NAT’L INST. OF STAND & TECH R I.C.

A111Q5 M05fi31

NBSIR 80-2165

Technical Activities 1980

Center for Absolute Physical

Quantities

Karl G. Kessler, Director

Center for Absolute Physical Quantities

National Measurements Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

October 1 980

.U56

80-2165

1080

c 1 2 r: National Bureau of Standards

Department of Commerce

Washington, DC 20234
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NBSIR 80-2165

#* * TECHNICAL ACTIVITIES 1980

CENTER FOR ABSOLUTE PHYSICAL

QUANTITIES

RATIONAL BUREAU

or STANDARDS

LIBRARY SEP 1 6 1981

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Karl G. Kessler, Director

Center for Absolute Physical Quantities

National Measurements Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

October 1 980

Prepared for: National Bureau of Standards

Department of Commerce

Washington, DC 20234

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity, Technology, and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
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f"P.' 3; S38
ABSTRACT

This report summarizes research projects, measurement method development, calibration and data evaluation activities carried during Fiscal

Year 1980 in the NBS Center for Absolute Physical Quantities. These

activities fall in the areas of: quantum metrology; measurements and

standards for the electrical units, temperature and pressure, length and

mass, time and frequency; and quantum physics.

Key words: Electrical measurements and standards; length and mass measurements and standards; temperature and pressure measurements and

standards; time and frequency; quantum metrology; quantum physics.

i

INTRODUCTION

This book is Part II of the 1980 Annual Report of the Center for

Absolute Physical Quantities and contains a summary of the technical

activities of the Center for the period October 1, 1979 to September 30, 1980.

The Center is one of the five resources and operating units in the

National Measurement Laboratory.

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

the technical activities of the Center Office staff, one for 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. An organization

chart of the Center is included at the end of the text.

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 Absolute Physical Quantities, B160 Physics

Building, National Bureau of Standards, Washington, D.C. 20234.

i i
.
TABLE OF CONTENTS

Page

ABSTRACT i

INTRODUCTION ii

SUMMARY OF TECHNICAL ACTIVITIES

Center Office 1

Quantum Metrology Group 5

Electrical Measurements and Standards Division 27

Temperature and Pressure Measurements and Standards Division . . 72

Length and Mass Measurements and Standards Division 113

Time and Frequency Division 122

Quantum Physics Division 150

CENTER ORGANIZATIONAL CHART 229
.
•

CENTER OFFICE

SUMMARY OF ACTIVITIES

FISCAL YEAR 1980

The Center Office includes several scientists who, in addition to

their administrative support function also engage in a variety of technical activities.

Technical activities of the Deputy Center Director, Dr. Ralph P. Hudson, include research, technical writing and international committee

activities related to low temperature physics and thermometry. During

the past year, the properties of CMN (cerous magnesium nitrate) power in

the millikelvin region were analyzed to reconcile the thermometric

behavior of powdered CMN with that of single crystal CMN. Dr. Hudson

continues to serve as Consulting Editor in Low Temperature Physics for

the forthcoming new edition of the McGraw-Hi 1 1 Encyclopedia of Science

and Technology and has written new entries on Adiabatic Demagnetization,

Low Temperature Thermometry, and Low-Temperature Physics. He was invited

to write a general review on the measurement of temperature published in

a recent issue of Review of Scientific Instruments. Dr. Hudson contributes

extensively to the international communication of progress in low

temperature thermometry and provides valuable technical assistance to

the NBS temperature program.

Mr. John W. Cooper provides theoretical assistance within the

Center and in other Centers to experimental groups working in the area

of atomic physics. He provides suggestions for key experiments to be

performed using current resources, assists in the planning and carrying

out of such experiments and provides interpretations and supporting

calculations.

As a part of his duties as assistant to the Center Director,

Dr. W.G. Schweitzer provides collaborative support to the Length and

Mass Measurements and Standards Division in the area of laser technology,

laser spectroscopy and precise laser wavelengths for standards in

metrology and spectroscopy.

1
PUBLICATIONS

B. E. Cole, J. W. Cooper, D. L. Ederer, G. Mehlman and E. B. Saloman,

"Stark Effect on Autoionizing Resonances in the Rare Gases," J. Phys. B. Atom. Mole. Phys. J_3 , LI 75 (1980).

V. L. Jacobs, J. Davis, B. F. Roznyai , and John W. Cooper, "Multiple

Ionization and X-Ray Emission Accompanying the Cascade Decay of Innershell Vacancies in Fe," Phys. Rev. A 21_, 1917 (1980).

B. E. Cole, J. W. Cooper, and E. B. Saloman, "Field Induced Autoionization

in Rare Gas Absorption Spectra Near the Ionization Threshold, Phys. Rev.

Lettrs. 45, 887 (1980).

R. P. Hudson, "Adiabatic Demagnetization," McGraw-Hill Encyclopedia of

Science and Technology.

R. P. Hudson, "Low Temperature Thermometry", McGraw-Hill Encyclopedia of

Science and Technology.

R. P. Hudson, "The Measurement of Temperature," Rev. Sci. Instrum. 51_,

(7), 871 (1980).

R. P. Hudson, K. Mitsui and R. L. Rusby, "Third Report of Working Group

No. 5, Comite Consultatif de Thermometrie, B.I.P.M. ," 13th Session,

Sevres, France, June 17-19, 1980.

R. P. Hudson, "Low Temperature Physics," McGraw-Hill Encyclopedia of

Science and Technology.

OTHER

R. P. Hudson and B. W. Mangum, "On the Question of an IPTS below IK,"

13th Session, Comite Consultatif de Thermometrie, B.I.P.M., Sevres,

France, June 17-19, 1980.

R. P. Hudson, "Susceptibilities of CMN Powder and Single Crystal at Very

Low Temperature: Are They Consistent?", Poster Session, Cornell Symposium

on Liquid and Solid 3 He, Cornell University, Ithaca, N.Y. , July 21-25,

1980.

2
INVITED TALKS

R. P. Hudson, "Practical Thermometry at Low Temperatures", chaired

session and led discussion. Conference on Low Temperature Thermometry,

The Institute of Physics, London, England, October 1, 1979.

R. P. Hudson, "Millikelvin Thermometry", conducted round-table session

at XVth International Congress on Refrigeration (I.I.R.) in Venice,

September 23-29, 1979.

3
COMMITTEE MEMBERSHIPS

K. G. Kessler, Chairman, American Physical Society, Committee on Arrangements, Washington Meeting.

K. G. Kessler, Chairman, Earle Plyler Award Committee, American Physical

Society.

K. G. Kessler, Board of Directors and Executive Committee, Optical

Society of America.

K. G. Kessler, Chairman, Optical Society of America, Publications

Committee.

K. G. Kessler, NBS representative, Consultative Committee for the

Definition of the Meter.

K. G. Kessler, member, American Institute of Physics Publishing Policy

Committee.

K. G. Kessler, Representative for the OSA to the AAAS Consortium of

Affiliates for International Programs.

K. G. Kessler, member. Commission 14, International Astronomical Union.

R. P. Hudson, member, Fritz London Memorial Award Committee 1973-81

(Chairman, 1976-8).

R. P. Hudson, member. Advisory Committee on Thermometry, International

Committee on Weights and Measures.

R. P. Hudson, Chairman of Working Group 5, Study of Practical Low

Temperature Thermometers below 30K, Advisory Committee on Thermometry,

International Committee on Weights and Measures; 1974-80.

R. P. Hudson, Chairman of Working Group 4, Extension of IPTS below 14K,

Advisory Committee on Thermometry, International Committee on Weights

and Measures; 1980-.

R. P. Hudson, member, International Institute of Refrigeration, Commission Al/2, Cryophysics & Cryoengi neeri ng.

R. P. Hudson, member, National Committee for 16th International Conference on Low Temperature Physics (LT16), August 1981.

R. P. Hudson, member, General Committee, Joint ISA-AIP-NBS Symposium on Temperature, March 1982; Editor-in-Chief of Proceedings.

R. P. Hudson, Consulting Editor in Low Temperature Physics for the

McGraw-Hi 1 1 Encyclopedia of Science and Technology and its Yearbooks.

J. W. Cooper, member, Atomic & Nuclear Data, Editorial Board.

4


QUANTUM METROLOGY GROUP

SUMMARY OF ACTIVITIES

FISCAL YEAR 1980

I. Overview

The Quantum Metrology Group is a diverse collection of scientists

engaged in no less than six experimental and theoretical areas all of

which involve precision measurements. Some of the experiments are at

the forefront of measurement technology. Because of our diversity and

small numbers, we are not a division and are thus attached to the Office

of the Director of CAPQ. The fields in which we have active programs

include gravity, quantum theory of measurement, atomic theory, laser

spectroscopy, X-ray spectroscopy using laboratory and synchrotron

radiation sources, precision X- and y-ray standards, and solar and

plasma physics. Our staff includes nine full-time and four part-time/

retired scientists at the Ph.D. level. In the near future an additional

staff person will be added to fill the vacancy created by the retiree.

The collaboration for six months of a Guest Worker from Czechoslovakia

proved beneficial during the past year and we look forward to collaborating

during the coming year with a Guest Worker from France. Both Guest

Workers arrived with external support and collaborated in the X-ray

spectroscopy and y-ray standards work.

The catalyst for the Group is its leader, R_;_ Deslattes , whose

interests over the years have included all of the above mentioned areas.

In August 1980, Deslattes took a one-year leave of absence from NBS to

head the Physics Division of NSF, but keeps in contact with the Group by

spending approximately two days a month at NBS. He also will participate

directly in a measurement at the Stanford Synchrotron Radiation Laboratory

(SSRL). In Deslattes 1 absence the administrative responsibility is

being shared by J_;_ Snyder and E^_ Kessler , Snyder having responsibility

for gravity, theory, and lasers, and Kessler having responsibility for

X-rays, y-rays, and solar and plasmas.

The six major areas of activity are described in the following

highlights. However it is proper that a few of these be amplified in

this overview because of their stage of development.

A joint initiative by our group in CAPQ, by the Center for Materials

Science, and the Naval Research Laboratory for construction of a beamline

at the National Synchrotron Light Source (NSLS) at Brookhaven National

Laboratory was funded in mid FY 79. Two beam ports and four beamlines

will be implemented with this group having responsibility for one of the

beamlines. A subgroup to accomplish this task has been assembled from

new hires (P^_ Cowan , T. Jach - 50%, and R^ Spal - 40%) and NBS staff

( R. LaVil la and A^ Heni ns ). The beamline will operate in a photon

energy range 0.5 to 5.0 keV and will be separated from the storage ring

by a window so that materials which would be incompatible with the high

vacuum technology can be studied. The line will include mirrors, a primary monochromator, a sample chamber, a secondary monochromator, and

an electron spectrometer. The NSLS X-ray storage ring is scheduled to

be operational by early 1982. The first task which will be attempted at

NSLS will be X-ray studies of inner-shell processes on noble gases.

This work is an extension of studies which have been done at SSRL.

5
This group has had a program (led by G. Luther) for the past several

years to measure the gravitational constant "G". The earlier results

from this work had up to now been somewhat disappointing because of

problems related to unexpected systematic drift in the torsion pendulum.

This problem now appears to be essentially solved, and the experiment

has progressed very rapidly over the past year. We believe that data

already collected will result in a new value for "G" that is roughly an order of magnitude better than the best presently known value.

6
II. TECHNICAL ACTIVITIES

1. Precision X-ray and y~ray Measurements

E. Kessler, A. Henins, R. Deslattes, W. Sauder

Objectives

Accurate wavelength standards in the 20 keV to 5 MeV region is the

primary objective of this project. For maximum use in comparisons with

theoretical calculations, these standards need to be related to the

Rydberg, R . The standards have taken the form of: a) X-ray transitions

which are used for testing relativistic self-consistent field calculations

b) y-ray transitions which are used for calibrating Ge detectors used in

mesic X-ray work and bent crystal spectrometers (relative energy measuring

instruments); and c) absorption edge determinations used in kaonic X-ray

measurements. The targeted accuracy is 0.1 to 1 ppm for y-rays, a few

ppm for X-rays, and 15 ppm for edge measurements.

Two fundamental constant determinations might result from wavelength measurements in the above mentioned regions. A measurement of

the electron-positron annihilation wavelength should lead to a value for

the fine structure constant. A measurement of capture y-ray cascades

for which the mass equivalent can be measured by mass spectroscopy

should lead to a mass-wavelength conversion factor.

Current Activities

Two facilities exist for precision X-ray and y-ray wavelength

measurements. They are both two axis flat crystal spectrometers

equipped with angle measuring interferometers. Knowledge of the angles

through which the y- or X-rays have been diffracted along with knowledge

of the lattice spacing of the crystals permits the wavelengths to be

calculated. One of the instruments is located at the NBS reactor

(y-ray measurements) while the other is located at the Radiation Physics

Building (primarily X-ray measurements).

Almost all activity in the past year has been concentrated on X-ray

measurements at the Radiation Physics Building facility. The instrument

is coupled to the 4 MeV electron Van de Graaff where high Z K series Xrays are being measured. Because of low intensity only Kot 1 , Ka2 , K3 X , and Kp 3 can be measured with an accuracy of a few ppm in a reasonable

time. We have completed measurements on Ag, Er, Au, Pb, and U and are planning measurements on Xe, Sm, W, and Th. Our measurements are compared

to relativistic self-consistent field calculations in order to illuminate

deficiencies in our theoretical understanding of atomic energy levels.

In an earlier publication in which available X-ray measurements were

compared to theoretical predictions, a discrepancy linear in Z was clearly evident. However our recent measurements on U suggest that the

discrepancy decreases for Z greater than Z ~ 85. The planned measurements mentioned above should provide more information concerning the

experimental -theoretical discrepancy as a function of Z.

7
A manuscript on the mass of the kaon is in the final stages of

preparation. Our contribution to this work was the measurement of the K

absorption edge of metallic Er foils (E ~ 57.5 keV) which had been used

by Gary Lum and Clyde Wiegand of Lawrence Berkeley Laboratory (LBL) in

a critical absorption measurement of kaonic potassium X-rays. By

combining the measured transmission of the kaonic X-rays (LBL) with the

absorption vs. energy determination (NBS), a new value for the mass of

the negative kaon (m

K = 493.640 ± 0.054 meV/c2

) was determined. This

result is in good agreement with the value recommended in the recent

Review of Particle Properties (m^ = 493.657 ± 0.02 MeV/c2

). Although

this result does not represent a major breakthrough, it does eliminate

concern about high order radiative terms.

Analysis of data recorded in the 40.6 keV y-ray of "Mo was completed. We were requested to measure this line by a group of researchers

from Columbia and Yale who used the line as a standard to calibrate

pionic X-ray spectra in order to determine a more accurate value for the

pi on mass. This line is very difficult to measure with a flat crystal

spectrometer because of low intensity (strong self absorption and

branching ratio of 2%) and short half life (T, - 67h). Although

statistics were so poor that no detailed profile analysis was possible,

a peak was clearly evident on the summed data. The measured energy of

this line is 40.58347 keV (± 4.2 ppm). Because the uncertainty of the

pionic X-ray measurements is ^ 6 ppm, further improvement of the standards will reduce the total uncertainty very little. Although we have

been encouraged by the Columbia/Yale group to remeasure this line with

the flat crystal spectrometer, we feel that a bent crystal measurement

of this line is more likely to lead to increased accuracy. The pionic

mass measurement has recently been published in Physical Review Letters

and a separate manuscript on the measurement of the 40.6 keV line has

been prepared.

Because the efficiency of the double flat crystal spectrometer is

a few x 10 11

, only very intense lines can be measured. Curved crystal

spectrometers have an efficiency ~ 103 greater than flat crystal spectrometers and are thus better suited for weak lines. In the mid 60' s a DuMond type curved crystal spectrometer was installed at the University

of Colorado cyclotron, but has not been used for several years. The

spectrometer has been transferred to NBS and is being upgraded by: 1)

installing precision angular contact bearings on the axis, 2) installing

a low friction ball screw drive, 3) equipping the axis with an angle

measuring interferometer, and 4) bending high quality crystals to a radius of four meters. Much of the machine work is nearing completion

and the spectrometer should be operational by early December.

The first task to which the bent crystal instrument will be applied

is the measurement of satellite lines from high Z K series X-rays. The

X-rays will again be produced at the NBS 4 MeV electron Van de Graaff.

Previous measurements on hyper satellite lines (double K vacancies) from

heavy elements have differed by more than three standard deviation from

theoretical calculations and we hope to shed more light on this controversy.

8
Accompl i shments

In work prior to 1979, a number 30) of optically-based y-ray

wavelength standards were established in the 0.06 to 1.1 MeV range.

These standards proved useful in calibrating muonic and pionic X-ray

spectra, bent crystal spectrometers, and Ge detectors.

In the past year this work has been extended to include measurements

on high Z X-rays, the Er K absorption edge, and the "Mo 40.6 keV y-ray

line. The Er edge and "Mo measurements are in the process of publication

while the high Z X-ray work will be reported when additional measurements

are completed.

A long manuscript which documents in detail our measurement procedures

and results has been accepted for publication in Annals of Physics.

Future Plans

Our future work will be directed toward extending our opticallybased y-ray standards: 1) toward higher energies, and 2) toward less

intense transitions.

Higher energies:

Our goal is to make precision wavelength measurements in the 5 MeV

region where the sources will be direct neutron capture sources in a reactor. The scientific values of the high energy measurements are more

accurate y-ray standards for calibration of Ge detectors, a measurement

of the wavelength-mass conversion factor by combining y-ray cascade

measurements with a mass difference measurement made with a mass spectrometer, and better resolution of complex nuclear spectra in the 2 MeV

range. Around 2 MeV, the flat crystal spectrometer has a resolution 100

times as great as a bent crystal spectrometer so that intense blended

spectra should be resolved. The Institut Laue Langevin (ILL), Grenoble,

France, has a high flux reactor with source manipulation capability.

Within the coming year, we hope to submit a proposal to ILL for placing

a flat crystal spectrometer at their reactor.

Knowledge concerning the behavior of our flat crystals at high

energies is essential so that we can predict linewidths and resolutions

that will be obtained with capture gamma-ray sources. To this end, we

plan to make y-ray measurements on transitions from 110^Ag which has

energies up to 1.5 MeV. This source can be irradiated in the NBS

reactor and removed to our measurement facility located in the Reactor

Building.

Weaker transitions:

Completion of a precision bent crystal spectrometer should permit

us to measure weaker transitions. We hope to be able to provide the

scientific community with X-ray and y-ray standards accurate to a few

ppm in regions in which intense transitions are not available. The "Mo

40.6 keV line mentioned above could be more easily measured with a precision bent crystal spectrometer.

9
Recent discussions concerning the non-zero mass of the neutrino

have created an interest in the 18 keV region because the end point of

the p spectrum of tritium is ~ 18 keV. Accurate energy standards may be

necessary for some of the experiments being planned. These standards

can probably be most easily measured with a precision bent crystal

faci 1 ity.

10
2. X-ray Diagnostics of Laboratory and Astrophysical Plasmas

A. Burek, R. Deslattes, A. Henins

Objectives

This project applies crystal diffraction theory and technology to

the study of X-ray spectra from laboratory and astrophysical plasmas.

In particular we have been involved in optimizing efficiency and resolution in spaceborne instrument design and crystal utilization. We provide

state-of-the-art calibration to help secure maximum scientific return

from each mission. Our work explores new approaches including development

of geometries and diffraction systems having characteristics not available

otherwise.

Current Activities

Critical effort in this area was prompted by a contract from Lockheed

via NASA to develop technology for and proceed with X-ray radiometric

and diffraction optics calibration of a large number of large aperture

flat and curved crystals to be used as dispersing elements in a high

resolution X-ray polychromator to study solar flares. Now that the

Solar Maximum Mission (SMM) is in orbit and returning high quality X-ray

spectra, we are continuing to work with the SMM team on various aspects

regarding the applications of crystal calibration to the analysis of

data. These activities involve development of ray tracing techniques

for experimentally determined curved crystal figures, development of

methods for deconvolving instrument functions from observed spectra and

evaluation of effects of off-axis reflections. A paper applying similar

techniques to the analysis of high resolution solar X-ray data has been

accepted for publication in the Astrophysical' Journal . As part of a Guest Investigator program funded by NASA, an observing program has been

defined and incorporated in the mission observing sequence that will

study the evolution of hot plasma in magnetically confined coronal

loops. This observing program utilizes certain unique features of the

physics of anomalous X-ray Bragg diffraction near absorption edges in

crystals to obtain plasma diagnostic information not otherwise possible.

A complementary laboratory study and theoretical modeling of Bragg

diffraction from resonant bound states in crystals has been completed.

The calibration exercise for SMM has generated a large amount of

data concerning the X-ray radiometric and diffraction properties of real

crystals that is of importance to workers in the plasma physics and

synchrotron radiation communities. We are compiling and extending this

data which we hope to publish. With regard to applications in the

synchrotron radiation area, we have identified, obtained and evaluated

two promising crystals that could make synchrotron primary monochromator

construction possible for wavelength regions hitherto inaccessible to

synchrotron users.

We are continuing to pursue the development of novel crystal

dispersing elements and have devoted some time to the problem of fabricating large lithium fluoride panels for a space experiment. We are also investigating the application of epitaxially grown heavy metal

crystals and multilayer structures to monochromator construction.

11
Development of such dispersing elements would dramatically decrease the

expense and enhance the prospects for high resolution X-ray spectroscopy

of X-ray stars.

Accompl ishments

We have continued to work with the SMM team on various aspects of

data analysis and have provided X-ray calibration data to a number of

other groups in the X-ray astronomy and plasma physics communities.

In particular, working in collaboration with NRL we successfully completed

an analysis that showed that “new" unidentified lines in solar flare

spectra were, in fact, crystal effects. Extension of the SMM program of

crystal evaluation has identified new crystals of great potential use

to synchrotron radiation users. Laboratory and theoretical work is

complete on a Guest Investigator experiment that will study high

temperature solar plasma.

Finally, a proposal to DOE for the development of efficient crystal

spectrometers and X-ray i nterferometers for inertial ly confined plasma

studies has been submitted and although not funded yet has been given

favorable reviews.

Future Plans

Now that the SMM spectrometers are operational, we hope to proceed

with data analysis as part of the SMM Guest Investigator observing program.

The proposal with DOE will involve the development of new types of crystal

spectrometers for laser plasma fusion studies and the investigation of

ways of applying X-ray interferometry to X-ray plasma diagnostics. An

essential part of this effort is providing calibrated "benchmarks" to aid

in the development of new instrumentation in this field.

12
3. One- and Two-Electron Spectra*

K. Harvey, G. Luther (50%)

Objectives

We are applying tunable lasers and laser-related techniques in

fundamental studies of simple atomic systems. The present effort aims

to obtain adequate technological capability in regard to sources of

coherent radiation with appropriate linewidths, intensities, and tuning

ranges together with techniques for wavelength measurement. We are also

developing, in a systematic way, atomic beam technology based on the use

of lasers for state selection and state analysis.

Current Activities

An atomic beam of optically pumped metastable hydrogen has been

demonstrated and is being optimized. This source will be exceptionally

valuable to the future progress of precision hydrogen spectroscopy here,

as well as to the current attempts at other laboratories to measure

parity violation in atoms as predicted by unified gauge theories of the

weak and electromagnetic interaction.

A precision measurement of an infrared transition between Rydberg

states in atomic hydrogen, which coincides with a C0 2 laser line, is

being pursued. This transition, which is in a region of the hydrogen

spectrum not yet examined with high resolution, has already been observed

here in a dc discharge with moderate resolution.

A detector employing a thermionic diode is being investigated to

determine its details of operation and its application to the study of

the Rydberg states of various atomic species.

The investigation of the energy of the first excited state of He

using anti-Stokes scattering was initially unsuccessful, and is presently

somewhat in a state of limbo due to the departure of the post-doctoral

student (Shay) who was primarily involved with the experiment.

Accomplishments

The hydrogen atomic beam chamber, which was funded through the NML

Director's reserve in 1979, is essentially complete. Lyman alpha and

Lyman beta lamps have been constructed and successfully operated. A

beam of metastable hydrogen has been produced using the Lyman beta lamp.

The thermionic detector has been thoroughly investigated with an

alkali vapor and the mechanism for its sensitivity and internal gain

established. The results of this investigation have been submitted for

publ ication.

Finally, several laser sources are now available including a high

power ion laser, tunable cw dye laser, pulsed dye laser, waveguide C02 laser and stabilized C02 laser.

*After a realignment of the group's task structure, the work formerly

described under Laser Spectroscopy of H and He now comes under this

new title.

13
Future Plans

Appropriate lamps and nozzles will be further improved to obtain an optimum optically pumped hydrogen beam. This development will be transferred to the group doing parity experiments. Also the experiment to

measure the infrared transition in the hydrogen Rydberg states will be

done with an atomic beam to vastly improve the resolution of the spectra.

The thermionic detector will be optimized to further enhance its

application to high resolution spectroscopy using the information

learned from previous studies. It will also be used to study other

systems such as He.

There is some possibility that the investigation of the energy of

the excited state of helium may be renewed part-time by one of the staff

(Luther). A renewed approach would probably replace the previous pulsed

discharge excitation by either a dc discharge or a pulsed microwave

discharge.

14
4. Gravity and Fundamental Theory*

G. Luther (50%), R. Hayward (Guest Worker) , W. Towler (IPA)

Objectives

Our present objectives are twofold, and at present only indirectly

related: An accurate measurement of the gravitational constant "G" , and

theoretical studies of the general limits of physical measurements.

The feeble effect of gravity on matter makes experimental investigation of the gravitational interaction one of the most difficult tasks in

contemporary physics. The Newtonian Gravitational Constant is the least

accurately known by several orders of magnitude of all the fundamental

constants and has resisted efforts by many experimenters to improve its

accuracy. Our primary experimental goal is a redetermination of "G" to

an accuracy that reflects the current state of the art. Secondary goals

include improving our understanding of the technical limitations and

possible solutions to overcoming these limitations. We also hope to be

able to set limits on any possible variation of "G" with distance.

Current Activities

The "G" experiment has been active since early summer, and data are being accumulated and reduced.by digital methods.

The theoretical effort during the past two years has been concerned

with the study of measurement at the quantum level. At the classical

level, the interference by the measuring apparatus is accepted as an unwelcome, but tolerable, effect which the individual making the measurement may take into account. This is not so at the quantum level, where

the interference causes uncontrollable and uncertain perturbations on the system being measured.

Accompl ishments

One of the major accomplishments in the "G" measurement has been

the experimental demonstration that the most important source of systematic

error in our earlier attempts was related to the surface physics of the

carbon fiber. The (necessary) operation of the pendulum in vacuum

caused a continuing, substantial, and irregular change in the torsion

constant of the fiber over a period of several months. The solution has

been to return to the traditional quartz fiber, overcoated with gold to

prevent static build-up. The new fiber has shown orders-of-magnitude

improvement in the stability of both the quiescent position of the

pendulum, and the torsion constant of the fiber.

A second major improvement has been the addition of magnetic damping

of the pendulum motion of the bob. The torsion pendulum now used has a rotational Q of approximately 10000 (decay time of about one month), but

lateral displacements decay in a few seconds.

*Formerly reported under "Newtonian Gravitational Constant" and "Fundamental

Theory"

15
The construction of the angle reading autocollimator using a Reticon photodiode array readout has been completed and the photodiode

array interfaced to the control computer. The software modifications

necessary to interpolate the angular position of the torsion pendulum

have been completed, and the pendulum position is now interrogated about

16 times per oscillation. This data is temporarily stored until the

completion of a run, and then processed off-line to determine the

pendulum period.

The initial results for the data collected during the last several

months indicate that we are now able to measure the torsion pendulum

period with sufficient precision to calculate "G" to a few dozen parts

in a million. When the dimensional metrology on the pendulum bob is

completed, we expect the uncertainty in "G" to be of the order of 50

ppm. This result will be roughly a factor of 10 better than the best

existing determination of "G".

We also now have sufficient data for different positions of the

test masses to detect any variation of "G" with distance to better than

one part in 1000. That should be sufficient to settle the present

controversy over the validity of the inverse R square law at laboratory

di stances.

Theoretical studies have made great strides during the past year in

the understanding of certain types of "quantum nondemolition11 measurements,

wherein a precision measurement of one specific observable is made such

that the measurement causes a "reduction of the wavefunction" . A

subsequent measurement of the same observable will yield the identical

result. The number of "quantum nondemolition 11 observables is rather

limited for a periodic system such as a harmonic oscillator. It can be

shown that the classical concepts of amplitude, phase and energy are not

quantum nondemolition variables and the ultimate measurement precision

obtainable will be limited by a quantum mechanical uncertainty principle,

whereas the measurement of position or momentum has no theoretical

limits. A scientific paper reporting these results is in preparation.

As yet, no experiment has reached the quantum level where these results

may be tested.

Future Plans

A full calculation of "G" using data from the last- several months

will be made in the near future. A new pendulum bob, with better known

dimensional metrology and a new fiber, will be installed if the results

of our analysis support our current belief that we are limited by

knowledge of the present system.

16
5. Optical Physics*

J. Snyder, H. Holt (40%)

Objectives

This program is concerned chiefly with theoretical and experimental

laser spectroscopy and the development of related technology.

Current Activities

The theoretical effort is aimed at understanding the details of the

interaction of light with atoms. Two of the investigations concern

experiments which are not well understood because the high laser intensities used invalidate the usual perturbation methods. One of the

experiments is being conducted in the Electricity Division, and the

related theoretical work is being done in collaboration with this group.

A third theoretical investigation is directed towards a possible

experiment to demonstrate Doppler-free resonances narrower than the

natural width, as recently proposed by Scully.

An experimental collaboration is presently underway with the

Molecular Spectroscopy Division in the Center for Thermodynamics and

Molecular Sciences. This collaboration involves the application of a recently developed technique for high-sensitivity saturated absorption

spectroscopy to the systematic study of alkali dimers using a tunable cw

dye laser.

Modification of the Fizeau wavemeter to reduce systematic errors

continues, and a decision to convert the wavemeter to a new computer and

I/O system has been made. The new computer control system will greatly

reduce the time required to make minor modifications in the wavemeter

software or electronics, and will allow the wavemeter to be routinely

used as a subsidiary instrument in a laboratory environment.

A novel electronic frequency meter is being developed for use with

Michel son- type "Lambda Meters". This frequency meter appears to have

the capability to reduce the standard deviation in the wavelength measurement by several orders of magnitude without an increase in integration

time or optical path length.

Accompl ishments

The results of a collaboration between one of us (Snyder) and a group at the University of Paris-North have been published. This work,

which was done in France in 1979, involved the development of a new technique for high-resolution saturated-absorption spectroscopy.

Two major problems with the Fizeau wavemeter have been solved, and

the instrument has seen some use as a laboratory instrument. One of the

problems was the systematic error introduced by accidental wavefront

*These activities were previously included under "Laser Spectroscopy of

H and He " and "Fundamental Theory".

17
curvature of the incident illumination. The effect of wavefront curvature

is to introduce an error in the measured period of the fringe pattern.

The size of the error is related to the amount of shear in the two

interfering beams at the detector array. A geometry has been

found for which the shear is compensated, and the curvature-induced

error is negligible. The second problem was the systematic error due to

the non-uniform amplitude of the fringe pattern. A solution to this

problem in the form of a simple digital filter was found and incorporated

into the software. Details of the filter have been published.

A remaining major source of systematic error in the wavemeter is

correlated with ambient temperature and is believed related to the

method of construction of the interferometer, but this has not yet been

conclusively demonstrated.

The wavemeter has now seen some limited use as a laboratory instrument

to monitor a dye laser wavelength as it scans a molecular spectrum. The

RMS noise in the measured wavelength is about 50 MHz at the fastest update

rate of about 60 msec. Signal averaging gives a resolution of about 5 MHz

at a rate of 8 sec per point.

A non-exclusive licensing agreement with Molectron was negotiated by

the National Technical Information Service, a sister agency within the

Department of Commerce. This agreement gives Molectron the right to

develop and market the Fizeau wavemeter. Unfortunately, they have not

been very actively pursuing this project, and there do not seem to be

any prospects for a commercial version of the Fizeau wavemeter appearing

in the immediate future.

A real-time, signal-averaging frequency meter was proposed as an instrument to improve the performance of the Michel son- type Lambda meters.

A "software" version of the instrument with limited frequency range has

been completed and demonstrated, and a hardware version is being designed

and constructed.

Future Plans

We hope to be able to demonstrate line narrowing below the natural

width in a transient, Doppler-free spectroscopy experiment similar to

that proposed by Scully. Our theoretical analysis suggests that line

narrowing by a factor of two should be observable.

The collaboration with the Molecular Spectroscopy Division will

continue. Our intention is to study simple molecular systems with high

resolution.

We believe that the remaining temperature problems with the Fizeau

wavemeter can be linked to the construction of the interferometer. A new interferometer, which should not have this sensitivity, has been assembled

and will be tested. The wavemeter will be converted to run on the new computer system, and the software modified to be run as a subroutine

call from FORTRAN. The computer will then be able to run as an experimental

control and data collection system in the laboratory.

18
6. X-ray Spectroscopy - Synchrotron Radiation

R. LaVilla, P. Cowan, A. Henins, R. Deslattes, T. Jach, R. Spal

Objectives

The primary objective of research in this area is to exposit the

finer, less understood details of X-ray spectra from atoms, molecules,

and eventually of condensed matter. Specifically, we scrutinize those

features of the X-ray spectra which are not explained by the simpler

theories of inner-shell dynamics. As details of the X-ray spectra from

free atoms are elucidated, a more precise understanding of inner-shell

processes will be gained. This understanding should in turn provide the

basis for deducing information on chemical binding from similar X-ray

spectral features obtained from molecular gases, liquids, and simple

solids. A secondary benefit of this research is the advancement of

experimental technology which must necessarily accompany these studies.

Current Activities

We are trying to maintain a balanced program of work involving inhouse laboratory spectroscopy, utilization of existing synchrotron

radiation facilities, and development of devices, strategies and programs

for the National Synchrotron Light Source to be operated at Brookhaven

National Laboratory.

We have been improving and extending our in-house experimental

facilities. To this end we have precisely calibrated the computer

controlled angular encoder system on our vacuum double crystal X-ray

spectrometer and are finishing the installation of a new X-ray power

supply for it. This will greatly enhance our measurement capabilities

of the L- and M-series spectra which have become of interest as a result

of our precision measurement program. We are also in the planning

stages of apparatus for performing X-ray standing wave experiments. Xray spectral features involving multiple electron transitions are also

being studied with on-site apparatus. Double electron excitation in

sodium vapor is apparent in transmission spectra observed at SURF-II

synchrotron ring. Satellite ‘lines in the L X-ray emission spectrum from

Ar were also measured by exciting Ar by electron bombardment and recording the soft X-ray spectrum with a grating spectrometer. Synchrotron

radiation has properties (i.e. , collimation, high flux, tunability,

etc.) that make it a desirable source for X-ray spectroscopy, particularly for studying low intensity features. For this reason our group

has been involved in an experiment at Stanford Synchrotron Radiation

Laboratory (SSRL) and is planning an experimental facility in conjunction with the Naval Research Laboratory (NRL) to be located at the

National Synchrotron Light Source (NSLS) which is being built at the

Brookhaven National Laboratory.

At SSRL, X-ray spectroscopic studies of photon-excited single and

multiple hole states near threshold have been made and are continuing.

The wiggler beamline at SSRL is used in combination with a secondary

polychromator in order to obtain spectra in the K0 region from Ar at

19
various excitation energies. These spectra are providing valuable

information and a great promise for future experiments. Preparations

for another another experimental run at SSRL before the end of the year

are underway.

The beamline presently being planned for NSLS will be one of the

first X-ray beamlines worldwide to be dedicated to the study of atomic

physics. Since the NSLS will be comparable to the brightest existing

synchrotron sources and since this beamline is being designed for our specific purposes/needs and available to users from NBS and NRL for

75 per cent of the time, we are anticipating a tremendous opportunity

to lead in this area of investigation.

Accompl ishments

The results obtained on near threshold excitation of Ar X-ray

spectra at SSRL, although limited by a number of failures of SSRL

equipment, have already excited much interest in the X-ray physics

community. Spectra taken with the incident X-ray energy below the K

single vacancy threshold suggest that resonant-raman scattering occurs. The origins of the and Kp" satellite lines are also evident from

the preliminary measurements of their excitation functions. These

results have been presented at the International Conference on X-ray

Processes and Inner-Shell Ionization in August 1980, and will be

published.

Transmission spectra for Na vapor taken at SURF-II exhibit two

features above the K threshold which have not been previously reported.

By comparing these features with the Mgl and Mgll optical spectra, it was concluded that these features are due to double excitations to

discrete states in the K continuum. These results and other details

of the Na transmission spectrum were presented at the VI International

Conference on Vacuum Ultraviolet Radiation Physics, June 1980.

