NAT'L INST. OF STAND & TECH

NBSIR 87-3587

Center for

Basic

Standards

QC

100

.U56

//87-35S7

1987

October 1987

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

NBSIR 87-3587

jCdmical

Activities 1987

Center for

Basic

Standards

Peter L. M. Heydemann

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Measurement Laboratory Center for Basic Standards

Gaithersburg, MD 20899

October 1987

U.S. DEPARTMENT OF COMMERCE, Clarence J. Brown, Acting Secretary National Bureau of Standards, Ernest Ambler, Director

ABSTRACT

This report summarizes the research and technical activities of

the Center for Basic Standards during the Fiscal Year 1987.

These activities include work in the areas of electricity,

temperature and pressure, mass and length, time and frequency,

quantum metrology, and quantum physics.

Keywords: Astrophysics; atomic and molecular physics; chemical physics;

electrical standards; fundamental constants; gravity measurements; laser

physics; length standards; mass standards; pressure and vacuum standards;

temperature standards; time and frequency standards; X-ray and gamma- ray

wavelength standards.
INTRODUCTION

This report is a summary of the technical activities of the NBS

Center for Basic Standards (CBS) for the period October 1, 1986 to

September 30, 1987. The Center is one of the four centers and

operating units in the National Measurement Laboratory.

The summary of activities is organized in six sections, one for

the technical activities of the Quantum Metrology Group, and one each

for the five divisions of the Center. Each division or group tells its

own story in its own way. In general, there is an overview followed by

a series of short reports on current projects. Then the publications,

invited, talks, committee participation and professional interactions

during the year are listed.

More information about particular work may be desired. To obtain

this, the reader should address the individual scientists or their

division, c/o Center for Basic Standards, B160 Physics Building,

National Bureau of Standards, Gaithersburg, Maryland 20899.

IV
TABLE OF CONTENTS

Abstract iii

Introduction iv

Electricity Division (521) 1

Temperature and Pressure Division (522) 45

Length and Mass Division (523) 93

Time and Frequency Division (524) 105

Quantum Physics Division (525) 155

Quantum Metrology Group (520.06, 526) 261

V

TECHNICAL ACTIVITIES: ELECTRICITY DIVISION

FISCAL YEAR 1987

INTRODUCTION AND OVERVIEW

The Electricity Division (ED) concerns itself with fundamental

electrical quantities such as current, voltage, and impedance at DC and low

frequencies (to roughly 100 kHz) over many orders of magnitude and at the

highest possible levels of accuracy. Its primary mission is to provide the

central basis for a reliable and consistent system of electrical

measurement throughout the U.S., including the Nation's scientific and

defense communities as well as industry and commerce; and to ensure that

the U.S. system is consistent with those of other countries and the

internationally accepted system (i.e,, the International System of Units or

SI).

The justification for all of the ED's work comes directly from the

Bureau's Organic Act, as amended, and is in its primary mission areas, that

is, the areas of responsibility for which the Bureau was originally founded

in 1901. The major technical areas which benefit from the ED's work

include fundamental physical theory; high technology-based R&D; electrical

power revenue metering, transmission, and distribution; industrial process

control; quality control in the manufacture of electronic components and

products; testing and maintenance of electronic systems, which includes

civilian contract suppliers of defense and aerospace programs; and national

defense requirements directly under the Department of Defense. End user

groups include scientists in universities; electric power utilities, both

public and private; electric equipment manufacturers; process engineers who

design, build and use industrial process control systems; manufacturers of

electronic components and consumer products; high technology civilian

companies and government agencies involved with communications, computers,

aerospace, transportation, health, and defense; and finally the armed

seirvices

.

It is probably not an overstatement to say that the Nation's electric

power system, the cost-effective manufacture of reliable consiamer goods,

the economic production of industrial materials, a viable national defense,

and R6cD at the cutting edge of science and technology, would not be

possible without adequate electrical measurements; and that the basis for

ail such measurements within the U.S. is the fundamental electrical units

the ED maintains and disseminates through its various services; the

measurement methods and instrumentation it develops; and the tests and

calibrations of standards and instruments it performs. For example, each

year well over one thousand calibrations are carried out on primary

electrical standards of voltage, resistance, capacitance, inductance, and

AC-DG difference that belong to some of the Nation's most important

corporations, utilities, universities and government organizations,

including Hewlett-Packard, General Motors, IBM, General Electric, Pacific

Gas and Electric, Rockwell, McDonnell-Douglas , Boeing, TRW, the TVA, the

FAA, and the DoD. These standards are used in turn to calibrate and

1
otherwise support a wide range of work-horse electrical measuring

instruments and systems numbering literally in the hundreds of thousands,

such as digital voltmeters (DVMs) , programmable voltage and current

sources, analog- to-digital and digital-to analog converters,

resistance/inductance/capacitance (RLC) meters, impedance bridges,

electrometers, oscilloscopes, data recorders, component and printed circuit

board testers, automatic test equipment (ATE) for weapons systems, etc.

Without reliable measurement results from such equipment, a technologically

sophisticated society like that of the U.S. could not even exist, let alone

advance

.

To fulfill its main responsibility of providing the central basis for

the U.S. electrical measurement system, the ED carries out work in eight

distinct but related areas with the following objectives:

1. Realize the SI definitions of basic electrical measurement units

such as the ampere, volt, ohm, and farad, thereby ensuring that the U.S.

legal electrical units are consistent with the internationally accepted

system.

2. Develop and maintain U.S. Legal or National Reference Standards for

the basic electrical units and related quantities, thus providing a central

basis for the U.S. system of electrical measurement.

3. Disseminate the basic electrical measurement units to users within

the U.S. via a variety of measurement and calibration services, and develop

new means for doing so, thereby ensuring the traceability of electrical

measurements made throughout the country to National Reference Standards.

4. Develop new methodologies and the required instrumentation and

standards which will lead to advances in the state-of-the-art of electrical

measurement, thus ensuring the availability to the technical community of

adequate measurement techniques.

5. Determine fundamental physical constants closely related to the

electrical units in order to provide the scientific community the means to

test basic physical theory.

6. Initiate and participate in international comparisons of the basic

electrical units, thus ensuring that the U.S. system of electrical

measurement is consistent with those of other countries.

7. Participate in voluntary national and international standardizing

activities related to the electrical units, and the fundamental physical

constants, in order to foster international compatibility of electrical

measurements, eliminate and prevent non- tariff barriers to trade, and

contribute to internationally acceptable data compilations.

8. Provide training for personnel active in the field of electrical

measurements and standards, including the presentation of seminars and

2
workshops, and the generation of tutorial written material, thereby

elevating the overall level of competence in the field.

In practice, the Division's work falls within two major categories: (1)

electrical dissemination services; and (2) fundamental electrical

measurements. The focus of the former is the maintenance and dissemination

of the basic electrical quantities such as voltage, resistance, and

capacitance; that of the latter the realization of the SI electrical units

and the development of standards based on phenomena such as the quantum

Hall effect. An introduction and overview to electrical dissemination

services immediately follows this introduction and overview of the

Division.

The principal projects in the fundamental electrical measurements

category are Realization of the SI Ampere, Realization of the SI Farad and

Ohm, Josephson Voltage Standards, Quantized Hall Resistance, Gamma-P and

the Fine -Structure Constant, and Fundamental Constants Data Center.

(Details of the objectives, current activities, FY 87 accomplishments, and

future plans for these and two other projects in this category are given in

individual reports following those for the electrical dissemination

services projects.)

The two principal goals of the above projects are (1) to deteirmine the

best possible values in SI units for the Josephson frequency-voltage

quotient 2e/h and the quantized Hall resistance Rg = h/e^ ; and (2) to put

into place and bring to a highly efficient operational state improved and

new apparatus to maintain the U.S. Legal Volt via the Josephson effect, the

U.S. Legal Ohm via the quantum Hall effect, and the U.S. Legal Farad via

the NBS calculable capacitor. The motivation is that the Consultative

Committee on Electricity (CCE) of the International Committee of Weights

and Measures (CIPM) plans to meet in September 1988 to adopt a new value

for 2e/h consistent with the SI, and a value for Rg consistent with the SI,

to be used by all national standards laboratories, starting January 1,

1990, to define and maintain their national representations of the volt and

ohm, respectively. This will lead to about a 9 ppm increase in the U.S.

Legal Volt and about a 1.6 ppm increase in the U.S. Legal Olim. While these

changes in the U.S. legal units will be disruptive for the user community,

the long-term benefits of international uniformity of electrical

measurements and their consistency with the SI should outweigh the

considerable cost of implementing the changes.

There has been good progress in all of the fundamental electrical

measurements projects this year as the individual project reports attest.

Especially noteworthy is the development of a Josephson array voltage

standard system to maintain the U.S. Legal Volt (it is now done on a weekly

basis since Feb. 1987 with an uncertainty of less than 0.02 ppm); the

discovery of the cause of a gross systematic effect in the NMR portion of

the proton gyromagnetic ratio (gamma-p) experiment; and the completion

publication, and wide distribution of the 1986 least-squares adjustment of

the fundamental physical constants. In general, all projects are now on

3
the threshold of yielding useful results for the CCE to consider in

adopting a new value for 2e/h and a value of Rg = h/e^ ; and in establishing

the means for maintaining routinely the U.S. legal units for voltage,

resistance, and capacitance with high accuracy as well as consistency with

the SI.

4
ELECTRICAL DISSEMINATION SERVICES: SUPPORT AND OPERATION

INTRODUCTION AND OVERVIEW

The goal of the work in this category is to enable all measurements of

electrical quantities performed in the U.S. to be made in terms of the U.S.

legal electrical units at the required levels of accuracy. The legal units

are provided to the user community via calibration and MAP (measurement

assurance program) services listed in NBS Special Publication 250 and its

appendices. The timeliness and adequacy of these seirvices must be ensured

by research and development work on new measurement techniques, standards,

and apparatus, since the quality of both MAP and calibration services

ultimately depends on the basic metrology competence of the NBS. Moreover,

the pre-eminence of the U.S. in high-technology areas, such as electronics,

avionics, communications, aircraft, and space vehicles has been made

possible by its sophisticated measurement capability, reflected in

automatic ATE systems and high-quality electronic instrumentation.

Advances and progress in these areas can be limited by measurement

constraints, such as the nonavailability of electrical instruments of

adequate accuracy. This condition can only be avoided if NBS maintains a strong R&D program to ensure the availability of adequate electrical

measurement methods and standards for the instrumentation industry.

The measurement services offered by NBS in the electrical area include

the calibration of primary standards of direct or DC voltage, direct

current or DC resistance, impedance at audio frequencies, and alternating

current and voltage, as well as MAP services for DC voltage and DC

resistance. Some measurements are also done on AC ratio standards of the

highest accuracy (inductive voltage dividers). In FY 87, 28 MAP transfers

and approximately 2494 calibrations will have been performed on 1348 basic

standards, as detailed at the end of this introduction and overview, for a total income of about $865 K for the year.

The majority of NBS calibration clientele is represented by the

National Conference of Standards Laboratories (NCSL) , which is a major

source of information for planning future calibration activities, as well

as a mechanism (through its technical committees) for disseminating NBS

electrical metrology information. This past year saw heavy interaction

between the Division management and the NCSL through it Measurement

Requirement and Education and Training Committees and interactions at

regional meetings, as well as the National Workshop and Symposium.

In recognition of the problems likely to occur following the January 1,

1990 changes in the U.S. Legal Volt and Ohm, a committee has been formed to

write and disseminate guidelines to assist the technical community in

making the adjustments required to bring their instriomentation, standards,

and procedures into compliance with the changes. The committee has met

twice, approved a detailed outline for the guidelines, and is in the

process of gathering background information. In the committee's view,

action required of standards laboratories is straightforward. However, the

magnitude of the change in the volt is large by comparison with the

5
intended accuracies of much modern test equipment and some control systems

as well. The most difficult part of the committee's job is to address

situations germane to high-accuracy instrumentation and systems with

embedded software control where the units, especially the volt, are incorporated in the software in a way transparent to the user and perhaps

not recognized as such by the designer. Where possible, such situations

and appropriate remedial action will be given via examples. The goal is to

have a complete document, ready for "plugging in" the final values of the

changes, by October 1988 when those values are finally decided. A first

draft is to be completed by January 1988. The committee currently has 20

members representing various sectors of industry and government and seven

from NBS. Electricity Division members participating in the committee are

N. B. Belecki (Chairman), R. F. Dziuba, B. F. Field, and B. N. Taylor.

The military, its defense systems contractors, and the instrumentation

community are the heaviest users of electrical calibration services and it

is from them that the most stringent measurement requirements arise. We

continue to maintain close ties with the DoD via the Calibration

Coordination Group and projects funded by that Group.

Measurement services support activities fall into two broad categories;

(1) the development of improved measurement methods and standards; and (2)

the automation of the measurement systems used to carry out both

calibrations and MAPs.

Work in the first category is directed toward improvement of the

processes by which the electrical units are maintained, scaled, and

disseminated. In the DC voltage area, the emphasis is on converting to the use of Josephson arrays to maintain the U.S. Legal Volt and on improved

dissemination by developing advanced solid-state standards based on Zener

diodes. The thrust in the DC resistance area is to improve scaling from

the U.S. legal unit at 1 to 1000 and 6453.2 0 for the SI ohm and

quantized Hall resistance experiments, respectively. Both cryogenic

current-comparators and Hamon devices are being employed in this effort.

In the impedance area the focus is replacing aged bridges with new bridges

that take advantage of modern electronics. One of these, an automatic

capacitance bridge to replace the 1957-vintage Type-2 bridge, is nearing

completion. In the AC-DC difference area, which supports AC voltage and

current measurements, the thrust of the work is to enhance the accuracy

available by investigating and adding improved standards to the set used as working standards, especially in the upper end of the frequency range.

In the second or automation category, several of the hardware systems

have been completed; future activities are aimed at the construction of

complex software systems to collect and analyze calibration data. This

activity is particularly heavy in the voltage and AC-DC difference areas. The DC resistance automation activity has increased this year due to

increased staff; work is progressing on three systems to calibrate

resistance standards at the 10-k Q level, in the range 100 to 1 Mfl (somewhat less accurately), and in the range from 10® Q up.

6
Details of the objectives, current activities, FY 87 accomplishments,

and future plans for DC Voltage, DC Resistance, Impedance, and AC Voltage

and Current are given in the following four project reports.

Estimated Calibration Workload -- FY 87

SP-250 51100's Resistance Measurements

521 Standard Resistors and Shunts

4 MAP Transfers

54100's Precision Apparatus

26 Inductive Voltage Dividers (44 tests)

52100's Impedance Measurements

188 Standard Inductors (277 tests)

163 Standard Capacitors (274 tests)

53100's DC Voltage Measurements

88 Standard Cell Enclosures (361 cells)

25 MAP Transfers

23 Unsaturated Cells

39 Zener-diode Based Standards (68 tests)

53300's Electrical Instrximents (AC-DC)

51 Standard Thermal Converter Instruments (1144 points)

Estimated FY 87 Billing $865,000

7
DC VOLTAGE

[B. F. Field, M. R. McCaleb, J. E. Sims, Liu Ruimin (GS)]

OBJECTIVES: To disseminate the U.S. Legal Volt to industry and government

laboratories via MAPs (measurement assurance programs) and the calibration

of customer standards; to support the DC voltage needs of standards

laboratories (and NBS) , especially at 10 V, through research and

development of calibration apparatus and improved voltage standards.

Continuous research and development is required to support the increasingly

accurate instrumentation available to industrial users.

CURRENT ACTIVITIES: (1) Calibration of customer standard cells sent to NBS,

(2) operation of a DC voltage MAP at 1.018 V, (3) calibration of customer

solid-state (Zener) standards at voltages other than 1.018 V, and (4) R6cD on improved Zener standards. Items (l)-(3) require accurate (0.01 ppm)

comparisons of customer or transport standards to NBS reference cells and

the maintenance of a stable/predictable volt. Automated measurement

systems are being used for these comparisons while the AC Josephson effect

provides a reproducible volt. Item (4) consists of developing improved,

transportable, solid-state standards with 0.05 ppm short-term stability at

10 V and 1.018 V. Improved solid-state voltage standards are needed to

support increasingly accurate DC calibrators (4 ppm basic DC accuracy) that

are now commercially available.

ACCOMPLISHMENTS: All NBS DC volt calibrations are now handled by one fulltime person using three automated measuring systems; one for customer

standard cells, one for MAPs, and one for solid-state references. We have

simplified the software for the data analysis and added new quality control

procedures. We replaced an unreliable Interdata minicomputer with a more

modern VAX minicomputer and converted all the software needed to produce

calibration reports to run on the VAX.

The month- to-month fluctuations of the volt have been reduced, and the

reliability and ease of maintaining the volt will be improved because we

are using a Josephson array and have completed two new standard cell

enclosures. In February 1987 we started to maintain the U.S. Legal Volt

using a series -connected array of Josephson junctions producing 1 V

directly instead of a two-junction 100/1-ratio potentiometer system. Since

the new system is easier to use, these measurements are now done weekly.

The new standard cell enclosures are of the Cutkosky/Field design but with

modernized control circuits. After cells are installed these will

supplement our primary and working cell groups, replacing an inadequate

commercial enclosure now in use.

Documentation of the standard cell calibration service is under

revision and will be submitted for publication as an NBS Special

Publication 250.

This year we completed a new automated measuring system for solid-state

references to support an increasing solid-state calibration workload and to

8
free the original system for Zener research. This additional system is a modified version of the original model developed at NBS . We also

constructed, tested, and delivered four systems for the DoD. While at NBS

all six systems (4 DoD, 2 NBS) were thoroughly compared and their results

agreed to 0.03 ppm, well within their individual estimated uncertainties of

0.075 ppm (la)

.

In February 1987 we hired M. R. McCaleb to replace a departed staff

member. He is vigorously pursuing a research program for the development of

a transportable Zener standard. As part of this program the original

automated Zener measurement system was refurbished by replacing the

computer, revising the software, and constructing new mechanical and

electrical fixtures to permit the testing of a large number of Zener diodes

and 10/1.018 volt voltage dividers.

We have developed a set of guidelines for the design of solid-state DC

voltage standards that detail what we believe is required in a modern

voltage standard to supplant present standards based on standard cells.

These guidelines were developed at the request of the DoD and submitted to

them for comments. The guidelines may be used either to guide the design

of future commercial products or the purchase of a standard and they are in

the process of being published as an NBS Technical Note.

Based on the above guidelines we are developing a transportable solidstate voltage standard that should be capable of transferring the volt

between two laboratories with an uncertainty of 0.1 ppm (la) or less. The

basic design has been completed and we are currently testing diodes,

voltage dividers, temperature control circuits, and other components for

inclusion in the prototype. We are planning to use temperature-compensated

Zener diodes mounted in TO-5 metal cans; fifty-six high-quality diodes have

been obtained and specially mounted. Our previous tests of glass-packaged

diodes have shown that their output voltages permanently shift anywhere

from 2 to 30 ppm when they are subjected to temporary gross temperature

changes (>10 “C)

.

A seventh seminar on MAP's for electrical quantities was held in San

Jose, CA in October 1986. The 42 attendees participated in five days of

lectures and hands-on workshops using computer-aided instruction covering

statistics, voltage metrology, quality-control techniques, and NBS MAP

procedures

.

FUTURE PLANS: We will continue periodic review of the measurement systems

and procedures for dissemination of the NBS volt. The VAX software will be

revised as staff time permits to reduce further the time required for

production of calibration reports.

For the development of transportable solid-state standards, two

research paths will be pursued simultaneously, with the first aimed at

providing a short-term solution. A design has been completed for a prototype standard using only existing available parts (references.

9
dividers, etc.)- If initial tests indicate that building a standard based

on this design would be useful, several standards will be built and

evaluated. Some of these may be used for a DC MAP at 10 V and 1.018 V and

to replace deteriorating NBS standard cell transport enclosures.

The second part of the program, which will initially be of lower

priority than the first, will concentrate on a longer-term solution. The

three main parts of this solution will be as follows: (A) Current research

indicates that resistive dividers contribute significantly to the

instability of commercial standards. We will investigate scaling

procedures, especially time-division dividers, and develop a substantial

competency in this method. (B) We will develop algorithms to deal with

"out-of- tolerance" references within multiple-reference standards to

optimize the predictability of the "average" voltage of the standard. (C)

We will continue to look into Zener diode packaging problems and eventually

investigate problems specific to the solid-state physics of Zener diodes.

DC RESISTANCE

[R. F. Dziuba, P. A. Boynton, T. P. Moore, J. D. Neal, H. S. Winters]

OBJECTIVES: To maintain and to disseminate the unit of resistance for the

U.S. Our goal is to provide industrial, educational, and governmental

laboratories with state-of-the-art, accurate, and reliable resistance

measurement services that are delivered in a timely, professional manner.

To achieve this goal it is necessary to develop new and improved resistance

standards and measurement techniques.

CURRENT ACTIVITIES: We calibrate resistors of decade values ranging from

10'^ to 10^^ 0. They are compared with NBS primary standards of the same nominal value. Resistance transfer standards, commonly known as Hamon

boxes, provide accurate ratios of 10:1 and 100:1 for intercomparing our primary standards between different resistance levels. Special Hamon boxes

are used to compare the NBS ohm to the 6453.20 fJ quantum Hall step.

Improvements in our resistance scaling process will result in lower NBS

uncertainties for customer and NBS calibrations. Completion of a cryogenic

current comparator bridge will help to verify our scaling process.

The NBS ohm as embodied in our 1-fi reference bank is about (1.60 ±

0.30) ppm less than the SI ohm as realized by calculable capacitor

experiments. The NBS ohm drifts at a rate of about -(0.06 ± 0.02) ppm/year

compared to the 6453.20 Q- level of the quantized Hall resistance.

Improvements in resistance scaling techniques will help pinpoint the value

and drift of the NBS ohm to a few hundredths and a few thousandths of a ppm, respectively. This will affect the international adjustment of

representations of the SI ohm planned for 1990.

Automation of the ring resistance bridge method will reduce the turnaround-time for calibrating customer Rosa-type resistors from 100 Q to 1 MTJ. Automation of the 10 kn and capacitance-discharge high megohm customer

10
calibration systems are also underway.

ACCOMPLISHMENTS: The figure compares the present and new NBS uncertainties

for the various resistance levels. These new uncertainties will become

effective before the end of CY 87 and are based on extensive measurements

and uncertainty reevaluations carried out during the past year in

connection with the documentation of our calibration services.

Our 1 n reference bank of resistors has been thoroughly analyzed; the

results indicate seasonal variations of some resistors of a few hundredths

ppm. We may be seeing the end of the useful life of these original Thomas

1 n resistors.

We determined the loading effect from 10 mW to 1 W for two Thomas 1 0

resistors that are critical components in the new NBS determination of the

proton gyromagnetic ratio.

We completed two special in-house transfers from 1 f2 to the 6453.20 Q

quantum Hall step as part of our collaborative effort with the quantum Hall

effect group to monitor the stability of the NBS ohm.

CALIBRATION OF STANDARD RESISTORS

10 ’

10

's

CL

Cl

>-2 1 <I—

CCUlo

z

=) 10

*'

10*’

We repackaged and thoroughly characterized eight 10 kfl standards to be

used for international comparisons with other national laboratories in

order to check scaling accuracy, and for MAP calibrations for U.S. clients.

We constructed a 1 kfJ/step Hamon resistance transfer standard to

replace one that had a significant load coefficient. This improves our resistance scaling from 100 0 to 10 Idl and will reduce the uncertainty

associated with scaling errors for customer 10 kiJ standard resistor

calibrations

.

o o

• = PRESENT

0 = NEW

10 ’’ 10 -’

1 10 ’ 10 ‘ 10 ‘

RESISTANCE (!1)

11
We completed construction of the automated ring resistance bridge for

comparing nominally- equal resistors from 100 fJ to 1 Mn. We are comparing

results obtained from this system to those obtained from the present DRRS

(direct reading ratio set) bridge method. Differences between the results

of the two methods have always been well within the NBS uncertainty.

FUTURE PLANS: Publish an NBS Technical Note on the NBS calibration service

for DC standard resistors.

Complete the automation of the modified Kelvin bridge for comparing NBS

and customer 10 kfl standard resistors to a precision of 0.01 ppm. These

measurements at the 10 kfl- level constitute our second heaviest workload

(next to the Thomas 1 0 measurements) with over 1500 measurements/year.

Completing this system will complete the automation of customer

calibrations from 1 n to 1 Mfl.

Complete a prototype of the automated capacitance-discharge measurement

system for high value resistors. This system will meet the demand for

resistor calibrations above 1 TO.

Participate with other national laboratories in an international

comparison of 1 Cl standards at BIPM in preparation for the adjustment of

the ohm planned for 1990. Spearhead an international comparison at the

10 Id^-level using NBS resistors.

Continue to collaborate on monitoring the stability of the NBS ohm

using the quantum Hall effect. Collaborate with those involved in the

absolute ohm experiment in order to determine a value for the NBS ohm in SI

units

.

Investigate the possibility of establishing a project to develop a new

class of transportable DC resistance standards. The goal would be to

develop standards that are less susceptible to environmental factors such

as temperature, humidity, vibration, and shock as are existing standards.

IMPEDANCE

[Y. M. Chang, G. R. Jones, Jr., C. R. Levy, S. Tillett, G. Zdral (PSC)]

OBJECTIVES: To maintain working standards for impedance measurements, and

related calibration facilities, in order to provide calibrations of client

impedance standards - capacitors, inductors, inductive voltage dividers

(IVDs) - over the broad range of values and frequencies and at the levels

of accuracy required by the U.S. user community; to improve NBS

capabilities in order to meet the current and future needs for impedance

measurements of this community.

12
CURRENT ACTIVITIES: These include construction and testing nine

capacitance bridges to automate and upgrade NBS calibration capability as well as that of the primary standards laboratories of the DoD and DoE;

replacing obsolete equipment with modern electronic instrumentation to

reduce calibration time and maintenance costs; documenting the impedance

calibration services; re-establishing the capacitance MAP service at the 1 nF level to permit users of 1 nF-standards to achieve an accuracy of 1-2

ppm; and completing two bridges to calibrate inductors at frequencies up to

100 kHz. A variation of the classical Maxwell-Wien design, they employ

IVDs and dynamic Wagner ground networks which also supply the bridge power.

ACCOMPLISHMENTS: The first four capacitance bridges have been completed

except for the mounting of reference capacitors and tuning of the current

pumps used to prevent loading of the primary transformers. A contract has

been recently let to New Systems Technology Corp. to complete the

construction of the last five of the nine bridges. The remaining work on

the first four bridges - adjusting the current pumps used to prevent

transformer loading, installing the fused-silica reference capacitors, and

calibrating the bridges - is currently underway.

To upgrade the overall capability of the impedance laboratory, tests

are being run to replace the old generator and detector used with the

Maxwell-Wien inductance bridge with a new synthesizer, amplifier, and a phase- locked detector. A new oscilloscope and a counter for general use have been ordered, tested, and accepted. A new automated commercial

capacitance bridge was also ordered. While it was intended for testing as

a possible MAP standard, it has been used for trouble-shooting and

component testing. Another will be ordered by the end of the FY. Testing

was completed on the automated thermometer bridge bought last FY and the

bridge is now in regular service. New benches have been received and

installed along with new power circuits.

Documentation covering the calibration of standard capacitors and

inductive voltage dividers is complete except for the error analysis, most

especially in the case of inductive voltage divider calibrations. The

capacitance documentation is being reviewed by Y. M. Chang, a new staff

member. All documents are being polished in preparation for publication,

provided the uncertainty analyses can be handled in a satisfactory manner.

A commercial capacitance bridge (Andeen-Hagerling Model 2500) was demonstrated at NBS last autumn and appeared to have transport

uncertainties smaller than 1 ppm. The largest discrepancy from NBS values

seen in the measurement of various capacitors in the lab was 0.8 ppm, the

A-H measured values being based on a 2-year old calibration of another

bridge through the Air Force primary standards laboratory. An A-H 2500 was bought and checked by using it to measure check standards immediately after

their calibration with the NBS Type-2 Bridge. A discrepancy at 100 pF in

the A-H 2500 and changes in results when co-axial chokes are used are being

investigated. The bridge's response to temperature and humidity changes is

being measured.

13
A meeting was held with representatives of ESI and LCIE (the French

national standards laboratory in the electrical area) about the new ceramic

capacitors to be made by ESI France and the measurement capabilities

required to support their incorporation into automated capacitance test

equipment systems to be made in the U.S. We await a prototype of these

improved capacitors since they could be the basis for an improved transport

standard. However, an earlier ceramic-dielectric capacitor from ESI France was evaluated using the A-H 2500 and found to have a high humidity

dependence

.

Calibration measurements were made on the ground network for one of the

new inductance bridges to determine the digital- to-analog converter

settings required for the network to produce the appropriate voltage ratio

for each of the values of inductance needed to be calibrated. Software to

do the tests was written. Several wiring problems with the ground circuit

have been identified and are being corrected. The current effort is

focused on finalizing the ground circuit.

FUTURE PLANS: Complete installation of capacitors, calibrate, and test

four capacitance bridges. Complete construction, less reference capacitors

and ovens, of five other automated capacitance bridges.

Replace the line conditioner used for powering various capacitance and

inductance bridges in the impedance lab. Install a phase- locked amplifier

system as a detector for the Type-2 capacitance bridge, and improve the

bath used to contain the fused-silica reference capacitors. Prepare for

the incorporation of the new automated capacitance and inductance bridges

into the calibration service.

Publish capacitance, inductance, and inductive voltage divider

calibration documentation as NBS Internal Reports. Document the new

inductance bridge and automated capacitance bridge.

Finish testing the A-H 2500 as a transport standard by shipping it to

several standards labs. If these tests indicate its suitability as a transport standard, reinstate the capacitance MAP service. Test prototype

ceramic-dielectric capacitors as received.

Complete the ground circuit for the new inductance bridge. Complete

assembly of and begin testing the prototype bridge.

AC VOLTAGE AND CURRENT

[J. R. Kinard, C. B. Childers, J. R. Hastings, T. E. Lipe

,

Ti-Xiong Cai (GS), T. G. Nordin (GS)]

OBJECTIVES: To establish and maintain NBS primary and reference standards

for AC-DC difference; to maintain working standards of AC-DC difference and

related comparator systems in order to provide calibrations of AC-DC

14
difference for client thermal voltage and current converters (TVCs and

TCCs) ; and to support the needs of standards laboratories using state-ofthe-art AC digital meters and calibrators by conducting research and

development into improved methods and apparatus.

CURRENT ACTIVITIES: These include improving the NBS primary, reference, and

working standards of AC-DC difference and their associated measurement

systems, the study and fabrication of TVCs for use in the megahertz region

to provide reduced calibration uncertainty, construction and testing of an automated TCC comparator system, preparation of user orientated

documentation, and arrangement of an international TVC intercomparison.

ACCOMPLISHMENTS: Significant improvements have been made in the AC-DC

difference calibration service this past year. As a result of a continuing

study of the NBS primary, reference, and working standards of AC-DC

difference, the uncertainties for the calibration of TVCs and TCCs have

been reduced. The uncertainties have been lowered by as much as 50 %,

depending on the voltage, current, and frequency involved. Almost all

uncertainties for voltages below 100 V up to 1 MHz have been reduced. The

complete matrix of the new uncertainties and calibration ranges is given in

the table.

Due to the development of new automated comparator systems and an expanded inventory of working thermoelements, the need for scheduling

calibrations on a queue, which was as long as nine months, has been

eliminated. Calibration requests are now essentially accepted on demand.

Two projects are well underway which are aimed at not only the

production of new knowledge regarding TVCs and TCCs , but also the

publication of tutorial notes directed specifically to the user community.

The first project concerns the recharacterization of TVCs after

thermoelement replacement and will provide a method and algorithm for

laboratories to determine new AC-DC differences without the complete

recalibration of a TVC set. The second study concerns the interaction of

current shunts and thermoelements. A guest scientist, Mr. T. Nordin,

supported by Holt Instruments Laboratories, Inc., is conducting this latter

effort. He has also assembled the first version of an automated comparator

system for TCCs.

Considerable progress has been made in the characterization of TVCs in

the megahertz region. A guest scientist, Mr. Ti-Xiong Cai, from the

Shanghai Institute of Testing Technology, P.R.C., is contributing to both

the theoretical and experimental work on this project. A semi -automated

comparator system has been built, and measurements are being taken in the

range 100 kHz- 100 MHz on newly constructed and existing TVCs. Close

coordination and liaison is maintained with Mr. Gregorio Rebuldela at the

NBS Boulder Laboratory for this work.

15
A document has been prepared describing the NBS standards and methods

used to support the AC-DC difference calibration service. Publication is

expected later this year, probably as a part of the Special Publication 250

series

.

An initial step has been made in a program to provide travelling

thermal -converter standards to support in-house checking of a laboratory's

TVC and TCC calibration capability. A multirange TVC has been transported

to the Navy Primary Standards Laboratory East in Washington, DC, and the

results of the exchange are being studied. The instrument will be sent to

additional labs if it proves to be suitable.

Arrangements have been made for an international intercomparison of

coaxial TVCs in the 1 MHz region between NBS and the National Institute of

Metrology and Shaoxing Industry Research Institute, China. The converters

have been characterized but plans to have the instruments hand-carried to

China became impractical. The transfer will go ahead as soon as appropriate arrangements can be made

.

FUTURE PLANS: Continue work on user-oriented tutorial notes regarding

recharacterization of TVCs after thermoelement replacement and the

combination of AC-DC differences for passive shunts and thermoelements.

Proceed with theoretical and experimental studies of TVC structures in the

1 MHz region. Prepare a tutorial short course on AC-DC measurements for

presentation at the Measurement Science Conference in January, 1988. Begin

the study of new multij unction- thermal -converter working standards and

amplifier-aided designs. Continue the program of visits and consultations

with major users including DoD laboratories. Transport travelling

standards to additional laboratories for evaluation. Ship coaxial TVCs to

Mr. Huang Di-Xiang at Shaoxing Industry Research Institute and to Mrs. Zhin

Zhin at the National Institute for Testing Technology, China. Maintain

accurate and timely AC-DC difference calibration service.

16
AC-DC DIFFERENCE CALIBRATION SERVICE

Frequency: 2-5

Hz

5-20

Hz

20 - 20k

Hz

20-50

kHz

50-100

kHz

0 . 1

- 0 .

5

MHz

0.5-1

MHz

Voltage Limits (V) 50 100 1000* 1000 1000* 100 100

Current Limits (A) 0.05 0.05 18[al 16

UNCERTAINTY (parts per million')!-^

Multirange TVCs > 100 V 50 70 100

^ 100 V 200 100 30* 50* 70* 100* 200*

Coax Single Range

TVCs > 100 V 20 30 50

5 V ^ X 5: 100 V 200 100 I 5

C C ] * 25* 40* 100* 200*

< 5 V 200 100 20 30 50 100* 200*

Special^ ^ 5 V ^ X ^ 100 V 10

TCCs > 5 A 100 150*

50 mA < X - 5 A 50 70*

- 50 mA 200 100 50 70*

‘indicates reduced uncertainty or extended voltage range, compared to the

previous NBS calibration service.

A at 20 Hz, increasing to 18 A from 100 Hz to 5 kHz; 16 A above 5 kHz.

20 A shunts are calibrated at less than rated current.

^^^The lower uncertainty applies at the crossover frequencies.

Uncertainties may be increased if the AC-DC differences are large or affected by self -heating or other instability.

^ ®

^ 20 ppm from 20 Hz to 100 Hz, 15 ppm at 100 Hz and above.

Normally available by prearrangement for coaxial, single range TVCs

between 100 Hz and 20 kHz. An additional cost and a longer turnaround time

at NBS are required.

17
REALIZATION OF THE SI AMPERE

[P. T. Olsen, R. E. Elmquist, with G. R. Jones, Jr,, W. D. Phillips,

E. R. Williams]

OBJECTIVES: To realize the SI definition of the ampere to an accuracy of

one part in 10^ . A realization of the SI ampere with a given uncertainty

is equivalent to determining the Josephson frequency-voltage quotient 2e/h

in SI units to essentially the same uncertainty.

This experiment is critical because measurements of various fundamental

constants indicate serious inconsistencies between past direct realizations

of the ampere and indirect determinations based on such constants. A new

measurement will help resolve these discrepancies, provide solid contact

between SI and as-maintained electrical units, and could even lead to

artifact-independent definitions of the kilogram and mole. Moreover, it

will provide the Consultative Committee on Electricity (CCE) the means to

select a new, international value for 2e/h to be used worldwide for

maintaining representations of the volt starting January 1, 1990,

CURRENT ACTIVITIES: Traditional absolute ampere experiments have measured

the force between current-carrying coils whose dimensions were carefully

determined. Dimensional uncertainties have been the major limitation in

accuracy. The new approach avoids dimensional measurement by comparing the

mechanical and electrical work done as one coil is moved in the magnetic

field produced by another coil. The experiment is performed in two parts.

First, we measure the voltage induced in one coil while it moves in the

magnetic field of the other current-carrying (i.e., field generating) coil.

Second, we measure the force exerted on the movable coil by the fieldgenerating coil when both carry current and the movable coil traverses the same path as in the first part of the experiment. From the measured

voltage and force, along with the current in the movable coil, times, and

displacements involved, quantities equivalent to electrical and mechanical

work are calculated and their comparison results in an absolute ampere

determination. The difficult dimensional measurement is thus replaced with

a straightforward voltage-displacement/time (i.e., velocity) measurement.

ACCOMPLISHMENTS: The installation of a new movable (or suspended) coil

made a dramatic improvement in the measurement of force as well as some improvement in the voltage-velocity ratio. The original suspended coil was designed for the superconducting magnet field-generating coil which can provide a magnetic field 100 times stronger than the present oil-cooled

room- temperature field-generating coil. It became apparent from early

measurements that with a few refinements, the apparatus could yield a competitive measurement without the superconducting magnet. The new

suspended coil readily allowed an increase in the force by a factor of 10

and a decrease in the scatter of the voltage measurements by a factor of 3.

The new suspended coil alone reduced the typical standard deviation of the

mean of a single weighing measurement from 1-2 ppm to 0.1-0.

3

ppm.

Likewise, the standard deviation of the mean of a single voltage

measurement went from a typical 0.8-1. 2 ppm to 0.3-0.

5

ppm.

18
A considerable amount of electronic damage occurred when the Nonmagnetic Building was struck by lightning. The main computer and interface

unit never satisfactorily performed again. It became necessary to replace

that computer with a dedicated unit. This replacement consumed well over a half year during which ampere measurements were not possible.

The intervening time was used to improve greatly all the electronics

associated with the experiment and to construct and introduce various

pieces of automation equipment. As a result, the weighing and velocity

measurements are fully automated, and the apparatus to allow switching

between measurement modes is currently being constructed.

A new balance wheel with optically polished quartz inserts has been

installed. Bands consisting of sixty filaments of a platinum- tungsten

alloy feed off tangentially from the quartz inserts to support each side

load.

FUTURE PLANS: Statistically, the present ampere apparatus has the

potential of producing an ampere result with an uncertainty of about 0.5

ppm. But we must convince ourselves that the result is in fact the truth

and contains no significant systematic error. To do this, many

measurements will be made under a wide variety of experimental conditions;

perturbations will be deliberately introduced into the experiment and

unexpected changes studied. Within the year, we expect to be able to

report a result to the CCE with an uncertainty considerably less than 1 ppm

based on the room- temperature magnet. We will then reduce the uncertainty

by about an order of magnitude by installing the superconducting magnet

since it will enable the force to be increased from 1.00 g to 1 kg and the

voltage from 20 mV to 1 V.

REALIZATION OF THE SI FARAD AND OHM

[J. Q. Shields, L. H. Lee, with G. R. Jones, Jr., H. P. Layer (523)]

OBJECTIVES: To build, maintain, and operate equipment for calibrating the

NBS standards of capacitance and resistance in terms of their SI

definitions to an accuracy of 1 or 2 parts in 100 million, and to assure

the compatibility of these standards with those of other countries.

Accurate realizations of the farad and ohm are required to assure the

compatibility of instruments (via resistance, inductance, and capacitance

calibrations) that are manufactured within the U.S. and for the

determination of certain fundamental constants. The NBS absolute farad and

ohm measurements make use of a calculable cross capacitor and a series of

bridges for comparing capacitors and resistors. The result of the

measurement sequence is an SI or absolute calibration of the NBS reference

standards of capacitance and resistance that is accurate to a few parts in

10®

.

These measurements can also be considered as fundamental constant

determinations, with applications to questions concerning the adequacy of

19
quantum electrodynamic theory and to the determination of more exotic

constants. For example, a reliable value of the ratio of the NBS ohm to

the SI ohm is required in order to obtain a value for the fine-structure

constant from a measurement of the proton gyromagnetic ratio and 2e/h as measured via the Josephson effect; and from a measurement of the quantized

Hall resistance in a two dimensional electron gas. It is also necessary

for the new NBS absolute ampere experiment.

CURRENT ACTIVITIES; The NBS calculable capacitor was completed a number of

years ago and is the most accurate in the world; a value for the NBS farad

and ohm in terms of the SI farad and ohm accurate to a few parts in 10® was obtained in 1974. Work is presently concentrated on refurbishing, re- evaluating, and using this equipment for a new determination of the

absolute farad and ohm with slightly improved accuracy. Other activities

include maintenance of the NBS unit of capacitance (the U.S. Legal Farad)

at the 10 pF level, and participation in international comparisons of

capacitance and resistance standards.

ACCOMPLISHMENTS; The voltage source and detector systems for the NBS

calculable capacitor have been completely modernized with a new

synthesizer, power amplifier, isolation/step-up transformer, pre-amplifier,

phase-sensitive detector, and computer for data acquisition and analysis.

Various parts of the optical interferometer system have been significantly

upgraded to provide finer, more continuous adjustments for the tilt of the

bottom interferometer flat and for the laser beam direction, expansion, and

collimation.

A recently replaced laser tube showed 1 x 10'^ stability over a two

week period. Calibration of the laser is made while in operation using a transportable, iodine-stabilized He-Ne laser provided by H. Layer of the

Length and Mass Division which the system is designed to accommodate.

The overall calculable capacitor system is now such that daily

measurements of a 10 pF, transportable capacitor can be made following one

or two days start-up and preliminary measurements. The standard deviation

for approximately five hours of measurements is 0.005 ppm. This is about

three times greater than would be expected from the precision of the

detector system alone and apparently results from calculable capacitor

changes. Although the average of the two cross capacitors should be

constant, the individual capacitors can and do change significantly due to

slight changes in temperature and the force of the PTFE guide ring. In

addition, smaller changes in the average of the two cross capacitors are present and are believed to result mainly from changes in the nonuniform

response of the PZT/pho to- transducer system.

FUTURE PLANS; A comparison of the NBS units of capacitance and resistance

will be repeated while keeping the calculable capacitor in operation. This

should yield an SI ohm realization with an uncertainty of considerably less

than 0.1 ppm by mid CY 88. Subsequent work will concentrate on reducing

the uncertainties in the measurements to the one or two parts in 100

20
million level (if possible) and to improving and otherwise upgrading the

apparatus to make the measurements easier to carry out. This is especially

true for the determination of the 10 pF transportable capacitor against the

calculable capacitor since this is the approach which will be used

routinely to maintain the U.S. Legal Farad even after the implementation of

the quantized Hall resistance as the means for maintaining the U.S. Legal

Ohm starting January 1, 1990. Absolute realizations of the ohm will be

coordinated with the NBS quantized Hail resistance measurements to ensure

the closest possible tie between the two. Another comparison of

capacitance units between NBS and NML (the Australian National Standards

Laboratory) is also planned, and possibly comparisons between NBS and other

national laboratories as well.

JOSEPHSON VOLTAGE STANDARDS

[R. L. Steiner, B. F. Field, J. Toots]

OBJECTIVES: To maintain the NBS or U.S. Legal Volt to an accuracy of 1-2

parts in 10® via the AC Josephson effect in superconductors; to conduct

associated research, e.g., to refine the procedures and test the components

for an optimum volt-maintenance system, to simplify the DC voltage

calibration of high precision digital voltmeters, and to fabricate

superconducting devices for voltage standard applications. There is close

collaboration on these secondary objectives with the Electromagnetic

Technology Division's Cryoelectronics Group, NEL-Boulder, the PhysikalischTechnische Bundesanstalt (PTB) , West Germany, and the Electrotechnical

Laboratory (ETL) , Japan.

Meeting these objectives provides not only improvements in the

maintenance of the NBS volt, but also better accuracy in national voltage

measurements through coordinated industrial and military use of similar

voltage calibration systems.

CURRENT ACTIVITIES: A new DC volt-maintenance system is now used to

maintain the U.S. Legal Volt. This system is based on a Josephson array

device of over 2000 junctions, as fabricated by the Boulder group. Under

millimeter wave (70-100 GHz) irradiation, the device generates many

thousands of quantized voltage steps proportional to the frequency, where

the assigned ratio is 2e/h = 483593.42 GHz/Vj^gg . With the array generating

1.018 V, commercial Zener reference standards are calibrated. This allows

weekly calibration of the primary and secondary standard cell baths (used

to calibrate client standards) through the fully automated cell measurement

system.

The array system's performance and accuracy when employing computerized

voltage step selection and various types of microwave sources, digital

voltmeters (DVMs) , and low thermal switches is being analyzed to optimize

the system's general ease of use, cost effectiveness, and accuracy. Other

array devices of different designs and materials, which were fabricated by

Hypres , Inc. and the Electrotechnical Laboratory (ETL) of Japan, have been

21
received for testing.

Since the Josephson array is capable of generating many voltages, it

can be used as a highly accurate voltage divider. The array system has

been used to calibrate several resistive divider networks. Work on an automated procedure to calibrate the linearity and gain of several tjrpes of

DVMs with better than 6 digit precision is under way.

ACCOMPLISHMENTS: Since February 10, 1987, the Josephson array has served

as the basis of the NBS volt. Figure 1 shows the calibrated average value

of standard cell groups 17 and 1500. When fitted to the predicted linear

drift in the cells, the standard deviation of the measurements is 0.015

ppm. The measurement system has been semi -automated to record and analyze

data, and to standardize the operation and monitor run errors. A weekly

calibration of the standard cell groups is now done with only about two

staff hours total time expenditure. The previous operation took about 16

staff hours and was thus performed once a month at most.

The Boulder Josephson array has been proven to be linear to within

about (0.02 ± 0.03) ppm (Fig. 2) in tests against two independent resistive

100:1 divider networks. One, a Cascade Interchange Comparator (CIC) , is a self calibrating string built up from matching consecutive resistors (10

0:10 O, 10 0 + 10 0:20 O, etc.). The second, a Series-Parallel Comparator

(SPC) , is based on a Hamon network of ten 100 0 resistors. This instrument

was used previously as part of the regular volt-maintenance system. It

originally showed a discrepancy when compared to the array of about 0.15

ppm, until a 0.15 fxV thermal offset error was traced to a bad connection in

the SPC. A series of tests between all three instruments compared the

relative ratios of each resistive network and the array device, from 10.18

mV to 1.018 V. All three agreed within a standard deviation of 0.03 ppm,

which is the typical measurement error for the available resistive

dividers

.

A preliminary procedure for the calibration of high precision DVMs

using an array has been defined and tested. A number of steps from -1 V to

+1 V are selected by a computer. Then the voltages measured directly by

22
the DVM under test are used to calculate its gain and linearity error. An

80 point test takes about 30 minutes, with very minimal operator adjustment

(of microwave power) . This is a significant time savings over standard

procedures, further enhanced by eliminating the need to calibrate a resistive reference divider. The fact that the array voltages are calculable values makes all this possible.

The final commercial 1 ppm voltage standard developed for the

Calibration Coordination Group (CCG) of the DoD has been completely tested

and shipped to the Navy Western Standards Laboratory. A probe with a tested replacement Josephson device is undergoing final leak testing before

shipment to the Navy Eastern Standards Laboratory.

FUTURE PLANS: Maintenance of the U.S. Legal Volt using the Josephson array

system will continue. A second complete array system is being built. This

will serve as a backup for the system dedicated to volt maintenance, an independent system for periodic checks of the primary system, and a research tool for testing new components and measurement techniques, e.g.,

DVM calibration. Also, a direct comparison of two side-by-side systems

will help establish the actual measurement accuracy of array-based systems.

Collaboration with NBS Boulder, PTB, and ETL will continue. System

modifications will be worked out should the new 10 V arrays produced by

Boulder be successful. Any improvements in electronic components will be

coordinated to keep the NBS Boulder and Gaithersburg laboratories

compatible

.

Further development of the DVM calibration routine will proceed.

Programming instructions for a variety of voltmeters is necessary. Also

needing study is the compatibility between the array and some voltmeters.

Those DVMs with problem characteristics such as input terminal noise or insufficient isolation from ground may require modifications to the

measurement system.

The thin film laboratory vacuum systems will be repaired. With some modifications to the existing deposition systems, it should be possible to resume fabrication of superconducting films, including attempts at new high

transition temperature films.

QUANTIZED HALL RESISTANCE

[M. E. Cage, C. T. Van Degrift, Dingyi Yu (GS)

,

with R. F. Dziuba,

W. J. Bowers (522)]

OBJECTIVES: To develop a resistance standard based on the quantum Hall

effect (QHE) with an accuracy of 0.01 ppm to serve as the basis for the NBS

or U.S. Legal Ohm (Ojjgg); to determine the fine-structure constant a to the same and unprecedented accuracy, thereby rigorously testing quantum

electrodynamic (QED) theory.

23
The QHE has the potential of providing the most accurate QEDindependent value of a, as well as an SI or absolute resistance standard

based on fundamental constants of nature. It would thus permit a definitive test of QED as well as allow NBS to maintain the U.S. unit of

resistance continually to very high accuracy in SI units. Moreover,

through the Consultative Committee on Electricity (CCE) , the QHE will

become the international basis for national representations of the ohm

starting January 1, 1990.

CURRENT ACTIVITIES: The method involves measurements of Rg , the quantized

Hall resistance (QHR) in a two-dimensional electron gas realized in the

inversion layers of GaAs/AlGaAs heterojunction devices when they are cooled

below 4.2 K in the presence of a strong magnetic field perpendicular to

both the current flow (I) and the Hall voltage (Vg ) . At each Hall step the

resistance Rg = Vg/I is quantized, and can be expressed as Rg = h/e^i =

/igC/2ai - 25,812.80/i Q, where h is the Planck constant, e is the

elementary charge, i is a quantum number, is the permeability of vacuum,

and c is the speed of light.

Currently we are: (1) using an 8 T magnet and the QHE to monitor the

national unit of resistance; and (2) assembling a new QHE laboratory,

including a sample preparation facility, which will allow us to monitor the

national unit of resistance with a 13 T magnet and 0.3 K ^He refrigerator

system while enabling us to expand our basic research using a second system

capable of attaining magnetic fields of 15 T and temperatures down to 30 mK

with a dilution refrigerator.

ACCOMPLISHMENTS: We have constructed, tested, and used a new automated QHR

measurement system that potentiometrically compares Rg with nominallyequal, temperature-controlled, wire-wound reference resistors Rg . The

typical total root- sum- square one-standard-deviation uncertainty is 0.007

ppm, three times smaller than for our automated QHR bridge system. The new

system has three independent levels of electrical shielding and thus the

exceptional leakage resistance of 3 x 10^^ Q.

We continued to monitor Oggg ; its drift rate is still about -0.054

ppm/year

.

The QHE Working Group of the CCE requested that the national

laboratories submit a set of suggested guidelines for making reliable QHR

measurements. We submitted a lengthy document separated into two sections:

(1) sample handling and characterization tests (cool-down procedures,

contact resistance measurements, temperature and current dependence

measurements, and flatness of the Hall steps); and (2) tests of QHR

measurement systems (leakage resistance measurements, detector gain and

linearity problems, and sample-reference resistor interchange errors).

A large fraction of FY 87 was devoted to the design, construction,

installation, and testing of components for the new QHE laboratory. There

are seven different vacuum systems, as well as gas-handling facilities for

24
^He, ^He, Ar, and N2 gases. A vacuum control panel and gas distribution

system was built and tested. This enables us to interconnect and

coordinate all the vacuum and gas systems, and to monitor them with a residual gas analyzer. The large collection of vacuum lines required for

the mechanical pumps, diffusion pumps, turbo-molecular pumps, control

panels, etc., was completed and leak tested.

There will be a top-loading ^He-^He dilution refrigerator for the 15 T

research magnet and a ^He refrigerator for the 13 T standards magnet.

Detailed designs were completed for both refrigerators; they will be nearly

identical so that the ^He refrigerator can be upgraded to a dilution

refrigerator if the need ever arises. The dilution refrigerator is being

assembled and vacuum tested.

The design work was completed for the vacuum- extraction sample probes.

Most of the components for six probes have been machined. The probes for

the research magnet and the standards magnet will be identical.

Standards -quality QHR samples continue to be difficult to obtain.

There are several potential suppliers of heterostructure films grown on single-crystal wafers, but they do not have the time or the incentive to

define Hall geometries on the wafers and to make electrical contacts on the

samples that remain ohmic at cryogenic temperatures in high magnetic

fields. We therefore began the design of, and the procurement of the parts

for, a sample preparation facility to perform these tasks.

FUTURE PLANS: The 13 T standards magnet has just been delivered. We will

thoroughly test it and then use it to make QHR measurements of the i = 2 and i = 4 Hall plateaus on the same sample. The 15 T research magnet

system has not yet been delivered because the vendor has had problems

making the most demanding of the four segments. They are now on the fourth

attempt.

FY 88 will be devoted mainly to ensuring that NBS provides the best

possible value of Rg to the CCE in preparation for the worldwide adoption

on January 1, 1990 of the QHE as the basis for national representations of

the ohm. We have achieved our goal of being able to compare Rg with

nominally- equal resistors Rg with an uncertainty of less than 0.01 ppm. We

will now concentrate on improving the accuracy of the step-down procedure

for comparisons between Rg and Ojibs • is to reduce this

uncertainty to 0.01-0.02 ppm and to tie our measurements as closely as possible to the NBS calculable capacitor realization of the SI ohm.

GAMMA-P AND THE FINE- STRUCTURE CONSTANT

[E. R. Williams, Sheng Ye (GS)

,

H. Sasaki (GS)

,

with G. R. Jones, Jr.,

P. T. Olsen, W. D. Phillips, V. E. Bower (GS)]

OBJECTIVES; To determine the proton gyromagnetic ratio to an accuracy

of a few parts in 10®

,

thereby obtaining a value of the fine structure

25
constant a to an accuracy of 0.02-0.03 ppm (the prime indicates protons in

a spherical sample of pure H2 O at 25 °C) . This will extend tests of

quantum electrodynamics (QED) , the Josephson effect, the quantum Hall

effect, and test our ability to monitor and maintain the NBS electrical

units. This improved value will be one of the most important contributions

to choosing the value of the quantized Hail resistance Rg to be adopted by

international agreement through the Consultative Committee on Electricity

(CCE) for maintaining laboratory representations of the ohm during the next

few decades

.

CURRENT ACTIVITIES: The jp experiment has two parts: First, we measure

accurately the dimensions of a precision solenoid, so that we can calculate

the magnetic field at the solenoid center when we pass a known current

through it; second, we measure the NMR frequency of an H2 O sample placed in

this field while measuring the solenoid current in NBS units. The ratio of

the NMR frequency to the calculated field is .

ACCOMPLISHMENTS: At the end of FY 86 we were stymied by a systematic

effect that made taking tTMR frequency measurements impossible. We finally

located the problem; it was caused by a voltage-dependent leakage inside a piece of stone used to hold the return leads to the solenoid. It was difficult to detect because of the low resistance of the solenoid in

parallel. Once discovered, it was easy to correct. The system has been

steadily improved; we can now obtain 0.02 ppm precision in both the

frequency measurements and the transfer-of -current measurements to the

electrical standards maintained in the Metrology Building, 1 . 5 km from our experiment. Figure 1 shows the NMR frequency versus the solenoid

temperature plotted as ppm changes in the frequency. Figure 2 shows the

measured and predicted magnetic field gradient around the solenoid center.

Both are in good agreement with predictions from the dimensional

measurements. Now that both the NMR and the dimensional measurements are working, we must combine the two so that they are made nearly at the same

time. In fact, we already have a preliminary value for 7p , but it will not

be publishable until a tedious evaluation of possible systematic errors is

completed.

In addition to obtaining good NMR results, we have developed a way to

eliminate one of the major remaining sources of uncertainty: the possible

correction for magnetic impurities in the solenoid coil form. We have

demonstrated that the entire solenoid can be measured with a special threecoil probe. With this probe we measured a small section cut from the

solenoid at the time of manufacture. We found x = (0.37 ± 0.05) x 10'® cgs

units which agrees with the value measured on a small sample using a SQUID

susceptometer . After we complete the other measurements, we will pass our solenoid through this new detector.

26
Data from "NMR GRAD DATA"

DISPLACEMENT (cm)

NMR FREQ, vs TEMP,

In Japan E. R. Williams worked with the ETL on their jp experiment.

During his two month stay they introduced the technique used at NBS to

eliminate frequency-dependent effects in measuring precision-solenoid

dimensions and used NBS programs to improve the field uniformity for their

NMR. Unfortunately, the ETL experiment will be limited to an accuracy of

about 0.5 ppm by the short length of their solenoid. A similar problem

limited the last NBS measurement, but the NBS solenoid was a little longer

and cooling fluid allowed some current compensation to increase its

effective length so that an accuracy of 0.2 ppm was obtained.

During his stay in Japan Dr. Williams conceived of a new method to

measure e^/h using a storage ring. Dr. T. Tomimasu of ETL has promised one month's use of ETL's storage ring for this experiment including the

personnel to run it.

FUTURE PLANS: We expect to have our measurements sufficiently complete

that a value can be given in the Conference on Precision Electromagnetic

Measurements (CPEM) abstract that we will submit in January 1988. We will

continue testing for systematic effects into late spring. We will then

disassemble the apparatus so we can pass it through the susceptibility

coils. We will present our results at CPEM and, of course, submit a recommended value for Rg to the CCE. We expect the relative uncertainty of

Rg to be less than 5 in 10®

.

LASER COOLING AND TRAPPING OF NEUTRAL ATOMS

[W. D. Phillips, P. L. Gould, P. D. Lett, and H. J. Metcalf (GS)]

OBJECTIVES: To develop techniques for and to study the physics of laser

cooling and trapping of neutral atoms. Motional effects, such as Doppler

and transit time, limit the performance of high resolution spectroscopy.

Cooling and trapping of atoms can reduce or eliminate these effects. Our

work on neutral atoms is thus complementary to similarly motivated work on

ions in the Time and Frequency Division, Cooling and Crapping of neutral

atoms also opens the possibility for studies in areas such as Bose-Einstein

27
condensation, atomic collisions at unprecedentedly low energies,

confinement of neutral antimatter, atom- surface interactions, and

manipulation of atoms and atomic beams.

CURRENT ACTIVITIES: We have developed a laser cooling technique which

produces continuous or pulsed slow atomic Na beams. Monovelocity beams

down to tens of m/s are available, as are stopped atoms with millikelvin

effective temperatures. We have magnetically trapped the laser cooled

atoms and we have demonstrated deflection and focussing of laser cooled

atomic beams

.

ACCOMPLISHMENTS: During the past year we have demonstrated the first

continuous loading of optical molasses and achieved atomic densities of

10® /cm^ , two orders of magnitude larger than has been reported for pulsed

loading. The optical molasses is formed at the intersection of three pairs

of counterpropagating laser beams. The cooling of these beams is so strong

that atomic motion is damped as if the atoms were in a viscous fluid.

Atoms reaching the molasses from our continuous atomic beam source "stick"

in it for times longer than 0.5 s, resulting in a dramatic build-up of

atomic density, to 10® /cm® or more. The density in the molasses is

28
considerably enhanced by techniques we have recently developed for the

enhanced continuous extraction of slow atoms from our Zeeman- tuned laser

decelerator

.

From simple considerations we can predict how the molasses confinement

time should vary with parameters such as laser tuning and the degree of

intensity imbalance between the opposing laser beams. We find that the

molasses should work best when the laser is tuned about a half linewidth

from resonance (where sensitivity to detuning is maximum) and should work

very poorly with even small imbalances of a few percent. In fact we find

that the optimal detuning is 2-3 linewidths and the molasses is relatively

insensitive to imbalance. The performance is generally better than

predicted by a simple theory, and more complete theories, taking into

consideration strong field effects, do not alter the character of the

predictions. At the moment we have no explanation for the anomalous

results

.

Using our continuously loaded molasses we have loaded a new kind of

optical trap. Two opposed, focused laser beams provide a longitudinal,

radiation pressure restoring force, while the dipole force provides

transverse confinement. Heating due to standing waves is avoided by

alternating the two laser beams in time, and cooling is provided by the

molasses during times when both trapping beams are off. The trap has a volume of 10" ^cm^ and so is about 10^ times larger than the pure dipole

trap demonstrated last year at Bell Labs.

We have continued attempts to observe the molasses phenomenon in a vapor cell with no success. After ruling out factors having to do with the

optical quality of the windows, tuning errors, and collisions, we are led

to speculate that the vapor may be in a non-equilibrium state which is

missing very slow atoms. This could be due to a relatively low energy

barrier in the atom-surface binding potential. We are considering

experiments designed to test this hypothesis.

FUTURE PLANS; We plan further studies of both molasses and the optical

trap. Additional measurements to be made on the molasses include the

atomic temperature as a function of experimental parameters. Preliminary

observations indicate that the temperature is lower than it ought to be

based on the simple theory, and this may give a clue to the explanation of

the anomalously good results. With the optical trap, we have the entire

range of measurements to make, since as of this writing only a first

observation has been made. Well depth, lifetime, temperature, confinement,

and capture volumes, all need to be measured as a function of experimental

parameters

.

Both molasses and the laser trap will be used for collision

experiments. They offer a unique opportunity to study ultra- low-energy

collisions, and we will be looking for associative ionization and radiative

association in Na-Na collisions at millikelvin temperatures in

collaboration with colleagues from the University of Maryland.

29
We are also considering, in cooperation with colleagues in the Time and

Frequency Division, experiments to test the hypothesis that atoms at

sufficiently low energy will reflect specularly from sufficiently cold

surfaces. This could lead to a bottle-type frequency standard, but without

the variable wall shift problems associated with hydrogen masers.

We also expect to return to experiments on magnetic trapping,

especially investigations of laser cooling in traps. These experiments

were deferred this past year because of the interesting results with

optical molasses.

Finally, work on the use of diode lasers to cool and trap neutral atoms

will be initiated with the arrival of NRC Postdoctoral Research Associate

R. N. Watts.

FUNDAMENTAL CONSTANTS DATA CENTER

[B. N. Taylor]

OBJECTIVES: To provide an international information center within the U.S.

for work in the general area of precision measurement and fundamental

constants (PMFC) , to analyze the consistency of measured values of the

fundamental physical constants resulting from different experiments, and to

obtain recommended values of fundamental constants for international use.

This is an important field for NBS because of the close relationship

between the fundamental constants and precision measurements, basic

measurement units such as the ampere, volt, and ohm, fundamental physics,

and state-of-the-art measurement technology. One of the purposes of this

project is to provide assistance and guidance in the PMFC area to both NBS

staff and university scientists, in particular, to advise them on the

potential impact of the experiments they are considering carrying out and

to keep them informed of related work currently underway in various

laboratories throughout the world.

CURRENT ACTIVITIES: These include: (1) keeping apprised of and maintaining

a complete reprint collection of the latest accomplishments throughout the

world in PMFC; (2) carrying out new least-squares adjustments of the

fundamental constants to obtain sets of recommended values; (3)

participating in the work of national and international groups, for

example, the CODATA Task Group on Fundamental Constants, the NAS/NRC

Advisory Committee on Fundamental Constants and Standards, and the

Josephson Effect and the Quantum Hall Effect Working Groups of the

Consultative Committee on Electricity (CCE) ; and (4) answering inquiries

from both within and without NBS relating to the PMFC field.

ACCOMPLISHMENTS: Extensive material was prepared on the best values of the

Josephson frequency-voltage quotient 2e/h and quantized Hall resistance

h/e^ for the 17th session of the CCE. After attending the meeting as NBS

30
representative, a talk on its profound results was presented at the annual

meeting of the National Conference of Standards Laboratories and a paper

prepared for and published in the Jan. /Feb. issue of the NBS Journal of

Research.

In collaboration with E. R. Cohen, Rockwell International, the 1986

Least-Squares Adjustment of the Fundamental Physical Constants (LSAFPC86) was completed and a report prepared and published as CODATA Bulletin 63

(Pergamon Press, Nov. 1986). The LSAFPC86 represents a major advance over

its 1973 counterpart; the uncertainties of the recommended values have been

reduced by roughly an order of magnitude due to the enormous advances made

throughout the PMFC field since 1973.

Extensive efforts were made to distribute widely the new adjustment and

the resulting set of recommenced values. About 400 copies of the CODATA

Bulletin were mailed to individual scientists throughout the world. A

general news release led to articles in Science, the New York Times, the

Christian Science Monitor, Science News, as well as other newspapers,

magazines, and journals. The 1986 recommended values were reprinted in

their entirety along with a summary of the CODATA Bulletin text in the

March/April issue of the NBS Journal of Research. A similar summary with a condensed table of values appeared in the May issue of Europhysics News and

will appear in the August issue of Physics Today. A slightly revised

version of CODATA Bulletin 63 was prepared for publication in the October

issue of the Reviews of Modern Physics. A wallet card giving the 1986

recommended values was prepared and published as NBS Special Publication

731

FUTURE PLANS: The wide dissemination of the new adjustment and set of

recommended values will continue.

A more detailed paper on the LSAFPC86 will be prepared and submitted

for publication in the Journal of Physical and Chemical Reference Data.

I will prepare for and attend the 1988 Conference on Precision

Electromagnetic Measurements (CPEM) to be held in Japan and three

associated meetings: that of the CODATA Task Group on Fundamental

Constants, the CCE Working Group on the Josephson Effect, and the CCE

Working Group on the Quantum Hall effect. New results relating to the

fundamental constants will be presented at CPEM 88 and subsequently used to

develop improved best values for the Josephson frequency-voltage ratio 2e/h

and quantized Hall resistance h/e^ to be used internationally for volt and

ohm maintenance purposes, respectively. The Josephson Effect and quantum

Hall Effect Working Groups of the CCE will meet at the time of CPEM to

review the relevant data and calculate best values.

31
PRECISION MEASUREMENT GRANTS

[NBS Precision Measurement Grants Committee; R. D.Deslattes, J. L. Hall,

B. N. Taylor (Chairman), D. J. Wineland]

OBJECTIVES: To award each year two new $30 k Precision Measurement Grants

(PMGs) and to renew each year four existing PMGs. (The PMGs are renewable

for two additional years beyond the initial year, at NBS' option.)

The NBS PMG program was initiated in 1970 and is funded by the NBS

Director. PMGs are awarded to scientists in U.S, academic institutions in

order to (1) promote and encourage fundamental research in the field of

precision measurement and fundamental constants and train future

measurement-oriented scientists, and (2) foster contacts between NBS

scientists and those researchers in the academic community who are actively

engaged in such work. While NBS has much research underway in this field,

there is considerable expertise and relevant work in U.S. colleges and

universities. It is the purpose of this project to tap this reservoir and

to foster the training of students who might eventually become NBS staff by

awarding grants to a selected number of outstandingly qualified, academic

researchers

.

CURRENT ACTIVITIES; PMG candidates are requested to submit a biographical

sketch and preproposal summary outlining the objective of their proposed

research, why they believe it to be important, and the general approach to

be used, including some indication of what they expect to accomplish in the

three year time period covered by the grant. On the basis of this

material, four to eight candidates are selected by the NBS Precision

Measurement Grants Committee and the Outside Advisory Committee (consisting

of four senior university professors) to submit more detailed proposals.

The same committees evaluate these, and on the basis of this evaluation,

the two recipients are selected. The criteria used to evaluate the

preproposals and full proposals include the importance of the proposed

research to science, the feasibility of the research, and the past

accomplishments of the applicant.

ACCOMPLISHMENTS: The procedures outlined above for selecting candidates,

which were first instituted in FY 77, were again used successfully in FY

87. Proposals were openly solicited via an advertisement in Physics Today,

announcements in appropriate trade journals and newsletters, and the

mailing of a brochure to the physics departments of all of the colleges and

universities in the U.S. which grant bachelor and higher degrees in physics

(about 850). Good proposals were received from 30 candidates, five of whom

were chosen to submit final, full proposals. The following are the two

recipients selected, their institutions, and project titles:

Wiley P. Kirk, Texas A&M University

Quantized Hall Resistance and Fine -Structure Constant

Investigations; A Study of Uncertainty Contributions

32
John D. Morgan III, University of Delaware

High Precision Calculation of Helium Atom Energy Levels

The aim of Kirk's research is to investigate mechanisms that contribute

uncertainties to the establishment of resistance standards and the

determination of the fine -structure constant based on the quantum Hall

effect. Three types of error sources will be studied; parallel conduction,

temperature - dependent- shifts , and sample dependent effects.

The aim of Morgan's research is the high-precision calculation of the

energies of the ground and excited states of the helium atom (or other

light helium- like ions) to match the recent advances in experimental laser

spectroscopic studies of transitions between these states with a precision

of better than 10“^ cm' ^

.

For FY 87, the Outside Advisory Committee consisted of Professors

Crampton, Fairbank, Larson, and Ritter.

The following grants were renewed in FY 87: G. Gabrielse, Harvard

University, Injection of Protons, Antiprotons, and Heavy Ions into a Penning Trap for Precision Mass Measurements; L. R. Hunter, Amherst

College, A New Method to Search for the Electric Dipole Moment of the

Electron; Frederick R. Raab, University of Washington, Atomic Physics Tests

of Gravity and the Equivalence Principle; and Daniel R. Stinebring,

Princeton University, High Precision Timing of Millisecond Pulsars. The

work of Gabrielse was especially successful this year --he demonstrated

the trapping of antiprotons in a Penning trap for the first time (the grant

was initially awarded in FY 86)

.

PTJTURE PLANS: FY 88 plans naturally focus on renewing the four eligible

current grants and awarding two new grants. Current and past recipients

will be invited to visit NBS and to present talks as appropriate, and

visits to current and past recipients will be made by NBS staff in

conjunction with other travel.

33
ELECTRICITY DIVISION SPONSORED SEMINARS/WORKSHOPS

Workshop on Electrical Measurement Assurance Programs, held October 26-31,

1986, San Jose, CA.

INVITED TALKS

N. B. Belecki, "Changes in the U.S. Legal Units of Voltage and Resistance,"

Los Angeles Chapter, Precision Measurements Association, Los Angeles, CA,

Nov, 1986.

N, B, Belecki, "Precautions in the Use of Gas-Dielectric Capacitance

Standards," Los Angeles Chapter, Precision Measurements Association, Los

Angeles, CA, Nov. 1986.

