengths can be used to reveal the different 

chemical species present in each morphological part. 

Adapting the ATR microscope objective to the IRps installed at U2B beamline 

has resulted in the ability to interrogate a lOpm spot on the surface of a single 

textile fiber to reveal variation in the surface treatment, e.g. permanent press, on a 

cotton fiber. Previously, 42pm was the practical limit with a conventional source. 

Figure 3 shows variation in spectra obtained using 10pm spots taken 15pm apart. 

165Ocm-I 

Figure 1. Corn 1650 cm-I peak 

igure 2. (right) Photomicrodosperm (right). Figure 3. (right) cotton fiber. 

1o.I) 

SO"?"m 8rn ,%a ,m 1- 1m 

w.m- Cm-') 

Figure 2. (top), Figure 3. (bottom). 
Diffraction-Limited Infrared Microspectroscopy of Polymer Laminates I TJ2B I 

Carl G. Zimba (MIT) 

By combining the chemical specificity afforded by infrared spectroscopy with 

the spatial resolution of optical microscopy, infrared microspectroscopy (IMS) has 

become a mainstay analytical tool in both academia and industry. While applications abound in a wide variety of fields including chemistry, physics, biology, 

polymer science, material science, forensic science, and art conservation, IMS has 

been limited in spatial resolution to sampling areas above ten microns in diameter. Replacing the traditional thermal emission source of a conventional infrared 

microscope with the infrared emission from the VUV ring at the NSLS, substantial 

improvements in both spatial resolution and signal-to-noise ratio of IMS measurements have been achieved, as illustrated in the figure below. (A false color image 

of this data was shown in the 1994 NSLS Activity Report on pages 118-9.) The 

sample used to obtain this data was a cross-section of a ten-layer polymer laminate, 

composed of alternating layers of a acrylic acid/ethyl acetate/methylmethacrylate 

copolymer and either poly(N-vinylpyrrolidone) or poly(viny1 alcohol), sandwiched 

between thick layers of polycarbonate and ethyl cellulose. The approximate thick- nesses of the individual layers in the interior of this laminate range from 2.5 to 4.5 

microns. The IMS data was acquired using a 3 micron wide slit sampling aperture 

oriented parallel to the laminate layers while the sample was rastered in 1 micron 

steps across the individual layers. Each of the layers can be easily discerned in this 

map of absorption intensity in the CH and OH stretching region. Presently, the 

lower limit of spatial resolution appears to be governed by diffraction effects and 

to be wavelength-dependent. In addition to this optical approach to improve the 

spatial resolution, various mathematical treatments, including chemometrics and 

correlation analysis, are being pursued. 

The Electronic Structure of GaN Measured Using ARP * 

S.S. Dhesi, C.B. Stagarescu, L.-C. Duda and K.E. Smith, R. Singh and T. Moustakas, (Boston University) 

Refractory 111-V nitrides such as GaN are an important class of wide band gap 

semiconductors, with possible use in optoelectronic, high power and high temperature devices. Advances in growth techniques have enabled the production of high 

quality single crystal GaN films on a variety of substrates. We have studied the 

electronic structure of thin film wurtzite (hexagonal GaN using angle resolved phoassisted molecular beam epitaxy at Boston University, and cleaned in the spectrometer chamber by Ga evaporation followed by repeated cycles of nitrogen sputtering 

and annealing in UHV. Samples showed sharp hexagonal LEED patterns, with no carbon and minimal oxygen contamination visible in Auger spectra following this 

procedure. The films were auto-doped n-type. Figure 1 shows initial results of our 

measurents of the GaN bulk and surface electronic structure. Clear band dispersion 

was visible in the ARP spectra, and this could be converted into the experimentally 

determined band structure of Fig. 1 by assuming a free electron final state. The 

solid lines in Fig. 1 are the results of an LDA calculation of the band structure by 

Rubbio et a2 (Phys. Rev. B 48 11810 1993)). The agreement with the calculation 

is excellent over a wide area of the Br' II ouin zone. Note, however, that a state was observed at the top of the valence band that has no counterpart in the calculated 

bulk structure. We tentatively identify this as a surface state, and have shown that 

it is sensitive to the absorption of 02. 

U4A 

toemission spectroscopy. Our samples were grown b y electron cyclotron resonance 

& 30 

si 

a 

S 

.- 

8 20 

10 

3600 3400 3200 3000 2800 

Wavenumber (cm- 1) 

Figure 1. 

Figure 1. Measured and calculated band structure of GaN. 

~ ~~~ 

* Work supported in part by the National Science Foundation under DMR-9504948. 
? 1 Angle Resolved Photoemission of of VzO3 and VOz Near the Metal- 1 TT ~ 1 U 5tA 1 Insulator Transition 

E. Goering, M. Schramme, 0. Mller, H. Paulin, M. Klemm, S. Horn (U. Augsburg), 

Q, 

~, 

M. L. denBoer (CUNY Hunter) 

Vanadium oxides have been studied for several decades because of their unusual properties, including temperature-induced metal-insulator transition (MIT) 

and electronic correlations in VOz and V203. However, good quality surfaces are 

hard to prepare, limiting angle-resolved photoemission. We have been able to mea- sure angular resolved photoemission on single crystals grown by chemical transport, 

which have specular surfaces and can be characterized by LEED after in situ heating in oxygen. Spectra were taken above and below the MIT for both materials. 

Fig. 2 shows angle resolved photoemission spectra of V203. Fig. 1 shows spectra 

of the VOz (110 (rutile) surface in both the metallic and insulating monoclinic 

spectra were fitted; the region near EF required a Fermi cutoff and two Gaussians, 

with linewidths 1.2eV and l.OeV,i.e., considerably larger than the instrumental resolution. 

The observed dispersion is much less than band structure calculations suggest [I], 

implying the electrons are less mobile than predicted. Two possible causes are: (a) 

Electron-electron correlations, which are expected in these materials. In fact, the 

two peak structure of the valence band in angle integrated measurements has been 

interpreted in terms of a lower Hubbard band (incoherent peak) and a coherent peak 

at EF. However, as band structure calculations predict the existence of two partially 

filled bands near of EF another explanation is possible. (b) Strong electron-lattice 

interactions, possibly related to the well-known structural instability of VOz and 

VzO3. This suggestion, while speculative, is perhaps supported by the observed 

peak widths, which are fit best not be Lorentzians (implying lifetime effects), but 

by Gaussians, implying broadening due to a superposition of lines, as would arise 

from coupling of electronic and lattice degrees of freedom. Such effects are observed, 

for example, for molecules chemisorbed on surfaces. 

[l] E. Goering, M. Schramme, 0. Mller, H. Paulin, M. Klemm, M. L. denBoer, 

and S. Horn, Physica B (in press). 

phases. The MI !r IS clearly reflected in these spectra. For quantitative analysis 

& * .I a * 1 

LC.X Figure 1. Normal emission photoemission of VOz 6110) rutile, above (solid) 

and below ( otted) the MIT (upper Figure 2. Normal emission photoemispart). Photon energies are indicated on sion of V2O3. Photon energies are indithe right. cated on the right. 

1 Photoemission Studies of Ordered and Disordered Cu-Au Alloys * 1 U4A 1 

Wei Liu, R.G. Jordan and S.L.Qiu (Florida Atlantic U.) 

Our interest in the electronic structure in CuAu and Cu3Au alloys is based on 

the fact that the CuAu alloy undergoes two transformations with increasing temperature: from CuAuI (L10-structure) to CuAuII (a one-dimensional long- period 

superlattice) at about 380 C and from CuAuII to disordered fcc at about 410 C. 

Cu3Au undergoes a transformation at about 390 C from the L12 structure to disordered fcc. Our objective is to gain some fundamental understanding of the driving 

force for these transformations. The order-disorder transformation depends on the 

competition between interatomic forces that, in turn, are intimately related to the 

underlying electronic structure. We have carried out a series of photoemission 

measurements from polycrystalline samples of CuAu and Cu3Au at different temperatures. Figure 1 shows the valence band spectra of CuAu in the ordered and 

disordered phases. There are considerable changes in the electronic structure in the 

region spanned by the Au-related d states. Figure 2 shows the shift of the Au 4f core 

level in CuAu alloy due to the phase difference. Similar changes in the valence band 

and core level spectra were also observed for Cu3Au alloy. It should be pointed out 

that using AES we found no significant difference in surface composition between 

the ordered and disordered phases. Thus, the changes we observe in the photoemission spectra are due to modifications in the electronic structure. More detailed 

data analysis is under way. 

e 

'1 

2 

RT - '$3w ............ 

.9 

2 2 

-10 -8 -6 -4 -2 0 2 

Binding Energy (eV) 

-90 -88 -86 -84 -82 -80 -78 

Figure 1. Valence band spectra of CuAu Binding Energy (eV) 

alloy in ordered and disordered phases Figure 2. Au 4f core level spectra of 

CuAu alloy in ordered and disordered 

* Supported by NSF Grant DMR- phases 

9500654. 
Electronic Structure of the Organic Superconductor -(BEDTTTF)Cu[N(CN)2]Br * 

C.B. Stagarescu, S.S. Dhesi, and K.E. Smith (Boston U.), R. Haddon (Bell Labs), 

U4A 

J. S. Brooks, (Florida State U.) 

The organic solid IC - f3EDT-TTF)Cu[N(CN)z]Br (where, BEDT-TTF = 

bis(ethylenenedithio1o)tetrat iafulvalene is a quasi-two dimensional (2D) conductor, with layers of BEDT-TTF stacks separated from each other by insulating anion 

sheets. This material, commonly referred to as ET, is metallic at room temperature 

and becomes superconducting at approximately 10 K. Despite extensive studies of 

the transport properties of this material, numerous aspects of the electronic structure of ET are unknown. We have begun a study of ET using angle resolved 

photoemission (ARP) spectroscopy and soft x-ray emission spectroscopy. Since ET 

is a layered material with a large unit cell, ARP will measure primarily the electronic structure of the outer layer. We have studied a series of crystals cleaved in 

UHV, and examined the electronic structure of the cleaved surfaces, ion bombarded 

surfaces, surfaces exposed to 02, and Cs- dosed surfaces. Figure 1 shows a series 

of normal emission spectra taken as a function of the angle of incidence of the light 

from a cleaved ET crystal. Virtually no emission is visible close to Ep in any of the 

spectra. This is likely to result from the poor quality of the cleaves, which are visibly rough. However, ARP can still provide information on the orbital charatcter of 

the valence band. As the angle if incidence is increased, the intensity of the feature 

at 3 eV below Ep increased dramatically. This is consistent with a C 2p character 

for this part of the valence band. These experiments are continuing, with emphasis 

on measuring the intrinsic electronic structure close to Ep. 

e 

Figure 1. ET normal emission as a function of photon angle of incidence. 

I C Is NEXAFS of LaQC82 

J. F. Armbruster, N. Nucker, S. Schuppler, D. Fuchs (Forschungssentrum Karlsruhe, FRG), R. H. Michel, M. M. Kappes (U. of Karlsruhe, FRG) 

Endohedral metallofullerenes like La@Csz should be rather stable in air. To study 

possible effects of air exposure, we determined the unoccupied electronic structure 

of air- and oxygen-exposed La@& by C 1s NEXAFS, taken both in transmission 

and in total electron yield (TEY) mode, and compared the results to annealed (M 

oxygen-free) films and to the parent compound (382. 

The figure depicts C Is NEXAFS for air and oxygen exposures and heat treatments. C82, after heating to 4OO0C, is shown at the top (a) for comparison. The 

fully air-exposed La@C82 spectrum (b) exhibits two features next to the main a* 

peak: a shoulder S at lower and a peak A at higher energies. After heating to 30OoC 

(c), S is reduced but still substantial, while A has vanished. S is further reduced by 

heating to 600 and 71OoC d), (f). These two traces are virtually identical, suggest02 at 5 x heating to 170°C 

from the dotted line denoting trace (f). Concurrent with this effect is a broadening 

and a slight shift of the a* feature, cf. (b). The surface-sensitive TEY data exhibits 

a behavior similar to the bulk; however, in (g’) peak A reappears, indicating that 

the surface region already saturates with oxygen. 

The NEXAFS for air- and oxygen-loaded La@Csz resembles closely the annealed 

C~Z. This suggests the simple view that the 3 electrons donated by La to the C82 

cage are in part removed by oxygen, thus in effect restoring the electronic structure 

of the empty cage. Caution is necessary, of course, since there is some mixing of La 

with cage orbitals, and since it is not clear yet if S could be caused by a Jahn-Tellerlike effect from lattice expansion. Also, for C82 the annealing temperature has to 

remain low and, thus, still some air may be left in those films. Still, we conclude 

that part of the intensity at S is due to such a “p type oxygen doping”. 

ing that air has been comp I etely removed from the films. The films were exposed to 

during exposure). In the latter case part of the intensity at Q,‘ is restored, as seen mbar before taking traces (e) (no heating) and g 

t,mmlSsim mode 

d 

282 284 286 288 290 Photon energy (ev) 282 284 286 288 290 maton energy (ev) 

* Work supported in part by NSF CAREER award DMR 95-01174. 

Figure 1. 
U4B ? I Magnetic Circular Dichroism Studies of FeV Alloys 00 

V. Chakarian and Y. U. Idzerda (NRL), C.T. Chen (Bell Labs) 

There are only a few elements in the periodic table that are ferromagnetic at 

room temperature, somewhat limiting the range of applications of magnetic materials. One way to extend the range of applications is to 'engineer' new magnetic 

materials formed of alloys and multilayers of these normally ferromagnetic materials. Among these alloys and multilayers, Fe-V system has been receiving a renewed 

attention. Studies have focussed on induced V moments as well as inverse magnetoresistance in artificially engineered Fe-V multilayers and alloys. The FeV alloys 

have some interesting properties in their own right. Based on numerous early neutron scattering experiments the alloy system is ferromagnetic at room temperature 

for V concentrations of up to 70 atThe induced V moments are as large as 1.2 

5B for in the dilute V limit and decrease rapidly to zero near 15 atthroughout the 

entire ferromagnetic phase, the V moments are anti-aligned to Fe moments which in 

turn decrease monotonically with increasing V concentration and finally reach zero 

near 70 atthis system does not display bulk antiferromagnetism. In this study, the 

magnetic characteristics of disordered FeV alloys have been studied via magnetic 

circular dichroism (MCD). The use of MCD allows the determination of Fe and V 

moments (the extraction of absolute V moments are somewhat more difficult but 

trends can be established). The measurements have been conducted in transmission on thin films grown in situ, minimizing surface effects and allowing for direct comparison of the measured moments to bulk moments determined via earlier neutron 

scattering experiments. The figures below show representative Fe and V absorption 

spectra as well as the corresponding MCD spectra. The V MCD spectrum, somewhat more complex than that of Fe due to different multiplet structure of V, clearly 

shows that V atoms possess a net moment anti-aligned to Fe moments as indicated 

by the positive MCD signal in the V L3 region. Surprisingly, though, for all the 

alloys studied, the orbital moment is near zero but positive, i.e., aligned with the 

Fe moments. A more detailed description of the experiment and the results for the 

entire ferromagnetic phase will be presented in an upcoming publication. 

VC is supported by the Office of Naval Research. 

700 710 720 730 

Photon Energy (eV) 

Figure 1. Representative Fe L-edge XAS 

and MCD spectra from a FeV alloy. 

510 515 520 525 

Photon Energy (eV) 

Figure 2. V L-edge XAS and MCD spectra for the FeV alloy of Fig. 1. 

Linearly Polarised Soft X-ray Resonant Magnetic Scattering from 

Fe,Mnl-,/Ir (001) Superlattices * U4B 

A. DCchelette-Barbara, J.M. Tonnerre, F. BartolomC, D. Raoux (CNRS, France), 

H.M. Fischer (CNRS, Univ. Nancy I, France), V. Chakarian (NRL), and C.C. Kao 

(NSLS) 

Soft x-ray resonant magnetic scattering (SXRMS) has been used in order to 

study the magnetic transition which occurs in Fe,Mnl-,/Ir(ROl) superlattices 

(SL's) for x=0.8. SQUID magnetometry and Mossbauer spectroscopy suggest a 

transition from an antiferromagnetic state to a ferromagnetic one for increasing 

x values. This result is remarkable since the bulk alloys are antiferromagnetic in 

the whole range of the alloy composition. Two samples, having an Fe concentration here and there of the transition (x=0.7 and x=O.Q), have been studied. 

The first sample, [(Feo..rMno.s)27;/(Ir)18,]2~, is labelled SL/0.7 and the second one 

[(Feo.sMno.l)z,,/(Ir),,;]z~ is noted SL/O.Q. SRXMS allows to discriminate the 

properties of Fe from those of Mn by working at their respective L-edges. Figure 1 

and 2 shows the energy dependence of the reflectivity measured using p-polarised 

soft x-rays in the transverse Kerr geometry as well as the derived asymmetry ratios. 

The incident angle was set to 15 degrees. While the whole shape of Ra is about the same for both samples and show a resonant effect near the Fe L3 and LZ edges, there 

is a strong decrease in the amplitude of the effect forSLIO7. For SL/O.Q alloy the 

maximum of the amplitude reaches 45% of magnetic effect where as for the sample 

where as for SL/0.7, the effect is of 3-4% only. The Fe magnetic moment appears 

to be much more affected by the change of the stoechiometry which is much more 

than that expected from SQUID measurements average magnetic moment: 1.75 

for SL/O.Q and 0.35 for SL/0.7). To discuss furt 6 er our experimental results, we 

need to fit the reflectivity curves and the asymmetry ratios. At the L2,3 edges of 

Mn and no magnetic effects have been observed within our statistic which suggests 

that Mn atoms do not carry a net magnetic moment or a very small one. 

0.01 - 0.4 

* 0.2 4 d B 

h 4 -0.2 z 

g 0.008 

- 0% 

g 

2 0.006 

- 0.004 

Y E 

4 o.oo2 -0.4 a 0 

700 710 720 730 740 

I -0.04 

Photon Energy (eV) 

Figure 1. Asymmetry ratio obtained on SL/OQ at fixed angle, &15, at the Fe 

0 700 710 720 730 740 

Photon Energy (ev) 

0.01 

0.02 5 

01 

.7 

-0.02 9 c 

L-edges. Figure 2. Asymmetry ratio obtained on SL/07 at fixed angle, 0=15, at the Fe 

* Work was supported by NSF Grant NO. L-edges. NSF-222-44-94. 
0 Is NEXAFS of Pr,Y1-,Ba~Cu30y Single Crystals 

M. Merz, N. Niicker, E. Pellegrin, S. Schuppler (Forschungszentrum Karlsruhe, 

FRG), M. Kielwein, M. Knupfer, M. S. Golden, J. Fink (IFW Dresden, FRG), C. 

T. Chen (SRRC, Taiwan), V. Chakarian, Y. U. Idserda (NRL), and A. Erb (U 

Geneve, Switzerland) 

Substituting Y in orthorhombic (Y,RE)B~zCU~O, by a rare-earth element RE 

has in general little effect on the superconducting properties. For RE = Pr, however, superconductivity is completely suppressed. To understand this effect we studied the unoccupied electronic structure of PrXY1-,BazCu3 0, using polarizationdependent 0 1s NEXAFS of detwinned single crystals. In this way, it was possible 

to identify hole states in the CuOz planes and the cuo3 chains and to give estimates 

of the relative contributions of the 0 2px, Zp,, and Zp, orbitals to these states. 

Fig. 1 shows the 0 1s NEXAFS for PrxY1-,BazCu306.9 for o = 0.0, 0.4, and 

0.8. The polarization was set parallel to the crystal axis a. With increasing Pr con- centration, the first peak above threshold decreases, while the second one increases 

substantially. In accordance with previous work, these peaks are attributed to the 

Zhang-Rice (ZR) state and to the upper Hubbard band (UHB). Among other things, 

Fig. 1 illustrates for the PrYBCO system the well-established transfer of spectral 

weight between the ZR state and the UHB, related to the Cu character of both 

features. 

In Fig. 2, the 0 1s NEXAFS for Pr0.aYo.zBazCu30, is compared for y = 6.9 

and 6.1. The UHB has the same intensity for both spectra. Thus, the additional 

states observed for y = 6.9 at the ZR state energy (cf. Fig. 1) cannot have any 

Cu character (as the ZR state does) but must be of different origin. This points 

to states resulting from Pr 4f - 0 2pT hybridization, the Fehrenbacher-Rice (FR) 

states. Expanding upon and quantifying this observation [l], we were able to test 

the current theoretical explanations for the Pr-induced suppression of superconductivity. While we can rule out models involving hole filling or charge transfer between 

the planes and the chains, a detailed evaluation [l] of our data is indeed consistent 

with approaches based on FR hybridization. 

U4B 

[l] M. Mers et al., to be published 

4 

e - 

g3 

22 

i 

3 

a 

z 

Dl 

0 

526 528 530 532 534 

Photon energy (eV) 

Figure 1. 

s3 

E 

._ 

.. 

C 

. 

$2 

n 

E 

"1 

0 

526 528 530 532 534 

Photon energy (eV) 

Figure 2. 

I High Temperature Metal-Insulator Transition of LaCo03 I U4B I 

3.-H. Park (NSLS), S-W. Cheong (Bell Labs.), and C. T. Chen (SRRC) 

Lac003 displays interesting electrical and magnetic anomalies in wide temperature range of OK to 700K. LaCoOs, which undergoes a gradual insulator to metal 

transition in the neighborhood of 500K, has been reported to exhibits a magnetic 

(diamagnetic to paramagnetic) transition around 90K upon heating. in the insulating phase. In order to understand this peculiar physical behavior, various groups 

have been proposed different interpretations based on partial experimental results. 

However, the nature of the transitions, both the low and high temperature transitions, are far away from the universal understanding. We have investigated the 

high temperature transition utilizing a high resolution photoemission spectroscopy. 

Fig. 1(a shows the photoemission spectra of the valence band including shallow 

transition temperature. The spectra were taken at llOeV photon with 7OmeV ex- perimental resolution. The binding energy was determined relative to the chemical 

potential of a clean Pt in electrical and thermal contact with the sample. As can 

be seen in Fig, 1(a), considerable spectral changes have been observed in whole 

valence band at the two different temperatures without any significant changes in 

the shallow core levels. This large spectral change in the entire valence band shows 

that the high temperature transition is accompanied with a symmetry change, indicating a spin state change probably the intermediate spin state to the high spin 

state). Furthermore, the insu I ator to metal transition has also been observed in the 

near-m spectra, which were taken at the same experimental conditions, as shown in 

Fig. l(b). At 450K, the spectrum starts well below the chemical potential, indicating the insulating state, and the band gap (a half of the band gap if the chemical 

potential lie at middle of the band gap) was estimated to be 250 meV 50 meV. 

At 700K, spectrum displays a finite spectral weight at the chemical potential even 

though the clear metallic Fermi edge feature is not observed due to the broad Fermi 

thermal function (4k~T 240 meV). 

core leve 1 s (0 29 and La 5p) below (450K) and above (700K) the high temperature 

im 

.- g 

s 

- 20 10 

Binding Energy (ev) 

Figure 1. High resolution valence band PES spectra above and below Tt-500K. 

(a) Broad range. (b) near p. 
P 

N I U4B I O I Polarization Dependence X-ray Absorption Studies of VzO3 

J.-H. Park (NSLS), L. H. Tjeng (U. of Groningen), J. W. Allen (U. of Michigan), 

C. T. Chen (SRRC), and P. Metcalf (Purdue U.) 

VzO3 system, which exhibits a paramagnetic metal to antiferromagnetic insulator transition upon cooling though the transition temperature TN 155K, has been 

considered as one of the prototype Mott systems. More than 500 papers related 

to this system have been published since the discovery of the transition in 1953, 

but the full understanding of the transition is very far away. The vanadium site 

in VzO3 has the trigonal point symmetry, in which the atomic five-fold 3d orbital 

splits into a singlet illg, a doublet egX,and a doublet egu. The d' configuration state 

of V3+ becomes either (alg)l(eg")l or (egT)2. Although the configuration state is 

widely accepted to provide a critical clue for understanding the transition, it is not 

established yet. Different studies have suggested different configuration states, and 

various models based on the different configuration states have been proposed to 

be applied for the metal-insulator transition. In order to clarify the occupation 

states in both the metallic and insulating phases, we have performed polarization 

dependence x-ray absorption measurements at V L2,3 and 0 K edges on well annealed stoichiometric V203 single crystals. The polarization dependence studies 

were performed in two different circumstances: the angle 0 between the electric 

field E vector of the incoming photon and the structural hexagonal c axis, in which 

the alg orbital lies, was set to be 15' (solid) and 75' (dotted). All the spectra in the 

figures consist of V L3 edge , V Lz edge, and 0 K edge absorption features in the 

512eV-519eV, 519eV-528eV, and 529eV-555eV photon energy regions, respectively. 

In the measurements, we found considerable polarization dependence, especially in 

8 the starting feature, which is deeply related to the corresponding core level to a1 

transition, of the each absorption edge, indicated by arrows in the figure. The 15 

spectra give more intensity at all three starting features both above and below TN, 

and further the polarization dependence turns out to be much stronger below TN. 

These results show that the occupation configurations are the mainly (e,")' state 

in both above and below TN but the mixi 

increases in the metallic phase. 

(a) T=170K (> TN) 

C 

510 520 530 540 550 

Photon Energy (ev) 

Figure 1. 

.-, g with the (alg)l(egT)l state strongly 

%$-&'-5w 

Photon Energy (ev) 

Soft X-ray Magnetic Circular Dichroism Study of Lal-.Sr,MnOs I U4B 1 

E. Pellegrin, L. H. Tjeng, F. M. F. de Groot, R. Hesper, G. A. Sawatzky (RUG), 

J. D. O'Mahony, C. F. J. Flipse (TUE), Y. Moritomo, Y. Tokura (JRCAT), C. T. 

Chen (SRRC) 

Soft x-ray magnetic circular dichroism (SXMCD) measurements have been performed on the 0 K- and Mn L-absorption edges of Lal-,Sr,MnOa single crystals 

in their ferromagnetic regime (see Fig. 1 and 2). This has been done using a recently developed experimental technique for magnetizing the samples offering the 

possibility to get high-accuracy SXMCD effect measurements on bulk specimen. 

The very strong doping-induced 0 K-edge prepeak intensity as shown in Fig. 

1 is proof of an enhanced 02p hole component of the doped holes. The orbital 

magnetic moment of this 02p component determined with the SXMCD difference 

spectra in Fig. 1 suggests a large spin moment on the 0 sites ferromagnetically 

coupled to the Mn moments. The shape of the Mn L SXMCD difference spectrum 

in Fig. 2 shows fine structures which are consistent with crystal field multiplet 

calculations assuming a local lattice distortion of the MnO6 octahedra even in the 

low-temperature metallic phase. 

250 

200 

.E: 150 

.g 100 

2 50 

0 

250 

p 200 

3 D I50 

.g 100 

5 50 

0 

526 528 530 S12 574 Si6 38 

Figure 1. 0 K soft x-ray magnetic circular 

dichroism spectra (a) La0.82Sro.18MnO3 

and (b) Lao.cST0.4 MnO3; solid (dotted) 

lines: spectra taken with the spin of the 

incident photons parallel (antiparallel) 

to the spin of the Mn3d majority electrons. Solid circles: SXMCD difference 

spectra resulting from the above data. 

The thin solid lines guides to the eye. 

,ooo \ U1,,6Sr,,4Mn0, Tb=371 K Mn L 

1 ,I 600 800E - .... . . . 

h 400 

2 200 

- 

IeL- 

~1ZW -41x1 

620 640 660 680 700 720 740 

Phvfun cricrpy IcV) 

Figure 2. (a) Mn L SXMCD spectra 

of La0.6 Sr0.4MnO3; solid (dotted) lines: 

spectra taken with the spin of the incident photons parallel (antiparallel) to 

the spin of the Mn3d majority electrons. 

(b) Solid line: SXMCD difference spectrum resulting from the above data after 

correction for the finite degree of circular polarization of 88%; dotted line: integrated difference spectrum. 
1 Nature of the Unoccupied Electronic States in SrzRu04 I U4B I 

M. Schmidt, N. Niicker, T. R. Cummins, D. H. Lu, S. Schuppler (Forschungszentrum Karlsruhe, FRG), F. Lichtenberg (Varta Batterie AG, FRG) 

SrzRu04 is the first noncuprate layered perovskite superconductor. At U4B, we 

determined the unoccupied electronic structure using 0 1s NEXAFS in fluorescence 

yield mode. The figure shows NEXAFS spectra for three orientations of the RuOz 

planes towards the polarization vector, with the 90' spectrum having been deduced 

from the 0' and 75' spectra. At the angle 0 = 0' (go"), only unoccupied 0 2p,,, 

(0 2pz) orbitals can be excited. 

Comparing the near-threshold features for 0 = 0' and 90' one notes that feature 

A, at hv = 528.5 eV, is pronounced for 0' and weak for 90°, and that its spectral 

weight is small relative to the other features. Of course, for 0 = 0' only half of 

the in-plane orbitals (P~,~) are detected. This means that for feature B, e. g., the 

spectral weight perpendicular to the plane is just twice as large as the in-plane 

weight - not 4 times, as the figure seems to suggest. This ratio is reversed for peak 

D. Peak C is less pronounced and appears more "isotropic". 

In SrzRu04, the main contribution near Ep comes from 0 2p states hybridized 

with Ru 4d states of t2, and e, symmetry that are split by about 4 eV. This and 

the spectral weight and angular dependence observed for peaks A - D leads to 

the following assignments: A and B result from the hybrids with t2, symmetry, C 

and D from those with e, symmetry. Presuming that for O(1) EF corresponds to 

529 eV (broken line in the figure), peak A is related to the apical oxygen, 0(2), 

whose binding energy is expected to be 1.5 eV smaller than for O(1) [l]. For 3, the 

large contribution of holes perpendicular to the planes is due to O(1) 2p, orbitals 

hybridized with Ru 4dra,yzr which are found in photoemission [2] to cross EF. 

Similarly, the in-plane contribution of B is caused by O(1) 2p, - Ru 4d,, orbitals, 

which also cross Ep. Peak C may be explained by Ru 4d, states hybridized with 

0 2p, states, since it has an in-plane and an out-of-plane contribution. Spectral 

weight at higher photon energies is more difficult to assign [3]. 

1 D. J. Singh, Phys. Rev. B 52, 1358 (1995). 

2 D. H. Lu et al., Phys. Rev. Lett. 76, 4845 (1996). ti 3 M. Schmidt et al., Phys. Rev. B 53, 14761 (1996). 

Figure 1. 

1 U4IR 1 Pump-probe, Far-infrared Study of Pair Breaking and Recombination in Superconducting b 

G.L. Carr and G.P. Williams (NSLS), D.B. Tanner (U. Florida) 

We have begun an investigation of the pair breaking and (quasi-particle recombination processes in low-T, superconductors using far-infrared pulses 2 rom the 

VUV ring. The recombination of quasi-particles into Cooper pairs depends on 

the electron-phonon coupling constant, and the relaxation of phonons with energy 

greater than 2A (the pair breaking energy). The q-p relaxation time is expected 

to be on the order of a nanosecond at liquid helium temperatures. Far infrared 

measurements are sensitive to superconductivity details, such as the condensate 

strength, magnitude of the energy gap, and perhaps variations in the occupation of 

electronic states. 

In our first study, we examined a thin niobium film. Fig. 1 shows the ratio of 

its transmission in the superconducting and normal states, along with the expected 

behavior, as calculated using BCS theory. The time-resolved study used pulses from an AlI-,Ga,As diode laser for the pump and far IR pulses from the VUV ring as 

the probe. Pulse duration for both sources was 2.211s (FWHM, limited by the laser 

diode). The diode delivered approximately 2nJ into an area of 0.2 cm2, sufficient to 

break approximately 1 pair in 1000. The complete transition from superconducting 

to normal state resulted in a -1OOyV signal change on the far IR detector; from 

this we estimate a NlOOnV photo-induced pair breaking signal. Fig. 2 shows the 

pair breaking signal, measured in a derivative mode. The signal magnitude is in 

agreement with our estimate, and the signal rise and fall times are consistent with a lifetime Nlns. 

Spectral analysis was impractical due to poor spectrometer efficiency below 25 

cm-l, and low laser power. Both problems will be surmounted when the timeresolved laser system and far IR beamline at U12IR become operational in 1997. 

2 I 

- to ** m ** 

** 

.- 

0) 

-50 

5 0 5 10 Pump-probe delay time Ins] 

- 1501 0 

0 

0.0 0 20 40 60 80 100 ,$O\' ' 6' 

Frequency [cm"] Temperature [K] 

Figure 2. Pump-probe correlation signal 

tom 3 . state transmission ratio for the Nb film. (top and temperature dependence (bot- Figure 1. Superconducting to normal 
? 

hl 

10 [Low-Frequency Modes in Polypeptides and Proteins 1 U4IR1 

M.R.Chance, A. Xie, B. Sclavi, Q. He, L.M. Miller, M. Sullivan (AECOM) 

Anharmonic motions leading to atomic rearrangements are essential for proteins 

to function. We report here the first far-infrared absorption studies on anharmonities of low frequency modes in protein model compounds, namely homopolymers of 

L-phenylalanine, L-Alanine, L-Leucine, and L-Tryptophan. 

The bright synchrotron light source was utilized in collecting high signal-to-noise 

data, so that it is possible to perform quantitative data analysis. The far-infrared 

absorption spectra of each model compound were collected at two temperatures 

(100 K and 295 K) in the region of 20-450 cm-l.The results show that (1) each 

of the homopolymers exhibit a small number of absorption bands in the re ion of 

50 to 150 cm-1, and the peak positions of these bands are well resolved; r2) the 

peak frequencies of far-infrared bands are temperature dependent, and decrease as 

temperature is increased from 100 K to 295 K; (3) the band-widths of these low 

frequency modes, obtained from Gaussian fits are narrower at lOOK as compared to 

those at 295 K. These results strongly infer that the low frequency modes in protein 

model compounds are highly anharmonic. The results are consistent with various 

computational studies, as well as indirect experimental studies. 

This method can be further extended to study anharmonicities of functionally important low frequency models in proteins, including hydrogen bonding interactions, 

metal-ligand interactions, and collective modes in proteins. 

I Doping Dependence of the IR Response of Laz-rSr,Cu04 

R. Henn, A. Wittlin, M. Cardona (Max-Planck Institut) and S. Uchida (U. of 

Tokyo) 

We have measured the c-axis complex dielectric function of Laz-zSrzCuOB by far 

infrared ellipsometry for different dopant concentrations a. Four phonons, which 

dominate the observed response, can be well decribed by Lorentzian profiles. Two of 

these modes are weak and appear as a consequence of the small orthorhombicity of 

these materials. The variation of the TO-frequency, the phonon lifetime (FWHM) 

and the oscillator strength of the two strongest (tertragonal) modes with the Sr 

content is given in the left figure. The TO-frequencies of both modes behave differently: the softening of the 500 cm-' mode can be related to an increase of the 

lattice parameter c, while the decrease of the a-axis lattice constant with doping 

results in a hardening of the 240 cm-I mode. 

Especially for the higher doped samples there is an electronic background present 

in our normal state data, which in a preliminary analysis is accounted for by a 

Drude-term contributing to the dielectric function. DC-resistivities extracted from 

the Drude-parameters obtained for the spectra taken at different temperatures are 

displayed in the figure on the right hand side and agree well with data in the literature. Our Drude-resistivities are conform with an almost temperature independent 

c-axis conductivity of the optimally doped sample with a = 0.15, while the over- doped sample with e = 0.2 exhibits an almost linear temperature dependence of the 

c-axis resistance. The variation of the temperature dependence with doping reflects 

reflects a change in the dominating scattering process of charge carriers. The well 

known linear temperature dependence of the resostivity within the CuOz-planes 

might indicate the same scattering process dominating the transport parallel and 

perpendicular to the CuOz-planes for the overdoped samples, whereas for the optimally doped sample different scattering mechanisms have to be considered for the 

transport along these directions. 

U41R 

X X 

Figure 1. 

L5 

'0.0 0.1 0.2 

.'~ 0.2 

v) :n oo.o 0.1 0.2 

0.1 

0.0 

X 

XX 

AA 

00 

Figure 2. 
I Carbon Dioxide Activation and Alkali Compound Formation I U4IR I 

F.M. Hoffmann (SCI-MED) D.G. Van Campen, G.P. Williams (NSLS), J. Paul 

(Royal Inst. of Tech., Sweden) 

The activation of carbon monoxide on metal surfaces is an important elementary step in many catalytic reactions, such as the alcohol synthesis reaction, or the 

water=gas shift reaction. Alkali promoters are frequently used to activate COZ in 

catalytic reactions and consequently the interaction of carbon dioxide with alkali 

metals has received much attention in surface science studies. The focus of the 

present work is on the vibrational chracterisation of reaction intermediates, particularly of the oxalate in co-evaporated systems of COz and K. The use of synchrotron 

radiation allows the K-0 vibrations in the far-IR to be studied, as well as all the 

other modes up to 2500 cm-'. The experiments were conducted by evaporating the 

K in a C02 atmosphere. The pressure of the C02 and the evaporation rate of the 

K could be controlled, thus controlling the stoichiometry, and providing selectivity 

for certain intermediates. 

1 .oo 

0.95 

0.90 

0.85 

elf+ 

I 1716 

I 

2353 

I I 1319 

I 

I 

1317 1620 

-q22 I 

1 I40 

2500 2000 1500 1000 500 

WAMNUMBER (cm") 

Figure 1. Reflectance changes induced by co-dosing with C02 and K with differ- 

? entratios. Top spectrum, COz rich, middle spectrum K:0=1.25, lower spectrum, 

t~ CO2 poor. GJ 

I U~IR 1 Simultaneous Infrared Spectroscopy and DC Resistivity Measurements on Adsorbate-covered Epitaxial Copper Films 

A. Otto, M. Hein (U. Duesseldorf, Germany), P. Dumas (LURE, U. Paris-Sud, 

France), G.P. Williams (NSLS) 

Previous far-IR reflectance studies at metallic surfaces, using synchrotron radiation, revealed two main intriguing features: - Dipole forbidden modes of the adsorbates are observed as anti-absorption infrared bands, with Fano-type lineshapes. 

- Broadband reflectance changes are simultaneously observed, with a continuous 

decrease in reflectivity reaching an asymptotic value at around 1500 cm-'. 

To account for these observations, B.N.J.Persson proposed a model based on resistivity theory. Accordingly, scattering of the conduction electrons by the adsorbed 

molecules results in the observed broadband IR absorption. This should be proportional to the change of the DC resistivity of a thin copper film by exposure to the 

same admolecules. The objective of the present study is to test quantitatively the 

theoretical predictions of the relationship between the IR broadband reflectance 

change and the DC resistivity, and to quantify the influence of the ratio of film 

thickness and skin depth on the strength and lineshape of the frustated motion 

of the admolecule. The experiments, performed in a first step, on CO adsorbed 

on a Cu(ll1) thin film grown on a Ti02 substrate, have revealed two important 

observations: 

1- A linear relationship between the DC resistivity change and the broadband 

reflectance change in the asymptotic limit( Fig.1). 

2- A non linear relationship between IR integrated intensity of the CO stretching 

mode and the DC resistivity change ( Fig.%) Theoretical calculations are underway 

to quantitatively account for these experimental results. 

Resistance change versus asymptotrc lhnlt 

Figure 1. Resistance change versus Figure 2. Integrated intensity of the CO 

asymptotic limit for increasing dose of stretch band of CO/Cu(lll) versus re- CO on a Cu(II1) film. sistance change at various exposures. 
U4IR Infrared Study of Fullerenes and Fullerides on Ag(lll), Au(ll0) and bP Cu(ll1) 

P.Rudolf (LISE-Namur, Belgique), P.Dumas (LURE and LASIR-CNRS, France), 

Y.J.Chaba1 (Lucent Technologies), D.Van Campen and G.P.Williams (NSLS) 

Synchrotron infrared reflection-absorption (IRAS) studies of CBO deposited on clean and alkali-covered Ag(lll), Au(ll0) and Cu(lll), have been performed. On 

bare substrates, the frequencies and intensities of the only observable dipole active 

mode are as shown in Fig.1. The remarkable observation is that the frequency shift, as well as the integrated intensity of the dipole active mode, does not follow what one could expect if charge transfer between the substrate and the C60 admolecule is the 

dominant mechanism. These results suggest that complex electron-phonon coupling occurs at these interfaces. Such a coupling is also thought to play an important 

role when c60 is deposited on 1ML K/Ag(lll). This is illustrated in Fig. 2. When 

C6o is adsorbed on 1ML of K pre-deposited on Ag(lll), an antiabsorption band 

is clearly seen, at the frequency position of the initial Ag(2) mode. However, for 

thicker alkali layers, two bands are observed: one, showing up as an absorption 

band at 1356 cm-’. This is the fulleride mode, of the ”bulk” phase. However, the 

observation of the antiabsorption mode shows that the entire alkali layer is involved 

with the process. 

a 

I 

,...I...,...,.. * 

1400 1420 1440 1480 1480 1500 

Wavenumbers (cm-1) wmmn(-” w-l-9 

Figure 1. Figure 2. 

I U5UA I Branch Crossings of Quantum Well States in Cu Films Deposited 

on Ni(001) * 

D.-J. Huang and P. D. Johnson (BNL - Physics) 

The existence of minority spin quantum well states in copper films deposited on a Co(OO1) substrate is well established.[l,Z] These states are thought to mediate 

the oscillatory exchange coupling in the associated magnetic multilayers with the 

anti-ferromagnetic configuration favored whenever the quantum well states cross the Fermi leve1.[3,4] 

Theoretical studies of this sytem predict a branch crossing whenever the binding 

energy of the quantum well states corresponds to a well defined d-resonance in the 

Co substrate. The branch crossing reflects the additional phase shift introduced at 

the interface by the scattering from a localized level. Whilst this phenomenon has never been observed in copper films deposited on Go, we show in this study that it 

is observable in copper films deposited on a Ni(.001) substrate. 

Copper films were deposited on a thin Ni film previously deposited on a Cu(OO1) 

substrate. As a function of thickness the binding energies observed for the quantum 

well states in the copper films were identical to those observed in the earlier studies 

using a Co substrate.[l,2] However as shown in the figure, at a thickness of 3-4 

monolayers of copper a branch crossing to the second branch starts to occur. We 

attribute this crossing to resonant scattering from the quantized Ni d levels in the 

substrate. Such a scattering will introduce a rapid oscillation in the wavefuction of 

the quantum well state. 

References. 1. K. Garrison, Y. Chang, and P.D. Johnson, Phys. Rev. Lett. 71, 

2801 (1993). 2. C. Carbone, E. Vescovo, 0. Rader, W. Gudat, and W. Eberhardt, 

Phys. Rev. Lett. 71, 2805 (1993). 3. D.M. Edwards, J. Mathon, R.B. Muniz and 

M.S. Phan, Phys. Rev. Lett. 67, 493 (1991). 4. J.E. Ortega, F.J. Himpsel, G.J. 

Mankey, and R.F. Willis, Phys. Rev. B 47, 1540 (1993). 

a’- 

B 3.0 - 

,I - 

Figure 1. The binding energies of quantum well states at the center of the surface 

Brillouin zone in Cu films deposited on Ni(001) (filled circles) and Co(OO1) (open 

symbols) as a function of Cu overlayer thickness. The data with open circles is 

taken from ref. 1 and that with open squares from ref. 4. 

* This work was supported by the DOE under Contract No. DE-AC02-76CH00016. 
The k-space Origin of the Long Period Oscillation in Fe/Cr Multilayers: A Photoemission Study of Epitaxial Cr Grown on an Fe(100) U5UA 

Whisker * 

J. Pearson, S. D. Bader (ANL), E. Vescovo, D.-J. Huang, P. D. Johnson (BNL), 

B. Heinrich (SFU) 

Fe/Cr multilayers are the prototype giant magnetoresistance (GMR) material. 

The microscopic origin of its 1.8 nm long-period oscillatory magnetic coupling is still 

being debated by theorists, while its short-period (of 2 monolayers) is universally 

ascribed to the nesting of the Cr Fermi surface in the <loo> direction. We have 

carried out angle-resolved photoemission experiments at the NSLS U5 undulator 

beamline to investigate the k-space origin of the long-period coupling. Exceptionally 

well-ordered and smooth Cr layers (0.8 - 5 nm) were deposited onto an atomically 

flat Fe(100) whisker at 300°C for epitaxial growth. We searched different candidate 

regions of k-space at off-normal geometry for thickness dependent Cr quantum-well 

(QW) states, and monitored their resultant photoemission intensity oscillations at 

the Fermi level (Ep). In the vicinity of the d-derived lens feature of the Fermi 

surface, the intensity at EF oscillates with a period of 1.7h0.2 nm as a function of 

Cr thickness. This indicates the d-derived QW states pass through EF periodically. 

This period coincides with that for the magnetic coupling in Fe/Cr multilayers, 

which suggests the extrema1 spanning vector across the lens as the origin of the 

long period oscillation. The work demonstrates that angle-resolved photoemission 

provides a novel methodology to distinguish the k-space origin of different oscillation 

periodicities in the interlayer magnetic coupling. 

0.9- 0 10 20 30 40 50 

tc, (A) 

Figure 1. The intensities at Ep vs. film thickness at kll = 0.72 in units of the 

surface Brillouin zone, I'X (around the "lens"), which yield a periodicity of 17&2 

A. Independent thickness sequences are indicated with different symbols. 

* Work at ANL is supported by DOE BES-MS under W-31-109-ENG-38 and ONR 

N-00014-94-F-0085; work at BNL by DOE under DE-AC02-76CH00016. 

I The U5UA SGM-beamline: First Tests on the Performances 1 U5UA I 

E. Vescovo, Q.-Y. Dong, G. Nintzel, D. Carlson, and S. Hulbert (NSLS) 

During this year a new beamline has been installed at the end of the US-undulator on the UV floor. It replaces an old toroidal single-grating monochromator serving 

the spin-polarized photoemission experiments. The new design is based on the 

use of 4 spherical gratings. The conceptual design is described in detail in ref.l. 

The main goals to be reached with this new SGM-beamline with respect to the 

old one are: 1) a superior photon energy resolution; 2) a flatter coverage of the 

available photon energies (10 - 160 eV); 3) a higher photon density at the sample. 

All the three have been reached. The energy resolution of the beamline has been 

tested at 30 eV photon energy using the Ar autoionization resonance lines. Typical 

results are shown in fig.1 where the excited np lines can be seen up to n=19. Fig.2 

shows a blow up of peak corresponding to n=16: a full width half maximum of 3.5 

meV is derived, giving a resolving power close to 10,000. Using typical entrance 

and exit slits settings which provide enough photon-flux to perform spin-resolved 

experiments, the photon energy resolution at 30 eV is still below 10 meV. The use 

of 4 different gratings greatly enhances the performances of the beamline at the 

high photon energies side. As an example, measurements of spin-polarized Fe 3p 

core-level spectra up to hv = 160 eV are now possible. Finally visual inspection of 

the fluorescent light emitted by a P-covered plate positioned in place of the sample, 

clearly shows sub-mm spot-size dimensions. 

[l] N.V. Smith et al., Nucl. Instr. Meth. A 347 , 119(1994) 

29.045 29.05 29.055 

Photon Energy (eV) Figure 1. The data are not normalized 

creasing background reflects the intensity of the first harmonic of the undulator. 

I 

to the incoming photon flux and the in- -~ - ~ I 

Figure 2. Short Scan around the Ar autoinization line corresponding to n = 16. 
b 1 U5UA 1 Spin-polarized Electronic Structure of Fe( 100): A New Surface- 

/related State 

~ 

E. Vescovo (NSLS), D.-J. Huang, P.D. Johnson (BNL- Physics) 

Magnetic surfaces and thin films display a magnetic behavior which can be quite 

different from that of the corresponding bulk materials. This is generally understood in terms of modification of the electronic structure as a result of the lowered 

symmetry and coordination number at the surface. In this connection, in recent 

years, a considerable experimental and theoretical effort has been devoted to the 

study of surface electronic structure of simple ferromagnets. Here we report on a spin- and angle-resolved photoemission study of 10 M1 Fe/W(110). Fe grows epitaxially on W(110). To probe the surface sensitivity of the spectral features, we 

exposed the clean surface to a few Langmuir (L of oxygen. Oxygen adsorbs in a 

surface has been already studied quite extensively by various groups [e.g. 1, 2J, 

at beamline U5 we have carried out spin- and angle-resolved photoemission on this 

system using p-polarized light, thereby sampling a different portion of the electronic 

structure. Our main result is the observation of a sharp surface related feature right 

at the Fermi level. In Fig. 1 the normal-emission spectrum of the clean Fe(ll0) 

surface is compared to that after 2 L oxygen exposure. Clearly the peak at the 

Fermi level is considerably reduced by the oxygen adsorption. The spin-resolved 

spectrum presented in Fig.2 reveals that this peak is of minority character. 

[l] A.M. Turner et al., Phys. Rev. B29, 2986 (1983) [2] E. Vescovo et al., Phys. 

Rev. B48, 285 (1993) 

sequence of structurally ordered structures on t h is surface. Although the Fe(ll0) 

4 3 2 1 0 

Binding Energy (eV) 

Figure 1. Normal emission spectra of 

clean (close circle) and 2 L oxygen covered (open diamond). 

10 MI FeIW(110) 

hv - 36 eV 

normal emission R 

4321 0 

Binding Energy (eV) -~ 

Figure 2. Spin-resolved spectrum of the 

clean Fe(ll0) surface. 

Photoemission Study of Ni-A1 Alloys * 

H. Niu, S.L. Qiu and R.G. Jordan (Florida Atlantic U.) 

I U7B 

There is a wide phase field in the near-equiatomic region of the Ni-A1 binary 

phase diagram. P'-NiAl has the CsCl structure and in order to preserve the overal 

lattice coherence the Ni-rich alloys within this phase field contain anti-site defects, 

i.e., some of the atoms on the AI sites are replaced by Ni atoms. On the other hand, 

the Al-rich alloys contain constitutional vacancies (since one can imagine that the 

'large' A1 atoms will not 'fit' on the Ni-sites). We are carrying out photoemission 

measurements of a number of near equi-atomic Ni-A1 alloys containing anti-sites 

defects and constitutional vacancies. Since the local environments of the Ni- and 

Al- sites in such alloys are expected to be rather different our aim is to investigate 

the effects of such 'imperfections' on the Ni and A1 core level shifts on alloying and 

differences in the lineshapes of the core level photoemissin spectra. A large body 

of spectra were collected over the summer using the facilities on the U7B. Figure 

1 and 2 show the A1 2s and Ni 3s core level spectra respectively and the data are 

currently being analyzed. 

P 

2 

1 

1 

-120 -119 -118 -117 -116 -115 -114 

Binding Energy (eV) 

Figure 1. A1 2s core level spectra. 

* This work is supported by NSF Grant 

DMR-9500654. 

I 

Ni-53%A1 

Ni-SO%AI 

Ni40%A1 

-116 ~- -114 -112 Binding -110 Energy -108 (eV) -106 Ni -104 

Figure 2. Ni 3s core level spectra. 

U14A Core Hole Decay Mechanisms in Ru Studied by Auger-photoelectron 

Coincidence Spectroscopy 

R. Gotter, R.A. Bartynski (Rutgers U.), X. Wu, S.L. Hulbert (NSLS), and H. 

Nozoye (Nat. Inst. of Materials and Chemical Research) 

The 4p core levels of the late 4d transition metals are particularly interesting as they are unusually broad, with the 1/2 spin-orbit component typically having a 

larger width than the 3/2 component. To explore the photoexcitation and decay 

mechanisms in these metals, the N23VV Auger spectrum of Ru(0001) has been 

measured in coincidence with 4p3p and 4plp photoelectrons. These coincidence 

spectra are shown as the circles with error bars in Figs. (a) and (b below. The solid 

of the valence band density of states, as would be expected in the independent 

electron approximation. The threshold region of the Auger spectrum in coincidence 

with Ru 4p3/, photoelectrons is consistent with the solid curve, but the lines width is 

of the experimental data is larger and the line shape exhibits structure indicative of 

significant electron-electron interaction. In contrast, the spectral weight of Auger 

electrons detected in coincidence with 4p1p photoelectrons is shifted away from 

threshold to lower kinetic energy. The dashed curved in the figure is an attempt 

to model the spectra the multiplets of the d6 configuration, appropriate if the core hole is fully screened prior to the Auger decay. The differences between the two 

experimental spectra could be explained if the high kinetic energy 5D multiplet 

term, couples more strongly to the 4ps/z than the 4p,/2 level. Calculations of these 

matrix elements are currently underway. 

curves in each figure is an attempt to model each spectrum with t h e self convolution 

Kinetic Energy (eV) 

Figure 1. 

U 14A Defects on the Ti02(110) Surface Observed by Auger-photoelectron 

Coincidence Spectroscopy 

W.K. Siu, R.A. Bartynski, (Rutgers U.) A. Namgia, A.H. Weiss, (U. of Texas 

Arlington), X. Wu, and S.L. Hulbert (NSLS) 

We have measured the lineshape of the Ti 3p core level in coincidence with Ti 

M23VV Auger electrons from the stoichiometric and defective TiOz(110) surfaces. 

Figs. l(a), (b), and (c) are coincidence core level spectra from the stoichiometric, 

900K vacuum annealed, and ion bombarded surfaces, respectively. The latter surface was subjected to - Art ions/cm2 at 500 eV. Figs. l(d), (e), and (f).show 

noncoincidence (singles) spectra from the same surfaces. The excess emission in the 

kinetic energy range of 68 - 70 eV in Fig. l(a) is attributed to Ti3' and Ti2+ ions 

associated with Ti sites adjacent to surface 0-vacancies. This emission accounts for 

-20% of the total Ti 3p emission on the stoichiometric surface, and arrises from 

residual surface defects (either point defects or step edges) at the -1% monolayer 

level; a concentration that does not produce a significant contribution to the single 

spectrum. The enhanced sensitivity in the coincidence spectrum is attributed to 

the extra charge density at the reduced Ti-sites as compared with Ti4+ sites. The 

assignment of this excess emission as defect induced is supported by the spectra 

in Figs. l(b) and l(e), where 900K annealing induces only a small (~4%) defectrelated shoulder in the singles spectrum, while in the coincidence spectrum, over 50% of the Ti 3p emission is associated with reduced Ti oxidation states. In Figs. 

l(d) and l(f), we see that, compared to the 900K annealed surface, ion bombardment produces a greater fraction of defect-related emission in the singles spectrum, 

but results in a very similar coincidence spectrum. This indicates that, for this 

ion dose, a similar concentration of surface defects are formed, and a substantial 

fraction of the defect-related emission in the single spectrum can be associated with 

subsurface damage. 

Figure 1. 
U15 Atomic-Site-Selective Core-Electron Excitation of 5-Oxohexanenitrile 

Isolated in D2 Matrices 

S. Sambasivan, A. T. Wen and D. M. Hanson (SUNY Stony Brook) 

Preliminary data of CHaCO(CH2)3CN isolated in Dz condensed on a 4.5 K KBr 

cryo-substrate, illustrates the atomic-site-selectivity in core-electron excitation. The 

chemical changes following soft x-ray irradiation in the matrices are monitored by 

in-situ Infrared spectroscopy. Figure 1 exhibit the intensity changes (before and 

after the irradiation) at the carbonyl (C-0) and nitrile (C-N) stretching frequencies. A negative peak here indicates a decrease in concentration of the parent 

molecule, while a positive peak signifies an increase due to new photoproduct formation caused by x-ray irradiation. The new peaks appearing at 2138 cm-1, in 

Fig.1 is been assigned to the carbon monoxide and a new CN compound respectively. The data indicate that, the IR intensity loss of the carbonyl stretching mode 

is approximately 5 to 10 times larger than that of the nitrile. Excitation were 

performed at C continuum (380 eV), 404 eV (N 

nance), 500 eV (N-continuum), 535 eV (0- , 425 eV N-shape reso- 560 eV ( 6 -continuum), 

showed the largest loss occurs at 380 eV, when the C Is electron is completely 

ionized. In addition, from Fig. 2, an enchancement enhancement in decrease in 

carbonyl stretches occurs at 404 eV and 535 eV, which are excitation of Is electrons 

of N and 0 to a (quasi) bound state (pre-edge) resonance. On comparison of num- ber of reactions per absorbed photon, we observed that the quantum yields were at least 20% higher at 0 and N resonance as opposed to continuum excitations. 

Such differences observed between bound state and ionization continuum excitation 

may be associated with the degree of ionization during the core-hole decay process. 

While the carbonyl groups in the reactant prefer the excitation at resonances for 

photodissociation, and nitrile group photodissociation favors continuum photon en- ergies. Although the exact mechanism leading to these results is still unclear at 

this point, the photodecomposition rates indicate site-selectivity in fragmentation 

following core-electron excitation. 

Figure 2. Intensity Change in the 5- 

Oxohexanenitrile C=O and CN Stretch 

with 2.8 Tera Photon Dosage at Various 

Energies. 

A BSTRA CTS 

X-Ray Beamlines 

Beamline X1A 

Determination of Urea/Urethane Ratios in Complex Polyurethanes using X-ray Microscopy . . H. Ade, A. P. Smith (NCSU), E. G. Rightor (Dow Chemical), and 

A. P. Hitchcock (McMaster U.) 

H. Ade, A. P. Smith (NCSU), S.G. Urquhart, A. P. Hitchcock (McMaster U.), and 

E. G. Rightor (Dow Chemical) 

J. Boese, A .Osanna, C. Jacobsen, J. Kirz, E. Tall (SUNY Stony Brook), and 

X. Zhang (Harvard U.) 

Critical Radiation Dose of Poly(ethy1ene terephthalate) (PET) ................................. 

X-ray Absorption Near Edge Structure of Amino Acids and Peptides ........................... 

The Application of Soft X-ray Microscopy to the in-situ Chemical Analysis of Ancient Spores 

in Organic-Rich Sedimentary Rocks ............................................................ G. D. Cody (Carnegie Institution of Washington), H. Ade (NCSU), and 

S. Wirick (SUNY Stony Brook) 

G. J. Flynn (SUNY Plattsburgh), S. Bajt, H. Chapman (LLNL), and 

Lindsay P. Keller (VA Associates) 

Carbon Measurements on Interplanetary Dust Particles ........................................ 

First Holographic Images of Fast-frozen Hydrated Biological Specimens ......................... S. Lindaas, M. Howells, D. Pinkas, C. Magowan, K. Downing (LBNL) and 

C. Jacobsen (SUNY Stony Brook) 

J. Maser, C. Jacobsen, J. Kirz, A. Osanna, S. Spector, S. Wang, and 

J. Warnking (SUNY Stony Brook) 

M.M. Moronne (LBNL) 

Commissioning of the Cryo Scanning Transmission X-ray Microscope ........................ 

Luminescent Molecular Probes for X-ray Microscopy ........................................ 

Morphological Characterization of Polycarbonate/Acrylonitrile-Butadiene-Styrene Polymer 

.. 

Blends ........................................................................................ 

Investigation of the Spinodal Decomposition of Constrained Thin Polymer Films with X-ray 

Microscopy .................................................................................... A. P. Smith, H. Ade (NCSU), D. Slep (Highlord Chemical), S. Qu, M. Rafailovich, and 

J. Sokolov (SUNY Stony Brook) 

NEXAFS Spectroscopy of Polymeric Isomers of Poly(ethy1ene terephthalate) (PET) ............ A. P. Smith, H. Ade (NCSU), S. G. Urquhart, A. P. Hitchcock (McMaster U.) and 

E. G. Rightor (Dow Chemical). 

A. P. Smith, T. Coffey, and H. Ade (NCSU) 

A. P. Smith, H. Ade, R. Fornes, R. Gilbert (NCSU) and C. Sloop (IBM) 

Characterization of the X1-STXM Spectroscopy Acquisition Mode Utilizing Carbon Dioxide .... 

NEXAFS Microspectroscopy of Macrophase-Separated Random Block Copolymer/ 

Homopolymer Blends .......................................................................... A. P. Smith, J. H. Laurer, H. Ade, R. Spontak (NCSU), A. Ashraf, and 

S. Smith (Procter and Gamble Co.) 

B-27 

B-27 

B-28 

B-28 

B-29 

B-29 

B-30 

B-30 

B-31 

B-31 

B-32 

B-32 

B-33 

B- 1 
Considerations for A Soft X-ray Spectromicroscopy Beamline ................................... B. Winn, X. Hao, C. Jacobsen, J. Kirz, J. Miao, B. Sullivan, S. Wirick (SUNY Stony Brook), 

H. Ade (NCSU), C. Buckley (King’s College), M. Howells (ALS), S. Hulbert (NSLS), 

I. McNulty (APS), T. Oversluizen (Creative Instrumentation) 

B-33 

X1-SPEM-I1 Application to Tribological Surfaces ............................................... H. Zhang, G. R. Zhuang, H. Ade (NCSU), C.-H. KO, B. Winn, J. Kirz (SUNY Stony Brook), 

S. Cameron, D. Leta (Exxon), S. Hulbert, and E. Johnson (NSLS) 

Characterization of Polymer Interfaces Using X-ray Microscopy ................................. C. G. Zimba (MIT), A. P. Smith and H. Ade (NCSU) 

STXM of Polymer Laminates: NEXAFS Microspectroscopy .................................... C. G. Zimba (MIT), A. P. Smith and H. Ade (NCSU) 

Beamline XlB 

The Vibrationally Resolved 0 1s Photoelectron Spectrum of COz ............................ A. Kivimaki, B. Kempgens, H.M. Koppe, K. Maier, M.N. Piancastelli, M. Neeb, and 

A.M. Bradshaw (FHI) 

B-34 

B-34 

B-35 

B-35 

Vibrational and Shake-up Excitations in C Is Ionisation of Ethane .............................. B-36 

H. M. Koppe, K. Maier, B. Kempgens, A. Kivimaki, M. Neeb, and A. M. Bradshaw 

(Fritz- Haber-Instit ut der Max- Planck- Gesellschaft , Germany) 

Improvement in Monochromator Performance on X1B .......................................... M. Neeb, A. Kivimaki, K. Maier, H.M. Koppe, B. Kempgens, and A.M. Bradshaw (FHI), 

F. Loeb and P.D. Johnson (BNL - Physics) 

Surface Studies of Model Supported Catalysts: Rh/CeOz (100) ................................. S.H. Overbury, D.R. Huntley, D.R. Mullins, K.S. Ailey and P.V. Radulovic (ORNL) 

B-36 

B-37 

Beamline X3Al 

Analysis of the Bias Due to Finite Size of the Peak Mask in Imaging Plate Integration 

Methods ....................................................................................... B-37 

R. Bolotovsky and P. Coppens (SUNY Buffalo) 

Electron Density Analysis at Synchrotron Sources .............................................. P. Coppens, R. Bolotovsky and A. Darovsky (SUNY Buffalo) 

B-38 

Resonance Scattering Studies of Mixed-Valence Complexes ..................................... B-38 

A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. Hummel and 

K. Wieghardt (Max-Planck-Institut fur Strahlenchemie) 

Temperature-dependence of the Electron Transfer in a MnllMnIlr(p-OH) Mixed-valence 

Complex ....................................................................................... B-39 

A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. Hummel and 

K. Wieghardt (Max-Planck-Institut, Germany) 

S. W. Huang, Y. L. Soo, Y. H. Kao (SUNY Buffalo) and A. Compaan (U. of Toledo) 

Studies of CdS/CdTe Heterostructures Using X-ray Scattering and XAFS Techniques ........... 

Investigations of Microstructures in ZnSe-based 11-VI Semiconductor Thin Films Grown 

by MBE and MOCVD ......................................................................... S. W. Huang, Y. L. Soo, Y. H. Kao, H. Luo, and T. J. Mountziaris (SUNY Buffalo) 

Grazing Angle Scattering and XAFS Studies of (Si,Ge)/Si Heterostructures ..................... S. W. Huang, Y. L. Soo, Y. H. Kao (SUNY Buffalo) and K. L. Wang (UCLA) 

The Electron Density of Th(SZP(CH3)2)4 ...................................................... B. B. Iversen, F. K. Larsen (U. of Aarhus), P. A. Reynolds (Australian National U.), 

A. Pinkerton (U. of Toledo), and A. Darovsky (SUNY Buffalo) 

J. B. Parise, K. Tan, C. Cahill and Y. KO (SUNY Stony Brook) 

B-40 

B-41 

The Structure of Type 1 GeSz ................................................................. 

B-39 

B-40 

B-41 

B-2 
Synthesis and Structural Characterization Using Synchrotron Radiation 

of(CgH13N2)2(H3O)(H20)][AgGe4Slo] .......................................................... B-42 

J. B. Parise, K. Tan (SUNY Stony Brook), and A. Darovsky (SUNY Buffalo) 

Thomas Schultz (Risoe National Laboratory) and Finn Krebs Larsen (Aarhus U.) 

Y. L. Soo, S. W. Huang, Y. H. Kao (SUNY Buffalo) and 

R. N. Bhargava (Nanocrystals Technology) 

Y. L. Soo, S. W. Huang, Y. H. Kao (SUNY Buffalo) and 

R. N. Bhargava (Nanocrystals Technology) 

The 154 K Phase Transition of Tetramethylammonium Tetrafluoroborate ....................... 

X-ray Induced Photoluminescence in Doped Nanocrystals ....................................... 

B-42 

B-43 

XAFS Studies of Tb-Doping in YZO3 ........................................................... B-43 

Beamline X3A2 

Resonance Scattering Studies of Mixed-Valence Complexes .................................... A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. Hummel 

and 

K.Wieghardt (Max-Planck-Institut fur Strahlenchemie) 

Crystallographic Study of Thermal Barrier Coating by X-ray Microdiffraction ................... Y. Gao, W. Has2 and C. A. Johnson (GE Corporate Research and Development) 

On-Line SAXS Study of Nylon 66 Fiber Deformation ........................................... B. Hsiao, A. Kennedy, R. Leach (DuPont), B. Chu, and P. Harney (SUNY Stony Brook) 

On-Line WAXD Study of Nylon 66 Fiber Deformation .......................................... B. Hsiao, A. Kennedy, R. Leach (DuPont), B. Chu, and P. Harney (SUNY Stony Brook) 

Time-Resolved Synchrotron SAXS Study of the Miscible Blends of Semicrystalline 

Poly(viny1idenefluoride) and Semicrystalline Poly( 1,4-Butylene Adipate) ........................ 

Synchrotron SAXS Study of Crystallization and Microphase Separation in Compatible Mixtures of 

L.-Z. Liu, B. Chu,(SUNY Stony Brook), R. St. J. Manley (McGill U.) 

Tetrahydrofuran-Methyl Methacrylate Diblock Copolymer and Polytetrahydrofuran ............. 

The Effects of Thermal Shocking on the Residual Stress in Si3N4 Ceramic Composites .......... 

Simultaneous SAXS/WAXD Morphological Studies of Nylon 66 Fibers .......................... 

L.-Z. Liu, F. Yeh and B. Chu (SUNY Stony Brook) 

A. Sahiner, D. Wittmer, and M. Sweeney (Southern Illinois U. at Carbondale) 

J. R. Sharrow, J. M. Schultz (U. of Delaware), B. S. Hsiao, and H. Chang (DuPont) 

B-44 

B-44 

B-45 

B-45 

B-46 

B-46 

B-47 

B-47 

SAXS Study of Gel-like Structures of Block Copolymers in DNA Separation Buffers ............. 

Nano-Structure of Gel-Surfactant Complexes ................................................... 

Formation and Struction of Micelles and Supramolecules of Pluronic P103 in 

Water/O-xylene Mixture ....................................................................... B-49 

B-48 

B-48 

C. Wu, T. Liu, and B. Chu (SUNY Stony Brook) 

F. Yeh, E.L. Sokolov, and B. Chu (SUNY Stony Brook) 

S. Zhou, J. Su and B. Chu (SUNY Stony Brook) 

Beamline X3Bl 

Single C-C bond in ((260);- ................................................................... G.M. Bendele (SUNY Stony Brook), P.W. Stephens (SUNY Stony Brook and NSLS), 

G. Oszldnyi, G. Bortel, G. Faigel, L. Grdnbsy (SZFKI, Budapest), and L. Forr6 (EPF, 

Lausanne) 

NazRbCBo is orthorhombic at low temperature ................................................. G.M. Bendele (SUNY Stony Brook), P.W. Stephens (NSLS and SUNYSB), K. Prassides, 

K. Vavekis, K. Kordatos (U. Sussex, UK), and K. Tanigaki (NEC Tsukuba) 

Powder Diffraction Structure of Indenyllithium ................................................. R.E. Dinnebier (Univ. of Bayreuth, Germany), P. W. Stephens (SUNY Stony Brook), 

U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, Germany) 

B-49 

B-50 

B-50 

B- 3 
Powder Diffraction Structure of MC5H6 (M= Li, Na, K) ........................................ B-51 

R.E. Dinnebier (U of Bayreuth, Germany), P. W. Stephens (SUNY Stony Brook), 

U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, Germany) 

R.E. Dinnebier (U. of Bayreuth, Germany), P. W. Stephens (SUNY Stony Brook), 

U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, Germany) 

R.E. Dinnebier, S. van Smaalen (U. of Bayreuth, Germany), F. Olbrich (U. of Magdeburg, 

Germany) and P. W. Stephens (SUNY Stony Brook) 

S. Heinemann (Bayerisches Geoinstitut, U. of Bayreuth, Germany) and R.E. Dinnebier 

(Lehrstuhl fiir Kristallographie, U. of Bayreuth, Germany) 

Alkali Occupancies and Fullerene Orientation in K4C60 and Rb4C60 ............................ C.A. Kuntscher, G.M. Bendele (SUNY Stony Brook), and P.W. Stephens (SUNY Stony Brook 

and NSLS) 

P.W. Stephens (NSLS and SUNY Stony Brook), C.L. Cleveland, U. Landman, M. Shafigullin, 

R.L. Whetten (GA Tech) 

P. Stephens (NSLS and SUNY Stony Brook), D. Balzar (NET and Inst. Ruder Boskovic), 

and H. Ledbetter (NIST) 

P. W. Stephens (NSLS and SUNY Stony Brook), M. Shafigullin, M.M. Alvarez, S.A. Harfenist, 

J.T. Khoury, T.G. Schaaff, I. Vesman, Z.L. Wang, A. Wilkinson, and R.L. Whetten (GA Tech) 

S. van Smaalen, R.E. Dinnebier (U. of Bayreuth, Germany), H. Katzke and 

W. Depmeier (U. of Kiel, Germany) 

Powder Diffraction Structure of Phenyllithium (C6H5Li) ........................................ B-51 

Ab initio Structure Determination of Two Polymorphs of RbC5H5 in a Single Powder Pattern ... B-52 

Structural Investigation of a Tetragonal Garnet: Ca3Mn2Ge3012 ............................... B-52 

B-53 

Atomic Structure of Gold Nanoclusters ......................................................... B-53 

High-resolution Study of the Ferroelectric BaTiO3. ............................................. B-54 

Crystals of Passivated Gold Nanocrystals ....................................................... B-54 

Powder Diffraction Structures of Cas[A112024](Mo04)2 (CAM) ................................. B-55 

Beamline X4A 

The Crystal Structure Determination of the SecA Translocation ATPase ..................... 

Structure Determination of the Entire Extracellular Portion of Human CD4 ..................... 

B-55 

B-56 

J.F. Hunt and J. Deisenhofer (HHMI, UT Southwestern) 

H. Wu, P.D. Kwong and W.A. Hendrickson (Columbia U.) 

Beamline X6A 

Determination of Transient Molecular Structure for Photoinduced Reaction Intermediates 

Using Time-Resolved Energy Dispersive XAS ................................................. B-56 

Contribution of Magnetic-EXAFS to the MCXD Signal at the Gd LrII Edge. ................... B-57 

K Absorption Edge Magnetic Circular X-Ray Dichroism of Fe-Ni alloys. ........................ B-57 

L. Chen, P. Lee, S. Weber, G. Jennings, J. Norris and P. Montano (ANL /U. of Chicago) 

K. J. Gofron, C. W. Kimball (NIU), P. L. Lee, and P.A. Montano (ANL) 

K. J. Gofrona, C. W. Kimballa (NIU), P. L. Lee, G. Jennings and P. A. Montano (ANL) 

Beamline X6B 

Anomalous Small-angle X-ray Scattering Characterization of Reactor Pressure Vessel Steels . . 

Study of Strain and Crystal Structure of Epitaxial Grown La-Ca-Mn-0 Thin Films ............. 

B-58 

B-58 

D. Alexander, (ANL) and P. Jemian, (UNI-CAT, Advanced Photon Source) 

M. C. Shih (NCHU, Taiwan), M.Y. Chen(NTU, Taiwan), T.S. Tsai (NCHU, Taiwan) 

Beamline X7A 

Bonding and Local Structure of Semiconductor Alloys, Inl-xGaxAs .......................... B-59 

S. J. L. Billinge and F. Mohiuddin-Jacobs (Michigan State U.) 

B-4 
Anomalous X-Ray Scattering Studies of Supermolecules and Aggregates in Organic Solution .... 

The Nature of Structural Defects in C15 NbCrz and Nb(Cr,V)z Studied by Synchrotron 

X-Ray Powder Diffraction ..................................................................... 

High Resolution Powder Diffraction at 0.5 A ................................................... 

Structural Studies of Giant Magnetoresistive TlzMnz07 ........................................ 

L. Chen, Q. Zhu, W. Svec, D. Price, M. Wasielewski (ANL) 

F. Chu (LANL), Q. Zhu (BNL), D. J. Thoma, and T. E. Mitchell (LANL) 

D. E. Cox (BNL) 

D.E. Cox (BNL), P.G. Radaelli [ILL, Grenoble), M Marezio (MASPEC-CNR Parma), and 

S.-W. Cheong (Lucent Technologies) 

Interfacial Roughness of Fe-CR GMR Superlattices ............................................. W. Dmowski and T. Egami (U. of Pennsylvania) 

Ultra-thin CeOz Overlayer on YSZ Studied by X-ray Surface Scattering ........................ W. Dmowski and T. Egami (U. Pennsylvania) 

High Pressure Diffraction Studies of Mercury-Based Superconductors ........................... J. A. Hriljac, I. Gameson, A. Asab and P. P. Edwards (U. of Birmingham, UK) 

Structural Studies of Bismuth Tin Oxides ...................................................... B.J. Kennedy (The U. of Sydney) 

Phase Characterization in Rapidly-Solidified Magnetic Materials ................................ L.H. Lewis (BNL - DAS), C.H. Sellers (INEL) and V. Panchanathan 

(Magnequench International) 

Investigation of Structural Changes in High-Temperature Treated Zeolite CaA .................. H. Meyer zu Altenschildesche, Y. Huang, G.T. Kokotailo, C.A. Fyfe (UBC, Vancouver), 

and D. Cox (BNL) 

Structural Study of the Layered Aluminophosphate Material NH4-Taranakite ................... H. Meyer zu Altenschildesche, G.T. Kokotailo, C.A. Fyfe (UBC, Vancouver), W. Schwieger 

(Universitat Halle), and D. Cox (BNL - Physics) 

J. B. Parise (SUNY Stony Brook) and K. Leinenweber (ASU) 

J.B. Parise (SUNY Stony Brook) and K. Leinenweber (ASU Tempe) 

J.-H. Park and J.B. Parise (SUNY Stony Brook) 

High Pressure Synthesis and Structural Refinement of the New Double Perovskite CaZTiSiOs ... 

Structural Characterization of A Novel Open Framework [(CSH~~N] [AgGezSs] (TEA-AgGS-SB1) 

Synthesis and Structure of a Novel Aurate: CdAu204. .......................................... 

Powder Diffraction Study of the Orientational Order of the Ammonium - Tetrahedra in 

NH4C1 and ND4C1 ............................................................................. W. Press, B. Asmussen, H. Krull, 0. Seeck (U. of Kiel, Germany), D. Cox, Q. Zhu (BNL) 

Polymorphism of the Crystalline Low-Temperature Phases of t-Butyl Chloride .................. R. Rudman, (Adelphi U.) 

Structure and Thermal Behavior of Fullerene Derivatives ....................................... M. R. Stetzer, P. A. Heiney, A. R. McGhie, J. E. Fischer, R. M. Strongin, B. M. Brandt, 

A. B. Smith I11 (U. of Pennsylvania), P. W. Stephens, R. E. Dinnebier, 

G. Bendele (SUNY Stony Brook), and Q, Zhu (BNL - Physics) 

P.M. Woodward, J.S.O. Evans, A.W. Sleight (Oregon State U.) 

R. A. Young (Georgia Institute of Technology) 

Phase Transitions and Thermal Expansion in Oxides at Low and High Temperatures ............ 

COS Location in Carbonate Apatite 

The Crystal Structure of Beta-Eucryptite from 20 to 873 K: A High-Resolution Powder 

Synchrotron X-ray Diffraction Study ........................................................... 

........................................................... 

H. Xu, P. J. Heaney, and D. M. Yates (Princeton U.) 

B-59 

B-60 

B-60 

B-61 

B-61 

B-62 

B-62 

B-63 

B-63 

B-64 

B-64 

B-65 

B-65 

B-66 

B-66 

B-67 

B-67 

B-68 

B-68 

B-69 

B-5 
An Increase of Structural Order Parameter in Fe-Co-V Soft Magnetic Alloy after 

Thermal Aging ................................................................................ B-69 

An Increase of Structural Order Parameter in Fe-Co-V Soft Magnetic Alloy after Thermal 

Aging .......................................................................................... B-70 

Q. Zhu (BNL-Physics), L. Li, M. S. Masteller and G. J. Del Corso (Carpenter Technology Corp.) 

Q. Zhu (BNL-Physics) 

Beamline X7B 

Control of Macromolecule Distribution Within Synthetic and Biogenic Single 

Calcite Crystals .............................................................................. B-70 

J. Aizenberg (Weizmann Institute), J.C. Hanson, T.F. Koetzle (BNL - Chemistry), 

S. Weiner and L. Addadi (Weizmann Institute) 

High Temperature Phase Transformations of Tetraalkylammonium Tetrafluoroborates. .......... J. Bager , F. Krebs Larsen (U. of Aarhus), T.M. Schultz (RisZ, Denmark), P. Norby and 

J.C. Hanson (BNL - Chemistry). 

Characterization of Catalysts by Temperature-Programmed Powder X-ray Diffraction ........... M.M. Burcham, K.K. (Lehigh U.), and J.C.Hanson (BNL- Chemistry) 

In Situ Studies of Hydrothermal Syntheses; Crystallization of Mg- and Zn-substituted 

Aluminophosphates ............................................................................ B-72 

A.N. Christensen (U. Aarhus), P. Norby and J.C. Hanson (BNL-Chemistry) 

A Variable Temperature X-Ray Diffraction Study of HCFC-124a Reactions on Cation 

Exchanged Faujasites .......................................................................... B-72 

B-71 

B-71 

M.F.Ciraolo, F.I.Poshni, P. Norby, C.P.Grey (SUNY Stony Brook), J.C.Hanson 

(BNL - Chemistry), and D.R.Corbin (Dupont) 

Structure and Phase Transitions in The Negative Thermal Expansion Material Zirconium 

Vanadate ...................................................................................... B-73 

J.S.O. Evans, A.W. Sleight (Oregon St. U.) and J. C. Hanson (BNL - Chemistry) 

The Structure of d-Co(en)3.A13P4016.3HzO .................................................... B-73 

M. J. Gray, A. P. Wilkinson (Georgia Tech) and J.C. Hanson (BNL - Chemistry) 

Structural Characterization of Hydrofluorocarbon-134 Adsorbed on Zeolite NaY using X-ray 

Powder Diffraction: Observation of Cation Migration and Strong Sorbate-Cation Interactions ... B-74 

C.P.Grey and F.I.Poshni (SUNY Stony Brook), A.F.Gualtieri (U. Modena), P.Norby and 

J.C.Hanson (BNL- Chemistry), and D.R.Corbin (DuPont) 

Real Time Combined Fe K-edge XANES and XRPD in-situ Study of Hydrothermal 

Synthesis of Zeolites from Natural Clay Minerals. ............................................... Alex F. Gualtieri (U. of Modena, Italy), P. Norby and J.C. Hanson (BNL - Chemistry) 

A.F. Gualtieri, (U.of Modena, Italy), P. Norby and J. Hanson (BNL - Chemistry), and 

G.Artioli (U. of Milan, Italy) 

J. C. Hanson, J. Araujo (BNL), Kenny Stahl (DTU), G. Artioli (U. Milan) 

J. C. Hanson (BNL- Chemistry), I. Mutikainen (U. of Helsinki), J. Pluth (U. of Chicago) 

R.A.Holroyd and J.M. Preses (BNL-Chemistry) 

T.R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

T. R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

T.R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

T.R. Jensen (U. Odense, Denmark), P. Norby, J. C. Hanson (BNL - Chemistry) 

B-74 

Kinetic Study of the Synthesis of Zeolite Li-A(BW) from Natural Kaolinites .................... B-75 

Computer Movies of Time-resolved Dehydration of Natural Zeolites ............................. 

Pyridine Adsorbed on Na-Faujasite: Low Temperature Single Crystal Studies 

Studies of Excited-State Lifetimes of Hydrocarbons ............................................. 

Investigation of Disorder Using Micro Single Crystal Diffraction Data ........................... 

Kinetic Study of Phase Transition of Microporous Lithium Zinc Phosphates ..................... 

Powder Diffraction Study of Co Substitution in Microporous Lithium Zinc Phosphate ........... 

B-75 

B-76 

B-76 

B-77 

B-77 

B-78 

B-78 

.................. 

................................. I Structural Investigation of a-LiZnAs04, Using a Micro Crystal 

B-6 
The Crystal Structure of a New Zinc Arsenate, Zng(As04)e '4Hz0. ............................. 

X-Ray Scattering Study of Simple Molecules Adsorbed on BN: Evidence for a 

Commensurate Phase of Kr .................................................................... D.E. Johnson, J. Hanson, and J.Z. Larese (BNL) 

In-situ Diffraction Study of Ion Exchange: Exchange of Analcime to Ammonium Analcime. ..... A.M. Krogh Andersen, E. Krogh Andersen and I.G. Krogh Andersen (U. Odense, Denmark), 

P. Norby and J.C. Hanson (BNL- Chemistry) 

T. R. Jensen (U. of Odense, Denmark) P. Norby and J. C. Hanson (BNL - Chemistry) 

In-situ Powder Diffraction Studies of Intercalation Processes: Intercalation of Alkane Diamines 

in a-Zr(HPO4)z.HzO and y-Ti(P04)(HzP04).2H20. ........................................... A.M. Krogh Andersen, E. Krogh Andersen and I.G. Krogh Andersen (U. Odense, Denmark), 

P. Norby and J.C. Hanson (BNL - Chemistry). 

In-situ Studies of Thermal Transformations in a-layered phosphates. ............................ A.M. Krogh Andersen (U. Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

The Crystal Structure of Tetragonal Zr(HP04)z by Synchrotron X-ray Single Crystal Diffraction 

and Neutron Powder Diffraction Data. ......................................................... A.M. Krogh Andersen (U. Odense), P. Norby, T. Vogt and J.C. Hanson (BNL - Chemistry) 

Crystal Structure of Dimethylamine Grown In-situ from Liquid ................................ R. K. McMullan, W. Klooster, P. Norby and J. C. Hanson (BNL-Chemistry) 

Real-Time X-Ray Powder Diffraction Studies of Li/Na Ion Exchange in Sodalite ................ P. Norby, J. Hanson (BNL - Chemistry), C. L. Cahill and J. B. Parise (SUNY Stony Brook) 

Hydrothermal Conversion of Zeolites Studied Using in-situ Powder Diffraction. ................. P. Norby and J.C. Hanson (BNL - Chemistry) 

Dehydration of Zeolite Li-A(BW); A Time Resolved Structural Study. ......................... P. Norby, J.C. Hanson (BNL), A. KremenoviC, V. Dondur and R. DimitrijeviC (U. Belgrade) 

Adsorption of Hydrofluorocarbons on Zeolites; An in-situ Powder Diffraction Study. ............. P. Norby, F.I. Poshni, M.F. Ciraolo, C.P. Grey, (SUNY Stony Brook) and 

J.C. Hanson (BNL - Chemistry). 

An In-situ X-ray Powder Diffraction Study of the Dehydration of Zeolite CsY ................... F.I.Poshni, M.F.Ciraolo, C.P.Grey (SUNY Stony Brook), A.F.Gualtieri (U. of Modena), 

P.Norby and J.C.Hanson (BNL - Chemistry) 

In Situ Thermal Transformations of Nickel/Cobalt Molybdates ................................. J. Rodriguez, J. Hanson, S.Chaturvedi (BNL- Chemistry) 

In-situ Powder Diffraction Study of Ca-ion Exchange of Zeolite MAP ........................... J. A. Stuart (Unilever, UK), P. Norby and J.C. Hanson (BNL - Chemistry) 

In-situ Crystallization of Mechanically Treated Zeolites. ........................................ B. SubotiC, C. KosanoviC (R. Bolkovid Inst., Zagreb), P. Norby and 

J.C. Hanson (BNL - Chemistry) 

G. Svensson (Chalmers U. of Technology, Gtiteborg, Germany), J. C. Hanson (BNL-Chemistry) 

Are the Chains in Solid HCN Parallel or Anti-parallel? ......................................... 

In-situ Time Resolved Powder Diffraction Studies of the Hydrothermal Synthesis of Antimony 

Sulfides Templated by Dimethylammonium ..................................................... K. Tan, J. B. Parise, Y. Ko,(SUNY StonyBrook) P. Norby, and J. C. Hanson (BNL) 

Competition Between Kinetic and Thermodynamic Control of Phase Transitions in 

Silica/Surfactant Mesophase Composites ....................................................... S. H. Tolbert and G. D.Stucky (U. of California/Santa Barbara), P. Norby and 

J.C. Hanson (BNL - Chemistry) 

Beamline X8A 

Iridium Optical Constants from X-ray Transmission Measurements, 2-12 keV ................ R. L. Blake (LANL), J. J. Fitch, D. E. Graessle, B. Harris, J. Juda (SAO), 

E. M. Gullikson (LBL). and M. L. Shattenburp: (MITI 

B-79 

B-79 

B-80 

B-80 

B-81 

B-81 

B-82 

B-82 

B-83 

B-83 

B-84 

B-84 

B-85 

B-85 

B-86 

B-86 

B-87 

B-87 

B-88 

v\ 

B- 7 
Modeling the Diffraction Efficiencies of the AXAF High Energy K. A., Transmission 

Gratings Above 2 keV ......................................................................... K.A. Flanagan, T.T Fang, C. Baluta, J.E. Davis, D. Dewey, T.H. Markert (MIT); 

D.E. Graessle, J. Drake, J. E. Fitch, J.Z. Juda, J. Woo (SAO); J. Bauer (U. of Hawaii) 

B-88 

Reflectivity Measurements of Multilayer Optics for Use on the Advanced Photon Source Soft 

X-Ray Beamlines .............................................................................. B-89 

K.J. Randall, J.Z. Xu (ANL), D. Graessle and J.J. Fitch (Harvard-Smithsonian Center for 

Astrophysics), S. DiFonzo, B.R. Mueller, W. Jark (Sincrotrone Trieste) 

Beamline X8C 

Iridium Optical Constants from X-ray Transmission Measurements, 2-12 keV ................. B-89 

R. L. Blake (LANL), J. J. Fitch, D. E. Graessle, B. Harris, J. Juda (SAO), E. M. Gullikson 

(LBL), and M. L. Shattenburg (MIT) 

Crystal Structure of the Metallo-beta-lactamase from B. fmgilis, and Preliminary Crystallographic 

Data for Enzyme-I and a Deletion Mutant of the Class A Bet&lactamase from S. Aweus ....... N. Concha, U. Pieper, S. Banerjee, and 0. Herzberg (U. of Maryland) 

B-90 

Beamline X9A, X9B 

Fimbrin and the Cytoskeleton ................................................................. 

Synchrotron Crystallography Structural Analysis of Profillin .................................... 

EXAFS Studies of the Zinc Derivative of Cytochrome-C: An Unusual Coordination State ....... 

S. Almo, S. Goldsmith, M. Sullivan (AECOM) 

S. Almo, M. Sullivan, J. Eads, N. Mahoney (AECOM) 

H. Anni (Thorn. Jeff. Med. Coll.), J. Vanderkooi (U. of Penn.), M.R.Chance, 

E. Scheuring (AECOM) 

J. K. Blasie, L. Prokop, E. Nordgren, J. Stzalka, L. Kneller, A. Edwards, 

R. Fischetti (Univ. of Penn.) 

Heterotropic Effects on the Active Site Structure of Hemocyanin ................................ L. Bubacco, R. Magliozzo, M. Wirt, J. Peisach (AECOM), L. Powers (Utah St.U.) 

Kinetics and Mechanism of Lipid Phase Transitions ............................................ M. Caffrey (Ohio SU) 

Protein Footprinting: Structures of Molten Globule States and Mass Spectrometic Analysis ..... M.R.Chance, M.D. Brenowits (AECOM) 

Time-Resolved Synchrotron X-ray Footprinting ................................................. M.R.Chance, M.D. Brenowitz, B. Sclavi, M. Sullivan (AECOM) 

Beamline X-9A : A Resource Devoted to Time-Resolved X-ray Footprinting ..................... M.R. Chance, M.D. Brenowitz, M. Sullivan (AECOM) 

AUTOFIT 1.0 : A New Software for XAS Global Mapping ..................................... M.R.Chance, W. Huang, E.Scheuring (AECOM) 

Global Mapping of EXAFS Data : Structure of the Photoproduct of Mb*CO ................... M.R. Chance, E. Scheuring, W. Huang (AECOM) 

Time-Resolved X-ray Spectroscopy on Microsecond Timescales ................................. M.R.Chance, E. Scheuring, A. Xie (AECOM) 

X-ray Reflectivity of Mechanically and Optically Rubbed Polyimides ............................ S. S. Ghosh, P. A. Heiney, M. R. Stetzer, 0. Y. Mindyuk (UPenn) and S. T. Sun (Alliant 

Techsystems) 

Z. Gu, C.B. Allan, S.B. Choudhury, M.J. Maroney (U. of Massachusetts) 

C. Lee, E. Scheuring, M.R. Chance, J. Peisach (AECOM) 

M. Maroney, S. Choudhury, C. Allan, Z. Ge (U. of Massachusetts) 

Resonance X-ray Diffraction Studies of Membrane Protein Monolayers .......................... 

XAS Studies of the Structure and Function of Ni in Chromatium Vinosum Hydrogenase ........ 

Structure and Kinetics: A Molecular Basis for Ligand Affinity In Hemeproteins ................. 

Biological Metal Clusters ....................................................................... 

B-90 

B-91 

B-91 

B-92 

B-92 

B-93 

B-93 

B-94 

B-94 

B-95 

B-95 

B-96 

B-96 

B-97 

B-97 

B-98 

B-8 
A Low Angle Diffraction Study of the Effects of Nucleotide Binding on the Structure of the 

Actomyosin Complex .......................................................................... K. Poole, P. Ellison, M. Lorenz, K. Holmes, (Max Planck Inst.), G. Evans, G. Rosenbaum, 

(ANL), P. Boesecke (ESRF), C. Cremo (Wash. St. U) 

L. Powers, M. Griep (Utah State U.) 

Y. A. Puius, Y. Zhao, M. Sullivan, D. Lawrence, Z.-Y. Zhang, 

S. C. Almo (Albert Einstein College of Medicine) 

L. Que, L. Shu, X. Wang, S. Mandal, K. Chen (U. of Minnesota) 

I. Sagi, C. Carmelli (Weizmann Inst.) 

I. Sagi, Z. Mingtao, C. Carmelli (Weizmann Inst.) 

R. Scarrow, N. Taufen, R. Ghiladi (Haverford Coll.) 

E. Scheming, M. Chance (AECOM), R. Banerjee (U. of Nebraska.), 

R. Matthews (U. of Michigan) 

L. Sharpe, L. Lyons (Grinnell Coll.) 

R. Sinclair, S. Hallam, M. Chen, L. Powers (Utah St. U.), B. Chance (U. of Penn.) 

The E. Coli Primase Zinc Structure is Sensitive to the Binding of ATP and High Magnesium .... 

Active Site Targeting of Protein Tyrosine Phosphatase 1B by Synchrotron Crystallography ...... 

EXAFS Studies of Nonheme Iron Enzymes .................................................... 

XAFS Analysis of a Transition State Inhibitor of Chloroplast CF-1 ATPase .................... 

Fe-S Centers in Energy Transducing Enzymes ................................................. 

Solution Iron-Edge XAS of Native Soybean Lipoxygenase-1 .................................... 

Global Mapping of XAS Data from Cobalamin Enzymes ....................................... 

The Relationship Between Structure and Conductivity in Polymer Electrolytes ................ 

Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants ..................... 

Time-Resolved RNA Footprinting: Structure-Function of Splicing Intermediates of the 

Tetrahymena Riboeyme ....................................................................... 

X-Ray Absorption and Resonance Raman Spectroscopy of Human Myeloperoxidase ............ 

S. Woodson (Univ. of Md.), M. Brenowite, B. Sclavi, M. Sullivan, M. Chance (AECOM) 

K. Yue, K. Taylor, J. Kinkade, R. Sinclair, L. Powers (Utah SU) 

Beamline XlOA 

X-Ray Characterization of Magnetic Epitaxial Multilayer Thin Films ........................ C-H. Lee (National Tsing Hua Univ), M.Y.Chern, C.Y.Huang (National Taiwan Univ), 

M.T.Tang (SRRC,Taiwan) and K.S.Liang (Exxon) 

B-98 

B-99 

B-99 

B-100 

B-100 

B-101 

B-101 

B-102 

B-102 

B-103 

B-103 

B-104 

BSmall-angle X-ray Scattering Studies of the Growth of Particles in Cethyltrimethylammoniumbromide 

Micellar Solution Added with Tetraethoxysilane ............................................... BT.-L. Lin, W.-J. Liu (Nat. Tsinghua U.), H. H. Shao, K. S. Liang (Exxon) 

04 

05 

Chirality, Structure and F’ree Energy of DNA Liquid Crystals .................................. H.H. Strey, R. Podgornik, D.C. Rau and V.A. Parsegian (NIH/DCRT/LSB), J. Wang 

(XFD/ANL), and E. Sirota (Exxon) 

B-105 

Beamline XlOB 

Unexpected Structure and Properties of w-unsaturated Thiols Self-assembled Monolayers on 

Au(l11) ...................................................................................... B-106 

T.Y.B. Leung, P. Fenter, F. Schreiber, P. Eisenberger and G. Scoles (Princeton U.) 

Structure of Rigid Biphenyl Monolayers by Vapor and Solution Phase Growth ................. 

Study of the Structure and Growth of Co-assembled Surfactant/Silica Films ................... 

F. Schreiber, T. Y. B. Leung, P. Fenter, and G. Scoles (Princeton U.) 

L. Zhou, P. Fenter, I. Aksay and P. Eisenberger (Princeton U.) 

B-106 

B-107 

B-9 
Beamline XllA 

Local Structure of V203 During the Metal-Insulator Transition ............................. A.Frenke1. E.A.Stern (U. of Washington) and F.A.Chudnovsky (Phys.-Tech. Inst., St. 

Petersburg, Russia) 

XAFS Study of Cation Valence State and Site Distribution in Natural Schorlomite and Melanite 

Garnet ....................................................................................... A.F. Gualtieri, S. Quartieri (U. of Modena, Italy), K. Pandya (NCSU) and 

G.M. Lamble (BNL - NSLS) 

D.Haske1 and E.A.Stern (U. of Washington) 

Sr-induced Local Distortions in Laz-cSrz CuO4 ................................................ 

X-Ray Absorption Spectroscopy Analysis of Lead and Zinc Speciation in a Contaminated 

D. Hesterberg, D. E. Sayers, W. Zhou, G. M. Plummer, and W. P. Robarge (NCSU) 

XAFS Characterization of Copper in Model Aqueous Systems of Humic Acid and Illite ........ D. Hesterberg, D. E. Sayers, W. Zhou, W. P. Robarge, and G. M. Plummer (NCSU) 

Application of X-ray Absorption Spectroscopy for Studying Pyromorphite Formation in Lead 

Contaminated Soil ............................................................................ 

Groundwater Aquifer ......................................................................... 

D. Hesterberg, W. Zhou, P. Zhang, D. E. Sayers, J. A. Ryan, and W. P. Robarge 

(NCSU and US-EPA) 

R.J. Reeder, P. Northrup (SUNY Stony Brook) and G.M. Lamble (BNL- NSLS) 

Characterization of Heavy Metal Incorporation in Calcite by XAFS Spectroscopy .............. 

XAFS Characterization of Heavy-Metal Contamination in the Unsaturated and Saturated Zones 

of a Soil Profile ............................................................................... 

The Kinetics of Nickel Sorption on Pyrophyllite as Monitored by X-ray Absorption Fine 

Structure (XAFS) Spectroscopy ............................................................... 

In Situ, XAS Studies Of Metal-Semiconductor Interactions ..................................... 

Evidence for Pb-phospate Cluster Formation at the Oxide-water Interface ..................... 

Studies of the Nature of Binding Sites of First Row Transition Elements Bound to Aquatic 

and Soil Humic Substances Using X-ray Absorption Spectroscopy .............................. 

Studies of the Nature of Cu2f and Pb2+ Binding Sites in Soil Humic Substances Using 

X-ray Absorption Spectroscopy ............................................................... 

X-Ray Absorption and Electron Paramagnetic Resonance Studies of Cu2f Sorbed to 

Silica: Surface-Induced Precipitation at Low Surface Coverages ................................ 

D. E. Sayers, D. Hesterberg, W. Zhou, W. P. Robarge, and G. M. Plummer (NCSU) 

A. M. Scheidegger, D. L. Sparks (U. of Delaware), and G. M. Lamble (NSLS) 

Z. Wang, P.T. Goeller, B.I. Boyanov, D.E. Sayers, and R.J. Nemanich (NCSU) 

F.J. Weesner and W.F. Bleam (U. of Wisconsin-Madison) 

K.Xia, W. Bleam, and P.A. Helmke (U. of Wisconsin-Madison) 

K. Xia, W. Bleam, and P. A. Helmke (U. of Wisconsin-Madison) 

K. Xia, W.F. Bleam (U. of Wisconsin-Madison), A.Mehadi, and R.W. Taylor (Alabama A&M 

u.1 

Beamline X12B 

Structure of Zn-fingers 1-6 of Transcription Factor IIIA (TFIIIA) Bound to a 31 bp 

DNA Site .................................................................................... R.S. Brown, R.T. Nolte, S.C. Harrison, (HHMI/Children’s Hospital Lab. of Molecular 

Medicine) 

Large Strain Deformation Studies of Oriented Triblock Copolymers with a Cylindrical 

Morphology .................................................................................. 

The Crystal Structure Determination of the SecA Translocation ATPase ....................... 

C. Honeker, E. L. Thomas (MIT), M.C. Cape1 (BNL - Biology) 

J.F. Hunt and J. Deisenhofer (HHMI, UT Southwestern) 

B-107 

B-108 

B-108 

B-109 

B-109 

B-110 

B-110 

B-111 

B-111 

B-112 

B-112 

B-113 

B-113 

B-114 

B-114 

B-115 

B-115 

B-10 
Structural Studies of the Yeast Bleomycin Hydrolase, Gal6 .................................... B-116 

L. Joshua-Tor, J. Rosenbaum (Cold Spring Harbor Lab), W. Zheng, H. Whelan and 

S. A. Johnston (UT-Southwestern) 

S. X. Lu , P. Cebe (Tufts U.), and Malcolm Cape1 (BNL - Biology) 

S. Ramaswamy, H. Eklund (Swedish U. of Agricultural Sciences) and B.V. Plapp (U. of Iowa) 

M. Skidmore, M. Sawaya (UCSD), S. Parkin, B. Rupp (LLNL), H. Hope (UCD), and 

G.Walter (UCSD) 

Structure and Relaxation of Polyimides Using Small Angle X-ray Scattering ................... 

Structure of Horse Liver Alcohol Dehydrogenase at 1.25 A Resolution .......................... 

Crystalization and Preliminary X-ray Analysis of Aa! Subunit of Protein Phosphatase 2A ...... 

B-116 

B-117 

B-117 

A Bent-Laue Crystal Monochromator for Monochromatic Radiography with an Area Beam . . Z. Zhong(NSLS), D. Chapman(CSRRI), W. Thomlinson, F. Arfelli, N. Gmiir and 

R. Menk (NSLS) 

L. Zhou and M. Luo (U. of Alabama at Birmingham) 

The Structure of Calicivirus ................................................................... 

B-118 

B-118 

Bearnline X12C 

X-ray Crystal Structures of the S229A Mutant and Wild Type MurB in the Presence of the 

Substrate Enolpyruvyl-UDP-N-Acetylglucosamine at 1.8 Resolution .......................... 

Crystal Structure of the FASCICULINB-MOUSE AcetyZchoZinesterase Complex ................ 

T. Benson, C. Walsh and J. Hogle (Harvard Medical School) 

Y. Bourne (TSRI), R.B.G. Ravelli (Lab. Crystall.& Structual Chem.), M. L. Raves, 

J. L. Sussman (Weizmann Inst.), P. Taylor and P. Marchot (UCSD) 

Structure of the Hydroxylase Component of Methane Monooxygenase from Methylosinus 

trichosporium OB3b at 2 A Resolution ........................................................ N. Elango, R. Radhakrishnan, W.A. Froland, C.A. Earhart, J.D. Lipscomb and 

D.H. Ohlendorf (U of Minnesota) 

Structural Studies of Nucleosomes. ............................................................ J. M. Harp, D. E. Timm (UTK), and G. J. Bunick (ORNL) 

The Structure of the Complex of Concanavalin A with Methyl Alpha-D-Arabinofuranoside ..... A.J. Kalb (Gilboa), F. Frolow, A.G. Evdokimov and R. Ventura (Weizmann Institute) 

Crystal Structures of Two Thermostable Bacterial Alcohol Dehydrogenases .................... Y. Korkhin, F. Frolow, A.J. Kalb (Gilboa) (Weizmann Institute of Science) 

Structure of Lyme Disease Antigen OspA Complexed with a Fab .............................. H. Li and C.L. Lawson (BNL - Biology) 

B-119 

B-119 

B-120 

B-120 

B-121 

B-121 

B-122 

Crystal Structure of A 

its Relationship to other Diiron Proteins. ...................................................... Stearoyl-acyl Carrier Protein Desaturase from Castor Seed and 

B-122 

Y. Lindqvist, W Huang, G. Schneider (Karolinska Institute) and J. Shanklin (BNL- Biology) 

Structure of Photolyzed Myoglobin ............................................................ G.N. Phillips, Jr. (Rice U.), J. Berendzen, (LANL), I. Schlichting, (Max Planck-Hedelberg), 

and R.M. Sweet (BNL - Biology) 

Structure of a Plant Profilin at 1.6 by MAD at X12C .......................................... R. Shigeta, K. Thorn (Princeton U.), H. Christensen (Nat U. Singapore), U. Lindberg 

(Stockholm U.), N.-H. Chua (Rockefeller U.), C. Schutt, (Princeton U.) 

Crystallographic Studies of hnRNP A1 ........................................................ R-M. Xu (Cold Spring Harbor Lab.) 

Structural Basis for Dimerization of Hepatitis Delta Antigen ................................... H. Zuccola and J. Hogle (Harvard Medical School) 

B-123 

B-123 

B-124 

B-124 

Beamline X13 

Characterization of the Elliptical Polarized Wiggler at the Iron K-edge ...................... B-125 

W. A. Caliebe, C.-C. Kao, P. Stefan, E. Johnson, D. P. Siddons, and J. B. Hastings (NSLS) 

B-11 
Generation of Coherent Soft X-rays with the Prototype Small Gap Undulator. ................. E. Dufresne, S.B. Dierker (U. Michigan) L.E. Berman and Z. Yin (NSLS) 

A Simple X-Ray Focusing Mirror Using Float Glass ........................................... Z. Yin, L. Berman (NSLS), S. Dierker, E. Dufresne (U. Michigan) and D.P.Siddons (NSLS) 

B-125 

B-126 

Beamline X14A 

Ordered Phases of a Langmuir Monolayer of an Azobenzene-containing Molecule. ........... M.K. Durbin, A. Malik, A.G. Richter, C.J. Yu, V. Bhashyam(N0rthwestern Univ.), 

R. Eisenhower(ORNL), and P. Dutta(N0rthwestern Univ.) 

Inelastic X-Ray Scattering Measurement of the Many-Body Local-Field Factor in Aluminum ... B. C. Larson, J. Z. Tischler (ORNL), E. D. Isaacs (Lucent Technologies), 

P. Zschack (U. of IL.), A. Fleszar (U. Wurzburg), and A. G. Eguiluz (U. of TN & ORNL) 

C.J. Sparks, T. Gog, G.E. Ice (ORNL), R.A. Eisenhower (U. of Illinois) 

Resonant Raman Scattering Excited by GeK, Radiation Internal and External to the Ge Atom 

Beamline X15A 

Adsorption and Structure of Selenite on the Calcite (10T4) Surface .......................... L. Cheng, P.F. Lyman (Northwestern U.), N.C. Sturchio (ANL) and 

M.J. Bedzyk (Northwestern U. and ANL) 

R. Itri, R. Zhang and M. Caffrey (Ohio State U.) 

T.-L. Lee (Northwestern U.), J. Zegenhagen (Max-Planck-Institut, Germany), 

P.F. Lyman (Northwestern U.) and M.J. Bedzyk (ANL & Northwestern U.) 

Spatial Resolution of the Variable-Period X-Ray Standing Wave Method ....................... 

Structural Study of 0.2 ML In/GaAs(OOl) 4x2 Surface ......................................... 

Atomic Resolution X-Ray Standing Wave Characterization of Self-Assembled Chromophoric 

Superlattices .................................................................................. W. Lin, T. -L. Lee, P. F. Lyman, J. Lee, T. J. Marks (Northwestern U.), 

M. J. Bedzyk (ANL & Northwestern U.) 

Dynamical Diffraction of Trapped X-rays on a Curved Crystal Surface ........................ C. Liu (Harvard U.) and J. A. Golovchenko (Harvard U. & Rowland Inst. for Science) 

Local Adsorption Geometry of Te/Si(OOl) Studied by XSW ................................... Paul F. Lyman (Northwestern U.), Michael J. Bedzyk (Northwestern U. and ANL), and 

Pedro A. Montan0 (U. of Illinois - Chicago & ANL) 

Surface Relaxation by X-ray Standing Wave and Surface-extendedxx-ray Absorption Fine 

Structure ..................................................................................... J. Woicik (NIST) 

Beamline X15B 

Extremely Dilute Impurities in Silica Optical Waveguides .................................... L. Niu, R. M. Atkins, M. A. Marcus, D. C. Jacobson, P. F. Glodis, and 

P. H. Chin (Bell Labs) 

Optically Active Er Centers in Si ............................................................. L. Niu, D. C. Jacobson, D. J. Eaglesham, and P. H. Citrin (Bell Labs) 

Pb-induced Instability in ZBLAN Glass ....................................................... L. Niu, A. R. Kortan, N. Kopylov, and P. H. Citrin (Bell Labs) 

Ti Silicides in Submicron Dimensions ......................................................... L. Niu, R. Tung, M. A. Marcus, and P. H. Citrin (Bell Labs) 

Distorted, Inequivalently Charged C~O Anions in Yb2.75C60 .................................... S. Schuppler (Bell Labs), E. Ozdas (Hacettepe U.), K. B. Lyons, A. R. Kortan, and 

P. H. Citrin (Bell Labs) 

B-12 

B-126 

B-127 

B-127 

B-128 

B-128 

B-129 

B-129 

B-130 

B-130 

B-131 

B-131 

B-132 

B-132 

B-133 

B-133 
Beamline X16A 

Structure of the Incommensurate Au/Si( 100)-5xl Surface .................................... B-134 

P. Bennett (ASU), D. Walko and I. K. Robinson (U.of Illinois) 

Oxygen-Induced Facetting of Cu( 115) ......................................................... B-134 

I. K. Robinson and D. A. Walko (U. of Illinois), H. L. Meyerheim and 

M. Albrecht (Inst. f. Kristallographie, U. Muenchen) 

Surface Structure of a-Ga(001) ............................................................... D. A. Walko, I. K. Robinson (U. of Illinois), Ch. Griitter, and J. H. Bilgram (ETH Ziirich) 

B-135 

Beamline X16C 

Oxide Growth on Cu(ll1) in Acidic Solution ................................................ 

Chemical Ordering in Lead Magnesium Niobate ............................................... 

Strain of GaN Thin Films on Sapphire (0001) ................................................. 

B-135 

B-136 

B-136 

Y. S. Chu and I. K. Robinson (U. of Illinois) 

D. M. Fanning and I. K. Robinson (U. of Illinois, UC) 

C. Kim, I. K. Robinson, J. Myoung, K.-H. Shim, and K. Kim (U. of Illinois, Urbana-Champaign) 

Beamline X17B1 

Measurement of the Fission Branch for the 103 keV State in 235U 

In situ Measurement of the Rheology of Silicate Garnets at High Pressure 

.......................... B-137 

B-137 

N. N. Ajitanand (SUNY Stony Brook), D. P. Siddons, and J. B. Hastings (NSLS) 

J.Ando, J.Chen, D.J.Weidner Y.Wu (CHiPR, SUNY Stony Brook), and Y.Wang (CARS, APS) 

..................... 

In situ Equation of State Measurements of Antigorite .......................................... K. Bose, A. Navrotsky (CHiPR, Princeton U.), P. J. Schields, J. Chen and 

D. J. Weidner (CHiPR, SUNY Stony Brook) 

Elasticity of Single Crystal MgO from Simultaneous X-ray and Ultrasonic Measurements to 

9 GPa and 1500 K in a Multi-Anvil Apparatus ................................................ G. Chen, Y. Sinelnikov, J. Cooke, D. J. Weidner and R. C. Liebermann 

(CHiPR SUNY Stony Brook) 

Rheology of Dry and Hydrous Phases of the CY and p Forms of (Mg,Fe)zSi04 .................. J. Chen, T. Inoue, Y. Wu, D. J. Weidner and M. T. Vaughan (CHiPR, SUNY Stony Brook) 

Pressure Induced Amorphisation in Zirconium Tungstate ZrW208 .... 1 ........................ J. Chen, J. B. Parise, R. Li (CHiPR, SUNY Stony Brook) and A. W. Sleight (OSU) 

Structural Studies of AgZS04 and T1X (X = C1, Br, I) by In-Situ ED-XRD to 6GPa and 55OoC 

Q. Chen and R. A. Secco, (U. West. Ont.), E.A. Secco, (St. Francis Xavier U.), J. Chen, 

M.T. Vaughan, G. Chen, J.Z. Zhang, and D.J. Weidner (CHiPR, SUNY Stony Brook) 

Microbeam Irradiation of Duck Embryo Brains: Relevance to Microbeam Radiation Therapy 

[MRT] of Brain Tumors in Infants ............................................................. F.A. Dilmanian, X.Y. Wu, X. Huang, M. Kershaw, B. Ren, D.N. Slatkin, K. Trandem 

(Medical, BNL), R. Menk, W.C. Thomlinson, and Z. Zhong (NSLS) 

Elasticity of Polycrystalline MgSiO3-Majorite from Simultaneous X-ray and Ultrasonic 

Measurements to 9 GPa and 1000 K in a Multi-Anvil Apparatus ............................... G. D. Gwanmesia (DSU), G. Chen, Y. Sinelnikov, J. Cooke, L. Flesch, M. T. Vaughan and 

R. C. Liebermann (CHiPR, SUNY Stony Brook) 

B-138 

B-138 

B-139 

B-139 

B-140 

B-140 

B-141 

Rheological Study of Hydrous ?-Phase Using in situ X-ray Diffraction ......................... B-141 

Elasticity of Polycrystalline Beta-Mg2Si04 From Simultaneous X-ray and Ultrasonic 

Measurements to 7 GPa and 900 K in a Multi-Anvil Apparatus ................................ 

T. Inoue, J. H. Chen, Y. Wu, D. J. Weidner and M. T. Vaughan (CHiPR, SUNY Stony Brook) 

B-142 

B. Li, J. Liu, L. Flesch (CHiPR, SUNY Stony Brook), G. D. Gwanmesia (DSU), J. Chen 

and R. C. Liebermann (CHiPR, SUNY Stony Brook) 

B-13 
Simultaneous X-Ray and Acoustic Measurements of Equations of State of Solids at High 

Pressures and Temperatures in Multi-Anvil Apparatus ........................................ B-142 

R. C. Liebermann, G. Chen, B. Li, G. D. Gwanmesia, J. Cooke, L. Flesch, J. Liu, Y. Sinelnikov, 

M. T. Vaughan, J. Chen, J. Zhang, Y. Wang and D. J. Weidner (SUNY Stony Brook) 

Thermal Equation of State of Stishovite ....................................................... J. Liu, J. Zhang, D. J. Weidner, L. Flesch, G. Chen, B. Li and R. C. Liebermann 

(SUNY Stony Brook) 

Elasticity of Ca(Ti,Si)03 Perovskite. .......................................................... Y. D. Sinelnikov, J. Zhang, and R. C. Liebermann (CHiPR, SUNY Stony Brook) 

Rheology of Cubic Boron Nitride at High Temperatures and Pressures ......................... J. S. Sweeney, J. Chen, D. J. Weidner, M. T. Vaughan (CHiPR, SUNY Stony Brook) 

Phase Relations and Equations of State for High-pressure Phases of Ferrosilite and Enstatite . . M. T. Vaughan, D. H. Lindsley, and Y. Silnelnikov (CHiPR, SUNY Stony Brook) 

T-CUP: A New High-pressure Apparatus for X-Ray Studies - Continued ...................... M. T. Vaughan, D. J. Weidner, and J. Chen (SUNY Stony Brook) 

A New Anvil Geometry for SAM-85 for High P, T X-ray Studies ............................... Y. B. Wang, D. J. Weidner, M. T. Vaughan (CHiPR, SUNY Stony Brook), and 

I. C. Getting (CHiPR, U. Colorado) 

Y. Wu, D.J. Weidner, J. Chen, G. Gwanmesia, and M. Vaughan (CHiPR, SUNY Stony Brook) 

J. Zhang and R. J. Reeder (CHiPR, SUNY Stony Brook) 

J. Zhang (CHiPR, SUNY Stony Brook) and F. Guyot (U. of Paris) 

Rheology Study of Py6oMjeO Garnet at High Pressure and High Temperature .................. 

Equation of State of Calcite-Structure Carbonates ............................................. 

Effect of Silicon Incorporation in Iron: Equation of State and Phase Transition ................ 

Beamline X17B2 

Bronchial Imaging Using Xenon K-Edge Dichromography .................................... R. H. O’Neil, J. Giacomini, E. Rubenstein, A. Van Kessel, H. Gordon (Stanford), 

W. Thomlinson, N. Gmur, Z. Zhong (NSLS) and D. Chapman (IIT) 

Contrast Imaging and Image Quantification With the Monochromatic CT - MECT ............ X.Y. Wu, F.A. Dilmanian, X. Huang, E.C. Parsons, B. Ren (BNL - Medical), W.C 

Thomlinson, Z. Zhong (NSLS), L.D. Chapman (I.I.T.), T.M. Button, and M.J. Petersen 

(SUNY Stony Brook) 

Beamline X17C 

Rheology, Strength, and Elasticity Anisotropy of Iron at High Pressures .................... H. Mao, J. Shu, R. J. Hemley (Carnegie Institute), and A. K. Singh 

(Nat. Aeronautical Lab., India) 

S. Peiris and D. Heinz (U. of Chicago) 

S. B. Qadri, E. F. Skelton, Y. Yang, B. R. Ratna (NRL), and J. Z. Hu (CIW) 

G. Shen, J. Hu, R. J. Hemley, H. Mao (Carnegie Institute), and T. S. Duffy (GSECARS) 

Compression of Seven ScS Compositions with Sc Lattice Vacancies ............................ 

Pressure Induced Structural Transitions in Nanometer Size Particles of PbS ................... 

High P-T Phase Diagram and Equation of State of Iron ....................................... 

In Situ Measurement of the Structural Transition Rate in Pd Associated with the 

Electrochemical Absorption of Deuterium ..................................................... E. F. Skelton, P. L. Hagans, S. B. Qadri, D. D. Dominguez (NRL), and J. Z. Hu (CIW) 

Beamline X18A 

Structure and Phase Transitions of Krypton in Porous Vycor .............................. 

Multiple X-ray Diffraction Studies of Decagonal Quasicrystals. ................................. 

D. W. Brown, P. E. Sokol (Penn. State U.), and S. N. Ehrlich (Purdue U.) 

R. Eisenhower, R. Colella (Purdue U.), B. Grushko (Julich) 

B-143 

B-144 

B-144 

B- 145 

B-145 

B-146 

B-147 

B-147 

B-148 

B-143 

B-146 

B-148 

B-149 

B-149 

B-150 

B-150 

B-151 

B-151 

B-14 
Spot Shapes of Bragg Reflections in Decagonal Quasicrystals .................................. R. Eisenhower (U. of Illinois), Steve Ehrlich (Purdue U.), Benjamin Grushko 

(Forschungszentrum Juelich, Germany) 

Anomalous X-ray Scattering Studies of a Lead Magnoniobate Single Crystal ................... V. Gosula, H. Chen (U. of Illinois), S. Teslic and T. Egami (U. of Pennsylvannia) 

High Temperature Studies of X-ray Scattering in a Lead Magnoniobate Single Crystal ......... V. Gosula, H. Chen (U. of Illinois), S. Teslic and T. Egami(U. of Pennsylvannia) 

Time and Depth Dependence Study of the Azimuthal Orientation in Confined Hybrid 

Smectic C* Films ............................................................................. 

Time Dependence Study of In-Plane Layers in Confined Hybrid Smectic C* Films ............. 

Anisotropic X-ray Diffuse Scattering Features in Lao,GPbo,4MnO3 .............................. 

Anomalous Diffraction Studies of CMR Materials ............................................. 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Haung (U. of Maryland) 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Huang (U. of Maryland) 

R. McQueeney (U. of Pennsylvania) 

S. M. Mini (Northern Illinois U. & ANL), J. Mitchell, D. Hinks (ANL) and S. N. Ehrlich 

(Purdue U.) 

X. Shi, J. B. Cohen, and T. 0. Mason (Northwestern U.) 

S. Teslic, T. Egami (U. of Penn.), V. Gosula and H. Chen (U. of Ill) 

T. S. Tsai (NCHU, Taiwan), M.Y. Chen(NTU, Taiwan), M.C. Shih (NCHU, Taiwan) 

Z. Wu (U. of Missouri-Columbia), S. N. Ehrlich (Purdue U.), B. Matthies, K. W. Herwig, 

and H. Taub (U. of Missouri-Columbia) 

Z. Wu, J. Wang (U. of Missouri-Columbia), S. N. Ehrlich (Purdue U.), B. Matthies, 

K.W. Herwig, and H. Taub (U. of Missouri-Columbia) 

Structural Studies of Self-Assembled Alkynyl Thin Film Materials ............................. C.-M. Yam, A. K. Kakkar (McGill U.), A. Richter and P. Dutta (Northwestern U.) 

The Structure of Diffuse Scattering in the Reciprocal Space of Al-Pd-Mn Quasicrystal. ......... Y. Zhang, R. Colella (Purdue U.), S. Ehrlich (NSLS), S. Kycia, A. Goldman, (Iowa StateU.) 

The Defect Structure Studies of La2-2Ca2Cu04-y Superconductors ........................... 

Atomic Structure of PMN Studied by Resonant X-ray Diffraction .............................. 

Structural Study of Giant Magnetoresistance Effect in La-Ca-Mn-0 Epitaxial Films ............ 

Epitaxial Structures of Butane and Hexane Monolayers Adsorbed on a Ag(ll1) Surface ........ 

Structure and Growth of %Alkane Films Adsorbed on the Ag(ll1) Surface .................... 

Beamline X18B 

Photocatalytic Reduction of Heavy Metal Ions on Derivatized Titanium Dioxide Nano-Particle 

Surface Studied by EXAFS .................................................................. L. X. Chen, T. Rajh, D. M. Tiede, P. A. Montan0 and M. C. Thurnauer (ANL) 

Structure of Supported Alkali and Alkaline Earth Modified Catalysts by X-ray Absorption 

Spectroscopy .............................................................................. 

Stabilization of Pd2+ Ions on H-ZSM-5 and Other Acidic Supports During the Selective 

Reduction of NO by CH4 .................................................................. 

E.J. Doskocil, S. V. Bordawekar, and R. J. Davis (U. of Virginia) 

D. E. Resasco, S. Stagg, W. Alvarez, and A. Ali (U. of Oklahoma) 

... 

Observation of Local Structural and Electronic Changes Accompanying Photodoping of 

YBa~Cu306+~ ................................................................................ T. A. Tyson, J. F. Federici, D. Chew, W. Savin (NJIT), L. Furenlid (NSLS), and 

W.Wilber (ARL) 

Beamline X19A 

Characterization of Phenyl Cuprate Solutions Using XANES ................................ H. Huang, J. Penner-Hahn (U. Michigan) 

B-152 

B-152 

B-153 

B-153 

B-154 

B-154 

B-155 

B-155 

B-156 

B-156 

B-157 

B-157 

B-158 

B-158 

B-159 

B-159 

B-160 

B-160 

B-161 

B-15 
Zn Speciation in Developing Xenopus Embryos as Detected by XANES ........................ K. Peariso, C. van Huis, R. Denver, and J. Penner-Hahn (U. Michigan) 

Structural Characterization of Ga-Substituted Ferredoxins ..................................... J. Penner-Hahn, K. Peariso (U. Michigan) E. Vo, H. Liu and J. Germanas (U. Houston) 

XANES Studies of Oxidation States of S in Humic Substances From Different Environmental 

Settings ...................................................................................... K. Xia, F. Weesner, and W. F. Bleam (U. of Wisconsin-Madison), P. R. Bloom, and U. L. 

Skyllberg (U. of Minnesota) 

J. Zhao, J. Rockwell, F. E. Huggins, F. Lu, and G. P. Huffman (U. of Kentucky) 

Structure of Ti in TiOz-SiOZ Catalysts ....................................................... 

Beamline X19C 

Sychrotron White Beam X-ray Topography Investigation of Influence of Annealing on 

CdZnTe Substrate ............................................................................ Y. Chen, M. Dudley (SUNY Stony Brook), D. R. Rhiger (Hughes Santa Barbara Research 

Center) 

Characterization of Processing Induced Defects in Silicon Device Using Synchrotron White Beam 

X-ray Topography ............................................................................ Y. Chen, W. Huang, W. Chen, M. Dudley (SUNY Stony Brook) 

Characterization of Structural Defects in Microgravity Grown CdZnTe Single Crystals 

Using Synchrotron White Beam X-ray Topography I1 ......................................... H. Chung, B. Raghothamachar, M. Dudley, and D. J. Larson, Jr. (SUNY Stony Brook) 

Investigations of Dislocation Distributions in Micrograviky Grown CdZnTe Single Crystals Using 

Synchrotron White Beam X-ray Topography .................................................. H. Chung, B. Raghothamachar, M. Dudley, and D. J. Larson, Jr. (SUNY Stony Brook) 

Studies of Defect Structures in Microgravity Grown CdZnTe Single Crystals Using Synchrotron 

White Beam X-ray Topography I ............................................................. H. Chung, B. Raghothamachar, M. Dudley and D. J. Larson, Jr. (SUNY Stony Brook) 

Studies of the Influence of Cooling Rate to Defect Microstructure Development in Microgravity 

Grown CdZnTe Single Crystals ............................................................... H. Chung, B. Raghothamachar, M. Dudley and D. J. Larson, Jr. (SUNY Stony Brook) 

Investigation of the Distribution and Configuration of Dislocations in Sulphur Doped InP Single 

Crystals I .................................................................................... H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome, AFB), 

A. Maniatty (RPI) 

Investigation of the Distribution and Configuration of Dislocations in Sulphur Doped InP Single 

Crystals I1 .................................................................................... 

B-161 

B-162 

B-162 

B-163 

B-163 

B-164 

B-164 

B-165 

B-165 

B-166 

B-166 

B-167 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), 

and A. Maniatty (RPI) 

Investigation of the Distribution and Configuration of Dislocations in Sulphur Doped InP Single 

Crystals I11 ................................................................................... B-167 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), 

and A. Maniatty (RPI) 

Modeling the Distribution of Dislocations Observed in MLEK Grown Fe Doped InP Single 

Crystals ...................................................................................... B-168 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), 

and A. Maniatty (RPI) 

Observation of Growth Striations in MLEK Grown InP Single Crystals Using Synchrotron 

White Beam X-ray Topography .............................................................. B-168 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome, AFB), and 

A. Maniatty (RPI) 

B-16 
Observation of Growth Striations in MLEK grown InP Single Crystals Using Synchrotron 

White Beam X-ray Topography I1 ............................................................. H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Lab., AFB), 

A. Maniatty (RPI) 

Studies of Dislocation Distributions in MLEK Grown Fe Doped InP Single Crystals Using 

Synchrotron White Beam X-ray Topography .................................................. B-169 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), 

and A. Maniatty (RPI) 

Characterization of Defect Structures in 3C-Sic Single Crystals using Synchrotron White Beam 

X-ray Topography ............................................................................ 

Characterization of Slip Dislocations in 6H-Sic Single Crystals Using Synchrotron White Beam 

Topography .................................................................................. 

W. Huang, M. Dudley (SUNY Stony Brook), and C. Fazi (Army Research Lab.) 

W. Huang, M. Dudley (SUNY Stony Brook), C. Fazi (ARL), and D. Willkinson (Novecon 

Technologies) 

Experimental Proof of the Energy Dispersion in Contrast Theory on Micropipe Image 

Format ion .................................................................................... W. Huang, M. Dudley (SUNY Stony Brook), S. Wang (ATMI), and 

C. Fazi (Army Research Lab.) 

Synchrotron White Beam Topography Studies of Residual Stress in Sic Single Crystal Wafers 

with Epitaxial Thin Films .................................................................... W. Huang, Q. Wang, M. Dudley, F. P. Chiang (SUNY Stony Brook), J. Parsons (Oregon 

Graduate Institute), and C. Fazi (ARL) 

N. Lei, Z. Huang, and S. A. Rice (U. of Chicago) 

N. Lei, Z. Huang, and S. A. Rice (U. of Chicago) 

In-plane Structure of the Liquid-Vapor Interfaces of Dilute Bismuth: Gallium Alloys ........... 

Structure of the Liquid-Vapor Interface of Tin: Gallium Alloy ................................. 

Studies On the Formation Mechanism of Small Angle Tilt Boundaries in Ga Doped Ge Single 

Crystals by X-ray Topography ................................................................ B. Raghothamachar, H. Chung, M. Dudley (SUNY Stony Brook), and D C. Gillies (NASA) 

Visibility of Growth Interfaces and Striations As a Function of Diffraction Geometry in Ga 

Doped Ge Single Crystals ..................................................................... B. Raghothamachar, H. Chung, M. Dudley (SUNY Stony Brook), and D C. Gillies (NASA) 

Characterization of Structural Defects in Vapor Grown CdTe Single Crystals by Synchrotron 

White Beam X-ray Topography ............................................................... B. Raghothamachar, H. Chung, M. Dudley (SUNY Stony Brook), D.C. Gillies, and 

W. Palosz (NASA) 

Comparison of Defect Structures in Microgravity (pg) and Terrestrially (lg) Grown CdZnTe 

Single Crystals by Synchrotron White Beam X-ray Topography ................................ B.Raghothamachar, H. Chung, M. Dudley, and D. Larson Jr. (SUNY Stony Brook) 

Investigations On the Effects of the Asymmetrical Gravity Vector on the Defect Distributions in 

Microgravity Grown CdZnTe Single Crystals .................................................. B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUNY Stony Brook) 

Studies On the Surface of a Microgravity Grown CdZnTe Boule by Synchrotron White Beam 

X-ray Topography ............................................................................ B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUNY Stony Brook) 

Synchrotron White Beam X-ray Topographic Characterization of Growth Defects in BridgmanStockbarger Grown CdZnTe Single Crystals ................................................... B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUNY Stony Brook) 

Morphology of Basal Plane Dislocations in 4H-Sic Single Crystal Wafers ...................... W. Si and M. Dudley (SUNY Stony Brook), R. Glass, V. Tsvetkov, and 

C. Carter, Jr. (Cree Research, Inc) 

B-174 

B-175 

B-169 

B-170 

B-170 

B-171 

B-171 

B-172 

B-172 

B-173 

B- 173 

B- 174 

B-175 

B-176 

B-176 

B-17 
Study of 6H-SIC Polytype Inclusions in 4H-Sic Single Crystals ................................ W. Si and M. Dudley (SUNY Stony Brook), R. Glass, V. Tsvetkov, and 

C. Carter, Jr. (Cree Research, Inc) 

W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and 

C. Carter, Jr. (Cree Research, Inc.) 

Investigations of 4H-Sic Epilayers on (1130) 4H-Sic Single Crystal Substrates ................. 

Investigations of Triangular Inclusions in 4H-Sic Epilayers on 4H-Sic Single Crystal Substrates: 

(I) Identification of Phases .................................................................... W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and 

C. Carter, Jr. (Cree Research, Inc.) 

Investigations of Triangular Inclusions in 4H-Sic Epilayers on 4H-SIC Single Crystal Substrates: 

(11) Effects of Superscrew Dislocations in substrates ........................................... W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and 

C. Carter, Jr. [Cree Research, Inc.) 

Investigations of Triangular Inclusions in 4H-Sic Epilayers on 4H-SIC Single Crystal Substrates: 

(111) Effects of Off-axis Angles of Substrates ................................................... W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and 

C. Carter, Jr.(Cree Research, Inc.) 

Studies of Growth Striations and Impurity Distribution of LEC Grown GaInSb Single 

Crystal ....................................................................................... J. Su, M. Dudley (SUNY Stony Brook), D. Fletcher, and 

W. Bonner (Johnson Matthey Electronics) 

J. Su, M. Dudley (SUNY Stony Brook), D. Fletcher, and 

W. Bonner (Johnson Matthey Electronics) 

Synchrotron White Beam X-ray Topographic Studies of LEC GaInSb Seed Transition Region . . 

A Comparison of Synchrotron White Beam and Lang X-Ray Topography of 6H-SIC Single Crystal 

Wafers ........................................................................................ 

Synchrotron White Beam X-Ray Topography of a Single Superscrew Dislocation in 6H-SiC 

W. M. Vetter and M. Dudley (SUNY Stony Brook) 

Through All(100) Faces ...................................................................... W. M. Vetter and M. Dudley (SUNY Stony Brook) 

Surface Scattering from Ternary Mixtures of Oil, Water, and Surfactant ....................... S.M. Williams, Z. Zhang, D.M. Mitrinovic, M.L. Schlossman (U. of IL- Chicago), and 

Z. Huang (BNL) 

Studies of Influence of Defects on the Performance of 4H-Sic Devices Using Synchrotron White 

Beam X-ray Topography: I. Defect Configuration ............................................. C. Yang and M. Dudley (SUNY Stony Brook), H. M. Hogood and 

S. Seshadri (Northrop Grumman Science and Tech. Center) 

Studies of Influence of Defects on the Performance of 4H-Sic Devices Using Synchrotron White 

Beam X-ray Topography: I1 - Influence of Defects ............................................ C. Yang and M. Dudley (SUNY Stony Brook), H. M. Hobgood and 

S. Seshadri (Northrop Grumman Science Tech. Center) 

Characterization of Defects in 4H-Sic Single Crystals by Synchrotron White Beam X-ray 

Topography .................................................................................. C. Yang, W. Si and M. Dudley(SUNY Stony Brook), H. M. Hobgood and 

S. Seshadri (Northrop Grumman) 

Beamline X20A 

X-ray Scattering Studies of the Passive Film on Fe(001) and Fe(ll0) ....................... A. J. Davenport (U. Manchester), L. J. Oblonsky, M. P. Ryan (BNL), M. F. Toney (IBM), 

and C. Vitus (BNL) 

A.C. Finnefrock, L.J. Buller, H.D. Abruiia, and J.D. Brock (Cornell U.) 

Time-Resolved Measurements of Overlayer Ordering in Electrodeposition ...................... 

B-18 

B-177 

B-177 

B-178 

B-178 

B-179 

B-179 

B-180 

B-180 

B-181 

B-181 

B-182 

B-182 

B-183 

B-183 

B-184 
Using X-ray Scattering to Examine Supra-molecular Organization and Surface-melting at 

Molecular Interfaces. .......................................................................... S.E. Girdwood, A.R. Kennedy, J.N. Sherwood (U. Strathclyde) and 

K.J. Roberts (Heriot-Watt U.) 

K.L. Ringland, S.G. Lemay, R.E. Thorne, and J.D. Brock (Cornel1 U.) 

Structure and Kinetics of the Sliding Q1 CDW in NbSe3 ...................................... 

Beamline X20B 

Nanosuspensions in Helium .................................................................. 

Morphological Investigation of Nylon 66 Fibers Using Radial Distribution Function Analysis . . , 

V.Kiryukhin, B.Keimer (Princeton U.), E.Gordon, and V.Khmelenko (IEPCP, Russia) 

J. R. Sharrow, J. M. Schultz (U. of Delaware), B. S. Hsiao, and H. Chang (DuPont) 

Beamline X20C 

Effects of Rubbing Polyimide Films .......................................................... J.M. Sands, S.K. Kumar (Penn State U.), T.P. Russell, and M.F. Toney (IBM) 

Beamline X21 

Resonant Raman Scattering at the Fe K-edge in Fez03 ..................................... 

High Energy Resolution Beamline ............................................................. 

Inelastic Xray Scattering from Single Crystal Sodium .......................................... 

High Resolution KCY Emission Studies of Iron(II1) Porphyrins .................................. 

W. A. Caliebe, C.-C. Kao, and J. B. Hastings (NSLS) 

W. A. Caliebe, C,-C. Kao, D. P. Siddons, and J. B. Hastings (NSLS) 

P.C.Chow and S.C. Moss (U. Houston), C.C. Kao and J.P. Hill (BNL) 

K. A. Daly (U. of Michigan), W. Caliebe, C.-C. Kao (NSLS) and 

James E. Penner-Hahn (U. of Michigan) 

Near-Threshold Behaviour of the Cu Kal,z Emission Spectrum ................................ M. Deutsch, 0. Gang, M. Fritsch (Bar-Ilan U., Israel) and C.C. Kao (BNL) 

Resonant and Non-resonant Inelastic X-ray Scattering Studies of Electronic Excitations ........ J.P. Hill, C.-C. Kao and W.A.C. Caliebe (BNL) 

Inelastic X-ray Scattering Spectroscopy in SrqCuOZC12 ........................................ E.D. Isaacs, P. Platzman (Bell Labs), C. Burns (Western Michigan U.), P. Abbamonte, 

M. Klein (U. of Illinois), and L. Miller (Ames Lab) 

X-Ray Resonant Raman Scattering in NiO: Resonant Enhancement of the Charge Transfer 

Excitations ................................................................................... C.-C. Kao, W. A. Caliebe, J. B. Hastings (NSLS), and J.-M. Gillet (U. Marne, France) 

Spin-Polarized Mn K-Edge Measurements of Doped LaMnO3 .................................. T. A. Tyson (NJIT), C.-C. Kao, W. Caliebe (NSLS), and J. J. Neumeier (FAU) 

Beamline X22A 

Real-Time X-ray Scattering Study of Sputter-deposited LaNiO3 Thin Films on Si 

Substrates .................................................................................... H. Y. Lee (SRRC, Taiwan), C. H. Lee (National Tsing Hua U., Taiwan) and K. S. Liang 

(Exon) 

L. J. Martinez-Miranda (U. of Maryland), G. M. Chow, L. K. Kurihara, D. Ma and 

P. E. Schoen (NRL) 

Structure Analysis of the Cu Metallization of AIN Using the Poly01 Method ................... 

In situ Structural Characterization of Lithium-ion Battery Electrode Materials ................. T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. Yang, J. McBreen (BNL - DAS), M.L. Daroux, 

and X.K. Xing (Gould Electronics) 

B-19 

B-184 

B-185 

B-185 

B-186 

B-186 

B-187 

B-187 

B-188 

B-188 

B-189 

B-189 

B-190 

B-190 

B-191 

B-191 

B-192 

B-192 
In Sziu Measurements of Texture and Phase Development in Bi-2223 Silver Cladded 

Superconducting Wires ....................................................................... B-193 

T.R. Thurston, U. Wildgruber, N.M. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC Corporation) 

J.X. Wang, R.R. Adzic, and B.M. Ocko (BNL - Physics) 

Anomalous Lattice Expansion of an Underpotentially Deposited Ag Bilayer on Pt(ll1) ........ B-193 

Beamline X22B 

Effect of Metallic Caplayers on the Magnetic Structure of Thin Cr(001) Films ............. P. BSdeker and H. Zabel (Inst. fiir Experimentalphysik/Festkorperphysik, Ruhr-U. at 

Bochum, Germany) 

C.J. CIarke, R.B. Lennox (McGill U), B.M. Ocko, D. Nguyen (BNL - Physics), 

M.H. Rafailovich, J. Sokolov and Z. Li (SUNY Stony Brook) 

E. DiMasi, 0. M. Magnussen, B. M. Ocko (BNL - Physics), M. Deutsch (Bar-Ilan U., Israel), 

H. Tostmann, 0. G. Shpyrko, M. J. Regan, and P. S. Pershan (Harvard) 

E. DiMasi, B.M. Ocko (BNL - Physics), W. Ke, R. Maoz, and J. Sagiv (Weizmann Institute of 

Science, Israel) 

M. Fukuto, K. Penanen, R.K. Heilmann, P.S. Pershan (Harvard U.), and 

D. Vaknin (Ames Lab & Iowa State) 

0. Gang(Bar-Ilan U., Israel), X.Z. Wu(ANL), B. Ocko(BNL), E. Sirota(EXXON), 

M. Deutsch(Bar-Ilan U.) 

D. Gidalevitz, 0. Mindyuk, J. Strzalka (U.Penn.), B. Ocko (BNL - Physics) and 

P. A.Heiney (U.Penn.) 

X ray Reflectivity Study of Gold Colloid Monolayers .......................................... 

Temperature Dependent Surface Structure of Liquid Mercury .................................. 

X-ray Reflectivity of Silane Multilayers ........................................................ 

X-Ray Scattering Study of Cso-propylamine Adduct Monolayers at the Gas-Water Interface .... 

Structure Control of Surface Freezing in Alcohol Melts by Additives ........................... 

X-ray Scattering From Discotic Liquid Crystalline Compounds at the Air-water Interface. ...... 

An X-ray Photoinduced Insulator-to-Metal Transition in a Colossal-Magnetoresistance 

Manganite .................................................................................... V. Kiryukhin, D. Casa, B. Keimer (Princeton U.), J.P. Hill, A. Vigliante (BNL), Y. Tomioka, 

and Y. Tokura (JRCAT, Japan) 

Time Dependence Study of In-Plane Layers in Confined Hybrid 

Smectic C* Films ............................................................................. 

Time and Depth Dependence Study of the Azimuthal Orientation in Confined Hybrid Smectic C* 

Films ......................................................................................... 

The 2D Ising Model: Br Electrodeposited on Ag( 100) ......................................... 

Two-Dimensional Monomolecular Pigment Assemblies at The Air-Water Interface ............. 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Huang (U. of Maryland) 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Haung (U. of Maryland) 

B.M. Ocko and J.X. Wang (BNL - Physics), T. Wandlowski (Ulm) 

D. Vaknin, B.W. Gregory, J. D. Gray, T.M. Cotton, W. S. Sturve (Ames Lab) and B.M. Ocko 

(BNL - Physics) 

J.X. Wang and R.R. Adzic (BNL - Physics) 

Surface Reconstruction at Metal-solid Polymer Electrolyte Interfaces .......................... 