The NSLS Participating Research Team (PRT) composed of personnel

from the Naval Research Laboratory, the NBS Center for Materials

Science and members of this Group received approval for our proposal

to instrument two of the twenty-eight synchrotron radiation ports at

the NSLS. In return the PRT is allocated 75 per cent of the beamtime

available at these ports for at least the first three years of operation.

Members of this group have the primary responsibility for the design

and construction of one of the PRT's six planned experimental stations

as well as an advisory responsibility for one other station. Designs

for the beamlines are progressing on schedule so that the facility

should be operational by January 1982.

Future Plans

The Group anticipates to continue the current research projects

while increasing the precision and detail of our results and to study

a wider range of samples as mentioned previously. We also plan to

continue in developing new areas of activity.

20
At NBS, electron excited soft X-ray spectra from atomic and

molecular gases and molecular gases and absorption spectra of metal

vapors in heat pipes will be studied. Absolute L and M wavelength

measurements on high Z elements will be obtained using the recently

calibrated vacuum instrument to complement the K series measurements

by E. Kessler on these elements. The My absorption edge of a bismuth

foil will also be measured absolutely with the vacuum instrument to

provide improved calibration for experiments performed by G.A. Beers

et al on Ka radiation from pionic deuterium. X-ray standing wave

experiments will commence. The purpose of the standing wave

experiments will be to study new aspects of the interaction of photons

with atoms in a crystal lattice and to demonstrate the use of this

technique for studying structure of certain materials.

At synchrotron radiation facilities the doubly differential X-ray

experiments will continue, initially at SSRL, then eventually at the

NSLS. The measurements for Ar K0 spectra excited near threshold will

be completed and then extended to the Ar Ka spectra and molecular

targets containing CjH and S. Near threshold excitation of electron

spectra by X-rays will also be used to study inner-shell processes.

In addition to the research program at synchrotron radiation facilities

planning, constructing, and bringing into operation the NSLS beamlines

at Brookhaven will be a major activity.

21
III. PUBLICATIONS

Quantum Metrology Group - 520.06

E.G. Kessler, Jr., R.D. Deslattes, W.C. Sauder and A. Henins, Precise

Y-ray Energy Standards, Proceedings of Third International Symposium on Neutron Capture Gamma-ray Spectroscopy and Related Topics, Upton, New

York, September 18-22, 1978, p. 427.

R.D. Deslattes, A. Henins and E.G. Kessler, Jr., Accuracy in X-ray

Wavelengths, NBS Special Publication 567, Proceedings of Symposium on Accuracy in Powder Diffraction, NBS, Gaithersburg, Maryland, June 11-15,

1979, p. 55.

J.J. Snyder, U.S. Patent, Apparatus and Method for Determination of

Wavelength, Patent No. 4,173,442 (1979).

J.J. Snyder, Algorithm for Fast Digital Analysis of Interference Fringes,

Appl . Opt. 1_9, 1223 (1980).

J. J. Snyder, R.K. Raj, D. Bloch and M. Ducloy, High-sensitivity Non! inear

Spectroscopy Using a Frequency-Offset Pump, Opt. Lett. 5, 163 (1980).

R.K. Raj, D. Bloch, J.J. Snyder, G. Camy and M. Ducloy, High-Frequency

Optically Heterodyned Saturation Spectroscopy Via Resonant Degenerate

Four-Wave Mixing, Phys. Rev. Lett. 44, 1251 (1980).

R.D. Deslattes, X-ray Monochromator Development for Synchrotron Radiation

Facilities, Nucl . Instr. Meth. 172 , 201 (1980).

A.J. Burek, D.M. Barrus, R.L. Blake and E.E. Fenimore, Analysis of Solar

X-ray Emission Line Profiles (to be published in Astrophysical Journal).

R.D. Deslattes, Primary Monochromators Using Crystal Diffraction, Nuclear

Instruments and Methods (in press).

G.K. Lum, C.E. Wiegand, E.G. Kessler, Jr., R.D. Deslattes, L. Jacobs, W.

Schwitz and R. Seki , Kaonic Mass by Critical Absorption of Kaonic-Atom

X-rays (to be published in Physical Review).

R.D. Deslattes, The Avogadro Constant, Annual Review of Physical Chemistry

(in press).

R.D. Deslattes, E.G. Kessler, Jr., W.C. Sauder and A. Henins, Remeasurement

of Gamma-ray Reference Lines, Annals of Physics (in press).

R.E. LaVilla, G. Mehlman and E.B. Saloman, Double Excitations in Sodium

Above the 2s Threshold (to be published in Journal of Physics B).

K. C. Harvey, Shielded Thermionic Diode Detector for Precision Spectroscopy

(to be published in Review of Scientific Instruments).

R.W. Hayward, The Macroscopic Harmonic Oscillator and Quantum Measurements,

Proceedings of The Second Marcel Grossman Meeting on Recent Developments in

General Relativity, Trieste, Italy, July 7, 1979 (to be published).

22
IV. INVITED TALKS

Quantum Metrology Group - 520.06

R.D. Deslattes, "Primary Monochromators Using Crystal Diffraction",

November 5, 1979, Joint USA/Japan Seminar on Synchrotron Radiation

Facilities, University of Hawaii, Honolulu, Hawaii.

R.D. Deslattes, "Precise Measurements of Normal and Exotic Atom Spectra",

November 15, 1979, Department of Physics Colloquium, University of

Oregon, Eugene, Oregon.

E.G. Kessler, Jr., "Absolute Gamma- and X-ray Wavelength Measurements",

December 5, 1979, Physics Department Colloquium, Illinois Institute of

Technology, Chicago, Illinois.

R.D. Deslattes, "Accurate Short Wavelength Measurements in the Spectra

of Normal and Exotic Atoms", February 6, 1980, Physics Department

Colloquium, University of Arizona, Tucson, Arizona.

J.J. Snyder, "Frequency-Offset Saturation Spectroscopy", February 11,

1980, Bell Telephone Labs Colloquium, Holmdel, New Jersey.

R.D. Deslattes, "Short Wavelength Spectra of Normal and Exotic Atoms",

March 27, 1980, Physics Department Colloquium, Michigan State University,

East Lansing, Michigan.

R.D. Deslattes, "Precision Short Wavelength Spectroscopy", April 9, 1980,

Physics Department Colloquium, Fermi lab, Batavia, Illinois.

R.D. Deslattes, "Threshold Behavior of Double Vacancy Atoms", April 10,

1980, Physics Department Colloquium, University of Illinois, Champagne,

Illinois.

R.D. Deslattes, "Accurate Atomic Inner-Shell Energies", April 29, 1980,

Spring Meeting of The American Physical Society, Washington, D.C.

R.D. Deslattes, "Multiple Vacancy Effects in X-ray Spectra", May 14,

1980, Physics Department Colloquium, University of Virginia,

Charlottesville, Virginia.

R.E. LaVilla, "The Sodium 2s Spectrum of Sodium Vapor", June 4, 1980,

VI International Conference on Vacuum Ultraviolet Radiation Physics,

Charlottesville, Virginia.

D. Bloch, R.K. Raj, J.J. Snyder and M. Ducloy, "High-Frequency Optically

Heterodyned Saturation Spectroscopy via Resonant Degenerate Four-Wave

Mixing", June 24, 1980, Eleventh International Quantum Electronics

Conference, Boston, Massachusetts.

J.J. Snyder, "Fizeau Wavemeter for Pulsed and CW Lasers", August 18,

1980, Institute of Optics Colloquium, University of Rochester,

Rochester, New York.

23
R.E. LaVilla, "Is and 2s Absorption Spectra of Sodium Vapor", September 26,

1980, Laboratoire de Chemie Physique, Universite Paris, Paris, France.

R.D. Deslattes, "Effect of Multiple Inner-Shell Vacancy on X-ray Spectra

of Atoms and Molecules", September 26, 1980, Atomic and Molecular Physics

Department Seminar, Argonne National Laboratory, Argonne, Illinois.

24
V. COMMITTEE MEMBERSHIPS

Quantum Metrology Group - 520.06

R.D. Deslattes, Member, NAS/NRC Committee for Fundamental Constants.

R.D. Deslattes, Chairman, Brookhaven National Synchrotron Light Source

Users Association (resigned because of appointment to the National

Science Foundation).

R.D. Deslattes, Member, Physics Advisory Panel, NSF (resigned when

assigned as Director of Physics Division at the National Science Foundation).

R.D. Deslattes, International Advisory Panel, 4th International Symposium

on Neutron Capture Gamma-ray Spectroscopy and Related Subjects, to be

held September 7-11, 1981, in Grenoble, France.

25
VI. SEMINARS FOR STAFF AND GUESTS

Quantum Metrology Group - 520.06

J.D. Silver, Clarendon Laboratory, University of Oxford, England - CAPQ

Colloquium, "Some Helium-Like Ions", October 1, 1979.

G.L. Borchert, European Organization for Nuclear Research, Suisse,

Switzerland - CAPQ Colloquium, "X-ray Energy Shifts", October 11, 1979.

W. Wing, University of Colorado/JILA, Boulder, Colorado - CAPQ Colloquium,

"Precision Spectroscopy in Highly Excited Beams", December 4, 1979.

P. Koch, Physics Department, Yale University, New Haven, Connecticut - CAPQ Colloquium, "Highly Excited Hydrogen Atoms: An Atomic Cornucopia",

January 9, 1980.

J.W. Farley, Department of Physics, University of Arizona, Tucson,

Arizona - CAPQ Colloquium, "The Effects of Thermal Radiation on Atoms",

May 7, 1980.

M. Ohno, Department of Physics, Chalmers University of Technology,

Goteborg, Sweden - CAPQ Colloquium, "Breakdown of a One-Electron Picture

in AES Spectra from Atoms and Solids", May 30, 1980.

T. Hberg, Helsinki University of Technology, Laboratory of Physics,

Otaniemi, Finland - CAPQ Colloquium, "Characteristic X-rays: Correlation

Effects and Final -State Interactions", May 30, 1980.

M. Ducloy, Universite Paris-Nord, Laboratoire de Physique des Lasers,

Villetaneuse, France - CAPQ Colloquium, "Doppler-Free High Frequency

Heterodyne Spectroscopy", July 2, 1980.

G. Grynberg, Ecole Polytechnique, Paris, France and E. Giacobino,

Universite Pierre et Marie Curie, Pari, France - CAPQ Colloquium,

"Doppler-Free Two-Photon Absorption in He Stability Near a Two-Photon

Transition", July 3, 1980.

G. Leuchs, University of Colorado/NBS/JILA, Boulder, Colorado - CAPQ

Colloquium, "Sensitive Detection of Microwave and Far Infrared Radiation

by Rydberg Atoms", July 3, 1980.

H. Borner, Institut Laue Langevin, Grenoble, France - CAPQ Colloquium,

"Recent Experimental Results in the Actinide Region Using the Curved

Crystal Spectrometer at the Institut Laue Langevin", September 17, 1980.

A. Bril let, Laboratoire de l'Horloge Atomique, Orsay, France - CAPQ

Colloquium, "Saturated Absorption in an External Fabry Perot: Applications

to Iodine at 612 nm" , September 29, 1980.

26


TECHNICAL ACTIVITIES

ELECTRICAL MEASUREMENTS AND STANDARDS DIVISION, 521

FISCAL YEAR 1980

Overview

The Electrical Measurements and Standards Division (EMSD) concerns

itself with the fundamental electrical quantities such as current, voltage and impedance at dc and low frequencies (to roughly 100 kHz) over

many orders of magnitudes 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 community as well as industry and commerce; and

to ensure that the U.S. system is consistent with those of other countries.

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

the Bureau's Organic Act, as amended, and is in its prime mission areas,

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

founded in 1901. The major technical problems which benefit from the

EMSD's work include fundamental physical theory; electric 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 the

civilian side of defense and aerospace; 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

services.

It is probably not an overstatement to say that the Nation's electric power system, the cost-effective manufacture of reliable consumer

goods, the economic production of industrial materials, and a viable

national defense would not be possible without adequate electrical

measurements. And that the basis for all such measurements within the

U.S. is the fundamental electrical units the EMSD maintains and disseminates through its calibrations and MAP's; the measurement methods and

instrumentation it develops; and the tests and calibrations of instruments and apparatus it performs. For example, each year several thousand

calibrations are carried out on primary electrical standards that belong

to some of the Nation's most important corporations, utilities and

government organizations, including Hewlett-Packard, General Motors, IBM,

General Electric, Pacific Gas and Electric, American Electric Power,

the TVA, the FAA, and the DoD.

To fulfill its responsibilities, the EMSD carries out work in the

following eight principal areas with the objectives as indicated:

27
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 which

will lead to advances in the state-of-the-art of electrical measurements,

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. Carry out international comparisons of the basic electrical

units, thus ensuring that the U.S. system of electrical measurements 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 eliminate and prevent non-tariff barriers to trade,

and to contribute to internationally acceptable data compilations.

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

measurements and standards, including the generation of tutorial written

material, thereby elevating the overall level of competence in the field.

The objectives, current activities, accomplishments and plans of

the various projects underway within the EMSD which contribute to these

principal areas are described in detail in the following project reports.

In brief, in the area of absolute realizations, good progress is being

made in the new experiment initiated last year to determine the ampere

by directly equating electrical and mechanical energy; and in the experiment to redetermine the NBS farad and ohm via the calculable capacitor.

In the area of maintenance and dissemination, the needs of the EMSD's

calibration clients were generally met. However, the situation remains

grave because of the loss of staff as a result of the recently mandated

ZBB cuts (see last year's Report). Indeed, the situation will be even more difficult in FY 81 since a number of the staff reductions did not

actually take place until FY 80 was well underway. Also, due to the

lack of staff, very little progress was made in furthering the automation

28
of the calibration facilities or in developing new MAP transport standards,

services, and software. However, some significant progress was made in

improving the fabrication of Josephson junctions for voltage standard

applications, and in understanding the interaction of microwave radiation

with tunnel junctions (nonequilibrium superconductivity).

In the area of new measurement methods, an innovative, microprocessorbased ac resistance thermometer bridge was essentially completed and work

begun on a similar capacitance bridge which will eventually be used in

the EMSD's capacitance calibration service.

In the area of precision measurement and fundamental constants, good

progress was made in constructing the apparatus required to carry out the

new Yp/a determination. Additionally, a new experiment to determine a and (simultaneously) to develop a new absolute resistance reference

standard based on the quantized Hall resistance in MOSFETS was initiated.

In the area of international comparisons, participation in a CCE/BIPMsponsored comparison of ac-dc thermal transfer standards was begun.

In the area of standardization, the EMSD staff continued to carry

out their many committee responsibilities.

Finally, in the area of training and education, lack of staff once

again prevented the EMSD from conducting its dc-lf Seminar. Also, the

pressure on the staff to maintain the status quo, especially in the calibration area, was such that no tutorial material could be generated.

(This situation will be alleviated to some extent in FY 81 with the

preparation of a user's manual for ac-dc thermal converters by a recent

EMSD retiree on a personal services contract.) On the other hand, a number of Guest Workers, an Industrial Research Associate, and two

Summer Students were successfully trained during the FY.

To summarize this introductory section, although the EMSD has

managed to survive a significant reduction of resources, in its present

state it can only hope to carry out the most rudimentary aspects of

its highly important mission outlined above.

29
REALIZATION OF THE SI AMPERE

(M.E. Cage, P.T. Olsen, W.D. Phillips, E.R. Williams)

Objective

The objective of this research is to measure the NBS Ampere in terms

of the SI units of mass, length, and time to an accuracy of at least one

or two parts in ten million, or nearly two orders of magnitude better than

has ever been previously achieved. Determination of the SI ampere is

periodically undertaken by NBS. This responsibility was given to the

NBS in its original charter as prescribed in the Organic Act.

Although the most modern scientific tools available at a given epoch

have been applied to the ampere experiment, there has not been a significant

decrease in uncertainty in this measurement (presently about 5 to 10 ppm)

in the past one hundred years. Continuing improvements in the measurements of other fundamental constants have permitted calculations which

indicate that there are possible errors in the present ampere determinations or in the measurements of these other fundamental constants. A

recently suggested method of directly measuring the NBS ampere in terms

of the SI unit by equating electrical and mechanical energy could reduce

the uncertainty of the experiment by at least a factor of 50. The new experiment could (i) resolve the present inconsistencies among the measured

values of a number of fundamental physical constants including the

Avogadro constant; (ii) provide a new value for 2e/h to be used internationally for Josephson-effect volt-maintenance applications, thereby

bringing the as-maintained electrical measurement system in closer

agreement with the SI and improving the international compatibility

of electrical measurements; (iii) provide a method for monitoring the

stability of the kilogram; (iv) eventually lead to an arti fact- independent

definition of the kilogram and mole within the SI; (v) provide a new means for continuously monitoring the absolute variations in the local

gravitational acceleration at a given site; (vi) provide information

concerning the reliability of the US-NBS density scale; and (vii) lead

to new, state-of-the-art advances in measurement science.

Current Activities

Any absolute ampere experiment involves measuring the force between

current-carrying conductors and measuring the dimensions of the conductors. Previous realizations of the ampere were eventually limited by

a measurement of the dimensions of some physical object, usually a coil

(copper wire wound on a cylindrical form). The new approach makes this

dimensional measurement indirectly, but more accurately, by measuring

the distance a coil travels in some interval of time and making a simultaneous measurement of a slowly varying "d.c." voltage. This first part

of a two part experiment, the calibration of the instrument, is expected

to be the final limitation. The second part, the weighing, will be

greatly improved in this approach over previous determinations since the mass required to counterbalance the vertical electromagnetic force will

be increased from a gram in a kilogram dead weight to a kilogram in

several kilograms dead weight.

30
The basic idea of the new experiment, which should enable an initial

measurement at the few parts in 10 7 level, and an eventual accuracy of a few parts in 108

, is to directly equate electrical and mechanical energy.

It may be briefly summarized as follows: A moveable coil is made to

traverse at a uniform velocity of about 0.5 mm/s a radial magnetic field

generated by two pairs of fixed coils. The approximate one-volt emf

generated at the terminals of the moveable coil while it is in motion

is measured in terms of the NBS as-maintained unit of voltage, which is

defined in terms of 2e/h as obtained from the Josephson effect. A

current, known in terms of the NBS as-maintained unit of current, is

then passed through the moveable coil. The force it experiences while

traversing the same magnetic field path as in the first part of the

experiment is measured using a balance with standard masses known in

terms of the kilogram. (The NBS unit of current is defined in terms

of the NBS units of voltage and resistance, the latter maintained via

a group of Thomas-type one-ohm resistors.) The relevant equation is

ka

anbs/a mgv

£nbs i nbs (qnbs/q)

1 1/2

0 )

where m is the mass equivalent of the force; g is the local value of the

gravitational acceleration and is known to 0.01 ppm from absolute gravimetry; s

Ng£

and I M0C are, respectively, the above-mentioned emf and current

NBS

measured in NBS units, and ^

35/Q is the ratio of the NBS to SI ohm, which

is known to 0.02 ppm from the Thompson- Lampard calculable capacitor. Since

coil dimensions need not be measured, our experimental design takes advantage of the high current densities obtainable with superconducting coils,

and the dimensional stability available at liquid-helium temperatures,

yet enables sensitive force measurements and velocity measurement to be

conveniently made at room temperature.

Construction of the cryogenic coils has been contracted for outside

NBS. While awaiting delivery of these coils, we are conducting a modified classical-electrodynameter or Pellat-balance experiment that is an equivalent approach to the new ampere experiment. In this experiment,

a coil rotates in a uniform magnetic field. The induced voltage and

rotational velocity are measured in the first part of the experiment,

and the torque exerted on the coil is measured in the second part.

Through this experiment we will develop all the measurement techniques

required for the final experiment, with the bonus that this preliminary

measurement will probably be the best ampere measurement ever made.

Accomplishments

A preliminary ampere experiment using the Pell at balance has been

completed. The results of this work were presented to the Conference on Precision Electromagnetic Measurements (CPEM) during June 1980. The

following specific accomplishments have encouraging projections for our

future experiments: (1) The entire measurement process was automated,

which is essential for simultaneous velocity and voltage measurements.

31
(2) A servo system that constrains the output voltage to be constant

has proved to be a good technique for obtaining stable relative motion

of the coils. (3) A two-frequency interferometer was modified to

measure the "time between fringes". (4) The signal -to-noise ratio

obtained for the voltage integral in the preliminary experiment is

projected to give a sub-ppm noise limit in the next Pel lat-balance

measurement and a part in 10 8 limit in the final experiment.

The coil system for the final experiment has been completely

redesigned: All superconducting coils now have the same diameter, and

the moveable coil is larger in diameter and will be outside the cryostat.

The new design reduced fabrication costs by a factor of two. This

simpler coil system will be mechanically more stable and the moveable

coil will be more accessible. Another design improvement is that the

velocity and voltage measurements will now be made between two room- temperature coils, so that the velocity drift of the cryogenic system will

be automatically compensated. The contract to construct the superconducting field coils has been let with an anticipated delivery date of

May 1981.

In collaboration with R.S. Davis of the Length and Mass Measurements

and Standards Division, we have obtained analytical solutions for the

equations of motion of single-pan balances with a center knife and crossed

load knives. These solutions predicted a new effect that depends upon

the equilibrium angle of the balance. The existence of this effect was experimentally confirmed. Results of the calculations and the experiment

will be published in the NBS Journal of Research. The calculations will

be used to optimize the force balance for the new ampere experiment.

The equilibrium-angle-dependent effect will be utilized to determine true

gravitational horizon for the balance beam.

Future Plans

Measurements of the NBS Ampere utilizing the Pell at balance will

continue. A solenoid which will provide twenty times more magnetic field

strength has been completed. The accessories for this solenoid are being constructed. A new non-metal lie arrestment assembly for the

balance is being constructed. It is expected that the Pell at Balance

will be in operation early in FY 81.

Numerous ampere measurements will then be made and sources of

possible systematic errors will be studied. The Pellat Balance ampere

measurements have the potential of yielding a ppm determination of the

NBS Ampere. Techniques developed here are directly applicable to the

eventual current balance.

The necessary apparatus for the current balance will continue to

be assembled. The superconducting field coils, contracted out, will

take from nine months to a year to receive. It will be calendar year

1982 before sub-ppm ampere measurements begin.

32
REALIZATION OF THE SI FARAD AND OHM

(R.D. Cutkosky, L.H. Lee, J.Q. Shields)

Objectives

The objectives of this project are to build, maintain, and operate

equipment for calibrating the NBS standards of capacitance and resistance,

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 that are manufactured within the

U.S.

The absolute farad and ohm measurements make use of a calculable

capacitor and a series of bridges for comparing capacitors and resistors.

The result of the measurement sequence is an absolute calibration of the

NBS reference standards of capacitance and resistance that is accurate

to a few parts in 108. These measurements can also be considered as fundamental constants measurements, with applications to questions con- cerning the adequacy of quantum electrodynamic theory and to the determinations 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.

Current Activities

The equipment was completed a number of years ago and is among the

best in the world. Work is presently concentrated on the preparation

of this equipment for a new determination of the absolute farad and ohm.

Other current activities include maintenance of the NBS unit of capacitance

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

capacitance.

Accompl ishments

Three capacitors of NBS construction have been circulating for many

years between the major national standards laboratories. This year for

the first time the capacitors were sent to the People's Republic of China.

Preliminary results from the National Institute of Metrology of China

indicate agreement between their unit of capacitance and the NBS unit

within their stated uncertainty of 0.35 ppm (standard error).

Preparation for the forthcoming absolute determinations of capacitance and resistance has resulted in the repair, replacement, or modification of several pieces of equipment. The equipment modified includes

the signal generator for the frequency dependent quadrature bridge and

the temperature controls for the oil bath and air baths which contain

the 10 pF reference capacitors.

In addition, a period of training and familiarization was needed in

order for J.Q. Shields to take over the actual measurements associated

with the absolute farad and ohm determinations. One phase of this

33
training took the form of an error analysis of the measurement system,

thus providing an independent assessment of those parts of the system

which had previously been considered in detail by R.D. Cutkosky alone.

Future Plans

New absolute farad and ohm measurements will be undertaken beginning

early in the fiscal year and probably occupying from three to six months.

Present thinking is that these measurements should be made on a yearly

basis for the next year or two so as to determine the drift rates of the

reference capacitors and resistors.
REALIZATION OF THE SI VOLT

(M.E. Cage, F.K. Harris, and L.H. Lee)

Objective

The objective of this project is to realize the SI volt directly by

force measurements in terms of the base SI mechanical units of length,

mass, and time interval, and the assigned SI magnetic constant.

The present volt assignment is derived from absolute ohm and ampere

determinations and is uncertain to the same extent (5 ppm or more). A

direct volt determination should be free from some of the systematic

errors of past ampere determinations. Furthermore, there is no conversion

of electrical energy to heat, which may have affected dimensional results

and balance operation in past ampere determinations. Thus it is hoped

that a direct determination of the volt may reduce the uncertainty in

its assigned value.

Current Activities

Our volt balance consists of a vertically aligned coaxial -cyl inder

electrode system with the low-voltage electrode in the annular space

between an inner and outer high-voltage electrode, and suspended from

the balance beam. The vertical electrical force on this suspended

electrode is compared by substitution to the mechanical force produced

by a known mass. The relation between electrical and mechanical forces,

(E2

|| = 2 mg),

requires that capacitance be measured against vertical electrode displacement; and the high-voltage electrode system is mounted on a carriage which

can be moved vertically on three guide rails, position being determined

using a laser interferometer.

It has been shown that horizontal electrical forces which are present if the system is not truly symmetrical about a vertical axis

may translate into a quasi -vertical force if the knife-edges of the

balance beam are not in a horizontal plane. Thus it is extremely

important that the electrode system be accurately symmetrical (within

a few microns) about an axis that is vertical (within a few seconds of

arc); the carriage movement of the high-voltage electrode system must

also be vertical within the same constraint. Thus this year's activities

have been centered on the development of techniques to accomplish these

objectives.

Accomplishments

Using the surface of a mercury pool as a reference horizon, we have

established vertical travel of the carriage-electrode system within

3 seconds over a 7 cm travel span. Over most of this distance — except

close to the end points — the departure from vertical is no more than

1 second. Using carriage motion and a non-contacting capacitance probe,

35
we have established symmetry of the high-voltage electrode system within

3-4 microns and vertical alignment within 3 seconds over a 5 cm carriage

travel. Alignment and symmetry adjustments on the suspended electrode

are not yet complete, but we have no reason to suppose these will not

finally be of equal quality.

Future Plans

We expect to complete symmetry adjustments and final assembly of

the electrometer early in the new fiscal year, so that force measurements

can be started. The operational stability and resolution of our balance

is about 1 pg. Thus, at the one-gram level, where our first force

measurements will be made, we should have a 1 ppm resolution. To make

force measurements at higher levels, we should lower the center of

gravity of the suspended electrode system. This will require substantial

modification of the suspension system, and will not be undertaken until we have assessed our results from the measurements at the one-gram level.

36
JOSEPHSON VOLTAGE STANDARDS

(G. Costabile, R.F. Dziuba, B.F. Field, C.J.P.M. Harmans,

L.B. Holdeman, J. Toots)

Objectives

The overall objective of this activity is to improve the maintenance

and dissemination of the unit of dc voltage for the U.S. through the

development of voltage standards based on the ac Josephson effect. The

activity encompasses a number of interrelated projects, each having

specific objectives within the purview of the overall goal.

The objectives of the Josephson Volt Maintenance Project are

(i) to maintain the U.S. legal volt by the ac Josephson effect using the

assigned value 2e/h = 483593.420 GHz/V^g^ and (ii) to improve the maintenance of the volt to a part in 10 8 or better by developing an allcryogenic voltage standard. The objective of the AF/ARMY/NAVY/KSRI 2e/h

Instrument Fabrication Project is to improve the maintenance of the unit

of dc voltage at the standards laboratories of the U.S. Armed Forces and

at the Korean Standards Research Institute by providing these laboratories

with Josephson voltage standards. The objectives of the CCG Josephson

Voltage Standards Research Project are (i) to develop an all -cryogenic

voltage standard, (ii) to develop reliable Josephson junctions which are impervious to the effects of room- temperature aging and of thermal

cycling between liquid-helium and room temperatures, and (iii) to develop

Josephson junctions from high-T

c superconducting materials. The objective

of the SRM Josephson-Device Project is to produce, for distribution

through the Office of Standard Reference Materials, well characterized

Josephson devices which can be repeatedly cycled, stored and shipped

unrefrigerated, and packaged to be compatible with commercial Josephson

voltage standards. The objects of the NASA Josephson-Device Research

Project are to produce low-T

c films, fabricate devices from these low-T

c films, and to investigate their microwave response (0.1-40 GHz) in order

to evaluate the high-frequency and non-equilibrium limitations of these

devices in radiation-detection and voltage-standard applications. Finally,

the objective of the Advanced Thin-Fi Im-Device Research Project is to

provide a vehicle for innovative research, with current emphasis on investigation of voltage standard applications of LEIT (Light Emission by

Inelastic Tunneling) junctions and unbiased arrays of hysteretic tunnel

junctions.

Current Activities

Approximately once a month the NBS Josephson voltage standard is

used to assign new emf values to two NBS reference groups of standard

cells, which are then used to assign values to customer standard cells.

Development of the all -cryogenic voltage standard is continuing, with

present efforts directed toward reducing noise effects that limit its

precision. Five commercial Josephson-effect voltage standards are undergoing acceptance testing in the EMSD, and will be delivered in turn

as they are made to meet specifications. Development of techniques for

37
producing lead-alloy (Pb-In-Au/Pb-Bi ) junctions is nearing completion,

and development of niobium-based junctions will be resumed early in the

fiscal year. Major modification of the thin-film deposition system that

is now used for lead-alloy devices is progressing, and will enable substrate heating, mask changing, easier substrate mounting, and eventual

sputter-etch cleaning of the substrates. The superconducting properties

of thin films of the low-T

c intermetallic compounds AuA 1 2 and Auln2 are being studied, and a study of microwave enhancement of superconductivity

of A1 films is continuing.

Accomplishments

In FY 80, there were ten comparisons of the Josephson voltage

standard against NBS reference groups of saturated standard cells. The

results of these measurements indicate that the primary reference group

NBS- 13 is drifting at the rate of -0.108 ppm/month. The all -cryogenic

Josephson standard has been kept cold (<80K) during the past year with

no apparent deterioration of any of its components, but external noise

coupled into the system still continues to limit its performance.

During FY 80 one commercial Josephson voltage standard was delivered

and a second is ready for delivery following final calibration. The

cause of a problem common to all instruments was pinpointed and eliminated. A combination of photolithography and stencil -mask techniques

has yielded the result that better than 90% of the devices now produced

are within 30 MHz of the design frequency, and about 80% are within

10 MHz; however, consistent production of sufficiently low tunnel conductance via sputter-oxidation has not yet been achieved.

A thorough analysis of magnetic torques in the Gyroscope Relativity

Experiment was carried out for NASA, Marshall Space Flight Center, and

some published results for certain torques were shown to be incorrect.

For each torque the maximum value of the appropriate parameter (the value

for which the torque equaled the design goal of 2x10 18 N-m) was computed,

and the results were tabulated.

Thin films of the intermetallic compound AuA1 2 with sharp superconducting transitions near that of bulk SRM material have been produced by

the technique of alternate deposition onto heated substrates of ultrathin layers with thickness ratios equal to the stochiometric ratio. The

energy gap of AuA1 2 and its temperature dependence have been measured

for the first time, and computer fitting of the data gives a BCS temperature dependence with a A(o)/T

c ratio slightly larger than the weak-coupl ing

limit. Microwave enhancement of superconductivity in A1 films has been

observed using a configuration in which one electrode of a tunnel junction was also a 50Q microstrip transmission line. At the frequency for

which the effect was maximum, the energy gap could be increased by as much

as a factor of two for temperatures near the equilibrium T , and the

transition temperature could be enhanced up to 16 mK above its equilibrium

value. A preliminary report of these results has been published (Phys.

Rev. Lett. 45, 1011 (1980)).

38
An experimental and theoretical investigation of photon-assisted

tunneling has been completed. A novel stripl ine-coupl ing scheme together

with the sharp gap structure that we were able to achieve in A1 tunnel

junctions enabled a thorough study of junction behavior from the fully

classical frequency regime to the fully quantum in a single device, and

a thorough test of the Tien-Gordon theory. An account of this work will

be publ ished.

Future Plans

Monthly comparisons of the Josephson voltage standard against NBS

standard-cell reference groups will continue. An improved low-noise

constant-current source for the al 1 -cryogenic Josephson voltage standard

will be constructed; a higher power microwave source that will enable

defluxing of the junction below the lambda point is on order. Since

low-melting-point materials are not evaporated in the EMSD/TPMSD UHV

Thin-Film Facility, a smaller ultrahigh vacuum deposition system acquired

from NOAA will be modified to accommodate sputter cleaning and oxidation

in addition to its present e-beam evaporation and codeposition capability.

A gas handling apparatus capable of maintaining partial -pressure ratio

and total pressure of two gases will be installed in the EMSD/TPMSD

Facility and a self-contained chilled water unit will be connected to

the 16 kW electron-beam power supply. The R&D for Pb-alloy Josephson

devices will be completed and R&D for niobium devices will be resumed.

The commercial Josephson voltage standards will be delivered in turn

as they are brought into specifications. The study of microwave

enhancement of superconductivity will be continued in order to increase

the understanding of the phenomenon, and the investigation of low-T

c thin-film devices will continue with the goal of obtaining devices with

identical electrodes and direct observation of radiation at the Riedel

si ngularity.

39
QUANTIZED HALL RESISTANCE

(M.E. Cage, R.F. Dziuba, andB.F. Field)

Objectives

The objectives of this project are to determine the fine-structure

constant, a, and to develop a resistance standard based on fundamental

constants, through measurements of the Hall resistance of Metal -OxideSemiconductor Field-Effect Transistors (MOSFET's) at temperatures below

2 K in magnetic fields greater than 10 T.

When a positive voltage is applied to the gate electrode of a MOSFET,

a thin layer of electrons (called the inversion layer) accumulates beneath

the oxide. This layer approximates a two-dimensional gas of free electrons.

The number of electrons in the inversion layer can be varied over two

orders of magnitude by changing the gate voltage, and thus the Fermi

level of the electron gas is an experimental variable. A magnetic field

B applied perpendicular to the inversion layer constrains the electron

motion to quantized orbits with discrete energy levels (Landau levels).

At sufficiently low temperatures, the Fermi level can be adjusted so that a given Landau level is completely filled while higher levels are completely empty, so that an inversion layer electron cannot be scattered

if the spacing between Landau levels (which is proportional to B) is sufficiently large. Under these conditions, a current flows between source

and drain without a voltage drop within the inversion layer, and the Hall

resistance (the ratio between the Hall voltage and source-to-drain current)

is given by

RH = a lm

Q

c/2i (1

)

where m^ is the permeability of vacuum (exactly equal to 4%xl0 7 H/m),

c is the speed of light in vacuum, a is the fine-structure constant,

and i is an integer.

Since resistances can be determined in SI units to within a few

hundredths of a ppm by means of the calculable capacitor, and since the

present uncertainty in the speed of light is 0.004 ppm, measurement of

the quantized Hall resistance of MOSFET devices can, in principle, be

used to determine the fine-structure constant. K. v. Klitzing has used

this technique to obtain a value of a that is in agreement with the

currently accepted best value, with an uncertainty of %1.3 ppm [Phys.

Rev. Letters 45, 494 (1980), and private communication]. The magnitude

of R hfalls within a relatively convenient range for small values of i:

R h = (25,813 L)/i. If experimental uncertainties can be reduced sufficiently, the technique can be used as the basis of an absolute resistance standard.

40
Current Activities

We are collaborating with the Solid State Physics Group of the Naval

Research Laboratory (NRL) in a study of the Hall resistances of existing

MOSFET devices using the NRL Magnet Facility. We are attempting to reproduce v. Klitzing's results using his measurement techniques. Our first

two runs have been on a Bitter magnet at 10 and 12 T. A 15 T superconducting magnet should be ready for use early in FY 81.

Accompl i shments

We have constructed a dewar probe system with which MOSFET devices

can be cooled to 1.3 K. We have designed and built a battery-operated

constant-current/constant- voltage source that is stable to better than

5 ppm, a battery-operated gate-voltage source with variable linear ramp

speed, and incorporated into the measurement system current- reversing

switches and two independent switches that can each select 12 different

device functions for measurements. We have mounted two MOSFET devices

that were fabricated at NRL, and results of our initial runs at 10 and

12 T indicate that the NRL devices were not suitable for these studies.

Future Plans

Dr. K. v. Klitzing sent us eight unmounted chips containing Hall

devices, which we received 29 August 1980. We will attempt to reproduce

his results at the few-ppm level using these devices and the superconducting (15 T) magnet at NRL in early FY 81. The results of these experiments will be helpful in determining the methods that should be used to

obtain results with sub-ppm uncertainties, and in determining whether

precise electrical measurements at the sub-ppm level are possible in the

electromagnetically noisy, high-field, cryogenic environment that is

required for the experiment.