N. B. Belecki, "History of the U.S. Legal Volt," Symposium for Innovation

in Measurement Science, Instrument Society of America, Geneva, NY, August

1987.

M, E. Cage, "The Quantum Hall Effect and its Application as a Resistance

Standard," American Physical Society, Williamsburg, VA, Nov. 1986,

M. E. Cage, "The Quantum Hall Effect," Department of Physics Colloquium,

Lehigh University, Bethlehem, PA, Dec. 1986.

M. E. Cage, "The Quantum Hall Effect and its Application as a New

Resistance Standard," National Conference of Standards Laboratories 1987

Workshop and Symposium, Denver, CO, July 1987,

R. F. Dziuba, "The NBS Ohm: Past-Present-Future," 1987 Measurement Science

Conference, Irvine CA, Jan. 1987.

R. F. Dziuba, "The NBS Ohm: Past-Present-Future," 1987 Symposium for

Innovation in Measurement Science, Instr\ament Society of America, Geneva,

NY , Augus t 1987.

B. F. Field, "Instrumentation for the Measurement of the Quantized Hall

Resistance Standard," Symposium for Innovation in Measurement Science,

Instrument Society of America, Geneva, NY, August 1987.

P. L. Gould, "Confinement of Ultra-Cold Atoms in Optical Molasses,"

Department of Physics Colloquium, University of Connecticut, Storrs, CT,

March 1987.

P. L. Gould, "Cooling and Confinement of Atoms Using Laser Radiation," IXth

Vivilov Conference on Nonlinear Optics, Novosibirsk, USSR, June 1987.

P. L. Gould, "Laser Cooling and Deflection of Atomic Beams," XI th

International Symposium on Molecular Beams, Edinburgh, Scotland, July 1987.

34
W. D, Phillips, "Cooling, Stopping and Trapping Atoms," NBS , Boulder, CO,

Sept. 1986.

W. D. Phillips, "Cooling, Stopping and Trapping Atoms," University of North

Carolina, Physics Colloquium, Raleigh, NC , Sept. 1986.

W. D. Phillips, "Radiative Forces on Atoms," Physics Department Colloquium,

University of Iowa, Iowa City, lA, Nov. 1986.

W. D. Phillips, "Laser-Cooling and Trapping Atoms," Physics Department

Colloquium, Towson State University, Towson MD, Dec. 1986.

W. D. Phillips, "Laser Cooling of Atomic Hydrogen," Workshop on Cooling,

Condensation, and Storage of Hydrogen Cluster Ions, SRI International, Palo

Alto, CA, Jan. 1987.

W. D. Phillips, "Cooling and Trapping Atoms: Reducing the Motional Limits

of Atomic Measurement," American Physical Society, New York, March 1987.

W. D. Phillips, "Optical Cooling and Trapping," National Research Council,

Ottawa, Canada, April 1987.

W. D. Phillips, "Historical Introduction to Radiative Forces" College de

France, Paris, May 1987.

W. D. Phillips, "Laser Cooling of Atomic Beams," College de France, Paris,

May 1987.

W. D. Phillips, "Optical Traps and Molasses," College de France, Paris,

June 1987.

W. D. Phillips, "Realization of the Ampere of the Systeme International,"

College de France, Paris, June 1987.

W. D. Phillips, "New Measurements with Optical Molasses," Eighth

International Conference on Laser Spectroscopy, Are, Sweden, June 1987.

W. D. Phillips, "Optical Traps and Optical Molasses," National Physical

Laboratory, Teddington, England, June 1987.

W. D. Phillips, "Optical Cooling and Confinement of Atoms," U.S. -Japan

Seminar on Quantum Mechanical Aspects of Quantum Electronics, Monterey, CA,

July 1987.

R. L. Steiner, "Josephson Arrays," Sandia National Laboratory, Albuquerque,

NM, March, 1987.

R. L. Steiner, "Calibration of Voltage Standards Using a Josephson Array,"

National Conference of Standards Laboratories 1987 Workshop and Symposium,

Denver, CO, July 1987.

35
R. L. Steiner, "Instrumenting Josephson Arrays for Use as Primary Voltage

Standards," Symposium for Innovation in Measurement Science, Instrument

Society of America, Geneva, NY, August, 1987.

R. L. Steiner, "Maintenance of the U.S. Legal Volt with a Josephson Array

at NBS , " Electrotechnical Laboratory, Tsukuba, Japan, Sept, 1987.

R. L. Steiner, "The Superconducting Josephson Array Voltage Standard,"

University of Puget Sound, Takoma, WA, Sept. 1987,

B, N, Taylor, "Possible Changes in the Electrical Units: Report on the

September 1986 Meeting of the Consultative Committee on Electricity,"

National Conference of Standards Laboratories 1986 Workshop and Symposium,

Gaithersburg, MD, Oct. 1986.

B. N. Taylor, "Impact of Quantum Phenomena on Fundamental Constants and

Electrical Units," XXIInd General Assembly of the International Union of

Radio Science, Tel Aviv, Israel, Sept, 1987.

C. T. Van Degrift, "The New NBS Quantum Hall Effect Laboratory,"

Electrotechnical Laboratory, Tsukuba, Japan, Sept, 1987.

C. T. Van Degrift, "Precision Measurements Using Tunnel Diode Oscillators,"

National Research Laboratory of Metrology, Tsukuba, Japan, Sept. 1987.

E. R, Williams, "Realization of the Ampere and Determination of the FineStructure Constant Based on the Gyromagnetic Ratio of the Proton," XXIInd

General Assembly of the International Union of Radio Science, Tel Aviv,

Israel, Sept. 1987.

E. R. Williams, "Testing Physical Theories Using Precision Electrical

Measurements," Electrotechnical Laboratory, Tsukuba, Japan, Oct. 1986.

E. R. Williams, "Realizing Electrical Standards: A problem in Precision

Dimensional Metrology," presented to Committee for Systematizing Nanometer

Technology, at the Tokyo Institute of Technology, Ookayama, Japan, Nov,

1986.

36
PUBLICATIONS FY 87

1 . In Print

N. B. Belecki, "Conference on Precision Electromagnetic Measurements," J.

Res. Natl. Bur. Stand. No. 4, pp. 235-236 (July-August, 1986).

L. R. Becker, B. F. Field, and T. E. Kiess, "Ten volt round-robin test

conducted on a solid-state DC voltage standard," IEEE Trans. Instrum.

Meas., IM-35 . No. 4, pp. 383-386 (Dec. 1986).

M. E. Cage, "Experimental aspects and metrological applications of the

quantum Hall effect," Chapter II in The Quantum Hall Effect . Ed. by R. E. Prange and S. M. Girvin (Springer-Verlag, New York, 1986) pp. 37-68.

M. E. Cage, R. F. Dziuba, B. F. Field, T. E. Kiess, and C. T. Van Degrift,

"Monitoring the U.S. legal unit of resistance via the quantum Hall effect,"

IEEE Trans. Instrum. Meas. IM-36 . No. 2, pp. 222-225 (June 1986).

E. R. Cohen and B. N. Taylor, "The 1986 adjustment of the fundamental

physical constants, a report of the CODATA Task Group on Fundamental

Constants," CODATA Bulletin 63, 36 pp. (Pergamon Press, Oxford, Nov. 1986).

E. R. Cohen and B. N. Taylor, "The 198.6 CODATA recommended values of the

fundamental physical constants," J. Res. Natl. Bur. Stand. 92, No. 2, pp

.

85-95 (March-April 1987)

.

E. R, Cohen and B. N. Taylor, "Fundamental physical constants, 1986

adjustments," Europhys . News 18, No. 5, pp. 65-68 (May 1987).

E. R. Cohen and B. N. Taylor, "Fundamental physical constants, 1986 CODATA

recommended values" (a wallet card giving values of selected constants from

the 1986 CODATA set of recommended values), E. R. Cohen and B. N. Taylor,

Natl. Bur. Stand. (U.S.), Spec. Publ. 731 (July 1987).

R. F. Dziuba, "The NBS ohm: past-present-future," Proc. 1987 Meas. Sci.

Conf . , Session VI-A, pp. 15-27 (Jan. 1987).

C. A. Hamilton, R. L. Kautz , F. L. Lloyd, R, L. Steiner, and B. F. Field,

"The NBS Josephson array voltage standard," IEEE Trans. Instrum. Meas.

IM-36 . No. 2, pp. 258-261 (June 1987).

F. L. Hermach, J. R. Kinard, and J. R. Hastings, "Multij unction thermal

converters as the NBS primary AC-DC transfer standards for AC current and

voltage," IEEE Trans. Instrum. Meas. IM-36 . No. 2, pp . 300-306 (June 1987).

K. B. Jaeger and B. N. Taylor, "U.S. perspective on possible changes in the

electrical units," IEEE Trans. Instrum. Meas. IM-36 . No. 2, pp . 672-675

(June 1987).

37
H. J. Metcalf and W. D. Phillips, "Electromagnetic trapping of neutral

atoms," Metrologia 22., No. 4, pp. 271-278 (1986).

W. D. Phillips and H. J. Metcalf, "Atomic beams," in 1987 McGraw-Hill

Yearbook of Science and Technoloev . Ed. by S. Parker (McGraw-Hill, New

York, 1987), pp. 97-99.

W. D. Phillips and H. J. Metcalf, "Cooling and trapping atoms," Scientific

American 256 . No. 3, pp . 50-56 (March 1987).

B. W. Ricketts and M. E. Cage, "Quantized Hall resistance measurements at

the National Measurement Laboratory, Australia," IEEE Trans. Instrum. Meas

.

IM-36 . No. 2, pp. 245-248 (June 1987).

B. N. Taylor, "Possible changes in the U.S. legal units of voltage and

resistance," J. Res. Natl. Bur. Stand. 91., No. 5, pp. 299-305 (Sept. -Oct.

1986)

.

B. N. Taylor, "Report on the 17th session of the Consultative Committee on Electricity," J. Res. Natl. Bur. Stand. 92, No. 1, pp . 55-61 (Jan. -Feb.

1987)

. Reprinted in Natl. Conf. Stand. Lab. (NCSL) Newslett. 22, No. 3,

pp. 11-40 (July 1987).

B. N. Taylor, "History of the present value of 2e/h commonly used for

defining national units of voltage and possible changes in national units

of voltage and resistance," IEEE Trans. Instrum. Meas. IM-36 . No. 2, pp.

659-664 (June 1987)

.

2 . In Press. In Review, or Nearing Completion

E. R. Cohen and B. N. Taylor, "The fundamental physical constants," Physics

Today.

E. R. Cohen and B. N. Taylor, "The 1986 adjustment of the fundamental

physical constants," Reviews of Modern Physics.

R. F. Dziuba, "Electricity Division DC resistance calibration services,"

NBS Special Publication 250.

B. F. Field, "Electricity Division standard cell calibration services," NBS

Special Publication 250.

B. F. Field, "Solid-state voltage standard performance and design

specifications," NBS Technical Note.

B. F. Field, "Electricity Division solid-state reference calibration

services," NBS Special Publication 250.

38
P. L. Gould, P. D. Lett, and W. D. Phillips, "New measurements with optical

molasses," to be published in Laser Spectroscopy VIII . the proceedings of

the Eighth International Conference on Laser Spectroscopy (Springer,

Berlin, 1987)

.

P, L. Gould, P. D. Lett, and W. D, Phillips, "Continuously loaded optical

molasses," in preparation.

J. R. Kinard, T. E. Lipe , and J. R. Hastings, "Electricity Division

calibration services for AC-DC difference," NBS Special Publication 250.

J. R. Kinard and T. E. Lipe, "Recharacterization of thermal voltage

converters after thermoelement replacement," NBS Journal of Research.

W. D. Phillips, P. L. Gould and P. D. Lett, "Cooling, Stopping and Trapping

Atoms," Science.

W. D. Phillips, P. L. Gould and P. D. Lett, "Electromagnetic manipulation

of atomic hydrogen," to be published in the proceedings of the Workshop on

Cooling, Condensation, and Storage of Hydrogen Cluster Ions, University of

Dayton Special Publication, 1987.

G. Marullo Reedtz and M. E. Cage, "An automated potentiometric system for

precision measurement of the quantized Hall resistance," NBS Journal of

Research

.

B. N. Taylor, "New values for the constants of physics," Physics News in

1987.

B. N. Taylor, "Atomic constants," 1989 McGraw-Hill Yearbook of Science and

Technoloev .

C. T. Van Degrift, S. M. Girvin, and M. E. Cage, "The quantum Hall effect,"

a Resource Letter for the American Journal of Physics.

E. R. Williams and T. Tominasu, "Measure h/e^ by counting electrons or ions

in a storage ring," Physics Letters.

39
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

N. B. Belecki, member, ANSI S82, American National Standards Institute

Committee on Electrical Standards, Instrumentation, and Devices.

N. B. Belecki, member. National Conference of Standards Laboratories (NCSL)

Measurement Assurance Committee.

N. B. Belecki, member. National Working Group, OIML (International

Organization of Legal Metrology) Pilot Secretariat 13, Measurement of

Electrical and Magnetic Quantities; and Co-chairman, U.S. National Working

Group, OIML (International Organization of Legal Metrology) Reporting

Secretariat 13.1, International Compatibility of National Primary Standards

Used for Instrument Verification.

N. B. Belecki, member, TC-2, DC and LF Standards, Instrumentation, and

Measurements Committee of the Instrumentation and Measurement Society,

Institute of Electrical and Electronics Engineers (IEEE)

.

N. B. Belecki, member. National Conference of Standards Laboratories

Education Liaison Committee.

N. B. Belecki, Chairman, National Committee on the Changes in the U.S.

Legal Volt and Ohm. (R. F. Dziuba, B. F. Field, and B. N. Taylor are also

members of the Committee)

.

R. F. Dziuba, member. Organizing Committee of the 1988 Conference on Precision Electromagnetic Measurements (to be held in Tsukuba, Japan), and

Guest Editor for the Conference Proceedings to appear in IEEE Trans.

Instrum. Meas . IM-38 (June 1989).

J. R. Hastings, member, TC-2, DC and LF Standards, Instrumentation, and

Measurements Committee of the Instrumentation and Measurement Society,

Institute of Electrical and Electronics Engineers (IEEE)

.

J. R. Kinard, member, TC-2, DC and LF Standards, Instriimentation, and

Measurements Committee of the Instrumentation and Measurement Society,

Institute of Electrical and Electronics Engineers (IEEE)

.

W. D. Phillips, member. Steering Committee for the NBS Discussion Group on Atomic Physics.

W. D. Phillips, member. Editorial Board of Progress in Quantum Electronics.

W. D. Phillips, member. Advisory Committee on Fundamental Constants and

Standards of the Division of Chemistry and Chemical Technology, Numerical

Data Advisory Board, National Academy of Sciences/National Research

Council/National Academy of Engineering.

40
W. D. Phillips, member, Steering Committee of the American Physical Society

Topical Group on Laser Science.

B. N. Taylor, member. Advisory Committee on Fundamental Constants and

Standards of the Division of Chemistry and Chemical Technology, Numerical

Data Advisory Board, National Academy of Sciences/National Research

Council/National Academy of Engineering.

B. N. Taylor, Chairman, NBS Precision Measurement Grants Committee.

B. N. Taylor, NBS representative. Consultative Committee on Electricity

(CCE) , International Committee of Weights and Measures (CIPM)

.

B. N. Taylor, member, ANSI C-42, American National Standards Institute

Committee on Definitions of Electrical Terms.

B. N. Taylor, member, CODATA (Committee on Data for Science and Technology)

Task Group on Fundamental Constants.

B. N. Taylor, Technical Advisor (Chairman, U.S. National Work Group) OIML

(International Organization of Legal Metrology) Pilot Secretariat 13,

Measurement of Electrical and Magnetic Quantities; and Co-chairman, U.S.

National Working Group, Reporting Secretariat 13.1, International

Compatibility of National Primary Standards Used for Instrument

Verification.

B. N. Taylor, NBS representative to the Executive Committee, Conference on Precision Electromagnetic Measurements (CPEM) , and Comptroller of CPEM.

B. N. Taylor, Coordinator, Consultative Committee on Electricity (CCE)

Working Group on the Quantum Hall Effect and member, CCE Working Group on

the Josephson Effect.

41
COLLABORATIONS, CONSULTING, MISCELLANEOUS ACTIVITIES

N. B. Belecki and R. F. Dziuba are collaborating with metrologists from six

Southern California Companies (Beckman Instruments, Electrical Standards

Repair Service, Ford Aerospace & Communications, Lockheed of California,

Rockwell International Anheim, and TRW) in a pilot experiment to develop

metrology for a "self-help" group MAP in resistance. The goal is a procedure by which companies could set up and run their own MAP, including

data reduction and error analysis, using NBS's calibration services and

their own transport standards. Some of the equipment is being furnished by

the NCSL Measurement Assurance Committee.

N. B. Belecki, Y. M. Chang, and C. R. Levy are collaborating with Electro

Scientific Industries (ESI) in the evaluation of ceramic-dielectric

capacitors for possible use as secondary standards and, more importantly,

MAP transport standards.

M. E. Cage, C. T. Van Degrift, and R. F. Dziuba are collaborating with

S. M. Girvin of the University of Indiana on the theoretical aspects of the

quantum Hall effect.

M. E. Cage, C. T. Van Degrift, and R. F. Dziuba are collaborating with D.

C. Tsui of Princeton University, and A. C. Gossard and H. L. Stormer of

AT&T Bell Laboratories, on quantized Hall resistance measurements of GaAsAlGaAs heterojunctions.

M. E. Cage, C. T. Van Degrift, and R. F. Dziuba, are collaborating with

M. Razeghi of Thomson-CSF, France, on quantized Hail resistance

measurements of GalnAs-InP heterojunctions.

M. E. Cage, C. T. Van Degrift, and R. F. Dziuba are collaborating with E.

Mendez of IBM on quantized Hall resistance measurements of GaSb-InAs

heterojunctions

.

B. F. Field is collaborating with a number of companies (John Fluke Mfg,

Co., Standard Reference Laboratories, Vahalla Scientific, Yellow Springs

Instruments, Compensated Devices) on the evaluation of improved solid-state

voltage standards.

B. F. Field is collaborating with personnel from the DoD Primary Standards

Laboratories (Redstone Arsenal, North Island Naval Air Station, Washington

DC Navy Yard, Newark Air Force Station) on the use and calibration of

commercial 10 V solid-state voltage standards as MAP transfer devices.

P. L. Gould is collaborating with the group of D. E. Pritchard at MIT on

the deflection of atomic beams by light.

J. R. Kinard is collaborating with personnel from the Navy Metrology

Engineering Division, Corona, CA, and the John Fluke Mfg. Co., on the

evaluation of solid-state thermal converters.

42
J. R, Kinard is collaborating with personnel from Ballantine Laboratories

on the evaluation of coaxial thermal voltage converters.

J. R. Kinard is collaborating with N. M. Oldham, NBS Electrosystems

Division, Center for Electrical and Electronics Engineering (CEEE) , NEL, in

the study of possible transport standards of AC voltage and current.

J. R. Kinard is collaborating with Mr. T. Nordin, C. P. D. Engineering, in

the study of current shunt and thermoelement combinations.

J. R. Kinard is collaborating with Mr. D. Stollery, Thermal Techniques

Ltd. , Essex, U.K. , on the improvement of thermal element design.

J. R. Kinard is collaborating with the staff of the Navy Primary Standards

Laboratory East on improved methods for the intercomparison of thermal

voltage converters.

P. T. Olsen is collaborating with personnel of the Navy's Primary Standards

Laboratory East (Washington Navy Yard) on the calibration of magnetometers.

W. D. Phillips is collaborating with M. G. Littman of Princeton University

on the spectroscopy of Rydberg atoms in electric fields and applications to

the measurement of the fine-structure constant.

W. D. Phillips is collaborating with J. Dalibard and C. Cohen-Tannoudj i of

Ecole Normale Superieur, Paris, on the laser trapping of neutral atoms.

W. D. Phillips, P. D. Lett, and P. L. Gould are collaborating with H. J.

Metcalf of SUNY, Stony Brook, on laser cooling and magnetic trapping of

atoms

.

W. D. Phillips is seirving on the Program Committee of the Third

International Laser Science Conference.

W. D. Phillips served as a member of the Program Committee for IQEC 87.

W. D. Phillips participated in Panel discussions of "Cooling in Traps" and

"Physics in Traps" at the Symposium on Physics of Stored and Trapped

Particles, Stockholm, Sweden, June 1987.

R. L. Steiner and B. F. Field are collaborating with C. A. Hamilton, R. L. Kautz , and F. L. Loyd of the Cryoelectronics Group of the Electromagnetic

Technology Division, CEEE, NEL, NBS/Boulder, and J. Niemeyer of the

Physikalisch-Technische Bundesanstalt , West Germany, on the development of

1 V Josephson array voltage standards.

43
R. L. Steiner and B. F. Field, with C. A. Hamilton of NBS/Boulder, are collaborating with K. Jaeger, Lockheed Missiles & Space Co., B.Barnaby,

Sandia Laboratories, and G. Trinite, Navy Metrology Engineering Division,

Corona, CA, on the construction of and operation procedures for Josephson

array voltage standards at their respective laboratories.

R. L. Steiner is collaborating with T. Endo of the Electrotechnical

Laboratory (ETL) , Japan, on the testing of Josephson arrays. He will visit

ETL for a week in Sept. 1987 to support the collaboration.

B. N. Taylor is collaborating with E. R. Cohen, Rockwell International, and

the CODATA Task Group on Fundamental Constants, on various aspects of data

analysis relevant to the fundamental physical constants.

E. R. Williams collaborated with H. Nakamura of the Electrotechnical

Laboratory (ETL) , Japan, on their proton gyromagnetic ratio and absolute

ampere experiments. He received a research fellowship from the Japanese

Industrial Technology Association for a two-month stay at ETL in the fall

of 1986 to support the collaboration.

E. R. Williams is collaborating on the realization of the SI volt with

Prof. V. Bego of the Electrotechnical Institute, University of Zagreb,

Yugoslavia, under the U . S

. -Yugoslavia Joint Board on Science and

Technology.

44
TEMPERATURE AND PRESSURE DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1987

DIVISION CHIEF'S OVERVIEW

DIVISION OFFICE ACTIVITIES

The Division secretarial staff and their general responsibilities are

as follows:

1) Secretary to Division Chief: S. Ramboz

2) Secretary to Temperature Group: N. McBryde

3) Secretary to Pressure and Vacuum Group: J. Packard

The abrupt retirement of Ms. McBryde at the beginning of the fiscal year

was followed by an unsatisfactory replacement and then, late in the fiscal

year, by an excellent choice: A. Salazar. Thus, through the extraordinary

efforts of the veterans Ms. Ramboz and Packard and the adroitness of

Ms. Salazar, the Division was able to cope with an unusually heavy work

load which included a bumper calibration year, several special calibration

documents, and renovation of office word processing equipment and software.

Thanks are due R. Kaeser for his assistance in the last category.

PERSONNEL

This year the Division saw the retirement of Mr. R. E. Edsinger from

the gas thermometry program and the reduction in force of Mr. R. B. Dove

from the low temperature and vacuum programs. Expansion of Division

programs into new areas awaits the success of the Process and Quality

Control Initiative for FY 88.

NEW PROGRAMS

For the first time in its history, the Division is employing the

instrument of the Industrial Research Fellow to explore new areas of

metrology. In fact, two such explorations were launched this past year.

The first is in particle detection using super cooled superconductive

colloids (A. Druckier, Applied Research Corporation). The second is in a new physical principle (speed of sound) for high temperature measurements

(D. Varella, Thermosonics)

.

NEWS ON EXTANT PROJECTS

As has been the practice in past years, the Division activities are categorized into 7 categories which are reported below.

45
I. HIGH TEMPERATURE SCALE RESEARCH

(M. Reilly, J. Schooley, R. Edsinger, and W. Bowers)

The temperature range covered here extends from 904 K (the upper limit

of the platinum resistor scale) to approximately 2400 K (the approximate

upper limit of NBS thermocouple calibrations) . This temperature range is

presently defined by standard thermocouples and radiation thermometers

using the Planck Law. For a variety of technical reasons, errors in

temperature measurement using these devices can become unacceptably large

(as much as 0.5 K for standard thermocouples, as large as 3 K for PlanckLaw radiation thermometers). Accordingly, the Division has initiated a program to address this problem. The goal is to develop a temperature

scale accurate to 20 ppm by comparing two instruments based on two physical

laws: the ideal gas law and the Planck radiation law. A further

consideration is to develop transfer standards based on special platinum

resistance thermometers or on the optical fiber thermometer. Development

of the optical fiber thermometer using the Planck radiation law is

coordinated with the other Division proj ects- -gas thermometry and hightemperature PRT's--as will be explained below.

I. A. OPTICAL FIBER THERMOMETER

The principal goals of the Optical Fiber Thermometer (OFT) program

are: (1) to establish accurate values for the thermodynamic temperature of

the thermometric fixed points, silver (962 °C) and gold (1064 °C), relative

to that of aluminum (660 °C) and (2) to provide a means of interpolating

temperature between these fixed points with an uncertainty not exceeding

20 ppm. Through its development and use as a primary thermometer, we hope

that the OFT can provide a basis for the formulation of a more accurate

temperature scale over the interval 630 to 1064 °C.

The OFT is rather like an optical pyrometer in which the lens has been

replaced by a long, slender light pipe that can be inserted directly into

the hot zone of a high-quality blackbody source to capture and transmit the

radiant flux. The light pipe (probe) is a single-crystal sapphire rod,

nominally 1 mm dicimeter and 30 cm long. The wavelength interval is defined

by a compound narrow-band interference filter (t}rpically an 800 nm peak

wavelength with a 25 nm bandwidth). The detector is a silicon photodiode.

Because sapphire has a high index of refraction, the probe can capture

significantly more flux than the optics of conventional pyrometers and, as a consequence, the OFT has greater sensitivity and can operate to lower

temperatures than those instruments. Thus we expect to use the OFT at low

temperatures (between the aluminum and silver points) and to compare it

with conventional radiometers at temperatures where they are sufficiently

sensitive (between the silver and gold points)

.

In principle, once the OFT is calibrated at a single temperature

within its range, it can be used to determine thermodynamic temperatures

over its entire range. In practice (excluding that caused by the

uncertainty in the numeric value assigned to the calibration temperature)

46
there are three major sources of error which limit its accuracy. In order

of importance, these are: (1) uncertainties in the optical properties of

the sapphire probe; (2) uncertainties in the spectral response

characteristics of the optical system (particularly the interference filter

and detector); and (3) uncertainties in the linearity of the detector and

the associated electronic circuitry.

The combined uncertainty in the corrections for the spectral response

and nonlinearity is estimated to be less than 100 ppm for the gold to

silver freezing-point radiance ratio measured at 800 nm. (This uncertainty

corresponds to an error of about 9 mK in the difference between the

thermodynamic temperatures of the gold and silver freezing points.)

The optical properties of the probe that are significant for our OFT

measurement are: (1) the reflectivity at the air-to-sapphire interface,

(2) the attenuation of the transmitted radiant flux due to absorption in

the probe, and (3) the loss of the transmitted flux (and likely gain of

unwanted background flux) due to scattering at the cylindrical surface of

the probe. These properties must be known for the temperature range of

interest as well as for the wavelength range within the passband of the

interference filter.

The reflectivity at the air-to-sapphire interface relative to that at

room temperature has been determined for temperatures from 400 to 1060 °C

and for wavelengths of 633 and 799 nm. The results were published in May

1986. The uncertainty in the correction for the reflectivity is estimated

to be less than 50 ppm for the gold to silver freezing-point radiance ratio

measured at 800 nm. (This uncertainty corresponds to an error of about

5 mK in the difference between the thermodynamic temperatures of the gold

and silver freezing points.)

At present, we believe that the dominant source of error is that due

to absorption and scattering processes which occur near the cylindrical

surface of the rod. The rods are cut from single-crystal sapphire boules

and then centerless ground to obtain the approximate diameter before the

finishing of the cylindrical surface by either mechanical or flame

polishing procedures. The grinding process leaves a finite damage layer of

complex microfractures which propagate into the material to a depth

(perhaps to several hundred micrometers) that depends upon the details of

the operation. This damage layer, which is the major cause of the

scattering, must be eliminated in the finishing step. The absorption

characteristic of the rod is then due mostly to impurities incorporated

into the crystal boule at the time it is grown.

We have developed several simple yet reliable experimental procedures

which allow us to determine the absorption and scattering characteristics

of the rods as a function of temperature and wavelength. During the last

several years, we have examined candidate rods from all known sources using

these and a variety of other techniques in order to identify causes of

their unsatisfactory optical properties. Taking advantage of the results

47
of these tests, one source has been able to significantly reduce the

scattering characteristic of his rods. Rods from this source probably

represent the ultimate quality available for the OFT experiments.

Three of these rods exhibit a range of total absorption and scattering

which varies from a low value 0.3% (rod#2 at 800 nm) to a high value of

1.5% (rod #1 650 nm) of the flux measured at 850 °C.

Our experiments indicate that the scattering error is independent of

both temperature and wavelength and corresponds to about 0.1% of the flux

measured. We believe that we can confidently apply the results obtained

through room- temperature experiments to estimate the error due to

scattering at high temperatures. An estimated uncertainty of 5% in the

scattering correction contributes 70 ppm error in the gold to silver

freezing-point radiance ratio measured at 800 nm. (This uncertainty

corresponds to an error of about 6 mK in the difference between the

thermodynamic temperatures of the gold and silver freezing points.)

Our experiments indicate that the absorption error is dependent on wavelength and, unfortunately, tends to increase irreversibly with exposure

of the rods in air at temperatures of 1000 °C or above. As a consequence,

it will be necessary to continuously quantify the change in absorption of

each rod during the course of the OFT experiments. The correction for

absorption error is the largest of all and is also the most difficult to

estimate. At the present time, we consider the uncertainty in the

correction to be about 10%. For rod #2 at 800 nm this estimate contributes

300 ppm error in the gold to silver freezing-point radiance ratio. (This

uncertainty corresponds to an error of about 26 mK in the difference

between the thermodynamic temperatures of the gold and silver freezing

points.) To reach the 20 ppm target accuracy for OFT temperature

determination, the accuracy of the absorption experiments must be improved

and the technique for estimating the correction must be refined so that the

error in the correction is less than 150 ppm.

In August 1987, we will begin a joint experiment with the Radiometric

Physics Division to intercompare the NBS gold and silver freezing-point

standards used for resistance and thermocouple themometry with those used

for radiation thermometry. The measurements will be made using the NBS OFT

together with the NBS Spectroradiometer . In addition, we expect the

results to provide a value for the difference between the thermodynamic

temperatures of the gold and silver freezing points which is accurate to

50 mK.

In response to inquiries regarding calibration services for commercial

OFT'S, we are now prepared to provide "special" calibrations on IPTS-68,

which also include a limited evaluation of the absorption and scattering

characteristics of the probe.

48
I.B. HIGH-TEMPERATURE GAS THERMOMETRY

This project involves the evaluation of the differences between the

Kelvin Thermodynamic Temperature Scale (designated t) and the International

Practical Temperature Scale of 1968 (designated tgg). The region of

interest is 0 °C to 660 °C, connecting gas thermometry reported earlier

from NBS (L. A, Guildner and R. E, Edsinger, J. Res. NBS , 80A, 703, 1976)

with the range wherein spectral radiation thermometry can provide

equivalent thermometric accuracy. The resulting thermodynamic data will

provide the basic information needed to replace the tgg by a superior

temperature scale.

During the past fiscal year, we completed two types of new gas

thermometer measurements to complement those reported last year. One group

of new measurements was made using 0 °C gas-bulb filling pressures

substantially below the 13.5 kPa pressure that had been chosen earlier as a compromise between minimizing the uncertainty arising from the imperfection

of ^He gas and minimizing the uncertainty arising from thermal

transpiration in the gas -bulb capillary. In the new measurements, made

using 0 °C filling pressures of 10 kPa and 7 kPa, the thermal transpiration

corrections became as large as 0.1 °C; nevertheless, the t-tgg results

agreed well with those obtained earlier. All of the results obtained to

date are shown in Figure 1

.

A second group of new gas thermometer measurements re-explored the ttgg differences at two defining fixed points of the IPTS-68, the freezing

points of Sn (232 °C) and of Zn (420 °C). These measurements were

performed in order to further elucidate the small discrepancy discovered

earlier between the original measurements at 457 °C published a decade ago

by Guildner & Edsinger and the more recent ones that were obtained with

somewhat different apparatus. The results, also shown in Figure 1,

indicate that the discrepancy is approximately proportional to the Celsius

temperature

.

As we stressed in last year's report, the largest uncertainty in the

results shown in Figure 1 arises from the fact that the thermal expansion

of the gas bulb is not well known. During the past year, we have completed

the re-construction of a dilatometer that is capable of ppm accuracy at

temperatures as high as 700 °C. The apparatus is shown schematically in

Figure 2. Temperature homogeneity of the sample chamber is enhanced above

400 °C by the inclusion of a potassium-based heat pipe as a liner for the

electrically heated furnace. Preliminary tests indicate that the

dilatometer operates in a satisfactory way under either manual or computer

control. We have cut five pieces from the gas thermometer bulb used to

obtain the data shown in Figure 1, and dilatometric measurements on samples

prepared from these pieces are under way. Staffing for the project is now

reduced to one person, following the retirement of R. E. Edsinger.

49
Thermodynamic - T68

Deviation (®CJ

ro ® ^ o Ln o ui o (Ji

Figure 1. Differences between Kelvin Thermodynamic temperatures and

IPTS-68 temperatures (t-tgg) above 0 °C. Solid line--NBS Gas Thermometry

results of 1976. Diamond- -Basis value of -0.08 °C at 457 °C currently in use for radiation thermometry determinations at higher temperatures

(shorter dashes). Circles--current NBS gas thermometry results with

nominal filling pressure 13.5 kPa. Triangles- -New results with nominal

filling pressure 10 kPa. Squares--New results with nominal filling

pressure 7 kPa.

50
Figure 2. New Chennai expansion apparacus. H —HeaC pipe surrounding

a copper Cempering block and Che sample assembly S. B1 —Band-Cype heaCers

ouCside heac pipe. W- -Fused silica window for viewing sample. I--MerriCCSaunders Fizeau inCerferoraeCer apparaCus with film recorder for

inCerference fringes (F) . C--ConCrol ChermomeCer. T--PlaCinum resisCance

ChermomeCer Co indicaCe sample CemperaCure. The sample CemperaCure can be

sCabilized auComaCically wichin 0.001 °C of any CemperaCure from abouc

-20 “C Co 700 °C

51
I.C. HIGH-TEMPERATURE PLATINUM RESISTANCE THERMOMETRY

The purpose of this project is to test high- temperature platinum

resistance thermometers as a long needed and more precise replacement for

thermocouple thermometry in defining a practical temperature scale. It is

expected that such devices will be adopted in the definition of the 1990

temperature scale.

The retirement of J. Evans has seriously compromised this program. A

reduced program will still be conducted by other Division members as they

conduct other temperature scale studies (viz. Reilly on OFT and Mangum on PRT program)

.

52
II. INTERNATIONAL PRACTICAL TEMPERATURE SCALE (IPTS-68)

(B. Mangum, G. Burns, M. Scroger, W. Bigge, J. Wise, G. Evans,

E. Pfeiffer, and G, Furukawa)

I I . A . THERMOCOUPLES

These cover the range from 273 K to 2400 K; the thermocouple

laboratory is managed by G. W. Burns with the assistance of M. G. Scroger.

The activities fail into two categories: routine calibrations and non- routine tests.

1. Routine Calibrations

Approximately 220 thermocouples were calibrated for 100 customers

during FY 87 producing approximately $110K in test fees.

2. Non-routine Tests

a. Thermometry for Jet Engines

With support from the U.S. Navy Metrology Engineering Center, NBS

is now developing a calibration procedure for the Howell Instruments

BH14101-40 JETCAL heater probe. This probe was specifically designed to

test the thermocouple harness of T400-CP-400 and T400-WV-402 jet engines.

These engines are manufactured by Pratt & Whitney of Canada and are the

military version of the PT6T engine. The T400 engine is used in the Navy's

UH-IN helicopter which is produced by Bell Helicopter Company. The

thermocouple harness is manufactured by SEMCO Instruments, Inc. The probe

had been previously designated by the Navy as "difficult to calibrate," due

to lack of a reliable standard. This probe has an immersion depth of about

one inch and the specified calibration temperature is 900 °C.

During FY 87, candidate "standard" thermocouples of both Type K and

Type N were obtained from SEMCO. The thermocouples are enclosed in an Inconel sheath which is 18 inches in length. The location of the measuring

junction relative to the sheath end closure has the exact specifications of

the thermocouples in the T400 harness. Their length permits these

thermocouples to be calibrated directly in the existing NBS metal freezingpoint standards, as well as in the furnaces used for the NBS comparison

calibrations. A new T400 engine thermocouple harness, plus nine individual

engine thermocouple probes (for the PT6T-3 engine) which also have the same junction and sheath end closure specifications as those for the T400

harness were also acquired from SEMCO.

The calibration stability of the 18 inch long. Inconel sheathed. Type

K and Type N thermocouples were determined when they were cycled repeatedly

and rapidly between room temperature and 900 °C. In addition, such

thermocouples were calibrated by comparison with Type S reference

thermocouples and their repeatability was determined in the BH14101-40

heater probe. The calibrated thermocouples were fitted with an adapter to

53
provide proper immersion in the heater probe and ensure that the assembly

closely simulated the thermal loading of a T400 engine thermocouple. The

calibration repeatability of several PT6T-3 engine thermocouple probes was also assessed in the BH14101-40 heater probe.

b. ASTM Committee Work

To assist ASTM Committee E20.04.02 with developing a new standard

specification for Type N thermocouple wire, some additional emf stability

tests with Type N and Type K thermocouples made from 0.128, 0.064, 0.032,

0.020, 0.0126, and 0.010 inch diameter wire (No. 8, 14, 20, 24, 28,. and 30

AWG, respectively) were carried out in accordance with procedures specified

in Draft No. 4 of the proposed ASTM standard, E20-D-16. The emf changes in

Type N and Type K thermocouples were determined during heating in air for

24 hours at the upper temperature limits recommended by the ASTM for the

particular wire size (as described in section 5. 3. 4.

3

of the proposed

standard) . In addition, the emf changes of Type N and Type K thermocouples

of each wire size were determined when they were thermally cycled between

room temperature and 550 °C as described in Section 5. 3.4,

2

of the proposed

standard.

The emf changes in the Type N thermocouples of all six wire sizes

after heating them for 24 hours in air at their recommended upper

temperature limits were small and ranged from -5 to +37 microvolts

(approximately -0.1 to + 1 °C, respectively). The changes found for the

T3rpe K thermocouples ranged from +57 to +115 microvolts, depending on the

wire size and the test temperature.

A detailed report covering the test procedures and apparatus used and

giving the stability data obtained was prepared, and it was presented at

the ASTM Committee E20.04.02 meeting on May 14, 1987, in Cincinnati. The

test results were used to set and support the allowable emf changes

specified for such tests in the standard.

c. Evaluation of Ultrasonic Thermometer Probes

The calibration stability of several ultrasonic thermometer

probes made by Thermosonics , Inc. was evaluated in the 1000 to 2400 °C

range. Such thermometers operate on the principle that the velocity of

sound in a medium is a unique function of temperature. An electrical

exciting coil is coupled to a magnetos trictive rod and is used to produce

high frequency ultrasonic waves which travel down the length of a temperature sensing rod joined to the magnetostrictive rod.

Circumferential notches, which produce reflections of the acoustical waves,

are machined in the sensing rod at locations where the temperature

measurements are desired. By measuring the time between reflections and

correlating it to temperature, a calibration curve is obtained and used to

calculate values of temperature from reflection time measurements.

Temperature profiles can be easily measured with such thermometers by

locating several notches along the length of the sensor rod. Use of this

54
physical principle may lead to more reliable temperature measurements than

is presently realized by thermocouples for temperatures above 1800 °C in

harsh environments

,

The ultrasonic thermometer probes tested at NBS consisted of thoriated

tungsten sensor rods (1.6 mm diameter) with notches located at about 5, 9,

and 13 cm from the tip of the rod. The sensor rods were welded to 3.2 mm diameter magnetostrictive rods to give an overall probe length of about

90 cm. The sensor rods were protected within a tantalum sheath having a 6.4 nun outer diameter.

The ultrasonic thermometers were tested in helium-gas in a hightemperature calibration furnace. The thermometers were installed in a cylindrical blackbody. The temperature of the blackbody was determined

with a transfer- standard optical pyrometer developed and constructed by the

IMGC in Torino, Italy.

In this manner, the calibration stability of several ultrasonic

thermometers during thermal cycling at temperatures up to 2400 °C was determined versus the blackbody. Their calibrations were found to be

repeatable to within about 1/4% in the 1500 °C to 2400 °C range during

three successive cycles of the thermometers between ambient temperature and

2400 °C. The calibration stability of one ultrasonic thermometer probe was also determined during heating in helium for 24 hours both at 2000 °C and

at 2200 °C. The rate of change of the thermometer calibration was found to

be about 0.1 °C/h at 2000 and about 1 °C/h at 2200 °C. Post-test

examination of the thoriated tungsten sensor rod from this probe with an energy-dispersive X-ray analyzer revealed that it had become contaminated

by tantalum transferred from the protective sheath. This contamination may

explain the thermometer drift obser'/ed. Plans are under way to expand this

study by means of an Industrial Research Associate program.

II. B. PLATINUM RESISTANCE THERMOMETRY

The objectives of this program are: (1) to maintain the IPTS-68(75)

in the range 13 K to 904 K (the region of the scale in which the standard

instrument is the SPRT) ; (2) to make improvements in the realization of

that scale; (3) to disseminate the scale (through calibrations, precision

measurement seminars, MAPs, lectures, publications, interactions with

standards -writing organizations, etc.); and (4) to prepare for a new

International Temperature Scale.

The following table outlines the SPRT calibration procedure.

55
SPRT Calibration Procedure

13 K to 500 K Capsule SPRT's Calibrations by comparison

against reference standards

78 K to 904 K Long-Stem SPRT's Calibrations by comparison

against reference standards

at 90 K and by use of fixed

points (TP of H2 O and

FP of Sn and Zn)

.

In the future, capsule PRT's to be calibrated over the range from 13.81 K

to 273.16 K will be calibrated in the EPT-76 automated laboratory instead

of in the manually-operated cryogenic calibration system in the PRT

laboratory

.

The new semi-automated laboratory for long-stem PRT's and for capsule

PRT's for use above 90 K is still under construction.

Some specific accomplishments during this FY include:

(1) The documentation of the platinum resistance thermometer

calibration service was revised, put in a format for publication as a supplement to SP 250, and will be submitted to the Washington Editorial

Review Board (WERB) for publication by the end of FY 87.

(2) Tin and zinc fixed-point cells are used in the calibration of

SPRT's and since there was a critical shortage of these in the PRT

Laboratory, several new cells of each were constructed. There are 9 new

cells (7 for long-stem and 2 for capsule SPRT's) of tin and 7 new cells of

zinc, filled with 99.9999+ % pure metals (SRMs 741 and 740, respectively).

The new Sn cells were tested during the past year and the testing of the Zn

cells will be completed next year. A paper will be written next year on

the results of the tests of the Sn and Zn cells.

(3) A new apparatus, incorporating an argon triple-point cell, that

is to be used in the calibration of long- stem and capsule SPRT's has been

under construction by the NBS shops as money was available. This apparatus

will accommodate 7 long- stem SPRT's and 6 capsule SPRT's. When

construction of this apparatus is completed and it has been tested, it will

replace the comparison apparatus currently used at the oxygen point.

(4) A grand total of 70 SPRT's were calibrated by the end of July of

this year and 17 are on hand awaiting calibration. The fees for these 87

SPRT's amount to $142,343.00.

56
During the calibrations of these SPRT's, further comparisons were made

between the manually-operated Guildline dc Current Comparator Bridge and

the automatic Cutkosky dc-Pulse Bridge in preparation for automation of

the measurement and analysis processes in the calibration of SPRT's.

(5) The contract with the Navy (of CCG) for the NBS to evaluate the

"best" commercial IPRT's (i.e., non-SPRT's) at temperatures from 0 to

650 °C was completed and a report written.

(6) Two Ag cells, one belonging to NBS (PRT laboratory) and one to

IMGC (Italy) , were compared directly in heat pipe furnaces moved into and

put into operation in the PRT laboratory. This gave us considerable

experience in handling and making measurements on HTPRT's at the Ag

freezing point (962 °C) and with operating heat pipe furnaces. The NBS cell

(Ag-79-1) appears to be significantly purer than the IMGC cell (Ag Lei 3).

Analysis of the data is in progress.

(7) A contract with the Navy (of the CCG) for the NBS to evaluate

several resistance bridges designed for use with SPRT's was completed and a report written. Four types of bridges were investigated, an F-18 from

ASL, an ATB 1250 from Neil Brown Instrument Systems (EG6cG) , and the two

types of Cutkosky automatic bridges from NBS. A brief report on the ac-dc

effect as measured at NBS was written also to the CCG.

(8) A fixed point at the melting point of indium is urgently needed

for calibration of capsule SPRT's, to provide a more accurate calibration

of long-stem SPRT's for the most accurate and precise work needed in

research, and to provide a check on the routine calibration of SPRT's.

With this in mind, we have been making a thorough investigation of the

indium melting/freezing behavior and of the reproducibility of the

melting/freezing-point temperature. We have two large cells of indium,

filled with 99.9999% pure indium, the cells being of sizes sufficient for use with long-stem SPRT's and capsule SPRT's. Each cell contains 1500 g of

indium encased in a Teflon inner container located in a stainless steel

outer container. These cells will be used in a furnace, currently being

constructed, in the PRT Calibration Laboratory to provide a freezing point

to be used as a check point in the routine calibration of SPRT's. Data

obtained on these cells are currently being analyzed and it is expected

that a paper describing the results of the investigation will be written

during the next year. Preliminary results indicate the pressure dependence

of indium to be 4.95 ± 0.05 mK/std. atm. and the freezing-point temperature

to be 156.6341 °C.

(9) The components for a furnace designed for use with the indium

cells described in (8) have been constructed and are currently being

assembled. When completed, the furnace will be installed in the PRT

Calibration Laboratory for use in routine calibrations of SPRT's.

57
(10) Some furnaces used for pre-heating SPRT's close to the

temperatures of calibration prior to their insertion into freezing-point

ceils are currently being constructed.

II . C . LABORATORY THERMOMETERS

Approximately 760 liquid- in-glass thermometers and 11 thermocouples

were calibrated by Ms . J. Wise. The number of additional thermometers

calibrated as special tests, including thermistors, industrial platinum

resistance thermometers and digital thermometers, was approximately 60.

J. Wise participated in the Precision Thermometry Seminar and

continued to work with ASTM as Secretary of Committee E-20, Thermometry.

She is also Secretary of Subcommittees E-20. 90, Advisory, and E-20. 05,

Liquid- in-Glass Thermometers and Hydrometers. J. Wise serves as a member

of ASTM Subcommittees E-20. 91, Editorial and Nomenclature and E-20. 08,

Medical Thermometry. In recognition of her service to the ASTM, Ms. Wise

received the ASTM Order of Merit and was made a Fellow of the ASTM.

A more efficient system of taking data for industrial grade platinum

resistance thermometers, using a digital voltmeter and constant current

source instead of a high resistance bridge, was developed.

The documentation on the calibration of liquid- in-glass thermometers

is being refined for publication.

58
III. LOW TEMPERATURE SCALE

(E, Pfeiffer, J. Schooley, J. Colwell, H. Marshak, W. Bowers,

and W. Fogle)

This project is divided into two parts: (1) the temperature region

covered by the EPT-76 (0.5 K -30 K) and (2) the region below 0.5 K covered

by the temperature scale NBS-CTS-1 (0.010 K - 0.5 K)

.

III. A. EPT-76: TEMPERATURE SCALE

As has been described in previous annual reports, the EPT-76

temperature scale has been realized by E. R. Pfeiffer. He has completely

"wrung out" the system and is preparing an NBS Journal of Research article

describing the system.

Calibrations on EPT-76 requested this FY were deferred to FY88 to

allow E. Pfeiffer to devote full time to emergency preparation and testing

of Zn and Sn freezing point cells urgently needed for the platinum

resistance calibration laboratory; and for a comparison of NBS and IMGC

silver freezing point cells.

III.B. EPT-76: SUPERCONDUCTING FIXED POINTS

SRM 767a contains six metallic samples (Nb, Pb , In, Al , Zn, and Cd)

.

The transitions between the normal and superconductive states of those

samples provide reference temperatures that are reproducible within

± -0.3 mK. The devices are used in thermometer calibration laboratories

and by individual scientists for the calibration of thermometers below

10 K.

Because of time distractions (editing of ASC-86 Proceedings and HighTemp Gas Thermometry) there was no activity in the SRM 767a project during

FY 87.

III.C. NBS-CTS-1

This scale, developed at NBS and distributed worldwide via SRM 768,

does not have international sanction. Research along parallel lines at

other national standards laboratories (KOL; PTB-Berlin; Helsinki) should

bring confirmation and the possibility of adoption of a provisional

international temperature scale from 1 mK to 500mK by the CCT when the next

scale is formulated. A brief position paper was submitted at the CCT

meeting in June. The general outline of this paper, that of using two

absolute thermometers (noise and nuclear orientation) to define the

pressure- temperature curve of the melting curve of ^He, was accepted by the

CCT. Intercomparisons among national standards labs would be conducted by

a round robin using special SRM 768 units. The NBS program adds to this

the use of a pseudo- thermodynamic thermometer- - the nearly ideal

paramagnetism of cerium magnesium nitrate (CMN) . Progress is the four

thermometer- areas this year is given below.

59
1 . SRM 768

Ten regular SRM 768 units were assembled, measured and prepared for

customers. This will still leave a backlog of two for FY 88.

Since NBS is to be the hub of a round robin using SRM 768 to

intercompare cryogenic temperature scales, three special SRM 768 units

(each contained in shields of cryoperm-10 and Nb) were constructed. One

has been tested twice, the others will be studied in FY 88.

2. CMN Thermometry

A CMN thermometer was designed and constructed last FY. This past

year, an auxiliary gas handling system and a SQUID susceptibility bridge

were built and tested by J. Colwell and W. Fogle. The complete system will

be ready for testing in September 1987. A theoretical analysis of the

expected response time and sensitivity of the CMN thermometer was conducted

by W. E. Fogle.

3. ^He Melting Curve Thermometry

As was reported last FY, two melting curve thermometers were tested.

One performed very poorly (very unstable) , while the other exhibited almost

all the qualities needed (it was deficient on long-term stability).

Therefore, this FY, a more robust device was tested in three thermal

cycles. To its examiner's (J. Colwell) disappointment, it too exhibited

instabilities. More rigorous tests were developed and applied to

quantatively characterize the instabilities.

4. Noise Thermometry

The major advance this year was the demonstration (R. J. Soulen, D.

Van Vechten, Phys . Rev., August 1987) that a very accurate, physics-based

model applies to the measured impedance of the R-SQUID which forms the

noise thermometer. The same model has been adapted to predictions of the

noise of the same circuit, and an experimental study to verify this model

is underway. Sufficient confidence in the model already justifies its

comparisons to the nuclear orientation thermometer (see III. A. 4 below),

5. Nuclear Orientation Thermometry

a. The computer based data acquisition system has been programmed

for use with the ®°CoCo(sc) thermometer. It, along with programs written

in DATAPLOT for the NBS-(CS)^ system, have been used in a preliminary

comparison experiment with the noise thermometer. Results in the

temperature range from ~7 to -23 mK show that the two thermometers disagree

systematically by about 0.3%. Further measurements are planned to resolve

this discrepancy. In addition, in two separate series of measurements the

®°CoCo(sc) thermometer reproduced the published value for the tungsten

superconducting transition temperature to within +0.1%; namely, +0.09 and

60
0.04%. However recent re-evaluation of the noise temperature data may make

the agreement slightly worse.

b. A systematic series of measurements was conducted in order to

determine the magnitudes of several temperature gradients between the

nuclear orientation thermometer and the main thermometer platform (i.e.,

gradients between the thermometer and copper mount, along the copper rod, across the screw connection between the copper rod and copper platform)

.

These results are very important for users of nuclear orientation

thermometers, to the NBS program and to users of copper rods and joints for

low temperature experiments (almost everyone in the business) . The results

are available as a contract report from W. Fogle.

c. The NATO supported collaborative [Dr. G. Eska (West Germany);

Prof. B. G. Turrell (Vancouver, Canada); Dr. R. M. Mueller, (West Germany);

and H. Marshak (NBS)] experiment to measure the A- transition in ^He (one

of the proposed fixed points for the melting curve) using nuclear

orientation thermometers has been delayed due to the relocation of Dr. Eska

to a professorship at Bayreuth University, Bayreuth, West Germany. He has

obtained a new high powered ^He/^He dilution refrigerator for his

laboratory and will be adding a large nuclear cooling stage to it in the

very near future. It is expected that the measurements at the A- transition

will be carried out on it in the next year. In the meantime we have added

a small nuclear cooling stage to Prof. Turrell' s dilution refrigerator in

Canada in order to perform an NMR/ON measurement on ^®^ReNi. At the

completion of these measurements we will be able to use it for absolute

nuclear orientation thermometry in the temperature region of -0.5 to -5 mK.

d. The collaborative (NBS - Freie Universitat Berlin - Bonn

Universitat) research work on the low temperature magnetic properties of

the rare earth system consisting of radioactive ^®°Tb in ^^^Tb single

crystals (sc) has again had a very productive year. In Berlin, we were

able to perform a nuclear double resonance experiment on this system. This

was the first successful double resonance measurement made on an oriented

nuclear spin system. As pointed out in last year's report, the terbium

single crystal system is very interesting in that, in addition to having a very large nuclear magnetic dipole interaction, it also has an extremely

large electric quadrupole interaction. The effect of the latter is to

split the single dipole resonance line into widely spaced subresonances.

The lowest subresonance i^2 (^^^^^itions between the m^ = +3 and the mj = +2

substates) was observed for the first time by us last year. Since at low

temperatures only the lowest magnetic substate (mj = +3) is appreciably

populated, observing the second subresonance (transitions between the

mj = +2 and the m^ = +1 substates) would be very difficult by standard

Nuclear Magnetic Resonance on Oriented Nuclei (NMR/ON) techniques.

However, by saturating the first subresonance (irradiating with rf of

frequency we were able to considerably enhance the population of the

mj = +2 substate. We then simultaneously irradiate with rf to obtain the

value 1/2 of the second subresonance. By measuring both of these

subresonance frequencies we were able to deduce precise values for both the

61
dipole and quadrupoie interactions in this system. The results of this

nuclear double resonance experiment was submitted to Physical Review

Letters for publication.

The above results along with magnetization measurements currently

being conducted here at NBS enable this terbium single crystal system to be

used for absolute nuclear orientation thermometry in the temperature range

of 10-125 mK. In the following figure we show the sensitivity functions

the ®°CoCo(sc), ^®^“HoHo(sc) and the ^®°TbTb(sc) nuclear orientation

thermometers. These three nuclear orientation thermometers cover the

region from -2 to ~1000 mK. Whereas the ®°CoCo(sc) and ^®°TbTb(sc)

thermometer are absolute in that the energy separations of their hyperfine

levels have been measured by NMR/ON, no NMR/ON measurement has yet been

carried out on the ^®®“HoHo(sc) thermometer. The energy separation of its

hyperfine levels have been measured Indirectly by calibrated resistance

thermometers, thus it remains a secondary thermometer.

A paper entitled "^®°TbTb(sc) : A New Absolute Nuclear Orientation

Thermometer for Use in High Magnetic Fields" will be presented at the XVIII

International Low Temperature Conference in Japan.

e. In addition to the two collaborative efforts mentioned above, a third,

and much smaller collaboration, is being carried out with a nuclear physics

group at the Los Alamos National Laboratory (see publications).

62
(i/ie)/(i‘o)Me

63

Figure

3.

Sensitlvicy

of

three

nuclear

orientation

(Tb,

Co,

Ho)

thermometers

versus

temperature.
IV. MEDICAL THERMOMETRY

( B . W . Mangxun and G . Evans

)

The goal of this program is to develop a set of temperature fixed

points and a means of using them to calibrate transfer standards for the

temperature region of interest (0 - 200 °C) to the medical community.

The following table outlines the temperature fixed point program.

Medical Temperature Fixed Points

Material Tf rc) Status

Indium 156.635 ± 0.002 SRM 1971

100 cells tested.

Succinonitrile 58.0805 ± 0.0015

Phenol

n-Lauric acid

n-Docosane

Rubidium

Ethylene carbonate

Gallium

40.92

43.95

43.89

39.303 ± 0.005

36.3238 ± 0.0004

29.772 ± 0.001

SRM 1970.

115 cells tested.

RSI article published.

NBS J. Res. paper

published.

SP 260-101 published.

Under study.

Unde r s tudy

.

Under study.

SRM 1969.

Article published

in TMCSI.

SP 260-87 published

Alternative to Rb

.

Paper published in

Metroiogia.

SRM 1968.

Several papers published.

Specific accomplishments this FY include;

(1) There is a special (even critical) need for two fixed points

bracketing the hyperthermia range used in cancer therapy. Those two points

64
should be at about 41 or 42 °C and 44 or 45 °C. Several materials have

been selected as possible candidates for those temperatures, and small

cells of phenol, n-lauric acid and n-docosane have been obtained for study.

Their freezing/melting behavior has been investigated and, although all

three of these materials look promising, n-lauric acid has been found to be

much more difficult to purify than n-docosane. Consequently, we have

chosen phenol and n-docosane as the materials for the two fixed points.

More cells of phenol and n-docosane have been ordered for a proper

investigation of their stability, reproducibility of their freezing-point

temperature from freeze to freeze, and the dependence of the freezing-point

temperature on impurities. The National Cancer Institute is now funding

some of this work.

(2) The investigation of the melting/freezing behavior of highpurity indium in small Teflon cells conducted previously showed the

feasibility of using this point (and realized in such small cells) as a temperature fixed point, and as an SRM. During FY 86, the NBS instrument

shops constructed 100 cells appropriate for the indium SRM (SRM 1971).

Those cells were filled with 99.9999+% pure indium, sealed under an atmosphere of dry argon, and 50 of them were tested for suitability to serve as SRM 1971 by about the end of September 1986. The remaining 50

cells were certified during the past year, a certificate written, and the

SRM made available for purchase.

65
V. DYNAMIC PRESSURE AND TEMPERATURE

(G. Rosasco, W. Hurst and R. Dove)

Goal

:

The goal of this project is to develop the means of measuring P and

T with high temporal response (10 ns) and high spatial resolution (mm^ ) . A

laser diagnostic technique based on nonlinear optical spectroscopy is used.

Specifically the project is designed to develop the algorithms for

inferring P and T from spectral lineshapes and intensities. A second goal

is to accumulate reference data and develop predictive theory for selected

gases of importance in diagnostic applications.

Accomplishments FY 1987:

Q-branch line broadening in hvdrogenic molecules:

A manuscript has been prepared which presents our analysis of the J

and collision partner dependence of the line broadening of the D2 isotropic

Q-branch for seif-broadening, and with the collision partners H2 , He, Ar,

and CH^ . This work, sximmarized briefly in last year's report, involves the use of an exponential gap law to describe the rotationally inelastic

portion of the line width and the determination of the contribution of

elastic vibrational dephasing (assumed independent of J) for the various

collision partners. Recently, our collaborators at the Johns Hopkins

University Applied Physics Lab, have verified our findings for the case of

D2 :He. Their calculation, a first principle close-coupling calculation

using an accurate ab Initio intermolecular potential, results in line

broadening coefficients within 5-10% of our measurements, and more

importantly, very good agreement (10%) with our estimates of the

contributions of rotational inelasticity and elastic vibrational dephasing.

The importance of elastic vibrational dephasing in the hydrogenic systems,

in particular for self-broadening, has only recently been realized.

Dr. K. C. Smyth, NBS Center for Fire Research, collaborated in this work.

A manuscript describing our measurements and analysis of line

broadening and shifting in the Q-branch of self-broadened HD also has been

prepared. The very large contribution from rotationally inelastic

collisions is analyzed by use of an exponential gap law. Comparisons can

be made in the case of HD with direct measurements of rates of rotational

energy transfer and with the results of other line broadening measurements.

Very good consistency is found in these various comparisons under the

assumption of a vibrational-state dependent rate for rotationally inelastic

collisions. In this analysis we find a rate in the first-excited

vibrational state which is approximately 30% larger than that in the ground

state. We note that a similar degree of vibrational state dependence is

found in the theoretical calculation, discussed above, on D2 :He. There is

a large number of first principle calculations available for the HD:HD

system. Our work, which agrees well with only one of these, should serve

as a critical test of theory for this well-known, long-studied system.

Prior experimental data were far too inaccurate to allow significant tests

66
of theory and intercomparisons of line broadening values such as those

discussed above. Dr. Smyth, Dr. A. D. May, U. of Toronto, and Dr. L. B. Petway, Howard U. collaborated in this work.

The study of the effects of simultaneous velocity and phase change

upon collision has continued this year with an experiment on D2 ;Ar up to

~34 atm. As described in last year's report, our measurements on D2

:

D

2 revealed an additional weak-component in the Q-branch spectrum which

'collapsed' into the strong central peak at higher densities, i.e.,

-15-20 amagat. This component was easily discernable in the Q-branch of

pure D2 only in the region 2.5-12 amagat. A two- line model was employed to

fit the D2 spectra which resulted in a correction, a 2-3% narrowing, of the

strong- component in the spectra. This narrowed component extrapolated

accurately to predict the high density (-20 amagat) single Lorentzian

lineshapes. In an attempt to further understand the source of this extra

component in the D2 spectrum, we extended our study to the D2 :Ar system, in

which the extra component is almost a factor of two more intense than that seen in pure D2

. The analysis of the experimental data is not yet complete;

however, we have seen definite evidence of a nonlinear density dependence

in the line broadening at densities above -18 amagat. This nonlinearity,

although small, i.e., of the order of 2%, can readily be extracted from our accurate line width determinations. The preliminary indications with

respect to the extra component are that it is collapsed into the main peak

at densities above -11 amagat, and that the corrected central peak will

extrapolate smoothly (nonlinearly with density) into the high density

linewidths. The high density spectra have single Lorentzian line shapes to

within our ability to measure them, i.e., down to the 1% of peak intensity

level

.

An experimental program to determine the effects of velocity and phase

changing collisions on the Q-branch spectrum of H2 has been initiated.

Self- and foreign gas broadening (with Ar) has been studied at room T, and

self-broadening measurements have been extended to 1000 K. These are the

first high accuracy linewidth studies of H2 above room temperature. In

this work, we also are interested in deviations from conventional theories

similar to those discovered in the case of D2

. No definite conclusions can

be presented at this phase of the research. This work is part of our ARO

contract

.

Application of exponential gap laws to predict Q-branch spectra:

A manuscript has been prepared which presents our results and analysis

of the J and temperature dependence of the Q-branch line broadening

coefficients of pure CO. A modified exponential gap law for the

state- to-state rates of collision- induced rotational energy transfer is

shown to account for the J (to J = 38) and T dependence (to 1500 K) . This

law, when combined with a full relaxation matrix based theory for the

Q-branch spectrum, gives reliable spectral predictions for the partially

collapsed, 1 atm spectra up to 1500 K. This work, the experimental

portion of which was conducted at the Combustion Research Facility at

67
Sandia National Labs in Livermore, CA, is the result of a collaboration

with Drs . L. A. Rahn and R. E. Palmer and involved our summer student

employee, Sharon Dohne

.

An experimental study of the collapse of the

temperatures is currently in progress. This is a collaboration with the Sandia staff under our ARO

CO Q-branch at high

continuation of the

contract

.

68
VI . PISTON GAGES

(V. Bean, G. Driver, W. Markus, B. Welch, and J. Houck)

Goal : The piston gage is the standard instrument for precise pressure

measurements in the range above the limits of manometry. The instrument

consists of a carefully made piston fitted into a matching cylinder which

is, in turn, connected to a pressure generating system. The piston is

loaded with measured weights, floated by adjusting the cylinder pressure

using a transmitting fluid, and rotated to relieve friction and to assure concentricity. The pressure is calculated as the ratio of the downward

force, due to the weights and the piston, to the effective area of the

piston-cylinder combination. Our goal is to determine the effective area

at atmospheric pressure , and the change in the effective area with

pressure, with an accuracy sufficient to; (A) provide American piston gage

manufacturers with the needed calibration services to keep their products

competitive in the world market; (B) meet the need for increased accuracy

requested by our calibration service customers, such as the DoE and DoD

laboratories; (C) participate effectively with other national standards

laboratories in setting international standards for pressure calibrations.

Commercially available gages span the range from 2 kPa to 1.4 GPa and

may be designed for use with gases or condensed fluids in appropriate parts

of the range.

Accomplishments During FY 87

A. Calibration Services

By the end of FY 87 we expect to calibrate 110 units for an income of

$180 K, a 50% increase over last year.

B. New Primary Standard for the Gas Calibration Service

We expect to reduce the measurement uncertainty of our gas calibration

service to 10 ppm by changing the primary standard from a controlledclearance piston gage to manometry. The first experiments were conducted

with the gas thermometer manometer which is capable of an uncertainty of

2 ppm over its range. Four carefully characterized piston gages, two made

of tungsten carbide and two of steel, have been calibrated using the

manometer with both helium and nitrogen at 3 pressures in the absolute

mode. A piston gage measures the difference in pressure at each end of the

piston. When the top of the piston experiences ambient atmospheric

pressure, the gage is operating in the gage mode. For the absolute mode,

the space at the top of the piston is evacuated.

These calibrations have been carried out three times: in 1983, 1984,

and 1986-87. The data of 1983 and 1984 were contaminated by faulty

equipment and by electrostatic forces generated within the piston gages.

These problems have all been corrected. We believe the 1986-87 data to be

valid. The two tungsten carbide gages are exceptionally well-behaved and

69
are being used to calibrate the gages used in the calibration service. The

repeatability and the independence of the area on the pressure for these

two gages is very satisfactory. The standard deviation of from a constant value is 1.3 ppm for the worst case.

There is one issue to be resolved before we incorporate these results

in the calibration service. These measurements were done in the absolute

mode. The calibration service operates, however, in the gage mode. By cross -floating pairs of these gages we have noted relative changes in the

apparent area between the gage and absolute modes as large as 23 ppm at one atmosphere using nitrogen. We believe the tungsten carbide gages are essentially free of the gage/absolute effect and that it is due primarily

to imperfect geometry of the steel pistons. This hypothesis needs to be

proven. Unfortunately, the gas thermometer manometer was not designed to

operate in the gage mode and would not be useful for this purpose without

extensive modifications. The study will be continued using the ultrasonic

interferometer manometer (see Section VII) which is more amenable to gage

operation. While its present accuracy does not match that of the gas

thermometer manometer, we believe it has sufficient stability and

sensitivity to resolve the gage/absolute question.

As part of our program to reduce our uncertainties, we have

established a mass measurement capability up to a maximum of one kilogram.

Preliminary data from a MAP with Division 523 indicate that our uncertainty

in measuring piston gage weights will be less than 0.1 ppm.

C. Basic Research on Gas-Operated Gages

The gage/absolute effect mentioned in Section B is a function of the

pressure, the gas, and the clearance between the piston and the cylinder.

To explore the physics of this effect, we have built an apparatus to

measure the change in gas density in the annular space between the piston

and the cylinder as a function of the piston engagement length of an operating piston gage. We will use several gases in both the gage and

absolute modes. The apparatus has been completed and demonstrated to work

well. We expect to begin the detailed studies in the near future.

D. Distortion of Piston Gages at High Pressure

The key to correctly calculating cylinder distortion with pressure is

to know the pressure in the annular space between the piston and the

cylinder as a function of piston engagement length. We have shown earlier

that this pressure profile can be calculated from the measured clearance

between the piston and cylinder. As the measurements available from

Division 731 are not adequate for our needs, we have developed our own capability to measure the changes of diameter as a function of length for

both cylinder bores and pistons. The apparatus has nanometer resolution

and better than 25 nanometer reproducibility. Figure 4 is a plot of the

diameter of the bore of a piston gage cylinder as a function of its length.

With this new capability, we will now be able to obtain the dimensional

70
Cylinder

bore

diameter,

Figure 4. Measured cylinder bore diameter plotted as a function

of cylinder length. The triangles represent measurements by

Division 731.

data needed to test theoretical results with the extensive measurements we have made of cylinder distortion.

E. High Pressure Standards

To meet the needs of the increased calibration workload we have had to

rob manpower from our high pressure program which has slowed our progress.

The parts for the new 280 MPa standard are all available but the gage is

yet to be tested. The new 700 MPa standard has been tested and works very

well. More work is needed to complete the characterization. The InSb

transducer has been demonstrated to have sufficient sensitivity to

determine the cylinder distortion coefficient of a controlled-clearance

piston gage at pressures as low as 70 MPa. It is expected to greatly

expedite the characterization of controlled-clearance piston gages and to serve as a transfer standard in the 700 MPa pressure range.

F. Pressure Fixed Points

Pressure fixed points are valuable not only for laboratory

intercomparison but also as an invariant against which standards can be

71
compared as a function of time. Two pressure fixed points have been

studied by Dr. Noel Bignell, a Guest Scientist from CSIRO, Sydney,

Australia; the CO2 vapor pressure at the temperature of the triple-point

of water, about 5 MPa; and the ice Ih-ice III- water triple-point, about

200 MPa.

Purity of the CO2 proved to be a major concern. The most consistent

measurements were on samples prepared by ourselves by heating NaHC03 and

passing the CO2 through three separate drying systems.

The experimental work is now finished on both materials and the data

are currently undergoing analysis.

72
VII. VACUUM AND LEAKS

(S. Dittmann, C. Ehrlich, A. Filippelli, R. Hyland, F Long,

D. Martin and C. Tilford)

OVERVIEW

This group develops standards, addresses instrumentation and

measurement problems, and provides services over 14 decades of pressure

from 350 kPa to below 10'® Pa, and four decades of flow (leaks) from 10"®

to 10'^^ moles/sec. (Note: 1 atm = 15 psi = 100 kPa, 1 Torr = 133 Pa, and

1 mole/sec = 2 x 10^ std cc/sec). This large range encompasses a great

deal of diversity. State-of-the-art uncertainties range from a few ppm to

factors of two or three. Instrumentation varies from the strictly

mechanical and very simple piston gage to complex electronic mass

analyzers. Applications include air transportation, food processing,

nuclear materials handling and fabrication, and semiconductor processing.