B-194 

B-194 

B-195 

B-195 

B-196 

B-196 

B-197 

B-197 

B-198 

B-198 

B-199 

B-199 

B-200 

Beamline X22C 

Resonant Magnetic X-ray Scattering in Er Films with Monolayer Y Superlattice Doping .... M. J. Conover, C. P. Flynn (U. of Illinois), A. Vigliante, and D. Gibbs (BNL - Physics) 

Resonant Magnetic X-ray Scattering in Ho Films with Monolayer Dy Superlattice Doping ...... M. J. Conover, C. P. Flynn (U. of Illinois), A. Vigliante, and D. Gibbs (BNL - Physics) 

B-200 

B-201 

B-20 
Determination of Magnetic Moment Directions Using X-ray Resonant Exchange Scattering ..... C. Detlefs, A. H. M. Z. Islam, A. I. Goldman, C. Stassis, P. C. Canfield (Ames Lab & ISU), 

J. P. Hill, and D. Gibbs (BNL - Physics) 

Magnetic and Structural Properties of Erbium Films .......................................... G. Helgesen (IFE, Norway), Y. Tanaka (RIKEN, Japan), J.P. Hill, P. Wochner, 

D. Gibbs (BNL-Physics), C.P. Flynn and M.B. Salamon (U. of Illinois) 

A. Hiess (EITU, CEA-Grenoble), S. Langridge (EITU, ESRF), M. Huth 

(U. Mainz, Germany), D. Gibbs (BNL - Physics), and G. H. Lander (EITU) 

J.P. Hill (BNL - Physics), C.-C. Kao (NSLS) and D.F. McMorrow (Riso) 

Resonant X-ray Scattering From a Thin Film of UPdzAls ..................................... 

K-Edge Resonant Magnetic Scattering from a Transition Metal Oxide: NiO .................... 

B-201 

B-202 

B-202 

B-203 

B-203 

B-204 

B-204 

Charge Ordering in the Layered Perovskite Lao.5Sr1.5Mn04 ................................... 

Studies of Zero Field Magnetic Structures of TbNi~Gez ........................................ 

J.P. Hill and B.J. Sternlieb (BNL - Physics) 

A. H. M. Z. Islam, C. Detlefs, A. I. Goldman, P. C. Canfield (Ames Lab), J. P. Hill, 

and D. Gibbs (BNL - Physics) 

D. Watson, W.J. Nuttall, E.M. Forgan, D.Fort (U. Birmingham, UK), and 

S.C. Perry (Keele U., UK) 

G.Watson (UMBC), D.Gibbs (BNL - Physics), V.Jahns and D.Zehner (ORNL) 

G.M. Watson, D. Gibbs (BNL - Physics), L.E. Berman (NSLS), G.H. Lander, H. Matzke (EITU), 

W. Ellis (LANL), and B.D. Gaulin (McMaster U.) 

Verifying Magnetic Structures Using X-Rays - Neodymium A Test Case. ....................... 

Ir( 100) Surface Structure Determination by X-ray Scattering .................................. 

Characterization of the Magnetic Disorder at the (001) Surface of U02 ........................ 

B-205 

B-205 

Beamline X23A2 

Cr-K-edge X-ray-Absorption Study of Cr Dopants in MgzSi04 and CazGeO4 Sol-gel Glasses B-206 

K. E. Miyano (Brooklyn College), J. C. Woicik (NIST), Ding Huang (Brooklyn College), 

P. Sujatha Devi, and H. D. Gafney (Queens College) 

X-ray Absorption Studies of Battery Materials ................................................ P. E. Stallworth (USNA); M. L. denBoer, S. Kostov, S. Greenbaum (CUNY, Hunter), and 

C. Lampe-Onnerud (Quantum Energy Technologies) 

J. N. Weber, H. D. Rosenfeld (DuPont) and M. A. Walters (NYU) 

XANES and EXAFS Characterization of Copper Halides in Nylon 6,6 ......................... 

B-206 

B-207 

A Look Inside the Unit Cell of Strained GeSi .................................................. J.C. Woicik, C.E. Bouldin (NIST), K.E. Miyano, (Brooklyn College), and 

C.A. King (Lucent Technologies) 

B-207 

Beamline X23A3 

Surface Defects and Fracture of Sapphire Single Crystals .................................... B-208 

Polishing Effects in Single-crystal Sapphire ..................................................... B-208 

X-ray Diffraction Imaging of Electrically Fixed Holograms in Strontium Barium Niobate (SBN) 

In situ X-ray Diffraction Imaging of Electrically Fixed Photorefractive Holograms in Barium 

Titanate ...................................................................................... 

In situ Measurements of Dislocation Structure Evolution in A1 Single Crystals Deformed in 

Tension ....................................................................................... 

D. Black, H. Burdette (NIST) and D. Harris (NAWC) 

D. Black, H. Burdette (NIST) and F. Schmid (Crystal Systems) 

G. Fogarty, B. Steiner (NIST), T. Chang, and J. Hong (Rockwell International) 

G. Fogarty, B. Steiner (NIST), M. H. Garrett, J. Martin, and R. Uhrin (Deltronic Crystal Ind.) 

L. E. Levine (WSU), G. G. Long, D. R. Black and Robb Thomson (NIST) 

B-209 

B-209 

B-210 

B-2 1 
Crack Correlation in Tensilely Strained Multifilamentary High-Tc Superconductor Composite 

Tapes ........................................................................................ R. D. Spa1 (NIST), G. N. Riley and C. J. Christopherson (American Superconductor Corp.) 

Residual Disorder in Low Pressure, Low Thermal Gradient LEC Gallium Arsenide Observed 

in High Resolution Diffraction Imaging ........................................................ B. Steiner, L.E. Levine (NIST), M. Brown, and D. Larson (Grumman) 

Beamline X23B 

X-ray Absorption Studies of Battery Materials ............................................... P. E. Stallworth (USNA); M. L. denBoer, S. Kostov, S. Greenbaum (CUNY, Hunter), and 

C. Lampe-Onnerud (Quantum Energy Technologies) 

M. Szulczewski, W.F. Bleam, and P. A. Helmke (U. Wisconsin-Madison) 

J. N. Weber, H. D. Rosenfeld (DuPont) and M. A. Walters (NYU) 

Measure of Hexavalent Chromium in Contaminates Soils ...................................... 

XANES and EXAFS Characterization of Copper Halides in Nylon 6,6 ......................... 

Beamline X24A 

X-ray Standing Wave Investigation of S/Ni( 100) ............................................. D. Heskett, J. Warner, and G. Sabatino (U. Rhode Island), D. Mullins (ORNL) and 

L.E. Berman (NSLS) 

X-Ray Standing Wave Studies of Self-Assembled Monolayer Growth ........................... F. Schreiber, P. Fenter, G. Scoles, P. Eisenberger (Princeton U.), L. Berman (NSLS), 

M. Bedzyk (Northwestern U. & ANL) 

R. Wehlitz, L. Pibida, J. C. Levin, and I. A. Sellin (U. of Tenn.) 

Angular Correlation Between Subsequently Emitted Auger Electrons .......................... 

Beamline X24C 

Band Structure of Nonlinear Crystal LiB305 in VUV Region Obtained From Reflection 

Spectra ...................................................................................... T.-J. Chen (Southern Illinois U.), W.R.Hunter (Sachs Freeman Assoc.), J. C. Rife (Naval 

Research Center), and R. Tao (Southern Illinois U) 

J. F. Seely, M. P. Kowalski, J. C. Rife, W. R. Hunter, and R. G. Cruddace (NRL) 

Characterization of Multilayer Coated Gratings and Mirrors ................................... 

Beamline X25 

Structure of the Quaternary NF-ATp/Fos/Jun/DNA Complex ............................... 

The Near-Threshold Evolution of the CuKas,* Satellites ....................................... L. Chen, S.C. Harrison (HHMI), A. Rao, P. Hogan, (Harvard Medical School) 

M. Fritsch (Bar-Ilan U., Israel), K. Hamalainen (Helsinki U., Finland), C. C. Kao (NSLS), 

0. Gang, M. Deutsch (Bar-Ilan U.) 

Structural Investigation of GaP Clusters in a Si Matrix, using Multiple Energy X-ray 

Holography (MEXH) ......................................................................... T. Gog (ORNL), R.-H. Menk (NSLS), R. Eisenhower,(U of Illinois) G. Le DUC, 

L. Berman, Z. Yin (NSLS) 

J.P. Hill (BNL - Physics), C.-C. Kao (NSLS) and D.F. McMorrow (Riso) 

C.R. Horne, E.J. Cairns (LBNL/UC, Berkeley), M.M. Grush and 

S.P. Cramer (LBNL/UC, Davis) 

J. Kuriyan (Rockefeller U. & HHMI) 

J. L. Libbert, J. A. Pitney and I. K. Robinson (U. of llinois, Urbana-Champaign) 

K-Edge Resonant Magnetic Scattering from a Transition Metal Oxide: NiO .................... 

High-Resolution XAS Investigations of MnOz Spinel-Based Li+ Intercalation Battery Systems . 

Crystallographic Studies of Cell Signaling and DNA Replication ............................... 

Multiple Energy Speckle in Reflectivity From Si( 111) Wafers .................................. 

B-22 

B-210 

B-211 

B-211 

B-212 

B-212 

B-213 

B-213 

B-214 

B-214 

B-215 

B-215 

B-216 

B-216 

B-217 

B-217 

B-218 

B-218 
X-ray Studies of Liquid Metal Surfaces: Oxidation and Alloy Surfaces ......................... M.J. Regan, H. Tostmann, P.S. Pershan (Harvard U.), O.M. Magnussen, E. DiMasi, 

B.M. Ocko (BNL), M. Deutsch (Bar-Ilan U., Israel) 

Structure and Kinetics of the Sliding &I CDW in NbSes ...................................... K.L. Ringland, S.G. Lemay, R.E. Thorne, and J.D. Brock (Cornel1 U.) 

Characterization of the Magnetic Disorder at the (001) Surface of UOp ........................ G.M. Watson, D. Gibbs (BNL - Physics), L.E. Berman (NSLS), G.H. Lander, 

H. Matake (EITU), W. Ellis (LANL), and B.D. Gaulin (McMaster U.) 

H. Wu, P.D. Kwong and W.A. Hendrickson (Columbia U.) 

Y. Yacoby (Hebrew U.), H. Baltes, R. Pindak, L. Pfeiffer (Lucent Technologies), 

R. Clarke (U. of Michigan), and L. Berman (NSLS) 

L. Zhou and M. Luo (U. of Alabama at Birmingham) 

Structure Determination of the Entire Extracellular Portion of Human CD4 ................... 

Two Beam Diffraction Interference Method for 2D Crystallography ............................ 

The Structure of Calicivirus ................................................................... 

B-219 

B-219 

B-220 

B-220 

B-221 

B-221 

Beamline X26A 

Tissue Localization of Metals Bioaccumulated in Marine Organisms Living in Sediments .... W. J. Berry, D. J. Borsay (US Env. Prot. Agency), and K. W. Jones (BNL - DAS) 

B-222 

Lead in Tadpole Brain ........................................................................ H. T. Cline (Cold Spring Harbor Laboratory), S. Witte (U. of Iowa), and 

Keith Jones (BNL - DAS) 

Distribution of Catalysts in Polyolefin Polymerization Particles ................................ W. C. Conner, Jr. (U. of Massachusetts) and K. W. Jones (BNL - DAS) 

Chemical Compositions of ”Cluster” Interplanetary Dust Particles ............................. G. J. Flynn (SUNY Plattsburgh), S.R. Sutton (The U. of Chicago), and S. Bajt (LLNL) 

Spatial Distribution of Lead in Chick Tibia .................................................... C. S. Fullmer (Cornel1 U.) and K. W. Jones (BNL - DAS) 

Migration and Reduction of Cr(V1) in the Presence of Fe(I1) .................................. D.B. Hunter, E.J. Gall, P.R. Nuessle and P.M. Bertsch (U. of Georgia) 

Behavior of Dissolved Molybdenum During Localized Corrosion of Austenitic Stainless Steel ... H.S. Isaacs and S.-M. Huang (BNL - DAS) 

Composition of Dredged Material From The NY/NJ Harbor ................................... K. W. Jones (BNL - DAS) and S.-R. Song (BNL and Yale U.) 

Synchrotron Radiation in the Study of the Annual Growth Ring of Trees ...................... R. R. Martin, T. K. Sham (U. of Western Ontario), and K. W. Jones (BNL - DAS) 

Structure Studies of Transition Metal Complexes in Fluid Inclusions at Elevated Temperatures . R. A. Mayanovic (Southwest Missouri State U.), A. J. Anderson (St. F’rancis Xavier 

U.-Canada), and S. Bajt (LLNL) 

G. Newman, S. Trowbridge (SUNY Stony Brook), and K. W. Jones (BNL -DAS) 

Stroke and Calcium Concentrations in the Brain .............................................. 

Study of Chemical State of Toxic Metals During the Life Cycle of Fly Ash Using X-Ray 

Absorption Near-Edge Structure .............................................................. J. Osbn, B. Torck, S. TorSk (KFKI Atomic Energy Research Institute, Hungary), and 

K. W. Jones (BNL - DAS) 

X-ray Fluoresence Imaging of Zinc in Xenops Embryos ....................................... K. Peariso, D.L. Tierney, C. VanHuis, R. J. Denver, and J. E. Penner-Hahn (U. of Michigan) 

XANES Mapping of Zinc in Xenopus Embryos ................................................ K. Peariso, D. L. Tierney, C. VanHuis, R. J. Denver and J. E. Penner-Hahn (U. of Michigan) 

Spatially Resolved Trace Element Heterogeneities in Apatite Measured via Synchrotron X-ray 

Fluorescence Microanalysis .................................................................... 

B-228 

B-228 

John Rakovan and Richard J. Reeder, (SUNY Stony Brook) 

B-222 

B-223 

B-223 

B-224 

B-224 

B-225 

B-225 

B-226 

B-226 

B-227 

B-227 

B-229 

B-23 
Selective Uptake of Co and Zn in Surface Sites on Calcite During Growth ...................... 

Elemental Microanalysis and Elemental Mapping on Biological Tissues 

(Rice Blast) System ........................................................................... B-230 

Analysis of Trace Elements: Au in Sulfides and Ni, Zn, Ga, Y and Zr in Garnet 

Selenium XANES of Contaminated Soils, Plant Residue, and Algae ............................ 

R.J. Reeder (SUNY Stony Brook) 

R. Rizzo (U. of Trieste, Italy) 

........................ 

Manganese Oxidation: A Characteristic of Susceptibility in the Pyriczldaria - Rice Disease 

D. G. Schulze, D.M. Huber, A.K.M. Shahjahan, M. Levy(Purdue U.), S. Bajt (U. of Chicago), 

and B. Illman (USDA Forest Products Lab.) 

I.M. Steele (U. of Chicago) 

T.K. Tokunaga (LBNL), S.R. Sutton (U. of Chicago), S. Bajt (LLNL), 

P. Nuessle (U. of Georgia), and G. Shea-McCarthy (U. of Chicago) 

............... 

B-229 

B-230 

B-231 

B-231 

Beamline X26C 

Real-Time Electromigration Strain Measurement on Individual A1 Interconnect Lines by 

White Beam Microdiffraction ................................................................ B-232 

G. S. Cargill I11 and P.-C. Wang, (Columbia University), and I. C. Noyan, E. G. Liniger, 

C.-K. Hu and K. Y. Lee (IBM Research) 

J. Pluth, L. Clark , S. Sutton (U. of Chicago), M. Helliwell (U. of Manchester), 

G. Harlow (Am. Museum of Nat. Hist.), and G. Shea-McCarthy (U. of Chicago). 

J.J. Song, Y.W. Kang, R.L. Kustom, B. Lai, D.C. Mancini, A. Nassiri (ANL), and 

V. White (U. Wisconsin ) 

V. Stojanoff (ESRF), D. P. Siddons (NSLS), E. Snell (NASA), T. Boggon and J. R. Helliwell 

(U. Manchester, UK.). 

T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. Yang, J. McBreen (BNL - DAS), M.L. Daroux, 

and X.K. Xing (Gould Electronics) 

X-ray Diffraction Data Collection for Microcrystals ............................................ 

Fabrication of a mm-Wave Accelerating Cavity, Using Deep X-ray Lithography ................ 

Characterization of Defects in Protein Crystals by Diffractometry and Topography ............. 

In situ Structural Characterization of Lithium-ion Battery Electrode Materials ................. 

B-232 

B-233 

B-233 

B-234 

Beamline X27A 

An Investigation into the Spatial Texture Distribution in Thermomechanically Deformed 

NdaFel4B-based Permanent Magnets ......................................................... T.R. Thurston, L.H. Lewis, U. Wildgruber, D.O. Welch (BNL- DAS), and 

V. Panchanathan (Magnequench International) 

In Situ Measurements of Texture and Phase Development in Bi-2223 Silver Cladded 

Superconducting Wires ....................................................................... T.R. Thurston, U. Wildgruber, N.M. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC Corporation) 

B-234 

B-235 

Beamline X27C 

Determination of Topology and Transport in Porous Media Using Synchrotron Computed 

Microtomography ............................................................................ P.M. Adler, J.-F. Thovert (IPGP, France), K.W. Jones, A.M. Peskin, D.P. Siddons, 

B. Andrews, and B. Dowd (BNL) 

Region of Interest Tomography Correction for Subvolumes of Large Core Samples .............. B. Andrews, B.A. Dowd, D.P. Siddons, and J. Yung (NSLS) 

X-Ray Microtomography Applications to the Characterization of Oil Reservoir Seal and Source 

Lithologies .................................................................................... W. Bell , R.D. Hazlett (Mobil Corp.), B. Andrews, B.A. Dowd, K.W. Jones, A. Peskin, 

and D.P. Siddons (BNL) 

B-24 

B-235 

B-236 

B-236 
X-ray Refraction Imaging (XRI) Applied to Mammography .................................... D. Chapman (Illinois Inst. of Tech.), W.Thomlinson, N. Gmiir, A. Zhong, R. Menk (NSLS), 

R.E. Johnson, D. Washburn,E. Pisano (U. of North Carolina), F. Arfelli 

(Sincrotrone Trieste), and D.Sayers (NCSU) 

B-237 

Applications of Synchrotron Microtomography in Experimental Petrology: Absorption 

Tomography of Pore Features in Synthetic Rock Samples ...................................... B-237 

T. Cohen, E. B. Watson (Rensselaer Polytech Inst.), B. Dowd, D. P. Siddons, B. Andrews 

and K. W. Jones (BNL) 

X-Ray Microtomography of Reservoir Sandstone for the Characterization of Porosity and 

Permeability .................................................................................. B-238 

M.E. Coles, R.D. Haalett, E.L. Muegge (Mobil Corp.), B. Andrews, B.A. Dowd, K.W. Jones, 

A. Peskin, D.P. Siddons (BNL), M. Schlackman (GTE), W.E. Sol1 (LANL), and 

P. Spanne (ESRF) 

X-Ray Microtomography of Fungal Deterioration of Wood ..................................... B.L. Illman (U. Wisconsin and Forest Products Lab.), B.A. Dowd and D.P. Siddons (NSLS) 

MECT’s Bent Laue-Laue Monochromator: Design and Test Results ........................... B. Ren, F.A. Dilmanian, X.Y. Wu, (BNL- Medical), L.D. Chapman, I. Ivanov 

(CSRRI, IIT) and Z. Zhong (NSLS) 

X-Ray Microtomography of Basalts ........................................................... D. Sahagian (U.N.H.), B.A. Dowd, K.W. Jones, D.P. Siddons, S. Song (BNL) 

Microstructures of Antarctic Meteorites in the Millimeter Size Range .......................... S.R. Sutton (The U. of Chicago), B.A. Dowd, K.W. Jones, D.P. Siddons, B. Andrews, 

A. Peskin (BNL) 

B-238 

B-239 

B-239 

B-240 

B-25 

X1A 

Determination of Urea/Urethane Ratios in Complex Polyurethanes 

using X-ray Microscopy 1 Critical Radiation Dose of Poly(ethy1ene terephthalate) (PET) * I X1A I 

H. Ade, A. P. Smith (NCSU), E. G. Flightor (Dow Chemical), and A. P. Hitchcock 

(McMaster U.) 

H. Ade, A. P. Smith (NCSU), S.G. Urquhart, A. P. Hitchcock (McMaster U.), and 

E. G. Rightor (Dow Chemical) 

Polyurethanes (PUR) are complex polymeric materials with polyether, polyurea, 

and polyurethane funcitonalities present in sometimes unknown quantities. The 

differentiation of polyurea and polyurethane functionalities is challenging, particularly when high spatial resolution is required to analyze precipitates in PUR foames. 

NEXAFS microscopy is a potentially powerful tool for the analysis of these materials. To verify this potential we have examined three model polyurethane compounds 

where the urea/urethane composition can be predicted from synthesis. NEXAFS 

spectra of these three compounds axe shown in Fig. 1 with the samples having 

a urea/urethane compositions of a) #258 = 22/6%, b) #259 = ll/ll%, and c) 

#260 = 6/22%, with a polyether fraction of 72 % in each case. The main area of interest in these spectra is the broad peak at 288-290 eV, which corresponds to 

the P*(C=O) excitations of urea and urethane functionalies' . After background 

subtraction and intensity normalization, the spectra are simulated with fractional 

sums of NEXAFS spectra from model urea, urethane, and polyether compounds'. 

The polyether fraction is assumed to be equal to the stoichiometric prediction. The 

results of this analysis are presented in Fig.2 for the three model compounds. The 

determined fractions of urea and urethane components are plotted against the predicted stoichiometry from the synthesis. At present, x-ray microscopy should allow 

compositional analysis with better than 10 percent precision. 

1 S. G. Urquhart 

*Work supported 

13 2 H. Ade et. al. 

Chemical. 

285 290 295 300 305 

Photon Energy (eV) 

Figure 1. NEXAFS spectra of three 

model polyurethane samples. See text 

tu for description. 4 

0,25 --Ty>7.---T-., , I I , , I I I , 

Ilrethone 

0.10 

a 

0.05 -A 

0.00 , , , , I., , , , I,, , , I,, , 

0.05 0.10 0.15 0.20 0.25 

Mole Fraction from Synthesis 

Figure 2. Comparison of the quantitative determination of the urea/urethane 

ratio with the expected composition. 

Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is based on 

the excitation of an inner shell electron into unoccupied molecular orbitals'. These 

core excitations provide a sensitive probe of the local electronic structure of the excited atom in the presence of the core hole but can also damage the sample and alter 

the chemical composition. This is also, if not more so, the case for Electron Energy 

Loss Spectroscopy in an electron microscope TEM-EELS). In order to understand 

the relative damage associated with TEM-EE L S and NEXAFS microscopy we have 

studied X-ray damage of the common polymer poly(ethy1ene terephalate) 

302 eV, as exhibited by changes in the PET NEXAFS spectrum. Fig. 1 

absorption spectra acquired from PET which had been exposed to 302 eV x-rays 

for dosages of a) no exposure, b) 1.00 x 10' Mrad, c) 1.84 x lo5 Mrad, and d) 

2.68 x lo5 Mrad. The spectral features at 285 eV and 288 eV decrease in intensity 

with increasing exposure while a transition at 286.5 eV increases in intensity. We 

have fitted gaussian functions for the spectral intensity changes with dose and estimated the average critical dose from three spectral features to be 1.386 =t 0.69 x lo6 

Mrad. By comparision to damage in TEM-EELS, a rule of thumb was devised that 

says that under the present typical data acquisition conditions utilized, NEXAFS 

microscopy can analyze areas 500 times smaller than TEM-EELS given the same 

radiation damage' . J. Stohr. NEXAFS Spectroscopy, Springer-Verlag (Berlin), 1992. 

E. G. Rightor et. al. J. Phys. Chem. (in press) 

c 

a 

787 284 286 288 290 292 294 296 282 284 286 288 290 292 294 296 

Photon Energy (eV) 

Figure 1. NEXAFS spectra acquired from PET after exposure to 302 eV x-rays for 

dosages of a) no dose, b 1.00 x 10' Mrad, c) 1.84 x lo5 Mrad, and d 2.68 x 10' 

exposure while an excitation at 286.5 becomes more pronounced. 

Mrad. The intensity oft h e excitations at 285 and 288 eV decreases wit k increasing 

* Work supported by NSF Young Investigator Award (DMR-9458060) and Dow 

Chemical. 
X-ray Absorption Near Edge Structure of Amino Acids and Peptides I X1A 

J. Boese, A .Osanna, C. Jacobsen, J. Kirz, E. Tall (SUNY Stony Brook), and X. 

Zhang (Harvard U.) 

Combination of the spatial resolution of soft x-ray microscopes with x-ray absorption near-edge structure (XANES) analysis provides a new means for chemical 

state mapping [l]. Comparison of near edge absorption resonances with reference 

spectra makes it possible to map the concentrations of different double bonds. We 

tried to explore the applicability of this method to protein specific imaging. All 

proteins in living systems consist of only 20 different amino acids, linked together 

via the peptide bond. We wanted to find out if a protein spectrum can be predicted 

from amino acid spectra. This depends on how much spectra are affected by the 

peptide bond. 

Preliminary work by X.Zhang and S.Williams [2] showed that a nitrogen edge 

XANES spectrum of the dipeptide consisting of arginine and aspartic acid was 

just the sum of the spectra of the two monomers. We have measured carbon 

edge XANES spectra of amino acids for the first time. Spectra of six amino acid 

monomers, four dipetides and one tripeptide were compared. Because of their heat 

sensitivity, amino acids cannot be evaporated but have to be analyzed in solid 

form. In order to obtain quantitative absorption measurements using transmission 

spectroscopy, the illuminated spot of the sample has to be of uniform thickness. 

Therefore a special sample preparation technique was used, and the spectra were 

obtained using the small spot size of the Stony Brook scanning transmission x-ray 

microscope at beamline X1A. 

The spectra of the dipeptides and tripeptides investigated can indeed be explained as the sum of the spectra of the monomers involved. A typical result is presented in 

Figure 1. The spectra of glycine (Gly), tyrosine (Tyr), and the Gly-Tyr dipeptide 

solid lines) are shown together with a weighted sum of the two monomer spectra 

dashed line). The peptide bond has only a very small effect on spectra analyzed. i t causes a very small shift (~0.3 eV) of the ?r* resonance near 289 eV towards 

lower energies. If this result holds in general, it would allow the prediction of 

spectra of simple proteins, which could be used in protein specific imaging with 

x-ray microscopes. 

X.Zhang, R.Balhorn, J.Mazrirnas, J.Kirz J.Struct.Bzol.,l16:335-344,1996 

X.Zhang Ph.D. Thesis, SUNY at Stony Brook, May 1995 

Figure 1. 

i 320 

The Application of Soft X-ray Microscopy to the in-situ Chemical 

Analysis of Ancient Spores in Organic-Rich Sedimentary Rocks 

G. D. Cody (Carnegie Institution of Washington), H. Ade (NCSU), S. Wirick 

(SUNY Stony Brook) 

Soft X-ray Imaging and C-NEXAFS has been used for the in-situ analysis of 

spores in a rank variable suite of organic rich sedimentary rocks. The acquisition 

of chemically based images contrast based on the intensity of the 1s-pi * transition of unsaturated carbon 0 , reveals a homogeneous chemical structure in the 

spore exine (cell wall). C-NEXAFS microanalysis indicates the path of chemicalstructural evolution of the sporopollenin bio/geopolymer with increasing thermal 

maturity. The most significant change in the C-NEXAFS spectrum is an increase in 

the con-centration of unsaturated carbon, presumably aromatic, with maturity. In- creases in the concentraion of unsaturated carbon are paralleled by losses of aliphatic 

and hydroxlyated aliphatic carbon components. Carboxyl groups are present in 

low and variable concentrations. Absorption due to carboxyl groups persists in 

the most mature specimen in this series. The results of this study reveal that 

the reactions that drive sporopollenin chemical structural evolution during thermal 

maturation are consistent with sequential dehydration, Diels-Alder cyclo-addition, 

and de-hydrogenation reactions that ultimately lead to a progressively aromatized 

bio/geopolymer. This chemical-structural evolution pathway is different than what 

has been determined for other organic constituents in these rocks. 

1s - X* 

0.28 

Recen 

280 285 290 295 300 

eV 

Figure 1. A Soft X-ray Image of a microspore in ancient sediments(- 90 MA). 

Contrast is based on absorption intensity 

at 285.5 eV, which corresponds to the lspi* transition of aromatic carbon. 

Figure 2. A Stack plot of the CNEXAFS spectra for micro-spore samples in a suite of samples ranging in 

thermal maturity. Thermal maturity 

is gauged by the magnitude of the reflectance (%R) of a co-existing organic 

phase in each sedimentary rock. 
Carbon Measurements on Interplanetary Dust Particles X1A 

G. J. Flynn (SUNY Plattsburgh), S. Bajt, H. Chapman (LLNL), and Lindsay P. 

Keller (VA Associates) 

Interplanetary dust particles (IDPs), typically -10 microns in size, have been 

recovered from the Earth’s stratosphere by NASA aircraft. These IDPs are samples 

of the dust emitted by comets as well as debris produced by the fragmentation 

and erosion of asteroids. On average, the IDPs contain -12 wt% carbon, about 

three times the carbon content of the most carbon-rich meteorites. These IDPs are 

believed to have been an important source of pre-biotic organic matter on the early 

Earth and possibly Mars. 

Transmission electron microscope examination of ultramicrotome thin sections 

of IDPs has identified graphite, poorly-graphitized carbon, and carbonate in IDPs, 

while two-step laser mass spectroscopy has identified polycyclic aromatic hydrocarbons (PAHs) in some IDPs. However, the relative abundances and spatial distributions of individual carbon-bearing phases have not been established. 

Thin sections fron three IDPs were examined using the Scanning Transmission 

X-ray Microscope (STXM on beamline X1A of the National Synchrotron Light 

tions reported by other techniques, the carbon distributiions were mapped, and 

X-Ray Absorption Near Edge Spectroscopy (XANES) measurements were made 

to determine the carbon bonding states present in selected carbon-rich regions. 

Carbon-XANES measurements at carbon-rich spots on two IDPs showed two peaks, 

at 285.6 and 288 eV, consistent with graphite or poorly-grahitized carbon. 

The third IDP was selected for analysis because prior Electron Energy Loss 

(EELS) measurements showed an usually broad pi* peak which did not match that 

of any carbon bearing phase identified in IDP’s. The higher energy resolution at 

X1A allowed us to resolve the broard pi* peak into two peaks, with energies of 284.8 

and 286.3 eV. A peak at 288.5 eV was also seen in this particle by both C-XANES 

and EELS. The peak at 286.3 eV was not seen in any of the phases previously identified in IDPs: graphite, poorly graphitized carbon, carbonate, silicone oil in which 

NASA collects IDPs), or the two PAHS (pyrene and dibenzoperylene . Ah 

c60, shows peaks at 284.5 eV, 286.0 eV, and 288.4 eV, while the IDP sample shows 

peaks at 284.8 eV, 286.3 eV, and 288.4 eV. The IDP spectrum, descibed in detail 

by Bajt et al. I, is consistent, within errors, with the pure CSO standard if the 

286.0 and 286.4 eV peaks of c60 overlap to form the IDP peak at 286.3 eV due to 

inadequate spectrial resolution or sample degradation. 

Further experiments are in progress to conclusively identify this carbon-bearing 

phase, obtain reference spectra of kerogens extracted from meteorites, and map and 

identify the carbon bearing phases in other IDPs. 

Source. The carbon abun d ances were determined, confirming the high concentrapeak energies are a good match to c60, fullerenes, though pure, we d -crystallized e three 

Bajt, S. et al. Lunar & Planetary Science XXVII, 57-58 (1996) 

X1A First Holographic Images of Fast-frozen Hydrated Biological Specimens 

S. Lindaas, M. Howells, D. Pinkas, C. Magowan, K. Downing (LBNL) and C. 

Jacobsen (SUNY Stony Brook) 

X-ray holography allows direct imaging of samples without the use of lenses. 

Our present technique employs photoresist (PMMA) to record the x-ray interference pattern, an atomic force microscope to examine and digitize the hologram, and a computer for numerical reconstruction. With this methodology, we have obtained 

sub 45 nm resolution images of room temperature biological specimens ’. However, 

to minimize radiation artifacts, even in single exposures of unfixed specimens, it is 

necessary to ”preserve” the specimen in a frozen state. To protect the specimen’s 

morphology against ice-crystal damage, it must be fast frozen to liquid nitrogen 

temperature. Taking advantage of techniques developed in the electron microscopy 

community we have developed a cryo-holography station at beamline X1A which 

is capable of obtaining holograms of specimens prepared by fast freezing and held 

at cryogenic temperatures. We have recently obtained the first holograms of fastfrozen hydrated biological specimens measured at cry0 temperatures ’. Fig. 1 is 

a hologram of fast-frozen hydrated malaria infected red blook cells measured at 

cry0 temperatures. Fig. 2 is the reconstructed image with a twin-image suppression algorithm implemented. This is an intermediate result and shows that the 

twin-image artifact is now the principle limitation to applications of holography. 

Our cryo-apparatus is already being upgraded to perform tomography experiments 

which we hope to report on soon. References: 1. S. Lindaas, et.al., ”X-ray holographic microscopy by means of photoresist recording and atomic-force microscope 

readout” J. Opt. SOC. Am.A 13, pp. 1788-1800 (1996), 2. S Lindaas, et.al, ”X-ray 

Holography of Fast-Frozen Hydrated Biological Samples” , to be published in X-ray 

Microscopy and Spectromicroscopy proceedings of XRM96 Springer-Verlag (Ed J. 

Pres. Fac. Fellow. Awd. RCD 92-53618 (CJ), and Comp. Sci. Grad. Fellow. 

Thieme et al.. This research supported in part by DOE A. Hollaender Fellow. ( A L) 

Figure 1. X-ray Gabor hologram (X=2.4 

nm) of fast-frozen malarial infected red 

blood cell. Readout using AFM (20482) 

pixels each (22 nm)2. 

Figure 2. Reconstructed image (z = 

425 pm with twin-image suppression implemented. Our work is concentrating 

on improving this algorithm. 
Fd 

w 

O I Commissioning of the Cryo Scanning Transmission X-ray Microscope I X1A I 

J. Maser, C. Jacobsen, J. Kirz, A. Osanna, S. Spector, S. Wang, J. Warnking 

(SUNY Stony Brook) 

X-ray Microscopy of biological specimens is severely restricted by radiation damage to the objects. To cope with this problem, we have developed a cryo-Scanning 

Transmission X-ray Microscope [l]. This system is designed to image hydrated 

objects of a thickness of several micrometers at temperatures of around 130 K. 

At these temperatures, structural changes to the sample due to radiation damage 

should be considerably reduced, enabling us to achieve higher spatial resolution and 

to take multiple images of one sample area for applications such as and chemical 

state mapping and tomograpy. Use of fast cooling methods will also allow us to 

freeze dynamical processes with a time constant of few milliseconds. 

The images shown below were obtained during our first commissioning run. All 

images are taken at a wavelength of X = 2.4 nm using a zone plate with an outermost 

zone width of 60 nm and a diameter of 160.um. For large -- photon flux, we used an 

exit slit of 200pm width. 

Spector, S. Wang, B. Winn, S. Wirick, X. Zhang. SPIE 2516, pp. 78 - 89, (1995). 

[l] J. Maser, H. Chapman, C. Jacobsen, A. Kalinovsky, J. Kirz, A. Osanna, S. 

I1 

1 

j 3~ 

Figure 1. A: Image of Ge test pattern, demonstrating good orthogonality of piezodriven fine scanning stage. B: Center of test pattern: lines and spaces of around 

110 nm can be resolved, which corresponds well to size of x-ray probe at 200p m exit slit. C, D: Images of plunge-frozen monkey kidney cells at T = 160 K. C: 

Image of a 2 mm x 2 mm area of sample, taken with the stepping-motor driven 

coarse scanning stage. D: Image of a 35 pm x 35 pm area of sample, ta 

Luminescent Molecular Probes for X-ray Microscopy 

M.M. Moronne (LBNL) 

Synchrotron based scanning x-ray microscopes are capable of Rayleigh resolutions 

approaching 50 nm, with improvements expected to reach 20 nm in the near future. 

To take advantage of this high resolution for biological studies, specific labels for 

subcellular targets are needed. Using the scanning x-ray microscope at beamline 

X1A of the National Synchrotron Light Source, modified for luminescence detection (SLXM), we have shown that lanthanide based fluors are sufficiently bright 

and radiation stable to be the basis of a family of x-ray excitable probes. Initial 

experiments using lanthanide-polychelate conjugates of avidin and a secondary antibody to label actin stress fibers, validated this approach; however, non-specific cell 

labeling by these original compounds seriously compromised image quality. Subsequent studies established that there were two main causes of non-specific labeling: 

a) insufficient acylation of polychelate amino groups and b) high molecular weight 

aggregates created by unwanted crosslinking of polychelate chains. 

We have addressed these problems in the last year by improved acylation techniques and by developing a biotinylated lanthanide-polychelate (bioLPC that is virsimplifies probes synthesis by eliminating the need for conjugation of the polychelate to large macromolecules such as antibodies that invariably generates a high 

percentage of cross linked aggregates. The biotinylated probe takes advantage of 

the tetravalency of avidin/streptavidin. For example, to label actin stress fibers, 

cells are treated with phalloidin-biotin (a specific probe for filamentous actin), followed by avidin, which has four biotin binding site. At this stage, only one avidin 

site is likely to be occupied by phalloidin-biotin leaving three available for binding 

to bioLPC. In this way, as many as 240 lanthanide atoms can be attached to a 

single molecular target, greatly increasing the brightness of the probe under x-ray 

excitation. 

The efficacy of this strategy was confirmed using a rhodamine tracer on the polychelate probe and confocal microscopy. We demonstrated that bioLPC is capable of 

labeling with a specificity fully equivalent to conventional avidin-biotin probes for 

actin microfilaments, microtubules, and FISH DNA probes. In April of this year, we achieved the best x-ray excited luminescent images to date using bioLPC to label 

in vitro preparations of microtubule assemblies and actin filaments in 3T3 mouse 

fibroblasts. We believe that this data establishes the effectiveness of lanthanide 

polychelate probes for scanning x-ray microscopy, and fully expect to achieve a five 

fold improvement in resolution over visible light microscopic methods. 

X1A 

tually free of non-specific labeling artifacts. Biotinylating the polyche 1 ate greatly 
X1A Morphological Characterization of Polycarbonate/AcrylonitrileButadiene-Styrene Polymer Blends * 

A. P. Smith, H. Ade, R. Fornes, R. Gilbert (NCSU) and C. Sloop (IBM) 

We employ the compositional sensitivity of Scanning Transmission X-ray Microscopy (STXM) to study the morphology of complex polymeric blends composed 

of polycarbonate (PC), styrene-acrylonitrile copolymer (SAN), SAN grafted on 

polybutadiene in latex form (SAN-g-PB), and titanium oxide (PC/ABS blends). 

These blends are utilized in computer housings and enclosures and we are interested in understanding the development of morphology and mechanical properties 

with repeated recycling of these materials. Some of the first steps in this study are 

the imaging of thin sections (100 nm) of the un-recyled material with the STXM. 

Figs. la and lb are micrographs that let us determine the morphology, and in 

particular highlight the nitrile (SAN) distribution. The SAN is shown to mainly 

accumulate at the interface between the dispersed SAN-g-PB and the continuous 

PC matrix. There is also evidence of free SAN within the PC matrix. In addition, 

in images acquired below the carbon edge not shown here, the titanium oxide can be located and is shown to be associated with the SAN/SAN-g-PB aggregates. 

Figure 1. (A) NEXAFS image of polycarbonate/ABS blend acquired at 285.45 

eV. PC is dark, SAN an intermediate gray and PB is bright. (B Same sample 

are regions with high nitrile concentrations (SAN), that typically enclose the PB 

particles. 

area acquired at 286.55 eV. The brightest features are PB, while t h e darker areas 

P 

W 

F * Work supported by NSF Young Investigator Award (DMR-9458060). 

Investigation of the Spinodal Decomposition Qf Constrained Thin 

X1A Polymer Films with X-ray Microscopy 

A. P. Smith, H. Ade (NCSU), D. Slep (Highlord Chemical), S. Qu, M. Rafailovich, 

and J. Sokolov (SUNY Stony Brook) 

We have begun a study of the spinodal decomposition of two polymers (bi-layers or blends) constrained to a surface with the X1-STXM. Previous work with Atomic 

Force Microscopy (AFM) has shown segregation of one polymer into spheroids 

within the other upon annealing but was unable to chemically differentiate the 

species'. By utilizing NEXAFS spectromicroscopy, we are able to identify the poly- mers and their location within the system. The first system observed was a bi-layer 

of immiscible polymers, polystyrene (PS) and poly(methy1 methacrylate) PMMA 

and an example of the morphology observed is shown in Fig. 1. This micrograph, acquired at an energy specific to the PMMA (288.4 eV), shows that the PS segregates 

into elipsoid like regions dark with the PMMA forming a shell around them and 

in the PSI differentiation of phases within this system is simple with NEXAFS microscopy. The second system observed, a blend of PS and poly(br0minated-styrene) 

(PBrS), was a more difficult test of the chemical differentiation via NEXAFS microscopy since the chemical structure of the materials is identical except a Br atom 

substituted on the phenyl ring of the PBrS. Fig. 2 shows a micrograph of this blend 

acquired at 286.2 eV (an energy specific to the C-Br bond and shows that the 

material will allow a determination of the dynamics of the decomposition reaction 

with increasing annealing time. 

a thin layer between the L) S dispersions. Due to the unsaturated bonding present 

PBrS segregates (dark regions) within the PS matrix (grey). b urther studies of this 

Investigator Award (DMR-9458060). 

Figure 1. micrograph of Figure 2. X-ray micrograph of PS/PBrS 

PS/PMMA blend showing segregation of blend showing PBrS dispersions within 

the PS matrix. The lightest area is an the PS within the PMMA. 

open area. 
X1A NEXAFS Spectroscopy of Polymeric Isomers of Poly(ethy1ene terephthalate) (PET) 

A. P. Smith, H. Ade (NCSU), S. G. Wrquhart, A. P. Hitchcock (McMaster U.) and 

E. G. Rightor (Dow Chemical). 

Due to the dependence of Near Edge X-ray Absorption Fine Structure (NEXAFS) 

spectroscopy on the local chemical environment of the excited atom' , differences in 

these absorption spectra might also be expected for different isomers of the same material. In order to investigate this phenomenon, we have acquired carbon K-edge 

absorption spectra of poly(dially1 phthalate) (1,2 PDP), poly(dially1 isophthalate) 

(1,3 PDP and poly(ethy1ene terephthalate) (1,4 PET), where the phthalate segmeta, para) of the methyl carboxylate groups on the phenyl ring. Fig. 1 displays 

the chemical structure of these materials and Fig. 2 shows the x-ray absorption 

spectra of a) 1,4 PET, b) 1,3 PDP and c) 1,2 PDP and demonstrates that while 

the spectra are similar in overall shape, there are differences. The most obvious 

difference between the spectra is the split in the a* peak at 285 eV present in the 

1,4 PET and absent in the other oligimers. This peak intensity splitting has been 

shown to be due to the conjugation between the carbonyl groupsand the aromatic 

group' which is absent in the oligimers due to differences in electronic structure 

(1,3 PDP) and non-planar geometry (1,2 PDP)3. In addition, the absolute energy 

of the peaks at 285 and 288 eV shift upwards by .3 eV between the 1,4 PET and 

the 1,2 PDP spectra. These spectra demonstrate that NEXAFS spectroscopy can 

be quite sensitive to isomer substitution in conjugated moieties. 

ment oft k ese polymers are isomers with different patterns of substitution (ortho, 

1 J. St6hr. NEXAFS Spectroscopy, Springer-Verlag (Berlin), 1992. 

2 E. G. Rightor et al. J. Phys. Chem. (in press) ti 3 S. G. Urquhart et. al. J. Phys. Chem. (submitted) 

Work supported by NSF Young Investigator Award (DMR-9458060) and Dow 

Chemical. 

?',I " ' I " " , " " I " " , " " , I 

0.0 

2M5 2911 795 300 305 

Photon Energy (ev) 

Figure 1. Chemical formulas of 1,4 PET, 

1,3 PDP, and 1,2 PDP. 

Figure 2. NEXAFS spectra of 1,4 PET, 

1,3 PDP, and 1,2 PDP demonstrating 

changes due to chemical isomerism. 

X1A Characterization of the X1-STXM Spectroscopy Acquisition Mode 

Utilizing Carbon Dioxide 

A. P. Smith, T. Coffey, and H. Ade (NCSU) 

We have developed a procedure for the performance characterization of the X1- 

STXM utilizing carbon K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of carbon dioxide (COz). This procedure is necessitated by the need 

to acquire NEXAFS spectra of complex polymeric molecules with many excitations 

for which an accurate understanding of STXM performance, particularly between 

different data runs, is absolutely vital. COz was chosen due to its non-toxicity at low 

concentrations and the existance of a high energy resolution NEXAFS spectrum in 

the literature'. The relatively simple spectrum of C02 allows for easy identification 

of microscope problems as shown in Fig. 1. Two different COz spectra acquired 

during periods of microscope problems are shown. Fig. la exhibits "absorption" 

saturation of the aast peak (290.74 eV) as well as an anomolous dip at 285 eV which 

is consistent with saturation of the photon counter. Fig. lb also exhibits absorption 

saturation of the rust peak but has an anomalous peak at 285 eV during another 

kind of STXM problem. - 

Several of the CO? NEXAFS snectral features are utilized to determine the absolute energy scale and to check for *monochromator non-linearity. The sharp Rydberg 

excitations are used for energy resolution determination by fitting gaussians to the 

acquired spectra. In addition, the saturation of the a* peak allows for a quantitative estimate of the higher order spectral contamination by acquiring C02 spectra 

with and without a pinhole to block the contamination. One particular adventageous feature of our procedure is that COz can be added to the He purge while the 

sample is in place to calibrate spectra of any sample directly in-situ (see Fig. 2). 

[l] Y. Ma et. al. Phys. Rev. A, 44: 1848 (1991) 

3 4- R 

I 1 

285 290 295 300 305 

Photon Energy (eV) 

Figure 1. NEXAFS spectra of COz exhibiting a) absorption saturation of the 

a* peak at a very low OD and a dip near 

285 eV; b) anomalous peak at 285.0 eV 

and saturation. Note offset of (a) by 1. 

285 290 295 300 305 

Photon Energy (eV) 

Figure 2. In-situ NEXAFS absorption 

spectrum of PET and COz. The apparent offset is due to the high concentration of COZ. Note saturation of ?r* at 

much larger OD than in Fig. 1. 
NEXAFS Microspectroscopy of Macrophase-Separated Random 

Block Copolymer/Homopolymer Blends X1A 

A. P. Smith, J. H. Laurer, H. Ade, R. Spontak (NCSU), A. Ashraf, and S. Smith 

(Procter and Gamble Co.) 

We have utilized NEXAFS microspectroscopy to study the morphology and com- position of a macrophase separated blend of poly[(styrene-r-isoprene)'-b- styrener-isoprene)"] random block copolymer (RBC) and homopolystyrene (PS \ with a 

mass ratio of 20/80 RBC/PS1. X-ray micrographs of the unstained sample appear 

identical to TEM micrographs of stained samples and show micron sized ellipsoidal 

dispersions of the RBC within the PS matrix2. However, the composition can not 

be assessed in this way. We have thus acquired micro-NEXAFS spectra of several 

dispersions in order to examine their composition. 

Fig. 1 shows NEXAFS reference spectra of the pure PS (a) as well as the pure 

RBC (b). Due to the presence of PS in the RBC and the comparable fraction of 

carbon-carbon double bonds in polystyrene and polyisoprene, the overall spectral 

shape of the RBC is similar to the PS spectrum. However, differences in the spectra are observed, especially in the 287-289 eV energy range. Fig. 2 shows NEXAFS 

spectra acquired from within two different RBC dispersions. The spectrum in Fig. 

2a closely resembles the pure RBC spectrum, indicating that this dispersion is very 

similar in composition to the pure RBC with little or no PS present. However 

the spectrum in Fig. 2b more closely resembles the PS spectrum indicating the 

presence of PS within the RBC dispersion. These spectra demonstrate that the 

RBC dispersions possess a non-uniform composition and may contain pure PS. 

This information is unavailable at the required spatial resolution using any other 

characterization method. 

1 A. P. Smith et al. Macromolecules (submitted). 11 2 J. H. Laurer et. al. Langmuir (submitted). 

Work supported by NSF Young Investigator Award (DMR-9458060). 

280 285 290 295 300 305 310 

Photon Energy (eV) 

280 285 290 295 300 305 310 

Photon Energy (eV) 

Figure 1. NEXAFS reference spectra of Figure 2. NEXAFS spectra of RBC dis- 

(ai pure homopolystyrene and (b) pure persions showing that dispersion (b) con- R C. tains PS, while (a) is "pure" RBC. 

I Considerations for A Soft X-ray Spectromicroscopy Beamline * 

B. Winn, X. Hao, C. Jacobsen, J. Kim, J. Miao, B. Sullivan, S. Wirick (SUNY 

Stony Brook), H. Ade (NCSU), C. Buckley (King's College), M. Howells (ALS), S. 

Hulbert (NSLS), I. McNulty (APS), T. Oversluizen (Creative Instrumentation) 

X1A 

The X1A soft x-ray undulator at the NSLS is the source for our experimental 

programs in spectromicroscopy. We require both spatial and temporal coherence. 

Due to the relatively large horizontal divergence of the electron beam in the low 

/beta strait section of the x-ray storage ring, it has been possible to split the beam 

using a scraping mirror into two branches: X1A used by our program and X1B used 

for high resolution spectroscopy. We are now rebuilding the X1A beamline to provide improved resolving power and essentially linear trade-off between photon rate 

at the zone plate and resolving power for the soft x-ray spectromicroscopy experiments. This new beamline will exploit both additional floorspace due to the NSLS 

building expansion and increases in the brightness of the x-ray ring. Our beam will 

be further split into two separate beamlines, both of which will use toroidal mirrors 

to focus the source on the monochromator entrance slits horizontally and to focus on the monochromator exit slits vertically. This separation comes at no loss of 

coherent flux and permits low thermal loading on the optics, since we need little 

more than the coherent fraction of the beam at the Fresnel zone plate for microfocusing. Because of the small angular acceptance for spatially coherent illumination 

of the zone plates and the use of an approximately satisfied Rowland condition, our 

monochromators have sufficient resolving power with fixed exit arms. Experiments 

can then be placed near the exit slits, with spatial coherence established by the exit 

slit size. Resolving power will be controlled by adjusting the entrance slit alone 

with no change of spatial coherence. The zone plates will be overfilled to be less 

sensitive to beam vibration and drift. 

H 0 R I ZO NTAL PLAN E 

ZP $;pi;; -- U 

EXSO ENSO 

y=:K!Ly!c?L~.-p-l,N - E .- U 

ZP MI0 

EXSO 

Figure 1. Focussing diagram in both the horizontal and vertical planes (not to scale) 

for both branches. Labels refer to undulator U, toroidal mirror M10, entrance slit 

ENSO, grating GO, exit slit EXSO, and zone plate ZP 

* X1A beamline supported in part by the DOE-BES, DOE-DMR and DOE-OHER, 

and by the APS. We thank our colleagues at Stony Brook, J. Dickerson, R. Hazel, A. 

Kalinovski, J. Maser, A. Osanna, I. Pogorelsky, S. Spector, S. Wang, and H. Zhang, at 

the LLBL, H. Chapman, and at the NSLS, E. Johnson and P. Takacs, for their input. We 

thank W. Mckinney for providing effic 
I X1-SPEM-I1 Application to Tribological Surfaces I XlA I 

H. Zhang, G. R. Zhuang, H. Ade (NCSU), C.-H. KO, B. Winn, J. Kirz (SUNY 

Stony Brook), S. Cameron, D. Leta (Exxon), S. Hulbert, and E. Johnson (NSLS) 

We presently investigate tribological surfaces in order to determine the distribution and the chemical state of various elements in a wear-scar. These applications are starting to produce the first scientific results after the upgrade of the scanning 

photoemission microscope (Xl-SPEM-11) to a MCD hemispherical sector analyzer. 

Three areas inside the wear-scar on the sample have been investigated. In one of 

the areas, a set of images (Fig.1) was acquired (75x75 pixels, 3x2.5 microns steps, 

600 ms dwell time and 187eV pass energy ) by centerin the MCD at the peaks of 

S 2p, P 2p, Zn 3d, Mo 3d, Fe 3p, C Is. A set of spectra rFig.2) was acquired within 

the image area by moving the sample along the wear scar. 

Due to the nature of the lubricant additives, it is expected that Mo and S, and 

Zn and P are highly correlated in these materials. The pattern of Mo looks similar 

to that of S 2p, but that of Zn also looks more like that of S rather than that of P. 

The pattern of C Is is very similar to that of a secondary yield image not shown 

here and to that of Mo 3d. Overall, there is not a particularly strong correlation 

between any two elements in these images or in the spectra, contrary to what was 

expected. We also observe that Mo and Fe exhibit significantly different spectral 

lineshapes in spectra from this tribological surface. these differences reflect different 

oxidation states and chemical compounds. 

Elemental maps of the wear-scars were produced and different although yet 

unidentified chemical states for Fe and Mo have been observed with point XPS 

spectra. While it is too early to draw definitive conclusions about the precise 

species and composition, we have observed chemical differences from areas that are well within the spatial resolution of the X1-SPEM-11. Higher resolution spectra of 

the specific elements of interest should be able to yield conclusive answers as to 

what the precise chemical nature of the local reaction layer is. 

Figure 1. Elemental maps of area 1 after 

subtracting the background in the outer 

channels of the 16 channel MCD that do 

not correspond to the elemental peak. 

(All images: 75x75 pixels, 3x2.5 micron 

steps, 600 ms dwell time). 

t 

3 

t 

p 

2 

2.1) 

2 .r 

.a 

7 

1.5 

1 .o 

0 .s 

00 

I.. . I ~nn ?m onn qsfi rnn sn n 

Binding Enerw 

Figure 2. Spectra from nominal locations as indicated in Fig. l. Both, Mo 

and Fe, exhibit different line shapes in 

these spectra reflecting different chemical species. 

1 Characterization of Polymer Interfaces Using X-ray Microscopy I X1A 1 

One of the issues of interest in the study of polymer laminates is the interpenetration of adjacent layers. To characterize this phenomenon, analytical techniques 

which can discern the different chemical components of the laminate must be used. 

While transmission electron microscopy (TEM) is typically used to characterize 

this class of samples, the images often do not have sufficient chemical contrast to 

completely resolve the issue at hand. An additional technique which has superior 

chemical sensitivity, albeit at lower spatial resolution, is scanning transmission x-ray 

microscopy (STXM). Shown in the two figures at the left below are the images of 

a polymer laminate with four layers obtained using energies of 286.7 and 281.8 eV. 

Each image is of a 10 x 10 micron sample area. The area in the upper right third of 

the image is that of air while the lower left half is that of the mylar base. Coated 

on the mylar base are three thin layers of polyurethane, poly(styrene acrylonitrile) 

[SAN], and carbon black [CB] in poly(viny1 alcohol) with approximate thicknesses 

of 0.3, 1.0, and 0.8 microns, respectively. Of interest in this study was the extent 

of migration of the SAN into the porous CB layer. TEM images indicated that the 

boundary between the two layers might be diffuse. By acquiring spectra at finely 

spaced intervals across the interface, we were able to demonstrate that the penetration of the SAN into the CB layer was less than 200 nm. As indicated in the plot 

below, the the absorption feature near 287 eV, which arises from the SAN, is clearly 

present in spectra of a sample area within the SAN layer (+600 nm) and absent in 

an area within the CB layer (-300 nm). The level of SAN absorption remains nearly 

constant as the interface is approached and then decreases quickly as the interface 

is crossed. 

C. G. Zimba (MIT), A. P. Smith and H. Ade (NCSU) 

NEXAFS Absorbance 

8 ,"(" I ,,,,,,( 

286.7 eV 43.25 

180 28% ZOO 295 300 306 310 

Photon Energy (eV) 

Figure 1. 
I STXM of Polymer Laminates: NEXAFS Microspectroscopy I X1A 1 

During the past year, we have characterized several polymer laminates using 

scanning transmission x-ray microscopy (STXM). In an imaging mode, the STXM can be used to acquire several images at different energies which exhibit different 

levels of ”chemical contrast” due to the vaiation in NEXAFS absorption by the 

various chemical components. In a spectroscopic mode it is also possible to obtain 

high quality NEXAFS spectra which are characteristic of the majority components 

in each layer of the polymer laminate. Shown in the left figure below is the image 

of a polymer laminate with ten layers obtained using an energy of 288.3 eV. The 

scale bar at the lower right of image indicates the size of the image. At this imaging 

energy, each layer can be clearly discerned along the y-direction of the image. Along 

the x-direction, folds in the ultrathin cross-sectioned sample can also be observed, 

indicating the internal stresses inherent in this multilayer coating. The small white area in the right side of the image is a tear in the cross-sectioned film. As indicated 

in the right figure below, NEXAFS spectra of each layer can be readily obtained. 

The spectra are plotted starting with that of the top layer in the image and ending 

with the bottom layer in the image. While the top spectrum is clearly that of 

polycarbonate, it is clear from the spectra that the third, fifth, and seventh layers 

are quite chemically similar as are the fourth, sixth, and eighth layers also. This is 

consistent with the composition of the coating where the third, fifth, and seventh 

layers were a mixture of Carboset polymers and the fourth, sixth, and eighth layers 

were coatings of Elvacite loaded with different aromatic dyes. It is clear from these 

studies that the imaging and spectral capabilities of STXM can yield considerable 

information about multilayer polymer laminates. While not demonstrated in this 

abstract, we have also been able to discern variations in the concentration of major 

components in some model coatings. 

C. G. Zimba (MIT), A. P. Smith and H. Ade (NCSU) 

:: 

84 ~

2 

0 280 X-Ray 283 290 Energy 295 (eV ZOO 

I The Vibrationally Resolved 0 1s Photoelectron Spectrum of COz 

and A.M. Bradshaw (FHI) 

I X1B 1 

A. Kivimaki, B. Kempgens, H.M. Koppe, K. Maier, M.N. Piancastelli, M. Neeb, 

Due to a recent change of grating on X1B it has been possible to measure the vibrational fine structure on an 0 1s photoelectron line for the first time. For C02 we 

have shown that the antisymmetric C-0 stretch (307 f3 mevdominates totally the 

vibrational fine structure on the 0 1s main line, in contrast to the totally symmetric 

vibrational mode observed on the C 1s line 161 *i’ meV. The antisymmetric mode 

that core orbital vibronic coupling plays a role. This was predicted almost 20 years 

ago by Domcke and Cederbaum [Chem. Phys. 25 , 189 (1977)]. Vibronic coupling 

in core ionization of equivalent atoms in a molecule also provides a mechanism for 

dynamic core hole localization. 

is dipole-forbidden within the Born-Oppen 6 eimer approximation, thus indicating 

Ot I I I I 

11.0 11.5 12.0 12.5 13.0 13.5 

Kinetic energy (eV) 

Figure 1. The vibrational fine structure on the 0 1s line of C02. The points are the 

experimental data. The dashed lines show the individual vibrational components 

resulting from a lease square fit, including post-collision interaction. 
Fd Vibrational and Shake-up Excitations in C 1s Ionisation of Ethane a I X1B I 

H. M. Koppe, K. Maier, B. Kempgens, A. Kivimaki, M. Neeb, and A. M. Bradshaw 

(Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany) 

In continuation of our high-resolution studies of dynamic effects in core excitation 

we have investigated ethane as the prototype for the alkane series. The comparison 

with our recent work on methane is also interesting. Moreover, in combination 

with experiments performed on acetylene and ethylene the results lead to a new 

understanding of the role of shape resonances and multiply excited states and revive 

the discussion concerning the correlation between the energy of the shape resonance 

and bond length. 

Maximum entropy deconvolution, the Poisson approximation for sudden limit 

conditions and coupled least-squares-fits were combined in the analysis to access 

the complex vibrational structure. The C Is photoelectron spectrum is dominated 

by two totally symmetric vibrational modes, namely, the C-H stretch VI and the 

C-C stretch v3. Upon ionisation the vibrational energies of v1 and VQ significantly 

increase to 407h5 meV and 176&5 meV, respectively. This is reflected in a reduction 

of the bond lengths by 0.036f0.002 A(C-H) and 0.043f0.002 A(C-C). The lifetime 

broadening is determined to be 98zk10 meV, in good agreement with theory. A 

possible mixing with certain asymmetric modes of very similar vibrational energy 

such as V5 cannot at present be excluded. The errors given here are therefore 

restricted to the analysis itself. Fig. 1 shows the results of a least-squares-fit with 

the dashed lines representing the individual vibrational states; after summation 

and convolution with the instrument profiles they give the full line through the 

data points. 

The shake-up structure of CzHe resembles closely that of CH4. The lowest lying 

satellite band (labelled '1') gains much intensity towards threshold which is thought 

to be due to conjugate shake-up processes. 

9.0 9.5 10.0 10.5 11.0 

Kinetic energy (eV) 

Figure 1. The C Is photoelectron spectrum of CzHo at hv = 301 eV. 

2 

40x103 C2H6 c's ,,v=352e~ 

Shake-up 8alelllles 5 30 

- It 

.g 20 C 

10 - - 

z 

0 I JC 40 30 20 10 0 

Relative binding energy (eV) 

Figure 2. The C Is shake-up satellites. 

Peak 1 is conjugate enhanced. 

Improvement in Monochromator Performance on X1B 

M. Neeb, A. Kivimaki, K. Maier, H.M. Koppe, B. Kempgens, and A.M. Bradshaw 

(FHI), F. Loeb and P.D. Johnson (BNL - Physics) 

The mechanically ruled, blazed grating (fused silica blank, 800 l/mm, Au coating; 

Hyperfine Inc., Boulder, USA) on the spherical grating monochromator at XlB 

was replaced in May 1996 by a holographically recorded, laminar grating (silicon 

blank, 800 l/mm, Au coating; Zeiss, Oberkochen, Germany). The Figure shows 

the photocurrent IO as measured on a gold-coated copper plate behind the exit slit 

immediately before (dotted line, gap = 39.5 mm) and after full (gap = 39.5 mm) 

and dashed-dotted (gap = 56.5 mm) line, respectively) the c 6 ange of grating. The 

normalized intensity [nA/mA,;,,*s] is displayed on the ordinate while the grating 

has been scanned from 280 to 980 eV photon energy. The transmission of the 

monochromator is now distinctly higher at energies above 450 eV. Note that the 

entrance slit during the tests with the new grating was approximately a factor 

of six narrower than for the previous measurements. For the same slit width the 

photon flux at the C 1s edge 300 eV) is approximately the same as before; at photon 

energies higher than 550 eV ((0 Is) the flux is a factor of 5-10 greater. The maximum 

in the photon intensity distribution has been shifted by the new grating from 400 

to above 600 eV. High resolution photoabsorption and photoelectron measurements 

up to 800 eV will now be possible with the first order of the grating, allowing a 

more effective use of the full energy range of the first harmonic of the X1-undulator 

(200-800 eV). In particular, the energy range above 500 eV will be interesting for 

many experiments since most of other high resolution spectroscopy beam lines at 

other facilities are presently used only below 500 eV. 

1 X1B 

300 400 500 600 700 800 900 

Photon energy (eV) 

Figure 1. Photon flux vs. photon energy measured at X1B behind the exit slit. 
1 Surface Studies of Model Supported Catalysts: Rh/CeOz (100) * 1 X1B 1 

S.H. Overbury, D.R. Huntley, D.R. Mullins, K.S. Ailey and P.V. Radulovic (ORNL) 

It is now well established that interactions between noble metal and reducible 

oxide supports can synergistically alter the activity for oxidation and reduction 

reactions, important for emission control catalysis. We have looked for such interaction in Rh supported on ceria. CeO2 films were grown epitaxially by laser ablation 

onto SrTiOs(100) substrates. X-ray diffraction and TEM indicate the films are single crystalline with (100 orientation. The surfaces of these films, before and after 

deposition of Rh, and fo 1 owing exposure of NO were studied by soft x-ray photoemission and x-ray absorption spectroscopy. Photoemission from the Ce 4d levels 

exhibited complex features which differed between a partially reduced surface, induced by sputtering and a fully oxidized surface. The complex structure of the Ce 

4d spectrum has been attributed to different final state occupancies in the Ce 4f 

level. Differences between the sputtered and the oxidized surfaces were also seen in 

the 0 Is absorption spectra. 

N Is photoemission and photoabsorption clearly distinguished between adsorbed 

atomic N and molecular NO. NO does not adsorb on the Rh free, fully oxidized 

surface, although small amounts adsorb upon a sputter reduced surface. The photoemission and photoabsorption sugest that NO adsorption on the sputtered surface 

leads to nitride formation. The amount of NO adsorbed on the Rh loaded surfaces 

correlated with Rh 3d intensity. The thermally induced conversion from molecular 

to atomic N was measured as a function of Rh coverage to determine substrate 

affects on Rh surface chemistry. Rh deposited on a sputtered surface was much 

more active for NO decomposition. Following NO exposure at room temperature, 

most of the NO decomposes to atomic N and 0 on Rh / Sputtered CeOz, whereas 

considerable molecular NO is observed on Rh / Oxidized CeO2. 

Analysis of the Bias Due to Finite Size of the Peak Mask in Imaging 

Plate Integration Methods X3A1 

R. Bolotovsky and P. Coppens (SUNY Buffalo) 

The "seed-skewness" method for integration of peaks on imaging plates provides 

an optimal integration mask for every peak, without any a priori information about 

the peak shape or profile, or about the background level in the integration box. The 

method is based on the fact that the skewness of the pixel intensity distribution 

in the integration box increases relative to the insignificant skewness of the noise 

distribution when a diffraction peak is superimposed on the noise in the integration 

box. The seed-skewness method identifies a contiguous area of pixels in the integration box responsible for the skewness increase, and defines this area as the peak 

mask. 

In further work we have derived theoretical estimates of the bias in the integrated 

intensities due to finite size of the peak mask, and compared the results with experimental values based on synchrotron intensity measurements over a single oscillation 

range with different experimental parameters such as exposure time, and scanner sensitivity. A positive bias is found in the very weak reflections, not only with the 

seed-skewness method, but also with standard-box integration results. Appropriate 

corrections are being devised to allow the data are to be used to their fullest extent 

in high-accuracy applications. 

* Research sponsored by the Division of Chemical Sciences, Office of Basic Energy 

Sciences, U.S. DOE at Oak Ridge National Laboratory, managed by Lockheed Martin 

Energy Research Corp. under Contract No. DE-AC05-960R22464. 

F 

w 
F 

W 

O0 I Electron Density Analysis at Synchrotron Sources I X3A11 

P. Coppens, R. Bolotovsky and A. Darovsky (SUNY BuffaIo) 

In the past two years we have been able to collect full synchrotron-data sets with 

an accuracy adequate for charge-density analysis. A data set at X = 0.656 A was 

collected on sodium nitroprusside, while full data sets at both 0.654 A and 0.394 A 

were collected on chromiumhexamine hexacyanochromium. The 0.394 A data set on the chromiumhexamine gives unprecedented resolution. It is collected at 50K on a crystal of 80 x 30 x 30 p, and contains 7026 observed reflections, of which 4250 

are in the range of 1.25 < sin 0 / X < 2.00 A-’. Refinement of subsets of the data 

with different sin 0 / X ranges pass the test of internal consistency, indicating that 

systematic errors have been minimized in the integration procedure. Further, more detailed, checks are being undertaken. 

range of R x2 #of refl. scale factor pi1 Ofcr(1) pi1 ofcr(2) 

A2 x 10-6 sinelk, A-1 

0.2-1.97 3.5 1.6 7026 9.142(9) 1297(5) 1202(5) 

A2 x 10-6 

1.0-1.97 3.7 1.4 5279 9.20(2) 1310(7) 1227(7) 

1.25-1.97 3.9 1.3 4250 9.08(3) 1280(12) 1207(11) 

Resonance Scattering Studies of Mixed-Valence Complexes 

A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. 

Hummel and K. Wieghardt (Max-Planck-Institut fur Strahlenchemie) 

Oxygen-bridged mixed-valence manganese complexes are model compounds for 

the manganese-containing photosystem 11, which catalyzes the water oxidation reaction and thereby produces dioxygen used by animals and aerobic bacteria during 

respiration. 

Following our earlier study of p-dioxo-(Mn(2,2’-bipyridyl)z)z (BF4 

second study was performed on the triclinic crystals of the complex 

O)~(,u-MeCOz) Mn(III)(MeC02)2, L = 1.4.7-trimethyl-1,4,7-triazacyclononane. 

Imaging plate data were collected at 15 different energies straddling the absorption edge. Results are shown in Figure 3. The shift of Mn(1V) relative to Mn(II1) 

is again evident, though its magnitude appears less than observed for the dipyridylcoordinated Mn-mixed-valence complex. This is unexpected, as the asymmetry of 

the Mn-0 bonds (1.882 and 1.864 A vs. 1.788 and 1.767 A) is larger here than for 

the first compound discussed above. With the higher resolution achieved, the preedge feature of the absorption curve is evident in the f’ curve of Mn(IV), but not in 

that of Mn(II1). This clearly indicates that the spectroscopic transition to the un- occupied state occurs at Mn(1V) rather than at Mn(II1). 1 Y. Gao, A. Frost-Jensen, 

M.R. Pressprich, P. Coppens, A. Marques and M. Dupuis, J. Am. Chem. SOC. 114, 

9214, 9214 (1992 . A. Frost-Jensen, Z. Su, N. K. Hansen and F. K. Larsen, lnorg. 

Chem. 34, 4244 /1995). 

L 

c 

0 a 

v a 

7 

c 

1 

Q) c 

-5 

-6 

-7 

-8 

-9 

-10 

6520 6540 6560 6580 

.--) Energy(eV) 

Figure 1. f’ of the two manganese atoms in Mn (IV)(p-0)2(p-MeCOz)Mn 

(III)(MeC02)zL, where L = 1.4.7 trimethyl-l,4,7-triazacyclononane, as determined 

from refinement of data at different wavelengths. 

Figure 1. Spherical atom refinements of the 0.394 

hexacyanochromium, indicating absence of &dependent bias in the data set. 

data on chromiumhexamine 
Temperature-dependence of the Electron Transfer in r MnIIMnlIl(p-OH) Mixed-valence Complex 

A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. 

Hummel and K. Wieghardt (Max-Planck-Institut, Germany) 

At room-temperature the Mn(II)Mn(III) mixed valence complex [ttacnMn( 11) (,u-0)( p-pivalonato)z Mn(II1)tt acn]( C104)2 (tt acn = 1.4.7 trimet hyl-1 ,4,7- 

triazacyclononane), shows only small differences in the bridging Mn-0 bond lengths, 

while a resonance scattering experiment gives little difference between the two Mnatom scattering factor curves. However, a 20K structure determination shows a much larger asymmetry in the molecular geometry. Thus, at ambient temperature 

the valence electrons are partially ’detrapped’ due to the smallness of the energy 

difference between the Mn(I1)-Mn(II1) and Mn(II1)-Mn(I1 configurations, while at 

low temperature the metal centers are distinct. From an al ysis of bond lengths observed at 20K, 62K and 293K, an estimate of the energy difference between the 

11-111 and 111-11 configurations of 100cm-l, or ~1200 Jmol-I is obtained. This is 

to our knowledge the first observation of a temperature-dependent equilibrium in 

mixed valence complexes. 

Figure 1. 

Studies of CdS/CdTe Heterostructures Using X-ray Scattering and 

XAFS Techniques * 

S. W. Huang, Y. L. Soo, Y. H. Kao (SUNY Buffalo) and A. Compaan (U. of 

Toledo) 

Heterostructures of CdS/CdTe form an important class of materials for the development of useful thin film photovoltaic (PV) devices. It is believed that the 

efficiency of many PV layer materials can be seriously affected by the interfacial 

microstructures. Thus far there has been no previous study of the interfacial structures in these heterojunctions. The x-ray scattering and XAFS techniques offer 

a convenient tool for nondestructive characterization of the interfacial roughness, 

correlation lengths of structural fluctuations, degree of intermixing of elements, and 

local structures around the constituent atomic species. Heterosturctures of various 

configurations have been prepared by sputtering under different annealing conditions. 

* Research supported by DOE under Grant DE-FG02-87ER45283, and by NREL. 
Investigations of Microstructures in ZnSe-based 11-VI Semiconductor 

Thin Films Grown by MBE and MOCVD * 

S. W. Huang, Y. L. Soo, Y. H. Kao, H. Luo, and T. J. Mountziaris (SUNY Buffalo) 

Various techniques of grazing incidence x-ray scattering, XAFS, and diffraction 

have been employed for nondestructive characterization of microstructures on buried 

interfaces in semiconductor heterojunctions and superlattices of ZnSe, ZnSSe, ZnFeSe, and ZnSeTe grown on GaAs substrates by MBE and MOCVD. The semiconductor films were prepared under different processing conditions and various 

compositions. The results are useful for a comparison of the two major epitaxial 

growth methods for this important class of semiconductors. This is particularly significant for fundamental studies as well as development of new blue lasers, detectors, 

modulators, light emitting diodes, and photovoltaic devices. Interfacial roughness, 

layer thickness, correlation lengths, and lattice strain in the films were obtained. 

This information allows a quantitative correlation of the overall film quality with 

various microstructural parameters. 

X3A1 

' Research supported by DOE under Grant No. DE-FG02-87ER45283. 

X3A1 Grazing Angle Scattering and XAFS Studies of (Si,Ge)/Si Heterostructures * 

S. W. Huang, Y. L. Soo, Y. H. Kao (SUNY Buffalo) and K. L. Wang (UCLA) 

The (Si,Ge)/Si heterostructures form a convenient system for physical studies 

of band structure engineering. The possibility of varying the Ge content affords 

a suitable degree of freedom to control the lattice mismatch and strain in layered semiconductor structures. We have been studying various Sil-xGex thin films 

grown on Si by molecular beam epitaxy under different growth conditions. This 

material also offers an ideal system for the study of fundamental physics concerning 

epitaxial growth of lattice-mismatched semiconductor layers as well as the interfacial morphology. Interfacial roughness parameters and lattice strain of Sil-xGex 

films with varying thickness epitaxially grown on Si 100) are determined using the 

techniques of grazing-incidence x-ray scattering (G I XS) and diffraction. We have 

discovered that the roughness of both the buried interface and sample surface follows a power-law scaling behavior as a function of film thickness for films below 

the critical thickness, and it undergoes a large change above the critical thickness. 

More recently, we have also performed XAFS measurements of the same set of films. 

These results show new interesting correlations between the interfacial roughness, 

lattice strain, and the local structures. Work is in progress to compare the interface 

morphology determined from our x-ray observations and the physical parameters 

obtained by other methods. 

' Research supported by DOE under Grant No. DE-FG02-87ER45283. 
I The Electron Density of Th(SZP(CH3)2)4 I X3A1 I 

B. B. Iversen, F. K. Larsen (U. of Aarhus), P. A. Reynolds, (Australian National 

U.), A. Pinkerton (U. of Toledo), and A. Darovsky (SUNY Buffalo) 

While it is possible to get structural information on actinide compounds from 

x-ray diffraction [l], the prospect of obtaining detailed electron density in- formation seems limited. This is primarily due to the dominance of the actinide core 

scattering relative to scattering from the bonding electrons. However in the present 

compound Th is at the origin of the unit cell in spacegroup P42212. Thus the Th 

core contributes only to the h+k+l=even reflections. The h+k+l=odd reflections 

can therefore be used to model the asphericity of the electron den- sities due to chemical bonding. To limit systematic errors it is imperative to use short wavelength 

radiation. We have collected a very large number of accurate Bragg diffraction data 

at 28 K using imaging plates and a DISPLEX cooler fitted with an antiscattering 

device. The internal consistency of the data is excellent, R(int)=0.033 for 36192 

reflections averaged to 11206 unique ((sint/l)max = 1.76A). Structural refinements 

show that it is possible to refine hydrogen positions and thermal parameters even in the presence of Th. Initial modelling of the electron densi- ties using the valence 

orbital formalism reveals that the Th atom is less ionic than expected. Comparisons 

with high quality theoretical calculations are in progress. The data also allow an contribution (f’ and f”) for 

J. C. S. Dalton, 1475-1480 

I The Structure of Type 1 GeSz X-3A1 

J. B. Parise, K. Tan, C. Cahill and Y. KO (SUNY Stony Brook) 

Open frameworks consisting of corner linked polyhedral elements are capable of 

occluding organic molecules and so are of interest for their potential as selective 

agents for molecular sieving, catalysis, ion exchange and ion conduction. The most 

common of these frameworks are the aluminosilicates. However, the range of materials capable of forming open frameworks has increased greatly over the past decade 

since synthetic routes to knit isolated tetrahedral Sn- and Ge-sulfide clusters into 

frameworks have been found. This was accomplished using two procedures: selfcondensation of the clusters in the presence of organic amines and condensation 

from solution using transition metal ions along with the organic amines. There is 

evidence that both the organic amines and the transition metal act as structure 

directing agents. However, no three dimensional network based only on the connection of GeSz tetrahedral units has been described. Type 1 is now shown to be 

such a framework based on x-ray structure determination from 30 micron single 

crytsa1s.s 

By taking a slurry of amorphous GeSz, MnCl 2, quinucilidine, and water, heating 

to 423 K for 3 days, single crytsals suitable for data collection using the imaging 

plate system at X-3 were obtained. The structure determined using this data consists of corner linked adamantine units, [GeS4Slo], corner-linkd to form an open 

framework akin to zinc blende (ZnS) or diamond (Figure 1). 

Figure 1. Structure of QUI-MnGeS-1 showing the connection of Ge4Slo adamantine 

units. Molecules found in the channels of the structure are omitted for clarity. 
X3A1 Synthesis and Structural Characterization Using Synchrotron Radiation of(C~H13N2)2(H30)(HzO)l[AgGecSlo] 

J. B. Parise, K. Tan (SUNY Stony Brook), and A. Darovsky (SUNY Buffalo) 

The open framework germanium sulfide system provides an opportunity to 

synthesize some compounds with certain designed structural features. A novel 

compound, [( CS H13 Nz)z (Hs O)( Hz O)] 

[AgGe4Slo] was obtained using hydrothermal technique. In this structure, the 

silver was coordinated to three Ge4Slo4- clusters in a trigonal plane fashion, realizing an expected structural type in this system. The single crystals of the compound were small and synchrotron radiationjimaging plate system made it possible to collect a set of high quality X-ray diffraction data for structural determination and 

refinement. A sample crystal, 30~30x40 pm in size was used for data collection at 

X3A1 beamline of NSLS in BNL with a 20x25 mm high resolution imaging plate 

as a detector . The wavelength was 0.394 Aand the maximum measured diffraction 

vector was 0.797. In total 13477 reflections including were collected in 36 imaging 

plates exposed in about 5 hours. These were merged to produce a data set containing 

4104 unique structure factors. The structure was solved using direct methods. The 

primary building units of the compound consist of tetrahedral [GeS4I4- and trigonal 

planar [AgS3I5- clusters. The [GeS4I4- units form [Ge4Slol4- adamantine-like clusters as secondary building units. The structure contains double chains, consisting 

of [Ge4SloI4- clusters connected by three coordinated silver (Figure below). These 

chains are infinite in [loo] and occlude two partially protonated Dabco [C~HI~NZ~] 

molecules, one hydroxynium [H30t] and one water [Ha0 , giving a charge balanced 

chemical formula of [(C~€I,N,),(H~O)(HZO)] [ Ag Ge4 Sld. 

Figure 1. 

X3A1 The 154 K Phase Transition of Tetramethylammonium Tetrafluoroborate 

Thomas Schultz (Risoe National Laboratory) and Finn Krebs Larsen (Aarhus U.) 

Tetramethylammonium Tetrafluoroborate (TMT) is an organic salt used as a 

supporting electrolyte in the field of electrochemistry. TMT has 2 phase transitions 

at 154 K and at 601 K, the nature of which is not yet entirely understood. At 298 

K, TMT has a tetragonal unit cell (see Fig. 1) containing 16-fold disordered BF, 

ions and ordered (CH3)4Nt ions. Lowering the temperature to 160 K diminishes 

the disordering of the BF; ions to &fold, freezing out a lowest energy configuration 

of these ions. At around 160K diffuse diffraction peaks appear at half order h- and 

k-values, the intensity of these grow rapidly upon further cooling. At around 155 K 

the half order diffraction peaks, start to split into 2 or 4 components. This splitting 

is explained by a model containing 4 orthorhombic twins, with unit cells twice as 

big as the tetragonal room temperature unit cell. In the period 22 August - 31 

August, 1996, we performed single crystal measurements at the 4-circle instrument 

at beamline X3A1. Using Imaging Plates, we collected TMT data sets at 298 K, 

240 K, 155 K, 145 K and 15 K. In addition careful measurements of the diffuse half 

order Bragg peaks and of the unit cell volume as a function of temperature (see 

Fig. 2) were carried out which will enable us to calculate the order parameter of 

the 154 K phase transition. 

wy Y 

Figure 1. The tetragonal unit cell of 

TMT at 298K, showing the ordered 

tetramethylammoniumions and the disordered tetrafluoroborate ions (indicated 

using large blue balls). 

3804 P 

0 50 I00 I50 200 250 300 

Temperature in Kelvin 

Figure 2. The variation of the TMT 

unit cell volume as a function of temperature, clearly showing the continous 

phase transition at around 154 K. 
I X-ray Induced Photoluminescence in Doped Nanocrystals * I X3A1 I I XAFS Studies of Tb-Doping in YzO3 * I X3A1 I 

Y. L. Soo, S. W. Huang, Y. H. Kao (SUNY Buffalo) and R. N. Bhargava (Nanocrystals Technology) 

Semiconductor nanocrystals chemically doped with transition metal or rare earth 

elements can exhibit novel optical properties which are not found in the bulk material. Both the quantum efficiency of photoluminescence (PL) and transition probablity are enhanced due to the effects of strong localization of electrons in the small 

particles. We are continuing a collaborative research program with Dr. R.N. Bhargava who first discovered this effect. This new class of material is of great interest for 

studying fundamental physics in systems of reduced dimensions. We have recently 

discovered that the PL output is sensitive to the energy of x-rays applied to excite 

the nanocrystals. The PL output exhibits EXAFS spectra which can be compared in 

detail with those measured by the conventional method of x-ray fluorescence. Thus, we have demonstrated a new site-selective technique for the detection of EXAFS. 

In view of its enhanced quantum efficiency and fast response, these nanocrystals 

are strong candidates for a new type of high-efficiency x-ray detector for a variety 

of technical applications. 

P +- 

Go 

Y. L. Soo, S. W. Huang, Y. H. Kao (SUNY Buffalo) and R. N. Bhargava (Nanocrystals Technology) 

X-ray absorption fine structure (XAFS) measurements have been made in Tbdoped nanocrystals of Y203 with different size distributions. The interatomic distances between the impurity and neighboring atoms, coordination number, local 

disorder, and effective valency determined for the nanocrystals are compared with 

those in bulk Y203:Tb. Significant local structural changes have been observed. 

These local structures are closely related to the observed novel optical properties. 

Interesting features were found by a comparison of the photoluminescence spectra 

induced by x-rays with those excited by ultraviolet radiation. 

* Research supported by DOE under Grant No. DE-FG02-87ER45283. * *Research supported by DOE under Grant DE-FG02-87ER45283. 
X3A2, 1 Resonance Scattering Studies of Mixed-Valence Complexes 

A. Darovsky, V. Kezerashvili, P. Coppens (SUNY Buffalo), T. Weyhermuller, H. 

Hummel and K. Wieghardt (Max-Planck-Institut fur Strahlenchemie) 

Oxygen-bridged mixed-valence manganese complexes are model compounds for 

the manganese-containing photosystem 11, which catalyzes the water oxidation reaction and thereby produces dioxygen used by animals and aerobic bacteria during 

respiration. 

Following our earlier study of pdioxo-(Mn(2,2’-bipyridyl)~)z (BF4 s.3&0,’ a 

second study was performed on the triclinic crystals of the complex L n(IV)L(p0)~ (p-MeC02) Mn(III)(MeCOZ )Z , L = 1.4.7-trimethyl-114, 7-triazacyclononane. 

Imaging plate data were collected at 15 different energies straddling the absorption edge. Results are shown in Figure 3. The shift of Mn(1V) relative to Mn(II1) 

is again evident, though its magnitude appears less than observed for the dipyridylcoordinated Mn-mixed-valence complex. This is unexpected, as the asymmetry of 

the Mn-0 bonds (1.882 and 1.864 A vs. 1.788 and 1.767 A) is larger here than for 

the first compound discussed above. With the higher resolution achieved, the preedge feature of the absorption curve is evident in the f’ curve of Mn(IV), but not in 

that of Mn(II1). This clearly indicates that the spectroscopic transition to the un- occupied state occurs at Mn(1V) rather than at Mn(II1). 1 Y. Gaol A. Frost-Jensen, 

M.R. Pressprich, P. Coppens, A. Marquez and M. Dupuis, J. Am. Chern. SOC. 114, 

9214, 9214 (1992 . A. Frost-Jensen, Z. Su, N. K. Hansen and F. K. Larsen, Inorg. 

Chem. 34, 4244 01995). 

---iW-- Mn(lV) Q) I + Mn(lll) I c 0 

aa 0 

aa 

2 -5 

- 

- -6 

c 

-9 

-1 0 

6520 6540 - 6560 6580 

Energy(eV) 

Figure 1. f’ of the two manganese atoms in Mn (IV)(p-O)2(pMeCOZ)Mn 

(III)( MeCOz)z L, where L = 1.4.7 trimet hyl- 1,4,7-triazacyclononane, as determined 

from refinement of data at different wavelengths. 

X3A2 Crystallographic Study of Thermal Barrier Coating by X-ray Microdiffraction 

Y. Gao, W. Hasz and C. A. Johnson (GE Corporate Research and Development) 

Yttria stabilized zirconia (YSZ) is a commonly used thermal barrier coating yw material for turbines. While the desirable phase for application is tetragonal 

r02, both cubic and monoclinic phases have been found as a result of high temperature aging or chemical contamination. The yttria content and phase composition are critical to the mechanical and physical functioning of the coating. 

We have developed a method at the beamline X3A2 to study polycrystalline 

YSZ coating by X-ray transmission microdiffraction using a wavelength below the 

Zr K-edge. The setup includes a high magnification CCD camera by which the 

X-ray beam position can be visualized from a TV monitor. The diffraction data 

was collected using a vacuum-mounted imaging plate system, and later converted 

into one-dimensional data for further analysis. Typical one-dimensional diffraction 

patterns (figure 1) show that this technique is capable of observing both cubic and 

monoclinic phases alone with the major tetragonal Zr02 phase. It has been known 

that the yttria content in tetragonal phase can be derived from its c/a ratio [1,2 . Moreover, the phase composition varies with firing temperature and aging time [3 1 . Therefore, crystallographic data could be used to derive the yttria content, which 

is of importance to tetragonal phase stability, and temperature history of a sample. 

[l] H. Toraya, J. Am. Ceram. SOC., 72 4), 1989, 662-664. [2] H. G. Scott, J. 

Adv. in Ceram. 3, 241-251 

Sciences of the U.S. Department of Energy (DE-FG02-86ER45231). 

Materials Sci., 19, 1975, 1527-1535. [3] R. 6 . Miller, J. L. Smialek, R. G. Garlick, 

The SUNY X3 beamline at NSLS is supported by the Division of Basic Energy 

Figure 1. Phase composition variation. Top: cubic phase; Bottom: monoclinic 

phase. 
I On-Line SAXS Study of Nylon 66 Fiber Deformation * I X3A2 I 

B. Hsiao, A. Kennedy, R. Leach (DuPont), B. Chu, and P. Harney (SUNY Stony 

Brook) 

On-line SAXS characterization of crystal morphology development during continuous drawing of a nylon 66 fiber at different temperatures were carried out at 

the X3A2 beamline. For the extraction of morphological information, we have 

adopted two unique procedures to analyze the 2D SAXS image. These procedures 

include the use of correlation function analysis to determine the lamellar crystal 

and amorphous thicknesses (1, and la), and invariant Q from the sliced meridional 

intensity(a1ong the fiber direction), and Porod analysis to determine the crystal 

fibril width Zf from the integrated equatorial intensity profile (perpendicular to the 

fiber direction). Results of the analysis from two different temperatures (16O0C and 

218OC) are shown in Figures 1,2, and 3. 

It is seen that both L and 1, increase with temperature. Since the cell parameter c, 

determined previously by WAXD,decreuses with increasing temperature, the notion 

of thermal expansion is inconsistent with this finding. In contrast, the hypothesis of 

melting the small crystals does explain well the increases in L and 1, (larger residual 

crystals) as well as the decrease in Q (at low draw ratios) by temperature. By 

comparing results from the two temperatures (near and above the Brill transition 

temperature), we conclude that drawing also induces melting of small crystals. 

However, this strain effect is less than the temperature effect. This is the reason 

why all morphological changes observed below the Brill temperature (at 160OC) is 

far more enhanced than those at 218OC where few small crystals are present. 

=so 

8160% 

-.-2I8~C 

1.0 1.1 1.2 1.3 1.0 1.1 1.2 1.3 

I Dlaw Ratio Draw Ratio 

d 

Draw Rath 

Figure 1. Morphological variables extracted from the SAX data. 

IF 

A 

u1 * This work is partially supported by a NSF-GOAL1 Grant(DMR-9629825). 

On-Line WAXD Study of Nylon 66 Fiber Deformation * 

B. Hsiao, A. Kennedy, R. Leach (DuPont), B. Chu, and P. Harney (SUNY Stony 

Brook) 

On-line studies of crystal structure development during continuous drawing of a 

nylon 66 fiber at different temperatures were carried out using wide-angle X-ray 

diffraction (WAXD) techniques at the X3A2 beamline. A 3-pinhole collimator was 

used to reduce the beam dimension to 0.3 x 0.3 mm'. WAXD images were recorded 

by image plates. The schematic diagram of our experimental setup is shown in 

Figure 1 below. The Brill transition was observed at about 160°C under all drawing 

conditions. However, form the analysis of the unit cell parameters, we confirm that 

the triclinic cell structure persists above the Brill transition temperature. With 

increasing temperature, the parameter u (dominated by hydrogen bonding) remains 

almost unchanged while b increases and c decreases (both show a step-change near 

the Brill transition. These results are shown in Figures 2 below. The constant value 

of a agrees with the argument that the hydrogen bonding is relatively immobile at 

high temperatures prior to melting. We thus suggest that the Brill transition is due 

to a premelting process of small crystals. As a result, the larger residual crystals 

undergo an enhanced anisotropic thermal expansion leading to the merging of two 

strong equatorial reflections. This hypothesis is consistent with the crystal density 

data which increases with temperature. 

X3A2 

4 

Figure 1. On-line draw machine dia- 4,0u 5,0u l6.'U 

gram. T(V T(9 T (V 

Figure 2. Unit cell parameters of nylon * This work 66 as a function of temperature. is partially supported by a 

NSF-GOAL1 Grant DMR-9629825 
Time-Resolved Synchrotron SAXS Study of the Miscible Blends 

of Semicrystalline Poly( vinylidenefluoride) and Semicrystalline X3A2 

Poly( 1,4-Butylene Adipate) 

Li-Zhi Liu, Benjamin Chu*,(SUNY Stony Brook), R. St. John Manley (McGill U.) 

Poly(vinylidenefluoride) (PVFz) and poly( 1,4-butylene adipate (PBA are thertallizable, the mixtures exhibit a complicated phase behavior. The melting points of 

PVFz and PBA are 175 and 60"C, respectively. The PVFz/PBA blend could form a single miscible amorphous phase above the melting point of PVFz, a two-phase 

morphology at a temperature between the melting points of PVFz and PBA, and 

a three-phase morphology below the melting point of PBA. In the present work, 

the crystallization dynamics of PVFz homopolymer and its blend with 60% PBA 

was studied. The sample was quenched from a single phase region (190°C) to a 

two-phase region (130°C first, as shown in Figure 1, and then further quenched to 

showed a decrease in long period with time when quenched to 13OoC, while the 

blend showed a little increase in long period with time. The peak intensity of both 

PVFz homopolymer and the blend showed an appreciable increase in the first 25 

seconds and reached a constant value at the same time Figure l), indicating that 

4"C, the blend showed a decrease in long period, as shown in Figure 2, and no PBA scattering peak was developed, indicating that, in this process, the crystalline 

structure of PBA was not very regular. 

modynamically miscible in the melt. Since both components oft hd e blen are crysa three-phase region (4" d ), as shown in Figure 2. The PVFz homopolymer sample 

the crystallization rate of the two samples were same. 6 hen further quenched to 

:0 51015202§303540 EUi- 0510152025333540 40

Time (s.4 Tim (sex) 

Figure 1. The time-dependent SAXS Figure 2. The time-dependent SAXS 

peak intensity of PVFz homopolymer peak intensity and the long period 

and the blend with 60% PBA when of PVFz of the blend when further 

quenched from 190°C to 130°C. quenched to 4°C. 

tion in Compatible Mixtures of Tetrahydrofuran-Methyl MethacrySynchrotron SAXS Study of Crystallization and Microphase Separalate Diblock Copolymer and Polytetrahydrofuran 

L.-Z. Liu, F. Yeh and B. Chu (SUNY Stony Brook) 

The crystallization and microphase separation of compatible mixtures of tetrahydrofuran methyl methacrylate diblock copolymers (PTHF b PMMA) with a tetrahydrofuran homopolymer PTHF) were studied by means of synchrotron small angle 

X-ray scattering (SAXSj. The crystallization of PTHF microphases in the blend 

showed almost no effect on the original phase separated structures in the amor- phous state of the blend before crystallization including, for example, the PMMA 

interdomain distance, as shown in Figure 1. After crystallization, the blends with an alternating lamellar structure showed an appreciable intensity increase in the 

higher-order scattering peaks, suggesting that the lamellar packing had become 

more regular. The separation distance between two PMMA cylinders (or spheres) 

had a great effect on the crystalline structure of the PTHF matrix microphase. 

When the separation distance between two PMMA cylinders was about two times 

larger than the long period of the neat PTHF homopolymer, a nearly ordered microcrystal packing could be formed in the PTHF matrix microphase. In the blends with 

30 wt% or less copolymer and with larger separation distances, the micro-crystals 

could have a very ordered packing, exhibiting sharp X-ray peaks similar to that of 

the PTHF homopolymer (Figure 2.). The PTHF matrix microphase also showed 

an increase in the long period with increasing copolymer weight fraction, as also 

shown in Figure 2. The relationship between the long period and the crystallization 

temperature was different for blends with different amounts of copolymer. 

M" I 

0 0.1 0.2 0.3 0.4 0.1 5 

B 

e 

400 g 

2M 

0 

0.0 0.2 0.4 0.8 0.8 1.0 1.2 t.4 

9 (nm-9 

Figure 1. SAXS profiles of blend TMT6 Figure 2. Crystalline scattering profiles 

with 60% homopolymer in the amor- of neat homopolymer and blends with 

phous state and crystallized at different 40% to 80% homopolymer; crystallizatemperatures tion temperature at 283K. 
The Effects of Thermal Shocking on the Residual Stress in SiSN4 

Ceramic Composites * 

A. Sahiner, D. Wittmer, and M. Sweeney (Southern Illinois U. at Carbondale) 

Residual stresses play an important role in the electrical, thermal, and mechanical 

properties in materials. The strain caused by this stress can be thought of as stored 

energy that is localized around some feature of the materials microstructure. The 

residual stress may originate from the mismatch between the crystal lattices caused 

by: a mismatch in coefficient of thermal expansion between the material phases during high temperature processing; preferred orientation of highly anisotropic phases; 

presence of metastable crystalline phases; density gradients across thin sections; 

and mechanical or thermal damage. Angle and energy dispersive x-ray diffraction 

experiments on Si3N4 ceramic composites are conducted in order to analyze the 

variations of the residual stress, as the preparation and the thermal treatment parameters are changed. Along with the elasticity theory, the shifts of the diffraction 

peak positions when the sample is tilted at various angles with respect to the incoming beam, are used to determine the stress in the sample. A detailed comparison of 

the residual stresses between the as-machined and the thermally shocked samples 

are made and the effects of thermal shocking temperature in terms of strength of 

the materials are discussed. In Fig. la, the 20-sin2$ plots for the data obtained 

on the beamline X3A2 of NSLS are shown for SisN+ samples. From the slopes of 

the linear fits and the 80 measurement from the powdered SisN4, the stress in the 

directions parallel and perpendicular to the surface were determined according to 

the elasticity theory. In these calculations, values of 304 GPa and 0.27 were used 

for the Youngs modulus and the Poissons ratio. The stresses (u11 and u33) are calculated for the (441), (531), and (303 peaks and the average of these calculations 

stress values (in and out-of-plane) are compressive except T=1400"C. The compression increases as the thermal shocking temperature rises from 900 to 1100°C. After 

reaching to the maximum at 1130°C (according to quadratic polynomial fit) the 

compression decreases in both directions and even turns into a tension at 1400°C 

in the parallel to the surface direction. 

are plotted with respect to thermal s h ocking temperature in Fig. lb. Both of the 

88.Esl ' ' ' ' ' ' mc 1. 0.0 0.1 0.2 0.3 0.4 0.5 

.in% 

Figure 1. 

* This work has been supported by Illinois Board of Higher Education. 

Simultaneous SAXS/WAXD Morphological Studies of Nylon 66 I Fibers 

J. R. Sharrow, J. M. Schultz (U. of Delaware), B. S. Hsiao, and H. Chang (DuPont) 

Two-dimensional simultaneous small-angle X-ray scattering (SAXS) and wideangle X-ray diffraction (WAXD) were used to investigate the morphology of nylon 

66 fibers. The beam, was reduced to 0.3 x 0.3 mm2 using a 3-pinhole collimator. 

Equatorial scans were taken from the WAXD images in order to obtain transverse 

crystal fibril widths. Deconvolution of the sliced WAXD patterns was accomplished 

by fitting the scans with four Gaussian curves. The four Gaussian curves represent the crystal (100) peak, the crystal (OlO), (110) doublet, the amorphous region, 

and the mesophase. While the amorphous phase is azimuthally independent, the 

mesophase is a broadly azimuthally dependent phase consisting of oriented amorphous material. A sample curve fit is displayed as Figure 1. The Scherrer equation 

was used to calculate the crystal fibril width from the crystal curve fits. For a fiber 

not subject to heatsetting, the average crystal fibril width was determined to be 

60a, while fibers subject to wet heatsetting displayed an increase in the transverse 

fibril dimension to 6511. These number are in good agreement with radial distribution function analysis yielding correlation lengths in the transverse direction. A 

slice of the SAXS meridional intensity profile, corrected by a Lorentz factor, was examined using the correlation function y(r) in order to calculate the crystal thickness 

along the fiber. The correlation function is given as: 

00 

r 

0 

where refers to the sliced profile, q = 4?rsin(O /A, Ib designates the liquid scatterconforms to a two-phase model, the first maximum of the correlation function yields 

the long period, crystal plus amorphous thicknesses. Figure 2 exhibits that fibers 

undergoing a wet heatset are characterized by a larger long period, 808, than fibers 

that have not been exposed to heatsetting, 708. 

ing profile and u is associated with the width o 1 the interface. If the fiber structure 

This work is supported by NSF-GOAL1 Grant (DMR-9629825). 

29, Degrees 

Figure 1. WAXS Gaussian Curve Fitting 

Method 

Figure 2. SAXS Correlation Functions 

Plot 
P + 

O0 SAXS Study of Gel-like Structures of Block Copolymers in DNA 

Separation Buffers X3A2 

C. Wu, T. Liu, and B. Chu* (SUNY Stony Brook) 

Block copolymer AmBnAm in a selective solvent and at an appropriate concentration and temperature can form a gel-like phase with regular structures. The 

gel-like phase was presumably formed by close-packing micelles with condensed hydrophobic cores and entangled hydrophilic shells. The structural studies of EnPmEn 

and BnEmBn type block copolymers [with P, E, and B representing, respectively, 

poly(oxypropylene), poly oxyethylene), and poly(oxybuty1ene)l in DNA separation 

buffers such as 1X TBE 89 mM Tris, 89 mM borate, 2 mM EDTA) and sequencSAXS technique. 

According to the capillary electrophoresis results, both EPE- and BEB-type block 

copolymers show good DNA separation abilities. The following is the brief summary. 

1. EPE-type copolymer: a. Micellar gel phase shows f.c.c. crystal structure. b. 

Higher copolymer concentration decreases intermicellar distance. c. Solvent does 

not effect f.c.c. micellar structure. d. Heating history of EPE gel preparation will 

effect ordering of crystalline domains. 

2. BEB-type copolymer: a. Micelles are assembled differently when compared 

with EPE-type copolymer. b. Hydrogen-bond destroyers, such as urea and formamide in the sequencing buffer, tend to decrease the average inter-domain distance 

of the gel-like structure. 

ing buffer (1X TBE, 3.5 d urea and 30% formamide) were performed by using the 

Nano-Structure of Gel-Surfactant Complexes * 

F. Yeh, E.L. Sokolov, and B. Chu* (SUNY Stony Brook) 

Polyelectrolyte gels interacting with oppositely charged surfactants can produce discrete volumn transition in aqueous solutions when the surfactant concentration is lower than its critical micelle concentration. A well-defined structure could be formed in the gel-surfactant complex. Two types of ordered 

nanoscale supramolecular structures have been observed in the complexes of cationic 

poly(diallyldimethy1ammonium chloride) (PDADMAC1) gels interacting with anionic sodium alkyl sulfates.' Our previous SAXS studies showed that the nanostructure formed by the PDADMAC1-sodium decyl sulfate (SDCS) complex could 

be melted at higher temperatures. This process leads to the formation of more extensive spatial regions of crystallinity. Fig. 1 shows a series of SAXS images 

of the PDADMAC1-SDCS complex obtained during recrystallization. The images 

were taken at room temperature, at 70"C, and at room temperature again after the 

sample was cooled down. It is evident that the type of nanostructure formed in the 

complex at 70°C is different - the sample has melted. Larger areas of crystallinity 

were formed after the sample was cooled from above the melting temperature (70°C) 

down to the room temperature. 

X3A2 

Figure 1. SAXS images of 25% EPE in sequencing buffer at different heating rates 

and the corresponding heating curves. - 

Figure 1. SAXS images of PDADMA-SDCS complex at different stages of heatingcooling process: 28°C (left), 70°C (center), and 29°C (right). 

* 1. Sokolov, Eugene L.; Yeh, Fengji; Khokhlov, Alexei R.; Chu, Benjamin; submitted. 
Formation and Struction of Micelles and Supramolecules of Pluronic 

P103 in Water/O-xylene Mixture X3A2 

Shuiqin Zhou, Jie Su and Benjamin Chu (SUNY Stony Brook) 

Both laser light scattering (LLS) and small-angle X-ray scattering (SAXS 

were used to study the water-induced formation and structure of micelles an 2 

structure of micelles have been studie d as a function of solubilized water content Z 

supramolecules of Pluronic P103 [(EO 17(P0)60(E0)17] in o-xylene. The ske and 

(the molar ratio of water to EO units) in micelles. In the dilute solution region (C 

< 0.28 g/mL), the aggregation number, N; the core radius, Rc; and the hard-sphere 

volume fraction, f, of micelles increase with increasing 2. However, the hydrodynamic radius, Rh, decreases with increasing Z. The change of micellar structure 

from low Z to high Z leads to a decrease of the corona thickness, Rs, of micelles 

until a constant value is obtained. At low Z values (Z < 0.9 ), micelles have a thick 

corona with Rs 17 nm because part of the poorly solvated PEO blocks are present 

in the corona. At high 2 values (Z > 1.8), the PEO blocks in the corona enter 

into the micellar core and the long solvated PPO blocks form loops in the corona 

resulting in a constant corona thickness of 9 nm. In the concentrated solution re- gion (C > 0.28 g/mL), and at lower Z values, bridging between micelles was formed 

due to the presence of PEO blocks in the corona. At high Z values, the packing of 

micelles form a stiff polymer network at a critical hard-sphere volume fraction f of 

0.49. The higher the Z value, the lower the critical gelation polymer concentration. 

Both face-center cubic and hexagonal supramolecular structures were observed in 

the concentrated solution region. 

108 

107 

106 

- 105 i 

.- a104 

2 

d 103 2 

v 

102 

IO’ 

100 

1 08 

107 

q 106 

I 

105 .g 

B 104 

103 

3 

4 4 nl 

mu 

0.0 0.5 1 .o 

C4.350 g/ml, Z=1. .. 

.. ... :. 

0.0 0.5 1.0 1.5 2.0 

SI nm-1 q/ nm-1 

Figure 1. Intensity profiles of SAXS 

of P103/water/o-xylene micelle solution 

with c = 0.164 g/mL at different Z valFigure 2. Intensity profiles of SAXS of 

Fd PlO3/water/o-xylene micellar gel at the 

$ ues. indicated concentration and Z values. 

I Single C-C bond in (C60):- * 

G.M. Bendele (SUNY Stony Brook), P.W. Stephens (SUNY Stony Brook and 

NSLS), G. Osrlinyi, G. Bortel, G. Faigel, L. Grlindsy (SZFKI, Budapest), and 

L. Ford (EPF, Lausanne) 

X3B1 

We have investigated the structure of the metastable dimer phases of 

A=K,Rb) via x-ray powder diffraction. In both materials, the dimer molecule orms through a single C-C interfullerene bond. 

The dimer phase of AC6o is obtained by quenching from high temperature to 

T=77K and subsequently cycling the temperature between 220K and 273K. X-ray 

powder diffraction spectra were then obtained at T=220K with k1.15k. Given the 

abundance of possibilities for the bonding mechanism, the location and orientation 

in the monoclinic unit cell of the dimer molecule, we have performed on the order 

of lo6 Rietveld refinements, mapping the orientations of the buckyballs in several 

possible space groups [l]. Among all cases considered, the single-bonded dimer in 

the tmns configuration gives the best fit. The final results of the refinements are 

(for K): Lattice parameters a=17.153(5)A, b=9.793(5)A, c=19.224(5)AL, p=124.lo. 

Space group P21/a (cell choice 3 of No. 14), C6o center at (0.007,0,0.246), K at 

(0,0.5,0.013) and (0,0.5,0.513). The Eulerian angles by which the buckyball is rotated in this position are 8=90°, 56=12’, $=281°. This is identical to the solution 

for Rb except for the rotation angle of the molecule around its bonding axis. 

covalently bonded 

(GO):- dimer anions form through a single C-C interfullerene bond. This type of 

bond is different from the four-membered rings of Ace,, and c60 polymers. Details 

of the analysis are given in [l]. 

I 

We have established that in these metastable phases of 

[l] G. Oszllinyi et ul., Phys. Rev. B 54, 11849 (1996) 

a. 

Figure 1. Single-bonded tmns (C,O):- dimer a. side view b. view along dimer axis 

* Work at the SUNY X3 beamlineis supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). Research at SUNY is supported by the NSF 

under grant DMR95-01325 
P 

v1 

O NazRbCGO is orthorhombic at low temperature * IX3B11 ~~ 

G.M. Bendelk(SUNY Stony Brook), P.W. Stephens (NSLS and SUNYSB), K. Prassides, K. Vavekis, K. Kordatos (U. Sussex, UK), and K. Tanigaki (NEC Tsukuba) 

We have studied NazRbCso, an alkali fulleride until now believed to be cubic at 

all temperatures (with a fcc+primitive cubic transition at around 300 K), at several 

temperatures using synchrotron x-ray powder diffraction measurements. 

At elevated temperatures the structure is indeed fcc (space group Fm3m, 

a=14.141A at 370K), and at room temperature the known primitive cubic phase 

(space group Paf) coexists. However, lowering the temperature to below 230K results in the appearance of peaks not consistent with the cubic structure, indicating a phase of lower symmetry. Indeed, the sample transforms slowly into an orthorhombic phase with lattice parameters of a=9.3819A, b=9.943.&, and c=14.559A (space 

group Immm) at T=180K. The cubic-iorthorhombic phase transition is extremely 

slow (fig. 1) and a small amout of the cubic phase remains quenched in even when 

the sample is cooled at a rate of only 1K/hr. between 230K and 180K. 

The most interesting feature of the orthorhombic phase is its strongly reduced 

distance between C& anions (9.38A) along the a direction. This strongly suggests 

covalent interfullerene bonding; however, the observed interfullerene separation is 

larger than in the known polymerised phases (9.11A) and almost identical to the 

singly-bonded dimer phases in AC60. 

Further work on this system is in progress. 

Powder Diffraction Structure of Indenyllithium * 

R.E. Dinnebier (Univ. of Bayreuth, Germany), P. W. Stephens (SUNY Stony 

Brook), U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, 

Germany) 

The crystal structure of the organometallic compound indenyllithium (LiCgH7) 

has been solved ab initio. The compound crystallizes in the orthorhombic space 

group Pnma (No. 62) with a = 20.5000(1) A, b = 3.9645(1) A, c = 8.3087(1) A, 

V = 675.27(1) A3 and d = 1.201 g ~m-~. Data collection was carried out at room 

temperature using a wavelength of 1.14894 A from double Si(ll1) monochromator 

and Ge (1101) analyzer. The 20 range used for the Rietveld refinement was 5.0 < 

20 < 59.9 . All positions of the carbon and lithium atoms were found by direct 

methods. The indenyl ring was refined as a rigid body and the hydrogen atoms were 

calculated in idealized positions. The actual Rietveld plot yields to R-wp=7.7%, 

R-p=5.2% and R-F2=8.5%. Figure 1 shows the structure of LiC9H7. The LiCgH7 

units are connected to polymeric chains along the crystallographic b axis. Herein the 

Li atoms are hapto5 coordinated by two indenyl rings. The indenyl rings are always 

bonded by the five member ring to the Li atoms. Because of the crystallographic 

mirror plane through the Li atoms and the indenyl ring, the indenyl rings are placed 

absolute coplanar and staggered. 

X3B1 

Figure 1. Powder spectra at T=220K as a function of evolved time. The strongest 

peak indexes to the cubic phase, all others to the orthorhombic phase. 

Figure 1. Polymeric chain of indenyllithium along b axes. 

* Work at the SUNY X3 beamline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). Research at SUNY is supported by the NSF 

under grant DMR95-01325 

* Work at the SUNY X3 bedneis supportedby the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). 
Powder Diffraction Structure of MC5H5 (M= Li, Na, K) * 

R.E. Dinnebier (U of Bayreuth, Germany), P. W. Stephens (SUNY Stony Brook), 

U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, Germany) 

X3B1 

The crystal structures of the basic organometallic compounds cyclopentadienyllithium (LiCsHs, l), -sodium (NaCsHs, 2) and -potassium (KC6H6, 3) have been 

solved initio. The following crystallographic data have been found: 1: orthorhombic Pnam, a = 10.2626(3) A, b = 11.1286(3) 8, c = 3.9366(1) 8; 2: orthorhombic 

Pnam, a = 10.1339(9) 8, b = 11.0064(10) 8, c = 4.7128(2) A; 3: tetragonal P-421c, 

a = 9.9742(4) 8, b = 10.5035(3) 8. Data collection was carried out at room temperature using a wavelength of 1.14937(1) Afrom double Si(ll1) monochromator and 

Ge (111) analyzer. The 20 ranges considered for the Rietveld refinements were: 1: 

10.0 < 20 < 53.0'; 2: 6.0 < 20 < 60.0'; 3: 7.0 < 20 < 60.0'; 

The positions of the carbon and metal atoms were found by direct methods 

and simulation techniques. The C6H6 rings were treated as rigid bodies and the 

hydrogen atoms were calculated in idealized positions. The actual Rietveld plots 

yielded to 1: F2 = 7.3%; 2: F2 = 8.9%; 3: F2 = 8.4%. All three compounds 

crystallize as polymeric chains along c-axis. The organic anion (CsHs-) is penta 

hapto bonded to the metal cations forming multidecker chain structures. In 1 and 

2 the chains are linear, in 3 the K cations form a bent zigzag chain with an angle 

of 138'. 

Na 

Figure 1. Polymeric chain of cyclopentadienylsodium (top) and cyclopentadienylpot assium (bottom). 

Powder Diffraction Structure of Phenyllithiurn (CeH5Li) * 

R.E. Dinnebier (U. of Bayreuth, Germany), P. W. Stephens (SUNY Stony Brook), 

U. Behrens (U. of Hamburg, Germany) and F. Olbrich (U. of Magdeburg, Germany) 

The crystal structure of the organometallic compound phenyllithium (CGHbLi) 

has been solved ab initio by high resolution powder diffraction. Crystallographic 

data are: space group P21/n, a = 11.527(1) 8, b = 4.554(1) 8, c = 10.406(1) 

8, V = 498.08(2) 8', Z = 4, dcalc.= 1.134 g ~m-~. The data were collected at 

293 K with a wavelength of 1.14966 A using a double Si(ll1) monochromator and 

Ge(ll1) analyzer in a 20 range of 5.0 < 20 < 49.03' for 16 seconds per step. 

The structure was solved by direct methods and difference-Fourier-analysis and 

subsequently refined by the Rietveld technique leading to final R-values of R-wp 

= 5.3010, R-p = 3.5% and R-F2 = 10.4%. Basefree phenyllithium crystallizes as a 

polymeric infinite ladder structure (Fig. l), which continues in the crystallographic 

b direction. The absolute unit of this ladder is a planar LizCz four member ring with 

an crystallographic inversion center in the ring. Interactions to the next LilCz rings 

leads to the polymeric structure. Each phenylanion is bonded to three different Li 

atoms. We can discribe this type of bonding as a 2 electron three center bonding 

(2e3c). Beside this, the p-electrons of the phenylring interacts with one of these 

three Li atoms. That way the coordination number of the Li atoms is four and 

therefore completed. 

X3B1 

i"' 

Li' 

Figure 1. Infinite ladder of phenyllithium. 

* Work at the SUNY X3 Beamline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). 

* Work at the SUNY X3 Beamline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). 
F 

uI Ab initio Structure Determination of Two Polymorphs of RbC5H5 N X3B1 in a Single Powder Pattern * 

R.E. Dinnebier, S. van Smaalen (U. of Bayreuth, Germany), F. Olbrich (U. of 

Magdeburg, Germany) and P. W. Stephens (SUNY Stony Brook) 

The structures of two polymorphic phases of solid RbCbH6 (RbCp) (Fig. 1, 2) 

have been solved ab initio by high resolution powder x-ray diffraction measured in a 

single powder pattern. The compound, crystallizes in space group Pbcm (phase II), 

Z=8, with unit cell parameters a= 9.3396(1) , b= 10.9666(1) , c= 10.5490(1) and in 

space group Pnma, Z=4 (phase I), with unit cell parameters a= 10.7990(2) A, b= 

8.6923(2) A, c= 5.7061(2) A. Data collection was carried out at room temperature 

using 1.15 A from double Si(ll1) monochromator and Ge (111) analyzer. The two 

phases could be separated by their different FWHM distribution. Both structures 

could be solved by means of direct mthods. For the Rietveld refinements, the Cprings rings were treated as rigid bodies and the hydrogen atoms were calculated 

in idealized positions. The actual Rietveld plot yields to R-F = 4.3% (phase I 

bent-polydecker sandwich structures, with an average Rb-Cp, (Cp-ring-centroid) 

distance of 2.97 8. Phase (I) contains a single chain along the a-axis whereas phase 

(11) contains two similar but crystallographically independent chains perpendicular 

to each other along the b-axis and along the c-axis. The chains are bent with 

Cp,-Rb- Cp, angles ranging from 123.5' to 136.5'. 

and R-F= 4.5% (phase 11). Both phases show polymeric zigzag chains, so calle d 

Figure 1. 

(phase 11). 

Unit cell drawing of RbCp 

* Work at the SUNY X3 Beamline is supported by the Division of Basic Energy Sciences, U.S. Dept. of Energy (DE-FG0286- 

ER45231). 

-: 

Figure 2. 

(phase I). 

Unit cell drawing of RbCp 

Structural Investigation of a Tetragonal Garnet: Ca3MnzGe3012 * 

S. Heinemann (Bayerisches Geoinstitut, U. of Bayreuth, Germany) and R.E. Dinnebier (Lehrstuhl fiir Kristallographie, U. of Bayreuth, Germany) 

Cubic Ca3MnzGe3012 (CMG) has a garnet structure and undergoes a phase transition to tetragonal symmetry below 520K [l]. Tetragonal (CMG) shows photo induced linear birefringence below 175K [l] and could possibly be used as a rewritable 

media for 3D holographic storage. The physical mechanism of this property is 

still unknown. Because of heavy twinning the structure of tetragonal CMG could 

not be determined by single crystal diffraction and has therefore been solved by 

high resolution powder diffraction. The lattice constants at room temperature are 

a=12.30801(3 A and c=12.32325(4) 8, in space group I41/a. 

a wavelength of 1.14945 A from double Si(ll1) monochromator and Ge(ll1) analyzer. The minimum FWHM was 0.02'20. The actual Rietveld refinement with 797 

reflections from 5'20 to 85'20 converged to R-Bragg = 5.6%. The structure can be desribed as a distorted garnet structure (Fig. 1) with MnOa octahedra distorted 

into two different species which build an ordered pattern. 

It can be shown that the phase transtion is improper ferroelastic and its driving 

force is a cooperative Jahn-Teller effect of the octahedral coordinated Mnst. This 

information will certainly help to investigate the mechanism of the photorefractive 

effect. 

X3B1 

X-ray pow d er diffraction pattern were recorded at different temperatures using 

Bedarev, V.A. and Gnatchenko, S.L. 1993): Low Temp. Phys. 20, 100 

Kazei, P. et al. (1983): Sov. Phys. J 

Figure 1. Part of the tetragonal garnet structure. 

* Work at the SUNY X3 beamlineis supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). 
Alkali Occupancies and Fullerene Orientation in K4Ce0 and Rb4C60 If I I I 

C.A. Kuntscher, G.M. Bendele (SUNY Stony Brook), and P.W. Stephens (SUNY 

Stony Brook and NSLS) 

The phase mixtures of alkali fulleride samples &C60 and Rb,Cao with stoichiometries close to z = 4 were examined by x-ray powder diffraction measurements 

at room temperature. 

All diffraction patterns exhibit the coexistence of either fcc or bcc minority phase. 

We have shown by Rietveld refinements that Ale60 is a line phase which is stable 

only for exact stoichiometry o = 4, with no vacancies in the alkali metal sites. 

The c60 molecules are disordered between two possible orientations within the bct 

lattice, where the three orthogonal two-fold rotation axes are aligned with the unit 

cell edges in space group I4/mmm. 

Figure 1 shows the part of the Rb4.01 C60 diffraction pattern which indicates the 

coexistence of the bcc minority phase RbeC60. The maximum number of counts for 

this pattern is 16660. The corresponding pattern of a sample Rb3.esCeo exhibits 

only diffraction peaks of the phases RbaCeo and Rb4Ceo. 

2000 1 

16.0 20 20.0 

Figure 1. 

* Work at the SUNY X3 beamline is supported by the Division of Basic Energy Sciences 

U.S. DOE (DE-FG02-86ER45231). Research at SUNY is supported by U.S. NSF (DMR95- 

01325). 

I Atomic Structure of Gold Nanoclusters * I X3B1 I 

P.W. Stephens (NSLS and SUNY Stony Brook), C.L. Cleveland, U. Landman, M. 

Shafigullin, R.L. Whetten (GA Tech) 

We use x-ray diffraction to study the structure of gold nanocrystals in the size 

range of 50-500 atoms. 

The samples are purified fractions of materials prepared and separated by methods described in Ref. 1. These techniques produce annealed clusters, passivated and 

encapsulated by self-assembled monolayers of alkylthiolates. The figure shows the 

x-ray diffraction profiles of two samples, determined by mass spectroscopy to consist of 140f10 and 220f20 Au atoms, respectively. Calculated diffraction profiles 

of several theoretically-favored AUN structures are shown for comparison. Dh denotes the Marks decahedron (roughly a pentagonal prism with notches in its edges), 

Ih the Mackay icosahedron, TO+ the truncated octahedron, and t-TO+ the truncated octahedron containing one stacking fault. Note the clarity with which the 

x-ray measurements can distinguish the various candidate structures. 

In contrast to previous work done by other groups, it is not required to assume any polydispersity or polymorphism to account for these diffraction profiles. 

1. R.L. Whetten et al., Adv. Mater. 8, 428 (1996). 

0 2 4 6 8 101214 

e (nm-1) 

Figure 1. 

* Supported by GA Tech Research Foundation, PackardFoundation, ONR, USDOE, 

and AFOSR. Figure 2. 
t? 

A I High-resolution Study of the Ferroelectric BaTiOs. 1x3~11 

rA 

P. Stephens (NSLS and SUNY Stony Brook), D. Balzar (NIST and Inst. Ruder 

Boskovic), and H. Ledbetter (NIST) 

Among ferroelectric materials, BaTi03 is particularly interesting for its simple 

Crystalline structure, good ferroelectric properties at ambient temperature, as well 

as chemical and mechanical stability, which facilitiates easy fabrication of ceramic 

samples. Both unpoled and poled BaTiOs pellets were studied by laboratory (Cu 

K,) and synchrotron x-ray sources. We used a shorter wavelength (0.62 2) with a 

triple-axis configuration to probe deeper below the surface, with superior resolution 

to the laboratory measurements. 

Lineshape analysis showed that the crystalline structure, particularly lattice parameters, remain unchanged upon poling. A sin2$ analysis of peak shift (not shown) 

indicates that no measureable change of elastic strain occurs upon poling. This 

indicates that poling may have induced excessive strain which was relieved by microcracliing, or that a majority of domains reverse the orientation. 

8.5 9.0 17.5 18.0 35.5 36.0 

Diffraction angle 2@ 

Figure 1. 

Crystals of Passivated Gold Nanocrystals * X3B1 

P. W. Stephens (NSLS and SUNY Stony Brook), M. Shafigullin, M.M. Alvarez, 

S.A. Harfenist, J.T. Khoury, T.G. Schaaff, I. Vezman, Z.L. Wang, A. Wilkinson, 

and R.L. Whetten (GA Tech) 

We are studying 3D arrays of Au nanocrystals of 50-500 atoms, passivated by selfassembled monolayers of alkylthiolate molecules.[l] The metal cores have diameter 

2R from 1.65 to 3.1 nm (based on mass spectroscopy) and the alkyl chains are 0.73 to 1.7 nm long. It is possible to seperate obtain fractions containing onIy 

nanocrystals of distinct shape and size by repeated crystallization from solution. 

Separated fractions can then be crystallized into 3D arrays, which can be studied 

by means of x-ray diffraction. We generally observe several orders of diffraction 

with d-spacings from 3.5 to -1.0 nm. The intensity distribution is that expected 

of a primitive (fcc, bcc, or bct) lattice of compact scatterers (the high-Z cores) 

surrounded by regions of low scattering power. Fig. 1 shows that the packing 

density (expressed as the Au volume fraction) is a smooth function of L/R, even as one passes from fcc to bcc structure. The atomic structure of the Au cores is 

described in an accompanying abstract. 

[l] R.L. Whetten et ab., Adwunced Muterials 8, 428 (1996). 

0 

I 

0 c4 ~ 

6 c6 i 

0 

0 $c os 

. bcclbct 

0.40 - 

0.35 - 

0.30 - 

0.25 - 

0.20 - 

0.15 - 

0.10- 

0.05 - 

0.00 81 1 I I I I I I I I I I I I 11 I I 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 

t=L 1 R -_____ 

Figure 1. 

* Supported by GA Tech Research Foundation, ONR, Packard Foundation and DOE 
Powder Diffraction Structures of Cas[A112024](MoO& (CAM) * I X3B1 I 

S. van Smaalen, R.E. Dinnebier (U. of Bayreuth, Germany), H. Katske and W. 

Depmeier (U. of Kiel, Germany) 

Powder diffraction at various temperatures between room temperature and 650K 

have revealed two first-order and one second order phase transition. The crystal 

structures of all four phases have been determined by Rietveld refinement. On 

decreasing temperature , the phases are cubic, I-43m, a = 9.29377(4) A; tetragonal 

(T2) P-4c2, a = 13.14536(6) A and c = 9.29224(8) A; tetragonal (Tl) P-4c2, a = 

13.12263(5) A and c = 9.32081(5) A; and orthorhombic Aba2, a = 26.14683(8) A, 

b = 13.07061(4 A and c = 9.31413(2) A. The T2 phase is a superstructure of the 

and a& is shorter than the cubic lattice constant. The phase transitions are found 

to be related to orientational ordering as well as positional ordering of the W0:- 

anions within the cages of the sodalite framework structure. 

cubic phase, w h ile the T1 phase has an additional distortion whereby c is longer 

Figure 1. Unit cell of T1 phase (Moo4 

tetrahedra are disordered). 

* Work at the SUNY X3 Beamline is supported by the Division of Basic energy Sciences, U.S. Dept. of Enernv (DE-FG0286- 

Figure 2. Unit cell of T2 phase (Moo4 

tetrahedra are disordered). 

The Crystal Structure Determination of the SecA Translocation AT- X12B, 1 Pase 1 X4A I 

J.F. Hunt and J. Deisenhofer (HHMI, UT Southwestern) 

SecA is the engine which drives the ATP-powered translocation of secretory proteins through the bacterial periplasmic membrane. Although SecA exists in a fully 

water-soluble form, it undergoes cycles of membrane insertion and retraction in the 

course of its ATPase cycle. SecA is believed to function as a molecular ratchet in 

the protein translocation reaction, pulling segments of the secretory protein through 

the membrane concomitant with the ATP-driven membrane insertion cycles. SecA 

also auto-regulates its own translation by binding to a specific RNA sequence over- lapping the initiator codon in its messenger RNA. The SecA protein possesses two 

tandem ATP-binding domains with approximately 30 percent identity to the ATPbinding cassettes of the ABC transporter superfamily of transmembrane transport 

proteins. Based on its domain organization, its sequence homology, and its activity, 

it has been proposed that SecA may have structural and mechanistic similarities to 

the ABC transporters. 

The crystal structure determination of the soluble, membrane-retracted state 

of SecA is now almost completed. Data collected on beamlines X12B and X4A 

at NSLS were instrumental in this process. Because our crystals only diffract to 

3.5 angstroms using a rotating anode source, our high resolution data (currently 

to 2.9 angstroms) was collected on beamline X12B. This beamline was also used 

for rapid derivative screening. Candidate crystals soaked in either Pt, Au, or Hg 

compounds were mounted and measured with the energy of the beam tuned to 

optimize anomalous data from the element in question. 2 X 4 degrees of data were collected very quickly in inverse beam geometry, and the anomalous chi-square 

at low resolution was used used as the criterion to determine whether collection 

of a complete data set was merited. The breakthrough derivative for the project 

was identified in this manner. Data collected on beamline X4A from a selenomethionyl derivative of SecA allowed the position of 33 methionines in the protein to 

be observed in an anomalous difference fourier using MIR phases (the 3.8 angstrom 

diffraction from this crystal was too weak to be useful for MAD phasing). 

The refinement of the structure is currently in progress. A working model for 

the domain rearrangements in the course of the SecA ATPase / transport cycle has 

been formulated, and, on this basis, further experiments are being designed to try 

to elucidate the structural mechanism by which the hydrolysis of ATP is coupled 

to transmembrane transport of nascent polypeptide chains. 

-- . ER45231). 
sd 

07 

Structure Determination of the Entire Extracellular Portion of Hu- X25, 

man CD4 X4A 

H. Wu, P.D. Kwong and W.A. Hendrickson (Columbia U.) 

Diffraction data from two different selenomethionyl CD4 crystals were collected 

at the selenium K-shell edge at beamlines X4A and X25 of NSLS. CD4 crystals 

were extremely weak which mandate high flux synchrotron radiation. Both data 

sets were recorded with Fuji imaging plates at 100K. These two data sets belong 

to space groups P41(2)22 and P2, respectively and were used to obtain molecular 

replacement solutions. Selenium anomalous difference Fouriers were used to confirm 

the correctness of the structures. 

X6A 

Determination of Transient Molecular Structure for Photoinduced Reaction Intermediates using Time-Resolved Energy Dispersive XAS 

L. Chen, P. Lee, S. Weber, G. Jennings, J. Norris and P. Montan0 (ANL and the 

U. of Chicago) 

We have obtained preliminary data for time-resolved XAS measurements of 

triplet excited states of ZnTPP and ZnOEP (zinc tetraphenylporphyrin and zinc 

octaethylporphyrin) in organic solutions using energy dispersive XAS beamline at 

X6A. A Nd-YAG laser pumped OPO laser system (Spectra Physics), provides a 

continuously tunable nanosecond laser pulses from 420 to 2000 nm at 10 Hz with 

pulse energies around 50mJ at 500 nm, is installed at the beamline. This laser is 

used to illuminate the molecules in order to create excited states or photoreaction 

intermediates. The laser pulses are synchronized with the diode array detector readout, treating the x-ray pulses as a continuous source. Currently the time-resolution 

of the measurements is limited to the 5-ms readout time of the detector. A special 

sample cell has been designed for the experiment where the X-ray path is much 

longer than the laser light path. This design is to compensate the discrepancy 

between the cross sections of the X-ray and laser light. Our preliminary results 

showed that the spectral difference between the triplet state and the ground state is 

comparable to the fluctuation of the dark current of the detector. Further improvement of the technique is in progress, where the detector current will be reduced 

and the better transmission for the laser light will be achieved. We are also looking 

into other molecular systems, such as electron donor-acceptor complexes, where the 

metal ions change oxidation states and ligation during a photoinduced chemical 

reaction. 
Contribution of Magnetic-EXAFS to the MCXD Signal at the Gd 

LIII Edge. 

K. J. Gofron, C. W. Kimball (NIU), P. L. Lee, and P.A. Montano (ANL) 

We measured, using an energy-dispersive spectrometer, the temperature dependence of the magnetic circular x-ray dichroism (MCXD) effect at the Gd LIrr edge 

from 88 K up to 335 K. In the ferromagnetic state, the MCXD spectrum consists 

of a main positive peak with pre-edge and post-edge features, including a positive 

peak at -7 eV observed for the first time. With the exception of the main peak 

all features vanish slightly above the transition temperature. In the paramagnetic 

region, the MCXD consists only of the main positive peak with a post-edge background slowly decaying away from it over the range of 90 eV. We find evidence that 

many of the observed near-edge features originate from magnetic EXAFS. 

X6A 

o 40 an 4u o N no Energy Lev1 Energy [.VI 

Figure 1. 

--- MCXD + dXAS B=05[T] 

40 20 u zu 40 6n 8n 

Energy [eVl 

Figure 3. 

Figure 2. Fd 

UI 

4 

Energy [eV] 

Figure 4. 

K Absorption Edge Magnetic Circular X-Ray Dichroism of Fe-Ni allovs. X6A 

K. J. Gofrona, C. W. Kimballa (NIU), P. L. Lee, G. Jennings and P. A. Montano 

We report Magnetic Circular X-ray Dichroism (MCXD) measurements in Fe-Ni 

alloys. We used an energy dispersive beamline in our measurements. A polychromator spectrum contains self reference both in intensity and energy since all energies 

are measured at the same time and remain stable during an energy scan since no 

movement of the x-ray optics is necessary. We measured the K absorption edges 

of Fe and Ni (s-p electronic states) in the d ferromagnetic alloys of Fe-Ni. We observe that the signal at the invar composition is of comparable strength as other 

(ANL) 

compositions in contrast to previous studies. We used cold rolled 

instead of powders. The measurements reveal changes of the M 

composition and crystal structure. 

Energy [eV] 

Figure 1. XANES (top) and MCXD Figure 2. XANES (top) and MCXD 

(bottom) spectra at the Fe K-edge. (bottom) spectra at the Ni K-edge. 
a, 

Y !n 
I Bonding and Local Structure of Semiconductor Alloys, Inl-,Ga,As I X7A I 

S. J. L. Billinge and F. Mohiuddin-Jacobs (Michigan State U.) 

To better understand the properties of semiconductor alloys, such as Inl-.Ga,As, 

it is imporatnt to study local structure, because it is significantly different from the 

implied average crystal structure. For example, although the average bond length 

of Inl-,Ga,As follows Vegards law over the entire concentration range of 2, it is 

known that the nearest neighbor bonding structure exhibits a bimodal distribution 

of shorter (Ga-As) and longer (In-As) bonds. We are using Pair Distribution Function (PDF) analysis of x-ray powder diffraction data, measured over a wide range 

of momentum transfer, Q = 4~sinB/X, to study the local structure of Inl-,Ga,As 

directly. By taking a Fourier transform of the measured total structure function, 

S(Q), we obtain the real-space atomic pair correlation function, G(T), which contams the information about the local structure directly. This approach utilizes both 

Bragg peaks, which determine the average crystal structure, and the diffuse scattering, which is responsible for resolving detailed local structure. The experiments were performed in reflection mode at 18K to reduce the effect of the thermal diffuse scattering. Fig.1 shows the structure function, Q[S(Q) - 11, for In,soGa.soAs. 

The circles in Fig.2a show our preliminary data of the PDF obtained for this sam- ple. The solid line is a least square profile fit to the data, assuming an average 

bond length. The difference curve between the experimental PDF and the model is 

shown in Fig.2b. We see that the virtual crystal approximation does not describe 

the experimental data well. In order to resolve the bimodal nearest-neighbor bond 

distribution directly in the PDF, we need to perform measurements to higher val- ues of Q. Our results will be compared with theoretical predictions for the local 

structure in collaboration with Prof. Thorpe at Michigan State University. 

(OI 60 I 

Figure 1. 

1000 

500 

6- 

- eo 

U 

500 

01 03 06 08 10 11 14 16 

r (nm) 

Figure 2. 

Anomalous X-Ray Scattering Studies of Supermolecules and Aggregates in Organic Solution 

L. Chen, Q. Zhu, W. Svec, D. Price, M. Wasielewski (ANL) 

Anomalous X-ray scattering (AXS) study has been conducted on a covalently 

linked modified chlorophyll dimer, and its corresponding monomer with zinc as the 

central metal ions. The molecule under AXS studies is a chlorophyll dimer cyclophane, where two covalent linkages connect two macrocycles side-by-side. The ester 

linkages will make the two chlorophyll rings to fold into a ”clam shell” like conformation. Our AXS experiment intends to probe the metal-metal distance in this 

”clam shell” like molecule in solid and in solution. Based on a preliminary molecular mechanical calculation, the metal-to-metal distance in bis-Zn-chlorophyllide 

cyclophane is 4.9 , a distance is beyond the probing range for EXAFS in disordered 

system. The coordination number of the metal ions is also an important structural factor in predicting the function of the molecule. We have found temperature 

dependence of the coordination state in these cyclophanes by EXAFS experiment, 

where the ligands bind to the metal at temperature below 200K, but not at room temperature. The coordination of the ligands requires the ”clam shell” to open 

up, thus this is related also to metal-to-metal distance in the molecules. The covi~ 

lently linked chlorophylls function as either electron donor or acceptor. The electron 

transport processes in these supermolecules are normally triggered by light. Thus, 

these supermolecules have potential applications as molecular devices. Structural 

parameters of these supermolecules are very important information in predicting 

their electron transfer properties. We have obtained AXS data for powder and 

solution of the dimer as well as the corresponding monomer. Significant differences in the spectral features have been observed between the dimer and monomer. However, in order to obtain Zn-Zn distance in this molecule, a correct method of 

background subtraction and data normalization is very crucial. We are in a process 

of completing the analysis of the AXS data. 
The Nature of Structural Defects in C15 NbCra and Nb(Cr,V)2 Studied by Synchrotron X-Ray Powder Diffraction 

High Resolution Powder Diffraction at 0.5 A * 

F. Chu (LANL), Q. Zhu (BNL), D. J. Thoma, and T. E. Mitchell (LANL) 

NbCrz-based C15 Laves phases are promising high temperature structural materials. Physical metallurgy and mechanical behaviors of the Laves phases are subjects 

of extensive investigations. In this work, the structural and defect characteristics 

of C15 NbCrz and its vanadium alloys have been studied using high-resolution synchrotron x-ray powder diffraction at X7A beamline of NSLS. Contrary to common 

belief, Rietveld refinement indicated that extra Nb atoms occupy Cr site in a Nbrich binary system and a formation of vacancies on Nb site in a Cr-rich phase, and 

it also revealed that V atoms occupy Cr sites in the ternary alloys. These results 

are inconsistent with the atomic size rule for the formation and stabilization of 

Laves phases. The alloying behavior and the defect structures/mechanisms in both 

binary and ternary NbCrz-based Laves phases are better understood in terms of 

the electronic structure of C15 NbCrz, calculated using the linear muffin tin orbital 

(LMTO) method. The total and 1-D projected density of electronic states show 

that the valence electrons of C15 NbCrz fill the Fermi level in such a way that some 

anti-bonding d-states are occupied, the system is therefore energetically unfavorable. This allows Nb or V atoms to substitute Cr, which lowers the Fermi level 

and de-occupies the anti-bonding d-states, resulting in a more stable compounds. 

Our results suggest that the electronic structure of certain Laves phases, e.g. C15 

NbCrz, could determine its alloying behavior, although the atomic size rule plays a dominant role in most of the Laves alloys. 

X7A 

* Work supported by the Div. of Materials Sciences, US Dept. of Energy under contract 

DE-AC02-76CH00016. 
Structural Studies of Giant Magnetoresistive TlzMnz07 * 

D.E. Cox (BNL), P.G. Radaelli (ILL, Grenoble), M Marezio (MASPEC-CNR 

X7A 

Parma), and S.-W. Cheong (Lucent Technologies) 

Recently giant magnetoresistive (GMR) behavior has been reported in the 

pyrochlore-type compound Tl2Mn2 07 [1,2], in which there is a simultaneous 

insulator-metal and paramagnetic-ferromagnetic transition at 23140 K reminiscent 

of the GMR manganite perovkite systems. A powder diffraction study of Tl2Mn207 

was carried out over the temperature range 20-300 K. An extended data set was collected at 300 K from a sample sealed in a 0.4 mm diameter capillary. Because of 

the high absorption of T1, a wavelength of 0.5003 8 was chosen so as to minimize 

systematic errors in the intensities, and a linear multiwire proportional detector 

filled with Kr at 234 bar and functioning in the escape-peak mode was used to en- sure good counting statistics. The sample was transferred to a cryostat, and scans 

performed over selected angular regions between 20-300 K in order to determine 

the lattice parameters and check for possible anomalies or symmetry changes at the 

paramagnetic-ferromagnetic transition analogous to those previously observed for 

the (La,Ca)MnOa system [3]. For these measurements a Ge (220) crystal-analyzer 

was used to improve the resolution, and a wavelength of 0.9999 8 (slightly below 

the T1 LIII edge) was chosen so that acceptable counting statistics were obtained. 

At 300 K the TlzMn207 pattern could be indexed on the basis of a face-centered 

cubic unit cell (a = 9.8948 8). Rietveld refinement gave results which were in good 

agreement with those recently reported by Subramanian and co-authors [4], i.e. T1: 

U11 = 0.0053(1) A2, Ul2 = -0.0017(2) 8'; Mn: U = 0.0016(2) A2; O(1): U = 

0.002(2) A2; O(2): x = 0.3266(9), U = 0.003(2) A2. However, attempts to determine the stoichiometry of the compound by refinement of the oxygen occupancy 

factors yielded inconclusive results; overall values of 6.6(1) or 7.4(1) were obtained 

depending on whether scattering factors for 02- or neutral 0 were used. Thus we cannot rule out the possibility of a few percent of vacancies on the O(2) sites. 

In contrast to the behavior found for the (La,Ca)MnOj system , the lattice 

parameter measurements showed no evidence of any anomalies or discontinuities at 

the insulator-metal transition at 120 K, nor any peak broadening suggestive of a 

lowering of the lattice symmetry. [l.] Y. Shimakawa, Y. Kubo and T. Manako. 

Nature 379, 53 (1996). [2.] S-W. Cheong, H. Y. Hwang, B. Batlogg and L. W. 