We will continue to collaborate with NBS theoreticians S.M. Girvin

and R.W. Rendell on possible theoretical limitations to the results

(e.g. , geometrical effects, the effects of localized states). We will

continue a close cooperation with P. Roitman of the Electron Devices

Division, with NBS fabrication of specialized Hall devices a future possibility. We will collaborate with NRL staff and P.J. Stiles of Brown

University in the design and fabrication of mask sets for Hall devices

of various geometries. The geometry dependence of these devices will be

carefully studied to find the optimum shape.

41
ADVANCED IMPEDANCE-MEASUREMENTS RESEARCH

(R.D. Cutkosky, L.H. Lee, J.Q. Shields)

Objectives

The objectives of this project are to conceive and investigate new techniques for making various electrical measurements, and to develop

and construct the physical standards necessary to support these measurements.

A significant number of electrical measurement problems are not

encountered often enough to attract commercial development of appropriate instrumentation, yet are of considerable importance to persons

engaged in exploratory research or in the measurement of fundamental

constants. Persons engaged in such activities are generally best

situated for connecting established techniques with new problems, and

consequently a project of this kind must be closely linked with projects

involving research activities.

Current Activities and Accomplishments

An automatic resistance-thermometer bridge suitable for small-scale

production was constructed this year, detailed construction plans were

prepared, and a technical paper on the instrument was published. Plans

for this bridge were sent to a number of people who had requested them.

Five copies of the bridge are under construction and nearing completion

in Division 522. Design work has been completed for modifying the above

bridges for operation up to 100 L. A new microprocessor system will be

used for this work. Microprocessor program development, formerly a slow

and cumbersome procedure involving the use of an Interdata 7-32 minicomputer, will now proceed much more quickly. A fair amount of experience

with the new system has already been acquired.

Some preliminary work has been done on a new fused-silica capacitance

standard. The geometry of the silica element has been pretty well established, but problems have been encountered with the application of the

electrodes. A lot of experimentation was done with a fi red-on platinumgold material that was recommended by and provided by Englehard. The

problem we had was with obtaining complete coverage of the silica within

a thin groove around the circumference of the silica disk, resulting in an unacceptable voltage dependence for the capacitance. Recent results

with an air-dry silver paste have been more promising, but a new temperature regulator must be built before final measurements are made.

Some other components for an automatic capacitance bridge have been

made, including most of the phase sensitive detector and most of the

frequency synthesizer. Final assembly and testing will probably not occur until the end of FY81

.

42
Future Plans

The most immediate task ahead is to see that a 100 L version of

the automatic resistance thermometer bridge is made available. This

instrument will be more readily accepted by others than the present

32 L version, which may induce someone into manufacturing it. Together

with this, it will be necessary to devise a guard driver to fit inside

all of these automatic bridges, which will not be dependent upon leakage

between the guard and the furnace.

We believe that the present automatic thermometer bridge is not

optimum in a number of respects. Improvements can be expected in the

manner of connecting the guard, in resolution, and in convenience.

It would not be out of the question to contemplate designing and

constructing another instrument for this work, possibly starting about

one year from now.

43
EDDY-CURRENT NONDESTRUCTIVE EVALUATION

(B. F. Field, G.M. Free)

Objectives

The eddy-current project has three principal objectives: the development of a calibration service for electrical conductivity standards in the

range 1 0%-l 00% IACS; the production of electrical conductivity standards

which will become NBS Standard Reference Materials; and the development

of an eddy-current flaw-detection system for measuring and graphically

displaying defects in nonferrous metal components and structures.

Eddy-current testing of metal components is prevalent in industry.

The primary uses are in the measurement of material properties and in

the detection of flaws. The tests have such applications as the sorting

of metals, the measurement of cladding thicknesses, and the sizing of

defects. Despite the large number of applications, adequate standards for

the calibration of eddy-current instruments do not exist. The development

of standard reference materials and a calibration service for electrical

conductivity will meet the need for accurate calibration of conductivity

test systems.

In the area of defect testing, industry uses "in-house" standards

for the calibration of instrument sensitivity, and consequently there is

little basis for intercomparison of test results. However, before defect

standards can be developed, instrumentation that will accurately characterize commonly encountered defects must be developed. Eddy-current

defect imaging is a possible method for characterizing defects in metal

structures. Sophisticated signal processing in the imaging system could

improve the accuracy of defect characterization by at least an order of

magnitude. Such an instrument would not require a highly skilled technician to interpret measurement results, thus making eddy-current defect

detection more practical for industrial use.

Current Activities

The electrical conductivity calibration service and the electrical

conductivity standard reference materials have as a common factor the

instrumentation developed to measure electrical conductivity. This con- sists of a direct-current measuring system by which the resistivity of

metal bars of rectangular cross section will be determined. These metal

bars will then become the primary conductivity standards at NBS. Using

an eddy-current bridge developed at NBS that is based on a new concept

in eddy-current measurement, comparison will be made between the primary

conductivity standards and either customer samples or SRM's to determine

their electrical conductivity.

For development of the eddy-current imaging system, a new probe

design is being developed using an array of electromagnetic field sensors. Sensors presently being fabricated and tested are precision wound coils

with geometries chosen with the help of several computer-aided-design

programs for determining the defect sensitivities of the coils. The probe

44
concept will be proven experimentally using metal standards with known

fabricated defects. Using the experimental data, appropriate models

will be developed for characterization algorithms to be implemented with

a desktop computer. The final output of the task will be a specialized

eddy-current probe and signal -processing hardware capable of real-time

defect characterization and graphical (video screen) display of defect

information.

A temperature controlled air bath is being developed for measuring

conductivity standards. The air bath eliminates the need for doing

measurements with the test samples immersed in oil, eliminating the

problem of lift-off associated with this type of measurement.

A standard on the measurement of electrical conductivity by eddy

currents is being written for ASTM Committee E7.07. This document is a joint effort by NBS staff and several representatives from industry.

The document will be circulated for approval at the January meeting of

the E7 committees.

Accompl i shments

The following was achieved during FY 80: (1) Two new eddy-current

bridges have been developed and are undergoing testing. These new bridges work on the variable frequency concept developed at NBS but are

much faster and easier to operate. One of the bridges also holds promise

of being able to measure accurately in the ppm range. (2) Three metal

bars have received the final machining process and are being characterized

with respect to electrical and geometrical parameters. (3) A series of

Standard Reference Materials have been produced. There are four standards

with approximate conductivity of 60%, 47%, 40% and 30% I ACS. There are

100 samples at each conductivity value. The standards have an anodized

surface to prevent surface deterioration. (4) The concept of electronically scanning a flat plate with eddy-currents to accurately locate discontinuities has been proven feasible. An experimental set-up to do this

has yielded good results. However, the initial design for printed circuit

coils fabricated for the defect imaging system has been evaluated and

rejected. (5) Hall effect devices were also investigated as possible

sensors for the imaging system. After sophisticated instrumentation was developed to eliminate pickup of stray fields, it was found that the

inherent noise level in the devices makes them unsuitable for this application. (6) A joint study with the Material Science and Standards Division

has been completed. The study was funded by NASA and a report entitled

"Nondestructive Evaluation of 2219 Aluminum Alloy—Relationship to Processing" was issued in April 1980. (7) The Volume "Proceedings of the Symposium" on the Eddy Current Character!’ ati on of Materials and Structures

which is to be published by ASTM as an STP has been edited and the preface

and introduction written. The volume should be available in early FY 81.

(8) Two sessions of the ASNT Fall Conference to be held in Houston,

Electrical and Magnetic Methods and Research, have been organized.

Speakers have been found and other work related to the sessions has

been completed. NBS personnel will be the chairmen at these sessions.

45
Future Plans

Plans for FY 81 include the following: (1) All dimensional and

electrical tests on the dc bar standards will be completed. The bars

will then be the basis for the unit of conductivity. (2) The electrical

conductivity calibration service will be announced and calibration of

customers samples will be initiated. (3) The 400 SRM's which have been

manufactured will be calibrated and offered for sale by the Office of

Standard Reference Materials. (4) Before offering (2) and (3) the details

and logistics of calibrations and reports will be established. (5) Work

will be completed on the characterization of the new eddy-current bridges

which have been built. (6) Work will continue on the constant- temperature

air bath. The goal of this work will be to make the temperature at which

the bath controls variable in the range 20-30 C. (7) Theoretical studies

and computer analysis will be conducted to determine the feasibility of

an absolute measurement of electrical conductivity. This measurement is

important in determining the existence of any error in the transfer of

the unit from the dc to the ac experiment. If it can be done with a high

enough degree of accuracy, this experiment would also replace the dc experiment as the point of origin for the unit of conductivity. (8) Present

sensor designs will be evaluated for use in the defect imaging system. If

a suitable sensor is found, a prototype array system will be assembled and

tested, and development of image processing software will be started.

46
ELECTRICAL MEASUREMENTS FOR CORROSION

(W.G. Eicke, J.E. Sims)

Objectives

The objectives of this project are to improve, both in quality and

techniques, the electrical measurements requisite to the study of underground corrosion.

Each year, tons of various metals are buried underground for various

purposes: pipelines carrying oil, gas, or water; transmission lines for

communications or electrical power; and support pilings, to mention a few.

Corrosion of all kinds has been estimated to cost the United States

billions of dollars annually, with underground galvanic corrosion responsible for a significant fraction of this loss. A variety of methods for

inhibiting underground corrosion have been developed, but in order to

evaluate these methods in the field, and to develop new protection

methods, an i_n situ measurement of the rate at which metals corrode is

essential

One approach is to use electrical techniques to measure the rate of

corrosion. In this approach, a current I is applied to the structure under

study, and the change in electrochemical potential Vis observed by using

a standard reference electrode. By varying I, a curve V(I) is obtained.

The rate of corrosion can be calculated from this measured current- vol tage

relationship. Since the measurements are made manually, this approach is

tedious and time consuming. Therefore the immediate objectives of this

project are to improve the above approach through automation or semi automation.

Current Activities

The activities now underway in the EMSD are an evaluation, in a laboratory situation, of a superposition of an alternating current on the

applied direct current as a means of improving the electrical measurements for determining corrosion rates; the development of methods to

automate these measurements; and the development of computer programs

to reduce the data obtained. The project activities are separated into

two tasks: Fourier Analysis Program Development (Task A) and Electrical

Measurements in Underground Corrosion (Task B).

Accompl ishments

The computer software, written for the Interdata 7/32, essentially

performs harmonic (Fourier) analysis. A BASIC program (PERIOD) determines the period of an arbitrary set of data. A subset of the data is

used as a "window." This window is characterized by a minimum, a maximum, and the number of points in the subset. The rest of the data is

searched until the window is located twice. This defines an estimate of

the period. Using an error function, the estimate is varied until minimum

error is located and an accurate value for the period is obtained.

Analysis of the results, obtained from running the program using a group

47
of simulated data sets, indicates this method is accurate to 0.1%. The

initial execution time of the program was slow because of the large size

of the data sets and the use of BASIC as the programming language. Therefore, the input and search portions of the program were rewritten in

Assembly language to substantially reduce the execution time.

Another BASIC program (DFT) calculates the discrete Fourier coefficients using standard techniques. Although accurate values are obtained,

this program usually requires several hours per data set. A new program

(FFT) employing FAST Fourier Transform methods reduces the number of com- putations such that this program only takes several minutes to run. Analysis of results from running the FFT program using simulated data sets

indicate this method has an accuracy of 0.15%.

Major problems were encountered with the 7/32 operating system (and

possibly some hardware) which required that an inordinate amount of time

be spent in maintaining the system. It appears that many of the problems

have now been corrected and we hope that this work will be completed

early in FY 81. An NBSIR will be written documenting this effort.

Major efforts have been directed toward developing an automated

system for measuring corrosion rates. Originally the work plans called

for developing prototype automated systems in the laboratory. However,

after further study and consultation with our collaborators in the

Chemical Stability and Corrosion Division (CSCD), we decided to develop

a system to be used in the field because we could not duplicate field

conditions well enough in the laboratory. Various parts of the overall

measurement technique were studied in detail and we found that the major

problem for an automated system was that of resistance compensation. A

number of possible methods were considered and a very promising method

was found and investigated. This method, a variation of a technique

developed at NBS by Haller in the 1950's, could be applied either manually

or with an automated system. Studies were made and a prototype constructed.

Tests in the laboratory indicate that the manual version allowed IR com- pensation on a wide range of resistances with an accuracy at least as good

as the methods currently in use. However, this method requires that the

measuring and compensation circuits be floating.

Possible automation techniques were investigated and we decided

that the best solution would be to first automate using conventional,

easily characterizeable instrumentation. Because the test site is not

readily accessible by computer, an HP9830 was selected as the control

device because of its availability. One objective of the CSCD's program

is to develop a small microcomputer-based instrument. With this objective in mind, we decided that all hardware developed for this first prototype would be compatible with that objective whenever possible. During

this FY we have developed an interface between the 9830 and instrumentation that meets the microcomputer objective. In addition, a prototype

solid-state scanner was designed and construction is nearly complete.

We have also collaborated with CSCP in setting up their test site

and in their investigation of solid reference electrodes by designing

48
and constructing a manual scanner for quickly measuring buried sample

electrodes.

Future Plans

It is anticipated that the Fourier program will be completed in

early FY 81, after which our entire effort will be directed toward

Task B.

49
GAMMA- P AND THE FINE- STRUCTURE CONSTANT

(M.E. Cage, P.T. Olsen, W.D. Phillips, E.R. Williams)

Objective

We plan to resolve the present discrepancy between experiments and

the predictions of quantum electrodynamics (QED), and to enable more

critical tests of QED, by carrying out an improved (a few parts in 108)

measurement of the gyromagnetic ratio of the proton, q . This should

r yield a value of the fine-structure constant that is accurate to 1-2 parts

in 108.

QED is among the most successful and accurate of all physical

theories. Although QED has predicted experimental results to higher

accuracy than any other theory, a slight discrepancy (0.33 % 0.14 ppm) now exists between the measured and predicted values of the anomalous

moment of the electron, a . Furthermore, a can be measured with

e e greater accuracy than it can be predicted, owing to uncertainties in

the fine-structure constant, a. Since the uncertainty in a is now dominated by the uncertainty in our most recent measurement, an improved

measurement of q will either confirm or resolve the present discrepancy

P

between theory and experiment.

Within a few years, both the experimental measurement of a

g

and calculations of a

g

based on QED will have accuracies (exclusive of the

uncertainty in a) of 1-2 parts in 108. Therefore, obtaining a comparably

accurate value of a is of high priority to the physics community. No

other laboratory has achieved the accuracy in q obtained at NBS. Our

P

closest competitor in quoted uncertainty, at the NPL in Great Britain,

disagrees with us (and with QED) by more than ten standard deviations.

The NPL work is not likely to be repeated or extensively reviewed.

Therefore, it appears that only the NBS effort is likely to lead to an improvement in the present knowledge of q^. The responsibility for

improving a to the point where the most critical tests of QED may be

made lies with us. We, therefore, plan to carry out a new measurement

of q by two relatively independent methods. The first is a redeterminar tion of q

p

by improving the recently completed method. The second is to

employ a new technique using Ampere's Law.

Current Activities

The gyromagnetic ratio of the proton is defined as the ratio of the

angular precession frequency

1^ of a proton in a magnetic field B to the

magnitude of the field,

q^ = lp/B. The precession frequency is measured

by standard nuclear magnetic resonance methods. The magnetic field is

calculated from the measured physical dimensions of a single-layer solenoid,

50
wound on a precision-ground quartz form, with a known electric current

in the turns of wire. In the recently completed experiment, the location

of each turn of the solenoid is found by an inductive pick-up probe and

a laser interferometer which locates the position of this probe. We are constructing a new solenoid and measuring apparatus that will reduce the

sources of error in the recently completed experiment. This new experiment will have the following improvements: (i) a reduced sensitivity

to the diameter of the solenoid; (ii) improved axial symmetry of the

inductive pick-up probe; (iii) an improved straight edge used to guide

the probe; (iv) an improved laser measuring system that will allow

measurement of all six degrees of freedom of the probe; (v) increased

S/N ratio for the NMR signal; (vi) improved temperature control;

(vii) improved calibrations of our length and electrical standards;

and (viii) capability for a direct measurement of all the susceptibility

corrections. These advances should produce an order of magnitude improvement in our q determination.

P

Because of the importance of this experiment to physics and because

recently reported results by another laboratory disagrees with our results,

we are planning to measure

q^ by an independent approach employing Ampere's

Law. The dimensional measurements of the solenoid will be replaced by a "mapping" of the magnetic field of the solenoid. In this new approach

it should be easy to test the systematic errors and estimate the accuracy

of the measurement. This is a significant improvement over the present

method, which requires numerous corrections and assumptions to obtain

high accuracy.

The construction of the major components for the new experiment is

underway. In order to meet our strict tolerances for these components,

we have been personally directing the day-to-day measurements made by

shop personnel at each stage of construction.

Accompl ishments

In order to measure the effect of the susceptibility of the quartz

solenoid form, we have constructed a 2.4-m-long, 0. 6-m-diameter auxilliary

solenoid into which the actual 0. 3-m-diameter solenoid can be inserted.

This will allow direct measurement of the change in magnetic field produced by the 0. 3-m-diameter quartz form. Construction and winding of the

large solenoid, which required modification of the shop's largest lathe,

is completed, and the coil is ready for installation in the nonmagnetic

faci 1 i ty.

The 0. 3-m-diameter , 2.4-m-long precision solenoid is the key to an improved value for q . After final lapping, the fused-silica form had

P

diameter variations of less than 5 mm and was out of round by less than

1 mm. A groove was then ground into the cylinder and final thread lapping

was begun. Accurate measurement of the entire solenoid must be made after

each hour of thread lapping. It is anticipated that the form will be

completed within the desired tolerances early in FY 81.

51
A 3-m-long straight edge has been lapped inside a 0. 23-m-diameter

fused-silica tube. This track is now straight to within %0.04 mm over

its entire length, which is sufficient to reduce the out-of-straightness

correction to about 5 parts in 108 (a factor of 5 better than the previous

straight edge. Final polishing may further improve this al ready- adequate

straightness.

We carried out an extensive design study to determine the best

compensation scheme for the new long solenoid. With the scheme selected,

the magnetic field will be uniform to within a few parts in 109 over

the NMR sample (4 cm in diameter) and to within a part in 10 7 over a volume 8 cm in diameter, and will be as insensitive to diameter variations

as a 2- km- long uncompensated solenoid. Thus the uncertainty in y due

r to the diameter measurement (the major limitation in the recently com- pleted y experiment) will be completely negligible.

P

Finally, the CAMAC centered data-acquisition system, which will

enable remote (300 m distant) control of the dimensional measurements

of the precision solenoid, has been made operational. This minicomputer

system is currently being used to control measurements in the absolute

ampere experiment.

Future Plans

We will continue to concentrate on the construction and the measurement of the precision solenoid. This solenoid is the key element for

both approaches.

We will assemble the apparatus required to improve the recently

completed measurement. This will occupy most of our time during the

next two years. We have chosen to concentrate on this approach rather

than the new Ampere's law approach because we feel confident that an improved value will be obtained within a few years. The reason for our confidence is our recent calculation that shows that the sensitivity

of y to the solenoid diameter has been eliminated, and our new straightedgepreduces the out-of-straight correction.

The susceptibility solenoid will be assembled. This solenoid will

stand on end with a shower of cooling water to control the temperature

to 0.01 °C with 2.5 kW of power in the wire. A current source with

short term stability of a part in 108 must be built to produce a constant

magnetic field. The smaller precision solenoid will be lowered into

this uniform field and the field change due to the susceptibility of

the precision solenoid will be measured with an NMR magnetometer.

The lapping of the precision solenoid and the final polishing of

the straight-edge will be completed at the same time as the susceptibility measuring system is being tested.

Our immediate goal is to have a preliminary pitch measurement by

the PMFC II conference, June 1981. This is ambitious because the sus- ceptibility measurement must be completed first.

52
LASER COOLING AND TRAPPING OF NEUTRAL ATOMS

(W.D. Phillips)

Objectives

The fundamental objective of this experiment is to use tunable

lasers to cool and confine neutral atoms. These atoms, cooled to as low

as 10 4 K, could be used for high-resolution spectroscopy in a number of

appl i cations.

Because spectroscopic techniques form the basis for the most precise physical measurements made today, NBS continues to work on extending the resolution of spectroscopy. Maintenance of time, frequency and

length standards has benefitted from advances in spectroscopy. Recent

advances in non-linear optical spectroscopy indicate that attempts to

achieve higher resolution must address the problems of second order

Doppler shift and broadening due to finite observation time. Cooling

and confinement of atoms are an answer to these problems. The use of

laser fields to cool and confine atoms has been suggested for a number

of years; recent developments in tunable lasers indicate that it is now

an experimental possibility.

This work is complementary to the trapped ion work of the Time and

Frequency Division in that, while directed toward the same aim of improved

spectroscopy, the use of neutral atoms presents different opportunities.

For example, cooled neutral atoms in highly excited (Rydberg) states

could be used for precision tests of theories of the Stark effect, precise measurement of electric fields, or the determination of the finestructure constant from Stark splittings. Cooled neutral cesium atoms

could be used in conventional atomic clocks to improve their performance.

High resolution spectroscopy of neutral atoms also has other possible

applications in atomic physics and fundamental constants, such as Lamb

shift or Rydberg determination. Cooled and trapped atoms might also be

used for very low energy or very well controlled collision studies.

Current Activities

Atoms which interact with laser light that is resonant with an atomic transition will experience forces due to the absorption and emission of light. These forces can in theory be used to confine and cool

the atoms. The forces are weak enough, however, that with present technology, atoms hotter than about 1 K cannot be confined. Therefore, we

need to cool the atoms considerably before trapping is possible.

We are now attempting to use the light from a tunable dye laser to

slow down a beam of sodium atoms enough that they may be confined in the

field of another laser beam. We are also considering confinement in

static magnetic or electric fields which can interact with the permanent

magnetic dipole moment of the sodium or the electric dipole moment which

53
exists in some excited states. While the atom cooling efforts are initially directed toward eventual trapping of atoms, they could also be

used to produce slow neutral beams which would be useful for atomic

clocks or other atomic spectroscopy.

Accompl i shments

During FY 80 we have studied the effects of long-time interaction

of a resonant laser beam with an atomic sodium beam. By studying the

changes in the absorption spectrum with power and polarization we have

learned about the effects of optical pumping under these conditions. We

have also modified our laser to allow very rapid frequency scanning and

have reproduced experiments which were claimed to demonstrate cooling

when initially performed elsewhere. We have shown that the apparent cooling effects are actually due to optical pumping, an effect which is so large that it masks any cooling which might be present. We have begun

the construction of apparatus that will provide an unambiguous measurement

of the cooling effects.

We have developed a computer program which calculates the effects

of optical pumping for long interaction times. This program appears to

be successful in predicting the results of some experiments, performed

elsewhere, which were not previously understood, but the calculation is

not wholly adequate for the present experimental situation.

Future Plans

During FY 81 we will make unambiguous measurements of the cooling

effect of a laser beam on an atomic beam. We hope that this will result

in the first demonstration of the ability to perform such cooling. Once

this is accomplished, we will study various methods for improving cooling

efficiency, such as application of magnetic fields, use of circular

polarized light, and driving rf transitions between the ground hyperfine

states to avoid optical pumping problems.

We will also refine our optical pumping calculation so that it

treats strong laser fields and atomic coherences more realistically. We

hope that this will provide us with a good theoretical discription of

what happens in the experiments and will guide the development of the

experimental program.

In summary, our immediate goal is to use lasers to significantly

slow a neutral atomic beam and to apply this to the trapping of neutral

atoms in electromagnetic fields. We hope that this will find application in spectroscopy, standards maintenance, atomic physics, fundamental

constants and electrical measurements.

54
FUNDAMENTAL CONSTANTS DATA CENTER

(B.N. Taylor)

Objectives

The objectives of this project are to provide an international information center within the U.S. for work in the general area of precision

measurements and fundamental constants, to analyze the consistency of

measured values of the fundamental constants that are obtained from different scientific fields, and to obtain recommended values of these con- stants for international use.

The close relationships that exist between the fundamental constants

and precision measurements, basic measurement units, fundamental physics,

and state-of-the-art measurement technology makes the subject a natural

one for NBS to be deeply involved in. One of the purposes of this project

is to provide assistance and guidance in the general area of precision

measurements and fundamental constants for both NBS staff and university

scientists, and in particular, to advise them as to which experiments should

be carried out and what work is currently underway in various laboratories

throughout the world.

Self-consistent “best values" of the fundamental constants, obtained

by means of least-squares adjustments, are required for a variety of purposes in science and technology; for example, in accurate calculations of

the energy levels of atoms that are of importance in nuclear fusion, or

for critical comparison of theoretical calculations with experiment.

Furthermore, as the basic invariants of nature, they can be expected to

form the basis for a system of reproducible, artifact-independent measurement units. Such a system is the ultimate long-range goal of metrology.

Current Activities

Current activities in the precision measurement-fundamental constants

(PMFC) field 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; (3) participating in the work of national and international

groups (for example, the CODATA Task Group on Fundamental Constants and

the NAS/NRC Committee on Fundamental Constants); (4) publishing the

quarterly "Preprints on Precision Measurement and Fundamental Constants"

for the OSRD (this publication lists preprints as well as reprints of

PMFC papers); (5) attending and organizing national and international

conferences on PMFC and visiting laboratories carrying out work in this

field; (6) serving as an editor of Metrologia in the area of Electrical

Measurements and Fundamental Constants; (7) carrying out collaborative

work with Soviet colleagues under the joint NBS-Gosstandart cooperative

agreement in metrology; and (8) answering numerous inquiries from both

within and without NBS relating to the PMFC field.

55
Accompl i shments

The following was achieved during FY 80: (i) Published four quarterly issues of Preprints on Precision Measurement and Fundamental Constants (PPMFC) ; (ii) Responded to numerous written and oral inquiries

regarding the fundamental constants; (iii) Revised the Table of Physical

and Numerical Constants for the 1980 Review of Particle Properties that

was prepared by the Particle Data Group and published in Rev. Mod. Phys.

52 , Part II, SI (1980); (iv) Attended meetings of the NAS/NRC Committee

on Fundamental Constants in April and August, mainly to help plan a report on the PMFC field to be written by the Committee. Its purpose

will be to demonstrate to various U.S. Government funding agencies the

importance of PMFC work to all of science and technology; (v) Attended

a meeting of the CODATA Task Group on Fundamental Constants to discuss

the plans for the 1981 least-squares adjustment (see below); (vi) Visited

several laboratories to discuss on-going PMFC research. The organizations visited (and the quantities being measured) included the University

of Washington (a

1*1

, m /m ) ; Colorado State University (Lamb shift, R ); G p G oo Stanford University (h/m ); University of Virginia (G); and PTB (N., y , G M p

SI Q, a); (vii) Participated in the annual meeting of the NSF Interagency

Atomic and Molecular Physics Group to represent NBS 1 interests in this

field as it relates to PMFC; (vi i i ) Continued organizing the Second

International Conference on Precision Measurement and Fundamental Constants (PMFC-II) to be held at NBS, Gaithersburg, June 8-12, 1981. A

mailing list was generated, several thousand first- announcement brochures

were sent out, the three organizing committees were completed, funds were

solicited from a number of organizations, the technical program was developed, speakers. were invited to give review talks, etc; and (ix) Continued to collaborate with E.R. Cohen, Rockwell International, on the

1981 least-squares adjustment of the fundamental physical constants which

is being prepared under the auspices of the CODATA Task Group on Fundamental Constants. The first draft of the 1981 adjustment should be

ready for review in April 1981 and the final version by the end of 1981.

International adoption by CODATA is expected in early 1982.

Future Plans

Plans for FY 81 include continuing the work carried out in FY 80:

(i) The quarterly PPMFC will be published as usual; (ii) inquiries will

be responded to as received; (iv) the May NAS/NRC meeting will be

attended, and specific contributions to the NAS/NRC report will be

prepared and submitted to the Committee Chairman; (v) and (ix) the

June CODATA meeting will be attended, and the draft adjustment that will

be prepared in the first half of FY 81 will be discussed. Based on these discussions and the new results reported at PMFC-II, the adjustment will be revised to final form by the end of 1981; (vi) laboratory

visits will continue as convenient; (vii) the 1981 NSF Interagency Group

meeting will be attended; and (vi i i ) the organizational work for PMFC-II

will be completed, the Conference held, and work begun on editing the

Conference Proceedings.

56
PRECISION MEASUREMENT GRANTS

(NBS Precision Measurements Grants Committee; B.N. Taylor, Chairman)

Objectives

The annual objectives are to award two new Precision Measurement

Grants of $25K (renewable for two additional years at the option of

NBS), and to renew four existing Grants. These Grants are awarded to

scientists in academic institutions in order to (i) promote and

encourage fundamental research in the field of measurement science in

colleges and universities, and (ii) foster contacts between NBS scientists and those researchers in the academic community who are actively

engaged in such work.

The importance of research in the precision measurement-fundamental

constants field has been covered in the project report entitled FUNDAMENTAL CONSTANTS DATA CENTER and the reader is referred there. It should

be noted that while NBS has a strong interest in this area and much

experimental work underway, it cannot do it all - there is much expertise

and relevant work in the colleges and universities. It is the purpose

of this project to tap this reservoir by awarding grants to a selected

number of outstandingly qualified, creative experimentalists. Only

those individuals working in areas of immediate or potential future

benefit to ongoing NBS programs are chosen as grantees. Thus, the work

carried out by the Grant recipients serves to compliment the efforts

of the Bureau's own staff in closely related areas, and thus to increase

their productivity. Selection is based primarily upon the originality

of the work proposed as described in formally submitted proposals.

Current Activities

There is a great deal of latitude in the kind of research which may

be considered for support under the Precision Measurement Grants program.

The key requirement is that it generally support NBS work in the field of

measurement science. This work includes experimental and theoretical

studies of fundamental physical phenomena which may lead to improved or

new measurement methods and standards; the determination of important

fundamental physical constants; and general research and development

on basic measurement techniques and instrumentation.

To simplify the proposal writing and evaluation process, candidates

are first 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 threeyear 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

senior university professors) to submit more detailed proposals. The

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

the two Grantees are finally selected. The criteria used in evaluating

the preproposals and full proposals include the importance of the

57
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 80. Proposals were openly solicited via an advertisement in Physics Today,

announcements in appropriate trade journals and newsletters, and the

mailing of a brochure to all of the college and university physics

departments in the U.S. (about 950). Proposals were received from 29

candidates, seven of whom were chosen to submit final, full proposals.

The two grantees selected from these seven were:

William C. Oelfke, University of Central Florida

Proposal Title: Quantum limited measurements of a harmonic oscillator

William H. Wing, University of Arizona

Proposal Title: Electrostatic trapping of neutral

atomic particles

Oelfke will explore experimental methods of evading the quantum

limited "back-action" of measurement. To be examined are alternatives

to standard measurement schemes designed to measure harmonic oscillator

observables which commute exactly (or approximately) with the harmonic

oscillator Hamiltonian and are not limited by the Heisenberg uncertainty

relation. Such measurement techniques "evade" or balance-out back action

on the measurement of the oscillator. The work relates to the detection

of gravitational waves and determining the quantum limit to measurement.

Wing will attempt to harmonically trap and cool excited neutral

atoms having positive Stark energies in an appropriate static, non- uniform (i.e., quadrupole) electric field. Potential benefits are a new means of high-resolution spectroscopy of such diverse systems as metastable (n=2) hydrogen and positronium atoms, Rydberg atoms, polar

molecules, development of frequency reference devices, etc. The initial

effort will be to detect trapped sodium Rydberg atoms to demonstrate the

correctness of the basic principles.

The following four $25K Grants were also renewed during FY 80:

C.W.F. Everett, Stanford University (Studies of the London Moment

Leading to a Precise Determination of h/m ); R.C. Ritter, University

of Virginia (Precision Mechanical Rotations for Fundamental Measurements); W.C. Sauder, Virginia Military Institute (Precise Determination

of the Gas Constant); and C.E. Weiman, University of Michigan (Measurement of Fundamental Constants Using Three-Level Resonances in Hydrogen).

For FY 80, the NBS Precision Measurement Grants Committee consisted of

Drs. Deslattes, Hall, Taylor and Wineland; the Outside Advisory Committee

of Professors Geballe, Kleppner, Rich and Robinson.

58
Also during FY 80, visits were made to a number of Grant recipients

to see and discuss their work first-hand. These included R.S. Van Dyck,

University of Washington; W.M. Fairbank, Colorado State University;

C.W. F. Everett, Stanford University; and R.C. Ritter, University of

Virginia.

Finally, discussions were held with NSF to see if there were any

possibility of that agency supporting the NBS Precision Measurement Grants

program so that it might increase in size. A very positive response was. received and a formal proposal requested. After talking with a number

of past Grantees and members of the two Committees, the following course

of action was decided upon: to request that the NBS Director increase

the level of NBS support so that each new Grant starting in FY 81 would

be in the amount of $30K to partially correct for inflation; and to re- quest sufficient funds from NSF so that the number of new Grants each

year could be doubled to four. (This implies 12 $30K Grants in effect

by FY 83, compared with the present six $25K Grants.)

Plans

FY 81 plans naturally focus upon awarding at least two new $25K

Grants and renewing the four existing $25K Grants by 30 September 1981.

However, every effort will be made to increase the size of the program

effective FY 81 as outlined above. To this end, a formal request will

be sent to the NBS Director and a formal proposal to NSF. Also, visits

to Grant recipients will continue if convenient (i.e., if they can be

accomplished in conjunction with other travel); and a number of grantees

will be encouraged to submit papers and to attend the Second International

Conference on Precision Measurement and Fundamental Constants to be held

at NBS in June 1981.

59
DISSEMINATION SERVICES: SUPPORT AND OPERATION INCLUDING MAP DEVELOPMENT

(N.B. Belecki, D.E. Bruch, C.R. Childers, L. R. Cooke, R.F. Dziuba,

R.C. Fronk, C.R. Levy, T.P. Moore, D.D. Prather, T.E. Wells,

E.S. Williams, A.R. Wise)

Objective

The overall objective of this project is to enable all measurements

of electrical quantities performed in the United States to be made in

terms of the U.S. legal electrical units at the needed levels of accuracy.

The legal units are provided to the user community by means of reimbursable

calibration and MAP services listed in NBS Special Publication 250 and

its appendices. The timeliness and adequacy of these services must be

ensured by research and development work on new measurement techniques,

standards, and apparatus, since the quality of both MAP's and calibrations

ultimately hinges on the basic metrology competence of the NBS.

The outputs of this project are used directly by the metrology com- munity — the major standards laboratories of industry, government, and

the academic world — and indirectly through them by industry for the

quality control of and maintenance of electronic products, for the control

of manufacturing processes in basic industry, for the support of research

and development aimed at the improvement of instrumentation, and in

response to Federal and state regulatory requirements, such as safetybarrier crash tests performed by automobile companies in compliance with

National Highway Traffic Safety Administration (DOT) regulations. In

large measure, 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 our country's sophisticated measurement capability, reflected in automatic test equipment (ATE) systems

and high-quality electronic instrumentation. Likewise, advances and

progress in these areas have been high because they have not been limited

by measurement constraints such as the nonavailability of electrical

instruments of adequate accuracy. This condition can only occur if

NBS maintains a strong R&D program to ensure the availability of adequate

electrical standards for the instrumentation industry.

Current Activities

The measurement services offered by NBS in the electrical area include the calibration of primary standards of alternating current and

voltage, impedance at audio frequencies, direct voltage, and resistance

at direct current, as well as MAP services for capacitance, dc voltage,

and resistance. Some measurements are also done on ac ratio standards

of the highest accuracy.

Measurement-services support activities fall into two broad categories: the development of improved measurement methods and standards

(including MAP development work), and the automation of the measurement

systems used to perform both calibrations and MAP activities. Work in

the former category is directed toward improvement of the processes by

which the ohm is maintained and scaled, and of both ac and dc voltage

60
and current measurement and dissemination techniques. In the automation

area, objectives are to complete automation of the systems used for ac-dc

difference measurements on thermal voltage converters (ac V&I), resistance measurements through 10 11 ohms, and standard cell calibrations.

I In FY 80, as a result of the recent ZBB decisions, three senior

staff people retired without replacement, and a senior technician who

also retired was replaced by a recruit from within NBS. In order that

critical functions could go on uninterrupted, much of the remaining

staff's time was consumed in training by those who left. In particular,

Dziuba and Moore received crucial training from Wells and Cooke on the

1 maintenance and dissemination of the ohm. Belecki and Cage received

some instruction in the area of ac-dc current and voltage measurements

i and standards at the hands of Williams. Also, efforts to find a suitable

replace for R. Kleimann, who left NBS last year, are continuing.

j Accompl ishments

| In FY 80, 23 MAP transfers and approximately 1600 calibrations of

ji basic standards were performed for about 170 companies and 11 government

agencies for a total income of about $355K for the year. The majority

of these companies are represented by the National Conference of Standards

, Laboratories (NCSL), which is a major source of information for planning

purposes, as well as a mechanism (through its technical committees) for

disseminating electrical metrology information. These services support

basic research and development work throughout NBS as well.