Reflecting this diversity, the activities of the group are divided into

four areas: Manometry, High Vacuum, Ultra High Vacuum, and Leaks. These

areas cooperate closely: Equipment and facilities are shared, standards in

one area are supported by calibrations from another, and personnel may move from one area to another as needed. In particular, leak standards use both

the techniques and equipment developed for high vacuum standards.

Richard Hyland is primarily responsible for manometry, although he

spends a significant amount of time on leak standards. Sharrill Dittmann

(formerly Wood) is responsible for High Vacuum, Albert Filippelli for Ultra

High Vacuum, and Charles Ehrlich for Leaks. Donald Martin provides

mechanical and technical support, Fred Long electronic support, and Charles

Tilford overall coordination. Bruce Dove, who provided part time technical

support, retired this winter. We have enjoyed the assistance of A. K.

Gupta and D. R. Sharma, Guest Scientists from the National Physical

Laboratory, India; Chris Sutton, a Guest Scientist from the Physics and

Engineering Laboratory, New Zealand; and Rodney Ray, a summer student from

Butler Community College.

The activities of the group are summarized below and detailed in the

following "area reports."

More effort was placed in the manometry area than in previous years.

The primary standard is the NBS-developed Ultrasonic Interferometer

Manometer (UIM) . A new design extending the range to 350 kPa (50 psi) was finished and evaluation begun. Several significant problems have been

encountered but, as of this writing, the instrument works over its entire

range and its low pressure performance is within a factor of two or three

of the existing UIM. Use of the new speed of sound values and several

changes have reduced the uncertainty for the present UIM to between 12 and

18 ppm, making it the most accurate pressure standard directly available to

NBS calibration customers. Our confidence in this uncertainty has been

strengthened by the agreement, to better than 1 ppm, of the recalibration

73
of a gas-operated piston gage with a previous calibration by the UIM in

1983/84. A systematic effort is being made to understand several

troublesome problems with gas-operated piston gages. This will include an evaluation of the dependence of piston gage effective areas on gas species

in both the gage and absolute modes of operation. Comparisons with the

piston gage standards of India and New Zealand will contribute to this

effort. An experiment to measure the triple point pressure of argon and to use it as a check or transfer standard is being set up in collaboration

with Chris Sutton.

The transition range (1 to 10'^ Pa) between the manometry and high

vacuum standards has been and is a troublesome gap in our standards. This

past year we have been able to make a preliminary comparison in this range

of gages calibrated by our two different standards. These results are not

optimum, being based on extrapolations of the calibrations, but do not

indicate any significant differences between the standards.

The rapid rise in the number of high vacuum calibrations experienced

in the last few years has leveled off, but the workload remains high.

Construction of a new high vacuum calibration chamber has again been

deferred because of uncertainty about an ultra high vacuum standard.

Significant progress has been made in automating both the operation of the

standard and data analysis. Satisfying agreement with vacuum standards at

the other major national labs is evident in a recently completed

international round-robin.

The Ultra High Vacuum program has had to face the "chicken and egg"

problem of simultaneously developing primary standards and evaluating

instrumentation. Several unexpected results were obtained in the initial

evaluation of UHV ion gages but it became clear that these results are consistent with observations at several other laboratories. This work will

continue along with an increased emphasis on residual gas analyzers. We

now believe that the quickest way to obtain an operational UHV standard

will be to obtain gage sensitivities by an extension of the technique used

in the current high vacuum standard, and independently determine gage

residual currents or "zero offsets." Towards this end, experiments are currently underway to evaluate the performance of the high vacuum standard

between 10"® and 10" ® Pa and to reduce the base pressure of the UHV

chamber

.

A significant effort has been required to get the new special test

service for leaks operating in an efficient manner. A major part of this

has been problems with the "standard" leaks submitted for testing, ranging

from dirty artifacts to a generic design fault. Previous experience with

new calibration services should have led us to expect this. Experiments

during this past year have given us a much better understanding of the

basic processes governing the behavior of helium diffusion leaks.

As our program has grown and is better known, the amount of time spent

on outside contacts and services has steadily increased. Much of this

74
benefits us as well as the user. Considerable time has been spent

organizing three workshops this year on UHV gages, the spinning rotor gage,

and leak measurements, but the two held so far have more than returned our efforts. Similarly, the increased time spent preparing and delivering

talks has been compensated by a broadening of our experience and contacts.

It is difficult to extend this corollary to calibration services. These

clearly are of value to the user, they pay dearly for them. But they do

take up increasing amounts of our professional staff time. This year we will bill about $75,000 for calibrations, about one staff year. This, and

a nontrivial load of internal calibrations, are all performed by master and

doctorate degreed staff. While the instrumentation and procedures tend to

be complicated, much of it is becoming "routine" or automated to the point

that significant professional staff time could be freed if calibration

technical support were available.

VII. A. MANOMETRY

Introduction

The 160 kPa ultrasonic interferometer manometer (UIM) was developed to provide continuous pressure measurements over an absolute or differential pressure range from 1 to 1,5 x 10^ Pa. Its design and

performance, along with the capabilities of the calibration service,

have been constantly upgraded. With the incorporation of the new speed of

sound data, the UIM now provides calibrations with an absolute accuracy

which is between 12 and 18 ppm, depending on the pressure, with a precision

of 0.015 Pa.

Calibrations are routinely done for the aerospace, pharmaceutical, and

semiconductor processing industries, as well as for various government

standards laboratories.

The capabilities of the UIM make it invaluable as a research tool as well, and it is being used to calibrate transfer standards for an ongoing

international laboratory intercomparison over the pressure range from 0.15

to 1500 Pa, evaluate the performance of gas operated piston gages, and

measure the argon triple point.

FY 1987 Activities

Data reduction for the international intercomparison in the .15 to

1500 Pa pressure range is nearly complete. Preliminary results indicate

acceptable levels of agreement between NBS , NPL-Teddington, CSIRO-Sydney

,

and PTB-Berlin, with a slight systematic offset from the latter.

The experiments to determine the effect of helium on the calibrations

of differential quartz helix bourdon gage pressure transducers had been

thought complete. However, based on the time constants associated with

helium permeation leak artifacts, it may be necessary to wait longer times

before any effects are seen, and one more set of experiments is planned.

75
The UIM was upgraded during the past year by the recalibration of its

platinum resistance thermometers and the addition of a seventh thermometer.

The software was modified to incorporate the new speed of sound values and

eliminate an occasional problem with the ultrasonic data acquisition

discovered during the speed of sound experiment. Other minor changes

necessary to achieve the accuracies discussed in the introduction have been

incorporated.

Work done in 1982, 83, and 84 suggested that the UIM might provide an alternative method for the calibration of low-range piston gages.

Experiments during that period led to the determination of effective areas

of one of the gages used routinely in the piston gage calibration service

with a standard deviation of 1.4 ppm. After the upgrading of the error

budget of the UIM and accounting for the new speed of sound data discussed

in last year's report, another round of piston gage experiments has been

initiated. The new average effective area for the same piston gage tested

three years ago agrees with the old value to within 1 ppm, although the

standard deviation has doubled. This experiment, although preliminary in

nature, indicates excellent long term stability for the UIM and this

particular piston gage. The results will also be part of an upgrade of the

error analysis for the UIM.

The capacity to accurately calibrate piston gages will be used to

compare piston gage calibrations in the pressure range from 10 to 160 kPa

with NPL-New Dehli and DSIR-Wellington. These intercomparisons are unde rway

.

A program has been initiated in conjunction with a guest scientist, C.

Sutton of the DSIR-Wellington, to measure the triple point pressure of

argon and develop portable triple point cells as check or reference

pressure standards.

For-fee calibrations were done this year on 18 capacitance diaphragm

gages. Calibrations also included the continued monitoring of a quartz

bourdon tube gage which is used as a transfer standard for the calibration

of altimeter setting indicators for FAA facilities. In addition,

calibrations and preliminary evaluations of an air data systems calibration

unit were done for the Navy Engineering Metrology Center. This exercise

also served as training for the Navy personnel who will operate one of the

2.8 meter UIM's being constructed here at NBS

.

The 2.8-meter (350 kPa) UIM's are the next extension of the UIM

technology. One of the 2.8-meter UIM's has been assembled, and coupled to

the new electronics. It has been demonstrated that there is adequate signal

strength over its entire operational range. Work continues on the software

development for its operation and evaluation of performance.

Several problems, including spurious ultrasonic signals, distorted

transducers, and leaking seals, were identified during early testing of the

76
2.8-meter manometer. Modifications have been made to correct these problems

in a 1 -meter UIM being built for the Sandia Primary Standards Laboratory.

Upon completion and successful testing of the 1 -meter instrument, similar

modifications will be made in the Navy's 2.8-meter UIM, as well as in a second 2. 8 -me ter UIM which will remain at NBS

.

FY 1988

In addition to the ongoing calibration work, the major projects for

the coming year will be the completion and evaluation of one of the 2.8

meter manometers, the characterization of low-range gas-operated piston

gages, and the determination of the argon triple point.

VII. B. UHV STANDARDS AND GAGING

The past year's efforts have been a continuation of the work started

in the preceding year, and have again been concentrated on the following

obj ectives

:

(1) Evaluation of gages [total pressure ionization gages

and residual gas analyzers (RGA) ]

.

(2) Development of a primary UHV standard (pressures < 10"^ Pa)

.

1 . UHV Gaging

a. Residual Currents : To measure total pressure with an ionization

gage, one needs to know the total ion current. However, in the UHV region

the gage's residual (pressure- independent) current may be comparable to the

ion current. Therefore, determination of the residual current is necessary

for accurate UHV pressure measurements. Unfortunately, this parameter is

often either unknown or only poorly known. We have employed two

independent methods to determine the residual current in several types of

UHV ionization gages including, an extractor gage and two modulated gages.

The key results were; (i) residual currents varied from gage to gage by

more than a factor of 10 among nominally identical gages and (ii) there was

no evidence of hysteresis in any gage's response to pressure changes. This

latter finding was somewhat unexpected for the measurements which were performed in H2 (as well as Hg ) , since other workers have seen significant

gas adsorption/desorption effects in ionization gages .

b. Ionization Gage Sensitivities : Ionization gage calibrations

performed on the existing NBS primary HV standard have shown increasing

scatter in the computed sensitivity of a gage as the pressure is reduced

below about 10”® Pa and, in some cases, the sensitivity appears to have a pressure dependence. However, at these pressures it is expected that the

gage's sensitivity will be constant. It is not yet clear to what extent

the apparent systematic changes are due to gage effects, or to low pressure

errors in the standard. Two possibilities are; (a) electron stimulated

77
desorption (ESD) of ions may be contributing significantly to the measured

collector currents (although the results in l.a. above indicate that this

is not the case) and/or (b) the assumptions used in calculating the

generated pressure may not be valid at the lowest pressures, in particular,

the assumption that the turbomolecular pump speed is pressure independent.

A new set of experiments just underway (June 1987) is designed to

evaluate the performance of UHV gages, set bounds on possible low pressure

errors in the primary standard, and help determine the low flow errors of

the flowmeter used for both the pressure standard and the leak standard.

c. UHV Gaging Workshop : An ultra-high vacuum gaging workshop,

organized by the vacuum standards group at NBS , was held November 3 and 4,

1986, in Gaithersburg, Maryland. Internationally-recognized experts in the

area of UHV gaging were among the 80 attendees at this workshop, which

addressed UHV gaging needs in different areas of vacuum science and

technology, past and present gaging research, performance of UHV gages, and

UHV standards. The emphasis was on total pressure ionization gages. The

presentations and personal exchanges at this meeting were invaluable in

helping the NBS vacuum standards group acquire some perspective on the

problem areas in UHV gaging. Further, it was gratifying to find that

others' experiences with residual currents and sensitivity measurements

were similar to ours.

d. Residual Gas Analyzers : The widespread and increasing use of

residual gas analyzers (RGA) in science and industry has prompted us to

investigate the possibility and practicality of calibrating such

instruments. To this end, over the past 2.5 years we have acquired 8

electric quadrupole and 2 magnetic sector instruments. There is a continuing accumulation of data and experience as a result of daily use of

these instruments in the course of both research and routine calibration

work with other gages. In addition, in the spring of 1987 we carried out a series of 2-3 day duration experiments on the short and long term stability

of these instruments. It is yet too early to draw conclusions about

relative performance but it has already become clear that RGA's equipped

with a secondary electron multiplier can exhibit rather long settling times

in response to a pressure step. Longer term systematic studies of both

stability and calibration procedures will begin in November 1987 with the

arrival of a Hungarian Guest Scientist.

2. UHV Standard (pressure < 10“ ® Pa)

The areas of UHV gaging and UHV standards are not independent.

Characterizing and understanding ionization gage behavior at pressures

below about 10“ ® Pa depends on the ability to obtain base pressures below

10“^ Pa, which is an order of magnitude below what is achieved in the

present NBS standard. In our approach to developing a new UHV primary

standard, we have (i) constructed a test chamber with the same material and

basic design as the existing standard and (ii) concentrated our efforts on identifying and reducing the sources of the residual gas background (mostly

78
H2 ) in the test chamber. The experiments planned or partially completed at

the time of last report have been completed, as well as some additional

experiments not then mentioned. Among these experiments, we mention the

following:

a. Extended C380 hour) High Temperature (450 °C) Baking . This reduced the

partial pressure of H2 in the chamber by a factor of about 3 over that

achieved with 250 °C bakes.

b. Hydrogen Permeation . Experiments with the diffusion of deuterium and

heavy water through stainless steel, at both elevated temperatures and at

room temperature, indicated that the influx of H2 as a result of permeation

of the vacuum chamber wail by hydrogen from atmospheric sources (H2 , H2 O,

CH^ ) is totally negligible at room temperature.

c. Cooling C-20 °C’) of Chamber . This resulted in a H2 pressure reduction

of only about 20%, rather than the order of magnitude (or more) reduction

expected, based upon the temperature dependence of the diffusion

coefficient for hydrogen in stainless steel and assuming that hydrogen

dissolved in the stainless steel is the only source of hydrogen. This

experiment, together with the results of experiments a. and b. above,

indicate that at the present time, the ultimate low pressure in the test

chamber is limited principally by the pump. However, even if this source

(pump) can be reduced to zero, it will still be necessary to reduce the

wall diffusion component by at least a factor of 2, to obtain an overall

factor of 10 reduction in the H2 partial pressure. As a consequence, it

now appears that further processing (vacuum furnace degassing) of the test

chamber is needed in order to reach our goal or that a different material

(aluminum) should be used.

d. Magnetic Bearing Turbomolecular Pump (TMP) . A new magnetic bearing TMP

was substituted for the TMP previously used. The after-bake H2 base

pressure was found to be about a factor of 2 larger than that previously

obtained with the other pump. This behavior is puzzling, because the H2 compression ratio for the new pump is specified to be 50 times greater than

that for the previously-used pump. Experiments with the new pump are continuing.

Our thinking on the subject of a primary UHV standard has evolved

during the course of the above -described experiments. If it can be

demonstrated that ionization gage sensitivity remains constant into the UHV

region, a dynamic (orifice/flowmeter) system to generate known pressures

<10‘® Pa may not be necessary. It may then be sufficient to achieve base

vacua low enough that residual currents can be determined directly. Then

the gage's sensitivity could be determined at higher pressures, with the

existing NBS primary standards.

Our plans for the coming year call for continued experimentation with

other types of pumps on our test chamber, as well as very close examination

of the existing HV standard at the low end (10“® Pa) of its range.

79
Decisions about design and construction of a new UHV standard hinge on the

results obtained in the above-described plan of investigation.

VII. C. HIGH VACUUM STANDARDS

The high vacutom standard is of the orifice-flow type and currently

covers the range 10'^ to 10“ ® Pa. Work this year has involved interactions

with several standards laboratories from around the world, work at the

upper and lower ends of the pressure standard, calibrations, and continuing

involvement in education and training.

As an extension of the International Vacuum Congress held in

Baltimore, MD, in November 1986, representatives of national standards

laboratories from six countries and KFA in Julich, West Germany, met at an NBS-organized workshop to discuss the spinning rotor gauge (SRG) as a transfer standard.

NBS participated in an international round robin conducted under the

auspices of BIPM with PTB , Berlin as the pilot laboratory. Four SRG's were

calibrated in argon and hydrogen gas at pressures between 2x10“^ and 4x10“^

Pa. The initial report from PTB is that their before and after calibrations

agreed to within +1% and that there was satisfying agreement between the

NBS results and all but one of the seven other standards laboratories.

This is most rewarding after instabilities of the transfer standards

compromised two previous comparisons. In addition, data were taken in

nitrogen where most of the work at NBS is done. Two check standards were carried throughout the work and their calibrations were within 1% of prior

values

.

Spinning rotor gages calibrated at NBS are now in use at IMGC, Italy,

and KSRI , Korea, and discussions have been held with NRG, Canada, to

exchange SRG's. Two calibrated rotors and a calibrated ion gauge will be

sent to NPL, India, this summer.

At higher pressures, four capacitance diaphragm gauges (CDG's) which

had been calibrated against the ultrasonic interferometer manometer were compared against two SRG's which had been calibrated against the primary

high vacuum standard. The intercomparison was carried out between 10“^ and

7 Pa, a region which includes the gap between the UIM and the high vacuum

standard and, as such, represents an extrapolation for both types of

gauges. After corrections were made for thermal transpiration in the CDG's

and for gas viscosity in the SRG's, the readings agreed to within about

0.6%. Of particular interest was the apparent success of the SRG gas

viscosity correction, which has been empirically determined by KFA, Julich

and adopted by the manufacturers. Interest in developing vacuum standards

to cover this range remains high.

Work has begun at pressures below 10'® Pa to study both the behavior

of the primary standard and the sensitivities of nude ion gauges of several

types. This is discussed further in the ultra high vacuum section.

80
The high vacuum calibration load did not increase significantly for

the first time since the service began in 1981. Thirty-one gauges were

calibrated for fee, 20 SRG's and 11 ion gauges. More gauges are coming

directly from manufacturers and many of our customers are industrial

calibration laboratories so most calibrations reach many end users. We are receiving increasing numbers of inquiries from the semiconductor industry

which had previously shown no apparent interest in gauge calibrations. Our

growing body of historical data on the long-term performance of the SRG,

both in our laboratory and after industrial use, has proven valuable to the

vacuum metrology community.

Initial work has been accomplished toward automating data collection

from the flowmeter that is an integral part of the standard. With the

forthcoming installation of platinum resistance thermometers in the

flowmeter, all of the data needed to calculate the pressure generated in

the calibration chamber will be available to a computer. In addition,

real-time analysis in now possible for certain vacuum gauges as a result of

the automation.

Education activities continue to be important. Sixteen students

attended the three-day, hands-on workshop on The Use of Spinning Rotor

Gauges to Calibrate Ion Gauges. Twenty- two people attended an informal

Spinning Rotor Gauge Users' Group in Baltimore, Md which was led by NBS

personnel. Telephone consultations make up the balance of the educational

activities

.

VII. D. LEAK STANDARDS

With the introduction last year of a Special Test Service for helium

permeation leak artifacts in the range 10'® to 10'^^ mol/s (2x10'^ to

2x10"^ atm cc/s @ 0 °C), activities this year have focussed on providing

this service in an effective and timely manner. Thus far nine leak

artifacts have been received into the Special Test Service, and at least

seven will have been evaluated and returned to the customer by the end of

the fiscal year. This includes two artifacts in use at the Three Mile

Island reactor (TMI). The Primary Leak Standard has been improved with a new manifold system that increases from two to six the number of artifacts

that can simultaneously be mounted for evaluation, without the necessity of

opening the vacuum system. This manifold, with dual pumping systems and a residual gas analyzer, provides the flexibility to measure flow rates from

one artifact while performing additional experiments with another.

A more detailed investigation into the properties of the helium

permeation artifact itself has yielded a much better understanding of the

fundamental processes governing the flow rate, and of the proper ways in

which to use these leaks. This has also resolved a discrepancy that exists

in the recent literature concerning the functional dependence of flow rate on various parameters. A primary issue is the time response of the leak

rate from an artifact to thermal fluctuations. On the one hand, it is well

known that the leak rate from an artifact can take several days to

81
stabilize when the leak reservoir is first filled with helium. On the other

hand, leak rates from artifacts are known to stabilize much more quickly

when subjected to discrete changes in temperature, even though the helium

reservoir pressure changes accordingly. Our experiments support that part

of the literature on the permeation of gases through vitreous glasses which

asserts that it is the helium concentration gradient in the glass, and not

the pressure gradient across the glass, that governs the flow rate.

The development and testing of a temperature-controlled leak artifact

has shown considerable promise toward providing a stable artifact for both

laboratory and field use. During observations made in the truck bay serving

the two reactors at TMI , using uninsulated leak artifacts, it became clear

that large thermal fluctuations in the truck bay could lead to serious

misuse of the leak artifacts. Insulating the artifacts helps, but an artifact that is thermally regulated offers a greater degree of stability,

and reduces the associated uncertainties. We have tested two different

temperature controller designs, one commercial and the other developed at

NBS . The NBS controller was found to give better regulation (10 mK vs. 200

mK) about a given temperature, however, both were found to yield

approximately the same shift in artifact temperature for a fixed change in

the temperature of the environment ( 0.3 K for an environmental change of

37 K, or 0.8% ). After final laboratory evaluation at NBS, an artifact of

this design will be sent to TMI for field testing.

The calibration schedule for the new special test service was badly

delayed by instabilities in a number of leaks belonging to outside

customers as well as NBS. After several months of testing the problem was traced to an improperly installed valve on the leaks which allowed helium

to leak out during heating and cooling cycling. Since this could cause

large errors with time the manufacturer was advised of the problem. He has

modified his assembly procedure and repaired the offending leaks.

Studies are being planned to evaluate the uncertainties associated

with using the Leak Comparator, in conjunction with leak artifacts that

have been measured on the Primary Leak Standard, to perform the entire

calibration of customer leaks.

A Standard Leak Calibration Workshop, to be held at NBS on Sept. 21-22

and co-sponsored with Sandia Laboratories, will provide a forum for sharing

our findings with the user community, as well as learning about other new

developments in this area. Besides talks directly related to leak

calibration and design, the workshop will feature speakers from the nuclear

transportation, electronics, refrigeration, and leak detector manufacturing

industries. Representatives from nuclear and military contracting

organizations, and national standards organizations, including the American

Society of Testing and Materials, American Vacuum Society, American Society

of Nondestructive Testing, American National Standards Institute and

authors of MIL specs, will also present talks outlining their

organization's activities.

82
INVITED TALKS

Temperature and Pressure Division (522)

G. W. Bums, "Thermocouple Calibrations at the NBS , " ASTh Temperature

Colloquium, Cincinnati, OH, May 13, 1987.

Sharrill Dittmann, "Where are the Challenges in Pressure Measurements,"

33rd International Instrumentation Symposium, Las Vegas, NV, May 7, 1987.

Charles D. Ehrlich "Status of the NBS Leak Standards Program," Fall

Conference of the American Society of Nondestructive Testing, New Orleans,

LA, October 2, 1986.

Albert R. Filippelli, "A Comparison of Three Types of Commercial UHV

Ionization Gages," AVS Florida Chapter, 16th Annual Symposium on Applied

Vacuum Science and Technology, Clearwater Beach, FL, Feb. 4, 1987.

Albert R. Filippelli, "Sensitivity and Residual Currents for Several

Commercial UHV Ionization Gauges," Workshop on UHV Gauging, Gaithersburg,

MD, Nov. 3-4, 1986.

W. S. Hurst, "Broadening and Narrowing of Raman Q-branch Spectral Lines of

Diatomic Molecules," Departmental Colloquium, Department of Physics, The

Pennsylvania State University, University Park, PA, Oct. 9, 1986.

Richard W. Hyland "Leak Artifacts - Calibrations and Considerations," AVS

New England Chapter (Annual symposium), Newton, MA, June 15, 1987.

B. W, Manguin, "Calibration, and the Associated Uncertainties, of Standard

Platinum Resistance Thermometers at the NBS," ASTM E-20 Colloquium,

Cincinnati, Ohio, May 13, 1987,

B. W. Mangum, "Standard Reference Materials for Use in Precision

Thermometry," National Conference of Standards Laboratories' 1987 Workshop

& Symposium, Denver, Colorado, July 15, 1987.

G. J. Rosasco, "The effects of velocity and phase changing collisions on

the lineshape of Raman Q-branch transitions in D2

, " Fall Meeting of the

Atomic and Molecular Physics Division, Canadian Association of Physicists,

Winnepeg, Manitoba, Canada, October 1986.

G. J. Rosasco, "The effects of velocity and phase changing collisions in

the D2 Q-branch spectrum," The Combustion Research Facility, Sandia

National Laboratories, Livermore, CA, April 1987.

G. J. Rosasco, "Phase and velocity changing collisions studied via the D2 Q-branch," The Johns Hopkins University Applied Physics Laboratory,

Laurel, MD

83
J. F. Schooley, "Properties of Bulk Superconductors", NBS Seminar on HighTemperature Superconductivity, May 26, 1987.

R. J. Soulen, Jr., "Tunneling Effects in Superconductors," NBS Seminar on High-Temperature Superconductivity, May 26, 1987.

R. J. Soulen, Jr., "Recent Advances in Pressure and Temperature

Measurements at NBS," Physikalisch-Technische Bundesanstalt , Braunschweig,

West Germany, June 2, 1987.

R. J. Soulen, Jr. "Recent Advances in Pressure and Temperature Measurements

at NBS," Phyusikalisch-Technische Bundesanstalt, Braunschweig, West

Germany, June 17, 1987

R. J. Soulen, Jr. "Progress in Division Pressure and Temperature

Standards," Navy CCG Planning Conference, Corona, CA, 1987.

Charles R. Tilford, "Vacuum Gages," Rocky Mountain Chapter of the American

Vacuum Society, Boulder, CO, April 1, 1987.

Charles R. Tilford, "Fundamentals of Vacuum Gaging and Calibrations,"

Northern California Chapter of the American Vacuum Society, San Jose, CA,

February 20, 1987.

Charles R. Tilford, "High Vacuum Gaging and Calibrations," Technical

meeting of the New England Chapter of the American Vacuum Society, Bedford,

MA, January 14, 1987.

84
PUBLICATIONS

Temperature and Pressure Division (522)

IN PRINT:

R. E. Edsinger, M. L. Reilly and J. F. Schooley, "Thermal Expansion of

Platinum and Platinum-Rhodium Alloys," J. Res. NBS , 333 Nov. /Dec.

(1987)

.

R. E. Edsinger and J. F. Schooley, "Gas thennometric determination of t (KTTS) vs t (IPTS-68) in the range 457°C to 660 °C," Paper No. CCT/87-4,

International Bureau of Weights & Measures, June 1987.

C. D. Ehrlich "Present Status of the Leak Standards Program at the National

Bureau of Standards," J. Vac. Sci. Technol. A, Vol. 5 , 125 (Jan. /Feb.

1987)

.

A. R. Filippelli, "Operation of a Bayard-Alpert Gauge in a Uniform 0-0.16

Tesla Magnetic Field," J. Vac. Sci. Technol. A5, March/April, 1987.

A. R. Filippelli, "Residual Currents in Several Commercial Ultrahigh Vacuum

Bayard-Alpert Gauges," J. Vac. Sci. Technol., Sept. /Oct. 1987.

G. T. Funokawa, "The Triple Point of Oxygen in Sealed Transportable

Cells," J. Res. NBS (USA) 91, 255-275(1986).

J. D. Cox and B. W. Mangum, "Evaluation of the Triple Point of

1 , 3-Dioxolan-2-One , " Metrologia, 23, 173-178 (1986/87).

B. W. Mangum, "Standard Reference Materials for Use in Precision

Thermometry," Proc . NCSL 1987 Workshop & Symposium, 44-1 to 44-10 (1987).

H. Marshak, "Nuclear Orientation Thermometry," Chap. 16, Low Temperature

Nuclear Orientation , eds . N.J. Stone and H. Postma (North-Holland,

Amsterdam, 1986), p. 769-820.

H. Marshak, J. N. Knudson, et al., "Excitation of the Isobaric Analog State

of ^®^Ho by Pion Single Charge Exchange," Phys . Rev. C 1382 (1987).

K. E. McCulloh, C. R. Tilford, C. D. Ehrlich and F. G. Long "Low-range

Flowmeters for use with Vacuum and Leak Standards," J. Vac. Sci. Technol.

A, Vol. 5 , 376 May/Jun (1987).

P. H, E. Meijer, Mustafa Keskin, and Erik Bodegom, "A Simple Model for the

Dynamics Towards Metastable States," J. Stat. Phy. 215 (1986).

P. H. E. Meijer, P. Pecheur and G. Roussaint, "Electronic Structure of the

Cd Vacancy in CdTe," Phys. Stat. Sol. (b) , 140 155 (1987).

85
P. H. E. Meijer and Marek Napiorkowski , "The three-state lattice gas as model for binary gas-liquid systems," J. Chem. Phys . 5771 (May 1987).

G. J. Rosasco, and W. S. Hurst "Dispersion of the electronic contribution

to the third-order nonlinear susceptibility of H2

, " J. Opt. Soc. Am. B 3 , 1251 (1986).

J. F. Schooley, "1986 Applied Superconductivity Conference, September 28-

October 3, 1986, Baltimore, MD," R. J. Soulen, Jr., V. A. Bardos, M. A.

Green, J. F. Schooley, Editors. IEEE Trans. Magn. , MAG -23 . No. 2, March

1987.

K. C. Smyth, G. J. Rosasco, and W. S. Hurst, "Measurement and rate law

analysis of D2 Q-branch line broadening coefficients for collisions with

D2 , He, Ar, H2 , and CH^ , " J. Chem. Phys. July 1987.

R. H. Ono , M. W. Cromar, R. L. Kautz , R. J. Soulen, J. H. Colwell, and

W. E. Fogle, "Current-voltage characteristics of nanoarapere Josephson

Junctions," Proceedings of the Applied Superconductivity Conference, IEEE

Trans. Magn., MAG-23 . 1670 (1987).

R. J. Soulen, Jr., and Deborah Van Vechten, "Impedance of radio- frequencybiased resistive superconducting quantum interference devices," Phys.

Rev. B 36, 3186 (1987) .

APPROVED FOR PUBLICATION:

A. R. Filippelli, "Emission from Atomic Nitrogen Produced by Electron

Impact on Nitrogen Molecules" (with D. L. A. Rail, F. A. Sharpton,

S. Chung, C. C. Lin, and R. E. Murphy); accepted for publication in the

Journal of Chemical Physics, Oct. 1987.

B. W. Mangum, "NBS Platinum Resistance Thermometer Calibration Service;"

revised version completed and to be published as a supplement to Special

Publication 250.

H. Marshak, W. D. Brewer, P. Roman and M. Bottcher, "^®°TbTb(sc) : A New

Absolute Nuclear Orientation Thermometer for Use in High Magnetic Fields,"

Japanese J. Appl. Phys.

H. Marshak, W. D. Brewer, E. Klein, K. Freitag and P. Herzog, "Nuclear

Double Resonance of ^®°TbTb Oriented at Low Temperatures," Phys. Rev. Lett.

P. H. E. Meijer, Mustafa Keskin, and M. Napiorkowski, "The Influence of

Electrical Field on Diffusion in Semiconductor Junctions," J. Appl Phys.

86
G. F. Molinar, J. C. Legras, V. E. Bean, V. H. Borovkov, J. Jager, A.

Keprt, S. L. Lewis, R. Lewisch, Mobius, L. Rydstrom, J. G. Ulrich, S.

Yamamoto, and S. Yi-Tang, "International Comparison of Pressure

Measurements in a Liquid Medium from 20 to 100 MPa," Proceedings of the

Xlth Conference of the International Association for the Advancement of

High Pressure Science and Technology, Kiev, USSR, 12-17 July 1987.

C. R. Tilford, Editor, Proceedings of the Ultra High Vacuum Gaging

Workshop, J. Vac. Sci. Technol., Sept/Oct., 1987.

C. R. Tilford, "The Speed of Sound in a Mercury Ultrasonic Interferometer

in Mercury," Metrologia, September 1987.

A. van Roggen and P. H. E. Meijer, "The Eddect of Electrode-Polymer

Interfacial Layers on Polymer Conduction. Part 2: Device Summary,"

Proceedings of Conference on Molecular Electronic Devices, Crystal City,

VA.

87
SEMINARS, WORKSHOPS, AND MEETINGS ORGANIZED OR CHAIRED

Temperature and Pressure Division (522)

Precision Thermometry Seminar, NBS , Gaithersburg, MD, October 20-24, 1986

A seminar which consists of integrated instruction in Platinum Resistance

Thermometry, liquid- in-Glass Thermometry, Thermocouple Thermometry and

Thermistor Thermometry which is given over a five-day period. Material

covered includes the IPTS-68 (International Practical Temperature Scale of

1968) ; its use in the laboratory; thermometers and instrumentation,

including automatic data acquisition; the treatment of calibration data;

and innovations in thermometry. Time is split between lecture sessions and

hands-on measurements in the laboratory.

Ultra-high Vacuum Gaging Workshop. The workshop was organized by members

of the Vacuum Standards Group at NBS. It was held on November 3 and 4,

1986 at the Sheraton-Potomac Hotel, Gaithersburg, MD. Topics were UHV

gauging needs in different areas of vacuum science and technology; past and

present gaging research; performance of UHV gages; and UHV standards.

Workshop on the spinning rotor gage as a transfer standard, NBS,

November 5, 1986.

Pressure Seminar, May 14 and 15, 1987.

Standard Leak Calibration Workshop, to be held September 21-22 at NBS,

Gaithersburg, MD.

Use of the Spinning Rotor Gage to Calibrate Ion Gages, class given at NBS,

February 25-27 and March 2-4, 1987.

ASTM E-20 Seminar on December 3, 1986. At this meeting. Dr. T. P. Wang of

Thermo Electric, Inc. of Saddle Point, NJ gave a presentation on "Thermocouples for High Temperature Applications". (Mangiom, Organizer and

Chairman)

ASTM E20.06, New Thermometers and/or Techniques. On December 2, 1986.

Mr. Philip Alderton of Instrulab, Inc. of Dayton, Ohio, presented a talk on and demonstration of Precision Resistance Bridges at this meeting.

(Mangum, Organizer and Chairman)

ASTM E20.06, New Thermometers and/or Techniques. On May 12, 1987. Mrs.

Carol Croarkin of the NBS presented a talk at this meeting. The talk was entitled "Derivation of Uncertainty Statements for Temperature

Measurements". (Mangum, Organizer and Chairman)

ASTM E-20 Seminar on May 13, 1987. At this meeting. Dr. B. W. Mangum and

Mr. George Burns of the NBS gave presentations on "Calibrations, and Their

Associated Uncertainties, of Standard Platinum Resistance Thermometers and

of Thermocouples at the NBS". (Mangum, Organizer and Chairman)

88
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Temperature and Pressure Division (522)

V. E. Bean, Chairman, AIRAPT (International Association for the Advancement

of High Pressure Science and Technology) Task Group on the International

Practical Pressure Scale.

V. E. Bean, Member, BIPM (International Bureau of Weights and Measures)

Consultative Committee for Mass and Related Quantities, Working Group on Medium Pressure.

V. E. Bean, Member, BIPM (International Bureau of Weights and Measures)

Consultative Committee for Mass and Related Quantities, Working Group on High Pressure.

G. W. Biims, Member, ASTM (American Society for Testing and Materials) E-20

Committee on Temperature Measurement; Member, Subcommittee E-20. 04,

Thermocouples

.

G. W. Bums, Member, ISA (Instrument Society of America) SP-1, Committee on Temperature Measurement (Thermocouples)

.

S. D. Dittmann (Wood), Chairman, AVS (American Vacuum Society) Subcommittee

on Subcommittee on the Use of Spinning Rotor Gauges as Transfer Standards.

C. D. Ehrlich, Co-Chairman, AVS American Vacuum Society) Calibrated Leak

Standards Subcommittee.

C. D. Ehrlich, Member, ASTM (American Society for Testing and Materials)

E-7, Committee on Nondestructive Testing; Vice-Chairman, Subcommittee

E7.08, Leak Testing Methods.

A. R. Filippelli, Member, (AVS) American Vacuum Society Committee for

Recommended Practice for Calibration of Residual Gas Analyzers.

G. T. Furukawa, Member, ASTM (American Society for Testing and Materials)

E-20, Temperature Measurement Committee; Subcommittee E-20. 03, Resistance

Thermometers; Subcommittee E-20. 04, Thermocouples; Secretary, Subcommittee

E-20. 06, New Thermometers; Member, Subcommittee E-20. 07, Fundamentals in

Thermometry; and Subcommittee E-20. 94, Publications.

R. W. Hyland, Board of Directors, Vacuum Technology Division of AVS

(American Vacuiim Society) .

R. W. Hyland, American Vacuum Society Subcommittee of Standards Committee

on the Use of Capacitance Diaphragm Gages as Transfer Standards.

89
B. W. Mangum, Member, NCCLS (National Committee for Clinical Laboratory

Standards) C002, Area Committee on Clinical Chemistry; Subcommittee SC. 01,

Enzyme Assay Condition, Working Group WG.Ol, Temperature Measurement and

Control; and Member, NCCLS COlO, Area Committee on InstruGlass Fever Thermometers

Thermometers; Working Group WG.03, Continuous Clinical Temperature

Monitoring Temperature Measurement Committee; Member, Subcommittee E-20.03,

Resistance Thermometers; Chairman, Subcommittee E-20.06, New Thermometers;

Member, Subcommittee E-20.07, Fundamentals in Thermometry; Subcommittee

E-20.08, Medical Thermometry, Working Group WG.02, Fever Thermometers;

Working Group WG.02A, Electronic Fever Thermometers; Working Group WG.02B,

Mercury-In-Glass Fever Thermometers; Working Group WG.02C, Disposable Fever

Thermometers; Working Group WG.03, Continuous Clinical Temperature

Monitoring Systems; Working Group WG.04, Clinical Laboratory Temperature

Measurement; and Member, Subcommittee E-20.90, Executive Subcommittee.

B. W, Mangum, Member, OIML PS12, International Organization of Legal

Metrology, Measurement of Temperature and Calorific Energy Committee, RS4,

Electrical Thermistor Thermometers.

J. F. Schooley, Delegate, Consultative Committee on Thermometry of the

International Committee on Weights and Measures (CIPM) ; and Delegate,

Subcommittee WG3, Replacement of IPTS-68.

J. F. Schooley, Delegate, OIML PS12, International Organization of Legal

Metrology Committee on Measurement of Temperature and Calorific Energy.

R. J. Soulen, Jr., Member NCSL (National Conference of Standards

Laboratories

.

R. J. Soulen, Jr., Member, ASTM (American Society for Testing and

Materials) E-20, Temperature Measurement Committee.

R. J. Soulen, Jr,, Member, ASTM (American Society for Testing and

Materials) BOOl, Committee Electrical Conductors, Subcommittee SC. 08,

Superconductors

.

R. J. Soulen, Jr., Member, International Committee on Weights and Measures

(CIPM), Consultative Committee on Thermometry (CCT) , WG4.

C. R. Tilford, Member, ASTM E-21, American Society for Testing and

Materials Space Simulation and Applications of Space Technology Committee,

Subcommittee SC. 04, Space Simulation Test Methods, Working Group WG.Ol,

Revision of Standards E296-70 and E297-70.

C. R. Tilford, Chairman, BIPM C002, International Bureau of Weights and

Measures Consultative Committee on Mass and Related Quantities, Working

Group WG.02, Working Group on Low Pressures.

90
C. R. Tilford, Member, RTCA SC150, Radio Technical Commission for

Aeronautics, Special Committee for Minimum Performance Standards for

(Aircraft) Vertical Separation Above Flight Level 290.

C. R. Tilford, Member, Board of Directors, Vacuum Technology Division of

the American Vacuum Society.

J. A. Wise, Secretary, ASTM E-20, American Society for Testing and

Materials Committee on Temperature Measurement; Secretary, Subcommittee

E-20. 05, Liquid- in-Glass Thermometers and Hydrometers; Member, Subcommittee

E-20. 08, Medical Thermometry; Secretary, Subcommittee E-20. 90, Executive

Subcommittee; and Member, Subcommittee E-20. 91, Editorial and Nomenclature.

91
• 'W''

'"-'’^W^ ^f\v''V^ .^:''^^. ’--Cv/,-;;' .'^4^-

>K‘^= : w

‘ i-^p:. <".:v «/ V :4 \: . Lat'^vf

!^iVi'3r-' J f' ** ii.fti V'. . -iLi • V , -A;^+-' ^ ^is; : - -

^ ^vUlr; tW®« .* t, ': <|.M : * ‘id . • -

:

r.F' i'/A» ';"'«^ f

>\^ 'tji;-'.. V.

-•,* lh^.''^}‘KL .*iu:=t/-*.‘.*.,»kr^ * !• ;;• ;.(»••

">>. . -.-A . - - * 'Ui A*'.'.! vf. £ t.$¥ \.’<s tViikijw idk m» ;-^'|fevj^

.i.: ,ti*' '”»'>-*

-j>?.' V .. V •:' V.- iV /?k>,-* ». cxd

'»' ' i K.--, I -:^ * •'»'' ‘'i'^ I?':

" = fy.f> 1 c.”

•

:, ^ /f:/|*-jtf

'';?• c:, :t'^ .irbii't.l’’ ., ^ |'•v.r^^r.U' ' , '«: -• * ?>'/ jjt\

< l" . . iS '/'"ti.-.'.y ;nn''?ti'.6V <i'' ^ ix'

<'ii

.

'<% y *

.\.y • >« .. .fr:' CA'

4i '.Gi*jTt fio*t»i:y ilijt ,«. S'- T«-^ '•: ri>aj^’tt4in*i

- >, / vrm

I<1

1 * ’i t* t

.1 r ‘y rir..

«

(V,rr7. \ At t "I i>«.i

t

. . ’ i"' »'.-,it IC'-^S 1'1\; if.» ic:i' I \^onA*r, ;iO'i ’i , M;

u- * .,,

.1' ^

' 1

''t<-A-''‘'-t , li^ oi- •fitiX't^r.x ^

.'. <V. •t) . t . < as; .ft. «• c#«ju.. t.vy

i'„ } < )

.

t. /• w

.* AU^ ' -n. AGKJTifi-'C^

,-jf:::\.n /t;:c1 u.A^iii'm itt

;vsr^ • -3 1 X«.n k*rCi^>^« . ». i. *,..h; y-yt Ksw-?o,v '

’

, “ ^ y ; ^. .,.^‘,'!;'j:%

-

- j.;ip

. '
LENGTH AND MASS DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1987

I. Overview

The Length and Mass Division (LMD) has the responsibility to: maintain

the U.S. primary standards for length, mass, and density; provide the first

level of transfer to secondary standards; and improve the standards and

measurement instrumentation through basic and applied research. The

Division also has responsibility for the NBS mass calibration service.

Many activities occur in support of these responsibilities.

Comparisons of the U.S. standards are made with the International Bureau of

Weights and Measures (BIPM) and with other national laboratories to ensure international concordance. A close working relationship is maintained with

the divisions in the National Engineering Laboratory which provide length

and force calibration services to the public. This cooperation not only

concerns the first level of transfer of dimensional quantities but also

includes the transfer of measurement techniques and instruments, such as the portable laser length standard, the submersible balance, and the load

cell mass comparator, which were developed in the LMD. Cooperative

projects with outside institutions, such as state metrology laboratories,

universities, and private corporations, ensure that our activities are relevant to the problems of the measurement community. The Division is

frequently requested to provide information and assistance to public and

private organizations which need state-of-the-art length and mass measurements and cannot obtain adequate support from the private sector.

Length activities this year involved achieving a value for the Rydberg

constant to a higher level of accuracy than had been previously achieved,

collaboration with the Electricity Division on length metrology related to

the redetermination of the NBS ohm by means of the reactivated NBS

calculable capacitor in an effort to have sufficient information to adopt a value for a working standard of resistance based on the quantized Hall

effect, continuing development of the laser controlled kilogram comparator,

and development of the scanning tunneling microscope as a position sensor

with sub-Angstrom resolution and as an optical heterodyne detector for use

in laser frequency comparisons.

Activities in the mass program focussed on: development of servo-controlled kilogram balances for primary mass comparisons; development of

retro-fitted servo-systems and automated weight changers for commercial

balances used in the calibration program; continuation of an international

round-robin to measure solid density artifacts; implementation of improved

quality controls for mass calibrations; participation in a new measurement

93
of the gas constant; and circulation of the new transportable mass measurement package to state and industrial metrology laboratories.

The DOD is continuing to sponsor a research activity aimed at the

development of stable capacitance standards. Robert Cutkosky of the Length

and Mass Division is providing the design and guidance for the technical

work, which is being carried out by Mr. Lai H. Lee of the Electricity

Division.

II. Technical Activities

1. Length Measurements and Standards

The length activities this year included realizing and disseminating

the length standard to industrial and scientific laboratories and the

continuation of projects to extend the applications of high precision

length measurements

.

A. NBS Portable Laser Length Standard

The NBS laser length standard continues to be the instrument which

generates the most interest for national and international laboratories

which are in the process of acquiring the capability of realizing the unit

of length to support science and industry. Activities this year involved

its use in the measurement of fundamental constants and in extending the

range of length measurements into the atomic domain. Formal contacts have

also been made with Hungary and India for the transfer of the laser length

standard technology and will involve additional technical cooperation in

the coming year.

ACCOMPLISHMENTS: The NBS portable laser length standard is currently

being used in a new measurement of the ohm by means of the calculable

capacitor in the NBS Electricity Division. This measurement is part of the

continuing international effort by the electrical standards community to

establish the quantized Hall effect as the primary standard of resistance.

Last year Howard Layer installed a laser system consisting of two lasers, an iodine stabilized laser reference and the cavity mode stabilized working

laser, and the electronics necessary to calibrate the working laser. He

has continued to assist John Shields in his efforts to upgrade the

performance of the calculable capacitor.

The Length and Mass Division is continuing to provide length

measurement support for the gamma -p measurement in the Electricity

Division.

The collaboration with Dr. William Lichten of Yale University on the

measurement of the Rydberg constant by using crossed atomic and optical

beams has been successfully completed and resulted in a value which has a

94
precision of several parts in 10^° . This result is consistent with

previous measurements and appears to be at the limit of accuracy which can

be achieved with visible radiation. An Extension of this work using

radiation in the near infrared is now being planned.

PLANS FOR FY 88; The work of providing access to the length standard

through the iodine stabilized laser will continue at approximately the same level as in FY 87. Plans are being made for a new Rydberg constant

measurement which would operate in the infrared and would be potentially

capable of improving on the visible measurement by perhaps as much as an order of magnitude. In this experiment a widely tunable waveguide CO2 laser will be stabilized on a saturated absorption of osmium tetroxide and

calibrated via the French optical frequency chain to obtain a higher

accuracy length standard. This measurement should exhaust the

opportunities for improving the Rydberg constant measurement with low

atomic number atoms

.

B. Servo-system for the NBS Scanning Tunneling Microscope

In the course of developing a capacitance motor and a highly

stabilized electronic driver for the electrostatically servoed mass

comparator, a collaboration between the Radiation Physics Division and the

Length and Mass Division resulted in the construction and operation of a scanning tunnelling microscope (STM). This instrument, in which a sharp

tungsten emitter is held within a few atomic diameters from a conducting

surface by a high stability servo system, has many applications within the

NBS and particularly the Length and Mass Division. It is a superior non- contacting probe and it provides a means of constructing an alternate

configuration for the metal- insulator-metal (MIM) diode which has been used

so successfully at NBS Boulder for comparing laser frequencies.

ACCOMPLISHMENTS: The major development of the servo system for the

scanning tunneling microscope has been completed and is in operation in the

Radiation Physics Division of the Center for Radiation Research. This

microscope presently has a vertical resolution of a few Angstroms and it

appears it will be capable of atomic resolution in both vertical and

horizontal directions as soon as the new vacuum instrument is operational.

The development of very high-stability high-voltage amplifiers was initially stimulated by the extreme sensitivity requirements of the STM.

The latest model has a 2000 volt output and a drift which approaches 1/10

ppm over a 15 minute period. This performance now exceeds the requirements

of the STM but will be crucial for servo ing the kilogram comparator.

With the completion of his collaboration on the servo- system for the

STM, Howard Layer has redirected his efforts toward the development of a scanning tunneling microscope for length metrology with sub-Angstrom

resolution.

95
PLANS FOR FY 88: Our contribution to the development of the STM has

been completed and substantial further collaboration is not anticipated.

However, several applications of this technology are of importance to the

Length and Mass Division and these include its use as a non-contacting

probe for length measurements and as a base for controlling the antenna

substrate distance of a MIM diode.

2. Mass Measurements and Standards

A. Servo-controlled Primary Kilogram Comparators

Two parallel projects are underway to develop completely new types of

automated mass comparators. Both use the same basic structural design:

cast aluminum base plates, symmetrical cast beam, etc. They differ in that

one will use laser sensing of the beam position, an electrostatic

servo-motor to restore the beam, and knife-edge pivots while the other will

use a simple electromagnetic beam servo-system and commercial flexure

pivots. Additional modifications have been made on the Voland balance

which is now being used to calibrate working standards for the calibration

laboratory

.

ACCOMPLISHMENTS: The Voland kilogram comparator has been operating

under servo control for over one year. It became clear during operation

that several aspects of the controls needed to be improved. The hydraulic

controls on the weight changer were completely redesigned. All electric

relays were repackaged in a robust chassis and a greater variety of

information is now displayed. The data acquisition is now semi-automatic:

temperature, barometric pressure and balance readings are all taken by the

computer; and the weight table is raised and lowered by computer control.

Measurements on the Voland could be completely automated if the weight

table could be rotated under computer control. A Cutkosky controller (a

stepper-motor driver developed for the robotic weighing arm) has been

constructed for this purpose and will be installed soon.

All of the major components, except for the electrostatic beam

restoring motor, have been completed and assembled for the new laser

servoed knife-edge balance. A capacitance motor has been chosen for this

balance because it does not require the use of magnetic materials even

though a magnetic system would be advantageous from many other points of

view. A very highly stabilized, low noise, high voltage electronic driver

for the capacitance motor has been developed and successfully tested on the

Scanning Tunneling Microscope. The capacitance motor is now under

development

.

A new project was initiated last year by Schoonover and Cutkosky to

construct an automated kilogram comparator with flexure pivots, an electromagnetic servo system, and the same cast beam and structural com- ponents designed for the knife-edge balance discussed above. This project

is divided into the following four steps:

96
1) Servo a beam with flexure pivots and demonstrate the required

sensitivity.

2) Demonstrate precision by repeated weighings of a 1 kg weight.

3) If precision is adequate, develop a weight changing mechanism

for intercomparing six 1 kg masses.

4) Investigate vacuum weighing.

The first step and the construction for the second step have been

completed. Tests of the precision are now underway.

PLANS FOR FY 88: Development and testing of the new kilogram

comparators will continue.

B. Quality Control System for Mass Calibrations

The goal of this project is to ensure that the mass calibrations

performed by NBS are compatible with the international system of mass measurements. The first step -- the recalibration of the U.S. national

prototype kilograms, K20 and K4, and two stainless steel kilograms at BIPM

-- has been completed and documented. Work is underway to calibrate a group of stainless steel check standards and working standards for the

calibration service. A new set of quality control procedures will be

implemented in the calibration laboratory to monitor the working standards.

ACCOMPLISHMENTS: The results of the BIPM recalibration have been

analyzed and published. The major conclusions from that work can be

briefly summarized in the following comments. The Pt-Ir standards must be

cleaned in exactly the same manner as that used by BIPM in order to achieve

comparable results. When the cleaning is properly done, repeated mass measurements agree to within 5 micrograms. After cleaning, the U.S.

national prototype K20 was found to be only 1 microgram below its 1948

value -- a difference that is well within experimental uncertainties. The

cleaning process removed approximately 20 micrograms. Repeated

calibrations of the two stainless steel weights, both at NBS and BIPM,

indicate a repeatability better than 30 micrograms. The majority of the

non-reproducibility seems to be due to the difficulties associated with the

air buoyancy correction.

The six stainless steel kilograms which will be used as check

standards and working standards in the calibration service have been

monitored for stability. Their densities have been determined to high

accuracy by hydrostatic weighing against our silicon transfer standards.

Their masses have been measured against the stainless steel standards which

were calibrated by the BIPM.

Now that our 1-kg mass comparator has a standard deviation of less than

0.0015 mg, it became clear that our usual cleaning method for stainlesssteel kilograms was removing 0.005-0.010 mg on each application. While

this is a small amount (less than the equivalent of one monolayer of

metal) , the fact that it appears to be monotonic rather than random has led

us to search for a less aggressive cleaning method. A review of

97
alternative methods has revealed several possibilities that are being

studied.

When these studies are complete, we will be in a position to introduce

improved quality controls to our routine calibrations. We anticipate that

the tie to the SI unit as maintained at the BIPM can be reestablished with

an uncertainty of about 0.020 mg/kg. We believe that, by establishing a hierarchy of stainless steel standards, we will be able to maintain the NBS

unit to better than 0.010 mg/kg for periods of years between comparisons of

platinum iridium and stainless steel kilograms.

PLANS FOR FY 88: The best cleaning method of those under study will be

adopted and the quality control system will be put in place and documented.

Special dust-free containers for the six stainless-steel kilograms will be

constructed.

C. Laboratory Automation for the Calibration Program

There is a growing need in the NBS mass calibration laboratory and in

the outside mass metrology community for automated mass comparators which

perform as well as or preferably better than the mechanical balances now in

common use. Modern electronic balances lack the combination of range and,

most importantly, the precision required in the NBS mass calibration

program. This deficiency has been overcome with the development of beam

servo system that has been installed on existing high-precision mechanical

balances

.

The goals of this project are to automate the data acquisition of the

balance observations and then to examine the possibility of automating the

total calibration process.

ACCOMPLISHMENTS: A successful electromagnetic beam servo system has

been developed and installed on the Voland kilogram comparator and on a Mettler model H315 balance used to calibrate the kilograms for the portable

mass measurement package.

The servo system has enabled us to examine several ways to avoid the

systematic errors that are known to be caused by thermal effects that arise

from the presence of the balance operator and thermal gradients between the

weights and the balance chamber. One approach has been to replace the

operator with a mechanical weight changer. A second approach is to use a servoed thermal soaking plate which forces thermal equilibrium between the

weights to be calibrated and the air in the balance chamber. Both

approaches have been successfully tested and can be adapted to some of the

mechanical balances used in the mass calibration program.

The remotely operated mechanical weight changers developed earlier for

the Mettler balance were manually operated systems with limited

applications. A new fully automatic robotic arm which is capable of

98
loading the balance with weights in various combinations from a preioaded

matrix has now been developed.

The special robotic arm has been constructed and programmed to

automatically load and unload a commercial electronic balance according to

a specified schedule. The present system will store 107 weights at a time on a temperature-regulated aluminum plate. Up to seven weights can be

placed on the balance at one time as called for by the schedule, so that

the usual weighing designs can be accommodated. Standard weighing designs

performed on 5-2-2-1 and 5-3-2-1 weight sets indicate that the process

standard deviations are comparable to those obtained using the present

manual techniques. Work is now underway to reinstall the equipment on a pier in the mass calibration laboratory for final evaluation.

A paper describing the six-axis stepper motor driver used to control the

robot arm has been submitted to the IEEE Transactions on Instrumentation

and Measurement. An abstract of a paper describing the entire weighing

system has been submitted to the Measurement Science Conference which will

be held in January, 1988.

PLANS FOR FY 88; Research and testing will continue on all of these

automated components until adequate performance has been demonstrated.

They will then be adapted for use in the calibration program.

D. Density of Solids

Working Group 5 of the Consultative Committee for Mass and Related

Quantities (CCM) has organized an international round robin of solid

density intercomparisons. NBS is serving as the pilot laboratory for these

measurements

.

ACCOMPLISHMENTS; The round robin has begun. NBS has made initial

measurements of the artifacts and shipped them to the next participating

laboratory. The artifacts include two stainless steel kilograms and two

800 g silicon crystals.

FUTURE PLANS; NBS will remeasure the density artifacts at the end of

the seven- laboratory round robin. As the pilot laboratory, we will also

analyze the data obtained by all participating laboratories and write the

preliminary report.

E. Portable Mass Measurement Package

This project, sponsored in part by the NBS Office of Weights and

Measures, is developing a transportable mass measurement package to assist

State and industrial metrology laboratories in assigning mass values to

kilograms, particularly those which have unusual shapes and densities and

require significant air buoyancy corrections. Most laboratories have

99
adequate balances but some lack the necessary axixiliary equipment and

experience to make accurate air buoyancy corrections. This package will

help to overcome these deficiencies. The package includes:

1. calibrated kilogram masses of various geometries and

densities

,

2. fractional mass standards for trimming mass differences at

various altitudes,

3. computer hardware and software for standardized data reduction

and statistical control,

4. air density instrumentation to measure temperature, barometric

pressure, and relative humidity, and

5. automatic data acquisition system for those laboratories

equipped to use it.

ACCOMPLISHMENTS: The complete package has been assembled and

calibrated. It has now been successfully circulated to 9 participating

laboratories in a round robin which included both state and industrial

laboratories

.

PLANS FOR FY 88: The Division will monitor the results of the round

robin and make any further modifications that are required. One of the

most important long-term objectives of this project is the training that

participants will receive by using the package. Many participants have

been exposed for the first time to state-of-the-art weighing techniques and

laboratory automation. It may be desirable later to develop a formal

training seminar based on the instrumentation and techniques used in this

package. A further objective is to extend the mass calibration capability

of the package from the 1 kilogram level down to 1 mg so that the

customer's mass standards can be calibrated and certified in his own

laboratory. The software for the extended package will be developed in FY

88 .

F. Frequency Dependencies of Resistors

Requests for data on the frequency dependencies of resistors have been

received from a number of sources, including the NBS Temperature and

Pressure Division and the Sandia National Laboratories. Six selected

100-ohm resistors of commercial manufacture were compared with a 100 ohm

coaxial resistor of NBS construction at various frequencies between dc and

400 Hz. The results are contained in a paper now undergoing editorial

review. The resistors used in the test were provided by NBS and The Sandia

Laboratories; the four bridges used were obtained from various sources

within NBS. It is possible that the coaxial standard will not be usable

for such testing very much longer, since the insulation used in its

construction has greatly deteriorated.

100
G. New Measurement of the Gas Constant

The measurements of the ideal gas constant, R, have been completed.

Richard Davis collaborated on the project led by M. Holdover of the

Thermophysics Division. His job was to measure the interior volume of a 3 liter acoustic resonator with an uncertainty less than 1 ppm, if possible.

He has succeeded in this . A draft report has been written which documents

that the volume measurement contributed only 0.8 ppm to the error budget of

R. The volume was determined three times over a period of six months. The

range of values was less than 1 ppm of the nominal volume, making it one of

the most precise measurements of its type ever reported. Davis'

involvement in the project has now been completed.

101
PUBLICATIONS

In Print

R. S, Davis, "Note on the Choice of a Sensitivity Weight In Precision

Weighing," Journal of Research of the NBS £2, 3, 239-242, May-June, 1987.

T. J. Quinn, C. C. Speake , and R. S. Davis, "A 1 kg Comparator Using

Flexure-strip Suspensions; Preliminary Results," Metrologia 23., 87-100

(1986/87)

.

P. Zhao, W. Lichten, H. P. Layer, and J. Bergquist, "New Value for the

Rydberg Constant from the Hydrogen Balmer-;9 Transition," Phys . Rev. Lett.

58, 13, March 30, 1987.

H. P. Layer, "Laser Length Metrology," Proceedings of the NCSL July 1987

Meeting.

R. M. Schoonover and J. E. Taylor, "Some Recent Developments at NBS in Mass

Measurements," IEEE Trans, on Instr. and Meas. IM- 35 . 4, 418-422, December

(1986) .

In Press. In Review, or Nearing Completion

R. D. Cutkosky, "A Six-Channel Stepper Motor Controller for Use in

Laboratory Instruments," to be published in IEEE Transactions on

Instrumentation and Measurement.

R. D. Cutkosky, "Frequency Dependencies of Precision Resistors," to be

published in Review of Scientific Instruments.

R. S. Davis, "Interpretation of a Between-Time Component of Error in Mass

Measurements," Proceedings of the 1987 Conference on Measurement Science.

M. R. Moldover, J.P.M. Trusler, T. J. Edwards, J. B. Mehl, and R. S. Davis,

"Measurement of the Universal Gas Constant, R, with a Spherical Acoustic

Resonator," to be submitted to the NBS Journal of Research.

M. R. Moldover, J.P.M. Trusler, T. J. Edwards, J. B. Mehl, and R. S. Davis,

"Measurement of the Universal Gas Constant Using a Spherical Acoustic

Resonator," Proceedings of the Third IMEKO Symposium on Thermal and

Temperature Measurement in Science and Industry; Sheffield, England, U.K.

,

September 15-17, 1987.

R. M. Schoonover and J. E. Taylor, "An Investigation of a User Operated

Mass Calibration Package," in progress.

102
INVITED TALKS

R. S. Davis, "Tracking the SI Kilogram," presented at NBS for the

Government -Indus try Data Exchange Program, April 27, 1987.

H. P. Layer, "Laser Length Metrology," presented at the NCSL Meeting in

Denver, CO, July 15, 1987.

H. P. Layer, "Laser Length Metrology," presented at the Precision

Measurements Association in Golden, CO, July 15, 1987

R. M. Schoonover, "Standards Lab Practice," presented at George Washington

University, April 24, 1987.

103
- m

v-!>', *j,e a. 3,

'

^ T^ f? :•:.? f ri .ut; ,, 0:5 •

. I#

'Mi -

''( ^

mr--'B

’’ ‘1 ~ /» icr "

-i'0*^’<:' t4 •'•”',^'r‘-'„ Sfe’ji ‘' "-•'.If - • ’

.vr-i - *= /

V

1* *

A,!'..

J>.

•

i ‘3 , *]

-^»- T' .>i(

k '-. \Jl

'- iU

' > .',sm\*vA* T l^' .V''

•' " .1 ;' C .’i- 0 ^ 'U - -

-.

i 'll .•

. ; i»‘. »r

JV t> ,. Tvi I- *!^ot.4

. ^ » ''V'- .*1)1

«.'Mi r»

'? '’>^

:' h tJ, ~L . ••« ''*€>• C •’•.r''#»r€ft#*«',W

'? I f.-.

';* I' ,‘wi^r'5»'' »'.i|4i I i^‘. ^

f r- . .. - y.'^’irM

i". "I -Ki-' > '^ nif p(j(£ f'v

* I'v

.1

' i^'.v!. rv. '.V.-

'

. -,J -ti

;,.. « •i»f4' rM(|. Cv^'Ji ..6.SV.;;; -V

.• J:.; 5' r? tiip,^'».tlP<f i)4PCC) '•* :i^

_

'%:

"ifVi ‘®^'^

'

'•KnT
TIME AND FREQUENCY DIVISION

FISCAL YEAR 1986

I . INTRODUCTION

The Time and Frequency Division, located in Boulder, is responsible

for the U.S. standards of time and frequency. There is a secondary

responsibility for the realization of the meter, since, by international

agreement, the standard of length is now based on the frequency standard,

the speed of light being a defined constant. The Division played a major

role in the measurement of the speed of light and the new realization of

the meter. However, responsibility for maintaining the practical meter

resides in the Length and Mass Division.

Section II of this report provides a separate, general discussion of some of the key issues facing the Division. The purpose of this discussion

is to provide a background against which the work of the Groups in the

Division can be understood. Following this, the work of the Division is

presented along organizational lines as shown below. Since there is some overlap between the work of several Groups, certain tasks are referenced in

more than one place.

Section Group Page

III Time and Frequency Services 108

IV Time Scale and Time and Frequency Coordination 115

V Phase Noise and Hydrogen Masers 121

VI Atomic Beam Standards 126

Each of these sections begins with a short description of the general

program and objectives of the Group along with a list of staff and guests

in the Group. In an effort to relate the Division's work to it's mission,

a set of objectives have been used. Any objective which is listed below

may appear in the description of the work of several Groups since there is

heavy overlap and collaboration between a number of the Groups. Specific

accomplishments and plans are listed under each objective.

Obi ectives

o Generate NBS time scales UTC(NBS) and TA(NBS)

.

o Maintain international time and frequency coordination.

VII

VIII

IX

Ion Storage

Laser Frequency Synthesis

Geophysical Measurements

131

137

143

105
o Provide radio and satellite broadcast services,

o Provide seminars and measurement services on a reimbursable basis,

o Develop advanced methods for time transfer.

o Establish the second and the meter for the International System,

o Perform research and development on new primary frequency standards,

o Perform basic studies in areas related to future frequency standards,

o Develop metrology for precise time, frequency and length measurements,

o Provide reference frequencies from the microwave to visible regions,

o Measure far infrared frequencies of atoms and molecules,

o Advise industry and government agencies on time and frequency metrology.

General

II, KEY ISSUES IN TIME AND FREQUENCY

The discussion below does not address the measurement technology and

broad range of user services which are now adequately handled by the

Division. Rather, it is aimed at defining where the Division is going or,

in some cases, where it should be going.

Time Transfer

Satellite time transfer has become the method of choice for

international time coordination with NBS playing a key role through

development of the GPS Common-View Method. With this advance, time and

frequency transfer is now limited by the performance of the primary

standards themselves and the Division now uses the technique to support

other applications (e.g., NASA Deep Space Network and studies of the

Millisecond Pulsar) . The Division is also working on two-way time transfer

using commercial communication satellites, a method which should provide

even higher-accuracy time transfer to support pending improvements in

primary standards. Satellite time transfer has substantially altered the

conduct of the Division operations and, in the future, it will play a larger role in the synchronization of major systems.

Primary Frequency Standards

Radiatively-cooled, trapped ions have been considered by many to be

the best choice for future standards. The first demonstration of a Beryllium standard operating at an accuracy of one part in 10^^ along with

the development of a 'commercial' ion standard have bolstered that view.

Slowed neutral beams, on the other hand, are in an embryonic stage and no

one has yet proposed a specific scheme for using them to produce a frequency standard much less demonstrating anything in the laboratory.

Nonetheless, recent progress in radiative cooling and focussing of neutral

atomic beams now presents the potential opportunity for the development of

an advanced frequency standard operating at a performance level which is

106
intermediate between that of the optically-pumped technology of NBS-7 and

the longer-term, but higher-accuracy performance expected for trapped ions.

The very highest accuracy primary standards will most likely operate

at frequencies in the optical region. This is due to the fact that,

regardless of the clock frequency, the observation time most often

determines the minimum linewidth and thus, the Q of the resonance increases

directly with frequency. For this reason, the Ion Storage Group has been

investigating an optical frequency standard based on mercury ions and it seems likely that they will demonstrate a prototype of such a device in the

next few years. While an optical frequency standard could be used directly

in the optical region, it poses another challenge if it is to be used as a reference for microwave and lower frequencies where it could then be used

as a time standard. The challenge is that of accurately relating an optical frequency to a microwave frequency. The Division has expertise in

this area, but all would agree that this is a difficult thing to do

routinely. Thus, it is important to initiate development of a simple,

reliable chain (frequency division or multiplication) linking the microwave

and optical regions. This could also provide for improvement of our realization of the meter and support optical frequency metrology which will

be needed to support coherent optical communication systems.

Time Scale

The imminent improvements in primary frequency standards place

additional requirements on the NBS time scale. The current time scale,

acting as a flywheel, varies in frequency on the order of 1 part in 10^^

per year setting the current requirement for time-scale calibration by

NBS-6 at once per year. At an accuracy level of 1 part in 10^^,

calibration would have to occur about once each month. In order to assure reliability in dissemination of time and frequency signals, time-scale

performance should be improved to increase the period between calibrations.

Efforts should continue to upgrade both the stability and reliability of

the ensemble. Research on time-scale algorithms should also continue,

since this can contribute significantly to time-scale stability.

Broadcast Services

The advantages of satellite time transfer are discussed at the

beginning of this section. It should be obvious that satellite broadcast

of time and frequency signals would improve significantly upon ground-based

broadcasts. NBS does operate a satellite broadcast service through the

GOES weather satellites, but that broadcast is limited in accuracy to 100

microseconds by the broadcast bandwidth and the tracking information

provided by operators of the GOES system. Communication satellites provide

the potential for a very simple broadcast service with accuracy in the

range of 100 ns to 1 fj,s

.

The Division and the National Research Council in

Canada are both studying this concept and considering cooperation, since a single broadcast service might well serve both countries.

107
Discussions with the electrical power industry suggest the need for

1 fis synchronization of power networks. Deregulation of the communication

industry poses synchronization problems at a similar level. The Division

is interacting with the latter industry through their timing standards

committee to support some collective resolution of the problems. A highaccuracy satellite service could be of value to both of these industries.

Measurement of Phase Noise

The aerospace industry is now starting to see procurements for space

hardware with specifications for components of very low phase noise.

Phase-noise measurements have been well developed at a few specific

frequencies for characterization of frequency standards, but little work

has been done on the methodology for such measurements in other regions of

the electromagnetic spectriom. The Division is now working to develop and

demonstrate phase-noise measurement systems in other important spectral

regions. This effort is coordinated with the work in Division 723 on broadband- thermal-noise standards. The work naturally involves the

development of stable reference oscillators and low-phase-noise

multipliers, components which are important in the Division's work on primary standards and frequency synthesis.

III. TIME AND FREQUENCY SERVICES

The Time and Frequency Services Group has the primary focus of direct

industry and other agency support. The Division broadcast services, the

Frequency Measurement Service, and the Time and Frequency Bulletin all fall

within their responsibility. In addition to these on-going services the

Group is working on two other projects: synchronization of clocks using

two-way satellite time transfer, and timing for space-borne communications

nodes. The Group's work is described in more detail below.

StaffD. W. Hanson, Project Leader

D. A. Howe

J. L. Jespersen

G . Kamas

M. A. Lombardi

R. E. Beehler (Broadcast Manager)

WWV. WWVB. Ft. Collins

J. E. Folley (Part-time)

J. M. Maxton

J. B. Milton, Chief Eng.

C. S. Snider

A. R. Trevarton

WWVH. Hawaii

A. Fabro (Part-time)

E. F. Farrow

M. Ferguson (Part-time)

N. Hironaka, Chief Eng.

D . Okayama

108
Convenient access to NBS standards of time and frequency is

accomplished for the majority of users through the radio broadcasts of

stations WWV, WWVH, and WWVB and a time code broadcast by the GOES

satellites. NBS also provides telephone time-of-day services, publications

of time and frequency values of other radio stations as received at NBS,

portable clock comparisons and calibrations. Seminars concerning time and

frequency metrology are regularly scheduled to acquaint users with

techniques for characterizing oscillators and distributing frequency and

time signals. Examples of important applications of time and frequency

services are given below.

Navigation

Celestial navigators need time to determine their precise location.

An error of 2 s could cause a ship to miss its destination by about 1 km.

Thus, military and commercial shipping and small boat owners depend in a life and death sense on the availability of the signals from WWV and WWVH.