Rupp, Jr. Solid State Commun. 98, 163 (1996). [3.] P. G. Radaelli, D. E. Cox, 

M. Marezio, S-W. Cheong, P. E. Schiffer and A. P. Ramirez. Phys. Rev. Lett. 75, 

4488 (1995). [4.] M. A. Subramanian, B. H. Toby, A. P. Ramirez, W. J. Marshall, 

A. W. Sleight and G. H. Kwei. Science 273, 81 (1996). 

* Work supported by the Div. of Materials Sciences, US Dept. of Energy under contract 46 

ua 

F DE-AC02-76CH00016. 

Interfacial Roughness of Fe-CR GMR Superlattices 

W. Dmowski and T. Egami (U. of Pennsylvania) 

X7A 

Fe-Cr superlattices exhibit giant magneto-resistance (GMR) effect which depends 

strongly on the preparation conditions. The x-ray reflectivity measurements show 

that with an increasing Ar pressure, the superlattice Bragg peaks become broad, 

their intensity decreased and the higher order finite size peaks strongly attenuated. 

Sputtering at an increased Ar pressure could cause atomic intermixing at the interface, change roughness at length scale comparable to electron mean free path and 

longer, affecting the magnetization process. To determine the more precise nature 

of the interface roughness in Fe-Cr multilayers we have studied both specular and 

off-specular x-ray scattering from several Fe-Cr multilayers produced by sputtering 

under different AI pressures. We have measured [Fe(30A)/Cr( 128)]10 superlattices 

which had been sputter-deposited in 4,5,6,7,8,9,10,11 and 12 mTorr of Ar. We used 

a position sensitive detector placed in the horizontal position to collect simultaneously the specular scattering intensity along 0, (z-component of the scattering 

vector Q being perpendicular to the film) as well as the off-specular intensity along 

Qy which is in the plane of the sample and perpendicular to the incoming beam. 

To analyze interface roughness in these three samples we obtained a 2 dimensional 

Fourier transformation (2DFT) of the intensity distribution in the Q.-Qu plane, 

I(r), and the height-height fluctuation function g(r). Significant difference is observed between specular and integrated intensities indicating large contribution of 

off-specular intensity to the total signal. We found that the interface roughness for 

the 4 mTorr sample is almost conformal (correlated roughness) while for the other 

roughness is uncorrelated from layer to layer. We observed changes at three different 

length scales at the interface with an increasing Ar pressure. At long separations 

interface is rougher at a higher Ar pressure. Interface roughness at this length scale 

is very likely to affect magnetization process. From our data it is clear that short 

range roughness becomes smaller with a higher Ar pressure. At the same time there 

is more intermixing at the interface. This suggests that the changes at the interface 

at short lengths are responsible for the observed increase in the MR effect 

Figure 1. Height-height fluctuation function g(r) for 4 and 7 mTorr samples at the 

second order Bragg reflection. 
Ultra-thin CeOz Overlayer on YSZ Studied by X-ray Surface Scattering X7A 

W. Dmowski and T. Egami (U. Pennsylvania) 

Ceria is an essential component as a catalyst support in three-way automotive 

catalytic converter due to its capability of storing oxygen under oxidizing and releasing oxygen under reducing conditions. It is not well understood why this particular 

mixture of oxides can achieve the role as a oxygen buffer and why its lifetime is 

limited. In order to address this issue and to understand the structural interplay 

at the ceria/zirconia interface, we studied the atomic structure of ultra-thin ceria 

layers deposited on single crystals of (001) oriented Y-stabilized zirconia (YSZ), in 

situ, during annealing in air using the synchrotron x-ray surface diffraction technique. We applied, for the first time, the energy dispersive mode of x-ray diffraction 

in the surface scattering experiment [l]. Our experimental geometry was typical for 

the surface scattering study, with the scattering vector nearly in the plane of the 

sample. The samples were placed on a heater and were annealed in air during the 

x-ray scattering measurement to observe structural changes with temperature. Our 

study shows that a CeOz epitaxial overlayer can easily be formed on a Y stabilized cubic zirconia by simple oxidation of Ce metal layer deposited on the surface. 

The lattice constant mismatch most likely induces formation of contiguous ceria 

islands. This microstructure of ceria may be important for catalytic function of 

ceria/zirconia interface. In-situ studies of a deposited cerium metal layer show the 

following evolution with temperature: 

- Crystallization of ceria starts at 420°C. 

- At 520°C crystallization is completed and interface is modified. - At 620°C preferential growth of some ceria grains occurs. 

- At 720°C cerium diffuses into the bulk. 

[l.] W. Dmowski, T. Egami, R. Gorte and J. Vohs, Physica B, 221 (1996) 420. 

Figure 1. Ce/YSZ at 520°C. Diffraction shows a part of a (400) zirconia rod. The 

ridge at Q. = 4.6A-I represents scattering from the ceria film. 

I High Pressure Diffraction Studies of Mercury-Based Superconductors I X7A I ~~ 

J. A. Hriljac, I. Gameson, A. Asab and P. P. Edwards (U. of Birmingham, UK) 

Continuing interest in High Temperature Superconductors is fueled, in part, by 

the discovery of new families of materials with even higher values of T,. One of the 

most recent examples [I] is the homologous family of Hg based systems of formula 

HgBazCa,-lCu,Oz,+z+td, and denoted as Hg-1201, Hg-1212 and Hg-1223 for n = 

1, 2 and 3, respectively. The latter material, Hg-1223, has a T, of 135 K which is 

the highest yet reported at ambient pressure. 

A common feature of nearly all High T, superconductors is that T,’s increase 

under pressure, typically by 1-2 K/GPa. The mercury systems are no exception, 

with reported values of dT,/dP of 1.75, 1 and 1.7-1.8 K/GPa for n = 1,2 and 3, 

respectively [2,3]. The structural changes as a function of pressure, however, have 

not been thoroughly investigated. In the work of Hunter et a1.[4], the crystal structures of the Hg-1201 and Hg-1212 systems were only investigated to 0.6 GPa, while 

the Hg-1223 system was studied to 9.2 GPa. In all cases only ambient temperature data was reported. In order to further elucidate the structural changes of the 

Hg systems under pressure, we have started a programme of high resolution X-ray 

powder diffraction studies of these systems at beamline X7A at both ambient and 

low temperatures. 

In the first set of experiments, only the Hg-1201 system (Fig 1) was investigated. 

Samples were loaded in diamond anvil cells with a mixture of methanol/ethanol 

as a pressure-transmitting medium. In addition, several small ruby chips were included for pressure calibration. Data sets were collected at ambient temperature 

to pressures of 6.74 GPa, and also from room temperature to 15 K at pressures 

of 2.9 and 6.2 GPa. The data analysis has so far consisted of measuring accurate 

lattice parameters for the ambient temperature data, Fig. 2. From this data we 

have determined the compressibilites along the &axis, 3.37~10-~ GPa-’, c-axis, 

5.69~10~~ GPa-I, and bulk modulus, 82.7 GPa. The compressibilities compare well 

with the earlier work of Hunter et al., whereas the bulk modulus is greater than 

their value (69.9) and much closer to that found for the other systems. Further 

analysis of all of the data is in progress. References [l] S. N. Putilin et al., Nature 

362, 226 (1993). [2] A. Klehe et al., Physica C 213, 266 (1992). [3] C. W. Chu, 

Physics and Chemistry of Molecular and Oxide Superconductors (1993). [4] B. A. 

Hunter et al., Physica C 221, 1 (1994). 

1.80 - 1 

0123458, 

PW.1 

Figure 2. Lattice Constants as a FuncFigure 1. Hg-1201 System Structure tion of Pressure. 
-. . 

-. X7A.l . - .- 

As part of a wider study of the structural arid electronic properties of pyrochlorc 

type metal oxides we have investigated the structure of the high temperature cu- bic form of BizSn207. Diffraction data were collected at room temperature and at 

650 C using synchrotron x-ray diffraction at the X7A beamline at the NSLS and 

high resolution neutron diffraction at the HRPD at ANSTOs HIFAR reactor. The 

synchrotron data were collected using a flat-plate geometry at 0.78Awith a Si(ll1) 

channel-cut monochromator and a Ge( 200) analyser. The reflections were indexed 

on a supercell with a = 21.4582A. Initial attempts to refine the synchrotron data 

alone demonstrated the Bi atoms were significantly displaced, presumably as a con- sequence of the presence of the Bi 6s lone pair electrons. However, these refinements 

were relatively unstable with respect to the positional and thermal parameters of 

the lighter 0 atoms. Consequently the structure was refined using the Rietveld 

method in the cubic space group F-43c in a combined x-ray/neutron refinement using the local Rietveld program LHPM. This refinement, whilst still in not complete 

reveals distortions in both the Bios and SnOe polyhedra. Efforts to solve the room 

temperature structure are in progress. 

pctural Studies of Bismuth Tin Oxides _. - .. . . -. 

R.J. Kennedy (The U. of Sydney) 

I Phase Characterization in Rapidly-Solidified Magnetic Materials * I X7A 1 

L.H. Lewis (BNL - DAS), C.H. Sellers (INEL) and V. Panchanathan (Magnequench 

International) 

Rapid solidification has been used as a synthesis route for the production of 

advanced permanent magnet materials based on the intermetallic composition 

REzFel4B (2-14-1), where R is a rare-earth element such as Nd, Dy or Pr. The 

quench rate of the melt, in the range 104-106 K/sec depending on solidification 

method, produces in the solid a nanoscale, multi-phase, non-equilibrium microstructure that is difficult to characterize by conventional laboratory x-ray diffraction 

methods. An advantage of utilizing synchrotron radiation to probe these materials 

is that the excitation of iron fluorescense by CUK~ radiation is avoided, and thus 

characteristics such as degree of crystallinity and minor phase content may be more 

clearly observed. 

Synchrotron powder x-ray diffraction has been performed using radiation wavelengths in the range 0.9A < X < 1.2A to examine the degree of crystallinity, lattice 

parameters, and minor phases present in a selection of rapidly-solidified RE2 Fel4Bbased materials. Research highlights are presented below: 

1). It has been verified that the addition of the specific elements Ti and C to 

the compound NdzFel4B prior to rapid solidification by inert gas atomization increases the glass-forming range of the 2-14-1 melt such that a large fraction of the 

as-quenched product possesses an amorphous or nanocrystdine structure. Since an increased proportion of the Tic-modified 2-14-1 powders exist in an overquenched 

@e., amorphous) state, relative to the unmodified powders, their magnetic properties may be more successfully optimized by brief annealing treatments. 

2). Unlike the compound NdzFelrB, the isostructural compound PrzFeleB holds 

promise as a permanent magnet material for low-temperature applications due to 

its lack of spin reorientation, during which the easy axis of magnetization gradually changes crystallographic direction in the vicinity of a specific temperature. 

In order to investigate the low-temperature magnetic properties, solid solutions of 

(Ndl-,Pr,)zFel*B were synthesized and their stoichimetry was verified by measurements of the lattice parameters. 

3). The next generation of permanent magnets may be a magnetic nanocomposite 

comprised of a hard-magnet phase intimately combined with a soft-magnetic phase 

of high saturation magnetization, known as an "exchange-spring'' magnet. X-ray 

diffraction was used to examine the nature of the phases that comprise a series of 

nanocomposite magnets consisting of the 2-14-1 compound and a-Fe. Preliminary 

results illustrate that each broad peaks constituting the a-Fe Bragg reflections actually contains two peaks, indicating that the phase may possess a shell of material of 

atomically-expanded material that contains Nd or B. Such an intermediate phase is 

expected to have important consequences with regards to the interphase exchange 

coupling and magnetic reversal. 

* Research performedunder the auspices of the USDOE, Division of Materials Sciences, 

Office of BES under Contract DE-AC02-76CH00016. 
P 

0, 

X7A 

* Investigation of Structural Changes in High-Temperature Treated 

Zeolite CaA 

H. Meyer zu Altenschildesche, Y. Huang, G.T. Kokotailo, C.A. Fyfe (UBC, Vancouver), and D. Cox (BNL) 

Knowledge of the thermochemical properties of zeolites is important for a variety 

of industrial applications. For example, most catalytic processes involving zeolites 

require elevated temperatures and the thermal stability of the catalysts is one of 

the major factors determining the efficiency of the processes. Another interesting 

application is the use as precursors for the manufacturing of dense aluminosilicate 

ceramics, since zeolites provide a homogeneous mixture of the oxides on an atomic 

scale. Thus diffusion processes are greatly simplified and the synthesis of a particular 

ceramic can often be achieved at significantly reduced temperatures. 

We have investigated fully Ca2'-exchanged zeolite A as part of a larger program 

to determine the framework stability as a function of cation content. When zeolite 

CaA is heated in air, a series of structural changes occur at temperatures of approx. 

2OO0C, 81OoC, and 850"C, respectively. As can be concluded from additional TGAand DTA-analyses, most of the zeolitic water is lost between 100 and 200°C. At 

temperatures above 85OoC zeolite CaA finally becomes x-ray amorphous. When 

zeolite CaA is heated to 810-85OOC for 24-48h, its properties change drastically. 

The most striking feature is the complete loss of microporous adsorption capacity. Moreover, the intensities in the x-ray diffraction pattern are strongly affected 

with the relative intensity of the hkl=200 reflection in particular being drastically 

increased with respect to all others. 

A Rietveld analysis of synchrotron diffraction data together with scanning electron micrographs revealed that the high-temperature treated material retains the 

zeolite A structure but becomes amorphous at these temperatures in a very slow 

process (days-weeks). The transformation to an amorphous phase starts on the 

outer surface of the individual crystallites and proceeds slowly inward. Moreover, 

angle-dependent broadening of Bragg reflections indicates that a significant amount 

of strain is introduced by heating the sample to temperatures above 80OoC. 

Figure 1. Powder diffraction pattern of CaA treated for 48 hours at 825OC. 

Structural Study of the Layered Aluminophosphate Material NH4- 

Taranakite 

H. Meyer zu Altenschildesche, G.T. Kokotailo, C.A. Fyfe (UBC, Vancouver), W. 

Schwieger (Universitat Halle), and D. Cox (BNL - Physics) 

Taranakite [l] is a mineral with idealized chemical composition HsM3A16(P04)8. 

18 H2O (M = K, NH4) which can be synthesized under similar conditions as framework AlP04s. Though the structure of Taranakite is unknown, there is strong 

evidence that it is not a framework aluminophosphate but a layered material. The 

interlayer recognition, i.e. the ordering, of the NHi-form is very high giving sharp 

reflections up to high angles (Figure 1). Moreover, crystallization occurs easily even at ambient temperatures and it has previously been suggested that Taranakite 

might form on contact of phosphate fertilizers with Al-rich clays [2]. On heating, 

the material first looses part of the interlayer water forming its lower hydrate Francoanellite. At temperatures between 100°C and 500°C gradually all the water, 

ammonia, and hydoxyl groups are lost and the material becomes x-ray amorphous. 

However, dense phases are formed only at temperatures well above 50OoC. These 

properties make Taranakite an interesting candidate for pillaring and as a catalyst 

support. 

The high-resolution x-ray powder pattern was successfully indexed with a = 

8.729A, b = 95.039-&, and space group R3c or R9c. The diffraction intensities were extracted using the LeBail method. The application of direct methods together with 

results from elemental analyses and solid state NMR experiments led to a partial 

determination of the layer structure. Rietveld refinement together with difference 

Fourier methods will be used to complete the structure determination. 

1 S. Fiore and R. Laviano, Am. Mzner., 1991, 76, 1722-1727. [I 2 W.F. Bleam, Ph.E. Pfeffer, and J.S. Frye, Chem. MzneTds, 1989, 16, 809-816. 

TIO Thela(degrses) 

Figure 1. Powder diffraction pattern of synthetic NH4-Taranakite showing the extremely high ordering of this layered aluminophosphate material. 
High Pressure Synthesis and Structural Refinement of the New Double Perovskite CazTiSiOs 

J. B. Parise (SUNY Stony Brook) and K. Leinenweber (ASU) 

Double perovskites form a large family of materials whose structures are made 

up of a framework of corner-linked octahedra similar to that of AB03 perovskites, 

but with the B cations ordered onto two distinct octahedral sites. This leads to the 

stoichiometry A2B’B’’Os with the B’ and B” cations forming a face-centered array 

like that of Na and C1 in rocksalt. The ordering of the B cations leads ideally to a 

reduction in symmetry from PmSm with cell parameter a (AB03 perovskite), to an 

Fm3m cell with cell parameter 2a (AzB’B”O6 perovskite). A further reduction in 

symmetry to P21 /c, due to rotations of octahedra in the framework, is also common. 

The structure of the Fm3m double perovskite is specified by 2 parameters, the unit 

cell parameter Q and an oxygen position parameter which sets the sizes of the two 

different octahedra. 

The double perovskite CazTiSiO6, which can be recovered to ambient by quenching from high pressure-high temperature conditions (Leinenweber et al., in prep), 

is midway along the join between CaTiOs and CaSiOs. This material is the first 

of the ordered double perovskites compounds to be found with silicon as one of the 

octahedral cations. 

Data, collected in high resolution mode using a Si(lll)/Ge(220) channel-cut 

monochromator/crystal analyzer combination (X=l.l5032(2)A)) confirmed the earlier observation of a powder diffraction pattern dominated by reflections indexed 

on the basis of a primitive cubic unit cell with a -3.7A. There was no obvious 

splitting of these peaks to indicate a symmetry lower than isometric. The weaker 

superlattice reflections consistent with the doubled F-centered cubic cell were also 

clearly present. The peak widths of the ordering reflections were consistent with 

those of the primitive reflections, indicating that both sets of peaks can be assigned 

to a single phase. Rietveld refinement of a starting model with Ca, Ti, Si and 0 

ordered into positions Ec, 4b, 4a and 24e of Fm3m lead to convergence with the following results: oxygen at 0.2372(4),0,0; Ca-0 (2.6217(1)A), Ti-0 (1.947(3)A) and 

Si-0 (1.758(3)A) 

Structural 

Characterization of A Novel Open Framework [(C8H20N][AgGe2Sg] X7A 

(TEA-AgGS-SB1) 

J.B. Parise (SUNY Stony Brook) and K. Leinenweber (ASU Tempe) 

Open frameworks consisting of corner linked polyhedral elements are capable of 

occluding organic molecules and so are .of interest for their potential as selective 

agents for molecular sieving, catalysis, ion exchange and ion conduction. The most 

common of these frameworks are the aluminosilicates. However, the range of materials capable of forming open frameworks has increased greatly over the past decade. 

For example, following their description by Krebs, synthetic routes to knit isolated 

tetrahedral Sn- and Ge-sulfide clusters into frameworks have been found. This was 

accomplished using two procedures: self-condensation of the clusters in the pres- ence of organic amines and condensation from solution using transition metal ions 

along with the organic amines. There is evidence that both the organic amines 

and the transition metal act as structure directing agents. Hydrothermal titration, 

the injection of reagents to thermally activated precursor species, can lead to novel 

metastable materials. One such material is the title compound (1). The structure 

of 1 (Fig. 1) was determined15 from data collected using a position sensitive detector at beamline X7A of the National Synchrotron Light Source (NSLS). A pattern 

suitable for Flietveld refinement was obtained by combining in 0.01. steps data from 

the central 2. of the detector, which was stepped at 0.25. intervals from 5 to 35. in 

26’. The starting model for Rietveld analysis, including the position of the [TEA]’ 

ion, was taken from the single crystal structure analysis of TEA-CuGS-SBi. The 

Ag compound is isostructural with this material with [Ge4SloI4- clusters linked to 

form a three dimensional framework (Fig. 1). The position of the organic template, 

which was refined using soft constraints, is similar in the structures of both Cu and 

AgGS-SB1. 

Figure 1. Tetrahedral clusters of [GekSlol4- anions joined by two-coordinated Ag’ 

ions (solid circles) in the structure of 1. For the sake of clarity the [TEA]+ ions 

occupying the cavities within the structure are omitted. 
td 

0, 1 Synthesis and Structure of a Novel Aurate: CdAusO4. I X7A 1 

J.-H. Park and J.B. Parise (SUNY Stony Brook) 

Because of its high electron affinity the stability of gold oxide is expected to 

be low. Indeed Auz03 decomposes to metallic gold below 25OoC, well below the 

temperature required to activate most solid state reactions. However the application 

of pressure can stabilize the oxide to temperatures where reaction can occur. This 

strategy has been used to produce a new aurate, CdAu204 by solid-state reaction of 

Cd(OH)2 and Auz03 in a welded gold capsule at 12GPa and 100O'C using a uniaxial 

split-sphere high-pressure apparatus (USSA 2000) at Stony Brook. Preliminary 

diffraction patterns indicated this material is isostructural with CaAuz 04. Because 

of the small quantity of material available from high pressure experiments above 

10Gpa, Synchrotron X-ray powder diffraction data were collected from a sample 

sealed in a 0.17 mm diameter glass capillary using the position sensitive detector 

(PSD) and a wavelength of 0.642803(1) at X7A. Two theta diffraction angles from 

6' to 65 ' were scanned through step intervals of 0.25' with a counting time of 30 sec. 

per step. The central 2 degree portion of the linear PSD at each of the 0.25 degree 

steps were combined to produce a pattern with 0.01 degree resolution. The sample 

capillary was rotated in order to obtain better powder averaging. The correction to 

the Debye-Waller factor (AB=0.69 A') was estimated. All peaks could be indexed 

on the basis of a tetragonal cell (&/a, a = 5.90644(1), c = 10.03859 (3) A and Z = 

4). The structure of CdAuz04 and consists of corner-linked AuO4 square planes and 

distorted CdOs dodecahedra. The smaller ionic radius and greater electronegativity 

of Cd compared with Ca causes a distortion from ideal AuO4 square planes. 

Figure 1. Projection of the structure of CdAuz04 along [loo]. The Cd ions are 

represented by the planes and circles. 

Powder Diffraction Study of the Orientational Order of the Ammonium - Tetrahedra in NH4C1 and ND4C1 

W. Press, B. Asmussen, H. Krull, 0. Seeck (U. of Kiel, Germany), D. Cox, Q. Zhu 

Ammoniumchloride crystals undergo an Ising-like order-disorder phase transition 

which displays a pronounced isotope effect. NH4C1 shows a first order transition 

at T, = 242.0K, whereas in ND4C1 the transition is nearly second order and at 

T, = 248.8K. In both cases the symmetry group for the high temperature phase 

is Pm3m (tetrahedra are disordered with two possible orientations) and for the 

low temperature phase P43m (tetrahedras are 'ferro'-ordered . For reflections hkl 

with all indices different a calculation of the x-ray structure h actor in both phases 

predicts a change of intensity in the range of 2%. As the unit cell does not change 

no superlattice reflections appear. 

For both materials powder diffraction measurements have been performed at several temperatures above and below T,. We used a wavelength of X = 0.7007A and 

got about 45 powder reflections in a range of wavevector transfer q up to 12A-I. 

A LeBail-fitting procedure has been used to extract the intensities of the measured 

reflections. The structure factor depends on the Cl--form factor (International Tables) and the NH:/ND:-form factor. The latter one has been calculated by a linear 

combination of atomic orbitals which allows to fit dx, the distance N++H/N*D, 

and the electron localisation near the nitrogen atom. 

As a result we get the Debye-Waller displacement of the Cl--ion as well as that 

of the ammonium tetrahedron. All fits show a distance dx of about 1.05A and 

a slightly increased electron density near the nitrogen atom. It is not possible to 

extract reliable information about the orientation of the ammonium tetrahedras up 

to now: the calculation seems to be too insensitive to this parameter. The best 

fit with an ND4C1 data set is shown in figure 1. There an R-factor of 0.033 was reached. The analysis is still in progress. 

X7A 

(BNL) 

. .. 

m a c 

.- L 

Figure 1. The structure refinement with the ND(C1 data set at T=255 K. The inset 

shows a zoom of the main picture, scaled by a factor of 10. 
X7A Polymorphism of the Crystalline Low-Temperature Phases of t-Butyl 

Chloride * 

R. Rudman, (Adelphi U.) 

t-Butyl chloride (tBC) has a pseudo-spherical molecular envelope and forms an 

orientationally-disordered plastic crystalline phase I as it is cooled below its freezing point. It then forms a partially ordered phase hi) prior to forming the ordered 

phase (111). Previous attempts to determine the crystal structure of Phase 111, were only partially successful. Recently, the study of tBC took on new relevancy for 

two reasons: Bartell and co-workers described a theoretically derived unit cell and 

crystal structure for Phase I11 and Ohtani and Hasabe, using DTA, reported a new 

phase, supposedly stable over a small 1.8K range (217.7 to 219.5K), between the 

known Phase I and 11. 

In this study the tetragonal Phase I1 (110) reflection and the fcc Phase I(111) 

reflection occur within 0.1’ 26’ of each other near the 1-11 transition temperature, 

at the wavelength used. Powder data were collected approximately every 0.3K 

between 215K and 220K, as well as at selected temperatures up to 235K. The 

Phase 11-( 110) reflection intensities decreased as the temperature increased and 

the Phase I-(111) reflection appeared at 217K, from which point it increased in 

intensity as the Phase II-(110) intensity continued to decrease. This significant, 

easily discernible pretransition activity, as tetragonal Phase I1 transformed to fcc 

Phase I, reveals that the phase transition is not a concerted sudden change in crystal 

structure but a gradual growth of Phase I accompanied by a loss of Phase 11. It is 

possible to have both phases exist simultaneously, at least during the timeframe of 

this investigation. Since these observations also account for the anomalous peaks 

in the DTA thermogram, it is concluded that no new crystalline phase is formed 

between 217.7K and 219.5K. These results agree with Ubbelohde’s description of a 

heterophase pretransition effect wherein two crystalline phases coexist over a small 

temperature region. 

Unfortunately, the several sets of powder data we collected at 15K, for the monoclinic Phase 111 of tBC, showed the presence of severe large crystallite formation so that it was not possible to refine the crystal structure using Rietveld analysis. 

Further work using a cryostat in which the sample is rapidly cooled is in progress. 

F 

0,- 

-J * The assistance of David Cox and Qing Zhu (BNL - Physics) is greatly appreciated. 

[Structure and Thermal Behavior of Fullerene Derivatives * 1 X7A] 

M. R. Stetzer, P. A. Heiney, A. R. McGhie, J. E. Fischer, R. M. Strongin, B. M. 

Brandt, A. B. Smith I11 (U. of Pennsylvania), P. W. Stephens, R. E. Dinnebier, G. 

Bendele (SUNY Stony Brook), and Q. Zhu (BNL - Physics) 

We have performed x-ray powder diffraction (XRPD) measurements using a position sensitive detector (PSD) in order to study the solid-state structures and thermal 

behavior of CSI H2 cyclopropane and C.53H6 cyclopropane. At room temperature, 

the c61 Hz cyclopropane molecules are orientationally disordered in a face-centered 

cubic lattice as is observed in the 6,5-annulene isomer. Unlike the annulene isomer 

of CslHz, the low-temperature orientationally ordered phase of the cyclopropane 

isomer appears to be face-centered orthorhombic with lattice parameters of 13.97 A, 

14.00 A, and 14.25 A, although there may be a slight monoclinic distortion of this 

orthorhombic cell. In addition, as differential scanning calorimetry (DSC) studies 

have revealed the presence of two ordering transitions centered around 213 K and 

separated by -10 K, we have carefully measured the XRPD as a function of temperature in the vicinity of these transitions in an attempt to identify the intermediate 

phase. 

XRPD studies of C63He cyclopropane, a ‘‘larger” cyclopropane in which the two 

hydrogens of C61& have been replaced by methyl groups, indicate that this material 

is orientationally ordered at all temperatures that fall within the stability regime of 

the molecule itself. Patterns were collected at temperatures ranging from 20 K to 

413 K, and the decomposition of the C63H6 molecules manifested itself in a sudden 

intensity decrease which was first observed in the 413 K pattern and remained even when the sample was cooled back down to room temperature. Preliminary attempts 

at indexing our room temperature data suggest that the ordered structure possesses 

tetragonal symmetry with a = 16.19 A and c = 11.39 A, although this indexing 

scheme leaves three weak peaks of anomalous widths unindexed. 

3 muu:--- ’ ’ ~ p- ’ 

T ROO K ! 

,. - u I .,,, L ,..,,..... 20 ZI 22 23 14 Zb 

28 (Degrees) 

Figure 1. A selected portion of the x-ray powder diffraction patterns for the three 

phases of C6lH2 cyclopropane. The patterns are offset for clarity. 

This work supported in part by NSF Grant DMR-MRL-92-20668; acknowledgment is 

made to Donors of Petroleum Research Fund, administered by American Chemical Society, 

for partial support of this research. 
X7A Phase Transitions and Thermal Expansion in Oxides at Low and High 

TemDeratures 

P.M. Woodward, J.S.O. Evans, A.W. Sleight (Oregon State U.) 

The recent descovery of negative thermal expansion in ZrWzOa from 0.3K to 

1050K has sparked great interest in compounds which show negative or zero thermal 

expansion. Compounds in the family Az( W04)a have framework structures which 

suggest they may also display negative thermal expansion. Dilatometer studies 

of Alz(WO*)a and A11.61no.t(W0~)3 indicate that these compounds show negative and essentially zero volume thermal expansion respectively. However, because 

these compounds are orthorhombic rather than cubic, no detailed information about 

the anisotropy of the thermal expansion behavior can be obtained from dilatometer 

data. Furthermore, even for volume thermal expansion, preferred orientation effects 

can result in misleading and inaccurate results. Therefore, the unit cell constants 

for these two materials were determined as a function of temperature from 300 to 

800K. Alz(WO*)s was found to have a small positive coefficient of thermal expansion, ai = 2.3~10-~ K-'. The expansion was almost entirely along the b axis. The 

other two cell dimensions, a and c, showed practically no change over the same temperature interval. All,6Ino,4(WO4)3 showed the same trends with slightly increased 

expansion in all three directions. Its coefficient of thermal expansion was 5.4~10-~ 

K-I. 

Tungsten trioxide has at least five stable phases between absolute zero and its 

melting point. The low temperature phase, €-WO3 is reported to exist below approximately 220K. At this temperature wO3 is reported to transform from the low 

temperature monoclinic form to the triclinic 6-W03 form. High resolution neutron 

diffraction data was collected at the HRNPD at BNL which has been used to refine 

the structure of WOJ at low temperatures (<150K). One unusual feature of the 

data was the presence of 6-W03 below the phase transition, even at 15K. High 

resolution synchrotron data was collected at 20K and 50K to validate the results 

of the neutron diffraction data, and to obtain more accurate tungsten positional 

parameters. Unfortunately, texture effects made the data unreliable for structural 

refinements. However, the synchrotron data did confirm the monoclinic symmetry 

(a=0.5278 nm, b=0.5156 nm, c=0.7664 nm, 0=91.762', space group=Pc) and the 

presence of 6-W03 (or a very similar phase). MgO has long been a primary choice as a substrate for the growth of cuprate based high temperature superconducting thin 

films, due to its low cost and availability as large single crystals. However, the lattice 

mismatch with YBCO is large and furthermore, the MgO surface degrades upon 

exposure to water vapor. For these reasons there is much interest in finding alternative substrate crystals which have a better lattice match to YBCO and preferably 

cubic symmetry from operating temperature (77K) to growth temperature (900K). 

The need for cubic symmetry and the absence of phase transitions over this temperature range are necessary to prevent formation of grain and twin boundaries, 

which are deleterious to the superconducting device performance. Lal-,Sr,AIOa-y 

crystals have been reported as cubic, and provide a good lattice match with YBCO. 

A powdered sample of this compound, with x=0.25, has been measured at room 

temperature and 15K. No evidence of line splitting, indicative of a lower symmetry 

stucture, was observed at either temperature. These findings suggest that this ma- terial may be an effective alternative to MgO as a substrate for high temperature 

superconducting thin films. 

~~~ ~~ I C03 Location in Carbonate Apatite 

R. A. Young (Georgia Institute of Technology) 

With Prof. J. C. Elliott of London (UK), we are working on carbonate apatite. 

The long standing question is just how the COS is oriented when it substitutes 

for OH in hydroxyapatite, as it does to some extent in human tooth enamel and 

bone. In tooth enamel and most synthetic hydroxyapatite preparations, the C03 

is disordered among several possible sites. This has made a clear definition of its 

orientation and location impossible. However, some specimens have been prepared 

(with special methods) in which the C03 is so well organized as to make the crystal 

symmetry monoclinic rather than the usual hexagonal (due to orientational disorder 

of the C03). Since single crystals are not available, Rietveld structure refinement 

with x-ray and neutron powder diffraction data must be used. We have not been 

able to determine the C03 orientation convincingly with, even, our first synchrotron 

(Daresbury) x-ray data on a specimen of a few mg. Neither has it been possible 

with a set of HRNPD (High Resolution Neutron Powder Diffractometer at BNL) 

data on a larger specimen which has a minor phase impurity. (It is very difficult 

to make a phase-pure specimen of sufficient sire.) It was our intention to do a 

combined refinement with the X-ray and the neutron data, along with rigid body 

constraints, using the GSAS program. 

With the GSAS Rietveld refinement program, we found that the differences between the two specimens, though small, are enough to vitiate this attempt to do 

combined refinement with the x-ray and neutron data sets on hand. Thanks to Dr. 

D. E. Cox, we then acquired a new set of synchrotron x-ray powder diffraction data 

(X-7A) on the same material on which we have the HRNPD data. We are working 

on the analyses and taking every opportunity to work physically together as well as by e-mail and FAX. Our progress is very slow. It is a difficult problem, even with the excellent data and analysis tools we have. There are 80 atoms in the unit 

cell besides the C03 and no guarantee that the C03 is in only one of the possible 

types of positions. The unit cell is, roughly, 10 by 20 by 7 A in space group P 1 

b, so there are a great many reflections and almost none clearly resolved. It is a 

challenging problem. However, we are still optimistic that useful new information 

will result from our efforts. 
The Crystal Structure of Beta-Eucryptite from 20 to 873 K: A HighResolution Powder Synchrotron X-ray Diffraction Study 

An Increase of Structural Order Parameter in Fe-Co-V Soft Magnetic 

Alloy after Thermal Aging 

H. Xu, P. J. Heaney, and D. M. Yates (Princeton U.) 

Beta-eucryptite (LiAlSi04), a stuffed derivative of the &quartz structure, is of 

considerable interest because of its superionic conductivity and near-zero thermal 

expansion [l]. A number of crystal structure analyses of 0-eucryptite [2-41 have 

demonstrated that its translational periodicity is doubled alon c and a relative to 

the P-quartz structure. Further, high- temperature neutron /%-61 and X-ray [4,7] 

diffraction experiments reveal an order-disorder transition involving Li ions at about 

740 K that is accompanied by a transient incommensurate phase. 

We have examined structural variations in P-eucryptite by high- resolution powder synchrotron X-ray diffraction with the crystal-analyzer method from 20 to 873 

K. Flietveld analysis shows that with increasing temperature the unit-cell parameter a increases while c decreases (Fi . 1A). The unit-cell volume decreases up to 523 K 

and increases thereafter (Fig. 1B$. While the variation in unit-cell parameters above 

room temperature can be explained by the repulsion between Li and Si/A1 in the 

a-b plane with a concomitant decrease in c, the low-temperature behavior is possibly due to distortions of [Sios] and [A1041 tetrahedra. Moreover, difference-Fourier 

electron-density maps reveal the localization of Li ions below room temperature 

and progressive positional disordering with increasing temperature above 298 K. 

At about 740 K, some Li electron-density maxima are distinctly split, raising the 

possibility that the incommensurate phase results from dynamical disorder of Li 

cations at this temperature. 

[l] Palmer, D.C. (1994) in Heaney, Prewitt and Gibbs (ed.), Reviews in Mineralogy, 29, MSA, DC, 83-122. [2] Buerger, M.J. 1954) Am. Min., 39, 600-614. 

[3] Tscherry, V., Schultr, H., Laves, F. (1972) Z. drist., 135, 161-198. [4] Pillars, 

W.W., Peacor D.R. (1973 Am. Min., 58, 681-690. [5] Guth, H., Heger, G. (1979) 

Holland, New York, 499-502. [6] Press, W., Renker, B., Schultz, H., Bohm, H. 

(1980) Phy. Rev. B 21, 1250-1257. [7] Tscherry, V., Laves, F. (1970) Naturwissenschaften, 57, 194. 

in Vashista, Mundy and S h enoy (ed.), Fast Ion Transport in Solids, Elsevier North 

Q. Zhu (BNL-Physics) 

Alloys of Fer~Co49V2 (HipercoT“ Alloy 50) both annealed and thermally aged, were studied using anomalous synchrotron x-ray at X7a beamline of NSLS and 

neutron powder diffraction. Rietveld and diffraction profile analysis indicated both an increase of the structural order parameter and a small lattice ezpunsion (-J 

0.0004 a) after aging at 450 “C for 200 hours [l]. In addition, a cubic minority 

phase (<0.3%) was identified in the “annealed” sample, which increased noticeably 

(0.3% + 0.8%) as a result of aging. Primitive reflections exhibit shorter crystal 

coherence length than that of the fundamental peaks, indicating the presence of 

antiphase domain boundaries in the alloys. The subtle changes in structural order are attributed to vanadium and iron interdiffusion at elevated aging temperatures. 

These results directly correlate with the observed changes in the magnetization 

behavior and challenge the notion that a “fully” ordered Fe-Co alloy demonstrates 

optimum soft magnetic properties. 

[l] Q. Zhu et. al. Appl. Phys. Lett. (in press). 

t? 

O, eucryptite on temperature. 

Figure 1. The dependence of (A) unit-cell parameters and (B) volume of pCD 
An Increase of Structural Order Parameter in Fe-Co-V Soft Magnetic 

Alloy after Thermal Aging 

Q. Zhu (BNL- Physics), L. Li, M. S. Masteller and G. J. Del Corso (Carpenter 

Technology Carp.) 

Alloys of Fe49Co49V2 (HipercoTM Alloy 50), both annealed and thermally aged, 

were studied using anomalous synchrotron x-ray and neutron powder diffraction. 

Rietveld and diffraction profile analysis indicated both an increuse of the structural 

order parameter and a small lattice ezpunsaon N 0.0004 .& after aging at 450 *C 

for 200 hours. In addition, a cubic minority p 6 ase (<0.3 d 0) was identified in the 

“annealed” sample, which increased noticeably (0.3% + 0.8%) as a result of aging. The presence of antiphase domain boundaries in the alloys was also revealed. 

These results directly correlate with the observed changes in the magnetization behavior and challenge the notion that a lq lq fully” ordered Fe-Co alloy demonstrates 

optimum soft magnetic properties. 

X7A Control of Macromolecule Distribution Within Synthetic and Biogenic X7B Single Calcite Crystals * 

J. Aizenberg (Weizmann Institute), J.C. Hanson, T.F. Koetzle (BNL - Chemistry), 

S. Weiner and L. Addadi (Weizmann Institute) 

The ability of organisms to exercise control over crystal growth is wonderfully exemplified by skeleton formation in echinoderms. A sea urchin spine is a unique composite of a single crystal of calcite and glycoproteins intercalated inside the crystal 

during its growth. Here we performed a detailed morphological and high-resolution 

synchrotron X-ray diffraction study of the textures of synthetic and biogenic calcite 

crystals. We show that the intracrystalline macromolecules from sea urchin spines, 

when allowed to interact with growing calcite crystals in vitro, selectively reduce 

the coherence lengths and degrees of alignment of the perfect domains in specific 

crystallographic directions. These directions also correspond to the newly-developed 

stable faces. In contrast, the defect distribution of young sea urchin spines composed 

entirely of spongy stereomic structure, is much more isotropic. In mature spines 

containing secondarily in-filled wedges of calcite, the degree of anisotropy is intermediate between the synthetic crystals and the young spines. The macromolecules 

extracted from young and mature spines are, however, very similar. These observations demonstrate the inherent capability of occluded matrix macromolecules to 

finely differentiate between crystal planes by stereochemical recognition processes. 

They also show that in biologically-produced calcite crystals this process can be 

overridden to produce a more isotropic material, due to sophisticated biological 

(cellular) control over the microenvironment of crystal growth. (Submitted to J. 

Am. Chem. SOC., August 1996) 

Figure 1. Average shapes of perfect domains of synthetic and biogenic calcite crystals. Coherence lengths, estimated from the diffraction peak widths, are used to 

define the distance between different crystallographic directions. the presence of 

intracrystalline proteins from reduced in the a* direction relative to c, indicating a 

specific protein crystal interaction. C- Sea urchin spi 

* Contract DE-AC02-76CH00016 with US DOE, Div of Chem. Sci.,Office of BES and 

Binational Sci. Foundation. 
X7B High Temperature Phase Transformations of Tetraalkylammonium 

Tetrafluor obor at es. * 

J. Bager , F. Krebs Larsen (U. of Aarhus), T.M. Schultz (Rise, Denmark), P. Norby 

and J.C. Hanson (BNL - Chemistry). 

Tetraalkylammonium tetrafluoroborates, RqNBF4, R = CH3, CzHb, n-C3H7 

and n-C+Hs show interesting thermal transformation behaviour with both lowtemperature and high temperature phase transformations( 1,2). The crystal structures are known only for the methyl and ethyl compounds (room temperature refs. 

3,4, low temperature ref 2). Static and dynamic order/disorder arrangements can 

be expected for both anions and cations in the structures. In order to characterize 

the high temperature phase transformations a powder diffraction study has been 

initiated. All compounds undergo one or more phase transitions between room temperature and the melting point. An intermediate high temperature phase, appearing only upon cooling, was observed for tetrabutylammonium tetrafluoroborate. 

Analysis of the powder diffraction data is in progress. 

1. G. Zabinska, P. Ferloni, M. Sanesi Thermochimica Acta, 122 (1987) 87-94. 

2. Thomas M. Schultz, Dissertation, Aarhus University 1996. 

3. G. Giusep etti, F. Mazzi, C. Tadini, P. Ferloni, S. Torre Zeitschrift Kristal4. G. Giuseppetti, C. Tadini, P. Ferloni, G. Zabinska, S. Torre Zeitschrift Kristallogr., 202 (1992p81-88. 

logr., 209 (1992) 509-511. 

, 1019 ^B 1,96 f"t 2L-,10 I" -29 * 5n 12" 

Figure 1. The figure shows the high temperature phase transformation of tetraethylammonium tetrafluoroborate. The room temperature structure is monoclinic. The 

high temperature phase can be indexed as cubic. 

* This work was supported by US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES) P 

3 and by the Danish Natural Science Research Council. 

Characterization of Catalysts by Temperature-Programmed Powder 

X-ray Diffraction 

M.M. Burcham, K.K. (Lehigh U.), and J.C.Hanson (BNL- Chemist;) 

Recently, W03/ZrOz has emerged as a useful solid acid catalyst in applications 

including alkane isomerization and ether synthesis. Tungsten oxide, as well as other 

dopants such as sulfate and yttria, is known to stabilize the tetragonal phase of the 

zirconia support. The catalyst, which is amorphous as prepared, is subjected to heat 

treatment during which the desired tetragonal phase is formed. If the heat treament 

is too severe, the monoclinic phase of zirconia forms, and the catalytic activity is 

reduced. Calcination was performed in situ in the X-ray diffractometer and the 

results illustrated the development of these phases in a WO3/ZrO2 catalyst. This 

information can be used to help develop a better calcination procedure for these 

catalysts. 

Another catalyst of interest is the ternary copper/zinc oxide/chromia methanol 

synthesis catalyst. The precursor of the final catalyst is a hydrotalcite-like hydroxycarbonate layered solid. Heat treatment of these copper-based catalysts yields 

the final catalytically active mixture of copper, zinc, and chromium oxides. Severe 

heat treatments of these catalysts lead to the formation of copper and zinc spinellike structures and reduced catalytic activity. X-ray diffraction measurements of 

the in situ calcination of this catalyst can also be used to refine the pre-treatment 

conditions for the methanol synthesis catalyst. 

In each case, catalyst precursors were placed in 0.5 mm quartz capillaries which 

were mounted in the diffractometer. Temperature was increased by a resistance 

heater also mounted in the diffractometer. XRD patterns were measured every ten 

minutes as the samples were heated from ambient temperature to 850°C. 

28, degrees 

Figure 1. XRD patterns of WOs/ZrOz Figure 2. XRD patterns 

taken as temperature was increased from of Cu/ZnO/Cr203 taken as temperature 

ambient to 850°C. was increased from ambient to 85OoC 
~ ~~ 

X7B In Situ Studies of Hydrothermal Syntheses; Crystallization of Mgand Zn-substituted Aluminophosphates * 

A.N. Christensen (U. Aarhus), P. Norby and J.C. Hanson (BNL-Chemistry) 

Open framework aluminophosphates are of interest as catalysts, especially when 

metal cations are substituted into the framework. Substituting divalent ions for 

trivalent aluminum creates a charged framework. This also means that charge 

compensating cations must be introduced into the cavities. This introduces some parameters, which can be varied in order to tune the catalytic properties. 

The present experiment was performed in order to compare crystallization behaviour of zink and magnesium substituted aluminophosphates. Four different 

pastes were prepared as starting materials. The template used was di-n-propylamine 

= PrzNH. Zink and Magnesium were introduced as the acetates. 

The compositions were: 

A and B: 1.0 PrzNH 0.4 ZnO 0.8 A1203 Pzos 40 HzO 

C: 1.0 PrzNH 0.4 MgO 0.8 A1203 Pz06 40 HzO 

D: 1.0 PrzNH 1.0 A1203 PzO~ 40HzO 

Crystallization of the gels were followed in-situ using temperature ramps and 

isothermal runs at temperatures between 25 and 200°C. 

Paste A gave an unidentified precursor phase, while the final product was MAPO39. Paste B, with the same composition, gave the same end-product, but occurrence 

of MAPO-46 was observed in the early stage of crystallization. While substituting 

Mg for Zn (paste C) did not effect the final product MAPO-39), occurence of 

11 seems to be the stable phase. The pure aluminophosphate paste (D) resulted in 

formation of ALPO-54, ALPO-31 and ALPO-11. 

MAPO-5 as an intermediate phase was observed. At hig 6 er temperatures MAPO5000 - 

no00 6onol 

Figure 1. 3-Dimensional plot. The intermediate phase is MAPO-5. 

* This work was supported by US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES) 

and by the Danish Natural Science Research Council. 

A Variable Temperature X-Ray Diffraction Study of HCFC-124a Reactions on Cation Exchanged Faujasites * 

M.F.Ciraolo, F.I.Poshni, P. Norby, C.P.Grey (SUNY Stony Brook), J.C.Hanson 

(BNL - Chemistry), and D.R.Corbin (Dupont) 

A study of the adsorption of Hydrochlorofluorocarbon (HCFC)-124a 

(CFzClCFzH) on zeolite ZnX is described. HCFCs are used as temporary CFC 

alternatives, since they are destroyed in the troposphere and only small amounts 

reach the ozone in the stratosphere. HCFC-124a is, for example, used as a replacement for CFC-l14(CFzClCFzCl) in refrigerant and air-conditioning applications. 

Basic and acidic molecular sieves have been suggested as materials for separating 

and trapping mixtures of CFCs, HFCs and HCFCs to remove impurities formed 

during the HFC and HCFC syntheses. 

In addition, our recent "F NMR studies have shown that HCFC-124a undergoes 

dehydrochlorination and dehydrofluorination reactions over ZnX at moderate temperatures. We have,therefore, been investigating a series of HFCs and HCFCs in 

order to determine some of the interactions that are responsible for the adsorption 

and catalytic properties of ZnX. Samples were prepared by first dehydrating the 

zeolites for 24 hours under vacuum at 400°C. Gas adsorption was carried out using a calibrated vacuum system. Samples were loaded in 0.5mm glass capillaries under 

dry nitrogen and sealed. Data was collected with an image plate at 3.5 sec/step 

with 900 steps. Figure 1 shows a ramp of HCFC adsorbed ZnX from 90 to 300°C. 

The first changes occur below 150°C and are most likely a consequence of cation 

migrations. No evidence of reaction is seen at this temperature from the NMR 

studies. A loss of intensity occurs at higher temperatures which can be attributed 

to desorption of the HCFC. In contrast, bare ZnX shows no changes throughout the 

temperature ramp. These results demonstrate the need to determine the structure 

of these materials in the presence of different adsorbates and binding sites. 

7 ~ ,,-.cia 

Figure 1. A ramp of HCFC-124a adsorbed ZnX from 90 to 300°C. 

* Acknowledgement is made to the donors of the Petroleum Research Fund, administrered by the Am. Chem. Society for partial support of this research and NSF for an 

interagency transfer of support to the USDOE, BES (DE-FG02-96ER14681. 
bucture and Phase Transitions in The Negative Thermal Expansion I vv,, I AID I Material Zirconium Vanadate 

J.S.O. Evans, A.W. Sleight (Oregon St. U.) and J. C. Hanson (BNL - Chemistry) 

Compounds in the ZrV 2-rP107 series show the unusual property of negative 

thermal expansion. Since these materials are cubic, this contraction with increasing 

temperature is isotropic in nature. At high temperature ZrVz07 has a simple 

cubic unit cell (a=8.8A), but undergoes two phase transitions on cooling (102OC 

and 72OC) and at room temperature has a unit cell with a 3x3~3 superstructure. 

Despite a number of studies (Powder X-ray/neutron diffraction, solid state NMR), 

the precise structure of the room temperature and intermediate phase remained 

unclear. 

To investigate the phase changes occurring we have collected full single crystal 

data sets of ZrVz07 at 3 temperatures, 25"C, 90°C and 102"C, and also limited 

data sets every 5'C from 25OC to 102'C, using a Fuji imaging plate system on beam 

line X7B. At 25OC a total of 77,000 reflections were recorded and merged (R=6%) 

to yield 6972 reflections with I>>3u. Of these 6647 are superlattice reflections. The 

structure has been refined to an RF of 3.6%, and consists of highly regular corner 

sharing ZrO6 octahedra and vo4 tetrahedra. Valence calculations show that each 

of the 6 Zr octahedral sites and 4 V tetrahedral sites have identical coordination 

environments, and there is no need to invoke chemically implausible bond distances 

or disordered oxygen models to describe the structure. 

As the structure is warmed to 72OC it undergoes a phase transition which retains 

the 3x3~3 superstructure, though in which the intensity of the superlattice reflections are markedly decreased. Peak positions of the superlattice reflections are 

observed to shift relative to those of the sublattice suggesting that this superlattice 

phase is incommensurate in nature. The intensity distribution of the superlattice 

reflections suggest that the modulations of the incommensurate phase are closely 

related to the polyhedral tilts observed at room temperature. Further work on this 

incommensurate phase is in progress. 

At 102OC the intensity of the remaining superlattice reflections is observed to fall 

drastically (and essentially to zero), and the structure can be successfully refined 

on the basis of a simple 8.8 Asubcell. Bond distances and angles over the entire 

temperature range studied suggest the phase transitions in ZrVz07 can be understood in terms of coupled 3 dimensional rotations of essentially rigid, undistorted 

polyhedra. Simple modelling on these assumptions is in progress, and it is hoped 

that this will help explain the origin of the incommensurate phase. 

I The Structure of d-Co(en)3.A13P4016.3HaO * I X7B I 

M. J. Gray, A. P. Wilkinson (Georgia Tech) and J.C. Hanson (BNL - Chemistry) 

There is increasing regulatory pressure to sell chiral pharmaceuticals in optically 

pure form. However, the preparation of such products requires the use of either 

enantioselective separations or synthesis technology. In principle, the use of chiral 

zeolitic materials is a potentially attractive approach to both enantioselective separations and heterogeneous catalysis, but a chiral zeolitic material has never been 

prepared in optically pure form. 

We have been exploring the use of chiral metal complexes as templates for the 

synthesis of chiral inorganic frameworks. Many of the new materials that we have 

made are only available as small single crystals or powders. Single crystal diffraction/imaging plate detection were used to obtain a diffraction data set for a sample 

of d-Co(en)3.Al3P4Ol6.3HzO. (C2221, a = 8.502, b = 14.620, c = 20.89 A, Z = 4, 

crystal size 20 x 20 x 80 1.1 m). This layered aluminophosphate was prepared using 

d-Co(en)s3+ as a template cation. It contains chiral A13P40163- macroanions with 

the metal complexes and water sandwiched between the layers (see Figure 1). We 

believe that it is the first example of a bulk inorganic material to be made with 

good optical purity by a template synthesis approach. 

? P ? 

Figure 1. A view down the a-axis of d-Co(en)a.Ab P4 OM .3Hz 0. 

* We are grateful to the Donors of the Petroleum Research Fund, administered by 

the American Chemical Society, and the Georgia Institute of Technology Molecular Design Institute, supported under ONR contract N00014-95-1-1116, and contract DE-ACOB76CH00016 with the US DOE, Div of Chem. Sciences, Office of Basic Energy Sciences for 

fundng this work 
Zeolite NaY using X-ray Powder Diffraction: Observation of Cation 

Structural Characterization of Hydrofluorocarbon-134 Adsorbed on 

Migration and Strong Sorbate-Cation Interactions * 

C.P.Grey and F.I.Poshni (SUNY Stony Brook), A.F.Gualtieri (U. Modena), 

P.Norby and J.C.Hanson (BNL- Chemistry), and D.R.Corbin (DuPont) 

Basic zeolites have been found to be effective for separating various hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) mixtures. This represents 

one approach for removing unwanted side products generated during the synthesis 

of the HFCs and for trapping halocarbon pollutants present in industrial wastes. 

We have been studying the adsorption of HFC-134a and HFC-134 on Y zeolites, 

with X-ray powder diffraction and 23Na MAS NMR, to investigate the interactions 

of the HFCs with the extra-framework and framework sites, and to determine how 

the HFC molecules are bound to the zeolite framework.’ 

A contraction of the volume of the unit cell (u.c.) is observed on gas adsorption 

in NaY and the interaction of HFC-134 with the extra-framework sodium cations is 

so strong that extra-framework sodium cations in the sodalite cages (site 1’) migrate 

into the supercages. These sodium cations are found on positions close to the site 

111’ positions of zeolite NaX, in the structural refinements of data collected at 100K. 

Both ends of the HFC molecules are bound to sodium cations, the HFC molecule 

bridging the site I1 and 111’ cations in the supercages. 

Changes in the cation positions occur as the 32HFC-l34/NaY sample is warmed 

from lOOK to room temperature. At 160K, a significant fraction of the site 111’ 

sodium cations move to the site I1 position, which becomes fully occupied. The 

cation migration is associated with an increase in the disorder of the HFC location. 

The system becomes increasingly disordered as the temperature is raised further: 

At approximately 205K, the remaining site 111’ cations move off the mirror plane 

and onto a general position. 

1. C.P.Grey, F.I.Poshni, A.F.Gualtieri, P.Norby, J.C.Hanson, D.R.Corbin, submitted (1996). 

* Support from the NSF (DMR-9458017and CHE-9405436, and through an interagency 

transfer of support to the US DOE (DE-AC 02-76CH00016)) and DuPont is gratefully 

acknowledged 

Real Time Combined Fe K-edge XANES and XRPD in-situ Study of I Hydrothermal Synthesis of Zeolites from Natural Clay Minerals. * I X7B I 

Alex F. Gualtieri (U. of Modena, Italy), P. Norby and J.C. Hanson (BNL - Chemistry) 

Variations in the chemical composition of zeolites is a well known phenomenon. 

A common feature of natural zeolites is the presence of Fe and other cations such as 

Sr, Li, Be, Cs and Pb mainly as subordinate or occasional elements. The question 

whether iron is present in the tetrahedral framework, or in extra-framework sites, 

or as micro-impurities of iron oxides and/or hydroxides is still under debate. There 

is, however, a general agreement, albeit not supported by clear experimental data, 

that iron is not substituting for A1 and/or Si in tetrahedral sites. 

Spectroscopic studies (optical absorption, Mossbauer, EPR) showed that Fe2+ detected in red heulandite crystals from Val di Fassa (Italy) is actually mainly present 

as hematite and marcasite inclusions, and that Fe3+ is located as extraframework 

cations [l]. XRD, SEM (EDAX), XPS, XAFS data carried out on a clinoptilolite 

and mordenite-bearing samples from Cuba revealed that Fe is not located in the 

tetrahedral framework but resides in an octahedral environment as extraframework 

cations in clinoptilolite [2]. The presence of iron in tetrahedral environment was, 

however, detected in synthetic samples such as Fe-silicalite and synthetic Fe-silicate 

analogues of mordenite [3]. Most natural zeolites are white or pale colored and show 

negligible content of Fe; in many occurrences, Fe-rich smectites are formed before 

or after the formation of zeolites and captures iron. 

We are interested in observing the role and behaviour of structural iron in hydroxides associated with clay minerals used as precursor for zeolite synthesis. The 

precursors were thermally activated and are structurally similar to those of natural 

glassy precursors of zeolites. We have chosen for the experiments thermally activated precursors of a disordered kaolinite and a smectite containing 1.2 and 3.4% 

of Fe203, respectively. The samples were heated at 6OO0C before the synthesis 

experiments. 

In-situ hydrothermal syntheses were carried out at the X7B beamline. A 120’ 

curved INEL Position Sensitive Detector was used to collect time resolved powder 

diffraction patterns. The starting mixture was loaded in a 0.7 quartz glass capillary and kept under a pressure of 10 atm. A hot air blower was used to keep 

the temperature at 100°C. Powder patterns and XANES spectra (6950-7200 eV) 

were collected during hydrothermal synthesis of zeolite A from the activated clay 

precursors. XANES spectra were collected in fluorescence mode by using an scintillation detector positioned close to the capillary. Albeit the data analysis is still in 

progress, preliminary data show that Fe is in octahedral coordination in the pseudoamorphous Fe-hydroxides at the beginning of the reaction and it does not change 

its environment during or after the formation of the zeolite phase. This supports 

the hypothesis that in conditions reproducing the natural environments Fe does not 

enter the framework structure of zeolites. 

References: [l] Bonnin D., Calas G. 1978) Bull. Mineral. lOl(395-398). [2] 

Marco J.F., Gracia M., Gancedo J.R., b onzales-Carreno T., Arcoya A., Seoane 

X.L. (1995) Hyperfine Interact. 95(53-70). 

E., Trautwain A. (1992) Zeolites, 12(180-182 

Chandwarkar A.J., Date S.K., Bill 

* This work was supportedby US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES.) 
X7B Kinetic Study of the Synthesis of Zeolite Li-A(BW) from Natural 

Kaolinites * 

A.F. Gualtieri, (U.of Modena, Italy), P. Norby and J. Hanson (BNL - Chemistry), 

and G. Artioli (U. of Milan, Italy) 

Following the study of the kinetics of synthesis of zeolite A and hydroxysodalite 

experiments were carried out at the X7B beamline, which is equipped with equipment for real time in situ studies. Hydrothermal syntheses were performed in 0.7 

mm quartz glass capillaries using an applied pressure of l0atm. inside the capillary. The capillaries were heated by a hot air stream, and time resolved data were 

collected using a Translating Imaging Plate Camera. 

Isothermal experiments were performed at 65,80,100,115 and 130°C. The raw integrated intensities of several Bragg peaks were converted into phase fractions and 

used to plot alfa-time curves. The population balance method and Avrami model 

were used for analysis of the kinetic curves[3]. The kinetic behaviour was studied 

in the light of the structural differences of the activated precursors (metakaolinite) 

as advanced in [4]. 

[lIGualtieri A.F., Norby P., Hanson J., Artioli G. (1996) in preparation for Phys. 

Chem. Min. [2]Gualtieri A.F., Norby P., Hanson J., Artioli G. 1996) in preparation 

for Microporous Materials. [SIThompson R.W., Dyer A. (19851 Zeolites, 5:202-210. 

[4]Gualtieri A.F. (1995) Phd thesis., Univ. Of Modena Italy. 

Figure 1. 3D plot showing in-situ synthesis (65OC) of zeolite Li-A(BW) from kaolinite Kga-1 activated at 60OoC. 

F * This research was supported under Contract DOE DE-AC02-76CH00016 Division of -4 

Chemical Sciences, BES. 

I Computer Movies of Time-resolved Dehydration of Natural Zeolites * I X7B I 

J. C. Hanson, J. Araujo (BNL), Kenny Stahl (DTU), G. Artioli (U. Milan) 

We have demonstrated that the structural changes occuring during dehydration of 

natural zeolites can be determined by measuring the time-resolved powder patterns 

at series of temperatures and refineing this data by Reitveld Powder refinement.[l] 

The changes can be made clear by movies made up from a series of picutres 

derived from the experimentally determined and refined coordinates. The program 

CERIUS2 was used to generate the frames. The movies can be viewed on www site 

http://www.chemistry.bnl.gov /x’lb/x7bhome.html 

The Laumontite movie illustrates the step-wise dehydration of the Calcium ion 

bound which is bound to the framework oxygen atoms and the water molecules. 

The framework variations during this dehydration are also illustrated[%]. 

The stilbite movie also shows large framework rearrangements which ultimately 

result in the breaking of one framework bond and the forming of a different framework bond[%]. 

1 K. Stahl and J. C. Hanson, J. Appl. Cryst. (1994) 27, 543-550 

2 K. Stahl, G. Artioli and J. C. Hanson, Phys. Chem. Miner.(1996) 23, 328-336 11 3 C. Cruciani, G. Artioli, A. Gualtieri, K. Stahl and J. C. Hanson, Amer. 

Minerologist .( submitted) 

Figure 1. Laumonite cavity. 

* Contract AC02-76CH00016 with US 

DOE Div. of Chem. Sci., Office of Basic 

Energy Sciences and the Swedish Natural 

Science Council Figure 2. Stilbite cavity. 
X7B 

P Pyridine Adsorbed on Na-Faujasite: Low Temperature Single Crystal 

Studies * 0, 

J. C. Hanson (BNL- Chemistry), I. Mutikainen (U. of Helsinki), J. Pluth (U. of 

Chic ago) 

Studies of the binding of adsorbants to zeolite solids can provide information 

about the selectivity of these materials in adsorption and catalysis. We have carried 

out single crystal studies of the binding of pyridine to Faujasite at five temperatures using both sintilation counter and image plate data collection techniques. The 

lowest temperature data was collected in a cryostat at temperature 20K. A Oxford 

cryocooler was used to collect data at 105K, 140K, 190K and 240K. The cryostat 

data was collected using a sintilation detector. There were 1667 reflections measured. They were merged with Blessing’s SORTAV program to give a symmetry R 

factor of .05. The image plate data were scanned offline on a Fuji Bas2000. The 

data were indexed, integreted and merged with the HKL package of Z. Otwinowski 

and W. Minor. There were 8204 reflections in the 105K data set which gave a symmetry R factor of .07. 

The binding sites were found from difference Fourier maps. The structures were refined with Shelxtl. The R factors were ,138 and .097 for the 20K and 105K data. 

The prydine binds in the super cage above the Na I1 in a manner similiar to the 

binding of benzene in NaY[l]. 

[l] A. N. Fitch, H.Jobic and A.Renouprez (1986) J. Phys. Chem. 90, 1311-1318 

Figure 1. Difference Fourier map 

through pyridine. Cryostat / scintilation 

counter data at 20K. 

I Studies of Excited-State Lifetimes of Hydrocarbons * I X7B I 

Saturated hydrocarbons, when irradiated with UV or x-rays, mostly decompose. 

However, bound, excited molecules are produced that can fluoresce (F 10-3), leading 

to determination of excited-state lifetimes. examination of these lifetimes as functions of excitation energy can provide information about energy flow and release 

during reactions. 1 During our studies of UV-fluorescence from cis- and trans-decalin 

excited by x-rays on beamline X7B, we realized that the relative fluorescence quantum yields of these molecules could be made absolute by comparison with the known 

fluorescence quantum yield of liquid benzene, measured under identical experimental conditions. Liquid benzene is well-known to exhibit a single excited-state fluorescence lifetime of 27 ns (1 = 295 nm) when excited by UV in the 250-270 nm region.% Since, in the liquid phase, fluorescence is observed only from the lowest 

(Sl) excited state, essentially independent of the excitation process, the same behavior is expected when the excitation process is due to recombination of ions in 

radiation tracks produced by electrons generated by x-ray absorption. When this 

experiment was performed at X7B, two lifetimes were observed, a short lifetime of 

1 ns and another of 10 ns, with approximately equal amplitudes. Explanation of 

this surprising result demands elimination of the possibility that the observation 

is an experimental artifact. Therefore, measurement of the fluorescence lifetime 

of the benzene sample with UV excitation using beamline U9B seemed in order. 

Fluorescence from three samples was observed: one, the same aliquot used on X7B, 

another, an assuredly purified sample, and, a third, a sample exposed in the cuvette used on X7B, with a Mylar window, glued to the cuvette with epoxy cement. 

Samples freshly bubbled with N2 exhibited the literature value of the fluorescence 

lifetime. Shorter lifetimes were observed from the same samples as atmospheric 

oxygen dissolved and formed charge-transfer complexes. It seems clear that further 

study of the x-ray-excited UV fluorescence behavior of liquid benzene needs to be 

pursued. 

References 1. R.A. Holroyd, J.M. Preses and J.C. Hanson, Radiat. Res., 135 312 

(1993). 2. W.P. Helman, J. Chem. Phys., 51 354 (1969). 

R.A.Holroyd and J.M. Preses (BNL-Chemistry) 

* This research was carried out at Brookhaven National Laboratory under Contract No. 

DE-AC02-76CH00016 with the U.S. Department of Energy and supported by the Division 

of Chemical Sciences, Office of Basic Energy Sciences 
* X7B Investigation of Disorder Using Micro Single Crystal Diffraction Data 

T.R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

A methode for preparing micro single crystals of Gr-LiZnPOe suitable for structure determination has been developed using an aqueous solution of HsP04, 

Zn(N0s)z and LiOH, at 70'C. The cristobalite type structure of Cr-LiZnPO4 has 

been solved [l] and disorder on the lithium and zinc positions were found [2]. Difference Fourier maps has proven valuable for characterization of these kinds of 

materials [3]. Due to the smallness of the crystals (39 x 16 x 18 ,urn3) it was decided 

to use the synchrotron X-ray radiation and an imaging plate (IP) system for the 

data collection at chemistry beamline X7B. 

The absorption edge of zinc in Gr-LiZnPOr was initialy found from a fluorecens 

spectrum. Two data sets were collected as $-scans, at different wavelength. Below 

the zinc edge, X = 0.9540 A, 20 = -40°, using steps of 8' in 4. A total of 1431 refl. 

(695 independent refl.) were measured form 23 IP. At the zinc edge, X = 1.2830 8, 

data were collected, at 20 = -40°, using steps of 8' in 4. The orthorhombic unit 

cell was refined from two independent IP, giving u = 10.019(2) 8, b = 4.966(1) A, 

and c = 6.675 1) A. 

114 (1995) 249. [2] T.R. Jensen, P. Norby, P.C. Stein and A.M.T. Bell, J. Solid 

Stute Chem. [3] M. Helliwell, J.R. Helliwell, A. Cassetta, J.C. 

Hanson, T.E. Ericsson, A. Krick, V. Kaucic and C. Frampton Acta Cryst. B52 

(1996) 479-486. 

[l] W.T.A. L arrison, T.E. Gier, J.M. Nicol and G.D. Stucky, J. Solid Stute Chem. 

117 (1995) 39. 

Figure 1. The crystal structure of GI-LiZnP04. Zn04 is shown as light shaded 

tetrahedra, Po4 as dark and Li as spheres. 

* This work was supported by contract DE-AC02-76CH00016 with the US DOE, Div. 

Chem. Sci. , BES, and by the Danish Natural Science and Technical Research Councils. 

Kinetic Study of Phase Transition of Microporous Lithium Zinc Phosphates 

T. R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

In situ powder diffraction has proven a valuable technique for kinetic studies of 

solid state or hydrothermal chemical reactions and phase transitions. LiZnP04 'HzO 

is a microporous material (zeolite ABW type structure) which transforms to 61- 

LiZnPOl by heating hydrothermally or dry to T > 130'C [1,2]. It is of interest to 

study phase transitions following different mechanisms. 

The starting material was a suspension of LiZnP04.HzO and LiNO3 in water 

to resemble the synthesis conditions. The samples were placed in 0.7 mm quartz 

capillaries and mounted in a special developed goniometer head allowing a pressure 

of Nz gas (up to 45 atm) to be applied. Several isothermal experiments were performed heating the samples up within one minute to a fixed temperature (16OoC < 

T < 210'C). The diffraction data were recorded using a position sensitive detector 

(INEL CPS 120) covering 120' in 20 and sampling time of 30s, 60s or 12Os, and X 

= 1.3080 A. Figure 1 illustrates a typical data set. 

Semi-automatic integration of selected Bragg reflections using a Gaussian peak 

shape allows extraction of data for kinetic studies. Figure 2 shows the formation of 

61-LiZnP04 using the (201) and (011) reflections. 

[l] T.R. Jensen, P. Norby, P.C. Stein and A.M.T. Bell, J. Solid Stute Chem. 117 

(1995) 39. [2] W.T.A. Harrison, T.E. Gier, J.M. Nicol and G.D. Stucky, J. Solid 

State Chem. 114 (1995) 249. This work was supported by contract DE-ACO2- 

76CH00016 with the US DOE, Div. Chem. Sci., BES, and by the Danish Natural 

Science and Technical Research Councils. 

X7B 

Figure 1. Conversion of LiZnPO4.HzO 

to 61-LiZnPO4 at 200'. 

tlmdml" 

Figure 2. Formation of br-LiZnPO4. 
46 

4 

X7B Powder Diffraction Study of Co Substitution in Microporous Lithium 

Zinc Phosphate * 

T.R. Jensen (U. of Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

Substitution of transition metal ions in microporous materials (e.g. ALPOs and related materials) are subject to intense interest due to potential catalytic activity. We have prepared a Co substituted zeolite type ABW material, 

Li(Zn/Co)PO$.HzO, and a cristobalite type material, 6r-Li(Zn/Co)PO4, from a gel 

with a modified composition (to [1,2]) using Zn/Co ratios of l/x, 0.05 < x < 0.5, 

pH 5-7. Li(Zn/Co)PO4*HzO was initialy forming but on heating (to T > 13OoC) 

it recrystalizes to 61-Li(Zn/Co)P04 with a higher Co content. The Co K edge of 

61-Li(Zn/Co)POc was measured to 7.762 keV using a fluorescence spectrum. Powder diffraction data were collected at different wavelengths above, on and below the 

Co K edge to determine the Co content and Co positions of the phases by Rietveld 

refinement, using 0.3 mm glass capillaries as sample holder. 

An understanding of the reaction mechanism can be gained in a study of 

the time dependence of, a(t , the degree of reaction. The phase transition of 

Li(Zn/Co)P04.HzO to dpLi)Zn/Co)P04 is of interest due to the increased Co 

content of the more dense 61-phase. Data were collected at isothermal (set) temperatures of 180, 190, 200, 210, 22OoC, using a wavelength above (42 eV) the Co K 

edge, X = 1.6111 A. 

The phase transition has also been studied with a combination of X-ray fluores- cence and powder diffraction, placing the gel in 0.7 mm quartz capillaries, heating 

rate of 1°C/min. Fluorescence spectre (7.72 to 7.87 keV) were measured in 75 steps, 

with counting time of 5 s/step. After each spectrum powder diffraction data were 

collected, at X = 1.6111 A, (counting time 300s/diag). 

[l] W.T.A. Harrison, T.E. Gier, J.M. Nicol and G.D. Stucky, J. Solid State Chem. 

114 (1995) 249. [2] T.R. Jensen, P. Norby, P.C. Stein and A.M.T. Bell, J. Solid 

State Chem. 117 (1995) 39. 

1 

Fi ure 1. 

L~?z~/c~)Po~. 

Powder diffraction patterns of Li(Zn/Co)PO4.HzO (upper) and 61- 

_________~~ ~ I Structural Investigation of a-LiZnAs04, Using a Micro Crystal * I X7B I 

T.R. Jensen (U. Odense, Denmark), P. Norby, J. C. Hanson (BNL - Chemistry) 

Single crystals of a-LiZnAsO4 suitable for structure determination were prepared 

from an aqueous solution of HsAsOs, Zn(NOs)2 and LiOH, under hydrothermal 

conditions at 240OC. Due to the smallness of the crystals (17 x 17 x 60 pm3) it was 

decided to use the synchrotron X-ray radiation beamline X7B and an imaging plate 

(IP) system for the data collection. A thin (4 pm) glass fiber was used for mounting 

the crystal on the Huber diffractometer. 

The data were collected at 26' = -40' and at 0' as a +-scan, using steps of 6' 

and 14'. The 39 IP (2304 reflections) were scaled together to give 917 independent 

reflections. The wavelength of the synchrotron X-ray radiation was, X = 0.95408. 

The hexagonal unit cell was refined from two independent IP, giving ah = 13.923(2) 

8, and ch = 9.395(2) 8. This is in agreement with results of Durif [l]. 

R3 the As/Zn distances to oxygen were intermediate to the expected values from known related compounds. Removing the 

centrosymmetry revealed that one As/Zn position in the 5.g. R3 splits up in one 

As- and one Zn-position (Le. an ortho arsenate with distinct As04 tetrahedra). 

The crystal structure of a-LiZnAsO4 is isomorph to e.g. a new phase of LiZnPO4 

prepared recently [2]. This phenacite like structure shows the characteristic nets of 

6-rings surrounded by six 4-rings stacked in the direction of the c-axis. 

[l] A. Durif, Bull. SOC. Franc. Miner. Crist. 84 (1961) 322. [2] X. Bu, T.E. Gier 

and G.D. Stucky, Acta Cryst C52 (1996) 1601. 

On refining the structure in s.g. 

Figure 1. The crystal structure of a-LiZnAs04 viewed along the c-axis. 

* This work was supported by contract DE-AC02-76CH00016 with the US DOE Div. 

Chem Sci., BES, and by the Danish Natural Science and Technical Research Councils. 

* This work was supported by contract DE-AC02-76CH00016, US DOE, Div. Chem. 

Sci., BES, and by the Danish Natural Science and Technical Research Councils. 
I The Crystal Structure of a New Zinc Arsenate, Zng(As04)G .4H20. * I X7B I __ 

T. R. Jensen (U. of Odense, Denmark) P. Norby and J. C. Hanson (BNL - Chemistry) 

Micro single crystal diffraction using synchrotron X-ray radiation and an imaging 

plate (IP) as dector is developing to an important technique for structural investigation of new materials. 

A hydrothermal synthesis were performed using H3As04, Zn(NO3 2 and LiOH 

morphologies. "Hexagonal rods" were identified to be a-LiZnAs04. "Plate-like" (< 

40w/w%) crystals and "octahedron-like" (< lw/w%) were mounted on the Huber 

diffractometer at beamline X7B and were indexed from two independent IP, each. 

The "octahedron-like'' crystals were found to be the well known Adamite phase, 

Zn2(AsOs)OH. The "Plate-like" crystals appeared to be a new triclinic phase with 

the unit cell dimensions: a = 6.68 8, b = 9.69 8, c = 10.04 8, a = 72.21", ,d = 

77.53" and y = 75.85'. Data were collected with the IP at, 26' = -40' and O", using 

&scans of 6" and 14', respectively (A = 0.9540 A). The 44 IP were scaled together 

giving 1819 independent reflections. The dimensions of the selected crystal was 83 

x 66 x 12 hm3. 

The structure was solved and refined in the s.g. Pi. It is built from distinct 

AsOs-tetrahedra and 4, 5- and 6-coordinated Zn atoms linked together to form a 3-dimensional network with channels running in the direction of the a-axis. The 

water molecules are placed in the channels. 

at 240°C. Optical microscopy of the batch revealed crystals with t k ree distinct 

Figure 1. The crystal structure of a new Zinc Arsenate, Zn~(AsO4)6'4H20, viewed 

along the a-axis. 

* This work was supported by contract DE-AC02-76CH00016 with the US DOE Div. 

Chem. Sci., BES, and by the Danish Natural Science and Technical Research Councils. 

X7B X-Ray Scattering Study of Simple Molecules Adsorbed on BN: Evidence for a Commensurate Phase of Kr 

D.E. Johnson, J. Hanson, and J.Z. Larese (BNL) 

We have initiated a series of experiments to investigate the layering behavior 

of small molecules (rare gases, light hydrocarbons, etc.) on highly-uniform BN 

powders. BN has a hexagonal crystal structure and lattice constants only a few 

percent larger than graphite. Therefore a comparison between the behavior of films 

adsorbed on graphite and BN should provide insight into the delicate balances 

between the adsorbate-adsorbate and adsorbate-adsorbent interactions which are 

responsible for the wide variety of phases and transitions observed for these systems. 

These measurements are aided by our use of image plate technology which allows 

rapid collection (51 min/exposure) of the data over a large Q-range (~600 cm2 

active area, 100 um resolution). 

Our first experiment was to observe the scattering from submonolayer films of 

Kr, due to its large cross section. It is well-known that Kr adsorbed on graphite 

exhibits a commensurate phase at low coverages which gives way to a compressed, 

incommensurate phase at higher coverages. It has been suggested that the slightly 

larger spacing of the BN substrate and its smoother corrugation would not permit 

a commensurate phase to form. However, our results clearly show the formation 

of a commensurate solid phase. As in the graphite case, this commensurate phase 

has a spacing consistent with the 43xJ3 R 30 structure, and can be driven to the 

incommensurate phase by increasing the Kr density. The change in peak position 

of the Kr (1,O) peak by either lowering the temperature or increasing the amount 

adsorbed is shown below (ML = monolayer) and is consistent with going from the 

43xJ3 R 30 structure to a close-packed structure. The diffraction profiles shown are the difference between exposures taken with BN and BN with adsorbed Kr. The 

peaks exhibit the characteristic saw-tooth or Warren profile and are clearly evident 

despite nearly coinciding with the BN (002) peak which is ~200 times more intense. 

These experiments are currently continuing and application to more complicated 

adsorbates such as CzH4 is expected. 

I 400 

5 350 

f 300 4 250 

E 200 

g 150 

$ 50 

a 14 I6 18 2 22 24 

c 

p 100 

Go 

__~ ~ ~ 

Q K') 

Figure 1. 
X7B In-situ Diffraction Study of Ion Exchange: Exchange of Analcime to 

Ammonium Analcime. 

A.M. Krogh Andersen, E. Krogh Andersen and I.G. Krogh Andersen (U. Odense, 

Denmark), P. Norby and J.C. Hanson (BNL- Chemistry) 

We have made preliminary experiments where we studied the kinetics of ammonium ion exchange of analcime. The natural zeolite analcime (sodiumform, with 

the standard formula Nal6[All6Si~2096].l6H~0) was exchanged to the ammonium 

form from molten NHsNOs at three temperatures (175, 180, and 2OOOC). An INEL 

CPS90 detector was used. The wavelength was 1.0987 A. During the exchange diagrams were taken with 5.17 minutes interval. When analcime in sodium form is 

changed to the ammonium form the crystal system is changed from orthorhombic 

to tetragonal. 

The rate of the ion exchange was estimated by determination of the time dependence of the integrated intensity of the 400 reflection of ammonium analcime 

and the intensity of the 332 reflection of sodium analcime. Figure 1 shows how the 

intensity of the two reflections varies with time. The curves were calculated from 

the following simple first order equations: For production of ammonium analcime: 

Intensity = -b(exp(-k(t-to)))+c . For consumption of sodium analcime: Intensity = b(exp(-k'(t-to))+c, where b, c, and k are parameters determined from the graph 

and to time of the start of the exchange. 

Arrhenius plots for the ammonium exchange were drawn. They are shown in 

Figure 2. We take the liniarity of these plots as indication that we are only dealing 

with one rate determining process. 

This work was supported by US DOE DE-AC02-76CH00016, Div. Chem. Sci., 

BES) and by the Danish Natural Science k esearch Council. 

rrtl6lFlg. 1. Ammonium Exchange of Analcime at 175 Centigrade 

, , , , , , , , , . . . . , . . . eqn- -b(exp(-k(x-lO)))+c. R34. . b=1984, c=2017.61, k0.0420969 . 

.$ 1500 

- 

332 reflection 01 Na analcime 

6 1000 400 relleCtion of NH,Analcime 

5oo t// < b=1403.71, c=66.7916, k=0.0468204 R48.r [ 50 100 150 

idlmlme in Minutes 

Figure 1. Ammonium exchange of analcime at 175°C. 

-2.4 

-2.6 

5 

-2.8 

-3.0 

nIl6lRg. 2. Arrheniusplot lor Ammonium Exchange of Analcime 

- ....,.,..,.... 

2.15 2.20 2.25 -3.2 ' ' ' ' ' ' 2.10 

nllBi1000fi K' 

Figure 2. Arrheniusplot for ammonium 

exchange of analcime. 

In-situ Powder Diffraction Studies of Intercalation Processes: Intercalation of Alkane Diamines in a-Zr(HPO.+)Z.H20 and y- X7B 

Ti(P04)(HzP04).2H~O. * 

A.M. Krogh Andersen, E. Krogh Andersen and I.G. Krogh Andersen (U. Odense, 

Denmark), P. Norby and J.C. Hanson (BNL - Chemistry). 

We have investigated whether time resolved powder diffraction can be used to 

study kinetics of intercalation of alkane diamines into layered phosphates (e.g. aZr(HP04)2.H20 (a-ZrP) and ~-T~(H~PO~)(PO~).~HZO (7-Tip)). The amine intercalation processes of these layered materials proceed discontinuously. This means 

that as soon as the intercalation starts the materials become multiphased. We re- port briefly some of the results from the experiment with a-ZrP. The experiment was made on X7B at room temperature. The detector was an INEL CPSSO detector. 

The sample was in a quartz capillary. A small amount of a concentrated solution 

of hexane diamine was introduced into the capillary, and the intercalation process 

was started by pressing this solution into contact with the a-ZrP. The graph below 

shows how the intensities of the 002 reflections of the a-ZIP and the intercalate 

change with time. 

When the part 

recorded in Figure 1 was ended we continued the experiment at 40 oC and later at 

60 oC. At these temperatures the reflection at 12.5 A disappear and new reflections 

appear as a sign of an increase of intercalated amine. The curves in Figure 1 were 

calculated from the following rate equations: for production of intercalate with 

d=12.5 A: Intensityp,,;) = -b(exp(-k;(t-to)))+c for consumption of a-ZIP with 

d=7.54 A : Intensitypo0,) = b(exp(-k,(t-to))+c, where b, c, and k are parameters 

determined from the graph and to time of the start of the intercalation. 

The experiments show that kinetic data for intercalation processes can be obtained by time resolved diffraction. 

The diffraction profiles were recorded at 20 seconds interval. 

Figure 1. Intercalation of hexanediamine in a-ZrP at room temperature. 

* This work was supported by US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES) 

and by the Danish Natural Science Research Council. 
In-situ Studies of Thermal Transformations in a-layered phosphates. I* 

A.M. Krogh Andersen (U. Odense, Denmark), P. Norby and J.C. Hanson (BNL - Chemistry) 

Layered phosphates of the a-type has the general formula M(IV)(HP04)2.H20, 

M(1V) being e.g. zirconium, titanium, tin or lead. We have used temperature resolved powder diffraction to study the thermal transformations of a-ZrP 

(Zr(HP04)Z.Hz 0), a-TiP (Ti(Hp04)z.H~ 0) and a-SnP (Sn(HP04 )z ' Hz 0). 

The three compounds are isostructural(1 , but do not undergo the same thermal 

phate phase with P-0-P links between the layers, which then transforms into cubic 

pyrophosphate M(IV)Pa07 (2). 

The experiments were carried out at X7B, using a position sensitive detector 

(INEL CPS90 . The wavelength was 1.0987 A. The samples were placed in 0.5 mm 

diagram was 30 seconds. 

Figure 1 shows a 3-dimensional plot of the thermal transformations of a-TiP 

when heating to 800°C. Formation of an anhydrous phase (Ti(HP04)z) is followed 

by condensation of the HPO4--groups whereby the layered pyrophosphate phase 

is formed and finally the cubic pyrophosphate phase. Figure 2 shows the transformation from the layered pyrophosphate phase to the cubic pyrophosphate phase. 

Relative crystallinity is estimated from integrated intensities of diffraction lines from 

transformations. Common to the compoun h s is the formation of a layered pyrophoscapillaries an d heated to 1000°C at a rate of 7.6'C/min. The counting time per 

.~ ~~ 

the two phases. ~~ 

I 

xx Figure 1. 3-dimensional plot of the thermal transformations of a-TiP 500 600 700 800 

Temperature (c) 

* This work was supported by US DOE Figure 2. Transformation in a-TiP 

(DE-*C02-76CH00016, Diva Chem. sci.2 from layered pyrophosphate to cubic pyBES) and by the Danish Natural Science Research Council rophosphate c 

ray Single Crystal Diffraction and Neutron Powder Diffraction Data. X7B 

The Crystal Structure of Tetragonal Zr(HP04)Z by Synchrotron X- I* I1 

A.M. Krogh Andersen (U. Odense), P. Norby, T. Vogt and J.C. Hanson (BNL - 

Chemistry) 

Layered zirconium and titanium hydrogen phosphates have been studied extensively because of their intercalation, catalytic, ion exchange and ion conductivity 

properties. Especially the intercalation chemistry of a-zirconium hydrogen phosphate, a-ZrP, Zr(HP04)z.HzO has attracted significant attention (1). Systematic 

studies of the hydrothermal syntheses and thermal transformations of zirconium 

and titanium phosphates (2) revealed the existence of a new phase in the zirconium 

system, having a very narrow window of formation. The composition of the new 

phase is Zr(HP04)a which is similar to the composition for dehydrated a-ZrP. The 

material was found to be tetragonal with a unit cell: a = 11.2593, c = 10.7691 A, 

spacegroup I4lcd. 

By carefully optimizing the hydrothermal syntheses conditions it was possible 

to grow very small single crystals of the tetragonal material. The crystals were too small for conventional single crystal diffraction. Data were collected on a 25 

x 25 x 50 pm crystal using imaging plate technique. The crystal structure was solved using direct methods. Neutron powder diffraction data were collected at the 

high resolution powder diffractometer at the HFBR. The atomic positions from the 

single crystal refinement was used as starting parameters for the neutron powder 

diffraction refinement. After some initial cycles of refinement, a difference Fourier 

map was calculated, and the hydrogen positions were easily found as holes in the 

map. 

The 0-H groups form a hydrogen bonded spiral along the 41 axes, with each 

hydrogen phosphate group both donating and accepting hydrogen bonds. Figure 1 

shows a space-filling representation of the structure, where the hydrogen bonding 

spirals are clearly visible. 

A. Clearfield and G.D. Smith, Inorganic Chemistry 8 (1969) 431. 

A.M. Krogh Andersen, Dissertation, Odense University 1993. 

* This work was supported by US DOE, DE-AC02-76CH00016, Div. Chem. Sci., BES, 

and by the Danish Natural Science Research Council. 
I Crystal Structure of Dimethylamine Grown In-situ from Liquid * I X7B I 

R. K. McMullan, W. Klooster, P. Norby and J. C. Hanson (BNL-Chemistry) 

As part of a project to study thermal motion of small molecules by neutron 

diffraction and inelastic scattering we have grown crystal of dimethylamine(DMA) 

from liquid in a capillary. The crystal was grown by slowly translating a capillary 

containing liquid DMA into a cold stream at 105 K. The capillary translation was accomplished by fixing the z translation knob while moving the phi axis motor. 

The data were collected using image plates and an offline Fuji Bas2000 image plate 

scanner. Two hemispheres of data were collected, with one set being measured with an attenuator to prevent saturation of the IP. The data was reduced with the HKL 

package of Z. Otwinowski and W. Minor. There were 1191 reflections measured on 

22 plates which were scaled to give an merging R(1) of 6.7% in a monoclinic space 

group P21 /c with unit cell of a=6.075, b=15.645, c=7.528, ,0=111.24. 

The structure was determined by direct methods. The hydrogen positions were 

all found in difference maps and the structure was refined to a Rl(F)= 5.3%, 

wR2(1)=14.5%. The CH distances were restrained to 1.0. 

The dominant feature of the structure is H-bonded chains as shown in Fig 1. 

\ 

\ 

I 

I 

Figure 1. Packing diagram showing H-bond chains. The thermal ellipsoids on the 

non-hyrdorgen atom are drawn at the 50% probability level. 

* This work was supportedunder contract DE-AC02-76CH00016 with the US DOE and 

supported by the Div. of Chemical Sciences, Office of Basic Energy Sciences. 

in Sodalite X7B Real-Time X-Ray Powder Diffraction Studies of Li/Na Ion Exchange 

P. Norby, J. Hanson (BNL - Chemistry), C. L. Cahill and J. B. Parise (SUNY 

Stony Brook) 

Hydrothermal and solid state ion exchange of lithium for sodium in natural sodalite has been studied utilizing the real time x-ray powder diffraction/imaging 

plate system at Beamline X7B. Slurries and dry mixtures of LiN03 or LiCl and 

sodalite were prepared in a 3:l Li:Na molar ratio and heated to 65OoC via a variety 

of pathways. Many experiments were necessary to determine the optimum reaction 

conditions to study this system. Such was found to be a ramp heating to 650°C over 

three hours with LiCl as the lithium source. Preliminary results indicate that the 

unit cell edge length of sodalite decreses from 8.878 to 8.482A. This contraction is 

expected, as the smaller lithium ions (ionic radius=1.23A) replace the larger sodium 

ions (ionic radius=1.54A). Rietveld refinement of the data at various times during 

the experiment is in progress. This analysis should provide information regarding 

the mechanism by which the exchange proceeds. 

I 

Figure 1. The sodalite,Na4AlaSi3OlzCl framework is defined by A104 and Si04 

tetrahedra. Oxygen atoms are small hollow circles; A1 and Si are small, black 

circles. Large black circles are the Na cations that are replaced by Li. Chlorine is 

not shown. 
1 Dehydration of Zeolite Li-A(BW); A Time Resolved Structural Study. I X7B 1 

Fd 

W 

W 

X7B Hydrothermal Conversion of Zeolites Studied Using in-situ Powder 

Diffraction. * 

P. Norby and J.C. Hanson (BNL - Chemistry) 

Hydrothermal conversion of zeolites is an alternative route for preparation of 

new zeolitic and aluminosilicate materials, and for preparation of pure and well 

crystalline samples. In order to understand the crystallization mechanism it is 

crucial to know how the hydrothermal conversion process proceeds; whether it is a 

reaction taking place in the solid phase, via formation of an intermediate amorphoius 

phase, or via a solution mediated process. 

Using in-situ powder diffraction combined with ex-situ Scanning Electron Microscopy (SEM we have followed the hydrothermal conversion of zeolite Na-LTA 

The hydrothermal conversion process was followed using a Translating Imaging 

Plate (TIP) camera, developed especially for time- temperature- and wavelength 

dependent powder diffraction studies(l,2 and references therein). Hydrothermal 

reactions were performed in 0.7mm quartz glass capillaries. 

Partially converted samples were prepared in-situ on the diffractometer, and by 

using the integrated intensities of diffraction peaks it was possible to estimate the 

conversion ratio. SEM images were obtained for two partially converted sample 

(40 and 60% conversion). The fit of crystallization curves and the SEM images 

made it possible to conclude that the hydrothermal crystallization proceeds via a 

solution mediated dissolution/cryst allization process. No signs of autonucleation 

mechanisms were observed. 

(1) P. Norby, Mater. Scd. Forum, 228-231 (1996) 147-152. (2) P. Norby, J. 

Appl. Cryst., (1996) in press. 

into zeolite Li- 4 (BW) using LiCl(,,) at temperatures between 200 and 260’C. 

P. Norby, J.C. Hanson (BNL), A. Kremenovid, V. Dondur and R. DimitrijeviC (U. 

Belgrade) 

In zeolite Li-A(BW), LiAlSiOr .HzO, the lithium cations in the &ring channels 

are tetrahedrally coordinated to three framework oxygens and a water molecule(1). 

Upon dehydration the 8-ring channels are elongated and narrowed, and the lithium 

cation coordinates across the channel, obtaining a tetrahedral coordination to only 

framework oxygen atoms(2). Thus, although the ABW topolygy of the zeolite 

framework is retained upon dehydration, rehydration is hindered because of the 

favourable Li-coordination in the anhydrous material. In most zeolites, which retain their framework topology upon dehydration, rehydration occur at ambient 

conditions. However, rehydration of the fully dehydrated Li-ABW is not possible 

even by submerging it in water. Only at hydrothermal conditions will it rehydrate 

to zeolite Li-A(BW). 

In order to follow the dehydration process we performed an in-situ powder diffraction study where zeolite Li-A(BW) was heated from RT to 8OO0C while collecting 

powder diffraction data using a Translating Imaging Plate TIP) Camera(3). Using 

the dehydration process, yielding information about framework distortions, water 

population cation positions etc. 

Figure 1 shows a 3-dimensional plot of the powder diffraction profiles obtained 

through dehydration and the thermal transformation into y-eucryptite. Figure 2 

shows the population of the water molecules, determined from Rietveld refinement, 

as a function of temperature. 

P. Norby, I.G. Krogh Andersen, and A. Norlund Christensen Acta Chem. 

Scand., A40 (1986) 500. 2. P. Norby ZeoEites 10 (1990) 193. 3. P. Norby, A. 

Darovsky, J.C Hanson, and I. Meshkovsky 1996 (In preparation). 

Rietveld refinement the crystal structure of zeolite Li-A(B a ) was refined through 

1. 

Supported by US DOE, Div. Chem. Sci., BES (DE-AC02-76CH00016) 

LTA --> ABW Hydrothermal conversion, 200°C I 

-0 10 20 30 40 50 60 70 I 

Time (Min.) - - 

Figure 1. In-situ preparation of partially converted samples 

* This work was supported by Contract DE-AC02-76CH00016, US DOE, Div. Chem. 

Sci., BES, and by the Danish Natural Science Research Council. 

, “dt 

Figure 1. 

090 ~ 

i $ 0.85 ~ - 

0.80 - 

0.75 - 

070- 

. . 

. 

0.. 

OMJ , 50 100 150 200 250 

TemP i‘C) 

Figure 2. 

m 
Adsorption of Hydrofluorocarbons on Zeolites; An in-situ Powder 

Diffraction Study. * 

P. Norby, F.I. Poshni, M.F. Ciraolo, C.P. Grey, (SUNY Stony Brook) and J.C. 

Hanson (BNL - Chemistry). 

Zeolites are extensively used for gas separation and adsorption, where both structural properties and extra framework cations play important roles. To understand 

the differences in adsorption properties towards different Hydrofluorocarbon (HFC) 

isomers we have initiated in-situ time resolved powder diffraction studies to determine binding sites, kinetics and mechanism of adsorption/desorption. By combinin 

the in-situ studies with MAS nmr and structural studies of pre-loaded samples(l7 we hope to gain insight in the adsorption process. 

In-situ adsorption/desorption experiments were performed using faujasite type 

zeolites loaded in 0.7mm quartz glass capillaries. The in-situ setup is described 

elsewhere(%). The equipment at X7B was modified to allow switching between vacuum and a known pressure of HFC during the experiment. The zeolite was first 

dehydrated an-satu under vacuum, and then cooled to the adsorption temperature 

(-10 - l0O'C). Adsorption was followed by time resolved powder diffraction using 

the Translating Imaging Plate 

at -~300'C under vacuum 

adsorption/desorption cycle was performed using different HFC gases, and varying 

the HFC partial pressure, the adsorption temperature, and the zeolite. 

The adsorption is very fast, and it was necessary to use time resolutions down 

to 5 seconds. Even with 5s time resolution it was possible to follow the kinetics of 

adsorption using the strongest zeolite diffraction peaks. 

1. C.P. Grey, F.I. Poshni, A.F. Gualtieri, P. Norby, J.C. Hanson and D.R. Corbin, 

(1996) Submitted. 2. P. Norby, Materials Science Forum, 228-231 (1996) 147-152. 

camera(%). The HFC was afterwards desorbed 

owing the process using the TIP-camera). The 

Figure 1. 3-D plot of powder diffraction profiles during adsorption of HFC-134 on 

zeolite Na-Y at room temperature. The dominating effect upon adsorption is a dramatic decrease of the intensity of the 111 reflection. 

* Supported by US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES) and NSF 

An In-situ X-ray Powder Diffraction Study of the Dehydration of 

Zeolite CsY 

F.I.Poshni, M.F.Ciraolo, C.P.Grey (SUNY Stony Brook), A.F.Gualtieri (U. of Modena) P.Norby and J.C.Hanson (BNL - Chemistry) 

Zeolites with basic porperties have been found to be effective, for example, as 

catalysts and for gas separations. A study of the structural properties and the 

location of the extra-framework cations is important in understanding their role in 

these processes. 

Differences can be observed by comparing the diffraction patterns of CsY dehydrated at two different temperatures: 500'C and 300'C (Figure 1). Preliminary 

Rietveld refinements show changes in the location of the extra-framework cations. 

For example, at a dehydration temperature of 3OO0C, almost all of the cesium 

cations are located in the SI1 position in the supercages. By 5OO0C, a significant 

fraction of the cesium cations are now located in the SI' positions in the sodalite 

cages and a decrease in the SI1 population is observed. In contrast, the sodium 

cations migrate from SI' to SI and SI1 positions. 

Subtle changes in the zeolite structure were followed by in-situ dehydration under 

vacuum. The sample was loosely packed in a 0.7mm quartz capillary and was ramped to a final temperature of 500'C over a period of 8 hours. Figure 2 shows 

the diffraction patterns during dehydration process obtained with the Translating 

Image Plate (TIP) set-up. 

Support from the NSF (DMR 9458017) and for an interagency transfer of support 

to the US DOE, BES (DE-FG02-76ER.14681) is gratefully acknowledged. 

Figure 1. X-ray Powder Diffraction Patterns of CsY dehydrated at 5000c (top) Figure 2. In-situ dehydration of Zeolite 

300'C (bottom). CSY 
I In Situ Thermal Transformations of Nickel/Cobalt Molybdates * I X7B I 

J. Rodriguez, J. Hanson, S.Chaturvedi (BNL- Chemistry) 

Nickel molybdate is a mixed oxide which can be potentially present in supported 

precursors of Ni-Mo hydro treatment catalysts. It is used as a catalyst for the ox- idative dehydro enation of propane and also serves as a precursor for Hydrodesulfurization (€IDS$ catalysts. Under atmospheric pressure, it has two stable phases; 

the a and the p phase. The /3 phase has a higher HDS activity than the 111 phase. It 

is therefore essential to understand the phase transformations of NiMo04 in order 

to correlate them to the catalytic activity. 

X-ray diffraction (XRD) patterns taken at X7B of XM004 (X=Co/Mo) as a function of temperature have given us insights into the various phase transformations 

that occur. The hydrated NiMo04 looses water by about 300 OC to form purely the 

p phase. On heating to 500 "C, the a phase starts to transform into the p phase 

and the transformation is complete by 700 'C. This p phase, on cooling to room 

temperature yields a mixture of the 111 and p phases. COMOOe .(HzO), dehydrates at 

a much lower temperature at about 100-200 OC to form the corresponding p phase. 

This p phase does not revert back to the a phase on being cooled to room temperature. The XRD patterns allow us to monitor the nature and the temperature of 

these transformations and also give us information about the kinetic parameters of 

these transformations. 

* X7B 

In-situ Powder Diffraction Study of Ca-ion Exchange of Zeolite MAP 

J. A. Stuart (Unilever, UK), P. Norby and J.C. Hanson (BNL - Chemistry) 

A series of in-situ experiments were performed in order to test the feasibility of 

observing real-time ion-exchange at a crystallographic level and to observe transient phases during Ca-ion exchange. This is of industrial relevance, as a primary 

application of zeolites is as ion-exchangers in washing powders, where the timescale 

of interest is in seconds or minutes. 

The sample examined was zeolite MAP (Maximum Aluminum P-zeolite), produced commercially as Doucil A24 by Crosfield, a Unilever company. This zeolite 

exhibits an unusual degree of structural flexibility, and its ion exchange isotherm 

suggests the presence of a significant two-phase region(1). Being a very rapid ion 

exchanger, both time resolution and angular resolution is of the essence. Figure 1 shows the experimental setup forin-situ powder diffraction studies of ion 

exchange from aqueous solutions. The sample was contained in a glass capillary, and 

a flow of solution was obtained by a nitrogen pressure. To minimise the development 

of a reaction front and to improve the flow, the zeolite column was as short as 

practicable. 

Experiments were performed under three conditions: A) In-situ ion exchange 

using a commercial rapid exchange material. B) In-situ ion exchange using a labprepared slow exchanging material. C) Diffraction paterns of lab-prepared equilibrated samples. 

The in-situstudies showed that it iwas possible to follow the ion exchange process, 

although refinements of the experimental setup is necessary. The existence of a twophase region is supported, but deviations from the model were observed. 

1) Adams et al., Proceedings 11th Int. Zeolite Conf., Seoul 1996 (in press). 

.,. x..."..l.-".."l " 

.5 or 0.7 mm capillq -i---- 

~~~ 

,& 

~. ~~ 

Figure 1. Time-resolved powder diffraction patern obtained during heating from . .. the a to the /3 phase. 

Figure 1. 

* Supportedby contract DE-AC02-76CH00016 with the US DOE by its Div. of Chemical 46 

00 

cn Sciences, Office of Basic Energy Sciences. * Supported by US DOE (DE-AC 02-76CH00016, Chem. Sci. Div., BES) 
Fd 

m 

X7B Q) In-situ Crystallization of Mechanically Treated Zeolites. * 

B. SubotiC, C. Kosanovid (R. BoHkoviC Inst., Zagreb), P. Norby and J.C. Hanson 

(BNL - Chemistry) 

One route of preparing high temperature aluminosilicate ceramics is by thermal 

transformation of zeolites. There are many advantages of this method, e.g. well 

defined starting material, homogeneous composition and low transformation temperatures. 

Recently it was shown that mechanochemical treatment of zeolites by ball milling 

produced amorphous materials having different thermal transformation properties 

that the parent zeolite(l,2). The transformation temperatures are lowered, and the 

phase composition of the high temperature ceramics formed are different than those 

obtained from the untreated zeolite. 

Time resolved high temperature powder diffraction experiments were performed 

using the Translating Image Plate (TIP) camera at X7B 3,4). The thermal transformation of mechanically treated zeolite K/Na-LTA into I alsite/kaliophphilite was 

followed and compared to thermal transformations of the parent zeolite. Clear differences both in transformation temperature and formation rates were observed. 

Figure 1 shows a 3-dimensional representation of the transformation of "amorphous 

zeolite K/Na-LTA" by heating to 95OoC. 

1. C. KosanoviC, J. BroniC, A. Ciimek, B. Subotid, I. Smit, M. StubiEar and A. 

Tonejc Zeolites 15 (1995) 247. 2. C. Kosanovid, B. SubotiC, I. Smit, A. Ciimek, 

M. StubiEar and A. Tonejc J. Muter. Sci. (1996) In press. 3. P. Norby, Mat. 

Scz. Forum, 228-231 (1996) 147. 4. P. Norby, A. Darovsky, J.C Hanson, and I. 

Meshkovsky (In preparation). 

Figure 1. 

* This work was supported by US DOE (DE-AC02-76CH00016, Div. Chem. Sci., BES) 

I Are the Chains in Solid HCN Parallel or Anti-Darallel? * I X7B I 

G. Svensson (Chalmers U. of Technology, Goteborg, Germany), J. C. Hanson (BNLChemistry) 

Two crystal structures of solid HCN are known. The phase transition between 

the low temperature form, space group Imm2, and the high temperature form, 

space group I4mm or P4/nmm, occurs at about 170 K. The main question is: are 

the HCN-chains parallel (Fig 1) or anti-parallel?. In principle, the problem can be 

reduced to a choice between two Bravais lattices, P (anti-parallel or I (parallel). 

An old single crystal structure determination [l] suggested par aA el chains while 

theoretical calculations have indicated anti-parallel chains [2] and parallel chains 

Neutron diffraction data, below and above Tc, from powders of HCN and DCN 

have been collected at Studsvik Neutron Research Laboratory in Sweden. At NSLS, 

at beamline X7B, synchrotron powder data were collected on HCN. These data 

show that HCN crystallize with an I-centered orthorhombic unit cell and a crystal 

structure with parallel HCN-chains, as shown in Fig. 1. In order to study the phase 

transformation data were also continuously collected, using a moving image plate, 

while the temperature was decreased from 170 to 125 K, Fig. 2. The transition was found to be completely reversible. 

[l] Dulmage, W.J. & Lipscomb, W.N., Acta Cryst. 4, 330, 1951. [2] Cummins, 

P.L., Bacskay, G.P., Hush, N.S. & Jnsson, B., Chem. Phys. Lett. 145 399, 1988. 

[3] Panas, I., Chem. Phys. Lett. 201 255. 

~31. 
In-situ Time Resolved Powder Diffraction Studies of the Hydrothermal Synthesis of Antimony Sulfides Templated by Dimethylammo- X7B 

nium 

K. Tan, J. B. Parise, Y. Ko,(SUNY StonyBrook) P. Norby, and J. C. Hanson (BNL) 

Under autogenous hydrothermal conditions, crystallization of antimony sulfide 

in the presence of organic templates produce a mixture of phases, which depend on temperature and heating conditions. Preliminary in-situ experiments on the DMASbS (DMA, dimethylammonium) system provide some insights into the chemistry 

of the digestion of crystalline starting materials and the structural transformation 

involved in the synthesis. Antimony and sulfur were mixed and ground into fine 

powders and then packed into a quartz capillary of 0.7 mm. Dimethylamine solution 

was injected into the capillary and the powder mixture was wetted gradually. The 

capillary was fitted into the head of a specially designed goniometer, which was 

mounted on a Huber diffractometer. A pressure of 300 psi was introduced into the 

capillary and an air heater was programmed to control the temperature. 

Upon heating the Sb and S first react to produce antimony polysulfides, which 

condensed quickly to form the S-rich precursor phase with an open structure DMASbS-SB8 at 100 oC. When the temperature is increased to 200 oC, the first open 

structures gradually transform to a new phase (DMA-SbS-SBE). The transformation was slow suggesting a solid-state reorganization to form the highly-ordered 

crystalline phase, DMA-SbS-SBE. 

250 I 

100 200 300 400 500 600 

Pixel sequence across the image plate (IP) ( IP movement: 3.75 pixel/min. ) 

Competition Between Kinetic and Thermodynamic Control of Phase 

Transitions in Silica/Surfactant Mesophase Composites 

S. H. Tolbert and G. D.Stucky (U. of California/Santa Barbara), P. Norby and 

J.C. Hanson (BNL - Chemistry) 

Ordered inorganic/surfactant mesophase composites represent a major advance 

in the synthesis of materials with nanoscale periodicity. The materials are formed 

by the self assembly of combined inorganic/organic species and represent a unique 

non-equilibrium solid phase. A key feature of these materials is that they can be 

calcined to remove the surfactant and produce an ordered mesoporous solid. 

In an effort to understand the kinetics and thermodynamics that control structure in these materials, we have followed phase transformations in these composites 

under hydrothermal conditions using real time X-ray diffraction. Transformations 

in polymerized silica/surfactant composites between hexagonal (P6m), lamellar, 

and micellar hexagonal (P63/mmc phases were observed. In all cases, the struccomponent of the composite, suggesting that this organic phase packing plays a 

dominant role in determining the observed structures of these materials. Similar 

packing constraints have be used to understand equilibrium structural changes in 

pure surfactant/water systems. In this case, however, all transformations are intrinsically non-equilibrium, exemplified by the observation that the transitions are not 

reversible. Thus, while organic packing may control the observed structures of these 

materials, the cross-linked inorganic component plays a large role in determining 

transformation energetics. 

Because of the detailed chemical control available during the synthesis of these 

materials, it is possible to observe both hexagonal (P6m to lamellar and lamellar to 

follow both forward and reverse reactions of a transformation that occurs far from 

equilibrium. Hexagonal to lamellar transformation are discontinuous (1st order) and 

proceed through a modulated lamellar phase. Lamellar to hexagonal transitions also 

proceed through a modulated lamellar phase, but in this case the reaction appears 

to be continuous (likely 2nd order). This result, along with further analysis of 

kinetic data obtained on these systems should proved insight into the energetic that 

control the structures observed in these materials. 

X7B 

tural transformations appeared to b e driven by packing constraints of the organic 

hexagonal transitions under similar conditions. This o d ers a unique opportunity to 

Figure 1. The phase transformation and phase formation during the hydrothermal 

synthesis of DMA-SbS 
'p 

00 

Iridium Optical Constants from X-ray Transmission Measurements, X8A, 

2-12 keV X8C 

R. L. Blake (LANL), J. J. Fitch, D. E. Graessle, B. Harris, J. Juda (SAO), E. M. 

Gullikson (LBL), and M. L. Shattenburg (MIT) 

Precise transmission measurements of free standing Ir foils and of Ir coatings on 

thin polyimide films have been made from 2 to 12 keV. These measurements were 

conducted to provide Ir optical constants in support of NASA's Advanced Astrophysics Facility (AXAF . Transmission measurements were made at small energy 

increments, matching t h ose used for reflectivity measurements, across the Ir Mand L-edge regions to study detailed edge structures. From these data the imaginary part (absorption coefficient) of the complex optical constant was derived at 

each energy increment. Real parts were computed from the imaginary parts via the 

Kramers-Kronig dispersion integrals. Most of the measurements had an accuracy 

within one percent for transmissions. Derived absorption coefficients are less accurate in the 6-12 keV range because the foil thicknesses were not optimum, and in the 

2-7 keV range because of foil thickness uncertainty and possible nonuniformity. Absorption coefficients were compared to the semi-empirical compilations commonly 

called the Henke Tables, with agreement as good as the estimated accuracy of those 

tables. Transmission derived absorption coefficients were also compared with reflectivity derived values, with agreement to plus or minus ten percent over 2-12 keV 

and within a two percent range over the high absorption region of the M-edges. 

At 10 keV transmission, reflection, and Henke Table results agreed within a two 

percent range. No other measured Ir absorption coefficients have been found in the 

literature. Our work will continue on additional foils and mirrors until systematic errors have been reduced to the one percent level. 

Modeling the Diffraction Efficiencies of the AXAF High Energy K. 

A., Transmission Gratings Above 2 keV 

K.A. Flanagan, T.TFang, C. Baluta, J.E. Davis, D. Dewey, T.H. Markert (MIT); 

D.E. Graessle, J. Drake, J. E. Fitch, J.Z. Juda, J. Woo (SAO); J. Bauer (U. of 

Hawaii) 

The High Energy Transmission Grating Spectrometer (HETGS) is a high-spectral 

resolution instrument which includes 336 individual transmission grating elements. 

It is designed to fly aboard the Advanced X-ray Astrophysics Facility AXAF , a 

are of two types. High energy gratings (HEGs) have a 2000 Angstrom period and 

an average bar height of 0.52 microns, with a line/period ratio of 0.6. Medium 

energy gratings (MEGs) have a 4000 Angstrom period and an average bar height 

of 0.37 microns, with a line/period ratio of 0.52. The calibration approach relies on synchrotron radiation (SR) tests of a few gratings to establish the validity and 

accuracy of the physical model we use. The model uses scalar diffraction theory, 

and considers the period, height, width, shape and tilt of the grating bar, as well as absorption by the polyimide support structure and the plaring base materials. 

The goal of the modeling is to obtain efficiencies accurate to the 1% level, except 

near absorption edges where the requirement is at the level of 5% to 10%. Gratings 

that have been tested at the SR facilities are then used as transfer standards in 

laboratory X-ray tests of each individual grating element, to minimize systematic 

errors and allow normalization against a known efficiency. We present here the 

results of a series of new SR tests performed at NSLS in October, 1995. These (and 

other) results are detailed in Flanagan, et al, SPIE Proceedings vol. 2808, 1996. 

One MEG grating (MA2047) and one HEG grating (HA2021) were tested. Both 

of these gratings were from AXAF flight lots. The focus was on a dense sampling 

of zeroth and first order diffraction efficiencies over most of the NSLS energy range 

of beamline X8A. The data and results of our model fitting for grating HA2021 

is presented in Figures 1 and 2, where the first and zeroth diffraction orders were 

fit simulatneously. Analogous results apply to the NSLS data for grating MA1047. 

Note that, for much of the energy region, the residuals are generally within the 

calibration goal. Future work will include modeling with data from higher orders 

obtained at NSLS in March, 1996) and data from PTB at energies below 2 keV. 6 e plan to explicitly take into account edge structure as we pursue modeling in 

this energy region. 

X8A 

NASA X-ray observatory scheduled for launch in 1998. The gratings oft dd e HE GS 

Figure 1. Best fit model and residuals Figure 2. Best fit model and residuals 

for the first order NSLS data of grating for the zeroth order NSLS data of gratHA2021 when both the first and the ze- ing HA2021 when both the first and the 

roth diffraction orders are fit simultane- zeroth diffraction orders are fit simultaously. Wing corrections have been in- neously. Wing corrections have been included. Residuals scale: -4% to +6%. cluded. Residuals scale: -15% to +5%. 
1 X8A I Reflectivity Measurements of Multilayer Optics for Use on the Advanced Photon Source Soft X-Ray Beamlines * 

K.J. Randall, J.Z. Xu (ANL), D. Graessle and J.J. Fitch (Harvard-Smithsonian 

Center for Astrophysics), S. DiFonzo, B.R. Mueller, W. Jark (Sincrotrone Trieste) 

The Advanced Photon Source (APS) is constructing a soft X-ray spectroscopy 

beamline (2ID-C) covering the photon energy range from 500 eV to 3 keV. It is 

based on a grazing incidence spherical grating monochromator [l]. The optical geometry is such that multilayer optical components (mirrors and gratings) will be 

necessary to reach energies above 2.6 keV. The optical element considered was the 

horizontal focusing mirror of %ID-C in which the undulator beam has an incidence 

angle of 88.75'. With a conventional single layer Rh coating, the calculated reflectivity drops very rapidly above 2.6 keV. The multilayer parameters were selected by 

comparison of several geometries using scalar reflectivity calculations. These calculations indicated that a Ni-C multilayer with 7 layer pairs, a d-spacing of 135A, 

and a gamma value of 0.33 would give us optimum performance. In the first of our 

measurements, we have tested the reflectivity of a multilayer sample produced with 

the triode sputtering system of the multilayer technology laboratory of Sincrotrone 

Trieste. The multilayer was deposited onto a float glass substrate with a measured 

6A rms surface roughness. 

The reflectivity measurements were made with the UHV reflectometer at X8A [2]. 

With the grazing incidence angle of the sample set at 1.25', the X8 double-crystal 

monochromator energy was scanned. The incident beam intensity and the reflected 

intensity were recorded, the ratio being shown in figure 1. The measured reflectivity 

agrees well with scalar calculation values including surface roughness. We plan to 

optimize parameters for this particular optical component by including both depth 

and lateral gradation of the d-spacing. Further, we plan to make measurements of 

test gratings with multilayer coatings. 

The X8-A reflectometer is extremely valuable to us since we can perform trial 

measurements on inexpensive sample substrates. This is necessary because of the 

cost of the high quality (51 prad slope error) water-cooled substrates required at 

the APS. Stripping and recoating of such optics, due to incorrect choice of multilayer 

parameters, will not be possible. 

K.J. Randall, J.Z. Xu, and E. Gluskin. Rev Sci Instr 66 4081 (1995). 

D.E. Graessle, J.J. Fitch, R. Ingram, J. Zhang Juda and R.L. Blake. Rev Sci 

Instr 66 2095 (1995). :m 

1 

I> . . 

*apNulF=-slirw 

Figure 1. Comparison of measured and calculated multilayer reflectivity. 

* Work supported in part by the U.S. Department of Energy, Basic Energy SciencesMaterials Sciences, under contract No. W-31-109-ENG-38. 

Iridium Optical Constants from X-ray Transmission Measurements, 

2-12 keV 

R. L. Blake (LANL), J. J. Fitch, D. E. Graessle, B. Harris, J. Juda (SAO), E, M. 

Gullikson (LBL), and M. L. Shattenburg (MIT) 

Precise transmission measurements of free standing Ir foils and of Ir coatings on thin polyimide films have been made from 2 to 12 keV. These measurements were 

conducted to provide Ir optical constants in support of NASA's Advanced Astrophysics Facility (AXAF . Transmission measurements were made at small energy 

and L-edge regions to study detailed edge structures. From these data the imaginary part (absorption coefficient) of the complex optical constant was derived at 

each energy increment. Real parts were computed from the imaginary parts via the 

Kramers-Kronig dispersion integrals. Most of the measurements had an accuracy 

within one percent for transmissions. Derived absorption coefficients are less accurate in the 6-12 keV range because the foil thicknesses were not optimum, and in the 

2-7 keV range because of foil thickness uncertainty and possible nonuniformity. Absorption coefficients were compared to the semi-empirical compilations commonly 

called the Henke Tables, with agreement as good as the estimated accuracy of those 

tables. Transmission derived absorption coefficients were also compared with reflectivity derived values, with agreement to plus or minus ten percent over 2-12 keV 

and within a two percent range over the high absorption region of the M-edges. 

At 10 keV transmission, reflection, and Henke Table results agreed within a two 

percent range. No other measured Ir absorption coefficients have been found in the 

literature. Our work will continue on additional foils and mirrors until systematic 

errors have been reduced to the one percent level. 

increments, matching t h ose used for reflectivity measurements, across the Ir M- 
Crystal Structure of the Metallo-beta-lactamase from B. fragilis, and 

Preliminary Crystallographic Data for Enzyme-I and a Deletion Mu- X8C 

tant of the Class A Beta-lactamase from S. Aureus 

N. Concha, U. Pieper, S. Banerjee, and 0. Herzberg (U. of Maryland) 

We had previously determined the structure of the metallo- beta-lactamase from 

B. fragilis at 1.85 Angs. resolution by MAD methods using the intrinsic zinc ions as the anomalous scatterers. A new data set was obtained at 2.15 Angs. using the CCD area detector at the X8C beamline. Diffraction data was collected from crystals 

obtained in the presence of cadmium instead of zinc. The crystals are isomorphous 

with those of the Zn-containing form with unit cell dimensions: a=b=78.1 Angs., 

c=139.7 Angs., and belong to the tetragonal space group, P4(3)2(1)2. The crystals 

were soaked in a solution containing a poor substrate, Tazobactam, with the goal of 

producing a stable complex that could be observed crystallographically. The 2Fo-Fc 

map of the refined structure shows no indication of any species bound in the active 

site. However, the data enable comparison between the Zn- and the Cd-bound 

molecule. 

In addition to the experiments on the metallo-beta-lactamase, we carried out a number of feasibility studies on crystals of a deletion mutant of a class A betalactamase from s. aureus. These crystals had a low rate of success upon freezing, 

and the few that froze well deteriorated a short time after starting data collection. 

Nevertheless, we were able to collect a partial data set. In addition, crystals of 

the bacterial Enzyme I, a member of the phosphotransfer system (PTS) involved in 

sugar transport across the bacterial membrane were checked. The enzyme I crystals 

diffracted to 7 Angs. resolution. 

~ I Fimbrin and the Cytoskeleton I X9B 1 

S. Almo, S. Goldsmith, M. Sullivan (AECOM) 

The strutucre of fimbrin, one of the members of a family of actin cross-linking proteins, is currently being examined by synchrotron crystallography. Fimbrin binds 

and cross-links filamentous actin, contributing to cytoskeletal structure and function. Fimbrin contains a calcium binding domain as well as two actin binding 

domains. Two actin binding domains of fimbrin have been crystallized and the 

strutucre will be solved using multiple isormorphous replacement. These crystals 

diffract to about 2.5 angstroms. To date, diffraction data has been obtained from 

the native crystal as well as from two heavy atom derivatives. Preliminary protein 

electron density maps, calculated from the diffraction data, show alpha helics to be 

a predominant secondary structural feature of fimbrin. Ultimately, to improve this 

protein map it will be necessary to collect data from the heavy atom derivatives to 

higher resolution. 
1 Svnchrotron CrvstalloaraDhv Structural Analysis of Profillin 1 X9B 1 

S. Almo, M. Sullivan, J. Eads, N. Mahoney (AECOM) 

Profilin is a ubiquitous 15kD protein required for the normal distribution of filamentous actin structures in vivo. Profilin binds PIPS, suggesting a possible link 

to signal transduction pathways. Profilins from different organisms have limited sequence homology, but highly homologous 3D structures, indicating an evolutionary 

pressure to maintain the protein fold. It has been the goal of our laboratory to 

combine crystallography and in vivo studies to examine the role of profilin in the 

cell. Two profilin data sets were collected at X9B. 

Crystals of P2 profilin, (a profilin isoform of Acanthamoeba castellani), which 

diffracted only to 4.OA using a rotating anode and diffracted to 2.OA at XgB, has a 

space group of F432 and unit cell parameters of a=b=c=241.28, a=b=g=90o. The 

atomic structure of P2 profilin will aid in the creation of mutants with which to 

study the specific lipid binding activity of this protein. Crystals of Saccharomyces 

cerevisiae profilin which diffracted weakly using a rotating anode, diffracted to 3.0 

A at X9B. The S. Cerevisiae crystals are of the P432 space group with unit cell parameters of a=b=c=127.66, a=b=g=gOo and were successfully reduced and scaled 

with an Rmerge of 5.8 percent. Most importantly, the S. Cerevisiae structure will 

allow us to design rational mutants for future in vivo structure function and studies 

on profilin. 

X9B EXAFS Studies of the Zinc Derivative of Cytochrome-C: An Unusual 

Coordination State 

H. Anni (Thorn. Jeff. Med. Coll.), J. Vanderkooi (U. of Penn.), M.R.Chance, E. 

Scheuring (AECOM) 

The structure of zinc (11)-substituted cytochrome c (Zn-Cytc), recently resolved 

by NMR, suggested that Zn is in an unusual coordination with six ligands (Anni 

et al., Biochemistry 1995, 34, 5744-5753). Furthermore, fluorescence line narrowing 

spectroscopy has shown that Zn becomes penta- coordinated upon protein unfolding. An hexa-coordinated state of Zn in Cytc is unique since there are no examples of 

any hexa-coordinated Zn-proteins, and there are no hexa-coordinated Zn-porphyrins 

in solution. Moreover, the particular coordination of Zn with five nitrogens and one 

sulfur ligand in Cytc is surprising, because even among the Zn organic compounds 

that are hexa-coordinated (27% of the 428 crystal structures) none is of the type 

(N) 5-Zn-(S) 1. Taken together these findings point to a tight protein modulation 

of the binding preference and strength of Zn to its ligands in Cytc. The Zn-edge 

extended X- Ray absorption fine structure (EXAFS) studies of Zn-Cytc were undertaken in order to define the central metal environment, specifically the distances of 

the Zn metal to its ligands and their nature. Both native and guanidine-denatured 

Zn-Cytc at neutral pH were measured, alongside with the corresponding Fe(II1)- 

Cytc references. 

The absorption spectra of the samples after EXAFS spectroscopy were measured 

to reconfirm protein integrity. Sets of experimental EXAFS data were fit to theoretical curves (FEFF 6.01) using a novel global mapping and refinement procedure 

(AUTOFIT 1.0) were obtained. This data analysis establishes the coordination of 

the Zn site in Cytc: an hexa- coordinated Zn in the native protein environment 

(Zn-Np=2.052A, Zn-Met80 (SD) =2.344, Zn- His(NE)=2.371A) and a mixture of 

penta-coordinated Zn states in the denatured sample (Zn-Np=%.lOA, Zn-His(NE) 

=2.10-2.20A). 
P 

a 

X9B t3 Resonance X-ray Diffraction Studies of Membrane Protein Monolayers 

J. K. Blasie, L. Prokop, E. Nordgren, J. Stzalka, L. Kneller, A. Edwards, R. 

Fischetti (Univ. of Penn.) 

Both soluble proteins and detergent-solubilized integral membrane proteins can 

be tethered to the surface of inorganic substrates via bifunctional organic chain 

molecules possessing a headgroup specific for the substrate surface and an endgroup 

specific for one or more residues exposed on the protein’s surface. Such tethering can 

provide a single, vectorially-oriented monolayer of the fully- functional protein on the surface of the substrate which is ideal for correlated structural and functional 

studies, especially if the solid substrate has been suitably tailored by Molecular 

Beam Epitaxy for x-ray (or neutron) diffraction studies. 

We have most recently employed sulfhydryl-endgroups for covalently tethering 

yeast cytochrome c, in which the heme iron atom was isomorphously replaced by 

cobalt, to the surface of Ge/Si multilayer substrates; the so-tethered cytochrome c 

monolayer was then used as a template to electrostatically bind detergent-solubilized 

mitochondrial cytochome aa3 oxidase to thereby form a vectorially-oriented monolayer of the bimolecular cytochrome c-cytochrome oxidase complex on the substrate’s surface. 

Resonance x-ray diffraction effects on the meridional kinematical x-ray diffraction 

from the cytochrome c heme cobalt atom and from the cytochrome oxidase heme a 

and heme a3 iron atoms have been detected, utilizing a position-sensitive proportional counter, with good signal-to-noise over a sufficiently wide range of photon 

momentum transfer Qz. The on-going analysis of these resonance effects on the 

meridional diffraction will permit an unambiguous determination of the locations 

of the resonant atoms within the already determined nonresonant profile structure 

of the bimolecular complex within the tethered monolayer. Such structural studies are critical to our understanding of the actual structure of this bimolecular complex and the role of this structure in intermolecular electron transfer phenomena, 

including the possible electrogenic nature of the intermolecular electron transfer in 

the generation of transmonolayer electrochemical potentials. 

Heterotropic Effects on the Active Site Structure of Hemocyanin 

L. Bubacco, R. Magliozzo, M. Wirt, J. Peisach (AECOM), L. Powers, (Utah St.U.) 

K-edge x-ray absorption and extended x-ray absorption fine structure (EXAFS) 

spectroscopies were used to investigate the effects of allosteric modifiers of oxygen 

affinity, on the coordination geometry of Cu(1) in Panulirus interruptus deoxy-Hc 

and subunit I1 of Limulus polyphemus deoxy-Hc. These modifiers included hydrogen ions, L-lactate, and chloride. The coordination geometry of the metal, which is 

evaluated based on the intensity of the Is 4pz transition, changes from pseudotetrahedral to trigonal with increasing pH. This structural alteration is correlated with 

increased oxygen affinity of the proteins at alkaline pH (Bohr effect). 

EXAFS analysis of both deoxy proteins at high and low pH demonstrate that 

coordination number and Cu-L bond lengths are not sensitive to pH. Thus, modulation of the coordination geometry of Cu(1) is a feature of the active site governed 

by the Bohr effect in Hc. 

I X9B 
I Kinetics and Mechanism of Lipid Phase Transitions I X9B I 

M. Caffrey (OhioSU) 

All of our kinetic measurements rely upon access to the corresponding equilibrium behavior of the lipid/water systems under investigation. Thus, temperaturecomposition (T-C) phase diagram construction is an integral part of our timeresolved studies. A separate ongoing project, concerned with establishing the 

relationship between lipid molecular structure, overall sample composition and 

mesophase behavior, also requires T-C phase diagram construction. Much of the 

mesophase identification and structure characterization required for mapping out 

a phase diagram can be done using an in-house rotation anode. However, our 

phase diagrams extend up to 100' C and occasionally go as high as 14OoC where 

time-dependent sample decomposition becomes becomes a major problem To obviate this limitation, all such measurements at and above 50'C are now done using synchrotron radiation where exposure times are down by an order of magnitude compared to the rotating anode. For this purpose, we have specially built a 

temperature-regulated sample holder accommodating up to 7 samples at a time that 

is used in conjunction with a multiple-frame image plate detector. Most recently, 

the temperature-composition phase diagram of monovaccenin (a C18:lcll monoacylglycerol) in water was constructed using small- and wide-angle x-ray scattering 

in the range of ca 0 C to 111'C and ca 0% to 60% (w/w) water in the heartin 

direction. The phase identified in the system include the lamellar crystalline (Lcy 

phase, the lamellar liquid crystalline (L) phase, the fluid isotropic (Fl) phase, two 

inverted cubic phases (Q23OIla3d; Q224, PnSm), and the inverted hexagonal (HII) 

phase. The monovaccenin/water phase diagram is remarkably similar to that of the 

monoolein (aC18:lcg monoacylglycerol)/water system. A portion of the current TC phase diagram for the monovaccenin system shows evidence of non-equilibrium 

behavior in the region below 60°C and above 20% (w/w) water that will require 

more detailed investigation. 

Protein Footprinting: Structures of Molten Globule States and Mass 

Spectrometic Analysis 

M.R.Chance, M.D. Brenowitz (AECOM) 

X9A 

Protein cleavage by x-ray generated hydroxyl radicals is much more difficult, than 

nucleic acid cleavage, occurring on timescales 10 x longer. Thus, it is not immediately apparent that these methods will be a boon to time resolved folding studies. 

However, they can identify solvent accessible regions in unusual pH states or where 

other (generally enzymatic) cleavage methods fail. Of longer term significance is 

our preliminary observations that substantial modification, revealed by mass spectrometry, occurs to the native protein after 50-150 milliseconds of exposure to the 

x-ray beam. 

For apomyoglobin, these modifications are revealed as a widening of the peak of 

the native protein in Matrix-Assisted Laser Desorption Time-of-Flight mass spectrometry methods. Electrospray-quadoupole MS, has identified variants with single 

modifications after only 150 ms exposure to the x-ray beam. These are currently being analyzed by enzymatic digest to pinpoint the regions of modification, which will 

then become reliable markers of folding processes or protein-protein interactions, 

and possible open up and entirely new avenue for footprinting research. 
Fd 

W 

,P I Time-Resolved Synchrotron X-ray Footprinting I X9A I 

MXChance, M.D. Brenowitz, B. Sclavi, M. Sullivan (AECOM) 

Hydroxyl radicals (OH) can cleave the phosphodiester backbone of nucleic acids 

and are valuable reagents in the study of nucleic acid structure and protein-nucleic 

acid interactions. Irradiation of solutions by high flux ”white light” x-ray beams 

based on bending magnet beamlines at the National Synchrotron Light Source 

(NSLS) yields sufficient concentrations of OH so that quantitative nuclease protection (”footprinting”) studies of DNA and RNA can be conducted with a duration of exposure in the range of 50 - 100 msec. The sensitivity of DNA and RNA 

to x-ray mediated OH cleavage is equivalent. Both nucleic acids are completely 

protected from synchrotron x-ray induced cleavage by the presence of thiourea in 

the sample solution, demonstrating that cleavage is mediated exclusively by free 

radicals. The utility of this time-dependent approach to ”footprinting” is demonstrated by obtaining a synchrotron x-ray ”footprint” of a protein-DNA complex and 

by a time-resolved ”footprinting” analyses of the Mg2+-dependent folding of the 

Tetrahymena thermophilia L-21 Sca I ribozyme RNA. 

Equilibrium titrations reveal differences among the ribozyme domains in the 

cooperativity of Mg2S-dependent folding. RNA folding progress curves over 

timescales of 30 sec. to several minutes were obtained for several regions of the 

ribozyme. The rate constants obtained for the P3-P7, P4-P6 and P5 domains are comparable with those obtained by Zarrinkar Williamson [Science 265: 918-924, 

19941 using a hybridization-competition assay and confirm the hierarchy of the 

folding of the ribozyme domains established by these investigators. The folding 

rates obtained for individual regions within domains suggest additional steps in 

the folding pathway. Synchrotron x-ray ”footprinting” is a new approach of general applicability for the study of time-resolved structural changes of nucleic acid 

conformation and protein-nucleic acid complexes (J. Mol. Bio., in press). 

Beamline X-9A : A Resource Devoted to Time-Resolved X-ray Footprinting 

M.R. Chance, M.D. Brenowitz, M. Sullivan (AECOM) 

X9A 

The demonstration of footprinting technology and the purchase and construction 

of a stopped flow instrument dedicated to the project created a dilemma for the 

Resource that has been resolved by the completion of construction of a new beamline dedicated to footprinting. Prior to this summer, all footprinting experiments 

had been conducted as a guest user on beamline X-19A of the NSLS. When the 

technology was under proof-of-principle development, this was not a hindrance. 

Generally, one beamline experimental day every 10 was available and the progress 

of experimentation was adequate. As the method has become more reliable not 

enough beamtime was available. 

The Resource had previously abandoned the construction of beamline X-gA, as 

a copy of beamline X-gB, since there was not a demonstrated need for a full second 

line devoted to XAS and diffraction. Yet, the beamline was substantially complete 

and the Resource, along with funds provided from the grants of Dr. Brenowitz and 

Dr. Chance, had the capability and expertise (in the person of Mr. Sullivan) to 

complete the line as a white beamline station, substantially closer to the source 

than X-19C, thus with an estimated 3-4 fold increased. As of 9/30/96, this station 

is in regular use. Thus, in the coming year, a substantial increase in footprinting 

results is expected. 

1-We currently have available to users a stopped flow device for rapid mixing and 

exposure to the x-ray beam. 

2-We also have a fast shutter for precisely defining the exposure time for ’7~tati~’7 

experiments. 
I AUTOFIT 1.0 : A New Software for XAS Global Mapping I X9B I ~ 

M.R.Chance, W. Huang, E.Scheuring (AECOM) 

We have developed a global mapping procedure, where crystal strutucre coordinates are refined to XAS data using the ab initio XAS code FEFF 6.01. A grid 

of hundreds of simulations are directly compared to the experimental data without 

the use of non-linear least squares fitting procedures to find the interatomic distances. Instead, each simulation is performed with different interatomic distances. 

The emphasis is on mapping the local and global minima and providing a detailed 

visual picture and error analysis in the comparison of alternative structures. 

The three dimensional structural coordinates utilized in the simulations are based 

on crystal structure models derived from structural databases. Thus, a particular 

geometry for the metal site is incorporated in this choice. Alternative structures 

with different geometries can also be selected, processed, and compared. This makes 

the structural assumptions about the site explicit and they must be justified based 

on ancillary structural information. Our suite of programs (called AUTOFIT 1.0) 

vary selected bond distances, compare the resulting ab initio simulations to the 

experimental data, and compute and plot a figure that displays 400-500 alternative 

solutions simultaneously. These programs are available to outside users free of 

charge and have been readied for release along with a manual for using the code. 

X9B Global Mapping of EXAFS Data : Structure of the Photoproduct of 

Mb*CO 

M.R. Chance, E. Scheuring, W. Huang (AECOM) 

X-Ray methods based on synchrotron technology have the promise of providing 

time- resolved structural data based on the high flux and brightness of the X-Ray 

beams. One of the most closely examined problems in this area of time-resolved 

structure determination has been the examination of intermediates in ligand binding to myoglobin. Recent crystallographic experiments using synchrotron radiation have identified the protein tertiary and heme structural changes that occur upon photolysis of the myoglobin-carbon monoxide complex at cryogenic temperatures Schlichting, I., Berendaen, J., Phillips, G, Sweet, R. Nature, 371, p.808-812 

(I994f). However, the precision of protein crystallographic data ( 0.2 A) is insufficient to provide precise metrical details of the iron-ligand bond lengths. Since 

bond length changes on this scale can trigger reactivity changes of several orders of 

magnitude, such detail is critical to a full understanding of metalloprotein structurefunction relationships. 

Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy has the potential for analyzing bond distances to a precision of 0.02 A, but is hampered by its 

relative insensitivity to the geometry of the backscattering atoms. Thus, it is often 

unable to provide a unique solution to the structure without ancillary structural information. We have developed a suite of computer programs that incorporate this 

ancillary structural information and compute the expected experimental spectra for a wide ranging series of Cartesian Coordinate sets. The programs systematically increment the distance of the metal to various coordinating ligands (along with their 

associated higher shells). Then, utilizing the ab initio EXAFS code FEFF 6.01, 

simulated spectra are generated, compared to the actual experimental spectra, and 

the differences computed. Thus, the details of the local minimum as well as the 

global problem are revealed in a single plot. This allows direct evaluation of the 

adequacy of competing solutions. 

The power of these programs are demonstrated in the examination of high signal 

to noise EXAFS data from a photolyzed solution sample of the myoglobin-carbon 

monoxide complex at 10 K. Evaluation of this data using our global mapping procedures placed the iron to pyrrole nitrogen average distances close to the value for 

deoxy myoglobin (2.05 +/-0.01 A), while the distance from iron to the proximal 

histidine nitrogen is seen to be 2.20 +/- 0.04 A. It is also shown that one cannot 

uniquely position the CO ligand based on the EXAFS data alone, as a number of 

reasonable minima (from the perspective of the EXAFS) are observed. This provides 

a reasonable explanation for the multiplicity of solutions that have been previously 

reported. The results presented here are seen to be in complete agreement with the 

crystallographic results within the respective errors of the two techniques however, 

the Extended X-Ray Absorption Fine Structure data allows the iron-ligand bond 

lengths to be precisely defined. 
sd 

(0 I Time-Resolved X-ray Spectroscopy on Microsecond Timescales I X9B 1 

M.Ryhance, E. Scheuring, A. Xie (AECOM) 

Time-resolved structure determinations are at the forefront of attempts to understand the mechanisms of protein reactions. We have demonstrated a system for collecting high quality x-ray absorption spectroscopy data on microsecond timescales. 

The method can be used for both full spectra accumulation and kinetic spectrophotometry. These experiments have vast potential, not only for examining metalloproteins, but also for observing the dynamic behavior of a wide range of chemical 

elements in conjunction with photochemical, rapid mixing, and temperature jump 

techniques. The following accomplishments have been made in the preceeding 12- 

month period: 

1 We have successfully increased the effective X-ray flux more than 10 fold by 

2) We have increased the signal-to-noise ratio by nearly 3 times, with the design, 

construction and reliable operation of time-resolved 14 channel window discriminator copuled to a computer controlled data acquisition system. 

3) We have permanently installed a 20 Hz Nd-YAG laser system with 532 and 

355 nm pump beams on beamline X-9B for initiating time-resolved photo-reactions. 

4) We have published two papers detailing these improvements, along with several published abstracts and meeting presentations and have another manuscript in 

imp I ementing the sagittal dynamic focusing monochromator. 

preparation. 

5) We have examined the dynamics of the myoglobin-CO photoproduct after a 

laser flash and observe the transit of water into the heme pocket consistent with 

the last step of the photo-dissociation reaction. 

X-ray Reflectivity of Mechanically and Optically RubbedPolyirnides I* _______~ 

S. S. Ghosh, P. A. Heiney, M. R. Stetzer, 0. Y. Mindyuk (UPenn) and S. T. Sun 

(Alliant Techsystems) 

We have measured the X-ray reflectivity of rubbed polyimide films used for liquid 

crystal alignment. Both mechanically rubbed polyimides and polyimides 'rubbed' 

by linearly polarized UV light were examined. The mechanical rubbing process 

creates microgrooves on the surface of the polyimide film. These microgrooves 

have a particular average spacing perpendicular to the rubbing direction, but in 

general run parallel to the rubbing direction. The off-specular reflectivity from a mechanically rubbed film featured additional intensity when the film was oriented 

with its rubbing direction parallel to the incident X-ray beam. This off-specular 

scattering arises from the height-height correlations of the microgrooves to the filmglass interface. 

The analysis of the specular reflectivities obtained from these films will produce 

a comparison of the roughness associated with both mechanically and optically 

rubbed films, parallel and perpendicular to the rubbing direction. We are able 

to use specular reflectivity to deduce an anisotropy in the roughness along the film 

surface because our resolution function is asymmetric. Since the resolution function 

extends much farther out of the scattering plane than in the scattering plane, the 

specular reflectivity can provide more information than just the electron density 

perpendicular to the surface. Some information about the film along its surface can 

also be deduced from the reflectivity. 

Figure 1. The reflectivity of a mechanically rubbed polyimide film with the rubbing 

direction a) parallel and b) perpendicular to the incident X-ray beam. The Kiessig 

fringes, total external reflection and the off-specular scattering are all evident in the 

image. 

* This work was supported by NSF Grant No DMR MRL 92-20668 and DMR 93-15341 
- ~ ~~ 

XAS Studies of the Structure and Function of Ni in Chromatium 

Vinosum Hydrogenase 

Z. Gu, C.B. Allan, S.B. Choudhury, M.J. Maroney (U. of Massachusetts) 

X9B 

The Ni, Fe hydrogenases (Hzases) usually exhibit five forms with distinct epr 

spectral characteristics and spanning four oxidation states. One question central 

to understanding te mechanism of the enzyme is the degree of participation of Ni 

center in the redox chemistry. Of the five forms, A and B have the same oxidation 

state both are oxidized), but differ greatly in their rates of reductive activation, and 

(SI) and then to form C, which is an active redox state of the enzyme and exhibits 

a distinct epr signal from an S = 1/2 center containing Ni. The enzyme can be 

further reduced to form R, which is fully reduced and epr silent. 