The self-balancing potentiometer developed last year for the comparison of thermal voltage and current converters (TVC) was incorporated in

the automated TVC system and support software produced to enable the

system to make square- law tests and ac-dc difference determinations automatically for any single range of voltage but over a broad frequency

range. The system is in the final stages of testing before its regular

use in the calibration activity.

A new commercial instrument for the measurement of alternating

voltages at audio frequencies at state-of-the-art accuracy levels (potentially better than ten ppm in the frequency range from 50 to 100 Hz)

is being evaluated. This instrument is based on a Wilkins mul ti-junction

thermo-element which may be suitable for primary standards applications

in general, and may offer an opportunity to upgrade our measurement capability to support new solid-state converters being incorporated in the

latest electronic instrumentation.

A set of commercial, high accuracy thermal converters was evaluated

for the International Bureau of Weights and Measures (BIPM) to assist

in the establishment of an ac voltage measurement and standards capability

there. The evaluation identified frequency-response anomalies which were

removed by the modification of the unit using a different type of resistor having little inductance.

61
In the area of MAP development, analysis of transport standard

performance data was begun by C. Reeves and K. Kafadar of the Statistical

Engineering Division. The purpose of this activity is to develop the

statistical base to permit fully automatic data analysis and computerized

decision-making in the production of volt MAP test reports. The present

study will serve as a pilot to future similar studies in other measurement areas and will lead to better documentation of uncertainties and the

data from which they are computed.

A number of new solid-state voltage reference devices were evaluated

for stability in the laboratory. This was done as a part of an effort

to develop a voltage MAP service to cover the commonly measured voltage

range from 0 to 1000 volts dc. If they prove successful, these devices

will be used as transportable ten- volt standards in conjunction with

existing transportable ratio dividers to provide NBS with the capability

of verifying another laboratory's measurement process over the above

range at sub-ppm accuracies.

Two new regional MAP's were started: one in the Los Angeles area

and the other in Northern California. The initial transfers of these

groups were underway at the close of the fiscal year. An additional

group was organized in the Oregon area. Nine new individual companies

were also added, bringing the total number of organizations served in

the voltage area to forty-four. In connection with this activity,

twenty-plus companies received consulting help from NBS, generally in

the areas of data analysis or reduction and low-level dc measurements.

Future Plans

Objectives for FY 81 include: a) the publication of two Technical

Notes regarding voltage and resistance measurements, standards, and

MAP's; b) the completion of automation of the ampere-turn balance for

resistance measurements; c) the completion of a statistical data base

on the performance of transportable voltage standards to enable automatic data checking and uncertainty computations for voltage MAP's;

and d) the design and construction of a microprocessor-based crossbar

switch controller to facilitate automation in the Volt Facility and

the resistance laboratory. Items b) and d) above are contingent upon

the addition to staff of an automation expert to replace R. Kleimann,

who left NBS in FY 79.

62
Publ i cations

V.E. Bower and R.S. Davis, The Electrochemical Equivalent of Pure Silver —

A Value of the Faraday, J. Res. NBS (U.S.) 85, No. 3, 175-191 (1980).

R.D. Cutkosky, An Automatic Resistance Thermometer Bridge, Conference on Precision Electromagnetic Measurements, 23-27 June 1980, Braunschweig, FRG,

p. 193, IEEE Catalog Number 80CH1497-71M.

O. P. Galkhova, T.H. Rozdestvenskaya, H. Hirayama, S. Harkness, P. Martin,

F.L. Hermach, E.S. Williams, An International Comparison of Thermal

Converters as AC/DC Transfer Standards, Conference on Precision Electromagnetic Measurements, 23-27 June 1980, Braunschweig, FRG, p. 343, IEEE

Catalog Number 80CH1497-71M.

James T. Hall, Louis B. Holdeman, and Robert J. Soulen, Jr., Microwave

Enhancement of Superconductivity in Aluminum Tunnel Junctions, Phys. Rev.

Lett. 45, No. 12, 1011 (1980).

Louis B. Holdeman, Magnetic Torque Calculations for the Gyroscope Relativity Experiment, NBS Interagency Communication (NASA Government Order

H-27908B) (February 1980).

P. T. Olsen, W.D. Phillips, and E.R. Williams, A Proposed Coil System for

the Improved Realization of the Absolute Ampere, J. Res. NBS (U.S.) 85,

No. 4, 257-272 (1980).

P.T. Olsen, M.E. Cage, W.D. Phillips, and E.R. Williams, The Realization

of the Ampere at NBS, Conference on Precision Electromagnetic Measurements,

23-27 June 1980, Braunschweig, FRG, p. 43, IEEE Catalog Number 80CH1497-71M.

R.M. Schoonover, R.S. Davis, and V.E. Bower, Mass Measurement at the

National Bureau of Standards: A Revision, Science 207 , pp. 1347-1348

(March 1980).

R.M. Schoonover, R.S. Davis, R.G. Driver, and V.E. Bower, A Practical

Test of the Air Density Equation in Standards Laboratories at Differing

Altitude, J. Res. NBS (U.S.) 85, No. 1, 27-38 (1980).

E. So and J.Q. Shields, Losses in Electrode Surface Films in Gas Dielectric Capacitors, IEEE Trans. Instrum. Meas. IM-28 , No. 4, 279 (1980).

E.S. Williams, A TE Comparator for Automatic AC/DC Difference Measurements, Conference on Precision Electromagnetic Measurements, 23-27 June

1980, Braunschweig, FRG, p. 349, IEEE Catalog Number 80CH1497-71M.

63
Invited Tal ks

Robert D. Cutkosky, "An Automatic Resistance Thermometer Bridge," Division

of Electrical Engineering, National Research Council, Canada, 14 May 1980.

Edwin R. Williams, "Testing Theories of Physics via Precision Magnetic

Measurements: Determination of the Proton Gyromagnetic Ratio and the

Absolute Ampere," MIT Francis Bitter National Magnet Laboratory, Cambridge,

MA, 19 May 1980.

64
Technical and Professional Committee Participation and Leadership

N.B. Belecki, member, ANSI C39/100, American National Standards Institute Committee on Electrical Standards, Instrumentation and Devices; and

Subcommittee on Reference Voltage Devices.

N.B. Belecki, member. National Conference of Standards Laboratories Automation Committee.

N.B. Belecki, member. National Conference of Standards Laboratories, C002,

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.

N.B. Belecki, 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, Calibration Task Group, Industry/Joint Services

Automation Test Project.

N.B. Belecki, member, U.S. Advisory Committee, IEC SC/13B, International

Electrotechnical Commission Committee on Indicating Instruments.

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).

R.D. Cutkosky, member, TC-2, DC and LF Standards, Instrumentation and

Measurements Committee of the Instrumentation and Measurement Society,

Institute of Electrical and Electronics Engineers (IEEE).

R.D. Cutkosky, Assistant Secretary, IEC TC25, International Electrotechnical Commission Technical Committee on Quantities, Units, and Their

Letter Symbols.

W.G. Eicke, Jr., member, ANSI C-18, American National Standards Institute

Committee on Specifications for Dry Cells and Batteries.

G.M. Free, member, ASTM E7, American Society for Testing and Materials

Nondestructive Testing; ASTM E7.07, Electromagnetic Methods; and E7.09,

Materials Inspection and Testing Laboratories.

G.M. Free, member, American Society for Nondestructive Testing, Electrical and Magnetic Methods Committee.

G.M. Free, Secretary, American Society for Nondestructive Testing, Research Division, Research Promotion Committee.

65
G.M. Free, member, American Society for Nondestructive Testing, Electronic Components Committee.

B.N. Taylor, member, Advisory Committee on Fundamental Constants of the

Division of Chemistry and Chemical Technology, Numerical Data Advisory

Board, National Academy of Sciences/National Research Counci 1 /National

Academy of Engineering.

B.N. Taylor, Co-editor, Preprints on Precision Measurement and Fundamental Constants, Office of Standard Reference Data.

B.N. Taylor, Chairman, NBS Precision Measurement Grants Committee.

B.N. Taylor, NBS representative, Consultative Committee on Electricity

(CCE), International Committee on Weights and Measures.

B.N. Taylor, Editor, Metroloqia , in area of Fundamental Constants and

Electrical Measurements.

B.N. Taylor, member, National Science Foundation (NSF) Interagency Atomic

and Molecular Physics Group.

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 Working Group)

OIML (International Organization of Legal Metrology) Pilot Secretariat

13, Measurement of Electric 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 Sponsor's Delegate, Executive Committee, Conference on Precision Electromagnetic Measurements.

B.N. Taylor, member, TC-2, DC and LF Standards, Instrumentation and

Measurements Committee of the Instrumentation and Measurement Society,

Institute of Electrical and Electronics Engineers (IEEE).

B.N. Taylor, member, Editorial Review Committee, Transactions on Instrumentation and Measurement, Institute of Electrical and Electronics

Engineers (IEEE).

T.E. Wells, member, RCL Measurement Subcommittee of the Power Instrumentation and Measurement Committee of the Power Engineering Society, Institute of Electrical and Electronics Engineers (IEEE).

E.R. Williams, member, ANSI MD105, American National Standards Institute

Committee on Medical Electronics.

66
Collaborations, Consulting, Miscellaneous Activities

N.B. Belecki consulted throughout the year with the staff of the Office

of Measurement Services on MAP activities at NBS and in industry. He

also represented OMS during the year in four meetings to advance regional

MAP activities in Portland, Pittsburgh, San Francisco, and upstate New York.

N.B. Belecki was one of a team of four NBS staff sent to consult to the

ORTON Foundation, a non-profit manufacturer of pyrometric cone standards

for the ceramics industry. ORTON requested assistance in re-establishing

their temperature standards and upgrading their measurement instrumentation.

N.B. Belecki and R.F. Dziuba consulted with D. Ober and colleagues from

the Center for Building Technology in support of their establishment of

apparatus for the precise measurement of the thermal conductivity of

building insulators.

N.B. Belecki participated in a panel workshop on Measurement Assurance

Programs at the annual meeting of the National Conference of Standards

Laboratories.

M.E. Cage collaborated with R.S. Davis of the Length and Mass Measurements and Standards Division (523) in obtaining analytical solutions

to the equations of motion of a single-pan balance for the freely-swinging,

the underdamped, the critically damped, and the electronical ly-servoed

cases.

M.E. Cage, R.F. Dziuba, and B.F. Field are collaborating with P.J. Stiles

of Brown University, P. Roitman of the NBS Electron Devices Division (721),

and members of the Mask Facility Group at the Naval Research Laboratory,

in the design and fabrication of mask sets for Hall devices.

M.E. Cage, R.F. Dziuba, and B.F. Field are collaborating with B.D. McCombe,

R.J. Wagner, and R. Clement of the Naval Research Laboratory in an experimental investigation of quantized Hall resistance in MOSFET devices using

the NRL High Magnetic Field Facility.

M.E. Cage, R.F. Dziuba, and B.F. Field are col laborating with S.M. Girvin

of the Surface Science Division (541) and R.W. Rendell of the Radiation

Physics Division (533) on the theoretical considerations in the quantized

Hall resistance experiment.

G. Costabile collaborated with R. L. Kautz of the Electromagnetic

Technology Division (724) on the application of arrays of hysteretic

junctions to a zero-bias Josephson voltage standard.

R.F. Dziuba consulted with Hughes Aircraft Co. on problems involving

qualification of high-power precision resistors for inertial guidance

appl i cations.

67
R.F. Dziuba provided consulting support to approximately twenty-five

companies on problems in precision resistance measurements and standards

appl i cations.

W.G. Eicke has consulted with personnel in the Office of Energy-Related

Inventions in the area of electrochemical power.

W.G. Eicke is collaborating with E. Escalante of the Chemical Stability

and Corrosion Division (561) on improvement of electrical measurements

in the field of corrosion.

B.F. Field and L.B. Hoi deman are collaborating with J. Leslie, C. Waters,

and T.D. Epley of Superconducting Technology, Inc., on the development

of a portable, reliable, and easy-to-use 1-ppm commercial Josephson-effect

voltage standard.

G.M. Free is collaborating with L. Schwartzendruber of the Metal Science

and Standards Division (564) on a program to correlate electrical con- ductivity (determined using eddy-current testing) with the tensile

strength of aluminum plate.

L.B. Holdeman and J. Toots are collaborating with P.N. Peters of NASA's

Marshall Space Flight Center in an investigation of microbridge- type

Josephson junctions for voltage standard and radiation detection applications.

L.B. Holdeman and G. Costabile are collaborating with R.J. Soulen, Jr.,

and D. Van Vechten of the Temperature and Pressure Measurements and

Standards Division (TPMSD, 522) in an investigation of low-T

c superconductors (Ir, AuA 1 2 , Auln2 ) and low-T

c superconducting devices.

L.B. Holdeman collaborated with R.J. Soulen, Jr., and J.T. Hall (TPMSD,

522) in an investigation of enhancement of the superconducting properties

of thin aluminum films by microwave radiation.

L.B. Holdeman and T.J. Jach of the Surface Science Division (541) are collaborating on an investigation of electron beam assisted oxidation

of metal surfaces and on an investigation of LEIT (light emission by

inelastic tunneling) junctions.

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 H. Holt (Quantum Metrology Group)

on problems related to dynamic Stark effects in multi photon spectroscopy

and long-time optical pumping in strong laser fields.

J.E. Sims is collaborating with U. Bertocci of the Chemical Stability and

Corrosion Division (561) on development of Fourier Analysis Program to

process electrochemical data in corrosion studies.

68
B.N. Taylor is collaborating with E.R. Cohen, Rockwell International,

and the CODATA Task Group on Fundamental Constants, on a new leastsquares adjustment of the fundamental physical constants to be completed

in 1981 for international adoption by CODATA in early 1982. This work

is also part of a collaborative effort with Soviet scientists from VNIIM

under the Joint NBS-Gosstandart collaboration in metrology.

B.N. Taylor is serving on the NML's Merit Pay Performance Review Board, and

served on the NBS Director's Task Force on Calibration and Related Measurement Services.

B.N. Taylor was a member of the IEEE Field's Award Committee that selected

the recipient of the 1981 Harry Diamond Award. He also served on the

committee which selected the 1980 Helmholtz Prize recipient.

B.N. Taylor organized and chaired a symposium "Standards for Physical

Measurement" at the April 1980 Washington Meeting of the American Physical

Society. The symposium was sponsored by the APS Division on the Applications of Physics.

B.N. Taylor is Chairman of the Conference Committee which is organizing

the Second International Conference on Precision Measurement and Fundamental Constants to be held at NBS/Gaithersbug, June 8-12, 1981.

B.N. Taylor serves as a member of the Editorial Review Board of the IEEE

Transactions on Instrumentation and Measurement, as an Editor of Metrologia

in the area of Electrical Measurements and Fundamental Constants, and

as Editor with D.R. Lide of NBS' quarterly Preprints on Precision Measurement and Fundamental Constants.

B.N. Taylor is NBS representative to and member of the Executive Committee

of the Conference on Precision Electromagnetic Measurements. He is also

one of NBS' representatives to NSF's Interagency Atomic and Molecular

Physics Group.

B.N. Taylor compiled the Table of Physical and Numerical Constants for

the 1980 Review of Particle Properties compiled by the Particle Data

Group.

J. Toots made numerous thin-film depositions as an informal service to

various research groups within NBS; e.g. sputtered conductive coatings

onto Ce02 samples for a fuel cell study program (J.R. Bethin, C.K. Chang;

561); sputtered and evaporated refractory films onto single-crystal

sapphire for applications in high-temperature expansion coefficient

measurements (L. Guidner, R. Edsinger; 522); deposition of gold contacts

onto carbon wafers for low- temperature thermometry (H. Marshak,

R. Soulen, B. Dove, 522).

J. Toots is collaborating with D.W. Braudaway, Sandia, on the implementation of a Josephson voltage standard at Sandia by producing Josephson

tunnel junctions for Sandia.

69
E.R. Williams, P.T. Olsen and W.D. Phillips are collaborating with K.A.

Krasnov, VNIIM, USSR, on the theoretical investigation of various new techniques for realizing the ampere using superconductivity and/or

cryogenics. This is part of a collaboration between NBS scientists and

Soviet scientists from VNIIM under the joint NBS-Gosstandart collaboration in metrology.
General Interest Highlights

The following is a list of the Division's accomplishments reported during

the past year in the general interest publications indicated.

1. Symposium on Eddy Current Characterization of Materials and Structures

G. Birnbaum and G. Free (NBS Monthly Highlights, October 1979).

2. Recipients Selected for Two New FY 80 Precision Measurement Grants - B.N. Taylor (NBS Monthly Highlights, October 1979).

3. Codata Task Group on Fundamental Constants Meets at NBS - B.N. Taylor

(NBS Monthly Highlights, November 1979).

4. The Precisely Precessing Proton - M. Baum (NBS Dimensions, November

1979).

5. In The Pursuit of Precision, NBS Grants for Research on Fundamental

Constants (NBS Dimensions, January/February 1980).

6. Eddy Current Imaging System - B.F. Field (NBS Dimensions, January/

February 1980).

7. Fine Structure Constant Determined to an Accuracy of 1 in 10 to the

7th - P.T. Olsen and E.R. Williams (National Measurement Laboratory

1979 Technical Highlights, NBS-SP 572).

8. Standards for Physical Measurement Symposium Held - B.N. Taylor

(NBS Monthly Highlights, June 1980).

9. Fundamental Constants Data Center - B.N. Taylor (NSRDS Reference

data report, May/June 1980).

71
i I I fl


TEMPERATURE AND PRESSURE MEASUREMENTS AND STANDARDS DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1980

1 . Overview

During the past year, the Temperature Measurements and Standards

Division was renamed the Temperature and Pressure Measurements and

Standards Division, (TPMSD) reflecting the incorporation into the Division

of the Pressure Group from the Thermophysics Division. This report will

include the past year's activities of both groups.

The Temperature Group pursues two major objectives: the provision

of calibration services, instruction, and consultation in precision

thermometry; and research intended to help replace the International

Practical Temperature Scale of 1968. The past year saw excellent progress

in both areas.

The Pressure Group has similar objectives. It provides the US

technical community with pressure calibration, instruction in precision

pressure measurement and consultation on pressure measurement problems.

Unlike the temperature counterpart, there is no international practical

pressure scale. However, there have been international comparisons of

high-quality manometers and piston gages.

Requests for precision temperature calibrations continued at a level similar to that of the previous year, some 1500 calibrations

costing an aggregate of approximately $150,000. In response co these

requests, the Division continued to provide a full-time calibration

person in both the Platinum Resistance Thermometry and the Li quid- inGlass laboratories and a half-time person in the Thermocouple Thermometer

Calibration Laboratory. Progress on the development of a computer-based

calibration apparatus continued to be satisfactory; this system is being

assembled and tested as part of the Measurement Assurance Program in

low-temperature thermometry.

The Precision Thermometry Seminars have been consolidated as a twice-yearly , one-week instructional session devoted to lectures and

laboratory work in platinum resistance, thermocouple, liquid- in- glass,

and thermistor thermometers. During the past year, the instruction has

been integrated into a single course rather than three separate parts,

and the attendance has been limited to 25 per session to avoid overcrowding.

Twelve reports on progress in fundamental thermometry experiments

within the Division were submitted to the 13th meeting of the Consultative

Committee for Thermometry, reflecting the impending replacement of the

1968 International Practical Temperature Scale. These can be grouped

into work on thermodynamic measurements of temperature, development of new or improved temperature reference devices, and development of new or improved standard thermometers.

Work in thermometry using funds transferred from other government

agencies continued to be done by the Division staff, although the proportion

72
of such work necessarily was reduced by the need to contribute to NBSwide special programs.

Increasingly, the TPMSD is asked to provide instruction to staff

members from less-well developed countries and to provide facilities for

colleagues of the Division who come to NBS from other national laboratories.

Within the past few years, we have worked with personnel from Australia,

Canada, Egypt, Korea, Italy, Brazil, Japan, West Germany, United Kingdom,

Saudi Arabia, Mexico and others.

The past year's work for the Pressure Group included some 80 calibrations

of piston gages, pressure transducers, and manometer systems, costing an aggregate $50,000, as well as the introduction of a service in ion gage

calibrations; the presentation of two Precision Pressure Seminars to a total of 19 participants; intercomparisons of both pressure and vacuum

standards with other national laboratory staffs; a modest amount of work

for other government agencies; and research in both pressure and vacuum

physics.

During the past year, a significant beginning was made in the study

of time-dependent temperature and pressure measurements. This project

grew out of a budget intiative presented in various forms over the past

several years. Currently staffed by a former NBS Postdoctoral Fellow

who is an expert in laser physics, this project has the potential for

uniting the metrology of temperature and pressure in an experimental

program leading to much-needed services in the time-dependence of temperature and pressure sensors.

The Division lost the services of five individuals during the past

year—Dr. H.H. Plumb, an expert in thermodynamic thermometry, and Mr.

J.L. Riddle, an expert in resistance thermometry, by retirements; and

Dr. D.D. Thornton, Mr. J. Hines, and Ms. D.L. Foster through resignations.

II. Technical Activities

This Section is composed of reports of laboratory work organized by

NBS Task designation. The discussion is based upon reports submitted by

individual staff members. Each subsection will include the names of

contributing staff, to enable the reader to communicate in more detail

with the appropriate scientist.

A. Task 111.21 —Dissemination of Temperature and Pressure Units

1. Platinum Resistance Thermometry (Dr. George T. Furukawa)

a. Standard Platinum Resistance Thermometer Calibration

During the period August 1, 1979, to August 1, 1980, the following

calibrations were performed by Mr. W.R. Bigge (with assistance from Mr.

Riddle) for a variety of industrial and governmental laboratories:

SP-250 Category No.

7.3B long stem 39

7.3C long stem 40

7.3E 4

73
The fees for these calibrations amounted to about $60,000. In addition,

eleven calibrations were performed on in-house thermometers.

A new bridge for the SPRT calibration laboratory was tested. A

thermostated reference resistor for the bridge is partially assembled.

A system for switching test SPRT's to the bridge has been wired. This

assembly work is being carried out by me with the help of Mr. Juan M. Figeroa, Guest Worker from Mexico, since Mr. Bigge is completely involved

with calibration.

During the coming year, we expect to continue assembly of the

Guildline bridge system for long-stem SPRT calibrations. We expect also

to begin combining the new computer-controlled measurement system (see

Section B4) and the new self-balancing resistance bridge of Cutkosky

(see Section B2) to renovate the capsule PRT calibration facility.

b. Measurement Assurance Program (MAP) in SPRT's

During FY 1980 SPRT MAP measurements for a pharmaceutical manufacturing

company were analyzed and reported; this company must control biological

processing temperatures. Their standards laboratory calibrates industrial

type PRT's as secondary standards in the range 0 to 122 °C at the level

of ± 0.01 °C accuracy to check the working thermometers. Considerable

consulting time was spent with them and their computation scheme and

calibration table output were reviewed before the MAP thermometers were

shipped to them. The MAP thermometers are now in the laboratory of an aircraft engine manufacturer, and a primary Department of Defense laboratory is next on the list.

c. American Society for Testing and Materials (ASTM) Work and Industrial

PRT Studies

I have been the secretary of the Resistance Thermometry Subcommittee

E-20.03 of the ASTM for the past five years. To work in other areas of

the ASTM Thermometry Committee, I have asked to be replaced, effective

at the next meeting in November 1980. In the meantime I agreed to be

the secretary of the Newer Thermometers Subcommittee E-20.06 ( B.W.

Mangum, Chairman), where the amount of time required as secretary will

be less than that involved as E-20.03 secretary. I will have more time

for writing and reviewing the hardware aspects of the industrial PRT

standards now being prepared. In April 1980, I arranged for the task

chairmen preparing different parts of the standard to work at the NBS

for two days in preparation for the June 1980 meeting in Chicago.

I have agreed to assist in the preparation of an ASTM resistance

thermometry book similar in scope to the thermocouple book STP 470A.

I will continue to be involved in the Temperature Fundamentals

Subcommittee E-20.07 for which I will prepare the first draft of a metal

fixed-point standard.

74
The design of the ASTM round- robin measurements for determining the

measurement capabilities of industrial standards laboratories was changed.

The initial plan was to circulate stainless-steel-sheathed SPRT's. When

the SPRT's were checked for calibration after measurements by four

laboratories, the calibration had changed beyond the expected measurement

uncertainties of the laboratories. Although it will mean more NBS

calibrations, the SPRT's will be shipped back and forth between the NBS

and the participating laboratories so that any change in calibration

will be detected before the thermometer goes to the next laboratory. The

ASTM round- robin measurements are now in progress.

Twelve industrial PRT's from two manufacturers were tested for

stability after heat treating them at 480 °C for four hours and then

measuring their resistances at the TP of water, tin point, and zinc

point. Three sets of measurements show changes in the thermometer

calibration that range from 2 mK to over 0.02K, depending upon the

thermometer and temperature. Measurements on more thermometers are needed before any conclusion can be drawn about which thermometer design

yields the best stability.

A standard PRT encased in a stainless-steel sheath apparently

appears rugged to industrial thermometrists ; however, the thermometer is

actually as shock sensitive to calibration changes as the glass-sheathed

SPRT's. Since the sheath does not break, calibration changes that are much larger than those we have normally seen with glass SPRT's have been

experienced in the ASTM round-robin work. Since the glass-sheathed

SPRT's are very expensive, we may use selected industrial type PRT

elements assembled in glass sheaths for the ASTM round-robin work. A

few elements have been purchased for testing. It is hoped that glasssheathed thermometers will be handled more carefully. The data that we obtain will fill in some of the gaps in our knowledge of industrial PRT

characteristics.

2. Thermocouple Thermometry (Mr. George W. Burns)

a. Thermocouple Thermometer Calibrations

During FY 80, some 270 thermocouple thermometers of all types were

calibrated, at a total cost of $40,000, by M.G. Scroger.

Computer programs were developed that enable us to give calibration

tables at 1 degree (C or F; IPTS-48 or IPTS-68) intervals for both Type

R and Type B thermocouples. This service is now available to our calibration

customers with no increase in our calibration fees.

b. Consultations on Thermocouple Thermometry

Many telephone calls were received last year from scientists and

engineers desiring advice and information on thermocouple thermometry.

No effort was made to catalog or characterize these requests or others

75
received by mail or personal visit, since both the requests and the

effort needed to respond to them varied greatly. On the average, however,

one or two such requests were received each working day.

As part of our consultation activity, I made a trip to the Orton

Foundation in Columbus, Ohio as part of an NBS team to assist the Orton

personnel with a planned recalibration of the pyrometric cones which

they manufacture. A report giving comments and recommendations concerning

the production and calibration of pyrometric cones was perpared for

Orton and it may be consulted if more details are needed.

c. ASTM Activity

Several drafts of a test method for measuring the insulation resistance

of compacted insulated thermocouple materials were prepared and issued

for Subcommittee 04 and E-20 letter ballots. A final draft of a revision

to ASTM Test Method E-220 on the comparison calibration of thermocouple

was completed and issued for Society ballot.

Chapters 8 and 11 of ASTM Manual STP 470A were revised. The revised

manuscript was recently sent to the printer. The new publication will

be STP 470B and it should be available earlier next year.

3. Liquid-in-glass Thermometry (J.A. Wise)

Well over 1,000 calibrations of 1 i quid- in-glass and other loweraccuracy laboratory thermometers were performed during the past year.

The resulting fees totaled some $70,000.

Plans were initiated to upgrade certain of the calibration baths in

order to accommodate the increasing numbers of high-precision thermistors

and other types of secondary thermometers. The stability limit of the

present baths, several millidegrees, is not suitable for the more precise

of these thermometers.

4. Precision Thermometry Seminars (Calibration Staff)

During FY 80, two seminars were held. They were attended by a total of 47 scientists and engineers, representing three foreign countries,

six US utilities, four US government agencies, one university, and 23 US

corporations. The seminars have been consolidated into a single entity

this year, comprising four and one-half days of instruction in precision

thermometry with platinum resistance, thermocouple, liquid-in-glass, and

thermistor thermometers, followed by a discussion of new developments in

thermometry. The participants in the seminars are encouraged to bring

forward particular problems in temperature measurement within their own organization.

76
5. Piston Gages (Mr. J.C. Houck and Mr. Bernard E. Welch)

a. Piston Gage Calibrations

Routine calibration of piston gages within the range, 1.4 kPa to

420 MPa are provided by Walter Markus and Greg Driver. Mr. Markus is

responsible for instruments operated on oil and Mr. Driver is concerned

with those instruments that are used with gas. Mr. Welch contributes by

scheduling work, analyzing data, checking reports, handling test folders,

trouble shooting and assisting in unusual or complicated tests. Instruments

tested during the past year include some 75 piston gages, manometers,

barometers, dial gages, capacitance gages and various types of transducers.

The estimated income for the group last year was $50,000.

b. Piston Gage—Mercury Manometer Comparison

Work was begun with Dr. L.A. Guildner on the intercomparison of the

NBS gas thermometer mercury manometer with three (3) commercial piston

gages (transfer standards). This work should significantly reduce the

systematic uncertainties associated with the air dead weight piston

gages used as NBS standards. Presently, basic concepts are being

discussed and equipment ordered.

c. Air Piston Gage Quartz Standard

We have begun to set up a quartz check standard on a test bench

that is used for calibrating air piston gages. The instrument will be

used at 100 kPa to monitor the pressure system that provides routine

calibrations within the range 1.4 kPa to 4.2 MPa. This will also allow

us to observe the performance of this type of transducer over an extended

period of time. Mr. Fred Long has been working on the electronics,

after which the device will be installed.

d. Pressure Measurement Seminars and Consultations

Two pressure seminars were held this year, one in the spring and

one in the fall. The two day sessions were limited to a maximum of

eight students; but in the future, this restriction will be lifted. The

course of instruction covers NBS primary standards (calibration and use)

as well as secondary gages used in the field.

We consulted with industrial and other government scientists and

engineers concerning the choice and calibration of equipment for pressure

measurements from 1.4 kPa to 1400 MPa. This information was presented

by phone, letter, or directly to visitors to our laboratory at NBS.

e. Laboratoire National d' Essais (LNE, Paris) Pressure Gage

Intercompari son

An intercomparison was made with the NBS primary gas standard

piston gage (PG4) over the range 0.4 to 3.9 megapascals (58 to 565 psi)

77
and LNE's oil operated simple piston and cylinder transfer piston gage

through an oil -gas capacitance-detected interface. The agreement was within 10 ppm for the area calculation of the LNE gage by NBS and their

value for the area. A report is being prepared for publication.

f. PG4 replacement and calibration.

New piston and cylinders have been obtained and fall rates measured.

"D" measurements, (which are the coefficients for the change in effective

area as a function of jacket pressure), will be made by the Korean Guest

Worker Seung Woong Han. This gage will replace the gage used in the LNE

comparison.

g. 4K psi piston gage facility

A new facility is planned incorporating two similar controlled

clearance piston gages for operation on both oil and gas. It will be

James Houck's major activity for the next 2 or 3 years.

6. Low Pressure Transducers (Mr. Richard W. Hyland)

a. Calibrations of Low-pressure Transducers.

During the year to date, a total of 7 capacitance diaphragm transducers

have been calibrated (as well as three of our own), some of them several

times. In addition, we calibrated two low- range, ball -type, dead-weight

testers. The income from the calibrations has been about $6200. At

least 3 more calibrations are expected by the end of the year, with

about $3600 of associated income.

The ball gages will be mentioned separately, because of the time

and results. The gages were both the same models, and were calibrated

against the long-column manometer. Three calibrations were made on the

first and, on the second, differing numbers of points were taken on 12

different days, using both nitrogen and argon. Additional time was spent comparing piston gages (PG 14 and 15) against the manometer and

against the ball gage. The amount of time spent was large because

systematic differences between the manometer and ball gages were far

outside of their combined error bands, and, at the time, we were in the

process of assuring ourselves that the long-column manometer and the

associated data reduction procedures, put into operation only 3 months

before, were operating properly. After many discussions among ourselves

and with the manufacturer of the ball gage, we decided that our calibrations

were correct. These results were substantiated by the gage's owner, who

checked one of the ball gages against a tilting air gage. As a result,

the manufacturers revised their own calibration techniques (in essense

by adding another calibration point which they had previously deemed

unnecessary) to correct the situation. We expect to calibrate one of

the updated versions this fiscal year.

78
During the course of the ball gage studies, the long column manometer

was compared from 77 to 900 Torr using our own PG 14 and PG 15, as well

as an Australian standard piston gage. The overall uncertainty of the

manometer in this range is 13 ppm systematic and 50 ppm random, relative

to the dead-weight testers. This is somewhat better than our claims of

1/104. In addition, a series_of long-term zero drift tests were taken,

indicating a stability of 10 4 Torr over a period of days. One of the

outstanding uncertainties still associated with the manometer is that of

the speed of sound in mercury.

b. Characterization of Capacitance Diaphragm Gages

During the first quarter of the year a series of tests were conducted

by Anita Calcatelli, a guest worker from the Istituto di Metrologia "G

Colonnetti" (IMGC) in Italy, on 1 and 10 Torr capacitance diaphragm

transducers. These tests were intended to give information on zero drifts and the effects of cycling, both with heaters on and off, and to

indicate as well the effects of reference pressure. The data were

analyzed in a manner now considered somewhat unsatisfactory. Firm

quantitative conclusions have not yet been reached, except on the zero drift data. The latter data were the subject of a report by Calcatelli

to NBS. The zero drift studies do indicate that, for work which requires

the maximum sensitivity of the transducers, a warm-up time on the order

of days might be required.

The remaining data indicate that changes in either the pressure or temperature environment—that is, pressurizing the transducers beyond

their range, turning off the heaters for several hours, or even raising

differential transducers from vacuum to atmospheric pressure with zero applied differential pressure—can shift the calibration curves of the

transducers significantly.

Under stimulus of this work, six of the transducers which have been

received for calibration have in fact been subjected to from 2 to 4

complete calibrations over periods ranging from one day to several

weeks, with changes in ambient conditions between calibrations. These

tests were under better control than those of Calcatelli, but confirm

the general conclusions of her work. The quantitative results are that,

while for any given calibration (which takes 2-4 hours) the transducers

are capable of performing in a manner which far exceeds specifications.

However, the variation encountered from one calibration to another if

ambient conditions are changed decreases the overall accuracy by about

an order of magnitude. As a result, beginning this month, the uncertainty

statements associated with our calibrations will now quote 10 standard

deviations (instead of 3) plus 1/10,000 of the reading.

c. Capacitance Diaphragm Gage Round Robins

Both the American Vacuum Society and the international laboratory

round robin intercomparisons of capacitance diaphragm manometers are getting under way. Two 1- Torr transducers and two 10-Torr transducers,

one of each range from two manufacturers, have been assembled into units

79
for ease of calibration. The packages still lack an ion pump which will

permit evacuation of the reference side to a level where the calibrations

are effectively absolute calibrations, but they are useable and we will

begin our calibrations this month.

The international comparisons will be made with the standards

laboratories in England, France, Australia, and Austria, as well as at

NBS. These same units will be used for the AVS series, with Boeing,

Rockwell International, Sandia, and MKS Instruments being likely participants.

d. Meetings and Consultations.

The American Vacuum Society meeting was held in New York in late

October. Meetings of the Standards Committee and Gaging Subcommittee

provided common grounds for discussions of the legal status of standards

writing groups, as well as of gaging problems. Further work was done on

a procedural standard for the calibration of vacuum gages, which has

been pending for several years.

In May, the American Society of Metals held a meeting in Detroit.

The NBS was asked to comment on a proposed metals industry standard for

calibrating gages used in vacuum heat treatment furnaces.

Also in May, a meeting was held at NBS concerning vacuum standards

for the Magnetic Fusion Energy program. At this meeting, a presentation

was made concerning properties of capacitance diaphragm transducers.

The material presented was based upon the zero-drift work of Calcatelli

and results obtained from various calibrations.

We have provided consultations during the past year to many persons

seeking advice on methods, instrumentation, and available standards.

e. Pressure Transducer Characterization (S.D. Wood)

This year marked the end of the pressure transducer characterization

service which we have run for four cycles. The characterization service

consisted of 35 tests designed to characterize the transducers with

respect to 18 parameters. Among these were zero stability, full scale

stability, temperature sensitivity, and voltage dependence. Final

reports usually run 150 to 200 pages and some attempt was made to accommodate

special requests from contractors. In FY 79, some 25 units were examined;

this year, 15 units were characterized, of which nine were from outside

laboratories.

We now have accumulated a wealth of data about many types of pressure

transducers. It can be used generically to correlate performance and

sensor type. However, this will take both time and considerable computer

codi ng.

