(For the period October 1, 1994 through September 30, 1995) 

Editors: 

J Hatings 

Layout: 

N.A. Wright 

E.Z. Rothman , ' 

The National Synchrotron Light Source Department 

is supported by the 

Office of Basic Energy Sciences 

United States Department of Energy 

Washington, D.C. 

Brookhaven National Laboratory 

Associated Universities, Inc. 

Upton, New York 11973-5000 

Undei Contract No. DErAC02-7GCH00016 with the 

United Srates Department of Energy 

MASTER 
~NTRODUCTION 

lNTRODUCTlON ,BY. THE CHAIRMAN ... ........................................................................................................... 2 

ENVIRONMENT, SAFETY AND HEALTH UPDATE ............................................................................................ 4 

USERS' EXECUTIVE COMMIITEE .................................................................................................................. 6 

Michael Harf 

William Thomlinson 

Paul Zschack 

SCIENTIFIC DISCIPLINES 

ATOMIC AND MOLECULAR SCIENCE ........................................................................................................ 10 

ENERGY DISPERSIVE DIFFRACTION ........................................................................................................... 13 

LITHOGRAPHY, MICROSCOPY, AND TOMOGRAPHY ..................................................................................... 17 

NUCLEAR PHYSICS .................................................................................................................................. 24 

SCA~ERING AND CRYSTALLOGRAPHY STUDIES OF BIOLOGICAL MATERIALS ................................................. 31 

TIME RESOLVED SPECTROSCOPY .............................................................................................................. 35 

UV PHOTOEMISSION AND SURFACE SCIENCE ........................................................................................... 40 

X-RAY ABSORPTION SPECTROSCOPY ....................................................................................................... 46 

X-RAY SCA-ITERING AND CRYSTALLOGRAPHY ........................................................................................... 51 

X-RAY TOPOGRAPHY ............................................................................................................................. 57 

Mei-Ling Shek 

Syed B. Qadri 

Gwyn P. Williams 

Craig E. Thorn 

Lonny Berman 

Jim Long and Jon Levin 

Sfeven Hulberf'and Chi-Chang Kao 

Lars Furenlid 

D. Pefer Siddons 

Michael Dudley 

MEETINGS & WORKSHOPS 

THE 1 995 NSLS ANNUAL USERS' MEETING ........................................................................................ 66 

1 7TH INTERNATIONAL FREE ELECTRON LASER CONFERENCE ...................................................................... 69 

MICRO BUNCHES WORKSHOP ................................................................................................................. 71 

Paul Zschack 

Ilan Ben-Zvi and Samual Krinsky 

Eric B. Blum and James B. Murphy 

.. 

ll 
DISCLAIMER 

Portions of this document may be illegible 

in electronic image products. Images are 

produced from the best available original 

document. 
OPERATIONS 

VUV MACHINE ........................................................................... :.....: ...................... ,/ ;. ......... ................ 74 

VUV STORAGE RING PARAMETERS ......................................................................................................... 78 

BEAMLINE TECHNICAL IMPROVEMENTS ..................................................................................................... 79 

X-RAY BEAMLINES ................................................................................................................................. 83 

X-RAY STORAGE RING PARAMETERS ....................................................................................................... 86 

Stephen Kramer 

Roger Klajky 

Roger Klajky 

PROJECTS 

THE NSLS SOURCE DEVELOPMENT LABORATORY .................................................................................... 90 

THE ACCELERATOR TEST FACILITY (ATF) ................................................................................................ 92 

Erik D. Johnson 

llan Ben-Zvi 

Frank Terrano and Mike Kelly 

NSLS FACILITY IMPROVEMENTS .............................................................................................................. 94 

ORGANIZATION 

NSLS ADVISORY COMMIITEES .............................................................................................................. 98 

NSLS STAFF ....................................................................................................................................... 1 00 

VUV BEAMLINE GUIDE ........................................................................................................................ 103 

X-RAY BEAMLINE GUIDE ...................................................................................................................... 107 

ABSTRACTS & PUBLICATIONS 

vuv BEAMLINE ABSTRACTS .................................................................................................................. A-1 

X-RAY BEAMLINE ABSTRACTS ................................................................................................................ B- 1 

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

NSLS STAFF PUBLICATIONS .................................................................................................................. D-1 

BNL FORMAL AND INFORMAL REPORTS ................................................................................................. D-4 

... 

111 


Michael Hart 

NSLS Chairman 

Another lean year, in which the budget remained 

level in at year dollars but fell in real terms. Nevertheless 

we saw a high level of scientific activity and facility 

development and improvement. The end of the Fiscal 

Year (FY 1995) brought substantial changes to the staffof 

the NSLS. It became necessary to solicit volunteers for a 

reduction in staffso as to allow for a redirection of funds 

into areas consideredvital to improve research operations. 

Many years of experience were lost when Arie van 

Steenbergen, George Stenby, Bob Larson, Ken Batchelor, 

Norman Fewell, Paul LeDoux and Clem Auguste volunteered to take retirement. The year ended with the certainty that FY 1996 would be the year in which the 

Scientific Facilities Initiative would be funded. 

Highlights and themes of the science program are 

summarized in articles by NSLS staffand users, providing 

an overview which displays the evidence of extreme diversity and high quality. The detailed publication lists and 

user's reports are described in later pages and in over 700 

publications in the journal literature. 

During theyear, in the March 1995 Newsletter, the 

concept of Beamline Confederations was first explored 

and this continues to be an important aspect of the future 

at NSLS for users and staffalike. In the present economic 

climate it has become increasingly difficult to obtain the 

necessary funds to ensure year round operations for all the 

beamlines. An increase in scale, through co-operation, 

collaboration and correlation ofplanning and investment 

could enable PRTs to achieve more than each would 

achieve alone. In areas such as Powder Diffraction, Structural Biology, X-ray Absorption Spectroscopy, and Reflectometry several beamlines exist at NSLS. In each case 

there are benefits to be won, through combined R & D in 

both soft-ware and hardware, through the common provision of spares and through the enhanced intellectual 

resources of a wider community. In some of these 

examples the combination of interest and expertise in the 

application of neutron probes is also of importance. 

The Structural Biology Addition was formally Dedicated on 10 May 1995 when Roland Hirsch from the 

DOE Office of Health & Environmental Research was 

2 

joined by BNL Laboratory Director Nicholas Samios, 

Denis McWhan (BNL Associate Director for Basic Energy Sciences) and William Studier, BNL Biology Department Chairman for a ceremonial ribbon cutting. 

Funds for this key development of user laboratory space 

included the DOE Office of Health & Environmental 

Research, BNL General Plant Project Funds (GPP), the 

Howard Hughes Medical Institute, Exxon and New York 

State University at Stony Brook. At the end of the year the 

users took possession of the laboratory space and the 

NSLS control room and ES&H staff planned to move 

too. 
I 

A Department of Energy Customer Satisfaction 

Survey was conducted by an experienced contractor under the direction of the DOE Task Force on the Science 

and Technology (S & T) business line. The NSLS 

provided the DOE with a contact list of users for the 

purpose of random polling, and extensive questionnaires 

were also completed by PRT members and by the Users’ 

Executive Committee. 80% of the customers of the S & 

T reported that they were “satisfied” or “very satisfied”. 

Yet another successhl year of machine improvements and operations was achieved; the energy of the 

VUV ring was increased to 800 MeV resulting in longer 

lifetime and a 30% increase in integrated current and 

plans were made to increase the booster energy to track 

that of the ring. Further improvements include the first 

demonstration of‘(top off mode in which quasi-continuous injection keeps the current near its maximum value 

and so reduces the effects of thermal cycling on beam line 

optics while maximizing the integrated current. On theXray ring maximum current operation was increased to 300 

mA and the Thermal Limits Task Force set out a plan for 

eventual running at up to 438 mA at 2.584 GeV or 250 

mA at 2.8 GeV after the replacement of the 34 Beryllium 

windows which presently limit such operating conditions. 

Early in the year the Elliptically Polarized Wiggler 

wasinstalledand testedinthex-13 R&D straight section 

of the X-Ray Ring . The modified Prototype Small Gap 

Undulator was reinstalled and operated at a 5.6 mm 

magnet gap ( 2.5 mm electron beam gap) to provide 2.5 

keVX-rays in the hndamental and 7.5 keVX-rays in the 

third harmonicwith apartidlifetime contribution ofonly 

36 hours. The Accelerator Test Facility provided access to 

15 currently approved experiments including the first 

demonstration of Inverse FEL acceleration of electrons, 

the observation of micro-bunching and the development 

of slice-emittance techniques for beam diagnostics. The 

NSLS hosted the 17th International Free Electron Laser 

Conference, an important meeting both in terms of 

content and timing in the definition of the next few years 

R & D towards fourth generation synchrotron radiation 

sources. 

A very productive year for our staff and users. 

3 
William Thomlinson 

Associate Chairman 

NSLS 

The ES&H activities at the NSLS during FY95 

focused on the implementation of old and new programs, 

getting prepared for the coming of the new Personnel 

Radiation Protection law on January 1,1996, and adjusting to several significant personnel changes. 

It is perhaps the personnel changes which are the 

most important issue which we faced. At the end ofFY95, 

we lost the services of our ES&H Coordinator, Kenneth 

Batchelor, our Quality Assurance Representative, Paul 

LeDoux, and our Safety Associate, Clement Auguste. It 

is never easy to lose so many people at one time, especially 

since some of them were key, highly experienced personnel on whom we had relied for many years. During this 

last year under the direction of Ken Batchelor, the NSLS 

finally achieved formal classification by DOE as a low 

hazard accelerator. That means that the DOE orders and 

guidelines which pertain to our operations are now clarified. Previously we had operated under the assumption 

that we would be low hazard, but we needed final 

approval. 

We have been very fortunate in being able to fill 

these openings with extremely qualified personnel who 

have already been putting their marks on the positions. 

The central position of ES&H Coordinator has been 

filled by Nicholas Gmiir who has extensive experience 

with safety issues regarding the medical research programs 

and as ALARA (As Low As Reasonably Achievable) Coordinator for the NSLS. It has already been a busy time since 

the new Radiation Protection Program, Federal Code 

lOCFR835, kicks in January 1,1996 and we have had to 

undergo reviews, revise many of our existing SEAPPMs 

(Safety and Environmental Administrative Policy and 

Procedure Manual), and write many new ones. 

The transition has been smooth and we are now 

pretty much up to speed. The position of ALARA 

Coordinator has been assumed by WilliamThomlinson, 

replacing Nicholas Gmiir. Under the policies of 

10CFR835, ALARA is much more formally recognized 

and mandated, so we have been busy naming new 

members to replace those who have left the Laboratory. 

4 

It has long been felt that ES&H should be an 

integrated concept at the NSLS, and the change of our 

QA Representative from Paul LeDoux to Dennis Klein 

has provided the perfect opportunity. Dennis Klein 

comes to the position from an extensive technical background and also as the NSLS Training Coordinator. We 

have thus been able to combine training and QA in a 

single office, reporting formally to both the ES&H Associate Chairman and to the Assistant to the Chairman for 

Administration. 

John Aloi has moved from his Operations Coordinator role to become a StaffEngineer in our group. The 

timeliness of this move cannot be underestimated. John 

is already giving the necessary attention to critical matters 

which had been neglected or not initiated. The arrival of 

these three individuals, workingwithThomas Dickinson, 

our Safety Officer, Andrew Ackerman, our Safety Engineer, and our S&EP representatives (Chris Weilandics, 

Rudy Zantopp and Eric Seebeck), ensures that we will be 

able to maintain our strong ES&H program. 

Most of the preparation for the start of the new 

Personnel Radiation Protection Program has centered 

around updating our SEAPPMs. The NSLS is in very 

good shape with regard to the new federal code since we 

have always maintained a strong safety and ES&H effort. 

The NSLS is proud of its record in, for example, user 

safety; communication to staff and users on essential 

safety issues, the formalizing of our ALARA program, 

reporting of off-normal events, and training. A recent 

review by BNLofourpreparations for 10CFR835 showed 

only a few minor areas that will need attention. 

The attention of the ALARA Committee this year 

was focused on obtaining reliable data on the radiation 

levels in offices in the NSLS which come from operation 

ofthe booster and theVUVKng. The datais now reliable 

enough to plan for reducing the levels through various 

shielding measures. These measures will be in addition to 

those taken in the past several years which have reduced 

the levels in all but a few offices to below NSLS administrative levels. There was some progress in removing 
radiological warning signs around the facility due both to 

decreased levels after shielding upgrades and changes in 

the administrative policies for posting. The Committee 

is working toward the goal ofhaving all radiation warning 

signs on office doors eliminated. There is much work yet 

to be done. 

The Electrical Safety Review of the NSLS Experimental Areas has been completed by Michael Buckley, 

John Aloi and Steve Kemp. This review was an intensive 

study of each beamline to determine what short term 

critical electrical hazards exist and what longer term, nonimmediate problems exist. There were many minor 

immediate problems found which are to be addressed by 

the beamline personnel. A study is now underway to 

address the larger, man-power intensive and costly issues 

(e.g., moving circuit breaker panels which do not meet 

access requirements). It is expected that the NSLS will 

share in the responsibility for correcting these deficiencies, using BNL and NSLS staffand resources. We hope 

to have completed this project by the end of FY96. Joe 

Sheehan, Electrical Engineer, is carrying out a similar 

review for the remainder of the NSLS technical space. 

Off-normal events, and the reporting ofthose events 

to DOE, are taken very seriously by the NSLS. We have 

historically had very few reportable events, a record which 

is due to our highly trained and professional staff, coupled 

with our trained and concerned user population. However, occasionally we do have such events and this year was 

no exception. Fortunately, none of the events resulted in 

injury to personnel, but in at least one case of violation of 

electrical safety (lock-out, tag-out) procedures, the potential existed. By following through on the reports and 

lessons learned from these events, the NSLS is attempting 

to become a safer environment in which to work. In the 

case of the electrical safety event, intensive re-training of 

cognizant stafffollowed, the SEAPPM covering lock-out, 

tag-out procedures was revised and it was clearly stated 

once again that safety on the job is the first priority for all 

staffmembers and guests. In other events, more clarity of 

administrative and interlock procedures has been necessary, followed by the issuing of policies and additional 

training. 
Paul Zschack 

Oak Ridge National Laboratory 

UEC Chair 

The Users' Executive Committee (UEC) continues 

to serve as a primary communication vehicle between the 

User community and the NSLS Administration. Representing the User Association, the UEC hosted four Town 

Meetings during 1995 to facilitate useful interaction 

between the NSLS staffand NSLS users. Following each 

Town Meeting, the UEC met with the NSLS management and the BNL Directorate to further discuss relevant 

issues. I extend sincere thanks to the UEC Membership, 

the NSLS staff and management, the BNL Directorate, 

and all other volunteers who took active roles in continuing the UEC mission throughout the last year. 

In addition to advocacy for user quality-of-life issues, the UEC has taken initiative and sanctioned a study 

panel to evaluate the current health of the PRTs and 

General User programs. Geraldine Lamble (NSLS), Jean 

Jordon-Sweet (IBM), and Robert Sweet (BNL - Biology) 

have spearheaded this effort. Results of this in-depth 

studywill beused toaidplanningforthefuture, andafinal 

report with specific recommendations has by now been 

provided to the NSLS Chairman. 

It has never been more important for users of the 

NSLS and NSLS staffand management to work together 

to find solutions to the problems ficing many research 

efforts at the NSLS. I believe we all recognize the need to 

be more creative to get more accomplished with fewer 

resources. One way to accomplish this is through economies ofscale brought about by beamline confederations or 

consortia. In one form or another, these will certainly be 

a part of our future. 

An example of the advantages of coordinated activities on a larger scale is the success of the Science Facilities 

Initiative in the BES budget. Hard work by the DOE and 

Facility Directors, and grass roots support from users was 

rewarded by an increase in the Basic Energy Sciences 

budget targeted for the National User Facilities. A 

portion of these funds have been made available to individuals for "...new capabilities or for upgrading existing 

research capabiliti es... at DOE-supported synchrotron faciliti es..." I am confident many outstanding proposals 

G 

have been submitted by NSLS users to the DOE for this 

grant support. We can also be hopeful that this Initiative 

results in a long-term increase in funding for synchrotron 

radiation research and is not simply a bump on the 

funding profile. 

The Scientific Program Support Committee (SPSC) 

remains as a standing subcommittee of the UEC and 

continues to provide aleading role in advocating the users' 

position on many technical and quality of life issues 

within the NSLS. Lars Furenlid (NSLS) and Mike 

Sansone (Exxon) currently co-chair the SPSC, which has 

become involved in safety and compliance issues such as 

the DOE chemical tracking. The SPSC continues to be 

a most effective body in support of user issues. 

The Annual Users' Meeting is the most visible 

function sponsored by the UEC. In addition to invited 

talks and a successful poster session, a satellite workshop 

on XAFS was held. This permitted users attending the 

Annual Meeting and traditional Workshops to also participate in the XAFS program. The popularity of the 

workshop programs has inspired a change for next year's 

annual meeting. To offer wider participation in the 

workshops, the program will be split into 2 days, providing the opportunity to attend 2 one-day workshops. The 

keynote address at the Annual Meeting was given by 

Robert Galvin, Chairman of the Executive Board of 

Motorola, Inc., and Chairman of the Task Force on 

Alternative Futures for the DOE National Labs. Mr. 

Galvin provided an eloquent and provocative opinion of 

the future of scientific research at the National Labs. 

Going beyond the Task Force Report, privatization is 

seen as the eventual form of the National research facilities. Not all users agreewithMr. Galvin's assessment, but 

this address certainly inspired much lively discussion. 

New to the 1995 meeting was the recognition of a 

Distinguished User to acknowledge the research efforts of 

an NSLS investigator. The inaugural Distinguished User 

was Cullie J. Sparks of the Oak Ridge National Lab whose 

contributions to synchrotron radiation research include 

work in focusing optics, diffuse x-ray scattering, and 
Users' Executive Committee and 

Special Interest Group Representatives 

[Front, from left fo ngbt) 

Paul Zschack (ORNL), Stephan Cinell (ANL), Michael Dudley (SUNY - Stony Brook), Eva Rothman (NSLS), 

Sue Wirik (SUNY - Stony Brook), and Peter Stephens (SUNY-Stony Brook). 

Chairman of the second UEC back in the early 1980s. 

The conference banquet was held at the Port Jefferson 

(Back, from left fo ngbf, Standing) 

Kim Mohanty (BNL-Physics), Dan Fischer (NIST), David Hanson (SUNY - Stony Brook), Jean Jordan-Sweet 

(IBM), Doon Cibbs (BNL-Physics), Jon Levin (U. of Tennessee), Kevin Smith (Boston U.), Boris Sinkovic (New 

York U.), Syed Qadri (NRL), and Craig Thorn (BNL-Physics). 

Absent from photo are Simon Bare (Dow Chemical), and David Johnson (Old Dominion U.). 

the NSLS User population in the future. The success of 

the Annual Meeting is primarily due to the hard work of 

the organizing committee. I am grateful to Steven Ehrlich, 

Linda Feierabend, Dan Fischer, Eva Rothman, and Sue 

Wirick for all their hard work and effort. 

Sometimes we take for granted just how easy it is to 

work effectively at the NSLS. The hard work of past UEC 

committees, past NSLS Chairpersons, the NSLS User 

Administration OGce, the NSLS staff, and the 

BNL Directorate should be acknowledged. 

7 


Mei-Ling Shek 

NSLS 

I. VALENCE ELECTRONIC EXCITATION 11. INNER-SHELL EXCITATION 

The thrust of the gas phase research on beamline 

U11 is discharge flow-photoionization mass spectrometry. From the photoionization efficiency spectra of HOI 

and IO, the adiabatic ionization energies have been determined, for the first time, for HOI @‘A’)+ HOP (XzA”) 

and IO (XTI,,J+ IO+ e3Z-). In addition to the vibrational structure of the cation, the photoionization of IO 

also displays autoionization features correlated wuth 

Rydberg excitations, as shown in Figure 1. 

On beamline UlSUA, Auger and resonance Auger 

spectra of methane are obtained as the basis of understanding the highly excited valence states of singly and 

doubly charged molecular ions due to core hole excitations in hydrocarbons. Figure 2 shows the Auger spectrum of methane following C 1s photoionization, as well 

as the resonance Auger spectra due to C 1s + 3s and 1s + 

3p excitations, at chosen photon energies based on the 

total ion yield spectrum. The shifts towards higher electron kinetic energies in the resonance Auger spectra are 

0.020- 

s .I 

c 

Ei 2 0.010- 

E. 

E 

E 

F: 

1 

d a 0.015- W 

m 

z 

0.005- 

0 

0.000- 

5 120 125 

WAVELENGTH (nm) 

130 

Figure 1 U11: Photoionization efficiency spectrum of IO (m/s = 143) at a 

nominal resolution of about 0.23 nm and 0.1 0 nm steps between I = 1 1 5.0 and 

130.0 nm. the arrow indicates the onset of ionization at 127.3 nm (IE = 9.74 

& 0.02 ev). The superposed lines indicate autoionization which presumably 

correlateswith a Rydbergprogression (1 26.2 nm/n*=5.18,124.3 nm/n*=6.17, 

123.2 nm/n* = 7.1 2,122.4 nm/n* = 8.1 9,121.9 nm/n* = 9.1 9, where n* = (W 

(IE - E,,))”=’and R= 1 3.60539 ev) that converges to an excited state of the cation 

at 120.0 nm (1 0.33, ev). [Z. Zhang (BNL-DAS), P.S. Monks, and L.J. Steif (NASA, 

MD), J.F. Liebman (U. of Maryland), R.E. Huie (NIST), S.C. Kuo, and R.B. Klemm 

(BNL-DAS)]. 

10 

consistent with the interpretation ofde-excitation ofRydberg 

states to 2-hole-1-electron valence final states. 

The dynamics of core 

hole excitation and de-excitation phenomenaarealso ofgreat 

interest on beamlineX1B. The 

feasibility of measuring threshold photoelectrons in coincidence with soft x-ray fluorescence has been demonstrated, 

thus enabling the elimination 

of line shape distortions due to 

post-collision interaction between the photoelectrons and 

core-hole induced Auger electrons. To overcome the low 

fluorescence yield of the firstrow elements, efficient detection is needed in conjunction 

with a high photon flux. A new 

instrument combining a timeof-flight zero-kinetic-energy 

(ZEKE) electron spectrometer 

with a large photon detector 

near the interaction region provides ahigh detection eficincy. 

Figure 3 shows the results for 

N,. The resonances below the 
':j 

Electron Kinetic Energy 

Figure 2a U13UA Auger 

Spectrum of CH, (excitation 

by hv = 296 ev). 

Figure2b Resonance. .-lger 

spectrum of CH, following 

Is + 3s excitation (hv = 

287.04 ev). 

Figure 2c: Resonance Auger 

spectrum of CH, following 

Is + 3p excitation (hv = 

288.00 ev). [S.Y. Chen, and 

D.M. Hanson (U. Stony 

Brook)]. 

N, lclnizatiim Threshold 

rFigure 3 X1B: From top to 

bottom, the coincidence 

spectrum, the ZEKE electron 

spectrum, and the soft x-ray 

fluorescence yield spectrum of 

the N, molecule. The solid line 

in the upper panel is a tentative 

four-Gaussian fit with the 

spacing locked to 0.31 eV. [J.-E. 

Rubensson, 1. Luning (KFA 

Julich), M. Neeb (FHI Berlin), S. 

Eisebitt (U. British Columbia), B 

Kupper, and W. Eberhardt (WA 

Julich)]. 

1s ionization limit in the coincidence spectrum give new information about the radiative 

decay dynamics. Further sensitivity enhancements are 

planned. 

Another study on 

beamlineXlB involvesthedoublyexcitedneutralstatesin CO 

and N,, following the recent 

finding of such 2-hole-2-particle states in the high resolution absorption spectra about 

4-7eVabovetheC lsandN 1s 

ionization thresholds. Figure 4 

shows the decay spectra due to 

C 1s and N 1s ionization and 

the decay of the doubly excited 

states above as well as below 

thresholds. The below threshold excited states have been 

previously obscured by 

Rydberg excitations in the absorptionspectrum. For CO and 

N,, the 2-hole-2-particle states 

about 4 eV above threshold 

have also been observed to undergo valence autoioni-zation. 

On beamline X24A, after the successll implementation of coincidence detection 

ofphotoelectrons or Auger electrons with fluorescent x-rays 

(reported last year), a study to 

understand angular correlations 

in the coincidence measurements has been initiated. X-ray 

scattering studies on OCS and 

atomic& have also been made 

on beamline X24A. 

Double ionization of He 

has been of great interest as the 

testing ground for understanding electron correlation. Measurements on the ratio of the 

cross-sections for double to 

single ionization of He were 

made in the last few years on 

beamlines X24A, X26C and 

XSA. The work has now been 

extended to beamline UlSUA, 

where an accurate determina11 
ll~lll~~ll~lll]l~l~lll~lll~lll 

resonant decay of 2h2p states in CO 

hv(eV)= 

294.9 

hob 

56 260 264 268 272 276 280 284 

Kinetic energy (eV) 

resonant decay of 2h2p states in N, hv (eV)= 

365 370 375 380 385 390 395 400 

Kinetic energy (eV) 

Figure 4X1B: Decay spectra of CO and N, excited around the C 1 s and N 1 s ionization thresholds at 296.1 eV 

and 409.9 eV, respectively. The decay of the doubly excited states above threshold show strong resonant features 

at 268 eV for CO and at 380 eV for N,, as can be seen in (b) and (d), respectively. The spectra in (a) and (c) show 

resonant-enhanced structures which are attributed to the decay of additional 2h2p states immediately below 

threshold. The leading ripple peak structure in all spectra is due to direct photoemission of the outer valence 

orbitals. The valence photoemission spectra of CO and N, are shown at the bottom as dotted lines. [M. Neeb, A. 

Kivimaki, B. Kempgens, H.M. Koppe, and A.M. Bradshaw (Fritz-Haber-lnstitut der Max-Planck-Cesellschafi, Berlin)]. 

tion of the ratio from the 

double ionization threshold 

at 79 eV to 700 eV is the 

goal. The experiment utilizes time-o f-flight detection 

of He+ and He++ with 

Rayleigh scattering as the 

prompt signal. Figure 5 

shows a comparison of data 

with theory. 

12 

h 

v s 

T 

+ 

Q, 

+f 

a, 

T 

I I I 

------I --___ I ---------- 

$5 

21 /// Presentwork 

Byron and Joachain, PR 14,l (1967) 

Carter and Kelly, PRA 24,170 (1981) 

----- 

1 

0 

100 200 300 400 500 600 700 

Photon Energy (eV) 

Figure 5 U13UA Comparison of present results with two early theoretical 

predictions. [J.C. Levin, G. Bradley Armen, and LA. Sellin (U. Tennessee)]. 
Syed B. Qadri Naval Research Laboratory 

Energy dispersive diffraction techniques at NSLS are extensively used in 

obtaining diffraction from samples ofmicroscopic dimensions such as with specimens contained in diamond-anvil cells 

(DAC) under extreme pressure and temperature conditions. The essential components of energy-dispersive x-ray diffraction (EDXD) system consist of an 

Si(Li) or intrinsic Ge detector and a FET 

preamplifier, both cooled by liquid nitrogen, andamultichannel analyzer (MCA). 

The use of this system in conjunction 

with the X17C beamline at the NSLS, 

which produces polychromatic x-rays using a high magnetic field of the superconductingwiggler (4.6-4.8Tesla) , has made 

possible the study of solid state phase 

transitions and equations of state in real 

time. With the advancement of diamond 

anvil cell technology, pressures as high as 

2.5-3.0 Mbar which are comparable to 

the pressure at the center of the earth 

(+ 3.5 Mbar) are routinely achieved. In 

the diamond anvil cell, the specimen is 

confined in the hole of a gasket between 

opposing diamonds and the pressure is 

"Y 

30 

25 2$ 

! 

g 20 

E 

5 a 

I 1lo 

5 

'10 15 20 25 30 35 40 

Figure 1 XI 7C:The energy dispersive x-ray diffraction patterns of 

the laser heated iron at 125 CPa, showing that a new diffraction 

line (arrow) develops as the diffraction lines from rFe disappear 

above 3000 K. The 100,101,1 IO, and 1 12 reflections of rFe are 

located at 17.33, 19.71, 30.07, and 35.81 keV, respectively 

(Ed=33.94 keVi\). The heating cycle starts with the bottom curve 

and moves upwards. (C. S. Yoo, J. Akella, A. J. Campbell, H. K. Mao, 

and R. J. Hemley, Science, 270,1473,1995). 

applied iy mechanically squeezing the diamonds. In the 

case of multi-megabar pressures, the size of the gasket 

hole hence the sample size is reduced to as small as 10 pm 

diameter. Thus the use of conventional x-ray sources 

becomes impractical, and intense synchrotron radiation 

becomes essential for high pressure research. The use of 

energy-dispersive x-ray diffraction is not limited to structural information at extreme pressure and temperature 

conditions, it is also extremely useful in single-crystal 

studies of microscopic dimensions approaching 40 nm 

diameters with volumes of attoliters. Highlights of the 

most recent work performed using EDXD techniques 

and wiggler-produced synchrotron radiation on beamline 

X17C are reviewed in this article. 

Since iron is the main component of the earth's 

core, studies of phase transitions at high pressures and 

temperatures are of fundamental interest to geophysicists. 

C. S. Yo0 from Lawrence Livermore National Laboratory 

in collaboration with associates at Carnegie Institution of 

Washington (CIW), using an integrated diamond-anvil 

cell, x-ray, and laser heating apparatus examined the iron 

phase diagram by directly probing the crystal structure of 

the phases in situ to 130 gigapascals (GPa) and 3500K. 

Their system consisted of three components (i) a Ndyttrium-aluminum-garnet laser heating system to heat the 

sample in the diamond-anvil cell, (ii) a microscope system 

to measure temperature andview the sample for alignment 

and direct observation, and (iii) a synchrotron x-ray and 

energy dispersive diffraction system. Figure 1 shows the 

x-ray diffraction patterns of the laser heated iron at 125 

13 
I 

P @Pa) 

Figure 2 X17C: Constraints for the phase diagram of iron. 

Various symbols indicate the phases of iron as determined by in 

sifu x-ray diffraction at high pressures and temperatures: liquid 

iron (1 ), E-Fe (m ), &'-Fe (A), yFe (s), and new crystalline (n). The 

area indicated by the large rectangle constrains the location of 

the ET liquid triple point. The hatched area indicates the P-T 

region of which the E' phase forms between 15 and 40 CPa. 

Previously reported phase boundaries are also reproduced for 

comparison: melting lines are reproduced from R. Boehler, 

Nature, 363,534, (1 993) (upper dashed lines), from S. K. Saxena, 

C. Shen, P. Lazor, Science, 260, 1312, (1993): ibid. 264, 405, 

(1 994), ( upper dotted line, and from 4. William ef a/., Science, 

236,181 ,1987, (dashed-dotted line), and e-b boundaries are 

shown from R. Boehler, Nature, 363,534, (1 993), (lower dashed 

line) and from S. K. Saxena efal., Science, 260,131 2, (1 993); ibid 

264,405, (1994) (lower dotted line). ( C. S. Yoo, J. Akella, A. J. 

Campbell, H. K. Mao, and R. J. Hemley,Science, 270,1473,1995). 

GPa and Figure 2 shows the phase diagram of iron. Iron 

in the hexagonal close-packed (hcp) phase (E-Fe) is stable 

from 50 to 110 GPa at high temperatures. The wide 

pressure range stability of E-Fe indicates that this polymorph should be the most relevant solid phase for earth's 

core. [see C. S. Yoo, J. Akella, A. J. Campbell, H. K. Mao, 

and J. R. Hemley, Science, 270, 1473, (1995)l. 

S. K. Saxena and his colleagues from the Institute of 

Earth Sciences, Uppsala University in collaboration with 

CIW using apparatus similar to the foregoing, showed 

that &-phase transforms to another phase (possibly a 

polytype double-layer hcp) at a pressure of about 38 GPa 

and at temperatures between 1200 and 1500K. This 

information has important implications for the phase 

relations in the earth's core. [see S. K. Saxena, L. S. 

Dubrrovinsky, P. Haggkvist, Y. Cerenius, G. Shen, and 

H. K. Mao, Science, 269, 1703-1704, (1995)l. 

14 

Iron sulfide (FeS) has been found in 

many meteorites and is a possible component of the cores ofEarth, Mars and other 

terrestrial planets. In models simulating 

the internal structure of the planets, accurate determinations of phase relations and 

densities of FeS at high pressure and high 

temperature are required. Previous phase 

transformations of FeS were performed at 

high pressure and at ambient temperature. 

Y. Fei and his colleagues from CIW using 

synchrotron x-ray diffraction measurements showed that FeS transforms to a 

hexagonal NiAs superstructure with axial 

ratio (c/a) close to the ideal packing ratio 

of 1.63 at high pressure and high temperature. They also determined the densities 

ofFeS IVat high pressure and temperature 

and used these data to evaluate the depth 

of the Martian core-mantle boundary and 

the sulfur content of the core. Figure 3 

shows the EDXD diffraction spectra ofthe 

different phases of FeS and Figure 4 the 

experimentally determined phase 

diagram.[seeY. Fei, C. T. Prewitt, H. K. 

Mao, and C. M. Bertka, Science, 268, 

The equation of state and phase stability are the most fundamental properties 

in the understanding the physics of materials at ultra high pressures. However, the 

reliability of equation of state determinations at large compressions is uncertain 

because the stress state at multimegabar 

1892-1894, (1995)l. 

static pressures is not well understood. 

Due, Hemley and Mao from CIW using synchrotron xray diffraction in a diamond anvil cell determined the 

equation of state, elasticity and shear strength of magnesium oxide to 227 GPa. Their equation of state can 

describe ultrasonic, shock, and static compression for 

MgO. They showed that it is possible to characterize 

material strength and elastic anisotropy at ultra high 

pressure directly from diffraction data. Their results also 

show that there are significant changes in the degree and 

character ofthe elasticanisotropy ofMg0 at high pressure 

and that the strength at high pressures differs significantly 

from predictions based on low-pressure measurements. 

[seeT. S. Due, R. J. Hemley, andH. K. Mao, Phy. Rev. 

Lett., 74, 1371, (19991. 

(Mg,Fe)SiO, perovskite is the predominant phase 

of the lower mantle and the most abundant mineral in 

Earth. C. Meade, H. K. Mao and J. 2. Hu from CIW 
Figure 3 XI 7C: Energy-dispersive x-ray diffraction 

spectra of the high-pressure-temperature phase of FeS 

(FeS IV) (upper spectrum) and the high pressure phase 

(FeS 111) (lower spectrum). The diffraction pattern of FeS 

IV was indexed with a hexagonal cell. The hkl indices 

are indicated from for each diffraction peak. The peak 

positions for FeS 111 are indicated by the interplanar d 

spacing in A. [ Y. Fei, C. T. Prewitt, H. fC Mao, and C. M. 

Bertka, Science, 268,1892, (1 995). 

FeSIV . 

d I ?I P=l5GPa 

T= 623 K 

Energy (keV) 

studied the crystallography of Earth's lower mantle 

using synchrotron x-ray diffraction from a laserheated diamond anvil cell. Their experiments show 

that silicate perovskite maintains its orthorhombic 

symmetry at 38 GPa and 1850K. Th eir a measurements at 65 and 70 GPa provide evidence for a 

temperature-induced orthorhombic-to-cubic phase 

transition and dissociation to an assemblage of 

perovskite and mixed oxides. If these phase transitions occur in Earth, they will require a significant 

change in mineralogical models ofthelower mantle. 

[see C. Meade, H. K. Mao, and J. 2. Hu, Science, 

268, 1743, 13951. 

Some of the other highlights of the work from 

CNGr include the work of DufFy etal. on the singlecrystal of brucite, Mg(OH),, to 14 GPa in a quasihydrostatic pressure medium using a DAC and 

EDXD synchrotron x-ray diffraction [see T. S. 

Due, J. Shu, H. K. Mao, and J. R Hemley, Pbys. 

Chem. Minerah, 22, 277, 19951. They proposed 

the structural change in brucite is driven by a 

destabilization of the H substructure as the materials are compressed. No evidence was found for a 

transition involving the Mg-0 substructure over 

the pressure range of the experiments. 

Skelton and associates from the Naval Research Laboratory (NE) have studied a number 

of high temperature superconductors, in search 

of evidence of structural inhomogeneities. By 

illuminating the samples with 10 pm beam, 

small changes in the c-axis lattice were detected 

and were interpreted as evidence of variations in 

the oxygen content in YB~CU,O,~ . For all 

samples, the data reveal small structural variations on a spatial scale 10 to 20 pm, heretofore 

not seen. For the YB~CU,O,~ the observed 

effect is believed to be due to changes in oxygen. 

In the case of N%-xCexCu04-y the observed 

structural variances are interpreted in terms of 

changes in the Ce content. These results emphasize the need for caution in interpreting experimental results for high temperature superconductors (HTS). As the smaller beam sizes are 

achieved, they are likely to observe significant 

structural defects in sub-pm length scales. Ideally, as spatial resolution increases, more subtle 

questions regarding the nature of the defect 

structures and their origins can be answered [see 

Skelton etal., SPIE, 2516,160,1995]. 

+Martian core 

g 1200 '"4 I 

IV 

Figure 4 X17C Experimentally determined phase 

diagram of FeS. Experimental data (reported only near 

the phase boundary) are represented by symbols. (m) 

FeS I, Nib-type structure with a (d3a,2c) unit cell; (1) FeS 

11, MnP-type structure; (0) FeS Ill, monoclinic?; (s) FeS IV, 

NiAs-type structure with a (2a,c) unit cell. 1 Y. Fei, C. T. 

Prewitt, H. K Mao, and C. M. Bertka, Science, 268,1892, 

15 
I 

I I I I 

20 25 30 35 40 45 

Energy (keV) 

Figure 5x1 7C: EDXD spectra of 8.2nm particle size PbS 

taken at different pressures. The onset of cubic-to - orthorhombic transition at a pressure of 30.0 kbar can 

be realized. 

G.S. Cargill I11 and P.C. Wang from Columbia 

University in collaboration with IBM Research and BNL 

Applied Science are developing a system for measuring 

strain, microstructure and composition using EDXD 

with micron or submicron spatial resolution on beamline 

X26C. They use 5 to 30 keV photons collimated and 

concentrated by a tapered glass capillary. [See their 

abstract under X26C abstracts]. In their experimental 

setup the hue patterns are measured using an area CCD 

detector while the lattice spacings and compositions are 

measured using an energy sensitive Si detector. 

The Pd-H system is probably the most extensively 

investigated of all metal-hydrogen systems. Nevertheless, 

some of its properties at high hydrogen concentration still 

remain unexplained. Skelton etal. from NRL using up to 

80 keV x-ray photons monitored the crystallography of a 

microspot 18~10-'~ m3 in volume, as D was electrochemically loaded into a 1 mm diameter Pd wire. Because of the 

penetrating power of the high energy x-ray photons 

available on X17C, this spot could be located anywhere 

within wire. Using this, the a-p transition induced in the 

Pd by the absorption (or desorption) of D was monitored 

from the outer edge to the core of the wire. Results show 

that, although the a-phase forms rapidly at both the 

surface and core, there is considerable delay in the initiation of the P-phase at the core compared to that at the 

surface. 

1G 

Qadri et al. from NRL initiated the work to determine the effect of nanometer size particles on the pressure 

induced phase transitions. For this the PbS particles were 

synthesized by a new technique. The three-dimensionally 

periodic and interconnected mesomorphous structure of 

a bicontinuous cubic phase was controlled through the 

pore size and ionic diffusion. The particles were extracted 

from the lipid micro structure and capped with thiol 

molecules. Their size and crystallinity were characterized 

by TEM and XRD. The high pressure studies were 

performed using polychromatic x-rays on X17C at NSLS. 

At 2.5 GPa pressure and room temperature, PbS transforms from the NaC1-structure to an orthorhombic phase. 

This transition is sluggish and accompanied by a large 

hysterisis. The results show a significant increase in the 

on-set of the transition pressure as the particle size was 

reduced. Figure 5 shows a series of EDXD spectra of PbS 

samples of 8.2 nm particle size as a function of 

increasing pressure. 
I 

LITHOG~PHY, MtCROSCOPY, AND T~MOCRAPHY 

G. P. Williams 

NSLS 

X-RAY MICROSCOPY 

General 

The X1A x-ray microscope beamline serves an increasing number of users, to the point where beam time is 

oversubscribed. Activities which have been reportedon in 

previous years continue to see further development. In 

the coming year, the beamline will be upgraded to have 

two, independently controlled monochromators with an 

optimized design providing increased flux and monochromaticity. This will lead to a downtime of several 

months, but increased productivity afterwards. 

The Stony Brook group continues to carry out 

studies involving imaging and chemical state mapping in 

biological samples. Also, at Stony Brook, a new scanning 

x-ray microscope system is being developed by J. Maser et 

al. in which the specimen will be held at liquid nitrogen 

temperature in a vacuum chamber. This will allow the 

examination of biological specimens which have been 

frozen with water in an amorphous (rather than crystalline) state, leading to more faithful specimen preparation 

and improved radiation robustness. Commissioning of 

the system began at the end of the year, and first cry0 

experiments are expected in the coming year. 

The North Carolina State group has continued 

studying various polymer samples in collaboration with 

Dow Chemical, AlliedSignal and DuPont. X-rayAbsorption Near Edge Structure, or XANES, microscopy is 

ideally suited for the study of multicomponent polymers 

and their morphology, structured and layered polymer 

systems, as well as the microchemical characterization of 

precipititates of unknown chemical composition. Soft 

X-ray Transmission microscopy operated in the XANES 

mode is also an excellent tool for acquiring high quality 

spectra from a variety of polymers which would be difficult to accomplish otherwise due to problems with sample 

preparation. Linear Dichroism microscopy has been 

utilized to semi-quantitatively determine the lateral order 

of Kevlar fibers. 

New Zone Pkztes 

In collaboration with Don Tennant ofAT&T Bell 

Laboratories, Steve Spector and Chris Jacobsen of Stony 

Brook have recently made new zone plates for the scanning transmission x-ray microscope which have an outer 

zonewidthof30 nm as opposed to thepreviouslyavailable 

45 nm (the resolution scales with zone width). These zone 

plates were fabricated using a new electron beam lithography system at Bell Labs, and were patterned by etching 

germanium. Present efforts are aimed at boosting the 

efficiency up to the level predicted by theory, and at using 

nickel plating for zone plate fabrication. 

Dark-jekd Imaging 

The Scanning Transmission X-ray Microscope 

(STXM), located at beamline XlA, usually forms absorption images of biological specimens using Fresnel zone 

plates. The wavelength is tuned to where there is a large 

difference in the x-ray absorption of carbon and oxygen to 

image micron-thick cells in water, for example. Signals 

other than absorption can be used to form an image, such 

as in dark-field imaging where only the x-rays scattered by 

the specimen are detected. Studies by Henry Chapman, 

Chris Jacobsen, and Jenny Fu (all of the department of 

Physics, SUNYat Stony Brook) haveshown that dark-field 

imaging is a particularly sensitive way of imaging 

colloidal-gold labels in cells. These small (on the order of 

20 nm in diameter) particles can be bound to specific 

antigens, genetic sequences, cellular organelles, or proteins so that specific functions of a cell can be localized. 

The techniques are highly developed in the electron 

microscopy community for labelling thin sections of cells, 

but whole cells are too thick to be imaged by electrons. 

Dark-field x-ray microscopy forms the bridge between 

fluorescence confocal microscopy and electron microsCOPYEven though the label particles are smaller than the 

resolution of the microscope they are still easily detected 

in the dark-field mode. A whole human fibroblast cell is 

shown in Figure 1 which has had the protein tubulin 

labelled with colloidal gold. The image is actually a 
composite of a bright-field image and 

a dark-field image. The bright-field 

signal is shown in grey-the color indicates thex-ray absorption, mainly due 

to carbon. The dark-field signal is 

shown in red, and reveals only microtubules (fibers composed of tubulin). 

The same cell was also examined in an 

electron microscope. While the resolution was much better, the electron 

microscope could not show the microtubules in regions of high carbon 

density, such as across the nucleus. 

The cell was prepared and labelled by 

Karen Hedberg, University of Oregon. 

Phase Retrieval Experiments 

Phase retrieval of images collected in the STXM at beamlineXlA 

has been achieved by applying the 

new method of Wigner-distribution 

deconvolution. This research, by 

Henry Chapman of SUNY at Stony 

Brook, has yieldedvery accurate highresolution images of the phase and 

amplitude of the x-ray transmission of 

various specimens, such as the 

0.5-micrometer-diameter latexsphere 

shown in the Figure 2. 

- 7w 

Figure 1 X1 A: Composite of dark-field and bright-field image of 

whole human fibroblast cell. Measurements made by Chapman 

et al. 

- 

To determine the x-ray phase retardation of an 

object, microdiffraction patterns (or coherent 

convergent-beam diffraction patterns) are collected in the 

STXM with a CCD detector. As the specimen is scanned 

in two dimensions, a 2-D microdiffraction pattern is 

collected at each point in the scan. The map of intensity 

recorded in a single element of the CCD versus the 

specimen position is acoherent image that can be thought 

of as being formed by a self-interferometric process. By 

four-dimensional Fourier transformation, the ensemble 

of images is analysed to find the relative phases of all pairs 

of image points that are separated by particular displacement vectors, from which a phase map can be determined. 

This method has also been used to map the phase errors 

(aberrations) of an Fresnel zone pate at the x-ray wavelength at which it is used for forming images, and for 

measuring the mutual coherence of an x-ray beam. In 

addition, super-resolved STXM images could be acquired 

by this method in making use of the high-angle diffraction 

data. 

18 

IR MICROSPECTROSCOPY 

General 

At the U2B beamline there have been a number of 

studies using the IR microspectrometer which is a 

Spetra-Tech IRuS instrument operated by 

Northrop-Grumman Corporation and the NSLS. This 

instrument operates at a spatial resolution close to the 

diffraction limit, i.e in the 3-1 5 micron range. It has been 

used for studies of materials ranging from semiconductors 

(Larry Carr, Northrop-Grumman) to human hair (Dave 

Wetzel et aZ., Kansas State U.) to minerals (Nicole 

Guilhaumou, Laboratoire de Geologie URA 13 16, Paris, 

France and Paul Dumas LURE-CNRS, Centre 

Universitaire, Paris-Sud) . 

Semiconductors and Devices 

Larry Carr of Northrop-Grumman has studied the 

ternary II-VI semiconductor compound CdZnTe, which 

is used for both electronic and optical applications. 
C 

0.5 

0.0 s 

-0.53 

-1.0; 

-I.? 

Y 

C 

-2.0 

0.0 0.5 1.0 1.5 

Position (pn) 

Figure 2XlA: (a) An image of the phase retardation 

of 400 eV x-rays transmitted through a 0.5- 

micrometer-diameter latex sphere, and a plot (b) 

from that image compared with the calculated phase. 

In (c) is part of the data set of coherent images 

collected in the STXM used for retrieving the phase. 

The location of each image in the grid is indicative of 

the location of the CCD pixel from which that image 

was formed. The nine images with bright 

backgrounds, for example, were recorded by CCD 

pixels that are illuminated by the annular pupil of the 

zone-plate. Each image is 1.5 micrometer wide. 

Measurements made by Chapman et a/. 

The studies are of the material in wafer form. 

Precipitates of Te were found in the material. These 

precipitates are only about 10 microns in diameter and 

thus beyond the capability of conventional IR 

microspectroscopy. 2-D maps can be made using the 

difference in transmission of Te in the IR as a contrast 

mechanism. In another study, Larry Carr also studied 

epi-layers for opto-electronic devices, and particularly 

those called vertical cavity surface emitting lasers. These 

are complex patterns of layers of III-V semiconductor 

compounds grown epitaxially on GaAs. These particular 

devices will see applications as flat panel displays. 

Human Hair 

Dave Wetzel(Kansas State University), in conjunction with Kathryn Kalasinsky (Div. of Forensic Toxicology, Armed Forces Inst. of Pathology, Washington, DC), 

has been studying drugs of abuse and their metabolites, 

deposited in human hair. The spatial resolution of a few 

microns permits drug traces to be mapped within thin 

longitudinal hair sections. Furthermore 5 microns corresponds to about 20 minutes of hair growth, so that the 

timing of drug use might be able to be determined. These 

studies are difficult since the absorption strength of the 

carbonyl band for example, a product of cocaine use, is 

only a few tenths of a percent. However the brightness 

and stability of the source do permit these measurements 

to be made. 

Fluid Inchions in Rocks 

Nicole Guilhaumou (Laboratoire de Geologie URA 

1316, Paris, France) and Paul Dumas (LURE-CNRS, 

Centre Universitaire, Paris-Sud) have studied fluid inclusions in oil-bearing mineral samples. These inclusions are 

in fluorite and were indeed found to contain oil, and CO, 

as bubbles. Measurements of the integrated intensities for 

the respective vibrational modes, allow chemical maps to 

be obtained for each component within the fluid inclusion. In Figure 3 (See Section Divider on Page 88) we 

show a photograph of an inclusion and then maps for the 

oil and the CO, (namely the antisymmetric stretch mode 

of CH, at 2920 cm-' and the symmetric stretch mode of 

CO, at 2335 cm-I). One clearly sees the location of these 

two components inside the inclusion. The relative intensity is related to the local density. If the oil is homogeneous, thevarious intensities are related to the thicknesses 

of the areas probed. In addition, the frequencies of the 

modes change with pressure, opening up the possibility of 

determining the pressure-temperature situation when the 

inclusions were formed. One can also test for water and 

in this case, no water bands were detected inside the 

inclusion. 

Toward Near-Field IR Microspectroscopy 

At the present time, the spatial resolution achieved 

at the IR microspectroscopy facility at beamline U2B is 

limited by diffraction to the wavelengths in use, i.e from 

3 - 15 microns. Near-field microscopy is a method for 

extending this spatial resolution by confining the light to 

a structure smaller than the wavelength, typically through 

the use of tapered light guides. However, such structures 

are often highly inefficient and appropriate only for very 

high brightness sources such as lasers. In a study using a 

13 micron pinhole to confine the beam, Larry Carr found 

that it was possible to drive waveguide modes in the 

19 
pinholestructure, resultingin an enhanced 

throughput for particular wavelengths. 

This is illustrated in Figure 4a, which 

shows the transmitted intensity pattern as 

a function of illumination position across 

the pinhole. Each panel represents an 

intensity “map” for a particular wavelength. At the top left is the case where the 

wavelength is short compared to the pinhole, so normal geometric optics describe 

the situation. At top right, the wavelength 

is 7 microns and two regions of enhanced 

throughput are observed. The pattern 

suggests that an 0 1 mode is being excited 

within the pinhole structure. Similarly, a 

single central region of enhanced throughput is observed for wavelengths near 14 

microns, indicating that the 00 mode is 

excited. Coupling to such modes is one 

method for improving the throughput 

while confining the light to asize substantially smaller than its wavelength. An 

understanding of the transmission properties of this and similar structures should 

be useful in optimizing an efficient 

near-field tip structure for 

microspectroscopy with synchrotron radiation. Extending this concept to smaller 

dimensions, in Figure 4b we show the 

ratio of 2 transmission spectra through a 3 

micron pinhole, which in the absence of 

noise would give a straight line at 1. It can 

X=Ppm ?.=7pm 

10 

- 5 f 

u 

E 

- ro 

0 Q 

s 

-5 

-1 0 

-10 -5 0 5 IO 

?.=lOpm 

10 

-5 f 

Ho 

Y 

C 

0 P 

-5 

-1 0 

.io -5 0 5 lo 

X-position bm] 

IO 

-5 f 

230 

u 

C 

0 P 

-5 

-1 0 

-io -5 0 5 lo 

h=14pm 

10 

- 5 E 

Y 

E 

JO 

s 

0 Q 

-5 

-1 0 

-10 -5 0 5 10 

X-position bm] 

Figure 4a U2B: (a). Towards near-field IR microspectroscopy. 

Intensities measured through a 13 micron pinhole at various 

wavelengths by Larry Can; (Northrop-Grumman). 

be seen that good performance is obtained even for 

wavelengths to almost 3 times the pinhole size. The actual 

spectrum is shown in the inset. 

Microtomography 

Acomputed microtomography users’ facility is presently being developed atX27C with the support of BNL‘s 

Computingand Communications Division (CCD), Mobil 

Corporation, and GTE. The facility will provide 

non-destructive volumetric images of specimens of variable size with resolutions from 1 to 100 microns, depending on the instantaneous field of view. The facility presently includes a 12-bit digital ccd camera to capture 2-D 

radiographs of each view angle. These radiographs are 

then processed within a reconstruction program to create 

2-D slices. The slices can be stacked to create a volume 

rendering using graphics programs such as Data Explorer, 

Iris Explorer or IDL. A user facility under development 

at CCD will also allow stereoscopic viewing of the reconstructed volumes in the near future. 

20 

Over the past year, 2-D slices as well as volume 

renderings have been obtained for pore structures of 

several seal rockand oil reservoir core samples provided by 

Mobil Corporation. The pore structure of the samples 

were resolved to 3 microns. Other samples analyzed at 

this CMT facility atX27C include meteorites, lead sulfate 

crystals growing in a glass matrix, and synthetic rock. 

Figure 5 (See Cover) shows a volume rendering of a test 

sample of 100 micron diameter glass spheres in a capillary 

of 5 micron wall thickness. 

X-RAY FLUORESCENCE MICROPROBE 

The X2GA x-ray fluorescence microprobe can map 

trace elemental distributions of ppm concentrations at a 

spatial resolution of about ten micrometers and has been 

used by SGa Bajt, Steve Sutton (CARS, U. of Chicago), 

Patterson Nuessle (SREL, U. of Georgia) and collaborators for a variety of systems from biology to geology. 

Increasingly, the microprobe is also being used for x-ray 
Wavelength [pm] 

I09 8 7 6 5 4 3 

I .I 

0 

(P 

rY 

3 1.0 

0.9 

0.8 

L -I 

I000 1500 2000 2500 3000 

Frequency [cm-I] 

Figure 4b U2B Reproducibility (noise) as a function of wavelength 

through a 3 micron pinhole showing the increased performance at 

shorter wavelengths due to the wave-guiding, near-field effects discussed 

in the text. The actual spectrum is shown in the inset. 

absorption spectroscopy measurements when both good 

spatial resolution and the sensitivity are required. Scientists from the Earth, planetary, and environmental sciences are still the major users of the beamline, although we 

observed increased interest among scientists from 

agronomy and forestry departments. 

The X26A x-ray fluorescence microprobe can map 

trace elemental distributions of ppm concentrations at a 

spatial resolution of about ten micrometers and has been 

used by SGa Bajt and collaborators for avariety ofsystems 

from biology to geology. Increasingly, the microprobe is 

also being used for x-ray absorption spectroscopy measurements when both good spatial resolution and the 

sensitivity are required. Scientists from the Earth, planetary, and environmental sciences are still the major users 

of the beamline, although we observed increased interest 

among scientists from agronomy and forestry departments. 

Earth Planetary and 

Environmental Studies 

One of the interesting 

experiments using trace element analysis and mappingwas 

performed on garnets by 

SUNY at Stony Brook (For 

Figure 6 See Section Divider 

on Page 64). Major element 

compositional zoning in garnets (of the elements Fey Mn, 

Mg, and Cay for example) is 

commonly used to evaluate the 

pressure, temperature, and reaction history ofmetamorphic 

rocks. The garnets in this rock 

display smooth increases in Fe 

abundance (30 to 38 wt. % 

FeO) and decreases in Mn 

abundance (5 to 0.4 wt. % 

MnO) from the core to the 

rim. Such zoning profiles are 

common in garnets and are 

typically interpreted as the 

product of a single 

garnet-forming reaction during a single episode of metamorphism with increasing 

pressure and temperature. 

However, what the synchrotronx-ray fluorescence (SXRI) 

scans show is that, unlike major elements, trace elements 

such as Y display oscillatory zoning which varies by orders 

of magnitude in abundance (3 to 4000 ppm). These 

variations in trace element zoning correspondwith changes 

in textural zoning within the garnet defined by the abundance of inclusions, something the major element zoning 

does not do. Thus, both textural and trace element zoning 

profiles suggest that these garnets grew from discontinuous reactions. 

Trace element zoning was studied also in alpha and 

beta quartz to understand their significance for the origin 

of comb layering in porphyry inclusions (US Geological 

Survey). A continued study on determination of trace 

element composition of stratospheric interplanetary dust 

particles (large versus small) and observation of Br loss in 

these particles as a function of time for which particles 

were exposed to the synchrotron radiation was performed 

(SUNY at Plattsburgh and CARS). 

In addition to a solid state detector, fluorescence has 

also been detected with a wavelength dispersive spectrometer (WDS). This has enabled a study of intracrystalline 

21 
rare earth element (REE) distributions in fluoroapatite. 

Observed partitioning of RE& argues against differential 

incorporation due to growth rate anisotropies but it 

supports the proposed model that differences in the 

atomicstructure between <OO 1> and <O 1 1> steps leads to 

differential incorporation in apatite (SUNY at Stony 

Brook). A reversal in the REE partitioning trend was 

observed for Pr and Nd suggesting than ion size has an 

effect on the partitioning between nonequivalent steps. 

Another study focused on the three dimensional spatial 

resolution of compositionally distinct growth sectors and 

subsectors in mineral crystals. Thesesectors andsubsectors 

preserved a record ofsurface processes and growth mechanisms. The goal of this study at the moment is to explain 

topaz crystal growth on a molecular scale (SUNYat Stony 

Brook). 

The determination of ferridferrous ratios in micrometer regions on amphiboles and glasses using the 

energyposition ofthe pre-edge peakin FeXANES spectra 

showed a good agreement with the results obtained by 

Mossbauer spectroscopy and wet chemistry techniques. 

This confirms previous results that the position of a 

pre-edge peak in the absorption spectrum is not very 

sensitive to the coordination geometrywhen using appropriate standards (Rutgers U. and CARS). Another way of 

looking at the near-edge region is studying pre-edge 

inelastic scattering using a WDS (BNL and CARS). 

Further progress has been made on determination of the 

structure and speciation of zinc complexes in individual 

fluid inclusions (only about 50 microns in size) using 

micro-EXAFS. Experiments at elevated temperatures, up 

to 350 degrees Celsius, were done with a well calibrated 

heating stage. The results suggest that Zn complex remained predominately ZnCIt-, the dominant complex of 

Zn observed at room temperature, but further experiments at even higher temperatures are underway (South 

West Missouri State U., St. FrancisXavier U. and CARS). 

Environmental studies included determination of 

oxidation states of Cr contaminated solid particles and the 

efficiency ofinsitucr reduction methods. Cr(VI)/Cr(III) 

ratios could be probed on particles as small as 40 microns 

and near-edge structure was correlated to WS measurements (SREL). The effect of oxidation state on chromium leaching for a contaminated/stabilized soil was also 

studied by a group from the US Army Corps of Engineers 

and scientists from Purdue University. The Savannah 

River Ecology Institute group conducted time resolved in 

situ Fe XANES measurements on clay minerals which 

catalyze the oxidation of organo-boron complexes used in 

reclamation of radio-Cs contaminated nuclear waste. 

Another type of time resolved in situ experiment was 

carried out to track selenium and chromium transport 

22 

and reduction across the boundary between ponded waters and sediments (LBL). The results showed reduction 

of Sew) to Se(IV) and ultimately Se(0) within specific 

zones in the sediments and were consistent with 

diffusion-limited transport calculation. Micro-XANES 

ruled out the possible formation of colloidal Se(0) and 

organo-Se compounds in these ponded waters. The 

chromium oxidation state was studied in a CCA pressure 

treated wood and it has been found that Cr was reduced 

to pure C?, on the surface and in the inner part of the 

wood (Forestry Dept., U. of Wisconsin). Iodine XANES 

measurements were acquired in a He environment to 

study iodine sorption on different minerals. Intriguing 

results showed that magnetite, biotite and pyrite (Fe rich 

minerals in this study) underwent different reactions 

when in touch with iodide or iodate solutions as compared to Fe poor minerals (BNL). 

In addition, a new 13 element Ge detector was 

successllly used to collect data with a 10 micron monochromatic collimated beam to study olivine grains from 

chondrites (primitive meteorites that usually contain mm 

sized spheres called chondrules) that are usually only 

20-50 microns in size and havevery low concentrations of 

Cr (U. of New Mexico and CARS). Without the 13 

element Ge detector this experiment would be impossible. The results obtained are significant because, based 

on the fact that transition of CP to C? occurs over avery 

narrow range of oxygen fugacity, the micro-XANES 

approach may lead to highly sensitive method for determining the redox conditions of formation for individual 

chondrules. 

Plant and Wood Diseme; 

The blast disease of rice, caused by the fungus 

Pyricularia gfiea, is one of the most important plant 

diseases worldwide because rice is a major source of food 

for 60% of the Earth's population. Manganese is an 

essential mineral element for photosynthesis, lignin synthesis, and other plant metabolic functions in its Mn2+ or 

Mn3+ forms, but when oxidized to Mn4+ it precipitates as 

physiologically unavailable Mn oxides and hydroxides. In 

the healthy areas of the leaf all of the Mn is in the 

physiologically available MnZ+ form. In the blue area, 

which corresponds to the lesion in the photograph Figure 

7,80% of the Mn is present as Mn4+ (See Section Divider 

on page 96). Thus most of the Mn in the lesion is in the 

unavailableMn4+ form. Oxidation ofsoluble MnZ+ to give 

insoluble Mn4+ oxides may be the first step in the mechanism bywhich the fungus infects healthyplants. Ifso, this 

research may provide important new information for 

combating this devastating plant disease. 
Manganese near-edge spectroscopy was also used to 

study the effects of two different fungi on wood (Forestry 

Dept., U. of Wisconsin). One study was an in vivo 

measurement of the Mn oxidation states on wood that 

had been attacked by a tree disease fungus. The other was 

to study a very dangerous white-root fungus (wood decay 

fungus). The results suggest that these quite different 

funguses both contain enzymes that oxidize Mn" to 

Mn4+. 

Electrochemistry 

The x-ray fluorescence microprobe was used to 

study the corrosion resistance of stainless steels. Presence 

of molybdenum in stainless steels is believed to improve 

the corrosion resistance, and different models have been 

proposed on how and why this happens. Some models 

suggest that molybdenum forms a salt layer during the 

dissolution ofthe steel, and this process was studied insitu 

atX26A. Scanning the beam across the steel, asalt layer on 

thesteel, andtheconcentrateddissolutionproducts within 

an artificial pit, concentrations changes of the constituent 

alloying elements were monitored. Results suggest that 

the salt layer was mainly formed by iron chloride and not 

molybdenum therefore negating proposed corrosion inhibition by a molybdenum forming salt layer (BNL). 

On the X26C beam line an experiment was preformed using x-ray fluorescence with high energy resolution spectrometer (total energy resolution of 1 eV or 

better). The analysis of x-ray fluorescence with this high 

energy resolution can provide detailed information on the 

electronic structure of the sample in addition to quantitative elemental analysis of the sample. Preliminary results 

from a series of chromium oxides demonstrate the sensitivity of this technique to the oxidation state of the sample 

(NSLS and CARS). 

LITHOGRAPHY 

Extreme Ultra- violet Projection Lithography 

AT&T Bell Labs continues to progress on beam line 

Ul3UB with the development of Extreme Ultraviolet 

Lithography (EUVL). The technique is the diffraction 

limited imaging ofcircuit features with dimensions around 

lOOnm using multilayer coated mirrors and light of 

wavelength around 13nm. The technique is one of the 

main contenders for the new lithography technology that 

is scheduled to be required around the turn ofthe century. 

The AT&T EUVL program at Brookhaven is part of a 

larger coordinated effort involving Intel, AMD, Sandia 

National Laboratory, Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, and 

Sematech. This year Kiyosho Fujii ofNEC, who has been 

working on EUVL for over a year, joined the AT&T 

group. 

The main progress this last year has been the assembly and commissioning of a new EUVL printing camera 

capable of imaging over a large field (For Figure 8, See 

Section Divider on Page 73). Significant progress has 

also been made on the interferometry techniques that are 

required to be developed in this wavelength range. The 

13nm interferometer based on U13UB has demonstrated 

that lateral shearing phase measuring interferometry can 

measure the wavefront of 13nm light to 0.02 waves rms. 

This is the required accuracy for measuring the wavefront 

at the image plane of EUVL cameras and represents one 

of the important first steps in the establishment of EW 

interferometry. 

LIGA 

In recent years the technique of LIGA, a German 

acronym which translates to X-Ray Lithography, Electroplating, and Plastic Molding, has emerged as the cutting 

edge technology in the manufacture of small, 

high-precision mechanical devices. 

At the NSLS, the X-Ray Ring provides a unique 

opportunity for the utilization of hard x-rays to extend 

high precision manufacturing using lithographic techniques to length scales on the order of centimeters. 

Conventional LIGA techniques typically yield structures 

less than 500 mm thick. The deep penetration of hard 

X-rays in the resist provides the additional opportunity to 

fabricate true 3-D objects with re-entrant geometries, in 

contrast to the 2-D structures typical of standard LIGA 

techniques. 

A research program based on this technique is 

currently being developed at the NSLS R&D beamline 

X27B by E. Johnson, I?. Siddons, and C. Milne. Current 

activities are focused on resist exposure and processing 

parameters with a view to optimizing device quality. 

23 
Craig E. Thorn 

BNL Physics Department 

Since beginning operations in 1990, the Laser 

Electron Gamma Source facility (LEGS) has routinely 

produced tagged-photons up to 330 MeV by backscattering laser light from 2.58 GeV electrons circulating in 

a storage ring of the National Synchrotron Light Source 

at BNL. Work is underway that will increase the energy 

to 470 MeV. The chief distinguishing characteristics of 

LEGS are the very high degree of polarization (-90%) of 

its photon beams, accompanied by very low backgrounds. The LEGS ficility was constructed by its BNL 

staff, assisted by a group from Frascati National Laboratory, Italy. The small BNL contingent shoulders most 

of the burden of the maintenance and operation of 

LEGS, as well as organizing the development of the new 

instrumentation needed to maintain state-of-the-art capabilities. 

Carrying out a research program requires a much 

larger group and collaborations with other institutions 

are essential. The “LEGS Collaboration” consists of 

BNL, Frascati, and five Universities: Rome-11, Virginia, 

VirginiaPolytechnic Institute, South Carolina, and Ohio. 

This LEGS Collaboration has been responsible for -2/3 

of the scientific research. The remaining 1/3 has been 

conducted by enlarged collaborations, including LEGS, 

with “outside” spokespersons of proposals that undergo 

a review process. (A basic requirement for approval of 

LEGS experiments is that polarization observables make 

a significant impact on the physics questions being 

addressed. This has resulted in a strong coupling to 

theoretical models and a focus on light nuclei.) 

POLARIZED COMPTON SCATTERING 

FROM THE PROTON 

New precision measurements of cross sections and 

polarization asymmetries in Compton Scattering of polarized photons from protons at 90” c.m. are presented 

for incident energies between 213 and 333 MeV. A long 

standing problem with earlier experiments that appeared 

to violate unitarity at the peak of the A is resolved. These 

24 

data have been compared to theories based on baryon 

resonance structure and to dispersion relations. Recent 

calculations using the proton polarizabilities are closest to 

the data, although inconsistencies are observed near the A 

resonance. 

Elastic (Compton) scattering of intermediate energy 

photons from the proton is a potentially rich source of 

structure information. It is sensitive to the proton’s 

electric and magnetic polarizabilities, to the deformation 

of the nucleon through the electric yNA coupling, and 

even to the sign of the no decay constant, FR . There are 

many published calculations for Compton scattering. These 

can be grouped into two general categories, those based on 

the baryon resonance spectrum or its underlying quark 

structure, and those relying upon unitarity and dispersion 

relations to phenomenologically describe elastic scattering 

in terms of photo-pion production. These calculations 

give significantly different predictions, particularly in the 

region of the A resonance. 

A lower unitarity bound on the Compton cross 

sections, which avoids the uncertainties of dispersion 

calculations, can be constructed by using n-production to 

evaluate the imaginary parts of the amplitudes while 

setting their real parts to zero. Beyond this, minimal real 

parts can be formed from the s- and u-channel Born and tchannel no-pole graphs. These exercises lead to a common 

conclusion. Previously published data near the peak of the 

A resonance, and particularly at 90” center of mass (c.m.), 

appear to completely exhaust these bounds, if not violate 

them, and leave no room for the t-channel dispersive 

contributions. 

The chief experimental background to Compton 

scattering comes from the y(p,no)p channel, where one 

high energy photon from no-decay is detected. The cross 

section for this process is -200 times that expected from 

Compton scattering. Both the p(y,y)p and the p(y,no)p 

reactions are completely specified by two kinematic 

observables. In this measurement, six quantities were 

measured: the beam energy, the scattered y-ray energy, the 

polar and azimuthal angles of the recoil proton, and the 

proton’s TOF and energy. This large degree of kinematic 
over-determination has two important consequences. First, it 

guarantees an accurate separation 

of the two competing channels, 

even at high beam energies. Secondly, it enables all detector eEciencies to be evaluated directly 

from the data itsel6 without resorting to simulations and thus 

avoiding their associated uncertainties. 

Thespin-averaged Compton 

cross sections for 9O'c.m from the 

present work (LEGS Exp. L8), 

corrected for finite detector acceptances, are plotted as the solid 

circles in Figure 1 together with 

previous results. There have been 

two other recent measurements of 

the Compton cross sections. At 

the Saskatchewan Accelerator Lab 

(SAL), simulations were used to 

extract the component from scattered bremsstrahlung (open 

circles), while in measurements 

with tagged photons at Mainz 

(cross in Figure l), highly collimated detectors were used to isolatecoincidences. Both areconsistent with our results. Data from 

the earlier CornelU61, Toky0/64, 

L'vov Dispersion Multipoles: 0 LEGSL8 

Full (FA93) x Mainz/95 

0 SAL193 

Re [A] + 0 A Illinois/67 

0 Moscow/66 i- Tokvol64 

Figure 1 : Spin-averaged Compton cross sections for 90" c.m. (see 

text for full description). 

Illinoisl67, and Bond76 experiments at energies higher 

or lower than the A peak are either consistent or slightly 

lower than the new group of measurements from LEGS, 

Mainz and SAL. Why these earlier results are so dramatiNEW MEASUREMENTS OF D(y,p)n AND 

SPIN PROBLEMS IN COUPLED NA/NN 

INTERACTIONS 

cally lower near the resonance energy is not known. 

The solid curve in Figure 1 is a prediction using the 

model of L'vov, in which recent (y,p) multipoles have 

been used to calculate the imaginary parts of the scattering 

amplitudes while low energy measurements of the proton 

polarizabilities have been used to fK the dispersion integrals. This gives a reasonable description of the new data, 

except for an over-prediction near the A peak. The dotted 

curve restricts the real parts to their Born and no-pole 

values, and the dashed curve gives the unitarity bound 

obtained by setting the real parts to zero. Although 

slightly lower bounds have been obtained with other pion 

multipoles, all are significantly higher near the A peak 

than the four points from CornelU61, Tokyo/64, 

Illinois/67 and Bonn/76. Although these four measurements appear to be in quitegood agreement, we assert that 

they are, nonetheless, quite wrong. 

New precision measurements ofthe reaction D (y,p)n 

taken with tagged, polarized photons, and covering a wide 

angular range, are presented for incident energies between 

113 and 3 15 MeV. In the region of the A resonance, the 

photodisintegration observables can potentially be used 

to probe the NA interaction. Coupled-channel calculations are in agreement with cross sections measured with 

linear polarization parallel to the reaction plane but fail to 

account for data taken with perpendicular kinematics. 

Although the A isobar dominates nuclear reactions 

from pion threshold to about 1 GeV, its interaction with 

the nucleon is still poorly known. Microscopic reaction 

models necessarily require a consistent treatment of the 

NA and NN interactions. While the parameters of the 

NN force can be directly determined from nucleon scattering data, the NA interaction must be inferred from 

processes such as nD+nNN andnD+NN for which the 
Figure 2: Angular distributions at 300 MeV for the two 

orthogonal spin state of the D(y,p)n reaction (see text for 

full description). 

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, nA or yA entrance channels, 

and leading to NN, nA or pNN final states. Several such 

calculations have been developed in recent years. In these 

works, the nD+nD and nD+nNN cross sections are 

reasonably well described, primarily because quasi-free 

scattering dominates there. However, pion and photon 

absorption channels have proven to be more challenging. 

The predicted effects of the NA interaction are of 

course largest near the energy of the A resonance, and 

polarization observables are expected to be rather sensitive 

to the NA potential. The reaction D(y,p)n can provide an 

interesting test for NN/NA coupled-channel models since, 

26 

as first noted by Leidemann and 

Arenhovel, both the cross section and the 

beam-polarization asymmetry are sensitive to the NA force. Unfortunately, 

comparisons with existing data have 

tended to be somewhat inconclusive due 

to a rather large spread in published results. Correlating the comparisons with 

cross sections and asymmetries, which 

might help remove some of the ambiguities, has been problematic because the 

two have never been measured in the same 

experiment. We present here highlights 

of recent measurements of the D(y,p)n 

reaction at the LEGS facility, which are 

the first to directly measure G,, and ol. 

Angular distributions at 300 MeVfor the 

two orthogonal spin-states are shown in 

Figure 2. 

In the y+N system, delta excitation 

is almostpurelyM1, althoughwhen transformed to the deuteron-CM many magnetic as well as electricmultipoles contribute. The dotted curves in the figures have 

been calculated by decomposing the elementary MI+ (isospin-3/2) multipole of 

y+N into a sum of Born and resonant 

terms. The resonance part was parameterized with a Breit-Wigner shape and 

the yNA coupling was extracted from the 

fit to the MI+ (3/2) amplitude, as determined from N(y,p) data. In the y+A CM 

frame, all multipoles with L14 were included. In this fitting procedure, the yNA 

coupling was allowed to be both complex 

and energy-dependent, thereby absorbing the effects of pion-rescattering, while 

preserving unitarity. The result reproduces the general 

features of the cross sections and polarization observables, 

particularly the shift of the resonance position from the 

free NA value (317 MeV) which is due mainly to pionrescattering, and the negative asymmetry in the region of 

the resonance which reflects the spin dependence of the 

elementary y+N amplitudes. Nonetheless, the dotted 

curves significantly underestimate the data in the region 

of the delta resonance. 

The discrepancy between these predictions and the 

data increases with energy, suggesting that the method of 

decomposing the amplitudes into background and resonant components is incomplete. Greater flexibility in the 

models can be obtained by dropping the Born terms in the 

y+N amplitudes and refitting a modified yNA coupling of 

. . ,. . 
the elementaryM,+ (3/2) multipole, now purelyresonant, 

to N(y,p) data. Such a procedure has the potential for 

double-counting pion-exchange current (n-MEC) contributions. This effect has been estimated and the associated uncertainty is shown as the light-shaded band. Since 

the amplitudes certainly must contain non-resonant terms, 

the improvement obtained with this effective coupling 

suggests that the use of static n-MEC is inadequate and 

non-local effects are important. 

In the region of the A resonance, the band of curves 

corresponding to the modified yNA coupling are centered 

slightly above the total cross section data, while their 

predictions at 90” are consistently low. This is due to a 

depression in the calculated angular distributions near 

90”, which grows with energy. A similar “90”-dip” is a 

common feature of most yA+pn calculations near 300 

MeV, even appearing in earlier works that did not include 

coupled-channel treatments. 

The behavior of the cross section measured with 

parallel kinematics (Figure 2, bottom), is quite well 

reproduced by the calculation with the modified yNA 

coupling, and even the fitted-yNA curve has the correct 

shape. The apparent “90”-dip” arises entirely from the 

predictions for the perpendicular spin orientation (Figure 

2, top). Although interference with the Born amplitudes, 

which contain high angular momentum components, can 

potentially affect angular distributions, this is evidently 

not the origin of the 90” depression since the fitted-yNA 

calculation, which explicitly includes the Born terms, has 

a similar shape. In addition, the modified-yNA predictions for are consistently higher than the data at forward 

and backward angles, although both the calculations and 

the data for converge to the values at 0” and 180” where 

the azimuthal polarization angle becomes undefined. 

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 

cross sections. Although the model parameters of the 

calculations discussed here were fitted to NN phase shifts, 

all assumed static NN potentials, with retardation effects 

included only in the NA and NN-NA-transition potentials. The additional use of retarded potentials in the NN 

interaction could significantly alter the angular momentum decomposition. 

~ ~ 

CDC Magnet XTAL Box 

pb Glass pn Bars End Cap Target Coil Corner Nal 

\ \ \ I / 

I 

/ 1 I \ 

Forward XTALBox Magnet Drift Target Wire Chambers Face Nal Cryostat Chamber Cryostat 

(CW 

y Be&n 

Figure 3: SPHICE, a Strongly Polarized Hydrogen and Deutemim ICE Target, and SASY, the 

Spin Asymmetry Array, at LEGS. 

27 
In summary, precise values for the cross section and 

beam polarization observables in deuteron photodisintegration are now available throughout the energy region 

sensitive to the NA force. Static-NN coupled-channel 

calculations are in good agreement with the new data 

taken in parallel kinematics but fail to reproduce the 

perpendicular polarization state. The inclusion of retardation, particularly in the n-MEC, and possibly an explicit treatment of 2n-channels, may be some of the more 

hopeful avenues to reconciling theory and experiment. 

THE DRELL-HEARN-GERASIMOV SUM 

RULE AND SPIN POLARIZABILITY OF 

THE NUCLEON 

A new phase of LEGS, with experiments beginning 

in 1996, will focus on measurements of double-polarization observables. This will involve a order of magnitude 

increase in the complexity of experiments and the associated instrumentation. The new collaboration responsible 

for the development of this phase - the LSC, or LEGSSpin Collaboration - consists of -45 physicists (including 

7 graduate students) from BNL, seven US Universities - 

(Christopher Newport, Norfolkstate, Ohio, South Carolina, Syracuse, Virginia Polytechnic Institute & SU, and 

Virginia), and five European institutions (Frascati, 

Genova, Giepen, IPN-Orsay, and Rome-11). The new 

experiments will utilize the highiy polarized LEGS photon beams and SPHICE, a frozen-spin hydrogen and 

deuterium target. An 430% 4n detector for neutrals and 

charged hadrons, SASY (the Spin Asymmetry array) will 

be constructed for these measurements. A drawing of 

SASY and SPHICE is shown in Figure 3. Much of 1996 

will be devoted to preparing for this new phase of activity. 

SPHICE represents an innovative new technology for 

polarized targets and its fabrication requires considerable 

preparation. First targets should be available at the 

beginning of 1997. Installation of the “core” elements of 

the SASY detector - large arrays of NaI(Tl), Lead Glass, 

and Plastic Scintillator - will take place early in 1996. The 

full design, including a superconducting solenoidal magnet and a Time Projection Chamber, will be installed by 

the end of 1997. 

SPHICE, a Strongly Polarized Hydrogen and Deuterium ICE Target, represents a new technology utilizing 

molecular HD in the solid phase. The coupling between 

the nucleon spin and the atomic lattice, which is primarily 

through molecular rotations, causes the spin allignment 

to relax back to the unpolarized state. This represents the 

chief limitation on conventional “frozen-spin’’ targets. 

However, the heteronuclear HD molecule, consisting of 

non-identical particles, does not have any restrictions on 

the orbital and spin angular momenta and hence can be in 

28 

the molecular-rotation state J=O, independent of the H or 

D spin orientations at low temperature. Thus, the spinlattice coupling, and the corresponding relaxation rates, 

are exceedingly small and imply a sample whose spins 

would remain “frozen” for many days even at 4°K. 

The forward Compton cross section for initial and 

final photon polarizations E and E’ has been given by 

Gell-Mann, Goldberger and Thirring as, 

+’ + + +’ A(o)=~(~)E E;+;~o~(o~)o - ( E 3 

where B is the target spinor. The spin independent$(&), 

and spin dependent, g(&) , amplitudes can be expanded 

in a Taylor series, 

fi02)=fio)+y (0102 + o(04) 

g(o2)=g(O)+fy(O)o2 + O(o4) 

where the prime-symbol indicates differentiation with 

respect to 02. Here,f(O) is the Thomson scattering limit 

that corresponds to oscillating the nucleon up and down 

with the electromagnetic field of the photon. j’(0) is 

identified with the sum of the electric and magnetic 

polarizabilities of the target and measures how the constituents of the target rearrange themselves in response to 

the applied electromagnetic field. In analogy, g‘(0) is 

referred to as the spin-dependent polarizability of the 

nucleon. The GGT dispersion relations provide a sum 

rule for this spin polgizability (y), 

y=g‘(O)=’IZ -0 do 

4n2 @j 

Here o~,~ and B~~ are the total reaction cross sections 

measured with the photon helicity oriented opposite to 

the nucleon polarization or parallel to it, respectively. 

Another GGT dispersion relation can be written down for 

do) 3 00 

g(0) - g(-) =‘I 01n-03n do 

412 07 

Low, Gell-Mann and Goldberger (LGG) have evaluated 

g(0) in terms of K, the anomalous magnetic moment of 

the target, 

g(0) = -CXK2/2m2 

Drell and Hearn, and independently Gerasimov (DHG), 

have noted that under the assumption g(=) = 0, asum rule 

is obtained that relates these polarized reaction cross 

sections to the anomalous magnetic moment of the target, 

In a recent work by members of this group, [Phy 

Rev., D50, R6681, (1994)], these integrals have been 

evaluated using the FA93 photo-pion multipole analysis 

of the VPI group to predict the spin dependent cross 

sections. This multipole set extends out to 1.7 GeV, and 
the integrals appear to have converged above about 1.2 

GeV. The result ofthese calculations for the average ofthe 

proton and neutron sum rules are summarized in Table 1. 

(In the literature the DHG sum rule is usually broken up 

into vector, V, scalar, S, and mixed vector-scalar, VS, 

components. The proton-neutron average corresponds 

to the VS sum rule.) The FA93 prediction of -225 x10" 

fm2 (or pb) for DHG,, shows impressive agreement 

(2.7%) with the value expected from the anomalous 

-65 x 10" fm2 

izability, comparisons can be made with Chiral perturbation theory. Relativistic-calculations for y have been reported that include all diagrams to the one-loop order, 

excluding those involving a delta. The delta effects are 

large, and they have estimated the contributions from the 

dominant diagrams. The result, -98 x loG fm4, is within 

14% of the FA93 evaluation. This is very encouraging 

agreement, although the final word must await a calculation which includes all delta contributions to the same 

+15 x 10" fm2 

magnetic moments, -219 x 10" fm2. For the spin polar- order. 

Table 1 : Multipole predictions forthey and DHC sum rules on the proton +neutron, compared with chiral perturbation 

theory predictions for y and with the magnetic moment predictions for DHC. 

Yv+s=l /2(YP+YJ 

DHG,=l/2(DHGp+DHGJ 

XPT 

-98~10-~ fm4 

FA93 (VPI-SAID) 

-86~10~ fm4

-225x1 0" fm2 

22Eg - (K; +K,z),- 

-219x10" fm2 

Since in xPT the delta contributions for the neutron and the proton are the same, the uncertainties in the oneloop calculation disappear when we consider the difference, 1/2(proton-neutron). These results are summarized in 

Table 2. Now, the relativistic one-loop value for y is in impressive agreement with the FA93 evaluation. However, 

in sharp contrast, the predictions for y are very different from the magnetic moment values - both in sign and a factor 

of 4 in magnitude. 

Table 2: Multipole predictions for the difference sum rules, 1 /2(proton -neutron), compared with chiral perturbation 

theory predictions for y and with the magnetic moment predictions for DHG. 

Yv+s= WYp-YJ 

DHGvts= 1 /2(DHGpDHGJ 

XPT 

-52 x loG fm4 

The results in Table 2 are quite puzzling. In 

principle, the different energy weightings of the and 

integrals admit the possibility that contributions above 

the 1.7 GeV limit of the VPI data base could bring the 

value up to that expected by the sum-rule, without 

appreciably affecting. However, 1.7 GeV is already so 

large that such differences would have to be huge in order 

to overcome the energy weighting. For example, 200 mb 

between 2 and 3 GeV, which would require a prominent 

FA93 (WI-SAID) 

-48 x fm4 

but as yet unidentified resonance; or a constant level of - 

20 mb extending out to 100 GeV, which would be much 

larger than the contributions of the resonance region in 

which the isospin structure of the D and N* states can be 

expected to enhance the proton-neutron difference. Apart 

from such scenarios, which seem highly unlikely, there are 

only two other possibilities. Either a) both the two-loop 

corrections to the spin polarizability are large and the 

existing multiples are wrong, or b) modifications to the 

29 
DHG sum rule are needed to fully describe the isospin 

structure of the nucleon. 

It is possible that the two-loop corrections to the 

calculations for y are large. Although this is not usually 

the case for expansions, it would not be without precedence. This would imply that the multipoles would have 

to be modified. Changing the multipoles would potentially affect the predictions for a variety of observables. 

Although it is possible to imagine complicated alterations 

that would leave cross sections and single-polarization 

observables largely unaffected, several double-polarization observables would have to change significantly. As 

yet, there are no measurements of these quantities. 

Alternatively, if the multipoles are basically correct, 

then the DHG sum rule requires at least a modification of 

the form, 

DHG,,+ DHG, - C 

and the simplest choice for the correction factor would be 

C=27~~[9~(-) -gn(-)], with$(-) =-gn(-) ~cL,. In other 

words, contrary to the original DHG assumptions, gp 

and would tend to nearly equal but opposite constants at 

high energy. The physical origins ofsuch constants would 

be quite interesting, although other choices for have also 

been proposed. The DHGm integral is just the Q' = 0 

limit of the Bjorken sum rule integral, and C= 0 has been 

assumed in modeling its Qz evolution. The Q2 dependence of a possible non-zero g(-) remains to be considered. 

This is a challenging question that will be pursued 

in planned experiments at many different laboratories. 

Since the key physics issues with the least model dependence are in the proton-neutron difference, each ofwhich 

involves cross section differences themselves, considerable 

care must be taken by the experimenters to minimize 

systematic uncertainties. The approach at LEGS is to 

carry out the proton and neutron measurements 

simultaneously with the new polarized target, 

SPHICE. 

LEGS is supported by theU.S. Department ofEnergy under Contract DE-AC02-76-CH00016, by the Instituto 

Nazionale di Fisica Nucleare, Italy, and by the U.S. National Science Foundation. 

30 

Y 
r , - - , - , 

,A' , 

'\ i -2 

SCATTERING AND CRYSTALLOGRAPHY - 

STUDIES OFBIOLOGICAL MATERIALS 

Lonny Berman 

NSLS 

HOLOGRAPHY 

In x-ray holography, the wavefield diffracted by a 

specimen is mixed with a reference wave to encode its 

amplitude and phase in a hologram. A team including S. 

Lindaas and M. Howells from Lawrence Berkeley National Laboratory, and C. Jacobsen and S. Spector from 

SUNY at Stony Brook, has used the coherent soft x-ray 

beam from the XlA undulator beamline to record in-line 

holograms on photo resists. The developed photo resist 

encodes the x-ray intensity distribution as a surface relief 

pattern on photo resist. Thus, the hologram, which has 

no inherent magnification, is well suited to being recovered by using a specially-built, linear field atomic force 

microscope to "read" the photo resist. The image is then 

reconstructed by Fresnel transformation of the digitized 

hologram in a computer (iterative algorithms are also 

under development for reduction of the so-called ''twin 

image" present in these in-line holograms). By this 

approach, 40 nm resolution images of fibroblasts have 

been obtained, and experiments will soon begin aimed at 

recording holograms of frozen-hydrated specimens using 

a cryo-holography system. 

MACROMOLECULAR 

CRYSTALLOGRAPHY 

On beam line XU, 12 new MAD (multiwavelength anomalous dispersion) phased structures werepublished in the past year (see X4A publication list). The 

method was extended bv the assortment of eleFigure 1 X12C: A representative electron density map of the 

a,, peptide crystal. See text for full description. 

ments now being used for MAD experiments. 

Of the structures reported, 8 were heavy atom 

derivatives (6 Hg, 1 Yb, and 1 U), 3 

selenomethionine-substituted, and the final one 

a Zn-containing protein. The energy range for 

experiments was extended to the U M, edge at 

3.728 keV (3.326 A) (Y. Liu and W. 

Hendrickson, unpublished) at the low energy 

end to the U LIII edge (17.17 keV, 0.72A) at the 

high energy end. At the low energy end, the 

experimenters showed the feasibility of exploiting the large (80 electron) anomalous signal. In 

the U LIII edge experiment, the structure of the 

cell surface adhesion molecule cadherin was 

determined (L. Shapiro, A.M. Fannon, P.D. 

Kwong, A. Thompson, M.S. Lehmann, G. 

Griibel, J.-F. Legrand, J. Als-Nielsen, D.R. 

Colman, and W.A. Hendrickson, Nature, 374, 

During the past year, data collection for 

MAD experiments on beamline X12C has become essentially automatic. The user prepares a 

script to define the data collection, including the 

use of the "Friedel flip" to measure Bijvoet pairs 

327-337, [1995]). 

31 
Figure 2 X12C: The solvent-accessible surface area of the outside (a) and inside (b) of the TYMV virion 

as visualized by GRASP (A. Nicholls, K. Sharp, and B. Honig, Profeins, 11,281 -296, [I 9911). The virion is 

made up of 180 copies of the 21 kD coat protein, arranged icosahedrally. The pentameric and hexameric 

units of coat protein are nearly indistinguishable on the outside of the virion, but are very different on the 

interior. 

if necessary; then, the sobare takes over. At each 

wavelength change, the absorption spectrum of the heavy 

atom is measured, the feature of the spectrum that defines 

a data collection wavelength (inflection point, peak, etc.) 

is analyzed, the monochromator is set to that feature, and 

data collection proceeds. Several MAD structures have 

been solved with this method. 

An exciting result from X12C, that was made possible by its versatile kappa diffractometer, was the direct 

solving of a 450-atom structure. This was the a, peptide, 

solved by G. PrivC of the University of Toronto and D. 

Eisenberg of UCLA. This peptide was designed to form 

an alpha helix and to self-assemble into a four-helix 

bundle. Data were taken from a crystal of the peptide to 

a resolution of 0.92 A while it was kept frozen at 100 K. 

The structure was solved by the direct method known as 

"shake-and-bake," developed by the Hauptman group in 

Buffalo. The resulting structure shows four antiparallel 

helices. A representative electron density map from this 

structure, revealing the atoms of a leucine residue, is 

shown in Figure 1. 

One of the classic structures in all of structural 

biology has been turnip yellow mosaic virus (TYMV), 

having been studied for over 50 years. In the 1960s, 

Caspar and Klug determined its surface structure in some 

of their earliest work on reconstruction of viruses from 

electron micrographs. In work done by M.A. Canady, A. 

32 

McPherson, and co-workers from the University of California at Riverside, the structure of this virus has been 

solved to 3.2 8, resolution, using techniques that have 

become standard for virus crystallographers (isomorphous 

replacement and molecular averaging). Many of the data 

used to solve the structure were measured at X12C. Use 

of the long working distance and 2 &angle tilt of the 

X12C diffractometer allowed data to be collected to 3.0 A 

resolution, even with one of the unit-cell edges being over 

500 A. 

The overall structure of TYMV is similar to that of 

other spherical viruses, with the surface of the virion 

displaying very prominent protrusions at the icosahedral 

fivefold and pseudo-sixfold axes (see Figure 2). These 

protrusions correspond to the pentameric and hexameric 

units of the coat protein (Figure 3). The structure of the 

monomer has the same so-called jellyroll fold as the plant 

viruses and several animal viruses such as polio and the 

common cold (Figure 4). TYMV is an interesting model 

for study ofvirus assembly because it has unusually strong 

protein-protein contacts. Also, it is able to release its RNA 

in vitro; it loses a pentamer or hexamer from the protein 

capsid. The research team predicts that it is most likely a 

pentamer that leaves, uncorking the virus to allow RNA 

release, since the pentamer makes fewer contacts with the 

protein capsid. This finding will lend insight to the study 

of the viral life cycle in infected cells with the prospect of 
U 

Figure 3X 12C: The pentameric (3a) and hexameric (3b) units of the TYMV capsid. The primary structure of the 

monomers is identical, but because they are placed in different environments in the capsid they each have a 

slightly different conformation. This is most evident at the N terminus, which crosses under the hexameric units 

but is disordered at the pentamer. This figure was generated using MOLSCRIPT, described by P.J. Kraulis, J.App/. 

Crysfa/ogr., 24,946-950, [I 9911). 

saving the lives of turnips worldwide. 

Turning to another MAD experiment, the structure 

of a specific complex between the p50 subunit of the 

transcription factor NFKB and DNA was solved using 

X25 and X4A, by C.W. Muller, F.A. Rey, M. Sodeoka, 

G.L. Verdine, and S.C. Harrison of the Howard Hughes 

Medical Institute and Harvard University (work reported 

in Namre, 373,311-317, [1995]). In particular, thevery 

high intensity available at X25 was essential to the success 

of this project. Three orthogonal views this complex are 

shown in Figure 5 (see Section Divider on page 8). The 

p50 protein(365 amino-acid residues in the form shown 

here) binds to DNA as a dimer. Its polypeptide chain 

(represented as a ribbon) folds into 2 domains (colored 

yellow and red). The amino-terminal domain(yel1ow) 

contains most of the segments that interact specifically 

with DNA; the carboxy-terminal domain (red) mediates 

dimerization. The DNA(b1ue) contains 11 base pairs. 

LAUE DIFFRACTION CRYSTALLOGRAPHY 

Recent work on X26C by B. Stoddard of the University of Washington involved the trapping of steadystate intermediates by the clever choice of site-directed 

mutants. The reaction investigated was that catalyzed by 

isocitrate dehydrogenase (IDH). The reaction proceeds 

in two steps. The first is the transformation of isocitrate 

to oxalosuccinate, an intermediate that had never actually 

been observed before this experiment. The second is 

conversion of this to a-ketoglutarate. Each of these is 

catalyzed by a different portion of the enzyme. The 

workers were able to prepare site-directed mutants of the 

enzyme that blocked first one, then the other step of the 

reaction. Then they determined the structure of the 

intermediate states of the enzyme through use of the hue 

diffraction method. Crystals of both mutants of IDH 

were mounted in flow cells. Diffraction data were taken 

first on the apo-enzymes, i.e. with no substrate nor 

cofactors present in the solution. Then the reactants were 

flowed into the cell and full three-dimensional data were 

taken. The species that were to be observed should 

represent a steady-state accumulation of intermediates of 

the reaction. The importance of using this rapid method 

for data collection was that the crystals themselves were 

not stable in the presence of the reactants-only a short 

time was available to take the data before the crystals fell 

apart. 

The results of the two experiments are revealed in 

Figure 6. On the left is shown the accumulation of the 

reactants NADP+ towards the bottom and isocitrate 

complexed to a magnesium ion at the top and towards the 

rear. Accumulation of the supposed intermediate 

oxalosuccinate is revealed in the right hand side of the 

figure. The dramatic difference that is seen between the 
Figure 4 X12C: The monomer of the TYMV 

capsid. The fold of the TYMV monomer is the 

canonical jellyroll fold, an 8 stranded p sheet. 

This fold has been found in almost every virus 

structure solved to date. The finding that the N 

terminus was interior to the virus was surprising, 

since immunological work had placed it on the 

exterior. TheTYMV coat protein is unique in that 

it has an unusually high number of prolines 

(1 0.5% of the residues). Very few prolines are 

found in the ordered secondarystructure; rather, 

they are concentrated at the ends of the p 

sheets, at the beginnings of the helices, and 

mostly in the outer loops. This figure was 

generated using MOLSCRIPT. 

two halves of the figure arises from the loss of electron 

density in the portion of the NADPH molecule that 

includes the nicotinamide ring and its phosphate backbone. This structure confirms nicely the appearance ofthe 

oxalosuccinate intermediate, which had only been proposed before this experiment. 

The author wishes to acknowledge the contributions to this section by Stephen Harrison (Harvard U.), 

Chris Jacobsen (SUNYOStony Brook), Craig Ogata 

(Howard Hughes Medical Institute) and Bob Sweet (BNL 

- Biology). 

Figure 6 X26C: See text for description. 

34 
Jim Long Naval Research Lab 

Jon Levin 

University of Tennessee 

I. INTRODUCTION 

The promise of using the pulsed nature of synchrotron radiation (SR) for time-resolved investigations, envisaged since the inception of dedicated storage rings, is 

being fulfilled by a stable community of users at NSLS. A - wide variety of experiments, encompassing the fdl range 

of available photon energies, from far-infrared to hard x 

ray, are presently carried out on gases, liquids, solids, and 

surfaces. The time domain ranges from subnanosecond, 

limited by the synchrotron pulse duration, to 100's of 

nanoseconds, limited by the synchrotron interpulse period. These parameters depend on which ofthe two rings 

at NSLS, the X-Ray or the VUV, is employed and are 

listed in Table 1. 

Most pulsed, time-resolved studies require that only 

one electron bunch circulate in the X-Ray 0 Ring 

rather than the usual 25 (7). The need for only one bunch 

(1-B) depends on the experiment. For example, the 

longer time window available between SR pulses in 1-B 

fills (see Table 1) may be necessary to record long time - 

decays. Similarly, a long time window circumvents - 

overlapping photoion time-of-flight spectra. Finally, the __ -- -~ 

number of photons per pulse increases in 1-B operations, 

by factors of -.3 on the VUV Ring and + 10 on the X-Ray 

Ring, with a concomitant improvement in signal for 

experiments with duty-factor limitations imposed by 

detectors or, in the case of some pump-probe studies, by 

low pump-laser repetition rates. The 1-B fills are scheduled for only limited periods to ameliorate the impact on 

other users caused by the reduced lifetime and iriected 

current. The X-Ray Ring is formally schedukdays of 1-B operations per year. Timing opere 

VUV Ring are scheduled with less formality: 8 or I - shifts, dependent on day ofweek, are requested a week in 

advance. 

Highlights of work performed on each ring are 

presented below. 

CI 

11. WRING 

U9B 

The time-dependent fluorescent emission from biological molecules reveals important information on their 

photophysical and structural properties. Most biological 

molecules begin absorbing only in the UV, requiring 

excitation with pulsed synchrotron radiation if conveTable 1 : NSLS Storage-ring characteristics relevant to time-resolved experiments. 

Maximum 

Radio Maximum Minimum interpulse Nominal 

bunches period (single duration 

bunch) (FWHM) 

1 VUV Ring 53 MHz 9 19 ns 170 ns 1.5 ns (a) 

(750 MeV) 

X-Ra Ring 53 MHz 30 19 ns 566 ns 0.6 ns (b) 

~ (2.5 8eV) 

Frequency number of interpulse period pulse 

(RF) 

(a) With 4th harmoniccavity powered, trapezoidal profile. Pulse lengths of 200 ps (calculated) expected in future 

special operations. 

(b) Single bunch, 90 mA beam current. 
nient tunability of the excitation energy is desired. 

When performed with 

photon energies less than 

the 7-eV water cutoff, 

fluorimetry is a desirable 

approach since natural 

aqueous environments 

may be employed. John 

Sutherland (BNL-Biology) and coworkers have 

been examining biological molecules such as peptides (protein building 

blocks) for some time using a fluorimeter capable 

of measuring the time decay of fluorescence and its 

polarization at preselected 

fluorescent wavelengths. 

Until recently, mapping out the wavelength 

dependence of the fluorescence decay time required time-consuming 

accumulations for each 

discrete wavelength, leading to inevitable gaps in 

emission wavelength and 

often necessitating that 

spectral resolution be 

compromised in order to 

reduce the time for each 

515 nm 

Time (ns) 200 230 nm 

Figure 1 U9B: Example of fluorescence excited by synchrotron radiation pulses of 

290- nm wavelength as obtained with the new fluorimeter on U9B. The fluorescent 

intensity is resolved simolfuneously into time t (after excitation), wavelength h, and 

polarization. The data for fluorescence polarization parallel (4 I) and perpendicular 

(A,) to the exciting synchrotron radiation polarization are displayed as separate relief 

plots of intensity I v5. t and h. The seven distinct time spectra correspond to the seven 

bunches in the ring at the time of the measurement. The sample is outer surface 

protein A (Osp A), a major antigen of the Lyme disease bacterium, in water at 6O C. 

This protein contains a lone tryptophan fluophor, which is believed to initiate a 

conformation change once it absorbs. The data suggest that the new conformation 

does not include a rotation of the tryptophan residue since the transition-dipole 

moments do not reorient in time, Le., I, does not grow at the expense of the initially 

populated moments which emit predominantly with Ilk The efficient data ratesfrom 

the new instrument will provide detailed dynamical information on biological 

molecules. (Lisa A. Kelly, John Trunk, Junyan Shi, and John C. Sutherland). 

accumulation. As described in last year's NSLS Activity 

Report, this is no longer the case with the commissioning 

of a new fluorimeter, capable of measuring the time decay 

spectrum simultaneously with an entire emission spectrum. The instrument uses a two dimensional 

histogramming memory to associate the time of arrival of 

a fluorescent photon, detected with a microchannel plate 

(MCP) at the output of the fluorescence spectrometer, 

with the photon's position, detected with a positionsensitive anode placed after the MCP and over which the 

emission spectrum is dispersed. 

In the past year, a new capability was added which 

enables the measurement, also simultaneously, of changes 

in the polarization anisotropy of fluorescent emission. 

When a rigid molecule is excited with linearlypolarized 

light, it fluoresces predominantly with the same polarization. However, since motion of the molecule after excitation will reorient the transition dipole, monitoring the 

fluorescence polarization both parallel and perpendicular 

36 

to that of excitation provides a unique means of assessing, 

for example, time-dependent protein conformational 

changes. To obtain the polarization information simultaneously, a Wollaston (double deviating) prism was introduced into the fluorescence optical train in order to 

separate the propagation directions of the two polarizations away from each other. This has the effect of 

producing two different wavelength spectra, one for each 

polarization direction, with one displaced above the other 

on the 2-dimensional position-sensitive anode at the 

output of the spectrometer. The fluorimeter thus now 

records in a four-dimensional space: fluorescence intensity I us. time, wavelength, and polarization. 

Figure 1 illustrates results obtained, inaequo at 6' C, 

from the lone tryptophan component of outer surface 

protein A (Osp A), a major antigen to the bacterium 

responsible for Lyme disease. The time axis encompasses 

one round-trip time of the VUV Ring, which was operating in 7-bunch mode so that seven distinct emission 

.. . . .. -. .> 
spectra, one for each pulse, appear. Fluorescence anisotropy is evident since Ill> IL. It is generally believed that 

a protein such as Osp A exhibits a conformational change 

in response to tryptophan photoexcitation. If as a result 

the tryptophan itself were to rotate, a time-dependent 

anisotropy would be observed, which these preliminary 

data suggest is not the case. 

U13 UA 

The many-body problem is pervasive in all of physics. In fact, it is not too much ofan exaggeration to say that 

the lack of an exact solution to even the three-body 

problem is at the root of most theoretical attempts at 

understanding physical phenomena. 

Helium is the simplest atomic three-body system, 

and therefore the simplest which can exhibit electronelectron correlation. As a result, photoionization of 

helium has long been used as a testing ground for understanding correlation phenomena, such as autoionization, 

correlation-satellite production (shakeup) and double 

photoionization. At higher photon energies, Compton 

scattering can produce single or double ionization of 

helium with a cross section which dominates that of 

photoionization. Theoretical prediction of the energy 

dependence of the double photo- or Compton ionization 

of helium is a fundamental problem in atomic physics 

which requires solution of the Coulomb three-bodyproblem. 

At low energies (the double-ionization threshold is 

at 79 eV), many measurements have been made of the 

ratio ofhelium double to single 

photoionization cross sections. 

Recent theories which relate 

the ratio due to energetic 

charged particle impact, which 

is well-established experimentally, to that following photoionization near threshold, have 

concluded that theexistinglowenergy measurements are systematically high. Jon Levin 

and co-workers have made helium ion time-of-flight measurements on Ul3UA extending from threshold to 700 eV 

which are consistently below 

earlier measurements and in 

better agreement with theory 

(Figure 2). 

111. X-RAY RJNG 

During single-bunch operations, at least four research groups conducted timing experiments on as many 

beamlines during 1995, with several groups working on 

more than one line. Historically, some beam lines have 

been used extensively during 1-B operations, and have 

even become oversubscribed. The result is that some 

groups perform experiments on several lines in order to 

obtain access to the relatively limited 1-B time. 

During the first beam time of a new proposal by 

Ralf Wehlia (working with Letitia Pibida, Jon Levin and 

Ivan Sellin, U. Tennessee), electron spectra as well as 

electron-electron coincidence spectra have been obtained 

around the argon K edge. Monochromatized synchrotron light intersected an effusive gas beam and electrons 

coming from this interaction region were detected with a 

cylindrical mirror analyzer (CMA) and a time-of-flight 

(TOF) spectrometer. The TOF spectrometer, whose use 

requires the availability of 1-B operations, and the CMA 

were mounted horizontally in a plane perpendicular to the 

photon beam. The CMA was equiped with a positionsensitive anode, thereby permitting measurement of the 

electron angular distribution. In order to detect electrons 

of low kinetic energies, the chamber was covered with pmetal on the inside. The electron spectra taken on the Ar 

1s-4p resonance reveal a complex structure of low kinetic 

energy Auger lines (particularly around 5 eV) not seen 

100 200 300 400 500 600 700 61 1 I L 1 

5- 

h 

g 4- Y 

5 3- 

$ Byron and Joachain" a, 

= 2- Hino et al., L,V formszo 

Hino et al, A formz0 

Pan and Kelly, A formz3 . -. . .- . . . 1 

Pan and Kelly, L formz3 --- 

I 9 1 .I. 8 

Figure 2 U13UA Near-threshold ratio of double to single photoionization of 

helium using monochromatic undulator radiation on U13UA (solid circles and 

solid triangles, present results) compared with available theory, as indicated, 

and published experimental results (from Jon C. Levin, C. Bradley Armen, and 

Iran A. Selling, Phys. Rev. Lett., in press). 

37 
I I I 

100 

h 

3 

0 

650 700 

Channel 

Figure 3 X24A 1-MM Auger 

lines in coincidence with the 

K-\343 Auger line on the Ar 

1s + 4p resonance. The 

dotted line corresponds to 

the non-coincident spectrum 

of the same Auger group 

arbitrarily scaled to the 

coincident spectrum. 

750 

before. However, the intensity is too low for a detailed 

analysis of these Auger lines yet, but will be part of future 

investigations. The main goal of these investigations was 

to record the Ar L-MM Auger lines in coincidence with 

one K-LLAuger line to disentangle the complex structure 

of the L-MM Auger group. While the CMA was tuned to 

the K-LuLu Auger energy, the group of L-MM Auger 

lines was detected with the TOF spectrometer. The 

coincident L-MM Auger spectrum shows a different 

structure than the corresponding non-coincident spectrum because of the decay-path selection in the first step 

(Figure 3). Further studies will include other “first-step” 

Auger lines (e.g. K-LM) and the angle correlation between 

the two outgoing Auger electrons. See also X24A Experimental Abstracts in this volume. 

x24c 

Photoelectron spectroscopy is extended from a probe 

of the ground state to one of the excited state through 

pump-probe photoemission. In this technique, a laser 

pulse first excites (i.e. pumps) electrons into normally 

unoccupied levels and a second W pulse, incident with 

controlled delay relative to the laser pulse, photoemits 

from the excited electron population. In this way the 

energies, wave vectors, and population dynamics of excited states are accessible directly. The technique is 

usually practiced with laser-based W sources on metals 

and semiconductors. However, Jim LongmaVal Research Lab) and coworkers have extended the technique to 

include the use of synchrotron radiation and, most recently, to examine non-traditional materials such as the 

fullerene CGo. 

38 

Figure 4 displays results obtained from a 420 A film 

of CGo deposited in situ on a copper substrate and subsequently photopolymerized at room temperature by exposure to copper-vapor laser pulses (hv=2.43 eV, 5-11s 

FWHM). The inset displays the photoelectron spectrum 

of excitons excited in the film, held at 84 K, by the same 

laser. For this spectrum, the laqer pulses were overlapped 

0.6 ns FWHM). Single-bunch operations maximized the 

number ofsynchrotron-radiation photons coincident with 

the laser pulses, which had a repetition rate of 6 kHz, 

much less than the synchrotron rate of 1.8 MHz (single 

bunch). The center energy of the exciton band lies below 

the band gap of solid CGo, reflecting the energetics of 

exciton binding, lattice relaxation, and, possibly, trapping 

at defects. \ \ 

Exciton dynamics governs efficiencies for phenomena as diverse as photochemical reaction, energy transfer, 

nonlinear optical properties, and triplet and free radical 

formation, and can also yield other information about the 

state of a sample. In many systems, singlet excitons decay 

into lower-energy triplet excitons through intersystem 

crossing and thus a 111 dynamical knowledge requires 

tracking both singlet and triplet populations. Optical 

techniques, such as transient absorption or photoluminescence, are valuable dynamical probes but, in general, 

cannot form a complete picture because any one experiment exhibits vastly different detection sensitivities for 

singlet and triplets. In contrast, photoelectron spectroscopy enjoys equal detection sensitivities. The decay 

dynamics of the exciton populations in photopolymerized 

C,, films were examined by monitoring the strength of the 

in timewith the synchrotronradiation / pulses (hv=8.5 eV, 
peak in the photoelectron energy spectrum (vertical line in 

the inset) as a hnction of the 

relative time between laser and 

synchrotron radiation pulses. 

In Figure 4, the microsecond decays were measured 

in25-bunch operations because 

long gate times could be used 

to integrate the signal over 

many synchrotron pulses without distorting the decay profile; the nanosecond data (filled 

circles) necessitated singlebunch operations. Triplet excitons comprise the long-lived 

component, which is found to 

be consistent with exponential 

decay. At shorter times after 

the laser pulse, the decay is 

complicated by higher-order 

(e.g. bimolecular) kinetics due 

to the large cma) exciton density. Coupledrateequations describing singlets, triplets, and free carriers, when integrated and fitted to the data, 

strongly suggest that both triplets and singlets contribute to 

the signal at early times. The 

singlet population converts to 

triplets through intersystem 

crossing (1 ns) and bimolecular 

1 .o CL II 420 A cdcu 

hv = 8.5 eV 

Photopolymerized 

. /Excited state signal 

- ,laserPulse 1 2 3 

E, (ev) relative to HOMO 

- J.. .h ' ,', ,', 1 ".' 1 "' " J1. 

-10 0 10 20 30 40 50 6d' 5 IO 15 20 25 

(ns) @) 

TIME AFTER PEAKOF LASER PULSE 

Figure 4 X24C Photoelectron spectrum (inset) of excitons excited in a 

photopolymerized film of C, by a 5-ns copper-vapor laser pulse and probed 

by a time-overlapped synchrotron pulse. Vertical bar denotes the energy, 

relative to the center of the highest occupied molecular orbital (HOMO), at 

which the time-dependent data in the main portion of the figure were taken. 

Numerical modelling strongly suggests that the data at short times (solid 

circles), taken in single-bunch mode, comprise both singlets, which decay 

within a few nanoseconds, and the long-lived triplets into which the singlets 

and free carriers convert. The kinetics are strongly influenced by the 

nonlinearities introduced by conversion scattering among the singlet, triplet, 

and free-carrier populations. The presence of triplets is confirmed by the long 

lifetimes (1 0-20 p) observed during 25-bunch operations (solid curve). (S. 

Chase, J. P. Long, R. Klaffky, W. R. Hunter, and M. N. Kabler). 

processes. Further analysis, including comparison of the 

different kinetics observed for polymerized and pristine 

(not shown) films, should yield new insights into exciton 

dynamics in molecular and polymeric solids. 

x25 

Despite the hndamental importance of the problem, theoretical predictions of the ratio of double-tosingle ionization of helium by high-energy photons have 

not converged (they vary by a factor of two). Jon Levin 

(with Brad Armen and Ivan Sellin, U. Tennessee) have 

conducted an ongoing program of research aimed at 

elucidating the roles of photoionization and Compton 

ionization in the 5-10 keV region, over which energy 

range Compton ionization gradually supplants photoionization as the dominant ionization mechanism, and 

Compton ionization alone from 10-20 keV. Singlebunch operations are critical for these measurements, 

which use the ring timing signal to differentiate between 

singly and doubly charged helium by time-of-flight methods. Time-of-flight techniques which require detection 

ofan ejected electron can introduce systematic biases, and 

pulsing of extraction fields produces broad ion time-offlight peaks, making discrimination against large-crosssection electron-impact ionization difficult. 

Because of the small double-ionization cross section 

(dmbarns at 20 kev), and low gas-phase target number 

density, the intense wiggler radiation available at X25 has 

proven crucial. Results to date have helped to differentiate 

among the several theories currently available (see X25 

Experimental Abstracts in this volume). 
UV PHOTOEMISSION AND SURFACE SCIENCE 

Steven Hulbert 

Chi-Chang Kao 

NSLS 

VALENCE BAND PHOTOEMISSION AND 

RESONANT PHOTOEMISSION 

Recently La,-xAxMn03 (A = Sr, Ca, Pb etc.) have 

attracted a great deal of attention because of the technological implications of their large magnetoresistance as 

well as the intriguing phase transitions associated with 

magnetoresistance in this class of materials. High resolution valence band photoemission and resonant photoemission have been used to reveal the electronic structure 

changes associated with the ferromagnetic transitions in 

La,x(Ca,Pb)xMn03 by J.-H. Park, C.-T. Chen, S.-W. 

Cheong, W. Bao, G. Meigs (AT&T Bell Labs), V. 

Chakarian andY. U. Idzerda (NRL) at beamline U4B. As 

shown in Figure 1 (a), the overall valence bandphotoemission spectra from both Lao~67Cao~33Mn03 and 

Lao,7Pbo.3Mn03 exhibit no changes with temperature. 

However, near the Fermi level, as shown in Figure l(b), 

a metallic Fermi edge dearly emerges with decreasing 

temperature for both samples. These data provide strong 

evidence that the ferromagnetic transition is closely related to a metal-insulator transition. To further investigate the microscopic origin of this paramagnetic-insulator-to-ferromagnetic-metal phase transition, the authors 

also performed resonant photoemission near the 

Mn 2p absorption edge to enhance the Mn 3d 

contribution to the valence band. With decreasing 

temperature, an energy shift of 0.2 eV was observed 

for the lowest binding energy state, 44. From these 

findings, it is argued that the physical origin of the 

phase transition lies in the close interplay between 

the charge fluctuation energy for electron hopping 

from the Mn+3 site to the Mn+4 site, and the spindependent electron hopping energy. 

Binding Energy (ev) Binding Energy (ev) 

Figure 1 U4B: High-resolution temperaturedependent photoemission spectra of 

La,,,Ca,,,MnO, (left panels) and Lao,7Pbo,,Mn0, 

(right panels) taken at 1 1 OeV photon energy: (a) 

wide range scans, (b) region near the Fermi level, 

and (c) Mn Zp,, edge on-resonant spectra. 

40 

Angle-Resolved Photoemission of Novel Materiak 

The electronic structure of low dimensional 

oxide conductors, organic superconductors, and 

wide band gap semiconductors is being studied 

using angle-resolved photoemission (ARPrby Kevin 

Smith and his group from Boston University using 

beamline U4A. Concerning the properties of the 

low dimensional oxides, the highlight of the year 

was the measurement of the full Fermi surface in 

Na0.9M06017, atwo dimensional conductor. A 

representative set ofARP spectra is shown in Figure 

2, while the full Fermi surface is presented in Figure 

3. Although primarily two-dimensional (2D) in 

nature, NaO,Mo6Ol7 displays numerous characteristics of a 1D conductor, in particular charge density waves and periodic lattice distortions. The 

explanation put forth for this by Whangbo, et al. 

[(Science, 252, 96 (1991)l was that the material 
possessed so-called hidden Fermi surface nesting. Hidden Fermi surface nesting is where a 

true 2D Fermi surface can be viewed as a 

combination of quasi-1D Fermi surface structures, all ofwhich can be linked by one nesting 

vector. Most of the Fermi surface in Figure 2 

can be constructed from two sets ofparallel 1D 

Fermi surfaces, running parallel the diagonals 

of the rectangular surface Brillouin zone. This 

measurement is the first direct confirmation of 

the validity of hidden Fermi surface nesting, a 

widely cited mechanism used to explain quasi1D phenomena observed in quasi-2D systems. 

Angle-resolved photoemission is also 

being used by Ph. Hofmann (ORNL) and E. 

W. Plummer (U. Tennessee) at beamline U12 

to study the electronicstructure oftheBe( lOi0) 

surface, and by X. Xu, R. G. Jordan and S. L. 

Qiu (Florida Atlantic U.) at beamline U4A to 

study the surface electronicstructure of CuAu. 

-1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 

k\l [OlO] (A-’) 

Figure 3 U4A: The measured Fermi surface for Na,,Mo,O,,. 

2 1 &=O 

Blnding Energy (eV) 

Figure 2 U4A: Angle-resolved photoemission 

spectra at 1 8eVphoton energy from Nao,,Mo,O,, 

as a function of detection angle. 

Spin Polarized Valence Band Photoemission 

from Magnetic Su$aces 

Photoemission studies of the quantum well states 

on Co, Ni and CoNi alloy substrates have been performed 

byagroup fromtheBNLPhysics Dept. (D.-J. Huangand 

P. D. Johnson). In several studies of noble metals deposited on ferromagnetic substrates, it has been shown that 

“quantum well” states exist, that they reflect the finite 

layer thickness, and that these states are highly spin 

polarized. As the thickness of the noble metal film 

increases, these states cross the Fermi surface with a 

frequency identical to that observed for the exchange 

coupling in the associated multilayers. These observations, taken together, lend support to the idea that the 

quantum well states mediate the coupling in the magnetic 

-- multilayers. Photoemission spectra recorded at k,, =0.765 

IX from Cu films deposited on Co(OO1) exhibit a small 

peak near the Fermi level with a thickness-dependent 

intensity modulation of approximately 3 layers, corresponding to spanning vectors at the neck of the copper 

Fermi Surface “dog bone”. A periodicity of three layers is 

close to that observed for oscillatory exchange coupling in 

the associated magnetic multilayers. Quantum well states 

at the center of the surface Brillouin in Cu films deposited 

on CoNi alloy substrates have also been identified. These 

states are less intense and have slightly lower binding 

energies than those in Cu on Co(OOl), particularly in the 

vicinity of the Fermi level. This observation can be 

41 
Y 

0 2 4 6 8 10 12 

CuThickness (ML) 

Figure4 U5UA:The binding energies of quantum well 

states at the center of the surface Brillouin zone in Cu 

films deposited on Ni(001) and Co(OOI), obtained 

from angle-resolved photoemission spectra excited 

with photons of energy 23 eV, as a function of Cu 

overlayer thickness. The Cu/Co(OOI) quantum well 

states (open circles [IC Garrision, Y. Chang, and P. D. 

Johnson, Phys. Rev. Lett. 71,2801 (1 993)] and triangles 

[J. E. Ortega, F. J. Himpsel, C. J. Mankey, and R. F. Willis, 

Phys. Rev. B47,1540 (1 993)]) exhibit brancheslabeled 

by integer quantum numbers v = 1, 2, 3 from left to 

right. In contrast, the binding energy dispersion of the 

Cu/Ni(001) states (solid circles) as a function of Cu 

thickness exhibits an abrupt jump from the branch 

with quantum numberv=l to the branch with quantum 

number -2. See text. 

explained by the difference in electronic structure of the 

substrates (single element vs. alloy). 

These results indicate that the degree of quantum 

confinement can be tuned by altering the electronic 

structure of magnetic substrates, for instance, by changing the relative elemental concentrations in the substrate. 

This in turn suggests the possibility of tuning the exchange coupling strength in the associated magnetic 

multilayers. Quantum well states in Cu films deposited 

on a Ni(001) substrate are also identified by using angle 

6-resolved photoemission, and their binding energy dispersion as a function of Cu thickness exhibits an abrupt 

jump from the branch with quantum number V= 1 to the 

branch with quantum number~=2, as shown in Figure 4. 

This branching jump results from the dramatic 

change in the phase shift of the reflection at the 

interface, a consequence of the resonant scattering of the sp-derived quantum well states in 

Cu by the Ni quantized d-bands. This branching jump suggests that the quantum-well-state 

picture can be applied to understand the magnetic-layer dependent oscillatory coupling in 

these systems. 

Another spin-polarizedvalence band photoemission study using the U5UA beamline 

during FY95 was that of chemisorbed Cs on Fe 

substrates, performed by a collaborative group 

consistingofD.-J. Huang (BNLPhysics Dept.), 

E. Vescovo (NSLS), D. M. Riffe (Utah State 

U.), P. D. Johnson (BNL Physics Dept.), I?. 

Abramowitz and J. L. Erskine (U. Texas Austin). In this work, spin-polarized and spinintegrated photoemission spectroscopies were 

used to investigate the electronic interactions 

between chemisorbed Cs atoms and ferromagnetic Fe films epitaxially grown on W( 110). 

The spin-integrated Cs 5p photoemission spectra are consistent with previously observed general trends in the coverage-dependent binding 

energy shifts ofalkali adatom core-level spectra. 

The Cs 5p binding energy in the first atomic 

layer decreases as the Cs coverage increases due 

to dipolar repulsion and band formation. The 

binding energies of Cs in the second layer are 

smaller than those in the first layer, an indication that the Cs-Cs interaction is weaker than 

the Cs-Fe interaction. In addition, the lifetime 

width of Cs in the first layer is much larger than 

those in thesecond layer. This dramatic change 

of lifetime width is suggestive of s-p hybridization in the first-layer-Csvalence electrons. That 

no measurable spin-polarization exists in the 

Cs 5p spectra suggests that there is little or no induced 

magnetic moment on Cs site, in contrast to the observation of an induced magnetic moment in chemisorbed 

oxygen and sulfur on ferromagnetic substrates. Data 

analysis is under way to understand the Cs-Fe electronic 

interactions. 

s 

42 
* Q 

- O.SQHLS/NI(ill) 

8 

7 

%6 

5 

55 

I4 m 

€ 

03 

z 

2 

1 

0- 0 

167 166 165 164 163 162 161 160 ’ 

Binding Energy (eV) 

B) I 

’ 166 165 164 163 162 161 160 

Binding Energy (eV) 

Figure 5 U13UA: Sulfur 2p photoemission spectra from (A) atomic sulfur and 

(B) methyl thiolate (CH,S) adsorbed on Ni(lO0) and Ni(l11) surfaces as a 

function of coverage or temperature. The spectra were recorded using 250 

eV excitation. 

CORE LEVEL PHOTOEMISSION 

Sofi X-ray Photoemission S;om Sulphur-Containing 

Molecules on Metal Su faces 

The surface chemistry group from Oak Ridge National Laboratory (David Mullins, Deborah Huntley and 

Steve Overbury) completed a series of experiments that 

demonstrated a direct correlation between the sulfur (S) 

2p core level binding energy and the adsorption site of the 

adspecies. They then applied this correlation in understanding the complex reaction chemistry of CH,SH on 

Ni(ll1). Since an early investigation of S on W(OOl), it 

has been hypothesized that lowering the coordination of 

the adsorption site lowers the S 2p binding energy. The 

most direct way to tat this hypothesis is to compare S 2p 

spectra for thesamespecies on different crystal faces ofthe 

same metal. Figure 5(A) shows how the S 2p peak 

position shifts to lower binding energy when the S moves 

from a four-fold site on Ni(100) to a three-fold site on 

Ni(ll1). The S 2p peak positions at high S coverage on 

Ni( 11 1) indicate that the surface has reconstructed, with 

some adsorption sites being the same as on Ni( 100) (fourfold) and others having an even higher coordination. A 

similar shift in the S 2p peak positions is seen for CH,S 

adsorbed on Ni(100) and Ni(ll1) in Figure 5(B). This 

group has also performed photoelectron diffraction experiments of this adsorption system which demonstrated 

that, at low temperatures, CH,S adsorbs in the three-fold 

site on Ni(ll1) and in the four-fold site on Ni(100). In 

the present work, a corresponding increase in the S 2p 

binding energy is seen between these two surfaces. When 

the Ni( 11 1) surface is heated to 250K, the S 2p spectrum 

becomes very complex. Applying what was learned from 

the atomic S spectra and the CH,S spectra at lower 

temperatures, it is now clear that the CH,S is decomposing and the Ni( 11 1) surface is reconstructing at 250K. 

The two S 2~,,~ peaks at 161.15 and 161.55 eV arise from 

atomic S in three-fold and four-fold sites, respectively. 

The S 2~,,~ peak near 163.30 eV results from CH,S that 

has shifted into a four-fold site on the reconstructed 

surface. 

The UC Riverside group (W.C. Simpson, J.A. 

Yarmofl) and the IBM group (W.H. Hung, F.R. McFeely) 

at beamline US also continued their work on the adsorption and reaction of halogens on semiconductor surfaces 

using core level photoemission spectroscopy. 
So$X-ray Resonant Fe L WAuger 

Spectroscopy porn Fe Su faces 

The spin-resolved core level photoemission group from the NYU Physics Dept. [B. Sinkovic, E. Shekel (NYU) 

and S. L. Hulbert (NSLS)] has performed the first spin-resolved L,-resonant photoemission measurement using their spin-resolving electron energy 

spectrometer and high-flux soft x-ray 

photons from the U13UA beamline. 

The spectral distribution of this giant 

resonance (2p3,,+3d*) is dominated 

by the Auger matrix elements and is 

found, in the case of Fe, to closely 

resemble the self-convolution of the Fe 

valence density of states. However, the 

magnitude of the spin polarization is 

measured to be significantly higher onresonance (Pon=37%) than the valence 

band spin polarization (Pv,=27%). 

These findings are consistent with a 

reduction of the triplet Auger matrix 

elements which, in turn, can be interpreted as being due to the existence of 

a Fermi hole, the exchange correlation 

responsible for keeping equal spins further apart, which effectively lowers the 

triplet Auger probability. This hypothesis was confirmed by measurement 

using off-13-resonant photons, which 

yielded smaller spin polarization 

(P0,20%) than PvB, as expected since 

the degree of spin polarization depends 

on the polarization of the initial core 

Figure 6 U13UA: Mesh surface: calculated spin polarization of the 

Fe CVV Augertransition as a function both of Auger matrixelement 

(singlethriplet ratio, proportional to the exchange correlation 

strength) and of the initial core-hole spin polarization P for a given 

valence band spin polarization (P,=2700). Open circle: measured 

electron-energy-integrated spin polarization of on-4-resonance 

Fe L,M,,M,, Auger spectrum (P,,,=370/0). Filled circle: off-4-resonance 

value (P,,=200/0). These measurements carry important information 

on both the spin polarization of the valence band and the relative 

strength of exchange correlation, and demonstrate the importance 

of exchange correlation in itinerant 3d-metals such as Fe. See B. 

Sinkovic, E.Shekel, and S. L. Hulbert, Pby5. Rev., B52,15703, (1 995). 

hole (which is different in the on- and off-resonant 

processes) assuming electron correlation effects are present. 

Thus, these measurements provide away ofstudying spindependent electron-electron correlation in magnetic materials (see Figure 6). These results suggest that electronelectron correlations are important in itinerant ferromagnets such as Fe. 

44 

_. .-' 

r . * _. 
,.... ........................... 

700 800 900 1000 1100 

0 cl -0.5 ~:~~ L_) 

32 1000 1100 1200 

o XlOO -1.0 

-1.5 

UJ2 

XI 

4 

-8 

0 

0.2 

0 -0.2 

cl 0.9 

E 

900 1000 1100 1200 1300 

Photon mergy (ev) 

Figure 7 U4B: L-edge extended x-ray absorption 

fine structure (EXAFS) transmission magnetic 

circular dichroism (MCD) spectra from Fe, Co and 

Ni thin films electron-beam evaporated onto 

one-micron-thick parylene substrates. For each 

material, the upper panel shows the x-ray 

absorption spectrum and the lower panel shows 

the MCD signal. The MCD signal is measured by 

alternating the sample magnetization at each 

photon energy. 

SOFT-X-RAY MAGNETIC 

CIRCULAR DICHROISM 

Transmission measurements from thin evaporated 

Fe, Co, Ni films were carried out by the NlU group Cy. 

U. Idzerda, V. Chakarian, and K. Kemner) and the 

AT&T group (J.-H. Park, G. Meigs, and C. T. Chen) at 

beamlineU4B to determine the absolute photoabsorption 

cross sections for these important elements. 

Photoabsorption coefficients of left- and right-circularly 

polarized soft x-rays were reported, as well as the total 

photoabsorption coefficients. This group also observed 

very large magnetic effects in the L-edge extended x-ray 

absorption fine structure (EXAFS) of 3d transition metals. Transmission MCD measurements extended to the 

EXAFS region were measured for Fe, Co, and Ni thin 

films grown under ultra-high vacuum conditions by ebeam evaporation. The EXAFS and magnetic EXAFS 

(MEXAFS) measurements for the L-edges of 3d transition metals are shown in Figure 7. The topmost panel of 

Figure 7 shows the FeXAS spectrum in which the vertical 

scale in the EXAFS region is expanded. The next panel 

shows the Fe MCD signal, where the vertical scale has 

been expanded. Similar measurements at the L-edge of Co 

and Ni thin films are shown in the remaining panels. 

Large EXAFS oscillations were observed in the MEXAFS 

spectra for all three samples. The amplitudes of the 

oscillations at the L edges are much greater than those 

observed at the K edges of the same elements. These 

authors also noted that the relative amplitude of the 

MEXAFS oscillations compared to the EXAFS oscillations is largest for Fe and smallest for Ni, although the 

ratio does not scale linearlywith the magnitude of 

the magnetic moment. 
Lars Furenlid 

NSLS 

INTRODUCTION 

X-ray Absorption Spectroscopy (XAS) is one of the 

key research tools available at the NSLS, and the last year 

was highly productive for the beamlines specializing in 

this technique. Nine beamlines on the X-Ray Ring and 

two on the W Ring now perform absorption spectroscopy on at least a part time basis. They are U1, U16B, 

X6A and B, X9B, XlOC, XllA, XlGC, X18B, X19A, 

One of the most active areas of development within 

theXAS field is insitu experiments, wherein some control 

or process is exerted on the sample while it is in the x-ray 

beam. Researchers now employ amyriad ofapparatus “on 

line” to accomplish everything from simply controlling 

temperature to actually growing samples with molecular 

beam epitaxy (MBE) chambers. The XAS Workshop of 

the 1996 NSLS Annual Users Meetingwill focus on these 

kinds of experiments, and presenters will discuss the 

X23A2, and X23B. In addition, XAS related experiments techniques they have developed. 

are at times carried out on 

the microscope at XlB, 

the microprobe onX26A, 

and on the wiggler 

beamlines X21 and X25. 

U4B is used for circular 

dichroism studies, and 

several other of the W 

linesare occasionally used 

for NEXAFS studies. This 

article presents some selected highlights from 

1995’s research activities 

at these beamlines. 

The extended x-ray 

absorption fine structure 

(EXAFS) technique is 

unique in its ability to 

determine structural pam lm Ilrn 1209 lm 

Figure 1 U4B: Standard EXAFS (above) and Magnetic EXAFS (below) measurements 

of Fe, Co, and Ni thin films. 

rameters in sample systems which lack long-range order 

and are hence unsuitable for x-ray or neutron diffraction 

studies. These include solutions, clusters, amorphous 

powders, heterogeneous mixtures, and thin films. EXAFS 

provides coordination numbers and bondlengths about a 

selected central atom for neighbors within -5 A distance, 

and can provide angular orientation information via 

polarization or multiple scattering effects. X-ray absorption near-edge spectroscopy (XANES) can provide complementary information about elements’ oxidation states 

and geometries. Much of the strength of the technique 

derives from the fact that samples can be solid, liquid, or 

even gaseous; at any temperature and any pressure. This 

versatility has resulted in the application ofXAS to a vast 

range of problems. 

46 

RESEARCH HIGHLIGHTS 

Magnetism and properties ofmagnetic materials are 

a hot research area, and a particular focus of recent work 

at beamline U4B. The combination of an energy range 

covering the third row transition metal L-edges and 

MCD capability enable a wide variety of experiments. 

Y.U. Idzerda, V. Chakarian, K. Kemner (NRL), J.-H. 

Park, G. Meigs, and C.T. Chen (AT&T) have made some 

of the first magnetic EXAFS (MEXAFS) measurements at 

this facility, studying 3d transition metal films grown on 

polymer substrates. The magnitudes of the L-edge 

MEXAFS were found to range from 5% to 0.5% of the 

corresponding EXAFS signals in Fe, Co, and Ni samples. 

Sample MWS spectra are shown in Figure 1. 

could be monitored. The researchers found that the anhydride formation rate correlated with the amount of V5 

present, identifyingthat component as required for catalysis, and that the catalyst 

reoxidation rate was always 

slower than thereduction with 

butane. 

L. Chen, M. 

Wasielewski, W. Svec, K. 

Huang, and I?. Montan0 

(ANL) studied modelsystems 

for the chlorophyll dimers important in photosynthesis. 

The distance between 

macrocycle planes and their 

configurations are believed to 

control their photophysical 

Figure 3 X6A: Magnetic Circular X-ray Dichroism spectra of the gadolinium I-,,, 

edge as a function of temperature from 94 to 350 K. 

properties. Using lab synthesized complexes in which two 

metal containing chlorophyll macrocycles are linked together via cyclophane linkages, the researchers looked for 

features in the EXAFS spectra resulting from a metalmetal interaction. Of samples with nickel, copper, and 

zinc, only the latter showed evidence for a metal-metal 

interaction: a peak at 3.5 A in the Fourier transform 

assigned as Zn-Zn (Figue 4). Addition of a coordinating 

base resulted in attenuation of the peak magnitude, as 

expected. The nickel bischlorophylls were found to vary 

between four, five, and six coordinate depending on the 

presence of coordinating bases and temperature. 

Nitrogenase, the protein system responsible for 

the direct fing of atmospheric nitrogen by plants, 

contains a [4Fe-4S]+2 cluster. R.C. Scarrow, N. Taufen 

(Haverford College), L.C. Seefeldt, and W.N. Lanzilotta 

(Utah State University) studied the interaction of 

nitrogenase iron protein with magnesium ATP to see 

whether the iron sulfur complex is affected. Previous 

results from other techniques had been interpreted to 

suggest that MgATP binding might partially convert 

the [4Fe-4S]+2 cluster into smaller [2Fe-2S]+ clusters. 

In experiments on beamline X3B, the research team 

found that XANES and full EXAFS spectra on the 

oxidized iron protein in the presence and absence of 

MgATP were essentially identical, however. In both 

cases, each iron was found to have approximately 3 

irons and 4 sulfurs as neighbors. 

The hydrogenases are among the few 

metalloproteins which contain the element nickel. Z. 

Gu, S.B. Choudhury, C.B. Allan, and M.J. Maroney 

(University of Massachusetts) are working to elucidate 

48 

the role of the nickel, which appears in an active site 

together with an iron atom. The team measured the 

nickel k-edge XAFS spectra of the carbon monoxide 

adduct of a specific organism’s hydrogenase along with 

the “CO off form generated via photodissociation. The 

effects on thespectraare ahalfevshifiin theedgeposition 

and a shortening of the Ni-Fe bondlength. The researchers interpret these results to indicate that the CO doesn’t 

bind to the Ni atom, but instead to the Fe site. 

S. Bajt (University of Chicago), J.F. Lee (SRRC), 

S.B. Clark (SREL, University of Georgia), G.M. Lamble 

(Brookhaven National Laboratory), C.A. Langton and J. 

0 2 4 6 

R(Angstroms) 

Figure 4X6B: Fourier-transformed Zn k-edge EXAFS of 

Zn-bis chlorophyll with and without pyridine in solution 

at 290 K. 
Oji (Westinghouse Savannah River Company) used 

XANES and EMS techniques on beamline XllA to 

investigate chromium waste as immobilized in cement. 

Chromium in the +6 oxidation state, as in CrOi-, is 

highly soluble and toxic in comparison to the Cp+ form. 

Hence, formulations of cements have been developed to 

favor the reduced form. As evident in Figure 5, simulated 

waste streams which consist initially of only C$+ are 

largely converted to CP+ in two of the cement mixtures. 

EXAFS results show that the large bondlength differences 

between the +6 and +3 forms can be used to help quantitate the relative amount in each state. 

D.L. Adler, and R. Nuzzo (University of Illinois) 

studied bimetallic clusters generated by depositing Re and 

Ir precusors on an alumina support and then activating 

with heat under flowing hydrogen gas. EXAFS spectra 

were recorded on these samples on beamline XI GC. The 

researchers made use of average coordination numbers to 

estimate cluster size, and the appearance or lack of 

ordered shells at distances beyond the first shell to infer 

position relative to the cluster core or periphery. They 

infer that Ir occupies core sites, while Re appears at the 

cluster edge. 

M.A. Vairavamurthy, S. Wang, B. Khandelwal, and 

B. Manowitz (DAS, BNL) have been studying sulfur in 

the environment, particularly in marine sediments. The 

researchers have previously established that sulfonates are 

a major class of the organic sulfur in near-surface marine 

sediments. In order to ascertain whether phytoplankton 

debris could be the source of this form of sulfur, the 

investigators measured S k-edgeXANES spectra ofsamples 

of various types of phytoplankton species on beamline 

X19A. Sulfonate sulfur was indeed found to be the 

dominant form in phytoplankton, in support of this idea. 

The dominance of sulfonates further suggests that they 

play an as yet unknown, but important role in the cellular 

biochemistry of marine phytoplankton. 

Researchers from the University of Michigan have 

been studying organocuprate reagents in solution in an 

effort to understand these potent tools for organicsynthesis. In the latest studies, H. Huang and J.E. Penner-Hahn 

performed Cu k-edge EXAFS measurements on 

phenylcopperprepared from theaddition ofphenyllithium 

to Copper(1)iodide at X19A. The Fourier transform 

magnitude, shown in Figure G, shows a very strong peak 

at just over 2i% which is consistent with a copper scatterer. 

A quantitative analysis suggests a Cu-Cu distance of 2.45 

A, which is shorter than the interatomic distance in 

copper metal, but similar to the distances observed in 

crystallized pentameric phenyl-copper clusters. Hence, 

the researchers conclude that similar species are present in 

solution. 

\ 

5980 6000 6020 6040 

ENERGY (eV) 

Figure 5 XI 1A: Chromium k-edge XANES of: (a) a 

Cr(V1) standard (K$rO,), (b-d) Cr waste in three 

different concrete mixture immobilizers, and (e) a 

Cr(ll1) standard (CrOOH). 

EXAFS experiments are optimally combined with 

other techniques to enhance the information content 

available at the start of the quantitative analysis. A.C. 

Carter, M.I. Bell, K.M. Kemner (NE), C.E. Bouldin, 

I 

cu-cu 

cu-c 

cu-c 

I 0 1 2 3 4 5 

Rtcl Ch 

Figure 6x1 9A: Fourier-transformed Cu k-edge EXAFS 

of phenylcopper in THF solution. 

49 

, ,^ .- . .. 

. 
7035 7045 7055 7065 

Emission berm (em 

Figure7X25: Iron $emission spectrum of oxidized, 

high-spin Rubredoxin excited at 7200 eV. 

J.C. Woicik (NIST), and S.A. Majetich (CMU) have used 

a combination of XAS, FTIR, and elemental analyses to 

determine the structure ofcadmium-selenide nanoclusters 

in work on X23A2. The combination of EXAFS and 

FTIRwas particularly fruitful as it was possible to observe 

that Se atoms at the surface of the clusters are bare, i.e. 

bound only to cadmium atoms with a net coordination 

less than that in the interior of the cluster. The FTIR 

spectra agreed, with no evidence for Se-ligand modes. 

Surface cadmium atoms, on the other hand, were confirmed to bind passivating perchlorates. 

Zeolites are large, open framework structures made 

up of tetrahedral silicon and aluminum oxide building 

blocks. Their pore and cavity structures make them ideal 

supports as catalysts, and they are employed in a number 

of industrial processes. M. Endregard (University of 

Trondheim), A.F. Gualtieri, S. Quartieri, G. Vezzalini 

(University of Modena), and K.I. Pandya (NCSU) studied the nature of iron found in four naturally occurring 

zeolites with spectroscopy on beamline X23B. The researchers worked to distinguish whether iron has (1) been 

substituted for Si or Al into the framework , (2) exists 

outside the framework, or (3) is associated with hydroxides or other impurities. From Fe k-edgeXANES studies, 

and in particular the relative magnitude of the 3d pip, it 

was concluded that the iron has largely octahedral coordination, which is inconsistent with simple substitution 

50 

into the framework. 

X. Wang, A. Froeschner, and S.P. Cramer (University of California, Davis) have demonstrated the first 

spin-polarizedXANES measurements on ametalloprotein 

using high-resolution monitoring of the iron $ fluorescence at beamline X25. The Fe $ emission spectrum of 

oxidized, high-spin Rubredoxin is split into two regions 

corresponding to decay into a spin-up or spin-down core 

hole (Figure 7). Thus by monitoring the appropriate 

fluorescence energy it is possible to separately measure the 

absorption spectraarising from excitation ofthe two inner 

shell electrons. The edges in Figure 8 demonstrate this 

well: as high spin Fe (111) has five d-shell electrons with the 

same spin, the quadrupole allowed ls-3d transitions are 

only available to the core electron with anti-parallel spin. 

Hence, only one of the absorption spectra shows the 

familiar 3d pip. 

CONCLUSION 

As in past years, the high scientific productivity 

illustrates that x-ray absorption spectroscopy is in a healthy 

state at the National Synchrotron Light Source. Good 

progress has been made in the move towards greater 

cooperativity between XAS beamlines: the first step of 

creatine: a common data collection Dackage to ease user " " 

support and training issues has been completed. 

Figure 8 X25: Spin-polarized iron k-edge XANES of 

oxidized, high-spin Rubredoxin illustrating different 

cross-sections for 1 s electrons with spin parallel and 

antiparallel to 3d electron spins. 
SMALL-MOLECULE SINGLE-CRYSTAL 

The use of imaging plate area detectors is extending 

from the field of protein crystallography into the smallmolecule regime. It is permitting the collection of data 

from samples previously considered too small for conventional point-by-point diffractometry. The use of an 

integrating area detector greatly reduces the time for data 

collection and minimizes the influence of instabilities in 

the beam and the beamline. X3A1 has been the location 

ofarange ofexperiments by thestony Brookgroup led by 

John Parise involving crystals with sizes in the 20 micron 

range. For example, K. Tan studied novel open-frame 

structures in Antimony Sulfide templated by 

dimethylammonium (prepared by hydrothermal synthesis), and J.-H. Park studied a new compound SrAu,O, 

prepared by a solid-state reaction of SrO, and Au203 at 

high pressure and several other compounds (Figure 1). 

Successful structure determinations were performed in 

spite of the small size of the crystals involved. 

POWDER DIFFRACTION 

Powder diffraction continues to show its effectiveness when even such small single crystal samples are 

unavailable. A wealth of new structures is reported in the 

Activity Report, and it is impossible to mention them all 

here. In an area which is not usually well-represented in 

SR-based powder work, that of phase identification, is 

addressed by R.E. Dinnebier and collaborators. They 

addressed the issue of polymorph impurities in drug 

compounds. Theywere able to demonstrate the ability to 

determine the presence of gamma-phase impurities in 

alpha-indomethacin, an anti-inflammatory drug, down 

to levels of at least 0.1% (Figure 2). This limit was 

imposed by the purity of the reference "pure" material 

available. 

The recent reports of giant magnetoresistance effects in La,,,CaxMn03 prompted Radaelli and coworkers 

to look for structural changes in this region. A rich variety 

of structural changes was reported around Tc, depending 

on the value of x. 

Figure 1 X3A1: Projection of the Structure of SrAu,O, along [loo]. The AuO, 

units and Sr ions are represented by the planes and circles. 

The ubiquitous imaging-plate finds application in powder-diffraction 

studies, too. Themovingimage-plate setup at X7B 

has provided a time-resolved capabilitywhich has 

allowed studies of a variety of reactions. An example is the KolbeSchmitt reaction for the 

production of salicylic 

acid. The reaction mechanism is still poorly understood in spite of its industrial importance. In situ 

diffraction from this system by a collaboration between X7B and X3 (P. 

Norby, J. Hanson, R. 

51 
2800 2400 

Figure 2X3B1: Intensity of the (1 20) reflection of the a-phase 

of indomethacin for various levels of a contamination. 

320

0.1% a 

Figure 3 X7B: In-situ X-ray Powder Diffraction diagrams of 

the carboxylation of sodium phenolate. 

52 

Dinnebier, and P. Stephens) has revealed a 

variety of intermediate phases (Figure 3). 

The detailed structure of these intermediates is currently being investigated using 

high-resolution powder diffraction. 

The hard x-ray spectrum from the 

superconducting wiggler which feeds 

beamline X17 is put to good use by the 

high-pressure diffraction community. Both 

X17C and X17B1 hosted a wide range of 

high-pressure experiments, primarily by 

the groups from SUNY at Stony Brook 

(CHiPR), NRLand the Carnegie Institute 

of Washington. The experiments performed range from studies of minerals 

under conditions similar to those deep in 

the earth's mantle, to investigations of the 

phase diagram of hydrogen at high pressure. An interesting example of the possibilities in a non-geological area is provided 

by the experiment of E. Skelton and colleagues who were able to study the absorption of deuterium into bulk palladium at 

high pressure. Although heavily studied, 

some of its properties at high concentration (45%) still remain unexplained. The 

high intensity available at X17C allows 

data to be collected from volumei as small 

as lo-" m3. They were thus able to study 

the dynamics of the alpha-beta transition 

(induced by D absorption/desorption) as a 

function of depth inside a bulk (lmm 

thick) sample. They show that whereas the 

alpha phase forms rapidly at all depths, 

there is considerable delay in the onset of 

the beta phase formation at the core of the 

sample. 

SMALL-ANGLE SCATTERING 

Bubeck and a collaboration involving Dow Chemical, Cornell and NSLS 

performed real-time studies of plastic deformation in rubber-modified engineering 

thermoplastics using the high-intensity wiggler beamline X25. They used a Reticon 

detector in combination with optical data 

to collect over 200,000 SAXS patterns 

with time resolution down to 3ms. They 

were able to show that previous conclusions regarding the importance of the different possible plastic strain mechanisms 
were incorrect, and to allow better engineering of new 

polymer blends. At beamline X3A2, A.D. Kennedy and 

a team from DuPont and SUNY Stony Brook has performed experiments using an apparatus which allows 

tensile deformation experiments without requiring high 

data rates. Their apparatus used a continuous-feed arrangement wherein a fiber is drawn from a spool over two 

rollers moving at different speeds (thereby imparting the 

strain). Since the process is continuous, high quality data 

can be collected. They were able to collect WAXS data 

showing a sufficient number of clear reflections to allow 

crystallographic analysis of the Brill transition, and to 

confirm that the transition results from anisotropic crystal 

F 

r 

a 

0. 

t 

i 

0 " 02.- 

r 

C 

i. 

a 

I. 

Q 80 ID0 

Rd8 

Figure 4aX3A2: Cylindrical co-ordinates for 

B02-Fl8: Calculated model (solid vs data 

(dashed). 

Or-l 

1.14 

0.1 XI 4 100 Pin Ternpersbn, (a) 

Figure 4b X3A2: Crystallinity index vs 

temperature. 

thermal expansion (Figure 4) . Inter-chain spacing within 

the H-bonded sheets remains essentially constant while 

inter-sheet spacing increases sharply, forming a metrically 

hexagonal structure. 

X-RAY HOLOGRAPHY 

In an interesting series of experiments at beamline 

X14A, T. Gog and collaborators have demonstrated a 

new technique for hard x-ray holography. By measuring 

the integrated fluorescence intensity as a function of 

sample orientation, they are able to reconstruct the local 

environment around a selected atom in a crystal. The 

technique they use is unusual in that it is the inverse of the 

more obvious technique of measuring the angular distribution of fluorescent radiation with a stationary sample. 

In the new scheme, the changes in the elastically-scattered 

radiation field as a function of sample orientation is used 

to probe the fluorescent atom position. It is in some sense 

a generalization of the standing wave technique. Tests of 

the idea on a Fe,O, crystal and a Ge crystal have demonstrated its potential. 

STANDING-WAVES 

The standing-wave method is not limited to crystalline substrates. Bedzyk and co-workers at X15A have 

performed some measurements in the total external reflection regime to investigate the adsorption ofa thin film 

ofcopper on apolymerlayer on apolished substrate. Such 

configurations are of growing interest to a variety of 

technologies. The variations in the standing-wave pattern 

near the substrate critical angle can give information on 

the location and thickness of the film following thermal 

treatment. The copper was seen to form relatively thick 

islands as deposited, and following annealing to become 

thinner. No interdiffusion ofthe copper into the polymer 

beyond 5 A was observed. One of the problems with the 

standing-wave method is the need for the adsorbate atom 

to provide a signal in response to excitation by the 

standing wave field strength. This has traditionally been 

x-ray fluorescence from a high-Z adsorbate. Many systems of interest involve low-2 adsorbates, making this 

technique inapropriate. Berman, Heskett and Kao have 

shown that photoemission can equallywell be used as this 

signal mechanism, and they studied half-monolayer coverages of CO on nickel (1 11) surfaces. They were able, 

using a cylindrical-mirror electron energy analyzer, to 

seperately record signals from carbon, oxygen and nickel 

core levels (Figure 5). Their results are consistent with 

those of recent SEXAFS and PED measurements, but not 

with earlier IR and EELS experiments. 

53 
n 

ux)O 2500 3000 

Kinetic Energy (ev) 

Figure 5aX25: Electron energy distribution 

curve of CO/Ni(l 1 1) measured at a photon 

energy of 3.055 keV. 

3 

-3 -2 -1 0 1 2 3 

Relative hergy (ev) 

Figure 5b X25: Measured XSW yields of the 

Ni2p,, 0 1 s, and C 1 s core levels as the bulk 

Ni(l11) Bragg reflection (at bottom) was 

scanned, compared with theoretical fits, for 

~(4x2) CO/Ni(l 1 1). 

MAGNETIC SCATTERJNG 

The first observation of surface magnetic scattering 

has been performed by G. Watson and collaborators 

taking advantage of the large resonant enhancements 

accessible near the Uranium M, edge. In experiments at 

beamlines X22C and X25 they were able to measure the 

dependance of the magnetic scattering truncation rod as 

a function of momentum transfer, photon energy and 

temperature, which gives information about the magnetic 

54 

order in the surface and near surface region of the sample. 

They have been able to model all this data, and have 

shown that the magnetic phase transition is continuous at 

the surface. This is not so surprising, but they also 

demonstrated that the sub-surface region also does not 

show first-order behaviour, in contrast to similar nonmagnetic surface-scattering results from other systems. 

The addition of a high-field superconducting magnet to 

the X22B spectrometer has enabled a series of magnetic 

scattering experiments on low-moment systems. An 

example of this is the work of V. Kiryukhin and collaborators to elucidate the magnetic phase diagram of the spinPeierls system CuGeO, (Figure 6). This material is a onedimensional antiferromagnet. At low temperatures the 

lattice dimerizes to lower the magnetic ground-state energy. The Zeeman energy corresponding to a 12T applied 

field lowers the energy of the first excited state enough to 

induce a transition into an incommensurate spin-lattice 

modulated phase. This phase had previously been inaccessible to scattering probes. These measurements have 

shown that this phase is a soliton lattice, and have given 

the inter-soliton distance and soliton width as a function 

of applied field and temperature. The measured soliton 

width is almost double that predicted theoretically, providing a challenge for the theory of one-dimensional 

quantum magnetism. 

,~_I_~___ -~ __ 

I (3.5 1 2.5) Superlattice Reflectior 

I 1088 

I 107 

1 

- 

0 

2 lo6 

v) lo5 

s 104 

c 5 io3 

W 

1 

c 

r 

3 

0 

x 

r?= v) 

- c 

1 o2 

1 .- n' 

2.45 2.47 2.49 2.51 2.53 2.55 

L (r.1.u.) 

Figure 6 X22B: Scans through the (3.5, 1, 2.5) 

superlattice reflection of CuGeO, at T4K in the 

Incommensurate phase. Successive scans were 

multiplied by 100 in order to achieve a constant 

offset on the logarithmic scale. The lines are the 

results of fits to resolution-limited Gaussians. 
DIFFUSE SCATTERING 

The study of x-ray diffuse scattering can provide 

information about disorder, both static and dynamic, in 

crystalline materials. Gibaud and collaborators have used 

the high-energy radiation available at beamline X17B 1 to 

advantage in such work. They point out that the Ewald 

sphere is so large at, say, 6OkeVit is essentially flat over the 

plane of the recording medium (in this case an imaging 

plate). This greatly simplifies the interpretation of such 

data, since only one scattering plane is imaged at a time, 

and the lines of constant indices are nearly straight. They 

illustrated these points with a series of measurements on 

a 3mm thick sample of KMnF, (Figure 7). They were 

able, for the first time, to image the entire RM branch of 

the Brillouin zone through two phase transitions, one at 

186K and a second at 100K. The R point condenses at 

18GK, but there is still intensity in the RM line until it 

disappears at 100K, as the M point condenses. 

INELASTIC SCATTERING 

It has long been held that a high-resolution study of 

the Compton scattering in the region where the core and 

valence contributions cross over would reveal a discontinuous change. This “Compton step” has never been 

observed experimentally. It has been assumed that this 

failure was a resolution problem. K. Hhdiiinen, using 

the high-resolution inelastic scattering instrument at 

X2 1 , has shown that the step is smeared out on a scale well 

above the resolution limit of that instrument. There is 

currently no theoretical model which can explain this 

smearing. The high-resolution fluorescence spectroscopic 

techniques developed at NSLS were put to an interesting 

use by W. Caliebe et al. at beamline X25. They used the 

spin-dependence of the fluorescence satellites to perform 

spin-dependent resonant Raman scattering studies of Gd 

at the LllI edge. The use ofa quarter-wave plate to generate 

circularly-polarized x-rays allows the selective excitation 

of spin-up or spin-down electrons in a magnetically 

aligned sample. The spin-orbit splitting is clearly observed in the dipole-allowed transition 

2p54P+15d0+3dg4E+15do. 

LIQUIDS 

Scattering from liquid surfaces received significant 

attention this year. Two liquid surface scattering stations 

were in operation, one at X22B and another atX19C. In 

addition the X22B setup was used at X25. Regan et a/. at 

X25 studied surface ordering in pure Hg and Ga. They 

observed differing behaviour in these two elements. In 

4 

(a) The [Ol 01 direction is vertical and the [I 001 

direction is horizontal. 

(b) The [Ol 01 direction is vertical and the [loll 

direction is horizontal. 

(c) The [OlO] direction is vertical and the [301] 

direction is horizontal. 

:igure7X17Bl: High energyx-raymonoLauepatterns 

If the (OOl), (1 01) and (1 03) scattering planes. 

55 
Hg they observed evidence of surface ordering, with the 

ordered layer thickness similar to the bulk pair correlation 

length. In Ga this ordered layer appears to extend deeper 

into the bulk liquid. 

Ning Lei and colleagues at X19C studied surface 

segregation of Bi in Bi-doped Ga. They found that the 

reff ectivity ofthe liquid surface could be well described by 

a model in which a complete Bi layer sits on top of bulk 

liquid Ga (Figure 8). They are currently extending this 

work to include Ga:Sn alloys. 

Metals were not the only liquids to be studied. The 

liquid-liquid interface in a ternary system ofwater, decane 

and C4E1 (an oil) were studied atX19C by Williams and 

co-workers. These systems exhibit ultra-low surface tensions and the interfaces are expected to have large-amplitude thermal fluctuations. The data suggests an interfacial roughness of order 50 A compared to the molecular 

size of 9 A. This difference is attributed to the enhanced 

thermal fluctuations. Deutsch and collaborators continued their studies of surface freezing in alkanes at X22B, 

moving towards an understanding of surface ordering in 

liquid binary alkane mixtures. These mixtures introduce 

an extra degree of freedom compared to pure alkane 

samples which may lead to prewetting, surface enrichment and surface layering. For large differences in alkane 

molecular weights, discontinuous changes were observed 

involving surface segregation and several 2-D structural 

phase transitions. Theoretical models are being developed to explain these observations. 

NUCLEAR RESONANT SCATTERING 

The properties of near-monolayers of rare gases 

adsorbed on graphite have been, and continue to be, the 

subject of much study for many years. Almost all of the 

previous work has concentrated on the static structure of 

such films using diffraction ofx-rays or neutrons. Even so 

there is still controversy surounding the details of the rich 

phase diagrams which have been uncovered. Nuclear 

resonant scattering offers the possibility of studying in 

detail the dynamics of these phases. D. Johnson performed such a study on beamline X12A. 83Kr has a 

convenient nuclear resonance at 9keV, and he was able to 

produce an optical system suitable for measuring the 

nuclear forward-scattering which contains the dynamic 

information. He discovered that there is significant lattice 

softening near a commensurate-incommensurate phase 

transition boundary, followed by a significant stiffening 

rn of the layer as it approaches completion. 

n 

L - 

0 

u 

CY 

LL 

-i-' 

-@ 

Q 

>\ 

v, 

c 

U 

i-, .- 

3 -0.5 - S 0.5 1.0 1.5 2.0 2.5 3.0 

1.5 

1 .o 

0.5 

0 

n 

Y 

7 1.2 

m 

u 1.0 

3 0.8 

0.6 

$ 0.4 

0 0.2 

Eo 

3 -10-5 0 5 10 15 

.- 

.- 

0 

Fig. a Fig. b 

:igure 8 X19C: (left) circles denote the experimentally obtained specular reflection after divided by the 

theoretical Fresnel reflectivity for gallium. The solid line denotes the fit to a complete bismuth monoiayer 

on top of bulk of liquid gallium. (Right) The atomic distribution to the interface, obtained from the fit. 

56 
This report outlines some of the significant 

results obtained from the two beamlines mainly 

comprising the NSLS X-ray Topography Special 

Interest Group: X19C and X23A3. 

A broad range of experiments has been carried 

out on X19C in the last year. The following are 

selected highlights. In a project funded by Cree 

Research Inc. via AEWNAFOSR, C. Carter, V. 

Tsvetkov and R. Glass of Cree Research Inc., and W. 

Si and M. Dudley of Stony Brook carried out a 

detailed study of micropipes (hollow core screw 

dislocations) in GH-Sic single crystals grown at Cree 

Research Inc. using PhysicalVaporTransportmethod. 

The Burgers vector of the micropipes, b, was determined using two relative and two absolute techniquesvia Synchrotron White BeamX-ray Topography, with good agreement being obtained for four 

sets of data. One of the absolute techniques involves 

the measurement of the lattice tilt either side of the 

dislocation core by recording transmission projection white beam images at different specimen-film 

distances and measuring the tilt angle between the 

two components of the bimodal images which are 

longitudinally shifted with respect to each other. An 

example showing the mutual shift of the bimodal 

dislocation image components recorded at two specimen-to-film distances is shown in Figure 1. From 

the lattice tilt S and image width W, both the sense 

and magnitude of Burgers vector could be determined The other absolute technique involves explicitly mapping the lattice tilt around the micropipe 

from topographs recorded in the transmission section geometryas shown in Figure 2. The diameters of 

corresponding hollow-cores of the dislocations (i.e. 

the diameters of the micropipes), D, were measured 

using Scanning Electron Microscopy. The relationship between micropipe Burgers vector magnitude 

and diameter, D = pb2/4n9, (p is shear modulus, y 

is specific surface energy), as predicted by Frank [F. 

C. Frank,Acta Cyst., 4,497-501, (1951)], was then 

tested. Good agreement was found, as shown in 

Figure 3. 

Figure 1 X19C: Projection transmission x-ray 

topographs showing a screw dislocation (micropipe) 

image M, in 6H-SIC, g=0006, h= 0.89 r\, recorded at 

two specimen-to-film distances Dsf. S is the lattice tilt, 

W is the image width. (a) Dsf = 5 cm, and (b) Dsf = 1 7 

= cm. Research supported by ARPNAFWL under 

Grant No. FY33615-95-C-5426 through Cree Research, 

Inc. under Grant No. 95-004. 