This report summarizes an XAS structural study of the Ni site in Chromatium 

vinosum Hzase as a function of redox poise. Data are presented for forms A, B, C, 

and R. Figure 1 shows the comparison of the Ni K-edge XANES spectra for these 

four forms. They reveal a maximum shift in the edge energy of 1.4(2) eV from B to 

R. A peak assigned to a ls+3d transition is discernible in all four spectra, but is 

ca. 3 - 6x larger in the oxidized forms (A and B) relative to the reduced forms 

and R None of the spectra reveal a ls+4p, (plus shakedown) transition near t e 

EXAFS spectra obtained from the four forms. The best fits to the data are Form 

A: 3 S 2.19(2)A + 2 N(0) 1.91(2) A + 1 Fe 2.69(5) 8; Form B: 3 S 2.10(2) A+ 3 

S 2.56(2).&; Form C: 4 S @ 2.20(2)A + 1 Fe 2.54(5) A; Form R: 2 S 2.16(2)A + 2 

S 2.22(2) A -t 1 S 2.66(5) A. These fits indicate the difficulty of discerning a Ni-Fe 

vector expected at 2.6 A in the presence of a long S scattering atom at a similar 

distance, as predicted from the crystal structure of the Hzase form D. gigas . They 

predict that the coordination sphere of the Ni contains only S in all but form A. 

This work is supported by NIH grant GM-38829 (MJM). Samples of C,v, H 2ase 

were provided by Simon P.J. Albracht (U. of Amsterdam). We are grateful for 

technical support from Hai Yang and Michael Sullivan. 

have 6 istinct epr spectra. Forms A and B are reduced to an epr silent intermediate 

r 

edge t h. at is diagnostic for four-coordinate planar geometry. Figure 2 compares the 

Structure and Kinetics: A Molecular Basis for Ligand AffiGty In 

Hemeprot eins 

C. Lee, E. Scheuring, M.R. Chance, J. Peisach (AECOM) 

This investigation aims at understanding the relationship between metal-ligand 

electron- nuclear couplin and bond lengths in oxyCo 11) porphyrin complexes, 

functional and paramagnetic analogues of 02-carrying hemoproteins. Coupling of 

the unpaired electron on the oxyCo unit of these proteins and models to an axial 

cobalt-bound 14N nucleus can be studied by electron spin echo envelope modulation (ESEEM) spectroscopy. The magnitude of the ESEEM-derived 14N electronnuclear hyperfine coupling and nuclear quadrupole coupling constants have been 

correlated with the electronic configuration of the trans cobalt- dioxygen bond. 

Both ligand hyperfine and nuclear quadrupole coupling decrease with an increase 

in the ionicity of the cobalt-dioxygen bond, i.e., its electronic structure shifts from a Co2+-02 towards a co3+- 02- configuration. An increase in the ionicity of the 

cobalt-oxygen bond would also suggests a shorter bond. Furthermore, a decrease in 

the axial 14N nuclear quadrupole coupling is indicative of an increase in the overlap 

between the 14N sp2 hybrid and the Co dz2 orbital and thus implies a decrease in 

the axial cobalt-nitrogen bond length. The present study therefore aims at testing 

the hypothesis that a decrease in cobalt-axial nitrogen electron-nuclear coupling is 

accompanied by a shortening of both the axial cobalt- nitrogen bond and the trans 

cobalt-oxygen bond using EXAFS spectroscopy. 

Axial cobalt-ligand bond length measurements have been carried out on several sets of samples. The first set is oxyCo[tetraphenylporphyrin(TPP)][lmethylimidazole (1-MeIm ] in 100 percent toluene, 9:l (v/v) toluene:CHZC12 and 

1:l toluene: CH2C12. ES k EM studies has found decreases 14N(l-MeIm) electronnuclear couplings with increasing polarity of the solvent (Aiso from 3.14 to 2.75 

MHz, e2qQ from 2.32 to 2.25 MHz . The second set of samples is oxyCo[(oNHCONHCGH5. The amide proton on R, the para substituent of one of the meso phenyls of TPP, is believed to interact electrostatically with the cobalt-bound axial 

02. ESEEM studies has found decreases in 14N( 1-MeIm) electron-nuclear cou- plings with increasing electron- withdrawing strength of R (or increasing acidity 

of the amide proton) (Aiso from 3.14 to 2.57 MHz, e2qQ from 2.32 to 2.13 MHz). 

EXAFS spectroscopy is used to test whether shorter cobalt-oxygen and shorter 

cobalt-nitrogen bonds are found for those complexes with smaller electron-nuclear 

coupling constants, Using our global mapping technique, we have seen that for the 

cobalt model compound in toluene, the iron oxygen bond length is 1.90 A, the ironimidazole bond length is 2.00 A, and the average distance of iron to the equatorial 

nitrogen bond lengths is 1.96 A (Co-Np). EXAFS studies of the methylene chloride 

induced structure show a contraction of the Co-Np distance by 0.02 A and a con- traction of the Co-N axial imidazole distance by 0.05 A, while the cobalt-oxygen 

distance is unchanged within the error. This provides a definitive structural correlation for the changes seen in ESEEM data and illustrates a strutctural mechanism 

for controling oxygen binding rates. 

X9B 

active site models of Cof11)- substituted globins. Co(1 I )-substituted globins are 

R)lTPP][l-MeIm] in 2.26 toluene, w h ere R=H, NHCOC(CH3)3, NHCOCH3 and 

Figure 1. Ni K-edge XANES of Spectra 

taken on redox poised samples of ChroFigure 2. Ni K-edge EXAFS Spectra 

W taken on redox poised samples of ChroCD matium vinosum hydrogenase. matium vinosum hydrogenase. -4 
1 Biological Metal Clusters 1 X9B 1 

M. Maroney, S. Choudhury, C. Allan, Z. Ge (U Mass) 

Enzyme and protein active sites containing two or more interacting metal centers now figure prominently in metallobiochemistry. Systems containing metal clusters composed of Fe atoms (e.g. ferredoxins, sulfite reductase, hemerythrin, ribonucleotide reductase, methane monooxygenase), Cu atoms (e.g. hemocyanin, 

tyrosinase, ceruloplasmin), Mn atoms (photosystem 11, catalase) and more than one element, or heteropolynuclear clusters (e.g. nitrogenase-Mo,Fe; cytochrome 

oxidase-Fe,Cu; hydrogenase and carbon monoxide dehydrogenase-Ni,Fe), have been 

identified. The ultimate goals of this project are to elucidate the structures of metal 

clusters in metalloproteins, to determine the roles these clusters serve in the function of the protein, and to understand how nature designs a cluster for a specific 

purpose. This knowledge will provide a detailed understanding of biological processes and will aid in the design of pharmaceutical enzyme inhibitors and catalysts 

for various reactions. During the current report period, we have completed studies of the structural changes that occur in the Ni site in Thiocapsa roseopersicina 

hydrogenase during the binding of CO, a competitive inhibitor of the enzyme that 

has been shown to bind in a terminal fashion to the enzyme. The XAS studies do 

not show any evidence that the CO molecule binds directly to the Ni site. The 

CO complex is light sensitive and exhibits reversible photodissociation of the CO 

ligand. During photochemical cycling, the edge energy shifts by 0.5 eV in a cyclic 

fashion, suggesting that the CO binds near the Ni site and influences its electronic 

structure. A likely binding site is the Fe atom 2.7 A distant from the Ni in the 

recently published crystal structure of the D. gigas enzyme. These results support 

earlier studies indicating that Ni is not the substrate/inhibitor binding site in the 

enzyme. 

A Low Angle Diffraction Study of the Effects of Nucleotide Binding 

on the Structure of the Actomyosin Complex 

K. Poole, P. Ellison, M. Lorenz, K. Holmes, '(Max Planck Inst.), G. Evans, G. 

Rosenbaum, (ANL), P. Boesecke (ESRF), C. Cremo (Wash. St. U) 

With an atomic model for the actin filament (Holmes et.al. 1990, Nature, 347: 44- 

49; Lorenz et. al. 1995, J. Mol. Biol. 246: 108-119) and the atomic coordinates for 

at least one form of the myosin motor protein (Rayment et.al. 1993, Science 262: 50- 

58) we are in a position to make use of high angle fibre diffraction data from myosin 

decorated actin filaments to refine a model structure of the complex. Nucleotidefree myosin subfragment-1 (Sl) isolated from both chicken skeletal and smooth 

muscles was introduced into overstretched rabbit psoas muscle fibres. In both cases 

the protein binds tightly to actin and this results in the intensification of the actin 

based layer lines in the X-ray pattern. Refining an actomyosin atomic model against 

the nucleotide-free skeletal S1 data produced a best fit which was similar to the 

model suggested by Rayment et. al. (1993) based on electron microscope evidence. 

ADP binding had very little effect on this diffraction pattern. The nucleotide-free 

(unphosphorylated or thiophosphorylated) smooth muscle S1 decorated filaments 

produced a very different diffraction pattern and the binding of ADP was shown 

to induce a structural change in the head resulting in a pattern similar to that 

from skeletal S1 decorated fibres. The Kd for ADP binding was shown to be ca. 2 

micromolar. 

It is most interesting that the two rigor complexes are structurally different. If 

the rigor structure represents the end of the power stroke then the data imply that 

at least some part of the power stroke in these two motors is produced by different 

configurational changes of the actomyosin complex. Alternatively, we must question 

our interpretation of the rigor structures themselves. We are in the process of 

refining the model against the smooth muscle S1 data but it is clear that the ADP 

induced structural change in the myosin head is very large and certainly involves 

the distal part of the head. This may reflect the tail wagging motion described 

by Whittaker et. al. 1995, Nature 378: 748-751, from their electron microscopic 

evidence. 

Data were collected on Fuji imaging plates at beamlines X9B at the NSLS, 

Brookhaven and BL4, ID2 at the ESRF, and scanned using a Fuji BAS2000 system. 

X9B 
The E. Coli Primase Zinc Structure is Sensitive to the Binding of 

ATP and High Magnesium 

L. Powers, M. Griep (Utah State U.) 

X9B 

Enzyme and protein active sites containing two or more interacting metal centers 

now figure prominently in metallobiochemistry. Systems containing metal clusters composed of Fe atoms (e.g. ferredoxins, sulfite reductase, hemerythrin, ribonucleotide reduct we, methane monooxy genase) , Cu atoms (e.g . hemocyanin, 

tyrosinase, ceruloplasmin), Mn atoms (photosystem 11, catalase) and more than one element, or heteropolynuclear clusters (e.g. nitrogenase-Mo,Fe; cytochrome 

oxidase-Fe,Cu; hydrogenase and carbon monoxide dehydrogenase-Ni,Fe), have been 

identified. The ultimate goals of this project are to elucidate the structures of metal 

clusters in metalloproteins, to determine the roles these clusters serve in the function of the protein, and to understand how nature designs a cluster for a specific 

purpose. This knowledge will provide a detailed understanding of biological pro- cesses and will aid in the design of pharmaceutical enzyme inhibitors and catalysts 

for various reactions. During the current report period, we have completed studies of the structural changes that occur in the Ni site in Thiocapsa roseopersicina 

hydrogenase during the binding of CO, a competitive inhibitor of the enzyme that 

has been shown to bind in a terminal fashion to the enzyme. The XAS studies do 

not show any evidence that the CO molecule binds directly to the Ni site. The 

CO complex is light sensitive and exhibits reversible photodissociation of the CO 

ligand. During photochemical cycling, the edge energy shifts by 0.5 eV in a cyclic 

fashion, suggesting that the CO binds near the Ni site and influences its electronic 

structure. A likely binding site is the Fe atom 2.7 A distant from the Ni in the 

recently published crystal structure of the D. gigas enzyme. These results support 

earlier studies indicating that Ni is not the substrate/inhibitor binding site in the 

enzyme. 

Active Site Targeting of Protein Tyrosine Phosphatase 1B by Synchrotron Crystallography 

Y. A. Puius, Y. Zhao, M. Sullivan, D. Lawrence, Z.-Y. Zhang, S. C. Almo (Albert 

Einstein College of Medicine) 

A collaborative project between Dr. Steven Almo (crystallographer), Dr. ZhongYin Zhang (enzymologist) and Dr. David Lawrence (synthetic chemist) has been 

established in order to design potential therpeutic agents based on the structures of 

protein tyrosine phosphatases. Since data collected on a rotating anode source have 

not been of sufficient resolution to adequately define the binding mode of ligands 

to the proteins in question, this effort has been undertaken using single-crystal 

diffraction data collected at beamline X9B. 

Using synchrotron methods, the structure of human protein tyrosine phosphatase 

1B (PTPlB) has been solved in complex with several synthetic non-peptide substrates to high resolution. The most promising of these complexes has been the 

structure (1.98 resolution, Rmerge = 5.2010, Rcryst = 18.2%) of an inactive mutant of PTPlB bound to a compound with a micromolar K,. It was expected 

that this ligand, a phosphotyrosine mimic, would bind in the active site; however, 

it actually possessed two mutually exclusive binding modes, one in the canonical 

pTyr-binding site, and the second in a previously unobserved phosphophenyl binding site. Since pTyr had not been seen to bind outside the active site before, this 

prompted a crystallographic investigation of PTPlB crystallized in the presence of 

high (> lOK,) concentrations of pTyr. In this high pTyr-complex (l.85A resolution, Rmerge = 4.2%,Rcryst = lS.l%), the second phosphotyrosine was in fact 

observed at the same location where the second non-peptide ligand bound. 

The elucidation of this second phosphotyrosine-binding site has provided information crucial to the design of a new class of tight-binding inhibitors of high specificity 

for PTPlB, which is becoming more important as the role of PTPlB in oncogenesis 

and non-insulin dependent diabetes mellitus becomes clear. 

Additional experiments include the solution of complexes between PTPlB and 

peptides to understand the determinants for binding extended substrates. One of 

these complexes (1.9A resolution, Rmerge = 3.5%, P212121, a = 66.35 A, b = 72.54 

8, c = 88.47 A) is currently undergoing refinement. 

X9B 
P 

c 

8 I EXAFS Studies of Nonheme Iron Enzymes I X9B 1 

L. Que, L. Shu, X. Wang, S. Mandal, K. Chen (U. of Minnesota) 

Several metalloproteins containing nonheme-iron centers have been investigated 

in the past year. This class includes methane monooxygenase, purple acid 

phosphatase, and stearoyl-ACPA-9 desaturase. Data was collected on methane 

monooxygenase hydroxylase (MMOH), one of the most extensively studied dilron enzymes. XAS analysis of MMOH suggests the presence of two Fe-Fe distances of about 3 A and 3.4 A, which are proposed to reflect two populations of 

MMOH molecules with either a bis(p-hydroxo) (p-carboxy1ato)- or a (phydroxo)(pcarboxylato) diiron 111) core structure, respectively. This paper has been published 

purple acid phosphatase from porcine uterus which allows us to look at the Fe(II1) 

and the Zn(I1) sites separately. In the phosphate complex of this derivative, the 

observation of Fe-Zn and M-P (M = Fe, Zn) distances of 3.3 and 3.2 A, respectively, 

indicates an FeZn(OR)2 core structure and phosphate is proposed to bind to the 

metal center in a bridging mode. This paper is in press (2). EXAFS data are being 

processed on stearoyl-ACPA-9 desaturase, which is a new member of the class of 

nonheme diiron enzymes. With the crystallographic data available for hemerythrin, 

ribonucleotide reductase and the hydroxylase component of methane monooxygenase, kidney bean phosphatase, and EXAFS data for the other proteins, we will be 

able to identify the common structural features that make up these dimetallic sites 

within this class and to discern the variations in structure that control mechanism 

and function. 

EXAFS analysis has also been crucial for the structure determination of unstable 

model complexes related to intermediate of nonheme proteins. Data was taken and 

analyzed on copper model complexes modeling copper dioxygen chemistry in metalloproteins, and this paper is in press (3). EXAFS data on iron model complexes 

have also been taken and are being processed. 

1-Shu, L., Liu, Y., Lipscomb, J.D., Que, L. Jr. "X-Ray Absorption Spectroscopic 

Studies of the Methane Monooxygenase Hydroxylase Component from Methylosinus trichosporium OB3b." JBIC 1, 209-217 (1996). 2-Wang, X., Randall, C.R., 

Que, L. Jr. "X-Ray Absorption Spectroscopic Studies of an FeZn Derivative of 

Uteroferrin." Biochemistry (1996 , in press. 3-Mahapatra, S., Halfen, J.A., Wilkinman, W.B. "Structural , Spectroscopic, and Theoretical Characterization of Bis(m0xo)dicopper Complexes, Novel Intermediates in Copper-Mediated Dioxygen Activation." J. Am. Chem. SOC. (1996) in press. 

(1). We have also co (ll ected and analyzed data on an Fe(II1) Zn(I1) derivative of the 

son, E.C., Pan, G., Wang, X., 3 oung, V.G., Jr., Cramer, C.J., Que, L., Jr., TolXAFS Analysis of a Transition State Inhibitor of Chloroplast CF-1 

ATPase 

I. Sagi, C. Carmelli (Weismann Inst.) 

X9B 

The membranes of chloroplast mitochondria and bacteria contain a proton ATPase which utilizes the electrochemical potential of protons for the synthesis of ATP 

from ADP and Pi. Similar to enzymes of other energy-transducting membranes, the 

chloroplast H+ ATPase consists of an intrinsic membrane sector CFO which mediates proton translocation and an extrinsic catalytic section CF1. From the known 

chemistry of GTP and ATP hydrolysis in other systems, it might be expected that 

catalysis in F- type ATPase proceeds through a pentacovalent phosphate intermediate. A penta-covalent phosphorous is also assumed to be a transition state 

intermediate since it is readily inhibited by the Pi analog vanadate. X- ray Absorption Fine Structure (XAFS) data on vanadium edge were collected on vanadate-CF1 

complex. Direct XAFS analysis of the pre-edge transitions and the EXAFS region 

clearly show a pentacovalent structure at the active site. These results suggests that 

a pentacovalent phosphorous exists as a transition state during ATP hydrolysis in 

CF1-ATPase from chloroplast. 
I Fe-S Centers in Energy Transducing Enzymes I X9B I 

I. Sagi, Z. Mingtao, C. Carmelli (Weizmann Inst.) 

Light absorbed by the photosynthetic pigments induces charge separation in photosystems I (PSI) driving electron transport from water to NADP+. One of the 

early electron acceptors in photosystem I (PSI) is a very low potential iron-sulfur 

cluster, Fx. Understanding the mechanism of action of PSI requires a knowledge 

of the structure of Fx and the structural changes induced by the electron transfer 

process through Fx. Although many of the components of PSI and their function 

are known, there is a little information about their special arrangement and their 

interaction with the amino acid residues of the polypeptide chains. Site directed 

mutations were performed on the psaB gene from the cyanobacterium on the two 

conserved cysteines 556 and 565. Each cysteine was substituted once with serine 

and once with histidine resulting in overall of four mutants of the B subunit, these 

cysteines are proposed to serve as two of the four ligands that binds the iron in Fx. 

We present the X-ray absorption fine structure XAFS) spectra of the mutated Fx 

site provides a direct assignment of the different ligands. 

in comparison to the native Fx spectra. The X 6 FS analysis of the mutated metal 

I Solution Iron-Edge XAS of Native Soybean Lipoxygenase-1 I X9B I 

R. Scarrow, N. Taufen, R. Ghiladi (Haverford Coll.) 

Lipoxygenases catalyze reactions of polyunsaturated fatty acids with dioxygen 

to form lipid hydroperoxides; in humans this is the first step in production of 

leukotrienes from arachidonic acid, a process involved in inflammatory response. 

All lipoxygenases have conserved amino acid sequence regions, a single non-heme 

iron, and share many spectroscopic and kinetic properties. 

Two independent crystal structures of the inactive native form of soybean lipoxygenase establish three histidine residues and the C-terminal carboxylate as ligands 

to the iron(I1) (Boyington, J. C.; Gaffney, B. J.; Amzel, L. M. Science 1993, 260, 

1482-1486; Minor, W.; Steczko, J.; Bolin, J. T.; Otwinowski, Z.; Axelrod, B. Biochemistry 1993, 32, 6320-6323. An asparagine side-chain carbonyl is suggested to 

which could be occupied by a water ligand. Our previous EXAFS analyses of frozen 

solutions of native lipoxygenase indicate a predominantly five-coordinate environment for the iron (11), but that this can be shifted to a six-coordinate environment 

by addition of 20 mM methanol, or higher concentration of glycerol, prior to freezing. As the coordination number increases, the average bond length increases by 4 

pm, from 213 pm to 217 pm (Scarrow, R. C.; Trimitsis, M. G.; Buck, C. P.; Grove, 

G. N.; Cowling, R. A.; Nelson, M. J. Biochemistry 1994, 33, 15023-15035). We 

recently re-investigated the effects of methanol on the X-ray absorption spectrum 

of native lipoxygenase, this time in solution at 4 C. The experiments were carried 

out at beam line X9B using a solution cell and constant temperature bath provided 

by the beam line. The spectra change very little for 0 to 10 percent (2 M) methanol, 

and are all similar to the spectrum of native lipoxygenase frozen without methanol. 

The refined bond lengths from EXAFS are 212 pm. Thus the iron(I1) in native 

soybean lipoxygenase-1 remains five-coordinate upon addition of methanol unless 

the sample is subsequently frozen. 

bind iron in one structure, an d both structures show a "vacant" coordination site 
td 

P fs Global Mapping of XAS Data from Cobalamin Enzymes X9B 

E. Scheuring, M. Chance (AECOM), R. Banerjee (U. of Nebraska.), R. Matthews 

(U. of Michigan) 

Cobalamin ezymes are unique in biology as the only active organometallic species 

known (cobalt-carbon bonds). The octahedral cobalt centered cofactors carry out 

critical methylation reactions and unusual carbon-carbon bond rearrangements in 

amino acid biosynthesis and fatty acid metabolism. Substantial progress in un- derstanding the structure-function relationships of these enzymes was recently provided. Crystallographic data on the 27 kDa fragment of the methyl-cobalamin 

(Mecbl) dependent enzyme methionine synthase (MS) from E. Coli [C. L. Drennan 

et al. Science, 266, 1669 (1994)] and on the 5-deoxyadenosyl-cobalamin Adocbl) 

dependent enzyme methylmalonyl-coenzyme A mutase (MMCoA) from bropionibacterium shermanii [F. Mancia et al. Structure, 1996, 4, 339.1 show that in both 

enzymes the cofactor undergoes dramatic structural changes upon enzyme binding. 

The most significant change involves the dimethylbenzimidazole (DMB) group of 

the cofactor, which in both cases is detached from cobalt and replaced by a His 

group of the enzymes. 

Both X-ray crystallographic structures have their limitations; the MS structure 

at 3 A resolution is not able to show distance variations in the cofactor structure in 

the order of 0.2 A or less with respect to the free cofactor state and the MMCoA 

structure was collected on a dominantly Co(I1) form of the cofactor lacking the 

adenosyl moiety. 

In order to examine the cobalt-ligand bond distances of free cofactor compared 

to enzyme bound species, we have collected XAS and compared it to FEFF calculations. Our results show that the structure of the cofactor stays the same in 

the Mecbl dependent enzyme MS both in the wild type Co(II1)-methyl and in the 

Co(I1 forms with respect to the free states but changes in the Adocl dependent 

A) similar to the crystallographic data which shows a 2.5 A Co-N axial distance 

for the Co(I1) state. Our EXAFS data for the Co-C bond shows two minima, one 

at around 1.99 A and one at 2.25 A. Based on recent RR data [R. Banerjee at al., 

unpublished results], the longer distance can be ruled out. 

We have also examined mutant forms of MS to examine the role of the His759, 

Asp757, and Ser810 residues in the hydrogen bonding network that controls the 

electronic structure of the ligand trans to the cobalt-carbon bond. X-ray edge results 

(in agreement with EPR data) on the Co(I1) form of the MS mutant H759G shows 

that replacing His759 with a Gly residue causes the formation of a four-coordinate 

species (identified by the b4pz transition with no Gly ligation to the Co. This 

mutant shows five magnitude decrease in the catalytic activity with respect to the 

wild-type Co(I1) (Matthews et al., Biochemistry, submitted). This is supported by our earlier result that a four-coordinate Co(I1) corrinoid species is very unstable 

(Wirt et al., J. Am. Chem. SOC., 1993, 115, 5299 and Scheuring et al, J. Phys. 

Chem., 1996, 100, 3344). The EXAFS results also support a four-coordinate species 

with an average Co- Neq distance of 1.89f0.01 A similar to other cobalamin species. 

The Co(I1) form of mutant D757N, in which Asp757 is replaced by a Glu, indicates 

similar geometry to that of the wild-type Co(I1). EPR data shows that this mutant 

is 70% bas-off and its activity is impaired by 50-fold. These results show that His759 

in MS is essential to the catalytic activity and any change in the hydrogen bonding 

network decreases the activity substantially. 

MM d oA. The Co-N axial bond to the DMB of Adocbl in MMCoA is very long (2.45 

The Relationship Between Structure and Conductivity in Polymer 

Electrolytes 

L. Sharpe, L. Lyons (Grinnell Coll.) 

This project involves the investigation of the coordination environments around 

transition metal ions incorporated in oxymethylene-linked poly ethylene oxide , OPEO, and poly[bis((methoxyethoxy)ethoxy)phosphazene], MEE L , using EXA d S 

spectroscopy. Both polymers exhibit ionic conductivity when mixed with various 

inorganic salts. They have the advantage of being completely amorphous at room 

temperature, an important property for high ionic conductivities. Little is known 

about the coordination environment around the metal or counter ions in the polymer 

salt complexes. We have systematically studied the ionic conductivity, composition, 

and ion coordination environment in the polymer electrolyte composed of CuC12 

dissolved in OPEO. The objective of this work is to determine the extent ion pairing 

occurs and how it effects the ion conductivity. The experimental strategy involved 

the preparation of a series of polymer electrolytes of varying CuC12 concentration in 

OPEO and then correlating the resulting conductivities to the copper coordination 

environment. We have found that both chloride ion and oxygen are present in the 

copper coordination sphere and that the degree of chloride ion coordination does 

affect the conductivity by reducing the number of free ions. In addition, the fact 

that Tg (glass transition temperature) varies in a similar manner as the C1/0 coordination ratio suggests that the chloride ions are in effect cross-linking the polymer 

chains which increases Tg. The increase in Tg indicates a reduction in polymer 

motion which also contributes to the decrease in the ion conductivity. This work 

has been published in RChemistry of MaterialsS(Vo1. 6, 1994, 1912). Presently, we are finishing work on the OPEO-CuBr2 system in which we have collected both 

Cu and Br EXAFS data. In the latest experimental run, we collected data on the 

MEEP-CuBr2 polymer electrolyte system. It will be interesting to compare the 

CuBr2 coordination environments in the comb branched MEEP polymer system to 

the linear OPEO polymer system. 
1 Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants 

R. Sinclair, S. Hallam, M. Chen, L. Powers (Utah St. U.), B. Chance (U. of Penn.) 

The globins and peroxidases, while performing completely different chemistry, 

share features of the iron heme active site: a protoporphyrin IX prosthetic group 

is linked to the protein by the proximal histidine residue. X-Ray absorption spectroscopy (XAS) provides a method to determine the local structure of iron heme 

active sites in proteins. Our previous studies usin X-Ray absorption spectroscopy 

have revealed a significant difference in the Fe-N ?e) bond length between the peroxidases and the globins (for a review, see Powers, L. in Molecular Electronics and 

Molecular Electronic Devices 3, 211: 1994, CRC Press Inc., Boca Raton, Florida). 

Globins typically have a Fe-N (e) distance close to 2.1A while the Fe-N (e) distance 

in the peroxidases is closer to 1.9A. We have proposed (Sinclair, R., Powers, L., 

Bumpus, J., Albo, A,, Brock, B. Biochem. 31: 4892, 1994) that strong hydrogen 

bonding to the proximal histidine is responsible for the shorter bond length in the 

peroxidases. Here we use site-specific mutagenesis to eliminate the strong proximal 

hydrogen bonding in cytochrome c peroxidase and to introduce strong proximal 

hydrogen bonding in myoglobin. Consistent with our hypothesis, elimination of the 

Asp-235-His hydrogen bond in CcP results in elongation of Fe-N (e) from 1.9 to 

2.1A. Conversely, introduction of a strong proximal hydrogen bond in myoglobin 

shortens Fe-N (e) from 2.1 to 1.9A. These results correlate well with other biochemical data. 

Time-Resolved RNA Footprinting: Structure-Function of Splicing Intermediates of the Tetrahymena Ribosyme 

S. Woodson (Univ. of Md.), M. Brenowitz, B. Sclavi, M. Sullivan, M. Chance 

(AECOM) 

The Mg2+ bound and Mg2+ free forms of the RNA ribosyme exhibit distinctly 

different patterns of hydroxyl radical reactivity. This illustrates the structural 

changes as solvent accesible regions become protected from hydroxyl radical (OH) 

attack upon folding. 

Thermodynamic analysis of ribozyme folding. The Tetrahymena ribosyme adopts 

a compact tertiary structure upon the addition of divalent cations. Protection from 

OH cleavage is believed to predominantly result from the decreased solvent accessibility of the phosphodiester backbone within the interior of the folded ribosyme. 

Thus, the isotherms and progress curves determined from the OH protection data are interpreted to reflect the folding of the ribozyme. It is assumed in this analysis 

that the rate of OH cleavage of RNA is linearly related to the solvent accessibility 

of the phosphodiester backbone. Quantification of individual sites of protection as 

a function of [Mg2+] reveals that the domains of the ribozyme bind Mg2+ with 

unique values for cooperativity and/or stoichiometry. 

The three sites analyzed within the P3-P7 domain are all characterized by Hill coefficients (nH) of 3-4, consistent with the high Mg2+ cooperativity observed in other 

studies.The equivalence of nH values for the three sites within the P3-P7 domain is 

indicative of the highly concerted nature of Mg2+ binding by the ribosyme. The 

high cooperativity of the Mg2+-dependent folding of the P3-P7 domain contrasts 

with the more moderate values (nH values clustering around 2) determined for the 

other domains of the ribosyme; these values are comparable with the "average" 

value of nH = 3 determined previously. The conclusion that can be drawn from 

these results is that the effects of Mg2+ ion binding are not uniformly distributed 

throughout the ribosyme. It is tempting to speculate that the binding of an additional Mg2+ ion is linked to the folding of the P3-P7 domain since nH cannot 

exceed the stoichiometry of the binding reaction. owever, identical Mg2+ stoiconcerted in the P3-P7 domain is an interpretation not excluded by the data 

main is consistent with the conclusion that Mg2+ binding follows the rate-limiting 

folding of P3 to form the active ribozyme. In the three-dimensional model of the 

Tetrahymena ribozyme core) this highly conserved region is buried deep in the core 

of the domain and forms the interface between the P4-P6, P3-P7 and P1 domains. 

The results developed in the last year 

demonstrate that time-resolved synchrotron x-ray "footprinting" is sensitive to 

time-dependent changes in local regions of OH protection of RNA. The rate of formation of tertiary interactions is followed in this assay by measuring changes in the 

accessibility of local regions of the RNA to the OH probe. The internal consistency 

of the OH kinetics data, and the consistency of the OH kinetics and hybridisationcompetition studies provides compelling evidence that these approaches accurately 

monitor the RNA folding reaction. We are continuing these studies at sub second 

timescales to better understand the folding process (J. Mol. Bio., in press) 

X9A 

chiometries with the cooperativity of Mg%+-depen 6" ent folding being more highly 

suggestion that an additional Mg2+ ion is linked to the folding of the P3- 2 7 The doKinetic analysis of ribosyme folding. 
X9B X-Ray Absorption and Resonance Raman Spectroscopy of Human 

M yeloperoxidase 

K. Yue, K. Taylor, J. Kinkade, R. Sinclair, L. Powers (Utah SU) 

Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host 

defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide 

to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. 

While MPO shows significant sequence homology with other peroxidases and this 

homology is particularly striking among the active site residues, MPO exhibits 

unusual spectral features and the unique ability to catalyze the oxidation of chloride 

ions. We have investigated the MPO active site with x-ray absorption and resonance Raman spectroscopies at neutral pH and also at the physiological acidic pH and 

have compared these results with those of horseradish peroxidase. The MPO heme 

environment was found to be inhomogeneous. At pH 7.5, the iron heme active site 

is 6-coordinate where the distal ligand is likely oxygen or nitrogen, but not sulfur. 

The heme is distorted compared to HRP, other peroxidases, and heme compounds, 

but at pH3, the distal ligand is lost and the heme is less distorted. HRP also loses 

its loosely associated distal water at this pH, but little change in heme distortion is 

observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion. 

XlOA X-Ray Characterization of Magnetic Epitaxial Multilayer Thin 

Films 

C-H. Lee (National Tsing Hua Univ), M.Y.Chern, C.Y.Huang (National Taiwan 

Univ), M.T.Tang (SRRC,Taiwan) and K.S.Liang (Exxon) 

Recently, we have successfully made epitaxial magnetic multilayers of yttrium 

iron garnet/gadolinium gallium garnet (YIG(lll)/GGG(111)) on the GGG single 

crystal substrates using the laser ablation deposition method. In this work, xray measurement which includes x-ray reflectivity, in-plane and plane normal x-ray 

diffractions and truncation rod measurement, were carried out to characterize in 

detail the epitaxial relation of the multilayer, noting that both YIG and GGG have 

the same cubic structure with a nearly identical lattice constant (0.03% difference). 

The prefection of epitaxy can be best revealed in the observation of the in-plane 

"forbidden" (1-10) peak (not shown) and truncation rod measurment which is shown 

in the following figure. 

The figure shows the truncation rod intensity of a sample measured from the 

in-plane GGG(2-42) peak along the plane normal direction. The sample consists 

of 12 alternative layers of YIG/GGG with each layer a thickness of one unit cell. 

The peak positions found in the truncation rod profile correspond to the period of 

superlattice of one YIG/GGG layer. This result indicates that the multilayer was grown epitaxially in a well-ordered solid on solid fashion. 

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Figure 1. 
in Cethyltrimethylammoniumbromide Micellar Solution Added with 

Small-angle X-ray Scattering Studies of the Growth of Particles r Tetraethoxysilane * 

T.-L. Lin, W.-J. Liu (Nat. Tsinghua U.), H. H. Shao, K. S. Liang (Exxon) 

0.1 ml of tetraethoxysilane (TEOS) was added to 10 ml of 1% cetyltrimethylammoniumbromide CTAB) micellar solution. The sample was kept at room temperature. Small-Ang I e X-ray scattering measurements were started at 12.5 hours from 

the addition of TEOS. The scattering angle was scanned from low to high angles. 

Each scattering curve took about three hours to finish. Figure 1 shows the measured scattering curves at different periods of the growing process. The scattering 

intensities were found to increase with time. This indicates that the particles grow 

larger with time. Simple Gunier plots give the radius of gyration of the particles of 

11.2, 13.2, 15.1, and 15.4 nm at 12.5, 15.5, 19, 24.5, and 28 hours, respectively. It is 

also noticeable that a small paek developes at Q near 1.2 l/nm. This may indicate 

there is some ordered structure. More detailed analysis is needed to determine the 

structure of the particles growed with the CTAB micelles as the template. 

LBtO 

a lB-l v Y 

16-2 

1E-3 

0.001 0.010 0.100 I. 000 

Q (114 

Figure 1. The scattering intensity in relative units as a function of the scattering 

vector measured at the time as indicated after the addition of TEOS to the 1% 

CATB micellar solution. 

* This work was supported by NSC, ROC. 

phirality, Structure and Free Energy of DNA Liquid Crystaly 

H.H. Strey, R. Podgornik, D.C. Rau and V.A. Parsegian (NIH/DCRT/LSB), J. 

Wang (XFD/ANL), and E. Sirota (Exxon) 

Liquid crystals of DNA are the simplest model systems for DNA packing in cell 

nuclei (e.g. dinoflagellates) or in pha e heads. In these systems typically just one extremely long (from 10m up to lm'j DNA molecule forms a macroscopic liquid 

crystal. We present a structural study on highly oriented DNA liquid crystals measuring the three dimensional structure factor S(q) using smd angle x-ray scattering 

at XlOA (BNL). The density of the DNA mesophases was controlled by the osmotic 

stress method. This method allows us to measure the equation of state and consequently changes in free energy in these systems. 

At high densities DNA orders in a columnar liquid crystal with short range and 

long range orientational bond order (line hexatic or N+6). The line hexatic phase 

is the three dimensional analog to the hexatic phase in two dimensions. At lower 

DNA densities we found an intermediate region with two distinct peaks in the x-ray 

structure factor, a sharper one with six-fold symmetry and a broader isotropic one. Since we hold all intensive variables (p,T,ps) fixed the measured S(q) should result 

from a single phase. At that point it is not yet clear whether this structure corresponds to a new phase located in between a columnar (non chiral) and cholesteric 

(chiral) arrangement of the DNA molecules. At even lower pressures we then found a phase transition to a cholesteric phase with a single broad first order maximum in 

S(q). The figure below shows a series of images showing the in-plane x-ray structure 

factor while passing through the line hexatic to cholesteric transition In these experiments the highly oriented samples were positioned in such a way that the average 

director points in the direction of the x-ray beam. The density of the samples was lowered by incresing the temperature of the bathing PEG 20,000MW solution. 

XlOA 

46°C 

Figure 1. 
r 

Fd 

r 

Unexpected Structure and Properties of w-unsaturated Thiols Selfassembled Monolayers on Au(ll1) * XlOB 

T.Y.B. Leung, P. Fenter, F. Schreiber, P. Eisenberger and G. Scoles (Princeton U.) 

A systematic surface x-ray diffraction study of the structures of monolayers of 

1-alkenethiols CH2=CH CHZ)~-ZSH) self-assembled on the gold (111 surface has 

the end of hydrocarbon chain was not expected to be significant, the structure of 

the undecenethiol (n=11) monolayer has been found to be very different from the 

methyl-terminated alkanethiol monolayer (CHa(CHz),-l SH). The unit mesh of the 

monolayers can be described as (1/3x4J3)R3O0, in contrast to a c(4J3x2J3)R30° 

unit mesh found for undecanethiol (n=11) monolayers. In addition to the structural 

differences, the undecenethiol monolayers have been found to be thermally more stable than the methyl-terminated counterparts. We find that although the methylterminated monolayers melt at -lOO°C, the undecenethiol monolayers only begin 

to thermally anneal at -130°C. 

We have also investigated if the same phenomenon exists for other chain lengths. 

We find that the even-chain thiols (n=10 and 18) adopt the same 2-dimensional 

symmetry and show similar thermal behavior as the methyl-terminated alkanethiols 

of the same chain-length. Therefore, these preliminary results indicate that the 

unusual structure and stability of the undecenethiol monolayers may occur only 

for w-unsaturated thiols with an odd number of carbons. Therefore we are actively 

preparing to measure the structures of other alkenethiols where n is odd. The above 

observations show that the self-assembly process is governed by a delicate balance 

of many interactions and that the introduction of a small perturbation can have an unexpectedly large impact. It is also possible that the behavior of the undecenethiol 

monolayers is caused by radiation induced phenomena such as a dimerization of 

the hydrocarbon groups that contain the double bonds. If confirmed by further 

work the results could open up a new avenue of research since most previous work 

on radiation-induced structural effects involved the production of defects (beam 

damage) instead of a new type of order. 

been performe 6 . Althoug 6 the perturbation caused by the double bon d insertion at 

* This work is supported by DOE under grant DE-FG02-93ER45503. 

1 XlOB I Structure of Rigid Biphenyl Monolayers by Vapor and Solution 

Phase Growth * 

F. Schreiber, T. Y. B. Leung, P. Fenter, and G. Scoles (Princeton U.) 

We have used grazing incidence x-ray diffraction to study the growth and the 

structural phases of self-assembled monolayers (SAMs) of biphenyl thiols (C&- 

C6&-CaH*-SH) on Au(ll1). 

For growth from solution we find diffraction peaks consistent with a fi x fi - structure (hexagonal phase). The average domain size, however, was only about 65 

In an attempt to improve the structural quality and to explore possible other 

phases, we employed growth from vapor under UHV conditions, which also enabled us to follow the growth in-situ. For growth at low temperatures (10 "C), we found 

in-plane Bragg peaks corresponding to a real-space distance of 3.4 A, which suggests that the phenyl rings of neighboring molecules are arranged in a pancake-like 

fashion. However, these peaks are not observed for higher sample temperatures. 

For growth at higher temperatures, where we think the layer is closer to its 

equilibrium structure, we find a completely different structure characterized by 

unit cell dimensions of 10 Ax 11.56 A. A possible structural model which would be 

consistent with the observed peaks features two molecules per unit cell with their 

long axes lying down on the surface and the sulfurs at opposite ends for the two 

molecules. While we have established the 2-D map of the diffraction peaks, the 

out-of-plane structure (rodscans) has not yet been fully determined. 

The structural quality of these SAMs is very high with domain sizes well above 

1000 A. Another remarkable feature is the high thermal stabilty of the abovedescribed structure. In several annealing and melting experiments we found the 

layers to be stable up to about 160 "C. A high-quality layer could be regained upon 

cooling back to room temperature. Even for exposures of several hours (at relatively 

low flux based on the vapor pressure) the structure did not change significantly, and a transition to the hexagonal phase has not yet been observed. 

In future experiments, we will explore further the vapor phase growth and try to 

find conditions, under which the hexagonal phase can be achieved. Moreover, we 

will study the growth kinetics and compare these to decane thiol SAMs which are 

more flexible with their hydrocarbon chain compared to the rigid phenyl rings. 

A. 

* This work supported by DOE (DE-FG02-93ER45503) and DFG (Schr537/2-1). 
Study of the Structure and Growth of Co-assembled Surfac- r- tant/Silica Films 

L. Zhou, P. Fenter, I. Aksay and P. Eisenberger (Princeton U.) 

In-situ and ex-situ X-ray studies have been performed on the self- assembled 

surfactant/silica thin films which are synthesized with CTAC and TEOS in a diluted 

acidic solution on freshly cleaved mica substrate. Although the growth of the bulk 

materials has been well studied, much less is known about the mechanism of growth 

of well-defined films. 

Under these solution conditions a film spontaneously adsorbs to the mica substrate [1]. Ex-situ X-ray measurements coupled with AFM measurements show that 

the film consists of a lattice of hexagonally packed tubes which are oriented parallel 

to the substrate surface. These films are highly ordered, well aligned along the substrate surface normal and strained with respect to the bulk hexagonal structure [1]. 

A striking feature of our data is that despite the quasi-hexagonal structure of the 

mica surface the tubes are only aligned along two of the equivalent next-nearestneighbor directions of the mica substrate surface. The absence of the alignment in 

the third direction (which is distinctive due to the distorted atomic arrangement 

of mica), provides direct evidence that the alignment of the tubes is due to an epitaxial arrangement in spite of the large lattice mismatch betwwen the film and the 

substrate spacings. 

Our in-situ X-ray measurement shows that there is a 7 hour induction time in 

the film nucleation. In Fig. 1, we show the specular reflectivity measurement at 

different times. We found no evidence of film growth or any ordered structure for 

7 hours after the substrate is exposed to the growth solution. After 7 hours, the 

film begins to grow rapidly with an increasing growg growth rate, such that the film 

thickness exceeds 1 micron after 2 hours following nucleation (Fig. 2). The 7 hour 

induction time and nonlinear growth rate of the film are both very surprising and 

interesting. We have also found similar growth behavior for silica substrate, which 

suggests that this growth behavior is independent of the nature of the substrate. 

These data suggest that the film growth proceeds in a very unusual fashion, and 

raise questions concerning the fundamental nature of the initial nucleation process 

and the microscopic mechanism of the growth. 

[l] 1.A.Aksay et al. Science, 273, 892-897 (1996) 

r 12 a:l .^2 

c 

0 

-I Figure 1. Figure 2. 

1 Local Structure of VzO3 During the Metal-Insulator Transition 1 XllA 1 ~~ 

A.Frenke1. E.A.Stern (U. of Washington) and F.A.Chudnovsky (Phys.-Tech. Inst., 

St. Petersburg, Russia) 

V203 undergoes a phase transition from an antiferromagnetic insulator to paramagnetic metal with the crystal structure changing from monoclinic to trigonal with 

a 1.4% decrease in volume and 0.11 k decrease in some of the V-V distances as 

the temperature is increased above 155 K. Measurements of the ZocaZ structure by 

XAFS may help to determine the mechanism of the transition. 

We performed single crystal XAFS measurements, orienting the c- axis parallel 

and perpendicular to the polarization of the synchrotron radiation. XAFS mea- surements were performed at the NSLS on beamline XllA at two temperatures 

below the phase transition for each orientation and two temperatures above. XAFS 

signals were analyzed by the UWXAFS software [1]. Theoretical scattering amplitudes and phases were generated using the FEFF6 code [2] for the monoclinic 

crystal structure. 

The results of the fits (Fig. 1) showed that the local structure of the samples 

remained monoclinic at all temperatures. The VO - V2 distance (between the pair 

of atoms lying nearly in the basal plane) decreased above the transition by 0.070 f 

0.025 k, but its absolute value remained 0.040 rt 0.025 longer than given by 

the trigonal structure of the diffraction measurement [3]. Another characteristic 

distance (along the c-axis) between VO - VI remained about 0.025 rt 0.02 A longer 

than in the trigonal structure, consistent with the static displacement of VO and Vz 

atoms in opposite directions in monoclinic structure. 

More distant group of collinearly arranged V atoms was analyzed separately. This 

group would produce two sets of paths with half path lengths of 7.255 k and 7.47 

k for the monoclinic structure and one group (7.38 A) for the trigonal structure. 

Figure 2 shows that the two distances remain split above the phase transition. 

Monoclinic distortions, therefore, persist locally in both phases. 

E. A. Stern et al., Physica B 208 & 209, 117 (1995). 

S. I. Zabinsky et d., Phys. Rev. B 52, 2995 (1995). 

P. D. Dernier and M. Marezio, Phys. Rev. B 2, 3771 (1970). 

3.05 

4 2.9 

3 2.85 

8 

D 5 2.8 

2.75 

2.7 

2.65 ' ' " ' ' ' 

0 50 150 200 250 300 350 loo Temperature, K 

Figure 1. V-V distances as determined 

by XRD (lines) and XAFS (symbols) for 

the nearest neighbors. 

75 

7 45 

u 74- 

c 

T1 

z 

; 735- 

73 - 

725 t f 

75 I 

f 7 45 

u 74- 

c ; 735- 

T1 

z 73 - 

725 t 

--I i I I 

I 

7.21 ' ' " ' ' ' I 0 50 100 150 200 250 300 350 Temperalure, K 

Figure 2. V-V distances as determined 

by XRD (lines) and XAFS (symbols) for 

the more distant neighbors. 
1 Sr-induced Local Distortions in Laz-, Sr,Cu04 I XllA I 

XAFS Study of Cation Valence State and Site Distribution in Natural Schorlomite and Melanite Garnet * 

A.F. Gualtieri, S. Quartieri (U. of Modena, Italy), K. Pandya (NCSU) and G.M. 

XllA 

Lamble (BNL - NSLS) 

Natural garnets are widespread rock-forming minerals in the Earth crust and 

upper mantle; they play a paramount role in the high temperature and high pressure petrogenetic processes and they are as well important markers of contact and 

regional metamorphic grade. The general chemical formula is X3Y223012 where 

X is an eight-coordinated site commonly occupied by Ca, Mg, Fe and Mn; Y is 

an octahedral site occupied by Al, Fe, Ti and Cr; Z is a tetrahedral site mainly 

occupied by Si and in minor amount by Fe, A1 and Ti. Schorlomite is a species 

of garnet containing more than one atom of Ti per formula unit. Melanite is the 

complementary varietal name for Ti-andradite which contains less than 1 Ti atom 

per formula unit [l]. In shorlomite, the tetrahedral site is not fully occupied by 

Si. This deficiency coupled with a large concentration of Ti and both Fe3+ and 

Fez+ makes the interpretation of the cation site distribution to be rather doubtful. 

Although several studies have been attempted on the role of Ti and Fe in shorlomite 

and Ti-andradite, no general agreement has been reached on this issue. Regarding Zr, at present a systematic study is still lacking. The present study attempts 

to clarify the crystal chemical role of Ti, Fe and Zr in schorlomite samples from 

Kola-Karelia ijolite-carbonatic complex (Russia and melanite samples from Monte 

dates for Si replacement by Fe and/or Ti in the tetrahedral Z site. The presence of 

Ti3+ has recently been claimed in melanite samples from Monte Vulture (Malitesta 

et al., 1995). Preliminary Fe and Ti-K-edges XANES and EXAFS spectra collected 

Vulture (Italy). The samples show a slight Si d eficiency and thus are good candiat the Frascati synchrotron facility 

tallographic sites are involved for 

indicate that at least two different crysand Fe (Quartieri et al., 1993a; 1993b). 

Experiments were carried out at XllA beamline which is equipped with a sagitally 

focusing double Si( 111) crystal monochromator. Samples were dispersed in boron 

nitride and the powder was loaded on an A1 sample holder which was fixed on a liquid N2 cold finger, allowing the data collection to be performed at low temperature. 

XANES and EXAFS spectra were collected both in transmission and fluorescence 

(Lytle detector) mode depending on the amount of the investigated element in the 

sample. Energy calibration was continuously checked by simultaneously monitoring 

reference spectra using an additional ion chamber detector placed behind the transmission set-up. Higher harmonic reflections from the monochromator were rejected 

by detuning the parallelism of the Si 111) crystals until the harmonic content was negligible. The K absorption edges w 6 ich were investigated are: Ti at 4.9637 KeV, 

Fe at 7.111 KeV, Zr at 18.2271 KeV. The data analysis of the XANES and EXAFS 

spectra is still in progress. 

[l] Deer W.A., Howie In Rock forming minerLondon. [2] Malitesta C., 

7 847-858). [3] Quartieri 

Eur.J. Mineral. 5(1101- 

(Mag. 57(249-256). [4] 

1109). 

* This work was carried out under DOE Contract Numbers DE-AC02-76CH00016 and 

DE-FG05-89ER45384. 

D.Haske1 and E.A.Stern (U. of Washington) 

SrS2 substitution for LaS3 in La2-rSr,CuOc leads to high T, superconductivity 

for 0.075 5 2 5 0.25 by inducing hole carriers in the Cu-0 planes. The mechanism 

of charge transfer, however, is not yet understood partly because of the lack of 

knowledge of the structure around the Sr atoms. Diffraction techniques yield Sr-0 

bond lengths which are necessarily the same as La-0 ones since Sr substitutes at 

the La site [l]. 

Recent experiments showed that the ratio of out of plane, 0 2p,, to in plane, 0 

2p,,, orbital character of the doped holes increases with SI doping [2] suggesting a key role of the O(2) apical oxygens in the hole doping mechanism. An accurate 

picture of the SI environment is needed to address these findings. 

We measured SI K-edge polarized XAFS on oriented powder with x = 0.075,O.l 

at T=20K. We discovered that Sr resides at the La lattice site (SI-Cu and Sr-La 

distances are, within 0.01 8, the same as La-Cu and La-La found in our La K-edge 

XAFS analysis [3]) but induces major structural distortions in neighboring oxygen 

atoms. In particular, its O(2) apical oxygen is split into two sites separated by 

0.30(4)a along the c-axis (see fig. 1). This anomaly was not found for the La-0(2) 

apical distance [3] and could result from a fluctuating number of holes at the Cu 

site nearby SI atoms (fig. 1) creating two equilibrium positions for the O(2) atoms. 

This hole-lattice interaction could be involved in the pairing mechanism leading 

to high T, [4]. In addition, the O(2) site closer to the Cu-0 planes couples more 

effectively to them and could explain the increase in 0 2pl character of holes with 

doping [2]. Fig 2 summarizes the distortions induced by Sr substitution. Further 

details will be reported elsewhere [5]. 

We acknowledge the valuable help of F. Perez, M. Suenaga and S. Heald in 

orienting the samples. This research has been supported by D.O.E. grant #DEFG06-90ER45425. 

-1' P. G. Radaelli et. al., Phys. Rev. B 49, 4163 (1994). 

'2' C. T. Chen et. al., Phys. Rev. Lett. 68, 2543 (1992). 

'3' D. Haskel et. ol., Phys. Rev. Lett., 76, 439 (1996). 

'4' P. W. Anderson et. al., Phys. Rev. Lett. 60, 132 (1988). 

'5' D. Haskel et. al., to be published. 

cu 

Sr 

Figure 1. Two site configuration of the 

O(2) apical to Sr. 

Figure 2. Schematic representation of 

the pattern of atomic displacements induced by SI substitution. 
X11A X-Ray Absorption Spectroscopy Analysis of Lead and Zinc Speciation in a Contaminated Groundwater Aquifer 

D. Hesterberg, D. E. Sayers, W. Zhou, G. M. Plummer, and W. P. Robarge (NCSU) 

The mobility and bioavailability of heavy metals in the environment is influenced 

by the solubility of the solid-phase chemical species present and aqueous phase speciation. The design of successful remediation technologies for contaminated sites 

also depends on chemical speciation. The formation of metal sulfides in the environment can potentially reduce the solubility and bioavailability of heavy metals, 

and have bearing on the optimal approach for remediation design. This project was 

initiated to assist in assessing remediation strategies for the By-pass 601 Superfund 

Site in Concord, North Carolina. The site was formerly used for a lead battery 

recycling operation. The objective of this study was to determine whether PbS 

and ZnS were dominant solid-phase species in samples taken from different parts 

of the aquifer at the study site. The occurrence of metal sulfide minerals would 

depend on the redox conditions in the aquifer. Groundwater aquifer samples were 

analyzed using EXAFS and XANES spectroscopies at Beamline X-11 to determine 

whether lead and zinc sulfide were dominant mineral phases. Aquifer solids collected from turbid groundwater samples by filtration contained between 150 and 

1,800 mg Pb/kg and between 100 and 250 mg Zn/kg. Results showed that none 

of the samples analyzed contained PbS as a dominant solid phase. XANES and 

EXAFS data both showed that one sample contained 70% of zinc bonded to sulfur, 

indicating that this portion of the aquifer had been under a sufficiently low redox 

potential to generate sulfides. In all other samples, first-shell bonding of Pb and Zn 

was primarily to oxygen. Comparison with standards indicated that PbO, PbC03, 

PbSOI, and ZnO were not dominant species in the samples. Figure 1 shows that 

Zn-S bonding was dominant only in sample Zn23, and therefore, remediation should 

target metal-oxygen bonded species. 

10 

5 

'0 12 3 4 5 6 7 8 

Radlal dielance (A) 

Figure 1. Stacked radial structure functions for Zn K-EXAFS data (k3-weighted) 

from solid-phase aquifer samples (Zn03, Zn09, ZnlO, Znll, and Zn23) and selected 

standards. Data are not corrected for phase shift. 

XAFS Characterization of Copper in Model Aqueous Systems of 

Humic Acid and Illite 

D. Hesterberg, D. E. Sayers, W. Zhou, W. P. Robarge, and G. M. Plummer (NCSU) 

Adsorption of heavy metals at mineral surfaces and complexation with reactive 

organic-matter functional groups are important processes regulating the solubility 

and fate of soil contaminants. The objective of this study was to determine spectroscopic features that distinguish Cu(I1) bonding to soil humic acid (HA) from 

bonding on an aluminosilicate mineral surface, and to characterize bonding in a mixed clay-organic system. EXAFS analyses were conducted on aqueous suspensions containing Cu(I1) in various forms: (i) complexed with soil humic acid (HA 

HA. Samples of pH 5.6 or 7.2 contained between 2.5 and 9 mmol Cu(II)/kg. XAFS 

analyses were done at Beamline X-11. Samples were analyzed in fluorescence mode 

at the Cu K-edge 8,979 eV) using a multielement detector. EXAFS fitting results 

lengths in the HA suspensions were consistently shorter than those of Cu-0 in the 

illite suspensions (1.92 to 1.93Aversus 1.95A1 respectively). The average Cu-0 bond 

length in the mixed illite-HA suspensions (1.94A) was intermediate between those 

of the single adsorbent systems at pH 5.6, and equal to that of Cu(I1) in HA at pH 

7 2 1 93.4 (Table 1 Average coordination numbers (N) and Debye-Waller factors 

sions. Although N also tended to be higher in the mixed suspensions compared 

with HA alone, no consistent trend in DW was observed. For the HA suspensions 

at pH 5.6, there appeared to be little effect of HA:& ratio on EXAFS results. Our 

results indicated that the addition of relatively low levels of HA to illite suspensions 

had a significant effect on average local bonding structure. 

at various HA:Cu ratios, (ii) bound to illite, or (iii) bound in a mixture of illite an J 

in Table 1 show t I, at at both pH 5.6 and 7.2, the average first-shell Cu-0 bond 

ci&j ten J ed to be h. igher in the illite suspensions compared with the HA suspenHA = 300 mg ooL& pH 5.6 5.4 1.93 o.Mm5 

HA=6wmg OOLS, pH5.6 5.8 1.93 O.oW8 

HA= 1mmg aCng.pH 5.6 5,s 1.93 0.m 

HA I ISM mg Wkg. pH 5.6 5.4 1.93 0.W5 

ITA i 24W mgaCng. pH3.6 5.7 1.92 0.oWS 

illite +HA - 12.5 mg Oorg, pH 5.6 5.9 LY4 -0.W 

illlie + HA - 25 mg Wg, pH 5.6 6.4 1.94 O.WI0 

illite. pH 5.6 6.6 1.95 O.WL0 

HA = 3M mg OCik& pH 7.3 6.5 1.93 0.W11 

illilc + HA - 12.5 mg ooLg, pH 7.3 6.5 1.93 O.oW3 

illite, pH 7.3 6.9 1.95 0.M16 

Figure 1. First-shell EXAFS fitting results for Cu in humic acid (HA), illite, and 

mixed illite-HA suspensions using a 5 mM Cu-acetate solution as a standard (N = coordination number, R = 1st-shell bond length, and DW = Debye-Waller factor). 

Numbers in parentheses are parameter standard deviations given as output from 

the University of Washington FEFF fitting program. 
Fd 

P 

XllA Application of X-ray Absorption Spectroscopy for Studying Pyromorphite Formation in Lead Contaminated Soil 

D. Hesterberg, W. Zhou, P. Zhang, D. E. Sayers, J. A. Ryan, and W. P. Robarge 

(NCSU and US-EPA) 

In-situ remediation techniques for soil contaminants are being developed to re- duce the cost of managing hazardous-waste sites. One technique being explored 

for lead-contaminated sites is treatment of contaminated soil with hydroxyapatite [Cas(POa)3OH] to fix lead as the very insoluble mineral chloropyromorphite 

[Pbs(P04)3Cl]. The objective of this study was to determine using extended x-ray 

absorption fine structure EXAFS) spectroscopy whether pyromorphite was formed 

samples came from the site of a lead smelter in the western U.S. and contained 

8,106 mg Pb/kg 39 mmol/kg). Laboratory experiments conducted at the US-EPA 

ratio = 5:l) for 240 d. Lead LrrI-EXAFS analyses completed at Beamline X-11A 

were used to characterize untreated soil, hydroxyapatite-treated soil, and residual soil Pb that was not removed from the treated soil by a sequential chemical 

extraction. Air-dried soil samples were analyzed at room temperature in fluorescence mode using a multielement detector, and a synthesized chloropyromorphite 

standard was analyzed in transmission mode. High-quality, low-temperature (10 

K) EXAFS spectra were also obtained for the extracted soil and pyromorphite 

standard. EXAFS data showed a shift to a longer average first-shell Pb-0 bond 

length in the treated soil, indicating that the treatment had changed the bonding 

structure of Pb. Low-temperature EXAFS spectra for the extracted soil lead and 

pyromorphite were remarkably similar in terms of the frequencies of the oscillations 

and the beat pattern (Fig. l), which provided strong evidence that the extraction 

residue was dominated by pyromorphite. A multiple-scattering peak at 4.4 A-1 in 

the pyromorphite spectrum only suggested that the soil pyromorphite was poorly 

crystalline. 

following experimental so !l treatments with hydroxyapatite. The contaminated soil 

Central Hill Fac' s, 'ty involved incubating hydroxyapatite-treated soil (P:Pb molar 

2 4 6 8 10 12 14 -0.10 I I ' ' ' ' ' ' I ' ' ' ' ' ' ' ' ' ' ' ' ' ' . ' ' ' ' 

k(A-') ___.. 

Characterization of Heavy Metal Incorporation in Calcite by XAFS 

Spectroscopy 

R.J. Reeder, P. Northrup (SUNY Stony Brook) and G.M. Lamble (BNL- NSLS) 

Coprecipitation is one of the environmentally important processes governing the 

distribution and fate of dissolved heavy metals in near-surface waters. Recently reported experimental work on the coprecipitation of divalent Co, Zn, Mn, Fe, Cd, SI, 

Pb, and Ba with calcite (a common authigenic phase in soils and aquifer materials) 

has shown strongly selective uptake in structurally distinct surface sites on the calcite 1014 face, resulting in element-specificl differential incorporation during crystal 

coprecipitated with calcite were collected (X11A) and analyzed to determine loca I growth. XAFS spectra of individual divalent heavy metals (Co, Zn, Pb, and Ba 

coordination in the bulk following surface-controlled differential uptake. Results of 

multi-shell fitting using FEFF6 and FEFFIT show that, despite their large difference 

in size, all four metals attain a coordination with six oxygens at distances that are consistent with octahedral coordination. Substitution of the metal ions therefore 

occurs in the Ca site, which is confirmed by second-shell distances. One conclusion is that despite distinct surface-site preferences and uptake patterns varying in 

magnitude by more than a factor of ten, bulk coordination differs only minimally. 

Therefore, differential surface uptake need not result in different coordination in 

the bulk calcite as heavy metal ions are buried during growth. A further conclusion 

is that relaxation around an impurity ion is very localized, and the corner-sharing 

structural topology of calcite facilitates the observed wide spectrum of impurity 

substitution. 

Figure 1. Comparison of Pb LIrr EXAFS spectra for the soil extraction residue 

(solid line, left axis) and chloropyromorphite (dotted line, right axis). 
[ XllA [ XAFS Characterization of Heavy-Metal Contamination in the Unsaturated and Saturated Zones of a Soil Profile 

D. E. Sayers, D. Hesterberg, W. Zhou, W. P. Robarge, and G. M. Plummer (NCSU) 

The fate of heavy-metal contaminants in the environment, and the design and 

success of remediation strategies at hazardous waste sites depend on the chemical 

speciation of the contaminants. XAFS spectroscopy has the potential for providing molecular-scale speciation of metals occurring at low concentrations in complex 

media such as soils. The objective of this study was to determine the chemical 

forms (species of heavy metals occurring at different depths in a contaminated soil 

the saturated zone of this soil is at -1 m depth, redox potential was expected to 

play a significant role in metal speciation, particularly with regard to metal-sulfide 

formation. Copper, zinc, lead, and chromium in field samples were characterized 

using XANES and EXAFS spectroscopies at Beamline X-11. The samples contained 

1,780 to 2,160 mg Cu/kg, 4,970 to 5,500 mg Zn/kg, 3,730 to 4,550 mg Pb/kg, and 

60 to 94 mg Cr/kg; and were analyzed in fluorescence mode using a multielement 

detector. Copper K-EXAFS data showed that the amount of first-shell Cu-S bonding increased relative to Cu-0 bonding with depth in the soil profile (see radial 

structure functions in Fig. 1). Based on relative coordination numbers of Cu-0 

and Cu-S bonding derived from EXAFS data fitting, the following percentages of 

Cu-S bonding were calculated for the soil samples: 36% (28-56 cm depth), 77% 

56-71 cm), and 81% (71-86 cm). K-XANES spectra suggested that CuS was the 6 ominant mineral species in the subsurface sample, consistent with expectations 

of a low oxidation-reduction potential in the water-saturated subsoil. Both Zn 11) 

indicating that available sulfide was preferentially bound with Cu(I1). CuS is thermodynamically more stable than ZnS and PbS. Cr K-XANES spectra showed that 

the less mobile and less toxic Cr(II1) species was dominant throughout the soil profile. The results suggest that the surface and subsurface horizons at the study site 

will respond differently to remediation treatments. 

at a superfun d site in the lower eastern coastal plain of North Carolina. Because 

and Pb(I1) were predominantly bonded with oxygen throughout the soil pro !i le, 

Figure 1. Radial structure functions for Cu(I1) in soil samples from different depths 

and selected standards. Data are not corrected for phase shift. 

The Kinetics of Nickel Sorption on Pyrophyllite as Monitored by 

X-ray Absorption Fine Structure (XAFS) Spectroscopy 

A. M. Scheidegger, D. L. Sparks (U. of Delaware), and G. M. Lamble (NSLS) 

The study examines the effect of reaction time (minutes to months) on the surface 

coordination environment of Ni sorbed onto pyrophyllite (2:l clay with little deviation from the ideal chemical formula (AlzSirOlo(0H)z) using XAFS. Ni sorption 

on pyrophyllite at pH = 7.5 ([Ni]in;tial = 3 mM, ionic strength I = 0.1 M (NaN03)) 

resulted in the presence of multinuclear Ni complexes within minutes. This can be 

clearly demonstrated in Figure 1. There is a small peak at R = 2.8 a in the radial 

structure function RSF) of pyrophyllite treated with Ni for 15 minutes (Fig. lf). 

The presence of mu I tinuclear Ni complexes after a sorption time of only 15 minutes 

(28% of the initial Ni sorbed; Table I.) is a rather surprising finding. Traditionally, 

adsorption (strictly a two-dimensional process) is considered to be the predominant 

sorption mode responsible for metal uptake on mineral surfaces within the first few 

hours. As reaction time progressed (15 min. to 24 h) and relative Ni removal in 

solution increased from 28% to 97% (Table I.) the number of Ni second-neighbor 

(N) atoms at a distance of 2.99-3.03 A increased from N = 1.4-4.5. This finding 

suggests the formation of multinuclear Ni complexes increasing in size with progressing reaction time. We propose that the formation of mixed Ni-A1 hydroxides 

may explain the observed bond distances and coordination numbers. Ni-Ni bond 

distances (3.0-3.03 8; Table I.) correspond well with those found in mixed Ni-A1 

hydroxides (3.03-3.05 A), but are distinctively shorter than those in Ni(OH)2(s) 

(3.09 A) [l]. Aluminum could have been released into solution and incorporated 

into mixed (Al, Ni) hydroxides. Indeed, macroscopic data suggest that the dissolution of nvroDhvllite is enhanced durine reaction with Ni relative to the dissolution 

in the dilk sorution [l]. 

" 

111. Scheidegger, A. M., Lamble, G. M. and Sparks, D. L. 1996. J. Colloid 

Inieiface Sci. in -press. 

Figure 1. Radial structure functions (RSFs) of pyrophyllite samples reacted with 

Ni for a.) 3 months, b.) 24h, c.) 12h, d.) 3h, e.) 75min, and f.) 15 min. The 

spectra are uncorrected for phase shift. Note the appearance of a peak at a R of 

about 2.8 A with increasing reaction time. 
F 

w I In Situ XAS Studies Of Metal-Semiconductor Interactions * 1 XllA I 

Z. Wang, P.T. Goeller, B.I. Boyanov, D.E. Sayers, and R.J. Nemanich (NCSU) 

A UHV system for in-situ studies of metal-semiconductor interactions has been 

designed and assembled at NCSU and recently installed and tested at beamline 

X-11A at the NSLS. The UHV system consists of interconnected deposition and 

analysis chambers, each of which is capable of maintaining a base pressure of approximately 1 x lo-’’ Torr. Up to three materials can be co-deposited on 25 mm wafers by electron-beam evaporation. Substrate temperature can be controlled in 

the range 30-12OO0C during deposition, and the growth process may be monitored 

with RHEED. The deposited materials and their reaction products can be studied 

in-situ with a variety of techniques: XAFS, AES, XPS, UPS, and ARXPS/UPS. A 

schematic overview of the experimental apparatus appears in Figure 1. 

We intend to use this equipment to study the stabilization of metal silicides codeposited on epitaxial Sil-,Ge, films. Initial EXAFS experiments on co and Si 

co-deposited in a 1:2 ratio on Sio.8Geo.z films indicate a stable silicide-SiGe contact. 

The silicide overlayer exhibits a CoSiz structure at all annealing temperatures used 

in this study (500-7OO0C). Weak CoSi signature (attributed to slight Co excess is 

the overlayer is detected below 6OO0C, and CoSiz formation is complete at 7OO0C. 

growth when co-deposited on epitaxial SiGe/Si(lOO) films, even when CoSiz “template” layers are employed. We are currently investigating the implications of this 

result on the structure, resistivity, and stability of the CoSiz-SiGe contact. 

In-situ RHE k D measurements indicate that CoSiz islands at the very early stages of 

GROWM CHAMBR ANALYTICAL CHAMBER 

mN1m mm a 

Figure 1. 

* This work was supported by DOE grants DE-FG05-93ER79236 and DE-FG05- 

89ER.45384 

Evidence for Pb-phospate Cluster Formation at the Oxide-water Interface 

F.J. Weesner and W.F. Bleam (U. of Wisconsin-Madison) 

Surfaces of hydrous oxide soil minerals strongly influence the mobility of solutes in 

the soil/water system. The common oxides of iron and aluminum can adsorb ions of 

either charge to varying degrees depending on relative concentrations and solution 

pH. The extent to which the adsorption from solution of one solute is affected by the 

presence of second solute is not generally predictable by current theory. Multiple 

adsorbates will always be present in environmental systems, therefore it is important 

to examine the interactions of co-adsorbates at the oxide/water interface. 

This abstract reports on progress in the understanding of Pb2+ binding to modified iron and aluminum oxide colloid surfaces in aqueous suspensions. Oxide surface 

modification is accomplished by populating the surface with excesses of common 

oxyanions such as HP042- and SO42-. We believe ternary surface structures form 

at the interface under certain conditions. We collected X-ray absorption spectra 

(XASL at the Pb LIII, S K and P K edges over the last year to test test this 

hy p ot esis . In the case of phosphate modification, we observe dramatic changes to both 

the near edge and fine structure regions of XAS spectra. While not identical, 

the spectra of Pb adsorbed to the phospahte treated samples are similar to the 

phospahte mineral hydorxypyromorphite. The experimental spectra suffer from a relative high degree of static disorder owing to multiple unique adsorption sites on 

our oxide adsorbents. This prevented detailed analysis of the structural paramenter 

of the sites, yet simulations of using a 3 site model, guided by structure refinements 

of Pb phosphate minerals leads us to the conclusion that a direct reaciton of Pb and 

phospate takes place at the surface. P K-edge spectra supported this conclusion, 

however only the A1 oxide system was studied due to high scattering background 

from the Fe oxide matirx. 

Adsorption of phosphate and sulfate to aluminum hydrous oxides is thought to 

follow inner-sphere (ligand exchange) and outer-sphere (electrostatic) mechanisms, 

respectively. Our results support this hypothesis judging from the presence (phosphate case) or absence (sulfate case) of scattering intensity that could be reasonably 

assigned to A1 in the second coordination shell. 
ements Bound to Aquatic and Soil Humic Substances Using X-ray 

Studies of the Nature of Binding Sites of First Row Transition ElAbsorption Spectroscopy 

K.Xia, W. Bleam, and P.A. Helmke (U. of Wisconsin-Madison) 

The coordination environments of first row transition elements (Co, Ni, Cu, and 

Zn) complexed by aquatic and soil humic substances were studied using x-ray absorption spectroscopy (XAS). With the assistance of bond network analyses, analysis of x-ray absorption near edge structure (XANES) spectra and radial structure 

functions (RSF) derived from extended x-ray absorption fine structure (EXAFS) 

spectra of Co, Ni, Cu, and Zn in humic substances indicate octahedral binding environment for Co and Ni, a tetragonally-distorted octahedral binding environment 

for Cu, and 6-coordinate binding environment for Zn. Analysis of EXAFS spectra of 

each element provides detailed information on the internuclear distances, bond angles, and Debye-Waller factors within the first two atomic shells surrounding Co, Ni, 

Cu, and Zn bound to humic substances. We interpret the presence of carbon atoms 

in the second atomic shell of the metal binding site as further evidence that Co, Ni, 

Cu, and Zn form inner-sphere complexes with humic substances. The number and 

type of ligands involved in the binding are different for different elements. 

Submitted to Geochim. Cosmochim. Acta., 1996. 

X11A Studies of the Nature of Cu2+ and Pb2+ Binding Sites in Soil Humic 

Substances Using X-ray Absorption Spectroscopy 

K. Xia, W. Bleam, and P. A. Helmke (U. of Wisconsin-Madison) 

We have investigated the binding environments of Cu2+ and Pb2+ complexed 

by soil humic substances using synchrotron-based x-ray absorption spectroscopy. 

With the assistance of bond network analysis, analysis of x-ray absorption near 

edge structure (XANES) and radial structure functions derived from extended x- ray absorption fine structure (EXAFS spectra of Cu-humate at pH 4, 5, and 6 

yielded a tetragonally-distorted octahe d ral binding environment with 4 0 atoms at 

an average distance of 1.94A, 2 0 atoms at an average distance of 2.02a, and 4 C 

atoms at an average distance of 3.13A. Analysis of Pb-humate samples at pH 4, 5, 

and 6 yielded 4 0 atoms at average distances between 2.46ho 2.32Aand 2 C atoms 

at an average distance of 3.26A. We interpret the presence of carbon atoms in the 

second atomic shell of the metal binding site as evidence that both Cu2+ and Pb2+ 

form inner-sphere complexes with soil humic substances. Within the pH range 4 to 

6, there is no significant change in the structure of the binding site for either Cu or Pb. 

Submitted to Geochim. Cosmochim. Acta,1996 

46 

I- + 

w 
P 

P 

X-Ray Absorption and Electron Paramagnetic Resonance Studies of 

Cu2+ Sorbed to Silica: Surface-Induced Precipitation at Low Surface X11A 

Coverages 

K. Xia, W.F. Bleam (U. of Wisconsin-Madison), A.Mehadi, and R.W. Taylor 

(Alabama A&M U.) 

Both EPR and XAFS spectroscopy were used to characterize the sorption of 

CuaS on silica surfaces at extremely low surface coverage (0.8 percent and 9.9 

percent monolayer). The binding structure of Cu2+ on silica surfaces revealed by 

XAFS experiment was compared to that predicted by EPR spectra. Our XAFS 

results show that Cu 2t hydroxide clusters form on silica surfaces even at surface 

coverage as low as 0.8 percent of a monolayer. However, we observed low EPR 

intensity and line-broadening which has been assigned to dipole-dipole interactions 

between isolated Cu2+ ions. The results of our XAFS studies indicate that the loss 

of EPR intensity and line-broadening can be traced to Cu(OH)2 clusters on silica 

surfaces. 

J. of Colloid Interface Sci. in print, 1996. 

X12B 

Structure of Zn-fingers 1-6 of Transcription Factor IIIA (TFIIIA) 

Bound to a 31 bp DNA Site 

R.S. Brown, R.T. Nolte, S.C. Harrison, (HHMI and Children’s Hospital Lab. of 

Molecular Medicine) 

Crystals of fingers 1-6 of TFIIIA bound to a 31 bp DNA contain a longer protein fragment and a longer DNA site than other Zn-finger complexes studied to 

date. They are in space group P1 (a=61.3, b=64.8, c=78.1, a=90.12, ,#=92.87, 

y=102.84). Diffraction extends to 3.d Data from flash-frozen crystals were collected at X12B using a MAR detector. A total of 629 degrees of native data and 

247 degrees of iodine derivative data were recorded. A difference Patterson has now been solved; there are two protein:DNA complexes per unit cell related by 

twofold non-crystallographic symmetry. Phase refinement and model building are 

in progress. 
1 X12B 1 Large Strain Deformation Studies of Oriented Triblock Copolymers 

with a Cylindrical Morphology 

C. Honeker, E. L. Thomas (MIT), M.C. Cape1 (BNL - Biology) 

Single-crystal triblock copolymers with a cylindrical morphology are deformed 

to large strains with simultaneous measurement of load, sample extension and 2- 

D small-angle diffrac- tion. The sample is oriented such that the incident beam 

is directed perpendicular to the cylinder axis while stretching in the transverse 

direction. After the initial deformation during which the cylinders move apart, the 

symmetry of the diffraction pattern is broken whereby each Bragg peak splits into 

a pair of peaks which move off the force axis and towards lower q. This X pattern 

forms at a well-defined strain (100%). TEM of the deformed samples indicates that 

the cylinders have bent into a chevron texture. Upon further deformation, the angle 

between the arms of the X continues to open reaching an asymptote (siml20) at 

the highest deformations. In order to probe the influence of molecular structure 

on deformation we investigated sev- era1 multi-block copolymers: a poly styrenea 12-armed SI star-block copolymer (isoprene core). The block molecular weights 

are: 15-69-15 for the SIS triblock, 10-50-10 for the SBS triblock and 12-44 for 

each SI diblock arm of the star (giving a span molecular weight of 12-88-12). The 

compositions are: 30 wt%, 32 wt%, and 27 wt% PS for the SIS, SBS, and star 

respectively. Figure 1 shows the X-angle as a function of deformation on loading. 

The SIS and star samples parallel each other quite closely. The SBS curve indicates 

the formation of the X-angle at the lowest deformations. At higher deformations 

the SBS curve crosses over and reaches a smaller asymptotic limit. Examination of 

the Figure 2 shows that the SBS sample has a much higher load bearing capacity. 

isoprene-styrene) SIS triblock, a poly(styrene-buta- diene-styrene) SBS trib \ ock and 

140 

120 

100 

5 80 

60 

40 

20 

0 0 I 0.5 

Star X 

1 1.5 2 2.5 3 3.5 4 

Strain 

Figure 1. Angle between the arms of the 

'X' observed in the 2-D diffraction patterns as a function of deformation. The 

SBS sample behaves qualitatively differ- : ent than either the Star or the SIS samg ples. 

1.8 "'""'-l 

1.6 

,-. 1.4 ri 9 1.2 

2 0.8 

0.6 

0.4 

0.2 

0 

I/) 

0 0.5 1 1.5 2 2.5 3 3.5 4 

Strain 

Figure 2. Stress vs. strain measured insitu for the samples shown in Figure 1. 

Note that the SBS sample has a much 

higher load-bearing capacity than either 

the Star or SIS samples. 

The Crystal Structure Determination of the SecA Translocation AT- X12B, 

Pase X4A 

J.F. Hunt and J. Deisenhofer (HHMI, UT Southwestern) 

SecA is the engine which drives the ATP-powered translocation of secretory proteins through the bacterial periplasmic membrane. Although SecA exists in a fully 

water-soluble form, it undergoes cycles of membrane insertion and retraction in the course of its ATPase cycle. SecA is believed to function as a molecular ratchet in 

the protein translocation reaction, pulling segments of the secretory protein through 

the membrane concomitant with the ATP-driven membrane insertion cycles. SecA 

also auto-regulates its own translation by binding to a specific RNA sequence overlapping the initiator codon in its messenger RNA. The SecA protein possesses two 

tandem ATP-binding domains with approximately 30 percent identity to the ATPbinding cassettes of the ABC transporter superfamily of transmembrane transport 

proteins. Based on its domain organization, its sequence homology, and its activity, 

it has been proposed that SecA may have structural and mechanistic similarities to 

the ABC transporters. 

The crystal structure determination of the soluble, membrane-retracted state 

of SecA is now almost completed. Data collected on beamlines X12B and X4A 

at NSLS were instrumental in this process. Because our crystals only diffract to 

3.5 angstroms using a rotating anode source, our high resolution data (currently 

to 2.9 angstroms) was collected on beamline X12B. This beamline was also used 

for rapid derivative screening. Candidate crystals soaked in either Pt, Au, or Hg 

compounds were mounted and measured with the energy of the beam tuned to 

optimize anomalous data from the element in question. 2 X 4 degrees of data were 

collected very quickly in inverse beam geometry, and the anomalous chi-square 

at low resolution was used used as the criterion to determine whether collection 

of a complete data set was merited. The breakthrough derivative for the project was identified in this manner. Data collected on beamline X4A from a selenomethionyl derivative of SecA allowed the position of 33 methionines in the protein to 

be observed in an anomalous difference fourier using MIR phases (the 3.8 angstrom 

diffraction from this crystal was too weak to be useful for MAD phasing). 

The refinement of the structure is currently in progress. A working model for 

the domain rearrangements in the course of the SecA ATPase / transport cycle has 

been formulated, and, on this basis, further experiments are being designed to try 

to elucidate the structural mechanism by which the hydrolysis of ATP is coupled 

to transmembrane transport of nascent polypeptide chains. 
P 

P 

& Structural Studies of the Yeast Bleomycin Hydrolase, Gal6 * 

L. Joshua-Tor, J. Rosenbaum (Cold Spring Harbor Lab), W. Zheng, H. Whelan 

and S. A. Johnston (UT-Southwestern) 

Resistance to antineoplastic drugs, whether intrinsic or acquired, is a central 

problem in treatment of human cancers. Bleomycin hydrolase is a cysteine protease 

discovered by its ability to hydrolyze the anticancer drug bleomycin and thus to 

limit its use in cancer therapy. The recent discovery of homologs of this intracellular, 

hexameric, 300 kD protein in yeast and bacteria implies a conserved cellular function 

for this protein, yet the only known natural substrate, bleomycin, is almost never seen by any of these cells. The yeast protein, Gal6 was found to bind nucleic 

acids. It binds preferentially to single-stranded DNA or RNA with a Kd of 10 

nM, and to nicks in double-stranded DNA Moreover, its expression is regulated by 

galactose and the iGAL regulon and Gal6 itself acts as a repressor for galactose 

regulated genes. Bleomycin hydrolase turns out to be, therefore, a rather surprising 

enzyme. It is a cysteine protease that binds nucleic acids, has been conserved 

from bacteria to humans, yet its cellular function is still unknown. In recent years, 

there has been considerable interest in intracellular proteases, since they seem to be 

involved in important regulatory processes. We are investigating the properties of 

the bleomycin hydrolases, both in terms of understanding how the various activities 

of the protein are linked and in understanding the mechanism for drug resistance. 

These will facilitate the elucidation of the conserved cellular function that is implied 

from its conservation from bacterial to humans. 

Having solved the structure of the mature yeast enzyme, we have begun to study 

various mutants and complexes. The first mutant is one where we replaced the 

active site cysteine with an alanine. Since the protein undergoes an autocleavage 

reaction, by clipping off its own C-terminal amino acid, this would enable us to 

have a look at one natural substrate, the C-terminus, sitting in the active site of 

the protein. This mutant was crystallized and similar to the case with the native 

crystals, these crystals are rather thin and diffract to about 3.5 Aon our home 

source. Therefore, it was essential to collect data using a synchrotron source. Due to 

radiation sensitivity, the crystal was cryocooled using an Oxford Cryosystem device 

and data were collected from a single crystal on beamline X12B to a maximum 

resolution of 2.05 8. The data are 97.3% complete with a final scaling R-factor is 

0.077 to that resolution. The structure was determined using the native structure 

of Gal6 and is currently being refined. The C-terminus including the last amino 

acid, which is cleaved in the mature enzyme, is clearly seen in the electron density 

maps. 

X12B 1 X12B 1 Structure and Relaxation of Polyimides Using Small Angle X-ray 

Scattering 

S. X. Lu , P. Cebe (Tufts U.), and Malcolm Capel (BNL - Biology) 

The thermoplastic polyimide, NEW-TPI, has been investigated using small angle X-ray scattering and thermally stimulated depolarization current measurements. 

SAXS was used to study the development of lamellar structure during isothermal 

or non-isothermal crystallization. The one-dimensional electron density correlation 

function was used to determine the structural parameters, such as long period, 

lamellar thickness, and linear crystallinity. The long period, lamellar thickness, 

and amorphous layer thickness all increase as the crystallization temperature in- creases from 300C to 360C. By combining melting point data with SAXS results we determine the side and fold surface free energy for the crystals, which are 29+/- 

3 and 41+/-3 ergs/cm-cm, respectively. Real-time SAXS was carried out during 

non-isothermal heating at 5C/min. The long period decreases while the lamellar 

thickness, linear crystallinity, and inter-phase thickness increase with increasing 

temperature. Results are interpreted using a lamellar insertion model. 

Sharon X. Lu, Peggy Cebe, and Malcolm Capel, "NEW-TPI Thermoplastic Polyimide: Structure and Relaxation Using SAXS and TSDC" J. Applied Polymer Science, vol. 57, 1359-1372 (1995). 

* This work is supported by NIH grant R01-CA71746 to L.J.; NIH grant R01-CA67982 

and a Tobacco Research grant to Stephen A. Johnston. 
I Structure of Horse Liver Alcohol Dehydrogenase at 1.25 A Resolution I X12B I ~ 

S. Ramaswamy, H. Eklund (Swedish U. of Agricultural Sciences) and B.V. Plapp 

(U. of Iowa) 

The structure of horse liver alcohol dehydrogenase (LADH), has been worked on 

for more than two decades. The structure of the protein has been refined to 1.8 

Ang resolution. Bryce Plapp has been studying the mechanism of enzyme catalysis 

of this enzyme, also for more than two decades. LADH shows evidence of tunneling 

and low barrier H-bonds from isotope effects (l), but the x-ray resolution is not high 

enough to confirm this structurally. The nicotinamide rings of the coenzyme rings in 

complexes with substrate analogs (NAD+ with pentafluorobenzyl alcohol or NADH 

with formylpiperdine) may be distorted, as suggested by molecular dynamics. The 

protein is a dimer of 374 residues per monomer, and the subunits may not be 

equivalent, as determined at 2.1 Ang. (2). The frozen crystals of the monoclinic 

form diffract to better than 1.2 A resolution. We have collected and processed a 

data set to 1.25 A and also computed initial maps. The maps were computed using 

the coordinates of the structure refined at 1.7 A resolution for a different complex. 

The intial difference map (figure 1) clearly indicates the position of the Penta fluoro 

benzyl alcohol. Initial look at the density around the Nicotinamide ring of the 

NAD (figure 2 )suggests that the C4 atom probably has the additional Hydrogen 

and NAD has been reduced to NADH. 

Refinment using maximum likelyhood methods followed by SHELX96 is in 

progress. There are 1500 residues in the asymmetric unit and more than a million 

reflections were measured to get over 350,000 unique reflections. This is probably 

the structure at this resolution with this many residues in the asymmetric unit. 

Acknowledgement: The proiect ." was supported .- bv the Swedish NFR for HE and 

by NIH for BVP. 

REFERENCES: (1) B. Bahnson, D.-H. Park, K.-H. Kim, B. V. Plapp, and J. P. 

Klinman (1993) Unmasking of Hvdroaen Tunneling in the Horse Liver Alcohol Dehydrogenise &action by site-DhectLd MutageneGs, Biochemistry 32: 5503-5507. 

(2) S. Ramaswamy, H. Eklund, and B. V. Plapp (1994) Structures of Horse Liver 

Alcohol Dehydrogenase Complexed with NAD and Substituted Benzyl Alcohols, 

Biochemistry 33: 5 23 0- 523 7. 

Crystalization and Preliminary X-ray Analysis of Aa Subunit of Protein Phosphatase 2A * X12B 

M. Skidmore, M. Sawaya (UCSD), S. Parkin, B. Rupp (LLNL), H. Hope (UCD), 

and G. Walter (UCSD) 

Protein phosphatase 2A (PP2A) is the most abundant serine/threonine phosphatase in mammalian cells and is important in a number of cellular processes such 

as cell division, development, and signal transduction. The dimeric core enzyme 

is composed of a catalytic C and regulatory A subunit which at times is bound 

by one of a family of regulatory B subunits. PP2A also forms complexes with 

the small DNA tumor viruses SV40 and polyoma and is involved in tumorigenesis. 

The A subunit has 15 nonidentical repeats of 38 - 43 amino acids. A model has 

been proposed whereby each repeat forms two amphipathic alpha helices that pack 

against the next repeat to make a long rod shape consistent with biophysical and 

site directed mutagenesis datal. 

The Aa subunit of human protein phosphatase 2A forms crystals in space group 

P21 with cell dimensions a = 104.0, b = 174.9, c = 168.2 A, and ,B angle = 90.2'. 

At cryogenic temperatures the crystals diffracted to a resolution of about 3.0 A. 

Based on the unit cell dimensions and a calculated molecular mass of 65,277 / Da, 

the Matthews coefficient of 3.17 AS / Da suggests eight molecules in the asymmetric 

unit. Data were collected on a single native crystal at NSLS Beamline X12B with 

a MAR Research imaging plate and Oxford Cryostream at 93 K. The final reduced 

data set has a maximum resolution of 3.0 A in the shell with > I</u = 1.8. A total 

of 188,109 observations were collected with 93,490 unique reflections in a data set 

that is 81 % complete with Rsym = 0.076. Additional time was used for screening 

possible heavy atom derivatives and collecting another data set on one putative 

derivative2. 

Ruediger R, Hentz M, Fait J, Mumby M, and Walter G. 1994. Molecular Model 

of the A subunit of protein phosphatase 2A: Interaction with other subunits and 

tumor antigens. J. Virol. 68:123-129 

Skidmore M, Sawaya M, Parkin R, Rupp B, Hope H, Everse S, and Walter G. 

1996. Crystallization of the Aa subunit of protein phosphatase 2A. Protein Science 

5:1198-1200. 

Figure 1. Figure 2. * This work was supported by PHS grant CA-36111 and UC-TRDRP to GW, DOE 

contract No. W-7405-ENG-48 to BR and NIH grant 5 T32 DK07233-20 to MRS. 
A Bent-Laue Crystal Monochromator for Monochromatic Radiography with an Area Beam 

Z. Zhong(NSLS), D. Chapman(CSRRI), W. Thomlinson, F. Arfelli, N. Gmiir and 

R. Menk (NSLS) 

A bent Laue crystal monochromator which can diffract a large area of monochromatic x-rays from a polyenergetic x-ray rotating anode source has been developed 

and tested at the X12A beam line using K fluorescence x-rays of Ba, La, Mo and 

Ag targets. The monochromatic beam, with a solid angle of more than 5 degrees 

x 5 degrees and energy range tunable from 15 keV to 100 keV, is completely separated from the white beam at a distance of less than 1 meter from the source. The absolute reflectivity of the monochromator ranges from 10 to 40% (depending on the energy of the x-rays being diffracted and the source size). The energy 

bandwidth of around 2% is controllable by varying the diffraction planes used, the 

crystal thickness, asymmetry angle and the bending radius. A single emission line 

from an x-ray tube source can be selectively diffracted into the entire exit-beam 

solid angle. Potential applications of the device include monochromatic beam diagnostic radiography and dual-energy subtraction imaging when the beam energy is 

tuned to bracket the K-edge of the radiographic contrast elements such as iodine. 

Fluorescence radiation from the target excited by the synchrotron white beam 

was used as the point x-ray source. The size of the source spot can be changed 

by changing the size of the incident synchrotron beam on the target (Fig.1). [111] 

reflections of 0.46 mm thick silicon crystals with different asymmetry angles were 

tested with bending radii between 0.3 and 1 meters. Differential bending was found 

essential to match the angle of the crystal planes with the divergence of the source at any point on the crystal to reflect the area beam uniformly. Fig.2 shows the 

image of the reflected beam after the crystal is aligned to reflect both the K,1 and 

K,z lines of a molybdenum target. The bending radius was 0.378 m which gave 

a source to crystal distance of 0.331 m. The image plate was placed at 300 mm from the crystal. It can be seen that the crystal is capable of staying within the 

FWHM of the reflection in the 25 mm high by 50 mm wide crystal except at the 

corners. The corresponding image size is 50 mm high by 100 mm wide. The vertical 

lines (glitches) in the diffracted beam were explained and indexed by simultaneous 

diffraction effects. 

This work was supported by US DOE contract DE-AC02-76CH00016 and ARPA 

contract AOB227. 

Figure 1. Experimental setup Figure 2. Image of the diffracted beam 

RlL, 

LThe Structure of Calicivirus x25 I 

Introduction: The recent rapid spread of a rabbit calicivirus through Australia 

to Europe demonstrated a potentially dangerous situation if a human calicivirus 

emerges. It is estimated that at least 42% of outbreaks of nonbacterial gastroenteritis in the U.S. are caused by this group of viruses [l]. The main difficulty in 

dealing with infections of small round-structured viruses (SRSV's) is the large diversity of the viral capsid protein [2]. 

We have purified and crystallized FCV strain F9 and a large 

amount (50% complete) of X-ray diffraction data to 3.OA resolution have been collected at synchrotron stations [3]. The space group of the crystal is C222, a=889W, 

b=996A, c=4362. A total of 226 images afforded 1,396,078 reflections, which is 

about 40% complete to 3.5A resolution. There are two independent particles in the 

unit cell, one sits on the a axis, the other on the b axis. Each of the particles is 

rotated by less than 2' from the ideal orientation. Model coordinates have been 

constructed based on the cryo-EM structure. The high resolution structure determination is well under way by using the molecular replacement density averaging-phase 

extension method. Although there were no improvement this time on the quality 

of the diffraction data collected at NSLS, we expect to collect better data in the 

future by use of the cryo-freezing technique. 

Discussion: Caliciviruses resemble the picornaviruses with which they were originally classified. Like the picornaviruses, the genomes of calicivirus bear a covalently 

attached protein (VPg) at the 51 end, and there is no cap structure at the 51 end 

of the subgenomic mRNA. However, caliciviruses differ from members of the picornavirus group in that RNA species smaller than the genomic RNA are synthesized 

intracellularly. A striking difference between caliciviruses and picornaviruses was 

found in their genome organization. The genomic RNA of picornaviruses encodes a 

single polyprotein which is co- and post-translationally processed to yield the mature viral proteins. No single large polyprotein precursor to all the viral proteins is 

known for calicivirus. The genes encoding for the structural polypetides are located near the 31 end of the genomic RNA. 

In our studies a feline calicivirus strain F9 was used for the X-ray structure 

determination. The comparative sequence analysis of capsid precursor proteins from 

FCV strains F9 and CFI/68 FIV demonstrated that variation was concentrated in 

two areas. 

Reference: Kaplan, J.E., R. Feldman, D.S. Campbell, C. Lookabaugh and G.W. 

Gary (19821, The frequency of a Norwalk-like pattern of illness in outbreaks of acute 

gastroenteritis. Am. J. Public Health 72:1329-1332. 

Wang, J., X. Jiang, H.P. Madore, J. Bray, U. Desselberger, T. Ando, Y. Seto, 

I. Oishi, J.F. Lew, K.Y. Green and M.K. Estes, 1994. Sequence diversity of small, 

round-structured viruses in the Norwalk virus group. J. Virol. 68:5982-5990. 

Zhou, L. and Luo, M. "Preliminary Analysis of Feline Calicivirus Crystals", Acta 

Crystallogr. D51:850-852, (1995). 

L. Zhou and M. Luo (U. of Alabama at Birmingham) 

Experimental: 
X-ray Crystal Structures of the S229A Mutant and Wild Type 

MurB in the Presence of the Substrate Enolpyruvyl-UDP-NAcetylglucosamine at 1.8 Resolution 

x12c 

T. Benson, C. Walsh and J. Hogle (Harvard Medical School) 

Data were collected on two variants of the enzyme, UDP-Nacetylenolpyvurylglucosamine reductase (MurB), wild type and a Ser 229 Ala mutant, in complex 

with the enolpyruvylglucosamine substrate. MurB catalyzes the second step of 

peptidoglycan biosynthesis in bacteria by reducing the enolpyruvyl moiety to a 

lactyl ether which serves to link the glycan and peptide strands of this biopolymer. 

Previously, synchrotron data had been collected on the wild type crystal to 2.7 

both at X4A (NSLS) and A1 (CHESS). The beamline geometry at X12C with the 

30cm Mar detector and 2theta arm for the detector made possible for the first time 

the collection of the high resolution data. The data collection and computational 

support during our run at X12C enabled us to complete indexing and integration 

of the data before leaving the synchrotron. Data were collection to the diffraction 

limit of the crystals, 1.8 resolution. The data collection statistics gave Rsym values 

of 4.1% for wild type and 4.2% for the Ser229Ala mutant with an average I/s 

of 31.8 and 24.8 respectively. Both structures have been refined to 1.8 with a 

crystallographic R-factor of 20.3% (wild type) and 20.2% (mutant) and with a free 

R-factor of 25.6% (wild type) and 24.6% (mutant). 

Biochemical comparison of the wild type and mutant enzymes revealed a dramatic kinetic defect observed for the Ser 229 Ala mutant in the second half reaction 

(an approximately 107 fold decrease in the reoxidation of FADH2). Comparison of 

the two high resolution structures revealed that the mutation eliminated a hydroxyl 

group which has previously been proposed to play a critical role as a proton donor 

during the second half reaction of MurB, namely reoxidation of FADH2 and reduction of the enolpyruvyl substrate. This single point mutation of residue 229 from 

serine to alanine also removed the water molecule which is hydrogen bonded to the 

serine hydroxyl in the wild type structure, thereby changing the hydrogen bonding 

network with in the active site. Structural analysis confirmed that the kinetic defect 

observed in the mutant is a direct result of the loss of the serine hydroxyl moiety 

rather than other nonspecific active site changes or general structural defects. 

Crystal Structure of the FASCICULINZ-MOUSE 

Acetylcholinesterase Complex x12c 

Y. Bourne (TSRI), R.B.G. Ravelli (Lab. Crystall.& Structual Chem.), M. 1;. Raves, 

J. L. Sussman (Weizmann Inst.), P. Taylor and P. Marchot (UCSD) 

Acetylcholinesterase (AChE) terminates the action of the neurotransmitter, 

acetylcholine, at central and peripheral cholinergic synapses. Fasciculins, that belong to the family of three-fingered snake toxins are the only known peptidic inhibitors of AChE. We have determined the crystal structure of fasciculin2 (Fas2) in 

complex with a recombinant, monomeric AChE from mouse (mAChE) at 3.2 A resolution [l]. The complex generated two indistinguishable hexagonal crystal forms, 

A and B, that belonged to space group P6522 with cell dimensions, a=b=75.5 b, 

c=556.2 A for form A, and a=b=128.4 b, c=556.6 A for form B [2]. Separation of 

the diffraction spots along the c axis was achieved at beam line X12C, owin to its 

MarResearch 300 mm imaging plate mounted on a CAD-4 diffractometer $EnrafNonius). A 3.2 b resolution data set,(85% complete, R,,,=8.9%), was collected 

from four form A crystals with a crystal-to-detector distance of 862 mm (X=l ) or 538 mm (X=1.5) and a 10.6 and 12.4' tilt, respectively. A second data set, 

at 3.5 b resolution (87% complete, R,,,=9.4%), was collected from four form B 

crystals with a distance of 757 mm (X=1.15 ) and a 10' tilt. The structure of form 

A was solved by a combination of molecular replacement and model building techniques, and refined to a crystallographic R-factor of 18.4% (R-free=29.4% for 5% 

of the reflections) using all 13,823 data in the 10 k to 3.2 k resolution range. The 

structure of form B was solved by molecular replacement using the refined model 

A, and refined to an R-factor of 20.8% (R-free=32.2%) using all 29,167 data in 

the 10 A to 3.5 A resolution range. Model B was found essentially identical with 

model A. [l] Y. Bourne, P. Taylor and Pascale Marchot. (1995) Cell 83, 503-512. 

[2] P. Marachot, R.B.G. Ravelli, M.I. Raves, Y. Bourne, D.C. Vellom, J. Kanter, S. 

Camp. J.L. Sussman, P. Taylor, (1996) Protein Sci. 5, 672-679 

Figure 1. Stereo pair view of the 3.2A resolution omit Fo-Fc electron density map 

(contoured at 2.5 u) showing the stacking interaction between Fas2 Met33 and 

mAChE Trp286 (middle) 
P 

w 

x12c Structure of the Hydroxylase Component of Methane Monooxygenase from Methylosinus trichosporium OB3b at 2 A Resolution 

N. Elango, R. Radhakrishnan, W.A. Froland, C.A. Earhart, J.D. Lipscomb and 

Methane monooxygenase (MMO catalyzes the insertion of an oxygen atom from 

membrane-bound copper-containing protein and a soluble iron-containing protein. 

Unlike cytochromes P-450 which use a heme prosthetic group to generate a high 

valent iron-oxo moeity FeV=O) capable of performing this chemistry, soluble MMO 

uses a p-oxo bridged d iiron center. In both cases these iron metalloenzymes are rather promiscuous recognizing a variety of alkanes, alkenes, ethers, and alicyclic, 

heterocyclic and aromatic compounds as substrates. A structural study of soluble 

MMO was undertaken to provide a structural foundation for understanding the 

basis of the catalytic process. 

Soluble MMO is composed of 3 protein components: a 245 kDa catalyticallycompetent (r2P2y2 hydroxylase (MMOH), a 38 kDa NAD(P)H-dependent reductase, and a 16 kDa regulatory protein known as component B. The structure of 

diferric form of MMOH from the type I1 methanotroph Methylosinus trichosporium 

OB3b has been determined to a resolution of 2 a using data collected at 2OoC on beamline X12C of the NSLS. The final structural model has 510 of 526 residues of 

the a chain, 385 of 394 residues of the p chain, 167 of 168 residues of the y chain, 

and 729 solvent molecules and produces a crystallographic R value of 0.162 using 

75570 reflections between 5 and 2 A resolution with F>2~7. The exceptionally clear 

electron density map revealed 15 isolated errors in the reported amino acid sequence 

including Glu209m, a ligand to Fel in the active site, which had been reported to 

be an aspartate and 28 consecutive errors in the y chain apparently arising from 

a shift in the reading frame. The two irons at the active site are octahedrally coordinated with a histidine and two glutamates plus a bridging glutamate and 2 

bridging hydroxyls. The irons differ in the sixth ligand-a solvent molecule for Fel 

and a glutamate for Fe2. 

The structure of MMOH from the type I methanotroph Methydococcus cupsulutus 

Bath has been determined by others using data collected at 4OC and at -160'C. 

As expected from the 66% homology in the amino acid sequence, the structures of 

these proteins are very similar (RMS difference in Ca's = 0.8 A. The active site 

structure of MMOH from M. trichosporium OB3b we determined at 2OoC is more similar to that of M. cupsulatusBath determined at -160°C than that determined 

at 4°C. In the frozen M. capsulutus Bath MMOH, the irons are separated by 3.1 

A and they are bridged by two hydroxyls. In the M. trichosporium OB3b MMOH 

the Fe-Fe distance is 3 A with the same bridging hydroxyls. In the M. cupsulutus 

Bath MMOH determined at 4OC the Fe-Fe distance is 3.4 A and one of the bridging 

hydroxyls has been replaced by an acetate. As this Fe-Fe distance is more similar to 

that of the reduced MMOH, we suggest that the reported structure of M. cupsulutus 

Bath MMOH determined at 4OC is that of the partially reduced protein. 

D.H. Ohlendorf (U of Minnesota) 

molecular oxygen into the C-H bon d of methane. MMO can be found in two forms-a 

I Structural Studies of Nucleosomes. * I x12c I 

J. M. Harp, D. E. Timm (UTK), and G. J. Bunick (ORNL) 

We have been involved in a project directed toward the solution of the high resolution structure of the nucleosome core particle. Diffraction quality of the nucleosome 

core particle crystals had been improved by reconstituting the particle using a 146 

bp DNA palindrome based on a nucleosome phasing sequence on alpha satellite 

DNA from the human X chromosome. Crystallization of the nucleosome particles was done in the microgravity environment provided on the United States Microgravity Laboratory (USML-2). Because of prolonged lauch delays we were only able to 

obtain a few small crystals. Data was collected on one of these crystals at lOOK 

using the MAR image plate detector on beamline X12C at the NSLS. The crystal 

provided excellent data to 2.5 A with an overall linear R-factor of 0.053. Recent 

experiments aboard the Mir space station have provided much larger crystals. 

As an adjuct to the nucleosome core particle studies, data were also collected on crystals of the histone octamer core of the nucleosome. Complete data sets 

were collected on a native chicken histone octamer crystal and on two heavy atom 

derivatives. The data were collected at lOOK on beamline X12C using the MAR 

image plate detector. The native crystal provided useful data to 2.5 A . Anomalous 

diffraction data were collected from a mercury thiocyanate derivative crystal and 

data were also collected from a mercury acetate derivative. These data sets are 

being used to solve the structure of the histone octamer at low temperature. 

* Research sponsored by the Office of Health and Environmental Research, USDOE, 

under contract No. DE-AC05-960R22464 with Lockheed Martin Energy Systems, Inc., 

and NIH Grant No. GM29818. 
The Structure of the Complexof Concanavalin A with Methyl AlphaD- Arabinofuranoside 

A.J. Kalb (Gilboa), F. Frolow, A.G. Evdokimov and R. Ventura (Weizmann Institute) 

Concanavalin A, a saccharide-binding protein (lectin) from the Jack bean, binds 

simple and complex saccharides having non-reducing gluco- or manno-pyranoside 

end groups as well as those having the five-membered-ring arabinofuranoside structure. High resolution crystal structures for saccharide-free concanavalin A and 

for its complexes with gluco- and manno-pyranosides have been reported. Recently, we have crystallized a complex of concanavalin A with methyl a1pha-Darabinofuranoside. At the resolution of the earlier study (2.7A), it was not possible 

to determine the conformation of the bound saccharide because the intrinsic flexibility of the five-membered ring precluded the use of an explicit model for the 

bound sugar. The present experiment has resolved this problem by extending the 

resolution limit to 1.7A, where the detailed structure of the bound saccharide can 

be clearly observed. This was ac;omplished by flash freezing of the crystal and 

the use of the high intensity, highly monochromatic X-ray beam,the excellent cryostatic device (Oxford Cryostream and the high quality imaging plate area detector 

(MAR30) available at beamline 2( 12C. Data collection was greatly facilitated by 

the excellent, user-friendly software and by the goniostatic crystal mount in use at 

this beamline. Data processing was easily accomplished simultaneously with data 

collection by means of an interface between the data collection and data processing 

programs. We collected 53,746 unique reflections with R(sym) of 6% on intensity, 

average redundancy of 3 and 95% completeness. Currently, the structure of the 

complex has a conventional Fl-factor of 26% (R-free 30%) with excellent geometry. 

The bound methyl alpha-D-arabinofuranoside, although smaller than the glucoand mannopyranosides, interacts with the saccharide-binding site of the protein in 

much the same way - via a network of seven hydrogen bonds and a multitude of van 

der Waals contacts. This mode of interaction corresponds closely to that which we predicted earlier on the basis of molecular mechanical considerations. 

~~ 

Crystal Structures of Two Thermostable Bacterial Alcohol Dehydrogenases 

Y. Korkhin, F. Frolow, A.J. Kalb (Gilboa) (Weizmann Institute of Science) 

Crystal structures of secondary alcohol dehydrogenases from Therrnoanaerobium 

brockii TBADH) and Clostridium beijerinckii (CBADH) have been determined. 

thermal stability as measured by the temperature of half inactivation in 60 min. 

Both enzymes were crystallized in holo- and coenzyme-free forms [l]. Four data 

sets were collected at beamline X12C. A 2.05 k data set was collected from holoCBADH crystals at lOOK with an overall completeness of 88.2%. Two data sets were 

collected from apo-CBADH crystals at 100K: the first data set to a resolution of 2.15 

A with an overall completeness of 79% and the second to a resolution of 2.4 A with an 

overall completeness of 98%. A 2.5 a data set was collected at ambient temperature 

from holo-TBADH crystals with an overall completeness of 88.4%. The structures 

were solved by molecular replacement using previously determined 2.8 k MIR apoCBADH structure as a model. Holo-CBADH structure was refined with X-PLOR 

to an R-factor of 21.6% (R-free=26.8%) and holo-CBADH was also refined with XPLOR to an R-factor of 21.7% (R-free=27%). Apo-CBADH structure refinement 

at 2.15 A resolution is currently underway. 

Comparison of CBADH and TBADH crystal structures has revealed the structural determinants of enhanced thermal stability of TBADH, which, apparently, comes from strengthening the interface between its subunits. 

Having compared apo- and holo-CBADH structures we identified the structural 

determinats for coenzyme specificity. Additionaly, a new zinc atom coordination 

and possible modulation of this coordination by the presence of the cofactor in the 

active site of the enzyme were revealed. 

Korkhin, Y., Frolow, F., Bogin, O., Peretz, M., Kalb(Gilboa), A.J., and 

Burstein Y.”Crystalline alcohol dehydrogenases from the mesophilic bacterium 

Clostridium beijerinckii and the thermophilic bacterium Therrnoanaerobium brockii: 

preparation, characterization and molecular symmetry”. Acta Cryst., D52, 882-886 

(1996). 

x12c 

These i4 ADP-dependent enzymes have 75% sequence identity but differ by 26°C in 

1. 
Y 

N 

N Structure of Lyme Disease Antigen OspA Complexed with a Fab * I x12C 

H. Li and C.L. Lawson (BNL - Biology) 

OspA is an abundant lipoprotein and a major antigen of the Lyme disease spirochete, Borrelia burgdorferi. The crystal structure of a soluble recombinant form 

of OspA was solved in a complex with the Fab fragment of a mouse monoclonal 

antibody and refined to a resolution of 1.9 A, based on data collected at NSLS 

beamlines X12C and X25 (Fig. lk Each data set was collected from a single 

crystal flash-cooled to 100 degrees . Data set Cys84-I1 was employed as the final 

native. Diffraction images were collected using MAR mage plate/scanner systems 

and were processed with DENZO. 

OspA has a novel repetitive antiparallel topology with a region of freestanding 

sheet. Conserved residues and a hydrophobic cavity buried in a positively charged 

cleft suggest a binding site for an unknown ligand. An exposed hypervariable region 

is predicted to be an important factor in the worldwide effectiveness of vaccines 

based on OspA. 

Diffraction Data and Phasing Statistics for the OspA-Fabl84.1 Complex 

Dataset Cys84-I Cys84-ll K,PtCI, lodo-Y Pb(CH,), 

XI 7C x75 xi 7c X17C XI 7C 

observed 155965 25471 9 87304 70488 89601 

unique 36731 58870 20837 1741 9 23461 

Resol 2.30 1.95 2.80 2.85 2.70 

Compl.% 97.9 97.1 98.2 88.5 99.3 

R,,,,% 5.2 (22.4) 4.8 (21.6) 8.0 (21.7) 8.6 (19.5) 6.9 (23.2) 

R,,,,% 6.8 10.5 6.6 

Phasing 1.61 (1.69) 1.24 l.Og(1.37) 

Figure 1. Numbers in parentheses indicate values for highest resolution shell (Rmerge) or for anomalous component (phasing power). 

x12c Crystal Structure of A 

from Castor Seed and its Relationship to other Diiron Proteins. 

Y. Lindqvist, W Huang, G. Schneider (Karolinska Institute) and J. Shanklin (BNLBiology) 

The three-dimensional structure of recombinant homodimeric D9 stearoyl-acyl 

carrier protein desaturase, the key enzyme in the conversion of saturated to unsaturated fatty acids, has been determined by protein crystallographic methods to a resolution of 2.4 . The structure was solved by a combination of single isomorphous 

replacement, anomalous contribution from the iron atoms to the native diffraction 

data and six-fold noncrystallographic symmetry averaging. The enzyme subunit of 

363 amino acids consists of a single domain built up from eleven a-helices. Nine of 

these form an antiparallel helix bundle. The fold of the enzyme subunit resembles 

that of the iron-containing subunit of ribonucleotide reductase and the hydroxylase 

component of the methane monooxygenase. The subunits in the dimer are tightly 

packed while the dimers pack loosely along a noncrystallographic threefold screw- axis. The enzyme subunit contains a diiron center, with ligands from four of the 

a-helices in the helix bundle. The iron ions are bound in a highly symmetric environment, with one of the irons forming interactions with the side chains of E196 and 

H232 and the second iron with the side chains of E105 and H146. Two additional 

glutamic acid side chains, E143 and E229 are within coordination distance to both 

iron ions. A water molecule is found within the second coordination sphere from 

the iron atoms, but there is no indication for a p-oxo bridge in the electron density 

maps. The lack of the E-oxo bridge and the rather long Fe-Fe distance (4.3) suggest 

that the crystals are the diferous form of the enzyme. 

Stearoyl-acyl Carrier Protein Desaturase 

* supported by BNL-LDRD, NIH-NIAID, and DOE-OHER 
I Structure of a Plant Profilin at 1.6 by MAD at X12C I Structure of Photolyzed Myoglobin I x12c I 

G.N. Phillips, Jr. (Rice U.), J. Berendzen, (LANL), I. Schlichting, (Max PlanckHedelberg), and R.M. Sweet (BNL - Biology) 

Myoglobin is a globular heme protein that reversibly binds ligands, such as 02, 

CO, and others. Single photons of visible light can break the covalent bond between 

CO and the haem iron in carbonmonoxy-myoglobin and thus form an unstable 

'geminate' state with the CO inside the protein. Using beamline X12C and a 

specially constructed helium cryo- stat, this geminate stated was trapped at about 

20K while a complete data set was taken to 1.5 Angstroms resolution. This work 

would not have been accomplished without the high quality beamline at X12C. 

The work has been published in Nature: 

Schlichting, I., Berendzen, J., Phillips, G.N., Jr., and Sweet, R.M., Crystal Structures of Photolysed Carboxy Myoglobin, Nature, 371, 808-812 (1994). 

R. Shigeta, K. Thorn (Princeton U.), H. Christensen (Nat U. Singapore), U. Lindberg (Stockholm U.), N.-H. Chua (Rockefeller U.), C. Schutt, (Princeton U.) 

Profilins are small eukaryotic proteins involved in modulating the assembly of 

actin microfilaments in the cytoplasm. Plant profilins are of interest because immunological cross-reactivity between pollen and human profilin may be the cause 

of hay fever and broad allergies to pollens. 

Collecting data on NSLS Beamline X12C, the determination of the Arabidopsis 

thaliana profilin isoform 1 structure using multiwavelength anomalous diffraction 

(MAD) proceeded in approximately 10 days from data collection to structure refinement to 1.6A. 

The fold of Arabidopsis profiin is quite similar to other classes of profilins solved 

previously (Figure l), but comparison of the structures of profilins from lower eukaryotes, mammals with a plant profilin allowed us to understand several important 

aspects of profilin function. 

For instance, although the actin-binding residues on profilin are not conserved, a 

comparison of these three structures allowed identification of conserved features of 

the contact surface at the level of atom type (Figure 2). These two surface features 

are conserved amongst nearly all profilins and may be responsible for the immune 

cross-reactivity of antibodies between human and plant profilins. 

Figure 1. Overall structure of Arabidopsis profilin.(left) Ribbon diagram of the 

fold of Arabidopsis profilin 1. profilin 1; 

every tenth residue is numbered. Figure 2. (right) The actin binding face of 

profilins. Residues correponding to the 

actin binding surface of (a) Arabidopsis 

profilin I, (b) Acanthameoba profilin I 

and (c) bovine profilin. Residues which 

are thought to contact actin are displayed on a ribbon representation (left 

column) and on a dark grey CPK van 

der Waals surface (right column). 

a) P62 

KX7 

XX 

GI 

TI1 

K115 

E82 

Figure 2. (continued) Only six structural 

features appear to be conserved binding determinants with actin across the 

kingdoms despite a near identity of the 

profiin binding site of actin. 
[Crystallographic Studies of hnRNP A1 I x12c I 

R-M. Xu (Cold Spring Harbor Lab.) 

Heterogeneous nuclear ribonucleoprotein (hnRNP A1 is one of the most abundant hnRNP proteins in the hnRNP complex. hnR k P A1 has been shown to be 

involved in regulating alternative 5’ splice site selection. It facilitates the efficient 

annealing of complementary RNA or DNA molecules. hnRNP A1 also contains a 

nuclear export signal, which is responsible for the hnRNP A1 shuttling between the 

nucleus and the cytoplasm. 

We have crystallized the RNA-binding domain of the hnRNP AI, termed UP1, 

which contains two RNA-recognition motifs. UP1 crystallizes in spacegroup P21 

with cell parameters a=37.98 8, b=43.92 A, c=55.75 8, beta=94.2 degree. A 

complete native data set to 1.9 A resolution has been collected. One mercuril 

derivative data set to 2.5 A resolution and one platinum derivative data set to 2.4 

A have also been collected. The mercurial derivative shows good isomorphism to 

2.5 A with the native crystal and it has produced interpretable electron density 

map. 
Characterization of the Elliptical Polarized Wiggler at the Iron K-edge I* 

W. A. Caliebe, C.-C. Kao, P. Stefan, E. Johnson, D. P. Siddons, and J. B. Hastings 

(NSLS) 

The straight section of the NSLS X-ray ring is used to test newly developped 

insertion devices. The newst device is an elliptically polarized wiggler, which has 

already been used intensively in the soft X-ray region between 500 eV and 1000 eV. 

Using a flat Si(ll1) monochromator the flux between 5 keV and 12 keV and the 

degree of polarization at the Fe K edge have been measured. Both measurements 

have been done with the EPW operating in DC-mode, which results in one helicity. 

The flux for both helicities is shown in fig.1. The difference in intensity results 

from different positions of the beam relative to the slit in front of the monochromator. The change in intensity at 7.1 keV results from Iron in the Be-windows. 

The flux is approximately 2.101'ph/s in a bandwidth of 0.2% and a solid angle of 

0.1 mradxl mrad. 

The degree of polarization has been determined using the difference of absorption 

of left and right circular polarized X-rays by a magnetized iron foil. The experiment 

has been done by inverting the direction of the magnetic field for one helicity, which 

gives the same information. The results for both helicities and opposite magnetic 

fields are shown in fig.2. The effect in these measurements is of the order of 0.05%. 

Comparing this value with published date and taking the polarization factor of the 

monochromator into account one obtains a degree of polarization of 50% for the 

EPW. 

3.5 -1 

3.0 I /J1\ 

..,. . .... 

1.0 . :' 

5 6 7 8 9 10111: 

I.* 8 I I 

5 6 7 8 9 10111: 

Energy [keV] P 

-0.10 7100 7105 7110 7115 7120 7125 7130 

Energy [.VI Figure 1. Flux of the EPW 

w 

I 

P 

h3 * This work was supported by US DOE Figure 2. MCD of Iron at the Fe K-edge uI grant DE-AC02-76CH00016. 

X13 Generation of Coherent Soft X-rays with the Prototype gall Gap 

Undulator. * 

E. Dufresne, S.B. Dierker (U. Michigan) L.E. Berman and Z. Yin (NSLS) 

We investigated the suitability of the Prototype Small Gap Undulator (PSGU) at 

X13 to generate coherent X-rays for X-ray Photon Correlation Spectroscopy (XPCS) 

experiments [l]. Since the coherent flux is proportional to the brightness times the 

wavelength squared, this new set up, compared to previous ones at X25[1], increases 

the coherent flux by using a longer wavelength and by using the large increase in 

brightness provided by the PSGU at 3 keV. The only optical element in the beamline 

was a Be window, so we were able to isolate its effect on the beam spatial profile. 

One meter downstream of it, we measured large spatial variations appearing as long 

horizontal stripes, with a vertical spacing of M 20 pm. The variation amplitude was larger at 3 keV than at 9 keV, and diminished when the beam was profiled 

4 cm behind the window. The energy and distance dependence seems qualitatively 

consistent with a focussing effect caused by the refraction of X-rays by the rough Be 

[2]. To limit the incident beam size to its smallest transverse coherence length (z 

lO,um~[l], we developed new slits for XPCS experiments controlled by DC motors. 

The s 't opening could be controlled to a fraction of a ,um reproducibly. They were 

designed to use inclined soft transmitting edges in order to reduce the parasitic 

diffraction from the slits at wavevectors near lop3 A-1. We observed a "phase 

peak" in the Fraunhofer diffraction patterns of these slits, caused by a periodic 

phase variation of the X-rays transmitted through the soft edges. The results are 

in good agreement with a simple model. In an attempt to increase the usable 

coherent flux, we focussed the beam by a factor of 20 in the vertical direction with 

a simple float glass mirror [3]. However, due to a systematic figure error and a large 

demagnification ratio, the transverse coherence was greatly reduced. To preserve 

the transverse coherence, we replaced the focussing mirror with a double multilayer 

monochromator. With the fundamental set at 4.1 A, we measured 2 x 10' ph/s at 

300mA in a 10 pm pinhole, and observed a diffraction pattern from this pinhole. 

In order to further optimize the flux, we used a double flat glass mirror assembly, 

which transmitted the full bandwidth of the fundamental. We obtained a substantial 

increase of coherent flux of 3X lo9 ph/s at 300mA in a 10 ,urn pinhole. Unfortunately, we found that the coherent flux decreased continuously with X-ray exposure by 

a factor of 300. We measured a 4 A rms roughness for the unexposed mirrors. 

After approximately 13 days of X-ray exposure, the rms roughness of both mirrors 

increased to values ranging from 84 to 284 A on the center of the beam footprint, 

indicating that the loss of coherent flux was caused by permanent X-ray damage. 

Although, the coherent flux increases for soft X-rays, an XPCS experiment is more 

difficult to perform at 3keV than at 8keV because the experiment must be done 

in He to reduce air absorption. The stronger absorption also limits the scattered 

intensity from the sample, which reduces the gain made in coherent flux. 

[2] A. 

Snigirev et al. NIM A 370 (1996) 634 [3] Z. Yin, L. Berman, S. Dierker, E. Dufresne, 

D.P. Siddons, SPIE Proceedings 2856, Dec. 1996. 

[l] See S. Dierker, NSLS Newsletter, July 1995 and references within. 

* E.D. acknowledges the support of NSERC. This work was supported by NSF Grant 

No. DMR-92-17956 and by DOE contract No DE-AC02-76CH00016. 
X13 46 

+ A Simple X-Ray Focusing Mirror Using Float Glass * 

Z. Yin, L. Berman (NSLS), S. Dierker, E. Dufresne (U. Michigan) and D.P.Siddons 

(NSLS) 

In our recent x-ray photon correlation spectroscopy (speckle) experiments at 

NSLS, one of the challenges is to increase the coherent photon flux through a pinhole, whose size is chosen to match the beam’s horizontal transverse coherence 

length lh. We adopted an approach to vertically focus the x-ray beam so as to 

match its vertical transverse coherence length 1, (at NSLS X13, E, N 50Eh, Eh N 12 

pm at 3 KeV) with lh. By demagnifying the vertical size by a factor of l,/lh, we expect to increase the intensity of the x-rays through the pinhole by the same factor 

while keeping the beam coherent. 

A piece of commercial 3/8” thick float glass, by virtue of its low surface roughness 

(w 3A rms), good reflectivity in the low photon energy range of interest and low 

cost, was chosen as the mirror material. A computer controlled motorized bender 

with a four point bending mechanism was designed and built to bend the float glass 

to a continuously variable radius of curvature from -700m (intrinsic curvature of 

the glass surface) to < 300m, as measured with the Long Trace Profiler at the BNL 

Metrology Lab. This mirror bender assembly allows us to continuously change the 

focal length of the x-ray mirror down to 0.5 m under our experimental conditions. 

At the NSLS X13 Prototype Small Gap Undulator (PSGU) beamline, we were able to focus the x-ray beam from a vertical size of 0.5 mm to ~25 pm at the focal 

point 54 cm from the mirror center, thus increasing the photon flux density by a 

factor of 20. Results also show that, as expected, at an incident angle of 9 mrad, 

the mirror cuts off the harmonics of the undulator spectrum, leaving a clean 3 KeV 

N 

fundamental for our experiments. 

c 5e+05g,m 

os+oo 20000 40000 60000 80000 100000 

Energy (ev) 

Figure 1. X13 PSGU spectrum before and after the mirror. The mirror 

(tilted at 9 mrad glancing incident angle) 

“cuts off” the higher harmonics, leaving a clean 3.1 KeV fundamental for the 

XPCS experiment. 

* Work supported by DOE under contract No. DE-AC02-76CH00016 and NSF 

Grant No. DMR 92-17956. ED acknowledges the support from NSERC. 

Figure 2. Vertical focusing by the float 

glass mirror. An incident beam of 

0.5mm vertical height is focused to 25 

pm (FWHM). 

X14A Ordered Phases of a Langmuir Monolayer of an Azobenzenecontaining Molecule. * 

M.K. Durbin, A. Malik, A.G. Richter, C.J. Yu, V. Bhashyam(N0rthwestern Univ.), 

R. Eisenhower(ORNL), and P. Dutta(N0rthwestern Univ.) 

We have used grazing incidence X-ray diffraction to study Langmuir monolayers 

of the molecule 4-octyl-4’-(carboxytrimethyleneoxy) azobenzene. We found only 

two phases over a broad range of temperatures and pressures, and the transition 

between them is strongly first order (compared to the weakly first order transition 

between two similar phases in straight-chain fatty acids). The diffraction patterns 

from these phases are shown in Figure 1, as intensity contour plots in the K,,:K, 

plane. Both phases have in-plane order, with a distorted hexagonal (DH) lattice. 

The low pressure phase has molecular tilt towards a nearest neighbor (NN tilt). 

At 12.5dyn/cm, there is a first order transition to a phase with tilt towards a 

next-nearest neighbor (NNN). These data are unexpected because studies of these 

monolayers using Brewster Angle Microscopy[l] and UV absorption[2] have suggested that the low pressure phase is fluid-like, while the high-pressure phase is 

solid-like. Our X-ray data clearly show that both phases have some degree of order and the two sets of peaks have similar full widths at half maximum, implying 

correlation lengths from lOOA to 300A. 

1. Y. Tabe and H. Yokoyama, J. Phys. SOC. Jpn. 63, 2472 1994 . 2. T. Kawai, J. Umemura, T. Takenaka, Langmuir 5, 1378 (19891. 

0.8- 

0.6- 

&N 0.4- 

0.2- . 

0.0’ 

&. 

n - 26.5 dydcm 

0.8 

0.6 

u~ 0.4 

0.2 

0.0 

=& 

1.0 1.1 1.2 1.3 1.4 1.6 1.6 

K (A-1) 9 

Figure 1. Contour plots of intensity (arbitrary units) as a function of wavevector 

components Key and K,, (top) at 26.5 dyn/cm,indicating an NNN tilted phase, 

and (bottom) 0 dyn/cm,typical of an NN tilted phase. 

* This work was supported under DOE grant no. DE-FG02-84ER45125 
X14A Inelastic X-Ray Scattering Measurement of the Many-Body LocalField Factor in Aluminum 

B. C. Larson, J. Z. Tischler (ORNL), E. D. Isaacs (Lucent Technologies), P. Zschack 

(U. of IL,), A. Flessar (U. Wiirsburg), and A. G. Eguilus (U. of TN & ORNL) 

Electron-electron interactions play an important role in the physical properties 

of metals, and, indeed, a large theoretical effort has been exerted toward understanding many-body exchange-correlation effects in electronic systems at metallic 

densities. Until now, however, quantitative analyses of large wave-vector (~2kp) 

measurements of the dynamical structure factor, S(q,w), in terms of the many-body 

local-field factor (LFF) have not been available. In this study', we have made inelastic x-ray scattering measurements on aluminum in the 2kp region using the 

X-14A beam line, and we have used first principles dynamical electronic response 

calculations, that include the actual band structure, to analyze these measurements 

in terms of the LFF, G(q,w). This work represents the first quantitative test of the 

LFF for simple metals in the critical large wave-vector range. 

The real and imaginary parts of the LFF were determined within a Hubbard 

model for q's ranging from 0.7-2.57kp (w from 10-70 eV) by adjusting the LFF (assumed to be constant in w) to match the S(q,w) measurements; excellent agreement 

was obtained. As shown in the figure, for q <1.5k~, the real part of the LFF is 

in rather good agreement with (static, i.e. real) theoretical calculations, resolving 

a lon standing difference between theory and electron scattering measurements 

of C&w) for that region. However, for q-2kp and larger, the experimentally determined LFF values are nearly twice as large as all calculations, suggesting that 

dynamical electron correlations are quite strong even in simple metals, and posing a challenge for theory. The combination of inelastic x-ray scattering measurements (at 

both 2nd and 3rd generation synchrotrons) and first principles electronic response 

calculations now provides the potential for detailed investigations of electronic ex- citations on a wide range of materials. 

1. B. C. Larson et al. Phys. Rev. Lett. 77, 1346 (1996) 

X14A Resonant Raman Scattering Excited by GeK, Radiation Internal 

and External to the Ge Atom 

C.J. Sparks, T. Gog, G.E. Ice (ORNL), R.A. Eisenhower (U. of Illinois) 

A low-energy satellite to K, fluorescence has long been observed, which has 

been shown to result from the emission of two electrons and one photon.' This 

radiative Auger effect challenges our understanding of x-ray excitation and decay 

processes. Despite the identification of the radiative Auger effect for almost 30 

years, no previous measurements have been made of the energy dependent behavior 

of the radiative Auger effect. All previous experiments were performed with incident 

photon and electron energies far above an absorption edge.' 

Our experiment compares the inelastic scattering from a Ge sample excited by 

synchrotron radiation tuned to the Ge K, energy (9876 eV) to the inelastic scattering from the same Ge sample excited by synchrotron radiation tuned near and 

above the K edge (11103 eV). Above threshold, the atom interacts with both the 

primary radiation field (11103 eV) and the self emitted Ge K, fluorescence (9876 

eV). As shown in Fig. 1, there is a marked energy shift between the inelastic spectra 

excited above and below threshold in the vicinity of the radiative Auger satellite. 

The measurements with the sample excited by 9876 eV x-rays contain a resonant 

Raman scattering peak in the vicinity of the radiative Auger satellite energy. This 

asymmetric peak results from a resonant excitation of the K hole and subsequent 

filling of the hole by an L electron.' Hence the resonant Raman line is designated the 

Ge K-L resonant Raman peak. The measurements at and above threshold include 

both resonant Raman scattering and the radiative Auger satellite. As illustrated in 

Fi . 1, there is -80 eV difference in energy at the leading ed es marked by arrows. 

811 T. Aberg, J. Utriainen, Phys. Rev. Lett. 22, 1346 (1969fj; 0. Keski-Rahkonen, 

J. Utriainen, J. Phy. B7, 55 (1974) [2] C.J. Sparks, Phys. Rev. Lett. 33, 262 (1974) 

8.2 8.4 8.6 8.8 9.0 

Energy (keV) 

Figure 1. Real and imaginary parts of the measured LFF, G(q,w), for A1 (full and 

empty symbols, respectively). Selected LFF's calculated for jellium with rs = 2.07 

are shown; see ref. 1 for details. f 

-4 

Figure 1. Inelastic resonant scattering from a Ge crystal excited with x-rays of 

energies which differ from the Ge K edge of 11103 eV by the energies shown. The 

incident energy for the resonant Raman curve labeled -1227 eV is Ge K at 11103 

eV - 1227 eV = 9876 eV which is the Ge K, energy. 
P 

r I Adsorption and structure of selenite on the calcite (1014) surface * I X15A I 

L. Cheng, P.F. Lyman (Northwestern U.), N.C. Sturchio (ANL) and M.J. Bedzyk 

(Northwestern U. and ANL) 

The adsorption of Se at the water-mineral interface is a phenomenon of major 

significance in environmental science. Se is potentially harmful to human and animal 

health. It is known that, in water, Se exists predominantly in the forms of two 

divalent inorganic oxyanions-selenite (Se03’-) and selenate (Se042-). 

The adsorption of selenite ions from a dilute aqueous solution onto a freshlycleaved calcite (1014) surface was studied with the X-ray standing wave (XSW) 

technique. Se03’- was found to selectively adsorb at the c0a2- site at the calcite 

surface, forming a two-dimensional solid-solution of the form Ca(SeO3),(COs)l-, 

at the interface. The local structure at the Se03’- adsorbate site was determined 

by the XSW triangulation of the site of the Se atom using the (1014), the (0006) 

and the (1120) reflection planes of calcite. These results are consistent with the 

geometry where the SeO3’- trigonal pyramid lies on the extrapolated co3 plane 

upon adsorption, with its apex Se atom pointing outward from the calcite crystal. 

The Se03’- adsorption saturated at a coverage of 0.02 monolayer. In addition, it 

was found that selenate adsorption on calcite under identical conditions 

resulted in a much lower 

63 Ca o Se 

Figure 1. 

00 

* Research supported by DOE BES contract No. W-31-109-ENG-38 to ANL. 

X15A Spatial Resolution of the Variable-Period X-Ray Standing Wave 

Method * 

R. Itri, R. Zhang and M. Caffrey (Ohio State U.) 

The variable period x-ray standing wave (XSW) technique has been applied in 

studies of Langmuir Blodgett (LB) films deposited on a gold mirror surface ren- dered hydrophobic with a self assembled octadecylthiol (ODT) monolayer. Films 

composed of the zinc salt of unbranched, saturated alkanoates with hydrocarbon 

chains varying in length from 16 to 24 carbons (C16 to C24) were investigated with a view to establishing the spatial resolution of the technique. X-ray reflectivity 

data indicates a mean value for the gold mirror surface roughness of 1.29 nm. Values of the first (<<z>>, mean position) and second (g’, variance) moments of the 

zinc label atom distribution within the films were obtained from x-ray fluorescence 

yield profile data. The results show that it is possible to observe differences in 

zinc position on the order of 0.1-0.2 nm which corresponds to the spatial resolution of the XSW method in the current application. Further, by assuming that the 

hydrocarbon chains of the zinc alkanoates are fully extended in an all-trans conformation, the results suggest that the long axis of the chains are tilted at an angle 

of M 36’ from the normal to the mirror surface for (318, M 28’ for C20 and C21 

and M 20’ for C22 and C23. For zinc lignocerate ((224) the hydrocarbon chain is 

oriented perpendicular to the mirror surface. In all cases, an apparent distribution 

half-width, F, of the zinc around the mean position in the adsorbed lipid layers 

was 1.63 nm. This corresponds to an intrinsic distribution half-width, uinl of 1.0 

nm, independent of hydrocarbon chain length, when mirror surface roughness has 

been deconvoluted. The <<.E>> value found for samples composed of zinc arachidate 

(C20) covered with an inverted bilayer of w-tricosenoic acid (UTA) indicates that 

the chains of zinc arachidate are also tilted in relation to the gold surface, with an 

angle of 18’ from the surface normal. For such films, a value of uin = 0.7 nm was found which indicates that the zinc ions in the lipid bilayer have a sharper distribution width in comparison with the uncoated zinc arachidate. Samples composed by 

zinc alkanoates (C21 and C24) with 2 inverted bilayers of wTA sandwiched between 

the hydrophobic gold mirror and the zinc-containing bilayer were found to have 

their hydrocarbon chains tilted at an angle of FZ 23’ for C21 and perpendicular to 

the mirror surface for C24. Such films have the same zinc label distribution width 

as those without the intermediate wTA bilayers. 

To M. Caffrey and R. Itri thanks FAPESP/SP and CNPq of Brazil for financial 

support. R. Zhang was supported by a University Posdoctoral fellowship from the 

graduate school of The Ohio State University. 

* Research supported by NIH (DK 36849 and DK46925) and the Petroleum Research 

Foundation of the American Chemical Society (3057-AC7). To M. Caffrey and R. Itri 

thanks FAPESP/SP and CNPq of Brazil for financial support. R. Zhang was supported 

by a University Postdoctoralfellowship from the gradue school of Ohio State U. 
I Structural Study of 0.2 ML In/GaAs(001) 4x2 Surface * I X15A I 

T.-L. Lee (Northwestern U.), J. Zegenhagen (Max-Planck-Institut, Germany), P.F. 

Lyman (Northwestern U.) and M.J. Bedeyk (ANL & Northwestern U.) 

STM) investigation [l], the 

indium-terminated GaAs(001) surface exhibited a (4~2\/c(8x2) reconstruction with 

bright straight rows running along the [110] direction. Based on this study, a dimer 

From a previous a scanning tunneling microscopy 

model, which is similar to the one proposed by Biegelsen et al. [2] for a 

GaAs(001) clean surface, was proposed for the In structure in the 

However, the detailed local structure for the In ad-atoms was not resolvable from 

the STM image. In this work, we applied the higher-resolution x-ray standing wave 

(XSW) technique to investigate the adsorbate - surface structure of low coverage In 

on GaAs(001). 

A (2x4) GaAs(001) clean surface was prepared in UHV by thermal desorption 

of an arsenic-capped GaAs(001) substrate. The (4~2)/c(8x2) In-terminated sur- face (@I,, = 0.2 ML) was obtained by In deposition at room temperature and a 

subsequent annealing at 450' C using our UHV-MBE system. The (004) XSW 

measurement (Fig. 1) shows that the In ad-atoms are located 1.61 A above the 

(004) diffraction planes. At higher In coverages (up to N 0.6 ML) we measured 

lower (004) coherent fractions. This is consistent with the ladder- type pattern 

observed by STM for 01, 2 0.5 ML [l], which suggests that more than one In 

structure coexists on the surface. For @I,, N 0.2 ML, we found that our off-normal 

XSW measurements do not agree with the dimer model proposed in Ref. [l]. We 

are consequently developing a new model for this surface structure. 

[l] U. Resch-Esser, N. Esser, C. Springer, J. Ze enhagen, W. Richter, M. Cardona, 

and B.O. Fimland, J. Vac. Sci. Technol. B 13(47, 1672 (1995). 

[2] D.K. Biegelsen, R.D. Bringans, J.E. Northrup, and L.-E. Swarte, Phys. Rev. 

B 41, 5701 (1990). 

I X15A I Atomic Resolution X-Ray Standing Wave Characterization of SelfAssembled Chromophoric Superlattices * 

W. Lin, T. -L. Lee, P. F. Lyman, J. Lee, T. J. Marks (Northwestern U.), M. J. 

Bedeyk (ANL & Northwestern U.) 

There is much current interest in molecule-based second-order nonlinear optical 

materials because of their potential applications in second harmonic generation, 

electrooptic, and photorefreactive devices. The synthesis of these materials, however, present a significant challenge for synthetic chemists because of the requirement of non-centrosymmetric arrangement of molecular chromophores. We have 

recently developed a self-assembly approach to constructing intrinsically acentric, 

structurally regular chromophoric superlattices which exhibit very large secondorder nonlinear optical (NLO responses. 

In this work, we have un d ertaken the first X-ray standing wave characterization of self-assembled multilayers (SAMs). These siloxane-based self-assembled stilbasolium multilayers possess intrinsic acentricity and exhibit very large second-order 

nonlinear optical responses. The locations of bromide anions within the SAMs were precisely determined using X-ray standing waves generated by total external reflection from mirror surfaces as well as by Bra g diffraction from layered synthetic microstructures. The large coherent fraction Ti..., small Gaussian distribution width) 

of the Br atoms provides a direct evidence for the high structural regularity of these 

self-assembled multilayers. Moreover, the anion surface coverage measured (2.5(5) x 

1014 Br-/cm2) is in excellent agreement with the cation surface coverage measured 

by second harmonic generation (2( 1) x IOL4 molecules/cm2). These results clearly 

demonstrate the utility of X-ray standing wave analyses as a quantitative structural probe for self-assembled mono- and multi-layers, especially for SAMs with 

incommensurate structures. 

0 (X = Br or I) ~~~~~~~ ~ ~~~ 

Figure 1. Figure 1. blank 

F 

w 

tQ 

co * Research supported by DOE BES contract No. W-31-109-ENG-38 to ANL and by * Research supported by DOE BES contract W-31-109-ENG-38 to ANL and by NSF 

NSF under contract No. DMR-9120521 to the MRC at NU. contract DMR-9120521 to the MRC at NU. 
Fd 

F 

X15A Dynamical Diffraction of Trapped X-rays on a Curved Crystal Surface * 

C. Liu (Harvard U.) and J. A. Golovchenko (Harvard U. & Rowland Inst. for 

Science) 

We report the first observation of the dynamical diffraction of surface trapped 

x-ray waves at the beam line X15A. A number of experiments have been performed 

at X15A during the past few years to explore the propagation of hard x-rays (wavelength -1 angstrom) on the surface of a curved silicon mirror. The x-ray wave is 

confined on the concave surface via total external reflection, forming a true x-ray 

surface bound state. The evanescent tail of each surface state penetrates into the 

bulk and interacts with the underlying crystal lattice, giving rise to diffraction effects. In particular, under the Bragg condition the surface eigenmode becomes the 

superposition of a forward and a diffracted waves, analogous to the x-ray eigenmode 

inside the bulk of a crystal under the Laue diffraction geometry. This year at X15A 

we have successfully excited and detected such diffracting surface eigenmodes on a curved thin silicon mirror. The discovery may have important applications in 

developing x-ray optical elements like lenses and wave guides, x-ray surface studies, 

and x-ray lithography applications in the future. 