80
B. Task 111.22— Development of New Temperature and Pressure Standards

1. High Temperature Thermocouple Thermometers (G.W. Burns)

Some tests were conducted to study the long-term, high temperature

performance of Nicrosil/Nisil and Type K thermocouples in air. Two

tests were run with bare, 1.6 mm diameter thermoelements, and one test

was run with 3.2 and 6.4 mm o.d. stainless steel sheathed, compacted MgO

insulated thermoelements. The primary purpose of the bare thermoelement

tests was to establish what effect Mg additions to the alloys have on their performance.

The first bare thermoelement test, which included four Nicrosil,

four Nisil, two KP, and two KN thermoelements, whose compositions had

been carefully characterized, was run for 3066 hours at 1100 °C. The KP

and KN thermoelements exhibited substantial emf drift and the KN thermoelements failed as a result of oxidation after 1000 to 1800 hours of

testing. None of the Nisil or Nicrosil thermoelements failed during the

test. The magnitude of the drift in Nisil thermoelements was found to

be inversely related to the Mg content. An alloy with 0.08 percent Mg

exhibited a change of 350 pV, while an alloy with 0.21 percent Mg changed

by less than 20 pV. The thermocouple formed from the most stable pair

of Nicrosil and Nisil thermoelements drifted by about 4 °C during the

3066 hour test.

Post-test examinations of samples from the above test were carried

out at NBS and at the Materials Research Laboratory, Department of

Defense, Australia (MRL). Metal! ographic examinations were performed at

NBS and ion microprobe analyses were conducted at MRL to determine the

solute depletion in the alloys.

A second test using thermoelements from the same batches as those

used in the first test was run at 1200 °C for 1270 hours. In this test

the KP and KN thermoelements failed after only about 400 hours of testing,

while all of the Nicrosil and Nisil thermoelements survived the 1270

hours of testing. Samples from this test will also be subjected to

post-test studies at NBS and MRL. Results of these two tests will be

the subject of a joint paper by NBS and MRL authors for the 6th Temperature

Symposium in 1982.

A test with four stainless steel sheathed Type K and four stainless

steel sheathed Nicrosil/Nisil thermocouples was also run for 2211 hours

at 1000 °C. The drift in the Nicrosil/Nisil thermocouples ranged from

1.5 to 4 °C, with the drift of 6.4 mm o.d. thermocouples being about

one-half that of the 3.2 mm o.d. thermocouples. The Type K thermocouples

exhibited about the same drift as the Nicrosil/Nisil thermocouples, but

they experienced various degrees of instability upon thermal cycling

between 1000 °C and room temperature.

81
It is expected that additional tests and studies of Nicrosil and

Nisi! thermocouple alloys will be carried out during the coming year

under a collaborative agreement between the NBS and the NRL and MNL in

Australia. The scope of this collaborative work should be formalized

before the end of this year.

2. High Temperature Fixed Points, Thermometers and Resistance

Bridges (J.P. Evans, L.A. Guildner, and R.D. Cutkosky)

a. High Temperature Fixed Points. (J.P. Evans)

One of the heat pipe furnaces to be used with the high- temperature

resistance thermometer testing was tested for temperature uniformity at

660 °C, 960 °C, and 1065 °C over the length of the heat pipe before a freezing point cell and its accompanying radiation shields had been

installed. It was found that in the region normally occupied by the

freezing point cell crucible the temperature was uniform within 0.3 °C

at 960 and 1065 °C, and within 0.6 °C at 660 °C. The furnace should

therefore provide an adequately uniform environment for the freezing

metal when the cell and radiation shields are in place. Furnace control

proved to be suitably responsive.

A silver point cell was installed in another of the heat pipe

furnaces. The high-purity silver sample used in the cell was obtained

several years ago from the NBS Office of Standard Reference Materials

(0SRM). The cell has not yet been fully tested because of thermometry

problems (see below). The gold point furnace has been assembled and

tested and the gold point cell parts have been prepared, but the cell

itself has not yet been assembled.

b. High Temperature Resistance Thermometers. (J.P. Evans)

Development of SPRT's capable of use at temperatures as high as 1100 °C is continuing. Many thermometers have been built and tested;

most of the testing has been done in the NBS Gas Thermometry laboratory.

Resistance thermometer measurements made at high temperatures

during the year, the first attempted in our own laboratory, revealed

several important problems having to do primarily with the thermometer

lead structure.

During the furnace probe at 1065 °C two of the thermometers suffered

breakage of one or more of the leads. This experience, coupled with

earlier experience in the Gas Thermometry laboratory in which thermometer

leads shorted out upon cycling from high temperatures, indicated that

the original lead design, consisting of short insulating tubes and

82
disks, did not adequately accommodate thermal expansion of the leads. A new lead configuration was designed to accommodate all thermal expansion

at the top of the thermometer by means of expansion coils located in an enlarged glass header. The platinum leads were placed in long, continuous

silica glass lead tubes extending from the resistor to the header. The

lead tubes were flared at the top end and attached to the silica glass

sheath at that point. The platinum leads were anchored to the lead

tubes at the bottom end before connection to the resistor. This arrangement allows most of the thermal expansion to be taken up by the coils in

the header, and it has the added advantage of keeping the resistor

position fixed relative to the silica glass sheath. To date, nine

thermometers have been constructed with this lead configuration, and no lead expansion problems have been encountered. Extensive cycling tests

are’ now under way on one of the thermometers to provide additional

experience with the design at high temperatures.

The first two thermometers made with the new lead design were found

to behave anomalously at the silver point because of electrical leakage

between the leads and from the leads to ground. In these two thermometers

the lead tubes were held in place close to the silica glass sheath by

quartz wool packing. At the suggestion of R. Cutkosky, the next two

thermometers were constructed with an electrical guard incorporated in

the leads. The silica glass lead tubes were held in place by rings made

of platinum wire spaced at 10 cm intervals along the leads. The rings,

connected together by a platinum wire thus formed an electrical guard

when connected to an appropriate potential within the resistance bridge,

eliminating the effect of leakage between individual leads and between

the leads and ground. It was found that the guard increased the measured

resistance by as much as the equivalent of 50 mk at the silver point,

and by even more at higher temperatures. The effect of the guard was barely detectable at the aluminum point and it was undetectable at lower

temperatures.

The next five thermometers (8001-8005) were made with the guarded

lead design, using a 20-cm guard ring spacing, and with resistors wound

on a new coil winder using annealed wire. One of the thermometers

(8005) had a 39 cm segment of Pt-10 percent Rh wire in one of the leads

to serve as a differential thermocouple. Initial values of the alpha

coefficient exceeded 0.003926 for all thermometers except 8005; its

alpha coefficient was 0.003920. Three of the thermometers (8001-8003)

were heated for 336 h at 1090 °C, after which the alpha coefficients

were found to have decreased to less than 0.003919. Work is now in

progress to determine and eliminate the source of this alpha decrease.

83
c. Automatic Measurements. (J.P. Evans)

The readout switches of all manually balanced instruments in the

HTRT laboratory have been connected to a computer through a special

interface so that dial settings can now be read into the computer

automatically. The computer has also been equipped with a digital

clock. A new automatic bridge (see Section B 2d) has been used extensively

in routine measurements and has proven to be very advantageous. When

values of resistance determined with the automatic bridge are normalized

with respect to the laboratory standard 10 ohm resistor, no significant

difference is found between them and values obtained with the 400 Hz

bridge. A computer program has been written to record automatically all

the measurements associated with the calibration of thermometers at

fixed points.

Most of the coming year will be devoted to the construction of

thermometers, and to assisting guest workers from Germany, Canada,

Italy, and Australia in building thermometers for their own laboratories.

It is expected that this effort will make the most effective and timely

contribution to the information required by the CCT as a basis for re- vising the 1968 IPTS.

d. Resistance Bridges for Thermometers (R.D. Cutkosky)

A micro processor-based, 32 ohm, automatic-balancing resistance

thermometer bridge was completed this year and a technical paper was

submitted to the 1980 Conference on Precision Electromagnetic Measurements

and will be published in the IEEE Transactions on Instrumentation and

Measurement. Five copies of this bridge, built with the assistance of

R.S. Kaeser and two NBS summer employees, L. Younkins and T. Fan, are nearing completion. Plans for this bridge have been sent to seven or eight people who have asked for them.

Design work has been completed for modifying the above bridges for

operation up to 100 ohms. One or more of the new bridges will be so modified after enough of them have been completed and checked out so that I can make use of the prototype. A new microprocessor development

system will be used for this work. Formerly, the microprocessor program

development was a slow and cumbersome prodecure involving the use of a minicomputer. It will now be possible to develop the program much more

quickly. A fair bit of experience has been obtained on the new system

but it has not yet been used for program composition.

A draft of a paper has been prepared which addresses the question

of guards for resistance thermometers. Comments and suggestions from

colleagues are being sought.

84
3. Temperature Reference Points- (G.T. Furukawa, R.J. Soulen, Jr.,

B.W. Mangum)

a. Transportable Fixed Points (G.T. Furukawa)

The platinum resistance thermometry program includes two types of

transportable fixed temperature points "sealed devices" and "open devices.

Each has advantages and disadvantages. The sealed devices have the

advantage of a smaller chance of contamination but over a long period

the internal gas composition and pressure may change through release of

absorbed gases, gas permeation, or chemical reaction. Although the open

devices have a greater chance of contamination, the gas composition over

the fixed-point substance can be easily monitored and controlled.

Examples of sealed devices are the argon and mercury triple-point cells;

open devices are tin-and zinc-point cells. Both types of device require

temperature controlled environments (furnace, cryostat, or bath) before

they can be used. Smaller samples require more precise temperature

control relative to the "fixed temperature point." Larger samples, such

as those used in tin or zinc cells, yield "freezing temperatures" that

are reproducible to better than ±0.1 mK even when the furnace is five

degrees or more below the freezing point. Smaller samples require

greater precaution against chemical contamination.

The purpose of the "temperature controlled bath" is to regulate the

heat exchange between the fixed-point device and the bath so that the

temperature gradient within the device will be minimized and the thermometer will sense the phase equilibrium temperature. In routine thermometer calibration, to avoid the error of calibrating the thermometer

at the bath temperature instead of at the fixed-point temperature, the

bath should preferably not be controlled extremely precisely. Otherwise,

a means for avoiding the error must be a part of the measurement routine.

The routine use of a check thermometer helps avoid this error.

Instead of controlling the bath temperature close to the fixedpoint temperature to reduce the heat transfer between the fixed-point

device and the bath, the heat transfer can be reduced by insulation.

This technique is being used with the mercury triple-point cell where a vacuum space plus radiation shields are used to reduce the heat transfer

during freezing or melting.

In all of the above fixed-point devices the thermal diffusivity of

the device, including the thermometer, is a major factor in the selection

of the technique. A device, or a measurement system including the

thermometer, of lower thermal diffusivity requires closer control of the

environment temperature or smaller heat transfer and a relatively longer

waiting time after a thermal disturbance.

In summary, we find that:

a) a cryostat with the environment temperature controlled very

close to the fixed temperature point is used with small sealed samples

such as argon, oxygen, and others. This applies also to the small

gallium cell developed by B.W. Mangum.

85
b. ) the furnace with relatively coarser temperature control is

used with larger samples, such as with tin, zinc, aluminum, and cadmium.

c. ) the insulation technique is used with relatively large sample

such as with mercury triple point when the bath temperature is necessarily

very different from that of the fixed-point temperature.

i) Argon triple point

Three argon triple-point cells of different designs were assembled

and temperature measurements were obtained employing six capsule SPRT'S

and two cryostats. In addition to the above three cells, a fourth cell

from Italy was also measured. The standard deviation of the measurements

was found to be ± 0.03 mK. This result demonstrates that the argon

triple point can be realized with high reproducibility, and furthermore

that the calibrations are stable.

The comparison of the results of the IMGC cell with those of our

cells showed that the argon in the IMGC cell is less pure than that in our cells. The argon used in our cells is nominally 99.9999 percent

pure. Because of the greater slope of the melting curve that is observed

with less pure samples, it is possible to obtain relatively higher

values for the extrapolated "100-percent melted" temperature with less

pure samples even though impurities usually depress the melting point.

One of our argon triple point cells was submitted for the Comite 1 Consultatif de Thermometrie program on the International Comparison of

Fixed Points by Means of Sealed Cells. To date, The International

Bureau of Weights and Measures (BIPM), National Institute for Metrology

(INM), and Canadian National Research Council (NRC) have submitted

results on the NBS-Ar cell. The measurements show that argon triple

point cells of different national laboratories agree within ± 0.1 to

±0.2 mK.

Many small refinements, particularly with respect to shape and size

to reduce the cost of machine shop work, can be made in our argon triple

point cell. However, in order to work with sealed cells of other

substances, I plan to prepare the data obtained thus far on argon for

publication. Any new thoughts on the design will be incorporated in the

cells for other substances.

ii) Oxygen triple point

The oxygen triple point (54.361 K) is one of the defining fixed

points of the IPTS-68. A miniature pressure cell was recently filled

with a commercially available sample of 99.999+ percent purity. The

cell is now being prepared for measurements. In order to obtain purer

oxygen, we will prepare some oxygen by thermal decomposition of potassium

permanganate. We plan to obtain some preliminary measurements on the

commercial sample soon.

86
iii) Krypton and Xenon triple points

We are fortunate in the cases of neon and argon that their natural

compositions are concentrated mostly in one isotope, i.e., 20 Ne at 90.9

percent and 40Ar at 99.6 percent. Consequently, their melting points

and triple points are relatively flat, that of argon being flatter than

that of neon. The triple points of krypton and xenon have been reported

to be 115.8 K and 161.4 K, respectively. These temperatures will be

useful in improving platinum resistance thermometry between 90 and 273

K. Unfortunately, in the cases of krypton and xenon their compositions

are distributed among several isotopes, i.e., in the case of Krypton:

82 Kr, 83 Kr, 84 Kr, and 86 Kr. are 11.56, 11.55, 56.90, and 17.37 percent,

respectively; in the case of Xenon: 129 Xe, 131 Xe, 132 Xe, 134 Xe, and

136 Xe are 26.44, 21.18, 26.80, 10.44, and 8.87 percent, respectively.

Their melting curves are therefore expected to be less flat, unless

their composition yields either a congruent or eutectic system of many

components. Isotopic separation at these higher mass levels are expensive,

e.g., while 99.95 percent 20 Ne is $54 a unit, 99 percent 86 Kr is $700 a unit and 99 percent 136 Xe is $35,000 a unit^

In terms of the ideal solution theory, the effect of the impurity

on the equilibrium temperature of a liquid-solid phase system is given

by T -T = N2 / A, where T is the equilibrium temperature with no impurity in the liquid phase, T is the equilibrium temperature with

mole fraction N2 of impurity in the liquid phase, and A = AH/RT 2 where

AH = molal heat of fusion and R = molal gas constant. The solid phase

is a pure major component in the theory, but with isotopic mixtures the

solid phase is most likely a solid solution of the isotopes. The theory

is still useful where similar systems are being compared, i.e., where

they all form solid solutions. At high purity, the liquidus and the

solidus are very nearly linear. Using the distribution coefficient k,

the equation for the solid solution case becomes T - T = N2 (l-k)/A.

For a given N 2 , the effect on the equilibrium temperature depends upon

A. For Ne, Ar, Kr, and Xe, A is 0.07, 0.02, 0.02, and 0.01, respectively.

On this basis, Kr should yield flatter melting curves than Xe. This is

corroborated by some published data.

Flatness of melting curves or freezing curves is highly desirable,

particularly when the measurement technique does not readily permit

accurate definition of the equilibrium condition. However, the calorimetric technique is able to define the temperature when the solid phase

is vanishingly small. Hence, as long as the equilibrium temperature

corresponding to the definable phase state is highly reproducible, that

temperature will be a good thermometric fixed point. The question then

is how reproducible is the temperature at 100 percent melted krypton and

xenon of natural composition.

To test these questions, a sample of 99.995 percent krypton has

been obtained for making triple point measurements in a sealed cell.

When funds permit, a sample of xenon will also be obtained.

87
b. Cryogenic Temperature Reference Points (R.J. Soulen)

Interest in the SRM 768 superconductive fixed points has been

encouraging: 31 units have been sold since 1978, with strong indications

from many attendees of the 1980 Cornell He3 Conference that more orders

are likely. Preparation and calibration of both SRM 767a and 768 are continuing.

An interesting and controversial aspect of the low-temperature

reference point work right now centers on a W sample calibrated at NBS

(T = 15.45 ±. 1 mK) and sent to Helsinki where they assigned (by extrapolation from a He3 fixed point at 1.04 mK) a value of 16.9 ± 0.1 mK.

There are ± 5 percent differences in the temperatures assigned the fixed

points of He3 by various laboratories, and the temperature extrapolation

error can explain the discrepancy. I have been asked to spend a month

in Helsinki to assist them in resolving this discrepancy.

c. Gal 1 i urn Temperature Reference Point (B.W. Mangum)

Seven steel cells were filled with Ga samples, six from one source

(each of a different lot) and one from another. The cells were pumped

and leak tested. Checks were made for outgassing of the teflon holder

and of the Ga in the cells.

It was necessary to construct a lid for a temperature-controlled

bath for testing and storage of the 10 Ga triple point cells after their

preparation so that intercomparisons could be made efficiently. It was found that electrical noise from the heater coil of the bath was too

large, however, to permit testing with SPRTs directly in the bath,

although zero-volt switching SCRs are used in the controller. The pickup from the field produced by the heater just produced too much interference

on the SPRTs.

After checking the SPRTs for "wetness," it was determined that

three of the five were "wet." Furthermore, it was determined that two

had leaks which must have developed when they were rewired after the

previous drying. Those two had not been used since. They were repaired,

leaks eliminated and then dried under vacuum at 225 °C. The three dried

SPRTs plus one other were then recalibrated without the usual annealing.

The correct procedure was developed for attaining melting curves of

the Ga samples in the seven sealed steel cells. Melting curves give an indication of the purity of samples. Consequently, melting curves were

obtained for each of the seven samples to check for reproducibility of

the melt following the standard preparation of the Ga mantles, to check

for effects of rapid freezes of the mantles, and to check the behavior

of the melting after the standard triple point had been prepared.

88
Immersion characteristics of the SPRTs in the steel cells containing

the Ga samples at the triple point were determined and hydrostatic head

effects were measured.

Direct comparisons of Ga samples by a.c. techniques using the

400 Hz Cutkosky bridge were attempted but found to produce results

different from those obtained using d.c. techniques (Guildline bridge).

This is unfortunate since a.c. techniques are much easier to use, are much less sensitive to vibrations, and in our own case have ten times

better resolution than the d.c. bridge. Intercomparisons of the different

Ga samples are currently being made using the Guildline bridge. These

are being made for different mantles of each sample.

4. Low Temperature Scale (EPT-76) Realization (E.R. Pfeiffer)

In 1978, a new international temperature scale, the 1976 Provisional

0.5 K to 30 K Temperature Scale (EPT-76), was promulgated. This scale

involves a wide variety of measurements and thermometers , so that NBS

has undertaken the task of correlating and collecting information and

apparatus for the new scale in a single laboratory.

Preliminary runs prior to FY 80 revealed serious problems with the

performance of the EPT-76 cryostat. During the first quarter of FY 80

improvements were made to the radiation shielding of the cryostat, and

an extensive experimental run was performed during which time intercomparison data were obtained on ten germanium resistance thermometers

(GRT), 2 platinum resistance thermometers (PRT), one rhodium-iron resistance

thermometer (RIRT), one platinum-cobalt resistance thermometer and 2

SRM 767 superconducting fixed point devices. During the run, 7 additional

“housekeeping" thermometers, at various locations in the cryostat, were

monitored to observe the cryostat performance. The cryostat was found

to operate successfully over the EPT-76 range of 0.5 K to 30 K, and

actually reached temperatures as low as 0.33 K. Further improvements to

the cryostat are expected to be only minor ones, and are contemplated

mainly to make its operation more economical.

An analysis of the above described intercomparison data, begun

during the second quarter of FY 80, revealed that some serious problems

still existed in the hardware and software of the data acquisition

system and in the design of the experiment. Our (E.R. Pfeiffer and R.S.

Kaeser) efforts during much of FY 80 were directed at identifying and

correcting these problems:

i) A digital voltmeter with greater resolution than earlier types

was purchased and installed. This voltmeter was expected to give

an order of magnitude greater precision in the measurement of low

resistances, as encountered, for example, in PRT and RIRT. The

installation of the new voltmeter in the automated data acquisition

system required substantial familiarization time and extensive

revision of the laboratory computer programs. In several respects,

the new voltmeter proved inferior to the original one; the latter

therefore has been re-installed in the measurement system. It may

be possible to adapt the new resistance bridge built by R. Cutkosky

(see Section B.2) for these measurements.

89
ii) A temperature- regulated oil bath was built to contain the

standard resistors used during the resistance measurements, and

efforts also were made to obtain better temperature control of

the laboratory environment. Some time was spent developing a better measurement routine for the in-si tu calibration of the

Julie "reference" resistors used in the thermometer measuring

circuit. The results (obtained using the original voltmeter)

indicate that d.c. resistance measurements can be made with an absolute error of about 10 ppm plus 3 standard deviations of

the measurement imprecision. The in-si tu calibration routine

that was eventually developed produced agreement within 5 ppm

for 2 Julie resistors also calibrated by the NBS Electricity

Division.

Additional efforts during the year included the loan of two calibrated GRT from the above intercomparison experiment to a typical

(NBS) user. Over the temperature range of interest, 0.33 K to 0.67

K, the agreement of the two GRT was always within 0.7 mk—much

better than the resolution required for the experiment (1 percent).

In addition to these results, our participation in the experiment

provided some insight into the problems of resistance thermometry

measurement that may be encountered by a (typical) user. Recently,

a third calibrated GRT was loaned to another user at NBS for use in

a helium lambda-point determination. Over the range 0.90 K to 5.0

K the calibration data are smooth and reproducible to about ±0.3

mK. Our goal is to improve the reproducibility to about 0.1 mK in

subsequent runs.

Our plans for the closing months of FY 80 and into FY 81 include an adaption of the new Cutkosky a.c. resistance bridge to our measurement

needs and a final test run of the EPT-76 cryostat to check out the

hardware, software, and design of the experiment. Based on those measurement

results, estimates will be made of the error and imprecision in our

realization and dissemination of EPT-76. At that time, dissemination of

the scale to outside users either through calibrations or a MAP, should

commence.

5. Low Temperature Thermometers (C. T. Van Degrift)

a. Resonant-Circuit Gas Thermometer.

The low temperature gas thermometer and the pressure sensor of the

supercooled water experiment are of the same design except for the power

gain of the tunnel diode. The following test results are therefore

mutually applicable.

We made long term drift tests of our new design which utilizes coin

silver material and has a removable circuit insert and a cross bar

coupling the diode to the diaphragm end of the resonator. These tests

were made with zero pressure differential across the diaphragm and

90
therefore determine the extent to which aging of the diode, bypass

capacitor, or relief of internal stresses affect the frequency. Tests

at temperatures up to 144 °C allowed us to measure the creep rate associated

with annealing of internal stresses caused by our press-fit assembly of

the sensors and allowed us to estimate an 0.001 ppm/day room temperature

drift rate. Direct measurements for several weeks at room temperature

showed a drift of less than 0.04 ppm/day even when the sensor was temperature

cycled between -100 °C and room temperature. Preliminary tests of the

creep under pressure were obscured by temperature instabilities, outgassing,

and internal creep. We will be making pressure driven creep tests

during the coming year from 0.7 K to 40 K and from -100 °C to +30 °C.

The low temperature gas thermometer has been vacuum sealed and

thoroughly annealed at room temperature. We are now selecting a low

power tunnel diode. When the thermometer is charged with 0.1 MPa helium

gas at room temperature, it will have a temperature coefficient of 330

KHz/K. The frequency noise should be smaller than 3 Hz and hence the

precision may be better than 10 uK. Direct testing, which will commence

in September 1980, will reveal the magnitude of drifts and irreproducibilities. Four more thermometers of similar design are expected to be

built duri ng FY81

.

b. Low Temperature Carbon Resistance Thermometers (R.J. Soulen)

Following suggestions from colleagues in West Germany we have

studied the R(t) characteristics of four carbon resistors from

10 mK < T < 200 mK. The resistors follow a very simple law

a = g0 + ct x exp (at 1 /4 )

which we can fit and use for interpolation to within a few tenths of a

mK. D. Van Vechten and I will continue to study their reproducibility

in collaboration with H. Marshak.

6. Thermodynamic Temperatures.

a. Gas Thermometry (L.A. Guildner)

Only one set of measurements has been made with the newly-built

high-temperature gas thermometer bulb during this fiscal year. There

was an additional run made in September 1979. Both runs commenced in

the region of the silver point, and also included 800 °C and 660 °C.

These measurements were exploratory, for the purpose of determining

apparatus settings and studying the behavior of the various parts. In

these measurements, we found that the gas thermometer shows good long

term stability, and is almost free of hydrogen. This latter has been a severe problem, of a nature that leads me to suppose that all other gas

thermometry is very likely to have been subject to it. The gas thermometer

already has survived a very long time at the silver point (~ 2000 h) in

addition to appreciable times at 800 °C and 660 °C.

91
With continued use, however, we experienced failure of some of the

high temperature platinum resistance thermometers (See Section B2). In

addition, the furnace essentially failed and had to be rebuilt. The

trouble was shorting of the heaters by metal oxides that spalled off the

furnace parts.

There were severe temperature gradients in the thermostat, but in

retrospect that was to be expected in view of the poor condition of the

heaters. More modest gradients have been a continuing problem.

We undertook to rebuild the furnace, with motivation to reduce the

work, to protect the windings from shorting and to give better control

over the temperature distribution. Special guard heaters and sensors

were incorporated that should be useful in dealing with immersion (i.e. , tempering) of the gas thermometers and of the PRT's.

We also have been assembling a new gas thermometer, with a change

of design in the suspension to reduce asymmetric heat flows (and through

total heat flow also). The present bulb is Bulb III, discussed in our

last paper. It has mixed compositions (i.e., 80 percent Pt 20 percent

on top, 88 percent Pt - 12 percent Ph on the sides and bottom) through

a misunderstanding in procurement. Such a design is undesirable, although

the thermal expansion of these two alloys is similar between 0° C and

460 °C (and the same at some point between 300 °C and 400 °C). Further,

the present bulb has spent too long at high temperatures. We are concerned

about contamination from the surrounding Inconel. There are other

changes involved that should improve the overall result, or make it

easier to obtain. R. Edsinger has worked on the thermal expansion

apparatus, in particular correcting some problems with the thermocouple

network, and installing some guard heaters to improve immersion. He must

find the right combination of coatings for his interferometer plates, in

order to measure the samples at 1100 °C. The present coatings melted in

going to that temperature. Work is now directed at improvement of

the controls, to get adequate stability and sensitivity. It is straightforward in the sense that we have solved these problems with the big

thermostat already.

b. Gamma Ray Anisotropy Thermometry (H. Marshak)

The overall objective of this program is to develop a low temperature scale covering the range of ~ ImK to IK, and as close to

thermodynamic as possible, using y-ray anisotropy thermometry. Only two

y-ray anisotropy thermometers are needed to cover this temperature

range, namely single crystal 60 Co Co (that is, 60 Co nuclei included in a Co single crystal) and

166m

Ho Ho thermometers. This y-ray anisotropy

temperature scale will be compared to other primary temperature scales

either directly, as R.J. Soulen and I are doing with the Johnson noise

thermometer, or indirectly using superconductive fixed point devices and

secondary thermometers. It will also be possible to put together y-ray

anisotropy SRM units.

92
i) 60 Co Co Single Crystal y-Ray Anistropy Thermometer

1 mK to 50 mK).

The comparison experiments between this thermometer and R.J. Soulen's

Johnson noise thermometer have been completed and the results published

in the journal Cryogenics. Our results, which cover the temperature

range of 10.2 mK to 50.5 mK show that both thermometers define the same temperature scale to within 0.5 percent. Although the agreement probably

can be improved to 0.1 percent, it may be more important to work below

the 10.2 mK limit imposed by the present NBS dilution refrigerators.

ii)

166m

Ho Ho Single Crystal y-Ray Anisotropy Thermometer

50 mK to 1 K).

Work on this thermometer is progressing well. I have completed the

first extensive measurements on this thermometer covering the range of

20 mK to 700 mK. Since the hyperfine interaction (energy level splittings)

for this system has not been accurately determined, I used the 60 Co Co

thermometer and calibrated germanium and carbon resistance thermometers

to determine these quantities. The results of my measurements have

enabled me to obtain values for the nuclear magnetic dipole and electric

quadrupole moments for 166

n

Ho. The magnetic dipole moment value is in

excellent agreement with that recently obtained by the Oxford group.

However, the quadrupole moment has the opposite sign to what is expected

in this mass region. It is possible that the sign of the electric field

gradient is wrong. Measurements are presently being made using a more

intense single crystal 166 Ho Ho thermometer to resolve this problem.

Further measurements are also planned to compare this thermometer directly

to some of the superconductive fixed points of SRM 767 and 768 and also

to the EPT-76 scale. There is also a possibility that we can directly

measure the hyperfine splitting in this system by an NMR/0N measurement.

If this is possible this thermometer would then be a primary thermometer

like the 60 Co Co single crystal thermometer.

c. Johnson Noise Thermometry with Josephson- Junction Detection

(R.J. Soulen, Jr.

)

H. Marshak and I published an article in Cryogenics which summarized

the results of our latest comparison. It is this work, coupled with

noise thermometry up to 0.5K and paramagnetic salt thermometry using

cerous magnesium nitrate (CMN) (30 mK <T<520 mK) , which constitutes the

basis for NBS-CTS-1 (our first cryogenic temperature scale). All of

these results have been obtained with an rf biased resistive superconducting

quantum interference detector (R-SQUID) in which the rf frequency is 22-

25 MHz. By the end of FY 80 we hope to make at least one improvement in

this system: i.e.

,

to use an audiofrequency phase locked loop to reduce

the circuit noise and thus to shorten the measurement time. An NBS

summer employee, D. McQueeney, has devoted 2-3 weeks of his stay at NBS

to the design and construction of this circuit.

93
Progress also has been made in a more adventuresome improvement in

R-SQUIDS—Gavin Park, a visitor from King's College, London, and D.Van Vechten

were able to markedly improve the 10GHz R-SQUID noise thermometer. A first

phase, accomplished by a former colleague and me, was to get a 10GHz RSQUID working at 1.5 K using waveguides to inject the microwaves. Phase

II was to replace the waveguide (inimical to dilution refrigerators) by

coaxial cables. The experiments were successful to the extent that (1)

the R-SQUID worked, (2) we obtained some resisti vely-shunted Josephson

junction data similar to that obtained for the 24 MHz R-SQUID, and (3) we obtained convincing noise measurements of the temperature of the He4

bath of 1.7K. Phase III is more complicated. It requires redesign of

the R-SQUID and adaptation of the coaxial cables to a dilution refrigerator

for measurements of the T

c values of Cd, Zn, A1 , In and possibly Pb.

Needed yet for Phase III are coaxial cables of high quality, yet

compatible with dilution refrigerators. No satisfactory cables are commercially available, so R.B. Dove constructed three prototype cables.

We have sent them to W. Ganz, NBS Boulder, who will examine their rf

properties (0-10GHz) (attenuation and reflection).

The program is nearly settled for the 6th International Conference

on Noise in Physical Systems to be held at NBS (Gaithersburg) from 6-10

April, 1981. The second Announcement has been sent out.

7. New Pressure Standards (J.C. Houck)

a. Viscosities of Liquids Used in Piston Gages.

Six fluids were compared using a 40,000 psi re-entrant piston gage

by measuring fall rates. These results indicate suitability of the

fluids for use in calibration; the results will be combined with V.

Bean's measurements to 100,000 psi for selection of a fluid for use in

our 100,000 psi standard gage. Probably within the next six months one

of the above fluids will be tried in the 100 K psi Standard Piston Gage,

necessitating recalibration of the gage.

C. Task 111. 23—Fundamental and Applied Research in Temperature

and Pressure Measurement.

1. Industrial Thermometry.

a. Thermometry for Coal Conversion (G.W. Burns)

The project concerned with thermocouple instrumentation for coal

conversion processes undertaken for the Fossil Energy Division of DOE

was terminated in February 1980. Several NBS-fabricated thermocouple

assemblies were evaluated in the reactor of the Bi-Gas pilot plant in

Homer City, Pa. during the latter part of the project. Stainless steel

sheathed, compacted insulated Nicrosil/Nisil thermocouples installed in

alonized type 310 stainless steel thermowells showed substantial improvement

in performance in Stage 2 of the gasifier over Type K thermocouple

assemblies previously used. Post-test examinations of a Nicrosil/Nisil

thermocouple after 200 hours of operation (at about 950 °C) revealed no evidence of chromic oxide formation in the positive thermoelement as had

94
been found previously in the KP thermoelements of Type K thermocouples

which had been operated in the gasifier.

Two NBS-fabricated thermocouple assemblies also were evaluated in

Stage 1 of the gasifier. Molybdenum sheathed W-Re thermocouples were

used in both assemblies. One assembly had a BeO thermowell and the other

had a thermowell of chemically vapor-deposited SiC. These assemblies

failed after less than 50 hours of operation (at about 1500 °C) showing

no improvement in performance over previously used assemblies having

Cr2 03 coated molybdenum thermowells.

G.W. Burns organized and chaired a session on temperature and other

instrumentation at the 1980 Symposium on Instrumentation and Control for

Fossil Energy Processes in Virginia Beach, Va. June 9-11.

b. Thermal Conductivity of Industrial Insulation (L.A. Guildner)

The thermal conductivity apparatus badly needs increased reliability,

to be achieved by greater ruggedness and simplicity. On the other hand,

the additional complexity of the apparatus has been most instructive.

It is not a production- line instrument, but is capable of reliable

interpretation. The measurements so far have been on two samples (one

load) of Fiberfrax, at 100 °C and 300 °C, and we are presently seeking

to measure them at 500 °C. We expect to continue up to 800 °C, then

invert the samples and repeat one or more temperatures. The next

material we expect to measure is Teflon.

2. Superconductivity Research

a. Inelastic Electron Tunnelling Spectroscopy (J.T. Hall)

I have completed a study (in collaboration with John Kirtley, IBM

Watson Laboratory) on the quantitative intensities in inelastic electron

tunnelling spectroscopy. The results will appear in Phys. Rev B,

July 15 (1980).

b. Resistively-Shunted SQUID Research (R.J. Soulen)

The goal of this project is to understand the impedance and noise

of an rf-biased R-SQUID circuit in order to gain greater confidence in

the temperature scale defined by the device.

For noise thermometry the impedance need only be measured to 100

ppm and the simple "RSJ model" published by Soulen & Giffard is quite

adequate. Another application of the R-SQUID as a secondary thermometer

however, dictates an inaccuracy of 10 ppm for a resolution of 0.1 mk. Our

measurement imprecision is presently at the 5-10 ppm level, and we have

seen interesting and curious departures at the 100-1000 ppm level from

the simple RSJ model. The burden of the effort then is to characterize

these departures and to improve the RSJ model by building into it a more

advanced circuit representation.

95
Drs. Soulen and Van Vechten have been collaborating with Dr. Robert

Peterson (NBS Boulder), who has been attempting to solve, with the aid

of the computer, a more elaborate RSJ model. The results show considerable

success, the major deficiency being that the model could not simulate

the effect of the rf tank circuit. More recently, with J. Gavin Park, we have made a breakthrough in characterizing the effect of the tank

circuit. We are developing a model with which we may finally be able to

simulate our results to the 10-ppm levels The final outcome of these 5

years of research will appear next FY.

c. Microwave properties of superconducting films and tunnel

junctions. (R.J. Soulen, Jr.)

J. Clarke (University of Califronia, Berkeley) reported superconducting

gap enhancement in A1 tunnel junctions irradiated by microwaves. We

estimated that the effect would be even larger and easier to see in Ir

tunnel junctions. In collaboration with L.B. Holdeman and J.T. Hall we looked at Ir junctions, but ran into problems. We saw heating due to

(1) poor quality rf coaxial cables and (2) poor absorption of microwaves

by the junctions due to unsuitable tunnel junction geometries. We

decided to put off the Ir measurements and work at higher temperatures

using A1 junctions. Because of the persistence and insight of Holdeman

and Hall, we finally observed the effect. We were only the second

laboratory to observe gap enhancement and we saw some new phenomena,

too. This work appeared recently in Physical Review Letters.