More sophisticated electronic navigation systems such as LORAN-C and the

Global Positioning System (GPS) must maintain time much more accurately.

An error of only 3 fxs could produce the same 1 km error for the navigator.

Systems Control and Synchronization

The electric power industry uses both frequency and time information

in the management of generation and distribution of electric power.

Frequency measurement has been fundamental to the industry for many years

and is satisfied by signals from WWVB and GOES. Time is becoming

increasingly important in the location and analysis of fast occurring

events (faults), measurement of power flow, and the control of systems to

minimize losses and avoid outages caused by exceeding stability limits.

Radio and TV stations need accurate frequency to broadcast signals at

exactly their assigned frequencies. They need accurate time to set clocks

so they can join the networks at the right instant. The aviation and

aerospace industries need accurate time for aircraft traffic control

systems and for synchronization at satellite and missile tracking stations.

The telecommunications industry needs time accurate to 1 fis and better

to synchronize communication's nodes spread over wide geographical areas. Divestiture by AT&T along with the growth of other major carriers poses

significant difficulty for synchronous transfer of calls through the

interfaces between companies. Increasing data rates in the newer digital

communication systems will further complicate system synchronization.

Data Acquisition

The FAA records accurate time on its audio tapes along with the

air-to-ground communications from airplanes. Having an accurate record of

when particular events occur can be an important factor in determining the cause of a plane crash or equipment malfunction.

109
Geophysicists and seismologists studying lightning, earthquakes,

weather, and other geophysical disturbances need time to synchronously and

automatically obtain data from wide geographical areas and to label

geophysical events. Other scientists use time for controlling the duration

of physical and chemical processes while astronomers use time for labeling

astronomical events, such as lunar occultations , eclipses, and pulses.

Science and Metrology

Manufacturers need time and frequency to calibrate counters, frequency

meters and test equipment. Accurate spectra of molecules including

information on pressure broadening are needed to accurately determine

atmospheric concentrations of important pollutants. Laser frequency

measurements provide accurate calibration frequencies for spectroscopists

and for radio astronomy as well as the means for realization of the meter.

OBJECTIVE: Provide radio and satellite broadcast services.

NBS offers several around-the-clock time and frequency dissemination

seirvices to the general public. In 1923, radio station WWV was established

by NBS and has been operated since that time. A sister station, WWVH was established in 1948, on the Hawaiian Island of Maui, and relocated to Kauai

in 1971. In 1956, WWVB began low frequency broadcasts. WWV's signal is

also offered by a telephone, not toll-free, by dialing (303) 499-7111. A

similar service from WWVH is available by dialing (808) 335-4363 in Hawaii.

Broadcasts from WWV and WWVH can be received on conventional shortwave

receivers nearly anywhere in the world. Broadcast frequencies include 2.5,

5, 10, and 15 MHz for both stations and 20 MHz from WWV only. Accuracies

within 1 ms can be obtained from these broadcasts if one corrects for the

station's distance from the receiver. These services also provide standard

frequencies, a BCD time code, astronomical time corrections, and certain

public service announcements from other government agencies. The telephone

service offers the capability of obtaining NBS time and audio frequency

signals. The caller can receive a time signal, accurate to 30 ms or better, about the maximum delay in cross-country telephone lines. WWVB

offers a direct path signal of greater accuracy than WWV or WWVH, but a special 60-kHz low frequency receiver is required. WWVB's signal includes

a binary coded system, needing special decoding equipment. The WWVB

broadcast covers the North American continent. These broadcast services

are coordinated with similar operations in other countries through active

participation in the international CCIR organization.

NBS time and frequency signals have been relayed through the GOES

geostationary satellites since 1975. The GOES broadcast covers North and

South America as well as major portions of the Pacific and Atlantic

including parts of Europe. More than 10 years of experience has shown that

such a system provides continuous time and frequency reception with more

no
dependable propagation characteristics than HF and LF broadcasts. The

satellite position broadcast with the time permits automatic correction for

variations in path delay resulting in time accuracy of 100 iss

.

FY 1987 Plans and Accomplishments

Complete the survey of WWV, WWVB, WWVH and GOES users and document results.

Accomplishment - The survey is in progress and will continue until

October, 1987. About 5000 responses were received as of August, 1987.

Results are being tabulated in a dBase format and, following analysis

of the results, a final report on the survey will be prepared.

Develop and implement staffing plans at Fort Collins and Hawaii that

respond to anticipated retirements of both Chief Engineers.

Accomplishment - The Chief Engineer at WWVH, Chuck Trembath, retired

on August 1, 1987. Noburu Hironaka, an engineer at WWVH, assumed the

responsibilities of Chief Engineer on that date and a new electrical

engineer was recruited to fill the vacancy created by the retirement.

The Chief Engineer at WWV/WWVB is now eligible for retirement, but has

decided to stay on for the foreseeable future. Arrangements made

several years ago provide backup for his eventual retirement.

Conduct tests of electronic voice synthesis system for improved broadcast

announcements

.

Accomplishment - Voice synthesis equipment has been delivered to WWV

by the National Weather Service, but the equipment manufacturer is

still working on the required software and hardware interfacing.

Testing will proceed as soon as the equipment is ready. Equipment

costs have been covered by the Weather Service.

Develop 2nd-generation, more -automated software for GOES time code

operations

.

Accomplishment - The software is essentially complete except for one data acquisition/plotting module. Improvements will continue to be

developed and implemented as appropriate.

Develop and implement an automatic tuning system for the standby WWVB

antenna

.

Accomplishment - The automatic tuning system is complete. Final

testing and implementation will be completed shortly.

Maintain reliable operations from WWV, WWVB, WWVH, and the GOES satellites.

Accomplishment - Outages for all services continue to be minimal at

levels varying from 0% (WWV) to about 0.1% (GOES) of total

transmission time. Improved backup for the electrical power system

for the GOES timing equipment has been developed and installed at

Wallops Island, Virginia.

Ill
FY 1988 Plans

Procure and install new energy-efficient transmitters for WWV. This will

include acceptance testing at the manufacturer's site and Fort Collins.

The objective is to replace outdated equipment and to reduce energy costs.

The savings should pay for the transmitters over the course of five years.

Prepare a final report on the findings of survey of users of services.

After the voice -synthesis equipment becomes operational, perform on-the-air

tests of the equipment. Determine acceptability of broadcasts by users

and, if successful, investigate options for acquiring additional systems

for Fort Collins and Hawaii to replace outdated magnetic recording systems.

Maintain reliable broadcasts from WWV, WWVB, WWVH and the GOES satellites.

Develop documentation for and lead U.S. Study Group 7 (Time and Frequency

Services) of CCIR. Head U.S. delegation to 1988 Interim Meetings of the

International CCIR Study Group 7. Contribute NBS input to CCIR handbook on satellite timing methods and resources.

OBJECTIVE: Provide seminars and measurement services on a reimbursable

basis

.

Frequency Measurement Service

The frequency measurement service is automated, modest in cost, and

provides traceability to NBS at a level of one part in 10^^ . The service

is based on common-view reception of low frequency signals from stations

such as WW^7B or Loran-C. This service provides the user with a data logger

and a low frequency receiver which is appropriate to the particular

location. A typical system contains a receiver, microcomputer, disc units

and printer-plotter. The user provides a dedicated phone line and modem so that the system data can be compared with data recorded at NBS providing

assurance that the users reference is accurate. To assist the user in

getting the most out of this system, the Division provides training with

the actual equipment.

Time and Frequency Bulletin

The Division continues distribution of it's Time and Frequency

Bulletin to over 500 service users. The bulletin provides information on

the performance of many useful references and notes events and service

changes of interest to users. It was expanded to cover new services.

112
Seminars

The annual Division seminar provides industry and other agencies with

information and training on the use of frequency standards . Special effort

is made to have the seminar support the introduction of new services and to

be of particular interest to the nations 's calibration laboratories.

FY 1987 Plans and Accomplishments

Continue operation of the Frequency Measurement Service. Implement the

automated training program so as to minimize staff hours spent on the

service

.

Accomplishment - Low turnover and good customer feedback indicate high

customer satisfaction with this service. Service growth during the

year was only modest since the Division decided to reduce promotion of

the service in order to stabilize it near the current size (48 users)

.

Provide a comprehensive Time and Frequency seminar (reimbursable)

.

Investigate the possibility of conducting the seminar off site so as to

provide the opportunity for more effective informal contact between the

attendees and the staff of the Time and Frequency Division.

Accomplishment - This year's seminar, which was fully subscribed

months in advance, was held off site at a local hotel. Many of the

attendees were from the communications industry (AT&T, MCI, SPRINT,

etc.). Guest lecturers from the communications industry and DOD

provided special emphasis on timing for communications.

FY 1988 Plans

Continue operation of the Frequency Measurement Service.

Provide a comprehensive Time and Frequency Seminar (reimbursable) . Develop

an improved method for demonstrating time-domain and frequency-domain

measurement systems to the large seminar audience.

OBJECTIVE: Develop advanced methods for time transfer.

The use of communications satellites for time transfer at all levels

of performance appears to be widely accepted. In a recent annual report,

the BIPM/BIH urged further development of the concepts. Much of this is

due to improvements in the available technology and significant reduction

in the cost of components and leased transceivers on satellites. At the

higher levels of performance, work reported by Japan and unpublished tests

involving NBS , USNO, and COMSAT Laboratories have demonstrated one-half

nanosecond time comparison precisions using two-way time exchanges through

a satellite. Additional tests have indicated that 20 ps comparisons are possible using the same techniques with higher transmission power levels.

NBS, USNO and the NRC in Canada have informally agreed to develop a

113
permanent time- transfer network to serve the three laboratories. All of

the necessary equipment has been acquired and tests will begin next year.

FY 1987 Plans and Accomplishments

Initiate development, with assistance from INTELSAT, of a satellite-based

network for nanosecond time comparisons between all major timing

laboratories in North America and Europe. Provide to each laboratory the

technical and regulatory information necessary to participate in the

network operation.

Accomplishment - The NBS satellite earth station came into full

operation early this year. Leased time through two commercial

communications satellites was obtained for $35 per half hour.

Subnanosecond precision was obtained in loop tests through these

satellites. For a time- transfer network covering North America and

Europe, INTELSAT has offered time on an Atlantic satellite for one year at no cost.

Begin operation of the two-way, time- transfer system on a limited basis

with a few laboratories.

Accomplishment - Because of problems in bringing earth terminals into

operation at USNO and NRC and because the INTELSAT satellite will not

be available until mid 1988, the operation of the two-way- timetransfer system has been delayed by at least a year. The satellite

delay is a result of problems with the Ariane launch rocket.

FY 1988 Plans

Perform two-way time comparisons between USNO, NRC and NBS using a domestic

communications satellite.

Procure, assemble and license a mobile KU-band earth station for

calibration of the two-way satellite facilities of NBS, USNO and NRC.

Begin trans -Atlantic time comparisons following availability of INTELSAT

satellite (to be launched).

OBJECTIVE: Advise industry and government agencies on time and frequency

metrology.

FY 1987 Plans and Accomplishments

Complete study of the synchronization of space-borne communications nodes.

Accomplishment - The study, identifying and evaluating technology

relative to DOD needs for space communications and other applications,

is complete. A timing architecture capable of supporting space

communication systems was proposed. Using this architecture, timing

sources and timing delivery to space platforms were examined.

114
Pending funding, implement a satellite tracking network and experimentally

determine how best to generate the satellite ephemeris required to support

a 0.1 /iS time and frequency broadcast service.

Accomplishment - Without funding, progress on the project was minimal.

FY 1988 Plans

Pending funding, simulate time transfer to space platforms through use of

two-way time transfer between earth stations.

IV. TIME SCALE AND TIME AND FREQUENCY COORDINATION

This Group has the responsibility for the operation and further

development of the NBS time scales and for coordination of these time

scales with other timing centers and the Bureau International de L'Heure

(BIH) . These time scales are, of course, a key responsibility since they

not only provide the basis for all services, but also serve as the stable

reference against which much of the Division gauges it's research. The

Group has developed a coordination scheme based on common view of the

Global Positioning System (GPS) satellites which is now the de facto

coordination approach for the world.

Staff

:

D. W. Allan, Project Leader

D . D . Davis

J . E . Gray

H. E. Machlan

T. K. Peppier

M. A. Weiss (Part-time)

J. Levine (1/2 time)

L. Ping-Ping (Guest Worker)

OBJECTIVE: Generate NBS time scales UTC(NBS) and TA(NBS)

.

NBS atomic time is generated from an ensemble of approximately twelve

commercial and one laboratory cesium-beam- frequency standards and two

laboratory hydrogen masers. The time of all the clocks is automatically

measured every two hours with a precision of a few picoseconds. The

UTC(NBS) and ATI time scales are computed following each measurement cycle

using a weighted-average algorithm. The small dispersion of the clocks

during the two hour interval between measurements makes it possible for NBS

to provide UTC(NBS) with 1 ns accuracy at all times. Coordinating with the

Bureau Internationale de L'Heure, UTC(NBS) is steered toward and kept

within 1 /is of UTC. ATI is a metrology tool, unsteered in time or frequency, and made to be as stable and uniform as possible.

115
At the end of each month, the TA(NBS) time scale is computed using a Kalman algorithm. This computation is optimvun in the statistical sense for

clocks having both white frequency noise and random-walk frequency noise, a good model for the clocks in the NBS ensemble. The second of TA(NBS) is

steered toward NBS ' s best estimate of the SI second based on periodic

calibrations of the ensemble by the primary frequency standard, NBS-6.

FY 1987 Plans and Accomplishments

Finish remodeling of the clock room. Accomplishment - All of the clock room equipment has been purchased,

all of the critical clock room rearrangement has been completed and

the recabling of the semi-rigid coaxial lines is proceeding in a systematic and orderly fashion -- having to be done while the time

scales are in full operation. The public display window is complete.

Implement new alignment procedure (developed by A. De March!) for

commercial cesium standards in the time scale to improve long-term

stability of the individual standards and thus of the time scale.

Accomplishment - Five poorly performing clocks, two belonging to NBS

and three sent by USNO to NBS for this study have been aligned per the

De March! procedure. Significant improvement was observed in all cases. One of the USNO clocks now performs as well as any commercial

cesium standard ever tested by the Division.

Install and test backup measurement system for the time scale.

Accomplishment - The backup measurement system has been installed, and

the tests were initiated in May, 1987. The testing will continue over

the next several months as the cabling is carefully changed on the

time-scale operating system so that the output is not perturbed.

Improve time-scale reference for the NBS Global Time Service.

Accomplishment - The new time- scale reference has been completed and

tested. The final cabling of it into the system is near completion.

FY 1988 Plans

Test and document the performance of the NBS Time Scales in order to

evaluate their performance for the most stringent of measurements, e.g.

comparisons with the millisecond pulsar.

Complete the semi-rigid coaxial connections for both the back-up and the

primary-measurement system and implement necessary software adaptations.

Contingent on the availability of funding, proceed with the acquisition of

a new time-scale computer.

Train several Division staff on the De March! alignment techniques for

commercial cesium standards.

116
OBJECTIVE: Maintain international time and frequency coordination.

A satellite-based, time- transfer system developed by the Division is

now in operation. Receivers are operating at: PTB in Braunschweig, West

Germany; OP in Paris, France; Goldstone, California; Madrid, Spain;

Canberra, Australia; NRC in Ottawa, Canada; lEN in Torino, Italy; RRL and

TAO in Tokyo, Japan; VSL in Delft, The Netherlands; NPL in England; NPL in

Israel; CSIRO in Australia; TUG in Austria; USNO in Washington, D.G.; and

NBS in Boulder. A computer-based, automatic-data-collection network

acquires data from the receivers. This data is combined with data from the

NBS Atomic Time Scale so that the time of the remote clock is known with

respect to UTG(NBS) to a precision of better than 10 ns after one day of

averaging. The Jet Propulsion Laboratory employs three receivers developed

by NBS in the same mode to provide frequency calibrations at a few parts in

10^^ between the sites of the NASA Deep Space Network. The GPS receivers

at most of the national timing centers now transfer their data via the

common-view technique to the International Time Bureau in Paris. This new

system has replaced Loran-C as the principal time and time- interval

transfer link for the SI second and the generation of the International

Atomic Time Scale (TAI)

.

FY 1987 Plans and Accomplishments

Transfer the software for handling GPS common-view data to the BIH.

Accomplishment - The NBS software has been successfully transferred to

the BIH, and BIH staff now generate the schedule for international

comparisons. In addition, BIH sent a staff member to NBS to acquire

techniques for optimal time and frequency transfer using GPS.

Study methods for improving the accuracy of time transfer using the common- view technique

.

Accomplishment - Using NBS developed software, several problems have

been identified and solutions proposed for improving the accuracy of

GPS time transfer by as much as an order of magnitude. In particular,

it appears that two -frequency measurements can provide a simple means

for more accurate determination of delay variations in the ionosphere.

Assist the BIH in determination of absolute time transfer by providing a delay-calibrated receiver to be carried to each of the participating timing

laboratories. Assist other national laboratories, as needed, with use of

GPS common-view time transfer.

Accomplishment - Two NBS calibrated GPS receivers were sent to the BIH

accompanied by a Division staff member. One receiver was then carried

to each of the European national time centers. A joint report and

paper analyzing the study revealed some problems, but verified that

the accuracy of the GPS common-view technique is at the 10 ns level.

117
FY 1988 Plans

Cooperate with BIH, USNO and the Naval Research Laboratory on calibration

and evaluation of GPS receivers for optimum time and frequency transfer.

Assist other national timing centers as appropriate with the use of GPS

common-view time transfer.

Develop the hardware and software needed to implement major improvements in

GPS common-view time transfer including evaluation of system biases.

Develop software to further streamline and automate international time

comparisons with the goal of weekly estimates of the world time ensemble.

OBJECTIVE: Develop metrology for precise time, frequency and length

measurements

.

Techniques for Measurement of Frequency and Frequency Stability

The Division has been a world leader in the development and

dissemination of the measures of frequency stability and their practical

implementation. The Division developed the de facto international standard

for practical specification of frequency stability and played a major role

in the development and test of the dual-mixer concept for measuring time,

frequency, and frequency stability providing for simple, precise

(picosecond) measurement of the difference between state-of-the-art

frequency standards. Work on the effects of phase noise on frequency

multiplication provided an explanation for numerous previous failures at

precision infrared synthesis. This new understanding of the multiplication

process then stimulated considerable improvement in the phase noise of

crystal oscillators and signal processing equipment. In the rf region, the

lowest noise crystal oscillators, buffer amplifiers, isolation amplifiers,

and frequency multipliers presently available are a direct outgrowth of

prototype designs and analysis developed at NBS . These low noise devices

have many applications in precise measurement as well as in the development

of new frequency standards such as the passive hydrogen maser, the stored

ion standard, and cesium standards.

Techniques for Characterizing Noise in Clocks

Memory of the rate of the primary standard is stored in a time scale, an ensemble of commercial cesium standards. The clocks in the time scale

don't have the accuracy of NBS-6, but they do have very good frequency

stability. The stability of a clock ensemble can be improved by increasing

the number of clocks, by improving the stability of individual clocks, by

wisely utilizing the clocks available, or by a combination of these

approaches. The Division has chosen to use a modest number of clocks

ensuring sufficient reliability, redundancy and variety (to avoid

118
systematics from a particular manufacturer) , but then to characterize the

clocks with enough care so that the algorithms which average the clocks

make optimum use of the performance of individual members of the ensemble.

The algorithms which control the time scale have evolved to their

current state through considerable work over a long period. UTC(NBS) is

generated by an algorithm which can be traced back 20 years. In order to

estimate the performance of this algorithm, several studies were conducted.

Using Kalman filters, a method was developed to model atomic clocks and

obtain maximum likelihood estimates of the model parameters from data on

the ensemble of clocks. Tests for the validity of the model and confidence

intervals for the parameter estimates were made and shown to be

statistically correct. A study was then made of the statistical

significance of frequency drift and this yielded additional important

insights. A second major development was a Kalman (or recursive) algorithm

for estimating time from the ensemble of atomic clocks. The algorithm

allows for the addition or deletion of clocks and provides for automatic

error detection and correction. This Kalman algorithm is now used to

generate the time scale TA(NBS). During this effort the earlier algorithm

which generates UTC(NBS) was found to be very near optimum in its

performance. Over the last year its stability was shown to be of the

highest order as it was found to be the most stable reference for the

characterization of the stability of the millisecond pulsar, PSR1937+21.

FY 1987 Plans and Accomplishments

Put environmental parameters into the time-scale data base and correlate

the time scale performance with them.

Accomplishments - The hardware was installed and measurements have

been taken for some time on various environmental parameters. The

data was archived, but not on the time scale computer. This will be

done when other higher priority work on the time scale is completed.

Assist others in the application of the time- series statistical methods to

other areas of metrology.

Accomplishment - A major paper on this topic was published in the IEEE

I6tM Transactions. The Statistical Engineering Division has now

initiated study of the ideas. Preliminary findings are good and they

have developed interesting insights into this statistical concept.

FY 1988 Plans

Evaluate the NBS time scales and algorithms to ensure confidence in

measurements such as comparisons with the millisecond pulsar.

Document the performance of the NBS algorithm for practical clock systems.

If funds and staff are available, continue study of the use of time-seriesanalysis techniques in other disciplines. A joint proposal with the

Statistical Engineering Division on this subject was made to management.

119
OBJECTIVE: Provide seminars and measurement services on a reimbursable

basis

.

Global Time Service

The Division now offers a service, based upon an NBS designed

receiver, which provides for highly precise time and frequency transfer to

a users site. A receiver, located at the users facility, communicates data

automatically to an NBS computer which stores the data, determines which

data elements are suitable for time- transfer calculations and provides an optimally filtered value for the time and frequency of the user's clock

with respect to the NBS Atomic Time Scales. The user is given an account

on the NBS computer through which he can access the results of the NBS

analysis. Tests between receivers in Colorado, Canada, Germany, France,

Spain, Wyoming, Louisiana, Washington, DC and California have demonstrated

time comparisons with precisions of better than 10 ns using an averaging

time of 13 minutes and frequency comparisons with a precision of 1 part in

10^^ for averaging times of four days.

Calibration of Atomic Standards

In conjunction with development of the time scale algorithms the

Division has developed a time and frequency measurement system with

exceptional performance. Clocks are now calibrated and characterized

through comparisons with the ensemble clocks using the same measurement

system which reads the ensemble clocks. This system is used as a reference

for research within the Division as well as for reimbursable calibrations.

FY 1987 Plans and Accomplishments

During planned tests of intentional degradation by DOD of the GPS signals,

determine the effect of the degradation on the accuracy of common-view time

transfer

.

Accomplishment - NBS has a representative on the committee which is

drafting a civilian-sector, interface control document to be

incorporated in a more general DOD document on GPS use. The committee

is considering solutions which would yield no degradation in accuracy

of time transfer.

Improve the algorithm for estimation of the perfonnance of remote clocks

(accessed through GPS) to improve accuracy and stability assessments.

Accomplishment - This work is complete and the algorithm is now

routinely used. The concepts have been shared with the BIH staff.

120
FY 1988 Plans

Expand the time scale measurement system to allow for additional input

ports for clock calibrations.

Continue participation on GPS committee with the goal of minimizing the

effects of GPS degradation on the transfer of time and frequency.

Develop and implement methods for eliminating or minimizing bias effects

which have been identified in GPS measurements.

OBJECTIVE: Advise industry and government agencies on time and frequency

metrology

.

FY 1987 Plans and Accomplishments

Provide assistance to GPS operations in the areas of improved steering of

GPS time, development of cross-link ranging for the GPS satellites and

determination of the sources of system biases.

Accomplishment - A joint study conducted by USNO, NRL and NBS was completed and the results have been published. Through computer

simulation, NBS demonstrated that time steering to 10 ns is

achievable. Implementation of the proposed concept is proceeding in a cooperative effort. Several sources of system bias have been

identified, but corrective measures must still be developed.

FY 1988 Plans

Continue to assist the Joint Program Office at Air Force Space Division on methods for GPS time steering.

Assist the Joint Program Office with consultation on proper methods for

utilizing clock ensembles and combining algorithms to improve reliability

and stability of the GPS reference systems.

V. PHASE NOISE AND HYDROGEN MASERS

In past years, the primary goal of this Group has been the development

of a passive hydrogen maser with good medium-term to long-term stability

for DOD requirements and for use in the NBS clock ensemble. The project,

which was funded by the Navy, has been quite successful. Two masers are currently operating in the ensemble and they have been out-performing the

commercial cesium standards by a wide margin. The maser technology has

been transferred to industry through the Industrial Research Associate

Program. The project has also addressed other issues of importance to the

121
Division. These include: line-center errors in high-performance servo systems and phase noise in frequency multipliers and synthesizers.

More recently the program emphasis has shifted to measurement of

phase-noise where emerging technology is pushing the state of the art. The

Group has just made a long-term commitment to the Department of Defense to

develop and demonstrate phase-noise measurement systems in the microwave

and millimeter-wave regions of the spectr\im. This work should result in

improved measurement systems for NBS and lower-phase-noise , microwave and

millimeter-wave synthesis to support development of primary standards as well as frequency synthesis into the optical regions of the spectrum.

Staff: F. L. Walls, Project Leader

A. J. D. Clements

L. L. Lewis (Industrial Research Associate)

T. E. Smith (Industrial Research Associate)

S. R. Stein (Industrial Research Associate)

OBJECTIVE: Generate NBS time scales UTC(NBS) and TA(NBS)

.

Active hydrogen masers have long been touted for their excellent

short-term stability, but long-term stability has generally been poor. The

NBS maser project has focussed on improving long-term stability in a passive maser which is simple and small. The goal has been a system which

will fit into a package equivalent to that of a commercial cesium standard.

The results obtained to date have been impressive. The best of these

masers provides medium- to-long-term stability equivalent to that of a cesium ensemble of approximately 20 high performance tubes. The

fundamental design advance has been the servo locking of the physical

cavity resonance to the hydrogen reference. The system also locks the

slave oscillator to the same atomic resonance. The obvious conclusion is

that the long-term stability of active hydrogen masers has been severely

degraded by cavity pulling effects and that variations in the wall shift

are extremely small relative to the present accuracy of primary standards.

FY 1987 Plans and Accomplishments

Complete the third passive hydrogen maser for the time scale and determine

the actual effect of the higher Q cavity on the maser performance. Convert

a second maser on the scale to getter pumping in order to improve its mean

time between failure.

Accomplishment - Work on this program has been slowed by a lack of

funding from the Naval Research Laboratory. The third maser is still

three or months away from completion. However, the second maser was retrofitted with a new vacuum system to improve reliability and it

should be back in service by December.

122
Continue to advise the staff of the cesi\am standard project on servo issues

including actual circuit implementations.

Accomplishment - Consultation with this Group is substantial involving

a number of servo design issues.

Explore new phase modulator concept theoretically and initiate experimental

study if appropriate.

Accomplishment - Based on the shortcomings of the phase modulators

used in NBS-6 and the small hydrogen masers, calculations on three

different designs have been performed. These are all inherently more stable and have smaller distortions. The most promising of these

should be easy to construct and involves very little manual

adjustment. A prototype is being built in order to verify the concept.

Purchase a commercial version of the passive hydrogen maser to improve

performance of the NBS ensemble.

Accomplishment - Purchase of this device was delayed because the

manufacture wasn't quite ready to accept fixed price orders. They are just beginning full tests of the maser and expect to be able to accept

orders in September 1987.

FY 1988 Plans

Through the Industrial Research Associate Program, test the performance and

environmental sensitivity of the commercial passive hydrogen maser.

Pursuant to positive results in the above tests, purchase a commercial

passive hydrogen maser for the time scale.

Continue to assist the cesium Group in the design of accurate servo systems

for NBS-7. This will include the evaluation of new modulator(s)

.

OBJECTIVE: Provide seminars and measurement services on a reimbursable

basis

.

Measurement of Phase Noise

The improved phase stability of components developed for the passive

maser have enhanced the Division capability to provide special calibrations

of phase noise in oscillators, amplifiers, frequency multipliers and

synthesizers from 5 MHz to 700 MHz. The new DOD contract for development

of phase-noise metrology through the microwave and into the millimeter-wave

region will permit increased automation of measurements. The goal is to

eventually cover the region from 5 MHz to 60 GHz for oscillators,

amplifiers, multipliers, dividers and synthesizers. The emphasis will be on the development of sound measurement methodology and transfer of this

methodology to industry and government laboratories.

123
FY 1987 Plans and Accomplishments

Modify the prototype phase-noise system to cover frequencies from 1 to

26 GHz with capability for computer control of gains, measurement

bandwidths and characteristics of the phase- lock loop.

Accomplishment - The prototype system for this frequency range was built and tested. The system automatically finds phase quadrature as needed for accurate measurements. Full automation of the phase- lockloop gain requires a custom microprocessor. The hardware is in hand

and the software written, but the system is not yet fully integrated.

Complete phase-noise system to cover frequencies from 5 MHz to 1 GHz with

capability for computer control of gains, measurement bandwidths and

characteristics of the phase- lock loop.

Accomplishment - The prototype system was constructed and tested. The

system automatically finds phase quadrature as needed for the

measurement and the noise floor is very low. The custom

microprocessor needed to interface the system with the computer

controller is in hand and most of the code has been written for it.

Develop a low-noise reference signal at 10.6 GHz.

Accomplishment - The phase noise of the best available microwave

sources has been reduced by 10 to 40 dB through use of a reference

cavity in a frequency lock loop. This composite system will

eventually by phase locked to a multiplied quartz oscillator system.

FY 1988 Plans

Complete automation of the 5 MHz to 1 GHz phase noise measurement system to

include an automated calibration of the accuracy to approximately ±1 dB.

Complete automation of the 1 GHz to 26 GHz phase noise measurement system.

Assemble and test a 33 to 50 GHz phase-noise-measurement system with a

1 GHz bandwidth. The accuracy goal is ±1 dB to 30 liHz and ±2 dB to 1 GHz.

Build and test a multiplier system to lock the 10.6 GHz microwave

oscillator to a quartz oscillator at 100 MHz. The 100 MHz oscillator will

then be phased locked to a 5 or 10 MHz oscillator for normal analysis.

OBJECTIVE: Establish the second and meter for the International System.

FY 1987 Plans and Accomplishments

Conduct experimental tests of new method for low-noise synthesis to X band

with funding from the Washington University and the Department of Defense.

124
Accomplishment - A very low noise divider system for dividing 100 MHz

down to 10 and 5 MHz was developed. The noise is about 30 dB less

than the best systems described in the literature. This will greatly

simplify the synthesis problems. Two new technologies which appear

capable of dividing 10 GHz down to 100 MHz were also identified.

Arrangements were made to obtain sample devices for testing. In the

meantime, development has started on a very low noise multiplier based

on harmonics of 500 MHz tied to 100 MHz. This will be used for

testing the dividers and perhaps for the final synthesis if, for some reason, the dividers are not suitable. The phase noise of an X-band

source was improved 20 to 30 dB by frequency locking the source to a high-Q cavity in a servo loop with a bandwidth of 2 MHz. For Fourier

frequencies between 20 kHz to 1 MHz from the carrier, the performance

is probably the best ever achieved for a room temperature device.

OBJECTIVE; Advise industry and government agencies on time and frequency

metrology.

Hydrogen Maser Technology

The passiye hydrogen maser deyeloped at NBS with partial military

funding has demonstrated exceptional frequency stability from a few seconds

to a few weeks. Based on 2 months of data, the stability is = 5x10'^^ at 1 day and = 3x10'^^ at 8 days. At a level of resolution of ± 3x10”^® /day,

the drift is unobservable. The time dispersion per day is a factor of 4 to

5 times better than the best available commercial cesium frequency

standards. Several Industrial Research Associates have worked with NBS on

this program. This cooperation continues and the first passive hydrogen

maser to be constructed in this collaboration is now in operation.

Quartz Crystal Resonators

Vibration sensitivity is presently one of the most severe difficulties

encountered when using a frequency standard in non- laboratory environments.

Although NBS no longer has an experimental quartz crystal research program,

consulting support is being provided to the U.S. Army and its industrial

contractors. A new method for temperature control of clocks which was developed in the hydrogen maser project would appear to offer promise for

quartz resonators. Interactions with industry on this concept will

continue through the year.

The Division has provided support to the quartz industry's effort to

develop standards permitting interchangeability of quartz oscillators. Two

workshops on the subject were organized in Boulder and the result appears

to be a rather simple measurement procedure based on impedance measurements

using commercial coaxial standards as references. The method provides full

traceability to National standards and forms the basis for solid U.S.

leadership in the development of standards at the international level.

125
Phase noise

With the initiation of new work on measurement and control of phase

noise, the Division is providing significant consultation on the subject to

science, industry and other government agencies. The Division has a clear

opportunity to provide a solid basis for phase noise metrology.

FY 1987 Plans and Accomplishments

Continue collaboration with Industrial Research Associates and the Naval

Research Laboratory on the passive hydrogen maser. Accomplishment - Work in this area has been more consultation than

collaboration, since the phase-noise program has dominated available

resources. Consultation with industry has focussed on the electronics

and discharge problems and that with NRL has covered oven problems.

Expand industrial and government contacts in the area of phase-noise

measurement and develop plans for dissemination of techniques for phasenoise measurement as they are developed.

Accomplishment - (1) An invited paper on "Low Noise Frequency

Synthesis" was presented at the Symposium on Frequency Control. This

paper reviewed practical limitations of circuits as well as recent

advances made at NBS . (2) Lectures on phase noise were prepared for a short course on frequency standards given in July. A variation of

these lectures was given in September at a short course on noise in

microwave and millimeter systems. (3) Consultation was provided to

the Applied Physics Laboratory and the National Security Agency on new

approaches for low-phase-noise microwave sources.

Additional Accomplishments

Accomplishment - A low noise amplifier with the best room- temperature

noise power, (2.5x10”^® A)(lxlO“^V) = 2.5x10“^^ W, was developed and a paper submitted for publication.

Accomplishment - A paper on concepts for compensated thermal

enclosures was presented at the Symposium on Frequency Control.

FY 1988 Plans

Continue consultation with industry and governmental agencies on methods

for measurement and control of phase noise.

VI. ATOMIC BEAM STANDARDS

This Group is responsible for operation of the current primary

frequency standard, NBS-6 and the development of NBS-7, the next generation

primary frequency standard which will be based on optically pumped cesium.

126
The objective is a standard which can be easily operated in a nearly

continuous mode with semi-automatic assessment of systematic errors at an accuracy level of 1 part in 10^^. The project is built upon successful

tests of the concept on field-size standards pumped by laser diodes.

Staff

:

R. E. Drullinger, Project Leader

D. J. Glaze

D. L. Hilliard

L. Holberg

J . P . Lowe

A. De Marchi (Guest Worker)

J. Shirley (Guest Worker)

I. Pascaru (Industrial Research Associate)

T. McClelland (Industrial Research Associate)

OBJECTIVE: Establish the second and meter for the International System.

Operation of the U.S. Primary Frequency Standard

Since 1968 NBS has designed and developed three new cesium devices:

NBS-4, NBS-5, and NBS-6. NBS-4 has a medium- length cavity of 50 cm, and

was built to test new ideas for improving the stability of cesium devices.

This standard is one of the most stable cesium clocks in the world,

achieving a stability of 7x10"^^. It should be noted here that no previous

NBS cesium frequency standards directly drove a clock; instead, they were used periodically to calibrate the frequency of an ensemble of commercial

cesium clocks that. NBS-4, because of its excellent stability, has served

as a working clock in the time-scale ensemble.

NBS-5 was built on the framework of NBS -3 and in turn served as the

basis for NBS-6, completed in 1975. The refinements incorporated include

greatly improved components to provide narrower resonance lines (25 Hz),

the ability to reverse direction of the atomic beam (which allows errors

due to asymmetries in the cavity to be diagnosed) , and other features

aiding analysis of performance. NBS-6 has an accuracy of 8x10'^^; more accurate but not quite as stable as NBS-4. Used together, these two

standards generate the U.S. standard second. A clock ensemble is used to

carry the second forward in real time so that it is continuously available.

FY 1987 Plans and Accomplishments

Shift responsibility for future evaluations of NBS-6 to 1 group. Past

practice involved rotation of this responsibility.

Accomplishment - Responsibility for evaluation of NBS-6 has now been

assumed by the Atomic Beam Standards Group.

Initiate an extended evaluation of NBS-6 using the De Marchi model to

127
account for Rabi pulling. Determine whether this evaluation procedure

allows for a reduction in the quoted uncertainty statement.

Accomplishment - NBS-6 was upgraded (improved electronic systems and

modified vacuum system) to minimize difficulties encountered in

previous evaluations. This has allowed evaluation in greater depth,

since beam reversals can be accomplished more rapidly. The result is

that the Group is learning a great deal more both about the standard

and the physics of cesium beams in general. In the longer term, a reduction in the quoted uncertainty of 8x10'^* may be possible, but

for now, some previously undervaluated systematic errors are proving

difficult to model. At the present, proving the historical evaluation

uncertainty is difficult.

As staff time becomes available, recharge NBS-4 with cesium and bring it

back into operation.

Accomplishment - Higher priority has been placed -on the study of

systematic errors in NBS-6 and the development of NBS-7 resulting in

delay of this project.

FY 1988 Plans

Complete current evaluation of NBS-6.

Recharge NBS-4 with cesium and bring it back into operation.

Study potential reduction of the uncertainty specification on NBS-6 and

determine the advisability (limited resources) of attacking this project.

OBJECTIVE: Perform research and development on new primary frequency

standards

.

Primary Cesium Standard Development

The known limitations to the accuracy of NBS-6 lie with the microwave

cavity phase shifts, exacerbated by the dispersive nature of the state

selection magnets. In addition, there are unknown shifts of the cesium

clock frequency associated with systematic effects which cannot be readily

studied in conventional systems. Replacing the magnets in a cesium

standard with optical pumping and detection using laser diodes should allow

the reduction of cavity-phase-shift uncertainties, and permit a better

understanding of the limitations of cesium standards. A small laboratory

version of the optically-pumped, cesium-atomic-beam frequency standard has

been constructed and performance demonstrated at < 7x10'

A larger test bed for the optically pumped standard has been designed

and the major components have been fabricated and assembled. This test bed

will serve as the basis for NBS-7. The system features a longitudinal

C-field and a novel Ramsey cavity which minimizes errors caused by

128
distributed cavity phase shift. The optical pumping concept provides the

means for minimizing errors due to end-to-end cavity phase shift.

FY 1987 Plans and Accomplishments

Initiate development of advanced electronic servosystem to achieve 10"®

splitting of the cesium resonance. Accomplishment - The modulator and demodulator/integrator are at the

heart of the servo system. A modulator promising improved linearity

has been designed tests are in progress. The demodulator/integrator

was designed and is under construction. Line splitting of 10"® still

appears reasonable. The frequency multiplier and odd-to-even

synthesizer have been fabricated and tested.

Develop practical laser systems for optical state selection and detection.

Accomplishment - A method for narrowing the linewidth and controlling

the frequency of diode lasers was developed in collaboration with a guest worker from France. It is now clear that this technique

provides spectrally pure radiation which does not substantially

increase the atomic-beam noise above the shot-noise limit. The

stabilized diode lasers will be available to meet the clock

development schedule, but additional study of the use of optical fiber

for coupling between the diode lasers and the clock is in progress.

Normal diode lasers are so sensitive to optical feedback that this

would not be considered. However, with less sensitivity to feedback,

the stabilized lasers might be usable with fiber.

Complete construction of the test bed for NBS-7 and demonstrate preliminary

operation (no error assessment)

.

Accomplishment - The design and fabrication of all of the major

components of the beam tube are complete. Testing of the individual

subsystems has been initiated and it is reasonable to expect that an atomic beam can be generated by the end of FY 1987.

Initiate experimental studies of light shift, cavity phase shift and

Majorana transitions.

Accomplishment - The need for theoretical study of systematic effects

along with procurement problems slowed the design and fabrication

processes so that the beam tube was not assembled until the end of the

fiscal year. This left no time for the experimental studies.

Initiate development of a computer-controlled system for automated

evaluation and operation of the standard.

Accomplishment - The basic concept for the automation of the standard

has been developed and the computer for controlling the system along

with some interfacing has been purchased.

FY 1988 Plans

Complete integration of all of the clock subsystems.

129
Determine the signal- to-noise performance and stability for the various

optical pumping schemes.

Initiate evaluation of the systematic uncertainties of the standard.

Initiate test of servo system concepts for locating the line center.

OBJECTIVE: Advise industry and government agencies on time and frequency

metrology.

Cesium Beam Technology

Recent advances in cesium beam technology which have come from

Division studies of optically pumped cesium clocks could improve the

performance of commercial devices. For example, this research could

improve both the long-term stability and the reproducibility after turn-on

of satellite based cesium clocks. These improvements involve the use of

laser diodes, cesium heat pipe ovens, optical pumping, and fluorescence

detection of atoms.

Much of this work is performed under contract from other government

agencies. In addition, the Division has formed an Industrial Research

Agreement with a manufacturer of cesium clocks. This agreement permits the

transfer of NBS research results to the private sector, and also brings

guest scientists from industry to the NBS laboratories.

FY 1987 Plans and Accomplishments

Under DOD sponsorship, continue to work with industry to assist in the

development of field-size frequency standards based on optical-pumping

concepts. The work is to include design of beam tubes, fluorescence optics

and laser-diode systems.

Accomplishment - The first engineering prototype clock has been

fabricated. As with the scientific prototypes before it, scattered

light at the windows is a problem. A second tube with improved

windows should be completed shortly.

Complete design and tests of modified recirculating cesium oven. Accomplishment - Life test on the simple recirculating ovens have

shown no deterioration in beam intensity. Based on calculation of the

integrated flux from one oven, it appears that the initial cesium

charge is nearly expended. This suggests that the beam intensity

remains stable to the end of the life of the oven.

Collaborate with De Marchi in completing tests of the Rabi-pulling model on commercial cesium standards and transfer information on this work to

industry and relevant government laboratories.

130
Accomplishment - With the Rabi-puiling model as a guide, several

poorly performing cesium standards were tuned to power- insensitive

operating points and then reevaluated. In every case the improvement

in stability was substantial. One standard now performs as well as any commercial standard ever evaluated by the Division. Several

government agencies have shown great interest in the result, since it

offers a cost-effective approach to improving the performance of

systems in the field.

FY 1988 Plans

Continue collaboration with industry on the development of optically pumped

cesium standards.

Complete fabrication and testing of the hybrid recirculating oven.

Contingent on funding, develop improved methods for optimal tuning of

commercial frequency standards and study the application of third order

servo systems as a means for completely eliminating Rabi-pulling effects.

VII . ION STORAGE

The long-term plans for primary frequency standards for the Division

involve an eventual shift to ion storage and radiative cooling. For the

present, the effort of this Group is being directed toward study of the

physics of the concepts. The Group has already demonstrated a Be"'’ ion

clock which operates at a performance level equal to that of NBS-6, the

present primary standard. While the focus of the work is ion standards,

the techniques are also applied to other problems of fundamental interest.

Staff

D. J. Wineland, Project Leader

J. C. Bergquist

J. J. Bollinger

W. M. Itano

C . H . Manney

F. Ascarrunz (Work Study)

L. R. Brewer (Postdoc)

S. L. Gilbert (Postdoc)

R. G. Hulet (Postdoc)

X. Shao (Guest Worker)

C. Weimer (Res. Assistant - CU)

131
OBJECTIVE: Perform research and development on new primary frequency

standards

.

Atomic Clock Based on Stored Ions

As a step towards realizing a primary frequency standard based on stored ions, the Division has developed a clock based on a ground state

hyperfine transition in ^Be'*’ . The combined uncertainties in all systematic

frequency shifts (such as those due to Doppler effects) are at the same level as those of the present U.S. primary time standard, NBS-6 which has

an uncertainty of about one part in 10^^

.

In these experiments, a few hundred ^Be'*’ ions were confined in a Penning trap and laser cooled to temperatures less than 1 K. An oscillator

was locked to a magnetic-field-independent hyperfine transition (~ 300 MHz)

using an optical-pumping, double-resonance technique. The measured

stability was about equal to that of a commercial cesium clock. Frequency

stability and accuracy performance can be improved in the future by using

an ion with a higher hyperfine frequency.

Farther in the future, it appears that the most accurate clocks will

be based on optical transitions in atoms or molecules. The main reason for

this conjecture is that the Q's for such transitions can be extremely high

(Q > 10^^). With this in mind, the S-+D quadrupole transition in Hg"^ has

been studied. The transition was observed for the first time in a miniature rf trap on a single Hg'^ ion. The present linewidth is limited by

the laser bandwidth, but this transition has a fundamental Q of about

0.5x10^^ (radiatively limited).

Trapped Ion-Cloud Studies

Studies are made of ion dynamics and the relation of these dynamics to

trap design. It appears that the principle limitation to accuracy of a frequency standard based on many ions stored in a Penning trap will be the

uncertainty in the second-order-Doppler (time-dilation) frequency shift due

to the rotation of the ion cloud. This rotation is a non-thermal effect

and is independent of the internal temperature of the cloud. Therefore

detailed studies of ion-cloud temperature, density and rotation are being

made using a two- laser, optical-optical, double-resonance technique.

A new concept for a frequency standard based on "sympathetic cooling"

is being studied theoretically and experimentally. In sympathetic cooling,

one ion species is cooled by Coulomb coupling with another ion species

which is laser cooled. This was proposed and demonstrated (on the Mg'*’ isotopes) a few years ago at NBS and has now been studied in more detail

using Hg"^ and Be"^ . The advantage is that the "clock" ions can be

continuously cooled, but ac Stark shifts from the cooling radiation can be

made negligibly small. This should result in substantially narrower

132
linewidths (less than 1 mHz) and reduction of errors due to the

second-order Doppler shift.

FY 1987 Plans and Accomplishments

Primary emphasis will be placed on narrowing the laser linewidth for the

S->D quadrupole transition in single Hg'*’ ions. This not only has a direct

bearing on the optical frequency standard, but will allow us to study the

motional sideband structure in this optical transition. This will allow

more accurate measurements of ion temperature and allow study of

limitations of ion cooling and the effects of imperfections in the traps.

A possible goal is the attainment of ions confined in the zero-point state

of the confining well.

Accomplishment - Recoilless absorption (optical Mossbauer effect) and

Doppler-effect-generated "phonon" sidebands of a single trapped ion

have been observed. The recoilless line has a direct application for

optical frequency standards. Cooling to the theoretical laser cooling

limit of 1.7 mK was verified by comparing strengths of the sidebands

of the carrier. The best resolution (limited by laser linewidth)

obtained to date is 30 kHz at 1.07x10^^ Hz.

Frequency Detuning (in MHz)

Figure 1. Quantized signal showing the electric-quadrupole-allowed

5d^° 6s ^S ^/2 ~ “^) " 5d^ 6s^ ^^5/2 (TMj = transition in a single, laser-cooled ^^®Hg'^ ion. The horizontal axis is the relative

detuning from line center in frequency units at 282 nm. The vertical

axis is the probability that the fluorescence from the 6s ~ fitst resonance transition, excited by laser radiation at

194 nm, is on. The recoilless absorption resonance (carrier) and the

Doppler sidebands due to the residual secular motion of the laser

cooled ion are clearly resolved.

Sympathetic cooling will be employed in a new experimental apparatus for

Be"^ and Mg"^ ions. Initial tests of a rf frequency standard (similar

to the ^Be"^ frequency standard) will be made. The new trap design (for the

133
superconducting magnet) emphasizes axial symmetry in order to avoid the

spurious heating observed in the previous ^Be'^ clock experiment.

Accomplishment - The new trap has been fabricated and initial tests

performed using ^Be'^ ions. With the increased magnetic field

stability, the linewidths of the field-dependent transitions are observed to be more than two orders of magnitude narrower than

previously obtained.

Careful theoretical analysis of limits to high-resolution spectroscopy and

frequency standards will be undertaken and written up.

Accomplishment - The first draft of the paper is complete. It covers

trade offs between signal- to-noise ratio (goes up with number of ions)

and 2nd-order Doppler shift (also increases with number of ions).

FY 1988 Plans

Improve the spectral purity of the 282 nm source for the Hg"^ optical

frequency standard. The basic approach is to frequency stabilize an existing laser to an ultra-stable, high-Q cavity.

Make first measurements of field- independent hyperfine transitions in ^Be"^ or ^^Mg'*’ with the new Penning trap in the superconducting magnet. The goal

is an accuracy exceeding one part in 10^^

.

OBJECTIVE: Perform basic studies in areas related to future frequency

standards

.

As an outgrowth of studies on ion clouds stored in Penning traps for

possible frequency standard application, several closely related basic

studies have been undertaken.

Search for Spatial Anisotropy

Frequency standards, including those based on atomic or nuclear

(Mossbauer) transitions, have traditionally played an important role in

testing gravitational theories. One example is measurements of the

gravitational red shift. In addition, the very high resolution attained in

trapped ion spectroscopy enables other sensitive tests of the Einstein

Equivalence Principle (EEP) . As a test of the EEP the frequency of the

^Be"^ "clock" transition (Mj = 1/2, Mj = -3/2) - (Mj = 1/2, Mj = -1/2) has

been compared to the frequency of a passive hydrogen maser to see if a correlation can be found with orientation in space. With a resolution

better than 0.1 mHz, no variation was observed. These results decreased

previous experimental limits by a factor of 300, but were superceded by

work at the University of Washington. A projected gain of a factor of 1000 over previous measurements should be achievable using ^^Mg'^ in the

superconducting magnet. Such measurements are a fairly easy extension of

searches for systematic frequency shifts in an ion frequency standard.

134
Non-Neutral Plasmas

In the language of plasma physics, the ion clouds in a Penning or rf

trap comprise a one- component , non-neutral ion plasma. In a small plasma

of laser cooled ^Be"^ ions stored in a Penning trap, we have observed

behavior which is indicative of the liquid state. In this case the Coulomb

coupling constant F was as high as 100. Calculations predict that at

r = 2, the pair correlation function should begin to show oscillations

characteristic of a liquid, and at much larger values of F (F - 170)

crystallization may take place. In our experiment a second laser was used

to probe the ion plasma and measure the temperature of the ions from the

Doppler broadening of the optical probe transition. The ion number density

was determined by measuring the (ExB) cloud rotation frequency. Because the

trap electric field and magnetic field were known, the space charge

electric field was extracted from the cloud rotation frequency and used to

determine the ion number density. Ion number densities of = 2 x 10^ /cm^

and temperatures of = 10 mK produced values of F = 100. Values of F large

enough to observe a liquid-solid phase transition should be accessible in

future versions of this experiment. If the theoretical cooling and density

limits can be obtained, values of F as large as 15,000 are perhaps possible

for Be"*" ions. Because experimental information on three-dimensional,

strongly-coupled plasmas is almost non-existent, these experiments can provide some useful tests of the theoretical calculations. The development

of a clear understanding of ion-cloud dynamics is fundamental to the

estimation of systematic errors in frequency standards arising from motions

of the ions.

FY 1987 Plans and Accomplishments

Perform more careful and complete studies of Hg"^ single- ion fluorescence

statistics. Investigate possibilities for observation of (1) single-ion

absorption, (2) motional sidebands in optical spectra, (3) cooling to

zeroth quantum level and (4) cooling in the sideband cooling limit.

Accomplishment - (1) The limit of absorption spectroscopy has been

achieved by observing direct absorption by a single atomic particle.

This was published in Optics Letters 12 , 399 (1987). (2) Motional

sidebands were observed (see Figure 1 under earlier accomplishment)

.

(3) & (4) Work on sideband cooling and cooling to zeroth quantum level

has been postponed. (Added Accomplishment) Quantum Jumps. Discrete

fluorescence changes in a three- level, optical-pumping scheme on single Hg'*' and Mg''’ ions were observed and compared to theory. The

results are shown in Figure 2. (Added Accomplishment) Quantum-Jump

Spectroscopy. Lifetimes and branching ratios of a single, metastable

Hg’'' ion were measured by analyzing the statistics of quantum jumps.

The only noise observed was the quantum noise of the ion.

135
150

100

50

0

tnc 1 ^r\ o^ 100

S -50 c" n o ^

CO

0)L- 1 O

p

CZ 100

50

0

() 200 400 600 800

Time (ms)

Figure 2. Fluorescence intensity as a function of time for samples of

three ions (top trace), two ions (middle trace), and one ion (bottom

trace) in an rf trap. The fluorescence changes suddenly each time a

Hg"^ ion either makes a transition to a metastable D-state (step down)

or back to the ground S-state from a D-state (step up). The

integration time per point is 1 ms.

Study Single-ion fluorescence statistics of Mg"^ . Experiments with this ion can be more accurately compared with theory. Examine the possibilities for

observation of stimulated Raman transitions on single Mg"^ ions.

Accomplishment - Mg"^ quantum jumps were examined theoretically (paper

accepted for publication) and recently observed (paper in

preparation) . Stimulated Raman transitions were investigated

theoretically, but the experiment has been postponed.

Initiate experimental study of Mg'^ nuclear diamagnetism, that is, magneticfield- induced, nuclear- shape distortions. This previously unobserved

effect can show up as a small perturbation to the Breit-Rabi formula and

could produce a small systematic error in frequency standards.

Accomplishment - The effect has been shown to be masked by a hyperfine- induced, gj -factor shift in third-order-perturbation theory

(N. Fortson, U. of Washington). Therefore, this project has been

temporarily shelved.

Study Bragg scattering of laser radiation from a strongly coupled ion

plasma. This can be done in the new trap being installed in the

superconducting magnet. The only missing element is the imaging, photoncounting tube which should arrive soon. Accomplishment - The apparatus for this experiment has been completed

and initial tests are in progress. (Added accomplishment) An

extensive study of the static properties of ion plasmas in three

136
experimental traps has been completed. Experimental studies of shear,

cloud shape, aspect ratio vs. rotation, and temperature equilibrium

were made and compared with theory. Results will be submitted to

Physical Review A shortly.

FY 1988 Plans

Hg"^ Single Ions. (1) Initiate sideband cooling studies to reach the zeroth

quantum level. (2) Complete studies of lifetime and branching ratios using

quantum-jump spectroscopy. (3) Investigate the spectrum of pseudomolecules

formed by two or more ions in a trap. (4) Develop narrower laser linewidth

for higher resolution studies of quadrupole resonance.

Ion Plasmas. (1) Investigate Bragg scattering on ^ Be'*' plasmas. (2) Look

for order is plasmas by imaging plasmas onto a photon-counting imaging

tube. A shell structure is predicted by theory. (3) Study ion plasmas in an rf trap with emphasis on reducing rf heating. (4) Investigate non- neutral plasmas using macroscopic (10 /im diameter) particles in an rf trap.

Synchrotron Frequency Divider. Assemble first test apparatus to isolate

single electrons in a new superconducting-magnet apparatus.

VIII. LASER FREQUENCY SYNTHESIS

This Group retains the expertise and facilities which were used in

earlier measurements of the speed of light and the subsequent work which

led to the redefinition of the meter in terms of the second. More

recently, this frequency synthesis has proven to be extremely useful as a basis for frequency and wavelength spectroscopic standards in the infrared

and far infrared. Of particular note is the generation (synthesis) of

tunable far infrared radiation (TuFIR) using either second-order or thirdorder mixing on the metal-insulator-metal, point-contact diode. The

generated radiation completely covers the far infrared part of the

spectrum. The Group continues to improve devices and concepts for

frequency synthesis. This will prove to be especially valuable for stored

ion standards in the visible part of the electromagnetic spectrum.

Staff

:

K. M. Evens on. Project Leader

D. A. Jennings

M. D. Vanek

C. DeMuynck (Guest Worker)

S. Davidson (Res. Assistant - CU)

S. Beaton (Res. Assistant - CU

;

I. Nolt (Guest Worker)

M. Schneider (Guest Worker)

E, C. C. Vasconcellos (Guest Worker)

J. S. Wells (Guest Worker)

137
OBJECTIVE: Provide reference frequencies from the microwave to visible

regions

.

Frequency References (Measured with Respect to the Cesium Standard)

The advances made by the Laser Frequency Synthesis Group in extending

direct frequency measurements from the microwave to the visible portion of

the spectrum are now being used to determine the frequencies of atomic and

molecular transitions. These measurements are hundreds of times more

accurate than the old wavelength measurements. The knowledge of the

frequencies of selected species allows the spectroscopist , astronomer, or atmospheric scientist to calibrate spectrometers and receivers with

appropriate atomic or molecular frequencies (or wavelengths)

.

The generation of reference frequencies with requisite accuracy

involves accurate heterodyne frequency measurements and the reliable

fitting and analysis of the spectral data. The CO2 laser which is

stabilized to CO2 itself furnishes the main frequency grid for all of the

measurements and is widely used for reference purposes.

The far infrared (0,1 to 5 THz . 3 mm to 60 urn)

The frequencies of several hundred optically pumped lasers have been

measured. Frequencies of > 800 lines were published this year in a review

paper. Rotational frequencies of CO, HC1,HF, and HBr have been measured.

The Infrared Region (25 to 200 THz, 1.5 to 12 urn)

The frequencies of hundreds of lines of OCS, DBr, CO, CO2 , N2 O, and NO

now furnish reference grids for this region. The methane line used to

stabilized the He-Ne laser is especially noteworthy. Atlases and tables of

reference frequencies covering selected infrared regions are available.

FY 1987 Plans and Accomplishments

Complete heterodyne frequency measurements on the asymmetric rotor,

nitrogen dioxide. These measurements will permit self calibration of NO2 in a Fourier-transform-spectroscopic study.

Accomplishment - The measurements were completed and the results

published as NBS Technical Note 1308.

Make heterodyne frequency measurements of hot-band features of OCS which

may be used with the Ritz combination principle to provide a calibration

table in the 2900 cm' ^ region.

Accomplishment - The measurements and analysis are complete and a paper describing the results is in preparation.

138
Make hecerodyne frequency measurements on high-J rotational transitions of

HF for use with TuFIR measurements to determine the best possible constants

for HF. Current values at 10 ^^m have uncertainties of 200 MHz.

Accomplishment - These measurements are in progress and should be

completed shortly.

Make heterodyne frequency measurements on the weak N2 O band at 1635 cm' ^

,

the 10°0-01^0 transitions. Calibration tables in the 1500-1700 cm' ^ region

are currently not available.

Accomplishment - The priorities in the NASA-NBS Frequency Standards

Program were reordered. This work was replaced by measurements of the

B, C, D and E bands in OCS . A publication of the results is in

preparation.

FY 1988 Plans

Measure the 1372 cm' ^ hot-band of OCS leading to molecular constants and

standard frequencies in the 520 and 2412 cm' ^ region as well.

Measure frequencies of spectral lines near 1635 cm' ^ in N2 O for use as standard reference frequencies.

Measure hot-band features in OCS near 1700 cm' ^ OCS as standard references.

Make accurate measurements on H2 O in the far infrared so that "impurity"

absorption at low pressure can be used to calibrate Fourier transform

spectrometers

.

OBJECTIVE: Establish the second and the meter for the International System.

Frequency Measurements Suitable for Realizing the Definition of the Meter

In 1982 the Comite Consultatif pour la Definition du Metre (CCDM)

proposed a new definition for the meter, namely that: "The meter is the

length of the path travelled by light in vacuum during a time interval of

1/299 792 458 of a second." In October of 1983 the General Conference of

Weights and Measures approved this change. With this definition the meter

can be realized from the wavelength of any laser which is stabilized to a narrow atomic or molecular absorption for which the frequency is known.

The wavelength A is determined from the relation \=c/v, where c is the

fixed value of the speed of light and v is the measured frequency of the

laser. Thus, the realization of the meter requires measurement of the

absolute frequency of spectral lines in the visible region. To this end,

the Division has performed two highly accurate frequency measurements of

hyperfine transitions in molecular iodine used for laser stabilization.

The absolute frequency of a dye laser stabilized on the o-hyperfine

component of the ^^^l 2 17-1 P(62) transition at 520 THz (576 nm) in iodine

139
was measured with respect to the CH^ stabilized 88 THZ (3.39 /im) . The

measured I 2 frequency was 520 206 808.547 MHz with a total uncertainty of

1.6 parts in 10^°. The absolute frequency of the 473 THz He-Ne laser

(633 nm) , stabilized on the i-hyperfine component of the I 2 11-5 R(127)

transition was measured with respect to CH^ . The measured frequency is

473 612 214.789 MHz for the i-hyperfine component with a total uncertainty

of 1.6 parts in 10^°. These frequencies, when used to realize the new

meter, represent a 25-fold improvement over the Krypton length standard.

OBJECTIVE: Develop metrology for precise time, frequency and length

measurements

.

Measurement of Frequency and Frequency Stability

Frequency metrology from the far infrared to the visible has been

greatly stimulated by work in the Division. An extremely important aspect

of this work was the first frequency measurement of the 3.39 /urn line of CH^

followed by the wavelength measurement of the line. The product is a value

for the speed of light nearly 100 times more accurate than the previously

accepted value. Coupled with frequency measurements of visible lines, this

has led to replacement of the Krypton lamp as the length standard and the

assignment of an exact value for the speed of light.

Recent work on the MIM diode has expanded the frequency difference

range over which measurements can be made by a factor of 100 (in the

visible) . This is expected to greatly simplify frequency metrology because

it reduces the number of frequency reference lines needed to cover this

spectral region.

Techniques for Laser Frequency Synthesis

Frequency synthesis is usually achieved in some non-linear device

which adds, subtracts and multiplies the frequencies of the radiations

incident on it. The Division has used W-Ni, metal- insulator-metal (MIM)

point contact diodes as detectors, harmonic generators, and mixers of

coherent radiation from the microwave to the visible region of the

spectrum. The MIM diode played a major roll in the frequency synthesis

chain which connected the cesium clock to the visible I 2

- stabilized lasers

and hence provided the realization of the meter from the new definition.

The MIM diode has been used for the past 20 years and the mechanical

and electrical engineering improvements have been steady. Recent use of

conical coupling along with off-axis parabolic focusing mirrors has led to an exciting new technique of generating tunable far infrared radiation.

Six tenths of a microwatt of cw, tunable-far- infrared radiation has been

generated by mixing 180 mW of radiation from each of two CO2 lasers in a MIM diode. The difference frequency was radiated from the MIM diode, and

was detected in a calibrated germanium bolometer. The use of a waveguide140
€©2 Laser with its greater frequency tunability as one of the Lasers used

to generate the difference frequency promises a compLete coverage of

tunabie cw radiation in the entire far infrared band from LOO to 6000 GHz.

RecentLy the HCL, CO, and HF spectra from 0.5 to 5.5 THz have been measured

and these simpie moLecuies now provide for exceiient caLibration standards

in that frequency range.

FY 1987 PLans and AccompLishments

Formulate plans for the development of a frequency synthesis chain coupling

a microwave frequency to the optical transition to the metastable ^ 05^2

state in Hg'*’ in support of the development of an optical frequency standard

based on that transition.

Accomplishment - In collaboration with the Phase Noise Project, a highly stable microwave oscillator is under development. This will

provide the low-end base for the chain. The first step in the chain

will involve multiplication using a Schottky-barrier or MIM diode to

about 0.5 THz. Several approaches can be taken with the higher

frequency elements in the chain and further study is needed to select

the best approach.

Continue the study of diode base materials and coatings for the tungsten

whiskers in an effort to develop more efficient and more stable mixers.

Accomplishment - The current-voltage curves for tungsten whiskers on

nickel, cobalt, and tin- telluride were studied and the results are being analyzed.

Initiate measurements of the spectral purity (phase noise) of the low-end

components for a multiplier chain in collaboration with Fred Walls.

Accomplishment - A new system which locks a 10 GHz oscillator to a

5 MHz quartz oscillator has been assembled and testing is in progress.

Initial results indicate a substantial reduction in phase noise.

FY 1988 Plans

Investigate the use of special high-frequency, Schottky diodes for

frequency synthesis in the far infrared.

Using the best available mixer, attempt to synthesize -0.5 THz from X band.

This will be the first link in the new chain connecting the microwave to

the optical region where the stored ion standard will operate.

OBJECTIVE: Measure far infrared frequencies of atoms and molecules.

High resolution spectroscopic measurements in the far infrared have

been advanced significantly through development (at NBS) of two measurement

techniques. These are used to make laboratory measurements, previously

inaccessible, which have bearing on atmospheric and astronomical studies.

141
Laser Magnetic Resonance (LMR) spectroscopy has been developed into an ultrasensitive technique (i.e., several orders of magnitude more sensitive

than microwave spectroscopy) for observing and measuring reactions

involving molecules. LMR techniques are singularly effective in measuring

parameters necessary to model the effects of pollutants (e.g.,

fluorocarbons, nitric oxide, etc.) in the atmosphere.

The new techniques of Tunable Far Infrared (TuFIR) spectroscopy

promises to enhance the LMR technique by measuring some of the same free

radicals at zero field. Zero field measurements will have greater

accuracy. The technique, an outgrowth of NBS frequency synthesis work

involving MIM diodes, also allows the measurement of all far- infraredactive molecules, not just paramagnetic ones.

FY 1987 Plans and Accomplishments

Search for the ions HeH'^ , ArH"^ and H2D+.

Accomplishment - New observations are difficult to plan. The ArH"'' ion was found and two unexpected finds were NeH"^ and N2H'^ ions. The

results are being analyzed and results will be published.

Measure the temperature dependence of the broadening coefficient for OH and

HCl. Measure the broadening of HF produced by O2 and N2

.

Accomplishment - The broadening coefficients for O2 and HCl produced

by O2 and N2 were measured.

Search for other molecules (frequency measurements and molecular constants)

such as H2O, H2O2, HO2 , HOCl and O3 . Accomplishment - Using TuFIR spectroscopy, the HD, CH, and H2^®0

molecules were found. Using LMR spectroscopy, a new molecular

species, metastable CH (^ 2 ) was identified, and LMR spectra of ^^CH

and ^ ^ CF were observed.

Finish work on the helium-cooled pre-filter detector.

Accomplishment - The work is in progress and will be finished shortly.

FY 1988 Plans

Continue improvements in TuFIR spectrometry and search for new species

interesting to radio astronomers and atmospheric spectroscopists . Install

a new photoconductive detector in the spectrometer to enhance sensitivity.

Build a higher power CO2 laser to pump the FIR laser and install a beam

splitter in the FIR laser.

Continue LMR spectroscopy of metastable molecular species to obtain new information on previously unknown species.

Search for the elusive HjO"^, H2D'^ , and NH"^ molecular ions.

142
IX. GEOPHYSICAL MEASUREMENTS

This is a small program conducted in JILA by Time and Frequency

Division staff. One of the projects involves construction and

demonstration of an apparatus for measuring intermediate baselines (25 km

to 50 km) with an uncertainty of 1/2 cm or less. The multiple-wavelength

technique that is used is closely related to satellite navigation and

timing problems which also require a complete accounting for atmospheric

dispersion. A second project involves use of an array of tilt detectors to

study properties of the earth's mantle and core-mantle boundary. These

tiltmeters are also installed in a seismic zone in Southern California to

investigate the utility of tilt measurements for earthquake prediction. A

third program involves the use of GPS signals for geodesy. This is a joint

effort involving 7 universities and funded by the National Science

Foundation.

Staff

:

J. Levine, Project Leader

J. A. Magyar

A. Brewer (Res. Assistant - CU)

B. Busby (Res. Assistant - CU, graduated 7/87)

M. Holt (Res. Assistant - CU)

K. Hurst (Res. Assistant - Columbia U.)

C. Meertens (Res. Assistant - CU, graduated 5/87)

C. Rocken (Res. Assistant - CU)

A. Levchenko (Guest Worker - USSR)

V. Sadofsky (Guest Worker - USSR)

OBJECTIVE: Develop metrology for precise time, frequency and length

measurements

.

Distance Measurement Techniques

The need to accurately determine the lengths of baselines on the

surface of the earth arises in many different contexts, ranging from the

calibration of tracks used for rocket tests to estimation of the relative

motions of large geographical regions in seismically active zones. This

work is particularly timely, since the use of timing techniques for such

distance measurement is expected to grow and a key roadblock to improved

resolution involves the dispersion of the atmosphere.

Geodesy from the GPS Satellites

Using signal time of flight from GPS satellites and radiometric

corrections for atmospheric and ionospheric dispersion, it appears that

143
very accurate geodetic measurements can be accomplished. A major program

in this area, funded by NSF, involves collaboration between a number of

universities to utilize this concept. This NBS Group has assumed

responsibility for hardware and software developments involving the GPS

satellites and for some aspects of the initial data reduction and analysis.

FY 1987 Plans and Accomplishments

Continue field tests of the three -wave length geodimeter system. Perform

measurements along calibrated baselines and determine the long-term

stability of the calibration constants of the system.

Accomplishment - Several tests of the multiple-wavelength system were

conducted over baselines ranging from a few meters in the laboratory

to a 23 km baseline between Boulder and Erie. The laboratory tests

were intended to evaluate the hardware and software in a controlled

environment and to evaluate the magnitudes of systematic errors in the

system. These tests showed that the hardware was stable and had

systematic errors whose magnitudes were at a level of 1 mm or less.

The field tests were conducted over baselines ranging from 900 m to

23820 m. These tests were intended to evaluate the stability of the

dispersion and distance determinations in the presence of typical

atmospheric turbulence and to compare the dispersion measurements with

direct end-point measurements of the atmospheric parameters. All of

the experiments were successful. Data was even taken. during sunrise

(when the sun shines almost directly into the telescope at the Western

end-point) and during the day when turbulence due to thermal

inhomogeneities is particularly severe. Measurements made during

continuous 36-hour runs showed fluctuations in distance of a few mm or

less, and the measured dispersion agreed well with simultaneous endpoint measurements made by NOAA.

Initiate analysis of GPS/Iceland data to extract network baselines.

Accomplishment - A campaign to acquire data in Iceland was completed

in July, and the reduction of the data was begun in early August. The

data were analyzed in two modes. The first analysis was a simultaneous least-squares adjustment of the entire network of

baselines using software developed in Berne and converted to run on our system. The second analysis used software developed by Texas

Instruments and involved individual solutions for the 1600+ baselines

using several VLBI stations as fixed reference points. The first

solution achieved typical closure errors of less than 1 ppm, while the

latter method showed uncertainties about an order of magnitude greater

(or more in some cases). A preliminary summary of the results was presented at the Fall meeting of the American Geophysical Union, and a publication is in preparation.

FY 1988 Plans

Conduct longer baseline tests of the multiple wavelength system. Initial

tests will focus on stability and reproducibility, so that an a-prior

144
knowledge of the baseline length is not necessary. Subsequent measurements

will be made over calibrated baselines. Install additional microwave

hardware to complete the microwave measurement of the water vapor (the

existing system is really only a 2,5 wavelength system).

Develop software to improve the analysis of GPS data. This will include

incorporation of data obtained by water vapor radiometers , The data

provides real-time measurement of the atmospheric-water-vapor correction,

A radiometer, obtained from JPL, will be incorporated into the system.