I Local Adsorption Geometry of Te/Si(OOl) Studied by XSW * I X15A I 

Paul F. Lyman (Northwestern U.), Michael J. Bedzyk (Northwestern U. and ANL), 

and Pedro A. Montan0 (U. of Illinois - Chicago & ANL) 

Adsorption of Te on Si is the critical first step in the growth of the direct, widebandgap semiconductor CdTe on Si. Apart from the potential commercial importance of that process, the adsorption of a group VI element (Te) on the (001) face 

of a group IV semiconductor (Si) might result in near-perfect passivation of the Si 

surface; the two dangling bonds per surface Si atom could be satisfied by a (1x1) 

arrangement of the hexavalent Te atoms. 

A recent LEED and STM study of the Te/Si(OO1) surface [l] revealed that although the local arrangement of Te atoms does appear to be (lxl), the larger size 

of the strongly adsorbed Te atoms results in occasional missing rows of Te; these 

relieve strain in the overlayer by allowing lateral expansion of the Te layer. We undertook an x-ray standing wave investigation to quantify the adsorption site, spatial 

distribution, and structural perfection of the Te adsorbate layer. Although good 

agreement was found with the lateral expansion of the Te atoms adumbrated by 

the STM work, a surprisingly large spatial distribution was found in the direction 

normal to the plane, not evident in the STM work. Also, it was quantitatively established that this vertical distribution is independent of coverage, indicating that 

the adatom-adatom interactions on the surface are likely to be attractive. 

[l] S.A. Yoshikawa et al., Surf. Sci. 321, L183 (1994). 

z 

& 1 ~L-3 

-10 0 10 20 30 40 50 

Figure 1. A schematic representation of the diffraction of surface trapped x-rays. 

(a) An incident x-ray beam at a glancing angle with respect to the mirror surface 

propagates along a helical trajectory in the q5 and zdirection. (b) Under Bragg 

condition the surface trapped x-ray is diffracted by the underlying crystal lattice, 

whose reciprocal lattice vector is parallel to the z direction. The actual propagation 

is described by the cynamical diffraction theory. 

* We acknowledge the assistance from Dr. Paul F. Lyman and Prof. Michael J. Bed~yk 

at Northwestern U. and ANL and the support from JSEP (N00014-89-J-1023). 

B-0, (wr) 

Figure 1. Te fluorescence and x-ray $0.5 

reflectivity from (004) XSW scan of g 

Te/Si(OO1) surfaces with M 1 ML and 0.4 $ 0 

ML Te coverage. -10 0 10 20 30 40 50 60 

0-0, (pr) 

* This work sPonsoredbY the u. s. DOE, Figure 2, Te fluorescence and x-ray Office of Basic Energy Sciences, Div. of Materials Sciences, contract W-31-109-ENG38, and by the NSF under contract to the 

MRC at Northwestern U. 

reflectivity from (022) xsw scan of 

Te/Si(OO1) surface with M 1 ML Te coverage. 
I X15A I Surface Relaxation by X-ray Standing Wave and Surfaceextendedxx-ray Absorption Fine Structure * 

J. Woicik (NIST) 

We have determined the atomic coordinates of the well characterized 1/3 ML 

Si(ll1 3x3-Ga interface through a combination of x-ray standing wave and surfacedicular distance of the Ga atoms to the Si bulk diffracting planes from XSW and 

the bong length of the Ga atoms to the top layer Si substrate atoms from SEXAFS, our structural determination includes the degree of substrate relaxation, a 

critical yet experimentally overlooked interfacial parameter. The Ga-first-Si layer 

bond length is determined to be 2.48 0.02 A, in complete agreement with the calculations of Northrup; however, the perpendicular distance of the Ga atoms to the 

Si bulk diffraction planes is found to deviate by nearly 0.2A. Future polarizationdependent SEXAFS which will measure the Ga-second-layer Si atom bond length 

should resolve this dilemna. 

exten d ed x-ray absorption fine structure. By independently measuring the perpenI'I'I'I'I'I'I'I'I 

'?k -2 . 

2 

-2 - 

2 3 4 5 6 7 8 9 1C 

k (8,-') 

R 

N',,,, = 3.3 f 0.3 

= 2.48 & 0.02 8, 

Fi ure 1. Surface EXAFS performed at the Ga K edge for 1/3 monolayer of Ga on Sitlll). Note that the Ga-first-Si layer bond length is significantly larger than the 

Ga-P bond length in cryatalline GaP (2.36 A). 

Fd 

w 

* This work was sponsored by the U.S. DOE, Office of Basic Energy Sciences, Div. of 

Materials Sciences, contract W-31-109-ENG-38, & by the NSF under contracts to the MRC 

at Northwestern U. 

r 

F 

I Extremely Dilute Impurities in Silica Optical Waveguides 

L. Niu, R. M. Atkins, M. A. Marcus, D. C. Jacobson, P. F. Glodis, and P. H. Citrin 

(Bell Labs) 

I X15B 

Optical transmission loss is one of the most important factors in defining the 

utility of a waveguide material. A long suspected source of small but significant 

losses in manufacturing silica fiber has been trace metal impurities such as Fe. 

Supporting evidence has only been suggestive because earlier measurements were 

either too insensitive, ill-defined, or far removed from early stages of fabrication 

where identification is least reliable (and most costly). NEXAFS measurements on a single silica preform, taken as a function of position within core vs cladding regions 

from two preform slices of different loss, established that between 3-5 times more Fe was indeed present within the core, and that a similar factor existed between the cores of the different slices. The concentration of Fe in the more lossy core was < 10 

ppb. Future work with a more efficient detector will allow greater accessibility to more dilute impurities (Cr and Ni), better overall quantification, and identification 

of different metal oxidation states. 
Fd 

P 

Optically Active Er Centers in Si 

L. Niu, D. C. Jacobson, D. J. Eaglesham, and P. H. Citrin (Bell Labs) 

X15B 

Because of its potential utility in optoelectronics, the 1.54-pm luminescence observed from excited Er in Si has generated a great deal of interest. Our previous 

EXAFS measurements of Er implanted in Czochralski and float-zone Si had identified two very different local structures around the Er: a sixfold cage of 0 atoms 

and a twelvefold cage of Si atoms, respectively. Only the former was argued to be 

optically active. Recent theoretical and experimental studies have since reported 

apparently conflicting evidence about the symmetry, composition, and relative con- centrations of these structures depending upon the implantation dose and energy 

of Er and the oxygen content and temperature of the Si host. More extensive 

EXAFS measurements, along with TEM micrographs, were obtained from Er implanted in Si under varying conditions. The new data clarify, reconcile, or correct 

all the conclusions of these recent works. Key to this study were the measured 

Er nearest-neighbor bond lengths, the coordination numbers, and the presence of 

silicide precipitates that had gone undetected. 

I Pb-induced Instability in ZBLAN Glass I X15B 1 

L. Niu, A. R. Kortan, N. Kopylov, and P. H. Citrin (Bell Labs) 

The predicted ultra-low optical losses at near-infrared wavelengths of ZBLAN 

(Zr/Ba/La/Al/Na) fluoride glasses holds promise for their application in optical 

waveguides and photonic devices. Their complex structure, however, has severely 

limited understanding how to optimize their composition for practical use. In particular, Ba is substituted with Pb to change its refractive index, but at some critical 

Pb concentration the glass devitrifies (recrystallizes). To gain insight into this phenomenon and see if it can be avoided, NEXAFS and EXAFS data from varying 

amounts of Pb-doped ZBLAN material in both glassy and intentionally crystallised 

phases were obtained, showing that the observed glass instability for Pb concen- trations > 10% is directly related to changes in the local electronic and geometric 

structure around the Ba cations. The instability was also seen to be strongly correlated with the similarity between the local Ba2+ environments in the glassy and 

crystallized phases. These results show that the Pb-induced glass instability is 

driven by the reduced effectiveness of the smaller Pbas to modify the network of 

ZrF, polyhedra, an unavoidable problem in these forms of fluoride glasses. 
~ I Ti Silicides in Submicron Dimensions 

L. Niu, R. Tung, M. A. Marcus, and P. H. Citrin (Bell Labs) 

The C54 phase of TiSi2 has the lowest resistivity of all refractory-metal silicides and is thus the material of choice for sub-0.25-pm ultra-large-scale-integrated 

technology. However, in narrow wires or thin films this thermodynamically stable 

phase is preceded by formation of a kinetically-favored, higher-resistivity C49-TiSiz 

phase. It is therefore important to determine growth procedures which facilitate the 

C49 -+ C54 transformation in confined silicide dimensions, and to develop methods for establishing the success of that process in as-prepared material. An EXAFS 

study was initiated of TiSi2 samples grown in 0.05-pm-thick films and 0.35-pm-wide 

wires on crystalline- and on heated, pre-amorphized-Si substrates. The relative concentrations of the C49 and C54 polymorphs were determined and found to be in 

excellent agreement with the trend of sheet resistivities measured from these same 

four samples. These preliminary results demonstrate that EXAFS data can provide 

direct, non-destructive characterization of silicides grown in small dimensions and 

under conditions where resistivity measurements might be impractical. They also 

suggest the possibility of structurally characterizing systems considerably smaller 

than those studied here, e.g., 0.1 pm. 

I Distorted, Inequivalently Charged c60 Anions in Yba.75C60 TX15B I 

S. Schuppler (Bell Labs), E. Ozdas (Hacettepe U.), K. B. Lyons, A. R. Kortan, 

and P. H. Citrin (Bell Labs) 

NEXAFS measurements from the highly reactive, superconducting, single-phase 

rare-earth fulleride, Yb~.76C60, establish that the Yb cations are exclusively divalent, indicating that the average negative formal charge of the C6o anions is 5.5. 

EXAFS (and Raman) measurements also show that the c60 anions are distorted in 

shape, despite their well ordered local structure around the Yb cations. Along with 

the fact that Yb2.76C60 contains three very different crystallographically inequivalent types of c60 anions surrounded by 8, 10, or 12 Yb cations, these findings are 

used to argue that the charge transferred from Yb to c60 is both anisotropically distributed on the anions and inequivalently partitioned among them within the unit 

cell. Specifically, the interactions between Yb and c60 are partly covalent, similar 

to (albeit weaker than) those between Pt and Cao in [(C6&,)sP]2Pt-C60, and the 

charge states of the three types of c60 anions are different, similar to (and more 

pronounced than) those of 0 in YBa2Cus07. Our results are shown to provide 

insight into the novel structure of Yb2.75C60 and to explain the origin of its unique 

value and distribution of anion charge. 
P 

P 

Structure of the Incommensurate Au/Si( 100)-5xl Surface * 

P. Bennett (ASU), D. Walko and I. K. Robinson (U.of Illinois) 

We have studied the Au/Si(100) surface with nominally 1 M1 Au annealed to 800C 

using surface X-ray diffraction. In previous LEED studies this structure was indexed as rt26x3. STM observations (Lin et a1 PRB47, 1993 p 3671) suggested instead a 

5x3 unit cell with a prominent row structure in the 5 direction and a disordered 

pattern in the 3 direction with a regular rt26 phase slip between rows. We find 

that it is in fact a 5x1 structure with a very strong incommensurate modulation 

vector Qlc=(0.44, 0.68). Preliminary analysis of the diffraction data suggest a 

missing-row model with 4 occupied and 2 missing Au rows in the 5x1 unit cell, 

giving a chisquare of 3 and a match with the data as shown in the figure below 

for a single domain. The incommensurate reflections are also shown but are not 

included in the structural analysis. They comprise a lattice of &IC convoluted with 

the 5x1 unit cell, with however most intensities nearly zero. In the figure we also 

show a simulated image produced by modulating the 5x1 missing rows model with 

the QIC vector. This bears a striking resemblance to the STM image of Lin et al. 

In particular, an approximate 5x3 ordering is apparent. Further refinement of the 

model to include displacements, structure factors for the incommensurate reflections 

and out of plane data (truncation rod profiles) is in progress. 

X16a 

- - -\J 

30 00-0 

0000 oooo 

IC f I’ 

Figure 1. 

I * Work supportedin part by NSF grants DMR9528503 (PAB) and DMR93-15691 (IKR). 

I Oxygen-Induced Facetting of Cu(115) I X16A 

I. K. Robinson and D. A. Walko (U. of Illinois), H. L. Meyerheim and M. Albrecht 

(Inst. f. Kristallographie, U. Muenchen) 

We monitored the distribution of facets on a Cu(115) surface as a function of 

oxygen dose at 300C. We measured diffraction in a plane intersecting the (115) 

crystal truncation rods (CTRs), at a distance of 0.9A-l below the (111) bulk Bragg 

peak. Most of the facet peaks were found to lie in the vertical plane perpendicular to 

the expected step-edges of the (115) surface, which is scanned in Fig 1. Additional 

facet CTRs were observed to form along (104) directions. ”Peak I” in figure 1 

corresponds to the (115) facet direction, which is present on the clean surface. 

“Peak I” evolves into ”Peak 11” after a latency period of 1OL dose. No changes 

are visible in the diffraction pattern throughout this latency period. Presumably, 

oxygen is decorating the ordered (115) facets without strong stuctural changes, until 

they become saturated with oxygen. ’Peak 11” then appears very suddenly with an 

abrupt transition. Unlike ”Peak I”, ”Peak 11” is not a well-defined facet direction, 

and slides continuously as a function of dose, until it arrives at a position of roughly 

(114). In figure 2, it can be seen that the heights of the two peaks interchange over a 

narrow range of dose, and that the width passes through a minimum. The position 

of ”Peak 11” then varies roughly linearly after ”Peak I” has gone. 

Finally, the intensity of ”Peak 11” then starts to drop and ”Peak 111” appears, 

which corresponds to a (113) facet. Simultaneous with the debut of ”Peak 11”, the 

two 104 facet CTRs begin to appear and rise linearly with dose after that; it is 

expected that the relative areas of the three facets will conserve a net (115) surface. 

The dose dependence of the various peak heights, positions and widths is shown in 

figure 2. 

.~ .. . .. . 

, 

Figure 1. Oxygen dose-dependence of 

the CTR diffraction near the (111) bulk 

Bragg peak. Different peaks correspond 

to differrent facet directions. As the dose 

increases, the peak moves from left to 

right. data of fig.1. 

Figure 2. Dose dependence of the peak 

heights and widths corresponding to the 
I Surface Structure of a-Ga(001) I X16A I 

D. A. Walko, I. K. Robinson (U. of Illinois), Ch. Grutter, and J. H. Bilgram (ETH 

Zurich) 

Orthorhombic a-Ga is unique among elemental metals in that its atoms form 

partially covalent bonds, resulting in dimers which are angled f16.9' from the [OOl] 

direction. Thus it is possible to form inequivalent (001) surfaces: by separating pairs 

of dimers (surface "A" in Fig. 1) or by cutting through the dimers (surface "B" 

in Fig. 1). Adding considerable challenge to any structural study of a-Ga is the 

material's low melting point, 29.76OC. 

Ab initio, total energy calculations have been performed [M. Bernesconi et al., 

Phys. Rev. Lett. 70, 3295 (1993)] which investigate the stability of the various 

a-Ga (001) surface structures. These calculations determined that bulk truncations 

"A" and ' B" are both unstable with respect to a new structure, which is a rearrangement of surface "A," and was termed a self-wetting of a-Ga by two layers of 

Ga-111. 

We have performed x-ray diffraction experiments in the X16A UHV chamber. 

Because of a-Ga's low melting point, the chamber was equipped with a load lock 

to install the samples without breaking vacuum in the chamber. After cleaning 

the surface with several Ar sputtering cycles, we measured structure factors along 

several rods (one of which is shown with fit in Fig. Preliminary fits to the 

layer Ga-I11 model. A refinement of fitting parameters and determination of atomic 

positions is ongoing. 

data indicate the surface is a rearrangement of surface 22.,,,, rather than the twow 

00 'I 

showing two possible places to form an I;, ';o-J" 

Figure 1. Atomic structure of bulk Ga, 

(001) surface. Thick and thin circles represent atoms at x = 0 and x = 0.5 respectively. Covalent dimerization of atoms is 

also schematically indicated. 

Figure 2. The (20L) rod (circles) and the 

best fit to date (line). 

Oxide Growth on Cu(ll1) in Acidic Solution 

Y. S. Chu and I. K. Robinson (U. of Illinois) 

The formation of aqueous oxide on a Cu(ll1) single crystal surface in perchloric 

acid at pH 4 was studied in-situ using X-ray diffraction. Formation and removal 

of copper oxide was controlled by imposing external electrostatic potential at the 

interface. Fig. 1 (Top) shows a typical cyclic voltammetry of Cu(lll), in which the 

positive peak around -0.3 V corresponds to formation of oxide, and the negative 

peak around -0.55 V corresponds to removal of oxide. Two distinct epitaxial oxides 

were observed. Both were identified as cubic cuprite (Cu20) with the (111) axis 

perpendicular to the surface but different in-plane orientations: 180 deg rotation 

between them at the interface (see Fig.2). In a native oxide on Cu(lll), both aligned 

and reversed oxides grow with about an equal ratio. However, in the solution at 

pH 4, an entirely different growth mechanism was observed. Fig. 1 (Bottom) shows 

the growth of both oxides as the potential was cycled. As the ptetnial was swept 

from A to B, both oxides grew at a comparable ratio, but, beyond B, only the 

reverse oxide continued to grow while the aligned oxide remained constant and 

eventually diminished. The amount of diffracted intensity and the L-diffraction 

profile indicate that the alined oxide never grows more than a few monolayers thick. 

This preferential oxide growth mechanism suggests that the aligned cuprite may be 

acting as a barrier to inhibit further oxidation. 

X16C 

Figure 1. Growth of epitaxial copper oxide. Top: cyclic voltammetry of Cu(ll1) 

in perchlorate solution at pH 4 and 10 

mV/sec. Positive and negative peaks 

correspond to formation and removal 

of Cu20, respectively. Bottom: Bragg 

peak during cycling of the potential. 

Figure 2. Side view of aligned and reversed oxides. In the oxide, the copper 

atoms are shaded. 
I Chemical Ordering in Lead Magnesium Niobate I X16C I 

D. M. Fanning and I. K. Robinson (U. of Illinois, UC) 

Superstructure reflections of a single crystal ( 2mm per side) of lead magnesium 

niobate (Pb[Mg,/3Nb2/3]03) were studied at beamline X16C. PMN is a ferroelectric 

relaxor with a Curie temperature of -7 C. It has a broad, frequency dependent 

transition to the ferroelectric state. PMN's structure is perovskite with the mixed 

B-site containing a MgZt or Nb6+ion. 

Integrated intensities were measured for about 80 reflections by scanning in the 

i100idirections. The width of each superstructure reflection was roughly constant 

and indicative of an ordered domain size of 20 A from the Scherrer equation: 

L=2T.0.94/AqFwHM 

The crystal was carefully mounted so that the beam entered and exited through 

the same face. In this way, the absorption correction was simply l/(sinOsinX). 

However, this correction is important as it critically affects the form of the data. 

The corrected structure factors as a function of momentum transfer are plotted 

in Figure 1. The shape of the data suggests that chemical ordering is the cause 

of PMN's superstructure reflections. In a chemically ordered sample, the structure 

factors are simply proportional to the difference in the ordered chemicals' form 

factors. Without the absorption correction, the data increase at first with q and 

then decrease. This would suggest a displacement ordering model. 

The fit to the data in Figure 1 represents our proposed model. We assumed 

one-to-one Mg:Nb chemical ordering within PMN's ordered regions and allowed the 

oxygen ions to displace towards or away from the B-sites (Figure 2). The best fit 

was found with an oxygen displacement of 0.1 A towards the smaller NbSt ion and 

away from the Mg2' ions. The Pb ions are believed to be randomly displaced about 

their ideal position, and we were unable to improve our fit by displacing those ions. 

PMN is unique in that its ratio of different B-site ions (Mg:Nb) is 1:2, yet it 

chemically orders in a 1:l ratio. Of course, the charge imbalance greatly restricts the 

size of these ordered domains. In future experiments, we plan to look at La-doped 

PMN crystals in which the La3+ ions provide an extra positive charge compared to 

the Pbat ions. This reduces the charge imbalance in the ordered domains, allowing 

them to grow larger. 

[ PMN superstructure reflections I 

--1 

Figure 1. Structure factors of the type 

(h+l/2, k+l/2,1+1/2) v. momentum 

transfer . 

.... .... ............. ... 

Figure 2. Ordered Mg and Nb ions in 

adjacent unit cells. 

I Strain of GaN Thin Films on Sapphire (0001) X16C 

C. Kim, I. K. Robinson, J. Myoung, K.-H. Shim, and K. Kim (U. of Illinois, 

Urbana-C hampaign) 

Recent interest in a short wavelength optical devices attracted much attention 

to 111-nitrides as wide band gap materials. With this increasing interest, much 

work has been done previously on optical and electronic properties of 111-nitrides. 

However, the strain of thin 111-nitride has not been extensively studied. Since 

the electronic and optical properties couple with the strain in thin films, a clear 

understanding of it is very important. 

We grew a series of GaN thin films on A1N buffer layer with sapphire (0001) 

substrate and measured both in-plane and out-of-plane lattice constants using x-ray 

diffraction as a function of film thickness. With Van der Merwe's equilibrium theory, 

we could explain our in-plane lattice constant results (Fig.1). The fit was derived 

from the assumption that the total energy of the system is at minimum. It was 

in excellent agreement with the experimental results even though we assumed that 

the effective range of the dislocation field is constant. More detailed consideration 

of energy terms for dislocation field did not affect the fit very much. 

The out-of-plane lattice constant is then fitted from the in-plane value using a 

Poisson ratio v = 0.38 (Fig.2). The best fit was obtained with v=0.44 which could 

be considered to be Poisson ratio for a thin GaN film. The critical thickness of this 

GaN film was obtained using the fit, and gave a value of 29 f 4 8. This compares 

favorably with the theoretical value obatined by Fischer of 31.5 8. 

3.20 

-3.18 

a =a, + (a,. aJhJh 

3.12 

f 3.10 

3.08 

h,=29 t4A 

3.084 .... - ................... I 10' 1 02 io3 1 o4 

GaN layer thickness (A) 

5.24 T I 

"="98 

Y OM 

- 

c=ce*c0v, so .a )be 

T 4 518- t 1 -- 

17 LaHioe oonstant o OF bulk GaN, 5 185 A 

5.181~1 

1 0' 102 io3 10' 106 

GaN layerthickness( A) 

Figure 1. A fit of in-plane lattice con- Figure 2. A fit of out-of-plane lattice 

stant of GaN. constant of GaN. 
td 

F 

W 

-4 

I Measurement of the Fission Branch for the 103 keV State in 235U I X17B1 I 

N. N. Ajitanand (SUNY, Stony Brook), D. P. Siddons, and J. B. Hastings (NSLS) 

From experimental studies of proton and alpha induced fission of 236U at deep 

sub-barrier energies an argument has been made for the existence of a fission branch 

of about in a low lying level around 103 keV. However, from all known theoretical considerations the fission probability of such a state is vanishingly small 

because of the formidable fission barrier. To investigate the experimental situation 

further it was decided to do a complementary experiment where the fission branch is 

measured for the level populated by resonance absorption of photons of appropriate 

energy. 

A single bunch white beam (3mm x 8mm) was incident on a silicon monochromator. The diffracted beam (peak 103 keV, fwhm 1.2 keV) was incident on a 200 

mg/cm2 metallic "'U target (A). The fission detector (lexan plastic) covered the 

target on its upstream side. Another 23'U foil (B) covered by plastic was kept just 

outside the incident beam to record background fissions due to neutrons and high 

energy photons (fig. 1). The incident photon spectrum was monitored by an InGe 

detector (fig. 2). Two irradiation runs, each lasting about 40 hours, were taken. 

In one run a neutron source was kept in the proximity of the uranium foils. The 

plastics were etched in 6.25N NaOH for 20 minutes at '70°C to reveal fission tracks. 

In the case of the run with the neutron source, similar numbers of well defined 

fission tracks were seen in both the plastics indicating that the transiting beam did 

not alter the properties of the plastic. In the run without any neutron source, no 

fission tracks were seen in either plastic. The total number of photons incident on 

the target in this run as measured by an Argon filled gas ion chamber was 5 x loi4. 

The width of the 103.02 keV state was calculated to be 1.2 x lo-' eV from its 

known life time (3.5 psec). This meant that the population of the state through 

resonant absorption was 5 x 10'. This translated to an upper limit of 2 x lo-' 

for the fission branch ruling out the state as a possible contributor to the observed 

sub-barrier fission enhancement in the particle experiments. 

LEXAN 

BEAM UFOIL A 

UFOIL 8 

LllXAN 

Figure 1. Arrangement of targets. 

h 

v 

u 

z 

E (keV) 

Figure 2. Incident spectrum. 

X17B1 In-situ Measurement of the Rheology of Silicate Garnets at High 

Pressure 

J.Ando, J.Chen, D.J.Weidner Y.Wu (CHiPR, SUNY, Stony Brook), and Y.Wang 

(CARS, APS) 

We have examined the rheolo ical properties of silicate garnets using the DIA type 

cubic anvil apparatus (SAM-858 at the X17B1 beam line. The mechanical data of 

deformation are collected from the shape change of diffraction peaks. This method 

was devised by Weidner et a1.(la2) at this beam line. We then observe the microstructures of recovered samples by TEM to understand the mechanisms of deformation 

processes. Using this experimental method, it is possible to observe the rheological 

behavior of mantle minerals under mantle conditions. Here we report the results for 

four garnets. They are Pyloo, PybOMj60, Py23A148Gr2aSp1 and Pye~A118Gr14Spl. 

The first two samples are synthetic garnets, and last two samples are garnets from 

natural rocks. Experimental conditions are 9 GPa confining pressure and temperatures up to 86OoC. Significant compositional effects of strength at all temperature 

range were observed for these samples. PyboMjSo and Py6sAllaGr14Sp1 were considerably stronger at higher temperature than the other samples. Natural samples 

suggest that yield strength of garnet increases with increasing pyrope content. But 

synthetic pure pyrope is weaker than Py23A14~Gr28Sp1. This weakness may be 

caused by new phase occurred between pyrope grains during experiment or minor 

glass phase in starting synthesiBed pyrope. TEM observation supports the first effect. Our result shows that the rheological behavior of silicate garnet depend greatly on it's composition. 

References: 

D.J.Weidner, Y.Wang, 

D.J.Weidner, Y.Wang, 

NSLS Activity Report, p310 (1992); 

M.T. Vaughan, Science, 266, p419-422, (1994) 
1 In-situ Equation of State Measurements of Antigorite I X17B11 

K. Bose, A. Navrotsky (CHiPR, Princeton U.), P. J. Schields, J. Chen and D. J. 

Weidner (CHiPR, SUNY,Stony Brook) 

The extent to which dense hydrous magnesium silicates can transport water to 

the mantle via mature, relatively cold subducting slabs depends on the thermodynamic properties of ”lower” pressure and temperature minerals such as talc and 

antigorite. In addition to thermoelastic data on talc, phase equilibria experiments 

of key reactions and calorimetric studies of phases in the MgO-H2O-SiOZ system 

that we have reported previously, we present here the results of in-situ equation of 

state measurements of natural antigorite, (Mg.seFe,04)48Si34 O8a(OH)62). 

The molar volume of antigorite, as a function of pressure (to 6 GPa) and temperature (to 823 K) was measured in-situ in a DIA-type multi-anvil high-pressure 

apparatus SAM-85) at the National Synchrotron Light Source. NaCl was used as 

1 % (for samples that were pressurized prior to heating) to less than 0.2 % of total pressure for samples that were cycled to high temperature after pressurization. 

Macroscopic deviatoric stress in the NaCl was determined from the relative strains 

of the diffraction peaks. The relative changes in V/VO as functions of pressure 

and temperature were determined by indexing the diffraction lines to a single layer 

monoclinic cell. 

The 298K unit cell volume data VO= 365.5 a3) can be fitted to a second-order 

Birch-Murnaghan equation of state \K’~gs = 4) with K = 58.7(3 GPa or to a thirdWe are currently indexing the hight temperature data (at P) to obtain thermal 

expansivity as the next step in the construction of a comprehensive, self-consistent 

data set. 

pressure ca r, ‘brant and also to reduce the deviatoric stress, which ranged from N 

order Birch-Murnaghan equation with K = 60.4 (2.9) GPa, an d K’29~ = 3.2 (0.1). 

Elasticity of Single Crystal MgO from Simultaneous X-ray and U1- 

trasonic Measurements to 9 GPa and 1500 K in a Multi-Anvil Ap- X17B1 

paratus 

G. Chen, Y. Sinelnikov, J. Cooke, D. J. Weidner and R. C. Liebermann (CHiPR 

SUNY, Stony Brook) 

The equation-of-state of MgO is of importance in understanding the seismic profiles of the lower mantle and in applications to in situ pressure standards in high 

temperature-pressure experiments. In our laboratory, we have developed techniques 

to enable precise ultrasonic interferometeric measurements of wave velocities in minerals to be performed to pressures of 9 GPa and temperatures of 1500 K using a 

DIA-type, cubic-anvil apparatus (SAM 85) installed on the superconducting wiggler 

beamline (X17B) at the National Synchrotron Light Source of the Brookhaven National Laboratory. X-ray spectra of both the polycrystalline specimen and the NaCl 

medium which surrounds it are monitored continuously; the former provides PVT 

data to compliment the velocity measurements and the latter the pressure standard. We have obtained new data on single-crystal MgO to simultaneous pressures 

of 7 GPa and temperatures of 1500 K, and compare these new data to the acoustic 

measurements of Spetzler (1970) to 0.8 GPa and 800 K using a specially-designed 

pressure-temperature path (see figure). 

P-T Path for MgO [I101 p-wave 

e 

G 

g, 

1400 

1000 

800 

7 

% 600 E 

3 

5 

# 400 

200 

0 

0 2 4 6 8 

Pressure (GPa) 

Figure 1. P-T Path of Ultrasonic Experiment 
Rheology of Dry and Hydrous Phases of the a! and 0 Forms of 

J. Chen, T. Inoue, Y. Wu, D. J. Weidner and M. T. Vaughan (CHiPR, SUNY, 

Stony Brook) 

Rheological properties of the different phases of olivine, both dry and hydrous, 

are important properties that constrain mantle convection and have implications 

regarding the origin of deep focus earthquakes. It is widely recognized that water 

considerably weakens olivine at confining pressures less than one GPa. However, 

in the P-phase, hydrogen is structurally bound, with uncertain implications on its 

ability to mechanically weaken this material. 

We carried out rheology measurements on these phases by monitoring the diffraction peak broadening as a function of pressure, temperature and time. The cubictype multi-anvil press SAM85 at the X17B1 beamline was employed in the experiments. The technique to derive strains of crystal grains produced by deviatoric 

stress in the high pressure cell has been described elsewhere. 

The dry or-phase sample is San Carlos olivine, and the ,&phase and hydrous 

&phases were synthesized using the USSA2000 press at Stony Brook. Recovered 

samples were ground and repressurized at room temperature up to 9 GPa in SAM85, 

then temperature was increased to 60OoC. FWHM analysis of the energy dispersive 

diffraction patterns showed that ,&phase is generally stronger than the olivine (or) 

phase, and the hydrous olivine is much weaker than dry olivine by 40OoC. Strength of 

the hydrous P-phase is similar to dry beta at this temperature and becomes slightly 

lower than dry beta by 60OoC. Thus, structurally bound water in the &phase may 

not significantly weaken this material. 

X17B1 (Mg,Fe)2Si04 

I Pressure Induced Amorphization in Zirconium Tungstate ZrWzOs I X17B1 I 

J. Chen, J. B. Parise, R. Li (CHiPR, SUNY, Stony Brook) and A. W. Sleight 

ZrWzOs has been reported to show a highly unusual property of isotropic negative 

thermal expansion over its entire stability temperature range of 0.3 to 1050 K at 

room pressure('). Evans et recently observed a phase transformation from 

cubic to orthorhombic structure at 2 kbar and room temperature. The high pressure 

phase also shows a negative thermal expansion from 0 to 300 K. This suggests that 

this material may have very unusual behavior under high pressure. 

We have carried out in situ x-ray diffraction measurements at very high pressure 

up to 200 kbar at X17B1. A newly developed T-cup multi-anvil high pressure cell(') 

was used for the pressure generation. The x-ray diffraction shows that under compression, ZrWzOs undergoes amorphization at 10 kbar, and the amorphous phase 

remains stable until 200 kbar at room temperature (Figure 1). Upon heating, the 

amorphous phase decomposes at 1000 K and 18 kbar. The behavior of ZrWzOs 

under pressure is interesting. The mechanism of the amorphization is under investigation. 

(OSU) 

References: 

(l)T. A. Mary, J. S. 0. Evans, T. Vogt, and A. W. Sleight, Science 272, 90 (1996). 

(')J. S. 0. Evans, J. D. Jorgensen, D. N. Argriou, Z. Hu, S. Short, R. Osborn, and 

A. W. Sleight (in preparation). 

llkbar 

I 

Figure 1. Diffraction patterns of ZrWz 08 at different pressures 
A X17B1 Structural Studies of AgZS04 and T1X (X = C1, Br, I) by In-Situ 

o ED-XRD to 6GPa and 55OOC 

Q. Chen and R. A. Secco, (U. West. Ont.), E.A. Secco, (St. Francis Xavier U.), 

J. Chen, M.T. Vaughan, G. Chen, J.Z. Zhang, and D.J. Weidner (CHiPR, SUNY, 

Stony Brook) 

High pressure (P) electrical conductivity measurements on T1X (X = C1, Br, I) 

and AgzSOa show distinct conductivity jumps with increasing temperature (T . For AgaSO4, this is associated with a transformation from low T orthorhombic ( B - 

phase) to high T hexagonal (a-phase) structure. The a-p phase boundary reaches 

a maximum at 1.6 GPa (observed only by differential thermal analysis (Pistorius, 

1965, J. Chem. Phys. 46, 2167)) and is accompanied by anomalous decreasing 

activation energy of conduction with P in this region. In-situ XRD experiments 

were therefore carried out to check for possible structural cause(s) of this anomalous 

behaviour. In the T1X system, structural studies were also carried out to investigate 

the nature of the conductivity increases. Energy dispersive XRD experiments were 

carried out at X17B1 using SAM85 with NaCl as the internal pressure calibrant. 

AgzS04: The ortho-hex structural transformation is confirmed in the XRD patterns at low P but there are marked differences at T > 45OoC between P < 1.6 GPa 

and P > 1.6 GPa as shown in the figure below suggesting a possible new phase in 

the high P, T region. The similarity of patterns at 22OC and 1 atm. before and 

after high P,T exposure indicate lack of reaction between sample and boron nitride 

container . T1X (X = C1, Br, I): Both TlCl and TlBr do not show any evidence of P- or 

T-induced modification of their 22OC and 1 atm cubic (CsC1) structure at P up to 

6GPa and T up to 550°C. In comparison, changes observed in T1I patterns are more complex as shown in the figure below. 

. . . . . . . 

40 60 80 100 0 

E (kev) E (keV) 

Figure 1. Figure 2. 

X17B1 Microbeam Irradiation of Duck Embryo Brains: Relevance to Microbeam Radiation Therapy [MRT] of Brain Tumors in Infants 

F.A. Dilmanian, X.Y. Wu, X. Huang, M. Kershaw, B. Ren, D.N. Slatkin, K. 

Trandem (Medical, BNL), R. Menk, W.C. Thomlinson, and Z. Zhong (NSLS) 

X-ray microbeam radiations have been studied at the NSLS [l] for their significant tissue-sparing effect when used unidirectionally. This effect allows microbeam 

radiation therapy [MRT] by crossfiring at the target volume (and thus diminishing 

the tissue sparing effect inside that volume). Because of the relatively small damage 

that MRT of a brain tumor would cause to normal tissues outside the target volume, 

and because of the extraordinary radiosensitivity of the maturing brain, our goal is 

to treat intractable brain tumors in infants. We studied the radiosensitivity of the 

duck embryo brain, a surrogate for the human infant brain, to parallel microbeams 

delivered 3-4 days before hatching (Le., 24-25 days into incubation). 

The beam bundle comprised 52 or 104 parallel microplanar beams, each 25 

pm wide and 11 mm high, 200 or 100 pm apart on center, respectively. The 

beam's critical energy was M 69 keV and the skin-entrance absorbed doses 

in the microbeams were 78, 156, or 312 Gy. Neither the polar nor the azimuthal angle of beam incidence on the head axis was known. An interim 

tabulation of survival quality is as follows. The ducks' age at the time of 

evaluation was M 4 months for EXD. I and M 3 months for EXD. 11. 

Exp. Beam spac. Entrance 

# on center absorbed 

I 200 78 

200 156 

I1 200 156 

100 78 

100 156 

100 312 

(Pm) dose (GY) 

unirradiated 

unirradiat ed ~~ ~ Duck embryos move spontaneousl 

#&of Number COMPLICATIONS 

eggs hatched neuro- non- none 

8 7 1 2 4 

8 8 0 0 8 

16 16 0 1 15 

5 4 1 0 3 

5 5 1 0 4 

5 4 1 0 3 

5 3 1 0 2 

logic neuro. 

8 4 0 0 4 

in their shell. This could have blurred the dose 

distribution and thereby elicited neurologic complications. Most of the irradiated 

ducks exhibited an M 10% lag in weight gain as compared with the unirradiated 

ducks; this lag disappeared by M 3 months. The survival results may be relevant 

clinically, as entrance doses in the 70-300 Gy range are likely to be used for MRT 

of infants' brain tumors. Gross examination and appropriate histological studies of 

the formalin-fixed brains have yet to be performed. 

rll. D.N. Slatkin. P. SDanne. F.A. Dilmanian. J.-0. Gebbers, and J.A. Laissue, LJ 

Proc. Natl. Acad: Sci. USA 92, 8783-8787, 1995. 

We would thank K. A. Bonti, A.B. Chituk, D.H. Corwin, W. F. Dean, J.F. Gats, 

A. N. Gifford. N. F. Gmiir. J.C. Heinrichs. D.D. Joel. 0. Rahmanan, P. Ramcharan. 

K.E. Rising, G.L. Rissland, T. S. Sandhu; R.B. Setlow, P. Som, K.A. Vodopia, and 

A.D. Woodhead for assistance. This research was supported by the Office of Health 

and Environmental Research, and U.S. DOE. 
Elasticity of Polycrystalline MgSiOs-Majorite from Simultaneous 

X-ray and Ultrasonic Measurements to 9 GPa and 1000 K in a X17B1 

Multi-Anvil Apparatus 

G. D. Gwanmesia (DSU), G. Chen, Y. Sinelnikov, J. Cooke, L. Flesch, M. T. 

Vaughan and R. C. Liebermann (CHiPR, SUNY, Stony Brook) 

Polycrystalline specimens of MgSiOs-majorite have been hot-pressed in a 2000- 

ton uniaxial split-sphere apparatus (USSA-2000) using a 10 mm MgO octahedral 

cell assembly and the techniques developed previously by Gwanmesia and Lieber- mann (1992; see also Gwanmesia et ol., 1993). These specimens have bulk densities 

identical to the X-ray density and exhibit compressional and shear wave velocities within 0.2% of the Hashin-Shtrikman bounds calculated from the single-crystal 

elastic moduli of Pacalo and Weidner (1996). In our laboratory, we have developed techniques to enable precise ultrasonic interferometeric measurements of wave velocities in minerals to be performed to pressures of 9 GPa and temperatures of 

1500 K using a DIA-type, cubic-anvil apparatus (SAM 85) installed on the superconducting wiggler beamline (X17B) at the National Synchrotron Light Source of 

the Brookhaven National Laboratory. X-ray spectra of both the polycrystalline 

specimen and the NaCl medium which surrounds it are monitored continuously; 

the former provides PVT data to compliment the velocity measurements and the 

latter the pressure standard. We have obtained new data on P and S velocities in 

the polycrystalline MgSiOs-majorite to 7 GPa at 1000 K. An example of the high 

quality of the acoustic interference patterns is given in the figure below. 

S-wave Interference Panern lor Mg-majorlte 

at -7 GPs 1OW K 

X17B1 Rheological Study of Hydrous y-Phase Using in sitv X-ray Diffraction _____ I 1 

T. Inoue, J. H. Chen, Y. Wu, D. J. Weidner and M. T. Vaughan (CHiPR, SUNY, 

Stony Brook) 

Water influences rheological properties of minerals. Especially, y-M zSiO4 , which 

is a high pressure polymorph of olivine, can accommodate a few wtk HzO in the 

crystal structure. It is important to examine the rheological property of hydrous 

y-phase because y-phase is the most abundant mineral in the mantle transition zone. 

Hydrous y-phase was synthesized at a pressure of 19 GPa and a temperature of 

130OOC using the MA-8 type apparatus (USSA-2000) at SUNY, Stony Brook. The 

composition of the recovered sample was measured by EPMA and the HzO content was measured by SIMS. The present hydrous y-phase includes about 2 wt% HzO. 

Using a T-Cup' , which is a new high-pressure apparatus for in-situ X-ray studies, 

embedded in SAM-85 at the X17B1 beam line, we studied the temperature-time dependence of microscopic deviatoric stress using the method developed by Weidner' . Pressure was increased to approximately 19 GPa at room temperature, and then 

heated to 4OO0C, 6OO0C, 8OO0C and finally 1000°C. At each temperature, the data 

was collected every 60 s for 40 to 80 min. We analyzed the microscopic strains from 

peak broadening for the (311) diffraction line. 

At 4OO0C, the microscopic strain was approximately 0.017, and slightly decreased 

with time. At 600°C and 8OO0C, those are approximately 0.01 and 0.005, respectively, and the strain was completely relaxed at 1000°C. The above results shows 

that the microscopic strain remains at even 800OC. Comparing with our previous 

studies of olivine, hydrous 7-phase is much stronger than olivine. We will continue 

to do this type of experiments of various minerals to clarify the rheology of the 

mantle transition zone. 

References: 

D.J. Weidner, Y.B. Wang, M.T. Vaughan, C.C. Koleda and I.C. Getting: T-Cup: 

A New High-pressure Apparatus for X-ray Studies, NSLS Activity Report, 140 

(1995). 

D.J. Weidner, Y.B. Wang and M.T. Vaughan: Strength of Diamond, Science, 266, 

419-422 (1994) 

Figure 1. 
F 

P 

Elasticity of Polycrystalline Beta-MgzSi04 From Simultaneous Xray and Ultrasonic Measurements to 7 GPa and 900 K in a Multi- X17B1 

Anvil Apparatus 

B. Li, J. Liu, L. Flesch (CHiPR, SUNY, Stony Brook), G. D. Gwanmesia (DSU), 

J. Chen and R. C. Liebermann (CHiPR, SUNY, Stony Brook) 

Polycrystalline specimens of the beta phase of MgzSiOl have been hot-pressed 

in a multi-anvil high pressure apparatus using the techniques described previously 

by Gwanmesia and Liebermann (1992). These specimens have bulk densities which are 99.6% of the theoretical density and, compressional and shear wave velocities which are within 0.5% of the of Hashin-Shtrikman bounds calculated from the 

single-crystal elastic moduli of Sawamoto et QZ. (1984). In our laboratory, we have 

developed techniques to enable precise ultrasonic interferometeric measurements of 

wave velocities in minerals to be performed to pressures of 9 GPa and temperatures 

of 1500 K using a DIA-type, cubic-anvil apparatus (SAM 85) installed on the superconducting wiggler beamline (X17B) at the National Synchrotron Light Source 

of the Brookhaven National Laboratory. X- ray spectra of both the polycrystalline 

specimen and the NaCl medium which surrounds it are monitored continuously; 

the former provides PVT data to compliment the velocity measurements and the 

latter the pressure standard. We have obtained new data on P and S velocities for 

a polycrystalline beta phase specimen to 7 GPa and 900 K. In the figure below, we 

plot the travel time of shear waves us. pressure at room temperature for the beta 

phase. 

I 

b 

L3 

A 

A 20 *~ 0 0 5 10 15 20 25 30 35 40 

Time (m) 

Figure 1. S-wave Travel Time vs. Pressure at Ambient T for beta phase. 

Simultaneous X-Ray and Acoustic Measurements of Equations of 

State of Solids at High Pressures and Temperatures in Multi-Anvil X17B1 

Apparatus 

R. C. Liebermann, G. Chen, B. Li, G. D. Gwanmesia, J. Cooke, L. Flesch, J. Liu, 

Y. Sinelnikov, M. T. Vaughan, J. Chen, J. Zhang, Y. Wang and D. J. Weidner 

(SUNY, Stony Brook) 

We have developed "specimen friendly" cell assemblies for multi- anvil, highpressure apparatus which enable precise ultrasonic interferometeric measurements 

of wave velocities in minerals to be performed to P > 12 GPa and T > 1300 K. These 

experiments initially utilized a 1000-ton Kennedy-Getting type press and a split 

cylinder module of Walker's design USCA-1000 combined with an ANUTECH 

(Li et al., GRL, 23,2259, 1996; Chen et al., Science, 272, 979, 1996 . We have 

recently adapted these techniques for use in a DIA-type, cubic-anv i apparatus (SAM 85) installed on the superconducting wiggler beamline (X17B) at the National 

Synchrotron Light Source of the Brookhaven National Laboratory see figure below). 

In this case, pressure is monitored continuously by observing with Ii -rays the change 

of volume of the NaCl standard which surrounds the sample. P wave measurements 

to 9.7 GPa on Lucalox alumina showed behavior very consistent with the data from 

the experiments in the USCA-1000 apparatus, in which pressure was estimated 

from observing the phase transitions in Bi and ZnTe. Subsequent experiments 

achieved simultaneous conditions of 7 GPa and approximately 1500 K and included 

direct determinations of the cell volume of the sample. Studies on polycrystalline 

specimens of MgSiOs-majorite and the beta phase of MgzSi04 and single crystals 

of MgO are reported elsewhere in this report by G. Gwanmesia, B. Li and G. Chen. 

ultrasonic interferometer to study bot 6 polycryst A ne and single crystal specimens 

Platinum Wire for Electric Co 

/' \ To Interferometer ' 

1 Boron NitrideGraphite Furnace 

Sprlng Loading Devide Acoustlc Transducer 

for Acoustic Transducer contact CulPt Foil far / Electric Contact 

Figure 1. Diagram of Anvil Insert and Cell Assembly for Ultrasonic Experiments 

in SAM 85 
Thermal Equation of State of Stishovite 

J. Liu, J. Zhang, D. J. Weidner, L. Flesch, G. Chen, B. Li and R. C. Liebermann 

(SUNY, Stony Brook) 

The pressure-volume-temperature (P-V-T) behavior in SiOz-stishovite has been 

studied using a DIA-type, cubic-anvil apparatus (SAM 85) and in situ synchrotron 

X-ray diffraction, 

A polycrystalline specimen previously hot-pressed in a uniaxial split-sphere apparatus was used. The P-V-T data to P > lOGPa and T > 1000°C were analysised 

using several approaches, including a temperature-dependent Birch-Murnaghan 

equation-of-state, isothermal compression and isobaric thermal expansion. The bulk 

modulus (KO) and axial compressibilities of stishovite are compared with values 

obtained from Brillouin scattering and diamond-anvil cell X-ray studies on single 

crystal stishovite and ultrasonic studies on polycrystalline specimens. 

The results obtained from different approaches show the whole data set is internally consistant. The temperature derivative of bulk modulus at zero pressure 

(s)po is measured for the first time to be -0.0355(106) GPa/K. 

X17B1 

I Bronchial Imaging Using Xenon K-Edge Dichromography 1 X17B2 I 

R. H. O’Neil, J. Giacomini, E. Rubenstein, A. Van Kessel, H. Gordon (Stanford), 

W. Thomlinson, N. Gmur, Z. Zhong (NSLS) and D. Chapman (IIT) 

Using medical imaging techniques pioneered at NSLS on X17B2 for coronary 

angiography, we have developed the use of xenon gas as a contrast agent for studies 

of the bronchial airways. Xenon gas has a K-edge absorption at 34.561 keV, slightly 

higher than the iodinated contrast agent used in previous coronary angiography 

studies. This similarity led to the use of xenon to perform the same task in the 

bronchial airways as iodine performed in the coronary arteries; the highlighting of 

the airways against other tissues. In this technique a mixture of 80% xenon and 20% 

oxygen is slowly inhaled by the subject to fill the anatomical dead space but not the 

alveolar space of the lungs. Unlike earlier contrast agents used in bronchography, 

xenon is a non-toxic inert gas requiring only a single 500 ml inhalation to acquire an image. After inhalation the subject is scanned through two coplanar beams of 

X-rays bracketing the K-edge of xenon. Two 600 element line detectors capture the 

data which is processed to produce a difference image that yields clear images of only 

the xenon filled structures. The images in figures 1 and 2 clearly show the trachea, 

mainstem bronchus and the bronchi down to the tertiary branch. Early detection 

of pulmonary disease processes may be possible using this technique. Work funded 

under DOE contracts DE-AC02-76CH00016 and DE-FG03-87ER60527. 

Figure 1. Flight Bronchi. Figure 2. Left Bronchi. 
td F 

$ Elasticity of Ca(Ti,Si)03 Perovskite. X17B1 

Y. D. Sinelnikov, J. Zhang, and R. C. Liebermann (CHiPR, SUNY, Stony Brook) 

Elastic properties in the CaTiO3 - CaSiO3 system have been in the focus of this 

work. Polycrystalline specimens of end-member CaTiOs perovskite and intermediate Ca(Ti.~6Si.z~)O~, Ca(Ti.6 si.6 03 perovskites were hot-pressed in a 2000-ton 

thesized at pressures of 15GPa and temperatures above 15OO0C. Compressional 

and Shear wave velocities were measured using ultrasonic interferometry technique 

at room pressure and temperature. Densities of the synthesized specimens has 

been found by Archimedes immersion to be within 1% of the X ray density. Estimated from the acoustic measurements value of bulk moduli for intermediate 

Ca(Ti.5 Si.6)Os perovskite and end-member CaTiOs perovskite are 188(1) GPa and 

175(1) GPa, and the shear moduli are G=109(1) GPa and 106(1) GPa, respectively. 

In-situ P-T synchrotron X ray diffraction study yielded isothermal bulk moduli of 

Ca(Ti.6Si.6)03 and CaTiOa, 182(5) GPa and 171(5 For un212(7) GPa and shear modulus, G = 112(5) GPa. Thus, predicted shear modulus 

of CaSiOs perovskite is 60% lower than that of MgSi03 perovskite. This implies 

the substantial importance of CaSi03 perovskite elastic properties in constraining 

the composition of the lower mantle. 

uniaxial split-sphere apparatus (U B SA-2000). Intermediate compounds were synGPa, respectively. 

quenchable CaSiO3 perovskite elasticity systematics 1 eads the bulk modulus, K = 

Rheology of Cubic Boron Nitride at High Temperatures and PresRIIT~R 

X17B1 _____ I I 

J. S. Sweeney, J. Chen, D. J. Weidner, M. T. Vaughan (CHiPR, SUNY, Stony 

Brook) 

The rheological properties of powdered and sintered polycrystalline cubic boron 

nitride (cBN) were investigated at 9.3 GPa and up to 1820 K. The cBN was strained 

by hydrostatic pressure in a DIA-type multi-anvil apparatus and by local deviatoric 

stresses induced by grain-to-grain contacts within the samples. Strain rates were 

investigated by heating the cBN and then collecting time-resolved energy dispersive 

x-ray diffraction spectra at intervals between 30 and 120 s. Strain due to deviatoric 

stress broadens the x-ray diffraction peaks. Strain-broadening is deconvolved by 

Fourier analysis from instrumental effects that are estimated from spectra at room 

temperature and pressure. For this analysis, diffraction peaks are fit to a split Pearson VI1 function since a split function accommodates asymmetry in the peaks and 

the Pearson VI1 function approximates the data better than Cauchy and Gaussian 

functions. Due to the quantity of data, automated proceedures are implemented 

for peak identification, background subtraction, peak fitting, and deconvolution. 
X17B1 Phase Relations and Equations of State for High-pressure Phases 

of Ferrosilite and Enstatite 

M. T. Vaughan, D. H. Lindsley, and Y. Silnelnikov (CHiPR, SUNY, Stony Brook) 

In two separate experiments, we have begun studying the high pressure phase of 

FeSiO3 known as ferrosilite 111, and the ilmenite phase of (Mg.9Fe,l)SiO3. 

As can be seen in the figure below, the Ilmenite phase of (Mg.9Fe.l)SiO3 occurs 

at high pressure, just below that of the perovskite phase. We lost the thermocouple during the experiment, so we were unable to get a good EOS. The EOS 

measurements were done outside the ilmenite stability field (using power to estimate temperature), and we were concerned that the ilmenite sample would convert 

to a lower pressure phase when heated. This, in fact, did not occur, so in future 

experiments we should be able to go to higher temperature. 

Ferrosilite I11 is known only as a phase quenched from high temperature (-12OOC 

and modestly high pressure (2-3 GPa). The quench phase is a 9-repeat pyroxenoi d 

polymorph of ferrosilite, with the formula FeSiOs. The purpose of the experiment 

is to determine if the quench phase is also the stable phase under the conditions at 

which it was formed. Due to experimental difficulties, the answer is still not known. 

In the first run, we started with the quench phase and increased pressure at room 

temperature to about 3 GPa, then heated. We had to heat fast, because we didn’t 

want the sample to transform to orthoferrosilite, which is the stable phase at this 

pressure and lower temperatures. Unfortunately, we overshot the Fs-I11 field, and 

melted the sample. In a second attempt, the thermocouple failed and temperature 

had to be estimated based on heater power. The sample at the final data point had 

transformed to orthoferrosilite, so we must have been slightly low in temperature. 

2500 

2000 

9 

g1500 

!? 

c 

Q) 

$000 

f 

500 

0 

MgSiO, FeSiO, 

y-Mg,SIO, + Stishovlte 

5 10 

Pressure, GPa 

Figure 1. Phase relations in MgSiOa and FeSiO3. 

T-CUP: A New High-pressure Apparatus for X-Ray Studies - Con- I tinued 

M. T. Vaughan, D. J. Weidner, and J. Chen (SUNY, Stony Brook) 

Last year we reported on the development of the TCUP apparatus’, a two-stage 

device using eight-cubic anvils to generate high pressure, with x-ray access. This 

year we have made the following advances in this apparatus: 

a) Extended the pressure range to 21 GPa, through the use of reverse-tapered 10 

mm Toshiba grade F WC anvils. Figure 1 shows cell pressure ws oil pressure data 

taken on the study of zIW~08.~ 

b) Developed cell assemblies for making Equation of State measurements, including using lanthanum chromite heaters. 

c) Extended the method for making strain measurements to higher pressure2”. 

Figure 2 shows the P-T path used for the P-(Mg,Fe)2Si0h3 

‘NSLS Activity Report, page B-140, 1995 

2J. Chen, Pressure Induced Amprphization in Zirconium Tungstate, this Report. 

3T. Inoue, Rheological study of hydrous 7-phase using in situ x-ray difiaction and 

J. Chen, Rheology of dry and hydrous phases of the CY andP forms of (Mg,Fe)aSiO+, 

both in this Report. 

20 I 900 

IOoo 1 1 

0 100 200 300 400 500 600 700 800 

Oil Pressure, bars 

:- 0-. - ~,-_ 

800 

700 

9 600 

e; 

3 500 

E 400 

300 

200 

100 

0 2 4 6 8 IO 12 14 16 18 20 

Pressure, GPa 

Figure 1. Pressure Performance of Figure 2. P-T path for one of the strain 

TCUP apparatus. measurements. 
P A New Anvil Geometry for SAM-85 for High P, T X-ray Studies * I X17B1 

A 

Y. B. Wang, D. J. Weidner, M. T. Vaughan (CHiPR, SUNY, Stony Brook), and I. 

C. Getting (CHiPR, U. Colorado) 

We have modified the conventional DIA anvils in order to improve their performance in terms of pressure capability and reliability. Figure 1 shows geometry of 

our new tapered WC anvils and Figure 2 the attainable pressure with the tapered 

anvils as compared to that of the conventional straight-flank anvils. Several points 

about this new geometry are worth noticing. 

1. As is evident from Figure 2, we have gained 30% in maximum attainable 

pressure compared to the conventional anvil geometry. Thus the tapered WC anvils 

give the pressure range comparable to that of straight sintered diamond anvils. 

2. The wedged anvil gaps act as pressure seals, thereby significantly reduced the 

number of blowouts, which used to cause failures in the experiments. 

3. The tapered anvil geometry greatly reduced hysteresis in the pressure -load 

relation, enabling us to obtain multiple heating cycles at various pressures, and 

allowed complete P-V-T measurements within the entire P- T space with a single 

experiment. 

4. The tapered anvil geometry significantly increased survival rate of the thermocouples to close to 100%. Counting all the factors together, we have increased 

our efficiency in the P-V-T experiments by a factor of 4 with the tapered anvils. 

Figure 1. Geometry of tapered anvils 

(four shown). The light gray portions are removed, leaving the dark gray anvil 

* This work was supported by the National Science Foundation under a grant to 

the Center for High Pressure Research. 

14 

2 12 

10 i 

28 

$6 

n. 

-4 

0 20 40 60 80 100120140160180 

Load, tons 

Figure 2. Pressure us. load for the 4/3.5 mm tapered anvils (open circles) and the 

4 mm straight anvils. Note that the 

curve for the straight anvils levels off at 

about 120 tons, where the tapered anvils 

generate a pressure that is about 30% 

higher. 

Contrast Imaging and Image Quantification With the Monochromatic CT - MECT * 

X.Y. Wu, F.A. Dilmanian, X. Huang, E.C. Parsons, B. Ren ( BNL, Medical), W.C 

Thomlinson, Z. Zhong (NSLS), L.D. Chapman (I.I.T.), T.M. Button, and M.J. 

Petersen ( SUNY, Stony Brook) 

One of the advantages of monochromatic x-ray beams for computed tomography 

(CT) is in imaging with contrast agents, where the monochromatic beam energy can be tuned just above the K-edge of the contrast element. Comparative iodine phantom studies between Multiple Energy Computed Tomography [MECT at X17B2 

in iodine image contrast over 120-kVp CCT. However, iodine’s K-edge is too low an energy for the CT of human body, except for the neck and the limbs. The present 

studies show that such an advantage exists also for Gd as a contrast agent. 

An 18-cm diameter acrylic phantom with thirty 11-mm diameter channels filled 

with Gd solutions from 0 to 1600pg Gd/ml was imaged with MECT at 50.34 keV 

and with CCT at 120 kVp. For the 1600 pg Gd/ml channels, MECT yields 138 HU 

while CCT only gives 64 HU. The noise ratio of MECT (50.34keV) to CCT(12OkVp 

the experimental MECT system parameters for both MECT and CCT (Le., 3 rad 

surface absorbed dose, 3 mm beam height, 0.922 mm detector pitch, and 0.25 mm detector-element dead space . Defining “constrast-to-noise ratio” (CNR) as the 

results a -3-fold CNR advantage for MECT compared to CCT. 

The Gd image contrast for the above measurements was accurate within the limits 

of the solution’s concentration accuracy. For CCT, however, such a quantification 

requires the knowledge of the effective beam energy throughout the image. Our 

computer simulations with an 18-cm water phantom that included small bone inserts 

as image-contrast indicators exhibited an average of 2.5 keV beam hardening for 

a 120-kVp CCT, despite the 1st-order beam hardening corrections (Le., Cupping 

corrections). The simulations also show that the difference between the bone image 

contrast at the phantom’s center and at its edge is 20 HU (typical noise was 2-3 HU). 

This corresponds to a 0.5 keV differential beam hardening. These results indicate 

the potential value of MECT in contrast imaging and in image quantification. 

X17B2 

and a conventional CT [CCT] showed that 33.3-keV MECT has a 3-fol d advantage 

is 1.4HU:1.9HU1 as obtained from computer simulations. These simulations use d 

figure of merit for judging (2 T image quality, we find from the above-mentioned 

* We thank J.A. Coderre, J.M. Dobbs, F. Giron, N. F. Gmiir, D. Greenberg, J.B. 

Hastings, S. Marcovici, R. Me&, C.T. Roque, D.P. Siddons, and D.N. Slatkin for their 

assistance. Research supported by the Office of Health and Environmental Research, and 

U.S. DOE. 
Rheology Study of PyGOMj40 Garnet at High Pressure and High 

Temperature 

Y. Wu, D.J. Weidner, J. Chen, G. Gwanmesia, and M. Vaughan (CHiPR, SUNY, 

Stony Brook) 

In situ X-ray diffraction measurements of the rheological properties of PyeoMj40 

garnet was completed up to 16GPa and 1000°C at the X-17B1 beam line using 

the newly designed high pressure apparatus T-cup' . The powder pysoMj40 garnet was first compressed to 16GPa and heated up gradually to 1000°C. By analysing 

the peak broadening for the (400) diffraction, we get the microscopic strains of the 

sample. 

Our result shows that the garnet sample reached yield point less than 6GPa 

at room temperature. Then 

the strength increased slowly with the increasing pressure. Under 16GPa confining pressure, we increased the temperature gradually, first to 4OO0C, 620°C, then 

8OO0C, and finally to 1000°C. The microscopic strain decreased noticeably with the 

increasing temperatures. Around 1000°C, the strain decreased almost to zero. At 

the specific temperature, we can see the microstrain decreased monotonically with 

time. And there is a linear relationship between log(&) and log(t). And the slope 

of the log(€) vs log(t) indicates that the exponent n of the power-law relationship 

decreases from 50 at 4OO0C to about 10 around 81OoC. This suggests the PysoMj40 

garnet may still be in the plastic regime at 80OoC. Also, the strain rate in the order 

of 

This is quite consistent with our earlier results2. 

s-l was measured for these temperature ranges. 

References: 

'Weidner, NSLS Activity Report, B-140 (1995); 

'Wu, NSLS Activity Report, B-141 (1995). 

Strain VS Time of PyBOMj40 garnet 

Equation of State of Calcite-Structure Carbonates 

Jianshong Zhang and Richard J. Reeder (CHiPR, SUNY, Stony Brook) 

Pressure-volume-temperature measurements have been carried out on NiCO3 and 

MnC03 carbonates using a DIA-type, cubic-anvil, high-pressure apparatus interfaced with synchrotron X-ray diffraction. These data, along with those obtained previously for magnesite (MgC03 and siderite (Feco3 using the same technique'I2, 

ates. 

A linear correlation between M-0 bond length and the room-temperature bulk 

modulus is, as expected, found in NiC03, FeCO3 and MnC03 carbonates. The 

product of the room-temperature bulk modulus and unit-cell volume at ambient 

condition is observed to be constant in these three compounds, similar to literature 

observations in other systems of isostructural series. Magnesite, however, deviates 

significantly from the linear trends in both correlations. It is speculated that car- bonates with alkaline elements as cations behavior differently at high pressures from 

those with transition metals as cations. 

X17B1 

allow us to systematically stu d y equation of state o 2 the calcite-structure carbonReferences: 

'Zhang, J., I. Martinez, F. Guyot, and S. K. Saxena: In sztuX-ray diffraction study on magnesite at high pressure and temperature, Phys. Chem. Mineral, in press. 

'Zhang, J., I. Martinez, and F. Guyot: In sitzlX-ray diffraction studies on mgnesite 

and siderites at high pressure and temperature, Terra Nova Suppl., V. 8, p70, 1996. 

Figure 1. Strain in PyeOMj40 garnet as a function of time. 
Fd 

P 

X17B1 Effect of Silicon Incorporation in Iron: Equation of State and Phase ~ .. ~~ ~~ I Transition 

J. Zhang (CHiPR, SUNY, Stony Brook) and F. Guyot (U. of Paris) 

Experiments have been carried out on iron and two iron-silicon alloys, Feo.glSio.og 

and Fe0.83Sio.l7, at high pressure and temperature up to 9 GPa and 1473 K, us- ing a DIA-type, cubic-anvil, high-pressure apparatus interfaced with synchrotron 

X-ray diffraction. Pressure-volume-temperature data were obtained for iron and 

Feo.91 Sio.09 and are analyzed using Birch-Murnaghan equation of state. With fixed 

KO at 4, we obtain for iron: 

KO = 154(2)GPa 

(6K/6T)p = -0.041(5)GPaK-' 

and 

for Feo.91 Sio.09 , we have 

KO = 156(2)GPa 

(6K/6T)p = -0.044(6)GP@K-' 

a300-773 = 4.71(14)K-'. 

and 

These results indicate that substitution of small amount of Si in iron would not 

have a significant effect on the equation of state parameters. Phase transition were 

studied in two experiments, one with iron and Feo.glSio.og loaded in the boron nitride 

container and the other Feo.glSio.og and Feo.~~Sio.l7. The bcc-fcc phase transition in 

Feo.glSio.0~ was observed at 7.5 and 9 GPa, but the temperatures of transition are more than 300 K higher than those in iron. Phase transition was not observed at 5 

GPa and lower pressures in Feo.slSio.og and in the entire experimental pressure and 

temperature range for Feo.83Si0.17. These observations indicate that incorporation 

of Si in iron strongly stabilizes the bcc structure in the system Fe-Si. In comparison 

with literature data at 1 atm., the present results also provide constraints on the 

compositional maxima of the 7-loop for the system Fe-Si as a function of pressure. 

Rheology, Strength, and Elasticity Anisotropy of Iron at High Pressures 

H. Mao, J. Shu, R. J. Hemley (Carnegie Institute), and A. K. Singh (Nat. Aeronautical Lab., India) 

The seismic anisotropy of the inner core may reflect the rheology of its solid 

constituents. We have conducted a 3-dimensional x-ray diffraction study of iron 

under uniaxial compression in a diamond cell at X17C of National Synchrotron 

Light Source. Rheological properties of /epsi[on-Fe, including orientational texture, 

shear strength, and elastic anisotropy, are studied at megabar pressures. 

With the 3-d x-ray diamond cell, energy dispersive x-ray diffraction (EDXD) can 

be obtained at any /phi, the angle between the diamond-cell axis and the diffraction 

vector. Relative intensities of EDXD peaks as a function of /phi reveals the preferred orientation of the polycrystalline sample. Under uniaxial stress, the /phi-Fe 

sample flows in the radial direction perpendicular to the stress. The intensity of 

002 reflection of the hexagonal close-packed iron reaches a maximum at /phi = 00 

and a minimum at /phi = 900, indicating the c-axis of /epsilon-Fe preferentially 

aligns with the maximum stress direction and the a-axis aligns with the maximum 

shear (flow) direction. 

The elastic moduli tensor (C(ij)), maximum stress (axial direction), minimum 

stress (radial direction), and average pressure can be calculated from the energy 

(or d-spacing) of EDXD peaks as a function of /phi. The difference between the 

maximum and minimum stresses provides an estimation of strength. At 52 GPa 

and 300K, we obtained C(11) = 689, C(12) = 298, C(33) = 702, C(13) = 270, C(44) 

= 419, and C66 = (C11 - C12)/2 = 195; all units in GPa. Calculated longitudinal 

velocities have a minimum in the a- (8.3 km/sec) and c- 8.3 km/sec) direction but 

a maximum in between a and c (9.5 km/sec). The 10 d o anisotropy in velocity is 

significantly larger than the 3% of the inner core. The present results, however, are consistent with the a-axis of e-Fe partially aligning with the shear direction 

perpendicular to the spin axis as a result of drag at the IOC interface. 

x17c 
Compression of Seven ScS Compositions with Sc Lattice Vacancies 

S. Peiris and D. Heinz (U. of Chicago) 

x17c 

The early transition metal chalcogenides display a wide range of compositions 

formed via metal or chalcogen deficiency from a parent stoichiometry. The Sc,S 

compositions (0.8<x<1.0) are such a system formed by vacancies in the metal sublattice of the rocksalt structure of SclS. 

Samples (synthesized by Tuenge [l]) from each composition were compressed to 50 

GPa, at room temperature in a Mao-Bell [2] diamond anvil cell. Energy dispersive 

x-ray diffraction was done on beamline X17C with the detector at a 20 angle of 

15'. Pressures were determined by including a few specks of gold with the sample 

and using a standard equation of state for gold [3]. The pressure(P -volume(V) 

data obtained were fit with fourth order Birch-Murnghan equations o f' state [4], to 

calculate thermodynamic parameters. Some of the equations of state thus obtained 

are shown in Fig. 1, and the thermodynamic parameters are shown in Fig. 2. 

We usually expect phases with lattice vacancies to be more compressible than 

space-filled lattices, which are more dense. However, our experiments reveal the 

isothermal bulk moduli (KO increasing with increasing vacancy content. These 

compositions with higher vacancy content have stronger, stiffer Sc-S bonds, because 

the higher oxidation state of Sc (>2) in the compositions with more vacancies, allow 

higher interaction of Sc 3d orbitals with S 3p orbitals [5,6]. 

The data obtained, and the P-VIVO equations of state for each composition, 

start converging by about 40 GPa. In addition the unit cell volumes obtained after 

decompression from 50 GPa to below 20 GPa are higher than the pre- compression 

volumes for the compositions with more vacancies. We suggest that these effects 

are due to the formation of dumbells-shaped S pairs at very high pressure in the 

compositions with more Sc vacancies. If these pairs were retained upon decompression the Sc in the lattice would be reduced to an oxidation state closer to $2, giving 

less compact Sc-S bonds and resulting larger unit cell volumes. 

1. R. T. Tuenge et al., J. Chem. Phys., 65, 2400 (1976). 

2. H. K. Mao et al., Rev. Sci. Instrum., 50, 1002 (1979). 

3. D. L. Heinz and R. Jeanloz, J. Appl. Phys., 55, 885 (1984). 

4. F. Birch, J. Geophys. Res., 83, 3543 (1978 . 

6. S. M. Peiris et al., Inorg. Chem., submitted. (1996). 

observations were explained b y the Extended Huckel calculations performed. The 

5. J. K. Burdett and J. F. Mitchell, Chem. Id ater., 5, 1465 (1993). 

Figure 1. Pressure-Volume equations of 

state for three ScS compositions. 

X in Bulk Modulus (dK0 /dP) (aK,'/ap) 

Kg (GPa) Kg' ~g" sc,s 

1.013+0.005 108t25 4+5 -5fl 

0.986k0.005 104f14 4f3 3.7k9.5 

0.892f0.003 135+18 0.8B.4 17f3 

0.875kO.006 130k29 1f5 24+5 

0.864kO.006 148A22 -0.4k3 23-1.3 

0.856B.007 145k28 2A4 3.5B.7 

0.838k0.004 149k23 -2+3 44k7 

Figure 2. Thermodynamic parameters 

obtained from P-V data. 

1 X17C 1 Pressure Induced Structural Transitions in Nanometer Size Particles I of PbS 

S. B. Qadri, E. F. Skelton, Y. Yang, B. R. Ratna (NRL), and J. Z. Hu (CIW) 

Semiconductors with reduced dimensions recently have been shown to exhibit 

electronic and optical properties which vary with the size of the particles. PbS and 

other Pb chalcogenides have attracted much attention due to their tunability over 

a wide spectrum. Relative to bulk crystals, the bandgap of the PbS nanoparticles was significantly blue shifted from the near-IR into the visible and near UV region 

with decreasing particle size. At elevated pressure (2.5 GPa), PbS undergoes a 

first order phase transition from the NaCl or B1 structure to an orthorhombic 

structure. The effects of particle sizes in the nanometer range on this transition have 

been investigated using energy-dispersive x-ray diffraction and diamond anvil cell. 

Relative to the bulk crystals, the onset of transition pressure showed a significant 

increase with decreasing particle size. The results also show that compressibility 

increases with decreasing particle size: this increase is continuous through the phase 

transit ion. 

20 25 30 35 40 45 

ENERGY, kev 

Figure 1. Diffraction spectra for the 54 

particles recorded at various pressures 

from the B1 (C) to the orthorhomica (0) 

phase. 

>' 

Pressure PPar . ~~ 

jo I 00 IO 10 so 10 50 BO 

~~ ~~ 

Figure 2. VIVO vs. pressure for three 

different particle sizes. 
P 

P 

High P-T Phase Diagram and Equation of State of Iron * 

G. Shen, J. Hu, R. J. Hemley, H. Mao (Carnegie Institute), and T. S. Duffy 

(GSECARS) 

An accurate determination of phase diagrams and P-V-T equations of state of 

iron provides critical constraints for models of the core. Laser-heated diamond-anvil 

cell, capable of generating ultrahigh pressures and temperatures has been improved 

with advancement and integration of in-situ x-ray microprobe and double hot-plate 

heating techniques. Significant progress in shaping and defining the temperature 

distribution in a laser-heated diamond cell has been made by coordinating the 

optimal laser characteristics, sample configuration, and optical arrangement. With 

double-focusing K-B x-ray mirrors, the spatial resolution and sensitivity of the x- ray diffraction microprobe have also been greatly improved, which enables precise 

measurements of a sample under uniform, well-defined high P-T conditions. 

For each pressure, temperature was varied, and x-ray diffraction patterns were taken for phase identification and density determination. For example, at 23 GPa 

at ambient temperature iron crystallizes in hexagonal-close-packed (hcp) e-Fe structure. As the temperature was raised to 1860 K, the hcp diffraction lines disappeared 

completely, and new lines corresponding to the face-centered- cubic (fcc) g phase 

appeared. The diffraction peaks of g iron disappeared above 2380 K and reappeared 

when the temperature was lowered to 2220 K, bracketing the melting temperature. 

The completeness of the transition is a clear indication that the sampled region for 

x-ray diffraction has uniform P-T, a major improvement from previous experiments. 

The liquidus phase changes from g -Fe at 45 GPa to e-Fe at 68 GPa, indicating a 

g-e-liquid triple point near 50 GPa. At high pressures, the present data indicate a melting curve close to but slightly higher than that of Boehler.1 

X17C 

R. Boehler, Nature 363, 534 (1993). 

In Situ Measurement of the Structural Transition Rate in Pd Associated with the Electrochemical Absorption of Deuterium 

E. F. Skelton, P. L. Hagans, S. B. Qadri, D. D. Dominguez (NRL), and J. Z. Hu 

Structural changes induced by the absorption of deuterium (D) into a Pd lattice 

were studied with very high energy (> 60 keV) photons. The a-to-p phase transition 

induced by the absorption of Pd into a 1 mm diameter Pd wire was monitored in 

a microspot 18 x m3 in volume as D was electrochemically loaded into the 

wire. Because of the long absorption length of 60+ keV photons, structural changes 

could be measured from the high energy diffraction peaks of Pd. The (422)-peak was monitored as a function of position and time from the edge to the core of the 

wire. From these data, it was determined that, under an electrochemical loading 

current of about 100 ma, the a-to-p phase transition moved from the edge to the core at a speed of 48 nm/sec. It also was determined that the a phase persists 

about 30% longer in the core that on the surface. These data represent the first 

time that the Pd lattice expansion and a-to-p transition rate have been measured 

in an electrochemical cell with a cylindrical cathode as a function of distance across the cathode. 

X17C 

(CIW) 

* This work is supported by NSF. 
kucture and Phase Transitions of Krypton in Porous Vycor I X18A I I Multiple X-ray Diffraction Studies of Decagonal Quasicrystals. I X18A I 

D. W. Brown, P. E. Sokol (Penn. State U.), and S. N. Ehrlich (Purdue U.) 

The equilibrium properties and kinetics of a fluid confined in mesoporous media are dramatically different from those in the bulk. The phase equilibria are substantially altered by the combined effects of finite pore size and substrate forces. Studies 

of the macroscopic behavior of the liquid-solid transition under such confinement 

have been published recently. Measurements of bulk thermodynamic variables, such 

as heat capacity, pressure, and the velocity of sound have been used to study the 

freezing of a variety of liquids in porous materials. In general, a large suppression 

of the liquid-solid transition temperature, up to 20% from the bulk, has been observed accompanied by a hysteresis between freezing and melting. The nature of 

the depression in the freezing point, whether due to finite size effects and related 

shifting of the phase diagram or inhibited nucleation of the solid, remains open. 

We have undertaken a study of the structure of krypton confined in the pores of 

thirsty Vycor glass. Vycor glass is approximately 70% Si02 and 29% BzOs. The 

B203 is chemically leached out to leave small pores making up 29% of the volume of 

the glass. The pores are considered to be approximatly cylindrical with and aspect 

ratio of 7:1. In our case the pores have a radius of approximately 70 A. 

Our sample was cooled to 120 K, in the liquid phase of bulk Kr. The Vycor was 

then loaded to various filling fractions with Kr gas. Diffraction measurements were done on cooling and warming. Typical x-ray diffraction patterns, with the pores 

filled to half of their capacity, can be seen in Fig. 1 as a function of temperature. 

The two broad peaks are due to the Vycor and the two sharp peaks on the right are due to the Be windows on the sample cell. The disappearance of the Kr diffraction 

peaks signifies the melting point of the liquid. The bulk freezing point of Kr is 115.8 

K. We have observed the freezing point to be at 101 K and the melting point to be 

at 106 K with the pores full to capacity. The freezing point drops to below 80 K 

and the melting point to 89 K when the pores are filled to 25% of capacity (Fig. 2). 

More complete analysis will yield information about such things as the mechanism 

of solidification, the strain the crystal is under, and the size of the crystallites. Work 

supported by a Petroleum Research Fund Grant ACS-PRF31907-AC5 & DOE Grant 

DE-FG02-85ER45183. 

MeiUng - 5OIfilting Freezing point 

I ImLI 

m~ - -102K -Freezing Point1 

R. Eisenhower, R. Colella (Purdue U.), B. Grushko (Jiilich) 

The problem under investigation is the structure of decagonal quasicrystals, the 

issue of centrosymmetry, and the effect of stoichiometry and composition. Phase 

information on structure factors is an important ingredient for structural investiations and the method used in this work is based on Multiple Bragg Scattering r Also called: YJmweganregung” = detour radiation. See: Q. Shen and R. Colella, 

Nature 329 232 (1987)], a situation in which two or more Bragg reflections are simultaneously excited in the crystal. Preliminary results were presented in the 1995 

NSLS Annual Report, for A1 68CullCo21 and A1 71Ni24Fes. 

In this abstract we report data for a different material: A1 72.6Ni16.6Coll. The 

lattice constants of all three quasicrystals are surprisingly identical. There are, however, differences in their structures. These differences are manifested in the phases 

of the Bragg reflections involved. What is measured, in a three-beam experiment, 

is the triplet invariant: = 6 = cj H +cj P-H -4 p, a linear combination of the 

phases. The main reflection for which azimuthal scans are presented below is called 

PI the simultaneous reflection is H and P - H is the coupling reflection. An example of the structural differences between two seemingly isomorphous quasicrystals 

is shown below. While the main and simultaneous reflections are the same for both 

plots, there are noticeable differences in the two “umweg” plots. While the plot for 

A1 71 Ni24Fe6 (Fig. 1) shows a strong asymmetry, the plot for A1 72.6 Ni16.sCo11 

(Fig. 2) is very symmetric, indicating a 6 value close to 90°, for which there would 

be no asymmetry at all. In both cases, the 6 values (50’ and 83’) are far from 

0’ and 180°, the only values compatible with a centrosymmetric structure. It is 

concluded that A1 72.5Ni16.6 Coli is also non-centrosymmetric. 

Figure 1. Figure 2. 
td 

CL I Spot Shapes of Bragg Reflections in Decagonal Quasicrystals I X-18A I 

R. Eisenhower (U. of Illinois), Steve Ehrlich (Purdue U.), Benjamin Grushko 

(Forschungszentrum Juelich, Germany) 

Decagonal quasicrystals consist of periodically stacked quasicrystalline layers. 

Each layer exhibits a classically forbidden 10-fold rotational symmetry axis. Existing in the transformation region between 3-D quasicrystalline and periodic structures, their structure is highly dependent upon stoichiometry and growth conditions. 

Complicating the study of the decagonal quasicrystal structure is the existence of 

the microcrystal structure, which consists of rotated rhombohedral domains and 

closely mimicks the decagonal structure. High-resolution reciprocal space scans on microcrystals reveal distinctive peak splitting. Similar experiments were performed on Ala~CullCozl and AhNi24Fes decagonal quasicrystals. In contrast to the 

microcrystalline phase, the precession photographs of the Al-Cu-Co and Al-Ni-Fe 

quasicrystals revealed normal spot shapes, and synchrotron rocking curve widths were narrow (.015 degrees FWHM). However, high-resolution reciprocal space scans 

reveal a complicated structure for the decagonal phase as well. Non-uniform smear- ing of intensity in the azimuthal direction was seen for the (10000) and equivalent 

reflections, whereas typical (Le. bullseye pattern) was seen for the (12110) and 

equivalent reflections. 

X18A 

Anomalous X-ray Scattering Studies of a Lead Magnoniobate Single 

Crvstal * 

V. Gosula, H. Chen (U. of Illinois), S. Teslic and T. Egami (U. of Pennsylvannia) 

Half integer superlattice reflections characteristic of ordered structure in 

Pb(Mgl/3Nb2/3)03 (PMN) single crystal have been measured using resonantv x-ray 

scattering near the Pb LIII absorption edge. These superlattice peaks have been 

previously measured through electron diffraction and explained by the two-phase 

Nb/Mg ordering model. The microscopic origin of these peaks remained controversial, specially since the effective scattering factor for these peaks is significantly 

smaller than in the case of complete ordering. By a similar approach, Nb was shown 

to contribute heavily to the scattering factor of the superlattice peaks, indicating its 

presence in the superstructure. In this experiment, the partial structure factor of the 

peaks with respect to lead was determined for three different half-integer peaks and 

showed a strong correlation. This constitutes strong evidence that Pb is involved 

in the superstructure, either through atomic exchange or large displacements. 

Figure 1. Plot showing both the total structure factor [S(T)] and its partial with 

respect to Pb [S(Pb)] for the 1/2(115) superlattice peak. 

* Work supported by DOE under grants DE-FG02-ER45183, DE-FG02-91ER45439 and 

IBHE-HECA. 
I X18A I High Temperature Studies of X-ray Scattering in a Lead Magnoniobate Single Crystal * 

Time and Depth Dependence Study of the Azimuthal Orientation ~18~' 

in Confined Hybrid Smectic C* Films * I X22BI 

V. Gosula, H. Chen (U. of Illinois), S. Teslic and T. Egami(U. of Pennsylvannia) 

A Pb(Mgl/3 Nb2/3)03 (PMN) single crystal was used for the study of ordering 

evolution as a function of temperature. The half-integer superlattice peaks were 

measured and the partial of the structure factor with respect to lead was determined 

using resonant x-ray scattering near the Pb Lrrr edge (two different energies). The 

intensities of several bragg peaks were also measured in order to determine the 

debye-waller factors of all the atoms involved in the structure. The intensities were shown to increase with the increase in temperature and aging was also noticed, 

as the intensities increased with aging time. The aging and temperature effects 

must be separated before the debye-waller factors and the ordering evolution of the 

superstructure can be appropriately determined. Thus, further work is needed in 

these high temperature scattering experiments. 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Haung (U. of Maryland) 

Confined hybrid liquid crystal films experience a competition between the aligning 

forces of the bounding surfaces. We have performed a depth profile dependence 

study of the in-plane ordering of a smectic C* liquid crystal mixture, mx5112, 

confined between a grated glass substrate and the air surface. This compound 

mixture has the following phase transitions: sm3 - smC* at 22.65OC; smC* - smA 

at 49.5"C; and smA - I at 57°C. The corresponding smectic layer spacings are 

33.303afor the smA phase; 29.97Afor the smC* phase; and 31.639Afor the sm3 

phase. 

The in-plane layer spacing oscillates between the bulk values of the smA and 

smC* phases as a function of time. This value varies also as a function of depth 

within the films and is close to the average of the two bulk spacings close to the 

liquid crystal glass interface. The azimuthal orientation of the layers varies both as a function of depth and of time within the films. In-plane layers close to the 

liquid crystal glass interface align close to the direction of the gratings' axis. The 

orientation of the layers close to the liquid crystal air interface rotate as a function 

of time to a direction perpendicular to the axis of the gratings, for samples thicker 

than 10pm, as illustrated on Table I. The mechanism for this rotation, which was 

previously observed both in samples thicker than 10pm and thinner than 3pm, is 

not clear at present. We are in the process of studying the depth dependence of the 

azimuthal orientation in greater detail. 

Layer Spacing (A) Or) - 15 pm $(') - 13 pm 

30.710 159 

30.770 20 

30.830 

30.360 

30.050 

30.640 

30.120 

31.160 

3 1,020 

30.630 

38 

24 

20 

20 

90 

78 

102 

23 

Figure 1. Table of Values of the azimuthal peak q5 corresponding to the layer spacing 

of the maximum peak for the 15-pm and 13-pm films. Data were obtained over a 16 

hour period for the 15pm sample and over a 90 hour period for the 13 pm sample. 

* This research was supported by a NSF-VPW Grant No. GER-94-50118, and a NSF 

Fd 

* Work supported by DOE under grants DE-FG02-ER45183, DE-FG02-91ER45439 and P 

cn 

IBHE-HECA. Grant No. ECS-96-96069. 
Time Dependence Study of In-Plane Layers in Confined Hybrid X18A, 

Smectic C* Films * X22B 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Huang (U. of Maryland) 

Liquid crytalline materials in constrained geometries exhibit properties that can vary significantly from the bulk properties of the material. Confined hybrid liquid 

crystal films experience a competition between the aligning forces of the bounding 

surfaces. We have studied the in-plane ordering of a smectic C* liquid crystal 

mixture, mx5112, confined between a grated glass substrate and the air surface. 

This compound mixture has a the following phase transitions: sm3 - smC* at 

20.65OC, smC* - smA at 49.5OC and smA - I at 57OC. The corresponding bulk layer 

spacings are: 31.303Afor the smA phase; 29.97Afor the smC* phase; and 31.639A 

for the low temperature Sm3 phase. 

We have observed that the in-plane layer spacing oscillates between values close 

to the smA bulk layer spacing and the smC* bulk layer spacing for samples with 

thicknesses in the range 10 - 20 pm. This oscillation is aperiodic in time, as shown 

in the Figure below. By contrast, thinner films show a slower variation of the value 

of the layer spacing with time, with a 0.6 percent oscillation over a 10 hour period. 

A depth profile study of the films shows that those layers located furthest from 

the glass grating interface show the largest variation in layer spacing over a 48 hour 

period. The layer spacing at the end of this period is approximately 0.3 percent 

larger than the bulk smC* spacing. In contrast, those layers closest to the glass 

grating interface remain close to the intermediate spacing value of 30.6A. 

The time oscillation may be the result of the competition between the two aligning 

surfaces in the smC* film. The in-plane layer at the grating interface favors a smAlike ordering, which relaxes through the thickness of the film. This relaxation is 

enhanced the farther the layers are from the glass interfaces or the thicker the films. 

The time oscillation and depth dependence of the layer spacings affect both the 

temperature and field dependence of these films. We are in the process of studying 

this behavior. 

Figure 1. Open circles: Time dependence of a 15pm and a 13pm film (combined). 

Open squares: time dependence of a 5pm film. 

* This work was supportedby a NSF-VPW Grant No. GER-94-50118, and a NSF Grant 

No. ECS-96-96069. 

I Anisotropic X-ray Diffuse Scattering Features in La0.6Pb0.4MnOa I X18A I 

R. McQueeney (U. of Pennsylvania) 

We have observed strong anisotropies in x-ray diffuse scattering from a single 

crystal of Lao.ePbo.4MnOs studied at room temperature with the X18A beamline 

using an incident energy of 12 keV.Two features distinguish themselves in the diffuse 

scattering. The first feature is the presence of square constant intensity contours 

for cuts in the hk-plane at constant 1 near the (4,0,0) Bragg reflection, as shown 

in the figure. Since the crystal is approximately a cubic perovskite, the diffuse 

scattering due to phonons should be isotropic. In addition to this feature, there 

also exists a large anisotropy of the diffuse scattering for the (h,+k,O)and (h,-k,O) 

regions near the (4,0,0) Bragg point. This, too, cannot be explained by the thermal 

diffuse scattering. 

The presence of these features indicates that there are significant atomic displacements above that due to phonons, and that special symmetry requirements 

are needed to explain the shape of the diffuse scattering. There is also a strong similarity to the diffuse scattering observed in the La2-sSr,Cu04 and Laz-,Sr,NiO4 

which show square intensities. In the case of the cuprate, the square is rotated by 

45 degrees. This diffuse scattering has been attributed to atomic strains caused 

by the inhomogeneous hole distributions within the transition metal-oxygen plane 

which arise from the substitutional doping. Thus, the manganese oxide compound 

may contain inhomogeneous charge distributions in the Mn-0 plane similar to the 

nickelate and cuprate compounds, which could shed some light on their interesting 

magnetic properties. These diffuse scattering features will be studied in much more detail in the future. 

Figure 1. Square diffuse scattering observed in within the (3.9,k,l) plane at room 

temperature for L a0 .e Pbo .4 MnOa . 
I Anomalous Diffraction Studies of CMR Materials * I X18A I 

S. M. Mini (Northern Illinois U. & ANL), J. Mitchell, D. Hinks (ANL) and S. N. 

Ehrlich (Purdue U.) 

We report the x-ray diffraction of a series of pseudo-perovskite, Lal-,Sr,MnO3, 

prepared at different pressures. The system is interesting because it is prototypical of colossal magneto resistive (CMR) materials. This perovskite system exhibits 

unusual coupling among magnetism, electronic transport, and structure. It is also 

thought to be mixed valent Mnt3/Mnt4. The Mn K-edge XANES on these materials show a small shift of increased energy indicatin increasing Mn valence as Sr 

content is increased. The MXCD of the Mn K-edge [] shows a negatve first peak, 

which is indicative of negative p-like spin density at the Fermi level, and an imbalance in the spin-dependent electronic density of states above the Fermi energy. 

Diffraction measurements were made at X18A, above and below the Mn K-edge 

(6539 eV), in in effort to clarify the electronic properties and structure of the Mn 

in these systems. 

[l] S.M. Mini, et all Mat. Res. SOC. Symp. Proc. Spring '96. 

* This work was supported by the State of Illinois under the IBHE/HECA Grant and 

the US. Department of Energy, Basic Energy, Science, Materials Sciences under Contract 

No. W-31-109-ENG-38 and DE-FG02-85ER45183 of the MATRIX PRT at the NSLS. 

The Defect Structure Studies of La2--+Ca3: CUO~-~ Superconductors I* 

X. Shi, J. B. Cohen, and T. 0. Mason (Northwestern U.) 

The local structure about Ca atoms in Laz-.Ca,Cu04-, samples is being studied 

by x-ray absorption fine structure (XAFS). The point defect modeling study of the 

Ca-doped system suggest that the majority defect species associate with the oxygen 

deficit (y>O) results primarily from dopant-vacancy associates rather than isolated 

oxygen vacancies. Ceram. 

SOC, bf 77[1], 81-88, (1994)). The association of oxygen vacancies with dopant will 

change the surrounding of the dopant. We have carried out studies on samples 

prepared with different oxygen partial pressures. Our XRD data shown there is no average structural change for the two samples. The fluorescence EXAFS was 

measured from below the Ca-K absorption edge to k=12 A-' above the edge. A 

"different" EXAFS technique is being used in the data analysis. The analysis of 

the results of defect structure is still underway. 

(L. Shen, P. A. Salvador, and T. 0. Mason,J. Am. 

* This work was supported by DOE Grant No. DE-FGO2-84ER45097/A015. 
F 

P 

Atomic Structure of PMN Studied by Resonant X-ray Diffraction * I X18A 

S. Teslic, T. Egami (U. of Penn.), V. Gosula and H. Chen (U. of Ill) 

We have studied the atomic structure of a PMN (Pb(Mg,/3Nba/303 single crystal 

using resonant x-ray scattering near the Pb L absorption edge. Superlattice peaks 

1/2<1,1,1> have been observed in PMN by electron diffraction and were used in 

support of a two-phase Nb/Mg ordering model to explain the relaxor ferroelectric 

behavior of PMN. In that model the peak arises because of 1:l Mg/Nb ordering, and 

the system phase separates into the micro-domains of Mg/Nb ordered phase and 

the Nb rich phase. However, such a phase segragation would produce huge charge 

imbalance and electrostatic energy cost. On the other hand, ordering of alternating 

layers of Nb and Mgz/,Nbl/s in the <111> direction is more likely. In this case 

the mixed layer would be chemically disordered with the sites randomly occupied 

by Mg and Nb. 

In the previous experiment Teslic, Egami and Vakhrushev observed that Nb 

heavily contributed to the 1/2 <1,1,1> peak, which is consistent with the idea 

of Nb/Mg, or Nb/(Mgl,SNbz/s, chemical ordering. The intensity of superlattice 

diffraction intensity can be explained by oxygen participation, since 0 tends to 

move toward Nb6+ which is smaller and higher in valence. At the same time, Pb 

atoms are displaced toward Mg atoms, since Pb-Mg repulsion is weaker than the 

Pb-Nb repulsion. These Pb and 0 displacements alternates from one (1,1,1) layer 

to another in the zone-center ferroelectric displacements. 

In this experiment small Pb contribution to the superlattice peaks was observed. 

Even without the detailed quantitative analysis we found this observation to be 

in agreement with the above analysis. Therefore, we propose that frustration between the local antiferroelectric tendency and the global ferroelectric tendency for 

Pb drives the system to the relaxor ferroelectric state, just as the mixture of ferromagnetic and antiferromagnetic interactions results in a spin-glass behavior. 

Structural Study of Giant Magnetoresistance Effect in La-Ca-Mn-0 

Epitaxial Films 

T. S. Tsai (NCHU, Taiwan), M.Y. Chen(NTU, Taiwan), M.C. Shih (NCHU, TaiX18A 

wan) 

Recently a considerable attention was attracted to the perovskite Mn oxides due 

to a giant magnetoresistance response in these materials. Since the reported magne: 

toresistance ratio in epitaxial grown La-Ca-Mn-0 films are much larger than metallic materials or bulk peroviskite structured oxides, therefore we intend to study the 

possible relation between the MR effect and the epitaxial grown films. The object 

of this experiment is to investigate whether the structures of deposited films will 

depend on the films’ thickness as its magnetroresistance properties do. Samples 

examined were prepared with same nominal composition but in various thickness. 

Experiments were carried to exam structures both parallel to the surface and normal 

to the surface. Since the substrate (LaAlO3) has smaller lattice constant (~33.79A) 

than the bulk La-Ca-Mn-0 (~3.89A) polycrystalline structure, therefore, deposited 

films were expected to have larger lattice constant in the a direction if the substrates 

do imposed strains on the film. However, no significant shift in the films’ peak positions were observed. Oscillatory diffraction intensities can be clearly observed alone 

the (001) direction in every samples prepared and these information insure the quality and the uniformity of deposited films. In-plane diffraction data roughly support 

this observation that films’ peaks are quite different from the substrate’s in plane 

peak. Nonetheless, the deposited films all show the same four fold symmetry as the 

substrate’s structure. Although there is no obvious difference in the films’ structure as their thickness increase, any possible subtle feather is still under analysis. 

* Work at the University of Pennsylvania was supported by the Office of Naval Research 

through N00014-91-J-1036. 

21.0 21.5 22.0 22.5 23.0 23.5 24.0 

28 

Figure 1. 

substrate. 

(001) diffraction data of a SOOA thick La-Ca-Mn-0 film on LaA103 
Epitaxial Structures of Butane and Hexane Monolayers Adsorbed 

on a Ag(ll1) Surface * 

Z. Wu (U. of Missouri-Columbia), S. N. Ehrlich (Purdue U.), B. Matthies, K. W. 

Synchrotron x-ry diffraction has been used to study the structure of butane (m 

X18A 

Herwig, and H. Taub (U. of Missouri-Columbia) 

C4H10) and hexane (~rC6H14) monolayers adsorbed on a single-crystal Ag(ll1 

azimuths with respect to the Ag( 10) direction, suggesting a higher-order commensurate phase. Assuming a herringbone structure as found for these monolayers on 

a graphite basal plane surface"' allows indexing the peaks as the (20) and (11) 

of the hexane monolayer. Once indexed and assuming three monolayer domains 

separated by 120', we can use the azimuthal angle between the two peaks and their 

radial position in reciprocal space to conclude that the unit cells of both monolayers 

are slightly oblique. In the case of butane, the peak positions are found to shift 

azimuthally by -0.5' and the film to compress slightly as the coverage is increased 

from one to three layers; but the unit cell remains oblique with an included angle 

in the range 84-85'. 

We have measured the temperature dependence of the butane monolayer (20) 

and hexane monolayer (21) peak positions both in the radial (Qper) and transverse 

(theta) directions. In the left-hand figure, we see that the butane monolayer ex- pands by -0.3% upon heating from 85 K to the melting point. Concomitant with 

this expansion, the monolayer rotates 0.25' toward the Ag(l0) azimuth. A similar 

rotation was also observed for the hexane monolayer as shown in the figure on the 

right. We suggest that this phenomenon may be an example of the Novaco-McTague 

effect in an elastically anisotropic molecular monolayer.' 

'K. W. Herwig, J. C. Newton, and H. Taub, Phys. Rev. B 50, 15287 (1994). 

'H. Taub, in The Time Domain in Surface and Structural Dynamics, NATO ASI, 

3A. D. Novaco and J. P. McTague, Phys. Rev. Lett. 38, 1286 (1977); J. P. 

surface. For both monolayers, two Bragg peaks are observed in plane at fixe d 

Vol. 228, Ser. C (Kluwer, Dordrecht, 1988), p.467. 

McTague and A. D. Novaco, Phys. Rev. B 19, 5299 (1979). 

Butane rnonaloyer (20) peak 

10 10 80 100 

(K) 

Hexone monolayer (21) peak 

80 IW 120 Iql 

WI 

Figure 1. 

* Supported by NSF Grant Nos. DMR-9011069 and DMR-9314235, the PRF Fund of 

the ACS, and DOE Grant No. DE-FG02-85ER45183 of the MATRIX PRT at the NSLS. 

Structure and Growth of %Alkane Films Adsorbed on the Ag(ll1) 

Surface * X18A 

Z. Wu, J. Wang (U. of Missouri-Columbia), S. N. Ehrlich (Purdue U.), B. Matthies, 

K. W. Herwig, and H. Taub (U. of Missouri-Columbia) 

We have continued our study of the structure of butane (mC4Hlo), hexane 

(?&6H14), and heptane (WC7H16) films adsorbed on a single-crystal Ag(ll1) 

surface. From the two Bragg peaks observed for both the butane and hexane monolayers, we infer a herringbone (HB) arrangement of these molecules which have an even number of carbon atoms. The unit cell appears to be slightly oblique rather 

than the rectangular cell originally assumed as is found for the HB phase of these 

monolayers on graphite.'" However, for the odd-numbered heptane molecule, the 

single monolayer Bragg peak is consistent with a rectangular-centered structure as 

found on graphite.' For all three monolayers, the Bragg peaks have a fixed in-plane 

angle with respect to the Ag( 10) azimuth, indicating a higher-order commensurate 

phase on the Ag(ll1) surface. 

The growth mode of the odd-carbon-numbered heptane film on the Ag(ll1) substrate has been compared with that of even-numbered butane and hexane films. 

All three films show the same coverage dependence of the specular reflectivity (see 

figure). Above two layers, a two-component lineshape emerges: a smoothly varying 

component attributed to the film and a sharp Bragg peak from the bulk particles 

having a specific crystal plane parallel to the surface. Apparently, a bulk plane is 

selected in which the molecular orientations are most compatible with those of the 

film. Thus we infer the same quasiepitaxial growth mode for the heptane film as 

for butane and hexane on Ag(ll1) and for butane on graphite.' Our results suggest 

that it may be a general feature of alkane adsorption on solid surfaces. 

'H. Taub, in The Time Domain in Surface and Structural Dynamics, NATO ASI, 

Vol. 228, Ser. C (Kluwer, Dordrecht, 1988), p.467. 

'K. W. Herwig, J. C. Newton, and H. Taub, Phys. Rev. B 50, 15287 (1994). 

3B. Matthies, K. W. Herwig, and H. Taub, unpublished. 

' Supported by NSF Grant Nos. DMR-9011069 and DMR-9314235, and DOE Grant 

No. DE-FG02-85ER45183. 
Fd 

F 

Structural Studies of Self-Assembled Alkynyl Thin Film Materials * I X18A 

C.-M. Yam, A. K. Kakkar (McGill U.), A. Richter and P. Dutta (Northwestern U.) 

An evaluation of the structure of molecularly self-organized thin films containing 

long chain rigid-rod alkynyl and dialkynyl chromophores via exclusive pi-pi interactions, is an Assential and crucial step for any device applications based on such 

systems in the field of optoelectronics, conductivity, photoresists etc. We have 

recently developed efficient synthetic methodologies to such supramolecular structures molecularly self-assembled on inorganic oxide surfaces. Monolayers of a variety of alkynyl and dialkynyl chromophores with varied chain lengths and acetylenic 

microstructures were prepared on single crystal silicon wafers (l”x3” single side 

polished, 95-105 mils thick). These thin films were first analyzed by in-house ellipsometry, followed by X-ray reflectivity studies on the X-18A beamline at the NSLS 

synchrotron facility. We are still analyzing the data from our last trip to NSLS 

(Sept. 3-10). A preliminary scanning of the data suggests that, in general, there is a good agreement in the thicknesses from X-ray reflectivity and ellipsometry mea- surements. Our ultimate goal is to study surface topochemical polymerization in 

these oriented alkynyl mono- and multilayered structures. Two of the major requirements for the latter process are orientation of alkynyl chromophores at an angle to 

the surface, and uniformity. X-ray reflectivity studies in combination with ellipsometry and FTIR-ATR are invaluable techniques to address these issues. We have 

also been interested in determining the effect of X-rays on the alkynyl thin films, 

since alkynyl chromophores are subject to radiation damage. In our future trips 

to BNL, we shall concentrate on the study of the structure of dialkynyl thin film 

assemblies before and after topochemical polymerization, to understand the mechanistic details of this phenomenon, and to develop a rational approach to materials 

based on alkynyl thin films. 

X18A The Structure of Diffuse Scattering in the Reciprocal Space of AlPd-Mn Quasicrystal. 

Y. Zhang, R. Colella (Purdue U.), S. Ehrlich (NSLS), S. Kycia, A. Goldman, (Iowa 

Stat eU .) 

Diffuse scattering has been measured along several planar sections of reciprocal 

space, perpendicular to a two-fold axis, in the neighborhood of the (0 4 6 0 4 6; M = 336, N = 208) Bragg reflection. The contour plots display the expected 2-fold 

symmetry, and are elongated along the H direction (Fig. 1). Very similar patterns 

are obtained at low temperature (20 K). Since icosahedral quasicrystals are supposed 

to be isotropic P.S. Spoor, J. D. Mainard, and A. R. Kortan. Phys. Rev. Letters 

75, 3462 (1995fl the observed anisotropy can be used to obtain the polarization 

directions of the atomic displacements responsible for the observed diffuse intensity. 

At large distances from the Bragg reflection, the contours split into “lobes” (Fig. 2). 

Peaks of diffuse intensity, as sharp as Bragg reflections, are found at even further 

distance from the Bragg reflection. (for example, at AQ = 0.0817 Awl). These are 

probably Bragg reflections corresponding to large values of the Miller indices. The 

temperature dependence of one particular such reflection, called peak B, is similar 

to that of a Bragg reflection, indicating the non-thermal origin of the peak. While 

the intensity near a Bragg reflection decreases like l/q2 with a good approximation, 

a somewhat different dependence (l/q2.2) is observed near peak B. 

H 

Figure 1. 

H 

Figure 2. 
Photocatalytic Reduction of Heavy Metal Ions on Derivatized Titanium Dioxide Nano-Particle Surface Studied by EXAFS 

L. X. Chen, T. Rajh, D. M. Tiede, P. A. Montan0 and M. C. Thurnauer (ANL) 

Photoirradiation on semiconductor particles, such as Ti02, creates charge separation on the particle surfaces. Consequently, the Ti02 particles with such a photoinduced charge separation act as either electron donors or acceptors to reduce or 

oxidize materials in the surrounding media. Ti02 colloid nanoparticles, especially 

surface-derivatized Ti02 particles, present different electronic properties than those 

of the bulk material. In some cases, the photoinduced redox reactions occur more 

effectively. This redox function has very important applications in environmental 

remediation and cleanup. However, the reaction mechanisms for the enhanced re- activity on the surfaces of the nanoparticles of Ti02 are not well understood. We 

have conducted in- situ EXAFS studies at the K-edge of titanium as well as the 

absorption edges of the heavy metals to extract structural information of Ti02 surface and metal ion surroundings in the photoreduction processes. As the first step 

towards characterization of the surface structure, we characterized the structures 

for the interior and surface Ti02 respectively by comparing the EXAFS spectra 

of Ti02 particles of different sizes. We have identified systematic changes on the 

pre-edge structures and the Fourier transformed EXAFS features according to the 

sizes of the Ti02 particles. These changes are the indications of increasing surface 

lattice disorder as the particle size gets smaller. In addition, we monitored the metal 

ion photoreduction of Cu+2 and Hg+2 on Ti02 colloid surface with and without 

surface-derivatization. The oxidation state of the metal ions in these processes can 

be identified directly by XANES at respective metal absorption edges. Derivatization of Ti02 surface by alanine enhances the efficiency of Cu+2 photoreduction 

compared to neat Ti02. We have identified the complex of alanine and Cu+2 by 

EXAFS and measured time dependence of CuO production with photoflumination 

of Ti02. Part of the results are shown in Fig. 1 and 2, which not only positively 

verified the formation of CuO, but also indicated multisteps of forming the metal 

clusters. Similar study was also conducted on Hg+2 solution. The structure and 

function relationship of the species involved in photoreduction will be discussed. 

1.4 

12 

1.0 

e o.8 

a 0.6 

0.4 

0.2 

0.0 -10 o io m P 40 

E (W 

Figure 1. XANES of Cu+2 as a functyion of illumination time in the Ti02 

catalyzed photoreduction with alanine 

derivatiz at ion. n 

2 3 4 5 

Figure 2. FT-EXAFS of Cu+2 on during 

the photoreduction on alanine derivatized Ti02 colloid surfaces. 

Structure of Supported Alkali and Alkaline Earth Modified Catalysts 

by X-ray Absorption Spectroscopy 

E.J. Doskocil, S. V. Bordawekar, and R. J. Davis (U. of Virginia) 

Alkali and alkaline earth oxides, both alone and on supports, are known to be 

solid base materials. However, very little is known about these materials despite 

their potential for many industrially important reactions. In an attempt to explore solid base structure-property relationships, we have been using in situ x-ray 

absorption spectroscopy (EXAFS and XANES) to determine the atomic structure 

near rubidium and strontium supported on a variety of carriers. 

X-ray absorption studies were performed at the Rb K edge on 5 wt% rubidium 

supported materials of various acidity. The XANES for these materials, as seen in Figure 1, varied on supports like carbon, silica, alumina, magnesia, and titania 

after heating to 773 K in flowing helium and cooling to 77 K. Analysis of the radial 

structure functions revealed that the Rb-0 distance correlates with support electronegativity, with the Rb-0 distance being 2.94 A for Rb on basic MgO and 2.80 

A for Rb on acidic SiOz. These results suggest that surface compounds have been 

formed by the incorporation of the alkali. Additional in situ XAS investigations involving the local structure near the rubidium atoms were conducted in the presence 

of 2-propanol in helium at a reaction temperature of 573 K for rubidium supported 

on carbon and alumina. The gaseous 2-propanol environment significantly affected 

the XANES for Rb on carbon by causing a narrowing of the white line, contrasting 

the negligible effect of adsorption observed for Rb on alumina. 

Results from XAS associated with the Sr K edge for 5 wt% strontium indicate 

that the structure near strontium is largely unaffected by the support environment. 

The radial structure functions shown in Figure 2 contain two peaks for Sr on MgO. 

The peak at 2 A is associated with Sr-0 and the one at 4 41 corresponds to either 

Sr-Sr or Sr-Mg distances. The second feature at 4 A is less prominent in the case of 

the carbon sample and is absent in the Si02 sample. The Sr-0 interatomic distances 

obtained through curve fitting are similar to that of the bulk oxide. Apparently the 

support plays a more crucial role in the structural rearrangement of the supported 

alkali than for the alkaline earth. 

-40 -20 0 20 40 60 80 100 

Energy I eV 

I , I I 

0 2 4 6 8 

RIA 

Figure 1. Rb K edge of various Rb modified supports. 

Figure 2. 

various Sr modified supports. 

Radial structure function of 
X18B Stabilization of Pd2+ Ions on H-ZSM-5 and Other Acidic Supports 

During the Selective Reduction of NO by CH4 * 

D. E. Resasco, S. Stagg, W. Alvarez, and A. Ali (U. of Oklahoma) 

The selective reduction of NO by methane has been studied on a series of Pd Catalysts. When supported on non-acidic materials, palladium is totally unselective 

for the conversion of NO and very active for the combustion of methane. By con- trast, low-loading Pd catalysts supported on acidic (protonic) materials (H-ZSM-5, 

H-Mordenite, sulfated zirconia exhibit much higher selectivity. 

catalysts before and after the reduction of NO in the presence of oxygen. These 

studies have demonstrated that, upon exposure to the reaction mixture (CH4 + 

NO + O,), Pd gets oxidized. The morphology of the oxidized Pd species strongly 

depends on the metal loading and the acidity of the support. On low Pd loading catalysts over acidic supports, the metallic Pd particles, initially present, are 

rapidly transformed in Pd2+ ions by the reaction mixture. By contrast, on the 

non-acidic materials, the Pd particles are transformed into PdO clusters. These 

clusters have high catalytic activity for the methane combustion, resulting in low 

SCR selectivities. 

X-ray absorption studies ( 2 ANES and EXAFS) were conducted on several Pd 

* This work was supported in part by the Donors of the Petroleum Research hd 

administered by ACS 

X18B Observation of Local Structural and Electronic Changes Accompanying Photodoping of YBa2Cu306+2 

T. A. Tyson, J. F. Federici, D. Chew, W. Savin (NJIT), L. Furenlid (NSLS), and 

W. Wilber (ARL) 

It was discovered by Kudinov et ul. [l] that changes occur in the normal state 

conductivity of oxygen deficient YBazC~306+~ (YBCO) on exposure to optical radiation (photodoping). The resistance was found to decrease by as much as 50 % with 

a maximum near x=0.38. This enhanced photoconductivity has been explained by 

two primary mechanisms, oxygen ordering and F-center formation, based on indirect 

measurements and qualitative arguments. Analysis of our c-polarized x-ray absorption measurements on thin films has revealed that photodoping of YBCO produces 

a local distortion of the CuO, chains. The axial Cu(1)-0(4) bond distribution splits 

into two components (see also Fig. 1 and the corresponding Cu-0 correlations are 

transfer of hole density into the CuOz planes accompanies photodoping. These results constitute the first direct structural evidence of photoinduced oxygen ordering 

and charge transfer in this system. 

found to be enhanced. In addition, c h anges in the XANES features indicate that a 

[l] V. I Kudinovet ul., Phys. Rev. B 47, 9017 (1993). 

Cu-Y/Ba 

0 1 2 4 5 w? 

Figure 1. Magnitude of the Fourier transform of k3 * XAFS for k = 2.8 - 11.7AP1 

for normal (solid line) and photodoped (dotted line) YBazCu306.4 system. The 

first peak (1-2 A) corresponds to the c-axis Cu-0 bond distribution. 
1 Characterization of Phenyl Cuprate Solutions Using XANES I X19A I 

H. Huang, J. Penner-Hahn (U. Michigan) 

Phenyl-copper reagents permit facile transfer of aryl groups in organic synthesis'. 

Of particular utility are solutions with a 1:l ratio of PhLi:CuI. Although the crystal structures of several phenyl-copper(1) compounds are now available, the solution 

structures of phenyl lithium/CuI mixtures remain poorly defined. We have previously measured EXAFS data for solutions of PhLi+CuI. These data were consistent 

with the presence of the crystallographically characterized2 [CugPhsl- ion in solution. In order to characterize the stoichiometry of this species and to explore the 

possibility that other phenylcuprates might exist in solution, we have completed an 

EXAFS titration of the PhLi+CuI system. The XANES data for PhLi:CuI ratios 

of 0.6 to 1.2 are shown in Fig. 1. There are three isosbestic points, demonstrating 

that only two spectroscopically distinguishable species contribute to the XANES 

over this concentration range, one with Ph/Cu 2 1.2, the other with Ph/Cu 5 0.6. 

The titration data for PhLi:CuI ratios of 1.2 to 2.0 are shown in Fig. 2. Once 

again, these are consistent with only two distinguishable absorbing species, one 

with Ph/Cu 2 2.0, the other with Ph/Cu 5 1.2. Since the spectra are different 

over the two concentration ranges, the overall solution system must have at least 

three distinct species, one with a Ph/Cu ratio 5 0.6, one with a Ph/Cu ratio 2.0 

and one with a Ph/Cu of 1.2. These results provide a substantially improved description of the solution structure: At intermediate PhLi:CuI ratios, the dominant 

ion is solution is [Cu~Phel-; EXAFS data (not shown) suggest that the species with 

Ph/Cu 2 2.0 is most consistent with the [CuPhzI-; The identity of the species with 

Ph/Cu 5 0.6 remains uncertain. These data provide direct evidence that there is 

no significant concentration of a species with a Ph/Cu ratio 1.0 in these solutions, 

in contrast with the standard picture of phenylcuprate chemistry. 

1. Posner, G. H. An introduction to Synthesis Using Organocopper Reagents; 

Wiley: New York, N. Y., 1980. 2. Edwards, P. G.; Gellert, R. W.; Marks, M. W.; 

Bau, R. J. Am. Chem. SOC. 1982, 104, 2072. 

300 , 300, 

0 89b0 9dOO 90110 . 9020 0 89b0 9d00 90'10 9d20 

Energy ( eV ) Energy ( eV ) 

Figure 1. XANES spectra for titration Figure 2. XANES spectra for titration 

of CUI with PhLi for PhLi:CuI < 1.2 of CUI with PhLi for PhLi:CuI > 1.2 

I X19A I Zn Speciation in Developing Xenopus Embryos as Detected by 

XANES * ~ ~~ 

K. Peariso, C. van Huis, R. Denver, and J. Penner-Hahn (U. Michigan) 

Zinc plays a crucial role both in development and in numerous other biochemical 

processes. Consequently, eggs that are fertilized and develop in the absence of additional maternal nutrition must contain, at the time of fertilization, sufficient Zn 

and other trace metals) for complete development. Thus, zebrafish and Xenopus 

the African clawed toad eggs both contain ca. 1 mM Zn. We have shown previchanges as a function of time after fertilization. We have now extended this work 

to Xenopus. The relatively large diameter (ca. 1 mm) of Xenopus eggs has permitted us to make measurements on single eggs with greater temporal resolution than 

was possible in the past. We find (Figure 1) that there are substantial changes in 

the average Zn environment in Xenopus as a function of time after fertilization. It 

is notable that these changes are complex and appear to reflect the formation of 

multiple Zn sites. This illustrates that we are observing a more complex process 

than simple consumption of a Zn binding protein. Detailed analysis of these data 

is in progress. 

[l] Walrath, L.; Tierney, D.; Penner-Hahn, J.; Berg, J., manuscript in preparation. 

ously [l] that the XAN d S spectra for fertilized zebrafish eggs show characteristic 

16 Cell Embryo 

8 Cell Embryo 

:iy 2 -SO! I I I I I I :I. I I I I I I I I I I I I I I I I I I 

9650 9660 9670 9680 9690 9700 

Energy ( eV) 

Figure 1. Time-dependent Zn XANES spectra of Xenopus eggs following fertilization. Spectra shown are difference spectra relative to an unfertilized control sample. 

Vertical dashed lines at 9662.5 eV, 9664.1 eV, and 9666.6 eV mark the critical points 

for the 1 cell difference spectrum, illustrating the change in spectra with time. 

* Supported in part by the NIH, Grant GM-38047 
1 Structural Characterization of Ga-Substituted Ferredoxins * I X19A I 

J. Penner-Hahn, K. Peariso (U. Michigan) E. Vo, H. Liu and J. Germanas (U. 

Houston) 

Ferredoxins are Fe/S electron transport proteins. In many cases, the Fe can be 

removed and replaced by a variety of other metals. Gallium replacement is attractive 

from the perspective of giving a protein that is amenable to characterization by 

NMR. The difficulty, however, with Ga substiution is that it is difficult to confirm 

that Ga has been subsituted into the correct location within the protein. 

Previous work [l] has shown that substitution of Ga into the FezSz site in Pseudomonas putidaferredoxin gives rise to a mononuclear Ga ferredoxin, with Ga(SR)* 

ligation. More recent work has shown that the FezSz ferredoxins from Anabaena 

and Trichomonas uaginalis can be substituted under conditions that place two Ga 

ions into each protein [2]. We have now used gallium K-edge EXAFS to determine 

the structure of the Ga substituted ferredoxins from Anabaena and 2'. vaginalis. 

The Fourier transform of the resulting EXAFS data is shown in Fig. 1. These 

data are dominated by a large Ga-S peak at ca. 2.3 8. In addition, there is a characteristic second shell peak at ca. 3 A, which is attributable to a Ga-Ga interaction. 

Detailed analysis of these data is in progress. 

[l] S. Kazanis, T.C. Pochapsky, T.M. Barnhart, J.E. Penner-Hahn, U.A. Mirza, 

B.T. Chait, J. Am. Chem. SOC., 117 (1995) 6625-6626.[2] Germanis, J. et al., J. 

Am. Chem. SOC. 118 (1996) in ' press. 

R+ a (A) 

Figure 1. FT of EXAFS data for Ga-substituted ferredoxins. Solid line, T. uaginalis; 

Dashed line, Anabena. 

* This work was supported by NIH Grant R01-GM-38047 and by the Texas Advanced 

Research Program. 

I X19A I XANES Studies of Oxidation States of S in Humic Substances &om 

Different Environmental Settings 

K. Xia, F. Weesner, and W. F. Bleam (U. of Wisconsin-Madison), P. R. Bloom, 

and U. L. Skyllberg (U. of Minnesota) 

Sulfur K-edge X-ray absorption near-edge structure spectroscopy (XANES) was 

used to illustrate the existence of multiple sulfur oxidation states in humic substances. Each oxidation state of sulfur in humic substances from aquatic and terrestrial environment was identified and the relative content of sulfur at each oxidation 

state was estimated. Our experiment results provide direct evidence for the existence of six major sulfur functional groups in humic substances studied: sulfhydryl or sulfides/polysulfides, thiophenes, sulfoxides, sulfites/sulfones, sulfonates, and sulfates. The results appear to reflect the environmental settings where the humic 

substances originally formed. The percentage of the most reduced organic sulfur 

(sulfhydryl or sulfide/polysulfide) in humic substances follow the sequence: aquatic 

sample higher than organic soil and higher than mineral soil. The percentage of 

most oxidized sulfur (sulfate ester) is the highest in humic substances from mineral 

soil, and the lowest in aquatic humic substances. Our study showed that there is 

great potential of using XANES to study the geo-transformation of sulfur in the 

environment. (Submitted to J. of Soil Sci. SOC. of Am., 1996) 
I Structure of Ti in TiOz-SiOz Catalysts * I X19A I 

J. Zhao, J. Rockwell, F. E. Huggins, F. Lu, and G. P. Huffman (U. of Kentucky) 

Mixed metal oxide catalysts are generally regarded as a solid solution of two 

oxides in which a small amount of minor oxide is incorporated into the major oxide 

by cation substitution. The generation of acidic sites is caused by an excess of 

positive or negative charge in binary oxide structure.' 

XAFS measurements were conducted for a series TiO2-Si02 catalysts prepared by 

coprecipitation over a range of Ti/Si ratio and the results were compared with sev- eral different forms of TiO2. The XANES for an initial precipitate of Ti02 (no SiOz) 

exhibits an enhanced pre-edge peak, in similar fashion to that for fer~ihydrite.~'~ 

For ferrihydrite, the phenomenon is attributed to tetrahedral Fe3+ sites at the 

nanoparticle surface. After calcination, the intensity of the peak is reduced due to 

the formation of crystalline Ti02 (anatase). Although the main spectral features of 

the TiOz-SiOz resemble those for rutile TiOz, the XANES shows a stronger pre-edge 

peak while the Fourier transform shows reduced peak heights at di2A, indicating 

the presence of small rutile Ti02 particles. Therefore instead of a solid solution, the 

TiOz-Si02 catalyst may be described as a composite in which small Ti02 particles are embedded in a Si02 medium. 

[l] K. Tanabe, Solid Acids and Bases, Academic Press, New York (1970). [2] J. 

Zhao, F. E. Huggins, Z. Feng, F. Lu, N. Shah, and G. P. Huffman, J. Catal, 143, 

499 (1993) [3] J. Zhao, F. E. Huggins, Z. Feng, and G. P. Huffman, Clays & Clay 

Minerals, 42, 737 (1994) 

1.2 

1 

0.8 

0.6 

0.4 

0.2 

0 

1 

._ 6 0.8 

0.6 1 0.4 

6 0.2 

1.2 

1 

0.8 

0.6 

0.4 

0.2 

0 

Ti02-Si02, Ti=5% 

-20 0 20 40 60 80 100 

Energy, eV 

Ti02-Si02, Ti=5% 

-20 0 20 40 60 80 100 

Energy, eV Distance, A 

Figure 1. 

* This work was supported by DOE contract No.DE-FC22-93PC3035. 

Sychrotron White Beam X-ray Topography Investigation of Influence of Annealing on CdZnTe Substrate * 

Y. Chen, M. Dudley (SUNY Stony Brook), D. R. Rhiger (Hughes Santa Barbara 

Research Center) 

CdZnTe, a technologically important 11-VI compound semiconductor, is the leading candidate material for use as substrates for the growth of HgCdTe layers. Since 

structural defects can propagate into a newly grown layer during epitaxial growth, 

it is important to improve the structural perfection of CdZnTe substrates. Due to 

the retrograde solubility of Te in solid CdZnTe resulting in the supersaturation of Te 

during cooling, Te precipitates are often observed in CdZnTe crystals. Post-growth 

annealing under Cd vapor is often performed to reduce the density of these precipitates. Synchrotron White Beam X-ray Topography has been used to study the 

influence of annealing on CdZnTe substrate under Cd vapor overpressure. Figure 1 

and 2 show corresponding x-ray topographs recorded in reflection geometry of two 

samples which are cut from the same original CdZnTe wafer. These samples are unannealed, and annealed at high temperature, respectively. Te precipitates are 

clearly observed as two kinematic lobes of dark contrast positioned in &g directions 

seperated by a large lattice distortion region showing no contrast in these figures. 

X-ray topographs revealed that the size and density of Te precipates is strongly 

influenced by the annealing. A low density and small sizes of Te precipitates are observed in the annealed samples. For the unannealed sample, high density and 

larger sizes of Te precipitates are observed. Other defects such as twins, subgrain 

boundaries are also revealed in these figures. 

x19c 

" , 

supported by Hughes Santa Barbara Research Center. Figure 2. 
Fd 

x19c 

Characterization of Processing Induced Defects in Silicon Device Using Synchrotron White Beam X-ray Topography 

Y. Chen, W. Huang, W. Chen, M. Dudley (SUNY Stony Brook) 

a 

A 

Processing induced defects play an important role in silicon device yield. Synchrotron White Beam X-ray Topography has been applied to nondestructively investigate such defects in devices fabricated on (111) Si single crystals. By using 

a specially designed scanning system, defect distributions with respect to device 

positions in 3 inch wafers can be clearly revealed. Precipitates, individual dislocations and slip bands generated by thermal and mechanical stress induced during 

thermal oxidation are observed _an_d charactgrized. In Figure 1 and 2, transmission 

topographs recording by using (131) and (311) refections show two sets of slip bands 

SI, SZ running parallel to the [211], [112] direction, respectively. It is also observed 

that S1 is out of contrast on the (311) reflection and SZ is out of contrast on the 

(131) reflection. By using the g.b=O criterion, the Burgers vectors of dislocations 

in two slip bands are determined to be parallel to the [Oil] and [110] directions, 

respectively. In these figures, we also can see some white areas which are actually regions of zero intensity caused by orientation contrast.The areas are associated with 

processing induced strain, which can lead to dislocation generation. The influence 

of these defect structures on device performance is being investigated. 

Figure 1. Figure 2. 

Characterization of Structural Defects in Microgravity Grown 

CdZnTe Single Crystals Using Synchrotron White Beam X-ray To- X19C 

pography I1 * 

H. Chung, B. Raghothamachar, M. Dudley, and D. J. Larson, Jr. (SUNY Stony 

Brook) 

A systematic study of defect structures in the ten wafers sliced from GCRC 

2IUSML-1 revealed a very high structural perfection in the region free from wall 

contact, while a pronounced twin structure was evident in wall contact regions. 

Figure 1 is a reflection topograph recorded from wafer 7. In the wall contact region, 

a twin (TI) running across the wafer was observed. Systematic investigation of the 

position of this twin in all the ten wafers sliced from GCRC 2 enabled one to recon- struct the twin configuration in this boule. The result is shown in Figure 2. It is 

worth noting that this twin was nucleated from the shoulder region and propagated 

through the boule during crystal growth. The twinned region occupies approximately 35 percent of the crystal volume. In addition, other two twins (Tz and T3) 

nucleated from wall contact peripheral regions were also revealed on Figure 1. In 

addition, an individual grain (G), nucleated from the partial wall contact region, is 

also observed. This indicates that the magnitude of stresses associated with wall 

contact can be very large, giving rise to the formation of a single grain separated 

from the twin oriented region (TI) by a curved, high angle grain boundary. In the 

matrix, which is solidified without wall contact, no formation of twins is observed. 

The distribution of these twins strongly indicated that they were nucleated during 

crystal growth to relieve stresses associated with wall contact. 

. -. 

Figure 1. 

* Work performed on the Stony Brook 

Synchrotron Topography Facility, Beamline 

X-lgC, and supported in part by NASA LUIder contract No. NAS8-38147. 

Figure 2. 
Investigations of Dislocation Distributions in Microgravity Grown 

CdZnTe Single Crystals Using Synchrotron White Beam X-ray To- X19C 

PograPhY * 

H. Chung, B. Raghothamachar, M. Dudley, and D. J. Larson, Jr. (SUNY Stony 

Brook) 

X-ray topographic observations revealed an uneven distribution of dislocations 

between the matrix and twin oriented regions. Figure 1 is a highly magnified reflection X-ray topograph recorded from the wafer '7IGCRC 2 showing the detailed 

defect structures. In the twin oriented region (TI), a well defined mosaic structure was revealed, while individual dislocations were clearly discerned in the matrix. 

Dislocation mosaic structures in CdZnTe crystals can be generated by dislocation 

gliding and climbing during post solidification cooling processes because supersaturated vacancies and thermal stresses induced during crystal cooling can facilitate 

dislocation movements to form an energetically preferred configuration (Mcdevitt 

et al, Mater. Lett. 4, p.451 (1986)). On the other hand, the twins are produced 

during growth so that they are created before the generation of the dislocation 

mosaic structures. The twin boundaries may act as barriers to the propagation of 

dislocations so that no formation of mosaic structure was observed in the matrix. 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Facility, Beamline X19C, and supported in part by NASA under contract No. NASS-38147. 

Studies of Defect Structures in Microgravity Grown CdZnTe Single 

Crystals Using Synchrotron White Beam X-ray Topography I * 

H. Chung, B. Raghothamachar, M. Dudley and D. J. Larson, Jr. (SUNY Stony 

~~ 

x19c 

Brook) 

Two flight samples (GCRC 1 and GCRC 2) were grown during the first United 

States Microgravity Laboratory mission (USML-1) using the seeded BridgmanStockbarger method of crystal growth. Figure 1 and 2 are Laue diffraction patterns 

recorded from wafers 1 and 2 sliced from GCRC 1. These wafers were cut from the 

region encompassing the seed transition region. It is worth noting that there are two sets of diffraction patterns superimposed. Since no twin relationship between 

the two grains could be determined, this observation indicated that two grains were 

nucleated in the initial stages of growth. The first grain (GI), which nucleated from 

the seed, is highly strained. On the other hand, the nucleation of a second grain 

(Gz) near to the ampoule wall was observed figure 1). The newly nucleated grain 

showed high crystalline quality and became 6 ominant in the subsequent stages of 

growth (figure 2), while the growth of the highly strained grain (GI) was terminated. This was perhaps due to unfavorable growth conditions for the initial grain. 

Study of all thirteen wafers from this boule enabled a reconstruction of the grain 

structure in this sample to be performed. The result is shown in Figure 3. 

i' 

Al YG14 

Figure 1. 

* Work performed on the Stony Brook 

Synchrotron Topography Facility, Beamline 

X-lgC, and supported in part by NASA under contract No. NASS-38147. 

- 3cm 

Figure 2. 

warm Li wsl8rw 

Figure 3. 

\"ere? t3 
Studies of the Influence of Cooling Rate to Defect Microstructure 

Development in Microgravity Grown CdZnTe Single Crystals * 

H. Chung, B. Raghothamachar, M. Dudley and D. J. Larson, Jr. (SUNY Stony 

Brook) 

Figures 1 (a) and (b) are reflection topographs recorded from a wafer sliced from 

GCRC 1 showing the defect structures in both the steady-state and gradient-freeze 

growth regions. The solidification rate of the latter is ten times larger than that 

of steady state growth. This change is strongly reflected by the different defect 

structures observed in the two regions. An X-ray topograph recorded from the 

gradient-freeze region [figure 1 (b)] shows a highly distorted image, indicating that 

this region is heavily strained. It is believed that very large axial thermal stresses 

can be generated by the large axial temperature gradient imposed by the rapid 

cooling process leading to severe deformation processes. In contrast, the crystalline 

quality of the steady-state growth regions (Le., the lower part of figure 1 (a)) is 

significantly higher than that of the gradient-freeze growth regions. Two sets of 

long, straight asymmetrically distributed small angle tilt boundaries (SBx and SBz), 

nucleated near the ampoule wall, and propagating into the interior of the wafer 

along the crystallographic [lOi] and [Oil] directions were evident. The separation 

and overlapping of these images arises from different senses of tilt between the 

neighboring subgrains. The tilt angles, which can be estimated from the variations 

of image width as a function of specimen-film distance, were determined to be of the 

order of 30-40 arc seconds. The configuration of these small angle tilt boundaries 

strongly suggests the onset of both slip and dislocation polygonisation processes on 

the [loll/ 111) and [Oil]/(ill) slip systems [Durose and Russell, J. Cryst. Growth, 

86, p.471 [1986)]. 

x19c 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Facility, Beamline X19C, and supported in part by NASA under contract No. NAS8-38147. 

Investigation of the Distribution and Configuration of Dislocations 

x19c 

H. Chung, W. Si, and M. Dudley (SUNY, Stony Brook), D. F. Bliss (Rome, AFB), 

A. Maniatty (RPI) 

During crystal growth, dislocations can be generated if growth accidents such as 

large temperature fluctuations and compositional inhomogeneity occur. In addition, dislocation multiplication and propagation can occur if thermal stresses are introduced during the cooling process. Investigations of the distribution and configuration of dislocations are important to determine the relationship between dislocation generation and the growth conditions used. Figure 1 is a highly magnified 

X-ray topograph enlarged near the outer surface of the crystal where the concave interface was observed. A region of very high dislocations density is revealed by the 

X-ray topograph. In contrast, regions of very low dislocation density were observed 

in the interior of the crystal (as shown in figure 2) where the growth interface remained convex to the melt. In the MLEK growth method, the axial temperature 

gradient in the melt is low (20-40°C/cm) so that a small temperature fluctuation 

can influence the stability of crystal growth [D. F. Bliss et. al. J. Cryst. Growth, 

128, p. 4511. An abrupt change in the morphology of the growth interface indicates 

the occurrence of a significant temperature fluctuation when the pulling process 

started. This can potentially upset the stability of crystal growth and lead to the 

high density of dislocations generated in this region to relieve large thermal stresses 

induced by the tempemture fluctuations. 

in Sulphur Doped InP Single crystals I * 

Figure 1. 

* Work performed on the Stony Brook 

Synchrotron Topography Facility, Beamline 

X-19C, and supported by ARPA/AFOSR 

Consortiumof Crystal Growth Research under Contract No. F496209510407 Figure 2. 
Investigation of the Distribution and Configuration of Dislocations 

in Sulphur Doped InP Single Crystals I1 * 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Labox19c 

ratory, AFB), and A. Maniatty (RPI) 

X-ray topographic observations (figure 1 (a)) revealed numerous slip bands (S) 

nucleated from the cylindrical outer surface of the boule and propagating into the 

interior of the crystal. In the growth of indium phosphide, boric oxide is used as an encapsulant to prevent the decomposition of the melt. The encapsulant also 

reduces the radiative heat loss from the outer surface of the crystal since Bz03 

acts as a heat shield. The maximum heat loss, therefore, occurs at the point where 

the hot solid material emerges from the encapsulant, which gives rise to maximum 

temperature gradients in this region. X-ray topographs revealed that slip bands are most likely to be nucleated at this stage to relieve the large thermal stresses. 

The distribution of excess resolved shear stresses in the crystal at various stages 

in the growth process has been calculated using an anisotropic thermo-elastic finite 

element model for InP single crystals. The result is shown in figure 1 (b). It is worth 

noting that the maximum excess resolved shear stresses are generated on the outer 

surface of the crystal at the point where the crystal emerges from the encapsulant. 

The calculated result is in good accord with the slip band distributions revealed by 

X-ray topography. 

tm 

! 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Facility, Beamline X19C, and supported by ARPA/AFOSR Consortium of Crystal Growth Research under 

Contract No. F496209510407. 

Investigation of the Distribution and Configuration of Dislocations 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboin Sulphur Doped InP Single Crystals I11 * x19c 

ratory, AFB), and A. Maniatty (RPI) 

Numerous slip bands nucleated from the periphery of the crystal were observed. 

The diffuse contrast in the slip bands and in their surrounding crystal volume 

revealed in most of reflections is due to the long-range strains associated with a 

high density of dislocations piling up on their slip planes. A judicious choice of 

proper projection and diffraction conditions enabled individual dislocations within a 

slip band to be clearly resolved. Figure 1 comprises transmission X-ray topographs 

recorded from a slip band showing the contrast variations of slip dislocations in 

different reflections. It is worth noting that individual dislocations are clearly visible 

in both (111) and (040) reflections, while only faint contrast associated with the 

intersection of the slip band on the X-ray exit surface can be discerned in both 

and (400) reflections. The dislocation Burgers vector b can, therefore, be 6"" etermined by using the g. b =O criterion, where g is the diffraction vector. The 

slip plane can also be determined by analyzing the projected direction and length of 

slip dislocations in different reflections. This slip band is, therefore, characterized to 

belong to the [011]/(111) slip system. Systematic characterization of all of the slip 

dislocations in this sample reveals that nine of the twelve possible <llO>/{lll} 

slip systems are activated at different stages of the growth process. Since slip 

processes were initiated from regions of stress concentration, studies of the spatial 

configuration of slip bands and the activation of slip systems in the as-grown crystal 

enable one to understand the relationship between the thermal conditions used and 

the crystalline perfection of the as grown crystals and provides useful information 

on thermal stress modeling. 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Facility, Beamline X19C, and supported by ARPA/AFOSR Consortium of Crystal Growth Research under 

Contract No. F496209510407. 
Modeling the Distribution of Dislocations Observed in MLEK Grown 

Fe Doped InP Single Crystals * 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), and A. Maniatty (RPI) 

X-ray topographic studies of dislocation distributions revealed that the density 

of dislocations changed along different crystallographic directions. In most of the 

wafers studied, a high density of dislocations can be observed near the peripheral 

regions along <loo> directions, while it reached a minimum along <110> directions. Figure 2 shows a well defined four-fold symmetric distribution of dislocations 

observed in wafers sliced from the intermediate growth stages. In order to investigate the origin of such dislocation distributions, a thermal stress model composed 

of uniformly distributed, com'pressive radial stress was introduced. 

Slip in crystals with the zinc blende structure such as InP can be activated 

on twelve {lll}/<llO> slip systems. The resolved shear stress for each of these 

slip systems for crystals grown along the [OOl] direction can be calculated usin 

Schmid's law. Figure 1 shows the calculated shear stress distribution on the (0015 

plane. The shear stress reached its maximum along the crystallographic <loo> 

directions, while it reached a minimum along the <110> directions. Since the 

overall dislocation density is proportional to the total excess resolved shear stress, 

which in turn is related to the local shear stress value, the calculated result is in 

good accord with the observed dislocation distributions. It is, therefore, expected 

that the compressive radial shear stresses likely to be experienced by the crystal 

during growth can give rise to dislocation generation which leads to the observed 

distribution. 

Figure 1. 

' Work performed on the Stony Brook 

Synchrotron Topography Facility, Beamline 

X-19C, and supported by ARPA/AFOSR 

Consortium of Crystal Growth Research under Contract No. F496209510407. 

3mm 

~ 

Figure 2. 

Observation of Growth Striations in MLEK Grown InP Single Crystals Using Synchrotron White Beam X-ray Topography * 

H. Chung, W. Si, and M. Dudley (SUNY, Stony Brook), D. F. Bliss (Rome, AFB), 

and A. Maniatty (RPI) 

In crystal growth, the morphology of the solid-liquid growth interface is strongly 

influenced by the growth conditions. Important information regarding the temperature profile of the melt, microscopic growth rate variations and the relationship 

between growth conditions and crystal perfection can be directly deduced through 

the observation of the shape of the growth interface at the various stages of growth. 

In Liquid Encapsulated Czochralski (LEC) growth methods, growth rate 

fluctuations caused by effects such as unstable thermal convection and crystal rotation can give rise to inhomogeneous dopant segregation along the instantaneous 

solid-liquid interface. Due to the effect of dopant incorporation, a lattice distortion 

(mainly a lattice parameter variation) across the solid-liquid interface can be introduced. If the lattice distortion creates a local misorientation which is greater than 

the perfect crystal rocking curve width, growth striations can be revealed on X-ray 

topographs as contours of equal effective misorientation. The high degree of strain 

sensitivity (Ad/d-10-6-10-8) of X-ray topography is particularly well suited for 

detecting the small strains associated with the small changes in dopant concentration. Thus the shape of the solid-liquid interface at various stages of growth can be 

determined through the observation of these striations. Figure 1 is a transmission 

X-ray topograph (g=004, X=0.45A) recorded from a (110) wafer sliced longitudinally from a heavily sulphur doped (1~2x10~~ atoms/cm3) InP crystal showing the 

morphology of growth interfaces at different stages of crystal growth. 

- 5mm 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Facility, Beamline X19C, and supported by ARPA/AFOSR Consortium of Crystal Growth Research under 

Contract No.F496209510407. 
Observation of Growth Striations in MLEK grown InP Single Crystals Using Synchrotron White Beam X-rav Topography I1 * x19c 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), A. Maniatty (RPI) 

The morphology of the growth interface at the different stages of crystal growth 

is clearly revealed by X-ray topography. In the initial growth period, when the flat 

shoulder of the crystal was formed, no pulling was employed. A growth interface 

convex to the melt is observed. However, a significant change in growth interface 

morphology occurred when the pulling process was initiated. A bimodal shape of 

growth interface, comprising a convex region in the center and two concave regions 

near the outer surface of the crystal was developed. The Likely reasons for this lie 

in the fact that the convection flow driven by buoyancy and surface tension changes 

when the pulling process begins. At this point, as the shoulder of the crystal 

emerges from the melt into the encapsulant, the thickness of the encapsulant above 

the crystal decreases as encapsulant moves into the region between the outer boule 

circumference and the crucible wall. Figure 1 is a schematic diagram showing the 

modification of the geometric configuration of the encapsulant at the various stages 

of the growth process and the corresponding growth interface morphology revealed 

by X-ray topographs. This change in the geometric configuration of the encapsulant 

leads to a dramatic modification of the convection and radiation heat transfer from 

both the top and cylindrical outer surfaces of the boule. These effects modify the 

global heat transfer environment of the growth process and potentially cause a 

change in the flow pattern of the melt, which gives rise to a modification of the 

growth interface morphology. 

bm il,a bc:r.etatrtw 

Figure 1. 