57 
Figure2 XI 9C:Asection 

transmission x-ray 

topograph showing a 

screw dislocation 

(micropipe) image M, in 

6H-Sic, g=0006, M.89 

r\, recorded atspecimento-film distance Dsf = 1 6 

cm. Research supported 

by ARPNAFWL under 

Grant No. FY33615-95- 

C-5426 through Cree 

Research, Inc. under 

Grant No. 95- 004. 

Figure3 XI 9C: Relationship 

between the magnitude of 

Burgers vector of screw 

dislocation, b, and the 

diameter of the associated 

micropipe, D. Research 

supported by ARPNAFWL 

under Grant No. FY33615- 

95-C-5426 through Cree 

Research, Inc. under Grant 

No. 95-004. 

451 

/+ 

40- 

35- 

30- 

25- 

20- 

15- 

10- 

Burgers vector magnitude, b*b, k 

(Thousands) 

58 
Figure 4 X19C: Synchrotron white beam X-ray 

topograph (g= 440, A= 0.64 A) recorded in 

reflection geometry from a (1 IO) InP wafer cut 

from a MLEK grown [OOI] boule showing slip 

bands (SB) originatingfrom the shoulder region of 

the boule. Research carried out undertheauspices 

of ARPNAFOSR Consortium for crystal growth 

research (Contract No. F496209510407). 

Figure 5 X19C: Synchrotron white beam X-ray 

topograph (g=400, h=0.52A) recorded in 

transmission geometry from a (001) InP wafer cut 

from a LEK grown [OOl] boule showing a well 

defined four-fold symmetric distribution of 

dislocations. Research carried out under the 

auspices of the Stony Brook ARPA/AFOSR 

consortium for crystal growth research (Contract 

No. F496209510407). 

In work carried out under the auspices of an MA/ 

AFOSR hnded consortium studying the growth of InP 

and other semiconductor crystals, V. Prasad, H. Zhang, 

W. Si, H. Chung, and M. Dudley of Stony Brook, and D. 

Bliss and A. Anselrno of Rome Airforce Laboratories have 

been correlating defect microstructures and interface shapes 

observed using Synchrotron White Beam X-rayTopography (SWSXT) with the theoretical predictions of heat 

transfer and stress generation during the single step, high 

pressure Kyropoulos growth of doped InP boules. Figure 

4 shows a reflection topograph recorded from a wafer 

sliced longitudinally from an [00 11 boule. Stress concentration, leading to slip band generation, is clearly observed 

at the neck region of the boule. This correlates well with 

stress calculations. Figure 5 shows the distribution of 

dislocations in a typical 001 wafer cut from a [OOl] boule. 

Note the four-fold symmetry of the dislocations’ distribution. This four-fold symmetry is predicted from resolved 

shear stress calculations, as shown in Figure 6. Interhce 

shape is often revealed on x-ray topographs due to the 

periodic variation on dopant concentration as the interface migrates during growth. Control of the shape of the 

interface is crucial to minimize defect generation and 

propagation, and its observation is a primary indicator of 

the degree of thermal control during the growth process. 

Figure 7 shows an example ofan observable interface. The 

observed shape agrees well with theoretical predictions 

pertinent to the particular growth chamber used [H. 

Chung, W. Si, V. Prasad, H. Zhang, andM. Dudley, to 

be published]. 
1101 

Figure 6X19C: Distribution of 

resolved shear stress in [OOI] 

LEK grown InP crystals subject 

to thermal-gradient-induced, 

uniformly distributed, radially 

compressive, hoop stresses. 

Stress calculations revealed that 

maximum stresses were 

concentrated in the <loo> 

directions while minimum 

stresses were induced in the 

<11 O> directions. The 

calculated results are consistent 

with our experimental 

observations. Research carried 

out under the auspices of the 

Stony Brook ARPA/AFOSR 

consortium for crystal growth 

research (Contract No. 

F496209510407). 

In a project funded by 

the Army Research Office 

and NSF I. Baker, X. Hu of 

Dartmouth College, and M. 

Dudley of Stony Brook have 

carried out detailed in situ 

straining studies of notched 

ice single crystals., in order 

to examine the generation 

and multiplication of dislocations in the vicinity of 

notches, and in particular to 

determine if a dislocationfree zone exists as previous 

etch pit investigations by 

other workers seemed to indicate. Results obtained fiom 

single crystals of three different orientations, numbered 

1 to 3, as shown in Figures 8, 

9, and 10, indicate that the 

deformation is dominated by 

basal plane dislocations. and 

that no dislocation free zone 

exists. 

GO 

Figure 7 X19C: Synchrotron White Beam X-ray Topograph (g=OOz, 

=0.45A) recorded from a longitudinal cut (1 IO) S doped In P wafer showing 

the morphology of the growth interface (I) and the formation of slip bands 

(S, toSJ Research carried out underthe auspices of ARPNAFOSRConsortium 

of crystal growth research (Contract No. F496209510407). 
Figure 8 X19C: Dislocation 

motion at notch tips in ice single 

crystals: (a) crystal and notch 

orientations for specimen 1. (b) 

Dislocation structure prior to 

loading. The (0001) planes are 

normal to loading direction and 

are, thus, horizontal and seen 

edge-on. (c) Image (load 

removed) taken after application 

of a stress of 0.22 MPa for 45 

minutes and 0.44 MPa for 20 

minutes at -1 3°C. Note that the 

dislocations have increased their 

lengths due toslide onthe basal 

planes. g=lOlO in both b and c. 

Research funded by the Army 

Research Office through Grants 

No. DAA-L03-92-G-0319 and 

No. DAA-H04-93-G-0061 and in 

part by the donors of the 

Petroleum Research Fund which 

is administered bythe American 

Chemical Society. 

Load 

4 i2io 

Figure 9 X19C: Dislocation motion at notch tips in ice single crystals: (a) Crystal and notch orientations of 

specimen 2. (b) Topograph (g=lOiO, load on) taken after application of a strez of 0.22 !!a for 10 minutes at 

-1 3°C. Note dislocation bundles which run in the Burgers'vectors directions [I 1201 and I21 IO]. Research funded 

by the Army Research Office through Grants No. DAA-L03-92-G-0319 and No. DAA-H04-93-G-0061 and in part 

by the donors of the Petroleum Research Fund, which is administered by the American Chemical Society. 
2iio 

[oi io] 

Figure 10 X19C: Dislocation motion at notch tips in ice single crystals: (a) Orientation of specimen 3 (b) 

Prior to loading (c) 0.1 5 MPa for 1 3 min. 0.31 MPa for 4 min., and 0.45 MPa for 7 min., at -1 5°C. Research 

funded by the Army Research Office through Grants No. DAA-L03-92-G-0319 and No. DAA-H04-93-C-0061 

and in part by the donors of the Petroleum Research Fund, which is administered by the American Chemical 

Society. 

62 
Continuing their investigation 

of defects inn CVD diamond, David 

R. Black and Harold B. Burdette 

from NIST and Mary Anne Plano, 

M. Dale Moyer and Miguel A. 

Moreno from Crystallume have observed individual defects in a 

: I 

j 

1 

! 

I 

0.2mm 

c 

I 

j 

, 

i---- 

I 

Figure 11 X23A3: A (1 11) asymmetric transmission image 

showing a stackingfault (S) in the substrate and a linear array of 

dislocations. (D) in the CVD film. 

homoepitaxial CVD diamond film A high-quality, lowstress 200 pm thick epitaxial diamond film was grown on 

a 400 pm thick high-temperature/high-pressure type IIa 

diamond. A direct correlation was found between defects 

in the film and substrate defects as shown in Figure 11. 

The area of the film with the lowest defect density was 

grown on a nearly defect-free part of the substrate. 

Within this region, individual defects are seen in the film. 

Stacking fauIts in the substrate, which terminate at the 

deposition surface, appear to result in linear arrays of 

dislocations in the film. These linear arrays are the same 

length as the termination line of the stacking fault and are 

comprised of individual dislocations, in regions where 

dislocatians in the substrate terminated at the 

surface, more strain was observed in the film. 

63 
Beamline X26A: Synchrotron x-ray fluorescence false color contour maps of major element concentrations (FeO and MnO), and of a trace element concentration (Y) for an almandine garnet from Connecticut, 

USA. Yellow color represents the highest concentration on these scans and the whole width of these 

scans is 4.25 mm. At lower left is a photomicrograph of this mineral. [A. Lanzirotti, State University of 

New York @I Stony Brook] 

Paul Zschack 

ORNL / Oak Ridge Institute for Science and Education 

NSLS Users' Executive Commitfee Chairman 

The NSLS held its 14th Annual Users' Meeting 

May 9-10, 1995 at Brookhaven National Laboratory. 

Associated with the 1995 Meeting, 5 parallel workshops 

were held on May Sth, and a satellite workshop on WS 

was well attended on May 7th. The workshop and hasreceived. 

scientific programs emphasized scientific productivity 

and recognition of the NSLS as a mature user facility. 

William Oosterhuis from the U.S. DOE next offered cautiouslyencouragingwords regarding the outlook 

for future funding, and was particularly optimistic about 

the favorable reception which the "Facilities Initiative" 

NSLS Acting Chairman Denis McWhan gave a 

report on the state of the facility. Even though the next 

(left to right): Cullie Sparks (Oak Ridge National 

Laboratory), Denis McWhan (Associate Director Basic 

Energy Science Programs, BNL and Chairman, 

National Synchrotron Light Source), and Tony 

Cheetham (University of California @ Santa Barbara). 

Following opening remarks by BNL Deputy Lab 

Director Marty Blume, Cullie Sparks (ORNL) gave the 

inaugural NSLS Distinguished User Presentation. This 

was a thoroughly enjoyable retrospective talk that served 

to remind all users that the reliable operations we currently enjoy did not come easily. Through a series of 

anecdotes, the efforts of many individuals were acknowledgedasimportantfortheevolutionoftheNSLS asauserfriendly facility. 

66 

Keynote Speaker, Robert Calvin, Chairman of 

the Executive Board of Motorola, Inc. and 

Chairman of the Secretary of Energy Advisory 

Board Task Force on Alternative Futures for the 

DOE National Laboratories. 

generation synchrotron sources are coming on line, the 

NSLS continues to be a vibrant, growing facility with 

planning for a Phase 3 upgrade and creation of PRT 

confederations. New beamline commissioning and PRT 

reorganizations indicate that the NSLS is continually 

adapting to accommodate the changing needs of the user 

community. 

The morning session ended with the Keynote Address, given by Robert Galvin, Chairman of the Executive 
Board ofMotorola Inc., and Chairman of the Secretary of 

Energy Advisory BoardTask Force on Alternative Futures 

for the DOE National Laboratories. Mr. Galvin provided 

timely insight on the role of Government in the creative 

process, and most eloquently described his vision for the 

eventual privatization of the National Laboratories. This 

is one step beyond the Task Force recommendation for 

corporatization of the National Laboratory facilities, and 

introduced users to provocative, challenging new concepts in scientific organization and administration. 

The traditional barbecue lunch provided the venue 

for Special Interest Group (SPIG) meetings and the User 

Executive Committee elections. Elected to serve 2 year 

terms were Doon Gibbs (BNL - Physics), Peter Stephens 

(SUNY @ Stony Brook) and Kim Mohanty (EXXON). 

In addition, recognizing a significantly growing research 

area, the User Association voted to create another special 

interest group for biology. 

After lunch, the scientific program began with Joel 

Berendzen (LANL) showing a wonderfully produced 

device concepts. Sam Krinsky (NSLS) detailed the commissioning of the Elliptical Polarized Wiggler, and operations to 100 Hz with no significant adverse impact on 

operations. With the exciting prospects of easily using 

circularly polarized light, the EPW holds great promise. 

Similarly, Peter Stefan (NSLS) discussed the exceptional 

performance of the Prototype Small Gap Undulator, and 

noted only minimal compromise on lifetime. T h e 

conference poster session, with 80 contributions, was held 

Tuesday afternoon concurrent with a cocktail reception. 

The wide diversity of contributions again documents the 

importance of research done at the NSLS in many scientific disciplines. This year, the conference banquet was 

held at the Port Jefferson Country Club where the wonderful view and exceptional food were enjoyed by all. In 

a short after-dinner presentation, the Users' Association 

and the NSLS staffacknowledged the 5 years ofleadership 

Denis McWhan has given as Chairman of the NSLS. 

The meeting resumed Wednesday morning when 

Eric Isaacs (AT&T Bell Labs) demonstrated use ofinelas- 

(left to right): Martin Blume (Deputy Director, 

Brookhaven National Labortory) and Louis 

Terminello (Lawrence Livermore National 

Laboratory, Chairman of SSRL Users' Executive 

Committee). 

(left to right): Xiaodong Zhang and Janos Kin 

(SUNY @ Stony Brook), with Christopher Buckley 

(King's College London). 

video demonstration of the crystallography of 

carbonmonoxy myoglobin. Steve Dierker (U. of Michigan) next provided exciting new results using coherent 

radiation to study complex fluids. Certainly, protein 

crystallography and speckle techniques will continue to be 

important programs at the NSLS and at other synchrotron facilities. 

The NSLS continues to work toward improved 

performance, as evident from the work on new insertion 

tic x-ray scattering in probing electronic structure in 

condensed matter systems. Unlike electron probes, x-rays 

provide good access to momentum transfer, and give a 

more complete picture of the dynamic structure factor. 

Myron Salmon (U. Of Illinois) next explained x-ray 

resonant magnetic scattering measurements used to detect the induced spin structure in a Dy-Lu alloy film. The 

growth during the last several years in magnetic scattering 

studies using x-rays is remarkable. In another important 

67 
area, Geraldine Lamble (NSLS) presented several examples of applications of XAFS techniques to study 

environmental problems. 

The next two talks demonstrated continued success 

on the W floor. First, John Gland (U. of Michigan) 

talked about the kinetics of organic reactions on metal 

surfaces using fluorescence yield measurements with ultra-soft x-rays. The morning session concluded when Eric 

Jensen (Brandeis U.) discussed advances in high-resolution photoemission techniques. Milli-electron volt resolution photoemission will become even more widely 

utilized in the next few years. 

The lunch break on the second day was an opportunity to acknowledge the Structural Biology building 

addition to the NSLS. Roland Hirsch from the DOE 

Office of Health & Environmental Research was joined 

by BNL Laboratory Director Nicholas Samios, Denis 

McWhan and BNL Biology Department Chairman William Studier for a ceremonial ribbon cutting. The dedication ceremonies, held indoors at Berkner Hall due to 

poor weather conditions, were attended by over 300 

meeting registrants and NSLS staff which indicates the 

importance of structural biology programs in the future. 

The final session began with Mike Toney (IBM 

Almaden) presenting an interesting talk on near surface 

structures in rubbed polymer films. Although there is 

technological relevance (for example, to flat panel displays), there is also fundamental interest in this behavior. 

Brenda Laster (BNL - Medical) presented an application 

of synchrotron radiation to cancer radiotherapy using an 

enhancement due to Auger electrons, and its potential for 

diagnostic imaging of malignant breast disease. Her 

enthusiasm for this work underscores the potential impact 

. 

I 

Attendees of the 1995 Annual Users' Meeting 

examing the display of one of the 24 exhibitors. 

of such medical applications. Finally, Mike Regan 

(Harvard U.) concluded the scientific program with a 

discussion of reflectivity measurements to understand the 

surface and near-surface layering structure of liquid metals. 

The business of the Meeting was concluded when 

the UEC, in executive session, selected Peter Stephens 

(SUNY) the UEC Chair-Elect and Chair of the Organizing Committee for the 1996 Annual Users' Meeting. 

Planning for the next meeting is already 

underway. 
ELECTRON LASER CONFERENCE 

Ilan Ben-Zvi and Samuel Krinsky 

NSLS 

Conference Chairmen 

The National Synchrotron Light Source has been 

pursuing the development of new radiation sources for a 

number ofyears. Groundbreaking theoretical and experimental work at BNL, and the NSLS in particular, has 

strongly contributed to the belief that the next generation 

of light sources will be Free-Electron Lasers (FELs). In 

1992 the Executive Committee of the International FEL 

Conference decided that BNL would host the 1995 FEL 

Conference. This decision was a recognition of the work 

done at BNL on this subject. 

The 17th International Free Electron Laser Conference and 2nd International FEL Users Workshop were 

held August 21-25 in New York City at the Marriott 

Marquis hotel on Times Square. The FEL Conference 

was co-chaired by Ilan Ben-Zvi 

and Samuel Krinsky and the 

Users Workshop was co-chaired 

by Erik Johnson and Glenn 

Edwards of Vanderbuilt University. The 267 attendees from 

15 countries met to discuss the 

advances in FEL technology 

taking place during thelast year 

throughout the world, and to 

consider the maturing scientific programs at Infrared FEL 

User Facilities. The FEL Conference and FEL Users Workshop were held in parallel sessions to allow a good interaction between the radiation 

source scientists and the radiation users. Over 300 papers 

were presented at the conference. The proceedings, to be 

published by North Holland, 

will include about 200 manuscripts in 600 pages of Nuclear 

Instruments and Methods. 

Among the subjects at the center stage of the conference 

were the development of short wavelength FEL and also 

high power devices at longer wavelengths. 

The participants of the conference enjoyed the 

outstanding facilities and rooms of the Marriott Marquis 

hotel as well as the opportunity to visit the Big Apple. 

Tickets to Broadway shows and City tours that were 

provided by the conference organizing committee were in 

great demand. The conference included two receptions 

(one each for the conference and workshop) and a banquet. Among the events at the banquetwas the traditional 

award ceremony of the FEL Prize and a chamber music 

concert. 

llan Ben-Zvi (far left) and conference attendees at Accelerator Test Facility (ATF) 

Beamline #2 which is the site of the inverse FEL experiment. The tour of the 

ATF was par t of the Wednesday visit to BNL. 

69 

71 
Beamline U13UA View looking into the Extreme Ultraviolet Lithography (EUVL) camera operated by 

AT&T Bell Laboratories of Lucent Technologies. The mask is on the block on the left, and the wafer is on 

the right. The 1X Offner camera is suspended overhead: it was assembled and in an initial commissioning phase during FY 1995 and will be capable of exposing wafers over a large (several square millimeter) 

area. Two low-energy (20-120 eV) Zeiss gratings (160 degrees included angle) were also commissioned, 

and a resolving power of 5000 was demonstrated at 63 eV photon energy. 

Stephen Warner 

VUV Ring Manager 

Stephen Warner, VUV Ring Manager 

has increased over FY 1994 level, due to 

an increase in the number of hours of 

operation. This increase resulted mainly 

from a decrease in maintenance and studies time. 

The major improvement in the 

VUV Ring operation has been an increase in the operating energy of the 

electron beam to 800 MeV. The actual 

increase in energy from field measurements in the dipole magnets was 8.6% or 

an increase from 744 to 808 MeV. This 

increase was confirmed by measurements 

of the undulator photon energy spectra. 

The advantage of this higher energy has 

been a reduction in Touschek scattering 

rate and an increase in beam lifetime by 

more than 40% (see Figure 7). This 

continues the steady increase in lifetime 

over the last four years, when the 4th 

harmonic RF cavity was commissioned 

and used to increase the electron bunch 

length. Figure 8 shows the improvement 

in the current per fill resulting from this 

improvement program. At the operating 

energy of 800 MeV, a typical 5 hour 

operational fill decays from 850mA to 

about 325 mA, almost a factor of two 

above the current level in 1992. The only 

negative side of this increase in energy has 

Figure 1 shows the breakdown of the VW Ring been the need to ra&p the energy down to the 744 MeV 

operating time for the Fiscal Year 1995. The monthly 

breakdown of these statistics is shown Figures (2 to 6). 

After a steady improvement in the reliability of operation 

over the past several years, the unscheduled downtime 

increased from under 2% to over 3%. This was largely the 

result of problems with the injection system arising from 

troubles with the new booster dipole power supply. This 

will be repaired in FY 1996 and the old power supply will 

remain available as a hot spare, reducing the likelihood of 

this situation causing a continued reduction of the beam 

reliability. Despite this trouble, the integrated current 

74 

injection level and back up again. This takes less than half 

a minute to ramp the energy, contributing very little 

impact on the hours of operation lost due to injection. 

However, after ramping to 800MeV, the dipole field 

undergoes a 15-20 minute relaxation to reach equilibrium 

at the higher field, due to thermal expansion from the 

higher current in the magnet coils. Since the field change 

occurs while the user photon optics are warming up and 

as a result of the Global Orbit Feedback System (GOFS) 

holding the beam stable, the users have yet to see any real 

impact from ramping the ring energy. It is planned that 
the booster peak energy will eventually be increased to 

match the VUV operating energy. Continuing this very 

successful increase in ring energy and lifetime will remain 

a high priority for theVUVRing, however this will not be 

done if the increase could risk the high reliability of 

operation that has been achieved. It should be noted that 

even at the energy level of 800 MeV, this represents a 14% 

increase in energy from the design value of 700 MeV and 

a 70% increase in synchrotron radiation power. 

The stability of the electron beam orbit was improved this year by the implementation of an RF Frequency Feedback System (RFFFS). This was done by 

programming a workstation rather than a micro-computer and it corrects the orbit every several seconds by 

adjusting the RF frequency a few Hertz out of 52.886 

MHz. This corrects the horizontal orbit motion by 

shifting the average beam energy (total energy change 

A - < 2x10 -5 or less than 5% of the natural energy spread E 

E 

of the beam) as the current and synchrotron power decay, 

a correction not possible with the present GOFS. The 

RFFFS has reduced the horizontal rms orbit motion by a 

factor three and the rms orbit motion at certain position 

monitors by a factor of 10 to 15. The system as expected 

has little improvement or adverse effect on the vertical 

orbit stability. Another improvement in operations has 

been the commissioning of a real-time tuning of the 

undulator gaps (U5U and U13U) during user operations. 

Although this is quite common in higher energy rings 

(e.g. X-Ray Ring), the lower energy of the VUV Ring 

makes orbit steering and betatron tune shifts have a 

greater impact on the bending magnet beamline users. 

The GOFS has always maintained a stable orbit during 

these changes, but the tune changes caused flux changes in 

the high resolution beamlines due to changes in the 

vertical beam size. A program was written to run on the 

workstations to compensate for the tune changes using 

the neighboring quadrupoles, while the gap is being 

changed. This has shown to be satisfactory for all affected 

beamlines and is now in routine operation. 

Figure 1: The breakdown 

of the VUV Ring usage 

based on total time (not 

scheduled time) for FY95. 

I VUV Ring Time Usagd 

(66.4%) Ope--*'--- - 

(3.3%) Downtime 

(3.0%) Injection 

Con/Com 

Ave. fill current: 835 mA 

Ave. charge rate: 105 mA/min 

Ave. lifetime at 500 mA: 287 min 

Total user integrated current : 

2933 A-Hrs (1 22.2 A-days) 

Total hours of operation: 581 7 hours 

Average operating current: 504 mA 

75 
~ 

VUV Ring 

Performance 

FY 1995 

5 200 

I 

a' 

E 

a 

100 

0 

CCT DEC FEB PPR JUN WG 

Figure 3: The total integrated current for the 

VUV Ring accumulated each month. 

02TDK:FEBPPRJUNW 

Figure 5: The VUV Ring vacuum pressure at 

500 mA beam current averaged over each 

month. 

150. 1 

Figure 2: The VUV Ring injection charge rate 

averaged over all fills in each month. 

mcEcR33ppR~pus 

Figure 4: The injection current averaged over 

all fills in a month for the VUV Ring. 

CCT DEC FEB PPR JUN AUG 

Figure6 TheVUV Ring exponential beam lifetime 

at 500 mA beam current (seven bunch operation 

only) averaged over each month. 
0 1 2 3 4 5 

Time (hrs) 

Figure 7: VUV beam lifetime comparison. 

A major new system was added to the VUV Ring 

during FY 1995, a Superconducting Magnetic Energy 

Storage device (SMES). This device was provided at no 

cost to the NSLS and can provide power to maintain the 

VUV Ring beam during transient loss of AC power for 

periods of up to five seconds. Although this system has 

switched-in,.many times while maintaining the beam in 

the ring, it has yet to prove itself as a solution to the power 

transient problem from an operational downtime point of 

view. Continued study may eventually prove the SMES 

technology as just such asolution, but in the meantime its 

cost and impact has not had a negative effect on operations. 

0 I , , , , , , , , 

0 I 2 3 4 5 

Time (hrs) 

Figure 9: VUV Ring top-off mode comparison. 

Finally, a test of the Top-Off Method of Injecting 

(TOMI) of the VUV Ring was performed in February. 

Figure 9 shows the current versus time for this study shift. 

The beam current was maintained by the injection system 

at 500 +25 mA over a 5 hour shift, by injecting 50 mA 

approximately every 18 minutes. With the average injection rate of the injection system this could be done in 30 

seconds or less, but typically was less than one minute. 

Measurements of beam orbit stability during TOMI 

showed factors of 4 to 8 reduction in the vertical and 

horizontal rms beam motion, respectively. This allowed 

high resolution (< 0.1%) IRscans to be made over periods 

of greater than an hour compared to 20 minutes during 

normal operations. The clear advantage to the users, 

besides orbit stability, will be reduced power loading 

effects on their photon beam optics. In order for TOMI 

Time (hrs) 

Figure 8: VUV current comparison. 

to become an operational reality, considerable effort will 

be in the areas of radiation safety, injection efficiency and 

reproducibility, and to reduce the injection transient 

beam motion (period less than 30 msec. out of the 1.2 

second injection pulse period). In fact TOMI has been 

the injection method of the VUV Ring for years (prior to 

800 MeV operations), but with a large dynamic range of 

current (850 to 250 mA). Once the technical problems 

are solved, allowing the shutters to remain open during 

the injections, the users could benefit from more stable 

beam and flux with the possibility to increase beam 

brightness without the concern of reduced lifetime that 

has plagued the VW Ring operations since its 

inception. 

77 
~ 

VUV STORAGE RING PARAMETERS AS OF NOVEMBER 1995 

Betatron Function (p, p,,) 11.1 m, 5.84 m * 

1240 pm, >45 pm (130 pm in normal ops.) * 

112 prad, >7.7 prad (22 prad in normal ops.) 

Source Size (G~, G,) 

Source Divergence (ox, G,,) 

Normal Operating Energy 

Peak Operating Current (multibunch ops.) 

Circumference 

Number of Beam Ports on Dipoles 

Number of Insertion Devices 

Maximum Length of Insertion Devices 

~JEJ 

B(P) 

Electron Orbital Period 

Damping Times 

Lifetime @ 200 mA with 52 MHz 

(with 211 MHz Bunch Lengthening) 

Lattice Structure (Chasman-Green) 

Number of Superperiods 

Magnet Complement 

Nominal Tunes (vx, v,,) 

Momentum Compaction 

RF Frequency 

Radiated Power 

RF Peak Voltage with 52 MHz (with 21 1 MHz) 

Design RF Power with 52 MHz (with 211 MHz) 

Synchrotron Tune (vJ 

Natural Energy Spread (o,/E) 

Bunch Length (20) 

(21ms with 21 1 MHz Bunch Lengthening) 

Number of RF Buckets 

Typical Bunch Mode 

Horizontal Damped Emittance (EJ 

Vertical Damped Emittance (E,,) 

Power per Horizontal milliradian (1 A) 

0.808 GeV 

0.85 amp (0.9 x 10l2 e-) 

51.0 meters 

17 

2 

- 2.5 meters 

19.9 i\ (622 ev) 

1.39 Tesla (1.91 meters) 

170.2 nanoseconds 

zxqy= 13 msec; ze = 7 msec 

360 min 

(590 min) 

Separated Function, Quad, Doublets 

4 

8 Bending (1.5 meters each) 

24 Quadrupole (0.3 meters each) c 12 Sextupole (0.2 meters each) 

3.14, 1.24 

0.0235 

52.887 MHz 

20.4 kW/amp of Beam 

80 kV (20 kV) 

50 kW (IO kW) 

0.0018 

5.0 x IO4, I, < 20 mA 

9.7 cm (I, < 20 mA) 

9 

7 

1.62 x lo7 meter-radian 

2 3.5 x 1010 meter-radian (2.8 x IO3 in normal ops.) 

3.2 Watts 

(28) 

* 

78 

Arc Source Parameters 

Betatron Function (pX,p,,) 

Dispersion Function (q,, qx) 

ax)# = -Fxy /2 

yxy= (1 +azu)@,, 

Source Size (ox, o,,) 

Source Divergence (a&,) 

1.18 to 2.25 m, 10.26 to 14.21 m 

0.500 to 0.062 m, 0.743 to 0.093 m 

-0.046 to 1.087,3.18 to -0.96 

0.738 to 0.970 m-', 1.083 to 0.135 m-' * 

536 to 568 pm, >60 to >70 pm (170-200 pm in normal ops.) * 

686 to 373 pad, 19.5 to 6.9 prad (55-20 prad in normal ops.) 

* 

cy is adjustable 
As determined from the NSLS User Administration 

databasestatistics, there was a total of2206 users working 

on scientific programs on both the X-Ray and VUV 

Storage Rings during FY 1995. The percentage breakdown of users according to home institution was 48.4 % 

from universities, 13.7% from abroad, 13.3% from industry, 8.3% from non-BNL DOE labs, 8.2% from 

BNL, 5.3% from government labs, and 2.7% from other 

U.S. institutions. Technical progress on the VUVandXRay beamlines is given below. 

VUV BEAMLINES 

There were a number of technical beamline improvements on the VUV Ring during FY 1995. At U2B 

there were developments on both the Spectra Tech scanning IR microspectrometer line and the Nicolet 750 IR 

spectrometer line for studies ofmaterials at high pressures. 

The vacuum portion of the microspectrometer line was 

upgraded and new input optics were installed. The 

microspectrometer was commissioned for use with 15X 

and 32X objectives and tests were conducted in the 

Attenuated Total Reflection mode. A new optical system 

with improved signal throughput was installed on the 

high-pressure branch line, and the capability of accommodating larger cryogenic pressure cells was added. 

At U4IR a new Michelson rapid-scan interferometerwas tested in vacuum for future installation. This unit 

has dynamic alignment of the fured mirror, to remove 

tracking errors in the moving mirror, and is capable of 

scanning at a more rapid rate, which is important in the 

far-IR. An upgrade of the existing Impact-400 Michelson 

interferometer electronics was also initiated. 

As a result of an extensive study of the effect of U5U 

undulator gap changes on the VUV Ring, a program was 

developed which maintains theVWRing horizontal and 

vertical tunes essentially constant during + 2 mm gap 

changes. This has the effect of lowering orbit shifts to a 

level acceptable to W users so that 30 minute advance 

notices are now required before U5U gap changes (as 

opposed to the prior 24 hour notice). 

Modification of the U5 spin analyzer power supplies significantly improved the energy resolution (at 30 

eV photon energy) of spin-integrated spectra to 70 meV 

and of spin-resolved spectra to 100 meV. 

The U5 diagnostic port was upgraded in several 

areas. A 2-D CCD camera with a Spiricon LBA-100 

beam analyzer was put on line so that beam size history 

could be stored on the NSLS computer. A fast vacuum 

photo diode and sampling scope, which gave a bunch 

length averaged over thousands of beam revolutions, was 

replaced with a solid state photo diode, a 10 GHz pulse 

amplifier and a 5 GHz scope to measure bunch lengths 

during a single pass of beam. 

During the winter 1994-5 shutdown, the U7A 

beamline was converted from a toroidal grating monochromator (TGM) to a spherical grating monochromator 

(SGM). The monochromator portion of the upgraded 

U7A beamline is optically identical to the Ul3UA and 

U4B SGMs. However, the collecting and focusing optic 

upstream of the monochromator is much different: the 

Kirkpatrick-Baa mirror pair, which is used in both the 

Ul3UA and U4B beamlines, is replaced by a single 

toroidal mirror. The slightly poorer focus produced by 

this toroidal mirror at the entrance slit of the SGM results 

in somewhat lower transmission through the entrance slit 

(but no degradation in photon energy resolution). However, this transmission loss is more than compensated for, 

in the soft x-ray region, by the elimination of one reflection. This new beamline geometry, dubbed the toroidalmirror SGM (TSGM), has the advantages of no horizontal deflections (so it can fit in smaller angular space) and 

of permitting low-cost TGM+TSGM. 

The multiparameter analyzer system, introduced on 

U9B in FY 1994 to measure the time dependence of 

fluorescence over a wide emission spectrum, was modified to permit determination of these quantities simultaneously for both vertically and horizontally polarized 

fluorescent light. The beamline control computer was 

upgraded to a 486 ISA computer. 

A photo elastic modulator with a LiF optical element was tested on U1 1. This system permits measurement of circular dichroism to about 120 nm. Also, a 

superconducting magnet capable of reaching 7.5 Tesla 

79 

-.- 

! .- I 
was tested. This magnet will be used to measure magnetic 

circular dichroism in the future. AU11 capital equipment 

project continued during FY 1995. The upgrade included improvements in: (1) computer hardware and 

software, (2) electronic and electrical equipment, and (3) 

the discharge flow-ionization mass spectrometer. 

The two low energy (20-120 eV) Zeiss gratings( 160 

degrees included angle) were commissioned on U13UA 

during FY 1995. A resolving power of 5000 was demonstrated at 63 eVphoton energy. On U13UB, lightcan be 

switched into any one ofthree instruments: a20 reduction 

Schwarzschild camera operatingat 6.8 and 13 nm; an “AtWavelength” interferometer operating at 13 nm; or a 1X 

Offner imaging camera operating at 13 nm. The interferometer, commissioned during FY 1995, is capable of 

carryingout classical interferometry experimentsat 13nm. 

The 1X Offner camera, assembled and in an initial 

commissioning phase during FY 1995, will be capable of 

exposing wafers over a large (several square mm) area. 

X-RAY BEAMLINES 

A major change occurred in X-Ray operations in 

June 1995 when the maximum operational current 

increased from 250 mA to 300 mA. To prepare for the 

higher current, water-cooled beryllium windows were 

replaced on beamlines X4C, XGA, XGB, and X2GA and 

nineteen white beam windows already in operation at 

250 mAwere checked for leaks. Anew beryllium window 

design effort was underway in FY 1995 with the goal of 

installing 17 new windows during the December 1996 

shutdown. Operations at 350 mA would commence in 

January 1997. 

FY 1995 startedoffwithanaggingproblemwith the 

liquid nitrogen transfer system which had slowed down to 

an excruciating fill time of 2.5 hours for a large dewar. 

This problem was remedied when an ice plug was thawed 

out by flowing warm helium gas through the transfer line, 

restoring fill times of less than 30 minutes. 

There were a number of technical improvements on 

X-Ray beamlines during FY 1995. On the X3A1 and 

X3A2 beamlines new optics were put into operation. 

Additional improvements included stabilization of them 

focused beam position at the sample using a second 

feedback loop to control the focusing mirror tilt. A 

miniature ion chamber is used for precise beam location. 

Also, a high energy Bonse-Hart ultra small-angle x-ray 

scattering instrument was constructed capable of operating at 0.65 A. 

The X4C beamline moved closer to an early commissioning phase with the acquisition of all the major 

80 

optical components. The variable focusing white beam 

mirror and mirror tank were assembled. The monochromator tank was delivered and fabrication of the monochromator bender and tilt and translation stages began. 

On the XGA beamline, a new 4-point crystal bender 

was built which incorporates water cooling, crystal alignment and crystal tension release devices. These features 

will reduce aberration and increase stability. A new 

version of the beamline control software, EXAFS, was 

developed which includes procedures for polarization, 

magnetic circular dichroism (MCD) and synchronized 

laser measurements. 

At X7B image plate data collection techniques were 

implemented for time-dependent powder diffraction. An 

image plate holder providing for controlled translation of 

the image plate past a slit, permitted the collection of 

complete series of powder patterns down to 10 second 

intervals. The X9A beamline was under construction. 

The hutch, photon shutter, primary aperture, and monochromator tank were completed. 

The X11A hutch was expanded to make room for 

various experimental setups including a 13 element detector, UHV chambers, a large LN, dewar and a catalysis rig. 

The X11A motor driver system was converted from the 

Measurematic system to an ACS Step-Pak system. A 

more robust support was constructed for the Lytle detector to damp mechanical vibrations. The X11B doublebounce harmonic rejection mirror was mounted and 

characterized. 

Anewfocusingmirrorwas installed onX12Cwhich 

increased flux through a 200 micrometer aperture by a 

hctor of 2.5. 

At X15A two additional circles were added to the 

diffractometer, bringing it up to four-circle capability. 

Also, a hemispherical electron analyzer was installed on 

the UHV X-ray diffraction chamber. 

A load lock was installed on the XlGA beamline 

diffraction chamber to allow for fast sample switching of 

Si( 11 1) experiments and to include chemical treatment 

steps in the surface preparation without breakingvacuum 

or losing alignment. At XlGC a UHV surface EXAFS 

chamber was commissioned. 

On the X17B2 angiography/MECT(multiple energy computed tomography) beamline the new patient 

chair, monochromator, filter and attenuator assemblies 

were used to image angiography patients. A new patient 

safety interlock system was also installed and tested. 

Beamline modifications resulted in the first MECT experiments being performed on phantoms and small animals in the imaging room. 

New computer systems were acquired for the X1 SA 

beamline and optical encoders were integrated with the 
monochromator. Software enhancements included improved backlash compensation for all motors. At XI 8B, a 

new monochromator was installed which covers the 7 

KeV to greater than 50 KeV range using the Si(ll1) 

reflection. This is a water-cooled, detunable monolithic 

device providing simple, stable operation. 

The X19A thin window system was installed. This 

system incorporates sensors and controls to close two fast 

valves in case of a window rupture. A number of other 

AtX24A, anew nickel-coatedsilicon primaryspherical mirror was specified, procured and characterized (less 

than 3 A RMS roughness). An increase of about two in 

flux delivered to the experimental chamber is expected at 

3 keV. Better on-line alignment controls were implemented to ease the stringency of off-line pre-adjustment 

of monochromator crystals. 

AtX26A there was continued improvement ofx-ray 

fluorescence and microbeam production instrumentaimprovements were 

implemented. A goniometer system for performing single crystal xray absorption experiments was developed. A 

triple-bounce crystal system significantly enhanced the operation of 

the line at the sulphur 

K-edge by reducing the 

detuning required for 

harmonic rejection. 

Data collection software 

was implemented which 

may become a standard 

for NSLS x-ray absorption spectroscopy 

beamlines. 

A high stability 

scanning stage was fully 

commissioned on the 

white beam topography 

camera on beamline 

X19C. This enables the 

recording of scanned 

images of very large 

The new control room with NSLS Operations Staff (counterclockwise from lower lefi) 

Lenny Pharr, Billy Jew, tony Rodriquez, Mike Santana, and John Aloi. 

single crystals in asingle exposure. A routine experimental 

program began at X22A, a high-flux beamline for electrochemical studies. The X22B hutch was modified to 

accommodate a collaborator's 13 Tesla superconducting 

magnet. This entailed upgrades to the spectrometer table, 

radiation shielding, mu-metal shielding around the hutch 

and to the magnet sample holder. Also, a positivefeedback vibration isolator and three-fold increase in 

sample translation range were implemented on the liquid 

surface spectrometer. 

At X23A2 the beamline computer system sohare 

was upgraded. The X23B upgrade to extend the energy 

range and to improve the focal spot continued with the 

successhl testing of a prototype monochromator and the 

testing of new x-ray mirrors in BNL's Optical Metrology 

Shop. The mirror surface roughness was below 5 A 

tion. Work continued on developing and testing 

Kirkpatrick-Baa microfocusing mirrors. The K-B mirrors have produced x-ray beam sizes down to two microns 

with gains of about 1000 over pinhole-produced beams. 

A CCD camera system was tested for microtomography 

applications. 

AtX27C development ofan x-ray microtomography 

ficility began. The instrument relies on a coole chargecoupled device imaging camera lens-coupled to a single 

crystal phosphor. A resolution less than 10 microns has 

been achieved with a 2mm x 2mm field of view. 

A pinhole camera became operational at X28C and 

was interfaced to the accelerator control system, as a 

storage ring diagnostic. Aslitted detector used with thexray pinhole also was used to study the frequency dependence of the beam size and beam position changes. 

4 

81 
Thermal calculations performed on stainless steel 

kt valve blades indicated that the blades might melt after 

being fired and before the front mask would have time to 

close (which is about 0.7seconds 011x24). Since theX24A 

fast valve had fired a number of times during stored beam 

conditions, it was inspected during the May 1995 shutdown. The blade had a hole burned through it, as 

predicted from the calculations. The 8 mil stainless steel 

blades onXlgAandX24Awere then replacedwith 10 mil 

thickmolybdenum blades. A test to fire theX24 fast valve 

with currents above 400 mA was planned for just prior to 

the December 1995 shutdown. 

A major improvement on the X-Ray floor was a 

building expansion betweenX1 andX12 which gave these 

beamlines more space by creating awalkway outside ofthe 

old building perimeter and provided these beamlines with 

new dedicated user labs. This same expansion provided a 

new expanded Control Room which began operation in 

September 1995 without any disruption to XRay operations. 

82 
The X-Ray Ring usage for FY 1995 is broken down 

in Figure 1. The percentage breakdown by categories is 

virtually the same as for FY 1994. There was a slight 

(1.6%) decrease in the operations percentage caused by 

thesimultaneous failureofthreeofthe four NWLBooster 

dipole power supply transformers in July. Operations 

were restored after the original Kirkoff supply was reactivated. Beam remained in the ring for 5 days, so that only 

2 days of operations were lost. The transformers that 

failed had aluminum sheet windings with compression 

crimps on the copper power feeds. They had failed at the 

junction of the copper feeds and the aluminum sheet. 

New transformers were ordered with copper sheet windings and copper bars silver-soldered to the copper windings. 

There was considerable activity on the X13 straight 

section during FY 1995. During the December 1994 

shutdown, the NSLS Prototype Small Gap Undulator 

(PSGU) was removed so that vacuum chamber flanges 

could be re-machined to reduce the minimum electron 

beam aperture from 3.8 mm to 1.0 mm. The Elliptically 

Polarized Wiggler (EPW) was installed in theXl3 straight 

section during this same shutdown. The EPW began 

operation at 2 Hz in April after studies shifts had demonstrated that it had a negligible effect on users' beam. 

During the May 1995 shutdown trim magnets were 

installed to better compensate for vertical orbit motion 

caused by the EPW. The PSGU was reinstalled during the 

May 1995 shutdown and, in August, the photon spectrum showed that the design goal was achieved: a 2.5 keV 

fundamental, and a 7.5 keV third harmonic for a 2.5 mm 

electron beam aperture and a 5.6 mm magnet gap. The 

partial lifetime contribution was 36 hours. Shortly afterwards, the PSGU began operations at a 4.0 mm electron 

beam aperture and 7.5 mm magnet gap. Due to the 

reduction in beam lifetime at gaps less than 4mm, 

anyoperation at less than 4 mm will require approval by XRay users. 

The maximum operational current of the X-Ray 

Ringincreasedfrom250 mA to 300 mAattheendofJune 

1995. Before this boost in current could occur, a number 

of upgrades and tests had to be performed to comply with 

I X-Ray Ring Time Usage I 

(57.7%) Operations 

(0.7%) Interlock 

(3.4%) Downtime I 

(1.7%) Injection 

7(23%) ConlCom 

(12.6%) Studies 

I I 

100 2 

$ 

E 

a 50 

0 

OCT DEC FEB APR JUN AUG 

Figure 1: The Breakdown of the X-Ray Ring usage 

based on total time (not scheduled time) for FY95. 

Figure 2: The total integrated current for the X-Ray Ring 

accumulated each month for FY95. 

83 
the recommendations of the NSLS X-Ray Thermal Limits Task Force. Four water-cooled white beam beryllium 

windows were replaced and nineteen white beam windows already in operation at 250 mA were checked for 

leaks. Also, the X-Ray Ring active interlock system, with 

the exception of X13, was certified after the calibration 

and linearity of the system was verified up to 350 mA 

during 25 bunch operation. Finally, the front end masks 

on X21 and X25 were interlocked so they could not close 

unless the wiggler gaps were 

open. At the present time, operation of the ring up to 438 

mA ( at 2.584 GeV) or up to 

250 mA at 2.8 GeV is possible 

during studies and template 

shifts. Beam lines having compatible beryllium windows and 

the proper radiation shielding 

will be allowed to operate during these shifts. 

In order for operations 

to occur at currents above 300 

mA for all beamlines, a sizeable number of beryllium windows will have to be replaced. 

Operation at 438 mA requires 

replacement of a total of 34 

additional windows. A new 

beryllium window design effort was underway in FY 1995 

with the goal of installation of 

17 new windows during the 

December 1996 shutdown, 

active interlock beam position monitor electronics were 

also upgraded. The AGC dynamic range was extended 

from 35 dB to 55 dB to allow prefill tests at 7 mA and to 

permit operations up to 434 mA. In the future, the 

improved electronics will be installed on the other ring 

bpms not in the active interlock system. 

There were several successful trial runs of the digital 

orbit feedback system in the horizontal plane. The 

sampling frequency of the orbit micro was increased from 

84 

c 

J 

Roger Klaffky, X-Ray Ring Manager 

which is halfway to the number required for 438 mA 

operation and more than required for 350 mA operation. 

Operationsat350 mAwouldcommencein January 1997. 

There was progress in further stabilizing the electron beam position and size during FY 1995. In late '94 

the global feedback gain was increased by a factor of 3 at 

low frequencies ant the bandwidth was increased from 60 

Hz to 200 Hz. To avoid changes in horizontal andvertical 

beam size occurring at specificXRF2 tuner positions ( i.e. 

higher order modes) during a fill, the xRF2 temperature 

ramp was adjusted. The XRF3 tuner temperature was 

adjusted so that its resonance occurred during the first 

hour after the fill which is the time that orbit corrections 

are made. Plans were made to attenuate these modes 

during the December1995 shutdown. To track these 

beam size changes, the X28 profile monitor Spiracon was 

intehced to the NSLS computer system to keep a daily 

history of beam size and position. 

To enable high current operations, the X-Ray Ring 

60 Hz to 500 Hz to allow the digital feedback system to 

work. The higher sampling frequency will prove useful in 

diagnosing rapid orbit motion problems. 

There were a number of steps taken to reduce 

downtime. A significant improvement resulted from 

running the RF systems with gap voltages adjusted so that 

if one system drops out, the three remaining systems can 

carry the beam load (up to 250 mA) without a beam 

dump. Also, the X-Ray Ring, VUV Ring, and Linac/ 

Boostervacuum systems were placed on emergency power. 

Considerable progress in the reliability of the NSLS 

water and compressed air systems was achieved by adding 

redundancy, and improving control and service ability. 

During the December 1994 shutdown, a third High 

Pressure Copper System water pump was installed allowing the pumps to operate within their design specifications. Pressure control was added to this system to 

maintain constant flow. The addition of cooling and 

compressed air from the BNL Central Chilled Water 
Facility (CCWF) provided needed redundancy to the 

NSLS chillers and air compressors. The four NSLS 

chillers and air compressors have stood alone when the 

CCW was down for maintenancehepair. Digital proportional integral controllers have significantly improved 

temperature control. Temperature jumps of 8 degrees F 

in the Low Pressure Copper water after an X-Ray dump 

or fill were reduced to 1 degree. Additionally, the RMS 

temperature changes in the water systems during stored 

beam conditions were reduced by a factor of 3 to 5. There 

was an ongoing effort to improve the serviceability of the 

proteus flow rate monitors by moving the proteus units 

from under the ring magnets and redesigning the plumbing to maintain a constant pressure boundary during 

testing and maintenance. To better track failure rates and 

pinpoint possible problems areas, there was implementation of color coding (according to time period of instdation) of water and air hoses, and of an air solenoid 

inventory. 

Finally, the new NSLS Control Room started up in 

September 1995, with no disruption to operations. 
X-hY STORAGE RING PARAMETERS AS OF NOVEMBER 1995 

-- -. 

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) 

hJEJ 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 (PI 

Arc Source Paramelers 

Betatron function (p,pJ 

Dispersion function (qx,qs) 

Y, = (1 +a,J@,y 

Source size (cx,oJ 

Source divergence (CS~,CJ~) 

1.0 to 3.8 m, 7.9 to 26.5 m 

0.47 to -0.11, -0.39 to 0.22 

0.952 to 0.962 ml, 0.81 to 0.52 m-l 

371 to 565 pm, 27 to 49 pm 

439 to 324 prad, 8 to 7 prad 

azv = -P',p -0.49 to 1.62, -3.4 to 4.5 

. Insertion Device Parameters . 

Magnet Complement 

32 Sextupole 

Nominal Tunes (v,, VJ 

Momentum Compaction 

R.F. Frequency 

Radiated Power for Bending Magnets 

R.F. Peak Voltage 

Design R.F. Power 

v, (Synchrotron tune) 

Natural Energy Spread (o,/E) 

Natural Bunch Length (20) 

Number of RF Buckets 

Typical Bunch Mode 

Horizontal Damped Emittance (EJ 

Vertical Damped Emittance (EJ 

Power per Horizontal milliradian (0.25A) 

2.584 GeV 

0.30 amp (10l2 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 

zx = zy = 6 msec; z, = 3 msec 

227 hrs (vRF = 700 kV) 

Separated Function, Quad Triplets 

8 

16 Bending (2.7 meters each) 

40 Quadrupole (0.45 meters each) c 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 

10.5 cm 

30 

25 

1.1 x IO7 meter-radian 

1 x 1Ol0 meter-radian 

23 watts 

86 
i 

87 
Beamline U2B: A photograph of an inclusion in fluorite. is shown above, and on the following page 

are maps of CO, (left) and oil (right) distribution in the inclusion. The locations of these two components are clearly seen inside the inclusion. The relative density is related to the local density. If the oil 

is homogeneous, the various intensities are related to the thickness of the areas probed. In addition, 

the frequencies of the modes change with pressure, opening up the possibility of determining the 

pressure-temperature situation when the inclusions were formed. Water can also be tested for, and in 

this case no water bands were detected inside the inclusion. [N. Cuilhaumou (Laboratoire de 

Ceologie, France) and P. Dumas (LURE-CNRS, Centre Universitaire, Paris-Sud)] 
-80 

High 

Abs. 

n 

Low 

Abs. 

-80 

0 

-60 -40 -20 

microns 

-60 -40 

microns 

-20 

-10 

-20 

-3 0 

-40 

-50 

-60 

-70 

0 

0 

-10 

-20 

-30 

-40 

-50 

-60 

-70 

0 
THE NSLS SOURCE DYELOPMENT LABOMTORY ' ; 

Erik D. Johnson 

SDl Project Manager 

The NSLS has a deep interest in providing its user 

community with state of the art resources for their research, now and in the future. Beyond its immediate 

function of satisfying the requirements of the existing 

storage ring users, the NSLS must endeavor to anticipate 

and provide for needs which may be, as yet, unimagined. 

Although this activity can follow many threads, source 

development is clearly an area where considerable progress 

can be realized. FEL based sources hold the promise many 

orders of magnitude improvement in peak power over 

storage rings, and access to phenomena at sub-picosecond 

time scales. 

For this reason, the NSLS has been engaged in the 

development of proposals for a Free Electron Laser user 

oriented facility operating in the Ultra-Violet for more 

than five years. This work culminated in the Deep UltraViolet FreeElectron Laser (D W-FEL) conceptual design 

reportwhichwas releasedin Januaryof 1994. It details the 

scientific motivation, and describes a user facility designed to meet those needs. The DW-FEL could produce picosecond pulses of W radiation at wavelengths as 

short as 75 nm and peak power of several hundred 

megawatts. A subsequent development proposes FEL 

operation in a chirped pulse mode which could produce 

4 femtosecond pulses at 88 nm with peak power of 100 

GW. 

Recognizing the potential impact of FELs on their 

core programs, the DOE commissioned the National 

Research Council to perform a study of Free Electron 

Lasers and Other Coherent Sources of Radiation to aid in 

evaluating their role in DOE programs. In its August 

1994 report, the NRC panel recommended support for 

preliminary R&D to establish the feasibility of constructing a user oriented FEL in the VUV. Acting on this 

recommendation, the NSLS established the Source Development Laboratory (SDL). In broad terms, the 

function of the SDL is to facilitate the coordinated 

development of sources and experiments to produce and 

utilize coherent sub-picosecond synchrotron radiation. 

90 

The SDL accelerator system is located in building 

729, and will consist of a high brightness short pulse linac, 

a station for coherent synchrotron and transition radiation experiments, ashort bunch storage ring, and an ultraviolet free electron laser utilizing theNISUS wiggler. This 

accelerator will be realized by installing a photocathode 

electron gun of the type developed at the BNL-ATF on 

the existing 230 MeV linac. With the addition of a 

magnetic pulse compressor, the linac will supply 1nC 

bunches with a 1OOp.m RMS CJ length (ca. 1000 A peak 

current). As outlined in the 1994 NSLS annual report, 

the accelerator part of the SDL program can be thought of 

as occurring in three stages; all based on the production of 

short electron bunches: 

I lOOpm Compressed Bunch Experiments 

I1 

I11 Compact Storage Ring with High Frequency RF. 

UP-FEL Ultraviolet Project Free Electron Laser 

For each of the sources, experiments utilizing the 

radiation they produce have been identified, and PI'S 

from outside BNL have agreed to participate in early 

utilization of these sources while still under development. 

This close interaction between end users and source 

developers will help to focus research activities on the 

properties of the sources which will be most important for 

the research they are designed to enable. 

The first stage of development represents establishment of the short pulse electron source and its characterization. One experiment planned with the recommissioned linac will utilize coherent transition radiation and 

an electron bunch to make pump-probe measurements of 

the response of highly excited dielectric media. This 

experiment also provides a method to diagnose and monitor the electron beam performance in subsequent experiments. The second stage is an incremental program of 

FEL source and experiment development which forms the 

centerpiece of the SDL program. It starts with Self 

Amplified Spontaneous Emission (SASE) operation of 
the FEL which is, at least conceptually, the most straightforward type of single pass FEL. With the addition of an 

energy modulation wiggler and dispersive section, operation with an optically seeded beam becomes possible. 

This allows for shorter wavelength radiation through 

Harmonic Generation and increased pulse energy by 

Chirped Pulse amplification. These experiments will 

extend the range of FEL operation to wavelengths below 

100 nm, and peak power exceeding 100 GW. The third 

stage, which may actually be carried on in parallel with the 

FEL program, explores the use of the short bunch beam in 

a storage ring. It represents a promising alternative to 

laboratory and much of the hardware are recovered from 

various curtailed or terminated programs. The 230 MeV 

linac is derived from the DARPASXLS project as is much 

of the storage ring. The 10 meter long NISUS undulator 

provides the amplifier for the FEL experiments. It was 

built by STI-Optronics for Boeing Space and Defense in 

Seattle as part of a contract with the US Army Space & 

Strategic Defense Commands Directed Energy Weapons 

Program. The FEL amplifier R&D component of the 

SDL is part ofa broad based collaboration involving many 

institutions interested in the development of short wavelength FEL technology, as recommended by the NRC 

Pictured in position at the Source Development Laboratory (SDL) with the National 

Synchrotron Light Source (NSLS) in the background, NISUS is being inspected by 

some of those at the NSLS involved in putting SDL together and planning its future 

experiments: (from left) Physicist llan Ben-Zvi; Erik Johnson, SDL Project Manager; 

Physicist Li-Hua Yu; and Samuel Krinsky, NSLS Deputy Chairman. 

FELs or conventional storage rings as a source ofcoherent 

radiation in the far-infrared. In this case the storage ring 

is the recovered XLS ring, modified to provide coherent 

radiation at 300p.m wavelengths and longer. This is 

accomplished by reconfiguring the ring to operate with a 

high frequency RF system, and a reduced momentum 

compaction lattice. 

Given the fiscal realities of today, the SDL program 

has been structured to utilize existing equipment to the 

greatest extent possible, and encourage collaboration both 

within and outside of BNL. To that end, the site for the 

report. Apart from 

BNL, this effort includes 

other DOE laboratories 

(CEBAF, LBL, LANL, 

SMC), industrial partners (Boeing, Northrup 

Grumman, STIOptronics), and universities (Duke, UCLA). 

Activities during 

1995 reflected the foundation phase for the 

SDL. Building 729 was 

expanded to accept the 

full SDL accelerator. 

The NISUS undulator 

was moved to its working location and connection of its control 

electronics was started. 

Reconfiguration of the 

linac and shielding was 

initiated as was planning 

for aclean room to house 

the laser systems. A 

Titaniumsapphire laser 

was specified and procured to drive the photocathode gun, and in 

future, act as a seed laser. Assembly of the electron linac is 

scheduled to be completed, with parallel activities in 

design and commissioning of equipment for the FEL and 

storage ring experiments. With the assembly of the 

accelerator well underway, the SDL will be an increasingly 

visible activity during 1996. Those of us directly associated with the project look forward to starting 

experiments in the following year. 
Ilan Ben-Zvi 

The NSLS has an active program in R&D in the 

production of short-wavelength coherent radiation 

through its involvement in the Accelerator Test 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 peer-reviewed facility like the ATF that 

is dedicated for long range R&D in accelerator and beam 

the ATF, there is a number of FEL experiments. A few of 

them are centered about ATF beam line #3, where a 

microundulator oscillator experiment is nearing operation and others are conducted on beam line #2, like the 

High Gain Harmonic Generation FEL. 

Asuperconducting 68 periodmicro-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 

_NJy WkRi </.A 

llan Ben-Zvi at the Accelerator Test Facility’s experiment hall. 

physics. In addition to its singular role, the ATF also has 

a unique combination ofa high-brightness 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, makes it an ideal site for R&D on Free-Electron 

Lasers (FEL). 

Among the 15 currently approved experiments on 

92 

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. 

TheFELexperimentmakes 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 undulator will 

be used to develop a 4 to 5 mm 

period, small gap undulatorprototype 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 beam line, has parameters that are very 

similar to those ofthe 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. The experiment 

is 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 the visible 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 VUVFELs. This approach is based on 

single pass, seeded FEL amplifiers driven by Tisapphire 

lasers. The final stage 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 beam line #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. 

The development of a high brightness electron 

beam is essential to the production of coherent short 

wavelength radiation. The length of both accelerator and 

wiggler of the 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 beam 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 of very high intensity RF electric fields. The 

generation and careful manipulation of such beams are 

areas of intense activity in accelerator physics, being the 

key to short wavelength FELs. 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 collaboration for 

the development of RF guns, one with SLAC and UCLA, 

and the other with Japan, KEK and Sumitomo. 

Two significant experiments have been recently 

reported by the ATF st&. 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 

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 drifi space between the gun and the 

linac. One picosecond bunch lengths 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. 

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 oflasers by electrons 

is a unique X-Ray source. Preliminary estimates indicate 

that it should be possible to generate elliptically polarized 

2 x lo8 photons pulse of 8 KeV x-rays using the ATPs 

future 1 TW CO, laser and its 70MeV linac. A contract 

for the construction of parts for the ATF’s compact 

picosecond Terawatt laser was 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, Dartmouth, MIT, Stanford, 

Stony Brook and UCLA) 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. 
NSLS FAC~LITY IMPROVEMENTS 

Frank Terrano 

Mike Kelly 

FY 1995 saw the completion of two construction 

initiatives alongwith several other facility related projects. 

The successful completion of these efforts has allowed us 

to make further progress toward our goals of enhancing 

the research environment, and generally making the 

NSLS a friendlier place for users to visit. 

In March of 1995 the NSLS took occupancy of the 

Structural Biology addition. The 6,300 square foot 

addition includes laboratories for X11, X10, X9, XSC, 

X6, and X3B1 shared with X7. It also houses a general 

user structural biology laboratory with a cold box, a 

general user laboratory, and a conference room. X9 and 

XSC have a shared cold box located between their laboratories. 

In December the NSLS took occupancy of the X1- 

X4 Control Room addition. This addition includes a 

laboratory for X4 with cold room, laboratories for X1A 

andX2, and storagelsetup space for X1B andX3. It also 

includes a new NSLS control room, almost doubling the 

size of the old one. The NSLS Safety Group and Building 

Manager now occupy this space close to the new control 

room. The old control room will house the off duty 

Operations Coordinators. The NSLS User shop, previously at the other end of the tunnel in building#535 has 

movedup onto the experimental floor, making it closer to 

the setup space and stockroom. 

Every beamline will now have a laboratory or setup/ 

storage area to support their operations. 

Structural 

Biology 

Addition 

XI -X4 Control Room Addition A 

94 
The connection oftheNSLS building to the Central 

Chilled Water Facility was completed. This will add 

greater flexibility as well as redundancy capabilities to the 

machine and comfort cooling of the facility. The final 

phase which will be to add connections for the experimental water system is expected to be completed in FY 1996. 

In May 1995, a Superconducting Magnet Energy 

Source (SMES) was installed for testing on the NSLS 

VUVRing. Acquired from the U.S. Air Force, the system 

is housed in a standard trailer adjacent to the east side of 

building 725. The SMES is designed to cut in when an 

AC power disturbance is detected and is expected to 

handle at least a 2 second power outage of the VW Ring 

with all its ancillary components. This should enable us 

to ride out LILCO power fluctuations which would have 

previously dumped the beam. Mer about a year or so 

testing, a decision will be made as to whether to place the 

entire facility on the SMES system. 

Building729, the Source Development Laboratory, 

was extended forty feet to house the NISUS wiggler and 

Linac tandem. A chiller was plumbed into the building 

which will handle machine cooling and comfort cooling - of the facility. 

Eric Sirota (Exxon Research & 

Engineering Co.) and Helmut 

Strey(N1ST) in one of the new 

laboratories on the NSLS 

experimental floor. 

Dedication of the NSLS Structural 

Biology addition on May IO, 1995: 

Roland Hirsch from the DOE Office of 

Health &Environmental Research (far 

right) was joined by (left to right) BNL 

Laboratory Director Nicholas Samios, 

Denis McWhan (BNL Associate 

Director for BEYActing NSLS Chair) 

and William Studier (BNL Biology 

Department Chairman) for a 

ceremonial ribbon cutting. 

95 

n 

F=----= 

I 

I- --*- 

Increasing Mn oxidation - > 
- N S LS-- ADVI s o RY C o M M ITTEE\S 

98 

1995-1996 

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: Paul Zschack, ORNL 

Vice-Chairperson: Peter Stephens, SUNY-Stony Brook 

Secretary: Sue Wirick, SUNY-Stony Brook 

Daniel Fischer, NlST 

Doon Cibbs, BNL-Physics 

Kim Mohanty, BNL-Physics 

Kevin Smith, Boston U. 

Ex-Officio: Eva Rothman, NSLS 

Past -Chairperson: Jean Jordan-Sweet, IBM 

Special Interest Group Representatives 

Special interest groups in areas of common concern communicate with NSLS 

management through the UEC. Group representatives were: 

Atomic and Molecular Science 

Biological Scattering Crystallography 

Energy Dispersive Diffraction 

Nuclear Physics 

Students and Post Docs 

Time Resolved Spectroscopy 

Topography 

UV Photoemission, Surface Science 

XAFS 

X-Ray Scattering, Crystallography 

I Imaging 

David Hanson, SUNY- Stony Brook 

Stephan Ginell, ANL 

Syed Qadri, Naval Research Lab 

Sue Wirick, SUNY- Stony Brook 

Craig Thorn, BNL-Physics 

David Johnson, BNL-Chemistry 

Jon Levin, U. of Tennessee 

Michael Dudley, SUNY-Stony Brook 

Boris Sinkovic, NYU 

Simon Bare, Dow Chemical 

Ben Ocko, BNL-Physics 

. . .. 
Science Advisory Committee 

The Science Advisory Committee (SAC) evaluates the science 

programs at the NSLS and makes recommendations to the Chairman. 

The SAC met in March of 1995 and its members were: 

B. Batterman, CHESS, Cornel1 U. 

Gene Dresselhaus, National Magnet Laboratory, MIT 

Richard Martin, Department of Physics, U. of Illinois 

Yves Petrof, ESRF 

David Shirley, Penn State University 

Janet Smith, Department of Biological Science, Perdue U. 

Chandra Varma, ATBT Bell Laboratories 

The General User Oversight Committe (GUOC) met in November 1994, March 1995, 

and July 1995 to allocate time on beamlines to each General User proposal for the 

FY 1995 cycles. GUOC members are drawn from the scientific community and usually 

serve a two year term. Members during FY 1995 were: 

UV Members X-Ray Members 

C.T. Chen AT&T David Adler AT&T 

Jan Hrbek BNL-Chemistry Kegang Huang ANL 

Eric Jensen Brandeis U. Simon Mochrie MIT 

Paul Stevens Exxon William O'Grady NRL 

Peter Stephens SUNY-Stony Brook 

Joseph Woicik NlST 

Brian DeVries Exxon Alex Darovsky SUNY-Stony Brook 

Boris Sinkovic NYU Benjamin Ocko BNL-Physics 

i 

General User Proposal Study Panels 

The Proposal Study Panels met in November 1994, March 1995, and July 7 995 to review and rate General 

User research proposals forthe FY 1995 cycles. PSP members are drawn from the scientific community and 

usually serve a two year term. Members during FY 1995 were: 

UV Panel X-Ray Spectroscopy Panel 

Steve Hulbert NSLS Bruce Bunker 

Theodore Madey Rutgers U. John Faber 

Cliff Olson Ames Laboratory Ronald Felton 

John Sutherland BNL-Biology William Orme-Johnson 

James McBreen 

Lynn Soderholm 

X-Ray Imaging/Other Panel Dale Sayers 

Ed Stern 

Harold Ade NCSU 

Jamshed Patel AT&T 

Bruce Steiner NlST 

X-Ray Biology 

Stephen Burley Rockefeller U. 

Keith Watenpaugh The Upjohn Co. 

I 

U. of Notre Dame 

Amoco 

Georgia Inst. of Tech. 

M IT 

BNL-DAS 

ANL 

NCSU 

U. of Washington 

X-Ray Scattering Panel 

Malcolm Capel BNL-Biology 

Philip Coppens SUNY - Buffalo 

Charles Prewitt Geophysical Lab 

Robert Fleming AT&T 

Simon Moss U. of Houston 

Ian Robinson U. of Illinois 

Cullie Sparks ORNL 

Ben Chu SUNY - Stony Brook 

General User Oversight Committee 

99 
ASSOCIATE CHAIRMAN 

Thodinson 

Es&H 

- 

I I 

OFFICER: Didrinson 

Ackerman, Aloi 

EXl?XMENTAL SUPPORT 

BFAMLINER~LD: 

Siddons 

Berman, Carr, Q. Dong, Dowd, Flaks, Furenlid, 

(Gmur), S. Hulberr, 

Khalid, Menk, Milne, 

P. Montana, Park, 

Shek-Steh,So, 

(Thodinson), 

VanCam en Vescovo, 

mniams,%u: Yin 

(Seebeck), (Weilandics), 

MEDICAL PROGRAMS: 

Scientific Adviso Committee (SAC) 1 User's fiecutive?ixnmittee (UEc) 1- 

I I 

Visitor: L.. Kelly I Student: Z. Zhang 

BEA~~LINE TECHNICIANS: SUPERVISOR: Lenhard 

Carlson, Greene, Nintzel, 

S. Thomas 

van Derlaske 

Johnson, Go, Steh, 

Student: Gliebe 

* Temporary 

** Reports to Denis McWhan, 

( ) 

Assoc. Dir. for Basic Energy Sciences 

PRT personnel or member of non-NSLS division 

100 

Bozoki, Murphy Safiiek, Yu 

Graves, Solomon, 

Aspenlieter, Lehecka 

Ben-Zvi 

Babzien, Malone, 

Po orelsky, SegaIoP, x %ang 

STUDENTS: CatlXMs, 

Fang, Liu, Palmer, 

TECH. SUPPORT: t SUPWWISOR: Cahill 

Montemagno, Harrington 
CHAIRMAN: Hart?" 

DEPUTY CHAIRMAN: Krinsky 

ASSISTAN~TOCHAIRMAN 

Terrano 

ADXIINISTRATION: - 

ADMINISTRATION: 

LEAD: J. Desmond 

DiFilippo, Koebel, 

LeBrun, White-DePace 

General User's Oversight Committee (GUOC) Proposal Study Panels (PSP) 

I 

e ELECTRICAL SYSTEMS: t STOCKROOXI: n I (Lamb). (Reisig) MECHANIWU. ENGINEERING: OPERATIONS: 

Woodle 

I. 

ENGINEERING: R Biscardi, 

Buda, Pietraski, H Sheehan, 0. Sin h, 

M. Thomas, J.9 Wang t ENGINEERING: Chou, 

Beauman, L nch, 

Mortazavi, {hleifer, Skaritka 

INJECTION: Blum 

VW: her 

BUMLINELWSON: KlaIlky 

x-RAU: Kl* 

CONTROL ROOM 

SUPERVISOR: Church 

OPERATORS: 

Jahnes, Rodriquez, Weiner, Zeitler 

COORDINATORS: 

LEADMAN: Kemp Buckle ,Jew, 

kar, 

e, Sanrana 

I' I 

c Systems: 

P. Sutherland" I COMPUTER SY~EMS: 

HEAD Keane (Acting) Dabrowski, Feng-Berman 

Flannigan,Langenbach, 

Pearson,Ramamoorthy, 

Smith, Tang 

DESIGNID~ING GROUP: 

Gross, Gugileimino, Kim taicu, Stelmach, 

Stoeber, Wiseman 

DATABASE DEVUOPhIENX 

Hicks 

USER ADMINISTRATION: 

HEAD: E. Rothman I Feierabend, Pinkston, 

N. Wright 

I1 I 

VACUUM GROUP: Foerster 

t TECH I TRAINING: Klein SUPERVISION: 

SR. SUP.: Rasmussen SR SUPERVISOR: McKenna 

MECH: Scheuerer 

VACUUM DeBoer 

UTILITIES: White 

PIS: Meier 

RF: DAlsace 

DIAGNOSICX Rambo 

ES&H Interlocks: 

Gallagher 

ELECT. DESIDNT: Neuls 

MECHANIW 

(Bellando), Breck, 

Newburgh, Po 

Radulescu, &senberg, 

Santangelo, 

II J 

POWER sUPPLIE% 

Borrelli, Fulkerson, 

Garrison, McDonald, Seda VACUUM: 

Caruso, de Toll, 

Fruedenberg, Lanni, 

Tardd 

(Custodial Stan) 

(Bounauito), I I RF:Broome, Ramira 

I (McPherson), 

CLEANING SHOP: CONTROLS & DIAGNOSTI~~: Cernyar Frisbie, Link, Nielson, Tallent 

PRT PERSONNEL: 

(S. Bennett), (Karlin), 

Best, Hughes (Lamble), (Mingino), 

DESIGN: 

CHECKER: L. Hulberc 

Bohenek, Rubino 

SPECIAL PROJECTS: Meier, 

Pietraski, Romano 

ELECTRICIANS: (Didio), 

(Hu hes),(La 1, (Roflzevik), (Txompson), 

(signed) Michael Hart, Chairman 

April 1,1996 

101 

Beam Research Mono. Affiliation Local Contact Spokesperson 

line Program 

U1 A SEXAFS, ARUPS, XPS ERG Exxon B DeVries 

51 6-344-4828 

51 6-344-5206 

J Chen 

908-730-2738 

U1 B (Conceptual) TGM Exxon P Stevens 

51 6-344-4828 

908-730-2584 

B DeVries 

51 6-344-4828 

51 6-344-5206 

U2A (Unassigned) 

U2B High pressure, 

pump-probe, high Tc 

abs., IR microscopy 

MI SUNY@SB 

BNL-NSLS 

Northrop Grumman 

C Williams 

51 6-344-7529 

C Carr 

51 6-344-5502 

51 6-346-9073 

U3A Time-resolved and DC ERG 

radiometry; reflectometry 

for optical constants 

Los Alamos Natl Lab 

Smiths Astro Obs 

Bechtel Nevada 

W Towell 

51 6-344-7245 

R Blake 

51 6-344-5521 

505-983-9683 

U3B (Conceptual) 

U3C Photoelectron spect.; ERG 

exp. system and detector 

calibrations 

Los Alamos Natl Lab 

Sandia Natl Lab 

W Towell 

51 6-344-7245 

R Barllett 

51 6-344-5708 

505-667-5923 

U4A ARUPS of solids,surfaces; TGM 

hi res. core level photoemission; total yield 

absorption 

AT8T 

BNL - NSLS 

Boston U 

M Shek 

51 6-344-5930 

J Rowe 

908-582-5878 

U4B Soft x-ray photoemission SGM 

spectroscopy; NEXAFS; 

SXMCD 

AT8T 

Naval Res Lab 

G Meigs 

51 6-344-7290 

908-582-3863 

202-767-3603 

Y ldzerda 

103 
Beam Research 

line Prorrvam 

Mono. Affiliation Local Contact Spokesperson 

U41R Vibr. spectr of molecules MI,WDI BNL-NSLS D Van Campen 

on surfaces; abs of hi Tc AT%T 51 6-344-2738 

superconductors; hi res Fairleigh Dickinson 51 6-344-741 9 

gas abs.; fast detectors Exxon 

Northrop-Grumman ATDC 

G Williams 

51 6-344-7529 

u5 Diagnostics BNL-NSLS R Nawrocky 

51 6-344-4449 

R Nawrocky 

51 6-344-4449 

BNL-NSLS S Hulbert 

E Vescovo 

51 6-344-7570 

51 6-344-7399 

E Vescovo 

51 6-344-7399 

u5u Spin polarized angleresolved ultraviolet 

photoemission 

TGM 

U6 Lithography WB IBM J Silverman 

91 4-945-2099 

J Silverman 

91 4-945-2099 

U7A Photoemission; 

SEXAFS; Fluorescence 

yield spectroscopy 

TGM BNL-NSLS 

BNL-Physics 

BNL-Chemistry 

Dow Chemical 

NlST 

U of Michigan 

4 Dong 

S Hulbert 

51 6-344-5505 

51 6-344-5507 

51 6-344-7570 

D Fischer 

51 6-344-51 77 

U7B Photoemission; 

SEXAFS 

PGM BNL-Physics 

SUNY@SB 

F Loeb 

51 6-344-2092 

M Strongin 

51 6-344-3763 

TGM IBM R McFeely 

91 4-945-2068 

R McFeely 

91 4-945-2068 

U8A ARUPS 

NEXAFS 

U8B ARUPS 

NEXAFS 

TGM IBM R McFeely 

91 4-945-2068 

R McFeely 

91 4-945-2068 

U8C Zone plate monochr 

evaluation; reflectivity 

measurements of thin 

films and multilayers 

ZONEPL. IBM R McFeely 

91 4-945-2068 

R McFeely 

91 4-945-2068 

U8D (Conceptual) 

Scanning soft x-ray 

microscopy 

IBM R McFeely 

91 4-945-2068 

R McFeely 

91 4-945-2068 

U9A (Planned) 

Lithography 

F Loeb 

51 6-344-2092 

M Strongin 

51 6-344-3763 

104 
Beam Research 

line Program 

Mono. Affiliation Local Contact Spokesperson 

U9B CD; MCD; time-resolved C-T 

fluorescence (lifetimes) 

BNL-NSLS 

BNL-Biology 

J Sutherland 

51 6-344-3406 

51 6-344-3279 

J Sutherland 

51 6-344-3406 

51 6-344-3279 

U1 OA (Unassigned) 

UlOB PSDgeneral vacuum 

R8D 

WB BNL-NSLS C Lanni 

51 6-344-41 00 

C Foerster 

51 6-344-4754 

U11 Cas phase photoionization and 

Spectroscopy 

NIM BNL-NSLS 

BNL-Biology 

Brandeis U 

BNL-DAS 

S Kuo 

51 6-344-7003 

B Klemm 

51 6-344-4001 

51 6-344-4022 

U12 High resolution core 

level Spectroscopy 

ARUPS 

TCM U of Pennsylvania 

Oak Ridge Natl Lab 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

E Plummer 

D Zehner 

61 5-974-2288 

51 6-344-551 2 

61 5-574-6291 

U12A High resolution core 

level spectroscopy 

(construction) 

TCM Oak Ridge Natl Lab 

U of Tennessee 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

E Plummer 

D Zehner 

61 5-974-2288 

51 6-344-551 2 

61 5-574-6291 

U12B Angle-resolved 

photoemission 

TCM 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 

61 5-974-2288 

E Plummer 

U13UA High res. VUV/sofl 

XAS and electron 

spectroscopy 

(incl. spin-pol 

photoem.) 

SCM BNL-NSLS 

Drexel U 

U of Wisconsin 

Brandeis U 

Rutgers U 

NYU 

S Hulbert 

51 6-344-7570 

x. wu 

51 6-344-5778 

S Hulbert 

51 6-344-7570 

U13UB Optical metrology for 

extreme ultraviolet 

projection lithography 

WB Sandia Natl Lab 

BNL-lnstrum 

Naval Res Lab 

A MacDowell 

51 6-344-5334 

A.MacDowell 

51 6-344-5334 

105 
Beam Research Mono. Affiliation Local Contact Spokesperson 

line Program 

U14A Solid state PGM BNL-NSLS 

photoemissions studies 

U14B Detector Research and WB BNL-NSLS 

Development 

U15 Soft x-ray spectroscopy TGM BNL-NSE 

(solids and gases) SUNY@SB 

SUNY@Buff 

U16A (Unassigned) 

U16B ARUPS; XPS; SEXAFS; ERG Cornell U 

stimulated desorption; Sandia Natl Lab 

NEXAFS 

106 

M Shek M Shek 

S Hulbert 

51 6-344-5930 51 6-344-5930 

51 6-344-7570 

J Hastings J Hastings 

51 6-344-3930 51 6-344-3930 

D Hanson D Hanson 

51 6-632-791 7 51 6-632-791 7 

R Merrill 

607-255-9857 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X1 A 

X1 B 

Soft x-ray imaging 10-80 A 

Soft x-ray spectroscopy 10-50 A 

X2A Surface scattering 

X2B 

X3A1 

X3A2 

X3B1 

X3B2 

X4A 

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 

Surface science 4-20 

Multiwavelength 4-30 

anomalous diffraction 

analysis of crystalline 

biological macromolecules 

BNL-NSLS 

SUNY@SB 

LBNL 

No Carolina St U 

ANL 

BNL-NSLS 

BNL-Physics 

FA - Juelich 

Fritz-Haber-lnst 

Exxon 

Exxon 

SUNY@SB 

SUNY@Buff 

SUNY@SB i 

SUNY@Buff' 

SUNY@SB 

SUNY@Buff 

SUNY@SB 

SUNY@Buff 

Howard Hughes Med In 

S Wirick 

51 6-344-4723 

51 6-632-8095 

P Johnson 

51 6-344-3705 

M Sansone 

201 -730-3388 

51 6-344-5759 

K Mohanty 

51 6-344-4402 

A Darovsky 

51 6-344-3770 

A Darovsky 

51 6-344-3770 

P Stephens 

51 6-344-5634 

51 6-632-81 56 

P Stephens 

51 6-344-5634 

51 6-632-81 56 

C Ogata 

51 6-344-7435 

J Kim 

51 6-344-4723 

51 6-632-81 06 

P Johnson 

51 6-344-3705 

K Liang 

908-730-3032 

D Noh 

908-730-2598 

P Coppens 

ext. 221 7 

71 6-645-6800 

P Coppens 

ext. 221 7 

71 6-645-6800 

P Coppens 

ext. 221 7 

71 6-645-6800 

P Coppens 

ext. 221 7 

71 6-645-6800 

W Hendrickson 

51 6-344-4938 

21 2-305-3456 

107 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X4B (Conceptual) 

x4c Diffraction measurements 7-20 

from biological 

macromolecules 

Howard Hughes Med In C Ogata 

51 6-344-7435 

W Hendrickson 

51 6-344-4938 

21 2-305-3456 

X5A Laser Electron Gamma 

Source (LEGS); medium 

energy nuclear physics 

80-400 MeV BNL-Physics C Thorn 

51 6-344-7798 

A Sandorfi 

51 6-344-7951 

X5B Diagnostic 

X6A Time and space resolved 4-20 

dispersive x-ray 

spectroscopy 

ANL P Lee 

51 6-344-5934 

51 6-344-3955 

P Montano 

708-252-6239 

X6B X-ray scattering 2.4-21.0 ANL 

Temple U 

Northwestern U 

BP 

P Lee 

51 6-344-5934 

51 6-344-3955 

P Montano 

708-252-6239 

X7A Structural char. through 

powder diffraction 

5-45, WB BNL-NSLS 

BNL-Physics 

Carnegie lnst of Was 

E I DuPont 

Mobil 

UOP 

Air Products Corp 

SUNY@SB/Alfred 

U of Cal @ Santa Barbara 

U of Pennsylvania 

D Cox 

Q Zhu 

51 6-344-381 8 

51 6-344-381 8 

51 6-344-5065 

D Cox 

51 6-344-381 8 

X7B Crystallography; 

wide angle scattering 

5-21 BNL-Chemistry J Hanson 

Swedish Nat Res Coun 

U of Helsinki 

51 6-344-4381 

U of Pittsburgh 51 6-344-4378 

T Koetzle 

51 6-344-4384 

X8A Photoionization crosssections; photoelectron 

spectr; mirror reflect.; 

detector calib.; spectr. 

0.26-5.9 Los Alamos Natl Lab 

Smiths Astro Obs 

EG&G Energy Meas 

Bechtel Nevada 

M Sagurton 

51 6-344-5708 

R Blake 

51 6-344-5521 

505-983-9683 

X8C Diffraction from 

biological macromolecules 

and detector calibrations 

5-20 Los Alamos Natl Lab 

Sandia Natl Lab 

LLNL 

ANL 

R Alkire 

51 6-344-5025 

G ldzorek 

51 6-344-7245 

505-667-8848 

X9A XAS 3.4-1 8.6 Albert Einstein 

College of Medicine 

M Sullivan 

51 6-344-3800 

M Chance 

51 6-344-3800 

71 8-430-2894 

108 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X9B Time resolved 

x-ray spectroscopy; 

scattering; diffraction; 

XAS 

3.2-1 8.8 Albert Einstein 

College of Med 

M Sullivan 

51 6-344-3800 

M Chance 

51 6-344-3800 

71 8-430-2894 

X1 OA Diffraction; small 

angle scattering; 

crysta I lograp h y; 

scattering 

XI OB Scattering; 

crystallography 

6-1 5.2 Exxon E Sirota 

908-730-3407 

K Mohanty 

51 6-344-4402 

8,12 Exxon D Noh 

908-730-2598 

B Zhang 

51 6-344-3553 

XlOC EXAFS 3.5-24.7 Exxon M Sansone 

51 6-344-5759 

201 -730-3388 

P Stevens 

51 6-344-4828 

9 0 8-73 0-2 5 8 4 

XllA EXAFS 4.5-35 No Carolina St U 

U of Connecticut 

BNL-NSLS 

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 

ANL 

G Lamble 

51 6-344-7734 

G Lamble 

51 6-344-7734 

XllB EXAFS 1.7-8 No Carolina St U 

U of Connecticut 

Mobil 

E I DuPont 

Naval Res Lab 

Hoechst Celanese 

Naval Surf Warf Center 

Notre Dame U 

U of Washington 

111 lnst of Tech 

Georgia lnst of Tech 

Rice U 

ANL 

BNL-NSLS 

G Lamble 

51 6-344-7734 

G Lamble 

51 6-344-7734 

X12A Instrument development BNL-NSLS DP Siddons 

51 6-344-2738 

51 6-344-5627 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

X12B Time-resolved and static 6-15 

x-ray diffr. of macromol. 

systems in both wide and 

small angle regimes 

BNL-NSLS 

BNL-Biology 

M Capel 

51 6-344-571 2 

M Capel 

51 6-344-571 2 

109 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X12C Protein crystallography 7.8-1 3.6 BNL-Biology R Sweet 

51 6-344-3401 

R Sweet 

51 6-344-3401 

X13 R8D optics development; BNL-NSLS 

soft x-ray utilization 

E Johnson 

51 6-344-4603 

E Johnson 

51 6-344-4603 

XI 4A Scattering; 3.5-40 Oak Ridge Natl Lab 

crystallography; U of Illinois 

spectroscopy 

T Cog 

51 6-344-561 4 

51 6-344-2583 

T Cog 

51 6-344-561 4 

51 6-344-2583 

X14B (Conceptual) WHITE Oak Ridge Natl Lab 

X-ray microprobe; x-ray 

micro-focussing; 

micro-diffraction 

T Cog 

51 6-344-561 4 

51 6-344-2583 

T Cog 

51 6-344-2583 

51 6-344-561 4 

X15A X-ray standing waves 3-20, WB ANL 

Northwestern U 

Harvard U 

P Lyman 

51 6-344-561 5 

51 6-344-7395 

M Bedzyk 

51 6-344-7395 

708-252-7763 

X15B SEXAFS 

EXAFS 

NEXAFS 

1.5-1 5 AT8T L Niu 

A MacDowell 

908-582-5275 

51 6-344-5334 

P Citrin 

908-582-5275 

X16A Surface diffraction 4-1 2 ATBT 

U of Illinois 

K Evans-Lutterodt K Evans-Lutterodt 

51 6-344-21 25 51 6-344-21 25 

908-582-21 54 908-582-21 54 

X16B Diffraction 7.85 AT8T A MacDowell E lsaacs 

51 6-344-5334 908-582-7261 

X16C Novel spectroscopy; 3-1 6 AT&T 

diffraction U of Illinois 

D Adler W Brown 

51 6-344-2686 908-582-3941 

X17A (Conceptual) 

X17B1 Chemical crystallography; 10-1 00, WB BNL-NSLS 

hi P physics; tomography; 

x-ray scattering; x-ray 

fluorescence microprobe 

DP Siddons J Hastings 

51 6-344-2738 51 6-344-3930 

51 6-344-5627 

110 
Beam Research Energy Affiliation local Contact Spokesperson 

line Program (keW 

X17B2 Medical research: 

Angiography; 

computed tomography; 

radiotherapy 

33.02,33.3 BNL-NSLS 

Stanford U 

Illinois lnst Tech 

No Shore U Hosp 

LBNL 

BNL-Medical 

SUNY@SB 

N Cmur 

51 6-344-2490 

W Thomlinson 

51 6-344-3937 

x17c J Hu 

51 6-344-5343 

202-686-241 0 

H Mao 

ext. 2467 

202-686-241 0 

Hi P research; energy 10-1 00, WB Naval Res Lab 

dispersive diffraction 

from microscopic sample 

volumes U of Chicago 

Carnegie lnst of Was 

U of Hawaii 

LLNL 

X18A Diffuse and surface 

scattering 

4-20 Purdue U 

Northwestern U 

U of Illinois 

U of Missouri 

S Ehrlich 

51 6-344-7862 

G Liedl 

31 7-494-41 00 

X18B EXAFS; optics char.; 4-26 

reflectivity measurements 

BNL-NSLS 

AlliedSignal 

UOP 

Chevron 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

X19A X-ray Absorption Sped.; 2.1 -25.6 

EXAFS and XANES 

BNL-NSLS 

UCA@Davis 

U of Kentucky 

U of Michigan 

BNL-DAS 

F Lu 

51 6-344-2338 

L Furenlid 

51 6-344-5699 

L Furenlid 

51 6-344-5699 

4-25,WB BNL-NSLS 

SUNY@SB 

Johns Hopkins U 

Army Research Lab 

U of Illinois 

U of Chicago 

M Dudley 

51 6-632-8500 

M Dudley 

51 6-632-8500 

X19C Topography; liquid 

surface scattering 

X2OA Scattering (hi Q-res) 5.6-1 2 MIT S Mochrie 

61 7-253-6588 

X2OB Scattering at fixed 

energy 

17.36 IBM 

MIT 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

S Mochrie 

61 7-253-6588 

X20C Scattering 4-1 1 IBM 

(hi and low Q res) 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

J Jordan-Sweet 

51 6-344-51 92 

91 4-945-3322 

111 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program MeV) 

x21 

X22A 

X22B 

High energy resolution > 4 BNL-NSLS 

inelastic scattering AT8T 

BNL-Physics 

SUNY @ Stony Brook 

ESRF 

ANL 

In-plane diffr. 8 refl. 10 Nom. BNL-Physics 

electro-chem. cond., and 

thin films and multilayer 

studies of surfaces under BNL-DAS 

High resolution x-ray 5-1 0 BNL-Physics 

diffraction Harvard U 

ANL 

X22C Diffraction studies of 3-1 2 BNL-Physics 

magnetic and structural ANL 

phase transformations; 

surface scattering 

X23A2 EXAFS 5.4-30 NIST 

X23A3 Topography; small- 5-30, WB NIST 

angle scattering 

X23B EXAFS; scattering; 3-1 1 Naval Res Lab 

crystallography 

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 

112 

>3 BNL-NSLS 

C Kao 

W Caliebe 

51 6-344-4494 

51 6-344-4795 

T Thurston 

B Ocko 

51 6-344-3761 

51 6-344-4299 

B Ocko 

J Hill 

51 6-344-4299 

51 6-344-4370 

51 6-344-3736 

D Cibbs 

G Watson 

51 6-344-4608 

51 6-344-221 1

J Woicik 

51 6-344-5823 

51 6-344-5236 

51 6-344-3923 

301 -975-5975 

S Chu 

D Fischer 

51 6-344-51 77 

J Kirkland 

51 6-344-2258 

R Deslattes 

301 -975-4841 

J Rife 

202-767-4654 

C Kao 

51 6-344-4494 

D Cibbs 

51 6-344-4608 

D Cibbs 

51 6-344-4608 

D Cibbs 

51 6-344-4608 

J Woicik 

51 6-344-5236 

51 6-344-5823 

C Long 

301 -975-5975 

T Elam 

202-767-301 4 

R Deslattes 

301 -975-4841 

M Kabler 

202-767-2223 

L Berman L Berman 

51 6-344-5333 51 6-344-5333 
Beam Research Energy Affiliation Local Contact Spokesperson 

line Program (keW 

X26A Dev. and application of 4-20, WB BNL-DAS 

analytical techniques U of Chicago 

(e.g. microprobe) U of Georgia 

BNL-Biology 

microscopy techniques; U of Chicago 

Laue diffraction protein BNL-Biology 

crystallography U of Georgia 

X26C Dev. and applic. of x-ray 4-30, WB BNL-DAS 

X27A Instrument development BNL-NSLS 

X27B Instrument development BNL-NSLS 

X27C Instrument development 

X28A Instrument development; 

Photon-based diagnostics 

and detector development 

diagnostics and 

detector development 

X28B Photon-based 

X28C Photon-based 

diagnostics and 

detector development 

X29A (Unassigned) 

X29B (Unassigned) 

X30 Diagnostic 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

BNL-NSLS 

S Bajt 

51 6-344-5596 

G Shea-McCarthy 

51 6-344-2229 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

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 

S Sutton 

31 2-702-9930 

S Sutton 

31 2-702-9930 

DP Siddons 

51 6-344-2738 

51 6-344-5627 

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 

113 
Beamline X7B: Time resolved powder diffraction patterns of thermal transformations in potassium 

nitrate obtained using the Translating Image Plate technique. [P. Norby and J.C. Hanson (BNL Chemistry 

Department), and A. Narlund Christensen (University of Aarhus, Denmark)] 

t 

I 

I 

% 

i 
From the Editor 

This year's Activity Report abstracts were 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 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, and we expect that for next year it will be 

available electronically two to three months before the printed product is released. 

Over 480 abstracts were received for this 1995 edition, which is about 10% more than last year when we 

also accepted paper submissions. We thank everyone who used the ESS, especially for the helpful feedback 

and suggestions. To access the completed abstracts as well as the ESS on the World Wide Web, select 

Open URL to get to the NSLS Home 

Page. Choose Electronic Submissions; all instructions are provided in both viewable and downloadable 

format. 

from the Mosaic File Menu, and enter http: //www .nsls . bnl .gov 

A- 1 
ABSTRACTS 

VUV Beamlines 

Beamline U1A 

Orientation of Ion Exchange Reacted Methylene Blue Molecules on Mica Investigated with 

NEXAFS ....................................................................................... A-7 

G. Hshner, A. Marti, and N. D. Spencer (Swiss Federal Institute of Technology, Zurich) 

Beamline U2B 

Microspectroscopy Characterization of 111-V Epi-layers for Optoelectronics ..................... 

IR Microspectroscopy Study of Te Precipitates in CdZnTe ....................................... 

Infrared Microspectroscopy of Oil Inclusions in Quartz and Fluorite Matrices .................... 

IR Transmission Studies on KCso Single Crystals ................................................ 

A-7 

G.L. Carr (Northrop Grumman ATDC) 

G.L. Carr and D.J. Larson, Jr. (Northrop Grumman ATDC) 

N. Guilhaumou (ENS-CNRS), P. Dumas (LURE), and G.P. Williams (BNL-NSLS) 

L. Mihaly (SUNY Stony Brook), S. Pekker (RISSP), L. Forro (EPFL), and G.L. Carr (Northrop 

Grumman ATDC) 

David L. Wetzel (Kansas State Univ.) 

A-8 

A-8 

A-9 

Localization of Infrared Sampling in Human Hair. ............................................... A-9 

Beamline U4A 

Alkali Adsorption on K0.3Mo03 ............................................................... A-10 

Klaus Breuer, Cristian Stagarescu, Kevin E. Smith (Boston University), Martha 

Greenblatt, William McCarroll (Rutgers University) 

Electronic Structure of the Quasi-Two Dimensional Conductor Nao.gMo6017 .................... Klaus Breuer, Cristian Stagarescu, Kevin E. Smith (Boston University) , Martha Greenblatt 

and Kandalam Ramanujachary (Rutgers University) 

Photoemission of Oxides around the Metal-Insulator Transition ................................. E. Goering, M. Klemm, S. Horn (U. Augsburg), and M. L. denBoer (Hunter CUNY) 

L.R. Masliah, R.G. Jordan and S.L. Qiu (Florida Atlantic University) 

C. Stagarescu, K. Breuer, K. E. Smith, (Department of Physics,Boston University), 

R. Haddon, (AT&T Bell Labs), J. S. Brooks, (Department of Physics, Florida State University) 

Xumou Xu, R.G. Jordan and S.L. Qiu (Florida Atlantic University). 

A-10 

A-11 

Electronic Structure along the A Direction in CuAu ............................................ 

Electronic Structure of the Organic Conductor K-(BEDT-TTF)~CU[N(CN)~]B~ ................. 

A-11 

A-12 

Surface States on the (100) and (001) Surfaces of Equi-atomic CuAu ............................ A-12 

A-2 
Beamline U4B 

Determination of Helicity-Dependent Absolute PhotoAbsorption Cross Sections at the L-edges 

of Fey Co, and Ni ............................................................................. V. Chakarian and Y.U. Idaerda (NRL), J.-H. Park, G. Meigs, and C.T. Chen (AT&T) 

V. Chakarian and Y.U. Idaerda (NRL), J.-H. Park, G. Meigs, and C.T. Chen (AT&T) 

Element-Specific Orbital and Spin Moments of Transition Metal Alloys via MCD ............... 

A-13 

A-13 

Giant Magnetic Effects in the L-edge Extended X-ray Absorption Fine Structure of 3d Transition 

Metals ......................................................................................... Y.U. Idaerda, V. Chakarian, and K. Kemner (NRL), J.-H. Park, G. Meigs, and C.T. Chen 

(AT&T) 

Y.U. Idzerda, V. Chakarian, G.A. Prinz (NRL), C. Gutierrea (S.W. Texas Univ.), H.J. Lin, G. 

Meigs, and C.T. Chen (AT&T) 

J.-H. Park, C. T. Chen, S.-W. Cheong, W. Bao, G. Meigs, (AT&T Bell Labs), V. Chakarian, 

and Y. U. Idzerda (NRL) 

J.-H. Park, S-W. Cheong, C. T. Chen (AT&T Bell Labs.), V. Chakarian, and Y. U. Idzerda 

Magnetic Field Dependence of Mn Moment in FeCo/Mn/FeCo Trilayers ........................ 

Electronic Aspect of Ferromagnetic Transitions in Lal-,(Ca, Pb), MnO3 ........................ 

Mn3+-Mn4+ Mixed Valence Deriven by Co Doping in LaMnO3 ................................. 

(NRL) 

Beamline U4IR 

A Study of Ethanol Adsorption on Si(100) Surfaces Using Mid-to Far-Infrared Spectroscopy . J. Eng, Jr., L.M. Struck, B.E. Bent, G.W. Flynn, (Columbia University), Y.J. Chabal, K. 

Raghavachari (AT&T Bell Laboratories), G.P. Williams (BNL-NSLS) 

J. Eng, Jr., L.M. Struck, B.E. Bent, G.W. Flynn (Columbia University), Y.J. Chabal, K. 

Raghavachari (AT&T Bell Laboratories), G.P. Williams (BNL-NSLS) 

R. Henn, J. Kircher, and M. Cardona (Max-Planck Institut), and G.P. Williams (BNL-NSLS) 

F.M. Hoffmann (Exxon Research and Engineering), J. Paul (Physics 111, Royal Institute of 

Technology, Stockholm, Sweden), and G.P.Williams (BNL-NSLS) 

M. Kovar, R.V. Kasza, K. Griffiths and P.R. Norton (Department of Chemistry, The University 

of Western Ontario), and G. P. Williams, D.G. Van Campen (BNL-NSLS) 

Study of Water Adsorption on a Si(100) Surface Using Far-Infrared Spectroscopy ............... 

c Axis Response of LazCuO4 studied by Far IR Ellipsometry ................................... 

FIR-Synchrotron Study of COz Activation and Alkali Compound Formation on Cu(ll1) ........ 

Infrared Spectroscopic Study of Water Adsorption on Ni(ll0) .................................. 

Far-Infrared Synchrotron Spectroscopy of Functionally Important Low Frequency Modes in 

Proteins ....................................................................................... A. Xie, Q. He, K. Hellingwerf. W.D. Hoff, E.M. Scheuring, B. Sclavi, M.R.Chance (Dept. 

of Physiology and Biophysics, Albert Einstein College of Medicine)(Dept. of Microbiology, 

Univ. of Amsterdam) 

Beamline U5U 

Quantum Well States of Cu Films on Magnetic Alloy Substrates ............................. D.-J. Huang and P. D. Johnson, (Dept. of Physics, BNL) 

A-14 

A-14 

A-15 

A-15 

A-16 

A-16 

A-17 

A-17 

A-18 

A-18 

A-19 

A-3 
Photoemission Studies of Chemisorbed Cs on Fe Substrates ..................................... D.-J. Huang, E. Vescovo (BNL), D. M. Riffe (Utah State Univ.), P. D. Johnson (BNL), P. 

Abramowitz and J. L. Erskine (Univ. of Texas Austin) 

Beamline U7B 

Core Level Lineshapes in FeRh Alloy ......................................................... Biao Zhao, R.G. Jordan (FAU), M.W. Ruckman, F.M. Jacobsen, Myron Strongin (BNL) 

Beamline U8A 

Room-temperature Chlorination of As-rich GaAs( 110) ........................................ W.C. Simpson (UC Riverside, MSD LBNL), D.K. Shuh (CSD LBNL), and J.A. Yarmoff 

(UC Riverside, MSD LBNL) 

Beamline U8B 

The Adsorption Behavior of Cl2 on GaAs(001)-4x6 .......................................... W.C. Simpson (UC Riverside, MSD LBNL), W.H. Hung (IBM), and J.A. Yarmoff (UC 

Riverside, MSD LBNL) 

W.C. Simpson, J.A. Yarmoff (UC Riverside, MSD LBNL), W.H. Hung, and 

F.R. McFeely(1BM) 

Remote Inductive Effects in the Si 2p Spectra of Halogenated Silicon ........................... 

Beamline U9B 

Electronic Absorption and Luminescence of Adenine Derivatives in Frozen Alcohol Glasses at 

77K ........................................................................................... 

L. A. Kelly and J. C. Sutherland (BNL) 

A-19 

A-20 

A-20 

A-21 

A-21 

A-22 

Secondary Structure of the Pleckstrin Homology Domain of PLC-delta .......................... A-22 

Scarlata, S. (Dept. of Physiology & Biophysics, SUNY Stony Brook) 

Scarlata, S., McBath, H. & Haspel, H., (Dept. of Physiology & Biophsics, SUNY Stony Brook) 

Effect of Increased Lipid Packing on the Conformational State of GLUT1 ....................... A-23 

Beamline U11 

Solution Circular Dichroism of 1,6-Anhydroglucopyranoside ................................... E.R. Arndt and E.S. Stevens (SUNY Binghamton) 

Photoionization Study of Ethanol and Radicals Derived From Ethanol: Theory and Experiment 

D. J. Bogan, F. L. Nesbitt, L. J. Stief (NASA/Goddard), J. L. Durant (SNL), S. C. Kuo, Z. 

Zhang and R. B. Klemm (BNL) 

Electronic Spectroscopy of Matrix-Isolated Adenine Derivatives at 12 K ......................... L. A. Kelly, E. D. Johnson, J. C. Sutherland (BNL) 

A Discharge Flow-Photoionization Mass Spectrometric Study of HOI: Photoionization 

Efficiency Spectrum and Ionization Energy ..................................................... P. S. Monks, L. J. Stief (NASA/Goddard), D. C. Tardy (Univ. Iowa), J. F. Liebman (Univ. 

Maryland/Balto. Co.), Z. Zhang, S. C. Kuo and R. B. Klemm (BNL) 

Experimental Determination of the Ionization Energy of 10(X2113/2) and Estimations of 

AfH"o(IO+) and PA(I0) ...................................................................... Z. Zhang (BNL), P. S. Monks, L. J. Stief (NASA/Goddard), J. F. Liebman (Univ. 

Maryland/Balto. Co.), R. E. Huie (NIST), S. C. Kuo and R. B. Klemm (BNL) 

A-4 

A-23 

A-24 

A-24 

A-25 

A-25 

......... ,. 

' . I. 
Beamline U12 

The electronic structure of Be(10-10) ......................................................... A-26 

Ph. Hofmann and E.W. Plummer (ORNL/University of Tennessee) 

Beamline U13UA 

Quantitative Calcium XANES ................................................................ A-26 

C. J. Buckley, S. J. Bellamy (KCL), X. Zhang (SUSB), G. Dermody (KCL), and S. L. 

Hulbert (BNL) 

S. Conrad, Q.-S. Xin, X.-Y. Zhu (Southern Ill. Univ.) and D. R. Mullins (ORNL) 

S. L. Hulbert (BNL) 

Jon C. Levin, G. Bradley Armen, and Ivan A. Sellin(U. Tennessee) 

D. R. Mullins (Oak Ridge National Lab) 

D. R. Mullins (Oak Ridge National Lab) 

D. R. Mullins and S. H. Overbury (Oak Ridge National Lab) 

B. Sinkovit, E. Shekel (NYU), and S. L. Hulbert (BNL) 

Thermal and Photochemical Deposition of Sulfur on GaAs(100) ................................ A-27 

Resolution test of Ul3UA 160°-included angle grating .......................................... 

Ratio of Double-to-Single Photoionization of Helium from Threshold to 700 eV ................. 

Adsorption and Reaction of Methanethiol on Ni Covered W(OO1) ............................... 

Adsorption Site and Orientation of S and CH3S on Ni(ll1) by Photoelectron Diffraction ........ 

The Coadsorption of S and Ni on W(OO1) ...................................................... 

Spin-polarized Fe LVV Auger spectra on- and off- L3-resonance ................................. 

A-27 

A-28 

A-28 

A-29 

A-29 

A-30 

Beamline U13UB 

Interferometry at A = 13nm .................................................................. J.Bjorkholm, B.LaFontaine, A.MacDowel1, Z.Tan, D.Tennant, O.Wood I1 (AT&T Bell 

Laboratories) 

A-30 

Beamline U15 

Chemistry Induced by Atomic-Site Selective Excitation in the Condensed Phase ............. A-31 

(Dept. of Chemistry, SUNY Stony Brook) 

Orientation of Ion Exchange Reacted Methylene Blue Molecules on 

Mica Investigated with NEXAFS 

MB on Mica, 1411. ImM CIS MB onMica. 14h. ImM Nls 

U1A 

-25 Photon Energy lev] 

I -0 Photon Energy [eV] 

Figure 1. NEXAFS spectra of MB on mica recorded at the Cls and Nls edges. Both 

edges exhibit transitions into unoccupied ?T* orbitals that show a strong angular variation in intensity. 4 

U2B Microspectroscopy characterization of 111-V epi-layers for optoelec- .- 

Optoelectronic devices, such as vertical cavity surface emitting laser (VCSEL) 

diodes, are patterned from complex layers of 111-V semiconductor compounds grown 

epitaxially on GaAs or other substrates. One VCSEL structure consists of two 

"mirrors" formed from GaAs/AlGaAs multilayer mirror stacks, above and below a quantum well structure that serves as the active medium. Fig. 1 indicates the 

overall device structure. Though intended for current bias operation, the device 

material can be tested by optical pumping with a focused laser. This can lead to 

microscopic damage near the focus spot, which can be investigated by IFl microtransmission. The spectra for two sites are shown in Fig. 2. The transmission for an undamaged site shows a complex oscillatory behavior, consistent with interference 

due to multiple internal reflections between the top surface and various interfaces 

between layers. The oscillation period Au is related to the layer depth through 

d = l/(2nAu) where n is the refractive index. Fourier analysis, combined with n M 3.5, allows the depth of the interfaces to be quantitatively determined. This is 

shown in Fig. 3. Note that the laser damaged area shows little evidence for of 

layering, indicating that major structural damage has occured. Since the sample can be scanned through the IR microspectrometer's focus, maps of layer depths and 

thicknesses can be extracted. 

Figure 1. Epi-layer structure of a vertical cavity surface emitting laser. 

0.6 

C 

0.4 

u1 

s 

loa 

iwo ZOO0 3Ooo 4wo €000 

Frequency [cm-'1 

Layer Depth Cm] 

Figure 3. Fourier analysis of interference 

pattern, indicating interface depths. 

Figure 2. Infrared microtransmission 

through damaged and undamaged VCSEL epi-layers. 
I Infrared Microspectroscopy of Oil Inclusions in Quartz and Fluorite 

Matrices 

, . i 

U2B 

* '. 

, . .,- 

. .. 

.. 

.. . ~. I 

Wnvolonglh Crnl 

108 6 4 2 

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// bu8: To 

f 0.2 

0.1 

o?OOO 2000 3000 _j 4000 5000 4000 5000 o?dOO 2dOO ' 3dOO 

Froquoncy [ern"] 

Figure 1. 

\ : i I. ! 

6 

.. ......... 1.. "f .... .. / ........ -... ..... ..... :I," .^ . j- .............. !. .. . . ... . 

Figure 2. 
:1 P. W. Stephens et al., Nature, 370, 636 (1994). 

2 D. Koller et al., J. Appl. Phys. 66, 1015 (1995). 

13 S. Pekker et al., Science, 265, 1077 (1994). 

.4 1 M. Carrard et al., submitted to Synthetic Metals. 

Figure 1. IR transmission spectrum measured on a single fiber of KCso. The beam 

is perpendicular to the fiber and the transmission does not depend on the direction 

of polarization. 

* This work has been supported by NSF grants INT-9414840 and DMR9501325 and rp 

a US-Hungarian Joint fund No. 225 and OTKA T4222. 

I Localization of Infrared Sampling in Human Hair. I U2B 1 ~ ~ ~ 

David L. Wetzel (Kansas State Univ.) 

Localization of drugs in human hair has been one of the difficult goals of forensic 

science. One approach involves the use of IR spectroscopy to detect the vibrational 

modes that can uniquely identify a given organic compound. Infrared microspectroscopy studies of longitudinally microtomed, single hairs embedded in paraffin 

have been conducted by K. Kalisinski (Armed Forces Pathology Research Laboratory). For these specimens, 20 X 100 pm sampling apertures were used to obtain 

sufficient signal through a typically 6 pm thick section. This aperture was stepped 

in 5 pm increments across the specimen producing a profile of the drug deposition or protein concentration across the hair. A higher spatial resolution is desirable, 

since human head hair grows approximately 1 cm per month, or about 13 pm an hour. If a dose of cocaine is metabolized in approximately 15 minutes, then the 

deposition of the dose would be localized to a 3 pm segment of hair. 

Using IR synchrotron radiation in combination with the FT-IR microspectrometer at U2B, we can improve the spatial sensitivity considerably. Sampling apertures 

of 5 pm or less, corresponding to a hair growth time of 22 minutes, are feasible. 

In addition to temporal sensitivity, the spatial resolution of the U2B microscope 

also enhances the chemical sensitivity, since the 3 pm segment of hair represents a 

larger fraction of the microspectrometer's sensing region, when compared to a more 

conventional 20 X 100 pm aperture. There remain sample preparation issues, such 

as microtoming appropriately thin and flat specimens compatible with the small IR 

sampling area. 
. .- ..... . . ..~ ~ 

*( Z: 6 61) 

. .. . 

0 

l-l 

4 
I Photoemission of Oxides around the Metal-Insulator Transition 

(Hunter CUNY) 

1 U4A 1 

E. Goering, M. Klemm, S. Horn (U. Augsburg, Germany), and M. L. denBoer 

During our measurement time in 1995 June we obtained photoemission spectra 

of single crystalline VzOs, VOZ, and MoOz in the photon energy range 25 to 100 

eV. Measurements were taken above and below the temperature TMI at which a 

metal-insulator (MI) transition occurs in V~03 and VOz. From fits of the Fermi 

energy cut off we estimate the energy resolution of the measurements to be 150 

meV, determined largely by the analyser. Since the crystals have less than cubic 

symmetry below the MI transition, spectra were taken for various orientations of 

the polarisation vector relative to the crystal axes. 

Fig. 1 shows spectra taken for VOZ at different incident energies above and below 

the transition. The various resolved features show dispersion which is particularly 

strong far from the Fermi energy EF but only weak for the features close to Ep. 

These features exhibit a prominent resonance, having maximum intensity at M 60 

eV, which is typical for V 3d states. (This effect is not evident in Figs. 1 and 2, in 

which spectra are normalized to their respective intensity maxima in order to show 

the dispersion.) 

At all incident energies, a Fermi cut off is observed. The width of the peaks fitted 

to the spectrum is larger than the energy resolution, implying that the intrinsic 

combined electron-hole lifetime is short. We now consider the differences between 

spectra of warm” (conducting) and Eold” (insulating) samples. When the sample 

is cooled below TMI, the main effect seen in Fig. 1 is that the intensity at Ep 

vanishes, suggesting the opening of a gap at the MI transition, which has been 

previously observed. Correspondingly, there is a slight increase in intensity just 

below Ep. On the other hand, at a different orientation of the sample, as shown 

in Fig. 2, the spectral changes at the MI transition are much more dramatic. We 

again see the opening of a gap, as expected. However, there is also a considerable 

increase in the intensity of the features just below EF, especially in the vicinity of 

the resonance at x 60 eV photon energy. Using this information, we can in principle 

determine the orientation, and hence the angular momentum character, of precisely 

those electronic states which are most involved in the metal-insulator transition. 

Similar measurements have been performed for VzO3 and MoOz. For these materials as well we observe only weak dispersion for features close to Ep. For VzO3 

the opening of a gap below TMI is suggested. 

The orientation dependence of the MoOz spectra is especially interesting in com- parison with that of the isostructural compound VOz. 

OrlontaUon - 11 -Warm - - Cold 

Figure 1. VOz 

OrlentaUon - 8 -Warm I Cold 

BhanEncrw lev 

Figure 2. VOz 

[Electronic structure along the A direction in CuAu * I U4A I ~~ 

L.R. Masliah, R.G. Jordan and S.L. Qiu (Florida Atlantic University) 

We have begun making a detailed study of the electronic structure in CuAu using a combination of experimental photoemission measurements and first principles 

calculations. Alongside we show some photoemission measurements obtained for 

the (111) surface at normal emission; the states that are being probed lie along the 

A direction in the Brillouin zone. In addition to a number of ”bulk” features we can also identify at least two surface states; there is a Shockley-type state at about 

0.5eV binding energy and a state at about 7.5eV that lies in the s-d gap very close 

to the band edge at the i?-point. 

We are currently carrying out electronic structure calculations for the (111) surface using a slab geometry. We will use the layer potential functions that are 

generated in first-principles photocurrent calculations for direct comparison with our photoemission measurements. (This work is being carried out in collaboration 

with Dr. B. Ginatempo, University of Messina.) Acknowledgments: We thank 

Dr. M.L. Shek for her help, guidance and patience. 

I I I I I I t 

}--A 

10 8 64 2 0 -2 

Binding Energy (eV) 

Figure 1. Photoemission spectra from CuAu(ll1) at normal emission. The photon 

energy is stepped in increments of 5eV from 25eV (bottom) to 70eV (top). The 

incidence angle is 60°. 

* This work was supported by a grant from NSF: DMR9120120 
P 

Electronic Structure of the Organic Conductor 

K~(BEDT-TTF)~CU[N(CN)~]B~ 

CL 

h3 

U4A 

C. Stagarescu, K. Breuer, K. E. Smith, Department of Physics, Boston University, 

R. Haddon, ATUT Bell Labs, J. S. Brooks, Department of Physics, Flora'da State 

University 

The organic conductor R-(BEDT-TTF)~CU[N(CN)~]B~ is a layered quasi-two dimensional material that is derived from the donor molecule BEDT-TTF. These 

charge transfer salts have received considerable interest, due to the occurrence of 

transitions to either a superconducting state or to a density wave phase below a 

critical temperature. 

We have studied the electronic structure of this organic conductor using angleresolved photoemission. Fig. 1 shows a typical spectrum, taken with 24 eV photons on a sample cleaved in situ. In general agreement with an earlier study of Liu et 

al. we do not observe significant emission intensity at the Fermi level (EF).' An 

interpretation of these results requires knowledge of the surface properties of this 

material. Fhese have not been studied up to date). Single crystals of K-(BEDTTTF)&u[ .(CN)z]Br are expected to cleave exposing the conducting layers. As 

the separation between these layers is larger than the escape depth of the photoelectrons, photoemission only probes the top layer of the sample. Only when 

the surface's stoichiometry is representative for the bulk, the observation of a low 

emission intensity at EF can be related to the electronic bulk structure of this 

conductor. It is therefore planned to systematically study the surface properties 

of these materials. In addition the electronic structure will be studied with X-ray 

emission spectroscopy, as this technique is not surface sensitive as photoelectron 

spectroscopy. Work supported in part by NSF CAREER AWARD DMR 95-01174. 

1. R. Liu et at. Phys. Rev. B51, 6155 (1995). 

14 12 10 8 6 4 2 Q=O 

I - . Biwl3Emgyo__' 

Figure 1. Normal emission ARP spectrum from R-(BEDT-TTF)zCU[N(CN)Z]BI 

~~ ~ 1 Surface states on the (100) and (001) surfaces of equi-atomic CuAu * 1 U4A I 

Xumou Xu, R.G. Jordan and S.L. Qiu (Florida Atlantic University). 

We are making a detailed experimental and theoretical investigation of surface 

states on the (100) and (001) surfaces of CuAu (Llo, layered tetragonal structure 

with c/a = 0.925). We have identified Tamm-type surface states on both the 100 

and (001) surfaces, labelled S1 and 52 on the accompanying figure for the (100) 

surface, located near the li?-point, and a Shockley-type state near the z-point in 

the binding energy range 0-lev on the (100) surface. By making a careful analysis 

of the dispersion of S1 and S2 on the two surfaces we have determined the surface 

lattice constants and we conclude that the (100) surface is not reconstructed. Preliminary calculations of the electronic structure at the CuAu(001) surface using a slab geometry, with an Au termination, shows the appearance of these Tamm-type 

states. More detailed calculations are underway. (This work is being carried out 

in collaboration with Dr. G.Y. Guo, Daresbury Laboratory.) Acknowledgments: 

We thank Dr. M.L. Shek for her help and advice. 

Figure 1. Photoemission spectra from the 

various emission angles in the (001) mirror 

surface of equi-atomic CuAu at 

The photon energy is 25eV with an incidence angle of 60'. 

* This work is supported by a NSF grant: DMR-9120120 
Determination of Helicity-Dependent Absolute PhotoAbsorption 

Cross Sections at the L-edges of Fe, Co, and Ni * ~__ 

V. Chakarian and Y.U. Idzerda (NRL), J.-H. Park, G. Meigs, and C.T. Chen 

(AT&T) 

The knowledge of absolute X-ray photoabsorption cross sections is a prerequisite 

in many experiments that employ photons as a probe. In this article, we present a method which enables the determination of the absolute photoabsorption cross sections in the soft X-ray region. Absorption spectra are obtained in transmission by 

using a photodiode mounted behind the samples which consist of a -50 A thin film 

evaporated in situ onto -1pm thick semi-transparent parylene, (hCsHe),,, substrate 

[l]. Th? measurements, made by employing circular polarized p otons, enable the 

determination of ,ut and p- corresponding to the absorption cross sections of leftand right-circular polarized photons (or photon spin parallel and antiparallel to 

the sample magnetization direction), respectively. The total photoabsorption cross section can also be obtained by using UT^^ = (p.+ + p- + ?0)/3, where PO = (?+. + 

p-)/2 is the photoabsorption cross section for hear polarized photons (not hehcity 

dependent). As an example, the figure below shows the corresponding cross sections 

per Fe atom, expressed in cm-'. The spectra were scaled to calculated absorption 

cross sections [2] in the pre- and post-edge regions and the atomic density in the 

film was assumed to be same as the bulk value. An independent confirmation of 

the resulting p~,,t was obtained by correlating the absorption strength at the Ls 

peak with ex-situ X-ray fluorescence measurements from a series of samples with 

different thicknesses. The two methods yield values that are very similar. The 

results for ferromagnetic Fe, Co, and Ni and as well as other non-ferromagnetic 3d 

elements will be presented in an upcoming publication. Note that in the case of a non-ferromagnetic material, all three curves shown in the figure would be identical. 

C.T. Chen et. al., NSLS Activity Report, p. A-25 1994 

J.J. Yeh and I. Lindau, Atomic Data and Nuclear Lk ata ables, 32, 1 (1985). 

700 720 740 760 

Photon hergy (eV) 

Figure 1. 

P 

(--L 

w * VC Supported by ONR. 

Element-Specific Orbital and Spin Moments of Transition Metal Alloys via MCD * 

V. Chakarian and Y.U. Idzerda (NU), J.-H. Park, G. Meigs, and C.T. Chen 

(AT&T) 

Magnetic circular dichroism (MCD), in conjunction with the recently developed 

sum-rules, can be used to decompose the total magnetic moment of a magnetic ma- terial into the orbital and spin moment contributions. In this article, we extend the 

use of the MCD method to transition metal alloy systems Fe,Col-, and Co,Nil-,. 

XAS spectra are obtained in transmission by using a photodiode mounted behind 

the samples which consisted of a thin film evaporated in situ onto semi-transparent 

rocess is discussed in detail elsewhere b]. As an exam le, the MCD spectrum psolid) from a thin film Fe48Cob2 alloy 

and its integral Gashed) are shown in Fig. 1, where p and q are the integrated 

MCD intensities over the Ls and Ls+L2 edges, respectively. Using these values, it 

is possible to directly obtain the ratio of orbital to spin moments, mr/m,, of each 

element. The measurements were repeated for a large number of alloy films spanning the entire Fe-Co-Ni phase diagram, and the results are shown in Fig. 2 don 

with Einstein-de Haas gyromagnetic ratio data [2] and theoretical predictions [3 

The preliminary results thus far indicate that the orbital and spin moments for eac 

of these elements do not vary significantly, within experimental uncertainty, away 

from their elemental values. This is in contradiction to the theoretically expected 

non-monotonic behavior of the orbital moment. The discrepancies may be, in part, 

due to the fact that the films used in the present work were random alloys. The 

results of this study will be presented in more detail in upcoming publications. 

U4B 

arylene substrates. The data reduction 

f 

-- 

C.T. Chen et: al., PhG. Rev. Lett., 75, 152 (1995): K. Adachi et. al., Magnetic Properties of Metals, Vol. 111/19a, p. 178 

Berlin, 1986). 

et. al., Phys. Rev. B, 45, 12911 (1992). 

Rptmaemy (oy) 

Figure 1. 

,*-. .. 0.044. , , I , , , 9 

Pe 25% 508 75% CO 25% 50% 758 NL 

Figure 2. * VC Supported by ONR. 
.. *: I - 

Magnetic Field Dependence of Mn Moment in FeCo/Mn/FeCo Trilayers * 

:.. j 

. . ;A 

, . -- 

U4B Giant magnetic effects in the L-edge extended X-ray absorption fine 

structure of 3d transition metals * 

0 

01 

00 

.oi 

U4B 

Figure 1. 

* VC Supported by ONR. 

Decreasirg Field 

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 

&xl.ied mgnetic Field (kW 

Figure 1. 

* VC Supported by ONR 
Electronic aspect of ferromagnetic transitions in Lal-,(Ca, 

Pb), Mn03 

~ 

U4B 

LaMnO3 is an antiferromagnetic insulator with MnSt. Substitution of La sites 

with alkaline earth elements, Le. Lal-,A,MnOs (A = Sr, Ca, etc), induces Mn4+ 

and the system becomes Mnst-Mn4+ mixed valent. Then the system exhibits an intriguing ferromagnetic transition, which arises 'ccolossal' magnetoresistance. It 

has also been found that the transition temperature as well as the magnetoresistance varies as a function of the lattice constant. Hence it is interesting to study 

La(Mnl-,Co,)Os system, in which the lattice constant also changes as a function 

of x. 

We have investigated La(Mnl-,Co,)Os by using x-ray absorption and resonant 

photoemission spectroscopies. Fig. (a) shows Co LZJ edge x-ray absorption spectra 

Of LaMno.86C00.1603 in comparison with those of Lac003 (Cost) and COO (CoZt). 

As can be seen in the figure, the spectrum of LaMn0.86Co0.1603, surprisingly, exhibits almost identical features in both LZ and LS regions to those of COO but com- pletely different from those of LaCoO3, showing that Co in LaMnO3 is not trivalent 

but divalent. These results indicate that Co doping creates Co2+-Mn4+ pairing 

shows Co 2p edge on- and off-resonance photoemission spectra of LaMno.86 c00.16 Lb? 3 

and induces the Mnst-Mn4+ mixed valent system as in Lal-,AmMn03. Fig. 

which were taken with 778.5eV and 775eV photon energies, respectively. In the on- resonance, the spectrum in the valence band region is completely dominated by Co 

3d emission due to a giant resonance enhancement. As can be in the difference 

spectrum shown in the bottom, the Co 3d lowest bonding energy states, which correspond to 6Tz and 'T1, locate M 0.7eV higher binding energy than the Mn 3d 

lowest binding energy state, which corresponds to 4Az. 

The data show that Co doping in LaMnOs changes the system to be Mn3+-Mn4+ 

mixed valent, not only the lattice constant. 

780 700 800 

Photon Energy (ev) 

Figure 1. Figure 2. 
rp 

U4IR A Study of Ethanol Adsorption on Si(100) Surfaces Using Mid-to 

Far-Infrared Spectroscopy 

J. Eng, Jr., L.M. Struck, B.E. Bent, G.W. Flynn, (Columbia University), Y.J. 

Chabal, K. Raghavachari (AT&T Bell Laboratories), G.P. Williams (BNL-NSLS) 

There has been considerable commercial interest [l] in the use of tetraethoxysilane 

(TEOS) as a silicon source for chemical vapor deposition processes related to Si02 

growth. In turn, this interest has motivated studies of ethanol adsorption on Si(100) 

surfaces, since it has been shown [2] that ethanol decomposes upon adsorption to 

form a bound ethoxy group which, through infrared (IR spectroscopy, has been 

Studies has been quite fruitful, they have also been limited by strong silicon phonon 

absorptions to frequencies above 1300 cm-l. 

In the studies described here, the adsorption of ethanol on clean Si(100) surfaces, 

has been investigated using a specially prepared cobalt implanted silicon sample as described in more detail in the companion summary about water adsorption on Si(100) found elsewhere in this Annual Review. The adsorption of three isotopes of 

ethanol (-do, -d3, -de) have been studied, and shown in the figure are the infrared 

spectra corresponding to approximately monolayer coverage of each isotope on clean 

Si(100). These spectra represent the first time that the skeletal modes of bound 

ethoxy groups have been observed on silicon surfaces, and show that the ethanol 

dissociatively adsorbs across the Si(100) dimer to yield a bound ethoxy group on one side and an adsorbed hydrogen on the other. Furthermore, the surface dipole 

selection rule, which results from the buried metallic layer, indicates that the ethoxy 

group is adsorbed such that the Caw axis of the methyl group is perpendicular to 

the surface, quite different from the bonding geometry for ethanol adsorption onto 

metals. Normal obtained by cab-inito methods have been successful in assigning all 

the major features in the ethanol-do spectrum and more calculations are underway 

to assign the features for the ethanol -d3 and -de spectra. 

determined to resemble the ethoxy groups in adsorbed 4 EOS. Though these IR 

L. Tedder, G. Lu, and J. Crowell, J. Appl. Phys., 1991, 69(10) 7037-49 

J. Crowell, L. Tedder, H. Cho, F. Cascarano, and M. Logan, JVST A 8(3) 

1864-70 

91.0- 

U4IR Study of Water Adsorption on a Si(100) Surface Using Far-Infrared 

Spectroscopy 

J. Eng, Jr., L.M. Struck, B.E. Bent, G.W. Flynn (Columbia University), Y.J. 

Chabal, K. Raghavachari (AT&T Bell Laboratories), G.P. Williams (BNL-NSLS) 

Understanding the bonding geometry and dynamics in the adsorption of water on Si( 100) surfaces is technologically important for device manufacture. Infrared (IR) 

spectroscopy is, in general, useful for studying bonding geometries and dynamics. 

For silicon, however, external reflection IR spectroscopy has poor signal to noise, 

while transmission IR spectroscopy is limited by phonon absorptions below -1400 

cm-' so that only high frequency vibrations such as those involving hydrogen can be observed. 

In the studies described here, specially prepared Cot implanted Si(100) wafers 

are used to overcome the problems mentioned above. After Cot implanted each 

wafer is annealed at 1000°C, which causes the subsurface cobalt to form an abrupt, 

semi-metallic, reflective COSi2 layer which is located 50 nm below the surface and 

is 50 nm thick. The annealing step also repairs the Si overlayer damaged during 

implantation, so that an ordered Si(100) 2x1 surface is obtained. In this type of 

sample, the silicon overlayer is optically thin, so that phonon absorptions do not 

dominate, yet chemically thick enough to exhibit the same surface chemistry as 

Si(100) wafers with no implantation. 

Using these Cot implanted samples, we have been able to perform spectroscopic 

studies in the far infrared for Hi'O, Hi60 and Di60 adsorption onto Si(100) surfaces. The spectra for Hi60 and DzO (shown below) indicate that water dissociatively adsorbs across the Si(100) surface dimer. Importantly, use of the cobalt 

implanted sample, along with the intense synchrotron light, has enabled us to see 

a weak mode at 896 cm-' in the Hi60 spectrum, which had not been previously 

observed. Normal mode calculations show that for Hk60 the Si-OH stretching mode 

and the Si-0-H bending mode are sufficiently close in energy to couple mechanically 

and split apart, resulting in a mode at 825 cm-I and at 896 cm-l. Thus, we have 

been able to resolve the puzzling isotope shift seen previously by electron energy 

loss spectroscopy (EELS) [l]. The features in the Hi80 and Dt60 spectra have dso 

been assigned, based on the calculations. 

[l] H. Ibach, et al., Solid State Communications, Vol. 42 No. 6, p457. 

I 

P 

co 

I e. I 

,' ./ ; .o ;, . , ?.' . .,'" I 

.. 

Infrared Spectroscopic Study of Water Adsorption on Ni(ll0) U41R 

TIONALLY IMPORTANT LOW FREQUENCY MODES IN PROFAR-INFRARED SYNCHROTRON SPECTROSCOPY OF FUNCU4IR 

TEINS * ll 

A. Xie, Q. He, K. Hellingwerf. W.D. Hoff, E.M. Scheuring, B. Sclavi, M.R.Chance. 

Dept. of Physiology and Biophysics, Albert Einstein College of Medicine , Bronx, 

NY 10461. Dept. of Microbiology, Univ. of Amsterdam, 1018 WS Amsterdam, The 

Netherlands. 

Low frequency modes of proteins arise from (1) large effective masses, resulting 

from coupled motions of a large number of atoms, and (2 weak bonds, such as 

of a protein. We study the structural origins, dynamic nature, and functional 

roles of low frequency modes of photoactive yellow protein, bacteriorhodopsin, and 

myoglobin, using far-infrared synchrotron spectroscopy (20 - 500 cm-'), and model 

compound analysis with homologous amino acid polymers. All proteins examined 

exhibit broad band absorption with small ripples of narrow bands; while homologous 

polymers display a few well-defined bands above 60 . One band around 110-150 is 

found in poly-L-Ala, -Leu, and -TIP with dominant a-helical structures, and absent 

in poly-L-Gly, -Val, and -Phe lacking cr-helical structures. Far-infrared difference 

spectroscopy is being applied to detect changes in collective modes of a protein from 

one state to another. Discussions will be presented concerning structural origins and 

biological importance of observed low frequency collective modes in proteins. 

hydrogen bonds and salt bridges, which are important for t h e high-order structure 

* This work was supported by grants from NIH RR01633, HL45989, and ONR N00014- 

95-1-0310. 
.',? - 

1 Quantum Well States of Cu Films on Magnetic Alloy Substrates I U5U I ~ ~ ~~~~~~~ 

D.-J. Huang and P. D. Johnson, Dept. of Physics BNL 

Quantum-size effects on electronic structure have been well studied in semiconductors and transition metals. Recently the quantum well states in the spacer layer 

of magnetic multilayers have been used to explain the oscillatory exchange coupling. 

In these magnetic multilayers the exchange coupling between adjacent ferromagnetic 

layers oscillates with the thickness of spacer layers. The quantum well states in Cu on fcc Co(OO1) have been found to be spin-polarized, preferentially with minority 

spin, and crossing the Fermi level with the periodicity identical to the oscillation 

periods of the exchange coupling in the associated magnetic multilayers. In the 

present work, we perform photoemission studies of the quantum well states in Cu 

films deposited on Co and CoNi alloy substrates. The quantum well states in Cu on CosoNizo alloy have been identified. shows that. As shown in Figure 1, these 

states are less intense and have slightly lower binding energies than those in Cu on Co OOl), particularly in the vicinity of the Fermi level. This observation can 

hybridization gap in CoaoNizo alloys moves away from the Fermi level as the Ni con- centration increases. Once the Cu quantum well states are located outside of this 

gap, the reflectivity reduces dramatically and the quantum well states are much less 

confined. Our results indicate that the degree of quantum confinement can be tuned 

by altering the electronic structure of magnetic substrates, for instance, changing 

the relative concentration in the substrate. This in turn suggests the possibility of 

tuning the exchange coupling strength in the associated magnetic multilayers. 

be we 6 reconciled with the electronic structure change in the substrates. The s-d 

4321 0 

Binding Enorgy (oV) 

Figure 1. Photoemission spectra of quantum well states in Cu films deposited 

p onCo8oNizo and Co substrates, The spectra are taken at normal emission with 23 

+, eV photonenergy. CD 

I Photoemission studies of chemisorbed Cs on Fe substrates I u5u J 

D.-J. Huang, E. Vescovo (BNL), D. M. €We (Utah State Univ.), P. D. Johnson 

(BNL), P. Abramowitz and J. L.- Erskine (Univ: of Texas at Austin) 

There is considerable interest in the nature of the bonding between alkali adatoms 

and metal surfaces. However the magnetic interaction between alkali atoms and 

ferromagnetic substrates has received less attention. In this work, we use spinpolarized and spin-integrated photoemission spectroscopies to investigate the electronic interactions between chemisorbed Cs atoms and ferromagnetic Fe films which 

are epitaxially grown on W 110). Spin-integrated Cs 5p photoemission spectra are 

consistent with previously o k served general trends in the coverage dependent binding energy shifts of alkali adatom core-level spectra. The Cs 5p binding energy in 

the first atomic layer decreases as the Cs coverage increases due to dipolar repulsion and band formation, as shown in Fig. 1. The binding energies of Cs in the 

second layer are smaller than those in the first layer, an indication that the Cs-Cs 

interaction is weaker than the Cs-Fe interaction. In addition, the lifetime width of 

Cs in the first layer is much larger than those in the second layer. This dramatic 

change of lifetime width is suggestive of s-p hybridization in the first-layer-Cs va- lence electrons. That no measurable spin-polarization exists in the Cs 5p spectra 

suggests that there is little or no induced magnetic moment on Cs site, in contrast to 

the observation of an induced magnetic moment in chemisorbed oxygen and sulfur on ferromagnetic substrates. Data analysis is under way to understand the Cs-Fe 

electronic interactions. 

15 14 13 12 11 10 

Binding Enorgy (oV) 

Figure 1. 5p photoemission spectra of chemisorbed Cs on 10-ML Fe films deposited on W(110). The spectra were taken with 30 eV photon energy and at temperature 

of 100 K 
? I CORE LEVEL LINESHAPES IN FeRh ALLOY I U7B I 

Biao Zhao, R.G. Jordan (FAU), M.W. Ruckman, F.M. Jacobsen, Myron Strongin h2 

(BNL) 

We have carried out photoemission measurements to study the lineshapes of the Fe and Rh core levels - concentrating particularly on 3s and 4s lineshapes, respectively - to monitor the local magnetic character in the antimagnetic 

and ferromagnetic (FM) states. We have investigated samples of pure Fe, pure 

h and equiatomic FeRh alloy. Characterizations of FeRh samples were done prior 

to photoemission measurements. X-ray diffraction shows that the FeRh alloy has a CsCl structure and its transition temperature was determined from the electrical 

resistivity measurements which is in good agreement with previous report. 

Figure 1 shows the Fe 3s core levels for pure Fe and FeRh alloy. No change in 

the line-shapes of the Fe 3s core level in FeRh alloy below and above the transition 

temperature ( 350 K). This indicates that the local moment on the Fe sites are 

same in both AF and FM states which is in agreement with our theoretical calculations using both FSM-ASW (Fixed-Spin Moment, Augmented Spherical Wave) 

and LMTO (Linear Muffin-Tin Orbital) methods. . The Rh 4s core level spectra for both pure Rh and FeRh alloy are shown in figure 2. This preliminary result 

shows no change in Rh 4s lineshape of FeRh alloy below and above the transition 

temperature. 

One possible reason is that the magnetic properties change significantly from the 

surface to the bulk for FeRh alloy and theoretical results reflect the bulk magnetic 

properties while the photoemission measurements reflect the surface properties. 

Slab calculations are under way to investigate the possible difference in magnetic 

properties between bulk and surface for FeRh. 

This work was supported by funds from the NSF, contract No. DMR-9120120. 

Room-temperature Chlorination of As-rich GaAs( 110) 

2 

U8A 

1.5 

3 

'I 2' 

0.5 

, 

0.5 

I 

0- -110 -105 -100 -95 -90 0'' -95-90 -85 -80 -75 

Energy (ev) Energy (eV) 

Figure 1. Figure 2. 
[The Adsorption Behavior of Clz on GaAs(001)-4x6 I U8B I 

W.C. Simpson (UC Riverside, MSD LBNL), W.H. Hung (IBM), and J.A. Yarmoff 

(UC Riverside, MSD LBNL) 

The initial stages of the room-temperature reaction of Cl2 with GaAs(001)-4x6 

to form GaCl3 and AsCls are studied using soft x-ray photoelectron spectroscopy. 

The results of this investigation are illustrated in Fig. 1, which shows the proportion 

of the Ga 3d core-level intensity derived from GaCl and GaC12 moieties, as well as 

the proportion of the As 3d core-level intensity arising from AsCl and AsClz. Note 

that exposures were carried out with a solid-state AgCl electrochemical cell, so the 

Cl2 dosage is reported in terms of the time-integrated current through the cell, in 

units of pA.min. 

It is found that the coverages of GaCl and AsCl increase linearly with the logarithm of the Cl2 exposure. This logarithmic exposure dependence of the coverage 

corresponds to a sticking coefficient that decays exponentially with coverage, as described by the Elovich equation [l], S 0) = a exp(-b0). The Elovich equation has 

been used to describe the oxidation o I a number of metals, alloys and semiconductors, but it is not supported by a unique microscopic model [2]. Coverage-dependent or reconstruction-dependent activation energies, or the weakening of back-bonds 

due to chlorine adsorption can all account for this behavior. At this time, further 

investigation is needed to determine which microscopic model best supports the 

adsorption kinetics observed for this system. 

The appearance of GaCl2 and AsCl2 following sufficiently large exposures indicates that chlorination occurs in a step-wise manner. An examination of the C1 2p 

level shows that the difference between C1 bound to Ga cannot be resolved from 

C1 bound to As, but that there is -0.5 eV difference in the C1 2p binding energy 

between the monochloride and dichloride moieties. 

1. S. R. Morrison, The Chemical Physics of Surfaces (Plenum Press, 

New York, 1990), Ch. 7. 

2. G. F. Cerofohni, G. La Bruna and L. Meda, Appl. Surf. Sci. 89 (1995) 361. 

0.25 

3 0.20 

0.16 . 

t 

0.00 0.05[ - J -1 100 101 102 103 

Figure 1. 

I Remote Inductive Effects in the Si 2p Spectra of Halogenated Silicon I U8B I 

W.C. Simpson, J.A. Yarmoff (UC Riverside, MSD LBNL), W.H. Hung, and F.R. 

McFeely(Il3M) 

Recent experimental evidence indicates that remote inductive effects may be 

significant for highly electronegative adsorbates, which would re uire extending the 

standard scheme for assigning chemical shifts in Si 2p spectraql]. To investigate 

this possibility for halo en systems, Si 2p spectra are collected from monofluorinated 

and polyfluorinated Siflll) and compared. 

Figure l(a)-(b) shows spectra collected from monofluorinated Si(ll1) and from 

the same sur ace following additional fluorination, which generated higher fluorides. 

Panel (c shows the difference between the two, which clearly contains no sub-1-eV 

shifts. dhis result restricts the possible types of remotely induced shifts that need 

to be considered for this system. 

For example, the data do not rule out the possibility that 1-eV shifts are induced 

by -SiF3 groups, in direct analogy to the 1-eV shifts induced by -sios, seen in 

ref. [l]. This would alter the interpretation of peak A, in Fig. 1 b). To consider 

with the data, but which includes the remote inductive effects of F atoms in -SiF3 

groups. It is found that extending the assignment rules in this way does not change 

the qualitative findings of earlier investigations, but does alter the quantitative results. 

1. M. M. Banaszak-Holl, S. Lee, and F. R. McFeely, Appl. Phys. Lett. 65 (1994) 

1097. 

this possibility, an extended set of assignment rules is suggested t 6 at is consistent 

. . . . . . . 

a) 40 L XeF2 L annei 

h v = 170 eV 

-5 -4 -3 -2 -1 0 1 

Binding Energy (ev, rel. bulk Si i 

Figure 1. 

U9B Effect of Increased Lipid Packing on the Conformational State of 

GLUTl 

Scarlata, S., McBath, H. & Haspel, H., Dept. of Physiol.& Biophys., SUNY Stony 

Brook 

In this study we used the optical facilities at BNL to measure the fluorescence 

lifetimes of the tryptophan residues of the facilitative glucose transporter (GLUTl). 

Glucose biding to GLUTl results in a structural change to an active conformation. 

The goal of this project was to determine whether increased lipid packing would 

stabilize this state. We and others have found that the fluorescence emission intensity and anisotropy are highly sensitive to GLUTl conformation. To determine 

whether these changes are a result of changes in fluorescence lifetime, we measured 

this parameter under various conditions. These measurements served to be valuable 

in determining that the binding of glucose statically quenches GLUTl fluorescence 

due to a movement of the interfacial tryptophan residues towards the ionic groups on the membrane surface and that increased lipid packing stabilizes this state. This 

work has been recently published Scarlata et al. (1995) Biochemistry 34, 7703-7711. 

I Solution Circular Dichroism of 1,6-Anhydroglucopyranoside I u11 I 

E.R. Arndt and E.S. Stevens (SUNY Binghamton) 

The Circular Dichroism (CD) spectrum of 1,6 anhydroglucopyranoside as prototypical of anhydrosugars was measured over the range of 170 to 230nm. A negative 

CD band was found at 183nm with a shoulder at 195 nm. A cross- over occurs at 176n, and the CD remains positive to the solvent limit. The spectrum strongly 

resembles that of a methyl-P-D-glucopyranoside film, except that the features are 

red-shifted approximately 7 nm in the anhydrosugar. The presence of the five 

membered ring is obviously in- culpated in the shift. [Supported by NIH Grant 

GM464551 

$2 

-0 

$1 3 z:-I 11-. 

-40 li0 180 lh & 2io 20 zio Zio 250 

Wadength (nM) 

Figure 1. 7.55 mg/ml Anhydroglucoside (aglu) in a 50 micron cell. 
.i 

, .* 

u11 Electronic Spectroscopy of Matrix-Isolated Adenine Derivatives at 12 

K* 

L. A. Kelly, E. D. Johnson, J. C. Sutherland (BNL) 

u11 Photoionization Study of Ethanol and Radicals Derived From Ethanol: 

Theory and Experiment 

D. J. Bogan, F. L. Nesbitt, L. J. Stief (NASA/Goddard), J. L. Durant (SNL), S. 

C. Kuo, Z. Zhang and R. B. Klemm (BNL) 

This study includes theoretical and experimental results for the ionization energies (1E)of ethanol, ethoxy radical, 1-hydroxyethyl radical, and the appearance 

energy (AE) of 1-hydroxyethyl cation from ethanol. Experimental measurements 

were obtained at the NSLS using a discharge flow-photoionization mass spectrometer (DF-PIMS) apparatus. Ab initio calculations were done at Sandia National 

Laboratory using the Gaussian-2 (G-2) method, which is a well characterized theoretical procedure which has been shown to yield accurate bond strengths and ionization energies. G-2 is a composite procedure that approximates a QCISD(T)/G311+G(3df,?p) calculation as a linear combination of smaller calculations. 

All experiments were conducted at 300K with a flow tube pressure of about 4 

Torr of helium and at flow velocities of about 1000 cm/s. Hydroxyethyl radicals, 

CzH40H or CzDaOH, were generated by the reaction of F atoms with ethanol, 

CzHsOH or CzD60H. Ethoxy radicals, C2D60, were produced by the reaction of 

CzD6 with NO2 via the reaction sequence: F + CzDe -+ CzD6 + DF; CzD6 + 

NO2 -+ CzD50 f NO. Radical concentrations in the flow reactor were lo1' to 1013 

molec./cm3. Photoionization efficiency (PIE) spectra were obtained by plotting the 

ratio ions/light as a function of wavelength. Analysis of the PIE curves yielded 

the following results that are compared to the calculated values in Table 1. The 

experimental uncertainty is f 0.05 eV or less in all cases. It was assumed that 

the lowest energy AE for loss of one hydrogen from ethanol gives 1-hydroxyethyl 

cation, and that IE(CH3CHOH) < IE(CHzCH20H . IE's for 1-hydroxyethyl radibehavior. AE's for CH3CHOHt and CD3CDOHt from dissociative ionization of 

the corresponding alcohol were measured from linearly ascending thresholds. 

The work at BNL was supported by the Division of Chemical Sciences. Office 

of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC02- 

76CH00016. 

cals and ethoxy radical were obtained from threshol d s that displayed weak step-like 

Neutral Ion Experiment Theory 

C,H,OH C,H,OH' 10.43 10.41 

C,D,OH GD,OH' 10.46 10.40 

CH,CHOH CH,CHOHt 6.73 6.68 

CDJDOH CD3CDOHt 6.70 6.67 

C,H,OH CH,CHOHt 10.81 10.79 

GD,OH CD,CDOH' 10.93 10.89 

C2DSO GW' 10.37 10.32 

Figure 1. Ionization Energy or Appearance Energy (in eV). 

Low temperature fluorescence and UV/VUV absorption measurements of purine 

and indole derivatives, isolated in argon matrices at 12K, have been carried out 

at beamline U11. Purine and indole derived chromophores are important light 

absorbing species in nucleic acids and proteins, respectively, of biological systems. 

Hence, the investigations were carried out to assess the fate of the initially produced 

electronically excited states subsequent to UV and VUV photon absorption. The 

matrix isolation experiments provide a means of investigating the spectroscopic 

properties of the isolated chromophores in a non-hydrogen bonding solvent. 

The substrates were isolated in condensed argon matrices at 12K, which served as transparent hosts down to 105 nm. Both steady-state and time-resolved luminescence measurements were carried out. No fluorescence was observed from the 

electronically excited singlet state of the purine and adenine derivatives. The observed emission was independent of excitation wavelength and was characterized as 

structured, long-lived phosphorescence from the lowest electronically excited triplet 

state of adenine (Figure 1). Since adenine is known to exist as a mixture of N(7)- 

H and N(9)-H tautomers, we investigated the N-7 and N-9 methylated adenine 

derivatives as tautomer models. The absorption (Figure l), excitation, and emission spectra not shown of 9-methyladenine were found to be quite similar to that 

blue-shifted with respect to both adenine and 9-methyladenine, suggesting that the 

N(9)-H tautomer is the major tautomer in matrix-isolated adenine. 

of adenine. L owever, t h e emission spectrum of 7-methyladenine was significantly 

wav*ienpm (mi 

matrix-isolated adenine 

(b) Emission spectra of 

in argon matrices at 12 K. 

* This work was supported by the U.S. DOE, Office of Health and Environmental 

Research, and the National Synchrotron Light Source. L.A.K. ahowledges the DOE 

Distinguished Postdoctoral Fellowship Program, administered by the Oak Ridge Institute 

for Science and Education, for support. 
I U1l I A Discharge Flow-Photoionization Mass Spectrometric Study of HOI: 

Photoionization Efficiency Spectrum and Ionization Energy I ull I Experimental Determination of the Ionization Energy of 10(X2113/2) 

and Estimations of AfH"o(IO+) and PA(I0) 

P. S. Monks, L. J. Stief (NASA/Goddard), D. C. Tardy (Univ. Iowa), J. F. Liebman 

(Univ. Maryland/Balto. Co.), Z. Zhang, S. C. Kuo and R. B. Klemm (BNL) 

Photoionization efficiency (Pm) spectra of HOI were measured over the wavelength range X = 115 to 130 nm (Fig. 1) and in the ionization threshold region, X = 

123 to 129 nm (Fig. 2), using a discharge flow-photoionization mass spectrometer 

apparatus coupled to a synchrotron radiation source. HOI was generated, in situ 

but in varying amounts, by three separate reactions: OH + 12; OH + CFJ; and 

O('P) + C2HJ. The PIE spectra displayed step-like behavior near threshold and 

the BO-I stretching frequency in the cation was determined to be 702 f 60 cm-'. 

A value of (9.811 f 0.020) eV was obtained for the adiabatic ionization energy (IE) 

of HOI from photoion thresholds, corresponding to the HOIt (X'A") t HOI(X'8') 

transition. Even though the present result appears to be the first reported determination of IE(HOI), the experimental value is compared with an estimated value 

previously derived via a trend analysis and it is considered in terms of trends in the 

series IE(HOX), where X = F, C1, Br and I. The branching ratio for [HOq/[IO] in 

the O(3P) + C2H61 reaction was estimated to be about 8/1 at T = 298 K, if we 

assume that the photoionization efficiencies for HOI and IO are the same at 10.3 

eV X = 120 nm T (h e work at B NL was supported by the Chemical Sciences Division, Office of 

Basic Energy Sciences, U.S. DOE, under contract No. DE-AC02-76CH00016. 

Z. Zhang (BNL), P. S. Monks, L. J. Stief (NASA/Goddard), J. F. Liebman (UNv. 

Maryland/Balto. Co.), R. E. Huie (NIST), S. C. Kuo and R. B. Klemm (BNL) 

Photoionization efficiency (PIE) spectra of 10(X211;) were measured over the 

wavelength range X = 115.0 to 130.0 nm (Fig. 1) and in the ionization threshold 

region, X = 126.0 to 130.0 nm (Fig. 2), using a discharge flow-photoionization mass 

spectrometer apparatus coupled to a synchrotron radiation source. Iodine oxide 

was generated by the reactions of 0 P) atoms with I2 and CFJ. The PIE spectra 

value of 9.736 f 0.017 eV was obtained for the adiabatic ionization energy Ph$ 

of IO, corresponding to the 10+(XsC-) t 10(X2113/2) transition. The separation 

between the first two steps in the PIE spectrum (which might be perturbed slightly due to autoionization) was used to derive the vibrational spacing of the cation, 

1060 f 160 cm-'. A Rydberg progression, presumably converging to the excited 

'A state of the cation, has a convergence limit that lies 0.596 eV above the ground 

state of the cation. A selected value for the bond dissociation energy of IO, DOo(I0) 

= 226 kJ mol-', leads to AfH"o(I0) = 128 f 4 kJ mol-'. From this value for the 

heat of formation of IO, estimates are made for AfH0o(IOt), AfH"o(HO1) and the 

proton affinity of IO. 

The work at BNL was supported by the Chemical Sciences Division, Office of 

Basic Energy Sciences, U.S. DOE, under contract No. DE-AC02-76CH00016, 

displayed step-function behavior. E rom the half-rise point of the initial ste 

i1;- 

1 O*05; I0.00 , , , , , , , , , , , 11s 120 125 

WAVELENGTH (nm) 

11s 

123 124 I25 126 127 128 1 Figure 1. Photoionization efficiency 

spectra of HOI between X = 115.0 and 

130.0 nm at 0.2 nm steps. The HOI WAVBLENGll# (nm) 

molecule was produced in-(a): by the reaction O(3P) + CZH& and in (b): by 

the reaction OH + CFJ. The positions 

of the "steps" in the PIE curves (126.3 

nm, 125.2 nm and 124.1 nm) are indicated by the superposed lines. 

Figure 2. Photoionization threshold region of HOI at a nominal resolution of 

0.13 nm and 0.1 nm steps between X = 

123.0 and 129.0 nm. The onset of ioniziG 

tion is at X = 126.35 nm (9.813 f 0.010 p eV). VI 

li5 Ib 

WAVBLBNUI'H (om) 

Figure 1. Photoionization efficiency 

spectrum of IO (m/z = 143) ] between 

X = 115.0 and 130.0 nm. The arrow indicates the onset of ionization at 127.3 nm (IE = 9.74 f 0.02 eV). The super- posed lines indicate autoionization which 

presumably correlates with a Rydberg 

progression hat converges to an excited 

state of the cation at 120.0 nm (10.332 

eV). 

41, I 'I I I 9.1 9* 

u(u0ri.n 9.8 

A) Photoionization threshold 

at a nominal 

between X = 126.0 and 130.0 nm. (B) Energy derivative of (A). The maximum 

in the derivative is at X = 127.35 nm (9.736 f 0.018 eV). 

(m/z = 143 

resolution of 0.23 nm an J 0.1 nm steps 
I The electronic structure of Be( 10-10) 1 u12 

Ph. Hofmann and E.W. Plummer (ORNL and University of Tennessee) 

Beryllium is a simple metal with most unusual properties both in the bulk and 

at the surfaces. In the bulk the electronic density of states has a minimum at the 

dispersions . We have determined the electronic structure of Be(10-10) with angle resolved 

photoemission. Our results clearly rule out the long termination and the experimentally determined dispersion of the surface states is given in Fig. 1 superimposed on the Chulkov’s calculation for the short termination. The major difference between calculation and experiment is that the two predicted surface states at the L 

point are not observed. This is probably due to a slight error in the energy of the 

projected bulk bands due to many body interactions. 

E.W. Plumme$ and J.B. Hannon, Prog. Surf. Sci. 46, 149 (1994). 

E.V. Chulkov, to be published. 

Surlace Brillouln Zone 

M 

Figure 1. Surface state dispersion on Be(lO-lO).The experimental points markers) 

are superimposed on the calculation for the short termination from Ref. t 21. 

I Quantitative Calcium XANES * 1 Ul3UA 

C. J. Buckley, S. J. Bellamy (KCL), X. Zhang (SUSB), G. Dermody (KCL), and 

S. L. Hulbert (BNL) 

The absorption spectra of five biologically significant calcium salts were recorded 

in total electron yield (TEY) mode at the Ca L edge. These spectra, taken at 

beamline U13UA, are to be used to assess the feasibility of generating spatial maps 

with chemical state contrast from calcified tissue imaged in transmission on the 

scanning transmission x-ray microscope (STXM) at beamline XlA[l] . Drift in energy locations were corrected using CaFz standards. Quantification was attempted 

in a two-stage process. Firstly the pre- and post- continuum step ‘plateau’ regions 

were fitted to cross-sections for the salt (using nominal composition and tabulated 

elemental values) plus an area fraction of substrate. The fitting was repeated with 

the additional constraint of constancy of a calcium equivalent peak integral. At 

both stages, spectra showing signs of distortion were rejected. 

Fig. 1 shows the calcium equivalent spectra for one series of experimental con- ditions. The details show the NEXAFS minor peak structure which precedes the 

main peaks. It is this structure which shows the variation between salts which we 

hope to exploit for chemical state mapping in the STXM. 

[l] C. J. Buckley, S. J. Bellamy, X. Zhang, G. Dermody and S. L. Hulbert, Rev. 

Sci. Instrum. 66, 1322 (1995). 

Figure 1. Calcium salt absorption spectra (from total electron yield signal). 

* This research was supported by DOE grant no. DEFGD2-89ER 60858. 

c . -0 
I Thermal and Photochemical Deposition of Sulfur on GaAs(100) * I U13UA I 

S. Conrad, Q.-S. Xin, X.-Y. Zhu (Southern 111. Univ.) and D. R. Mullins (ORNL) 

The interaction of sulfur with GaAs(100) is of great interest due to its importance in surface passivation. We have investigated the thermal and photochemical 

deposition of S on GaAs(100) from HzS using soft x-ray photoelectron spectroscopy (SXPS). The deposition of S can be achieved by exposing GaAs(100) to H2S at 

substrate temperatures 2 550 K, a result of the irreversible dissociation of H2S on the surface. Both the rate and extent of sulfur deposition is enhanced by white 

light synchrotron radiation. More than twice as much S was deposited using eight 

cycles of dose/irradiate/anneal compared to the saturation S coverage obtainable 

by thermal decomposition alone. The photoassisted deposition showed no evidence 

of saturation. 

Heating of S covered GaAs 100) to 2 700 K results in a well ordered (2x1 surface 

temperature stabilized surface is characterized by two well defined states of S, both 

bonded to Ga atoms. One state can be attributed to surface gallium sulfide while the 

other to sub-surface S which replaces As atoms. This interpretation is supported 

by the observation that the As/Ga ratio, as determined by the 3p SXPS peak 

intensities, decreases linearly with increasing S coverage. 

, 

recdptruction, as evidenced 6 y low energy electron diffraction (LEED). d his high 

I Resolution test of U13UA 160°-included angle grating I Ul3UA I 

S. L. Hulbert (BNL) 

In addition to the 174'-included angle gratings (300, 600, and 1200 lines/mm) 

typical of now-"standard" Spherical Grating Monochromators (SGM), two 160'- 

included angle gratings (600 and 1200 lines/mm have been installed and com- missioned at beamline U13UA. These latter two "low-energy" gratings require two 

post-deflecting mirrors, at 12' downward-cieflecting and 5' upward-deflecting grazing angles of incidence, to make the diffracted beam coincident with that of the 

174'- included angle "high-energy" gratings. 

The photon energy range covered by the low-energy gratings is 20-150 eV. One 

of the best photon-energy resolution tests in this photon energy range is to measure 

the double-excitation Rydberg resonances of He below the N=2 threshold of Het, as shown for the SX700 monochromator at BESSY by Domke, et al. [Phys. Rev. 

Lett. 69, 1171 (1992 and, more recently, for a standard SGM at ALS by Kaindl, 

et al. [abstract for V J V XI, Tokyo, 19951. 

As a resolution test, this series was measured using the 600 line/mm low-energy 

grating at Ul3UA and a purpose-built gas cell filled with 25mTOrr He. As shown 

in Fig. 1, the (~p~2n-t) states are observable out to n=13, which corresponds to a resolving power of at least 5000. This resolution is quite good, considering that 

there are three resolution-determining optical elements in this branch of U13UA 

(an SGM designed specifically for this hoton energy range would use only a single 

resolution-determining optical element f 

-0.02 

-0.04 1 

64.9 55.0 65.1 6.2 65.3 65.4 H.5 6.6 

[rvl 

* Research supported by a State of Illinois HECA grant for the Advanced Radiation 

Source (xyz)i a Camilleand Hemy DreYfus New FaCUltY Award (xyz) mdbY the Division 

of Chemical Sciences, Office of Basic Energy Sciences, U. S. Department of Energy under 

contract DE-AC05-960R22464 with Lockheed Martin Energy Research Corp. (DRM). 

Figure 1. Autoionizing resonances of doubly excited Helium below the N=2 threshold (P2) of He+. The (sp,an+) states are Seen out to n=13, which corresponds to a resolving power 25000. 

?1 
,. 

.'.- , 

-. ... 

Adsorption and Reaction of Methanethiol on Ni Covered W(OO1) * 

U13UA Ratio of Double-to-Single Photoionization of Helium from Threshold to 700 eV * 

Jon C. Levin, G. Bradley Armen, and Ivan A. Sellin(U. Tennessee) 

Theoretical prediction of the energy dependence of the double ionization of helium 

by a single photon is a fundamental problem in atomic physics which requires solution of the Coulomb three-body problem. In ,the independent-particle framework, 

in which the photon can interact directly with only one electron, double ionization 

by a single photon can proceed only by electron-electron correlation. As a result, 

photoionization of helium has long been used as a testing ground for understanding 

correlation phenomena. 

Despite the importance of the problem, and the abundance of widely varying 

theoretical predictions at all energies, available data are definitive only for a few 

eV above the double-ionization threshold (79 eV), where the ratio of double-tosingle ionization of helium has been shown to be in good agreement with Wannier 

Theory. Nevertheless, available theories and measurements essentially span the 

space between the two theoretical curves shown in Fig. 2. It was the goal of our work on U13UA to obtain an accurate determination of the energy-dependent ratio 

of double-to-single photoionization of helium from threshold to 700 eV. 

Figure 1 illustrates a spectrum obtained at 200 eV. Shown are both charge states 

of helium along with a prompt signal due to Rayleigh (elastic) scattering of photons 

from the target gas. Care was taken to assure that low energy light from the 

monochromator or collimating slit assemblies was filtered from the beam. 

Our measured ratios have smaller statistical errors than previous results, and 

show a broad maximum at about 180 eV. Ratios reported here are typically 10% 

lower than earlier measurements. 

U13UA 

Chnnncl 

Figure 1. Time-of-flight spectrum of helium obtained with 200 eV photons. * Research supported by the Division of Chemical Sciences, Office of Basic Energy 

Sciences, U. S. Department of Energy under contract DE-AC05-960R22464 with Lockheed 

Martin Energy Research COT. 

Figure 2. Comparison of present results 

with two early theoretical predictions * Work supported by NSF 

c 

rn 
Adsorption Site and Orientation of S and CH3S on Ni(ll1) by 

Photoelectron Diffraction * 

D. R. Mullins (Oak Ridge National Lab) 

U13UA Adsorption Site and Orientation of S and CH3S on Ni(ll1) by 

Photoelectron Diffraction * 

D. R. Mullins (Oak Ridge National Lab) 

U13UA 

Methanethiol (CH3SH) adsorbs as methylthiolate (CH3S) on Ni(ll1) at 100 K. 

When the sample is heated to 250 K, some of the thiolate decomposes forming 

atomic S and some is transformed into a thiolate with a much lower S 2p binding 

energy. The difference between these two thiolates is not known for certain. Based on the relative binding energies, it was hypothesized that the CHsS formed at 100 

K adsorbed in a lower coordination binding site than the thiolate formed at 200 K. 

Angle resolved photoelectron diffraction experiments have been performed utilizing 

the S 2p photoemission from these two states in order to determine there adsorption 

sites and the orientation of the C-S bond. 

Atomic S is known to adsorb in the FCC 3-fold hollow site on Ni(ll1). The 

sample was mounted so that the Ni-S bond axis aligned along the emission direction as the sample was rotated. The first panel shows the relative S 2p intensity at 

different emission angles for an electron emitted with a kinetic energy of 200 eV. 