3. Measurements with Resonant Circuits. (C. Van Degrift)

a. Solid He-3 Experiment. With the thermometer calibration of FY

1979 complete we prepared the apparatus to measure P(T,H) at constant V. During March and April 1980 we tested the complete apparatus using an external phase-locked loop to monitor the frequency of the pressure

sensing resonator. The 8 tesla magnet was successfully tested at its

full field and the effect of the field on the pressure sensor and thermometers

was measured. At temperatures below 80 mK, we saw anomalies which were

subsequently traced to inadequate heat lagging of the three germanium

thermometers. The pressure sensor worked properly up to its design

maximum of 7 MPa but only had a precision of 500 Pa. The Hall probe

performed better than expected attaining a resolution of 10 uT at a field of 8 T. A slow decay of 200 uT/hour when the magnet was persistent

could easily be measured.

During May the pressure sensor resonator was repolished and set

with a five times smaller capacitive gap for five times greater sensitivity.

The thermometers were more carefully heat lagged and our special SRM 768X

was attached to recheck the thermometers. A run from June to July

confirmed that the thermometers were now reading correctly and have

changed their calibration during the last year by no more than 0.05mk.

We were able to make good measurements of the thermal conductivity of

our favorite construction material, coin silver (90% Ag-10% Cu) in zero

field. It was also determined that we should change from the phaselocked loop readout of the pressure resonator to a tunnel diode oscillator.

96
Even though the phase- locked loop method can in principal have less

noise and power dissipation than a tunnel diode oscillator, it is too

difficult to avoid systematic errors associated with cable resonances

when used to measure a low Q resonator such as we must use in our 8

tesla magnitic field.

We are now selecting the best tunnel diode for the pressure sensor

and will prepare the apparatus for a complete P(T,H) run early in FY81

Calculations indicate that a measurement which is made in 100 ms wi 1

require a dc energy of 400 nJ and have a precision of 0.07 Pa while a 10 ms measurement will require 40 nJ and have a precision of 0.22 Pa.

b. He-4 Lambda Point Experiment

Postdoctoral Research Associate Michael DiPirro has nearly finished

fabrication of the apparatus to measure the dielectric constant of

liquid He-4 near the lambda point. His apparatus consists of three

reentrant resonators made using four pieces of polished niobium all

sintered together at 2000 °C. The sintering assures excellent thermal

contact and mechanical alignment and rigidity.

A crucial part of the apparatus is the gas thermometer which was separately tested and shown to have a precision of better than 100 nK,

to drift by less than lOpK/day, and to have a reproducibility of 1 mK

upon temperature cycling to 100 K. The frequency noise test was limited

by ambient vibrations and the drift test by the precision of a companion

germanium thermometer. The 1 mK change upon temperature cycling to 100

K leads us to believe that the gas thermometer is likely to be reproducible

to better than 1 nK for excursions around 2 K. Other experiences with

creep in coin silver and copper have indicated that creep diminishes by

roughly an order of magnitude for every 10 to 20 percent drop in temperature.

The complete apparatus including a vacuum can, 2 K cold plate, and

wiring will be tested just before M. DiPirro leaves for a permanent

position elsewhere. He will, however, remain associated with the experiment

to its conclusion.

c. General Tunnel Diode Oscillator Work.

A paper entitled "Modeling of Tunnel Diode Oscillators" by Craig

Van Degrift and David P. Love (Texas A&M) has been written. It describes

three progressively more accurate and complicated methods of modeling

the performance of tunnel diode oscillators with particular emphasis on non-linear effects.

We have been able to obtain some tunnel diodes manufactured by a new planer technique and packaged in a nearly non-magnetic casing. We

are testing these for their 1/f noise and ability to withstand thermal

shock and cycling. Preliminary results show that they do indeed temperature cycle very well and furthermore that they change only slightly

from room temperature. However, they have more capacitance than we

desire. We expect that the manufacturer can produce diodes with much

97
smaller junction capacitance and that this new manufacturing technique

will produce diodes which are superior in all respect to previous designs.

Isadoro Campisi, a graduate student at Louisana State University

has visited for a week to discuss his work on a triple superconducting

reentrant resonator tunnel diode oscillator experiment. This type of

oscillator is described in literature in the Soviet Union as promising

exceptional frequency stability for gravitational radiation detector

purposes. For the past two years we have been supplying Mr. Campisi

with advice and minor hardware.

4. High Pressure Research. (Vern E. Bean)

a. Properties of CC1 4 Under Pressure

5.

D. Wood and I have carried out the first part of a study of

spherical molecules using pressure as the probing mechanism. Specifically,

we have investigated the melting and freezing curves of CC1 4 between

0 and 350 MPa and between 225 K and 350 K. This molecule forms the

so-called plastic crystals found among spherical molecules.

CC1 4 has three solid forms over the region of interest which are characterized by face-centered cubic (fee), rhombohedral , and monoclinic

structures. The fee phase is metastable with respect to the rhombohedral

phase. The melting and freezing curves of these two phases are separated

by a few kelvins. However, what is of greatest interest to us is the

behavior of the fee phase at high temperature and pressure. At a point

near 275 K and 100 MPa, this phase slowly ceases to exist. The change

is not particularly sharp or well defined. In addition, while the fee

phase may be encountered during a cooling toward the rhombohedral phase,

it will never be encountered while melting the rhombohedral phase.

The data leading to a paper on the dual melting curves of CC1 4 have

some features that tend to make one think that CC1 4 violates the 1st law

of thermodynamics as the various solid phases are formed. Having far

greater confidence in the 1st law than in our understanding of CC1 4 , we

built a high pressure adiabatic calorimeter to look at the energy involved

in the formation and fusion of these solid phases. The driving energy

for these phases is provided by pressurized N2 which allows us to freeze

and melt along an isotherm. The CC1 4 and the N2 are separated by a lead

balloon, a critical feature of the device. We have tested the apparatus

only enough to have confidence that it will work. There are almost

certainly many other fluids that have yet undiscovered dual melting

curves. We shall pursue study of them as time permits.

b. Capacitance Measurement as a Function of Pressure.

Using two sample cells, one of the Naval Academy design and construction

and one designed at NBS we have made absolute capacitance measurements

of CC1 4 in both of the plastic crystal phases and in the liquid phase as

a function of pressure along several isotherms which will contribute to

our understanding of these rather unusual phase transformations. This

part of the CC1 4 work is now complete and will be published. These

measurements were made at the Naval Academy under a NBS cooperative

research agreement.

98
The next step in this program is to study the capacitance changes

due to pressure induced rotor-nonrotor phase transitions in plastic

crystals to see if this phenomenon is metrological ly useful. We are also interested in looking for a capacitance anomaly in super-pressed

polar fluids that is of interest to fluid theoreticians.

c. Compressibility of Fluids Having Spherical Molecules.

Originally, we expected to use ultrasonic techniques to make these

measurements, but it is now felt that the experiment will be cleaner and

easier if we use capacitance techniques. The concept is to make simultaneous

capacitance measurements as a function of temperature and pressure on two

samples of fluid, one of constant volume, the other having a constant

number of molecules of sample. The only necessary correction to the

data accounts for the compressibility of the stainless steel of the

sample cell ( a very small effect). Point by point differences in the

two data sets gives the fluid compressibility directly. I have designed

an apparatus for this experiment which is intended for use over the

temperature range -100 °C to 200 °C and at pressures up to 1.4 GPa.

D. Martin is building it. It is in the final stages of assembly and

will become operational in early FY 81. The data will be taken at the

Naval Academy using their automatic bridge operated by a Trident Scholar

who will use this project as his senior thesis.

Fluids to be studied include CC1 4 , of course. This work is of

interest because it:

i) is an essential element in the testing of models for equations

of state of fluids; and

ii) is expected to be a useful probe into the metastable

super-pressed fluid state before freezing occurs.

d. Viscosity as a Function of Pressure.

A certain amount of oil flow in the annular space between the

piston and cylinder is an essential feature for the operation of piston

gages. As pressure increases, viscosity increases logarithmically

resulting in decreased oil flow and so viscosity is a vital concern of

pressure metrol ogi sts. We designed and built a high pressure viscometer

to study candidate piston gage fluids. D. Martin, F. Long and I created

the hardware and Martin Turner, an NBS summer employee, made most of the

measurements. We have studied 8 fluids at room temperature and up to

700 MPa (10 s psi) which is half of the maximum design pressure of the

apparatus. We have corresponded with other national metrology laboratories seeking their suggestions for fluids of interest.

99
e. Light Scattering Under Pressure.

Dr. V. Fratello, an NBS Postdoctoral Fellow, has been studying the

scattered light from super pressed liquid ortho- terphenyl looking for

features that may give theorists a handle on the calculation of such

metastable conditions. In order to know when one has super-pressed

conditions, one must know where the melting curve is. We set about to

find it using equipment of my design and construction and a sample

purified by Dr. Fratello. He is nearly finished with the measurements.

He has good data up to 500 MPa (75,000 psi) which we will publish in the

late winter. We have also spent some considerable time working on his

sample pressure cell for the light scattering experiment which he borrowed

from W. Daniels of the University of Delaware.

5. Low Pressure Research. (Ken McCulloh)

A high vacuum ion gage comparator was constructed starting from a surplus high vacuum coating _system. This comparator allows the calibration

of vacuum gages between 10 2 and 10 6 Pa by comparison with reference

gages calibrated at the National Physical Laboratory in England and the

Physikalisch-Technische Bundesanstalt in West Germany. The comparator

has been used to determine nitrogen sensitivities from 10 5 to 10 2 Pa

for lots of from 2 to 4 each of 5 different types of commercial hot

cathode ionization gage tubes by direct comparison with a reference

gage. Two types which show promise for use as transfer gages have been

identified for further evaluation.

A prototype ion gage controller has been designed and built. Minor

refinements will be made, and several copies will be produced in early

FY 81. These controllers, which are not commercially available, are required for precise control of ionization gage tubes.

The present ion gage comparator is effectively limited to use with

nitrogen by its ion pump. This defect and several other less serious

problems are being remedied by the construction of an improved high

vacuum calibration system utilizing a mercury diffusion pump. This

system is largely completed but awaits the delivery of the mercury

diffusion pump. Operation by early fall of 1980 is anticipated.

Initially the system will be used as a flow comparator for calibration

by direct comparison with a reference gage. However, since this is a two-chamber system with an orifice of accurately calculable conductance,

it will eventually be converted into a primary standard by addition of a throughput meter.

A two day workshop exploring the vacuum measurement problems of the

magnetic fusion program was held during April 1980. This discussion

significantly improved the understanding of both the NBS and DOE attendees

of the fusion program, problems and the capabilities and limitations of

vacuum metrology.

100
6. Studies of Aircraft Altimetry Equipment (S.D. Wood)

The Pressure Group has been interested in aviation safety for some

time. The aeronautical industry is a large, important and visible part

of the economy which depends very directly on pressure measurements for

safety. Our first survey of altimeters was done several years ago.

After meeting with the FAA several times, NBS was asked to assess the

current performance of altimeter setting indicators (ASIs) and the

effectiveness of the FAA calibration procedures.

The first part of our task was to obtain or design a suitable

transfer standard. The unit needed to be rugged and reliable under

various field conditions and needed to maintain its precision and

accuracy (0.01% full scale) throughout the survey. We relied heavily on the results of several years' data from the transducer characterization

service to select a pressure sensor. This sensor was then packaged with

a level, heaters, and a DVM in a rugged case. The unit was designed to

fit under an airplane seat and was "portable" (40 lbs). Associated with

the unit were a piston gage (which stayed at NBS) and a small vacuum

pump.

The survey consisted of visiting nine airports at least once and

checking the ASIs and local calibration equipment (other ASIs and Weather

Service manometers) and discussing performance histories and problems

with the people who maintain the units. In the course of the study, it

became apparant that the Weather Service is the cornerstone of the FAA

ASI calibrations and so we visited the regional headquarters in New York

where we compared our transfer standard to their standard manometers.

Finally, we stopped at the National Airways Facilities Experimental

Center, the FAA's research facility, where we checked their manometer

and talked with the staff.

We have recommended to the FAA that their calibration procedure be

strengthened and that they maintain a transfer standard which could be

used to check all of their ASIs against a single source. The results

have been discussed in three reports.

7. Physics of Thin Films. (W.S. Hurst and M. L. Reilly)

The aim of the thin film work this year was to (1) investigate Sibased capacitance structures as temperature sensors and (2) investigate

some of the promising cermet materials for use in resistive temperature

sensors.

A collaborative effort was begun to work on Si -based capacitance

sensors. This has been with Stephen J. Fonash and S. Ashok of Penn

State and James Comas of the Naval Research Lab. In addition we have

received some help from the semiconducting processes group here at NBS.

The Si devices are now in the process of fabrication and testing. Comas

provided ion implantation of selected impurity levels into the Si, and

101
Fonash is performing the annealing schedules and investigating the

semiconductor parameters. We will investigate the temperature sensitivity

and stability. These devices are now at Penn State, and we will begin

looking at some of them in September. In addition, we have worked some with Fonash on the modeling of the device characteristics in the temperature-sensitive barrier region where the impurities are implanted.

The depositions for more Zr02 -based capacitance sensors have been

done. These will be fabricated into probes, tested at NBS and then

delivered to the National Institutes of Health (NIH) for further testing

by R. Berger.

8. Laboratory Automation. (W.S. Hurst)

Various problems were solved in assembling the laboratory computer

systems. However, the systems are well suited to many calibration and

research tasks in the division and provide us with relatively powerful

and cheap laboratory automation. M.L. Reilly and I learned enough of

the machine-language encoding procedures that drivers could be written

to properly implement the printers. This was done after software bought

outside proved to be poorly written and indadequate.

These systems now support the IEEE-488 general purpose instrumentation bus and our older data collection systems. In addition, as a bonus, a moderately powerful text editor has been implemented. A limited

hard-copy graphics capability is also in operation.

The following tasks face us this coming year. First, some time

will be required to acquaint new users with the system. This seems to run between 1/2 to 4 days per new user, depending upon conditions.

Secondly, we should create one or two new systems for other division

laboratories. Next, it seems clear that some effort should be spent

connecting to the NBS National Measurement Lab word processing facility,

and then instructing the division staff how to make use of it. These

tasks can probably be finished during FY81. In addition, there are other tasks that would be worthwhile accomplishing. The first would be

to replace the outdated MIDAS data collection systems with something

else. A prime candidate is the CAMAC data collection system, which

exists as an IEEE standard and for which there are many manufacturers of

modules. We need to implement more powerful graphics, perhaps screen

graphics as well as high-resolution pen graphics. (For the latter we

have the hardware, but need to upgrade the software). Lastly, a more

powerful operating system is available and may be required in some

experiments. It will run 5 to 10 times faster than the present one and

would more than double the amount of memory available for programming.

102
9. Characteristics of Industrial Resistance Temperature Detectors

(RTD's) (Dr. B.W. Mangum)

a. Characteristics of Industrial Resistance Temperature Detectors

(RTD's).

A study of RTD's was begun and work on this is progressing well.

After 15 thermal cycles of 20 RTD's from room temperature to 235 °C

(total time of ~ 200 hrs. at 235 °C), followed by measurements after

each cycle at 0 °C, 20 °C, 40 °C, 60 °C, 80 °C and 100 °C, we discovered

that the lead solder junctions on the leads had severely oxidized (although

sensors and solder junctions were heated in an Ar atmosphere), causing

an apparent change in the RTS's resistances. Ten RTD's with AuSn solder

junctions and 10 RTD's with welded junctions are now being tested.

Following this evaluation, the remaining RTD's will be appropriately

connected to the leads and investigated for stability upon thermal

cycling. An interesting feature found for almost all of the 20 RTD's

investigated so far is that although they may show changes equivalent to

a few (2-5) mK at any temperature between 0 °C and 100 °C upon thermal

cycling, they undergo a considerably larger change (a decrease) in

resistance (equivalent to 20 - 30 mK) subsequent to being tested over

the range 0-100 °C. The amount of the decrease appears to be a function of time after calibration from 0 - 100 °C. It is possible that

this is due to shunting of the RTD by moisture inside the thermometer.

b. Standards Activities.

I wrote three sections of a "Guide to Accurate Temperature Measurements

in the Clinical Laboratory" and participated in writing three others for

the Temperature Subcommittee of the Area Committee on Instrumentation of

the NCCLS. This Subcommittee has now finished writing "Guide to

Selection of Thermistors" for the NCCLs.

In ASTM, we completed writing proposed standards on thermistors,

electronic fever thermometers, and disposable melting-point-type fever

thermometers. We are working on drafts for disposable liquid crystal

fever thermometers and on draftsfor thermometers using thermistors. The

standard on liquid-in-glass fever thermometers has been adapted and

published. The proposed standards listed above are ready for E 20 ballot.

c. Hydrated-Sal t References Points.

D.D. Thornton, working with two Guests Workers, R. Magin and

J.A. Statler, has studied transitrons in hydrated salts as possible

medical reference temperatures. They have submitted a manuscript on the temperatures of hydration of Na2 S0 4 '10H2 0, KF‘2H2 0, Na2 HP0 4 ’7H2 0

salts as temperature fixed points for publidation in NBS Journal of

Research.

103
10. Time-Dependent Temperature and Pressure Measurements (G. Rosasco)

The major effort over the last 8 months has been in obtaining the

resources to start our program in optical measurements of temperature

and pressure. We have obtained the promise of re-programmed staff

assistance to augment my own efforts, and some $250,000 has been spent

to equip a laboratory.

I have prepared work plans for FY 81 and FY 82. We should have

reached two major goals at the end of this period:

GASES: Definitive predictive equations for the line intensity,

position and width of nitrogen gas for use as a temperature and pressure measurement probe.

SOLIDS: Tests of the utility of a line position/width standard

for temperature measurements above room temperature by

optical fluorescence.

11. Thermometry in Resource Recovery (M. L. Reilly)

As a response to the reprogramming effort in TPMSD, in February of

1979 Martin Reilly began working with various members of the Chemical

Thermodynamics Division (CTMS) on the design and construction of a large-scale flow calorimeter for the determination of the calorific

value of resource-derived fuel (RDF). Because of his background in both

thermometry and calorimetry, the transition to the new program was

smooth. He spent nearly full time with the program as well as coordinating the activities of members of TMSD in support of the program.

Beginning in March, D. Thornton set up the data acquisition system which

was used in trial experiments of a prototype combustor for the 25-gram

calorimeter. He then designed and wrote specifications for the data

acquisition and computation system to be used for the 25-gram as well as the large-scale calorimetric experiments.

During FY 80 Reilly has continued to work full time on the calorimetry problem. Thornton, while on temporary assignment at a university,

continued to be active through consultation by telephone. He also made

two trips to NBS to assist in the installation of specific components of

the data acquisition and computation system. Thornton resigned from

the NBS in May and Reilly has taken over responsibility for the continuing

development of that phase of the program.

John Evans, using his own system, tested the performance of a number of individual components of the new data acquisition for their

implementation. Evans has helped in the construction of the thermocouples

used in the 25-gram calorimeter. He has taught Reilly and Ryan of the

NBS Center for Thermodynamics and Molecular Science (CTMS) how to

correctly weld thermocouple junctions and helped them to use the equipment in his laboratory to fabricate thermocouples for the prototype

large-scale combuster.

104
George Burns provided advice about the selection, location and

installation of thermocouples for use in the prototype large-scale

combuster. He supplied the wire used to make the thermocouples. He

also supplied a high-pressure thermocouple feedthrough for use in

special experiments designed to determine RDF ashing temperatures within

a combustion bomb.

Wilbur Hurst, although not officially assigned to the resource

recovery program, has contributed significantly to the TPMSD effort

through his guidance and assistance in the setup of analysis of experimental data. He has provided operating systems which extend the capabilities of the laboratory computer to satisfy the particular needs of

the calorimetry program. He has also willingly loaned components from

his system for troubleshooting and made his portable system available

for logging thermocouple data from the prototype large-scale combustor

located at the hazards laboratory.

During November and December of FY 80 a series of experiments were

carried out in the prototype 25-gram calorimeter. The major contributions

from TPMSD were (1) the design and construction of the thermocouple

systems to measure temperatures in the input and exhaust gas streams,

(2) construction of the exhaust stream gas-analysis train, (3) furnishing

a Mueller bridge system (complete with operator) for measuring the

temperature of the working fluid using platinum resistance thermometry

and (4) writing all the computer programs and software necessary to log

and analyze the data. These measurements were discussed at an April

meeting of ASTM and at the August meeting of the Calorimetry Conference.

In February and March further experiments were conducted to determine

heat- leak corrections from the prototype 25-gram calorimeter. The

Mueller bridge system was modified to make measurements semi-automatic.

Additional computer programs were written to refine the logging and

analysis of the data. Also in March, a series of experiments were

conducted to determine the ashing temperature of RDF combusted in a bomb

calorimeter. For these experiments TPMSD contributed advice on thermocouple design as well as a high pressure feedthrough for the thermocouple

wires. The results of these experiments were also discussed at the

April ASTM meeting.

During May and June the design and construction of the prototype

combustor for the large-scale calorimeter were carried out. TPMSD input

involved the selection of the thermocouple material and the design and

construction of the couples.

In July and August more than 14 trial burns were carried out in the

prototype combustor. After each burn significant modifications were

made to the combustor, the thermocouple network and the sample configuration.

105
These experiments were also discussed at the Calorimetry Conference in

August and a film sequence of a burn will be shown at the ASME meeting

at NBS in September.

In September the final version of the 25-gram calorimeter is to be

assembled in the new laboratory space in the Engineering Mechanics

building. Test measurements will begin as soon as the assembly is

complete (perhaps by mid-October).

During FY 81 the measurements to establish correspondence between

the results obtained with the 25-gram flow calorimeter and those of the

combustion bomb are to be completed. The construction of the largescale calorimeter will begin.

106
III. PUBLICATIONS AND INTERACTIONS

During Fiscal Year 1980, the Temperature and Pressure Measurements

and Standards Division staff participated in a great variety of activities.

Many of these have been mentioned in passing in the previous sections of

this report; for the convenience of the interested reader, however, they

are categorized in this section.

a) Sponsored Conferences. Two conferences were sponsored by the

Division during the past year. On the 29th, 30th, and 31st of October,

1979, a Topical Conference, "Problems in Modern Thermometry" was held at

the NBS. The conference featured five lectures by well-known US scientists;

"Coherent Anti -Stokes Raman Spectroscopy Thermometry in Gases", by

A. C. Eckbreth of the United Technologies Research Center, East Hartford,

Connecticut;

"The Effect of Crystalline Imperfections on the Low Temperature

Behavior of Cerous Magnesium Nitrate," by G. Zimmerman, Department of

Physics, Boston University;

"A Temperature Scale Based on High Temperature Platinum Resistance

Thermometry," by L.A. Guildner, TPMSD, NBS, Gaithersburg;

"Noise Thermometry Methods and Applications," by T.V. Blalock,

Department of Electrical Engineering, University of Tennessee, Knoxville;

"Time Response Characteristics of Temperature Sensors," by T.

Kerlin, University of Tennessee, Knoxville.

These lectures, occurring over a three-day period, provided the

staff of NBS as well as other scientists in the Washington, D.C. area

with an opportunity to discuss timely problems in temperature measurement.

A second conference, "Vacuum Measurement Standards for Magnetic

Fusion Energy," covering the two-day period May 20-21, 1980, was jointly

sponsored by the TPMSD and the Office of Fusion Energy of the U.S.

Department of Energy. The topics included;

"Vacuum Measurement Problems in Plasma Confinement and Surface

Physics Diagnostics," involving J. DeGrassie of General Atomics Corporation,

I. Henins of Los Alamos Scientific Laboratory, A. Razdow of MIT, W.

Schwenterly of Oak Ridge National Laboratory, F. Dylla of Princeton

Plasma Physics Laboratory, and M. Malinowski of Sandia Livermore Laboratory;

107
"Ion Gage Sensitivity Problems," by R. Hseuh of Brookhaven National

Laboratory;

"Neutral Beam Cryopump Development," by N. Schwenterly of Oak Ridge

Laboratory and T. Batzer of Lawrence Livermore Laboratory;

"Tritium-Related Problems in the TFTR Acceptance Testing," by F. Dylla of Princeton Plasma Physics Laboratory;

"TSTA—Tritium Problems," by C. Walthers of Los Alamos Scientific

Laboratory;

"State of the Vacuum Measurements Art," involving C.R. Til ford of

the NBS TPMSD, G. Messer of Physikalisch-Technische Bundesanstal t

,

Berlin, K. Poulter of the National Physical Laboratory in England, W.

Taylor of Sandia Laboratory, and N. Wilson of Los Alamos Laboratory;

"Commercial Ion Gage Sensitivities," by K. McCulloh, of the NBS

TPMSD;

"Capacitance Diaphragm Gage Performance," by R. Hyland of the NBS

TPMSD;

"TSTA Tritium Pressure Gage Performance," by S.D. Wood of the NBS

TPMSD;

As a result of this conference, particularly troublesome problems

in vacuum measurements and vacuum standards were highlighted, and

potential solutions to these problems were suggested.

b) Talks by Division staff.

V. Bean. Plastic Crystal Phases in Carbon Tetrachloride, Gordon Research

Conference on Orientational Disorder in Crystals, Santa Barbara, California,

Jan. 15, 1980.

M. DiPirro. Heat Capacity Studies of 3 He in 4 He Films, Sigma Xi Luncheon

Talk, NBS, November 1979.

M. DiPirro. 3 He on the Surface of 4 He: A nearly Ideal 2-Dimensional ZD

Fermi Liquid, Center for Absolute Physical Quantities Colloquium, NBS,

March 1980.

M. DiPirro. 3 He in 4 He Films: A Doubly Two Dimensional System, International Conference on ordering in Two Dimensions, Lake Geneva, Wis.,

May 1980.

G.T. Furukawa. A measurement Assurance Program—Thermometer Calibration

at the Conference on Testing Laboratory Performance Evaluation and

Accreditation, Sept. 25-26, 1979, Gaithersburg, Maryland.

108
L. A. Guil drier. A Temperature Scale Based on High Temperature Platinum

Resistance Thermometry, (co-author J.P. Evans). A Topical Conference on Problems in Modern Thermometry (presented by CAPQ) Oct. 29, 30, 31,

1979, NBS.

J.T. Hall. Photon-Assisted Quasiparticle Tunneling in the Region

Intermidi ate Between the Classical and Quantum Limits, March 1980 meeting

of American Physical Society, New York.

J.T. Hall. Search for Microwave Enhancement of the Energy Gap in

Aluminum Films, March 1980 meeting American Physical Society, New York.

J. T. Hall. Tunnel ing Spectroscopy. Cathol ic University Physics Department,

April 1980, Wayne State University, Physics Department April 1980,

Hewlett-Packard, Research Division, June 1980, Florida Atlantic University,

Physics Department, May 1980.

R. Hyland. Capacitance Diaphragm Gage Performance, at NBS-sponsored

meeting on Vacuum Standards for the Magnetic Fusion Energy Programs.

May 21 , 1980.

B.W. Mangum. Standard Reference Materials, (gallium melting point

temperature standard), for the 1980 meeting of the American Physical

Society.

H. Marshak. Nuclear Orientation Thermometry and the NBS Comparison of

Scales, Low Temperatures Group, The Institute of Physics, London, England,

October 1 , 1979.

H. Marshak. Nuclear Orientation of 166m

Ho in 165 Ho Single Crystal, July

1980. West Berlin.

H. Marshak. New Developments in Thermometry and Related Research, July

1980. Bonn, West Germany.

H. Marshak. Ordered Nuclear Spin Systems: Thermometry, Magnetism and

Nuclear Physics Katolieke University Leuven, Institution Voor Kern-en

Stal ingsfysi ka, Leuven, Belgium, September 18, 1979.

H. Marshak. Nuclear Orientation Thermometry Using 60 CoCo and

166|J HoHo,

Kamerlingh Onnes Lab der Ri jksuniversiteit te Leiden, Leiden, Nederland,

September 21 , 1979.

K. E. McCulloh. Nitrogen Sensitivities of a Sample of Commercial Hot

Cathode Ionization Gage Tubes, (co-author C.R. Tilford) paper given

at AVS meeting, Detroit, Mich., Oct. 1980.

R. Soulen, Jr. Development of an Absolute Temperature Scale Using Noise

and Nuclear Orientation Thermometry, (co-author H. Marshak) International

Institute of Refregeration, Venice, Italy, Sept. 25, 1979.

R. Soulen, Jr. Noise Thermometry at NBS and Superconductive Fixed Point

Determinations Below 0.5 K, Institute of Physics, London, Oct. 1, 1979.

109
R. Soulen, Jr. Use of Superconductivity for Thermometry, October 1979,

New Brunswick, New Jersey.

C.R. Til ford. Vacuum Standards, American Vacuum Equipment Manufacturers

Association, New York, Oct 15, 1980.

C.R. Tilford. Survey of Altimeter Calibration Accuracy, (co-authors

S. D. Wood and A.J. Linquist) 1980 Air Data Systems Conference, Colorado

Springs, Colo. May 8, 1980.

B.G. Turell. Magnetic Structure Determined by Nuclear Orientation, (coauthor H. Marshak) Solid State Commun. 30, 677 (1979)

S.D. Wood. Survey of Altimeter Setting Indicators, (co-author C.R.

Tilford) 1980 Air Data Systems Conference, Colorado Springs, Colo,

May 8, 1980.

c. Publications.

Vern E. Bean, "The Dual Melting Curves of Carbon Tetrachloride," High

Pressure Science and Technology, B. Vodar and Ph. Marteau, editors;

p. 638, Pergaman Press, Oxford (1980).

Vern E. Bean, "Absolute High Pressure Measurements," High Pressure Science

and Technology, B. Vodar and Ph. Marteau, editors; p. 231, Pergaman

Press, Oxford, (1980).

Vern E. Bean and Sharrill D. Wood, "The Duel Melting Curves and Metastability of Carbon Tetrachloride,," J. Chem. Phys. 72, 5838 (1980).

Vern E. Bean, "Pressure as a Probe of Molecular Interactions," NBS

Special Publication 572, 46, (1980).

Robert K. Cutkosky, "Guarding Techniques for Resistance Thermometers,"

Manuscript, 1980.

Michael J. DiPirro and Francis Gesparini, "Two Dimensional 3 He in 4 He

Films," Physical Review Letters 44, 269 (1980).

Michael J. DiPirro, Bidyut Bhattacharyya, and F.M. Gesparini, "Some

Properties of Nuclepore Filters," Review of Scientific Instruments 51_,

846 (1980).

Michael J. DiPirro and F.M. Gesparini, " 3 He in 4 He Films, A Doubly Teo

Dimensional System," Proceedings of the International Conference on Ordering in Two Dimensions, to be published by North Holland, Oct. 1980.

L.A. Guildner, "Accuracy of Realizing Thermodynamic Temperatures by

Gas Thermometry," PTB-Mittei 1 ungen 90, Jan. 1980.

J.T. Hall, L. Holdeman and R.J. Soulen, Jr., "Frequency Dependence of

Photo-Assisted Tunniling Superconducting Tunnel Junction: The Classical

to the Quantum Limits," "Microwave Enhancement of Superconductivity in

A1 Tunnel Junction," (in preparation).

110
J. Kirtley and James T. Hall, "Theory of Intensities in Inelastic Electron

Tunneling Spectroscopy: Orientation of Absorbed Molecules," Physical

Review B, in press (1980).

B.W. Mangum and D.D. Thornton, "Determination of The Triple-Point Temperature

of Gallium," Metrologia 15, 201-215 (1979).

H. Marshak and B.G. Turell, "y-Ray Emission From Oriented Nuclei in a Multi axis Nuclear Spin System: 16sinHo," Solid State Communications,

Vol . 30, pp. 655-681, 1979.

H. Marshak, "Nuclear Orientation," 5th Edition, McGraw-Hill Encyclopedia

of Science and Technology.

H. Marshak, "Nuclear Orientation of

166m

Ho in 165 Ho Single Crystal," to

be published in Journal of Hyperfine Interactions.

K. E. McCulloh and C.R. Til ford, "Nitrogen Sensitivities of a Sample of

Commercial Hot Cathode Ionization Gage Tubes," Sept. 1980, to be published

in Journal of Vacuum Science.

G.F. Molinar and Vern E. Bean, "Mercury Melting Line Determination up to

1200 MPa by the Electrical Resistance Method," High Pressure Science and

Technology, B. Vodar and Ph. Marteau, editors, p. 244, Pergaman Press,

Oxford (1980).

G.F. Molinar, Vern E. Bean, James Houck and Bernard Welch, "The Mercury

Melting Line up to 1200 MPa," Metrologia, ljj, 21 (1980).

E. Polturak, R. Rosenbaum and R.J. Soulen, Jr., "Anomalous Cooling Power

of Dilution Refrigerators and the Heat of Transport of He3 - He4 Solutions,"

Cryogenics, Volume 19, Number 12, December 1979.

J. F. Schooley, G. A. Evans, G. T. Furukawa, H. Marshak, R.J. Soulen,

B. W. Mangum, R.P. Hudson, R, Kaeser, and E. Pfeiffer, "Summary of Recommendations to the CCT from the National Bureau of Standards, USA," (1980).

J.F. Schooley, G.A. Evans, and R.J. Soulen, "Preparation and Calibration

of the NBS 767: a Superconductive Temperature Fixed-Point Device,"

Cryogenics, April, 1980.

R.J. Soulen, Jr. and R.B. Dove, "Superconductive Fixed Point Device SRM

768," National Bureau of Standards, Cryogenics, 1979.

C. R. Tilford, S.D. Wood and A.J. Lindquist, "Survey of Altimeter Calibration

Accuracy," proceedings 1980 Air Data Systems Conference U.S. Air Force

Academy, CO, May 5-8, 1980.

C.R. Tilford and Donald Martin, "High Sensitivities Gas/Oil Pressure

Separator," to be published in the Reviews of Scientific Instruments.

C.R. Tilford, S.D. Wood and Ray Colao, "Survey Report: Altimeter Setting

Indicators," FAA SRDS Technical Letter Report, Rd-80-6-LR. 1980.

Ill
B.G. Turrel and H. Marshak, "Magnetic Structure Determined by Nuclear

Orientation, Solid State, Communication 30, 677 (1979).

D. Van Vechten, R.J. Soulen, and R. L. Peterson, "Behavior of the DC

Impedance of an RF-Biased Resistive Squid," Proc. IC-SQUID, Berlin (1980)

S.D. Wood and C.R. Tilford, "Survey of Altimeter Setting Indicators,"

Proceedings 1980 Air Data Systems Conference, Colorado Springs, CO. May

5-8, 1980.

112



LENGTH AND MASS MEASUREMENTS AND STANDARDS DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1980

I. OVERVIEW

The Length and Mass Measurements and Standards Division activities

during the past year were directed towards: (1) activities pursuant to

goals and programs identified during the April 1978 reorganization of

the Bureau and, (2) providing laboratory facilities and measurement

capabilities necessary to accomplish these tasks.

The responsibility of the length program is to maintain, develop,

and improve the foundations of length metrology and to provide the means

and methods of making length measurements consistent with the primary

standard of length. This goal is being realized through several activities:

through laser intercomparisons which maintain concordance in the definition

and the realization of the meter with other national and international

laboratories, by developing improved and innovative technology which

will increase the accuracy of length measurement, and by providing

calibration and transfer services at the highest level for domestic

civil, academic, and industrial institutions which have measurement

responsibilities, and finally, by providing assistance to public and

private organizations whose measurement activities are in the national

interest and who cannot obtain adequate technical support from the

private sector. It is important to remember that the responsibilities

for length measurements and standards as compared to routine length

calibration (gage blocks, line scales, etc.) are administratively

distinct functions, the former residing in the National Measurement

Laboratory and the latter in the National Engineering Laboratory.

The activities of the length group to build up laboratory facilities

and to re-establish an iodine stabilized helium-neon laser capability

have been largely completed. Efforts will now be focused on the stabilized

mercury laser project and a program of innovation and development into new areas of relevance.

The mass group has the responsibility for the scientific aspects of mass measurements including development of mass comparators of the

highest precision. The group also concerns itself with those scientific

experiments where the most stringent mass measurements are required, in

NBS and in the scientific community. Finally, it includes participation

in the international comparison of national realizations of the SI mass

unit, the kilogram. The small size of the mass group (two people)

dictates that efforts be carefully focused on areas chosen for their

importance to primary mass metrology and their efficient exploitation of

available resources. Current projects included the improvement of our

primary kilogram comparator, the determination of air buoyancy corrections

in the weighing process, the certification of silicon density Standard

Reference Materials (SRM's), and documentation of the load cell mass comparator in order to facilitate wide-spread use of this device.

113
II. Technical Activities: Length

Stabilized Helium-Neon Lasers

The iodine stabilized helium-neon laser is the (J>e da^xo length

standard in this country as well as internationally. The responsibility

for maintaining and promulgating the length standard in the United

States rests in the CAPQ and in large measure in the Length and Mass

Division. While the prototype design and testing was completed in the

previous year, full implementation and application have occured this

year. In all, eight complete units have been completed: one is being

used in NEL for calibration services, two for local gravitational

acceleration (small g) measurements (JILA and U.S. Air Force), two for

spectroscopic calibration, two for Length and Mass Division measurements

and one as a loaner for use in experiments which occur from time-to-time

such as the calculable capacitor and the y measurement. Additional

experience with these systems has served to*

3 reinforce the observation

that state-of-the-art stability has been achieved in a portable instrument.