Continue GPS data analysis for measurements at various sites including

recent campaigns in Southern California in collaboration with MIT and

measurements in Hawaii in collaboration with Peter Bender and others. The

measurements are motivated by geophysical considerations. Measurements of

several baselines near Boulder will also be made. This series of baselines

("The Colorado Triangle") is designed to test improvements in the analysis

software and the importance of water-vapor corrections.

Geophysical Tilt Measurements

FY 1987 Plans and Accomplishments

Test usefulness of the tiltmeter as a short-period, surface-wave

seismometer to improve resolution in tests of the model.

Accomplishment - Calibrations of various tiltmeter configurations

were conducted using a specially designed test jig. This jig applies

small tilts to the sensor and measures the impulse and step responses.

The data were reduced to show the performance in both the time and

frequency domains, A sensor was also installed in a borehole in

Boulder and event-detection software was designed to sample the

instrxament whenever an earthquake was detected. While the

measurements were successful, they showed that the response of the

instriament in the seismic band is not sufficiently flat to permit use

as a seismometer without significant data deconvolution using the

measured impulse response. Analysis of the data from Yellowstone was also completed. The Yellowstone data will continue to used to

evaluate the tiltmeters for earthquake prediction. The first phase of an investigation of the coherence between tiltmeters installed in

Yellowstone and in Southern California is nearly complete,

FY 1988 Plans

Continue operation of several tiltmeters in Southern California and in

Yellowstone National Park, Contingent on funding, install additional

instruments at a site (Durmid Hill) that is deemed to have a significant

probability for an earthquake in the near future. The NBS instrioments have

been incorporated into several regional networks to provide real-time

comparisons of data from different instruments. The proposed instruments

at Durmid Hill will be included in this network, and this data will be sent

directly to the USGS central analysis system in Menlo Park,

145
NOTICE OF TALKS

D. W, Allan, "Process of Atomic Time Keeping and Time Coordination,

National Physical Laboratory, Jerusalem, Israel, August 1987.

D. W. Allan, "Measuring the Stability of Precision Oscillators," and

"Comparison of Remote Clocks Using GPS in Common-view," Tel Aviv

University, August 1987.

D. A. Allan, "Global Timing via GPS Satellite in Common-view," and

"Millisecond Pulsar Rivals Best Atomic Clock Stability," International

Union of Radio Science (URSI) , Tel Aviv, Israel, August 1987.

D. W. Allan, "Estimating the GPS Ephemeris Plus Propagation Errors and

Their Effect on Time and Frequency Transfer," Alst Annual Symposium on Frequency Control, May 28, 1987.

D. W. Allan, "Millisecond Pulsar Rivals Best Atomic Clock Stability," Alst

Annual Symposium on Frequency Control, May 27, 1987.

J. C. Bergquist, "Quantum Jumps in a Single Atom," University of Stanford,

Stanford, CA, Dec. 8, 1986

J. C. Bergquist, "Quantum Jumps in a Single Atom," NOAA, Boulder, CO, Jan.

27, 1987.

J. C. Bergquist, "Single Atom Spectroscopy," International

Quantum/Electronics Conf . , Baltimore, MD. , April 30, 1987.

J. J. Bollinger, "Liquid and Solid Plasmas," Gordon Conference on Atomic

Physics, July 1987.

J. J. Bollinger, "Sympathetic Cooling of Positrons by Atomic Ions," Intense

Positrons Beam Workshop, Idaho Falls, June 1987.

J. J. Bollinger, "Strongly Coupled Nonneutral Ion Plasmas," Conference on Atomic Processes in Plasmas," September, 1987.

K. E. Evenson, "Tunable Far Infrared Spectroscopy," Univ. of Tucson, March

1987.

K. M. Evenson, "The Last Measurement of the Speed of Light," University of

Arkansas, Fayetteville, Ark., May 1, 1987.

K. M. Evenson, "Tunable Far Infrared Laser Spectroscopy," 11th

International Conference on Submillimeter & IR Waves, Pisa, Italy, Oct. 21,

1986

D. W. Hanson, "Secure Military Communications Can Benefit from Accurate

Time," MILCOM '86 Conference, Monterey, CA, Oct. 5-9, 1986.

146
D. W. Hanson, "Elements of Low-Cost, Operational Two-way Satellite Time

Transfers," International Union of Radio Science (URSI) , Tel Aviv, Israel,

Aug. 26, 1987.

D. A. Howe, "Ku-Band Satellite Two-way Timing Using a Very Small Aperture

Terminal (VSAT) , 41st Annual Symposium on Frequency Control, May 28, 1987.

D. A. Howe, "Stability Measurements of Ku-band Spread Spectrum Two-way Time

Transfer Equipment," 18th Annual Precise Time and Time Interval (PTTI)

Applications and Planning Meeting, Dec. 3, 1986.

W. M. Itano, "The Observation of Quantum Jumps in Hg+," Eighth

International Conference on Laser Spectroscopy," Are, Sweden, June 22,

1987.

W. M. Itano, "Review of High Precision Spectroscopy of Atomic Ions in

Traps," Workshop and Symposium on the Physics of Stored and Trapped

Particles, University of Stockholm, June 24, 1987.

J. Levine, "Applications of Geophysical Measurements to Relativity," Rocky

Mt. Theoretical Physics Meeting, Laramie, Wyoming, Oct. 15, 1987.

D.B. Sullivan, "Activities and Plans of the Time and Frequency Division of

the National Bureau of Standards," 18th Annual Precise Time and Time

Interval (PTTI) Meeting, Dec. 3, 1986.

F. L. Walls, "Low Noise Frequency Synthesis," 41st Annual Symposium on Frequency Control, May 28, 1987.

F. L. Walls, "Analysis of High Performance Compensated Thermal Enclosure,"

41st Annual Symposium on Frequency Control," 41st Annual Symposium on Frequency Control, May 29, 1987.

M. A. Weiss, "A Calibration of GPS Equipment at Timing Laboratories in

Europe," 18th Annual Precise Time and Time Interval (PTTI) Applications and

Planning Meeting, Dec. 3, 1986.

D. J. Wineland, "Single Ion Spectroscopy," New York APS Meeting, March

1987.

D. J. Wineland, "Cooling Limits in Traps," Symposium on the Physics of

Stored and Trapped Particles, Sweden, June 1987.

D. J. Wineland, "Spectroscopy of Single Atoms," Boston DAMOP (APS) Annual

Meeting, May 1987.

D. J. Wineland "Ion Traps for Large Storage Capacity," Workshop on Cooling,

Condensation, and Storage of Hydrogen Cluster Ions Workshop, SRI, Jan.

1987.

147
D. J. Wineland, "Fundamental Limits to Spectroscopic Accuracy," Workshop on Fundamental Measurements on Optically Prepared Atoms, NBS , Gaithersburg,

MD, Sept. 29-30, 1986.

PUBLICATIONS

D.W. Allan, "Millisecond Pulsar Rivals Best Atomic Clock Stability," 18th

Precise Time and Time Interval Meeting (Washington, DC, 1986) pp. 453-466.

D. W. Allan, Characterization, "Optimum Estimation, and Time Prediction for

Precision Clocks," 17th Precise Time and Time Interval Meeting (Washington,

DC, 1986) pp. 45-67.

E. C. Beaty, "Simple Electrodes for Quadrupole Ion Traps," Journal of

Applied Physics 2118 (1987).

R.E. Beehler and D.W. Allan, "Recent Trends in NBS Time and Frequency

Distribution Services," Proceedings of the IEEE, Special Issue, 74, 155

(1986) .

J.C. Bergquist, R.G. Hulet, W.M. Itano and D.J. Wineland, "Observation of

Quantum Jumps in a Single Atom," Physical Review Letters 1699 (1986).

J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Recoilless Optical

Absorption and Doppler Sidebands on a Single Trapped Ion," Physical Review

A 36, 428 (1987)

.

L.R. Brewer, J.D. Prestage, J.J. Bollinger, and D.J. Wineland, A High-F,

Strongly-Coupled, Non-Neutral Ion Plasma, Strongly Coupled Plasma Physics . (Plenum Publishing Company, 1987) pp . 53-64.

J.M. Brown, L.R. Zink, D.A, Jennings, K.M. Evenson, A. Hinz, and I.G. Nolt,

"Laboratory Measurement of the Rotational Spectrum of the OH Radical with

Tunable Far-Infrared Radiation," The Astrophysical Journal 307 . 410 (1986).

J. M. Brown, J.E. Schubert, R.J. Saykally, and K.M. Eyenson, "The FarInfrared Laser Magnetic Resonance Spectrum of the CF Radical and

Determination of Ground State Parameters," Journal of Molecular

Spectroscopy 120 . 421 (1986).

K. V. Chance, I.G. Nolt, L. Zink, D.A. Jennings, K.M. Eyenson, M.D. Vanek,

and J.V. Radostitz, "Collisional Broadening of HCl Rotational Transitions

Using Tunable Far-Infrared Radiation," 11th International Conference on Infrared and Millimeter Waves (Pisa, Italy, 1986).

A.L. Cooksy, R.J. Saykally, J.M. Brown, and K.M. Evenson, "Accurate

Determination of the Fine Structure Intervals in the ^P Ground States of

^^C and ^^C by Far Infrared Laser Magnetic Resonance," The Astrophysical

148
Journal 3^,828 (1986).

R.E. Drullinger, J. Shirley, D.J. Glaze and L.W. Hollberg, "Progress Toward

an Optically Pumped Cesium Beam Frequency Standard," 40th Annual Symposium

on Frequency Control (Philadelphia, PA, 1986) pp. 428-431,

K.M. Evenson, D.A. Jennings, L.R. Zink, and K.R. Leopold, "Tunable Far

Infrared Laser Spectroscopy," 11th International Conference on Infrared and

Millimeter Waves (Pisa, Italy, 1986).

A. Hinz , J.S. Wells and A.G, Maki, "Heterodyne Measurements of Hot Bands

and Isotopic Transitions of N20 Near 7.8 pm," Z. Phys . D - Atoms, Molecules

and Clusters 5 , 351 (1987).

D.A. Howe, "Stability Measurements of Ku-Band Spread Spectrum Two-Way Time

Transfer Equipment," 18th Precise Time and Time Interval Meeting

(Washington, DC, 1986) pp. 437-451,

M. Inguscio, G. Moruzzi, K.M. Evenson, and D.A. Jennings, "A Review of

Frequency Measurements of Optically Pumped Lasers from 0.1 to 8 THz ,

invited review in Journal of Applied Physics R161 (1986),

D.A. Jennings, K.M, Evenson, L.R. Zink, C. Demuynck, J.C. Destombes, and B.

Lemoine, "High Resolution Spectroscopy of HF from 40 to 1100 cm' ^ : Highly

Accurate Rotational Constants," Journal of Molecular Spectroscopy 122 . 477

(1987) .

D.A. Jennings, K.M. Evenson, M.D. Vanek, I.G. Nolt, J.V. Radostitz, and

K.V. Chance, "Air- and Oxygen-Broadening Coefficients for the O2 Rotational

Line at 60.46 cm' ^ , Geophysical Research Letters 14, 722 (1987).

D.A. Jennings, R.E. Drullinger, K.M. Evenson, C.R. Pollock and J.S. Wells,

"The Continuity of the Meter: The Redefinition of the Meter and the Speed

of Visible Light," NBS Journal of Research 92, 11 (1987).

W.J. Klepczynski, H.F. Fliegel and D.W. Allan, "GPS Time Steering," 18th

Precise Time and Time Interval Meeting (Washington, DC, 1986) pp . 237-250.

K.R. Leopold, "Far Infrared Laser Magnetic Resonance Detector of NH and ND

(a^A)," J. Chem. Phys. M, 324 (1986).

K.R. Leopold, L.R. Zink, K.M. Evenson, and D.A. Jennings, "Far Infrared

Spectrum of Sodium Hydride," Journal of Molecular Spectroscopy 122 . 150

(1987) .

K.R. Leopold, K.M. Evenson E.R. Comben and J.M. Brown, "The Far-Infrared

Laser Magnetic Resonance Spectrum of the ^^OH Radical: Determination of

Nuclear Hyperfine Parameters," Journal of Molecular Spectroscopy 122 . 440

(1987)

.

149
K.R. Leopold, L.R. Zink, K.M. Evenson, D.A. Jennings, and M. Mizushima,

"The Far Infrared Spectrum of Magnesium Hydride," Journal of Chemical

Physics M, 1935 (1986).

K.R. Leopold, K.M. Evenson, E.R. Comben, and J.M. Brown, "The Far Infrared

Laser Magnetic Resonance of the Radical: Determination of Nuclear

Hyperfine Parameters," Journal of Molecular Spectroscopy 122 . 440 (1987).

W. Lewandowski, M. Weiss and D. Davis, "A Calibration of GPS Equipment at

Timing Laboratories in Europe," 18th Precise Time and Time Interval Meeting

(Washington, DC, 1986) pp. 265-282.

R.J. Saykally, K.M. Evenson, D.A. Jennings, L.R. Zink, and A. Scalabrin,

"New FIR Laser Lines and Frequency Measurements for Optically Pumped

CD3OH," International Journal of Millimeters and Infrared Waves 8, 653

(1987) .

D. B. Sullivan, "Activities and Plans of the Time and Frequency Division of

the National Bureau of Standards," 18th Precise Time and Time Interval

Meeting (Washington, DC, 1986) pp . 1-10.

E. C.C. Vasconcellos , S.A. Davidson, J.M. Brown, K.R. Leopold and K.M.

Evenson, "Rotational and Hyperfine Constants of Vibrationally Excited NH

(a^A; v=l)," Journal of Molecular Spectroscopy 122 . 242 (1987).

E.C.C. Vasconcellos, D.A. Jennings and K.M. Evenson, "Frequency Measurement

of the Solitary Ethyl Alcohol Laser Line," Int. J. of Infrared and

Millimeter Waves 7, 291 (1986).

E.C.C. Vasconcellos, J. Wyss, and K.M. Evenson, "Frequency Measurements of

Far Infrared ^^CHjOH Laser Lines," International Journal of Infrared and

Millimeter Waves 647 (1987).

M.A. Weiss and D.W. Allan, "Using Multiple Reference Stations to Separate

the Variances of Noise Components in the Global Positioning System," 40th

Annual Symposium on Frequency Control (Philadelphia, PA, 1986) pp. 394-404.

D.J. Wineland and W.M. Itano, "Laser Cooling," Physics Today 34 (1987).

D.J. Wineland, J.J. Bollinger, W.M. Itano, and J.D. Prestage, "Angular

Momentum of Trapped Atomic Particles, Journal of the Optical Society of

America B 2, 1721 (1987)

.

P. Zhao, W. Lichten, H.P. Layer and J.C. Bergquist, "Remeasurement of the

Rydberg Constant," Phys . Rev. A 5138 (1986).

P. Zhao, W. Lichten, H.P. Layer and J.C. Bergquist, "New Value for the

Rydberg Constant from the Hydrogen Balmer-^ Transition," Physical Review

Letters 18, 1293 (1987)

.

150
L.R. Zink, D.A. Jennings, K.M. Evenson, A. Sasso, and M. Inguscio, "Stark

Spectroscopy Using Tunable Far Infrared Radiation," Journal of the Optical

Society of America B 4, 1173 (1987).

L.R. Zink, M. Vanek, J.S. Wells and A.G. Maki, "NO2 Heterodyne Frequency

Measurements with a Tunable Diode Laser, a CO Laser Transfer Oscillator and

CO2 Laser Standards," NBS Technical Note 1308 (1987).

L.R. Zink, J.S. Wells, and A.G. Maki, "Heterodyne Frequency Measurements on

N2 O Near 1060 cm" ^ , Journal of Molecular Spectroscopy 122 . 426 (1987).

PUBLICATIONS IN PROCESS

D.W. Allan, "Should the Classical Variance Be Used as a Basic Measure in SI

Standards Metrology?," submitted to 1986 Conference on Precision

Electromagnetic Measurements

.

B. Dahmani , L. Hollberg, and R.E. Drullinger, "Optical Frequency

Stabilization of Semiconductor Lasers," submitted to Optics Letters.

David A. Howe, "Ku-Band Satellite Two-way Timing Using a Very Small

Aperture Terminal (VSAT) , " submitted to 41st Frequency Control Symposium

and IEEE UFFC.

D.A. Howe, "Progress Toward One Nanosecond Two-Way Transfer Accuracy Using

Ku-Band Geostationary Satellites," submitted to IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

R.G. Hulet and D.J. Wineland, "Quantum Jumps via Spontaneous Raman

Scattering," submitted to Physical Review A.

M. Inguscio, L.R. Zink, K.M. Evenson and D. A. Jennings, "Sub-Doppler

Tunable Far Infrared Spectroscopy," submitted to Optics Letters.

Wayne M. Itano, J. C. Bergquist, Randall G. Hulet and D. J. Wineland, "The

Observation of Quantum Jumps in Hg'*’ , " submitted to 8th International

Conference on Laser Spectroscopy.

W.M. Itano and D.J. Wineland, "Laser Spectroscopy of Trapped Atomic Ions,"

submitted to Science Magazine.

Steven R. Jefferts and Fred L. Walls, "A Low Noise Cascode Amplifier,”

submitted to NBS Journal of Research.

I.G. Nolt, J.V. Radostitz, G. DiLonard, K.M. Evenson, D.A. Jennings, K.R.

Leopold, M.D. Vanek, L.R. Zink, A. Hinz , and K.V. Chance, "Accurate

Rotational Constants of CO, HCl, and HF: Spectral Standard for the 0.3 to 6 THz (10 to 200 cm' ^ Region," submitted to Journal of Molecular

Spectroscopy

.

151
M. Schneider, A. Hinz, A. Groh, K.M. Evenson, and W. Urban, "CO Laser

Optogalvanic Lamb-dip Stabilization from 5.0 to 6.3 /im on CO," submitted to

Applied Physics B.

F.L. Walls, "Low Noise Frequency Synthesis," submitted to 41st Frequency

Control Symposium (Philadelphia, 1987).

F.L. Walls, "Analysis of High Performance Compensated Thermal Enclosures,"

submitted to 41st Frequency Control Symposium (Philadelphia, 1987).

F.L. Walls, "Characteristics and Performance of Miniature NBS Passive

Hydrogen Masers," submitted to 1986 Conference on Precision Electromagnetic

Measurements

.

F.L. Walls, "Errors in Servosystems Using Sinusoidal Frequency (Phase)

Modulation," submitted to the IEEE Transactions on Ultrasonics,

Ferroelectrics , and Frequency Control.

M.A. Weiss and D.W. Allan, "Precision Time and Frequency Transfer by

Weighting and Smoothing of GPS Common View Data," submitted to 1986

Conference on Precision Electromagnetic Measurements.

D.J. Wineland, W.M. Itano, J.C. Bergquist and R.G. Hulet, "Laser Cooling

Limits and Single Ion Spectroscopy," submitted to Physical Review A.

D.J. Wineland, "Ion Traps for Large Storage Capacity," submitted to the

Proceedings of the Workshop on Cooling, Condensation, and Storage of

Hydrogen Cluster Ions.

L.R. Zink and M. Mizushima, "Pure Rotational Far Infrared Transitions of

^^©2 in Its Electronic and Vibrational Ground State," submitted to the

Journal of Molecular Spectroscopy.

L.R. Zink, K.M. Evenson, D.A. Jennings, G. Moruzzi, and M. Inguscio,

"Direct Frequency Measurement of the K=6 Asymmetry Splittings in CH3 OH,"

submitted to the Journal of Molecular Spectroscopy.

SEMINARS ORGANIZED

NBS Time and Frequency Seminar. July 21-23, 1987, Boulder, Colorado.

SPECIAL REPORTS

J. L. Jespersen and D. W. Hanson, "Space Communications Timing, to be

published as RADC Report.

152
PARTICIPATION AND LEADERSHIP

D. W. Allan, Study Group VII, International Radio Consultative Committee

(CCIR)

D. W. Allan, IEEE IM TC-3 Frequency and Time.

D, W. Allan, NASA Team Member for Shuttle Timing Experiment

D. W. Allan, URSI, Commission A.

R. E. Beehler, CCIR Study Group 7; International Chairman of Interim

Working Party 7/4 on "Improved Time Coordination and Dissemination Using

Satellites"

.

K. M. Evenson, URSI Commission D.

D. W, Hanson, Member Technical Advisory Committee for TDRSS, NASA Satellite

Program.

D. A. Jennings, Member CCDM.

J. L. Jespersen, Chairman IRIG Timing Committee.

G. Karaas , Measurement Assurance Subcommittee, National Conference of

Standards Laboratories.

J. Levine, Chairman, Electronic Shops.

J. Levine, National Academy of Sciences, Committee on Geodesy

J. Levine, Board of Review of Science Institute

J. Levine, NBS Computer Users Committee

D. B. Sullivan, URSI Commission A

D. J. Wineland, Committee for NBS Precision Measurement Grants

D. J. Wineland, Program Committee of the Division of Electron and Atomic

Physics, American Physical Society

153
I< Li/Ik - •! ',<J,; 3S5S ;.^.'i;'i,...' l'^i>'J ,

- -.-' ' _ i

‘f- ' '-n-': : snii&iT "joi 3^'^assii jiEftcT iS.3A^ _

; i34.;K 4?’>;y- >-3. ^'V f%rp^. . ";• J3

:. t^?'

1- ..' ’?

'j; att-^v

'-.V

•'•

: .---rrl^Jl." -ri

I--; it jl 55 <' .i;-.fi .f"A ,'.(

, ,;si'^ jT^t .y?'i .s?'*

'- "’i^-0'-=' ^..

' ?I _: ’-'^j!.

tls - /«- o’ PIM nsmlM^ ,

^«^f’.|l‘J *» '- »'livt -Vs HU’l *-t. ,

ce •V.. /of

c^f’.t'j V '- I’livt -Vs HU’l *-t. , M

f

’^ ‘Vjkt

. a» /i.w-3 *'s#i4i*4

a«U‘.|,£ ;-|i

feivl

‘ ^ I • f V y ’•-.ft.

'

<f

i i'\U '

\ a f: '[ 'Ll j

., -•>.'T 9 h''? "^o vpiohiBri-f'' . / -

- - LZ'S^I lr>_i>;. - '1 Irs'aii.Vidv,

--‘*>’V- .. < .. i?-u-j-t.l 3;if^v‘'^ r>jrtvsifi?0-»

‘"t

" ... ... J'ii: t _ irtor.vs't, U.tr:d ri,

.., .t„., _.r f - -

* j , ’>4» i i’*i ' :t

' ">i/'i’k- vpV 1 «^ »f . t±i

r.if^.lZ ' n J(t59’*VJ^ tsjH nu * Si^-*^ t.’i 0'6.'t J

' >£3fK)vJ

^*-i> :i" »

.' •• rJo.^oS' ;A;.^''#-i n

* *-^ “* *

' /A J.'ily ;cf.; p9^d-Ur

5U; rOi ’r;i '4

, _ _

t.' /- ’ttfanSir , 'tt'p.li:-* ^|•..i.^i.# r.

C -'»-^ '

/:

eei i-ii ;l^'

44-:.
QUANTUM PHYSICS DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1987

Page

Overview 156

Summaries of QPD Research Programs 158

Publications of QPD scientists, their graduate students 184

and Post-docs, and Visiting Fellows

JILA Visiting Fellows for 1986-87 207

JILA Visiting Fellows for 1987-88 209

Scientists working at JILA on sabbatical or other leave

(other than Visiting Fellows) 211

Conferences Sponsored at JILA 216

Seminars and colloquia given at JILA 217

Invited talks given by QPD scientists 224

Technical and professional committee participation and

leadership by QPD Scientists 229

Consulting by QPD scientists 233

Other agency research undertaken by QPD scientists 235

Trips sponsored by others for QPD scientists 238

University and department committee memberships

of QPD scientists 250

Graduate students and postdoctoral research associates

supervised by QPD scientists 255

Courses taught at the University of Colorado by QPD

scientists 257

Background on JILA 258

155
OVERVIEW

The Joint Institute for Laboratory Astrophysics^ (JILA) continues to grow

and thrive:

o Although Carl Lineberger's term as Chairman of JILA came to an end on December 31, his efforts on behalf of JILA and the success of the new

building continue unsparingly. He is succeeded by Gordon Dunn, who

brings to the position eight years of experience as Chief of the

Quantum Physics Division.

o Construction of the new JILA building should be complete by January

1988. The building will provide an additional 16,000 square feet of

desperately needed office and laboratory space. The National Science

Foundation and the Department of Education are each providing $500 K

toward its cost.

o JILA is pleased to welcome two new Fellow Adjoints, Douglas 0. Gough

and Eldon Ferguson. Gough is a theoretical astrophysicist at the

Institute of Astronomy, University of Cambridge. His research is in

astrophysical fluid dynamics with special emphasis on helioseismology.

Ferguson is a chemical physicist at the Universite de Paris - Sud.

His main interests are in ion chemistry, atmospheric processes and

interstellar chemistry. Together with Neal F. Lane, Michael J.

Seaton, Stephen J. Smith and Richard N.Zare, they bring the number of

Fellow Adjoints to six.

o Stephen R. Leone has received a John S. Guggenheim Fellowship for his

research in chemical dynamics. He plans to use his Fellowship to

study three areas of physics likely to affect chemical physics in the

years ahead.

o David J. Nesbitt has received an Alfred P. Sloan Fellowship for

unrestricted use in research of his choice, directed in particular

toward starting innovative projects.

o JILA has proposed that NSF provide partial support for a JILA Center

for Theoretical Atomic, Molecular and Optical Physics.

o During the past year. Quantum Physics Division scientists have:

Developed laser stabilization techniques to produce laser

linewidth of 50 millihertz with a frequency predictability better

than 100 millihertz for more than 1 minute.

Found that the relativistic precession rate for the lunar orbit,

as determined from lunar laser ranging data, agrees to 10%

accuracy with the rate calculated in 1916 by DeSitter from

general relativity.

156
Determined that there is no differential free-fall acceleration

down to 5 parts in 10 ^° between U238 and Cu, thereby establishing

better experimental limits on any possible Fifth Force over the

range 0.2 km to 10^ km.

Discovered an exact solution to the saddle point equations for

the Stark ionization of hydrogenic ions in states with non-zero

angular momentum.

Developed a technique to map the surface structure of rapidly

rotating stars using high spectral resolution profiles of

emission lines.

Partially resolved a serious discrepancy between calculations and

measurements, both by JILA scientists, for electron impact

excitation of the simple lithium- like ion of beryllium.

Demonstrated the dominance of, and measured for the first time,

the effective cross sections for the excitation of Ar atoms and

N2 molecules by fast neutrals in electrical discharges at very

high electric field to gas density ratios.

Measured atom-atom energy- transfer cross sections differentially

with respect to scattering angle.

Provided the first demonstration of the existence of multiple,

stable conformations (i.e., geometrical isomerism) in hydrogen

bonded molecular complexes.

Measured for the first time Ba* velocity distributions in a wellcharacterized electric drift field, showing that contrary to

theoretical prediction, spreading in the transverse direction at

low field strengths is similar to that in the parallel direction.

^Through the Quantum Physics Division, NBS participates in the Joint

Institute for Laboratory Astrophysics -- a cooperative enterprise between

NBS and the University of Colorado. More background on the Institute is

included as the last section in this report.

157
RESEARCH PROGRAMS

FUNDAMENTAL AND PRECISE MEASUREMENTS

Laser Stabilization and Stopped Atoms - J, L. Hall

The application of stable laser techniques to fundamental

spectroscopic problems requires the availability of stable - but widely

tunable - cw dye lasers. The a priori incompatibility of high stability

with wide tunability (not to mention with the rapidly-flowing intracavity

free dye stream) has greatly prolonged the development of such lasers. A

key new technology being developed in Hall's lab arises out of a collaboration with Professor T. W. Hdnsch, formerly of Stanford University.

The method can work with the output of any cw laser since the active

transducer is located outside the laser cavity. The technique uses both an electro-optic phase modulator and an acousto-optic frequency shifter to

provide effective frequency/phase correction of the laser field after the

laser has produced its output. The present effort is to integrate this

concept with the controller of a commercially-available stabilized dye

laser system. In addition to frequency correction, the system provides

optical isolation against optical feedback to the laser source and can be

configured to provide effective intensity control as well. There is strong

commercial interest in this device, and a patent application has been filed

jointly with Stanford.

The next major challenge is to develop refined methods of

tuning/guiding/offsetting the laser's frequency to enhance the mid- and

long-term stability. Hall's group has now developed an interferometric

scan technique for wide scans {hu/u < 10%) and moderate accuracy

{hu < 100 kHz) . They have filed for patent coverage on this system, called

the "rf Sigmameter", which is also attracting commercial interest. The

basic idea is that a Michelson interferometer can be configured with two

inputs so that optical frequency changes are manifested as changes in the

phase of a locally-generated rf waveform. With the powerful methods of

electronic phase-locked circuitry, it is possible to develop an optimal

signal for guiding the tunable laser. The attractive feature of this

concept is that scanning errors are non- accumulating

,

so that enormous

frequency scans can be accomplished without nonlinearity and distortion.

For modest scans (±3.5 GHz) of still higher accuracy, for example scanning

over the (potentially) Hz-wide absorption of Hg'*’ in an ion trap, optical

heterodyne phase/frequency locking techniques can be used as demonstrated

in earlier work at JILA.

An interesting application of the JILA tunable sideband technique is

the conversion of an atomic beam to a static gas sample at millikelvin

equivalent temperature. The velocity deceler^ation of the atomic beam is

provided by the directed momentum transfer from the laser to the

counter- running atomic beam, about 30,000 absorption/random-emission events

being required to suppress the initial thermal velocity and stop a beam of

sodium atoms dead in their tracks. During this process, the changing

158
velocity- induced Doppler shift sweeps through about 100 resolvable natural

linewidths. The availability of the inertia-free sideband frequency

sweeping capability (using a swept frequency oscillator to feed the

broadband electro-optic modulator) has been fundamentally useful in this

work, enormously simplifying the interpretation of these atom-cooling

experiments. Hall's group has obtained a three-dimensional residual

velocity distribution of 3 m/s RMS, equivalent to a kinetic temperature of

about 8 mK, which is in quantitative agreement with the fundamental limit

imposed by the natural linewidth. Hall is now preparing to follow this

stage with a period of post-cooling, pumping a 20-fold weaker line to

obtain higher resolution. This work will open qualitatively new regimes of

"atomic beam" physics, including gravity-effects as a first-order

consideration, atom bouncing, and atom aggregation with "atom mirrors"

formed by pulsed, reversing curved wavefronts. One of the most exciting

prospects for spectroscopy implicit in this work is the availability of

long perturbation-free coherent interaction times, certainly 10s to 100s of

milliseconds, bringing the prospect for Hz-level resolution.

As an adjunct to this work. Hall and his group are pressing the limits

of laser stabilization to a passive material optical reference cavity.

Lowering the noise and drift rate of such a locked source will allow slower

servo loops in guiding onto an atomic resonance. The lower bandwidth there

will thus lead to lower frequency noise of the system. In addition, the

cavity locking techniques are interesting in their own right because of

possible application in inertial guidance (passive laser-driven ring

resonator gyroscopes), local oscillator stabilization for space satellite

communication, and as the optical reference source for gravity wave

detectors based on interferometry. The scientists in Hall's group have

generated and measured beat stability of two independent lasers well below

the 100 millihertz level, which would correspond to laser linewidths of the same value if the cavity used for the locking were equivalently stable. By

means of heterodyne techniques with a laser stabilized on an I 2 reference

line, they found that the previous reference cavity was profoundly

influenced by temperature rates of change, barometric changes, and

floor-tilt effects. A new cavity support/isolation structure has

dramatically helped such problems, as has a Peltier cooler-based thermal

controller located inside the vibration/acoustic/thermal isolation box

("Quiet house"). Temperature variations of ± 2 . 5 mK are now obtained,

which are further attenuated and filtered by the thermal controller on the

reference cavity structure. The presently observed 100 Hz amplitude at

24-hours period will allow ~ 500-fold improvement on the Kennedy-Thorndike

experiment, which checks that the velocity-dependent transformation of time

and length are equivalent. The increased space and improved environmental

control planned for the new JILA addition will certainly help these laser

stability experiments to approach their goal of reaching the fundamental

limits

.

In collaboration with Professor H. J. Kimble of the University of

Texas (Austin) , Hall has made the first measurements and demonstration

experiments in which a practical, significant level of "squeezing" has been

obtained. Rather than the 7% effect reported by the initial Bell Labs

159
team, they have shown a factor of 2.5 effect. While the full metrological

implication of these results may only become clear over a half-decade

timescale, it is already obvious that dramatically enhanced measurement

sensitivity will be available for important national objectives such as Earth-based searches for gravitational radiation.

Laser Gravitational-Wave Observations in Space - P. L. Bender and

J. E. Faller

Funding to the University of Colorado is continuing under the NASA

Innovative Research Program to support studies of possible laser

gravitational wave observations in space. The basic concept for the

experiment has been described in earlier annual reports. It requires

placing a cluster of three spacecraft in Earth- like orbits around the Sun,

with separations between the spacecraft of about one million kilometers.

By choosing the orbit parameters properly, the baselines from the center

spacecraft to the other two can be made to stay roughly perpendicular and

equal in length to about 0.1% over periods of some years.

As discussed earlier, studies of expected gravitational wave signals

due to binary star systems have been carried out by D. Mils, R. F. Webbink

(former JILA Visiting Fellow) and Bender. To summarize briefly, it appears

that the power spectral density of signals due to different types of binary

star systems will be above the instrumental sensitivity for frequencies

from roughly 10'^ Hz to 10'^ Hz. Since about 10® binaries in our galaxy

contribute to the signals, it will not be possible to resolve individual

sources unless they are unusually close by. Exceptions are double neutron

star binaries and close white dwarf binaries with frequencies near 10"^ Hz,

for which the number in the galaxy is fairly small.

On the basis of the studies on sources of gravitational waves, it has

been concluded that additional efforts should be made to improve the

gravitational wave sensitivity at frequencies near 1 Hz . As a result of

developments in Nd Yag lasers pumped by laser diode arrays, it now appears

that transmitted laser powers of up to about 3 W can be used to reduce the

shot noise limitations, and shortening of the interferometer length to

about 10^ km probably is desirable. The resulting shot noise limit to the

sensitivity would be roughly 3 x 10'^^ Hz‘°-^. These questions will be

explored further by R. T. Stebbins and Hils (University of Colorado), along

with Bender and Faller. •

Mercury Orbiter Relativity Satellite - P. L. Bender

M. A. Vincent and Bender have investigated the accuracy with which the

orbit of a small relativity satellite around Mercury could be determined

from high-accuracy tracking data from the Earth. The most accurate results

have been obtained by considering only tracking periods when the solar

radiation hitting the satellite is not eclipsed by Mercury. Doppler

tracking data with 1 x 10'^^ accuracy and range data with 3 cm accuracy

160
were assumed for 40 carefully chosen 8 -hour periods, and the rms range

uncertainty was found to be 4.2 cm. Including allowances for uncertainties

in the tracking station location, the Earth's rotation, and the atmospheric

propagation correction, the total uncertainty in the Earth-Mercury distance

would be about 6 cm.

A possible conceptual design for the relativity satellite also has

been studied. Roughly 0.5 W of transmitted power at X-band and 0.2 W at

K-band would be required with a 30-cm diameter antenna. The total

spacecraft power needed during ranging is about 10 W. The thermal control

problems are not serious because of the 2500 km altitude. The total

spacecraft mass would be 50 kg or less, so it could be included as a small

part of a possible future mission to Mercury.

Optical Imaging Interferometry in Space - P. L. Bender and J. E. Faller

Some preliminary work on a specific concept for an intermediate

imaging interferometer in space has been carried out by Stebbins, Bender

and Faller. The basic idea is to use roughly 15-meter long sections of

graphite -epoxy truss structure or other low-expansion material for the

basic interferometer structure. Three such sections could be used in a Y-shaped configuration, with about 15 afocal telescopes located along the

axis. The light from each telescope interferes with that from each of the

other telescopes to give an optical image. Careful thermal design would

make the distortion rate for the interferometer relatively small. Laser

measurements from two control blocks located on a mast perpendicular to the

plane of the Y would be used to monitor the overall distortion and provide

corrections for the optical paths with 10”^ wavelength stability over a typical observing time of roughly two hours. The laser measurement system

is similar to that planned for the POINTS (Precision Optical Interferometry

in Space) astrometric interferometer being developed by R. D. Reasenberg

and others at the Harvard/Smithsonian Center for Astrophysics.

With 50-cm diameter telescopes, the aperture coverage would be

dilute. However, quite high magnitude sources could still be observed with

good spectral resolution. The spatial resolution would be nearly an order

of magnitude better than for the Hubble Space Telescope at the shortest

wavelengths observable with the interferometer.

High Accuracy Atomic Mass Measurements - G. H. Dunn

Dunn is making a major change in the direction of his program to

measure atomic masses to ultra-high precision - a part in 10^° and better.

The goal is to use Penning ion trap technology, with which he has some 15

years experience, to explore important physical phenomena: atomic and

nuclear binding energies, excitation energies of highly ionized species,

nuclear and molecular isomer binding energies, neutrino mass, and masses of

superpositions of states. These measurements bear on determinations of the

fundamental constants and Avagadro ' s number in particular.

161
This program will use a Penning hyperbolic cell in a highly uniform

magnetic field. A superconducting solenoid with fields up to 7 Tesla,

uniform to better than 2 x 10‘® over a 3 mm sphere, and stable to better

than 5 x 10'®/hr for over 100 hr will be delivered soon. Superconducting

flux trap rings near the trap should produce stability to better than 10"^.

Cyclotron resonances of single ions will be detected and the frequency

measured. Special cool GAS FET amplifiers are being developed for

detection of the high-frequency fempto-amp size currents involved. Dunn

expects that the next year will be spent in design and construction, and

that the project will yield results within 2-3 years.

Dunn is collaborating on this project with F. Walls of the Time and

Frequency Division, and he consults frequently with D. Wineland of the same Division. He is assisted by a graduate student, S. Jefferts.

GEOPHYSICAL MEASUREMENT METHODS

Gravity Gradiometer - J. E. Faller

Faller and M. McHugh have constructed a fluid-float Eotvds experiment

using Cu and Pb as the test masses to test the suggestion of a new "Fifth

Force" over the 1-10 meter range. This target-of-opportunity experiment

has resulted in the temporary suspension of their gravity gradiometer float

studies. But as these two experiments are complimentary in terms of

possible error sources and experimental limits of precision, they are also

making progress with gradiometer studies.

Absolute Gravimeter Cp) - J. E. Faller

The absolute value of g continues to play a significant role in the

determination of certain physical constants and standards. With the

accuracies obtainable today, its measurement also has broad application to

geophysics and geodesy. With these purposes in mind, Faller and

T. Niebauer, together with J. Gschwind and A. Joll of the Defense Mapping

Agency (DMA) (both assigned to work in JILA) have completed the construction of six absolute gravimeters. These instruments are based on the freefall interferometric method; A freely falling mass that contains a corner

cube serves as a mirror in one arm of a Michelson interferometer. The

times at which selected interferometric fringes occur are used to calculate

the acceleration of the mass by the Earth's gravity. A stabilized laser,

used as a light source in the interferometer, provides the standard of

length, while an atomic frequency standard provides the standard of time.

A new dropping mechanism eliminates several sources of systematic errors,

and a long period isolation device greatly decreases the instrument's

sensitivity to ground vibrations.

In the summer of 1985, Faller participated in the Second International

Comparison of Absolute Gravity Instruments held at the BIPM. All

measurements were transferred to the same site using an ensemble of

162
relative gravimeters. During the past year, Faller has analyzed his

results and determined a transferred value for Serves Point A5 , His value

differs from the average value by 1.2 /igal and from the average obtained by

rejecting three "outlying" measurements by 0.3 ^gal!

The JILA, the Canadian, the West German, the National Geographic

DMA/NGS, the Austrian and the Finnish instruments all appear to be working

well. During this past year, Niebauer, McHugh and Faller used the dropping

chambers from two of the JILA absolute instruments, together with, first

the Finnish and later the DMA/NGS dropping chambers, to carry out a Galilean test of the Fifth Force hypothesis using U233 and Cu as the freefalling dropped masses. They measured no differential acceleration down to

5 parts in 10^°, thereby establishing better experimental limits on any

possible Fifth Force over the range 0.2 km to 10^ km.

Water Vapor Calibrator Measurement - P. L. Bender

S. J. Walter and Bender are working under NASA funding to develop a microwave-optical system to improve the accuracy of the correction to

microwave distance measurements due to atmospheric water vapor. Since

optical distance measurements are affected much less by water vapor, the

difference between microwave and optical measurements to an aircraft at

about 6,000 meters altitude would serve to determine the microwave distance

correction. The basic transmitter and receiver for the calibrator have

been constructed and tested in the laboratory. A 35.25 GHz microwave

carrier from a Gunn diode oscillator and a roughly 830 nm optical carrier

from a laser diode are modulated at 1.5 GHz in the transmitter. The

modulation signals are recovered in the receiver, amplified, filtered,

down-shifted to 15kHz, and then compared in phase. Phase-lock circuits to

stabilize the frequencies of the Gunn diode oscillator in the transmitter

and another one in the receiver have been constructed. Work also is being

started on the construction of an image motion compensator, which will

automatically direct the light received in the aircraft in later tests onto

the avalanche photo-diode detector, despite rapid and irregular tilts of

the aircraft. The accuracy goal for the calibrator is 2 to 5 mm.

GPS Measurements in the Hawaiian Islands - P. L. Bender

Signals from the Global Positioning System (GPS) satellites have been

used during the period 28 March - 12 April, 1987, to measure the distances

between sites on Kauai, Oahu and Maui in the Hawaiian Islands. The main

scientific goal was to obtain a direct measurement of the vector distance

between the satellite laser ranging station on Maui and the NASA Very Long

Baseline Interferometry station on Kauai. These stations are both used in

measurements of the motion of the Pacific Plate with respect to the North

American Plate, the Australian Plate, and other plates.

163
Geodetic Precession Rate from Lunar Laser Ranging Data - P. L. Bender

Studies with B. Bertotti (University of Pavia, Italy) and I. Cuifolini

(University of Texas) have shown that present lunar laser ranging data

provide the first experimental demonstration of the famous Geodetic

Precession effect calculated by DeSitter in 1916 on the basis of general

relativity. The actual geodetic precession rate for lunar perigee agrees

with the rate calculated from general relativity to 10% accuracy.

The method used in the analysis was to calculate analytically the

expected change in the lunar range as a function of time if a different

geodetic precession rate had been used in the computer calculations of the

lunar orbit, and then to show that such a change could not be absorbed by

changing any of the other parameters or starting conditions in the problem.

Basically, the motion of lunar perigee with respect to the Sun can be

determined with an accuracy of better than 2 milliarcseconds per year

because the solar perturbations of the lunar orbit cause roughly 1% changes

in the Earth-Moon distance. The motion of the Earth with respect to the

planetary dynamical frame (i.e., the non-rotating frame determined from

planetary motions) is known to higher accuracy from the Viking Lander

tracking data. In addition, the planetary dynamical frame was found not to

rotate with respect to extragalactic radio sources at the 3 milliarcsecond

per year level by comparing Earth rotation results from lunar laser ranging

and from Very Long Baseline Interferometry (VLBI)

.

ASTROPHYSICAL MEASUREMENT

Atmospheric Parameters of Hot Stars - D. G. Hummer

In a continuing project to determine accurate values for the

atmospheric parameters of hot stars. Hummer, D. Abbott and B. Bohannan, and

Hummer's student S. Voels are carrying out a detailed analysis of the line

spectra of 16 hot stars they observed at Kitt Peak National Observatory to

high photometric precision (S/N of order 300) . The analysis is based on non-LTE stellar models that account for radiation scattered back into the

star by its stellar wind, an effect shown by Hummer to be important for hot

luminous stars. This so-called "wind blanketing" causes the value of the

effective temperature inferred from stellar spectra to be significantly

lower than would be found if the effect were ignored. Seven stars have now

been analyzed, and work on the remaining nine is now well underway. The

results for Zeta Puppis appear to settle a long-standing uncertainty of

about 40%. Also, the method of determining temperatures of hot stars from

measured energy distributions has been shown to be utterly unreliable; many

temperatures in the literature could be in error by 25% or more.

An analysis of this kind gives accurate values of the effective

temperature and surface gravity, and can be extended to yield the chemical

composition. A program has been set up in collaboration with a group

headed by Professor R. Kudritzki, Director of the Institute for Astronomy

and Astrophysics of the University of Munich, to determine as accurately as

164
possible the stellar parameters of 20 to 30 stars in our galaxy and in each

of the Magellanic Clouds. In view of the widely different elemental

abundances of these three galaxies, these data will provide the first

obseiT'/ational tests of stellar evolution theory that can discriminate among

alternative theories of mass loss and convective overshooting.

Hummer and Kudritzki have pointed out that by using the terminal

velocity of a star's stellar wind, which can be measured from line

profiles, in addition to the effective temperature and surface gravity, it

is possible to infer the absolute luminosity, and hence the distance to the

star. The method uses purely spectroscopic data and contains no calibration or empirical correlations. It can be tested definitively in

the next few years when distances to some "nearby" hot stars will be

measured accurately by satellite observations using trigonometrical

methods. Meanwhile, Hummer is testing the method by analyzing spectra of

stars for which distances are known independently.

Equation of State - D. G. Hummer

Hummer, in collaboration with D. Mihalas (Visiting Fellow), has been

working for the past three years on the development of an improved equation

of state for material with temperatures and densities in the range

3.5 < log T < 7.0 and -12 < log p < -2. This work is part of the

international "opacity project", of which Hummer is a co-founder and co- director. The approach is to minimize, with respect to ail level

populations, the free energy, which depends on, among other things, the

internal partition function. The evaluation of the expression for the

internal partition function for atomic systems has long been recognized as one of the primary unsolved problems of statistical physics. Hummer had

previously shown that the value of this quantity is controlled in

moderately dense plasmas by the Stark ionization of excited atomic states.

He has recently given a treatment of this problem that accounts for the

oscillatory nature of the plasma microfield, which appears now to be the

dominant mechanism. This work is supported by experiment.

Collisional -Radiative Recombination - D. G. Hummer

In an ongoing collaboration with P. J. Storey (University College

London) , Hummer has been involved in an improved and extended calculation

of radiative recombination line intensities and total recombination rates.

This calculation includes the effects of electron collisions, which become

crucial as the electron density increases. Hummer and Storey have recently

completed the calculations for H I and He II, giving the intensities for

all transitions between states with upper and lower principal quantum

numbers up to 50 and 29, respectively. This wide range is necessitated by

the extended wavelength range expected for infrared astronomy within the

next few years. The calculation of the corresponding results for the

hydrogenic ions of C, N, and 0 is now complete.

165
Hummer and L. Smith (University of Wollengong, Australia) have used

the He II results, as well as preliminary results for non-hydrogenic carbon

ions computed earlier by Hummer and Storey, to determine the C/He ratio of

17 Wolf Rayet stars from spectra obtained by Smith for this purpose.

Modeling of Supemovae Atmospheres - D. G. Hummer

The determination of distances to remote galaxies is one of the most

important astronomical measurement problems and one of the primary goals of

the Space Telescope. Such distances would yield the Hubble constant and

perhaps even the value of the deceleration parameter. Supernovae are prime

candidates for this purpose, as they are both bright and fairly well

understood. One method free of the empirical calibrations that have

plagued this area is to determine the (large) rate of expansion and the

intrinsic flux from an analysis of line profiles. The angular diameter can then be obtained from the ratio of the intrinsic to observed flux. Two or more observations well separated in time then yield the distance from the

ratio of the change in expansion velocity to the change in angular

diameter. But realistic models of supernovae atmospheres are needed to

extract this information from the observations. Abbott has computed models

that give continuum fluxes with many of the features of Supernova 1987a,

and a computer code to calculate the corresponding line spectra is well

advanced.

Free-Free Opacity - D. G. Hummer

Although the free-free cross section for hydrogenic ions can be

expressed exactly in terms of certain hypergeometric functions, the

numerical evaluation of these quantities poses an extremely difficult

computational problem. Hummer has developed a method of evaluating the

thermally- averaged free-free absorption coefficient that is at least an order of magnitude more accurate than previously available computer codes

and is probably two orders of magnitude faster.

Radiative-Collisional Switching in Non-LTE Calculations - D. G. Hummer

The equations describing the level populations in an optically thick

gas, combined with the equations of radiative transfer, are notoriously

non-linear. For 20 years they have been solved by a multi-dimensional form

of the Newton-Raphson method. But in many interesting cases this

procedures fails to converge. Hummer and his student Voels recently

encountered a severe form of this problem in attempting to model the

atmospheres of hot, helium-rich stars. When the atmosphere was assumed to

be in LTE, the equations converged; when the radiative rates dominated

(non-LTE) , they blew up. Hummer was able to show that by multiplying the

radiative rates by a parameter that was initially small and allowed to

increase as the iterations proceeded, he could obtain solutions for

arbitrary helium abundances. This simple technique, which essentially

166
defines a series of intermediate problems for the iteration process to

follow, is extremely valuable for the whole field of low-density gasradiation investigations.

Measurements of Magnetic Fields in Cool Dwarf Stars - J . L. Linsky

Linsky and his Ph.D. thesis student, S. Saar, are pursuing a major

program to measure surface magnetic fields on stars cooler than the Sun.

They have already obtained results on stars cooler than had previously been

possible to measure; they have also developed an analysis technique to take

into account for the first time the saturation of optically thick

absorption lines.

These measurements confirm the hypothesis that magnetic fields are at

the heart of solar- like phenomena by showing that stars with the most

energetic phenomena, for example flares and enormous starspots, also have

the strongest measured field strengths and spatial coverage. Three

additional conclusions may be drawn from these measurements and the field

parameters in somewhat warmer stars. First, the field strength is

determined by hydrodynamic processes in the photosphere and not by dynamo

field creation processes in the stellar interior. Second, stars with

energetic or widespread magnetic-related phenomena have fields that cover

nearly the whole star, indicating a high rate of field production in the

stellar interior. Third, the fraction of the stellar surface covered by

magnetic fields depends on the stellar rotation, as would be expected if

fields were amplified by the dynamo process.

Planning for Future Space Observatories to Obtain Ultraviolet and X-Ray

Astrophvsical Data - J . L. Linsky

Linsky is participating in the detailed planning of several

astronomical missions. The most immediate is the Hubble Space Telescope to

be launched in 1989/90. Linsky has been a co- investigator on the High

Resolution Spectrograph (HRS) since 1978 and has participated in the major

decisions that have led to the design and construction of this instrument.

The HRS will obtain spectra with resolution up to 10^ covering the spectral

region 110-320 nm. Linsky is also a co- investigator on the Space Telescope

Imaging Spectrograph (STIS) , now being designed to replace the HRS five

years after launch. This instrument will have high spatial imaging

capability as well as high spectral resolution over the extended spectral

range 110-1100 nm.

In 1985 Linsky was appointed an Interdisciplinary Scientist and member

of the Science Working Group for the proposed Advanced X-Ray Astrophysical

Facility (AXAF) . This 1.2-m grazing incidence telescope is being planned

to obtain high resolution X-ray spectra of stars and galaxies in the mid1990' s. Linsky 's specific interest is high-throughput spectroscopic

observations of stars to measure stellar coronal temperatures, densities,

and flow velocities.

167
During the last year Linsky collaborated with colleagues at several

universities and the NASA Goddard Space Flight Center to write a proposal

to NASA to study a proposed far ultraviolet spectroscopic explorer satellite called LYMAN. This satellite would contain a grazing incidence

telescope and spectrograph to cover the 10 - 200 run spectral range at both

low and high spectral resolution.

Microwave Measurements of Stars - J. L. Linsky

Linsky and S. Drake (Goddard Space Flight Center) have several

projects underway to study microwave emission from stars. They have now

completed a survey of microwave emission from 39 of the closest stars that

are more luminous and cooler than the Sun. This survey at 5 and 15 GHz was made using the National Radio Astronomy Observatory's Very Large Array

(VLA) . The purpose was to measure mass loss rates for a class of stars

(giants and supergiants of spectral types G, K, and early M) for which

there was little data heretofore. Microwave emission from these stars is

thermal bremsstrahlung from the ionized component of the circumstellar gas

leaving the star. Drake and Linsky have now extended this program to study

the mass loss from the coolest M giant stars, many of which are SiO maser

emitters. They have also completed an extensive survey of microwave

emission from close binary stars and from binary systems containing white

dwarf companions and strongly enhanced heavy metal abundances.

Linsky and postdoctoral research associate J. Bookbinder have begun a large survey of microwave emission from the coronae of low mass flaring

stars called M dwarfs. The goals of this ambitious project are to

understand the microwave emission mechanisms and coronal heating processes

by studying an unbiased volume- limited sample of stars with differing

masses, ages, and rotation rates.

Models for the Outer Atmosphere Lavers of Stars - J. L. Linsky

Linsky and colleagues C. Jordan (Oxford University) and A. Brown (JILA

postdoctoral research associate) have completed work on a set of detailed

models for the outer atmosphere of solar type stars. These models describe

the amount of emitting material in the chromosphere, transition region and

corona. The models were constructed to match ultraviolet emission line

fluxes observed by the International Ultraviolet Explorer satellite and Xray fluxes observed by the Einstein X-ray Observatory.

Doppler Imaging of Active Regions on the Surfaces of Stars

J . L. Linsky

Linsky and his Ph.D. thesis student, J. Neff, are obtaining maps of

the surface structure of stars using a technique they developed called

Doppler imaging. This technique involves the analysis of high spectral

resolution, high signal- to-noise (by astronomical standards) profiles of

168
emission lines from rapidly rotating stars obtained at a large niimber of

aspect angles (phases). As a star rotates, bright regions (called plages)

on its surface first appear at one limb with a large blue shift, then move

across the visible surface with increasing Doppler shift and then disappear

over the receding limb with a red shift corresponding to the rotational

velocity of the star. This new technique can be used to infer the

existence of plages, their spatial location, size, and brightness contrast,

information essential for modelling their atmospheres.

Ultraviolet Spectral Diagnostics of Solar Flares - K. B. Gebbie

Geophysical responses to solar activity are dominated by enhanced

electromagnetic and particle fluxes associated with solar flares. This

highly energetic radiation can cause irregular, impulsive ionospheric

disturbances that affect the intensity, frequency and phase of radio

signals. Thus an ability to understand and predict flare events is crucial

for maintaining and improving our communication systems.

The structure and evolution of flares in the solar transition region

(10^ < Tg < 10^) is much less well understood than in either the lower

chromosphere or the corona. It is in this region that the intense EUV

resonance lines of neutral and ionized helium have a crucial role not only

in determining the physical conditions during many phases of the flare, but

also as a diagnostic tool for studying these conditions.

Gebbie, in collaboration with J. G. Porter (NASA/Marshall Space Flight

Center) and L. J. November (National Solar Observatory), have derived time

sequences of He I and He II resonance line intensities at several sites

within the flare of 15 June 1973 from observations obtained with the Naval

Research Laboratory's slitless spectroheliograph on Skylab. The data were compared with predictions of six model flare atmospheres based on two

values for the heating rate and three for the flux of photoionizing coronal

X-rays. The inferred soft X-ray flux is 40 - 400 times that in the quiet

Sun. Throughout the range of conditions in the flare kernels, the He II La

line is found to be formed by collisional excitation, thereby contributing

to the local cooling of the plasma at temperatures above 6 x 10^ K. For

the higher Lyman lines, the primary process at several sites is

photoionization and recombination at temperatures near 2.5 x 10^ K.

Rapid Ultraviolet Brightenings in Active Regions - K. B, Gebbie

J. Toomre and Gebbie, in collaboration with Porter are pursuing their

discovery of rapid changes in the ultraviolet emission from bright sites in

active regions, as a Guest Investigator Program on the repaired Solar

Maximum Mission (SMM) satellite. Their analysis of C IV and Si IV line

emission observed with high spatial and temporal resolution suggested that

heating events of modest amplitude occur almost continually at many sites

in active regions. Such heating events suggest that magnetic field

reconnection in an active region is proceeding almost stochastically, with

169
modest events occurring far more frequently than those with large

amplitudes. This may be evidence in the transition region for the

"magnetic burning" or "topological dissipation" advocated by Parker as a means of heating the corona.

All pre- and post-repair ultraviolet data with sufficient time

resolution have now been analyzed to compare the behavior of the rapid

brightenings in different active regions and to relate it to available

measures of activity and magnetic characteristics. Solar-Geophysical Data

Reports from NOAA, Ha flare reports and GOES satellite X-ray data provide

the primary measures of activity. These sources are supplemented by Ha

movies from Big Bear to check for any unreported subflare activity.

Magnetograms from Kitt Peak National Observatory have been examined when

available for the days of the SMM observations.

Together these data show that the observed bright sites tend to fall on magnetic neutral lines between two regions of opposite polarity within

active regions, a characteristic they share with members of the flare

family. Older active regions that are decreasing in size and producing few

flares tend to show little or no intensity variations for many consecutive

orbits. Such brightenings as are observed are typically less than 50% in

amplitude over the background level. The more active regions appear to

show brightenings of substantially higher amplitude and frequency, some sites bubbling almost continuously with fluctuations lasting 40 to 60 s.

The distribution of brightening events with amplitude is now

reasonable, for the frequent, short-lived events seen here complement the

less frequent UV impulsive events, involving say fourfold increases in

brightness, studied variously with Skylab, OSO-8 and SMM. Clearly a broad

spectrum of events is present, and our observations reveal that the

threshold for the brightenings that can be detected is much lower in

amplitude, and the variations much more rapid, than previously supposed.

ATOMIC AND MOLECULAR PHYSICS

Electron-Molecule Interactions - D. W. Norcross

This theoretical program is devoted to large scale computational

studies of bound and continuum states of electrons interacting with simple

molecules. The reaction process can take several forms and have a variety

of products, e.g., rotational and vibrational excitation of the molecule,

capture of the electron to form a molecular negative ion, or dissociation

of the molecule into other atomic and molecular fragments. The effort is

primarily developmental -- inventing and extending numerical techniques for

more rigorously representing the electron-molecule interaction, and for

treating ever more complicated molecules and processes -- but opportunities

to produce useful data are not overlooked. Results apply to studies of

many practical and fundamental processes, e.g., laser modeling, physics of

the interstellar medium, and in studies of chemical reaction dynamics.

170
Production work in the recent past has included detailed calculations

of cross sections for vibrationally elastic scattering of electrons by HF,

HCL, CO and (linear) HCN; for ro-vibrational excitation of HF and HCL by

electrons, and of CO by positrons; and calculations of the attachment

energies of the three lowest negative ion states of HCl" as a function of

internuclear distance.

Due to the presence of sharp threshold structures in vibrational

excitation of polar and many nonpolar molecules, an accurate computational

treatment of this process demands complete and rigorous inclusion of the

effects of nuclear dynamics in the theoretical formalism. To this end the

partial-wave coupled scattering code has been generalized to further allow

for the coupling of a manifold of lower vibrational states, while still

incorporating reliable treatments of the tricky exchange interaction and

the complicated correlation and polarization forces. Preliminary

calculations of the 0-1 vibrational excitation cross section in HF, within

Sigma symmetry, show good agreement with experimental results. Production

runs for H2 , an important and oft-studied molecule for which the best

current theoretical and experimental results are in serious disagreement,

are in progress.

An improved package for the calculation of asymptotic solutions of

scattering equations has been completed and successfully married to the

molecular scattering code. This will permit the first practical and

realistic calculations of the binding energies of weakly bound and diffuse

molecular negative ion states, and perhaps also highly excited states of

neutral molecules. The richest prize will be new results for the lowest

bound states of HF”, HCl”, and HCN”. This will finally uncover the full

spectrum of the infinite number of bound sates that can be trapped in the

field of a polar molecule, and provide the first systematic connection

between negative ion resonances and true bound states as function of

internuclear distance.

Electron Impact Excitation of Atoms and Atomic Ions - D. tf. Norcross

This group is pursuing several fundamental and applied problems in the

theory and computational physics of electron impact excitation. Excitation

by electron impact is a primary source of energy transfer and radiation

emission in both fusion and astrophysical plasmas. The needs for a vast

amount of data for these processes, for both modeling and diagnostic

purposes, are well documented, and the impossibility of generating all the

necessary data by measurements is almost universally, if reluctantly,

accepted. Since theory must be relied upon to provide the bulk of the

data, it must be tested against measurements for carefully selected special

cases. These cases, in turn, must be designed either to test or stretch

particular aspects of the theory (e.g., transitions near thresholds,

involving excited states, resonances, or state-selected projectiles or targets) , or to check out particular novel experimental techniques under

development (e.g., photometric calibration, recoiling- and merged-beam

techniques, and angular distribution measurements).

171
A systematic series of calculations has been completed for Be'*'. It

has now been shown that neither an elaborate multi-configuration expansion

for the electron-core interaction, nor an exhaustive treatment of virtual

excitation into the continuum, has any significant impact. While the longstanding discrepancy in the polarization of the fluorescence radiation

associated with this excitation has been resolved (ancient theoretical

formalism was found to be in error), a stubborn 18% difference with Dunn's

high precision measurements for the total cross section remains. In

anticipation of new measurements, the latest series of calculations is

being extended to provide a comprehensive set of differential as well as total cross sections.

Detailed calculations for ions in the sodium isoelectronic sequence

have been initiated with work on the doubly-charged ion Al'*^. Using the

scattering code in a mode with all channels closed, binding energies have

been computed for many of the low-lying bound states of Al'*', for which

inclusion of polarization leads to much improved predictions of the

ionization energies.

A project on electron- impact excitation of magnesium- like ions has

also been completed. Rate coefficients have been calculated for S V,

ArVII, CaXIII, Fe XV and Ni XVII for 120 transitions in each ion. The

results are tabulated on a logj^g grid at 15 temperatures extending over

three orders of magnitude, a format suitable for various plasma

applications. In anticipation of future scattering calculations, atomic

structure calculations for boron isoelectronic sequence ions are in

progress with emphasis on the C II eigenfunction expansion (which is the

most demanding of all the ions in the sequence)

.

A collaboration with one of JILA's Visiting Fellows is being pursued,

leading toward the development of a relativistic version of the IMPACT

close-coupling code for electron-ion scattering. Toward this end a series

of calculations on the ions of the heavier alkaline earths (Ca'*' , Ba'*', and

perhaps Sr'*'), that will provide non-relativistic benchmark results, has

been initiated.

Electron-Atom and Atom-Atom Collisions Processes - A. C. Gallagher

The electric breakdown and conduction of a gas and the radiation from

the resultant plasma are of importance in lasers and area lighting, in

switching and power generation, and in the diagnostics of man-made and

astrophysical plasmas. The radiative and electrical properties of these

hot gases depend on electron-atom and atom-atom collision processes, which

couple the kinetic energies of the particles into radiative transitions and

vice versa. During this year, Gallagher has collaborated with postdoctoral

research associates P. Arcuni and M. Harris, and graduate students

K. Gibble, X. Hahn, M. 0' Callaghan, and G. Schinn, to study several kinds

of collision processes that occur in these hot gases. As it is neither

practical nor economical to investigate all specific species and processes

of current or potential interest, these investigations are designed to

172
obtain highly detailed diagnostics of a few specific processes, thereby

guiding and testing basic understanding applicable to all similar

processes. Specifically, Gallagher and his colleagues are carrying out the

following experiments.

An experiment to measure fully differential electron excitation of Na

atoms from the 3S to 3P state is underway. This experiment uses a completely new approach, the detection of differential cross sections by

Zeeman splitting and recoil Doppler shift, to allow measurements that are fully differential in M , , and 9 . Excellent signals and accurate

threshold-region partial cross sections with respect to M and Mg have been

obtained. Measurements of the 9 dependence are in progress. These

measurements test theories in the critical threshold region with orders of

magnitude more detail than has previously been available.

Differential inelastic atom-atom energy- transfer collisions

(A* + B - A + B*) are being measured in a crossed-beam apparatus. Such

measurements critically test understanding of the interactions and

collisions. Gallagher and his colleagues use supersonic metal-atom beams

with well-defined velocities and detect the energy transfer from one optically excited beam (A*) to the other by laser induced fluorescence from

the final state (B*) . The recoil Doppler shift in the B* absorption

spectrum can be analyzed to yield the differential cross sections with

respect to scattering angle. They have now completed the first

measurements in which A and B are both Na atoms, and are now analyzing

these data. Based on the excellent signals and results here, mixed-alkali

collision experiments such as Na-K are now being set up.

Another experiment measures total atom-atom collision cross sections

and stimulated radiation processes in Sr vapor. Here fluorescence

transients following pulsed radiative excitation of Sr are being diagnosed

to establish radiative and collisional pathways to many excited states,

leading ultimately to a highly excited and ionized vapor.

Silane Neutral Chemistry - A. C. Gallagher

The quality and utility of hydrogenated amorphous silicon (a-Si:H)

film photovoltaics have increased every year since their initial production

in 1976. Efficiencies of 10% are now routinely achieved compared with

crystal silicon cell efficiencies that are now about 20%. Because a-Si:H

can be deposited inexpensively from a discharge as a thin layer on large

areas, it is a leading contender for solar power generating systems, as well as large-area photoconductors. It is also being developed in many

companies for area display and reading. In spite of this impressive

progress, major improvements in deposition rate, large-area reliability,

stability, and efficiency are still believed to be feasible.

Since 1979, Gallagher and his group have been studying the discharge

and surface processes that lead to the film production in order to assist

this progress with improved understanding of the microscopic processes.

173
During the last year, they have worked on the surface chemistry in these

discharges as well as on disilane and germane discharges. Along with

modeling of the surface reactions, based on observations of molecules in

the discharges, they have studied the radical reaction probabilities with

the growing a-Si:H surface. Models for the gas and surface processes are developed and compared with all the observations.

A New Method for Electron-Ion Collision Measurements - G. H. Dunn

It has long been recognized that a new method must be found for

measuring cross sections for electron- impact excitation of ions. The bulk

of the measurements to date have used crossed beams and a fluorescence

detection technique. Only four measurements have been done for ions of

charge greater than one. A few measurements have been made of relative

differential cross sections for excitation of singly charged ions over a narrow range of angle and energy. A new method is required to understand

excitation of multiply charged ions and the role of resonances, as well as to study indirect processes in ionization of ions (excitationautoionization, resonant-excitation-double-ionization, etc.).

Dunn, C. Timmer, and other students and post-docs have developed a new

method to meet this need. Trochoidal merger-demerger analyzers are used to

merge an electron and ion beam and to disperse inelastically scattered (or

ejected) electrons from excitation (or ionization). The dispersed

electrons are detected on position-sensitive detectors. One thus has

detection efficiencies approaching unity compared with efficiencies of the

order 10'^ or less in fluorescence or normal scattered electron

configurations

.

The new method promises to be useful primarily at energies near

threshold for excitation. The apparatus has been built, fully assembled,

and testing is in progress. Both electron and ion beams have been

successfully put through the apparatus, measurement electronics and

software have been tested, and measurements should be forthcoming in the

near future. The apparatus will be moved to Oak Ridge National Laboratory

(ORNL) for work on multiply charged ions after work at JILA on one or two

singly charged ions is complete.

In other work on electron ion collisions, the group continued its

close collaboration with ORNL, and participated in measurements of

ionization of highly charged iron ions. Total cross sections were measured

in crossed beams for the electron impact single ionization of Fe^^'*’, Fe^^'*’, and Fe^^'*’. In all cases, the indirect process of excitation-autoionization

proved to be either comparable to or much larger than direct ionization.

No real evidence was found for the resonant-excitation double

autoionization mechanism.

174
Kinetics of Metastable Ho and No A. V. Phelps

Phelps and his colleagues are making measurements of collision

processes responsible for the production and loss of molecular metastables

in electrical discharges in H2 and N2

. Such discharges are important in

devices such as hydrogen thyratrons , negative ion sources using H2 , and

high power gas lasers using N2

.

A. B. Wedding (CU) and Phelps have extended measurements of the

collisional destruction of H2 (c^IIy) metastables to include the measurement

of collisional coupling between the c^H^ state and the state. They

find that the probability of metastable destruction by this process is

small compared to the total destructions probability of essentially unity.

Wedding and Phelps are using the technique of laser absorption

following perturbation of the density by a second laser to measure the

destruction rate coefficient for the metastable state of N2

. This

state has recently been proposed as the energy storage reservoir

responsible for the onset of instabilities in high power CO2 -N2 lasers.

Initial results show that the destruction rate coefficient is about an order of magnitude smaller than for the H2 metastables investigated

previously.

Collision Processes in Electrical Discharges at Very High E/n

A. V. Phelps

Phelps and colleagues are making experimental tests of models they

have developed to describe the behavior of electrons, ions and fast atoms

in gas discharges at very high electric field to gas density ratios, E/n.

The analyses of the spatial distribution of emission from steady-state, low

current discharges led to the hypothesis that the optically forbidden

states of N2 molecules and Ar atoms are being excited as the result of

collisions of fast neutrals with the gas molecules. In the case of Ar the

ionization produced in such collisions was sufficient to produce an ion

avalanche. The fast Ar atoms are produced in charge transfer collisions of

Ar'*' with the gas atoms and have average energies of about 100 eV at the

higher E/n.

D. A. Scott (CU on CSIRO fellowship) and Phelps have completed

measurements of the time dependence of the light emission from Ar at gas

densities below those required for steady-state discharges by using a pulsed laser illuminated photocathode to provide the initiating electrons.

They find that at very high E/n most of the 811 run emission occurs in the

form of a slowly varying, wave-like transient consistent with excitation

from ions and/or fast atoms, rather than simultaneously throughout the gas

as expected for electron excitation. As yet incomplete analyses of the

waveforms indicate that the excitation of the 811 nm emission is produced

by fast atoms. On the other hand, the 750 nm emission is primarily the

result of electron excitation.

175
In collaboration with L. C. Pitchford of GTE Laboratories Inc., Phelps

has continued calculations of electron transport and reaction coefficients

in gases at very high electric fields. Their principal concern has been

with the modeling of electron motion in the very high E/n experiment

described above.

Collaboration with NBS /Gaithersburg - A, V. Phelps

The exchange visits of Phelps to NBS/Gaithersburg were continued

during April and May of 1987. During the visit he worked in the Applied

Electrical Measurements Group on the calculation of electron transport and

reaction rate coefficients for mixtures of SFg with gases such as N2 , CO2 , O2 , Ar and Ne. This work is in support of an experimental program in the

area of the chemical effects of corona discharges being carried out under

R. J. Van Brunt for the Department of Energy. These calculations have been

incorporated into the discharge chemistry models, reported at appropriate

engineering meetings, and prepared for publication.