The enhanced emission near 40 deg. is the result of backscattering from the Ni 

surface atom. The absence of enhanced emission at 0 deg. indicates that S is 

adsorbed in the FCC hollow with no second layer Ni atom beneath it. The S 2p 

angular dependence from CH3S formed at 100 K is shown in the second panel. The 

pattern is qualitatively similar to the angular dependence from atomic S, indicating 

that the CHJS is adsorbed in the FCC hollow site and that the C-S bond is not 

oriented normal to the surface. The S 2p angular dependence for CHJS formed at 

250 K is shown in the third panel. This result suggests that this thiolate is not 

adsorbed in the FCC site. Results at higher photoelectron kinetic energies indicate 

that the enhanced emission at 0 deg. is due to forward scattering along the C-S 

bond which is oriented normal to the surface. 

~~~~~~~~ 

2 1.5 

11.0 **?, 

os -20 0 20 40 W 80.20 0 20 40 Bo 60.20 0 20 40 60 Bo 

Emission Angle (deg) 

Figure 1. 

* Research supported by the Division of Chemical Sciences, Office of Basic Energy 

Sciences, U. S. Department of Energy under contract DE-AC05-960R22464 with Lodcheed 

Martin Energy Research Corp. 

I The Coadsorption of S and Ni on W(O0l) * U13UA 

D. R. Mullins and S. H. Overbury (Oak Ridge National Lab) 

The coadsorption of S and Ni on W(OO1) was studied using S 2p photoemission. 

Figure 1 shows an annealing set for 0.5 ML of Ni deposited at 100 K on 0.5 ML 

of S on W(OO1). The bottom spectrum is from S on clean W(OO1). At 100 K two 

new S 2p states appear with S 2p3/, binding energies of 161.55 and 162.00. When 

the sample is annealed to 500 K, the 161.55 eV state disappears and the 162.00 eV 

state increases in intensity. We interpret the 161.55 eV state as interface SI residing 

either underneath or next to the adsorbed Ni. The 162.00 eV state results from S on top of the Ni film. When the sample is annealed to 1000 K , the signals from 

S on W(OO1) and S on the Ni film merge into a new, broader state with a S 2~912 

bindin energy of 162.45 eV. This new state is attributed to S adsorbed on a Ni / 

W(OOl7 surface alloy which is known to form near 750 K when the Ni coverage is 

less than 1 ML. 

Figure 2 shows S 2p spectra for various coverages of Ni deposited at 100 K on < 0.5ML of S on W(OO1) and then annealed to 1000 K. It can be seen that each 

coverage results in a distinct S 2p state. When the Ni coverage is 0.5 ML, the S 2p 

signal has a binding energy that is closest to the S 2p peak position on W(OO1). An 

unexpected result is that the S on 2 ML of Ni has a higher binding energy (closer to 

the position on W 001)) than S on 1 ML of Ni. At intermediate coverages, multiple 

of Ni and 2 ML of Ni. 

states are observe 6 reflecting S adsorbed on patches of clean W, Ni/W alloy, 1 ML 

100 105 184 183 102 181 ' 

Binding Energy (eV) 

Figure 1. 

IO 

* Research supported by the Division of 

Chemical Sciences, Office of Basic Energy 

Sciences, U. S. Department of Energy under 

contract DE-AC05-840R21400 with Lockheed Martin Energy Systems, hc. 

8 Nils/ W(OO1) -1000 K 

7- NI(001) 

7l 8- 

$5- 

2 PMLNI 

Y 

m 

5 4- 1MLNi 

2 

z 3- 

2 

5 0.5MLNI 7- 

NoNi 

OT#,,L,S 

167 166 165 184 163 162 181 160 

Blnding Energy (eV) 

Figure 2. 
? I Spin-polarized Fe LVV Auger spectra on- and off- La-resonance I Ul3UA I 

B. Sinkovid, E. Shekel (NYU), and S. L. Hulbert (BNL) 

We report the first on-La-resonant (2p312 --f 3d') spin-resolved Auger electron 

spectra (SPAES . By comparing the measured net spin polarization of Fe corevalence-valence ICVV) Auger electrons excited by on- and off-La-resonant photons 

with the calculated Fe valence band spin polarization, we address the question: to 

what extent are spin-dependent interactions, or exchange correlations, present in 

band-like ferromagnetic metals such as Fe. The main difference between on- and 

off-resonant CVV Auger processes is in the degree of spin polarization of the initial 

core hole, which for Fe is highly polarized on-resonance and nearly completely unpolarized off-resonance. Correlation between this core hole and the valence electrons 

can be measured via the spin polarization of the outgoing CVV Auger electron. 

However, if correlation effects are not significant for Fe, the spin polarization will 

be equal to the polarization of the valence electrons Pva=0.27. 

The principal results of our SPAES experiments on Fe, taken using the NYU 

spin-resolving electron spectrometer, are shown in Figs. 1 and 2. Although the 

shapes of all four measured spectra in Fig.1 (symbols) agree with the calculated 

spectra (lines),the degree of spin polarization on-resonance (P,,=0.37, Fig.l(a is 

significantly greater than PVB, whereas the off-resonance value (P,rr=O.20, gig. 

l(b)) is significantly lower than PVB. These findings are consistent with the triplet 

final-state Auger matrix element being significantly weaker than that of the singlet 

state (singlet/tripletz3/2). This, in turn, can be interpreted as being due to a Fermi hole, or a spin-spin electron correlation responsible for keeping equal spins 

further apart, effectively lowering the triplet Auger probability. 

We suggest that this is a general phenomenon, as depicted in Fig. 2: SPAES 

carries important information both on the spin polarization of the valence band and 

the relative strength of exchange correlation.In particular, SPAES demonstrates the 

importance of exchange correlation in itinerant 3d-metals such as Fe. 

w 

0 

and minority-spin 

3M46M46 Auaer elecFigure 

tron s ectra (hv=82OeV)-fro& a 30A 

Fe/AgfO01) film, and the convolution of 

majority-spin (solid line) and minorityspin (dashed line) broadened (1.5eV) Fe 

density-of-states (DOS) with total FeDOS. (b) as in (a) except using onresonant excitation (hv=707eV). The 

shaded region represents the direct Fe 

valence band photoemission. 

Figure 2. Calculated spin polarization of the Fe CVV Auger transition 

as a function of Auger matrix element 

amplitude (strength of electron-electron 

exchange correlation, or singlet/triplet 

probability) and of initial core-hole 

spin polarization. The measured 

electron-energy-integrated spin polarizations of FeL&!f.&l46 Auger spectra 

on-resonance (hv=707eV; e) and offresonance (hv=820eV;o) are shown. 

(Interferometry at X = 13nm 1 Ul3UB [ 

J.Bjorkholm, B.LaFontaine, A.MacDowell, Z.Tan, D.Tennant, O.Wood I1 AT&T 

Bell Laboratories 

It is considered a requirement to characterize the imaging optics used in Extreme 

Ultraviolet Lithography (EUVL) with the light that they image. Therefore there 

is a requirement to develop interferometry techniques that operate at 13nm wavelength. We have built an 'At Wavelength' interferometer on U13UB to develop 

such technology. We have carried out the initial measurements that demonstrate 

that this interferometer is able to characterize the wavefront phase to an accuracy 

of 0.02waves rms. at a wavelength of 13nm. This was achieved by analyzing the 

spherical wavefront generated by illuminating a pinhole (diameter = 2.5 micron). 

The light that passes through the pinhole undergoes diffraction and yields a characteristic Airy pattern on an area CCD detector placed after the pinhole. This 

spherical wavefront acts a source that can then be used to test whether the interferometry works. The interferometry technique used is shearing interferometry (1) 

where the wavefront is diffracted from a grating and the zero and first orders are 

allowed to interfere. In this way the wavefront acts as a reference to itself. 

The experimental setup consists of a grating placed about 4 mm beyond the 

pinhole and the transmitted light is collected by a CCD. Figure 1 shows the interference pattern formed on the CCD. The light is diffracted in the vertical plane 

and the image shows the overlap of zero, +l and -1 orders. The horizontal bars 

are the interference patterns. The mode of data collection is the phase shifting 

interferometric technique (2) whereby the grating is shifted a/4 of a period and an interferogram recorded for each grating position. We have developed the code 

that allows us to analyze these interferograms. By analyzing interferograms from 

orthogonal gratings and stitching the results together a 3D map of the phase of the 

wavefront can be generated. Figure 2 shows such a plot of the wavefront. It shows 

the wavefront phase where the spherical wavefront is cut by the grating positioned 

after the pinhole. The shape is expected to be a parabola (i.e. defocus - the 'focus' 

for a pinhole optic is at the pinhole) and the analysis code yields a departure from 

pure defocus behavior by 0.02 waves rms over the full surface. Such a sensitivity is 

adequate to characterize the wavefront of an EUVL camera. 

1. "Optical Shop Testing". Chapter 4. M.V.Mantravadi, Wiley Interscience Pub. 

(1992), D.Malacara ed). 

Interscience Pub. (1992), D.Malacara (ed) 

2. "Optical Shop I, esting". Chapter 14. J.E.Greivenkamp, J.H.Brunning, Wiley 

Figure 1. EUV Shearing Interferograms 

of a spherical wavefront for 5 different 

positions of the shearing grating. Figure 2. 3D map of the measured phase of the spherical wavefront. 
U15 Chemistry Induced by Atomic-Site Selective Excitation in the Condensed Phase 

S. Sambasivan, J. Glatthaar, J. Eckwert, S.L. Anderson, and D.M. Hanson Dept. 

of Chemistry, SUNY at Stony Brook 

By using monochromatic soft x-rays it is possible to excite or ionize core electrons 

in molecules selectively. The atomic site of the core hole and the electronic configuration of the core hole final state can be selected by tuning the photon energy to 

various bound state resonances or into the ionization continuum. 

The consequences of such excitation for various molecules (e.g. nitrous oxide, 

- acetone, benzaldehyde, cyanobenzene, cyanobenzaldehyde) in different cryogenic 

matrix environments are being elucidated. A deuterium matrix at 4.5 K is used 

to minimize ionization of the host material, and Fourier transform infrared spectroscopy is used to monitor the chemical reactions. 

For example, nitrous oxide deposited in a matrix at 4.5 K at a concentration 

of 0.5% is irradiated with soft x-rays (380 eV> below the nitrogen 1s-ionization 

threshold, at the nitrogen and oxygen 1s-ionization edges (405 and 535 eV), and in 

the nitrogen and oxygen 1s-ionization continua (425 and 560 eV). In a deuterium 

matrix the dominant reaction products formed at all photon energies are DzO, 

DOzS, and OD. In a neon matrix various nitrogen oxides (NO, NOz, NzOs, NzOz-, 

NOz, and NOzt) are formed with N202-, N203, and NO2 being formed only at the 

ionization edges. No photoproducts appear in the infrared spectra with irradiation 

at 380 eV, which is below the threshold for core electron excitation. This result 

indicates that the chemistry results from core electron excitation and not from 

valence ionization of either the guest or the matrix molecules. 

Measurements of quantum yield, the concentration dependence, and the effects 

of deposition and annealing conditions are being used to detemine the reaction 

mechanisms that produce these products. 

p 

w 

Figure 1. Difference Infrared Spectra of N20 in Deuterium, Neon and Argon ma- trices irradiated with Soft X-rays and Electron Beam, + 

ABSTRACTS 

X-Ray Beamlines 

Beamline X1A 

X-ray Absorption Near Edge Structure (XANES) of Poly(ethy1ene terephthalate) (PET) and 

Polyarylate (PAR) ............................................................................ H. Ade, A. P. Smith, V. Zhuang (NCSU), D.-J. Liu, J. Marty, A. Monisera, and 

J. Chung (Allied Signal) 

H. Ade, V. Zhuang, A. P. Smith (NCSU), and P. Schmitz (Ford Motor Co) 

Saia Bajt (Univ. of Chicago), Henry N. Chapman (SUNY, Stony Brook), George J. Flynn 

(SUNY, Plattsburgh), and Lindsay P. Keller (MVA Inc.) 

Phase-retrieval X-ray Microscopy via Wigner-distribution Deconvolution. ....................... Henry N. Chapman (SUNY, Stony Brook) 

Dark-Field X-ray Microscopy of Immuno-Gold-Labeled Cells. ................................... Henry N. Chapman, Chris Jacobsen, and Jenny Fu (SUNY, Stony Brook) 

Inner Shell Spectroscopy and Imaging of a Subbituminous Coal ................................. G.D.Cody, R.E.Botto (ANL), H.Ade (NCSU), S. Behal, M.Disko (Exxon) and S.Wirick 

(SUNY, SB) 

X-ray Absorption Near Edge Structure (XANES) of Polyethylene (PE) and Polypropylene (PP) 

Carbon Imaging and Carbon-XANES Measurements on an Interplanetary Dust Particle. ........ 

The Application of Soft X-Ray Microscopy to the In-Situ Analysis of Sporopollenin/Sporinite 

in a Rank Variable Suite of Organic Rich Sediments ............................................ 

Miscibility of Poly(ethy1ene terephthalate) (PET) and Polyarylate (PAR) in PET/PAR Polymer 

Blends. ........................................................................................ D.-J. Liu, S.-C. Lui (Allied Signal), V. Zhuang, H. Ade (NCSU), A. Monisera, J. Marty, 

and J. Chung (Allied Signal) 

Morphologies of Ternary Polymer Blends Studied with X-ray Microscopy ....................... D.-J. Liu, S.-C. Lui (Allied Signal), V. Zhuang, H. Ade (NCSU), A. Monisera, J. Marty, 

and J. Chung (Allied Signal) 

Development of a Cryo Scanning X-Ray Microscope. . :. ......................................... J. Maser, C. Jacobsen, A. Kalinovsky, J. Kirz, A. Osanna, S. Wang (SUNY at Stony Brook) 

Structured Latex Particles Characterized by Scanning Transmission X-Ray Microscopy .......... Gary Mitchell, Mike Cheatham, Yohannes Chonde, Joan Marshall (Dow Chemical), 

Harald Ade, and Vera Zhuang (NCSU) 

F. Polack (LURE), D. Joyeux (IOTA) 

G. D. Cody, R. E. Botto (ANL), H. Ade (NCSU), S. Wirick (SUNY, SB) 

Interferential differential phase contrast on X1A STXM ......................................... 

Semi-Quantitative Determination of the Lateral Orientation in Kevlar Fibers using X-ray Linear 

Dichroism Microscopy .......................................................................... 

Micro-chemical Characterization of Methylene Diphenyl Diisocyanate (MDI) based Polyurethane 

Foams using X-ray Microscopy ................................................................. 

XANES Spectroscopy of Polyurethane Model Polymers ......................................... 

A. P. Smith, H. Ade (NCSU), B. Hsiao and S. Subramoney (DuPont Inc.) 

A. P. Smith, H. Ade (NCSU) and E. Rightor (Dow Chemical) 

A. P. Smith, H. Ade (NCSU), and E. Rightor (Dow Chemical) 

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-33 

B-34 

B-1 
High Resolution Fresnel Zone Plates for Scanning X-ray Microscopy ............................ S. Spector, C. Jacobsen (SUNYSB), and D. Tennant (AT&T) 

B-34 

Beamline X1B 

Autoionization into the 1s-l Continuum Following Excitation of Doubly Excited Neutral 

States in CO and N2 ......................................................................... B-35 

B. Kempgens, H.M. Kijppe, A. Kivimaki, M. Neeb and A.M. Bradshaw (Fritz-Haber-Institut 

der Max-Planck) 

Deexcitaion Spectroscopy of RblCeo ........................................................... B.Kessler, L.Baumgarten, J.Liining, S.Cramm, W.Eberhardt (KFA), and J.E.Fischer (UPenn) 

Electronic Decay Spectra of Doubly Excited Neutral States in CO and Nz ...................... M. Neeb, A. Kivimkiki, B. Kempgens, H.M. Kijppe and A.M. Bradshaw (Fritz-Haber-Institut 

der Max-Planck) 

Beamline X2A 

Surface Critical Behavior of the betal-beta2 Phase Transition in V2H ........................ R. Paniago, P.C. Chow, H. Reichert, S.C. Moss (University of Houston), S. Schmid, T.H. 

Metzger, J. Peisl (University of Munich), K.S. Liang (Exon) 

Beamline X3A1 

The Synthesis of a Novel 2-Dimensional Antimony Sulfide, Using Synchrotron Imaging 

Plate Data [C4HlON]2[Sb8Sl3].0.15H20 and its Structure Solution ........................... K. Tan, Y. KO, J. B. Parise (SUNY, Stony Brook) and A. Darovsky (SUNY, Bufalo 

B-35 

B-36 

B-36 

B-37 

The Use of Imaging Plates for Accurate Electron Density Studies at Helium Temperatures ...... R. Bolotovsky, P. Coppens, A. Darovsky and V. Kezerashvili (Chemistry, SUNY, Buffalo, & 

BNL) 

The Structure of TMA-CuGS-2, (Cuo.44Geo.&32.23)4(Ge4S8)3.6(CH3)4N from Synchrotron/Imaging 

Plate Data. .................................................................................... B-38 

Synthesis and Structure of Novel Aurates: SrAu204 and BiqAu~Og. ............................ B-38 

Pair-density Function Analysis of PEOX/Si02 Composite Materials ............................ B-39 

B-39 

J. B. Parise, K. Tan, Y. KO (SUNY, Stony Brook), A. Darovsky (BNL) 

J.-H. Park, K. Tan, J. B. Parise (SUNY, Stony Brook), A. Darovsky (BNL) 

H. D. Rosenfeld, R. L. Harlow and I. A. David (DuPont) 

H. S. Sheu, C. C. Wang, C. R. Lee, Y. Wang(Chem., National Taiwan Univ.), A. Darovsky, R. 

Bolotovsky and P. Coppens(SUNY, Buffalo & BNL) 

Charge Density Studies Using High Energy Synchrotron Radiation at 20K ...................... 

A Novel Antimony Sulfide Templated by Dimethylammonium .................................. Kemin Tan, Youhghee Ko,Jaehyun Park and John. B. Parise (SUNY, SB), Alex Darovsky 

(BNL) 

Beamline X3A2 

Draw Induced Crazing in PET Fibers: Temperature Effect ................................... Paul Harney, Benjamin Chu, Alan Kennedy, Roger Leach ( SUNY, 

Stony Brook; DuPont Central Research & Development) 

Paul Harney, Benjamin Chu, Alan Kennedy, Roger Leach (SUNY at Stony Brook,; DuPont 

Central Research and Development ) 

A.D.Kennedy, B.S.Hsiao, R.A.Leach (DuPont Central Research), P.Harney, 

B.Chu (SUNY, Stony Brook) 

On-line WAXS of PET Fibers During Draw Induced Crazing ................................... 

WAXS Measurements of 6,6 Nylon Yarn Structure .............................................. 

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B-40 

B-41 

B-41 
Valence-specific Resonance Diffraction with Imaging Plates Applied to the Mixed-valence Enzyme 

Model Complex Mn'VL(/1-0)2(/1-MeC02)Mn''' (MeC02)2, L = 

1,4,7-trimethyl-1,4,7-triazacyclononane ......................................................... 

Self Assembly of Block Copolymer Poly(oxyethy1ene-oxypropylene-oxyethylene) L64 in 

V. Kezerashvili, A. Darovsky and P. Coppens (SUNY,Buffalo & BNL) 

o-xylene/water System ......................................................................... Li-Zhi Liu, Vinh-Bao Buu, Benjamin Chu (SUNY, Stony Brook) 

SAXS Study of the Miscible Blends of Semicrystalline Poly(viny1idenefluoride) and Semicrystalline 

Poly(1,CButylene Adipate) .................................................................... Li-Zhi Liu and Benjamin Chu, R. St. John Manley (SUNY, Stony Brook; McGill University) 

SAXS Studies of Surfactant . Cationic Gel Products ............................................ E. Sokolov, F. Yeh, B. Chu, S. Starodubtsev, A. Khokhlov (SUNY, Stony Brook; Moscow State 

University.) 

Morphological Changes During Secondary Crystallization and Subsequent Melting in Poly(ether 

ether ketone) as Studied by Real Time Small Angle X-Ray Scattering ........................... Ravi Verma (DuPont& Virginia Tech.), Herve Marand (Virginia Tech.) and Benjamin Hsiao 

(DuPont) 

Interaction of Polyelectrolyte Gels of Poly (Diallyldimethylammonium Chloride) with 

Surfactants .................................................................................... Fengji Yeh, and Eugene L. Sokolov, Benjamin Chu (SUNY, Stony Brook) 

Beamline X3B1 

Search for Structural Phase Transitions in Rb2.90c60 ......................................... G.M. Bendele, P.W. Stephens (SUNY, Stony Brook), and J.E. Fischer (Univ. Penn) 

G.M. Bendele, P.W. Stephens (SUNY, Stony Brook), D. Mihailovic, and P. Venturini 

(Univ. of Ljubljana) 

G.M. Bendele, P.W. Stephens (SUNY, Stony Brook), A.M. Rao, P.C. Eklund (Univ. of 

Kentucky, Lexington), and A. Moravsky (Russian Academy of Sciences) 

Powder Diffraction of Alkakalkaline-earth Fullerides ............................................ G.M. Bendele, P.W. Stephens (SUNY, Stony Brook), T. Yildirim (NIST), and J.E. Fischer 

(Univ. Penn) 

Detection Limit for Polymorphs in Drugs Using Powder Diffraction ............................. R. E. Dinnebier, P. W. Stephens (SUNY Stony Brook), S. Byrn (Purdue Univ.), V. Andronis 

and G. Zografi (Univ. Wisconsin, Madison) 

Structure of Sodium-para-hydroxy-benzoate by Powder Diffraction .............................. R. E. Dinnebier, P. W. Stephens (SUNY, Stony Brook), M. Pink, and J. Sieler 

(Univ. of Leipzig) 

R. E. Dinnebier, P. W. Stephens (SUNY, Stony Brook), M. Pink, and J. Sieler 

(Univ. of Leipzig) 

R.E. Dinnebier, P.W. Stephens (SUNY Stony Brook), M. Pink, J. Sieler (Univ. of Leipzig), 

and P. Norby (Chemistry, BNL) 

G. Faigel, G. Bortel, M. Tegze, G. Oszlanyi (Research Inst. for Solid State Physics, Budapest), 

L. Forro (EPF), and P.W. Stephens (SUNY, Stony Brook) 

R. L. Harlow, Z.-G. Li, N. Herron and E. M. McCarron (DuPont) 

TDAEC60: Low-temperature Structural Studies ............................................... 

Structure of C60 Polymerized at Low Pressure .................................................. 

Structures of C6H5OA (A = K, Rb, Cs) by Powder Diffraction ................................. 

Structures of C~HE;OK . 2 C6H5OH and C6H5OK . 3 CGH~OH by Powder Diffraction ........... 

Frustrated Phase Separation in the "Intermediate" FCC Phase of K1C60. ....................... 

Crystal Structure Analyses Using Ab Inito Powder Diffraction Techniques: The Failures ........ 

Problematic Structure Determination of a Small Organic Molecule via Ab Initio Powder Diffraction 

Techniques. .................................................................................... R. L. Harlow, Z. Li, W. J. Marshall, K.H. Gardner, N. Herron and P. A. Meenan (DuPont) 

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B-49 

B-50 

B-3 
The Structure of PrPdSb via Resonance Scattering ............................................. A. Mehta (Univ. of Nebraska), P. W. Stephens (SUNY Stony Brook), S. K. Malik (TIFR), and 

K. A. Gschneidner, Jr. (Ames Lab) 

Z. H. Ming, S. Huang, Y. L. So0 and Y. H. Kao, (SUNY, Buffalo), and T. Cams and 

K. L. Wang (UCLA) 

Z. H. Ming, Y. L. Soo, S. Huang and Y. H. Kao (SUNY, Buffalo), and K. Stair, G. Devane, 

and C. Choi-Feng (Amoco) 

G. Oszlanyi, G. Bortel, G. Faigel, M. Tegze (Research Institute for Solid State Physics), P.W. 

Stephens (SUNY, Stony Brook), and L. Forro (EPF) 

Y. L. Soo, Z. H. Ming, S. W. Huang and Y. H. Kao (SUNY, Buffalo), and R. N. Bhargava 

(Nanocrystals Technology) 

X-ray Scattering and Absorption Studies of (In,Mn)As Thin Films on GaAs .................... Y. L. Soo, Z. H. Ming, S. Huang and Y. H. Kao (SUNY, Buffalo), M. Tanaka (University 

of Tokyo), H. Munekata (Tokyo Institute of Technology), and L. L. Chang (Hong Kong 

University of Science and Technology) 

P. W. Stephens (SUNY, Stony Brook), P. C. Eklund, and A. M. Rao (Univ. of Kentucky) 

Peter Stephens (SUNY, Stony Brook) and Rani Johnson (East Hampton High School) 

Interface Morphology in Lattice-Mismatched (Si,Ge) Thin Films on Si .......................... 

Structural Ordering in InGaAs/GaAs Superlattices ............................................. 

Comparative Structural Study of AlCso (A=K, Rb, Cs) ........................................ 

Luminescence Yield and X-ray Absorption Spectra in Doped Semiconductor Nanocrystals ....... 

Structure of Photo-polymerized CEO ............................................................ 

The Microabsorption Correction in Quantitative Analysis. ...................................... 

Beamline X3B2 

Kinetic Roughening in Ag Homoepitaxy ...................................................... William C. Elliott (University of Missouri-Columbia), Paul F. Miceli (University of 

Missouri-Columbia), Teddy Tse (SUNY-Stony Brook), Peter W. Stephens (SUNY-Stony 

Brook) 

T. Tse and P.W. Stephens (SUNY, Stony Brook) 

T. Tse and P. W. Stephens (SUNY, Stony Brook) 

Domain Growth in the Submonolayer Epitaxial System Pb on Ni(001) .......................... 

Adsorption Sites of Pb on Ni (001) and Cu(OO1) vs. Temperature ............................... 

Beamline X4A 

Transcriptional Initiation: Structural Analysis of the TBP/TFIIA/TATA Complex. .......... Jim Geiger (Howard Hughes Medical Inst., Yale University MB&B) P. B. Sigler 

(H HMI Yale University MB&B) 

A. Zdanov, C. Schalk-Hihi, A. Gustchina, and A. Wlodawer (NCI-FCRDC) 

Crystal Structure of Human Interleukin-10 at 1.6A Resolution .................................. 

Beamline X6A 

Time-resolved Energy Dispersive XAS ......................................................... Determination of Transient Molecular Structure for Photoinduced Reaction Intermediates Using 

L. Chen, Argonne National Laboratory/Univ. of Chicago 

The Transient Redox Kinetics of Vanadium Phosphate: An in situ Dispersive XANES Study .... George Coulston, Richard Harlow (DuPont), Simon R. Bare (Dow), Harold Kung, Kari 

Birkeland, Greg Bethke (Northwestern), John Quintana, Joe Georgopoulos (DND-CAT), and 

Peter L. Lee (Argonne) 

K Absorption Edge Magnetic Circular X-Ray Dichroism of Fe-Ni Alloy ......................... K. J. Gofron, C.W. Kimball (NIU), P.Lee, G.Jennings, P. A. Montan0 (ANL) 

B-4 

B-50 

B-51 

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B-53 

B-54 

B-54 

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B-55 

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B-56 

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B-57 

B-58 
MCXD Studies of the Single Crystal of Nd2Fel4B (001) ........................................ K. J. Gofron, C. W. Kimball (NIU), P.L. Lee, P. A. Montano (ANL), P. Canfield, and M. J. 

Kramer (Ames Lab) 

Temperature Dependence of the MCXD at the Gd L3 edge ..................................... K. J. Gofron, C. W. Kimball (NIU), P. L. Lee, P. A. Montano, G. Jennings (ANL) 

MCXD Studies at Fe K Edge in Ordered and Disordered Fe3Pt Invar Alloy ..................... K. J. Gofron, C. W. Kimball (NIU), P. L. Lee (ANL), C. Yahnke (NIU), G. Jennings, and 

P. A. Montano (ANL) 

B-58 

B-59 

B-59 

Simultaneous Multi-wavelength Anomalous Diffraction (SMAD) : An Energy Dispersive 

Synchrotron Diffraction Method for Macromolecules ............................................ B-60 

Peter L. Lee (ANL) and Craig M. Ogata (HHMI) 

Beamline X6B 

Determination of Metal-Metal Interactions and Coordinations States of a Model Compound for 

Photosynthesis ................................................................................ B-60 

In-Situ X-ray Diffraction Study of Langmuir Blodgett Deposition .............................. B-61 

L. Chen, M. Wasielewski, W. Svec, K. Huang, P. Montano(ANL) 

M.K. Durbin, A. Malik, A.G. Richter, R.S. Ghaskadvi, and P. Dutta (Northwestern 

University), and K.G. Huang (Argonne National Lab) 

K. J. Gofron, C. W. Kimball (NIU), P. L. Lee (ANL), C. Yahnke(NIU), P. A. Montano, M. 

Engbretson (ANL) 

A. Malik, M.K.Durbin, A.G.Rkhter, D.J.Campbel1, C.A.Mirkin, P.Dutta (Northwestern Univ.) 

and P.Lee (ANL) 

Effect of the Cation on the Structure of Fatty Acid Salt Langmuir-Blodgett Films ............... A. Malik, M. K. Durbin, A. G. Richter P. Dutta (Northwestern University), P. Lee and 

K. Huang (Argonne National Laboratory) 

Incipient Stage Formation of Porous Silicon ..................................................... H. You, K. Huang, and S.S. Yoo, Z. Nagy (ANL) 

Magnetism of Ordered and Disordered Fe3Pt by MCXD ........................................ B-61 

X-ray Diffraction Studies of Non-sulphur Self Assembled Monolayers ............................ B-62 

B-62 

B-63 

Beamline X7A 

Structure of "BaTaNz.l?l" from a Combination of X-ray and Neutron Data .................. V. Balbarin, F. DiSalvo (Cornell), H. Yamane (Sendai) J. Parise (SUNY, StonyBrook) 

High Pressure and Low Temperature Study of the LTO to LTT Phase Transition in 

Lal.~75Bao.l25Cu04 ............................................................................ B-64 

B-63 

M.K. Crawford, R.L. Harlow, E.M. McCarron (DuPont), S.W. Tozer (NHFML), 

D.E. Cox (BNL) 

Study of Local Atomic Order in Pd-Ni-P Glasses Using Resonant X-ray Diffraction ............. W. Dmowski and T. Egami (Univ. Penn.), Y. He and R. Schwarz (Los Alamos) 

Structure of CeOz Overlayer Studied by Energy Dispersive X-ray Diffraction .................... W.Dmowski, S.Fu and T.Egami (Univ. of Penn) 

Interfacial Structure of Giant Magnetoresistance Fe-Cr Multilayers .............................. W.Dmowski, D.Louca, T.Egami (Univ.Penn), D.Kelly and 1.Schuller (UCSD) 

Cu+land Fe+3 Occupancy in Cu0.5Fe2.sO4 ..................................................... T. T. Eagen (Alfred Univ.), D.E. Cox (BNL), S. Dattaguru, and R.L. Snyder (Alfred Univ.) 

Phase Identification in Gas-atomized REzFe14B Alloys ......................................... L. Henderson Lewis (BNL), C. H. Sellers (INEL), V. Panchanathan (Magnequench) 

Crystal Structure of ZrzNiD5 ................................................................... C.J. Howard, M.M. Elcombe (ANSTO), S.J. Campbell (ADFA) and D.E. Cox (BNL) 

B-64 

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B-67 

B-5 
Structural Analysis of Lao.7Sro.3Mn03 Above and Below the Curie Temperature ................ Michael C. Martin, D. E. Cox, and G. Shirane (Physics, BNL), Y Endoh and K. Hirota 

(Tohoku University), Y. Moritomo and Y. Tokura (University of Tokyo & Joint Research 

Center for Atom Technology) 

Ab-initio Structure Solution from Power Data Using Resonant Scattering ....................... R. J. Papoular, D. E. Cox (BNL), and W. Prandl (Univ. Tubingen) 

The Symmetry of Garnets on the pyrope (Mg3AlzSi3012) . enstatite (MgSiO3) join. ............ J. B. Parise, Y. Wang (SUNY, Stony Brook), G. Gwanmesia (Delaware State, Dover), 

J. Zhang, R. C. Liebermann and D. J. Weidner (SUNY, Stony Brook) 

P.G. Radaelli (ILL), M. Marezio (CNRS& AT&T Bell Labs) and D.E. Cox (BNL) 

H. D. Rosenfeld and R. Barton, Jr. (DuPont) 

S. Teslic and T. Egami (Univ. of Penn.), S. Vakhrushev (Ioffe Inst.) 

Structural Studies of the Metal-insulator Compounds BaVS3 and Lal-,ChMnO3 .............. 

Polymer Fiber Morphology Assessment Using Real Space Analysis of X-ray Diffraction Data .... 

Study of atomic structure in PMN single crystal using resonant x-ray diffraction ................ 

Pair Distribution Function (PDF) Studies of the Impact of Processing Chemistry on Local 

Order in PZT Solid Solutions 

A. P. Wilkinson (Georgia Tech), S. Teslic, T. Egami (Univ. Penn.), Q. Zhu, 

and D.E. Cox (BNL) 

.................................................................. 

Structural and Electronic Properties of GaN Films Grown on Sapphire by Molecular Beam 

Epitaxy ........................................................................................ Q. Zhu (BNL), A. Botchkarev, W. Kim, 0. Aktas, A. Salvador, B. Sverdlov, H. Morkos 

(Univ. of Ill.,Urbana-Champaign), S. -C. Y. Tsen, and D. J. Smith (Arizona State Univ.) 

Polymer and Dimer Formation in Alkali-metal Intercalated c60 ................................. Q. Zhu, D. E. Cox, (BNL) and J. E. Fischer (Univ. of Penn.) 

Beamline X7B 

Calcareous Sponge Spicules: Presence of Amorphous and Crystalline Phases in the Same 

Element ....................................................................................... J.Aizenberg, L.Addadi, S.Weiner (Weizmann Institute of Science), J.Hanson, T.F.Koetzle 

(BNL) 

Biologically-induced Reduction in Symmetry at the Level of the Crystal Domain Shape ......... J. Aizenberg, L. Leiserowitz, S. Weiner, L. Addadi (Weizmann Institute of Science), 

J. Hanson, and T.F. Koetzle (BNL) 

Thermal Decomposition of Silvercarbonate Studied by Powder Diffraction Methods. ............. E. Krogh Andersen, I.G. Krogh Andersen (Univ. Odense), P. Norby, J.C. Hanson (BNL) 

A Synchrotron X-Ray Study of Piezoelectric Moduli, Ferroelectric Switching and Domain 

Reversal in CsTiOAsO4 and KTiOP04 under an Applied Electric Field ......................... Rindert Bolt, Joergen Albertsson and Goeran Svensson, (Inor.Chem., CTH), Kenny Stahl, 

(Inor. Chem. 2, Lund Univ.) and J. C. Hanson,(BNL) 

Development of Synchrotron Diffraction Methods for Structure Determination with Small Single 

Crystals ....................................................................................... R. W. Broach (UOP Res.), J. J. Pluth (Univ of Chicago), R. M. Kirchner 

(Manhattan College), J. C. Hanson (BNL), J. Phillips and J. Fait (Seimens Anal. Inst.) 

In-situ Powder Diffraction Studies of Zeolite Syntheses; Magnesium Substituted Alumino 

Phosphates. .................................................................................... A. Nmlund Christensen (Univ. Arhus), P. Norby (BNL) 

Time Resolved Dehydration Studies of the Layered Aluminophosphate 

d,l-Co(en)s A13P4016 xHzO .................................................................... 

Synthesis of Zeolite A from Thermally Activated Natural Kaolinites. ............................ M. J. Gray, A. P. Wilkinson (Georgia Tech), P. Norby and J. Hanson (BNL) 

Alex F. Gualtieri (Univ. of Modena), P. Norby and J. Hanson (BNL), and G. Artioli 

(Univ. of Milan) 

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B-72 

B-73 

B-73 

B-74 

B-74 

B-75 

B-75 
Rietveld Refinement of Synchrotron Data Collected in Transmission Geometry Using an 

Imaging Plate Detector: Application to Standard mZrO2 ...................................... Alex F. Gualtieri (Univ. of Modena), P. Norby, J. Hanson and J. Hriljac (BNL), and 

G. Artioli (Univ. of Milan) 

Jonathan Hanson (BNL), Arild Moen (Univ. Trondheim), David G. Nicholson (Univ. 

Trondheim), Kenny Stdhl (Univ. Lund) 

R. A. Holroyd, J. M. Preses, J. C. Hanson (BNL) 

C. C. Landry, G. D. Stucky (U.C., Santa Barbara), J. C. Hanson, and P. Norby (BNL) 

A Time-Resolved Thermal X-Ray Powder Diffraction Study on CoSAPO-34 .................... 

Track Effects in Hydrocarbon Liquids Exposed to X-rays ....................................... 

In-situ Studies of Phase Transitions in Silicate Mesostructures 

Structure a Volatile Calcium P-Diketonato Tetraethylene-Pentamine 

.................................. 

Chelate [Ca(thd)z (N~C~H~S)] .................................................................. 

[Mg(thd)~ (N~CGH~~)] .......................................................................... 

I. Mutikanen, T. Hannienen, M. Leskela (Univ. Helsinki) and J. Hanson (BNL) 

Structure of A Volatile Magnesium P-Diketonato N,N,N’,N’-tetramethylenethylediamine Chelate 

I. Mutikainen, T. Hatanpaa, M. Leskela (Univ. Helsinki), A. Gualieri (Univ. Modena) and J. 

Hanson (BNL) 

Hydrothermal Conversion of Zeolites; an In-situ Powder Diffraction Study. ...................... P. Norby, J.C. Hanson (BNL) 

Carboxylation 

P. Norby, 

Brook) 

of Alkali Phenolates; an In-situ Powder Diffraction Study. ........................ J.C. Hanson (BNL), M. Pink (Univ. Leipzig), R. Dinnebier, P. Stephens (SUNY, Stony 

Siemens Smart CCD Detector Applied to Diffraction with Synchrotron Radiation from X7B at 

NSLS .......................................................................................... 

The Adsorption of Hydrofluorocarbons and Hydrochlorofluorocarbons on Basic Molecular Sieves 

3. Phillips, J. Chambers, and J. Fait (Siemens Analytical Instruments) 

F. Poshni, C. P. Grey (SUNY, Stony Brook), A. F. Gualtieri, P. Norby, J. C. Hanson 

(BNL), and D. R. Corbin (DuPont CR&D) 

Beamline X8A 

Reflectance Calibrations of AXAF Witness Mirrors in the Ir M-edge Region ................. D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzzi, D.A. Schwartz (SAO), R.L. Blake 

(LANL) 

Optical constants from transmission and reflection measurements ............................... R.L. Blake(LANL), B.H. Harris, J.J. Fitch, D.E. Graessle, and D.A. Schwartz(SA0) 

Beamline X8C 

AXAF Synchrotron Calibrations of Ir-coated Witness Mirrors over 5-12 keV ................. D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzzi, D.A. Schwartz (SAO), 

R.L. Blake (LANL) 

The Use of Synchrotron Radiation in the Calibration of AXAF 5-12 keV ........................ D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzzi, D.A. Schwartz (SAO), R.L. Blake (LANL) 

Beamline X9A and X9B 

Manipulating Mesophase Behavior of Hydrated DHPE: an X-ray Diffraction Study of 

Temperature and Pressure Effects ............................................................. M. Caffrey, (Ohio State University) 

David S. Auld, Ke Zhang (Biostructures Institute), Marcello Montorzi, Kenneth H. Falchuk and 

Bert L. Vallee (Harvard Med. Sch.) 

XAFS Studies of the Zinc Storage Protein of Xenopus laevis Oocytes ........................... 

B-76 

B-76 

B-77 

B-77 

B-78 

B-78 

B-79 

B-79 

B-80 

B-80 

B-81 

B-81 

B-82 

B-82 

B-83 

B-83 

B-7 
Time-resolved X-ray Spectroscopy of Hemeproteins : Novel Methods of Data Acquisition and 

Analysis Applied to MbCO Relaxation Phenomena ............................................. 

An XAS Study on CO Adducts of [NiFe] Hydrogenases ......................................... 

B-84 

M.R. Chance, A. Xie, L.M. Miller, R.F. Fischetti, E.M. Scheuring, W.X. Huang, Y. Hai, M. 

Sullivan, B. Sclavi (Albert Einstein College of Medicine) 

Zhijie Guy Suranjan B. Choudhury, Christian B. Allan and Michael J. Maroney (Univ. Mass.) 

B-84 

Structural Studies of Discotic Liquid Crystals .................................................. P. A. Heiney, S. Ghosh, N.C. Maliszewskyj (Penn), and Philippe Henderson (Shell Research) 

EXAFS and XANES Studies of Nitrile Hydratases .............................................. Mark J. Nelson, John G. Cummings (DuPont), Lewellyn Durney, Daihung Duong, and 

Robert C. Scarrow (Haverford College) 

Metal Cluster Active Sites in Proteins .......................................................... Lawrence Que, Jr., Gaofeng Pan, Lijin Shu, and Xuedong Wang (University of Minnesota) 

EXAFS of Azotobacter vinelandii Nitrogenase Iron Protein: MgATP does not Disrupt the [4Fe-4S] 

B-85 

B-85 

B-86 

Cluster ........................................................................................ B-86 

R. C. Scarrow, N. Taufen (Haverford College), L. C. Seefeldt (NSF), and W. N. Lanzilotta 

(Utah State University) 

Structure-function of Cobalamin Dependent Enzymesf X-ray Absorption Studies of Methionine 

Synthase From E. Coli ......................................................................... B-87 

E. Scheuring (Albert Einstein College of Medicine), S. Huang (Univ. Michigan), R. G. Matthews 

(Univ. Michigan), and M. R. Chance (Albert Einsten College of Medicine) 

X-ray Absorption Spectroscopy Comparison of the Active Site Structures of Phanerochaete 

Chrysosporium Lignin Peroxidase Isoenzymes H2, H3, H4, H5, H8, and H10 .................... R. Sinclair, B. Copeland, I. Yamazaki, and L. Powers(Nationa1 Center for the Design of 

Molecular Function, Utah State University) 

Timothy L. Stemmler and James E. Penner-Hahn (The University of Michigan) 

T.Stemmler, J-Penner-Hahn (Univ Michigan), D.Ash and T.Sossong (Temple Univ) 

D.Tierney, J.Penner-Hahn (Univ of Michigan), and F. Yamakura (Juntendo Univ) 

Structural Characterization of the Effects of Halide Inhibition On Mn Catalase ................. 

XAS of Rat Liver Arginase. Characterization of the Mnz Core During Catalase Turnover ....... 

XAS of Superoxide Dismutase. Use of a Sagitally Focused Beam to Avoid Photoreduction ...... 

B-87 

B-88 

B-88 

B-89 

Structure of Binary and Ternary Complexes of Zinc and Cobalt Carboxypeptidase A as 

Determined by XAFS .......................................................................... Ke Zhang (Biostructures Institute) and David S. Auld (Harvard Med. Sch.) 

Beamline XlOA 

Phase Behavior of Liquid Crystals in Silica Aerogels .......................................... 

Chain Length Dependence of the Cn/Au(lll) Tilt Structure .................................... Noel A. Clark, A.G. Rappaport, T. Bellini, and B.N. Thomas (University of Colorado) 

P. Fenter, A. Eberhardt, K. S. Liang and P. Eisenberger (Princeton Univ.) 

Beamliiie XlOB 

Growth of Self-Assembled Monolayers: Decanethiol/Au( 111) .................................. A. Eberhardt, P. Fenter, B.T.Y. Leung, and P. Eisenberger (Princeton Univ.) 

Structure and Evolution in an Organic Thin Film: PTCDA/Au(lll) ........................... P. Fenter, L. Zhou, P. E. Burrows, S. R. Forrest and P. Eisenberger (Princeton Univ) 

Structure of w-Substituted Self-Assembled Monolayers .......................................... T. Y. B. Leung, A. Eberhardt, P. Fenter, P. Eisenberger, and G. Scoles (Princeton Univ) 

Beamline XlOC 

Fe and Mo K-edge EXAFS of CO-inhibited A.v. Nitrogenase ................................ B. J. R. Weiss, S. P. Cramer (U. C., Davis), R. Tittsworth, and B. J. Hales (Lousiana 

State Univ.) 

B-8 

B-89 

B-90 

B-90 

B-91 

B-91 

B-92 

B-92 
Beamline XllA 

Lead Speciation of a Mixed Soil Component System Using EXAFS .......................... B-93 

B-93 

T.E. Alcacio, G.M. Lamble, A. Scheidegger and D.L. Sparks (Univ. of Delaware, and BNL 

Chromium Speciation in Hazardous, Cement-based Waste Forms ............................... S. Bajt (CARS, Univ. of Chicago), J. F. Lee (Synchrotron Radiation Research Center), 

S. B. 

Clark (SREL, Univ. of Georgia), G. M. Lamble (BNL), C. A. Langton, L. Oji (Westinghouse, 

Savannah River Co.) 

W.R. Berti (Du Pont), G.M. Lamble (BNL), S.D. Cuningham, and J.W. Huang (Du Pont) 

D.L. Brewe (Univ. of Washington), S.M. Heald (Pacific Northwest National Lab), B. Barg, F.C. 

Brown, K.H. Kim, and E.A. Stern (Univ. of Washington) 

Local Structural Studies of Ti-Zr Alloy Silicide Thin Films on Si ................................ Yuan Dao, Robert J. Nemanich, and Dale E. Sayers (North Carolina State University) 

An XAFS Study of Structural Fe in Thermally Activated Natural Kaolinites. ................... Monica Endregard (Univ. of Trondheim), and Alex F. Gualtieri (Univ. of Modena) 

XAS Studies of Highly Nonplanar Cobalt(II1) Porphyrin Complexes ............................ M. Endregard (Univ. of Trondheim), G.M. Lamble (BNL), 

C.J. Medforth (U.C., Davis), C. Muzzi (U.C., Davis), D.G. Nicholson (Univ. of Trondheim), 

K. Shea (U.C., Davis), K.M. Smith (U.C., Davis) 

XAFS and Developing Plants for Phytoremediation ............................................. 

Progress in Fabricating Capillary Fibers for X-ray Concentrators ............................... 

B-94 

B-94 

B-95 

B-95 

B-96 

CVD Growth of 111-V Quantum Wires and Dots in Microporous Hosts; Indium K-edge 

XAFS of the Local Coordination of the 111-V Semiconductor Clusters ........................... Wendy Flavell, Heather Yates and Jonathan Agger (UMIST), David Nicholson, Arild Moens 

(Univ. of Trondheim), and Geraldine Lamble, Larry Fareria (BNL) 

B-96 

Solution of the Structure of Disordered Mixed Salts ............................................ A.Frenke1 and E.A.Stern (Univ. of Wash.), A.Vorone1 (Tel-Aviv Univ.), S.Heald (PNL) 

Nature of the Sr Induced Structural Phase Transition in Laz-,Sr,CuO4 ........................ D.Haske1 and E.A.Stern (University of Washington) 

XAFS Studies of MnSe/ZnTe Superlattices ..................................................... A. J. Kropf, B. A. Bunker, J. K. Furdyna, Q. Lu (Notre Dame), and K. M. Kemner (NRL) 

EXAFS Studies on Cu(I1) Ions Exchanged in H-SAPO-5 and CoSAPO-5 and -34 Molecular 

Sieves ......................................................................................... 

Geraldine M. Lamble (BNL), Arild Moen (Univ. Trondheim) and David G. Nicholson (BNL) 

Geraldine M. Lamble (BNL) and Richard J. Reeder (SUNY, Stony Brook) 

Q. Lu, B. A. Bunker, A. J. Kropf, S. W. Short, S. H. Xin, J. K. Furdyna (Notre Dame) 

X-ray Study of Atomic Correlations in ZnCdSeTe Epitaxial Thin Films ........................ Q. Lu, B. A. Bunker, H. Luo, A. J. Kropf, K. M. Kemner, J. K. Furdyna 

XANES as a Local Structural Probe 

B. Ravel and E.A. Stern (Univ. of Wash.) 

Mechanism of Se042- Substitution in Calcite: an EXAFS Study .............................. R. J. Reeder (SUNY), G. M. Lamble (BNL), J-F. Lee (SRRC), and W. J. Staudt (SUNY) 

Investigation of Ni Sorption on Pyrophyllite: An X-ray Absorption Fine Structure (XAFS) 

Spectroscopy Study ........................................................................... 

Formation of the Ferritin Iron Mineral Occurs in Plastids ...................................... 

XAFS Study of Zn2+ Incorporation into Calcite (CaC03) ...................................... 

XAFS Investigation of Thermal Structural Disorder at GaSb/AlSb Superlattice Interfaces ....... 

.......................................................... 

A. M. Scheidegger, D. L. Sparks (Univ. of Delaware), and G. M. Lamble (BNL) 

G.S.Waldo, E.Wright, Z.H.Whang, J.F.Briat, E.C.Thei1, and D.E.Sayers (NCSU) 

B-97 

B-97 

B-98 

B-98 

B-99 

B-99 

B-100 

B-100 

B-101 

B-101 

B-102 

B-9 
Beamline X12B 

Large Strain Deformation Study of an Elastomeric Single-Crystal Triblock Copolymer Using Synchrotron SAXS ........................................................................... B-102 

C. C. Honeker, B. L. Carvalho, E. L. Thomas (MIT) and M. Capel (BNL) 

Sidney Lees (Forsyth Dental Center), and Malcolm Capel (BNL) 

Sharon X. Lu, Peggy Cebe (Tufts University) and Malcolm Capel (Biology, BNL) 

Diffraction Spacing Measurements of Collagen in Turkey Leg Tendon and Rat Tail Tendon ..... B-103 

B-103 

B-104 

Structure of Semicrystalline Polyimides Using Real-time SAXS ................................ 

Low-angle X-ray Diffraction Studies of Type I1 Collagen in Bovine Articular Cartilage ......... M. Volpi (Univ. Ct.), D.W. Chester (Univ. Ct.), J.-H. Zhang (Univ. Ct.), M.S. Capel (BNL), 

E.P. Katz (Univ. Ct.) 

Dr. Dale Wigley, (Laboratory of Molecular Biophysics, University of Oxford) 

Structure of DNA Ligase ...................................................................... B-104 

Beainline X12C 

Mimicks Melanoma Associated Antigen ...................................................... Crystallographic Analysis of an Fab Fragment of Anti-Idiotypic Antibody MK2-23 that 

B-105 

Nenad Ban, John Day, Alexander McPherson (UCR), Xinhui Wang and Soldano Ferrone 

(NYMC) 

Report on Data Collected from TMV Protein Crystals at NSLS Beamline X12C, April 1-10, 1995. .............................................................................. B-105 

The Structure of Turnip Yellow Mosaic Virus (TYMV) ........................................ 

Beamline X12C, June 27-30, 1995 ......................................................... z.'. 

The P-state Structure of the Profi1in:P-Actin Complex at 2.65 AResolution ............ L.. ..... 

Balaji Bhyravbhatla and Donald L. D. Caspar (FSU) 

Mary A. Canady, Steven B. Larson, and Alexander McPherson, (U.C., Riverside) 

B-106 

Brief Report on Data Collected from Liquid Crystalline Tobacco Mosaic Virus Specimens at NSLS 

B-106 

B-107 

Arunava Chattejee, Donald L. D. Caspar (FSU), and Dieter Schneider (BNL) /. 

J.K. Chik (Princeton Univ.), U. Lindberg (Univ. of Stockholm), R.M. Sweet (BNL), and 

C.E. Schutt (Princeton Univ.) 

Crystal and Molecular Structure of the Human Adenovirus Maturation Protease with its 

J. Ding ( Physics, SUNY,Stony Brook), W.J. McGrath, R.M. Sweet, and W.F. 

Mangel (Biology, BNL) 

11 Amino-acid Cofactor ....................................................................... B-107 

X-ray Crystal Structure of the Hydroxylase Component of Methane Monooxygenase from 

MethyZosinw t~ichosporium OB3b. ............................................................ B-108 

High Resolution Crystal Structure of 5' Nuclease Domain from Taq Polymerase ................ 

Natesan Elango, R. Radhakrishnan, Wayne A. Froland, Cathleen A. Earhart, 

John D. Lipscomb and Douglas H. Ohlendorf (Univ. of Minnesota) 

So0 Hyun Eom, Jimin Wang, and Thomas A. Steitz (Yale) 

B-108 

Crystal Structure Taq Polymerase with a DNA Duplex Product Bound to the Polymerase Active 

Site .......................................................................................... B-109 

Structure of Allosteric Threonine Deaminase from E. Coli ..................................... B-109 

Structure Determination of Transaldolase from E.coli .......................................... B-110 

Structure Studies of Neurotrophin-3 ........................................................... B-110 

Crystal Structure of Thermus Aquaticus DNA Polymerase ..................................... B-111 

So0 Hyun Eom, Jimin Wang, and Thomas A. Steitz (Yale) 

Gilliland, G. and Eisenstein, E. (CARB) 

J.Jia, W.Huang, Y.Lindqvist, G.Schneider (Karolinska Institute) 

Kelly, J.A. (UCLA), Singer, B. (Amgen), and Yeates, T.O. (UCLA) 

Youngsoo Kim (Yale/Yeungnam Univ.), So0 Hyun Eom (Yale), Jimin Wang (Yale), DaeSi1 Lee (Korea Research Institute of Bioscience and Biotechnology), Se Won Suh (Seoul 

National Univ.), and Thomas A. Steitz (Yale) 

B-10 
Crystal Structure of Fe(II1)-Zn(I1) Purple Acid Phosphatase with Phosphate Bound to the Active 

Site .......................................................................................... 

Crystal Structute Determination of L-aspartate-P-semialdehyde dehydrogenase (ASADH, E.C. 

T. Klabunde, N. Straeter, R. Froehlich, H. Witzel, B. Krebs (Univ. of Muenster) 

1.2.1.11) ...................................................................................... Kryger, G., Petsko, G.A. and Ringe D. (Brandeis Univ.) 

Crystal Structure of the A Domain from the a subunit of Integrin CR3 (CDllb/CD18) ........ Jie-Oh Lee, Robert Liddington (DFCI, HMS) 

Two conformations of the integrin A-domain (I-domain): a pathway for activation? ............ Jie-Oh Lee, Robert Liddington (DFCI, HMS) 

Crystal Structure of a Lyme-disease Antigen in Complex with an Antibody .................... Hong Li and Catherine L. Lawson (BNL) 

Structural Studies of Stearoyl-acyl Carrier Protein Desaturase from Castor Seed ............... Y.Lindqvist, W.Huang, G.Schneider (Karolinska Institute), and JShanklin (BNL) 

Viral Protein VP16 ........................................................................... Y.Liu, C. Huang, W. Herr, and X. Cheng (Cold Spring Harbor Laboratory) 

DNA Modification by HhaI Methyltransferase ................................................. M. O’Gara (Cold Spring Harbor Lab.), R.J. Roberts (NEB), X. Cheng (Cold Spring Harbor 

Lab.) 

Shake-and-Bake solution of CY^ at 0.92A resolution ............................................. G. PrivC (Univ. of Toronto/OCI) and D. Eisenberg (UCLA) 

Crystallographic Studies of Adenylosuccinate Lyase from B. subtilis ........................... Matthew Redinbo, Todd 0. Yeates; Univ. of California, Los Angeles 

High-Resolution X-Ray Diffraction Data of Gene V Protein of bacteriophage fl. ............... Matthew M. Skinner and Thomas C. Terwilliger (Los Alamos National Laboratory) 

Structure of the Actin:Profilin:Rhodamine-phalloidin Complex ................................. N. Vogelaar (Princeton Univ.), U. Lindberg (Stockholm Univ.), R.M. Sweet (BNL), and 

C.E. Schutt (Princeton Univ.) 

Crystal Structure of the DNA Polymerase from Phage RB69, an CY Family and Replication 

Polymerase. .................................................................................. Jimin Wang (Yale), A. K. M. Sattar (Yale), Jim Karam (Tulane), W. H. Konigsberg (Yale) 

and Thomas A. Steitz (Yale) 

Casein Kinase I ............................................................................... R. Xu, G. Carmel, J. Kuret, and X. Cheng (Cold Spring Harbor Laboratory) 

Report on Data Collected from Insulin and Osteogenic Protein (OP-1) Crystals at NSLS Beamline 

X12C, April 1-10 and June 27-30, 1995 ........................................................ Bin Yu and Donald L. D. Caspar (FSU) 

Beamline X14A 

X-ray Diffraction Study of Tilted Phases of Langmuir Monolayers 

M.K. Durbin, A. Malik, A.G. Richter, R. Ghaskadvi, and P. Dutta (Northwestern 

University), and Thomas G6g (Oak Ridge National Lab) 

T. Gog (ORNL), P.M. Len, C.S. Fadley (UC, Davis), D. Bahr, C. Sanchez-Hanke, 

G. Materlik (HASYLAB) 

T. Gog (ORNL,HASYLAB), P.M. Len, C.S. Fadley (UC, Davis), D. Bahr, C. Sanchez-Hanke, 

G. Materlik (HASYLAB) 

T. Gog (ORNL), R.H. Menk, F. Arfelli (BNL), P.M. Len, C.S. Fadley (UC, Davis) 

.......................... 

Atomic Resolution Imaging with Multi-Energy X-ray Holography (MEXH) .................... 

X-ray Fluoresence Holography: Imaging the Atomic Environment in Hematite (Fe203) ........ 

Multi-Energy X-ray Holography: Images of Ge( 100) ........................................... 

B-111 

B-112 

B-112 

B-113 

B-113 

B-114 

B-114 

B-115 

B-115 

B-116 

B-116 

B-117 

B-117 

B-118 

B-118 

B-119 

B-119 

B-120 

B-120 

B-11 
Study of Surface Active Poly(pyrro1es) using Synchrotron X-ray Diffraction .................... T. Herod, G.Weekaseekra, T. Servay, R.S. Duran (University of Florida/ ONR/ Micron 

Semiconductor, Inc.), M. Durbin, A. Malik, and P. Dutta (Northwestern University) 

Inelastic X-Ray Measurements of the Local-Field Factor for a Simple Metal .................... B. C. Larson (ORNL) 

X-Ray Measurement of the Local-Field Factor for Aluminum .................................. B. C. Larson (ORNL), J. Z. Tischler (ORNL), E. D. Isaacs (AT&T Bell Labs), P. Zschack 

(ORNL), A. Fleszar (UniversitZt Wiirzburg), and A. G. Eguiluz (University of Tennessee and 

ORNL) 

E.D. Specht, A. Goyal, D.M. Kroeger (ORNL), J.A. DeLuca, J.E. Tkaczyk, and 

J.A. Sutliff (GE) 

Q.J. Wang, M. Eisner, P.R. Crippa, S.C. Moss (University of Houston) 

P. Zschack, T. Gogg (ORSL/BNL) L. Zecca (1.T.B.A.-CNR) 

Control of the Colony Microstructure of High T, Superconductors ............................. 

X-ray Diffraction of Human Brain Neuromelanin and Synthetic Neuromelanin ................. 

Beamline X15A 

X-ray Standing Wave Measurements of a Metal/Polymer Interface ........................... M.J. Bedzyk (ANL and Northwestern Univ.), B. DeKoven (Dow Chemical), P.F. Lyman 

(Northwestern Univ.), and M. Radler (Dow Chemical) 

The Use of X-ray Standing Waves and Evanescent-Wave Emission to Study Buried Strained-Layer 

Heterostructures .............................................................................. T.-L. Lee (Northwestern Univ.), Y. Qian (Northwestern 

Univ. and ANL), P.F. Lyman (Northwestern Univ.), J.C. Woicik, J.G. Pellegrino (NIST) and 

M.J. Bedzyk (Northwestern Univ. and ANL) 

Surface Structure of Submonolayer Phases of Sn/Si(OOl) ....................................... Paul F. Lyman (Northwestern Univ.) and Michael J. Bedzyk (Northwestern Univ. and ANL) 

Surfactant-Mediated Epitaxy of Metastable SnGe Alloys ....................................... Paul F. Lyman (Northwestern Univ.) and Michael J. Bedzyk (Northwestern Univ. and ANL) 

Structure and Ad-Atom Thermal Vibrational Amplitude for the Ga/Si(001) Surface ........... Yonglin Qian and Michael J. Bedzyk (ANL and Northwestern Univ.) 

An X-ray Standing Wave Study of Surface Kinetics: Bismuth Adsorption on Si(OO1) ........... Y. Qian (ANL and Northwestern Univ.), P.F. Lyman, T.-L. Lee (Northwestern Univ.) and 

M.J. Bedzyk (ANL and Northwestern Univ.) 

J.C. Woicik (NIST), P.F. Lyman (Northwestern), and M.J. Bedzyk (Northwestern and ANL) 

Surfactant-assisted Growth of Ge on Si(ll1) ................................................... 

Beamline X15B 

Quantifying Zn Doping in InGaAsP/InP Laser Structures ................................... L. Niu, R. F. Karlicek, 

and P. H. Citrin (AT&T Bell Labs) 

L. Niu, A. R. Kortan, and P. H. Citrin (AT&T Bell Labs) 

L. Niu, L. F. Schneemeyer, T. D. Harris, and P. H. Citrin (AT&T Bell Labs) 

X-ray Absorption from Pb-modified Fluoride Glasses .......................................... 

Structural Characterization of Cr4+-YAG Crystals Lasing at 1.5 pm ........................... 

Size and Composition of Luminescent Oxidized Si Nanocrystals ................................ 

Cation Charge State and Local Structure in the Rare-earth Fulleride Yb2.75Cco ................ S. Schuppler, L. E. Brus, and P. H. Citrin (AT&T Bell Labs) 

S. Schuppler (AT&T Bell Labs), E. Ozdas (Hacettepe Univ.), K. B. Lyons, A. R. Kortan, and 

P. H. Citrin (AT&T Bell Labs) 

S. Schuder. L. N. Pfeiffer. K. W. West. and P. H. Citrin (AT&T Bell Labs) 

Identifying Point Defects in Si-doped GaAs Using NEXAFS and EXAFS ...................... 

B-12 

B-121 

B-121 

B-122 

B-122 

B-123 

B-123 

B-124 

B-124 

B-125 

B-125 

B-126 

B-126 

B-127 

B-127 

B-128 

B-128 

B-129 

B-129 
Beamline Xl6A 

Diffraction Study of an Etched InP Grating ................................................. K.Evans-Lutterodt (AT&T) and P. Imperatori (ICMAT-CNR) 

Structural Study of the ZnSe/GaAs Interface .................................................. P. Imperatori (ICMAT-CNR), K. Evans-Lutterodt (AT&T Bell Labs) and R. Felici 

(ISM-CNR) 

Chinkyo Kim, D.A. Walko, and I.K. Robinson (University of Illinois, Urbana-Champaign) 

Sb/Si(lll)-(,/3x,/3)R30° Structure Determination ............................................ 

Growth of Cu Islands on Cu(ll0) ............................................................. D.A. Walko, K.L. Whiteaker, and I.K. Robinson (University of Illinois, Urbana) 

Beamline X16C 

Development of Local Structure in Sol-gel Derived Lead Zirconate Titanate Thin Layers .... D.L. Adler, S.S. Sengupta and D.A. Payne (Univ. of Illinois, Urbana) 

Superstructure Peaks in Lead Magnesium Niobate (PMN) ..................................... D. Fanning, D. Adler, and I. Robinson (Univ. of Illinois) 

Beamline X17B1 

Equation of State on MgA1204 Spinel ....................................................... 

In-situ Diffraction Study of the Cation Distribution in the Olivine Solid Solution of NizSiO4 

G. L. Chen, J. I. Ando, Y. B. Wang, and D. J. Weidner (CHiPR, USB) 

and MgzSi04 at High Pressure ................................................................ 

Effect of Pressure on Cation Distributions in Nickel Aluminate Spinel (NiA1204) ............... 

Quantitative X-ray Diffraction with an Imaging Plate at High Pressure and Temperature ...... 

J. H. Chen, R. Li, J. B. Parise, D. J. Weidner, Y. B. Wang, M. T. Vaughan, P. J. Schields 

(CHiPR, USB) and J. Kung (Australian National University) 

J. H. Chen, J. B. Parise, D. 3. Weidner, R. Li, Y. B. Wang and M. T. Vaughan 

(SUNY, Stony Brook) 

J. H. Chen, D. 3. Weidner, M. T. Vaughan, R. Li, J. B. Parise, and Y. B. Wang 

(Center for High Piessure Research, SUNY, Stony Brook) 

AgI/AgzSe04: A Glassy and Crystalline Fast Ion Conductor. Determination whether AgI 

Containing Glasses Have a Biphasic Structure ................................................. C. Cramer, D.L. Price, M.-L. Saboungi (ANL), and S.W. Martin (Iowa State University) 

X-ray Microbeam Pseudotherapy Vs. Therapy Using Two Cross-fired Arrays Through Normal 

Vs. Tumor-bearing Rat Brains ................................................................ F.A. Dilmanian, D.N. Slatkin, X.Y. Wu (BNL); J.-0. Gebbers (Cantonal Hospital), J.A. Laissue 

(University of Bern), and P. Spanne (ESRF) 

B-130 

B-130 

Simultaneous Resistivity and In-situ X-ray Determination of Phase Transitions in Bismuth in a 

Multi Anvil Apparatus ........................................................................ B-136 

L. M. Flesch, J. E. Urish, G. D. Gwanmesia, and R. C. Liebermann (ChiPR, SUNY, Stony 

Brook) 

In situ High-pressure X-ray Diffraction Study of FeSi .......................................... F. Guyot (IPGP), J. Zhang (CHiPR, SUNY, Stony Brook), I. Martinez (ENS) 

Equation of State of Stishovite ................................................................ J. Liu, G. Chen, and R. C. Liebermann (CHiPR & SUNY, Stony Brook) 

P. J. Schields (CHiPR, SUNY, Stony Brook), K. Bose (CHiPR, Princeton), Y. B. Wang, 

and D. J. Weidner (CHiPR, SUNY, Stony Brook) 

B-136 

B-137 

Characterizing the Unit-cell Volume of Talc as a Function of Pressure and Temperature ........ B-137 

Exploring the Stress-Induced Transformation of FCC Tic to the 8H HCP Polytype Using High 

Pressure and High Temperature ............................................................... B-138 

P. J. Schields (CHiPR, SUNY, Stony Brook) 

B-13 

B-131 

B-131 

B-132 

B-132 

B-133 

B-133 

B-134 

B-134 

B-135 

B-135 
Equation of State of Ca(Ti,Si)03 Perovskite ................................................... Y. Sinelnikov, J. Kung, and Y. B. Wang (ChiPR & SUNY, Stony Brook) 

Thermal Equations of State of Garnets Along the Pyrope-Majorite Join ....................... Y. B. Wang, D. J. Weidner, J. Z. Zhang, I. Martinez, Y. J. Wu, G. L. Chen, 

Y. Sinelnikov, M. T. Vaughan, R. C. Liebermann, (CHiPR, SUNY, Stony Brook) and 

G. D. Gwanmesia (Delaware SU) 

D. J. Weidner, J. H. Chen and Y. B. Wang (CHiPR, SUNY, Stony Brook) 

Studying Rheology Under Mantle Pressure and Temperature Conditions ....................... D. J. Weidner, Y. B. Wang, G. L. Chen, and J. I. Ando (CHiPR, SUNY, Stony Brook) 

D. J. Weidner, Y. B. Wang, M. T. Vaughan, C. C. Koleda (CHiPR & SUNY, Stony Brook) 

and I. C. Getting (ChiPR & Univ. Colorado, Boulder) 

The Time-resolved X-ray Strength Study of Two Garnet Powder Samples ...................... Y. Wu, Y. Wang, J. Ando, D. J. Weidner, and M. T. Vaughan (CHiPR, SUNY, Stony Brook) 

In situ X-ray Diffraction Studies of Iron and Iron Silicide at High Pressure and Temperature . . J. Zhang (CHiPR, SUNY, Stony Brook) and F. Guyot (IPGP) 

P-V-T Measurements of Siderites at High Pressure and High Temperature ..................... J. Zhang (ChiPR, SUNY, Stony Brook) and I Martinez (ENS) 

Synchrotron X-ray Scattering Study of the N-IC Phase Transition in RbzZnCle ................ M.P. Zinkin, R.A. Cowley (Oxford), D.F. McMorrow (Riso), J.P. Hill (BNL) 

CY - p - 7 Phase Transformations in (Mg,Fe)zSi04 ............................................ 

T-Cup: A New High-pressure Apparatus for X-Ray Studies ................................... 

Beamline X17B2 

K-edge Subtraction CT Imaging using the Angiography System ............................. A.M. Charvet (ESRF), F. Arfelli (BNL/INFN), R. Menk (BNL) and Z. Zhong (BNL/SUNY) 

Comparison of Different Detectors Used in Noninvasive Coronary Angiography with Synchrotron 

Radiation .................................................................................... B-143 

R.H. Menk, F.Arfelli, D.Chapman, N. Gmiir, W.Thomlmson, Z.Zhong (BNL) 

B-138 

B-139 

B-139 

B-140 

B-140 

B-141 

B-141 

B-142 

B-142 

B-143 

Three-energy Coronary Angiography Imaging ................................................. B-144 

W. Thomlinson, L.D. Chapman, N. Gmiir and Z. Zhong (BNL), R. Petr (Science Research 

Laboratory, Inc.) 

Monochromatic CT Image Sensitivity: Results from Preclinical Multiple Energy Computed 

Tomography [MECT] ........................................................................ B-144 

X.Y. Wu, F.A. Dilmanian, B. Ren, J. Kress, J.A. Coderre, D.N. Slatkin (BNL); M. Shleifer, 

W.C. Thomlinson, Z. Zhong (BNL); D. Chapman (I.I.T.), T.M. Button, F. Giron, Z. Liang, M.J. 

Petersen, C.T. Roque (SUNY, Stony Brook) 

Beamline X17C 

Pressure-Volume/Temperature Data on Platinum ............................................ Y. Cerenius, S. K. Saxena, and P. Haggkvist (Institute of Earth Science, Uppsala 

University) 

L. S. Dubrovinsky, S. K. Saxena, and P.Haggkvist (Institute of Eatrh Sciences, Uppsala 

University,) 

Andrzej Grzechnik, and Paul F. McMillan (Materials Research Group, Arizona State 

University) 

Iron at High Pressure and Temperature: The Stability of New Beta-Iron Phase ................ S. K. Saxena, L. S. Dubrovinsky, and P. Haggkvist (Institute of Earth Science, Uppsala 

University) 

E. F. Skelton, S. B. Qadri, P. L. Hagens, D. D. Dominguez (NRL), and J. Z. HU (CIW) 

Pressure-Volume Data on Platinum and Rhenium ............................................. 

High-pressure Phase Transitions in LiVO3 and alfa-NaVO3 .................................... 

Monitoring the Absorption of Deuterium into Palladium ....................................... 

B-14 

B-145 

B-145 

B-146 

B-146 

B-147 
Beamline X18A 

X-ray Scattering Studies of Liquid Crystalline Polymer Solutions under Shear Flow ......... W. Burghardt, K. Hongladarom, V. Ugaz, D. Cinader (Northwestern), J. Quintana (DNDCAT, APS), and B. Hsiao (DuPont) 

S. N. Ehrlich, G. L. Liedl, P. Metcalf, S. Soma and J. Honig (Purdue University) 

Structural Measurements of NiSz-=Se, ........................................................ 

XSCAN X-ray Data Acquisition and Analysis Software for the MATRIX X-18A X-ray 

Scattering Beam Line at the NSLS ............................................................ S. N. Ehrlich, J. A. Schwanof (Purdue Univ.), X. Yang (Howard Hughes Med. Inst.) and 

G. L. Liedl (Purdue Univ.) 

Rachel Eisenhower and Roberto Colella (Purdue University),Benjamin 

Grushko(Forschungszentrum Juelich) 

R.S. Goldman (Carnegie Mellon University), K.L. Kavanagh, H.H. Wieder (University of 

California, San Diego), and S.N. Ehrlich (Purdue University) 

R. Harlow and P. Carcia (DuPont) 

A. K. Kakkar, C. M. Yam (McGill Univ.), A. Richter and P. Dutta (Northwestern Univ.) 

Multiple X-Ray Diffraction Studies of Decagonal Quasicrystals ................................ 

High Resolution X-ray Diffraction Investigations of InGaAs-based Heterostructures 

Ar-Sputtered Pt/Co Multilayers with Large Anisotropy Energy and Coercivity ................. 

............ 

Structural Studies of Self-Assembled Alkynyl Thin Film Materials ............................. 

B-147 

B-148 

B-148 

B-149 

B-149 

B-150 

B-150 

Interface Structure in ZnSe-GaAs Heterostructures ............................................ 

X-ray Thermal Diffuse Scattering (TDS) Study of the Impurity Effect on the Anharmonic Lattice 

Dynamics for the Para-to-ferroelectric Phase Transformation in BaTiO3 ....................... 

In situ X-ray Diffraction Studies of YBCO/LaA103 Superlattices .............................. 

Epitaxial Growth of n-Alkane Monolayers on a Ag(ll1) Surface ............................... 

V. Mahadev, S. N. Ehrlich, and G. L. Liedl (Purdue Univ.) 

B-151 

B-152 

B-152 

N. Takesue, H. Kubo, (Nippon Steel Co.) and H. Chen (Univ. of Illinois, Urbana-Champaign) 

S. Williams and J.B. Ketterson (Northwestern Univ.) 

Z. Wu, J. Wang, (Univ. of Missouri, Columbia) S. N. Ehrlich, (Purdue Univ.) B. Matthies, K. 

W. Herwig and H. Taub (Univ. of Missouri, Columbia) 

Y. Zhang, R. Colella, S. N. Ehrlich (Purdue Univ.), S. Kycia and A. Goldman 

(Iowa State Univ.) 

Diffuse Scattering Studies in Al-Pd-Mn Quasicrystal ........................................... 

B-151 

B-153 

Beamline X18B 

X-ray Absorption Spectroscopy of Titanium-containing Molecular Sieves ..................... 

Renovation of Beamline X-18B for High Energy X-ray Spectroscopy ........................... R.J. Davis, Z. Liu, J.E. Tabora, and W.S. Wieland (Univ. Virginia) 

S. Khalid, L. Furenlid and P. Siddons ( BNL ) 

B-153 

B-154 

Beamline X19A 

Chlorine XANES Analysis of Stepwise Combustion Tests on Coal .......................... 

Structural Characterization of Phenylcopper in THF Solution ................................. 

F. E. Huggins, J. Zhao, F. Lu, G. P. Huffman (Univ. of Kentucky), M-I. M. Chou, 

and J.M. Lytle (Illinois State Geological Survey) 

H. Huang and J.E. Penner-Hahn (University of Michigan) 

Magnetic properties of Ni Porphyrins ......................................................... M.W. Renner (DAS), K.M. Barkigia (DAS), J. Fajer (DAS), L.R. Furenlid (BNL) 

Structural Studies of Ni(I1) Porphyrins ........................................................ Mark W. Renner, Kathy M. Barkigia, Jack Fajer (DAS,BNL), Lars R. Furenlid (BNL) 

Single Crystal EXAFS Studies of Nickel(I1) Porphyrins ........................................ M.W. Renner (DAS), J. Fajer (DAS), K.M. Barkigia (DAS) and L.R. Furenlid (BNL) 

B-154 

B-155 

B-155 

B-156 

B-156 
In situ XAFS Spectroscopic Studies of DCL Catalysts. ....................................... Naresh Shah, Jianmin Zhao, Fulong Lu, Frank E. Huggins and Gerald P. Huffman 

(University of Kentucky) 

D.L. Tierney, R.J. Denver, and James E. Penner-Hahn (Univ of Michigan) 

Characterization of the Zn in Xenopus Eggs ................................................... 

Sulfonate Sulfur and not the Sulfide Sulfur Dominates the Composition of Marine 

Phytoplankton ................................................................................ 

Di- and Polysulfide Cross Linking in the Formation of Humic Polymers in Marine Sediments ... Murthy A. Vairavamurthy, S.Wang, B. Khandelwal and B. Manowitz (BNL) 

M.A. Vairavamurthy, W. Zhou and B. Manowitz (BNL) 

Beamline X19C 

Investigation of Dislocation Distributions in InP Single Crystals Using Synchrotron White 

Beam X-ray Topography .................................................................... H. Chung, W. Si, M. Dudley, and V. Prasad (SUNY, Stony Brook), A. Anselmo and 

D. F. Bliss (USAF, Rome Laboratory) 

Characterization of Structure Defects in 2,12-Undecanedione/Urea Single Crystals by 

Using Synchrotron White Beam X-ray Topography ........................................... H. Chung, M. Dudley (SUNY Stony Brook), M. E. Brown, and Mark D 

Hollingsworth (Indiana University) 

Studies of Twinning in 2,10-Undecanedione/Urea Inclusion Compounds 

Using Synchrotron White Beam X-ray Topography ........................................... H. Chung and M. Dudley (SUNY, Stony Brook), M. E. Brown and Mark D. Hollingsworth 

(Indiana University) 

Synchrotron White Beam X-ray Topography Characterization of Structural Defects in 2,lOH. Chung, M. Dudley (SUNY Stony Brook), M. E. Brown, and Mark D. Hollingsworth 

(Indiana University) 

Characterization of Structural Defects in HgCdTe Epilayers by Using Synchrotron White Beam 

H. Chung, M. Dudley (SUNY, Stony Brook), and Sanghamitra Sen (Hughes Santa Barbara 

Research Center) 

Undecanedione/Urea Inclusion Compounds ................................................... 

X-ray Topography ........................................................................... 

Synchrotron White Beam X-ray Topography Studies of Interfacial Dislocations in SiGe/Si 

Heterostructures ............................................................................. 

Characterization of Growth Defects in THM grown HgCdTe Single Crystals by Using Synchrotron 

White Beam X-ray Topography .............................................................. 

H. Chung, M. Dudley (SUNY, Stony Brook), and J. Wu (General Instrument) 

H. Chung, B. Raghothamchar, and M Dudley (SUNY, Stony Brook), 

D. C. Gillies (NASA Marshall Space Flight Center) 

Studies of Interface Demarcation and Structural Defects in Ga Doped Ge Single Crystals Using 

Synchrotron White Beam X-ray Topography ................................................. H. Chung, B. Raghothamachar, M. Dudley (SUNY, Stony Brook), M. Lichtensteiger, and 

D. C. Gillies (NASA Marshall Flight Center) 

Studies of Defect Structures in PVT grown CdZnTe single crystals Using Synchrotron White 

Beam X-ray Topography ..................................................................... H. Chung, B. Raghothamachar, M. Dudley (SUNY, Stony Brook), W. Palosz, and D.C. Gillies 

(NASA Marshall Space Center) 

Synchrotron White Beam X-ray Topography Characterization of Twin Structures in Vapor Grown 

CdZnTe Single Crystals ...................................................................... H. Chung, B. Raghothamachar, M. Dudley (SUNY, Stony Brook), W. Palosz, and D.C. Gillies 

(NASA Marshall Space Flight Center) 

B-16 

B-157 

B-157 

B-158 

B-158 

B-159 

B-159 

B-160 

B-160 

B-161 

B-161 

B-162 

B-162 

B-163 

B-163 
Studies of Twinning in LEK Grown InP Single Crystals by Using Synchrotron White Beam X-ray 

Topography .................................................................................. H. Chung, W. Si, M. Dudley, V. Prasad (SUNY, Stony Brook), A. Anselmo, and D.F. Bliss 

(USAF, Rome Laboratory) 

Characterization of Defect Structures in (111) 3C-Sic Single Crystals by Synchrotron 

Topography .................................................................................. W. Huang, M. Dudley (SUNY, Stony Brook), 

and C. Fazi (Army Research Lab) 

Application of Synchrotron White Beam Multiple Diffraction Line Analysis in Measurement of 

Curvature of Single Crystals Induced by Lattice Mismatch .................................... W. Huang, M. Dudley (SUNY, Stony Brook), J. Parsons (Oregon Graduate IInstitute), and 

C. Fazi (Army Research Lab.) 

Characterization of Deformation in Single Crystals by Synchrotron White Beam Absorption 

Edge Contour Mapping ....................................................................... W. Huang, M. Dudley (SUNY, Stony Brook), J. Parsons (Oregon Graduate Institute), 

and C. Fazi (Army Research lab.) 

Measurement of Residual Stress in Single Crystals by Synchrotron White Beam Divergence 

Analysis ...................................................................................... W. Huang, M. Dudley (SUNY, Stony Brook), J. Parsons (Oregon Graduate Institute), 

and C. Fazi (U.S. Army Research Lab.) 

W. Huang, M. Dudley (SUNY,Stony Brook), J. Parsons (Oregon Graduate Institute), and C. 

Fad (Army Research Lab.) 

Observation of Dislcoation Contrast Reversal Induced by Strain Field ......................... 

Surface Segregation and Layering in the Liquid-vapor Interface of a Dilute 

Bismuth : gallium Alloy ........................................................................ Ning Lei, Zhengqing Huang and Stuart A. Rice (Univ. of Chiago) 

Characterization of X-ray Spatial Coherence and Its Propagation .............................. B. Lin, M. Meron, P. J. Viccaro (Univ. of Chicago), M. L. Schlossman, S. Williams (Univ. of IL, 

Chicago) 

B-164 

B-164 

B-165 

B-165 

B-166 

B-166 

B-167 

B-167 

Characterization of Structural Defects in ZnSe by Synchrotron White Beam X-ray Topography 

B. Raghothamachar, H. Chung, M. Dudley, (SUNY, Stony Brook), B. Fitzpatrick (Optical 

Semiconductors, Inc.) 

Studies on the Influence of Post Solidification Cooling Rate on the Crystalline Perfection of 

CdZnTe Single Crystals by Synchrotron White Beam X-ray Topography ....................... B. Raghothamachar, H. Chung, M. Dudley, D. J. Larson Jr. (SUNY, Stony Brook) 

Surface Topography Studies of an as-grown Boule of CdZnTe .................................. B. Raghothamachar, H. Chung, M. Dudley, D.J. Larson Jr.(SUNY, Stony Brook) 

Synchrotron X-ray Topographic Studies on the Causes and Nature of Twinning in CdZnTe 

B. Raghothamachar, H. Chung, M. Dudley, D.J. Larson, Jr.(SUNY, Stony Brook) 

Crystals ...................................................................................... 

Bridgman Grown CdZnTe Single Crystals ..................................................... Synchrotron X-ray Topography Studies of Formation of Slip Bands and Subgrain Boundaries in 

B. Raghothamachar, H. Chung, M. Dudley, D.J. Larson Jr.(SUNY, Stony Brook) 

The Application of Synchrotron X-Ray Radiation to the Development of Time Resolved Methods 

for the Study of RNA Folding ................................................................. B. Sclavi, M. Sullivan, M. Chance, M. Brenowitz (Albert Einstein College of Medicine), and 

S. Woodson (Univ. of Maryland) 

Applications of Absorption Edge Contour (AEC) Mapping in Fe Doped InP Single 

Crystal Wafers ................................................................................ W. Si, H. Chung, M. Dudley,V. Prasad (SUNY, Stony Brook), A. Anselmo, and D. F. Bliss 

(USAF, Rome Laboratory) 

B-168 

B-168 

B-169 

B-169 

B-170 

B-170 

B-171 

B-17 
Investigation of Defect Structures in Sn Doped InP Single Crystals by Synchrotron X-ray 

Transmission Topography ..................................................................... W. Si, H. Chung, M. Dudley, V. Prasad (SUNY, Stony Brook), A. Anselmo, and D. F. Bliss 

(USAF, Rome Laboratory) 

Study of Defect Distributions in S doped InP Single Crystals by Synchrotron X-ray Reflection 

Topography .................................................................................. W. Si, H. Chung, M. Dudley, V. Prasad (SUNY, Stony Brook), A. Anselmo and D. F. Bliss 

(USAF, Rome Laboratory) 

Study of Effect of Magnetic Field on Fe Precipitates in Fe-doped InP Single Crystals 

Using Synchrotron White Beam X-ray Topography ............................................ W. Si, H. Chung, M. Dudley, V. Prasad (SUNY, Stony Brook), A. Anselmo and D. F. Bliss 

(USAF, Rome Laboratory) 

Examination of High Quality 4h-sic Single Crystal Wafers by Synchrotron White Beam X-ray 

Transmission Topography ..................................................................... W. Si, M. Dudley (SUNY, Stony Brook), and C. H. Carter, Jr. (Cree Research, Inc.) 

Observation of 3C-Sic Inclusions in 4H-Sic Epitaxial Films Grown on 4H-Sic Single Crystal 

Substrates .................................................................................... W. Si, W. Huang, M. Dudley (SUNY, Stony Brook), H. S. Kong and C. H. Carter, Jr. (Cree 

Research, Inc.) 

Determination of Burgers Vectors of Screw Dislocations in 6H-Sic Single Crystals: I. Projection 

Topography .................................................................................. W. Si, S. Wang, M. Dudley (SUNY, Stony Brook), and C. H. Carter, Jr. (Cree Research,Inc.) 

Determination of Burgers Vectors of Screw Dislocations in 6H-Sic Single Crystals: 11. Section 

Topography .................................................................................. W. Si, S. Wang , M. Dudley (SUNY, Stony Brook), C. H. Carter, Jr. (Cree Research Inc.) 

Observation of Growth Defects in GaInSb Single Crystal by Synchrotron White Beam X-ray 

Topography .................................................................................. J. Su, H. Chung, M. Dudley (SUNY, Stony Brook), D. DiMarzio (Grumman Corp.), 

D. Fletcher, W. Bonner (Johnson Matthey Electronicss) 

Synchrotron White Beam X-ray Topographic Investigation of Growth Processing in GaInAs Single 

J. Su, H. Chung, M. Dudley (SUNY, Stony Brook), D. Fletcher, and W. Bonner (Johnson 

Matthey Electronics) 

J. Su, M. Dudley (SUNY, Stony Brook),T. McLelland, B. Goldfrank (Frequency 

Electronics Inc.) 

J. Su, W. Si, M. Dudley (SUNY, Stony Brook), T. McLelland, and B. Goldfrank (Frequency 

Electronics Inc.) 

W. M. Vetter, M. Dudley (SUNY, Stony Brook) 

Crystal ....................................................................................... 

Studies of Quartz Crystal Bars Using Synchrotron White Beam X-ray Topography ............. 

Comparison of Quartz Resonator Bonding Strain by Synchrotron White Beam Topography .... 

X-Ray Topography and Fluorescence Microscopy of a Basal Cut 6H-Sic Wafer ................ 

X-Ray Topography and Laser Scanning Confocal Microscopy of a Longitudinal Cut 

6H-Sic Wafer ................................................................................. W. M. Vetter and M. Dudley (SUNY, Stony Brook) 

S. Wang, W. Huang, M. Dudley (SUNY, Stony Brook), M. Spencer (Howard University), 

and C. Fazi (Army Research Lab.) 

S.M. Williams, Z. Zhang, and M.L.Schlossman (University of Illinois, Chicago) 

Synchrotron White Beam X-ray Topographic Characterization of PVT 3C-Sic Crystals ....... 

Microemulsion-Oil Interfaces in Ternary Liquid Systems ....................................... 

B-18 

B-171 

B-172 

B-172 

B-173 

B-173 

B-174 

B-174 

B-175 

B-175 

B-176 

B-176 

B-177 

B-177 

B-178 

B-178 
Beamline X20A 

X-ray Scattering Studies of the Passive Film on Fe (110) ................................... Alison J. Davenport, Carissima M. Vitus (DAS, BNL), and Michael F. Toney (IBM, 

Almaden Research Center) 

GIXD Measurements of Initial Strain Relaxation in Sil-,Ge, Thin Films ...................... J.L. Jordan-Sweet, P.M. Mooney, M. Lutz, R.A. Feenstra, and J.O. Chu (IBM) 

Interfacial Roughness and Giant Magnetoresistance in Sputtered Co/Rh Multilayers as 

Studied with X-ray Scattering ................................................................. Stuart P. Parkin and Michael F. Toney (IBM, Almaden Research Center) 

B-179 

B-179 

B-180 

Beamline X20B 

Structural Phase Transitions and Magneto-Elastic Effects in USbo.aTeo.2 and USb. .......... W.J. Nuttall, S.C. Perry, D.R. Bowyer, W.G. Stirling (U. Keele) G.H.Lander (E.I.T.U.) 

and 0. Vogt (E.T.H.) 

B-180 

Beamline X20C 

In-situ, Simultaneous Three-Probe Measurement of Structural Transformations in Metal 

Silicides. ....................................................................... .: ............. J.L. Jordan-Sweet, L.A. Clevenger, C.A. Cabral, Jr., R.A. Roy, C. Lavoie, K.L. Saenger 

(IBM), G.B. Stephenson, S.A. Brauer (ANL), K.L. Ludwig, Jr., and G. Morales (Boston 

Univ.) 

Effects of Rubbing Parameters on Surface Orientation of BPDA-PDA Polyimide ............... James M. Sandsm, Sanat K. Kumar (Pennsylvania State University), Thomas P. Russell and 

Michael F. Toney (IBM, Almaden Research Center) 

M.P. Zinkin, R.A. Cowley (Oxford), D.F. McMorrow (Riso), and J.P. Hill (BNL) 

Synchrotron X-ray Scattering Study of the N-IC Phase Transition in RbZnCl4 ................ 

B-181 

B-181 

B-182 

Beamline X21 

Inelastic X-Ray Scattering Study of Diamond ................................................ W.A.Caliebe, C.-C.Kao, J.B.Hastings (BNL), M.H.Krisch, F.Sette (ESRF), K.Hiimiiliiinen 

(University of Helsinki) 

W.A.Caliebe, C.-C.Kao, J.B.Hastings (BNL), M.H.Krisch, F.Sette (ESRF), K.Hiimiiliiinen 

(University of Helsinki) 

L.R. Furenlid (BNL), W.A. Caliebe (BNL), M.W. Renner (DAS, BNL), E. Fujita (Chem., BNL), 

and C.-C. Kao (BNL) 

K. 

Hamaliiinen, S. Manninen (Helsinki Univ.), C.-G. Kao, W. Caliebe, J. B. Hastings (BNL), and 

A. Bansil (Northeastern Univ.) 

Inelastic X-Ray Scattering Study of LiF ....................................................... 

K-y Fluorescence Spectroscopy of Ni(1) and Ni(I1) Complexes ................................. B-183 

High Resolution Compton Scattering from Li .................................................. B-184 

B-182 

B-183 

Inelastic X-ray Scattering Studies of Electronic Excitations .................................... J.P. Hill, C-.C. Kao, W.A. Caliebe, D. Gibbs (BNL), D. Reanik (NIST) and 

J.P. Wilcoxon (SNL) 

B-184 

. Inelastic X-ray Scattering Study of NiSz_,Se, .................................................. E. D. Isaacs (AT&T Bell Labs), C. A. Burns, (Western Michigan University), T.Thio, J. W. 

Bennett (NEC Research Institute), W.’ Caliebe, and C.-C. Kao (BNL) 

Beamline X22A 

In-situ X-ray Investigation of Metal-hydrogen Electrodes in, Thin Film Ni-MH Batteries ..... N. Jisrawi, G. Reisfeld (BNL-Physics),’ H. Wiesmann (BNL-DAS), T. Thurston, 

M. W. Ruckman, B. Ocko and M. Strongin (BNL-Physics) 

B-185 

B-185 

B-19 
X-ray Identification of Peaks in Cyclic Voltammetry from Nb/Pd Multilayers in a 

KOH Electrolyte ............................................................................... N. Jisrawi, G. Reisfeld (BNL-Physics), H. Wiesmann (BNL-DAS), T. Thurston, 

M. W. Ruckman, B. Ocko and M. Strongin (Physics, BNL) 

Microstructural Study of at-C Films: Relation to Residual Stresses ............................ L. J. Martinez-Miranda (Univ. of Maryland), J. P. Sullivan, T. A. Friedmann, M. P. Siegal 

(SNL), T. W. Mercer, and N. J. DiNardo (Drexel Univ.) 

The Commensurate-incommensurate Transition of Br on the Au( 100) Electrode. ............... B.M Ocko, O.M. Magnussen (BNL, Physics), J.X. Wang (BNL, DAS), T. Wandlowski (Ulm) 

Small Angle X-ray Scattering (SAXS) Investigations of Metal and Semiconductor Nanoscale Size 

Clusters ...................................................................................... 

Synchrotron X-ray Scattering Characterization of High Temperature Superconducting Wires ... T.R. Thurston (BNL), J.P. Wilcoxin, and S. Craft (SNL) 

T.R. Thurston, U. Wildgruber, N. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC) 

The Effects of Hydrogen Adsorption/evolution and Bisulfate Coadsorption on the Structure of 

Underpotentially Deposited T1 Adlayers on Pt(ll1) ........................................... J.X. Wang, R.R. Adzic (BNL, DAS), B.M. Ocko, O.M. Magnussen (BNL, Physics) 

Beamline X22B 

Structure of Electrode Surfaces in the Course of Electrocatalytic Reactions: Oxidation of 

CO, Glucose And Formaldehyde on Reconstructed and Unreconstructed Au(100) ............ R.R. Adzic, J.X. Wang (BNL, DAS), B.M. Ocko, O.M. Magnussen (BNL, Physics) 

Surface Freezing in Binary Mixtures of Normal Alcohols ....................................... 

B-186 

B-186 

B-187 

B-187 

B-188 

B-188 

B-189 

B-189 

A.K. Doerr, 0.Gang-(Bar-Ilan Univ.), X.Z. Wu (Northern Illinois Univ.), O.M. Magnussen, B.M. 

Ocko(BNL), E.B. Sirota (Exon) and M. Deutsch (Bar-Ilan Univ.) 

W. J. Foster, M. C. Shih, and P. S. Pershan (Harvard University) 

M. Fukuto, P.S. Pershan (Harvard), D.Vaknin, and J.Y. Wang (Ames Lab & Iowa State) 

V. Kiryukhin, B. Keimer (Princeton University), J. P. Hill, and A. Vigliante (BNL) 

V. Kiryukhin, B. Keimer (Princeton University), J. P. Hill, and A. Vigliante (BNL) 

S.D. Kosowsky, P.S. Pershan (Harvard Univ.), K.S. Krisch, J. Bevk, M. Green, L.C. Feldman 

and P.K. Roy (AT&T Bell Labs) 

X-ray Diffraction Studies of Thiols on Liquid Hg .............................................. O.M. Magnussen, B.M. Ocko (BNL), M.J. Regan, P.S. Pershan (Harvard), and M. Deutsch 

(Bar-Ilan) 

A Study of the SmC* Liquid Crystal-Glass Substrate Interface ................................ L. J. Martinez-Miranda (Univ. of Maryland, College Park) 

X-ray Induced Electrostatic Charging of Helium Films ......................................... K.Penanen, P.S.Pershan, M.Regan, and 1.F.Silvera (Harvard) 

Charge Density Waves and Strain Waves in Epitaxial Cr-Films ................................ P. Sonntag, P. Biideker, H. Zabel (Ruhr-Universitat) 

Magnetic Phase Diagram of Holmium: An X-ray Scattering Study. ............................ A. Vigliante, J. P. Hill, Doon Gibbs (BNL), V. Kiryukin, B. Keimer (Princeton) 

An X-ray Scattering Study of Methyl Eicosanoate ............................................. B-190 

X-ray Scattering Study of Ceo-propylamine Adduct Monolayers at the Gas-Water Interface .... B-190 

Influence of Quantum Impurities on the Soliton Lattice in CuGeO3. ........................... B-191 

Magnetic Phase Diagram of the Spin-Peierls System CuGeO3 .................................. B-191 

Si-based MOS Devices Studied by X-ray Reflectivity .......................................... B-192 

B-192 

B-193 

B-193 

B-194 

B-194 

B-20 
Beamline X22C 

The Magnetic Structure of GdNi2BzC by Resonant and Non-Resonant X-Ray Scattering ... C. Detlefs, A. I. Goldman, C. Stassis, P. C. Canfield, B. K. Cho (Ames Lab), J. P. Hill, 

and D. Gibbs (BNL) 

Charge Density Waves in Doped Chromium ................................................... J.P. Hill and B.J. Sternlieb (BNL) 

Incommensurate Antiferromagnetism in the Intermetallic Superconductor HoNizBzC ........... J.P. Hill, B.J. Sternlieb, D. Gibbs (BNL), C. Detlefs, A.I. Goldman, C. Stassis, P.C. Canfield 

and B.K. Cho (Ames Lab.& ISU) 

Observation of X-ray Magnetic Scattering in NdzCu04 ........................................ J.P. Hill, A. Vigliante, D. Gibbs (BNL), J.L. Peng and R.L. Greene(Univ. Maryland) 

X-ray Magnetic Scattering from Single Crystals of UPd2A13 ................................... S. Langridge (ESRF, EITU), G.H. Lander (EITU), N. Sat0 (U. Sendai), and D. Gibbs (BNL) 

X-ray Magnetic Scattering from Single Crystals of UPtGe ..................................... S. Langridge (ESRF, EITU), G.H. Lander (EITU), Y. Yamaguchi (IMR), and 

D. Gibbs (BNL) 

S. Langridge (ESRF), J.A. Paixlo (Univ. Coimbra), G.H. Lander (EITU) and 

D. Gibbs (BNL) 

X-ray Magnetic Scattering of HoPr Random Thin Film Alloys. ................................ A. Vigliante, J. P. Hill, Doon Gibbs (BNL), M. J. Christensen, D. F. McMorrow (RISO), G. 

Helgesen (IFE), R. A. Cowley, M. R. Wells, and R. C. C. Ward (Oxford) 

G. M. Watson, Doon Gibbs (BNL), G.H. Lander, H. J. Matzke (EITU), B.D. Gaulin 

(McMaster), L.E. Berman (BNL)and W. Ellis (SNL) 

X-Ray Scattering Studies of Vicinal Au(001) .................................................. G.M. Watson, Doon Gibbs (BNL), D.M. Zehner (ORNL), Mirang Yoon and S.G.J. Mochrie 

B-199 

B-199 

Resonant Magnetic X-ray Scattering Study of DyFe4Als ....................................... 

Glancing-Incidence X-Ray Magnetic Scattering Studies of the UOz (001) Surface ............... 

(MITI 

B-197 

B-197 

B-198 

B-198 

B-200 

B-200 

B-201 

B-201 

Charge Density Waves in Laz-,-,Nd,Sr,Cu4. ................................................. 

The Surface Structure of Au(ll1) in the Presence of Organic Adlayers - A Combined 

Electrochemical And Surface X-ray Scattering Study .......................................... Th. Wandlowski (Ulm), B. M. Ocko, O.M. Magnsusen (BNL, Physics), W. Wu, and J. 

Lipkowski( Guelph) 

The Effects of Hydrogen Adsorption/evolution and Bisulfate Coadsorption on the Structure of 

Underpotentially Deposited T1 Adlayers on Pt(ll1) ........................................... J.X. Wang, R.R. Adzic (BNL, DAS), B.M. Ocko, O.M. Magnussen (BNL, Physics) 

X-Ray Study of Orientational Correlations in C~O above 260K ................................. P. Wochner, J.D. Axe (BNL), P.C. Chow, S.C. Moss (Univ. of Houston), J.W. Dykes, 

S.H. Irons, J.Z. Liu, R.N. Shelton (Univ. of California, Davis) 

A. Vigliante, J. Tranquada, J. D. Axe, Doon Gibbs, B. Ocko (BNL) 

B-195 

B-195 

B-196 

B-196 

Beamline X23A2 

The Surface Structure of Cadmium Selenide Nanocrystallites as Determined by EXAFS, 

FTIR, and Elemental Analysis ............................................................... B-202 

A.C. Carter (NRL), M.I. Bell (NRL), K.M. Kemner (NRL), C.E. Bouldin (NIST), J.C. 

Woicik (NIST), S.A. Majetich CMU) 
EXAFS Study of Co/X Multilayers ........................................................... 

XAFS Studies of MnSe/ZnTe Superlattices .................................................... M. Franklin and R. Loloee (Michigan State University) 

A. J. Kropf, B. A. Bunker, J. K. Furdyna, Q. Lu (Notre Dame), and K. M. Kemner (NRL) 

XAFS Investigation of Thermal Structural Disorder at GaSb/AlSb Superlattice Interfaces ...... Q. Lu, B. A. Bunker, A. J. Kropf, S. W. Short, S. H. Xin, J. K. Furdyna (Notre Dame) 

X-ray Study of Atomic Correlations in ZnCdSeTe Epitaxial Thin Films ........................ Q. Lu, B. A. Bunker, H. Luo, A. J. Kropf, K. M. Kemner, J. K. F’urdyna 

K. E. Miyano (Brooklyn College), J. C. Woicik (NIST), D. Huang (Brooklyn College) 

XANES study of Cr Dopants in Oxides ....................................................... 

Beamline X23A3 

Processing .................................................................................... 

Diffraction Imaging of ZnSe Substrates for Blue/Green Emitters ............................... 

Studies of Plasma-Sprayed Deposits Using USAXS ............................................ 

Tape by Microradiography .................................................................... 

Microstructural Control of the Pore and Grain Size Evolution in Silicon Nitride During 

A.J. Allen, G.G. Long, S. Krueger, J. Wallace (NIST), and C.J. Hwang (Dow) 

David Black, Harold Burdette (NIST), Gene Cantwell (Eagle-Picher Research Lab) 

J. Ilavsky (SUNY, Stony Brook/ NIST), G. G. Long, and A.J.Allen (NIST) 

Submicron Resolution Strain Mapping of an In-situ Strained High-Tc Superconductor Composite 

R.D. Spa1 (NIST), G.N. Riley and C. Christopherson (American Superconductor Corp.) 

Beamline X23B 

Fe in Natural Zeolites: Can it Be Localized by XAFS? ..................................... M. Endregard (Univ. of Trondheim), A. F. Gualtieri, S. Quartieri, G. Vezzalini (Univ. of 

Modena), and K.I. Pandya (NCSU) 

Study of microstructure of NLO active chromophoric self-assembled multilayers using specular reflectivity .................................................................................... A. Malik, W. Lin, M. K. Durbin, S. B. Roscoe, A. G. Richter, T. J. Marks and P. Dutta 

(Northwestern University) 

Beamline X24A 

Angular Correlation in Electron/X-ray Coincidence Spectroscopy ............................ U. Arp (NIST), T. LeBrun, S. Southworth, M. Jung (ANL), and J. Cooper (UMD) 

Resonant X-ray Fluorescence Study of Uranium Oxides ........................................ S. M. Butorin, J. Nordgren (Uppsala Univ.), Y. Ma (Univ. of Washington & Pacific Northwest 

Labs.), K. E. Miyano (Brooklyn College), D. C. Mancini (Univ. of Lund), B. A. Karlin (NIST), 

and D. K. Shuh (LBL) 

D. Heskett (URI), L.E. Berman, and C.-C. Kao (BNL) 

Terrence Jach (NIST), S. M. Thurgate (Murdoch Univ.), Y. Zhang, R. Colella (Purdue Univ.), 

S. W. Kycia (Cornel1 Univ.), and A. I. Goldman (Iowa State Univ.) 

X-ray Standing Wave Investigation of (lx2)Rb/Cu(llO) ....................................... B-209 

Dynamical Bragg Diffraction and X-Ray Standing Waves from Quasicrystal AlPdMn .......... B-209 

B-202 

B-203 

B-203 

B-204 

B-204 

B-205 

B-205 

B-206 

B-206 

B-207 

B-207 

B-208 

B-208 

Non-dipolar Asymmetries of Photoelectron Angular Distributions .............................. 

X-ray Scattering of Atoms and Molecules ...................................................... 

An Electron-electron Coincidence Experiment Near the Ar K-edge ............................ 

B-210 

M. Jung, B. Kriksig, D.S. Gemmell, E.P. Kanter, T. LeBrun, 

S.H. Southworth, and L. Young (Argonne National Laboratory) 

K. Miyano (CUNY), U. Arp (NIST), and S. Southworth (ANL) 

R. Wehlitz (AvH Foundation), L. Pibida, J.C. Levin, and I.A. Sellin (Univ. of Tenn.) 

B-210 

B-211 

B-22 
Strain Relaxation of Ultrathin InAs/GaAs(001) Films ......................................... J.C. Woicik (NIST), K.E. Miyano (Brooklyn), J.G. Pelligrino (NIST), P.S. Shaw (NIST), S.H. 

Southworth (NIST), and B.A. Karlin (BNL) 

Beamline X24C 

Refractive and Extinction Indices of Lithium Triborate in 55-71 eV Region ................. T. J.Chen(SIU),W.R.Hunter(SFA),R.Zitter,R.Tao(SIU),J.C.Rife(NRL) 

Photoemission and C-1s Near-edge Absorption from Photopolymerized CSO Films .............. B.S. Itchkawitz (Fritz-Haber-Institut),J.P. Long (NRL), T. Schedel-Niedrig (FritzHaber-Institut), M.N. Kabler (NRL), A.M. Bradshaw, R. Schlogl (Fritz-Haber-Institut), 

W.R. Hunter (SFA, Inc.) 

Structural Determination of the @iC( lOO)-c(2x2) Surface from C-1s Surface-Core-Exciton and 

Si-2p Absorption .............................................................................. J. P. Long (NRL), V. M. Bermudez (NRL), D. E. Ramaker (George Washington Univ.) 

J. F. Seely, M. P. Kowalski, J. C. Rife, R. G. Cruddace (NRL), T. W. Barbee, Jr. (LLNL), 

and W. R. Hunter (SFA Inc.) 

Characterization of Soft X-Ray Multilayer Gratings and Mirrors ............................... 

Beamline X25 

X-Ray Standing Wave Investigation of ~(4x2) CO/Ni(lll) ................................... 

Real-Time Small-Angle X-ray Scattering Studies of Rubber-Modified Engineering 

Thermoplastics ............................................................................... 

L.E. Berman (BNL), D.R. Heskett (Univ. Rhode Island), and C.-C. Kao (BNL) 

R. A. Bubeck, C. F. Broomall, B. G. Landes, D. E. Parker, R. Ramsey, R. Scott, 

J. Warakomski, (Dow Chemical Company), E. J. Kramer (Cornel1 University), and 

L. E. Berman (BNL) 

Spin Resolved X-Ray Resonant Raman Scattering ............................................. W.A.Caliebe, C.-C.Kao, L.E.Berman, J.B.Hastings (BNL), M.H. Krisch, F. Sette (ESRF), 

and K.HZmZ1Zinen (University of Helsinki) 

Determination of Transition Metal Electronic Structure Using High Resolution X-Ray 

Fluorescence Spectroscopy .................................................................... Kelly A. Daly (University of Michigan), Melissa M. Grush (University of California, Davis) 

and James E. Penner-Hahn (University of Michigan) 

B. S. DeDecker (Howard Hughes Medical Institute), R. O'Brien (Yale), P. J. Fleming (Howard 

Hughes Medical Institute), S. P. Jackson (Wellcome/CRC Insititute) and P. B. Sigler (Howard 

Hughes Medial Institute and Yale) 

The Crystal Structure of a Hyperthermophilic Archaea TATA Binding Protein ................. 

Near-edge studies of the Excitation of the Ka! satellites in copper .............................. M.Deutsch, 0.Gang (Bar-Ilan Univ.), K.HZrnXinen (Helsinki Univ.), C.C.Kao (BNL) 

Structure of the High Affinity Complex of an Inositol Trisphosphate with a Phospholipase C 

Pleckstrin Homology Domain ................................................................. K.M.Ferguson (Yale), M.A.Lemmon, J.Schlessinger (NYU) and P.B.Sigler (H.H.M.1, Yale) 

SC Harrison and CM Lawrence (HHMI, HU, Children's Hospital) 

Structural Studies of the Human Transferrin Receptor and a bZIP Protein/DNA Complex ..... 

The 2.0 A Crystal Structure of a Heterotrimeric G Protein .................................... David Lambright (Yale University) and Paul Sigler (Howard Hughes Medical Institute, Yale 

University) 

Ratio of Double-to-Single Photo- and Compton Ionization of Helium ........................... Jon C. Levin, G. Bradley Armen, and Ivan A. Sellin (Univ. Of Tennessee) 

Coherent X-Ray Reflectivity From Oxidized Si (111) Surfaces .................................. J. L. Libbert, I. K. Robinson, (Univ. Illinois), R. Pindak, R. M. Fleming (AT&T), 

S. B. Dierker (Univ. Michigan) 

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 

B-2 19 

B-23 
Polarization Dependent Scattering from DyLu Superlattices ................................... 

X-ray Studies of Liquid Metal Surfaces ........................................................ 

Observation of Speckle from a Protein Crystal ................................................. 

K.V. O’Donovan, M.B. Salamon (UIUC), B.A. Everitt (NVE, Inc.), T. Thurston, D. Gibbs 

S.B. Dierker and L. Berman (BNL) 

M.J. Regan, P.S. Pershan (Harvard), O.M. Magnussen, B.M. Ocko (BNL), M. Deutsch 

(Bar-Ilan Univ.), L.E. Berman (BNL) 

I. K. Robinson, J. L. Libbert (University of Illinois), R. Pindak, R. M. Fleming (AT&T), 

S. B. Dierker (University of Michigan), B. Yu and D. L. D. Caspar (Florida State University) 

X. Wang, A. Froeschner and S.P. Cramer 

Y. Wang (Yale University), Y. Jiang (Yale University), M. Sprinzl (University of Bayreuth), 

P. B. Sigler (Yale University & HHMI) 

Glancing-Incidence X-Ray Magnetic Scattering Studies of the UOz (001) Surface ............... G. M. Watson, Doon Gibbs (BNL), G.H. Lander, H. J. Matzke (EITU), B.D. Gaulin 

(McMaster), L.E. Berman (BNL)and W. Ellis (SNL) 

Spin-polarized XANES of First Metalloprotein - Demonstration with Rubredoxin .............. 

Complex of elongation factors EF-Tu and EF-Ts .............................................. 

Beamline X26A 

Micro-XAFS Investigations on Aqueous Metallic Species in Fluid Inclusions up to 43OOC ... Alan J. Anderson (St. Francis Xavier Univ.), Robert A. Mayanovic (Southwest Missouri 

State Univ.), SGa Bajt (Univ. of Chicago) 

Chemical Speciation of Uranium in Contaminated and Chemically Remediated Soils by 

Micro X-ray Absorption Spectroscopy ......................................................... P. M. Bertsch, D. B. Hunter, and P. R. Nuessle (University of Georgia) 

Quantitative Microanalysis of Oxidation State Ratios in Complex Silicate Minerals - (I) Fe in 

Amphibole ................................................................................... J. S. 

Delaney (Rutgers Univ.), M. D. Dyar (West Chester Univ.), S. Bajt and S. R. Sutton (CARS, 

Univ. of Chicago) 

George J. Flynn (SUNY, Plattsburgh), Saga Bajt and Stephen R. Sutton (CARS, 

Univ. of Chicago) 

George J. Flynn (SUNY, Plattsburgh), Saga Bajt, and Stephen R. Sutton (CARS, 

Univ. of Chicago) 

Mark Fuhrmann (BNL), SaSa Bajt (CARS, Univ. of Chicago), 

and Martin Schoonen (SUNY, Stony Brook) 

Albert L. Hanson (BNL), and Saga Bajt (CARS, Univ. of Chicago) 

Micro-XANES of Iron Redox States in Wood During Degradation by Fungi ................... B. L. Illman (Univ. of Wisconsin, Forest Products Lab), S. Bajt (CARS, Univ. of Chicago), 

P. Nuessle (SREL, Univ. of Georgia) 

Behavior of Dissolved Molybdenum during Localized Corrosion of Austenitic Stainless Steel .... H. S. Isaacs and S-M. Huang (BNL) 

Three-dimensional Characterization of Surface-controlled Trace-element Zoning Patterns Using 

In-situ Detection and Chemical Analysis of Extraterrestrial Material Captured in Aerogel ...... 

Trace Element Measurements in Interplanetary Dust ......................................... 

Sorption of Iodine Species on Some Minerals .................................................. 

Investigation of the Pre-edge Absorption XANES Structure .................................... 

Synchrotron X-ray Fluorescence Microanalysis ................................................. 

Fe by Organoborates .......................................................................... 

P. A. Northrup, and R. J. Reeder (SUNY, Stony Brook) 

A Time Resolved In Situ XANES Study of Surface-Enhanced Reduction of Smectite Structural 

P. R. Nuessle, W. P. Gates, D. B. Hunter, and P. M. Bertsch (University of Georgia) 

B-24 

.. 

B-219 

B-220 

B-220 

B-221 

B-221 

B-222 

B-222 

B-223 

B-223 

B-224 

B-224 

B-225 

B-225 

B-226 

B-226 

B-227 

B-227 

~ ~~ 

.., ~ . 

,., I :: f. .<.,,:: .? - , I. 

,, * .., 
REE Intrasectional Zoning in Apatite, Determined Using Synchrotron X-ray Fluorescence 

Microanalysis (SXRFMA) ..................................................................... J. Rakovan, and R. J. Reeder (SUNY, Stony Brook) 

Terry L. Rinehart, Darrell G. Schulze (Purdue Univ.), R. Mark Bricka (US Army Corps 

of Eng.), SaEa Bajt (Univ. of Chicago), and Ernest R. Blatchley, I11 (Purdue Univ.) 

Darrell G. Schulze, Don M. Huber, A. K. M. Shahjahan, Morris Levy (Purdue Univ.), 

Saia Bajt (Univ. of Chicago), and Barbara Illman (USDA, Forest Products Lab.) 

Real time, In-situ Tracking of Selenium Transport and Reduction Across the Boundary Between 

Chromium Leaching versus Oxidation State for a Contaminated Solidified/Stabilized Soil ...... 

Oxidation State of Manganese in Rice Blast Fungal Lesions .................................... 

Ponded Waters and Sediments Using Micro-XANES ........................................... Tetsu K. Tokunaga (LBL), Saia Bajt (CARS, Univ. of Chicago), Stephen R. Sutton 

(CARS, Univ. of Chicago), and Patterson R. Nuessle (SREL, Univ. of Georgia) 

Beamline X26C 

X-Ray Fluorescence Analysis With High Energy Resolution ................................. W.A.Caliebe(BNL), Saga Bajt(University of Chicago), C.-C. Kao(BNL) 

White Beam Microdiffraction for Spatially Resolved Strain, Microstructure, and Composition 

G. S. Cargill I11 and P.-C. Wang (Columbia University), and I. C. Noyan and E. Liniger, 

(IBM Research) and K. W. Jones (BNL Applied Sciences) 

Mapping ...................................................................................... 

Search for Structural Modulations in UPt3 Using Laue Diffraction ............................. B. Ellman, M. Sutton, L. Taillefer (McGill University), 

and G. SheaiMcCarthy (University of Chicago) 

The Effect of Microgravity on the Protein Crystal Growth: Concanavalin A As a Case Study . . G. Shoham and L. Arnowitz (University of Jerusalem), V. Stojanoff and D. P. Siddons 

( BNL, BNL) 

Fabrication of a mm-wave Undulator Cavity Using Deep X-ray Lithography ................... J. J. Song, B. Lai, D. C. Mancini, A. Nassiri (APS/ANL), A. D. Feinerman (University of 

Illinois, Chicago), G. M. Wells, and V. White (University of Wisconsin, Madison) 

Laue Crystallographic Studies of Enzymatic Intermediates: Isocitrate Dehydrogenase .......... Barry L. Stoddard, Jill M.Bolduc, Dave H. Dyer (Fred Hutchinson Cancer Research Center, 

Basic Sciences Division), William G. Scott (Medical Research Council, Cambridge), 

Robert M. Sweet and Paul Singer (BNL) 

X-ray Topography of Tetragonal Lysozyme Crystals .......................................... V.Stojanoff and D. P. Siddons (Brookhaven National Laboratory), L. Monaco, P. Vekilov, F. 

Rosenberger (CMMR, University of Alabama, Huntsville) 

B-228 

B-228 

B-229 

B-229 

B-230 

B-230 

B-231 

B-231 

B-232 

B-232 

B-233 

X-ray Topography: a Tool for Protein Crystal Quality Diagnosis * ............................. B-233 

V. Stojanoff (BNL), E.H. Snell (Univ. Manchester, UK), D.P. Siddons (BNL) and J.R. Helliwell 

(Univ. Manchester, UK) 

Use of Laue Diffraction Patterns in both Macromolecular and Small-Molecule Crystallography . Joel L. Sussman, Vivian Stojanoff (BNL), Raimond B.G. Ravelli, M.A. Frederik H. van den 

Broek (Utrecht University), Ling Peng (Universite' Louis Pasteur), Mia L. Raves and Israel 

Silman (Weizmann Inst. of Science) 

B-234 

Beamline X27A 

In Situ X-ray Diffraction Structural Characterization of Hydrogen Uptake in an Operating 

Nickel-Metal-Hydride Electrode .............................................................. B-234 

T.R. Thurston, N. Jisrawi, S. Mukerjee, and J. McBreen (BNL) 

Small Angle X-ray Scattering (SAXS) Investigations of Metal and Semiconductor Nanoscale Size 

Clusters ...................................................................................... B-235 

T.R. Thurston (BNL), J.P. Wilcoxin, and S. Craft (SNL) 
Synchrotron X-ray Scattering Characterization of High Temperature Superconducting Wires ... B-235 

T.R. Thurston, U. Wildgruber, N. Jisrawi, M. Suenaga, Y.L. Wang (BNL), and 

P. Haldar (IGC) 

Beamline X27C 

Tail Studies of a Bonse-Hart-Camera ........................................................ B-236 

Measurements of the Spatial Frequency Dependent Detective Quantum Efficiency of the FUJI 

Image Plate .................................................................................. B-236 

Monochromatic Beam Mammography Studies with an Image Plate Detector ................... B-237 

J.M.Ablett (Kings College), W.A.Caliebe, J.B.Hastings, D.P.Siddons (BNL) 

R.H.Menk, F.Arfelli, D.Chapman, N.Gmur, W.Thomlinson, Z.Zhong (BNL) 

W. Thomlinson (BNL), R.E. Johnston(Univ. North Carolina) E. Pisano(Univ. North Carolina) 

D. Washburn(Univ. North Carolina) C. Burns(Univ. North Carolina) F. Arfelli (BNL, INFN di 

Trieste, Italy), L.D. Chapman (BNL), N. Gmiir (BNL), R. Menk (BNL), Z. Zhong (BNL), Dale 

Sayers (North Carolina State Univ., Raleigh) 

B-26 
X-ray Absorption Near Edge Structure (XANES) of poly(ethy1ene 

terephthalate) (PET) and polyarylate (PAR) 

H. Ade, A. P. Smith, V. Zhuang (NCSU), D.-J. Liu, J. Marty, A. Monisera, and J. 

Chung (Allied Signal) 

We have acquired high resolution XANES spectra of poly(ethy1ene terephthalate) 

(PET) and polyarylate (PAR) which will serve the following dual purpose: (i) they 

will allow us to better understand the spectroscopy of relatively complex polymers 

by revealing subtleties of the XANES due to the higher energy resolution achieved, 

ii) they will serve as model spectra for comparison with spectra to be acquired I rom PET/PAR blends. In the latter study the objective will be to determine the 

respective partial dissolution of these polymers in phase separated polymer blends 

composed of the two polymers as a function of blend composition. The fitted spectra 

are shown in Figure 1, while the chemical structure is displayed in Figure 2. We are 

in the process to assign all spectral features needed to provide the best fit. Several 

of the low intensity features have not been seen previously. Unfortuneately, data 

acquired from other reference samples shows that there is a preferential orientation 

in these samples and hence some polarization dependence. This will complicate a 

fully quantitative analysis of the dissolution in blends of these polymers, but will 

not affect the spectroscopic assignment. 

1. Work supported in part by NSF Young Investigator Award, DMR-9458060 

(HA). We thank H. Chapman for his help during some of the data acquistion. 

X1A 

280 285 290 295 300 305 310 280 285 290 295 300 305 310 Photon Enorgy (ev) Photon Energy (ev) 

Figure 1. XANES spectra of PET and PAR 

a 

Rl 

PET PAR 

Figure 2. Chemical structures of PET and PAR 

X-ray Absorption Near Edge Structure (XANES) of polyethylene 

(PE) and polypropylene (PP). 

H. Ade, V. Zhuang, A. P. Smith (NCSU), and P. Schmitz (Ford Motor Co) 

Polyolefine polymers and polymer blends are extensively utilized in the automotive industry. We are in particular interested in characterizing the morphology of PP 

and PP-co-PE polymer blends in the bulk and near surfaces in order to understand 

its effect on paint adhesion. We have thus acquired XANES spectra of polyethylene 

(PE) and polypropylene PP) with the XI-STXM. Since both polymers are aliphatic 

and contain predominant 1. y saturated bonds the expected differences are very small. 

Only the relative ratio of C-'C and C-H bonds should be slightly different in these 

materials. The XANES spectra as acquired with the X1-STXM are shown in Figure 

1. PE has clearly a double peak near 288 eV, and additional structure above 290 

eV, while the respective regions in PP are much more rounded and smooth. We are 

not aware of any work in which the double peak feature in PE has been o b served 

previouslyl. These spectra were acquired from an area about 30 microns square 

and shoul therefore represent an average of micro-crystalline regions in the PE. 

Nevertheless, the PE spectrum might exhibit some polarization dependence related 

to preferential orientation of the material due to sectioning rather than be representative of an isotropic material. The spectral features near 285 eV are only partly 

due to imperfect I-zero normalization which is confined to this energy range. It also 

reflects a low concentration of double bonds in these materials, possibly caused by 

radiation damage. The spectral differences observed make us hopeful to be able to 

study the polymer blends of interest with the X1-STXM. 

1. Work supported in part by NSF Young Investigator Award, DMR-9458060 

(HA). We are grateful to R. Spontak for sectioning these materials. 

X1A 

PE Absorption Spectra 

I 

0.5 

0.0 

280 285 290 295 300 305 310 280 285 290 295 300 305 310 

Photon Energy (eV) 

Figure 1. XANES spectra of PE and PP 

Photon Energy (eV) 
CARBON IMAGING AND CARBON-XANES MEASUREMENTS tQ 

00 

ON AN INTERPLANETARY DUST PARTICLE. 

Sasa Bajt (U. of Chicago), Henry N. Chapman (SUNY at Stony Brook), George 

J. Flynn (SUNY at Plattsburgh), and Lindsay P. Keller (MVA Inc.). 

The nature and distribution of carbon in interplanetary dust particles (IDPs) are 

important because IDP carbon has been proposed as a major source of pre-biotic 

organic material on the early Earth (I) and may have been equally important on the surface of early Mars (2). Both the abundance and the types of carbon in IDPs 

have exobiology implications. 

An N 12 pm chondritic-porous IDP L2008F4) was embedded in sulfur and miscanning transmission x-ray microscope (STXM) at beam-line X1A. High resolution 

images of an IDP section were taken at energies above and below the carbon K-edge. By taking differences in the logarithm of the intensity at each pixel, images of the 

carbon density were obtained. The C-mapping indicated that the section contains 

an estimated 34 vol. % of carbon. 

The bonding state of carbon can be inferred from the x-ray absorption near-edge 

structure (XANES). Carbon-XANES spectra, shown in Fig. 1, were obtained at 

four locations on the IDP section, identified as having high carbon concentrations. 

In most areas the spectra showed three pre-edge resonances, although one region 

showed no peaks. The three peaks are T* resonances due to carbon double or triple 

bonds. At least two distinct phases of carbon were identified. 

Supported by NASA (Grant No. NAGW-3651\, the NSF (Grant No. BIR9419574) and the DOE (Grant Nos. DE-FG02-89ER60858 and DE-FGO2- 

92ER14244). 

crotomed into thin sections, N 80 nm t 6 ick. The sections were analysed using the 

f; . E. Anders, Nature 342, 255 (1989 . G. J. Flynn, Lunar Planet. Sci. X IV, 493 1993). 

XIA 

~. 

g -0.2 

Ill 

Patch p 3 

- 111 Ill 

-0.2 ........................................ 

260 270 280 290 300 U 260 270 280 290 300 

Energy (eV) Energy (eV) 

Figure 1. Carbon XANES spectra of four regions on a ultratomed section of an IDP. The spectra have been vertically displaced for clarity. 

X1A Phase-retrieval x-ray microscopy via Wigner-distribution deconvolution. 

Henry N. Chapman (SUNY at Stony Brook) 

The microdiffraction plane of a scanning transmission x-ray microscope (STXM) 

contains a mixture of diffraction and holographic information. By collecting a microdiffraction pattern at each point in a scan of a specimen it is possible to phase 

the patterns, as has been described by Rodenburg and Bates 1). It has been shown 

bright-field images collected as a function of detection position is the convolution 

forming lens. This is the first demonstration of the method using x rays. 

Experiments have been carried out at XlA, using the CCD-STXM as previously 

described (2). The data presented here were recorded at a wavelength of 3.2 nm, 

using a zone-plate that has a numerical aperture of 0.036 at this wavelength. 

A microdiffraction data set from a sample consisting of 0.5-pm latex spheres was collected. The incoherent bright-field image and retrieved phase image are shown 

in Fig. 1, where (a) represents the incoherent bright-field, measuring the intensity 

transmission of the specimen and (b) shows retrieved phase image, displayed with 

black = -2.1 rac, white = 0.7 rad. Scalebar is 1.0 micron. Another data set of a sigle 

latex sphere was also collected and deconvolved, and a line from the resulting phase 

image is plotted in Fig. 2. The theoretical phase is also plotted on this graph. As can be seen, the phase measurement agrees quantitatively with theory. The estimated 

errors of the measurements are 0.1 radian in phase and 4% in amplitude. However, 

further analysis has shown that greater accuracy can be achieved (an error of 0.03 

radian in phase) by utilising a greater proportion of the vastly overdetermined 

data set. The result is that the phase of the zone-plate pupil is also determined. 

Hence the method offers a highly accurate way of measuring x-ray optical constants, gives quantitative microscopic images, and can be used as a very sensitive way to 

characterise x-ray optics. 

that the complete data set (which is equivalently the set o i! all coherent dark- or 

of the Wigner distribution function (WDF) of the specimen wit h that of the probeRodenburg and R. H. T. Bates, Phil. Trans. R. SOC. Lond. A 339, 

Chapman, C. Jacobsen, & S. Williams, Rev. Sci. Instr. 66, 1332 

' Suiported by the NSF (Grant No. BIR-9419574) and the DOE (Grant No. DEFG02-89ER60858). 

Poslllon bm) 

Figure 2. Plot from an image of the retrieved phase of the complex transmission of a single latex sphere. Also shown 

is the theoretical phase retardation. 
DARK-FIELD X-RAY MICROSCOPY OF IMMUNO-GOLDHenry N. Chapman, Chris Jacobsen, and Jenny Fu (SUNY at Stony Brook) 

The methods of immuno-labelling make visible the presence of specific antigens, 

proteins, genetic sequences, or functions of a cell. With visible-light microscopy, 

such as confocal fluorescence microscopy, labelled whole cells can be examined at a 

resolution approaching 0.25 pm, whereas electron microscopes can image labelled 

thin section at much higher resolution. X-ray microscopy bridges the gap between 

light microscopy and electron microscopy, in that cells can be viewed at resolutions 

about five times better than the best confocal light microscopes, free of artifacts 

due to sectioning or dehydration. In x-ray microscopy, dark-field imaging has been 

shown to be an ideal way of imaging colloidal gold (I). The dense, sub-resolution, 

colloidal gold particles scatter strongly and can be detected with high contrast in 

the dark-field mode. Colloidal gold is a common label used in electron microscopy. 

Thus, the huge literature of well-documented labelling protocols can be applied 

directly to x-ray microscopy. 

1. This sample 

has also been examined in a transmission electron microscope $TEM).Comparison 

of the STXM and TEM images shows that the DF image is almost entirely due 

to scattering from the labels whereas the BF image shows contrast mainly due 

to the absorption by the carbon of the cell. The apparent diameter of a labelled 

microtubule in both the STXM DF and TEM images is about 60 nm, and labels 

separated by 70 nm can be easily resolved. 

1) H. N. Chapman, C. Jacobsen, S. Williams, and J. Fu, Ultramicros. (accepted . I; upported by the NSF (Grant No. BIR-941957) and the DOE (Grant No. D 4 - FG02-89ER.60858). 

Images of immunogold-labelled fibroblasts are shown in Fi . 

Figure 1. (A STXM dark-field image, and (B) STXM bright-field image, of a 

tubulesof the cell. The bright-field image is a map of the absorption, due mostly 

tocarbon, whereas the dark-field image is a map of the scattering, primarily from 

the label. The cell was prepared by K. Hedberg, University of Oregon. 

fibroblastlabel 1 ed with silver-enhanced 10-nm immunogold, attached to the micro- 

(0 

Inner Shell Spectroscopy and Imaging of a Subbituminous Coal I X1A 

G.D.Cody, R.E.Botto (ANL), H.Ade (NCSU), S. Behal, M.Disko (Exxon) and 

S.Wirick (SUNYSB) 

Inner-shell microspectrosopy has been used to provide in-situ microanalysis of organic and inorganic constituents within Wyodak subbituminous coal (APCS No.2). 

Two specimens were prepared, one loaded with Cazt and the other rinsed in HCL. 

Carbon NEXAFS spectroscopy was used to determine the chemical structure of 

liptinitic and huminitic macerals. Liptinite was characterized by an abundance of 

alphatic carbon, evident by the intensity of absorption assigned to the transition 

from carbon's 1s orbitial to a mixed valence/Ryberg state; a low concentra$on of 

aromatic carbon, evident by low-intensity absorption associated with a 1s- a transition; and an appreciable quantity of carboxylic functionality, evident through a 

relatively intense absorption associated with a 1s- a * transition due to C=O. The 

huminite exhibits fine structure indicative of an abundance of both aromatic and 

aliphatic carbon. The presence of polyhydroxylated aromatic carbon and carbonyl 

associated with carboxylic acids is also clearly indicated. In addition to carbonaceous heterogeneities, chlorine-rich inclusions were also identified. These were observed to strongly absorb in the energy range near 270eV corresponding to Cl's 2s 

absorption edge. The inclusions are anticipated to be inorganic chlorides, precipitates which formed following the rinse in dilute HCL. Imaging and spectroscopy on 

the calcium's 2p absorption edge reveals that the chloride's cation is not calcium, 

although calcium is detected in the huminite of the Cazt loaded coal. 

C-NEXAFS: Resinlte Inclusion 

C Is - n* 

0.4 

0 

0.2 0 

280 215 200 295 300 

0V 

280 285 290 295 300 

eV Figure 2. C-NEXAFS spectrum of 

liptinite. Not: the minimal intensity 

of the 1s- absorption band near 

285.5eV and the very intense mixed 

valence/Rydberg absorption band near 

288eV. 

Figure 1. C-NEXAFS spectrum of huminite. Intense bands associated with aromatic, hydroxylated a~~matic carbon, 

and aliphatic carbon are clearly evident. 
4d 

W 

0 The Application of Soft X-Ray Microscopy to the In-Situ Analysis 

of Sporopollenin/Sporinite in a Rank Variable Suite of Organic Rich 

Sediments 

X1A X1A Miscibility of poly(ethy1ene terephthalate) (PET) and polyarylate 

(PAR) in PET/PAR polymer blends. 

D.-J. Liu, SA. Lui (Allied Signal), V. Zhuang, H. Ade (NCSU), A. Monisera, J. 

Marty, and J. Chung (Allied Signal) 

We have acquired images and oint spectra from PET PAR polymer blends 

50/50). The morphologies of the PET/PAR 75/25 and PET/PAR 50/50 polymer 

blends are shown in Figure 1. In general, the domains become smaller as the 

PAR concentration is rising. This suggests that mixing gets facilitated and the two 

polymers become more miscible at the larger PAR concentrations. Point spectra 

acquired from the respective phases when compared to model spectra of PET and 

PAR' indicates directly that the PAR gets progressively dissolved in the PET and 

PAR concentration increases. A careful analysis of the data should allow us to 

provide a quantitative description as a function of blend composition. This kind of 

measurement and problem can be uniquely addressed with the X1-STXM, since soft 

x-ray XANES microscopy can provide the chemical sensitivity and spatial resolution 

necessary to make observations that go beyond merely mapping of morphology of 

these blends. 

1. H. Ade, A. P. Smith, V. Zhuang, D.-J. Liu, S.-C. Lui et al., this activity 

with different overall compositions [PET/PAR 75/25, PET/ 1 AR 63/37, PET/PAR 

report. 

9458060). 

2. HA acknowledges support from NSF (NSF Young Investigator Award, DMRC-NEXAFS: Sooroaollm 

F 

C 

B 0.01 

0.28 

216 280 286 290 206 DO0 506 

eV - 5 pm 

Figure 1. The C-NEXAFS spectra of sporinite/sporopollenin from samples A-F. 

With increasing maturity in the coal samples there is an increase in the intensity of 

Is- T * near 285eV indicating either an increase in aromatic or olefinic carbon. 

Figure 1. X-ray micrographs at a photon energy of 285.3 eV of PET/PAR 75/25 

(left) and PET/PAR 50/50 (right). 

li 
Morphologies of Ternary Polymer blends studied with X-ray Microscopy 

Figure 1. Left: Micrograph acquired at 299 eV. Both LDPE and Kration appear 

relatively dark. Right: Micrograph acquired near 285 eV. LDPE is very transparent 

and appears bright. 

X1A Development of a Cry0 Scanning X-Ray Microscope. I X1A ~~ 

J. Maser, C. Jacobsen, A. Kalinovsky, J. Kirz, A. Osanna, S. Wang (SUNY at 

Stony Brook) 

Imaging of biological objects in x-ray microscopes is limited by radiation damage 

to the sample. This limits the spacial resolution obtainable from these samples and 

the number of images that can be taken from a specific sample area. The latter 

is important for spectrally resolved imaging and 3D reconstruction. Cryo electron 

microscopy has shown improved structural stability of frozen hydrated samples. To 

take advantage of this, we are currently developing a cryo-scanning transmission 

x-ray microscope (cryo-STXM) which is designed to image frozen hydrated objects 

at a temperature of below -160' C. In order to allow us reconstruction of a 3D 

image of an object, cryo-STXM is designed to allow tilting of the sample in excess of +/ - 60'. Unlike existing x-ray microscopes, the cryo-STXM is designed to be run 

at a vacuum of M lo-' torr. This should allow good thermal insulation of the cold 

sample from the environment, help to reduce thermal drifts, and lead to acceptably 

low contamination rates. Also, the absorption of x-rays in air is avoided. 

This eliminates image noise due to variations of x-ray absorption in ambient 

helium and should make it possible to use the full spectral range of the water window 

for imaging, Le. wavelength between 2.4 nm and 4.5 nm. Most notably, spectral scans with wavelengths around the nitrogen absorption-edge - at a wavelength of 

3.1 nm - should be possible. A first test of the mechanical motions and the detector 

of cryo-STXM have been performed at X1. Full cryo operation is about to start. 

vacuum chamber 1 

,-- sample position 

B) piezo driven 

flexure stage for holder high resolution 

C) stepping-motor 

driven linear stage = 

for large field 

anticontaminator 

Figure 1. Setup of cryo-STXM. The x-ray beam is perpendicular to the paper 

plane. The sample is held in the cryo holder (A). An airlock allows change of sample 

without breaking the vacuum. A stepping-motor driven coarse scanning stage(C) 

is used for changing between different sample areas, and to switch to an alignment 

pinhole and a resolution test pattern. High resolution scans of smallsample areas 

are performed by a pieeo-driven flexure stage (B). 
w 

w 

References: 

1. J. Vanderhoff, J. Park and S. El-aasser, in "Polymer Latexes", ACS SympoSpringer Verlag, New York, 1992 p. 208 

and 230. 

X1A Structured Latex Particles Characterized by Scanning Transmission 

X-Ray Microscopy 

Figure 1. Scanning transmission x-ray micrographs of hollow latexes obtained at 

x-ray energies of 288.4 eV on the left and 286.0 eV for the image on the right. Each 

image is 7.5 m wide x 7.6 m high. 

I Interferential differential phase contrast on X1A STXM I X1A I 

F. Polack (LURE, Orsay, France), D. Joyeux (IOTA, Orsay, France) 

Scanning transmission X-ray microscopes (STXM) normally provide pure absorption images. There is however a growing interest for phase microscopy, mainly 

for its expected ability to reduce the damages from energy absorption. We have 

set-up an experiment on the X1A STXM, in order to produce a differential phase 

contrast. It consists in illuminating the sample with two, mutually coherent close 

spots, instead of one. They produce in the objective and detector planes, a pattern 

of several fringes the position of which is sensitive to object phase gradients or steps as shown on figure 1. If the detector is shaped in order to detect the flank of one 

fringe, the set-up is able to detect hase steps between the spots or phase slopes. 

Young slits, with aspect ratio 11, are used to produce 2 spots separated by one 

diffraction radius (0.05 pm). The observed fringe profile is close to the theoretical 

Sinc'(x) modulated cosine profile and the measured 0.8 contrast of the central fringe 

is in good agreement with the value estimated from beam-line data. In a preliminary 

experiment (94), images of polyimide slabs, 1.1 pm thick, w.5 pm wide, w.9 pm 

spacing were made with and without the phase sensitive detection. Figure 2 shows an average of such image profiles over 90 lines. Due to the strong absorption of the 

object, the phase effect consist in the small overshoot visible on side b. 

In an attempt to visualize pure phase contrast at the wavelengths available with 

X1A STXM, an object made of polystyrene beads in water was chosen this year. 

Unfortunately, despite the injection of a large helium flow into the microscope, the 

absorption of the residual oxygen near K edge was so large that no image could be 

detected. Nevertheless, a new two-element solid state detector for the fringe shift 

detection, was successfully tested. 

Figure 2. Signal profiles of STXM images of polyimide slabs, 1.1 pm thick, 

part of a polyimide zone plate (courtesy G. Schmahl, Goettingen) : a) energy transmission (without phase sensitive detection), b) energy and phase sig- nal with phase sensitive detection. Profiles are averaged on 90 image lines. 

aFigure 1. Fringe shift observed in the 

detector plane as a phase step was moved 

through the double focal spot. 
Semi-Quantitative Determination of the Lateral Orientation in Kevlar 

Fibers using X-ray Linear Dichroism Microscopy X1A 

Spectrum of Matrix Spectrum of Precipitate 2.5- 3.0 

Micro-chemical Characterization of Methylene Diphenyl Diisocyanate 

(MDI) based Polyurethane Foams using X-ray Microscopy 

-0.5; -0.5; 

280 290 500 310 320 280 290 300 310 320 Photon Energy (eV) Photon Energy (eV) 

X1A 

Figure 1. Absorption spectra of the precipitates and matrix in an MDI based 

polyurethane foam. 
Fd I X1A I W ,+ 1 XANES Spectroscopy of Polyurethane Model Polymersers ~~ 

A. P. Smith, H. Ade (NCSU), and E. Rightor (Dow Chemical) 

Previous urethane foam characterization, particularly of mechanically detremental small precipitates, utilized electron energy loss spectroscopy (EELS) and x-ray 

absorption near edge structure spectroscopy'''. The interpretation of 

the acquired data is facilitated of spectra from model polymers and 

molecular analogues. Due to the intrinsically lower radiation damage and better 

energy resolution achievable with XANES as compared to EELS, we have acquired 

spectra of several model polymers of significantly higher quality than previously 

achieved, thus aiding greatly in data interpretation. Four polymers have been studied, each representing a different aspect of methylene diphenyl diisocyanate (MDI) 

polyurethane foam chemistry3 : (i) polyurea, a model for urea functionalities, (ii) 

BM, a model of the 'hard' urethane segments, (5) BO, predominantly a long chain 

olyether linked by urethane functionalities which models the poly01 functionalities, 

iv) B2, a combination of BM and BO serving as a model of the MDI foam itself. 

1. S. G. Urquhart et al., J. Polymers. Sci, B.: Polymers. Phys. 33 (1995) 1592. 

2. A. P. Smith, H. Ade and E. Flightor. 'Micro-chemical Characterization of ...), 

p. 

this activity report. 

9458060) and the Dow Chemical Company. 

3. C. P. Christenson et al., J. Polymers. Sci, B.: Polym. Phys. 24 (1986) 1401. 

4. HA acknowledges support from NSF (NSF Young Investigator Award, DRMPolyurco Spectrum BM Spectrum 201' , ' .- ' ' 1 

J 00 , 3 -. 280 285 290 295 3W 305 310 

Pnolon Energy (09 

280 285 200 295 3CQ 305 310 

PhO!O" cnsqy (e9 

80 Spectrum 82 Speclrum 

Figure 1. XANES Absorption spectra of four polyurethane model polymers. 

I High resolution Fresnel zone plates for scanning x-ray microscopy I X1A I 

S. Spector, C. Jacobsen (SUNYSB), and D. Tennant (AT&T) 

We have fabricated high resolution Fresnel zone plates for use in the Scanning 

Transmission X-ray Microscope (STXM) at X1A. A Fresnel zone plate is the principle focusing optic in the STXM and usually determines the spatial resolution that can be achieved by the microscope. A Fresnel zone plate consists of a series of 

concentric rings or zones and its resolution is approximately equal to the outer zone 

width. We have fabricated zone plates with outer zone widths as small as 30 nm, 

and preliminary results indicate improved resolution compared to the 45 nm zone 

plates used previously. The efficiency of the new zone plates is 4.3% at 3.1 nm; 

this is less than the theoretical efficiency of 10.5%, but it is still high enough for 

practical use in the STXM. 

The zone plates have been fabricated in up to 180 nm of Ge using a trilayer 

technique similar to one described previously [l]. The pattern is written using a JEOL JBX-6000FS e-beam lithography system. This machine can deliver 100 PA 

into a 5 nm spot, but it is not optimized for circular structures. We believe some of 

the loss in efficiency in our zone plates is due to variations in the line width caused 

by the current method of drawing circular structures. We are working to improve 

the method used to draw circular structures by modification of the manufacturer's 

software. 

[l] D. Tennant, et all J. Vac. Sci. Technol. B 8, 1970 (1990). 

Figure 1. Scanning electron micrograph 

of the 30 nm outer zones of the zone 

plate. 

Figure 2. High resolution x-ray transmission image of a test pattern taken in 

the STXM at X1A.The image was made 

using a zone plate with a 30 nm outer 

zone width. 
~~ 

X1B Autoionization into the Is-' continuum following excitation of doubly 

excited neutral states in CO and Nz 

B. Kempgens, H.M. Koppe, A. Kivimiiki, M. Neeb and A.M. Bradshaw (FritzHaber-Institut der Max-Planck-Gesellschaft, Berlin) 

h- g 

E '- 

5: 

a 

4- 

v 

v1 

z .. 

A strong energy dependence of the vibrational fine structure on the C 1s and N 

1s main photoelectron lines has been observed for CO and Nz at excitation energies 

47 eV above the core ionization threshold. The branching ratio of the individual 

vibrational components changes markedly and higher vibrational quanta are excited 

compared to spectra measured at a few eV higher photon energy. This behaviour 

suggests that the Is-' state is not reached by direct photoionization but via an intermediate state. Indeed, for both molecules doubly excited 2h2p states have 

recently been observed about 4 eV above threshold in high resolution absorption 

spectra. These neutral states, which are energetically in the continuum, can populate the Is-' final state by valence autoionization. The two-step autoionization 

rocess causes the variations in the vibrational fine structure seen in the spectra P a) and (c) of the Figure. The autoionization process competes with the resonant 

Auger decay of the 2h2p states into ionized valence final states. 

2345 4567 I 

hv=433.3 eV 

14 15 16 17 21 22 23 24 

Kinetic energy (eV) Kinetic energy (eV) 

Figure 1. The vibrationally resolved C 1s and N 1s main photoelectron lines of CO 

and Nz measured at two different excitation energies. The photon energies in (a) 

and c), which are 5.2 eV and 6.6 eV, respectively, higher than the core ionization 

thres 6 old, correspond to the double excitation region in the absorption cross section. 

Note the enhancement of higher vibrational levels. The photon energies in (b and 

(d) correspond to values of 16.6 eV and 23.4 eV, respectively, above threshol d and 

here the vibrational fine structure is less prominent. t+ 

VI 

Deexcitaion Spectroscopy of RblCso I X1B 

B.Kessler, L.Baumgarten, J.Liining, S.Cramm, W.Eberhardt (KFA), and 

J.E.Fischer (UPenn) 

We studied the well-characterized orthorhombic phase of RblC60 [l] by direct 

photoemission and resonant photoemission using the absorption from the Cls core 

level into the second unoccupied state (LUMO+1) of the fullerene compound. Figure 1 shows the valence-band region of RblC60 recorded with a photon energy of 

396.2eV. The main peak-at a binding energy (BE) of about -15eV is due to photoemission from the Rb-4p levels. The positions of the features at BEs up to about 

-10eV correspond to the occupied bands of c60 (see inset). The emission at the 

lowest BE of about -2.5eV is attributed to the highest occupied molecular orbital 

(HOMO) of c60, the peak at about -4eV corresponds to the HOMO-1. Both or- bitals are r-derived for the undoped fullerenes but may undergo hybridization upon 

alkali doping. 

A comparison of valence-band spectra for different photon energies is given in 

Figure 2. The contribution of the Cls photoemission with 2nd.order photon energy (-2eV < BE < EF has not been subtracted from the spectra. An intensity 

and 285.6eV. In this photon-energy range a transition from the Cls core level into 

the second unoccupied state of the c60 (LUMO+1) can take place. This excited 

state causes a resonant enhancement of the HOMO-1 photoemission by a deexcitation process which cannot be observed off-resonance. A possible resonant intensity 

increase of the HOMO is hidden by the 2nd order peak, but obviously no dramatic 

effect can be detected for the other c60 derived features. The contribution of the deexcitation process to the photoemission therefore demonstrates that the LUMO+1 

level in RblCao is not completely delocalized. Q] Electronic Properties of Novel Materials: Physics and Chemistry of Fullerenes an Derivatives, H.Kuzmany, J.Fink, M.Mehring, S.Roth (eds.), World Scientific, 

Singapore (1995). 

enhancement close to B B =-4eV can be observed for photon energies between 285.3 

Rbl %o 

hvn396.ZeV 

hv (e") 

286.00 

285.75 

285.60 E 285.50 

285.35 

z 285.30 

285.05 

h 

2 li 

f 

-16 -12 -8 -4 E, 

BINDING ENERGY (eV) 

Figure 2. Resonant photoemission from 

C60. Rbi Go. 

-16 -1 2 -8 -4 
w 

Q) 

Klnolic onorgy (oV) 

X1B Electronic decay spectra of doubly excited neutral states in CO and 

N2 

Figure 1. Decay spectra of CO and Nz excited around the C 1s and N 1s ionization 

thresholds at 296.1 eV and 409.9 eV, respectively. The decay of the doubly excited 

states above threshold show strong resonant features at 268 eV for CO and at 380 

eV for Nz, as can be seen in (b) and (d respectively. The spectra in (a) and (c) 

show resonant-enhanced structures whic are attributed to the decay of additional 

2h2p states immediately below threshold. The leading triple peak structure in all 

spectra is due to direct photoemission of the outer valence orbitals. The valence 

photoemission spectra of CO and Nz are shown at the bottom as dotted lines. 

I Surface Critical Behavior of the betal-beta2 Phase Transition in V2H I X2A I 

R. Paniago, P.C. Chow, H. Reichert, S.C. Moss (University of Houston), S. Schmid, 

T.H. Metzger, J. Peisl (University of Munich), K.S. Liang (Exon) 

We have studied the influence of the surface on the betal-beta2 phase transition 

of V2H using depth-resolved grazing incidence X-ray diffraction AGID). This second 

order transition is characterized by the change of the interstiti occupancy of the 

hydrogen atoms from ordered to random between (101) planes, which can be determined from the hydrogen-induced distortions of the host lattice. First, using in-lab 

bulk x-ray diffraction, an effective bulk critical exponent beta was determined to be 

0.34 +- 0.04 at the specific concentration of 0.49 (H/V, as determined from hydrogen 

weight-loss measurements). At a slightly higher concentration prior data yielded 

beta=0.17. The present crystal traverses a 2-phase region which in turn may com- plicate the study of the critical behavior. Our GID results indicate an increase of 

beta from 0.37 to 0.77 in the near-surface region of the crystal and an ordered phase 

persisting up to 8 Kelvin above the bulk critical temperature, as opposed to a bulk 

ordered phase that persists 1.0 Kelvin above the phase boundary. As a signature 

of the presence of a two-phase region we do not observe critical diffuse scattering. 

However, the surface does show a distinct disordering behavior compared to the 

bulk, and similar to an ordinary transition. Since a superficial oxide layer was kept 

to avoid hydrogen losses on heating, its induced fluctuating interaction constants 

(quenched surface disorder) at the surface do not modify the overall behavior of the 

hydrogen ordering. Prelimlnary data on the ordering kinetics indicate a somewhat 

sluggish behavior at the surface which is driven by a more rapid bulk ordering. This 

shows that the ordering process is predominatly driven by the bulk. * Work supported by a Max Planck Research Award (S.C.M. and J.P.) and by the NSF on DMR92-08450. R.P. thanks CNPq (Brazil) for support. 

Figure 1. Vanishing of the (3/2 0 

3/2) superlattice peaks at incidence an- gle alpha-i equal to the critical angle for 

temperatures below and at Tc. 

Fig. 2 

- 

Rodumd I 04 Tomponturo IT -T$Te 1 0" 

Figure 2. Double log-plot of the su- perlattice integrated intensity as T approaches Tc. 
The Synthesis of a Novel 2-Dimensional Antimony Sulfide, using 

Synchrotron Imaging Plate Data [C4HlON]2[Sb8S13].0.15H20 and 

its Structure Solution 

K. Tan, J. Parise, Y. KO (SUNY Stony Brook), and A. Darovsky (SUNY Buffalo) 

Recently series of main group sulfide compounds, for example, thioantimonates, 

thiostannates and thiogermanates have been synthesized using hydrothermal techniques. Specifically, the thioantimonates show a remarkable variation of stoichiometries and structures. A novel antimony sulfide, [C,HlON]2[Sb8Sl3].0.15H20 was synthesized hydrothermally and its structure was determined from a small single 

crystal ( 20 mpm 20 mpm 60 mm ) using Synchrotron Imaging Plate Data. The 

new compound consists of centrosymmetric Sb16S264- planar clusters. Each cluster 

is connected to four others through two edge-sharing and two corner-sharing SbS3 

pyramids, forming an extended sheet. The protonated pyrrolidine molecules reside 

between the parallel stacked sheets. The structure is triclinic (space group P-1 with 

a=6.929(2 , bd6.747 2) , c=17.976(4) A, a=94.84(1 , b=95.41(1) and =125.28(1). 

86ER45231. We thank the National Science Foundation ( DMR 94- 13003) for 

support. 

Acknow 1 edgments: SJ ork at X-3a supported under 2J .S. DOE contract DE- FG02- 

Parise, J. B. ; KO, Y. Chem. Mater. 1992, 4, 1446. 

Wang, X. Eur J. Solid State Inorg. Chem.1995, 32, 303 

X3A1 X3A1 The Use of Imaging Plates for Accurate Electron Density Studies at Helium Temperatures * 

R. Bolotovsky, P. Coppens, A. Darovsky and V. Kezerashvili (Chemistry, SUNY 

at Buffalo, and SUNY X3 beamline at BNL) 

Short-wavelength synchrotron radiation, helium cryogenic techniques and the 

oscillation method, have been combined in electron density studies, using imaging plates as detectors. To test the potential and limitations of imaging plates 

in accurate work, a simple transition metal complex, chromiumhexamine hexacyanochromium, Cr(NHa)6Cr(CN)6 was selected for study. X-rays at wavelengths 

of 0.656 A and 0.394 A are obtained at the sideways X3A1 diffraction station [l]. 

A specially designed antiscattering device [2] allows use of a cryostat in conjunction with imaging plates. The imaging plate data were reduced using the program 

HIPPO based on the seed-skewness peak integration method [3]. The electron 

density analysis was erformed by Fourier methods and with the aspherical atom 

multipole formillism E]. The deformation density maps clearly show bonding features and illustrate the advances made since the first charge density study with 

synchrotron radiation, performed ten years ago at CHESS on the same compound 

[I] A. Darovsky, I. Meshkovsky, P. Coppens, J. Synch. Rad. 2, 77 (1995 . [2] A. Darovsky, R. Bolotovsky, P. Coppens, J. Appl. Cryst. 27, 1039 (1994). (31 R. 

Bolotovsky, M. A. White, A. Darovsky, P. Coppens, J. Appl. Cryst. 28, 86 (1995 . 

Lee, P. Coppens, Acta Cryst. B42, 359 (1986). 

[SI. 

[4] N. K. Hansen, P. Coppens, Acta Cryst. A34, 909 (1978). [5] F. S. Nielsen, 12 . 

Figure 1. The sheet structure of [C4HlON 2[Sb8S13].0.15H20. Each Sb16S264- 

sharing SbS3 pyramids. The connections between clusters are also made by fused - semicubes. Two crystallographic unique pyrrolidine molecules, which are assumed 

to be protonated, are within the parallelogram- shaped apertures and between the 

sheets, which are stacked parallel to [loo]. 

* Research supported by the National Science Foundation (CHE9317770). Research 

carried out in pat at the NSLS at BNL which is supported by the US- Department of 

Energy, Division of Materials Sciences and Division of Chemical Sciences. The SUNY X3 

beamline at NSLS is supported by the Division of Basic Energy Sciences of the U.S. DOE 

cluster is connected to four others throug h two edge-sharing and two cornerE 

-a (DE-FG02-86ER45231). 
* ... ; 

The structure of TMA-CuGS-2, 

(Cuo.44Geo.ssSz.z3)4( Ge&)3.6( CH3)4N from Synchrotron/Imaging 

Plate Data. * 

J. B. Parise, K. Tan, Y. KO, (SUNY, StonyBrook), A. Darovsky (BNL) 

Single crystals of (cu0.44 Geo.~ieS2.23)4(Ge4S~)3.6(CH3)4N (TMA-CuGS-2) were 

synthesized hydrothermally. The structure was determined using data collected 

from 20 pm crystals at X-3A1. 

This compound consists of Ge4Slo4- adamantine clusters, corner-sharing with 

MS, units (M = Cu,Ge; x = 3 or 4>, forming an open framework with tetramethylammonium cations residing within four intersecting channels. Disorder in the 

M-sites causes the composition of the framework to deviate from the ideal stoichiometry, G~o.~~Mo.z~S~, realized when M = Cu and x = 4. This is consistent 

with results obtained from electron-probe microanalysis. The structure refinements 

were carried out in space group I-43d with cell parameter a=20.629 1) A. F 

in the synchrotron imaging plate experiment. Trial refinements in space groups R3 

unique weak reflections of the type hhl, 2h+l=4n2, forbidden in 1-43 d , were detected Ourteen 

and I213 suggest t 1 eir origin in either weak ordering or multiple scattering effects. 

Figure 1. 

* Work at Stony Brook supported by NSF grant DMR-93-1003. 

1 Synthesis and Structure of Novel Aurates: SrAuzO4 and BidAuzOg. I X3A1 

J.-H. Park, K. Tan, J. B. Parise (SUNY Stony Brook), A. Darovsky (X3, BNL) 

The new compound SrAuzO4 was prepared by solid-state reaction of SrOz and 

A11203 in a welded gold tube at lOGPa and 1200C using a uniaxial split-sphere 

high-pressure apparatus (USSA 2000) as described previously. [l] Because of the 

small size of the single crystals (10 x 10 x 20mm3), synchrotron x-ray diffraction 

was used to collect data for structural determination and refinement. Two sets of 

imaging plate data with different exposure times were collected at room temperature. An oscillation angle of 25 degree with 5 degree overlap between consecutive 

frames, was used for the data collection. SrAuzOl (141/a, a = 6.161(2) A, c = 

10.144(2) A and Z = 4) is isostructural with CaAuzO4. [2] It consists of cornerlinked Au04 square planes and distorted SrOs dodecahedra (Figure 1). The AuO4 

units are stacked in a staggered fashion in columns along [loo] and [OlO] to produce a 

square-antiprismatic arrangement of oxygens between them. The intersection of the 

columns form cavities containing the SrOB units. Another aurate Bi4Au209, also 

prepared at the same conditions, has been studied using the synchrotron/imaging 

plate data. It has a basic structure similar to LaaAuz09. [3] Its superstructural 

properties are under investigation. 

Work at StonyBrook supported by NSF grant DMR9413003. (1) Gasparik, T. High Pressure-High Temperature, 1993, 25, 245. (2) Park, J.-H.; Parise, J. B. Chemistry of Materials, 1995, 7, 1055. (3) Ralle, M.; 

Jansen, M. J. Alloys Comps. 1994, 203, 7-13. 

Acknowledgements: 

Figure 1. Projection of the structure of SrAuzO4 along [loo]. The Auo4 units and 

Sr ions are represented by the planes and circles. 
I Pair-density Function Analysis of PEOX/Si02 Composite Materials I X3A1 

H. D. Rosenfeld, R. L. Harlow and I. A. David (DuPont) 

It has been our goal to prepare composite materials of an organic polymer and an 

inorganic glass in which the molecules of each component were intimately entwined 

within those of the other. Such a structure would be a molecular interpenetrating or semi-interpenetrating network, depending on whether the polymer molecules 

were cross-linked or linear, respectively, and would consist of only one phase. A 

combination of poly(ethy1oxazoline) (PEOX) with Si02 in a ratio of 33/67 appeared 

to meet the "one phase" criterion when the composite was characterized by a wide 

variety of techniques. However, in-house wide-angle diffraction scans on composites 

with varying PEOX/Si02 ratios proved difficult to interpret since there was little 

change in the broad peaks of these amorphous materials. 

It was then decided to study this material using the pair-distribution technique 

to see if we could distinguish a true one-phase composite from a two-phase physical mixture. Wide angle diffraction patterns were collected on beamline X3A1 at a wavelength of 0.6535 A in a low-resolution mode consisting of a receiving slit 

and a scintillation counter. Data was collected on four samples: pure SiOz, pure 

PEOX, a physically mixed sample of PEOX and Si02 in a 33/67 ratio, and the 33/67 

PEOX Si02 composite material. Background was measured and appropriately subtracte d from each pattern. After further corrections for Compton scattering and 

absorption effects, the resulting patterns were Fourier transformed to yield the PDF 

patterns. An analysis of all four patterns quickly showed that the distribution of 

the densities of the distances between atomic pairs in the 33/67 PEOX/Si02 com- posite corresponded to that calculated for a single phase structure but not to that 

calculated for a two-phase structure. On the other hand, the distribution derived 

for the physically mixed composite clearly corresponded to that calculated for a two-phase and not a single-phase structure. 

X3A1 Charge Density Studies Using High Energy Synchrotron Radiation 

at 20K * 

H. S. Sheu, C. C. Wang, C. R. Lee, Y. Wang(Chem., National Taiwan Univ., 

Taipei), A. Darovsky, R. Bolotovsky and P. Coppens(SUNY Buffalo and BNL) 

We have performed charge density studies at NSLS, using imaging plates(1P) 

and a Displex cryostat CT20 equipped with a anti-scatter device' at the fixed angle 

X3A1 station. A wavelength of 0.394A from a Si(200) monochromator was used. 

The reduction on the absorption and the extinction should be apparent. Seventyone frames of diffraction data are collected on IP for a LiB306 crystal at 20K, the 

maximum sinO/X is 1.77 A-'. A total of 4451 unique observed reflections is resulted 

after averaging the equivalents, the interset agreement index is 0.051. The "seedskewness" method' is used for the intensity data rocessing. Thirty-one frames of 

data,are collected on a Fe(phen)z(NCS)Z crystal~.08x0.08x0.04mm) at 20K, the 

data resolution is up to 1.036A-'. A total of 4211 unique reflections is yielded after 

averaging the equivalents, the interset a reement 0.054. One hundred and thirtyfive frames of data are collected on a CofC404)(HzO)z crystal(O.lx0.1x0.1 mm) at 

20K. There is an apparent phase transition between the room temperature and 20K. 

When the crystal is cooled below 200K, substantial peak broading is observed. It 

is still so at 66K. But at 20K, peaks are sharpening, however not as sharp as those 

at room temperature. 

1. A. Darovsky, R. Bolotovsky and P. Coppens, J.App1. Cryst.,1994,27,1039. 

2. R. Bolotovsky, M. A. White, A. Darovsky and P. Coppens, J. Appl. 

Cryst.,1995,28,86. 

* The SUNY X3 beamlineat NSLS is supportedby the Divisionof Basic Energy Sciences 

of the US Department of Energy (DE-FG02-86ER45231). We wouldlike to acknowledge 

the National Science Council of ROC for financial support of this work. 
I A Novel Antimony Sulfide Templated by Dimethylammonium * I X3A1 I 

KEMIN TAN, YOUHGHEE KO, JAEHYUN PARK and JOHN. B. PARISE Dept. 

of Earth and Space Sciences, SUNYSB, Stonybrook, NY11794 ALEX DAROVSKY 

SUNY X3 beamline 

Hydrothermal synthesis has produced a new open framework antimony sulfide, 

[CzHsN [Sb4S7]. A small single crystal of this compound, 0.020 x 0.03 x 0.04mm 

in size, h as been used in the x-ray experiments for structure analysis. Two sets of 

data were collected with different rotation axes measured at the X- 3A1 beamline 

using imaging plates as area detectors. This was done to ensure a complete set of 

unique data were collected. 

The structure of the sulfide ( S.G.: Cmca., Cell parameters: a = 9.9704(7) A, b 

= 11.652(2) A and c = 25.979(3) k) consists of inter-locking double chains, which 

are formed from two Sb4S7 single chains through S-S bridges. Protonated dimethylamine molecules reside within double chains' openings, which can be treated as 18-membered rings. The structural building units of this material are very similar 

to that found in the open framework antimony sulfides templated by piperazinium 

[I] and enthylenediamomnium [2]. 

1 Parise, J. B. & KO, Y. Chem. Mater. 4(1992)1446-1450. I1 2 Tan, K., KO, Y. & Parise, J. B. & KO, Y. Acta Cryst. C50(1994)1439- 1442 

br 

Draw Induced Crazing in PET Fibers: Temperature Effect I X3A2 

Paul Harney, Benjamin Chu, Alan Kennedy, Roger Leach (Dept. of Chemistry, 

SUNY at Stony Brook; DuPont Central Research and Development) 

On going study of the morphological changes in fibers by synchrotron x-ray scattering has been enhanced by the design and construction of a miniature draw unit. 

On-line drawing of fibers is better suited for comparison to industrial processing 

techniques. This method appears ideal for obtaining the long exposure times necessary for fiber scattering volumes which tend to be small. 

Use of the draw unit for SAXS and WAXS experiments has provided better precision of morphological changes as the temperature is raised above the T,. Between 

30°C and 5OoC, the typical cross SAXS pattern showed an initial increase in the 

meridional spike as seen in Fig 1. WAXS data, shown in Fig 2 remained unchanged 

through these temperatures. At about 6OoC, SAXS intensity began to decrease, and was marked by an increase in orientation observed in the WAXS data as evident 

from an increase in equatorial intensity and corresponding decrease in the meridional intensity. By 7OoC little evidence of crazing was seen in the SAXS patterns, 

and the meridional WAXS peak began to show increased asymmetry. Assuming a baseline of amorphous material for subtraction, the remaining WAXS pattern 

appeared similar to the mesomorphic form' of PET. The formation of the mesomorphic form of PET seemed to correspond with the disappearance of the craze 

SAXS pattern. 

[l] Parravicini, L. Leone, B. Auriemma, F. Guerra, G. Petraconne, V. DiDino, 

G. Bianchi, R. and Vosa, 

R. J. Appl. Poly. Sci.52, 875-885 (1994). 

T-IOC 

T-4OC 0. T-IOC 

+ T-60C 

P61C 0 T-l0C 0 T-8OC A T-90C 

+ v T4SC 

VA + 

P 

I'I'l.1' 

0.0 0.2 0.4 0.6 0.8 1.0 0 1 2 3 4 I (nm9 I (nu..') 

Figure 1. Structure of the antimony sulfide templated by dimethylammonium. Figure 1. Meridional SAXS from PET Figure 2. Meridional WAXS of PET 

fibers: Temperature effect. fiber: Temperature effect. 

* Work at Stony Brook supported by NSF grant DMR-93-1003 . .- 
1 On-line WAXS of PET Fibers during Draw Induced Crazing I X3A2 I 

....'..,.'....'...-- 

.: 20000 - '. 

.. .. 

il:. 16000 - 

io000 5ooo;L; 

0- 

Paul Harney, Benjamin Chu, Alan Kennedy, Roger Leach (Dept. of Chemistry, 

SU NY at Stony Brook, Stony Brook, NY 11794; DuPont Central Research and 

Development, Experimental Station, Wilmington, DE) 

A miniature draw unit was developed to better reproduce fiber processing and 

to facilitate further X-ray scattering measurements of this phenomenon. Unlike 

stretching a fiber, the sample is constantly being replenished in the drawing process. In conjunction with intense synchrotron radiation, this allows for the longer 

exposure times dictated by the small fiber scattering volume (- 1 x lo7 pm ' for a 1 mm beam diameter). 

WAXS analysis was performed to correlate crystallization with crazing in amor- phous PET fibers. A phase transition was observed at the natural draw ratio 

(NDR), (approximately 2.15). Fig. la and b show the meridional and equatorial profiles, respectively, for the WAXS patterns for draw ratios: 2.1 and 2.2. 

Draw ratios below the NDR appeared to represent mostly the amorphous phase with minimal organization as observed in DR=2.1. In the strain-hardening region, 

above the NDR (DR=2.2 , the intermediate or mesomorphic phase' developed as 

the craze microstructure correlates with the onset of the mesomorDhic form during 

is typical for drawing PE !r below the Tg. It, therefore, seems that breakdown of 

strain hardening. 

G. Bianchi, R. and Vosa, R. J. App2. PoZy. Sci. 52, 875-885 (1994). 

" 

[l] Parravicini, L. Leone, B. Auriemma, F. Guerra, G. Petraconne, V. DiDino, 

12000 J 

0 DR-1.1 

1iooo - 10000 - DR-1.1 

' ' ' ' ' ' '. . '. '. ' '. ' ' ' ' ' '. ' - 

0000 - 8000 - 3 7000 - c: 

5 5000 - 

ZOO0 

1000 

01 

0 01.1.1 

DR-1.1 

WAXS Measurements of 6,6 Nylon Yarn Structure 

A.D.Kennedy, B.S.Hsiao, R.A.Leach (DuPont Central Research, Wilmington DE), 

P.Harney, B.Chu (SUNY at Stony Brook) 

I X3A2 

Structure change of a drawn, semi-crystalline, 6,6 nylon yarn was monitored insitu during tensile deformation (1 to 30% strain) at 30 to 225OC on beam-line X3A2. 

Yarn was continuously taken from a package and strained over heated pins between 

two rolls moving at different speeds. This steady state process provides continu- ous sample replenishment and removes time constraints inherent in conventional 

stretching experiments. 

The 2D WAXS patterns were fit to a three phase structure model: crystal + both 

oriented and isotropic amorphous. Concentration of each was indexed by 2D integration. Substantial crystal melting occurred at 100 to 2OOOC with a concomitant 

increase in oriented amorphous content but little change in isotropic amorphous. 

Crystal melting was reduced at higher strains. Above 2OO0C, crystal content remains constant but oriented amorphous is converted to isotropic. Observations are 

strikingly consistent with solid state NMRl which shows three levels of N-H mo- bility above Tg: fixed H-bonds in crystals, both isotropic and a hindered motion 

in amorphous regions; the fraction of material with isotropic motion increased as 

temperature approached the melt. 

High image quality (ten clear reflections) allowed crystallographic analysis. Collapse of the two strong equatorial reflections into a single peak, the so-called Brill 

transition, began at about 100°C and was complete at 160. Our analysis confirmed 

that the transition results from anisotropic crystal thermal expansion. Inter-chain 

spacing within the H-bonded sheets remains essentially constant while inter-sheet 

spacing increases sharply, forming a metrically hexagonal structure. Expansion is 

attributed to CH2 libration within the crystals[l]. 

[l] H.Miura, J.Hirshinger and A.D.English, Macromolecules, 1990, 23, 2153 and 

2169 

1w 

Rdl 

Figure 1. Cylindrical co-ordinates for 

B02-Fl8: Calculated model (solid) vs 

data (dashed). Figure 2. Crystal index vs temperature. 
*. . , ,. 

Valence-specific resonance diffraction with imaging plates applied 

to the mixed-valence 

enzyme model complex Mn'VL(p0)2(pMeC02)Mn''' (MeC02)2, 

L = 1,4,7-trimethyl-1,4,7-triazacyclononane * 

X3A2 

I I' 

I. 

V. Kezerashvili, A. Darovsky and P. Coppens (SUNY/Buffalo and BNL) 

The title compound (Fig. 1) is a catalytically-active model compound of the 

catalase enzymes. Single-crystal imaging plate data have been collected at a number 

of wavelengths in the vicinity of the absorption edge. Given the known structure, 

the anomalous scattering factor f' of the two Mn atoms can be determined sitespecifically. A shift of the absorption edge of Mn(1V) relative to that of Mn(II1) is 

evident in Fig 2. In addition, the pre-edge feature visible in the fluorescence curve is 

evidently based on a transition at Mn(1V) rather than Mn(II1 , as only the former 

The experiment shows that information on the electronic structure of transition 

metal atoms can be obtained rapidly by resonance scattering. The results have 

implications for time-resolved studies of electron transfer. 

shows f' fine structure at the energy of the pre-edge feature ( 4 ig. 2). 

Figure 1. 

* Research carried out in part at 

the National Synchrotron Light Source at 

Brookhaven National Laboratory which is 

supported by the US DOE, Div. of Materials Sciences and Div. of Chemical Sciences. The SUNY X3 beamline at NSLS is 

supported by the Division of Basic Energy 

Sciences of the US Department of Energy 

(DE-FG02-86ER45231). Support of this 

work by the National Science Foundation 

(CHE9317770) is gratefully acknowledged. 

i 

t -1 

-1 

6 1520 6540 6560 6580 

d Energy 

Figure 2. 

X3A2 Self assembly of block copolymer Poly(oxyethy1ene-oxypropyleneoxyethylene) L64 in o-xylenelwater system 

Li-Zhi Liu, Vinh-Bao Buu, Benjamin Chu (Department of Chemistry, SUNY at 

Stony Brook) 

In recent years, there have been a number of studies dealing with the Phonic 

L64 in aqueous or nonaqueous solvents. However, the behavior of L64 at high 

concentrations is not often studied. Therefore, at high concentrations, their colloidal 

behavior is still not very clear. 

In our experiments, we selected a total copolymer concentration of C= 0.617g/mL 

to study the aggregate structures as a function of water-to-EO molar ratio 

(Z=[HzO] [EO]) by synchrotron SAXS at 25OC. 

solving L64 in o-xylene. Then calculated amounts of water were added to each 

sample to get four different water-to-EO molar ratios: 0.9, 1.4, 1.7, 2.1. We an- nealed the samples for a few days before the SAXS experiments. 

The graphs obtained are shown below. For the samples with Z=O.9 and 1.4, the 

first order peaks are observed but the high order peaks did not appear. For the 

solutions with Z=1.7 and 2.1, besides the main peaks, the SAXS profiles contain 

higher order peaks, with the Bragg ratios of 1: 4'1': 7l/' and 1:3l/' :4'/':7'/' 

respectively, suggesting that the microstructures formed are hexagonal. 

Four so I utions with an initial concentration of 0.617g/mL were prepared by dis900 

800 

9 

? 700 

d 

.- 0 

u) 

600 c - 

3 

- 500 

400 

300 I t I I I I 

0.0 0.5 1 .o 1.5 2.0 2.5 

qw-9 

Figure 1. SAXS profiles of L64/Cyclohexanol samples. 
SAXS Study of 

the Miscible Blends of Semicrystalline Poly(viny1idenefluoride) and 

Semicrystalline Poly( 1,4Butylene Adipate) 

loo 7 

X3A2 

80 

% 

.- b - 00 P 

d 

*$ 40 

c1 

u 

9 

20 

0- 

0.0 0.2 0.4 0.0 0.0 1.0 1.2 1.4 

, q (urn.') 

Figure 2. SAXS curves of PBA (filled 

ho- 

- 

- 

- 

- 

[SAXS Studies of Surfactant - Cationic Gel Products 

E. Sokolov, F. Yeh, B. Chu, S. Starodubtsev, A. Khokhlov (Dept. of Chem., SUNY 

Stony Brook; Physics Dept., Moscow State University.) 

SAXS studies of slightly crosslinked gels of poly-(diallyldimethylammonium chloride - acrylamide) random copolymer cationic gels in aqueous solution have been 

performed at the X3A2 beamline at NSLS. The gels with various degrees of 

crosslinking and diallyldimethylammonium chloride (DADMACl - acryl amide 

also exposed to dilute solutions of anionic surfactants - sodium alkyl sulfates. Gel 

complexes with sodium decyl (SDCS dodecyl (SDS), tetradecyl (STS), and hexThe d-spacing of the crystals did not depend on the degree of crosslinking, instead 

it decreased with increasing DADMACl content. Crystal-like structure disappeared 

below a threshold value for DADMACl content. Formation of crystal-like structures 

occurred at surfactant concentrations well below saturation in the external phase. 

When the surfactant concentration exceeded the critical micelle concentration in 

the external phase the diffraction phenomenon disappeared. 

(AAm) contents were studied. Scattering curves are presented in h ig 1. Gels were 

adecyl (SHS sulfates exhibit crystal- k 'ke structures for the gels with high contents 

of DADMA A 1. Sodium octyl sulfate complexes showed semicrystalline properties. 

DADMACl mlmt 

low, 

9w* 

- 

...... 1% 

5 W. 

2% 

..... 

.,.. 

-- ai 

1 

0.0 0.5 1.0 1.5 2.0 2.5 ~ 

c -SDCS (C 

0 I 2 3 4 5 6 7q,nm-l 

mil Firrure 2. SAXS mofiles of surfactantgeT complexes fo; various surfactants. 

Figure 1. SAXS profiles of plain gels Charge density loo%, crosslinking ratio 

with 1/200 crosslinking ratio. 1/200. 
4d 

A 

A 

Ravi Verma (DuPont and Virginia Tech.), Herve Marand (Virginia Tech.) and 

Benjamin Hsiao (DuPont) 

Poly(ary1 ether ether ketone) [PEEK] is a semicrystalline polymer which exhibits 

the double endothermic melting behavior. A "low endotherm" is observed in a 

differential scanning calorimetry scan at about 5-15C above the crystallization temperature in addition to the high endotherm at about 340C. It is also established 

that the low endortherm develops linearly with log of crystallization time. We have 

monitored the development of the low endotherm and subsequent meltin via real 

time small angle X-ray scattering (SAXS) using synchrotron radiations tbeamline 

X3A2). SAXS data was analyzed via a novel combination of the correlation and 

interface distribution functions. Our analysis indicates that the development of the 

low endotherm is accompanied by the formation of secondary lamellar stacks. The 

relative amount of the secondary lamellar stacks is estimated by the normalized 

height of the first minimum in the interface distribution function (see Figures). 

Our analysis indicates that the (1) amount of secondary lamellar stacks increases 

linearly with annealing time during crystallization and (2) decreases substantially 

at temperatures corresponding to the low endotherm during melting. 

This work was supported by the National Science Foundation under DMR 91- 

2004 93-57512 and also by the DuPont Central Research and Development. 

Morphological Changes During Secondary Crystallization and Subsequent Melting in Poly(ether ether ketone) as Studied by Real Time X3A2 

Small Angle X-Ray Scattering 

Figure 1. Morphological variables during 

heating at 2.5C/min of a PEEK sample 

isothermally crystallized at 300C for 1 

hr. The total scattering invariant (Q) 

is plotted against the left abscissa. The 

height of the first minima (g1,x) in the 

interface distribution function is plotted 

against the right abscissa. 

4.~-Irlm. 

101 

tm 

."--.-h.ak.rl.n,lu 

ld I I6 3 an 4 0 

wmrr) 

Figure 2. Morphological variables during 

isothermal melt crystallization and subsequent annealing at 316C. The height 

of the first minima is proportional to 

the relative amount of secondary lamellar stacks in the semicrystalline polymer. 

X3A2 

Interaction of Polyelectrolyte Gels of Poly (Diallyldimethylammonium Chloride) with Surfactants 

Fengji Yeh, and Eugene L. Sokolov, Benjamin Chu (Department of Chemistry, 

SUNY at Stony Brook, New York 11794-3400) 

From fluorescence studies of excimer formation of Sodium Dodecyl Sulfate (SDS) 

and pyrene in both gel phase and external aqueous phase, structure of surfactant aggregates in a polyelectrolyte network was found to be different from that of micelles 

in water'. In order to study the structures inside the gels, small-angle X-ray scattering (SAXS was used to investigate the polyelectrolyte-surfactant complexes of the 

MAC1). 

Fig. 1 shows the SAXS profile of PDADMACl gel in the presence of SDS with 

concentration in the external phase below the SDS critical micelle concentration 

(cmc). The sharp peaks demonstrate that the SDS molecules form a highly ordered 

structure inside the gels. Fig. 2 shows the effects of changing the charge contents of 

the polyelectrolyte gel from 100% charged to neutral. The diffraction peaks of the 

complex decrease with gel charge content. There is no structure formation observed 

in neutral gel. 

[l] Filippova, O.E.; Makhaeva, E.E.; Starodubtzev, S.G. Polymer Science 1992, 

34, 602. 

SDS and t h e cationic network of polydiallyldimethylammonium chloride (PDAD01234507 

q (nm9 q (nm.9 

Figure 1. SAXS profile of PDAD- Figure 2. SAXS profile of various charge 

MAC1(100%, 1/200) in SDS. contents of PDADMAc1(1/200) in SDS. 
I 

12 7 

: 

I4- 

SEARCH FOR STRUCTURAL PHASE TRANSITIONS IN I RbxsnCm * 

0000 T=295K A f 

00 

-0 

A -60 00 

0 

A 

-4s . % AA ' 

$wo 1 ,L A AAA AA A AA AA AA 

0, 

G.M. Bendele, P.W. Stephens (SUNY Stony Brook), and J.E. Fischer (U. Penn) 

We have carried out an x-ray powder diffraction study of a phase-pure sample 

of the superconducting alkali-fulleride Rbs c60 with measurements at T=20K, 33K, 

295K, 460K and 575K. Its structure is well known to be cubic (space group Fm3m) 

with a=14.43k at room temperature. Rietveld refinements of this model clearly 

yield unit occupancy for the octahedral Rb site and 95% occupancy for the tetrahedral Rb site resulting in a total stoichiometry of Rb2.90C60. 

Given the extremely large thermal B-factor of the octahedral Rb, we have 

searched for evidence of any off-center displacement of this atom. Refining structural 

models with different amounts and directions of displacement from the (1/2,0,0) position does not change the quality of fit, as long as the amount of displacement is 

small enough for the B-factor to remain positive (fig. 1). Since this amount decreases smoothly as T decreases, we conclude that the Rb atom is indeed located 

in the center of the octahedral site. 

Previous %b NMR measurements show 3 lines below T=443K, although the 

structural model has only 2 different Rb sites. We do not see any structural change 

associated with the disappearance of the third NMR line. 

Finally, comparing spectra at T=20K and T=35K our data excludes any structural change associated with the superconducting transition of Rbs C60 at Tc=29K. 

2- 

1- 

0:. 

A -66 

.I oooo T=20K 

*O 

00 A 

B*L 

Os0 AA -60 

AA~A bAu UA'*i 00 

I TDAECso: Low-temperature structural studies. * I XGTl 

G.M. Bendele, P.W. Stephens (SUNY Stony Brook), D. Mihailovic, and P. Venturini (Univ. of Ljubljana) 

Recent reports [l] have shown differences in AC susceptibility of the organic 

ferromagnet TDAE-Cso below 20K depending on the thermal history of the sample 

above 30K. It was sug ested [l] that merohedral ordering of the buckyballs in the 

known monoclinic cell721 is responsible for this. 

We have recorded x-ray powder diffraction patterns of this sample using 

1.15A selected by double Si(ll1) monochromator and Ge(ll1) analyzer. Room 

temperature data shows that the sample contains at least one phase other than 

quenched to T=77K and then warmed to T=90K (top of fig. 1) and (ii) slow-coole 

over 8 hours to T=90K (bottom of Figure 1). 

the known [2] structure of TDAE-C~O. We then compare data with the sample 

be assigned to the known [2] structure of TDAE-Cso (indishow no difference at all. However, there are clear differences 

elong to this structure, some highlighted in fig. 1. We con- clude that the effects discussed in [l] occur in a phase other than the one known 

until now. We are planning further studies to investigate the nature of this phase. 

1 D. Mihailovic et al., Science 268, 400, 1995 

121 P.W. Stephens et al., Nature 355, 331 \1992] 

5 6 7 8 9 10 

Figure 1. Intensity vs. 20 

* Work at the SUNY X3 beemline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FGO286-ER45231). Research st SUNY is supportedby the NSF 

under grant DMR-92-02529. 

* Work at the SUNY X3 beamline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). Research st SUNY is supportedby the NSF 

under grant DMR-92-02529. 
tb I Structure of CSO polymerized at low pressure. * I X3B1 I 

G.M. Bendele, P.W. Stephens (SUNY Stony Brook), A.M. Rao, P.C. Eklund (Univ. 

of Kentucky, Lexington), and A. Moravsky (Russian Academy of Sciences) 

We have performed x-ray diffraction measurements on a C60 polymer transformed 

at low pressure. X-ray patterns were collected of the pellet-like sample held both 

parallel top of fig. 1, upper) and perpendicular (lower) to the diffraction vector k. 

rection of compression has selected a preferred orientation. Accordingly, we present 

data collected on samples chopped up (bottom of fig. 1, diamonds). We see that 

this spectrum is a combination of the reflection and transmission spectra. 

We cannot index all peaks in this spectrum to any one phase. However, the three 

unit cells of the known phases of pressure-transformed C60 [l] do index all peaks. 

Using the published [l] atom positions we have fitted this spectrum to a mixture of 

the 3 phases, varying only scale factors. The resulting fit would not be considered 

good in a true powder experiment, but is sufficient to conclude the three-phase 

nature of this sample. The fit is the solid line (bottom of fig. 1 with peak markers 

and tetragonal T, 20%) phases. The uniaxial applied stress evidently forces the 

in experiments with true hydrostatic pressure. 

This c \ early shows that the sample has an anisotropic structure and that the diindicating peak ositions for the rhombohedral (R, 20%), ort 1; orhombic (0, 60%) 

fullerene molecu P es close enough to form bonds at lower applied forces than are seen 

[l] M. Nunez-Regueiro et al., Phys. Rev. Lett. 74, 278 (1995) 

, , ,,,I I , , I,, I I , II I1 I I 

6 1, II a ,I I 111 I, I I I I,, I1S11 It , I, 111 If, 0 I I II I 11' IO 111:1Y1111 I I1 

0.04 0.08 0.12 0.16 0.20 

Figure 1. Intensity vs. sin8/X 

~ 

* Work at the SUNY X3 beamlineis supportedby the Divisionof Basic Energy Sciences, 

U.S. Dept. of Energy (DEFG0286-ER45231). Research at SUNY is supported by the NSF 

under grant DMR-92-02529. 

I Powder diffraction of alka1i:alkaline-earth fullerides. * I X3B1 I 

G.M. Bendele, P.W. Stephens (SUNY Stony Brook), T. Yildirim (NET), and J.E. 

Fischer (U. Penn) 

We have studied the phase diagram of AP1Ba3--.CBo (A = K, Rb, Cs) using xray powder diffraction. The data was recorded using 0.7A selected from Si(ll1) 

monochromator and Ge(ll1) analyzer. 

We have found stable phases of ABazCeo-for A = K, Rb and Cs. These phases 

have the same fcc structure (space group Fm3m) as ASCeo. The alkali atoms occupy 

the large octahedral sites at (1/2,0,0 with an accordingly large thermal parameslightly less than integer occupancy. Raman spectroscopy shows evidence of a charge transfer of 5 electrons per buckyball and none of these samples are superconductors. 

Figure 1 shows a Rietveld refinement (R,,=9%) of this model for RbBazCao. 

ter, while Ba occupies the tetrahedra 1 sites at (1/4,1/4,1/4) with an indication for 

5 10 15 20 25 30 35 40 

Figure 1. Intensity vs. 28 

- 

* Work at the SUNY X3 beamline is supported by the Division of Basic Energy Sciences, 

U.S. Dept. of Energy (DEFG0286-ER45231). Research st SUNY is supportedby the NSF 

under grant DMR-92-02529. 

,- . .. .. 
I Detection limit for polymorphs in drugs using powder diffraction. * I X3B1 I STRUCTURE OF SODIUM-PARA-HYDROXY-BENZOATE BY 

R. POWDER DIFFRACTION * E. Dinnebier, P. W. Stephens (SUNY Stony Brook), S. Byrn (Purdue Univ.), 

V. Andronis and G. Zografi (U. Wisconsin, Madison) 

The qualitative and quantitative detection of small traces of polymorphs plays a 

very important role in pharmacology, We have used mixtures of the Q and 7 phases 

of the anti-inflammatory drug indomethacin (C19HlsC1N04) as a test case. 

First we determined the previously unknown lattice parameters of Qindomethacin as a = 18.2883(8)8, b = 25.3866(6)8, c = 5.4927(4)8, p = 94.592'. 

From the extinction rules we can deduce P21 or P21/m as possible space groups. 

The number of formula units per unit cell is probably 6. 

We investigated mixtures of 10, 1, 0.1, 0.01 and 0.00 weight-% Q phase in 7. 

0.1% CY could easily be detected with its five strongest peaks. It is difficult to 

quantify the detection limit below O.l%, since the starting 7 from which these 

samples were prepared evidently contained a trace of a. Further work with samples 

of higher purity is underway. The 120) peak of the CY phase and the (010) (0.15% 

of strongest peaks) peak of the 7 p i, ase are shown in the scans below. 

X3B1 

3000 

2000 

1000 

800 -J 

3200 1 

A n 0.1% a 

2800 - 

2400 

6.10 8.20 6.30 6.40 6.50 6.60 6.70 

y201 

Figure 1. 

* 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 was supported by the 

-a NSF under grant DMR92-02529. 

R. E. Dinnebier, P. W. Stephens (SUNY Stony Brook), M. Pink, and J. Sieler 

(Univ. of Leipzig, FRG) 

The crystal structure of Sodium Para-Hydroxy-Benzoate NaCTHs09 has been 

solved ab initio from powder data. The lattice parameters in P21 are a = 

16.0367(1)8, b = 5.37604(6 8, c = 3.63307(3)8, p = 92.867(1)'. There are two 

About 400 peaks were extracted for use in the direct method program SIRPOW 

with which it was possible to determine the entire structure. Of the two possible 

space groups, P21 and P21/m, only the first allowed a satisfactory fit to all the 

intensities. The relatively high R,,-factor of 19.0% is due to severe anisotropic 

micro-strain in the material. The FWHM of neighboring peaks can differ by a factor 

of up to 3.5. The implementation of a strain model including sufficient refinable 

parameters in a Rietveld program is under progress. 

The structure consists of layers of distorted NaO6 prisms and phenol rings perpendicular to the layers pointing up and down. The Na-0 distances vary between 

2.26 and 2.888. These oxygens are coordinated by 3 Na and 1 0 in the form of a 

distorted tetrahedron. The molecular structure is held together by van der Waals 

forces between the phenyl groups of different layers and additional H-bridge bonding 

between the oxygens (0-0 distance of 2.948). The layered structure perpendicular 

to the a axis is shown in fig. 1. 

formula units in the unit ce ll . 

WWLL 

Figure 1. 

* 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 was supported by the 

NSF under grant DMR92-02529. Research at UL was supported by the DFG and the 

Fond der Chemischen Industrie in Germany. 
I Structures of CsHsOA (A = K, Rb, Cs) by powder diffraction * I X3B1 I 

R. E. Dinnebier, P. W. Stephens (SUNY Stony Brook), M. Pink, and J. Sieler 

(Univ. of Leipzig, FRG) 

The crystal structure of industrially important C~HE~OK has been solved ab initio 

from powder data. The lattice constants for CeH60K in Pna2l are a = 14.1005(1)81, 

b = 17.9126(1)8L1 c = 7.1650(4)A. 

X-ray powder diffraction patterns were recorded using 1.15A (A= K, Rb) and 

0.7A (A=Cs) from double Si(ll1) monochromator and Ge(ll1 analyzer. About 

it was possible to detect the positions of A and some candidate 0. In the next stage, 

we searched for the center of gravity locations of the phenyl rings by replacing them 

with diffuse pseudo-atoms having the same number of electrons but a rather high 

temperature factor. It was possible to Rietveld-refine such structures to Bragg-Rfactors around 30%. Grid searches on the rigid body orientation of the phenyl ring 

led to refinable coordinates for all of the non-hydrogen atoms Rwp = 16.1%, RF = 

The very unusual structure provides a flagrant violation of Pauling's rule that 

atoms of a given type should have similar coordination. Note that one set of potassium atoms sits at the center of an oxygen octahedron, while the others are linked 

to three oxygens and one phenyl ring. 

300 peaks were extracted for use in the direct method program SI k POW with which 

7.3% for 855 reflections). CeHbORb and C6H1joCs were foun 6 to be isotructurd. 

STRUCTURES OF C6HsOK - 2 CsHsOH and C6HsOK. 3 CsHsOH 

BY POWDER DIFFRACTION 

t 

X3B1 

* Work at SUNY X3 beamline is supported by the Division of Basic Energy Sciences, 

US Dept. of Energy (DE-FG0286-ER45231). Research at SUNY was supported by the 

NSF under grant DMR-92-02529. Research at UL was supported by the DFG and the 

Fond der Chemischen Industrie in Germany. 

U 

\I b\ I 
*- , 

FRUSTRATED PHASE SEPARATION IN THE "INTERMEDIATE" FCC PHASE OF KlCso. * X3B1 

10 15 20 25 30 35 40 45 

20 (deg.) 

Figure 1. 

* Work at the SUNY X3 beamline is supported by US DOE (DE-FG0286-ER45231), at 

Budapest by OTKA grants, at Lausanne by the Swiss National Foundation for Scientific % Research, and at Stony Brook by the NSF. 

Crystal Structure Analyses Using Ab Inito Powder Diffraction Techniques: The Failures 

R. L. Harlow, Z.-G. Li, N. Herron and E. M. McCarron (DuPont) 

There has been a great deal of interest in the determination of crystal structures 

using ab initio powder diffraction techniques. While the successes of the technique 

have been well publicized, its failures have, unfortunately, been condemned to eternal darkness. We have recently had a number of failures which we are continuing 

to investigate in the hopes of eventually understanding why these cases proved so 

difficult. HAlF4, a potential catalyst in the CFC-substitution program, has yet to 

be solved. Its powder diffraction pattern is characterized by broad peaks which 

made the unit cell determination rather difficult. We have used electron diffraction 

to verify two of the axes and have even attempted to use the 2-D intensity data 

to solve the structure in projection. We have also obtained a pair-density function 

(data from X17b which shows that there may be some unusual AI-A1 distances, 

hedrally coordinated, neutron diffraction data (HFBR-HRNPD) which essentially 

has verified the unit cell and symmetry, and acid-base information which suggests 

that the proton is locked up in some fashion. Despite the intense effort and all of 

this indirect structural information, we have been unable to solve the structure. 

Mo205(OMe)2, a model compound for interaction of methanol with Mo03-type 

catalysts, IS an example of a different type. The unit cell determination appeared 

to be straightforward despite the fact that the peaks were broad and the location of 

the Mo atom was readily determined from a Patterson map. Six oxygen atoms were 

subsequently located around the Mo and even the methyl carbons could be seen. 

The refinement of this structure gave an R value of 11%, i.e. the fit between the 

observed and calculated data was very good. Nonetheless, while the structure had 

some chemically reasonable features, it also had some which were not reasonable: 

e.g. 0-Mo-0 angle of 60 deg. A neutron powder diffraction dataset (HNRPD) was collected on a deuterated sample: the model developed from the x-ray data does 

not fit this pattern at all (R = 50%). 

The large peak width is the common feature of the synchrotron patterns of these 

two compounds. This feature not only makes the process of determining the unit 

cell more difficult but it also blurs the high-angle peaks apparently making it much 

more difficult to solve the structure. We are continuing to use electron diffraction 

techniques in the hopes of obtaining starting structures for these two phases. We 

would like to solve and refine these two structures in order to understand exactly why they proved to be so problematic. 

solid-state A1 N nR R data which clearly indicates that all of the A1 atoms are octa- 
. ,_ - 

PROBLEMATIC STRUCTURE 

DETERMINATION OF A SMALL ORGANIC MOLECULE VIA 

AB INITIO POWDER DIFFRACTION TECHNIQUES. 

~3~1 

7 0 

N\ 

II 'NII rn II 

O I 

H 

I The Structure of PrPdSb via Resonance Scattering I X3B1 I 

A. Mehta (U. of Nebraska), P. W. Stephens (SUNY Stony Brook), S. K. Malik 

(TIFR), and K. A. Gschneidner, Jr. (Ames Lab) 

The crystal structure of PrPdSb is thought to be composed of triangles of PrPd-Sb. An X-ray powder diffraction pattern was collected at a wavelength of 1.15 & (upto d of 0.9 A) in parallel beam diffraction geometry with a double Si(ll1) 

incident beam monochromator and Ge(ll1) analyzer before a Na-I detector. Lattice 

symmetry was found to be hexagonal with a = 4.58801(1) 8, and c = 7.80300(4) 

A. The extinction space group symmetry was determined from a tabulation of the 

observed Bragg reflections. Extinction conditions suggest two possible structures for 

PrPdSb: one in which Pd and Sb randomly occupy the basal sites of the triangles 

disordered structure - PBammc) and the other in which Pd and Sb are ordered 

Refinement of these two structures yield very similiar fits (RBragg = 9.9% for 

the disordered structure versus RBragg = 10.0% for the ordered structure). The 

similarity of the fits is not suprising in the light of the fact that x-ray scattering cross section of Pd is very similar to that of Sb. 

A second diffraction pattern was collected 20 eV below the Pd K-edge (Le. at 

24.325 KeV) where the scattering contrast between Pd and Sb was enhanced by 

5 e due to resonance effects. Refinement of the two structures using resonance 

data indicated a slight preference for the ordered structure (RBragg = 8.8% versus 

RBragg = 9.2%). The structural fit was, however, still unsatisfactory so difference 

Fourier synthesis (DFS) maps were generated to determine the cause of the misfit. 

The,DFS maps show that the basal sites of the Pr-Pd-Sb triangles (Le. Pd and 

Sb) are split by 0.3 A. Using DFS maps in conjunction with Pd-Pd and Sb-Sb 

distances determined from structures of Pd and Sb metals, a new structure for 

PrPdSb is proposed. In the new structure, Pd and Sb are ordered in the Pr-Pd-Sb 

triangles but the triangles themselves are disordered. The disorder can be best 

represented by a random mixing of two types of Pr-Pd-Sb triangles denoted by the 

configuration Sb-Pr-Pd and Pd-Pr-Sb in space group Pea/,,,. Refinement of the 

"locally" ordered structure using the resonance diffraction data yields RBragg of 

7.5%, which is a statistically significant improvement (using Hamilton's R-factor 

analysis) over both the disordered and long range ordered structures of PrPdSb. 

(pci,mc). 

Figure 1. 
Interface Morphology in Lattice-Mismatched (Si,Ge) Thin Films on 

Si * 

1 Structural Ordering in InGaAs/GaAs Superlattices * I X3B1 I X3B1 

Z. H. Ming, Y. L. Soo, S. Huang and Y. H. Kao (SUNY at Buffalo), and K. Stair, 

G. Devane, and C. Choi-Feng (Amoco) 

For a pseudomorphic multilayer structure consisting of thin layers of dissimilar 

semiconductors, it is possible to achieve electronic energy band "tailoring" by a con- trol of strain in the material due to lattice mismatch, and to adjust their electronic 

and optical properties to suit the needs of device applications. When the layer 

thickness of the constituent semiconductors exceeds a critical thickness, the strain 

becomes unstable against lattice relaxation in the layer semiconductors, which usu- ally give rise to disordered structural changes such as formation of misfit dislocations 

and clusters. However, it was discovered in the InGaAs/GaAs superlattices that 

coherent strain can be partly released in the form of structural ordering in a low 

dimension. Our x-ray scattering studies have revealed a lateral thickness modulation in the [110] direction with a quasi-period of 400 A. These x-ray results are also 

in good agreement with direct observation of spatial variation by high resolution 

transmission microscopy (HRTEM). The resultant material may thus be viewed as an MBE grown-in array of quantum wires. Structural parameters pertaining to the 

morphology of interfaces and thickness variations are obtained. The interfaces in 

these superlattices are found to be highly correlated, and the layers all show a high 

degree of crystallinity. Further work is in progress to assess the underlying physical 

parameters which are responsible for the formation of one-dimensional microstructures in superlattices by MBE. A control of these growth parameters wiU be very 

useful for the preparation of arrays of quantum wires for various applications. 

* Research supported in part by DOE under grant DE-FG02-87ER45283. Research 

carried out in part at the National Synchrotron Light Source at Brookhaven National Laboratory which is supported by the U.S. DOE, Division of Materials Sciences and Division 

of Chemical Sciences. The SUNY X3 beamline at NSLS is supported by the Division of 

Basic Energy Sciences of the US. Department of Energy (DE-FG02-86ER45231). 

* Research supported in part by DOE under grant DE-FG02-87ER45283. Research 

carried out in part at the National Synchrotron Light Source at Brookhaven National Laboratory which is supported by the U.S. DOE, Division of Materials Sciences and Division 

of Chemical Sciences. The SUNY X3 beamline at NSLS is supported by the Division of 

Basic Energy Sciences of the U.S. Department of Energy (DE-FG02-86ER45231). 

E 

F 
cn 

KJ 

G. Oszlanyi, G. Bortel, G. Faigel, M. Tegze (Research Institute for Solid State 

Physics, Budapest), P.W. Stephens (SUNY Stony Brook), and L. Forro (EPF Lausanne, Switzerland) 

A general trend is established by comparing the lattice parameters of isostructural 

&C&J (A=K, Rb, Cs) polymers. The remarkably large differences of their physical properties (Ref. 1) can be related to the variation in the orthorhombic b lattice 

parameter through the interchain fullerene separation. 

phase a[A] b[A] c[A] 

KCeo 9.11 9.95 14.32 

RbCao 9.13 10.11 14.23 

CsCao 9.10 10.21 14.17 

COMPARATIVE STRUCTURAL STUDY OF AlCso (A=K, Rb, X3B1 CS) * 

Figure 1 shows a Rietveld refinement of CSCSO (with a small fraction of unreacted c60. The structural model is that published in Ref. 2, which was mangled in last 

years' annual report. The temperature dependence of the unit cell dimensions of 

is shown in Fig. 2, which clearly supports van der Waals bonding along 

the orthorhombic b and c axes, and covalent bonding along a, as determined from 

earlier Rietveld refinements.[2] 

F. Bommeli et al., Phys. Rev. B51, 14794 (1995). 

P.W. Stephens et al., Nature 370, 636 (1994). 

Luminescence Yield and X-ray Absorption Spectra in Doped Semiconductor Nanocrystals * 

::;: 

9.13 

X3B1 

Figure 1. 

* Work supported by Hungarian OTKA 

grants, Swiss Nat'l Foundation for Scientific Research, and US NSF. The SUNY X3 

beamlineis supportedby the US DOE under 

grant DEFG-0291-ER45231. 

14.33 

14.32 

14.31 

9.89 - 

14.26 0 50 100 150 2M) 250 3M) 

TEMPERATURE (K) 

Figure 2. 

* Research supported in part by DOE under grant DEFG02-87ER45283. Research 

carried out in part at the National Synchrotron Light Source at Brookhaven National Laboratory which is supported by the U.S. DOE, Division of Materials Sciences and Division 

of Chemical Sciences. The SUNY X3 beamline at NSLS is supported by the Division of 

Basic Energy Sciences of the U.S. Department of Energy (DE-FG02-86ER45231). 
I X-ray Scattering and Absorption Studies of (In,Mn)As Thin Films I Y9R, I 

Y. L. ,500, Z. H. Ming, S. Huang and Y. H. Kao (SUNY at Buffalo), M. Tanaka 

(University of Tokyo), H. Munekata (Tokyo Institute of Technology), and L. L. 

Chang (Hong Kong University of Science and Technology) 

The advent of 111-V diluted magnetic semiconductors, first successfully synthesized by Munekata et al., offers enormous opportunities for the development of new 

electronic and optoelectronic devices in which some characteristic physical properties can be continuously tuned by an external magnetic field. For a physical 

understanding of this new class of materials and in light of this important device 

potential, we have started a systematic study of the interfacial microstructures and 

local structures in various Inl-,Mn,As films grown on GaAs by molecular beam 

epitaxy. The methods of grazing incidence x-ray scattering, x-ray diffraction and 

extended x-ray absorption fine structure are used, from which the interfacial roughness in the layer structure, changes in lattice constants due to strain and lattice 

mismatch, local environment surrounding the Mn atoms, coordination number, epilayer thickness, and local disorder are determined. Microstructures in MnAs films 

prepared with different first-layer growth conditions are compared. Our measurements indicate that the template effects can cause significant differences in the local 

structures and crystallinity of the MnAs epitaxial layers. Substitution of Mn atoms 

for the In-sites is found in samples either grown at low substrate temperatures (near 

20OoC) or with a low Mn concentration (about 1 atomic percent). These results 

provide the first direct experimental evidence for 111-V diluted magnetic semiconductors obtained by substitutional doping of Mn impurities in InAs. Further work 

is in progress to investigate the possibility of controlled doping in p- and n-type 

materials and the local structures around various magnetic impurities. 

* Research supported in part by DOE under grant DE-FG02-87ER45283. Research 

carried out in part at the National Synchrotron Light Source at Brookhaven National Laboratory which is supported by the U.S. DOE, Division of Materials Sciences and Division 

of Chemical Sciences. The SUNY X3 beamline at NSLS is supported by the Division of 

Basic Energy Sciences of the U.S. Department of Energy (DE-FG02-86ER45231). 

I STRUCTURE OF PHOTO-POLYMERIZED C6i~ * 

P. W. Stephens (SUNY Stony Brook), P. C. Eklund, and A. M. Rao (Univ. of 

Kentucky, Lexington) 

When exposed to ultraviolet or visible light in vacuum, solid films of c60 become insoluble, evidently through the formation of inter-fullerene covalent bonds 

[I]. We have investigated the attendant structural modifications using x-ray diffraction. Films were deposited and exposed to light, and the resulting polymerization 

monitored with Raman scattering separately from the x-ray experiments. The reparameter shrinks continuously with increasing polymerization. We have modeled 

this process as a random network of two types of springs, representing van der 

Waals and covalent bonds, respectively. Quantitative analysis is hampered by the 

(evidently) inhomogeneous light exposure to the rather thick films. Accordingly, we 

will repeat the experiments with thinner films. 

sults clearly show that the solid d 60 film retains its fcc structure, but its lattice 

[l] A.M. Rao et al., Science 257, 955 (1993) 

600 i 

Photopolymerized (1 57 hrs.) 

400 

- 

0 

$ 

g 200 \ 

c 

v) 

c 

Pristine film 0 .- E 

E 400 

B 

I z 

- c 

200 

6 8 10 12 14 16 

20 ["I 

Figure 1. 

* 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 was supported by the 

NSF under grant DMR-92-02529, and at UKy by NSF OSR-9452895. 
THE MICROABSORPTION CORRECTION IN QUANTITATIVE 

ANALYSIS. * 

Peter Stephens (SUNY Stony Brook) and Rani Johnson (East Hampton High 

School) 

In applying powder x-ray diffraction to quantitative analysis of solid mixtures, 

it is generally necessary to correct the measured intensities for microabsorption, 

i.e., the different absorption constants for the various constituents of the mixture. 

While the correction for this effect is well known (Ref. l), it requires knowledge of the 

average grain sizes of each component and their absorption constants. Using tunable 

radiation to vary absorption constants, we can determine the parameters necessary 

to make the Brindley correction directly, without an independent measurement of 

particle size. 

To demonstrate this technique, we prepared mixtures of NIST Standard Reference 

Materials: 102~1% by weight A1203 in Cr203, and collected data at wavelengths 

of 1.54Aand 0.7k. The table below shows that, even for these finely ground powders, the Brindley correction is significant at Cu K,, whereas it is negligible at 

the shorter wavelength. The advantage of synchrotron radiation for these measurements is clear, in that the resolution is not significantly degraded in using shorter 

wavelengths . 

X3B1 

Absorption constant Derived weight 

x Ab 03 c1203 fraction A1203 

1.54A 126 cm-' 912 cm-' 7.5% 

0.7A 12 97 9.2% 

The results are consistent with the Brindley correction for particle sizes of N1,um. 

Clearly this technique could be extended to direct measurements of the particle sizes 

by collecting data at several wavelengths. 

[I] G.W. Brindley, Phil. Mag. 36, 347 (1945). 

* Work at the SUNY X3 beadneis supportedby the Division of Basic Energy Sciences, 

USDoE (DE-FG0286-ER45231). Research at SUNY was supported by the NSF under grant 

DMR-92-02529. 

Kinetic Roughening in Ag Homoepitaxy 

William C. Elliott (University of Missouri-Columbia) Paul F. Miceli (University of 

Missouri-Columbia) Teddy Tse (SUNY-Stony Brook) Peter W. Stephens (SUNYStony Brook) 

We have studied, in situ, the kinetic roughening of the Ag(ll1) and Ag 100) surfaces to relate the height difference correlation function to specific detahs of 

surface kinetic 

These two orientations have contrasting properties; Ag(ll1) growth is dominated 

by the step-ledge diffusion barrier and is multilayer, whereas the Ag(100) surface 

undergoes layer-by-layer growth. X-ray specular reflectivity measurements are used 

to characterize the surface, allowing the rms roughness to be determined at different 

stages of growth. Below 300K for the Ag(ll1 surface, we observe a power law exponent consistent 

with Poisson statistics p=1 2); however, diffusion over the step-ledge barrier bein a smaller exponent. The temperature dependence is in agreement with recent 

computer simulations3 which studied the effect of a step-ledge diffusion barrier on 

eDitaxid growth. The Ag(100) surface is observed to have exponents smaller that 

1 X3B2 

comes significant at 400 d and the growing surface roughens more slowly, resulting 

-\ I tke Ag&lfl) surface. , C. Elliott, P. F. Miceli, T. Tse and P. W. Stephens, Proceedings of the 

4th International Conference on Surface X-ray and Neutron Scattering. To appear 

1. 

- -- in Physica B. 

2. P. F. Miceli, W. C. Elliott, T. Tse and P. W. Stephens, to be published. 

3. Z. Zhang, J. Detch and H. Metiu, Phys. Rev. B, 48 4972 1993). 

Supporting grants: NSF DMR-9202528, DOE DEFG02-86E k 45231, University 

of Missouri 

Research Board. 

ioo io' io2 io3 io 

Thickness (A) 

Figure 1. 
ADSORPTION SITES OF Pb ON Ni (001) AND Cu(OO1) vs. TEMPERATURE * DOMAIN GROWTH X3B2 IN THE SUBMONOLAYER EPITAXIAL 

SYSTEM Pb ON Ni(001) * 

¶.I 

an 

ld 

10 

0.6 

00 

za 

In 

16 

06 

.$ :.: 

E IO - 01 

00 

l.6 

I .o 

06 

on 

1.6 

1.0 

06 

00 

00 01 01 oa 04 06 oe 07 os 

Covorage 

X3B2 

Figure 1. Ni(ll0) intensity vs. Pb cov- erage 

14 - 

62- 

4n - 1 .4- 

' 40- 

ld - 

32, 

* 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 was SUPported by the NSF under pant DMR92- 

02529. 

Figure 1. 

* Workat the SUNY X3 beamlineis supportedby the Divisionof Basic Energy Sciences, 

U.S. Dept. of Energy (DE-FG0286-ER45231). Research at SUNY was supported by the Figure 2. cu(110) intensity vs. Pb COVVI erage VI NSF under grant DMR92-02529. 
! 

i 

\ I. 

cn 

o) Transcriptional initiation: Structural analysis of the TBP/TFIIA/TATA complex. X4A 

Jim Geiger (Howard Hughes Medical Inst., Yale University MB&B) P. B. Sigler 

(H HMI Yale University MB&B) 

The goal of this project is to investigate structure-function relationships of eukaryotic transcription initiation. for RNA polymerase 11, there are a host of general 

transcription factors that must associate at the promoter with the polymerase before transcription initiation begins. Some are required for the initiation of all genes 

(TFIID, TFIIB) in vivo and in vitro, while some are required on a subset of promoters, or serve to activate transcription, but are not necessary for basal levels of 

in vitro transcription. TFIIA falls in the later category. An essential gene in yeast, 

TFIIA counteracts the effects of transcriptional repressors and may be involved in 

the activity of transcriptional activators. It increases the association of TBP to the 

TATA box by three orders of magnitude, and extends the TBP footprint on DNA 

by seven base pairs in the upstream direction. 

We have crystallized and produced a preliminary electron density map of a com- plex of TBPITFIIAITATA to 3.0 angstroms resolution using two data sets collected 

at X25: a derivative where both TFIIA and TBP proteins have been substituted 

with selenomethionine, and a derivative where only TFIIA has been substituted 

with selenomethionine. The later data set is also the highest resolution data so far 

collected on this complex and will be used to refine the structure to 2.8 angstroms 

resolution. More recently we have conducted a double edge Se/Br MAD experiment 

at X4A which produced a far superior and interpretable electron density map that 

is presently being traced. 

1. Auble, D. T.; Hahn, S. Genes Development 1993, 7, 844-56. 

2. Meissner, W.; Holland, R.; Waldschmidt, R.; Seifart, K. H. Nucleic Acids 

Research 1993, 21, 1013-8. 

I Crvstal structure of human interleukin-10 at 1.6A resolution I X4A I 

A. Zdanov, C. Schalk-Hihi, A. Gustchina, and A. Wlodawer (NCI-FCRDC) 

Interleukin-10 (IL-10) is a cytokine produced by activated T cells, B cells, keratinocytes, and monocytes. It has been shown to inhibit the synthesis of a number of 

cytokines, including interferon 7, IL-2, IL-3, tumor necrosis factor and granulocytemacrophage colony-stimulating factor. Human IL-10 has been shown to exist in 

solution as a homodimer, composed of two polypeptide chains of 160 amino acids 

each. The subunits within the dimer are non-covalently associated, although each 

subunit contains two intra-chain disulfide bonds. Structure of IL-10 at room temperature (RT) has been solved by MIR by using five heavy-atom derivatives [l] and 

refined at l.8A resolution against data collected on RAXIS-IIC image plate system 

coupled with a RU-200 generator. 

We were able to collect diffraction data to 1.5A resolution at low temperature (LT), 100"K, using synchrotron radiation, beamline X4A. Sigma M-3516 mineral oil 

was used as a cryoprotectant. A total 91 frames of 1.5" oscillations with exposition 

time 55 sec. per frame were collected. Crystal to detector distance was 150 mm. The data were processed with the DENZO program package; Rmerge is 7.2% at 

1.5A resolution. However, since the data in the last resolution shell (1.6A-1.52) 

were of poor quality, we used in the refinement only data to l.6A. 

LT data allowed us to locate four extra N-terminal amino acid residues and a number of side chains which were not visible before. We identified 175 "new" water 

molecules and three ammonium sulfate anions. It is interesting that at LT the unit 

cell (space group P3221) became more "trigonal" a = b = 69.53A, c = 70.54A 

versus a = b = 70.27A, c = 70.31A at RT. The molecule itself appears to contract 

slightly at LT, similar to what was found in the studies of the Ribonuclease-A at 

different temperatures [2]. The overall change in the unit cell volume between room 

and 100°K temperatures is 1.8% or 5336A3. A detailed paper on LT IL-10 crystal 

structure is in preparation. 

[l] A. Zdanov, C. Schalk-Hihi, A. Gustchina, M. Tsang, J. Weatherbee and A. 

Wlodawer, Structure 3, 591-601(1995). 

[2] R.F. Tilton Jr., J.C. Dewan, G.A. Petsko, Biochemistry, 31, 2469-2481(1992). 
X6A Determination of transient molecular structure for photoinduced reaction intermediates using time-resolved energy dispersive XAS. 

L. Chen (Argonne National Laboratory/University of Chicago) 

A time-resolved XAS experiment has been set up at the beamline to study laser 

induced molecular structural changes using energy dispersive x-ray absorption spectroscopy. A Nd-YAG laser pumped OPO laser system (Spectra Physics offers a 

pulse energy 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. As the first 

experiment, we have tried to detect the triplet state structures of ZnTPP (zinc 

tetraphenylporphyrin) and ZnOEP zinc octaethylporphyrin), which have lifetimes 

tures undergo distortions at the triplet state where the symmetry of the molecules 

change from D4h to D4v or D2, this hypothesis is yet to be confirmed. We are now in a process to optimize the experimental conditions and explore other suitable molecular systems to study. The outcome of this study will lead to molecular structure 

determination with higher time resolution at the third generation synchrotron. 

continuously tunable nanosecond laser pulses from 420 to 2000 nm at 10 A z with a 

of 26 and 56 ms respectively at 77K. L ased on previous studies, the molecular strucX6A The Transient Redox Kinetics of Vanadium Phosphate: An in situ 

Dispersive XANES Study 

George Coulston, Richard Harlow (DuPont), Simon R. Bare (Dow), Harold Kung, 

Kari Birkeland, Greg Bethke (Northwestern), John Quintana, Joe Georgopoulos 

(DND-CAT), and Peter L. Lee (Argonne) 

Butane oxidation to maleic anhydride is the only selective alkane oxidation process currently practiced on a commercial scale. Since its development over 20 years 

ago, this process has received a great deal of attention from the catalysis commu- nity; primarily because of hopes that struture-performance relationships derived for 

the VPO system would lead to development of catalysts for other alkane oxidations. 

Despite this interest, many basic questions remain unanswered. 

For example, it has long been known that lattice oxygen (as opposed to adsorbed 

oxygen) plays an important role in the mechanism of butane oxidation, but there 

have been no reports in the literature providing direct evidence of which oxidation 

states of vanadium are involved in the reaction. In addition, phosphorus enrichment 

is known to increase the selectivity of vanadium phosphates for production of maleic 

anhydride, but the reasons for this effect are still unclear. Our collaborative research 

program at NSLS-X6A has been directed at answering these two very important 

questions. In a typical experiment, a catalyst cell with Be windows is used to 

contain a 150 pm wafer of catalyst. 

A bent Si(ll1) crystal is used to focus a polychromatic x-ray beam onto the wafer, 

and the transmitted beam is dispersed onto a multichannel photodiode detector. 

With this configuration, the complete XAS spectrum can be collected with adequate 

S/N in 1 sec. The reactor exit is in-line with a mass spectrometer so the production 

of maleic anhydride can be followed during the experiment. The V K-edge XANES 

data have been analyzed using conventional curve fitting of the edge and pre-edge 

features as well as with a factor analytic approach. The latter is particularly well 

suited for analysis of time resolved data because the entire data set is analyzed at 

once, and there is no need to normalize the spectra or to use external standards. 

In a series of experiments using a1-VOPO4/SiOz1 the reaction gas was cycled 

between air and butane. At all temperatures studied, the overall rate of reduction was always faster than that for reoxidation of the catalysts, although the initial 

rate of reoxidation was faster for T<420°C. In the case of a phosphorus enriched 

sample (P:V=1.95) at 32OoC, the rate of reduction increased to 0.016s-', while the 

rate of oxidation decreased to 0.01s-l. This suggests that phosphorus may play a role in C-H bond activation, but that it has its largest impact on the process 

by which lattice oxygen is restored. Furthermore, at all temperatures studied, the 

maleic production rate, as determined by the mass spectrometer, tracked the decay 

of the Vs6 component of the catalyst, clearly identifying that component as being 

required for production of maleic anhydride. 
. .I 

. .: . . 

4d UI 

00 

.. , 

,, :<: 

* X6A 

K absorption edge Magnetic Circular X-Ray Dichroism of Fe-Ni alloy. 

.. 

. .; .I 

Figure 1. MCXD spectra at Fe K edge 

in alloys. 

* This work was supported by the State 

of Illinois/NIU-HECA and Department of 

Energy under contract W-31-109-Eng-38 

Figure 2. MCXD spectra at Ni K edge 

in alloys. 

I MCXD studies of the sinnle crystal of NdzFel4B (001). * 1 X6A I 

K. J. Gofron, C. W. Kimball (NIU), P.L. Lee, P. A. Montano (ANL), P. Canfield, 

and M. J. Kramer (Ames Lab) 

The MCXD temperature dependent studies of a single crystal of NdzFelaB have 

been done across sprin reorientation at 120 K. The MCXD allowed us to study 

magnetic behavior of individual atomic species in a complex material. In these 

studies we used microfocussing property of the energy dispersive beamline in order 

to study small samples. The MCXD signal at Nd LZ absorption edge exhibits a change of about 10% across the reorientation temperature. In the same time 

the room temperature MCXD at K edge of Fe is three times higher than that for 

elemental Fe. 

15x1 OO3 

ic 

8 E5 

-0- 80 K - 300 K 

MCXD at Nd & 

-40 0 40 80 

Energy [eV] 

Figure 1. MCXD at Nd LZ for Ndzb'e14f) 

across spin reorientation temperature. 

* This work was supported by the State 

of Illinois/NIU-HECA and the Department 

of Energy under contract W-31-109-Eng-38 

3L 

2- 

1- 

Q 0-J 

2-1- 

-2- 

4x1 O?7 

-10 0 10 20 30 

Energy [eV] 

Figure 2. MCXD at Fe K edge for 

NdzFe14B. 
I Temperature Dependence of the MCXD at the Gd L3 edge * I X6A I 

K. J. Gofion, C. W. Kimball (NIU), P. L. Lee, P. A. Montano, G. Jennings (ANL) 

We measured the temperature dependence of the magnetic circular X-ray dichroism (MCXD effect at the Gd Gd LJ absorption edge using an energy dispersive 

beamline. T h e intensity of MCXD features follows closely the standard magnetization curve. In the ferromagnetic region, well below 290 K, the features do not change 

appreciably. Above the transition temperature, paramagnetic region, the intensity 

of the MCXD decrease strongly with temperature but are observable even at the 

highest studied temperatures, 350 K. The main positive MCXD peak is observed 

at all studied temperatures from 77 K up to 350 K. The peak persists above the 

zero field ordering temperature (290 K), this is related to the effect of the magnetic 

field. However, the main focus of the studies is on the presence of the quadrupolar 

term observed as a feature below the edge. We find that the quadrupolar peak 

strength does not change significantly over the whole range of temperatures below 

the reorientation temperature. Thus the coefficients of the quadrupolar term are 

not strongly temperature dependent as previously assumed. The quadrupolar peak 

vanishes slightly above the ordering temperature. In addition, magnetic EXAFS 

oscillations are observed above the valence band region. 

100 

.- 

200 300 0 0 40 80 

Energy [eV] . _-. .. .. _-_-- Energy [eV] T -.-- . , [KI -- 

Figure 1. Temperature dependence of MCXD at Gd LJ edge (center). Main peak 

height (left) as a function of temperature and the MCXD spectrum at 94 K (right). 

4d * This work was supported by the State of Illinois/NIU-HECA and Department of 

(D Energy under contract W-31-109-Eng-38. Cll 

MCXD studies at Fe K edge in ordered and disordered FesPt invar 

alloy. * 

K. J. Gofron, C. W. Kimball (NIU), P. L. Lee (ANL), C. Yahnke (NIU), G. Jennings, and P. A. Montano (ANL) 

We have studied magnetism of FesPt invar alloy at K edge of Fe. Circularly 

(greater than 95%) polarized x-rays were incident normal to the sample surfaces. 

Samples were magnetized perpendicular to the surface with field of 1 T using electromagnet. We observe that the MCXD signal at Fe K edge in FesPt is twice larger 

and twice broader in energy than in elemental Fe. The K edge MCXD for Fe in 

FesPt exhibits complicated strccture of positive and negative peaks which have very 

different intensities for ordered and disordered phases of Fe3Pt alloy. 

B1 

E 

0 

-1 

-3 2x10 

-hPt - FaPt 

cold rolled . 

-40 0 40 -40 0 40 

--Ir 

Fe3Pt 

cold rolled 

-40 0 40 

Energy teV1 

-Fe 

cold rolled I 

[. 

-40 0 40 

Figure 1. MCXD from cold rolled (disordered), heat treated (ordered) FesPt and 

elemental Fe. Below are the corresponding XANES. 

* This work was supported by the State of Illinois/NIU-HECA and Department of 

Energy under contract W-31-109-Eng-38 
Fd 

m 

0 Simultaneous Multi-wavelength Anomalous Diffraction (SMAD) : 

An Energy Dispersive Synchrotron Diffraction Method for Macromolecules * 

X6A 

Peter L. Lee (ANL) and Craig M. Ogata (HHMI) 

A new synchrotron data acquisition method, Simultaneous Multi-wavelength 

Anomalous Diffraction (SMAD), employing a variable bandwidth curved crystal 

monochromator (polychromator) coupled with an energy selecting grid plate has 

been developed. The preliminary data collected of a myoglobin crystal were erformed at the X6A beamline at the National Synchrotron Light Source (NSLSY. It 

has demonstrated the ability to measure reflections at six different wavelengths and 

their Bijvoet pairs at the same time. On one diffraction image, we record both the 

dispersive and Bijvoet information from a myoglobin crystal for Multi-wavelength Anomalous Diffraction (MAD) phasing. 

* Work is sponsored by the US Department of Energy, Office of Basic Energy Sciences, 

Division of Materials Sciences, under contract W-31-109-ENG-38 and the Howard Hughes 

Medical Institute. 

DETERMINATION OF METAL-METAL INTERACTIONS AND 

COORDINATIONS STATES OF A MODEL COMPOUND FOR 

PHOTOSYNTHESIS 

L. Chen, M. Wasielewski, W. Svec, K. Huang, P. Montan0 I 

Chlorophyll dimers play very important roles in energy and electron transfer in 

natural photosynthesis. In order to study the dimers in natural photosynthesis, the 

interactions between the macrocycles in the dimers have been studied via various 

optical spectroscopies and magnetic resonance via various synthetic model com- pounds. One of such model compounds is bismetalchlorophyll cyclophane, where 

two chlorophyll macrocycles are connected via two cyclophane linkages. However, 

the structural detail of such compounds in solution, distance between the macrocycles, the coordination numbers and their correlation with the photophysical properties of the compounds was not available. We studied the metal-metal interaction 

and the coordination states of the central metal in covalently linked chlorophyll 

dimers with different central metal atoms (Zn+2, Ni+2, and Cu+2) using XAS. 

The metal-metal interaction determines the distance between the two chlorophyll 

rings. This distance and the coordination state of the central metal atom square 

We observed a possible metal-metal interaction in bis-zinc-chlorophyll cyclophane 

in toluene solution with a Zn-Zn distance of 3.5 Angstroms and that interaction 

disappears when pyridine, a strongly binding ligand, is added into the solution 

(see Figure 1). This metal-metal interaction, however, was not observed in corresponding Cu and Ni compounds, indicating that the configuration of the dimer is 

strongly determined by the properties of the central metal ions. The coordination 

states of the Ni bischlorophylls are strongly dependent on temperature, where the 

hexa-coordination is observed at the 200K or below, and square-planar and pentacoordination is observed at 290K (see Figure 2). This indicated that the ligands, 

such as pyridine and pyrasine, can be used as probes for the conformation of the 

chlorophyll dimers. We are continuing this study to further investigate the con- formation and photophysics correlation in these molecules and what we can learn 

about natural photosynthesis from photophysics of the bischlorophylls. 

planar, pyramid or octahedral) are correlated to the photophysics of the mo i ecules. 

F 

8 

t 

3 

0 2 4 

R(Angstroms) 

Figure 1. FT-EXAFS of Zn-bis chlorophyll without and with pyridine in solution at 290K. 

Y 

Y. 

-20 -10 0 10 20 30 40 60 60 

ENERGY (ev) 

Figure 2. XANES of Ni-chloroophyll and 

bixchlolrophyll complexes. 
[In-Situ X-ray Diffraction Study of Langmuir Blodgett Deposition * I X6B I 

M.K. Durbm, A. Malik, A.G. Richter, R.S. Ghaskadvi, and P. Dutta (Northwestern 

University), and K.G. Huang (Argonne National Lab) 

We used grazing incidence diffraction to study the Langmuir-Blodgett (LB) deposition process. A comparison of the results of X-ray studies of ex-situ LB films' and 

their precursor films on water' demonstrates that there is no obvious correlation 

between the phase of a monolayer on water and the phase on the solid substrate 

after deposition. In particular, monolayer films of fatty acids on solid substrates 

have been generally found to be untilted and hexagonal, even when deposited from a phase which is known to have tilted molecules and a distorted hexagonal (DH) 

lattice. It is not clear when or how the transition from the phase observed on the 

liquid to the phase observed on the solid takes place. The change might take place as a function of distance from the water meniscus, or it might occur as a thin layer 

of water between the monolayer film and the substrate dries. With our in-situ Xray trough, we could study the film as it was deposited, while the temperature and 

humidity remained the same. We were able to observe structures similar to those 

seen on the water surface; in particular we observed distorted hexagonal and tilted 

phases at low temperatures. Figure 1 (top) shows a contour plot of diffraction data 

taken from a heneicosanoic acid (Czl acid) monolayer on a water subphase pH=2). 

The data from Fig. 2 was taken during deposition (the beam spot was 2mm above 

the water meniscus). The fact that there are two peaks indicates a DH structure 

and the fact that one peak is off-plane (K, > 0) indicates that the molecules tilt 

towards a nearest neighbor. As temperature was increased, the monolayer became 

hexagonal, as is observed on the water surface as well. However, upon decreasing 

the temperature, we were not able to recover the original distorted hexagonal phase. 

1. M.C. Shih, J.B. Peng, K.G. Huang, and P. Dutta, Langrnuir 9, 776 (1993) 

2. B. Lin, M.C. Shih, T.M. Bohanon, G.E. Ice, and P. Dutta, Phys. Rev. Lett. 65, 

Figure 1 (bottom) is data from a Czl acid monolayer deposited on a glass su b strate. 

191 (1990) 

td 

Figure 1. 

I Magnetism of ordered and disordered FeaPt by MCXD I X6B 1 

K. J. Gofion, C. W. Kimball (NIU), P. L. Lee (ANL), C. Yahnke(NIU), P. A. 

Montano, M. Engbretson (ANL) 

We studied element and orbital specific magnetism of the FesPt invar alloy at 

the LJ and Lz edges of Pt, as well as K edge of Fe. Circularly (60%) polarized 

x-rays were incident normal to the sample surfaces. The samples were magnetized 

erpendicular to the surface with a field of IT. The MCXD signals for the ordered 

disordered) alloy are 14% (20% at Lz edge and 12% (18% at LJ edge. The MCXD 

exhibits a complicated structure of positive and negative peaks. The L edge results 

are used to estimate orbital and spin magnetic moments of Pt. 

This work is supported by the Department of Energy under contract 0-31-109- 

Eng-38 and NIU-HECA/State of Illinois. 

signal at the LJ and Lz edges o 2 Pt are of opposite sign. 4 he K edge MCXD of Fe P 

IA 

Figure 1. MCXD at LJ edge of Pt for 

heat treated (ordered) FesPt. 

Figure 3. MCXD at Lz edge of Pt for 

heat treated (ordered) Fe3Pt. 

Figure 2. MCXD at La edge of Pt for 

cold rolled (disordered) Fe3Pt. w * This work was supportedby the U.S. Dept. of Energy grant no DE-FG02-84ER45125. 

Figure 4. MCXD at LZ edge of Pt for 

cold rolled (disordered3 FesPt. 
X-ray diffraction studies of non-sulphur self assembled monolayers 

A. Malik, M.K.Durbin, A.G.Richter, D.J.Campbell, C.A.Mirkin, P.Dutta (Northwestern Univ.) and P.Lee (ANL) 

Spontaneously adsorbed monolayers have received much attention for their potential in tailoring surface properties for a variety of applications. Some adsorbate 

molecules not only form chemical bonds with surfaces but also self-organize into 

highly ordered structures referred to as self-assembled monolayers (SAM). We and 

other groups have deposited SAMs of thiols on Au(ll1) and studied their structures 

by in-plane X-ray diffraction and AFM. We have analyzed SAMs of azobenzeneand fullerene-terminated alkanethiols by these techniques. 

The chemical nature of the thiol-Au interaction has not yet been elucidated. 

Many feel that the nature of surface attachment involves an Au-thiolate bond, 

but others have postulated that the sulfur atoms dimerize on the surface to form 

disulfide-like structures. Many questions remain concerning the relative importance 

of adsorbate-surface interactions, intermolecular interactions, and kinetic barriers 

to surface mobility. To probe this issue we have synthesized octadecaneselenol and 

created SAMs of these molecules on Au 111). Preliminary results indicate that the 

find that the adsorbates form a hexagonal structure, rotated 30' from the Au(ll1) 

lattice, with nearest neighbor spacing of 5.7k. A radial scan along the R30' direction 

is shown in figure la. The film thickness was estimated to be ~20k from the rod scan (figure lb). By comparing the annealing properties of these monolayers to 

that of octadecanethiol SAMs we can learn more about the relative strengths of 

surface-adsorbate interactions and the relative barrier associated with site-to site 

exchange. 

I X6B 

structure of these films are somewhat 6 ifferent than that of dodecaneselenol. We 

0.0 1'0.0 -1 1.10 1.15 120 135 1.30 1.35 1.40 0.0 02 0.4 0.6 0.8 1.0 

Q, cn-9 Q. cn-9 - . .. 

Figure 1. 

I X6B I Effect of the cation on the structure of fatty acid salt LangmuirBlodgett films 

A. Malik, M. K. Durbin, A. G. Richter P. Dutta (Northwestern University), P. Lee 

and K. Huang (Argonne National Laboratory) 

Using surface x-ray difraction,we have studied Langmuir-Blodgett films of fatty 

acid salts containing lead, cadmium and calcium cations. We find that both the 

in-plane and off-plane structures of these films change as a function of the cation 

present. Both the lead stearate and cadmium stearate multilayers have a distorted 

hexagonal (centered rectangle) in-plane unit cell. In contrast the calcium arachitate 

multilayers have a triclinic structure triangular unit cell with all sides of different 

is also very different in these systems. 

While the lead samples show long range positional correlation along the surface 

normal direction (at least up to 4 monolayers), the correlation only extends to two 

monolayers in the cadmium samples. In the calcium samples there is no correlation ' 

between layers. 

Radial scans for the three kinds of multilayers studied are shown in figure 1. The 

two peaks for the lead stearate film correspond to rectangular unit cell dimensions 

a=7.33k and b=4.98k, while the cadmium stearate peaks correspond to a=7.57k 

and b=4.84k. The area per molecule is ~18k' in both cases. The three peaks in 

the calcium data correspond to unit cell dimensions a=4.77k, b=4.45k, c=5.11k. 

The area per molecule in this system is 19.57k'. 

The rod scans at the 1.53k-' peak for the three systems are shown in figure 2. 

From the width of these peaks we estimate the correlation lengths in the surface 

normal direction to be look, 50k and 25k for lead, cadmium and calcium multilayers. These correspond to 4 layers, 2 layers and 1 layer respectively. The tilt angle 

of the chains is 8-9O in all three cases. 

l)A.Malik, M.K.Durbin, A.G.Richter, K.Huang and P.Dutta, Phys. Rev B 52, 

654 2)A. Malik, M.K.Durbin, A.G.Richter, K.Huang and P.Dutta, Thin Solid Films 

in press. 

This work supported by US Dept. of Energy grant no. DE-FG02-84ER45125 

lengths). The structure normal to pane (l 

Figure 1. Radial scans for a 5 layIO, 

er<d lead stearate, 5 layered cadmium 

stearate and 6 layered calcium arachitate 

films. 

Figure 2. Rod scans at the kZ,=1.53k-' 

peak for the three systems. 
I Incipient stage formation of porous silicon * I X6B I 

H. You, K. Huang, and S.S. Yoo, Z. Nagy (ANL) 

It has been widely recognized that porous silicons or porous semiconductors in 

general are potentially very important materials for future industrial applications. 

Their main characteristic for potential applications is luminasence at visible ranges. 

In addition they can easily be manufactured with or into the existing silicon-based 

electronic devices with anodic dissolution technique. However, In spite that the wide 

recognition of importance of the materials and intense research of the materials a relatively little attention is given to and little is known about how the anodic 

dissolution process initiate the formation of the pores at the interface and proceed 

to the deeper into the samples. This motivated us to perform the in-situ x-ray 

scattering investigation of solution/silicon single crystal interfaces. 

In this study, we examined pore formation at the surface of p-type silicon with a resistance of 0.015 n/cm. HF:HzO:C2He0=1:1:2 solution was used and current 

densities were varied between 10 mA/cm2 to 200 mA/cm2. 

An example set of x-ray reflectivity scans is shown in Fig. 1. The top most scan is the scan for a fresh sample surface before dissolution begins. The surface oxide 

has been removed by the solution leaving the bare silicon (100 surface exposed 

angles. In addition, the slop of the reflectivity changes initially but does not after a few successive dissolutions. On the other hand, the critical angle, above which 

the reflectivity starts significantly deviates from a constant value, gradually but 

persistently decreases throughout the entire set of successive dissolutions. The 

density estimated from the critical angle of the last scan is as small as 40% of the 

original silicon density. From this observation the process of anodic dissolution in 

forming porous silicon favors a pore shape which is cylindrically symmetric and 

the radius changes with a power-law regardless of the pore density or length. A 

theoretical understanding of this phenomena will be important in any attempt to 

modeling of the anodic dissolution. 

to the solution. All the reflectivity scans are linear in the log- 1 og scale at large 

Structure of "BaTaNz.l?l" from a combination of x-ray and neutron I data * 

V. Balbarin, F. DiSalvo (Cornell), H. Yamane (Sendai) J. Parise (StonyBrook) 

The title phase was prepared from the reaction of a pressed pellet of nitrided 

barium and tantalum (V) nitride in a 1:l metals ratio at 1400 OC for 3 hrs under a blanket of clean nitrogen gas. Chemical analysis performed on the fine, purple 

powder returned 8.55% N and 52.82% Ta by mass; at that time insufficient sample was available to allow an analysis for Ba. The analysis suggests the stoichiometry 

BaTaN2.1, normalized to 1Ta. 

The x-ray diffraction data, collected at X-7A at X=0.69827(1) A using a position 

sensitive detector, Ge(ll1 monochromator, and sample in a 0.3mm dia. capillary, 

with preliminary evaluations of the sample at Cornell; a=6.03 and c=10.11 A. The 

structure was solved using the x-ray data and Patterson techniques in space group 

P63/mmc and was confirmed to be similar to the high temperature form of the 

hexagonal perovskite BaMnOs-,. 

Further refinement was carried out using a set of neutron powder diffraction data 

collected at room temperature at the HFBR. The refined model can be summarized 

as follows: BaTaN2.1, a=6.0274(4), 10.1055(7) A; P63/mmc; Ta(1) at site 4f ('/g, 

2/3, -0.099(1)) Ba(1) at site 2d ('/3, '/3, '/4) Ba(2) at site 4e (0, 0, 0.0446(8)) with 

occupancy 0.5 N(1) at site 6g (0, '/2, 0) with occupancy 0.92(1) N(2) at site 6h 

(0.795(1 , 0.590(1), '/4 with occupancy 0.48(1)) 

value of 0.022(1) A2; for the sites occupied by nitrogens it was fixed at 0.02 A2. 

The refined values of the occupancies for the N-composition is close to that expected 

from the chemical analysis - N2.1 per Ta site. The distribution of vacancies in the 

hexagonal perovskite structure is not random however, being concentrated in the 

N2 site. 

could be indexed on the b asis of a hexagonal unit cell. The data are consistent 

The 2- isplacement parameter for the sites occupied by metals, was refined to a 

Figure 1. A series of x-ray reflectivity scans made after successive dissolutions of 

silicon. The scans are vertically offset for clarity. 

td 

Q) 

w * Supported by Department of Energy, under Contract No. W-31-109-ENG-38. * This work was supported by NSF Grant No. DMR93-1003. 
I, .; f 

X7A High Pressure and Low Temperature Study of the LTO to LTT Phase 

Transition in Lal.s.rr;Bao.lzr;Cuo,~ 

M.K. Crawford, R.L. Harlow, E.M. McCarron (DuPont); S.W. Tozer (NHFML, 

Florida); D.E. Cox (BNL) 

We have performed a high pressure, low temperature x-ray diffraction study of 

the LTO to LTT structural transition in Lal.e76Bao.126 CuO4. This phase transition 

leads to a drastic suppression of superconductivity which is not yet understood. 

The reported partial restoration of superconductivity under pressure stimulated our study. The structural work was performed using a Merrill-Bassett diamond 

anvil cell with a 4:l methanol to ethanol pressure medium. The hydrostatic nature 

of this medium is illustrated by the diffraction pattern shown in Figure 1. The 

diffraction linewidths are limited by the position sensitive detector resolution of 

0.05 degrees. Measurements at a number of temperatures and pressures suggest 

that pressure first stabilizes a Pccn low temperature phase. Higher pressures lead 

to the I4/mmm high temperature phase becoming stable at all temperatures from 

300 K to 15 K. 

2.0 l.5~,li--.~~~ ~~~.~

ic/--J--pIl 

B 

e 1.0 9 0.4 

4 0.5 0.2 

0.0 0.0 

280 285 290 295 300 305 310 280 285 290 295 300 305 310 

Photon Encrgy (ev) Pholon Energy (cV) 

c 1.0 ' 0.5 f 0.5 

0.0 0.0 

280 285 290 295 300 305 310 280 285 290 295 300 305 310 

Pholon Energy (cV) Photon Energy (eV) 

Figure 1. 

X7A Study of local atomic order in Pd-Ni-P glasses using resonant x-ray 

diffraction * 

W. Dmowski and T. Egami (U. Penn.), Y. He and R. Schwarz (os Alamos) 

We have studied short range atomic order of three PdhoN40P20 metallic glasses, 

annealed at different temperatures, by resonant x-ray scattering at the Pd K, absorption edge. Using the energy dependence of the atomic scattering factor we 

obtained total and differential structure factor and then by Fourier transform, differential pair distribution function. The Pd differential pair distribution function 

describes distribution of atoms in the structure with the Pd atom in the origin and 

allows to study changes in environment of this atom. We examined quantitatively 

many experimental factors affecting experiment near the absorption edge like energy 

dependence off and proper selection of energy windows monitored by detector to 

account for fluorescence and Compton scattering. We measured the ratio of K,/& 

above the edge to correct for K, fluorescence. We determined, frequently neglected, 

polarization of the primary beam. Figures 1 shows obtained differential structure 

factor correctly normalized at high Q. Figure 2 presents average (solid line) and 

differential pair distribution function. 

Results show that P-Ni and P-Pd form shortest distances in the structure. The 

annealing of the glass at high temperature leads to short range ordering of P atoms 

which may be responsible for the observed embrittlement. 

oa - 

02. 

:: 

.. 

2 3 I I8 7 8 0 10 

R IAI -. 

Figure 1. Differential structure factor 

obtained at Pd K, edge. Figure 2. Average (solid line) and dif- 

.ferential pair distribution functions for 

Pd-Ni-P metallic glass obtained at the 

Pd absorption edge. * The work at U. f Penna. was supported 

by the NSF Grant DMR9120688. 

I 0 lk'l I 
1 Structure of CeOz overlayer studied by energy dispersive x-ray diffraction. * 

W.Dmowski, S.Fu and T.Egami (Univ. of Penn), 

One of the experimental difficulties we encounter in carrying out the surface x-ray 

scattering measurement is that the scattered intensity tends to be very low, since 

the scattering volume is small and the Bragg peaks are spread normal to the surface 

forming rods. Accordingly a linear detector is often used in order to achieve parallel 

photon counting. An alternative, and sometimes superior, method to overcome this 

problem is to use the energy dispersive x-ray diffraction technique (EDXD). This 

method uses a white radiation source, and the structural information is obtained 

by the spectroscopy of the diffracted x-rays measured at a fixed diffraction angle. 

The spectrum of the diffracted rays is obtained by the use of a solid state semiconductor detector, such as an intrinsic Ge or Li-drifted Si detector, combined with a multi-channel pulse height analyzer (MCA). Using the EDXD method at a grazing 

angle incidence, in the evanescent wave regime, we studied the atomic structure of 

ceria (CeOz overlayers deposited on the 001 surface of a cubic Yttrium stabilized 

the MCA that was obtaine at 2q=26.13 degrees with the sample in the [l 0 01 direction aligned along the scattering vector. The rection aligned along the scattering 

vector. The incident and final angles (the angles the incident incident and scattered 

beams make with the surface of the sample), ai and af, were set above the critical 

scattering angle. The well defined diffraction pattern from the CeOz overlayer indicates that it forms an oriented epitaxial thin film on the zirconia crystal. In this 

work we have demonstrated that the energy dispersive mode can be successfully 

used in surface diffraction studies. We were able to observe characteristic features 

such as the transmissivity and truncation effects on the diffracted intensity. The 

main advantage of using the energy dispersive mode is high intensity of the scattered x-rays. This allows us to collect data fast and from even smaller scattering 

volumes. Additionally a family of Bragg diffraction peaks that line up in the same 

direction can be observed at once. Furthermore, monitoring the fluorescence from 

various elements can be used to study the concentration depth profile. 

d zirconia (Y J Z, ZrOz/Y203 single crysth. dgure 1 presents a spectrum stored in 

I Interfacial Structure of Giant Magnetoresistance Fe-Cr Multilayers * I X7A I 

W.Dmowski,D.Louca,T.Egami (U.Penn), D.Kelly and 1.Schuller (UCSD) 

Fe-Cr multilayers exhibit giant magnetoresistance effect which depends strongly on the preparation con tions. It is observed that GMR effect can be significantly 

enhanced, up to 300%, by increasing AI pressure, from 4 to 12 mTorr, during dc 

sputtering while other parameters are kept constant. There are many stu es indicating the role of the interfacial structure on the magnetoresistance effect. To elucidate 

this point we have performed x-ray ffraction study of three Fe(30A)/Cr(12A)]10 superlattices which had been sputtered in 4, 7, and 10 mTorr of AI. We used position 

sensitive detector in horizontal setup to collect simultaneously specular scattering 

intensity (Qz perpendicular to the film) and off-specular intensity with Qy parallel 

to the plane of the sample. This technique [l allows to study the effect of the 

in-plane sorder such as interface roughness or d efects at various length scales. In 

conventional low angle diffraction analysis the effect of interdiffusion or intermixing 

cannot be separated from the interface roughness. From our study we found that 

with increasing AI pressure, there are changes at the interface at three different 

length scales. The height-height fluctuation function shown in the Fig. 1, is a two - dimensional Fourier transform of the intensity in the Qx-Qy plane and describes 

interface roughness. It shows that at large lateral spacing interface roughness is 

increasing with AI pressure. This effect is likely to affect magnetization process. 

However, at short lengths interface becomes smoother which may lead to the increased electron mean free path. From the integrated in the Qx- Qy plane intensity 

we were able to deduct that there was more interface inter ffusion with higher AI 

pressure. Intermixing at the interface can randomize spin dependent scattering 

potential which would lead to bigger magnetoresistance effect. 

1. X. Yan and T. Egami, Phys. Rev. B 47, 2362 (1993) 

p 2.5 C $ 2.0 

1.5 51 

0 1.0 

= 0.0 

v 

I- t 0.5 - 

68 kbar 

14lmmm 

~ 10 20 2Q (dw) 30 40 50 

Figure 1. Diffraction pattern in energy dispersive mode from the surface overlayer 

of CeOz and single crystal zirconia substrate. 

F 

cn 

* Supported by National Science Foundation. The work at University of Pennsylvania Q) 

was supported by the NSF Grant DMR91 20688. * The Work at U.Penn was supported by the NSF Grant DMR91 20688 
46 I X7A I Q) 

Q) 1 Cu+l and Fe+3 occupancy in Cu0,~Fe2.604 

0 

*: 

i' 

m 

T. T. Eagen (Alfred U.), D.E. Cox (BNL), S. Dattaguru, and R.L. Snyder (Alfred 

A copper ferrite sample (Cuo.~Fe2.604) was processed from CuO and Fe203. 

These two compounds were taken in stoichiometry, calcined initially at 950 'C, 

ball milled, sieved to -325 mesh, heated to 1350 "C in a platinum crucible, and 

then rapidly quenched into motor oil which was being simultaneously stirred. An 

initial literature survey indicated that the crystal system was cubic [l], the space 

group was Fd3m [2], and the oxygen site and lattice parameter were 0.388 and 

8.413(3) A. The sample was run on the X7A beam line at Brookhaven National 

Laboratory. Three runs were performed using capillary samples at three separate 

wavelengths, 1.7440A, 1.380219, and 1.5000A. The powder patterns were then re- fined in a two-step process profile fitting followed by structural refinement) with 

tained using ABS (VAX program at BNL,1995). The refined lattice parameter 

and ion occupancies for the 1.7440A pattern were determined to be 8.41550(3)A 

and [cUo.~~~(~)Feo.~~~(~)][cUo.~~~(~)Fe~.~~~(~)]~~. The intensity R-factor of the refinement was 2.94, the weighted R-factor was 4.83, and the residual was 4.95, as indicated by the profile fit in Figure 1. 

1 E. Prince, and A. G. Treuting, Acta Crystallographica, 9, 1025 (1956). 11 2 N. F. M. Henry, and K. Lonsdale, International Tables for X-Ray Crystallography, Vol.1, the Kynoch Press, 340 (1965). 

[3] J. Mexmain, Ann Chim, Centre Industrield'Eveux, 297 (1971). 

u.1 

PROFPV (version 3.2 by To b y and D.E.Cox,1989). Absorption correction was ob- 

~ 

L' I1 I 20 40 60 80 100 I20 

28. degrees 

Figure 1. The experimental data (k1.744019) and a Rietvelt fit of the profile. 

X7A PHASE IDENTIFICATION IN GAS-ATOMIZED REzFe14B ALT,OYS * 

L. Henderson Lewis (BNL), C. H. Sellers (INEL), V. Panchanathan (Magnequench) 

The process of inert-gas atomization IGA is being explored as a method to 

of isotropic bonded magnets. IGA has several advantages over the conventional 

melt-quenching method: it can produce a large quantity of powder in one step, 

and it has the potential to be significantly more economical. Initial experiments, 

however, have proven that the IGA starting ingot composition must be strongly en- riched in both rare-earth and boron contents in order to obtain magnetic properties 

comparable to the conventional bonded magnets. We present here results obtained 

by x-ray diffraction performed on various powder size fractions of both as-quenched 

and annealed alloys produced by the IGA process to determine the identity of the 

impurity phases present and the degree of crystallinity of the primary RE2Fel4B 

phase. 

X-ray diffraction patterns were obtained in air at room temperature in the range 

10' 5 2Q 5 40' with wavelengths in the range 0.9 19 - 1.1 A on samples made of 

commercial grade alloys with the following nominal compositions: 

Fe14 Ndo.Q~Dyo.o1Pro.o1 2.93 BO.QzAlO.O8)1.33 Batch 434-2); 

and Fel4(Nd0.93Dy0.07)2.64B1.28 (Batch 447). Each sample was divided into vari- ous size fractions from less than 5 mm to more than 150 mm. The following results were obtained: 

1). All size fractions consist overwhelmingly of the well-crystallized RE2Fel4B 

phase, with no significant amorphous component. The background signals of the 

smaller, unannealed samples are always higher than that of their larger or annealed 

counterparts; additionally, the peak widths are always smaller for the larger and/or 

annealed size fractions. 

2 . The amounts of impurity phases are very small, but they are often unidentithe IGA process would be expected to produce metastable phases. 

3). When the impurity phases could be identified it was found that the larger 

size fractions invariably contained a-Fe, an undesirable product in the formation of 

permanent magnets. Upon annealing it was consistently found that the intensity 

of the a-Fe signal decreased while that of the g-Fe203 signal increased, indicative 

of iron oxidation in low-oxygen environments. Other impurities were found to be 

hexagonal RE203 and a-Fez 03. 

4). Least-squares determinations of lattice parameters indicate that the nature of 

the 2-14-1 phase differs with both particle size and annealing. In specific, it is found 

that the c-parameter of unannealed portions of Batch 435-2 decrease smoothly as 

particle size increases, a result that we have interpreted as indicative of a segregation 

of Dy to the larger-sized particles. Additionally, it is consistently found that the 

c-parameters decrease upon annealing. 

produce precursor powders based on the 63 E2 elJB composition for the formation 

Fell I Ndo.~~Dyo.07Pro.o1 II 2.90 BO.Q6A10.4)1.32 ( B atch 435-2); 

fiab 1 e. This is not a surprising result because the highly non-equilibrium nature of 