P 

* Work performed on the Stony Brook Synchrotron Topography Beamline X-19C, and r 

01 * supported by ARPA/AFOSR under Contract No. F496209510407. 

Studies of Dislocation Distributions in MLEK Grown Fe Doped InP 

Single Crystals Using Synchrotron White Beam X-ray Topography X19C 

H. Chung, W. Si, and M. Dudley (SUNY Stony Brook), D. F. Bliss (Rome Laboratory, AFB), and A. Maniatty (RPI) 

A series of wafers sliced perpendicular to the [OOl] growth direction from a Fe 

doped InP boule were studied. The recorded X-ray topographs revealed that the 

density and distribution of dislocations changed at the different stages of crystal 

growth. A uniform distribution of dislocations of very high density were observed 

in both the initial and final stages of crystal growth, while in the intermediate 

growth stages, a four-fold symmetric distribution of dislocations was revealed separated by regions of low dislocation density. Figure 1 (a) is a transmission X-ray 

topograph recorded from a wafer sliced near to the seed. A twin lamella (T) nucleated from the flat shoulder of the crystal was observed. The X-ray topograph 

also revealed that a high density of dislocations was generated in this region. The 

density of dislocations reaches a maximum in the peripheral re ions of the wafer 

along the crystallographic <loo> directions. Figure 1 (b) and (cy are transmission 

topographs recorded from wafers sliced from the intermediate growth stages. A well 

defined four-fold symmetric distribution of dislocations is evident. The regions of 

high dislocation density are again observed to lie near the periphery of the wafer 

along <loo> directions, while the density of dislocations reaches a minimum along 

<110> directions. Figure 1 (d) is a transmission X-ray topograph recorded from a 

wafer sliced near to the tail end of the boule. This topograph revealed a uniformly 

distributed, high density of dislocations. 

* 

Figure 1. 

* Work performed on the Stony Brook Synchrotron Topography Beamline X-lgC, and 

supported by ARPA/AFOSR under Contract No. F496209510407. 
t? 

F 

x19c 0” Characterization of Defect Structures in 3C-Sic Single Crystals using Synchrotron White Beam X-ray Topography * 

W. Huang, M. Dudley (SUNY Stony Brook), and C. Fazi (Army Research Lab.) 

3C-Sic is one of the most promising of the Sic polytypes for application to active 

devices. However, large and high quality 3C-Sic crystal are very difficult obtaine. 

Recently, the Baikov method has been used to grow relatively large size (111) 3CSic crystals. In order to examine the crystal quality, Synchrotron White Beam 

X-ray Topography (SWBXT) is employed to provide detailed characterization of 

defect content in these crystals. Due to its unique capabilities, SWBXT can reveal 

the overall uniformity of crystal structure as well as local defect configurations. 

Figure 1 shows an X-ray transmission topograph 

recorded from a 3C-Sic crystal. The presence of Pendellosung fringes, labeled PF, 

at the top left edge of the crystal indicates the high quality of this crystal. Stacking 

faults are found in the middle of the crystal, as indicated by SF. Dislocations, 

indicated by D, are also observed. Partial dislocations bounding the stacking faults 

are indicated by PD and inclusions by I. Some evidence for the existence of growth 

sector boundaries, G, is also visible. The presence of growth sector boundaries is 

likely to be indicative of differences in impurity segregation rates between adjacent 

sectors. Such differences may have a detrimental influence on device performance. 

Lines indicated by L are related to the surface step morphology. Since the bottom 

of the crystal is attached to a carbon rod during the growth process, this region 

is covered by carbon and does not show a clear facet feature. Layer structures of 

double positioning twins, 3C(I) and 3C(II), are also found in most of the crystals 

examined. A thin layer of 3C(II) is located at the bottom of the crystal and its 

quality is relatively poor compared with that of the 3C(I) region. 

Apparently this kind of structural preference eliminates the influence of double 

positioning boundaries, which benefits device fabrication. 

d 

Figure 1. Synchrotron white beam x-ray transmission topograph showing defect 

structures in 3C-Sic crystal. 

* Research supported by U.S. Army Research Laboratory, Adelphi, MD, and U.S. 

Army Research Office (Grant numbers DAAH04-94-G-0091 and DAAH04-94-G-0121, contract monitor Dr. John T. Prater). Topography carried out at the Stony Brook Synchrotron Topography Station, Beamline X19C, at the National Synchrotron Light Source 

in Brookhaven National Laboratory, which is supported by DOE. 

x19c Characterization of Slip Dislocations in 6H-Sic Single Crystals Using 

Synchrotron White Beam Topography * 

W. Huang, M. Dudley (SUNY, Stony Brook), C. Fazi (ARL), and D. Willkinson 

(Novecon Technologies) 

Major types of defects in commercial PVT 6H-Sic wafers are super-screw dislocations approximately perpendicular to the basal plane and dislocation networks lying 

in the basal plane. However, in the Lely Sic platelet examined recently, super-screw 

dislocations are not observed. As shown in figure 1, in addition to stacking faults, 

indicated by S and basal plane dislocations, indicated by D, slip bands, indicated 

by SB, are visible. Similar slip bands are also observed in a 6H-Sic wafer cut from a boule, as shown in figure 2. These slip dislocations appear to be edge or mixed in 

character. They are slightly inclined to the surface normal of the wafer. Slip bands 

appear to emanate from the inclusions, indicated by I, in both crystals. The regions 

with highest dislocation density also have the highest inclusion density, underlying 

the connection between the two. 

Figure 1. Synchrotron white beam x-ray 

transmission topograph showing defect 

distribution in Lely 6H-Sic platelet. 

* Research supported by U.S. Army 

Research Laboratory, Adelphi, MD, and 

U.S. Army Research Office (Grant numbers DAAH04-94-G-0091 and DAAH04-94- 

G-0121, contract monitor Dr. John T. 

Prater). Topography carried out at the 

Stony Brook Synchrotron Topography Stb 

tion, Beamline X19C, at the NSLS in BNL, 

which is supported by DOE. 

Figure 2. Synchrotron white beam x-ray 

reflection topograph showing defect distribution in 6H-SIC wafer. 
Experimental Proof of the Energy Dispersion in Contrast Theory on 

Micropipe Image Formatiom 

Synchrotron White Beam Topography Studies of Residual Stress in 

Sic Single Crystal Wafers with Epitaxial Thin Films * 

W. Huang, M. Dudley (SUNY Stony Brrok), S. Wang (ATMI), and C. Fazi (Army 

Research Lab.) 

Double images of super-screw dislocations and micropipes in Sic single crystals 

can be observed in synchrotron white beam x-ray transmission topograph, as shown 

in figure l(a). Analysis of these images enables the magnitudes of the tilt of the 

lattice planes relative to the core to be determined. Super-screw dislocations of opposite sign can also be distinguished. Crystal lattice on either side of a micropipe tilt on opposite directions, which corresponds to the strain field of a screw dislocation 

It is believed that energy dispersionJAX/X) of synchrotron white beam con- tributes to direct image formation in S BXT. This has been proved experimentally. A Mo filter, with an absorption edge at 0.6198 A, was used so as to impose an abrupt change in spectrum intensity near the peak of the spectrum. The specimen 

was properly oriented so that the range of diffraction wavelengths around micropipe 

spans the absorption edge of the filter. Therefore the intensity of one side of the 

micropipe is lower than that of the other side, as shown in figure 2(b). * Research supported by U.S. Army Research Laboratory, Adelphi, MD, and 

U.S. Army Research Office (Grant numbers DAAH04-94-G-0091 and DAAH04-94- 

G-0121, contract monitor Dr. John T. Prater). Topography carried out at the 

Stony Brook Synchrotron Topography Station, Beamline X19C, at the NSLS in 

PI. 

-- BNL, which is supported by DOB. 

Figure 1. (a). Transmission topograph 

2 showing micropipes in SIC wafer. Figure 2. 

using Mo Lter. 

b). Same topograph recorded 

W. Huang, Q. Wang, M. Dudley, F. P. Chiang (SUNY, Stony Brook), J. Parsons 

(Oregon Graduate Institute), and C. Fazi (ARL) 

The deposition of epitaxial layers and metallization layers often induces stresses 

in both the epitaxial layers and underlying substrates, which greatly affect the microelectronic performance of subsequently manufactured devices, potentially even causing device failure. Therefore the characterization of stress and strain fields in 

the thin films and substrates is essential in device fabrication. Synchrotron white 

beam x-ray topography (SWBXT), which is commonly used to image individual 

defects and defect distributions in single crystals, is employed to determine the deformation in 6H-Sic single crystals with 3C-Sic thin films grown on them. Due 

to the mismatch of mechanical and thermal properties between the substrate and 

epitaxial layer, residual stress exists in both. When the film is deposited, it strains 

the substrate, which bends until equilibrium is reached. The curvature of the substrate can be determined by absorption-edge-contour (AEC) mapping. Figure 3 (a) 

through (d) (g)=lOI, X =0.618A) show a series of AEC recorded from one of the 

samples analyzed. Figure l(e) shows an AEC map obtained by rotating the specimen through increments of 0.1OC. To calculate the in-plane film stress, Stoney’s 

equation was modified. Figure 2 show the stress distribution in two mutually perpendicular directions in part of a wafer. The coordinate system was selected such 

that the wafer lies in xy plane and the origin is at a point on wafer edge. The 

film free area is indicated by ”substrate” while the film covered area is indicated 

by ”film”. Because of the high contour resolution and high efficiency of data collection, this technique is considered to be superior to monochromatic x-ray contour 

mapping. 

Figure 1. (a)-(d) a series of absorption 

edge contours and (e) absorption edge 

contour map. 

* Research supported by U.S. Army 

Research Laboratory, Adelphi, MD, and 

U.S. Army Research Office (Grant numbers DAAH04-94-G-0091 and DAAH04-94- 

G-0121, contract monitor Dr. John T. 

Prater). Topography carried out at the 

Stony Brook Synchrotron Topography Station, Beamline X19C, at the National Synchrotron Light Source in Brookhaven National Laboratory, which is supported by 

DOE. 

(4 (b) 

Figure 2. Distribution of stress (a) in x 

direction and (b)in y direction in part of a wafer. 
In-plane Structure of the Liquid-Vapor Interfaces of Dilute Bismuth: 

Gallium Alloys 

N. Lei, Z. Huang, and S. A. Rice (U. of Chicago) 

x19c 

The in-plane structure functions in the liquid-vapor interfaces of two bismuth:g&um alloys (0.18 atomic % Bi and 0.07 atomic % Bi) have been studied by 

grazing incidence x-ray diffraction. The higher concentration alloy exhibits, at 25OC, 

43OC and 77OC, segregation of Bi into nearly complete monolayer atop the bulk alloy; at each temperature the Bi monolayer has the structure of a two-dimensional 

supercooled liquid. The intensity distribution of the diffuse x-ray scattering at qr = 

1.0 2-l and 1.5 A-' is used to calculate the surface tension of the alloy at 77OC; the 

value obtained is 570 f 30 dynes/cm. This value is related to the structure of the 

liquid-vapor interface. The in-plane diffraction data for the lower Bi concentration 

sample can be explained by assuming that the segregated Bi atoms form dimers 

and trimers. 

Structure of the Liquid-Vapor Interface of Tin: Gallium Alloy x19c 

N. Lei, Z. Huang, and S. A. Rice (U. of Chicago) 

The liquid-vapor interface structure of a tin (wt 9%):ga alloy has been studied 

by in-plane grazing incidence x-ray diffraction, and by diffuse and specular x-ray 

reflectivity measurements. The in-plane data, suggest that there is tin segregation 

at the interface, in excess of its concentration in the bulk liquid. The specular 

reflectivity data suggest a layered structure for the interface. The data (specular) 

taken at 41 "C and 57 OC suggest that the distance between the segregated tin 

and the top layer of ga is about 2.5A, which is smaller than the sum of the radii 

of ga and tin in their pure liqquid phases. At 26 OC, this distance is about 2.8 

A, still smaller than the sum of the pure liquid atomic radii, possibly indictive of a phase transformation between 26 OC and 41 OC. Sample shape measurements 

yield a surface tension which increases with increasing temperature, consistent with 

the fact, according to the Gibbs adsorption iosterm for an ideal mixture, at higher 

temperatures there are fewer tin atoms at the interface. 
x19c Studies On the Formation Mechanism of Small Angle Tilt Boundaries in Ga Doped Ge Single Crystals by X-ray Topography * 

B. Raghothamachar, H. Chung, M. Dudley (SUNY, Stony Brook), and D C. Gillies 

(NASA) 

Dislocation structures in Ga doped Ge single crystals were characterised by synchrotron white beam x-ray topography in the reflection geometry. Figure 1 shows 

a triangular shaped region of high dislocation density originating from the seed. 

The dislocations are aligned to form dislocation cell structures and small angle tilt 

boundaries. During growth from the seed, dislocations present in the seed crystal are replicated into the newly grown regions of the crystal formed during the 

subsequent stages of solidification. Dislocations can also be generated from high 

stress concentration sites such as the shoulder regions of the crystal and the initial 

transient growth stage when growth conditions are not stable. These dislocations 

lying on the (111) planes can propagate into the newly formed crystal in the directions normal or nearly normal to the growth front. The growth interfaces are 

highly concave to the melt initially and hence, the replicated dislocations will be 

directed towards the center of the crystal since line directions normal to the growth 

front are energetically preferred. Thus the dislocations converge towards the central 

region and as the growth conditions stabilize, the curvature of the growth interface 

is reduced and very few dislocations are generated. The replicated dislocations 

which have converged at the central region form pileups and are pinned by the 

doped atoms. Further propagation is therefore eliminated and the dislocations realign during post solidification cooling to form cellular structure and small angle 

tilt boundaries. 

Figure 1. Reflection topograph (g = 333, X = 0.871) from a Ga doped Ge crystal 

showing the dislocation cell structures (C) and small angle tilt boundaries (SB) 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, NSLS, 

BNL and supported by NASA Marshall Space Flight Center 

Visibility of Growth Interfaces and Striations As a Function of 

Diffraction Geometry in Ga Doped Ge Single Crystals * 

B. Raghothamachar, H. Chung, M. Dudley (SUNY, Stony Brook), and D C. Gillies 

(NASA) 

Figures l(a) and (b) are two reflection topographs recorded from a Ga doped 

Ge single crystal subjected to Peltier pulsing during growth in two different sample 

geometries. In fig 1 a), the diffraction vector g is along the growth direction and 

therefore perpendicu (l ar to the growth interface. The melt back interface and the 

growth striations generated by Peltier pulsing are clearly visible. 

the diffraction vector used was perpendicular to the growth direction and there ore parallel to the growth interface. In this image, the melt back interface and most of 

the striations are invisible; only very faint striation contrast from the highly curved 

interfaces can be discerned. Rocking curve width calculations reveal that the latter 

reflection is more strain sensitive than the former and hence, any displacement 

components parallel to the interface should be visible. Since, no contrast is observed 

from the interface, it indicates that the lattice is distorted normal to the growth front 

and hence the displacement vector associated with the growth interface is normal 

to the interface plane. Hence, the growth striations are invisible when the g vector 

is parallel to the interface (g.ii=O criterion). Thus the visibility of growth interfaces 

is a sensitive function of diffraction geometry and choice of proper diffraction vector 

with respect to the interface is important. 

x19c 

In figure Ilb), 

Figure 1. Reflection topographs recorded using different diffraction geometries (a) 

g = 333, X = 0.87 A and (b) g = 246, X = 0.65 A, showing contrast variations in 

the images of the melt back interface (I) and growth striations (S) generated by 

Peltier pulsing 

* Work performed on the Synchrotron Topography Project, Beamline X-l9C, NSLS, 

BNL and supported by NASA Marshall Space Flight Center 
tp 

P 

2 Characterization of Structural Defects in Vapor Grown CdTe Single 

Crystals by Synchrotron White Beam X-ray Topography * x19c 

~ 

B. Raghothamachar, H. Chung, M. Dudley (SUNY, Stony Brook), D.C. Gillies, 

and W. Palosz (NASA) 

Defect structures in vapor grown CdTe single crystals were characterized by synchrotron white beam x-ray topography in the reflection geometry. Figure 1 shows a 

reflection topograph recorded from a CdTe single crystal. A twin TI is revealed by 

orientation contrast. Another twin Tz is also present as shown but there is no orientation contrast from this region because for this particular reflection, the reflecting 

planes in the matrix and twinned region are coincident. However, diffraction con- trast clearly demarcates the twin and matrix regions. By detailed analysis of back 

reflection Laue patterns recorded from each twin related region, it was determined 

that the twins TI and T2 are 180' rotation twins about the (111) and (11-1) plane 

normals respectively. It has also been observed that the twinned regions themselves 

undergo twinning. Second order (TB2) and third order (TB3) twin boundaries are observed. The central regions of the crystal appear to have much lower dislocation density than the peripheral regions. In some regions on the periphery, 

cellular arrangement of dislocations can be discerned. Higher dislocation density 

at the periphery indicates dislocation generation due to stresses from wall contact. 

Several spots of white contrast are probably precipitates or inclusions. These are 

concentrated in the matrix regions. Subgrain boundaries which are usually formed 

by polygonization of dislocations are also present in some regions. 

Figure 1. Reflection topograph taken from a CdTe single crystal showing the two 

twinned regions (TI and Tz), twin boundaries (TB), subgrain boundaries (SB) 

and inclusions (P) 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, NSLS, 

BNL and supported by NASA Marshall Space Flight Center 

Comparison of Defect Structures in Microgravity (pg) and Terrestrially (lg) Grown CdZnTe Single Crystals by Synchrotron White X19C 

Beam X-ray Topography * 

B.Raghotharnachar, H. Chung, M. Dudley, and D. Larson Jr. (SUNY, Stony 

Brook) 

In a microgravity environment, gravity-dependent effects such as buoyancy, convection and hydrostatic pressure are minimized and diffusion controlled non-wetting 

growth can be achieved resulting in reduced stress generation which in turn minimizes the occurrence of twinning and deformation. CdZnTe wafers sliced from 

boules grown in microgravity and in normal gravity conditions were characterized 

by synchrotron white beam x-ray topography. Figure 1 shows a transmission topograph (g = i13, A= 0.42 A) recorded from wafer no.4 sliced from the steady 

state growth region of microgravity grown boule GCRC-2. The image shows a very 

low dislocation density (5X102-1.2X103/cm2) with individual dislocations (D) being clearly resolved. Other defects observed are Te precipitates revealed by singular 

dark spots(P) and lamellar 180' rotation twins(T) about the (111) plane normal. 

Figure 2 shows a transmission topograph (g = 113, A= 0.42 A) taken from a sample 

sliced from NDVDT-3 which was grown under identical growth conditions except 

for gravity. Slip bands generated from the peripheral regions are clearly visible. The 

sample shows a very high dislocation density of the order of 105-106/cmZ. Clearly, 

the microgravity samples show much higher structural perfection than ground-based 

samples due to minimization of growth stresses. 

Figure 1. 

* Work performed on the Synchrotron 

Topography Project, Beamline X-19C, 

NSLS, BNL and supported by NASA Marshall Space Flight Center Figure 2. 
Investigations On the Effects of the Asymmetrical Gravity Vector 

on the Defect Distributions in Microgravity Grown CdZnTe Single X19C 

Crystals * 

B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUNY, Stony 

Brook) 

Defect distributions in CdZnTe single crystals grown by the BridgmanStockbarger method in a microgravity environment were compared to similar crystals grown terrestrially under the same conditions. Synchrotron white beam x-ray 

topography in the reflection geometry was used to characterize the defect distributions. Figures 1(a) and (b) respectively show reflection topographs imaged from 

wafers sliced from the steady state growth regions in microgravity grown sample 

GCRC-1 and terrestrially grown boule NDVDT-1. An asymmetrical distribution of 

slip bands along the 1011 and the [Oil] directions on either side of the sample is 

observed in figure l(a \ . In contrast, figure l(b) shows a more symmetrical distribution of dense slip bands. These slip bands are nucleated in the peripheral regions 

by stresses generated from wall contact. The microgravity grown boule was subjected to an asymmetrical residual gravitational field which induced non-uniform 

wall contact resulting in different levels of stress around the circumference of the 

boule which caused the asymmetrical slip band distribution. In ground based sam- ples the hoop stresses generated by uniform wall contact are symmetic resulting in a symmetric slip pattern. Note that the magnitude of stress in microgravity conditions is much lesser than that under gravity and therefore the slip bands in ground 

based samples are much denser than the microgravity samples. 

Figure 1. (a)Reflection topograph(g = 133, X = 0.98A) from wafer #4 of pg grown 

boule GCRC-1 showing two sets of asymmetrically distributed slip bands (SI and 

Reflection topograph(g = 335, X = 0.7A) from a wafer of ground based 

showing two sets of symmetrically distributed slip bands (SI and 

S2). 

Studies On the Surface of a Microgravity Grown CdZnTe Boule by 

Synchrotron White Beam X-ray Topography * 

B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUNY, Stony 

x19c 

Brook) 

Results obtained from previous microgravity experiments strongly indicate that 

single crystals grown under non-uniform wall contact conditions show an asymmetrical defect density distribution with lower defect densities observed in regions with 

no wall contact because of lower stresses. Therefore, a special tapered boule geometry as shown in fig l(a) was developed so that crystal growth free from wall contact 

can be achieved. A boule with this geometry (GCRC-2) was grown aboard space 

shuttle flight USML-2. Figure l(a) shows an optical photograph of the as grown 

boule . A region approximately 2cm in length free from wall contact was grown. 

Synchrotron white beam x-ray topography was used to study the surface of the as grown boule in order to characterize the true microstructure developed during the 

growth process. Figure l(b) shows a reflection topograph taken from the surface 

of the boule. The seed transition region reveals the presence of 180' rotation twin 

lamellae about the (111) plane normal. Because of the rough surface morphology of 

the region grown without wall contact, resolution of defects is not possible but the 

topograph indicates that no twins are nucleated and no significant lattice distortion 

is apparent. However, as soon as this region reestablishes wall contact, a twin is 

nucleated indicating that stresses associated with wall contact may have an effect 

on twin generation. 

Figure 1. y)Optical photograph and (b X-ray reflection topograph recorded from 

and defect structures (twins TI and Tz). 

the tapere microgravity grown sample d CRC-2 (USML-2) showing the morphology 

* Work performed on the Synchrotron Topography Project, Beamline X-lgC, NSLS, 

BNL and supported by NASA Marshall Space Flight Center 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, NSLS, 

BNL and supported by NASA Marshall Space Flight Center 
Synchrotron White Beam X-ray Topographic Characterization of 

Growth Defects in Bridgman-Stockbarger Grown CdZnTe Single 

Crystals * 

B. Raghothamachar, H. Chung, M. Dudley, and D. J. Larson Jr. (SUN 

Brook) 

q , Stony 

Vertical Bridgman -Stockbarger method of crystal growth was used to grow a single crystal boule of CdZnTe. (111) wafers sliced from this boule were examined 

by synchrotron white beam x-ray topography in the reflection geometry. Figure 1 

shows a reflection topograph imaged from wafer 3 which was cut from the initial part 

of the steady state growth region of the boule. Several slip bands running across 

the middle of the boule are observed. These slip bands overlap a previously existing 

dislocation cellular structure indicating that slip could possibly have occured during 

post solidification cooling. By analysing projec_ted directions in different reflections, 

the slip system was determined to be [101]/(111). A twin T is revealed by orientation contrast. By detailed analysis of back reflection Laue patterns recorded from 

the twin related region, it was determined that the twin is 160 rotation twin about 

the (11i) plane normal. The twinned region has two sets of slip bands [lOZ]/(lil) 

and [ilO]/(lli) respectively). Absence of a second slip system in the matrix indicates that the slip was initiated in the twinned region and did not propagate into 

the matrix since the twin boundaries act as barriers to slip dislocations. Since the 

twin was formed before deformation occurred it is probably a growth twin. 

Figure 1. Reflection topograph (g = 335) from wafer 3 of 

showing defects such as slip bands (Si and S,), subgrain 

180' rotation twin (T) 

CdZnTe boule N2FST-1 

boundaries (SB) and a 

Morphology of Basal Plane Dislocations in 4H-Sic Single Crystal 

Wafers * 

W. Si and M. Dudley (SUNY Stony Brook), R. Glass, V. Tsvetkov, and C. Carter, 

Jr. (Cree Research, Inc) 

In PVT grown 4H-Sic single crystals, there are mainly two types of dislocation 

structures: superscrew dislocations with their Burgers vectors running along the 

[OOOl] axis, and basal plane dislocations whose both line directions and Burgers 

vectors are confined on the (0001) planes. In X-ray topography of low absorbing 

crystals such as Sic, the dislocation lines become visible by the kinematic contrast due to effective misorientation of the reflecting lattice planes in the elastically 

strained region surrounding the dislocation core. In a high quality (0001) 4H-Sic 

wafer we studied, the bimodal, double line contrast was observed from these basal 

plane dislocations, as shown in a synchrotron transmission topograph. The dislocation A seems to be pinned at points PI and P2 by other dislocations and bows out 

to form the beginnings of a Frank-Read source. Detailed analyses of these dislocations including determination of their Burgers vectors and calculation of dislocation 

image width are being investigated. 

Figure 1. 

g = 1210, 

A synchrotron transmission X-ray topograph from a (0001) 4H-Sic 

X = 0.75 A, BD indicates basal plane dislocations. 

wafer, 

* Work performed on the Synchrotron Topography Project, Beamline X-lgC, NSLS, * Work performed on the Synchrotron Topography Project, Beamline X-lgC, and supBNL and supported by NASA Marshall Space Flight Center ported by ARPA/AFWL under Grant No. FYl457-95-03108. 
I Study of 6H-Sic Polytype Inclusions in 4H-Sic Single Crystals * I x19c I 

W. Si and M. Dudley (SUNY Stony Brook), R. Glass, V. Tsvetkov, and C. Carter, 

Jr. (Cree Research, Inc) 

Currently 

more than 200 polytypes of Sic have been reported. The common polytypes with 

technical importance are 4H, 6H, and 3C-Sic. Since these polytypes coexist over a wide range of temperatures, inclusions of secondary polytypes can occur when 

crystals are grown inproperly. In a (1120) oriented 4H-Sic single crystal wafer we studied, small regions (inclusions) with different color from the substrate have been 

occasionally observed using optical microscopy. In order to identify the character of 

these inclusions, synchrotron transmission Laue diffraction patterns were recorded 

from these regions as shown in Figure 1. By analyzing and indexing this pattern, 

it is found that the inclusion belongs to a 6H-SIC polytype. Similar result has 

been reported that 15R-SIC inclusions exist in 6H-Sic single crystals'. 1. Shaoping 

Wang, Ph.D. Thesis, State University of New York at Stony Brook, 1996, p. 85. 

Sic is well known for its exhibition of many polytype structures. 

Investigations of 4H-Sic Epilayers on (1120) 4H-Sic Single Crystal 

Substrates * 

W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and C. 

Carter, Jr. (Cree Research, Inc.) 

In order to investigate the effects of 4H-Sic substrates on the crystalline quality 

of 4H-Sic epilayers, (1120) oriented substrates, other than commonly used (0001) 

oriented substrates, were used to grow 4H-Sic epilayers. Figure (a) shows the surface morphology of a 4H-Sic epilayer grown on a (1130) 4H-Sic substrate. The 

epilayer surface is smooth, specular, and featureless, which implies very good crystalline quality of the epilayer. The faint line on the picture indicates a micropipe in 

the substrate. Figure (b) is the reflection topograph recorded from the same region. 

The major defects revealed are superscrew dislocations in the substrate, probably 

due to the fact that the strain fields of the superscrew dislocations in the substrate 

penetrate into the newly grown epilayer and therefore are picked up by reflection 

topography. There is no polytype other than 4H-Sic in the epilayer revealed in 

the reflection topograph. The reflection topograph recorded from the epilayer is 

very similar to that from !he substrate before epitaxy growth, and the quality of 

epilayers grown on the (1120) substrates is very good. 

x19c 

Figure 1. Synchrotron transmission Laue patterns recorded from a (1130) 4H-SIC 

wafer containing a 6H-SIC region close to the edge of the wafer. [IIZO] direction is 

parallel to the incident X-ray beam direction. 

sd 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, and sup- CL 

-4 

-4 ported by ARPA/AFWL under Grant No. FY1457-95-03108. 

Figure 1. 4H-Sic epilayers on (1130) 4H-Sic substrates, (a). a NOM micrograph 

and (b) the reflection topograph g = 2202, X = 0.71 A) recorded from the same region, M indicates a micropipe, s D indicates superscrew dislocations. 

* Work performed on the Synchrotron Topography Project, Beamline X-lgC, and supported by ARPAjAFWL under Grant No. FY1457-95-03108. 
P 

t-' 

2 Investigations of Triangular Inclusions in 4H-Sic Epilayers on 4HSic Single Crystal Substrates: (I) Identification of Phases * 

W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and C. 

Carter, Jr. (Cree Research, Inc.) 

In the case of 4H-Sic epitaxial growth on (0001) substrates, one of the big obstacles is the occurrence of triangular inclusions in the epilayer. In this study, 

Synchrotron White Beam X-ray Topography (SWBXT) and Nomarski Optical microscopy (NOM have been used to study the character of these trian ular inclusions. The 4 B -Sic substrates used are misoriented by 3.5' from (0001~ toward 

<ll20>. It has been revealed by analysis of X-ray diffraction patterns that there are 

two additional phases, 3C(I)-Sic and 3C 11)-Sic, present in the 4H-Sic epilayer' . 

shown in Figures (a) to (d). Evidently, all triangular inclusions belong to one or the 

other of the two 3C-Sic structural configurations. Most of the triangular inclusions 

are single crystal 3C-Sic, although they appear to be severely strained. There is 

only one triangular inclusion consisting of both 3C(I) and 3C(II)-SIC, which implies 

the existence of a double position boundary (DPB) within the inclusion'. Therefore it is unambiguous that those triangular defects in 4H-Sic epilayers studied are 

3C-Sic inclusions. 

x19c 

The detailed correlation between the NO & micrograph and reflection topographs is 

1. W. Si et at, 1995 NSLS Annual Activity Report, p. B-173. 

2. H. S. Kong et all J. Mater. Res., Vol. 4, No. 1, (1989), p. 204. 

C 

h rn -_ 

.gInvestigations of Triangular Inclusions in 4H-SIC Epilayers on 4HSic Single Crystal Substrates: (11) Effects of Superscrew Disloca- X19C 

tions in substrates * 

W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and C. 

Carter, Jr. (Cree Research, Inc.) 

It is well known that in 4H-Sic single crystal substrates, there exist superscrew 

dislocations along the [OOOl] axis with their magnitudes of Burgers vectors equal to 

a multiple of the lattice constant c (c = 10.05 A). Figure 1 shows (a) a NOM micro raph of the epilayer and (b) a back-reflection topograph. Triangular inclusions 

(TI?, growth pits (P), and scratch (S marks are observed on the micrograph. The 

the same size. The directions from the apex of the triangle to the base are [1210] 

directions, which correspond to the down-step directions (direction of lateral step 

growth). The length of altitude from base of the triangle to the peak is around 

97 to 120 pm. The density of growth pits is approximately 3.5x104cm-', and the 

diameter is around 1 pm. Superscrew dislocations including micropipes (M) and 

elementary screw dislocations (ED) show circular white features on the topograph. 

By comparison, it is evident that there is no obvious correlation between superscrew 

dislocations and IC-Sic triangular inclusions. Also there is no evidence showing 

that the growth pits are related to the superscrew dislocations since the density of 

growth hillocks is one order of magnitude higher than that of superscrew dislocations (about 103cm-'). 

triangular inclusions consist of the s h allow and hillock-like varieties with rou_gh_ly 

Figure 1. 4H-Sic epilayers on 4H-Sic substrates misoriented by 3.5' from 

(a). a NOM micrograph, (b). the reflection topograph from the same 

SIC, g 3 1i06, X = 0.78 A , (c). the reflection topograph of 3C(I)-Sic, g = 202, X 

= 0.91 A , and (d). the reflection topograph of 3C(II)-Sic, g = 131, X = 0.67 A. 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, and supported by ARPA/AFWL under Grant No. FY1457-95-03108. 

Figure 1. 4H-Sic epilayers on the 4H-Sic substrates misoriented by 3.5' from 

(0001), (a). a NOM micrograph, and (b) the back-reflection topograph recorded 

from the same region, g = 00024, X = 0.83 A. 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, and supported by ARPA/AFWL under Grant No. FY1457-95-03108. 
Investigations of Triangular Inclusions in 4H-Sic Epilayers on 4HSic Single Crystal Substrates: (111) Effects of Off-axis Angles of X19C 

Substrates * 

W. Si and M. Dudley (SUNY Stony Brook), H. S. Kong, J. Sumakeris, and C. 

Carter, Jr. (Cree Research, Inc.) 

One method of preventing the formation of triangular inclusions during Sic epitaxial growth is to use substrates misoriented from (0001). The vicinal surfaces 

of such off-axis substrates provide high densities of surface steps, which promotes a step-flow mechanism and facilitates the Sic homoepitaxy. However, in 4H-Sic 

epitaxy, the occurrence of triangular inclusions still existed when substrates misoriented by 3.5' from (0001) were used. One possible way to reduce or eliminate the occurrence of inclusions in 4H-Sic epilayers is to further increase the off-axis angle 

of the approximately (0001) oriented substrates, i.e., from the commonly used 3.5' 

misorientation to 6.5' and 8.0'. Figure (a) shows a reflection topograph recorded 

from the epilayer grown on a 6.5' off-axis 4H-Sic substrate. It was found that both 

density and dimension of triangular inclusions is greatly reduced. In the case of 

substrates misoriented by 8.0' from (OOOl), the triangular inclusions were virtually 

eliminated, as shown in Figure (b). The crystalline quality of 4H-Sic epilayers 

grown on the substrates misoriented by 8.0' from (0001) was very good. 

Figure 1. Reflection topographs (g = 1114, X = 0.78 A) recorded from epilayers 

rown on 4H-Sic substrates misoriented by a) 6.5' from (0001) and (b) 8.0' from boo 1 1, showing superscrew dislocations (S 6 ), small angle boundaries (SB), and 

triangular inclusions (TI). 

* Work performed on the Synchrotron Topography Project, Beamline X-19C, and supported by ARPA/AFWL under Grant No. FY1457-95-03108. 

Studies of Growth Striations and Impurity Distribution of LEC 

Grown GaInSb Single Crystal 

J. Su, M. Dudley (SUNY Stony Brook), D. Fletcher, and W. Bonner (Johnson 

Matthey Electronics) 

The LEC grown Gao.97Ino.03 Sb single crystal have been studied using synchrotron 

white beam X-ray topography (SWBXT).The transmission topopographs recorded 

from the sample reveal high contrast growth striations which are perpendicular to 

the growth direction.These striations offer a convenient way to study the crystal 

growth because they clearly delineate the crystal growth profile.In present studies, 

efforts have been made to investigate the relationship between impurity distributions 

and growth striations by using SWBXT and a CAMEBAX electron microprobe 

with a resolution of 10-'wt% and a penetration depth of 0.5 pm. Figures 1 and 

2 below show the measurement results of two lines performed along the growth 

direction. The results reveal that indium concentrations have periodic distributions 

when crossing the growth striations. The indium concentrations measured just on the striations show relatively higher values, such as positions #3, #15, #18 in 

Figure 1, and #9, #14, #22 in Figure 2. The indium concentrations on the regions 

immediately after the striations show lower values, such as #7, #8 in Figure 1, and 

#4, #8, #12 in Figure 2. The present studies show that the impurity concentrations 

change with the formation of growth striations, and the striations have highest 

indium content. The reason can be explained as that the indium accumulates at 

the solid-liquid interface during growth, and its content influences the latent heat of 

the solidification which will influence the microscopic growth rate. This fluctuation 

in the instantaneous microscopic growth rate during the LEC growth will give rise 

to the periodic accumulation of indium concentration. This difference in impurity 

content will cause the local lattice strain which produces the growth striation images 

in X-ray topography. 

Figure 1. Indium concentration as a Figure 2. Indium concentration as a 

function of positions along line #4, 

indium concentration distribution indium concentration distribution 

measurement position map. 

function of positions along line #5, 

measurement position map. 
x19c Synchrotron White Beam X-ray Topographic Studies of LEC GaInSb 

o Seed Transition Region 

J. Su, M. Dudley (SUNY, Stony Brook), D. Fletcher, and W. Bonner (Johnson 

Matthey Electronics) 

Ternary 111-V semiconductor materials become more attractive due to their se- lectable lattice parameters and bandgaps. However, obtaining defect-free ternary 

semiconductor substrates is still an object that people make efforts. In this study, 

Synchrotron White Beam X-ray Topography (SWBXT) was applied to analysire the 

defect mechanisms in the [111] LEC grown Gao.97Ino.03 seed transition region which 

is the critical region of LEC growth. A longitudinally cut slice has been studied 

Q, 

using SWBXT. Fi 

growth striations 

perpendicular to the growth direction at 

tions are observed 

are also revealed. The feature marked SS are surface scratches. Another transimission X-ray topograph with (g=lllX=O.56A)is shown in Figure 2. The dislocations 

which appeared in Figure 1 show no contrast or weak contrast in Figure 2. Therefore, the Burgers vector of these dislocations can be determined as 1/2[110]. The 

studies indicate that 1/2[110] dislocations can be generated at the shoulder region 

during LEC growth, and some dislocation are observed to propagate inside the bulk 

from the seed transition region. 

2mm 2 mm 

Figure 1. Transmission X-ray topo- Figure 2. Transmission X-ray topograph (g=lll X=0.54A) recorded from graph (g=ill X=0.56A)recorded from 

Gao.p.rIno.03Sb seed transition region Gao.97Ino.03Sb seed transition region 

showing dislocations (D), growth stria- showing that the dislocations appeared 

tions (GS), and (111) facets (F). in (a)have no or weak contrast. 

A Comparison of Synchrotron White Beam and Lang X-Ray Topography of 6H-Sic Single Crystal Wafers * 

W. M. Vetter and M. Dudley (SUNY, Stony Brook) 

Back-reflection Synchrotron White Beam (SWB) images of basal-cut Sic wafers 

(as in figure 1) are characterized by black rings with white centers of various diameters that are associated with the surface intersections of superscrew dislocations 

of various sized Bur ers vectors. Such SWB images are a composite of a harmonic 

series of reflections ?006n), where n=3,4,5 ... in the the case of the X19C beamline 

white beam spectrum. Nevertheless, their contrast is sharp. The Lang image shown 

in figure 2 (g=(0018), X=CuKa1=1.54A, 8~=66.5', FWHM=l5.6prad) taken using copper characteristic radiation has a Full Width Half Maximum (FWHM) and 

a Bragg angle comparable to those of the g=(0024) SWB reflection (X=1.24Al 

8~=80O, FWHM=lg.gprad) which is the fourth harmonic in the series. The similarities between these values and those between the features in these two topographs 

suggest that g=(0024) is the most important component of the back-reflection image. The Lang image shows ring-like images for the largest Burgers vector superscrew dislocations similar to those seen in the SWB image, however the black rings are larger and their centers are smaller. In the cases of the smaller Burgers vector 

superscrew dislocations, the white centers are absent. 

Figure 1. Back-reflection SWB topograph. 

* Work performed at Beamline X-19C, 
Synchrotron White Beam X-Ray Topography of a Single Superscrew 

Dislocation in 6H-Sic Through All{ 100) Faces * 

Surface Scattering from Ternary Mixtures of Oil, Water, and Surfactant 

W. M. Vetter and M. Dudley (SUNY Stony Brook) 

Micropipes, the hollow cores of superscrew dislocations that lie along the cdirection in Sic single crystals, are quite deleterious to the performance of semiconductor devices. In the x-ray topography of longitudinal-cut samples of these 

crystals, topographs in the reflection (006) show dislocation image contrast associated with strain along the c-axis of the crystal, which is also the direction of 

the dislocations’ Burger’s vectors. In a (110) reflection, whose g-vector is perpendicular to the c-axis and the dislocations’ Burger’s vector, there is also an image 

of the superscrew dislocation formed, albeit weaker than the corresponding image 

in the (006) reflection. This dislocation image is thought to represent the strain 

components of the superscrew dislocation in directions perpendicular to the c-axis, 

resulting from stresses arising at the surface of the micropipe. 

To determine whether these strains are anisotropic in all possible reflections where 

g = {110), we have excised a hexagonal prism-shaped section from a 6H-SIC wafer, 

100pm wide, polished along the six (100) crystallographic faces, such that a single 

micropipe ran along the axis of the sample. The x-ray topographs in figure 1, taken 

through three of these (100) faces using three different (110) g-vectors, show that 

the dislocation images in each are essentially similar-two dark lines with a constant 

separation. However, the contrast may change somewhat between different g-vectors 

at the same point along the dislocation line, perhaps reflecting varying stresses and 

the emission of dislocations along an irregularly surfaced micropipe. 

Figure 1. X-ray topographs using three different g={ 110) reflections. 

P 

(*, 

* Work performed at the Synchrotron Topography Project Station, Beamline X-lQC, 

supported by U.S. Amy Research Office under grant numbers: DAALOQ-94-G-0091 and 

DAAL04-94-G-0121. 

F 

P 

S.M. Williams, Z. Zhang, D.M. Mitrinovic, M.L. Schlossman (U. of IL- Chicago), 

and Z. Huang (BNL) 

We have made x-ray scattering measurements from the oil-microemulsion interface of several ternary mixtures that include one of the surfactants, C&1, CeE2, or 

C10E4 (n-alkyl polyglycol ether CHa(CHz);-1 (OCH2CH2)jOH). 

The mixtures using C4E1 or CeE2 yield qualitatively similar results. The mixtures with C10E4 have much rougher interfaces (u > 200 8) and data interpretation 

for this system is at a primitive stage. Here we discuss studies of a CqEl-waterdecane (1:1:3) mixture at 35.00”C prepared in a vapor-tight sample cell. Under these 

conditions the solution is in a three-phase state with a middle-phase microemulsion. 

The primary experimental challenge is that the x-ray beam fully traverses the diameter of one of the bulk phases. The concurrent absorption and bulk scattering 

requires a small sample that, in turn, demands a very small x-ray beam (10 pm 

vertically) with a small divergence (20 pads). In our sample cell design, the x-rays 

pass through 75 mm of the upper phase, necessitating the use of high energy x-rays. 

The absorption length of the upper decane-rich phase (at 35°C) at 15 keV is 15 mm, 

resulting in an absorption loss of 99%. By using a multilayer monochromator crystal at the X19C surface spectrometer we have adequate intensity to perform these 

experiments (loll photons/sec at 15 keV in a 0.5 mm x 1 mm spot). 

The reflectivity data (from the oil-microemulsion interface) is fit very well by 

the distorted wave Born approximation yielding a roughness u = 57 & 3 8. This 

value is much larger than the largest molecular size (-10 A) and is indicative of a 

strongly fluctuating interface. Surface diffuse scattering was measured as a function 

of varying reflection angle for fixed incident angle. Using the distorted wave Born 

approximation and the roughness determined from the reflectivity only, it is not 

possible to make an adequate fit to the data. An excellent fit is obtained if the 

roughness parameter along with the interfacial tension and a constant background 

are fit. This fit has a roughness, u=75 i- 5 A, that is much larger than that 

determined from the reflectivity. For both fits the interfacial tension is similar (for 

u = 75 f 5 A,r = 0.08 dynes/cm; for u = 57 zk 3 A, y = 0.12 dynes/cm). 

Although the reason for the failure of the distorted wave Born approximation to 

describe this data is unclear at this stage, it may be due to the assumption of a step-function interface in describing the diffuse scattering. If true, this would be the 

first experiment to show the effect of a more complicated interface on the surface 

diffuse scattering, thereby providing an experimental probe of complex and strongly 

fluctuating interfaces. 
Studies of Influence of Defects on the Performance of 4H-Sic Devices Using Synchrotron White Beam X-ray Topography: I. Defect X19C 

Configuration 

C. Yang and M. Dudley (SUNY Stony Brook), H. M. Hogood and S. Seshadri 

(Northrop Grumman Science and Tech. Center) 

Currently Sic development is shifting from 6H to 4H polytype because of the 

larger electron mobility (800 vs 370 cm2/V-s) and lower donor activation energy 

(45 vs 90 meV) of 4H-Sic compared to 6H-SIC. Two 4H-SIC wafers (both with 

diodes on one surface) were characterized using synchrotron white beam X-ray 

topography. The influence of defects on performance of these 4H-Sic devices has 

been investigated. Figure 1 shows Back-reflection topograph of wafer A (g=00024, 

A=0.829A) and figure 2 shows Back-reflection topograph of wafer B (g=00024, 

k0.831A). In both figure 1 and fi ure 2, the small white circles are associated 

with elementary screw dislocations g b=lc, where c is the lattice parameter along 

<0001> axis) (marked as S) are visible. Also some trapezium shaped defects are 

visible. They are associated with 3C-Sic polytype inclusions (marked as P). The 

size of the inclusions is about 150 pm. It is noteworthy that one inclusion (marked 

as P1) could not be observed through optical microscopy was clearly revealed by 

back-reflection topography. This is because this inclusion is below the surface of the 

epilayer. Work performed on the synchrotron topography project, beamline X19C 

and supported by Northrop Grumman Science Tech. Center under U.S. Goverment 

Prime Contract N00014-95-C-0132. 

Studies of Influence of Defects on the Performance of 4H-Sic Devices 

Using Synchrotron White Beam X-ray Topography: I1 - Influence of X19C 

Defects * 

C. Yang and M. Dudley (SUNY, Stony Brook), H. M. Hobgood and S. Seshadri 

(Northrop Grumman Science Tech. Center) 

The influence of polytypes as well as elementary screw dislocations on the performance of the 4H-Sic devices has been investigated. First, by comparing the 

topographs and optical micrographs of the two wafers with the map of diodes (See 

Table l), it is found that all diodes with 3C-Sic inclusions in them show poor perfor- mance. In other words, all diodes with good performance are free of 3C inclusions. 

It is concluded that the polytypes have detrimental effects on the performance of 

the devices. Second, we can also make a comparison of the superscrew dislocation 

density between the diodes with good performance and those with poor performance 

See Table 2). From the table we can see clearly that the superscrew dislocation 6 ensity in poor performance devices is much higher than that in good performance. 

This suggests that the superscrew dislocations may have adverse effect on the performance of the devices. Further study of the effect of superscrew dislocations on the performance of devices are planned subject. 

1 mm 

Figure 1 

1 mrn t 

m/ 

Figure 2. 

Figure 1 

* Work performed on the Synchrotron 

Topography Project Beadne X-19C and 

supported by Northrop Grumman Science 

Tech. Center under U.S. Government Prime 

Contact No. N00014-95-C-0132 

Supersnew dislocation Diodes with good Diodes with poor de& (xlO"/wd) pcdommce performance 

Diodes ofrype "al" 7.080 12.98 

mods of twc "bl" 6.731 8.162 

Diodes of trps 51" 9.997 16.94 

AI1 diode8 8.625 10.62 

Figure 2. 
Characterization of Defects in 4H-Sic Single Crystals by Synchrotron White Beam X-ray Topography * 

C. Yang, W. Si and M. Dudley(SUNY, Stony Brook), H. M. Hobgood and S. 

Seshadri (Northrop Grumman) 

It has been established [I] that synchrotron x-ray back-reflection geometry is 

particularly useful for imaging superscrew dislocations in 6H-SIC single crystals. 

Here we report the application of this technique to 4H-Sic single crystals. Fig- ure 1 shows a high magnification back-reflection topograph of a 4H-SIC wafer. In 

this figure the black rings with white centers of various diameters correspond to 

superscrew dislocations. The larger of these circular features on this topograph are 

associated with 'micropipes'( marked as M). The smallest of these circular features 

are associated with elementary screw dislocations (marked as S). Besides there are 

some black and white lines connecting the circular features ,which correspond to 

the basal plane dislocations ( marked as BD). The total numbers of micropipes 

in this figure is 7 and their density is 78/cm2. The density of elementary screw 

dislocations in region A (See figure 1) is 2800 /cmz. The observation of individual 

basal plane dislocations and elementary screw dislocations is an indication of the 

good crystalline quality of this region. 

[l] M. Dudley, S. Wang, W. Huang, C. Carter, V. Tsvetkov and C. Fazi, J. Phys. 

D: Appl. Phys. 28(1995) A63-A68. 

x19c 

Figure 1. 

td 

00 

* Work performed on the Synchrotron Topography Project Beamline X-19C and supportedhy Northrop Grumman Science Tech. Center under US. Government Prime Contact 

No. N00014-95-C-0132 

CI 

~ ~~~ I X-ray Scattering Studies of the Passive Film on Fe(OO1) and Fe(ll0) I X20A I 

A. J. Davenport (U. Manchester), L. J. Oblonsky, M. P. Ryan (BNL), M. F. Toney 

(IBM), and C. Vitus (BNL) 

Despite decades of work, the passivating oxide films that protect (normally reac- tive) metals from corrosion are still poorly understood. This is because the films are 

very thin (typically a few nanometers) and are formed in aqueous environments so 

that ex-situ measurements are susceptible to changes in the film upon removal from 

the solution in which they grew. The structure of the passive film on iron has been 

the subject of particularly intense study (1,2 and References therein), but there is 

still no consensus on questions as basic as to whether the film is amorphous or crystalline. However, recent in-situ STM measurements of the passive film formed on 

Fe suggest that the surface is crystalline with a proposed yFe203-Fe304 structure 

(2) that is supported by in-situ XANES (1). To confirm and expand upon these 

results, we have conducted in-situ and ex-situ X-ray scattering experiments on the 

passive film formed at high potentials on Fe(ll0) and (001). 

The Fe crystals were passivated by potentiostatic polarization for one hour at 

+0.4V vs. MSE in borate buffer (pH 8.4 . Our methodology is to collect a complete 

selected in-situ data to compare with the ex-situ experiments. In such a comparison 

there is excellent agreement, which demonstrates that the passive film formed under 

these conditions is not altered by emersion. 

The diffraction data show that the passive films are epitaxially aligned with the Fe 

crystals. For the film on Fe(llO), we find oxide(ll1 I Fe(ll0) and oxide[i10]11Fe[002], 

whilst for l?e(OOl), oxide(001)11Fe(001) and oxi 4 e 100]11Fe[llO]. From the peak 

widths, we estimate in-plane domains sizes of 60A and 45A for films formed on 

Fe(001) and Fe(llO), respectively. A quantitative crystal refinement of the integrated diffraction intensities has been conducted for the passive film on Fe(001). 

We conclude that the film structure is not one of the bulk forms of iron oxide (see 

figure). Rather the film sturcture is similar to the spinel FesO4, but with a large 

fraction of the tetrahedral sites vacant (~80% occupancy), a smaller fraction of the 

octahedral sites vacant (~95% occupancy), and some displacement of the (full occupied) oxygen anions from the positions occupied in Fe3os. Further experiments 

will probe the dependence of the oxide structure on potential. 

1. A.J. Davenport and M. Sansone, J. Electrochem. SOC. 142, 725 (1995). 

2. M.P. Ryan et al., J. Electrochem. SOC. 142, L177 (1995). 

data set ex-situ (where the backgroun d scattering is small), and then to collect 

I I lob I 

Figure 1. Experimental and model structure factors. 
1 X20A 1 Time-Resolved Measurements of Overlayer Ordering in Electrodeposition * 

A.C. Finnefrock, L.J. Buller, H.D. Abruiia, and J.D. Brock (Cornell U.) 

In many electrochemical systems, one or more monolayers of an adsorbate may 

be deposited at a potential less negative than the Nernst potential. The growth 

mechanisms involved in this so-called underpotential deposition (UPD) have been 

the subject of intense controversy for over a decade. Recent static x-ray scattering 

measurements on the underpotential deposition of Cu2+ on Pt(ll1) in the presence 

of C1- in an HC104 solution have noted the existence of a structure ascribed to an 

adsorbed CuCI bilayer. 

We have performed in situ time-resolved surface x-ray scattering measurements 

on this UPD system. Our data show that copper is electrodeposited onto the 

surface less than 0.02 seconds after the potential is stepped. In contrast, our timeresolved x-ray scattering data indicate that the overlayer structure requires from 2 

to 5 seconds to develop long-range order. Because the surface ordering and charge 

transfer rates are so distinct, we effectively have a deposition process followed by a two-dimensional ordering process. 

We are presently extending these measurements to include absolute reflectivity 

measurements of the specular and off-specular crystal truncation rods. Through 

these, we hope to study mass-transfer of ions near the electrode surface and other 

aspects of the deposition process. 

Figure 1. (a) Applied potential steps. (b) Transient current response. (c) Peak 

intensity of overlayer super-lattice peak. The development of long-range periodic 

order in the overlayer (panel c) requires significantly more time than that required 

for the electrodepositionof material onto the electrode surface (panel b). 

Using X-ray Scattering to Examine Supra-molecular Organization 

and Surface-melting at Molecular Interfaces. * 

S.E. Girdwood, A.R. Kennedy, J.N. Sherwood (U. Strathclyde) and K.J. Roberts 

(Heriot-Watt U.) 

Our work involves a study of the structural nature of the solid/liquid interactions 

taking place at the growth interface of crystals. Of particular interest to us is the 

development of a more generally ecceptable model for the growth interface. To carry 

out this work we are using a powerful combination of X-ray reflectivity and surface 

diffraction techniques to probe the nature of molecular ordering on organic surfaces 

and how such ordering is changed during crystallisation. Information gained from 

these experiments is being used to refine our current model of the growth interface structure and hence, to improve the predictive capability of crystal growth 

morphology computation routines. 

Whilst surface x-ray techniques have been applied to inorganic systems quite 

extensively, their application within the broader areas of organic interface and rn* 

terials chemistry has been very limited and is ripefor exploitation. The success 

of this project depends on linking predictive computational chemistry techniques 

with experimental evidence of interface structures under realistic conditions. This 

experimental work is only possible using synchrotron radiation and results from it 

will have major ramifications, at both fundamental and appliad levels, to a range of 

fields in which control of crystal morphology is of great importance such as materials 

purification, colloid science, biotechnology and surface engineering. 

* This work was supported by Cornell University’s Materials Science Center, NSF Grant 

No. DMR-88-1858-AO2. 

* We wish to acknowledge the UK Engineering and Physical Sciences Research Council 

for the funding of this work 
I Nanosuspensions in Helium I X20B 1 I Structure and Kinetics of the Sliding &I CDW in NbSea * I Y:? I 

K.L. Flingland, S.G. Lemay, R.E. Thorne, and J.D. Brock (Cornell U.) 

We have performed detailed measurements of both the structure of the sliding &I 

charge-density wave (CDW) and the kinetics of its relaxation from the sliding to the 

pinned state. High q-resolution data obtained at X25 demonstrate unambiguously 

that the equal time phase-phase correlation function does not decay algebraically 

at large distances. That is, 

The detailed structure of the sliding state is still a major issue and recent models have predicted an assymptotic algebraic decay of the phase-phase correlation 

function$. An algebraic decay produces a line-shape that traces out the resolution 

function near the center of the peak but has additional scattering in the wings. 

In contrast, we measure the full width at half maximum of the &I satellite in the 

sliding state to be roughly 66% broader at lox threshold than the same satellite 

in the pinned state. (The Q1 satellite in the pinned state is also broader than our 

resolution .) 

Similarly, our time resolved measurements of the relaxation of the Q1 CDW 

from the sliding to the pinned state also contradict the predictions of the suggested 

equations of motion. Specifically, the peak intensity increases monotonically with 

time after the current is switched off. The solution to the proposed equation of 

motion has the form 

where F(q is the quenched random field and D is the diffusivity. This expression 

has a "dip' in the intensity. Our data does not exhibit such a dip. This discrepancy 

implies that either a non-linear term is missing from the equation of motion or that 

the random field, F(3, is not quenched. 

0 5 10 I5 20 25 30 35 

Time [~econd~] 

Figure 1. Peak intensity of (0 1+Q1 0) satellite as a function of time. Current is 

turned off at t = 3 seconds. 

* This work was supported by NSF Grant No. DMR-9501119 

V.Kiryukhin, B.Keimer (Princeton U.), E.Gordon, and V.Khmelenko (IEPCP, Russia) 

The structure and thermal properties of a novel type of suspension of impurity 

atoms and molecules in helium were studied in a series of x-ray diffraction measurements. The suspensions were prepared by injecting a jet of helium containing 

diluted amounts of impurity atoms or molecules (especially Ne and N2) into superfluid helium at T=1.5K. By this technique the formation of microcrystals of the 

impurity species is prevented. X-ray powder patterns taken after preparation of the 

suspensions indicated the presence of a bulk amount (-lcm3) of nanocrystallites of 

the impurity species (typical diameter 30A) in the liquid (see Fig 1, 2 There is also 

evidence for even smaller entities e.g. single atoms) dissolved in t h. e liquid. The 

was drained out of the sample cell. The nitrogen nanocrystallites persisted essen- tially unchanged up to temperatures of about 15K, far above 4.2K, the evaporation 

temperature of pure helium. At T=15K the diffraction profiles suddenly became 

instrumentally narrow, indicating a sudden coalescence into microcrystallites. The 

coalescence temperature of the neon nanocrystals was about 2.5K. 

These results can only be understood by hypothesizing a shell of helium bound 

to the nanocrystals by van-der-Waals interactions, which prevents their coalescence 

at low temperatures. Helium is the only element whose large zero-point motion 

prevents it from forming a solid phase at ambient pressure. The observation of 

nongaseous helium in the van-der-Waals shells at temperatures up to 15K is therefore remarkable and must be explained in the framework of quantum many-body 

physics. In addition to fundamental concepts in quantum physics, our experiments are also expected to stimulate new developments in matrix isolation spectroscopy. 

suspensions were stable for many 6 ours, remarkably even after the liquid helium 

20 (degrees) 5 10 15 20 

Figure 1. X-ray powder pattern for 

the nanosuspension of Ne in helium at 

T=1.5K. The signal is the superposition 

of liquid helium and neon nanoclusters 

signals. form close packed structure. 

0 

20 (degrees) Figure 2. The data of Fig 1 with the liquid helium signal subtracted. This data 

shows that the sample is composed of 

Ne nanoclusters (typical size -3OAand 

smaller). Neon atoms in the clusters 
P 

F 

X20B Morphological Investigation of Nylon 66 Fibers Using Radial Distribution Function Analysis 

J. R. Sharrow, J. M. Schultz (U. of Delaware), B. S. Hsiao, and H. Chang (DuPont) 

The morphology of nylon 66 fibers was probed by application of Radial Distribution Functions (RDFs) to diffraction patterns. A four circle diffractometer, 

operating at a wavelength of 0.7092A, was used to obtain equatorial scans of var- ious fibers previously exposed to different processing conditions. Each sample was 

held in a fixed position, as the 26 arm was rotated from 148' to 4' in intervals of 

0.075 degrees (1.24 nm-l <q< 9.39 nm-l). 

RDFs are real space operations giving the number density of atoms displaced a 

distance r from an atom selected to be at the center. Physically, the RDF is expressed as 47rr2p(r), and commonly presented as a reduced RDF, G(r) = 4 47rr[p(r)- 

pol, where po is the average number density. The RDF is computed as a Fourier 

transform of the measured intensity after correction for incoherent scattering. This 

type of transformational method offers the advantage that the calculation of the 

correlation length requires no prior assumption as to the presence or absence of a 

crystalline phase. The correlation length is the distance at which the amplitude 

of the fairly periodic oscillations on the order of several angstroms, becomes similar to that of the "noise". This noise is caused by the upper limit of integration. 

Fourier transformation involves integration in reciprocal space from 0 to infinity, 

but it is impossible to obtain such data experimentally. Therefore, the structurally 

dependent oscillations in the RDF curves are moderated by "noise" in the form of 

wavelets. These wavelets, with a period of 27r/Kmar, determine the resolution in 

real space. 

Figure 1 displays the reduced radial distribution function, G, as a function of r. 

The spacing of the oscillations in these curves is on the order of the intracrystalline 

spacing, about 4A. The control fibers, prepared in the absence of heatsetting, are 

characterized by a correlation length of approximately 65A while fibers subject to 

wet heatsetting, have an increased correlation length of 75A. Drops in magnitude, 

present at approximately ld and 38& are noticeable in both curves and persist over a spacing of a few Angstroms. These observations imply that crystalline fibril 

is roughly 65A to 7'5A in the dimension transverse to the fiber axis, but contain 

small aefects at consistent spacings. This work supported BY NSF-GOAL1 grant 

(DMR-9629825). 

, I 1 L.;L. +pJ&- 

riAnlgm 

Figure 1. Reduced radial distribution func. for control fiber, wet-heatset fiber. 

Effects of Rubbing Polyirnide Films x20c 

J.M. Sands, S.K. Kumar (Penn State U.), T.P. Russell, and M.F. Toney (IBM) 

In the process of characterizing the effects of rubbing polymer surfaces under 

finite loads, we have performed a series of experiments in which various parameters 

involved with rubbing polymer surfaces have been varied, and grazing incidence 

x-ray scattering (GIXS) has been applied in order to characterize the effects which occur as a result of rubbing and curing polymer films. Synchrotron based GIXS 

experiments using a well defined incident beam allow one to probe the range of 

polymer films structure in a depth dependence geometry ranging from 5 nm to bulk 

film scattering. 

Following recent experiments, a model describing the orientation of polymer 

chains in the surface under rubbing is being developed which shows how the effects of rubbing are consistent with the usual pheomena of yielding in polymer 

materials; the concept is expected, thou h perhaps not obvious as the polymer material investigated has a high modulus $10.5 GPa), high strength (300 MPa), and 

high glass transition temperature (%4OO0C). 

Polymer films of BPDA-PDA (bisphenylenedianhydride-p-diamine) were prepared on silicon substrates by spin casting from a precursor solution of poly(amic 

acid). The precursor films are subsequently heated to temperatures from 200 to 

400'C in order to create the polyimides. Films prepared in this way show that the 

structual order present is dependent upon the imidization conditions (figure 1.) 

Rubbing parameters which have been investigated include rubbing distance, applied load, and film thickness. In each of these classes, a critical value exists above 

which changes in the structural characteristics of teh scattering profiles are observable. The existenc of these threshhold values support the high probability of 

yielding as the primary mechanism of deformation. Since the applied force is not 

the "observed force" at the polymer surface, it is necessary to show how the results 

observed by GIXS are consistent with the yielding model in a free standing polymer 

film. This task remains to be completed at this time. 

8°.0'2 

E 

P 

- 

IO.008 

A0.004 

0.4 1.12 1.84 2.58 3.28 4 

Q LA-'] 

Figure 1. Effects of imidization temperature on the scattering profiles observed for 

BPDA-PDA films on Si(100) substrates. The samples were heated for 3 hours at 

the temperatures indicated in the inset. 
~ 1 Resonant Raman Scattering at the Fe Klezge in Fez03 * I x211 

W. A. Caliebe, C.-C. Kao, and J. B. Hastings (NSLS) 

Resonant Raman scattering (RRS) is a two-photon scattering process where the 

energy of the incident photon is tuned through the absorption edge and the fluorescence is analyzed. This method allows to seperate different electronic excitations 

in the absorption edge because the energy resolution is not dominated by the core 

hole life time of the deep lying core hole. 

The 

absorption edge is shown in fi 1. Observing the fluorescence for these three different incident energies (see fig.27 reveals three different transitions which are clearly 

seperated. The first two transitions are excitations into empty 3d-orbitals. The 

3d-orbitals split in an octahedral field into the eg and tzs orbitals which are seperated by approximately 1.5 eV. Excitations into these orbitals result into relatively 

sharp peaks at hwl - Rwz=705.5eV for hwl=7113.4eV and Rwi - hwz=707.2eV 

for hwl=7114.8eV. These narrow peaks are also observed as small steps in the 

scan for hw1=7118.8 eV. This last scan measures excitations into states with s- and 

p-character. Calculations to explain these data are planned for the future. 

The experiment has been done at the Fe K-edge in Hematite (FezOs). 

1.25 . 

- 

rn 

t 5 1.00 t 

4 

0.25 

7100 7120 

6 0.04 

:: 0.02 * 

7110 7115 7120 

Energy [eV] 

7140 7160 7180 

Energy [eV] 

1 7200 

40 

7 30 

E 

0 0 N 

Y B 20 

c 2.. 

c (Y - 

= 10 

0 

700 705 710 715 720 725 730 

Energy loss [eV] 

Figure 1. Fe K absorption edge in 

Hematite. The absorption spectrum 

starts with some weak fine structure at 

E=7110eV (see the inset), which corresponds to excitations into empty 3dlevels. This absorption has quadrupol 

character and is thus very weak. This 

structure is followed by the dominating 

"white line" at eV, which is the 

absorption into empty 4p-levels. 

Figure 2. €honant &man scattering of 

Hematite at h~1=7113.4 eV (open circles), hw1=7114.8 eV (full circles) and 

Rwl=7117.8 eV (rhombs). The error bars are given by small vertical lines or 

are smaller than the symbol size. * This work was supported by us DOE 

grant DE-AC02-76CH00016 

High Energy Resolution Beamline * I x21 

W. A. Caliebe, C,-C. Kao, D. P. Siddons, and J. B. Hastings (NSLS) 

The wiggler beamline X21 is dedicated for inelastic X-ray scattering with high 

energy resolution. In order to obtain an energy resolution of better than 0.3eV a 

new monochromator and a toroidal mirror have been installed. 

A high energy resolution is usually obtained using a dispersive set-up of two 

crystals. The problem of this set-up is that the beam moves for energy changes. 

This problem has been solved using two double crystal monochromators which have 

one asymmetric and one symmetric reflection. The sequence of the reflections is 

asymmetric-symmetric-symmetric-asymmetric. The two symmmetric reflections in 

the middle have no influence on the resolution. Their only purpose is to keep the 

exit of the beam fixed. 

The asymmetric reflections have miscuts of 16O and -16" respectively. These two 

reflections are aligned dispersively resulting in a resolution of AE=220 meV. The 

monochromators are directly behind the source because a focussed beam coming 

from a mirror would worsen the resolution. 

The mirror is a Zerodur glass with bending radius R=l km and r=42 mm. The 

mirror is coated with Platinum in order to reject higher harmonics. The mirror is 

located in 16 m from the source and 8 m from the sample. The focus at the sample 

is 500x300 pm'. The flux at the sample is 22L~1010photons/s. 

45001 T I 

,3000 - 3, 

f 

.s 

1500 - 

0 0 measurement . 

i 

0 

7908.0 7908.5 7909.0 7909.5 

Energy [.VI 

maGmum is AE=270eV which is the 

convolution of the monochromator and 

* This work was supported by US DOE analyser widths. 

grant DE-AC92-76CH00016. 
46 

F I Inelastic Xray Scattering from Single Crystal Sodium I x21 I 

P.C.Chow and S.C. Moss (U. Houston), C.C. Kao and J.P. Hill (BNL) 

In condensed matter physics, unlike high energy physics, we know the identity 

of the particles of interest (electrons) and their interactions (Coulomb). What is 

of difficulty is handling the consequences of the many-body interactions in order to 

explain the physical properties of a system. Inelastic xray scattering data, S(q,w), 

contain information on the time and space correlations of the electrons of the system. 

Because of the weak intereaction of xrays with electrons, inelastic xray scattering 

is an ideal method for measuring many-body effects in solids. In our initial ex- periments on X21, our approach is to study the simple metal free-electron metal 

sodium. We have prepared a single crystal of Na, 11 mm in diameter, and sliced the 

crystal to produce a 2 mm thick slab with mosaic spread of 0.2". The spectrometer 

analyzer was a Si(555) spherically bent cyrstal, set to accept 9839 eV xrays. Our 

monochromator consisted of 2 pairs of Si (220) crystals. The inelastic spectra were 

taken by changing the incident energy, yielding energy loss data. The overall energy resolution was about 1 eV and data was taken in transmission geometry. For 

K=KF, a peak in the spectrum 7 eV away from the elastic line was clearly seen, 

which corresponds to the plasmon collective excitation of the conduction electrons 

in Na. For K=~KF, see Fig.1, the broadening of the spectrum is attributed to single 

particle excitations. The feature at 30eV corresponds to the Na L edge. In other 

systems, corresponding spectra shows a double peak structure, whose cause is still 

to be determined. Our data show that this feature is absent in Na. Future studies 

will concentrate on collecting data in high symmetry directions of the single crystal. 

I High Resolution KCY Emission Studies of Iron(II1) Porphyrins x2 1 

K. A. Daly (U. of Michigan), W. Caliebe, C.-C. Kao (NSLS) and James E. PennerHahn (U. of Michigan) 

High resolution x-ray emission has been used to investigate hyperfine electronic 

structure of transition metal complexes. Electronic interactions that were previously detectable only with polarized measurements on oriented crystals have been 

resolved using isotropic samples. X-ray emission intensity was collected as a function of excitation and emission energy producing a three-dimensional surface plot. 

Data were collected in the excitation regions of Is + 3d, Is + 4p and other transitions in the edge area. The emission region data were collected in the area of Ka 

emission (2p + Is) for [Fe(III)(octaethylporphyrin)(THF)~]ClO~. Each iron exists 

in a Jahn-Teller distorted octahedral environment and is in a high-spin state. The 

data display information on d-orbital degeneracy, atomic orbital occupancy, coordination environment and electronic interactions. Figure 1 shows representative Ka 

emission spectra collected at various points before and on the K-absorption edge. 

The Ka lines of the three excitation energies show different peak maxima energies, a slight change in Ka1:Kaz peak height ratio, and a significant peak width 

fluctuation. These changes are all indicative of changes in the overall spin and 

angular momentum of the system. Calculations performed with Frank de Groot 

of the University of Groningen show the effects are not predicted through simple 

continuum state multiplet calculations in conjunction with resonant Raman theory. 

Interpretation of a complete data set, to be collected at a later date, should give 

more detailed information on the electronic structure and orbital occupancy of the 

molecule. 

No Single Crystal 28=20° 

,125 

8 1.00 

D 

0 

- 

E 0.75 . 

a 

" 

$0.50 - 

- 0.25 

I 5 IO 15 20 25 N 35 

herqy Loss ($4 

Figure 1. Inelastic scattering of single crystal Na in the [211] direction at K=%KF 

1 

I 6385 6390 6395 61w 6405 6410 6415' 

____~ Energy ~~~ 

Figure 1. Ka emission spectra of [Fe(III>(OEP)(THF)~]C10~. The Kal and Ka2 

emission lines were collected at excitation energies of 7112.5 eV, which is in the 

pre-edge region, 7120 eV, which is low on the absorption edge, and 7134 eV, which 

is at the maximum of the absorption edge. The spectra are normalized to the same 

peak height. 
I Near-Threshold Behaviour of the Cu Kal,~ Emission Spectrum I x21 I 

M. Deutsch, 0. Gang, M. Fritsch (Bar-Ilan U., Israel) and C.C. Kao (BNL) 

The Cu Kcrl,z emission spectrum was studied by photoexcitation near the K edge, 

using the new four-bounce monochromator/focussing mirror combination, and a 

spherically bent Si(444) analyeer.The measured FWHM resolution of the system 

was -0.45 eV at an incident energy of Eincident ~9 keV. 

Three regimes were observed with increasing Eincident. The first, Eincident < 

8981 eV, is just below the edge at 8981 eV. The linear peak shift, the fast intensity 

decrease and the line shape distortions, due to the Resonant Raman Effect, are all 

clearly observed as shown in Fig. 1. 

The second regime, 8981eVIEinCid,,t18995 eV is above the K edge, but still 

below the threshold for ad-spectator transitions which require an aditional 10-15 

eV photon energy to create the initial hole state. Unlike for higher energies, 

the lineshape here is a pure lorenteian, as shown by the solid line in Fig. 2. 

In the third regime, &,&dent 2 9000eV, ad-spectator transitions are energetically 

allowed, and contribute with increasing intensity to the lineshape. As shown in Fig. 

2, these contributions are most pronounced on the low-energy side of the Kai 

line. This study then demonstrates clearly that the well-known asymmetric lineshapes of the emission lines of the iron-group elements originate in the 3d-spectator 

transitions. While the analysis is still in progress, the results so far indicate that 

the intensity of the ad-spectator transitions increase smoothly from threshold and 

saturates at -100 eV above it, indicating a shake-off origin for these transitions, as 

we also found recently for the Kaj,+ satellites of copper'. 

1. M. Deutsch, 0. Gang, K. Hamalainen and C. C. Kao, Phys. Rev. Lett. 76, 

2424 (1996). 

, -7 , I 

0.020 - ~~~ 

D 

- 0.015 ~ 

I 

- 0.010 L 

804.0 804.4 804.8 805.2 805.6 

Eemisrion [xlo' eV1 

x2 1 Resonant and Non-resonant Inelastic X-ray Scattering Studies of Electronic Excitations 

J.P. Hill, C.-C. Kao and W.A.C. Caliebe (BNL) 

Inelastic x-ray scattering offers unique capabilities in the study of electronic excitations, allowing regimes of momentum and energy transfer to be probed that are inaccessible with any other technique. In simple metals, this opens up the important regime of wave-vectors around 2k~, where dramatic departures are seen 

from the simplest many-body theory, the RPA. The origin of these discrepancies 

has been the source of some considerable debate. One explanation is that it is 

higher order corrections to the RPA that are relevant. The second view holds that 

band structure effects are significant. By studying the excitation spectrum in both 

liquid and solid phases, the influence of the LRO may be determined experimentally. Following on from our earlier work, on liquid Li and Na, we have studied Al, 

which is of particular interest as a nearly-free-electron metal, yet displays significant orientation-independent fine structure in the response. As shown in Fig. 1, 

the response in the liquid phase is very similar to that of the solid, suggesting that 

the overall shape of the response is not determined by the LRO. However, the fine 

structure evident in the solid phase is much reduced in the liquid phase, demonstrating unambiguously that it results from the LRO and is not a many-body effect. 

These results support our earlier conclusions from the Li and Na data. 

In a separate body of work, we have carried out resonant inelastic scattering 

studies on NdzCu04, the parent compound of a high-Tc family. In these experiments, the incident photon energy is tuned through the Cu K-edge, and the energy 

loss spectrum is studied. In the vicinity of the K-edge, a resonant feature is seen with a constant energy loss of - 6 eV. It is speculated that this is a charge transfer 

process, involving the Cu site and the Oxygen ligand. 

AI Q=2q, 

7- 

204080 

0 20 &el,w 80 loo 

Energy Loss (eV) 

Figure 1. 
t"j 

P 

Inelastic X-ray Scattering Spectroscopy in SrzCuOZClz x21 

E.D. Isaacs, P. Platzman (Bell Labs), C. Burns (Western Michigan U.), P. Abbamonte, M. Klein (U. of Illinois), and L. Miller (Ames Lab) 

The electronic structure of the cuprate superconductors continues to be the focus 

of intensive study because of the possibility of gaining insight into the mechanism of 

high-Tc superconductivity. Since superconductivity evolves continuously from the 

insulator by doping, the electronic structure of the parent insulators is of particular 

interest. Optical studies (q=O k') show that the lowest lying excitation in all of the 

parent high-Tc insulators is at about 2 eV. These studies have also shown a transfer 

of spectral weight upon doping from the feature at 2 eV to a mid-gap excitation at 

lower energies. The exact nature of of these excitations are not well understood. 

Characterization of the excitations at intermediate energies is important for theories on high-Tc in order to test the various model Hamiltonians. 

We have studied the electronic excitation spectrum at in the parent high-Tc 

coumpound SrzCuOzClz with 0.5 eV energy resolution. Our spectra reveal a feature 

at 2 eV, near the insulating gap observed optically, and an optically forbidden 

transition at about 5.5 eV (see figure 1). We assign the 2 eV excitation to a charge 

transfer from an occupied oxygen p-band to an unoccupied copper d-level. The 5.5 

eV excitation we ascribe to an intra-d-band transition which may be directly related 

to the Hubbard U. We have also measured the momentum transfer dependence along 

two directions in the Cu-0 plane. Along the (210) direction the charge-transfer gap 

disperses weakly giving a band width of about 0.5 eV. In contrast, along the (110) 

direction there is a feature that disperses by as much as 1.5 eV. These results are consistent with very recent electron energy loss spectra taken in the same material. 

They ascribe the anisotropic dispersion to the anisotropy of the antiferromagnetic 

background and the fact that an electron-hole pair can move through the lattice more easily than a single hole. 

These studies have been made possible by recent advances at beamline X21 and our development of spherically bent analyzers. The main advance at X21 is the new monochromator with 0.2 eV energy resolution. With further improvements 

expected at X21, in particular larger horizontal accpetance, we expect to be able 

to reduce our collection times by a factor of two to four. The scan shown in figure 

1 took about 15 hours to obtain. 

202468 

Energy to= (eV) 

Figure 1. Inelastic x-ray scattering in the parent high-Tc insulating compound 

SrzCuOzClz at a momentum transfer, q=0.8 A-'. This scan was taken at beamline 

X21 with an energy resolution of 0.5 eV with q along the [210]. 

X-Ray Resonant Raman Scattering in NiO: Resonant Enhancement 

of the Charge Transfer Excitations * 

C.-C. Kao, W. A. Caliebe, J. B. Hastings (NSLS), and J.-M. Gillet (U. Maine, 

France) 

We report the results of a hard x-ray high resolution XRRS study of NiO, one 

of the prototypical Mott-Hubbard systems. Inelastic x-ray scattering spectra near the NiO valence band emission energy were measured as the incident photon energy 

scanned through the Ni K absorption edge. 

A new spectral feature, which is not observed for incident energies far away 

from the absorption edge, appears in the inelastic scattering spectra in addition 

to the valence band emission spectrum. While the average energy of the valence 

band emission spectrum remains constant, the average energy of this new feature 

disperses linearly with the incident photon energy. The average energy transfer 

of this new feature is about 6.5eV, close to the recently reported anion-to-cation 

charge transfer energy of NiO. 

The new loss featureand its resonant behavior are interpreted in terms of a cluster 

model or the Anderson impurity model. 

x2 1 

2.0 

- 1.5 c c

3 

4 

25 1.0 

& 

e! 

- 0.5 

v) c 

c 

0 

8310 8320 8330 8340 8350 8360 8370 

Photon Energy [eV] 

Figure 1. a) Ni Kabsorption spectrum of NiO; b) normal valence band x-ray emission spectrum of NiO; c) Resonant inelastic x-ray scattering spectrum of NiO obtained with the incident photon energy tuned to the main peak of the absorption 

spectrum (a) 

* This work was supported by US DOE grant DE-AC02-76CH00016. 
1 Soin-Polarized Mn K-Edge Measurements of Doped LaMnOs I x21 I 

T. A. Tyson (NJIT), C.-C. Kao, W. Caliebe (NSLS), and J. J. Neumeier (FAU) 

Recent work by von Helmolt et ai. [l], revealed that Lal-,A,MnOa (A=Ca, 

Sr, ... ), exhibits large magnetoresistance values at low temperature and high fields 

(60 kOe and 77 K). The large change in conductivity is concomitant with a insulator 

to metal transition. No detailed studies of the changes in the Mn 3d spin density 

with temperature or doping have been performed. 

The Mn Kp spectrum provides a direct method to probe the total Mn 3d unpaired 

spin (S) and effective charge density on the Mn sites. Temperature dependent Kp 

emission spectra are shown below (Fig. 1) for the 30% Ca system measured above 

and below T,= 250 K. There is a reduction in intensity of the main line above 

the Curie temperature. Hence S may be changing with temperature. The effective 

charge on the average Mn site is not changing, however. It is possible that the degree 

of hybridization i.e. the mixing of the Mn 3d and 0 2p changes with temperature 

in concert with local structural changes [2] previously found. Models of the CMR 

materials must incorporate these effects. Detailed analysis of Mn Kp spectra will 

assist in determining the essential physics and correct Hamiltonian (see [3]) for this 

system. 

R. von Helmolt et aZ., Phys. Rev. Lett. 

T. A. Tyson et al., Phys. Rev. B, 53, 13985 

A. J. Millis, P. B. Littlewood and B. I. 

references therein. 

Rev. Lett. 74, 5144 

(1695). 

E 

2 

w 0 

Q) 

Q 

(I) 

C 

0 

v) 

v) 

w 

> 

.- 

.- 

E 

4 

X 

2.5 

2 

1.5 

1 

0.5 

0 

6486 6488 490 649 6494 6496 

Energy (e4j 

Y 

k' c-l Figure 1. The Mn Kp spectrum of 30% Ca doped LaMnOa measured at 80 K (solid 

line) and room temperature (RT = 300 K, dotted line). 

X22A Real-Time X-ray Scattering Study of Sputter-deposited LaNiOs 

Thin Films on Si Substrates 

H. Y. Lee (SRRC, Taiwan), C. H. Lee (National Tsing Hua U., Taiwan) and K. S. 

Liang (Exxon) 

LaNiOs (LNO) is a perovskite-type metallic oxide having the same type of structure as that of ferroelectric films, which provides a good crystallographic com- patibility with the ferroelectric layers and can be used as the bottom electrode 

in fabricating the integrated ferroelectric capacitors on Si. Recently, highly (100)- 

oriented LNO films on different substrates by radio frequency magnetron sputtering 

method was prepared successfully' . In a previously study', an intermediate layer 

of about 10 nm was found at the interface between substrate and overlayer. This 

particular layer of unidentifiable structure is of great interest in the understanding of the growth mechanism of LNO thin films and the subsequent development of 

highly textured ferroelectric thin films. In this work, real-time x-ray reflectivity and 

diffraction measurements under in-situ sputtering conditions were applied to study 

the growth mechanism of LNO on Si substrate. The experiment was performed at 

the nearly commissioned beamline X22A using 10.4 KeV phptons. Samples were prepared via a 6 kW/cm2 rf magnetron sputtering system under 10 mTorr of 02 

and Ar mixture gases. Different structures of thin films were found under different 

growth conditions. However, we were able to tune sputtering conditions to simulate 

the growth of the special structure of our interest. In a particular growth condition, our results clearly identify an intermediate layer which grows in the first 10 min of 

deposition, as observed from the reflectivity curves shownat left. The in-situ x-ray 

diffraction patterns (at right) show that this intermediate layer is an amorphous 

layer. Sequential growth measurements show the development of the film texture in 

details. As shown, a significant increase of 100) diffraction intensity relative to that 

structure is developed on the top of this intermediate 1ayer.Detailed data analysis 

is in progress. The authors would like to thank the hospitality and help from Dr. 

B. Ocko, Ms. J. Wang and Mr. S. Coburn at X22A beamline. 1. C.C.Yang, et.al., 

Appl. Phys. Lett., 66, 2643 (1995). 2. H.Y.Lee and T.B.Wu, J.Mater. Res. 

of (110) as the deposition time increase, in 6 icating that the preferred (100) textural 

Figure 1. 

0 012 

3 

- m 0008 

9 

- 

0 004 

0 000 20 30 40 

20 (degree) 

Figure 2. 
P 

F 

X22A Structure Analysis of the Cu Metallization of A1N Using the Poly01 

Method * 

L. J. Martinez-Miranda (U. of Maryland), G. M. Chow, L. K. Kurihara, D. Ma 

and P. E. Schoen (NRL) 

The poly01 method was used to produce the electrodeless Cu metallization of 

A1N substrates. This method results in the formation of a nanostructured Cu 

powder. The substrates were placed in the polyol solution and brought to reflux 

for times ranging from 15 to 60 minutes. For each time, the substrates were placed 

horizontally near the bottom of the solution, or vertically dipped in the solution. We 

used a combination of small angle xray sacttering and grazing incidence asymmetric 

Bragg scattering (GIAB) to characterize the structure evolution of the deposited 

films. 

Films deposited at short reflux times (15 minutes) did not show evidence of Cu 

metallization. In addition, we observed a difference in the small angle signal between 

horizontally depososited films and vertically deposited films, which became more 

apparent the longer the reflux time. The figure below shows a comparison between 

the small angle signal for the vertically and horizontally depostied films, refluxed 

for 45 minutes. There is a signal in the 4nm range for the vertically deposited film 

at glancing incidence. The abscence of such a signal for the horizontally deposited 

film can be attributed to the presence of copper oxide in this film. Although the 

oxide is present in both vertical and horizontal films, our GIAB measurements show 

that the latter have a large concentration of oxide near the surface of the film. This 

layer is polycrystalline in nature, but does not consist of nanometer size building 

blocks. A more detailed analysis of these films is in progress. 

0.05 - '0. 

- 0. 

20.04 - 4 0.03 - ?@?? 

il I 1.5 3. 0 

tth [degl 

' ' ' ' ' ' 

Figure 1. Comparison of the small angle signal at glancing incidence for the V-45 

(open circles) and H-45 samples (closed circles). 

* This work was supported by an internal UMD Grant and by the NRL 6.2 and NRLTEW programs on Nanostructured Materials. 

~~ 

In situ Structural Characterization of Lithium-ion Battery Elec- X27A, 

trode Materials 1 X22A/ 

T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. %ng, J. McBreen (BNL - DAS), 

M.L. Daroux, and X.K. Xing (Gould Electronics) 

The low cost, high operating voltage, and low toxicity of Li,Mnz04 make it a 

good candidate for use as a cathode in lithium-ion battery cells. However, this 

material can not be reproducibly manufactured yet, a problem which arises in large 

part because the structural properties of Li,Mnz 04 vary considerably with synthesis 

conditions. The structure also changes during the lithium intercalation process, so 

studies of operating battery cells may help resolve some of these issues by allowing one to separate structural properties dependent on the lithium content from those 

dependent on the underlying manganese-oxygen skeleton. We report here some of our initial results from combined electrochemical and synchrotron x-ray scattering 

measurements performed on operating cells. 

X-ray diffraction experiments were performed at X27A with 24.5 keV photons 

and at X22A with 10 keV photons. Cells of approximate dimensions 2cm x 3cm x 

0.5mm were manufactured by Gould Electronics, sealed at the factory, and mounted 

in a transmission geometry on the spectrometer with no modzficatzons. Even though 

the x-ray beam must penetrate through the external case, electrolyte, and binding 

materials in this geometry, the high flux of a synchrotron allows data with reasonable 

counting rates to be taken [I]. 

An example of the structural information that can easily be obtained with this 

technique is illustrated in the right figure. Here 26' scans taken through the 

Li,Mnz04 (333), (511), (440), and (531 peaks are presented (the (440) peak is 

partially obscured by an aluminum pea li at 20.3'). The data have been offset 

from each other for clarity, and they show the evolution of these peaks as the cell was discharged from 3.90 volts to 2.94 volts. The data indicate that expanded and 

nonexpanded phases coexist over a certain range of voltages. Other structural properties such as this two phase coexistence and their relationships to electrochemical 

properties are discussed in reference [2]. 

T.R. Thurston et al. Appl. Phys. Lett. 69, 194 (1996). 

N.M. Jisrawi et al. J. Electrochem. SOC., submitted. 

Figure 1. 26' scans (x=0.501a) showing the evolution of two-phase coexistence as 

a battery cell is discharged. 
In Situ Measurements of Texture and Phase Development in Bi- x27~, 

2223 Silver Cladded Superconducting Wires 1 X22A( 

T.R. Thurston, U. Wildgruber, N.M. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC Corporation) 

During the past two years, techniques for characterizing silver-cladded Bi-2223 

superconducting wires with hard x-rays have been developed at X27A [l]. In order 

to penetrate through the silver cladding, the incident x-ray energy is tuned just 

below the silver edge at 25.5 keV. The samples are also examined in a transmission 

geometry, so bulk structural properties are probed. Using these techniques, we have 

previously shown in ez situ experiments that both the c-axis alignment (texture) 

and Bi-2223 phase development have large effects on the current carrying capacity 

of fully processed wires. 

More recently, we have begun experiments where the phase and texture development of Bi-2223 are monitored as it grows from precursor materials (typically 

Bi-2212 plus CuO etc.) within its silver sheath. This in situ work has been done 

in an x-ray compatible furnace with temperature stability of 0.2"C at 83OoC. The 

figure below shows the phase and texture development of a typical sample during 

the first 50 hours of processing. The solid line represents the temperature program 

followed. The furnace was ramped from room temperature up to 600°C, held at 

6OO0C for 6 hours, ramped again from 600°C to 840°C over a period of 12 hours, 

and then held at 840°C. Bi-2223 phase content (represented by the open triangles) 

began to develop only after reaching 840OC. On the other hand, the weighted average of the Bi-2212 and Bi-2223 texture, represented by the (200) FWHM (closed 

circles), improved significantly while the sample was being ramped from 600°C to 

84OoC. Thus, the texturing and phase development mechanisms are largely decoupled. The implications of this and many other in situ experimental results are discussed in reference [2]. 

T.R. Thurston et al. J. Appl. Phys. 79, 3122 (1996). 

T.R. Thurston et al. J. Mat. Res., submitted. 

10 20 30 40 50 

haoling llms (houn) 

Figure 1. Time Dependence of the Phase and Texture Development in a Multifilament Wire. 

Anomalous Lattice Expansion of an Underpotentially Deposited Ag 

Bilayer on Pt(ll1) 

J.X. Wang, R.R. Adzic, and B.M. Ocko (BNL, Physics) 

X22A 

Incommensurate metal monolayers and bilayers are usually compressed compared 

to the bulk solids because of the reduced coordination at the surface. Here, we show 

an unusual example of lattice expansion in both, lateral and vertical directions in a hexagonally close-packed bilayer. The bulk lattice constant of Ag is larger by 4 

percent than that of Pt. At high underpotentials, Ag forms a commensurate (1x1) 

monolayer on Pt(ll1). Near the bulk deposition potential, a second Ag layer is 

deposited which causes restructuring of the first adlayer. The two mutually com- mensurate Ag adlayers form a hexagonal Ag bilayer which is rotationally aligned 

but incommensurate in lattice spacing with the Pt substrate. As shown in Fig. 

la, the diffraction peak (dashed line) is centered at 0.94 along the (0,K) axis. At 

potential 20 mV negative of the bulk deposition potential, an additional peak appears at 0.96 (solid line) which corresponds to the bulk Ag lattice spacing. These 

data demonstrate that the in-plane lattice spacing of the Ag bilayer is expanded 

by 2.1 percent compared to the bulk Ag. From analysis of the specular reflectivity 

(Fig. lb), and the surface rods at (0.94,0.94) and (0,0.94) (Fig. 2), we find that the 

Ag-Ag layer spacing is 2.56 a which indicates an expansion of 8.4 percent from the 

layer spacing of bulk Ag(ll1). These unusual lattice expansions are likely due to 

the charge transfer from the Ag bilayer to the Pt substrate which has been reported 

from surface stress and x-ray photoelectron spectroscopic measurements. Other as- pects of this system, such as, surface alloy formation and fcc/hcp stacking of the 

second layer, will be discussed at a later date. 

8000 

4 6000 

v 8 4000 

,% 2000 

- =o 

a, 

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x 

0) 

c 

0.92 0.94 0.96 0.98 

K (units of b*) h 10-3 

$ 10-5 

- P10-6 

f 10-7 

5 

& IO-^ 

a 

2 10-4 

._ 

1 

c 

0123456 

L (units of c') 

Figure 1. 

0 (0.94,0.94,1) 

-the best fit 1500 

2ooo 

0 0.5 1 1.5 2 2.5 3 x 

E 

.- c 

L 

2 -2000 

% 1000 

73 

3 1500 P rn 

- 

500 

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L (units of c*) 

Figure 2. 
4d c--L 

X22B Effect of Metallic Caplayers on the Magnetic Structure of Thin 

Cr(OO1) Films * 

P. Bodeker and H. Zabel (Inst. fur Experimentalphysik/Festkorperphysik, Ruhr-U 

at Bochum, Germany) 

We have investigated the effect of 20 A thick metal cap layers on the spin structure in 2000 A thick epitaxial Cr(001) films. In bulk Cr there exist three equally 

populated domains with SDWs propagating along the three {001}-directions in the 

bcc lattice. Our previous measurements on plain Cr(001) films as well as on Cr films 

capped with a thin Fe layer have shown a strong redistribution of the occupation of 

these three domains. In the case of the Fe capped Cr film the SDW becomes completely re-oriented with a single Q-vector now laying in the film plane. We have now continued our investigation of possible proximity effects between magnetic cap layers and Cr SDWs, as well as effects due to hybridization and epitaxial strain induced 

by the cap layer. To this end we have chosen ferromagnetic Co and paramagnetic 

Pd cap layers. In the left panels of Fig. 1 we show the incommensurate satellite 

peaks at the Cr(Ol1) position and around the Cr(002) reflection. Between the left 

and right panels the scattering geometry and scan directions are sketched. For Co on Cr only SDWs occur in the K-direction similar to the situation already observed 

for Fe on Cr. Pd, although not ferromagnetic, exhibits a large Stoner enhancement 

factor. Our results for the SDWs in the Pd/Cr sample are shown in the right panel 

of Fig. 1. Here satellites in both scan directions can be recognized, indicating that 

the respective SDWs propagate in the film as well as perpendicular to it. Thus 

here only a partial re-orientation of the CDW/SW occurs. The re-orientation of the 

SDWs by ferromagnetic cap layers may be understood in terms of frustration effects 

induced by steps and kinks at the interface of monatomic height which disturb the 

interlayer exchange coupling between the FM layer and Cr. This frustration is also 

expressed in a short coherence length of the SDWs and in distorted line shapes. In 

contrast, the behavior of the SDWs in the Pd/Cr sample is completely different. 

The satellite peaks are narrow and sharp indicating well defined SDWs with much 

longer coherence. In fact, in Pd/Cr the satellite peaks are much better defined 

than in pure Cr layers of comparable thickness. We suggest that the Pd cap layer 

becomes exchange polarized by Cr, which in turn, acts as an amplification of the 

SDW in the Cr layer. 

Figure 1. Scans around the Cr(Ol1) and Cr(002) Bragg-reflection through possible 

positions of satellite reflections in a 2000 A Cr(001) film capped with 20 A details see text. 

* Supported by the DFG through SFB 166 

I X ray Reflectivity Study of Gold Colloid Monolayers I X22B I 

C.J. Clarke, R.B. Lennox (McGill U), B.M. Ocko, D. Nguyen(BNL, Physics), M.H. 

Rafailovich, J. Sokolov and Z. Li (SUNY, Stony Brook) 

The structure of Langmuir films of gold colloids, consisting of 2nm diameter gold 

particles coated with Cy4 thiol chains, was studied by X ray reflectometry and grazing incidence diffraction, over a range of compression and surface pressure. Figure 

1 shows the isotherm, and figure 2 shows the specular reflectivities measured at the 

points marked. At large values of the area per particle (i.e. low surface pressure) 

the reflectivity indicates a single layer, approximately 1.5nm thick, corresponding 

to a monolayer of the gold colloid. The roughness of this layer is about lnm, which 

probably arises from polydispersity in the size of the gold colloid, and incomplete 

monolayer coverage at large areas (islands of the colloid film can be seen on the 

water surface until a certain compression is reached). At an area of approximately 

6.5nm2 per particle, a transition occurs. This is seen as a steep rise in the isotherm. 

Fringes appear in the reflectivity, indicating a change in thickness. The data can be 

interpreted by a model, consisting of water, a 2.5nm gold layer, a 1.5nm hydrocarbon layer, and a second 2.5nm gold layer. Thus a monolayer to bilayer transition 

has taken place. In the bilayer, the centre to centre spacing of the gold layers is 

4nm. As the layer is compressed further, the amplitude of the fringes increases, 

indicating that more of the film is being converted from monolayer to bilayer. 

The in-plane structure of the layers was studied with grazing incidence diffraction, at the same points on the isotherm as the specular reflectivity. In each case, a 

diffraction peak was observed at an angle of 2.9". This corresponds to an in plane 

spacing of 3.8nm, between the centres of the gold particles in good agreement with 

served, and the peak is fairly broad. This indicates that while there is a constant 

nearest neighbour spacing in the layer, there is no long range order. The intensity 

of the peak drops sharply at the point where the monolayer-bilayer transition occurs, and the peak width correspondingly increases. This suggests that there is no correlation in the position of the particles between the two layers. 

Further experiments have also investigated the effects of temperature and alkyl 

chain length in this system. 

the 4nm from specular reflectivity of the bilayer). No hig 6 er order peaks are obFigure 1. Surface pressure - area isotherm for the gold colloid. The points 

indicate the ions where the reflectivity 

was measured. Features in the isotherm, can be indentified with changes in the 

structure of the layer with the aid of 

techniques such as reflectivity. 

1 

0 01 0.2 0.3 0.4 0.1 

qlX' 

Figure 2. The specular reflectivites corresponding to the points marked on the 

isotherm in figure 1. The fringes arise 

when the film goes from a monolayer to 

a bilayer. 
I Temperature Dependent Surface Structure of Liquid Mercury I X22B I 

E. DiMasi, 0. M. Magnussen, B. M. Ocko (BNL, Physics), M. Deutsch (Bar-Ilan 

U., Israel), H. Tostmann, 0. G. Shpyrko, M. J. Regan, and P. S. Pershan (Harvard) 

The free surface of a liquid metal presents a special challenge to theory. Both the 

rapid change in density at the interface and the presence of the free electron gas are expected to contribute to the atomic structure at the surface. One prediction 

is that atomic layering should occur at the liquid-vapor interface, and this has 

recently been observed in surface x-ray scattering studies of liquid gallium and 

liquid mercury. One unresolved issue is to what extent such intrinsic layering may 

be independent of thermal fluctuations. 

We have extended x-ray reflectivity measurements of the Hg surface from room 

temperature to just above the melting point of -38.9 ‘C. The sample is contained 

in a glass cell in which the Hg sample can be poured under a passivating hydrogen 

atmosphere. A small liquid nitrogen cryostat and cold finger are suspended underneath the sample cell. The apparatus is supported on an active vibration isolation 

unit mounted directly on the Harvard/BNL liquid surface spectrometer. 

Fig. 1 shows the reflectivity R(qz) for qe up to 2.5 A-’, for several different 

temperatures. At room temperature (dashed line), the reflectivity is attenuated 

faster than that predicted by Fresnel theory for a flat Hg interface (RF, solid line), 

indicating a surface roughness of order 1 A. The broad peak in the reflectivity at 

q M 2.2 kl, emphasized in the plot of R/Rp (Fi . 2), indicates atomic layering 

close to the surface. As the temperature is reduced ?symbols), the amplitude of the 

peak increases substantially, demonstrating the reduced effect of thermally induced 

disorder on the surface layering. 

100 , 7- 

Fresnel 

Hg, room temperature 

t14.7 C 

-22.2 c 0 -36.5 C 

4 

L 53 

! ’ , , ’ , ’ , ’-, 

0 1.6 1.8 2.0 2.2 2.4 2.6 

9, (A-1) Figure 1. Temperature dependence of 

the X-ray reflectivity R(qL) of liquid 

mercury. 

Figure 2. Measured reflectivity normalized to the Fresnel reflectivity Rp. 

I X-ray Reflectivity of Silane Multilayers 

E. DiMasi, B.M. Ocko (BNL, Physics), W. Ke, R. Maoz, and J. Sagiv (Weizmann 

Institute of Science, Israel) 

The assembly of molecules into ordered films on solid substrates is of considerable 

technological interest. Up to now, such multilayers have been produced in a stepwise 

linear fashion, where the topmost layer serves as a template for the next in each 

cycle of the assembly process. 

Recently a novel stepwise exponential growth method has been reported for longchain silane multilayers on Si substrates [l]. Here, additional layers are produced 

by an intercalation process in which each layer within the film acts as a template 

for assembly, so that the entire film is replicated at each iteration. So far these ”self 

replicating” films have been studied by infrared spectroscopy and scanning force 

microscopy, which yield information about the bulk material deposited, molecular orientation, and surface morphology. However, these studies do not probe the 

structure of individual layers in the film. 

We have performed x-ray reflectivity measurements of silane multilayers prepared 

by both self replication and conventional layer-by-layer growth. Our study provides 

direct evidence for the multilayer structure of films obtained by the self replicating 

process. 

The reflectivity R(qz) for 8-layer films produced by both methods is shown in 

Fig. 1. The reflectivity decreases faster at large qe than that of a perfectly flat Si 

interface, indicating a substantial surface roughness of order 5 A. The existence of 

multiple oscillations demonstrates the presence of well ordered layers. The broad, 

weaker peak at M 0.34 A in the self replicated film is due to a bilayer length scale 

which is not produced in the layer by layer process. Measurements on 4-layer films 

show less pronounced oscillations, demonstrating that the thinner multilayers are 

more susceptible to the effects of substrate roughness. 

We are grateful to Dr. K. Ogawa of Matsushita Electric Ind. Co. Ltd. (Kyoto) 

for providing NTS material. 

J. Sagiv, accepted to Nature 

S. Matlis, E. DiMasi, B. M. Ocko, and 

----layer by layer 

qz LA-’] 

Figure 1. X-ray reflectivity R(qz) for 8-layer films grown layer by layer (- - -) and 

by self replication (. . ., offset xlO-’ for clarity). Solid line: Fresnel reflectivity of a sharp Si interface. 
X22B 

Fd 

+ 

a the Gas-Water Interface 

X-Ray Scattering Study of (260-propylamine Adduct Monolayers at 

M. Fukuto, K. Penanen, R.K. Heilmann, P.S. Pershan (Harvard U.), and D. Vaknin 

(Ames Lab & Iowa State) 

We have performed reflectivity and grazing-incidence diffraction(G1D) on Cmpropylamine adduct(C6OPA Langmuir monolayers(LM on water (22'C), contained 

suggestions from previous isotherm (Fig. lb) and reflectivity measurements[l] that 

the LM is homogeneous at A-150A2/molec. For A>150-~160A~/mol. , the LM 

coexists with empty regions that vanish on compression. GID scans (background 

scattering subtracted) are shown in Fig. la. The peak position at -0.42A-I for A= 

180 and 140A2/mol. roughly corresponds to the average nearest neighbor distance 

of -J 15a, which is comparable to the diameter of a C6OPA molecule. 

The widths indicate that at these areas the LM is a 2-D amorphous phase which 

BAM images indicate is solid-like. We believe that this is the first observation of 

the x-ray structure factor for an amoq~hous 2-D LM. The slight shift in the GID 

peak position for 100AZ/mol. is much smaller than would be expected if the LM 

was homogeneously compressed. Fig. 2a shows reflectivity data normalized to the 

Fresnel reflectivity for water. The data for A= 180 and 140A2/mol. can both be fit 

by a single layer model (Fig. 2b, c). The excess electron density in the model for 

180A2 is lower than for 140A2 , consistent with the observed lower reflectivity for the 

inhomogeneous LM. In contrast, the data for 80A2/mol. requires a 2-box model(Fig. 

2d), suggestive of the onset of a second layer. Harvard contribution to this work was supported by NSF-DMR-95-23440 and NSF-DMR-94-00396. Ames Lab is operated 

by ISU for the DOE under Contract No. W-7405-Eng-82. Reference: [l] D. Vaknin 

et al., Langmuir 11, 1437 (1995); M. Fukuto et al., NSLS Act. Rept.(1995) 

W 

in a sealed teflon trough fi d ed with He. Brewster ang l) e microscopy confirmed the 

2.0 

77 I 1.5 .- 

c = 

- 

$1.0 

I 

0 P - 

I 

- E 

-0.5 

0 

I 

I __._.. 

I 

0.3 0.5 0.7 0.9 1.1 

Q,, 

2 

1 

0.5 

CP 

2 0.2 

0.1 

0.05 

0.02 

0.01 

0 0.2 0.4 0.6 -30 -20 -lo O lo 

Qz P-'I 2 [AI 

Figure 1. (a)GID scans for 180(0), Figure 2. R/Rp(a) and elec. density for 

140(sqr), and 100A2((n). (b) Isotherm. 180(o,b), 140(sqr,c), and 80A2(A,d). 

Structure Control of Surface Freezing in Alcohol Melts by Additives 1 X22B 1 

0. Gang(Bar-nan U., Israel), X.Z. Wu(ANL), B. Ocko(BNL), E. Sirota(EXXON), 

M. Deutsch(Bar-Ilan U.) 

Following the discovery of surface freezing (SF) in alkane and alcohol melts', 

we explored the possibility of controlling SF by specific additives. Due to the 

bilayer structure of their surface phase, and ability to form H-bonds by their OH 

groups, alkanols (CnH2,+1OH, denoted C,) were studied first with water and 1,3- 

propanediol (PD as additives. In water vapour environment, the shorter period of 

by a fixed 2.2-2.8 A for all lengths studied, n = 16 - 28. This is attributed to water 

molecules intercalating in between, and H-binding to, the top and bottom layers 

of the bilayer, as found also for bulk hydrated alkanols. A model based on this 

structure (Fig. 1 inset) fits the data very well, as shown in Fig. 1. PD doping also 

swells the bilayer equally. Strikingly, it allows tuning of the surface layer between a bilayer and a monolayer by varying the temperature and PD concentration. Fig. 2 

show a period doubling of curve (a) relative to (b), indicating a bilayer-to-monolayer 

structural transition. The sharp intensity jumps in the inset indicate first-order 

transitions between these phases. These studies demonstrate that structural control 

of surface-frozen layers by judiciously chosen additives may indeed be possible. 

1. X. Z. Wu et al., Phys. Rev. Lett. 70, 958(1993);Eur. Lett. 30, 283(1995). 

the observed mo cl ulations of hydrated C, (Fig. 1) indicates a swelling of the bilayer 

66 67 68 69 70 

Ternperoture [" C] 

' p? a rnonolyer (T=69" C) 

b bilayer (T-68' C) 0.0 

0 0.1 0.2 0.3 0.4 0.: 
X22B X-ray Scattering From Discotic Liquid Crystalline Compounds at 

the Air-water Interface. * 

D. Gidalevitz, 0. Mindyuk, J. Strsalka (U.Penn.), B. Ocko (BNL, Physics) and P. 

A. Heiney (U.Penn.) 

We present the first grazing incidence X-ray diffraction study of Langmuir films 

of discotic compounds at the air-water interface. Such films are the precursors to 

heavily studied Lan muir-Blodgett films; the disc-shaped molecules are expected 

to adopt a face-on &angular) or edge-on (columnar) structure. The subjects of 

our study were two model discotic liquid crystalline compounds: the hexa-(p-ndodecyloxybensoyl) derivative of hexasubstituted azacrown-Ne (compound 1) and 

hexapentyloxytriphenylene (compound 2). The X-ray specular reflectivity (XR) and 

grazing incidence X-ray diffraction (GIXD) measurements were performed at X22B 

beamline at NSLS of Brookhaven National Laboratory at 18’C. Compounds 1 and 2 

were spread from chloroform on the pure water surface displaying areas per molecule 

of 220a2/moZ (compound 1) and 70A2/mol (compound 2). GIXD measurements 

of azacrown compound did not yield any peaks while triphenylene compound yield 

the single peak at q,,=0.45A-1, which corresponds to lateral spacing of 13.90A. 

The specular reflectivity data were analyzed using the two-box model (Fig. 1). The 

model reflectivity curve for compound 1 yielded the face on arrangement of the 

molecules on the water surface, the calculated reflectivity curve for compound 2 

shows the edge on composition. 

COMPOUND 1 COMPOUND 2 

1.2 Fzpf 1.6 

10 14 

1.2 0.8 1 .o 

0.6 0.8 

06 

04 

02 

04 

02 

00 00 

01 02 03 04 05 06 07 01 02 03 04 05 06 07 

(<&) (<(”‘, 

Figure 1. Measured and calculated x-ray specular reflectivities (normalized to Fresnel reflectivity R/RF of the pure water) of compounds 1 (left) and 2 (right) on the 

pure water surface. 

Fd 

* We are grateful to D. Vaknin for the use of his trough. This work was supported by F 

CD 

-J NSF-DMR-92-20668 and NSF-DMR-93-15341. 

An X-ray Photoinduced Insulator-to-Metal Transition in a ColossalMagnetoresistance Manganite 

V. Kiryukhin, D. Casa, B. Keimer (Princeton U.), J.P. Hill, A. Vigliante (BNL), 

Y. Tomioh, and Y. Tokura (JRCAT, Japan) 

Recently manganese oxides of general formula A1-,BIMn03 have captured the 

attention of many physicists and engineers. For some compositions these materials 

undergo magnetic field driven insulator-to-metal transitions (”colossal magnetoresistance”), the physics of which is still poorly understood. Here we report that in 

one such compound, Pr0.7Ca0.3MnO3, a transition from an insulating, antiferromagnetic, to a metallic, ferromagnetic state can also be driven by illumination with 

x-rays at low temperatures (Zt40K). 

At T-200K it undergoes 

metal-to-insulator transition which is associated with charge and magnetic ordering 

of the charge carriers. The charge ordering is accompanied by the lattice distortion. 

The low temperature magnetic structure is antiferromagnetic with small spin canting. The material can be driven back to the metallic state by applying magnetic 

field of about 4 Tesla at low temperatures. This metallic state is ferromagnetic and 

does not show charge ordering. This field induced transition is associated with large 

hysteresis; the material remains metallic after the field is ramped back to zero, but 

reverts to the charge ordered state upon subsequent heating above 60K. 

We report that the insulator-to-metal transition at low temperatures can also be 

induced by the x-ray irradiation. Fig 1 shows that the intensity of the charge ordering reflection decreases continuously with x-ray illumination; no change is observed 

when the beam is switched off. The diminution of the charge ordering is accompanied by the dramatic increase in conductance (more than 6 orders of magnitude, 

see Fig 1). With the x-ray beam off, the system remains in the metallic state for 

many hours without degradation. The x-ray induced conductivity can be annealed 

out on heating above 60K, as shown in Fig 2. This temperature is equal to the 

annealing temperature of the magnetic field induced phase. Also, both phases have 

the same value of conductivity at low temperatures. This close analogy between the 

photoinduced and field induced phases strongly suggests that they are identical. In 

this case themagneticproperties of the sample change dramatically with illumination 

from canted antiferromagnetic to ferromagnetic. To our knowledge, a photoinduced 

antiferromagnetic-to-ferromagnetic transition has thus far not been observed. This 

effect may have applications in x-rap detection and x-rav 1ithoeraDhic patterning of 

ferromagnetic nanostructures. 

X22B 

At high temperatures Pr0.7Cao.3MnO3 is metallic. 

Conductivity IO’ , I 07.;-,,o-‘ - 

,/m* (,at) 

Figure 2. Conductivity measured on 

cooling before x-ray illumination (dotted 

curve) and on heating after illumination 

with x-rays for a moderate amount of 

time (solid curve). 

Figure 1. X-ray exposure dependence of 

the intensity of (2 1.5 0) Bragg reflection 

characteristic of charge ordering, and of 

the electrical conductance, at T=5K. 
tp 

P 

Time Dependence Study of In-Plane Layers in Confined Hybrid X18A, 

Smectic C* Films * X22B 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Huang (U. of Maryland) 

Liquid crytalline materials in constrained geometries exhibit properties that can vary significantly from the bulk properties of the material. Confined hybrid liquid 

crystal films experience a competition between the aligning forces of the bounding 

surfaces. We have studied the in-plane ordering of a smectic C* liquid crystal 

mixture, mx5112, confined between a grated glass substrate and the air surface. 

This compound mixture has a the following phase transitions: sm3 - smC* at 

20.65"C, smC* - smA at 49.5"C and smA - I at 57°C. The corresponding bulk layer 

spacings are: 31.303Afor the smA phase; 29.97Afor the smC* phase; and 31.639A 

for the low temperature Sm3 phase. 

We have observed that the in-plane layer spacing oscillates between values close 

to the smA bulk layer spacing and the smC* bulk layer spacing for samples with 

thicknesses in the range 10 - 20 pm. This oscillation is aperiodic in time, as shown 

in the Figure below. By contrast, thinner films show a slower variation of the value 

of the layer spacing with time, with a 0.6 percent oscillation over a 10 hour period. 

A depth profile study of the films shows that those layers located furthest from 

the glass grating interface show the largest variation in layer spacing over a 48 hour 

period. The layer spacing at the end of this period is approximately 0.3 percent 

larger than the bulk smC* spacing. In contrast, those layers closest to the glass 

grating interface remain close to the intermediate spacing value of 30.6h. 

The time oscillation may be the result of the competition between the two aligning 

surfaces in the smC* film. The in-plane layer at the grating interface favors a smAlike ordering, which relaxes through the thickness of the film. This relaxation is 

enhanced the farther the layers are from the glass interfaces or the thicker the films. 

The time oscillation and depth dependence of the layer spacings affect both the 

temperature and field dependence of these films. We are in the process of studying 

this behavior. 

31 2 - 

31 0 

I ZNB0 

E 30 6 u DO O 

k30 4 0 

0. 

0 

0 i ?n 2 

300- 0 

-1 . ,,.-.., . ....,-! 0 I 02 ai I 2 lo yl loo I time lhourrl 

Figure 1. Open circles: Time dependence of a 15pm and a 13pm film (combined). 

Open squares: time dependence of a 5pm film. 

Time and Depth Dependence Study of the Azimuthal Orientation ~18A, 

in Confined Hybrid Smectic C* Films * I X22Bl 

L. J. Martinez-Miranda, Y. F. Hu, T. K. Misra and M. W. Haung (U. of Maryland) 

Confined hybrid liquid crystal films experience a competition between the aligning 

forces of the bounding surfaces. We have performed a depth profile dependence 

study of the in-plane ordering of a smectic C* Iiquid crystal mixture, mx5112, 

confined between a grated glass substrate and the air surface. This compound 

mixture has the following phase transitions: sm3 - smC* at 22.65OC; smC* - smA 

at 49.5"C; and smA - I at 57°C. The corresponding smectic layer spacings are 

33.303Afor the smA phase; 29.97Afor the smC* phase; and 31.639Afor the sm3 

phase. 

The in-plane layer spacing oscillates between the bulk values of the smA and 

smC* phases as a function of time. This value varies also as a function of depth 

within the films and is close to the average of the two bulk spacings close to the 

liquid crystal glass interface. The azimuthal orientation of the layers varies both as a function of depth and of time within the films. In-plane layers close to the 

liquid crystal glass interface align close to the direction of the gratings' axis. The 

orientation of the layers close to the liquid crystal air interface rotate as a function 

of time to a direction perpendicular to the axis of the gratings, for samples thicker 

than 10pm, as illustrated on Table I. The mechanism for this rotation, which was 

previously observed both in samples thicker than 10pm and thinner than 3pm, is 

not clear at present. We are in the process of studying the depth dependence of the 

azimuthal orientation in greater detail. 

Layer Spacing (A) $(") - 15 Frn $(") - 13 

30.710 

30.770 

30.830 

30.360 

30.050 

30.640 

30.120 

31.160 

3 1.020 

30.630 

159 

38 

24 

20 

20 

20 

90 

78 

IO2 

23 

Figure 1. Table of Values of the azimuthal peak d, corresponding to the layer spacing 

of the maximum peak for the 15-pm and 13-pm films. Data were obtained over a 16 

hour period for the 15pm sample and over a 90 hour period for the 13 pm sample. 

* This work was supportedby a NSF-VPW Grant No. GER-94-50118, and a NSF Grant 

No. ECS-96-96069. 

* This research was supported by a NSF-VPW Grant No. GER-94-50118, and a NSF 

Grant No. ECS-96-96069. 
1 The 2D Ising Model: Br Electrodeposited on Ag( 100) I X22B 1 ~~ 

B.M. Ocko and J.X. Wang (BNL, Physics), T. Wandlowski (Ulm) 

One of the basic tenets in the theory of second order phase transitions is the 

notion of universality; the critical behavior is determined by the symmetry and 

dimensionality. The present grazing incident angle x-ray scattering study shows 

that the electrodeposition of halides (chloride, bromide, and iodide) on the Ag(100) 

electrode represents an example of the 2D Ising phase transition. As displayed in 

Fig. 1, the disordered state is characterized by the random (lattice gas) adsorption 

in four-fold hollow sites and the ordered state is characterized by a ~(2x2) structure. 

At a critical potential there is a second order transition between these two states. 

In Fig. 2 we show the correspondence between the cyclic voltammetry and the 

x-ray scattering results for Br on Ag(100). The change in intensity at (1,0,0.12) 

below the critical potential occurs because the bromide preferentially adsorbs in 

the four-fold hollow sites. By modeling the intensity as an interference between 

the scattering from the silver and bromide, we are able to obtain a measure of 

the bromide coverage over the entire potential range. The maximum coverage thus 

obtained, 0.47, is in good agreement with the coverage of 1/2 determined from 

the in-plane diffraction pattern. In addition, the intensity at (1/2,1/2,0.12) should 

scale as a power-law with an exponent twice that of the order parameter. The 

fitted exponent of 0.15 (solid line) is slightly greater than the Ising prediction of 

1/8 (dashed line). 

Figure 1. (a) Real Space model of adsorbed bromide (filled 

Ag(100) surface (open 

shows random (lattice 

four-fold sites and right side shows the 

ordered ~(2x2) adlayer. (b) Reciprocal 

space pattern where the diamonds correspond to diffraction features from the 

~(2x2) structure. (c) X-ray scattering intensity at the lowest order in-plane posi- E 

co tion from the ~(2x2) structure. Eo 

-1.2 -1.0 -0.8 -0.6 -0.4 

EA~/A~CI 

ray scattering 

I X22B I Two-Dimensional Monomolecular Pigment Assemblies at The AirWater Interface 

D. Vaknin, B.W. Gregory, J. D. Gray, T.M. Cotton, W. S. Sturve (Ames Lab) and 

B.M. Ocko (BNL, Physics) 

Synchrotron X-ray diffraction at grazing angles of incidence (GID) and reflectivity techniques have been employed to determine the structure of charged water 

soluble pigments that are absorbed to oppositely charged lipid monolayers at the 

air-water interface. Surface pressure versus molecular area isotherms and X-ray 

scattering studies of the lipid dihexadecyl phosphate (DHDP) show substantial differences when spread on pure water or when spread on micro-molar solution of 

phthalocyanines (PC) or porphyrins (PY). Figure 1 shows the normalized reflectivity from a monolayer of DHDP on PC solution along with the corresponding 

refelctivity from the same monolayer on pure water (dotted line). The analyses 

of the reflectivity in terms of three strata (%box model, Le., lipid tail, lipid head 

group, and pigment) suggest that the pigment forms a homogeneous densely-packed 

monomolecular layer incorporating iodine and water molecules. Furthermore, GID 

scans from the same monolayer reveal that a highly ordered pigment-lipid mono- layer is formed at the air-water interface as indicated by Bragg reflections and their 

corresponding rod scans (see Fig. 2). On the other hand, GID scans from the lipid 

on pure water show a single 2D Bragg reflection corresponding to the hexagonal 

ordering of individual untilted alkyl chains dashed line Fig. 2), consistent with 

by the presence of the pigment showing that the pigment modifies the ordering of 

the lipid. Our detailed structural studies on the molecular length scale help in the 

design of light harvesting devices that mimic photosynthesis. 

the reflectivity measurements (see Fig. 1.) . !r his reflection is significantly affected 

Figure 1. Normalized reflectivity from a 

DHDP monolayer spread on micro-molar 

solution of PC. Solid curve is the calculated reflectivity based on the electron 

density model structure shown in inset. 

The dotted line shows the measured re- flectivity from DHDP when spread on pure water. 

$0.025 

L 

S 

2 0.020 

~ 

~ 0.015 + a, 

.! 0.010 1 

E 0.005 \ Z 

0 000 1 

-~ 

0.0 0.5 1 .o 1.5 

~ DHDP on PC solution 

Figure 2. In-plane diffration patterns at 

grazing angles of incidence from mono- layers of DHDP spread on PC solution 

(solid line) and on pure water (dashed 

line). Inset shows the rod scan of the 

2D Bragg reflection associated with the 

ordering of the complex pigment-lipid 

monolayer at 0.22 (InvAngs). 
Fd Surface Reconstruction at Metal-solid Polymer Electrolyte Interfaces I X22B 0 

J.X. Wang and R.R. Adzic (BNL, Physics) 

The structure of the Au(ll1) surface in contact with a recast Nafion film has 

been studied as a function of potential by using grazing incident angle x-ray diffraction. The high penetration depth of x-ray makes possible to probe the electrode 

surface covered by 1-3 pm Nafion film. Unlike usual aqueous electrolyte solutions, 

where both cations and anions are free to move, the negatively charged sulfonated 

groups in Nafion are fixed on the polymer chain and the balance of the interface 

charge is achieved mainly through a change of the cation concentration within the 

double layer as shown in Fig. la. At sufficiently negative potentials, four diffraction peaks (Fig. lb) appear around (O,l), which are characteristic of the Au(ll1) 

(23 x &)reconstruction. The diffraction intensity at a reconstruction peak position 

was monitored while cycling the potential in the double layer potential region. As 

shown in Fig. 2a, the background subtracted diffraction intensity vanishes completely at the most positive potential. This provides a convincing example of a charge-induced lifting of the Au(ll1 reconstruction in the absence of anion adsorption. In comparison with the Au ? 111) electrode in NaC104 solution, the lifting 

of reconstruction is shifted positively by about 0.2 V. This is likely due to the in- crease of the separation between the planes carrying charge at the Nafion/electrode 

interface compared to at a solution/electrode interface where the negative charges 

are carried by the mobile anions and are located close to the electrode surface. 

This, in turn, causes a slower positive charge increases at the metal surface with 

increasing potential which is necessary for the reconstruction lifting. These results 

demonstrate that the Nafion coating is stable over a large potential range and is 

suitable for studying surface properties and the ion distribution effects on surface 

electrochemical processes at single crystal surfaces. 

,-. 9000 

I 2 7000 

Y 5000 

.- 3 

p 3000 

- 1000 

c 

(u 

c 

c 

-4 -2 0 2 4 

@ (degrees) 

Figure 1. 

-0.8 -0.4 0 0.4 0.8 

EAg/AgCI ("1 

Figure 2. 

Resonant Magnetic X-ray Scattering in Er Films with Monolayer Y 

Superlattice Doping 

M. J. Conover, C. P. Flynn (U. of Illinois), A. Vigliante, and D. Gibbs (BNL, 

Physics) 

Below its 85K NCel temperature, Er has a c-axis modulated (CAM) phase, in 

which individual atomic moments lie along the hcp c-axis but are subject to a longitudinal sinusoidal modulation. From about 52K to the 20K Curie temperature, 

a basal-plane spiral with the same periodicity, r,, is added to the CAM structure. 

Past synchrotron experiments have shown that, for several small ranges of temperature below 54K, r, locks to values commensurate with the lattice via a series of 

periodic phase advances known as spin slips. In the present experiment, we study 

the lock-in states of 7, for Er films which have been altered by periodically introducing monolayers of Y into the Er structure. Three such samples were studied, 

with superlattice periods A = 19.4, 28.9, and 32.6 atomic layers. Measurement 

of r, vs temperature was accomplished by tuning the photon energy to the LIII 

absorption edge (E = 8.362 keV) of Er and measuring the position of the primary 

magnetic satellite to the (004) reflection. The temperature dependence of r, for the 

three samples is shown in Fig. 1. The A=19.4 sample has strong lock-ins at 5/19 

and at 2/7, while the A=28.9 has no 2/7 lock-in and has a more gradual approach 

to the 5/19 state. Lock-in behavior to a single wave vector is suppressed in the 

A=32.6 sample. Epitaxial strain is thought to couple the Er magnetic states to the 

Y layers, both as an overall homogeneous strain and as a periodic strain modulation. One possible explanation of the 5/19 lock-in state in the A=19.4 sample is 

that the strain modulation couples to the spin-slip period of 19 layers, although the 

evidence from the other samples indicates the influence of the homogeneous strain 

term. 

The University of Illinois portion of this project is supported by grant ONR 

N0014-94-1-0068. Work performed at Brookhaven is supported by the US DOE 

under contract no. DE-AC02-76CH00016. 

0.3 

0.29 

C 0.28 

pE 0.27 

0.26 

0 

v 

0.25 

0 10 20 30 40 50 60 70 80 

Temp (K) 

Figure 1. Magnetic wave vector rm (in units of c*) in Er/Y for superlattice 28.9, 

and 32.6 atomic layers. 
x22c Resonant Magnetic X-ray Scattering in Ho Films with Monolayer 

Dy Superlattice Doping 

M. J. Conover, C. P. Flynn (U. of Illinois), A. Vigliante, and D. Gibbs (BNL, 

Physics) 

Below its 132K NCel temperature, hcp Ho has a spiral magnetic phase, in which 

atomic moments lie in the basal plane and rotate by a temperature-dependent turn 

angle (b with each layer along the c axis. Basal plane anisotropy distorts the spiral by 

pulling the spins toward the six easy b-axis directions, and it favors magnetic wave 

vectors 7, which are commensurate with the lattice. Past synchrotron experiments 

have shown that, over small temperature ranges, the magnetic wave vector r, locks 

to the lattice via a series of periodic phase advances known as spin slips. In the 

present experiment, we study the lock-in states of r, for two Ho films which have 

been altered by periodically introducing monolayers of Dy into the Ho structure and 

compare them to a pure Ho film of the same total thickness and grown by the same 

method. Measurement of r, vs temperature was accomplished by tuning the photon 

energy to the LIIr absorption edge (E = 8.075 keV of Ho and measuring the position 

7, data. The low-temperature lock-in state of r, reaches progressively lower values 

with increasing concentration of Dy, although the bulk 1/6 phase which accompanies 

the ferromagnetic transition in bulk Ho is not reached in any of these samples. Past 

studies of Ho films indicate that epitaxial strain and clamping tend to increase 

the lock-in value of T, relative to that of bulk Ho, but the present study suggests 

that the Dy layers partially overcome this epitaxial influence, either via lattice 

mismatch strains or by changing the in-plane anisotropy barrier. The University of 

Illinois portion of this project is supported by grant ONR N0014-94-1-0066. Work 

performed at Brookhaven is supported by the US DOE under contract no. DEAC02-76CH00016. 

of the primary magnetic satellite of the (004) re A ection. Figure 1 summarizes the 

0.26 1 I I I I IO 

0.24 - 

g- 0.22 - 

,E 0.20 

0 

v 

0.18 . 

0 4000AHo C 

- 0 Ho16IDyI ooo0 

- 

- 

m 1 I6 

0.16 I I I I 'I I 

0 20 40 60 80 100 120 

Temp (K) 

Figure 1. Magnetic wave vector r, (in units of c*) in Ho/Dy for two superlattices o (Ho 16 layers / Dy 1 layer, and Ho 8 / Dy 1) and a film of Ho with no Dy. c 

Determination of Magnetic Moment Directions Using X-ray Resonant Exchange Scattering * 

C. Detlefs, A. H. M. Z. Islam, A. I. Goldman, C. Stassis, P. C. Canfield (Ames Lab 

& ISU), 3. P. Hill, and D. Gibbs (BNL, Physics) 

We present magnetic structure determinations for SmNizBz C and NdNizBzC by 

means of x-ray resonant exchange scattering (XRES). Both compounds order in a 

commensurate antiferromagnetic structure with modulation wave vector (5, 0, $). 

Using an asymmetric geometry that is particularly convenient for small crystals, 

we measured the variation of the integrated intensity of the magnetic reflections as a function of the Bragg angle to determine the magnetic moment directions. 

The measured data are in good agreement with model calculations assuming magnetic moment directions parallel to (1,0,0) for the Nd compound and (0, 0, 1) for 

SmNizBzC (Fig. 1). A resonant feature observed below the Sm La-absorption edge 

(Fig. 2), similar to unexplained effects found in other light rare earth compounds, is 

identified as quadrupolar XRES and is further used to obtain additional information 

about the direction of the magnetic moment. 

Intensity [counts/sec @ I=100mA] 

01 r cn N cn E, a I 1 1 I I 

IIIIII 

^^^^_^ ZkNElp19~CP9b8iE. 

0. 0. 0. 0. a. 0. 

--,-.--- zbsktpIE.Spzb 

..k"-*I-*I-N4m-m 

----1- 

9 9 9 9 4 9 -mrN-N-m*lclN 

II/III 

Figure 1. The integrated intensity of 

magnetic reflections of SmNizBz C (filled 

circles) and NdNizBzC (open circles) 

along with model calculations for a magnetic moment parallel to the (0, 0, 1 

(solid line) and (1, 0, 0) (dashed line] axes of the samples. 

* Work supported by U.S. DOE W-7405- 

Eng-82 and DE-AC02-76CH00016 

zl I I J I I 

Intensity [counts/sec 0 1=100mA] 

N cn r cn 0 cn 0 4 0 

Figure 2. Energy scans of the (-f, 0,l) 

magnetic reflection across the Sm Lz,s 

absorption edges. The fluorescence yield 

is plotted as an energy reference. 
P 

e 

N I Magnetic and Structural Properties of Erbium Films 1 x22c I 1 Resonant X-ray Scattering From a Thin Film of UPdaAls I x22c I 

G. Helgesen (IFE, Norway), Y. Tanaka (RIKEN, Japan), J.P. Hill, P. Wochner, D. 

Gibbs (BNL), C.P. Flynn and M.B. Salamon (U. of Illinois) 

The magnetic and structural properties of two erbium thin films (thickness 2 1pm) grown epitaxially on Lu and Y substrates have been studied using res- onant magnetic x-ray scattering. These substrates, respectively, compress or ex- pand the erbium a-axis lattice constants relative to the bulk and clamp them at 

the film/substrate interfaces, thereby introducing epitaxial strain. The temper% 

ture dependence of the c- and &axis lattice constants, magnetic wave vector r, and 

magnetic order parameters of the films were measured. The qualitative features of 

the magnetic phase behavior mirror those of the bulk, including scaling of the critical exponent p of the observed harmonics and the existence of lock-in transisitions 

to commensurate wave vectors found in the bulk. The magnetic phase transitions, 

however, exhibit marked hysteresis and the magnetic structures are characterized 

by multiphase coexistence and limited correlation lengths. The low temperature T 

= 5/21 phase of bulk erbium is supressed in both films, and is replaced in Er/Lu 

by two new phases with wave vectors r = 6/25 and 12/49. Qualitative c-axis strain 

profiles were deduced from specular reflectivity measurements and reveal that the 

Er/Y film is more distorted than the Er/Lu film. 

lo-’ 

1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 

L [c*l 

Figure 1. Scan along the (O,O,L) direction in reciprocal space for the 9500 a Er film 

on a Lu substrate at temperature T = 60 K. The photon energy was tuned to the 

Er LIII absorption edge at E = 8.36 keV. 

~~ ~~~ 

A. Hiess (EITU, CEA-Grenoble), S. Langridge (EITU, ESRF), M. Huth (U. Mains, 

Germany), D. Gibbs (BNL, Physics), and G. H. Lander (EITU) 

UPdzAl3 is a so called magnetic heavy-fermion superconductor. An antiferromagnetic order (TN = 14K) of ferromagnetic (0 0 1) layers of moments coupled + - + - along the hexagonal c direction with a relatively large ordered moment of rn = 0.85,~~ coexists at low temperatures with superconductivity (T, = 2K). To 

understand the interplay of superconductivity and magnetism in the compound, an important question relates to the dimensionality of the magnetic interactions. Thin 

films of UPdzAla were prepared (in Mains) by electron beam co-evaporation of the 

elements on a LaA103 substrate resulting in a film that was ordered in the hexagonal c direction. The mosaicity of the film used (thickness = 1500A) was about 

0.3deg. for the specular reflections (0 0 L). 

We have observed magnetic scattering from the (0 0 1/2) specular reflection 

Fig. 1) for temperatures T < 9K using photons tuned to the Miv absorption edge 

E = 3.728keV) of uranium. The intensity was about 1000cts/sec at T = 3.8K, the 

correlations are the same as found in the bulk material (TN = 14 Ii ), but exist only 

lowest temperature available. The principal results are as follows: 1) The magnetic 

at significant lower temperatures. (2) Although the transport properties indicate an 

antiferromagnetic ordering at about T = 9K, the x-ray results on the thin film show no sign of saturation down to T = 3.8K. (3) The widths of the magnetic reflection in 

both the transverse and longitudinal directions seem to saturate at about T = 6K 

and are at low temperatures not significantly different from those of the charge 

peaks. (4) Surprisingly, the (0 0 3/2) magnetic reflection was not observed. 

In conclusion our x-ray results establish that the magnetic correlations in the film 

are of the same form as in the bulk, but static disorder in the arrangement or the 

quasi-twodimensional geometry seems to prevent the formation of true long-range 

order in the film. 

Figure 1. Temperature dependence of the intensity and the width of the magnetic 

reflection at the (0 0 1/2) position. 
K-Edge Resonant Magnetic Scattering from a Transition Metal Ox- x22c, 

ide: NiO X25 

J.P. Hill (BNL, Physics), C.-C. Kao (NSLS) and D.F. McMorrow (Fliso) 

Resonant x-ray magnetic scattering exploits enhancements in the cross-section 

occurring when the incident photon energy is tuned through an atomic absorption 

edge. Large enhancements were first observed at the Lrr,III edges in Ho and explained in terms of electric multipole transitions. In addition to the L edges much 

larger enhancements are expected, and observed, at the Mrv,v edges of the actinides for which the dipole excitation is to the localized, highly polarized 5f levels. 

Conversely, resonant scattering at a K-edge is expected to be considerably weaker 

because the strong (dipole transitions involve s and p levels for which there is no 

spin-orbit correlation of eit h er the core level or the intermediate state. Nevertheless, 

K-edge studies would be of some interest because of the window they would provide on transition metal compounds, which make up arguably the most interesting of 

magnetic systems. 

We report the observation of K-edge resonant magnetic scattering in the antiferromagnet NiO, for which an approximately two-fold increase in the scattering 

is observed at an energy corresponding to a quadrupolar feature in the absorption spectrum (Fig.1). Quadrupole excitations couple to d-like states at a K-edge 

and for transition metals these are the magnetic states. Thus, the high degree 

of polarization of the localized 3de states compensates for the small size of the 

quadrupolar matrix elements and an observable enhancement results. From the 

ratio of the non-resonant to resonant magnetic scattering, we estimate that the first 

order quadrupolar resonant scattering amplitude is 0.016r0, which is of the same order of magnitude as similar terms in the rare earths. These studies provide for the 

possibility of element specific magnetic diffraction in such notable transition metal 

oxides as the high Tc cuprates and colossal magnetoresistance manganites. 

NiO T=300 K 301. I .,I, I, 3000 

! 

I Charge Ordering in the Layered Perovskite Lao.sSrl.sMnO4 x22c 

J.P. Hill and B.J. Sternlieb (BNL, Physics) 

There has been intense recent interest in the phenomena of charge ordering in 

various perovskite systems. Motivation for this is twofold. First, high-Tc cuprates 

for which, in some materials, a real space separation of holes and spins into an 

ordered phase consisting of antiferromagnetic “stripes” has been observed. This 

ordering competes with, and coexists, with the superconductivity and sheds new 

light on the background electronic and magnetic state from which the superconductivity arises. Secondly, the colossal magnetoresistance maganites, which are 3D 

perovskites of the form Al-,B.MnOa, where A=lanthanide, B=Ca, Sr or Ba, also 

exhibit charge ordering. In these systems, the charge ordering is associated with 

dramatic changes in the conductivity. For some compositions this is reversed be an applied magnetic field, resulting in an insulator-metal transition; the colossal 

magnetoresistance. 

We have carried out x-ray studies of the charge ordering in a layered perovskite Lao.aSrl.bMnO4, which is isostructural with the nikelates Laz-OSr,Ni04 

and LazNiO4+6 for which the striped order was first observed. The x-ray experiments, together with complimentary neutron scattering studies, revealed that the 

formal valence of Mnt3.‘ orders at T,, N 217 K, in an alternating Mnt3/Mnt4 

pattern, with a unit cell of &a x &a x c. Experiments with as-prepared, and 

freshly cleaved samples revealed that this ordering is extremely sensitive to changes 

in the stoichiometry and domains of 2&a x 2&a x e were also seen in coexistence 

with the preferred ordering in the samples that had been exposed to the air for 

some time. This explains previous disrepancies in the literature between various 

electron diffraction studies. The neutron scattering work revealed that at TNN 

110 K, the moments on the Mn ions order antiferromagnetically, with a unit cell of 

2JZa x %&a x 2c. 

.a 10’ 

io5 

E 

8 lo6 

1 o8 

7 

ly1 io4 

f lo3 

10’ 

i lo2 

0.2 0.4 0.6 0.8 1.0 1.2 

t (rid I, , I .i I . I . 10 

8.30 8.32 8.34 8.36 8.38 Energy (keV) 

Figure 1. Figure 1. 
Studies of Zero Field Magnetic Structures of TbNizGez x22c 

A. H. M. Z. Islam, C. Detlefs, A. I. Goldman, P. C. Canfield (Ames Lab), J. P. 

Hill, and D. Gibbs (BNL, Physics) 

The magnetic properties of TbNizGez are intriguing. This material crystallizes 

in ThCrzSiz structure (14lmmm). Susceptibility measurements have shown that 

this compound is anisotropic with two magnetic transitions at z9.25K and w16.5K 

in small applied field. As a first step to understanding the microscopic magnetic 

behavior, the zero field magnetic structures were studied using the technique of 

x-ray resonant exchange scattering on beam line X22C. The magnetic wave vector 

of the low temperature structure is (0 0 3/4), while the higher temperature phase 

orders with a wave vector of (0 0 0.76). All the data were collected at the Tb 

LIII-edge where the resonant enhancement was the largest. The Q-dependence 

of magnetic satellites in both the phases were carefully measured using symmetric 

[O 0 Lh] and asymmetric [fl 0 7ftr] scattering geometries where 7 = 3/4 and 

0.76. Detailed modelling of the magnetic structures to best fit the observed Qdependence is in progress. Preliminary analysis shows a large c-axis moment at the 

Tb sites. It is assumed that Ni is not moment bearing in this material as known 

from measurements on similar compounds. 

x22c Verifying Magnetic Structures Using X-Rays - Neodymium A Test 

Case. 

D. Watson, W.J. Nuttall, E.M. Forgan, D.Fort (U. Birmingham, UK), and S.C. 

Perry (Keele U., UK) 

We report here further progress on our investigations of the antiferromagnetic 

ordering of elemental neodymium. These measurements build upon our previous 

determination of the energy dependencies of the resonantly enhanced magnetic scattering at the Nd L-edges and also a detailed study of the incommensurate magnetic 

modulation wavevector [I]. Those measurements allowed us to address the question as to whether the modulation wavevectors in neodymium exhibit lock-ins to a 

subtle series of commensurate values [2]. The natural high resolution of the x-ray 

technique allowed us to confirm that the wavevector modulation is indeed smoothly 

incommensurate. 

Recently we have made measurements, on resonance at the LII edge, of a large 

number of magnetic satellites from the double-q structure of Nd at 10 K, and have 

shown that these intensities can be used in a refinement of the magnetic structure. 

There is remarkably good agreement with all the major components of moment 

on the hexagonal sites, but the cubic site moments given by x-rays are a factor 

of 2 smaller than the neutron ones. This is probably not due to the different 

temperatures (10K vs. 6K), since a less complete neutron experiment at 10K [3] 

also gives moments on the cubic sites that are larger than the X-ray ones. These 

results are currently being prepared for publication [4]. 

Following the formalism outlined by Hill and McMorrow [5] we have recently 

extended our measurements to include a quantitative assessment of the polarization properties of the magnetic scattering, and have measured the incommensurate 

lattice distortion satellites associated with the magnetic ordering. These measure- ments complement our related neutron diffraction studies of this material under 

hydrostatic pressure [6]. 

We intend to continue our x-ray measurements at X22-C to include a fuller consideration of the ordering of the 'cubic sites' within the double-hexagonal close packed 

structure. This will require the use of the Joule-Thompson liquifier available at 

X22-C in order to assess those phases (triple-q and quadruple-q) in which the cubic 

sites are also spontaneously ordered. Such ordering of the cubic sites occurs for 

temperatures below 8K. 