The frequency stability for the 1000 sec. measurement period is about

3 x 10 13 (Av/v), and, because of the wide-band servo system (400 Hz at

the unity gain point), the system stays locked in environments which

cause lower gain, narrower band-width systems to break lock. This is an asset for applications in locations which cannot be made as quiet as a laser laboratory. Several visits have been made to electronic instrument

manufacturing firms in an effort to promote commercial production and

sale.

International intercomparisons have resulted in the observation of

several systematic frequency offsets, the origins of which have not been

clearly identified (power dependent shift and absorption cell specific

shift). Because the elimination of these offsets in an internal cell

stabilized laser is made difficult as a consequence of the nonlinear

interaction between the gain characteristic of the He-Ne gain tube and

the absorption of the iodine cell, experiments have been initiated which

utilize an external absorption cell. While the technology involved in

external stabilization is significantly more complex than internal cell

technology, it is the only way to measure the offsets between the lock

point of the stabilized lasers and the center of the iodine hyperfine

line. We anticipate absolute reproducibility to improve to several

parts in 10 12 . It is apparent that, for the short term, such a system

will replace the internal cell laser as our principle reference laser.

With this system other neon and iodine transitions can more easily be

studied and their suitability for wavelength markers in the visible

spectrum determined.

Stabil ized Mercury Laser

The iodine-stabilized helium-neon laser system is providing an inexpensive and compact length standard at the 5 parts in 10 11 level.

The characteristics which limit it to this value will not be easily

ameliorated and substantial motivation exists to explore and develop

other systems whose performance will exceed 5 10 10 11 or which have

other desirable characteristics. The efforts in the Length Measurements

114
i and Standards Division in this direction are complementary to similar

efforts in other Divisions in CAPQ in which much of the pioneering work

has occurred in the past and is continuing., Several versions of an optically pumped mercury laser have been constructed which operate at

546 nm and which will be stabilized using an internal and external

iodine absorption cell. Output powers of up to 2 mW have been obtained

but thermal stability and pump lamp cavity problems have prevented

reliable operation. The goal is to design an instrument which is more

complex than the widely used argon- ion laser and which is as reliable as the helium-neon laser. At the present time the difficulties are primarily

! engineering.

The importance of the mercury green line in many classical measurements is well known and interest exists in some quarters (for example in

sugar polarimetry) to utilize laser technology in its present activities.

Mercury is a good candidate for a laser system as it is heavy and has a narrow gain-bandwidth which promotes single- frequency operation. In

addition a coincidence has been found between the 198 Hg lasing line and

| an iodine 129 I absorption line thereby assuring the possibility for

intra-cavity saturated- absorption stabilization. It is also interesting

to observe that the mercury laser is in proximity to the frequency

doubled 1.15 pp He-Ne line and that a direct frequency comparison between

the two can be made with the addition of a CO^ line (10 pm) and 17 GHz

from a klystron. Thus the mercury laser represents the highest frequency

oscillator in the microwave to visible frequency chain and will become

important in the efforts to redefine the meter in terms of the second

and a conventional value for the speed of light.

Staff and Equipment Needs

The length effort presently has three professionals, two physicists

and a mechanical engineer who are involved with laser systems - their

stabilization, characterization, and application to measurements and

standards for spectroscopy and metrology. While the present personnel

are versatile and can perform a wide variety of tasks, insufficient time

exists to accomplish all of the goals which are desirable.

A modest increase in staff would allow our interest in fundamental

quantities to be transformed into productive activity. A NRC postdoctoral

fellow will be energetically sought to work on this program.

Long Range Plans

It is the responsibility of the Length and Mass Division, along

with other Divisions in the Center for Absolute Physical Quantities, to

provide the highest precision length standards and measurements capabilities for spectroscopy and metrology. The contribution of the Length

and Mass Division complements those previously-established capabilities

which exist in other Divisions in the CAPQ by providing coupling between

the highest resolution work (e.g. involving molecular beam technology)
and the academic and industrial communities through intermediate-precision

standards (e.g. the intra-cavity iodine stabilized helium-neon laser)

and activities which promote their use. Much ground has been gained in

re-establishing the capability of providing laser length standards for

use within the Bureau and information, in the form of blueprints and

schematic diagrams, for institutions outside of the Bureau who have the

need for such a standards. In addition, while most of the necessary

laboratory facilities are now operational, a large amount of specialized

electronic control equipment must still be constructed. Such a program,

because of the initial absence of laboratory capability, will require

substantial effort as it must be remembered that each active electrooptic component requires at least one electronic servo control and

sometimes nested control loops. The design of these systems, however,

is now routine because of the theoretical work on the stabilized

system. When adequate control electronics is available some of the more

interesting aforementioned studies will be begun in earnest among which

are the measurement of Rydberg Constant (in collobration with W. Lichten,

Yale University) and the stabilization of optically-pumped molecular and

dimer lasers. It is now clear that many candidates for length standards

exist and, when resources allow, they will be investigated.

III. Technical Activities: Mass

A. Kilogram Conservation.

1. Objectives. The kilogram is now unique among S.I. units in

that its definition still relies on a mutable artifact. The precision

with which two such artifacts may be compared approaches 1 ppb. It is

of obvious importance that a mass comparator with this precision be

maintained in order that inchoate problems with the mass unit be identified

well before they impinge on the measurement system derived from the

kilogram artifact. It is an objective of our program to maintain such a comparator and to make use of it as outlined above.

2. Current Activities. Work continues on improving our primary

kilogram comparator. This balance was built commercially several years

ago and is based on the design of NBS-2. (This latter balance was designed and built at NBS and now serves as the prime comparator at the

BIPM. ) A new hydraulic cylinder to raise and lower the weight table in our balance is being installed. In addition, we are fabricating platinum

counterweights for use with the balance. Such counterweights will

enable us to intercompare platinum kilograms on the single-pan balance

while maintaining the balance in buoyant equilibrium.

3. Accomplishments. The prototype kilograms of the United States,

K4 and K20, have been placed in new enclosures which are designed to

offer improved protection from atmospheric pollutants. In addition,

physical security for the prototypes has been strengthened. The precision

of our kilogram comparator has been improved by a factor of two during

the past year. We believe that the present precision of this balance, 3

ppb, may yet be improved upon.

116
4. Future plans. We believe that the precision of our balance is

now high enough to warrant recalibration by the BIPM of our kilograms K4

and K20. We will arrange such measurements in the coming year. In

addition, we expect to contribute to the working groups established by

the CIPM to examine the major problems in primary mass metrology.

B. Air Buoyancy.

1. Objectives. We are undertaking a program to improve our understanding of buoyancy corrections in the weighing process. Such

corrections, now based on Archimedes* Principle and a semi -empi ri cal

equation of state for moist air, dominate the uncertainty when platinum

and stainless-steel kilograms are compared on the best balances. By

making use of an evacuable enclosure and a kilogram balance with servo

control, we intend a systematic study of this problem.

2. Current Activities. The stainless-steel enclosure is being

completed. A force transducer for the servo-controlled balance has been

made; the servo electronics have been designed and are being assembled.

3. Accomplishments. Reports of our experiments testing normal air

buoyancy correction practices have appeared in Science and the NBS

Journal of Research . The construction of the apparatus described above

is well along although not yet complete.

4. Future Plans. During the next year, we expect to complete both

the vacuum chamber and the modifications of the balance which it will

enclose.

C. Density SRM* s.

1. Objectives. The motivation for this project is to make available

to interested users the highly-precise density information contained in

the silicon artifacts which were used in the determination of the Avogadro

constant by Deslattes et a^. In the latter experiment, the volumes of

four single-crystal pieces of silicon were determined through a direct

link to the krypton length standard. The final uncertainty for the

volume determination was less than 2 ppm—considerably better than could

have been achieved using standard techniques, which rely on turn-of-thecentury data for the density of distilled water. We believe the density

of the four silicon crystals has not (nor could it) change significantly

since the initial density determination. It is, therefore, our intention

to transfer volumetric knowledge of these crystals to other silicon

crystals which may then be provided to users through the Standard Reference

Materials (SRM) program.

117
2.

Current Activities. Approximately 15 kg of single-crystal

silicon have been purchased. In conjunction with the NBS Optical Shop, we are now beginning the tedious task of fashioning this raw material

into objects of 200 g and 100 g. We are also modifying a commercially

available top- loading balance for use in the hydrostatic comparisons of our "new" and "old" silicon and recalibrating our working standards of

mass.

3. Accomplishments. We have demonstrated the feasibility of the

balance modification mentioned in the preceding paragraph using a 1 kg

top-loading electronic balance. Briefly, the force transducer and pan

of the balance are separated from the electronics and completely submerged

in an inert fluorocarbon liquid. The servo electronics are then altered

slightly with the result that the submerged balance meets virtually all

of its original performance specifications. One now has a hydrostatic

balance with no suspension wire breaching the fluid-air surface and with

all the convenience of a modern top-loading balance. The SRM program,

which will require our certification of some seventy-five artifacts,

will benefit from this technology as applied to a similar top-loading

balance of 30 g capacity and 0.0001 g precision.

4. Future Plans. We expect to complete the SRM project in the

next fiscal year. At this time, there are several national laboratories

independently pursuing programs to acquire a density metrology of the

same level of accuracy as our own. It would be extremely useful to

arrange a round robin calibration of silicon objects with these laboratories when feasible.

D. Load Cell Mass Comparator.

1. Objectives. The Office of Weights and Measures (0WM) has a goal of providing state laboratories with a convenient device for

tolerance testing of 50-pound weights. The proposed device must offer

advantages of speed and ease of use. Additionally, the resolution must

be well in excess of the 2 g tolerance on these weights. A concept,

developed by R. M. Schoonover of this Division, for achieving the

desired goals has been supported by 0WM.

2. Current Activities. Because the load cell mass comparator has

evoked considerable interest in the metrological community, both from

users and manufacturers, we are now documenting the mechanical and

electronic package in order to facilitate wide-spread use of this device.

3. Accomplishments. A working 50-pound comparator with a precision

of 0.03 g has been constructed. In addition, an inexpensive electrical

package has been designed and fabricated. The package (based on a circuit of R. D. Cutkosky of this Center) has the merit that its large

on-scale range (100 g) is useful in adjusting weights to tolerance.

4. Future Plans. The 0WM intends a field test of the device in

the state laboratory of Texas. We expect to be involved in this project

as consultants.

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PUBLICATIONS

Length & Mass Measurements & Standards Division (523)

William E. Anderson and Richard S. Davis, "Measurements on Insulating

Materials at Cryogenic Temperatures", NBSIR 79-1950, Final Report under

DOE Contract No. EA-77-A-01-6010, Task No. A023-EES, August 1979.

V. E. Bower and R. S. Davis, "The Electrochemical Equivalent of Pure

Silver - A Value of the Faraday", J. Res. Nat. Bur. Stand. 85, 3, MayJune 1980.

Frank E. Jones, Randall M. Schoonover and John F. Houser, "In-Tank

Measurement of Solution Density", J. Res. Nat. Bur. Stand. 85, 3 MayJune 1980.

Howard P. Layer, A Portable Iodine Stabilized Helium-Neon Laser, IEEE

Transactions on Instrum, and Measurement.

H.P. Layer and W.R.C. Rowley, R.M. Marx (National Physical Laboratory,

Teddington, England), NPL-NBS Iodine Stabilized He-Ne Laser Intercomparison,

Metrologia, Optics Letters.

R. M. Schoonover, R. S. Davis and V. E. Bower, "Mass Measurement at

NBS - A Revision", Science, Vol. 207, pp. 1347-1348, 21 March 1980.

R. M. Schoonover, R. S. Davis, R. G. Driver and V. E. Bower, "A Practical

Test of the Air Density Equation in Standards Laboratories at Differing

Altitude", J. Res. Nat. Bur. Stand. 85, 1, January-February 1980.

R. M. Schoonover, "A Simple Gravimetric Method to Determine Barometer

Corrections", J. Res. Nat. Bur. Stand.

R. M. Schoonover and R. S. Davis, "Quick and Accurate Density Determination of Laboratory Weights", Proc. of 8th Conf. of IMEK0 Tech. Comm.

TC3, Measurement of Force & Mass, Weighing Technology, 9/9-11/80, Krakow,

Poland.

Randall M. Schoonover and Frank E. Jones, "Buoyancy Correction & Weighing

on Analytical Balances", Analytical Chemistry.

119
INVITED TALKS

Length & Mass Measurements & Standards Division (523)

H. P. Layer, "Recent Developments in Iodine Stabilized Helium-neon

Lasers", June 25, 1980, Conference on Precision Electromagnetic Measurements, Braunschweig, Germany.

H. P. Layer, "Design, Construction and Performance of Iodine Stabilized

Lasers", Hewlett-Packard Laboratories, Palo Alto, California, July 14,

1980.

H. P. Layer, "Design, Construction and Performance of Iodine Stabilized

Lasers", Boeing Aerospace Co., Seattle, Washington, July 16, 1980.

R. M. Schoonover, presented a lecture at a George Washington University

Continuing Engineering Education Program, "Operating Techniques for

Standards and Calibration Laboratories", April 17, 1980.

R. M. Schoonover, "Quick and Accurate Density Determination of Laboratory

Weights", 8th Conf. of IMEKO Tech. Comm. TC3, Measurement of Force &

Mass, Weighing Technology, September 9-11, 1980, Krakow, Poland.

120
COMMITTEES

Length & Mass Measurements & Standards Division (523)

R. S. Davis, member, American Society for Testing & Materials, E41.06,

Weighing Devices, subcommittee of E.41, Laboratory Apparatus.

R. M. Schoonover, member, American Society for Testing & Materials,

E41.06, Weighing Devices, subcommittee of E.41, Laboratory Apparatus.

121



TIME AND FREQUENCY DIVISION

SUMMARY OF ACTIVITIES

FISCAL YEAR 1980

I. OVERVIEW

The Time and Frequency Division provides innovative product prototypes, research results, and services to a variety of users that include

small businesses, various U.S. Government agencies, the systems synchronizer, the researcher, and the average citizen. Innovative product

prototypes include the TV time system which introduced the technology

that resulted in TV captioning for the deaf; the prototype satellite

time receiver which has stimulated receiver development by several

companies for new product lines; the new quartz standards with improved

stability and accuracy which may grow into an industrial product; and

the passive hydrogen standard which has the promise to be a major product

line in a rapidly expanding position- location market.

Commercial TV time systems are currently being manufactured by

eight companies but the number of units sold is being limited by several

network stations using frame synchronizers, which breaks the NBS-to-user

direct link. The concept—created by NBS staff—of TV captioning has

been developed through efforts of PBS (Public Broadcasting System) into

captioning for the deaf. A National Captioning Institute has been

created to caption TV programs.

The NOAA GOES satellite time system was initiated as a joint program

to serve the NOAA data collection programs and to disseminate highly

accurate time. Commercial versions of the time code receiver have been

developed by three manufacturers. To date, several hundred receivers

have been sold and delivery backlogs of several months have been reported

by the manufacturers.

The quartz and rubidium standards improvements are more recent, and

the extent of industrial application have yet to be measured. The

latest innovative potential product is the passive hydrogen standard

which has demonstrated parts in 10 15 stability for one week averaging

times. Because of the small size, relatively small power requirements,

and favorable stability/cost ratio, the passive hydrogen standard may

| have great demand (many hundreds of units) for high stability applications.

An embryonic prototype product presently under development is a reasonably priced Global Positioning System (GPS) receiver which is

designed to allow nanosecond time coordination utilizing the GPS system.

Although GPS receivers are available at $150,000 per unit, the NBS

receiver is being developed for common- view time coordination applications,

is anticipated to have a market price of approximately $20,000, and will

|i be a user alternative to maintaining his own primary standard.

122
Research outputs have been concentrated in removing the limitations

of atomic standards and developing high accuracy measurement technology.

Trapped ion cooling research is in progress to remove the Doppler limitations of present atomic standards. Although not applicable to cesium,

the techniques could lead to parts in 10 15 accurate atomic standards,

and open up new fields in very high resolution spectroscopy. Frequency

synthesis that extends frequency based measurements in the infrared and

visible region has allowed the measurement of benchmark frequencies that

are being used in atmospheric and isotope separation programs in other

agencies. The development of laser stabilization techniques has allowed

the adoption of standard lasers—most notable are the helium-neon and

the carbon dioxide laser systems.

In addition to the removal of Doppler effects from primary standards,

one of the most notable problems in time, frequency, and wavelength

standards development is the multiplication or division of frequencies

between the visible and the microwave. Division efforts at multiplication

will lead to a proposal to redefine the length standard in terms of

frequency techniques in the 1982 time period. However, the practical

utilization of a microwave standard as a visible length standard, or an optical length standard as a one-tick per second clock is yet to be

demonstrated. One possible solution to this problem has been suggested

by Division personnel —the synchrotron divider. Because of the radical

nature of the suggestion, 3 to 5 years will be required to demonstrate

and prove the technique. Although success is not certain, the potential

impact of the device, in operational standards in particular, and in

applications in general, is so high that this technique could be one of

the most important NBS outputs to date.

The services provided by the Division cover a wide spectrum. Time

and frequency information, as well as general interest information, is

transmitted on several frequencies from radio stations in Hawaii and

Fort Collins, Colorado. Higher precision information is available from

code transmissions from the NOAA GOES satellite, and the highest precision

information, where available, is provided by a calibration of the color

subcarrier from major network stations originating programs on the east

and west coasts and from calibrations of selected Loran-C broadcasts.

In addition to these general services, a limited Measurement Assurance

Program (MAP) service is being developed which will allow locally available time and frequency information to be calibrated and made "traceable"

through an NBS computer operated system.

Although not strictly a service, the time scale and time coordination is fundamental to the research and services provided by the Division.

The time scale is developed from the output of a set of commercial

cesium standards and NBS-4 and NBS-6. The time scale is required to

evaluate the national standards of frequency (NBS-4 and NBS-6) and new

and highly stable standards such as passive hydrogen; to provide time

information for services; to provide a measure of the SI second for the

international time scale (TAI), and to provide time on a working basis

to assist along with others in the generation of TAI and its companion

time scale, UTC. However, without effective coordination mechanisms,

NBS would be an island of standards without effective access by the

123
users or known relation to other international standards. At present,

international coordination is accomplished through several Loran-C links

to Europe. These links are not accurate enough to transfer time at the

limits of the time scale accuracy. Experiments utilizing GPS and other

satellite systems are being planned to improve the international coordination of time.

The users of our products are diverse. Division innovative prototype

products have led to the establishment of GOES satellite receiver product

lines in three companies. The TV prototype receivers have led to 8

companies manufacturing line- 10 and frequency calibration equipment.

The technology developed in the Division and broadened by PBS has led to

the sale of over 17,000 captioning systems to date, an order rate of

1800 per month, and a backlog of 4 weeks by the manufacturer.

The output from the frequency metrology programs is being used by

astronomers to identify molecules in space, by N0AA and NASA for pollutant

measurement and monitoring programs, by DOE research labs for isotope

separation programs, by other NBS Divisions as calibrations for molecular

spectra, and by N0AA and NCAR in atmospheric modeling programs. The

stabilized lasers are being used in precision spectroscopy by researchers

in state, federal, and private labs. The aggregate of laser frequency

measurement data will be the foundation of a set of spectral tables from

100 GHz to 1,000 THz which will become as important as the microwave

spectrum tables that have been developed over the years at NBS.

The hardware outputs of the frequency metrology program in the

Division and in JILA have resulted in a "defacto" methane stabilized

laser length standard in industry. The stabilized laser geodimeter

being developed for high accuracy, long baseline measurements will be

integrated into Geological Survey earthquake monitoring and prediction

programs, can be used by N0AA and the military to accurately measure

water vapor content over long baselines, and could be a first step in

developing intrinsic standards for atmospheric measurements.

The improvements in application standards such as rubidium and

hydrogen are being studied for the Global Positioning System (GPS) and

the findings are available to manufacturers to improve the stability of

their commercial standards. High stability passive hydrogen standards

may have significant impact on high stability timing systems and scientific experiments, and commercial applications should lead to the introduction of a new industrial product line. The promised improvement in

cesium standards will increase the accuracy of prototype primary standards,

and will be available for commercial exploitation for the higher accuracy

segment of the market.

The users and applications of Division dissemination services

include the small boat owner as a sole source for navigation, the larger

ship as a routine time reference and to gain access to other navigational

systems or as a back-up navigational source, the power distribution com- panies for fault location and system synchronization, the communication

system operator for system calibration, the FAA and other federal agencies

for event documentation, the remote military unit for setting navigation

124
aids, the large computer system user to document events, and the citizens

to set their watches. It has been estimated through NBS surveys,

receiver manufacturers, and trade journals that tens of thousands of

people and systems use Division services. The users are numerically

distributed in a pyramidal shape with the lower accuracy user at the

base, and the highest accuracy user at the apex.

II. TECHNICAL ACTIVITIES

1. Primary Standards

During the last five years, the Division has followed the internal

strategy of concentration on standards research, to maintain a minimal

effort in the operational time scale, to completely evaluate the primary

standard for absolute accuracy about once each year and not continuously

operate the primary standards as clocks in the time scale, and to utilize

research results for quantum step improvements in frequency standards

and the time scale. There are several reasons for this strategy—the

availability of external research funds due to the influence of the GPS

system, the specialized talents that have been aggregated in the Division,

the apparent desire of NBS management to pursue high quality research,

and the confidence that research will result in significant improvements

in NBS standards and credibility in the scientific and standards fields.

In addition, present microwave frequency standards are based on concepts

developed 15 to 25 years ago. These concepts have generally reached

maturity. In order to provide a thrust for further advancements, con- ceptual changes in the approach rather than better engineering are required.

The major emphasis during the last year has been research to remove

the limitations of atomic beam standards and the updating of the time

scale. Cesium is, and will continue to be, the international standard

of time and frequency for the next decade. In conventional cesium

beams, the first-order Doppler shift is avoided—to first ordei—by

using a Ramsey cavity. However, fixed phase differences between the

cavity ends cause biases in the frequency. These phase differences are caused by the finite conductivity of the cavity, and cannot be removed

except by using superconducting cavities. Continuous sweeping of the

phase difference (with a second frequency) removes the fixed phase

offset. The two-frequency experiments conducted during the last year

indicate that crosstalk between microwave cavities may have been responsible for an observed frequency offset. Further work in FY81 should

determine the importance of crosstalk related systematics in a future

standard.

Optical state selection increases signal-to-noise by pumping all

atoms into the desired state, decreases sensitivity to distributed phase

shift across the opening of the cavity, and provides a means to increase

the understanding of the frequency shifts caused by Majorana transitions.

The goal of this effort is to demonstrate that all the atoms can be

pumped into the F = 4, ny = 0 state. The attainment of this goal would

result in a factor of 16 enhancement in usable beam and greatly reduce

125
I

I

II

I

i|| the background as compared to present Cs designs. Moreover, the lack of

population in the other hyperfine sub- levels should permit a study of

Majorana transitions. These transitions occur between the magnetic

state selection region and the Ramsey cavity region in current Cs beam

designs and are a concern in the accuracy of cesium standards. In

addition, the lack of population in other sub-levels should reduce the

| influence of their Rabi peaks by one or two orders of magnitude as compared to traditional designs, thus permitting operation at a lower

C-field. Experiments are underway to evaluate the improvements due to

optical pumping. During FY81, diode lasers will be evaluated in state

|! selection. Success in this effort will simplify operational implementation of this state selection technique. Development of the two- frequency

method and optical pumping state selection are key areas of research

j directed toward improving the accuracy of cesium primary standards by

almost an order of magnitude.

I

A major limitation of all atomic standards is due to Doppler effects.

When ions stored in an electromagnetic trap are cooled with laser radiation within the Doppler linewidth but at a frequency below the line

|J center, kinetic energy is removed from the ion system by radiation. In

| addition to the radiatively selected ion, other ions in the trap will

also be cooled because of Coulomb interactions. Experiments conducted

during the last year indicate that ions can be radiatively cooled into

the mi Hi -Kelvin range, ions can be stored for hours to days, and hyperfine linewidths of 0.2 Hz can be achieved. Further improvements should

lead to linewidths between 0.001 to 0.1 Hz with high signal-to-noise.

Given hyperfine transition frequencies of order 10 10 Hz, quality factors

of order 10 11 to 10 13

, approximately 103 to 10 s times larger than present

cesium devices, are anticipated.

While laser cooling is much more difficult to achieve with cesium,

cooled ions have many potential advantages. The ions can be stored for

long periods in a container which has small, calculable perturbations to

the energy levels; first and second-order Doppler effects can be essentially eliminated; and once trapped and cooled, either microwave or optical transitions (or both) can be used as frequency and length standards. Projected frequency stability! of a cooled ion microwave standard

is of the order of 10- 12 to 10- 14

z and the stability of the device

will be limited by the available local oscillators to drive the transition, while for optical frequency stapdards, projected frequency stabilities are of order 10- 14 to 10- 16

z In order to achieve the best

j performance, it is likely that a full sized passive or active hydrogen

maser or a greatly improved crystal oscillator will be required for the

local flywheel microwave oscillator. Work on more stable laser flywheel

oscillators is also being pursued in conjunction with the stored ion

effort. Absolute accuracies of 10- 15 and frequency stability in the low

10- 16 range for days to weeks are anticipated. In addition to the

advantages for standards, the cooled ion technique is ideal for spectroscopic research on ions. Because of its broad impact on high precision

metrology, it is anticipated that cooled ion technology will be an active Division program for at least the next 5 years.

During the next year, the two-frequency excitation and laser state

selection experiments on cesium will be completed and experimental

126
results will be evaluated and published. If anticipated results are obtained, preliminary designs and experiments toward NBS-7 will be

undertaken in FY82, and a schedule for construction, operation, and

testing will be established by the end of FY84.

Since the initial development of passive hydrogen standards in the

Division two years ago, significant progress has been made toward introducing improved clocks to the time scale. Prototype devices have been

constructed, tested, and delivered to OA sponsors who have shared in the

development costs. Stability of 1 x 10- 14 in one week has been measured

for the passive standard and two more are planned for inclusion in the

time scale by December 1980.

A prime obstacle to an optical time standard has been the inability

to develop an operational means to run a one pulse per second clock from

an optical frequency laser. Frequency division using a one electron

synchrotron may remove this obstacle. This concept, developed in the

Division, is based on the cyclotron, synchrocyclotron, and synchrotron

method to accelerate charged particles. Instead of using a localized

microwave field to drive the charged particle, a well collimated, Gaussian

laser beam, focused to a spot diameter of approximately one wavelength,

will be used to drive an electron in a Penning trap. The electron

should absorb energy from the laser radiation field, and will cycle at

and be phase locked to a very small subharmonic of the laser frequency

if the electron spends on the order of one cycle of the laser radiation

in the laser beam. The subharmonic frequency is observed by an image

current, hence a single electron is required to precisely define the

phase of the output signal. During FY81, microwave synchrotron division

will be attempted to determine the stability of the one-electron orbit.

If stability and image current signal-to-noise are sufficient, infrared

laser division will be attempted in FY82. Results of preliminary experiments and pressures due to other high priority programs will determine

the direction and speed of this project.

During the last year, the time scale has been completely rebuilt.

A PDP-11/70 is the heart of the new system; dual mixer techniques are utilized in the new measurement system (capable of 10- 16 accuracy); a totally new time scale algorithm based on Kalman theory has been initiated;

and input capability of up to 30 clocks has been built into the system.

The driving force for the new time scale was two-fold. First, the old

time scale could not handle more than 9 clocks, requiring major disruptions

in time scale operation to test new clocks. Second, the precision of

the old time scale hardware limited the ability to measure high stability

clocks, like the NBS passive masers, and to evaluate NBS-6. When completed,

the time scale will allow completely automated time scale operation; the

evaluation of high stability standards against the ensemble; the real

time testing of new time scale algorithms; and the evaluation of the

primary standards. With the addition of the three passive masers, the

new NBS time scale should be the most stable scale in the world. Time

scale algorithms will be the subject of a special conference to be held

in Boulder in conjunction with the 1982 CPEM conference. Although the

implementation of the time scale was the single largest program in the

standards area, most of the milestones should be completed in the first

months of FY81 and resources can be diverted to other high priority

programs, although some work on new time scale algorithms will continue.

127
NBS-6 was completely evaluated during the last year. Evaluations

include the measurement of cavity phase shift by reversing the beam

direction several times, calculating second-order Doppler shift from the

velocity distribution which is determined by de-volving the Ramsey

pattern line profile, measuring the magnetic field and checking the

various operating conditions of the device, and accounting for all the

error sources. The one-sigma accuracy of NBS-6 is 8 x 10- 14 .

NBS-6 actually calibrates the frequency of the NBS time scale,

which, in turn, is compared over many months with other national and

international time scales, and then to the NRC and PTB primary frequency

standards. Since NBS is approximately one mile above sea-level, NBS-6

is corrected for a gravitational blue-shift of 18 parts in 10 14 . The

Loran-C link adds an uncertainty of nearly 10 x 10- 14 between NBS and

the BIH. NRC, PTB, and NBS have agreed to a few parts in 10 14 over the

last three years with an uncertainty of 15 x 10- 14 .

2. Coordination

The coordination group is the newest group in the Division and was created when it was determined that coordination of time scales was the

weakest link in the international time program. Currently, time is

coordinated over long distances by monitoring Loran-C (with an accuracy

of under one microsecond over a period of a year) and by periodic portable

clock trips (with an accuracy of tens of nanoseconds). The Loran-C link

to the BIH is the operational link between NBS and international time

scales, but satellite coordination experiments have been carried out by

several countries, including the U.S. In 1979, a series of experiments

was carried out between NBS, USNO, and NRC in one link, with NRC and BIH

on another link. These experiments demonstrated the potential of nano- second (precision) operational coordination over large distances. The

initial NBS satellite link was made available through the cooperation of

an NIH contractor at the University of Colorado Medical Center in Denver,

and included a clock carry to Denver for every experiment. In a later

portion of the experiment, Comsat Labs loaned NBS a transportable satellite terminal, which permitted on-site operation from NBS.

Although many satellite systems have been investigated in an attempt

to find a suitable combination to adequately serve national and international needs, the costs and hardware requirements at all the potential

locations made the resource problem significant. Although the military

can conceive of and initiate large capital equipment projects, the

Bureau and the Division find capital intensive programs difficult to

justify. Therefore, alternative systems were investigated and two

potential options were identified—two way Loran-C, and common- view GPS.

Common-view GPS coordination takes advantage of a military position

location system and, because of geometric considerations, is not critically dependent on ultimate accuracy of ephemeris data (e.g., a 25

nanosecond ephemeris error corresponds to only a 2 nanosecond timing

error). In normal position location applications, the receiver costs

are approximately $150K, which makes this another capital intensive

system. However, because of an historic involvement with satellite and

time receivers, and a unique digital electronics capability, the Division

128
is completing a GPS receiver, which can be used for common- view coordination, for parts and assembly costs of appoximately $6K and an estimated

commercial cost (after NBS prototype development) in the $20-$25K range.

During FY81, the receiver will be completed and tested, and initial GPS

experiments will be performed and evaluated. By FY82, if evaluation

tests are successful, prototype GPS common-view coordination experiments

will be conducted between NBS, the Naval Observatory, and NRC. Because

of the potential importance in high accuracy time coordination for space

as well as military applications, other agency funds have been made

available to partially support the receiver development effort. For

example, NASA requires parts in 10 13 coordination at their tracking

sites in Australia, Spain, and California for their deep space programs.

In August 1981, an extremely critical correction will be made to navigate

the Voyager 2 around Saturn and on to Uranus. Estimates indicate that

time coordination using GPS and the NBS developed time receivers would

save in excess of $1M per year over using their antenna system and deep

space noise correlation techniques.

Position and time are intimately related, therefore research on position location systems have direct impact on time dissemination

systems. NBS and NOAA are engaging in a joint program to use the GOES

time code combined with the GOES position as a means of finding the

location of unanchored buoys reporting data through the GOES data retrieval

system. This program is scheduled for completion in FY81.

Because of the size, potential, and importance of the GPS system,

GPS will likely play an important role in the future of time dissemination

and time coordination. However, the political and military questions of

degredation of accuracy for nonmilitary users, the economic questions of

receiver costs, the military questions of access to the system, and the

technical questions of standards performance in space remain as potential

roadblocks to the full realization of GPS. On the other hand, the

Division cannot dismiss the GPS potential and turn to other options

until the roadblocks are proven to be insurmountable. The Division will

maintain its input into the GPS design and implementation through contacts

with the USNO and SAMSO, and its efforts to make the GPS time transfer

as accurate and general as possible within national security guidelines.

Definitive answers to all questions should be available before the

scheduled 1985 implementation date.

3. Dissemination

Access to the NBS standards of time and frequency is via 2.5, 5,

10, 15, and 20 (at WWV only) MHz services from two radio stations located

at Ft. Collins, Colorado and Kauai, Hawaii; a 60 KHz service from Ft.

Collins; a satellite time code from the NOAA GOES satellite; and non-NBS

broadcasts usable as transfer standards (such as calibrations of the

color subcarriers of major east and west coast TV networks and Loran-C

and Omega Navigation System transmissions); and occasional portable

clock trips.

WWV was relocated and WWVB was built at Fort Collins in the 1962-65

period at a cost of $1.5M, and WWVH was relocated to Kauai in 1970 at a

129
cost of $1.2M. Using the GNP deflators, the present capital value of

the radio stations is $6.1M in plant, facilities, and land in Fort

Collins (WWVH is located on a military establishment). After a major

cost reduction program due to automation and substantial staff reductions

in the 1974-1977 period, the radio stations began a period of minimum

subsi stance level operation that will be continued for the foreseeable

future. During the last year, the stations transmitted at better than

99.9% of the time indicating the success of the automation programs

which were carried out inhouse.

Current annual operational expenses at the stations have been cut

by $400K relative to the level projected before automation, in spite of

the fact that electric power bills have increased dramatically in the

last few years and presently stand at the $254K level.

In addition to routine maintenance at the station, the transmitters,

time code generators, environmental control systems, antenna support

systems, and electric power systems at WWVB have been updated during the

last year, so that a 15 year lifetime can be expected from the improved

systems.

During the last ten years, the dissemination research program was

born, blossomed, and faded, but operational programs resulting from this

research are in place within and outside the Division. Late in the

1960's, an effort to identify new options for time and frequency dissemination was undertaken. As a result of this effort, Congress allocated

$455K to the Dissi mi nation Reseach program for TV, satellite, and Omega

Service implementation in FY73. This Congressional initiative, plus the

WWVH initiative, made the time and frequency dissemination programs the

most successful of all NBS programs in obtaining Congressional initiative

funding for NBS programs. These research programs resulted in the

development of the GOES service, TV time and frequency calibrations (and

captioning for the deaf), and the beginnings of the MAP program. In

addition to numerous technical papers regarding the research results,

the dissemination research program earned 6 NBS awards including the

Harris Applied Research Award, 2 Department of Commerce awards (a Bronze

medal and an Inventor's Award), two patents, an IR-100 award, and an Emmy Award (for the modification of the Division developed TV Time

technique for captioning for the deaf). Today, there is essentially no time and frequency dissemination research being conducted in the Division.

The GOES time code, transmitted at 468 MHz from two NOAA satellites

and fed from an uplink from Wallops Island, VA, has been operational for

three years. This time code was the first routine time broadcast from a satellite, but because it was established mainly to serve the NOAA data

buoy system, the transmission frequency is in the satellite meteorology

band, not in the 400 MHz time and frequency allocated band. During the

last year, the automation and upgrading of the Wallops Island time code

instrumentation was completed. The new triply-redundant system allows

updating and troubleshooting via phone lines from Boulder, more frequent

updating of the satellite position information included in the format,

and improved monitoring and control of the timing signals. The updating

was extremely successful, and no maintanance travel to Wallops Island

130
was required during the year. During FY81, direct access to the NOAA

computer in Suitland, MD for satellite position information is planned.

This direct access (assuming that suitable arrangements can be made with

NOAA) will eliminate Division ephemeris calculations, provide better

real time data, and reduce the Division costs for the operation. In

FY82, the GOES time code operation will join the radio stations in the

minimum subsistence mode of operation. Although the present formal

agreement between NBS and NOAA for the GOES time code ends in 1982,

another 5 year commitment is anticipated.

The TV frequency calibration service is one of the most accurate

means to access the NBS standards outside of portable clock trips. However, TV technology is changing and the industry trend towards the use

of frame synchronizers at some network stations may gradually reduce the

usefulness of the TV technique for frequency calibrations except within

local geographical areas. It is anticipated that sales of commercial TV

calibration systems will decline during the next few years, and the

future of this system is uncertain. However, the NBS calibration system

is completely automated and now requires only a few hours per month of

effort to keep the system operating.