~~~ 

* Research performed under the auspices of the U.S. D.O.E., Division of Materials 

Sciences, Office of Basic Energy Sciences under Contact No. DEAC02-76CH00016 
Crystal Structure of ZrzNiDB 

C.J. Howard, M.M. Elcombe (ANSTO), S.J. Campbell (ADFA) and D.E. Cox 

The synchrotron work reported here was undertaken in support of a neutron 

diffraction study of the crystal structure of (nominal) ZrzNiDs. 

The initial measurements were made at room temperature. The first was made 

with the sample in a 0.45 mm capillary using 0.08 nm X-rays, the second was from a flat plate sample at wavelength 0.15 nm, and the third from a flat plate sample 

prepared after sieving using 0.1294 nm X-rays. Note that an X-ray pattern had 

been recorded earlier using BigDiff at the Photon Factory, Japan. 

The pattern recorded at room temperature at 0.08 nm Figure 1) closely resembled that from tetragonal ZrzNi, but with the high resoution \ of the X7A peak 

splitting indicative of a triclinic distortion could be seen. A reasonable fit could 

be obtained assuming a body-centered cell with a=0.6802, b=0.6812, c=0.5691 nm, 

a=90.22,fi=89.83,~=89.68°. There was some evidence of even more peak splitting, 

and the presence of additional peaks not indexed on the above cell was confirmed 

by the measurements made at longer wavelengths. 

Further measurements were made with a capillary sample, using wavelength 0.08 

nm, at temperatures above room temperature. At 106°C, the highest temperature measured, the main phase was clearly tetragonal (Figure l), with a=0.6816, 

c=0.5675 nm. Additional weak peaks, not indexed on the tetragonal cell, were 

attributed to a second phase present in small amounts. On cooling (below about 

95'C), the main phase transforms to a lower symmetry (triclinic) structure and 

the minor phase persists. The minor phase is thought to be responsible for the 

unaccounted peaks seen at high resolution at room temperature. We are presently 

examining the higher temperature patterns in an attempt to identify the second 

phase present in our sample. If successful in this, we are confident a two-phase 

analysis of the X-ray and neutron data will lead to a complete structure solution. 

I X7A 

(BNL) 

Structural Analysis of Lao.7Sro.3Mn03 Above and Below the Curie 

Temperature 

ZRNIDSonnA 

A-OQA 

stop tlro I om dop I 

X7A 

Figure 1. Diffraction patterns from ZrzNiDs recorded at 0.08 nm using X7A. The 

upper pattern was recorded at 106OC and the lower at room temperature. 

Lao.7Sro.3MnO3 is in the family of the recently discovered giant magnetoresistance (GMR) materials which is caused by an as yet unknown mechanism. It is a metallic ferromagnet with a Currie temperature of N 380K. The structure of 

Lao.7Sr0.3Mn03 is known_ to be rhombohedral with an R26 phonon mode condensation resulting in an R3c point group [3]. We acurately measured the a and c 

hexagonal unit cell lattice constants as a function of temperature, as shown in Figure 1. As the sample is cooled through the Currie temperature, a decreases more 

rapidly causing a decrease in the unit cell volume. 

Full Rietveld analysis was carried out on powder diffraction scans at sample 

temperatures of 433K (above T,), 298K, and 14K. We did not find evidence for any static Jahn-Teller type distortions above or below T,. Nor did the Debye-Waller 

factor for the oxygen atoms agree with a recent polaron theory [4] which expected 

it to decrease below T,. 

We conclude that the structure of Lao.7Sr0.3MnO3 is Rfc at all temperatures and 

that polaronic effects above T, are small if any. Further studies will include different 

stoichiometries to explore the relations between structure and GMR phenomena. 

Michael C. Martin et al., Phys. Rev. B to be pubtished. 

A.J. Millis et al., Phys. Rev. Lett. 74, 5144 (1995). 

LJa?SmtMnOJ Hexagonal Cell hs0,80q131\ 

6.808 u . IJaS 

000 320 040 080 000 400 420 440 460 

9/7/95 Temperature (K) 

Figure 1. Rfc lattice parameters as a function of temperature. The hexagonal unit 

cell is used; solid lines are fits to quadratic temperature dependencies and the error 

bars are shown smaller than the data point symbols. 
Q) 

03 

on,J P*rr'BRSON - Sr PATTERSON - z=O. 10 sr PATTERSON - ZUO. SO 

Figure 1. Partial Patterson maps of SI alone for sections at z = 0.0, 0.19 and 0.50 

respectively, from which Sr coordinates 0.16,0.25,0.19 are deduced. 

Ab-initio structure solution from powder data using resonant scattering * X7A 

* 

The Symmetry of Garnets on the pyrope (Mg3A12Si3012) - enstatite 

(MgSiO3) join. * X7A 

Kat0 and Kumazawa (1985) 

Angel et al. (1989) Am. Mineral. 74, 509-512. 

* Work at X-7a supported under US DOE contract DE-AC02-76CH00016; The Stony 

Brook High Pressure Laboratory supported by the State of New York and the NSF through 

its Science and Technology Initiative Grant to CHiPR. 
X7A Structural studies of the metal-insulator compounds BaVS3 and 

Lal-, Ca,MnO3 

P.G. Radaelli (ILL), M. Marezio (CNRS-Grenoble, AT&T) and D.E. Cox (BNL) 

BaVSs has long been regarded as one of the most interesting one-dimensional 

compounds displaying a temperature-driven metal-insulator (M-I) transition 

-80K as well as a hexagonal-orthorhombic structural phase transition ~240K). k1 ecent y, considerable attention has been devoted to another M-I compound, the 

perovskite manganese oxide Lal-,Ca,MnO3. In this system, for 0.25~50.4, the MI transition is coupled with ferromagnetic spin ordering, and TM-I coincides with 

the Curie temperature Tc. Both temperatures are raised in an applied magnetic 

field, thereby producing a giant magnetoresistive (GMR) effect. For xz0.5, with 

decreasing temperature, the compound becomes first ferromagnetic ~225K), then 

perexchange magnetic coupling. Temperature-dependent data were obtained at the 

X7A beamline on well-characterized powder samples of BaVS3 and Lal-. Ca,MnO3 

(x=0.25, 0.50 and 0.67), using a wavelength of 0.7015A and a Ge(220) analyzer crystal in the diffracted beam. The structural and M-I transitions of BaVS3 are evident 

in the behavior of the lattice parameters and of the unit cell volume (Figure 1). In 

particular, the data confirm the second-order nature of the structural transition, 

and indicate that, at the M-T transition, there is a sudden volume increase with 

decreasing temperature, consistent with recently obtained dilatometric results[l]. 

For Lal-,Ca,MnO3 , the magnetic and M-T transitions are associated with significant lattice changes. For x=0.25, there is a significant volume contraction at 

Tc (AV/Vz0.0013, Figure 2). This effect is much too large to be due simply to 

magnetostriction, and it is likely to be due to the increase of the metallic nature of 

the bonds[%]. The x=0.50 Sam le show much larger changes of the lattice parameters at the magnetic transitionf2’J. Through a relatively broad region with an onset 

at ~220K, the b lattice parameter drastically decreases, while those along the aand c- axes increase. Rietveld refinements based on X7A extended data sets, later 

confirmed by neutron powder diffraction data, indicate that these anomalies are 

associated with a Jahn-Teller-type distortion of the MnOe octahedra. 

[l] T. Graf, D. Mandrus, J.M. Lawrence, J.D. Thompson, P.C. Canfiels, S-.W. 

Cheong and L.W. Rupp, Unpublished (1994). 

[2] P.G. Radaelli, D.E. Cox, M. Marezio S.-W. Cheong, P.E. Schiffer and A.P. 

Ramirez, to be published in Phys.Rev.Lett(l995). 

antiferromagnetic (-155K), due to competition between double exc 6 ange and suFigure 1. Lattice parameters and unit Figure 2. Lattice parameters and unit 

cell volume of of BaVS3 as a function of cell volume of Lao.7sCao.zeMnO3 as a a, y temperature. function of temperature. (D 

Polymer Fiber Morphology Assessment Using Real Space Analysis of 

X-Ray Diffraction Data 

H. D. Rosenfeld and R. Barton, Jr. (DuPont) 

We have developed a method of assessing polymer fiber morphology using real 

space analysis of synchrotron x-ray diffraction data. This method yields percent 

crystallinity, crystallite size, and a histogram describing the probability of finding a crystallite with its c-axis tilted theta degrees from the fiber axis. It is applicable 

to both well-crystallized and poorly crystalline samples, and is independent of as- sumptions regarding the so called disordered polymer phase. The method requires 

two diffraction scans per sample (equatorial and meridional), the ability to access 

the momentum transfer range 0.5 Ang-’ <= q <= 18 Ang-l, low background, 

and high intensity. Since X7a provides the required beamline characteristics, it 

was used to test the method on several samples of NOMEX* aramid. Our results 

demonstrated the ability of real space analysis of polymer fiber morphology, us- ing synchrotron x-ray diffraction data, to accurately describe NOMEX* samples 

with widely different degrees of crystallinity and orientation. The method has since 

been tested successfully on Nylon fibers using data collected at the X3al and X20b 

beamlines. 

It is our expectation that it is applicable to a wide range of polymer fiber systems. * Registered Trade Mark of the DuPont Company 
I., 

,, . ' 

.. 

.. 

X7A Study of atomic structure in PMN single crystal using resonant x-ray 

diffraction * 

S. Teslic and T. Egami (U. of PA), S. Vakhrushev (Ioffe Inst., St. Petersburg, 

Russia) 

We have studied the atomic structure of a PMN (Pb(Mgl,3Nb2/3)03) single 

crystal using resonant x-ray scattering near the Pb LIIr and Nb K, absorption 

edges. 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. However, the microscopic origin 

of the superlattice peaks has been controversial. Our results shown below indicate 

that Nb is heavily contributing to this peak, which is consistent with the idea of 

Nb/Mg, or Nb/(Mg21~Nb~/~), chemical ordering. However, the effective scattering 

factor of this peak is about 6, while for full ordering should be close to DZ = 29. 

This discrepancy cannot be explained by oxygen participation, since oxygen tends 

to move toward Nb6+ which is smaller and higher in valence, thus exacerbate the 

discrepancy. On the other hand, the Pb atoms are displaced toward Mg atoms 

since Pb-Mg repulsion is weaker than the Pb-Nb repulsion. This Pb displacement 

will compensate the difference in the scattering power between Nb and Mg and 

make the effective smaller. Then Pb must be polarized in antiferroelectric manner, 

while the sample has random local ferroelectric polarization resulting in the relaxor 

ferroelectricity. Indeed the data at the Pb edge show a negative contribution to 

the structure factor from Pb but it is too small. We believe that dominant factor 

must include both chemical ordering (possibly forming of Nb and Mg clusters) and 

correlated atomic displacements. 

Figure 1. Intensity of the (1/2, 1/2, 5/2) 

peak as a function of energy near the Nb 

K-edge. 

Figure 2. Intensity of the (1/2, 1/2, 5/2) 

peak as a function of energy near the Pb 

L-edge. 

* Work at the University of Pennsylvania 

was supported by the Office of Naval Research through N00014-91-J-1036. 

X7A Pair Distribution Function (PDF) Studies of the Impact of Processing 

Chemistry on Local Order in PZT Solid Solutions * 

A. P. Wilkinson (Georgia Tech), S. Teslic, T. Egami (U. Penn.), Q. Zhu, and D.E. 

Cox (BNL) 

An inhomogeneous distribution of cations on the B sublattice of perovskite ferroelectric solid solutions is known to have important consequences for the materials 

dielectric properties. In many materials it leads to relaxor behavior and properties that are desirable in devices such as mechanical actuators. The distribution of 

cations in perovskite solid solutions is known in some cases to be dependent on the 

processing conditions used, for example, in lead scandium tantalate. 

We are exploring the impact of sol-gel processing chemistry on solid solution 

homogeneity and the dielectric properties of a series of ferroelectrics including PZT 

iPb[Zrl-.Ti.]O3). Initially, two samples of PZT 33/67 prepared using slightly 

ifferent processing conditionse were examined. Data were coll$cted for both samples 

using a wavelength of 0.4986 A over the range Q = 0.6 - 24.3 A-l. Pair distribution 

functions were calculated for each of the samples using Rosenfeld's X-ray PDF 

package. The PDFs indicate that the different processing conditions used in the 

preparation of the two samples led to different local structure in the solid solutions. 

Further data analysis and complementary neutron studies are currently underway. 

* We are grateful to Georgia Institute of Technology for the financial support of this 

work. 

.- 
Structural and electronic properties of GaN films grown on sapphire 

by molecular beam epitaxy * 

Q. Zhu (BNL), A. Botchkarev, W. Kim, 0. Aktas, A. Salvador, B. Sverdlov, H. 

Morkos (U. of IIl.,Urbana-Champaign), S. -C. Y. Tsen, and D. J. Smith (Arizona 

State U.) 

GaN and related materials, thanks to the recent breakthrough [I], have demonstrated tremendous potential for applications in short wavelength optoelectronics 

and high temperature/power electronics [2]. Despite the technological importance 

of GaN, correlation between microstructure and the physical properties is still lacking. 

The structural characteristics of GaN films grown on sapphire substrates by 

molecular beam epitaxy (MBE have been investigated using high-resolution synchrotron x-ray diffraction and e 1 ectron microscopy, and compared to their electrical 

and optical properties. We find remarkable correspondence between the in-plane 

structural order (coherence length and mosaic spread) and the electrical and optical properties. Contrary to common belief, our observations show unequivocally 

that the out-of-plane structural features, which are considerably better developed 

than the in-plane counterparts, can not be used for determining the material quality 

with respect to their optical and electrical activity. In particular, the (001) mosaic 

spread is not a good indicator of film quality [3]. The structural correlations of the 

GaN film, the A1N buffer layer and the sapphire substrate are explored and com- pared to their growth conditions. The issue of in-plane stacking fault (hcp - fcc) is 

also addressed using x-ray scans along the (101) direction. We find no significant 

feature of stacking disorder due to fcc-to-hcp defects in all these films, which is 

consistent with the TEM observation. 

H. Amano et. al., Jap J. Appl. Phys. 28 L2112, (1989). 

Q. Zhu et. al. Appl. Phys. Lett. (submitted). 

H. Morkos, et. al., Science 267, 51 (1995). 

* This work was supported by the US Department of Energy, Division of Materials 

Science under contract No. DEAC0276CH00016, by NSF Grant DMR9314326, by the 

Office of Naval Research with M. Yoder and Dr. Y. S. Park as monitors, and by the Air 

Force Office of Scientific Research with Dr. G. L. Witt as the monitor. H. M. was funded 3 by AFOSR under a URRP program. 

I Polvmer and dimer formation in alkali-metal intercalated CG~ * I X7A I 

Q. Zhu, D. E. Cox, (BNL) and J. E. Fischer (U. of Penn.) 

Rocksalt-type MC60 has been a subject of tremendous interest since its early 

discovery [l]. Its high-T structure is similar to the superconducting com- pounds, but with only one charge transfer. Band structure calculations predicted 

rocksalt MC60 to be a metal, however all the experiments indicated otherwise. Separately, NazMC60 exhibits anomalously low T, which deviates from the T, vs. lattice 

constant relation according to BCS theory. 

Synchrotron x-ray powder diffractions revealed common tendency for c60 ions 

in both materials to coalesce and to form dimers [2] and polymers [3,4]. Our 

results [2 indicated that in competition with polymer formation and with equiKC60 transforms to a metastable orthorhombic dimer phase with a 9.34 A centerto-center separation. It is obtained by quenching from above 423 K to 298 K and 

immediately cooling below 270 K. On the other hand, the cubic trianionic fulleride 

superconductors Na2RbC60 and Naz CsC60 exhibit a reversible conversion into or- thorhombic polymers under modest pressures (< 3 kbar) and ambient temperature 

[4]. Structure refinement based on high-resolution synchrotron powder x-ray profiles reveals polymer chains with 9.35 A intermolecular separation, comparable to 

that in the metastable monoanionic dimer and polymer phases of KC60 and Rbc60 

[2,3]. These examples reinforce current ideas about the necessary conditions for fullerene/fulleride intermolecular bonding, namely reduced inter-Ceo spacing and an adeauate derrree of molecular rotational dvnamics. 

librium p h ase separation (O<<x<O.l) plus K3C60), the cubic monoanionic 

Q: Zhu e; al., Phys. Rev. B 47, 13948"(1993 Q. Zhu, D. E. Cox, and J. E. Fischer, Phys. dkv. B 51,3966 (1995): P. w. SteDhens et. al.. Nature 370. 636 (1994). 

,I 

[4j Q. Zhu, PAYS. Rev. B'52, R723 (1995). 

Figure 1. 

* This work was supported by the US ff% ma Department of Energy, Division of Materials Sciences under contract No. DEACO2- 

76CH00016. Figure 2. 
Calcareous sponge spicules: presence of amorphous and crystalline 

phases in the same element * 

J.Aizenberg, L.Addadi, S.Weiner (Weizmann Institute of Science, Israel), J.Hanson, 

T.F.Koetzle (BNL) 

X7B 

Some organisms form stable minerals that would never precipitate under ambient 

conditions in an inorganic environment, or if formed are unstable precursors of more stable compounds. One of the most fascinating examples is biogenic amorphous 

calcium carbonate, because its transformation into crystalline polymorphs is not 

only thermodynamically favored, but also kinetically fast. The calcareous sponges 

(Porifera form a wide variety of spicules, each of which is generally thought to be 

observed between the spicule mineral and inorganically formed calcite crystals. 

Our attention was drawn to the fact that an additional amorphous mineral phase 

may be present, by the observation that the intensities of the diffracted beam from 

single Cluthrina triradiate spicules (100 microns across) accounted for only about 

20% of the expected value of an equivalent volume of a pure single calcite crystal. 

To investigate this phenomenon, synchrotron powder diffraction data were collected 

for Clathrina spicules and compared to analogous measurements of two controls: 

(i) pure calcite and (ii) spicules of the ascidian PyaTapachydermatina which are composed entirely of amorphous CaC03. The samples were finely ground, and 0.3 mm glass capillaries were filled completely with the powder to ensure that the same amount of material was subjected to the X-ray beam in each experiment. Narrow 

slit measurements were performed with a step size of 0.01 deg and sampling time 

of 10 sec/step using the Huber diffractometer. 

The powder X-ray diffraction pattern (below) of ClathTina spicules shows in 

addition to the sharp calcite reflections, an intense but broad peak around 20 = 15 

deg, indicative of the presence of an amorphous phase. 

On the basis of these and addition electron microscope observations, we deduce 

that the spicule is composed of a core of calcite embedded in a thick amorphous 

calcium carbonate layer and apparently covered by a thin calcitic sheath. The 

formation of composite structures in which amorphous and crystalline phases coexist 

apparently endows the biogenic material with advantageous properties, that may 

be interesting to investigate. 

compose 2 of a single crystal of Mg-bearing calcite. Differences have, however, been 

10 

Figure 1. 

* US DOE contract DE-AC02-76CH00016 Div of Chem. Sci. Office of Basic Energy 

Science and US-Isreal Binational Sci. Foundation 

X7B Biologically-induced reduction in symmetry at the level of the crystal 

domain shape 

J. Aizenberg, L. Leiserowitz, S. Weiner, L. Addadi (Weizmann Institute of Science, 

Israel), J. Hanson, and T.F. Koetzle (BNL) 

Organisms can exert a remarkable degree of control over crystal growth. One means of achieving this is by the adsorption of specialized macromolecules on specific planes of the growing crystals. With continued growth of the crystal, the 

macromolecules are incorporated inside the crystal bulk. In previous studies we observed that this strategy used to control single crystal texture and morphology, may 

result in an effective reduction in crystal symmetry at the level of the microscopic 

domain shape. In this study we have examined in detail one type of calcareous 

sponge spicule, that is a beautiful example of how the biological environment induces a reduction in crystal symmetry. The Sycon asymmetric triradiate spicule 

was specifically chosen for this study, because each is composed of a single crystal 

of calcite, but their morphologies do not reflect the hexagonal symmetry of calcite. 

Two rays of each spicule develop perpendicular to the symmetry-related (-102) and 

(1-12) pl.anes, and the third ray grows perpendicular to the 0-16) calcite plane. 

control synthetic calcite crystals and four triradiate spicules. Two spicules were 

measured intact, two others were subdivided into three different rays and each was studied separately. Fig. 1 shows diffraction peak profiles of the representative (104) 

and (012) families of reflections for three rays of the same spicule. In every case 

reduction in symmetry is observed in the coherence lengths among symmetry-related 

crystallographic directions. Larger coherence lengths and smaller angular spreads are observed in the crystallographic directions coincident with, or close to, the 

directions of the morphological axes of the spicule rays. The reconstructed shapes 

of the domains of perfect structure unequivocally show the extent of reduction in 

symmetry that can be achieved for each of the growing subunits of the same crystal 

(Fig. 2). The average shapes of highly anisotropic perfect domains of each spicule 

ray reflect to a remarkable degree the macroscopic morphology. The synthetic 

crystals show no such reduction in symmetry. 

Although the manner by which such exquisite control is achieved is not known, we envisage it involving a combination of oriented nucleation with either physical or stereochemically-driven adsorption. Support: US DOE contract DE-ACO2- 

76CH00016 Div of Chem Sci.,BES and US-Isreal BSF 

The diffraction peak profiles in the w- and w/20-scan mo d es were monitored for 

Figure 1. Figure 2. 
X7B Thermal decomposition of silvercarbonate studied by powder diffraction methods. * 

E. Krogh Andersen, I.G. Krogh Andersen (U. Odense, DK), P. Norby, J.C. Hanson 

(B NL) 

A Synchrotron X-Ray Study of Piezoelectric Moduli, Ferroelectric 

Switching and Domain Reversal in CsTiOAsO4 and KTiOP04 under 

an Applied Electric Field * 

Silvercarbonate is a thermally unstable compound, which when heated will decompose into silveroxide and carbondioxide. By further heating silver oxide is decomposed into a fine powder of pure silver and oxygen. The transformations are 

clearly visible as silvercarbonate is a greenish powder, silver oxide is pitch black 

and the silver metal is obtained as a white/yellowish powder. We intend to study 

the structural detailed involved in the thermal decomposition process, and as a 

preliminary experiment powder diffraction data were collected using a Translating 

Image Plate System. Figure 1 shows the powder diffraction profiles extracted from 

the image plate data as a function of temperature. The transformations are clearly 

visible as distinct changes in the diffraction patterns. Figure 2 is a small section 

of the image on the Image Plate, showing the same section as in Figure 1. A 

closer examination of the diffraction patterns reveals that immediately before the 

phase transformations changes in the powder diffraction patterns occurs indicating changes in the crystal structure. Powder diffraction data obtained from image 

plates are suitable for Rietveld refinement and the structural changes preceding the 

decomposition reactions will be further investigated. 

X7B 

Figure l. Powder diffraction patterns 

showing the decomposition of silver car- bonate. 

* This work was supported under contract DE-AC02-76CH00016 with the US Department of Energy by its Division of Chemical Sciences, Office of Basic Energy Sciences 

and by the Danish Natural Science Research 

w Council 

Figure 2. TIPS image of the decomposition of silver carbonate. 

* Work supportedunder contract AC02-76CH000016 with US DOE by its Div of Chem. 

Sciences, Office of Basic Energy Sciences, the Swedish Natural Science Council and European Commission 
I' 'C 

;;? Development of Synchrotron Diffraction Methods for Structure Determination with Small Single Crystals * X7B In-situ powder diffraction studies of zeolite syntheses; Magnesium 

substituted alumino phosphates. * 

A. NZrlund Christensen (U. Arhus), Poul Norby (BNL) 

In-situ powder diffraction was used to follow the syntheses of magnesium substituted aluminophosphate molecular sieves. Substitution of trivalent aluminum into 

the tetrahedral framework of aluminophosphates with divalent cations is important 

in order to tailor catalytical properties of the materials. 

Magnesium substituted aluminum phosphates (MAPO's) were synthesized from 

astes made from the following chemicals: MgO or Mg(Ac)z ~HzO, Al(OH), .HzO 

rc atapal), 85 % H3P04, NaOH, 37 % HC1, and the templates triethylamine (EtsN), 

tripropylamine (Pr3N), di-n-propylamine (PrzNH), and tetramethylammonium hydroxide Me4Nt) Molar ratios of pastes: 

AlzO3, PzO~, 25.0H~O C: 2.OPrzNH, 0.3Mg0, 0.85A1203, PzO~, 25.0H~O D: 

1.91Pr3N1 0.17Mg0, 0.96A1203, Pz06, 25.2H20 E: 2.19Me4Nt , 0.21HC1, 0.29Mg0, 

0.81A1203, Pz06, 32.0HzO The in situ measurements of the crystallization of the 

amomhous gels at temDeratures UD to 2OO0C showed in most cases the appearance 

X7B 

A: 1.5 0 t3NI 0.02Na20, 0.2Mg0, Alz03, PzO~, 27.8Hz0 B: 1.5PrzNH, 0.2Mg0, 

of pr;cursor-phases formed before *the formation of the final products. 

Some of the precursor phases have not yet been identified. 

The obtained results are the following: 

A: Precursor is M~A~(PO~OH)ZOH-~H~O. Products are MAPO-47 and MAPO5. The growth rate of MAPO-5 is faster than that of MAPO-47. At 13OoC MAPO-5 

is only formed in minor quantities and MAPO-47 is the main reaction product. At 

18OoC MAPO-5 and MAPO-47 are formed in approximately equal amounts. 

B: Two unidentified precursor phases are formed. At 12OOC a sodalite like phase 

is formed. At 2OOOC the reaction product is a mixture of MAPO-46 and MAPO-39. 

C: Two unidentified precursor phases are formed. At 2OOOC the reaction product 

is a mixture of MAPO-39 and MAPO-46. The formation of MAPO-46 is faster than 

that of MAPO-39. 

D: The reaction product in the temperature range 25 - 2OO0C is MAPO-36 E: At 

temperatures up to 75OC the precursor phase M~A~(PO~OH)ZOH.~HZO is formed. 

At temperatures from 90 to 12OOC a sodalite like phase is formed. 

* This work was supported by contract DE-AC02-76CH00016 with the US Department 

of Energy by its Division of Chemical Sciences, Office of Basic Energy Sciences and by the 

Danish Natural Science Research Council. 

* This work was supported by contract DE-AC02-76Ch000016 with the US DOE by Div 

of Chemical Sciences, Office of Basic Energy Sciences 
Time Resolved Dehydration Studies of the Layered Aluminophosphate d,l-Co(en)s Al3P4OI6 xHzO * 

Synthesis of zeolite A from thermally activated natural kaolinites. * I X7B I 

Alex F. Gualtieri (Univ. of Modena, Italy), P. Norby and J. Hanson (BNL), and 

G. Artioli (Univ. of Milan, Italy), 

Zeolite A is by far the most studied zeolite and the most employed zeolitic ma- terial for industrial purposes [l]. It can be synthesized using clay minerals such as 

kaolinite [2]. In order to activate the kaolinite for the reaction, it is necessary to perform a thermal treatment at about 600-800' C [3]. The experiments we performed 

deal with the formation of zeolite A from two kaolinites with a different density 

of structural disorder. The samples are Kga-1 and Kga-2, international standards 

from Georgia, USA exhibiting a different density of planar faults [4]. The samples are activated at 800'C. The syntheses are achieved by hydrothermal leaching 

of the activated powders throughout a NaOH solution in the temperature range 

70-110'C. The solution is cleansed by means of a 0.5 mm diameter syringe in a 0.7 mm Lindemann glass capillary. The applied pressure inside the capillary is 10 

Atm. The reaction syntheses are followed by angular dispersive experiments. The 

detector used is a translating Imaging Plate. The isothermal experiments are performed at 70,80,9,100,110 ' C. The heating rate used to reach the set temperature 

is about 100 ' C/min. The reaction is followed by observing the modification of the 

intensity of the scanned portion of the diffraction rings as a function of time. The 

image collected and stored in the plate is scanned using a He-Ne laser beam stimulation in an IP Fuji BAS2000 scanner. The integrated intensities are normalized 

and transformed into phase fractions and conversion values to plot the alfa/time 

curves. The conversion vs. time plots enable to elaborate on the kinetic mechanism 

of the reaction process and to calculate the value of the activation energies and frequency factors. n in both cases is greater than 4 thus the process can be described 

as an interface controlled acceleratory reaction with random nucleation (increasing 

rate and 3D growth (constant rate) of the crystals of the cubic phase. When the 

may be the coalescence and impingment of the forming nuclei. n has a tendency to 

drop at higher temperature and this can be directly related to the decrease of the 

random nucleation rate for thermodynamic reasons. In fact, at higher temperature, 

hydroxysodalite phase is more stable than (Ostwald's law) and the decrease of the 

nucleation rate for both samples is due to a competition of forming nuclei of the 

two phases. 

[l] Drag E.B., Miecznikowski A., Abo-Lemon F. and Rutkowski M. (1985). Synthesis of A, Xe Elsevier Science Publishers. 

2 Kerr G.T 1966 . J.Phys.Chem. 4, 1047-1050. 

3 Barrer €LA., Co 1 e J.F., Sticher H .(1968). J.Chem.Soc. (A) 10, 2475-2485. I1 4 Gualtieri A.F. (1966). PHD thesis. Univ. of Modena (Italy). 

coe 2 cient n of the Avrami equation is so large the rate limiting step of the reaction 

X7B 

* We are grateful for financial support from the Georgia Tech Molecular Design Institute 

and acknowledment is made to the Donors of the Petroleum Research Fund. administered 

by the Americin Chemical Society, for partial support of this research. The work at NSLS was supported by US DOE contract DE-AC02-76CH00016 with Div. of Chem. Sci., Office * This research is supported under contract DE-AC02-76CH00016 wii 

Energy by its Division of Chemical Sciences, Office of Basic Energy Sciences 

the US dept of 

2 of Basic Energy Sciences. 
, .-, 

.a ~ 

-I 

cn Rietveld refinement of synchrotron data collected in transmission geometry using an Imaging Plate detector: application to standard m- X7B 

ZrOz * 

Alex F. Gualtieri (Univ. of Modena, Italy), P. Norby, J. Hanson and J. Hriljac 

(BNL), and G. Artioli (Univ. of Milan, Italy) 

We have performed the Flietveld refinement of m-ZrOz (standard material selected by the commission on powder diffraction of the IUCr to undertake a round 

robin of Flietveld refinement). The data were collected at X7B using a flat Imaging 

Plate detector, which is a powerful tool when fast data collections are required. An 

energy. When later stimulated by visible light, it is capable of emitting photostimulated luminescence (PSL , the intensity of which is proportional to the absorbed 

Prior to the collection, the sample was ground, sieved and mounted on a 0.3 mm Lindemann quartz capillary and placed on a standard goniometer head. The 

accurate value of energy (A= 0.9583 A) is calibrated using the standard material 

LaBe. The exposure time is 10 min and the pattern is collected in the range 0-64.5 

4he data reduction accounts for a variety of corrections embracing the polarization of the synchrotron beam, the Lorentz factor, the absorption, the correction for 

the flat IP geometry, and the IP zero shift. The corrections produce working data 

suitable for a Rietveld refinement using the programs: 1) a modified for Imagin 

Plate data version of The X-Ray Rietveld System XRS-82 Baerlocher (1982); 2f 

General Structure Analysis System GSAS (Larson & Von Dreele, 1995). The agreement factors (R,s are lower than the values reported in the IUCr round robin for 

geometry despite the use of a synchrotron source. 

The refined unit cell constants and the atomic positions are consistent with the 

single crystal data. The refined thermal parameters are in close proximity to the 

single crystal data showing that it is possible to get reliable and consistent thermal parameters in Debye-Scherrer geometry using synchrotron radiation. We can state that an accurate data reduction of the transmission data collected using 

synchtrotron radiation provide Rietveld refined parameters of sufficient accuracy 

and precision. 

[l] Amemija, Y. (1990). Synch. Rad. News 3, 21-26. 

[2] Bourgeois, D., Moy, J.P., Svensson, S.O. & Kvick, A. (1994). J. Appl. Cryst. 

X-ray intensity. The deta il s of the mechanism are well described in [l] and [2]. 

28 sin8 /A=0.55). 

synchrotron data k ecause the instrumental resolution is intrinsically poorer in this 

C. (1982). Inst. fur Krist. & Petrogr., ETH, Zurich. 

and Von Dreele, R.B. (1995 “GSAS. General Structure Analysis System,” Report LA UR 86-748. Los Alamos I4 ational Laboratory. 

* This research is supported under contract DE-AC02-76CH00016 with the US Department of Energy by its Division of Chemical Sciences, Office of Basic Energy Sciences. 

A Time-Resolved Thermal X-Ray Powder Diffraction Study on 

CoSAPO-34 

Jonathan Hanson[l], Arild Moen [2], David G. Nicholson[2], Kenny Stihl [3] ([l] 

Department of Chemistry, BNL; [2] Department of Chemistry (AVH) Univ. of 

Trondheim, N-7055 Trondheim, Norway; [3] Inorg.Chem.2, Univ. of Lund, POB 

124, S-22100 Lund, Sweden) 

Microporous, microcrystalline aluminium phosphates (ALPOs), metal- substituted aluminium phosphates (MeALPOs and silicon-substituted analogues 

(SAPOS) are interesting candidates for cat al ytic studies and there is a continuing growth in the Microporous, microcrystalline aluminium phosphates (ALPOs), 

metal- substituted aluminium phosphates MeALPOs) and silicon-substituted analogues (SAPOs) are interesting candidates f or catalytic studies and there is a continuing growth in the size of the family of compounds since they were first synthesised 

in 1982[1]. Because of their structural relationships to the zeolites the materials 

are often termed zeotypes. The zeotypes are monophasic crystalline solids in which 

the active sites are distributed in a spatially uniform manner throughout the bulk. 

Thus, some of them can be used as uniform heterogeneous catalysts. In this con- nection, the most significant feature of zeotypes is their microporous nature which 

means that nearly all of the accessible surface area is actually inside the crystallites. For example, over 99.5% of the surface area of a lmm diameter crystallite 

is internal. Consequently, most of the All P and/or metal atoms are effectively 

surface atoms, although they are located deep inside the material. and this means 

that bulk physical techniques such as EXAFS can actually be regarded as surface 

techniques in these special cases .We have previously published some of the results 

of EXAFS studies using the facilities of XllA [2 - 41. 

In CoSAPO-34 the cobalt atoms enters the framework by substituting A1 111) in 

on calcination t blue to green at 500 C with a change to greyish-blue on cooling in 

moist air). The object of the present study is use time-resolved powder diffraction 

(X7B) to map the structural changes that occur whilst the as-synthesised sample is 

being heated upto 500 C. The results are currently being analysed. The work at BNL was supported by US DOE contract DE-AC02-76CH00016 

with the Division of Chemical Sciences, Office of Basic Energy Sciences and the 

Swedish Natural Science Council. 

[l] S.T. Wilson, B.M. Lok, C.A. Messina, T.R. Cannan, E.M. Flanigen, J. Am. 

Chem. Soc.1982, 104, 1146 

[2] A. Lund, D.G. Nicholson, G. Lamble and B.Beagley, J. Materials Chem., 1994, 

the form of Co 11). The material is interesting because it undergoes colour c 6 anges 

4, 1723. 

1995, 5, 485. 

1995, 5, 785. 

[3] M.Endregard, D.G. Nicholson, M. Stocker and G. Lamble, J . Materials Chem. 

[4] M.Endregard, D.G. Nicholson, M. Stocker and G. Lamble, J. Materials Chem. 
I Track effects in hydrocarbon liquids exposed to x-rays * I X7B I I In-situ studies of Dhase transitions in silicate mesostructures * IX7B I 

R. A. Holroyd, J. M. Preses, J. C. Hanson (BNL - Chemistry Dept. 

Absorption of X-rays in hydrocarbon liquids leads to photoelectrons which produce dense tracks of secondary ionization. Charge recombination of these ions forms 

excited states in the track. The excited states will be singlet with high probability 

when the recombination is of geminate partners, because the spins remain correlated. As the X-ray energy decreases, the density of ionizations along the track 

of the photoelectron increases and the probability of recombination with ions from 

other ionization events will increase. This non-geminate recombination is of uncor- related ions and the yield of singlets is expected to decrease as the X-ray energy 

decreases. Such "track effects" are of interest to radiation chemists and theoretical 

predictions' have been made of the magnitude of this effect. 

In this study we measured the relative yield of excited singlet states for three 

hydrocarbons by the intensity of the UV fluorescence and as a function of X-ray 

energy. X-rays from 6 to 14 keV were obtained from a 311 Si crystal monochromator 

at X7B. The X-ray beam passed through a Nz-filled ionization chamber, to monitor 

the beam intensity prior to entering the sample cell. The cell was made of quartz but 

had a 1 mil mylar entrance window for the X-ray beam. UV fluorescence emerging 

from the back of the cell was collected by a spherical mirror and focused on the 

window of a photomultiplier tube (EMI). The fluorescence beam passed through an interference filter to cut out stray hght. The tube was operated in the single photon 

counting mode. 

The results for trans-decalin are shown in figure 1. The fluorescence yield from 

singlet states decreases with decreasing X-ray energy, that is, as the track density 

increases. The results need to be corrected for the lifetime of the excited states, Tobar 

which also decreases as the energy decreases; i.e.: Yield of singlets = fluorescence 

yield/r&, The results are compared with computer simulations', which predict a 

decrease in singlet yields with decreasing X-ray energy in this range (solid line). 

Similar results are obtained for cis-decalin and dodecane. This confirms that recombination of uncorrelated ions in the dense track leads to the formation of more 

triplet excited states and consequently reduces the yield of singlet excited states. 

Measurements will be made down to 4 keV in the near future. 

[l] W. M. Bartczak, A. Hummel, Chem. Phys. Lett. 208, 232, 1993 

4d 

4 

* This work was supported by contract DE-AC02-76CH000 4 Div of Chemical Sciences, Office of Basic Energy Sciences 

6.r th the US DOE -y its 

C. C. Landry, G. D. Stucky (U.C. Santa Barbara), J. C. Hanson, and P. Norby 

Mesoporous silicates are produced by a solution templating process which involves 

cooperative self-assembly of the organic and inorganic regions of the material. 

We have used in-situ X-ray diffraction at the NSLS to monitor phase changes 

in these products upon heating, with the goal of gaining control over the polymerization process. Silicate polymerization in these experiments was induced by 

heating the sample hydrothermally to 150 OC in quartz or glass capillaries. The 

detection system consisted of an image plate placed behind a slit; time resolution was accomplished by moving the image plate behind the slit at a fixed rate. After 

(BNL) 

one hour of heating, conversion of the hexagonal (Ha phase to a new rectangular 

phase, which we have desi nated R,, was phase trans- no additional changes 

were observed upon cooling to room temperature. 

The macroscopic structure of these inorganic/organic assemblies is dependent 

upon the local effective surfactant packing parameter g=V/a,l, where V is the total 

volume of the surfactant chain plus any co-solvent molecules between the chains, a. 

is the effective head group area at the micelle surface and 1 is the kinetic surfactant 

tail length. Changes in this parameter are thus directly proportional to changes 

in V. Small values of g tend to stabilize more locally curved surfaces (Ha) while 

larger values stabilize flatter surfaces Qp). We propose that the phase changes 

solution from hydrolysis of the inorganic precursor tetraethylorthosilicate (TEOS , 

since the silicate becomes less flexible as it polymerizes at high temperature, fixing 

the Q, phase in place. We anticipate performing further experiments aimed at 

gaining better control over the polymerization process through external addition of 

co-solvents and hydrolysis of new inorganic precursors. 

formed into the cubic (QP$ mesostructure 

observed in our experiment are cause 6 by the movement of ethanol, present in 

into the organic micellar region at high temperatures. The changes are not reversib 1' e 

* This research was carried out at BrookhavenNational Laboratory under contract DEAC02-76CH00016 with the US. Dept. of Energy and supportedby its Division of Chemical 

Sciences, Office of Basic Energy Sciences. C.C.L. and G.D.S. acknowledge support from the 

US. National Science Foundation under the Materials Research Laboratory grant program 

(DMR9123048). 
_.., 

, .i 

- STRUCTURE OF 

PENTAMINE CHELATE [Ca(thd)z(NsCsHm)] 

A VOLATILE CALCIUM P-DIKETONATO TETRAETHYLENE- X7B 

Figure 1. View of the Title Compound. 

one disordered amine ligand has been 

omitted. sphere with amine ligands. Figure 2. View of the Ca coordination 

X7B 

Structure of A Volatile magnesium P-Diketonato N,N,N’,N’- 

tetramethylenethylediamine Chelate [Mg(thd)z(NzCsH~s)] 

I. Mutikainen, T. Hatanpaa, M. Leskela (Univ. Helsinki), A. Gualtieri (Univ. 

Modena) and J. Hanson (BNL) 

In recent years there have been growing interest towards volatile -diketonates 

of alkaline earth, rare earth and transition metals. Reason for the interest is that 

these compounds can potentially be used as precursors in the preparation of oxide 

thin films by chemical vapor deposition CVD). The main requirements for precuraffected by the structure of the complex: monomeric and coordinatively saturated 

complexes are most volatile. If the -diketonate ligands do not saturate the coordination of the central metal, which is the case with alkaline earth metals heavier than 

Be, the coordination number will be fulfilled by oligomerisation or solvate molecule 

coordination. By adding different Lewis bases the coordination number can be fulfilled and oligomerisation and solvation molecule coordination avoided. The crystal structure of Mg(thd)z-N,N,N’,N’-tetramethylenethylenediamine was measured 

using synchrotron X-rays lambda=1.0088A) at 153 K using image-plates and offhol. The crystals are monoclic, space group P21/c (nr. 14), with a=10.091(4), 

b=19.133(5), c=17.021(4)A, =93.22(3) deg., Z=4, R=0.072 for 3072 reflections 

having 1>2sigma(I). The coordination sphere of Mg is octahedral with two thd 

molecules coordinating to Mg via four oxygen atoms and the tetramethylenethylendiamine via both nitrogen atoms. The bond lengths in the Mg coordination sphere 

vary from 1.990(2) to 2.020(2)A for Mg-0 and 2.261(3) to 2.294(3)A for Mg-N. 

This work was supported by contract DE-AC02-76CH00016 with the US DOE 

by its Division of Chemical Sciences, Office of Basic Energy Sciences. 

sors used in CVD are high volatility an 6 thermal stability. Both of properties are 

line Fuji 2000 scanner. T i, e complex was crystallized from ’super dry’ ethylalco40 

Figure 1. View of the Title Compound. 
X7B Hydrothermal conversion of zeolites; an In-situ powder diffraction 

studv. X7B Carboxylation of alkali phenolates; an in-situ powder diffraction studv. 

P. Norby, J.C. Hanson (BNL) 

By using hydrothermal conversion of zeolites it is in some cases possible to synthesize materials which are otherwise impossible or difficult to obtain. The metastable 

nature of zeolites makes them suitable as starting materials. Especially conversion 

of one zeolite into another is of interest in order to obtain purer or novel zeolites. 

Hydrothermal conversion of zeolite Na-LTA has e.g. been used in the synthesis of 

pure and well crystalline zeolite Li-A(BW), LiAlSiOa HzO(1). 

In order to study the nature of hydrothermal conversion of zeolite LTA in detail an in-situ powder diffraction study has been performed. Hydrothermal conversions 

were performed at temperatures up to 260°C and pressures up to 45 atm. All 

syntheses were carried out in 0.5 or 0.7 mm quartz glass capillaries mounted in a 

ferrule. Pressure was applied from a cylinder of compressed nitrogen in order to 

maintain hydrothermal conditions. Time resolved powder diffraction patterns were 

collected using a Translating Image Plate System (TIPS built especially for timeX7B. Figure 2 shows an example of time resolved powder diffraction data obtained 

during hydrothermal conversion of zeolite Na-LTA with an aqueous solution of LiCl 

at 26OoC. The result in this experiment is actually a mixture of two zeolites; zeolite 

Li-AYW) as the major product with minor quantities of a cancrinite type zeolite. 

*T is work was supported under contract DE-AC02-76CH00016 with the US 

Department of Energy by its Division of Chemical Sciences, Office of Basic Energy 

Sciences and by the Danish Natural Science Research Council. 

and temperature- and wavelength- dependent powder d iffraction experiments at 

P. Norby, J.C. Hanson (BNL), M. Pink (U. Leipzig), R. Dinnebier, P. Stephens 

(SUNY, Stonybrook) 

For more than 100 years it has been known that carboxylation of e.g. phenolates 

using carbon dioxide under pressure is possible(l,2). This so called Kolbe-Schmitt 

reaction is one of the most important industrial processes in the production of 

salicylic acid, a starting material for production of e.g. pharmaceuticals as aspirin. 

Although it is therefor a process of major industrial and economical importance, the 

mechanism of the reaction is still poorly known. Using the in-situ powder diffraction 

equipment(3) at X7B we have performed real time powder diffraction studies of the 

reaction at temperatures up to 150°C using COZ pressures up to 4 atm. 

The in-situ experiments showed that even at room temperature sodium phenolate 

reacts with COz and forms an disordered phase, which is probably a NaOC&-C02 

adduct. Upon heating this is transformed into a well crystalline phase as shown 

in Fig. 1. This phase we succeeded in preparing on the diffractometer. A high 

resolution powder diffraction pattern was obtained at the beamline X3A1, and it was possible to determine the unit cell. The structure solution is in progress. 

Upon further heating, the crystalline NaoC&~C02 phase decomposes, and the 

starting material reappears. At temperatures above ca. 14OoC a new poorly crystalline phase is formed, probably another NaOC&,-C02 phase. Upon prolonged 

heating conversion to poorly crystalline sodium salicylate was observed. 

This work was supported by contract DE-AC02-76CH00016 with the US Department of Energy by its Division of Chemical Sciences, Office of Basic Energy Sciences 

and by the Danish Natural Science Research Council. 

1. H. Kolbe, J. pr. Chem., 10, (1874) 98. 

2. J. Schmitt, J. pr. Chem., 38, (1885 397 3. P. Norby, "In-situ time resolved 

sented at EPDIC IV, July 10-14 1995 in Chester. Materials Science Forum, Trans. 

Tech Publications Ltd. 

synchrotron powder diffraction studies o 2 syntheses and chemical reactions." PreFigure 1. Powder diffraction patterns I 

obtained during hydrothermal conversion of zeolite LTA with aqueous LiCl 

4 at 26OoC W 

Figure 2. 

Figure 1. In-situ X-ray Powder Diffraction diagrams of the carboxylation of 

sodium phenolate. Figure 2. 
. _' % 

O0 0 

I.- 

SIEMENS SMART CCD DETECTOR APPLIED TO DIFFRAC- X7B 

TION WITH SYNCHROTRON RADIATION FROM X7B AT NSLS 

;., , 

.L '. , 

J. Phillips, J. Chambers, J. Fait Siemens Analytical Instruments, 6300 Enterprise 

Lane, Madison, WI 53719-1173 

The performance of A Siemens CCD detectors with a 2K chip was evaluated using 

radiation from bending magnet beamlines at SSRL and NSLS and from a rotating 

anode source with three type of optics. Also the goniometer was set up with the w - 26' axis horizontal, with a fast shutter to allow for short and accurate exposures 

and with provision for incident beam monitoring by the data collection software. 

Wavelengths close to 1 A were used exclusively. Data on lysozyme with Rsym of 

7.2% to 1.5 A was obtained in 5.5 hrs. Data on luciferase, which has a 302Aaxis 

was was obtained in 8.0 hrs with Rsym of 13.6% to 3.4 A. The system was also used 

for small molecule crystallography, solving a porphyrin, a zeolite and a carborane 

structure previously unsolved because of poor or small crystals. The system was also used for time-resolved powder diffraction and diffraction by multilayers on a macroscopic single crystal substrate. NSLS Data Sets: 

Lysozyme: Unit cell dimensions a=b=79.1 c=37.9; Space group P43212 Frame 

width=0.15 deg. Frame time=15 sec.; 667 frames Total elapsed time= 5.5 hrs Total 

number reflections= 80875 

Total unique = 19439 Rsym=7.2% to 1.5 A 97.7% complete 

Luciferase: Unit cell dimensions a=59.9 b=112.7 c=301.8; Space group P212121 

Frame width=0.2 deg. Frame time=30 sec.; 660 frames 

Total elapsed time=8.25 hrs Total number reflections=53825 Total unique = 

C7NlBlOH15: 

Unit cell dimensions a=7.246 b=18.429 c=18.140 

26128 Rsym=l2.9% to 2.7 ; 86% complete 

=92.482 deg.; Space group P21/n Frame width=0.5 deg. Frame time=15 sec.; 

720 frames (hemisphere of data) 

Total elapsed time=6 hrs Total number reflections=5134 Total unique reflections=2153 Rsym=l2.1% to 0.86 Ang ; 92.5% complete Solved by SHELXTL direct 

methods and refined to R1=0.068 

Sodalite: Unit cell dimensions a=8.8465 

Space group Im-3m Frame width=0.5 deg. Frame time=45 sec.; 150 frames Total 

elapsed time=2.5 hrs Total number reflections=278 Total unique reflectionsd"7 

Rsym=7.2% to 0.891 Ang. ; 100% complete Solved by SHELXTL direct methods 

and refined to R1=0.041 

Fe Silicide on Si(ll1): Sample with 10 overlayers shows diffraction peaks and 

thermal diffuse scattering in a "powder scan" of 400 frames, 15s and 0.1 deg. each. 

The experiments at NSLS X7B were performed with Jonathan Hanson and mem- bers of the Catalysis group of the Chemistry Department at Brookhaven National 

Laboratory. 

We thank Ivan Rayment of the Enzyme Institute of the University of Wisconsin, 

Madison for the lysozyme and luciferase crystals. William Clegg, University of Newcastle and Kenneth Wade, University of Durham provided the carborane crystal. 

The sodalite study was with Joseph Pluth, University of Chicago and R. Broach, 

UOP. The multilayer diffraction was with Peter Eng, University of Chicago. 

The Adsorption of Hydrofluorocarbons and Hydrochlorofluorocarbons 

on Basic Molecular Sieves * 

F. Poshni, C. P. Grey (SUNY Stony Brook), A. F. Gualtieri, P. Norby, J. C. Hanson 

(BNL), and D. R. Corbin (DuPont CR&D) 

The syntheses of hydrofluorocarbons HFCs), the environmentally friendly alterthan the syntheses of the CFCs and involve many more steps. Unwanted HFC and 

hydrochlorofluorocarbon (HCFC isomers are often produced, and purification of 

the products remains a concern. b or example, the isomer HFC-134 (CFzHCFzH) is 

a common byproduct during the synthesis of HFC-134a (CFsCFHz Basic molecular sieves have been shown to be effective in separating a variety of k FC/HCFC gas 

mixtures [l]. We have been investigating the adsorption of HFC-134 and HFC-124a 

(CFZHCFzCl) on zeolite Na-Y, to determine both how the gas molecules are bound 

to the zeolites, and whether there are any changes in the occupation and positions 

of the extra-framework cation sites. 

Samples of dehydrated NaY were loaded with 32 molecules of HFC-134 HCFC124a per unit cell, packed into 0.3 mm glass capillary tubes in a glove b ox and 

sealed. Diffraction experiments on both the loaded and bare zeolites were performed at room temperature and at 100 K. Data was collected with the Fuji Image 

Plate system, at a wavelength of 0.9338 A, and showed significant changes between 

the bare (top) and HFC loaded samples middle and bottom) in Figure 1. Structure 

refinements were performed using the b SAS and XRS-82 programs. The coordinates of the framework atoms and Na sites of Na-Y as a starting model for the bare 

zeolite were taken by Fitch et. al.[2]. Difference Fourier maps were used to locate 

the sodium and HFC positions. Electron density from the HFC molecules was observed at low temperatures in the supercages of the zeolite. Rigid body constraints were initially imposed for the modelling and localization of the HFC molecule. 

natives to the CFCs for refrigerant an 6 blowing applications, are more complex 

D. R. Corbin and B. A. Mahler, W.O. 94/02440 (February 3, 1994). 

A.N. Fitch, H. Jobic, H. Renouprez, J. Phys. Chem., 90, 1311 (1986). 

Figure 1. 

* NSF grant DMR-9458017 and DE-AC02-76CH00016 US DOE by its Division of Chemical Sciences, Office of Basic Energy Sciences and by the Danish Natural Science Research 

Council. 
Reflectance Calibrations of AXAF Witness Mirrors in the Ir M-edge 

Region * ~ ~~ ~~ 

D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzsi, D.A. Schwarts (SAO), R.L. 

Blake (LANL) 

Systems and procedures have been completed for reflectance calibrations of witness mirrors to the coatings of flight optics of NASA's Advanced X-ray Astrophysics 

Facility (AXAF) in the 2-6 keV range on NSLS Beamline X8A. This energy range 

includes the M-absorption edges for iridium, the coating material for AXAF. The 

flight optics and associated witness mirrors are being coated, and completion of 

all eight elements and the 40 synchrotron witness mirrors is expected by February 

1996. The X8A calibrations will be completed by Launch Date, in September 1998. 

Each mirror requires approximately four to five days of run time to calibrate in full 

detail. This detail includes angle scans at eight energies for alignment and layer 

modeling purposes, and eight energy scans at fixed grazing angle covering the full 

range. The required grazing angles are all less than 1.5 degrees. The energy detail 

is as broad as 25 eV in the continuum range above 3500 eV, but is as narrow as 1 eV in the troughs of the M-edges, where such detail is necessary to specify the 

reflectance accurately. Approximately 400 energy points are included in the energy scans. The iridium shows certain unique spectral features, including more extended 

XAFS than we have seen on either gold or platinum mirrors, which we have studied 

previously on this beamline. The Mv and Mrv absorption edge troughs appear at 

2080 eV and 2156 eV respectively, some 40 eV higher than the tabulated electron 

binding energies typically published for iridium (e.g. Bearden and Burr, Rev. Mod. 

Phys. 1967 . We discovered similar results for the Mv and Mrv absorption edges 

onset of the absorption due to the behavior of the density of states, most recently 

calculated for gold by A. Owens et al. (submitted to Ap. J. Lett. 1995). The AXAF 

spectroscopic devices, including the AXAF CCD Imagin Spectrometer (ACIS) and 

the High-Energy Transmission Grating Spectrometer fHETGS), will require the 

energy detail provided by our calibrations to meet the mission's scientific goals. In 

addition, certain elements of the ACIS and the HETGS are being calibrated in part 

at NSLS through collaboration with us. Information on the repeatability and uniformity of the coatings, and the level of 

molecular contamination, will be available soon, as work continues to calibrate more 

of the 40 witness mirrors. The reflectance at the M-absorption edges is significantly 

affected by molecular contamination, as we have reported previously. 

for gold an d platinum. The displacement of these edges may be the result of a slow 

I ODtical constants from transmission and reflection measurements I %?> I 

R.L. Blake(LANL), B.H. Harris, J.J. Fitch, D.E. Graessle, and D.A. 

Schwarts(SA0) 

A program is underway to measure foil transmissions and mirror reflectivities of 

suitably prepared samples. By application of the Fresnel equations and KramersKronig relations to terms derived from the measurements one can obtain both the 

real and imaginary parts of the complex dielectric constant for the material, which 

may be an element or compound and in any state. At the energies accessible on 

X8C/A(1-15 keV)chemical binding effects are small or can be accounted for. A 

reflectometer test station RTS) with one arc sec angular accuracy and capable of 

measurements in this program, and also serves other users for efficiency measurements of transmission gratings, reflection gratings, multilayer gratings, windows, 

routine operation in ultra- I, igh vacuum is used for both transmission and reflection 

detectors, etc. 

Improvements in the x-ray ring stability made over the last year by NSLS scientific 

and technical staff now allow our 0.1 percent precision measurements to yield optical 

constants with one percent accuracy in many cases. Over the last two years we have 

measured: 

1. Ir reflectivity versus energy and angle over the M-edge region (2000-3500eV 

2. Mo reflectivity of single crystal, polycrystalline, secondary- recrystallized sing e 

crystals,and evaporated samples( at 5 and 10 keV). 

3. 11, Pt, and Au foil transmissions versus energy over M- and L-edge regions. 

New data on Pt and Au will permit optical constants n and k to be determined as accurately as the thickness can be measured-our primary limitation for transmission 

measurements. For reflectivity data the primary limitation is from surface surface 

roughness. Both of these factors are to be improved through collaborations in future 

work. New data for Ir in both reflection and transmission are the only data available 

from measurements over the M- and L- edge regions. 

1 

4d 

01 

w * Supported by NASA (NAS8-40224) and the US DOE. 
I AXAF Synchrotron Calibrations of Ir-coated Witness Mirrors over I vo,., I AOb 15-12 keV-* 

D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzzi, D.A. Schwartz (SAO), R.L. 

Blake (LANL) 

Reflectance calibrations of witness mirrors to the coating processes for AXAF 

Advanced X-ray Astrophysics Facility) flight optics are proceeding rapidly on NSLS I, eamline X8C. To date, 10 mirrors have been calibrated, including at least two 

mirrors from each of the innermost three elements to be flown. The remaining 

elements will be coated within the next four months. Approximately 30 mirrors 

will be calibrated in the X8C range, with varying degrees of detail. 

X8C provides the most sensitive test of the uniformity and repeatability of the 

AXAF coating processes, because it covers the upper end of the full 50-12,000 eV 

calibration range. Angular accuracy down to one arc second is required at 10 keV 

because of the steepness of the iridium critical angle cut-off at that energy. The 

critical angle at 10 keV is approximately 27.4 arc minutes, which is also the mean grazing angle of AXAF's innermost mirror pair. Therefore an accurate calibration 

will be required through this energy and angle range. Beamline X8C together with our reflectometer perform remarkably well at maintaining this angular certainty 

under normal operations. Notwithstanding, significant improvement is expected 

with the use of the new NSLS Digital Feedback Stabilization system in the near future. 

Calibration efforts have reduced the time required per mirror to approximately 

2.3 days, including operator and storage ring overheads, excluding accidental beam 

dumps. 

The coating process, which must be completed twice for each element to produce 

the required witness mirrors, is quite reproducible, indicating that we may be able to 

reduce the amount of data and operational detail required in future measurements. 

Mirrors coated in separate processes have been shown to be consistent within about 

1 - 1.5% in all cases excluding the interference fringes. This implies that the coating 

density is very uniform and reproducible from coating run to coating run. Using a Fresnel equation model with uniform layer thicknesses and a modified DebyeWder roughness factor, we are able to fit the AXAF witness mirror reflectance 

data to within 1% relative residuals for optical constants and layer thicknesses. 

The optical constants are very similar to those published by Henke et al. (Atomic 

Data and Nuclear Data Tables, 1995) if we assume a 1.5% decrement in the coating 

density below bulk for iridium. The calibration is therefore within its error budget 

requirements, and we are now well on our way to completing a calibration of AXAF over 5-12 keV within 1% relative error and with full energy detail. 

THE USE OF SYNCHROTRON RADIATION IN THE CALIBRATION OF AXAF 5-12 keV * 

D.E. Graessle, J.J. Fitch, B. Harris, J.P. Cobuzzi, D.A. Schwartz (SAO), R.L. 

Blake (LANL) 

During the past five years, significant efforts have been made to develop systems 

and procedures for calibration of NASA's Advanced X-ray Astrophysics Facility 

(AXAF) using synchrotron radiation. The goal for the calibration is to provide 

AXAF mirror efficiency versus energy within 1% relative error over the 50-12,000 

eV energy range. AXAF has four pairs of nested Wolter Type I mirrors, which are internally-reflecting conic sections. As planned, witness mirrors to the coating 

processes for each of the AXAF flight mirrors would be brought to the synchrotron 

for calibration of reflectance versus energy and angle. The X8C beamline provides 

the upper range for the calibration, specifically 5-12 keV. Some thirty mirrors in all 

must be calibrated in this energy range. The mirror coatings are approximately 300 

A of iridium over a 100 A chromium binding layer on Zerodur substrates. Scans 

of reflectance versus energy and angle would be required, and would be analyzed 

for optical constants and coating layer thicknesses using a Fresnel equation model. 

The critical grazing angle for iridium above 5000 eV is less than one degree. 

The systems and procedures to be used on X8C are essentially completed. We 

have obtained reflectance measurements in the 5-12 keV range with acceptable 

accuracy and precision. Using the Fresnel model with uniform layer thicknesses 

and a modified Debye-Waller correctionfor scatter due to microroughness, we are able to fit reflectance versus angle of incidence down 1% values of R with less than 

1% relative residuals. Calibration of a mirror may be completed in a three-day 

period with normal operations and infrequent beam dumps. 

Sample-to-beam alignments are critical to the accuracy of the data. At 10 keV, 

the critical angle cut-off is quite steep, so that an angular error of one arc second produces a one-percent error in reflectance, which exceeds the error budget allowance. 

Our X8C studies have shown that this degree of angular accuracy is usually attainable in our system. The reflectometer operates with a horizontal plane of incidence, 

the p-polarization plane at a synchrotron. 

Calibrations of witness coupons to the actual flight optics are in progress. 

* Supported by NASA (NAS8-40224) and the US DOE. * Supported by NASA under NAS8-40224 and by the US DOE. 
Manipulating mesophase behavior of hydrated DHPE: An x-ray 

diffraction study of temperature and pressure effects. 

M. Carey (Ohio State University) 

A pressure-temperature phase diagram for 1,2-dihexadecyl-sn-glycerol-3- 

phosphoethanolamine (DHPE) in 50 of 1 to 1,200 bar and 65 to 90 C. The lamellar gel (Lb’) phase prevails at high pressure and low temperature. It gives way 

successively to the lamellar liquid crystalline (La) and inverted hexagonal (HII) 

phases as pressure is lowered and temperature is raised. Measurements were made 

using synchrotron-based x-ray diffraction and a high pressure beryllium cell. The 

pressure-dependence of the Lb’/La transition temperature, dTm/dP, is 25 2 C/kbar. 

Compression/expansion in the lamellar phases was highly anisotropic. The isothermal pressure-dependence of the chain packing and lamellar repeat distance, (d/P)T, 

in both the La and Lb’ phases was insensitive to temperature in the range studied. 

The average (d/P)T value for the lamellar repeat in the La and Lb’ phases and 

for the chain packing repeat in the Lb’ phase is 3.00.1, 1.180.06, and -0.1170.04 

/kbq respectively. In like manner, the isobaric temperature-dependence of the 

cham packing and lamellar repeat distance, (d/T P, in both the La and Lb’ phases 

lamellar repeat in the La and Lb’ phases and for the chain packing repeat in the Lb’ 

phase is -0.1540.005, -0.0530.003, and 0.00430.0002 /C, respectively. The absolute 

value of the ratio of the isothermal pressure- and isobaric temperature-dependence 

of all structure parameters measured, including area per chain, is remarkably close 

to the dTm/dP value reported above. A careful evaluation of mesophase structure 

parameters, one-dimensional electron density profile and wide-angle diffraction profile has enabled us to describe in considerable detail the structure response of the 

Lb’ phase in hydrated DHPE to temperature and pressure. Problems that can arise 

due to x-ray damage were evaluated. 

is insensitive to pressure in the range studied. 4 he average (d/T)p value for the 

XAFS Studies of the Zinc Storage Protein of Xenopus laevis Oocytes I* 

David S. Auld, Ke Zhang (Biostructures Institute), Marcello Montorzi, Kenneth 

H. Falchuk & Bert L. Vallee (Harvard Med. Sch.) 

X. laewis vitellogenin is a zinc protein containing 1 g at of zinc per mol of protein 

of MW 220,000 (1). It is a central component of a zinc distribution system that is 

involved in a) zinc transfer from liver to oocyte sites b) zinc storage in unfertilized 

eggs and c) zinc exchange from storage molecules to apoproteins in the embryo. 

The basic protein unit in yolk platelets is derived from the proteolytic processing of 

vitellogenin. The vitellogenin cleavage products phosvitin and lipovitellin remain 

associated with each other in a microcrystalline state in the yolk platelets. The 

purified lipovitellin contains 1 g at of Zn per mol of protein while the phosvitin contains none (1). Our initial XAFS studies have been directed toward the examining 

Zn in yolk platelets and purified vitellogenin and lipovitellin. 

The XAFS spectra of the vitellogenin, yolk platelet suspension and solid 

lipovitellin are essentially identical (2). The results show the Zn is bound to 4.0 

N/O at 1.98 A. The XAFS spectrum of a suspension of yolk platelets with a zinc 

concentration of about 1 mM differs from yolk platelets solubilized in 1 M NaC1, 

pH 7.5 (Fig. 1) while the spectra for yolk platelets and lipovitellin dissolved in 1 

M NaCl are essentially identical (Fig. 2). Analyses of these spectra indicate the 

Zn is bound to 4 N/O atoms at 1.98 A in the microcrystals of’the yolk platelets 

but has a C1 ion or S atom coordinated to the zinc in the NaCl solubilized states 

of both the yolk platelets and the purified lipovitellin. These results suggest one of 

the N/O ligands in the crystalline suspension of the yolk platelets may be a water 

molecule that is displaced most likely by a chloride ion in the solution state. 

1. Montorzi, M., Falchuk, K. H., & Vallee, B.L. Biochemistry 34, 10851-10858, 

1995. 

2. Auld, D. S., Zhang, K., Montorzi, M., Falchuk, K. H., & Vallee, B.L. in 

preparation. 

4. 

4N 0 s Qm WW 0,760 qeop 

Figure 1. XAFS spectra for yolk platelet E, eV suspension (circles) and solubilized in 

NaCl (line). Figure 2. XAFS spectra of yolk platelets 

(circle8 and lipovitellin (line) solubilized 

inNa . * Supported by NIH grant GM-47534. 
An XAS Study on CO Adducts of [NiFe] Hydrogenases 

M.R. Chance, A. Xie, L.M. Miller, R.F. Fischetti, E.M. Scheming, W.X. Huany 

Y. Hai, M. Sullivan, B. Sclavi Department of Physiology and Biophysics, Albert 

Einstein College of Medicine, Bronx, NY 10461 

Time-resolved x-ray structural data has become feasible based on the high flux 

and brightness of synchrotron 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 (Schlichting et al. Nature, 371, p.808 (1994)). However, the precision 

of protein crystallographic data (-0.2 ) is insufficient to provide precise metrical 

details of the iron-ligand bond lengths. Using time-resolved x-ray data acquisition 

techniques on microsecond to millisecond timescales along with simulations based on the ab initio Extended X- Ray Absorption Fine Structure code FEFF 6.01, we ana- lyzed data taken on photolyzed solution samples of the myoglobin-carbon monoxide 

complex from 10- 260 K. We provide precise metrical details for the Mb*CO state 

at 10 K and structural information based on x-ray edge data for microsecond and 

longer time relaxations above the glass transition. 

X9B 

* This research was supported by grants from NIH HL-45892 and RR-01633 and NSF 

BIR-9303830. 

TIME-RESOLVED X-RAY SPECTROSCOPY OF HEMEPROTEINS : NOVEL METHODS OF DATA ACQUISITION AND 

ANALYSIS APPLIED TO MBCO RELAXATION PHENOMENA * 

X9B 

D 0.8 

0.6 

0.0 

8300 8320 8340 Energ$$ e380 8400 

Figure 1. Ni K-edge XANES spectra of 

the CO adduct of Chromatium vinosum 

hydrogenase and its photoproduct. 

Figure 2. Ni K-edge EXAFS spectra and 

fits of the CO adduct of Chromatium vinosum hydrogenase and its photoproduct. 
I Structural Studies of Discotic Liquid Crystals 1x913 I 

P. A. Heiney, S. Ghosh, N.C. Maliszewskyj (Penn), and Philippe Henderson (Shell 

Research, Belgium) 

to characterize a series 

derivatives. 

At the air-water interface, the molecules are oriented "edge-on" to the interface, 

and are presumed to pack cofacially. This orientation is preserved upon transfer to a solid substrate. The resulting multilayer films are lamellar, with the constituent 

disks organizing into columns aligned along the axis of deposition. The attachment 

of terminal hydroxyl groups to the aliphatic substituents of the disks results in 

the develo ment of correlations between layers and distinct tilts (approximately 

40 degrees! of the disks with respect to the layer normal. Within the plane of 

the film, measured d-spacings larger than the nominal size of the disks may be 

attributed to superlattice ordering of tilts of the molecules with respect to the 

column axis. The in-plane order is best characterized as "liquid-crystalline" with 

evidence of paracrystalline disorder. On heating, the films exhibit an irreversible 

phase transition to a state resembling the bulk Dhd phase, in which the disks are 

still organized in columns with no intracolumnar tilt. 

We have used grazing incidence x-ray diffraction 

of Langmuir-Blodgett films of mono- and bi-function 

Supported by NSF Grants DMR-MRL 92-20668, DMR 93-15341. 

EXAFS and XANES Studies of Nitrile Hydratases 

Mark J. Nelson, John G. Cummings (DuPont), Lewellyn Durney, Daihung Duong, 

and Robert C. Scarrow (Haverford College) 

Nitrile hydratases are metalloenzymes that catalyze the hydration of nitriles to 

amides. We are studying two classes of these - those that contain low- spin Fest and 

those that contain low-spin Cost. A subset of the iron nitrile hydratases is expressed in an inactive form and activated by light. We are studying the metal coordination 

environments of examples of each of these classes as part of a program to elucidate 

the chemical mechanisms of light activation and nitrile hydration. We have shown 

that the iron nitrile hydratases have a biologically novel NsSzO coordination with 

three histidines, two cysteines, and a hydroxide. The Fe-S bonds are slightly shorter 

at pH 9 (where the enzyme is inactive) than at pH '7, explaining dramatic differences 

in the Fe-S region of resonance Raman spectra. Subtle changes in the Fe-S bonds 

are also seen in the presence of inhibitors. We have collected data for the cobalt 

enzyme and a series of model complexes. Preliminary analysis suggests that the 

novel NsSz0 coordination is preserved in this class of nitrile hydratase, as expected 

based on amino acid sequence homologies. This confirms that the cobalt nitrile 

hydratase is a cobalt-sulfur protein, the first, we believe, to be characterized. 

I X9B 
._/ . ..:.,.. 4':.' 

' ,! . i; . -' i'. 

.i. - 

.. 

, -- 

,-*: 

EXAFS of Azotobacter vinelandii Nitrogenase Iron Protein: MgATP 

does not Disrupt the [4Fe-4S] Cluster * 

46 I Metal Cluster Active Sites in Proteins I X9B I 

Lawrence Que, Jr., Gaofeng Pan, Lijin Shu, Xuedong Wang, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 

In the past decade we have investigated a number of metalloproteins containing nonheme-iron centers. This class includes catechol 2,3-dioxygenase (2,3-CTD), 

pur le acid phosphatase, methane monooxygenase, and stearoyl desaturase. 

17 We have obtained and analyzed data for 2,3-CTD and its substrate complexes. 

A 5-coordinate iron site with an average Fe-ligand distance of 2.09 8, is found in 

00 

0) 

observation of Fe-Zn and M-P (M = Fe, Zn) distances of 3.3 and 3.2 8,, respectively, 

indicates an FeZn(0R 2 core structure with phosphate bound to the metal center 

3) Data was also collected on methane monooxygenase from Methylosinus trichosporium OB3b, in which an Fe-Fe separation of 3.0 is observed which we associate with an Fez OR 2 diamond structure, consistent with the crystal structure of 

4 Stearoyl ACP A' desaturase is the newest member of this class of proteins and 

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. 