Collaboration with Overseas Scientists - A. V. Phelps

During FY 87 two collaborative projects were conducted involving

overseas scientists. Work with K. Tachibana (Kyoto University and former

CU postdoc) was completed on the excitation of Ne metastables by electrons

under swarm conditions. The experiments had been carried out by Tachibana

and Phelps at JILA and the data analysis was done at JILA and at Kyoto.

Phelps initiated a project in collaboration with G, N. Haddad (CSIRO,

Australia) to demonstrate the sensitivity of electron swarm experiment and

analyses for N2 to the cross sections for rotational excitation at electron

energies near 0.1 eV. Phelps made approximate calculations at JILA, which

were confirmed by Haddad's exact calculations at CSIRO. These analyses

also demonstrated that recently proposed and recommended theoretical cross sections are in error by at least a factor of two at electron temperatures

of importance in ionospheric models.

JILA ATOMIC COLLISION CROSS SECTION DATA CENTER - J. W. Gallagher

The JILA Data Center under the direction of J. W. Gallagher has

carried on an active program to compile and evaluate data in the areas of

electron and photon collisions with atoms, ions, and simple molecules.

Several projects entailed collaboration with Data Center visitors who

participated in the review and evaluation of data in their fields of

expertise

.

176
FY 1987 Accomplishments

1. Absolute Cross Sections for Molecular Photoabsorption , Partial

Photoionization, and Ionic Photofragmentation Processes

.

J. W. Gallagher,

C, E. Brion, J. A, R. Samson, and P. W. Langhoff

This review discusses methods of measurement and calculation, and

compares cross sections for photoabsorption below the ionization threshold,

partial channel photoionization cross sections and asymmetry parameters,

and dissociative photoionization cross sections for 21 molecules,

2. Collisional Alignment and Orientation of Atomic Outer Shells.

I. Direct Excitation by Electron and Ion Impact. N. 0. Andersen,

J. W. Gallagher, and I. V. Hertel

In collisional excitation, the alignment and orientation of the target

charge cloud are represented by either four or five "natural parameters".

Four such parameters are used in the fully coherent case exemplified by

helium; five are used in the incoherent cases both with conservation of

atomic reflection symmetry, as exemplified by atomic hydrogen, and without

conservation of atomic reflection symmetry, as exemplified by the rare

gases. This review presents an extensive discussion of the physical

meaning of this parametric representation for each case and a comprehensive

compilation of measured and calculated data for electron collisions with

atomic targets and for ion-atom collisions with similar configurations.

3. Rate Data for Inelastic Collision Processes in the Diatomic Halogen

Molecules. 1986 Supplement. J. I. Steinfeld

This report updates a compilation published in 1984.

Work in Progress

1. Collisions of Electrons with Atoms and Molecules . Atomic Data for

Fusion, Vol. II. A collaboration with Oak Ridge National Laboratory

2. Review of Electron Impact Optical Excitation Functions for Atoms and

Atomic Ions. D. W. 0, Heddle

3. Orientation and Alignment Parameters in Atomic Collisions . Part II.

Quasimolecular Excitation

.

N. 0. Andersen, J. W. Gallagher, and

I. V. Hertel

4. A collaboration was started with R, J. Van Brunt of NBS , Gaithersburg,

who has developed procedures for checking the consistency between

dielectric strength data for gas mixtures and available information on electron transport and electron collision cross sections for the mixture

constituents. Large-scale application of this method requires computer

access to a wide variety of data; to meet this need, plans have been made

for Van Brunt to access the Atomic Collision Data Base. To complement this

177
effort, swam data will be added to the data base.

The Atomic Collisions Data Base

Conversion from the IMF to the CDCS data base management system has

been completed. A tape of the cross sectional data resident in the Data

Base was sent to the International Atomic Energy Agency for incorporation

into their data base. In FY 1988, an interactive retrieval program will be

refined for general (public) use. Major expansion of the Data Base content

in connection with some of the planned projects is expected in 1988.

FY 1988 Plans

An evaluated compilation of cross sections for electron-molecule

collision processes is planned in collaboration with Michael A. Morrison of

the University of Oklahoma, Norman, and R. J. Crompton of the Australian

National University, Canberra. In preparation, identification and

collection of pertinent papers and some data collection will begin in FY

1988.

S. J. Smith will be updating the Data Center's Multiphoton

Bibliography (NBS Publ. LP-92 + Suppl. 1-4) series for 1983-1987 inclusive,

preparing a report commenting on the general quality of available

inforaation relative to projected needs, and identifying needs for

refinement and extension of experimental programs. The Data Center will

provide support for this project with a literature search, acquisition of

pertinent articles, preparation of an indexed bibliographic file, and

preparation of the final bibliography.

CHEMICAL PHYSICS

Ultra-lov Temperature Ion-Molecule Reactions - G. H. Dunn

The Penning trap used for measuring and studying ion-molecule

reactions near 10 K has been revised to allow for the "creation" of a substantially larger initial ion sample and for direct variation of the

temperature over the range 7 K to 100 K. In this revised trap ortho- and

para-hydrogen can be introduced and used separately. Dunn and graduate

student M. Schauer are making changes and testing the apparatus.

State-resolved Dynamics via Infrared Laser Absorption Spectroscopy

D. J. Nesbitt

Nesbitt is pursuing four areas of research into molecular structure

and dynamics using ultra high sensitivity infrared absorption techniques:

1) Spectroscopy of weakly bound clusters in a supersonic molecular beam by

direct absorption of a tunable difference frequency laser; 2) Gas-solid

178
interactions by monitoring the nascent quantum state distributions of

sublimation of simple molecular solids into a vacuum; 3 ) Intramolecular

energy distribution in jet cooled hydrocarbon molecules; and 4 ) Laser flash

photolysis studies of transient radicals via time resolved laser

absorption.

C. Lovejoy and Nesbitt have already obtained high quality spectra of

several van der Waals and hydrogen bonded molecules. Study of these

prototypic, weakly bound species provides new information on the nature of

bonding, collisional energy transfer in the gas phase, and the extremely

important issue of the time scale for intramolecular vibrational

relaxation. Their novel technique uses time resolved, direct infrared

absorption of a high resolution tunable difference frequency laser in a slit supersonic expansion. The slit expansion device provides a two-orderof -magnitude enhancement in absorption path length, but still allows the

extreme cooling, lack of spectral congestion and propensity for cluster

formation characteristic of a supersonic jet. In addition, much like a stream of water through a slit aperture, hydrodynamic effects in the slit

expansion geometry serve to collimate the velocities along the plane of the

expansion. This results in dramatically reduced Doppler widths in an unskimmed molecular beam.

Using these techniques, Lovejoy and Nesbitt have obtained the first

infrared spectra of a variety of complexes, including ArHF, HFN2, HFCO2,

(HF)2, HFN2O, HFH2, (002)2- M^riy different vibrational states in each

complex have been elucidated, which permits study of intermolecular

potentials and coordinates far from the equilibrium geometry. Some key

observations resulting from these studies are: 1 ) Depending sensitively on

the nature of the vibration, internally excited complexes can be extremely

metastable even with up to 40 times the energy to dissociate; 2 ) In loosely

bound complexes, large amplitude quantum motion leads to extensive

vibrational averaging of observable quantities (such as molecular

rotational constant) and hence a high dependence on particular ro- vibrational quantum state; 3 ) Isomers in molecular complexes can exist, and

exhibit two different, stable structures with completely different and

assignable spectra; 4 ) Particularly in systems containing H2, tunnelling

effects from weak multiple minima in the potential can be observed and

analyzed by virtue of spectral doublings resolvable in our apparatus.

These studies are raising new and challenging theoretical questions about

the nature of full 3 -dimensional solutions of the multibody Schrodinger

equation in molecular systems near the dissociation limit.

M. Schuder and Nesbitt are investigating the quantum state dynamics of

sublimation phenomena. Their approach relies on ultra sensitive detection

of molecules that have freshly sublimated into a vacuum, before collisions

can scramble the nascent quantum states. The sublimation process can be

stimulated by gentle heating of the surface by a pulsed laser. The first

phase of the experiment has recently been successful and is resulting in

Doppler lineshape velocity profiles of subliming HF thin films. Such

information provides insight into the nature of solid gas interaction at

the interface, as well as determining by detailed balancing the sticking

179
coefficients for collisional deposition as a function of quantum state.

A. Mcllroy and Nesbitt are exploiting the novel properties of slit jet

expansion to study the dynamics of vibrationally excited, but ultra cold,

hydrocarbons. A given vibration in a molecule, if excited, can eventually

relax into a linear combination of many other vibrational modes via

intramolecular relaxation pathways. Spectroscopically, the fingerprint of

this intramolecular relaxation is line broadening or excess fine structure

in the spectrum, which is completely obscured at room temperature. Studies

in the cooled jet environment, however, elegantly avoid this difficulty and

permit a detailed spectroscopic investigation of intramolecular dynamics in

a collision-free regime. Some recent results to come out of these

experiments are: 1) Even in relatively stiff molecules such as cyclopropane, we observe a J dependent rotationally induced mixing of

vibrational levels above J = 6 due to internal Coriolis interactions; 2) In

larger systems such as isobutane, vibrational mode mixing at the CH stretch

level is already so extensive that discrete ro-vibrational structure is

washed out even at the < 8 K jet temperature.

A. Schiffman and Nesbitt are in the process of building a new

experiment to study transient radicals by time and frequency resolved

absorption spectra. A pulsed excimer laser will be used to cleave

photolytically appropriate molecular precursors in a fast gas flow to

generate highly reactive radical species. By use of a tunable IR laser

probe collinear with the photolysis beam, weak transient absorbance signals

from the radicals can be detected, signal averaged and analyzed for the

desired kinetics. First efforts will be directed towards OH in order to

characterize the infrared integrated absorption strengths of this

atmospherically important radical. This experiment has just recently

become fully operational. We now have developed methods for single

frequency scanning the F-center under computer and servo loop control, as well as capturing transient IR signals for later analysis.

A new experiment is presently being built for diode laser probing of

molecular species in supersonic jets. The diode laser will permit

extension of our earlier efforts to a much wider region of the IR spectrum.

In particular, we will be able to look at clusters containing the strong IR

chroraophores NO, N2O, CO2 , CO, SO2 , and OCS. At present we are building up

the vacuum system and expansion device, as well as gaining experience in

stabilizing and scanning single frequency diode lasers. The first

molecular effort will be towards characterizing (N0)2 in the region near 5 microns. This system is of fundamental interest since pioneering

picosecond experiments at NBS Gaithersburg have indicated predissociation

lifetimes that depend sensitively on internal vibrational state.

Photofragmentation Dynamics - S. R. Leone

Photodissociation processes of molecules are providing some of the

most detailed results of state-resolved chemical dynamics in recent years.

These photofragment processes are particularly important because they are

180
similar to the latter half of a collision, which in principle could

represent a chemical transformation. While many groups have explored the use of laser-induced fluorescence to probe the states of diatomic

fragments, few laboratories have considered the possibilities of detecting

infrared emission, which can ultimately be extended to more complex

polyatomic fragments.

R. Fletcher, E. Woodbridge, and Leone have completed a major new

apparatus to study photodissociatation dynamics using time-resolved Fourier

transform infrared (FTIR) emission spectroscopy. The method has now been

shown to be highly successful in obtaining rotationally resolved product

state information on the HF diatomic from the photolysis of 1,1-CH2CFC1 and

the CCH radical fragment from dissociation of acetylene.

By another technique, W. Hess, J. Smedley, and Leone have been

studying the atomic fragments of small molecule photodissociation. This

technique, invented in these laboratories, uses a tunable diode laser or an F-center laser to probe by laser gain and absorption the accurate quantum

yields of atomic electronic states. Two new problems have recently been

investigated: the yield of spin orbit excited atoms of Br* from bromine

molecules and the yield of excited I* atoms from ICN. In the

photodissociation of bromine, the contributions of several molecular

electronic states were mapped in detail by measuring the yield of excited

Br* atoms. This allowed the first clear assignment of the intensity of the

A state continuum in the Bt2 absorption spectrum. In ICN, an accurate

study of the yields of I* provided a direct confirmation that previous data

were erroneous for this molecule and allowed a reanalysis of the electronic

bands in the absorption spectrum and a unification of all existing data.

Ion-Molecule Collision Dynamics - S. R. Leone

Several extremely exciting breakthroughs have been made this year to

increase the powerful repertoire of methods to study ion dynamics.

A single mode dye laser technique has been used to study ion velocity

distributions for the first time in a well-characterized electric drift

field region, work carried out by R. Dressier, H. Meyer, V. Bierbaum,

A. Langford, and Leone. The Ba'^ ion was drifted in a He buffer gas of a flowing afterglow apparatus, and the velocity distributions were recorded

by scanning the single mode dye laser and detecting laser- induced

fluorescence. The measurements obtained several fundamentally new pieces

of information. In addition to measuring the drift velocity as a function

of field strength (and hence the mobility) the temperatures (i.e.,

spreading of the ion velocity distribution) both parallel and transverse to

the electric field were obtained for the first time. According to theory,

for a heavy ion in a light buffer, the spreading in the parallel direction

should be significantly greater than in the transverse direction. At low

field strengths, they have been observed to be the same. These results

open up a tremendous number of new possibilities to detect ion velocity

distributions optically under well-characterized conditions and to compare

181
the measurements to theory and provide refinements to the theoretical

analyses

.

A pulsed laser has been used by the same researchers to probe the

alignment of ions drifted in He. The alignment comes about because of

the anisotropy of the potential of interaction between the ions and the

buffer gas. The measurements show a substantial alignment effect, which

has been quantified as a function of field strength. In addition,

theoretical work has been carried out to characterize how to measure

alignment parameters under conditions of saturated laser- induced

fluorescence. Another theoretical treatment has been developed to relate

calculated cross sections for mj changing collisions to the magnitudes of

the observed alignment effects. Since the alignment will undoubtedly

affect the mobility, new measurements are in progress to study

simultaneously the alignment and velocity distributions of individual

rotational states of the CO'*' ion.

A discovery about a Penning ionization process has been made by

D. Sonnenfroh (NRC postdoctoral fellow) and Leone. Using a novel apparatus

in which metastable states of Ne are reacted with rotationally cold N2

molecules, a higher level of rotational detail has been revealed about the

Penning process. The rotational distributions within each vibrational

level show strong bimodality when the nitrogen is initially cooled to 8 K.

At room temperature, this modest bimodality is not observable. The two

rotational distributions are accounted for by the fact that the potential

surface for the Penning ionization has two regions of electron transfer,

caused by a change in the gradient of the repulsive potential as a function

of distance of approach. New investigations are underway to calculate the

accurate potentials that give rise to this fine detail in the reaction

dynamics

.

Energy Transfer - S . R . Leone

Energy transfer processes are important in a wide variety of

environments, including laser and discharge media, interstellar space, and

the upper atmosphere. The most exciting results in this area

(notwithstanding the energy transfer work involved in the Ba'*' velocity

distributions and the alignment mentioned above) have been in the study

of alignment effects on electronic energy transfer of Ca and Sr atoms. In

new experiments, W. Bussert and Leone have been able to measure several

energy transfer processes as a function of alignment both in the forward

and reverse directions. Thus, for the first time, the symmetries of both

states involved in the electronic curve crossing have been determined.

Experiments have also explored collisions with molecules. Although many of

the molecular collision partners display little or no alignment effects,

several molecules show strong effects, including H2 and CO2. Finally, a series of studies was made to investigate the alignment effects when two or more energy transfer channels are available. Surprising selective effects

are observed, for example, in one case where the parallel alignment is

preferred to form one product state and the perpendicular alignment is

182
required to form another.

Surface Dynamics - S. R. Leone

K. Carle ton, B. Bourguignon, and Leone have initiated a program in

surface scattering dynamics and the growth of semiconductors. This project

involves the use of lasers as tools for determining the participation of

individual vibrational and electronic states of the gas phase species in

the epitaxial kinetics and dynamics of surface semiconductor growth. The

first work involves the growth of GaAs semiconductors on silicon single

crystals. Measurements have been made using laser induced fluorescence

detection of Ga atoms as they scatter and desorb from a Si(lOO) crystal to

determine the binding energy of Ga atoms on the silicon surface. The

results show a high binding energy (2.9 eV) , which is similar to the energy

of binding of As atoms on Si.

Leone and his colleagues have succeeded in probing the dynamics of the

two different spin orbit states in the Ga, and have derived a model of the

two-state desorption kinetics to explain the results. Structural studies

using low energy electron diffraction show that the Ga forms ordered

overlayers on Si up to coverages of one monolayer, most likely forming two

bonds to the silicon surface and one Ga-Ga dimer bond. Structures for the

Ga overlayers have been postulated. Finally, the dynamic measurements

reveal that the Ga atoms have mobility in only one dimension on the silicon

surface. The results have important implications for the industrial

considerations of the growth of GaAs on silicon. For example, the binding

energy considerations show that both Ga and As have equal propensity to

bind to the clean silicon surface, thus explaining the difficulties

previous researchers had with the growth of antiphase domains.

183
PDBLICATIONS

Quantiom Physics Division (525)

B, Bohannan, D. C. Abbott, S. A. Voels and D. G. Hummer, 'Photospheres of

hot stars. II. An analysis of Zeta Puppis,' As trophys . J. 308, 728-735

(1986) .

*N. Andersen and I. V. Hertel, 'A fresh look at alignment and orientation

in collisional excitation,' Comments At. Mol. Phys

.

19, 1-34 (1986).

*T. Andersen, K. R. Lykke, D. M. Neumark and W. C. Lineberger,

'Autodetachment study of the electronic spectroscopy of FeO',' J. Chem.

Phys. 86, 1858-1867 (1987).

*T. Andersen, (H.-P. Neitzke) , M. Kimura and N. F. Lane, 'Coherence study

of Li(3^D) excitation in 2.5-15.0 keV Li'^-He collisions,' J. Phys. B: Atom.

Molec. Phys. 20, 1789-1799 (1987).

*J . N. Bardsley and (M. J. Cornelia), 'Ionisation of a one -dimensional

hydrogen atom by a resonant electric field,' J. Phys. B: Atom. Molec. Phys

19, L565-568 (1986).

*J . N. Bardsley, 'Excited-state stability and x-ray lasers,' Opt. Lett. 11

612-613 (1986).

*M. J. Barlow, 'The determination of the masses of Magellanic Cloud

planetary nebulae using [0 II] doublet ratio electron densities,' Monthly

Notices Roy. Astron. Soc

.

227, 161-183 (1987).

(B. Bertotti, I. Ciufolini) and P. L. Bender, 'New test of general

relativity: Measurement of geodetic precession rate for lunar perigee,'

Phys. Rev. Lett. 58, 1062-1065 (1987).

*(U. Hefter, G. Ziegler, A. Mattheus , A. Fischer) and K. Bergmann,

'Preparation and detection of alignment with high m selectivity by

saturated laser optical pumping in molecular beams,' J. Chem. Phys. 85,

286-302 (1986).

*(J. Beavan, K. Hurst), R. Bilham and (L. Shengold) , 'A densely spaced

array of sea level monitors for the detection of vertical crustal

deformation in the Shumagin Seismic Gap, Alaska,' J. Geophys . Res. 91,

9067-9080 (1986).

NOTE: Names in parentheses are authors who are not connected with JILA,

NBS or CU. List does not include JILA publications by JILA CU Fellows and

their associates.

‘Entries with stars are those resulting from the work of JILA Visiting

Fellows

.

184
PUBLICATIONS

Quantum Physics Division (525)

(K. Hurst) and R. Bilham, 'Hydrostatic levels in precision geodesy and

crustal deformation measurement,' J. Geophys

.

91, 9202-9216 (1986).

*E. Bohm-Vitense , 'Theory of transition-layer emission measures and

coronae,' As trophys . J. 317, 750-759 (1987).

(T. S. Bastian) and J. A. Bookbinder, 'First dynamic spectra of stellar

microwave flares,' Nature 326, 678-680 (1987).

P. L. Bornmann, 'Turbulence as a contributor to intermediate energy storage

during solar flares,' Astrophys . J. 313, 449-455 (1987).

(T. R. Ayres, P. Judge, C. Jordan), A. Brown and J. L. Linsky, 'Highdispersion observations of Alpha Bootis (Kl III) with the International

Ultraviolet Explorer,' A.strophys. J. 311, 947-959 (1986).

A. Brown, (D. Reimers) and J. L. Linsky, 'High dispersion lUE observations

of hybrid-chromosphere stars,' in New Insights in Astrophysics, 8 Years of

UV Astronomy with lUE (ESA SP-263, 1986), pp . 169-172.

A. Brown, J. L. Linsky, (S. A. Drake and W. Herbst) , 'Ultraviolet and

optical variability of RY Tauri,' in New Insights in Astrophysics, 8 Years

of UV Astronomy with lUE (ESA SP-263, 1986), pp. 177-179.

(F. M. Walter), A. Brown, J. L. Linsky, (A. E. Rydgren, F. Vrba, M. Roth,

L. Carrasco, P. F. Chugainov, N. I. Shakovskaya and C. L. Imhoff ) , 'X-ray

sources in regions of star formation. II. The pre-main-sequence G star

HDE 283572,' Astrophys. J. 314, 297-307 (1987).

A. Brown, 'Variable radio emission from the 4 Draconis system,' Astrophys.

J. (Letters) 312, L51-53 (1987).

(C. Jordan, T. R. Ayres), A. Brown, J. L. Linsky and (T. Simon), 'The

chromospheres and coronae of five G-K main-sequence stars,' Monthly Notices

Roy. Astron. Soc

.

225, 903-937 (1987).

(P. B. Byrne, J. G. Doyle), A. Brown, J. L. Linsky and (M. Rodono)

,

'Rotational modulation and flares on RS CVn and BY Dra stars. VI. Physical

parameters of the chromospheres/transition regions of V711 Tau (HR1099) , II

Peg and AR Lac during October 1981,' Astron. Astrophys. 180, 172-182

(1987) .

K. L. Carleton and S. R. Leone, 'Laser probing of gallium spin orbit state

desorption,' in Proceedings, Industry-University Advanced Materials

Conference (Metallurgical Society of AIME, 1987), p. 9.

185
PUBLICATIONS

Quantum Physics Division (525)

L. M. Cousins and S. R. Leone, 'T-V energy transfer and the exchange

reaction of H(D) + HF at 2.2(2. 1) eV; Vibrational state distributions by

time and wavelength resolved infrared fluorescence,' J. Chem. Phys

.

86,

6731-6737 (1987).

*(R. L. Waterland) , J. B. Delos and M. L. Du, 'High Rydberg states of an atom in parallel electric and magnetic fields,' Phys. Rev. A 35, 5064-5080

(1987) .

*(M. Hottoka, B. Roos) , J. B. Delos, (R. Srivastava, R. B. Sharma and W. S.

Koski) , 'Collisions of with Ne,' Phys. Rev. A 35, 4515-4525 (1987).

D. J. Donaldson and S. R. Leone, 'Time-resolved FTIR photofragment emission

spectroscopy; HCl vibrational distributions from the 193 nm photolysis of

chloroethylenes , ' Chem. Phys. Lett. 132, 240-246 (1986).

D. J, Donaldson and S. R. Leone, 'Laser photolysis, infrared fluorescence

determination of CH3 (i/ 3 ) vibrational deactivation by He, Ar, N2 , CO, SFg

and (CH3)2C0,' J. Phys. Chem. 91, 3128-3131 (1987).

M. L. Du and J. B. Delos, 'Effect of closed classical orbits on quantum

spectra: Ionization of atoms in magnetic field,' Phys. Rev. Lett. 58,

1731-1733 (1987).

G. H. Dunn, 'Experiments on dielectronic recombination -- A review,' in

Atomic Processes in Electron-Ion and Ion-Ion Collisionsrj (F. Brouillard,

Ed., Plenum, New York, 1986), pp . 93-115.

S. E. Barlow, J. A. Luine and G. H. Dunn, 'Measurement of ion/molecule

reactions between 10 and 20 K, ' Int . J. Mass Spectrom. Ion Proc. 74, 97-

128 (1986).

G. H. Dunn, 'Tuneable resonances: Dielectronic recombination,' in Report

IPPJ-AM-^7 , Institute of Plasma Physics, Nagoya, Japan (1986), pp . 148-153.

G. H. Dunn, 'Overview of electron-ion collisions,' in Report IPPJ-AM-48,

Institute of Plasma Physics, Nagoya, Japan (1986), pp . 20-23.

*P. E. Engelking, 'Approximate rotational band shifts,' J. Phys. Chem. 90,

4544-4545 (1986).

>'=’P. C. Engelking, ' Photoinduced evaporation of charged clusters,' J. Chem.

Phys. 85, 3103-3110 (1986).

*(V. Vaida, M. McCarthy), P. C. Engelking, (P. Rosmus, H.-J. Werner and P.

186
PUBLICATIONS

Quantvun Physics Division (525)

Botschwina) , 'The ultraviolet absorption spectra of the A ^ X ^A^

transition of jet-cooled ammonia,' J. Chem. Phys

.

86, 6669-6676 (1987).

*(P. Rosmus , P. Botschwina, H.-J. Werner, V. Vaida) , P. C. Engelking and

(M. I. McCarthy), 'Theoretical A ^A^ X ^A^ absorption and emission

spectrum of ammonia, ' J. Chem. Phys. 86, 6677-6692 (1987).

*M. Belsley, A. Streater, K. Burnett, P. Ewart and J. Cooper, 'Observation

of radiative transfer of polarized light,' J. Quant. Spectrosc . Radiat.

Transfer 36, 163-173 (1986).

J. Faller, T. Niebauer, W. Hollander (and 31 other authors), 'Results of

the second international comparison of absolute gravimeters in Sevres

1985,' in Bull. d'Information No. 59, December 1986 (Bureau Gravimetrique

International, Toulouse), pp. 89-103.

A. Gallagher, 'Amorphous silicon deposition rates in diode and triode

discharges,' J. Appl. Phys. 60, 1369-1373 (1986).

A. Gallagher, 'Surface reactions in discharge and CVD deposition of

silane,' Mat. Res. Soc . Symp . Proc. 70, 3-10 (1986).

A. Gallagher and ( J . Scott), 'Gas and surface processes leading to

hydrogenated amorphous silicon films,' in Solar Cells 21, 147-152 (1987).

( J . G. Porter), K. B. Gebbie and (L. J. November), 'The excitation of

helium resonance lines in solar flares,' in The Lower Atmosphere of Solar

Flares, Ed. D. F. Neidig (National Solar Observatory), p. 84 (1986).

*D. M. Gibson, 'What stellar (solar) radio observations teach us about the sun (stars),' in Solar Terrestrial Physics, INDO US Workshop 1984-

Proceedings (M. R. Kundu, B. Biswas, B. M. Reddy and S. Ramadurai, Eds.,

National Physical Laboratory, New Delhi, 1986), pp . 43-57.

*E. B. Gliner and (V. A. Osherovich) , 'Formation of a solar coronal

transient with forerunner,' As trophys . J. 312, 412-422 (1987).

*D. C. Griffin and (M. S. Pindzola) , ' Dielectronic recombination of highly

ionized iron,' Phys. Rev. A 35, 2821-2831 (1987).

*(P. F. Dittner, S. Datz , H. F. Krause, P. D. Miller, P. L. Pepmiller, C. Bottcher, C. M. Fou) , D. C. Griffin and (M. S. Pindzola), 'Dielectronic

recombination of the Be-like ions: , N^'*',

0^'*’ and F^'*’, ' Phys. Rev. A 36,

33-39 (1987).

*(R. D. Cowan) and D. C. Griffin, 'Effects of configuration mixing on

187
PDBLICATIONS

Quantiun Physics Division (525)

computed dielectronic-recombination rates,' Phys . Rev. A 36, 26-32 (1987).

J. L. Hall, 'Stabilizing lasers, for applications in quantum optics,' in

Quantum Optics IV, Proceedings of the Fourth International Symposium,

Hamilton, New Zealand, February 10-15, 1986 (J. D. Harvey and D. F, Walls,

Eds., Springer-Verlag, 1986), pp. 273-284.

(H. J, Kimble) and J. L. Hall, 'Intracavity frequency doubling for the

generation of squeezed states of light,' in Quantum Optics IV, Proceedings

of the Fourth International Symposium, Hamilton, New Zealand, February

10-15, 1986 (J. D. Harvey and D. F. Walls, Eds., Springer-Verlag, 1986),

pp. 58-69.

(L.-A. Wu, H. J. Kimble), J. L. Hall and (H. Wu) , 'Generation of squeezed

states by parametric down conversion,' Phys. Rev. Lett. 57, 2520-2523

(1986) .

J. L. Hall, Ma Long-Sheng and G. Kramer, 'Principles of optical phase

locking; with application to internal mirror He-Ne lasers phase locked via

fast control of the discharge current,' IEEE J. Quant. Electron. (Special

Issue on Applications of QE to Frequency Standards, Clocks and Rotation

Sensors) QE-23, M7-^37 (1987).

M. W. Hamilton, K. Arnett, S. J. Smith, (D. S. Elliott, M. Dziemballa and

P. Zoller) , 'Saturation of an optical transition by a phase-diffusing laser

field,' Phys. Rev. A 36, 178-188 (1987).

W. P. Hess and S. R. Leone, 'Absolute I* quantum yields for the ICN A state

by diode laser gain-vs-absorption spectroscopy,' J, Chem. Phys. 86,

3773-3780 (1987).

D. Hils, J. E. Faller and J. L. Hall, 'Practical sound- reducing enclosure

for laboratory use,' Rev. Sci. Instrum. 57, 2532-2534 (1986).

(R. P. Kudritzki) and D. G. Hummer, 'Intrinsic parameters of hot blue

stars,' in Luminous Stars and Associations in Galaxies, lAU Symposium 116

(Reidel, Dordrecht, 1986), pp . 3-18.

D. G. Hummer and (P. J. Storey), ' Recombination- line intensities for

hydrogenic ions. I. Case B calculations for HI and Hell,' Monthly Notices

Roy. Astron. Soc

.

224, 800-818 (1987).

D. E. Kelleher and (E. B. Saloman) , 'Rydberg states with anisotropic ion

cores: Stark effect,' Phys. Rev. A 35, 3327-3338 (1987).

D. E. Kelleher, (E. B. Saloman and J. W. Cooper), 'Electric field effects

on structure in the continuum, ' in Photons and Continuum States of Atoms

138
PUBLICATIONS

Quantum Physics Division (525)

and Molecules (N. K. Rehman, C, Guidohe and M. Allegrini, Eds,, SpringerVerlag, 1987), pp. 68-75.

J. F. Kelly and A. Gallagher, 'Efficient electro-optic modulator for

optical pumping of Na beams,' Rev. Sci. Instr. 58, 563-566 (1987),

P. T. Keyset and J, Faller, ' Liquid- supported torsion balance as a gradiometer, ' in lA-th Gravity Gradiometer Conference, U.S. Air Force

Academy, Colorado Springs, 11-12 February 1986 (T. J. Fundak, Ed,, AFGL,

Hanscom AFB, MA, 1987), Paper 21.

*J . G. Kirk and P, Schneider, 'On the acceleration of charged particles at

relativistic shock fronts,' Astrophys. J. 315, 425-433 (1987).

(R. W. Schwenz) and S. R. Leone, 'Near-resonant collisional energy transfer

in Sr(5s6p ^P^) -- rare-gas systems,' Chem. Phys . Lett. 133, 433-439

(1987) .

V. M. Bierbaum and S. R. Leone, 'Optical studies of product state

distributions in thermal energy ion-molecule reactions,' in Structure/

Reactivity and Thermochemistry of Ions (NATO AST) (P. Ausloos and S. G.

Lias, Eds., Reidel, Dordrecht, 1987), pp. 23-55.

D. A. Dolson and S. R. Leone, 'A reinvestigation of the laser-initiated

Cl2/HBr chain reaction; Absolute rate constants and the v=2/v=l ratio from

Cl + HBr goes to HCl(v) + Br, ' J. Phys. Chem. 91, 3543-3550 (1987).

J. Levine, ( J . 6. Harrison and W. Dewhurst) , 'Gravity tide measurements

with a feedback gravity meter,' J. Geophys . Res. B 91, 12835-12841 (1986).

S. A. Drake and J, L. Linsky, 'Microwave continuum measurements and

estimates of mass loss rates for cool giants and supergiants,' Irish

Astron. J. 17, 288-294 (1986).

J. L. Linsky, 'Modeling extended chromospheres,' Irish Astron. J. 17,

343-351 (1986).

(M. Rodono , G. Cutispoto, V, Pazzani , S. Catalano, P. B. Byrne, J. G.

Doyle, C. J. Butler, A. D. Andrews, C. Blanco, E. Marilli) , J. L. Linsky,

(F. Scaltriti, M. Busso, A. Cellino, J. L. Hopkins, A. Okazaki, S. S.

Hayashi, M. Zeilik, R. Elston, G. Henson, P. Smith and T. Simon),

'Rotational modulation and flares on RS CVn and BY Dra-type stars. I. Photometry and spot models for BY Dra, AU Mic , AR Lac, II Peg and V711 Tau

(=HR 1099),' Astron. Astrophys. 165, 135-156 (1986).

(F. M. Walter) and J. L. Linsky, 'Activity in warm stars: lUE observations

of early F dwarfs,' in New Insights in Astrophysics, 8 Years of UV

189
PUBLICATIONS

Quantum Physics Division (525)

Astronomy with lUE (ESA SP-263, 1986), pp. 103-106.

J. L. Linsky, J. E. Neff, B. D. Gross, T. Simon, (A. D. Andrews and M.

Rodono) , 'Where do flares occur in RS CVn systems? -- Analysis of the

October 3, 1981 flare on V711 Tau = HR 1099 observed by lUE,' in New

Insights in Astrophysics , 8 Years of UV Astronomy with lUE (ESA SP-263,

1986), pp. 161-164.

J. L. Linsky (and the Investigation Team for Proposed NASA LYMAN Phase A

Study), 'The proposed LYMAN far ultraviolet spectroscopic explorer,' in New

Insights in Astrophysics , 8 Years of UV Astronomy with lUE (ESA SP-263,

1986), pp. 537-549.

(K. Eriksson, M. Saxner, B. Gustafsson, T. R. Ayres), J. L. Linsky and (J.

Andersen), 'TZ Fornacis - An eclipsing Capella-like system observed with

the lUE,' in New Insights in Astrophysics , 8 Years of UV Astronomy with lUE

(ESA SP-263, 1986), pp . 225-227.

(R. C. Henry, J. Mur thy, H. W. Moos, W. B. Landsman), J. L. Linsky, (A.

Vidal-Madjar and C. Gry) , ' lUE study of the very local interstellar

medium,' in New Insights in Astrophysics, 8 Years of UV Astronomy with lUE

(ESA SP-263, 1986), pp. 555-558.

(C. J. Butler, M. Rodono) and J. L. Linsky, ' lUE spectra of flares on AU

Mic,' in New Insights in Astrophysics , 8 Years of UV Astronomy with lUE

(ESA SP-263, 1986), pp . 229-232.

J. L. Linsky, (W. B. Landsman, B. D. Savage, S. R. Heap, A. M. Smith and J.

C. Brandt), 'The HRS GTO program to study the neutral hydrogen column

density and D/H ratio in the local interstellar medium, ' (COSPAR) Adv.

Space Res. 6, 91-94 (1986).

J. L. Linsky, 'Physics of partial redistribution and radiative transfer in

stellar atmospheres,' in Radiative Properties of Hot Dense Matter III (B.

Rezsnyoi, C. Hooper, R. Cauble, R. Lee, and J. Davis, Eds., World

Scientific, Singapore, 1987), pp. 333-373.

J. L. Linsky, 'An investigation of stellar coronae with AXAF, ' As trophys

.

Lett. Commun. 26, 21-34 (1987).

(C. J. Butler, J. G. Doyle, A. D. Andrews, P. B. Byrne), J. L. Linsky, P. L. Bornmann, (M. Rodono, V. Pazzani and T. Simon), 'Rotational modulation

and flares on RS CVn and BY Dra systems II. lUE observations of BY Draconis

and AU Microscopii , ' Astron. As trophys

.

174, 139-157 (1987).

S. A. Drake, T. Simon and J. L. Linsky, 'A VLA radio -continuum suivey of a sample of confirmed and marginal barium stars,' Astron. J. 93, 163-167

190
PUBLICATIONS

Quantum Physics Division (525)

(1987) .

( J . Murthy, R. C. Henry, H. W. Moos, W. B. Landsman), J. L. Linsky, (A.

Vidal-Madjar and C. Gry) , ' lUE observations of hydrogen and deuterium in

the local interstellar mediiim, ' As trophys . J. 315, 675-686 (1987).

(C. Jordan) and J. L. Linsky, 'Chromospheres and Transition Regions,' in

Exploring the Universe with the lUE Satellite (Y. Kondo, Ed., Reidel,

Dordrecht, 1987), pp. 259-293.

(Y. Kondo, W. Wamsteker, A. Boggess, M. Growing, C. De Jager, A. L. Lane),

J. L. Linsky and (R. Wilson) Eds., Exploring the Universe with the lUE

Satellite (Reidel, Dordrecht, 1987).

I. R. Little-Marenin and (S. J. Little), 'A search for technetium (Tell) in

barium stars,' Astron. J. 93, 1539-1541 (1987).

C. M. Lovejoy and D. J. Nesbitt, 'High sensitivity, high-resolution IR

laser spectroscopy in slit supersonic jets: Application to N2HF and

1/5 + i/j^ - 1/ 5 ,

' J. Chem. Phys

.

86 , 3151-3165 (1987).

C. M. Lovejoy and D. J. Nesbitt, 'Slit pulsed valve for generation of longpath-length supersonic expansions,' Rev. Sci. Instr. 58, 807-811 (1987).

C. M. Lovejoy, M. D. Schuder and D. J. Nesbitt, 'Direct IR laser absorption

spectroscopy of jet-cooled CO2HF complexes: Analysis of the HF stretch

and a surprisingly low frequency i/g intermolecular CO2 bend, ' J. Chem.

Phys. 86 , 5337-5349 (1987):

C. M. Lovejoy and D. J. Nesbitt, 'The near- infrared spectrum of ONNHF - direct evidence for geometric isomerism in a hydrogen bonded complex,'

J. Chem. Phys. 87, 1450-1451 (1987).

*T. M. Miller, D. G. Leopold, K. K. Murray and W. C. Lineberger, 'Electron

affinities of the alkali halides and the structure of their negative ions,'

J. Chem. Phys. 85, 2368-2375 (1986).

J. Mitroy, 'Generalized oscillator strength for the 3s-3p transition in

sodium,' Phys. Rev. A 35, 4434-4436 (1987).

*A. Muller, D. S. Belie, B. D. DePaola, N. Djuric, G. H. Dunn, D. W.

Mueller, and C. Timmer, 'Experimental measurements of field effects on dielectronic recombination cross sections and Rydberg product-state

distributions,' Phys. Rev. A 36, 599-613 (1987).

*A. Muller, G. H. Dunn, (D. W. Mueller, N. Djuric, B. D. DePaola, D. S.

Belie), C. Timmer, (K. Tinschert, C. Achenbach, G. Hofmann, R. Sauer, E.

191
PDBLICATIONS

Quantum Physics Division (525)

Salzborn and R. Becker), ' Electron- ion collisions: Dielectronic

recombination and ionization,' Nuclear Instrum. Math, in Physics Res. B23,

254 (1987).

*G. A. Natanson, 'Relationship between least-squares-surface and CellesDarling's hyperspherical coordinates,' Chem. Phys . Lett. 134, 301-306

(1987)

.

J. E. Neff, J. L. Linsky, (W. B. Landsman and K. G. Carpenter), 'Correcting

observed stellar Lyman alpha profiles for the effects of interstellar

absorption and geocoronal emission,' in New Insights in Astrophysics, 8

Years of UV Astronomy with lUE (ESA SP-263, 1986), pp. 669-672.

(M. Rodono, P. B. Byrne), J. E. Neff, J. L. Linsky, (T. Simon, C. J.

Butler, S. Catalano, G. Cutispoto, J. G. Doyle, A. D. Andrews and D. M.

Gibson), 'Rotational modulation and flares on RS CVn and BY Dra stars. III.

lUE observations of V711 Tau (=HR1099) , II Peg, and AR Lac,' Astron.

Astrophys. 176, 267-284 (1987).

(H. Petek), D. J. Nesbitt (D. C. Darwin and C. B. Moore), 'Visible

absorption and magnetic-rotation spectroscopy of ^CH2

: The analysis of the

b ^B^ state,' J. Chem. Phys. 86, 1172-1188 (1987).

(H. Petek), D. J. Nesbitt (C. B. Moore, F. W. Birss and D. A. Ramsay),

'Visible absorption and magnetic-rotation spectroscopy of ^CH2

: Analysis of

the ^Aj^ state and the ^Aj^-^Bj^ coupling,' J. Chem. Phys. 86, 1189-1205

(1987)

.

*W.-T. Ni, ' Polarized-body experiments and equivalence principles,' in

Proceedings of the Fourth Marcel Grossman Meeting on General Relativity (R.

Ruffini, Ed., Elsevier, 1986), pp. 1335-1346.

*W.-T. Ni, 'Quantum-mechanical noise in an interferometer: Intrinsic

uncertainty versus measurement uncertainty,' Phys. Rev. D 35, 3002-3007

(1987)

.

K. T. Taylor and D. W. Norcross, 'Alkali-metal negative ions. IV.

Multichannel calculations of K‘ photodetachment,' Phys. Rev. A 34,

3878-3891 (1986).

R. B. Christensen, D. W. Norcross and A. K. Pradhan, ' Electron- impact

excitation of ions in the magnesium sequence. II. S V, Ar VII, Ca IX, Cr

XIII, and Ni XVII,' Phys. Rev. A 34, 4704-4715 (1986).

D. W. Norcross, 'Rotational and vibrational excitation of molecules by low

energy electrons,' in Swarm Studies and Inelastic Electron-Molecule

192
FUBLICATIONS

Quantum Physics Division (525)

Collisions (L. C. Pitchford, B. V. McKoy, A. Chutj ian and S. Trajmar, Eds.,

Springer Verlag, 1987), pp. 217-237.

F. A. Parpia, D. W. Norcross and F. J. da Paixao, ' Electron- impact

excitation of the resonance transition in Be'*’: An ab initio treatment of

core-correlation and -polarization effects,' Phys . Rev. A 34, klll-lArl^k

(1986)

.

*F. W. Perkins and E. G. Zweibel, 'A high magnetic Reynolds number dynamo,'

Phys. Fluids 30, 1079-1084 (1987).

A. V. Phelps, 'Relations between electron-molecule scattering and swarm

experiments and analysis,' in Swarm Studies and Inelastic ElectronMolecule Collisions (L. C. Pitchford, B. V. McKoy, A. Chutj ian and S.

Trajmar, Eds., Springer Verlag, 1987), pp. 127-141.

(D. C. Gregory, L. J. Wang, F. W. Meyer) and K. Rinn, 'Electron impact

ionization of iron ions: Fe^^'*', Fe^^'*', and Fe^^'*', ' Phys. Rev. A 35, 3265-

3264 (1987).

K. Rinn, (D. C. Gregory, J. L. Wang, R. A. Phaneuf and A. Mueller),

'Electron impact ionization of 0^'*’: Improved measurements,' Phys. Rev. A

36, 595-598 (1987).

R. M. Robertson and A. Gallagher, 'Reply to the 'Comment on silane

pyrolysis and the insertion of silylene into molecular hydrogen' ,

' J. Chem.

Phys. 86, 3059-3060 (1987).

*S. V. ONeil, P. Rosmus, D. W. Norcross and (H.-J. Werner), 'Bound

electronic states of HCl',' J. Chem. Phys. 85, 7232-7240 (1986).

*R. Grobe , G. Leuchs and K. Rzazewski, 'Migration of population to higher

angular-momentum Rydberg states through the degenerate Raman coupling,'

Phys. Rev. A 34, 1188-1194 (1986).

S. H. Saar and J. L. Linsky, 'New measurements of photospheric magnetic

fields in late-type stars and emerging trends,' (COSPAR) Adv . Space Res. 6,

235-238 (1986).

*(Y. Kawai) , H. Saio and (K. Nomoto) , 'Off-center ignition of nuclear

burning in merging white dwarfs,' As trophys . J. 315, 229-233 (1987).

*(U. Lee) and H. Saio, 'Low frequency oscillations of uniformly rotating

stars and a possible excitation mechanism for variable B stars,' in Stellar

Pulsation , Proceedings of a Conference Held as a Memorial to John Cox at

193
PUBLICATIONS

Quantum Physics Division (525)

the Los Alamos National Laboratory, Los Alamos, NM, August 11-15, 1986 (A,

N. Cox, W. M. Sparks and S. G. Starrfield, Eds., Springer-Verlag, 1987),

pp. 102-105.

*H. Saio, ( J . K. Cannizzo and J. C. Wheeler), 'A linear thermal stability

analysis for the vertical structure of alpha model accretion disks,'

Astrophys. J. 316, 715-720 (1987).

*(U. Lee) and H. Saio, 'Non-adiabatic analysis of low-frequency

oscillations of uniformly rotating stars,' Monthly Notices Roy. Astron.

Soc. 225, 643-651 (1987).

*(C. Parigger, P. Hannaford) and W. J. Sandle, 'Polarization switching

versus optical bistability: Experimental observations for a = 1 to

jupper _ Q transition in a Fabry-Perot cavity,' Phys . Rev. A 34, 2058-2072

(1986)

.

*W. J. Sandle, (C. Parigger and R. J. Ballagh) , 'Optical bistability and

polarization switching utilizing two- level atoms with lower- level

degeneracy,' in Optical Chaos, SPIE Vol. 667 (Society of Photo-optical

Instrumentation Engineers, Bellingham, WA, 1986), pp. 62-67.

*A. Streater, J. Cooper and W. Sandle, 'On time-dependent radiative

transfer,' J. Quant. Spectrosc . Radiat. Transfer 37, 151-156 (1987).

*C. L. Sarazin, 'X-ray halos in galaxies and clusters of galaxies: Theory,'

in Dark Matter in the Universe , lAU Symposium 117 (Reidel, Dordrecht,

1987), pp. 183-199.

•*(R. E. White III) and C. L. Sarazin, 'Star formation in X-ray cluster

cooling flows,' Astrophys. J. 318, 612-620 (1987).

*(R. E. White III) and C. L. Sarazin, 'Numerical models of star formation

in X-ray cluster cooling flows,' Astrophys. J. 318, 629-644 (1987).

*(C. P. O'Dea), C. L. Sarazin and (F. N. Owen), 'Narrow-angle tail radio

sources and the distribution of galaxy orbits in Abell clusters,'

Astrophys. J. 316, 113-126 (1987).

*(R. E. White III) and C. L. Sarazin, 'Determining star formation rates in

X-ray cluster cooling flows,' Astrophys. J. 318, 621-628 (1987).

J. E. Smedley, W. P. Hess, H. K. Haugen and S. R. Leone, 'Transient gainversus-absorption laser probing of spin-orbit states, kinetics and

dynamics,' in Proceedings, 9th Inteimational Symposium on Gas Kinetics , J.

Chim. Physique 84, 385-391 (1987),

194
PDBLICATIONS

Quantum Physics Division (525)

J. E. Smedley, H. K. Haugen and S, R. Leone, ' Collision- induced

dissociation of laser-excited Br2 [B ;v' , J ' ]

: Formation of

Br*(2p^^2) + Br(^P3 / 2 ) at energies 1-5 kT below dissociation,' J. Chem.

Phys. 86, 6801-6812 (1987).

S. J. Smith, 'Experimental investigations of the role of laser field

fluctuations in non-linear optical absorption processes,' in Quantum

Optics, Proceedings of the VI International School of Coherent Optics (A.

Kujawski and M. Lewenstein, Eds., Polish Acad. Sci. Instit. of Phys.,

1986)

, pp. 265-274.

*S. Starrfield and (M. A. J. Snijders), 'Of galactic novae,' in Exploring

the Universe with the lUE Satellite (Y. Kondo, Ed., Reidel, Dordrecht,

1987)

, pp. 377-393.

*(Th. Sauter, W. Neuhauser, R. Blatt) and P. E. Toschek, 'Observation of

quantum jumps,' Phys. Rev. Lett. 57, 1696-1698 (1986).

*(H. Schroder, K. Schultz) and P. E. Toschek, 'On the line shapes of laser

intracavity absorption,' Opt. Commun. 60, 159-165 (1986).

*R. Blatt, W. Ertmer, P. Zoller and J. Hall, 'Atomic-beam cooling: A

simulation approach,' Phys. Rev. A 34, 3022-3033 (1986).

195
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

D. C. Abbott and P. S. Conti, 'Wolf-Rayet stars,' in Annual Review of

Astronomy and Astrophysics (in press).

S. A. Drake, D. C. Abbott, (T. S. Bastian, J. H. Bieging, E. Churchwell, G

Dulk) and J. L. Linsky, 'The discovery of nonthermal radio emission from

magnetic Bp-Ap stars,' As trophys . J. (in press).

S. Alston, 'The impulse approximation for central, modified Coulomb

potentials,' Phys , Rev. A (submitted).

C. W. Ambruster, (S. Sciortino and L. Golub), 'Rapid, low level X-ray

variability in active, late-type dwarfs,' Astrophys. J. Suppl. (in press).

(0. Elgaroy, P. Joras, 0. Engvold, E. Jensen, B. R. Pettersen, T. R.

Ayres), C. Ambruster, J. L. Linsky (M. Clark, W, Kunkel, and F. Marang)

,

'Ultraviolet emission lines and optical photometry of the flare star AT

Microscopii , ' Astron. Astrophys. (submitted).

*A. J. Anderson and (H. G. Scherneck) , 'The geoid obtained from SEASAT

altimetry and its relationship with lithospheric structure of FennoScandia,' J. Geophys . Res., SEASAT Issue (in press).

*(D. M. Neumark) , K. R. Lykke , T. Andersen and W. C. Lineberger,

'Autodetachment spectroscopy of negative ions,' in Proceedings of the

Second International Laser Science Conference (in press).

*K. R. Lykke, D. M. Neumark, T. Andersen, V. J. Trapa and W. C. Lineberger

'Autodetachment spectroscopy and dynamics of CH2CN' and CD2CN" , ' J. Chem.

Phys. (submitted).

P. Arcuni and (D. Schneider), ' Emission- line profiles of helium

autoionization states after excitation by fast Li and He ions,' Phys. Rev.

A (submitted)

.

*M. J. Barlow, 'Observational aspects of massive stars,' in Massive Stars,

Proceedings of the Ath British-Spanish School in Astrophysics (M. Moles,

ed. , in press)

.

*K. Bergmann, 'State selection via optical methods,' in Atomic and

Molecular Beam Methods (G. Scoles, Ed., Oxford Univ. Press, in press).

*(U. Hefter) and K. Bergmann, 'Spectroscopic detection methods,' Chapter 9

in Atomic and Molecular Beam Methods (G. Scoles, Ed., in press).

196
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

*R. Bilham, 'Southern San Andreas fault geometry and fault-zone

deformation: Implications for earthquake prediction in the Coachella

Valley, California, ' presented at the National Earthquake Prediction and

Evaluation Council, to appear in U.S. Geological Survey Report.

*E. Bohm-Vitense , 'Analysis of the transition layer and corona of Procyon,

Astrophys . J. (submitted).

•*E. Bohm-Vitense, 'Analysis of the solar transition layer and corona,'

Astrophys. J. (submitted).

A. Brown, 'Radio emission from pre-main sequence stars in Corona

Australis,' Astrophys. J. (Letters) (submitted).

W. Bussert and S. R. Leone, 'Orbital alignment effects in the Ca(4s5p ^Pj^)

to Ca(4s5p ^Pj) electronic energy transfer with molecular collision

partners,' Chem. Rhys. Lett, (in press).

W. Bussert, D. Neuschafer and S. R. Leone, 'The effect of orbital alignment

on the forward and reverse electronic energy transfer Ca(4s5p ^Pj^) + M *—

+

Ca(4s5p ^Pj) + M with rare gases,' J. Chem. Rhys, (in press).

W. Bussert and S. R. Leone, 'State-specific orbital alignment effects in

electronic energy transfer: Sr(5s6p ^P^) + M -> Sr(5s6p ^Pj, 4d5p , ^F3 ) + M, ' Chem. Rhys. Lett, (in press).

J.-P. Caillault and (D. J. Helfand) , 'The Einstein soft X-ray survey of the

Pleiades,' (Student Prize Lecture) Astron. Soc. New York (in press).

J. -P. Caillault and (S. Zoonematkermani) , 'The Einstein survey of the young

stars in the Orion nebula,' Adv. Space Res. (COSPAR) (in press).

K. L. Carleton and S. R. Leone, 'Laser probing of gallium atom interactions

with silicon (100) surfaces,' J. Vac. Sci. Technol. B (in press).

*S.-I Chu, 'Multiphoton processes in intense laser fields,' in Rroceedings

,

Workshop on Atomic Spectroscopy and its Related Dynamical Rroperties

(Instit. of Atomic and Molecular Science and National Tsing-Hua University

in Taiwan, R.O.C., June 23-25, 1984, in press).

(G. S. Agarwal) , C. V. Kunasz and J. Cooper, 'Fluctuation induced Hanle

resonances in phase conjugation,' Rhys. Rev. A (submitted).

L. M. Cousins and S. R. Leone, 'T-V energy transfer and chemical reactions

197
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

of laser-produced hot H and D atoms,' Radiochim. Acta (Proceedings, Hot

Atom Symposium, Mt. Fuji, Japan, May 1987) (in press).

*(R. L. Waterland) , J. B. Delos and M. L. Du, 'Excited states of an atom in

collinear electric and magnetic fields,' Phys . Rev. Lett, (submitted).

*J . B. Delos, (R. L. Waterland) and M. L. Du, ' Semiclassical interpretation

of eigenvectors for excited atoms in external fields,' Phys. Rev. A

(submitted)

.

R. A. Dressier, H. Meyer and S. R. Leone, 'Laser probing of the rotational

alignment of drifted in helium,' J. Chem. Phys. (submitted).

R. A. Dressier, H. Meyer, A. 0. Langford, V. M. Bierbaum and S. R. Leone,

'Direct observation of Ba"^ velocity distributions in a drift tube using

single-frequency laser- induced fluorescence,' J. Chem. Phys. (submitted).

G. H. Dunn, 'Resonances in electron-ion collisions,' in Proceedings of the

VI National Workshop on Atomic and Molecular Physics, Varanasi, India,

December 8-13, 1986 (World Scientific, Singapore, in press).

S. E. Barlow and G. H. Dunn, 'The effects of isotopic substitution on abstraction reactions of ammonia ions with hydrogen at very low

temperatures,' Int . J. Mass Spectrom. Ion Proc. (in press).

*P. C. Engelking, 'On van der Waals stabilization of bubbles,' Phys. Rev.

Lett, (submitted).

J. E. Faller and (A. Sakuma) , 'Ballistic methods of measuring 'g' -- the

direct free fall and the symmetrical rise and fall methods compared,

Metrologia (submitted)

.

A. Gallagher, ' Doppler- free lineshapes,' in Proceedings, Sth International

Conference on Spectral Line Shapes (in press).

A. Gallagher, 'Laser spectroscopy of inelastic collisions,' in Proceedings,

First Symposium on Laser Spectroscopy

,

Pecs, Hungary, August 1986 (in

press)

.

A. Gallagher, 'Surface reactions in silane discharges,' in Proceedings of

the XIII International Symposium on the Physics of Ionized Gases, Sibenik,

Yugoslavia, September 1986 (in press).

A. Gallagher, 'Apparatus design for glow-discharge a-Si:H films --

198
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

Deposition,' Int . J. Solar Energy (submitted).

A. Gallagher, 'Neutral radical deposition from silane discharges,' J. Appl.

Phys

.

(submitted).

( J , G. Porter), K. B.Gebbie and (L. J. November), 'Helium resonance lines

in solar flare of 15 June 1973,' Solar Physics (submitted).

*(M. S. Pindzola) and D. C. Griffin, 'Double auger processes in the

electron- impact ionization of lithium-like ions,' Phys. Rev. A (submitted).

*(M. S. Pindzola), D. C, Griffin and (C. Bottcher) , 'Theoretical

calculations of indirect processes in electron- impact ionization of atomic

ions,' Comments At. Mol. Phys. (submitted).

*D. C. Griffin (M. S. Pindzola and C. Bottcher), 'Distorted-wave

calculations of the electron- impact ionization of highly ionized Na-like

ions,' Phys. Rev. A (submitted).

J. L. Hall, D. Hils, C. Salomon, and J.-M. Chartier, 'Towards the ultimate

laser resolution,' in Proceedings , Eighth International Conference on Laser

Spectroscopy (in press).

M. Harris, J. F. Kelly and A. Gallagher, 'Observation of three-body

collisional transfer between atomic levels,' Phys. Rev. A (in press).

(H. K. Haugen), W. P. Hess and S. R. Leone, 'Application of semiconductor

diode lasers to probe photodissociation dynamics,' in Proceedings

,

International Laser Science Conference, Seattle (1986).

D. Hils and J. L. Hall, 'The response of a Fabry-Perot cavity to phase

modulated light,' Rev. Sci. Instr. (in press).

D. G. Hummer and (D. Mihalas) , 'The equation of state for stellar

envelopes. I. An occupation probability formalism for the truncation of

internal partition functions,' As trophys . J. (submitted).

(D. Mihalas, W. Dappen) and D. G. Hummer, 'The equation of state for

stellar envelopes. II. Algorithm and selected results,' As trophys . J.

(submitted)

.

(J. Puls) and D. G. Hummer, 'The Sobolev approximation for the line force

and line source function in a spherically-symmetrical stellar wind with

199
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

continuum opacity,' Astron. As trophys

.

(submitted).

(P. J. Storey) and D. G. Hummer, 'Recombination- line intensities for

hydrogenic ions. II. Case B calculations for C VI , N VII and 0 VIII,'

Monthly Notices Roy. Astron. Soc

.

(submitted).

D. G. Hummer and S. A. Voels, 'Radiative-collisional switching: A powerful

technique for converging non-LTE calculations,' Astron. Astrophys.

(submitted)

.

D. G. Hummer, 'Exact evaluation of the classical saddle-point critical

field for Stark ionization with non-zero angular momentum,' Rhys. Rev. A

(submitted)

.

L. F. Smith and D. G. Hummer, 'C/He abundances in WC stars,' Monthly

Notices Roy. Astron. Soc. (submitted).

*(L. P. Presnyakov) and R. K. Janev, 'Excitation and ionization processes

in electron-multiply charged ion collisions,' in Proceedings , Vinis

Symposium (in press).

B. M. Jelenkovic and A. V. Phelps, 'Excitation of N2 in dc electrical

discharges at very high E/n, ' Rhys. Rev. A (submitted).

(D. H. Oza, R. L. Greene) and D. E. Kelleher, 'Collisional broadening of

the Balmer alpha transition of H and He"^ in plasma,' Rhys. Rev. A

(submitted)

.

P. T. Keyser, 'Forces on the Thieberger accelerometer,' Rhys. Rev. Lett.

( submitted)

.

*J . G. Kirk and P. Schneider, 'Cosmic ray acceleration at relativistic

shocks,' in Proceedings , Third George Mason Fall Workshop on Astrophysics,

Supermassive Black Holes (in press).

*J . G. Kirk and P. Schneider, 'Particle acceleration at shocks: A Monte

Carlo method,' Astrophys. J. (in press).

*J . G. Kirk, 'Pitch-angle anisotropy of low energy low at interplanetary

shocks,' Astrophys. J. (submitted).

*M. Sikora, J. G. Kirk, M. C. Begelman and P. Schneider, 'Electron

injection by relativistic protons in active galactic nuclei,' Astrophys. J.

(Letters) (in press).

200
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

*P. Schneider and J. Kirk, 'Fermi acceleration at shocks with arbitrary

velocity profile,' As trophys . J. (Letters) (submitted).

L. J. Kovalenko and S, R. Leone, 'Innovative laser techniques in chemical

kinetics: A pedagogical survey,' J. Chem. Ed. (submitted).

S. R. Leone and V. M. Bierbaum, 'Laser probing of product state

distributions in thermal energy ion-molecule reactions,' Faraday Discussion

No. 84 (submitted).

J. Levine, 'Automatically running an indirect command file at some future

time,' RSX Multi-Tasker (submitted).

G. H. Lin, J. R. Doyle, M. He and A. Gallagher, 'Argon sputtering analysis

of the growing surface of hydrogenated amorphous silicon films,' J. Appl.

Phys

.

(submitted).

(B. E. Woodgate, A. Boggess, T. R. Gull, S. R. Heap, V. L. Krueger, S. P. Maran, R. W. Melcher, F. J. Rebar, H. D. Vitagliano, R. F. Green, S. C.

Wolff, J. B. Hutchings, E. B. Jenkins), J. L. Linsky, (H. W. Moos, F. Roesler, R. A. Shine, J. G. Timothy, D. E. Wiestrop, M. Bottema and W.

Meyer), 'Second generation spectrograph for the Hubble Space Telescope,' in

Proc., Society of Photo-Instrumentation Engineers (in press).

(W. B. Landsman, J. Murthy, R. C. Henry, H. W. Moos), J. L. Linsky, (A.

Vidal-Madjar and C. Gry) , ' lUE observations of neutral hydrogen and

deuterium in the local interstellar medium,' Adv. Space Res. (COSPAR) (in

press)

.

J. L. Linsky, 'What is the essential physics of mass loss from late- type

stars?' in Circumstellar Matter, lAU Symposium 122 (Reidel, Dordrecht, in

press)

.

J. L. Linsky, 'Requirements for theoretical models of outflows,' in Mass

Outflows from Stars and Galactic Nuclei (Reidel, in press).

(S. A. Drake), J. L. Linsky and (M. Elitzur) , 'A radio continuum survey of

the coolest M and C giants,' Astron. J. (in press).

(D. Ebbets, B. Fowler), J. L. Linsky and (R. Madden), Eds., Proceedings of

the Eighth Workshop on the Vacuum Ultraviolet Radiometric Calibration of

Space Experiments held at the Joint Institute for Laboratory for

Astrophysics, National Bureau of Standards and University of Colorado,

201
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

March 18-19, 1987 (in press).

C. M. Lovejoy, (D. D. Nelson Jr.) and D. J. Nesbitt, 'Hindered internal

rotation in jet cooled H2HF complexes,' J. Chem. Phys

.

(submitted).

*(W. Happen), D. Mihalas , D. G. Hummer and (B. W. Mihalas) , 'The equation

of state for stellar envelopes. III. Thermodynamic quantities,' As trophys

.

J

.

(submitted)

.

J. Mitroy, 'Coulomb phase effects in electron-ion scattering,' Phys. Rev.

Lett

.

( in press)

.

*(S. Sapers, V. Vaida) and R. Naaman, 'Photodissociation of CH3 I clusters

probed by multiphoton ionization,' J. Chem. Phys. (submitted).

*(D. J. Donaldson, V. Vaida) and R. Naaman, 'Ultraviolet absorption

spectroscopy of dissociating molecules: Effects of cluster formation on the

photodissociation of CH3 I

, ' J. Chem. Phys. (in press).

*(D. J. Donaldson, S. Sapers, V. Vaida) and R. Naaman, 'Photodissociation

of methyl iodide clusters,' in Large Finite Systems (B. Pullman, Ed., in

press)

.

*(S. Cohen), R. Naaman and ( J . Sagiv) , 'Rotational state-resolved

translational energy distributions of NO scattered from organized

amphiphilic monolayers,' J. Chem. Phys. (submitted).

*(D. J. Donaldson, V. Vaida) and R. Naaman, 'Ultraviolet absorption

determination of intramolecular predissociation dynamics in (CH3 l )2 and

(CD3 l) 2 , ' J. Phys. Chem. (submitted).

(F. M. Walter), J. E. Neff, (D. M. Gibson), J. L. Linsky, (M. Rodono, D. E. Gary and C. J. Butler), 'Rotational modulation and flares in RS Canum

Venaticorum and BY Draconis systems. IV. The spatially resolved

chromosphere of AR Lacertae,' Astron. Astrophys. (in press).

D. J. Nesbitt, 'Slit jet IR absorption spectroscopy of molecular

complexes,' in Structure and Dynamics of Weakly Bound Molecular Complexes

(Reidel, in press).

D. J. Nesbitt, 'Structure and dynamics of molecular clusters via high

resolution IR absorption spectroscopy,' in Proceedings , 0-E LASE '87 and

Electro-Optic Imaging Systems and Devices Symposium (in press).

202
PUBLICATIIONS

Quantmn Physics Division (525)

(submitted and in press)

*W.-T. Ni, 'Quantum-mechanical measurement noise in a Michelson

interferometer using general squeezed-state light sources,' Chinese J.

Phys . ( in press)

.

T. M. Niebauer, M. P. McHugh and J. E. Faller, 'Galilean test for the fifth

force,' Phys. Rev. Lett, (submitted).

A. V. Phelps, 'Excitation and ionization coefficients,' in Proceedings of

the Fifth International Symposium on Gaseous Dielectrics (Pergaraon, in

press)

.

(K. Tachibana) and A. V. Phelps, 'Excitation of the Is^ and Is^ levels of

neon by low energy electrons,' Phys. Rev. A (in press).

A. V. Phelps, 'Discharges at extremely high values of E/n and low

currents,' in Proceedings , International Conference on Phenomena in Ionized

Gases (in press).

A. V. Phelps, B. M. Jelenkovic and (L. C. Pitchford) , 'Simplified models of

electron excitation and ionization at very high E/n, ' Phys. Rev. A

(submitted)

.

A. K. Pradhan, 'Opacity project: Astrophysical and fusion application,' in

Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysics and

Fusion Research, Physica Scripta (in press).

D. Belie and A. K. Pradhan, 'Dielectric recombination,' Comments At. Mol.

Phys. (submitted).

A. K. Pradhan, 'Rate coefficients for electron impact excitation of

magnesium- like ions,' At. Data Nucl. Data Tables (submitted).

A. J. S. Hamilton, W. D. Vacca, and A. K. Pradhan, 'Analysis of the

spectrum of the type V supernova SN 1986J,' in SNRs and Their Interaction

with ISM, lAU Symposium 101 (Reidel, in press).

*N. F. Ramsey, 'Quantum mechanics and precision measurements,' IEEE Trans.

Instrum. Meas . IM-36 (in press).

*N. F. Ramsey, 'Time and the physical universe,' in Council of Scholars

(Library of Congress, in press).

*N. F. Ramsey, 'The electric dipole moment of the neutron,' in Proceedings,

Stored Particle Conference, Physica Scripta (submitted).

203
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

*N. F. Ramsey, 'Precise measurement of time,' American Scientist

(submitted)

.

S. H. Saar, 'Improved methods for the measurement and analysis of stellar

magnetic fields,' Astrophys. J. (in press).

S. H. Saar, J. L. Linsky and (M. S. Giampapa) , '4 meter FTS observations of

photospheric magnetic fields on M dwarfs,' in Observational Astrophysics

with High Precision Data, 27th Liege International Astrophysical

Colloquium, June 23-26, 1987 (in press).

*(Y. Kawai) , H. Saio and (K. Nomoto) , 'Steady state models of white dwarfs

accreting helium or carbon/oxygen- rich matter,' Astrophys. J. (submitted).

*C. L. Sarazin, 'A simple cooling flow model for x-ray coronae around

elliptical galaxies,' in Proceedings of the Greenbank Workshop on Gaseous

Haloes around Galaxies (in press).

*C. L. Sarazin, 'Mass distributions in elliptical galaxies at large radii,'

in lAU Colloquium 127 (Reidel, in press).

*C. L. Sarazin and (R. E. White III), 'Steady-state cooling flow models for

normal elliptical galaxies,' Astrophys. J. (in press).

C. J. Schrijver and (J. Cote), 'The relation between the Ca II K line-core

flux density and the magnetic flux density on the Sun, ' in Proceedings

,

Fifth Cambridge Workshop on Cool Stars, Stellar Atmospheres and the Sun (in

press)

.

(F. M. Walter) and C. J. Schrijver, 'Activity in warm stars,' in

Proceedings , Fifth Cambridge Workshop on Cool Stars, Stellar Atmospheres

and the Sun (in press).

J. E. Smedley, H. K. Haugen and S. R. Leone, 'Laser determinations of 'hot

band' quantum yields: Br*(^Pj^^ 2 ) formation in the continuum absorption of

Br2 at 510-550 nm, ' J. Chem. Phys

.

(in press).

D. M. Sonnenfroh and S. R. Leone, 'A rotationally resolved LIF study of the

products of the thermal energy Penning ionization reaction:

Ne*(^P2 ) +N2 ,' J. Chem. Phys. (submitted).

D. M. Sonnenfroh and S. R. Leone, 'Bimodal rotational distributions of N2

''’ produced in the thermal energy Penning ionization of N2 by Ne*(^P2 )

,

' Int

.

20^
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

J. Mass Spectrom. Ion Proc. (in press).

*(W. M. Sparks), S. Starrfield and (J. W. Timran) , 'Nova outburst modeling

and its application to the recurrent nova phenomena,' in Proceedings,

Workshop on the 1985 Outburst of RS Ophiuchi (in press).

*S . Starrfield and (W. M. Sparks), 'A review of the classical nova

outburst,' in Proceedings , Workshop on Cataclysmic Variables, Bamberg,

Germany, June 1986 (in press).

*S . Starrfield, 'A theoretical and observational review of results on nova

explosions occurring on ONeMg white dwarfs,' in Proceedings , Paris

Conference on New Directions in Nucleosynthesis

,

held at the Institut

d' As trophysique , July 7-11, 1986 (in press).

*S . Starrfield, 'Using nonradial pulsations to determine the envelope

composition of very evolved stars,' in Proceedings , Paris Conference on New

Directions in Nucleosynthesis

,

held at the Institut d' Astrophysique , July

7-11, 1986 (in press).

*(E. M. Sion), S. Starrfield, (M. E. Van Steenberg, W. M. Sparks, E. P. Ney, J. W. Truran and R. E. Williams), 'A high resolution observation of

the line of sight to Nova V693 CrA 1981,' Astron. J. (submitted).

*(A. N. Cox), S. Starrfield, (R. B. Kidman) and W. D. Pesnell, 'Pulsations

of white dwarf stars with thick hydrogen or helium surface layers,'

Astrophys. J. (submitted).

*S. Starrfield, 'A review of the ultraviolet studies of galactic novae,' in

New Insights in Astrophysics , 8 Years of Ultraviolet Astronomy with lUE

(ESA SP-263, 1986), pp. 239-245.

R. Stebbins and (P. R. Goode), 'Waves in the solar photosphere,' Solar

Phys

.

(submitted).

R. T. Stebbins, P. L. Bender and J. E. Faller, 'Proposed studies of a 30

meter imaging interferometer concept,' in Proceedings of the ESA Workshop

on Optical Interferometry, Granada, Spain (in press).

D. S. Belie, R. A. Falk, C. Timmer, G. H. Dunn, 'Absolute cross section

measurements for electron impact ionization of Al"^, Cd'*' and Hg'*', ' Phys.