References 

1 B.Lebech, J.Wolny and R.M.Moon, J.Phys., Cond.Mat., 6, 5201 (1994) 11 2 D.Watson, E.M.Forgan, W.J.Nuttall, W.G.Stirling and D.Fort, Phys.Rev.B 

53, 726 (1996) 

-3 B.Lebech, J.Appl.Phys., 52, 2019 (1981) 

'4 D. Watson, W.J. Nuttall, E.M. Forgan, D. Fort and S.C. Perry, 

:to be published 

5 J.P.Hill and 

'61 D. Watson, E.M. Forgan, W.J. Nuttall, P.E. Sokol, S.J. Shaikh, 

S.W. Zochowski and D. Fort, J. Phys.: Condens. Matter 8, 5049 (1996). 

k 1 

.F.McMorrow, Acta Cryst. A52, 236 (1996) 
I Ir(100) Surface Structure Determination by X-ray Scattering * I X22C I ~ 

G.Watson (UMBC), D.Gibbs (BNL, Physics), V.Jahns and D.Zehner (ORNL) 

The (001) surfaces of Au and Pt reconstruct in vacuum to form quasihexagonal 

overlayers. These overlayers exhibit temperature-dependent incommensurabilities 

and rotational transformations. At the highest temperatures, the Au(001) surface 

disorders while Pt roughens. Previous LEED work has shown that the Ir(001) 

surface reconstructs to form a commensurate (1x5) overlayer at 300K. We were motivated by these results to use x-ray scattering to determine if the Ir(001) surface 

reconstruction becomes incommensurate on heating to higher temperatures and 

whether at the highest temperatures the surface disorders or roughens. 

We find that the Ir(001) surface is commensurate from 300 to 2000 K, and that 

above 2000K the surfaces appears rough. 

We have performed specular and non-specular reflectivity measurements of the 

Ir(001) surface for temperatures between 300 and 2200 K. The temperature dependence of the specular reflectivity is illustrated in Fig. 1 where, at high temperatures, 

the scattering at the (001) anti-Bragg position is shown to be diffuse and to exhibit 

a power-law dependence on transverse wavevector as expected for a rough surface. 

This identification is supported by the temperature dependence of the superstructure and off-specular truncation rod intensities at grazing incidence. 

On the other hand, we have also investigated the metastable (1x1) phase which 

exists on Ir(001) at room temperature. This phase has considerable intensity in the 

off-specular truncation rod reflections as compared to the high temperature (1x1) 

phase. 

1. I I I I I. 

2 $ 0.02 . Y 

0.002 - 

0.001 ' ' I I I I 

-0.8 -0.4 0 0.4 0.8 

A8 [Des.] 

Figure 1. Specular reflectivity profiles obtained at 1082 and 2052 K. 

* Research at ORNL is sponsored by the US Division of Materials Sciences, US DOE, 

contract No. DE-AC05-960R22464 with Lockheed Martin Energy Research Corp. Work 

performed at BNL is supported by the US DOE contract DE-AC02-76CH00016. 

Characterization of the Magnetic Disorder at the (001) Surface of x22c, I UO2 I x25 I 

G.M. Watson, D. Gibbs (BNL, Physics), L.E. Berman (NSLS), G.H. Lander, H. 

Matzke (EITU), W. Ellis (LANL), and B.D. Gaulin (McMaster U.) 

In our earlier work, we showed that the temperature-dependence of the scattering 

along a (110)-type magnetic truncation rod of a U02(001) surface appeared to 

vanish continuously as the temperature is raised to the bulk NCel temperature, TN 

= 30.2 K.l This is suprising since the bulk transition, as observed by neutron and xray scattering, is discontinuous.' This behavior may be understood as an example 

of surface induced disorder wherein magnetic disorder propagates from the near 

surface volume into the bulk as the temperature approaches TN. In order to further 

characterize this behavior, we have performed measurements of the four equilavent 

(1 lO)-type magnetic truncation rods and of the specular magnetic reflectivity. Rod 

intensities were obtained both as a function of temperature at fixed wavevector and as a function of momentum transfer at a number of temperatures. The magnetic 

specular reflectivity shown in Fig. 1 is especially sensitive to the decay of the 

magnetic order parameter profile along the surface normal direction. At the higher 

temperatures, the reflectivity away from the bulk Bragg reflection falls off faster 

than it does at lower temperartures. This indicates that the width of the magnetic 

profile increases with temperature. In fact, our data seem to suggest that this width 

diverges as T approaches TN. 

G.M. Watson, et al., Physica B 221, 405 (1996); ibid. Phys. Rev. Lett. 77, 

751 (1996). 

B.C. Frazer et al., Phys. Rev 140, A1448 (1965); B.M.T. Willis and R.I. Taylor, 

Phys. Rev. Lett 17, 188 (1965); G.M. Watson et al., Phys. Rev. B 53, 686 (1996). 

h 

to3, . , . , I 

102 - 

10' - 

6 100 - 

5 10.' - 

Q 10-2 - 

- 

\ z 

Y 

2 - 

~ 

- 

- 

0.7 0.8 0.9 1.0 1.1 1.2 1.3 

t [Units of c*] 

Figure 1. Specular magnetic reflectivity profiles near the (001) bulk magnetic Bragg 

reflection obtained at 10.2, 26.9, 29.6 K utlizing a Au(ll1) reflection for a polarization analyzer. Peak count rates at beam line X25 were approximately 5x106 cps 

at a beam current of 200 mAmp. 
04)9 OC09 0209 0109 WW 0665 0865 
XANES and EXAFS Characterization of Copper Halides in Nylon ~23~2, 

636 X23B 

J. N. Weber, H. D. Rosenfeld (DuPont) and M. A. Walters (NYU) 

Copper halides have been added to nylon polymer for over 40 years and are widely 

recognized as one of the most effective anti-oxidants for polyamides. Despite their 

long commercial use little is known about the structural and chemical details of the 

copper halides in the polymer, in part due to their low concentrations, on the order 

of 100 ppm Cu. XANES and EXAFS coupled with polymer and model compound 

synthesis and other analytical techniques offer a very promising approach to study 

this important chemical system in situ. 

Our XANES results indcate that, independent of the oxidation state of the metal, 

Cu(1) or Cu(II), when the copper halide anti-oxidant is added to the polymer during 

processing, the initial state of the copper upon extrusion is the Cu(1) ion. As the 

nylon polymer is permitted to equilibrate with the atmosphere, absorbing oxygen 

and moisture, the cuprous ion is oxidized to cupric ion which we have observed in 

almost all equilibrated samples. Thus in the final commercial polymer the copper 

appears predominantly as the cupric ion. In addition, we have confirmed earlier 

work by others that the lavender/pink color occasionally seen in copper-containing 

polyamides is due to colloidal copper metal. We have also observed orientation 

effects for Cu(I1) phthalocyanine pigment in nylon fiber using polarized XANES. 

The pigment forms needle-like crystals in the polymer which are oriented along the 

fiber axis during spinning and drawing. We believe that this is the first observation 

of orientation of an additive in fibers using XANES. 

Our preliminary EXAFS results indicate that the cupric ion in nylon is coordinated by the amine and carboxylate end groups of the polymer and that the amide 

function does not play a significant role in coordination. We have prepared a series of model cupric amine nitrate compounds and one model cupric amine acetate 

compound which reproduce very closely the EXAFS spectra of the cupric ion in nylon. These spectra are distinctly different from those of Cu(I1) carboxylate model 

compounds. In these amine-containing model systems the copper ion is coordinated 

by four planar amine groups and two axial nitrate or acetate groups which form a 

distorted octahedral environment around the cupric ion. Thus we believe that the 

cupric ion in nylon is coordinated in a similar manner. Solubility studies of cupric 

ion in low molecular wt. liquid amides provides additional evidence that the amide 

function is not significantly coordinated to the cupric ion in amides. Current work 

in progress includes the study of the environment surrounding the halide ions in 

nylon and the chemical reactions occurring in the anti-oxidant during oxidation of 

the polymer. 

I A Look Inside the Unit Cell of Strained GeSi 

King (Lucent Technologies) 

J.C. Woicik, C.E. Bouldin (NIST), K.E. Miyano, (Brooklyn College), and C.A. 

The local structure within the unit cell of strained GeSi layers grown on Si(OO1) 

has been examined by polarization-dependent extended x-ray absorption fine structure (pd-EXAFS). First-neighbor bond lengths are found to deviate only slightly 

from their natural values; however, strain-induced distortions of the cubic-unit cell 

lead to measurable polarization-dependent changes in first-shell coordination and 

second-shell distances. A unifying picture of bond lengths and elasticity in strainedlayer semiconductors is presented. 

0.3 

9- 0s 0.2 

GexSil-, 

x = 0.21 

&llh - 

&LA - 

I 

0.0 

0 1 2 3 4 5 6 

Radius (A) 

Figure 1. Fourier transforms of the Ge K-edge EXAFS from a 21 % Ge GeSi alloy 

grown on Si(OO1). The data were taken with the polarization vector aligned normal 

and parallel to the sample normal. 
P 

h3 

Surface Defects and Fracture of Sapphire Single Crystals 

David Black, Harold Burdette (NIST) and Dan Harris (NAWC) 

X23A3 

Modulus Of Rupture (MOR) bars are used to measure the fracture strength of 

sapphire in four point bending. It is expected that surface defects will control the 

fracture strength. In order to produce sapphire of the highest strength at the lowest 

cost we must understand which flaws control fracture and how they are introduced 

into the surface. In a preliminary experiment we have used x-ray topography to 

record surface reflection images of 15 MOR bars prior to fracture. After fracture 

testing 5 bars survived in only two pieces and were examined again. We observed a variety of features in the images such as, subgrain boundaries, scratches, sleaks, 

gouges and dislocations. We then tried to correlate the features observed in these 

images with the measured fracture strength. Based on our preliminary observations 

we have arrived at several general conclusions: 1) Strength is not correlated to 

the presence of a subgrain boundary, misoriented by 7 arcseconds, in the gauge 

region; 2) Longitudinal gouges (parallel to the tensile direction) do not degrade 

the strength; 3) The strongest samples showed no wide transverse scratches and/or 

sleaks; 4) Wide transverse scratches and/or sleaks can weaken the sample. It was also observed that the residual scratches/sIeaks observed by topography are not 

observed by optical microscopy in reflection, transmission or Nomarski. Based on 

these preliminary observations a statistically significant sample set is being tested. 

Polishing Effects in Single-crystal Sapphire 

David Black, Harold Burdette (NIST) and Frederick Schmid (Crystal Systems) 

X23A3 

Because of its combination of optical and thermal properties, large single-crystal 

sapphire is being used as uncooled windows and domes for anti-ballistic missiles. In 

these applications the crystals will experience thermal shocking and large thermally 

induced stresses. These stresses may lead to failure. One factor affecting the fracture 

strength of these brittle materials is surface flaws. To produce the strongest windows 

and domes, processing induced surface and subsurface damage must be controlled. 

Therefore, diagnostic tools are required which are sensitive to this damage. To this 

end we have used grazing incidence x-ray topography to examine sapphire surfaces. 

In this technique the sample is oriented for a selected asymmetric surface diffraction. 

The incidence energy is then tuned so that the incident angle is near the critical 

angle for total external reflection. This provides high sensitivity to defects at or very 

near the surface. The sensitivity of this method was demonstrated by observing a 

(1129 diffraction at a nominal energy of 9.4 keV. When the energy was increased 

distinct. 

100 e 1 ectron volts the polishing related features in the image became much more 
X-ray Diffraction Imaging of Electrically Fixed Holograms in Strontium Barium Niobate (SBN) 

G. Fogarty, B. Steiner (NIST), T. Chang, and J. Hong (Rockwell International) 

High resolution x-ray diffraction imaging has been used to obtain the first images 

of fixed photorefractive holograms in strontium barium niobate (SBN). The results 

of these experiments should help in the optimization of the fixing process in SBN, 

and in the development of high density holographic optical data storage systems. 

In electrical fixing, an electric field pulse slightly lower in amplitude than the 

ferroelectric coercive field is applied to a photorefractive crystal in which a hologram 

has been written. It has been believed that the superposition of this applied field and 

the photorefractive space-charge field causes the formation of a ferroelectric domain 

pattern that mirrors the original hologram. Since the domains are stable, the fixed 

hologram has a much longer lifetime than the as-written hologram, which tends to 

decay quickly. The original hologram is also easily reconstructed by apllication of 

an electric field pulse of the opposite polarity to the fixing pulse. However, the fixed 

ferroelectric domain pattern had never been observed directly until recently, and 

this has made optimization of the fixing process a difficult task. 

Diffraction imaging was performed on a lmm thick sample of SBN in which a simple plane wave photorefractive hologram of 11 micrometers period had been recorded 

and fixed electrically. Laue geometry (002) images (Figure 1) clearly show the fixed 

hologram. The fixed hologram is not seen in Laue geometry images with diffraction vector perpendicular to [OOl], confirming that the fixing is indeed achieved 

via the formation of anti-parallel ferroelectric domains. No individual domains can 

be distinguished in any of the images, indicating that any micro-domains present are below the 1 micrometer resolution limit of the nuclear emulsion plates used to 

record the images. This is encouraging, as the size of micro domains will be a limiting factor in the ultimate storage capacity of any system using electrically fixed 

holograms. 

X23A3 

E 

o 

Figure 1. Enlargement of (002) diffraction image at lOkeV in Laue geometry of 

SBN sample with 11 micrometer period fixed photorefractive hologram. W 

In situ X-ray Diffraction Imaging of Electrically Fixed PhotorefracX23A3 tive Holograms in Barium Titanate 

G. Fogarty, B. Steiner (NIST), M. H. Garrett, J. Martin, and R. Uhrin (Deltronic 

Crystal Ind.) 

High resolution x-ray diffraction imaging has recently been used to investigate one of the principle problems hindering the development of commercial holographic 

optical data storage systems. 

Photorefractive materials, such as barium titanate, have long been considered 

potential media for very high density volume holographic optical data storage systems. While the potential data density is high (10' bits/cm'), several problems 

have hindered the development of commercial holographic data storage systems. 

The principle difficulty has been the short lifetime of as-recorded holograms in the 

most efficient materials (barium titanate and SBN). Over time, the optically induced 

photorefractive space-charge distribution that encodes the hologram will dissipate, 

lowering the signal-to-noise-ratio of the hologram, and eventually erasing it. One 

solution to this problem is to "fix" the space charge distribution by applying to the 

photorefractive material a uniform electric field with amplitude slighty lower than 

the coercive field necessary to produce ferroelectric domain reversal. The superposition of this uniform field with the spatially varying space-charge field is believed 

to produce a spatially varying ferroelctric domain pattern that mimics the original mace-charge field. However. this ferroelectric domain pattern had never been 

directly observed. 

This model of the electrical fixing process has been tested by in situ diffraction 

imaging of Dhotorefractive holonrams written and fixed in real time on beamline 

X2313: One such diffraction image can be seen in Figure 1. It proved possible 

to watch the growth of the ferroelectric domain pattern of the fixed hologram in 

real time via a medium resolution (10 micrometer) resolution x-ray video camera. High resolution (1 micrometer) nuclear emulsion plate images (Figure 1) show even 

greater detail, including individual domains within the fixed hologram. Preliminary 

analysis of the images has shown that the quality of the fixed hologram is strongly 

degraded by pre-existing ferrolectric domains, and is also influenced byt the presence 

of other crystal defects.. High quality, completely poled samples are thus required 

for successful fixing. 

Figure 1. Enlargement of (002) diffraction image at 10 keV in Laue geometry of 

an electrically fixed hologram in barium titanate. The period of the hologram is 50 

micrometers. 
Fd 

N 

X23A3 

In sztu Measurements of Dislocation Structure Evolution in A1 Single Crystals Deformed in Tension 

L. E. Levine (WSU), G. G. Long, D. R. Black and Robb Thomson (NIST) 

When a metal is plastically deformed, its material properties change dramatically 

in a process usually referred to as work hardening. The underlying reason for 

these changes is the evolution of complicated dislocation structures that take the 

form of cells at large strains. This dislocation pattern formation is very sensitive 

to such parameters as the crystallographic orientation of the strain axis, sample 

temperature, strain rate and the starting microstructure of the sample. We are 

conducting experiments on single-crystal A1 to examine this dislocation structure 

evolution in situ while simultaneously measuring the stress and strain of the sample. 

Since the formation of dislocation cells is a bulk process and since these cells 

usually extend over several micrometers in size, a minimum sample thickness of 

approximately 50 micrometers is required for in situ experiments. This eliminates 

the use of electrons as a possible probe leaving X-rays and neutrons as the most 

viable candidates. The high brightness and small source size of X-ray synchrotron 

radiation, along with the high spatial resolution and sensitivity of X-ray detectors, 

makes X-rays the preferred probe for these in situ measurements. The most suitable 

X-ray techniques include high-resolution diffraction imaging and small angle X-ray 

scattering (SAXS); these in situ experiments are being conducted on X23A3. 

To conduct these X-ray experiments, we first designed and built a computercontrolled low-profile tensile stage that is both small and light enough to be mounted 

on an X-ray goniometer. It can deform a specimen in situ while simultaneously 

measuring the average longitudinal stress and the average linear strain. 

These experiments require dog-bone shaped single-crystal specimens with a low 

defect density. To produce the required samples, we designed and built our own 

crystal growing facility that uses a modified soft-mold growth process. Since any 

mechanical processing of the single-crystal A1 samples would introduce unacceptable 

numbers of defects, all processing is done chemically. 

Stereographic diffraction images were obtained from a single 1 mm thick A1 crystal deformed in situ; these images were taken at strain values of OX, 0.45%, 1.06%, 

1.94%, 2.74%, and 3.65%. Individual images were then taken at strains of 4.52010, 

5.40%, 7.20% and 9.00%. In these images we observed small-angle tilt boundaries, 

dislocation braids, slip bands, cell structure evolution, local accumulation of singlesigned edge dislocations, and a pronounced inhomogeneity of the local dislocation 

structure evolution. The stress-strain curve for this sample was obtained simultaneously with the X-ray measurements. 

Using an identicall oriented crystal, SAXS scans were obtained in situ at strains 

of 0%, 0.47%, 1.282 2.50%, 5.0%, 8.33010, and 16.67%. The power law behavior of these scans shows large systematic changes, thus demonstrating that these 

SAXS measurements are very sensitive to changes in the dislocation structure of 

the deforming sample. 

To interpret these and future scattering results, we have developed our own theoretical approach to the problem of X-ray scattering from dislocated materials and 

have finished a thorough and rigorous analysis of scattering from screw dislocations. 

Comparison between our resulting analytical model and computer simulations shows 

near-perfect agreement. We are currently working to extend this analysis to edge 

dislocations which should allow quantitative parameters to be extracted from our 

X-ray scattering data. 

I X23A3 1 Crack Correlation in Tensilely Strained Multifilamentary High-Tc 

Superconductor Composite Tapes 

R. D. Spa1 (NIST), G. N. Riley and C. J. Christopherson (American Superconductor 

Corp.) 

To study fracture in high-Tc superconductor composite tapes, a Bi-2223/Ag tape 

consisting of 19 Bi-2223 filaments sheathed in a Ag matrix was microradiographed 

at zero strain (as received), then tensilely strained along its axis to 0.80% and 

microradiographed again. The microradiography was done at 24.75 keV with an asymmetric Bragg diffraction microscope operating at 38X magnification, equipped 

with an x-ray sensitive two-dimensional CCD array with 19 pm pixels, producing images with 0.5 pm pixels. The face of the 150 pm thick tape was oriented 

perpendicular to the beam. 

Figure 1 is a microradiograph of a 1100 X 330 ,urn2 region of the tape at 0.80% 

strain, in which the tape axis is vertical. The dark regions on the left and right sides, 

in which the average transmission is about 12%, are 5 (left side) and 4 (right side) 

filaments stacked along the beam, while the bright region in the middle, in which the 

average transmission is about IS%, is the matrix. The bright lines, running roughly 

horizontally across the full width of each dark region, are cracks in the filaments, 

which are strain-induced since they are absent from the zero strain image. In both 

stacks of filaments, the cracks are concentrated in two distinct bands, about 90 to 

150 pm apart in the left stack and 55 pm apart in the right one. The upper band in 

the left stack connects by extrapolation smoothly to the lower one in the right stack, 

and likewise to a band in the adjacent stack on the left side (not shown), suggesting 

a tendency for crack correlation between adjacent stacks. The axial strain across the 

two bands in the left stack, determined by comparing the zero and non-zero strain 

images, is about 5%. Since this value is more than 20 times the fracture strain of 

bare Bi-2223 filaments, it is expected that all 5 filaments in the stack are fractured 

in this region. Examination of a larger region containing 13 crack bands reveals an average band spacing of 320 pm, and a tendency for bands to occur in closely 

spaced pairs, as in Fig. 1. These observations provide parameters for electrical and 

mechanical models of the tape. 
X23A3 

Residual Disorder in Low Pressure, Low Thermal Gradient LEC 

Gallium Arsenide Observed in High Resolution Diffraction Imaging 

B. Steiner, L.E. Levine (NIST), M. Brown, and D. Larson (Grumman) 

High resolution diffraction images of low thermal gradient, low pressure, LEC 

silicon-doped gallium arsenide reveal a degree of crystalline order far higher than 

that found in earlier in undoped conventional LEC crystals. 

In one of these modified LEC crystals, no distinct volume irregularity was observed where it is unstrained by its mount. 

In a second modified LEC crystal, only a set of surface-treatment-related dislocations was prominent. 

The third crystal exhibits two distinct sets of quasi periodic dislocations. One of 

these, shown in Figure 1, consists of a set of 60' dislocations. The second, Figure 

2, consists of a set of 30' dislocations, which are composed of alternating screw and 

60' dislocations, which have the same Burgers vector. All result from slip along 

(111) planes, but different ones. 

In all three crystals, the streaking features characteristic of conventional LEC 

material are greatly reduced. Moreover, the cellular defect arrangement and the 

very low angle <110> subgrain boundaries also characteristic of conventional LEC 

material are completely absent. Silicon thus seems to have inhibited, but not prevented completely, the strain associated with (110) antiphase boundaries in this 

material. 

Figure 1. Asymmetric (202) diffraction 

image of set of 60' dislocations oriented 

in the [Oll] direction. They display 1/2 

[110] Burgers vectors, whicih are associated with glide along the (111) system. p These images were recorded at 10 keV. F 

Figure 2. Asymmetric (202) diffraction 

image of set of 30' dislocations oriented 

in the [112] direction. These are com- pound dislocations, consisting of alternating [loll screw and [Oll] 60' dislocations, both with 1/2 [loll Burg- ers vectors, associated with glide along 

the (111) system. These images were recorded at 10 keV. 

I X-ray Absorption Studies of Battery Materials 

P. E. Stallworth (USNA); M. L. denBoer, S. Kostov, S. Greenbaum (CUNY, 

Hunter), and C. Lampe-Onnerud (Quantum Energy Technologies) 

In the past year we have investigated the structure and electronic properties of a number of lithium battery cathodes, including the alloyed spinels, LiMnz-,Fey04 

and LiMnz-,Cr,O+, a nickel-based spinel series, a hydrogen manganese sulfatebased cathode series and the system Li,V6013, using solid state nuclear magnetic resonance (NMR) to examine the environment of the Li and x-ray absorption to 

study the environment of the transition metal host. We report here results on the 

system LizV6Ola which demonstrate that the material goes through several distinct 

regimes as a function of Li intercalation o. [I] 

Li,VgO13 samples with z = 0, 0.5, 1, 1.5, 2, 3, 4, 5, and 6 were measured. 

Representative V K edge x-ray absorption spectra are shown in Fig. l(a). The 

"white line" peak after the edge is proportional to the number of s --t p transitions, 

in effect probing unoccupied p final states. The white line peak, Fig. l(c), grows 

dramatically with o. The "pre-edge" region is due to s --t d transitions which, while 

dipole-forbidden, become allowed in non-octahedral symmetry as the V 3d states 

mix with the Op states. Therefore the strength of this transition is proportional 

to the deviation from local octahedral symmetry of the vanadium site. Fig. l(b) shows this transition first increases slightly with increasing z for z < 1 and then 

decreases rapidly for o > 1.5. These changes are summarized in Fig. 2(a), which 

also shows the result of EXAFS analysis of the V K edge. Both the near-edge and 

EXAFS show a slight increase in the distortion from octahedral symmetry with 

increasing a: for o < 1, followed by a dramatic increase in such distortion from a = 

1 to 3, with little change thereafter. The increase in the ratio of the first to second 

EXAFS peak, shown in Fig. 2(b), indicates disorder beyond the first V-0 distance 

increases rapidly beyond z = 1. NMR shows at low z, Li ions occupy a single site, 

increasingly favoring locations near Vs5 ions as o increases. At higher o, Li ions 

occupy a variety of sites, and strong relaxation mechanisms become important as 

the lithium content increases, due to paramagnetic interactions with both Vs4 and 

PS. 

[l] P. E. Stallworth, S. Kostov, M. L. denBoer, S. G. Greenbaum and C. LampeOnnerud, submitted to J. App. Phys. 

Figure 1. 
I Measure of Hexavalent Chromium in Contaminates Soils * I X23B I 

M. Szulczewski, W.F. Bleam, and P. A. Helmke (U. Wisconsin-Madison) 

Because chromium is a common industrial contaminant, accurate characterization 

of chromium speciation in the environment is important. An independent method, 

such as XANES, is needed to verify current methods of extraction or exchange. 

The pre-edge regions of the XANES spectra for Cr(V1) and Cr(II1) are dramatically different. A strong pre-edge peak appears due to a 3d-4p mixing orbital 

whenever Cr(V1) present. It is well-known that the area of this peak is proportional 

to the amount of Cr(V1) present in a sample. Figure 1 shows an overlay of this preedge region of the XANES spectra of 6 physical mixtures with varying fraction of 

Cr(VI):Cr(III) ratios in the standards. The deconvolution of the pre-edge region 

into a linear combination of four gaussian peaks and an arctangent step function 

gives a value for the normalized area of the 3d-4p mixing peak. The correlation 

curve derived from these areas displays the linear relationship between the relative area of the pre-peak and the fraction of Cr(V1) present (Figure 3). We then deconvoluted the pre-edge region of the XANES spectrum for each of our contaminated 

soils, and obtained a value for the fraction of Cr(V1) present based on the correlation curve. Even in the extremely contaminated soils, the Cr(VI):Cr(III) ratio was never over 0.5. 

The advantage of XANES spectroscopy is that the total quantity of Cr(V1 is 

seen, regardless of its chemical state (dissolved, adsorbed, or precipitated). W h en 

we compare the amount of Cr(V1) detected by XANES spectroscopy analysis, we see that current analytical methods (performed elsewhere) greatly underestimate 

the concentration of Cr(V1) present in contaminated soils. 

Figure 1. Cr K-edge spectra of 

the pre-edge region of standard physical mixtures with varying fractions of 

Cr(VI):Cr(III). 

* Research supported by U.S. Department of Agriculture Hatch Program No. 

WI-3681. We would like to acknowledge 

the assistance of Drs. Geraldine Lamble, 

Lars henlid, John Kirkland, and Timothy 

Elam. 

‘T 

Figure 2. Calibration curve from physical mixtures of varying fractions of 

Cr(VI):Cr(III). 

XANES and EXAFS Characterization of Copper Halides in Nylon X23A2, 

16.6 1 X23B 1 ~~ 

J. N. Weber, H. D. Rosenfeld (DuPont) and M. A. Walters (NYU) 

Copper halides have been added to nylon polymer for over 40 years and are widely 

recognized as one of the most effective anti-oxidants for polyamides. Despite their 

long commercial use little is known about the structural and chemical details of the 

copper halides in the polymer, in part due to their low concentrations, on the order 

of 100 ppm Cu. XANES and EXAFS coupled with polymer and model compound 

synthesis and other analytical techniques offer a very promising approach to study 

this important chemical system in situ. 

Our XANES results indcate that, independent of the oxidation state of the metal, 

Cu(1) or Cu(II), when the copper halide anti-oxidant is added to the polymer during 

processing, the initial state of the copper upon extrusion is the Cu(1) ion. As the 

nylon polymer is permitted to equilibrate with the atmosphere, absorbing oxygen 

and moisture, the cuprous ion is oxidized to cupric ion which we have observed in 

almost all equilibrated samples. Thus in the final commercial polymer the copper 

appears predominantly as the cupric ion. In addition, we have confirmed earlier 

work by others that the lavender/pink color occasionally seen in copper-containing 

polyamides is due to colloidal copper metal. We have also observed orientation 

effects for Cu(I1) phthalocyanine pigment in nylon fiber using polarized XANES. 

The pigment forms needle-like crystals in the polymer which are oriented along the 

fiber axis during spinning and drawing. We believe that this is the first observation 

of orientation of an additive in fibers using XANES. 

Our preliminary EXAFS results indicate that the cupric ion in nylon is coordinated by the amine and carboxylate end groups of the polymer and that the amide 

function does not play a significant role in coordination. We have prepared a series of model cupric amine nitrate compounds and one model cupric amine acetate 

compound which reproduce very closely the EXAFS spectra of the cupric ion in nylon. These spectra are distinctly different from those of Cu(I1) carboxylate model 

compounds. In these amine-containing model systems the copper ion is coordinated 

by four planar amine groups and two axial nitrate or acetate groups which form a 

distorted octahedral environment around the cupric ion. Thus we believe that the 

cupric ion in nylon is coordinated in a similar manner. Solubility studies of cupric 

ion in low molecular wt. liquid amides provides additional evidence that the amide 

function is not significantly coordinated to the cupric ion in amides. Current work 

in progress includes the study of the environment surrounding the halide ions in 

nylon and the chemical reactions occurring in the anti-oxidant during oxidation of 

the polymer. 
rX-ray Standing Wave Investigation of S/Ni( 100) I X24A I 

D. Heskett, J. Warner, and G. Sabatino (U. Rhode Island), D. Mullins (ORNL) 

and L.E. Berman (NSLS) 

We have used the technique of Back-Reflection X-ray Standing Waves (BRXSW) 

to investigate the structure and geometry of sulfur on the Ni(100) surface (Ref. 1). 

We prepared this system by dosing H2S in lOOL increments onto the Ni(100) surface 

at room temperature. The dosing was then followed by an anneal to ~500K. The 

purpose of the anneal was to drive off residual H atoms that were left on the surface 

after the H2S dissociated. Based on the intensity of the S 1s core level, we found 

that 200L was sufficient to saturate the surface with sulfur see Figure 1). Based on 

our own and other previous investigations of the S/Ni(100 5 system, the saturated 

S/Ni(100) surface corresponds to a well-ordered (2x2) structure. 

We next performed x-ray standing wave measurements of this overlayer in both 

the (200) and (111) Bragg reflection geometries. Based on the high coherent fractions measured in both geometries, we can conclude that the sulfur atoms were very well-ordered both parallel and perpendicular to the Ni(100) surface. Based 

on triangulation of the coherent positions from both sets of measurements, we determined that the S atoms were bonded in four-fold hollow sites at a distance of 

1.32f.02 A above the ideal (100) Ni plane (see Figure 2), in good agreement with 

other structural measurements of this system (Ref. 2). 

We are in the process of carrying out a similar XSW study of 

methanethiol/Ni(lOO). The strong cross-section to excite the S Is core level as shown in our spectra indicates that this technique can be employed to investigate 

sub-monolayer coverages of sulfur and sulfur-containing molecules on surfaces. 

1. D. Heskett, J. Warner, G. Sabatino, D. Mullins, and L. Berman, in preparation. 

2. T. Yokohama, H. Hamamatsu, Y. Kitajima, Y. Takata, S. Yagi, and T. Ohta, 

Surf. Sci. 313, 197 (1994). 

sulfur 

coher pas 

- 

- + 75t 01 i coher frac - 70+01 

coher pos = +.031.01 1 coher frac = 1.00*01 

I/\ 0 

-3 -2 -1 0 1 2 

Relative Energy (eV) - 

em 7w 800 900 IMO >IO0 

Klnstlc Energpy(aV) 

Figure 1. S 1s core level spectra of the 

system S/Ni(100) as a function of H2S 

exposure. 

Figure 2. Measured XSW yields of the 

Ni LMM Auger and S 1s core emissions as the bulk Ni(200) Bragg reflection (at 

bottom) was scanned, compared with 

theoretical fits, for (2x2) S/Ni(100). 

w 

I X-Ray Standing Wave Studies of Self-Assembled Monolayer Growth I X24A I 

F. Schreiber, P. Fenter, G. Scoles, P. Eisenberger (Princeton U.), L. Berman (NSLS) 

M. Bedzyk (Northwestern U. & ANL) 

We have followed the vapor phase growth of the self-assembled monolayer of decane thiol (C10) on Au(ll1) surfaces using both x-ray standing waves (XSW) and 

x-ray photoelectron spectroscopy (XPS). In contrast to a number of studies which 

find that solution phase growth of this system proceeds via simple Langmuir growth 

with a single time constant, we have found that there are two time scales in the 

vapor phase adsorption process: a fast process which saturates with rather small ex- posures (-2OL), and a slow process which does not reach completion until exposures 

of-1OOOOL. From the sulfur signal at the saturation at each "plateau" of the uptake curve (and correcting for electron attenuation through the completed monolayer , we derive a sulfur coverage of -0.35fO.lML for the initial adsorption process 2 1 

ML=4.6x10I4 molecules/cm2, which is the coverage of the saturation ~(4x2) phase). 

This coverage is consistent with the coverage of the known "striped" phase, in which 

the molecules lie down on the surface and has a coverage of 0.27ML. These data 

provide unambiguous evidence that the vapor phase growth of ClO/Au(lll) proceeds in a two-step process, with the first rapid step covering the surface, and the 

second slower step bringing the monolayer to completion. 

How does the sulfur-Au 'bond' vary through the growth process, as the monolayer 

goes from the low density "striped" phase to the saturation ~(4x2) phase? To determined this directly, we have used x-ray standing waves, using the back reflection 

geometry to probe the sulfur position with respect to the underlying Au lattice. 

While a full characterization of the S/Au bonding structure is not yet completed, 

we have performed measurements in the (111) Bragg reflection geometry, which 

probes the height of sulfur above the gold surface, d. From these measurements, 

we have found that d=2.56f.O2Afor a coverage of -0.27ML (corresponding to the 

"striped" phase , while d=2.59f.O2Afor a coverage of 1.OML (corresponding to the 

saturated ~(4x2 phase; see Figure l), with similar results at intermediate cover- ages. This imphes that there is no significant change in the vertical S-Au spacing 

in the growth process, so the drastic changes of the monolayer structure are due 

to changes in the density of adsorbed molecules and the related orientation of the 

hydrocarbon chain, as opposed to changes in the S/Au bond. 

\ 

Figure 1. Measured XSW yields of the Au Mg and S Is core emissions as the bulk 

Au(ll1) Bragg reflection (at bottom) was scanned, compared with theoretical fits, 

for ~(4x2) ClO/Au(lll). 
Fd 

N 

Angular Correlation Between Subsequently Emitted Auger Electrons I X24A 

R. Wehlitz, L. Pibida, J. C. Levin, and I. A. Sellin (U. of Tenn.) 

Using the single-bunch mode of the X-ray ring, we have measured the angular 

correlation between Auger electrons which are emitted in a cascade-like decay pro- cess after resonant photoexcitation. The set-up used for this experiment consists of a time-of-flight (TOF) spectrometer whose axis is aligned with the electric vector 

of the monochromatized synchrotron radiation and a cylindrical mirror analyzer 

(CMA) whose axis is aligned perpendicular to the TOF spectrometer and the photon beam direction. The monochromator was tuned to the Ar 1s + 4p resonance (3203.5 eV) and the photon beam was intersecting an effusive beam of argon atoms. 

The CMA, equipped with a position sensitive detector (PSD mounted downstream 

the azimuthal and polar angles of emission in the source region, which is imaged 1 

to 1 in the CMA image space, for all azimuthal angles and a band of polar angles 

simultaneously. Thus energy-selected AI K&,3 La,3 Auger electrons were collected 

at a variety of angles relative to the axis of the TOF spectrometer which was used to 

detect in coincidence the entire group of LMM Auger electrons from about 120 eV 

to 230 eV kinetic energy simultaneously. In other words, the TOF was detecting 

the LMM Auger electrons at one angle while the CMA was detecting the precursor 

KL2,3&,3 Auger electrons from 48' to 132' with respect to the TOF axis. We 

accumulated enough intensity to see a remarkable angular correlation between a 

distinct slice (b) of the LMM Auger group and the KLL Auger electrons while 

other slices (a and c) of the LMM group exhibit isotropy. The large non-isotropic 

angular correlation observed for the distinct slice accompanies the detection of the 

first-step KLL Auger electron in a particular direction, thereby breaking the symmetry so as to reveal the correlation. Because the KLL and LMM energies are so 

different, we believe the large non-isotropic angular correlation observed represents an alignment effect rather than a dynamical post-collision interaction effect. 

of its energy selection aperture, permits registering not on 1' y the energy, but also 

1 X24C 1 Band Structure of Nonlinear Crystal LiB305 in VUV Region Obtained From Reflection SDectra * 

Tian-Jie Chen (Southern Illinois U.), W.R.Hunter (Sachs Freeman Assoc.), J. C. 

Rife (Naval Research Center), and R. Tao (Southern Illinois U) 

The production of coherent VUV and soft x-ray radiation by nonlinear optical 

techniques is a highly desirable goal. Lithium triborate (LBO) is a popular nonlinear 

optical crystal, favored for its high nonlinear susceptibility, high damage threshold, 

and broad transparency spectrum. French['] has calculated the band structure, 

has not been verified experimentally. LBO's strong interband absorption begins 

at about 165 nm (~7.5 eV), and transmission is poor at higher photon energies; 

therefore, it was thought that it was impossible to generate second harmonic beyond 

this energy. To sidestep this obstacle, it has been proposed[21 that in the case of strong absorption a reflection configuration can be used for second harmonic 

generation as far as a double resonance condition is met. 

To find the suitable energy band sets which meet the double-resonance condition, we have measured the reflection spectra in the 6-11 ev region. The experiments 

were carried out at the X-24C beamline of the National Synchrotron Light Source 

at Brookhaven National Laboratory. The samples were LBO crystals 6 x 6 x 2 mm3 

and laser grade polished. A oscillator model['] was used to derive the refractive 

indices and extinction indices from the spectra. Six absorption peaks were found 

from the extinction index curves. 

The results show: 

(1) By the comparison with the data calculated by group theory and French's 

numbers. the six observed Deaks are identified as the nB1 -mA? transitions. 

(2) The strong absorptiin edge originates from the second highest valance band, 

instead the highest valence band. 

(3) There are two band sets which meet the double-resonance condition with 

accuracy hw21 - hw3z < rt0.10ev where 1, 2, and 3 is the initial, intermediate 

and final state respectively; hw21, hw23, hW3l is the energy difference among them. WL is the fundamental laser frequency. The double resonance condition requires: 

WL = w12, 2w~ = w32; and all three dipole transitions 1 + 2, 2 + 3, and 1 + 3 are allowed. 

[1]R.French,J.Ling,F.Ohuchi,C.ChenlPhys.Rev.~44,8496(l99l).[2]T.Chen, 

R.Zitter,R.Tao,Phys.Rev.A51,706 (1995).[3]T.Chen, R.Zitter,R.Tao,W.Hunter, and 

J .Rife, Ph ys . Rev. B52,13 70 3 ( 1 995). 

Figure 1. Polar plot showing the angular correlation between three slices (a, b, and 

c) of the LMM Auger group and the KL2,3L2,3 Auger electrons. 

* *This research is supported by the IllinoisConsortium for Advanced Radiation 

Sources(CARS); and the U.S. Department of Energy under contract DE AC 02-76CH00016 

through NSLS at Brookhaven National Lab. 
I Characterization of Multilayer Coated Gratings and Mirrors I X24C I 

J. F. Seely, M. P. Kowalski, J. C. Rife, W. R. Hunter, and R. G. Cruddace (NRL) 

Diffraction gratings and mirrors with multilayer coatings are characterized in the 

soft x-ray and extreme ultraviolet regions. The multilayer coatings are designed 

to have high reflectance at wavelengths and angles of incidence that are important for the study of laboratory, solar, and astrophysical plasmas. The efficiencies 

of the multilayer coated gratngs, and the reflectances of the mirrors with similar 

coatings, are measured as functions of the angle of incidence and the wavelength 

of the incidence light. The measured reflectance is compared to model calculations 

that account for the layer thicknesses, the interfacial roughness parameters, and 

the optical constants of the materials. The gratings have blazed or laminar groove 

profiles and are fabricated by the holographic ion-beam etched process. The multilayer coating is matched to the groove profile so that the coated grating has optimal 

efficiency at the angle and waveband of interest. 

I Structure of the Quaternary NF-ATp/Fos/Jun/DNA Complex 

L. Chen, S.C. Harrison, * ('HHMI) A. Rao ', P. Hogan ', (+Haward Medical 

School) 

Activation of NF-AT (nuclear factor of activated T-cells) is a key step in signaling 

from the antigen-stimulated T-cell receptor. NF-AT consists of a specific component 

6NF- ATP) and the Fos/Jun heterodimer of AP-1. Crystals of the DNA-binding 

omain (approx. 300 residues) of NF-ATP, the bZIP elements of Fos and Jun, and a 20 bp segment of DNA bearing a site from the IL-2 enhancer, are in space group 

P21 (a=64.9, b=85.7, c=83.6, p=112.4'). Diffraction from flash-frozen crystals 

extends to 2.6 A. Data have been collected at X25 from crystals containing SeMetsubstituted NF-ATp (3 wavelengths) and from crystals derivatized with CH3 HgS 

(1 wavelength - Hg L-edge). The Hg locations have been determined from an anomalous difference Patterson; the Se sites have been determined; a MAD/MIR 

phase determination is in progress (August 28, 1996). 
X25 Fd The Near-Threshold Evolution of the CuKa3,4 Satellites w 

cn M. Fritsch (Bar-nan U., Israel), K. Hamiilainen (Helsinki U., Finland), C. C. Kao 

(NSLS), 0. Gang, M. Deutsch (Bar-Dan U.) 

Our previous measurements' of the near-edge-photoexcited Cu Ka3,c satellites 

showed that a) the onsets of the a3+aL and the a4+a' lines are separated by 10-15 

eV, and (b) t 6 e spectral shape saturates -50 eV above threshold, above which only 

the intensityincreases but no shape changes occur. Those studies did not resolve 

accurately the threshold energies, nor the spectral shape changes in the immediate 

vicinity of the threshold, issues that were addressed this period. Fig. 1 shows an accurate determination of the different onset energies for the four satellite lines. The 

shape evolution is shown in Fig. 2. The spectra were corrected for various energy 

dependent effects, and subtracted by the Ka contribution. The shape is observed to 

change considerably with increasing excitation energy due to the different thresholds 

and cross-section energy dependences of the individual lines underlying this highly 

overlapping spectrum. Quantitative analysis, now in progress, will determine these 

dependences and providing the first such data for the virtually unexplored adiabatic 

regime of the x-ray satellite emission process. 

1. M. Deutsch et aI,Phys. Rev. Lett. 70, 2424(1996). 

/ -I A 

50 c 40 

I I 1 

Eincident [x1o2 ev1 

99.0 99.5 100.0 100.5 101.0 101.5 

Figure 1. Onset energies of the satellite 

spectrum components. near threshold. 

Figure 2. The spectral shape evolution 

X25 Structural Investigation of GaP Clusters in a Si Matrix, using Multiple 

Energy X-ray Holography (MEXH) 

T. Gog (ORNL), R.-H. Menk (NSLS), R. Eisenhower,(U of Illinois) G. Le Duc, L. 

Berman, Z. Yin (NSLS) 

Measurements using Multiple Energy X-ray Holography (MEXH) have been conducted to study the structure of small ( 50 A GaP clusters in a single crystal silicon 

the novel MEXH technique into the realm of "diluted" samples, i.e. samples with 

concentrations of fluorescing atoms equivalent to only a few monolayers, and for the 

sake of this novel nano-crystal material, where implanted clusters are closely lattice 

matched with the host matrix thus making a seperation of substrate and cluster 

contributions in regular diffraction experiments extremely difficult. 

A flat-plate sample was mounted on a six-circle diffractometer and oriented with 

respect to a substrate reflection perpendicular to its surface. Tuning the energy of 

the incident x-ray beam to values above the Ga K absorption edge and rotating the 

sample around the surface normal at varying incident angles, Ga fluorescence was 

recorded, which, after a removal of background and application of absorption and 

detector dead time corrections yielded a preliminary hologram. Inversion of this 

hologram by Fouriertransformation shows an as of yet ill-resolved direct image of 

the GaP clusters, however, the four-fold symmetry of the Ga sublattice with atoms 

at an approximately correct distance can easily be discerned, providing proof that 

x-ray holographic methods with atomic resolution in connection with current synchrotron radiation sources are capable of addressing structural questions in diluted 

samples. However, collection of data covering reciprocal space in finer increments 

and more complete volumes are neccessary to generate acceptable direct images of 

GaP clusters embedded in their host Si matrix. 

matrix. These measurements were of particu '1 ar interest, both in terms of extending 
P 

N 

I- 

-4 

K-Edge Resonant Magnetic Scattering from a Transition Metal Ox- X22c, 

ide: NiO 1x25 I 

J.P. Hill (BNL, Physics), C.-C. Kao (NSLS) and D.F. McMorrow (Riso) 

Resonant x-ray magnetic scattering exploits enhancements in the cross-section 

occurring when the incident photon energy is tuned through an atomic absorption 

edge. Large enhancements were first observed at the Lrr,rrI edges in Ho and ex- plained in terms of electric multipole transitions. In addition to the L edges much 

larger enhancements are expected, and observed, at the Mrv,v edges of the ac- tinides for which the dipole excitation is to the localized, highly polarized 5f levels. 

Conversely, resonant scattering at a K-edge is expected to be considerably weaker 

because the strong (dipole transitions involve s and p levels for which there is no 

K-edge studies would be of some interest because of the window they would provide on transition metal compounds, which make up arguably the most interesting of 

magnetic systems. 

We report the observation of K-edge resonant magnetic scattering in the antiferromagnet NiO, for which an approximately two-fold increase in the scattering 

is observed at an energy corresponding to a quadrupolar feature in the absorption spectrum (Fig.1). Quadrupole excitations couple to d-like states at a K-edge 

and for transition metals these are the magnetic states. Thus, the high degree 

of polarization of the localised 3d8 states compensates for the small size of the 

quadrupolar matrix elements and an observable enhancement results. From the 

ratio of the non-resonant to resonant magnetic scattering, we estimate that the first 

order quadrupolar resonant scattering amplitude is 0.016r0, which is of the same order of magnitude as similar terms in the rare earths. These studies provide for the 

possibility of element specific magnetic diffraction in such notable transition metal 

oxides as the high Tc cuprates and colossal magnetoresistance manganites. 

spin-orbit correlation of eit h er the core level or the intermediate state. Nevertheless, 

NiO T=300 K 3000 

25 . 

8 

e 

P 4 10 

5 

10 

8.30 8.32 8.34 8.36 8.38 

Energy (keV) 

NiO T=300 K 

8.30 8.32 8.34 8.36 8.38 

Energy (keV) 

Figure 1. 

X25 High-Resolution XAS Investigations of MnOz Spinel-Based Lif Intercalation Battery Systems 

C.R. Horne, E.J. Cairns (LBNL/UC, Berkeley), M.M. Grush and S.P. Cramer 

(LBNL/UC, Davis) 

The purpose of this research is to develop a thorough atomic and electronic 

understanding of the intersertion process for Lit in Li,MnzO4 and derivative manganese oxides in order to improve the Li storage capability and/or insertion rate of 

high-performance, rechargeable Li cells. LiZMnzO4-based compounds are desirable 

positive electrodes for Li cells as they possesses high potential vs, Li/Li', low toxicity, and are relatively low cost. To achieve the goals, we are applying synchrotron 

radiation X-ray techniques. The Lit intsertion reaction for Li,Mn204 occurs over 

two voltage regions depending on x, the level of Lil. Lio.oMnz04 + x Li' + xe-t, 

Li,Mn204. 

For 0 5 x < 1, the cell discharges at 4V while for 1 x 1.8, the discharge occurs 

on a 3V plateau. As Lis inserts, the Mn IV) species are reduced to Mn 111). Xdistorts into a tetragonal structure with c/a = 1.16 through a cooperative JahnTeller distortion due to the Mn reduction'". Initial experiments at NSLS Beamline 

X-25 involved measuring the XANES for a series of Li,Mnz04 battery electrodes 

discharged to values of x = 0.0 to 2.2 at intervals of 0.2. The cells were discharged 

slowly and allowed to equilibrate before the Li,Mna 0 4-containing positive electrode 

was removed. The transmission spectra for each electrode are shown below. Upon 

examination of the spectra, several features stand out. Within the 4V plateau a 

slight difference in the edge is noticed for x > 0.6 which coincides with a small drop 

in cell voltage within the 4V plateau. For the 3V plateau an inflection in the edge 

becomes prominent which is indicative of distorted Mn-0 octahedrajn agreement 

with XRD results in the literature'. 

Between x = 1.4 and x = 1.6 the tetragonal distortion increases to the degree that 

the XANES resembles that of a square planar structure as the axial oxygen ligands 

move away from the Mn04 plane lowering the Is + 4p, transition energy versus 

transitions to the co-planar Mn 4p, and 4p, orbitals. Additionally, there is a higher 

frequency component appearing at approximately 7 eV above the main peak and 

the pre-edge region changes in the spectra of x 2 1.6 samples. References: 1. M.M. 

Thackeray, W.I.F. David, P.G. Bruce, and J.B.Goodenough, Mat. Res. Bull., 18, 

461-472 (1983). 2. T. Ohzuku, M. Kitawaga, and T. Hirai, J. Electrochem. SOC., 

137, 769-775 (1990). 

ray diffraction experiments have shown t 6 at for x > 1, the cubic spine '1 lattice 

Figure 1. XANES 

8.=.u, e" 

of Li,Mn204 for: LH - x 5 1.0, RH- x > 1.0. 
Fd 

b3 

E Crystallographic Studies of Cell Signaling and DNA Replication 

J. Kuriyan (Rockefeller U. & HHMI) 

1 X25 

Structure of the C-terminal region of p21WAFl/CIP1 complexed with human 

PCNA: 

The arrest of DNA replication in response to the detection of DNA damage is 

a fundamental mechanism by which the cell minimizes the potential transmission 

of lethal mutations. One mediator of this response is the protein p%lWAFl/CIPl 

hereafter referred to as p21), an inhibitor of the cyclin dependent protein kinases 

cdks) that control the initiation of the S phase of the cell cycle and concomitant I NA replication. An elevation of nuclear levels of the tumor suppresser protein p53 

occurs upon detection of DNA damage. This stimulates transcription of p21 as part 

of a p53 signaling pathway in which the cessation of DNA replication is coupled to 

stalling of cellular mitosis. 

p21 is a member of a family of cdk inhibitory proteins, including p27Kip1 , p57Kip2 and p27XIC1 that share sequence similarity in their N- terminal regions. 

These highly conserved regions are by themselves sufficient to inhibit cyclin-cdks 

that function at major transition points in the cell cycle. p21 is also able to directly 

inhibit DNA replication by binding tightly to and blocking the action of the DNA 

polymerase processivity factor PCNA (proliferating cell nuclear antigen). PCNA 

is a DNA tracking protein that is required for the rapid and processive replication of DNA by the polymerases d and e because it forms a sliding clamp that 

tethers the polymerase to DNA during strand synthesis. The C-terminal region 

of p21WAFl/CIPl is distinct from that in p27Kipl and p57Kip2, and contains 

a PCNA-binding sequence. The overexpression in mammalian cells of C-terminal 

fragments containing this region is sufficient to arrest DNA replication. The PCNAbinding functionality of p21 appears to reside entirely in the C-terminal 22 residues 

of the protein, which also suffice to block PCNA-mediated DNA replication directly. A peptide corresponding to these 22 residues binds to human PCNA with 

high affinity, comparable to that of the intact p21 protein (Kd 2.5 nM, as measured 

by biosensor analysis), and efficiently inhibits DNA synthesis in vitro. 

Using data measured at beamline X25, we have determined the crystal structure 

of human PCNA complexed with a peptide corresponding to the 22 C-terminal 

residues of p21, determined at a resolution of 2.6 Angstroms.. p21 binds to PCNA 

in a 1:1 stoichiometry, with an extensive array of interactions that include the 

formation of a b sheet with the inter-domain connector loop of PCNA. An intact 

trimeric ring is maintained in the structure of the p21- PCNA complex, with a 

central hole available for DNA interaction. The ability of p21 to inhibit the action 

of PCNA is therefore likely to be due its masking of elements on PCNA that are 

required for the binding of other components of the polymerase assembly. 

The p21-PCNA interface has the hallmarks of a tight and specific molecular 

interaction, and by its ability to block DNA replication it maps regions of the 

PCNA surface that are likely to be important for polymerase attachment. These 

regions on PCNA are also potential targets for the design of small molecule analogs 

that might mimic the action of the p21 peptide. 

[ Multiple Energy Speckle in Reflectivity From Si(ll1) Wafers I X25 

J. L. Libbert, J. A. Pitney and I. K. Robinson (U. of llinois, Urbana-Champaign) 

When a coherent x-ray beam is reflected from a rough surface the intensity distribution on a screen far away from the surface exhibits a granular structure commonly 

referred to as "speckle." This speckle pattern arises from random phase shifts across the coherent wave front due to reflection from differing heights on the rough surface. 

The speckle pattern can be thought of as Fraunhofer diffraction from an aperture 

illuminated by a wave with unit amplitude but with a randomly varying phase. The 

phases are proportional to qz and the height of the suraface relative to some arbitrary zero height. Thus, if one could recover the phases from the speckle pattern, the 

morphology of the illuminated region of sample would be known. It may be possible 

to recover the phases up to additions of multiples of 2~. Removing this ambiguity 

from the phases could be accomplished by taking a second speckle pattern of the same region but with slightly different phase contrast. In an attempt to recreate 

the surface morphology of a Si (111 wafer over a length scale of several hundred 

at several different energies. The multiple energies gives us a phase contrast mechanism that should allow the unambiguous determination of the phases. Figure 1 

shows a series of scans across the reflected beam from a Si (111 wafer illuminated 

at grazing incidence by a 5pm diameter coherent x-ray beam. 4 he same region of 

the sample is being illuminated in each scan while the x-ray energy is changed. The 

differences arise from the enhanced sensitivity to surface roughness at higher qz. 

The scans were taken by scanning a 24pm pinhole across the reflected beam in the 

26' direction at a distance of 1.25m from the sample. 

microns we have measured the spec I! le patterns of the same region of the sample 

fi 

.d 

-A- 

,-,.,., -600 -400 -200 0 200 400 600 

A2Qrad) 

Figure 1. Speckle patterns in the reflected beam from a Si (111) wafer. The same 

region of the sample is illuminated in all three scans but the x-ray energy is varied. 
X-ray Studies of Liquid Metal Surfaces: Oxidation and Alloy Surfaces [ X25 I 

M.J. Regan, H. Tostmann, P.S. Pershan (Harvard U.), O.M. Magnussen, E. DiMasi, 

B.M. Ocko (BNL), M. Deutsch (Bar-Ilan U., Israel) 

We have studied the oxidation of liquid Ga surfaces and the effect of alloying 

on the surface structure by x-ray reflectivity (XR). By exposing liquid Ga at room temperature to 02 doses as small as 180 Langmuirs (L), well-defined oscillations in 

the XR are observed (Fig. l), indicating the formation of a 5 A thick oxide film. 

The oxide thickness and rou hness do not change with dosage up to 1600 L nor 

with temperature up to 300 C [l]. This is in contrast to bare liquid Ga, which 

is already roughened significantly at 170 OC [2]. This is a good indication that 

the oxide layer provides rigidity to the liquid surface and is likely a solid; grazingincidence diffraction measurements indicate that the film is amorphous or poorly 

crystallized. Results on a liquid Ga-In alloy at the eutectic composition show a clear 

enrichment of In at the topmost surface layer, expected from the Gibbs adsorption 

rule due to the smaller surface tension of In. The 25% increase of the XR over the Fresnel, observed in Fig. 2b for 0.7k1<q, < 1.8a-l, is a clear sign of surface 

enrichment by a layer of electron density higher (i.e. In) than the bulk (Ga-In). 

Model fits assign the enrichment to a single In layer, with subsequent layers at the 

bulk eutectic composition (Fig. 2b). This work has been supported by grants from 

the DOE, DE-FG02-88-ER45379 and DE-AC02-76-CH00016, and the NSF, DMR94-00396 and DMR-91-13782. rll M.J. Regan et ~2.. submitted to Phws. Rev. B 

5 

(1996). [2] M.J. Regan et al., P&s. Rev. 

1 o7 

106 

1 o5 

10' 

J o3 

102 

10' 

100 

1 of 

LL \ E 

E Figure 1. Fresnel-normalized reflectivi- p ties of liquid Ga surfaces us. 02 dosage. (0 

g54, 9730'(1996). 

l"""'I 

I.I.8.I.I 

-5 0 5 10 15 

2 (a) 

4 

3 

- - - 2 In layers 

a- 

>2 

1 

0 0.5 1.0 1.5 2.0 2.5 3.0 

4, K') 

Figure 2. Fitted density profiles 

(a) and Fresnel-normalized reflectivity curves (b) for the liquid Ga-In eutectic 

alloy. 

1 1 X20A, I Structure and Kinetics of the Sliding &I CDW in NbSeB * vI)c 

K.L. Ringland, S.G. Lemay, R.E. Thorne, and J.D. Brock (Cornell U.) 

We have performed detailed measurements of both the structure of the sliding Q1 

charge-density wave (CDW) and the kinetics of its relaxation from the sliding to the 

pinned state. High q-resolution data obtained at X25 demonstrate unambiguously 

that the equal time phase-phase correlation function does not decay algebraically 

at large distances. That is, 

The detailed structure of the sliding state is still a major issue and recent models have predicted an assymptotic algebraic decay of the phase-phase correlation 

functiont. An algebraic decay produces a line-shape that traces out the resolution 

function near the center of the peak but has additional scattering in the wings. 

In contrast, we measure the full width at half maximum of the Q1 satellite in the 

sliding state to be roughly 66% broader at lox threshold than the same satellite 

in the pinned state. (The Q1 satellite in the pinned state is also broader than our 

resolution .) 

Similarly, our time resolved measurements of the relaxation of the Q1 CDW 

from the sliding to the pinned state also contradict the predictions of the suggested 

equations of motion. Specifically, the peak intensity increases monotonically with 

time after the current is switched off. The solution to the proposed equation of 

motion has the form 

where F(Q is the quenched random field and D is the diffusivity. This expression 

has a "dip' in the intensity. Our data does not exhibit such a dip. This discrepancy 

implies that either a non-linear term is missing from the equation of motion or that 

the random field, F(g, is not quenched. 

II-T , I I I, 

- 2 4500 i 3 4000 

E 3500 

p 3000 

a ?500 

0 5 IO 15 20 25 30 35 

lime [seconds] 

Figure 1. Peak intensity of (0 1+Q1 0) satellite as a function of time. Current is 

turned off at t = 3 seconds. 

~ ~ ~~ 

* This work was supported by NSF Grant No. DMR-9501119 
P 

N 

0” Characterization of the Magnetic Disorder at the (001) Surface of x22c, 

uo2 X25 

G.M. Watson, D. Gibbs (BNL, Physics), L.E. Berman (NSLS), G.H. Lander, H. 

Matzke (EITU), W. Ellis (LANL), and B.D. Gaulin (McMaster U.) 

In our earlier work, we showed that the temperature-dependence of the scattering 

along a (110)-type magnetic truncation rod of a U02(001) surface appeared to 

vanish continuously as the temperature is raised to the bulk Nkel temperature, TN 

= 30.2 K.l This is suprising since the bulk transition, as observed by neutron and xray scattering, is discontinuous.’ This behavior may be understood as an example 

of surface induced disorder wherein magnetic disorder propagates from the near 

surface volume into the bulk as the temperature approaches TN. In order to further 

characterize this behavior, we have performed measurements of the four equilavent 

(llO)-type magnetic truncation rods and of the specular magnetic reflectivity. Rod 

intensities were obtained both as a function of temperature at fixed wavevector and 

as a function of momentum transfer at a number of temperatures. The magnetic 

specular reflectivity shown in Fig. 1 is especially sensitive to the decay of the 

magnetic order parameter profile along the surface normal direction. At the higher 

temperatures, the reflectivity away from the bulk Bragg reflection falls off faster 

than it does at lower temperartures. This indicates that the width of the magnetic 

profile increases with temperature. In fact, our data seem to suggest that this width 

diverges as T approaches TN. ’ G.M. Watson, et al., Physica B 221, 405 (1996); ibid. Phys. Rev. Lett. 77, 

751 (1996). ’ B.C. Frazer et al., Phys. Rev 140, A1448 (1965); B.M.T. Willis and R.I. Taylor, 

Phys. Rev. Lett 17, 188 (1965); G.M. Watson et al., Phys. Rev. B 53, 686 (1996). 

L [Units of c.1 

Figure 1. Specular magnetic reflectivity profiles near the (001) bulk magnetic Bragg 

reflection obtained at 10.2, 26.9, 29.6 K utlizing a Au(ll1) reflection for a polarization analyzer. Peak count rates at beam line X25 were approximately 5x106 cps 

at a beam current of 200 mAmp. 

Structure Determination of the Entire Extracellular Portion of Hu- X25, 

man CD4 I X~A/ 

H. Wu, P.D. Kwong and W.A. Hendrickson (Columbia U.) 

Diffraction data from two different selenomethionyl CD4 crystals were collected 

at the selenium K-shell edge at beamlines X4A and X25 of NSLS. CD4 crystals 

were extremely weak which mandate high flux synchrotron radiation. Both data 

sets were recorded with Fuji imaging plates at 100K. These two data sets belong 

to space groups P41(2)22 and P2, respectively and were used to obtain molecular 

replacement solutions. Selenium anomalous difference Fouriers were used to confirm 

the correctness of the structures. 
1 Two 'Beam Diffraction Interference Method for 2D Crystallography I X25 1 

Y. Yacoby (Hebrew U.), H. Baltes, R. Pindak, L. Pfeiffer (Lucent Technologies), 

R. Clarke (U. of Michigan), and L. Berman (NSLS) 

The two beam diffraction interference method [l] provides the amplitude and 

phase of the Fourier transform of the X-ray dielectric function of 2D crystals allowing a direct determination of their structure. This method was tested using an aperiodic 

GaAs/AlAs multilayer epitaxially grown on [110] cleaved GaAs. After exposure to 

air, a 1OOOk gold film was evaporated on several samples. The X-ray beam entered 

the samples as shown in Fig.1 and the diffracted beams (d) were observed from the 

top. In the samples with the gold, the incident beam was reflected and the reflected 

beam was also diffracted. The main objective of the experiments was to establish 

if these two diffracted beams interfere and to obtain the phase information. 

We measured the intensity of the diffracted beams as a function of position along 

4 distinct Bragg rods for samples with and without the gold film and for different 

angles of incidence, a. In samples without the gold film, and hence no reflected 

beam, it was confirmed that the intensity of the diffracted beams is independent 

of a. One spectrum along the [h,h,l] Bragg rod is shown in Fig.2. The calculated 

spectrum, assuming the nominal epitaxial growth structure but with 5 amorphous, 

oxided, capping layers and with a roughness of f2 layers, is also shown (solid line . When the gold film is present the intensities depend on CY (solid circles in Fig.%]. 

The intensities were calculated both assuming that the diffracted beams coherently 

interfere (solid line in Fig.2) and without interference (dotted line). It is evident that 

interference must be included. Using the measured intensity spectra of samples with 

and without the gold layer the differential phase, cos(B1 - 82 - cj), was calculated 

along each Bragg rod. An example for [h,h,l] is shown as solid circles in Fig.1. 

Here, d, is the phase difference between the incident and reflected beams and 81 

and 02 are the phases of the X-ray dielectric Fourier transform function at pairs of 

points separated by Aq. = %sin a). We calculated the same function using the 

agreement with the experimental determination proving that the pairs of diffracted 

beams are coherent and interfere with each other providing phase information. 

structural parameters described a 6 ove. The result (solid line in Fig.1) is in fair 

[l] Y. Yacoby, Solid State Communications, 91, 529 (1994). 

1.6 

IO 

0.6 

- *" $ 0.0 

a.6 

.ID I 

0.6 0.10 LT~ 0.m as om as 

h 

Figure 1. 

0.65 070 0.75 0.88 0.85 090 

h 

1 The Structure of Calicivirus 

L. Zhou and M. Luo (U. of Alabama at Birmingham) 

Introduction: The recent rapid spread of a rabbit calicivirus through Australia 

to Europe demonstrated a potentially dangerous situation if a human calicivirus 

emerges. It is estimated that at least 42% of outbreaks of nonbacterial gastroenteritis in the U.S. are caused by this group of viruses [l]. The main difficulty in 

dealing with infections of small round-structured viruses (SRSV's) is the large diversity of the viral capsid protein [2]. 

We have purified and crystallized FCV strain F9 and a large 

amount (50% complete) of X-ray diffraction data to 3.OA resolution have been collected at synchrotron stations [3]. The space group of the crystal is C222, a=889A, 

b=996A, c=436A. A total of 226 images afforded 1,396,078 reflections, which is 

about 40% complete to 3.5A resolution. There are two independent particles in the 

unit cell, one sits on the a axis, the other on the b axis. Each of the particles is 

rotated by less than 2' from the ideal orientation. Model coordinates have been 

constructed based on the cryo-EM structure. The high resolution structure determination is well under way by using the molecular replacement density averaging-phase 

extension method. Although there were no improvement this time on the quality 

of the diffraction data collected at NSLS, we expect to collect better data in the 

future by use of the cryo-freezing technique. 

Discussion: Caliciviruses resemble the picornaviruses with which they were originally classified. Like the picornaviruses, the genomes of calicivirus bear a covalently 

attached protein (VPg) at the 51 end, and there is no cap structure at the 5/ end 

of the subgenomic mRNA. However, caliciviruses differ from members of the picornavirus group in that RNA species smaller than the genomic RNA are synthesized 

intracellularly. A striking difference between caliciviruses and picornaviruses was 

found in their genome organization. The genomic RNA of picornaviruses encodes a single polyprotein which is co- and post-translationally processed to yield the mature viral proteins. No single large polyprotein precursor to all the viral proteins is 

known for calicivirus. The genes encoding for the structural polypetides are located near the 3/ end of the genomic RNA. 

In our studies a feline calicivirus strain F9 was used for the X-ray structure 

determination. The comparative sequence analysis of capsid precursor proteins from 

FCV strains F9 and CFI/68 FIV demonstrated that variation was concentrated in 

two areas. 

Reference: Kaplan, J.E., R. Feldman, D.S. Campbell, C. Lookabaugh and G.W. 

Gary (1982), The frequency of a Norwalk-like pattern of illness in outbreaks of acute 

gastroenteritis. Am. J. Public Health 72:1329-1332. 

Wang, J., X. Jiang, H.P. Madore, J. Bray, U. Desselberger, T. Ando, Y. Seto, 

I. Oishi, J.F. Lew, K.Y. Green and M.K. Estes, 1994. Sequence diversity of small, 

round-structured viruses in the Norwalk virus group. J. Virol. 68:5982-5990. 

Zhou, L. and Luo, M. "Preliminary Analysis of Feline Calicivirus Crystals", Acta 

Crystallogr. D51:850-852, (1995). 

Experimental: 

Figure 2. 
Tissue Localization of Metals Bioaccumulated in Marine Organisms 

Living in Sediments * 

W. J. Berry, D. J. Borsay (US Env. Prot. Agency), and K. W. Jones (BNL - DAS) 

The sediments of many of the rivers, lakes, and estuaries of the United States are contaminated with toxic metals and other compounds from municipal and industrial 

sources. Physiological effects on test organisms caused by metals in sediments cannot be understood from dry weight metals concentrations alone. This understanding 

requires the knowledge of which phases in the sediment are controlling bioavailability. Much work has already been done on the factors controlling the bioavailability 

of cadmium, copper, lead, nickel, and zinc, and mixtures of these metals. The 

results of this work indicate that the ratio of acid volatile sulfide (AVS) and simultaneously extracted metal (SEM: the metal measured in the extract from the 

AVS procedure) can be used to predict the acute and chronic toxicity of metals in 

sediments. Sediments in which the ratio of SEM/AVS is < 1.0 are not toxic, while 

sediments with SEM/AVS ratios greater than 1.0 may be toxic. This phenomenon 

is related to the capacity of sulfide to bind divalent metal when SEM/AVS is < 

1.0, such that the metal will not be bioavailable. Several bioaccumulation studies 

have been done in which test organisms have accumulated metals from sediments 

with SEM/AVS ratios of < one. This is not what would be predicted by the theory, 

and as a result, we are interested in finding out where in the organism the metals 

are bioaccumulated. If the metal accumulated in these sediments with SEM/AVS 

ratios < 1.0 is primarily adsorbed on the surface epithelium of the organism or a 

component of sediment incompletely purged from the gut, and not incorporated 

into the tissues, this would help to confirm our theories about bioavailability in 

these sediments. If the metal is accumulated in the tissues themselves, this may 

force us to reconsider some of our hypotheses. It is difficult to get adequate samples 

for chemical analysis of individual tissues from these test organisms, because they 

are typically quite small. Synchrotron-radiation induced x-ray emission (SRIXE) is 

a tool that can localize sites of metals accumulation with both good spatial resolution and sensitivity, a task which is difficult using other methods. As a first step we exposed a typical marine bioaccumulation test organism, the clam worm, Nereis 

virens, to a mixture of cadmium and nickel in a water-only test to evaluate the use- fulness of SRIXE in localizing metal accumulation in this species. Clam worms were exposed to a mixture of 1,250 g/L nickel and 500 g/L cadmium in filtered seawater 

for 7 days in individual glass beakers. Exposures were conducted in the dark at 15 

C. Tissues were embedded in paraffin and sectioned at 10 m and mounted on 7.0 m thick polyimide film. Data were accumulated for Ca, Fe, Ni, and Zn. Cd could be 

observed, but the intensity was too low for measurements to be made in scan mode. 

Ca, Fe, Ni, and Zn were found in the epithelium, as well as in muscle, nerve, and 

gut tissues, as might be expected from a water-only exposure. The results obtained 

show that SRIXE is suitable for these investigations and that further testing using 

metals-spiked sediments can be performed. In this next phase, worms exposed to 

a series of sediments spiked with various levels of SEM/AVS will be examined to 

pinpoint the location of bioaccumulated metal, especially in those worms exposed 

to sediments with SEM/AVS < 1.0. 

X26A 

* Research suppported in part by US DOE Contract No. DE-AC02-76CH00016. 

1 Lead in Tadpole Brain * X26A I 

H. T. Cline (Cold Spring Harbor Laboratory), S. Witte (U. of Iowa), and Keith 

Jones (BNL - DAS) 

Many studies both in humans and animals have established the deleterious effects 

of lead on the developing brain. There have also been a number of animal studies. For example, Lindh et al. [l] measured the microscopic distribution of lead in 

the cerebellum of suckling rats using micro-proton-induced x-ray emission ( PIXE). 

They measured lead concentrations in white matter and the granular, Purkinje, and 

molecular layers and found values of about 20 5g/g dry weight. The concentrations were high enough to permit a detailed mapping of the lead distribution with the 

microprobe. Cline et al. [2] have investigated the effects of much lower lead concentrations on the neuronal growth in the retinotectal system of frog tadpoles. In 

this experiment, the concentrations of lead are so low that making maps of the lead 

distribution was not easily practicable. However, their work showed changes in the 

histology of the retinal ganglion cell axon arborizations that was a function of the 

magnitude of the lead dose. Further, they found that treatment with the chelating 

agent, 2,3 dimercaptosuccinic acid DMSA) helped to reverse the damage caused 

by lead. A direct measurement oft 6 e lead concentration in the optic tectum was 

desired to directly verify the presence of lead in the region of study. The amount 

of material available for analysis precluded determinations using techniques such as atomic absorption spectroscopy (AAS). It was anticipated from the nanomolar doses 

administered to the test animals that it would be feasible to make the determination 

with SRIXE albeit with some difficulty. Samples were prepared by making 1 5m 

microtomed sections from 10 different animals that had been exposed to lead and 10 

that had not been. The sections were mounted on 7.6 5m polyimide film for SRIXE 

analysis. The measurements were carried out blind. Each section was measured 

for varying times of about 5500 s with an 8 5m 8 5m size beam. The estimated 

concentrations found were about 200 and 100 parts per billion (ppb) dry weight. 

Estimates of the ratios between the two sets of specimens were made by considering the Pb/Zn ratio so that dependence on specimen thickness was removed. The 

results confirmed the presence of lead in the optic tectum. In retrospect, the precision of the measurement could have been improved by the use of thicker sections 

and a larger beam size. Making a detailed map of the lead distribution probably 

awaits, however, the use of an undulator at a third generation synchrotron source such as the Argonne Advanced Photon Source (APS) or the European Synchrotron 

Radiation Facility (ESRF). The results of the work demonstrate, in any case, the 

way in which SRIXE can be applied to the determination of a very small number 

of atoms in a small sample volume. [l] U. Lindh, N. G. Conradi, and P. Sourander. 

Acta Neuropathol. 79, 149 (1989). [2] Cline, H. T., Witte, S., and Jones, K. W. 

Proc. Nat. Acad. Sci. USA 93, 9915-20 (1996). 

1 

* Research supported in part by US DOE Contract No. DE-AC02-76CH00016. 
Distribution of Catalysts in Polyolefin Polymerization Particles * 

W. C. Conner, Jr. (U. of Massachusetts) and K. W. Jones (BNL - DAS) 

I X26A 

Supported catalysts of various types play a major role in petroleum refining and 

in the manufacture of various type of polymers. Measurements on several types of 

catalysts have been made at the NSLS X26 beam lines using SRIXE and computed 

microtomography (CMT) as complementary techniques. The methods have been 

applied to the study of polyolefin polymerization particles, fluid catalytic cracking 

(FCC) catalysts, and hydrotreating catalysts with most of the effort devoted to 

examination of the polymerization particles. Two types of supported catalysts used 

in production of polyolefin polymerization particles were studied: silicasupported 

Cr and Ti-supported MgC12. They are ideal for study using CMT. X-ray CMT 

is normally based on the contrast provided by differences in the linear x-ray absorption coefficients of materials in the path of the beam. Both catalysts and 

supports are much more highly absorbing than the polymer material. Fragments 

of the initial catalyst particle are thus readily detected and their positions within 

the growing polymer particles are determined. CMT has proved to be a unique, 

powerful technique to study the catalyst/polymer agglomerate in situ (3- m pixel 

size). This information provided the first detailed picture of the changes in this 

complex industrial process as a function of the amount of polymer produced. Initial studies showed that, for certain commercial catalysts, the catalyst fragments were convected toward the periphery of the catalyst/polymer particle during the 

initial stages. This has many ramifications as to the heat and mass transfer during the beginning of the polymerization process. This knowledge has already been 

employed in the design of new catalysts and the control of current polyolefin processes. As the polymerization proceeds, the catalyst fragments become too small 

to be readily detected by CMT. We used SRIXE (10 m beam size) to analyze the 

distribution of catalyst fragments for higher yields. Thin sections of the polymer 

were cut using a microtome. Two-dimensional maps of the concentrations of the 

catalysts and supports could then be made. The map was obtained using 17- m and 33- m steps in the two-dimensions in a 40 12 matrix. Interestingly, this clearly 

shows the location of large catalyst fragments, as seen in the tomographic sections, 

but, in addition, a uniform distribution of the catalyst was found over the entire area of the polymerization particle giving evidence of smaller catalyst fragments. 

The results suggest the possibility of following the overall process of fragmentation 

in much more detail than has been possible in the past. These analyses are crucial 

to understand not only the progress of polymerization at higher yields, but, more significantly, the recently developed (and developing) commercial processes involving sequential polymerizations. In these processes the product polymer/catalyst 

from a first reactor ise sent to a second reactor where a second polymerization is run producing a polymer of different composition. In this manner, a micro-mixed 

composite polymer is produced. The same catalyst catalyzes both processes; although, different monomer compositions, activators and modifiers are present in 

the second reactor. It is crucial to understand the catalyst fragment distribution 

coming from the first reactor in order to understand the polymerization process in 

the second reactor, including the mass and energy transport throughout the growing 

catalyst/polymer particle. Many co-polymerization processes are being developed 

based on this sequential polymerization approach. 

ha 

N 

w * Research supported in part by US DOE Contract No. DE-AC02-76CH00016. 

Chemical Compositions of ”Cluster” Interplanetary Dust Particles I X26A 

G. J. Flynn (SUNY Plattsburgh), S.R. Sutton (The U. of Chicago), and S. Bajt 

(LLNL) 

Interplanetary dust particles (IDPs) are collected from the Earth’s stratosphere 

by impact onto a rigid collection surface, covered with a thin layer of silicone oil, 

carried by a high-speed aircraft. IDPs are separated into two types, based crudely on structural strength: 1) those which remain intact, and, 2) those which fragment on 

collection (called ”cluster particles”) which are recognized by a high concentration 

of fragments in a small region on the collector surface. 

[l] reported that deuterium enrichments in cluster particles are ”larger, more common, and have higher variability than previously measured 

IDPs.” We undertook a chemical comparison between cluster particles and IDPs 

collected intact. Fragments from 8 different clusters were analyzed using the Xray Fluorescence Microprobe at X26A. One fragment showed significant depletions 

in Zn (<O.OlxCI), Ge, and S, compared to the abundances in primitive CI-type 

meteorites. This pattern was previously observed in IDPs which experienced se- vere atmospheric entry heating [2]. Two fragments showed smaller Zn depletions 

(0.2 to 0.4xCI), suggesting less severe heating. The other 5 fragments have Zn 

contents 2C1, suggesting they experienced comparatively little entry heating, and 

little thermal alteration of their chemistry. 

The five cluster fragments which show no evidence of severe atmospheric entry 

heating each have contents of the volatile elements C1, Cu, Zn, Ga, Ge, Se, and Br 

which exceed CI-type meteorite concentrations, and S which is near or exceeds CI. 

The average pre-atmospheric content of elements having nebular condensation temperatures lower than Mn is enriched relative to CI by factors of 2 to 6 for Cu, Zn, 

Ga, Ge, and Se, and by a much larger factor for Br in these cluster fragments. This 

equals or exceeds the average concentrations of these elements previously measured 

in small (~10 microns) IDPs collected from the Earth’s stratosphere [3]. Sulfur, usu- ally present at -CI level in smaller IDPs [3], averages 1.4xCI in these 5 fragments. 

These cluster fragments have substantially higher concentrations of the elements 

having low nebular condensation temperatures than we measured in large (>35 micron) IDPs collected intact [4], suggesting a correlation between structural strength 

and chemical composition, with the weakest particles being the most volatile rich. 

Messenger et al. 

1 Messenger, S. et al. (1996) Lunar Planet. Sci. XXVII, 867-868. 

2 Flynn, G. J. et al. (1993) Lunar Planet. Sci. XXIV, 497-498. 

3 Flynn, G.J. et al. (1996 ”The Abundance Pattern of Elements...”, ASP 

4) Flynn, G.J. et al. (1995) Meteoritics, 30, 505. 

Conference 1 Series, Vol. 140, AS L Press, 291-294. 
P 

w 2 Spatial Distribution of Lead in Chick Tibia * X26A 

C. S. Fullmer (Cornell U.) and K. W. Jones (BNL - DAS) 

Lead in bone is of interest for several reasons. From the practical standpoint, 

the in-vivo measurement of lead in bone has been widely used for epidemiological 

studies and to a lesser extent for clinical diagnostic applications. Nevertheless, the 

kinetics for the accumulation and desorption of lead in bone are not well understood. 

On a more fundamental level, lead in bone is of interest for two reasons. First, bone 

is the largest repository of the body burden of lead which may be mobilized during 

a number of physiological and pathological conditions such as endocrine status, osteoporosis, renal disease, certain nutritional challenges, and, in particular, during 

pregnancy and lactation. Second, it is now known that lead may influence bone 

development, growth, and function in a variety of ways. Clinical and experimental 

studies have shown that Pb ingestion may both increase and decrease serum levels 

of the vitamin D hormone 1,25-dihydroxyvitamin D, thereby altering intestinal Ca 

absorption and, presumably, parathyroid hormone (PTH levels. Each of these is 

critical to normal bone cell function and mineralization. T h us, there is an enormous 

potential for both direct and indirect Pb-Ca interactions at the cellular and extracellular level, with lead, exerting multiple influences on several biological processes. 

The purpose of this experiment was twofold. First, to evaluate, histologically, the 

changes in bone development due to Pb intoxication in normal Ca and C%deficient 

animals. Second, to assess the feasibility of synchrotron-radiation induced x-ray 

emission (SRIXE) analysis of the microdistribution of lead in bone, as well as the 

changes in Ca distribution which accompany lead intoxication. For these studies, 

two-week old normal growing chickens were changed to diets either normal or deficient in Ca, each containing either 0 or 0.3% lead, for an additional two weeks. 

The histological sections showed that Pb ingestion resulted in somewhat diminished 

metaphyseal cartilage cores, but had no apparent effect on the epiphyseal growth 

plate or secondary spongiosa. Low Ca chicks, as compared to normal, exhibited a 

substantially thinner growth plate, as well as thinner and shorter metaphyseal car- tilage cores. In chicks ingesting the low Ca diet containing Pb, the growth plate was 

markedly thicker than normal and the cartilage cores were greatly reduced in width 

and distal projection. In addition, the primary spongiosa was relatively wide and 

the secondary spongiosa was poorly defined with few and thin trabeculae. These 

results indicate that the effects of Pb on bone growth and development are very 

much dependent on dietary Ca level. However, whether the observed effects are 

due to direct actions of Pb on bone, indirect effects on calciotropic hormones, or 

both, remain to be determined. SRIXE was used to produce two-dimensional maps 

of significant areas of the bones that included both cartilage, trabecular, and compact bone. The maps demonstrate the potential of SRIXE in detailing the tissue 

distribution of Pb as well as its relationship to Ca distribution. In each case, normal 

Ca and low Ca, Pb and Ca are similarly distributed in the columns of calcifying 

cartilage of the primary spongiosa. Especially evident in the low Ca situation is the 

Pb-associated disruption of new trabecular bone formation (secondary spongiosa) 

with substantially diminished deposition of both Ca and Pb. These results indicate 

that Pb and Ca deposition in bone are similar and that disruption of bone growth 

and mineralization by Pb influences the distribution of both cations. 

* Research supported in part by US Department of Energy Contract No. DE-ACO2- 

76CH00016. 

I Migration and Reduction of Cr(V1) in the Presence of Fe(I1) * I X26A 

D.B. Hunter, E.J. Gall, P.R. Nuessle and P.M. Bertsch (U. of Georgia) 

Contamination of soils and groundwater by Cr(V1) is of increasing concern because of its high mobility in the environment and its toxicity to plants, animals, and 

humans. Chemical reduction of Cr(V1 by Fe(I1) salts can immobilize Cr 111) as inleaching. The conditions under which Cr(II1) could be remobilized are dependent 

upon the solid phase speciation and coassociation of Cr with other soil constituents 

following implementation of in situ reduction technologies. These conditions are 

influenced by the geochemistry of the system, including mineralogy, solution pH 

and chemistry, and the presence or absence of natural organic materials. Thus, success of reduction/immobilization of Cr(V1) as an in situ remediation technology 

is dependent on controlling the reduction process to favor the formation of specific 

mixed (Fe,Cr) oxyhydroxide phases. We have developed a column transport assembly in which Cr(V1) containing ion exchange phases are introduced above various 

model soil constituents (sand, mixed cationic/anionic exchange resins, etc.) and 

placed in the x-ray microprobe at X26A to examine the efficacy of various in situ 

remediation technologies based on reduction/immobilization. Solutions containing 

Fe(I1) salts can be injected into these columns at varying flow rates and the resultant 

transport and reduction of Cr(V1) can be monitored by XRF and XANES under a 

wide range of solution and substrate chemistries. Figure 1A illustrates the relative 

spatial distribution of Cr in a typical column after reaction with Fe(I1) (data points 

represent the average of a section 0.3 mm wide by 0.01 mm tall . Cr is localized at 

two more localized regions at 4 and 8 mm. XANES measurements at these locations 

indicate complete reduction of Cr(V1 to Cr(II1) inferred by the loss of the sharp 

soluble (Fe,Cr) oxyhydroxide phases, t h us limiting the possibility of reoxi 6 ation and 

the original region of packing approximately 1 mm from top o r' column, as well as 

pre-edge feature indicative of Cr VI). k igure 1B shows a typical XANES spectra for 

oxidized Cr at 1 mm before Fe(1 I ) injection and Figure 1C illustrates reduced Cr at 

all locations after injection. These results indicate significant migration of Cr down 

the column despite reduction of Cr(V1) to the relatively insoluble Cr(II1) species. 

These initial experiments are being expanded to investigate additional aspects migration and oxidation state behaviors of Cr(V1) under environmentally relevant and 

well defined model situations. 

A B C 

- 

Y 6 2 0.6 0.4 :I, r/, 1 i;, ), , , ,I 0.4 

0.2 0.2 - 

to 0' 

0 1 2 3 4 5 R 7 8 9 10 -15 -5 5 15 25 35 -15 -5 5 15 25 35 

Distance Along Column (mm) Re1 Energy (eV) Rsl Energy (eV) 

Figure 1 

* This reserch was supported by Financial Assistance Award Number DE-FCO9- 

968R.18546 from the U.S. DOE to the University of Georgia Research Foundation and 

by ERDA/WSRC subcontract AA46420T 
Composition of Dredged Material From The NY/NJ Harbor * 

K. W. Jones (BNL - DAS) and S.-R. Song (BNL and Yale U.) 

X26A 

Shipping activities in the NY-NJ Harbor are threatened by restrictions on dredging of navigational channels and private berthing areas because of concerns about 

the fate and effects of contaminated sediments caused by ocean disposal of dredged 

materials. Current proposals for solutions to the problem include the use of confined disposal facilities, borrow pits, land disposal, and various decontamination 

technologies. While many investigations of the nature of organic and metallic sediment contaminants have been performed, further measurements are needed to understand the transport of contaminants in the sediments at the particle-size scale, to 

give insight into the efficacy of various decontamination technologies, and to verify 

the stability of post-treatment end products. The present investigation is based on 

the use of x-ray beams from the NSLS to investigate samples using synchrotroninduced x-ray emission (SRIXE), x-ray absorption near-edge structure (XANES), 

and computed microtomography (CMT). The micrometer-scale spatial resolution 

made possible by the high-intensity synchrotron beams are essential for study of 

the sediments since a major fraction of dredged sediment particles are less than a few hundred micrometers in diameter. Initial experiments were performed with 

sediments from Newtown Creek, an estuary that forms a natural boundary between 

the Boroughs of Brooklyn and Queens in New York City. These sediments are typical of those found across the Harbor and contain elevated levels of toxic organic 

and metallic compounds. Native sediments were size-fractioned by water washing 

and sieving and subjected to SRIXE measurement. Metal concentrations were relatively constant for particle sizes up to 1 mm. Hence, simple physical separation 

of the sediments by size is unlikely to be a useful technique for segregating highfrom low-contaminant-bearing particles. Further measurements will be made to 

determine the variability of the metal concentrations in the bulk samples and for 

individual grains within each size distribution as well as by different particle types, 

i.e., clay or quartz. Investigations of the spatial distributions of contaminants were begun by measuring the radial concentrations in spherical concentrations. Preliminary results verify the common assumption that the metals are contained in 

a surface layer rather than distributed through the entire volume of the particle. 

Some measurements were also made on particles that had been treated by different 

decontamination technologies to ascertain their differences. XANES measurements 

were carried out to determine the quantity of the carcinogenic Cr6+ present relative to the less toxic Cr3+. We plan to explore the feasibility of making combined 

absorption and fluorescent CMT measurements to determine the structure and composition of individual grains of the sediments before and after processing as well as 

the particle/pore space relationship. 

P 

N 

* Research support in part by US DOE Contract No. DE-AC02-76CH00016 and Section 

405 of the Water Resources Devlopment Act of 1992 Agreement No DW89941692 with the 

US Environmental Protection Agency. 

N 

X26A Behavior of Dissolved Molybdenum during Localized Corrosion of 

Austenitic Stainless Steel 

H.S. Isaacs and S.-M. Huang (BNL-DAS) 

An in situ study of chemistry of molybdenum during localized corrosion of stainless steel in chloride solutions has been carried using energy dispersive x-ray techniques. An artificial pit was used to maintain a one dimensional diffusion geometry 

by dissolving back the cross section of strip of Type 316 stainless steel foil mounted 

in an epoxy resin. A high intensity 8 mm diameter polychromatic x-ray beam at 

Beamline X26A was scanned across the steel, a salt layer on the steel, and the 

concentrated dissolution products within the artificial pit. The resulting x-ray fluorescence was analyzed to determine changes in concentration of the constituent 

alloying elements. It has been found that the salt layer on the steel was formed 

mainly by iron chloride and all other alloying elements present at relatively lower 

concentrations than in the steel. Virtually no chromium remained in the salt layer. 

Also, little molybdenum was present negating proposed corrosion inhibition by a 

definitive molybdenum forming salt layer. Within the concentrated artificial pit 

solution it was found that alloying elements dissolved and migrated down a concentration gradient, but closer to the mouth of deep approx. 2mm) pits, precipitation 

processes. 

of molybdenum occurred to a minor extent that di 6 not affect the localized corrosion 

7w 

MM 

50.3 50.34 50.38 

u Position (mm) 50.3 50.32 50.34 50.36 9.38 

Position (m) Figure 1. Variations of X-ray Intensity for Fe Cr, Ni and Mo across the 

steel/solution interface at a potential of 

3 Vsce. 

Figure 2. Ratios of the X-ray intensities of elements shown in (a) across the 

interface. 
td f3 

X26A Synchrotron Radiation in the Study of the Annual Growth Ring of 

Trees * 

R. R. Martin, T. K. Sham (U. of Western Ontario), and K. W. Jones (BNL - DAS) 

We have carried out a preliminary study of the content and spatial (seasonal) distribution of metals in a tree-ring specimen at the X26C microprobe beamline using 

the Synchrotron X-ray Fluorescence Analysis (SXRFA) technique. This study was carried out in connection with some other studies (SEM, SIMS) which show that 

some elements seem to be confined to regions on the order of micrometers in the 

tree rings. In this study, the x-ray fluorescence results show that the distribution 

of Ca and K across the tree ring exhibit a close correspondence consistent with 

conventional wisdom. The perhaps more interesting observation was the distribution of Cr, Co, Fe and Mn. The appearance and disappearance of these elements 

are incredibly abrupt across a site within approximately 10 microns. This is the 

first time such an aggregate has been observed in situ by any technique. Based on these results, we are convinced that SXRFA has the desired sensitivity and spatial 

resolution for the study of metals in tree rings. It will be an exciting new area of 

research in dendrochemistry. 

* Research supported in part by US DOE Contract No. DE-AC02-CH00016. 

Structure Studies of Transition Metal Complexes in Fluid Inclusions 

at Elevated Temperatures 

R. A. Mayanovic (Southwest Missouri State U.), A. J. Anderson (St. Francis Xavier 

U.-Canada), and S. Bajt (LLNL) 

There is a significant lack of understanding concerning the molecular structure 

of metal complexes in hydrothermal environments leading up to and above supercritical conditions. Fluid inclusions, which are microscopic pockets of fluid (containing ppm concentrations of Zn, Fe, Pb, etc.) trapped in host crystals, are ideally 

suited for temperature-dependent studies on coordination and structure of metal 

ions in hydrothermal fluids using XAFS. Temperature dependent Zn and Fe K-edge 

XAFS spectra were collected in the fluorescence mode from individual fluid inclusions (dia. ~60 pm in quartz from a pegmatite dyke in the Saxonian Granulite 

(see figure) indicates that the dominant zinc complex in the inclusions at all temperatures ranging from 25°C to 430°C was ZnClZ-. The Zn-C1 mean-square relative 

displacement a2 increased uniformly with temperature, from a value of 0.0043A2 

at 25°C to 0.0089A2 at 430°C. The clear dominance of ZnC1:- in the inclusions at 

all meaurement temperatures can partly be attributed to the high chloride concentration of the inclusions (est. up to 9 mol/kg). The Zn-C1 bonds of the ZnCl4'- 

complex were found to exhibit a reduction in length (by nearly 2% at 430°C compared to the value at 25°C) with temperature (see inset figure). We speculate that 

the contraction of the Zn-C1 bond length is due to either a progressive reduction of 

the dielectric constant of the liquid phase or due to the ZnC1:- complex becoming 

increasingly more dehydrated with temperature, resulting in stronger Zn-C1 bonding. Preliminary results from fitting of the Fe K-edge data indicate that the iron ion was predominantly hydrated from 25°C to 100 "C and probably somewhat above 

this temperature. The Fe-0 distance was close to 2.lOA with roughly six water 

molecules in the first hydration shell at both temperatures. At 200°C and above 

(to 5OO0C), the iron ion was predominantly coordinated by the chlorine ligands, coinciding with the dissolution of the halite (NaCl), which typically occurs at about 

-26OOC. The FE K-edge XANES changed progressively with temperature, indicating that the overall nature of the iron chloro complex(es) might have been changing. 

The average number of chlorine ligands increased uniformly from roughly three at 

200°C to four at 500°C. Conversely, the Fe-C1 bond length decreased uniformly 

from 2.29a at 200°C to 2.25a at 500°C. 

Massif, Germany. E;! itting of the Zn K-edge Fourier transform data using FEFF6 
I Stroke and Calcium Concentrations in the Brain * I X26A I 

G. Newman, S. Trowbridge (SUNY Stony Brook), and K. W. Jones (BNL -DAS) 

There are wide reaching disturbances of Ca+2 metabolism under conditions of 

ischemia. At ischemia onset, there is depolarization of the tissue with release and 

accumulation of glutamate and Kt in the extracellular space (ECS). Early depolarization results in a rise of free cytoplasmic Ca+2 due to release of Ca+2 from 

intracellular stores and influx from ECS. As hypoxia limits ATP generation and 

acidosis results from the anaerobic glycolysis which accelerates in an effort to compensate, Ca+2 cannot be properly sequestered and concentration gradients in the 

cell gradually disintegrate. As Ca+2 rises toward 5 5M in the cytoplasm the mitochondria develop membrane pores which permit free movement of all molecules less 

than 1000 MW. Eventually, ischemic brain undergoes anoxic depolarization with 

massive release of KS into the ECS and entry of Ca+2 into the cell. 

The present experiment was designed to test the hypothesis that tissue Ca+2 

is regulated independent of extracellular Ca+2 concentration. Brain slices isolated 

from rat hippocampus were incubated in buffers with a range of Ca+2 concentrations from 4.5 mM to 0.001 mM. Buffer Ca+2 was labeled with 45Ca. A volume of 

distribution for 45Ca was calculated at each buffer Ca+2 and total tissue Ca+2 can 

be calculated from that volume. Contrary to expectations, based on the experiments 

with 45Ca, it appears that the volume of distribution remains nearly constant from 

4.5 mM to below 0.5 mM so that tissue Ca+2 is directly related to extracellular 

Caf2. Even below 0.5 mM external Ca+2, the rise in the volume of distribution is 

not very great so that the relationship between tissue and buffer Ca+2 remains very 

nearly linear. In this experiment, it is assumed that 1) all tissue Ca+2 pools are labeled by 45Ca during the one hour incubation with isotope or at least that 2) the 

fraction of labeled tissue Ca+2 remains constant at all buffer Ca+2. Either or both 

of these assumptions may be incorrect. There is need, therefore, to measure tissue 

Ca+% independently of radiolabeling by exchange equilibrium and thus determine 

the fraction of tissue Ca+2 which equilibrates as a function of buffer Ca+2. 

The approach we chose was to repeat the slice incubations to create the con- centration response curve, but without 45Ca in the buffer and to measure tissue 

Ca+2synchrotron-radiation induced x-ray emission (SRIXE) which has high-spatial 

resolution combined with excellent minimum detection levels. Measurements were made on 450 5m thick sections of rat hippocampus for buffer concentrations from 0 

to 4.5 mM. The Ca concentrations were normalized to the tissue K concentrations 

to remove uncertainties arising from variations in tissue thickness. 

These experiments suggest that the assumption that 45Ca labels either all or a 

constant fraction of Ca+2 is not valid. Certainly the results suggest that when 

buffer Ca+2 is below 1 mM a significant portion of the tissue Ca+2 is not labeled 

by 45Ca. A rough estimate of the size of the unlabeled Ca+2 pool is about 0.1 

mM. Questions surrounding the 45Ca measurements take on greater significance in 

light of our recent finding that, in brain slices, ischemic injury is accompanied by 

irreversible uptake of 45Ca in a tissue compartment. The nature of the compartment 

may hold an important clue for how Ca+2 contributes to irreversible tissue injury 

in ischemia. 

F 

* Research supported in part by US DOE Contract No. DE-AC02-76CH00016 (KWJ); N 

N 

NINDS S28429-01A1 and VA Merit Review (GCN, ST). 

Study of Chemical State of Toxic Metals During the Life Cycle of 

Fly Ash Using X-Ray Absorption Near-Edge Structure * 1 X26A 1 

J. Osin, B. TGrok, S. Torok (KFKI Atomic Energy Research Institute, Hungary), 

and K. W. Jones (BNL - DAS) 

The non-destructive X-Ray Absorption Near-Edge Structure (XANES) method was applied for the quantitative determination of chromium and arsenic species in 

coal fly ash. In order to study the chemical state changes caused by deposition and 

sedimentation of the particles, land fill and river sediment samples obtained in the 

neighbourhood of power plants were also investigated. The XANES measurements were carried out in fluorescent mode. For achieving quantitative results on the ration 

of the close lying oxidation state forms, a nonlinear fitting model was developed to 

process the obtained XANES spectra. The features of the spectra such as the white 

line, the multiple scattering resonance peak and the absorption edge are modelled 

with analytical functions. The obtained results show that chromium is present 

mostly (> 95%) as Cr(II1) in fly ash and the chemical state remains the same after 

deposition and sedimentation. Arsenic is present in pentavalent form in fly ash and 

land fill samples, while the possible As(II1) content of sediment samples is around 

40%. To be published in X-Ray Spectroscopy 

* Research supported in part by US Dept. of Energy Contract No. DE-AC02- 

76CH00016. 
I X26A c*j X-ray Fluoresence Imaging of Zinc in Xenopus Embryos * N 

K. Peariso, D.L. Tierney, C. VanHuis, R. J. Denver, and J. E. Penner-Hahn (U. of 

Michigan) 

Xenopus embryos have been shown to have relatively large amounts of zinc, on 

the order of 1 mM [I]. Since the embryo develops without the influx of maternal 

nutrients, the metals it contains at the time of fertilization must supply its needs 

throughout development. Our initial work has focused on the characterization of 

spatial changes in zinc that take place during development. Preliminary x-ray fluoresence images ( Figures 1 and 2 ) have been obtained for different stages of development using the NSLS x-ray microprobe at X26A. The 10um x 1Oum spot size offers 

the resolution necessary to observe localization trends of the zinc in the embryos 

at various stages during their early development. By determining the location of 

Zn during embryonic development, coupled with information provided by XANES 

and EXAFS, we may gain insight into the role of zinc in the development of the 

Xenopus embryo. [l] Montorzi, M., Falchuck,K.H., and Vallee, B.L. (1994)Biochem. 

Biophys. Res. Commun. 200, 1407-1413. 

XANES Mapping of Zinc in Xenopus Embryos * 

K. Peariso, D. L. Tierney, C. VanHuis, R. J. Denver and J. E. Penner-Hahn (U. of 

Michigan) 

Differences have been observed in the zinc XANES of unfertilized Xenopus 

oocytes compared to their embryos at various stages of development. Preliminary x-ray fluoresence images have been made using a monochromatic beam on the 

NSLS microprobe at X-26. The energy selective, two-dimensional images obtained 

at wavelengths corresponding to the largest deviations in the XANES spectra show 

distinct differences in their regions of peak fluoresence intensity (Figures 1 and 2). 

Determining differencesin the fluoresence intensity at specific wavelengths will offer 

the opportunity to map the location of different types of zinc during various stages 

of Xenopus embryo development. Characterizing the spatial and temporal changes 

for different types of zinc will aid our ability to determine the role that different 

zinc environments play in embryogenesis. 

X26A 

Figure 1. White beam, two-dimensional 

x-ray fluoresence image of an unfertilized 

Xenopus oocyte. 

* Supported in part by the NIH Grant 

GM-38047 

Figure 2. White beam, two-dimensional 

x-ray fluoresence image of an &cell 

Xenopus embryo. 

Figure 1. Two-dimensional x-ray fluoresence image of a 16-ceU Xenopus embryo 

at 9665 eV. 

* Supported in part by the NIH Grant 

GM-38047 

Figure 2. Two-dimensional x-ray fluores- ence image of a 16-cel.l Xenopus embryo 

at 9693 eV. 
w 

Spatially Resolved %ace Element Heterogeneities in Apatite Measured via Synchrotron X-ray Fluorescence Microanalysis 

John Rakovan and Richard J. Reeder, (SUNY, Stony Brook) 

X26A 

Apatite, Cab(PO&)a(F,OH,Cl), is the most abundant naturally occurring phosphate mineral on earth, and the behavior of trace elements in apatite is of con- siderable significance in geology, materials science, and biology. For example, the 

presence of Mn and REEs in apatite gives it luminescence properties that are of 

great utility in both the phosphor and laser industries, and heavy metal sequestering by apatite is important in our understanding of the fate and transport of toxic 

species in the body. We have conducted extensive studies of trace element distributions in apatite using synchrotron X-ray fluorescence microanalysis (SXRFMA) 

at the X26A beamline of the National Synchrotron Light Source. These analyses 

are part of a larger study on the influence of the surface structure of apatite on trace element incorporation during growth. SXRFMA and cathodoluminescence 

show step specific incorporation of REEs, Y, SI, and Mn in apatite. Growth steps 

with orientations [OOl] and <011> on the face show different affinities for the trace 

elements studied. In the trivalent REE series La, Ce, and Pr are enriched in regions 

under the [OOl] steps (vicinal subsectors), relative to <all> steps. REEs heavier 

than Pr are depleted in the [OOl] vicinal subsector, relative to <011> vicinal subsectors. Figure 1 shows the concentration of La and Y for line scans between the 

[OOl] and <011> subsectors. This reversal in the distribution trend of the REEsSS 

suggests that ionic size plays an important role in the differential incorporation. 

It is proposed that differences in the atomic structure, specifically the characteristics of protosites, between [OOl] and <011> steps lead to differential incorporation 

and the observed differential distribution of trace elements (intrasectoral zoning). 

Atomic scale models of protosites on these steps show coordination differences that 

are consistent with this proposal (Rakovan and Reeder, 1996). Genetically similar 

trace element heterogeneities, known as sectoral zoning, have also been found. The 

observed sectoral zoning of Sm and Nd has been used in a novel manner to determine 

the age of crystallization for apatites from Llallagua, Bolivia (Rakovan and Reeder, 

submitted). Ref. Rakovan, J., & Reeder, R.J. (1996) Geochimica et Cosmochimica 

in press). Rakovan, J., McDaniel, D.K., & Reeder R.J. (submitted) Earth 

anetary Science Letters. 

[Olil , [ool] 

70.4 70.0 77.6 77.2 Line scan distance (mm) 

p3 

W 

p3 Figure 1. 

79.7 79.6 79.5 79.4 Line scan dhtnace (mm) 

X26A Selective Uptake of Co and Zn in Surface Sites on Calcite During 

Growth 

R.J. Reeder (SUNY Stony Brook) 

Coprecipitation experiments from aqueous solution at room temperature reveal 

that Co(I1) and Zn(I1) exhibit opposite preferences for incorporation among multiple surface sites present on the calcite 1014 face during spiral growth. Polygonized 

regions that compose the flanks of growth hillocks (so-called vicinal faces) consist 

of predominantly straight fundamental growth steps whose orientations differ from 

one vicinal to the next. Metal incorporation sites within the growth steps have 

been shown to differ in local coordination between nonequivalent steps, resulting in 

differential incorporation of trace metals during crystal growth. 

Synchrotron X-ray fluorescence microanalysis using an EDS detector was used to 

document the patterns and magnitude of the incorporation differences for divalent 

Co and Zn. Despite their similar ionic size, Co(I1) and Zn 11) exhibit exactly opacross boundaries separating nonequivalent vicinals (Figs. 1 and 2). This observation demonstrates that factors other than size (and charge) govern the uptake 

and final incorporation of metal ions into nonequivalent surface sites on calcite. 

Consequently, future attention should be focused on the structural characteristics 

of surface sites, as well as on the nature of the species and reactions at the growth 

posite preferences of step-selective incorporation, as shown b y SXRFMA traverses 

surface. 

700 

600 

c\ 

E 500 Q 

Q 

v 

400 

0 

300 

200 

0 50 100 150 200 250 300 

Scan distance (pm) 

Figure 1. Traverse across a near-surface 

section of a calcite (1014) face showing the in Co(I1) concentration between 

nonequivalent vicinal faces b’ and a, having growth steps with different orientations. 

700 

600 

- 500 

E 

Q 

400 

& 300 

200 

100 

v 

0 50 100 150 200 250 300 

Scan distance (pm) 

Figure 2. Traverse across a near-surface 

section of a calcite (1014) face showing the in Zn(I1) concentration between 

nonequivalent vicinal faces b’ and a. 

trend is opposite that for Co(I1). 
Fd 

h3 

X26A Elemental Microanalysis and Elemental Mapping on Biological Tissues 

R. Flizzo (U. of Trieste, Italy) 

Alginate gel beads are used to immobilise cells for a number of fermentation pro- cesses. The suitability of the immobilisation technique depends on the microscopical 

gel strength. For alginate the above property depends on the calcium distribution. 

In fact, calcium is the gelling-inducing agent in alginate systems. We investigated 

gel beads as large as 0.7 mm with a resolution of 20 microns. The data obtained 

showed that calcium is not homogeneously distributed across bead sections exhibiting the highest concentration at the bead surface. This result led to conclude that 

the gel strength is higher at the bead surface than in the core of the system. Beads 

obtained in different experimental conditions, such as calcium concentration and 

ionic strength, are presently under investigation. 

A current problem of the radiologists is a precocious diagnosis of arthritis by 

Magnetic resonance imaging (MRI). This non-invasive technique shows that articular cartilage present a discontinuous laminar appearance due to the presence in the 

tissue of bound and free water in different proportion. A certain identification and 

knowledge of the distribution of the cartilage components responsible of the water 

immobilisation become necessary to establish if a perturbation of their normal distribution can be linked to a variation in the NMR images and to the beginning of 

the pathological status. 

On this line we have compared the distribution of both collagen type I1 (the 

principal protein of cartilage), and proteoglycans (a complex of glycosaminoglycans 

and proteins) with the NMR images of the tissue. Collagen was characterised by 

histological procedures and by the biochemical determination of 'the amount of hydroxyproline (a characteristic amino acidic component). Glycosaminoglycans have 

been characterised by histological examinations, by the content of uronate (a characteristic sugar component) and by SRIXE for their sulphur contents. Evidences 

have been obtained that while collagen distribution parallels the laminar appearance of MR images, the distribution of proteoglycans is more uniform. The sulphur 

distribution show that glycosaminoglycans are differently distributed in the habitually loaded and unloaded regions of articular cartilage. It was therefore concluded 

that the MR images reflect more the water bound to collagen than that bound the 

proteoglycans. 

Elemental analysis of hairs from Egyptian Mummies has been performed using a microbeam in order to investigate only the core of the hairs. The elemental 

abundance has been compared with modern hairs. Preliminary experiments on the 

Fe, Zn, and Sr distribution determination have been performed in order to check 

the suitability of the microscopic x-ray emission analysis for these fossil materials. 

Manganese Oxidation: A Characteristic of Susceptibility in the 

Pyricdaria - Rice Disease (Rice Blast) System X26A 

D. G. Schulze, D.M. Huber, A.K.M. Shahjahan, M. Levy(Purdue U.), S. Bajt (U. 

of Chicago), and B. Illman (USDA Forest Products Lab.) 

Micro x-ray absorption near edge structure (XANES) spectroscopy documented 

that manganese was oxidized from the physiologically active Mn2$ form to the 

non-available Mn4$ form in necrotic lesions on rice leaves infected by Pyricularia 

grisea, the causal agent of rice blast. Detailed analysis of six isogenic rice cultivars differing in resistance/susceptibility to twelve races of the fungal pathogen 

demonstrated that manganese oxidation occurred only in compatible (susceptible) 

combinations of the pathogen and plant. Although manganese was oxidized in the 

few necrotic cells invaded by the pathogen in hypersensitive type resistant reactions, 

pathogenesis was restricted to the few cells invaded by the pathogen and there was 

no chlorosis of tissues surrounding the necrotic cells. Manganese oxidation was not 

detected in fully resistant reactions, although this may be due to the small size of 

these lesions relative to the x-ray beam. The concentration of Mn2$ in chlorotic tissues surrounding susceptible reactions was lower than observed in adjacent healthy 

tissue. Similar manganese-oxidation reactions were not observed in mechanically 

wounded rice tissue, and indicate that the oxidation of manganese in necrotic tissue 

is pathogen induced and not a result of mechanical disruption of the plant cell by 

fungal invasion. The fungus is a strong oxidizer of manganese in culture, and the 

ability to oxidize manganese may be a significant factor determining the virulence 

of P. grisea and susceptibility of the rice plant to disease. 
X26A Analysis of Trace Elements: Au in Sulfides and Ni, Zn, Ga, Y and 

Zr in Garnet 

I.M. Steele (U. of Chicago) 

Synchrotron based x-ray fluorescence has the potential for trace element analysis 

from small samples. In particular we have used this technique for two geologically 

significant studies. The first involves the concentration and distribution of low levels 

of gold in sulfides from potential ore bodies. This information is important to determine both the economic viability and benefaction procedures necessary for mining. 

The second study involves the analysis of indicator minerals whose chemistry may 

indicate the presence of diamonds either in exploration or at particular mining sites. 

Using samples of sulfides bearing rocks from a working mine in Brasil, p?lished 

section were made of representative samples. Sulfides were first characterized by 

electron microprobe and were found to include arsenopyrite, pyhrrotite, and pyrite. 

Energy dispersive analysis is not possible because all sulfides have significant arsenic 

which has a intense interference near the gold L-alpha lines. Wavelength scans using 

the wavelength dispersive spectrometer clearly showed resolution of the Au line 

albeit on a steep background from As. Using sulfide standards peak and background 

positions were determined and a detection level based on counting statistics of about 

2 ppm was determined. For most applications this level is below the economic 

level of gold for profitable mining; it does not compare with levels based on SIMS 

techniques. 

Using the test samples, analysis were made for the 3 main sulfides. Gold was 

detectable in nearly all arsenopyrites, some pyrrhotites, and in no pyrites for all 

samples. The overall levels of Au correlated with bulk Au analyses but the specific new information was in which phases the Au was concentrated. The Au distribution was not homogeneous; analyses of arsenopyrite from any one sample could show a 

range of 5 in concentration. Parallel analyses for these same samples for the same grains are being also made at the Geological Survey of Canada. Initial results 

show a fair correlation between the two techniques. The fair agreement is most 

likely a function of inhomogeneity and the different spatial volume for analysis. A 

joint publication is being prepared comparing the techniques and describing the 

application to the specific geologic problem. 

Trial analyses for trace elements in garnet showed that Ni (a geothermometer can be easily analyzed at the several ppm level with an error of less than 5% base i on counting statistics. Ga and Zn are at very low levels but can be detected. Y and 

Zr present problems as neither can be analyses with the WDS system. The EDS 

analyses are time consuming and qualitative at best. Major efforts will be made 

to perfect WDS analyses of all 5 elements. Samples obtained from new kimberlite 

fields in western Canada are being supplied as the diamond bearing quality has 

been determined; this will be the major activity in the coming year. 

I Selenium XANES of Contaminated Soils, Plant Residue, and Algae 1 X26A I 

T.K. Tokunaga (LBNL), S.R. Sutton (U. of Chicago), S. Bajt (LLNL), P. Nuessle 

(U. of Georgia), and G. Shea-McCarthy (U. of Chicago) 

Mechanistic understanding of selenium cycling between surface waters, sediments, 

and organisms requires information on its oxidation state in the various environmental compartments of the cycle. This study, conducted at NSLS beamline X26A, 

utilizes XANES for determination of Se oxidation states of sediments, decomposing 

plant residue, and algae. All of these samples were in previously exposed to Se in its 

The Goose Lake 

seasonal pool at Kesterson Reservoir, and from the San Luis Drain which previously 

(1981-1986) served as the conveyance structure for delivering seleniferous agricultural drain waters to Kesterson Reservoir. XANES of these environmental samples 

were compared with those of model compounds Se(O), Se(IV), Se(VI), Se-cystine, 

and Se-methionine, mixed as dry powders into soil matrices. 

All samples contained Se in reduced forms. Absorption edge spectra of these 

samples indicate that Se occurs as a mixture of Se(0) and organo-Se forms. Contributions due to Se(V1) and Se(1V) were less than 10% of the total Se in each 

sample. These results are very similar to those obtained at the later stages of an 

Se reduction, micro-XANES experiment conducted at X26A during the previous 

year. The outstanding problem of distinguishing Se(0) and various organo-Se forms 

in these environmental samples will be pursued in upcoming studies. This will include collection of higher-quality spectra on environmental samples, and inclusion 

of additional Se model compounds. The clear identification of Se(0) versus vari- ous organo-Se forms is environmentally important because the elemental form is of 

relatively much lower toxicity than many of the simple organic forms. 

Fd 

f3 

w 

P 
tp 

PJ 

X26C Real-Time Electromigration Strain Measurement on Individual A1 

Interconnect Lines by White Beam Microdiffraction 

G. S. Cargill I11 and P.-C. Wang, Columbia University, and I. C. Noyan, E. G. 

Liniger, C.-K. Hu and K. Y. Lee, IBM Research 

A synchrotron-based x-ray microdiffraction system has been developed and used 

on beamline X26C for the first real-time electromigration related strain measure- ments with micron scale spatial resolution and strain sensitivity on the order of 

2E-4. A tapered glass capillary was used to form a concentrated 10pm diameter 

white x-ray beam. The samples studied were 10pm-wide, O.5pm-thick and 200pmlong A1 interconnect lines covered with a 1.5pm-thick Si02 passivation layer. The 

electromigration test was performed at 267oc by passing 0.6E6 A/cm2 current 

through the A1 line for about 69 hours. With an energy-dispersive detector the 

reflections from Al(111) planes at nine positions along the conductor line were collected repeatedly during electromigration in a symmetric reflection geometry, and 

thus the Al(111) plane spacings perpendicular to the sample surface were determined. Figure 1 shows the values of the ”effective lattice parameter” aeff obtained 

from the measured Al(111) plane spacings at the chosen positions along the conductor line at T = 2670C before electromigration and after 15 hours and 69 hours of 

electromigration. Before electromigration the A1 line was in a biaxial compressive 

thermal stress state, and due to Poisson expansion the perpendicular values of aeff 

were larger than the strain-free value ao. After 15 hours of electromigration, the 

perpendicular values of aeff at the first three positions (no. 7, 8 and 9) decreased 

due to the relief of the in-plane compressive stress, while the values at the rest of 

the positions near the anode end no. 1-6) increased because of the enhancement of 

removal of atoms from the grain boundaries near the cathode end of the conductor 

line, and the deposition of atoms into grain boundaries near the anode end. After 

69 hours of electromigration, further stress relaxation at positions 6-8 had brought 

the perpendicular values of aeff closer to the strain-free value. The values of a,ff 

indicating stress-buildup at positions 2-6 after 15 hours had been replaced by a less uniform, more relaxed set of values, attributed to plastic deformation of the 

aluminum and deformation or fracture of the passivation. 

the in-plane compressive stress. !r his result can be explained qualitatively by the 

I X-rav Diffraction Data Collection for Microcrvstals I X26C I 

J. Pluth, L. Clark , S. Sutton (U. of Chicago), M. Helliwell (U. of Manchester), G. 

Harlow (Am. Museum of Nat. Hist.), and G. Shea-McCarthy (U. of Chicago). 

The purpose of the study was to determine whether beamline NSLS X26C could 

be used to collect data for very small single crystals. The data were collected using 

the oscillation method, monochromatic radiation and recorded on Fuji image plates. 

A diffraction pattern was collected for each crystal to determine if it was single. Full 

data sets were then recorded for high quality crystals. The final goal of this study was to solve the unknown crystal structures of the microcrystals. The smallest 

crystal for which a data set was collected was raite (5x5x100p3). The data sets are 

currently being processed, data quaility is being evaluated and attempts to solve 

the unknown crystal structures are being made. A summary of the crystals studied 

and their current status is given below: 

raite: Na4Mn3Sia(O,OH)24.9HzOl C222, a=30.6 b=5.31 c=18.20, 5x5x100p3, 

data collected at 5 deg. steps in one minute, 19 frames, wavelength=1.127. 

choloalite: CuPb TeOs)z.HzO, cubic, a=12.519, 20x20x20p3, 5 deg. steps in one 

min., 0-95 deg., 19 I rames, wavelength=0.966. 

epistolite: Nab TiNbz (Si2 07)~ 03F.5H20, monoclinic, 10x50x50p3, crystals bad. 

quetzalcoatlite: Cu4Zns (TeO3)3(OH)18 ,c6322, a=10.097 c=4.944, 60x60x60p3 , 

karnasurtite: (Ce,La,Th)(Ti,Nb)(A1,Fet3)(Si,P)207(OH)4 .3HzO, Trigonal, 

crystals gave no diffraction pattern. 

.. .. 

20x100x100p3 ,crystals bad. 

p=100.66 y=92.09, 20x100x100p3, good crystal found but lost. 

tion pattern recorded, 10 deg. 30 sec. 

tokkoite: Kq Ca4 Si7 01 7 (0, OH, F)4 ,triclinic, a= 10.37 b= 25.3 9 c=7.27 a= 9 1.67 

diopside: MgCaSizOd, C2/c, a=9.752 b=8.927 c=5.252 p=105.82, 30p3, diffraczorite: Cmmm, a=23.24 b=7.24 c=6.96 x2?) from powder, 10x10x2p3, a few 

spots that could be from crystal were recor 6 ed. 

Position number 

1234567 8 9 

4 070 

0 50 100 150 200 

Distance from anode end [pm] 

Figure 1. Measured perpendicular values of a,ff along the interconnect line before 

electromigration, and after 15 hours and 69 hours of electromigration. The arrow indicates the strain-free value of aeff. 
Fabrication of a mm-Wave Accelerating Cavity, Using Deep X-ray 

Lithography * 

J.J. Song, Y.W. Kang, R.L. Kustom, B. Lai, D.C. Mancini, A. Nassiri (ANL), and 

V. White (U. Wisconsin ) 

The possibility of fabricating mm-wave radio frequency cavities using deep xray lithography (DXRL is being investigated. The frequency of operation can be 

from 30 GHz to 300 G A z, operating mode in either TM or TE-mode, depending 

on the application. For most applications, a complete structure consists of two 

mirror-image planar half structures assembled face-to-face. The fabrication process 

includes manufacture of precision x-ray masks, exposure of positive resist by x-rays 

through the mask, resist development, and electroforming of the final microstructure. The precision Hard x-ray mask was made by means of an surface mask, using 

soft x-ray lithography for pattern transfer into poly-methylmethacrylate (PMMA) 

on a 200-pm thick Si wafer, followed by electroplating of 35-pm Au at CXrL (Center 

of X-ray Lithography) in Wisconsin. 

For the DXRL process, PMMA was used as the positive resist, either as an 1- 

mm sheet glued or 200-pm film cast onto a Cu substrate. The NSLS (National 

Synchrotron Light Source) X26C beamline in Brookhaven was used to expose the 

resist. Fig.1 shows transmitted x-ray intensity through various filters during PMMA 

exposures for DXRL at NSLS. 99.9% OFC(oxygen free copper) was electroplated 

onto the developed PMMA structure, and then polished by the diamond-lapping. 

Fig.2 shows SEM picture of the rectangular cells of the constant-impedance 30-cell 

108-GHz cavity structure.The cavity will be aligned with the optical fibers on the 

grooves and then initial test will be performed with HP 8510 network analyzer. 

[l] J.J.Song, et. al., will be presented and submitted to SPIE’96 Symposium on Micromachining and Microfabrication, Austin, TX, Oct 14-15, 1996. 

[2] J.J.Song, et. on Workshop under the Joint 

Auspices of Division of Particles and Fields and Division of Physics of Beams, 

Snowmass, Colorado, July 8, 1996. 

X26C 

al., submitted to 1996 Proc. 

Figure 1. Transmitted x-ray intensity 

during PMMA exposures for DXRL at 

NSLS, (watt/cm3) 

sd3 

* This work was supported by DOE Con- p3 

w 

tract W-31-109-ENG-38. 

Figure 2. SEM picture of the rectangular 

cells of the constant-impedance cavity. 

1 X26C 1 Characterization of Defects in Protein Crystals by Diffractometry 

and Topography ~~ 

V. Stojanoff (ESRF), D. P. Siddons (NSLS), E. Snell (NASA), T. Boggon and J. 

R. Helliwell (U. Manchester, UK.). 

We have studied the crystalline perfection of several samples of proteins grown 

both in space (i.e. zero-gravity conditions) and in ground-based control experiments. We were able to perform triple-axis diffractometry on selected diffraction 

spots using an imaging-plate system to index the crystal orientation, followed by 

conventional diffractometry. A superficial view of the data provides no definite 

pattern to the qualities of the earth- grown us the space-grown samples. Figure 1 

shows a contour map of the diffracted intensity in theta-2theta space, clearly showing two strong, well- seperated peaks. Figure 2 shows a diffraction topograph taken 

at the low-angle peak. Note that the outline of the diffracting region is not sharp, 

i.e. the sample ’domains’ are not physically distinct. The optical configuration for 

these measurements included a silicon (l,l,l) monochromator and analyser, with no focussing elements. 

Figure 2. X-ray diffraction topograph of 

Figure 1. the same Bragg spot, with Oset to coBra€% Peak, showing 2 Well-sePeratej incide with the low-angle peak in figure 

0-20 map of the (3,-11,-8 

peaks. 1. 
P 

E3 

In situ Structural Characterization of Lithium-ion Battery Elec- X27A, 

trode Materials X22A X27A An Investigation into the Spatial Texture Distribution in Thermomechanically Deformed Ndz Fel r B-based Permanent Magnets 

T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. Yang, J. McBreen (BNL - DAS), 

M.L. Daroux, and X.K. Xing (Gould Electronics) 

The low cost, high operating voltage, and low toxicity of Li,Mnz04 make it a good candidate for use as a cathode in lithium-ion battery cells. However, this 

material can not be reproducibly manufactured yet, a problem which arises in large 

part because the structural properties of Li,MnzOq vary considerably with synthesis 

conditions. The structure also changes during the lithium intercalation process, so 

studies of operating battery cells may help resolve some of these issues by allowing one to separate structural properties dependent on the lithium content from those 

dependent on the underlying manganese-oxygen skeleton. We report here some of our initial results from combined electrochemical and synchrotron x-ray scattering 

measurements performed on operating cells. 

X-ray diffraction experiments were performed at X27A with 24.5 keV photons 

and at X22A with 10 keV photons. Cells of approximate dimensions 2cm x 3cm x 0.5mm were manufactured by Gould Electronics, sealed at the factory, and mounted 

in a transmission geometry on the spectrometer with no modifications. Even though 

the x-ray beam must penetrate through the external case, electrolyte, and binding 

materials in this geometry, the high flux of a synchrotron allows data with reasonable 

counting rates to be taken [l]. 

An example of the structural information that can easily be obtained with this 

technique is illustrated in the right figure. Here 28 scans taken through the 

Li,Mnz04 (333), (511), (440), and (531 peaks are presented (the (440) peak is 

partially obscured by an aluminum pea 1 at 20.3'). The data have been offset 

from each other for clarity, and they show the evolution of these peaks as the cell 

was discharged from 3.90 volts to 2.94 volts. The data indicate that expanded and 

nonexpanded phases coexist over a certain range of voltages. Other structural properties such as this two phase coexistence and their relationships to electrochemical 

properties are discussed in reference [2]. 

[l T.R. Thurston et al. Appl. Phys. Lett. 69, 194 (1996). 

[2] N.M. J' israwi et al. J. Electrochem. SOC., submitted. 

T.R. Thurston, L.H. Lewis, U. Wildgruber, D.O. Welch (BNL- DAS), and V. 

Panchanathan (Magnequench International) 

Quantifying the relationship between crystallographic texture and magnetic properties is highly desirable for engineering high energy-product magnets. However, 

determining the texture of melt-quenched magnets from NdzFel4B-based alloys is 

challenging because they possess a nano-scaled microstructure that is complicated 

by the presence of multiple phases, both ferromagnetic and paramagnetic. This microstructure leads to exchange-spring type magnetic behavior which nullifies standard magnetic remanence procedures for texture determination. 

To overcome these experimental difficulties, new techniques for measuring the texture of bulk permanent magnets have been explored recently. Hard x-ray transmission geometry diffraction experiments were performed on a series of NdzFel4B-based 

magnets with varying die-upsets. The spatial homogeneity of the c-axis alignment 

was examined perpendicular and parallel to the pressing axis. The figure shows the 

FWHM of the rocking curve of the (006) peak along the direction perpendicular to 

the pressing axis for a 60% die-upset sample. It can be seen that the c-axis alignment is best in the center region of the magnet and becomes progressively worse 

as the perimeter of the magnet is approached. Samples with lower deformation 

levels possess more uneven texture distributions than do those with high deformation levels, and the degree of orientation seems to develop discontinuously around 

a deformation level of 50%. 

Bulk magnetization measurements were also performed on each sample and cor- related with the texture properties determined from x-ray diffraction. It was found 

that the coercivity is much more sensitive to the degree of c-axis alignment than is 

the remanence. The coercivity decreases significantly with increasing deformation 

level, while the remanence is largely unaffected for deformation levels exceeding 

30%. More details of this work, as well as recommendations for improving production procedures which follow from these experiments, are given in reference [l]. 

[l] L.H. Lewis et al., submitted to J. Mag. & Mag. Mat. 

2% 

Figure 1. 28 scans (k0.501A) showing the evolution of two-phase coexistence as 

a battery cell is discharged. 

g 10 

.9 1, ,,, , ,,, ,, ,, ,, , , ,, ,,, , ,, ,, , , ,j 0 

-15 -10 -5 0 5 10 15 

perpendicular lranrlation (mm) 

Figure 1. Spatial Homogeneity of the Texture in a 60% Die Upset Sample. 
In Situ Measurements of Texture and Phase Development in Bi- x27~, 

2223 Silver Cladded Superconducting Wires 1 X22A1 

T.R. Thurston, U. Wildgruber, N.M. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC Corporation) 

During the past two years, techniques for characterizing silver-cladded Bi-2223 

superconducting wires with hard x-rays have been developed at X27A [l]. In order 

to penetrate through the silver cladding, the incident x-ray energy is tuned just 

below the silver edge at 25.5 keV. The samples are also examined in a transmission 

geometry, so bulk structural properties are probed. Using these techniques, we have 

previously shown in ez situ experiments that both the c-axis alignment (texture) 

and Bi-2223 phase development have large effects on the current carrying capacity 

of fully processed wires. 

More recently, we have begun experiments where the phase and texture development of Bi-2223 are monitored as it grows from precursor materials (typically 

Bi-2212 plus CuO etc.) within its silver sheath. This in situ work has been done 

in an x-ray compatible furnace with temperature stability of 0.2'C at 830°C. The 

figure below shows the phase and texture development of a typical sample during 

the first 50 hours of processing. The solid line represents the temperature program 

followed. The furnace was ramped from room temperature up to 600"C, held at 

600'C for 6 hours, ramped again from 6OO0C to 840°C over a period of 12 hours, 

and then held at 840°C. Bi-2223 phase content (represented by the open triangles) 

began to develop only after reaching 840°C. On the other hand, the weighted average of the Bi-2212 and Bi-2223 texture, represented by the (200) FWHM (closed 

circles), improved significantly while the sample was being ramped from 600°C to 

840°C. Thus, the texturing and phase development mechanisms are largely decoupled. The implications of this and many other in situ experimental results are 

J. Appl. Phys. 79, 3122 (1996). 

J. Mat. Res., submitted. 

hoellng lime (hours) 

E Figure 1. Time Dependence of the Phase and Texture Development in a Multifilament Wire. 

Determination of Topology and Transport in Porous Media Using 

Synchrotron Computed Microtomography * 

P.M. Adler, J.-F. Thovert (IPGP, France), K.W. Jones, A.M. Peskin, D.P. Siddons, 

B. Andrews, and B. Dowd (BNL) 

We have previously examined1 the geometrical structure of the pore space in a 

sample of Fontainebleau sandstone using synchrotron computed microtomography 

(CMT). The tomographic data made it possible to obtain the topology of the void 

space of the sample and its macroscopic permeability and conductivity using the 

method of reconstructed porous media.2 The present work is aimed at extending 

the investigation to a number of samples which cover a range of porosity values. 

The work was carried out using the computed microtomography apparatus at the 

NSLS X27 beam line. Our initial survey work was done with a voxel size of 15 5m on samples of Vosges sandstone, Massangi's limestone, and Laroux limestone. A 

comparison of the results of the present investigation of these materials with the 

initial results obtained for the Fontainebleau sandstone will 

be made. The intent is to develop an approach which can be used to model large 

scale petroleum reservoir structures 

1. P. Spanne, J. F. Thovert, C. J. Jacquin, W. B. Lindquist, K. W. Jones, and P. 

M. Adler. Phys. Rev. Lett. 73, 2001 (1994). 2. J. Yao, P. Frykman, F. Kalaydjian, 

J. F. Thovert, and P. M. Adler. J. Colloid. Interface Sci. 156, 

478 (1993) and references therein. 

*Research supported in part by US Department of Energy Contract No. DEAC02-76CH00016. 

* Research supported in part by USDOE Contract DE-AC02-76CH00016. 
E X27C Q, Core Samples 

Region of Interest Tomography Correction for Subvolumes of Large 

B. Andrews, B.A. Dowd, D.P. Siddons, and J. Yung (NSLS) 

Typically, data generated by X-Ray computed microtomography on geological 

samples require full volume imaging of the sample. In other words, the linear 

dimension of the detector array must extend beyond the projected width of the 

material under study. This is typically called global tomography; a map of the 

linear attenuation coefficients over the entire exposed volume is generated. In local 

tomography, only a region of interest within the full volume is reconstructed. We 

have been using conventional global tomography algorithms to process full volume 

microtomography data. With our present configuration, however, only 1 to 2 mm diameter cores can be fully imaged with high resolution (3 to 5 microns). 

In our first efforts to construct high resolution tomograms over a 1 mm region 

of interest within cylindrical volumes of 2 to 20 mm, we have applied a straightforward geometrical correction to the global algorithms already in place. Only the 

transmission data through the region of interest was needed to implement this cor- rection and perform the reconstruction. The effect of the correction can be seen in 

the figures below. Without the correction, a significant cupping artifact is evident. 

The correction has been applied with good result, to oil reservoir sandstone, basalt, 

fontainebleu, and berea. Further work is being carried on to allow us to extend 

the algorithm to any geometry, and to improve contrast and resolution for region 

of interest X-Ray microtomography. 

w 

*Thanks to B. Illman, USDA Forest Products Lab. 

Figure 1. Global reconstruction applied 

to lmm of 6mm D basalt,with no correction. 

Figure 2. Same lmm diameter of basalt, 

with subvolume correction, histograms 

included. 

X27C X-Ray Microtomography Applications to the Characterization of Oil 

Reservoir Seal and Source Lithologies 

W. Bell , R.D. Hazlett (Mobil Corp.), B. Andrews, B.A. Dowd, K.W. Jones, A. 

Peskin, and D.P. Siddons (BNL) 

Synchrotron X-Ray microtomography has been used, for the first time, to look at 

the 3-D structure of source and seal rocks. Source rocks contain the material from 

which useful hydrocarbons oil and gas) are generated by prolonged application of 

origin, these hydrocarbons can migrate, primarily under buoyant forces, through 

porous rocks. The barriers to further (upward) migration of reaction products are called seals. The physical properties of the seal and source rocks determine the 

holdup, flow rate, leak rate, and accumulation of migrating oil as well as its quality ( 

gas to oil ratio.) Characterization of these materials is important in the development 

of models that predict oil and gas accumulations in potential petroleum basins. 

The material examined, seals a deep (w10000-ft) producing reservoir in the Gulf 

of Mexico. Traditional physical methods of analysis have elucidated some physical 

characteristics. Mercury porosimetry studies, N2 absorption analysis, as well as novel gas and brine permeability experiments have established the following properties: 

heat and pressure associate 6 with burial of sediments. Expelled from their site of 

Table 1 Physical Characterization of GOM Seal Material 

He Expan. BET Surf. Area Perm. @ 15OOpsi Conf. Sample Grain Water Porosity 

N2 Horiz. Vert. Vert. Depth Density loss. vol% gas gas brine ft g/cc vol% m2/g 

m2/cc -10000 2.72 25. 24. 43. 94. 20 mmD 2 mmD 2 nD 

Mercury porosimetry shows significant pore sizes (necks and bodies) distributed 

around 400 and 2000 Angstrom diameters; the data is shown in Figures 1 and 2. 

Microtomography experiments will continue to investigate these novel materials. 

Macroscopic features such as fractures and unexpected disconnected voids have been 

identified; pore structure is below the current resolution limit of this technique. This 

work has demonstrated our potential ability to capture the intricate geometry of 

either natural or induced microfractures. The spatial distribution of minerals has 

also been of significant interest. 

This work was funded in part by ACT1 grant from USDOE DE-AC0276CH00016. 

0.2 02 

0.15 0.l5 

. 

8 5 0.1 8 0.1 

0.05 om 

iwooo Irma loo0 1w m lo0000 loo00 lo00 100 20 

PoreMametrr, A -4 

Figure 1. Mercury Porosimeter Data on 

Seal Rock: GOM 10,000 ft Figure 2. Hg Intrusion Poresize Distribution 
I X-ray Refraction Imaging (XRI) Applied to Mammography I X27C I ~ 

D. Chapman (Illinois Inst. of Tech.), W.Thomlinson, N. Gmiir, A. Zhong, R. Menk 

(NSLS), R.E. Johnson, D. Washburn,E. Pisano (U. of North Carolina), F. Arfelli 

(Sincrotrone Trieste), and D.Sayers (NCSU) 

We discuss here an imaging technique, X-ray Refraction Imaging (XRI which can 

technique can be applied to thick and therefore highly absorbing materials. It is not 

limited to materially thin samples and/or high x-rays experience in traversing the 

object. The images are almost completely scatter-free. The combination of these 

properties has resulted in images of mammography phantoms which have dramatically improved contrast and spatial resolution over standard imaging techniques. It 

is potentially applicable to mammography and other fields of medical x-ray imaging and to radiology in general, such as non-destructive testing and x-ray computed 

tomography. 

Screening mammography has proven to be an effective procedure in identifying 

early breast cancer. Two large randomized trials have demonstrated that breast cancer mortality among screened women over 50 years old can be reduced at least 

30% when compared with unscreened controls. The cancers found by mammography 

tend to be smaller and of less advanced stages than those found by breast physical examination or breast self-examination. Smaller and lower stage breast cancers have better survival rates. Unfortunately, approximately 10% of clinically obvious 

breast cancers are not visible with mammography. This occurs most frequently in 

patients with large amounts of breast glandular tissue. The density of this tissue 

tends to obscure underlying pathology. Premenopausal women and women undergoing estrogen replacement therapy are more likely to have dense glandular breasts. 

The National Cancer Institute, The American College of Radiology (ACR) and the 

American Cancer Society (ACS), among other organizations currently advocate annual screening mammograms for women over the age of 50. Screening under age 

50 is more controversial. It is desirable to increase the sensitivity of mammography 

applied to younger women so that their cancers are apparent at a much earlier stage 

of development. This earlier detection may result in significantly reduced mortality 

in this population. 

be used to independently visualize the refraction and absorption of an o b ject. This 

Petrology: Absorption Tomography of Pore Features in Synthetic 

Applications of Synchrotron Microtomography in Experimental 

Rock Samples * 

T. Cohen, E. B. Watson (Rensselaer Polytech Inst.), B. Dowd, D. P. Siddons, B. 

Andrews and K. W. Jones (BNL) 

The nature of fluid-filled porosity in rocks of the Earth’s lower crust and upper 

mantle is of basic interest. In these regions, the elevated P-T conditions result in 

significant solubilities of the rock-forming minerals in any contacting pore fluids 

that might be present. Under these circumstances, the fluid/rock assemblage will 

tend toward geometric configuration that minimizes the total interfacial energy of 

the system. Generally speaking, if the energy of the mineral/fluid interface is low 

relative to the grain boundaries (mineral/mineral interfaces , the fluid will tend to 

channels. If, on the other hand, the energy of the mineral/fluid interface is relatively high, the fluid will segregate to grain corners to form isolated pores. These 

contrasting fluid distributions have profoundly different implications for the bulk 

properties of the rock: in simple terms, a rock containing an interconnected fluid 

phase is likely to exhibit markedly enhanced transport properties such as electrical 

conductivity, dissolved component diffusivities, and permeability. The ”wetting” 

behavior of C-0-H fluids in a variety of monomineralic rocks can be investigated 

by subjecting synthetic samples to high P-T conditions in the presence of small 

amounts of fluid. By use of quenching experiments, it is possible to show that some 

fluids in some rocks are indeed interconnected e.g., water in quartzite at 800 C and 

10 kbar), while others exist as isolated pores [e.g., C02 in dunite). However, it is 

necessary to rely almost exclusively on indirect methods of geometric characteristics 

including assessment based on a single 2D section, or on the observed enhancement 

of bulk-rock diffusion by the presence of a fluid. Synchrotron computed microtomography has been used for direct and thorough characterization of pore features 

produced in high P-T experiments. Porous, cylindrical rock specimens with grain 

sizes of 50-100 m were synthesized in a piston-cylinder apparatus. An experimental 

measurement was made of the microgeometry of the inclusions. Pore spaces were clearly delineated. Work is currently in progress to determine the porosity and 

connectivity of the specimen using the medial axis formalism developed previously 

with W. B. Lindquist and coworkers. The results will be compared to values inferred 

from bulk porosimetry measurements. 

penetrate grain edges to form a continuously interconnecte d network of grain edge 

* Research supported in part by USDOE Contract DE-AC02-76CH00016. 
Fd 

Kl 

X-Ray Microtomography of Reservoir Sandstone for the Characterization of Porosity and Permeability * 

M.E. Coles, R.D. Hazlett, E.L. Muegge (Mobil Corp.), B. Andrews, B.A. Dowd, 

K.W. Jones, A. Peskin, D.P. Siddons (BNL), M. Schlackman (GTE), W.E. Sol1 

(LANL), and P. Spanne (ESRF) 

Synchrotron X-ray microtomography at the X27C beamline has been used to 

provide large, high resolution 3-D renderings of pore networks in reservoir rocks 

supplied by Mobil Corporation. The data gathered over the past year has been 

used to model single and multiphase flow properties in actual digital representations of the porous rocks from which hydrocarbons are produced. With this kind of 

information, we have been able to examine the tortuous pathways available for fluids 

to flow within the rock. We have been able to simulate experiments related to hydrocarbon extraction efficiency through the use of network modeling. Furthermore, 

the thresholded CMT images have served as the boundary condition framework for 

more rigorous computational fluid dynamics simulations of oil being displaced by 

injected fluids. 

A sample of a North Sea Brent sandstone acquired at 2.7 micron resolution is 

shown in the accompanying figure. We show a 3-D representation of the cylindrical volume with a wedge removed to reveal the interior. Given also are interior 

orthogonal slices which reveal the extent of detail captured in this 470 md sample. 

These images demonstrate the ability of CMT to simultaneously capture intergranular porosity and elements of microporosity in a 3-D pore network. The sharpness 

of grain boundaries at this magnification attests to the quality of image data. We 

can certainly see variations in mineralogy and can begin to digest surface compositional information important for rock-fluid interactions, i.e. wettability. Such high 

resolution CMT images of the actual pore interconnections in rocks will provide nec- essary data for the development and testing of improved multiphase flow relations 

and physically correct upscaling methods. 