5) We have also examined the EXAFS of model complexes related to intermediates of these iron proteins; these results are published [3-51. Data was also taken and 

analyzed on copper model complexes modelin the copper dioxygen chemistry in 

metalloproteins, and this paper is published [6f In two cases, the EXAFS analysis 

has been crucial for the structure determination of these unstable model complexes. 

[l] Shp, L., Chiou, Y.-M., Orville, A. M., Miller, M. A., Lipscomb, J. D., Que, 

L. Jr. Biochemistry 34: 6649-6659 (1995 . 

S. . Chemistry & Biology 2: 409-418 (1995 . 

Y., Kitagawa, T., Methur, R., Heerwegh, K. Reed, C. A., Randall, C. R., Que, L. 

Jr. Tatsumi, K. J. Am. Chem. SOC. 116: 9071-9085 1994). 

Lachicotte, R. J., Zang, Y., Que, L. Jr. Inorg. Chem. 34: 1036-1039 (1995 . f] Dong, Y., Fuji, H., Hendrich, M. P., Leising, R. A., Pan, G., Randall), C. R., 

W' kinson, E. C., Zang, Y., Que, L. Jr., Fox, B. G., Kauffmann, K., Mnck, E. J. 

[6] Mahapatra, S., Halfen, J. A., Wil L 'nson, E. C., Pan, G., Cramer, C. J., Que, 

Am. Chem. SOC. 117: 2778-2792 (1995 

L. Jr., Tolman, W. B. J. Am. Chem. SOC. 117: 8865-8866 (1995). 

in a bridging mode. T h is paper is in preparation. 

the enzyme from L1 et ylococcus capsulatus (Bath) taken at -16OoC [2]. 

its d ata is currently being analyzed. With the crystallographic data available for 

5"] Rosenzweig, A. C., Nordlund, P., 4 akahara, P. M., Frederick, C. A., Lippard, 

[3] Kitajima, N., Tamura, N., Amagai, I4 ., Fukui, H., Moro-oka, Y., Mizutani, 

(41 Randall, C. R., Shu, L., Chiou, Y.-M., Hagen, h . S., Ito, M., Kitajima, N., 

X9B 

....a. . 

4 

Go .- 0 0.6 

0.4 -4 

E 0.2 

-8 0.0 

> 

2 4 6 81012 

k (&I, E,, = 7125 eV) 

7120 7160 7200 

X-ray Energy (eV) 

Figure 1. Baseline corrected and normalized Fe K-edge XAS of FePox in the absence (thin line) or presence (thick line) of MgATP, and of 

(dots). a) Edge; successive spectra are offset by 0.1. b) E 

* supported by National Science Foundation Grant MCB-9315835 

. -. 
STRUCTUREFUNCTION OF COBALAMIN DEPENDENT ENZYMES: X-RAY ABSORPTION STUDIES ON METHIONINE 

SYNTHASE FROM E. COLI * 

X-ray Absorption Spectroscopy Comparison of the Active Site Structures of Phanerochaete chrysosporium Lignin Peroxidase Isoenzymes 

H2, H3, H4, H5, H8, and H10 * 

X9B 

R. Sinclair, B. Copeland, I. Yamazaki, and L. Powers(National Center for the 

Design of Molecular Function, Utah State University) 

The iron heme and its immediate environment can provide information that is 

pivotal to our understanding of the structural and mechanistic features that confer 

unusual properties to the heme peroxidases. X-ray absorption spectroscopy (XAS), 

which is ideally suited for the investigation of the local environment and electronic 

structure of the heme iron of hemeproteins, has been used to characterize a variety 

of lignin peroxidase and manganese- dependent peroxidase isoenzymes produced by 

the white rot fungus Phanerochaete chrysosporium. The data suggest no differences 

within the error in the first coordination shell of iron for the isoenzymes H2, H3, H4, 

H5, H8, and H10 examined in this study. The pyrrole nitro ens are at a distance of 

2.05 [0.015] A, the proximal histidine nitrogens are at 1.93 70.021 A, while the sixth 

ligands are located at 2.17 [0.03] A. Significant differences are observed in higher 

coordination shells which may be related to differences in conformational differences 

in the heme. 

* This work is supported by NIH grants, RR01633 (M.R.C.) and GM-24908 (R.G.M.). * NIH RR01633 

1 
Structural Characterization of the Effects of Halide Inhibition on Mn 

Catalase * X9B XAS of Rat Liver Arginase. Characterization of the Mnz Core During 

Catalase Turnover * 

T.Stemmler, J.Penner-Hahn (Univ Michigan), D.Ash and T.Sossong (Temple Univ) 

Arginase catalyzes the hydrolysis of arginine to ornithine and urea. As arginine is 

the substrate for NO synthase (NOS), arginase may be important in regulating NOS 

activity. Rat liver arginase contains a dinuclear Mn active site [l] and is thus similar 

in structure to other dinuclear metalloproteins, including Mn catalase. Consistent 

with this structural similarity, arginase has recently been found to catalyze slowly 

the disproportionation of H202 [2]. We previously reported EXAFS and k ANEd 

for Mn catalase [3-41. Here we describe recent extensions to include arginase. The 

ultimate goal of this work is to establish the features that distinguish the arginase 

and catalase active sites. 

Recently it has been found (Ash & Sossong, unpublished results) that the addition 

of H202 in the presence of ornithine gives an initial burst of 02 production, followed 

by slow, irreversible inactivation of the catalase activity. The XANES (not shown) 

indicate that the Mn remains Mn(I1). This is in contrast to the behavior of Mn 

catalase, where addition of H202 gives a mixture of Mn(I1) and Mn(II1) [4]. The 

absence of significant change in the XANES spectra suggests that the ornithine + 

inactivation does not result in any significant change in the local environment of the 

Mn in arginase. In contrast, there is a significant change in the EXAFS spectrum 

of the inactivated enzyme see Figure). There is no significant d n--.Mn peak in the spectrum for native arginase. However, a new peak appears at a distance corresponding to a Mn-Mn distance of ca. 

3.4 8, following inactivation, suggesting that there has been a significant change in 

the dinuclear Mn site. 

[l] Reczkowski, R. S.; Ash, D. E. J. Am. Chem. SOC. 1992, 114, 10992-4. [2] 

Khangulov, S. V.; Pessiki, P. J.; Barynin, V. V.; Ash, D. E.; Dismukes, G. C. 

Biochemistry 1995, 34, 2015-2025. [3] Waldo G. S.; Yu, S.; Penner-Hahn, J. E. 

J. Am. Chem. SOC. 1992, 114, 5869-70. [4] Waldo, G. S.; Penner-Hahn, J. E. 

Biochemistry 1995, 34, 1507-1512. 

X9B 

Figure 1. Fourier transforms for reduced Mn catalase. 

* Supportedin part by the NIH, Grant GM-45205 to JEPH 

Figure 1. FT before and after inactivation with ornithineSH2 02. 

* Supportedin part by the NIH, Grant GM-45205 to JPH 
XAS OF SUPEROXIDE DISMUTASE. USE OF A SAGITTALLY 

FOCUSED BEAM TO AVOID PHOTOREDUCTION * 

D.Tierney, J.Penner-Hahn (Univ of Michigan), and F. Yamakura (Juntendo Univ) 

Superoxide dismutase (SOD) catalyzes the disproportionation of superoxide to 

H202 and 02 while cycling between an oxidized and a reduced state. The Fe and Mn 

SODS constitute a family of closely related proteins [l], having homologous folding 

patterns and complete conservation of metal ligation. Despite this similarity, Mn 

and Fe are not necessarily interchangeable. If the Thermus thermophilus or E. coli 

MnSODs are reconstituted with Fe, the resulting protein is inactive [2]. Similarly, the Pseudomonas ovalis FeSOD loses activity when reconstituted with Mn [3]. 

In order to compare, at high resolution, the structures of the Fe and Mn enzymes 

and to determine the structure of the enzyme when substituted with the "wrong" metal [4], we have undertaken EXAFS measurements of FeSOD [5], and native and 

Fe substituted MnSOD. The latter are limited by the sensitivity of the MnSOD 

to photoreduction. In contrast to the Fe enzyme, where photoreduction is relatively slow [5], Mn(II1)SOD and Fe(II1) substituted MnSOD suffer extremely fast 

photoreduction, giving > 50% reduction in ca. 10 hours at 40K. 

To avoid photoreduction, we used the sagitally focused beam at X9-B to focus 

the incident x-rays to a small spot and translated the sample horizontally at the 

end of each scan. Recent measurements (see Figure) confirm the utility of this 

approach. The difference XANES spectra for conventionally measured data show 

clear evidence for photoreduction. In contrast, there is no detectable photoreduction 

for the data measured using the sagitally focussed beam. Analysis of these data is 

in progress. 

[I] Stallings, W.; Pattridge, K.; Strong, R.; Ludwig, M. J. Biol. Chem. 1984, 

259, 10695-9. [2] Yamakura, F.; Suzuki, K. J. Biochem. (Tokyo) 1980, 88, 191-6. 

[3] Ose, D.; Fridovich, I. Arch. Biochem. Biophys. 1979, 194, 360-4. [4] Yamakura, 

F.; Matsumoto, T.; Terauchi, K. Free Radical Res. Commun. 1991, 13, 329-34. 

[5] Tierney, D.; Metzger, A.; Ludwig, M.; Penner-Hahn, J. Biochemistry, 1995, 34, 

1661-1668. 

X9B 

-1004 I 

7100 7120 7140 7160 7180 7200 7120 7140 7160 7180 7 

Energy Energy 

(ev) 

I 

Figure 1. Difference XANES spectra relative to first scan. A Conventional B) 

Measured as described in text. Elapsed time ca. 16 hours in eack case. 

* Supportedin part by the NIH, Grant GM-45205 to JEPH 

Structure of Binary and Ternary Complexes of Zinc and Cobalt Carboxypeptidase A as Determined by XAFS * 

Ke Zhang (Biostructures Institute) and David S. Auld (Harvard Med. Sch.) 

X9B 

Carboxypeptidase A, ZnCPD, is typical of a wide range of ex0 and endometalloproteases that have 3 protein ligands and a water molecule bound to a catalytic Zn 

atom. Such enzymes generally have bell-shaped pH-activity profiles (EH2 tf EH tf 

Ekwhere the concentration of the catalytic species EH is regulated by PKEH~ and 

This XAFS study has determined the structure and pH behavior of binary and 

ternary product complexes of CPD A in order to examine the role of the Zn-bound 

water in catalysis. Increasing the pH from 7 to 10 of its L-Phe complex results in 

the same type of progressive changes in the near-edge XAFS spectrum as is seen 

for ZnCPD (1 but the changes are complete by more than 1 pH value below that 

that show E binds the protonated form of L-Phe more tightly than EH, thus in 

effect decreasing the value of PKEH. 

Addition of azide to ZnCPD.L-Phe at pH 7 markedly changes the Zn coordination 

sphere (Fig. 2) from 4 N/O atoms at 2.021 A and 1.4 N/O atoms at 2.54 A to 3.9 

N/O atoms at 1.995 A. The XAFS spectra of the ternary complex is pH independent 

from 7 to 9 (Fig. 2) in agreement with the ionization of the water being the source 

of the spectral changes in the free enzyme and its binary L-Phe complex (2). The 

enzyme.azide-L-Phe complex is likely bound in a manner analogous to that expected 

for a post-transition state in a bi-product complex for peptide hydrolysis i.e. the 

carboxylate anion of the peptide bound to the Zn and the protonated form of L-Phe 

H-bonded to the catalytic Glu-270 carboxylate. 

P EH: 

observed for d nCPD (Fig. 1). The results are in agreement with kinetic studies 

1. Zhang, K. & Auld, D. S. Biochemistry 32, 13844-13851, 1993. 

2. Zhang, K. & Auld, D. S. Biochemistry, in press. 

Figure 1. XAFS spectra of ZnCPD-LPhe at pH 6.56 (solid) and 8.83 (circles). 

* Supported by NIH grant GM-47534. 

RDF of ZnCPDSL-Phe-azide 

and 8.81 circles) and 

pH 6.65 (6iamonds). 
Whavior of Liquid Crystals in Silica Aerogels * I XlOA I Chain Length Dependence of the Cn/Au(lll) Tilt Structure * XlOA 

Noel A. Clark, A.G. Rappaport, T. Bellini, and B.N. Thomas (University of Colorado, Department of Physics, Condensed Matter Laboratory, Boulder, GO) 

Phase behavior in the presence of externally induced disorder is an area of current 

research in statistical physics. Liquid crystals LCs) are particularly interesting in 

tional ordering, which is readily affected by surface interactions, the phase behavior 

of liquid crystals can be strongly influenced by incorporation into porous solid media of high surface to volume ratio. The most basic LC translational ordering is 

the nematic - smectic A (NA) transition, wherein a one dimensional layering of 

molecules into a stack of 2d liquid-like layers appears. 

We report the results of an X-ray diffraction study of the smectic A layer structure 

with the liquid crystal incorporated into the pores of silica aerogel This is the first 

quantitative study of the effect of externally induced disorder on liquid crystal layer 

structure. The LC is incorporated into silica aerogels, highly porous solids formed 

by dehydration of suspensions of aggregates of nm dimension silica particles. The 

aerogel pores, ranging in mean size from IZOA to ~OOA form a continuously con- nected volume which can occupy a volume fraction 4 approaching unity (4 < 0.95 

in the experiments reported here), of high surface to volume ratio. The results show 

that the aerogel confinement radically alters the nematic - smectic A transition. At 

the lowest temperatures local smectic ordering extends out to dimensions comparable to the pore size or somewhat larger, but for temperatures near the bulk nematic - smectic A transition, the smectic order is strongly suppressed. 

this context. Because they posses rather wea I, orientational and partial translac 

Figure 1. Correlation lengths for smectic A ordering vs temperature T for bulk 

8CB and 8CB in a series of silica aerogels of indicated pore size. The divergence 

at the bulk NA transition of the bulk correlation lengths for smectic ordering along 

the director (11) and normal to the director (I) isalso shown. The smection order 

is strongly suppressed at temperatures near the bulk transition, but ultimately 

grow to be comparable to or larger than the pore size. Although the bulk smectic 

correlations are highly anisotropic [Ell >> El], the x-ray lineshapes show that in the 

aerogel the correlations are nearly isotropic. 

* Supported by NSF Grant DMR 92-23729 

We use grazing incidence x-ray diffraction to study the systematic structural 

dependence of an archetypal self-assembled monolayer as a function of the chain 

length, n. The monolayer consists of n-alkyl thiol molecules, CHa(CHz),,-iSH (Cn, 

10<n<30), self-assembled on a Au(ll1) surface. At room temperature, the 2D 

structure is described by a C(4x2) unit mesh 1,2,3] at all chain lengths. We find 

drocarbon chain length which is characterized by distinct 'long' (11116) and 'short' 

(11514) chain length regimes, as well as a continuous structural variation within 

each regime [4]. For example, the tilt angle for 11514 is 3' greater than the tilt 

angle for n216, and the tilt direction shows a clear trend of shifting away from 

the NNN direction as the chain length decreases. Furthermore, there appears to 

be a discontinuous change in the tilt angle between these two regimes. A parameterization of the hydrocarbon packing leads to the conclusion that the long and 

short chain length regimes closely resemble the orthorhombic and monoclinic chain 

packing of n-alkanes. These systematic structural changes are apparently due to 

the conflicting requirements of epitaxy and molecular packing, and is driven by the 

changing intraAayer interaction 

strength (which is proportional to hydrocarbon chain length). . [I] N. Camillone 111, C. E. D. Chidsey, G.-Y. Liu, and G. Scoles, J. Chem. Phys. 

98, 3503 (1993 

that there is a systematic dependence of the t !l t structure as a function of the hyP. Fenter, d: Eisenberger, and K. S. Liang, Phys. Rev. 

P. Fenter, A. Eberhardt, and P. Eisenberger, Science 266, 1216 

P. Fenter, A. Eberhardt, K. S. Liang and P. Eisenberger, 

* This work is supported by DOE award number DEFG02-93ER45503. 
Growth of Self-Assembled Monolayers: Decanethiol/Au( 111) 

4d 

(0 

CL 

XlOB Structure and Evolution in an Organic Thin Film: PTCDA/Au(lll) * 

latticis under kineticany limited growth conditions. 

152, 65 (1995). 

[l] P. Fenter, P. Burrows, P. Eisenberger, and S. R. Forrest, J. Cryst. Growth 

XIOB 

* Supported by MRSEC grant number DMR-94-00362 and the AFOSR 
I . . :I 

., . 

.. 

F 1 XlOB I (0 tu I Structure of w-Substituted Self-Assembled Monolayers * 

T. Y. B. Leung, A. Eberhardt, P. Fenter, P. Eisenberger, and G. Scoles (Princeton 

Univ) 

We have performed initial grazing incidence x-ray diffraction studies of the structure of w-substituted alkyl thiols, CH2=CH-(CH2 &3H, self-assembled on Au(ll1) 

layer structure and properties, and as a clear structural basis for understanding the 

stereochemistry of reactive beams with the terminal double bond. The monolayers 

are grown by vapor deposition, and studied under ultra-high vacuum conditions. 

Although the substitution of the inert -CH3 group by a double bond functionality was not expected to have a significant impact upon the monolayer structure, our initial results indicate that these monolayers have a 2D structure different from 

that of the -CH3 terminated compounds, and remarkably, exhibit a much higher 

thermal stability. The unit mesh of the w-substituted monolayer has dimensions of 

4.997Aby 17.32A, as compared to the C(4x2) structure [1,2] of the -CH3 terminated 

monolayer which has dimensions of 9.994Aby 8.66A. Furthermore, the w-substituted 

monolayer does not exhibit the centered rectangular symmetry found for the -CH3 

terminated monolayer [3], since we do not find any systematic absences of the Bragg 

rods. 

A second surprising feature is that the thermal stability of this system is much 

higher than that of the alkyl thiol system. For instance, we find that the w- substituted monolayers begin to show signs of re-arrangement at temperatures above 

120°C, whereas similar chain length alkyl thiols melt at approximately 65OC. These 

observations indicate that small changes to the molecular structure can induce large 

changes in the monolayer structure and stability. 

TIIN. Camillone 111, C. E. D. Chidsey, G.-Y. Liu, and G. Scoles, J. Chem. Phys. 

surfaces to determine what affect small chemical c h anges may have upon the mono- 

_. 

98: 4503 (1993). 

P. Fenter, P. Eisenberger, and K. S. Liang, Phys. Rev. Lett. 70, 2447 (1993). 

P. Fenter, A. Eberhardt, and P. Eisenberger, Science 266, 1216 (1994) 

* This work is supported by DOE award number DEFG02-93ER45503 

Fe and Mo K-edge EXAFS of CO-inhibited A.v. Nitrogenase I XlOC 

B. J. R. Weiss, S. P. Cramer (U. C. Davis), R. Tittsworth, and B. J. Hales (Lousiana 

State U.) 

Nitrogenase is nature's agent for fixing nitrogen, converting atmospheric dinitrogen into ammonia for plant, animal and human consumption. The enzyme contains 

two metalloproteins: the Fe protein, which contains an Fe:S center, and the larger 

MoFe protein, containing both an Fe:S cluster and the Mo:Fe:S cofactor. While the 

crystallographic structure of the resting state is known, CO and (of even greater interest) N2 bind to reduced states which cannot be crystallized, and whose structure 

is unknown. 

We are using both Fe and Mo Kedge EXAFS to look for structural changes in 

the reduced intermediates and to determine which atoms are involved in substrate 

and inhibitor binding. While there are multiple iron atoms in each of the proteins, 

there is a single molybdenum atom located at the active site; thus, information 

from the Mo K-edge is much more specific, and any shifts should be indicative of a change in the redox state of molybdenum, and imply direct involvement of the Mo 

atom in nitrogen fixation. 

EXAFS scans were taken at both the Fe and Mo Kedges of CO-inhibited A.v. 

nitrogenase. We were able to reproduce previous data sets, and the resulting fourier 

transforms are shown below compared to Fe and Mo EXAFS of resting state A.v. 

nitrogenase. Further analysis is currently underway. 

Preliminary work was also done on C2H2-inhibited A.v. nitrogenase at both Fe 

and Mo Kedges, and on "deep turnover'' nitrogenase at the Mo Kedge. 

Mo-S 

Fe-S 

miiolted 

CO-hhbisd 

Fe.Mo - 

01234567 

IT miioltcd 

b!?@bsQ 01234561 

Figure 1. Fourier transforms of Fe K- Figure 2. Fourier transforms of Mo Kedge EXAFS edge EXAFS 
Lead Speciation of a Mixed Soil Component System Using EXAFS I XllA 

T.E. Alcacio, G.M. Lamble*, A. Scheidegger and D.L. Sparks U. of Delaware, 

*NSLS, BNL 

The chemical behavior of any element in the environment depends on the nature 

of its components. Most natural systems are quite heterogeneous and have both 

mineral and organic phases present. Thus, there is a potential for many species 

to be present. The actual form or species needs to be determined in order to gain 

insight into the physical chemistry of natural systems as well as into the nature 

of pollutant interactions. In this study, Extended X-ray Absorption Fine Structure 

Spectroscopy was utilized to determine the local chemical environment of Pb treated 

pyrophyllite and gibbsite. Both minerals were then mixed together in a 1:l ratio 

and studies of the EXAFS spectra was performed as well. The radial distribution 

function for the gibbsite shows a first coordination shell occurring at 2.01 and a second coordination shell at 3.60 . These distances, which are uncorrected for phase 

shifts, are comparable to bond distances expected for Pb-0 and Pb-Pb respectively. 

In contrast, the pyrophyllite which has nearly a 4X greater surface area shows only 

one peak at 1.90 (Pb-0) and no second coordination shell. 

We suggest the formation of Pb polynuclear species on the gibbsite surface results 

from greater crowding of lead atoms on the surface. 

When the two samples undergo mixing, the spectra for the mixed component 

system agrees well with the prominent features displayed by the spectra for the two 

individual components. It is hoped that this study will spur further investigations 

of heterogeneous systems which model natural systems. 

0.00 

0.04 

: 0.02 

B 

a 

; 0.00 

E 

B 

6 

W Carnpnrlson 01 Pb 011 Pyropl~ylllle. 

Pb on Clbbsile and Pb 011 Mix ol Both . /\ 

I-= 1.73 )Iinol Pbnl" Gibbsiie 

+ 3.47 ~IIIIOI PI, III'* ~yrop~iy~~iie 

Figure 1. Fourier transform of pyrophyllite (lower), gibbsite (middle), and mixture(top) of both. w 

Chromium speciation in hazardous, cement-based waste forms 

S. Bajt (CARS, U. of Chicago), J. F. Lee (Synchrotron Radiation Research), Center, Taiwan), S. B. Clark (SREL, U. of Georgia), G. M. Lamble (BNL), C. A. 

Langton, L. Oji (Westinghouse Savannah River Company) 

Chromium contaminated waste streams can result from metal plating or finishing 

processes, where Cr is usually present as the highly soluble and toxic Cr0:- species. 

Cement-based forms are frequently used to immobilize such liquid wastes. Studies 

on chromium release from these waste forms indicate that CrOz- diffuses rapidly, 

and is significantly more mobile than reduced Cr3+. Consequently, formulations of 

cements have been developed to control the chromium speciation in situ to favor the 

less soluble and less mobile Cr3" ion. Therefore the knowledge of the oxidation state 

and local environment of Cr in situ is essential to predict long-term contaminant 

release from the waste form. 

XANES and EXAFS techniques were used to determine the oxidation states and 

local environment of Cr in cement-based waste forms. Simulated waste solutions 

were prepared using NazCrO4, and mixed with cement materials to give 2500 

ppm Cr in solid matrix. Three mixtures and two standards were analyzed in this 

experiment (Table 1). Mix 1 consisted of slag, Mix 2 of slag, fly ash and Portland 

cement, and Mix 3 of Portland cement only. Figure 1 shows the near edge spectra 

from the Cr K-edge of five samples. It is quite clear that the structural environment 

of Cr in Mix 1 is very similar to Cr in CrOOH. The XAFS spectrum Cr in Mix 3 

and Mix 1 agree very well with those of Cr-0 in Cr0:- and CrOOH, respectively. 

The large difference in the Cr-0 distances in these two environments are easily 

distinguishable. Coordination numbers for Mix 2 suggest that this mixture consists 

of about 25% Cret and 75% Cr3+ species (Table 1). 

Results show that the Cr in untreated Portland cement formulations remains as toxic Cret, while slag additives to the cement reduce Cra+ to the less toxic, less 

mobile Cr3" species. EXAFS analysis suggests that the Crat species is surrounded 

by four nearest oxygen neighbours, while reduced Cr3+ species is surrounded by six 

oxygen atoms. 

I XllA 

Table 1 

Sample N (as%) R(i0.02) in A 

K2CrO4 4.90 1.65 

mix #3 5.40 1.66 

mix##2 1.31, 4.93 1.65, 1.98 

mix #1 6.46 1.98 

Figure 1. Near ed e spectra from Cr K- c-00~ 6.21 1.98 

KO00 0000 0020 0040 

ENERGY (cv) 

edge of KzCr04 a) Mix #3 b Mix 

#2 (c), Mix #1 (!) knd CrOO$ (L). Figure 2. (Table) 
F I XAFS and Developing Plants for Phytoremediation I XllA I v) 

I+ 

W.R. Berti (Du Pont), G.M. Lamble (BNL), S.D. Cuningham, and J.W. Huang 

(Du Pont) 

Traditional solutions to remediate Pb-contaminated soils rely primarily on excavation, stabilization with cement, and landfilling. These techniques are invasive 

and expensive, resulting in drastically disturbed soils and landscapes. Phytoremediation uses plants and soil conditioning agents to remediate contaminated soils in an "eco-friendly" manner. 

Phytoextraction, or biomining, uses plants to remove or destroy contaminants 

from the soil matrix. For the phytoextraction of Pb, there is a need to find, breed, or develop plants that can translocate Pb from roots to the tops. The Pb is then 

removed by harvesting and processing the above ground portion of the plants. For 

this technology to be effective, however, plant tops must "hyperaccumulate" Pb in 

excess of 1% dry-weight basis). We regularly find roots of plants that contain as 

high as 1%. Jhe tops of these plants, however, rarely have total Pb concentrations as high as 0.1%. Information provided by XAFS about the forms of Pb in plant 

parts and its location within the plant may be valuable in this research. It may help 

guide selection of plant species and traits to use in the development or breeding of 

Pb-hyperaccumulating plants. 

The figure shows overlaid XAFS data from Pb uptaken in corn roots and in 

ragweed. Well defined features in the spectra indicate that the Pb structural form 

is also well defined. The similarities between the spectra indicate that the Pb is 

uptaken-in a very similar form in both the ragweed and the corn roots. 

-0.04 

k(A-'l 

I Progress in fabricating capillary fibers for x-ray concentrators I XllA I 

D.L. Brewe (U. of Washington), S.M. Heald (Pacific Northwest National Lab), B. 

Barg, F.C. Brown, K.H. Kim, and E.A. Stern (U. of Washington) 

Guiding x-rays down the inside of tapered capillaries is a means to increase the 

flux density from synchrotron light sources, without some of the disadvantages 

inherent in some other techniques. We have demonstrated that a process based on techniques for fabrication of glass fibers may be used to produce tapered capillaries 

with inlet diameters on the order of 150pm or more and outlets on the order of 1pm 

or less '. Several capillaries made from pure silica glass were manufactured and 

the performance was tested at X11A. Pure silica has the advantages of radiation 

hardness, and freedom from potential problems arising from fluorescence of heavier 

elements in the capillary, in formulations such as lead glass. Measured transmission 

ofx-rays from linear capillaries with inlet diameters of ~150pm and outlet diameters 

of 1.3 - 1.4pm is on the order of 2% for an x-ray energy of 10KeV, with corresponding 

intensity gains of up to -270 (see Table). 

Calculated and measured transmission efficiencies are in fairly good agreement , leading to the expectation that efficiencies predicted by calculations to be attainable from optimal profiles ' are a realistic goal. We have also made progress in 

fabricating capillaries with profiles predicted by calculations to provide greatly improved transmission over the linear capillaries. We are in the process of testing 

these capillaries, and constructing improved apparatus for supporting and aligning 

the capillaries in the x-ray beam. 

rll K.F. Voss. K.H. Kim. E.A. Stern. F.C. Brown. and S.M. Heald. Nucl. Inst. 

M&h. A347, 390 (1994). ' 

SP E Proc., Vol. 2516 (1995). I"] D.L. Brewe, S.M. Heald, B. Barg, F.C. Brown, K.H. Kim, and E.A. Stern, 

capillary length inlet/outlet intensity measured calculated 

diameters gain efficiency efficiency 

#17 875mm 106/12.4pm 32 44% 99.5% 

#19 

#I2 360mm 145/1.4pm 239 2.2% 

548mm 150/1.3pm 274 2.1% 4.25% 

2.90% 

Figure 1. Comparison of raw XAFS data from Pb uptaken by Corn Roots (solid 

line) and Ragweed (broken line). 

Figure 1. Summary of measurements and calculations for three capillaries. The 

x-ray energyfor the measurements was 10KeV. 
i 

I Local Structural Studies of Ti-Zr Alloy Silicide Thin Films on Si I XllA I 

Yuan Dao, Robert J. Nemanich, and Dale E. Sayers (North Carolina State University) 

Previously, we have been shown that the C49 phase of TiSiz can be stabilized at 

high temperatures by co-evaporation of a small amount of Zr with Ti. The resulting 

C49 Ti-Zr alloy silicide thin films exhibit improved thermal stability compared to 

C54 TiSi2 films. In order to understand this further, the local atomic structure 

around the Ti and Zr sites was studied using extended x-ray absorption fine structure (EXAFS) analysis (See Fig. 1). The distances of the Ti-Si and Zr-Si shells in 

the C49 Til-,Zr,)Siz thin films are similar to those of the Ti-Si and Zr-Si shells in 

a Bragg-Pauling like behavior. The Ti-Ti distances in the C49 (Til-,Zr= Si2 thin 

silicide thin films is longer than the Ti-Ti distances. The Ti-Ti shell in the C49 

alloy silicide thin film splits into two sub-shells. 

The Ti-Ti short distance increases more significantly with the Zr content than 

that of the Ti-Ti long distance. The Ti-Ti short distance shell in the C49 alloy 

silicide is more disordered than that of the Ti-Ti long distance. This may be due 

to the asymmetry of the Ti-Ti short distance shell, and therefore, the Ti-Ti short 

distance shell may have the ability to adjust its lattice positions to lower the strain 

energy introduced by the Zr atoms. The C54 TiSi2 has only one Ti-Ti shell, which 

is symmetric about the central Ti atom and may not have the ability to adjust the 

lattice positions to lower the strain energy. 

the C49 !c iSi2 and ZrSiz respectively, and do not change with composition. This is 

films vary linearly with the Zr content x. The Ti-Zr shell distance in the CJ 49 alloy 

60 

50 

40 

30 

20 

10 

0 

XllA An XAFS study of structural Fe in thermally activated natural 

kaolinites. * 

Monica Endregard (Univ. of Trondheim, Norway), and Alex F. Gualtieri (Univ. 

of Modena, Italy) 

Kaolinite is the main mineralogical component in clays. Besides, its importance 

resides in the large use of this mineral as a precursor for ceramic products. Its 

structure consists of a stacking of 1:1 Si centered tetrahedral and Al centered octahedral layers along the c axis. The way the layers stack can be affected by extensive 

faulting (planar disorder) resulting in low-defective and highly-defective structures 

such as kaolinite international standards KGa-1 and KGa-2 which contain 14 and 

50 % of faulted sequences, respectively. The structural state of kaolinite influences 

the kinetic of the HT processes leading to the formation of metakaolinite and mullite.[l] Because abrupt transformations affect the octahedral Al environment of the 

faulted sequences during the phase transitions, a study of such changes may provide 

information about the process. Mossbauer [2 and EPS [3] studies shoewed that Fe 

of Fe bearing kaolinites thermally treated at various temperatures can be highly informative concerning these structural changes. Fe K-edge (7112 eV) XAFS spectra 

of KGa-1 and KGa-2 at RT, 600, 800 and 1100 OC and selected model compounds 

were collected simultaneously in transmission and fluorescence mode at 298 and 80 

K. The energy calibration was checked by simultaneously measuring XAFS on a Fe foil using a reference detector. The higher harmonic reflections were rejected by 

detuning the Si( 1ll)monochromator crystals to 70 %. The information contained in 

the XANES spectra coupled with the EXAFS analysis suggests that the Fe coordination decreases upon thermal treatment from 6 to 4 accompanied by a shortening 

of first shell bond distances. 

in natural kaolinites usually substitutes for A \ in the lattice. Thus, an XAFS study 

1 2 3 4 5 

Radial Distance (A) Figure 1. Fourier transform magnitude of the k3 weighted Fe K-edge EXAFS of 

disordered kaolinite samples (KG+2) at RT and heated at 6OO0C and 80OoC. Figure 1. Fourier transforms (solid lines) and the R-space fitting results (dotted 

lines) of k3-weighted Ti K-edge EXAFS of the C49 (Til-,Zr,)Siz thin film samples P (x= 0, 0.1, 0.2 and 0.3). cn numbers DE-AC02-76CH00016 and DE-FG05-89ER45384. 

* This work was supportedby The Norwegian Research Council andDOE under contract 

Gualtieri A.F. (1995). PhD thesis, Univ. of Modena, Italy. 

MacKenzie K.J.D. (1969 Clay minerals 8, 151-160. 

Jefferson D.A., Tricker kJ., and Winterbottom A.P. (1975). Clays and Clay 

Min. 23, 355-360. 
I 

XAS Studies of Highly Nonplanar Cobalt(II1) Porphyrin Complexes * XllA Hosts; Indium K-edge XAFS of the Local Coordination of the 111-V 

CVD Growth of 111-V Quantum Wires and Dots in Microporous 

I Semiconductor Clusters * 

Wendy Flavell, Heather Yates and Jonathan Agger (UMIST, UK), David Nicholson 

and Arild Moens (Univ. of Trondheim, Norway); Geraldine Lamble and Larry 

Fareria (BNL) 

This work is aimed at the growth of ordered quantum wire and dot structures 

inside the cage and channel structure of host microporous materials, by deposition 

of compound semiconductors. Here, we aim to use XAFS to study the local environment of InP clusters introduced into materials including Alp&-5 and MCM-41 

by MOCVD. The work forms part of an EC ESPRIT I11 Basic Research Project. 

The reactants used in the MOCVD growth were trimethylindium and phosphine 

in hydrogen carrier gas, and these were introduced sequentially into the host material. Station X11A was used to study the In K-edge of the implanted semiconductor. 

These measurements were complemented by studies of the P K-edge using station 

3.4 at SRS. CLRC Daresburv Laboratorv. ". UK. and bv "P MASNMR, EDAX, 

XRD, HRTEM and PL. 

amounts of InP showed that long range order is maintained within the implant. 

Analysis of the In K-edge data from A1P04-5 samples loaded with differing 

The position of the first P shill in"all samples was unchanged from its-distance 

of 2.54 Ain a bulk InP standard. The first In shell was located at 4.17 A, very 

close to its distance in InP. Additional oxygen atoms at around 3.45 Awere located, 

originating from the bonding of the implant to the zeolite framework. These observations confirm suggestions from MASNMR, PL and from P K-edge EXAFS that 

the local structure of the implant is not significantly distorted from that in bulk 

InP. This result is in contrast to measurements taken from a sample in which only 

the first of the MOCVD reagents, trimethylindium, was introduced into the host. 

Here, strong bonding of In to the zeolite framework was observed, with 3 0 atoms 

coordinated at 2.14 A. No long range order which could be attributed to bulk In was 

observed. This confirms earlier work by 'H NMR and CARS, which suggested that 

the first introduced MOCVD precursor reacts at the acid sites within the zeolite 

[l1PLM.W. Anderson, G.K. Logothetis, M.E. Pemble, A.G. Taylor, N.C. Wallace an .M. Yates, J. Adv. Mater. Opt. Elect. 2, 313(1993). 

* This work was supported by the Norwegian Research Council and the DOE under 

contract numbers DE-AC02-76CH00016 and DE-FG05-89ER45384. * This work was supported by the EC. 
I Solution of the structure of disordered mixed salts I XllA I 

A.Fkenke1 and E.A.Stern (Univ. of Wash., Seattle), A.Vorone1 (Tel-Aviv Univ., 

Israel), S.Heald (PNL) 

We have solved, for the first time, the structure of a disordered system of mixed 

salts including its buckling about the average structure, using X-ray absorption 

fine structure (XAFS) method and molecular dynamics (MD) simulations. Recent 

XAFS measurements on mixed disordered crystals of the average NaCl structure 

have revealed essential differences from the periodic structure [l]. We have extended 

the measurements to span the full range of concentrations in the RbBr(x)C1(1-x) 

system. We find that the concentration - weighted average of interatomic distances 

spacing, given by diffraction, 

in the middle of the x-range. Such 

determined the buckling angles 

determined with XAFS is greater than the 

the gap between the two being as large as 0.04 a difference is consistent with bond buckling 

by XAFS analysis and rms values of the buckling angles were found to maximize 

at 10-12 deg. for the 50 % concentration of Br at 10 K. We demonstrate also that 

the buckling has to be accompanied by lattice strains and obtain the strain energy 

from the MD simulations. Simulations have shown that the strains are necessary to 

maintain the average NaCl structure of these systems. We estimate that the strain 

energy, measured at low temperature, would be partially (55 %) released at the 

elevated temperatures, due to the thermal expansion. The residual strain energy was used to estimate the melting point depression of these mixtures and excellent 

agreement with experiment is found. 

1. A. Frenkel, E. A. Stern, A. Voronel, M. Qian, M. Newville, Phys. Rev. Lett., 

71, 3485 (1993); Phys. Rev. B 48, 12449 (1993). 

XllA Nature of the Sr induced structural phase transition in 

Laz-,Sr,CuOB 

D.Haske1 and E.A.Stern (University of Washington) 

The local structure about La atoms in oriented Laz-,Sr,CuOl crystals is investigated by means of polarized X-ray Absorption Fine Structure (XAFS) measurements. Diffraction results [l] indicate that the SI induced structural transformation at low temperature from orthorhombic (LTO) to tetragonal (HTT) involves 

decreases, on the average of the tilt angle of the CuO6 octahedra to zero Fig 1 

phase, with no apparent effect of the structural phase boundary on the transport 

properties. 

Polarized XAFS results [2] show that the SI induced phase transition exhibits 

displacive character, at least up to x M 0.15, which is manifested through a decrease 

in the tilt angle of the CuO6 octahedra, in agreement with the diffraction results. At 

higher Sr content, however, the local tilts stop changing but start disordering over 

long range giving raise to the average HTT structure (Fig. 2). The absence of an effect of the Sr induced phase boundary at low-T on the superconducting properties 

is probably related to the lack of a significant change in the local structure over 

scales comparable to the superconducting coherence length in this material. This 

suggests that the correlation length of LTO tilts in the superconducting HTT phase 

is somewhat greater than 30& a result that can be confirmed by other techniques 

sensitive to intermediate range order such as the Pair Distribution Function (PDF) 

of neutron diffraction or atomic resolution imaging in the TEM. 

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 #DEMagnetic measurements (11 show that bulk superconductivity persists in t h e HT 4 

FG06-90ER45425. 

P. G. Radaelli et. al., Phys. Rev. B 49, 4163 (1994) 

D. Haskel et. al., Phys. Rev. Lett. 76, p.439 (1996). 

Figure 1. Schematic representation of 

the LTO structure. In the HTT phase, 

diffraction results indicate that the tilt 

angle of the CuOe octahedra is, on the 

average, zero. 

I 

Figure 2. La-O(2) distances as a function of 2 as obtaned from the polarized 

XAFS analysis at T=20K. The neutron 

diffraction results are also shown. 
EXAFS Studies on Cu(I1) Ions Exchanged in H-SAPO-5 and 

CoSAPO-5 and -34 Molecular Sieves Sieves 

Polarization dependent XAFS, employing the total electron yield (TEY 

energy discriminating fluorescence detection techniques, has been used to stu d y and the 

structure of MnSe/ZnTe (001) superlattices grown by MBE. These superlattices 

consist of 100-300 periods of A/B layers with A and B ranging between 4 and 

25 monolayers. Neutron scattering data on these materials show an unique antiferromagnetic helimagnetic phase at low temperature which is tunable by varying 

the thickness, temperature and strain of the MnSe layer (T. M. Giebultowicz, et. 

al., Phys. Rev. B (Rapid Comm.) 46, 12076, 1992). 

Of particular interest is the interface between the magnetic MnSe layers and 

the ZnTe layers, which act as a non-magnetic buffer, magnetically isolating the 

individual MnSe layers, and the effect of the interface on the strain in the MnSe 

layers. Polarization dependent XAFS taken at different edge energies coupled with 

x-ray diffraction results can distinguish between different models of the structure 

at the interface. 

In the data shown below, one can clearly see the effect of the lattice mismatch 

between MnSe and ZnTe as the MnSe bonds bend, while stretching only minimally, 

to accommodate the ZnTe lattice spacing. This reduces the first shell amplitude of 

the the XAFS for x-ray polarization vector perpendicular to the plane of superlattice 

growth relative to the amplitude of the XAFS for the polarization vector in the plane 

of the superlattice layers. 

XllA 

0.030 

8 0.020 < 

s 

m 

E 

0.010 

(D 

00 

- parallel poladration --- perpendicular poladzaUon 

XAFS Studies of MnSe/ZnTe Superlattices 

Radial Distribution (Angstroms) 

Figure 1. Mn Edge Fluorescence Data (Sample 900622A) 

Geraldine M. Lamble[l], Arild Moen[2] and David G. Nicholson [1]NSLS, BNL 

[2]Department of Chemistry(AVH), Univ.of Trondheim, N-7055, Norway Trondheim,Norway 

Microporous, microcrystalline aluminium phosphates (ALPOs), metal- substituted aluminium phosphates (MeALPOs and silicon-substituted analogues 

studies and there is a continuing growth in the size of the family of compounds since they were first synthesised 

in 1982[1]. 

Because of their structural relationships to the zeolites the materials are often 

termed zeotypes. The zeotypes are monophasic crystalline solids in which the active 

sites are distributed in a spatially uniform manner throughout the bulk.Thus, some 

of them can be used as uniform heterogeneous catalysts. In this connection, the most 

significant feature of zeotypes is their microporous nature which means that nearly 

all of the accessible surface area is actually inside the crystallites. For examplelover 

99.5area of a lmm diameter crystallite is internal. Consequently, most of the All P 

and/or metal atoms are effectively surface atoms, although they are located deep 

inside the material and this means that bulk physical techniques such as EXAFS can actually be regarded as surface techniques in these special cases.We have reviously 

published some results of EXAFS studies using the facilities of XllA - 41. In 

CoSAPO-34 the cobalt atoms enters the framework by substituting Al(II1) in the 

form of Co(I1). The material is interesting because it undergoes colour changes on 

calcination (blue to green at 500 C with a change to greyish-blue on cooling in 

moist air). The object of the present study is use XAS to study the environments 

of the Cu- and Co- atoms in the as-synthesised and calcined materials. EXAFS and 

other techniques show that attempts to incorporate Cu into the framework of the 

molecular sieve during the hydrothermal synthesis lead to reduction to Cu(1) with 

subsequent disproportionation to Cu-metal [5]. Data were collected for a series of 

formulations a liquid N2 temperature. The results of this first part of the XAS study 

are currently being analysed. We have recently measured the catalytic activity with 

resDect to NO reduction r61 and the next stage in the study is to record XAS of 

(SAPOS) are interesting candidates for cataytic 1' 

selected samples in an in %u cell. 

Chem. 

- 

[l] S.T. Wilson, B.M. Lok, C.A. Messina, T.R. Cannan, E.M. Flanigen, J. Am. 

soc.1982, 104, 1146 

[2] A. Lund, D.G. Nicholson, G. Lamble and B.Beagley J. Materials Chem., 1994, 

4. 

1723. 

[3] M.Endregard, D.G. Nicholson, M. Stcker and G. Lamble J . Materials Chem.. 

1995, 5, 

485. 

[4] M.Endregard, D.G. Nicholson, M. Stcker and G. Lamble J. Materials Chem.. 

1995, 5, 

785. 

[5] A. Moen and D. G. Nicholson, J. Chem. SOC. Faraday Transactions, 1995, 

(in press) 

[6] A. Moen, Ph.D Thesis, Trondheim, 1995. 
I XAFS study of Zn2+ incorporation into calcite (CaC03) XAFS Investigation of Thermal Structural Disorder at GaSb/AlSb 

Superlattice Interfaces 

I XllA I X11A, 

X23A2 Geraldine M. Lamble (BNL) and Richard J. Reeder (SUNY, Stony Brook) 

The mobility and abundance of Zn2+ and other heavy metal species in natural waters are largely controlled by uptake onto mineral surfaces via adsorption or coprecipitation. Coprecipitation of dissolved heavy metal species with calcite, 

CaCOs, is known to be very effective in limiting dissolved concentrations and restricting mobility. However, recent coprecipitation studies have documented that 

dissolved metal ions show distinct preferences for different surface sites during layer 

growth. Zn2+ shows a surface site preference that differs from the behavior expected on the basis of ion size. Although differential incorporation occurs at distinct surface sites, it has been thought that Zn2+ occupies only the single Ca site in the 

bulk. 

As a first step toward understanding the Zn2+ incorporation mechanism, we have 

obtained XAFS spectra of the Zn K-edge (9659 eV) for synthetic Zn-bearing calcite 

samples. The fitting results for the Zn-bearing calcite indicate a Zn first shell with 

6.7 (+ - 1.0 oxygen atoms at a distance of 2.11 (+ - 0.02 A. These values compare 

suggests that Zn2+ occupies only the Ca site in the bulk structure. Therefore, the 

different surface sites represent multiple surface expressions of a single bulk site. 

favora kl ly with expected values for Zn in octahedr av coordination with oxygen. This 

Figure 1. Fourier transforms of raw XAFS data from the K-edge of Zn in Calcite 

full line) with that of Zn in ZnCO3 (broken line). The coincidence of the first L ourier transform peak provides a direct indication that Zn is in an octahedral 

coordination with 0, as in ZnCO3 and thus occupies the Ca site in calcite, as is 

confirmed by the XAFS analysis. 
4d 

cL 0 I X-ray Study of Atomic Correlations in ZnCdSeTe Epitaxial Thin I X11A. 1 I X23A2 I 0 I Films 

Q. Lu, B. A. Bunker, H. Luo, A. J. Kropf, K. M. Kemner, J. K. Furdyna 

X-ray Absorption Fine-structure Spectroscopy (XAFS) have been performed at 

approximately 90K to study the local structure of thin films of the 11-VI quaternary 

alloy Zno.6 Cdo.6 Seo.bTeo.6. Samples were grown by molecular beam epitaxy (MBE) on (100) GaAs substrates, 4' miscut towards the (111)B direction with a ZnTe 

buffer layer. The XAFS data indicate that there are more Zn-Se and Cd-Te bonds in 

the alloy than expected for a random arrangement. The results imply the formation 

of high-strain local structure and indicate that electronic pairing energies dominate 

over strain energy. These results are similar to the earlier observation of interlayer 

switching in ZnTe/CdSe superlattices. Although no long-range ordering is observed 

in our room-temperature diffraction measurements, the preference of Zn-Se and CdTe bonding also implies a tendency to spontaneously form a composition-modulated 

microstructure. 

I XANES as a Local Structural Probe * 

B. Ravel and E.A. Stern (U of Wash.) 

I XllA I 

We measured the x-ray absorption near-edge structure XANES) at the titanium 

PbTiO3 and BaTiO3 data were collected in fluorescence at room temperature from 

single domain, single crystal samples. At room temperature PbTiO3 and BaTiO3 

both possess tetragonal crystal structures. EuTiO3 is cubic at all temperatures and 

the data was collected in transmission on a polycrystalline sample. The XANES 

spectrum is sensitive to the symmetry of surrounding atoms about the transition 

metal site in transition metal oxides. When the centrosymmetry about the transition metal site site is broken, p character from the surrounding oxygen atoms is 

mixed with the empty d orbitals, allowing a dipole transition with a strength related 

to the square of the magnitude of the displacement of the Ti atom. In transition 

metal oxides, this transition appears in the XANES spectrum as a peak in the 

pre-edge region, shown in Fig. 1 around 4966 eV. 

By collecting data on single crystals, we used the polarization of the synchrotron 

beam to measure the directional dependence of the displacement of the Ti atom in 

PbTiO3 and BaTiO3. In EuTiO3 we see no pre-edge peak, consistent with its cubic 

structure. In PbTiO3, we see a strong peak when the electric vector of the x-rays 

is at a 19' angle to the c-axis (PbTiO3-c in Fig. 1 and a weak peak when entirely 

perpendicular to the c-axis. The local distortion o the Ti atom in PbTiO3 is along 

the long axis of the tetragonal crystal. This is consistent with the measured peaks. 

In BaTiO3, we see that the pre-edge peak is of similar size when the electric 

vector forms a 45' angle to the c-axis as when it is perpendicular. Although the 

crystal is of a tetragonal structure, the local displacement cannot be along the axis 

of macroscopic polarization. Our results are consistent with chain structure model 

of Comes et al. [l] In this model, the Ti atom is displaced along one of the (lll), 

(ill), (ill), and (ill) directions. The vector average of these displacements leads 

to a tetragonal long range structure. The scalar average is equal in both crystal 

polarizations, thus the peaks are of similar size. 

We have shown that XANES is a direct probe of local distortions in transition 

metal compounds which yields significant information without the need for extensive 

analysis. With further analysis, the magnitude of the displacement can be measured 

and these experiments can be performed as a function of temperature. Thus XANES 

is a owerful tool for the study of structural phase transitions. 

K edge on three Ti containing perovskites, EuTiO3, Pb (r io3, and BaTiO3. The 

[lpsol. St. Comm., 6, 715, (1968) 

Figure 1. The near-edge peaks of our titanate perovskites. 

* This work supported in part by DOE Grant No. DE-FG06-90ER4525 
I Mechanism of Se04'- substitution in calcite: an EXAFS study I XllA I 

R. J. Reeder (SUNY), G. M. Lamble (BNL), J-F. Lee (SRRC), and W. J. Staudt 

(SUW 

Analysis of Se-K-edge XAFS spectra of calcite grown from Se04'- -bearing aque- ous solutions at 25OC reveals the local environment of Se incorporated in calcite. 

The position of the Se K-edge is consistent with oxidation state 6+, and the first 

shell contains four 0 atoms at a distance of 1.63 A, confirming that Se is present 

as the tetrahedral Se04'- complex ion. The second shell is split and is best fitted 

by approximately 2 Ca atoms at 3.17 A and approximately 4 Ca atoms at 3.49 A. 

The coordination indicated by the split second shell is consistent with substitution 

of the Se04'- ion in the cos site of the calcite, which has six nearest-neighbor Ca 

atoms. The large size of the Se04'- ion and tetrahedral geometry cause significant 

distortion of the site that is consistent with the observed Se-Ca distances. Two 

possible models for the local coordination of the Se04'- ion are suggested that 

involve corner sharing of the SeO4 tetrahedron with neighboring Ca octahedra. 

The results suggest that other complex anions - particularly the geochemically 

important s04'- ion, which is also tetrahedral but slightly smaller than Se04'- - may also substitute in the co3 site of carbonates. 

a b 

Axla1 Non-axial , 

Figure 1. Two possible coordination schemes for SeO4 substitution in the c03 site 

of calcite. (a) Axial position of the Se04 tetrahedron requires a 3+3 split Ca shell 

and (b non-axial position requires a 2+4 split Ca shell. We favor the 2+4 split 

Ca she h of the non-axial position on the basis of its smaller disruption to the anion 

packing and its more obvious coordination. The analysis also favors (a) but cannot 

rule out (b). 

XllA Investigation of Ni Sorption on Pyrophyllite: An X-ray Absorption 

Fine Structure (XAFS) Spectroscopy Study 

A. M. Scheidegger, D. L. Sparks (Univ. of Delaware), and G. M. Lamble (NSLS, 

BNL) 

Sorption reactions at the solid-water interface decrease solute mobility and often 

control the fate, bioavailability and transport of metal ions in soils and groundwaters. A thorough understanding of the structural environment of metals at the 

solid-water interface is therefore of fundamental importance. In this study, XAFS 

spectroscopy was used to discern the local atomic structure of Ni 11) sorbed onto 

(A12Si4010(OH)2 of 2:l clays. Its dioctahedral structure consists of essentially 

with the permanent charge of planar clay surfaces can be avoided and sorption of 

ions on pyrophyllite can be ascribed to only edge surface sites. Figure 1 illustrates 

radial structure functions (RSFs) of Ni treated pyrophyllite samples at pH = 7.5 

and at surface sorption densities G, of b.) 3.1, c.) 2.0, d.) 1.0, e.) 0.49, and f.) 0.27 

mol m-2 compared to the spectrum of a crystalline Ni(OH)2(s) model compound a. The spectra are uncorrected for phase shift. Note the appearance of a peak at a 

of about 2.7 with increasing sorption density. This peak, also present in Ni(OH)2, 

represents the second Ni shell and reflects backscattering among multinuclear Ni 

complexes. Data analysis revealed that the first coordination shell consists of 6 

0 atoms at 2.02-2.04 .1 For the second shell, XAFS data suggest a single Ni-Al/Si 

distance (2.96-3.03 ), indicative of edge sharing of Ni and A1 octahedra and possibly 

the presence of mixed Ni-A1 hydroxides. As Ni surface loading on pyrophyllite increased, the number of Ni second-neighbor atoms at a distance of 2.99-3.00 increased 

from N 1 to N 5. The presence of multinuclear surface complexes was depicted at 

low surface loading and at reaction conditions undersaturated with respect to the 

formation of Ni(OH)2(s). This observation suggests that the total coverage of sur- face sites is not necessary for the formation of multinuclear surface complexes and 

implies that the pyrophyllite surface promotes hydrolysis and multinuclear complex 

formation. 

l),. A.M. Scheidegger, G.M. Lamble, and D.L. Sparks. 1995. Environ. Sci. 

Tec nol., in press. 

pyrophyllite. Pyrophyllite, shows little deviation from the ideal c 6 emical formula 

neutral tetrahedr ai -octahedral-tetrahedral layers. Hence, the complexity associated 

B 

Figure 1. Radial structure functions (RSFs) of Ni treated pyrophyllite samples at 

various sorption densities compared to the spectrum of a crystalline Ni(OH)2(s) 

model compound 
F 

0 h? I XllA 

G.S.Waldo, E.Wright, Z.H.Whang, J.F.Briat, E.C.Theil, and D.E.Sayers (NCSU) 

Ferritin in plants is a nuclear-encoded, multi-subunit protein found in plastids; an N-terminal transit peptide targets the protein to the plastid, but the site for 

formation of the ferritin iron mineral is unknown. In biology, ferritin is required to 

concentrate iron to levels needed by cells ( 10-7M), for above the solubility of the 

free ion M); the protein directs the reversible phase transition of the hydrated 

metal ion in solution to hydrated Fe-oxo mineral. Low phosphate characterizes the 

solid phase iron mineral in the center of ferritin of the cytosolic animal ferritin, but 

high phosphate in the hallmark of iron mineral in prokaryotic ferritin and plant (pea 

seed) ferritin. Earlier studies using x-ray absorption spectroscopy (EXAFS) showed 

that high concentrations of phosphate present during ferritin mineralization in vitro 

altered the local structure of Fe in the ferritin mineral, mimicking the prokaryotic 

type, whether the protein was from animals or bacteria. Using EXAFS to analyze 

the iron environment in pea seed ferritin now shows that the natural ferritin mineral 

in plants has an Fe-P interaction at 3.26A similar to bacterial ferritin; phosphate also 

prevented formation of the longer Fe-Fe interactions at 3.5Afound in animal ferritins or in pea seed ferritin reconstituted without phosphate. Such results indicate that 

ferritin mineralization occurs in the plastid, where the phosphate content is higher; a corollary is the existence of a plastid iron up take system to allow the concentration 

of iron in the ferritin mineral. 

F I Formation of the Ferritin Iron Mineral Occurs in Plastids1 

Large Strain Deformation Study of an Elastomeric Single-Crystal 

Triblock Copolymer using Synchrotron SAXS X12B 

Figure 1. SAXS pattern of an oriented triblock copolymer with a cylindrical morphology deformed in a direction 

transverse to the cylinder axis vertical). 

The view direction is perpen 6 icular to 

the cylinder axis. 

Figure 2. Bright field electron micrograph of a sample deformed to 180 percent. The isoprene regions have been 

preferencially stained dark with osmium 

tetroxide to provide mass-thickness contrast. 
STRUCTURE OF SEMICRYSTALLINE POLYIMIDES USING 

REAL-TIME SAXS 

specimen holder. 

No change in spacing was observed for RTT immersed in saline but ethylene 

glycol induced an increase in the spacing of 1.111. However, there was a significant 

decrease in the spacing for both MTLT and UTLT. Ethylene glycol induced no significant change in the spacing. 

UTLT in 0.15M saline: d = 14.55f0.11A; 

1.5M saline = 14.03f0.25b2hange = 3.6% 

MTLT d = 13.69f0.12A; 

13.21f0.19AChange = 3.5% 

Since the decrease in spacing is almost the same there can be no mineral between 

the collagen molecules in MTLT as hypothesized. There is prior evidence that 

mineral crystallites exist within the gap between colinear collagen molecules. 

X12B 

0 

W * National Institute on Aging Grant AGO2325 

Diffraction Spacing Measurements of Collagen in Turkey Leg Tendon 

and Rat Tail Tendon * X12B 
Low-angle x-xay diffraction studies of type I1 collagen in bovine articular cartilage. * 

* Supported by NIH grant AR 37604 

X12B I Structure of DNA Ligase I X12B 1 ______ 

Dr. Dale Wigley, Laboratory of Molecular Biophysics, The Rex Richards Building, 

University of Oxford, South Parks Road, Oxford OX1 3QU, UK 

DNA ligase is the enzyme responsible for ligating Okasaki fragments during the 

replication of DNA. There are two classes of enzyme, those which use an ATP 

cofactor and those which utilise NAD+. Both classes of enzyme proceed via an adenylated enzyme intermediate. The ATP-dependent enzymes range in molecular 

weight from over lOOkDa for the human type I enzyme, down to 4lkDa for the 

enzyme from bacteriophage T7. 

We have cloned, overexpressed and crystallized the T7 ligase. The crystals are of 

the orthorhombic spacegroup P21212, with one ligase monomer in the asymmetric 

unit. The crystals diffract to around 2.5A resolution and data have been collected 

to 2.7A on a single frozen crystal on beamline X12B at NSLS. These data have been 

used for the refinement of the model of the apo-enzyme. 

The final structure reveals that the enzyme consists of two domains with a large 

cleft between them. The 

enzyme appears to operate via a "base-flipping" mechanism which is similar to that 

proposed for other enzymes, but initially for the HhaI methyltransferase. 

The active site is in the larger of the two domains. 
" 

Crystallographic Analysis of an Fab Fragment of Anti-Idiotypic Anx12c tibody MK2-23 that Mimicks Melanoma Associated Antigen * 

Nenad Ban, John Day, Alexander McPherson (UCR), Xinhui Wang and Soldano 

Ferrone (NYMC) 

Monoclonal antibody MK2-23 bears an internal image of the antigenic determinant defined by anti-high molecular weight-melanoma associated antigen (HMWMAA) mAb 763-74, and has been shown to induce anti- HMW-MAA immunity 

in patients with malignant melanoma. It currently sees use as a therapeutic for 

patients having advanced cases of certain melanoma. 

Crystals of the Fab fragment of mAb MK2-23 have been grown from PEG 3350. 

These crystals belong to the orthorhombic space group P212121 with unit cell dimensions ad'5.3, b=78.2, c=83.0 angstroms. Crystallographic data was collected 

from one existing crystal at Brookhaven National Laboratory synchrotron. The 

data to 2.4 angstroms resolution was 5% complete. Crystal structure was determined by molecular replacement using the real space Patterson search method of 

Huber, as implemented in X-PLOR, with several Fab models as probes. Search results were filtered using Patterson correlation coeficient refinement. The structure 

of the molecule is currently being refined. 

We hope that this study will provide additional insights into the mechanism of 

molecular mimicry by anti-anti-idiotypic antibodies, and that it wiU reveal information about the three dimensional structure of the HMW-MAA epitope that is 

recognized by the idiotypic antibody in this cascade. 

* This investigation was supported by PHS grants CA37959 and CA5114 awarded by 

the National Cancer Institute, DHHS and by grants from the NIH (no. GM40706-03), from 

the NSF and from NASA (NAG-804). 

______~~ 

x12c Report on data collected from TMV protein crystals at NSLS beamline X12C, April 1-10, 1995. 

Balaji Bhyravbhatla and Donald L. D. Caspar (FSU) 

Data collection: 

Data was collected on crystals of the four layer disk aggregate of tobacco mosaic 

virus coat protein at pH 8.00. The unit cell parameters of the crystal in space group 

P21212 are 220.84 A in a, 171.70 A in b and 226.17 A in c. Room temperature data was collected using the CCD detector of Walter Phillips 

(BFandeis University). Low temperature (liquid Nitrogen) data was also collected 

using the MAR imaging plate available at the beam line. Data was collected in 

two passes wherever possible. One was a low resolution sweep (1/40 A to 1/3.5 A 

spacing) and the second a high resolution (1/10 A to 1/2 A spacing) sweep using 

both detector systems. 

Some long stills and small oscillations were also collected using the MAR imaging 

plate. The stills were from 3OOsec to 600sec exposures. The interest is to locate and 

map any diffuse scattering from the crystals. 

Data reduction: 

The data collected using the CCD detector has not been processed yet due to 

some technical difficulties, involving the conversion of the data frames to a DENZO 

readable format. 

The MAR data was collected mostly at LN2 temperatures. Although all the 

crystals exhibited twinning, we have so far been able to reduce one partial data set. 

The Rsyms for the data are 5 % to 2.2 A spacing. 

The completeness is only about 20 %. The second partial data set is still being 

worked on. The twinning of the crystal has prevented us from integrating the data 

accurately. The Rsyms for the second dataset are around 15 %. Due to this poor 

statistics we have been unable to merge the two data sets satisfactorily. There are 

two other partial data sets which will be processed. 

A comparison of the 2.2 A resolution MAR data currently processed to the 2.4 

A resolution cryo data set presently being used to refine the crystal structure gives a scaling of about 11 %. A complete estimate of the quality can be had after we 

process all the remaining data sets. 

One room temperature low resolution data set was collectd using the MAR. 

That data also is from a twinned crystal therefore we are experiencing difficulties in 

processing. It appears that the two lattices can be separated to obtain two partial 

data sets. Methods for processing overlapped reflections are being explored. 
:I 

CL 

o a, The Structure of Turnip Yellow Mosaic Virus (TYMV) x12c 

Figure 1. A 3.58 A electron density map of the TYMV coat protein at the five fold 

axis of the virion. 

Brief report on data collected from liquid crystalline tobacco mosaic 

virus specimens at NSLS beamline X12C, June 27-30, 1995. 

Arunava Chatterjee, Donald L. D. Caspar (FSU), and Dieter Schneider (BNL) 

Diffraction data were collected from exceptionally well oriented liquid crystalline 

specimens of tobacco mosaic virus common and dahlemense strains that had been 

prepared at Children's Cancer Research Foundation by K. C. Holmes and D. L. D. 

Caspar in 1959-1960. By tilting the specimens to record high-angle near meridional 

diffraction, data to 1.25 angstroms resolution was recorded from the best oriented 

samples. This data is currently being processed to refine atomic models directly 

against the diffraction data by convoluting model transforms with the experimentally measured specimen orientation distribution and the point-spread function of 

the recording system. 

Using the complete data recorded, including accurate measurement of the low 

resolution diffraction, difference maps will be calculated between data and refined 

atomic model to map the partially ordered solvent structure. The data from the 

dahlamense specimen provides information about the incommensurate periodic perturbation of the helical coat protein structure. It appears from the data recorded 

from the dahlamense specimens that the perturbation of the protein structure near 

the outer surface of the virus particle, although regularly periodic, is not very highly 

ordered. 

Development of improved methods of data processing and structure refinement 

for the TMV fiber diffraction data will provide the most detailed information about 

structure and solvent interactions of any non-crystalline macromolecular assembly. 

These methods will be applicable to the analysis of other helical biological assemblies. 
_'.. I The P-state Structure of the Profilin:P-Actin Complex at 2.65 

AResolution * 

J.K. Chik (Princeton Univ.), U. Lindberg (Univ. of Stockholm), R.M. Sweet 

(NSLS), and C.E. Schutt (Princeton Univ.) 

While in the crystalline state, &actin complexed to profilin can undergo structural transitions in response to changes in the crystal bathing solution. The structure of the profilin:actin (P:A) complex in 3.2 M NH4S04 with 10 mM ATP (pH 

6.5 

&he structure of another crystalline state, the P-state, has now been determined 

for crystals bathed in 1.8 M KP04 with 1mM ATP (pH 7.5). P:A crystals are of 

P212121 symmetry with a=38.14 A, bd2.45 A, and c=185.7 A. Data was 87.3% 

complete to 2.65 Awith an Rmergc of 8.2%. The structure was solved by molecular 

replacement using the T-state model and has been refined to an R-factor of 20.4% 

with an Rf,,, of 33.0%. Compared to the T-state, the P-state actin showed a 9.6 

degree opening of the cleft separating the large and small domains and the hydration 

of previously solvent-excluded ATP phosphates. No divalent cation could be placed 

with confidence in the P-state structure. Profilin was virtually identical in the two 

crystal states. 

[l] C.E. Schutt, J.C. Myslik, M.D. Rozycki, N.C.W. Goonesekere, and U. Lindberg, Nature 356, SlO(1993). 

the T-state, has been determined [I]. 

1 I .I 

Figure 1. Ca trace of P- and T-state p-actin using profilin (not shown) for alignment. 

* This work supported by NIH grant GM44038 

Crystal and molecular structure of the human adenovirus maturation x12c protease with its 11 amino-acid cofactor 

J. Ding (SUNY-Stony Brook, Physics), W.J. McGrath, R.M. Sweet, and W.F. 

Mangel (BNL-Biology) 

The three-dimensional structure of the human adenovirus-2 proteinase complexed 

with its 11 amino-acid cofactor, pVIc, was determined at 2.6A. resolution by x-ray 

crystallographic analysis. The fold of this protein has not been seen before. However, it represents an example of either subtly divergent or powerfully convergent 

evolution, because the active site contains a Cys-His-Glu triplet and oxyanion hole 

in an arrangement similar to that in papain. Thus, the adenovirus proteinase represents a new, fifth group of enzymes that contain catalytic triads. pVIc, which 

extends a P-sheet in the main chain, is distant from the active site, yet its binding 

increases 300-fold the catalytic rate constant for substrate hydrolysis. The structure 

reveals several potential targets for antiviral therapy. 

All diffraction data were measured on the MAR Research 300-mm diameter 

imaging-plate scanner, mounted on the 0 arm of a FAST (Enraf Nonius) diffractometer at Beamline X12C of the NSLS. Native data from one crystal were measured 

to 2.d resolution with an X-ray wavelength of 1.15A; derivative data from three 

crystals were measured at 1.07A (at the peak of the absorption "white line" of 

heavy atoms in the crystal) to a resolution of 3A. The crystals had symmetry P61; 

the unit cell dimensions were a=b=114.2, c=50.1A. The asymmetric unit contained 

one molecule with a mass of 24,500Da. 

The structure was solved by SIRAS (single-isomorphous replacement with anoma- lous scattering from a KzPtC14 derivative. Heavy atoms were located with program 

phasing power led to a mean figure of merit for 6819 reflections of 0.77. Solvent 

flattening was performed [5] with PHASES. Amino-acid residues were fitted with 

program 0 [3 , The molecular model was refined by conju ate-gradient minimiza10,500 observations to 2.d resolution was Rf,,, = 0.23. 

HASSP [4]. S 2 RAS phases were calculated with the PHASES package [2]. Strong 

tion and simu 1 ated annealing with the program X-PLOR [fJ. The final residual for 

[l] Bruenger,A.T. Version 3.1. Yale University. [2] Furey,W. 

and Swaminathan,S. Assoc. Meeting Abstr., PA33, 18, 

(1991) Acta Crys- 

& Eisenberg,D. (1987) Acta 

Enzymol., 115, 90-112. 

OHER, and NSF. 

I I I 

I I I 

Figure 1. Stereo diagram of the folding of the adenovirus protease. The ancillary 

peptide is shown at the front of the beta sheet. 
4d 

c.' 

, 0 

I OI, x12c X-ray crystal structure of the hydroxylase component of methane 

monooxygenase from Methylosinus trichosporium OB3b. 

Natesan Elango, R. Radhakrishnan, Wayne A. Froland, Cathleen A. Earhart, John 

D. Lipscomb and Douglas H. Ohlendorf (University of Minnesota) 

Methanotrophic bacteria utilize methane as their sole source of cellular car- bon and energy. Methanotrophic oxidation of methane is catalyzed by the en- zyme methane monooxygenase [MMO] which is expressed in either a soluble or 

membrane-bound form. The soluble form of MMO consists of 3 protein components: a hydroxylase [MMOH] (245kDa), a NADH-coupled reductase (38.4kDa), 

and a regulatory protein called component B (15.8kDa). While all three protein 

components of MMO are required for efficient oxidation of methane, the MMOH 

has been shown to contain the active site necessary for activation of molecular oxygen and substrate oxidation[l]. MMOH is a dimeric protein each monomer of which 

has 3 polypeptide chains (a& of 526, 394 and 168 residues, respectively. Each a 

mechanism based on reductive activation of dioxygen and homolytic cleavage of the 

C-H bond of methane (substrate radical intermediate) has been proposed. 

MMOH from Methylosinus trichosporium OB3b crystallizes in C2221 space group 

with a monomer (aPr) per asymmetric unit, The cell dimensions are a= 264.498, 

b= 71.16A and c= 139.448 [2]. X-ray diffraction data were collected from sev- eral single crystals at Brookhaven National Laboratory, beamline X12C at 18OC. 

The structure was determined by molecular replacement (MR using a monomer 

R factor of the model for OB3b MMOH is 16.2% for data to 28 resolution. The 

XPLOR program suite was used for both MR and model refinement. 

The heart-shaped dimer of MMOH, composed primarily of a helices, sits on a crystallographic 2-fold axis. The diiron cluster is located between 4 long helices of 

the a chain and is 138 under the nearest solvent-exposed surface of the molecule. 

The irons in each cluster are bridged by 2 hydroxides and both oxygens of a glutamic 

acid carboxylate. The iron atoms are also coordinated by the N6 of 2 histidines, 

061 of 3 glutamates, and an exogenous water molecule making both irons hexa 

coordinate. The geometry of the diiron cluster and the ligand structure are more similar to that seen in flash frozen Bath MMOH [4] than in the search model [3]. 

This current study has also shown that the published sequence [5] of p chain has 

28 consecutive sequence errors near the C terminal region, in addition to another 

13 errors randomly distributed over the 3 polypeptide chains. Most notable among 

these is that Asp209 in the a chain is actually Glu209, a ligand to one of the irons. 

[l] Fox, B. G., Froland, W. A., Dege, J. & Lipscomb, J. D. (1989). J. Bid. Chem. 

[2) Froland, W. A., Dyer, D. H., Radhakrishnan, R., Earhart, C. A., Lipscomb, 

J. D. & Ohlendorf, D. H. (1994). J. Mol. Biol., 236, 379-381. 

[3] Rosenzweig, A. C., Fredrick, C. A., Lippard, S. J. & Nordlund, P. (1993). 

5"] Rosenzweig, A. C., Nordlund, P., Takahara, P. M., Fredrick, C. A. & Lippard, 

[5] Cardy, D. L. N., Laidler, V., Salmond, G. P. C. & Murrell, J. C. (1991). Mol. 

subunit contains a p-hydroxy L ridged diron cluster in its active site. A catalytic 

of MMOH from Methylococcus cupsulutus Bath[3] as the searc h model. The final 

264 10023-10233. 

Nuturn, 366, 537-543. 

S. . (1995). Chem. Biol., 2, 409-418. 

Microbial., 5, 335-342. 

High resolution crystal structure of 5' nuclease domain from Taq 

polymerase 

So0 Hyun Eom, Jimin Wang, and Thomas A. Steitz (Yale) 

After years of prolonged Taq polymerase crystallization incubation, a small crystal form with its largest size of 0.05 mm appeared along with regular intact Taq 

polymerase crystals. The new crystal form belongs to body-centered tetragonal 

lattice with its dimensions of 121.6 X 121.6 X 75.7 8. An electrophoresis analysis 

of dissolved crystals indicates that there is aa about 33 Kd fragment present in the 

crystal, a size equivalent to 5' nuclease domain of Taq polymerase. One data set 

to 2.5 8 resolution was collected on MacScience image system at 1 hour exposure 

per picture using a home radiation source from a single crystal. Due to low photon 

counts, an overall merging R-factor for multiple observations was 20.7%. Data were 

extended to 2.0 8 from the same crystal with the merging R-factor of 6.4% using 

the NSLS X12C beamline. The exposure per image was 10 minutes, perhaps the 

longest ever taken at the beamline. The distribution of I/sigma verses resolution 

suggests that the crystal is likely to diffract to much higher resolution with longer 

exposures, or stronger beam intensities or larger crystals. We are currently in the 

process of solving the structure by the molecular replacement method. This structure determination can provide atomic details of the 5' nuclease structure which the 

intact Taq polymerase only partially provided. In combination with site-directed 

mutagenesis, we hope to understand the reaction mechanism of 5' nuclease and 

its functional role in the excision of Okazaki RNA fragments in the lagging-strand 

DNA replication. 
Crystal structure Taq polymerase with a DNA duplex product bound 

to the polymerase active site. 

So0 Hyun Eom, Jimin Wang, and Thomas A. Steitz (Yale) 

To elucidate the mechanism of DNA polymerase , we have crystallized taq DNA 

polymerase with a blunt ended DNA duplex at the polymerase active site. The 

cocrystal is in the same trigonal space group as the apo Taq polymerase. Although 

they diffracted to 3.5-3.8 A resolution on a home radiation source, diffraction data 

have been extended to 3.0 A at the NSLS X12C beamline. 

The complex structure reveals that the DNA duplex binds tangentially to the cleft 

that is formed by Fingers and Thumb domains, with a 3' terminus to the conserved 

carboxylates. The first base-pair of the duplex stack against two highly conserved 

aromatic residues of CY helix 0 with its DNA axis vertical to the CY helix. The 

orientation of the duplex DNA on the polymerase is similar to that observed earlier 

in an editing complex with Klenow fragment. There are extensive interactions 

between conserved residues in the polymerase and bound DNA duplex, particularly 

in the duplex minor groove. These latter interactions may play an important role 

in promoting the fidelity of this polymerase. 

I Structure of Allosteric Threonine Deaminase from E. Coli I x12c I 

Gilliland, G. & Eisenstein, E. (CAFLB) 

The biosynthetic threonine deaminase from E. coli is an allosteric tetramer. Each 

chain comprises 514 residues and one PLP group. Several crystal forms have been 

analyzed be X-ray diffraction. The unliganded structure is expected to be solved 

in an orthorhombic crystal form. A synchrotron dataset in a trigonal crystal form was collected from a crystal grown in the presence of excess valine, and is expected 

to shed light on the allosteric regulation of this enzyme. (Valine is an allosteric 

ligand.] The crystals of this form grow from 4.4M sodium formate at neutral pH, 

and be ong to space group P3(1)21 with a=162.5 and c=128.7 and one tetramer in 

the asymmetric unit. The dataset is 85% complete at 2.9A resolution with Rsym 

= 0.11. 
,'. .'I .. 

', . , 

1 Structure Determination of Transaldolase from E.coli 1 x12c I 

J.Jia, W.Huang, Y.Lindqvist, G.Schneider(Department of Medical Biochemistry 

and Biophysics, Karolinska Institute, Sweden) 

Transaldolase (D-sedoheptulose-7-phosphate:D-glyceraldehyde-3-phosphate 

dihydroxyacetone- transferase, EC 2.2.1.2) is a ubiquitous enzyme which catalyzes a 

reversable transfer of a dihydroxyacetone moiety, derived from fructose-6-phosphate 

to erythrose-4-phosphate yielding sedoheptulose- 7-phosphate and glyceraldehydephosphate. The structure was solved with the MIR method using native data and 

five heavy compound derivative datasets. On beamline X12C using a 30 cm MAR 

research image plate system, the resolution of the native data set could be increased significantly, from 2.2A to 1.87 A. A partial data-set (83% complete from 

6.0-1.87A1 Rsym 6.2% with no reflections rejected) has been collected. This data 

merges readily with the native data we collected with a rotating anode as X-ray 

source(R-merge=8.8%) This merged dataset is 91.3% complete, 82.8% of the total 

reflections were collected in the highest resolution shell 1.97-1.87A. This dataset 

is now used for the final crystallographic refinement of the model solved with the 

MIR method. The electron density maps calculated with this dataiset have improved considerably and consequently, the model of the transaldolase structure is 

more accurate. The current R-free and conventional Rfactor for the protein model are 23.8% and 20.0% respectively. 

I Structure studies of neurotrophin-3 I x12c I 

Kelly, J.A. (UCLA), Singer, B. (Amgen), and Yeates, T.O. (UCLA) 

Neurotrophin-3 (NT-3) is a member of a family of neurotrophic factors whose 

function is to promote the survival and maintenance of certain neuronal populations. 

NT-3 has been crystallized in 2 forms. Orthorhombic crystals, space group P21212, 

diffracted to 2.5A resolution and have cell dimensions a I 37.97A b G 51.90A c 3 65.99A. The second form is space group P43212, with cell dimensions a I b I 

66.90A, and c I 108.66A. The tetragonal crystals diffracted to 2.d resolution. 

Phases for both forms were obtained by molecular replacement using nerve growth 

factor as the search model. 
-. 

. :-I Crystal Structure of Fe(II1)-Zn(I1) Purple Acid Phosphatase with 

Phosphate Bound to the Active Site 

i 

x12c I Crystal structure of Thermus aquaticus DNA polymerase 1 x12c 

Youngsoo Kim (Yale, Now in Yeungnam University. Korea),Soo Hyun Eom (Yale), 

Jimin Wang (Yale),Soo Hyun Eom (Yale), Jimin Wang (Yale),Dae-Sil Lee (Korea 

Research Institute of Bioscience and Biotechnology),Biotechnology), Biotechnology),Se Won Suh (Seoul National U.) and Thomas A. Steitz (Yale). 

The DNA polymerase from Thermus aquatics (Taq polymerase), famous for its 

use in the polymerase chain reaction, is homologous to E. coli. DNA polymerase I 

( pol I). Like pol I, Taq polymerase has a domain at its amino terminus (residues 

1-290) that has 5’ nuclease activity and a domain at its carboxy terminus that 

catalyses the polymerase reaction. Unlike pol I, the intervening domain in Taq 

polymerase has lost the editing 3’-5’ exonuclease activity. Although the structure 

of the Klenow fragment has been known for ten years, that of the intact pol I has 

proved more elusive. The crystal structure of Taq polymerase was determined at 

2.4 a resolution using a data set collected on the NSLS X12C beamline; it shows 

that the structures of the polymerase domains of the thermostable enzyme and of 

the Klenow fragment are nearly identical, whereas the catalytically critical carboxylate residues that bind two metal ions are missing from the remnants of the 3’-5’ 

exonuclease active site of Taq polymerase. The first view of the 5’ nuclease domain, 

responsible for excising the Okazazi RNA in the lagging-strand DNA replication, 

shows a cluster of conserved divalent metal-ion-binding carboxylates at the bottom 

of a cleft. The location of this 5’ nuclease active site some 70 8, from the polymerase active site in this crystal form highlights the unanswered question of how 

this domain works in concert with the polymerase domain to produce a duplex DNA 

product that contains only a phosphate nick. 

T. Klabunde, N. Straeter, R.. Froehlich, H. Witzel, B. Krebs (Univ. of Muenster) 

Purple acid phosphatases containing a dinuclear Fe(II1)-Me(I1) center (where Me 

can be Fe or Zn) in their active site catalyse the hydrolysis of activated phosphoric 

acid esters and anhydrides like ATP, at a pH range from 4 to 7. The characteristic 

purple color of this subclass of acid phosphatases results from a tyrosine to Fe(II1) 

charge transfer transition at approximately 560 nm. Interactions with phosphate, 

which is a competitive inhibitor of the phosphatase activity, have been investigated 

in several spectroscopic studies in order to understand the detailed mechanism of 

ester hydrolysis. The X-ray structure of the dimeric 111 kDa Fe(II1)-Zn(I1) kidney 

bean purple acid phosphatase (kbPAP with phosphate bound to the active site 

has been determined at a resolution o 2 2.7 Ang using the structure of the native 

enzyme as a starting model [Straeter, N., Klabunde, T., Tucker, P., Witzel, H., and 

Krebs, B. (1995) Science, 1489-14921. Furthermore the data for the native structure 

could be improved to 2.65 Ang. In native kbPAP the iron ion is coordinated by 

Tyr-167, His-325, and Asp-135 and the zinc ion by His-286, His-323, and Asn-201. 

The two metals are bridged monodentately by Asp-164. In the inhibitor complex 

the oxyanion binds in a bidentate bridging mode to the two metal ions, replacing 

two of the presumed solvent ligands present in the native enzyme form. As also proposed for the native structure a bridging hydroxide ion completes the coordination 

spheres of both metal ions to octahedral arrangements. In the phosphate-enzyme 

complex the third and the fourth oxygen atom of the phosphate group interact 

with the imidazolium cations of His-202 and His-296. Both structures are consistent with a mechanism of phosphate ester hydrolysis involving a nucleophilic attack on the phosphorus by an Fe(II1 -coordinated hydroxide ion. The negative charge 

evolving at the phosphorus in t h e assumed pent&coordinated intermediate might 

be withdrawn by the two metal ions and by His-202 and His-296. 

Figure 1. Active site region of kbPAP displaying the metal coordinating ligands 
x12c Crystal Structure Determination of L-aspartate-P-semialdehyde dehydrogenase (ASADH, E.C. 1.2.1.11) x12c Crystal Structure of the A Domain from the a subunit of Integrin 

CR3 (CDllb/CD18\ 

Kryger, G., Petsko, G.A. and Ringe D. (Brandeis University) 

The enzyme L-aspartate-P-semialdehyde dehydrogenase (ASADH, E.C. 1.2.1.11) 

is an NADP-linked dehydrogenase that is encoded by the asd gene in Escherichia 

coli. The reaction catalyzed by this enzyme, which reversibly converts L-aspartateP-semialdehyde to L-P-aspartyl-phosphate, is located at a key branch point in the 

metabolic pathway of aspartate to other amino acids. 

To understand the mechanism and specificity of ASADH better, its three dimensional crystal structure determination was carried out by single isomorphous 

replacement and multiple wavelength anomalous diffraction methods. ASADH crystals are extremely sensitive to radiation damage caused by the x-rays, they diffract 

poorly in a home-lab x-ray source, and only one heavy-atom derivative was found 

after extensive searches (the Hg atom in PCMB). These crystal characteristics made 

it imperative that the data will be collected at a wavelength-tunable, very intense, 

x-ray source. This was achieved at the Brookhaven National Laboratories NSLS 

X12-C, run by Dr. R. Sweet. The structure was solved using three datasets collected at this beam line, one native at a resolution of up to 2.68L, and two datasets 

at different wavelength from a single Hg derivatized crystal at 3.08L. Data were collected from the two crystals at cryogenic temperature. The structure determination 

is at the initial model fitting stage at the time this abstract is written. 

Jie-Oh Lee, Robert Liddington (DFCI, HMS) 

Integrins are plasma membrane proteins that mediate adhesion to other cells and 

to components of the extracellular matrix. The interactions of several integrins with 

their extracellular ligands are mediated by an A-type domain (generally called the 

I-domain in integrins). We have determined the high resolution crystal structure of 

the I-domain from the a chain of integrin CR3. The domain adopts a classic a/b 

"Rossmann" fold and contains an unusual Mg2+ coordination site at its surface. 

One of the coordinating ligands is the glutamate side chain from another I-domain 

molecule. We suggest that this site represents a general metal ion-dependent adhesion site (MIDAS) for binding protein ligands. We further propose that the b 

subunits of integrins contain a MIDAS motif within a modified I-domain. Our crystal structure will allow reliable models to be built for other members of the I-domain 

superfamily and should facilitate development of novel adhesion modulatory drugs. 

METHODS: The structure was solved using multiwavelength dispersion (MAD) 

technique with a selenomethionine derivative. All the MAD data and high resolution 

native data were collected on beam line X12C. Data were processed to an Rsym 3- 

4% and completeness is 99%. MAD phase were determined to 2.08L resolution using 

program MLPHARE (overall figure of merit=0.65). The structure was refined to an 

R factor of 21% at 1.78L resolution with good geometry. The final model contains 

all non-hydrogen atoms of residues D132 to K315 and 150 water molecules. 
x12c Two conformations of the integrin A-domain (I-domain): a pathway 

for activation? 

Jie-Oh Lee, Robert Liddington (DFCI, Harvard Medical School) 

Integrins are a family of cell adhesion molecules expressed on cell surface. Most 

integrins are rapidly and reversibly activated in response to agonists, leading to 

highly regulated cell adhesion. This activation is associated with conformational 

changes in their extracellular portions. The interactions of several integrins with 

their ligands are mediated by a type A-domain (generally called the I-domain in 

integrins). We have described previously the structure of a 'liganded' I-domain 

grown in the presence of Mg2+, and now report the structure of an 'unliganded' 

form grown in the presence of Mn2+. Comparison of the two crystal form reveals a change in metal coordination which is linked to a large (10A shift of the Cterminal helix and burial of two phenylalanine residues within the h ydrophobic core 

of the Mn2+ form. Our observations provide the first atomic resolution view of 

conformational changes in an integrin domain, and suggest a link between these 

structural changes and a change in adhesiveness. 

METHODS: Data were collected to 2.OA resolution on beam line X12C using a MarResearch imaging plate, with wavelength of 0.98A. Data are 99% complete and 

Rsym is 6% (27% in outer shell). The structure was solved by molecular replacement 

using the Mg%+/I-domain structure as the search model. The structure was refined 

using XPLOR and manual model building to a final R factor of 21%. The final 

model comprises all non-hydrogen atoms of residues D132 to A318 and 100 water 

molecules. 

Crystal structure of a Lyme-disease antigen in complex with an antibody. 

Hong Li and Catherine L. Lawson Biology Department, Brookhaven National Laboratory 

Borrelia burgdorferi is the organism responsible for Lyme disease on Long Island. 

OspA is an abundant surface protein of the Borrelia spirochete that has been found 

to trigger immunopathological processes. To aid in vaccine development for Lyme 

disease, the crystal structure of OspA and its complex with the Fab fragment of a monoclonal antibody (Fab184.1) is being determined. 

Recent efforts have focused on collecting higher resolution native data and heavy 

atom derivatives (Pt and I . A mutant form of recombinant OspA (Ser69 --t Cys69) 

suitable conditions were found to freeze the crystals in a nitrogen gas stream. A 

native data set to 2.3 A was collected at the X12C beamline of the NSLS, and a 

Cys69 data set to 1.9 A was collected at the X25 beamline. 

A partially refined OspA-Fab184.1 model was obtained by tracing an electron 

density map calculated with a combination of multiple isomorphous replacement and 

molecular replacement phases. The protein backbone trace for OspA was confirmed 

by difference Fouriers between two Ser --t Cys single mutants and the wild type 

OspA data sets, and by a platinum site near the sole methionine residue of OspA. 

The current protein model consists of residues 7-257 of OspA (28 kD) and all 

residues of Fab184.1 (50 kD) with an overall isotropic temperature factor. The 

crystallographic residual factor R is 29% and free R is 37%. Further refinement of 

the model is currently underway. 

The secondary structure of OspA is in qualitative agreement with results obtained 

by circular dichroism studies [l] at beamline U9. OspA consists mostly of &sheet 

with one a-helix (the last 9 residues). OspA is composed of two domains, an Nterminal @sheet domain (residues 1-116) and a partially closed C-terminal &barrel 

domain (residues 117- 257). 

[l] France, L. L.; Kieleczawa, J.; Dunn, J. J.; Hind, G. and Southerland, J. C. 

(1992). Biochimi. et Biophy. Acta 1120:59-68. 

x12c 

has allowed the growth of i' arger crystals (0.14mm x 0.1 mm x 0.6 mm).In addition, 

Figure 1. Partially refined structural model of OspA-Fab184.1. OspA is represented 

by ribbon model. 
.- 

, -,. 

w 

rp 

w 

: ::. , 

. ' i' 

x12c Structural studies of Stearoyl-acyl Carrier Protein Desaturase from 

Castor Seed 

-2ein VP16 I x12c I 

Y.Liu, C. Huang, W. Herr, and X. Cheng (Cold Spring Harbor Laboratory, Cold 

Spring Harbor, New York 11724) 

The herpes simplex virus HSV) encoded protein VP16 is not only an essential 

early (IE) gene expression. VP16 is one of the most potent transcriptional activa, 

tors identified in eukaryotes. It forms a multiprotein complex with cellular proteins 

Oct-1 and HCF to activate viral IE gene transcription by binding to TAATGARAT 

elements in the IE promoters . This binding enables the activation domain of VP16 

to interact with the basal transcriptional machinery and activate transcription of 

the viral IE genes. Therefore, structural studies of VP16 will lead to an understanding of multiprotein-DNA interactions involved in transcriptional regulation. Since 

transcription regulation is intimately related to cell growth, cell cycle control, and 

oncogenesis, VP16 has been a subject of intensive studies. A three-dimensional crystal structure of VP16 will not only shed light on the mechanism of VP16 function, 

but also facilitate further biochemical characterization of the protein. 

A construct encoding a GST-fusion with the central region (amino acids 48- 

412) of VP16 that is sufficient for VP16 induced complex formation but lacks the 

activation domain has been made. The fusion protein was purified on a glutathioneagarose column, and VP16 was released from the fusion by thrombin digestion at 

the junction between the GST and VP16 sequences. Thrombin and VP16 were then 

separated by Q-sepharose column chromatography. Purified VP16 was crystallized 

by the hanging-drop method into rod-like crystals with an average dimension of 

0.2 x 0.2 x 1.0 mm3 at 16C. Preliminary results indicate that the VP16 protein 

crystallizes into an orthorhombic space group with unit cell dimensions of a=60 

A, b=77 A, c=83 A. The crystals diffract X-ray beyond 3 A and the structural 

determination is underway. 

structural component of the LI SV viron, but also the activator of HSV immediate- 
DNA Modification by Hhd Methyltransferase I x12c 

M. O’Gara (Cold Spring Harbor Lab.), R.J. Roberts (NEB), X. Cheng (Cold Spring 

Harbor Lab.) 

In 1993, we solved and published the structure of the M.Hha1-AdoMet complex 

(Cheng et al., 1993). From this binary structure determined at 2.5 A resolution, we 

learned that the M.Hha1 folds into two broad domains: a catalytic domain that con- tains catalytic and cofactor-binding regions, and a DNA-recognition domain. Later, 

we solved and published the ternary structure for a chemically-trapped covalent reaction intermediate between the M.Hha1, a duplex 13-mer DNA oligonucleotide 

containing methylated 5-fluorocytosine at its target and reaction product AdoHcy 

(Klimasauskas et al., 1994). This structure determined at 2.8 A resolution reveals 

the three-dimensional basis for the functions of amino acids implicated in DNAsequence specificity, catalysis and cofactor binding. The DNA is bound in a cleft 

between the two domains. The structure is the first to demonstrate ”an amazing 

distortion in DNA induced by a methyltransferase”, Le., the substrate nucleotide is 

completely flipped out of the helix during the modification reaction. The structure 

also provides a clear example of induced-fit for both protein and the DNA in the 

sequence-specific substrate binding by M.Hha1. 

The above ternary structure represents one step of the reaction pathway. During the past year, we crystallized, collected, and solved structures of M.HhaI with 

cognate DNA and methylated DNA, in the presence of S-adenosyl-L-homocysteine. 

The structures of these two complexes have been refined to crystallographic Rfactors of 0.189 and 0.178, respectively, at 2.7 A resolution. The two structures 

reveal that 1) both unmethylated %’-deoxycytidine and 5-methyl-2’-deoxycytidine 

(2) the C5 methyl group of the flipped 5-methyl-2’-deoxycytidine lies in between 

the C5 and the sulfur of S-adenosyl-L- homocysteine, (3) two water molecules, held 

near the hydrophobic edge of the flipped cytosine (C5 and C6) by two conserved 

amino acids Gln-82 and Asn-304) and the phosphoryl oxygen of the phosphate 

the proton from C5, and (4) the protonation of ring N3 of the cytosine during the 

methylation reaction may occur through a water-mediated interaction between the 

terminal carboxyl group of Glu-119 and the amino group of the methionine moiety 

of S-adenosyl-L-methionine. 

Cheng, X., Kumar, S., Posfai, J., Pflugrath, J.W., Roberts, R.J. (1993) Cell 

74, 299-307. Cheng, X., Kumar, S., Klimasauskas, S., Roberts, R.J. (1993) Cold 

Spring Harbor 

Symp. Quant. Biol. 58, 331-338. S. Klimasauskas, S. Kumar, R.J. Roberts, and 

X. Cheng. (1994) Cell 76, 357-369. 

S. Kumar, X. Cheng, S. Klimasauskas, S. Mi, J. Posfai, R.J. Roberts, and 

G.G.Wilson. (1994) Nucleic Acids Res. 22, 1-10. X. Cheng (1995) Curr. Opin. 

Struc. Biol. 5, 4-10. X. Cheng (1995) Annu. Rev. Biophys. Biomol. Struct. 

24, 293-318. M. O’Gara, K. McCloy, T. Malone, and X. Cheng (1995) Gene 157, 

135-138. G. Schluckebier, M. O’Gara, W. Saenger, and X. Cheng (1995 J. Mol. 

Biol. 247, 16-20. Malone, T., Blumenthal, R.M., Cheng, X. (1995) J. Id 01. Biol. 

M. O’Gara, S. Klimasauskas, R.J. Roberts, and X. Cheng. submitted 

completely k ip out of the DNA helix and fit into the active site of the enzyme, 

group 3’ to t 6 e flipped nucleotide, may serve as the base for the elimination of 

253, 618-632. 

Figure 1. 2Fo-Fc electron density map 

Figure 2. View down helix axis 
I Crystallographic Studies of Adenylosuccinate Lyase from B. subtilis I X12C I ~ 

Matthew Redinbo, Todd 0. Yeates; University of California, Los Angeles 

Adenylosuccinate lyase (ASL) from Bacillus subtilis is a 200 kDa homotetramer 

that catalyzes two steps of de novo purine biosynthesis leading to the formation 

of AMP and IMP, both steps involving the beta-elimination of fumarate. A single 

point mutation in the human ASL gene has been linked to mental retardation with 

autistic features, and ASL also plays an important role in the bioprocessing of antiHIV therapeutics, Recombinant B. subtilis ASL, which shares 70% sequence identity 

with human ASL, has been crystallized. Diffraction on an in-house Rigaku generator 

with an R-AXIS IIc imaging plate yielded data to 3.8 A resolution for crystals 

frozen to 100 K. Data collection at beamline X12C at the NSLS at Brookhaven 

National Laboratory extended the resolution to 3.3 A, also using crystals frozen 

to 100 K (Rmerge=B.l%, 93% complete, < I > / < u >=5.4 for data between 

3.4 and 3.3 A resolution). B. subtilis crystals are of space group P6122 or P6522 

and have a relatively long c-axis of approximately 280 A. The MAR detector at 

beamline X12C mimics three circle eometry and allowed the orientation of the 

c*-axis approximately along the phi frotation axis which faciliated the collection 

isomorphous replacement is in progress, and we consider the higher resolution data 

collected at X12C to be a crucial step in the progress of the structure determination 

of B. subtilis ASL. 

of a complete, higher resolution data set. d tructure determination by multiple 

x12c High-Resolution X-Ray Diffraction Data of Gene V Protein of bacteriophage fl. 

Matthew M. Skinner and Thomas C. Terwilliger, Los Alamos National Laboratory, 

LS-8 M888 Los Alamos, NM 8'7545 

Gene V protein (GVP) of bacteriophage fl is involved in DNA replication. It 

binds to single-stranded nucleic acids with high affinity but little sequence specificity. GVP coats single-stranded DNA during bacteriophage fl replication, forming an ordered superhelical protein-DNA complex. This protein-DNA complex facilitates packaging of the ssDNA into new phage particles. The GVP is a member of 

the OB-fold superfamily of proteins. The X-ray Crystallographic structure of GVP has been determined by our laboratory at l.8A. GVP is a dimer with identical subunits. The monomer of GVP 

forms a distorted five stranded anti-parallel beta barrel. The protein portion of 

GVP has been used to model the single-stranded DNA into a left-handed superhelical complex. In addition, the structure of GVP is being used to study protein 

stability by determining crystal structures of site-directed mutants in the core of 

the protein. 

We recently extended the high-resolution X-ray diffraction data of GVP to 1.4k 

at beamline X12C (Fig 1.). The data are of excellent quality with a Rsym on I of 

5.3%. Data is complete to 96% and protein atomic refinement is under investigation. 

Figure 1. A portion of the film plate showing X-ray Diffraction to 1.4A. 
I Structure of the Actin:Profilin:Rhodamine-phalloidin Complex * I X12C I 

N. Vogelaar (Princeton Univ.), U. Lindberg (Stockholm Univ.), R.M. Sweet 

(NSLS), and C.E. Schutt (Princeton Univ.) 

One of the main goals of our laboratory is to understand the nature and structure of actin-its conformational flexibility, how it binds to other proteins, and the 

manner in which it self-associates to form microfilaments. Toward these ends, our 

lab has determined the structure of the “T-state” actin:profilin complex [l]. In that 

structure, we observed extensive actin-actin interactions and speculated that they 

may be related to contacts in the actin filament. The current work supports this 

hypothesis in that we have demonstrated using confocal fluorescence microscopy 

that rhodamine-phalloidin binds to actin:profilin crystals. Phalloidin is known to 

bind and stabilize actin filaments but does not interact significantly with actin 

monomers. Data from a single, frozen, rhodamine-phalloidin-soaked actin:profilin 

crystal was collected and was 94% complete to a resolution of 2.3A. The RJym was 

8.1%. The space group is P212121, with cell constants of a=37.69 A, b=71.77 A, 

and cd87.33 A. Molecular replacement was done using the “P-state” actin:profilin 

structure [2] using 8-4 Adata. The crystallographic residual using the resulting 

model was 35%. Preliminary results indicate that the actin cleft is more open than 

the “T-state” structure, but more closed than the “P-state” structure. Although 

the rhodamine-phalloidin site has not yet been determined, both the ATP and the 

calcium ion have been tentatively placed. Refinement is continuing. 

[I] C.E. Schutt, J.C. Myslik, M.D. Rozycki, N.C.W. Goonesekere, and U. Lindberg, Nature 356, 810(1993). 

x12c Crystal structure of the DNA polymerase from phage RB69, an Q 

family and replication polymerase. 

Jimin Wang (Yale), A. K. M. Sattar (Yale), Jim Karam (Tulane), W. H. Konigsberg 

(Yale) and Thomas A. Steitz (Yale) 

T4 DNA replication is one of the best studied systems. APof ten T4 encoded 

components at the replication fork have been cloned and overexpressed and subject to extensive biochemical and biophysical studies. The center component of the 

replicase, the gene 43 product (gp43 or T4 DNA polymerase, is the enzyme rewhich eukaryotic polymerases belong. T4 DNA polymerase possesses two enzymic 

activities, 5’-3’ polymerase and 3’-5’ exonuclease, in addition to its ability to bind 

its own mRNA as autogenous translation regulation. 

Bacteriophage RB69 is a distant relative of T4 phage family. Many of RB69 

encoded proteins show high similarity with T4 proteins. Their gp43 or DNA polymerases share 62% identity and 75% similarity. 

The crystal structure of RB69 DNA polymerase has been solved at 3.8 A resolution in an orthorhombic space group (P212121) using two mercurial derivatives, 

and at 5.0 A in a monoclinic space group (P21) using one mercurial derivative using a home x-ray radiation source. The diffraction data have been extended to 2.8-3.1 

A for the orthorhombic space group using 10 crystals and to 3.2-3.5 8, for the mon- oclinic from 6 crystals using the intense x-ray radiation source at the NSLS X12C 

beamline. The structure has then been extended to the resolution limits using noncrystallographic averaging procedures among one copy of molecule in P212121 and 

two copies in P21. 

The crystal structure of RB69 DNA polymerase reveals that the polymerase 

consists of five domains called amino terminal (N), 3’-5’ exonuclease (Exo), Fingers, 

Palm and Thumb. Domains N and Exo are located at the amino terminus and 

possesses 3’-5’ exonuclease activity, respectively. Both domains are within the first 

388 amino acids, whose structure was previously solved as a fragment of the T4 DNA 

polymerase. The remaining carboxy terminal polymerase domains form a cleft that 

contains three catalytically important carboxylate residues located at the bottom of 

this cleft. The Palm domain containing these carboxylates has an identical topology as Palm domains of the HIV reverse transcriptase and the Klenow fragment of pol 

I. The fingers and thumb domains, however, have structures that are unique to the 

corresponding parts of the other DNA polymerases of known structures. Four of 

five domains (N, Exo, Palm and Thumb) are arranged within a plane, and the fifth 

domain (Fingers) with 50 A long helices protruding at the back. In comparison to 

the relative positioning of the 3’-5’ exonuclease to the polymerase in the Klenow 

fragment, the exonuclease domain in RB69 DNA polymerase has been translocated 

from the template strand side to the primer strand side of the presumedly bound 

DNA duplex product. 

sponsible for DNA synthesis. T4 DN 4 polymerase is a pol Q family polymerase, to 

F 

CL 

CL 

4 * Supported by NIH grants GM44038 and A130743 
I. 

1 Casein kinase I I x12c I 

R. Xu, G. Carmel, J. Kuret, and X. Cheng (Cold Spring Harbor Laboratory, Cold 

.,, . . ., 

Report on data collected from insulin and osteogenic protein (OP-1) crystals at NSLS beamline X12C, April 1-10 and June 27-30, 1995. x12c 

Casein Kinase I (CKI) is a serine/threonine specific protein kinase that is ubiquitous in eukaryotic organisms. Last year we solved the structure of the catalytic 

domain of CKI from Schizosaccharomyces pombe in complex with MgATP at 2.0 

A resolution (Xu et al., 1995). The crystals were formed in a trigonal space group 

(P3221). This year, we solved the crystal structure of CK1 complexed with an inhibitor CKI7, refined to a crystallographic R-factor of 17.8at 2.5 A resolution. 

A large family of isoquinoline sulfonamide compounds inhibits protein kinases 

by competing with ATP, yet interferes little with the activity of other ATP-using 

enzymes such as ATPases and adenylate cyclases. One such compound, N-(2- 

aminoet hyl)-5-chloroisoquinoline-8-sulfonamide PKI'i'), is selective for CK1 isolated from a variety of sources. The CK1-CKI structure provides new insights 

into the mechanism of the ATP-competing inhibition and the origin of their selectivity toward different protein kinases. Selectivity for kinases versus other enzymes 

is achieved by hydrophobic contacts and the hydrogen bond with isoquinoline ring. 

We propose that the hydrogen bond involving the ring nitrogen-2 atom of the isoquinoline must be preserved, but that the ring can flip depending on the chemical 

substituents at ring positions 5 and 8. Selectivity for individual members of the 

kinase family is achieved primarily by interactions with these substituents. 

References: 

G. Carmel, B. Leichus, X. Cheng, S.D. Patterson, U. Mirza, B.T. Chait, and J. 

Kuret. 1994. J. Biol. Chem. 269, 7304-7309. 

R. Xu, G. Carmel, R.M. Sweet, J. Kuret, and X. Cheng (1995) EMBO J. 14, 

R. Xu, G. Carmel, J. Kuret, X. Cheng. submitted 

1015-1023. 
I X-ray Diffraction Study of Tilted Phases of Langmuir Monolayers * I X14A I 

M.K. Durbin, A. Malik, A.G. Richter, R. Ghaskadvi, and P. Dutta (Northwestern 

University), and Thomas Gijg (Oak Ridge National Lab) 

We used grazing incidence diffraction to study tilted phases of Langmuir mono- layers, and discovered a new phase in which the molecules tilt in a non-symmetry 

direction. We were also able to observe the transition from a tilted phase with 

ordered backbone planes to one with disordered backbone planes. We studied 

arachidic (CZO) acid and nonadecanoic (Cis) acid along a 0°C isotherm, and along a 15dynes/cm isobar. The isotherm passes through four different phases. Each phase 

has a different tilt symmetry. Figure 1 shows the tilt magnitude and orientation 

(azimuth) as a function of pressure. The highest pressure phase is untilted (U As 

(NNN tilt, 4 = 30"). The third phase has intermediate tilt (I tilt, 30' > 4 > 0"), 

and the lowest pressure phase has nearest neighbor tilt (NN tilt, 4 = 0"). 

The isobar remained entirely within the NN phase, but it has been suggested that 

the NN phase be subdivided into two phases. At low temperatures, the molecules are 

expected to have a herringbone packing, whereas at high temperatures they should 

have no orientational order. The orientational order and the tilt both contribute to a distortion of the hexagonal lattice. The distortion can be measured, and the effect 

due to tilt subtracted out. The distortion due entirely to orientational ordering of 

the molecules is plotted in Figure 1. There is a clear transition near 30°C from 

non-zero distortion to no distortion. 

the pressure is lowered, the molecules begin to tilt towards a next-nearest neig 1 bor 

I. &A A A 

35 - 

25 ..... 00 .. P ................. 

, m.. 

30 ,, ................................... 

0 

20 ............. 0- d&. .................... e . .a 

0 A0 

Ei5.. 

10.. .... ... 

5--. ' Y ....... 

0. ' : **: A*-* : :-: 9 

0.00 _.__. ..__.___.._______________.__. w-5 .._..-.- . w--' .. 

. -0.02- m. . -8' 

'& -0.04- 

. 

, . Figure 1. Tilt behavior of CZO acid along 0 l-0 . io . io io io 

a 0°C isotherm. Temperature ("C) 

0 5 10 15 20 25 30 35 

Pressure (dynedcm) .O.oB- 

[ A Orientation 0 Magnitude1 

Figure 2. Distortion due to molecule 4d * This Work was supported by the U-S. backbone ordering along a 15dyn/cm Dept. of Energy grant no. DE-FGO2- isobar. (D 84ER45125. 

m 

. 

X14A 

Atomic Resolution Imaging with Multi-Energy X-ray Holography 

(MEXH) 

T. Gog (ORNL), P.M. Len, C.S. Fadley (UC Davis), D. Bahr, C. Sanchez-Hanke, 

G. Materlik (HASYLAB) 

Multi-energy x-ray holography (MEXH is introduced as a new technique for 

monochromatic synchrotron radiation incident on the sample to generate an internal 

scattering field and monitors fluorescence from specific atoms to determine the 

electric field strength at the center of these atoms. Scanning an extended volume 

of reciprocal space and converting the resultant intensity distribution by Fourier 

transform, a real space image of the immediate atomic environment around an emitter is obtained. 

MEXH can be regarded as the x-ray equivalent to multi-energy electron emission 

holography and as an inversion of the more conventional idea of x-ray fluorescence 

holography (XFH). In contrast to XFH, however, image aberrations known to drastically distort single energy holograms are effectively suppressed by this multi-energy 

approach. 

MEXH was applied to a natural slab of single-crystal Hematite (FezOs), which 

consists of alternating layers of iron and oxygen and can be conveniently described 

directly imaging atomic structures in the b ulk or at surfaces of solids. It utilizes 

lattice. The figure below shows a real-space reconstruction of an in Hematite. Clearly to be seen are iron atoms on the six nearest a central emitter as well as-atoms on corner sites of the underlying 

hexagonal grid, up to distances of about 8 A 

Figure Holographic reconstruction of an iron (0,0,1) layer in Hematit (Fez Os) 
Figure 1. Holographic reconstruction of the Ge(100) plane 

F 

0 

N X-ray Fluoresence Holography: Imaging the Atomic Environment in 

Hematite (Fe203) X14A Multi-Energy X-ray Holography: Images of Ge( 100) 

... . - .- 

X14A 
X14A Study of Surface Active Poly(pyrro1es) using Synchrotron X-ray 

Diffraction * 

T. Herod, G.Weekaseekra, T. Servay, and R.S. Duran (University of Florida), M. 

Durbin, A. Malik, and P. Dutta (Northwestern University) 

Previous investigations which reported the successful imaging of polypyrroles 

using Scanning Tunneling Microscopy (STM) triggered our interest in further elucidating the structural organization of these polymers in monomolecular layers. One 

way of improving the informational content of an STM image would be to disrupt 

the periodicity along the polymer chain. To accomplish this we prepared copolymers of 3-hexadecyl pyrrole (3HDP) and N-octadecyl pyrrole (NOP). The different 

substitution would allow for the the resolution of the monomer units and to locate 

the polymer backbone. As an aid in this investigation, the structure of the polymer, 

copolymer, and corresponding monomers, were investigated at the air-water interface using synchrotron x-ray diffraction. X-ray measurements were performed at 

the Oak Ridge National Laboratory on beamline X14 of the National Synchrotron 

Light Source. The experimental setup has been described in previous publications. 

Langmuir films of the pure 3HDP and a mixture of 50:50 (m) 3HDP and NOP 

were prepared at a temperature of 25OC and a surface pressure of 5 mN m-l. 

Diffraction data was acquired for each of these systems. Interpretation of these 

results are still being formulated. One off-plane diffraction peak (K, = 0.10-0.50 

A-' was seen at K,, = 1.46 A-1 for the pure 3HDP and two off-plane peaks, 

1.47 and 1.44 A-1 were seen for the mixed monomer system. Interpretation of 

these results are still pending. Polymerization of the pure monomer, and mixtures, 

were accomplished via chemical oxidation with 0.03 M ammonmium persulfate on 

the water surface for 70 minutes, with a constant surface pressure of 5 mN m-'. 

The surface pressure was then increased to 20 mN m-l and x-ray data acquired. 

Single (triply-degenerate) in-plane diffraction peaks were seen for the homopolymer 

and the copolymer at 1.47 Awl. This data supports the model of a 2-dimensional 

hexagonal lattice with lattice constant of 4.9 A with the alkyl chains standing normal 

to the water surface. 

K&' 

Figure 1. Diffraction of poly(3-Hexadecylpyrrole) at the air-water interface. td r 

hY 

CL * Supportedin part by ONR, and Micron SemiconductorJnc. 

X14A Inelastic X-Ray Measurements of the Local-Field Factor for a Simple 

Metal 

B. C. Larson (ORNL) 

Recent first principles calculations by Fleszar et al.5 have shown that band structure effects are responsible for the double peak in the dynamic structure factor 

S(q,w) for aluminum. Their results suggested that de tailed measurements of S(q,w) as a func tion of energy loss w and wave vector q near twice the Fermi wave vector, 

2 kF, could now be used to get information on the physics of short-range electron correla tions in simple metals. The X-14 beam line at the National Synchrotron 

Light Source has been used to measure S(q,w) near 2kF for aluminum as shown 

in Fig. 1. The measurements are compared to ab initio cal culations of S(q,w in 

order to obtain experimental insight into the details of the (static Hubbard- li ke 

many-body local field factor, G(q). In the figure, the curves labeed 1 So refer to 

non-interacting electron-hole pairs propagating in the band structure of aluminum. 

The RPA, TDLDA, and TDHF curves refer to calculations for three different forms 

of G(q): RPA corresponds to mean-field calculations where G(q) = 0; the TDLDA 

curves refer to a time-dependent extension of the local density approximation in 

which G(q) 92; and the TDHF curves refer to a G(q) (derived from time-dependent 

Hartree-Fock calculations 6) that is strongly peaked a with magnitude 2 near 2 

kF. There is remarkable agreement between the TDHF calculations and the measurements up to 2 kF, indicating that G(q) for aluminum reaches a value 2. A 

value this large rules out most existing models for G(q), and the departure from 

TDHF above 2 kF requires additional work. Direct fitting of G(q,w) as a dynamic 

local field factor is in progress. 

- 

20 

I5 

10 

6 

0 

Figure 1. X-ray measurements and theoretical calculations of the dynamical structure factor for aluminum along the 013 direction. The open circles denote the 

measurements and the lines represent calculations as defined in the legend. 
I. , 1' , 

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I X-Ray Measurement of the Local-Field Factor for Aluminum I X14A I 

B. C. Larson (ORNL), J. Z. Tischler (ORNL), E. D. Isaacs (AT&T Bell Labs), P. 

Zschack (ORNL), A. Flessar (Universityat Wiirzburg), and A. G. Eguilus (University of Tennessee and ORNL) 

Recent first principles calculations [l have suggested that band structure effects 

minum. The calculations suggested further that detailed measurements of S($, w) 

as a function of energy loss w and wave vector q near twice the Fermi wave vector, 

2kF, could now be used to get information on the physics of short-range electron 

correlations in simple metals. The X-14 beam line has been used to measure S($, w) 

near 2kF for aluminum as shown in Fig. 1. The measurements are compared to 

ab initio calculations of S($,w) in order to obtain experimental insight into the 

details of the (static) Hubbard-like many-body local field factor, G(q). In the figure, the curves labeled So refer to non-interacting electron-hole pairs propagating 

in the band structure of aluminum. The RPA, TDLDA, and TDHF curves refer to 

calculations for three different forms of G(q): RPA corresponds to mean-field calculations where G(q) = 0; the TDLDA curves refer to a time-dependent extension 

of the local density approximation in which G(q) N q2; and the TDHF curves refer 

to, a G(q) (time-dependent Hartree-Fock calculations [2]) that is strongly peaked 

with magnitude N 2 near 2kF. There is remarkable agreement between the TDHF 

calculations and the measurements up to 2k~, indicating that G(Z w) for aluminum 

are responsible for the double peak in t k e dynamic structure factor S($, w) for alurules out most existing models for G(q), and 

calls for additional work. Direct fitting of 

is in progress. 

and A. G. Eguilus, Phys. Rev. Lett. 74, 590 (1995). 

J. T. Devreese, Phys. Stat. Sol. (b) 147,173 (1988). 

I Control of the colony microstructure of high T, superconductors I X14A I 

E.D. Specht, A. Goyal, D.M. Kroeger (ORNL), J.A. DeLuca, J.E. Tkacsyk, and 

J.A. Sutliff (GE) 

T11 CazSrzCusO, (Tl-1223) high-?', superconductors grown on polycrystalline 

substrates have been shown to have high critical current densities (J,) even at high 

temperatures and in high magnetic fields. Because polycrystalline substrates are used, these results make T1-1223 a promising material for high-current applications 

requiring long lengths of wire, such as power transmission, magnets, generators, 

and motors. 

The high J, has been shown to result from local crystallographic alignment in the 

films[l]. While the films have no global in-plane alignment, "colonies" of aligned 

grains can be as large as a mm, containing thousands of grains. While high J, has 

been reported within a single highly-aligned colony, optimum J, over long lengths 

requires an in-plane, intracolony mosaic of ~20 deg. FWHM. 

T1-1223 films are grown by exposing a precursor material to TlzO vapor[2]. Microdiffraction[3] was used to analyze the average colony size and mosaic as afunction 

of the exposure time (Fig. 1) and the TI20 flow rate (Fig. 2). An optimum colony 

size was produced by using a low flow rate and long exposure time, which leads to 

a complete reaction at a slow rate. 

1 E.D. Specht et al., Physica C 242, 164 (1995). 

2 J.A. DeLuca et al., Physica C 205, 21 (1993). 

3 E.D. Specht et al., Physica C 226, 76 1994). 11 This work was supported by the U.S. D 6 E Office of Advanced Utility Concepts - Superconducting Technology Program and Division of Materials Science under 

contract DE-AC05-840R21400 with Lockheed Martin Energy Systems, Inc. 

0 

0 

1 20' ' ' ' ' . ' ' ' ' ' 

31 0 5 10 15 20 25 

T1,O reaction time (min.) 

Figure 1. X-ray measurements and theoretical calculations of the dynamical structure factor for A1 along the [013] direction. 

Figure 1. Dependence of colony mosaic on time exposed to TlzO Figure 2. Dependence of colony mosaic on TlzO flow rate 
I X-ray diffraction of human brain neuromelanin and synthetic neu- I . . I A14A I romelanin. * 

Q.J. Wang, M. Eisner, P.R. Crippa, S.C. Moss [Physics Dept., University of Houston) P. Zschack, T. Gogg (ORSL/NSLS Beamlke X14) L.- Zecca (1.T.B.A.-CNR, 

Milan, Italy) 

Four samples were studied in both transmission and reflection (high-q). The first 

sample is natural human neuromelanin consisting of a pressed powder disk of 3mm 

in diameter and 0.15mm in thickness. The second sample is enzymatic neuromelanin 

synthesized at Houston. The third sample is auto-oxidized dopamine melanin with 

Fe3+ ions, while a fourth sample is auto-oxidized neuromelanin with Fe3+ ions. The 

three synthetic samples are disks of lOmm in diameter and about lmm in thickness. 

The X-ray photon energy at X14 was chosen at 16KeV. The proposed molecular 

formula of theses samples is essentially CT~H~OZ NeOszS3Fe. We may note that 

the first sharp peaks of all three synthetic neuromelanins are between q=1.6Aj-' 

and q=1.'78L-l while the first sharp peak of the human brain neuromelanin is at 

q=1.32A-'. These peaks have in the past [l] been associated with interplanar order. 

In addition the synthetic samples have more detailed structure compared with the 

natural sample at higher q. Nonetheless the higher-q data seems similar in all which 

indicates that they have similar planar structures. 

These raw data sets are being processed to remove the measured Compton scattering (through the use of X14 analyzer/PSD detector) and are being reduced to 

provide S(q) for further analysis. 

1. J. Chen S.C. MOSS, M. Eisner and P. Zschack, Pigment Cell Res. 7 255 

(1994), 7,263 fi994) 

I X-ray Standing Wave Measurements of a Metal/Polymer Interface * I X15A 

M.J. Bedzyk (ANL and Northwestern U.), B. DeKoven (Dow Chemical), P.F. 

Lyman (Northwestern U.), and M. Radler (Dow Chemical) 

There are a growing number of technological interests in the optical, electronic, 

magnetic, and catalytic properties of structures derived from thin metallic films 

evaporated on polymeric films. We are developing the use of x-ray standing waves 

(XSW) as an in-situ, chemically sensitive structural probe for profiling these structures. As a trial, the morphology and possible thermal diffusion of a thin Cu layer 

deposited on a siloxane-based polymer film that coated a Au mirror was studied 

with XSW. The results suggest that the thin Cu film forms 'islands' when deposited 

and that the projected width of the Cu distribution changes after annealing. The 

diffusion of Cu into the polymer film is less than 5 Abefore and after annealing. 

The long-period XSW was generated above the Au mirror surface by total external reflection TER). The XSW period ( D = X/2sin 0 ) is infinite when the beam 

angle (e, ) the period is D, = 80 Afor Au. Figure 1 depicts the data and fit for a 

sample with a thin Cu layer ("2 A) deposited on a ~500 Afilm at room temperature. The oscillations in the reflectivity (Kissig fringes) reveal the thickness of the 

and roughness of the two interfaces (4 A). The striking oscillations 

in the (530 Cu 2 fluorescence occur when the extrema of the XSW move past the Cu 

layer. Assuming a Gaussian profile, the model curve indicates the Cu film is <z> 

= 531 Aabove the Au surface with a projected width of 23 A. If the Cu layer were 

uniformly 2 Athick and perfectly parallel to the Au surface, the Cu modulations 

would not be noticeably attenuated at higher angles within the TER region (since 

2 Ais small compared to the XSW period). The observed damping is most likely 

due to Cu islanding. After vacuum annealing to 300°C for 1 hour (with no Cu 

loss), there is no significant change in the modulation period indicating that the 

Cu distribution has the same average height <z> above the Au mirror (Fig. 2). However, the Cu modulations are now stronger at higher angles, indicating that the 

thickness of the Cu layer as projected along the surface normal has decreased to 14 

is parallel to t 6 e plane of the mirror, and shortens at finite angles. At the critical 

A. 

Fig. 2 

no. I 2h Cu I61oA Slloxano I AY Mirror E; 9.60 koV 

II "I w4 &...-,A" wx .: .u Y" 4 

93 

5i 

1 2 P2 

m 

- t 

1' 

? t 8 81 

I: 0, I 

0 et 1 * .OI*,. 

e I-* 

Figure 1. * Sponsored in part by the US DOE 

(BES-DMS), under contract W-31-109- 

ENG-38, and by the NSF under contract to 

-' 

O2 * Research at Houston was supported by the U.S. DOE/BES on contract DE-FGO5- 

87ER 45325. the MRC at Northwestern U. 0 (mrad) 
X15A The Use of X-ray Standing Waves and Evanescent-Wave Emission 

to Study Buried Strained-Layer Heterostructures * 

T.-L. Lee (Northwestern U.), Y. Qian (Northwestern U. and ANL), P.F. Lyman 

(Northwestern U.), J.C. Woicik, J.G. Pellegrino (NIST) and M.J. Bedzyk (Northwestern U. and ANL) 

A heteroepitaxial structure consisting of 1 ML InAs grown on GaAs(001) and 

subse uently capped with 25 A GaAs was examined by the x-ray standing wave (XS4 method. By monitoring the In L fluorescence while scanning through the 

GaAs(OO4) Bragg reflection, the indium position is measured to be 0.22 a above the 

nearest GaAs(004 diffraction plane (Fig. 1). This corresponds to a perpendicular 

elasticity theory ('7.3%). We also demonstrate that, by limiting the emission takeoff 

angle cyu of the observed As La! fluorescence, the evanescent-wave-emission effect can be used in conjunction with the XSW method to determine the strain-induced 

displacement of the cap layer in the growth direction (Fig. 2). This displacement 

(0.47 a) is measured to be twice the displacement of the indium layer. 

strain of 7.7% wit 1 in the InAs layer, which is in good agreement with macroscopic 

ic -1 ii 

8 - 8" [pad] 

Figure 1. 

* This work was sponsored by the U. 

S. Department of Energy, Office of Basic Energy Sciences, Division of Materials 

Sciences, under contract W-31-109-ENG-38, 

and by the NSF under contract to the MRC 

at Northwestern University. 

-20 0 20 40 60 80 100 120 

e - e, [pad] 

Figure 2. 

I Surface Structure of Submonolayer Phases of Sn/Si(OOl) * I X15A I ~ 

Paul F. Lyman (Northwestern U.) and Michael J. Bedzyk (Northwestern U. and 

ANL) 

Adsorption of -monolayer quantities of Sn on the Si(OO1) surface results in a rich 

surface phase diagram of LEED superstructures [l]. A striking STM investigation 

strongly suggests that these phases are constructed from various arrangements of a few basic structural building blocks; specifically, highly buckled dimers are prevalent on the surface [2]. To understand the chemical composition and local geometrical 

structure of these surface phases, we undertook an x ray standing wave (XSW) 

investigation of the known phases of Sn/Si(OOl). Our results appear to bear out 

the STM hypothesis that the local structure of the various phases is similar. 

For coverages below 0.75 ML, our results are most consistent with the presence 

of Sn-Sn dimers, buckled by about 13'. For this buckling angle, the two Sn atoms 

of the dimer are nearly out of phase from one another with respect to the (004) 

reflection XSW. This manifests itself as a low value of the (004) Sn coherent fraction, 

but a reasonably high (022) Sn coherent fraction (see Fig. 1). Above 0.75 ML, the 

(004) coherent fraction increases abruptly, which is due to a sharp change in the 

buckling angle (to < -lo0) and/or to occupancy of the second Sn layer. These 

second layer sites are certain to be populated upon exceeding a monolayer. 

[l] K. Ueda, K. Kinoshita, and M. Mannami, Surf. Sci. 145, 261 (1984). [2] A.A. 

Baski, C.F. Quate, and J. Nogami, Phys. Rev. B 44, 11167 (1991). 

c 

- 

f 1.2 

B - 

51 

s 

c 

c 08 

4 0.6 

C 

0.4 

e 

L 

c 0.2 1 

Snl Sl(OO1) 

v 

6 0.2 0.4 0.6 0.8 1 1.2 1.4 

Sn Covaraga (ML) 

Figure 1. Sn coherent fractions and coherent positions from (004) and (022) XSW scans as a function of Sn coverage for Sn/Si(ool) 

* This work was sponsored by the U. S. Department of Energy, Office of Basic Energy 

Sciences, Division of Materials Sciences, under contract W-31-109-ENG-38, and by the 

NSF under contract to the MRC at Northwestern University. 
I Surfactant-Mediated Epitaxy of Metastable SnGe Alloys * I X15A I 

Paul F. Lyman (Northwestern U.) and Michael J. Bedzyk (Northwestern U. and 

ANL) 

Adsorption and growth of Sn on Ge surfaces represents a highly mismatched 

(~15%) case of IV-IV epitaxy. Stemming from the fact that the diamond-structure 

allotrope of Sn (gray, or a-Sn) is a zero-gap semiconductor, alloys of Sn and Ge are 

predicted to have useful and interesting electronic properties, such as a direct band 

gap and high carrier mobilities. However, the equilibrium solid solubility of Sn in Ge 

is quite low, and metastable alloys are difficult to construct even by MBE methods 

due to rapid segregation of Sn to the growth front. We have begun to explore the 

possibility of employing a surfactant species (i.e., one having a low surface energy 

to thus construct metastable SnGe multilayers or alloys. 

We undertook an x-ray standing wave (XSW , low-energy electron diffraction 

sibility of surfactant-mediated epitaxy. By using Bi as a surfactant species, we 

suppressed the segregation mobility of the Sn heterolayer during subsequent Ge 

overgrowth (measured by AES). Fig. 1 depicts the XSW fluorescence modulation 

from the Bi overlayer after various SnGe growths. This renders a direct measure of 

the Bi adsorption height relative to the bulk lattice planes (c.f. table of coherent 

positions in Fig. 1); owing to the larger lattice spacing of Sn, the adsorption height 

is increased upon Sn growth, but remains unchanged (up to a modulus of the lattice 

d-spacing) upon Ge overgrowth. These facts firmly establish that the Bi surfactant 

does indeed segregate to the surface. Furthermore, our XSW measurements reveal a well-ordered (>70%) Sn heterolayer after -20 ML Ge overgrowth in the presence 

of a surfactant. 

to kinetically suppress the ability of the Sn to segregate during Ge overgrowth an d 

(LEED), and Auger electron spectroscopy (AE 2 ) investigation to study the feaX15A Structure and Ad-Atom Thermal Vibrational Amplitude for the 

Ga/Si(001) Surface * 

Yonglin Qian and Michael J. Bedzyk (ANL and Northwestern U.) 

In an earlier study of the structure of the Ga/Si(001) surface, we had found that 

Ga adsorbs at room temperature as a dimer, residing above unbroken Si dimers, 

and oriented arallel to those dimers [I]. In the present work, we have employed 

mal vibrational 

Ga adatom vibration amplitude along the surface normal direction was thereby determined to be 0.135 & 0.01 A. Furthermore, by reducing the uncertainty of the 

vibrational amplitude, this result allows us to determine the Ga ad-dimer bond 

length (measured previously using an (022) reflection) with much higher accuracy 

(2.58 f 0.04 A than in our previous studies. 

fundamental f004) and harmonic (008) x-ray standing wave (XSW) 

measure the lattice positions and ther- on a 0.3 ML Ga/Si(001) surface. The 

measurements (Figs. la 

[l Y. Qian, LI .J. Bedzyk, S. Tang, A.J. Freeman, and G.E. Franklin, 

P x ys. Rev. Lett. 73, 1521 (1994). 

u 

1.5 

8 

ir 

$1 

0.5 

I 

-10 -5 0 5 IO I5 20 25 30 

f,, = 0.34 f 0.02 

ir 

.? - OW^ '"'-'-'-'.- 2 4 6 8 IO 12 14 

0 - 0, $md) 

Figure 1. Experimental data and best fit for the fluorescence yield and reflectivity 

versus 0 for: (a) the (004) reflection and (b) the (008) reflection. 

* This work was sponsored by the U. S. Department of Energy, Office of Basic Energy 

Sciences, Division of Materials Sciences, under contract W-31-109-ENG-38, and by the 

NSF under contract to the MRC at Northwestern University. 

* This work was sponsored by the U. S. Department of Energy, Office of Basic Energy 

Sciences, Division of Materials Sciences, under contract W-31-109-ENG-38, and by the 

MRC at Northwestern U., under contract to the NSF. 
.. . .. .. 

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F 

g 

An X-ray Standing Wave Study of Surface Kinetics: Bismuth Adsorption on Si(OO1) * X15A I Surfactant-assisted growth of Ge on Si(ll1) 1 X15A I 

Y. Qian (ANL and Northwestern U.), P.F. Lyman, T.-L. Lee (Northwestern U.) 

and M.J. Bedzyk (ANL and Northwestern U.) 

hase for Bi adsorption on the Si(OO1 surface is coverage-dependent, with a (1x27 phase stable at coverages 

8 > 0.5 M L , and a (2x2) phase stable for coverages 8 < 0.5 ML [l]. To test these 

predictions, we used the x-ray standing wave (XSW) technique to experimentally 

investigate the temperature- and coverage-dependent surface structure and reaction 

kinetics of Bi adsorption on the Si(OO1) surface. 

We deposited 0.2 ML of Bi on the Si 001)-(2x1) at room temperature. Subsetemperatures ?Fig. 1). The (1x2) and (2x2) phases possess markedly different adsorption heights [1l1 and so fractional surface phase compositions of the (1x2), (2x2) 

and a disordered phase could be determined from these high resolution measurements (Fig. 2). The (2x2) Bi phase that is predicted to be the low coverage structure was found to be a metastable phase. It undergoes an irreversible phase transition 

to the stable (1x2) phase upon annealing. The thermal activation energy of 0.4 rt 

It has been theoretically predicted that the stable 

quently, we ac uired a series of (004) XS & measurements after annealing to various 

0.2 eV and exponential prefactor of 10-1 Hz for the (2~2)-to-(lx2 

determined from the conversion rate at different temperatures. 

demonstrates a new approach for investigating the kinetics of surface transitions. 

[l] S. Tang and A. J. Freeman, Phys. Rev. B 50, 1701 (1994). 

J.C. Woicik (NIST), P.F. Lyman (Northwestern), and M.J. Bedzyk (Northwestern 

and ANL) 

The x-ray standing wave technique, Auger-electron spectroscopy, and low-energy 

electron diffraction have been applied to the study of Bi surfactant-assisted growth 

of Ge on Si(ll1). The original Bi-terminated Si(ll1) surface is found to exhibit a 

fi x fiR30 LEED pattern, and the Bi position, 0.9'7 d Si ill), corresponds to 

of the first Si layer. Upon submonolayer deposition of Gel the Bi adatoms are displaced up to the surface, and Ge grows on the Si surface as a coherent, strained 

double layer. The Bi segregation is evidenced by an increase in the Bi adsorption 

height, as measured by XSW, and the fact that there is no reduction in Bi Auger 

intensity or change in the LEED pattern. Evidence for the Ge double layer are the 

measured Ge coherent fraction (F = 0.64) and position (P = 1.08). In contrast, the 

expected parameters for an unstrained perfect crystalline Ge double layer having 

the Ge lattice parameter would be F = 0.71 and P = 1.04, respectively. 

the sum of the Bi and Si covalent radii for Bi atoms direct \ y atop the Si atoms 

"40 .5 0 5 10 I5 20 21 

0-0, Urndl 

Figure 1. A series of (004) XSW measurements after isochronal anneals. 

1 

0 300 400 500 600 700 

Annealing Temperature (K) 

bULC. 

em U under contract to the NSF. 
I Quantifying Zn Doping in InGaAsP/InP Laser Structures 

L. Niu,B. F. Karlicek, and P. H. Citrin (AT&T Bell Laboratories) 

Precise control of dopant concentrations, which is generally important in fabricating semiconductor devices, is particularly critical for Zn-doped InGaAsP/InP 

laser structures operating in the 1.3 - 1.5 pm range. Too much Zn (typically 

> 2x 10'8atoms/cc) leads to excessive diffusion into the active layer, increasing 

Ling thresholds and reducing efficiency, while too little Zn causes carrier leakage 

around that layer, degrading its high temperature performance. Such low doping 

levels and tight tolerances require highly sensitive and precise diagnostics, characteristics well matched to the conventionally used technique of SIMS. Using improved 

fluorescence detection capabilities, we have applied NEXAFS to a variety of Zndoped InP structures and shown that this approach provides substantially higher 

precision than SIMS and has the additional benefit of being non-destructive. We 

have also established that there is a well-defined concentration regime in which substitutional occupation of Zn is linearly proportional to Zn exposure. Apart from 

determining more reliable growth parameters in the fabrication of these high performance diode lasers, our findings demonstrate the general utility of x-ray absorption 

spectroscopy for non-destructive quantification of dilute dopants in semiconductors. 

X15B I X-ray Absorption from Pb-modified Fluoride Glasses I X15B I 

L. Niu, A. R. Kortan, and P. H. Citrin (AT&T Bell Laboratories) 

ZBLAN fluoride glasses (Zr/Ba/La/Al/Na), with theoretical ultra-low optical 

losses at near-infrared wavelengths, suggest potential applications in optical fibers 

and in hosts for optical lasers and amplifiers. After two decades of study, however, 

there is very limited structural understanding of these materials. Useful applications 

demand an adjustable range of refractive indices, which are obtained by partial substitution of some of the elements of ZBLAN. Lead is the most popular substituent 

for Ba, but above critical Pb concentrations the stability of the glass significantly 

decreases. To understand this phenomenon, ZBLAN glasses have been studied using 

NEXAFS and EXAFS. It was found that only at Ba sites and only under unstable 

glass conditions (i.e., high Pb concentrations) are structural and electronic changes 

observed. These changes indicate that the glass stability is almost exclusively related to the local structure of the Ba atoms, which are believed to modify the glass 

by randomly occupying the interstitial sites of the ZrF,-polyhedra network, thereby increasing the corner sharing with respect to edge sharing. 
Fd 

CL 

h? 00 I Structural Characterization of Cr4+-YAG Crystals Lasing at 1.5 pm I X15B I 

L. Niu, L. F. Schneemeyer, T. D. Harris, and P. H. Citrin (AT&T Bell Laboratories) 

A new laser material, Cr4+-Y3A160n, has been studied as a potential source for 

optical communications at 1.5 pm. Solid-state lasers typically offer advantages of 

reliability, noise, and cost. The novelty and challenge of this material lies in overcoming the natural tendency of dopant Cr3+ ions to substitute both tetrahedral and 

octahedral A13+ sites and favor instead, using co-dopants such as Ca2+ for charge 

compensation, substituting optically active Cr4+ ions on only A13+ tetrahedral sites. 

Optimization of crystal growth parameters for achieving this is made difficult by 

the lack of suitable structural characterization methods. Chromium and calcium 

K-edge EXAFS experiments have been used to identify the concentration of Cr4+, 

Cr3+, and Ca2+ in different environments as a function of various growth parameters. Preliminary results have already ruled out the role of several parameters that 

had been believed to be significant. 

I Size and Composition of Luminescent Oxidized Si Nanocrystals I X15B I 

S. Schuppler, L. E. Brus, and P. H. Citrin (AT&T Bell Laboratories) 

The study of nanosized systems is of growing interest, particularly in materials 

involving Si because of their potential applications to optoelectronic technology. 

As part of a broad program to identify and characterize the visibly luminescent 

species in anodically grown (H-passivated) porous Si, we have investigated sizeselected fractions of luminescent Si nanocrystals prepared from pyrolysis of disilane 

with subsequent oxidation in 02. The optical and structural properties of these 

nanocrystals, ox-Si,, made them ideal model systems for studying luminescence 

activity because of their chemical inertness due to the outer oxide shell) and their 

luminescing in the visible region with outer diameters 5 30 8, are beyond imaging 

or diffraction capabilities for determining internal structure and composition, x-ray 

absorption measurements were required. We obtained Si K-edge NEXAFS data 

from four size-selected groups of ox-Si, particles with mean outer diameters of 

96, 45, 33, and 26 8,. In each group a small but discernible feature was observed 

approximately midway between the well-separated (w 7 eV) absorption edges of 

the Si, and Si02 components, corresponding to incompletely oxidized Si at the Si,- 

Si02 interface. From the relative edge jumps and densities of the three components 

and from the outer diameters of the spherical particles, the mean inner diameters 

of the Si, cores and thicknesses of the interfacial SiO, and outer Si02 layers were 

determined. The outer diameters varied a factor of 4 and the corresponding core 

diameters of 78, 31, 17, and 11 8, varied a factor of 7, but the SiOz- and SO,-layer 

thicknesses of 6.5 and 1.5 8, remained remarkably constant. These findings, coupled 

with the varying luminescent energies of the different sized particles, convincingly 

ruled out earlier suggestions that either Si02 or SiO, is the optically active species. 

Instead, our results showed that it is the inner Si, cores which are responsible for 

the optical activity. The dimensions of these cores and the strong similarity of 

their luminescent behavior to that observed in a series of porous Si samples proved 

essential in characterizing these latter heterogeneous and more chemically reactive 

materials. 

simple spherical shape (determined from T B M imaging). However, since particles 
1x15~ I Cation Charge State and Local Structure in the Rare-earth Fulleride 

Yb2.75C60 

Identifying Point Defects in Si-doped GaAs using NEXAFS and EXAFS 

S. Schuppler (AT&T Bell Labs), E. Oedas (Hacettepe U.), K. B. Lyons, A. R. 

Kortan, and P. H. Citrin (AT&T Bell Labs) 

Recently discovered electron-donor intercalated C60 fulleride compounds have received much attention because of their extraordinary physical properties. Most notably, record high superconducting temperatures for organic systems have been observed in alkali-metal fullerides, prompting exploration for other elements as donors. 

Superconductivity has so far been demonstrated in monovalent alkali-metal donor 

compounds (K, Rb, CS)~ C60 and divalent alkaline-earth donor compounds CabC60 

and (SI, Ba)sCso. Expanding the search to the predominantly trivalent rare-earth 

RE) metals has resulted in only one reported case of successful donor intercalation, h, 2.76 C60, which becomes superconducting below 6 K. 

We have obtained NEXAFS measurements from the single-phase form of this 

rare-earth fulleride which indicate that the cation is exclusively divalent. EXAFS 

data have also been obtained which show that there exists strong local ordering of 

the surrounding c60 molecules. Two well-defined average Yb-C nearest-neighbor 

distances separated by 0.18 & 0.03 Awere observed, corresponding to the Yb(I1) 

cations occupying off-centered octahedral and tetrahedral interstices of the f.c.c. c60 sublattice. Heating Yb2.76C60 above 670' C was shown to produce an amorphous carbidic phase containing Yb(II1). Our results, combined with thermodynamic arguments and analogues in organometallic compounds, have been used to 

explain the observed single-crystal structure of Yb2.76 C60 and to infer expectations 

for forming fullerides with other RE metals. 

X15B 

S. Schuppler, L. N. PfeSer, K. W. West, and P. H. Citrin (AT&T Bell Laboratories) 

The problem of electrical deactivation, i.e., the decrease (trapping) of active 

carriers due to defects with increasing donor concentration, is encountered in all 

semiconductors, but it is particularly severe in GaAs highly doped with Si, its most 

common n-type dopant. Amphoteric Si can occupy both n-type Ga sites (Sio.) and 

p-type As sites (SA.), so the electrical deactivation has generally been attributed to 

acceptor-Si atoms trapping free-electron carriers. Using NEXAFS data to measure 

directly the upper limit concentration of Si atoms occupying such p-type As sites, 

we showed last year that only about half of the observed electrical inactivity was 

due to this autocompensation mechanism. Identification of the dominant defects 

responsible for the additionally missing carriers was made this year using EXAFS. 

Analysis of data obtained from Si,Gel-, model systems (z = 0.03, 0.20, and 0.50) 

and comparison with data from highly Si-doped GaAs revealed a comparatively 

large number of both neutral SiGa-SiAs dimers and small Si, clusters. The relative 

concentrations of these two point defects, along with the two monomer defects SiGa 

and SiAsl were found to depend on the total Si doping level and the orientation of 

the GaAs surface during growth. 
CL 

w 0 

IdJ *ins 

- 0) Leo0 - 

1MO 

m400- 

- 

- 

- 

- 

- 

a4 - - 

- 

398 IO0 IO1 4.02 

H h1.u) 

Figure 1. Diffracted intensity as function of H, for constant L. 

Diffraction study of an etched InP grating I X16A Structural X16A study of the ZnSe/GaAs interface 

P. Imperatori (ICMAT-CNR, Italy), K. Evans-Lutterodt (AT&T Bell Labs.) and 

R. Felici (ISM-CNR, Italy) 

Heterovalent semiconductor heterojunctions such as ZnSe/GaAs present a remarkable correlation between the interface composition in the early growth stage 

and the final value of the valence band offset. In order to better understand this 

correlation, an x-ray diffraction study of the ZnSe/GaAs interface was performed. 

We investigated a set of samples grown by molecular beam epitaxy, with a different 

Zn/Se beam pressure ratio (0.1,l and 10 respectively and having the same thickness (50 A). For each sample we measured the cryst truncation rod scattering at 

different photon energies, just above and below the k-edges of Zn, Ga, As and Se, in 

order to change the atomic scattering factors and better separate the contribution 

of each element to the atomic structure of the interface. Figure 1 shows one of the 

measured rod at two different energies. We also looked for reconstructions peaks 

at the interface, due to the presence of possible (Ga,Se) interfacial compounds, 

but no evidence of such peaks was found. Data analysis to determine the atomic 

arrangement at the interface is currently underway. 

J 

Id 

lo" 

s Id 

lo' 

Id 

Id 

5 

1 [r.l.u] 

Figure 1. Intensities of the (OOL) rod for incident photon energies below (solid line) 

and above (dashed line) the Zn k-edge. 

. *, 
i I Sb/Si( ll1)-(d3xd3)R3O0 structure determination X16A 

o Si Sb 

Growth of Cu Islands on Cu(ll0) * 

'? Figure 1. Patterson function of d3xJ3- Figure 2. Milk stool trimer model of 

t; Sb/Si(lll) d3xd3-Sb/Si( 11 1) CL 

X16A 

8 t: 100 

ti 

i3 

$ 

f IO 

.. 

-050 -020 -0.10 -000 010 020 0.30 h (RLU ) 

8 t: 100 

ti 

i3 

$ 

f IO 

.. 

-050 -020 -0.10 -000 

h (RLU ) 0 IO 020 0.30 40 I 4.2 44 4.6 4.8 50 52 I 

1ooo/r (I/%) 

Figure 1. 

CTR with Om5 ML Of cu deposited at 

= 218 K. 

Transverse Scan Of cu(llo) Figure 2. Arrhenius plot of fitting parameter h,. Each measurement corre- sponds to a separate deposition of 0.5 

ML at a flux of z 4~10-~ ML/s. 

* Supported by NSF DMR 93-15691 
'I . 

)--L 

o Is Development of local structure in sol-gel derived lead zirconate titanate thin layers * X16C 

I.. 

~ 

D.L. Adler, S.S. Sengupta and D.A. Payne (Univ. of Illinois, Urbana) 

EXAFS analysis was carried out to determine the evolution of local structure in 

lead zirconate titanate (PZT) thin layers prepared by a sol-gel technique. Earlier 

results obtained for partially heat-treated below 50OoC) bulk gels indicated the 

In the present study, thin layers of were spin-coated on polycrystalline alumina 

substrates and initially heat-treated to 300°C to remove organics. The amorphous 

coatings were then sequentially heat-treated to various temperatures between 400- 

625OC for EXAFS analysis. As expected, the first nearest neighbor for all metal 

cations was oxygen. For lead titanate (PT), a clear and definite change in second 

shell coordination was evident upon heat-treatment: between 450°C and 5OO0C, the 

cation distribution in the second shell of Ti changed abruptly from nearly all Ti to 

mostly Pb, with a corresponding increase in the bond distance. Evolution to A-0-B 

type bonding, representative of the basic perovskite building block, was complete by 

55OoC. The third shell, however, showed a lack of order even at 55OoC, suggesting 

that the characteristic long-range order of the crystalline phase had not fully developed, and required further heat treatment. Fig. 1 compares the magnitudes of the 

Fourier transform for experimental Ti K-edge data at two different temperatures, 

with previously obtained results for amorphous bulk gels (heat-treated at 375OC) 

and crystalline PT. In contrast to PT, the PZT70/30 and lead zirconate (PZ) specimens did not show a sharp change in second neighbor coordination during heat 

treatment up to 625OC. Further analysis is in progress. 

presence of separate Ti-0-Ti, Zr-0-Zr and Is b-0-Pb networks. 

8 

i! 

0146810 

R R.1 

* This work was supported by the Dept. of Energy under Contract No. DEFGOB91EFt.45439. 

I Superstructure peaks in lead magnesium niobze (PMN) ~ (XGCI 

D. Fanning, D. Adler, I. Robinson (U. of Illinois) 

A single crystal sample of lead magnesium niobate PMN) was studied on the 

to paraelectric phase transition near room temperature. Relaxors are also characterized by their high dielectric constants and frequency dependent behavior. PMN 

has the general perovskite structure (a=4.04 A) with Pb on the corner, 3 0 atoms on the faces and a random distribution of Mg and Nb ions (in a 2:1 ratio) on the 

body centered site. 

The sample was found to have well formed superstructure peaks of type (h+1/2, 

k+1/2,1+1/2) (h,k,l integers) which had widths on the order of 0.01 A-' indicating 

a domain size around 100 A. Electron diffraction experiments have shown that this 

domain size is not affected by annealing or preparation technique. Hence, it is not 

certain whether these domains are related to PMN's ferroelectric behavior. 

Radial scans were made through many half-order peaks, and their integrated 

intensities were calculated. Figure 1 is a plot of IF1 vs. 141 for superstructure 

reflections of one set of data at room temperature. 

X16C beamline. PMN is a ferroelectric "relaxor," exhi 6 iting a broad ferroelectric 

Superstructure reflections of the 

type (h+ 1 /2 , k+l/2,1+ I 12) I 

I 

€ 

T 

Momentum transfer, 1st ,(A-') 

Figure 1. 
u1 emsseJd 

01 6 9 L 9 S C E 2 IO 
I 

F 

0 + Effect of Pressure on Cation Distributions in Nickel Aluminate 

Spinel (NiA1204) X17B1 

References: 

John B. Parise and Rui Li, AGU 1995 Spring Meeting (M32A-09). 

'Jiuhua Chen, Donald J. Weidner, Michael T. Vaughan, 

'Robert Hazen and Alex Navrotsky, Am. Min. to be published. 

3Jeanette Roelofsen, et al., Am. Min. 77, 522 (1992). 

. 

Quantitative x-ray diffraction with an imaging plate at high pressure and temperature 

J. H. Chen, D. J. Weidner, M. T. Vaughan, R. Li, J. B. Parise, and Y. B. Wang 

(Center for High Pressure Research, University at Stony Brook) 

Crystal structure determinations of high pressure phases of minerals and structure 

refinements of minerals as a function of pressure and temperature require quantitative measurements of diffraction peak intensities. Energy dispersive diffraction 

(EDD) methods are widely applied to a large volume press for experimental con- venience. However, with these methods it is difficult to derive reliable diffraction 

intensities due to uncertainty in the spectrum of the incident radiation and difficulty in making precise corrections for absorption by the pressure medium and 

other surroundin materials. To get quantitative diffraction data, angle dispersive 

diffraction ADD? using monochromatic radiation is more reliable. At the X17B1 

beamline, t h e Stony Brook group has set up an EDD system with the large volume 

press SAM85. With this apparatus, we have established an ADD system with a highly sensitive area detector imaging plate (IP A Laue-Bragg monochromator 

is adopted in the system and the radiation can k. e easily switched between white 

and monochromatic mode by moving the beam stop at the downstream side of the 

monochromator. Orientation of the IP is aligned by taking full Debye rings on the 

plate, and the inclination is corrected by the relation 

X17B1 

f K = -Y2' +d L 

x -x- x +x- where f is the inclination angle, d the center offset, YI = +2 and YZ = +2 . A double cassette holder is adopted. Sample-to-IP distance is derived from the double exposures. Diffraction intensities are obtained by integrating the diffraction arcs recorded on the IP. The observed data are processed by the General Structure Analysis System (GSAS) program for the structure refinement. Quantitative diffraction 

data on NiAlz04 spinel and the olivine solid solution of NizSiOa and MgzSiO4 have 

been collected at high pressure and temperature to study the cation distribution in 

the crystals as function of pressure and temperature. 

c 
X17B1 AgI/AgzSeOa: a glassy and crystalline fast ion conductor. Determination whether AgI containing glasses have a biphasic structure 

C. Cramer, D.L. Price, M.-L. Saboungi (ANL), and S.W. Martin (Iowa State 

University) 

AgI-containing glasses are fast ion conductors showing tremendous dc conductivities reaching values of about lo-' W'cm-' at room temperature. So far, a lot 

of work has been done to link the high ionic conductivity to structural features of 

these glasses. A crucial question is how the AgI enters the glass network. There 

has been debate whether or not this sort of glasses contain a biphasic structure 

forming AgI rich regions within the glassy matrix. Whereas normal x-ray and neutron diffraction techniques just yield the total structure factor including all kinds 

of correlations, anomalous x-ray diffraction (AXD) can determine structure factors 

due to specific elements. 

On X17B1 we performed AXD ex eriments on two sorts of AgI containing glasses 

(xAgI (1 - x)AgzSe04 and xAgI. (? - x)AgPOs) of various compositions, looking 

at the K-absorption edges of Ag and I. The investigated Q-range covered 0.5 A-' 

to 15 A-', Especially, we obtained the differential structure factors AS*,(Q) and 

A&(Q of 0.4AgI. O.6AgPOs from diffraction data taken near and far beyond the 

silver 225.486 keV, 25.224 keV) and the iodine K-absorption edges (33.313 keV, 

32.836 keV) . Based on Reverse Monte Carlo Simulations Borjesson et al. [1,2] have calculated 

partial structure factors for an AgI phosphate glass of similar composition. It turns 

out that the differential structure factors we get can be constructed by superimposing Borjesson et a1.k calculated partial structure factors of the relevant elements. 

The differential structure factor ASA,(Q) is strongly dominated by Ag-Ag and Ag-I 

correlations (the weight of Ag-P and Ag-0 correlations are much smaller). By comparing our data with Borjesson et al.'s results, we can conclude that a minimum 

at about 0.7 A-1 is due to Ag-I correlations, a maximum at about 1 A-' and a 

minimum at about 2 A-' are due to both Ag-Ag and Ag-I correlations. For the 

differential structure factor AS,(Q) we find that a minimum at 1 A-' is due to I-P 

and 1-0 correlations and a maximum at 2 8-l to I-P and 1-1 correlations. These 

results can be taken as experimental confirmation of Borjesson at al.'s computer 

simulations, indicating that - although there might be conducting pathways of AgI - there is no hint of the formation of so-called "AgI clusters" or " AgI microdomains" 

with a crystal like structure. 

[l] L. Borjessen, W.S. Howells, Solid State Ionics 40/41, 702 (1990) 

[2] L, Borjesson, R.L. Mc. Greevy, J. Wicks, Journal de Physique 111, Vol. 22, 

gt C2-109(1992) 

X-ray microbeam pseudotherapy vs. therapy using two cross-fired 

arrays through normal vs. tumor-bearing rat brains * 

F.A. Dilmanian, D.N. Slatkin, X.Y. Wu (Medical Dept., BNL); J.-0. Gebbers (Cantonal Hospital, Lucerne, Switzerland); J.A. Laissue (University of Bern, Switzerland); P. Spanne (ESRF, Grenoble, fiance) 

Microplanar (microbeam) radiation therapy (MRT) [l] research with the X17B1 

beam filtered through 0.25 mm Gd has shown a substantial tissue-sparing effect to 

1250 Gy when rat brains are irradiated unidirectionally in many (5 100) parallel 

slices, each 5 47 pm wide and 5 12 mm high, with 75-200 pm spacing on center [2,3]. 

It is postulated that this effect is from the survival of endothelial and, perhaps, other 

cells between individual slices, which later divide and replace lethally irradiated 

cells. This enables MRT when a target is crossfired. In a pseudotherapy experiment 

matching a therapy experiment [3], Fischer 344 rats were irradiated prone with right 

anteroposterior and lateral arrays at entrance absorbed doses of 625 Gy or 312 Gy; 

the slices were 27 pm wide and 12 mm high; each array had 100 slices, 100 pm 

on center. In the therapy experiment [3], similar rats with N 40 mg, imminently 

(N 7 d) lethal, right intrastriatal 9L gliosarcomas were irradiated 14 days after 

tumor initiation. 

There were eight rats in each of the 625- and 312-Gy pseudotherapy groups. Fig. 1 shows the survival histograms of the former and those of similar therapy 

groups. All 312-Gy normal rats survived > 60 d. Necropsies show that, although 

tumor (if any and brain tissues are ablated in most 625 Gy-crossfired rats, those 

Gy leads to longer survivals of tumor-bearing than of normal rats, perhaps because 

the tumor shifts vital midline structures leftward. The reverse survival pattern 

is observed after the 312 Gy irradiations, apparently because of N 50% failure in 

tumor control. 

[l] D.N. Slatkin, P. Spanne, F.A. Dilmanian, and M. Sandborg, Med. Phys. 19, 

[2] D.N. Slatkin, P. Spanne, F.A. Dilmanian, J.-0. Gebbers, and J.A. Laissue, Proc. 

Natl. Acad. Sci. USA 92, 8783-8787, 1995. 

[3] D.N. Slatkin, F.A. Dilmanian, M.M. Nawrocky, P. Spanne, J.-0. Gebbers, D.W. 

Archer, and J.A. Laissue, Rev. Sci. Instrum. 65, 1495-1460, 1995. 

X17B1 

tissues are abated 1 only in N 1/2 of 312 Gy-crossfired rats. Crossfiring with 625 

1395-1400, 1992. 

- 

.p 100 $ 80 

60 

2 40 

2; 

p. 

-20 0 20 40 60 80 100 120 

* Days Post Irradiation 

Figure 1. Survival histograms, irradiation on day 0: a) unirradiated, tumor; b)625 

Gy, normal; c) 312 Gy, tumor; d) 625 Gy, tumor. 

* We thank N.F. Gmiir, M. Kershaw and B. Ren for assistance. Research supported by 

the Office of Health and Environmental Research, U.S. DOE. 
.. ’ 

(I: 
I 

Characterizing the unit-cell volume of talc as a function of pressure 

and temperature * 

I Equation of state of stishovite I X17B1 I X17B1 

J. Liu, G. Chen, and R. C. Liebermann (CHiPR and USB) 

Stishovite, a high-pressure polymorph of silica with the rutile structure, has been 

the subject of much research because it is a candidate component for the mantle 

of the earth. As such, its elastic and thermodynamic properties are important for 

interpretations of seismic observations and for modelling the phase equilibria in 

stishovite-bearing phase assemblages at high pressures and temperatures. Previous 

acoustic studies have constrained the bulk modulus KO and its pressure derivative 

K;. However, little is known about its equations of state at simultaneous high 

pressure and temperature. 

The purpose of this study is to determine the P - V - T behavior of stishovite 

within its P-T stability field using a DIA-type, cubic-anvil apparatus (SAM 85) and 

in situ x-ray diffraction techniques on the X17B superconducting wiggler beamline 

at NSLS. In this beam time, we successfully obtained P - V - T data for stishovite 

in the temperature range from 3OoC to llOO°C and pressures from 1 bar to 11 

GPa. Analyses of the data show that pressure environment of the sample during 

the experiment is near hydrostatic (deviatoric stress was lower than 0.4 Kbar at all 

pressures and temperatures). 

We are currently modelling these data to determine the temperature derivative 

of the bulk modulus. 

455 

450 

445 

440 .!.- 

8 a 435 

Fig. 1. Talc volume vs. pressure. 

430 

425 

420 

Figure 1. Unit cell volume of talc as a function of pressure at temperatures ranging 

from 300 K to 1025 K. 

* This work was supported by the NSF under a grant to the Center for High Pressure 

Research. 
i I I. 4 

F 

w 

OI, 

, *' 

Exploring the stress-induced transformation of FCC TIC to the 8H 

HCP polytype using high pressure and high temperature X17B1 

~ 1 Equation of State of Ca(Ti,Si)03 Perovskite ~~ 

X17B1 
i 

X17B1 Thermal Equations of State of Garnets Along the Pyrope-Majorite 

Join 

Y. B. Wang, D. J. Weidner, J. Z. Zhang, I. Martinez, Y. J. Wu, G. L. Chen, Y. 

Sinelnikov, M. T. Vaughan, R. C. Liebermann, (CEPR, USB) and G. D. Gwanmesia (Delaware SU) 

Pressure-volume-temperature (P - V - T) relations of garnets along the pyrope 

join have been experimentally determined up to 11 GPa and 

Well-sintered, polycrystalline samples, with compositions 

Py62Mjas and Py20Mjso , respectively, were previously synthesized in a 2000-ton 

uniaxial split-sphere apparatus (USSA-2000) recovered with controlled P-T paths 

in order to minimize residual internal stresses. 

The equation-of-state experiments were carried out with samples embedded in 

NaC1, which was used as the pressure standard as well as to provide a quasi hydrostatic environment at high temperatures. For each P - V - T measurement, 

non-hydrostatic stress components in the samples were evaluated from the NaCl 

spectra, following the method given in (1 These stresses were relaxed at above 

1000 K, and the spectra collected on cooing were the least contaminated. Only 

such hydrostatic spectra were used to extract quantitative equation-of-state data. 

As the materials were metastable, the P - V - T data were collected under the 

conditions where the behavior was reversible (up to 1073 K). 

A new anvil geometry design has greatly enhanced the capability of varying 

pressure during one single experiment, allowing a complete coverage in pressure 

along several isotherms at 1073, 873, 673, 473 and 300 K, respectively. These 

P - V - T data allowed extraction of isothermal, isobaric, as well as isochoric 

properties. [Ref: (l) Weidner et all Hiah Pressure Research. GeoDhvs. Monoer. 67, 

pp 13-17, 1992. 

KTo = 162(3)GPa 

V, = 909.05(12)cm3 / mol 

Ii" TO = 4.4(5) 

( $$)p = -0.0 - 21(2)GPa / I 

a, = 1.946(65)~ 10-*T K-' 

Figure 1. Thermoelastic paramete 

tracted from the data. a0 is the 

pressure thermal expansion. 

1540 

" 1520 

4 15W 6 1480 

3 1480 

1440 

14204 , , , I I 

0246610 

Prowro. OP4 

Figure 2. P-V-T data for PjezMjs~. 

Solid circles room temperature data that 

are contaminated by non-hydrostatic 

stress (and thus are not used in 

equation of state fit). Open circles 

quasi-hydrostatic data; curves result of 

fit using the high-temperature BirchMurnaghan equation of state (from bottom up, temperatures are 300, 473, 673, 

873, and 1073 K, respectively). 

I a - p - 7 phase transformations in (Mg,Fe)zSiOe I X17B11 

D. J. Weidner, J. H. Chen and Y. B. Wang (CEEPR, USB) 

(Mg,Fe)zSiO4 olivine (a phase) is the most abundant mineral in the upper man- tle. Under pressure and temperature, the (Mg,Fe)zSiOa olivine under oes a phase 

transformation to the modified spinel (p) phase, then to the spinel (-fj phase, and 

then some higher pressure phases. The a-p-y phase transformations are believed 

to result in the discontinuities of seismic wave velocity at 400 and 520 km depth of 

the earth's transition zone. These phase transformations are strongly dependent on 

composition (Mg/Fe ratio) as well as pressure and temperature. There are contin- uous investigations on the a-p-y phase transformations, and the topology of the 

phase diagram is well known. However, there are still some questions concerning 

details of the phase diagram such as the composition of the coexisting a, p and 

7 phases on the univariant boundary and the phase equilibrium for the system 

MgzSiO4 - FezSi04. 