Rev. A (in press)

.

*(V. M. Baev, K.-J. Boiler, A. Weller) and P. E. Toschek, 'Detection of

spectrally narrow light emission by laser intra-cavity spectroscopy,' Opt.

205
PUBLICATIIONS

Quantum Physics Division (525)

(submitted and in press)

Commun. (submitted).

*P. S. Toschek and (V. M. Baev), 'One is not enough: Intra-cavity

spectroscopy with multi-mode lasers,' in Arthur L. Schawlow -- Lasers,

Spectroscopy and Ideas (Springer-Verlag, in press),

*(F. Dorsch) , S. Geltman and P. E. Toschek, ' Laser- induced collisional

energy transfer in thermal collisions of lithium and strontium,' Phys . Rev.

A (submitted)

.

0. Vilhu and (F. M. Walter), 'Chromospheric-coronal activity at saturated

levels,' As trophys . J. (in press).

0. Vilhu, (B. Gustafsson and B. Edvardssoh) , 'Spectroscopy of the rapidly

rotating K-star HD 36705,' As trophys . J. (in press).

0. Vilhu and J. L. Linsky, 'Detection of X-ray emission from the young low- mass star Rossiter 137B,' Puhl. Astron. Soc . Pacific (in press).

*R. F. Webbink, 'Late stages of close binary systems -- clues to common

envelope evolution,' in Critical Observations vs. Physical Models for Close

Binary Systems, Proceedings of the Beijing Colloquium on Close Binary

Systems, 7-13 November 1985 (K.-C. Leung and D.-S. Zhai, Eds., Gordon and

Breach, New York, in press).

*(P. A. Teng, F. D. Lewis) and E. Weitz, 'Infrared laser induced

homogeneous catalysis of olefin isomerization,' J. Am. Chem. Soc.

(submitted)

.

N. C. Wong and J. 730

L. Hall, 'A high resolution measurement of water vapor overtone absorption

in the visible by frequency modulation spectroscopy,' J. Opt. Soc. Am. B

(submitted)

,

206
1986-1987 VISITING FELLOWS

Quantum Physics Division (525)

Visiting- Fellow

John Delos

Klaus-Peter Dinse

Donald C. Griffin

John G. Kirk

Dimitri Mihalas

Ron Naaman

Norman Ramsey

Home Institution

Department of Physics

College of William

and Mary

Williamsburg, VA

Universitat Dortmund

Experimentelle Physik III

Dortmund

West Germany

Department of Physics

Rollins College

Winter Park, FL

Max Planck Institut fur

Astrophysik

Garching, West Germany

Department of Astronomy

University of Illinois

Urbana, IL

Department of

Isotope Research

Weizmann Institute of

Science

Rehovat, Israel

Department of Physics

Lyman Laboratory of

Physics

Harvard University

Cambridge , MA

Area of Work

Theory of electron

detachment and excited

atoms in strong fields.

High sensitivity

detectors using

lasers, optical/RF

"Ramsey Fringes ,

and magnetic

resonance

.

Theoretical atomic

structure and

electron- ion

collision theory.

Accreting neutron

stars and the

associated physics of

strongly magnetized

plasmas

.

The atmospheres of

stars and the

physical processes

that occur in many

astrophysical

bodies

.

Reaction dynamics in

the presence of

"solvent" molecules

attached to one of the

reactants

.

Precision measurements,

atomic and molecular

physics

.

207
1986-1987 VISITING FELLOWS

Quantum Physics Division (525)

Visitinjt Fellow Home Institution Area of Work

Hideyuki Saio Department of Astronomy Stability and evolution

Faculty of Science of stars.

University of Tokyo

Tokyo, Japan

208
1987-1988 VISITING FELLOWS

Quantum Physics Division (525)

Visitine Fellow Home Institution Area of Work

David C . Clary University Chemical

Laboratory

Cambridge University

Cambridge, United Kingdom

Theory of molecular

collision in

processes

in the gas phase

.

James M. Farrar Department of Chemistry

University of Rochester

Rochester, NY

Low energy ionneutral

interactions, crossed

beam studies of

reactive collisions.

Jack Feinberg Department of Physics

University of

Southern California

Los Angeles, CA

Optical computing;

interactions of

light with matter.

Jvihan Frank Max Planck Ins ti tut fur

Astrophysik

Garching, West Germany

Accretion in active

galactic nuclei and

binary systems.

Ivan Hubeny Astronomical Institute

Czechoslovak Academy of

Sciences

Ondrejov, Czechoslovakia

Stellar atmospheres,

atomic processes,

line scattering,

numerical simulations

Wm. Lowell Morgan Lawrence Livermore

National Laboratory

Livermore, CA

Computer simulation

of atomic and

molecular processes,

gas -surface

interactions

.

Per Ake Nordlund Copenhagen University

Observatory

Copenhagen, Denmark

Dynamics of the

solar atmosphere.

Artur Stolz School of Surveying

University of

New South Wales

Kensington, Australia

Global positioning

system and laser

ranging.

209
1987-1988 VISITING FEUiWS

Quantum Physics Division (525)

Visiting Fellow

John Weiner

Peter Zoller

Home Institution

Department of Chemistry

University of Maryland

College Park, MD

Institute for

Theoretical Physics

University of Innsbruck

Innsbruck, Austria

Area of Work

Inelastic collision

dynamics in simple

systems

.

Interaction of laser

light with atoms,

multiphoton processes,

laser physics, quantum

optics, electron

correlation effects.

210
SCIENTISTS WORKING AT JIIA ON SABBATICAL OR OTHER LEAVE

(Other than Visiting Fellows)

Quantum Physics Division (525)

P. S. Conti H.J.G.L.M. Lamers

Space Research Laboratory

Utrecht, The Netherlands

J . Cooper Girish Agarwal

Hyderabad, India

Dan Wells

Waikato, New Zealand

G. H. Dunn Eldon Ferguson

CNRS (Centre Nationale de Recherches

Scientifiques)

Orsay, France

Alfred Muller

Justus -Liebig-Universitdt Giessen

Strahlenzentrum

Ins ti tut fiir Kernphysik

Giessen, West Germany

A. C. Gallagher J. Kelly

University of Idaho

Moscow, ID

J. W. Gallagher

Data Center

Nils Andersen

Institute of Physics

University of Aarhus

Aarhus , Denmark

R. Van Brunt

National Bureau of Standards

Gaithersburg, MD

K. B. Gebbie Francoise Bely-Dubau

Observatoire de Nice

France

211
SCIENTISTS WORKING AT JILA ON SABBATICAL OR OTHER LEAVE

(Other than Visiting Fellows)

Gebbie (cont.

J. Hall

S. R. Leone

J . Levine

Quantum Physics Division (525)

) Alan Gabriel

Laboratoire de Physique

Stellar et Planetaire du C.N.R.S.

Verrieres-le- Buis son

France

Y. Krause

Albuquerque , NM

Motoichi Ohtsu

Tokyo Institute of Technology

Yokohama, Japan

Brian Petley

National Physical Laboratory

Teddington, England

Fuj io & Kazuko Shimizu

Universities of

Tokyo and of

Electro -Communications

Tokyo, Japan

Dan Walls

Waikato, New Zealand

F. Winterberg

University of Nevada

Reno , NV

Professor Yao

Tiarjin, Peoples Republic of China

Pavel Rosmus

Fachbereich Chemie der

J. W. Goethe-Universitat

Frankfurt am Main

West Germany

V . Levshenko and

A. Sadofsky

Institute of the Physics of the Earth

Moscow, USSR

(Visit under Soviet - U.S. exchange)

212
SCIENTISTS WORKING AT JILA ON SABBATICAL OR OTHER LEAVE

(Other than Visiting Fellows)

J. L. Linsky

R- A. McCray

Quantiom Physics Division (525)

Kjell Eriksson

Upsalla Observatory

Upsalla, Sweden

Juhani Huovelin

Observatory and Astrophysics Laboratory

University of Helsinki

Helsinki, Finland

Don Lamb

Department of Astronomy

University of Chicago

Chicago, IL

Osmi Vilhu

University of Helsinki

Helsinki, Finland

Shih-I Chu

University of Kansas

Lawrence, KS

Timothy Ka liman

High Energy Astrophysics

NASA-Goddard Space Flight Center

Greenbelt, MD

Randy Ross

Holy Cross College

Worcester, MA

Peter G, Sutherland

Department of Physics

McMaster University

Hamilton, Ontario, Canada

Hai Shou Yang

Astrophysics Division

Geophysics Department

Peking University

Beijing, Peoples Republic of China

213
SCIENTISTS WORKING AT JIIA ON SABBATICAL OR OTHER LEAVE

(Other than Visiting Fellows)

Quantum Physics Division (525)

McCray (cont.)

D. J. Nesbitt

D, W. Norcross

S . J . Smith

J . Toomre

Qu Qin Yue

President, Nanjing University

Nanjing, Peoples Republic of China

Ted Lindeman

Department of Chemistry

Colorado College

Colorado Springs, CO

Michael Fink

University of Notre Dame

Notre Dame, IN

Michael Morrison

Department of Physics

University of Oklahoma

Norman, OK

Ken Taylor

Department of Applied Mathematics

Royal Holloway Sc Bedford New College

Egham, Surrey

England

Daniel S. Elliott

School of Electrical Engineering

Purdue University

West Lafayette, IN

Mei Ying Hou

Institute of Physics

Chinese Academy of Science

Beijing, Peoples Republic of China

Gerd Leuchs

Max-Planck Institute fur Quantenoptik

Garching, West Germany

Kumar Chitre

Tata Institute for Fundamental

Research

Bombay, India

214
SCIENTISTS WORKING AT JIIA ON SABBATICAL OR OTHER LEAVE

(Other than Visiting Fellows)

Quantum Physics Division (525)

Toomre (cont.) Douglas Gough

Institute of Astronomy

University of Cambridge

United Kingdom

Edgar Knob lock

Department of Physics

University of California

Berkeley, CA

Michael Proctor

Department of Applied Mathematics &

Theoretical Physics

University of Cambridge

United Kingdom

Nigel Weiss

Department of Applied Mathematics &

Theoretical Physics

University of Cambridge

United Kingdom

Jean- Paul Zahn

Observatory of Pic du Midi

Toulouse, France

215
CONFERENCES SPONSORED

Quantum Physics Division (525)

Division of Chemical Physics Symposia, at New York APS Meeting, March 1987.

S, R. Leone, Organizer, "Innovative Chemical Processes on Semiconductors

and Surfaces."

Fifth Cambridge Workshop on Cool Stars, Stellar Systems and the Sun,

University of Colorado, Boulder, Colorado, July 8-11, 1987. J. L. Linsky

was Chairman of the Scientific Organizing Committee.

Eighth Workshop on the Vacuum Ultraviolet Radiometric Calibration of Space

Experiments, JILA, Boulder, Colorado, March 18-19, 1987. J. L. Linsky w^as

Chairman of the Scientific Organizing Committee.

The Fourth International Conference on Multiphoton Processes,

JILA/University of Colorado, Boulder, Colorado, July 13-17, 1987.

S. J. Smith, Conference Chairman.

216
SEMINARS AND COLLCXJUIA

Quantum Physics Division (525)

JILA Colloquia

Charles Shank (AT&T Bell Laboratories) - Spectroscopy with Femtosecond

Optical Pulses, October 7, 1986.

Norman Ramsey (JILA Visiting Fellow, Harvard University) - Experiments on Time Reversal Symmetry and Parity, October 21, 1986.

Peter Toennies (Max-Planck Institute fur Stromungsforschung) - November 4, 1986.

Klaus-Peter Dinse (JILA Visiting Fellow, Institut fur Physik, University of

Dortmund) - High Resolution Spectroscopy With Optical Noise

Excitation, November 18, 1986.

Roger Miller (University of North Carolina) - Infrared Spectroscopy and

Vibrational Predissociation of Weakly Bound van der Waals Molecules,

December 2, 1986.

Yong-Ki Kim (NBS , Gaithersburg) - Relativistic Effects in Electron-Atom

Collisions, December 16, 1986.

Walther Johnson (Notre Dame) - Many Body Perturbation Theory Calculations

of PNC Amplitudes for Heavy Atoms, January 27, 1987.

Tom Gallagher (University of Virginia) - February 10, 1987.

Y. R, Shen (University of California, Berkeley) - Nonlinear Optics Probing

of Adsorbates at Interfaces, February 24, 1987.

Ron Naaman (JILA Visiting Fellow, Weizmann Institute of Science) - Reactions of Clusters- -and Inside Clusters, March 10, 1987.

Robert W. Field (Massachusetts Institute of Technology) - Two Digit Theory

for Eight Digit Spectra: Finding the Periodic Table in Molecular

Spectra, April 21, 1987.

Daniel Kleppner (Wolfe Professor of Phyics, MIT) - Eigenstates of Chaos,

May 5, 1987 (E. U. Condon Lecture).

John Kirk (Max Planck Institut fur Physik und Astrophysik, Munich) - Particle Acceleration at Shocks: From the Solar Wind to Active

Galactic Nuclei, May 12, 1987.

217
SEKIHARS MJD COLLOQUIA

Quantum Physics Division (525)

Joint JIIA/Astrophvsics Planetary and Astronomical Sciences Colloquia

John Hillier (Harvard- Smithsonian Center for Astrophysics) - The Winds From

Wolf-Rayet Stars, October 6, 1986,

Joseph Silk (University of California, Berkeley) - A Biased View of Galaxy

Formation, November 3, 1986.

Margaret Geller (Harvard-Smithsonian Center for Astrophysics) - Bubble,

Bubble, Toil and Trouble: The Foamy Structure of the Universe,

November 10, 1986.

David Eichler (University of Maryland) - Collisionless Shocks and the

Origin of Cosmic Rays, November 17, 1986.

Carl Pennypacker (Lawrence Berkeley Laboratory) - Recent Results From the

Berkeley Automated Supernova Search, November 24, 1986.

Steven Kawaler (Yale University) - Dancing Down the Road to the Stellar

Graveyard, December 1, 1986.

Robert Reasenberg (Harvard-Smithsonian Center for Astrophysics) - POINTS:

Astrophysics and Light Deflection with 5 Microarc Second Accuracy,

December 3, 1986 (with Physics Department).

Jacqueline Van Gorkom (National Radio Astronomy Observatory) -HI Imaging

of Radio Galaxies, December 8, 1986.

Hedeyuki Saio (JILA Visiting Fellow, University of Tokyo) - Pulsations in

Luminous Helium Stars, February 3, 1987.

Anne Cowley (Arizona State University) - The Nature of the Low-Mass X-Ray

Binaries, April 13, 1987.

Alexei Filippenko (University of California, Berkeley) - Evidence for LowLuminosity Seyfert Nuclei in Nearby Galaxies, April 28, 1987.

John Kirk (JILA Visiting Fellow, Max Planck Institut fiir Physik und

Astrophysik, Munich) - Particle Acceleration at Shocks: From the

Solar Wind to Active Galactic Nuclei, May 12, 1987.

218
SEMINARS AND COLLCXJUIA

Quantum Physics Division (525)

Special JILA Seminars

H. A, Gebbie (Imperial College London) - Water Polymers in the Atmosphere,

October 28, 1986.

Tom Wlckham-Jones (University of Colorado) - Studies of Vibrational Energy

Transfer of Small Molecules, November 12, 1986.

Dan Walls (University of Waikato, New Zealand) - Progress and Ideas About

Squeezed Light, December 19, 1986.

Joachim Krause (University of New Mexico) - The Correlated Emission Laser

Problem: Mode-locking or Real Sub-Schawlow-Townes Linewidths?,

J anuary 8 , 1987.

John Delos (JILA Visiting Fellow, College of William and Mary) - Collisions of Negative Ions with Atoms, January 13, 1987.

John Delos (JILA Visiting Fellow, College of William and Mary) - Rotational

Coupling in Ion-Atom Collisions, March 4, 1987.

Joel Bregman (NRAO) - Models for Cooling Flows in Clusters of Galaxies,

March 4, 1987.

F. Winterberg (Desert Research Institute) - Possible Experimental Test of

Einstein Theory of Relativity Against the Lorentz-Po incare Ether

Theory of Relativity, April 9, 1987.

Henk Spruit (Max-Planck Institut fiir Astrophysik, Garching, West Germany)

- Stationary Shock Waves in Accretion Disks, April 16, 1987.

Peter Martin (MIT) - Momentum Transfer to Atoms Moving Along a Standing

Wave, May 13, 1987.

Cool Stars Seminars

Loris Magnani (University of Maryland) - Kinematical Structure of the High

Latitude Molecular Clouds, October 1, 1986.

John Stocke (University of Colorado) - Jets From Young Stars:

L1551/IRS-5, October 8, 1986.

Karel Schrijver (JILA) - Emission From the Outer Atmosphere of a Star Like

the Sun: A Construction Kit, October 15, 1986.

219
SEMINARS AM) COLLOQUIA

Quantum Physics Division (525)

Cool Stars Seminars (cont.)

Osmi Vilhu (Helsinki University, Helsinki, Finland) - EXOSAT and EINSTEIN

Archive Study of Cool Rapid Rotators: VW Cephei and HE 36705,

November 19, 1986.

Steve Saar (JILA) - Correlated lUE and Magnetic Field Observations of Xi

Bootis A, December 19, 1986.

David Muchmore (Heidelberg University, Heidelberg, West Germany) - Molecular Cooling and Gas Dynamics in Stellar Atmospheres,

January 14, 1987.

Ken Carpenter (Goddard Space Flight Center) - The Latest Information on Red Giant Winds: Alpha Orionis and Its Friends, March 17, 1987.

Herman Marshall (Space Sciences Lab, UC Berkeley) - Uses and Abuses of the

EUVE, March 24, 1987.

Steve Saar (JILA) and Karel Schrijver (JILA) - Relations Between Radiative

and Magnetic Fluxes for the Sun and Stars, at Last, April 1, 1987.

Tom Ayres (University of Colorado) - The Chilling Truth About the Solar

Chromosphere, April 7, 1987.

Guenter Wiedemann (Goddard Space Flight Center) - Five Micron Observations

of CO in Stars, April 7, 1987.

J. Huovelin (Helsinki University, Helsinki, Finland) - Mysteries of

HD199178, May 5, 1987.

J. L. Linsky (JILA) - Requirements for Theoretical Models of Outflows,

May 20, 1987.

Chemical Physics Colloquia

William P. Reinhardt (University of Pennsylvania) - Spectra of Atoms In

External Fields, October 3, 1986.

Marshall D. Newton (Brookhaven National Laboratory) - Kinetics of Electron

Transfer Between Transition Metal Complexes: An Ab-initio

Perspective, October 10, 1986.

Edward F. Green (Brown University) - The Interaction of Alkali Atoms with

Silicon Surfaces: Equilibrium and Dynamics, October 17, 1986.

220
SEMINARS AND COLLOQUIA

Quantum Physics Division (525)

Chemical Physics Colloquia (cont.)

Robert C, Dunbar (Case Western Reserve University) - Photochemistry and

Relaxation in Gas Phase Ions, October 24, 1986.

J. Barrie Peel (La Trobe University) - Photoelectron Spectroscopy of

Molecular Dimers and Clusters, November 7, 1986.

R. Bruce Weisman (Rice University) - Direct Studies of Azoalkane

Photodissociation Using Time Resolved CARS Spectroscopy,

November 14, 1986.

Chris W. Patterson (Los Alamos Scientific Laboratory) - Adiabatic Switching

and Quantum Chaos, November 21, 1986.

R. Benny Gerber (University of Tel-Aviv) - Energy Levels and Dynamics of

Highly Excited Vibrational States, December 12, 1986.

Paul Houston (Cornell University) - Correlated Chemistry -- The Legacy of

Johann Christian Doppler, February 13, 1987.

James L. Skinner (Columbia University) - Energy and Electron Transfer in

Disordered Crystals: Quantum Percolation, February 20, 1987.

Wayne Hess (JILA) - I* Quantum Yields By Diode Laser Gain vs. Absorption

Spectroscopy, February 25, 1987.

James L. Farrar (University of Rochester) - Reactive Scattering From

Multiple Minimum Potentials, February 27, 1987.

Edward. S. Yeiang (Iowa State University) - Laser-Based Spectroscopic Probes

and Their Applications in Physical and Analytical Chemistry, March 13,

1987.

Richard B. Hall (Exxon) - Laser Probes of Surface Reaction Kinetics,

April 10, 1987.

Allan Laslette Smith (Drexel University) - Spectroscopy and Thermochemistry

of Sulfur A.llotropes, April 17, 1987.

C. R. Brundle (IBM, Almaden, California) - XPS Studies, in Conjunction with

Other Techniques of Reactions at Well-Defined Metal Surfaces,

April 24, 1987.

221
SEIGHARS AND COLLOQUIA

Quantum Physics Division (525)

Chemical Physics After Dark Seminars

Peter Toschek (JILA Visiting Fellow, UniversitAt Hamburg) - Intracavity

Laser Absorption Spectroscopy, October 8, 1986.

Julian Coutts (JILA) - Excimer Lasers and Why They Don't Work as Well as You'd Like Them, October 22, 1986.

John Smedley (JILA) - Collisional Release of Br2 , October 29, 1986.

H. C. W. Beijerinck (Eindhoven University, The Netherlands) - Polarization

Effects in Collision-Induced Intramult ip let Mixing for Nee**,

November 5, 1986.

Zeev Vager (Weizmann Institute, Israel) - Molecular Structure

Determination by the Coulomb Explosion Technique, November 12, 1986.

Chris Lovejoy (JILA) Spectroscopy of van der Waals Molecules in a Slit

Supersonic Expansion, December 3, 1986.

Bruce Koel (CIRES) - Chemistry of Nitrogen Dioxide on Metal Surfaces,

December 10, 1986.

Jamie Donaldson (JILA) - State Resolved Studies of Dissociative Systems,

December 17, 1986.

Bruce Wedding (JILA) - Tales From Down Under or Concentration Gradient

Influences on Electron Transport in Gases Under a Uniform Electric

Field, January 14, 1987.

Hrvoje Petek (Institute for Molecular Science, Japan) - Quantum State

Dependence of Singlet-Triplet Mixing and Collision Induced

Intersystem Crossing in Singlet + Triplet CH2- February 11, 1987.

Sean Moran (University of Colorado) - Photoelectron Spectroscopy of

Sulfur-Containing Anions, February 18, 1987.

Wayne Hess (JILA) - I* Quantum Yields By Diode Laser Gain vs. Absorption

Spectroscopy, February 25, 1987.

Kermit Murray (JILA) - Spectroscopy and Autodetachment Dynamics of PtN“

,

March 11, 1987.

222
SEMINARS AND COIJXQUIA

Quantum Physics Division (525)

CheiBical Physics After Dark Seiainars (cont.)

Ron Naaman (JILA Visiting Fellow, Weizmann Institute of Science) - The

Physics of Surfaces Covered With Organized Organic Monolayers,

April 1, 1987.

Nancy Levinger (JILA) - Photofragmentation and Photoabsorption of Large

AR^+ Clusters, April 22, 1987.

David Nelson (Harvard University) - Molecular Beam Electric Resonance

Studies of Ammonia Dimer, April 29, 1987.

Kenn Arnett (JILA) - Depolarization of Resonance Fluorescence With Finite

Bandwidth Lasers, May 6, 1987.

223
INVITED TALKS

Quantum Physics Division (525)

P, L. Bender, "Laser Gravitational -Wave Antennas in Space," Workshop on Gravitational Wave Physics and Astronomy, MIT, Cambridge, Massachusetts,

November 10, 1986.

P. L. Bender, "Sources and Sensitivities for Laser Gravitational -Wave

Observations in Space at Hz to Micro-Hz Frequencies," Physics Department

Colloquium, University of Colorado, Boulder, Colorado, February 4, 1987.

G. H. Dunn, "A Tuneable Atomic Reaction: Dielectronic Recombination," 9th

Conference on the Application of Accelerators in Research & Industry, North

Texas University, Denton, Texas, November 11, 1986.

G. H. Dunn, "A Tuneable Atomic Reaction: Dielectronic Recombination," Tata

Institute of Fundamental Research, Bombay, India, December 1, 1986.

G. H. Ehinn, "Dielectronic Recombination," Physical Research Laboratory,

Ahmedabad, India, December 3, 1986.

G. H. Dunn, "Resonances in Electron-Ion Collisions," VI National Workshop

on Atomic and Molecular Physics, Banaras Hindu University, Varanasi, India,

December 10, 1986.

G. H. Dunn, "Electron-Ion Excitation: Past and Future (?)," Annual Meeting

of the APS Division of Atomic, Molecular and Optical Physics, Cambridge,

Massachusetts, May 22, 1987.

J. E. Faller, "The Physics of Basketball: An Introduction to Scientific

Thinking," Physics Department, Lake Forest College, Chicago, Illinois,

November 20, 1986.

J. E. Faller, "The New Roles of Gravity in Physics," Physics Department,

Lake Forest College, Chicago, Illinois, November 21, 1986.

A. C. Gallagher, "Partial Cross Sections for Na 3S-3P Excitation by

Electrons," Gaseous Electronics Conference, Madison, Wisconsin,

October 9, 1986.

A. C. Gallagher, "Electronic Energy-Transfer Processes in the Alkali and

Alkaline-Earth Metal Vapors," AFOSR Molecular Dynamics Conference,

Cambridge, Massachusetts, October 15, 1986.

A. C. Gallagher, "Gas and Surface Mechanisms Leading to a SI:H Films," 1987

Materials Research Society, Palo Alto, California, January 26, 1987.

A. C. Gallagher, "Surface Reactions on Amorphous Silicon Films," American

Physical Society Conference, New York, New York, March 19, 1987.

224
INVITED TALKS

Quantxjm Physics Division (525)

A. C. Gallagher, "Two-Photon Doppler-Free Line Shapes," International

Quantum Electronics Conference, Baltimore, Maryland, April 30, 1987.

A. C. Gallagher, "Optical Diagnostics of Electron-Atom Collisions," DOEFundamental Interactions Branch Conference, Cambridge, Massachusetts,

May 22, 1987.

A. C. Gallagher, "A New Approach to Fully Differential Electron Excitation

Cross Sections," International Symposium on Polarization and Correlation in

Electronic and Atomic Collisions, Belfast, Ireland, July 30, 1987.

J. L. Hall, "Measurement of Axial Velocity Distribution of Laser-Cooled

Atomic Beam," Optical Society of America, Seattle, Washington,

October 22, 1986.

J. L. Hall, "High Performance Laser Frequency Stabilization Using an External Electro-Optic Phase Shifter," Optical Society of America, Seattle,

Washington, October 24, 1986.

J. L. Hall, "Stable Lasers: Progress and Applications," Canadian National

Research Council, Ottawa, Ontario, Canada, December 10, 1986.

J. L. Hall, "Phase-Stable Lasers: Progress and Applications," University

of Arizona, Tucson, Arizona, January 22, 1987.

J. L. Hall, "Noise Reduction in the Relative Phase of Two Lasers,"

International Conference on Quantum Electronics, Baltimore, Maryland,

April 28, 1987.

J. L. Hall, "Progress Toward Phase-Stable Lasers," International Conference

on Quantum Electronics, Baltimore, Maryland, April 29, 1987.

J. L. Hall, "Toward The Ultimate Laser Spectroscopy," Geoffrey Frew

Lecture, Australian National Conference on Lasers, Surfers' Paradise,

Queensland, Australia, May 1987.

J. L. Hall, "Toward The Ultimate Laser Resolution," Eighth International

Conference on Laser Spectroscopy, EICHOLS, Are, Sweden, June 23, 1987.

S. R. Leone, "Laser Probing of Chemical Reaction D3mamics," Institute for

Space and Astronautical Research, Tokyo, Japan, October 1986.

S. R, Leone, "Laser Studies of Molecular Photochemistry," Department of

Pure and Applied Science, University of Tokyo, Japan, October 1986.

S. R. Leone, "Recent Advances in Laser Chemistry," Institute for Physical

225
INVITED TALKS

Quantxim Physics Division (525)

Chemistry Research, Tokyo, Japan, October 1986.

S. R. Leone, "Laser Probing of Chemical Reaction Dynamics," University of

Tokyo, Kongo, Chemistry Department, Japan, October 1986.

S. R. Leone, "Laser Studies of Photofragmentation and Free Radical

Kinetics," Tohoku University, Sendai, Japan, October 1986.

S. R. Leone, "Laser Probing of Chemical Reaction Dynamics," Tokyo Institute

of Technology, Tokyo, Japan, October 1986.

S, R. Leone, "Laser Studies of Molecular Kinetics," University Electro

Communications, Institute for Laser Science, Tokyo, Japan, October 1986.

S. R. Leone, "Laser and Infrared Probing of the Thermal Energy Ion Molecule

Reactions," Nagoya Meeting - Symposium on New Techniques in Reaction

Dynamics, Japan, October 1986.

S. R. Leone, "Laser Gain vs. Absorption Probing in the Infrared," Hirota

Group Meeting, Institute for Molecular Science, Okazaki, Japan,

October 1986.

S. R, Leone, "Laser Probing of Chemical Reaction Dynamics," Institute for

Molecular Science, Okazaki, Japan, October 1986.

S. R. Leone, "Laser Probing of Chemical Reaction Dynamics," Keio

University, Yokohama, Japan, October 1986.

S. R. Leone, "Laser Studies of Molecular Photofragmentation and Free

Radical Kinetics," Tsukuba Science City, Environmental Laboratory, Japan,

November 1986.

S. R. Leone, "Time Resolved FTIR and Laser Studies of Surface

Interactions," Department of Pure and Applied Sciences, University of

Tokyo, November 1986.

S. R. Leone, "Laser Probing of Chemical Reaction Dynamics," Kyushu

University, Kyushu, Japan, November 1986.

S. R. Leone, "Laser Studies of Molecular Photofragmentation and Free

Radical Kinetics," Symposium on Photochemistry, Osaka, Japan,

November 1986.

S. R. Leone, "Laser Studies of Surface Deposition; Ga on Si," Hitachi

Central Laboratory, Tokyo, Japan, November 1986.

S. R. Leone, "Product State Analysis of Chemical Reaction Dynamics,"

226
INVITED TALKS

Quantiim Physics Division (525)

Chemistry Department Colloquium, Washington University, St. Louis,

Missouri, December 9, 1986.

S. R. Leone, "Laser Probing of State-Selected Dynamics in the Gas Phase and

on Surfaces," University of California, Santa Barbara, California,

April 1987.

S. R, Leone, "Laser Probing of State-Selected Dynamics," University of

Tokyo, Japan, May 27, 1987.

S, R. Leone, "T-V Energy Transfer and Chemical Reactions of Laser Produced

Hot H and D Atoms," XIII International Symposium on Hot Atom Chemistry,

Mt. Fugi, Japan, May 1987.

S. R. Leone, "Alignment Effects in Atomic and Molecular Energy Transfer,"

Xth Conference on Molecular Energy Transfer, Emmetten, Switzerland,

August 27, 1987.

S. R. Leone, "Alignment Effects in Electronic Energy Transfer and Reactive

Events," NATO Advanced Research Workshop, "Selectivity in Chemical

Reactions," Bowness-on-Windemere , United Kingdom, September 9, 1987.

S. R. Leone, "Laser Probing of Product State Distributions in Thermal

Energy Ion-Molecule Reactions," Faraday Discussion No. 84, "Dynamics of

Elementary Gas Phase Reactions," Birmingham, United Kingdom,

September 15, 1987.

J. L. Linsky, "Recent Progress in Understanding Phenomena in Cool Star

Atmospheres Using High Resolution Spectroscopy and Monitoring Techniques,"

169th Meeting of the American Astronomical Society, Pasadena, California,

January 7, 1987.

J. L. Linsky, "Stellar Magnetic Fields and Microwave Radiation: The SolarStellar Connection," Naval Research Laboratory, Washington, D. C.,

January 29, 1987.

J. L. Linsky, "Stellar Surface Structure and Magnetic Fields," Physics

Department, NM Institute of Mining and Technology, Socorro, New Mexico,

February 17, 1987.

J. L. Linsky, "Magnetic Fields in Cool Stars: Recent Measurements and the

Effects of Fields on Atmospheric Structure," Department of Physics, Arizona

State University, Tempe , Arizona. March 20, 1987.

J. L. Linsky, "Stellar Surface Structure: Spots and Active Regions on RS

227
INVITED TALKS

Quantum Physics Division (525)

CVn Binaries and Flare Stars," Infrared Astronomy Group (IRAM) , Universite

Scientifique et Medicale, Grenoble, France, April 24, 1987.

J. L. Linsky, "Requirements for Theoretical Models of Outflows," Second

Torino Workshop on Mass Outflows from Stars and Galactic Nuclei, Turin,

Italy, May 8, 1987.

J. L. Linsky, "Recent Advances in the Measurement of Stellar Magnetic

Fields," Uppsala Observatory, Uppsala, Sweden, May 11, 1987.

J. L. Linsky, "Stellar Surface Structure as Revealed By Doppler Imaging and

Rotational Modulation Studies of RS CVn Binaries and Flare Stars," Uppsala

Observatory, Uppsala, Sweden, May 1987.

D. J. Nesbitt, "High Resolution, Direct Absorption Laser Spectroscopy in

Supersonic Jet Expansions: Vibrational Dynamics of Molecular Clusters,"

University of Utah, Department of Chemistry, Salt Lake City, Utah,

February 2, 1987.

D. J. Nesbitt, "Extreme Vibration-Rotation Coupling in Floppy Molecules,"

Telluride Summer Research Institute, Telluride, Colorado, June 22-27, 1987.

D. J. Nesbitt, "IR Spectroscopy of Molecular Clusters," Telluride Summer

Research Institute, Telluride, Colorado, June 22-27, 1987.

D. J. Nesbitt, "Direct Absorption IR van der Waals Spectroscopy in Slit

Supersonic Jets; Molecular Pinballs, Hinges, and Helicopters," 1987

Conference on the Dynamics of Molecular Collisions, Wheeling,

West Virginia, July 17, 1987.

D. J. Nesbitt, "Rovibrational Dynamics of Bimolecular Clusters via IR Laser

Absorption Spectroscopy in Slit Supersonic Jets," Faraday Discussions of

the Royal Society, Birmingham, United Kingdom, September 22-24, 1987.

D. W. Norcross, "Theory of Electron-Molecule Collisions," 40th Annual

Gaseous Electronics Conference, Georgia Institute of Technology, Atlanta,

Georgia, October 13, 1987.

A. V. Phelps, "Excitation and Ionization Coefficients, 5th International

Symposium on Gaseous Dielectrics, Knoxville, Tennessee, May 4, 1987.

A. V. Phelps, " Discharges at Extremely High E/n and Low Currents,"

International Conference on Phenomena in Ionized Gases, University of

Swansea, Swansea, United Kingdom, July 13, 1987.

228
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

P. L. Bender, Member, Fundamental Physics and Chemistry Panel, Space

Science Board Study: Major Thrusts in Space Science: 1995-2015.

P. L. Bender, Member, Technical Working Group on Imaging Interferometry in

Space, NASA.

P. L. Bender, Editorial Board Member, II Nuovo Cimento.

P. L. Bender, Member, Geostationary Platform Earth Science Steering

Committee, NASA.

P. L. Bender, Member, Working Group 1 on Recent Plate Movements and

Deformation, Inter-Union Commission on the Lithosphere.

P. L. Bender, Member, Crustal Dynamics Working Group, NASA.

G. H. Dunn, Member, Executive Committee, Division of Electron and Atomic

Physics, American Physical Society.

G. H, Dunn, Member, Panel on Scientific Opportunities for the Use of Cooled

Heavy Ion Storage Rings, Committee on Atomic and Molecular Science,

National Research Council.

G. H. D\xnn, Chairman, Political Advisory Committee, Division of Electron

and Atomic Physics, American Physical Society.

J. E. Faller, Member, Working Group II of the International Gravity

Commission.

J. E. Faller, Member, Special Study Group 3.86, "Estimation of Absolute

Gravimetric Determinations," of the International Gravity Commission.

J. E. Faller, Member, Special Study Group 3.87, "Development of Worldwide

Absolute Gravity Net," of the International Gravity Commission.

J. E. Faller, Member, U. S. Interagency Gravity Standards Committee.

J. E. Faller, Member, Management Operations Working Group on Lunar Ranging.

J. E, Faller, Member, Physics Departments' "Geophysics Committee".

J. E. Faller, Member, External Awards Subcommittee of the American

Geophysical Society.

J. E. Faller, Member, Directing Board of IGC (International Gravity

229
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantiun Physics Division (525)

Cominission) .

A. C. Gallagher, Member, Army Basic Research Steering Committee.

J. L. Hall, Delegate, Consultative Committee for the Definition of the

Meter (BIPM) , Sevres, France, 1970 - present,

J. L. Hall, Chainnan, International Steering Committee for Conferences on Laser Spectroscopy.

J. L. Hall, Member, NBS Committee for NBS Precision Measurement Grants.

J. L. Hall, Member, Ad hoc Oversight Committee for Air Force Ring Laser

Gyro Program.

J. L. Hall, Member, Advisory Committee to the Global Oscillation Group,

National Solar Observatory.

J. L. Hall, Member, AMO Subcommittee of Physics Division, Academy of

Science

.

D. G. Hummer, Member, Editorial Board, Computer Physics Communications.

D. G. Hummer, Member, Steering Committee of the United Kingdom Collaborative Computational Project on Stellar Atmospheres,

D. G. Hummer, Co-Director, International Stellar Opacity Project.

S. R. Leone, Chairman, Division of Chemical Physics, American Physical

Society, 1987-1988,

S. R. Leone, Editorial Advisory Board, Chemical Reviews, 1982-1988.

S. R. Leone, Associate Editor, Journal of Chemical Physics, 1984-1987.

S. R, Leone, Committee on Atomic and Molecular Science, National Research

Council, 1986-1989.

S. R. Leone, Executive Committee, Division of Physical Chemistry, American

Chemical Society, 1984-1987.

S. R. Leone, Editorial Advisory Board, Journal of Physical Chemistry,

1984-1990.

S. R. Leone, Member, NRC Committee, Army Research Office Review Board,

230
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

1984-1988.

J. L. Linsky, Member, Users' Committee, National Solar Observatory.

J. L. Linsky, Member, Users' Committee, International Ultraviolet Explorer

Satellite

.

J. L. Linsky, Member, Management and Operations Working Group, Solar and

Heliospheric Physics Section, NASA.

J. L. Linsky, Chairman, Management and Operations Working Group, Astronomy

and Relativity Section, NASA.

J. L. Linsky, Co-Investigator, High Resolution Spectrograph, Space

Telescope

.

J. L. Linsky, Member, Far Ultraviolet Spectrograph Explorer Science Working

Group

.

J. L. Linsky, Member, Scientific Organizing Committee for the International

Conference "A Decade of Ultraviolet Astronomy with the lUE Satellite," to

be held in Greenbelt, Maryland, April 12-15, 1988.

J. L. Linsky, Member, International Ultraviolet Explorer (lUE) Proposal

Review Panel.

J. L. Linsky, Member, Infrared Astronomy Satellite (IRAS) Proposal Review

Committee

.

J. L. Linsky, Member, Science Advisory Council, Mount Wilson Institute.

J. L. Linsky, Interdisciplinary Scientist on the Advanced X-Ray Astrophysical Facility (AXAF) and Member of the AXAF Science Working Group,

NASA.

J. L. Linsky, Member, Astrophysics Council, NASA.

J. L. Linsky, Member, lUE Long Range Planning Committee.

J. L. Linsky, Member, National Optical Astronomy Observatory (NOAO)

Director's Advisory Committee.

J. L. Linsky, Member, Committee on Coordinated Ground-Based and Space

Observing, NOAO.

J. L. Linsky, Chairman, Scientific Organizing Committee, Fifth Cambridge

231
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

Workshop on Cool Stars, Stellar Systems, and the Sun, Boulder, Colorado,

July 7-10, 1987.

J. L. Linsky, Chairman, Steering Committee, Synoptic High Resolution

Spectroscopic Observing Group.

J. L. Linsky, Member, Committee to Study the Long Term Goals for the

National Optical Astronomical Observatory, Association of Universities for

Research in Astronomy (AURA)

.

J. L. Linsky, Member, Scientists on Spaceborne Interferometry, NASA.

J. L. Linsky, Chairman, Infrared Astronomy Project Concepts Evaluation

Panel, NASA.

J. L. Linsky, Member, Astrophysics Data Operations Study Committee, Goddard

Space Flight Center, NASA.

J. L, Linsky, Co-Investigator, Space Telescope Imaging Spectrograph, NASA.

J. L. Linsky, Member, External Committee to Evaluate the Astronomy Program

at the University of Maryland.

D. J. Nesbitt, Member, Organizing Subcommittee for IQEC '88, "Fundamental

Laser Spectroscopy and Physics."

D. W. Norcross, Member, Panel on Theoretical Atomic and Molecular Sciences

of the Committee on Atomic and Molecular Sciences of the National Research

Council

.

D. W. Norcross, Member, Working Group Supervising Collaborative Computational Project 2 (Continuum States of Atoms and Molecules) of the U.K.

Science and Engineering Research Council, 1983 - present.

D. W. Norcross, Member, Publications Committee, Division of Electron and

Atomic Physics of the American Physical Society, 1985-1986.

232
CONSULTING

Quantum Physics Division (525)

P. L. Bender

Dr. Bender is consulting with the University GPS Consortium concerning

the accuracy of determining tectonic motions with signals from the

Global Positioning System satellites.

A. C. Gallagher

Dr. Gallagher is consulting with the Lamp Division and Corporate

Research Division of General Electric Corporation.

J. L. Hall

Dr. Hall is consulting with the Theoretical Astrophysics Group at

Caltech in the area of laser techniques for gravity wave detection,

and informally with colleagues in industry involved with stable laser

design and application, and also consults with:

Advisory Committee to the Global Oscillation Network Group, National

Solar Laboratory.

D . G . Hummer

Dr. Hummer consults for the X-ray laser project at Livermore and

Los Alamos Laboratories.

S. R. Leone

Dr. Leone does consulting with TRW on certain optical and laser

problems involving high power systems and with Spectra Technology on laser chemical physics.

233
CONSULTING

Quantum Physics Division (525)

J. L. Linsky

Dr, Linsky consults with NASA concerning (1) future programs in the

area of ultraviolet X-ray and infrared astronomy, (2) future programs

in solar and heliospheric physics, (3) operations and long range

planning for the International Ultraviolet Explorer satellite, (4)

definition of the proposed LYMAN Far Ultraviolet Spectroscopic

Explorer satellite, (5) definition of the proposed Advanced X-ray

Astronomical Facility, (6) calibration and initial operations of the

Space Telescope High Resolution Spectrograph, (7) data operations for

future missions, (8) interferometry from space, and (9) future

infrared astronomy missions.

Dr. Linsky consults with the National Optical Astronomy Obseirvatory

(NOAO) and the Association of Universities for Research in Astronomy

(AURA) concerning (1) operation of the National Solar Observatory and

Sacramento Peak Observatory, (2) planning for coordinated ground-based

and space obseirvations , (3) potential need for a large -aperature

ground-based solar telescope, (4) planning for synoptic high

resolution spectroscopic observations, and (5) the long term goals of

the NOAO.

D. W, Norcross

Dr. Norcross is consulting with the Theoretical Atomic and Molecular

Physics Group at the Lawrence Livermore Laboratory on problems related

to laser modeling, and is a Visiting Scientist (consultant) to

Division T-4 of the Los Alamos Laboratory on problems related to

electron collisions with atoms, ions, and molecules.

A. V, Phelps

Dr. Phelps does informal consulting and advising with DoD and DoE

laboratories and their industrial and university contractors in the

area of atomic and molecular processes in high power switches, laser

induced breakdown and charged particle beam propagation. For the

Lawrence Livermore National Laboratory this has been formalized by the

granting of support for a postdoc.

234
OTHER AGENCY RESEARCH

Quanttun Physics Division (525)

P. L. Bender NASA Detailed translocation analysis of

regional LAGEOS crustal movement data.

P. L. Bender NASA Integrated water vapor calibrator

measurements

.

P. L. Bender &

J. E. Faller

NASA Laser gravitational wave observations in

space

.

G. H. Dunn DOE Determine atomic, molecular, and nuclear data

pertinent to the magnetic fusion energy

program.

J. E. Faller AFGL Absolute gravity studies.

J. E. Faller DMA-N Absolute "G" co-op program.

J. E. Faller MERADCOM Fabrication of two gravity gradiometers for

subsequent field testing and evaluation.

J. E. Faller NASA Examination and evaluation of the laser

lunar ranging multi- lens telescope.

J. E. Faller NGS Routine maintenance of the absolute

instrument during fiscal year 1987.

J. E. Faller,

P. L. Bender, &

R. T. Stebbins

NSF Development of very lov; frequency

isolation systems for ground-based

gravitational -wave interferometers

.

A. C. Gallagher AFOSR Electronic energy transfer processes in the

alkali/alkaline earth metal vapors.

A, C. Gallagher DOE Spectroscopic diagnostics of electron- atom

collisions

.

A. C, Gallagher SERI Diagnostics of glow discharges used to

produce hydrogenated amorphous silicon

films

.

K. B. Gebbie &

J . Toomre

NASA X-ray bright points on the quiet Sun and

rapid UV brightening in active regions.

235
OTHER AGENCY RESEARCH

Quantum Physics Division (525)

K. B. Gebbie 6e J

.

Toomre

NASA Basic research in solar physics: Energy

transport in the solar envelope and

atmosphere

.

J. L. Hall ONR Precision atomic beam spectroscopy using

stabilized lasers.

D. G. Hummer NASA High resolution spectrograph observing

program.

D . G . Huntroer NASA Astrophysical theory program.

D. G. Hummer NSF Theory and observation of expanding

atmospheres of early type stars.

S. R. Leone AF Diode laser probing excited iodine atoms.

S. R. Leone AFOSR State-resolved dynamics of ion-molecule

reactions in a flowing afterglow.

S. R, Leone AFOSR Electronic energy transfer processes in the

alkali/alkaline earth metal vapors.

S. R. Leone AFOSR Laser measurements of state-resolved Ga

and atom scattering.

S . R . Leone ARO Excimer laser photolysis studies of

translation- to-vibration energy transfer.

S. R. Leone DOE Time-resolved free radicals and laserinitiated chain reactions.

S. R, Leone NASA Innovative methods for the measurement of I*

quantum yields and kinetics by diode laser

gain -versus -absorption.

S . R . Leone NSF State-resolved molecular dynamics.

J. L. Linsky NASA Interdisciplinary scientist on X-ray Astrophysical Facility

the Advanced

(i\XAF) .

J. L. Linsky NASA Hubble Space Telescope Imaging

Spectrograph

J . L . Linsky NASA An Einstein suirvey of the soft X-ray

236
OTHER AGENCY RESEARCH

Quantum Physics Division (525)

background and young stars in the Orion

Nebula.

J. L. Linsky NASA International Ultraviolet Explorer studies of

astronomical sources (2 grants)

.

J. L. Linsky NASA Basic research in solar physics (2 grants)

.

J . L . Linsky NASA Hubble Space Telescope High Resolution

Spectrograph (2 grants)

.

J. L. Linsky NASA A test of the Golub et al scaling laws.

J. L. Linsky NASA HEAO-2 Data Analysis Proposals.

D. J. Nesbitt ACS State-resolved infrared vibrational dynamics

of supersonic expansion cooled molecules.

D. J. Nesbitt AFOSR Infrared transition moments and collisional

dynamics

.

D. J. Nesbitt NSF Direct IR laser absorption spectroscopy in

linear supersonic jets.

D. J. Nesbitt RES CORP State-resolved laser infrared absorption

studies of molecular sublimation dynamics.

D. J. Nesbitt SLOAN SLOAN Research Fellowship.

D. W. Norcross DOE Atomic and molecular collision processes.

D. W, Norcross DOE Electron impact excitation of atomic ions.

A. V. Phelps AFWAL Detection of excited states by laser induced

fluorescence

.

A. V. Phelps LLL Non-equilibrium electrons in gases.

237
TRIPS SPONSORED BY OTHERS

P. L. Bender

Quantum Physics Division (525)

October 13-17, 1986 - Washington, D.C.

Attended a meeting of the NASA Crustal Dynamics

Working Group;

Attended a meeting of NASA Lunar Laser Ranging

Working Group;

Consulted with Dr. G. Newton at NASA Headquarters

concerning optical imaging interferometry in space.

Sponsor: NASA Goddard.

November 7-12, 1986 - Cambridge, Massachxisetts

.

Presented an invited talk at the Workshop on Gravitational Wav^l*hysics and Astronomy;

Consulted with Dr. R. Reasenberg and others.

Sponsor: Massachusetts Institute of Technology.

December 9-11, 1986 - San Francisco, California.

Attended the Fall Meeting of the American Geophysical

Union.

Sponsor: NASA Goddard.

February 7 - March 7, 1987 - Canberra, Australia.

Participated in the meeting of the NASA Operational

Lunar Laser Ranging Management Operations Working

Group and the NASA Operational Readiness Review.

Sponsor: NASA Goddard.

March 22-31, 1987 - Pasadena, California.

Attended meetings of the NASA Crustal Dynamics Working

Group, the NASA Management/Operations Working Group

on Lunar Laser Ranging, and related groups at the Jet

Propulsion Laboratory;

Consulted with Professor R. Drever and others at

Cal Tech and with Dr. J. Williams at JPL;

Attended meeting of NASA Technical Working Group on Imaging Interferometry in Space at the Jet Propulsion

Laboratory.

Sponsors: NASA-Goddard.

May 17-22, 1987 - Baltimore, Maryland.

Attended the meeting of the American Geophysical

Union.

Sponsor: NASA Goddard.

238
TRIPS SPONSORED BY OTHERS

Bender (cent.)

G. H. Dunn

J. E. Faller

Quantum Physics Division (525)

August 17-21, 1987 - Vancouver, 3.C., Canada.

Attended 19th General Assembly of the International

Union of Geodesy and Geophysics.

Sponsor: NASA Goddard.

November 9-12, 1986 - Denton, Texas.

Attended the Ninth Conference on the Application of

Accelerators in Research and Industry at North Texas

State University and gave an invited talk.

Sponsor: Department of Energy.

November 28- December 17, 1986 - Bombay, Ahmedabad,

New Delhi, and Varanasi, India.

Visited Dr. Mathur and others at the Tata Institute of

Fundamental Research for Nuclear Science and

Mathematics (Bombay)

;

Visited with Dr. V. B. Sheorey, Dr. D. P. Dewangen and

others at the Physical Research Laboratory

(Ahmedabad)

;

Visited the National Physical Laboratory

(New Delhi)

;

Attended the VI Indian National Workshop on Atomic

and Molecular Physics and presented an invited

paper (Varanasi)

.

Sponsor: National Science Foundation.

January 11-13, 1987 - Argonne, Illinois.

Attended a Workshop on "Opportunities For Atomic

Physics Using Slow, Highly-Charged Ions," at the

Argonne National Laboratory.

Sponsor: Argonne National Laboratory.

October 16-17, 1986 - Washington, D. C.

Attended Management Operation Working Group Meeting on Laser Ranging at Goddard Space Flight Center.

Sponsor: Defense Mapping Agency

Hydrographic/Topographic Center.

239
TRIPS SPONSORED BY OTHERS

Faller (cont.)

A. C. Gallagher

Quantum Physics Division (525)

February 6-14, 1987 - Canberra, Australia.

The Lageos and Lunar Laser Ranging Facility as part of

the Laser Ranging Management Operations Working Group

(MOWG) has not been performing up to expectations for

2 years. Accordingly, NASA asked Dr. Faller, as a member of the MOWG, to help salvage it and make the

large U.S. government investment cost-effective.

Sponsor; NASA Goddard.

March 24-26, 1987 - Los Angeles, California.

Attended Lunar Laser Ranging Management-Operations

Working Group Meeting.

Sponsor: AF Geophysics Laboratory,

May 18-21, 1987 - Baltimore, Maryland.

Attended meeting of the American Geophysical Union

where Dr, Faller' s absolute gravimeter was on display.

Sponsor: Defense Mapping Agency,

Hydrographic/Topographic Center.

January 24-28, 1987 - Palo Alto, California.

Attended the 1987 Amorphous Silicon Subcontractors'

Review Meeting and presented an invited talk.

Sponsor: Solar Energy Research Institute.

March 17-19, 1987 - New York, New York.

Attended meeting of American Physical Society.

Sponsor: Solar Energy Research Institute.

April 26-May 1, 1987 - Baltimore, Maryland.

Attended the Conference on Lasers and ElectroOptics, and XV International Conference on Quantum

Electronics

;

Gave a talk at the IQEC Meeting.

Sponsor: Solar Energy Research Institute.

May 17-22, 1987 - Cambridge, Massachusetts.

Attended the American Physical Society meeting and

contributed 3 posters.

Attended the DOE Chemical Science-Fundamental

Interaction Branch Contractors Conference and gave an invited talk.

Sponsor; Solar Energy Research Institute.

240
TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

J. L. Hall November 9-17, 1986 - Boston, Massachusetts.

Participated in the NSF panel concerned with Gravity

Wave Research in the U.S.;

Attended a Dean's Committee Meeting for faculty

recruiting at Harvard University.

Sponsors: National Science Foundation and Harvard

University.

December 9-11, 1986 - Ottawa, Canada.

Interacted with colleagues at the National Research

Council concerning stable lasers, laser techniques,

and realization of the meter; presented an invited

colloquium.

Sponsor: National Research Council.

January 21-23, 1987 - Tucson, Arizona.

Presented an invited lecture, "Phase-Stable Lasers - Progress and Applications," and interacted with

colleagues in the Optical Sciences Center,

University of Arizona, regarding scientific

problems of mutual interest.

Sponsor: University of Arizona.

May 4-25, 1987 - Sydney, Surfers Paradise, Brisbane,

Canberra, and Melbourne, Australia.

Visited university and government research labs

(Sydney, Surfers Paradise, Brisbane, Canberra, and

Melbourne)

;

Presented the Frew Lecture at the National Meeting of

the Australian Academy Science and Institute of

Physics (Canberra)

.

Sponsor: Australian Academy of Science.

D . G . Hummer September 20 - October 20, 1986 - London, England and

Munich, West Germany.

Worked with M. J. Seaton and P. J. Storey on opacity

project and recombination calculation and attended

meeting and Steering committee meeting of

Collaborative Computational Project on Stellar

Atmospheres (London)

;

Worked with R. P. Kudritzki and J. Puls on radiationdriven stellar winds (Munich)

.

Sponsor: NATO Grants.

241
TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

Hummer (cont.) November 9-15, 1986 - Boston, Massachusetts.

Ongoing collaboration with Professor G. B, Rybicki of

Harvard- Smithsonian Center for Astrophysics on transfer of radiation high-speed gaseous flows.

Sponsor: Smithsonian Institution.

December 8-18, 1986 - London, England.

Attended meeting of Opacity Project and worked with

P. J. Storey on collisional-radiative

recombination.

Sponsor: NATO Grants.

January 23-25, 1987 - Austin, Texas.

Attended a workshop on accretion disks and gave an invited paper on our calculation of line profiles

formed in accretion disks.

Sponsor: University of Texas.

April 26-29, 1987 - Washington, D. C.

Met with S. Heap (NASA) and R. Kudritzki to plan High

Resolution Spectrograph program for hot stars.

Sponsor: NASA Goddard.

June 18 - August 21, 1987 - London, England; Munich,

West Germany; Paris, France.

Worked with Dr. Peter Storey, University College

London, on ongoing collaboration on collisionradiative recombination calculations (London)

;

Worked with Professor R. Kudritzki, Institute for

Astronomy and Astrophysics, Munich, on new method

of distance determination to hot stars (Munich)

;

Attended Opacity Project Meeting at Paris Observatory

and presented two papers (Paris);

Worked with Dr. Peter Storey (London).

Sponsors: NATO Grants.

242
TRIPS SPONSORED BY OTHERS

S. R. Leone

Quantiun Physics Division (525)

October 1 - November 13, 1986 - Tokyo, Sendai, and

nearby cities in the Tohoku District; Nagoya,

Okazaki, Kyoto, Nara, and other cities in the

Kyushu District; Okazaki, Tokyo, Japan.

Six-week Fellowship from the Japanese Society for the

Promotion of Science (JSPS) during which time Dr. Leone

visited various universities & laboratories;

(1) University of Tokyo:

Professor Soji Tsuchiya, Department of Pure

and Applied Sciences,

Professors Kuchitsu, Kondow, Tominaga, and

Tasumi, Department of Chemistry.

(2) Tokyo Technical Institute:

Professors Tanaka, Obi, Sato in the

Department of Chemistry.

(3) Keio University:

Professor Kaya, Department of Chemistry.

(4) Institute for Physical Chemistry Research:

Drs . Kasuya, Takami, and Arai.

(5) Institute for Environmental Studies:

Drs, Akimoto, Washida, and Inoue.

(6) Tohoku University, Sendai:

Professor Ito, Department of Chemistry,

Professor Sato, Scientific Institute of

Measurements

,

Professor Takebe, Department of Nuclear

Engineering.

Delivered lectures and collaborated on experiments.

(Tokyo, Sendai, and other nearby cities);

Attended the Chemical Reaction Dynamics Symposium and

gave an invited talk (Nagoya)

;

Visited the Institute for Molecular (IMS) Science and

visited labs, gave invited talks, and collaborated on

IR diode laser studies of excimer laser

photochemistry with Professor Hirota (Okazaki)

;

Gave talks at labs and universities (Kyoto, Nara);

Visited Professor T. Ogawa (Kyushu University) and

other laboratories and universities in various

cities (Kyushu District)

;

Visited the IMS (Okazaki)

;

Sponsor: Japanese Society for the Promotion of

Science

.

243
TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

Leone (cont.) December 8-9, 1986 - St. Louis, Missouri.

Visited Washington University and presented a seminar.

Sponsor: Washington University.

March 15-19, 1987 - New York, New York.

Chairman at a meeting of the Division of Chemical

Physics of the American Physical Society;

Participated in meeting of the American Physical

Society for which Dr. Leone had organized a major

symposium on "Innovative Chemical Processes on Semiconductors and Surfaces."

Sponsor: The American Physical Society.

April 23-25, 1987 - Santa Barbara, California.

Presented a seminar and gave a talk at the University

of California.

Sponsor: University of California, Santa Barbara.

May 22-29, 1987 - Mt. Fuji, Japan.

Presented an invited talk at the 13th International

Hot Atom Symposium and interacted with colleagues.

Sponsor: International Hot Atom Symposium.

July 12-17, 1987 - Oglebay Park, West Virginia.

Attended the 1987 Conference on the Dynamics of

Molecular Collisions and presented an invited

"overview" talk on experimental reaction dynamics.

Sponsors: The Conference.

September 6-17, 1987 - Bowness-on-Windemere

,

Birmingham, United Kingdom.

Attended NATO Advanced Research Workshop and

presented an invited talk (Bowness-on-Windemere)

Attended Faraday Discussion #84 and presented an invited paper (Birmingham)

.

Sponsors: NATO Advanced Research Workshop and

Faraday Discussion.

J. L. Linsky October 6-7, 1986 - Tucson, Arizona.

Attended a meeting of the National Optical Astronomy

Observatory Visiting Committee.

Sponsor: National Optical Astronomy Observatories,

Association of Universities for Research In

Astronomy, Inc. (AURA).

244
TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

Linsky (cont.) October 9-10, 1986 - Greenbelt, Maryland.

Attended a meeting of the Astrophysics Management

Operations Working Group at Goddard Space Flight

Center.

Sponsor: Battelle.

October 27-29, 1986 - Cambridge, Massachusetts

.

Attended a meeting of the AURA Committee on Future

Directions for the National Optical Astronomy

Observations at the Center for Astrophysics.

Sponsor: National Optical Astronomy Observatories

(AURA)

.

November 3-5, 1986 - Greenbelt, Maryland; Huntsville,

Alabama

.

Attended a meeting of the lUE Long Range Planning

Committee (Greenbelt, Maryland);

Attended a meeting of the AXAF Science Working Group

(Huntsville)

.

Sponsors: Creative Management Corporation and NASA

George C. Marshall Space Flight Center.

November 9-10, 1986 - Greenbelt, Maryland.

Attended a meeting of the AXAF Science Working Group

Sponsor: NASA George C. Marshall Space Flight Center

November 30 - December 2, 1986 - Washington, D. C.

Attended a meeting of the Committee on Space

Astronomy and Astrophysics of the National Academy

of Sciences.

Sponsor: National Academy of Sciences.

December 9-12, 1986 - Baltimore, Maryland.

Attended a meeting of the Astrophysics Management

Operations Working Group.

Sponsor: Battelle.

December 18, 1986 - Pasadena, California.

Attended a meeting of the Mount Wilson Institute.

Sponsor: National Optical Astronomy Observatories

(AURA)

.

245
TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

Linsky (cont.) January 14-16, 1987 - Tucson, Arizona.

Attended a meeting of the National Optical Astronomy

Observatory's Committee on Future Directions for

NOAO.

Sponsor: National Optical Astronomy Observatories

(AURA) .

Janiiary 27-30, 1987 - Tucson, Arizona; Washington,

D. C.

Attended a meeting of the SYNOP Spectrograph Committee

(Tucson)

;

Presented an invited Colloquium at the Naval Research

Laboratory (Washington, D.C.).

Sponsors; Naval Research Lab and NASA

George C. Marshall Space Flight Center.

February 8-10, 1987 - Washington, D. C.

Attended a meeting of the NASA Astronomy Relativity

Management Operations Working Group (ARMOWG)

.

Sponsor; NASA Goddard.

February 17-18, 1987 - Albuquerque, New Mexico.

Gave an invited colloquium at New Mexico Tech and

discussed collaborative observing programs with

Dr. David Gibson and astronomers at the NRAO Very

Large Array.

Sponsor: New Mexico Institute for Mining and

Technology

.

February 23-24, 1987 - Baltimore, Maryland.

Attended a meeting of the Astrophysics Management

Operations Working Group.

Sponsor: Battelle.

March 10-12, 1987 - Greenbelt, Maryland.

Participated in the International Ultraviolet

Explorer (lUE) Proposal P.eview.

Sponsor: Creative Management Corporation.

March 19-21, 1987 - Phoenix, Arizona.

Gave an invited Physics Department Colloquium.

Sponsor: Arizona State University.

246
TRIPS SPONSORED BY OTHERS

Quantvm Physics Division (525)

Linsky (cont.) March 29-31, 1987 - Pasadena, California.

Participated in the IRAS Proposal Review at the

California Institute of Technology.

Sponsor: California Institute of Technology.

April 7-10, 1987 - Greenbelt, Maryland.

Attended a meeting of the Space Telescope Imaging

Spectrograph Team.

Sponsor: NASA Goddard.

May 17-19, 1987 - Tucson, Arizona.

Chairman of the SYNOP Meeting^hich met at the NOAO.

Sponsor: National Optical Astronomy Observatories,

(AURA)

.

May 21-22, 1987 - Washington, D.C.

Attended a meeting of the NASA Supernova Science

Working Group at the Goddard Space Flight Center.

Sponsor: NASA.

May 31 - June 5, 1987 - Madrid, Spain.

Attended a meeting of the lUE Long Range Planning

Committee and the NASA-ESA-SERC Three Agency lUE

Coordinating Committee.

Sponsor: Creative Management Association.

June 9-11, 1987 - College Park, Maryland.

Attended a meeting of the AXAF (Advanced X-ray

Astronomical Facility) Science Working Group.

Sponsor: NASA George C. Marshall Space Flight

Center

.

June 15-20, 1987 - Vancouver, British Columbia, Canada

and Victoria, British Columbia, Canada.

Attended a meeting of the American Astronomical

Society (Vancouver)

;

Attended a meeting of the Space Telescope High

Resolution Spectrograph Team (Victoria)

.

Sponsor: NASA Goddard.

David J. Nesbitt October 14-17, 1986 - Boston, Massachusetts.

Attended an AFOSR Meeting.

Sponsor: AFOSR.

247
TRIPS SPONSORED BY OTHERS

Nesbitt (cent.)

D. W. Norcross

A. V. Phelps

Phelps (cont.)

Quantvim Physics Division (525)

January 12-17, 1987 - Los Angeles, California.

Attended SPIE Conference and presented a talk;

Presented talk at University of California at

Irvine

;

Presented talk at University of Southern California.

Sponsors: SPIE, University of Southern California,

and University of California at Irvine.

February 2-4, 1987 - Salt Lake City, Utah,

Presented a talk at the University of Utah;

Presented a talk at Utah State University.

Sponsors: University of Utah and Utah State

University.

July 12-17, 1987 - Oglebay Park, West Virginia.

Attended 1987 Conference on Dynamics of Molecular

Collisions and presented a talk.

Sponsors: The Conference.

May 21-22, 1987 - Cambridge, Massachusetts.

Attended DOE Atomic Physics Workshop.

Sponsor: Department of Energy.

July 1-4, 1987 - Washington, D. C.

Met with Physics Division, National Science

Foundation.

Sponsor: Department of Energy.

July 16 - August 3, 1987 - England.

Attended ICPEAC Conference and Satellite meetings in

Daresbury, Egham, and Oxford.

Sponsor: Department of Energy.

July 6-10, 1987 - Zagreb, Belgrade, Yugoslavia.

Visited the Institute of Physics of the University

Zagreb (Zagreb)

;

Visited the Institute of Physics, Belgrade,

(Belgrade)

.

Sponsors: U.S. - Yugoslavia Joint Board.

September 28 - October 1, 1987 - Monterey,

248
TRIPS SPONSORED BY OTHERS

D. M. Soimenfroh

Quantum Physics Division (525)

California.

Attended 1987 SDIO/DARPA Services Annual Propagation

Review.

Sponsor: AFWAL, Wright-Patterson AFB.

July 12-17, 1987 - Oglebay Park, West Virginia.

Attended the 1987 Conference on the Dynamics of

Molecular Collisions.

Sponsor: Air Force Weapons Lab, Kirtland.

249
UNIVERSITY AND DEPARTMENT COMMITTEE MEMBERSHIPS

P. L. Bender

G. H. Dunn

Quantum Physics Division (525)

Thesis Committees for:

D. N. de Vries

Physics Department, University of Colorado

T. M. Niebauer

Physics Department, University of Colorado

S. J. Walter

Physics Department, University of Colorado

T. M. Van Dam

Geological Sciences Department, University

of Colorado

Chairman of JILA

Graduate Committee, Department of Physics

JILA Shops Committee

Member, several Ph.D. examinations committees

Thesis Committees for:

M. Alexander

Chemistry Department, University of Colorado

S. Jefferts

Physics Department, University of Colorado

M. Schauer

Physics Department, University of Colorado

C. Timmer

Physics Department, University of Colorado

J . Van Doren

Chemistry Department, University of Colorado

E. Wahlin

Physics Department, University of Colorado

250
UNIVERSITY AND DEPARTMENT COMMITTEE MEMBERSHIPS

J. E. Faller

A. C. Gallagher

K. B. Gebbie

Quantum Physics Division (525)

Geophysics Committee, Department of Physics

Graduate Advisor for:

H. Godwin

Physics Department, University of Colorado

M. McHugh

Physics Department, University of Colorado

T, Niebauer

Physics Department, University of Colorado

JILA Space Committee

Chairman, Thesis Committees for:

J . Doyle

Physics Department, University of Colorado

K. Gibble

Physics Department, University of Colorado

X. Han

Physics Department, University of Colorado

M. 0' Callaghan

Physics Department, University of Colorado

G. Schinn

Physics Department, University of Colorado

M, Troyer

Physics Department, University of Colorado

Thesis Committee for:

D. Haber

Astrophysical , Planetary and Atmospheric Sciences

Department, University of Colorado

JILA Executive Committee

251
UNIVERSITY AND DEPARTMENT COMMITTEE MEMBERSHIPS

J. L. Hall

D . G . Hujnmer

S . R . Leone

Quantvim Physics Division (525)

Chairman, Thesis Committees for:

Z. Miao

Physics Department, University of Colorado

M. Winters

Physics Department, University of Colorado

Thesis Committees for:

P. Becker

Astrophysical , Planetary, and Atmospheric Sciences

Department, University of Colorado

J. Doggett

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

S. McCandless

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

S. Voels

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

Final Ph.D. Defense Committee for:

M. Alexander

Chemistry Department,

K. Carleton

Chemistry Department,

K . Lykke

Chemistry Department,

J. Smedley

Chemistry Department,

JILA Visiting Scientists

University of Colorado

University of Colorado

University of Colorado

University of Colorado

Office

.

252
UNIVERSITY AND DEPARTMENT COMMITTEE MEMBERSHIPS

J. L. Linsky

D. J. Nesbitt

D, W. Norcross

Quantuin Physics Division (525)

University Space Science and Policy Task Force

Search Conunittee for a faculty position in

Theoretical Astrophysics, Department of

Astrophysical , Planetary, and Atmospheric Sciences

Thesis Committees for:

T. Bastian

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

J. Neff

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

S. Saar

Astrophysical, Planetary, and Atmospheric Sciences

Department, University of Colorado

Co-Chairman, JILA Colloquium Committee

JILA Data Center Advisory Committee

Library Committee, Department of Chemistry

Chairman, Chemical Physics After Dark Seminar Series

JILA Executive Committee, January 1985 - December

1986.

Chair, JILA Computing Committee

Chair, JILA Building Committee

Comprehensive Exam Committee, Department of Physics

JILA Data Center Advisory Committee.