X27C 

Figure 1. High resolution CMT subvolume of a North Sea Brent sandstone, 

k=470md: with cutaway, b) X-directional slice, c) Y-directional slice, d)Cross section 

~~ 

* Work sponsoredby ACT1 grant for collaborative work between BNL, Mobil, and GTE, 

through DOE contract DEAC02-76CH00016 

X-Ray Microtomography of Fungal Deterioration of Wood * 

B.L. Illman (U. Wisconsin and Forest Products Lab.), B.A. Dowd and D.P. Siddons 

(NSLS) 

A new class of synchrotron x-ray computed tomography was used to make non- destructive tomographic images of solid Southern yellow pine (SYP) wood and SYP 

during degradation by wood decay fungi. Computed microtomographic (CMT) images were obtained with spatial resolution of 3 microns using the recently assembled 

station at X27 (Dowd, 1996). This third generation CMT station employs Charge 

Coupled Device (CCD) area detectors for higher resolutions and faster acquisition 

times, optimized reconstruction algorithms and fiber optic link to a 3-dimensional 

stereo viewing theater. Wood samples (3mm cubes) were scanned at high resolution using CCD detector array with 329 x 259 small pixels where 1 row of pixels 

constitutes a single 2-dimensional slice of the specimen. The 500 horizontal slices 

comprising each data set were stacked to reconstruct the 3-dimensional volume of 

the specimen. Color images were computer-generated in 2-dimension to portray 

single slices of select cross sectional areas (Figure 1) and 3-dimensional volumes of 

the wood. Reconstructed volumes were viewed on 3-dimensional video at the stereo 

viewing theater. The CMT images of SYP and decay fungi provide information 

about spatial relationship between xylem vessels, inter- and intracellular areas of 

tracheids and clear structural alterations by degrading fungi. The models developed 

in this work will provide needed information about the chronology and location of 

structural damage to wood and aid in determining the chemical mechanisms of 

lignocellulose degradation. 

X27C 

Figure 1. 

* This research was supported by USDA grant 94371031016 and USDA Forest Service. 
I MECT’s Bent Laue-Laue Monochromator: Design and Test Results I X27C I 

B. Ren, F.A. Dilmanian, X.Y. Wu, (BNL- Medical), L.D. Chapman, I. Ivanov 

(CSRRI, IIT) and Z. Zhong (NSLS) 

A bent Laue-Laue monochromator has been constructed in a collaboration 

between the Center for Synchrotron Radiation Research and Instrumentation 

(CSRRI), Illinois Institute of Technology (IIT) and the Multiple Energy Computed 

Tomography (MECT) group. The design, which was inspired by the earlier bent 

Laue-Laue work by D. Chapman and C. Schulze, was chosen because of a) the 

rocking curve is wide and has a flat top, thus minimizing the sensitivity of the twocrystal system to individual crystals’ vibrations and distortions; b) the system has a high throughput; c) the sytem has low harmonics; and d) the energy bandwidth 

is low in the Cauchois geometry. The design includes the following features (see 

table below): a) the crystals are Si< 331 > with 22” asymmetric angle; b) both 

crystals are bent to about 20-m radius; c) both crystals employ Laue diffraction 

”upper case” to eliminate Laue spot contamination; d) the crystals are 1.1 mm 

thick (1st) and 1.5 mm thick (2nd); e the benders are four-rod mechanisms, with 

two fixed and two adjustable rods. Tke force on each adjustable rod is cotrolled 

by two independent springs on the ends, allowing removal of crystal twisting and 

facilitating symmetric bending. 

Radius Thickness Darwin Width Integ. Reflect. Max. Reflectivity 

Flat 1.1 mm 1.6 prad 0.9 prad 

20 m 1.1 mm 47.5 pad 30.3 prad 64% 

20 m 1.5 mm 64.6 pad 39.3 prad 61% 

The tests used an 1/4” A1 beam filter, the full 8-cm horizontal width of the X27C 

beam, and a 0.5-mm vertical beam height. First, the tilt angle x was adjusted using 

both crystals unbent. Next, for each crystal at different bending radii the rocking curve was measured using the other crystal unbent as an analyzer; the bending radii were deduced from these widths. The Darwin widths were set to 43 and 63 pradian 

for the 1st and 2nd crystal, the corresponding bending radii were 22 m and 21 m respectively. Figure 1 shows the corresponding single bent crystal rocking curves 

obtained with a 3 mm x 0.5 mm beam. 

We thank E. Black, B. Dowd, D. Feske, G. Haigis, J.B. Hastings, A. King, W. 

Lavender, A. Lenhard, C. Schulze, M. Shelton, D.P. Siddons, S. Simpose, W.C. 

Thomlinson, G. Vanderleski, S. Wang for assistance. Research supported by the 

Office of Health and Environmental Research, U.S. Department Of Energy. 

k I 

-60-40-20 0 20 40 60 

Rocking Angle [pradion] 

-6Q-40-20 0 20 40 60 

Rocking Angle [pradian] 

Figure 1. Shows the corresponding single bent crystal rocking curves obtained with a 3 mm x 0.5 mm beam. 

I X-Ray Microtomography of Basalts * I X27C I 

D. Sahagian (U.N.H.), B.A. Dowd, K.W. Jones, D.P. Siddons, S. Song (BNL) 

Models of volcanic eruption dynamics are related to the understanding of the 

kinetics of bubbles. There is a strong dependence on the expansion or migration of 

bubbles during the magma rise for both explosive and effusive volcanos, The shape 

and size distribution of bubbles in basaltic magma are the important parameters 

needed to estimate lava viscosity and flow rate and nucleation, growth, coalescence 

rates of bubbles in erupting magmas and active lava flows. Meanwhile, the distribution of bubbles may be used to infer paleoelevation and/or paleoatmospheric 

pressure. The connectivity and tortuosity of the bubbles will tell us about water 

transport through the rock, of interest to hazardous waste disposal sites. But, cur- rent measurements of bubble size morphology and distribution in basaltic lava flows 

are limited because of the lack of techniques for obtaining three-dimensional images. 

To overcome this limitation, we have explored the use of synchrotron x-ray com- puted microtomography (CMT) at the X27C beamline to quantitatively measure 

the properties of bubbles in basaltic lava flows. These basaltic samples, collected 

from Africa, are rich in different size fractions of vesicles. The preliminary results 

show very good 3D images of bubble morphology, size distributions and connectivity in vesiculated basaltic samples. A typical volume image is shown in the Figure. 

Further plans include the use of 3D medial-axial method to quantitatively determine 

the properties of bubbles, such as porosity, permeability, and size distributions. 

Figure 1. 3-D Rendering of an African basalt. Pore sizes are on the order of 0.5 

mm. 

* Work supported by USDOE Contract DE-AC02-76CH00016. 
Fd ta 

* x27c Microstructures of Antarctic Meteorites in the Millimeter Size Range 

S.R. Sutton (The U. of Chicago), B.A. Dowd, K.W. Jones, D.P. Siddons, B. Andrews, A. Peskin (BNL) 

High energy synchrotron radiation can be used to image the internal microstructures of extraterrestrial objects, such as rare Antarctic meteorites using computed 

microtomography (CMT). The microtomography technique allows a number of 

physical properties of the specimen to be determined non-destructively such as locations and size distributions of clasts, fusion crust thickness, modal abundance 

of phases, porosity, density, and possibly the distributions of terrestrial weathering 

products. The location of clasts is of interest, for example, in developing sampling 

strategies and allocation plans for rare objects such as those from the Moon and 

Mars. Fusion crust thickness is important in understanding the velocity and trajectory distribution of the millimeter -sized objects that make up the bulk of the 

extraterrestrial matter accreted by the Earth. For example, the surprisingly small 

degree of heating experienced by some large 30 micrometer) micrometeorites is 

specimens in the 4-9 mm diameter range have been obtained to test the value of 

this approach. Initial CMT images show the well-defined spatial distribution, size 

distribution and morphologies of clasts in the "pebbles". The resolution used in 

this initial survey was not high enough to resolve the fusion crust on the objects. 

Future work using higher resolution will allow a detailed study of fusion crusts to 

be conducted. 

not predicted by atmospheric heating models. .i. wenty-one ordinary chondrite (L5) 

* This work supported under NASA grant NAGW-3651. 
Beamline U1 A 

B.E. Bent, “Mimicking Aspects of Heterogeneous Catalysis: Generation, Isolation and Reacting Proposed Surface 

Intermediates on Single Crystals in Vacuum”, Chemical Reviews, 96, 1361, (1996). 

J.G. Chen, “Carbide and Nitride Overlayers on Early Transition Metal Surfaces: Preparation, Characterization and 

Reactivities”, Chemical Reviews, 96, 1477, (1996). 

J.G. Chen, B. Fruhberger, J. Baumgartner, and B.D. DeVries, “Characterization of the Electronic, Structural and 

Catalytic Properties ofvanadium Carbide: A Comparison ofVC/V( 1 10) Model System with Powder VC Catalysts”, 

The Chemistry ofTransition Metal Carbides and Nitrides, edited by S.T. Oyama, Blackie Academic and Professional, 

NewYork, p. 439, (1996). 

J.G. Chen, B. Fruhberger, and M.L. Colaianni, ‘‘NEWS Characterization of the Surface and Bulk Properties of 

Transition Metal Oxides”,/. of Vac. Sci. and Tech., A14, 1668, (1996). 

B. Friihberger, J.G. Chen, J. Eng, Jr., and B.E. Bent, “Reactivities of Carbon- and Nitrogen-Modified Mo(110): A 

Comparison ofModification Effects by Surface and InterstitialAdatoms”,J Oflac. Sci. and Tech.,A14,1475, (1996). 

G. Haehner, A. Marti, W. R. Caseri, and N. D. Spencer, “Orientation and Electronic Structure of Methylene Blue 

on Mica: A Near Edge X-Ray Absorption Fine Structure Spectroscopy Study”,/. Chem. Pbys., 104/19,7749, (1996). 

M.X. Yang, M. Xi, Y. Yuan, and B.E. Bent, “NEXAFS Studies ofHalobenzenes and Phenyl Groups on Cu( 1 1 l)”, Surf: 

Sci., 341,9, (1995). 

Beamline U2B 

J.V. Badding, and D.C. Nesting, “Thermodynamic Analysis of the Formation of Carbon Nitrides Under Pressure”, 

Chem. Mat., 8, 535, (1996). 

G.L. Carr, D. DiMarzio, M.B. Lee, and D.J. Larson, Jr., “Infrared Microspectroscopy of Semiconductors at the 

Diffraction Limit” Semiconductor Characterization: Present Status and Future Needs, edited by Bullis, Seiler, and 

Diebold, AIP Press, p. 418, (1996). 

A.F. Goncharov, V.V. Struzhkin, M.S. Somayazulu, R.J. Hemley, and H. Mao, “Compression of Ice to 210 GPa: 

Infrared Evidence for a Symmetric Hydrogen Bonded Phase”, Science, 273, 218, (1996). 

R J. Hemley, H.K. Mao, A.F. Goncharov, M. Hanfland, and V.V. Struzhkin, “Synchrotron Infrared Spectroscopy 

to 0.15 eV of Hz and D2 at Megabar Pressures”, Pbys. Rev. Lett., 76, 1667, (1996). 

c- 1 
Beamline U3C 

H. Tao, U. Diebold, V. Chakarian, D.K. Shuh, J.A. Yarmoff, N.D. Shinn, and T.E. Madey, “RadiationInduced 

Decomposition of PF3 on Ru(OOOl)”,]. Vac. Sci. Tecbnol., A13, 2553-2557, (1995). 

Beamline U4A 

K. Breuer, C. Stagarescu, K.E. Smith, M. Greenblatt, and K. Ramanujachary, “Observation of Hidden Fermi Surface 

Nesting in a Two Dimensional Conductor”, Pbys. Rev. Lett., 76, 3 172, (1 996). 

J.E. Rowe, D.M. Riffe, G.K. Wertheim, and J.C. Bean, “Photoemission Measurement of Equilibrium Segregation at 

GeSi Surfaces”,]. Appl. Pbys., 76, 4915, (1994). 

K.E. Smith, K. Breuer, D.M. Goldberg, M. Greenblatt, W. McCarroll, and S.L. Hulbert, “Defects in Quasi-One 

Dimensional Oxide Conductors: &,3MO03’’, Mat. Res. SOC. Proc., 375, 133, (1995). 

H.-S. Tao, C.-H. Nien, T.E. Madey, J.E. Rowe and G.K. Wertheim, “Faceting of W( 11 1) Induced by Pd and Pt 

Adlayers - A Photoemission Study”, Surf: Sci., 357, 55, (1996). 

G.K. Wertheim, J.E. Rowe, D.N.E. Buchanan, and P.H. Citrin, “Surface-Ion Core-Level Shifts in Alkali Halides”, 

Surf: Sci. Lett., 319, L41, (1994). 

G.K. Wertheim, J.E. Rowe, D.N.E. Buchanan, and P.H. Citrin, “Experimental Interatomic Auger Rates in Sodium 

Halides”, Phys. Rev. B51, 13669, (1995). 

G.K. Wertheim, J.E. Rowe, D.N.E. Buchanan, and P.H. Citrin, “Valence-Band Structure of Alkali Halides 

Determined From Photoemission Data”, Pbys. Rev. B51, 13675, (1995). 

Beamline U4B 

V. Chakarian, Y.U. Idzerda, H.-J. Lin, C.J. Gutierrez, G.A. Prinz, G. Meigs, and C.T. Chen, “Canted Coupling of 

Buried Magnetic Multilayers”, Pbys. Rev., B53, 11313, (1996). 

V. Chakarian, H.-J. Lin, Y. U. Idzerda, E. E. Chaban, G. Meigs, J.-H. Park, C. J. Gutierrez, G. A. Prinz, and C. T. 

Chen, “Element-Specific Vector Magnetometry (ESVM) Via Soft X-ray Magnetic Circular Dichroism”, Mat. Res. 

SOC. Symp. Proc., p. 375, (1995). 

C.T. Chen, Y.U. Idzerda, C.-C. Kao, L.H. Tjeng, H.-J. Lin, and G. Meigs, “Magnetic Properties of Multilayers from 

Soft X-ray Magnetic Circular Dichroism”,]. Mat. Sci and Eng, B31,49, (1995). 

C.T. Chen, Y.U. Idzerda, C.-C. Kao, H. Tjeng, H.-J. Lin, and G. Meigs, “Magnetic Structure of Multilayers from 

Soft X-ray Magnetic Circular Dichroism,” Mat. Res. Soc., 375, 59, (1995). 

Y. Fukumoto, A.R. Moodenbaugh, M. Suenaga, D.A. Fischer, K. Shibutani, T. Hase, and S. Hayashi, “Effect of 

Oxygen Partial Pressure During Postheat Treatment on Bi2Sr2CaCu20y/Ag Tapes”, ]. Appl.. Pbys., 80, 1, (1996). 

A.R. Moodenbaugh, D.A. Fischer, Y.L. Wang, and Y. Fukumoto, “Superconductivity, Oxygen Content, and Hole 

State Density in BizSrl.?sCa1.2sC~208.18+~(-0.09<yI) and Bil,6Pbo.4Sr1.9Ca2C~302)), Pbysica, C268, 107-1 14, 

(1996). 

J.-H. Park, C.T. Chen, S.-W. Cheong, W. Bao, G. Meigs, V. Chakarian, andY.U. Idzerda, “Electronic Aspects of the 

Ferromagnetic Transition in Manganese Perovskites”, Phys. Rev. Lett., 76, 42 15, (1 996). 

c-2 
Beamline U41R 

M.R. Chance, A. Xie, Q. He, and R.M. Hochstrasser, “Ultrafast Studies ofElectronics States and Protein Bound Water 

Molecules in Bacteriorhodopsin”, ]. Biophysical, 70, A24 1, (1996). 

C.J. Hirschmugl, and G.P. Williams, “Chemical Shifts and Coupling Interactions for the Bonding Vibrational Modes 

for Co/Cu(lll) and (100) Surfaces”, Pbys. Rev., B52, 14177, (1995). 

A.E. Russell, L. Rubasingham, P.L. Hagans, and T.H. Ballinger, “Cell and Optics Design for in situ Farinfrared 

Spectroscopy of Electrode Surfaces”, Electrocbimica Acta, 41, 637, (1 996). 

G.P. Williams, “Infrared Synchrotron Radiation: Introduction and History”, Syncb. Rad. News, 8.15, 8, (1 995). 

A. Xie, Q. He, K. Hellingwerf, W.D. Hoff, E.M. Scheuring, B. Sclavi, M.R. Chance, K. Wynne, and G. Haran, “Farinfrared Synbchrotron Spectroscopy of Functionally Important Low Frequency Modes in Proteins”,]. Biophysical, 70, 

A338, (1996). 

Beamline U8B 

T.D. Durbin, D.A. Lapiano-Smith, F.R. McFeely, F. J. Himpsel, and J.A. Yarmoff, “The Chemisorption and Reaction 

of Dichlorosilane on Ge(100) and Ge(ll1) Surfaces”, Suf Sci., 330, 147-155, (1995). 

S. Lee, M. M. Banaszak Holl, W. H. Hung, and F. R. McFeely, “Photoemission Assignments of H,Si04_, Fragments 

in the Si/SO, Interface Region”, Appl. Pbys. Lett., 68, 1081, (1996). 

F.R. McFeely, K.Z. Zhang, M. M. Banaszak Holl, S. Lee, and J.E. Bender IV., “An Inquiry Concerning the Principles 

of Si 2p Core Level Shift Assignments at the Si/SiOz Interface”,]. Vac. Sci. Tecbnol., B14,2824, (1996). 

W.C. Simpson, T.D. Durbin, P.R. Varekamp, and J.A. Yarmoff, “The Growth of GaF3 Films on GaAs( 110) at 

Elevated Temperatures Studied with Soft X-ray Photoelectron Spectroscopy”,]. AppL. PbyJ., 77,275 1-2758, (1995). 

W.C. Simpson, W.M. Tong, C.B. Weare, D.K. Shuh, and J.A. Yarmoff, “The Temperature Dependence of the Cl2l 

GaAs(1 IO) Surface Product Distribution”,]. Cbem. Pbys., 104, 320-325, (1996). 

W.C. Simpson, P.R. Varekamp, D.K. Shuh, and J.A. Yarmoff, “Soft X-ray Photoelectron Spectroscopy Study of the 

Reaction ofXeF2 with GaAs”,]. Vac. Sci. Tecbnol., A13, 1709-1713, (1995). 

J.A. Yarmoff, V. Chakarian, T.D. Durbin, C.W. Lo, D.K. Shuh, W.C. Simpson, and P.R. Varekamp, “Photon 

Stimulated Desorption of Halogens”, Nucl.. Instrum. Metbs., 101, 60-63, (1995). 

Beamline U9B 

E.R. Arndt, and E.S. Stevens, “A Conformational Study ofAgarose by Vacuum UVCD”, Biopolymers, 34,1527-1534, 

(1994). 

E.R. Arndt, and E.S. Stevens, “Vacuum Ultraviolet Circular Dichroism of Gellan-Family Polymer Films from Water 

and Dimethy Sulfoxide”, Carbohydrate Research, 280, 15-26, (1996). 

A. Buku, U. Mirza, and K. Polewski, “Circular Dichroism (CD) Studies on Biological Activity of Mast Cell 

Degranulation (MCD) Peptide Analogs”, Int. ]. Peptide Protein Res, 44, 410-413, (1994). 

J.M. Flanagan, J.S. Wall, M.S. Capel, D.K. Schneider, and J. Shanklin, “Scanning Transmission Electron Microscopy 

and Small-Angle Scattering Provide Evidence that Native Escherichia coli ClpP is a Tetradecamer with an Axial Pore”, 

Biocbemistry, 34, 10910-10917, (1995). 

c-3 
L.L. France, P.G. Paitti, J.F.E. Newman, and F. Brown, “Modeling Biologically Relevant Peps using Circular 

Dichroism with Synchrotron Radiation and High Temperature Molecular Dynamics”, Molecular Modeling, edited 

by T.F. Kumosinsky and M.N. Liebman, American Chemical Society, pp. 45-60, (1994). 

L.L. France, P.G. Piatti, J.F.E. Newman, I. Toth, W.A. Gibbons, and F. Brown, “Circular Dichroism, Molecular 

Modeling and Serology Indicate that the Structural Basis on Antigenic Variation in Foot-andmouth Disease Virus is 

a-helix formation”, Proc. NatL Acad. Sci., 91, 8442-8446, (1994). 

R.B. Hill, J.M. Flanagan, and J.H. Prestegard, “1H and 15N Magnetic Resonance Assignments, Secondary Structure 

and Tertiary Fold of Eshcerichia coli DnaJ(1-78)”, Biochemistry, 34, 5587-5596, (1995). 

E. Johnson, and J.C. Sutherland, “Ultraviolet Free-Electron Laser Facility at Brookhaven National Laboratory”, 

Synchrotron Radiation in the Biosciences, edited by B. Chance, D. Deisenhofer, S. Ebashi, D.T. Goodhead, J.R. 

Helliwell, H.E. Huxley, T. Iizuka, J. Kirz, T. Mitsui, E. Rubenstein, N. Sakabe, T. Sasaki, G. Schmahl, H. Sturhmann, 

K. Wuthrich, and G. Zaccai, Clarendon Press, Oxford, pp. 739-747, (1994). 

L.A. Kelly, J.G. Trunk, K. Polewski, and J.C. Sutherland, “Simultaneous Resolution of Spectral and Temporal 

Properties of UV and Visible Fluorescence using Single-Photon Counting with a PositionSensitive Photomultiplier”, 

Rev. Sci. Instrum., 66, 1496-1498, (1995). 

S. Krinsky, and C.-C. Kao, “Time Varying Elliptically Polarized Wiggler at the NSLS”, Synch. Rad. News, 815, 38- 

39, (1995). 

J.H. Kycia, V. Biou, F. Shu, S.E. Gerchman, V. Graziano and V. Ramakrishnan, “Prokaryotic Translation Initiation 

Factor IF3 is an Elongated Protein Consisting ofTwo Crystallizable Domains”, Biochemistry, 34,6183-6187, (1 995). 

A. Lempicki, M.H. Randles, D. Wisniewski, M. Balcerzyk, C. Breacher, andA.J. Wojtowicz, ‘‘LUA103: Ce and other 

Aluminate Scintillators”, IEEE Trans. in Nucl. Sci., 42, 280, (1995). 

A. Lempicki, A. J. Woj towicz, and C. Brecher, “Inorganic Scintillators”, Wide-Gap Luminescent Materials: Theory 

and Applications, edited by S.R. Rotman, pp. 1-65, (1996). 

O.C. Mullins, and X. Wang, “Fluorescence Lifetime Studies of Crude Oils”, Applied Spectroscopy, 48, 977-984, 

(1 994). 

K. Polewski, D. Zinger, J. Trunk, D. Monteleone, and J.C. Sutherland, “Fluorescence ofMatrix Isolated Guanine and 

7-MethylguanineY’, J. Of Photochemistry avzd Photobiology”, B24, 169- 177, (1 994). 

C.Y. Ralston, S. Mitra-Kirtley, and O.C. Mullins, “Small Population of One to Three Fused-Aromatic Ring Moities 

in Asphaltenes”, Energy &Fuels, 10, 623-630, (1996). 

J.C. Sutherland, “Circular Dichroism Using Synchrotron Radiation: From Ultraviolet to X-rays”, Circular Dichroism: 

Conformational Analysis of Biomolecules, edited by G.D. Fasman, pp. 599-633, (1996). 

X. Wang, and 0. Mullins, “Fluorescence Lifetime Studies of Crude Oils”, Applied Spectroscopy, 48,977984, (1994). 

A.J. Wojtowicz, M. Balcerzyk, E. Berman, and A. Lempicki, “CexLa1_,F3: Optical Spectroscopy and Scintillation 

Mechansisms”, Phys. Rev., B49, 14880, (1 994). 

c-4 
Beamline U10 

C.L. Foerster, “Ultra-High Vacuum System of the Brookhaven National Synchrotron Light Source”, Proceedings 

International Conference on Vacuum Science & Technolo? and SRS Vacuum SystemsINCOVAST 95, Accelerators 

and SRS Systems, 1, pp. 36-57, (1995). BNL 62537. 

C.L. Foerster, C. Lanni, J.R. Noonan, and R.A. Rosenberg, “Photon Stimulated Desorption Measurement of an 

Extruded Aluminum Beam Chamber for the Advanced Photon Source”,]. Vac. Sci. Tecbnol., A14/3,1273, (1996). 

BNL 62542. 

C.L. Foerster, C. Lanni, C. Perkins, M. Calderon, and W. Barletta, “Photon Stimulated Desorption (PSD) 

Measurements of Extruded Copper and of Welded Copper Beam Chambers for the PEP I1 Asymmetric B-factory”, 

]. Vac. Sci. Tecbnol., A13/3, 581, (1995). BNL 61082 

Beamline U11 

P.S. Monks, L.J. Stief, D.C. Tardy, J.F. Liebman, 2. Zhang, S.C. Kuo, and R.B. Klemm, “A Discharge FlowPhotoionization Mass Spectrometric Study of HOI: Photoionization Efficiency Spectrum and Ionization Energy”,]. 

Pbys. Cbem., 99, 16566, (1995). 

D.C. Tardy, S.C. Kuo, Z. Zhang, and R.B. Klemm, “Ionization Energy of tert-Butyl-d9 Alcohol and the Appearance 

Energy of Protonated Acetone: A Nonequilibrium Dissociation”,]. Pbys. Cbem., 100, 8144, (1996). 

R.P. Thorn, Jr., P.S. Monks, L.J. Stief, S.C. Kuo, Z. Zhang, and R.B. Klemm, “The Photoionization Efficiency 

Spectrum, Ionization Energy and Heat of Formation of Br20”,]. Pbys. Cbem., 100, 12199, (1996). 

Z. Zhang, P.S. Monks, L.J. Stief, J.F. Liebman, R.E. Huie, S.C. Kuo, andR.B. Klemm, “Experimental Determination 

of the Ionization Energy of IO(X2113/2) and Estimations of the Heat of Formation of IO+ and the Proton Affinity of 

IO”, ]. Pbys. Cbem., 100, 63, (1996). 

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J.C. Levin, G.B. Armand, and I.A. Sellin, “Photoionization and Compton Double Ionization of Helium from 

Threshold to 20 keV”, Pbys. Rev. Lett., 76, 1220, (1996). 

B. Sinkovic, E. Shekel, and S. L. Hulbert, “Spin-Resolved Fe L3M45M45 Auger Transition on- and oflesonance: The 

Effect of Exchange Correlation”, Pbys. Rev., B52, 15703, (1995). BNL 62536 

Beamline U1 SUB 

J.E.Bjorkholm, A.A.MacDowel1, 0.R.Wood 11, Z.Tan, B.LaFontaine, and D.M.Tennant, “Phase Measuring 

Interferometry”]. Vac.Sci. Tecbnol., B13/6,2919, (1995). 

Beamline U14A 

Z.M. Stadnik, G.W. Zhang, M. Akbari-Moghanjoughi, A.-P. Tsai, and A. Inoue, “Physical Properties ofAl -Cu-FeMn Icosahedral Alloys” Proceedines of the 5th International Conference on 0-uasicrvstals, Avignon, 1995, edited Ch. 

Janot and R. Mosseri, World Scientific, Singapore, p. 530, (1 995). 

G.W. Zhang, and Z.M. Stadnik, “Partial and Total Densities of States in Icosahedral Al70Pd20Mn10”, Proceedings 

of the 5th International Conference on Ouasicrystals, Avignon, 1995, edited by C.H. Janot and R. Mosseri, World 

Scientific, Singapore, p. 552, (1995). 

c-5 
Beamline U15 

S. Huang, Z.H. Ming, Y.L. Soo, Y.H. Kao, M. Tanaka, and H. Munekata, “X-ray Scattering and Absorption Studies 

of MnAsIGaAs Heterostructures”,]. Appl. Pbys., 79, 1435, (1996). 

C.I. Ma, D.M. Hanson, K. Lee, and R.G. Hayes, “Dynamical Behavior of Electronic States of NH32+ Prepared From 

N Is Ionization ofhmonia”,]. Electron Spectrosc. Relat. Pbenom., 75, 83, (1995). 

Z.H. Ming, S. Huang, Y.L. Soo, K.H. Kao, T. Carns, and K.L. Wang, “Interfacial Roughness Scaling and Strain in 

Lattice Mismatched Si0.4Ge0.6 Thin Films on Si”, Appl. Pbys. Lett., 67, 629, (1995). 

Y.L. Soo, S.W. Huang, Z.H. Ming,Y.H. Lo, H. Munekata, andL.L. Chang, “III-VDilutedMagneticSemiconductor: 

Substitutional Doping of Mn in I&”, Pbys. Rev., B53, 4905, (1996). 

C-6 
Beamline X1 A 

H. Ade, B. Hsiao, G. Mitchell, E. Rightor, A. P. Smith, and R. Cieslinski, “X-ray Microscopy of Polymeric 

Materials”, Mat. Res. SOC. Proc. 375 , 293-302, (1995). 

H.N. Chapman, J. Fu, C. Jacobsen, and S. Williams, “Dark-Field X-ray Microscopy of Immunogold-labeled 

Cells”,]. Micro. SOC. Am., 2, 53-62, (1996). 

H.N. Chapman, C. Jacobsen, and S. Williams, “A Characterization of Darkfeld Imaging of Colloidal Gold 

Labels in a Scanning Transmission X-ray Microscope”, ULtramicroscopy, 62, 19 1-21 3, (1 995). 

G. D. Cody, R. E. Botto, H. Ade, and S. Wirick, “Soft X-ray Microscopy and Microanalysis: Applications in 

Organic Geochemistry”, PIE, 2516, 185-196, (1996). 

T. Crowder and H. Ade, “A Low Pressure Parallel Plate Proportional Counter Optimized for Detection of 

Nitrogen Fluorescence”, Rev. Sci. Instrum., 66, 2303-2305, (1995). 

K. K. Goncz and S. S. Rothman, “A Trans-Membrane Pore can Account for Protein Movement Across Zymogen 

Granule Membranes”, Biocbim., Biopbys. Acta, 1238, 91-93, (1 995). 

W.S. Haddad, I. McNulty, J.E. Trebes, and E.H. Anderson, “Ultrahigh Resolution X-ray Tomography”, PIE, 

2516, 102-107, (1995). 

C.-H. KO, J. Kirz, K. Maier, B. Winn, H. Ade, S. Hulbert, E. Johnson, and E. Anderson, “Chemical State 

Mapping on Material Surfaces with the X1A Second Generation Scanning Photoemission Microscope (X1A 

SPEM-11)”, SPZE, 2516, 150-159, (1995). 

J. Maser, H. Chapman, C. Jacobsen, A. Kalinovski, J. Kirz, A. Osanna, S. Spector, S. Wang, B. Winn, S. Wirick, 

and X. Zhang, “The Scanning Transmission X-ray Microscope at the NSLS: From XANES to Cryo”, SPZE, 2516, 

78-89, (1995). 

X. Zhang, R. Balhorn, J. Mazrimas, and J. Kirz, “Mapping and Measuring DNA to Protein Ratios in Mammalian 

Sperm Head by XANES Imaging”, ]. Struct. Bio., 116, 335-344, (1996). 

Beamline X1 B 

S. Eisebitt, J. Luning, J.E; Rubensson, T. van Buuren, S.N. Patitsas, T. Tiedje, M. Berger, S. Arens-Fischer, S. 

Frohnhoff, and W. Eberhardt, “Soft X-Ray Emission of Porous Silicon Nanostructures”, J. Electr. Spectr., 79, 135, 

(1996). 

P.D. Johnson, Y. Liu, 2. Xu, and D.-J. Huang, “Spin-Polarized Photoemission Studies of the 3s Core Levels in Fe 

and CO”, J ELectr. Spectr., 75, 245, (1 995). 

B. Kempgens, B. Itchkawitz, K.J. Randall, J. Feldhaus, A.M. Bradshaw, H.M. Koeppe, F.X. Gadea, D. Nordfors, 

J. Schirmer, and L.S. Cederbaum, “Dynamic Effects in the C Is Excitation Spectra of Ethene Isotopomers”, 

Gem. Pbys. Lett., 246, 347, (1995). 

A. Kivimacki, M. Neeb, B. Kempgens, H.M. Koeppe, and A.M. Bradshaw, “The C Is Auger Decay Spectrum of 

the CH4 Molecule: The Effects of Vibrational Fine Structure, Double Excitations and Shake-up Transitions”, J 

Pbys., B29, 27091, (1996). 

c-7 
H.M. Koeppe, B. Kempgens, A.L.D. Kilcoyne, J. Feldhaus, and A.M. Bradshaw, “Autoionisation of Doubly 

Excited States in the C Is Photoexcitation of CO”, Cbem. Pbys. Lett., 53, 4120, (1996). 

H. M. Koeppe, B.S. Itchawitz, A.L.D. Kilcoyne, J. Feldhaus, B. Kempgens, A. Kivimaeki, M. Neeb, andA.M. 

Bradshaw, “High-Resolution C Is Photoelectron Spectra of Methane”, Pbys. Rev., A53, 4120, (1996). 

H.M. Koeppe, A.L.D. Kilcoyne, J. Feldhaus, and A.M. Bradshaw, “Relaxation Effects in C 1s Photoionisation of 

CO: A High Resolution Photoelectron Study in the Near-Threshold Region”, /. Electr. Spectrosc. Rel. Pben., 75, 

97, (1995). 

M. Neeb, A. Kivimaeki, B. Kempgens, H.M. Koeppe, J. Feldhaus, and A.M. Bradshaw, “Core Hole DoubleExcitation and Atomic-Like Auger Decay in Nz”, Pbys. Rev. Lett., 76, 2250, (1995). 

M. Neeb, A. Kivimaeki, B. Kempgens, H.M. Koeppe, and A.M. Bradshaw, “Excitation Energy Dynamics 

Observed in N2 Auger Spectra Near the K-Shell Threshold,/. ELectr. Spectrosc. ReL. Pben., 79,445, (1995). 

J-E. Rubensson, J. Luning, M. Neeb, M. Biermann, B. Kuepper, and W. Eberhardt, “Core-Level 

Photoionization-Decay Coincidence Spectroscopy of Free Molecules”, /. Elect. Spect. ReL. Pben. , 75,47, (1 996). 

J-E. Rubensson, J. Luning, M. Neeb, B. Kuepper, S. Eisebitt, and W. Eberhardt , “Photoelectron-Soft-X-rayFluorescence Coincidence Spectroscopy on Free Molecules”, Pbys. Rev. Lett, 76, 39 19, (1996). 

M. Schmidbauer, A.L.D. Kilcoyne, H.M. Koeppe, J. Feldhaus, and A.M. Bradshaw”, Shape Resonances and 

Multi-Electron Effects in the Core-Level Photoionization of COz”, Pbys. Rev., A52,2095, (1995). 

2. Xu, Y. Liu, P.D. Johnson, and B.S. Itchkawitz, “Magnetic Structure of Monolayer-Range Cr Films Deposited 

on Fe(001)”, Pbys. Rev., B52, 15393, (1995). 

Beamline X2A 

A.P. Baddorf, A.K. Swan, and J.F. Wendelken, “Comment on In-Plane Lattice Reconstruction of Cu(00 l)”, Pbys. 

Rev. Lett., 76, 3658, (1996). 

K. Kimura, J.B. Cohen, S. Chandavarkar, and K.S. Liang, “Surface Atomic Ordering of Cufiu(OO1) Above T,”, 

Pbysica, B221, 101, (1995). 

R. Paniago, S. Schmid, T.H. Metzger, P.C. Chow, H. Reichert, S.C. Moss, J. Peisl, and K.S. Liang, “Surface 

Induced Changes in the Critical Behavior of the Phase Transition in V2H”, Pby~ica, B221, 210, (1995). 

Beamline X2B 

F.M. Auzerais, J.H. Dunsmuir, B. Ferreol, N. Martys, J. Olsen, T.S. Ramakrishnan, D.H. Rothman, and L.M. 

Schwartz, “Transport in Sandstone: A Study Based on Three Dimensional Microtomography”, Geopbys. Res. 

Letts., 23/7, 705-708, (1996). 

B.B. Ferreol and D.H. Rothman, “Lattice Boltzmann Simulations of Flow Through Fontainebleau Sandstone”, 

Transport in Porous Media, 20, 3-20, (1 995). 

E.N. Landis, E.N. Nag, D.T. Keane, and N. Huynh, “Observations of Internal Fracture in Mortar using X-ray 

Microtomography”, Proceedings of the 1996 ASCE Engineering Mechanics Specialty Conference, pp. 637-640, 

( 19 96). 

C-8 
E.N. Landis, E.N. Nagy, D.T. Keane, and S.P. Shah, “Observations of Internal Crack Growth in Mortar using Xray Microtomography”, Proceedings of the 2nd International Conference on Nondestructive Testing of Concrete 

in the Infrastructure, pp. 54-59, (1996). 

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Beamline X5 

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c-12 
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C-13 
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C-14 
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C-15 
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M.A. Murphy, E. Nordgren, R.F. Fischetti, J.K. Blasie, L.J. Peticolas, and J.C. Bean, “A Structural Study of the 

Annealing of Akylsiloxane Self-Assembled Monolayers on Silicon by High-Resolution X-Ray Diffraction”, J. 

Pbys. Cbem., 99/38, 14039-14051, (1995). 

M.J. Nelson, B.A. Brennan, D.B. Chase, R.A. Cowling, G.N. Grove, and R.C. Scarrow, “Structure and Kinetics 

of Formation of Catechol Complexes of Ferric Soybean Lipoxygenase-I”, Biocbemisty, 34, 1521 9-1 5229, (1 995). 

L.A. Prokop, R.M. Strongin, A.B. Smith, 111, J.K. Blasie, L.J. Peticolas, and J.C. Bean, “Profile Structures of 

Vectorially Oriented Monolayers of Detergent-Solubilized Ca+zATPase from Sarcoplasmic Reticulum”, Biopbys. 

J., 70,2131-2143, (1996). 

P.J. Riggs-Gelasco, T.L. Stemmler, and J.E. Penner-Hahn, “XAFS of Dinuclear Metal Sites in Proteins and 

Model Compounds”, Coord. Cbem. Rev. , 144,245-286, (1995). 

M.J. Ryle, W.N. Lanzilotta, L.C. Seefeldt, R.C. Scarrow, and G.M. Jensen, “Circular Dichroism and X-ray 

Spectroscopies of Azotobacter Vinelandii Nitrogenase Iron Protein”,J. Bid. Cbem., 271, 155 1-1557, (1996). 

R.C. Scarrow, B.A. Brennan, J.G. Cummings, H. Jin, D.J. Duong, J.T. Kindt,and M.J. 

Nelson, “X-Ray Spectroscopy of Nitrile Hydratase at pH 7 and 9”, Biocbemisty, 35, 10078, (1996). 

E.M. Scheuring, W. Clavin, M.D. Wirt, L.M. Miller, Y. Lu, N. Mahoney, A. Xie, J.J. Wu, and M.R. Chance, 

“Time-Resolved X-ray Absorption Spectroscopy of an Enzymatically Important Coenzyme B12 Derivative”, J. 

Pbys. Cbem., 100, 3344-3348, (1996). 

E.M. Scheuring, S.Huang, R.G. Matthews, and M.R. Chance, “Structure-Function of Cobalamin Dependent 

Enzymes: X-Ray Absorption Studies on Methionine Synthase from E. Coli”, Biophysicd J., 70, A437, (1996). 

L.C. Seefeldt, M.J. Ryle, W.N. Lanzilotta, R.C. Scarrow, and G.M. Jensen, “Circular Dichroism and X-Ray 

Spectroscopies of Azotobacter Vinelandii Nitrogenase Iron Protein: MgATP and MgADP Induced Protein 

Conformational Changes Affecting the [4Fe-4S] Cluster and Characterization of a [2Fe-2S] =46orm”, J. Biol. 

Cbem. 271, 1551-1557, (1996). 

C-16 
R. Sinclair, B. Copeland, I. Yamazaki, and L. Powers, “X-Ray Absorption Spectroscopy Comparison of the Active 

Site Structures of Pbanerocbaete Cbysosporium Lignin Peroxidase Isoenzymes H2, H3, H4, H5, H8, and HlO”, 

Biocbemisty, 34, 13176, (1995). 

T.L. Stemmler, Kinetic and Spectroscopic Characterization of the Native and Inhibitor Bound Forms of the 

Lactobacillus PLantarum Mn Catalase and Related Proteins. PhD. Thesis., University of Michigan, May 1996. 

T.L. Stemmler, T.M. Barnhart, J.E. Penner-Hahn, C.E. Tucker, P. Knochel, M. Bohme, and G. Frenking, 

“Structural Characterization of Organocuprate Reagents. EXAFS Spectroscopy of Ab Initio Calculations”, J. Am. 

Cbem. SOC., 117, 12489-12497, (1995). 

H.T. Tsang, C. J. Batie, D.P. Ballou, and J.E. Penner-Hahn, “Structural Characterization of the Mononuclear 

Iron Site in Pseudominas Cepacia Phthalate DBO 1 Dioxygenase Using X-Ray Absorption Spectroscopy”, J. Bid. 

Inorg. Cbem., 1,24-33, (1996). 

K. Zhang, and D.S. Auld, “Structures of Binary and Ternary Inhibitor Complexes of Zinc and Cobalt 

Carboxypeptidase A as Determined by XAFS”, Biochemistry, 34, 16306-1 6312, (1995). 

T. Zhu, The Effect of Anti-Viral PeDtides on the Physical Properties of Membranes, PhD. Thesis, Ohio State 

University, June 1996. 

Beamline X1 OA 

W.H. De Jeu, J.D. Shindler, S. Chandavarkar, R.M. Geertman, and K. Liang, “On the (Absence of-) Surface 

Melting in Biphenyl”, Surf: Sci., 342, 341, (1995). 

J.H. Je, D.Y. Noh, H.K. Kim, and K.S. Liang, “A Real-Time X-ray Scattering Study of Sputtering Growth of 

TIN Films”, in Application of Svnchrotron Radiation Techniques to Materials Science, edited by D.L. Perry, et 

al., MRSSymp. Proc., 375, 1, (1995). 

J. Li, K.S. Liang, N. Camillone 111, T.Y.B. Leung, and G. Scoles, “The Structure of n-Octadecane Thiol 

Monolayers Self-Assembled on Au(O0 I) Studied by Synchrotron X-ray and Hellium Atom Diffraction”, J. Cbem. 

Pbys., 102, 5012, (1995). 

J. Li, K.S. Liang, G. Scoles, and A. Ulman, “Counterion Overlayers at the Interface Between an Electrolyte and an 

w-Functionalized Monolayer Self-Assembled on Au. An X-ray Specular Reflectivity Study”, Langmuir, 11,441 8, 

(1 995). 

D.Y. Noh, M. Hong, Y. Hwu, J.H. Je, and J.P. Mannaerts, “Strain Relaxation in Fe3(Al,Si)/G&: An X-ray 

Scattering Study”, AppL. Pbys. Lett., 68, 1528, (1996). 

D.Y. Noh, Y. Hwu, and M. Hong, “X-ray Scattering Studies of the Interfacial Structure ofAu/G&”, Pbys. Rev., 

B51,4441, (1995). 

S.B. Rivers, W.N. Unertl, H.H. Hung, and K.S. Liang, “Order-Disorder Transition at the (001) Surface of a 3 

at.% Au-rich Cu&u Crystal”, Pbys. Rev., B52, 12601, (1995). 

E.B. Sirota, H.E. King, Jr., H.H. Shao, and D.M. Singer, “Rotator Phases in Mixtures of n-Alkanes”,J. Pbys. 

Cbem., 99,798, (1995). 

C-17 
X.Z. Wu, H.H. Shao, B.M. Ocko, M. Deutsch, S.K. Sinha, M.W. Kim, H.E.J. King, and E.B. Sirota, “Surface 

Crystallization and Thin Film Melting in Normal Alkanes”, Dynamics in Small Confining Systems 11, edited by 

J.M. Drake, J. Klafter, R. Kopelman, and S.M. Troian, Mat. Res. Soc. Symp. Proc., 366, 15, (1995). 

Beamline X11 A 

D.B. Aldrich, Y.L. Chen, D.E. Sayers, and R.J. Nemanich, “Titanium Germanosilicide Phase Formation During 

the Ti-Sil_,Ge, Solid Phase Reactions”, Mat. Res. Soc. Symp. Proc., 402, 405, (1996). 

D.B. Aldrich, Y.L. Chen, D.E. Sayers, R.J. Nemanich, S.P. Ashburn, and M.C. Ozturk, “Effect of Composition 

on Phase Formnation and Morphology in Ti-Sil_,Ge, Solid Phase Reactions”,]. Mater. Res., 10, 2849, (1995). 

D.B. Aldrich, Y.L. Chen, D.E. Sayers, R.J. Nemanich, S.P. Ashburn, and M.C. Ozturk, “Stability of C54 

Titanium Germanosilicide on a Silicon-Germanium Alloy Substrate”, J. Appl. Pbys., 77, 5 107, (1995). 

D.B. Aldrich, H.L. Heck, Y.L. Chen, D.E. Sayers, and R.J. Nemanich, “Film Thickness Effects in the Ti-Sil,Ge, 

Solid Phase Reaction”,J Appl. Pbys., 78, 4958, (1995). 

D.B. Aldrich, F.M. D’Heurle, D.E. Sayers, and R.J. Nemanich, “Interface Stability of Ti(Sil-yGey)2 and Sil_,Ge, 

Alloys”, Mat. Res. Soc. Symp. Proc., 402, 21, (1996). 

D.B. Aldrich, R.J. Nemanich, and D.E. Sayers, “Bond-Length Relaxation in Sil_,Ge, Alloys”, Pbys. Rev., B50, 

15026, (1994). 

E.M. Coe, L.H. Bowen, J.A. Speer, Z. Wang, D.E. Sayers, and R.D. Bereman, “The Characterization of a 

Polysaccharide Iron Complex (Niferex)”, J. Inorgan. BioCbem., 58,269, (1995). 

Y. Dao, A.M. Edwards, R.J. Nemanich, and D.E. Sayers, “Local Structural Studies of (Til-,ZrJSiz Thin Films on 

Si( 1 1 l)”, Pbysica, B208-209, 5 13, (1995). 

Y. Dao, A.M. Edwards, H. Ying, Y.L. Chen, D.E. Sayers, and R.J. Nemanich, “Structural and Electrical 

Properties of (Ti0.9Zro.~)Si2 Thin Films on Si(l1 l)”, Appl. Phys. Lett., 65, 2413, (1994). 

Y. Dao, D.E. Sayers, and R.J. Nemanich, “Morphology and Stability of (Tio.9Zro.l)Si2 Thin Films on Si(ll1) and 

Si(100) Formed in UHV” Thin Solid Films, 270, 544, (1995). 

Y. Dao, D.E. Sayers, and R.J. Nemanich, “Phase Stabilities and Surface Morphologies of (Til_,Zr,)Siz Thin Films 

on Si(lll)”,J Appl. Pbys., 78, 6584, (1995). 

P.T. Goeller, Z. Wang, D.E. Sayers, J.T. Glass, and R.J. Nemanich, “Epitaxial Films of Cobalt Disilicide (100) 

Evaporated onto Si( 100) From a Mixed Source”, Mat, Res. Soc. Symp. Proc., 402, 5 1 1, (1 996). 

Q. Lu, “XAFS Investigations of Structural ProDerties at Internal Interfaces”, Ph.D. Dissertation, Notre Dame 

University, May 1996. 

A.N. Mansour, C.A. Melendres, S.J. Poon, Y. He, and G.J. Shiflet, “An X-ray Absorption Near-edge Study of the 

Structure of Passive Films on Amorphous Al-Fe-Ce Alloys”, J. Electrochem. Soc., 143, 614, (1996). 

M. Marcus, D. Jacobson, A. Vredenberg, and G.M. Lamble, “Concentrations and Annealing Effects on 

Photoluminescence and Local Structure of Erbium Implanted Silica”, J. Of Non-Cystl. Solids, 95, 232, (1996). 

c-18 
RA. Mayanovic, and B.A. Bunker, “Observation of Anisotropic Vibrational Amplitudes due to Thermal Motion 

at a Cu/A1203 Interface”, Pbys. Lett., A202, 225, (1995). 

J. McBreen, X.Q. Yang, and H.S. Lee, “X-ray Absorption Studies of NiBrz(PE0)s and ErBr3(PE0)12 

Complexes”, Macromol. Symp., 105, 185, (1996). 

W.E. O’Grady, K.I. Pandya, K.E. Swider, and D.A. Corrigan, “In Situ X-ray Absorption Near Edge Structure 

Evidence for Quadrivalent Nickel in Nickel Battery Electrodes”,/. Electrochem. SOC., 143, (1996). 

K.I. Pandya, S.W. Heald, and J.A. Hriljac, “Characterizations by EXAFS, NMR and Other Techniques of Pt/ 

NaY Zeolites at Industrially Relevant Low Concentrations of Platinum”, /. Pbys. Cbem., 100, 5070, (1 996). 

G. Pfeiffer, J.J. Rehr, and D.E. Sayers, “The Near-Edge Structure of a-AszS3 and Pressure Induced Changes”, 

Pbysica, B208/209, 385, (1995). 

G. Pfeiffer, J.J. Rehr, and D.E. Sayers, “XAFS Near-Edge Structure ofAszS3: A Comparison of Experiment and 

Theory”, Pbys. Rev. , B51, 804, (1995). 

A.M. Scheidegger, G.M. Lamble, and D.L. Sparks, “Ni Absorption on Pyrophyllite: An XAS Study, Environ. Sci. 

Tech., 30, 548, (1996). 

N.D. Triantafillou, S.E. Deutsch, 0. Alexeev, J.T. Miller, and B.C. Gates, “Ir/KLTL Zeolites: Structural 

Characterization and Catalysis of r\-Hexane Reforming, J OfCatalySs, 159, 14, (1996). 

2. Wang, D.B. Aldrich, Y.L. Chen, D.E. Sayers, and R.J. Nemanich, “Silicide Formation and Stability of Ti/SiGe 

and Co/SiGe”, Tbin SolidFiLms, 270, 555, (1995). 

Z. Wang, D.B. Aldrich, P. Goeller, R.J. Nemanich, and D.E. Sayers, “Characterization of Zirconium 

Germanosilicide Formed by Solid State Reaction of Zr with Sil-,Ge, Alloys”, Mat. Res. SOC. Symp. Proc., 402, 

387, (1996). 

Z. Wang, R.J. Nernanich, and D.E. Sayers, “EXAFS and XRD Studies of Phase Formations of Co in Reactions 

with Si-Ge Alloys”, Pbysica, B2081209, 567, (1995). 

A. Zhao, and B.C. Gates, “Hexairidium Clusters Supported on Y-Al2O3: Synthesis, Structure, and Catalytic 

Activity for Toluene Hydrogenation”, /. Am. Cbem. Soc., 118, 2458, (1996). 

Beamline X12B 

M.V. Brillhart, P. Cebe, and M.S. Capel, “Real-Time X-ray Scattering of Binary Polymer Blends: Poly(Buty1ene 

Terephthalate)/Polycarbonate”, Advances in X-ray Analysis, edited by Predecki, et al, Plenum, 38, p. 489, (1995). 

M.S. Capel, G.C. Smith and B. Yu, “One- and Two-Dimensonal X-ray Detector Systems at NSLS Beamline 

X12B, for Time-Resolved and Static X-ray Diffraction Studies”, Rev. Sei. Instrum., 66/2,2295, (1995). 

Y.Y. Cheng, P. Cebe, M.S. Capel, H. Schreuder-Gibson, A. Bluhm, and W. Yeomans, “Small-Angle X-ray 

Scattering Study of Liquid-Crystalline Polycarbonates based on Alpha-Methyl Stilbene Mesogen and MethyleneContaining Flexible Spacer”, /. Polymer Sci, Part B-Polymer Pby., 33/17, 2331, (1995). 

c-19 
J.M. Flanagan, J.S. Wall, M.S. Capel, D.K. Schneider and J. ShanMin, “Scanning Transmission Electron 

Microscopy and Small-Angle Scattering Provide Evidence that Native Escbericia coli ClpP is a Tetradecamer with 

an Axial Pore”, Biochem., 34, 10910, (1995). 

J.L. Fulton, D.M. Phnd, J.B. McClain, T.J. Romack. E.E. Maury, J.R Combes, E.T. Samulski, J.M. Desimone 

and M.S. Capel, “Aggregation of Amphiphilic Molecules in Supercritical Carbon-Dioxide-a Small-Angle X-ray 

Scattering Study”, Langnzuir, 11, 4241, (1995). 

R.B. Knott, M.S. Capel, S. Hansen, and R.E. Schumacher, “A Small-Angle Scattering Study of the Binding of 

Cyclosporin-a to Cyclophillin”, J. Appl. Cyst., 28, 546, (1 995). 

S.X. Lu, P. Cebe, and M.S. Capel, “Structure and Relaxation using SAXS and TSDC”,J. Appl. Polymer Sci., 57, 

1359, (1995). 

S.X. Lu, P. Cebe, and M.S. Capel, “Thermal Stability and Thermal Expansion Studies of PEEK and Related 

Polyimides”, Polymer, 37/14,2999, (1996). 

A.J. Quantock, N.J. Fullwood, E.J-M.A. Thonar, S.R. Waltman, M.S. Capel, M.C. Kincaid, M. Ito, S.M. Verity 

and D.J. Schanzlin, “Stromal Descements and Endothelial Changes in Macular Dystrophy Type 11”, Invest. 

Opthamol. & Ws. Sci., 37, 1019, (1996). 

A.J. Quantock, G.K. Klintworth, D.J. Schanzlin, M.S. Capel, M.E. Lenz, and E.J-M.A. Thonar, “Proteoglycans 

contain a 4.6 A Repeat in Macular Dystrophy Corneas: X-ray Diffraction Evidence”, Biophys. I., 70, 1966, 

(1 996). 

G.J. Salomons, M.A. Singh, J.A. Gupta, W.A. Foran, M.S. Capel, and J.R. Clarke, “Apparatus for SAXS 

Measurements of Polymer Deformation”, Rev. Sci. Instmm., 67/4, 1748, (1996). 

G.J. Salomons, M.A. Singh, L.G. Hiltz, L.H. Pan & W.R. Newson, “SAXS Study of Deformation Mechanisms in 

Liquid Rubber-Toughened Polystyrene”, NIM, B97, 282-286, (1 996). 

H.S. Subramanya, A.J. Doherty, S.R. Ashford, and D.B. Wigley, “Crystal-Structure of an ATP-Dependent DNALiagse from Bacteriophage T-7”, Cell, 85/4, 607-616, (1996). 

Y. Tselikas, N. Hadjichristidis, R.L. Lescanec, C.C. Honeker, M. Wohlgemuth, and E.L. Thomas, 

“Architecturally-Induced Tricontinous Cubic Morphology in Compositionally Symmetric Miktoarm Starblock 

Copolymers”, Macromolecules, 29, 3390-3396, (1996). 

D. Xia, C.A. Yu, J. Deisenhoffer, J.Z. Xia, and L. Yu, “3-Dimensional Structure of Beef Heart Mitochondrial 

Cytochrome BC(1) Complex”, Biophysical J., 7/2, TMU5, (1996). 

X. Xie, T. Kokubo, S.L. Cohen, U.A. Mirza, A. Hoffmann, B.T. Chait, R.G. Roeder, Y. Nakatani, and S.K. 

Burley, “Structural Similarity Between TAFS and the Heterotetrameric Core of the Histone Octamer”, Nature, 

380, 316-322, (1996). 

C.A. Yu, J.Z. Xia, A.M. Kachurian, L. Yu, D. Xia, H. Kim, and J, Deisenhofer, “Crystallization and Preliminary 

Structure of Beef Heart Mitochondrial Cytochrome BC( 1) Complex”, Biochim. et Biophys. Acta-Bioenerg., 12751 

12, 47-53, (1996). 

i c-20 

I ~ 
Beamline XI 2C 

N.O. Concha, B.A. Rasmussen, K. Bush, and 0. Herzberg, “Crystal Structure of the Wide-Spectrum Binuclear 

Zinc P-Lactamase from Bacteroides Fragilis”, Structure, 4, 823-836, (1996). 

J.Z. Ding, W.J. McGrath, R.M. Sweet, and W.F. Mangel, “Crystal Structure of the Human Adenovirus 

Proteinase with its 1 I-Amino-Acid Cofactor”, EMBO, 15, 1778-1783, (1996). 

J. Fajer, K.M. Barkigia, D. Melamed, R.M. Sweet, H. Kurreck, J. von Gersdorff, M. Plato, H.C. Rohland, G. 

Elger, and K. Mobius, ‘‘Molecular Structures of Porphyrin-Quinone Models for Electron Transfer”, J Phys. 

Cbem., 100, 14236-14239, (1996). 

C.H. Kang, R. Chan, I. Berger, C. Lokshin. L. Green, L. Gold, and A. Rich, “Crystal Structure of the T4 regA 

Translational Regulator Protein at 1.9 A Resolution”, Science, 268, 1170-1 173, (1995). 

Y. Kim, S. Eom, J. Wang, D. Lee, W. Suh, and T. Steitz, “Crystal Structure of Thermus Aquaticus DNA 

Polymerase”, Nature, 376, 612-616, (1995). 

T. Klabunde, N. Straeter, R. Froehlich, H. Witzel, and B. Krebs, “Mechansim of Fe(II1)-Zn(I1) Purple Acid 

Phosphatase Based on Crystal Structures”, J MOL. BioL., 259, 737-748, (1996). 

A. Matte, H. Goldie, R. Sweet, and L. Delbaere, “Crystal Structure of Escherichia coli Phosphoenolpyruvate 

Carboxykinase- A new Structural Family with the P-loop Nucleotide Triphosphate Hydrolase Fold, J Mol.. 

Biol., 256, 126-143, (1996). 

Beamline X13 

Z. Xu, I. McNulty, K.J. Randall, L. Yang, E. Gluskin, E.D. Johnson, and T. Oversluizen, “X13A: A Versatile Soft 

X-ray Undulator Beamline”, Rev. Sci. Instrum., 66, 1827, (1 995). 

Beamline X14A 

T. Gog, P.M. Len, G. Materlik, D. Bahr, C.S. Fadley, and C. Sanchez-Hake, “Multiple-Energy X-ray 

Holography: Atomic Images of Hematite (Fe103)”, Phys. Rev. Lett., 76/17, 3132-3135, (1996). 

T. Gog, R.H. Menk. F. Arfelli, P.M. Len, C.S. Fadley, and G. Materlik, “X-ray Holography with Atomic 

Resolution: Trying to Make it Work, Synch. Rad. News, 9/3,30-35, (1996). 

A. Goyal, E.D. Specht, D.M. Kroeger, and T.A. Mason, “Effect of Texture on Grain Boundary Misorientation 

Distributions in Polycrystalline High Temperature Superconductors”, Appl. Pbys. Letts., 68,711, (1 996). 

A. Goyal, E.D. Specht, D.M. Kroeger, J.E. Tkaczyk, C.L. Briant, and J.A. DeLuca, “Crystallization of Colonies 

of Locally Aligned Grains During Thallination of Spray-Pyrolyzed T1Ba2Ca2Cu30x Thick Films”, Appl. Phys. 

Letts., 67, 2563, (1995). 

G.E. Ice, G.S. Painter, L. Shaffer, C.J. Sparks, F.W. Averill and X. Jiang, “Nanoscale Structure in Crystalline 

Solid Solution Alloys”, Nanostl.uctu~edMaterials., 7, 147, (1996). 

c-2 1 
B.C. Larson, J.Z. Tischler, E.D. Isaacs, P. Zschack, A. Fleszar, and A.G. Eguiluz, “Inelastic X-ray Scattering as a 

Probe of the Many-Body Local-Field Factor in Metals, Pbys. Rev. Lett., 77/7, 1346, (1996). 

H. Roelofs, B. Schonfeld, G. Kostorz, W. Buhrer, J.L. Robertson, and P. Zschack, “Atomic and Magnetic ShortRange Order in Cu-17at. % Mn”, Scripta Mater., 34, 1393, (1996). 

E.D. Specht, and A. Goyal, “Microdiffraction Measurements of the Effects of Grain Alignment on Critical 

Current in High Temperature Superconductors”, X-Rav Microbeam Technolow and Applications, Edited by W. 

Yun, PIE, p. 170, (1995). 

J.Z. Tischler, B.C. Larson, L.A. Boatner, E.E. Alp, and T. Mooney, “Time-Sliced Mossbauer Absorption 

Spectroscopy using Synchrotron Radiation and a Resonant Bragg Monochromator”, 1. Appl. Pbys., 79, 3686, 

(1 996). 

Beamline X15A 

K.G. Huang, J. Zegenhagen, J.M. Phillips, and J.R. Patel, “Interface and Overlayer Structure of Epitaxial CaF2 

Thin Films on Si(111): An X-ray Scattering Study”, Physica, B221, 19, (1996). 

T.-L. Lee, Y. Qian, P.F. Lyman, J.C. Woicik, J.G. Pellegrino and M.J. Bedzyk, “The Use of X-ray Standing 

Waves and Evanescent-Wave Emission to Study Buried Strained-Layer Heterostructures”, Pbysica, B221, 437, 

(1 996). 

P.F. Lyman, Y. Qian, and M.J. Bedzyk, “Analysis of the Dimerized Sb/Si(001)-(2xl) Surface by X-Ray Standing 

Waves”, Mat. Res. SOC. Symp. Proc., 375, 121, (1995). 

P.F. Lyman, Y. Qian,T.-L. Lee, and M.J. Bedzyk, “Adsorbate Structure and Vibrations on the Bi/Si(OOl)-(lx2) 

Surface”, Pbysica, B221,426, (1996). 

Y. Qian, P.F. Lyman, and M.J. Bedzyk, “X-Ray Standing Wave Studies of Metal Ad-Dimers on Si(OOl)”, 

ScanningMicroscopy, 9, 969, (1995). 

Y. Qian, P.F. Lyman, T. Lee, and M.J. Bedzyk, “Thermal Vibration Amplitudes and Structure of Sb on Si(OOl)”, 

Pbysica, B22 1, 436, (1 996). 

Beamline X15B 

L. Niu, A.R. Karlicek, M. Geva, and P.H. Citrin, “Dopant Quantification by X-ray Absorption Spectroscopy: Zn 

in InP”, Mat. Res. Soc., Proc., 406, 509, (1996). 

Beamline X16A 

C.A.M. Carvalho, H. Hashizume, A.W. Stevenson, and I.K. Robinson, “Electron Density Maps for the Si(ll1) 

7-7 Surface Calculated with the Maximum-Entropy Technique using X-ray and Electron-Diffraction Data”, 

Proceedings of the 4th International Conference on Surface X-ray and Neutron Scattering, Pbysica, B221,469- 

486, (1996). 

H.L. Meyerheim, S. Pflanz, R. Schuster, and I.K. Robinson, “Surface X-ray Diffraction on the Potassium Induced 

Reconstruction of the Ag(O0 1) Surface”, Proceedings of the 4th International Conference on Surface X-ray and 

Neutron Scattering, Pbysica, B221, 140-143, (1996). 

c-22 
H.L. Meyerheim, S. Pflanz, R. Schuster, and I.K. Robinson, “X-ray Structure Analysis on the K-Induced 

Reconstruction of Ag(O0 l)”, Proceedinss of the 4th International Conference on Surface X-ray and Neutron 

Scattering, Pbysica, B221, 134-140, (1996). 

I.K. Robinson and P. J. Eng, “Comparison of Surface and Bulk Short-Range Order in Cufiu”, Pbys. Rev. B52, 

I.K. Robinson, W. Moritz, F. Jona, and M.A. van Hove, “In-Plane Lattice Reconstruction of Cu(lOO)”, Pbys. Rev. 

Letts., 76, 3659, (1996). 

9955-63, (1995). 

I.K. Robinson, K.L. Whiteaker, and D.A. Walko, “Cu Island Growth on Cu(1 lo)”, Proceedings of the 4th 

International Conference on Surface X-ray and Neutron Scattering, Pbysica, B22 1, 70-76, (1 996). 

R. Schuster, and I.K. Robinson, “Reconstruction-Induced Compression of the Cu( 1 10) Surface”, Pbys. Rev. Lett., 

76, 1671, (1996). 

K.L. Whiteaker, I.K. Robinson, C. Benson, D.M. Smilgies, N. Onda, and H. von Kaenel, “Disordered Structure 

of Cubic Iron Silicide Films on Si(lll)”, Pbys. Rev., B51, 9715-21, (1995). 

Beamline X16C 

L.H. Greene, A.C. Abeyta, I.V. Roshchin, I.K. Robinson, J.F. Dorsten, T.A. Tanzer, and P.W. Bohn, “Optical 

Detection of the Superconducting Proximity Effect”, PIE, 2696, 21 5-222, (1996). 

Beamline X17B1 

M. Kunz, K. Leinenweber, J.B. Parise, T.C. Wu, W.A. Bassett, K. Brister, D.J. Weidner, M.T. Vaughan, and Y 

Wang, “The Baddeleyite-Type High Pressure Phase of Ca(OH)2”, High Press. Res., 14, 3 1 1-3 19, (1 996). 

I. Martinez, J. Zhang, and R.J. Reeder, “In Situ X-ray Diffraction at High Pressure and High Temperature of 

Aragonite and Dolomite. Evidence for Dolomite Breakdown to Aragonite and Magnesite”, Amer. Min., 81, 61 1- 

624, (1996). 

Y. Wang, and D.J. Weidner, “(dm/dT)P of the Lower Mantle”, Pageopb Specialhsue, 146, 533-549, (1996). 

Y. Wang, D.J. Weidner, and F. Guyot, “Thermal Equation of State of CaSios Perovskite”,J Geopbys. Res., 101, 

661-672, (1996). 

J. Zhang, B. Li, W. Utsumi, and R.C. Liebermann, ‘‘In Situ X-ray Observations of the Coesite-Stishovite Phase 

Transition: Reversed Phase Boundary and Kinetics”, Pbys. Cbem. Miner., 23, 1-10, (1996). 

Beamline X17B2 

R.E. Johnston, D. Washburn, E. Pisano, W.C. Thomlinson, D. Chapman, N.F. Gmur, Z. Zhong, and D. Sayers, 

“Preliminary Experience with Monoenergetic Photon Mammography” PIE, 2432,434-441, (1 996), BNL 

62393. 

J.A. Laissuc, P. Spanne, F.A. Dilmanian, M.M. Nawrocky, J.-0. Gebbers, D.N. Slatkin, and D.D. Joel, 

“Mikrobestrahlung von Gliosarkomen der Ratte: Zell-und Gewebelasionen”, Schweiz. Mea! Wocbenscbr., 125, 

1887, (1995). 

C-23 
E. Rubenstein, J.C. Giaocomini, H.J. Gordon, J.A.L. Rubenstein and G. Brown, “Xenon K-Edge 

Dichromographic Bronchography: Synchrotron Radiation Based Medical Imaging NucL. Instrum. und Metb. in 

Phys. Res., A364, 360, (1995). 

W. Thomlinson, “Synchrotron Radiation Applications in Medical Research”, Proceedins of the International 

Conference on Industrial Amlications of Svnchrotron Radiation, pp. 98-126, (1996), BNL 62631. 

W. Thomlinson, “Transvenous Coronary Angiography in Humans with Synchrotron Radiation”, Proceedings of 

the International School of Phvsics “Enrico Fermi”. Course CXXVIII-Biomedical Adications of Synchrotron 

Radiation, edited by E. Burattini, and A. Balera, 10s Press, pp. 127-153, (1996), BNL 60834. 

Beamline X17C 

J. Akella , “The Diamond Anvil Cell: Probing the Behavior of Metals under Ultrahigh Pressures”, Science and 

Technolog Review of Lawrence Livermore National Laboratory, pp. 17-27, (1996). 

T. S. Duffy, J. Shu, H. K. Mao, and R. J. Hemley, “Single-Crystal X-ray Diffraction of Brucite to 14 GPa”, Phys. 

Cbem. Minerak 22,277-28 1, (1 995). 

T. S. Duffy, C.4. Zha, R. T. Downs, H. K. Mao, and R. J. Hemley, “Elastic Constants of Forsterite Mg2Si04 to 

16 GPa”, Nuture, 378, 170-173, (1995). 

H. Hua, J. Liu and Y. K. Vohra, “Pressure-Induced Amorphization in Gadolinium Scandium Gallium Garnet by 

X-ray Diffraction and Spectroscopic Studies”,J Phys., Condense. Mut., 8 , 139-145, (1996). 

K. J. Kingma, H. K. Mao, and R. J. Hemley, “Synchrotron X-ray Diffraction of Si02 to Multi-Megabar 

Pressures”, High Pressure Res., 14, 363-374, (1996). 

J. Liu and Y. K. Vohra , “Photoluminescence and X-ray Diffraction Studies on -Sm Doped Yttrium Aluminum 

Garnet to Ultrahigh Pressures of 338 GPa”,J Appl. Pbys., 79, 7978-7982, (1996). 

J. Liu and Y. K. Vohra , “Fluorescence Emission from High Purity Synthetic Diamond Anvil to 370 GPa”, AppL. 

Phys. Lett., 68,. 2049-2051, (1996). 

H. K. Mao and R. J. Hemley, “Energy Dispersive X-ray Diffraction of Micro-Crystals at Ultrahigh Pressures”, 

High Pressure Res., 14, 257-267, (1996). 

H. K. Mao and R. J. Hemley, “Experimental Studies of Earth Deep Interior: Accuracy and Versatility of 

Diamond Cells”, Phil. Truns. R. SOC. Lond., A354, 1-18, (1996). 

L. J. Parker, T. Atou, and J. B. Badding, “Transition Element-like Chemistry for Potassium under Pressure”, 

Science, 273, 95-97, (1996). 

S. M. Peiris, J. S. Sweeney, A. J. Campbell, and D. L. Heinz, “Pressure-Induced Amorphizations of Covellite, 

CuS”,]. Cbem. Pbys., 104, 11-16, (1996). 

S. K. Saxena, “Earth’s Core”, Current Science, 69, 914-917, (1995). 

S. K. Saxena, L. S. Dubrovinsky, P. Haggkvist, Y. Cerenius, G. Shen, and H. K. Mao, “Synchrotron X-ray Study 

of Iron at High Pressure and Temperature”, Science, 269, 1703-1704, (1995). 

C-24 
M. S. Somayazulu, L. W. Finger, R. J. Hemley, and H. K. Mao, “New High-pressure Compounds in MethaneHydrogen Mixtures”, Science, 271, 1400-1402, (1996). 

C. S. Yoo, J. Akella, A. J. Campbell, H. K. Mao, and R. J. Hemley, “Phase Diagram of Iron by in situ X-ray 

Diffracton: Implications for the Earth’s Core”, Science, 270, 1473-1475, (1995). 

Beamline X18A 

F.Y. Hansen, L. W. Bruch, and H. Taub, “The Mechanism of Melting in Submonolayer Films of Nitrogen 

Molecules Adsorbed on the Basal Planes of Graphite”, Pbys. Rev., B52, 8515-8527, (1995). 

K. W. Henvig, B. Matthies, and H. Taub, “Solvent Effects on the Monolayer Structure of Long n-Alkane 

Molecules Adsorbed on Graphite”, Pbys. Rev. Lett., 75, 3154-3157, (1995). 

K. Hongladarom, V. Ugaz, D. Cinader, W. R. Burghardt, J. P. Quintana, B. S. Hsiao, M. D. Dadmun, W. A. 

Hamilton and P. D. Butler, “Birefringence, X-ray Scattering and Neutron Scattering Measurements of Molecular 

Orientation in Sheared Liquid Crystalline Polymer Solutions”, Macromolecules, 29, 5346-5355, (1 996). 

S. Mansour, G. Liedl and R. Vest, “Microstructural Developments and Dielectric Properties of Rapid Thermally 

Processed PZT Thin Films Derived by Metallo-organic Decomposition”, J. Am. Ceram. Soc, 78/6, 16 17-23, 

(1995). 

S.M. Williams, S. Maglic, C. Thomas, C.T. Lin, M.J. Wagoner, R.P.H. Chang, and J.B. Ketterson, “Growth and 

in situ Characterization of YBa2Cu3Ox/LaAlO3 Superlattices”, Appl. Pbys. Lett., 68, 1485, (1 996). 

Yao, S. N. Ehrlich, G. Liedl and J. M. Honig, “Properties of NiS2_x Se x (x = 0.51, 0.55,0.63)”, Metal-insulator 

Transitions Revisited, Edited by P. P. Edwards and C. N. R. Rao, Taylor & Francis Ltd., pp. 129-142, (1995). 

Beamline X18B 

K.C.C. Kharas, D.-J. Liu, and H. J. Robota, “Structure-Function Properties in Cu-ZSM-5 NO Decomposition 

and NO SCR Catalysts”, Catalysis Today, 26/2, 129, (1995). 

D.-J. Liu, and H.J. Robota, “X-ray Absorption Spectroscopic Study of Cu in Cu-ZSM-5 During No Catalytic 

Decomposition”, Reduction of NitroEen Oxide Emissions, edited by U.S. Ozkan, S.K. Agarwal, and G. 

Marcelin, ACS Symposium Book Series, No. 587, 12, 147, (1995). 

Beamline X19A 

K. Chae, S. Jung, Y. Lee, C. Whang, Y. Jeon, M. Croft, D. Sills, P. Ansari, and K. Mack, “Local Density of 

Unoccupied States in Ion-Beam-Mixed Pd-Ag Alloys”, Pbys. Rev., B53, 10328, (1996). 

K. Chae, Y. Lee, S. Jung, Y. Jeon, M. Croft, and C.Whang, “Valence Band Electronic Redistribution in IonBeam-Mixed Pd-Ag Alloys”, Nucl. Instrum. andMetbs. In Pbys. Rev., BlO6, 60, (1995). 

E. Devlin, A. Kostikas, A. Simopoulos, A. Jankowski, M. Croft, and T. Tsakalakos, “Hyperfine Interactions and 

Magnetic Properties of Fe/Pt Multilayers”, J. Nano., Mat., 6, (1 995). 

G.P. Huffman, 2. Feng, D. Bailey, J. Rockwell, J. Zhao, and F.E. Huggins, “Liquefaction of Commingled Waste 

Plastics Containing PVC”, ACSDiv. Fuel Cbem., 41/3, 1043, (1996). 

C-25 
F.E. Huggins, F. Goodarzi, and C.J. Lafferty, “Mode of Occurrence of Arsenic in Subbituminous Coals”, Energy 

&Fuels, 10/4, 1001, (1996). 

F .E. Huggins, S. Srikantapura, B.K. Parekh, L. Blanchard, and J.D. Robertson, “XANES Spectroscopic 

Characterization of Selected Elements in Deep-Cleaned Fractions of Kentucky #9 Coal”, ACS Diu. Fuel Cbem., 

4113,764, (1996). 

F.E. Huggins, J. Zhao, G.P. Huffman, C.-H. Kao, and A.R. Tarrer, “Investigation of Zinc Additives in 

Coliquefaction of Waste Lubricating Oil and Bituminous Coal”, J Environ. Sci. Health, A31, 1755, (1996). 

S. Morante, L. Furenlid, G. Schiavo, R. Zwilling, and C. Montecucco, “Zinc Coordination in Tetanus 

Neurotoxin, Astacin, Thermolysink and Alkaline Protease Studied by X-ray Absorption Spectroscopy”, Eur. J 

Biocbem., 235, 606, (1996). 

M.J. Nelson, B.A. Brennan, D.B. Chase, R.A. Cowling, G.N. Grove, and R.C. Scarrow, “Structure and Kinetics 

of Formation of Catechol Complexes of Ferric Soybean Lipoxygenase- 1 ”, Biocbemisty, 34, 1 52 19, (1995). 

R.C. Scarrow, B.A. Brennan, J.G. Cummings, H. Jin, D.J. Duong, J.T. Kindt, and M.J. Nelson, “X-ray 

Spectroscopy of Nitrile Hydratase at pH 7 and 9”, Biocbemisty, 35, 10078, (1996). 

C.L. Senior, L.E. Bool, G.P. Huffman, and F.E. Huggins, “A Fundamental Investigation of Toxic Substances 

from Coal Combustion”, ACS Diu. Fuel Cbem., 41/3, 786, (1996). 

A. Sahiner, M. Croft, Z. Zhang, M. Greenblatt, I.Perez, P. A. Metcalf, H. Jahns, G. Liang, and Y. Jeon 

“Electronic Structure Anisotropy and d-Configuration in Ni-Based Materials”, Pbys. Rev., B53, 9745, (1 996). 

A.D. Shah, G.P. Huffman, F.E. Huggins, N. Shah, and J.J. Helble, “Behavior of Carboxyl-Bound Potassium 

during Combus ion of an ion-exchanged Lignite”, Fuel Proc. Tecbnol., 44, 105, (1995). 

N. Shah, J. Zhao, F.E. Huggins, and G.P. Huffman, “In Sitzl XAFS Spectroscopic Studies of Direct Coal 

Liquefaction Catalysts”, Energy &Fuels, 10/2,417, (1996). 

T. Yamamoto, M. Croft, R. Shull, and H. Hahn, “Phase Identification of a Superparamagnetic Iron-Oxide/Silver 

Nanocomposite”, J Nano. Mat., 6, 965, 1995). 

J. Yan, M. Greenblatt, A. Sahiner, D. Sills, and M. Croft, “Ruddlesden-Popper Zirconium Sulfides- a Novel 

Preparation Method and Characterization of Electronic structure”, J ofALLoys and Compounds, 229, 126, (1 995). 

J. Zhao, F.E. Huggins, 2. Feng, and G.P. Huffman, “Characterization of Impregnated Iron Catalysts on Coal”, 

Energy &Fuels, lO/l, 250, (1996). 

Beamline X19C 

H. Chung, M. Dudley, M.E. Brown, and M.D. Hollingsworth, “Synchrotron White Beam X-ray Topography 

Characterization of Defect Structures in 2,1O Undecanedione/Urea Inclusion Compounds”, Mol. Cyst Liq. Cyst., 

276, 203, (1996). 

H. Chung, B. Raghothamachar, M. Dudley, and D.J. Larson, Jr., “Synchrotron White Beam X-Ray Topography 

Characterization of Structural Defects in Microgravity and Ground Based CdZnTe Crystals”, Space Processing of 

Materials, SPIE ,2809,45, (1996). 

C-26 
H. Chung, B. Raghothamachar, W. Zhou, M. Dudley, and D.C. Gillies “Studies of Interface Demarcation and 

Structural Defects in Ga doped Ge Single Crystals by Synchrotron White Beam X-Ray Topography”, 

Applications of Synchrotron Radiation to Materials Science, edited by L. Terminello, S. Mini, D. L. Perry, and 

H. Ade, Mat. Res. SOC. Symp. Proc., 437, (1996). 

M. Dudley, ”Growth Defect Studies in Sic Single Crystals”, Mol. Cyst Liq. Cyst., 278, 37 , (1996). 

2. Huang, A. A. Acero, N. Lei, S. A. Rice, Z. Zhang, and M. L. Schlossman, “Structural Studies of SemiFluorinated Hydrocarbon Monolayers at the Air/Water Interface’: /. Cbem. SOC., Faraddy Trans., 92, 545 (1996). 

W. Huang, M. Dudley, and C. Fazi, “Characterization of Defect Structures in 3C-Sic Single Crystals”, IIINitride. Sic and Diamond Materials for Electronic Devices, edited by D.K. Gaskill, C. Brabdt and R. J. 

Nemanich, Mat. Res. SOC. Symp. Proc., 423, (1996). 

W. Huang, Q. Wang, M. Dudley, F.P. Chiang, J. Parsons, and C. Fazi, “Synchrotron White Beam Topography 

Studies of Residual Stress in Sic Single Crystals Wafers with Epitaxial Thin Films”, Evolution of Epitaxial 

Structure and Morpholoy , edited by A. Zangwill, D. Jesson, R. Clarke, and D. Chambliss, Mat. Res. SOC. Symp. 

Proc., 399,425, (1996). 

W. Huang, S. Wang, M. Dudley, P. Neudeck, J.A. Powell, and C. Fazi, “Characterization of Defect Structures in 

Lely 6H-SIC Single Crystals Using Synchrotron White Beam X-ray Topography”, Applications of Synchrotron 

Radiation Techniques to Materials Science, edited by L. Terminello, N. Shinn, G. Ice, K. D’Amico, and D. 

Perry, Mat. Res. Soc. Symp. Proc., 375, 313, (1995). 

X. Hu, I. Baker, and M. Dudley, “Dynamic In Situ Synchrotron X-ray Topographic Observations of Dislocations 

in Notched Ice Crystals”, Applications of Synchrotron Radiation to Materials Science, edited by L. Terminello, S. 

Mini, D. L. Perry, and H. Ade, Mat. Res. SOC. Symp. Proc., 437, (1996). 

X. Hu, I. Baker, and M. Dudley, “In Situ X-ray Topographic Observations of Notches in Ice”, Scriptu Met., 34, 

491, (1996). 

K. Jia, I. Baker, F. Liu, and M. Dudley, “Observation of Slip Transmission Through a Grain Boundary in Ice”,]. 

Mater. Sci., 31, 2373, (1996). 

N. Lei, Z. Huang and S.A. Rice, “Surface Segregation and Layering in the Liquid-Vapor Interface of a Dilute 

Bismuth:Gallium Alloy”, J Cbem. Pbys., 104, 4802, (1 996). 

F. Liu, I. Baker, and M. Dudley, “Dislocation/Grain Boundary Interactions in Ice Crystals”’, Phil. Mag., A71, 15, 

(1995). 

F. Liu, I. Baker, and M. Dudley, “Thermally Induced Dislocation Loops and Stacking Faults in Polycrystalline 

Ice”, Phil. Mag., A71, 1, (1995). 

W. Si, H. Chung, M. Dudley, V. Prasad, A. Anselmo, and D.F. Bliss, “Study of Defect Structures in MLEK 

Grown InP Single Crystals by Synchrotron White Beam X-ray Topography”, Proceedings of the Eighth 

International Conference on Indium Phosphide and Related Materials, Institute of Electrical and Electronics 

Engineers, p. 610, 1996). 

C-27 
W. Si, M. Dudley, C. H. Carter, Jr., R. Glass, and V. F. Tsvetkov, “Determination of Burgers Vectors of Screw 

Dislocations in 6H-SIC Single Crystals by Synchrotron White Beam X-ray Topography”, Applications of 

Synchrotron Radiation to Materials Science, edited by L. Terminello, S. Mini, D. L. Perry, and H. Ade, Mat. Res. 

Soc. Symp. Proc., 437, (1 996). 

W. Si, M. Dudley, P. Li and R. Wu, “Microstructure and Interfaces in TiB2/Ti-46Al-3Cr Alloy Composites”, 

Covalent Ceramics 111-Science and Techno1og;v of Non-Oxides, edited by A.F. Hepp, G.S. Fischmann, P.N. 

Kumpta, A.E. Kaloyeros, and J.J. Sullivan, Mat. Res. Soc. Symp. Proc., 410,405, (1996). 

W. Si, M. Dudley, P. Li and R. Wu, “Solid State Interfacial Reactions Between TIC Thin Films and Ti& 

Substrates” Thermodynamics and Kinetics of Phase Transformations, Mat. Res. Soc. Symp. Proc., 398, 275, 

(1996). 

W.M. Vetter and M. Dudley, “Characterization of Micropipes and other Defect Structures in 6H-SIC Through 

Fluorescence Microscopy”, Diaznostic Techniques for Semiconductor Materials Processing, edited by 0. 

Glembocki, S.W. Pang, F.H. Pollack, and F. Celii, Mat. Res. Soc. Symp. PTOC., 406, 561, (1996). 

G.M. Watson, B.D. Gaulin, D. Gibbs, G.H. Lander, T.R. Thurston, P.J. Simpson, H.J. Matzke, S. Wang, M. 

Dudley, and S. Shapiro, “On the Origin of the Second Length Scale Found Above TN in U02”, Phys. Rev., B53, 

686, (1996). 

J.M. Winter, Jr., and R.E. Green, Jr., “Real-Time Synchrotron Topography Using a CID Array Camera with 

Digital Image Acquisition and Processing”, Adv. in X-ray Analysis, 38, 21 5, (1995). 

Beamline X20 

J.R.A. Carlsson, “Properties and Crystallization of Amorphous Si-Based Binary Allov Thin Films”, Ph.D., 

Linkoping University, (1995). 

Q. Feng, “Study of the Three Dimensional Random Field Isine Model: Magnetic X-ray and Neutron Scattering, 

Magnetization and Heat Capacitv”, Ph.D., MIT, (1996). 

Q.J. Harris, “Synchrotron X-ray Scattering Studies of Novel Phase Transitions in Svstems with Coupled Order 

Parameters”, Ph.D., MIT, (1996). 

Q.J. Harris, Q. Feng, R.J. Birgeneau, K. Hirota, G. Shirane, M. Hase, and K. Uchinokura, “Large Length-Scale 

Fluctuations at the Spin-Peierls Transition in CuGeOs”, Phys. Rev., B52/21, 15420, (1995). 

J.L. Jordan-Sweet, P.M. Mooney, M.A. Lutz, R.M. Fennstra, J.O. Chu, and F.K. LeGoues, “Unique X-ray 

Diffraction Pattern at Grazing Incidence from Misfit Dislocations in SiGe Thin Films”,J AppL Phys., 80/1, 89, 

( 1 9 96). 

P.M. Mooney, J.L. Jordan-Sweet, G.B. Stephenson, F.K. LeGoues, and J.O. Chu, “High Resolution X-Ray 

Diffraction Measurements of Strain Relaxed SiGe/Si structures”, Advances in X-ray Analysis, 38, 18 1, (1995). 

P.M. Mooney, J.L. Jordan-Sweet, K. Ismail, J.O. Chu, R.M. Feenstra, and F.K. LeGoues, “Relaxed Sio.7Geo.3 

Buffer Layers for High Mobility Devices”, Appl. Pbys. Lett., 67/16, 2373, (1995). 

M. J. Ramstad, “Instabilities of Vicinal Silicon (1 11) Surfaces”, Ph.D., MIT, (1996). 

C-28 
R.F. Saraf, C. Dimitrakopoulos, M.F. Toney, and S.P. Kowalczyk, “Near Surface Structure of Solvent-Free 

Processed Polyimide Thin film”, Langmuir, 12, 2802, (1996). 

S. Song, “Faceting and Tricriticality in the Orientational Phase Diagram of Stepped Si(l13) Surfaces: 

Synchrotron X-ray Scattering Results”, Ph.D., MIT, (1996). 

V. Svilan, “Texture Analysis in Submicron Structures of Titanium Silicide”, M.S., MIT, (1996). 

G. M. Watson, D. Gibbs, S. Song, A. R. Sandy, S. G. J. Mochrie, and D. M. Zehner, “Faceting and 

Reconstructions of Stepped Au(l1 l)”, Pbys. Rev., B52, 12329, (1995). 

D. Weller, A. Carl, R.J. Savoy, T.C. Huang, M.F. Toney, and C. Chappert, “Structural Transitions and Magnetic 

Anisotropy in Ultrathin Co Wedges on Pt( I 1 1) Investigated with the Magneto-Optical Kerr Effect”, /. Pbys. 

Cbem. Solids, 56, 1563, (1995). 

Y. Xie, K.F. Ludwig, Jr., R. Bansil, P. Gallagher, X. Cao, and G. Morales, “Small-Angle X-ray Scattering Studies 

of Semidilute Polystyrene-Cyclohexane Solutions”, Pbysica, A232, 94, (1 996). 

M.J. Young, “Eauilibrium and Non-Eauilibrium Phenomena in Two- and Three-Dimensional Correlated 

Systems”, Ph.D., MIT, (1996). 

Beamline X2 1 

W.A. Caliebe, C.-C. Kao, L.E. Berman, J.B. Hastings, M.H. Krisch, F. Sette, and K. Hamdainen, “SpinResolved Resonant Raman Scattering”, /. Appl. Pbys., 79, 6509, (1996). 

M. Deutsch, 0. Gang, K. Hiimdainen, and C.-C. Kao, “The Onset and Near Threshold Evolution of the Cu 

K-a X-ray Satellites”, Pbys. Rev. Lett., 76, 2424, (1 996). 

E.D. Isaacs, “Inelastic X-ray Scattering and the Metal-Insulator Transition”, Fen-oelectrics, 176, 249, (1 996). 

E.D. Isaacs, and P.M. Platzman, “Inelastic X-ray Scattering”, Physics Today, 49/2,40, (1996). 

E.D. Isaacs, P.M. Platzman, P. Metcalf, and J.M. Honig, “Inelastic X-ray Scattering Study of the MetalAntiferromagnetic Insulator Transition in V203”, Pbys. Rev., Lett., 76,421 1, (1 996). 

A.T. Macrander, R.C. Blasdell, P.A. Montano, and C.-C. Kao, “Inelastic X-ray Scattering from 6H-SIC”, Wide 

Bandgap Semiconductors and Devices, edited by F. Ren, et al, ELectrocbemicaLSociety, 95/21, 98-102, (1995). 

Beamline X22A 

B.M. Ocko, O.M. Magnussen, J.X. Wang, R.R. Adzic, and T. Wandlowski, “The Structure and Phase Behavior 

of Electrodeposited Halides on Single-Crystal Metal Surfaces”, Pbysica, B221, 238-244, (1 996). 

B.M. Ocko, O.M. Magnussen, J.X. Wang, and T. Wandlowski, “One-Dimensional CommensurateIncommensurate Transition: Bromide on The Au( 100) Electrode”, Pbys. Rev., B53, R7654, (1996). 

M. Suenaga, V. Fukumoto, P. Haldar, T.R. Thurston, and U. Wildgruber, “Effects of Axial Tensile and Bending 

Strains on Critical Currents of Mono- and Multicored (Bi,Pb)2Sr2Ca2Cu2) io-Ag Tapes”, AppL Pbys. Lett., 67, 

3025, (1995). 

C-29 
T.R. Thurston, U. Wildgruber, N. Jisrawi, P. Haldar, M. Suenaga, and Y.L. Wang, “Synchrotron X-ray 

Scattering Measurements of Bulk Structural Properties in Superconducting (B~,P~)~SI-~C~~CU~O~O-A~ Tapes”, /. 

Appl. Pbys., 79, 3122, (1996). 

T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. Yang, J. McBreen, M.L. Daroux, and X.K. Xing, “Synchrotron 

X-ray Diffraction Studies of the Structural Properties of Electrode Materials in Operating Battery Cells”, Appl. 

Phys. Lett., 69, 194, (1996). 

T.H. Wandlowski, J.X. Wang, O.M. Magnussen, and B.M. Ocko, “Structural and Kinetic Aspects of Bromide 

Adsorption onAu(100)”,]. Pbys. Chem. ,100, 10277, (1996). 

Beamline X22B 

R.R. Adzic, and J.X. Wang, “Atomic Structure of Active Sites in 02 Reduction on Au( 11 l)/Tlad Electrodes in 

Acid and Alkaline Solutions”, Proceedings of the Symposium on Oxygen Electrochemistry, Edited by R.R. Adzic, 

F.C. Anson and K. Kinoshita, ELectrocbenzicaLSociety, 95/26, 61, (1995). 

V. Kiryukhin, B. Keimer, J.P.Hi11, and A. Vigliante, “Soliton Lattice in Pure and Diluted CuGeOs”, Pbys. Rev. 

Lett., 76,4608, (1996). 

O.M. Magnussen, M.J. Regan, E.H. Kawamoto, B.M. Ocko, P.S. Pershan, N. Maskil, M. Deustch, S. Lee, K. 

Penanen, and L.E. Berman, “X-ray Reflectivity Studies of The Surface Structure of Liquid Metals”, Pbysicu, 

B221, 257, (1996). 

X.Z. Wu, B.M. Ocko, M. Deutsch, E.B. Sirota, and S.K. Sinha, “Surface Freezing and Surface-Phase Behaviors in 

Binary Mixtures of Alkanes”, Pbysica, B221, 261, (1996). 

Beamline X22C 

C. Detlefs, A.I. Goldman, J.P. Hill, D. Gibbs, C. Stassis, P.C. Canfield, and B.K. Cho, “The Magnetic Structure 

of GdzNiBzC by Resonant and Non-resonant X-ray Scattering”, Pbys. Rev., B53, 6335, (1996). 

P.M. Gehring, A. Vigliante, D.F. McMorrow, D. Gibbs, C.F. Majkrzak, G. Helgesen, R.A. Cowley, R.C.C. 

Ward, and M.R. Wells, “Observation of Two Length Scales Above T, in a Holmium Thin Film”, Pbysica, B221, 

398, (1996). 

J.P. Hill, C. Detlefs, B.J. Sternlieb, A.I. Goldman, D. Gibbs, C. Stassis, P.C. Canfield, and B.K. Cho, 

“Incommensurate Antiferromagnetism in the Intermetallic Superconductor HoNi2B2CY’, Pbys. Rev., B53, 3487, 

( 1 996). 

J.P. Hill, and D.F. McMorrow, “X-ray Resonant Exchange Scattering: Polarization Dependence and Correlation 

Functions”, Acta Cyst., A52, 236, (1 996). 

W.J. Nuttall, S. Langridge, W. G. Stirling, G. H. Lander, B. Lebech and 0. Vogt, “X-ray Scattering Study of the 

Two Magnetic Correlation Lengths in Uranium Antimonide”, Pbys. Rev., B52, 4409, (1 996). 

B.J. Sternlieb, J.P. Hill, U.C. Wildgruber, G.M. Luke, B. Nachumi, Y. Moritomo, and Y. Tokura, “Charge and 

Magnetic Order in Lao.5Srl.5MnOq”, Pbys. Rev. Lett., 76, 2169, (1996). 

D. Watson, E.M. Forgan, W.J. Nuttall, W.G. Stirling and D. Fort, “High Resolution Magnetic X-ray Diffraction 

From Neodymium”, Phys. Rev., B53,726, (1996). 

C-30 
G.M. Watson, B.D. Gaulin, D. Gibbs, G.H. Lander, T.R. Thurston, P.J. Simpson, H.J. Matzke, S. Wang, M. 

Dudley, and S.M. Shapiro, “On the Origin of the Second Length Scale Found Above T, In U02”, Pbys. Rev., 

B53, 686, (1996). 

G.M. Watson, D. Gibbs, G.H. Lander, H.J. Matzke, B.D. Gaulin, L.E. Berman, and W. Ellis, 

“Grazing-Incidence X-ray Magnetic Scattering Studies of U02(001) Surfaces”, Pbysica, B221, 405, (1 996). 

G.M. Watson, D. Gibbs, G.H. Lander, B.D. Gaulin, F.E. Berman, H.J. Matzke, and W. Ellis, “An X-ray 

Scattering Study of the Magnetic Structure Near the (00 1) Surface of UOz”, Pbys. Rev. Lett., 77,75 1, (1 996). 

Beamline X23A2 

K.A. Carrado, and S.R. Wasserman, “Stability of Cu(I1)- and Fe(II1)-Porphyrins on Montmorillonite Clay: An Xray Absorption Study”, Cbem. Mater., 8,219, (1996). 

V. Chakarian, Y.U. Idzerda, K.M. Kemner, J.-H. Parks, G. Meigs, and C.T. Chen, “Giant Magnetic Effects in 

the L-edge EXAFS of 3d Transition Metals”,J. Appl. Pbys., 79, 6493, (1996). 

G.M. Chow, L.K. Kurihara, K.M. Kemner, P. Schoen, A.M. Ervin, S. Keller, Y.D. Zhang, N. Shen, J. Budnick, 

and T. Ambrose, “Structural, Morphological, and Magnetic Study of Nanocrystalline Co-Cu Powders 

Synthesized by the Polyol Process”, J. Mat. Res., 10, 1546, (1 995). 

D. Fauteux, A. Massucco, M. vanBuren, B. Ouyang, S.G. Greenbaum, S. Kostov, and M.L. denBoer, “A 

Comparitive Study of LiMn2Oq from Various Sources”, Mat. Res. SOC. Symp. Proc., 369, 29, (1995). 

C.L. Foiles, M.R. Franklin, and R. Loloee, “Structure and Magetism in Mo/Co Multilayers”, Magnetic Ultrathin 

Film, Multilayers and Surfaces”, edited by A. Fert, G. Guntherodt, B. Heinrich, W.F. Eglehoff, JR., E.E. 

Marinero, and R.L. White, Mat. Res. SOC. Symp.Proc., 384, 97, (1995). 

K.M. Kemner, W.T. Elam, V.G. Harris, Y.U. Idzerda, and J.A. Wolf, “Distinguishing the hcp and fcc Phases of 

the Metalizastion of Diamond by Polarization-Dependent EXAFS”, J. Vac. Sci. Tecbnol., B14, 3207, (1996). 

K.M. Kemner, W.T. Elam, D.B. Hunter, and P.M. Bertsch, “EXAFS Studies of the Local Environment of Cs in 

CsBr-dibenzo-l8-crown-6 Ether Solutions and Powders”,J. Pbys. Cbem., 100, 11698, (1996). 

K.M. Kemner, W.T. Elam, Y.U. Idzerda, J.A. Wolf, and G.A. Prinz, “Polarization-Dependent Extended X-ray 

Absorption Fine Structure Measurements of Metastable Fcc Co on (100) Diamond”, Appl. Pbys. Letts., 68, 3389- 

3391, (1996). 

K.M. Kemner, V.G. Harris, V. Chakarian, Y.U. Idzerda, W.T. Elam, C.-C. Kao, Y.C. Feng, J.C. Lodder, and 

J.C. Woicik, “The Role of Ta and Pt in Segregation within Co-Cr-Ta and Co-Cr-Pt Thin Film Magnetic 

Recording Media”, J. Appl. Pbys., 79, 5345, (1996). 

K.M. Kemner, V.G. Harris, W.T. Elam, Y.C. Feng, D.E. Laughlin, and J.C. Woicik, “Polarization-Dependent 

XAFS Studies on the Role of Ta in the Compositional Segregation of Co-Cr-Ta Magnetic Recording Media”, 

IEEE Trans. on Mag., 31, 2806, (1995). 

K.M. Kemner, V.G. Harris, W.T. Elam, and J.C. Lodder, “EXAFS Studies and Simulations of Local Anisotropy 

in Co78Cr22 Films”, Mat. Res. SOC. Symp. Proc., 375, 21, (1995). 

c-3 1 
J.P. Kirkland, and W.T. Elam, “An UHV-Compatible Fixed-Exit Two-Crystal Monochromator”, Rev. Sci. 

Instrum., 66/2,2135-2137, (1995). 

J.P. KirWand, and W.T. Elam, “The Naval Research Laboratory’s new Hard X-ray Beamline at the National 

Synchrotron Light Source”, Rev. Sci. Instrum., 66/2, 1709-171 I, (1995). 

J.P. Kirkland, V.E. Kovantsev, C.M. Dozier, J.V. Gilfrich, W.M. Gibson, Q.-F. Xiao, and K Umezawa, 

“Wavelength-Dispersive X-ray Fluorescence Detector”, Rev. Sci. Instrum., 66/2, 1410-1412, (1995). 

J. McBreen, X.Q. Yang, H.S. Lee, and Y. Okamoto, “EXAFS Studies of Mixed Salt CoBrz/LiBr-PEO 

Complexes”, Electrochimica Acta, 40, 21 15, (1995). 

S. Mukerjee, and J. McBreen, “Hydrogen Electrocatalysis by Carbon Supported Pt and Pt Alloys”, J. Electrochem. 

Soc., 143,2285, (1996). 

B. Ouyang, X. Cao, H.W. Lin, S. Slane, S. Kostov, M.L. denBoer, and S.G. Greenbaum, “Lithium-7 NMR 

Studies of Lil-&002 Battery Cathodes”, Mat. Res. Sol. Symp. Proc., 369, 59, (1996). 

L. Soderholm, U. Staub, S. Skanthakumar, and M.R. Antonio, “The Oxidation State and Magnetic Behaviour of 

Tb in High-T, Related Materials”, Mat. Res. Soc.Proc., 376, 529, (1995). 

U. Staub, L. Soderholm, S. Skanthakumar, and M.R. Antonio, “Oxidation State and Magnetic Properties of 

Pb2Sr2Tbl-,Y,Cu308”, Phys. Rev., B52, 9736, (1995). 

S.R. Wasserman, R.E. Winans, and R. McBeth, “Iron Species in Argonne Premium Coal Samples: An 

Investigation using X-ray Absorption Spectroscopy”, Energy Fuels, 10, 392, (1 996). 

Beamline X23A3 

A.J. Allen, S. Krueger, G.G. Long, H.M. Kerch, H. Hahn, and G. Skandan, “Small-Angle Neutron Scattering 

Studies of Ceramic Nanophase Materials”, NanostructuredMateriaLs, 7, 113-126, (1996). 

A.J. Allen, S. Krueger, G. Skandan, G.G. Long, H. Hahn, H.M. Kerch, J.C. Parker, and M.N. Ali, 

“Microstructural Evolution During the Sintering of Nanostructured Ceramic Oxides”, /. Am. Ceram. SOC., 79, 

1201-12 12, (1996). 

A.J. Allen, G.G. Long, H.M. Kerch, S. Krueger, G. Skandon, H. Hahn, and J.C. Parker, “Sintering Studies of 

Nanophase Ceramic Oxides”, Ceramic International, 22, 275-280, (1996). 

G. Fogarty and M. Cronin-Golomb, “The Strain Problem in Photorefractive Crystals”, Optics Letters, 20, 2276- 

2278, (1995). 

G. Fogarty and M. Cronin-Golomb, “Surface Strain Effects on Photorefractive Gratings”, CLEO 95, OSA 1995 

Technical Digest Series, p. 261, (1995). 

G. Fogarty, B. Steiner, M. Cronin-Golomb, R. Uhrin, and J. Martin, “High-Resolution X-ray Diffraction 

Imaging of Anti-Parallel Ferroelectric Domains in Barium Titanate and Strontium Barium Niobate”, Technical 

Digest of Photorefractive Materials, Effects. and Devices, pp. 9-12, (1995). 

C-32 
S. Krueger, A.J. Allen, G. Skandon, G.G. Long, H. Hahn, and H.M. Kerch, “Small-Angle Scattering Methods for 

Studying the Sintering of Nanophase Ceramic Compacts”, Neutron Scatterinn in Materials Science, edited by 

D.A. Neumann, T.P. Russell, and B. Wuensch, MRSSymp. Proc., 376, 359-364, (1995). 

Beamline X23B 

G.M. Chow, L.K. Kurihara, K.M. Kemner, P. Schoen, A.M. Ervin, S. Keller, Y.D. Zhang, N. Shen, J. Budnick, 

and T. Ambrose, “Structural, Morphological, and Magnetic Study of Nanocrystalline Co-Cu Powders 

Synthesized by the Polyol Process”, J Mater. Res., 10, 1546, (1 995). 

K.M. Kemner, W.T. Elam, D.B. Hunter, and P.M. Bertsch, “EXAFS Studies of the Local Environment of Cs in 

CsBr-dibenzo-l8-crown-6 Ether Solutions and Powders”, J. Pbys. Chem., 100, 11698, (1996). 

K.M. Kemner, W.T. Elam, Y.U. Idzerda, J.A. Wolf, and G.A. Prinz, “Polarization-Dependent Extended X-ray 

Absorption Fine Structure Measurements of Metastable fcc Co on (100) Diamond, Appl. Pbys. Letts., 68, 3389, 

(1996). 

K. M. Kemner, V. G. Harris, V. Chakarian, Y. U. Idzerda, W. T. Elam, C. -C. Kao, Y. C. Feng, J.C. Lodder, 

and J. C. Woicik, “The Role of Ta and Pt in Segregation Within Co-Cr-Ta and Co-Cr-Pt Thin Film Magnetic 

Recording Media”, J Appl. Pbys., 79, 5345, (1996). 

K. M. Kemner, V. G. Harris, W. T. Elam, Y. C. Feng, D. E. Laughlin, and J. C. Woicik, “PolarizationDependent XAFS Studies on the Role of Ta in the Compositional Segregation Within Co-Cr-Ta Magnetic 

Recording Media”, IEEE Trans. Magn. 31, 2806, (1995). 

K.M. Kemner, V.G. Harris, W.T. Elam, and J.C. Lodder, “EXAFS Studies and Simulations of Local Anisotropy 

in C078Cr22 Films”, Mat. Res. Soc. Symp. Proc., 375, 21, (1995). 

J.P. Kirkland, and W.T. Elam, “An UHV-Compatible Fixed-Exit Two-Crystal Monochromator”, Rev. Sei. 

Instrum., 6612, 2135, (1995). 

J.P. Kirkland, and W.T. Elam, “The Naval Research Laboratory’s new Hard X-ray Beamline at the National 

Synchrotron Light Source”, Rev. Sci. Instrum., 6612, 1709, (1995). 

J.P. Kirkland, V.E. Kovantsev, C.M. Dozier, J.V. Gilfrich, W.M. Gibson, Q.-F. Xiao, and K. Umezawa, 

“Wavelength-Dispersive X-ray Fluorescence Detector”, Rev. Sei Instrum., 6612, 1410, (1995). 

Beamline X24A 

S.M. Butorin, D.C. Mancini, J.-H. Guo, N. Wassdahl, J. Nordgren, M. Nakazawa, S. Tanaka, T. Uozumi, A. 

Kotani, Y. Ma, K.E. Miyano, B.A. Karlin, and D.K. Shuh, “Resonant X-ray Fluorescence Spectroscopy of 

Correlated Systems: A Probe of Charge-Transfer Excitations”, Phys. Rev. Lett., 77, 574, (1996). 

B. Krassig, M. Jung, D.S. Gemmell, E.P. Kanter, T. LeBrun, S.H. Southworth, and L. Young, “Nondipolar 

Asymmetries of Photoelectron Angular Distributions”, Pbys. Rev. Lett., 75, 4736, (1995). 

T. LeBrun, S.H. Southworth, M.A. MacDonald, and Y. Azuma, “A Comparison of Radiative and Non-Radiative 

Resonant Raman Studies of the Inner Shell Electronic Structure of Atoms”, Atomic and Molecular 

Photoionization, Universal Academy Press, p. 303, (1 996). 

c-33 
P.S. Shaw, U. Arp, and S.H. Southworth, “Measuring Nondipolar Asymmetries of Photoelectron Angular 

Distributions”, Phys. Rev., A54, 1463, (1996). 

J.C. Woicik, T. Kendelewicz, S.A. Yoshikawa, K.E. Miyano, G.S. Herman, P.L. Cowan, P. Pianetta, and W.E. 

Spicer, “Surface Sensitive X-ray Standing Wave Study of Si(l11) 43x43 -Ag” Phys. Rev., B53, 15425, (1996). 

J.C. Woicik, K.E. Miyano, J.G. Pellegrino, P.S. Shaw, S.H. Southworth, and B.A. Karlin, “Strain and Relaxation 

in InAs and InGaAs Films Grown on GaAs(001)”, Appl. Phys. Lett., 68, 3010, (1996). 

Beamline X24C 

T.-J. Chen, R.N. Zitter, R. Tao, W.R. Hunter, and J.C. Rife, “Optical Constants of Lithium Triborare Crystals 

in the 55-71 eV Region,” Phys. Rev., B52, 13703 (1995). 

M.P. Kowalski, T.W. Barbee, R.G. Cruddace, Jr., J.F. Seely, J.C. Rife, and W.R. Hunter, “Efficiency and LongTerm Stability of a Multilayer-Coated, Ion-Etched Blazed Holographic Grating in the 125-133 A Wavelength 

Region”, Appl. Opt., 34, 7338, (1995). 

M.P. Kowalski, R.G. Cruddace, Jr., J.F. Seely, J.C. Rife, W.R. Hunter, and T.W. Barbee, Jr., “The EW 

Performance of an Ion-Etched Blazed Diffraction Grating”, ]. Electron. Spectro. Related Pbenom., 80, 473, (1 996). 

J.P. Long, B.S. Itchkawitz, and M.N. Kabler, “Photoelectron Spectroscopy of Laser-Excited Surfaces by 

Synchrotron Radiation”,]. Opt. SOC. Am., B13, 201, (1996). 

J.P. Long, V.M. Bermudez, and D.E. Ramaker, “Structural Determination of p SiC(lOO)-c(2x2) from C Is 

Surface Core Exciton and Si 2p Absorption”, Phys. Rev. Lett., 76, 991, (1996). 

P.E. Pehrsson, J.P. Long, J.E. Butler, and M. Marchywka, “Electrochemically-Induced Surface Chemistry and 

Negative Electron Affinity on Diamond (loo)”, Appl. Phys. Lett., 67, 3414, (1995). 

J.F. Seely, R.G. Cruddace, M.P. Kowalski, W.R. Hunter, T.W. Barbee, J.C. Rife, R. Eby, and K.G. Stolt, 

“Polarization and Efficiency of a Concave Multilayer Grating in the 135-250 A Region and in Normal-Incidence 

and Seya-Namioka Mounts”, Appl. Optics 34,7347 (1 995). 

J.F. Seely, W.R. Hunter, and M.P. Kowalski, “Transmittance of a Thin Saran Film in the 45-584 A Wavelength 

Region”, Appl. Opt., 34,7945, (1995). 

J.F. Seely, M.P. Kowalski, R.G. Cruddace, J.C. kfe, T.W. Barbee, Jr., and W.R. Hunter, “High Resolution 

Spectroscopy Using Normal-Incidence Multilayer Gratings”, W and X-ray Spectroscopy of Astrophysical and 

Laboratory Plasmas, edited by K. Yamashita and T. Watanabe, UniversalAcademy Press, p. 225, (1996). 

J.F. Seely, M.P. Kowalski, R.G. Cruddace, J.C. Rife, T.W. Barbee, Jr., W.R. Hunter, and G.E. Holland, “HighEfficiency Holographic Ion-Etched Gratings with Multilayer Coatings and Operating On-Blaze at Normal 

Incidence in the 130-300 A Range”, Multilayer and Grazing Incidence X-Ray-EW Optics 111, PIE, 2805, 

( 1 996). 

J.F. Seely, M.P. Kowalski, W.R. Hunter, T.W. Barbee, Jr., R.G. Cruddace, and J.C. Rife, “Normal-Incidence 

Efficiencies in the 1 15-340 A Wavelength Region of Replicas of the Skylab 3600 1 /mm Grating With Multilayer 

and Gold Coatings”, Appl. Opt., 34, 6453, (1995). 

c-34 
Beamline X25 

W.A. Caliebe, C.C. Kao, L.E. Berman, J.B. Hastings, M.H. Krisch, F. Sette, and K. Hamdainen, “Spin Resolved 

Resonant Raman Scattering”,J Appl. Pbys., 79, 6509-651 1, (1996). 

M. Deutsch, 0. Gang, K. Hamalainen, and C.-C. Kao, “Onset and Near Threshold Evolution of the Cu KCX XRay Satellites”, Pbys. Rev. Lett., 76, 2424-2427, (1 996). (key publication). 

E. Dufresne, R. Bruning, M. Sutton, B. Rodricks, and G.B. Stephenson, “A Statistical Technique for 

Characterizing X-Ray Position-Sensitive Detectors”, Nucl. Instrum. Metbods Pbys. Res., A364, 380-393, (1995). 

B.A. Everitt, M.B. Salamon, B.J. Park, C.P. Flynn, T. Thurston, and D. Gibbs, “X-Ray Magnetic Scattering from 

Nonmagnetic Lu in a Dy/Lu Alloy”, Pbys. Rev. Lett., 75, 3182-3185, (1995). 

J. Goldberg, A. Nairn, and J. Kuriyan, “Structural Basis for the Regulation of Calmodulin-Dependent Protein 

Kinase I”, Cell, 84, 875-887, (1996). 

G. Helgesen, J.P. Hill, T.R. Thurston? and D. Gibbs, “An X-Ray Scattering Study of Higher Harmonic Satellites 

Near the Antiferromagnetic Phase Transitions in Rare Earth Metals”, Pbys. Rev., B52, 9446-9454, (1995). 

D. Heskett, P. Xu, L. Berman, C.C. Kao, and M.J. Bedzyk, “The Geometric Structure of Rb/Cu(l 11) 

Investigated with X-Ray Standing Waves: Rb Coverage Dependence”, Surf Sei., 344,267-275, (1 995). 

D.G. Lambright, J. Sondek, A. Bohm, N.P. Skiba, H.E. Hamm, and P.B. Sigler, “The 2.0 A Crystal Structure of 

a Heterotrimeric G Protein”, Nature, 379, 31 1-319, (1996). 

J.C. Levin, G.B. Armen, and I.A. Sellin, “Photoionization and Compton Double Ionization of Helium from 

Threshold to 20 keV, Pbys. Rev. Lett., 76, 1220-1223 (1996). (key publication) 

O.M. Magnussen, M.J. Regan, E.H. Kawamoto, B.M. Ocko, P.S. Pershan, N. Maskil, M. Deutsch, S. Lee, K. 

Penanen, and L.E. Berman, “X-Ray Reflectivity Studies of the Surface Structure of Liquid Metals”, Pbysica, B221, 

257-260, (1996). 

J. Sondek, A. Bohm, D.G. Lambright, H.E. Hamm, and P.B. Sigler, “Crystal Structure of a G-Protein p-y 

Dimer at 2.1 A Resolution”, Nature, 379, 369-374, (1 996). 

L. Tong, C. Qian, M.-J. Massariol, P.R. Bonneau, M.G. Cordingley, and L. Lagace, “A New Serine-Protease Fold 

Revealed by the Crystal Structure of Human Cytomegalovirus Protease”, Nature, 383, 272-275, (1996). (Key 

publication) 

M.A. Wall, D.E. Coleman, E. Lee, J.A. Iniguezlluhi, B.A. Posner, A.G. Gilman, and S.R. Sprang, “The Structure 

of the G Protein Heterotrimer G(I-a-l)P(l)y(2)”, Cell, 83, 1047-1058, (1995). 

G.M. Watson, D. Gibbs, G.H. Lander, B.D. Gaulin, L.E. Berman, H.J. Matzke, and W. Ellis, “X-Ray Scattering 

Study of the Magnetic Structure Near the (001) Surface of UOz ”, Pbys. Rev. Lett., 77, 751-754, (1996). (Key 

publication) 

G.M. Watson, D. Gibbs, G.H. Lander, H.J. Matzke, B.D. Gaulin, L.E. Berman, and W. Ellis, “GrazingIncidence X-ray Magnetic Scattering Studies of U02(00 1) Surfaces”, Pbysica, B221, 405-407, (1996). 

c-35 
Beamline X26A 

J.S. Delaney, S. Bajt, M.D. Dyar, S.R. Sutton, G. McKay, and P. Roeder, “Comparsion of Quantitative 

Synchrotron Micro XANES Felll/(Fell+Felll) Results for Amphibole and Silicate Glass with Independent 

Measurements”, Lunar Planet Sci., XXVII, 299, (1996). 

J.S. Delaney, S. Bajt, S.R. Sutton, and M.D. Dyar, “In Situ Microanalysis of Fe3+/CFe Ratios in Amphibole by Xray Absorption Near Edge Structure (XANES) Spectroscopy”, Mineral Spectroscopy, 5, 165, (1996). 

J. Flynn, S. Bajt, and S.R. Sutton, “Evidence of Weakly Bound Bromine in Large Interplanetary Dust Particles 

from the Stratosphere”, Lunar Planet. Sci., XXVII, 367, (1996). 

J. Flynn, F. Horz, S. Bajt, and S.R. Sutton, ‘‘In Situ Chemical Analysis of Extraterrestrial Material Captured in 

Aerogel”, Lunar Planet. Sci., XXVII, 369, (1996). 

D.I. Kaplan, M.E. Sumner, P.M. Bertsch, and D.C. Adriano, “Chemical Conditions Conducive to the Release of 

Mobile Colloids from Ultisol Profiles”, SoilSci. SOC. Am. J., 60, 269, (1996). 

R.J. Reeder, “Interaction of Divalent Cobalt, Zinc, Cadmium, and Barium with the Calcite Surface During Layer 

Growth, Geocbimica et Cosmocbimica Acta, 60, 1543, (1996). 

R. Rizzo, M. Grandolfo, C. Godeas, K.W. Jones, F. Vittur, “Calcium, Sulphur, and Zinc Distribution in Normal 

and Arthritic Articular Equine Cartilage: a Synchrtoron Radiation Induced X-ray Emission (SRIXE) Study”, J 

ExptL. Zoology, 273, 82, (1995). 

D. Schulze, T. McCay-Buis, S.R. Sutton, and D.M. Huber, “Manganese Oxidation States in Gauemannomyces 

Infested Wheat Rizospheres Probed by Micro XANES Spectroscopy”, Pbytopatbology, 85, 990, (1995). 

D. Schulze, S.R. Sutton, and S. Bajt, “Determination of Manganese Oxidation State in Soils Using X-ray 

Absorption Near-Edge Structure (XANES) Spectroscopy”, Soil Sci. SOC. ofAmer. J, 59, 1540, (1995). 

R. Sutton, S. Bajt, and R. Jones, “In Situ Determination of Chromium Oxidation State in Olivine from 

Chondrules”, Lunar Planet, Sci., XXVII, 1291, (1996). 

Beamline X26C 

J.M. Bolduc, D.H. Dyer, W.G. Scott, R.M. Sweet, D.E. Koshland, and B.L. Stoddard, “Mutagenesis and Laue 

Structures of Enzyme Intermediates - Isocitrate Dehydrogenase”, Science, 268, 13 12, (1995). 

P.J. Eng, M.L. Rivers, B.X. Yang, and W. Schildkamp, “Microfocusing 4-keV to 65-keV X-rays with Bent 

Kirkpatrick-Baez Mirrors”, SPIE, 2516,41, (1995). 

K. Moffat, “Macromolecular Crystallography on the Millisecond to Nanosecond Time Domain”, Time Resolved 

Electron and X-ray Diffraction, edited by P.M. Rentzepis, SPIE, 2521, 182, (1995). 

K. Moffat, and R. Henderson, “Freeze Trapping of Reaction Intermediates”, Curr. Opin. Struct. Biol., 5, 656, 

(1995). 

K. E. Ng, G. Getzoff, and K. Moffat, “Optical Studies of a Bacterial Photoreceptor Protein, Photoactive Yellow 

Protein, in Single Crystals”, Biocbemistly, 34, 879, (1995). 

I C-36 
Z. Ren and K. Moffat, “Deconvolution of Energy Overlaps in Laue Diffraction”,/. Appl. Cyst., 28, 482, (1995). 

2. Ren and K. Moffat, “Quantitative Analysis of Synchrotron Laue Diffraction Patterns in Macromolecular 

Crystallography”,]. AppL. Cyst., 28, 461, (1995). 

2. Ren, K. Ng, G.E.O. Borgstahl, E.D. Getzoff, and K. Moffat, “Quantitative Analysis of Time-Resolved Laue 

Diffraction Patterns”, ]. Appl. Cyst., 29, 246, (1 996). 

B.L. Stoddard, A. Dean, and P.A. Bash, “Combining Laue Diffraction and Molecular Dynamics to Study Enzyme 

Intermediates”, Nature Struct. BioLogy, 3, 590, (1996). 

X. Yang, and K. Moffat, “Insights into Specificity of Cleavage and Mechanism of Cell Entry from the Crystal 

Structure of the Highly Specific Asfergillus Ribotoxin, Restrictocin”, structure, 4, 837, (1996). 

Beamline X27A 

M. Suenaga, Y. Fukumoto, P. Haldar, T.R. Thurston, and U. Wildgruber, “Effects of Axial Tensile and Bending 

Strains on Critical Currents Mono-and Multicored (Bi,Pb)2SrzCa2Cu3010-Ag Tapes”, Appl. Pbys. Letts., 67, 

3025, (1995). 

T.R. Thurston, N.M. Jisrawi, S. Mukerjee, X.Q. Yang, J. McBreen, M.L. Daroux, and X.K. Xing, “Synchrotron 

X-ray Diffraction Studies of the Structural Properties of Electrode Materials in Operating Battery Cells”, AppL 

Pbys. Letts., 69, 194, (1996). 

T.R. Thurston, U. Wildgruber, N. Jisrawi, P. Haldar, M. Suenaga, and Y.L. Wang, “Synchrotron X-ray 

Scattering Measurements of Bulk Structural Properties in Superconducting (Bi,Pb)2SrzCa2Cu3010-Ag Tapes”, /. 

OfAppl. Pbys., 79, 3122, (1996). 

Beamline X27C 

R.E. Johnston, D. Washburn, E. Pisano, W. Thomlinson, D. Chapman, N.F. Gmur, 2. Zhong, and D. Sayers, 

“Preliminary Experience with Monoenergetic Photon Mammography”, Medical Imaging 1995, Physics of 

Medical Imaging, PIE, 2432, 434, (1 995). 

W.B. Lindquist, S.-M. Lee, D.A. Coker, K. Jones, and P. Spanne, “Medial Axis Analysis of Void Structure in 

Three Dimensional Tomographic Images of Porous Media”,]. Of Geopbys. Res. Sol. Earth, B101, 8297, (1996), 

BNL 61573. 

c-37 

M. Babzien, I. Ben-Zvi, J. Fischer, A.S. Fisher, K. Kusche, I.V. Pogorelsky, and T. Srinivasan-Rao, “A 

High Power Picosecond Nd:YAG/C02 Laser System for Electron Guns Laser Acceleration and FEL”, 

Proceedings of Lasers ‘94 Conference, Quebec, Canada, STS Press, p. 253, (1995), BNL 61399. 

I. Ben-Zvi, E. Blum, E.D. Johnson, S. Krinsky, J.B. Murphy and L.H. Yu, “NSLS Source Development 

Laboratory”, SPIE Conference Proceedings Electron Beam Sources Sources and Charged-Particle Optics, 

edited by Eric Munro and Henry l? Freund, PIE, 2522,483, (1995). BNL 62173. 

E.B. Blum, “A Proposed NSLS X-Ray Ring Upgrade Using B Factory Technology”, Proceedings of the 

1795 Particle Accelerator Conference and International Conference on High Enery Accelerators, p. 

263, (1995), BNL 61744, May 1975. 

E. Bozoki, A. Friedman, and S. Ramamoorthy, “First Results with a Nonlinear Digital Orbit Feedback 

System at the NSLS”, Particle Accelerator Conference and International Conference on High-Enery 

Accelerator, 4, pp. 2696-2698, (1995), BNL 61745. 

K. Breuer, K.E. Smith, M. Greenblatt, W. McCarroll, and S.L. Hulbert, “Dominant Role of the Surface 

in Photoemission from Quasi-one Dimensional Conductors: &.3MoOgu”, J. Phys. Chem. Solids, 57, 

1803, (1996), BNL 63984. 

W. Broome, R. Biscardi, J. Keane, l? Mortazavi, M. Thomas, and J.M. Wmg, “RF System for the NSLS 

Coherent Infrared Radiation Source”, Proceedinm of the 1995 Particle Accelerator Conference, 3, 1626, 

(1995), BNL 61759. 

C.J. Buckley, S.J. Bellamy, X. Zhang, G. Dermody, and S. Hulbert, “The NEXAFS of Biological 

Calcium Phosphates”, Rev. Sci. Instrum., 66, 1322, (1995), BNL 63149. 

S.V. Bulanov, T.J. Esirkepov, N.M. Naumova, F. Pegoraro, and I.V. Pogorelsky, and A.M. Pukhov, 

“Controlled Wake Field Acceleration via Laser Pulse Shaping, IEEE Trans. on Plasma Sci., 24,393, 

(1996),BNL62847. 

D. Chapman, W. Thomlinson, E Arfelli, N. Gmur, Z. Zhong, and R. Menk, et al. “Mammography 

Imaging Studies Using a Laue Crystal Analyzer”, Rev. Sci. Instrum., 67, 9, (1996), BNL 62394. 

T.T. Chou, C.N. Yang, and L.H. Yu, “Bose-Einstein Condensation of Atoms in a Trap”, Phys. Rev. Lett., 

A5316 4257, (1996), BNL 63638. 

D- 1 
S.B. Dierker, R. Pindak, R.M. Fleming, I.K. Robinson, and L. Berman, “X-Ray Photon Correlation 

Spectroscopy Study of Brownian Motion of Gold Colloids in Glycerol”, Pbys. Rev. Lett., 75/3,449-452, 

(1996), BNL 62551. 

M. Deutsch, 0. Gang, K. Hamalainen, and C.-C. Kao, “Onset and Near Threshold Evolution of the Cu 

K% X-ray Satellites”, Pbys. Rev. Letts., 76/14, 2424, (1996), BNL 63776. 

Y.E Feng, S.K. Sinha, E.E. Fullerton, G. Grubel, D. Abernathy, D.E Siddons, and J.B. Hastings, “X-Ray 

Fraunhofer Diffraction Patterns from a Thin-film Waveguide”, Appl. Pbys. Lett., 67/24, 3647-3649, 

(1996), BNL 62734. 

C.L. Foerster, C. Lanni, J.R. Noonan, and R.A. Rosenberg, “Photon Stimulated Desorption 

Measurement of an Extruded Aluminum Beam Chamber for the Advanced Photon Source”, J vdc. Sci. 

Tecbnol., A14/3, 1273, (1996), BNL 62542. 

F. Gao, G.L. Carr, C.D. Porter, D.B. Tanner, G.I? Williams, C.J. Hirschmugl, B. Dutta, X.D. Wu, and 

S. Etemad, “Quasiparticle Damping and the Coherence Peak in Yba2Cu307-;, Pbys. Rev., B54/1, 700, 

(1996), BNL 63692. 

E. Gluskin, D. Franchon, EM Ivanov, J. Maines, E.A. Medvodko, E. Trakhtenberg, L.R. Turner, I. 

Vasserman, G.I. Erg, Y.A. Evtushenko, N.G. Gavrilov, G.N. Kulipanov, A.S. Medvedko, S.E Petrov, 

V.M. Popik, N.A. Vinokurov, A. Friedman, S. Krinsky, G. Rakowsky, and 0. Singh, “The Elliptical 

Multipole Wiggler Project”, Proceedings of the 1995 Particle Accelerator Conference, pp. 1426- 1428, 

(1996), BNL 61858. 

K. Hamdainen, S. Manninen, C.-C. Kao, W. Caliebe, J.B. Hastings, A. Bansil, S. Kaprzyk, and EM. 

Platzman, “High Resolution Compton Scattering Study of Be”, Pbys. Rev., B54/8, 5453, (1996). 

C.J. Hirschmugl, and G.P. Williams, “Chemical Shifts and Coupling Interactions for the Bonding 

Vibrational Modes for Co/Cu(lll) and (100) Surfaces”, Pbys. Rev., B52, 14177, (1995), BNL 62539. 

G. Ingold, I. Ben-Zvi, L. Solomon, and M. Woodle, “Fabrication of a High-Field, Short-Period 

Superconducting Undulator”, Nucl. Instrum. and Metb. in Pbys. Res., A375, 45 1, (1 996), BNL 

R.E. Johnston, D. Washburn, E. Pisano, W.C. Thomlinson, L.D. Chapman, F. Arfelli, G. Gmur, 2. 

Zhong, and D. Sayers, “Mammographic Phantom Studies with Synchrotron Radiation”, Radiolog, 200, 

659-663, (1 996), BNL 62733. 

R.E. Johnston, D. Washburn, E. Pisano, W.C. Thomlinson, D. Chapman, N.F. Gmur, Z. Zhong and D. 

Sayers, “Preliminary Experience with Monoenergetic Photon Mammography”, SPIE, 2432,434, (1996), 

BNL 62393. 

M.H. Kirsch, F. Sette, U. Bergmann, C. Masciovecchio, R. Berbeni, J. Goulon, W. Caliebe, and C.-C. 

Kao, “Observation of Magnetic Circular Dichroism in Resonant Inelastic X-ray Scattering at the L3 

Edge of Gandolinium Metal”, Pbys. Rev., B54118, 12673, (1996), BNL 63772. 

D-2 
C.-H. KO, J. Kirz, H. Ade, E. Johnson, S. Hulbert, and E. Anderson, “Development of a Second 

Generation Scanning Photoemission Microscope with a Zone Plate Generated Microprobe at the 

National Synchrotron Light Source”, Rev. Sci. Instrum., 66, 1416, (1995), BNL 63148. 

B. LaFontaine, D.L. White, O.R. Wood, 11, A.A. MacDowell, Z.Q. Tan, G.N. Taylor, D.M. Tennant, 

and S.L. Hulbert, “Real-Time Observations of Extreme Ultraviolet Aerial Images by Fluorescence 

Imaging”,J kc. Sci. Tecbnol., B12,3576, (1994), BNL 63153. 

A.T. Macrander, PA. Montano, D.L. Price, VI. Kushnir, C.R. Blasdell, C.-C. Kao, and E.R. Cooper, 

“Inelastic X-ray Scattering from Tic Single Crystals”, Pbys. Rev., B54/1, 305, (1996), BNL 63774. 

S. Morante, L. Furenlid, G. Schizvo, F. Tonello, R. Zwilling, and C. Montecucco, “Zinc Coordination in 

Tetanus Neurotoxin, Astacin, Thermolysin, and Alkaline Protease Studied by XRay Absorption 

Spectroscopy”, Ear. /own. of Biocbem., 235,606, (1 996), BNL 6254 1. 

J.B. Murphy, “Issues and State of Art for Short Bunches in e+/e- Storage Rings”, AIP Conference 

Proceedings, 367, p. 109, (1996), BNL 63851. 

R.J. Nawrocky, and S.L. Kramer, “Single-Turn Beam Position Monitor for the NSLS VUV Electron 

Storage Ring, Proceedines of the 1995 PAC and International Conference on HighEnerr 

Accelerators, p. 2509, (1995), BNL 61758. 

D.T. Palmer, R.H. Miller, H. Winick, X.J. Wang, K. Batchelor, M. Woodle, and I. Ben-Zvi, “Microwave 

Measurements of the BNL/SLAC/UCLA 1.6 Cell Photocathode RF Gun”, 1995 Particle Accelerator 

Conference, (1 9954, BNL 61 85 1. 

D.T. Palmer, R.H. Miller, H. Winick, X.J. Wang, K. Batchelor, M. Woodle, and I. Ben-Zvi, 

“Simulations of the BNL/SLAC/UCLA 1.6 Cell Emittance Compensated Photocathoce RF Gun Low 

Energy Beam Line”, 1995 Particle Accelerator Conference, p. 2432, (1995), BNL 61852. 

I.V. Pogorelsky, “Relativistically Strong COz Laser Driver for Plasma-Channeled Particle Acceleration”, 

STS Press, pp. 104-1 11, (1996), BNL 62845. 

I.V. Pogorelsky, I. Ben-Zvi, W.D. Kimura, N.A. Kurnit, and F. Kannari, “Picosecond C02 Laser for 

Relativistic Particle Acceleration”, Inpared Pbys. and Tecb., 36/1, 341-354, (1995), BNL 60452. 

I.V. Pogorelsky, A. vansteenbergen, M. Babzien, I. Ben-Zvi, R. Fernow, J. Gallardo, K.P. Kusche, T. 

Srinivasan-Rao, X.J. Wang, W.D. Kimura, G.H. Kim, R.D. Romea, Y. Liu, D. Cline, J.R. Fontana, A. 

Fisher, J. Sandweiss, X.J. Qui, and J.-M. Fang, “Inverse Cherenkov and Inverse FEL Accelerator 

Experiments at the Brookhaven Accelerator Test Facility”, STS Press, pp. 96-103, (1996), BNL 62846, 

A. Pullia, L. Furenlid, H.W. Kraner, G. Bertuccio, PJ. Pietraski, and D.P. Siddons, “High Resolution 

Multi-Element Solid-state Detectors”, Rev. Sci. Instrum., 67/9, 1, (1996), BNL 62735. 

D-3 
X. Qui, K. Batchelor, I. Ben-Zvi, and X.J. Wang, “Demonstration of Emittance Compensation Through 

the Measurement of the Slice Emittance of a 10 Picosecond Electron Bunch”, Pbys. Rev. Lett., 76/20, 

3723, (1996), BNL 62386. 

X.Z. Qiu, X.J. Wang, K. Batchelor, and I. Ben-Zvi, “Conceptual Design of a Charged Particle Beam 

Energy Spectrometer Utilizing Transition Radiation Grating, Proceedines 1995 Particle Accelerator 

Conference, p. 241 1, (1995), BNL 61743. 

X.Z. Qui, X.J. Wang, K. Batchelor, and I. Ben-Zvi, “Transition Radiation Electron Beam Diagnostic 

Study at the ATF”, 1995 Particle Accelerator Conference, p. 2530, (1 995), BNL 61850. 

S. Ramamoorthy, P Pearson, and J. Smith, “Error Handling in the NSLS Control System”, 1995 

Particle Accelerator Conference and International Conference on High-Enery Accelerator, 4, 2250- 

2253, (1995), BNL 61761. 

J.L. Rothman, and E.B. Blum, “Charge Balancing Fill Rate Monitor”, Proceedings 1995 Particle 

Accelerator Conference and International Conference on High Enerw Accelerators, 4, p. 2450, (1995), 

BNL 61760, May 1995. 

J. Safranek, ‘‘A Low Emittance Lattice for the NSLS X-ray Ring”, Proceedings of the 1995 IEEE Particle 

Accelerator Conference, pp. 266-268, (1 995), BNL 6 1847. 

J. 

K, 

Safranek, 0. Singh, and L. Solomon, “Orbit Stability Improvement at the NSLS X-ray Ring, 

pp. 271 1-2713, BNL 61848. 

J. Safranek, “Experimental Determination of Linear Optics including Quadrupole Rotations”, 

Proceedincs of the 1995 IEEE Particle Accelerator Conference, pp. 28 17-28 19, BNL 6 1853. 

M.L. Shek, “Soft X-ray Studies of a c(4x2)* B-SiC(100) Surface”, Suqf Sci., 349, 317-332, (1996), BNL 

62 177. 

D. Siddons, Y. Feng, S. Sinha, E. Fullerton, G. Grubel, D. Abernathy and J. Hasting, “X-ray 

Fraunhofer Diffraction Patterns from a Thin-Film Waveguide”, Appl. Pbys. Lett., 67/24, 3647, (1 996), 

BNL 63146. 

0. Singh, S. Krinsky, PM. Ivanov, and E.A. Medvedko, “Orbit Compensation for the Time Varying 

Elliptically Polarized Wiggler”, Rev. Sci. Instrum., 67/9, 1-6, (1996), BNL 63952. 

0. Singh, S. Ramamoorthy, J. Sheehan, and J. Smith, “Upgrade of NSLS Timing System”, 1995 

Particle Accelerator Conference and International Conference on High-Enerw Accelerator, 4, pp. 2223- 

2225, (1995), BNL 61756. 

B. Sinkovic, E. Shekel, and S. Hulbert, “Spin-resolved FeL3M45M45 Auger transition On and Off 

Resonance: The Effect of Exchange Correlation”, Pbys. Rev., B52, 15703, (1995), BNL 62536. 

D-4 
J. D. Smith, S. Ramamoorthy, and Y.N. Tang, “NSLS Control System Upgrade”, Nucl. Instrum. And 

Meths. In Pbys. Rev., A352, 114, (1994), BNL 61019. 

I? Stefan and S. Krinsky, “Experience With Small-Gap Undulators”, Rev. Sci. Instrum., 6719, 3346, 

(1996), BNL 63150. 

PM. Stefan, S. Krinsky, G. Rakowsky, and L. Solomon, “Small Gap Undulator Experiment on the NSLS 

X-Ray Ring”, Proceeding 1995 IEEE Particle Accelerator Conference, p. 2435, (1995), BNL 61878. 

May 1995. 

Y.N. Tang, and J.D. Smith,. “History Data Collection, Retrieving and Display in the NSLS Control 

System”, 1995 Particle Accelerator Conference and International Conference of High Energ 

Accelerators, 4, pp. 2253-2255, (1 995), BNL 6 1757. 

W. Thomlinson, “Synchrotron Radiation Applications in Medical Research”, Proceedings of the 

Internationl Conference on Industrial Apdications of Svnchrotron Radiation, Hyogo Prefecture, Japan, 

pp. 98-126, (1996), BNL 62631. 

W. Thomlinson, “Transvenous Coronary Angiography in Humans with Synchrotron Radiation”, 

Proceedings of the International School of Physics “Enrico Fermi”. Course CXXVIII-Biomedical 

Applications of Synchrotron Radiation, edited by E. Burattini and A. Balera, 10s Press, Washington, 

DC, pp. 127-153, (1996), BNL 60834. 

X.J. Wang, M. Babzien, K. Batchelor, I. Ben-Zvi, R. Malone, 1.V Pogorelsky, X. Qui, J. Sheehan, J 

Skaritka, and T. Srinivasan-Rao, “Experimental Chararacterization of High Brightness Electron 

Photoinjector”, Nucl. InstTum. &Metbs., A375, 82, (1 996), BNL 62623. 

X.J. Wang, T. Srinivasan-Rao, K. Batchelor, M. Babzien, 1. Ben-Zvi, R. Malone, I. Pogorelsky, X. Qui, J. 

Sheehan, and J. Skaritka, “Experimental Results of the ATF In-Line Injection System”, 1995 Particle 

Accelerator Conference, p. 890, (1995), BNL 61743. 

L. H. Yu, “An Exact Solution for Quantum Tunneling in a Dissipative System”, Pbys. Rev., A54, 3779, 

(1996), BNL 63106. 

D-5 
F. Arfelli, C. Burns, D. Chapman, N. Gmur, R.E. Johnson, R. Menk, E. Pisano, D. Sayers, W. 

Thomlinson, D. Washburn, and 2. Zhong, “Data Acquisition and Analysis of Mammography Images at 

the NSLS”, BNL 62935, (1996). 

I. Ben-Zvi, and S. Krinsky, (Editors), “Program and Abstracts - 17th Intl. Free Electron Laser 

Conference and 2nd International FEL Users Workshop”, BNL 61982, October 1995. 

E.B. Blum, “Short Bunch Research at Brookhaven National Laboratory, Micro Bunches Workshop”, 

BNL 62388, November 1995. 

E.B. Blum, “Observation of Coherent Transition Radiation at the Accelerator Test Facility”, BNL 

62738, February 1996. 

W. Broome, and J. Wang, “Reactive Robinson Instability in the NSLS X-Ray Ring”, BNL 62789, 

January 1996. 

D. Corridon, “Design of a Diagnostic Area-Type Beam Position Monitor for X-Ray Beamlines at the 

National Synchrotron Light Source”, BNL 63383, August 1996. 

N. Gmur, “Structural Biology Research at the National Synchrotron Light Source”, BNL 629 16, 

J. Hastings, “Workshop: Research and Development Plans for High Power Spallation Neutron Testing at 

BNL”, BNL 63614, August 1996. 

NSLS Staff and Collaborators, “Lighting the Way to the Future: An Anthology of Improvements, 

Developments, and Research by NSLS Staff and Collaborators”, BNL 63477, September 1996. 

I.V. Pogorelsky, “CO2 Laser Technology for Advanced Particle Accelerators”, Presented at Meeting of the 

American Physics Society, BNL 63249, May 1996. 

1.V Pogorelsky, “High Intensity Laser Synchrotron X-ray Source”, BNL 62447, November 1995. 

X. Qiu, J. Sheehan, and J. Skaritka, “High-Brightness Electron Beam Generation Using Emittance 

Compensation in a High-Gradient Photocathode RF Gun”, BNL 62336, October 1995. 

A.G. Ruggiero, “Negative Ion Injection by Charge Exchange at 2.4 GeV, BNL 623 10, October 1995. 

A.G. Ruggiero, “Design Considerations on a Proton Superconducting Linac”, BNL 623 12, October 

1995. 

X.J. Wang, T. Srinivasan-Rao, K. Batchelor, M. Babzien, I. Ben-Zvi, J. Fischer, R. Malone, I. Pogorelsky, 

X. Qiu, J, Sheehan, and J. Skaritka, “High-Brightness Electron Beam Generation using Emittance 

Compensation in a High-Gradient Photocathode RF Gun”, BNL 62336, May 1996. 

D-6