Aiming to investigate these questions, we have carried out in-situ diffraction 

studies on the (Mg,Fe)zSiOd system at the X17B1 beamline. Double-sample assemblies are used in each run. Starting materials have different composition, 

(Mgo.eFeo.l)zSiO4 and (Mg0.8Feo.2)zSiO+. The pressure and temperature are increased up to 14GPa and 13OO0C, and cross and recross the univariant boundary. 

Energy diffraction patterns are taken at different P-T conditions near the univariant 

boundary. A series patterns are also taken as a function of time while the pressure 

and temperature are held constant. In Run No. ABG23, we found that p phase 

is present at 12GPa and 1000°C and is not present at 12GPa and llOO°C, which 

locates the univariant boundary. 

The structure refinement program GSAS is applied to analyze the energy dispersive data. A good Rietveld analysis can be obtained by fitting the incident spectrum 

first (Figure 1). Messages of phase fractions and atomic occupation fractions come 

out from the analysis while the atomic positions are fixed. The data analysis is still 

under progress. 

Figure 1. An example of Rietveld fitting for the energy dispersive diffraction patterns of (Mgo.sFeo.z)2Si04 at high pressure. 
., .. 

i ; , 

Studying Rheology Under Mantle Pressure and Temperature Con- I X17B1 I ditions * 

D. J. Weidner, Y. B. Wang, G. L. Chen, and J. I. Ando (CHiPR, USB) 

Measurement of rheological properties of Earth materials in a multi-anvil devices 

is accomplished with the aid of a synchrotron generated X-ray probe. Deviatoric 

stresses are generated by compressing a polycrystalline powder as a result of the 

interaction between individual grains. The stress is quantified by measurement of 

the broadening of the diffraction peaks. Generally, the magnitude of the deviatoric 

stress will exceed the nominal pressure unless the sample fails or flows. The change 

of the peak width with time defines the strain rate of the sample. Taken together, 

these data provide constraints on the rheological properties for these conditions. 

In situ X-ray diffraction measurements of MgAlz O4 spinel under 10 GPa confining 

pressure and temperatures up to ll0O'C provide an example of such data. Strain 

rates of the order of lo-' s-l were measured at 600'C with deviatoric stresses of 

the order of a few GPa, over a duration of four days. The total plastic strain in the 

sample amounted to a few per cent. 

The observed stress-strain-rate-temperature relations quantitatively agree with 

those for the spinel given by Frost and Ashby Deformation-Mechanism Maps The 

Plasticity and Creep of Metals and Ceramics, 1984 and correspond to the plasticitypower law creep boundary for this material. The current limits of this approach are 

defined by the resolution of X-ray energy. 

Future improvements will come using monochromatic sources with high resolution 

detection systems. This will enable lower stress determinations and hence higher 

temperatures. 

, Slronglh-Splnolvs~nmol.918-9112PJ5 , 

Figure 1. Strain in MgAlz04 spinel and PysoMjso garnet at 10 GPa and 600'C 

over a period of four days. 

* This work was supported by the NSF under a grant to the Center for High Pressure 

Research 

I T-Cup: A New High-pressure Apparatus for X-Ray Studies I X17B1 I 

D. J. Weidner, Y. B. Wang, M. T. Vaughan, C. C. Koleda (CHiPR and USB) and 

I. C. Getting (CHiPR and U Colorado at Boulder) 

We have designed and tested a new apparatus for in-situ X-ray diffraction studies 

under high pressures and temperatures. The apparatus is a two-stage system; the 

first stage is a steel cylinder split into six parts and fastened onto the upper and 

lower guide blocks, enclosing a cubic cavity (19.5 mm edge length and the [lll] 

axis of the cube stays vertical) which contains the second stage anvil assembly. 

The hydraulic press used for SAM-85 DIA guideblocks is used to apply up to 200 

ton load. The second stage is assembled outside the press and consists of eight WC 

cubes each with 10 mm edge length separated by spacers. Each cube has one corner 

truncated into a triangular face; the eight truncations form an octahedral cavity in 

which the pressure medium is compressed. 

The cell assembly is an octahedron made of semi-sintered MgO or boron-epoxy. 

Incident x-ray beam passes through the gaps between WC cubes in the [110] direction of the eight-cube assembly and diffracts off parallel to one of the (100) planes, 

through gaps between the WC anvils, with a diffraction vector 35.3' from the vertical plane. A special holder is built for a solid-state detector for energy dispersive 

mode at several 28 angles. We compressed NaCl at room temperature to 160 ton 

force and generated 18+ GPa pressure. Decker's equation of state for NaCl was used to determined pressures in the cell assembly. 

Oil Pressure, bars 0 100 200 300 400 500 600 700 800 900 1OC 2w ......... 180. 

leu .. XVA 

170 . leu 

. 

- 

0 20 40 60 80 100 120 140 160 

Ram Load, Tons 

Figure 1. Results using Toshiba F-grade WC cubes with various truncation sizes, 

pressure media, gasket systems, and taper angles near the truncation. Light grax 

line show results using Kenametal carbide cubes. 
The Time-resolved X-ray Strength Study of Two Garnet Powder 

Samples * X17B1 In situ X-ray diffraction studies of iron and iron silicide at high 

pressure and temperature * X17B1 

Y. Wu, Y. Wang, J. Ando, D. J. Weidner, and M. T. Vaughan (CHiPR, USB) 

The time dependence of microscopic deviatoric stress can provide a direct measurement on the viscosity of minerals at high pressure and temperature. Using a 

DIA-type cubic anvil apparatus (SAM-85) at the X17B1 beam line, we studied this 

problem on two powdered garnet samples with different composition. One is the 

pure pyrope (Py1oo), another is 50% pyrope and 50% majorite Py60Mj60). The two 

to 9 GPa at room temperature, and then heated to 675OC, finally heated to 86OoC. 

Using the method developed by Weidner(1u2*3) , We analyzed the microscopic strain 

from peaking broadening for the (400) and (420 diffraction lines. During the inthe two garnets both became almost constant after 5 GPa, which is an indication 

of the samples' strains have reached their yield point. Continuing increasing the 

pressure after the yield point, the strain values of these two garnets are becoming nearly the same. Keeping the pressure at 9 Gpa and temperature at 675OC, 

we studied the relaxation process with time of the two garnets by observing the 

changes in the diffraction peak width. The microscopic strain of Py60Mj60 decreased monotonically with time, first very fast, then became much slower Figure). 

The microscopic strain of Pyloo almost immediately decreased to zero. &hen the 

temperature was further raised to 86OoC, the microscopic strain of the majorite 

rich garnet Py60Mj60) continued to weaken. From this experiment, we conclude 

high temperature. The microscopic strains of the two garnets show quite different temperature dependence at high temperature and pressure although their yield 

points at room temperature are nearly the same. Thus the composition of garnet 

has a great influence on its mechanical properties. Further studies on the viscosity 

of garnets from the time-resolved relaxation process are being carried out. 

References D.J. Weidner, 

D.J. Weidner, Y. Wang, 

samples were simultaneously compressed (in different parts o I the same chamber) 

crease of the pressure at room temperature, we o b served the microscopic strains of 

that Py60 hi jso is much stronger than pure pyrope (Pyloo) at high pressure and 

D.J. Weidner, Y. Wang, NSLS Annual Report, 1993; 

Y. Wang, M.T. Vaughan, Science, 266, p419-422, 1994; 

M.T. Vaughan, Geophys. Res. Lett., 21, 753-756, 1994 

Figure 1. 

py60Mj60 

the (400) 

1 

Strain in two garnets as a function of time. The filled symbols represent 

and the open symbols represent the pure pyro e. The diamonds are for 

line in both cases, and the squares are for the &20) line. 

* This work was supported by the NSF under a grant to the Center for High Pressure 'p 

P 

I& 

P Research 

J. Zhang (CHiPR, USB) and F. Guyot (PGP, Paris) 

Silicon has been proposed to be an important alloying element in the outer core 

of the Earth. Discussion of possible incorporation of silicon during the formation 

of the core needs high-pressure and high-temperature data on the Fe-Si alloys. In 

this study, we performed experiments on iron and iron silicide Feo.glSio.og up to 10 

GPa and 1000°C, using a DIA-type, cubic-anvil apparatus (SAM85) in conjunction 

with in situ X-ray diffraction. The two samples were loaded in the same boron 

nitride capsule and separated by NaCl that also serves as pressure standard. Upon 

heating, the transition from bcc phase to fcc phase of iron was observed at 475&8 

GPa, 52533 GPa, 550f6 GPa, and 625&4 GPa. The transition from hcp phase to 

fcc phase of iron occurred at 5OO0C and 9 GPa. These results are consistent with 

previous in situ x-ray studies (e.g., Akimoto et ~l., 1987). For Feo.~~Sio.o~, the first 

appearance of fcc phase was observed at temperatures that are 250-300°C higher 

than that in pure iron at 7.5 and 9.5 GPa. At both pressures, however, the transition 

in Feo.~~Sio.o~ wassluggish and did not complete up to 1000°C. At 5 GPa and lower 

pressures, no fcc phase of Feo.91Sio.09 was observed at high temperature. Implication 

from these observations is that incorporation of Si in Fe strongly stabilizes the bcc 

structure. It is also proposed that the amount of Si that can be incorporated in 

fcc structure increases with pressure. During the cooling the reversibility of phase 

transformations in iron is kinetically controlled: at 7-8.5 GPa, the fcc phase was first transformed to the hcp phase at 3OO0C and then to the bcc phase at 100OC; 

at 5.5-7 GPa, however, the bcc phase first appeared at 4OO0C and the hcp phase 

then started growing at 200OC; at pressures below 4 GPa, the transition between 

the bcc phase and fcc phase of iron was reversible within 2OOC. 

The kinetics of the back transformation in iron is likely due to (1) metastability 

of hcp phase and (2) lower transition temperatures at high pressures because of the 

negative slope of the phase boundary. 

Reference: Akimoto S., T. Suzuki, T. Yagi and 0. Shimomura (1987), Phase diagram of iron determined by high-pressure/temperature X-ray diffraction using 

synchrotron radiation, in High Pressure Research in Mineral Physics, ed. by M. 

Manghnani and Y. Syono, pp. 149-154. 

* This work was supported by the NSF under a grant to the Center for High Pressure 

Research. 
Synchrotron X-ray scattering study of the N-IC phase transition 

in RbzZnCld 

J. Zhang (CHiPR, USB) and I. Martinez (ENS Lyon, France) 

It has been recognized that magnesite and siderite might be major reservoir 

for carbon in the Earth' mantle (e.g., Katsura et al., 1991; Li et al., 1995). To 

understand the stabilities of carbonates, physical properties at high pressure and 

temperature are needed. We have continued to work on the P-V-T measurements 

of carbonates, using a DIA-type, cubic anvil apparatus (SAM-85) interfaced with 

in situx-ray diffraction at the X-17B1 beam line. In this study, we used the natural 

siderite samples of compositions (Fe.998, Mn,ooz)CO3 and (Fe.60, Mg.38, Mn.oz)COs as the starting material. 

Isothermal volume measurements were obtained at pressures and temperatures 

up to 9 GPa and 1273 K by the following procedures: (1) compression at room temperature to the maximum pressure, followed by heating to the desired temperature (usually 1073 K) and cooling to room temperature; (2) decompression to 

the next pressure of interest with repetition of heating and cooling cycles. From 

these measurements, the following physical parameters can be derived based on the 

Birch-Murnaghan equation of state and relevant thermodynamic relations: (1) bulk 

modulus at room temperature and its pressure and temperature derivatives; (2) 

thermal expansion as functions of pressure and temperature; 

and (3) thermal pressures for a given volume. In combination with our previous 

work on magnesite MgC03 (Zhang et al., 1995), it is also possible to examine variations in these physical properties with iron-magnesium substitution in carbonates. 

References 

Katsura T, Y Tsuchida, E Ito, T Yagi and W Utsumi (1991), Stability of magnesite under the lower mantle conditions, Proc. Japan Acad., 67, 57-60. 

Li X, J Nguyen, and R Jeanloz 1995), COZ and HzO in the deep Earth: An 

Deep Earth and Planetary Volatiles, in press. 

Zhang J, I Martinez, F Guyot, P Gillet, and SK Saxena (1995), In situ x-ray 

diffraction study on magnesite at high pressure and high temperature, Phys. Chem. 

Minerals, submitted. 

experimental study using the laser- 6 eated diamond cell, Proc. of Conference on 

~17~1, 

x20c 

* This work was supported by the NSF under a grant to the Center for High Pressure 

Research 

E X17B1 P-V-T measurements of siderites at high pressure and high temperature * 

A 

'a 

P c 

c 

d 

102 

lo2 

L (R') -1.6 -1.5 -1.4 

L (A-~ Figure 1. Critical scattering measured on x2Oc. Note the presence of a second 

component in the scattering. Figure 2. Critical scattering measured on X17. 
I K-edge Subtraction CT Imaging using the Angiography System * I X17B2 I 

A.M. Charvet (ESRF), F. Arfelli (NSLS/INFN), R. Menk (NSLS) and Z. Zhong 

(NSLS/SUNY) 

1. Framework 

We are interested in subtraction CT imaging of the human brain at the K-edge 

of iodine as a possible tool for in-vivo neurological studies of cerebral ischemia. 

Ischemia is the tissue damage resulting from a diminished blood supply. It is hoped 

that this technique will allow quantitative concentration measurements of contrast 

agents carried by the blood stream, such as iodine, giving access to blood volume 

measurements (a.k.a perfusion) in various areas of the brain. 

The work reported here was intended as a preliminary evaluation of the suitability of the NSLS X17B2 angiography system for K-edge subtraction CT imaging of 

phantoms under dosimetry conditions comparable to that of a medical brain scan- ner. Potential problems included the vertical crossing angle of the two beams and 

dose rates differing by two orders of magnitude in angiography and CT. 

2. Method and measurements 

The angiography system simultaneously provides two monochromatic X-ray 

beams bracketing the iodine K-edge (33.17 keV). Both beams are about 5” wide and cross at the patient/sample position with a vertical angle between them of about 

1 mrad. The intensity profile of both beams is measured simultaneously in a few 

milliseconds with a 600 element dual array silicon detector. Absolute intensity of 

the X-rays incident on the patient/sample is provided at the beamline, expressed 

in dose. For CT a rotation stage was used instead of the vertical translation used 

in angiography mode. 

Various samples and phantoms were imaged to test the system, including an excised cow heart and a cow tail (with bone) with iodine-filled tubes inserted in 

them. In each case monochromatic CT images were obtained above and below 

the iodine K-edge, and the subtraction carried out. In addition, a dual energy 

subtraction image was obtained using 33 keV and 99 keV as the two energies by 

using the harmonics present in the X-ray beam. 

Images of a 4” diameter plexiglass phantom with iodine-filled holes of dimensions 

1/4”, 1/8” and 3/32” were taken with iodine concentrations of 12 mg/cm3, 3.7 

mg/cm3 and 0.082 mg/cmg. The images were reconstructed from 360 projections. 

3. Results 

Concentrations down to 0.082 mg/cm3 in 1/4” diameter details were visible in 

the reconstructed subtraction images. This is a very encouraging result since it can be further improved upon. 

These preliminary measurements have shown that the Angiography system on 

X17B2 is well suited to take K-edge subtraction CT images of phantoms at the 

iodine K-edge. It will be possible to use it to determine the minimum iodine con- centration which can be accurately measured on K-edge subtraction CT images 

under conditions (dosimetry in particular) scalable to an in-vivo brain CT scanner. 

* Work funded by DOE Contract No. DE-AC02-76CH00016 (AUI) and by a Fihone5d 

E Alpes Contract to Joseph Fourier University 

I Comparison of different detectors used in noninvasive coronary an- I v, ~~~ I 

At present, and in the near future, only the line scan geometry with synchrotron 

radiation used at the NSLS, HASYLAB and ESRF provides enough precision and 

time resolution to resolve the distal parts of the coronary arteries down to a size 

of 1 mm in diameter after a transvenous injection of the contrast agent. The 

limitations are of a technical nature and mainly due to the detector systems used in 

this application. During the last year we carried out measurements to compare the 

detector systems used at the NSLS X17B2 beamline and at the medical beamline at 

HASYLAB in Hamburg. At X17B2 we use a solid state Li drifted Si strip detector in 

current mode while at HASYLAB a multi-channel gaseous ionization chamber also 

driven in current mode is used. Both detector systems are able to resolve a coronary 

artery even in its distal parts down to a diameter of 1 mm if the photon flux behind 

the patient is high enough to satisfy the requirements of Poisson statistics (20000 

photons per pixel). For this flux the zero spatial frequency detective quantum 

effiency (DQE) of both detector systems is comparable and about 0.6. For lower 

fluxes, however, the solid state detector has higher DQE values than the gaseous 

detector due to a noise level of about 10 photons (at 33 keV) in comparison to 88 

photons, respectively. In both cases the noise level is dominated by the read out 

electronics. It should be pointed out that the intrinsic noise level of the gaseous 

detector itself is negligible. For both detectors the spatial frequency dependent 

DQE is similar with slight advantages for the gaseous detector. This is mainly due 

to a spatial resolution of 0.98 LP/mm (gas detector) instead of 0.8 LP/mm for the 

solid state detector. At the moment the dynamic range of both systems is limited 

by the read out electronics and a value of 32000 for the solid state detector and 

43000 for the gaseous detector was found. The dynamic range of the electronics 

of the gaseous detector is nearly independent of the integration time (from 0.8ms 

to 400ms). In the case of the solid state detector the dynamic range is directly 

proportional to the integration time. The quantitative evaluation of the patient 

images taken so far shows that the average flux behind large iodine filled structures 

like the ventricles might differ from 2000 to 15000 photons per pixel depending on the physical conditions of the patient. Unfortunately one of the three arteries 

(circumflex) is normally hidden by these structures in all projections. In order to 

resolve the circumflex artery ( 2 mm in diameter filled with lOmg ml iodine) with a signal-to-noise-ratio of three, 2000 photons per pixel are neede 1 and in most of 

the cases this is obtained for reasonable skin entry doses (3-5rad per frame). At 

the same time the electronics’ noise should be at least 3 times smaller than the 

associated Poisson noise of 44 photons. Taking into account that the maximum 

number of photons behind the lung areas observed was 2640000 photons per pixel a 

dynamic range of at least 18 bits is required. That is two to three times more than 

the dynamic range of the present systems. 

* This work was supported by the US Dept of Energy Contract No. DE-AC02-76ch00016 
Fd I Three-energy Coronary Angiography Imaging * 

W. Thomlinson, L.D. Chapman, N. Gmiir and Z. Zhong (NSLS), R. Petr (Science 

Research Laboratory, Inc.) 

The use of three monochromatic beams provides a technique of resolving the bone as well as improving iodine and soft tissue images taken with synchrotron beams. 

The standard two-energy image analysis uses an assumption that the bone and soft 

tissue absorption coefficients have the same energy dependence. Such is the case 

for our present program and artifacts are, in general, not a problem. However, this 

assumption can lead to significant image artifacts if the two energies are not within 

200-300 eV of the contrast agent absorption edge. We are developing a compact 

radiation source which uses characteristic radiation lines as much as 2.5 keV apart. 

At the NSLS, the angiography monochromator is a bent-Laue Si(ll1) crystal 

which produces the two primary beams about 130 eV above and below the iodine Kabsorption edge. In addition, the third harmonic of these energies is also present at 

alevel of about 0.4%. We were able to image an angiography pig heart phantom first 

with the two standard beams, and then with a single beam at the third harmonic. 

With proper calibration of the system, we then had two images near 33.17 keV and 

one at 99.9 keV. The subtracted three-energy images provided iodine, soft tissue 

and bone images of excellent quality. The analysis also provided a pixel map of the 

three components of the phantom. Using this information, it was then possible to 

generate images corresponding to those which would be obtained with any set of two or three-energy beams. The results demonstrate very clearly that for two energies 

more than a few hundred eV apart, the image quality rapidly degrades. This is 

important because the compact source images would contain significant artifacts 

unless a third energy image were to be obtained. 

I X17B2 

* This work was supported by the US Department of Energy Contract No. DE-ACOS76CH00016. 

.- 

Monochromatic CT image sensitivity: results from preclinical mul- I X17B2 I tiple energy computed tomography [MECTl 

X.Y. Wu, F.A. Dilmanian, B. Ren, J. Kress, J.A. Coderre, D.N. Slatkin (Medical 

Dept., BNL); M. Shleifer, W.C. Thomlinson, Z. Zhong (NSLS, BNL); D. Chapman 

(I.I.T.), T.M. Button, F. Giron, Z. Liang, M.J. Petersen, C.T. Roque (SUNY at 

Stony Brook) 

Images from the monochromatic CT MECT, being developed for the human head 

and neck imaging, are presented. MECT is expected to be used for imaging the 

composition of carotid artery atherosclerotic plaque in terms of lipid/cholesterol, 

fibrous, and calcified tissues. 

A Laue-Laue monochromator with two flat Si< 111 > crystals, and two CdW04- 

photodiode array detectors, one with 0.5 mm pitch and second with 1.84-mm pitch 

collimated to 0.92 mm elements (Analogic Corp.) were used. Images were acquired 

at 24' s-l rotation speed. The monochromator was detuned to 15-20% peak intensity at a fixed dose rate. For some images two separate 360°-data sets were collected 

with a 1/2 detector pitch lateral offset, then interlaced. Reference data were collected before and after each slice. The residual variations in the beam profile shape 

due to monochromator instabilities was 0.2% peak-to-peak. 

Fig. 1 shows a standard "low-contrast" phantom insert, inside a 10.5 cm diam. 

acrylic cylinder imaged with MECT (left, high-res. det., no interlacing, 43 keV, 

1.9 mm slice height) and with conventional CT (CCT, right, 80 kVp, 3 mm slice 

height), respectively. The phantom had 5 inserts of 8.0, 5.6, 4.0, 2.8, and 2.0 mm diam. and 0.6% contrast. Images had the same spatial resolution N 6.5 lp/cm), an dose times slice height N 6 cGy . . The image noise (S.b.) was N 1.5 

cylinder containing 5 inserts of six 11-mm diam paraxial channels filled with iodine 

solutions of 240, 120, 60, 30, 15 and 0 pg I/cc was imaged with MECT (33.25 keV) 

and CCT (100 kVp, mean energy ~45 keV . Fig. 2 shows CT numbers in one set 

not optimized for the size of the phantom. 

We thank J. Gatz, N. Gmiir, D. Greenberg, R. Greene, J. Hastings, X. Huang, A. 

Lenhard, E. McKenna, R. Menk, P. Siddons, G. Smith, F. Staicu, M. Woodle (BNL) 

and E. Becker, S. Marcovici (Analogic Corp., Peabody, MA) for their assistance. 

Research supported by the Office of Health and Environmental Research, U.S. DOE. 

Hounsfield Unit (HU) for Id ECT and N m?l 3 U for CCT. A 135-mm diam. acrylic 

of channels; the 240-pg-I cc values are 26 J? U for MECT and 13 HU for CCT. The 

MECT image noise was h igher at 33.25 keV than at 43 keV, because 33.25 keV is 

Figure 1. Figure 2. 
A modified diamond-anvil cell as originally designed by Schifferl and others (Ming 

et al., 1987) was used to obtain the pressure-volume-temperature data on platinum. 

Gold was used as an internal standard for pressure measurement and for correcting 

the thermocouple determined temperatures. The cell was heated externally under a constant flow of argon. The sample was pressurized between diamonds of 450 

micron culet size. In all, 46 pressure-volume-temperature data are available in the 

pressure range of 1 atm to 15 GPa over the temperature range of 300 toto 900 K. 

L. C. Ming, M. H. Manghnani, J. Balogh (1987) High-pressure Research in Mineral Physics. TERRAPUB, Tokyo, 69-74. 

The available equations of state for platinum and rhenium are largely based on 

shock-wave data. Therefore, we considered it important to obtain pressure-volume 

data on these two metals, which are finding important application as standards 

in laser-heating experiments both as hot plates and for in-sity X-Ray studies. We 

pressurized Pt in a Mao-Bell cell with three different solid media: NaC1, MgO, and 

brucite Mg(0H 2. Rhenium was pressurized with MgO and with Pt in two separate 

50 GPa. By combining the metals with the solids of different compressibilities, we 

hope to obtain not only the P-V data but also learn about the influence of different 

degrees of non-hydrostatic conditions on EoS. 

experiments. T h e highest pressure reached in these experiments was between 30 to 
High-pressure Phase Transitions in LiVO3 and alfa-NaVOa 

Andrzej Grzechnik, Paul F. McMillan; Materials Research Group, Arizona State 

University 

LiVO3 and alfa-NaVO3 were studied in situ at high pressure in a diamond cell, 

using energy-dispesive X-ray diffrac tion at the X17C beam- line. Pressures were 

derived from the Au internal standard. The peak PO si s- s, unit cell parameters, 

and unit cell volumes were measured to 50 GPa. 

LiVO3 and alfa-NaVO3 have crystal structures related to the mono- clinic silicate 

pyroxenes, C2/c. They are built up of corner-shared chains of the tetrahedral V0:- 

units along [OOl], bound in a crystal network by the external ca s at two nonequivalent sites, M1 and M2. Upon pressurizing, both compounds exhibit sluggish 

phase transi s from 3 to 5 GPa and from 4 to 6 GPa, respectively. Thereafter, the 

diffrac tion patterns showed no changes up to 50 GPa. The sforma s were identified 

by observa of the growth of the peaks corresponding to the phase with the sixfold coordinated vanadium ca as well as merging of the peaks for ambient pressure 

phases. A tentative unit cell for the high pressure phases for both compounds is 

based on the rhombohedral unit cell of LiNbO3. High pressure phase of LiVO3 was non-quenchable, whereas the diffrac - pattern for the quenched sample of NaV03 

showed the presence of both ambient pressure and high pressure phases. 

We propose a structural model for the high pressure displacive phase - si s in 

LiVO3 and alfbNaVO3. In this model, the observed sluggish sforma s involve 

breakdown of the chain yroxene structure. The displacement of the oxygen atoms 

in the b-c plane (the C2J phases causes the rota of the tetrahedral and M2 octaheV ca and the oxygen anions in its second neighbor shell can be short enough for the 

V ca to change its coordination to six-fold. Such model is in accord with the informa 

inferred from our high pressure infrared and Raman data for both compounds. 

I X17C 

dral chains. Eventually, this disp 1 acement is so large that the distances between the 

Iron at High Pressure and Temperature: The Stability of New BetaIron Phase x17c 
I Monitoring the Absorption of Deuterium into Palladium I X17C I 

E. F. Skelton, S. B. Qadri, P. L. Hagens, D. D. Domingues (NRL), and J. Z. HU 

The Pd-H system is probably the most extensively investigated of all metalhydrogen systems. Nevertheless, some of its properties at high (> 85% hydrogen 

concentration still remain unexplained. The work recently performe d on X17C 

represents the first in situ monitoring from microscopic volumes deep within a Pdlattice as D is absorbed (or desorbed). Conventional x-ray sources, such as K-alpha 

radiation from a Cu tube, will only penetrate the first few microns of Pd. However, 

the high energy (> 80 keV) x-ray photons available on Xl’i’C, allow two orders of 

magnitude deeper penetration into the Pd. Moreover, because of the multiple order 

of magnitude increase in the synchrotron beam intensity, diffraction data can be 

obtained from extremely small volumes. For example, data were collected from a 

microspot only 18 x 10-l’ m3 in volume. This spot could be located anywhere 

within a 1 mm diameter Pd wire. Using this, the alpha-beta transition induced 

in the Pd by the absorption (or desorption) of D was monitored from the outer 

edge to the core. Results show that, although the alpha-phase forms rapidly at 

both the surface and the core, there is considerable delay in the initiation of the 

beta-phase at the core, compared to that at the surface. Other features of the 

structural changes associated with the absorption of D into Pd have been observed. 

These details may lead to an improved understanding of this system, especially at 

high concentration levels, and could shed light on claims made for anomalous power 

production mechanisms in this system. 

(CJW 

X18A X-ray scattering studies of liquid crystalline polymer solutions under 

shear flow * 

W. Burghardt, K. Hongladarom, V. Ugas, D. Cinader (Northwestern), J. Quintana 

(DND-CAT, APS), and B. Hsiao (DuPont) 

Liquid crystalline polymers (LCPs) derive much of their technological utility as 

a result of the ability of flow fields encountered during processing to influence the 

molecular orientation state in the final product. We have used x-ray scattering as an in situ probe of molecular orientation in model LCP solutions [poly(bensyl 

glutamate) (PBG) in m-cresol, hydroxypropylcellulose (HPC) in water, and HPC 

in m-cresol], that are subjected to shearing flow in a rotating parallel disk flow 

cell. The flow cell consists of aluminum and steel disks that rotate relative to one 

another. Thin mica sheets are glued to the surface, and apertures are cut out of 

the plates to provide x-ray transmission. Image plates were used to collect twodimensional scattering patterns. Exposure times could be made as short as a few 

seconds, enabling transient processes to be studied. 

Figure 1 shows a typical scattering pattern, in which the flow direction is vertical. 

A double-lobed scattering pattern is observed, where the width of the peaks may be 

related to the degree of molecular orientation (through an orientation parameter, 

S). These solutions have also been studied at Northwestern University using flow 

birefringence as a probe of molecular orientation. We find excellent self-consistency 

between these two quantitative measures of molecular orientation. In all systems, 

molecular orientation is seen to increase with shear rate in steady shear flow. However, the model systems behave differently during relaxation. 13.5 wt % PBG in 

cresol exhibits an increase in orientation upon flow cessation, while the HPC solutions exhibit decreasing orientation during relaxation. These opposite trends were 

also seen in previous birefringence studies, where they were related to differences 

in the evolution of macroscopic rheological properties of the LCP solution during 

relaxation. 

Finally, we have carried out preliminary experiments on a highly concentrated (40 

wt %) solution of PBG in cresol. It has recently been reported that the rheological 

behavior of PBG solutions changes abruptly above concentrations of 35 wt %. Our 

x-ray scattering measurements suggest the presence of a more highly ordered phase 

in the 40% solution, that we have tentatively identified as hexagonal. At high 

shear rates, it appears that this ordered phase is disrupted, and a typical nematic 

scattering patterns such as is seen in Figure 1 is recovered. These phenomena will 

be the object of further detailed studies. 

Figure 1. 2-D scattering pattern observed in 60 wt % HPC in water, subjected to 

shear flow at 100 1/8. 

* This work was supported through the NSF Materials Research Center 
,, . . . 

XSCAN X-ray Data Acquisition and Analysis Software for 

the MATRIX X-18A X-ray Scattering Beam Line at the 

NSLS * 

,.' 

X18A 

Structural Measurements of NiSz-sSes * CL X18A 

A versatile and easy-to-use computer software package has been developed for 

equipment control, data acquisition and analysis at the MATRIX X-18A x-ray scattering beam line at the National Synchrotron Light Source. The software runs on any IBM compatible personal computer running under MS-DOS and makes use of the GPIB and AT-Bus interfaces. The menu driven program is user-friendly 

for a wide range of x-ray experiments through control of all aspects of the x-ray 

beam line. Equipment interfaces include counter-timer, stepping motor controllers, 

multi-channel analyzer and temperature controller. XSCAN can perform motions 

and scans in real space and reciprocal space and can do user designed scans using 

an external file scan capability, which reads in an ASCII file of positions for up to 

six diffractometer motions plus the x-ray energy and scans them in order. Integrated routines calculate orientation matrices for up to 20 reflections and can fit 

x-ray peaks using six different function types. Extensive help files are available and 

the data input is rigorously checked for proper form and consistency with software 

limits. 

The XSCAN software has been evaluated by many users, both novice and experienced. Modifications have been integrated into the system to assist users. Plans are presently underway to upgrade the software to run under Windows NT complete 

with OLE support, multi-threading and Postscript capabilities. 

* This work is supported by U.S. Department of Energy Grant No. DEFGOB- * This work is supported by U.S. Department of Energy Grant No. DE-FGOB85ER45183. 85ER.45183. 
- otc OtC 

- stc i*c \ - 0% - OSC p - SEC - 6SC 

- 09c - O9C 

- (q (0 s9c -- S9C 

,1)ix(oi6us loqlmuizs) m 91‘007.. 08‘001. 98’002- 0.3‘007.’ E.3‘OOZ. 00’107.’ 
CL 

0 

01 

R. Harlow and P. Carcia (DuPont) 

Pt/Co multilayers are candidates for a high density magneto-optical recording 

media. When Pt/Co multilayers are sputtered in AI, however, they generally have 

smaller anisotropy energies and smaller coercivities than vapor-deposited multilayers. Since Ar-sputtering is preferred in manufacturing, we have sought methodoloies that would simultaneously improve both the anisotropy (Keff) and coercivity 

c) of Ar-sputtered films. It has been found that the magnetic properties can be 

ramatically improved if the Pt/Co multilayers were sputtered on granular Pt un- derlayers made by etching thin Pt layers initially 20-40 A thick. Multilayers grown on these Pt underlayers maintain a physically segregated, collumnar microstructure with excellent 111)-fcc texture as determined by electron probe microscopies 

and in-house x-ray 6 iffraction techniques. The desired magnetic properties reach a 

maximum when the Pt underlayer is approximately 33 A and decrease substantial 

when the underlayer is either ca. 17 A thicker or thinner. In-house x-ray diffraction 

measurements indicated that there was a strong correlation between the magnetic 

properties and the texture of the multilayer. To examine the textural properties in more detail, three samples with Pt underlayer thicknesses of 17, 33 and 50 A were studied at X18a using a very small focused 

beam (ca. 1 x 1 mm) and high-resolution optics (Ill-Ge analyzing crystal). Concentrating on the main peak from the lOx(3 A Co + 8 A Pt) multilayer, it was easily 

demonstrated that the rocking curve for the sample with the 33 A underlayer was very sharp, 0.006 deg., while those of other two samples were quite broad, greater 

than 1.0 deg. The low-angle region of the 33 A sample was in general characterized 

by a multitude of peaks and fine-structures corresponding to interferences between 

the different layers and surfaces. As expected, the other samples showed far fewer 

peaks in this region. Curiously, the main (111)-fcc reflection for all three samples 

was barely visible in the wide-angle diffraction scans. While the intesity of this 

peak was expected to be small for the 17 A underlayer sample, this peak should 

have nicely visible in the 33 A sample because of its high texturing and in the 50 A 

sample simply because of its thick Pt layer. Fixing the Bragg angle and scanning in 

both omega and chi failed to improve the situation. Thus, while these experiments 

have confirmed the earlier findings that the texturing of the 33 A sample is higher 

than that in either the 17 or 50 A cases, they have raised other questions about the 

nature of these films which are still unanswered. 

Ar-Sputtered Pt/Co Multilayers with Large Anisotropy Energy and 

Coercivity X18A 

Structural Studies of Self- Assembled Alkynyl Thin Film 

Materials X18A 
.. .- j 

X-ray thermal diffuse scattering (TDS) study of the impurity effect on the anharmonic lattice dynamics for the 

Dara-to-ferroelectric Dhase transformation in BaTiOs * 

X18A 

I Interface Structure in ZnSe-GaAs Heterostructures * 

V. Mahadev, S. N. Ehrlich, and G. L. Lied1 (Purdue Univ.) 

_... 

Three ZnSe-GaAS heterostructures, with different surface stoichiometries of (001 

GaAs, were studied. They were MBE grown ZnSe on (i) As rich ~(4x4) GaAs, (E 

intermediate coverage (4x6) GaAs, and, (iii) As deficient (4x3) GaAs. Two thicknesses of ZnSe were examined, 15 and 100 nm. High resolution transmission electron 

microscopy studies indicated a formation of an interface compound in cases (E) and 

(iii) but not (i). Grazing incidence x-ray Bragg-reflection-diffraction was utllized 

to analyze the interface structures in these heterostructure samples. Variable penetration relative to the interface depth was achieved relative to the thinner ZnSe by 

variation of the glancing angle from 0.12 to 0.5 degrees. 

Out-of-plane scattering was measured for all samples with a systematic study of 

the fundamental reflections and all possible superstructure reflections. No superstructure reflections were observed in any of the three cases with either thickness 

of ZnSe. For the 15 nm ZnSe layer only the fundamental reflections were observed 

for ZnSe at 0.12 degree glancing angle that corresponds to an effective penetration 

of less than 15 nm. At the 0.36 degree glancing angle, just penetrating through the 

15 nm ZnSe, broad peaks were observed on the high angle side of the fundamental 

reflections for cases 

vations would indicate that the superstructure present at the time of deposition is 

not preserved in any of the three cases. In the As-rich case (i , the results would 

interface transition. In the Ga-rich cases the broad peaks observed are consistent 

with a thin strained transition layer. A simulation model based upon a tetragonally 

distorted, disordered GazSe3 interfacial layer fits the observed diffraction data. 

and (iii) as shown in the figure below. At the 0.5 degree 

glancing angle only fundamental reflections were again observed. These obserbe consistent with an abrupt transition from the substrate to t h e thin film with no 

h 

en 

c 

3 

.- 250 

200 

150 

100 

50 

0 

036 degrees incidence angle 

* This work is supported by U.S. Department of Energy Grant No. DE-FGOZ 

85ER45183. 

N. Takesue, H. Kubo and H. Chen (Univ. of Illinois at Urbana-Champaign) 

Addition of impurities may vary the Curie temperature (T,) associated with the 

para-to-ferroelectric phase transition in terms of the lattice harmonicity and anharmonicity. One of the purposes of our research is to make clear the role of impurities 

through the anharmonic dynamics in a prototypical perovskite ferroelectric BaTiO3. 

Two BaTiO3 single crystals with one containing 0.3 at% Fe'" substitutionally 

replacing for Ti4+ have been examined by in-situ x-ray thermal diffuse scattering 

measurement near T, at X18A. Results from the pure sample show twoare attributed to the overdamped [OlO] TO mode and to the anisotropic on-(100) 

TA modes [l]. The TDS distribution and temperature dependence of the intensity 

(Fig. 1) agree well with the previous neutron inelastic scattering results. 

The TDS distribution from the Fe-doped sample shows a similar pattern to that 

of the pure sample. However, it also displays a different (positive) temperature 

dependence of the intensity (Fig. 2) as well as a more isotropic distribution for 

small 9's. Impurities may have reduced the anharmonic interatomic force constants. 

Currently, the TDS calculation is being done through the normal mode analysis 

based upon the rigid shell model for both samples. 

TDS distribution around the Bragg peaks on the 100 relplane; they 

[l] N. Takesue, M. Maglione and H. Chen, Phys. Rev. B51, (1995) 6696. 

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 9 [0101 9 POI 

Figure 1. TDS vs. q [OlO] for the pure sample (left), and for the doped sample 

(right). 

* This work is supported by the U.S. Department of Energy 
, 

I '. 8 

Epitaxial Growth of n-Alkane Monolayers on a Ag(ll1) 

Surface * I X18A I In situ X-ray Diffraction Studies of YBCO/LaA103 Superlattices X18A I I I 

S. Williams and J. B. Ketterson (Northwestern Univ.) 

We have constructed a multi-target sputtering cell equipped with mylar windows, 

enabling us to study the growth of multi-layer films in situ. The faced magnetron 

sputtering guns have four targets, with the active target selected by rotating the 

cathode. In this way, multi-layer films can be deposited while the substrate remains 

fixed, preserving the x-ray alignment. 

Our most recent studies have involved the growth of YBazCu~O,/LaA103 su- perlattices. A good lattice match and perovskite structure make LaA103 ideally 

suited for YBCO. We were able to grow high quality superlattices with satellite 

peaks of up to fourth order. Since our sample cell allows us to study the films in 

real time, we were able to observe the effects on annealing on the quality of the 

films by observing the decay of the satellite peaks. We used a program written by 

Eric Fullerton in order to fit the superlattice spectra and determine the degree of 

interdiffusion and roughness in our layers. We found no change in the superlattice 

spectra when the annealing temperature was below 800°C. Above this temperature, 

we observed a decay in the satellite peaks corresponding to increased interdiffusion 

at the interfaces. 

Z. Wu, J. Wang, (Univ. of Missouri-Columbia) S. N. Ehrlich, (Purdue Univ.) B. 

Matthies, K. W. Herwig and H. Taub (Univ. of Missouri-Columbia) 

Synchrotron x-ray diffraction has been used to study the structure of butane ncrystal Ag( 111) surface, complementing previous neutron diffraction experiments 

with deuterated forms of these monolayers on an exfoliated graphite s~bstratel-~. 

The unit cell of all of these monolayers on graphite is rectangular with a herringbone 

arrangement of the molecules for butane' and hexane' and a rectangular-centered 

cell for heptane3. We have found that on the Ag(ll1) surface, the monolayers grow 

with a well-defined orientational relationship with the substrate apparently forming a higher-order commensurate structure. The structural parameters, including the 

monolayer orientation, are given below. It has been assumed that the butane and 

hexane unit cells remain rectangular as on graphite. For a monolayer of (n-C4Hlo) 

the lattice constants are a = 8.111 and b = 7.49A and the monolayer orientation 

is Gzo 18 deg from Ag(l0) azimuth. For a monolayer of (n-CsH14) the lattice 

constants are a = 16.11 and b = 5.201 and the monolayer orientation is Gzl 14 

deg from Ag(l0) azimuth. For a monolayer of (n-C7H16) the lattice constant is d 

11 = 4.691 and the monolayer orientation is G11 12.5 deg from Ag(l0) azimuth. 

For the hexane/Ag( 111) system, specular reflectivity measurements are consistent 

with the adsorbed molecules oriented with their carbon skeletal plane parallel to 

the Ag(ll1) surface as on graphite. Also, the monolayer lattice parameters give the 

same area of the unit cell as on graphite. We observe a 0.5% thermal expansion of 

the monolayer between 120 K and the melting point at 151 K. Coincident with this 

expansion, the monolayer rotates 0.12 deg further away from the Ag(l0) azimuth. 

It would be interesting to see whether the orientational epitaxy and rotation of 

these n-alkane monolayers on the Ag(ll1) surface can be understood in terms of 

theories previously applied to simpler molecules on graphite4#'. 

C4HlO), hexane (n-CeHl4), and heptane (n-C.rH16) monolayers adsorbed on a sing \ e1. H. Taub, in The Time Domain in Surface and Structural Dynamics, 

NATO ASI, Vol. 228, Ser. C (Kluwer, Dordrecht, 1988), p. 467. 

2 K. W. Herwig, J. C. Newton, and H. Taub, Phys. Rev. B, 50, 15287 (1994). 

3. B. Matthies, K. W. Herwig, and H. Taub, unpublished. 

4. A. S. Novaco and J. P. McTague, Phys. Rev. Lett., 38, 1286 (1977). 

5. F. Grey and J. Bohr, Europhys. Lett., 18, 717 (1992). 

* Supported by NSF Grant Nos. DMR-9011069 and DMR-9314235, the PRF of the 

ACS, and DOE Grant No. DEFG02-85ER45183. 
Diffuse Scattering Studies in AI-Pd-Mn Quasicrystal I X18A 

Y. Zhang, R. Colella, S. N. Ehrlich (Purdue Univ.), S. Kycia and A. Goldman 

(Iowa State Univ.) 

It is of interest to study the distribution of diffuse scattering surrounding Bragg 

reflections in a nonperiodic crystal, because useful information may be obtained 

for a better understanding of the atomic structure. A photograph (Fig. 1) was 

taken using a monochromatic x-ray beam (A = 0.711 A) impinging on a stationary 

thin slice of Al-Pd-Mn quasicrystal, about 0.38 mm thick, set perpendicular to the 

beam. A two-fold axis direction was parallel to the x-ray beam. The photographic 

film was placed behind the crystal, perpendicular to the x-ray beam. Our attention 

concentrated on the four spots marked by arrows, which are "clouds" of diffuse scattering surrounding Bragg spots located on two-fold axes. The distribution of diffuse 

scattering surrounding those four Bragg reflections is very irregular. However, the 

crystal region responsible for the diffuse scattering visible in the photograph is very 

perfect. A rocking curve taken with the same x-ray beam, in a symmetric Lauecase geometry, .yielded a rocking curve whose width was resolution limited 

arcsecs.). Detded (hlel) scans, taken along planes perpendicular to a two-foll=s 

direction, revealed a very complicated structure of diffuse scattering, with no resemblance to the expected 1/q2 dependence. Figure 2 is an example. The Bragg 

reflection is located at the center, "behind" the plane of the figure. Plans are under 

way to explore the diffuse scattering surrounding other Bragg reflections, and to see 

the effect of temperature. 

Figure 1. 

HL scon with KI-2.841 

Figure 2. 

X18B X-ray absorption spectroscopy of titanium-containing molecular 

sieves * 

R.J. Davis, Z. Liu, J.E. Tabora, and W.S. Wieland (U. Virginia) 

The first structural characterization by Ti K edge EXAFS and XANES of ETS10 and aluminum-free Ti-beta molecular sieves was performed [Davis et al. Catal. 

Lett. 34, 101 (1995)]. 

A TS-1 sample was also studied for comparison. The near edge spectrum of TS-1, 

shown in Figure 1, revealed an intense pre-edge feature characteristic of Ti atoms in 

tetrahedral coordination. However, the pre-edge peak for ETS-10 in Figure 1 was quite small and shifted in energy, which is consistent with the known octahedral 

structure surrounding Ti atoms in the material. Analysis of the EXAFS for ETS-10 

revealed an average Ti-0 interatomic distance of 2.00 0.01 which is longer than the 

Ti-0 distance (1.95 ) in anatase. For Ti-beta, an intense pre-edge peak is present 

in the near edge spectrum and the intensity, energy and width of this peak are the 

same as for TS-1. 

In addition, the average Ti-0 interatomic distance in Ti-beta and TS-1 was 1.80 

0.01 , which is significantly shorter that the distance measured in ETS-10. The 

EXAFS and XANES results indicate that the Ti sites in aluminum-free Ti-beta are 

structurally identical to the tetrahedral sites in TS-1. This conclusion is supported 

by the similarity of the UV absorption thresholds for the two samples. 

X-ray absorption spectra were also recorded with methanol or 2-propanol adsorbed on the Ti-beta and TS-1 molecular sieves. Alcohol adsorption decreased 

the intensity and broadened the Ti pre-edge peak for both samples, demonstrating a local chemical interaction with the Ti sites. Methanol adsorption lengthened 

the average Ti-0 bond to 1.83 0.01 . The similarity of the x-ray absorption spectra for aluminum-free Ti-beta and TS-1 in the presence of alcohols suggests that 

the Ti sites in the two frameworks are chemically indistinguishable for vapor-phase 

adsorption of alcohols at low concentrations. 

t 

--o 

Energy I CV 

Figure 1. Ti K edge spectra for ETS-10, TS-1 and Ti-beta zeolites. 

* This work was supported by the National Science Foundation (CTS-9257306) and the 

donors of the Petroleum Research Fund administered by the ACS (24446-G5). 
Fd 

rp 

I Renovation of Beamline X-18B for High Energy X-ray Spectroscopy I X18B 1 

The beamline X-18B is back in operation since August 1995 under the NSLS 

management and support. The old Galvachenko type monochromator and its housing has been replaced with a new Si(ll1) channel cut monochromator inside a cross chamber for an easy access for repairs and modifications. 

The new monochromator is under lo-' - lo-' torr vacuum and it is water cooled 

with the gravitational flow and water pump circulation system. This avoids any 

mechanical vibrations and temperature variations. The first crystal has a water 

cooled copper backing block with an indium-gallium liquid eutectic alloy in between for improved surface contact and themal conduction. The harmonic rejection 

is achieved by rotating the second crystal at its weak link using a spring loaded 

micrometer. The energy is scanned by rotating the first crystal along its central 

axis by a 30 cm lever arm outside the housing, linearly driven by a micrometer and a five phase motor system. 

The energy range of this monochromator is 8 - 31 KeV with an energy resolution 

of about The 3 eV wide kink, typical of a copper metal edge is highly resolved 

when a 0.3 mm slit is being used at the upstream of the monochromator (fig. 1 

The ion chamber current output of this spectrometer was also measured and'it was found comparable to ather beamlines and to the expected theoretical values 

The separation between the crystals is only 3.5 mm and therefore the variation 

in the exit height of the beam is negligible. In the worst case of Ni - EXAFS ( 

K-edge at 8.333 KeV ) it is less than 45 microns for a typical 1200 eV scan. One 

disadvantage of the channel cut is the presence of multiple beams at the outlet, 

however, once the fundamental beam is identified a laser inside the hutch is used as a reference to keep track of that beam. In addition the crystals can also rotate 

in chi direction which sometimes can be used to displace the position of crystal 

glitches if they appear at a sensitive position in an XAS spectrum. 

w 

VI S. Khalid, L. Furenlid and P. Siddons ( BNL ) 

(fig. 2). 

20 

. 1.5 1 "\ 

Figure 2. Current output from Si(ll1) 

X18B channel cut mono. Beam current 

normalized to 100 mA, Nz flow in 10 cm ion chamber. 20 m from the source (fully 

-1 

4, 

I 

nm 

..... "70 I) - 

Figure 1. Energy resolution at copper edge. tuned). 

I Chlorine XANES Analysis of Stepwise Combustion Tests on Coal * I X19A I 

F. E. Huggins, J. Zhao, F. Lu, G. P. Huffman, Univ. of Kentucky, Lexington, KY 

40506, M-I. M. Chou, and J.M. Lytle, Illinois State Geological Survey, Champaign, 

IL 61820 

The release of chlorine from high chlorine (i0.3 wtinvestigated by means of C1 

K-edge XANES of stepwise combustion tests. The coals were exposed to air at 

5OoC temperature intervals between 2OO0C and 800°C for an hour and the residues 

(char or ash) were subsequently examined by C1 XANES spectroscopy at room temperature using a standard Lytle fluorescence X-ray detector. Although the 

XANES spectra of C1 in both untreated coals are closely similar, the results indicate 

different C1-containing intermediate compounds are formed for the two coals. The 

English coal, but not the Illinois coal, exhibits the formation of NaCl in the vicinity 

of 200 - 3OO0C note small peak at 12 eV in Figure 1) and both coals appear to 

exhibit organo-c 6 lorine species (note sharp peak at -1 ev in Figure 1) in the chars 

formed at somewhat higher temperatures (300 - 500OC). Based on the reduction 

of the step-height of the C1 K-edge, the concentration of chlorine remaining in the 

char or ash formed at temperatures above 4OO0C is less than 10% of that of the 

original coal (Figure 2). 

These data are being used (i) to explain the variable behavior of chlorine in com- bustion of different coals; (ii) to understand the corrosiveness of C1 in combustion 

of high-C1 coals; and (iii) to establish whether significant volatile organochlorine 

forms can be formed during coal combustion. 

I , '&--h,_4 I '0 zm urp sm wo 1.m 

-20 0 Energy. eV 20 40 Char Preparation Temperature 

Figure 1. Left: C1 XANES of coal as a function of temperature. Right: Variation 

of the chlorine content as a function of temperature. 

* This work is supported by Cooperative Agreement, DEFC-22-PC92521, between the 

U.S.Department of Energy, the Illinois Clean Coal Institute, and the Illinois Coal Development Board. 
! 

I 

I 

I IN THF SOLUTION 

H. Huang and J.E. Penner-Hahn (The University of Michigan) 

In previous work, we have characterized the structure of organocuprate and 

cyanocuprate reagents in THF solution [l-41. These studies demonstrated that 

the dominant Cu species in solutions formed from CuX+nRLi X=CN, R=Me, Bu, 

Ph, n=1,2; and X=I, R=Me,Ph, n=2) were mononuclear alky (I cyano-, dialkyl-, or diarylcuprates. The only example of ohgimerization that we found was in the case of 

the parent material, CuCNe2LiC1, which appears to form (Cu- CN-Cu-) , o li gomers 

[3]. In the present report, we describe the recent extension of these studies to include the characterization of phenyl copper reagents. In these systems, we find clear 

evidence for oligomerization. 

Phenyl copper (and related reagents) have proven to be extremely versatile in 

organic synthesis. For example, is was reported that phenyl copper can be use to 

stereospecifically deliver a phenyl group to conjugated enones. The Fourier transform of the EXAFS data for 0.2 M phenylcopper, prepared by the addition of one 

equivalent of phenyl lithium to Copper(1) iodide, is shown in the Figure. It is clear 

that there are substantial outer shell peaks in these data. The peaks at R+a M 

1.5, 3.3, and 4 8are consistent with those expected for a Cu-phenyl interaction. 

Curve fitting results using FEFF 5.0 suggest that these are most consistent with 

the presence of a single phenyl group bound per Cu. The remaining peak, at R+a 

x 2 A is significantly more intense than any of the Cu-C peaks. The large peak can 

only be modelled by including a Cu-Cu scatterer at ca. 2.45 8. This distance is 0.1 

8 shorter than the Cu-Cu distance in Cu metal, suggesting that this feature is not 

due to contamination of the solutions by Cu decomposition products. This short 

Cu distance is consistent with the Cu-Cu distances seen in previously crystallized 

pentameric phenyl-copper clusters, suggesting that similar species are present in 

THF solutions of phenyl-Cu. 

[l] Barnhart, T. M.; Penner-Hahn., J. E. Physica B 1995, 208-209, 709-710. [2] 

Barnhart, T. M.; Huang, H.; Penner-Hahn, J. E. J. Org. Chem. 1995, 60, 4310-11. 

31 Stemmler, T. L.; Barnhart, T. M.; Penner-Hahn, J. E.; Tucker, C. E.; Knochel, IJ .; Bohme, M.; Frenking, G. J. Am. Chem. SOC. 1995, in press. [4] T.Stcmmler; 

Penner-Hahn, J. E.; Knochel, P. J. Am. Chem. SOC. 1993, 115, 348-350. 

Figure 1. 

Magnetic properties of Ni Porphyrins 

M.W. Renner (DAS), K.M. Barkigia (DAS), J. Fajer (DAS), L.R. Furenlid (NSLS) 

Metalloporphyrin p-cation radicals are models for the active sites in a variety of 

biological systems including photosynthesis and heme catalysis. How the unpaired 

electrons of the metal and oxidized porphyrin interact is important to understanding 

the reaction chemistry in these biological processes. 

The relative symmetries of the macrocycle and metal d-orbitals which contain the 

unpaired electrons have been proposed to be responsible for the two spins interacting 

via ferromagnetic or antiferromagnetic coupling. 

We have recently been investigating a series of sterically crowded metalloporphyrins in which the macrocycle adopts a distorted S4 saddle conformation. 

The low-spin Ni(I1) complex is unable to bind axial ligand to form a high-spin 

species. One electron oxidation of the Ni(I1)P (P = octaethyltetraphenylporpohyrin) affords a macrocycle centered radical. Upon addition of bases (methanol, 

pyridine, etc.) results in an EPR spectra characteristic of a Ni(II1) porphyrin. 

However, from x-ray crystallography the Ni-N distances (about 2.0 ) are characteristic of a high-spin. 

To resolve the issue of the nickels oxidation state and magnetic properties we 

have studied the Ni x-ray absorption near-edge structure (XANES). 

The metals edge energy has been shown to be sensitive to the oxidation state 

of the metal. The XANES spectra for Ni 1I)P and one-electron oxidation product 

of Ni(I1)P + pyridine are shown in the fs gure below. The edge position remains 

constant for both samples, therefore the macrocycle is oxidized. The loss of the 

pre-edge peak indicates that the pyridine coordinates to the Ni(I1) in the oxidized 

sample. To explain the EPR and crystallographic data the nickel must be high 

spin (S=l) and antiferromagnetically couple with the macrocycle radical (S=1/2) 

to afford a pseudo (S=1/2) Ni(II1). The saddle shaped distortion in the macrocycle 

appears to be essential for magnetic interaction between the unpaired electrons of 

the macrocycle and metal d orbitals. 

I X19A 

- NI(II)OETPP 

......... Nl(ll)OETPP(pyddlno); CIO; 

1 ,....I*... 

8320 8330 8340 6350 8360 8370 8380 

Energy (ev) 
.j ,< , 

Single Crystal EXAFS Studies of Nickel(I1) Porphyrins 

. ' ..' . I. 

I Structural Studies of Ni(I1) Porphyrins * I X19A I X19A 

Mark W. Renner, Kathy M. Barkigia, Jack Fajer (BNL - Dept. of Applied Science), 

Lars R. Furenlid (NSLS), 

Metalloporphyrins are the prosthetic group in a variety of biological systems. The 

structure of these porphyrins is believed to be important in altering their reactivity 

and physical properties. The metal-nitrogen distances in porphyrins are sensitive 

to conformational changes in the macrocycle, shorter distances reflect increased 

distortions. We present here a comparison of the Ni-nitrogen distances for a series 

of Ni(I1) porphyrins as determined by EXAFS and single crystal X-ray defraction. 

The porphyrins studied have meso substituents which increase in size from methyl 

(1) < propyl 2) < isopropyl (3) < tert-butyl (4). 

shorter than the single-crystal X-ray and EXAFS distances. For this series the Ni-N 

distances decrease as the size of the meso groups increase. Steric interaction with 

the larger meso substituents and the macrocycle causes the porphyrin to distort. 

Comparison of the solution and single-crystal results for 1 and 2 confirm that these 

porphyrins have multiple conformations of similar energy in solution and in the solid 

state. Some care must be used when extrapolating single crystal x-ray defraction 

results to the macrocycles conformation in solution or in the biological systems. 

The Ni-N 6 istances from solution EXAFS for 1 and 2 are on the average 0.06 

Compound R (A) EXAFS R (A) X-XWY 

1 1.91 1.953 

2 1.90 1.957 

1.96* 

3 1.91 1 .a96 4 1.84 MI 

* single crysM EXAFS. 

Figure 1. 

* This work was supported by the Division of Chemical Sciences, U.S. Department of 

Energy, Washington, D.C., under contract No. DEAC02-76CH00016. 

8320 8330 8340 8350 8360 8370 8380 

Ni(I9 tetra-propyl porphyrin 
.- 

I 

I In situ XAFS Spectroscopic Studies of DCL Catalysts. . * I X19A I 

Naresh Shah, Jianmin Zhao, Fulong Lu, Frank E. Huggins and Gerald P. Huffman 

(University of Kentucky) 

We have designed and constructed an in-situ cell for XAFS investigation 

of direct coal liquefaction (DCL) catalysts (figure 1). This design of cell can reproduce elevated temperature (up to 500 "C) and hydrogen pressure (up to 1800 

psig hydrostatic pressure) employed in the liquefaction reactors while letting a synchrotron generated x-ray beam pass through. 

Using this cell, several catalyst systems have been successfully examined: 

Black thunder coal ion-exchanged using iron acetate solution to get 3.78 wt.% e 

loading, (2) 5 wt.)of binary ferrihydrite catalyst (containing 5 wt.% SiOz) in Blind 

Canyon ( ECS-17 coal and (3) 5 mt.% of citric acid treated ferrihydrite catalyst in 

Blind Canyon (D CS-17) coal. All three iron-based catalyst systems investigated, 

exhibited transformation of the iron oxyhydroxide phase to pyrrhotite. The transformation temperatures were different for different systems. This transformation 

occurred over a range of temperature conditions. This lack of a sharp transition can be due to either (1) a nonhomogeneous transition within the sample matrix, 

i.e., some (smaller?) catalyst particles transform at a lower temperature and some 

at a little higher temperature, or, 2) there are more than one transformation. The 

formation are dependent on the dispersion and the structure of the ferrihydrite. 

%) 

results clearly demonstrated that t I, e kinetics of the ferrihydrite to pyrrhotite transQos 

IW3t 

Figure 1. Schematic of the high pressure high temperature XAFS cell for in situ 

characterization of direct coal liquefaction (DCL) catalysts. 

* Research supported by the U.S. Dept. of Energy under DOE Contract No. DE-FC22- 

93PC93053 as a part of the research programof the Consortium for Fossil Fuel Liquefaction 

F 

4 Science (CFFLS) 

Characterization of the Zn in Xenopus Eggs * 

D.L. Tierney, R.J. Denver, and James E. Penner-Hahn (Univ of Michigan) 

In recent years, Zn has come to be recognized as an essential trace element in a tremendous range of biological functions [I], and has been suggested [2] to be a major regulatory ion in metabolism. For example, the pool of labile Zn (i.e., 

accessible to chelators), increases synchronously with the onset of apoptosis (active 

cell death) [3]. At the other end of the developmental spectrum, decreases in free 

Zn are teratogenic [4]. Despite the obvious importance of Zn, relatively little is 

known about the mechanisms by which it regulates cell growth and development. 

Eggs that develop in closed conditions (i.e., without the influx of maternal nutrients during development) must contain, at the time of fertilization, all of the metals 

that are necessary for development. Typical levels are ca. 1 mM Zn and 0.5 mM 

Fe, with lower levels of other essential trace elements [5]. We have recently shown 

that the average structure of the Zn in zebrafish eggs, as determined by XANES, 

changes during the early stages of development [6]. Following fertilization, but prior 

to the mid-blastula transition MBT), there is an increase in the white line intensity. 

found in the unfertilized eggs. Recently, we have extended this work in an effort 

to determine if these spectral changes are similar across species. We used Xenopus (African clawed frog) eggs, since these have volumes that are nearly an order 

of magnitude larger than those of zebrafish eggs, thus permitting measurements on single eggs. The Figure shows difference XANES spectra for fertilized eggs after the 

MBT minus unfertilized eggs. It is clear that similar difference spectra are seen for 

fish and frogs. We are presently extending these results to characterize the detailed 

time dependence of the Zn structure. # Vallee, B.; Falchuk, K. Physiol. Rev 1993, 73, 79-118. [2] Frausto da Silva, J.; 

W' ams, R. In The Biological Chemistry of the Elements Clarendon Press: Oxford, 

1991; pp 299-318. 31 Zalewski, P.; Forbes, I.; Seamark, R.; Borlin haus, R.; Betts, 

W.; Lincoln, S.; dard, A. Chemistry Biology 1994, 1, 153-161. 741 Hornvall, H.; 

Falchuk, K.; Geraci, G.; Vallee, B. Biochem. Biophys. Res. Commun. 1994, 200, 

1398-1406. 51 Nomizu, T.; Falchuk, K.; Vallee, B. Mol. Reprod. Dev 1993, 36, 

I X19A 

After the MBT, the average 8 n environment is similar, but not identical, to that 

419-23. [6] 47 alrath, L.; Tierney, D.; Penner-Hahn, J.; Berg, J. 1996, in preparation. 

140 

40 

20 4 

9630 9640 9650 9660 9610 9680 9690 9700 Energy 

(CV) 

Figure 1. Difference XANES for eggs after MBT minus unfertilized. 

* Supportedin part by NSF IBN-9496321 to RJD & NIH GM-38047 to JEPH 
X19A Sulfonate Sulfur and not the Sulfide Sulfur Dominates the Composition of Marine Phytoplankton * 

Di- and Polysulfide Cross Linking in the Formation of Humic Polymers in Marine Sediments * 

Murthy A. Vairavamurthy, S. Wang, B. Khandelwal and B. Manowitz 

Living organisms play an important catalytic role in the environmental and geochemical transformations of sulfur, changing the chemical properties of sulfur com- pounds and their distribution in the atmosphere, soils, waters and sediments. In 

the oceans, sulfur transformations are largely mediated by phytoplankton which as- similate seawater sulfate as the sole sulfur source to make the reduced organic sulfur 

compounds. The biosynthesized organic sulfur in marine phytoplankton comprises 

0.5 to 1 basis, and includes a variety of functional forms. Major forms of this sulfur include organic sulfides, sulfonium compounds, sulfonates, and sulfate esters. 

The relative quantitative composition of the various forms are not known. Several 

studies suggest that sulfonium compounds, pFrticularly dimethylsulfonium propionate DMSP), constitute an important fraction of cellular organic sulfur in some 

phytop (l ankton species, but it is generally believed that sulfide sulfur is the dominant form. Recently, sulfonates were found to be a major class of compounds in 

near-surface marine sediments, constituting about 20-40 and phytoplankton debris 

was invoked as a possible source for their origin, among other potential mechanisms. A variety of marine algae are known to contain sulfonates, but if they are 

to be a major source of sedimentary sulfonates, then they must contain high levels of these compounds. In an attempt to better understand the composition of 

the different forms of sulfur in phytoplankton, we used x-ray absorption near-edge 

structure (XANES) spectroscopy for both qualitative and quantitative speciation of 

sulfur. Figure 1 shows XANES spectra of some phytoplankton species representing 

major types in the oceans, diatoms, dinoflagellates, premnesiophytes and chlorophytes. We deconvoluted these spectra with spectra of model compounds to obtain 

quantitative information of the sulfur forms present. Our results show that the 

oxidized sulfonate sulfur and not the reduced sulfide sulfur as the dominant form 

of sulfur in phytoplankton. The presence of high concentrations of sulfonate-sulfur 

in phytoplankton suggests that the latter could be a major source of sedimentary 

sulfonates. Furthermore, the dominance of sulfonates suggests that they play an important role in the cellular biochemistry and physiology of marinephytoplankton, 

which are still unknown. 

X19A 

1 

e x 

2470 2430 am 2170 24m 2480 am 24en am am 2430 am 

Enew (OW 

Figure 1. Sulfur K-edge XANES spectra of different types of phytoplankton 

* This work was supported by the U.S. DOE, Division of Engineering and Geosciences 

of the Office of Basic Energy Sciences under Contract No. DEAC02-76CH0016. 

Figure 1. 

* Supported by the U.S. DOE, Division of Engineering and Geosciences of the Office of 

Basic Energy Sciences under Contract No. DE-AC02-76CH00016. 

I 'I 
I 

,. 1 

Characterization of structure defects in 2,12-Undecanedione/Urea 

single crystals by Using Synchrotron White Beam X-ray Topography * 

Investigation of Dislocation Distributions in InP single crystals Using 

Synchrotron White Beam X-ray Topography * x19c X19C 

H. Chung, W. Si, M. Dudley, and V. Prasad (SUNY Stony Brook), A. Anselmo 

and D. F. Bliss (US Air Force Rome Laboratory) 

Synchrotron White Beam X-ray Topography (SWBXT) has been applied to investigate dislocation distributions in a transverse cut InP wafer grqwn by the liquid 

encapsulated Kyropoulos (LEK) technique. Our preliminary results reveal that the 

dislocation density is higher near the periphery and the middle of the crystal and 

reaches a minimum in the intermediate area. Figure 1 is an enlargement of a transmission X-ray topograph recorded near the periphery of the crystal. As revealed 

by the image, a dislocation network with uniform density is evidenced. Since the 

dislocation density is at just about resolution limit, a dislocation density of approximately 10' cm-' can be deduced from the topograph. In contrast to Figure l(a), 

Figure l(b) is a transmission X-ray topograph recorded from the intermediate region 

of the sample showing a very low dislocation density, in which individual dislocations (D) were clearly discerned. Since dislocation propagation and multiplication 

can occur when thermal stresses induced by thermal gradient during crystal growth 

and post-growth cooling processes are higher than the critical resolved shear stress 

(CRSS), our observations strongly suggest that a high level thermal stress is concentrated in the periphery and the middle of the crystal. Therefore, an optimization 

of thermal conditions is expected to be important to the reduction of dislocation 

density in these crystals. 

Figure 1. 

* Acknowledgments: Research carried out under auspices of the ARPA/AFOSR Consortium of Crystal Growth Research (Contract No. F496209510407), work performed on 

the Synchrotron Topography Project, Beamline X-19C. 

I I 

Figure 1. 

* Acknowledgements: Work performed 

on the Synchrotron Topography Project, 

Beamline X-19C. 

- . . -. . . -. . - . .. . . . .. . 

.. .a .. .. . I:.: . :___ I . . . __ __ ..- 

b 

Figure 2. 
Studies of Twinning in 2,10-Undecanedione/Urea Inclusion Compounds Using Synchrotron White Beam X-ray Topography * 

Synchrotron White Beam X-ray Topography Characterization of 

Structural Defects in 2,10-Undecanedione/Urea Inclusion ComDounds * H. Chung and M. Dudley (SUNY Stony Brook), M. E. Brown and Mark D. 

Hollingsworth (Indiana University) 

Twinning in 2,10-undecanedione/urea was investigated by using Synchrotron 

White Beam X-ray Topography (SWBXT). X-ray transmission topographs recorded 

from different regions show that the crystal is divided into five twin-related regions. 

Each region in the crystal is revealed on the topographs by orientation contrast arising from the mutual misorientation of adjacent regions. Using a combination of pinhole Laue pattern analysis and topographic orientation contrast analysis, the twin 

operation was determined. The twin structure in this specimen can be represented 

using stereographic projections as shown in Figure 1. In this figure, the orientation 

relationships of these twin related regions are revealed; the contact points of these 

projections label the poles of the composition planes. The rotation angle, which 

would be exactly 60' if it were hexagonal, ranges from 59.1' io 61.8', as determined by measuring the angles between the [010]-[130], [130]-[130] and [ljO]-[OiO] 

directions from pinhole Laue diffraction patterns. 

X19C 

61.8' 

- 

61.P 

Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-19C. 

H. Chung and M. Dudley (SUNY Stony Brook), M. E. Brown and Mark D. 

Hollingsworth (Indiana University) 

Twin structures in a crystal of the urea inclusion compound (UIC) of 2,lOundecanedione were investigated using Synchrotron White Beam X-ray Topography 

SWBXT). Twin configurations, directly observed via orientation contrast, were I ound to comprise both large-volume, macroscopic twins and thick twin lamellae. 

Upon detailed analysis, one can find that there were five superimposed diffraction 

patterns in the crystal studied. This observation indicates that the crystal was divided into five twin-related regions (indicated by TI to T6) with different rela, 

tive orientations. Other defects such as inclusions and dislocations (indicated as I 

and D, respectively) were also observed. Detailed analysis of contrast variations of 

dislocations in different reflections shows that the dislocations are out of contrast 

when reflections with g vectors perpendicular to their line directions are used. By 

using the g . b=O criterion, one can determine that these dislocations are of screw 

character with Burgers vector parallel to the [130] direction. 

I. I-- 

Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-19C. 
x19c 

Characterization of Structural Defects in HgCdTe Epilayers by Using 

Synchrotron White Beam X-ray Topography * 

H. Chung and M. Dudley (SUNY Stony Brook), Sanghamitra Sen (Hughes Santa 

Barbara Research Center) 

tern was observed. From detailed investigations of the structure of cross hatching, 

one can find that the pattern comprises slip band networks lying along the three 

<110> directions. Figure 1 (b) shows an enlarged X-ray topograph in which individual dislocations are clearly visible. By calculating the projected length and 

directions of dislocation segments in different reflections, one can determine that 

these dislocations belong to the [011]/(111) slip system. Perhaps due to the influences of interdiffusion of substrate and layer components and the resulting mismatch 

between the substrate and the grown layer, the two regions with epi thickness of 

0 and 3 microns, respectively were highly strained. It is also worth noting that 

defects such as a 180' rotation twin (T) and Te precipitates (P) and the associated prismatic punching of dislocation loops in star-like patterns are also revealed 

on Figure 1 (a). From the distribution of the cross-hatching which initiates from 

the periphery and propagates into the interior of the sample, one can expect that 

slip processes occur to relieve stresses concentrated at the periphery of the wafer 

induced either by thermal gradients or by the mechanical fasteners which support 

the wafer. 

Figure 1. 

x19c Synchrotron White Beam X-ray Topography Studies of Interfacial 

Dislocations in SiGe/Si Heterostructures * 

H. Chung and M. Dudley (SUNY Stony Brook), J. Wu (General 1nstrument)t) 

Synchrotron White Beam X-ray Topography (SWBXT has been applied to the 

SiGe thin film grown on the (100) Si substrate is investigated. In Figure 1 (a), a 

transmission X-ray topograph recorded by using (040) reflection shows two sets of 

well defined misfit dislocations, D1 and Dz, running parallel to the [Oll] and [Oli] 

directions, respectively. It is also observed that these dislocations are out of contrast 

when reflections with g vectors parallel to the dislocation line directions are used. 

By using the g - b=O criterion, these misfit dislocations_ are determined to be of 

edge in character with Burgers vectors parallel to the [Oil] and [Oll] directions. To 

investigate the misfit dislocation depth distribution, section X-ray topography was also employed. Figure 1 (b) shows a section topograph recorded from the central 

region of the sample. A extensive dark region with a thickness of approximately 

15 pm from the top surface is observed. This area corresponds to the position of 

the SiGe epilayer. This observation strongly suggests that the as-grown thin film 

is highly strained. Moreover, irregular linear features (indicated by L) arising from 

severe lattice distortions in the region near to the surface layer were also observed. 

The development of a better understanding of the origin of the lattice distortions 

is needed to improve the crystalline quality of these as-grown SiGe thin films. 

study of growth defects in SiGe/Si heterostructures. In t h e present study, a 15pm 

Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beam4d 

P 

0) 

P line X-19C1 and supported by Hughes Santa Barbara Research Center 

* Acknowledgements: Work performed 

on the Synchrotron Topography Project, 

Beamline X-19C. 
CL 

N 

cn 

tg 

x19c 

Characterization of Growth Defects in THM grown HgCdTe Single 

Crystals by Using Synchrotron White Beam X-ray Topography * Doped Ge Single Crystals Using Synchrotron White Beam X-ray X19C 

Studies of Interface Demarcation and Structural Defects in Ga 

~~ 

Topography * II 

H. Chung, BTRaghothamachar, and M. Dudley (SUNY Stony Brook), M. Lichtensteiger and D. C. Gillies (NASA Marshall Flight Center) 

Synchrotron White Beam X-ray Topography (SWBXT) has been successfully applied to characterize marked growth interfaces in Ga doped Ge single crystals. The 

techniques employed in interface demarcation include modifications of cold zone 

temperature, mechanical pulsing and Peltier pulsing. As revealed by our observations, the visibility of a marked growth interface is a sensitive function of the 

diffraction conditions. A combination of the correct orientation of the active reciprocal lattice with respect to the interface plane and the necessary strain sensitivity 

controlled by the rocking curve width of the reflection proves to be the prerequisite 

for interface visibility. This prerequisite can easily be achieved by using synchrotron 

radiation since the tunability of the synchrotron source provides great flexibility in 

the choice of proper diffraction conditions. Moreover, the wide spectral range in 

the synchrotron source enables multiple topographic images to be recorded in a 

single exposure. Abundant information concerning defect structures in the crystal is also obtained. Figure 1 shows a topograph recorded from a Ga doped Ge 

crystal. Growth interfaces (I) induced by Peltier pulsing are clearly visible. Other 

defects such as small-angle tdt boundaries (SB), precipitates (P) and dislocation 

cell structures (C) were also observed. Direct evidence of dislocations present in the 

seed crystal propagating into the as-grown crystal through the melt-back interface 

during crystal growth was also obtained. 

Figure 1. Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-19C, and supported by NASA Marshall Space Flight Center under Grant No. NCCS53. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-lgC, and supported by NASA Marshall Space Flight Center under Grant No. NCCS53. 

... .. . -. . . 
Studies of Defect Structures in PVT grown CdZnTe single crystals 

Using Synchrotron White Beam X-ray Topography * 

.. 

x19c 

Figure 1. 

Synchrotron White Beam X-ray Topography Characterization of 

Twin Structures in Vapor Grown CdZnTe Single Crystals * 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-19CI and supportedby NASA Marshall Space Flight Center under Grant No. NCCI4d 

g 

w 53 

x19c 

Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project, Beamline X-19C1 and supportedby NASA Marshall Space Flight Center under Grant No. NCC8- 

53. 
.I '. . , , .I 

CHARACTERIZATION OF DEFECT STRUCTURES IN (111) 

3C-SIC SINGLE CRYSTALS BY SYNCHROTRON TOPOGRAPHY * 

.C , i 

X19C 

;c *. . __. 

i' 

x19c Studies of Twinning in LEK Grown InP Single Crystals by Using 

Synchrotron White Beam X-ray Topography 

+ 

H. Chung, W. Si, M. Dudley, and V. Prasad (SUNY Stony Brook), A. Anselmo 

and D.F. Bliss (US Air Force Rome Laboratory) 

InP is the basic material for long wavelength optoelectronic devices. Its importance for high frequency devices also increases continuously. Their applications lead 

to an increasing demand for InP substrates of high crystalline quality, i.e., twin-free 

and low dislocation density. Extensive attention is paid to suppress the occurrence 

of twinning. However, due to a low stacking fault energy, InP crystals have a very 

strong tendency to twin. In spite of the growth twin-free crystals has been reported, 

it is still difficult to develop a set of growth conditions which can reproducibly produce twin-free crystals. In this report, Synchrotron White Beam X-ray Topography 

(SWBXT has been applied to study twins in liquid encapsulated Kyropoulos (LEK) 

pograph showing a long, thin twin lamella. From detailed analyses of the Laue 

diffraction patterns recorded from this region, one can determile that the twinned 

region is related to the matrix by a 180' rotation about the [111] axis. The surface 

normal of the twin related region is parallel to the [ZZT] direction. Figure 2 is a series of stereographic projections showing the twin operation. 

Acknowledgments: Research carried out under auspices of the ARPA/AFOSR 

Consortium of Crystal Growth Research Contract No. F496209510407), work pergrown In I! single crystals. Figure 1 is a highly magnified transmission X-ray toformed on the Synchrotron Topography & roject, Beamline X-19C. 

Figure 1. 

a b . - - - - - -. - -. - -- --. . - . . 

Figure 1. Transmission synchrotron topographs recorded from (111) 3C-Sic crystal 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-19C, supported by U.S. Army Research Laboratory under grant No. DAAL02-92- 

R-9147/2FE425 and U.S. Army Research Office under grant numbers DAAH04-94-G-0091 

and DAAH04-94-G-0121- 
APPLICATION OF SYNCHROTRON WHITE BEAM MULTIPLE 

DIFFRACTION LINE ANALYSIS IN MEASUREMENT OF CURVATURE OF SINGLE CRYSTALS INDUCED BY LATTICE MIS- x19c 

W. Huang, M. Dudley (SUNY at SB); J. Parsons (Oregon Graduate Institute); C. 

Fazi (Army Research Lab.) 

Multiple diffraction lines appear in synchrotron x-ray topographs in bent crystals 

or epitaxially grown single crystals. These multiple diffraction lines can be interpreted according to the dynamical theory of x-ray diffraction as equal-inclination 

fringes. Since they are sensitive to small deformations in the crystal lattice, multiple 

diffraction line analysis can be used to measure the deformation field induced by 

bending or deposition of thin films. Figure 1(a) shows a transmission topograph 

recorded from a 6H-Sic wafer with 3C-Sic thin film grown on it. Since there is a 

lattice mismatch between the substrate and epilayer, residual stress exists in this 

wafer. Some narrow strips, or multiple diffraction lines which are indicated by ar- rowheads, with relatively lower intensity are visible. The position of the multiple 

diffraction lines changes when the crystal is rotated, as shown in figure l(b). The 

movement of these lines as a function of crystal rotation represents the curvature of 

the crystal so that the deformation field can be calculated. Additional strain fields 

induced by inclusions, indicated by I, are also visible. 

Figure 1. 

TALS BY SYNCHROTRON WHITE BEAM ABSORPTION 

CHARACTERIZATION OF DEFORMATION IN SINGLE CRYSI EDGE CONTOUR MAPPING * 

W. Huang, M. Dudley (SUNY at SB); J. Parsons (Oregon Graduate Institute); C. .- Fazi (Army Research lab.) 

Residual stresses due to lattice mismatch between epitaxial layers and substrates 

can greatly affect the microelectronic performance of a device. Measurement of the 

curvature induced in a wafer by the stress in a thin film has long been used as a 

convenient and accurate technique for the determination of the deformation field. In 

this work, synchrotron white beam absorption edge contour mapping is employed to 

determine the curvature in a 6H-Sic wafer with a 3C-Sic epitaxial layer. Because of 

its high contour resolution and the high efficiency of data collection, this technique 

is considered to be superior to monochromatic x-ray contour mapping. A Mo filter, 

with an absorption edge at 0.618 A, has been used so that there is an abrupt 

change in spectrum intensity. When the specimen is properly oriented with respect 

to the incident beam, a variation of observed contrast occurs when the range of 

diffract wavelengths span the absorption edge of the filter, forming an absorption 

edge contour. Upon rotation of the crystal a new crystal position will reflect at the 

absorption edge and a new contour appears, as shown in figures 1(a through (d). 

can be calculated by measuring the displacement of absorption edge contours as s 

function of rotation angle and the in plane strain field can be solved from several 

contour maps recorded in different diffraction conditions. This technique could 

potentially be used in the real time recording of stress formation and relaxation. 

Figure l(e) shows an absorption edge contour map. The curvature o 2 the specimen 

Figure 1. 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-l9C, supported by U.S. Army Research Laboratory under grant No. DAAL02-92- 

R9147/2FE425 and U.S. Army Research Office under grant numbers DAAH04-94-G-0091 

and DAAH04-94-G-0121. 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-19CI supported by U.S. Army Research Laboratory under grant No. DAAL02-92- 

R9147/2FE425 and U.S. Army Research Office under grant numbers.DAAH04-94-G-0091 

and DAAH04-94-G-0121. 
MEASUREMENT OF RESIDUAL STRESS IN SINGLE CRYSTALS BY SYNCHROTRON WHITE BEAM DIVERGENCE 

ANALYSIS * 

The deposition of epitaxial layers and metallization layers often induces residual 

stresses which may result in device failure. Therefore the characterization of stress 

and strain fields in thin films and substrates is important in device fabrication. 

Synchrotron white beam topography, which is commonly used to image individual 

defects and defect distributions, can also be used in quantitative Bragg angle mapping. This technique has been used to measure the stress and strain fields in 6H-Sic 

single crystals with 3C-Sic thin films grown on them. Figure l(a) shows transmission diffraction images recorded from the crystal with the film at x-ray exit surface 

and figure l(b) shows the quantitative Bragg angle map. Figure l(b) was recorded 

by multi-exposure using an x-ray beam of 0.5mm by 5mm in size to image different 

positions in the crystal. The Bragg angle of each intersection of diffracted lines can be measured. Larger film-specimen distance leads to higher measurement accuracy. 

Since there is a non-uniform deformation field in the crystal, the variation in Bragg 

angles is visible. The deformation in the film covered area is different from that in 

the film free area. A combination of white beam absorption edge contour mapping 

and quantitative Bragg angle mapping allows the residual stress and strain field be 

X19C 

__ _ 

calculated. An accuracy in A d / d of lo-' can be achieved. 

(0 

a 

Figure 1. 

I OBSERVATION OF DISLOCATION CONTRAST REVERSAL I qr. ,._ I 

AlYCj IINDUCED BY STRAIN FIELD * 

W. Huang, M. Dudley (SUNY at SBB); J. Parsons (Oregon Graduate Institute); ,. .- r. 

C. Fazi (Army Research Lab.) 

Synchrotron white beam x-ray topography has been used to study GH-Sic wafers 

with 3C thin films grown on them. Figure l(a) is a reflection topograph recorded 

from a such wafer. The penetration depth is large enough to reveal information from 

both film and substrate. It shows that the contrast from dislocations in the filmcovered region is different from that in film-free regions. The same phenomenon can be observed in the transmission topograph shown in figure l(b). Close observation of 

the boundary between the film-covered and film-free regions shows that the overall 

diffracted intensity from the film-covered area was enhanced These area contrast 

differences may be attributed to the substrate strain field associated with the thin 

film. The diffracted intensity from the film- free region was near the value calculated 

for a perfect crystal, and it increased with the lattice strain up to almost the value 

calculated for an "ideally imperfect" crystal, for which the diffracted intensity is 

proportional to Fh2 instead of Fh. The intensity of the dislocations is between 

these values so that the dislocations appear to be dark in the film-free region and 

light in the film-covered region. This means that the thin film region is highly 

strained. 

This result has been proved by the measurement of rocking curve widths of film 

area and substrate area. The rocking curve width of the film region is much larger 

than the theoretical perfect crystal value. 

a- b =rn 

- - - - - . _- 

I 

Figure 1. (a) Synchrotron reflection topograph and (b) transmission topograph 

showing dislocation contrast reversal. 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-19C, supported by U.S. Army Research Laboratory under grant No. DAAL02-92- 

R-9147/2FE425 and U.S. Army Research Office under grant numbers DAAH04-94-G-0091 

and DAAH04-94-G-0121. 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-19CI supported by US. Army Research Laboratory under grant No. DAAL02-92- 

R-9147/2FE425 and U.S. Army Research Office under grant numbers DAAH04-94-G-0091 

and DAAH04-94-G-0121. 
Surface segregation and layering in the liquid-vapor interface of a 

dilute bismuth:gallium alloy 

Ning Lei, Zhengqing Huang and Stuart A. Rice (U. of Chiago) 

The atomic density distribution normal to the liquid-vapor interface of a bismuth: gallium mixture (0.18% Bi and 99.82% Ga in mole) has been studied by the 

measurement of the x-ray specular reflection in the range of qr E [0.3 , 2.6 A-11. 

The reflection curve, measured at temperature - 25OC, after devision by the theoretical Fresnel reflectivity factor for gallium, is shown as circles in Fig. a. We can fit 

the data very well to a complete bismuth monolayer on top of bulk liquid gallium, 

and the fit is shown in solid line in the figure. The vertical atomic density profile 

obtained from the fit is shown in Fig. b. Besides the reflection measurements, our 

in-plane data show that there is a bismuth liquid peak plus liquid gallium scattering, and thus reproduce the data obtained earlier by our group. Measurements 

have been carried out at three temperatures. Our current work is on the surface 

structure in the gallium:tin alloy system. 

n L 

.$ 1.5 

0 

2 1.0 ' 0.5 3 

.- bo 

v) 

S 3 -0.5 - S 0.5 1.0 1.5 2.0 2.5 3.0 

q [PI 

Fig. a 

'XU 

$ 0.4 

.- 0 0.2 

Eo 

3 -10-5 0 5 10 15 

0 

= PI 

Fig. b 

Figure 1. (Left) Circles denote the experimentally obtained specular reflection after 

divided by the theoretical Fresnel reflectivity for gallium. The solid line denotes the 

fit to a complete bismuth monolayer on top of bulk of liquid gallium. (Right) The 

atomic distribution to the interface, obtained from the fit. 

4d 

4 

Characterization of X-ray Spatial Coherence and Its Propagation I X19C 

B. Lin, M. Meron, P. J. Viccaro (U of Chicago), M. L. Schlossman, S. Williams 

(U of IL, Chicago) 

X-ray beams of varying degrees of partial spatial coherence have been prepared 

and characterized by using two slits, and the diffraction of these beams from optical gratings have been measured. The experiments were carried out at a bending 

magnet source at the NSLS (X-19C). The resulting diffraction patterns for optical 

gratings are analyzed in terms of an x-ray mutual coherence function, used to describe the propagation of the coherent wavefront in the visible light regime. The 

diffraction and speckle pattern from the surface are the result of the mutual co- herence function describing the degree of partial coherence of the beam convoluted 

with the interference function of the grating. We show that the speckle patterns 

formed from partially coherent wavefronts contain relevant information concerning the interference function characterizing the grating surface. 

Forming diffraction patterns, or x-ray speckles, with partially coherent x- rays as a probe of the surface relaxes the requirement for the interference, therefore gaining 

in the "effective" coherent flux. In addition, detailed knowledge on the propagation 

of the spatial coherence of x-rays aids in defining the physical characteristics of 

optical elements in the beamline which must preserve the coherence wave front of 

x-rays. 

I 00 

e 10-2 

i$' P 10-4 

s 

h 2 10-6 

- 

10-8 

-0 04 -0 02 0 00 0 02 0 04 

mrad 

Figure 1. Fraunhofer diffraction patterns measured from two vertical slits; 

the first slit is 3.5 meter upstream of 

the second slit. The size of the second slit was varied from 0.5 microns to 

20 microns while the first slit was fixed 

at 50 microns. The solid lines are fits 

of data (represented by the diamonds) 

to an intensity function which is the 

Fourier transform of the coherence function (shown in Fig. 1) multiplied by 

the autocorrelation function of the second slit. 

0 5 10 15 20 25 The size of the second slit (microns) 

Figure 2. The mutual coherence function 

defined by the two slits depicted in Fig. 

1; it describe the degree of partial (spatial) coherence as a function the second 

slit with the first slit fixed. 
Studies on the influence of post solidification cooling rate on the 

crystalline perfection of CdZnTe single crystals by synchrotron white 

beam x-rav toDonraDhv * 

I. 

X19C 

B. Raghothamachar, H. Chung, M. Dudley,(SUNY at Stony Brook), B. Fitzpatrick 

(Optical Semiconductors, Inc.) 

ZnSe is an important 11-VI semiconductor possessing a large direct energy band 

gap and therefore, good electroluminescence which makes it a candidate material 

for light emitting diodes and lasers. However, defects such as dislocations, twins, 

subgrain boundaries, etc. which can be routinely introduced in the crystal during 

growth can be potentially detrimental to device performance. Hence, identification 

and characterization of defect structures in this material is of paramount importance. Synchrotron white beam x-ray topography has been used to study structural 

defects in ZnSe crystals. Figure 1 shows a reflection topograph taken from a ZnSe 

single crystal grain. In the lower regions of the figure, we can see several white 

bands which are actually regions of zero intensity caused by orientation contrast. 

This occurs because of the presence of several microtwins. Microtwinning occurs at the high growth temperatures used, due to the small differences of free energy 

between zinc blend and wurtzite structures, and temperature fluctuations. Contin- uous phase transformation between these two structures results in change in the 

stacking sequence in the [Ill] direction leading to twinning. Figure 1 also reveals 

bands of zero intensity running across the microtwins. This orientation contrast is 

associated with subgrain boundaries which are formed during post growth cooling as a result of polygonization of dislocations. Upper parts of the figure reveal distortion which is associated with inhomogeneous strain associated with a distorted 

lattice. This could again be due to temperature fluctuations. 

F 

0 

cn 

Figure 1. Reflection topograph from a ZnSe single crystal grain showing microtwinning (T), subgrain boundaries (SB) and lattice distortion (A). 

x19c 

Characterization of structural defects in ZnSe by synchrotron white 

beam x-ray topography * 

* Work performed on the Synchrotron Topography Project, Beamline X19C. 

B. Raghothamachar, H. Chung, M. Dudley, D. J. Larson Jr. (SUNY at Stony 

Brook) 

CdZnTe single crystals grown by the seeded Bridgman method in a microgravity 

environment aboard space shuttle flight USML-1 were examined by synchrotron 

white beam x-ray topography. The microgravity environment is expected to improve crystalline perfection because of the absence of hydrostatic forces and gravity 

driven convection. After growth, the CdZnTe boule was subjected to accelerated 

post solidification cooling down its length. Wafers sliced from regions cooled at different cooling rates were examined by transmission topography. Figure 1 a) shows 

The image shows the very low dislocation density, with individual dislocations D) 

the straight lines lying parallel to the [I101 directions are characterized as lamellar 180 rotation twins(?') about the [lli] plane normal. Figure l(b) shows a 

topograph recorded from a more rapidly cooled region of the boule. It is obvious 

that this regions exhibits a relatively higher dislocation density in addition to the 

presence of extremely fine Te precipitates. Due to the retrograde solubility of Te in 

solid CdZnTe, supersaturation of Te results in precipitation during cooling. Clearly 

the dislocation density as well as the size and density of Te precipitates are strongly 

influenced by the cooling rate. In conclusion, higher cooling rates are deleterious to 

the crystalline perfection of CdZnTe single crystals. 

a transmission topograph recorded from a region cooled with a low coo L ng rate. 

capable of being resolved. The singular dark spots are Te precipitates (P) w I, ile 

Figure 1. Transmission topographs (g = II3, X = 0.42 A) recorded from different 

regions of a wafer sliced from a CdZnTe boule (a) from a slowly cooled region of 

the boule showing individual dislocations (D) and precipitates (P) and (b) from a 

rapidly cooled region of the boule. 

____ 

* Work performed on the Synchrotron Topography Project, Beamline X19C and supported by NASA Marshall Space Flight Center. 
I Surface topography studies of an as-grown boule of CdZnTe * I x19c I 

B. Raghothamachar, H. Chung, M. Dudley, D.J. Larson Jr.(SUNY at Stony Brook) 

Synchrotron white beam x-ray topography was used to study the surface of an as- grown CdZnTe boule(GCRC-1) grown in a quarts ampoule by the seeded BridgmanStockbarger method of crystal growth in a microgravity environment aboard space 

shuttle flight USML-1. Topography of the surface of the as grown boule, before 

cutting enables one to observe the true microstructure developed during the growth 

process, with no possibility of artifacts, for example due to polishing or cutting, to 

exist. In addition, effects due to thermal mismatch associated with rapid cooling as well as due to ampoule contact are likely to give rise to deformation microstructures 

concentrated near the periphery of the boule which is precisely the volume examined 

in surface topography studies. A reflection topographic image taken from the surface 

of the GCRC-1 boule is shown in Figure 1. Detailed examination of this image 

revealed extensive slip band network@) as well as high levels of surface strains 

in those regions that were in partial or full contact with the ampoule. Twins(T) 

appear to nucleate at regions of partial wall contact. Regions of no wall contact 

show a low defect density with little or no surface strain. Thermal stresses arising 

from rapid cooling as well due to ampoule wall contact are found to be the causes 

for these defect microstructures. Thus, surface topography of the boule is important 

in correlating the as grown deformation microstructure to the growth conditions. 

Figure 1. Reflection topograph recorded from the outer surface of GCRC-1 boule 

showing twins (T) and slip bands (S). 

* Work performed on the Synchrotron Topography Project, Beamline X19C and sup4d 

P 

m ported by NASA Marshall Space Flight Center. 

x19c Synchrotron x-ray topographic studies on the causes and nature of 

twinning in CdZnTe crystals * 

B. Raghothamachar, H. Chung, M. Dudley, D.J. Larson, Jr.(SUNY at Stony Brook) 

Synchrotron white beam x-ray topography has been used to characterise twinning in CdZnTe crystals. A wafer sliced from a CdZnTe boule grown by the seeded 

Bridgman-Stockbarger method in a microgravity environment was used for our studies. Figure 1 (a) shows a synchrotron white beam x-ray reflection topograph which 

easily reveals the matrix and twinned regions by orientation contrast. Correlating the position of the wafer to the overall boule microstructure, it was found that the 

twin T1 nucleated from the shoulder region of the boule where a bubble is present. This clearly indicates that the nucleation of the twin occurred during growth due 

to disturbances at the growth interface caused by the changing diameter of the 

shoulder as well as the presence of the bubble. Figure l(b) and (c) show Laue back 

reflection topographs recorded from the matrix and twinned region (TI) respectively, showing the orientations of these two re ions. The twinned region is related 

to the matrix by a 180' rotation about the [lllg] axis. Similarly, the twinned region 

Tz is related to the matrix by 180' rotation about the [ill] axis. Stress caused by ampoule wall contact could be the possible cause for the nucleation of twin Tz. 

.. 

a 

Figure 1. (a)Synchrotron white beam x-ray topograph (g = 133, X = 0.98 A) showing twin related regions T1 and Tz revealed by orientation contrast. Laue 

back reflection patterns recorded from (b matrix and (c)twinned region Ti show 

that the twinned regions are related to t h e matrix by a 180' rotation about the 

[lll] axis. 

* Work performed on the Synchrotron Topography Project, Beamline X19C and supported by NASA Marshall Space Flight Center. 
. '. > 

w 

0 

4 Synchrotron x-ray topography studies of formation of slip bands and 

subgrain boundaries in Bridgman grown CdZnTe single crystals * x19c 

howing the slip bands SI and Sz. (b)Reflection topograph from GCRC-1 wafer 

Figure 1. (a)Reflection topograph from GCRC-1 wafer # 4 (g = 404, X = 

7 (g = 044, X = 0.76 A) showing sub-grain boundaries SB1 and SBz. 

* Work performed on the Synchrotron Topography Project, Beamline X19C and sup 

ported by NASA Marshall Space Flight Center. 

x19c The Application of Synchrotron X-Ray Radiation to the Development of Time Resolved Methods for the Study of RNA Folding 

B. Sclavi, M. Sullivan, M. Chance, M. Brenowitz (Albert Einstein College of 

Medicine), and S. Woodson (Univ. of Maryland) 

The radiolysis of water by high energy x-rays produces free electrons and hydroxyl radicals. Hydroxyl radicals, which can break the phosphodiester backbone 

of DNA and RNA, have proven to be valuable reagents in the study of nucleic acid 

structure and protein-nucleic acid interactions. Irradiation of solutions containing 

32P labeled RNA by a high flux "white light" x-ray beam, X19C at NSLS, yields sufficient concentrations of hydroxyl radicals so that folding studies can be conducted 

with single basepair resolution at millisecond timescales. Preliminary studies of the 

MgZt dependent folding of the Tetrahymena Sca I ribozyme are presented. This 

synchrotron based technology is a novel method with which to examine the timeresolved structural changes of nucleic acid conformation and protein-nucleic acid 

complexes. 

This work was supported by NIH grants RR 01633, GM 39929, 51506 and GM 

46686. 

... .. .. 
x19c Applications of absorption edge contour (AEC) mapping in Fe doped 

InP single crvstal wafers * 

W. Si, H. Chung, M. Dudley, and V. Prasad (SUNY Stony Brook), A. Anselmo 

and D. F. Bliss (USAF Rome Laboratory) 

Among synchrotron white beam x-ray topography techniques, AEC mapping is a unique technique which can accurately determine the strain field distribution in a single crystal sample. It is based on the principle that when a deformed single crystal 

is irradiated by a white beam of synchrotron radiation, different areas of the crystal 

will diffract different wavelengths of x-rays available in the continuous spectrum 

of the incident beam. A significant variation of observed contrast occurs when the 

range of diffracted wavelengths spans the absorption edge (A,,,,) of the specimen or of a suitably chosen filter material which is inserted in the path of the beam. If an orientation is chosen such that a certain area of the sample will reflect wavelengths 

below that of the edge, the diffraction intensity will be correspondingly greatly 

attenuated; while in the other area of the sample, which reflects wavelengths above 

that of the edge, the diffracted intensity is only slightly modified. Upon rotation 

of the crystal by a known amount about a known axis, the positions which were 

diffracting at Xedge will select a new wavelength and consequently a new position 

will diffract at Xedge. In this way the distortion field in the crystal can be mapped. 

Preliminary results obtained from an Fe doped InP wafer are shown in Fig. 1, 

where g = 022, Xedqe = 0.443'71A1 OB = 6.138'. In the figure, the frame denotes 

the incident beam size, and the absorption edge sweeps across the sample as the 

crystal rotates through 0.02' steps. The sensitivity, (Ad/d), here is of the order of 

one part in io3. 

Figure 1. 

* Acknowledgments: Research carried out under auspices of the ARPA/AFOSR Consortium of Crystal Growth Research (Contract No. F496209510407), work performed on 

the Synchrotron Topography Project, Beamline X-19C. 

Investigation of defect structures in Sn doped InP single crystals by 

synchrotron x-ray transmission topography * 

W. Si, H. Chung, M. Dudley, and V. Prasad (SUNY Stony Brook), A. Anselmo an 

d D. F. Bliss (USAF Rome Laboratory) 

Large size InP single crystals (Sn doped, concentration: 5.90~10'~ atoms/cc) 

were grown by a high pressure, in-situ synthesis technique. (110) wafers (- 40 x 

'70 x 1 mm' were cut from the [OOl] axis grown boule. Transmission geometries 

transmission topographs, g= 320, X = 0.51 A, which shows a) precipitates (P) 

here is ,ut = 4.4, with X = 0.51 A, linear absorption coefficient ,u = 44.3 l/cm, and 

thickness t = 0.1 cm. Under such high absorption conditions, precipitates exhibit 

two-lobe black-white contrast, with the dark lobe on the side of positive g. This 

indicates that the lattice of the matrix around the precipitate is under tenGon. 

The micro-twin lamella (about 10 ,urn in width) is a 180' rotation twin (f(ll1) 

twin planes). This long thin twin lamella originating from the seed, runs through 

the whole wafer, reiterating the importance of the examination of the seed crystal 

before crystal growth. 

were adopte d to characterize the defect structFres in the crystals. Figure 1 shows 

and dislocations (D), and (b) a micro-twin lamella (T). The a 6 sorption condition 

I 

Figure 1. 

* Acknowledgments: Research carried out under auspices of the ARPA/AFOSR Consortium of Crystal Growth Research (Contract No. F496209510407), work performed on 

the Synchrotron Topography Project, Beamline X-19C. 
" 

Study of effect of magnetic field on Fe precipitates in Fe-doped InP 

single crystals using synchrotron white beam x-ray topography * 

:' 1 

x19c 

. . _.. .J I 

I ..'. 

.% 

I. '.. . 

, *. . 

I I~ 

Study of defect distributions in S doped InP single crystals by synchrotron x-ray reflection topography * 

W. Si, H. Chung, M. Dudley, and V. Prasad (SUNY Stony Brook), A. Anselmo 

and D. F. Bliss (USAF Rome Laboratory) 

High quality InP single crystals (S doped, concentration: 3.90~ 10" atoms/cc) 

were grown by a high pressure, in-situ one-step synthesis technique. (110) wafers 

(w 40 x 60 mm2 in size, 1 mm thick) were sliced from the single crystal boule, 

with [OOl] as the pulling direction. For the synchrotron white beam x-ray topography, reflection geometries were adopted to characterize the defect distributions in 

the crystals. Both slip bands and growth striations were revealed. Figure 1 shows 

reflection topographs of a S-doped InP single crystal, = 440, X = 0.74 A, which 

reveals (a) slip bands (SB), and (b) growth striations fGS). Most slip bands were 

generated from the shoulder region of the boule, indicatin that stress is concentrated in this region. There are two sets of slip planes, &?ill) and rt(li1). The 

traces of the intersection of &(ill) and &(lil) with sample surface plane (110) are 

&[ll2] and &[llZ] directions, respectively. Growth striations which are convex to 

the melt were found in some areas. The shape of the growth striation reveals the 

shape of the solid-liquid interface during crystal solidification, which can provide 

some useful information for the thermal modeling of the crystal growth process. 

* Acknowledgments: Research carried out under auspices of the ARPA/AFOSR Consortium of Crystal Growth Research (Contract No. F496209510407), work performed on 

the Synchrotron Topography Project, Beamline X-19C. 

Figure 1. 

* Acknowledgments: Research carried out under auspices of the ARPA/AFOSR Consortium of Crystal Growth Research (Contract No. F496209510407), work performed on 

the Synchrotron Topography Project, Beamline X-19C. 

.- 
(Eds.) MRS Symp. Proc. 375, 313, 1995. 

Figure 1. Figure 1. 

';d 

5 

UJ 

* Acknowledgments: Work performed on the Synchrotron Topography Project, Beamline X-19CI and supported by ARPA/AFOSR under Grant No. FY1457-95-03108 through 

Cree Research, Inc. under Grant No. 95-004. 

* Acknowledgments: Work performed on the Synchrotron Topography Project, Beamline X-l9C, and supported by ARPA/AFOSR under Grant No. FY1457-95-03108 through 

Cree Research, Inc. under Grant No. 95-004. 
CL 

3 

* Work performed on the Synchrotron Topography Project, Beamline X-19C1 and supported by ARPA/AFOSR under Grant No. FY1457-95-03108 through Cree Research, Inc. 

under Grant No. 95-004. 

Determination of Burgers vectors of screw dislocations in 6H-Sic 

single crystals: I. Projection topography * x19c 

Determination of Burgers vectors of screw dislocations in 6H-Sic 

single crystals: 11. Section topographv * x19c 

W. Si, S. Wang , and M. Dudley (SUNY Stony Brook), C. H. Carter, Jr. (Cree 

Research Inc.) 

A white-beam section topograph geometry has been used to measure the magnitude of the Burgers vector of superscrew dislocations in the 6H-Sic single crystals. 

This method consists of illuminating the sample by a strip of highly collimating 

white beam (less than 20 pm). Section topographs were taken in symmetric transmission, i.e., using Bragg planes perpendicular to the thin crystal platelet and perpendicular to the screw dislocation. In such cases the lattice tilts are easily derived 

from the linear displacements of Bragg diffracted beams. In principle, the lattice 

tilt T around the screw dislocation can be described as: T = b/2ar, where b is 

the magnitude of Burgers vector, r is the distance from the dislocation core. As to 

the white beam diffraction geometry, the deviation of Bragg angle AeB would be 

2T. Assuming the incident beam is strictly parallel, the displacement Y recorded 

in the x-ray film at sample-to-film distance D,f would be: Y Ei D,fAf?B (AOB is 

very small) = 2D,fT, thus b = nYr/D,f. Figure 1 shows the lattice tilt T around a screw dislocation, and Figure 2 shows a white beam section topograph of a screw 

dislocation, D,f = 16 cm, g = 0006, X = 0.89 A. From the hyperbolae drawn on the 

pictures, the magnitude of the Burgers vector is 62.6 A (upper left lobe), and 45.0 

A (lower right lobe), which again corresponds to 3c to 4c (c is the lattice constant 

along [OOOl] axis, c = 15.17 A). 

Diotanm. r 

Figure 1. 

* Acknowledgments: Work performed on 

Project, Beamline X-19C1 and supportedby 

ARPA/AFOSR under Grant No. FY1457- 

95-03108 through Cree Research, Inc. under 

Grant No. 95-004. 

the Synchrotron Topogrvhy 
ccI &Jj i_.... . iil 

Wh I 

lr ::- I.: .. . 
'',. 

Studies of quartz crystal bars using synchrotron white beam x-ray 

topography * 

J. Su, M. Dudley (SUNY Stony Brook),T. McLelland, B. Goldfrank (Frequency 

Electronics Inc.) 

Quartz crystal (a-quartz) resonators are an important part of modern commu- nication and satellite navigation systems. Defects in these crystals can introduce 

detrimental frequency offsets. The sweeping process, which is electric-field driven, 

solid-state diffusion at elevated temperature, is applied to purify the crystals. Xray reflection topography has been used to study the defects in swept synthetic 

quartz crystal bars which are used to make high precision SC cut quartz resonators. The bars are of X and Z surface orientations, and have dimensions of 

182mmx18mmx15mm. Figure 1 shows reflection topographs of -X and -Z surfaces 

from one of bars. On the -X surface, dislocations (D) are clearly observed , some dislocations end at surface. In the -Z surface, the emergent ends of dislocations which 

may be decorated with impurities are revealed, also sweeping induced impurity ac- cumulations (IA) are visible on the surface. From the distribution of dislocation 

outcrops and their associated strains on the -X surface, it can be determined that 

the dislocations are nearly parallel to Z axis. 

Sawyer Y bar # KOG4-1 -x surface, g= (GI 1) h=0.38A. 

g- 

/ 

Comparison of quartz resonator bonding strain by synchrotron white 

beam topography * 

J. Su, W. Si and M. Dudley (SUNY Stony Brook), T. McLelland and B. Goldfrank 

(Frequency Electronics Inc.) 

Manufacturing induced defects play an important role in quartz resonator device yield. Bonding strain can be extremely deleterious to resonator performance. 

SWBXT is a non-invasive technique which is very suitable for the study of such 

defect distributions. Samples with different bonding process have been studied by 

SWBXT, those which have thermal compression (TC) bonding and those which 

have undergone epoxy bonding. Figures 1 and 2 show the reflection topographs of 

a resonator with TC bonding and a resonator with epoxy bonding. The bonding 

strain (S) is nearly invisible in Figure 1, but, in Figure 2, the bonding process induced larger strain fields (S) at the resonator periphery, and some strain field even 

extends into the central region, where is the active oscillating area of a precision 

resonator. This will inevitably influence the resonator performance. This work 

clearly shows that epoxy bonding process creates more strain than the TC bonding 

process. Dislocations (D) and electrode induced strain fields (ES) are revealed in 

the Figures. 

4 

-S 

- 2 mm 

Figure 1. Reflection topograph of a res- ' 2mm Sawyer Y bar # KOG4-I z surface, g=( 115) X=O.SZ,L onator with TC bonding. - 

Figure 1. Reflection topographs of -x and -Z surfaces from quartz bar K064-1, 

* Work performed on SynchrotronTopography Project: Beamline X19C, and supported 

(a) p-1i4 

* performed on Synchrotron To- Figure 2. Reflection topograph of a respography Project: Beamline X-lgC, SUP- onator with epoxy bonding. 

by Frequency Electronics Inc. ported by Frequency Electronics Inc. 
.* 

X-Ray Topography and Laser Scanning Confocal Microscopy of a 

Longitudinal Cut 6H-SIC Wafer * x19c 

- a,-" 

b) (dl 

Figure 1. 

4d 

rf 

-a 94-G-0091 and DAAL04-94-G-0121. 

* Acknowledgements: Work performed at the Synchrotron Topography Project Station, 

Beamline X-lgC, supportedby U.S. Amy Research Office under grant numbers: DAALO9- 

X-Ray Topography and Fluorescence Microscopy of a Basal Cut 6HSic Wafer * x19c 

Figure 1. 

* Acknowledgements: Work performed at the Synchrotron Topography Project Station, 

BeamlineX-l9C, supportedby U.S. Army Research Office under grant numbers: DAALO9- 

94-G-0091 and DAAL04-94-G-0121. 
. 

.. .. . 

cL 

3 SYNCHROTRON WHITE BEAM X-RAY TOPOGRAPHIC x19c 

CHARACTERIZATION OF PVT 3C-Sic CRYSTALS * 

S. Wang, W. Huang, M. Dudley (SUNY at SB); M. Spencer (Howard University); 

C. Fazi (Army Research Lab.) 

Synchrotron White Beam X-ray Topography (SWBXT has been used to study 

100) 3C- Sic single by the sublimation P 4 T technique at Howard 

bniversity. Figures l(a) and are transmission synchrotron topographs recorded 

from the same area of the iC wafer. Figure l(a) shows that the 3C-Sic wafer 

is a single crystal. Although there are many contrast features on the topograph, no individual dislocations or slip bands can be resolved. The overall poor quality 

of the image suggests that the crystal may contain a high density of defects. The 

most striking features in figure l(a) are the white patches, indicated by arrowheads. 

These white patches correspond to square shaped defects observable by optical micrograph with polarized light. Each square defect actually consists of four planar 

defects forming a pyramid, and as such are referred to as “pyramidal defects”. In 

fact, the four planar defects in each pyramidal defect were found to be parallel to 

the four (111) planes with their four sides parallel to the [110] crystallographic 

directions. In figure l(b) the “pyramidal defects” were imaged exclusively as dark 

patches. The correlation of the dark patches with the “pyramidal defects” is clearly 

demonstrated. Detailed analysis suggest that the ”pyramidal defects” may be as- sociated with extended planar faults parallel to the (111) planes. These faults are 

decorated with impurities or impurity clusters (the inclusions) and therefore there 

are large strains associated with them. Further investigation is needed to elucidate 

the nature of these pyramidal defects. 

Figure 1. Transmission synchrotron topographs recorded from (100) 3C-Sic wafer. 

* Acknowledgements: Work performed on the Synchrotron Topography Project Beamline X-19C, supported by U.S. Army Research Laboratory under grant No. DAAL02-92- 

R-9147/2FE425 and U.S. Army Research Office under grant numbers DAAH04-94-G-0091 

and DAAH04-94-G-0121. 

~~ ~ I Microemulsion-Oil Interfaces in Ternary Liquid Systems I x19c I 

S.M. Williams, Z. Zhang, and M.L.Schlossman (University of Illinois at Chicago) 

X-ray reflectivit and surface diffuse scattering were used to study the 

microemulsion-oil liquid-liquid) interface in a ternary system of water, decane, 

and C4E1 (CHs(C 2)3(OCHzCHz OH). These systems exhibit ultra low surface 

tensions and are expected to have arge amplitude thermal fluctuations at the interfaces (similar to those at the oil-monolayer-water interface recently discussed by 

McClain et al. in Phys. Rev. Lett. 72, 246 (1994)). 

Preliminary data taken at the X19C liquid surface scattering spectrometer is 

shown below for scattering from the oil-microemulsion interface of a C4EI-waterdecane (1:1:3 by volume mixture at 35.OO0C. The solution is in a vapor-tight polycarbonate sample cell. i-rays pass through 0.001’’ mylar windows attached to the 

body of the cell and through the upper oil phase to scatter off the interface. 

Specular reflectivity data measured as a function of the wave vector normal to the 

interface are shown in Fig. 1. Surface diffuse scattering measurements as a function 

of the exit angle beta in the plane of incidence) for a fixed incident angle of 0.055 

and the surface diffuse scattering data indicates an interfacial roughness of 51A 

+/- 3A. This roughness can be attributed to surface-tension dominated thermal 

fluctuations at the interface. 

6 1 

degrees are shown in I ig. 2. Preliminary analysis of the specular reflectivity data 

1 

P 

2 0.1 .- 

B 1 0.01 

a 

0.001 z 

o.oO01 

I 0.01 0.02 0.03 0.04 0.05 0.06 0.07 

I’d 0.d5 0.01 0.0;5 0.d2 O.Oi5 0.03 0.I Beta [degrees] 

Q@’) Figure 2. Surface scattering showing 

peaks at the critical angle for total reflection and at the angle for specular reflection. Figure 1. Reflectivity data as a function 

of wave vector normal to the interface. 
I 

I X-ray Scattering Studies of the Passive Film on Fe(ll0) I X20A I ~~ 

Alison J. Davenport, Carissima M. Vitus (DAS, BNL), andlMichYe1 F. Toney (IBM 

Almaden Research Center) 

Despite decades of work, there is still little understanding of the passivating 

oxide films that protect (normally reactive) metals from corrosion. This is because 

they are very thin (typically a few nanometers) and are formed in an aqueous 

environment so that ex situ measurements are susceptible to any changes in the 

film when they are removed from the solution in which they grew. The structure of 

the passive film on iron has been the subject of particularly intense study (Refs. 1 

and 2, and references therein), but there is still little consensus on questions as basic 

as to whether the film is amorphous or crystalline. However, recent in situ STM 

images of passive films on iron (2) suggest that the surfaces are crystalline with 

proposed structures (7FezU3/Fe304) that are supported by in situ XANES and 

EXAFS measurements (1). To confirm and expand these recent findings, we have 

performed in-situ and ex-situ X-ray scattering experiments on the passive oxide 

formed on Fe(ll0) single crystals. Such measurements probe the entire film rather 

than just the surface layer. The Fe(ll0) single crystal was passivated by potentiostatic polarization for ~60 

minutes at +0.4V vs MSE in borate buffer (pH 8.4). In situ data were obtained 

with the electrode poised at this potential, while for our ex-situ measurements, the 

electrode was emersed and placed in a flowing He atmosphere. Our methodology was 

to perform detailed measurements ex situ, where the background X-ray scattering is 

small since there is no electrolyte), and then collect selected in situ data to compare 

between the in situ and ex situ data, showing that the passive film formed under our conditions was not altered by removal from the electrolyte and from potential 

control. 

The observed diffraction pattern from the passive oxide on Fe(ll0) is that of 

7FezUs or FeaU4, which confirms the STM and XANES results. At this point 

we cannot distinguish between these two structures, although a careful intensity 

analysis should permit this distinction. Our data also show that perpendicular to the surface +yPezU3/Pe304(111) )I Fe(llO), while parallel to the surface 

7FezU3/FesO4(I10) 11 Fe 002). The latter orientational relationship is quite is 

reasonable, since in these 6 irections the lattice mismatch between the metal and 

oxide is less than 0.4%. From the diffraction peak widths, we find that parallel to 

the substrate the grain size is %4-5nm, and that there appear to be planar defects, 

such as stacking faults. The data also show that the passive oxide is twined (e.g., 

both 7FezOs/Fe3Ua(lll) and 7Fe?Os/.FesOa(iil) orientations are observed), although there is an asymmetry to this twining that we do not presently understand. 

with t h e ex situ measurements. In such a comparison, there was excellent agreement 

J. Electrochem. SOC. 142, 725-730 (1995). 

G.E. Thompson, J. Electrochem. SOC. 142, 

1 X20A I GIXD Measurements of Initial Strain Relaxation in Sil-,Ge, Thin I Films 

J.L. Jordan-Sweet, P.M. Mooney, M. Lutz, R.A. Feenstra, and J.O. Chu (IBM) 

Strain-relaxed step-graded SiGe layers have been shown to have relatively low 

threading dislocation densities and thus can serve as substrates for high-mobility 

FETs having strained Si, SiGe, or Ge channels. Step-graded structures grown by 

UHV-CVD at low temperature relax via a Modified Frank-Read 

(MFR) mechanism by which dislocations are formed by the reproduction of “corner dislocations” that glide into the substrate on (111) planes. A series of experiments have been performed at X20A using triple-axis x-ray diffraction to study the 

properties of strain relaxation in these structures. (For references, please see X20 

publications list). We also have used grazing-incidence x-ray diffraction (GIXD to 

measure the initial stages of strain relaxation in thin single-composition SiGe fi 1 ms 

epitaxially grown on Si(100). 

GIXD permits the direct measurement of in-plane lattice parameters of SiGe films 

that are too thin to yield good results from normal-geometry triple-axis techniques. 

We see a unique “X”-shaped pattern in H-K reciprocal space maps of diffracted 

x-ray intensity from SiGe films that have relaxed via the MFR mechanism. 

Contours of intensity are seen along the <110> directions from the (-4 0 0) 

reciprocal lattice peak with the introduction of the first dislocations. For higher 

dislocation densities the “X”-shaped contours are anisotropically distorted; and a 

satellite peak, corresponding to the lattice parameter for a partially relaxed film, 

becomes identifiable at lower H. 

In contrast, H-K reciprocal space contours from thin SiGe films that have relaxed 

by roughening and subsequent random nucleation of dislocations display broad, 

oval-shaped contours centered at the (-4 0 0) reciprocal lattice point for the film. 

Numeric simulations of GIXD from a variety of dislocation arrangements were 

performed in order to understand the origin of the “X” pattern. We show that 

this pattern arises from an array of long misfit dislocations running in the <110> 

directions. We also calculate accurate values for the composition and strain in these 

SiGe layers from the measured in-plane and out-of-plane lattice parameters. (Submitted to Journal of Applied Physics). 

0’02 7 

-0.01 I I -4.02 -4.01 -4.W -1.99 -1.98 

H (W r.1.u) 

Figure 1. H-K reciprocal space contours of 700 A of Si.76Ge.26 grown at 5OO0C and 

relaxed 4% by the MFR mechanism. 
Structural Phase Transitions and Magneto-Elastic Effects in 

USbo.BTeo.2 and USb. 

4.5 

~ 

X20B 

- 3.5 a 

Y 

0 

F 

0 

o 

$ 2.5 

- 1.5 

E al 

c 

c 

Interfacial Roughness and Giant Magnetoresistance in Sputtered 

Co/Rh Multilayers as Studied with X-ray Scattering X20A 

0.5 

I.,.,. 

-0.08 -0.04 0 0.04 0.08 

Q, LA-'] 

Figure 1. Diffuse scattering data at the forth multilayer Bragg peak for Co/Rh(llO). 

These have been corrected for sample area and X-ray absorption, but not dynamical 

effects. QII is the component of the scattering vector parallel to the surface. The 

lines show best fits to these data, which were used to determine the correlation 

lengths. Figure 1. 

Figure 2. 
I In-situ, Simultaneous Three-Probe Measurement of Structural I V,,A,-, 1 A4Ub I Transformations in Metal Silicides. 

J.L. Jordan-Sweet, L.A. Clevenger, C.A. Cabral, Jr., R.A. Roy, C. Lavoie, K.L. 

Saenger (IBM), G.B. Stephenson, S.A. Brauer (ANL), K.L. Ludwig, Jr., and G. 

Morales (Boston U.) 

The formation of low-resistance-silicide source, gate, and drain contacts for submicron circuits is a critical processing step in semiconductor CMOS logic and memory manufacturing. Instrumentation has been developed for the in-situ monitoring 

of structural transformations to low-resistance phases in these materials, in the 

form of blanket thin films, arrays of patterned lines (gratings), and microelectronic 

structures. 

A special furnace chamber has been constructed which performs rapid thermal 

annealing (RTA) ramps up to 35 "C/sec, and has the capability for simultaneous 

real-time measurement of x-ray diffraction, four-probe sample resistivity, and optical scattering. At a bending magnet beamline equipped with synthetic multilayer 

monochromator optics and a linear diode array detector which intercepts -10" in 

28, changes can be measured on a millisecond timescale. Not only can fast processes 

be monitored in this way, but a large matrix of materials sets and process parameters can be quickly evaluated. The average cycle-time for a phase transformation 

measurement and sample change with this configuration is 520 minutes. 

Results have been published of measurements of TiSiz C49 (high resistivity to 

gate conductors 21; identification of a metal-rich Ti silicide [3]; and the effect of a 

C54 (low resistivity) transformations in arrays of sub-micron hnes [l] and C Ill OS 

Ti interlayer on E oSiz phase formation [4]. 

1. R.A. Roy, et al., Appl. Phys. Lett. 66(14), 1732 (1995). 

2. L.A. Clevenger, et al., J. Mater. Res. 10(9), 2355 (1995). 

3. L.A. Clevenger, et al., Thin Solid Films, submitted. 

4. C. Cabral, Jr., et al., Mat. Res. SOC. Symp. Proc. 375, 253 (1995). 

Effects of Rubbing Parameters on Surface Orientation of BPDAPDA Polyimide ~ 

James M. Sands and Sanat K. Kumar (The Pennsylvania State University), Thomas 

P. Russell and Michael F. Toney (IBM Almaden Research Center) 

We previously showed that rubbing BPDA-PDA polyimide films orients most 

of the polymer chains within a thin surface region along the rubbing direction [l] 

and that this results in the alignment of liquid crystals in contact with the polyimide. In an effort to understand the mechanism of polyimide surface orientation 

and liquid crystal alignment, grazing incidence X-ray scattering (GIXS) has been 

applied to characterize the effects of various rubbing parameters on the resulting 

polymer orientation. In these experiments, BPDA-PDA thin films rubbed under 

varying load, distance, and rate were examined. By looking at the X-ray scattering with the scattering vector aligned parallel and perpendicular to the direction 

of the rubbing, one can establish the degree of orientation in the polymer surface 

with a depth resolution of 5019. GIXS profiles show that there is a critical load 

and distance required in order to cause surface orientation (Figure la). Using the 

onset of discernible orientation as a gauge, the force required to cause orientation of 

the polyimide molecules is found to be quite small (Figure lb). The small force is 

surprising as one expects significant restrictions to chain mobility, due to the high 

Tg of the bulk polymer (653 K). The ease with which the polymer surface orients 

questions the relationship of Tg (a bulk phenomenon) to thin films. 

[l] M.F. Toney, et. al., Nature, 374, 709 (1995). 

Figure la Figure lb n ........ I 

100 0.005 

- 10-1 - 0.004 

e 

f 10-2 $0,003 

5 

x 

I 

Io-' 

io-' 

- 

- 0.002 

Q [Ami] 

0.001 - 

# ['I 0.5 1.0 1.5 2 0 2.5 3.0 -30 0 30 60 

Figure 1. a GIXS profile for 573K imidized BPDA-PDA buffed under 2gm/cm2 

at lcm/s. A olid line is Q oriented parallel to rubbing direction. Dashed line is 

Q oriented perpendicular to the rubbing direction. Insets show the distance over 

which the samples were buffed. b)GIXS scans showing the degree of orientation in 

the surface under various loading. Data is obtained by fixing incidfnce angle and 

scattering position and rotating the sample in the beam (Q = 0.81~4). Distance of 

buffing is 50cm. Direction of rub is 0. Inset shows buffing loads. 
Synchrotron X-ray scattering study of the N-IC phase transition 

in RbzZnCle 

M.P. Zinkin, R.A. Cowley (Oxford), D.F. McMorrow (Riso), J.P. Hill (BNL) 

Below T, M 303 K, RbzZnCld undergoes a continuous phase transition from 

a normal crystalline (N) phase, to one-dimensionally modulated incommensurate 

(IC) phase characterized by a modulation wavevector q. The transition can be 

characterized by a two-component primary order parameter corresponding to the 

amplitude and phase of the modulation wave, the transition is expected to belong 

to the 3D-XY universality class. Higher harmonics of the modulation wave form a 

class of secondary order parameters for the transition. 

Measurements of the temperature dependences of the intensities of the satellite peaks corresponding to the primary order parameter and the next two higher 

harmonics were performed on X20C. The resulting order parameter exponents are 

= 0.35 f 0.01, pz = 0.87 f 0.01, and p3 = 1.50 f 0.04, in good agrement with 

recent theoretical predictions for the 3D-XY universality class. 

Figures 1 and 2 show the critical scattering above T, measured on X20C and 

X17B1 respectively. The second, sharp, component in the X20 data corresponds to 

critical fluctuations on length scale N 10 times those of the broad component visible 

in both data sets. The penetration depth of the 10 keV X-rays used on the X20 

experiment was M 20 pm, whereas the 60 keV X17B1 experiment was performed 

in transmission, the M 2 mm penetration depth being approximately equal to the 

sample thickness. This data is evidence for a near-surface origin of the second length 

scale scattering. The measured temperature dependence of the width of the broad 

component of the critical scattering results in a value of the inverse correlation 

length exponent u = 0.66 -+ 0.02, in agreement with the 3D-XY result. 

~17~1, 

x20c 

-0.60 -0.55 -0.50 -0.45 -0.40 -0.35 

L (k') -1.6 -1.5 -1.4 .. 

L (A-l) Figure 1. Critical scattering measured on x2oc- Note the Presence of a second 

component in the scattering. Figure 2. Critical scattering measured on X17. 

Inelastic X-Ray Scattering Study of Diamond * I x21 

W.A.Caliebe, C.-C.Kao, J.B.Hastings (NSLS), M.H.Krisch, F.Sette (ESRF, 

France), K.Hamiilainen (University of Helsinki, Finland) 

We have measured the dynamical structure factor S(Q, w) of diamond with an 

energy resolution of 1 eV FWHM and Q between 0.7 A-' and 3.4 A-' in the highly 

symmetric (001) and (111) direction. In this range the spectra are dominated by 

bandstructure effects, which results in completely different shape and behavior of 

the spectra in both directions. 

The spectra in the I'L direction are dominated by transitions from a low lying vi^ 

lence band into allmost parallel conduction bands. The resulting peaks show almost 

no dispersion but they change in intensity with increasing Q. This change results 

from the q-dependence of the transtion matrix elements. The I'X direction shows 

less and broader peaks. The broadening can be explained by a larger bandwidth of 

each band. 

Diamond (001) 

0 25 50 75 100 125 1 

Energy loss [ev] 

Figure 1. Spectra of diamond in the rX 

direction 

* Supported by US DOE under contract 

# DEAC02-76CH00016. 

Diamond (111) 

- 4 

700 

500 

600 

7 

0 

% 400 

2 

2 300 

- c 

0 

YI 

Y 

.- 

a) c 

- 

200 

'oo0 0 25 50 Energy 75 loss [eV] 100 125 

Figure 2. Spectra of diamond in the rL 

direction 

0 
I Inelastic X-Ray Scatterinn Study of LiF * 1x21 I 

W.A.Caliebe, C.-C.Kao, J.B.Hastings (NSLS), M.H.Krisch, F.Sette (ESRF, 

France), K.Hamfiltiinen (University of Helsinki, Finland) 

Inelastic X-Ray Scattering is a usefull technique to study electronic excitations 

in solids and liquids. By tuning the energy difference between the monochromator 

and the analyzer to an absorption edge, this edge can be studied with a much higher 

incident energy. By changing the scattering angle, different absorption channels are 

excited which results in a change of the line shape. 

We studied with high energy resolution the Li K-edge at -60 eV with an incident 

energy of 7.9 keV for different scattering angles. The spectra are shown in figure 

1. For small Q, they show a relatively narrow peak at an energy loss of 62.5eV. 

This peak increases with increasing Q up to Q=5.7a-l. At medium Q, this peak 

broadens and shifts finally at higher Q to 61.5eV. The increase in intensity can 

be explained by the expression given by Mizuno and Ohmura[l . The shift can be 

explained by the fact that we deal with two peaks, which over 1. app at medium Q 

and cause the broadening. The peak at 62.5eV can be attributed to the ls-+2p 

transition while the peak at 61.5 eV is the 1~42s transition which is optically forbidden. For this reason we do not see this transition at small Q but at higher Q 

the matrix element belonging to this transition increases and finally dominates the 

whole absorption process. A more detailed quantitative analysis is in progress. 

[l] Yikio Mizuno and Yoshihiro Ohmura, J. Phys. SOC. Jap.22, 445, 1967 

loo l_l.I.I.I.I 

55 57 59 61 63 65 

Enorgy IOSS [ov] 

Figure 1. Inelastic X-Ray Scattering spectra for different Q. The vertical lines 

indicate the two peak positions corresponding to the ls-2~ (62.5eV) and 1~42s 

(61.5 ev) transition. 46 

w 

00 

W * Supported by US DOE under contract # DE-AC02-76CH00016. 

broad, double peaked feature. 

*O I- r 1340 0345 

Figure 1. High resolution fluorescence spectra of Ni+' and Ni+' for an incident 

energy of 8340 eV. An energy shift of ~2 eV of the fluorescence line is clearly visible in the spectra and can be attributed to the different oxidation state. 

* Supported by US DOE under contract # DE-AC02-76CH00016. 
; .\ 

I00 A 

;i 

1 , -1. .. . .I 

-, 

High resolution Compton scattering from Li I x21 

., ~ 

. .. 

.. 

Inddonl Enorgy (ov) 

I Inelastic x-ray scattering studies of electronic excitations I x21 I 

J.P. Hill, C.C. Kao, W.A. Caliebe, D. Gibbs (BNL), D. Reznik (NIST) and J.P. 

Wilcoxon (SNL) 

Traditionally the study of electronic excitations has been performed with techniques such as electron scattering and photoemission. Inelastic x-ray scattering 

offers a new window on the study of such processes. It has the advantage that 

the scattering is weak, i.e. in the kinematic limit, for all momentum transfers so 

that both collective and single-particle excitations may be studied and the results 

simply interpreted. In this work, the spectrometer was configured to provide a lev 

resolution with the ability to scan both the incident and final energies. This is 

particularly flexible arrangement, allowing a wide range of electronic phenomena to 

be studied. 

We have carried out preliminary experiments on a number of electronically interesting materials. These include metallic clusters and in particular, mono-dispersed 

samples of aluminum. Here the interest lies in quantum finite size effects which are 

expected to change the excitation spectrum for small (M 30A) cluster size. Initial 

experiments on large clusters (500 A> exhibit bulk-like behavior and work is cur- rently in progress on smaller cluster sizes. We have also studied carbon nanotupes. 

These consist of graphite sheets “rolled up” to form tubes on the order of 10A in 

diameter and 1pm long. For thin walled cylinders, a surface plasmon at 15 eV was seen in electron diffraction experiments. In our x-ray work, we did not observe the 

surface plasmon, however a peak due to the interband transitions is observed at 

5eV. In addition a peak at 30eV, which is ascribed to a plasmon excitation of all 

four valence electrons is observed. In fig. 1, we show the dispersion of these features. 

Finally, the technique of resonant inelastic x-ray scattering, in which the incident 

photon energy is tuned to an absorption edge has been explored in the vicinity of 

the LIII edge of holmium. Data analysis is ongoing. 

1% . . I 

-E*, (e9 8o om 

Figure 1. Left: Total Compton profile of Li measured by scanning the incident 

energy. Right: Fermi break of Li (SI1 [IlOl). The solid line represents the KKR 

theory. Figure 1. Energy loss spectra from carbon nanotubes, taken at a number of mo- mentum transfers. 
' .I , 

~ 

Inelastic X-ray Scattering Study of NiSz-,Se, I x21 

E. D. Isaacs (AT&T Bell Labs), C. A. Burns, (Western Michigan University), 

T.Thio, J. W. Bennett (NEC Research Institute), W. Caliebe, and C.-C. Kao (BNL) 

Mott-Hubbard systems are interesting because they display a rich variety of 

ground states not predicted by simple band theory. In particular, metal insulator trasitions can occur as a result of electron correlations. 

In NiSz-,Se, there is a Mott-Hubard metal-insulator transition for x-0.5 at a temperature of ~80 K. The NiSZ-,Se, is an excellent system in which to study this 

transition since there is no change in the symmetry of the system as a result of the 

transition, as is seen in most other Mott-Hubbard insulators. Recent photoemission 

data [l] has suggested that the addition of Se to NiSz crystals reduces the size of the 

insulating gap, inducing the transition to the metallic phase at lower temperatures. 

Our data was taken on a single crystal of NiSl.sSeo.6 which was placed in a closed 

cycle refrigerator with a Be window to allow x-ray access. Measurements were taken 

at incident energies of 8344 eV in order to take advantages of resonant scattering 

from the Ni. The scattered intensity was measured as a function of energy loss for 

energy losses from -5 to 25 eV with a resolution of -lev. We observed a peak in 

the spectrum at an energy loss of about 4.5 eV. We believe that this feature is due 

to the Mott-Hubbard gap in the crystal. Even with the resonant enhancement we 

only had about 1/2 count per second in the loss peak. Data was taken at several 

different reciprocal lattice vectors in both the insulating and metallic phases. 

Our measurements did not show any significant changes between the metal (T 

-100K) and the insulator (T-70K) phases. Such effects have been seen in the MottHubbard insulator Vz03 [2]. Photoemission studies on NiSz-,Se, show a shift of 

about 0.15 eV for the valence band (at low q). We did see q-dependent changes in 

the energy loss peak. The change in intensity is due in part to a spectral weight 

shift to the Compton energy (h2qz/2m), but there is also evidence for dispersion of 

the eak. Future studies of this system with higher energy resolution are planned. 

Y7A.Y. Matsuura, Z.-X. Shen, D. S. Desseau, C.-H. Park, T. Thio, J. W. Bennett, an 0. Jensen, preprint of article submitted to PRL. 

[2] E. D. Isaacs, P. M. Platzman, P. Metcalf, and J. M. Honig, submitted to PRL. 

0 

0 

E 

10 

-6 0 - 6 10162025 

(*v) 

w Figure 1. Mott-Hubbard Gap in NiS1.sSeo.s in the metallic phase at 100 K at several 

momentum transfers. Numbers in parentheses are Compton Energies. cn 

X22A In-situ x-ray investigation of metal-hydrogen electrodes in thin film 

Ni-MH batteries 

N. Jisrawi, G. Reisfeld (BNL-Physics), H. Wiesmann (BNL-DAS), T. Thurston, 

M. W. Ruckman, B. Ocko and M. Strongin (BNL-Physics) 

Materials changes during the electrical discharging of a thin film Ni-MH battery 

were investigated using x-ray diffraction. The metal-hydrogen anodes were Nb/Pd 

multilayers of the configuration Nb/Pd/Nb/Pd where the Nb thickness ranged from 

200 to 800 A and the Pd thickness was 200 A. The multilayers were deposited on 

Cr-coated glass and placed in a thin windowed electro-chemical cell containing a 

1M KOH electrolyte. A two terminal configuration employing a NiOOH counter 

electrode was used. After charging the cell to a two terminal voltage of 1.2 VI the 

cell was discharged through a 10 Kf.2 resistor and the current monitored. The rate 

of discharge was slow and x-ray diffraction spectra taken at the points indicated on 

the figure 1. The x-ray spectra in figure 2 show the amount of hydrogen in the Nb or Pd because their lattices expand when hydrogen is introduced into the lattice. 

The Nb[llO] and Pd[lll] Bragg peaks shift to smaller 20 when charged with 

hydrogen and return to the metallic position when discharged. It is believed these 

spectra are among the first taken during the operation of a battery and show how the 

hydrogen content is related to battery function. The limited amount of electrolyte 

over the electrode affects the reaction at the electrode surface and may account for 

the anomalous drop in the battery current before all of the hydrogen is discharged 

from the anode. 

This work was supported by the USDOE Div. of Materials Science under CRADA 

BNL 94-03 and Contract No. DE-AC02-76CH00016. 

4000 m! 

E 

m 

H 

w 

-1.6 -1.2 -0.8 -0.4 0.0 

V[VOltS] 

Flguro 2 

7 

6 

5 

4 I 

\ 

I '\ 

I 

3 

2 

1 

LI....,..,.,..,. 

26 27 28 29 30 31 32 33 

20 (des ) 

Figure 1. Battery discharge curve (i vs 

t). 

Figure 2. X-ray spectra taken at the positions marked on figure l. 
Fd w 

N. Jisrawi, G. Reisfeld (BNL-Physics), H. Wiesmann (BNL-DAS), T. Thurston, 

M. W. Ruckman, B. Ocko and M. Strongin (BNL-Physics) 

We conducted a x-ray diffraction study of hydrogen uptake by glass-supported 

Nb/Pd multilayers in an electrochemical experiment. 

The metal-hydrogen anodes were Nb/Pd multilayers of the configuration 

Nb/Pd/Nb/Pd where the Nb thickness ranged from 200 to 800 A and the Pd 

thickness was 200 A. The multilayers were deposited on Cr-coated glass and placed 

in a thin windowed electro-chemical cell containing a 1M KOH electrolyte. A two 

terminal configuration employing a NiOOH counter electrode was used. 

The samples were charged and discharged by a standard cyclic voltammetry apparatus over a voltage range of -1.4-0 V at a scan rate of 1 mV/s. The rate of 

scanning was slow and x-ray diffraction spectra taken at the points indicated on the 

figure 1. The x-ray spectra in figure 2 show changes in the the amount of hydrogen 

in the Nb or Pd because their lattices expand when hydrogen is introduced into the 

lattice. The Nb[llO] and Pd[lll] Bragg peaks shift to smaller 28 when charged with 

hydrogen and return to the metallic position when discharged. It is believed these 

spectra represent one of the first in-situ probes of hydrogen charging of an electrode 

using synchrotron radiation-based x-ray diffraction and provide a convincing identification of CV peaks with the hydrogen phases formed during electrolytic charging 

of a thin film bimetallic electrode. 

X22A X-ray identification of peaks in cyclic voltammetry from Nb/Pd multilayers in a KOH electrolyte * Microstructural Study of at-C Films: Relation to Residual Stresses * 

4 ............................. 

'1 A. 

0 2 4 6 8 10 12 

TIME (hrs.) 

X22A 

.2 Nb[llO] I I 

Figure 1. Cyclic-voltammetry (CV) for a Nb/Pd multilayer. 

III.III ..~I~~~.,.~.~II...III.II * This work was supported by the US- 26 27 28 29 30 31 32 

Figure 2. X-ray spectra taken at the positions markedon figure 1. 

DOE Div. of Materials Science under 20 (des.) 

CRADA BNL 94-03 and Contract No. DE 

AC02-76CH00016. 

I.".I~'"I'''".'.'I.'"I 

Fig. 

6 

5 

4 

3 

2 

1 

* Work supported by the US Dept. of Energy contract No. DE-AC094AL85000. NJD 

acknowledges partial support from NSF Grant No. DMR93-13047 
The commensurate-incommensurate transition of Br on the Au( 100) 

electrode. 

B.M Ocko, O.M. Magnussen (BNL/Physics), J.X. Wang (BNL/DAS), T. Wandlowski (Ulm) 

X22A 

Electrodeposited bromide on the Au(100) surface forms a commensurate c(4 x 

24 R45’ monolayer with a coverage of 1/2 over a range of applied potentials. Here 

the 1! romide atoms reside in two-fold sites rather than four-fold hollows ordinarily 

found for this coverage. At a critical potential the bromide adlayer undergoes a continuous transition to a uniaxial-incommensurate c(& x p)R45’ monolayer where p 

decreases from 1.00 to 0.87 in terms of the commensurate length. The incommensurate phase is well described a uniform compression and is inconsistent with sharp 

domain-walls. The quadratic scaling of the peak widths with the incommensurate 

component of the wavevector suggests that the incommensurate phase exhibits “cumulative disorder”. The potential dependent structure of the bromide adlayer is in 

excellent agreement with the electrochemical characteristics. 

Small Angle X-ray Scattering (SAXS) Investigations of Metal and 

Semiconductor Nanoscale Size Clusters 

II r2a 

X22A, 

X27A 

Figure 1. Real space sketch (a,b) of the 

commensurate C(~X 24)R45’ and incommensurate c(4 x p)R45’ phase and 

the corresponding reciprocal space patterns (c,d). 

0.125 1 (b) 

Or 

0.30 0.35 

0.100 - 0.075 . 

0.050 - 

0.025 . 

I 

0.40 0.45 0.50 0.55 0.60 

Vob [N/WI 

Figure 2. (a Cyclic voltammogram from 

the Au(lOO] surface in 0.05 M NaBr 

and (b) the corresponding incommensurabdity (E) as a function of the applied potential in both sweep directions 

c(4 x p)R45’ phase. The solid line is a power-lawfit to the incommensurability 

with @=0.40. 
c.' 

W 

w The effects of hydrogen adsorption/evolution and bisulfate coadsorption on the structure of underpotentially deposited T1 adlayers 

on Pt(111) * 

X22A, 

X22B 

Synchrotron X-ray Scattering Characterization of High Tempera- x27~, 

ture Superconducting Wires X22A 

J.X. Wang, R.R. Adzic (BNL/DAS), B.M. Ocko, O.M. Magnussen (BNL/Physics) 

T1 forms an incommensurate, aligned-hexagonal phase in acid and alkaline solutions at the most negative potentials prior to its bulk deposition or hydrogen 

evolution. The monolayer compresses, thus the T1 coverage increases, with decreasing potential. In acid solutions, this phase exists in the potential region where 

hydrogen adsorption and evolution occur in the absence of Tlt (Fig. 1). Underpotential deposition (UPD) of T1 suppresses hydrogen adsorption but does not shift 

the onset of hydrogen evolution. On the other hand, the competition of T1 UPD 

with hydrogen adsorption/evolution causes a slightly lowering of T1 coverage and a significant decrease of the in-plane ordering of the T1 monolayer. 

In sulfuric acid solution, a (4 x 4)R3Oo diffraction pattern was observed over a 0.28 V wide potential range, which corresponds to the potentials between the two 

major peaks in the voltammogram. The involvement of both T1 and anion species 

in the (4 x &)R30° lattice structure can be inferred from the absence of the 

diffraction signal in the solutions without either TlS or bisulfates. Specular reflectivity data support the model with 1 3 monolayer of T1 at the hollow sites. It is, 

however, difficult to determine, direct y from surface x-ray scattering, the bisulfate 

coverage and its adsorption sites. The similarity of bisulfate adsorption (without 

T1) and coadsorption (with T1) features in the voltammograms and the positive 

potential shift in the latter case suggest that bisulfate coadsorption is primarily 

through the interaction between bisulfate and Pt. This leads us to the model with 

bisulfates coadsorbing at the hollow sites of the T1 adlayer. In the top view picture 

shown in Fig. 1, T1, Pt, S, and 0 are represented by the circles with the diameters 

corresponding to their relative atomic sizes. It can be seen that the model gives 

adequate interatomic spacings. [im;i 

0.4 -10 

0.3 -10 

92 0 01 0.4 0.6 M 

GUM 

Figure 1. T1 coverages in the aligned-hexagonal (circles) and the 4 x 4)R3O0 

with (solid line) and without(dashed line) 5mM Tit. Sweep rate 20 mV/s. 

(triangles) phases as a function of E and voltammograms in 0.05 M 6 zso4 solutions 

* This work is supported by the DOE, contract DEAC02-76CH00016 
Structure of electrode surfaces in the course of electrocatalytic reactions: oxidation of CO, glucose and formaldehyde on reconstructed 

and unreconstructed Au(100) * ~ 

R.R. Adzic, J.X. Wang (BNL/DAS), B.M. Ocko, O.M. Magnussen (BNL/Physics) 

Atomic scale information on the structure of a catalytic surface during the course 

of reaction has been a goal of surface scientists for many years. There is no information on the stability and activity of reconstructed surfaces in electrocatalytic 

reactions. Here we demonstrate the in situ application of the Surface X-ray Scattering (SXS) to electrocatalysis. Grazing incident angle x-ray diffraction was used to determine the in-plane structure of the Au(100) surface during the oxidation of CO, glucose, and formaldehyde. 

The reconstruction of Au(100) gives rise to a diffraction peak around (1.205, 1.205, 

0.1) position in reciprocal space. This peak is consistent with the hexagonal pattern with A =1.205 ~t0.002, where A is the hexagonal wave vector along the (110) 

direction. 

The electrochemical oxidation of glucose, formaldehyde and CO on gold single 

crystal electrodes are known as structure sensitive reactions with the reactant adsorption preceding the charge transfer. The adsorption of these molecules at negative potentials does not cause a lifting of the reconstruction of the Au(100) surface. 

The potential dependence of the intensity of the reconstruction peak at (1.205, 

1.205, 0.1) was measured in HClOI and NaOH solutions in the absence and in the 

presence of the oxidation of of organic molecules. The oxidation of these molecules 

occurs before, or at the onset of the lifting of the reconstruction. No significant 

change in the kinetics of the reconstruction lifing and recovering is caused by the 

adsorption and oxidation of glucose, CO and formaldehyde. The recovery of the 

reconstruction by the negatively charged electrode surface is a rather slow process. 

This slow recovery of the reconstruction allows us to measure the reaction rates at 

both reconstructed and unreconstructed surfaces over the same potential range. Since the electrooxidation of the above three molecules are structure sensitive 

reactions, a distinct difference in the surface structure of the Au 100) (1x1 and the 

reconstructed is expected to produce an effect on their Lneics. 'I! he unresurface was found to be more active than the hexagonally 

for all three reactions. The apparent heterogeneous 

one order of magnitude larger for the unreconstructed 

Au(lOO)-(lxl) surface. There are two possible origins of the observed difference in 

the activity of the reconstructed and unreconstructed Au 100) surfaces. First, the 

adsorption of these molecules is stronger on the open (100 -(lxl) surface compared 

to the hexagonal close packed surface. Besides that, the reaction is enhanced by 

the stronger adsorption of HzO and AuOH which facilitate the oxidation of CO and 

chemisorbed intermediates in these reactions. 

f 

X22B 

'p 

e 

03 

(0 * This work is supported by the DOE, contract DE-AC02-76CH00016 

Surface freezing in binary mixtures of normal alcohols * I X22B 

A.K. Doerr, O.Gang (Bar-Ilan U.,Israel), X.Z. Wu (Northern Illinois U.), O.M. 

Magnussen, B.M. Ocko (BNL), E.B. Sirota (Exon) and M. Deutsch (Bar-Ilan U.)] 

Surface freezing has been observed recently at the free surface of pure alcohols, 

alkanes and binary mixtures of alkanes with different chain lengths. At temperatures 

up to 3C above bulk freezing temperature, measurements reveal the formation of a crystalline monolayer on normal alkane mixtures and a bilayer on pure alcohols. 

X-ray reflectivity, grazing incidence diffraction and Bragg rod measurements have 

been carried out on the binary mixtures of the alcohol-alcohols and alcohol-alkanes. 

The measurements (Fig.1) show the formation of a bilayer on the alcohol mixtures. 

In some cases the upper layer of the frozen bilayer consisted only of the longer 

chain component and the lower layer-of the shorter chain only. Grazing incidence 

diffraction indicates hexagonal packing and long range positional order within the 

surface layer. In order to describe the Bragg rod measurements (Fig.2) a lateral 

positional shift between the two layers is required as shown in the inset of Fig.2. 

This shift is similar to the shift observed for pure alcohols. A surface layer on 

alcohol-alkane mixtures was obtained only if the chain length of the alkane was about twice the length of the alcohol. In this case the transition from a monolayer 

to a bilayer has been observed. Additional phase transitions in the surface layer 

have been detected in surface tension measurements. 

loo 

10-s 

10-0 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 

qz LA-'] 

Figure 1. X-ray reflectivity for alcoholalcohol mixture CzzOH(30%) in CleOH 

(circles). The solid line is a fit to the 

data. In the insert the e--density corresponding to the fit is plotted. 

* Supported by the U.S. - Israel Binational Science Foundation, Jerusalem 

Figure 2. Bragg rod at in-plane diffraction peak position q7=1.488ft-' for 30% 

CzzOH in ClsOH. The solid line is a 

fit to the data, based on the real-space 

model in the inset. 
I ,, 

I-: . ,- 

X-ray Scattering Study of CEO-propylamine Adduct Monolayers at 1 An X-ray Scattering Study of Methyl Eicosanoate the Gas-Water Interface * 1 X22B I X22B 

W. J. Foster, M. C. Shih, P. S. Pershan (Harvard University) 

Relaxed Langmuir monolayers of methyl eicosanoate were studied using Brewster angle microscopy (BAM) and grazing incidence x-ray diffraction (GIXD). The 

structure of the various phases in this system were determined and compared to 

previous isotherm and microscopy measurements. 

At high pressure and low temperature, an untilted, orthorhombic phase, U CS), 

U S , is observed, beginning at N 12OC. Above 21OC and at high pressure, allotatorI $1 -kke phase is seen, with an undistorted, untilted structure. 

At low pressure and low temperature, a crystalline phase with tilt toward nearest 

neighbor, I Lz”), is observed. At a temperature of N 14OC, there is a transition to 

the temperature continues to be raised at low pressure, there is a transition to a 

phase where the two F(L2’) peaks have the same values of Qmy, here called the T 

phase. 

is observed. As the temperature is increased, a second untilted, orthorhombic p 6 ase, 

a phase wit (h tilt toward next-nearest neighbor, F(Lz’), at low pressure. Finally, as 

- 1 1 I I- 

&* 

Temperature [degrees C] 

Figure 1. T-T phase diagram of Methyl Eicosanoate. The phases are represented as follows: I(Lz”), o F(Lz’), @ T, x U(CS), o U(S), # R(LS). The solid lines represent 

phase boundaries. In the case of the U(CS)-U(S)-R(LS) transitions, the shaded 

regions represent observed limits of coexistence due to supercooling or superheating. 

* This work was supported by grants NSF-DMR-91-13782 and NSF-DMR-94-00396. 

The experiments were carried out on the Harvard/BNL liquid surface reflectometer on 

beam line X22B at the NSLS, BNL. This facility is supported by DEAC02-76CH00016 

Figure 1. Relaxation isotherm measured 

at T= 17.5 degC. 

ai 02 OJ 0.4 05 ot 

Figure 2. Reflectivity normalized by 

Fresnel reflectivity. The fit (solid line) 

corresponds to the electron density profile shown in the inset. 
I Influence of Quantum Impurities on the Soliton Lattice in CuGeOs. I X22B 

V. Kiryukhin, B. Keimer (Princeton University), J. P. Hill, A. Vigliante (BNL) 

Magnetic Phase Diagram of the Spin-Peierls System CuGeOa I X22B 

V. Kiryukhin, B. Keimer (Princeton University), J. P. Hill, A. Vigliante (BNL) 

The interaction of localized impurities with correlated electron systems is a topic of great current interest in fields ranging from one-dimensional magnetism to high 

temperature superconductivity. A particularly interesting observation has recently 

been made in the spin-Peierls compound CuGeO3. In this material the spin chains 

consist of spin 1 2 CuZt ions which interact antiferromagnetically with their nearest 

neighbors. In t h e absence of impurities the spin chains dimerize at low temperatures and form a nonmagnetic collective singlet state, the spin-Peierls state. Several 

groups have substituted dilute amounts of ZnZt spin-0) or Nizt spin 1 for CuZt 

and found that the spin-Peierls state is rapidly rep (l aced by a Nee1 state ( .-2 his behavior undoubtedly reflects a competition between the interchain magnetic exchange 

interaction (which favors the NOel state) and the spin-lattice coupling (which favors 

the spin-Peierls state), but it has not yet been explained why the balance between 

these two interactions is tipped by diluting the spin-chains. The goal of our x-ray 

experiment was to elucidate the effects of impurities on the magnetic phase diagram of CuGeOs on a microscopic level. We studied the spin-Peierls superlattice 

reflections in two samples, CuO.986ZnO.016 GeO3 and CUO.Q~N~O.OZG~O~, as a function of magnetic field and compared the results with analogous measurements in 

pure CuGeO3. Both samples undergo spin-Peierls transitions, but the transition 

temperature and the commensurate-incommensurate (C-IC) transition fields are 

depressed. While the C phase remains long range ordered, we found that the IC 

superlattice reflections are severely and anisotropically broadened (Fig. 1). In the 

spin chain direction the correlation length is the longest but even in this direction 

it is comparable to the average distance between the impurities. This presumably 

means that the magnetic solitons are strongly pinned at or near the impurities. 

While the IC wavevector discontinuously jumps to a nonzero value at the C-IC 

transition of pure CuGeOa signaling a (weakly) first order transition, there is no 

sign of such a discontinuity in the diluted samples. This indicates that the C-IC 

transition becomes second order as impurities are added, but further studies are 

necessary to prove this point definitively. We are also planning further experiments 

on samples with higher impurity concentrations in order to elucidate the crossover 

from the spin-Peierls to the NBel state. 

Figure 1. Scans through the (3.5,1, 2.5) reflection of Cuo.~e6Zno.o16GeO3 a) parallel 

and b) perpendicular to the spin chains. The scan in b) is along (3.5, 1, 0 , only 9' 

away from the &axis. The temperature is 4K and the 10 Tesla and 11.6 4 esla data 

are below and above the C-IC transition respectively. The data for 11.6 Tesla were 

multiplied by 10. 

4d 

CL 

One Dimensional (1D) quantum magnetism has been the subject of great 

experimental and theoretical interest for the last three decades. In certain 1D 

magnets, coupling of the spin degrees of freedom to the lattice results in a low 

temperature structural transition, the spin-Peierls transition, at which the lattice 

dimerizes to lower the magnetic ground state energy. The lattice coupling allows 

the application of x-ray scattering techniques to this problem. 

We have shown that synchrotron radiation combined with a superconducting 

magnet capable of generating a 13 Tesla field is a very powerful tool to study a particular such 1D magnet, the recently discovered sgin-Peierls compound CuGeO3. 

In this system the Zeeman energy corresponding to a - 12T field lowers the energy 

of the first excited state enough to drive a magnetic field induced transition into an incommensurate (IC) spin-lattice modulated phase. 

The nature of this phase is intimately related to the nature of the excitation 

spectrum and has been the subject of much theoretical work. Prior to our experiments the IC phase had been inaccessible to scattering probes. By measuring first 

and (weak) third harmonics of the IC superlattice reflections (see Fig. 1) we have 

shown that the high-field phase is a multisoliton state (soliton lattice) and measured both the intersoliton distance and the soliton width as a function of field and 

temperature. The resulting magnetic phase diagram, consisting of commensurate, 

incommensurate, and undistorted phase, is in qualitative agreement with theoretical predictions. In particular, we have confirmed the prediction that the IC phase 

is reentrant in temperature over a certain field range. However, our data analysis 

has also revealed some startling quantitative discrepances with extant theoretical 

predictions. In particular, the measured soliton width is almost twice as large as 

predicted. An explanation of our data is a challenge for the theory of 1D quantum 

magnetism, and we expect significant interest in our work in theoretical community. 

63.5 1 2.5) Suporlalllco Roflocllon 

lo F------l 

L (.leu.) J 

Figure 1. Scans through the (3.5, 1, 2.5) superlattice reflection of CuGeO3 at T=4K 

in the Incommensurate phase. Successive scans were multiplied by 100 in order to 

achieve a constant offset on the logarithmic scale. The lines are the results of fits 

to resolution-limited Gaussians. 
. . ,~ 

Fd w 

h2 

1 Si-based MOS devices studied by x-ray reflectivity I X22B 

S.D. Kosowsky, P.S. Pershan (Harvard Univ.), K.S. Krisch, J. Bevk, M. Green, 

L.C. Feldman and P.K. Roy (AT&T Bell Labs) 

Specular reflectivity measurements were performed on a series of polySi/SiOz/Si(OOl) MOS structures, with thin (<lo0 A) oxide layers, which are relevant to current microchip technology. The samples consisted of single crystal 

substrates with Si02 layers grown on top. A 2500 A heavily-doped polycrystalline 

silicon (poly-Si) layer formed the conducting cap. The devices were prepared at 

AT&T production and research facilities in Allentown, Orlando and Murray Hill, 

under different sets of growth and annealing conditions. The goal of this work is to 

relate structural properties to processing parameters. 

Two reflectivities are shown below with the corresponding real space profile derived by fitting the x-ray scattering with a layered model. The two data sets shown 

are from two identically fabricated MOS capacitors, except that one had a final 

activation anneal b) and one did not (a). The reflectivity data, R(q), has been 

divided by the weh-known Fresnel curve, Rf(q , and the corresponding real space 

space model. (1) The steep fall off in the R/R, for q<0.2 A-' results from the 

rough poly-Si/vacuum interface. This interface is 15-50 A rough (rms), with higher 

roughness values resulting from higher annealing temperatures. (2) The bump in 

the R/Rf of the unannealed sample, centered at q=0.55 A-', corresponds to a dense, 5 Ang layer at the SiO2/Si(OOl) interface. This layer is unstable to hi h 

temperature (>800 "C) annealing as it is absent from the annealed sample. 6) The oscillations in the unannealed sample, corresponding to the oxide thickness, 

are modulated. This modulation implies structure at the Si02 /poly-Si interface as 

well, and a diffuse, 3-8 A layer allows the data to be fit. The absence of modulation 

in the annealed sample is due to the disappearance of the SiO2/Si(OOl) layer upon 

annealing. 

(D 

fits are also shown below. Several features oft l! e data can be interpreted in a real 

1 '.I0 t 1 

Figure 1. Fresnel normalized reflectivi- -m o m an m BO IW I (9 ties for two MOS samples, one annealed 

(b) the other not (a),otherwise prepared 

identically. the two samples. 

Figure 2. Real space density profiles for 

X-ray diffraction studies of thiols on liquid Hg * 

O.M. Magnussen, B.M. Ocko (BNL), M.J. Regan, P.S. Pershan (Harvard), M. 

Deutsch (Bar-Ilan, Israel) 

We have previously demonstrated that liquid Hg [l] and Ga [2] exhibit surface 

induced layering, in accordance with decade old theoretical redictions. Here we 

present x-ray scattering results on films of organic molecules [alkane-thiols) on the 

liquid Hg surface. For thiols with hydrocarbon chain lengths between 8 and 18 

molecules well-defined mono- and qultilayer structures were observed. As an example, the normalized x-ray reflectivity spectrum, R/Rj , from an adsorbed octadecanethiol monolayer on Hg is shown in the figure along with the spectrum from the 

pure Hg/vapor interface. The interference between the reflected amplitudes from 

the vapor/thiol and thiol/Hg interfaces gives rise to the observed modulated reflectivity spectrum. The modulation period corresponds to a fully extended alkane 

chain and the amplitude supports the notion of a densely packed monolayer. Remarkably, the essential features of the reflectivity, including the quasi-Bragg peak 

and the dip at small qzl are identical with and without the thiol monolayer. This 

clearly supports the notion that the surface layering is an intrinsic feature of the Hg 

surface. For higher dosages of thiols very smooth multilayer structures are formed. 

Complementary in-plane x-ray diffraction measurements indicated that thiol multilayers are well ordered and are packed in a distorted hexagonal arrangement parallel 

to the surface plane while no in-plane ordering was observed for thiol monolayers. 

[l] O.M. Magnussen et al., Phys. Rev. Lett. 74, 4444 (1995) [2] M.J. Regan et 

al., Phys. Rev. Lett. 75, 2498 (1995) 

I X22B 

0 0.5 1.0 1.5 2.0 2.5 

Q, 

Figure 1. X-ray reflectivity (R/Rr) from the clean Hg vapor interface (dashed line) 

and from a octadecane thiol (18 carbon atoms) terminated Hg surface (circles). 

~ 

* This work has been supported by the DOE and the NSF under Contract No. DEAC0276CH00016, DEFG02-88-ER45379, and NSF-DMR-9400396. 
4d 

F 

(D 

W * Research supported by NSF Grant No. ECS-92-01986 

I A Study of the SmC* Liquid Crystal-Glass Substrate Interface * I X22B I 

L. J. Martinez-Miranda (U. of Maryland at College Park) 

We have studied the structural evolution as a function of film thickness of films 

of the room temperature smC* mix mx5112, which has a smA - smC* at 46"C, 

deposited on 10pm period gratings. There is a homogeneously aligned layer for 

films as small as lpm thick, which is ten times smaller than the critical thickness 

observed for similar films of the compound 8CB [l]. The experiments used 9keV 

x-rays, focused on a spot of 2mmz at the sample position. The detector slits were 

kept at a 10(vertical)x4(horizontal)mmz opening. We studied the regions of varying 

smectic layer orientation by changing the value of the angle x: this scan is equivalent 

to changing the value of the out of plane component of 1 in reciprocal space. The 

diffraction angles 0,20 are held constant at the Bragg value for mx5112. At x = 

90°, the observed scattering corresponds to smectic layers parallel to the surface of 

the gratings (molecules perpendicular to the plane of the substrate). Conversely, at 

x = O", the signal observed corresponds to smectic layers aligned perpendicular to 

the plane of the substrate (molecules parallel to the plane of the substrate). The 

nominal angle of incidence ct in these runs was !".Finally, we performed azimuthal 

&scans as well as in-plane Bragg scans at x = in order to observe the degree of 

in-plane disorder. For these scans, q5 = 0" corresponds to the [loo] direction. 