Thesis Committee for:

T. Gorczyca

Physics Department, University of Colorado

253
UNIVERSITY AND DEPARTMENT COMMITTEE MEMBERSHIPS

A. V. Phelps

Quantum Physics Division (525)

Thesis Committees for

J. Doyle

Physics Department, University of Colorado

M. 0' Callaghan

Physics Department, University of Colorado

G . Schinn

Physics Department, University of Colorado

254
GRADUATE STUDENTS AND POSTDOCTORAL RESEARCH ASSOCIATES SUPERVISED

Quantum Physics Division (525)

Graduate Students Postdoctoral Research

Associates

L. Bender S . D . Swartz

S. J. Walter

X. -P. Wu

M. A. Vincent

H. Dunn A. Cache 1 in

S. Jefferts

M. Schauer

K. Timmer

E. Wahl in

J. L. Forand

K. Rinn

D. Swenson

E. Fallen H. Godwin

M. McHugh

T. Niebauer

C. Gallagher J. Doyle

K. Gibble

X. Han

M. 0' Callaghan

G. Schinn

M. Troyer

P . Arcuni

M. Harris

G. Lin

L. Hall M. Winters

M. Zhu

J. M. Chartier

C. Salamon

N. C. Wong

G . Hummer C . Hackman

S. McCandliss

S. Voels

Y. Xu

D. C. Abbott

Y. Yan

R. Leone K. Carleton (NSF)

L. Cousins

W. Hess

K. Knutsen

G. H. Lin

J . Smedley

R. Smilgys

C. Taatjes

E. Woodbridge

H. Beijers

V. Bierbaum (25%)

W. Bussert

D. J, Donaldson (NSERC)

R. Dressier

R. Fletcher

H. Meyer

R. Robinson

D. Sonnenfroh (NRC)

K. Yamasaki

255
GRADUATE STUDENTS AND POSTDOCTORAL RESEARCH ASSOCIATES SUPERVISED

Quantvun Physics Division (525)

J. L. Linsky

D. J. Nesbitt

D. W. Norcross

A. V. Phelps

Graduate Students

J. Neff

S . Saar

W. Hovingh

C . Lovej oy

A. Mcllroy

A. Schiffman

M. Schuder

T. Gorczyca

H.-L. Zhou

Postdoctoral Research

Associates

C. Ambruster

J. Bookbinder

A. Brown

J. P. Caillault

P. Judge

K. Schrijver

D. Nelson (NRC)

S. Alston

J, Mi troy

A, Pradhan

G. Snitchler

V. T. Gylys

A, B. Wedding

256
COURSES TAUGHT AT UNIVERSITY OF COLORADO

J. L. Hall

S. R. Leone

J. L. Linsky

D. J. Nesbitt

D.. W. Norcross

A. V. Phelps

Quantum Physics Division (525)

Laser Stabilization - Physics 696

Physical Chemistry Laboratory Course - Development and

Construction of New Experiments

Special Topics in APAS : Stellar Atmospheres - APAS 650

(Fall 1987)

Chemistry 558 - Quantum Chemistry (Fall 1986)

Chemistry 452 - Quantum Chemistry (Fall 1987)

Recitation - Physics 112 (Spring 1987)

Physics III - Recitation (Fall 1986)

257
BACKGRD13ND ON JIIA

Quantum Physics is the division through which NBS participates in

the Joint Institute for Laboratory Astrophysics, a cooperative enterprise between NBS and the University of Colorado (CU) . In collaboration

with University faculty and visiting scientists, the Division conducts

the kind of long-term, high-risk research on which the Bureau's ability

to provide standards, measurements, and data ultimately depends. The

Division's objectives include:

o Developing the laser as a refined measurement tool and applying it

to tests of fundamental postulates of physics such special and

general and relativity.

o Improving the theory and instrumentation required to measure astrophysical and geophysical quantities such as the cosmic distance

scale, the acceleration of the Earth's gravity, and the long distances involved in determining crustal movements.

o Researching new techniques for measuring interactions involving

atoms and molecules, to provide data essential in areas such as nuclear fusion, advanced lighting, and laser development.

o Developing and applying measurement techniques to advance fundamental understanding of microscopic molecular processes such as those that occur in combustion and laser- initiated chemical

reactions

.

o Interacting with University faculty and visiting scientists to

maintain expertise at the forefront of research in physics.

o Transferring the results of its research and the technology

developed to the Nation's industries, universities and other

government agencies.

o Exchanging ideas and skills with other scientists in NBS through

visits, seminars and longer-term interchanges of personnel.

A direct outgrowth of the national space program in the early 1960s

JILA was formed in response to a report of the Space Science Board of

the National Academy of Sciences. That report pointed to serious gaps

in our basic understanding of the behavior of atoms and molecules in

terrestrial, planetary, solar and stellar atmospheres. The unifying

theme for the Institute therefore became the physics of gaseous

atmospheres. Since then, however, JILA has responded to changing

national needs and to the requirements of its parent organizations.

Thus the Institute has become a world leader not only in atomic and

molecular science and astrophysics but also in precision measurement,

laser physics, and certain areas of geophysics.

258
JILA STAFFING 1987-1988

Total - 223

Perm. Ph.D. Scientists - 27

Other Sen. Scientists - 1

0

Sen. Research Assoc. - 7

Postdocs - 46

Graduate Students - 71

Visiting Fellows - 12

Admin. Support - 23

Tech. Support - 27

259
The permanent senior scientists or "Fellows if JILA" , of which

there are currently 23, form a governing body that sets policy, subject

to review by the Director of NBS and the President of the University. A

Chairman, elected every two years by the Fellows, has much the same role

as the chairman of an academic department. Assisted by an executive

committee, he is responsible for operating the Institute within the

policies set out by the Fellows. Of the 23 Fellows, 10 are fulltime

faculty members from the Departments of Physics, Chemistry, and Astrophysical, Planetary and Atmospheric Sciences; 13 are NBS employees, of

which 12 are in the Quantum Physics Division and 1 is in the Time and

Frequency Division. Although these scientists work side by side, sharing facilities and responsibility for the success of the Institute, each

remains officially responsible to his respective employer, NBS and its

Director in one case, CU and the academic department in the other.

Through their adjoint faculty appointments, NBS scientists at JILA

have both the opportunity and responsibility to teach courses and participate in other faculty activities. This gives them access to graduate and undergraduate students, some of whom become interested in pursuing research directed toward NBS goals. Of 72 graduate students in

JILA, 38 are supeirvised in their research by NBS scientists; of 41 postdoctoral research associates, 24 work with NBS scientists. Some have

subsequently joined NBS and now occupy positions of leadership; others

are carrying the knowledge and skills acquired at NBS to the Nation's

industries, universities and other government agencies. Of over 100

graduate students and research associates supervised by NBS staff at

JILA during the past 8 years, 20% are now in industry, 20% in government

agencies, and the remainder largely in universities.

Besides the graduate students and postdoctoral research associates,

the Visiting Fellows Program is probably the single most important factor in maintaining an atmosphere of change and excitement in JILA. The

Program provides partial funding for some ten internationally distinguished scientists a year to spend up to twelve months at JILA collaborating with resident scientists. Since its inception 24 years ago, the

Program has become internationally renowned. More than 220 senior

scientists from 29 foreign countries as well as the U.S. have participated. The number of applicants exceeds the number of positions typically by a factor of four; in accordance with the Memorandum of Understanding, applicants are chosen according to scholarly achievement, demonstrated interest in the scientific and technical objectives of JILA,

and the recommendations of their peers.

For NBS and University researchers alike, perhaps the greatest

attraction of JILA is the large concentration of scientific talent in

atomic and molecular physics and closely related areas. Neither

institution, with its broad responsibility for measurement in one case and for education in the other, could justify such a large number of

senior scientists in a single area. Together these researchers are able

to collaborate, exchange ideas and attract visiting scientists in a way

that would be impossible for two smaller groups operating separately.

260
QUANTUM METROLOGY DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1987

BACKGROUND & OVERVIEW

This relatively small group evolved from earlier organizational forms

and is associated with efforts whose emphasis and scope have changed

notably over the past decade. A persistent core has been, however, a conscious attempt to focus on those areas of fundamental physics where

progress is conditioned on advancement of measurement technology. Of the

several directions in which such a program might take form, ours has

emphasized unification of the electromagnetic (frequency/wave length) scale.

Although some of our earlier work included establishing linkages between

the radio-frequency domain and the visible region, by far the dominant part

has concerned extension of this congruent scale through the x-ray region

and into the 7 - ray region, thus far reaching approximately 4 MeV. To

accomplish this work, parts of which remain in progress, it was necessary

to make significant progress in the measurement of small distances and

small angles. Dividends from these efforts have included determination of

elementary particle masses, tests of QED in few-electron and muonic atoms,

determination of fundamental constants and atomic energy levels. A

synoptic view of the present state of this work will be given below.

A second theme having long persistence has focussed on clarifying the

mechanisms responsible for the finer details of inner-shell spectra from

atoms, molecules and simple solids. The particular conundrum formulated by

one of us (RDD) thirty years ago concerns the aliasing effect of multivacancy processes on phenomenological spectra. Far from being small and

readily recognizable, these effects are easily shown to be large and so entangled with the presumably better understood single-vacancy spectra as

to make progress very slow - slow to the point that the field was effectively abandoned. Since even single -vacancy processes are difficult

to treat satisfactorily from the theoretical side, good calculations of the

normal complement of multi-vacancy contaminants remain prohibitively

laborious. One needs instead an experimental approach capable of

separating this complex phenomenology into its components and effectively

stripping away the multiple-vacancy contributions. This much was already

understood in principle and been given some limited demonstration over twenty years ago, but systematic applications had to await not only the

coming of age of dedicated synchrotron radiation facilities but also the

development of high efficiency beamline optics and their dedication to

systematic investigations in this area. All of this is now realized (as

will be shown below) in the Division's Beamline X24-A at the National

Synchrotron Light Source (NSLS) in Brookhaven. Not only has this ansatz

borne out these expectations but the facility has opened already several

new domains, perhaps even more tantalizing than the original conundrum.

261
Beyond the core programs, others have come and gone over the past

decade sometimes reflecting individual interests, sometimes special

opportunities, and sometimes new directions for possible programmatic

growth. Examples include; a laser chemistry program which evolved from a need (still present) for producing kilogram quantities of ^®Si which became

a pioneering effort in laser catalysis and isotope enrichment. This, in

turn, dissolved in the face of overwhelming external competition but

yielded several excellent smaller programs which remain productive

elsewhere in NBS . An opportunity to collaborate with Jesse Beams in his

later years became a serious long-term, though ultimately sub-critical,

effort on the Newtonian gravitational constant, G, its spatial derivative

and the associated assertions of the equivalence principle; this work is

terminated but might re-awaken, its principal protagonist (Luther) is at

Los Alamos. A market for semi-good laser wavelength measurements led to

several Inventions in this area by J.J. Snyder, one of which (the Fizeau

wavemeter) is reasonably well commercialized by now, Snyder is at Lockheed

Research Laboratories (Palo Alto) . —

We are presently embarked on yet another excursion with G. Greene as the main driving force. This aims at developing a fundamental physics

beamline at the new NBS Cold Neutron Guide Hall and at several specific

neutron physics experiments to be carried out initially at the High Flux

Reactor of the Institut Laue-Langevin (ILL) in Grenoble. Significant

external support has emerged (from DOE) for the initial phase of this work

while additional resources are being made available through the Guide Hall

project itself. The present situation is reviewed below while it remains

to be seen if the potentially large growth in this area can be accommodated

within this small group.

At the risk of some distortion, the Division's work has been

amalgamated into three categories, namely; precision spectroscopy of x- rays and 7-rays (including x-ray interferometry and lattice

intercomparisons); inner-shell physics (including both synchrotron

radiation work and that done here with conventional sources as well as surface studies and dynamical diffraction); and, neutron physics. Not

included in this year's report are reports on our efforts on x-ray

spectroscopy from earth-orbiting platforms and the Z-systematics of x-ray

spectra.

TECHNICAL ACTIVITIES

Precision X-Ray Spectroscopy :

Extension of optically based electromagnetic wavelength measurements

from the visible through x-ray and into the 7-ray region was, in its modern

form, initiated in the Division. The key concept is elementary and easily

stated while full realization of its potential remains a formidable

exercise. One begins by appreciating the extraordinary uniformity of

synthetic semiconductor crystals (especially Si) with which we have been

262
gifted by the industrial community. One notes, as well, that laser

interferometry is easily refined to sub-atomic dimensions. Evidently given

any procedure for registering the passage of lattice planes on a carriage

whose progress is otherwise noted by optical means secures a lattice

parameter measurement in terms of a visible wavelength. Nowadays one might

think of noting the passage of lattice planes by tunneling microscopy (as

occupied some of our pre-1964 thoughts); as it turned out the realization

of crystal Moire interferometry by Bonse and Hart furnished a more readily

accessible lattice passage decoder which has been used in all work to date.

Given a calibrated crystal from the above XROI (x-ray/optical

interferometry) exercise, determination of reference wavelengths is a straightforward application of the Bragg-Laue condition (A=2dsin9) provided

absolute angle -measurement of the requisite refinement is at hand. There

were (and are) two rather different domains: At longer wavelengths , A=d,

relatively large angles are involved (30® -60°) for which a variety of

encoding and circle-reading schemes offer sub-ppm capability when carefully

operated and calibrated from first principles, i.e., circle closure. At

shorter wavelengths, A«d, small diffraction angles are involved (typically

A/d=10”^) where a particularly refined form of angle interferometry

(55«10"^ arcsec) was needed and new forms of first-principles calibration

had to be developed. Nowadays we are approaching 0.01 ppm in this type of

work. A step of considerable practical importance was omitted from the

discussion so far to emphasize its conceptual simplicity. Specifically,

crystals emerging from the XROI exercise are not well suited to other

purposes, e.g., 7 -ray diffraction or soft x-ray diffraction. This problem

has been addressed by development of several schemes for comparing slightly

unequal crystal repeat distances. The most recently realized and most

refined of these techniques appears capable of robust operation at the 0.01

ppm level but is presently limited to somewhat worse errors by sample

perfection and specimen preparation problems.

Until about ten years ago one might have imagined that our work would

terminate with production of we 11 -documented secondary standards in the x- ray and 7 -ray region. That is to say we considered that other groups would

then apply these to the wavelength calibration of spectra appropriate for

QED tests (muonic and electronic atoms) and for the determination

elementary particle masses (especially pions and kaons as well as 2 ^ and

the neutron). Actually, much of the early effort went in this direction,

but we began to realize the utility of being more directly involved in the

final experiments. Direct involvement provides unique opportunities, for

excimple, the possibility of directly measuring the n-p capture 7 using our primary instrumentation, i.e., avoiding additional error contribution due

to use of transfer standard and a (much lower resolution) bent-crystal

instrument. We also became active in accelerator-based experiments by

introducing a family of high-resolution focussing instriaraents with position

sensitive proportional counters as detectors. This process has led to

several experimental activities both in the U.S. and in Europe at heavy- ion

accelerators as well as further work (described below) at the Grenoble

high- flux reactor.

263
In spite of all these positive developments, this entire area of work

spent several of the past years under a serious cloud. The circumstances

leading to this long and difficult period was that subsequent to the

initial NBS XROI experiment, work at the PTB in Braunschweig gave a discordant value for the crystal repeat distance in a similar specimen

(albeit one having different ancestry) . The discrepancy emerged around

1980 and its resolution resisted analysis for several years. A major

decision around 1983 was to re-establish the NBS experiment with important

improvements especially as regards control of systematic sources of error.

In January 1986 a rather subtle but quite serious error in the early NBS

work became clear from the new experiment. Its elimination cleared up most

of the discrepancy, but left our need for a definitive new result

unsatisfied. (This is a hard experiment to bring into anything resembling

statistical control and has grown harder with the addition of on-line

diagnostics which are themselves subject to drift and error). As described

below these problems have yielded (grudgingly) to persistent effort

including a very recent "breakthrough” that has tripled the useful XROI

scan range. Interferometric measurements appear now (August 1987) to be

yielding data at the level of 0.01 ppm (statistical uncertainty) per

overnight run.

Gaithersburg activities :

As mentioned above, our most serious and urgent problem has been the

large discrepancy between our (1974-76) measurements of a Si lattice

parameter and the subsequent (1979-82) results from PTB. Over the past

four years, we established two major efforts to deal with this important

question. Firstly, the entire x-ray/optical interferometer (XROI)

experiment was reconstructed with major improvements. These include (1) use of a frequency-agile, offset- locked slave laser to drive the system

through each x-ray interference profile studied; (2) provisions of a unique

and sensitive 4-beam path curvature interferometer for on-line trajectory

characterization; full computer-controlled automation; and, (3) an advanced

non-contacting, servoed vibration isolation system. Secondly, an entirely

new lattice spacing comparator (the delta-d machine) was built so the

question of sample- to-sample variability could be addressed with a precision well in excess of the targeted accuracy range.

At the last panel meeting it was possible to report that the origin of

the NBS-PTB discrepancy had been identified and that the delta-d machine

had achieved initial operation with a promising outlook. In the case of

the XROI experiment, through the on-line path monitoring capability, a serious systematic error was uncovered which arose from a combination of

pitch error larger than indicated by x-ray fringe contrast and an Abbe

offset differing slightly from zero owing largely to x-ray beam non- uniformity. Our efforts to follow this trail began in the winter of 1986

and required installation of a considerably up-graded table suspension

before reliable control could be obtained. Subsequent data runs in March,

264
June, and September showed good concordance (better than 0.1 ppm) and gave

numerical values which substantially remove the NBS-PTB discrepancy. Small

differences actually remained but these were well within the range of

generally expected sample- to-sample variability.

The year since v;as devoted to progressively more successful efforts to

achieve a result having defensible accuracy consonant with the evident

potential in this experiment. This has required still more intense

attention to path interferometry and, ultimately to the correction of the

path itself. As operated last year, loss of fringe contrast limited the

XROI scan range to ~ 72 optical orders while requiring appreciable

corrections for "pitch" and "yaw" errors in the trajectory. It was very

recently (June 1987) possible to eliminate most of the "yaw" error

mechanically while introducing an electrically driven pitch corrector which

substantially eliminates pitch error. The last mentioned step allows a much greater scan range which is ultimately limited by drifts which

accumulate with the time required to cover the scanned range. At present,

a viable compromise seems to be a scan of 198 optical fringes with a resulting statistical error for each round trip (3 hours) of about 0.02

ppm.

It is presently proving difficult to analyze the data thus obtained in

a way that fully exploits its potential accuracy but progress appears at

hand with a now hoped for estimate of accuracy to be below 0.03 ppm. (All

work on this project is carried out by RDD with occasional but vital

assistance from AH.)

Meanwhile progress on the Ad machine and its operation has continued

(through the efforts of EGK with sample preparation by AH) . Several

serious technical problems were encountered and overcome, however, the main

challenge and difficulty remains associated with production of sufficiently

uniform specimens having adequately controlled thickness values. The Ad

diffractometer is equipped with a sub-millisec angle interferometer having

a range of ±15°. It is mounted on a massive vibration isolated surface

plate in the basement. The instrument is surrounded by a curtain- type

enclosure and the crystals are thermally shielded. Two x-ray tubes are used to permit simultaneous recording of "left" and "right" (nondispersive) curves. Operation of both tubes is with a single x-ray power

supply and two constant potential units. Computer software automatically

controls the spectrometer and permits round-the-clock comparisons of four

crystal samples.

The spectrometer uses a long transfer crystal (=10 cm long x 1 cm

high) on a rotating axis whose angular position is measured with a polarization sensitive Michelson interferometer. The crystals whose

lattice spacings are being compared reside on a motorized slide and are automatically moved in and out of the x-ray beam. These crystals are approximately 1 cm x 1 cm and are equipped with piezo-electric "tippers"

which permit establishing parallelism of the planes of the transfer and

test crystals. The long transfer crystal and four test crystals were

265
oriented, cut, and etched from several silicon samples. Non-dispersive

double -crystal reflections from thin samples (-0.5 mm) of nearly equal

(5t<10 fi) thickness showed the expected narrow fine structure on the

normal x-ray profile. This fine structure which is about 0.02 of the FWHM

makes the comparison of profile positions much more precise. Although

great care was exercised during the crystal preparation to insure that

crystal thicknesses were within the required tolerances, we are still

apparently limited by this step. First profiles were recorded in the

spring of 1986 and, after some modifications to improve both performance

and convenience, profiles containing symmetric distinct fine structure were

obtained. As of September 1986 the instrument's potentialities had been

well demonstrated. With the then evident clear delineation of expected

hyperfine detail one easily saw lattice constant differences (Ad's) near

0.05 ppm with the expectation of accuracies at or below 0.01 ppm after more

careful analysis.

The intervening months have seen development of progressively more

refined temperature measurement and control as required for realization of

potential accuracy indicated above. They have also seen the "discovery"

that the generation of crystals we have in hand appear to have non-flat

atomic planes. These are apparently spherical with curvature centers on

the growth axis and radii > 10 km. While we are aware of new efforts (for

example at Wacker Electrochemie) to remedy this difficulty, it represents a distinct practical limit to what can be done with specimens currently

available

.

X-Ray Spectroscopy - Brookhaven :

The Division has been involved for several years in the NBS/NRL

Participating Research Team (PRT) at the National Synchrotron Light Source

(NSLS) . The PRT supports five beamlines using radiation from a single

bending magnet on the x-ray ring. Following the long-standing interest in

x-ray and inner-shell physics noted above, we built and now operate

beamline X24-A which is equipped with a double-crystal monochromator

designed to deliver x-rays in the 1-5 keV photon-energy range; this

complements other PRT beamlines that deliver lower (10-2000 eV) and higher

(3-12 keV) photon energies, respectively. In its operable energy range,

X24-A provides the most intense and narrowest-band-width synchrotronradiation beam presently available in the world by virtue of several novel

design features. These features include horizontal collection of a full 8 mrad of radiation from the NSLS bending magnet, novel mirror coatings, and

pre -monochromator collimation and post-monochromator focussing optics to

improve resolving power. The available energy range of X24-A includes

inner-shell thresholds for all but the lightest elements, making it useful

for several forms of x-ray spectroscopy, including high-energy-resolution

x-ray fluorescence and x-ray photoemission, as well as for studies of

surface diffraction and interference effects in crystals.

The beamline has performed well since becoming operational in late

FY85. However, its productivity is naturally linked directly to the

266
schedule and performance of the NSLS facility. Fortunately, for the first

five months of FY87, the x-ray ring at NSLS performed exceptionally well,

setting new records in maximum beam current (>200 mA) and lifetime (>24 h)

during this period. Unfortunately, at the beginning of March, 1987, the

x-ray ring was turned off for the NSLS Phase II shutdown to install several

insertion devices, to improve beam injection capabilities, and to make many

other changes. We expect this shutdown to last well into FY88 .

During the available beam time in FY87, four of the five months were concentrated on x-ray spectroscopy of atoms, molecules, and simple solids.

With the x-ray ring, the beamline, and a high-energy-resolution secondary

fluorescence spectrometer all in good working order during this period,

several new avenues of research in inner-shell physics were opened.

Molecular studies, in particular, experienced a renaissance; advances in

several aspects of molecular x-ray spectroscopy occurred almost

simultaneously. One especially exciting development has been the

observation of strongly polarized x-ray fluorescence following core- electron excitation to unoccupied valence molecular orbitals. Initial

studies of this "new" phenomenon in the Cl K-edge regions of CH3 CI and the

freons have illustrated its possible utility as a structural tool that is

both atom-specific and highly sensitive. Its sensitivity is enhanced by

the rapid decay times involved in x-ray fluorescence which effectively

preclude vibrational or rotational disorientation, producing a "snapshot"

of the molecular excited state. The polarized-fluorescence results also

suggest many other experiments, including further spectroscopy in the gas

phase and orientational studies of solids and adsorbates.

Other phenomena also have been observed at sub- threshold resonances in

molecules. With resonant excitation, we have observed for the first time

(in the freons and CH3 CI) that the K/3 fluorescence (electrons in valence

molecular orbitals filling the Cl Is vacancy) shifts to lower energy by a few electron volts in comparison to high-photon-energy excitation (i.e.,

well above the Cl Is threshold) . These energy shifts reflect screening of

the valence electrons by the "spectator" electron which is put into an excited-state valence orbital by the resonant sub- threshold excitation.

Changes in fluorescence photon energy with incident photon energy also can

be induced by the resonance Raman effect, a phenomenon which has been

observed in all the systems studied and from which the "state specific"

chemical shift is clearly distinguished.

Using above- threshold incident energies, the previously mentioned

fluorescence-polarization phenomena have been shown to be sensitive to the

molecular symmetry of continuum resonances such as shape resonances.

Small, but significant degrees of polarization at these continuum features

have aided in their spectral assignment. Further above threshold, multivacancy, or satellite, transitions become energetically accessible. It is

now possible, with beamline X24-A and its accompanying secondary

spectrometer, to carefully study the threshold behavior of these satellite

transitions by observing their fluorescence decay as a function of incident

photon energy. Extensive studies along these lines have been made for the

267
molecule CH3 CI, as well as for the solid KCl,

While the Cl-containing molecules studied at X24-A have illustrated

several interesting and newly observed phenomena that are generally

explainable within our present understanding, work on the molecule SFg

appears to show qualitatively different effects which do not conform to

conventional wisdom. For example, in measurements of S Ka fluorescence,

which results from an inner -she 11 S 2p electron filling the S Is vacancy in

SFg, the spin-orbit doublet of the Ka radiation normally has a 2:1

intensity ratio. However, in a range of incident energies below the S Is

threshold, this intensity ratio becomes approximately 1 : 1 , and even 1:2 at

certain energies. Also in this sub- threshold energy range, two very broad

symmetric and unstructured peaks are observed in the Ka fluorescence

spectrum which change in energy with the incident photon energy. These two

observations in SFg are unprecedented in molecular x-ray spectroscopy, and

indicate the likely presence of new inner-shell phenomena not hitherto

expected.

Along with the molecular x-ray spectroscopy studies, work continued on atoms and solids, too. Additional results, taken with high fluorescence

energy resolution, have been obtained for sub- threshold excitation in

atomic Ar. These new results for Ar Ka radiation clarify the importance of

resonant -Raman effects, especially when the incident photon energy is detuned from the sub- threshold excitation energy. More studies of multivacancy states in Ar above the K-shell threshold have been completed, also

with higher resolution and improved statistics. For solids, we have

studied the Ka and K/9 radiation near the K edges of both potassium and

chlorine in KCl. The primary goal of this work has been to elucidate the

multi-vacancy components of the rather complicated absorption spectra at

these two edges; this work has enjoyed good success but produced few

unanticipated results.

The remaining usable beam time at X24-A, approximately one month, was devoted to two collaborative efforts. The first, in association with J.

Rowe and F. Sette of AT&T Bell Laboratories, studied the adsorbed species

S, Cl, Se, and Te on a Cu(lOO) single crystal. The conventional technique

of surface extended x-ray absorption fine structure (SEXAFS) was used to

determine the geometric site of each adsorbate on the Cu crystal. In

conjunction with SEXAFS a new technique, back-reflection x-ray standingwave analysis, was applied to the same systems, both to compare the two

techniques and to obtain complementary information to the SEXAFS results.

The new technique shows great potential, especially coupled to the high

energy resolution of the X24-A beamline. The results also demonstrate the

power of x-ray standing-wave analysis to determine short-range order even

at elevated temperatures. This capability is unique to this approach, and

may become thereby the most useful characteristic of all types of x-ray

standing-wave techniques.

The second collaborative effort was with J. Kortright, P. Flag, and

R.C.C. Perera of the Center for X-Ray Optics at the Lawrence Berkeley

Laboratory (LBL) . The LBL workers developed a plane multilayer-coated

268
mirror that was installed in beamline X24-A in place of the usual first

mirror. The multilayer, which consisted of 16 layer-pairs of SiC and V

(=147 A thickness for each layer-pair) on a SiC substrate, represented the

first such device designed specifically for use as an optical element in a synchrotron- radiation beamline. In this first attempt, we were able to

confirm three basic requirements for multilayer-based optics. First, the

multilayer survived the in situ heat load of a 100 mA, 2.5 GeV beam from

the NSLS x-ray ring with no apparent damage. Second, the reflectivity

properties of the multilayer as a function of mirror tilt and photon energy

were generally reasonable, in some cases approaching theoretical values.

Finally, the heat load on the first crystal of the X24-A double-crystal

monochromator was reduced significantly, lowering its normal operating

temperature (uncooled, except radiatively) from 90°C to 60“C.

At the beginning of March, 1987, the x-ray ring was shut down for an extended time and is presently scheduled for recommissioning to begin in

January 1988. During the shutdown period over the latter part of FY87,

work is proceeding in two directions. First, one member of the X24-A team,

P.L. Cowan, has been working at HASYLAB in Hamburg, West Germany since

April. There, he is continuing the study of x-ray standing-wave effects,

just getting under way at X24-A before the shutdown, in collaboration with

G. Materlik's group at DESY. Studies of the effects of non-dipole

transitions in x-ray standing-wave measurements, application of x-ray

standing-wave analysis (both conventional and in back reflection) to

studies of electrochemical deposition on metals, and studies of the

Diffraction of Evanescent X-rays during Total External Reflection (DEXTER)

are underway. The DEXTER studies may include further work on the

production of narrow x-ray beams and the potential to exploit x-ray

standing-wave effects produced in this geometry for structural studies of

both epitaxial overlayers and monolayer adsorbates on surfaces.

Second, a major upgrade of beamline X24-A is proceeding during this

shutdown. Many improvements in the operation and performance are expected,

some of the most important of which are listed below. Several new beamposition and beam- intensity monitors will be installed in the beamline.

Particularly important will be the installation of a beam-position monitor

close to the electron-beam source that will be sensitive to beam motions of

50 microns or less. The present system of orbital-position monitoring in

the x-ray ring has been insufficient to monitor and control the beam to the

tolerances required by X24-A. This new position monitor constitutes a first step in solving this very serious problem.

The collimating and focussing mirrors in the beamline also will

receive needed attention. The support structures providing angular and

linear motion for both mirrors will be reworked to improve sensitivity and

stability. In addition, the second mirror, which focusses the

monochromatic synchrotron radiation onto the sample, will be repolished.

It was found recently to have a gross surface roughness of approximately

75-lOOA rms , 10 times worse than the best available. Repolishing should

improve both its reflectivity and its focussing properties.

269
The double -crystal monochromator also will be enhanced, primarily by

increasing the number and types of available crystals, and by water-cooling

the first crystal, the one which "sees" intense white radiation reflected

from the first mirror. New crystals to be developed and tested include

quartz and beryl, both of which will allow us to utilize the beamline at

lower energies (down to and below 1 KeV) than presently available with

Si(lll) crystals. Water-cooling of the first crystal will promote

stability of the monochromator, possibly enhancing resolution, and will

permit use of low-melting-point crystals.

At the experiment end of the beamline, more improvements are planned.

Additional vacuum components will be installed to permit gas-phase

photoemission experiments. These experiments will augment and complement

the present x-ray spectroscopy measurements. Also to be included in the

upgrade is a larger and faster computer system for data collection,

transfer, and analysis, making X24-A a more effective user-oriented

facility.

During FY87, the Quantum Metrology Group (QMG) supported two fulltime staff (P.L. Cowan and D.W. Lindle) and one full-time NSLS technician

(B. Karlin) at BNL. Additional collaborative support has come from R.E.

LaVilla, R.D Deslattes, J. Cooper, and A. Heninife of the QMG, and from T.

Jach of the Center for Radiation Research.

Fruitful collaboration with scientists from other institutions has

continued in FY87. Already mentioned were joint projects with scientists

from AT&T Bell Laboratories, and from Lawrence Berkeley Laboratory. The

molecular x-ray fluorescence studies have benefitted from the help of

R.C.C. Perera (LBL) in the work on the freons. We have also received

theoretical support from P.W. Langhoff and his group at Indiana University

for the work on fluorescence polarization. A joint article on our findings

and their calculations for CH3 CI is in preparation. Further experimental

work on x-ray diffraction effects was done on the NBS Materials Science

Beamline by P.L. Cowan in collaboration with members of the Institute for

Materials Science. Preliminary results of this work indicated the

possibility of producing extremely narrow x-ray beams, with potential

application to x-ray microscopy and lithography. Finally, discussions have

begun with A.C. Parr (Center for Radiation Research) and J.L. Dehmer

(Argonne National Laboratory) on the feasibility of bringing their highresolution photoelectron spectrometer to X24-A to initiate gas-phase

photoemission in this energy range. To date, only two such studies in the

2-5 keV photon-energy range have been published.

X-Ray Spectroscopy - Gaithersbure :

Both independently and in support of X24-A work our longstanding

efforts in x-ray physics continue "in-house." The 2 emission profile

from a number of 3d metals have been reported in the past with highly

divergent results. Some investigators found fine structure on the profiles

270
and others with comparable resolution reported a smooth profile. In view

of the future use of a few of these emission lines for calibration markers

of the highly ionized one-electron spectra, we recorded the Kctj^ 2 profile

of Fe, Co, and Cu with high dispersion, high statistical quality and the

absence of any mechanical motion. The source, analyzing crystal and

position sensitive detector were oriented on a large granite surface plate.

No fine structure was observed with spectra that had one million counts in

the peak channel.

A current high quality theoretical calculation of the wavelength for

the 2s-+ls and Ss-^ls transitions of high-Z elements has stimulated the

remeasurement of L spectral lines of some selected elements including the

measurement of the xenon L spectrum.

Theoretical studies have shown that the 5s hole level of the actinide

metals and compounds should be very much influenced by 5s” ^-•^5p‘ ^ 5d' ^ 5f ( ef

)

super-Coster-Krbnig (sCK) fluctuation or configuration interaction. The Th

M x-ray spectrum was obtained by direct excitation from Th02 . The measured

Th M3 0j^ emission profile provides the first experimental evidence of the

splitting with an unusual width of the 5s hole level of thorium.

Theoretical work in support of the X24-A experiments has been

initiated by J. Cooper, who recently joined the Division. The overall goal

of this theoretical support effort is to provide a more detailed

understanding of near- threshold inner-shell processes than is currently

available. In the present context this involves activity in the following

areas

A. Identification of effects that are well understood and are likely

to be important in the reduction of existing data,

B. Theoretical calculations of energy levels and of absorption cross sections and fluorescence intensities to compare with existing

data, and

C. Suggestions for new experiments.

None of the above activities are carried out in a vacuum; (A) and (C)

involve active collaboration with other members of the QMG , and (B)

involves collaboration with other theorists both at NBS and elsewhere.

A survey of the literature of existing work on the resonant Raman

effect has revealed that the major effort both experimentally and

theoretically has been directed towards the study of structure in

emission spectra due to two-electron processes, but that relatively

little has been done on spectra taken with excitation energies close to

threshold where two-electron excitation is forbidden by energy

considerations. The classic work in this area is the work done at SSRL

by the Divison, which demonstrated the "turning off" of K-/9 satellites in

argon when the incident photon energy was lowered to below the double271
excitation threshold. The same work also revealed multiple emission

structures at incident energies near or below the threshold for singlevacancy production which were interpreted as being due to resonant Raman,

Rayleigh, and Compton scattering.

The more recent data taken at the NSLS seems to indicate that the

resonant Raman effect; i.e., the shifting of the main emission line to

lower energies when the incident energy is tuned below the single -vacancy

ionization threshold accompanied by one or more additional peaks due to

discrete single-electron excitation, is extremely important and has been

observed in most of the spectra obtained. Recent theoretical work has

shown that it should be possible to "sort out" the resonant Raman effects

via a deconvolution of the observed absorption spectrum followed by an integration to obtain a predicted emission spectrum. The predicted

spectrum can then be compared with the observed one to assess the

importance of other effects.

K-shell photoionization has until recently been regarded as a wellunderstood process. Simple screened hydrogenic calculations typically

yield cross sections which agree with experiment to within 10-20% and

better agreement is obtained using central-potential models. Such

calculations have now been performed for all elements of the periodic

table and are an important part of the NBS data base of x-ray attenuation

coefficients; they are also used to provide estimates of cross sections

where experimental evidence is not available. Recently there have been

attempts to improve the theoretical calculations via more sophisticated

models, particularly in the near- threshold region where discrepencies

with experiment are largest. Argon has been a "test case" in most of

these calculations because the cross section is well known and one does

not have to worry about solid-state effects. The most sophisticated of

these calculations (Dirac-Fock approximation including all effects of core relaxation) yields results near threshold which are still 8% lower

than experimental values. Earlier attempts to improve the cross sections

led to discrepencies.

In order to examine in more detail the various effects which should

be considered in the absorption calculations near threshold, as well as

to provide more detailed understanding of the doubly excited resonances

in argon which have been observed both in the NSLS experiments and in

earlier work at SSRL, a series of detailed calculations have been

undertaken. Fortunately, the "apparatus" needed for these calculations,

a set of computer programs written by R. Cowan of Los Alamos, was available and had been installed on the NBS computer system by members of

the atomic- spectroscopy group. Thus the usual start-up time of large

scale-computations was avoided. Results (to date) of these calculations

are as follows:

1. The results of previous calculations have been confirmed. As in

previous work, the effects of core relaxation have been found to be

extremely important and the calculations provide a detailed

272
analysis of these effects.

2. Although the programs used are not fully relativistic, the major

relativistic effects on the wave functions can be included.

Relativistic effects on the cross sections are below the 1% level

as expected.

3. The calculations have led to a new interpretation of the structure

observed in the region 15-50 eV above threshold. The first two

features which have been tentatively assigned as Is 3p^4s^ and

ls3p^4p^ now appear to be due to ls3p^d^. While the analysis is

not complete, the strengths, energy positions, and asymmetries of

these resonances obtained from the calculations are consistent with

the observed spectra.

Grenoble Activities:

Crystals whose lattice spacing have been accurately measured are used to make wavelength measurements for x- and gamma-rays. Since the

wavelengths are determined through the Bragg- Laue relation A=2dsin9 and

the crystal lattice spacing d is known, the wavelength measurements are diffraction angle measurements. Our goal is to make 0.1 ppm wavelength

measurements of 5 MeV (A=2xl0'^^m) gamma-rays and along the way determine

the combination of fundamental constants Ny^h/c, to make a better

determination of the neutron mass from a measurement of the deuteron

binding energy, and to make precise measurements of gamma-ray widths

(nuclear lifetimes) and wavelengths (i.e., binding energies) which are of

interest to the nuclear physics community.

These y-ray measurements are taking place at the high-flux reactor

operated by the Institut Laue-Langevin in Grenoble, France. This is the

only reactor in the world which has a horizontal beam tube for viewing

samples held near the core and facilities to change samples during

reactor operation. The spectrometer (GAMS-4) is a double flat crystal

spectrometer equipped with polarization sensitive Michelson

interferometers for diffraction angle measurements. The interferometers

are calibrated by measuring the external angles of an optical polygon and

constraining the sum of the angles to equal 2n

.

During the past year the question of the proper choice of crystals

for the diffraction of 5 MeV radiation was carefully considered from both

the theoretical and experimental side. Since the efficiency of the GAMS4 spectrometer is very low (=5 x 10"^^ at 5 MeV) and the diffraction

angles are very small (=0.1 deg. for Si [440] at 5 MeV), the crystals

must be chosen to optimize the count rate and resolution. In the

dynamical theory of diffraction from perfect crystals, there is a phenomenon called thickness pendellbsung intensity oscillations. By

careful selection of the crystal thickness for a given energy and

diffraction order, the available integrated intensity can be increased by

a factor of =3.5. This permits an increase in the order of diffraction

273
which results in larger diffraction angles and higher resolution.

In November, 1986, Si and Ge crystals tuned for the 1.381 MeV line

from the reaction ^®Ti (n, 7 )'*®Ti were tested. The Ge crystals (1.83 and

2.92 mm thick mixed orders) were designed for the [220] and [440]

reflections, while the Si crystals (1.62 mm thick) were designed for the

[440] reflection. Profiles were recorded for the above mentioned energy

and orders as well as for other orders and energies. The agreement of

the theoretically predicted and the experimentally measured profiles and

relative intensities for Si was excellent, but the Ge crystals showed

excess broadening and reduced intensity which appears to be related to

crystal imperfection. The data recorded during this run clearly

demonstrated the ability to maximize count rate and resolution by careful

choice of crystal thickness. Theory predicts rocking curve widths of

0.014 arcsec (resolving power, S=6.9xl0'') for the Si [440] reflection at

1.381 MeV. The measured widths were = 0.016 arcsec (S=6.0xl0^).

Two new sets of Si crystals were manufactured to take full advantage

of the thickness pendellosung intensity oscillation phenomenon. One set

with a thickness of 2.72 mm was chosen for the Si [660] reflection of the

above mentioned 1.381 MeV line Ti (predicted width = 0.006 arcsec,

R = 2.6x10^) while the other set (mixed orders) with thicknesses of 4.41

and 6.95 mm was chosen for the Si [220] and Si [440] reflections of the 5 MeV gamma-rays from the reaction ^^N(n,y)^^N. In May 1987, the 2.72 mm

Si crystals were tested. The measured width of the Si [660] reflection

at 1.381 meV was 0.014 arcsec, more than double the predicted width.

Acoustical and floor vibration noise broaden the profile about 0.006

arcsec but probably cannot account for the entire excess width. Further

data analysis and measurements, one hopes, will provide an explanation.

Efforts to further reduce environmental noise are proceeding.

Also in May and June 1987, precision measurements of the 1381 keV

line and several angle calibrations were made in order that this intense

line could serve as a local standard and the frequency of angle

calibrations could be reduced. The angle calibrations were stable at the

2 X 10“^ level and the wavelength measurements had an uncertainty of 5 x

10'^. In the course of temperature and pressure stabilization of the

spectrometer, another instability may have been introduced. Also, as the

resolution has increased, the contribution of mechanical and acoustical

vibrations to profile widths has become larger. In order to robustly

achieve an accuracy of 1 x 10“^, a factor of 5 improvement is needed.

Vibration isolation, pressure and temperature stability, interferometer

stability, and electronics stability are all being carefully investigated

as contributors to measurement instability.

In addition to the high-energy, high-accuracy measurements, the

GAMS-4 facility has been used extensively for excited-state nuclear

lifetime measurements during the past year. When a nucleus at rest emits

a gamma-ray, it recoils. If this same nucleus emits a second gamma-ray

while it is recoiling, the second gamma-ray will be Doppler broadened.

274
Knowledge of the velocity distribution of the recoiling nucleus and a measurement of the Doppler broadening of the line profile of the second

gamma-ray permits an estimation of the lifetime of the excited nuclear

state. The high resolution of the GAMS-4 spectrometer permits the direct

determination of Doppler broadening of the gamma- ray profiles. Nonwavelength dispersive parallel scans are compared to wavelength

dispersive anti-parallel scans to obtain estimates of the Doppler

broadening.

This technique has been applied to the 1381, 1498, 1585, and 1761

lines from the reaction ^®Ti(n, 7 ) ^®Ti and appears to be valid for

lifetimes in the 10”^^ to 10“^® sec range. The broadening is not a small

part of the measured widths as the following results show: 1498 keV - FWHM = 518 eV, instrumental width = 202 eV; 1585 keV - FWHM = 290 eV,

instrumental width = 214 eV; 1761 keV - FWHM = 386 eV, instrumental

width = 237 eV. Lifetime measurements have also been recorded for

excited states of ^^Ci and ^^Fe. Many of the transitions of interest are quite weak so that recording times of 5 to 10 hours per profile are needed to obtain adequate statistics.

The careful choice of crystals for diffraction has opened up another

area of opportunity for the GAMS-4 facility. The same fine structure

oscillations used on the Ad machine to compare lattice spacing have been

seen on the GAMS-4 spectrometer with gamma-rays. By comparing the

measured oscillating profiles with the theoretical prediction, electronic

structure factors can be derived. Electronic structures have been

accurately determined in this manner using x-rays. The GAMS-4 facility

makes it possible to extend these measurements into the gamma-ray region

where questions of crystal thickness and absorption are less critical.

Scientists whose main interest is solid state physics are interested in

collaborating with us on these measurements and a joint proposal for beam

time is being submitted.

Reactor beam time is awarded through peer-reviewed proposals. Since

the reactor port is shared by GAMS-4 and two curved crystal spectrometers

(GAMS-1, R=5 . 8 m; GAMS-2-3, R=24 m) competition is keen for reactor time.

In addition, the demonstration that nuclear lifetimes in the 10"^^ to

10”^® sec range and electronic structure factors can be measured with the

high resolution GAMS-4 spectrometer has created significant demand by

nuclear and solid-state physicists for the use of GAMS-4. In the long

run, intense scientific interest in the NBS GAMS-4 facility is a very

positive factor, but for the short run we face rather intense competition

for beam time for the high accuracy, high energy fundamental constants

measurements which are our primary interest.

Neutron Physics :

As part of a major new initiative aimed primarily toward neutron

scattering, the NBS has initiated construction of a National Cold Neutron

Facility adjacent to the existing NBS research reactor. This facility.

275
employing cold neutrons from a new in-pile cyrogenic source will include

a large experimental hall and numerous experimental stations. Two of

these stations are to be used for the study of basic neutron physics and

their operation will be the responsibility of the Division.

An initial scientific program is now underway and planning for a longer range program is in progress. The initial effort is aimed at the

determination of the neutron lifetime and investigating new methods for

high accuracy neutron dosimetry. The longer range projects include a ultra low vibration, inertial platform for neutron interferometry and the

establishment of a high-flux polarized neutron facility for weak

interaction physics including tests of parity and time-reversal

invariance

.

The neutron lifetime is a fundamental physical constant which is of

considerable importance in several areas of nuclear, particle, and

astrophysics. It is a primary input for calculations concerning the

details of the Big Bang, the nature of supernova core collapse, and the

rate of production of neutrinos in the sun. It is also a necessary

parameter for tests of the standard model of weak interactions as well as for calculations giving limits on the number of neutrino species. Two

experiments involving Division participation are in progress. The first

a collaboration between NBS and the University of Sussex (U.K.) which is

supported primarily by grants from the Department of Energy (to NBS) and

the Science and Engineering Research Council, U.K. (to Sussex). This

work is provisionally scheduled for a preliminary run at ILL in the

summer of 1988. The apparatus will then return to the U.S. for final

data collection on the (then completed) Cold Neutron Facility. The

second experiment is a collaboration between Los Alamos, NBS, Drexel, and

Harvard and will have it's initial runs at the NBS reactor.

As an outgrowth of both of these lifetime efforts, a variety of new

techniques for absolute neutron flux determination are under development.

In collaboration with personnel from the NBS neutron dosimetry group, and

the European Center for Nuclear Measurements (Geel, Belgium); these new

techniques will be intercompared and tested with existing standards. If

successful, these new methods could provide new primary neutron dosimetry

standards as well as leading to improved neutron cross-section

determinations for important nuclear materials.

In addition to this work, one of us (GLG) has continued active

participation in various planning groups for future neutron facilities.

These include the National Steering Committee for the Advanced Neutron

Source and the National Academy of Sciences Panel on University Research

Reactors

.

276
INVITED TALKS

Quantum Metrology Division (526)

Paul L. Cowan, "Novel Crystal Geometries for X-Ray Monochromators," at

the Stanford Synchrotron Radiation Laboratory Workshop on High- Power XRay Crystal Monochromators, Palo Alto, CA, October 22, 1986.

Paul L. Cowan, "Research Activities at NSLS Beamline X-24A," at the

National Synchrotron Light Source Lunchtime Seminar at Brookhaven

National Laboratory, Upton, NY, January 29, 1987.

Paul L. Cowan, "X-Ray Fluorescence Spectroscopic Studies of Atoms and

Molecules," at the Division of Applied Physics Seminar - Brookhaven

National Laboratory, Upton, NY, February 17, 1987.

Paul L. Cowan, "Polarization Effects in X-Ray Fluorescence," at the

Workshop on New Directions in Soft X-Ray Near-Threshold Phenomena,

Asilomar Conference Center, Pacific Grove, CA, March 3, 1987,

Paul L. Cowan "Research Results from A High Energy Resolution Synchrotron

Radiation Beamline," At the Stanford Synchrotron Radiation Laboratory,

Palo Alto, CA, March 5, 1987.

Paul L. Cowan, "Research Results from a High-Energy-Resolution X-Ray

Beamline," at the Hamburger Synchrotron Strahlungs labor , HASYLAB at DESY,

Hamburg, W. Germany, May 15, 1987.

Paul L. Cowan, "Predictions and Observations of the Diffraction of

Evanescent X-Rays," at the Institut fur Grenzflachenforschung und

Vakuumphysik KFA Julich, Julich, West Germany, May 21, 1987.

Paul L. Cowan, "Predictions and Observations of the Diffraction of

Evanescent X-Rays," at the Physics Department of the University of

Munich, Munich, West Germany, June 2, 1987.

Paul L. Cowan, "New Directions in X-Ray Emission Spectroscopy," at the

BESSY synchrotron radiation facility, Berlin, West Germany,

June 11, 1987.

Paul L. Cowan, "Research Results from a High-Energy-Resolution X-Ray

Beamline," PTB, Berlin, W. Germany, June 12, 1987.

John W. Cooper, "Resonant Raman Revisited," Chemistry Department, Indiana

University, May 22, 1987.

277
Maynard S. Dewey, "High Accuracy, Absolute Wavelength Determination of

Capture Gamma Ray Energies for E < 5 MeV and the Direct Determination of

Binding Energies in Light Nuclei," International S3nnposium on Capture

Gamma-Ray Spectroscopy," at Leuven University, Brussels, Belgium, August

31, 1987.

Richard D. Deslattes, "Why Precision Spectroscopy Needs Naked Ions," at

the University of Virginia, Charlottesville, VA, October 3, 1987.

Richard D. Deslattes, "High Resolution X-Ray Experiments," at the Ninth

Conference on the Application of Accelerators in Research and Industry,

North Texas State University, Denton, Texas, November 10, 1986.

Richard D. Deslattes, "The Unification of the Electromagnetic Scale," at

the School of Physics, Georgia Tech., Atlanta, Georgia, January 7, 1987.

Richard D. Deslattes, "A New Approach to Sub-Picosecond Nuclear

Lifetimes," at the Nuclear Physics Seminar, Michigan State University,

Lansing, MI, February 17, 1987.

Richard D. Deslattes, "Atomic Spectroscopy with Nuclear Machines," at the

Physics Colloquium, Michigan State University, Lansing, MI, February 17,

1987.

Richard D. Deslattes, "X-Ray Fluorescence Near Threshold," at the

Workshop on New Directions in Soft X-Ray Near-Threshold Phenomena,

Pacific Grove, CA, March 1, 1987.

Richard D. Deslattes, "Accurate Spectroscopy in the X-Ray Region," at the

Symposium on Atomic Spectroscopy and Highly-Ionized Atoms," Lisle,

Illinois, August 17, 1987.

Richard D. Deslattes, "Fluorescent and Scattered Spectra: NearThreshold Excitation of Atoms, Molecules and Solids," at the 14th

International Conference on X-Ray and Inner-Shell Processes (X-87),

Paris, France, September 14, 1987.

Geoffrey L. Greene, "Fundamental Neutron Physics," at a Colloquium,

University of Missouri, Columbia, Missouri, January, 20, 1987.

Geoffrey L. Greene, "Controls and Safeguards for University Research

Reactors," at the National Academy of Sciences Workshop on University

Research Reactors, Berkeley, CA, February 2, 1987.

Geoffrey L. Greene, "The Investigation of Fundamental Interactions with

Cold Neutrons," at the University of Virginia, Charlottesville, VA, April

13, 1987.

Geoffrey L. Greene, "Cold Neutrons and Hot Physics," at NBS , University

278
of Colorado, Boulder, Colorado, May 14, 1987.

Geoffrey L. Greene, "Requirements for Fundamental Neutron Physics at the

Advanced Neutron Source," at the National Steering Committee Meeting for

the Advanced Steady State Neutron Source, Crystal City, Virginia, June

19, 1987.

Geoffrey L. Greene, "Fundamental Neutron Metrology," for the Colloquium

at the Commission of European Communities, Central Bureau for Nuclear

Measurements, Geel, Belgium, August 13, 1987.

Geoffrey L. Greene, "Determination of the Neutron Mass and the

Implications for Fundamental Constants," at the International Conference

on Neutron Physics, Kiev, USSR, September 22, 1987.

Robert E. LaVilla, "X-Ray Spectra of Molecules," at a Chemistry

Department Seminar, Indiana University, Bloomington, Indiana, November

20, 1987.

Dennis W. Lindle , "Atomic Physics with an Intense Synchrotron-Radiation

Source: Experimental Aspects of the Emerging Possibilities," at the

Workshop on New Directions in Soft X-Ray Near-Threshold Phenomena,

Pacific Grove, CA, March 3, 1987.

279
PUBLICATIONS - 1987

Quantum Metrology Division (526)

1 . In Print

U. Becker, H.G. Kerkhoff, D.W. Lindle, P.H. Kobrin, T.A. Ferrett, P,A.

Heimann, C.M. Truesdale, and D.A. Shirley, "Orbital-Collapse Effects in

Photoemission from Atomic Eu," Phys . Rev, A 2858 (1986).

S. Brennan, P.L, Cowan, T. Jach, R. LaVilla and R.C.C. Perera, "Optical

and Spectral Characteristics of an Insertion Device Used Both as a Wiggler and an Undulator," Nucl. Instr. Meth. 246 . 37 (1986).

*C,E. Brion, D.W. Lindle, P.A. Heimann, T.A. Ferrett, M.N. Piancastelli

,

and D.A. Shirley, "Photoelectron Branching Ratios and Partial

Photoionization Cross Sections for Production of the (2ai)‘^ State of H2 O

up to 200 eV," Chem. Phys. Lett. 128 . 118 (1986).

P.L. Cowan, S. Brennan, T. Jach, M.J. Bedzyk, and G. Materlik,

"Observations of the Diffraction of Evanescent X-Rays at a Crystal

Surface," Phys. Rev. Lett. 2399 (1986).

R.D. Deslattes, "Multivacancy Effects in Atomic and Molecular Spectra,"

Australian Journal of Physics 39., 845 (1986).

K.G. Dyall, and R.E. LaVilla, "The Argon K Suprathreshold Structure,"

Phys. Rev. A (Nov. 1986).

*T.A. Ferrett, D.W. Lindle, P.A. Heimann, H.G. Kerkhoff, U.E. Becker, and

D. A. Shirley, "Sulfur Is Core-Level Photoionization of SFg , " Phys. Rev. A

34, 1916 (1986).

*P.A. Heimann, U. Becker, H.G. Kerkhoff, B. Langer, D. Szostak, R.

Wehlitz, D.W. Lindle, T.A. Ferrett, and D.A. Shirley, "Helium and Neon

Photoelectron Satellites at Threshold," Phys. Rev. A 3782 (1986).

E. G. Kessler, and R.D. Deslattes, "One-Electron and Inner Shell Energy

Levels in High Z Atoms," Physica Scripta 34, 408 (1986).

*D.W. Lindle, T.A. Ferrett, P.A. Heimann, and D.A. Shirley, "Increasing

Quantum Yield of Sodium Salicylate Above 80 eV Photon Energy:

Implications for Photoemission Cross Sections," Phys. Rev. A 1131

(1986) .

G. Luther, P.L. Cowan, A. Henins , and S. Brennan, "New Two Dimensional

Position Sensitive Proportional Detectors Using Charge Division," Nucl.

Instrum. Meth. A246 . 537 (1986).

280
R.C.C. Perera, R.E. LaVilla, P.L. Cowan, "Cl-K)3 Emission Spectra of CFCI3 Excited by Synchrotron Radiation Below, 4 eV Above, and 50 eV Above the

Cl- Is Binding Energy," Proceedings of the Vlllth International Conference

on Vacuum Ultraviolet Radiation Physics . Lund Sweden, August 1986.

*J.W. Cooper, C.W. Clark, C.L. Cromer, T.B. Lucatorto, B.F. Sonntag, and

F. S. Tomkins, "Resonant Structure in 3p Subshell Absorption of Excited

and Ionized Manganese," Phys . Rev. A 3970 (May, 1987).

R.D. Deslattes, "High Resolution X-Ray Experiments," Nucl. Inst. Meth. B

24/25 . 52 (1987).

R.D. Deslattes, M. Tanaka, G.L. Greene, A. Henins , and E.G. Kessler, Jr.,

"Re -Measurement of a Silicon Lattice Period," Proceedings of the

Conference on Precision Electromagnetic Measurements June 23-27, 1986,

IM36 #2 (June 1987).

*T.A. Ferrett, M.N. Piancastelli , D.W. Lindle, P.A. Heimann, and D.A.

Shirley, "Resonance Effects in the Inner-Valence Levels of SFg in the

Photon-Energy Range 52-72 eV," Chem. Phys. Lett. 134 . 146 (1987).

G. L. Greene, "Accurate Positional Servo for Use with Pneumatically

Supported Masses and Vibrationally Isolated Tables," Rev. Sci. Instr. 58 . 1303 (1987).

A. Henins, "Variable Radius Crystal Bender," Rev. Sci. Instr. 1173

(1987) .

E. Kaerts, P.H.M. Van Assche, G.L. Greene, and R.D. Deslattes, "Crystal

Reflectivity for Bent Crystal Spectrometers," Nucl. Instr. Meth. A 256 . 323 (1987).

*D.E. Kelleher, E.B. Saloman, and J.W. Cooper, "Electric Field Effects of

Structure in the Continuum" in Photons and Continuum States of Atoms and

Molecules . M.R. Rahman, C. Guidutti and R. Allegrini, eds. SpringerVerlag, Berlin, 1987.

*D.W. Lindle, P.A. Heimann, T.A. Ferrett, M.N. Piancastelli, and D.A.

Shirley, "Photoemission Study of Kr 3d - np Autoionizing Resonances,"

Phys. Rev. A 35, 4605 (1987).

*D.W. Lindle, P.A. Heimann, T.A. Ferrett, and D.A. Shirley, "Helium

Photoelectron Satellites: Low-Energy Behavior of the n=3-5 Lines," Phys.

Rev. A 35, 1128 (1987)

.

*V.I. Mishin, G.G. Lombardi, J.W. Cooper, and D.E. Kelleher, "Effects of

Very Low Electric Fields on Narrow Autoionizing States in Gadolinium,"

Phys. Rev A. 35, 664 (1987).

281
R.C.C. Perera, R.E. LaVilla, and G.V. Gibbs, "Cl-K^ Emission of

Ch lorome thanes and Comparison with Semi-Empirical and Ab Initio MO

Calculations," J. Chem. Phys . 4824 (1987).

*M.N. Piancastelli , D.W. Lindle , T.A. Ferrett, and D.A, Shirley, "The

Relationship Between Shape Resonances and Bond Lengths," J. Chem. Phys.

M. 2765 (1987).

2 . In Press. In Review, or Nearing Completion

R.D. Deslattes, "Accurate X-Ray Spectroscopy," Proceedings of Workshop on Opportunities for Atomic Phvsics Using Slow. Highly-Charged Ions (in

press) (1987)

.

*T.A. Ferrett, P.A. Heimann, H.G. Kerkhoff, U. Becker, D.W. Lindle, and

D. A. Shirley, "Photoelectron Asymmetry Parameter of the S 2p Level of

SO2

, " Chem. Phys. Lett, (in press) (1987).

*T.A. Ferrett, D.W. Lindle, P.A. Heimann, W.D. Brewer, U. Becker, H.G.

Kerkhoff, and D.A. Shirley, "Lithium Is Main-Line and Satellite

Photoemission: Resonant and Nonresonant Behavior," Phys. Rev. A (in

press) (1987)

.

G.L. Greene, E.G. Kessler, Jr., R.D. Deslattes, M. S. Dewey, and H.

Burner, "Determination of the Neutron Mass and Implications for

Fundamental Constants," Proceedings of the International Conference on Neutron Physics . Kiev, USSR (submitted) (1987).

*P.A. Heimann, D.W. Lindle, T.A. Ferrett, S.H. Liu, L.J. Medhurst, M.N.

Piancastelli, D.A. Shirley, U. Becker, H.G. Kerkhoff, B. Langer, D.

Szostak, and R. Wehlitz, "Shake-off on Inner-Shell Resonances of Ar, Kr,

and Xe , " J. Phys. B (in press) (1987).

F. Hoyler, H. Borner, S. Robinson, G.L. Greene, and E.G. Kessler, Jr,,

"Recent Developments at the ILL (n,y) Facilities," Proceedings of the 6th

International Symposium on Capture Gamma-Ray Spectroscopy (submitted)

(1987) .

E. G, Kessler, G.L. Greene, M.S. Dewey, R.D, Deslattes, H. Borner, and

F. Hoyler, "High Accuracy, Absolute Wavelength Determination of Capture

Gamma Ray Energies for E < 5 MeV and the Direct Determination of Binding

Energies in Light Nuclei," Proceedings of the 6th International Symposium

on Capture Gamma-Ray Spectroscopy (submitted) (1987).

J.B. Kortright, P. Plag, R.C.C. Perera, P.L. Cowan, D.W. Lindle, and B.

Karlin, "Multilayer-Coated Mirrors as Power Filters in SynchrotronRadiation Beamlines," Nucl. Instrum. Meth. (in press) (1987).

282
D.W. Lindle , P,L. Cowan, R.E. Lavilla, T. Jach, R.D. Deslattes, J.

Sheehy, T. Gil, and P.W. Langhoff, "Polarization of X-Ray Fluorescence,"

(in preparation).

*D.W. Lindle, T.A. Ferrett, P.A. Heimann, and D.A. Shirley, "Complete

Photoemission Study of the He Is^ 3s3p Autoionizing Resonance," Phys

.

Rev A (in press) (1987).

R.C.C. Perera, R.E. LaVilla, P.L. Cowan, T. Jach, and B. Karlin, "Cl-K^

Emission of CFCI3 Excited by Synchrotron Radiation Below and Above Cl- Is

Binding energy: Perturbation Effects in a Highly Excited Neutral

Molecule," submitted to Physica Scripta (1987).

*M.N. Piancastelli , D.W. Lindle, T.A. Ferrett, and D.A. Shirley, "Reply

to Comment on 'The Relationship Between Shape Resonances and Bond

Lengths," J. Chem. Phys. (in press) (1987).

P.M.H. Van Assche, E. Kaerts, G.L. Greene, and R.D. Deslattes, "Crystal

Reflectivity for Bent Crystal Spectrometers," Proceedings of the 6 th

International Symposium on Capture Gamma-Ray Spectroscopy (submitted)

(1987) .

3 . Patents

G.L. Greene, Non-Contacting, Electro-Pneumatic Servo for Vibration

Isolation. (U.S., E.E.C., and Japanese Patents Pending)

•*Based on work performed prior to joining QMG.

283
TECHNiaAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Metrology Division (526)

John W. Cooper - Board of Editors, Atomic and Nuclear Data

John W. Cooper - Physics Editor, NBS Journal of Research

John W. Cooper - Member, NBS Washington Editorial Review Board

John W, Cooper - CBS Representative, NBS Computer Users Committee

Paul L. Cowan - Executive Committee, National Synchrotron Light Source

Association of Users

Richard D. Deslattes - American Physical Society, Division of Electron

and Atomic Physics, Chairperson, 1986-1987

Richard D. Deslattes - Member, Panel on Scientific Opportunities for the

Use of Cooled Heavy Ion Storage Rings.

Richard D. Deslattes - Member, Organizing Committee of the 14th

International Conference on X-Ray and Inner-Shell Processes (X-87)

Geoffrey L. Greene - Member, Ad Hoc National Steering Committee for the

Advanced Neutron Source (1986 - )

Geoffrey L. Greene - Member, National Academy of Sciences/National

Research Council Committee on University Research Reactors (1986- )

Dennis W. Lindle - Co-Chairman, Organizing Committee for "Workshop on New

Directions in Soft X-Ray Near-Threshold Phenomena," Asilomar, CA, March

1987

Dennis W. Lindle - SSRL User's Organization Executive Committee, 1984-86

284
COLLABORATIONS, CONSULTING, MISCELLANEOUS ACTIVITIES

P.L. Cowan is collaborating with Michael Seuls of AT&T Bell Laboratories

on developing total reflection standing waves for studies of organizing

monolayers

.

P.L. Cowan is collaborating with Ken Liang of EXXON Research Labs

involving glancing incidence x-ray diffraction studies of surface and

interface structure.

P.L. Cowan and D. W. Lindle are collaborating with Jack Rowe and

Francesco Sette of AT&T Bell Laboratories on structure studies of

adsorbates on crystal surfaces, development of a new experimental

technique (normal incidence x-ray standing wave analysis) , and studies of

post-collisional interactions of Auger electrons.

P.L. Cowan and D.W. Lindle are collaborating with J. Kortright, P. Plag,

and R.C.C. Perera of the Center for X-Ray Optics, Lawrence Berkeley

Laboratory on multi-layer mirrors as power filters in synchrotronradiation beamlines.

P.L. Cowan, R.E. LaVilla, and D.W. Lindle are collaborating with R.C.C.

Perera of Lawrence Berkeley Laboratory on x-ray fluorescence of freons

.

R.D. Deslattes is collaborating with Robert Dunford, Argonne National

Laboratory

R.D. Deslattes is collaborating with the University College, London on

the high resolution Bragg crystal spectrometer for the HESPP Mission,

(also with the Rutherford Appleton Laboratory)

.

R.D Deslattes is collaborating with H. Beyer, Gesellschaft f]qr

Schwerionenforschung (GSI) Darmstadt, FRG on spectra of heavy ions.

G.L. Greene is collaborating with J. Byrne and P. Dawber at Sussex

University on the measurement of the neutron half life.

G.L. Greene is collaborating with Los Alamos, Drexel University and

Harvard University on the measurement of the neutron half life.

G.L. Greene is collaborating with D. Gilliam (Center for Radiation

Research, NBS) and J. Pauwels (European Center for Nuclear Measurements,

Geel, Belgium) on absolute neutron dosimetry.

D.W. Lindle is collaborating with P.W. Langhoff (Indiana University) on polarization of molecular x-ray fluorescence.

285
f. '96i ,isr?'i*«v)’ rrol3asi*»*? |i«l '^:.

fe;\. ' T'f " ’’ ^ ..

I'f

.. ,,

• ..

. '. _ . 2"i

• "wvSspPJPj

"

<i.\ ./.-I' «.

' '- 4 V ,- ',

5 % s' ji i zi'i ’; (Mif :,ij, .•.ri7j ;5^n^b^ii;^a*i v;i- r-# 'aaoafoi tiHi-

>. . T.i;:^'.si ^ -s.ggjf'A ?v.c Rnpi3jat;vtfl

• * .,. V

• ^-.t< v/sS? 't»,4. 'jA'’j.«fy, . v< 3t';-rj at ' Ki««t|r»tt-x>»:s|K

A .'} .,f' 'h\;.'.j-i..Vi--',' Sl

f^TLe t'tturuU .W.a tma •niRVoJ):-^^^"''''

‘'j..U7‘5? sp.!- '. Li'raqp •:.( 4'^ :e: _$fl:).5«> aa^jrsl- AD.,.tyi5f--&

'' ^’" ' '"'''' ^

. wHtasad

• . -fe'i -V.--,.,;: . jr. .I^B;,.)-;;' iril.'Wjr ;K V- ij.

! '©aftj' !'7

v- '* "'. wjrt a.'I-.j’

• J: »• n**. ?•*;:’ '•' •• V. :r».J./T-Vj'r

t'v^ j..-. no7.»JcviA Li:r-^-J3{Uiyi: wU Kitw

'

.. • •* .«n.,TMg ^ •i" '.>ii ‘^ar “^'''o»i

#. / I

( 1

1

-

f., ;l

' 't!

'7 -t, ' .Tfc>V'--^“’' '

^ I '^'"> } iVv «'!''

fia- t* v:~\'^'.\ jk3j- au -,. r . .Jbfci witnif^' (}'KD'» ^nuiT^a'Jv^n.yJJolT^^pr''

^.-> •..•^:'' t f -H’-'

' -'Vi^ ': ifi-a .••:-* uori pa on.*«9iwtJ39tu eih no

4.-. . '-. /V' ;V l-jy»-.‘‘, «1>J[ l<rl« iiirHc-^OtJAlXoa zl'

>-. • '. • r - i|- ;.i t(t r,.f.fl-9*.'i i,*B.fl 3A.' rro

T 3

• '' j t \3 aK'J> -fJ 30i.ie'./oW£..M<a.*i

;. i»l7i/-'i '.'; : ^Jt'f'^ 4i»'iq<.jii}S j ^l<^<iP^Jfi^ t hijs^ (SifK \4^ . , VTt3*>Wiso5 aii/loadfi fro

A-j>’-i ‘j W’.*j fi3jw loo ti iU

aour!fto^s»'yOi#ii X!^3 x ifclup^Ioa ,^<j • -3."

7^

. j
, NBS-114A (REV. 2-8C) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 87-3587

2. Performing Organ. Report No. 3. Publication Date OCTOBER 1987

4. TITLE AND SUBTITLE

Technical Activities 8j - Center for Basic Standards

5. AUTHOR(S)

Peter L.M. Heydemann

6. PERFORMING ORGANIZATION (If joint or other than N BS, see in struction s)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. ContracL/Grant No.

8. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State, ZIP} 10.

SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FlPS Software Summ.ary, is attached.

11.

ABS i RACT (A 200-^ord or less factual summary of most significant in formation, I f document includes a significant

bi bliography or literature survey, mention It here)

This report sumniarizes the research and technical activities of the Center for Basic

Standards during the Fiscal Year 1987. These activities include work in the areas

of electricity, temperature and pressure, mass and length, time and frequency, quantum

metrolo,gy, and quantum physics.

12.

KEY WORDS (Six to twelve entries; alphabetical oraer; capitalize only proper names; and separate key words by semicolon s) Astrophysics; atomic and molecular physics; chemical physics; electrical standards,

fundamental constants; gravity measurements; laser physics; length standards; press'urs

a.nd. vaciuim standards ; temnerature standards time and frecuencj''^ standards ; .(—ray ana

13. availability gamma-ray wavelength standards

Unlimited

I j For Official Distribution. Do Not Release to NTIS

I Order From Suoenntenaent of Documents, U.S. Government Printing Office, tVashington, 20402.

^7; Order From National Technical Information Service (NTIS). Sormgfield. VA. 22161

).C.

14. NO. OF

PRINTED PAGES

288

15. Price

$24.95

USCOMM-OC S043-P30
WSSSIWWsS

: . w'v^t* ‘iigi irt^yi ^,r«w»..»».-J. ^ ..'Siesta -Sie**. I „J,:

../oSSi-.,

•V''{;^^:'’%r; v;‘"^ '\p vr;J:( '.f :va6w

'

' '"?y ' •' ' -. 7

-

„. ;

;,,,*

SJ’-" 1 )

’‘•wi'C'Vv-S'iJ'iP.’i 'i'. VJft-c,' • «'iavi iisvAt ^94tt»A4.>n>o.\ Hi

»-»V<-^‘'nfv^ »*rvMH 1'^, J»*tii-.'iv4 -' A ’ ,' -,'{*,?i! >'. jtcjV’'' . ft j muAEiJua^nii

'fo

ft- ' •»

t : •, » “l-.Z', £3T^j,^ 3T3,?^mo5"^dVa 'fis'%^

' ^^,'i

-?3TOM Y«/

.h '•••wi »* .•I 'Sij'-w rt’3.<4^ • '^)--^ ,.r3t»-'.,'

T

' '•.: .U.-'T.;'m '

•J(?TCi a*Uil.r '51 5^ C £S«lh5*¥b »f 'o v<i'on\r-.i( Un.i3'S'.= 'VO:

4-& 'T f?7 -AiiL::UJi?sai/e

e*- jV 2<?iC * . «d;^

Tw^ffvjuc

• t!' fA*f r- ‘fi’’ •sa-or-'? ^i .w r\»bvo »< «t<'Sk-!?;:piv*i

'.'ii -lipvi'z }.:St,, iiK-^.'-fq: -Jsivis '>= 1, u'SiT. V*'

'I. A'> }OB'nA». b,0,*£.U ,J,J.»iY*fntO<sd, V®

'i

- "

tf'-SX ,.AV qZ .'U^(Tvf) a>fVT®lt HoMi/teifT J(®fl®tj|i‘(

iFf

"

. ':%

'^:r i
V*