We have concentrated on the structural evolution of order in mx5112 films of 

thicknesses ranging between 2 and 15 pm. Films thinner than 10pm exhibit an evolution of molecular layer spacing as a function of depth within the sample. In 

particular, the layers closest to the LC-glass interface show a time dependence in 

azimuthal ordering, with the molecules rotating in the direction of the gratings over a 5- hour period. The LC layers are more smb-like near the LC-glass boundary in 

this case. The in-plane LC layer spacing stabilizes at an intermediate size beyond a film thickness of lOpm, while the out-of-plane spacing decreases in the same region. 

This result suggests that the LC-glass interface pins the layer tilt, leaving the film 

in a quenched state. A quantitative analysis of these results is in progress at the 

moment. 

In addition to the measurements above, we have studied the LC-glass interface on both a 15pm mx5112 film as well as a 29pm 8CB film by performing a reflection 

scattering study through the surface of a 0.25 mm grated glass substrate, on the airLC-glass confined system. A comparison with the above results on mx5112 shows 

consistency in the observations performed through either interface. This part of the 

project uses the absorption of the xray beam by both glass and the LC to control 

the penetration depth of the beam through both. This measurement constitutes a very important step in our ability to observe the structure of LC interfaces in 

prototype LC devices. 

[l]. E. Smela and L. J. Martinez-Miranda, J. Appl. Phys.,77, 

1923 (1995). 

I X-ray Induced Electrostatic Charging of Helium Films I X22B I 

K.Penanen, P.S.Pershan, M.Regan, and 1.F.Silvera (Harvard) 

It is well known that free electrons can be held onto the free surface of liquid helium through either their own image charges or through the effect of an externally 

applied electric field. The resultant electrostatic pressure causes films to thin. We 

have measured x-ray specular reflectivity from static films of isotopic mixtures of 

helium with an intense x-ray beam in the temperature range between 0.37 K and 

1.3 K. Normally, no significant thickness variation with x-ray intensity is expected 

over a wide range of temperatures when the film is superfluid. We have found 

that even modest x-ray intensities affect the thickness of films containing only trace 

amounts of 'He. Figure 1 shows the measured ratio R/Rpresne~ for a mixture with 

trace amounts of 'He at 0.47K for three different intensities. The thickness for small 

intensities is of order 200 A, in agreement with the theory and pure 4He data for 

higher temperatures taken by Lurio et al. At higher intensities the film thins, with 

poorly defined thickness due to variation of the intensity with the incident angle. 

At higher concentrations of 'He the period of the interference fringes becomes irregular and the determination of the film thickness becomes problematic. Figure 2 

demonstrates this point. We believe that the effect is due to x-ray produced photoelectrons, which thermalize in the vapor and then reside on the surface, attracted 

by both the film and a charged substrate. The temperature and concentration dependence is then due to the transport properties of the electrons at the surface. It 

may be possible to study the 2-D electron gas produced in this way by diffraction 

techniques . This research was supported by Grants No. NSF-DMR-89-20490 and No. NSFDMR-88-12855. NSLS, Brookhaven National Laboratory, is supported by DOE 

Contract No. DE-AC02-76CH00016 

001 0.04 0.07 0.10 n I, /A"* 

Figure 2. Structure factor as a function 

of the wave vector transfer Q = ?sin0 " ,.,-v, 

for a range of temperatures and bulk 'He 

concentrations. The curves were sep+ 

rated by 0.5 for clarity. 

Figure 1. X-ray dosage effect on a film 

containing trace amounts of 3He 

I Charge density waves in Laz-,-,Nd,Sr,Cu4. I X22B I The surface structure of Au(ll1) in the presence of organic adlayers 

- A combined electrochemical and surface x-ray scattering study. 

A. Vigliante, J. Tranquada, J. D. Axe, Doon Gibbs, B. Ocko (BNL) 

Several Studies on cuprate systems have established that the suppression of the 

superconductivity in Laz-=Ba,CuO4 when x=1/8, requires both a hole concentration of 1/8 per Cu and a distortion from the low-temperature-orthorhombic (LTO) 

to the low-temperature-tetragonal (LTT) structure. One system that is particularly 

convenient to investigate this phenomena is La2-m-yNdySr,Cu04 with y=0.4 and 

x=0.12, due to the coexistence of the 1/8 hole concentration and the LTT phase. 

J. Tranquada et al. [Nature 375, 561 (1995)] have found evidence, by Neutron 

Diffraction, of long-period commensurate ordering of antiferromagnetic stripes separated by charge domain walls in the LTT phase. The magnetic modulation peak 

associated with the spin stripes order was clearly observed at (1/2, 1/2fe, 0) with 

~=0.12. The charge modulation peak associated with the hole stripes order should 

be essentially two dimensional, with the modulation wave-vectors (f26, 0, 0) for the 

vertical stripe layers and (0, f2e, 0) for the horizontal stripe layers. The neutron 

experiment shows the evidence of a peak in the LTT phase at (0, 2-26, 0) with E= 

0.12. The intensity of the observed peak is N lo-' that of the strong (0, 2, 0) 

nuclear reflection. Since Neutron Scattering detects the modulation charge peak indirectly, a complementary X-Ray Scattering experiment was performed to confirm 

the Neutron results. A small peak, of the order of N lo-' with respect to the charge 

Bragg peak (0, 2, 0), at (0, 1.76, 0) was observed below the LTO-to-LTT transition 

temperature of T,=70K. The presence of a high, sample related, background and 

the two dimensional character of the scattering made this experiment quite difficult 

and further studies are needed to better quantify this phenomena. 

Th. Wandlowski (Ulm), B. M. Ocko, O.M. Magnsusen (BNL Physics), W. Wu, J. 

Lipkowski( Guelph) 

In-situ x-ray scattering studies of the Au(ll1 electrode surface have been carried 

incidence angle diffraction. At sufficiently negative potentials the (pxfi) surface 

reconstruction forms with a stripe separation p = 23. The formation of a twodimensional condensed uracil film or a complete monolayer of planar-oriented pyridine or 2,2'-bipyridine hinders the lifting of the reconstruction. Whereas the stripe 

separation increases continuously over a 0.6V range, in the base electrolyte the 

presence of the organic compounds blocks this process considerably. Only a small, 

step-like increase in p is observed, where the adlayer is disordered. There exists a 0.7V hysteresis between the lifting and the subsequent formation of the reconstruction. The pxd) phase reappears at potentials where a gas-like adlayer is 

employed to study the time dependence of this substrate transitions for the system 

uracil/Au(lll). The kinetic studies demonstrate that the substrate surface reconstruction/deconstruction kinetics follow nucleation-and-growth-based mechanisms. 

The lifting of the reconstruction in the presence of uracil proceeds in two steps, 

which involve the disintegration of the (pxd) phase and the transformation of a 

disordered surface structure into an ordered (1 xl) phase. The potential-induced reconstruction can be described by an Avrami-type formalism with exponents ranging 

between 1.9 and 2.3. 

out in KC104 solutions containing uracil, pyri d. ine or 2,2'-bipyridine using grazing 

formed again. d yclic diffractograms and potential step measurements have been 

tls 

-20 0.0 20 40 Kl 80 loo 

4.8 4A OJI 04 0.8 t1s 

Ewd" 

Figure 2. Time dependence of the 

(0,1,0.2) intensity after application of a potential step from either ?=-0.8 V (A) or 0.70 V (B) to various final potentials. 

Figure 1. Cyclic Voltammogramm for 

uracil and stripe separation for some or- ganics on Au(ll1). 
.. . . .. 

-. 

The effects of hydrogen adsorption/evolution and bisulfate coadsorption on the structure of underpotentially deposited T1 adlayers 

on Pt(ll1) * 

J.X. Wang, R.R. Adzic (BNL/DAS), B.M. Ocko, O.M. Magnussen (BNL/Physics) 

T1 forms an incommensurate, aligned-hexagonal phase in acid and alkaline solutions at the most negative potentials prior to its bulk deposition or hydrogen 

evolution. The monolayer compresses, thus the T1 coverage increases, with decreasing potential. In acid solutions, this phase exists in the potential region where 

hydrogen adsorption and evolution occur in the absence of T1+ (Fig. 1). Underpotential deposition (UPD) of T1 suppresses hydrogen adsorption but does not shift 

the onset of hydrogen evolution. On the other hand, the competition of T1 UPD 

with hydrogen adsorption/evolution causes a slightly lowering of T1 coverage and a 

significant decrease of the in-plane ordering of the T1 monolayer. 

In sulfuric acid solution, a (4 x 4)R3Oo diffraction pattern was observed over a 0.28 V wide potential range, which corresponds to the potentials between the two 

major peaks in the voltammogram. The involvement of both T1 and anion species 

in the (4 x ~)R30° lattice structure can be inferred from the absence of the 

diffraction signal in the solutions without either T1+ or bisulfates. Specular reflectivity data support the model with 1 3 monolayer of T1 at the hollow sites. It is, 

coverage and its adsor tion sites. The similarity of bisulfate adsorption (without 

T1) and coadsorption :with T1) features in the voltammograms and the positive 

potential shift in the latter case suggest that bisulfate coadsorption is primarily 

through the interaction between bisulfate and Pt. This leads us to the model with 

bisulfates coadsorbing at the hollow sites of the T1 adlayer. In the top view picture 

shown in Fig. 1, T1, Pt, S, and 0 are represented by the circles with the diameters 

corresponding to their relative atomic sizes. It can be seen that the model gives 

adequate interatomic spacings. 

X22A, 

X22B 

however, difficult to determine, direct I y from surface x-ray scattering, the bisulfate 

Figure 1. T1 coverages in the aligned-hexagonal (circles) and the 6 x 4)R30° 

with (solid line) and without(dashed line) 5mM Tit. Sweep rate 20 mV/s. 

(triangles) phases as a function of E and voltammograms in 0.05 M B zSO4 solutions 

* This work is supported by the DOE, contract DE-AC02-76CH00016 

I X-Ray Study of Orientational Correlations in CSO above 260K * I X22B I 

P. Wochner, J.D. Axe (BNL), P.C. Chow, S.C. Moss (U. of Houston), J.W. Dykes, 

S.H. Irons, J.Z. Liu, R.N. Shelton (U. of California, Davis) 

Premonitory orientational fluctuations above the first order phase transition of 

C6o at 260K have been studied by diffuse X-ray scattering experiments. These 

experiments probe the orientational pair correlations between c60 molecules as a function of their separation and therefore the orientational potential. In addition 

to the diffuse scattering due to the orientational disorder of single molecules, we 

have observed zone boundary diffuse scattering at the X-points related to the Pa3 

low temperature structure up to 300K (Fig. 1). An additional set of diffuse peaks, 

which are even at room temperature comparable in intensity to the former ones, 

L. Pintschovius et al. 

of both sets of diffuse 

peaks shows only a weak increase in approaching T,, indicative of a strongly first 

order transition. Additional intensity with a very weak tem erature dependence but 

similar correlation length has also been found at (0.5,0.5,0p and (0.5,0,0) positions. 

The diffuse intensity at the L, C and A points has probably its origin in competing 

phases which are not stabilized at low temperatures. The analysis of the data using 

orientational model potentials is in progress and will be a good test for all the 

theoretical models predicted so far. 

have been found at (0.5,0.5,0.5) positions (L-point) Fig. 1). Similar results 

have recently been reported by P. Launois et al. 

[2]. The temperature dependence of the integrated 

P. Launois, SI Ravy, R. Moret, Phys. Rev. B 52, 5414 (1995) 

L. Pintschovius, S.L. Chaplot, G. Roth, G. Heger, PRL. 75, 2843 (1995) 

1110) done lhrouah 1236) at 265K 

Figure 1. Contour plot of diffuse intensities in the (110) reciprocal lattice plane 

centered on the (236) Pa9 reciprocal lattice point. The X-point at (236) and the 

L-points at (2.5,2.5,5.5 and (1.5,3.5,5.5) are marked by a dot and a square, respecto the strongly Q-dependent background from Laue-scattering off the single c60 

molecules. 

tively. The apparent s h ift of the diffuse maxima away from these positions is due 

* Work at BNL supportedby the Divisions of Materials Science, USDOE, under contract 

DE-AC02-76CH00016 and at Houston by the NSF on DMR-9208450 and the State of Texas 

at the Texas Center for Superconductivity. 
x22c The Magnetic Structure of GdNizBzC by Resonant and NonResonant X-Rav Scatterina * 

10' 

C. Detlefs, A. I. Goldman, C. Stassis, P. C. Canfield, B. K. Cho (Ames Lab), 

J. P. Hill, and D. Gibbs (BNL) 

- 

Resonant and non-resonant X-ray magnetic scattering techniques have been used 

to study the low temperature magnetic structure of GdNiZBzC. 

As the temperature was lowered below 19.4 K, the NCel temperature, magnetic 

scattering developed as satellites of the charge peaks at (hrtqa, k, I) with qa ranging 

from 0.550 to 0.553 over the temperature range studied. As shown in fig. 1, the low 

temperature (T 5 13.6 K) scans of the (2 - qa, 0,O) peak taken at the Gd LZ energy 

exhibit a strong resonant scattering contribution. Above approximately 13.6 K, 

however, the resonant enhancement of the magnetic scattering is essentially absent 

(see fig. le so that the intensity and line shape of the magnetic scattering observed 

non-resonant magnetic scattering persists up to the NCel temperature. 

The cross sections for the resonant and nonresonant magnetic scattering show 

that the absence of significant resonant scattering at the magnetic wave vector 

between 13.6 K and 19.4 K, and the presence of non-resonant scattering imply that, 

in this temperature region, the ordered moment is oriented in the basal plane and 

transverse to the modulation wave vector (e. g. M 11 b for the a-axis modulation), as was found for ErNizBzC by neutron diffraction. Below 13.6 K, however, the 

observation of resonant enhancement implies that an ordered component of the 

moment exists in the scattering (a,c)-plane. 

In order to determine, more precisely, the direction of the moment below 13.6 K, 

we have carefully measured the integrated intensity of a series of satellites along 

the a*-axis both on and off the resonance condition at the lowest temperature 

accessible (3.5 K). From these measurements, we deduce that below 13.6 K the 

moment remains transverse to the propagation direction and acquires a component 

out of the basal plane. 

at the Gd i 2 edge is comparable to the non-resonant data set taken at 7.0 keV. The 

210' 

2 

'lo'. 

21$- 

10' 

g 

Figure 1. The results of fits to the complete data set obtained from the non-resonant 

(a,b,c) and resonant (d,e,f) measurements showing the evolution of position, intensity and width of these peaks. Fd 

w 

CD 

4 * Work supported by DOE DE-AC02-76CH00016. 

. 

- 

.+k -4 

Charge Density Waves in Doped Chromium * I x22c 

J.P. Hill and B.J. Sternlieb (BNL) 

The [Ar]3d64s1 electronic configuration and bcc crystal structure of pure 

chromium metal results in a band structure whose major components in reciprocal 

space are an electron octahedra at the zone center, I' and a somewhat larger hole octahedra located at the corners, H, of the Brillouin zone. Large portions of the Fermi 

surface can then be "nested" via an incommensurate wave-vector Q% = (lf6,0,0). 

As a result, a linear spin density wave (SDW) forms below the Nee1 temperature 

TN = 311K, accompanied by a charge density wave (CDW) of twice the wavevector. These phenomena are exquisitely sensitive to electron density. Doping with 

electron donors, such as manganese or rhenium increases the size of the electron 

pocket and drives the system towards commensurability. While the SDW in doped 

systems has been much studied, in particular by neutron scattering, the CDW has 

not yet been observed. X-rays are particularly well matched to the study of CDW's 

and we have therefore carried out a preliminary study of C~o.g~siWno.oor. We find 

that as in pure chromium there is a CDW of twice the wave-vector of the SDW 

observed by neutron scattering. In fig. 1 we show a scan taken along the (HOO) 

axis which displays two satellites of the (200 Bragg peak, corresponding to the two 

which implies that the modulation is not sinusoidal. 

This in turn implies that the SDW is not sinusoidal either. Similar behavior 

has been previously seen in pure chromium. Interesting questions for future work 

include a study of the temperature dependence of the harmonics which will provide 

information on the coupling of the CDW to the SDW, and a high resolution study 

of lineshape widths to elucidate pinning effects. 

choices of nesting vector. In addition, we o 13 serve a second harmonic to the CDW 

* Work supported by DOE DE-AC0276CH00016 
x22c Incommensurate Antiferromagnetism in the Intermetallic Superconductor HoNizBzC * 

J.P. Hill, B.J. Sternlieb, D. Gibbs (BNL), C. Detlefs, A.I. Goldman, C. Stassis. 

P.C. Canfield and B.K. Cho (Ames Lab. and ISU). 

Superconductivity arises from the Bose condensation of Cooper pairs; a pairing 

of electrons of opposite momenta and spin. In most superconductors even dilute 

concentrations of paramagnetic impurities suppress To , or destroy the superconductivity completely. However, for antiferromagnetic order the competition is less 

direct and the two ground states can, in principle, coexist microscopically. Interest 

in this competition has been reawakened by the discovery of a new class of magnetic 

superconductors, RNiz Bz C. These have superconducting transition temperatures, 

TC as high as ToA6.6 K (for R=Lu) and Ndel temperatures as high as TN = 10.3K 

(for R=Dy). The antiferromagnetism is characterized by a rich variety of phases 

among the different members of the series, including simply commensurate and 

incommensurate structures. 

We have carried out a study of the magnetic phase behavior of HoNizBzC 

(Tc=8.5K1 TN M 7K), utilising resonant magnetic x-ray scattering. This compound exhibits a large reduction, or extinction, of the superconducting order parameter 

in the incommensurate antiferromagnetic phase. We find that at low temperatures, 

T<5 K, the superconductivity coexists with a well ordered, commensurate Ndel 

state with a correlation length of M 5300A. 

In the incommensurate antiferromagnetic state, 5K < T < 7K, we find two phase 

coexistence between an a-axis modulation and a c-axis basal plane spiral. Fig. 1 

shows a scan along the (OOL) direction in the vicinity of the (003) position, taken in 

the incommensurate phase. Surprisingly, the c-axis structure is characterized by two 

wave-vectors. One of these modulations is extremely well ordered, with correlation 

lengths well in excess of 5000A while the other is more disordered, E = 600A at 

T=5.4 K. In addition, short range ordered fluctuations of the commensurate phase, 

observed for T>5 K, are present above Tc-1~. We believe that these are the result 

of local strains. 

HoNi2B2C (OOL) Scan 

u18 290 292 294 296 298 aw 3 02 

L (r.1.u.) 

Figure 1. L Scan in the vicinity of the (003) antiferromagnetic reciprocal lattice 

position 

* Work supported by DOE W-7405-ENG-82. 

Observation of x-ray magnetic scattering in NdzCu04 * I x22c 

J.P. Hill, A. Vigliante, D. Gibbs(BNL), J.L. Peng and R.L. Greene(U. Maryland) 

In order to develop a comprehensive understanding of the high Tc superconductors, it is useful to study the parent compounds to characterize the underlying 

insulating state from which the superconductivity develops. Of particular interest 

are their magnetic properties, and here common features are seen in LazCu04, the 

progenitor of the hole doped superconductors, and NdzCuO4 and PrzCuO4, the pre- cursors of electron carrier superconductivity. There are, however, some important 

differences, including the presence of the rare-earth ions in the electron superconductors. These ions carry localized 4f moments, which can themselves order. In this 

work, we report a study of NdzCuO4, utilizing resonant x-ray magnetic scattering. 

The main advantage of this technique is the possibility of separating the ordering of the Nd moments from that of the Cu moments by tuning the incident energy to 

a Nd absorption edge. In addition, high spatial resolution offers the possibility of 

examining mesoscopic length scales. 

The experiments were performed by tuning the incident energy to the Nd LI, LII, 

and LIII absorption edges. The largest count rates, up to 300 counts per second, 

were obtained at the LII edge. Antiferromagnetic long range order is seen below 

TNd = 37 K. The Bragg peaks are resolution limited, corresTonding to correlation 

lengths of taa 2 2300f100A in the plane and 2 7500zk400A perpendicular to the 

plane. Polarization analysis confirms that the scattering is magnetic in origin and 

consistent with a dipole excitation, suggesting that the Nd 5d bands are polarized. 

In fig. 1 the intensity of the (0.5,0.5,8) magnetic Bragg peak is plotted as a function 

of temperature. There is no appreciable ordered Nd moment above T M 37K. At 

low temperatures the ordered moment is seen to rise rapidly. These results confirm 

earlier interpretations of neutron-scattering data. 

Figure 1. Magnetic Bragg peak intensity as a function of temperature. Solid line is a guideto the eye. 

* Work supported by NSF DMR 9209668 
I X-ray magnetic scattering from single crystals of UPd2A13 

S. Langridge (ESRF, EITU), G.H. Lander (EITU), N. Sat0 (U. Sendai), and D. 

Gibbs (BNL) 

The aim of this experiment was to examine the critical scattering in the heavyfermion compound UPdzAls. The crystal, which had previously been examined by 

neutrons, was polished but not annealed. A mirror finish was apparent to the eye. 

The mosaic FWHM=0.12’. Magnetic scattering of ~15,000 cts/sec was observed at 

the (0,0,1.5) reflection below TN. The results of the experiment provide (probably) 

little information about the intrinsic properties of UPdzAls, but new insight into 

the “two-length scale” problem. Two figures of the “raw data” are given below, 

both from scans of the (0,0,1/2) reflection. 

Figure 1 shows the decrease of intensity with T. Note especially the linear T scale. 

Scattering can stiU be seen at a reduced temperature t = 0.35, which is highly 

unusual. The width of this scattering increases considerably, also approximately 

linearly on semilog scale, but the extracted widths depend on the fits to the data. 

Figure 2 shows the change of the position of the center of the antiferromagnetic 

(O,O, 0.5 peak as a function of T. Over this range the “apparent” c-axis changes 

by ~0.6 4 0. In fact, the bulk c-axis spacing does not change, but the material giving 

rise to the magnetic “critical” scattering exhibits a change in d-space. More likely, 

this represents a change of TN at the surface and the changing width is related 

to the particle size. TEM studies are now in progress to characterise the surface. 

Different fitting procedures are also under consideration. 

-1- 

12’ 

3’ 

:4: 

., Figure 2. Change of position in L of the 

Figure 1. Decrease of centre of the magnetic scattering as a intensity with T 

=f for the (0,0,1/2) reflection. function of T. W 

D. Gibbs et al. Phys. Rev. B 43, 5663 (1991) 

J. P. Hannon et al., Phys. Rev. Lett. 61, 1245 (1988) 

S. Kawamata et al. JMMM 104-107, 51 (1992) 

R. A. Robinson et al. Phys. Rev. B 47, 6138 (1993) 
4d 

h2 

0 

0 

120 

im 

E 

c P- 

! 

6- 

20- 

Resonant magnetic x-ray scattering study of DyFedAls I x22c 

S. Langridge (ESRF), J.A. PaixLo (U. Coimbra), G.H. Lander (EITU) and D. 

Gibbs (BNL-Physics) 

- 

- 

DyFedAls has the tetragonal body centred structure of ThMnlz. In the RFedAle 

@=Actinide or rare-earth) systems almost all the Fe atoms sit on the 8(f . This 

allows a study of both the transition metal and rare-earth sublattices anhof the 

interactions between them. From neutron and transport property studies [l] the Fe 

atoms are known to order at ~175K with a temperature independent wave-vector of 

7=(0.133,0;133,0), close to the commensurate value of 2/15. At approximately 35K 

the Dy atoms order with the same magnetic wave-vector. The magnetic structure 

is complex and not completely characterised. Using a polished single crystal (with a mosaic width of 0.04') resonant magnetic x-ray scattering was observed at the 

Dy LrIr resonance (E=7.79keV . Representative scans are shown in figure 1 around 

the (220) and (330) charge pea h s. Around the (220) charge peaks symmetric satellites were observable at the +r and f27 positions. The energy and temperature 

dependence of the f.r peak show that it is magnetic in origin whilst the f27 peaks 

arise from a displacement of the Fe atoms. The crystallographic symmetry is such 

that only the Dy atoms contribute to the scattering around the odd satellites (lower 

panel in figure 1). No scattering was observed at the 37 position. Following the 

superlattice peaks as a function of temperature (figure 2) it is clear that a signal 

exists at the (3&7,3f.r,0) position up to zllOK. Resistivity and susceptibility me% 

surements also indicate an anomaly in this temperature range [l]. The scattering is 

also strongly energy dependent. Since electric dipole contributions usually dominate 

the enhanced magnetic scattering we can speculate that the scattering is a result 

of the polarisation of the 5d conduction electrons by the Fe field. Below 30K there 

is a large enhancement in the magnetic signal corresponding to an increase in the 

ordered Dy moment consistent with neutron and Mossbauer measurements [2,3]. 

Similar effects have been observed in a Nd high Tc parent compound [4]. Neutron 

scattering experiments are scheduled to define the magnetic moment direction and 

further x-ray studies of the polarisation and temperature dependence of the superlattice peaks (and harmonics) aim to identify the origin of the high temperature 

scattering. 

[l] Buschow and van der Kraan, J. Phys. F 8 1978) 921.; [2] Paixfio and Lebech. 

et al. submitted to Phys. Rev. B. 

Private communication (1995).; [3] Gubbens et E!l . J.M.M.M. 27 (1982) 61.; [4] Hill 

Figure 1. The superlattice peaks around 

the (220) (Top) and (330) (Bottom) 

charge peaks at T=9K, E=7.79keV. 

Figure 2. Temp. dependence of the su- perlattice peaks. Inset shows the intensity which exists above the Dy ordering 

temp. (~35K). 

I X-ray magnetic scattering of HoPr random thin film alloys. 

A. Vigliante, J. P. Hill, Doon Gibbs (BNL), M. J. Christensen, D. F. McMorrow 

(RISO), G. Helgesen (IFE), R. A. Cowley, M. R. Wells, R. C. C. Ward (Oxford) 

Rare earth elements have very similar physical, chemical and electronic properties which allows an almost complete solubility, but very different magnetic structure. Appropriate choices of rare-earth elements based on ordering temperature, 

anisotropy and controlled growth parameters by Molecular Beam Epitaxy, can tailor the magnetic phase behavior of alloys. We report a quantitative X-ray magnetic 

scattering study of the magnetic phase behavior of HoPr site-random alloys, as function of concentration. The heavy rare-earth Ho exhibit antiferromagnetic or- der below T~=132K, forming a basal-plane spiral with a propagation vector along 

the c-axis of the hcp structure. In contrast, the light rare-earth Pr, crystallizes 

in a double hcp structure (dhcp) and is antiferromagnetic only below TN =0.05K. 

Magnetic order in Pr can be achieved by in-plane uniaxial stress or by alloying. 

Chemical and magnetic structural characterization of samples, in concentration 

ranges of 20%<Ho<80%, were studied. The correspondent phase diagram and the 

temperature dependence of the magnetic wave-vectors are shown in Figure1 and 

Figure 2. By allowing the Ho concentration to vary, the chemical structure changes 

from hexagonal close-packed, to Samarium structure and to double hexagonal closepacked. These changes in the chemical lattice are followed by striking changes in 

the magnetic structure and in the low-temperature lock-in transformations. X-ray 

resonant magnetic scattering was performed to isolate the magnetic ordering on the Ho and Pr atoms separately, by tuning the energy to the Ho LIrr and the Pr 

L1.r edges, and to measure the induced moment on the Pr atoms as function of 

concentration. 

I' . I' . ' . 'I 140 .I. 

II 

llcmqn&I sn I 

II 

II 

11 

II 

II 

I1 

It 

II 

I 

II 

II 

I .I 

I 

II 

I1 

I1 

I1 

dhcp 

I I* 

I* I 

Figure 1. Magnetic Phase Diagram of Figure 2. Magnetic wavevector 7 as 

HOPI random thin film alloys. function of temperature. 

, d' I. .. 

. -. 
Glancing-Incidence X-Ray Magnetic Scattering Studies of the UOZ x22c, 

(001) Surface I x25 I I X-Ray Scattering Studies of Vicinal Au(001) 

G. M. Watson, Doon Gibbs (BNL), G.H. Lander, H. J. Matzke (EITU), B.D. 

Gaulin (McMaster), L.E. Berman (BNL)and W. Ellis (SNL) 

Traditionally, x rays have been used as a probe of the atomic structure in condensed matter. As was first shown by de Bergevin and Brunel[l], x rays can also be 

used to study magnetic structures. However it is the enhancement of the magnetic 

scattering cross section when the incident photon energy is tuned to an absorption edge that has made x ray scattering an especially useful probe of magnetic 

structures. Here we present the first resonant x-ray scattering measurements of the 

with the incident x ray energy tuned to the U MIV edge at 3.728 keV. The line 

indicates the best fit to a model consisting of the ideal, bulk-truncated, magnetic 

structure, and includes Fresnel effects. We find that the scattering shown in Fig. 

1 exhibits an enhancement when the incident photon energy is tuned to the resonant condition, as expected. Remarkably, scattered intensity at grazing-incidence 

appears to continuously vanish at the bulk Neel temperature. This is in contrast to 

the bulk magnetic order which is strongly discontinuous. 

[l] F. de Bergevin and M. Brunel, Phys. Lett. 39A, 141 (1972). 

x22c 

12 

10 

2 

0 

0 0.05 0.10 0.11 0.20 

L (wt of n) 

Figure 1. Intensity of the (1OL) magnetic truncation rod measured at three temperatures below the bulk Neel temperature of 30.2 K.Inset: Transverse scan through 

the (1OL) rod at L = 0.06. 

1300 

1200 

h 

25 1100 W 

tilted t (001) facet coexis 2 

E future study 

E 1000 

900 

800 

0 5 10 

MISORIENTATION ANGLE (DEGREES) 

Figure 1. Orientational Phase Diagram for Au(001) miscut towards [110]. 
M 

M 

o 

-. .’ X23A2 The surface structure of cadmium selenide nanocrystallites as determined by EXAFS, FTIR, and elemental analysis 

A.C. Carter (NRL), M.I. Bell (NRL), K.M. Kemner (NRL), C.E. Bouldin (NIST), 

J.C. Woicik (NIST), S.A. Majetich CMU) 

Extended x-ray absorption fine structure (EXAFS), fourier transform infrared absorption (FTIR), and elemental analysis were used on a variety of CdSe nanocrystallites NC’s) in order to study their surfaces. All CdSe NC’s were grown by 

standar d microemulsion techniques. Two sets of NC’s samples were made. One set was made so that only the size of the NC’s were varied, while the surface treatment was kept the same. The other set was made so that only the surface treatment was varied, while the size distribution was kept the same. For the EXAFS experiments, 

reference compounds were made so that differential measurements could be made, 

reducing the ambiguity of analysis. FTIR was found to be an excellent probe of 

the local environments of the surface Cd and Se atoms. The surface Cd atoms are 

passivated by pyridines and perchlorate groups. EXAFS was able to confirm the existence of perchlorate groups attached to the surface Cd atoms. Elemental analysis 

also supports the existence of C1 in the samples. The lack of any SeO and SiMe3 in 

the FTIR signal indicates that the surface Se atoms are bare. Fourier filtered first 

shell EXAFS spectra indicate that the only thing bonding to Se in the NC samples 

is Cd with a reduced coordination number from the bulk, suggesting surface Se 

atoms are bare. This indicates the existence of amany Se lone pair orbitals that can trap an excited hole. 

I EXAFS Study of Co/X Multilayers I X23A2 I 

M. Franklin and R. Loloee, Michigan State University 

Metallic multilayers involving Co produce a wide variety of magnetic effects and a mixture of structures. Co/Cu and Co/Ag are giant magneto- resistance (GMR 

has a change in magneto-anisotropy as layer thickness increases and Co/Mo is a system with conflicting claims about structure. We have begun fluorescence EXAFS 

studies for these systems with the Co layer thickness fixed at 2 monolayers (ML) as 

a means of testing the affects of structure upon magnetic properties. 

With these artificially layered samples, the choice of a suitable standard becomes a problem. We have chosen data for pure Co metal as a standard which can be 

used to identify trends reliably. Initial results for our samples have produced one 

confirmation of results obtained for thicker layers and two features requiring further 

study. Confirmation. An earlier study of Co y ML/ Ag 17 ML samples indicated 

the apparent coordination number of the first shell for Coi decreased from 12 to 8 

as y decreased from 17 to 3 while the saturation magnetization remained essentially 

constant [l]. The 2 ML Co results are consistent with those results. Featurel. 

A number of earlier studies [2,3] for thicker Co/Cu samples agreed that the coor- dination number for Co remained constant at 12 and that it was not possible to 

distinguish between Co and Cu atoms in that first shell. However, initial results 

for Co 2 ML/Cu y ML have the coordination number increasing monotonically by 

2Oincreases from 3 to 17. The Debye-Waller and R(NN) values do not change significantly from values found for the thicker samples and thus this increase is not a 

simple correlated parameter change. Feature2. The EXAFS signals in Co/Mo and 

Co/Pd samples with 2 ML Co layers have a qualitative change in their form: The 

siganls appear to be a smoothly decaying single frequency. Thjis changes suggest 

local disorder. XRD data for CVo/Mo also indicates disorder and magnetism is 

lost. XRD data for Co/Pd indicates good long range order and magnetism is not 

lost. We are varying our analysis procedures to find a reliable quantitative measure 

of the local disorder in these samples. 

[l] C. L. Foiles, et al. MRS Symp. 307,149 (1993). [2] S. Pizzini, et al., Phys. 

Rev. B 47, 8745 (1993). [3] C. L. Foiles, et al., MRS Symp. Proc. 375,207 (1995). 

systems for which a mixture of FCC and HCP structures is ofetn claimed. Co/P d 
I 

XAFS Investigation of Thermal Structural Disorder at GaSb/AlSb 

Superlattice Interfaces 

XllA, I XAFS Studies of MnSe/ZnTe Superlattices xila, 

X23A2 A. J. Kropf, B. A. Bunker, J. K. Furdyna, Q. Lu (Notre Dame), and K. M. Kemner 

Polarization dependent XAFS, employing the total electron yield (TEY and 

energy discriminating fluorescence detection techniques, has been used to stu d y the 

structure of MnSe/ZnTe (001) superlattices grown by MBE. These superlattices 

consist of 100-300 periods of A/B layers with A and B ranging between 4 and 

25 monolayers. Neutron scattering data on these materials show an unique antiferromagnetic helimagnetic phase at low temperature which is tunable by varying 

the thickness, temperature and strain of the MnSe layer (T. M. Giebultowicz, et. 

al., Phys. Rev. B (Rapid Comm.) 46, 12076, 1992). Of particular interest is the interface between the magnetic MnSe layers and 

the ZnTe layers, which act as a non-magnetic buffer, magnetically isolating the 

individual MnSe layers, and the effect of the interface on the strain in the MnSe 

layers. Polarization dependent XAFS taken at different edge energies coupled with 

x-ray diffraction results can distinguish between different models of the structure 

at the interface. 

In the data shown below, one can clearly see the effect of the lattice mismatch 

between MnSe and ZnTe as the MnSe bonds bend, while stretching only minimally, 

to accommodate the ZnTe lattice spacing. This reduces the first shell amplitude of 

the the XAFS for x-ray polarization vector perpendicular to the plane of superlattice 

growth relative to the amplitude of the XAFS for the polarization vector in the plane 

of the superlattice layers. 

(NRL) 

0 

Radial Distribution (Angstroms) 

Figure 1. Mn Edge Fluorescence Data (Sample 9006224) 
,, 'I' 'I: 

N 

tb 

o 

.I 

X-ray Study of Atomic Correlations in ZnCdSeTe Epitaxial Thin XllA, 

Films X23A2 

I XANES study of Cr dopants in oxides I X23A2 I 

K. E. Miyano (Brooklyn College), J. C. Woicik (NIST), D. Huang (Brooklyn College, Sujaatha Devi, and H.D. Gafney (Queens College) 

The presence of Cr4+ in Cr-doped MgzSiO4 (forsterite) is critical to the lasing 

of this material. Other promising Cr-doped oxides are presently being synthesized, 

and the oxidation state of the dopant Cr atoms is always a critical parameter. Xray Absorption Near Edge Structure (XANES data were recorded at the Cr K 

oxidation state. Transmission and fluorescence spectra were acquired using the 

Si (311) double-crystal monochromator, ion chambers, and a Lytle fluorescence 

detector equipped with a vanadium filter. 

XANES spectra were collected from the following standards: Cr metal, CrClz, 

CrzO3, CrOz, and CrOs as standards for the 0, 2+, 3+, 4+ and 6+ oxidation states 

of Cr, respectively. The Cr-doped NaAlOz samples yield a near edge spectrum that 

is clearly indicative of the Crat oxidation state. Although optical measurements 

have signalled the presence of Cr4+ in NaA102 upon synthesis, this measurement 

indicates that the Cr is susceptible to further oxidation with time. The doped 

MgzSi04 samples, on the other hand, are known to have stable Cr. Our initial 

attempts to interpret the spectra from these samples focussed on the strong preedge 

peak, which appears in the spectra for higher oxidation states. Also, in the XANES 

from the standards, the position of the main absorption edge, determined from 

the peak in the first derivative of the spectra, is observed to have a direct variation 

with oxidation state. In light of this dependence, analysis of the edge position in the 

forsterite compound suggests that the Cr in this sample exists in several oxidation 

states. 

edge for Cr dopants in MgzSi04, NaAlOz, an d Si02 in order to evaluate the Cr 
Microstructural control of the pore and grain size evolution in silicon nitride during processing. 

A.J. Allen, G.G. Long, S. Krueger, J. Wallace (NIST), and C.J. Hwang (Dow) 

Ultra small-angle x-ray scattering (USAXS) was combined with multiple smallangle neutron scattering (MSANS) to study the microstructural evolution during 

sintering of the technologically important structural ceramic silicon nitride. USAXS 

studies utilized maximum entropy (MaxEnt) size distribution analysis to determine 

volume-weighted pore size distributions during late sintering. Fig. 1 relates to 

pressureless-sintered MgO-doped commercial grade SisNa , Fig.2 to gas-pressuresintered YzOs-doped research grade SisN4. Porod, MSANS and volume-weighted 

mean pore diameters, and some mean grain diameters from SEM images, are marked 

in Fig. 1. At high density, grains coarsen while pores shrink slightly. Comparison of 

MSANS and Porod pore diameters (from SANS or USAXS Porod scattering) confirms that sintering is stable, pore size distributions neither narrowing nor broadening with densification. A change in pore size distribution, evident at 92% TD, is 

probably associated with microcracking as equiaxed alpha grains start to transform 

to elongated beta phase grains. Fig. 2 shows broad unimodular pore size distributions, with pore shrinkage apparent at high densities (grain coarsening similar to 

MgO-doped case). Complete absence of a separate fine pore population indicates a 

likely absence of microcracking during the phase transformation. MaxEnt volume 

fractions are less than true porosities, likely due to a reduced scattering contrast 

from the sintering aid, combined with glassy silica phases, lining the pore space 

Porod diameters deduced from USAXS with corrections for contrast reductions). 6 ifferences in pore size evolution for the two cases are striking, illustrating how 

such studies can quantify differences in the statistically-representative microstructural evolution under varied processing conditions. 

- - -92.9%TD (3) 

- - .95.6% TD (4) 

......... 96.8%TD (5) 

0 200 400 600 800 1000 

Diameter (nm) 

2.5 ..., ...,...,...,... -83.6%TD (1). 

- -85.4%TD (2). 

--. 88.O%TD (3): 

--.--99.6%TD (4): 

0 POROD 

+ MEAN 2.0 - 

0 200 400 600 800 1000 

Diameter (nm) 

Figure 1. Volume-weighted porosity Figure 2. Volume-weighted poros- distributions in late-stage pressureless- ity distributions in late-stage pressuresintering of MgO-doped silicon nitride. sintering of yttria-doped silicon nitride. 

I Diffraction Imaging of ZnSe Substrates for Blue/Green Emitters I X23A3 I 

David Black, Harold Burdette (NIST), Gene Cantwell (eagle-Picher Research Lab) 

The unique capabilities of X23A3 have been used to study the defect microstructure of ZnSe single crystals grown by Eagle-Picher. We have observed defects such as subgrain boundaries, inclusions, inhomogeneous strain and residual subsurface 

damage. Surface reflection images show a texture which is related to the bulk defect 

density. Subsurface damage, observed from as polished crystals with nearly mirror 

smooth surfaces, results from the processing of thee wafers from the as-grown boule. 

Highly asymmetric (grazing incidence) diffraction images improve our sensitivity to 

surface damage and these images have revealed an "orange peel" texture in the microstructure that probably results from chemo-mechanical polishing of the surface. 

The high quality of the crystals allowed us to obtain anomalous transmission images 

as shown below. The dislocation density calculated from selected areas is between 

640 and 1300/cm2. 
h7 

0) 

o X23A3 Submicron Resolution Strain Mapping of an In-situ Strained HighTc Superconductor Composite Tape by Microradiography 

R.D. Spal (NIST), G.N. Fliley and C. Christopherson (American Superconductor 

Corp.) 

Strained multifilamentary Bi-2223/Ag high-Tc superconductor composite tapes 

exhibit substantial critical current (IC) at strains well past the critical strain at 

which IC drops sharply from its unstrmned value (Otto et al., IEEE Trans. Appl. 

Supercond. 3, 915, 1993). To study this behavior, the strain distribution in a 

tape tensilely strained in-situ to 0.91% was determined non-destructively by microradiography. Figure l shows pre- and post-strain images recorded digitally by an asymmetric Bragg diffraction microscope at 24.4 keV. The two bright vertical 

streaks in the post-strain image are strain- induced cracks in the filaments. Figure 

2 shows the strain distribution along the filaments, determined by image analysis. 

Each point in the graph represents a 20 pm wide strip across the full image height; 

its abscissa is the strip's position in the pre-strain image, and its ordinate is the 

strip's horizontal displacement from pre- to post-strain images. 

The magnitudes of the discontinuities are the opening dimensions of the cracks. 

The relatively small variation in displacement away from the discontinuities shows 

the strain is concentrated at the cracks. 

Studies of Plasma-Sprayed Deposits using USAXS I X23A3 

-a r ,--' 1. a - 

c 

+ Q perpendicular to substrate U 

a 

!! 

z 

W 

r 

W 

< 

-I 

0 

10'10 10'8 10'6 10-4 0.+' . . ' . 

107 10.14 10'12 
I Fe in natural zeolites: can it be localized by XAFS? I X23B I 

M. Endregard (Univ. of Trondheim, Norway), A. F. Gualtieri, S. Quartieri, G. 

Vezzalini (Univ. of Modena, Italy), and K.I. Pandya (NCSU). 

Zeolites are microporous crystalline solids with a framework structure composed 

of corner sharing TO4 tetrahedra. Si or Al are the usual T elements which can be 

replaced partially by other elements such as Fe generally in small percentages). 

its nature is in many cases unclear and debated. Three major hypotheses have been 

advanced in literature: 1) Fe substitutes for A1 in the framework, 2) Fe is present as an extra-framework cation, 3) Fe is structurally related to impurities such as hydroxides or oxides. It is experimentally difficult to elucidate the state of Fe because 

submicronic iron hydroxide and -oxide particles can not be separated from the zeolite material. If Fe is present as a exchangeable cation, low concentrations make it 

difficult to detect Fe in the exchanged solution. Furthermore, a sample can contain 

iron in all three possible sites. Mossbauer and XAS studies devoted to localizing 

Fe in zeolites have been successfully performed on synthetic samples [l], whereas, 

to the authors knowledge, not on Fe in natural samples. Local structural information about Fe derived from XAFS can provide some information on the state 

of Fe in zeolites. If Fe substitutes for All the zeolite lattice would require Fe to 

be tetrahedrally coordinated to 4 0. While Fe present as extra-framework cations or hydroxide/oxide impurity phases would most likely contain six-coordinated Fe. 

Three samples have been selected among a variety of natural zeolites: a mordenite 

[2], a ferrierite [3], and a heulandite [4] containing about 0.71, 3.29, and 1.55 % of 

FezO3+FeO, respectively. We have collected RT Fe K-edge XAFS data in fluorescence mode on these samples and selected model compounds. Figure 1 shows the 

normalised XANES spectra of the zeolite samples. The intensity and position of the 

pre-edge peak has been used as a useful diagnostic feature of the coordination of 

Fe.[l Preliminary analysis of our data is consistent with Fe in prevalent octahedral 

11 Bordiga S., Geobaldo F., Lamberti C., Zecchina A,, Boscherini F., Genoni F., 

eofanti G., Petrini G., Padovan M., Geremia S., and Vlaic G. (1995). Nucl. Instr. 

and Meth. in Phys. Res. B97, 23-27. 

XRF or EPM analyses of natural samples often s 6 ow minor amounts of iron, but 

ror d ination. 

Passaglia E. (1975). Contrib. Mineral. Petrol. 50, 65-77. 

Alietti A,, Passagka E., and Scaini G. (1967). Am. Min. 52, 1562-1563. 

Passaglia E. (1969). Per. Mineral. 2, 237-243. 

0 Figure 1. Normalised Fe K edge spectra for the investigated natural zeolites. -4 

I X23B I Study of microstructure of NLO active chromophoric self-assembled 

multilayers using specular reflectivity 

A. Malik, W. Lin, M. K. Durbin, S. B. Roscoe, A. G. Richter, T. J. Marks and P. 

Dutta (Northwestern University) 

We have used specular reflectivity to probe the microstructure of chromophoric 

self-assembled multilayers containing high p chromophores. These films were prepared by a repetition of a three step process consisting of depositing a coupling 

agent, the NLO active chromophore, -and a capping agent. We have investigated 

the structural changes that take place due to to subtle changes in the molecular 

building blocks. Films containing 1 to 10 layers were studied and the thickness increases linearly with number of layers in all cases. A plot of thickness verses number 

of layers, for the systems studied is shown in figure 1. Typical reflectivity data for 

these systems are shown in figure 2. 

We first studied the effect of changing the anion in the coupling agent. Systems 

containing chlorine, bromine or iodine were compared. We find that the average layer thickness in films containing the chlorine and bromine coupling agents 

both agree well with molecular models (26.4A for the chlorine system, 25A for the 

bromine system). In contrast the average thickness increases to 36Awhen we switch 

to the iodine system. 

We used the chlorine coupling agent to study the differences in films containing 

two different chromophores. Stilbazolium and azobenzene chromophores were compared. We find that films containing azobenzene chromophores tend to be thinner 

(23.2A per layer than films with stilbazolium chromophores. 

P.Dutta and T.J. Marks, Angew. Chem. Int. Ed. Engl. 34, 1497 1995). 

2) S.B.Roscoe. A.A.Kakkar. T.J.Marks, A.Malik, M.K.6urbin. W.Lin, 

1) W.Lin, S. 3 itzchaik, W.Lin, A.Malik, M.K.Durbin, A.G.Richter, G.K.Wong, 

G.g.Wong and P.Dutta, Langmuir in press. 

search Center of Northwestern University (Grant DMR9120521) 

. 

This work was supported by the NSF-MRL program through the Materials Re- 

. ct&k.-*.m#.-d"-c&.. 

&dbp 014611 

Figure 1. 

number of layers for the four systems. 

Thickness as a function of Figure 2. Typical reflectivity data for 

multilayers (6 layers) of the systems 

studied. 
Angular Correlation in Electron/X-ray Coincidence Spectroscopy 1 X24A I 

U. Arp (NIST), T. LeBrun, S. Southworth, M. Jung (ANL), and J. Cooper (UMD) 

Last year we reported a new coincidence technique to select a certain decay 

pathway in the deexcitation cascade of an atom after deep inner-shell photoionization/excitation. The resulting spectra could be explained using Hartree-Fock 

calculations [1,2]. Certain intensity changes in coincident recorded electron spectra compared to normal electron spectra motivated a theoretical study on angular 

correlation effects [3] in the coincidence spectra. When two particles are detected 

coincident with some angular resolution, angular correlation will affect the spectra. 

In this case the propagation direction of the detected fluorescence photon defines 

the quantization axis for the angular distribution in the following Auger-process. 

In the theoretical analysis of the experiment we found intensity changes depending 

on the direction in which the photon is detected. Knowing this we initiated an 

experiment aimed at these effects and first preliminary results using a large area 

avalanche photo diode showed agreement with theory. 

T. LeBrun et al., in preparation for Phys. Rev. Lett. 

U. Arp et al., in preparation for Phys. Rev. A. 

N. Kabachnik et al. J. Phys. B: At. Mol. Opt. Phys. 24, 2249 (1991). 

1 Resonant x-ray fluorescence study of uranium oxides 

S. M. Butorin, J. Nordgren (Uppsala U., Sweden), Y. Ma (U. of Washington and 

Pacific Nothwest Labs.), K. E. Miyano (Brooklyn College), D. C. Mancini (U. of 

Lund, Sweden), B. A. Karlin (NIST), and D. K. Shuh (LBL) 

The U 5f-to-3d x-ray fluorescence spectra of UOZ and U03 were recorded at 

different excitation energies near the U 3d threshold. For UOz, the resonant part of 

the fluorescence (Fig.1) consists of the "recombination" line and a broad structure 

at lower energies which can be attributed to the core-hole decay to the states of 5f2 

and 5pv (v stands for a hole in the valence band) configurations, respectively. This 

shape of the resonant spectra is due to the configuration mixing in the ground and 

intermediate states of the x-ray fluorescence process as a result of the transfer of an electron from the valence band to the 5f level. For UOs, the triple-line shape of the 

U 5f-to-3d fluorescence spectrum (Fig.2) excited with 3563.9-eV photons indicates 

that the ground state of uo3 is a mixture of 5p, 5f'v and 5i?v2 configurations. 

Tuning the excitation energies to satellites in the U M6 absorption edge of UOa at 

about 3 eV and 10 eV above the main absorption maximum leads to an enhancement 

in the transition rate to 5f'v and 5Pv2 states in fluorescence spectra at about 8.5 eV 

and 14.5 eV below the recombination peak, respectively. These resonances indicate 

the charge-transfer origin of absorption satellites. 

7 

2i 

't 

b 

2 

3520 3530 3540 3550 3560 3570 

Energy [CV] 

Figure 1. The U M5 x-ray absorption 

and resonant U 5f-to-3d x-ray fluorescence spectra of UOz. The arrows indicate the excitation energies used for the 

fluorescence spectra. 

Emission 

Y 

3555.7 CV 

3520 3530 3540 3550 3560 3570 

Energy [eV] 

Figure 2. The U x-ray absorption 

and resonant U 5f-to-3d x-ray fluorescence spectra of uo3. The arrows indicate the excitation energies used for the 

fluorescence spectra. 
I 

I X-ray Standing Wave Investigation of (lx2)Rb/Cu( 110) 

D. Heskett (URI), L.E. Berman, and C.-C. Kao (NSLS) 

1 X24A 

The 1x2) missing row reconstructions of FCC (110) metal surfaces induced by 

surface reconstructions. We have carried out the first investigation of such a system 

using the technique of x-ray standing waves (XSW). Our XSW investigation of 

the system Rb/Cu(llO) was carried out on beamline X24A in the back-reflection 

typical data set from our (111) measurements of the Rb 2p3/, core level. Our 

most significant result is the relatively high coherent fraction we observed for the 

rubidium atoms in this geometry (-0.5-0.8), indicating a relatively high degree of 

order parallel to the surface along the [Ol] direction, which is across the missing rows. This result is quite different from our previous study of Rb/Cu(lll) (1,2), 

for which we observed very low coherent fractions (<0.2) for all coverages in the 

geometry parallel to the surface. For Rb/Cu(llO) we account for our results by 

assuming that the missing row nature of the reconstruction "locks" the Rb atoms 

into the missing row troughs. In a recently completed XSW study which probed 

the order in the [lo direction along the rows, we found the degree of order to be 

which is consistent with our other results. 

1. X. Shi, C. Su D. Heskett, L. Berman, C.-C. Kao, and M. Bedzyk, Phys. Rev. 

B49, 14638 (1994 

2. D. Heskett, 8. Xu, L. Berman, C.-C. Kao, and M. Bedzyk, Surface Science, in 

alkali a 6 sorption have served as prototypic systems for the study of adatom-induced 

configuration with measurements in the geometries. Auger and 

photoelectrons were collected with a n Figure 1 we present a 

significantly reduce d , as indicated by a very low coherent fraction for this case, and 

press. 

1170 eV Rb Zpv Photoelectron XSW Dab, 1 ML Rb/C\I(110) 

I""""'I 

-2 -1 0 I 2 

Relative Energy (eV) 

Figure 1. The x-ray standing wave yield for the Rb 2p312 core level for 

(Ix2)Rb/Cu(llO) taken in the (111) reflection centered around an incident photon energy of 2974 eV. The upper curves are the XSW yield (dots) and simulation 

using dynamical diffraction theory (solid line). The lower curves are x-ray reflectivity (crosses) and fit (solid line). (0 

X24A Dynamical Bragg Diffraction and X-Ray Standing Waves from Quasicrystal AlPdMn 

Terrence Jach (NIST), S. M. Thurgate (Murdoch U.), Y. Zhang, R. Colella (Purdue 

U.), S. W. Kycia (Cornell U.), and A. I. Goldman (Iowa State U.) 

X-ray diffraction from very perfect quasicrystal specimens might be expected to 

demonstrate the nature of dynamical diffraction in the quasilattice. The Darwin 

width of the rocking curve is due to a "structure factor" which does not originate 

from a periodic unit cell. The meaning of the a and p branches of the dispersion 

surface is less clear than for atoms occupying periodic positions relative to the 

diffraction planes in a normal crystal. 

We have observed diffraction from the 420024) and (640046) reflections of an 

curves observed by scanning the X24A monochromator in energy display Darwin 

widths consistent with dynamical theory (Fig.1). X-ray Ka fluorescence observed 

from the A1 atoms during the scan exhibits x-ray standing wave behavior similar 

to that of a crystalline material (Fig. 2). The data suggest a "coherent position" 

for the A1 atoms and the first direct observation of long range ordering of specific 

elements in the quasicrystal. 

AlPdMn quasicrystal in the back-reflection $ ragg geometry (8~=90'). The rocking 

0,=90°, Diflrncllon Ponk Enorgy Scan AI Ka Fluomsconco Enorgy Scan 

Figure 1. Figure 2. 
I Non-dipolar asymmetries of photoelectron angular distributions I X24A 

M. Jung, B. Krassig, D.S. Gemmell, E.P. Kanter, T. LeBrun, S.H. Southworth, 

and L. Young (Argonne National Laboratory) 

We have measured the non-dipolar contributions to the Ar Is, Kr 29, and Kr 2p 

photoelectron angular distributions using 2 - 5 keV polarized x-rays from beamline 

X24A. The non-dipolar interaction results in a forwardlbackward asymmetry with 

respect to the photon beam. This asymmetry was measured by rotating an electron 

spectrometer about the polarization vector with a fixed polar angle of 54.7', thus 

eliminating the angular dependence on the p parameter. Figure 1 shows the setup 

used in the experiment. The CMA was used for normalisation. We rotated the 

parallel plate analyser (PPA several times in steps of 15' with a dwell time of 

Figure 2 shows our measured values of the non-dipolar asymmetry parameter 7 

for Kr 2s in comparison with Cooper's calculations [l], which include interference between the electric-dipole and electric-quadrupole photoionization amplitudes. The 

Kr 2s asymmetry is directed forward near threshold, is slightly backward directed 

for electron energies between 900 eV and 2300 eV, and becomes increasingly forward directed at higher energies. The 7 parameter for AI 1s and Kr 2p shows a 

very different energy dependence but is also in good agreement with Coo er's 11 

Cooper, Phys. Rev. A 47, 1841 (1993) 

typically 1 minute and a tot a time of 5 minutes per point. 

and Bechler and Pratt's [2] calculation. You can find further details in [3]. fl] J. SJ . 

A. Bechler and R.H. Pratt, Phys. Rev. A 39, 1774 (1989); 42, 6400 (1990) 

B. Kraessig et. al., Phys. Rev. Let. 75, 4736 (1995) 

X-ray scattering of atoms and molecules 

K. Miyano (CUNY), U. Arp (NET), and S. Southworth (ANL) 

The diagram K beta fluorescence spectrum of OCS after 1s photoionization of 

sulphur 13 has been known for many years. A recent calculation by Meehan et al. [2] 

which initiated this experiment in which we looked in the fluorescence after resonant 

excitation or the resonant inelastic scattering using a bend crystal spectrometer. 

The resonance fluorescence appears different from the diagram fluorescence opening a rich source of information on molecular structure, even more so if a polarization analysis is performed, which gives directly information on the symmetry of the 

involved molecular states. In a second experiment we were looking for the Comptonscattering of atomic argon at 2982 eV and 4000 eV incident photon energies. We 

found very broad peaks at energies lower compared to the Rayleigh-scattered peaks, 

but these peaks are shifted by the same energy at both energies, which makes clear 

that this is no Compton-scattering. Much more likely is a scattering process were a valence electron is photoionized and then recombines to a highly excited state [3]. 

1 X24A 

predicte L a strong influence of the spectator electron in the resonant scattering case, 

R.C.C. Perera and R.E. Lavilla, J. Chem. Phys. 81, 3375 1984). F.P. Larkins, to be publishe 6 . and L.P. Pitaevskii, Quantum ElectrodynamArJet w 

Figure 1. Experimental setup with coor- dinates used for the description of photoelectron angular distributions. 

:\ 

0.4 . 

Kr 2s 

-1 : 

0 IMX) Moo 3Mx) 

Eloclmn klnolic onorgy (oV) 

Figure 2. Asymmetry parameter 7 in dependence on electron kinetic energy for 

Kr 2s compared with Coopers theoretical values. 

c 
An electron-electron coincidence experiment near the Ar K-edge * I X24A 

R. Wehlitz, L. Pibida, J.C. Levin, and I.A. Sellin (Univ. of Tenn.) 

During our first beam time of this project we have taken electron spectra as well as electron-electron coincidence spectra around the AI K-edge. The monochromatized synchrotron light was intersecting an effusive gas beam. Electrons comin 

from this interaction region were detected with a cylindrical mirror analyzer (CMA? 

and a time-of-flight TOF) spectrometer. The TOF spectrometer was mounted horbeam. The CMA was equipped with a position sensitive anode, thereby capable of 

measuring the angular distribution of electrons. In order to detect electrons of low 

kinetic energies, the chamber was covered with p-metal on the inside. The electron 

spectra taken on the AI 1s --f 4p resonance reveal a complex structure of low kinetic 

energy Auger lines particularly around 5eV) not seen before (Fig. 1). However, 

be part of future investigations. The main goal of our investigations was to record 

the AI LMM Auger lines in coincidence with one KLL Auger line to disentangle 

the complex structure of the LMM Auger group. While the CMA was tuned to 

the KL2L3 Auger line, the group of LMM Auger lines was detected with the TOF 

spectrometer (Fig. 2). Unfortunately the line width was broader than expected due 

to our electronics. Modifications for our next beam time are expected to increase 

the time resolution and will enable us to analyze the line structure of the LMM 

Auger lines. 

izontal and the CM 6 was mounted vertical in a plane perpendicular to the photon 

the intensity is too (l ow for a detailed analysis of these Auger lines yet, but will 

Strain relaxation of ultrathin InAs/GaAs(001) films 

I 40 c"'"'''' 

=! 

W 

cd 

X24A 

VI 

4. 

9 

0 20- V 

Kinetic energy (eV) 
1 ,-', .* , 

1. 

F 

N 

IN Refractive and extinction indices of Lithium Triborate in 55-71 eV 

region * 

T.J.Chen (Southern Illinois U.), W.R.Hunter (Sachs Freeman Assoc.), R.Zitter, 

R.Tao (Southern Illinois U.), J.C.FLife (NRL) 

Nonlinear optical crystal lithium triborate (LiBs06, or LBO) has direct band 

ga at -7.8 eV, therefore it is opaque in 55-71 eV region. The refractive indices 

nj&x,y,z), and extinction indices kj (j=x,y,z) for three principal polarizations were derived from the measured reflection spectra in 55-71 eV region. In the derivation, 

the electric dipolar oscillator model was used: assuming nj(E) and kj(E) can be 

obtained by the complex refractive indicies B=n+ik, and it can be found by Snell's 

law: 

sin0 = iijsinej 

And the complex refractive index 5 is related to the complex dielectric constant Cj 

1 M;j(E;j -E) M;jI';j 1+c [ Cj = iij" = 1 + 47+j = - E)Z + qj + - E)Z + r; i 

where the summation goes over i=1,2,3,4,5,b,r; the osillators of 1-5 represent the 

transitions observed in our experiments. All other oscillators outside our spectral 

region are represented by two terms: the b for higher energy side, and r for lower 

energy side. Then the Fresnel formula was used to calculate the reflectance to fit 

the experimental data. The following parameters were obtained from the best fit 

and are listed in the table: 

r I 29.0 I 9.56 I 15.8 I 41.5 I 5.7 I 15.2 I 47.9 I 3.46 I 8.8 

b I 86.0 I 2.80 I 6.0 I 86.0 I 2.20 I 6.0 I 86.0 I 0.80 I 6.00 

Figure 1. 

* This work is supported by IUinois Board of Higher Education. 

Photoemission and C-1s near-edge absorption from photopolymerized CSO films * 

B.S. Itchkawits (Fritz-Haber-Institut, Berlin),J.P. Long (NRL), T. Schedel-Niedrig 

(Fritz-Haber-Institut, Berlin), M.N. Kabler (NRL), A.M. Bradshaw, R. Schlogl 

(Frits-Haber-Institut, Berlin), W.R. Hunter (SFA, Inc.) 

Photopolymerization of pure C60 films has been characterized using valence-band 

and C-1s photoemission and near-edge absorption spectroscopy [l]. Figure 1 compares valence-band PES of pristine films with those of films polymerized to saturation at 300K by pulsed radiation from a Cu vapor laser (2.43 eV, 5 ns). Data for 

four synchrotron-radiation energies are shown, along with calculated (LDA) densities of states for C6o molecules (solid curve) and polymerized dimers[2]. Simdarities 

between measured and calculated features are evident. The C-1s data suggest that 

roughly 12% of all C atoms is engaged in new bonding. The photopolymerization 

efficiency at 84K is less than 1% of that at 300K. Kinetics at three fluences are illustrated in Fig. 2, which shows the rise with dose of a simple saturating function 

of the amplitude A of spectral features associated with polymerization. The rate 

constant, shown vs. peak laser intensity in the inset, becomes sublinear at high 

intensity. This suggests concentration dependent recombination of those excited 

states which are precursors to polymerization. The line in the inset is an extrapolation of prior Raman data [3] for laser intensities lower by a factor lo6 than used 

B.S. Itchkawitz et al., Chem. Phys. Lett. 243, 211 (1995). 

M.R. Pederson and A.A. Quong, Phys. Rev. Lett. 74, 2319 (1995). 

Y. Wang et al., Chem. Phys. Lett. 211, 341 (1993). 

-a 4 4 -2 0 

Energy (ev) 

Figure 1. 

* Supported in part by the German Federal Ministry of Science and Technology 

8 

$2 3 
X24C Structural Determination of the PSiC(lOO)-c(2x2) Surface from C-1s 

Surface-Core-Exciton and Si-2p Absorption * 

J. P. Long (NRL), V. M. Bermudez (NRL), D. E. Ramaker (George Washington 

The C-terminated (100) surface of PSiC, which reconstructs as ~(2x2 is impormodels sketched in the figure, have been proposed for this surface. We have measured the polarization dependences of the near-edge absorption spectra of two C-ls 

surface core excitons (SCE). A sample of data is shown in the figure. Thresholds are 

markedland insets show angle dependences. These data establish conclusively that 

the n structure, with staggered rows of a-bonded C dimers bridging underlayer 

Si dimers, is correct. This conclusion is supported both by Si L-edge NEXAFS, 

which provide evidence for Si dangling-bond states present only in the n-bonded 

model, and by MO cluster calculations, which identify these Si states and which 

support our interpretation of the polarization data. This work also verifies recent 

ab-initio calculations. Furthermore, we observe a strong resonant photoemission in 

the valence band which accompanies the de- excitation of the C-1s SCE. C dimers on SiC(1OO)-c(2x2) are isolated and thus produce relatively strong SCE absorption 

features, unlike the extended states on diamond (111)-(2xl). 

Univ.) 

tant for its chemical inertness and thermal stability. Two structures, t k e n and u 

Figure 1. 

* This work was supported in part by the 

Office of Naval Research 

PHOTON ENERGY (av) 

Figure 2. 

I Characterization of Soft X-Ray Multilayer Gratings and Mirrors 

J. F. Seely, M. P. Kowalski, J. C. Rife, R. G. Cruddace (NRL), T. W. Barbee, Jr. 

(LLNL), and W. R. Hunter (SFA Inc.) 

Multilayer-coated diffraction gratings and mirrors have been characterized in the 

soft x-ray region using the monochromator and reflectometer at beamline X24C. 

The multilayer coatings (e.g. Mo/Si and W/B4C are sputter deposited and are 

for astrophysical, solar, and laboratory applications. The grating substrates are 

produced by the holographic ion-etched process or are replicas of ruled master 

gratings. The mirror substrates are flats or spherical and are super-polished. The 

reflectance of the multilayer mirrors and the efficiency of the multilayer gratings are 

measured in the energy range 10-1000 eV and at angles ranging from near normal 

to grazing. 

I X24C 

designed to have high reflectance at the energies an h angles of incidence of interest 
ox ' gen ' - ' ' ' ' nicl;eld 

mger pos = +12&01 coher pos = -.Ol*Ol coher mc = .8&.05 -4, mher mc = 9h.01 

-3 -2 -I 0 1 2 

Relative hergy (e9 t 01 ' ' ' ' ' . ' ' ' 

zwo m 3200 Figure 2. Measured XSW yields of the 

Ni2p3/2 , 0 Is, and C 1s core levels as the 

bulk Ni(ll1) Bragg reflection (at bottom) was scanned, compared wlth theoretical fits, for ~(4x2) CO/Ni(lll). 

Kinetic Energy (e9 

Figure 1. Electron energy distribution 

curve of CO/Ni(lll) measured at a photon energy of 3.055 keV. 

X25 Real-Time Small-Angle X-ray Scattering Studies of Rubber-Modified 

Engineering Thermoplastics 

R. A. Bubeck, C. F. Broomall, B. G. Landes, D. E. Parker, R. Ramsey, R. Scott, 

J. Warakomski, The Dow Chemical Company, Midland, MI 48674; E. J. Kramer, 

Cornell University, Ithaca, NY 14853, and L. E. Berman, NSLS, Brookhaven National Laboratory, Upton, NY 11973 R. A. Bubeck, C. F. Broomall, B. G. Landes, 

D. E. Parker, R. Ramsey, R. Scott, J. Warakomski, The Dow Chemical Company, 

Midland, MI 48674; E. J. Kramer, Cornell University, Ithaca, NY 14853, and L. E. 

Berman, NSLS, Brookhaven National Laboratory, Upton, NY 11973 

Real-time small-angle X-ray scattering (RTSAXS) studies were performed on a series of rubber-modified thermoplastics. These include rubber-toughened syndiotactic polystyrene (sPS), High Impact Polystyrene (HIPS), and Acrylonitrile 

Butadiene Styrene-type copolymers ABS). The data from the rubber-toughened 

phases are nearly identical, thus permitting the study by RTSAXS of a toughened 

semi-crystalline polymer without undue SAXS interference from scattering from 

the crystalline lamellar microstructure. Linear small-angle X-ray scattering patterns were measured at successive time intervals as short as 3 ms. using a Reticon 

detector coupled to an optical multichannel analyser. The patterns were analyzed 

to determine the plastic strain due to crazing. Simultaneous measurements of the 

absorption of the primary beam by the sample using a semi-transparent beam stop 

fitted with a pin diode allowed the total plastic strain to be computed. The plastic 

strain due to other deformation mechanisms (e.g. particle cavitation and macro- scopic shear deformation) was determined by the difference. The contribution from 

microscopic shear deformation was determined from video-based optical data obtained along with the RTSAXS data. The run was very productive in data with the 

equivalent of over 200,000 linear SAXS patterns being generated. Activity is now focused on developing and using software to rapidly analyse this great quantity of 

data, while in the interim data from key samples are analysed individually. 

Using this technique, samples of commercial thicknesses can be studied at high 

rates of deformation without the inherent limitations of microscopy and its requirement of thin samples (i.e., plane strain constraint is maintained on sample mor- phology). Contrary to the conclusions drawn from many previous dilatation-based 

studies, it has been demonstrated that the strain due to noncrazing mechanisms, 

such as rubber particle cavitation, and deformation of the glassy ligaments between 

rubber particles, is more significant than the contribution due to crazing. One 

example of how the contribution from each mechanism of deformation can be delineated is with a comparison of acrylonitrile ethylene styrene (AES) and acrylonitrile 

styrene acrylate (ASA systems in an SAN matrix. Manipulatlng the graft and 

yield, but not much additional crazing. Presumably, this is the result of better 

grafting of the rubber particles to the matrix and, thereby, inducing a balanced 

triaxial dilation force on the particles rather than having the particles prematurely 

detach from the matrix. Manipulating the ASA particle size in an AES/ASA blend 

resins resulted in about a 50to microshear and rubber particle cavitation, and a doubling the contribution due to crazing at fracture. These results are consistent 

with the mechanical testing of the samples wherein the AES/ASA blend was found 

to have greater impact strength than the straight AES system. 

sPS is of interest because the speci d c gravity of the crystalline and amorphous 

crosslinking levels in t 1, e AES system results in a ten-fold increase in microshear 
i 

Determination of Transition Metal Electronic Structure Using High 

Resolution X-Ray Fluorescence Spectroscopy * 

I Spin Resolved X-Ray Resonant Raman Scattering * 

W.A.Caliebe, C.-C.Kao, L.E.Berman, J.B.Hastings (NSLS), M.H. Krisch, F. Sette 

(ESRF, France), K.HamElEinen (University of Helsinki, Finland) 

I X25 X25 

In the last 20 years many different techniques have been developed in order to 

study the spin resolved electronic structure of many metals. We combined one of 

these techniques, X-Ray Magnetic Circular Dichroism (XMCD , with X-Ray Resonant Raman Scattering in order to study the LIII-edge of d d. We excited the 

intermediate states 2p64P5d1 (quadrupolar transition) and 2p64fnt15d0 (dipolar 

transition) with circular polarized X-rays and observed with high energy resolution the fluorescence emitted during the decay into the final states 3d94fn5d' and 

3d94fnt15d0 respectively. The final data, including corrections for the degree of 

polarization, angle between the magnetic field and the photon beam, and the magnetization are shown in figure 1. The relatively weak quadrupolar transition is 

clearly separated from the strong dipolar one, which is split into two peaks with 

different electron spin. This techniques allows to obtain information about the LIII-edge in Gd but we 

also obtain indirectly information about the MIV,V-edge, because the final state is 

the same. A more detailed analysis is in progress. 

8000 I I 

6000 0 tt 

t$ 

2000 

n " 

1185 1190 1195 1200 1205 1210 1215 

E,-$ lev1 

Figure 1. Spin resolved resonant raman spectra of Gd. The two curves represent 

the intensity for parallel and antiparallel electron and photon spin. 

* Supported by US DOE under contract # DE-AC02-76CH00016. 

wk 61'88 ab692 wL Id. ...,... ...,.. ...,... 

Emission Energy (cV) 

Figure 1. 

* With thanks to Prof. Stephen Cramer for the use of equipment and to Prof. William 

H. Armstrong for the manganese compound. hded in part by NIH grant GM-45205. 
1x25 I I The crystal structure of a hyperthermophilic Archaea TATA binding 

protein 

B. S. DeDeckew, R. O'Brient, P. J. Fleming*, S. P. Jackson$& P. B. Sigler* 

(*Howard Hughes Medical Institute and Yale University; tYale University; 

SWellcome/CRC Institute and Cambridge University) 

Hyperthermophilic organisms have an optimal growth temp. above 8OC and are able to grow at temp. exceeding 9OC (1 , Based on phylogenetic st dies most hyIt has been proposed that the common ancestor of all existent life was a hyperthermophile, and that relatively modern mesophilic biology is an adaptation from an 

earlier hot environment (3). The organism Pyrococcus woesei is a hyperthermophilic 

Archaea found near deep-sea hydrothermal vents with an optimal growth temp. of 

105C. In concurrence with the observation that the Archaea cell and the eukaryotic 

nucleus share a common ancestor, homologues of the eukaryotic transcription factor 

TATA binding protein (TBP) have recently been cloned from P. woesei and other 

Archaea species (4, 5). The crystal structures of two eukaryotic TBPs are known, 

one from the plant species Arabidopsis thaliana at 2.1 8, resolution and the other 

from the yeast Saccharomyces cereuisiae at 2.6 8, resolution (6, 7). Here we report 

the structure of the Archaea TBP from P. woesei at 2.2 8, resolution, with the 

native data set for this study having been collected at the NSLS X25 beamline. 

At room temp., P. woeseiTBP binds DNA with an affinity a 1,000 fold lower than 

its eukaryotic homologues. This characteristic, as shown by the crystal structure, 

is due in part to the dramatically different electrostatic surface of Archaea TBP. In 

addition, the P. woesei TBP structure demonstrates a correlation between protein 

packing and hyperthermostability. This hyperthermophilic protein is currently the 

most efficiently packed of all reported structures in the PDB; exceeding the previous 

theoretical limit of protein core packing density which is that found in crystalline 

hexane (8). This structure offers a window into the evolution of eukaryotic transcription and the structural basis of thermostability. 

[l] M. W. W. Adams. (1993) Enzymes and proteins from organisms that grow 

near and above 1OOC. Annu. Rev. Microbiol. 47: 627-658. 

[2] C. R. Woese, 0. Kandler, M. L. Wheelis. (1990) Towards a natural system of 

organisms: Proposal for the domains Archae, Bacteria, and Eucarya. Proceedings 

of the National Academy of Sciences, USA 87: 4576-4579. 

acterial Evolution. Microbiological Reviews : 221-271. 

4 T. Rowlands, I?987) Baumann, S. P. Jackson. (1994) The TATA-Binding Protein: 

3 C. R. Woese. 

A Genl. Transcription Factor in Eukaryotes and Archaebact. Sci. 264: 1326 1329. 

[5] T. L. Marsh, C. I. Reich, R. B. Whitelock, G. J. Olsen. (1994) Transcription 

factor IID in the Archae: Sequences in the Thermococcus celer genome would en- code a product closely related to the TATA-binding protein of eukaryotes. Proc. 

Natl. Acad. Sci. USA 91: 4180-4184. 

r61 D. B. Nikolov. et al. (1992) Crystal structure of TFIID TATA-box binding 

perthermophilic genera have been classi d ed as Archaea, while two E& Bacteria (2). 

11 

. ,- pr6tkin. Nature 360 40-46. 

structure of veast TATA-binding protein and model for 

- 

[7] D. I. Chasman, K. M. Flaherty, P. A. Sharp, R. 

Natl. Acad.-Sci. USA 90: 817&8^178. 

ume, Group Volume Distributions and Packing Density. J. of Mol. Bio.82: 1-14. 

[8] F. M. Richards. (1974) The Interpretation of Protein Structures: Total VolNear-edge studies of the Excitation of the KCY satellites in copper * I X25 

M.Deutsch, O.Gang (Bar-Ilan U., Israel), K.Hamiiliiinen (Helsinki U., Finland.), 

C.C.Kao (BNL) 

We measured the photoexcited lineshape of the Kar satellite spectrum of Cu, for 

excitation energies from below to above the KL edge ( 9800-11200 eV ). In con- trast to the expectations of an abrupt edge structures in the fluorescent spectrum, 

corresponding to different L-spectator transitions, a smooth increase of the intensity was found. This points to a pure shake-off origin for the excitation process. 

The evolution of the lineshape and intensity from its appearance (10050 eV) up to 

its saturation (11200 eV) was studied. By fine tuning the excitation energy near threshold we found an energy difference of ~20 eV in the opening of the two channels (ar',ar4 and ar~,ari ) which originate in 2p spectator transitions with different 

total momenta. Below this critical excitation energy (10050 eV) the satellites van- ish. The opening energy of the channels agrees with the Z+1 approximation and our relativistic Dirac-Fock calculations, which also show a reasonable agreement 

with the lineshape measured. Analysis reveals that the shape of the satellite is basically unchanged from slightly above the threshold (~10050 eV) up to the highest 

excitation energy measured (11200 eV). Only the intensity of the complex grows. 

Calculations in the adiabatic and transition-to-sudden approximation are re- quired to elucidate this point. 

8.070 8.085 

Emission [ke"] 

Figure 1. Measured Kar satellite spectrum of copper for the incident energies 

listed. 

* Supported by the German-Israel Science Foundation, Jerusalem. 

250 

200 

150 

- 

v s 

- 

100 

50 

0 

10.0 10.5 11.0 

Eincident [keV] 

Figure 2. Intensity variation of the four 

satellite components with increasing incident energy. 
I 

X25 Structure of the high afinity complex of an inositol trisphosphate with 

a DhosDholiDase c Dleckstrin homolow domain. 

K.M.Ferguson(Yale), M.A.Lemmon, J.Schlessinger(NYU) and P.B.Sigler(H.H.M.1, 

Yale) 

PH domains have been identified on the basis of primary sequence similarity of an approximately 100 amino acid motif found in many proteins involved in signaling processes. In phospholipase C-6 (PLC-6) this domain is located towards the Nterminus of the protein in a region responsible for high affinity inositol trisphosphate 

and phosphatidyl inositol bisphosphate binding. We have solved the X-ray crystal 

structure of the high-affinity 210 nM, [l]) complex between the pleckstrin homolThe structure was solved by multiple isomorphous replacement plus anomalous scattering using phase information from a data set collected at X-25 on crystals grown from seleno-methionine protein, plus data from a mercury derivative collected on 

a home source. The structure has been refined to 1.9 A resolution against the 

data collected at X-25, to a final R-value of 20.5 % (22 u data). The fold of the 

PLC-61 PH domain is similar to others of known structure. Ins(l,4,5)Ps binds in 

the center of the positively charged face of the electrostatically polarized domain, 

@3/@4 loops of the PH domain. 

interact extensively, while the 1- 

amino acids in PLC-61 PH that 

contact Ins(1,4,5)Ps have counterparts in the Bruton's tyrosine kinase (Btk) PH 

domain where mutational changes cause inherited agammaglobulinemia, suggesting a mechanism for the loss of function in Btk mutants. Using electrostatics and varying levels of head-group specificity, PH domains may localize and orient signaling 

proteins providing a general membrane targeting and regulatory function. 

ogy (PH) domain from rat PL L -61 and inositol-(1,4,5)-trisphosphate (Ins(1,4,5)Ps). 

making extensive interactions with the 

The 4- and 5-phosphate groups of Ins 

phosphate participates in one hydrogen 

and Schlessinger,J. (1995) Proc. 

Lemmon,M.A., Schlessmger, 

X25 Structural Studies of the Human Transferrin Receptor and a bZIP 

protein/DNA complex. * 

S.C. Harrison and C.M. Lawrence (HHMI, HU, Children's Hospital) 

Human transferrin receptor (TfR): We made significant progress in this very 

challenging structure determination. 

Data were collected from crystals of SeMet substituted TfR. There are too many 

methionine residues for this to be a first isomorphous derivative, and the unit cell 

is too large for this to be a good candidate for MAD experiments, but the data will 

be important for phasing, once a first conventional derivative is obtained, and for 

tracing a polypeptide chain. The SeMet data set is '7Ocomplete to 6 ; the Rmerge 

for all data is 0.095. We also collected additional native data, which merged well 

with data (to 3.2 ) collected previously at CHESS. 

A bZIP protein/DNA complex: A data set, complete to 2.8 (Rmerge = 0.060) 

was collected from crystals of a multiple mutant of GCN4, bound to a C/EBP DNA 

site. The goal of the structure determination is to understand bZIP specificity, since 

the mutated residues change the specificity to that of CE/BP, despite the fact that 

all but one are a non-contacting positions. The structure has now been determined 

by molecular replacement using these data, and refinement is in progress. 

* This work was supported by the Howard Hughes Medical Institute 
I The 2.0 %, Crystal Structure of a Heterotrimeric G Protein * Ratio of Double-to-Single Photo- and Compton Ionization of Helium I ~25 I X25 

~ 

David Lambright (Damon Runyon-Walter Winchell Fellow, Yale University) and 

Paul Sigler (Howard Hughes Medical Institute, Yale University) 

Heterotrimeric guanine nucleotide binding proteins (G proteins; subunits a, p, 

and 7) couple agonist stimulated heptahelical receptors, located at the cell surface, 

to a variety of intracellular signaling pathways. We have recently completed the 

2.0 A crystal structure of the heterotrimeric (GDP bound) form of transducin, the 

heterotrimeric G protein that couples the light activated photoreceptor rhodopsin to 

the visual signaling cascade in retinal rod cells. The structure was solved at 3.0 by 

multiple isomorphous replacement using isomorphous differences from a Hg( 0Ac)z 

derivative and isomorphous as well as single wavelength anomalous differences from a CHaHgCl derivative and a selenomethionine Se-Met) derivative substituted in the 

intensities were collected at the peak of the Se absorption edge using the X25 

beamline of the NSLS at Brookhaven. The Se-Met derivative was essential for 

obtaining initial phases. The initial MIR map was improved with solvent flattening 

and histogram matching. 

The model has been refined with simulated annealing against the Se-Met intensities from 6.0 to 2.0 resolution. The present model has an R-value of 23.5 % for 

all data (22.0 % for data > 2 u) and a free R-value of 30.6 % (29.2 % for data > 2 

u) for a randomly selected subset (10 %) of the data omitted prior to the start of 

refinement. A manuscript describing this work is in preparation. 

a: subunit. In order to maximize the Bijvoet 6 ifferences for the Se-Met derivative, 

190 180 170 160 150 140 130 120 110 

Ion Flight Time (ns) 

0: 4 6 8 lo I2 14 I6 I* 20' Photon Energy (keW 

Figure 1. Time-of-flight spectrum of helium obtained with 20 keV photons. Figure 2. Comparison of present results 

with several recent theoretical predictions. * Work supported by NSF 
I Coherent X-Ray Reflectivity From Oxidized Si (111) Surfaces I x25 I Polarization Dependent Scattering from DyLu Superlattices 

J. L. Libbert, I. K. Robinson, (Univ. Illinois), R. Pindak, R. M. Fleming (AT&T), 

S. B. Dierker (Univ. Michigan) 

X25 

We have examined the reflectivity from several oxidized Si (111 surfaces illumix-ray diffraction CXD technique is sensitive to the distribution of steps on these 

displays both a specular and a diffuse, non-specular component which is related to 

the distribution of steps on the surface[l]. Under CXD conditions the non-specular 

component will exhibit fine structure related to the specific arrangement of the 

steps on the surface. Motion of the steps will change the detailed appearance of 

the 'speckle' pattern. Figure 1 shows three speckle patterns from slightly different 

areas of an oxidized Si(ll1) surface each taken after shifting the illuminating beam 

by less than its width, simulating motion of the steps. These scans were taken at 

q=O.O9 A-' by scanning a 20 pm pinhole located 1.25 m behind the sample across 

the reflected beam from a 5 pm source aperture. Changes of the speckle pattern 

with time, similar to those seen in Fig. 1 can be expected if the surface steps are 

caused to move as during growth or etching situations. By studying the time dependence of these changes it should be possible to deduce the step diffusion rates 

of the processes. Figure 2 shows chan es in a speckle patterns due to etching a Si 

surface with a buffered HF solution. [4 S. K. Sinha, et. al. Phys. Rev. B, 38, 2297 

(1988) 

nated by a coherent x-ray beam. We were able to demonstrate t h at the coherent 

surfaces and the 0 motion' of these steps. The x-ray reflectivity of a rough surface 

dctoclor pinhole position Om) 

Figure 1. Figure 2. 

LlRW 

Figure 1. Lorentzian fits to data taken 

off-resonance at 9.295 keV. The right 

peak is the 2nd order superlattice peak 

on the low Q side. 

3.04 3m 3.72 3.70 380 3.04 

LlRLU 

Figure 2. Same configuration as Figure 

1, but these fits are to data taken on resonance at 9.240 keV. 
I X-raygudies of Liquid Metal Surfaces* 

M.J. Regan, P.S. Pershan (Harvard), O.M. Magnussen, B.M. Ocko (BNL), M. 

Deutsch (Bar-Ilan Univ., Israel), L.E. Berman (NSLS) 

In liquid metals the delocalization of the near surface conduction electrons cou- pled with the dominating Coulombic interactions suppresses positional fluctuations 

of the near surface ion cores, As a result, it is predicted that the top several layers 

of atoms parallel to the surface will be ordered, resulting in a damped oscillatory 

electron density profile, in contrast to the monotonic profile of non-metallic liquid 

surfaces. Although this prediction is now over two decades old, it was hitherto 

not rigorously tested experimentally in spite of efforts by a number of groups. In 

this report period we have used x-ray reflectivity to unambiguously demonstrate 

surface-induced layering in liquid gallium[l] and mercury[%] with atomic-scale resolution. 

The main results for liquid Ga are contained in fig. 1 and provide clear evidence 

that a surface induced atomic layering exists. These features are consistent with an extremely flat liquid/vapor interface, layer spacing similar to the Ga atomic dimensions, and layering that extends into the bulk a 1/e length of 3 atomic diameters 

(6-7 A). 

We have also carried out measurements of the Ga surface between 24 and N 

180 C. The large change in reflectivity that was measured shows no appreciable 

variation in the width of the peak, indicating that the layering decay length is 

unchanged. However, the amplitude of the density variation is clearly reduced 

presumably through increased capillary wave roughness. * This work has been supported by grants from the DOE, DE-FG02-88-ER45379 

and DE-AC02-76-CH00016, and the NSF, DMR-94-00396 and DMR-91-13782. 

M.J. Regan et al., Phys. Rev. Lett. 75, 2498 (1995). 

O.M. Magnussen et al., Phys. Rev. Lett. 74, 4444 (1995). 

Observation of Speckle from a Protein Crystal 

I. K. Robinson, J. L. Libbert (University of Illinois), R. Pindak, R. M. Fleming 

(AT&T), S. B. Dierker (University of Michigan), B. Yu and D. L. D. Caspar (Florida 

State University). 

We sought to evaluate the possibility of using coherent diffraction to investigate 

dynamical fluctuations in protein crystals. Protein crystals are now widely believed 

to be made up of multiple molecular conformations, and fluctuations between these 

states may be of biological relevance. 

We examined a crystal of cubic insulin mounted in a glass capillary in contact 

with saturated mother liquor. By rapidly aligning the crystal by means of its square 

(100) faces, we examined the strong 002 reflection using a 5pm incident beam and a 20pm analyzer pinhole at 1.3m to achieve laterally coherent diffraction conditions. 

The X25 W/B4C mutilayers gave us an incident flux of lo7 per sec with sufficient 

temporal coherence to reach the 002 reflection at 26' = 1.1'. 

The results indeed show a multiply peaked structure in scans across the diffracted 

beam in the horizontal direction (26' is vertical). The full-width of the peaks is 

roughly equal to the 90pm expected for the central Fraunhofer diffraction maximum. 

Analo ous structure was seen in the vertical direction, parallel to 26' (data not 

shown!. However, this pattern was not stable: the notation "A,B,C,D" shows the 

same scan executed at a sequence of positions on the sample separated by lOpm 

horizontally. In particular, scans "A" and "C" were at the same place, but show 

strong differences. After this series was taken, little further 'life' remained anywhere 

in the sample. It is therefore not clear whether the observed effects were caused by 

radiation damage or not, so a future experiment with Limmortal' crystals using a 

cryocooler is planned. 

I X25 

5 

4 

3 

g 

2 

1 

Figure 1. Measured x-ray reflectivity, 

normalized to the Fresnel theory, for liquid gallium at room temperature. Inset 

shows the best-fit density profile. 

Figure 2. Normalized reflectivity data 

for liquid gallium at room and elevated 

temperatures. 

Rear pinhole position [urn] 

Figure 1. Coherent diffraction patterns recorded from different parts of a cubic 

insulin crystal. 
X25 Spin-polarized XANES of First Metalloprotein - Demonstration with 

Rubredoxin 

X. Wang, A. Froeschner and S.P. Cramer 

During our fall beamtime, we conducted high resolution KP fluorescence experiments at Fe K-edges using spin state selective detection. We have successfully 

measured first KO emission spectrum and spin-polarized X-ray Absorption Near 

Edge Structure (XANES) of an Fe protein, pf. Rubredoxin. The Kp emission 

spectra for high-spin oxidized Rubredoxin, excited at 7200 eV, are shown in Fig. 1. 

The spectrum is split into two regions. The main peak (known as Kp1,3) is found 

at around 7057.5 eV, while the satellite (KP') is at 14 eV lower energy side. The 

spin-polarized XANES are shown in Fig. 2. The spin-down edge is measured by 

monitoring the fluorescence at the KP peak and the spin-up edge at the Kp' region. 

The difference between the spectra is clearly shown in the pre-edge region. In the 

spin-down spectrum, there is a strong feature about 9 eV below the edge, which can 

be assigned to ls--t3d transitions, while there are not any distinct features in the 

spin-up spectrum. For high-spin d5, all the spin-up states were occupied while 5 

spin-down states are still available. When monitoring spin-up transitions (selecting 

KP'), there are no transitions allowed by the spin-selection rules, while spin-down 

transitions (detecting at KP) are allowed. The Kp detected edge also shows sharper 

features when compared to the regular K-edge (detected by transmission or total 

fluorescence) since the lifetime broadening of 1s core hole is eliminated. 

There is some fine structure on the pre-edge features, which may correspond 

to the splitting between the t2g and eg levels (10 Dq is assigned as the energy 

difference) in tetrahedral symmetry, is not seen in normal absorption edges since 

the 10 Dq around 1.1 eV) is buried within the Is core hole lifetime broadening 

(1.25 eV). I here are also more features on the top of the absorption edges, not 

visible in the normal K-edge, which will require more extensive analysis. Each of the protein spectra presented below are the result of between 5 and 7 

hours of signal averaging, with the exception 15 hrs of spin-up XANES spectra. 

Fd 

E Figure 1. KP emission spectrum of Rb. F 

I' .... ....... .... 1 'nm nw nw nm nm m Ma0 F=w (-0 

Figure 2. Spin-polarized XANES of Rb. 

Complex of elongation factors EF-Tu and EF-Ts 

Y. Wang (Yale University), Y. Jiang (Yale University), M. Sprinsl (University of 

Bayreuth), P. B. Sigler (Yale University and HHMI) 

The structure of the complex of bacterial elongation factors Tu and Ts has been 

studied by xray crystallography. The structure determination of the complex will 

provide important information on the mechanism of nucleotide exchange in elongation factors and other members of the GTPase superfamily. A native crystal of the 

complex has been measured to 3 A at the X25 beam line of NSLS. It has a P21 form 

with a=120 A, b=127 A, c423 A, b=90.3. At present time derivative crystals are 

under study to solve the structure. 

I X25 
I 

w 

w 

w 

*' . 

Glancing-Incidence X-Ray Magnetic Scattering Studies of the UOz x22c, 

(001) Surface X25 

.. , . 0 0.05 0.10 0.15 020 

L (UnH1 of 0) 

Figure 1. Intensity of the (1OL) magnetic truncation rod measured at three temperatures below the bulk Neel temperature of 30.2 K.Inset: Transverse scan through 

the (1OL) rod at L = 0.06. 

I X26A I Micro-XAFS investigations on aqueous metallic species in fluid inclusions up to 43OOC 

Alan J. Anderson (St. Francis Xavier Univ., Canada), Robert A. Mayanovic 

(Southwest Missouri State Univ.), Saga Bajt (U. of Chicago) 

The x-ray microbeam capability of this beam line was used to collect XAFS 

spectra from aqueous zinc species in individual fluid inclusions at elevated temperatures. The fluid inclusions examined in this pilot study occur in quartz and are 

typically less than 100 pm in their longest dimension. Synchrotron x-ray fluorescence (SXRF and microthermometric analyses indicate that the studied inclusions 

35 wt% NaCl equivalent. Zn K-edge micro-XAFS measurements were made on a single fluid inclusion at temperature intervals of approximately 50 degrees, ranging 

from room temperature to 43OoC. Examples of the XAFS spectra collected from 

test solutions and high temperature fluid inclusions are shown in the figure below. 

The x-ray optics included using a single Si(ll1) channel-cut monochromator, an 8:l 

Al(Pt coated) focusing mirror, and a pinhole aperture positioned at the focal plane. 

The XAFS spectra were collected in the fluorescence mode using a Si(Li) detector. 

A programmable heating stage mounted on the X-Y-Z- mobile stage of the x-ray 

microprobe beam line was used to heat the sample. 

Initial results indicate that the tetrahedral chlorozinc(I1) complex, ZnClf-, is 

the dominant aqueous zinc species in the fluid inclusions up to 400°C. This result 

is surprising in view of previous solubility studies which indicate that the neutral 

complex ZnClzO is dominant at temperatures greater than 3OO0C in solutions in 

the 0.5-5.0 M total chloride range. Reasons for this discrepancy are currently under 

investigation. 

We have demonstrated that structure of metal complexes in high temperature solutions can be obtained directly by using the micro-XAFS technique on individual 

fluid inclusions. This method may be applied to studies of synthetic fluid inclusions of known composition, in order to provide new insights on metal complex 

stability and coordination in high temperature-high pressure aqueous electrolyte 

solutions. Such studies are important for understanding the thermodynamics of 

metal complexes in hydrothermal fluids occuring in crustal rocks, nuclear reactors, 

and geothermal power generators. 

contain meta Ai ferous (Mn, Fe, Zn, Pb, Sb) chloride brines with a salinity of about 

r .- 
X26A Chemical Speciation of Uranium in Contaminated and Chemically 

Remediated Soils by Micro X-ray Absorption Spectroscopy * 

P. M. Bertsch, D. B. Hunter, and P. R. Nuessle (University of Georgia) 

Employing spatially resolved XAS and X-ray fluorescence (SXFU?) spectroscopy 

we have investigated the distribution and chemical speciation of U in contaminated 

soils and sediments. X-ray absorption near edge structure (XANES) spectroscopy 

demonstrated significant spatial heterogeneity in the oxidation states of U in the 

samples that was clearly discernible on a 20 to 100 pm scale. As a result of this 

spatial heterogeneity, we developed a three point calibration method to rapidly determine U oxidation states. The total counts obtained with the monochromator 

positioned at the U(IV) edge were divided by the total counts when the monochromator was positioned at the maximum of the U(V1) white line, i.e.,12 eV above 

the UIIV) edge, with both being normalized to the background collected at -50 

eV beow the absorption edge. The reproducibility in the ratio obtained for 11 

replications of the U(1V) and U(V1) reference samples was UO,(c) = 0.55 zt 0.03 

and UOit = 0.25 f 0.01. This enhances the ability to collect oxidation state information at much lower U concentrations in a reasonable time frame and allows for 

the examination of hundreds of individual grains or for the generation of oxidation 

state distribution maps at a 20 pm spatial resolution. Experiments conducted on a 

thin section of mixed U containing mineral phases where full XANES spectra were 

also collected on selected regions confirmed the ability of the method to delineate . This experimental apto evaluate the efficacy 

of a number of liviviants and other chemical remediation technologies. 

proportions of U in different oxidation states 

proach is currently being applied to U 

* This research was supported by contract DE-AC09-76SR00819 between the University of Georgia and the US. Department of Energy 

X26A Quantitative microanalysis of oxidation state ratios in complex silicate minerals - (I) Fe in amphibole 

J. S. Delaney (Rutgers U.), M. D. Dyar (West Chester U.), S. Bajt and S. R. 

Sutton (CARS, U. of Chicago) 

The amphiboles are chemically and crystallographically among the most complex 

of the silicate minerals found in common rock types. Unlike many common minerals 

amphibole can have ferric/ferrous iron ratios varying between 0 and 1 depending on 

the substitution of H+ into the crystal lattice. The samples studied here have bulk 

ferric/ferrous ratios varying from 0.18 to 1.0 determined previously by Mijssbauer 

spectroscopy [I] and wet chemistry 21. 

Synchrotron microXANES SmX analyses of the ferric/ferrous ratio made in 

50x30 micrometer areas, and t iI e Mossbauer and wet chemical bulk analyses agree 

well. The SmX technique uses the position of the pre-edge feature of the Fe Kabsorption XANES spectrum [3] and the ferric ferrous ratios of amphiboles were 

based on ratios in pure hematite (l.O), magnetite (0.67) and synthetic fayalite (0.0) 

[3]. Comparison of results from the two techniques shows good consistence between 

microbeam and bulk techniques and suggests that the influence of the crystal structure on the XANES pre-edge of the amphibole minerals is minimal. Systematic 

variation of ferric/ferrous ratios within a single amphibole crystal was repeatably 

observed and identified as oxidation state zoning. 

This represents the first microanalytical measurement of oxidation state variation 

within a single natural crystal. Ferric/ferrous ratios in complex minerals such as 

amphibole can be reliably measured with nearly comparable spatial resolution to 

microanalysis techniques used for major element abundance determination. The 

demonstrated ability to measure zoning in crystals permits to monitor the influence 

of oxygen and water fugacity changes during the crystallization of amphibole in 

natural silicate systems for the first time. Synchrotron microXANES analysis of 

oxidation states in mineral systems provides a powerful new tool for studying natural 

crystalization environments. 

calibrated against both the Mbssbauer data an d an independent linear calibration 

References: [l] Dyar et al. (1993 Amer. Mineral. 78, 968. 

Cosca et al. (1991) Contrib. Ll ineral.Petro1. 108, 472. 

Bajt et al. (1994) Geochim. Cosmochim. Acta 58, 5209. 
.. . , 

hY 

rp 

N 

, 

X26A 

In-situ detection and chemical analysis of extraterrestrial material 

captured in aerogel * 

I ,'- 

L ' ' 

1 ., 

George J. Flynn (SUNY at Plattsburgh), Saga Bajt and Stephen R. Sutton (CARS, 

U. of Chicago) 

Low density silica aerogel has been used for the intact capture of micrometeorites 

and space debris on earth orbital satellites and it is the capture material proposed for 

the "Stardust,' cometary flyby and sample return mission. Typical 5 to 50 micron 

extraterrestrial particles and earth orbital debris are decelerated in the aerogel, and 

come to rest several millimeters beneath the surface. In-situ chemical analysis is 

desirable to determine which of the captured particles are space debris (typically 

composed of All Al-oxide, or metals) and which are extraterrestrial (typically of 

chondritic meteorite composition). 

Six fragments of the Allende meteorite, each 30 to 50 microns in size, were captured in a silica aerogel of density 20 mg/cc, after being shot at the aerogel at about 

3 km/sec. These fragments were buried at depths ranging from 1.1 to 4.9 mm below 

the surface of the aerogel. 

We examined these six fragments using the X-ray Microprobe at Beamline X26A. 

They were located using the video-microscope imaging system, and x-ray fluorescence spectra were acquired. The fluorescence x-rays are attenuated by passage 

through the aerogel, thus the sensitivity for low-Z elements decreases with increasing burial depth. We detected Cr, Nil Fe, Cu, and Zn in all six particles, but 

detected Ca only in the particles buried to less than 3.6 mm, and detected a very 

weak A1 fluorescence only in the particle buried at 1.1 mm. The detection of the volatiles Cu and Zn provides an unambiguous way to distinguish between man-made steel fragments orbital debris) and chondritic micrometeorites which have abundant Zn and Cu \ . The in-situ detection and analysis of 

on earth-orbiting satellites or on cometary flyby/sample return missions is feasible 

using the X-Ray Microprobe at Beamline X-26A. 

Allende I ragments demonstrates that in-situ analysis of aerogel capture cells flown 

ALOA I DUST * 

George J. Flynn (SUNY at Plattsburgh), Saga Bajt, and Stephen R. Sutton (CARS, 

U. of Chicago) 

As part of a continuing study of the chemical composition of interplanetary dust 

particles (IDPs) recovered from the Earth's stratosphere by NASA, we measured the 

abundances of elements from Cr to Sr in 13 large IDPs (each 35 to 50 microns in size) 

using the X-ray Microprobe at Beamline X-26A. The average composition of these 

13 large IDPs is very similar to the composition of the CI chondritic meteorites, 

which are believed to represent the solar composition. The averages of the volatile 

elements Cu, Zn, Gal Gel and Se all within about 20% of the CI composition in this 

set of large IDPs. This is distinctly different from the results we have previously 

measured on 51 smaller IDPs (generally 10 to 20 

enrichments of the volatiles Cu, Zn, Gal Gel and 

This suggests large IDPs which are strong enough to resist fragmentation 

ection, are chemically different from typical smaller IDPs, and may reflect a difference in the source(s) being sampled by the two types of IDPs. A subgroup 

of the smaller IDPs (9 of 51 particles) have a composition similar to CI meteorites 

and these large IDPs (1). 

Bromine is enriched relative to the CI meteorites in most of these large IDPs as it 

is in the smaller IDPs (1). We observed that two Br-rich IDPs (Br >300 ppm which 

and second analyses, presumably due to sample heating during the first analysis. 

In follow-up experiments on 5 Br-rich IDPs, we demonstrated that, over a 2-hour 

period of exposure to the x-ray beam, a roughly exponential loss of Br occurs. After this period the Br concentration remains constant for beam exposures of up 

to 12 hours. Since the beam heating is small, the observations suggest there are 2 

types of Br in these IDPs, a very weakly bound Br component, possibly Br surface 

contamination, and a more strongly bound Br component, presumably bound in a mineral phase. No loss of Zn or Cu was observed, indicating they are more strongly 

bound than the Br. Experiments to determine if C1 and S are also lost are presently 

in progress. 

REFERENCES: 1. Flynn, G.J. et al. (1993) Lunar and Planet Sci. XXIV, 495- 

496. 

were each analyzed twice showed about a factor of two Br loss between t h e first 

* This work was supported by NASA Planetary Materials and Geochemistry grant * This work was supported by NASA Planetary Materials and Geochemistry grant 

NAG-9-459 (GJF) and NAGW-3651 (SRS) NAG-9-459(GJF) and NAGW-3651(SRS) 
I Sorption of iodine species on some minerals I X26A I ~~ ~~ 

Mark F'uhrmann (BNL), Saga Bajt (CARS, U. of Chicago), Martin Schoonen 

(SUNY at Stony Brook) 

This study represents part of a systematic experimental research program to 

investigate the interactions between aqueous iodine species and geomaterials. In 

this abstract we report the development of a XANES technique to examine the 

speciation of iodine in solutions on mineral surfaces in contact with those solutions. 

Using XANES we determined the speciation of iodine in solution and on the 

surfaces of minerals in contact with several iodine solutions. The analysis was performed at the synchrotron x-ray microprobe beam line X26A. The iodine Ls 

edge is at 4.557 keV which is close to the low hardware limit (4 keV of the Si(ll1 

with He gas, the flux of the x-rays was almost the same as if the x-rays were in 

vacuum. The low energy of the iodine edge and interferences caused by some other 

elements (the most troublesome was Ca) required use of solution concentrations of 

iodine that are much higher than those found in the environment. 

Having established that iodine speciation was discernible through XANES, we 

were then able to examine its speciation on minerals and solutions in contact with 

them. Intensity of the iodine signal above the absorption edge obtained in fluorescence mode was used to determine the concentration of iodine in the liquid and on 

the solid of each sample. 

Magnetite sorbed iodide from solution but not iodate. Biotite, in contrast, sorbed 

iodate from the buffered solution but did not take up any iodide. In neither case 

was sorption accompanied by any obvious change in speciation. However, there is a slight change in the scan on iodide on the solid phase of magnetite in which the 

6 eV shoulder is less distinct than in the reference solutions. This may represent a mixture of iodide and iodine on the magnetite surface while the solution in the 

same cell contains iodide. 

In the pyrite/iodate system, iodine was removed from solution accompanied by 

reduction from iodate to iodine in both solid and liquid phases. Significant sorption 

resulted in the very low value for (intensity of the iodine signal in the liquid 

divided by its intensity on the solid) of 0.5. The pH was lowered to 4.1 by dissolution 

of the pyrite surface, even though the solution was buffered. Iodine speciation can 

be controlled by pH and this is probably the case here, but there was a strong signal 

from 12 given by the slurry indicating sorption. In the pyrite/iodide system there 

was no sorption and no change in speciation in either the liquid or the slurry. The 

high value of 1~1s indicates that iodide is enriched in the supernate compared to 

the slurry, the result of ion exclusion caused overlapping charge fields of mineral 

grains repelling the similarly charged iodide ion. 

monochromator. By enclosing the whole end of the beamline in a p 1 astic bag fiUe d 

Investigation of the pre-edge absorption XANES structure I X26A 

Albert L. Hanson (BNL), and SaSa Bajt (CARS, U. of Chicago) 

The pre-edge scattering of x rays is being studied with a high energy resolution 

wavelength dispersive spectrometer to determine how valence states of the scattering atoms can be extracted directly from the scatter spectra. At an energy of a 

few electron volts below the absorption edge of iron, spectra from iron in the $3 

valence state exhibit peaks characteristic of resonant, inelastic scattering. However, 

if the iron exists in the $2 valence state, there are no peaks characteristic of the 

resonant, inelastic scattering. Because of the substantial differences in the scatter spectra between iron in the +2 and the +3 valence states, this scattering is a 

promising technique for quantitative analyses of the valence states. Present effort 

is to determine the accuracy of such an analytical technique. 

duction of Smectite Structural Fe by Organoborates * X26A 

1.6 % 

on 

- 

5 1.2 

- 8 

5 0.4 ----3 Hour. 

L 

- -Untreated n 0.8 

m ---z Hour. 

0 -----s Hour. z 

- 

0 

-20 0 20 40 60 80 

Rolatlva Energy (oV) 

Figure 1. 

Three-dimensional characterization of surface-controlled traceelement zoning patterns using synchrotron x-ray fluorescence microanalysis 

11 

X26A 

SWy-1 montmorillonite 

* This research was supported by contract DE-AC09-76SR00819 between the 

University of Georgia and the U.S. Department of Energy 

Fe Reduction 

0.6 

- 0.5 em 0.4 

0.3 

0.2 

e 

- 

E 0.1 

0 

8 

o/ 

/ 

P 

P ' +NQ-l 

-3 -swy-1 

0.64 0.01 0.88 1.05 1.12 -0.1E. ' " ' ' ' ' " ' " " " ' ' ' " ' ' ' ' " ' J 

','A .o' 1,. . .VI 

Figure 2. 
.I 

, '. 

N 

00 

N X26A REE intrasectional zoning in apatite, determined using synchrotron 

x-ray fluorescence microanalysis (SXRFMA) I X26A I Chromium Leaching versus Oxidation State for a Contaminated Solidified/Stabilized Soil 

Terry L. Rinehart, Darrell G. Schulze (Purdue Univ.), R. Mark Bricka (US Army 

Corps of Eng.), Saga Bajt (Univ. of Chicago), and Ernest R. Blatchley, I11 (Purdue 

Univ.) 

The toxicity, solubility, and mobility of chromium in soil are strongly dependent 

upon its oxidation state. Solidification/stabilization (S/S) is a potential method for 

preventing Cr leaching from contaminated soil. We evaluated the leaching behavior 

of untreated and solidified/stabilized Cr contaminated soil samples obtained from 

two locations at a military facility in Louisiana. The leaching of Cr, as measured by 

the Toxicity Characteristic Leaching Procedure (TCLP was expected to be depensize distribution were obtained for each sample and portions of each sample were 

solidified with Type I Portland cement. The oxidation state of Cr was determined 

by x-ray absorption spectroscopy (XAS). The sample from Site 1 contained 478 

mg/kg total Cr while the sample from Site 2 contained 1272 mg/k total Cr. 

The TCLP Cr concentration for Site 1 untreated soil was 3.4 mgfL and 2.0 mg/L 

for the S/S treated sample. The sample from Site 2 had TCLP Cr concentrations 

below the analytical detection limit (<1.0 mg/L) for both untreated and S/S samples. The XAS data showed the presence of the more mobile and soluble Crt6 at 

Site 1 but not at Site 2. The use of Portland cement alone was not effective in reducing the CrS6 to the less soluble and less mobile CrS3, or in physically preventing 

leaching of CI+~. 

dent upon the Cr oxidation state. The pH, cation exc k ange capacity and particle 
I 

Oxidation State of Manganese in Rice Blast Fungal Lesions I X26A 

Darrell G. Schulze, Don M. Huber, A. K. M. Shahjahan, Morris Levy (Purdue 

Univ.), Sea Bajt (Univ. of Chicago), and Barbara Illman (USDA Forest Products 

Lab.) 

The blast disease of rice is one of the most important plant diseases worldwide 

because rice is a major source of food for 60% of the world's population. Manganese 

is an essential mineral element for photosynthesis, lignin synthesis, and other plant 

metabolic functions in its Mn2+ or Mn3+ forms, but when oxidized to Mn4+ it 

precipitates as physiologically unavailable Mn oxides and hydroxides. Pyricularia 

grisea (Cooke) Sacc., the fungal causative agent of rice blast, is a strong Mn oxidizer 

in agar culture. Thus, fungal oxidation of Mn may be an important part of the 

disease processes. 

We used micro x-ray absorption near edge structure (XANES) spectroscopy to 

compare Mn oxidation states in healthy areas of rice leaves with Mn oxidation states 

in blast lesions caused by P. grisea. Healthy tissue contained only Mn2+, whereas 

blast lesions contained significant quantities of Mn4+. 

These results suggest that the ability to oxidize Mn may be a significant factor 

in determining the virulence of P. grisea and that resistant rice varieties may have 

developed strategies to suppress or prevent Mn oxidation by the fungus. 

across the boundary between ponded waters and sediments using X26A 

Real time, in-situ tracking of selenium transport and reduction 

micro-XANES I/ 

Tetsu K. Tokunaga (LBL), SaSa Bajt (CARS, U. of Chicago), Stephen R. Sutton 

(CARS, U. of Chicago), and Patterson R. Nuessle (SREL, U. of Georgia) 

Contaminated transport in sediments and waters are being studied using the synchrotron x-ray microprobe and x-ray absorption near edge structure (XANES), in 

order to obtain direct, noninvasive, real time data on trace element concentrations. 

These methods are being used to test models of reactive transport which invoke the 

importance of micro-scale heterogeneities and processes. Many important reactions 

controlling chemical cycling in the environment occur at and very near the boundaries between sediments and overlying waters. The synchrotron x-ray fluorescence 

microprobe at the NSLS was used in monochromatic mode (micro-XANES) to obtain spatially- and temporally-resolved speciation of Se in a water-sediment system. 

This present study has focused on diffusion and reduction of selenium at boundaries 

between sediments and ponded waters. 

Earlier, larger-scale experiments on transport of selenium from ponded waters 

into sediments indicated that reduction reactions were taking place within a few 

millimeters of the water-sediment boundary. In our most recent work, Se transport and reaction were studied in a 20 mm, saturated sediment column, over which 

waters containing Se in the form of soluble Se(V1 were hydrostatically ponded. 

monochromatic microbeams at 250 to 500 pm increments, at a set of x-ray energies which permitted determinations of Se concentrations and oxidation states. In 

addition, selected locations within these columns were scanned over the com lete 

XANES region. This micro-XANES experiment permitted trackin of Se(V1 reduction at pond-sediment boundaries. Results show reduction of Se VI) to Se IV), 

and ultimately to Se(0) within specific zones in the sediments. The 0 ocation of the 

active reduction zone was within the surface 2 mm in an extremely reducing sediment, while it was displaced several mm deeper in a less reducing sediment. These 

results are consistent with diffusion-limited transport calculations. The possibility 

that organo-Se compounds may also accumulate in reducing zones is currently under 

consideration. Micro-XANES results ruled out the possible formation of significant 

concentrations of colloidal Se(0) and of organo-Se compounds in these ponded waters. 

Vertical profiles through the water and sediment co 1 umns were scanned in front of 
'I,., 

, I' 

X-Ray Fluorescence Analysis With High Energy Resolution * 

W.A.Caliebe(NSLS), SaEa Bajt(University of Chicago), C.-C. Kao(NSLS) 

X-ray fluorescence is a well established analytical technique for elemental analysis in both basic and applied research. The energy resolution of Si(Li) or Ge(Li) 

solid state detectors, 150 eV to 200 eV, cannot resolve the small energy shifts in 

fluorescence energy or changes in lineshape. Therefore, we used a high energy resolution Rowland circle spectrometer based on a Si(333) analyzer. The crystal is 

spherically bent to a radius of 1 m and has an effective diameter of 35 mm. In this 

experiment we analyzed the Cr Ky fluorescence line (E4980 eV) in three different 

oxidation states, 0, +3 and $6. The fluorescence was excited using the focused 

white radiation at the beamline X26C. 

X-ray fluorescence lines originating from the decay of shallow core electrons or valence electrons should be particularly sensitive to the electronic structure of the 

sample. These fluorescence lines provide information about the occupied electronic 

states. The Ky fluorescence lines directly reflect changes inthe valence band so 

that differences in the oxidation state should be directly visible in the spectra. The 

figure shows the Ky line of the three different Cr samples. Ch metal shows a single 

peak at 5988eV, while that of Cr3+ and Cr6+ show additional satellite features. 

In comparison with that of Cr metal the energy of the main Cr3+ Ky line shifts 

by -4.4eV while that of the Cr6+ remains at the same energy. Also, a second peak 

appears at 5968.5 eV for Cr3+ and 5972.3 eV for CrSt. As expected, the Ky line 

is relatively sensitive to changes in the oxidation state. Theoretical calculations are needed for detailed interpretation of these lines. It should be noted that the 

fluorescence yield decreases by a factor of 7.5 from the Ka! to the KP line and by 

another factor of 20 to 30 from the KP line to the Ky line. 

I X26C I x26c I White Beam Microdiffraction for Spatially Resolved Strain, Microstructure, and Composition Mapping 

G. S. Cargill I11 and PA. Wang, Columbia University, and I. C. Noyan and E. 

Liniger, IBM Research, together with K. W. Jones, BNL Applied Sciences 

A system for strain, microstructure and composition measurements with micron or submicron spatial resolution in crystalline materials are being developed on beamline X26C. This system uses 5 to 30 keV radiation collimated and concentrated by a tapered glass capillary, together with an area CCD detector for measuring Laue 

patterns and an energy sensitive Si detector for measuring lattice spacings, as illustrated in Fig. l. Novel features are that the sample being studied need not 

be rotated in making strain measurements, which facilitates spatial resolution on micron and submicron scales, and that polycrystalline samples can be studied with 

spatial resolution on the order of their grain size. This system has been used for 

spatially resolved strain measurements and grain orientation mapping of polycrystalline films. Two mapping modes have been used: reciprocal-space mapping and 

real- space mapping. For reciprocal-space mapping the sample is fixed in position 

(x,?) and the SSD is raster-scanned over a range of angles a! and P. At each SSD 

position, the scattering angle 26'(a!,@) is calculated and scattered intensities are measured for energy windows of the multi-channel analyzer corresponding to var- ious (hkl) reflections. In this way, the orientations of grains within the irradiated 

and scattered intensities are measured for energy windows corresponding to 6iRerent (hkl) reflections as the sample position is raster- scanned in x and y. From these 

measurements, the locations of grains having the specified orientations are determined. Strain measurements are made using energy dispersive diffraction patterns 

from single grains, like that shown in Fig. 2(b). 

volume are determined. A result from such measurements is shown in Fig. 2(a 

For real-space mapping, the SSD is fixed at a particular scattering angle 26' alp 

IOW ---. ..._.____.... 

Lso 5915 5970 5975 5980 598 5990 1995 

t",W [.VI 

Figure 1. Ky fluorescence line for Cr metal, Cr3+ and Cr6+. 

* We would like to thank Dr. Douglas B. Hunter (SREL) for preparing the chromium 

oxide samples. This work was partially supported by US DOE grant DE-FG02-92ER14244, 

DEAC02-76CH00016 (BNL), and NASA grant NAGW-3651. 

**.A -Ln 

(0) (b) 

Figure 2. Diffraction from a 4pm thick 

A1 (4 wt.% Cu) film. (a) An A1 (111 

intensity map in reciprocal space. (b Energy dispersive diffraction pattern for 

detector position determined from (a), 

showina the (111) and (222) diffraction 

lines frGm one'grdn within t6e irradiated 

Figure 1. volume, as well as CuKa and CuKP fluiffraction/microfluorescence system. orescence lines. 

Schematic of x-ray microd- 
I Search for Structural Modulations in UPt, Using Laue Diffraction 1 X26C I 

B. Ellman, M. Sutton, L. Taillefer (McGiU University), and G. Shea-McCarthy 

(University of Chicago) 

Among the materials believed to exhibit unconventional superconductivity, UPts 

is unique in possessing two well defined superconducting phases in zero magnetic 

field. Generally, the multiple phases are believed to arise from the symmetrybreaking effect of an extremely weak antiferromagnetic order parameter. With mo- ments lying in the hexagonal plane, the AFM order would stabilize otherwise degenerate superconducting states at two different temperatures, leading to the observed 

behavior. However, any symmetry breaking field would play a similar role, including crystallographic distortions. Recent transmission electron microscopy (TEM) 

studies [1,2] of Upt~ have suggested the presence of long wavelength (M 60A) modulations of the underlying P6-3/mmc structure. In the case of single crystal whisker[l] 

samples (which grow spontaneously from the melt), the modulation has been shown 

to exist over many microns. TEM, however, requires extreme sample preparation 

techniques (e.g., ion milling) that might introduce artifacts. We have performed 

Laue diffraction measurements at X26C to try and detect the modulations. The 

ability of Laue experiments to cover a large volume of k-space makes them an ideal 

tool to search for a modulation whose exact structure is imperfectly known. 

The samples were a whisker approximately 0.1 x 0.05 x 2mm3, and a larger sample 

cut from a bulk crystal. The data were taken using unfocused white beam and a diffuse background subtracted. 

A typical diffraction pattern of the whisker, using an exposure of 5 s, is shown in 

Fig. 1. Careful indexing is required to identify Bragg peaks due to an incommensurate modulation in the presence of the many peaks generated by the underlying 

structure. The result of such an analysis is shown in Fig. 2, where only relatively 

intense peaks have been shown. After further analysis of this and other patterns, 

we will be in a position to either identify the modulation in an undisturbed sample or set a convincing limit on the presence of crystallographic symmetry breaking 

factors in UPt3. 

B. Ellman, A. Zaluska, and L. Tdefer, Physica B 205, 346 (1995). 

P.A. Midgley et al., Phys. Rev. Lett. 70, 678 (1993). 

Figure 1. Laue diffraction pattern of a 

single crystal whisker of UPt3.The crys- tal is oriented such that the a-c plane is 

rotated 19 degrees about E with respect 

to the image plate. CL 

Figure 2. Predicted Laue peak positions 

for the data of figure 1. By carefully 

comparing the theory and data, we may 

either identify or exclude reflections due 

to a structural modulation. 

‘On- I X26C I The effect of microgravity on the protein crystal growth: 

canavalin A as a case study * 

G. Shoham and L. Arnowitz (University of Jerusalem, Jerusalem, Israel), V. Stojanoff and D. P. Siddons (BNL-NSLS) 

The present report is part of a long range project on the study of the effect 

of microgravity on the growth of macromolecules. The Space Shuttle is a potential platform for growth of protein crystals of exceptional quality. Our goal with 

this preliminary work is to show that crystals grown under microgravity conditions 

present improved lattice perfection. Monochromatic as well as Laue techniques will 

be employed to access the crystal quality. Concanavalin A crystals grown under 

identical conditions except for gravity have been grown on Space Shuttle mission 

STS 69 (at close to 0 g) and at the laboratory (lg, Kennedy Space Center) by the 

membrane dialysis technique. The crystals were brought to the NSLS immediately 

after the Space Shuttle landing. Several methods were used to access the quality of 

the crystals: monochromatic x-ray topography, the Laue method, and the rotation or oscillation photography. X-ray topography showed that crystals grown under 

microgravity conditions present in general a smaller concentration of defects then 

there counter parts grown on the ground. However, different salt concentrations also 

affect the quality of the crystals. These results are in agreement with the diffraction 

data collected. Crystals grown at 0 g diffracted well beyond 1.2 angstrom resolution, while the 1 g counterparts diffracted to a resolution limit of about 1.6 a only. 

The evaluation of the results is still in progress and will be divulged shortly. Nevertheless, these preliminary results strongly suggest that micro-gravity environment 

could be used to extend the resolution limit of protein crystals, at least in the cases 

when all other crystallization conditions have been optimized. 

* The support of Biocars, and especially of Ms. G. Shea McCarthy, is gratefully adcnowledged. This preliminary micro gravity study was made possible with the great assistance 

and support of IDEA and BioServe Space Technologies. 
w 

N 

Figure 1. 

X26C Fabrication of a mm-wave undulator cavity using deep x-ray 

lithography 

I 108GHz 

R 312MNm 

Frcqucncy 

Shunt 

Quality Fnctor Q 2160 

Pcnk Power P 29.1 kW 

Charge Pyticlc Energy 

Deflection Fnclor > 0.0467 

Undulntor Wavelength A 1.0 mm NumbcrofPencds N 80 

Lcngth I 8cm 

Gap Height g 0.6cm 

650-750 MeV 

Figure 2. Table I - The 108-GHz undulator parameters with the APS linac/rf 

gun. 

Laue crystallographic studies of enzymatic intermediates: isocitrate 

dehydrogenase 

Barry L. Stoddard, Jill M. Bolduc, and Dave H. Dyer (Fred Hutchinson Cancer 

Research Center, Basic Sciences Division), William G. Scott (Medical Research 

Counci, Cambridge, England), Robert M. Sweet and Paul Singer (BNL Biology 

Dept.) 

Site-directed mutagenesis, enzyme kinetics, and fast Laue diffraction were used 

to solve the structures of two different, sequential intermediates which accumulate as steady-state complexes during turnover by isocitrate dehydrogenase, and to 

visualize the structural mechanism of electron transfer for this enzyme. 

Two kinetic mutants, which display large, unique rate barriers at separate steps 

of the catalytic mechanism, were used to visualize these species within the overall 

reaction pathway. These two site-directed mutants, Tyrosine 160 to Phenylalanine 

(Y160F) and Lysine 230 to Methionine (K230M), are amenable to either singleturnover or steady-state Laue experiments. Each mutant displays a wild-type rate 

constant for one half-reaction, but a substantial rate decrease for the other half 

reaction, producing two different rate-limited intermediates. 

Based on the available kinetic parameters in the crystal, polychromatic x-ray 

diffraction data were collected from several crystals of each mutant before and 

after substrate binding at beamline X-26C at the Brookhaven National Synchrotron 

Light Source. Difference maps were then calculated with experimentally determined 

Fourier coefficients: [Fo (after substrate) -Fo (before substrate)] acalc, using phases 

calculated with protein coordinates prior to any refinement and then after an initial 

round of refinement against the Laue data. No substrate or water molecules were 

included in either phase calculation. The strongest features of the maps calculated 

at either stage are identical and easily modelled by the components of the ratelimited enzyme complexes. The initial R-factors for the protein model prior to 

refinement were ap roximately 30%; the R-factor after initial refinement were both 

approximately 192 The final refined R-factors after inclusion of substrates and 

metal were 18.3% and 17.4%, respectively. 

The difference map calculated for the tyrosine mutant (Y160F indicates the acwhich is trapped prior to hydride transfer. The protein fold, active site architecture, 

and conformation of bound isocitrate are unchanged relative to wild type enzyme 

with the exception of the side chain hydroxyl), as is the ensuing rate of enzymatic 6 ecarboxylation. The distance and orientation of the nicotinamide ring are consistent with the stereochemical transfer of the single proton from the chiral 2-R carbon 

of isocitrate to the re-face of the cofactor C4. Conversely, the difference map calculated for the lysine mutant (K230M) shows strong density for a bound sugar/metal 

complex but indicates that the nicotinamide ring and adjoining ribose and phosphate backbone of the cofactor are disordered, consistent with the conversion of 

the charged NADP+ to NADPH which is known to occur for this mutant with a rate unaffected by the mutation. The resulting rate-limited species, oxalosuccinate, 

has been confirmed by difference mapping and refinement is bound in a manner 

analogous to isocitrate; this is consistent with previous reports of oxalosuccinate 

acting as a catalytically competent substrate for the reverse hydrogenation reaction 

and the enzymatic decarboxylation. 

cumulation of a rate-limited Michaelis complex of isocitrate, NA b' P+, and Mg++ 
, 

I 

F 

N 

W 

W 

X-ray topography of tetragonal Lysozyme crystals 

V.Stojanoff and D. P. Siddons, Brookhaven National Laboratory, Upton, New York 

11973. L. Monaco, P. Vekilov, F. Rosenberger, CMMR, University of Alabama at 

Huntsville. 

I X26C 

same crystals after the topographic observations. The temperature/supersaturation 

regimes during crystal growth, the defect density detected by X-ray topography, and 

the diffraction resolution obtainable from the crystals were all strongly correlated. 

[l]Stojanoff, V., Siddons, D. P., Monaco, L., Vekilov, P. and Rosenberger, F. 

Submitted. [2 Stojanoff, V. and Siddons, D. P. (1995) Acta Cryst. A. accepted. 

I CCBM-6, J. Crystal Growth. [4]Stojanoff, V., Siddons, D. P., Monaco, L., Vekilov, 

P. & Rosenber er, F. Proceed. American Crystallographic Assn., abstract M132, 

Montreal CAI 71995). [5]St ojanoff, V., Siddons, D. P., Monaco, L., Vekilov, P.& 

Rosenberger, F. 

3]Vekilov, P., L onaco, L., Thomas, B. R., Stojanoff, V. and Rosenberger, F., Proc. 

Conference on Protein Crystal Growth, Panama City, USA, (1995). 

The support of Mr. D. Berman, Mr. N. Tempel, Ms. H. Kycia and Ms. G. 

Shea-McCarthy (CARS) are greatly apprec.iated. 

Figure 1. Figure 2. 

IX-ray topography: a tool for protein crystal quality diagnosis* I X26C I 

V. Stojanoff', E.H. Snell', D.P. Siddons' and J.R. Helliwel12 - ('BNL, 'Chemistry 

Department, University of Manchester, UK) 

For many years a significant effort has been made towards the growth of better 

quality macromolecular crystals for structural studies. Usually, the quality of the 

crystals is inferred from x-ray diffraction data, but recently, crystal growers have 

been trying to employ characterization techniques that would allow direct measurement of the quality of the protein crystal. 

Monochromatic x-ray topographic methods were used to compare the quality of 

lysozyme crystals grown in a dialysis reactor under identical conditions except for 

their exposure to the gravitational field. Fi ure la shows a topograph of a lysozyme 

crystal grown on the ground (1 g condition?, and figure Ib shows the topograph of a crystal grown on board of the NASA Space shuttle IML-2 mission 0 g condition). 

grown under 0 g condition shows large quite perfect regions while the crystal grown 

as a control in an 1 g environment presents a high density of defects along the whole 

crystal. 

Bosch, R., Lautenschlager, P., Potthast, L., and Stapelmann, J. 

of Crystal Growth 122, 310-316; Snell, E. H., Weisgerber, S., 

Weckert, E., Hoelzer, K. and Schroer, K. (1995) Acta Cryst D51 in press. 

Related publications and presentations at conferences: V. Stojanoff, D. P. Siddons, E. H. Snell and J. R. Helliwell to be published J. Syn. Rad. (1995 ; V. 

Stojanoff, E. H. Snell, D. P. Siddons and J. R. Helliwell submitted to Acta dryst 

A significant difference in the quality of the crystals was observe 6 . The crystal 

E. H. Snell, S. Weisberger, J. R. Helliwell, F. Weckert, K. Holzer and K: 

roc. ICCBM - 6, J. Crystal Growth. 

of G. Shea McCarthy of BioCARS is gratefully acknowledged. The 

Rigaku Corporation is thanked for financial support to JRH which covered EHS's 

expenses travelling to the NSLS. EHS has been funded by an EPSRC studentship. 

The European Space Agency is thanked for providing the flight opportunity on the 

NASA Space Shuttle IML-2 mission. 

(4 (b) 

Figure 1. Monochromatic x-ray topograph of a lysozyme crystal grown for the IML2Space Shuttle Mission in a normal gravity condition (a) and under microgravity 

condition (b). 
I '. , 

, .*'. 

Use of Laue Diffraction Patterns in both Macromolecular and SmallMolecule Crystallography 

. -- .. , ," 

X26C X27A 

In Situ X-ray Diffraction Structural Characterization of Hydrogen 

Uptake in an Operating Nickel-Metal-Hydride Electrode 

T.R. Thurston, N. Jisrawi, S. Mukerjee, and J. McBreen (BNL) 

With the advent of lap top computers, portable video cameras, and especially new 

regulations promoting electric vehicles, a dramatic increase in demand for battery 

systems has occurred. There are many conflicting factors that must be satisfied 

for a battery system to be commercially viable, so it is not surprising that the 

most promising new battery systems, such as the nickel-metal-hydride system, are 

underutilized and not well understood. 

The metal hydride alloys that have performed best as anodes in battery systems 

have been based on LaNi6 or ZrNiz prototype alloys, but with the substitution of 

various other elements such as Ce, Co, Fe, Mn, etc. for portions of the La, Zr, and 

Ni. A typical example of such an alloy is Zr0.6Ti0.~V0.6Nil.lMno.~Feo.z, which is the 

alloy we examined here. From a fundamental point of view, it is not understood why 

the substitution of these various metals improves the hydrogen uptake performance 

of the alloy. To date, most improvements in nickel-metal-hydride alloy technology 

have come about through trial and error methods. 

In this abstract we demonstrate that it is possible to obtain structural data on such alloys as they charge and discharge hydrogen under in situ electrochemical 

conditions. With such an approach, information useful for guiding the development 

of better nickel-metal-hydride alloys can be obtained. 

The experiments were performed on X27A with a Si(ll1) monochromator and 

LiF(2OO) analyzer. The x-ray energy was set at 24.5keV, and a transmission scattering geometry was used, so the bulk of the 0.3mm thick electrode was probed. The 

hard x-ray energy also allowed us to examine the electrode even when it was in a 6 

molar KOH electrolyte solution. An electrochemical cell was specially constructed 

for this experiment, and the electrode was charged and discharged several times 

while x-ray diffraction experiments were being performed. 

The main point of this abstract is that we were abIe to obtain x-ray diffraction 

peaks with counting rates up to 30,00O/sec under these conditions, and readily 

monitor the structural state of the bulk of the alloy (not just a few microns within 

the surface as hydrogen was electrochemically charged and discharged. The volume 

the coexistence of two phases with different hydrogen densities analogous to the 

gas absorption behavior of this alloy were confirmed. Thus, this work demonstrates 

that it is possible to routinely monitor the structure of commercially viable nickelmetal-hydride electrodes under in situ electrochemical conditions. 

change oft h e unit cell was easily determined as a function of electric potential, and 
. .-.I 

Synchrotron X-ray Scattering Characterization of High Temperature Superconducting Wires 

x27~, 

X22A 

Recently, there has been a dramatic rise in interest in nanoscale size materials. 

This has occurred largely because new techniques have been developed to manufacture these materials in greater quantities. It has also been recognized that nanoscale 

size materials often have unique and desirable properties that are different from the 

corresponding bulk properties. For example, the catalytic properties can become 

greatly enhanced when a material is reduced to nanoscale dimensions. 

Two of the most basic properties that must be characterized when making 

nanoscale clusters are the average cluster size and the polydispersity of the clusters 

in a sample. The size can often be roughly estimated from electron microscopy 

measurements, but the only way to determine both parameters while averaging ove 

the entire sample volume is through small angle x-ray scattering experiments. 

To fulfill this characterization need, we have constructed a Bonse-Hart camera which can be mounted at the X22A beam line. Unfortunately, the upstream 

monochromator crystal of this beam line scatters in a horizontal geometry, so we 

have had to place a vertically scattering collimator crystal before the sample posi- tion. This has usually been a 5-bounce channel cut Si 111 crystal. The analyzer 

up, we have been able to obtain a dynamic range of nearly loQ with a range in q 

from to 10' A-'. 

The samples we have examined were made using an inverse micelle technique 

which produces samples with very good polydispersity characteristics. Therefore, 

the small angle scattering curves show interference effects wiggles) and it is rather 

We have examined a number of cluster samples including Au, Pd, Rh, and MoSz 

that have been prepared under differing conditions and with differect average sizes. 

More materials will be examined in the future as the inverse micelle technique is 

developed further. 

crystal is also a 5-bounce channel cut Si(ll1) crystal. Ivh it this rather simple set 

simple to then fit the SAXS data to obtain the size and PO \ ydispersity of a sample. 

Small Angle X-ray Scattering (SAXS) Investigations of Metal and 

Semiconductor Nanoscale Size Clusters 

X22A, 

X27A 
I Tail Studies of a Bonse-Hart-Camera * I X27C 1 

J.M.Ablett (Kings College, London, Great Britain), W.A.Caliebe, J.B.Hastings, 

D.P.Siddons (NSLS) 

In order to determine the structure or ordering of samples with spacings in the nano- to micrometer range one has to use softer X-rays or to go to small diffraction 

angles. The latter can be done by using long flight paths and position sensitive 

detectors (slit collimation) or by using an analyzer crystal (angular collimation). 

This idea was proposed and implemented by Bonse and Hart in 1965. Theoretically, 

these so called Bonse-Hart-cameras should result in very narrow peaks which can be described by a power law, I N On, where I is the intensity, 8 the deviation 

of the maximum of the peak and n the number of reflections. To our knowledge 

this is confirmed experimentally only for a small q-range (8 <10 arcsec) or for low 

intensities (Imam N 10' photons/s). 

The aim of this experiment was to find or to exclude different reasons for the 

broadening of the peak. For this purpose we built a Bonse-Hart-Camera, using two 

Si(ll1) channelcuts, each with 4 reflections and operating at -12kev 

effect of air scattering was eliminated by keeping both crystals in an The intensity increased due to no absorption by the air, but the peak shape did 

not change. In order to study the thermal diffuse scattering (TDS), we used three 

different approaches: we kept the first crystal at room temperature by cooling it, 

we measured the intensity behind the second crystal with a dispersively mounted 

second analyser crystal and we mounted a very narrow slit between both crystals 

in order to eliminate the TDS from the first crystal. All three approaches had no effect on the line shape so that we can only claim that air scattering and TDS are 

probably not the reasons for the still unexplained broadening. 

More experimental and theoretical studies are planned for the next year. 

~ 

* Supported by US DOE under contract # DEAC02-76CH00016. 

Measurements of the spatial frequency dependent detective quantum 

efficiency of the FUJI image plate * 

R.H.Menk, F.Arfelli, D.Chapman, N.Gmur, W.Thomlinson, Z.Zhong (NSLS) 

As part of the mammography project at the NSLS X27C RD beamline, which is 

described somewhere else in this report, we carried out a number of measurements 

in order to evaluate the performance of a Fuji image plate detector used together 

with the Fuji BAS 2000 image plate reader. Typical reading parameters were a sensitivity of 1000, a latitude of 4 and a resolution size of 0.1 mm. The energy of 

the monochromatic beam was 18 keV. The image plate is a photon integrating pixel 

detector which can be characterized by the spatial frequency dependent detective 

quantum efficiency (DQE f)). Once an image is detected the DQE(f) describes 

how the input image signL-to-noise ratio is degraded by the detector, taking into 

consideration the image noise and the spatial resolution. For integrating detectors 

with a position resolution given by the modulation transfer function MTF(f)) and 

DQE(f) = DQE(f=O,N) . 11 MTF(f) 11 /NPS(f), with DQE(f=O,N) = QE/(1 4- ( 

ua2 /QE N)) where QE is the quantum efficiency of the detector, N the average number of incident photons per pixel and ua is the instrinct noise of the detector 

including read out electronics' noise. The intrinsic noise was measured from an 

unexposed image plate and a noise equivalent of 3 photons at an energy of 18 keV was found. The QE of the ima e plate for this energy is approximately 0.98. Plain 

field images (100 mm. 150 mm7, acquired in line scan mode with an approximately 

0.5 mm high - 100 mm wide synchrotron beam were used in order to measure the 

DQE(f=O,N) and the NPS(f). Variations of the flux ( from 5 to 5350 photons per 

pixel) in the plain field were achieved using several plastic absorbers of different 

thickness. The incident photon number was monitored with an ionization chamber. 

An image of a sharp edge phantom was used to obtain the edge spread function from 

which the MFT could be calculated, applying a numerical derivation and a FFT 

algorithm. Since the signal-to-noise ratio in the image is SNRimage = sqrt(DQE(ft. 

SNRpoisson, details larger than 0.5 mm are transmitted without degradation if t e 

flux is sufficient ( 2 100 photons at that energy) which means that no additional 

dose is acquired to a patient or phantom in order to achieve the signal-to-noise-ratio 

given by the Poisson statistics. For smaller details, however, one has to increase the 

dose to achieve the same image quality. At a detail size of 5 LP/mm the DQE(f) 

drops to zero, which means that no information is transmitted at all (figure 1). 

the associated image noise defined by the noise power spectrum (NP A (f)) one finds 

I *. 

u 

Figure 1. Spatial frequency dependent DQE for N 2 100 photons at 18 keV per 

pixel 

* This work was supported by the US Dept. of Energy Contract No. DEAC02- 

76CH00016 
,_ , 

.. 

Monochromatic beam mammography studies with an image plate I detector * 

W. Thomlinson', R.E. Johnston', E. Pisano', D. Washburn', C. Burns', F. 

Arfelli'8', L.D. Chapman', N. Gmiir', R. Menk', Z. Zhong', Dale Sayers4 

('National Synchrotron Light Source, 'University of North Carolina, 'INFN di Trieste, Italy, 4North Carolina State University, Raleigh) 

Preliminary experiments have been carried out at the NSLS X27C beamline to 

explore potential improvements in breast imaging contrast using monochromatic 

x-rays. Fuji ST3 PSP image plates read by a model 2000 Fuji reader and standard 

mammography film were used as detectors. In our present study, images were obtained of an ACR radiology phantom and a Lucite contrast detail phantom at 16, 

18, 20, and 22 keV. Phantom thickness varied from 15 to 82 mm. The phantom 

and the image plate were translated vertically through the stationary fan beam. 

Exposure to the image plates or film was controlled by the scan rate and various 

attenuators. The synchrotron images were compared to images obtained with a 

conventional mammography unit to evaluate improvements in contrast and image 

quality. The preliminary results show better contrast for the monochromatic beam 

images with lower absorbed dose in the phantom. The ACR phantom is a standard 

used to evaluate mammography system performance. It has a set of masses, fibrils, and calcifications embedded in wax. Our images of the ACR phantom scored 

consistently better than those taken with the standard system. 

* This research was supported by NIH RO1 CA60193, the Dept.of Radiology, UNC and 

5d r9 

0 

4 US DOE DE-AC02-76CH00016. 

Beamline UIA 

J.G. Chen, “Selective Activation of C-H and C=C Bonds on Metal Carbides: A Comparison of Reactions of n-Butane 

and 1,3 Butadiene on Vanadium Carbide Films on V(l lo)”, ]. of Cata&, 154, 80, (1995). 

J.G. Chen, B.D. DeVries, B. Friihberger, C.M. Kim, and 2.-M. Liu, “Spectroscopic Characterization of Thin 

Vanadium Carbide Films on a Vanadium (1 10) Surface: Formation, Stability and Reactivities”, Proceedings of the 

4lstAVS Conference,]. of Vac.. Sci. and Tech., A13, 1600, (1995). 

J.G. Chen, C.M. Kim, B. Friihberger, B.D. DeVries, and M.S. Touvelle, “ANEXAFS Determination ofthe Oxidation 

State ofvanadium Carbide onV( 1 10): Observation of Charge Transfer from Vanadium to Carbon”, SurJf Sci., 321, 

145, (1994). 

R. Kapoor, S.T. Oyama, B. Friihberger, B.D. DeVries, and J.G. Chen, “Characterization of Early Transition Metal 

Carbides and Nitrides by NEXAFS”, Catalysis Letters, 34, 179, (1995). 

C.M. Kim, B.D. DeVries, B. Friihberger, and J.G. Chen, “AHREELS and NEXAFS Characterization ofAtomic and 

Molecular Oxygen Species on aVanadium (110) Surface”, SurJf Sci., 327, 81, (1995). 

P.J. Lasky, P.H. Lu, M.X. Yang, R.M. Osgood, Jr., B.E. Bent, and P.A. Stevens, “NEXAFS Measurement Indicating 

a Tilted Molecular Orientation for Methyl Halides on GaAs(1 lo)”, SurJf Sci., 336, 140, (1995). 

T.J. Lenk, V.M. Hallmark, C.L. Hoffman, J.F. Rabolt, D.G. Castner, C. Erdelen, and H. Ringsdorf, “Structural 

Investigation of Molecular Organization in Self-Assembled Monolayers of a Semifluorinated Amidethiol”, Langmuir, 

10,4610-4617, (1994). 

M. Xi, M.X Yang, S.K. Jo, B.E. Bent, and P.A. Stevens, “Benzene Adsorption on Cu(ll1): Formation of a Stable 

Bilayer”,]. Chem. Phys., 101, 9144, (1994). 

Beamline U2B 

J.-L. Bantignies, C. Cartier dit Moulin, H. Dexpert, A.-M. Flank, and G.P. Williams, “Asphaltene Adsorption on 

Kaolinite: Characterization by Infrared Microspectroscopy and X-ray Absorption Spectroscopy”, Compte Rendzi 

derAcad Sci. Paris, 320,699, (1995). 

c- 1 
R. Biscardi, G. Ramirez, and G.P. Williams, “Effects of RF Side-Bands on Spectral Reproducibility For Infrared 

Synchrotron Radiation”, Rev. Sci. Instrum., 66, 1856, (1995). 

G.L. Carr, M. Hanfland, and G.P. Williams, “The Mid-Infrared Beamline at the NSLS Port U2B”, Rev. Sci. Instrum., 

66, 1643, (1995). 

G.L Carr, J. Reffner, and G.P. Williams, “Performance of an Infrared Microspectrometer at the NSLS”, Rev. Sci. 

Instrum., 66, 1490, (1995). 

R.J. Hemley, and H.K. Mao, “Progress on Hydrogen at Ultrahigh Pressures”, in Elementary Processes in Dense 

Plasmas, edited by S. Ichimaru, and S. Ogata, Addison-Wesley, Reading, Mass., pp. 269-280, (1995). 

R.J. Hemley, H.K. Mao, T.S. Due, J.H. Eggert, A.F. Goncharov, M. Hanfland, M. Li, M. Somayazulu, W. Vos, 

and C.S. Zha, “Dense Hydrogen on The Outer Solar System: Implications from Recent High-pressure Experiments”, 

in DeeD Earth and PlanetarvVolatiles, edited by K. Farley, American Institute of Physics, College Park, MD, pp. 250- 

260, (1995). 

R.J. Hemley, Z.G. Soos, M. Hanfland, and H.-k. Mao, “Charge Transfer States in Dense Hydrogen”, Nature, 369, 

384, (1994). 

J.A. Reffner, P.A. Martoglio, and G.P. Williams, “FT-IR Microscopical Analysis With Synchrotron Radiation: The 

Microscope Optics and System Performance”, Rev. Sci. Instrum., 66, 1298, (1995). 

D.L. Wetzel, “Microbeam Molecular Spectroscopy of Biological Materials”, in Food Flavors: Generation, Analysis, 

and Process Influence, edited by G. Charalambous, Elsevier, p. 2039, (1995). 

Beamline U3C 

D.R. Mullins, and P.F. Lyman, “Enhancement of Selective Decomposition: Methanethiol on C Covered W(OOl)”, 

J Pbys. Cbem., 99, 5548, (1995). 

Beamline U4A 

K. Breuer, D.M. Goldberg, K.E. Smith, M. Greenblatt, and W. McCarroll, “Resonant Photoemission Study of the 

Electronic Structure of &.3Mo03”, Solidstate Comm., 94,601, (1995). 

U. Diebold, H.-S. Tao, N.D. Shinn, and T.E. Madey, “Electronic Structure of Ultrathin Fe Films on TiOz(110) 

Studied with Soft-x-ray Photoelectron Spectroscopy and Resonant Photoemission”, Pbys. Rev., B50,14474, (1 994). 

Y. Wu, H.-S. Tao, E. Garfunkel, T.E. Madey, and N.D. Shinn, “Growth, Interfacial Alloying, and Oxidation of 

UltraThin Al Films on Ru(OOOl)”, SuyJ;‘ Sci., 336, 123, (1995). 

c-2 
Beamline U4B 

V. Chakarian, Y.U. Idzerda, G. Meigs, E.E. Chaban, J.-H. Park, and C.T. Chen, “Element-Specific Vector 

Magnetometry With Magnetic Circular Dichroism”, Appl. Phys. Lett., 66,3368, (1995). 

V. Chakarian, Y. U. Idzerda, G. Meigs, and C. T. Chen, “Applications of Soft X-ray Magnetic Circular Dichroism”, 

IEEE Trans. Map., 31,3307, (1995). 

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”, Mater. Res. 

SOC. Symp. Proc., 375, (1995). 

J. Chen, J. Christiansen, S.J. George, J. van Elp, R Tittsworth, B.J. Hales, S. Al-Ahmad, D. Coucouvanis, N. 

Campobasso, J.T. Bolin, and S.P. Cramer, “Extended X-ray Absorption Fine Structure and L-Edge Spectroscopy of 

Nitrogenase Molybdenum-Iron Protein”, Molybdenum Enzymes, Cofactors, and Model Svstems, edited by I. Stiefel, 

D. Coucouvanis, and W.E. Newton, ACS Symposium Series, p. 535, (1994). 

O.C. Mullins, S. Mitra-Kirkley, J. van Elp, and S.P. Cramer, “Molecular Structure ofNitrogen in Coal fromXANES 

Spectroscopy”, Applied Spectroscopy, 47, 1268-1275, (1993). 

G. Peng, J. van Elp, H. Jang, L Que, Jr., W.H. Armstrong, and S.P. Cramer, “L-Edge X-ray Absorption and X-ray 

Magnetic Circular Dichroism of Oxygen-Bridged Di-nuclear Iron Complexes”, ]. Am Chem. Soc., 117,2515-2519, 

(1995). 

L. She, J.M. Tonnerre, D. Raoux, J.F. Bobo, M. Piechuh, M. DeSantis, P. Troussel, J.M. Brot, V. Chakarian, C.- 

C. Kao, and C.T. Chen, “Resonant Magnetic Scattering in Soft X-ray Range Using Multilayers”, J. Map. Map. 

Mater., 148,68, (1995). 

J.M. Tonnerre, L. She, D. Raoux, B. Rodmacq, M. DeSantis, P. Troussel, J.M. Brot,V. Chakarian, C.-C. Kao, E.D. 

Johnson, and C.T. Chen, “X-Ray Resonant Magnetic Scattering at L-Edges of 3d Transition Metals using 

Multilayers”, Proceeding of the First EuroDean Synchrotron Radiation Conference, Nucl. Instrum. AndMeth. In Phys. 

Rev., B97,444, (1995). 

J. van Elp, G. Peng, B.G. Searle, S. Mitra-Kirtley, Y.-H. Huang, M.K. Johnson, Z.H. Zhou, M.W.W. Adams, M.J. 

Maroney, and S.P. Cramer, “Electronic Structure and Symmetry in Nickel L Edge X-ray Absorption Spectroscopy: 

Application to a Nickel Protein”,]. Am. Chem. SOL, 116, 1918-1923, (1994). 

J. van Elp, G. Peng, Z.H. Zhou, M.W.W. Adams, N. Baidya, P.K. Mascharak, and S.P. Cramer, “Nickel L-Edge Xray Absorption Spectroscopy of Pyrococcus Furiosus Hydrogenase”, Inorg. Chem., 34,2501-2504, (1995). 

J. van Elp, S.J. George, G. Peng, B.G. Searle, Z.H. Zhou, M.W.W. Adams, C.T. Chen, and S.P. Cramer, “Soft Xray Magnetic Circular Dichroism on a Paramagnetic Bioinorganic System”, X-ray and Ultraviolet Polarimetrv, edited 

by S. Fineschi, PIE, 2010, 181, (1993). 

c-3 
Beamline U41R 

C.J. Hirschmugl and G.P. Williams, “Signal to Noise Improvements with a New Far-IR Rapid-Scan Michelson 

Interferometer”, Rev. Sci. Instrum., 66, 1487, (1995). 

C.L.A. Lamont, B.N.J. Persson, and G.P. Williams, “Dynamics of Atomic Adsorbates: Hydrogen on Cu( 1 1 l)”, 

Chm. Pbys. Letts., 243,249, (1995). 

K. Lin, R. Tobin, and P. Dumas, “Adsorbate-Induced Changes in the Broadband IR Reflectance of a Metal: Oxygen 

on Cu(lOO)”, Pbys. Rev., B49, 17273, (1994). 

K. Lin, R. Tobin, and P. Dumas, “Infrared Spectroscopy of Formate on Oxygen Predosed Cu(100): Broadband 

Reflectance and Low Frequency Vibrations”,]. Vac. Sci. & Tech., 13, 1579, (1995). 

M.C. Martin, X. Du, and L. Mihaly, “Infrared Studies of Single Crystal C60: Silent and Higher Order Vibrational 

Modes”, Proceedings of the 1994 International Winterschool on Electronic Properties of Novel Materials: Progress 

in Fullerence Research, edited by H. Kuzmany, J. Fink, M. Mehring, and S. Roth, World Scientific Publishing Co., 

p. 353, (1994). 

C.A. Melendres, B. Beden, and G.A. Bowmaker, “Far Infrared Spectroscopy of a Platinum Electrode in situ Using a 

Synchrotron Source”,]. Electroanal Chem., 383, 191, (1995). 

Beamline U5U 

N. Brookes, Y. Chang, and P.D. Johnson, “The Ag/Fe(001) Interface”, Pbys. Rev., B50, 15330-15336, (1994). 

P.D. Johnson, “Spin Polarized Photoemission Studies ofMagnetic Quantum Well States”, /. Map. Map. Mat., 148, 

167-171, (1995). 

D. Li, J. Mattson, J. Pearson, S.D. Bader, and P.D. Johnson, “Photoemission Study of Quantum Confinement by a 

Finite Barrier; Cu/Co(wedge)/Cu(lOO)”, Pbys. Rev., B51,7195-7199, (1995). 

D. Li, J. Pearson, S.D. Bader, D.N. Mcllroy, C.Waldfried, and P.A. Dowben, “Spin Polarized Photoemission Studies 

oftheExchangeSplittingofthe Gd 5dElectronsNear the CurieTemperature”, Pbys. Rev., B5 1,13895-13898, (1995). 

B. Sinkovic, P.D. Johnson, N.B. Brookes, A. Clarke, and N.V. Smith, “A Spin Polarized Auger Electron Diffraction 

Study of the Magnetic Poisoning of Fe(001) by Sulfur”, Pbys. Rev., B52, R6955-6958, (1995) 

Beamline U8B 

M. M. BanaszakHoll, S. Lee, andF. R. McFeely, “CoreLevel Photoemissionand the Structure oftheSi/SiO;! Interface: 

a Reappraisal.”, Appl. Pbys. Lett., 65, 1097 (1994). 

M. M. Band Holl, and F. R. McFeely, “The Si/SiO2 Interface: New Structures and Well-Defined Model 

Systems.”, Pbys. Rev. Lett., 71, 2441, (1994). 

c-4 
S. Lee, S. Makan, M. M. Banaszak Holl, and F. R.McFeely, “Synthetic Control of Solid/Solid Interfaces: Analysis of 

Three New Silicon/Silicon Oxide Interfaces by Soft X-ray Photoemission.”, J. Am. Chem. Soc., 116, 11819, (1994). 

Beamline U11 

T.J. Buckley, R.D. Johnson, 111, R.E. Huio, Z. Zhang, S.-C. Kuo, and R.B. Klemm, “Ionization Energies, Appearance 

Energies and Thermochemistry of CF2O and FCO”,]. Phys. Chem., 99,4879, (1995). 

B.A. McDougall, T. Balasubramanian, and E. Jensen, “Phonon Contribution to Quasiparticle Lifetimes in Cu 

Measured by Angle-Resolved Photoemission”, Phys. Rev., B51, 13891, (1995). 

P.S. Monks, L. J. Stief, M. Krauss, S.C. Kuo, Z. Zhang, and R.B. Klemm, “ADischarge Flow-Photoionization Mass 

Spectrometric Study of the NO3(2A2’) Radical: Photoionization Spectrum, Adiabatic Ionization Energy and Ground 

State Symmetry”,]. Phys. Chem., 98, 10017, (1994). 

L.J. StieK F.L. Nesbitt, W.A. Payne, S.-C. Kuo. W. Tao, and R.B. Klemm, “Rate Constant and Reaction Channels 

for the Reaction ofAtomic Nitrogen with the Ethyl Radical”, J. Chem. Phys., 102,5309, (1995). 

A.J. Yencha, A. Hopkirk, J.R. Grover, B.-M. Cheng, H. Lefebvre-Brion, and F. Keller, “Ion-Pair Formation in the 

Photodissociation of HF and DF”,]. Chem. Phys., 103,2882, (1995). 

2. Zhang, S.-C. Kuo, R.B. Klemm, P.S. Monks, andL.J. Steif, “ADischargeFlow-PhotoionizationMassSpectrometric 

Study of the FO(X2IIi) Radical: Photoionization Efficiency Spectrum and Ionization Energy”, Chem. Phys. Lett., 229, 

377, (1994). 

Beamline U12B 

P.F. Lyman, and D.R. Mullins, “Structural Rearrangements in the C/W(lOO) Surface System”, Phys. Rev., B51, 

13623, (1995). 

Beamline U13UA 

C.J. Buckley, S.J. Bellamy, X. Zhang, G. Dermody, and S. Hulbert, “The NEXAFS of Biological Calcium 

Phosphates”, Rev. Sci. Instrum., GG, 1322, (1995). 

G.S. Dermody, The Development of a Transmission X-ray Flux Monitor for an Undulator Beamline on a 

VacuumUltraviolet Svnchrotron Storace Ring, Master of Science, London University, (1995). 

K. Lee, S. L. Hulbert, P. Kuiper, D. Ji, and D. M. Hanson, “Auger, Zero-Energy Photo-Electron, Coincidence 

Spectroscopy (AZEPECO): Chemical-Site-Selective Auger Electron Spectroscopy”, Nucl. Instrum. Metbods , A347, 

446, (1994). 

D.R. Mullins, D.R. Huntley, and S.H. Overbury, “The Nature of the Sulfur-Induced Reconstruction on Ni(l1 l)”, 

Su$ Sci., 323, L287, (1995). 

c-5 
T.S. Rufael, D.R. Huntley, D.R. Mullins, and J.L. Gland, “Adsorption and Reactions ofBenzenethio1 on theNi( 11 1) 

Surface”,]. Phys. Chem., 98, 13022, (1994). 

T.S. Rufael, D.R. Mullins, J.L. Gland, and D.R. Huntley, “Methyl Thiolate on Ni( 1 11): Multiple Adsorption Sites 

and Mechanistic Implications”,]. Phys. Chem., 99, 11472, (1995). 

E.E. Shekel, Spin Polarized Photoelectron Spectroscopy in the Soft X-ray Regime, PhD., New York University, 

January, (1995). 

B. Sinkovic, E. Shekel, and S. L. Hulbert, “Spin-Resolved Iron Surface Density of States”, Phyx. Rev., B52, R8696, 

(1995). 

K. E. Smith, K. Breuer, D. Goldberg, M. Greenblatt, W. McCarroll, and S. L. Hulbert, “Defects in Quasi-One 

Dimensional Oxide Conductors: &.3MoO3”, Mat. Res. SOC. Svmp. Proc., 375, 133, (1995). 

C. Woodbridge, Electronic Decay and Subsequent Fragmentation of Methane Induced bv Soft X-rays, PhD., 

University at Stony Brook, December, (1995). 

Beamline U13UB 

B. LaFontaine, A.A.MacDowel1, Z.Tan, G.N.Taylor, D.L.White, D.M.Tennant, and 0.R.Wood 11, “Real-Time, 

Sub-Micron Fluorescence Imaging of Extreme Ultraviolet Aerial Images”, OSA Proceedings on Extreme Ultraviolet 

Lithographv, edited by F. Zernike and D.T. Attwood, Optical Society ofAmerica, Washington, DC, Vol. 23, pp. 177- 

181, (1994). 

B. LaFontaine,A.A. MacDowell, Z. Tan, D.L. White, G.N. Taylor, J.E. Bjorkholm, D.M. Tennant, andS. Hulbert, 

“SubMicron, Soft X-ray Fluorescence Imaging, Appl. Phys. Lett., 66,282-284, (1995). 

B. LaFontaine, D. L. White, A. A. MacDowell, Z. Tan, D. M. Tennant, and 0.R.Wood 11, “Extreme Ultraviolet 

Moire Interferometry”, OSA Proceedings on Extreme Ultraviolet Lithography, edited by F. Zernike and D.T. 

Atnvood, Optical Society of America, Washington, DC, Vol. 23, pp.167-170, (1994). 

B. LaFontaine, D.L. White, O.R. Wood 11, A.A. MacDowell, Z. Tan, G.N. Taylor, D.M. Tennant, and S. Hulbert, 

“Real Time Observation ofExtreme Ultra-Violet Aerial Images by Fluorescence Micro-Imaging, ]. Vac. Sci. Technol., 

B12,3576-3579, (1994). 

B.M. Lum, A.R. Neureuther, B. LaFontaine, A.A.MacDowel1 and O.R. Wood 11, “Validation ofModeling Hoechst 

AZ PN114 for EUV Projection Lithography and Investigation of Difision Effects”, OSA Proceedings on Extreme 

Ultraviolet Lithography, edited by F. Zernike and D.T. Attwood, Optical Society ofAmerica, Washington, DC, Vol. 

23, pp.184-192, (1994). 

A. MacDowell, “Extreme Ultraviolet Lithography at the NSLS”, Synch. Rad News, 7, 14-17, (1994). 

C-6 
2. Tan, A.A. MacDowell, B. LaFontaine, J.E. Bjorkholm, R.R. Freeman, M.D. Himel, D.M. Tennant, D. Taylor, 

O.R. Wood 11, W.K. Waskiewicz, D.L. Windt, and D.L. White, “At-Wavelength Metrology of 13nm Lithography 

Imaging Optics”, Rev. Sci. Imtrum., GG, 2241-2247, (1995). 

2. Tan, A.A. MacDowell, B. LaFontaine, J. Russo, J. Bjorkholm, D.M. Tennant, D.W. Taylor, M.D. Himel, O.R. 

Wood 11, R.R. Freeman, W.K. Waskiewicz, D.L. White, S. Spector, A. Ray-Chaudhuri, and R.H. Stulen, “AtWavelength Metrology of EUVL Cameras Using Lateral-Shearing Interferometry”, OSA Proceedincs on Extreme 

Ultraviolet LithograDhy, edited by F. Zernike and D.T. Attwood, Optical Society ofAmerica, Washington, DC, Vol. 

23, pp. 151160, (1994). 

G.N. Taylor, R.S. Hutton, S.M. Stein, C.H. Boyce, O.R. WoodII, B. LaFontaine,A.A. MacDowell, D.R.Wheeler, 

G.D. Kubiak, A.K. Ray-Chaudhuri, K. Berger, and D. Tichenor, “Extreme W Resist Technology: the Limits of 

Silylated Resist Resolution”, SHE, 2437,308, (1995). 

G.N.Taylor, R.S. Hutton, S.M. Stein, C.H. Boyce, B. LaFontaine,A.A.MacDowell, D.R.Wheeler, and0.R. Wood 

11, “Limitations to Silylated Resist Technology”, OSA Proceedings on Extreme Ultraviolet Lithozraphy, edited by F. 

Zernike and D.T. Atnvood, Optical Society ofAmerica, Washington, DC, Vol. 23, pp.182-183, (1994). 

D.L. White, O.R. Wood 11, S. Spector, A.A. MacDowell, and B. LaFontaine, “Modification of the Coherence of 

Undulator Radiation”, Rev. Sci. Imtrum., 66, 1930-1933, (1995). 

O.R. Wood 11, J.E. Bjorkholm, K.F. Dreyer, L.E. Fetter, M.D. Himel, R.R. Freeman, D.M. Tennant, J.E. Griffith, 

G.N. Taylor, W.K. Waskiewicz, D.L. White, D.L. Windt, A.A. MacDowell, B. LaFontaine, B. Lum, A.R. 

Neureuther, J.B. Kortright, E.K. Gullikson, and K.B. Nguyen, “Experiments and Simulations of EW Lithographic 

Resist Patterning at Wavelengths From 7 to 40 nm”, OSA Proceedings on Extreme Ultraviolet Lithography, edited 

by F. Zernike and D.T. Attwood, Optical Society ofAmerica, Washington, DC, Vol. 23, pp.83-88, (1994). 

O.R. WoodII, J.E. Bjorkholm, L. Fetter, M.D. Hime1,A.A. MacDowell, D.M.Tennant, B. LaFontaine, J.E. Griffith, 

G.N. Taylor, W.K. Waskiewicz, D.L. Windt, J.B. Kortright, E.K. Gullikson, and K. Nguyen, “Wavelength 

Dependance of Resist Sidewall Angle in Extreme Ultraviolet Lithography”, J Vac. Sci. Techno., B12, 3841-3845, 

( 1 994). 

Beamline U14A 

Z.M. Stadnik, G.W. Zhang, A.2. Tsai, and A. Inoue, “Electronic Structure of Decagonal AI65Co15Cu20 and 

Al7oCol5Nil5”, Phys. Rev., B51, 11358, (1995). 

Z.M. Stadnik, G.W. Zhang, A.-P. Tsai, and A. Inoue, “Electronic Structure of Icosahedral A165Cu20Ru15 Studied 

by Photoemission Spectroscopy”, Phys. Rev., B51,4023, (1995). 

Z.M. Stadnik, G.W. Zhang, A.-P. Tsai, and A. Inoue, “Are Decagonal Quasicrystals the Hume-Rothery Phases?”, 

Phys. Lett., A198,237, (1995). 

c-7 
Z.M. Stadnik, G.W. Zhang, A.-P. Tsai, and A. Inoue, “Photoemission Studies of Stable, Icosahedral Alloys”, 

Aperiodic ‘94, Proceedings of the International Conference on Aperiodic Crystals, edited by G. Chapuis and W. 

Paciorek, World Scientific, Singapore, p. 249, (1995). 

Z.M. Stadnik, G.W. Zhang, A.-I?. Tsai, and A. Inoue, “Synchrotron-Radiation Studies of Valence Bands in Stable, 

Decagonal A165Co15Cu~0 and A17&015Ni15”, Aperiodic ‘94 Proceedings of the International Conference on 

Aperiodic Crystals, edited G. Chapuis and W. Paciorek, World Scientific, Singapore, p. 254, (1995). 

G.W. Zhang, Z.M. Stadnik, A.-P. Tsai, A. Inoue, and T. Miyazaki, “Electronic Structure of Icosahedral Alloys: The 

Case of fl65Cu2oOs15”, 2 Pbys., B97, 439, (1995). > 

c-8 
Beamline XIA 

H. Ade, A.P. Smith, S. Cameron, R. Cieslinski, G. Mitchell, B. Hsiao, and E. Rightor, “X-ray Microscopy in 

Polymer Science: Prospects of a “New” Imaging Technique”, Polymer, 36, 1843-1848, (1995). 

C.J. Buckley, S.J. Bellamy, X. Zhang, G. Dermody, and S. Hulbert, “The NEXAFS of Biological Calcium 

Phosphates”, Rev. Sci. Instrum., 66, 1322-1324, (1995). 

H.N. Chapman, C. Jacobsen, and S. Williams, “Applications of a CCD Detector in a Scanning Transmission Xray Microscope”, Rev. Sci. Imtrum., GG, 1332-1334, (1995). 

G.D. Cody, R.E. Botto, H. Ade, S. Behal, M. Disko, and S. Wirick, “C-NEXAFS Microanalysis and Scanning Xray Microscopy of Microheterogeneities in a High-Volatile A Bituminous Coal”, Energy & Fueh, 9,75-83, 

( 1 995). 

G.D. Cody, R.E. Botto, H. Ade, S. Behal, M. Disko, and S. Wirick, “Inner-Shell Spectroscopy and Imaging of a 

Subbituminous Coal: in situ Analysis of Organic and Inorganic Microstructure Using C(ls)-, Ca(2p)-, and Cl(2s)- 

NEXAFS”, Energy &Fuels, 9,525-533, (1995). 

L. Haddad, “Demonstration of Ultra High Resolution Soft X-ray Tomography Workshop on Scientific 

Applications of Coherent X-rays”, SLAC Reuort, edited by J. Arthur, G. Matterlik, and H. Winick, Stanford, CA: 

SLAC, 437, pp. 179-191, (1994). 

W.S. Haddad, I. McNulty, J.E. Trebes, E.H. Anderson, R.A. Levesque, and L. Yang, “Ultrahigh Resolution X-ray 

Tomography”, Science, 2GG, 12 13-121 5, (1 994). 

J. Kirz, C. Jacobsen, and M. Howells, “Soft X-ray Microscopes and Their Biological Applications”, Quarterly 

Reviews ofBiophysics, 28, 33-130, (1995). 

C. -H. KO, J. Kirz, H. Ade, S. Hulbert, E. Johnson, and E. Anderson, “Applications of the XlA Scanning 

Photoemission Spectromicroscope for Element Identification on Material Surfaces”, Mat. Res. SOC. Symp. Proc., 

375,303-305, (1995). 

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, 1416-1418, (1995). 

I. McNulty, W.S. Haddad, J.E. Trebes, and E.H. Anderson, “Soft X-ray Scanning Microtomography with 

Submicrometer Resolution”, Rev. Sci. Instrum., GG, 1431-1433, (1995). 

D. Sayre, and H.N. Chapman, “X-ray Microscopy”, Acta Cryst., A51,237-252, (1995). 

S. Williams, C. Jacobsen, J. Kin, J. Maser, S. Wirick, X Zhang, H. Ade, and M. Rivers, “Instrumentation 

Developments in Scanning Soft X-ray Microscopy at the NSLS”, Rev. Sci. Instrum., 66, 1271-1275, (1995). 

X. Zhang, C. Jacobsen, S. Lindaas, and S. Williams, “Exposure Strategies for PMMA From in situ XANES 

Spectroscopy”,]. Vac. Sci. TechnoZ., B13, 1477-1483, (1995). 

X. Zhang, H. Ade, C. Jacobsen, J. Kirz, S. Lindaas, S. Williams, and S. Wirick, “Micro-XANES: Chemical 

Contrast in thescanning Transmission X-ray Microscope”, NucZ. Imtrum. Meth., A347,431-435, (1994). 

c-9 
Beamline X1 B 

W. Eberhardt, “Spectroscopy and Dynamics of the Electronic Decay of Core Electron Excitations in Isolated and 

Chemisorbed Molecules”,. In Application of Synchrotron Radiation to High Resolution Studies of Molecules and 

Molecular Adsorbates on Surfaces, edited by W. Eberhardt, Springer Series in Surface Science, 35,203, (1995). 

S. Eisebitt, J.E. Rubensson, M. Nicodemus, T. Boske, S. Bliigel, W. Eberhardt, K. Radcrmacher, WS. Mantl, and 

G. Bihl mayer, “Electronic Structure of Buried a-FeSi, and P-FeSi, Layers: Soft X-ray Emission and Absorption 

Studies Compared to Band-Structure Calculations”, Phys. Rev., B50, 18330-18340, (1994). 

B.S. Itchkawitz, B. Kempgens, H.M. Koppe, J. Feldhaus, A.M. Bradshaw, and W.B. Peatman, “Absolute 

Photoabsorption Cross-Section Measurements of Simple Molecules in the Core-Level Region”, Rev. Sci. Instrum., 

66, 1531, (1995). 

H.M. Koppe, A.L.D. Kilcoyne, J. Feldhaus, and A.M. Bradshaw, “Photon Energy Dependence of the Vibrational 

Fine Structure in Core Level Photoemission Spectra Near Threshold”,]. Chin. Cbem. SOC., 42,255, (1995). 

J. Liining, J.E. Rubensson, S. Eisebitt, and W. Eberhardt, “Selectively Excited Core-to-core Fluorescence of 

Potassium Halides”, Phys. Rev., B51, 10399-10405, (1995). 

M. Neeb, A. Kivimiiki, B. Kempgens, H.M. Koppe, and A.M. Bradshaw, “Conjugate Shake-up-enhanced Auger 

Transitions in N2”, Phys. Rev., A52, 1224, (1995). 

Z. Xu, Y. Liu, P.D. Johnson, B. Itchkawitz, K. Randall, J. Feldhaus, and A. Bradshaw, “A Spin Polarized 

Photoemission Study of the Fe 3s Multiplet”, Phys. Rev., B51,7912-7915, (1995). 

Beamline X3A1 

R. Bolotovsky, A. Darovsky, V. Kezerashvili, and P. Coppens, “The Use of Imaging Plates in Electron Density 

Mapping with Synchrotron X-rays”, ]. Synch. Rad, 2, 18 1, (1995). 

R. Bolotovsky, M.A. White, A. Darovsky, and P. Coppens, “The “Seed-Skewness” Method for Integration of 

Peaks on Imaging Plates”,]. AppZ. Cyst., 28, 86, (1995). 

B. Chu, F. Yeh, Y. Li, P.J. Harney, J. Rousseau, A. Darovsky, and D.P. Siddons, “Construction of a High-Energy 

Bonse-Hart Ultrasmall-angle X-ray Scattering Instrument”, Rev. Sci. Instrum., 65,3233, (1 994). 

B. Chu, Q.C. Ying, F.-J. Yeh, A. Patkowski, W. Steffen, and E.W. Fischer, “An X-ray Photon Correlation 

Experiment”, Langmuir, 11, 1419 (1995). 

A. Darovsky, R. Bolotovsky, and P. Coppens, “An Anti-Scatter Device for Low Temperature Crystallographic 

Experiments with Imaging Plates”,]. AppZ. Cyst., 27, 1039, (1994). 

A. Darovsky, V. Kezerashvili, R. Harlow, and I. Mutikainen, “Structure of Oxidized Forms of Neodymium and 

Praseodymium (Bis)phthalocyanines”, Acta Cyst., B50, 582, (1994). 

A. Darovsky, I. Meshkovsky, and P. Coppens, “A Multi-Wavelength Monochromator for the X3A1 Fixed-Angle 

Station at the National Synchrotron Light Source”,]. Synch. Rad., 2,77, (1995). 

A. Darovsky, I. Meshkovsky, and P. Coppens, “Compact Monochromator for the Multipurpose X3 Synchrotron 

Beamline at NSLS”, Rev. ofSci. Inrtrum., 6612, 2085, (1995). 

c-10 
K. Tan, Y. KO, A. Darovsky, and J.B. Parise, “The Synthesis of a Novel Open Framework Sulfide, 

CuGe,S,.(C,H,),N and its Structure Solution using Synchrotron Imaging Plate Data”,]. Am. Chem. SOC., 117, 

7039, (1995). 

Beamline X3A2 

S. 2. D. Cheng, S. W. Lee, E. Von Meerwall, and B. S. Hsiao, “RMolecular Shape Effects on the Crystallization, 

Melting and Morphology of Star Poly(ethy1ene oxide) Fractions”, ACS Polym. Prep., 36/1,259, (1995). 

Y.W. Cheung, R.S. Stein, B. Chu, and G. Wu, “Evolution of Crystalline Structures of Poly(epsi1om-caprolactone) 

(PCL)/Polycarbonate (PC) Blends. 1. Isothermal Crystallization Kinetics as Probed by Synchrotron Small-Angle 

X-ray Scattering, Macromolecules, 27, 3589, (1 994). 

M. deBoissieu, P. Stephens, M. Boudard, C. Janot, D.L. Chapman, and M. Audier, “Anomalous X-ray 

Diffraction Study of the AlPdMn Icosahedral Phase”,]. Pbys. Condem. Mat., 6, 10725, (1994). 

P. Harney, B. S. Hsiao, A. D. Kennedy, and B. Chu, “Synchrotron SAXS Studies of Glassy PET Fiber During 

Deformation”, ACS Polym. Prep., 36/1, 308, (1995). 

B. S. Hsiao, B. B. Sauer, R. A. Leach, B. Chu, P. Harney, H. G. Zachman, and S. Seifert, “New Insight of 

Isothermal Melt Crystallization Via Time-Resolved Simultaneous SAXSIvlrAxD Measurements”, ACS Polym. 

Prep., 36/1,342, (1995). 

B. S. Hsiao, B. B. Sauer, R. Verma, B. Chu, P. Harney, H. G. Zachman, and S. Seifert, “New Insight of 

Isothermal Melt Crystallization Via Time-Resolved Simultaneous SAXS/WAXD Measurements”, Macromolecules, 

28,6931-6936, (1995). 

X. Lu, W. P. Stechle, Jr., B. Hsiao, and R. A. Weiss, “Thermally Induced Microstructure Transitions in a Block 

Copolymer Ionomer”, Macromolecules, 28,2831-2839, (1995). 

B. B. Sauer, and B. S. Hsiao, “Effect of Heterogeneous Distribution of Lamellar Stacks on Amorphous 

Relaxations in Semicrystalline Polymers”, Polymer, 36/1,2553-2558, (1995). 

A. Spijkerman, A. Meetsma, J.L. de Boer, Y. Gao, and S. van Smaalen, “Modulated Structure of NiTa,,Se, in its 

Incommensurate Charge-Density-Wave State at 16K”, Pbys. Rev., B52,3892, (1995). 

M. Takenaka, K. Linliu, Q. Ying, B. Chu, and D. Peiffer, “Synchrotron Small Angle X-ray Scattering of Slow 

Spinodal Decomposition in a Block Copolymer”, Macromolecules, 28,2700, (1995). 

R. Verma, A. Biswas, and B. S. Hsiao, “Small Angle X-Ray Scattering for Lamellar Semi-crystalline Systems: 

Some Novel Data Analysis Techniques”, ACS Polym. Prep., 36/1,348, (1995). 

R. Verma, B. Chu, B. S. Hsiao, and H. Marand, “Real Time SAXS Studies of Lamellar Level Morphological 

Development in PEEK”, ACS Polym. Prep., 36/1,346, (1995). 

G. Wu, B. Chu, and D.K. Schneider, “SANS Study of Micellar Structure of PEO-PPO-PEO Aqueous Solution”, 

]. Pbys. Cbem., 99,5094, (1995). 

G. Wu, B. Chu, and D.K. Schneider, “Small-angle Neutron Scattering Study of Polymeric Micellar 

Structures”, J. Phys. Chem., 98, 12018, (1995). 

c-11 
Beamline X3E1 

T. Ami, M.K. Crawford, R.L. Harlow, Z. Wang, D.C. Johnston, Q. Huang, and R.C. Erwin, “Magnetic 

Susceptibility and Low Temperature Structure of the Linear Chain Cuprate Sr,CuO,”, Pbys. Rev., B5 1,5994, 

(1995). 

M.K. Crawford, R.L. Harlow, E.M. McCarron, D.E. Cox, and Q. Huang, “Effects of Structural Phase 

Transitions on Superconductivity and Magnetism in Substituted Derivatives of La,CuO,”, Physica C, 235-240, 

170, (1994). 

M.K. Crawford, R.L. Harlow, E.M. McCarron, N. Herron, W.E. Farneth, W. Donahue, B.A. Parkinson, andJ. 

Schirber, “Synchrotron X-ray Powder Diffraction Study of Electrochemically Oxidized L~CUO,+~ and 

$-xNdxCu04+.’’,J Pbys. Chem. Soli& 56, 1459, (1995). 

A. Darosky, L. Meshkovsky, and P. Coppens, “Compact Monochromator for the Multipurpose X3 Synchrotron 

Beamline at NSLS”, Rev. Sci. Instrum., 66/2, 2085, (1995). 

R.E. Dinnebier, P.W. Stephens, J.K. Carter, A.N. Lommen, P.A. Heiney, A.R. McGhie, L. Brard, and A.B. 

Smith 111, “X-ray Powder Diffraction Structure of Triclinic C6,BrZ4(Br2)2)), J AppL. Cystall., 28, 327, (1995). 

N. Herron, D.L. Thorn, and R.L. Harlow, “Molecular Precursors to Functional Materials” , Moleculary Designed 

Ultrafine/Nanostructured Materials, edited by K. E. Gonsalves, MRS Svmp. Proc., 351, (1994). 

N. Herron, D.L. Thorn, R.L. Harlow, G.A. Jones, J.B. Parise, J.A. Fernandez-Baca, andT. Vogt, “The 

Preparation and Structural Characterization of Two New Phases of Aluminum Trifluoride”, Chem. Of Mater., 7, 

75, (1995). 

D. Koller, M.C. Martin, P.W. Stephens, L. Mihdy, S. Pekker, A. Jdnossy, 0. Chauvet, and L. Ford, “Polymeric 

Alkali Fullerides are Stable in Air”, AppZ. Pbys. Letts., 66, 1015, (1994). 

A.R. McGhie, J.E. Fischer, P.W. Stephens, R.L. Cappelletti, D.A. Neumann, W.H. Mueller, H. Mohn, and 

H.U. ter Meer, “Phase Transitions in Solid C70: Supercooling, Metastable Phases and Impurity Effect”, Pbys. 

Rev., B49, 12614, (1994). 

Z.H. Ming, S. Huang, Y.L. Soo, Y.H. Go, T. Carns, and K.L. Wang, “Interfacial Roughness Scaling and Strain 

in Lattice Mismatched Si,,Ge,, Thin Films on Si”, Appl. Pbys. Lett., 67, 629, (1995). 

Z.H. Ming, Y.L. Soo, S. Huang, Y.H. Go, K. Stair, G. Devane, and C. Choi-Feng, “Thickness Modulation of 

InGaAs/GaAs Superlattice Studied by Large Angle X-ray Scattering, Appl. Pbys. Lett., 66, 165, (1994). 

Z.H. Ming, Y.L. Soo, S. Huang, Y.H. Kao, K. Stair, G. Devane, and C. Choi-Feng, “X-ray Scattering Studies of 

Interfacial Microstructures in InxGa,JdGaAs Superlattices”, Mat. Res. SOC. Symp. Proc., 375, 171, (1995). 

Z.H. Ming, Y.L. Soo, S. Huang, Y.H. Kao, J.C. Tsang, and S.S. Iyer, “Interfacial Microstructures of Ultrathin Ge 

Layers on Si Probed by X-ray Scattering and Fluorescence Yield”, AppZ. Pbys. Lett., 65, 1382, (1994). 

G. Oszldnyi, G. Bortel, G. Faigel, M. Tegze, L. Grdnisy, S. Pekker, P.W. Stephens, G. Bendele, R. Dinnebier, G. 

Mihay, A. Jdnossy, 0. Chauvet, and L. Forr6, “Dimerization in K,C6, and RblC60)), Pbys. Rev., B51, 12228,. 

(1995). 

c-12 
Y.L. Soo, S.W. Huang, Z.H. Ming, Y.H. Kao, H. Munekata, and L.L. Chang, “Investigation of Local Structures 

Around Mn Atoms in Inl,MnxAs Diluted Magnetic Semiconductors Using EXAFS”, Mat. Res. SOC. Symp. Proc., 

375,27, (1995). 

Y.L. Soo, Z.H. Ming, S.W. Huang, Y.H. Kao, R.N. Bhargava, and D. Gallagher, “Local Structures Around Mn 

Luminescent Centers in Mn-doped Nanocrystals of ZnS”, Phys. Rev., B50,7602, (1994). 

M.A. Subramanian, M.K. Crawford, R.L. Harlow, T. Ami, J.A. Fernandez-Baca, Z.R. Wang, and D.C. Johnston, 

“Sr,RhO, and SrJrO,: Structural and Magnetic Studies of 4d and 5d Transiton Metal Analogs of LqCuO,”, 

Pbysica C, 235-240,743, (1994). 

T. Yilidrim, J.E. Fischer, R. Dinnebier, P.W. Stephens, and C.L. Lin, “Fulleride Superconductors and 

Orientational Order: T, us. Lattice Constant in NqRbxCsl-xCG,,”, Solid State Commun., 93,269, (1995). 

Beamline X3B2 

T. Tse, P.W. Stephens, and P.J. Eng, ‘‘Epitaxy and Domain Growth of Pb on Ni(001)”,]. Phys. Conden. Mat., 6, 

6111, (1994). 

Beamline X4 

T.E. Benson, D.J. Filman, C.T. Walsh, and J.M. Hogle, “An Enzyme-Substrate Complex Involved in Bacterial 

Cell Wall Biosynthesis”, Nature Struct. BioL, 2, 644-653, (1995). 

F. Dyda, A.B. Hickman, T.M. Jenkins, A. Engelman, R. Craigie, and D.R. Davies, “Crystal Structure of the 

Catalytic Domain of HIV-1 Integrase: Similarity to Other Polynucleotidyl Transferases”, Science, 266, 198 1- 

1986, (1994). 

M.M. Georgiadis, S.M. Jessen, C.M. Ogata, A. Telesnitsky, S.P. GoK and W.A. Hendrickson, “Mechanistic 

Implications from the Structure of a Catalytic Fragment of Moloney Murine Leukemia Virus Reverse 

Transcriptase”, Structure, 3, 879-892, (1995). 

G. Ghosh, G. Van Duyne, S. Ghosh, and P.B. Sigler, “Structure of NF-KP p50 Homodimer Bound to a KP Site”, 

Nature, 373,303-310, (1995). 

J. Goldberg, H.-B. Huang, Y.-G. Kwon, P. Greengard, A.C. Nairn, and J. Kuriyan, “Three-Dimensional 

Structure of the Catalytic Subunit of Protein SerineIThreonine Phosphatase-l”, Nature, 376,745-753, (1995). 

S. R. Hubbard, L. Wei, L. Ellis, and W. A. Hendrickson, “Crystal Structure of the Tyrosine Kinase Domain of 

the Human Insulin Receptor”, Nature, 372,746-754, (1994). 

T. S. R. Krishna, X.-P. Kong, S. Gary, P. M. Burgers, and J. Kuriyan, “Crystal Structure of the Eukaryotic DNA 

Polymerase Processivity Factor PCNA”, CeLL, 79, 1233-1243, (1994). 

J. W. Lee, M. Chan, T. V. Law, H.J. Kwon, and B. K. Jap, “Preliminary Cryocrystallographic Study of the 

MitochondrialCytochrome bc, Complex: Improved Crystallization and Flash-cooling of a Large Membrane 

Protein”,]. Mol. BioL., 252, 15-19, (1995). 

N. Q. McDonald, N. Panayotatos, and W.A. Hendrickson, “Crystal Structure of Dimeric Human Ciliary 

Neurotrophic Factor Determined by MAD Phasing”, EMBO]., 14,2689-2699, (1995). 

C-13 
C. W. Muller, F. A. Rey, M. Sodeoka, G. L. Verdine, and S.C. Harrison, “Structure of the NF-@ p50 

Homodimer bound to DNA”, Nature, 373,311-317, (1995). 

C. M. Ogata, and W.A. Hendrickson, “Protein Structures from MAD Experiments at the HHMI Beamline Xu 

at the NSLS”, Synch. Rad. News, 8, 13-18, (1995). 

L. Shapiro, A. M. Fannon, P.D. Kwong, A. Thompson, M.S. Lehmann, G. Grubel, J.-F. Legrand, J. As-Nielsen, 

D.R. Colman, and W. A. Hendrickson, “Structural Basis of Cell-cell Adhesion by Cadherins”, Nature, 374,327- 

337, (1995). 

J.-L. Staudenmann, W.L. Zotterman, D.W. Cook, C.M. Ogata, and W. A. Hendrickson, “The Howard Hughes 

Medical Institute Cassette for Storage Phosphor Plates”, Rev. Sci. Instrum., 65,608-61 1, (1994). 

C. E. Stebbins, S. Borukhov, M. Oriova, A. Polyakov, A. Goldfarb, and S.A. Darst, “Crystal Structure of the 

GreA Transcript Cleavage Factor from Esherichia coli”, Nature, 373, 636-640, (1995). 

T.M. Tanaka Hall, J. A. Porter, P. A. Beachy, and D.J. Leahy, “A Potential Catalytic Site Revealed by the 1.7-8L 

Crystal Structure of the Amino-Terminal Signalling Domain of Sonic Hedgehog”, Nature, 378,212-216, 

(1 995). 

L. Tong, S. Pav, D. Lamarre, L. Pilote, S. LaPlante, P. C. Anderson, and F. Jung, “High Resolution Structures of 

Recombinant Human Renin in Complex with Polyhydroxymonoamide Inhibitors”, J Mol. BioL, 250,211-222, 

(1995). 

A. Qu, and D. J. Leahy, “Crystal Structure of the I-domain from the CD1 la/CD18 (LFA-l,a, p2) Integrin”, 

PNAS, 92, 10277-10281, (1995). 

G. Zhang, M. G. Kazanietz, P. M. Blumberg, and J. H. Hurley, “Crystal Structure of the Cys2 Activator-Binding 

Domain of Protein Kinase Cg in Complex with Phorbol Ester”, Cell, 81,917-924, (1995). 

Beamline X5 

G. Blanpied, M. Blecher, A. Caracappa, C. Djalali, G. Giordano, K. Hicks, S. Hoblit, M. Khandaker, O.C. 

Kistner, G. Matone, L. Miceli, C. Molinari, B. Preedom, D. Rebreyend, A.M. Sandorfi, C. Schaerf, R.M. 

Sealock, H. Stroher, C.E. Thorn, S.T. Thornton, C.S. Whisnant, H. Zhang, and X. Zhao, “Polarized Compton 

Scattering from the Proton”, Phys. Rev. Lett., 76, 1023-26, (1996). 

G. Blanpied, M. Blecher, A. Caracappa, C. Djalali, M.-A. Duval, G. Giordano, K. Hicks, S. Hoblit, M. 

Khandaker, A.M. Sandorfi, C. Schaerf, R.M. Sealock, C.E. Thorn, S.T. Thornton, K. Vaziri, C.S. Whisnant, and 

X Zhao, “New Measurements of 2H(,p)n and Spin Problems in Coupled NBNN Interactions”, Phys. Rev., C52, 

R455-59, (1995). 

A. Honig, Q. Fan, X. Wei, A.M. Sandorfi, and C.S. Whisnant, “New Investigations of Polarized Solid HD 

Targets”, Nucl. Inst. Meth. in Phys. Res., A356, 39-46, (1995). 

M. Khandaker, and A.M. Sandorfi, “Dependence of the Ratio of Electric to Magnetic ANY Couplings on the A+ 

Mass in Single-pion Photoproduction”, Phys. Rev., D5 1, 3966-68, (1995). 

C- 14 
G.S. Adams, H. Baghaei, A. Caracappa, W. Clayton, A. D’Angelo, S. Hoblit, M. Khandaker, O.C. Kistner, T. 

Kobayashi, R. Lindgren, L. Miceli, C. Ruth, A.M. Sandorfi, C. Schaerf, R.M. Sealock, C. Smith, P. Stoler, D.J. 

Tedeschi, C.E. Thorn, S.T. Thornton, K. Vaziri, C.S. Whisnant, and E.J. Winhold, “Measurement ofTd +pm” 

at Large Nucleon Momenta”, Phys. Rev., C51, 17-22, (1995). 

A.M. Sandorfi, C.S. Whisnant, and M. Khandaker, “Incompatibility of Multipole Predictions for the Nucleon 

Spin-Polarizability and Drell-Hearn-Gerasimov Sum Rules”, Phys. Rev., D50, R668 1, (1 994). 

Beamline X6A 

G. Jennings, and P.L. Lee, “EXGAFS: A Data Acquisition System for High-speed Dispersive EXAFS 

Measurements Implemented Using Object-Oriented Programming Techniques”, Rev. Sci. Instrum., 66, 1391- 

1393, (1995). 

P.L. Lee, M.A. Beno, C.M. Ogata, G.S. Knapp, and G. Jennings, “Diffraction Applications Using the Energy 

Dispersive Beamline X6A at the National Synchrotron Light Source”, Rev. Sci. Instrum., 66, 1425-1427, (1995). 

Beamline X6B 

J. Bai, M. Tomkiewin, and P.A. Montano, “Resonant X-reflectivity Measurements of a Ni/Fe Alloy Thin Film: a 

Composition Profile”, Zeitschrifzf;lr Physik, B97,465, (1995). 

M.A. Beno, G.S. Knapp, P. Armand, D.L.Price, and M.-L. Saboungi, “Application of New Synchrotron Powder 

Diffraction Techniques to Anomalous Scattering From Glasses”, Rev. Sci. Instrum., 66, 1308-1310, (1995). 

J.M. Block, M.A. Baysal, A.B. Travis, and K. Slifer, “Transparent Nondiffracting Polarization Rotation Regime: 

A Synchrotron X-ray Study”, Phys. Rev. Lett., 75,256-259, (1995). 

W.B. Caldwell, D.J. Campbell, K. Chen, B.R. Herr, C.A. Mirkin, A. Malik, M.K. Durbin, P. Dutta, and K.G. 

Huang, “A Highly Order Self-Assembled Monolayer Film of an Azobenzenealkanethiol on Au( 11 1): 

Electrochemical Properties and Structural Characterization by Synchrotron in-Plane X-ray Diffraction, Atomic 

Force Microscopy, and Surface-Enhanced Raman Spectroscopy”,/. Am. Chm. Soc., 117,6071-6082, (1995). 

L.X. Chen, 2. Wang, G. Hartwich, I. Katheder, H. Scheer, A. Scherz, P.A. Montano, and J .R. Norris, “An X-ray 

Absorption Study of Chemically Modified Bacterial Photosynthetic Reaction Centers”, Chm. Phy. Lett., 234, 

437-444, (1995). 

K.G. Huang, M. Ramanathan, and P.A. Montano, “Argonne National Laboratory X6B Beamline at NSLS: A 

Versatile Facility”, Rev. Sci. Instrum., 66, 1688-1690, (1995). 

K.G. Huang, J. Zegenhagen, J.M. Phillips, and J.R. Patel,, “Two Dimensional Structural Modulation of 

Epitaxial CaF2 Overlayers on Si(l1 l)”, Phys. Rev. Lett., 72,2430, (1994). 

Q.D. Jiang, K.G. Huang, M. Rao, and J. Zegenhagen, “The Initial Stage of the Epitaxial Growth of RBqCu,O,-x 

Thin Films”, Physica C, 235-240, 677-678, (1994). 

M. Ramanathan, and P.A. Montano, “Versatile Double-Crystal Fixed Exit Monochromator for X-ray 

Synchrotron Radiation”, Rev. Sci. Instrum., 66, 1754-1756, (1995). 

C-15 
I. Song, B. Rickett, P. Janavicius, J.H. Payer, and M.R. Antonio, “In situ Total-Electron-Yield Sulhr K-edge 

XAFS Measurements During Exposure of Copper to an SO2-containing Humid Atmosphere”, Nucl. Instrum. 

Meth. Pbys. Res., A360, 634-641, (1995). 

I. Song, M.R. Antonio, and J.H. Payer “An Iron K-edge XANES Study of Iron and Iron Oxides for the Cathodic 

Disbonding of Fusion Bonded Epoxy in Alkaline Aqueous Solution”, ]. Electrochem. Soc., 142,2219-2224, 

(1995) 

Beamline X7A 

T. Ami, M.K. Crawford, R.L. Harlow, Z.G. Li, T. Vogt, Q. Zhu, and D.E. Cox, “A Neutron and Synchrotron 

X-ray Scattering Study of Sr2Cu03,6 Synthesized under Moderate Pressure: a New Compound Related to 

Superconducting Sr,CuO,,”, Physica, C235/240, 1003, (1994). 

T. Ami, M.K. Crawford, R.L. Harlow, Z. Wang, D.C. Johnston, Q. Huang, and R.C. Erwin, “Magnetic 

Susceptibility and Low Temperature Structure of the Linear Chain Cuprate Sr2Cu0,”, Pbys. Rev., B51, 5994, 

(1995). 

C. Bezou, A. Nonat, J.-C. Mutin, A.N. Christensen, and M.S. Lehmann, “Investigation of the Crystal Structure 

of 4-CaSO,, CaS04-0.5H20, and CaS04-0.6H20 by Powder Diffraction Methods”, J. Solid State Chem., 117, 

165, (1995). 

K. Breuer, D.M. Goldberg, K.E. Smith, M. Greenblatt, and W. McCarroll, “Resonant Photoemission Study of 

the Electronic Structure of I&MoO,”, Solidstate Comm., 94, 601, (1995). 

RW. Broach, N.K. McGuire, C.C. Chao, and R.M. Kirchner, “Direct Methods Structure Determination 

FromSynchrotron Powder Diffraction Data of a New Clathrasil, TMA Silicate”,]. Pbys. Chem. Solid, 57/10, 

1363, (1995). 

M.K. Crawford, R.L. Harlow, E.M. McCarron, D.E. Cox, and Q. Haung, “Effects of Structural Phase 

Transitions on Superconductivity and Magnetism in Substituted Derivatives of LqCuO,”, Pbysica, C235-240, 

170, (1994). 

M.K. Crawford, R.L. Harlow, E.M. McCarron, N. Herron, W.E. Farneth, W. Donahue, B.A. Parkinson, and J. 

Schirber, “Synchrotron X-ray Powder Diffraction Study of Electochemically Oxidized LqCuO,, and 

Lq -X NdxCu04+6)),]. Pbys. Chem. OfSoLid,56, 1459, (1995). 

T. Egami, “Determining Medium Range Order by Powder Diffraction”,]. Pbys. Chem. Solid, 56, 1407, (1995). 

L.W. Finger, D.E. Cox, and A.P. Jephcoat, “A Correction for Powder Diffraction Peak Asymmetry Due to Axial 

Divergence”, J. AppL Cyst., 27, 892, (1 994). 

L.W. Finger, R.M. Hazen, and B.A. Fursenko, “Refinement of Crystal Structure of BaSi40, in the Benitoite 

Form”,]. Pbys. Chem. Solid, 56/10, 1389, (1995). 

J. E. Fischer, “Intercalation Compounds of Solid C6,’” Phvs. & Chem. Of Fullerenes, edited by K. Prassides, 

NATO ASISeries, 443, 223, (1995). 

J.E. Fischer, G. Bendele, R. Dinnebier, P.W. Stephens, C.L. Lin, N. Bykovetz, and Q. Zhu, “Structural Analysis 

of Fullerene and Fulleride Solids from Synchrotron X-ray Powder Diffraction”,]. Phys. Chem. Solid, 56, 1445, 

(1995). 

C-16 
N. Herron, D.L.Thorn, and R.L. Harlow, “Molecular Precursors to Functional Materials”, Molecularlv Desimed 

Ultrafine/Nanostructured Materials, edited by K.E. Gonsalves, MRS Svmn Proc., 351, 31, (1994). 

N. Herron, D.L. Thorn, R.L. Harlow, G.A. Jones, J.B. Parise, J.A. Fernandez-Baca, and T. Vogt, “Preparation 

and Structural Characterization of Two New Phases of Aluminum Trifluoride”, Chem. Mater., 7,75, (1995). 

R.M. Kirchner, and J.M. Bennett, “The Structure of Calcined AlP0,-41: a New Framework Topology 

Containing One-Dimensional 10-Ring Pores”, Zeolites, 14, 523, (1994). 

S.J. LaPlaca, J.F. Bringley, B.A. Scott, and D.E. Cox, “Structure of La5Cu5013,35 by High Resolution Synchrotron 

X-ray Diffraction”, J Solid State Chem., 118, 170, (1995). 

K. Leinenweber, J. Linton, A. Navrotsky, Y. Fei, and J.B. Parise, “High-Pressure Perovskites on the Join CaTiO, 

FeTiO,”, Phys. and Chem. Minerah, 22,251, (1995). 

K. Leinenweber, and J.B. Parise, “High-Pressure Synthesis and Crystal Structure of CaFeTi,O,, a new Perovskite 

Structure Type”,]. Solidstate Chem., 114,277, (1995). 

R.F. Lobo, M. Pan, I. Chan, R.C. Medrud, S.I. Zones, P.A. Crozier, and M.E. Davis, “Physicochemical 

Characterization of Zeolites SSZ-26 and SSZ-33”,]. Phys. Chem., 98, 12040, (1994). 

N.K. McGuire, C.A. Bateman, C.S. Blackwell, and S.T. Wilson, “Structure Refinement, Electron Microscopy, 

and Solid-state Magic Angle Spinning Nuclear Magnetic Resonance Characterization of A1P04-52 An 

Aluminophosphate with a Large Cage”, Zeolites, 15,460, (1995). 

R.E. Morris, J.J. Owen, and AX. Cheetham, “The Structure of La4Ti9OZ4 from Synchrotron X-ray Powder 

Diffraction”,]. Phys- Chem. Solid, 56/10, 1297, (1995). 

R.E. Morris, S.J. Weigel, N.J. Henson, L.M. Bull, and A.K. Cheetham, “A Synchrotron X-ray Diffraction, 

Neutron Diffraction, 2’Si MAS NMR, and Computational Study of the Siliceous Form of Zeolite Ferrierite”,]. 

Am. Chem. SOC., 116, 11849, (1994). 

J.B. Parise, D.R. Corbin, and L. Abrams, “Structural Changes Upon Sorption and Desorption of Xe from CdExchanged Zeolite rho: A Real-time Synchrotron X-ray Powder Diffraction Study”, Microporous Materiah, 4,99, 

(1995). 

J.-H. Park, and J.B. Parise, “High-Pressure Synthesis and Structure of a new Aurate, CaAu204”, Chem. Mater., 7, 

1055, (1995). 

D.M. Poojary, D. Grohol, and A. Clearfield, “Crystal Structure of Uranyl Chloromethylphosphonate from X-ray 

Powder Diffraction Data”,]. Phys. Chem. Solid, 56/10, 1383, (1995). 

D.M. Poojary, B. Zhang, and A. Clearfield, “Structure of a Mixed Phosphate/Phosphonate Layered Compound 

from Synchrotron X-ray Powder Diffraction Data”, Angew. Chem., 33,2324, (1994). 

H.D. Rosenfeld, and T. Egami, “A Model of Short and Intermediate Range Atomic Structure in the Relaxor 

Ferroelectric Pb(Mg,,3Nb2,J0,”, Ferroelectrics, 158, 351, (1994). 

H.D. Rosenfeld, and T. Egami, “Short and Intermediate Range Structural and Chemical Order in the Relaxor 

Ferroelectric Lead Magnesium Niobate”, Ferroelectrics, 164, 133, (1995). 

C-17 
D. Sandford, M. Fendorf, A.M. Stacy, W.L. Holstein, and M.K. Crawford, “Observation of Hendricks-Teller 

Partial Order in a Tetragonal Cuprate Superconductor: La,,,Nd,~,4Na,~,,K,,o,,Cu04~~, Phys. Rev., B50, 941 9, 

(1994). 

J.E. Schirber, W.R. Bayless, A.R. Kortan, E. Ozdas, 0. Zhou, D. Murphy, and J.E. Fischer, “Pressure Studies of 

Alkali, Alkaline Earth and Rare Earth Doped C,, Superconductors”, Science and Technolop of Fullerene 

Materials, edited by P. Bernier, T.W. Ebbesen, D.S. Bethune, R.M. Metzger, L.Y. Chiang, and J.W. Mintmire, 

MRS Symp. Proc., 359, p. 289, (1995). 

G.C. Smith, D.E. Cox, and A.P. Jephcoat, “X-ray Position Resolution in Proportional Chambers in the Region 

of 100 pm (FWHM) Above the Xenon K-edge”, Nucl. Imtrum. AndMeth., A350,621, (1994). 

M.A. Subramanian, M.K. Crawford, R.L. Harlow, T. Ami, J.A. Fernandez-Baca, Z.R. Wang, and D.C. 

Johnston, “Sr2Rh04 and Sr,Ir04: Structural and Magnetic Studies of 4d and 5d Transition Metal Analogs of 

La,,CuO,”, Physica, C235/240,743, (1994). 

T. Yildirim, L. Barbedette, J.E. Fischer, C.L. Lin, P.W. Stephens, and P.E. Sulewski, “Structure-Property 

Correlations in Fullerence Intercalation Compounds”, Physics and Chemistry of Fullerenes and Derivatives, 

edited by H. Kuzmany, J. Fink, M. Mehring, and S. Roth, World Scientific, Singapore, p. 379, (1995). 

T. Yildirim, L. Barbedette, K. Kniaz, J.E. Fischer, C.L. Lin, N. Bykovetz, P.W. Stephens, P.E. Sulewski, and S.C. 

Erwin, “Fullerene Superconductors: Effects of Molecular Orientation and Valence”, Science and Technolow of 

Fullerene Materials, edited by P. Bernier, T.W. Ebbesen, D.S. Bethune, R.M. Metzger, L.Y. Chiang, and J.W. 

Mintmire, MRS Symp. Proc., 359, p. 273, (1995). 

Q. Zhu, “Pressure-induced Polymerization of Ternary Fulleride Superconductors”, Phys. Rev., B52, R723, 

(1995). 

Q. Zhu, D.E. Cox, and J.E. Fischer, “Phase Transitions in KC,,: Dimer Formation via Rapid Quenching, Phys. 

Rev., B51,3966, (1995). 

Beamline X7B 

J. Aizenberg, L. Addadi, J. Hanson, L. Leiserowitz, T.F. Koetzle, and S. Weiner, “Morphogenesis of Calcitic 

Sponge Spicules: A Role for Specialized Proteins Interacting with Growing Crystals”, FASEBJ, 9,262-268, 

(1995). 

S. Asbrink, J.C. Hanson, A. Waskowska, and I. Uszynski, “Remarks on the Diffraction by the Diamonds of the 

High-pressure Diamond-Anvil Cell”, High Pressure Res., 12, 171-174, (1994). 

A.N. Christensen, P. Norby, and J.C. Hanson, “Chemical Reactions in the System MgO-MgCl,-H,O Followed 

by Time Resolved Synchrotron X-Ray Powder Diffraction”,]. Solid State Chem., 114, 556, (1995). 

J. Kansikas, I. Mutikaninen, U. Long, M. Nelson and A. Kvick, “Synchrotron X-ray Structure of a Zeolite ZSM39 Analogue”, BUZZ. Suc. Cat. Cien, 13, 121-126, (1994). I 

J.Z. Larese, and Q.M. Zhang, “Phase Transitions of Argon Multilayer Films on Graphite: Evolution from 

Multilayer Film to Bulk Solid”, Phys. Rev., B51, 17023-17027, (1995). 

V.N. Molchanov, R.A. Tamazyen, V.I. Simonov, M.K. Blomberg, M.J. Merisalo, and V.S. Mironov, “Structure 

and Superconductivity in Tl,BqCaCu,O,”, Physica C, 229,331-345, (1994). I 

c-18 
Beamline X8A 

D.V. Morgan, R.J. Bartlett, and M. Sagurton, “Single-Photon Multiple Ionization ofArgon in the K-edge 

Region”, Pbys. Rev., A51, 2939, (1995). 

M. Sagurton, R.J. Bartlett, J.A.R. Samson, 2.X He, and D. Morgan, “Effect of Compton Scattering on the 

Double-to-Single Photoionization Ratio in Helium”, Pbys. Rev., A52,2829, (1995). 

Beamline X8C 

R.W. Alkire, E.P. Sullivan, F.D. Michaud, W.J. Trela, R.J. Bartlett, and R. Rothe, “Performance of Beamline 

X8C at the NSLS”, Nzlcl. Imtr. AndMeth. In Pbys. Res., A352, 535-541, (1994). 

0. El-Kabbani, K. Judge, S.L. Ginell, L.J. DeLucas, and T.G. Flynn, “Crystallization and Preliminary Structure 

of Porcine Aldehyde Reductase/NADPH Binary Complex”, Acta Cyst., D5 1,605-608, (1995). 

0. El-Kabbani, K. Judge, S.L. Ginell, D.A.A. Myles, L.J. DeLucas, and T.G. Flynn, “Structure of Porcine 

Aldehyde Reductase Holenzyme”, Nature Struct. Bio., 2, 687-692, (1995). 

L. Tabernero, C.Y. Chang, S.L. Ohringer, W.F. Lau, E.J. Iwanowin, W. Han, T.C. Wang, S.M. Seiler, D.G.M. 

Roberts, and J.S. Sack, “Structure of a Retro-binding Peptide Inhibitor Complexed with Human AlphaThrombin”,]. Mol. Bid, 246, 14-20, (1995). 

Beamline X9B 

J.C. Andrews, R. Cinco, H. Dau, M.J. Latimer, W. Liang, T. A. Roelofs, A. Rompel, V.K. Yachandra, K. Sauer, 

and M.P. Klein, “Photosynthetic Water Oxidation: Structural Insights to the Catalytic Manganese Complex”, 

Pbysica B, 208, 657-659, (1995). 

D.S. Auld, and K. Zhang, “Making Zinc Visible”, FASEB J., Vol. 9, A1326, (1995). 

M.J. Baldwin, T.L. Stemmler, P.J. Riggs-Gelasco, M.L. Kirk, J.E. Penner-Hahn, and V.L. Pecoraro, “Structural 

and Magnetic Effects of Successive Protonations of Oxo Bridges in High Valent Manganese Dimers”,]. Am. 

Gem. SOC., 116, 11349-11356, (1994). 

T.M. Barnhart, and J.E. Penner-Hahn, “EXAFS Characterization of Methyl and Phenyl Cuprates in Solution”, 

Pbysica B, 208-209,709-710 (1995). 

J. Briggs, and M. Caffrey, “The Temperature-Composition Phase Diagram and Mesophase Structure 

Characterization of Monopentadecenoin in Water”, Biopbys. J., 67,,1594-1602, (1994). 

J. A. Chupa, J.P. McCauley, Jr., R.M. Strongin, A.B. Smith, 111, J.K. Blasie, L.J. Peticolas, and J.C. Bean, 

“VecoriallyOriented Membrane Protein Monolayers: Profile Structures via X-ray Interferometry/Holography”, 

Biophys.J., 67, 336-348, (1994). 

J.A. Chupa, J.P. McCauley, R.M. Strongin, A.B. Smith, J.K. Blasie, L.J. Peticolas, and J.C. Bean, “Vectorially 

Oriented Membrane Protein Monolayers: Profile Structure via X-Ray InterferometrylHolography”, Biopbys. ]., 

67,336-348, (1994). 

c-19 
K. Clark, J.E. Penner-Hahn, M. Whittaker, and J.W. Whittaker, “Structural Characterization of the Copper Site 

in Galactose Oxidase Using X-ray Absorption Spectroscopy”, Biochemistry ,33, 12553-12557, (1 994). 

G. Czerlinski, M. Isaacson, R. Ramires, S. Chen, B. Kanagal, C. Venkatesh, and L. Powers, “A Fast Micro-Flow 

Apparatus”, Rev. Sei. Instrum., 66,2604, (1995). 

H. Dau, J.C. Andrews, T. A. Roelofs, M.J. Latimer, W. Liang, V.K. Yachandra, K. Sauer, and M.P. Klein, 

“Structural Consequences of Ammonia Binding to the Manganese Center of the Photosynthetic Oxygen Evolving 

Complex: An X-Ray Absorption Study of Isotropic and Oriented Photosystem I1 Particles”, Biochemistry ,34, 

5274-5287, (1995). 

V.J. DeRose, M.J. Latimer, J.L. Zimmermann, I. Mukerji, V.K. Yachandra, K. Sauer, and M.P. Klein, “Fluoride 

Substitution in the Mn Cluster from Photosystem 11: EPR and X-Ray Absorption Spectroscopy Studies”, Chem. 

Phys., 194,443-459, (1995). 

J. Dong, and K. Zhang, “A Method for Constructing Unknown Orientation Dependent Spectra from a Group 

of Spectra in Polarized XAFS Experiments”, Physica B ,208/209, 161-165, (1995). 

Y. Dong, H. Fujii, M.P. Hendrich, R.A. Leising, G. Pan, C.R. Randall, E.C. Wilkinson, Y. Zang, L. Que, Jr., 

B.G. Fox, K. Kauffmann, and E. Munck, “A High-Valent Nonheme Iron Intermediate. Structure and Properties 

of [Fe2(p-O)2(5-Me-TPA),](CI0,),”,]. Am. Chem. Soc.,ll7,2778-2792, (1995). 

B.A. Eipper, A.S. Quon, R.E. Mains, J.S. Boswell, and N.J. Blackburn, “The Catalytic Core of Peptidylglycine 

Alpha-Hydrovlating Monoovgenase: Investigation by Site-Directed Mutagenesis, Cu X-Ray Absorption 

Spectroscopy, and Electron Paramagnetic Resonance”, Biochemistry ,34,2857-2865, (1 995). 

Z. Farhangrazi, B. Copeland, T. Nakayama, T. Amachi, I. Yamazaki, and L. Powers, “Oxidation-Reduction 

Properties of Compounds I and I1 ofdrthrobactor Ramosm Peroxidase”, Biochem., 33,5647, (1994). 

Z. Farhangrazi, M. Fossett, L. Powers, and W. Ellis, “Variable-Temperature Spectroelectrochemical Study of 

Horseradish Peroxidase”, Biochem., 34,2866, (1 995). 

N. Kitajima, N. Tamura, H. Amagai, H. Fukui, Y. Moro-oka, Y. Mizutani, T. Kitagawa, R. Methur, K. 

Heemegh, C.A. Reed, C.R. Randall, L. Que, Jr., and K. Tatsumi, “Monomeric Carboxylate Ferrous Complexes 

as Models for the Dioxygen Binding Sites in Non-Heme Iron Proteins. The Reversible Formation and 

Characterization of p-Peroxo Diferric Complexes”, /. Am. Chem. SOC., 116, 9071-9085, (1994). 

M.P. Klein, “Perspectives on Magnetic Resonance and X-ray Absorption Spectroscopy”, in Biochemistry. 

Biochemical SDectroscoDv, Methods in Enzymolow, edited by K. Sauer, Academic Press, 246,529-536, (1994). 

R. Koynova, and M. Caffrey, “Phases and Phase Transitions of the Hydrated Phosphatidylethanolamines”, Chem. 

Phys. Lipid, 69, 1-34, (1994). 

R. Koynova, and M. Caffrey, “Phases and Phase Transitions of the Hydrated Glycoglycerolipids”, Chem. Phys. 

Lipid, 69, 18 1-207, (1 994). 

R. Koynova, and M. Caffrey, “Phases and Phase Transitions of the Hydrated Sphingolipids”, Biochim. Biophys. 

Acta, 1255,213-236, (1995). 

J. Landro, E. Schmidt, P. Schimmel, D.L. Tierney, and J.E. Penner-Hahn, “Thiol Ligation of Two Zinc Atoms 

to a Class ItRNA Synthetase: Evidence for Unshared Thiols and Role in Amino Acid Binding and Utilization”, 

Biochemistry, 33, 14213-14220, (1994). 

c-20 
M.J. Latimer, A. Rompel, J.H. Underwood, V.K. Yachandra, and M.P. Klein, “A Simple In-Hutch Assembly for 

X-ray Harmonic Suppression”, Rev. Sei. Instrum., 66, 1843-1845, (1995). 

M.J. Latimer, V.J. DeRose, I. Mukerji, V.K. Yachandra, K. Sauer, and M.P. Klein, “Evidence for the Proximity of 

Calcium to the Manganese Cluster of Photosystem 11: Determination by X-Ray Absorption Spectroscopy”, 

Biochemistry, 34, 10898-10909, (1995). 

M.J. Latimer, The Role of Calcium in the Oxvgen Evolving. Center of Photomstem 11, PhD. Dissertation, 

University of California, Berkeley, CA (1995). 

W. Liang, Structural and Oxidation State Studies of the Manganese Cluster in the Oxvgen Evolving Comdex of 

Photosystem 11, PhD. Dissertation, University of California, (1995). LBL-Report 36632 

M. Lorenz, K.J. Poole, D. Popp, G. Rosenbaum, and K.C. Holmes, “An Atomic Model of the Unregulated Thin 

Filament Obtained by X-Ray Fiber Diffraction on Oriented Actin-Tropomyosin Gels”, /. Mol. Biol., 246, 108- 

119, (1995). 

H.D. Lujan, M.R. Mowatt, J.J. Wu, Y. Lu, A. Lees, M.R. Chance, and T.E. Nash, “Purification of a VariantSpecific Surface Protein of Giardia Lamblia and Characterization of its Metal-Binding Properties”, /. Biol. Cbem., 

270, 13807-13813, (1995). 

S. Mahapatra, J.A. Halfen, E.C. Wilkinson, G. Pan, C.J. Cramer, L. Que, and W.B. Tolman, “A New 

Intermediate in Copper Diooxygen Chemistry: Breaking the 0-0 Bond to Form a (CU~(~-O~)~+ Core”, /. Am. 

Cbem. Soc., 117,8865-8866, (1995). 

N.C. Maliszeswskyj, P.A. Heiney, J.Y. Josefowin, T. Plesnivy, H. Ringsdorf, and P. Schuhmacher, “Structure of 

Langmuir Blodgett Films of Star-Shaped Oligomeric Discogens”, Langmuir, 11, 1666-1674, (1995). 

L.M. Miller, and M.R. Chance, “Structural and Electronic Factors That Influence Oxygen Minityes: A 

Spectroscopic Comparison of Ferrous & Cobaltous Myoglobin”, Biochemistry ,34, 10170-10179, (1995). 

L.M. Miller, Distal and Proximal Control of Oxvgen Binding and Release in Hememoteins, PhD. Dissertation, 

Albert Einstein College of Medicine, June 1995. 

I. Mukerji, J.C. Andrews, V.J. DeRose, M.J. Latimer, V.K. Yachandra, K. Sauer, and M.P. Klein, “Orientation of 

the Oxygen-Evolving Manganese Complex in a Photosystem I1 Membrane Preparation: An X-ray Absorption 

Spectroscopy Study”, Biocbemistry , 33,9712-9721, (1994). 

K.J. Poole, K.C. Holmes, G. Evans, G. Rosenbaum, I. Rayment, and M. Lorenz, “Control of the Actomyosin 

Interaction”, Biophysical]., 68,348S, (1995). 

L. Powers, M. Lauraeus, K.S. Reddy, B. Chance, and M. Wikstrom, “Structure of the Binuclear Heme IronCopper Site in the Quinol-oxidizing Cytochrome aa3, from Bacillus subtih”, Biocbim. Biopbys. Acta ,1183, 504- 

512, (1994). 

C.R. Randall, L. Shu, Y.M. Chiou, K.S. Hagen, M. Ito, N. Kitajima, R.J. Lachicotte, Y. Zang, and L. Que, Jr. 

“X-Ray Absorption Pre-Edge Studies of High-Spin Iron (11) Complexes”, Inorg. Chem., 34, 1036-1 039, (1995). 

R.S. Rowlett, M.R. Chance, M.D. Wirt, J.R. Royal, M. Woodroffe, Y.A. Wang, R.P. Saha, andM.G. Lam, 

“Kinetic and Structural Characterization of Spinach Carbonic Anhydrase”, Biochemistry, 33, 13967-13976, 

(1994). 

c-21 
R.C. Scarrow, M.G. Trimitsis, C.P. Buck, G.N. Grove, R.A. Cowling, and M.J. Nelson, “X-Ray Spectroscopy of 

the Iron Site in Soybean Lipoxygenase-1: Changes in Coordination upon Oxidation or Addition of Methanol”, 

Biochmistry, 33, 15023-15035, (1994). 

E.M. Scheuring, Structural and Electronic Effects in Cobalamins and Model Comoounds: Their Importance in 

the Enzvmatic Processes, PhD. Dissertation, Albert Einstein College of Medicine, May 1995. 

L. Shu, Y.M. Chiou, A.M. Orville, M.A. Miller, J.D. Lipscomb, and L. Que, Jr. “X-Ray Absorption 

Spectroscopic Studies of the Fe(I1) Active Site of Catechol 2,3-Dioxygenase. Implications for the Extradiol 

Cleavage Mechanism”, Biochemistry, 34, 6649-6659, (1995). 

H.L. Tang, B. Chance, A. Mauk, L. Powers, K.S. Reddy, and M. Smith, “Spectroscopic, Electrochemical, and 

Ligand Binding Properties of the Horse Heart Metmyoglobin His64Try Variant”, Biochim. Biophys. Acta, 1206, 

90-96, (1994). 

D.L. Tierney, J.A. Fee, M.L. Ludwig, and J.E. Penner-Hahn, “X-Ray Absorption Spectroscopy of the Iron Site in 

Escherichia Coli Fe(II1) Superoxide Dismutase”, Biochemistry, 34,1661-1668, (1995). 

J. Wang, and M. CafFrey, “Locating Calcium in Membranes with X-Ray Standing Waves”, ]. Am. Chem. SOC., 

117,3304-3305, (1995). 

X. Wang, Soectroscooic Studies of Uteroferrin and Its Substrate Analogues, MS Thesis, University of Minnesota, 

1995. 

M.D. Wirt, M. Kumar, J.J. Wu, E.M. Scheuring, S.W. Ragsdale, M.R. Chance, “Structural and Electronic 

Factors in Heterolytic Cleavage: Formulation of the Co(1) Intermediate in the Corrinoid Protein from 

Clostridium Thermoaceticum”, Biochemistry, 34, 5269-5273, (1995). 

V.K. Yachandra, K. Sauer, and M.P. Klein, “Recent Studies on the Mn Complex Involved in Photosynthetic 

Water oxidation”, Proc. of the US-laDan Binational Conference on Dynamic Aspects of the Photochemical 

Reaction Center, Toyko, Japan. p. 32, (1995). 

V.K. Yachandra, “X-ray Absorption Spectroscopy and Applications in Structural Biology” in Biochemical 

Suectroscouv, Methods in Enzymologv, edited by K. Sauer, Academic Press, 246,638-675, (1994). 

K. Zhang, J. Dong, and D.S. Auld, “A Time-Resolved Study of Substrate Hydrolysis by Carboxypeptidase A”, 

Physica B, 2081209, 719-721, (1995). 

X.Y. Zhang, M.T. Pope, M.R. Chance, and G.B. Jameson, “High-Valent Manganese in Polyoxotungstates. 1. 

Manganese (IV) Keggin Derivatives”, Polyhedron,14, 1381-1392, (1995). 

Beamline XI OA 

P. Fenter, P.E. Burrows, P. Eisenberger, and S. Forrest, “Layer by Layer, Quasi-Epitaxial Growth of a Crystalline 

Organic Thin Film”,]. Cyst. Growth, 152, 65, (1995). 

P. Fenter, A. Eberhardt, and P. Eisenberger, “n-Alkyl Thiols Self-Assemble as Disulfides on Au( 11 l)”, Science, 

266, 1216, (1994) 

M. Linford, R.M. Weymouth, P. Fenter, P. Eisenberger, and C.E.D. Chidsey, “Alkyl Monolayers on Silicon: 

Reaction of 1-Alkenes with Hydrogen Terminated Silicon”,]. Amer. Chem. SOC., 117, 3145, (1995). 

c-22 
G.-Y. Liu, P. Fenter, C.E.D. Chidsey, D.F. Ogletree, P. Eisenberger, and M. Salmeron, “An Unexpected Packing 

of Fluorinated n-Alkane Thiols on Au( 1 1 1): A Combined Atomic Force Microscopy and X-ray Diffraction 

Study”,]. Chem. Phys., 101,4301, (1994). 

C.A. Melendres, Y.P. Feng, D.D. Lee, and S.K. Sinha, “X-ray Diffuse Scattering for the in situ Study of 

Electrochemically Induced Pitting on Metal Surfaces”,]. Electrochem. SOC., 142, L19, (1995). 

Beamline XI OC 

G. Meitzner, and J. Sinfelt, “X-Ray Absorption Studies of the Electronic Structures of Pd-Ag and Pd-Au Alloys”, 

Cad Letts., 30, 1, (1995). 

Beamlines XI 1 A E, XI 1 B 

M. Balasubramanian, Y.D. Zhang, J.I. Budnick, K.E. Gonsalves, and T.D. Xiao, “Studies on Nanostructed M50 

Type Steel Using X-ray Absorption Spectroscopy and NMR”, Mat. Res. SOC. Symp. Proc., 195,351, (1994). 

M. Balasubramanian, D.M. Pease, J.I. Budnick, T. Manzur, and D.L. Brewe, “Local Environment of Transition 

Metal Ternary Dopants in p Phase Transition Metal Aluminides”, Phylica, B208/209,493, (1995). 

M. Balasubramanian, Y.D. Zhang, J.I. Budnick, and D.M. Pease, “Local Environment of Fe in Nanostructured 

M50 Type Steel Samples”, NanostructuredMat., 249, 5, (1995). 

M. Balasubramanian, D.M. Pease, J.I. Budnick, T. Manzur, and D.L. Brewe, “Site Occupation Tenddncies for 

Ternary Additions (Fe,Co, Ni) In p Phase Transition Metal Aluminides”, Phys. Rev., B51, 8102, (1995). 

D.L. Brewe, D.M. Pease, and J.I. Budnick, “Corrections of Residual Fluorescence Distortions for a GlancingEmergence-Angle X-ray Absorption Technique”, Phys. Rev., B50, 9025, (1994). 

M. Endregard, D.G. Nicholson, M. Stocker, and G. Lamble, “Absorption and Thermal Decomposition of 

Cobaltcenium Ions on Microporous AlPOi5 Studied by XAS 13C Solid State NMR and FT-IR”,]. Mater. 

Chem., 5,785, (1995). 

M. Endregard, D.G., Nicholson, M. Stocker, and G. Lamble, “Cobaltcenium Ions Absorbed on Large-Pore 

Alumininophosphate VPI-5 Studied by XAS, 13C Solid-state NMR and FT-IR”,]. Mater. Chm., 5,485, 

(1995). 

A. Frenkel, V. Voronel, A. Katzir, M. Newville, and E.A. Stern, “Buckled Crystalline Structure of Disordered 

Mixed Salts”, Physica, B208/209,334, (1995). 

A. Frenkel, A. Rubshtein, V. Voronel, and E.A. Stern, “Comparative Radial-Distribution Analysis of the Short 

Range Order in Metallic Glass Al,,lLao,9 and Crystalline Al1,La;, Physica, B208/209,398, (1995). 

S.M. Heald, J.E. Amonette, G.D. Truner, and A.D. Scott, “An XAFS Study of the Oxidation of Structural Iron 

in Biotite Mica by Solutions Containing Br, or H202)), Physica, B208/209,604, (1995). 

D.T. Jiang, Z.Q. Gui, S.M. Heald, T.K. Sham, and M.J. Stillman, “XAFS of Silver(1) Metallothionein”, Physica, 

B208/209,729, (1995). 

D.T. Jiang, S.M. Heald, T.K. Sham, and M.J. Stillman, “Structures of the Cadmium, Mercury, and Zinc 

Thiolate Clusters in Mettallothionein: XAFS Study of 25-Mt, Cd,-Mt, HG-MT, and Hgl,-MT Formed From 

Rabbit Liver Metallothionein”,]. Am Chem. SOC., 116, 11004, (1994). 

C-23 
D.T. Jiang, T.K. Sham, P.R. Norton, and S.M. Heald, “Charge Redistribution in AuZn: An X-ray-Absorption 

Near-Edge-Structure Study”, Pbys. Rev., B49,3709, (1994). 

S. Kawi, 0. Alexeev, M. Shelef, and B.C. Gates, “Highly Dispersed MgO-Supported Model Pd-Mo Catalysts 

Prepared From Bimetallic Clusters”,]. ufPbys. Cbem., 99, 6926, (1995). 

S. Kawi, J.-R. Chang, and B.C. Gates, “Cluster Catalysis: Propane Hydrogenolysis Catalyzed by MgO-Supported 

Tetrairidium”,].ufPbys. Cbem., 98, 12978, (1994). 

S. Kawi, and B.C. Gates, “Tetra- and Hexairidium Clusters in NaX Zeolite Cages: Synthesis, Reactivity, and 

Characterization by Infrared and Extended X-ray Absorption Fine Structure Spectroscopies”, ].of Pbys. Cbem., 99, 

8824, (1995). 

K.M. Kemner, and B.A. Bunker, “Gas-Amplified Electron-Yield X-ray Detection at Low Temperatures”, Rev. Sci. 

rnrtrum., 65,3667, (1994). 

K.M. Kemner, B.A. Bunker, H. Luo, N. Samarth, J.K. Furdyna, M.R. Weidmann, and K.E. Newman, “Atomic 

Rearrangement at Interfaces in ZnTeKdSe Superlattices”, Pbys. Rev., B50,4327, (1 994). 

G.M. Lamble, “Design and Operation of a UHV Double-Bounce Harmonic Rejection Mirror for XAFS Studies”, 

Rev. Sci. Immm., 66, 1422, (1995). 

G.M. Lamble, “Workshop on Techniques and Experimental Methods for X-ray Absorption Fine Structure 

Spectroscopy”, Rev. Sci. Immm., 66,2383, (1995). 

G.M. Lamble, J.F. Lee, W.J. Staudt, and R.J. Reeder, “Structural Studies of Selenate Incorporation into Calcite 

Crystals”, PbyJica, B208/209, 589, (1995). 

J.F. Lee, S. Bajt, S.B. Clark, G.M. Lamble, C.A. Langton, and L. Oji, “Chromium Speciation in Hazardous 

Cement-based Waste Forms”, Pbysica, B208/209, 577, (1995). 

A. Lund, D.G. Nicholson, G. Lamble, and B. Beagley, “X-Ray Absorption Spectroscopic Study of the AlPOi5: 

Ferrocene Inclusion Compound and its Thermally Decomposed Products”,]. Mater. Cbem., 4, 1723, (1994). 

A. Lund, D.G. Nicholson, R.V. Parish, and J. Wright, ‘‘57Fe Mossbauer Spectroscopic Studies of the Ferrocene 

Molecular Reorientation in AlPOi5 and AlP0,-8 Frameworks”, Acta Cbem. Scand., 48,738, (1994). 

A.N. Mansour, and C.A. Melendres, “XAFS Investigation of the Structure and Valency of Nickel in some 

Oxycompounds”, Pbysica, B208/209, 583, (1995). 

A.N. Mansour, C.-P. Wong, and R.A. Brizzolara, “Atomic Structure of Amorphous Al,,,,CoxCex (x=8,9, and 10) 

and Al,,Fe,,Ce,, Alloys: An XAFS Study”, Pbys. Rev., B50, 12401, (1994). 

R.A. Mayanovic, Q. Lu, B.A. Bunker, A.J. Kropf, and J.R. Buschert, “Glancing Angle XAFS and X-ray 

Reflectivity Study of Cu Thermal Vibration Amplitude at the Cu-A1,03 Interface”, Pbysica, B208,405, (1995). 

J. McBreen, and S. Mukerjee, “In situ X-ray Absorption Studies of Pt-Ru Electrocatalyst”, ]. Electrocbem. Soc., 

142,3399, (1995). 

S. Mukerjee, J. McBreen, J.J. Reilly, J.R. Johnson, G. Adzic, K. Petrov, M.P.S. Kumar, W. Zhang, and S. 

Srinivasan, “In situ X-ray Absorption Spectroscopy Studies of Metal Hydride Electrodes”, ]. Electocbem. SUC., 142, 

2278, (1995). 

C-24 
M. Nicholson, and D.G. Nicholson, “Reduction of Copper(I1) with Subsequent Disproportionation of Copper(1) 

During the Hydrothermal Syntheses of Microporous Silicoaluminium Phosphates SAPO-5 and -11”, ]. Cbem. SOC. 

Faraday Trans., 91,3529, (1995). 

K.I. Pandya, “Multiple-Scattering Effects in X-ray-Absorption Fine Structure: Chromium in a Tetrahedral 

Configuration”, Pbys. Rev., B21, 15509, (1994). 

K.I. Pandya, A. Russell, J. McBreen, and W.E. O’Grady, “EXAFS Investigations of Zn(I1) in Concentrated 

Aqueous Hydroxide Solutions”,]. OfPbys. Cbem., 99, 11967, (1995). 

R.J. Reeder, G.M. Lamble, J.-F. Lee, and W.J. Staudt, “Mechanism of SeOk Substitution in Calcite: An XAFS 

Study”, Geocbimica st Cosmoshimica Acta, 58, 5634, (1994). 

A. Rubshtein, Y. Rosenberg, A. Frenkel, V. Manov, E. Veliyulin, A. Voronel, and E.A. Stern, “Structural, 

Thermal, and Electrical Properties ofAl-Rich Metallic Glass”, Mat. Sci. Forum, 179/181, 839, (1995). 

D.L. Sullivan, R.D. Roark, J.G. Ekerdt, S. E. Deutsch, and B.C. Gates, “Reaction and Spectroscopic Study of 

Silica-Supported Molybdenum (IV) and Tungsten (IV) Dimers”,]. ofPbys. Cbem., 99,3678, (1995). 

N.D. Traintafillou and B.C. Gates, “Magnesia-Supported Tetrairidium Clusters Derived From [Ir4(CO)12]”, /. of 

Pbys. Cbem., 98, 8431, (1994). 

N.D. Triantafillou, J.T. Miller, and B.C. Gates, “Iridium Clusters in KLTL Zeolite: Structure and Catalytic 

Selectivity for ?-Hexane Aromatization”,].ofCatal. 155, 131, (1995). 

N.D. Triantafillou, S.K. Purnell, C.J. Papile, J.-R. Chang, andd B.C. Gates, “A Family of Rhenium Subcarbonyls 

on MgO: Structural Characterization by Extended X-ray Absorption Fine Structure Spectroscopy”, Langmuir, 10, 

4077, (1994). 

2. Xu, and B.C. Gates, “Cyclohexene Hydrogenation Catalyzed by MgO-supported Tetrairidium Clusters”, ]. of 

Cafal., 154,335, (1995). 

2. Xu, F.-S. Xiao, S.K. Purnell, 0. Alexeev, S. Kawi, S.E. Deutsch, and B.C. Gates, “Size-Dependent Catalytic 

Activity of Supported Metal Clusters”, Nature, 372,346, (1994). 

Beamline XI 2C 

J.-0. Lee, P. Rieu, M.A. Amaout, and R. Liddington “Crystal Structure of the A Domain from the cx Subunit of 

Integrin CR3 (CDllb/CD18)”, Cel, 80,631-638, (1995). 

I. Schlichting, J. Berendzen, G.N. Phillips, Jr., and R.M. Sweet,“Crystal Structure of Photolyzed Carbonmonoxy 

Myoglobin”, Nature, 371, 808-812, (1994). 

R.-M. Xu, G. Carmel, R.M. Sweet, J. Kuret, and X. Cheng, “Crystal Structure of Casein Kinase-1, A PhosphateDirected Protein Kinase”, The EMBO lournal, 14, 1015-1023, (1995). 

Beamline Xl4A 

R.D. Aburano, H. Hong, J.M. Roesler, K. Chung, D.-S. Lin, P. Zschack, H. Chen, and T.-C. Chiang, 

“Boundary Structure Determination of Ag/Si( 11 1) Interfaces by X-Ray Diffraction”, Pbys. Rev., B52, 1839, 

(1995). 

C-25 
R.D. Aburano, H. Hong, J.M. Roesler, D.-S. Lin, T.-C. Chiang, and P. Zschack, “X-Ray Study of the Ag/ 

Si(ll1) Interface”, Su$Sci. Lett., 339, L891, (1995). 

J. Cheng, S.C. Moss, M. Eisner, and P. Zschack, “X-Ray Characterization of Melanins l.”, Pipent CeLL Research, 

7,255, (1994). 

A. Goyal, E.D. Specht, D.M. Kroeger, T.A. Mason, D.J. Dingley, G.N. Riley, Jr., and M.W. Rupich, “Grain 

Boundary Misorientations and Percolative Current Paths in High-Jc Powder-in-Tube Bi-2223”, App. Phys. Lett., 

66,2903, (1995). 

A. Goyal, M. Paranthaman, Qing He, F.A. List, E.D. Specht, D.K. Christen, D.M. Kroeger, J.E. Tkacyzk, and P. 

Haldar, “Fabrication, Processing, and Properties of T1- 1223 Conductors”, IEEE Transactions in Applied 

Superconductivity, 5, 1405, (1995). 

A. Goyal, E.D. Specht, D.M. Kroeger, D.K. Christen, J.E. Tkaczyk, J.A. DeLuca, and J.A. Sutliff, “Effect of the 

Colony Microstructure on Transport Critical Current of High-Jc TI-1223 Thick Films”, Proceedincs of the 1995 

International Workshop on Superconductivity co-sponsored by ISTEC and MRS, p. 453, (1995). 

E.D. Isaacs, P. Zschack, A.P. Ramirez, C.S. Oglesby, and E. Bucher, “Antiferromagnetic Order in 

Superconducting UPt3: An X-Ray Magnetic Scattering Study”, J Appl. Phys., 76, 6133, (1994). 

E.D. Isaacs, P. Zschack, C.L. Broholm, C. Burns, G. Aeppli, A.P. Ramirez, T.T.M. Palstra, E.W. Erwin, N. 

Stucheli, and E. Bucher, “Antiferromagnetism and its Relation to the Superconducting Phases of UPt,”, Phys. 

Rev. Lett., 75, 1178, (1995). 

X. Jiang, G.E. Ice, C.J. Sparks, and P. Zschack, “Recovery of SRO Parameters and Pairwise Atomic 

Displacements in a Fe,,,Ni,,, Alloy”, Mat. Res. SOC. Symp. Proc., 375,267-273, (1995). 

V.M. Kaganer, I.R. Peterson, R.M. Kenn, M.C. Shih, M.K. Durbin and P. Dutta, “Tilted Phases of Fatty Acid 

Monolayers”, Chem. Phys. Lett., 102, 9412, (1995). 

D.M. Kroeger, A. Goyal, and E.D. Specht, “Paths for Current Flow in Polycrystalline High Temperature 

Superconductors”, Proceedings of the 1995 International Workshop on Superconductivity Co-Sponsored by 

ISTEC and MRS, p. 217, (1995). 

C.J. Sparks, G.E. Ice, X. Jiang, and P. Zschack, ‘Static Displacements ofAtoms in Crystalline Metallic Solid 

Solutions”, Applications of Svnchrotron Radiation Techniaues to Materials Science 11, Mat. Res. SOC. Proc., 

375,213, (1995). 

E.D. Specht, A. Goyal, D.M. Kroeger, J.A. DeLuca, J.E. Tkaczyk, C.L. Briant, and J.A. Sutliff, “The Effect of 

Colonies of Aligned Grains on Critical Current in High Temperature Superconductors”, Physica C, 242, 164, 

(1 995). 

J.Z. Tischler, J.D. Budai, D.E. Jesson, G. Era, P. Zschack, J.M. Baribeau, and D.C. Houghton, “Ordered 

Structures in SixGe,-x Alloy Thin-Films”, Phys. Rev., B51, 10947, (1995). 

J.E. Tkanyk, J.A. Sutliff, J.A. DeLuca, P.J. Bednarczyk, C.L. Briant, Z.L. Wang, A. Goyal, D.M. Kroeger, D.H. 

Lowndes, and E.D. Specht, “Texture and Transport in Spray Pyrolyzed T1BqCa,Cu30, Thick Films”,]. Mater. 

Res., 10, 2203, (1995). 

C-26 
Beamline XI 5A 

E. Artacho, P. Molink-Mata, M. Bohringer, G.E. Franklin, J.R. Patel, and J. Zegenhagen, “Microscopic 

Structure of the Discommensurate Phases in Ge(1 1 1)/Ga. I. Atomic Structure Within Domains”, Pbys. Rev., B51, 

9952, (1995). 

G.E. Franklin, M.J. Bedzyk, J.C. Woicik, C. Liu, J.R. Patel, and J.A. Golovchenko, “Order-to-Disorder Phase 

Transiton Study of Pb on Ge(lll)”, Pbys. Rev., B51,2440, (1995). 

G.E. Franklin, E. Fontes, Y. Qian, M.J. Bedzyk, J.A. Golovchenko, and J.R. Patel, “Thermal Vibration 

Amplitudes and Structure ofAs on Si(OOl)”, Pbys. Rev., B50,7483, (1994). 

P.F. Lyman, Y. Qian, and M.J. Bedzyk, “Adsorbate Structure and Substrate Relaxation for the Sb/Si(100)-(2x1)”, 

Sqf Sci., 325, L385, (1995). 

Y. Qian, and M.J. Bedzyk, “Structure and Ad-Atom Thermal Vibrational Amplitude of the GdSi(001) 2x1 

Surface”,]. Vac. Sci, Tech., A13, 1613, (1995). 

Y. Qian, N.C. Sturchio, R.P. Chiarello, P.F. Lyman, T.-L. Lee, and M.J. Bedzyk, “Lattice Location of Trace 

Elements Within Minerals and at Their Surfaces with X-ray Standing Waves”, Science, 265, 1555, (1994). 

S. Tang, A.J. Freeman, Y. Qian, G.E. Franklin, and M.J. Bedzyk, “Combined Theoretical and Experimental 

Investigations of the Adsorption Geometry of Ga on Si(100) at Low Coverage”, Pbys. Rev., B51, 1593, (1995). 

J. Wang, and M. Caffrey, “Locating Calcium in Membranes with X-ray Standings Waves”,/. Am. Cbem. Suc., 

117,3304, (1995). 

J.C. Woicik, G.E. Franklin, C. Liu, R.E. Martinez, 1.-S. Hwong, M.J. Bedzyk, J.R. Patel, and J.A. Golovchenko, 

“Structural Determination of the Si( 11 1)1/3x1/3-Bi Surface by X-ray Standing Waves and Scanning Tunneling 

Microscopy”,PbyJ. Rev., B50, 12246, (1994). 

J. Zagenhagen, E. Artacho, P.E. Freeland, and J.R Patel, “Surface Structures of Si(l1 l)/Ga”, PbiL Mag., B70, 

731, (1994). 

J. Zegenhagen, T. Siegrist, E. Fontes, L.E. Berman, and J.R. Patel, ‘‘Epitaq of Ultrathin Films of YB%Cu30, on 

Sr(001) Investigated With X-ray Standing Waves”, Solid State Cornmun., 93,763, (1995). 

Beamline X15B 

L. E. Brus, P. F. Szajowski, W. L. Wilson, T. D. Harris, S. Schuppler, and P. H. Citrin, “Electronic Spectroscopy 

and Photophysics of Si Nanocrystals: Relationship to Bulk c-Si and Porous Si”,/. Amer. Cbem. Suc., 117,2915- 

2922, (1995). 

E. Ozdas, A. R. Kortan, N. Kopylov, A. P. Ramirez, T. Siegrist, K. M. Rabe, H. E. Bair, S. Schuppler, and P. H. 

Citrin, “Superconductivity and Cation-Vacancy Ordering in the Rare-Earth Fulleride Yb,,5C 

126-129, (1995). 

Natnre, 375, 

S. Schuppler, D.L. Adler, L.N. Pfeiffer, K.W. West, E.E. Chaban, and P.H. Citrin, “Identifying and Quantifying 

Point Defects Using X-ray Absorption Spectroscopy: Si-doped GaAs”, Pbys. Rev., B51, 10527-10538, (1995). 
S. Schuppler, S.L. Friedman, M.A. Marcus, D.L. Adler, Y.-H. Xie, F.M. Ross, T.D. Harris, W.L. Brown, Y.J. 

Chabal, L.E. Brus, E.E. Chaban, P.F. Szajowski, S.B. Christman, and P.H. Citrin, “Size, Shape, and Composition 

of Luminescent Species in Oxidized Si Nanoclusters and H-Passivated Porous Si”, Pbys. Rev., B51, 10527, 

(1995). 

S. Schuppler, S.L. Friedman, M.A. Marcus, D.L. Adler, Y.-H. Xie, F.M. Ross, T.D. Harris, W.L. Brown, Y.J. 

Chabal, P.F. Szajowski, E.E. Chaban, L.E. Brus, and P.H. Citrin, “X-ray Absorption Spectroscopy From Porous 

Si and Oxidized Si Nanocrystals”, Adications of Svnchrotron Radiation Techniques to Materials Science, edited 

by L.J. Terminello, N.D. Shinn, G.E. Ice, K.L. D’Amico,and D.L. Perry, MRS Symp. Proc., 2,375, (1995). 

S. Schuppler, S. L. Friedman, M.A. Marcus, D.L. Adler, Y.-H. Xie, F.M. Ross, T.D. Harris, W.L. Brown, J.J. 

Chabal, P.F. Szajowski, E.E. Chaban, L.E. Brus, and P.H. Citrin, “Size, Shape, and Crystallinity of Luminescent 

Structures in Oxidized Si Nancolusters, and H-Passivated Porous Si”, Microcrvstdline and Nanocrvstalline 

Semiconductors, edited by R.W. Collins, C.C. Tsai, M. Hirose, F. Koch, and LE. Brus, MRS Svmp. Proc., 358, 

(1995). 

Y.-H. Xie, G.H. Gilmer, C. Roland, P.J. Silverman, S.K. Buratto, Y.J. Cheng, E.A. Fitzgerald, A.R. Kortan, S. 

Schuppler, M.A. Marcus, and P.H. Citrin, “Semiconductor Surface Roughness: Dependence on Sign and 

Magnitude of Bulk Strain”, Pbys. Rev. Lett., 73,3006-3009, (1994). 

Y.-H. Xie, G. H. Gilmer, C. Roland, P. J. Silverman, S. K. Buratto, Y.J. Cheng, E. A. Fitzgerald, A. R. Kortan, S. 

Schuppler, M. A. Marcus, P. H. Citrin, “Step Energies and Roughening of Strained Layers - Reply”, Pbys. Rev. 

Lett. 74,4963, (1995). 

Beamline X16A 

P.A. Bennett, M.Y. Lee, P. Yang, R. Schuster, P.J. Eng, and I.K. Robinson, “Template Structure at the Silicon/ 

Amorphous-Silicide Interface”, Pbys. Rev. Lett., 75,2726, (1995). 

J.L. Dawson, K. Krisch, K.W. Evans-Lutterodt, M.-T. Tang, L. Manchanda, M.L. Green, D. Brasen, G.S. 

Higashi, and T. Boone, “Kinetic Smoothening: Growth Thickness Dependence of The Interface Width of the 

Si(OOl)/SiO, Interface”,]. Appl. Pbys., 77,4746, (1995). 

Evans-Lutterodt, and M.-T. Tang, “Angle Calculations for a 2+2 Surface X-ray Diffractometer”, ]. AppZ. Cyst., 

28,318, (1995). 

H.L. Meyerheim, W. Moritz, H. Schulzj P.J. Eng, and I.K. Robinson, “Anharmonic Thermal Vibrations 

Observed by Surface X-ray Diffraction for Cs/Cu(OOl)”, Surf: Sci., 333, 1422, (1995). 

S. Pflanz, H.L. Meyerheim, W. Moritz, I.K. Robinson, H. Hrnis, and E.H. Conrad, “The Anisotropic Roughing 

Transition of the Ag( 1 10) Surface: X-ray Reflection Profile Analysis Using the Domain Matrix Method”, Phyx 

Rev., B52,2914, (1995). 

H. Reichert, P.J. Eng, H. Dosch, and I.K. Robinson, “Thermodynamics of Surface Segregation Profiles at 

Cu,Au(OOl) Resolved by X-ray Scattering”, Pbys. Rev. Lett., 74,2006, (1995). 

I.K. Robinson, P.J. Eng, and R. Schuster, “Origin of the Surface Sensitivity in Surface X-ray Diffraction”, Acta 

Pbys. Polonica, A86, 513, (1994). 

R. Schuster, P.J. Eng, and I.K. Robinson, “Anomalous Coverage Behavior of the Cs-Ag Distance on Cs/Ag(l lo)”, 

Surf: Sci., 326, L477-L482, (1995). 

C-28 
Beamline X16B 

E.D. Isaacs, P. Zschack, C.L. Broholm, C. Burns, G. Aeppli, A.P. Ramirez, T.T.M. Palstra, R.W. Erwin, N. 

Stucheli, and E. Bucher, “Antiferromagnetism and It’s Relation to the Superconducting Phases in Upt;, Pbys. 

Rev. Lett., 75, 1178, (1995). 

Beamline X16C 

K. Konstadinidis, R.L. Opila, M.A. Marcus, K. Short, A.E. White, A.O. Ibidunni, A. Davenport, and H. Isaacs, 

“X-ray Absorption Study of Ti and Cr Reactions with Triazine and Polyimide”, Mat. Res. SOC. Symp. Proc., 233, 

345, (1994). 

I.K. Robinson, H. Graafsma, A. Kvick, and J. Linderholm, “First Testing of the Fast Kappa Diffractometers at 

NSLS and ESRF”, Rev. Sci. Instrum., 66, 1765, (1995). 

S.S. Sengupta, L. Ma, D.L. Adler, and D.A. Payne, “Extended X-ray Absorption Fine Structure Determination of 

Local Structure in Sol-gel-derived Lead Titanate, Lead Zirconate, and Lead Zirconate Titanate”, J Mat. Res., 10, 

1345, (1995) 

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, (1995). 

Beamline X17B2 

D. Chapman, W.C. Thomlinson, N.F. Gmur, J.P. Dervan, T. Stavola, J. Giacomini, H. Gordon, E. Rubenstein, 

W. Lavender, C. Schulze, and A.C. Thompson, “Effects of Spatial Resolution and Spectral Purity on Transvenous 

Coronary Angiography Images”, Rev. Sci. Instrum, 66/2, 1329-1331, (1995). BNL 60861 

N.F. Gmur, D. Chapman, W. Thomlinson, A.C. Thompson, W.M. Lavender, K. Scalia, N. Malloy, J. Mangano 

and J. Jacob, “NSLS Transvenous Coronary Angiography Beamline Upgrade and Advanced Technology 

Initiatives”, Rev. Sci Instrum., 66/2, 1357-1360, (1995). BNL 60857 

C. Schulze, and D. Chapman, “PEPO: A Program for the Calculation of the Reflectivity of Cylindrically Bent 

Laue Crystal Monochromators”, Rev. Sci. Instrum., 66/2,2220-2223, (1995). BNL 61689 

Beamline XI 7C 

T. S. Duffy, R. J. Hemley, and H. K. Mao, “Equation of State and Shear Strength at Multimegabar Pressures: 

Magnesium Oxide to 227 GPa”, Pbys. Rev. Lett., 74, 1371-1374, (1995). 

T. S. Duffy, C. Meade, Y. Fei, H. K. Mao, and R. J. Hemley, “High-Pressure Phase Transition in Brucite 

Mg(OH),”, Am. Mineral, 80,222-230, (1995). 

Y. Fei, and H. K. Mao, “In situ Determination of the NiAs phase of FeO at High Pressure and High 

Ternperature”,Science, 266, 1678-1 680, (1 994). 

Y. Fei, C. T. Prewitt, H. K. Mao, and C. M. Berth, “Structure and Density of FeS at High Pressure and High 

Temperature and the Internal Structure of Mars”, Science, 268, 1892-1894, (1995). 

G. Gu, Y.K. Vohra, J.M. Winand, and J.C. Spirlet, ‘(Pressure-Concentration (P-X) Diagram for the Ce-Th Alloy 

System”, Scripta Metallurgica et Materialia, 32, 208 1, (1995). - 

C-29 
R. J. Hemley, and H. K. Mao, “Progress on Hydrogen at Ultrahigh Pressures”, in Oji Seminar Volume: 

Elementarv Processes in Dense Plasmas, edited by S. Ichimaru, and S. Ogata, Addison-Wesley Pub. Co., Tokyo, 

pp. 271-282, (1995). 

R. J. Hemley, H. K. Mao, T. S. Dufi, J. H. Eggert, A. F. Goncharov, M. Hanfland, M. Li, M. Somayazuh, W. 

Vos, and C. S. Zha, “Dense Hydrogen in the Outer Solar System: Implications from Recent High-pressure 

Experiments”, in Volatiles in the Earth and Solar Svstem, edited by K. A. Farley, Am. Inst. Physics, New York, 

pp. 250-260, (1995). 

C. C. Kim, A. R. Drews, E. F. Skelton, S. B. Qadri, M. S. Osofsky, M. E. Reeves, and D. H. Liebenberg, 

“Volume Dependence of the Superconducting Transition Temperature for the High Temperature 

Superconductor HgB~Ca,-~PbxCu,0,+8,” Phys. Rev., B50/18, 13778, (1994). 

K. J. Kingma, R. J. Hemley, H. K. Mao, and D. R. Veblen, Reply to McNeil and Grimsditch‘s Comment on 

“New High-Pressure Transformation in a-Quartz”, Phys. Rev. Lett., 72, 1302, (1994). 

H. K. Mao, “Pressure Alchemy”, Rev. High Pressure Sei. Tech.-]apanese High-pressure Soc., 3, 8-1 1, (1994). 

H. K. Mao, R. J. Hemley, and A. L. Mao, “Recent Design of Ultrahigh-Pressure Diamond Cell”, in High 

Pressure Science and Technolow-1993, edited by S. C. Schmidt, J. W. Shaner, G. A. Samara, and M. ROSS, ATP 

Press, NewYork, 2, pp. 1613-1616, (1994). \ 

C. Meade, H. K. Mao, and J. Hu, “High-Temperature Phase Transition and Dissociation of (Mg,Fe)SiO, 

Perovskite at Lower Mantle Pressures”, Science, 268, 1743-1745, (1995). 

E. F. Skelton, S. B. Qadri, M. S. Osofsky, A. R. Drews, P. R. Broussard, J. 2. Hu, L. W. Finger, T. A. Vanderah, 

D. Kaiser, J. L. Peng, S. A. Anlage, R. L. Greene, J. Giapintzakis, and D. M. Ginsberg, “Direct Observation of 

Microscopic Inhomogeneities in High T, Superconductors”, SPIE Proc., 25 16, (1995). 

Y. K. Vohra, T.S. McCauley, and S.S. Vagarali, “Applications of Isopure and Natural Abundance Synthetic 

Diamonds in High Pressure Research”, in Advances in New Diamond Science and Technolog, edited by S. 

Saito, N. Fujimori, 0. Fukunaga, M. Kamo, K. Kobashi, and M. Yoshikawa, MYU, Tokyo, p. 391, (1994). 

Beamline X1 SA 

J.B. Cohen, “Long-Range Ordering in the Early Stages of Precipitation-A Brief Review”, Metallurgical and 

Materiah Transactions A, 25A, 2564-68, (1994). 

R. Colella, “Enantiomorphism and Multiple Beam Diffraction. Revised”, Acta Cyst., A51,438, (1995). 

R. Colella, Multiple Bragg Scattering and the Phase Problem in X-ray Diffraction. I Perfect Crystals”, Comments 

Cond. Matt. Phys., 17, 175, (1995). 

R. Colella, “Multiple Bragg Scattering and the Phase Problem in X-ray Diffraction. I1 Mosaic Crystals”, 

Comments Cond Matt. Phys., 17, 199, (1995). 

K.W. Herwig, B. Matthies, and H. Taub, “Preparation of Long-alkane Monolayers Adsorbed on Exfoliated 

Graphite for Neutron Diffraction Studies”, Neutron Scattering in Materials Science, edited by D.A. Nuemann, 

T.P. Russell, and B.J. Wuensch, Mater. Res. SOC. Svmp. Proc., 376, (1994). 

K.W. Herwig, J.C. Newton, and H. Taub, “Structure and Growth of Butane Films Adsorbed on Graphite”, Phys. 

Rev., B50, 15287-15297, (1994). 

C-30 
X.B. Kan, H. Renevier, J. Quintana, J.L. Peng, and J.B. Cohen, “Anomalous X-ray Diffuse Scattering Study of 

Short-Range Order in Nd,-xCexCuO,-y”,]. App. Phys., 77/1,34-40, (1995). 

S. Mansour, G. Liedl, and R. Vest, “Microstructural Developments and Dielectric Properties of Rapid Thermally 

Processed PZT Thin Films Derived by Metallo-Organic Decomposition”, ]. Am. Ceram. Suc., 78/6, 1617-23, 

(1995). 

J.L. Parrill, J.B. Cohen, and Y.-W. Chung, “Ultra-High Vacuum Grazing Incidence Small Angle X-ray Scattering 

Camera for in situ Surface Analysis”, Advances in X-ray Analvsis, edited by J.V. Gilfrich, et al., 37,413-418, 

(1994). 

H. Renevier, X.B. Kan, J.P. Quintana, K.J. Zhang, and J.B. Cohen, “Local Order in Y~%CU~-~CO~O,, 

Studied by Anomalous Diffuse X-ray Scattering”,]. Mat. Res., 9/12,3050-58, (1994). 

N. Takesue, M. Maglione, and H. Chen, “X-ray Thermal-Diffuse-Scattering (TDS) Study of Soft Modes in 

Paraelectric BaTiO,”, Phys. Rev. Lett., 51/10, 6696-6699, (1994). 

C. Venkatraman and G.L. Lied, “Oriented Texture in YbpC~,0,-~ Films Synthesized From Amorphous 

Precursors”, /. Of Electr. Mat., 23, 1 1, (1 994). 

H. Zhang, H. Sato, and G.L. Liedl, Possible Effect of Oxygen Content on the Under-Doped Characteristics of 

the La,-xSrxCuO,+, Compound”, Physica, C234, 185-89, (1 994). 

Beamline X18B 

D.-J. Liu, and H.J. Robota, “In situ Characterization of Cu-ZSM-5 by X-Ray Absorption Spectroscopy: XANES 

Study of Cu Oxidation State in Cu-ZSM-5 During the Selective Catalytic Reduction of NO by Hydrocarbons”, 

Appl. Catal., B4, 155, (1994). 

Beamline X19A 

M.R. Antonio, and L. Soderholm, “Cerium Valence in Cerium-Exchanged Preyssler’s Heteropolyanion Through 

X-ray Absorption Near-Edge Structure”, Inurg. Chem., 33, 5988-5993, (1994). 

M.J. Baldwin,T.L. Stemmler, P.J. Riggs-Gelasco, M.L. Kirk, J.E. Penner-Hahn, and V.L. Pecoraro, “Structural 

and Magnetic Effects of Successive Protonations of Oxo Bridges in High Valent Manganese Dimers”,]. Am. 

Chem. Suc., llG, 11349-11356, (1994) 

L.J. Blanchard, J.D. Robertson, S. Srikantapura, B.K. Parekh, and F.E. Huggins, “Potentially Hazardous Trace 

Elements in Kentucky Coals”, ACS Diu. Fuel Chem., 40,828-833, (1995). 

C. Bouldin, L. Furenlid, and T. Elam, “MacXAFS: An EXAFS Analysis Package for the Macintosh”, Physica, 

B208/209, 190-192, (1995). 

M. -I. M. Chou, J.M. Lytle, Y.C. Li, F.E. Huggins, G.P. Huffman, and K.K. Ho, “Chlorine in Five Illinois Coals 

and Three British Coals: An X-ray Absorption Near-Edge Structure (XANES) Spectroscopy Investigation”, ACS 

Diu. Fuel Chem., 40,402-406, (1995). 

M.-I. M. Chou, W.P. Pan, F.E. Huggins, J.M. Lytle, L. Liu, G.P. Huffman, and K.K. Ho, “Chlorine in Coal and 

Boiler Corrosion”, Proceedincs, Eleventh Annual Pittsburgh Coal Conference, Pittsburgh Energy Technology 

Center (U.S. DOE), Pittsburgh, PA, pp. 359-364, (1994). 
A.J. Davenport, J.A. Bardwell, and C.M. Vitus, “In Situ XANES Study of Galvanostatic Reduction of the Passive 

Film onIron”,]. Electrochem. Soc, 14213,721-724, (1995). 

T.I. Eglinton, J.E. Irvine, A. Vairavamurthy, W. Zhou, and B. Manowitz, “Formation and Diagenesis of 

Macromolecular Organic Sulfur in Peru Margin Sediments”, Organic Geochemistry, 22,78 1-799, (1994). 

L.R. Furenlid, M.W. Renner, and E. Fujita, “US Studies of Ni(I), Ni(II), and Ni(II1) Complexes”, Physica, 

B208-209,739-742, (1994). 

H. Hu, LE. Wachs, and S.R. Bare, “Surface Structure of Supported Molybdenum Oxide Catalysts: 

Characterization by Raman and Mo L,-edge XANES”,]. Phys. Chem., 99, 10897, (1995). 

G.P. Huffman, F.E. Huggins, N. Shah, F. Lu, and J. Zhao, “XAFS Studies of Coal”, ACS Diu. Fuel Chem., 39, 

77-80, (1994). 

G.P. Huffman, N. Shah, F.E. Huggins, L.M. Stock, K. Chatterjee, J.J. Kilbane, 11, M.-I. M. Chou, and D.H. 

Buchanan, “Sulfur Speciation of Desulfurized Coals by XANES Spectroscopy”, Fuel, 74, 549-5525, (1995). 

G.P. Huffman, N. Shah, J. Zhao, F.E. Huggins, T.E. Hoost, S. Halvorsen, and J.E. Goodwin, Jr., “In situ XAFS 

Investigation of K-Promoted Co Catalysts”,]. Catahsis, 15 1, 17-25, (1995). 

F.E. Huggins, and G.P. Huffman, “Chlorine in Coal: An XAFS Spectroscopic Investigation”, Fuel, 74,556-569, 

(1995). 

F.E. Huggins, B.K. Parekh, J.D. Robertson, and G.P. Huffman, “Modes of Occurrence of Trace Elements in 

Coal: Geochemical Constraints from XAFS and PDLE Spectroscopic Analysis of Advanced Coal Cleaning Tests”, 

International Conference on Coal Science (Oviedo, Spain ), Conference Proceedings, Elsevier, Amsterdam, pp. 

175-180, (1995). 

F.E. Huggins, M.M. Taghiei, and G.P. Huffman, “XAFS Spectroscopic Investigation of Element Speciation in 

Carbonaceous Materials From Coliquefaction of Coals and Waste Materials”, Book of Abstracts , Emercing 

Technologies in Hazardous Waste Management VI, edited by D.W. Tedder, American Chemical Society, Vol. 11, 

pp. 993-996, (1994). 

F.E. Huggins, J. Zhao, N. Shah, and G.P. Huffinan, “Modes of Occurrence of Trace Elements in Coal From 

XAFS Spectroscopy”, ACS Diu. Fuel Chem., 39, 504-510, (1994). 

G. Liang, R. Barber, Y. Tang, M. Croft, J. Cobb, and J.T. Markert, “Transition from a Mixed-Valent System to a 

Magnetically Ordered Kondo Lattice in Ce(NiSi),-x(CuGe)x”, Phys. Rev., B51,214, (1995). 

G. Liang, Y. Guo, W. Xu, D. Badresingh, J. Chen, A.Sahiner, M. Croft, 0. Beom-hoan, and J.T. Markert, “XRay Absorption Studies of Electron Doping and Band Shifts in %-xCe,CuO,, (R=Pr, Nd, Sm, Eu, Gd)”, Phys. 

Rev., B51, 1258, (1995). 

J. Liu, Y. Gagnon, J. Gauthier, L. Furenlid, P. L‘Heureux, M. Auger, 0. Nureki, S. Yokoyama, and J. Lapointe, 

“The Zinc-Binding Site of Escherichia coli Glutamyl-tRNA Synthetase is Located in the Acceptor-Binding 

Domain”,]. Biol. Chem., 270, 15162-15169, (1995). 

M. Najih, F.E. Huggins, and G.P. Huffman, “Determination of Chromium Oxidation States in Coal 

Combustion Products by XAFS Spectroscopy”, ACS Diu. Fuel Chem., 40, 808-812, (1995). 

C-32 
R. Nitsche, M. Winterer, M. Croft, and H. Hahn, “EXAFS Study on Nanostructured Zirconia and Yttria”, NzicZ. 

Instrum. andMeth., B97, 127-132, (1995). 

D.M. Pfund, J.G. Darab., J.L. Fulton, and Y. Ma, “An XAFS Study of Strontium Ions and Krypton in 

Supercritical Water”,]. Phys. Chem., 98, 13102-13107, (1994). 

M.W. Renner, L.R. Furenlid, and A.M. Stolzenberg, “Effects of Metal-Centered Reduction on the Structural, 

Electonic, and Coordination Properties of Nickel and Copper Octaethylisobacteriochlorins”, ]. Am. Cbm. SOL, 

117,293-300,(1995). 

P.J. Riggs-Gelasco, Structural Characterization of the Mancanese Cluster of the Oxyzen Evolvinp Complex of 

Photosvstem I1 Usinp X-rav Absorption Spectrsocopy, PhD. Thesis, Advised by J.E. Penner-Hahn, University of 

Michigan, (1994). 

A. Sahiner, M. Croft, S. Gua, I. Perez, 2. Zhang, M. Greenblatt, P. Metcalf, H. Johns, and G. Liang, “Polarized 

XAS Studies of Ternary Nickel Oxides”, Phys. Rev., B51, 5879, (1995). 

S. Shah, A. Ward, and A. J. Davenport, “Characterization of Tellurium-Based Conversion Coatings by X-Ray 

Absorption Near-Edge Structure and Fourier Transform Infrared Spectroscopy”, Cowosion, 5 1/1, 67-70, (1 995). 

N. Shah, J. Zhao, K.R.P.M. Rao, F.E. Huggins, and G.P. Huffman, “In situ XAFS Spectroscopic Studies of DCL 

Catalysts”, International Conference on Coal Science (Oviedo, Spain), Elsevier, Armsterdam, pp. 1279-1284, 

(1995). 

D.L. Tierney, J.A. Fee, M.L. Ludwig, and J.E. Penner-Hahn, “X-Ray Absorption Spectroscopy of the Iron Site in 

E Coli Fe(II1) Superoxide Dismutase”, Biochemistry, 34 , 1661-1668, (1995). 

A. Vairavamurthy, W. Zhou, E. Eglinton, and B. Manowitz, “Sulfonates: a Novel Class of Organic Sulfur 

Compounds in Marine Sediments”, Geochimica et Cosmochimica Acta, 58,468 1-4687, (1994). 

A. Vairavamurthy, B. Manowitz, W. Zhou, and Y. Jeon, “Determination of Hydrogen-sulfide Oxidation 

Products by Sulfur K-edge XANES Spectroscopy”, The Environmental Geochemistry of Sulfide Oxidation, 

edited by C. Alpers and D. Blowes, American Chemical Society, Washington, DC, 505, pp. 412-30, (1994). 

G.S. Waldo, and J.E. Penner-Hahn, “The Mechanism of Mn Catalase Peroxide Disproportionation: 

Determination of Mn Oxidation States During Turnover”, Biochemistry, 34, 1507-1512, (1995). 

R.T. Witkowski, S. Hattman, L. Newman, K. Clark, D.L. Tierney, J.E. Penner-Hahn, and G. McLendon, “The 

Zinc Coordination Site of the Bacteriophage Mu Translational Activator Protein, Com”, ]. MOL BioL, 247, pp. 

753-64, (1995). 

J. Zhao, 2. Feng, F.E. Huggins, N. Shah, G.P. Huffman, and I. Wender, “Role of Molybdenum at the Iron 

Oxide Surface”, ]. CataLysis, 148, 194- 197, (1 994). 

J. Zhao, F.E. Huggins, 2. Feng, and G.P. Huffman, “Ferrihydrite: Surface Structure and Its Effects on Phase 

Transformation”, Clays and Clay Minerah, 42,737-746, (1994). 

2. Zhu, Y. Gu, S.C. George, M.A. Wilson, F.E. Huggins, and G.P. Huffman, “ A Study of Sulphur and Nitrogen 

in Two High Sulphur Coals”, International Conference on Coal Science (Oviedo, Spain), Elsevier, Armsterdam, 

pp. 1681-1686, (1995). 
Beamline XI 9C 

I. Baker, and F. Liu, “An in situ Study of Dislocation/Grain Boundary Interactions Using X-ray Topography and 

TEM”, in Defect-Interface Interactions, edited by E.P. Kvam, A.H. King, M.J. Mills, T.D. Sands, and V. Vitek, 

Mat. Res. SOC. Svmp. Proc., p. 319, (1994). 

H. Chung, B. Raghotamachar, J. Wu, M. Dudley, D.J. Larson, Jr., and D.C. Gillies, “Characterization of 

Growth Defects in CdZnTe Single Crystals by Synchrotron White Beam X-ray Topography”, in Defect and 

ImDurtiv-Engineered Semiconductors and Devices, edited by S. Ahok, J. Chevallier, I. Akasaki, N.M. Johnson, 

and B.L. Sopori, Mat. Res. SOC. Symp. Proc., 378,41, (1995). 

D. DiMarzio, D.J. Larson, Jr., L.G. Casagrande, J. Wu, M. Dudley, and P.-K. Liao, “Defect Mapping of 

CdZnTe Substrates”, in Proceedings of the 1993 IRIS Soecialtv Group on Infrared Materials, (August 16-17, 

19932, ERIM, Ann Arbor, MI, p. 69, (1994). 

M. Dudley, W. Huang, S. Wang, J.A. Powell, P. Neudeck, and C. Fazi, “White Beam Synchrotron Topographic 

Analysis of Multipolytype Sic Device Configurations”,]. Pbys. D. Appl. Pbys., 28, A56, (1994). 

M. Dudley, S. Wang, W. Huang, C.H. Carter, Jr., and C. Fazi, ‘White Beam Synchrotron Topographic Studies 

of Defects in 6H-Sic Single Crystals”,]. Pbys. D. Appl. Phys., 28, A63, (1994). 

Z. Huang, M.L. Schlossman, A.A. Acero, 2. Zhang, N. Lei, and S.A. Rice, “Thermal Expansion Coefficient of a 

Water-Supported Perfluoro-n-Eicosane Monolayer”, Langmuir, 1 1, 2742, (1 995). 

W. Huang, S. Wang, M. Dudley, P. Neudeck, J.A. Powell, and C. Fazi, ‘Computer Aided Synchrotron White 

Beam X-ray Topographic Analysis of Multipolytype Sic Device Configurations”, in Applications of Synchrotron 

Radiation Techniaues to Materials Science, edited by L. Terminello, N. Shinn, G. Ice, K. D’Amico, and D. 

Perry, Mat. Res. SOC. Symo. Proc., 375, 327, (1995). 

F. Liu, I. Baker, and M. Dudley, “A New Method to Characterize Dislocations Loops”, in Applications of 

Svnchrotron Radiation Techniaues to Materials Science, edited by L. Terminello, N. Shinn, G. Ice, K. D’Amico, 

and D. Perry, Mat. Res. SOC. Svmp. Proc., 375,319, (1995). 

F. Liu, and I. Baker, “Synchrotron X-ray Topographic Studies of Grain Boundaries”, Microscopy Society of 

American Bulletin, 24, 351, (1994). 

S.P. Tobin, F.T.J. Smith, P.W. Norton, J. Wu, M. Dudley, D. DiMarzio, and L. Casagrande, “The Relationship 

Between Lattice Matching and Crosshatch in LPE HgCdTe on CdZnTe Substrates”, ]. Elect. Mat., 24, 1189, 

(1995). 

b 

S. Wang, M. Dudley, C.H. Carter, Jr., V.F. Tmetkov, and C. Fazi, “Synchrotron White Beam Topography 

Studies of Screw Dislocations in 6H-Sic Single Crystals”, in Aodications of Svnchrotron Radiation Techniques 

to Materials Science”, edited by L. Terminello, N. Shinn, G. Ice, K. D’Amico, and D. Perry, Mat. Res. SOC. 

Svmp. Proc., 375,281, (1995). + 

S. Wang, M. Dudley, W. Huang, C.H. Carter, Jr., V.F. Tsvetkov, and C. Fazi, “Characterization of Defects in 

Silicon Carbide Single Crystals by Synchrotron X-ray Topography”, in Proceedings of International Workshop on 

Semiconductor Characterization: Present Status and Future Needs”, edited by W. Murray Bullis, David G. Seiler, 

and Alain Diebold, American Institute of Physics, p. 278, (1995). 

c-34 
Beamlines X20A, X20B, E, X20C 

R.J.Birgeneau, Q.Feng, Q.J.Harris, J.P.Hil1, A.P.Ramirez and T.R.Thurston, “X-Ray, Neutron Scattering, 

Magnetization, and Heat Capacilty Study of the 3D Random Field Ising Model”, Pbys. Rev. Lett., 75, 1198, 

(1995). 

J.D. Brock, A.C. Finnefrock, K.L. Ringland, and E. Sweetland, “Detailed Structure of CDW in a Quenched 

Random Field”, Pbys. Rev. Lett., 73,3588, (1994). 

C. Cabral, Jr., L.A. Clevenger, G.B. Stephenson, S. Brauer, G.Morales and K. Ludwig, Jr., “In Sitzr X-ray 

Diffraction and Resistivity Analysis of CoSi, Phase Formation With and Without A Ti Interlayer at Rapid 

Thermal Annealing Rates”, Mat. Res. Symp. Proc., 375,253, (1994). 

L. Clevenger, R.A. Roy, C. Cabral, Jr., K.L. Saenger, S. Brauer, G. Morales, K.F. Ludwig, Jr., G. Gifford, J. 

Bucchignano, J. Jordan-Sweet, P. DeHaven, and G.B. Stephenson, “An in situ Study of C54-TiSi2 Formation in 

Submicron Salicide and Polycide Structures”,]. Mater. Res., 10,2355, (1995). 

B.J. Factor, T.P. Russell, and M.F. Toney, “The Near Surface Structure ofAromatic Polyimides: The Effect of 

Precursor Isomers”, Faraday Disc., 98, 319, (1995). 

R.F.C. Farrow, R.F. Marks, G.R. Harp, D. Weller, T.A. Rabedeau, M.F. Toney, and S.S.P. Parkin, “MBE 

Growth of Artificially-Layered Magnetic Metal Structures”, in Molecular Beam Epitaxy: Apdications to Key 

Materials, edited byR.F.C. Farrow, Noyes, New York, p. 623-744, (1995). 

J.G. Gordon, O.R. Melroy, and M.F. Toney, “Structure of Metal-Electrolyte Interfaces: Copper on Gold( 1 11) & 

Water on Silver(l1 l)”, Electrochim Acta, 40, 3, (1995). 

Q.J. Harris, Q. Feng, R.J. Birgeneau, K. Hirota, K. Kakurai, J.E. Lorenzo, G. Shirane, M. Hase, K. Uchinokura, 

H. Kojima, I. Tanaka, and Y. Shibuya, “Thermal Contraction at the Spin-Peierls Transition in CuGeO,”, Pbys. 

Rev., B50, 12606, (1994). 

Q.J. Harris, D.Y. Noh, D.A. Turnbull, and R.J. Birgeneau, “Hexatic Order in Thin Smectic F Liquid Crystal 

Films”, Pbys. Rev. E, 51, 5795, (1995). 

G.A. Held, and J.D. Brock, “Calculation of X-Ray Diffraction Profiles from Vicinal Surfaces”, Phys.Rev., B51, 

7262, (1995). 

G.A. Held, D.M. Goodstein, and J.D. Brock, “Phase Separation and Step Roughening of Vicinal Si( 11 1): An XRay Scattering Study”, Pbys. Rev., B51,7269, (1995). 

J.L. Jordan-Sweet, P.M. Mooney, and G.B. Stephenson, “High Resolution X-Ray Diffraction Measurements of 

Graded SiGe Multilayer Structures”, Applications of Svnchrotron Radiation Techniaues to Materials Science 11, 

Mat. Res. SOC. Symp. Proc. 375,201, (1995). 

P.M. Mooney, F.K. LeGoues, and J.L. Jordan-Sweet, “Dislocation Nucleation Barrier in SiGeISi Structures 

Graded to Pure Ge”, Appl. Pbys. Lett., 65,2845, (1994). 

P.M. Mooney, J.L. Jordan-Sweet, J.O. Chu, and F.K. LeGoues, “Evolution of Strain Relaxation in Step-Graded 

SiGeISi Structures”, Appl. Pbys. Lett., 66/26, 3642, (1995). 

W.J. Nuttall, D.Y. Noh, B.O. Wells, and R.J. Birgeneau, “Isothermal Melting of Near-Monolayer Xenon on 

Single-Crystal Graphite”, ]. Pbys. Condens. Matter, 7,4337-4350, (1995). 

c-35 
R.A. Roy, L.A. Clevenger, C. Cabral, Jr., K.L. Saenger, G.B. Stephenson, S. Brauer, J.L. Jordan-Sweet, J. 

Bucchigano, G. Morales, and K.F. Ludwig, Jr., “In Situ X-ray Diffraction Analysis of C49-C54 Titanium Silicide 

Phase Formation in Narrow Lines”, Appl. Pbys. Lett., 66/14, 1732, (1995). 

S. Song, and S. G. J. Mochrie, “Attractive Step-Step Interaction, Tricriticality, and Faceting in the Orientational 

Phase Diagram of Silicon Surfaces Between [113] and [114]”, Pbys. Rev., B51,10068, (1995). 

S. Song, M. Yoon, and S. G. J. Mochrie, “Faceting, Tricriticality, and Attractive Interactions Between Steps in the 

Orientational Phase Diagram of Silicon Surfaces Between [113] and [5512]” Su$ Sci., 334, 153, (1995). 

S. Song, S. G. J. Mochrie, and G. B. Stephenson, “Faceting Kinetics of Stepped Si(l13) Surfaces: A TimeResolved X-Ray Scattering Study”, Pbys. Rev. Lett., 74, 5240, (1995). 

M.F. Toney, T.P. Russell, J.A. Logan, H. Kikuchi, J.M. Sands, and S.K. Kumar, “Near-Surface Alignment of 

Polymers in Rubbed Films”, Nature, 374,709, (1995). 

M.F. Toney, J.G. Gordon, M.G. Samant, G.L. Borges , O.R. Melroy, D.Yee, and L.B. Sorensen, “The In situ 

Atomic Structure of Underpotentially Deposited Monolayers of Pb and T1 on Au( 1 11) and Ag(ll1): A Surface 

X-Ray Scattering Study”,/. Pbys. Cbem., 99,4733, (1995). 

M. Yoon, S. G. J. Mochrie, D. M. Zehner, G. M. Watson, and Doon Gibbs, “Periodic Step-bunching on a 

Miscut Pt(ll1) Surface”, Su$ Sci., 338,225, (1995). 

Beamline X21 

K. Hamalainen, M. Kirsch, F. Sette, C.-C. Kao, W. Caliebe, and J.B. Hastings, “A High Resolution X-ray 

Spectrometer Based on a Cylindrically Bent Crystal in Non-Dispersive Geometry”, Rev. Sci. Instrum., 66, 1525, 

(1995). 

C.-C. Kao, K. Hamalainen, M. Krisch, D.P. Siddons, T. Oversluizen, and J.B. Hastings, “Optical Design and 

Performance of the Inelastic Scattering Beamline at the National Synchrotorn Light Source”, Rev. Sci. Instrum., 

66, 1699, (1995). 

I I. , . ./ ,. , ,, ..* , _.,, .,., ~ 

- . 1 . . . , , . . 

M.H. Krisch, C.-C. Kao, F. Sette, W.A. Caliebe, K. Hamalainen, and J.B. Hasting, “Evidence for Quadrupolar 

Contribution to the Absorption Cross Section at the LIII Edge of Gadolinium in Gadolinium Gallium Garnet”, 

Pbys. Rev. Lett., 74,4931, (1995). 

A.T. Macrander, V.I. Kushnir, and R.C. Blasdell, “Performance of Spherically Focusing Ge(444) Backscattering 

Analyzers for Inelastic X-ray Scattering”, Rev. Sci. Instrum., 66, 1546, (1995). 

Beamline X22B 

R. R Adzic, J. Wang, and B.M. Ocko, “Structure of Metal Adlayers During The Course of Electrocatalytic 

Reactions: 0, Reduction on Au( 1 1 1) With TI Adlayers in Acid Solution”, Electrochimica Acta, 40, 83-89, (1995) 

M. Deutsch, X.Z. Wu, E.B. Sirota, S.K. Sinha, B.M. Ocko, and O.M. Magnussen, “Crystalline Bilayers on the 

Surface of Molten Alcohol”, Europbys. Lett., 30,283-288, (1995). 

W.J. Foster, Jr., X-ray Optical Studies of Thin Organic Films, PhD.Thesis, Harvard University, June, 1995. 

W.J. Foster, M.C. Shih, and P.S. Pershan, “The Sructure and Phases of a Relaxed Langmuir Monolayer of Methyl 

Eicosanoate as Determined by Grazing Incidence X-ray Diffraction and Brewster Angle Microscopy”, Proc. Of 

C-36 
Materials Research Society. Symposium AA: Applidations of synchrotron Radiation Techniques to Materials 

Science 11, Boston, MA, edited by D.L. Perry, G. Ice, N. Shinn, K. D’Amico and L. Terminello, p. 187, (1995). 

A. Gibaud, D.F. McMorrow, and P.P. Swaddling, “Determination of the X-ray Scattering Lineshape From a Nb 

Film Using Synchrotron Radiation”,]. Phys. Chern., 7,2645-54, (1995). 

G.S. Kellog, P.S. Pershan, E.H. Kawamoto, W. Foster, M. Deutsch, and B.M. Ocko, “X-ray Reflectivity 

Measurements and Landau Theory of Smectic Wetting in nCBIBenzy1 Alcohol Mixtures”, Phys. Rev., E51,4709, 

(1995). 

S.D. Kosowsb, C.H. Hsu, P.S. Pershan, J. Bevk, and B.S. Freer, “X-ray Scattering Studies of SiO/Si/Ge(001)”, 

Appl. Surjf Sci., 84, 179, (1995). 

O.M. Magnussen, B.M. Ocko, R.R. Adzic, and J. Wang, “X-ray Diffraction Studies of Ordered Chloride and 

Bromide Monolayers at the Au(ll1)-Solution Interface”, Phys. Rev., B51,5510-5513, (1995). 

O.M. Magnussen, B.M. Ocko, M.J. Regan, K Penanen, P.S. Pershan, and M. Deutsch, “X-ray Reflectivity 

Measurements of Surface Layering in Liquid Mercury”, PhyJ. Rev. Lett. 74,4444, (1995). 

B.M. Ocko, O.M. Magnussen, R.R. Adzic, J. Wang, ZShi, 2. and J. Lipkowski, “A Critical Comparison of 

Electrochemical and Surface X-ray Scattering Results at the Au( 11 1) Electrode in KBr Solutions”, ]. Electroanl. 

Chem., 376, 35-39, (1994). 

W. Polewska, J.X. Wang, B.M. Ocko, and R.R. Adzic, “Scanning Tunneling Microscpy Studies of 

Electrodeposited Thallium Monolayers on Au( 1 1 1) in Alkaline Solution and a Comparison With Surface X-ray 

Scattering Data”, ]. Electroanal. Chern., 376,41-48, (1994). 

J.P. Rieu, J.F. Legrand, A. Renault, B. Berge, B.M. Ocko, X.Z. Wu, and M. Deutsch, “Melting of 1-alcohol 

Monolayers at the Air-Water Interface. I) X-ray Reflectivity Investigations”, ]. Pbys. II, 5, 607-619, (1995). 

E. Smela, and L.J. Martinez Miranda, “Effect of Substrate Preparation on Smectic Liquid-Crystal Alignment .2. 

Further Results and Modeling, ]. OfAppl. Phys., 77, 1923-1929, (1995). 

E. Smela, and L.J. Martinez Miranda, “Effect of Substrate Preparation on Smectic Liquid-Crystal Alignment .3. 

The Significance of Thermal History”,]. OfAppl. Phys., 77, 1930-1933, (1995). 

P. Sonntag, P. Bodeker, K. Brohl, T. Thurston, and H. Zabel, “Charge-Density Waves and Strain Waves in Thin 

Epitaxial Cr Films”, Nucl. Imtrurn. AndMeth. In Phys. Res., 97,468-471, (1995). 

Beamline X22C 

N. Bernhoeft, A. Stunault, C. Vettier, F. de Bergevin, D. Gibbs, T.R. Thurston, S.M. Shapiro, J.B. Hasting, P. 

Dalmas, G. Helgesen; and 0. Vogt, “Antiferromagnetic Layer Formation in UAS”,]. Map. and Map. Mater., 

140/144, 1421-1422, (1995). 

J.P. Hill, G. Helgesen, and D.Gibbs, “X-ray Scattering Study of Charge- and Spin-Density Waves in 

Chromium”, Phys. Rev., B51, 10336-10344, (1995) 

G.H. Lander, W.G. Stirling, S. Landridge, and D. Gibbs, “Resonant X-ray Scattering in 5f Magnetism”,]. Map. 

Map. Mater., 140/144 , 1349-1352, (1995). 

G.H. Lander, W.G. Stirling, S. Langridge, C.C. Tand, and D. Gibbs, “Resonant Magnetic X-ray Scattering: a 

New Probe for Actinides”,]. OfAlhys & Compound, 213/214, 114, (1994). 

c-37 
S. Langridge, W.G. Stirling, G.H. Lander, and J. Rebizant, “Resonant Magnetic X-ray Scattering Studies of 

NpAs. I. Magnetic and Lattice Structure”, Pbys. Rev., B49, 12010, (1994). 

S. Landridge, W.G. Stirling, G.H. Lander, and J. Rebizant, “Resonant Magnetic X-ray Scattering Studies of 

NpAs. 11. The Critical Regime”, Pbys. Rev., B49, 12022, (1994). 

C.F. Majkrzak, J.F. Ankner, N.F. Berk, and D. Gibbs, “Neutron and X-ray Diffraction Studies of Magnetic 

Multilayers”, Mametic Multilavers, edited by R.E. Watson and L.H. Bennett, World Scientific Pub., pp. 299- 

354, (1994). 

D.F. McMorrow, J.A. Simpson, R.A. Cowley, D.A. Jehan, R.C.C. Ward, M.R. Wells, T.R.Thurston, and 

D.Gibbs, “The Magnetic Structure of Holmium-Erbium Superlattices”, ]. Map. and Map. Mater. , 1401144, 

1550-1553, (1995). 

W.J. Nuttall, S. Langridge, W.G. Stirling, G.H. Lander, B. Lebech, D. Gibbs, and 0. Vogt, “Resonant X-ray and 

Neutron Diffraction Study of USbo.8Te0,2)), Pbys. Rev., B52,4409-19, (1995). 

D.F. Paul, M.J. Cooper, and W.G. Stirling, “Design of an X-ray Beamline on a Bending Magnet at the ESRF For 

Magnetic and High Resolution Diffraction”, Rev. Sci. Instrum., 66/2, 1741-44, (1995). 

P. Swaddling, D.F. McMorrow, R.A. Cowley, R.C.C. Ward, and M.R. Wells, “Determination of the Interfacial 

Roughness Exponent in Rare Earth Superlattices”, Pbys. Rev. Lett., 73, 2232 (1994). 

D. Watson, E.M. Forgan, W.G. Stirling, W.J. Nuttal. S.C. Perry, M.M.R. Costa, and D. Fort, “Magnetic X-ray 

Diffraction From Samarium”, ]. Map. andMap. Mater., 140-144,743-744 (1995). 

X.Z. Wu, B.M. Ocko, H. Tang, E.B. Sirota, S.K. Sinha, and M. Deutsch, “Surface Freezing in Binary Mixtures 

ofhes: New Phases and Phase Transitions”, Pbys. Rev. Lett., 75, 1332 (1995). 

M. Yoon, S.G.J. Mochrie, D.M. Zehner, G.M. Watson, and D. Gibbs, “Periodic Step-Bunching on a Miscut 

Pt(ll1) Surfke”, Szcrf: Sci., 338,225, (1995). 

I.. 

Beamline X23A2 

M. R. Antonio, J. Malinsky, and L. Soderholm, “Synthesis and Properties of Lanthanide-Exchanged Preyssler’s 

Heteropolyanions”, Materials Research Society Proceedings, 368, 223, (1993.. 

Y. Azuma, H.G. Berry, D.S. Gemmell, J. Suleiman, M. Westerlind, I.A. Sellin, J.C. Woicik, and J.P. Kirkland, 

“Attenuation of Photons at 3 to 14 keV Energies in Helium”, Pbys. Rev., A51,447, (1995). 

B.B. Buchanan, J.J. Bucher, D.E. Carlson, N.M. Edelstein, E.A. Hudson, N. Kaltsoyannis, T. Leighton, W. 

Lukens, H. Nitsche, T. Reich, K. Roberts, D.K. Shuh, P. Torretto, J.C. Woicik, W-S. Yang, A. Yee, and B.C. 

Yee, “A XANES and EXAFS Investigation of the Speciation of Selenium Following Bacterial Uptake”, Inorg. 

Cbem., 34, 1617, (1995). 

P. Crespo, A. Hernando, A. Garcia Escorial, K.M. Kemner, and V.G. Harris, “Extended X-ray Absorption Fine 

Structure Studies of Heat-treated FCC-FeCu Powders Processed via High-Energy Ball-Milling”, ]. AppL Phys., 76, 

6322, (1994). 

M. Fernandez-Garcia, C. Marquez Alvarez, and G.L. Haller, “XANES-TPR Study of Cu-Pd Bimetallic Catalysts: 

Application of Factor Analysis”,]. ofPhys. Chem., 99, 12565, (1995). 

C-3 8 

_. 

I’ ~:’x,. .I ,, . 

. . 1.. : . . -, . 
C.L. Foiles, M.R. Franklin, R. Loloee, R. Clarke, and T.I. Morrison, “EXAFS Study of Co/Cu Multilayers: MBE 

Versus Sputtered”, Amlication of Synchrotron Radiation Techniques to Materials Science 11, edited by L.J. 

Terminello, N.D. Shinn, G.E. Ice, K.L. D’Amico, and D.L. Perry, Materials Research Society Symposium 

Proceedincs, 375,207-212, (1995). 

K.M. Kemner, B.A. Bunker, H. Luo, N. Samarth, J.K. Furdyna, M.R. Weidmann, and K.E. Newman, “Atomic 

Rearrangement at Interfaces in ZnTe/CdSe Superlattices”, Phys. Rev., B50,4327, (1 994). 

K.M. Kemner, A.J. Kropf, and B.A. Bunker, “Gas-amplified Electron-yield X-ray Detection at Low 

Temperatures”, Rev. Sci. Insmm., 65, 3667, (1994). 

W. Lin, S. Yinchaik, W. Lin, A. Malik, M.K. Durbin, A.G. Richter, G.K. Wong, P. Dutta, and T.J. Marks, 

“New Nonlinear Optical Materials: Expedient Topotactic Self-Assembly of Acentric Chromophoric 

Superlattices”, Angew. Chem. Int. Ed Engl., 34, 1497, (1995). 

R.A. Mayanovic, and B.A. Bunker, “Observation of Anisotropic Vibrational Amplitudes due to Thermal Motion 

at a Cu/Al,O, Interface”, Phys. Lett., A202,225, (1995). 

R.A. Mayanovic, Q. Lu, B.A. Bunker, A.J. Kropf, and J.R. Buschert, “Glancing Angle XAFS and X-ray 

Reflectivity Study of Cu Thermal Vibration Amplitude at the Cu-A1203 Interface”, Physica 23, 208,405, (1995). 

J. McBreen, XQ. Yang, H.S. Lee, and Y. Okamoto, “X-ray Absorption Studies of Mixed Salt Polymer 

Electrolytes: ZnBr,/CaBr,-PEO, ZnBr,/LiBr-PEO, and ZnBr,/RbBr-PEO Complexes”, ]. Electrochem. SOC., 142, 

348, (1995). 

D.A. McKeown, “X-ray Absorption Spectroscopic Study of Cu in an Amorphous Cu-silicate: Chrysocolla”, ]. 

Non-Ctystalline Solid, 180, 1, (1994). 

S. Mukerjee, S. Srinivasan, M.P. Soriaga, and J. McBreen, “Effect of Preparation Conditions of Pt Alloys on 

Their Electronic, Structural, and Electrocatalytic Activities for Oxygen Reduction: XRD, XAS and 

Electrochemical Studies”,]. Phys. Chem., 99,4577, (1995). 

S. Mukerjee, S. Srinivasan, M.P. Soriaga, and J. McBreen, “Role of Structural and Electronic Properties of Pt and 

Pt Alloys on Electrocatalysis of Oxygen Reduction: An in situ XANES and EXAFS Investigation”, ]. Electrochem. 

SOC., 142, 1409, (1995). 

U. Staub, M.R. Antonio, L. Soderholm, M. Guillaume, W. Henggeler, and A. Furrer, “Tb Oxidation State and 

Hybridization in Yo~,Tb,,~9Ba2Cu30,~,: A Magnetic Susceptibility-&d X-ray Absorption Study”, Phys. Rev., B50, 

7085, (1994). 

J.E. Tabora, and R.J. Davis, “Structure of Fe, Mn-Promoted Sulfated Zirconia Catalyst by X-ray and IR 

Absorption Spectroscopies”, J Chem. SOC. Faraday Trans., 91, 1825, (1995). 

Beamline X23A3 

A.J. Allen, and R.A. Livingston, “Small-Angle Scattering Study of Concrete Microstructure as a Function of Silica 

Fume, Fly Ash or Other Pozzolonic Additions”, Proc. 5Th CANMET/ACI Conference on Fly Ash, Silica Fume, 

Slag and Natural Pozzolans in Concrete, Edited by V.M. Malhotra, American Concrete Institute, Detroit, Mi, pp. 

1179-1200, (1995). 

I. Baker, F. Liu, M. Dudley, and D.R. Black, “In situ Synchrotron Radiation X-ray Topographic Studies of 

Polycrystalline Ice”, Proc. IAHR-94, Trondheim, Norway, pp. 416-425, (1995). 

c-39 
D.R. Black, H.E. Burdette, L. Robins, M.A. Plano, M.D. Moyer, M.A. Moreno, L. Pan, D. Kania, and W. 

Banholzer, “The Defect Microstructure of Thick Homoepitaxial Diamond Films”, Proc. ICNDST-4, Kobe, 

Japan, pp. 251-256, (1994). 

D.R. Black, H. Burdette, R. Linares, and P. Doering, “X-ray Diffraction Imaging of Free-Standing CVD 

Diamond Films”, Proc. 4Th Int’l Svmp. On Diamond Materials, Reno, NV, pp. 467-472, (1995). 

D. Black, H. Burdette, M.A. Plano, M.D. Moyer, M. Moreno, J. Ager, and A. Chen, “Observation of Individual 

Defects in a Homoepitaxial Diamond Film”, Proc. 4Th Int’l Svmp. On Diamond Materials, Reno, NV, p.564, 

(1995). 

L. Cassagrande, D. Larson, D. DiMarzio, J. Wu, M. Dudley, D.R. Black, and H. Burdette, “Growth of LargeArea High-Quality CdZnTe Substrates by Computer-Controlled Vertical Bridgman Method”, PIE, 2228,21- 

32, (1994). 

X. Hu, K. Jia, I. Baker, and D. Black, “Dislocation Mobility in HC1-Doped Ice”, Application of Synchrotron 

Radiation Techniques to Materials Science. 11, edited by L.J. Terminello, N. Shinn, G.E. Ice, K.L. D’Amico, and 

D.L. Perry, MRS Svmp. Proc., 375, pp. 287-292, (1995). 

J. Ilavsky, A.J. Allen, G.G. Long, S. Krueger, H. Herman, C.C. Berndt, and A.N. Goland, “Anisotropy of the 

Surfaces of Pores in Plasma Sprayed Alumina Deposits”, Proc. Of the International Thermal Spray Conference 

lITSC ‘951, Kobe, Japan, pp. 483-488, (1995). 

S. Krueger, G.J. Olson, D. Johnsonbaugh, and T.J. Beveridge, “Characterization of The Binding of Galluim, 

Platinum, and Uranium to Pseudomonas Fluorescens by Small Angle X-ray Scattering and Transmission Electron 

Microscopy”, Appl. & Environ. Microbiol., 59,4056-4064, (1993). 

W.E. Luecke, S.M. Wiederhorn, B.J. Hockey, R.F. Krause, and G.G. Long, “Cavitation Contributes 

Substantially to Tensile Creep in Silicon Nitride”,]. Am. Ceram. SOL, 78/8,2085-2096, (1995). 

M.A. Plano, M.D. Moyer, M. A. Moreno, D.R. Black, H.E. Burdette, L. Robins, L.S. Pan, D.R. Kania, and W. 

Banholzer, “Properties of Thick Homoepitaxial Diamond Films”, in Diamond. Sic and Nitride wide Bandgap 

Semiconductors, edited by C. Carter, Jr., G. Gildenblat, S. Nakamura, and R. Nemancih, MRS Proc., 339, pp. 

307-312, (1994). 

S.M. Wiederhorn, W.E. Luecke, B.J. Hockey, and G.G. Long, “Creep Damage Mechanisms in Si,N,”, h 

Tailoring of Mechanical Properties of Si&$ Ceramics, edited by M.J. Hoffmann, and G. Petzow, Kluwer 

Academic Publishers, the Netherlands, pp. 305-326, (1994). 

Beamline X23B 

G. M. Chow, L. K. Kurihara, K. M. Kemner, I?. E. Schoen, W. T. Elam, A. Ervin, S. Keller, Y. D. Zhang, J. 

Budnick, and T. Ambrose, “Structural, Morphological and Magnetic Study of Nanocrystalline Cobalt-Copper 

Powders Synthesized by the Polyol Process”,]. ofMater. Res., 10, 1546, (1995). 

P. Crespo, A. Hernando, A. Garcia Escorial, K. M. Kemner, and V. G. Harris, “Extended X-ray Absorption Fine 

Structure Studies of Heat-Treated FCC-Fe5,,Cu5, Powders Processed via High-Energy Ball-Milling”, ]. Appl. Pbys., 

76 110, 6322-6324, (1994). 

K. M. Kemner, W. T. Elam, D. B. Hunter, and P. M. Bertsch, “EXAFS Studies of CsBr-dibenzo-18-crown-6 

ether Solutions”, Pbysica B, 208/209,735, (1995). 

C-40 

. 1 .. I’.’..*. 
K. M. Kemner, V. G. Harris, W. T. Elam, and J. C. Lodder, “EXAFS Studies and Simulations of Local 

Anisotropy in Co,,Cr,, Films”, Mat. Res. SOC. Symp. Proc. 375,21, (1995). 

K. M. Kemner, V. G. Harris, W. T. Elam, and J. C. Lodder, “Polarization-Dependent EXAFS Studies of 

Chemical and Structural Anisotropy in Sputter-deposited Co,,Cr,, Films”, IEEE Trans. Map., 30/6, 4017, 

(1994). 

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. Kirkland, 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), 1709-1711, (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). 

K.M. Robinson,and W.E. O’Grady “X-ray Diffraction and Electrochemical Study on the Oxidation of Flame 

Annealed Au (100) Single Crystal Surfaces,”]. Ekctroanal. Gem., 384, 139-144, (1995). 

Beamline X24C 

V.M. Bermudez, and J.P. Long, “Characterization of Reconstructured Sic( 100) Surfaces Using Soft X-ray 

Photoemission Spectroscopy”, Appl. Pbys. Lett., 66,475, (1995). 

B.S. Itchkawitz, J.P. Long, T. Schedl-Niedrig, M.N. Kabler, A.M. Bradshaw, R. Schlogl, and W.R. Hunter, 

“Photoemission and C Is Near-edge Absorption From Photopolymerized C,. Films”, Chem. Pbys. Lett., 243,211, 

(1995). 

T. Kendelewicz, J.E. Klepeis, J.C. Woicik, S.H. Southworth, C. Mailhiot, M. VanSchilfgaarde, M. Methfessel, A. 

Herrera-Gomez, and K.E. Miyano, “Large-Angle Bond-Rotation Relaxation for CdTe( 1 lo)”, Pbys. Rev., B5 1, 

10774, (1995). 

W.R.L. Lambrecht, B. Segall, J. Rife, W.R Hunter, and D.K. Wickenden, “W Reflectivity of GaN: Theory and 

Experiment”, Pbys. Rev., B51, 13516, (1995). 

M.A. MacDonald, S.H. Southworth, J.C. Levin, A. Henins, R.D. Deslattes, T. LeBrun, Y. Azuma, P.L. Cowan, 

and B.A. Karlin, “Evolution of X-ray Resonance Raman Scattering into X-ray Fluorescence from the Excitation of 

Xenon Near the L3 Edge”, Pbys. Rev., A51,3598, (1995). 

J.C. Woicik, J.G. Pelligrino, S.H. Southworth, P.S. Shaw, B.A. Karlin, C.E. Bouldin, and K.E. Miyano, 

“Accomodation of Strain in Ultra-thin InAs/GaAs Films”, Phys. Rev., B52, R2281, (1995).. 

Beamline X25 

L.E. Berman, “Preserving the High Source Brightness with X-Ray Beam Line Optics”, Rev. Sci. Instrzim. , 66, 

2041-2047, (1995). 

S. Brauer, G.B. Stephenson, and M. Sutton, “Perfect Crystals in the Asymmetric Bragg Geometry as Optical 

Elements for Coherent X-Ray Beams”,]. Synch. Rad., 2, 163-173, (1995). 

J.D. Brock, A.C. Finnefrock, K.L. Ringland, and E. Sweetland, “Detailed Structure of a Charge-Density Wave in 

a Quenched Random Field”, Pbys. Rev. Lett., 73,3588-3591, (1994). 
Y. Cho, S. Gorina, P.D. Jeffrey, and N.P. Pavletich, “Crystal Structure of a p53 Tumor Suppressor-DNA 

Complex: Understanding Tumorigenic Mutations”, Science, 265, 346, (1 994). 

F.M.F. de Groot, S. Pizzini, A. Fontaine, K. Hbdiiinen, C.C. Kao, and J.B. Hastings, “Local-Spin-Selective XRay Absorption and X-Ray Magnetic Circular Dichroism of MnP”, Phys. Rev., B51, 1045-1052, (1995). 

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”, Phys. Rev. Lett., 75,449-452, (1995). 

W. Dmowski, R.J. McQueeney, T. Egami, Y.P. Feng, S.K. Sinha, T. Hinatsu, and S. Uchida, “Temperature 

Dependent X-Ray Diffuse Scattering from Single Crystals of La-Sr-Cu-O”, Phys. Rev., B52, 6829-6839, (1 995). 

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 DyLu Alloy”, Phys. Rev. Lett., 75, 3182-3185, (1995). 

M.M. Grush, G. Christou, K. Hbdiiinen, and S.P. Cramer, “Site-Selective XANES and EXAFS: A 

Demonstration with Manganese Mixtures and Mixed-Valence Complexes”,]. Am. Chem. Soc., 117, 5895-5896, 

(1995). 

C.W. Miiller, F.A. Rey, M. Sodeoka, G.L. Verdine, and S.C. Harrison, “Structure of the NF-Kl3 p50 

Homodimer Bound to DNA”, Nature, 373, 311-317, (1995). 

M.J. Regan, E.H. Kawamoto, S. Lee, P.S. Pershan, N. Maskil, M. Deutsch, O.M. Magnussen, B.M. Ocko, and 

L.E. Berman, “Surface Layering in Liquid Gallium: X-Ray Reflectivity Study”, Phys. Rev. Lett., 75,2498-2501, 

(1995). 

J. Sondek, D.G. Lambright, J.P. Noel, H.E. Hamm, and P.B. Sigler, “GTPase Mechanism of Gproteins from the 

1.7 Crystal Structure of Transducin a-GDP-AlF;”, Nature, 372,276-279, (1994). 

S. Song, and S.G.J. Mochrie, “Attractive Step-Step Interactions, Tricriticality, and Faceting in the Orientational 

Phase Diagram ofsilicon Surfaces Between [113] and [114]”, Phys. Rev., B51, 10068-10084, (1995). 

S. Song, S.G.J. Mochrie, and G.B. Stephenson, “Faceting Kinetics of Stepped Si(l13) Surfaces: A Time-Resolved 

X-Ray Scattering Study”, Phys. Rev. Lett., 74, 5240-5243, (1995). 

Eeamline X26A 

A.J. Aldykiewin, Jr., H.S. Isaacs, and A.J. Davenport, “The Investigation of Cerium as a Cathodic Inhibitor for 

Aluminum-Copper Alloys”, ]. Electrochem. Soc., 142,3342-3350, (1 995). 

A.J. Anderson, R.A. Mayanovic, and S. Bajt, “Determination of the Local Structure and Speciation of Zinc 

Complexes in Individual Fluid Inclusions by Micro-XAFS”, The Canadian Mineral, 33,499-508, (1 995). 

S. Bajt, and A.L. Hanson, “An Investigation of the Iron Pre-edge XANES Structure”, Rev. Sei. Immm., 66, 1502- 

1504, (1994). 

S. Bajt, S.R. Sutton, and J.S. Delaney, “Microanalysis of Iron Oxidation States in Earth and Planetary Materials”, 

Physica, B208/209,243-244, (1995). 

S. Bajt, S.R. Sutton, and J.S. Delaney, “Microanalysis of Iron Oxidation States in Silicates and Oxides Using Xray Absorption Near Edge Structure (XA.NES)”, Geochim. Cosmochim, Acta, 58,5209-5218, (1995). 

C-42 
C. Dalpe, D.R. Baker, and S.R. Sutton, “Synchrotron X-ray-Fluorescene and Laser-Ablation ICP-MS 

Microprobes: Useful Instruments for Analysis of Experimental Run-Products”, The Canadian Mineral, 33,48 1- 

498, (1995). 

A.J. Davenport, and M. Sansone, “High Resolution in situ XANES Investigation of the Nature of the Passive 

Film on Iron in pH 8.4 Borate Buffer”,]. Electrochem. SOC., 142,725-730, (1995). 

A.J. Davenport, J.A. Bardwell, and C.M. Vitus, “In situ XANES Study of Galvanostatic Reduction of the Passive 

Film on Iron”,]. Electrochem. SOC., 142,721-724, (1995). 

H. Isaacs, J.-H. Cho, M.L. Rivers, and S.R. Sutton, “In situ X-ray Microprobe Study of Salt Layer During Anodic 

Dissolution of Stainless Steel in Chloride Solution”,]. ElectrochemicalSoc., 142/4, 11 11-1 118, (1995). 

A. Lanzirotti and G.N. Hanson, “U-Pb Dating of Major and Accessory Minerals Formed During Metamorphism 

and Deformation of Metapelites”, Geochimica et Cosmochimica Acta, 59,25 13-2526, (1995). 

R.A. Mayanovic, A.J. Anderson, and S. Bajt, “Development of Micro-XAFS: Applications to Studies of Single 

Fluid Inclusions”, Physica, B208/209,239-240, (1995). 

P. Northup, and RJ. Reeder, “Evidence for The Importance of Growth-Surface Structure to Trace Element 

Incorporation in Topaz”, American MineraZogist, 79, 1167-1 175, (1994). 

J. Rakovan and R.J. Reeder, “Differential Incorporation of Trace Elements and Dissymmetrization in Apatite: 

The role of Surface Structure During growth”, American Mineralogist, 79, 892-903, (1994). 

S. Shah, A. Ward, and A.J. Davenport, “Characterization of Tellerium-Based Conversion Coatings with XANES 

and FTIR”, Corrosion, 51,67-70, (1995). 

S. Sutton, S. Bajt, J. Delaney, D. Schulze, and T. Tokunaga, “Synchrotron X-ray Fluorescence Microprobe: 

Quantification and Mapping of Mixed Valence State Samples Using Micro-XANES”, Rev. Sci. Instrum., 66, 

1464-1467, (1995). 

K.L. Thomas, et al., “An Asteroidal Breccia: The Anatomy of a Cluster IDP”, Geochimica et Comzochimica Acta, 

59/13,2797-2815, (1995). 

T. Tokunaga, S.R. Sutton, and S. Bajt, “Mapping of Selenium Concentrations in Soil Aggregates with 

Synchrotron X-ray Fluorescence Microprobe”, Soil Science, 158,421-433, (1994). 

Beamline X26C 

P.-C. Wang, C.S. Cargill 111, and I.C. Noyan, “Strain Measurements and Laue Diffraction With Microbeams”, 

MRS Spmp. Proc., 375,247, (1995). 

B.X. Yang, M.L. Rivers, W. Schildkamp and P. Eng, “GeoCARS Micro-Focusing Kirkpatrick-Baa Mirror 

Bender Development”, Rev. Sci. Instyurn., GG, 2278-2280, (1995). 
U. Bergmann, S.D. Shastri, D.E Siddons, B.W. Batterman, and J.D. Hastings,. “Temperature Dependence 

of Nuclear Forward Scattering of Synchrotron Radiation of a-57Feyy, Phys. Rev., B50/9,5957-5961 , (1 994), 

BNL 60854. 

L.E. Berman, “Preserving the High Source Brightness with X-ray Beamline Opticsyy, Rev. Sci. Instrum., 66, 

2041-2047, (1995), BNL 60859. 

L.E. Berman, “Structural Biology at the National Synchrotron Light Sourceyy, Synch. Rud. News, 8/4, 11- 

15, (1995), BNL 62171. 

L.E. Berman, “Review of Optical Engineering Volume 34, Special Edition on High Heat Flux Optical 

Engineering”, Synch. Rud. News, 8/4,37, (1995), BNL 62176. 

R. Biscardi, G. Ramirez, and G.E Williams, ‘(Effects of RF Side-Bands on Spectral Reproducibility for 

Infrared Synchrotron Radiation”, Rev. Sci. Instrum., 66, 1856, (1995), BNL 60862. 

E.B. Blum, and L. Solomon, “Calculated and Measured Fields in Superferric Wiggler Magnets”, The Art 

and Science of Magnet Design, A Festschrift in Honor of Klaus Halbach, Lawrence Berkeley Laboratory, 

VO~. 1, pp. 29-37, (1995), BNL 60980. 

E. Bozoki, “Closed Orbit Related Problems: Correction, Feedback and Analysis”, AIP Conference 

Proceedings, 315, p. 43, 1994, BNL 61251. 

J.L. Bantignies, C. Moulin, H. Dexpert, A.M. Flank, And G.P. Williams, “Asphaltene Adsorption on 

Kaolinite: Characterization by Infrared Microspectroscopy and X-ray Adsorption Spectroscopy”, Compte 

Rendu derAcud. Sci. Puris, 320,699, (1995), BNL 61879. 

K. Batchelor, M. Babzien, I. Ben-Zvi, R. Fernow, J. Fischer, A. Fisher, R. Malone, I. Pogorelsky, T. SrinivasanRao, J. Sheehan, and X Wang, “Operational Experience on the Brookhaven National Laboratory Accelerator 

Test Facilityyy, Proceedinm 4th European Particle Accelerator Conference, edited by V. Suller and C. PetteJean-Genez, World Scientific, Vol. 1, pp. 736-738, (1994), BNL 60739. 

I. Ben-Zvi, “Milestone Experiments for Single Pass W/X-Ray FELs”, Nucl. Imtrum. And Meths. In Phys. 

Res., A358, 54, (1995). BNL 60827. 

E. Bozoki, and A. Friedman, “The Use of Neural Networks in the Orbit Control of Accelerators and 

Storage Rings”, AIP Conference Proceedinm, 315, p. 103, 1994, BNL 61253. 

E. Bozoki, and A. Friedman, “Neural Networks and Orbit Control in Accelerators”, Proceedinzs 4th EuroDean 

Particle Accelerator Conference, London, 2, p. 1589, (1994), BNL 60586. 
K. Breuer, K.E. Smith, D. Goldberg, M. Greenblatt, W. McCarroll, and S.L. Hulbert, “Defects in QuasiOne Dimensional Oxide Conductors: I&Mo03”, Mat. Res. SOC. Symp. Proc., 375, 133, (19951, BNL 

61406. 

G.L. Car, M. Hanfland, and G.P. Williams, “The Mid-Infrared Beamline at the NSLS Port U2B”, Rev. 

Sci. Imtrum., 66, 1643, (1995), BNL 60893. 

D. Chapman, W. Thomlinson, N.F. Gmur, J.P. Dervan, T. Stavola, J. Giacomini, H. Gordon, E. Rubenstein, 

W. Lavender, C. Schulze, and A.C. Thompson, “Effects of Spatial Resolution and Spectral Purity on 

Transvenous Coronary Angiography Images”, Rev. Sci. Instrum., 66/2, 13291331, (1995), BNL 60861. 

C.L. Foerster, “Ultra-High Vacuum System of the Brookhaven National Synchrotron Light Source”, 

Proceedinm International Conference on Vacuum Science & Technolog and SRS Vacuum SystemsINCOVAST 95, Indore, India, Vol. 1, pp. 36-57, (1995), BNL 62537. 

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 Bfactory”,/. Ec. Sci. Zchnol., A13/3, 581, (1995), BNL 61082. 

Fontana, J.R., Kimura, W.D., Steinhauer, L.C., Pogorelsky, I., “Design Analysis for a 100 MeV Inverse 

Cerenkov Laser Accelerator”, Proceedings of the 1993 Particle Accelerator Conference, Washington, DC, 

p. 2614, (1993), BNL 60092, February 1994. 

A. Friedman, and E. Bozoki, “A Digital Feedback System for Transverse Orbit Stabilization in the NSLS 

Rings”, Proceedinm International Conference on Accelerator and Large Experimental Physics Control 

Systems, Berlin, Germany, NIM, A352, p. 393, 1995, BNL 49670. 

A. Friedman, and E. Bozoki, ‘X Digital Feedback System for Transverse Orbit Stabilization”, Proceedings 

4th EuroDean Particle Accelerator Conference, London, England, 2, p. 1586, 1994, BNL 60629. 

A. Friedman, and E. Bozoki, “Eigenvector Method for Optimized Orbit Correction”, ATP Conference 

Proceedings, 315, p. 43, 1994, BNL 61252. 

L.R. Furenlid, M.W. Renner, and E. Fujita, “XAS Studies of Ni(I), Ni(II), and Ni(II1) Complexes”, Physica, 

B208/209,739-742, (1994), BNL 61084. 

N.F. Gmur, D. Chapman, W. Thomlinson, A.C. Thompson, W.M. Lavender, K. Scalia, N. Malloy, J. 

Mangano, and J. Jacob, “NSLS Transvenous Coronary Angiography Beamline Upgrade and Advanced 

Technology Initiatives”, Rev. Sci. Instrum., 66/2, 1357-1360, (1995), BNL 60857. 

C.J. Hirschmugl, and G.P. Williams, “Chemical Shifts and Coupling Interactions for the Bonding Vibrational 

Modes for CO/Cu(l11) and (100) Surfaces”, Pbys. Rev., B52, 14177, (1995), BNL 62539. 

C.J. Hirschmugl, and G.P. Williams, “Signal to Noise Improvements with a New Far-IR Rapidscan 

Michelson Interferometer”, Rev. Sci. Instrum., 66, 1487, (1995), BNL 60892. 

C.J. Hirschmugl, and G.E Williams, “Infrared Synchrotron Radiation Introduction and History”, Synch. 

Rad. News, S/5, 8, (1995), BNL 62171. 

D-2 
E.D. Johnson, ”Scientific Opportunities for FEL Amplifier based VUV and X-Ray Research”, Nucl. Imtrums. 

andMeths. in Phys. Res., A358, 544-547, (1995), BNL 61411. 

E.D. Johnson, D.E Siddons, J.Z. Larese, and J.B. Hastings, “Observation of Nuclear Forwardscattering 

from 83Kr in Bulk and Monolayer Films”, Phys. Rev., B15/12,7909-7911, (1995), BNL 61404. 

C.C. Kao, K. Hamalainen, M. Krisch, D.E Siddons, T. Oversluizen, and J.B. Hastings, “Optical Design 

and Performance of the Inelastic Scattering Beamline at the National Synchrotron Light Source”, Rev. Sci. 

Instrum., 66, 1699, (1995), BNL 61410. 

W.D. Kimura, G.H. Kim, R.D. Romea, L.C. Steinhauer, I. Pogorelsky, K.E Kusche, R.C. Fernow, X. 

Wang, and Y. Liu, “Laser Acceleration of Relativistic Electrons Using the Inverse Cerenkov Effect”, Phys. 

Rev. Letts., 74/4, 546-549, (1995), BNL 60522. 

S. Krinsky, “Optimization of Accelerator System Performance at the NSLS”, Rev. Sci. Instrum., 66,2017, 

(1995). BNL 60766. 

B. LaFontaine, A.A. MacDowell, Z. Tan, D.L. White, G.N. Taylor, O.R. Wood, J.E. Bjorkhholm, D.M. 

Tennant, and S. Hulbert, “Submicron, Soft X-Ray Fluorescence Imaging, Appl. Phys. Letts., 66,282-284, 

(1995), BNL 61698. 

C.L.A. Lamont, B.N.J. Persson, and G.E Williams, “Dynamics of Atomic Adsorbates: Hydrogen on 

Cu(l1 l)”, Chem. Phys. Letts., 243,249, (1995), BNL 62538. 

Y. Liu, Y. Gagnon, J. Gauthier, L. Furenlid, E L’Heureux, M. Auger, 0. Nureki, S. Yokoyama, and J. 

Lapointe, “The Zinc Binding Site of Escherichia coli Glutamyl-tRNA Synthetase is Located in the AcceptorBinding Domain”, J Of Biol. Chem., 270, 15162-15169, (1995). BNL 61412. 

J. Milne, E.D. Johnson, and G.C. Smith, “Use of Primary Electron Counting for Detection of Ultra-Sofi 

X-rays with a Low-Pressure Multi-Step Gaseous Detector”, Rev. Sci. Instrum., 66/2, 2330-2332, (1 999, 

BNL 61413. 

I. Pogorelsky, J. Fischer, K.E Kusche, M. Babzien, N.A. Kurnit, I.J. Bigio, R.F. Harrison, andT. Shimada, 

“Subnanosecond Multi-Gigawatt CO2 Laser”, IEEE Tournal of Quantum Electronics, 3 1, p. 556, (1995), 

BNL 60399. 

I. Pogorelsky, W.D. Kimura, C.H. Fisher, F. Kannari, and N.A. Kurnit, ‘Xpproach to Compact Terawatt 

COz Laser System for Particle Acceleration”, 6th Workshop on Advanced Accelerator Concepts, Lake 

Geneva, Wisconsin, 335, p. 405, (1995), BNL 60826. 

I. Pogorelsky, W.D. Kimura, and Y Liu, “Waveguiding by Axicon-Focused Laser Beams”, 6th Workshop 

on Advanced Accelerator Concepts, Lake Geneva, Wisconsin, AIP, 335, p. 419, (1995), BNL 60774. 

X.Z. Qui, X.J. Wang, K. Batchelor, and I. Ben-Zvi, “Conceptual Design of a Charged Particle Beam 

Energy Spectrometer Utilizing Transition Radiation Grating, Nucl. Imt. And Meth. In Phys. Res., A363, 

520-525, (1995), BNL 61849. 

J.A. Reffner, EA. Martoglio, and G.P. Williams, “FT-IR Microscopical Analysis with Synchrotron Radiation: 

The Microscope Optics and System Performance”, Rev. Sci. I~trum., 66, 1298, (1995), BNL 61083. 

D-3 
C. Schulze, and D.Chapman, “PEPO: A Program for the Calculation of the Reflectivity of Cylindrically 

Bent Laue Crystal Monochromators”, Rev. Sci. Instrum., 66/2,2220-2223, (1995), BNL 61689. 

D.P. Siddons, J.B. Hasting, U. Bergmann, F. Sette, and M. Krisch, “Mossbauer Spectroscopy using 

Synchrotron Radiation: Overcoming Detector Limitations”, Nucl. Instrum. andMetb. in Pbys. Res., B103, 

371-375, (1995), BNL 61407. 

B. Sinkovic, E. Shekel, and S.L. Hulbert, “Spin-Resolved Fe L3M45M45 Auger Transition on and OffResonance-The Effect of Exchange-Correlation”, Pbys. Rev., B52, 15703, (1995), BNL 62536. 

B. Sinkovic, E. Shekel, and S.L. Hulbert, “Spin-Resolved Iron Surface Density of States”, Pbys. Rev., B52, 

R8696, (1995), BNL 61405. 

L. Solomon, W. Graves, and I. Lehrman, “Magnetic Field Measurements of the Harmonic Generation FEL 

Superconducting Undulator at BNL-NSLS”, Nucl. Instrum. And Metbs., 358, 41 1-413, (1995), BNL 

61409. 

EM. Stefan, S. Krinsky, G. Rakowsky, and L. Solomon, “Operation of a Small-Gap Undulator on the 

NSLS X-ray Ring”, Art and Science of Magnet Design, A Festschrift in Honor of Klaus Halbach, p. 161, 

(1995), BNL 61053. 

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”, NucZ. Instrum. AndMetbs. In Pbys. Res., A356 

159-166, (1995), BNL 60356. 

X.J. Wang, I. Pogorelsky, K. Kusche, Y. Liu, and R. Fernow, “Inverse Cerenkov Laser Acceleration Experiment 

at the ATF”, Proceedings of the 17th International Linac Conference, pp. 810-812, (1994), BNL 60737. 

X.J. Wang, T. Srinivasan-Rao, K. Batchelor, I. Ben-Zvi, and J. Fischer, “Photoelectrons Beam Measurement 

from a Magnesium Cathode in a RF Electron Gun”, Proceedinm of 17th International Linac Conference, 

pp. 407-409, (1994), BNL 60738. 

G.P. Williams, J. Reffner, and E Martoglio, “FT-IR Microscopical Analysis with Synchrotron Radiation: 

The Microscope and System Performance”, Rev. Sci. Instrum., 66, 1298, (1995), BNL 61083. 

X.Y. Wu, EA. Dilmanian, 2. Chen, B. Ren, D.N. Slatkin, D. Chapman, M. Shleifer, EA. Staicu, and W. 

Thomlinson, “Multiple Energy Computed Tomography (MECT) at the NSLS: Status Report”, Rev. Sci. 

Instrum., 66/2, 1346-1347, (1995), BNL 

L.H. Yu, “Exponential Decay of Wavelength in a Dissipative System”, Pbys. Letts., A202, 167, (1995), 

BNL 60927. 

L.H. Yu, C.M. Hung, D. Li, and S. Krinsky, “Scaling Function for Free-Electron-Laser Gain Including 

Alternating Gradient Focusing, Pbys. Rev. Lett., E51, 813, (1999, BNL 49122. 

J. Zegenhagen, T. Siegrist, E. Fontes, L.E. Berman, and J.R. Patel, “Epitaxy of Ultrathin Films of 

Yba2Cu307-6 on SrTiO3(001) Investigate With X-ray Standing Waves”, Solid State Commun., 93, 763, 

(1995), BNL 60863. 

D-4 

. . ..,_I . .-: , . . .- .’ 
N. Gmur, “Research by Industry at the National Synchroton Light Source”, BNL 61553, March 1995. 

Y. Liu, and I.V. Pogorelsky, “Gas Breakdown Limits for Inverse Cherenkov Laser Accelerators”, BNL 

61876, June 1995. 

I.V. Pogorelsky, ‘XTF C02 Laser System Upgrade to Terawatt Peak Power”, BNL 61849,1995. 

I.V. Pogorelsky, “Electron Acceleration in Plasma Channels with Terawatt C02 Laser”, BNL 61482, 

February 1995. 

I.V. Pogorelsky, “High-Intensity Laser Synchrotron X-ray Source”, BNL 62447, 1995. 

X.Z. Qiu, X.J. Wang, and I. Ben-Zvi, “Proposal for Using Optical Transition Radiation for Electron 

Beam Alignment and Emittance Measurement for the Free Electron Laser Experiments at ATF”, BNL 

60999, November 1994. 

E.Z. Rothman, “1994 Activity Report, National Synchrotron Light Source” BNL 52455, March 1995. 

J. Safranek, and S. Krinsky, ‘Coupling Correction Using Closed Orbit Measurements”, BNL 61246, 

December 1994. 

J. Safranek, and M. Lee, “Calibration of the X-ray Ring Quadrupoles, BPMs and Orbit Correctors using 

the Measured Orbit Response Matrix”, BNL 61250, December 1994. 

X.J. Wang, K. Batchelor, I. Ben-Zvi, and M. Woodle, “Proposal for Testing a New Generation 

Photocathode RF Gun at Accelerator Test Facility”, BNL 60979, October 1994. 

D-5