The only program in the dissemination area that is not on a minimum

subsistence level is the Measurement Assurance Program (MAP). The concept

of the MAP technique is the automated calibration of locally received

time and frequency information coordinated through a telephone connection

to an NBS computerized monitoring system. The MAP service is being

developed on other agency funding using off-the-shelf commercial equipment

(no NBS responsibility to repair or calibrate this equipment). The

locally received time information can be from GOES, WWVB, Omega, Loran-C,

or TV. The MAP concept is extremely important in long range planning

because high precision time and frequency transfer will increasingly be

piggybacked on other types of communication systems. In the long run,

most access to the NBS standards will be through the calibration of

other transmissions, i.e., the stabilized transmission frequency of a communication system, the transmission from a GPS satellite, etc.

Therefore, the MAP concept—calibration of locally available signals

will be important for cost-effective traceability to NBS standards.

4. Frequency Metrology

The objective of the frequency metrology task is to develop and

apply frequency based metrology from the microwave to the visible. The

task has two important parts —frequency synthesis and applications.

The frequency synthesis effort is motivated primarily by the needs

of the international standards community and the needs of other agencies

requiring precise frequency based measurements and metrology. The Division

has demonstated that frequency synthesis to the visible was feasible

through a joint experiment with the Canadians, where a 1.15 micron laser

was doubled to a visible frequency in a crystal and a saturated absorption was used for stabilization. This experiment completed the feasibility demonstration phase of the frequency multiplication into the visible.

131
During the last CCDM meeting in 1979, it was recommended that if

length metrology could be accomplished more accurately by frequency

based metrology, the definition of the meter should be changed to take

advantage of the increased measurement accuracy. NBS made a commitment

to extend frequency based metrology to the visible region with parts in

109 uncertainty before the 1982 CCDM meeting.

For the CCDM effort, a scheme has been developed to mix the fifth

harmonic of a locked 11.5 micron C02 laser with a signal from a color

center laser operating at 2.3 micron, whose second harmonic is locked to

a 1.15 micron HeNe laser. The second harmonic of the 1.15 micron laser

is locked to a saturated absorption line in iodine. During the last

year, the 130 THz C0 2 line was measured to a precision of 0.6 parts in

10- 9

, design and parts ordering for the YAG pumped KC1 : Li Cl (F2 +)

A

color

center laser was completed, and the iodine saturable absorption system

was completed. During FY81, an NRC postdoc will complete the construction

of the color center laser, and preliminary attempts at the 109 measurement

will be completed. By early FY 82, final measurements of the 520 THz

iodine line will be completed, an error estimate will be made and documented, and the results will be forwarded to the CCDM in advance of the

1982 meeting.

The C0 2 laser is one of the main lasers used in the frequency metrology program. These lasers have been in a state of development and

refinement at NBS since 1969, and serve a multitude of functions including

routine frequency synthesis up to 100 Thz, where they serve as secondary

standards and as high power optical pumps for infrared lasers (such as the alcohol lasers). The latest versions have increased mechanical

stability and no Brewster windows in order to reduce the spectral linewidth to approximately 6 KHz, a factor of three better than previous

designs.

The first significant milestone in the synthesis effort occurred in

1973 when two C02 lines (one at 32 THz in the 9 micron band and one at

29 THz in the 10 micron band) were measured with respect to the cesium

standard, each carbon dioxide line being measured with an uncertainly

of about 25 KHz (~10- 9

). Since that time, over 80 lines in the normal

C0 2 bands have been measured at NBS, and over 600 lines have been measured by other laboratories using the original NBS 9 and 10 micron benchmark frequencies. All of these lines were measured with lasers stabilized by C0 2 saturated absorption techniques. The uncertainty of the NBS

measurements is about one part in 109

.

During the last year, 18 lines in the [011 !! - 111 0] band of 13 C 16 0 2 near 11.6 microns were measured with the stabilized 13 C02 laser as the

source. In addition to the 100 plus carbon dioxide lines, 287 alcohol

and difluoromethane FIR laser lines have been measured and published.

The measurement of these FIR lines was made possible by the highly

stable carbon dioxide lasers ability to generate a near continuum of far

infrared frequencies which can be beat with the alcohol laser frequencies.

The alcohol and difluoromethane laser lines were measured because of the

importance of these alcohol lasers in infrared spectroscopy, and because

of the need for these measurements for space and astromonical research.

132
In other areas of the frequency synthesis program, the frequencies

of new 13 C0 2 laser hot band (Ol 1 ! - 11 1 0) were measured. These new hot

band measurements were required to supplement the normal 13 C0 2 laser

frequency range and thus extend frequency measurements of the \) 1 band of

OCS at 11.6 microns across the band center. Both normal

Q

and hot band

lasing lines of 13 C02 were also used to measure key [20°0 - 10°0] hot

band lines of OCS in order to predict frequencies for the 2v x band at

5.8 microns. OCS is one of two molecules selected for use as an absorption frequency/wavelength standard— the other molecule is N 2 0. These

linear molecules were selected because they lend themselves to exact

analyses and hence to reliably calculated frequency values. Additionally,

they have many lines in the 5 to 12 micron range and the frequency

spacing between lines is the same order as the tuning range for a tunable

laser, i.e., 15-30 GHz. Current state-of-the-art for tunable lasers

requires such absorption frequency/wavelengh standards to provide spectroscopic calibrations to better than 3 MHz. These calibrations are important

in federal and commercial isotope separation, in atmospheric pollution

monitoring, and in space research programs.

In the 11.6 micron measurements, the diode laser was locked to the

center of the OCS absorption line, and the beat frequency between the

diode laser and a known 13 C02 laser frequency was measured. The accuracy

of these measurements is ± 2MHz in the best cases. The experimental

range of the frequency measurement system will increase upon receipt of

a 1500 MHz bandwidth HgCdTe detector to replace an existing 100 MHz

device. In FY81, the OCS 2\> 1 band measurements will be completed by

using the same technique except with a CO reference laser and, in turn,

the laser reference lines will be measured with respect to the C02

standards.

These same techniques will also be applied to several isotopic

species of OCS such as 18 0CS, 0 13 CS, and 0C34 S in order to expand the

total number of reference frequencies available. Frequency measurement

on N 2 will also start in FY81. The [10°0 - 00°0] band at 8 micrometers

is of greatest interest. The ideal method of making these measurements

at 8 microns with a MIM diode will require a technological breakthrough

and some effort will be directed toward that goal. An alternate approach

will involve an indirect route through measurements of the [00°1 - 00°0]

band at 4.4 microns and calculations performed in the Molecular Spectroscopy Division. The measurement of these reference standard frequencies

is directed toward NASA programs for atmospheric pollution monitoring

and analysis and other research programs being undertaken at major

university and government labs, such as the University of California,

Berkeley (to search for OCS in the atmosphere of Venus), and Los Alamos

(for potential isotope separation programs). The ultimate objective of

this program is to provide accurate reference frequencies between 1 and

20 microns based on the C0 2 laser frequency measurements which are measured with respect to the cesium standard. The priorities in the

completion of these measurements are determined by user needs.

Ramsey fringes have long been used to stabilize microwave oscillators

and as an analytic tool to determine the velocity pattern in atomic beam

standards. Two years ago, Ramsey fringes were observed for the first

133
time in the visible using a Ne beam at NBS, JILA. One of those original

contributors to optical Ramsey fringes in neon helped bring the method

to fruition in calcium a year later. However, a present experiment

using a C0 2 laser, Ramsey fringes, and a cooperative effort of French

and Division personnel may result in a factor of approximately 50 increase

in resolution at 10 pm over the best previous measurements. A large

70 cm cell (at the University of Northern Paris) is being used to observe

10 pm transitions in the 0s0 4 molecule with three interrogation regions.

A highly stabilized C0 2 laser beam is used to observe an infrared Ramsey

pattern. Although the experimental setup is not yet complete, the large

lasers operation necessary for narrow Ramsey fringes, the long cell

length (20 m), the large beamwidth necessary for signal-to-noise, and

the high stability of the laser and retroflector system may result in

the observation of a 30 Hz transit time limited linewidth. The significance of this is that heretofore undetected molecular structure

which can affect line shapes can be investigated. Also, this system

makes it possible to measure the relative frequency separation of a number of 10 pm lines with much higher accuracy than previously possible.

Once the frequency of one of these lines is carefully measured, an absolute frequency reference in the 10 pm region with at least a factor

of 10 improvement over the present C0 2 grid will be established. Plans

for FY81 include the completion of the 10 micron Ramsey work to observe

narrow lines in 0s04 , and the completion of the analysis of the original

calcium recoil pattern to theoretically explain the observed power

shift. Because of budget limitations and the high priority of the CCDM

experiments, this area of the 10 micron and optical standards program

will be terminated during FY81, unless outside resources can be obtained.

The extension of this work to attempt to observe theoretically predicted

structure on the Ramsey pattern at the 1 to 2 Hz level will be left to

the French labs, which are able to obtain funding from the the French

equivalent of the NSF.

Laser Magnetic Resonance (LMR) was initiated in a 1966 experiment

at NBS. Laser Magnetic Resonance spectroscopy expanded because of its

high sensitivity and the advent of the optically pumped far-infrared

lasers. During the last year, LMR spectrometers were transferred to

N0AA in exchange for funds to purchase a new computer controlled magnet

and parts for a better LMR spectrometer system. The new magnet will

result in a 3 times improvement of signal-to-noise because of the larger,

more homogeneous field area. The new laser system will eliminate a previous positive feedback loop from the alcohol laser to the pump

laser. LMR work completed during the year includes the measurement of

the CH and OH spectra. Spectroscopy planned for FY81 includes remeasuring

the atomic carbon fine structure levels to obtain a more precise value

of the 12 C and 13 C frequencies, fit the observed spectra of CH to obtain

transition frequencies and molecular constants important in radio astronomy,

and to search for the rotational spectra of SiH. Although the emphasis

for the next two years will be the observation and measurement of free

radical parameters, flexibility will be maintained in order to make

specific measurements required by atmospheric modelers or for pollution

controversies.

134
Another major area of frequency application is the laser geodimeter.

This instrument is an outgrowth of previous work on laser strainmeters.

In the early 1970s, a 30-meter interferometer was constructed in the

Poor Man Mine in Boulder Canyon as part of the measurement of the velocity

of light. The interferometer was converted to a laser strainmenter by

the addition of a methane-stabilized helium-neon laser. This strainmeter

was able to detect earth tides, as well as higher frequency disturbances

(e.g. , earthquakes and nuclear explosions). A study of the earth tides

led to one of the most definitive measurements to date of the nearly

diurnal resonance produced by the interaction of the core and the mantle.

The system was also used to set an upper bound on the gravitational wave

flux reaching the earth from the crab pulsar. This work received some

NSF funding through the University of Colorado, but was supported mostly

by Division funds.

At the same time as the strainmeter was being used for earth tide

work, its limitations—mostly the fact that it was not in a tectonically

active area and that it was almost impossible to move—became more

apparent, and interest shifted to the possibility of constructing a portable instrument. Such an instrument would measure distances directly

through the atmosphere rather than through an evacuated pipe, and so some means of determining the refractivity of the atmosphere was essential.

Several attempts at constructing such an instrument had been undertaken by other groups in Boulder in the past (in NOAA and what is now

ITS), and some of the equipment was inherited. A three wavelength

one-way device was planned that, in principle, would be limited solely

by the fluctuations and the chromatic aberration of the atmosphere.

Partial NASA funding was received, and most of the instrument was completed. In the meantime, the Geological Survey has come to appreciate

the utility of the multiple wavelength approach, and has offered additional funds to complete the project.

As designed, the geodimeter should be able to measure distances on the order of 50 km with an uncertainty of a few mm. It could also be

used as a refractometer; that is, an instrument that determines the

index of refraction of the atmosphere. In this application, it would be

used to correct distance measurements obtained by other techniques

(e.g., single wavelength terrestrial instruments or satellite measurements).

During the last year, the microwave portion of the device was completed and the two laser systems are being completed. During FY81,

the instrumentation will be completed. In FY82, the geodimeter will be

field tested to determine its accuracy, and field tests are planned in

earthquake active areas in California. The precision length measurement

potential of the geodimeter are also expected to be applied for accurate

range measurements to satellites to be used in precision measurement

experiments by NASA to determine crustal motion, to accurately determine

survey benchmarks, and to measure atmospheric water vapor. Atmospheric

water vapor is of great interest in remote sensing, especially by the

military for the prediction of path effects on high power lasers.

135
I

In parallel with the geodimeter efforts, other agencies have re- quested the development of other geophysics instrumentation. During the

last year, the development of an array of very high precision tiltmeters

was begun for the Air Force, and the operation of a cryogenic gravity

meter for the University of California was undertaken. These efforts

were mostly in response to solicitations from these agencies in recognition of Division expertise in the area of precision measurements.

The interest in atmospheric water vapor, potential ability to

accurately measure it, the longer term goal to replace calibrated measurement systems with intrinsic measurements, the availability of other

agency funds, and the availability of inhouse expertise resulted in the

initiation of a program to determine the physics of phase changes in

atmospheric water vapor. This three year program was begun last year

and the first experimental results are not expected until FY81.
III. PUBLICATIONS AND INTERACTIONS

Included in the pages of this section are the following:

§ Publications

§ Invited Tal ks

§ Technical and Professional Committee Participation and

Leadership

§ Seminars

§ Consulting and Advisory Participation

§ Special Reports

§ Trips Sponsored by Others

137
PUBLICATIONS

Time and Frequency Division (524)

S. R. Stein and J. P. Turneaure, Superconducting Resonators: High Stability Oscillators and Applications to Fundamental Physics and Metrology,

AIP Conf. Proc., Future Trends in Superconductive Electronics, 192-213

| (1978).

F. L. Walls, D. J. Wine! and, and R. E. Drul linger, New Possibilities for

Frequency Standards Using Laser Cooling and Detection of Stored Ions,

Proc. 32nd Annual Symposium on Frequency Control, 453-459 (1978).

I

1

!

j S. Jarvis, Jr., D. J. Wineland, H. Hellwig, and R. M. Garvey, A New

Method to Eliminate Cavity Phase Shift in Cesium Beam Standards, Proc.

9th Annual PTTI, 571 (1978).

R. M. Garvey, H. Hellwig, S. Jarvis, Jr., and D. J. Wineland, Two-frequency

Separated Oscillating Fields Technique for Atomic and Molecular Beam Interrogation, IEEE Trans, on Instrumentation and Measurement, IM-27 (1978).

D. J. Wineland, R. E. Drullinger, and F. L. Walls, Radiation Pressure

Cooling of Bound Resonant Absorbers, Phys. Rev. Lett. 40, 1639-1642 (1978).

F. L. Walls and S. R. Stein, A Frequency-lock System for Improved Quartz

Crystal Oscillators Performance, IEEE Trans, on Inst, and Meas. , IM-27 , 249-252 (1978)

Helmut Hellwig, Precise Time and Frequency, 19th General Assembly of

USRI (1978).

D. W. Allan and Helmut Hellwig, Time Deviation and Time Prediction Error

for Clock Specification, Characterization, and Application. Proc. 1978

Position Location and Navigation Symposium (PLANS), 29-36 (1978).

Massimo Inguscio, Franco Strumia, K. M. Evenson, D. A. Jennings, A.

Scalabrin, and S. R. Stein, Far-infrared CH3 F Stark Laser, Opt. Lett. 4,

9-11 (1979).

N. Ashby and D. W. Allan, Practical Implications of Relativity for a Global Coordinate Time Scale, Proc. URSI Symp. on Time and Freq. (1979).

Helmut Hellwig, Microwave Time and Frequency Standards, Proc. URSI Symp

on Time and Freq. (1979).

S. R. Stein, Space Applications of Superconductivity: Resonators for High

Stability Oscillators and Other Applications, Cryogenics Journal (1979).

J. C. Bergquist and D. J. Wineland, Laser to Microwave Frequency Division

Using Synchrotron Radiation II, 33rd Annual SFC (1979).

D. J. Wineland and R. E. Drullinger, Laser Coolings of Ions Bound to a Penning Trap, Proc. 6th Vavilov Conf. on Non-linear Optics and 4th International Conf. on Laser Spectroscopy (1979).

138
D. J. Wineland and Wayne Itano, Laser Cooling of Atoms, Phys. Rev. A 20,

(1979).

S. R. Stein, Impact of Improved Clocks and Oscillators on Communications

and Navigation Systems, Proc. 11th Annual PTTI Meeting, 31-36 (1979).

D. J. Wineland, Limitations on Long-Term Stability and Accuracy in Atomic

Clocks, Proc. 11th Annual PTTI Meeting, 31-36 (1979).

F. L. Walls, Prospects for Advances in Microwave Atomic Frequency Standards.

Proc. 11th Annual PTTI Meeting, 619-640 (1979).

J. Jespersen, G. Kamas, and M. Weiss, Voice Announcements of Time: A New

Approach, Proc. 11th Annual PTTI Meeting, 363-383 (1979).

R. E. Beehler, D. D. Davis, J. V. Cateora, A. J. Clements, J. A. Barnes,

and E. Mendez-Qui nones, Time Recovery Measurements Using Operational GOES

and TRANSIT Satellites, Proc. 11th Annual PTTI Meeting, 283-312 (1979).

James L. Jespersen, Some Implications of Reciprocity for Two-way Clock

Synchronization, Proc. 11th Annual PTTI Meeting, 175-184 (1979).

D. A. Howe, F. L. Walls, Howard E. Bell, and Helmut Hellwig, A Small,

Passively Operated Hydrogen Maser, Proc. 33rd Annual Symp. on Freq.

Control (1979).

C. C. Costain, J. S. Boulanger, H. Daams, NCR; B. W. Hanson, R. E. Beehler,

A. J. Clements, D. D. Davis, NBS, et.al.. Two-way Time Transfer via

Geostationary Satellites: NCR/NBS, NCR/USNO, and NBS/USNO via Hermes and

NRC/LPTF (France) via Symphonie, Proc 33rd Annual Symp. on Freq. Control

(1979).

A. Risley, S. Jarvis, Jr., and J. Vanier, Study of the Dependence of

Frequency upon Microwave Power of Wall -Coated and Buffer-Gas Filled

Passive Rb8 Frequency Standards, Proc. 33rd Annual Symp. on Frequency

Control (1979).

K. M. Baird, K. M. Evenson, D. A. Jennings, and F. R. Petersen, Extension

of Absolute Frequency Measurements to the Visible: Frequencies of Ten

Hyperfine Components of Iodine, Opt. Lett 4, 263-264 (1979).

R. L. Barger, J. C. Bergquist, D. J. Glaze, and T. C. English, Resolution

of Photon-recoil Structure of the 6573 8 Calcium Line in an Atomic Beam

with Optical Ramsey Fringes, Appl. Phys. Lett. 34, 850-852 (1979).

R. J. Saykally and K. M. Evenson, Laser Magnetic Resonance Measurement

of the 2

3 P Z -23 P 1 Splitting in Atomic Oxygen, J. Chem. Phys. 71,

1564-1566 (1979).

Artemi o Scalbrin and Kenneth M. Evenson, More Strong cw FIR Laser Lines

from Optically Pumped CH 2 F 2 , Opt. Lett. 4, 277-279 (1979).

139
J. C. Bergquist, R. L. Barger, and D. J. Glaze, High Resolution Spectros-

! copy of Calcium Atoms, Proc. 4th International Conference on Laser Spectroscopy (FICOLS) (1979).

R. E. Drullinger and D. J. Wineland, Laser Cooling of Ions Bound to a Penning Trap, Laser Spectroscopy IV , H. Walther and K. W. Rothe, Eds.,

Springer-Verlag, Berlin Heidelberg New York, Springer Series Opt. Sci. 21

j (1979).

1

1

R. J. Saykally and K. M. Evenson, Observation of Pure Rotational Transitions in the HBr+ Molecular Ion by Laser Magnetic Resonance, Phys. Rev.

!

j Lett. 43, 515-518 (1979).

B. E. Warner, K. B. Persson, and G. J. Collins, Metal Vapor Production

by Sputtering in a Hollow Cathode Discharge: Theory and Experiment,

J. Appl . Phys. 50 (1979).

George Kamas and Sandra Howe, Time and Frequency User's Manual, NBS

SP 559 (1979).

! J. A. Barnes and H. H. Sargent III, Sunspot Cycle Simulation Using Random

Noise (Abstract), Conf. Proc. NCAR (1979).

W. G. Harter, F. R. Petersen, and H. P. Layer, Evidence of Tumbling

Multiplets in Saturation Absorption Spectra of SiF4 , Opt. Lett 4, 90 (1979).

D. A. Jennings, F. R. Petersen, and K. M. Evenson, Direct Frequency

Measurement of the 260 THz (1.15 pm) 20 Ne Laser: and Beyond, Laser Spec- troscopy IV , H. Walther and K. W. Rothe, Eds., Springer-Verlag, Berlin

Heidelberg New York (1979).

A. Scalabrin, F. R. Petersen, K. M. Evenson, and D. A. Jennings, Optically

Pumped cw CH2 D0H FIR Laser: New Lines and Frequency Measurements, International Journal of Infrared and Millimeter Waves 1, 117 (1980).

F. R. Petersen, A. Scalabrin, and K. M. Evenson, Frequencies of cw FIR Laser

Lines from Optically Pumped CH2 F2 , International Journal of Infrared and

Millimeter Waves 1, 111 (1980).

A. G. Maki and J. S. Wells, High-Resolution Measurement and Analysis of

the Infrared Spectrum of Nitric Acid near 1700 cm- 1

, J. Mol. Spectrosc. 82 , 427-434(1980).

1 __ D. W. Allan and M. A. Weiss, Accurate Time Comparison Using a GPS Satellite in Common-View, Proc. 34th Annual Frequency Control Symposium, (1980).

D. J. Wineland, J. C. Bergquist, Wayne Itano, and R. E. Drullinger, Double

resonance and Optical -pumping Experiments on Electromagnetical ly Confined,

Laser Cooled Ions, Opt. Lett. 5, 245 (1980).

R. J. Saykally and K. M. Evenson, Direct Measurement of Fine Structure in

the Ground State of Atomic Carbon by Laser Magnetic Resonance, Astrophys.

| Journ. 238, 1107-1111 (1980).

I 140
R. E. Drullinger, D. J. Wineland, and J. C. Bergquist, High-resolution

Optical Spectra of Laser Cooled Ions, Appl. Phys. 22, 365-368 (1980).

F. Russell Petersen, Kenneth M. Evenson, Donald A. Jennings, and Artemio

Scalabrin, New Frequency Measurements of Optically Pumped 12 CH3 0H,

IEEE Journ. Quantum Electron. QE-16 , 319-323 (1980).

J. A. Barnes, H. H. Sargent III, and P. V. Tryon, Sunspot Cycle Simulation

Using A Narrowband Gaussian Process, NBS Tech. Note 1022 (1980).

Philip Ekstrom and David Wineland, The Isolated Electron, Scientific

American 243, 105 (1980).

141
INVITED TALKS

Time and Frequency Division (524)

J. C. Bergquist, "Saturated Absorption Optical Ramsey Fringes and

Synchrotron Frequency Dividers," Yale University, New Haven, CT,

March 7, 1979 and University of Connecticut, Storrs, CT, March 8, 1979.

A. S. Risley, "Study of the Dependence of Frequency Upon Microwave Power

of Wall -Coated and Buffer Gas Filled Passive Rb87 Frequency Standards,"

33rd Annual Symposium on Frequency Control, Atlantic City, NJ, May 31,

1979.

D. A. Howe, "A Small Passively Operated Hydrogen Maser," 33rd Annual

Symposium on Frequency Control, Atlantic City, NJ, May 31, 1979.

J. C. Bergquist, "Laser to Microwave Frequency Division Using

Synchrotron Radiation," 33rd Annual Symposium on Frequency Control,

Atlantic City, NJ, May 31, 1979.

J. C. Bergquist, "High Resolution Spectroscopy of Calcium Atoms," 4th

International Conference on Laser Spectroscopy, Rottach-Eagern, West

Germany, June 12, 1979.

S. R. Stein, "Frequency and Time: Present Status and Future Prospects,"

33rd Annual Symposium on Electromagnetic Compatibility (EMC) and Instrumentation & Measurement (I&M) IEEE, Boulder, CO, April 27, 1979.

J. A. 1979.Barnes

,

"Time Standards," Kiwanis Club, Boulder, CO, June 13,

F. L. Walls, "Future of Quartz Resonator Thermometry," Workshop on: Techniques for Measurement of Thermodynamic Properties, Linn-Denton

Junior College, Albany, Oregon, August 21, 1979.

L. L. Lewis, "Parity Nonconservation in Atomic Bismuth," International

Workshop of Neutral Current Interactions in Atoms, Cargese, Corsica,

September 10-14, 1979.

K. M. Evenson, "Unification of Time and Length Standards via Laser

Frequency Measurements," American Physical Society, Rochester, NY,

October 12/13, 1979.

D. J. Wineland, "Limitations on Long-Term Stability and Accuracy in

Atomic Clocks," Eleventh Annual Precise Time and Time Interval (PTTI)

Applications and Planning Meeting, Greenbelt, MD, November 27, 1979.

S. R. Stein, "Impact of Improved Clocks and Oscillators on Communications

and Navigation Systems," Eleventh Annual Precise Time and Time Interval

(PTTI) Applications and Planning Meeting, Greenbelt, MD, November 27, 1979.

F. L. Walls, "Prospects for Advances in Microwave Atomic Frequency

Standards," Eleventh Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting, Greenbelt, MD, November 29, 1979.

142
K. M. Evenson, "Essentials of Frequency Measurements to the Visible and

Redefinition of the Meter," NBS Center for Absolute Physical Quantities,

Gaithersburg, MD, November 13, 1979.

K. B. Persson, "Theory of the Hollow Cathode Discharge and Modeling of

Lasers Based on Sputtering and Charge Transfer," Lasers '79 Conference,

Orlando, FL, December 20, 1979.

J. A. Barnes, "The Solar Sun Spot Cycle as an ARIMA Process," American

Geophysical Union, Boulder, CO, November 13, 1979.

R. E. Beehler, "Operational Time Dissemination via GOES and TRANSIT

Satellite Systems," Eleventh Annual Precise Time and Time Interval

(PTTI) Applications and Planning Meeting, Greenbelt, MD, November 28,

1979.

D. J. Wineland, "Laser Induced Magnetron Compression (Expansion) of Ions

Stored in a Penning Trap," American Physical Society (DEAP) Meeting,

Houston, TX, December 11, 1979.

W. M. Itano, "Frequency and Time Standards Utilizing Laser Cooled Ions,"

American Physical Society (DEAP) Meeting, Houston, TX, December 11,

1979.

S. R. Stein, "Frequency Stability Results for a Modified Cesium Beam

Tube," 34th Annual Frequency Control Symposium, Philadelphia, PA, May

28-30, 1980.

D. J. Wineland, "Laser Cooling of Stored Ions," University of Chicago,

Chicago, IL, April 18, 1980.

D. J. Wineland, "Optical Pumping and Double Resonance Experiments on Laser Cooled Ions," IEEE, Quantum Electronics Conference, Boston, MA,

June 23, 1980.

J. S. Wells, "Heterodyne Measurements and Frequency Calibration Tables

for the 11.6 pm Band of Carbonyl Sulfide (0CS)," 35th Symposium on Molecular Spectroscopy, Columbus, OH, June 19, 1980.

W. M. Itano, "High Resolution RF Spectroscopy of Laser Cooled 25Mg

+ Ions,"

International Conference on Atomic Physics, Cambridge, MA, August 7, 1980.

J. C. Bergquist, "Methods of High Resolution Laser Spectroscopy - From

Ramsey Fringes to Radiation Pressure Cooling," Colorado State University,

Ft. Collins, CO October 10, 1980.

W. M. Itano, "Laser Cooling of Trapped Ions," Molecular Physics Labs, SRI

International, Menlo Park, CA, September 11, 1980.

D. J. Wineland, "Spectroscopy of Laser Cooled Ions," Washington University,

St. Louis, M0, September 10, 1980.

D. J. Wineland, "Particles at Rest in Space: The Spectroscopist 1 s Ideal,"

University of Colorado, Boulder, CO, September 24, 1980.

143
L L. Lewis, "Atomic Parity Violation Experiments," U.S. -Japan Seminar

on Nonlinear Laser Spectroscopy, Kauai, Hawaii, September 8-12, 1980.

D. J. Wineland, "Atoms at Rest in Space: The Spectroscopi st' s Ideal,"

Johns Hopkins University, Laurel, MD, November 5, 1980.

144
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Time and Frequency Division (524)

D. W. Allan, Study Group VII, International Radio Consultative

Committee (CCIR)

D. W. Allan, Program Chairman, 1982 CEPM

D. W. Allan, Consultative Committee for the Definition of the Second (CCDS).

D. W. Allan, IEEE IM TC-3 Frequency and Time

R. L. Barger, International Union of Radio Science (URSI)

J. A. Barnes, Consultative Committee for the Definition of the Second

(CCDS), CCIR.

J. A. Barnes, IEEE Technical Committee on Frequency and Time: Subcommittee

on Frequency Stability

J. A. Barnes, JPL, Hydrogen Maser Comparison Test Formal Review Board

R. E. Beehler, CCIR Study Group VII; International Chairman of Interim

Working Party 7/4 on "Improved Time Coordination and Dissemination Using

Satel 1 ites"

R. E. Beehler, PTTI Editoral Committee

D. D. Davis, Member Technical Advisory Committee for TDRSS, NASA Satellite

Program

K. M. Evenson, URSI Commission D

J. L. Jespersen, Chairman IRIG Timing Committee

J. L. Jespersen, CCIR

G. Kamas, Measurement Assurance Subcommittee, National Conference of

Standards Laboratories

S. L. Howe, PTTI Editorial Committee

S. R. Stein, PTTI Technical Program Committee

F. L. Walls, IEEE IM TC-3 Frequency and Time

F. L. Walls, Steering Committee, 3rd Symposium on Frequency Standards and

Metrology

F. L. Walls, Technical Program Committee, PTTI

D. J. Wineland, Committee for NBS Precision Measurements Grants

145
SEMINARS

Time and Frequency Division (524)

Time and Frequency Users' Seminar, Boulder, CO, April 30 - May 1, 1980.

Time and Frequency Users' Seminar, Boulder, CO, August 27-28, 1980.

146
CONSULTING AND ADVISORY PARTICIPATION

Time and Frequency Division (524)

J. L. Jespersen Consulting with the Defense Communication Systems on TV captioning techniques.

J. L. Jespersen consulting with National Telecommunications and Information

Administration on TV captioning techniques.

J. L. Jespersen consulting with National Oceanic and Atmospheric Administration

on development of weather dissemination on GOES Satellite.

D. D. Davis consulting with National Oceanic and Atmospheric Administration

on- maintenance and operation of GOES equipment.

A. J. D. Clements consulting with National Oceanic and Atmospheric Administration on maintenance and operation of GOES equipment.

J. A. Barnes consulting with IAU, Commission 31.

147
SPECIAL REPORTS

Time and Frequency Division (524)

Final Report - CCG 79-142: "Satellite-Controlled Clock Study," R. E. Beehler, Principle Investigator.

Final Report - NOAA Contract No. 31 USC 686: "Study of the Feasibility

of Using GOES for Position Location," J. L. Jespersen, Priciple Investigator,

A. J. D. Clements, D. D. Davis, M. Weiss, Contributors.

Final Report - Samso Contract No. SMS 0400, "Global Positioning System

Clock Development for Time and Frequency Division," D. W. Allan and

F. L. Walls, Principal Investigators.

148
TRIPS SPONSORED BY OTHERS

K. M. Evenson

J. Levine

J. L. Jespersen

D. J. Wine! and

Time and Frequency Division (524)

October 11-13, 1979 - Webster, New York

Invited speaker at October American Physical

Society Fall Meeting. Presented "The Unification of Time and Length Standards via Laser

Frequency Measurements."

Sponsor: American Physical Society

October 10, 1979 - Houston, Texas

Invited speaker at joint Physics/Geology

colloquium.

Sponsor: Dept, of Physics, Rice University

November 8-9, 1979 - Washington, D.C.

Attended a meeting of the Panel on Global

Positioning System, National Academy of Science.

Sponsor: National Research Council

April 8 - 29, 1980 - New Delhi, India

Served as technical consultant in India to organize

an International Telecommunications Union (ITU)

sponsored seminar on Time and Frequency Technology

conducted by the National Physical Lab of New Delhi.

Sponsor: ITU in cooperation with the United Nations

Development Commission

April 17-18, 1980 - Chicago, Illinois

Presented colloquium concerning Laser Cooled Ions.

Sponsor: The Enrico Fermi Institute, University of

Chicago

September 11, 1980 - St. Louis, Missouri

Presented colloquium entitled "Spectroscopy of

Laser Cooled Ions.

Sponsor: Physics Dept. , Washington University

149


QUANTUM PHYSICS DIVISION

SUMMARY OF ACTIVITIES

Fiscal Year 1980

I. OVERVIEW

The Quantum Physics Division (QPD) was created as the vehicle for

the NBS participation in the Joint Institute for Laboratory Astrophysics

(JILA), which is a cooperative enterprise of the National Bureau of

Standards and the University of Colorado.

When JILA was formed in 1962, "Laboratory Astrophysics" focused

special attention on aspects of astronomy and atomic physics which were

relevant to the well-defined national interest in space which prevailed

at that time. However, since its inception, JILA has responded to the

changing national needs and to the requirements of its parent organizations. The association of atomic and molecular science and astrophysics

at JILA has been mutually beneficial. Experimental and theoretical

contributions have been made not only to these areas but also to laser

physics, precision measurements, geophysics, and data and measurements

necessary for the understanding of reaction mechanisms in the atmosphere; to the collection and evaluation of the scientific data; and

to the education of scientists.

Recognizing the dynamic nature of the unique partnership, and the

need for the formal agreement between institutions to allow for evolving

goals with changing national interests. Dr. Ernest Ambler, Di rector of

the National Bureau of Standards and Dr. Roland Rautenstraus, President

of the University of Colorado, in March 1976 signed an ammendment to the

Memorandun of Understanding which states:

"In view of these contributions and the importance of atomic

and molecular science as basic to the principles and standards

of modern measurements, as well as the vitality of astrophysics

as a major science in the academic environment, the purpose and

role of the Joint Institute for Laboratory Astrophysics shall

continue to evolve and expand beyond the areas of science outlined in the original Memorandum of Understanding.

• It will, for the fields of atomic and molecular science,

astrophysics, and broadly related areas such as laser physics

and chemistry, continue to provide a center for the dissemination and exchange of ideas and data through, for example, the

Visiting Scientists Program.

• It will, in these fields, continue to provide for the education of scientists at the graduate and postdoctoral levels.

150
o It will, through the collaboration of its scientists from

the National Bureau of Standards and the University of Colorado,

and through research and teaching in these fields, continue to

be cognizant of and responsive to the missions of its parent or- ganizations as well as the national needs which are affected by

these missions. Toward these ends it will continue to promote

close interactions with its colleagues in both institutions."

At the time of the April 1978 reorganization of NBS, the Bureau

stated that the QPD as part of the Center for Absolute Physical Quantities:

a Engages in research in atomic and molecular physics at the

forefront of the field and performs basic, highly accurate

measurements and theoretical analyses that help establish

a reliable foundation for scientific and technological

measurements and data.

a Performs work such as the measurement of natural constants,

the development of new basic standards and the determination of key data and processes in atomic and molecular

physics.

• Maintains through its association with the University of

Colorado and through its Visiting Scientist Program, ac- tive contact with and experience in advanced research in

physics.

® Disseminates information of its scientific activities to

other areas of NBS through visits and longer term interchange of personnel

.

• Maintains a staff and structure to respond quickly to new ideas and reprogramming.

The Quantum Physics Division currently has substantial research

programs in five general areas, to be discussed in more detail later:

1. Fundamental precision measurements . Work here includes

programs in laser stabilization, Ramsey fringes, Rydberg

levels, quantum defect, blackbody radiation shift of atomic

energy levels, tests of special relativity, Eotvtts experiment, fundamental limitations in interferometry , and detection of gravity waves.

2. Chemical physics . Programs are in laser- initiated, chemical chain reactions, ion-molecule reaction dynamics, and

photofragmentation infrared emission spectroscopy.

151
3. Astrophysical measurement . This includes programs investigating solar atmosphere convection, thermodynamic properties of solar flare plasmas via Skyl ab spectra, cool star

atmospheres via IUE satellite observations, chromospheres

and coronae of stars, and radiation transport.

4. Atomic and molecular physics and interactions. Current

programs are in exci tation/i om zati on/recombination of ions

by electron impact, trapped ion dynamics, ion-molecule processes, rate coeffi cents, line broadening, potential functions, laser photoionization and Raman spectroscopy, atoms

in intense chaotic radiation fields, theory of multi photon

processes, laser-induced collisions, electron scattering

from polar molecules, secondary electrons from ionization,

modeling of electric discharges, and atomic and molecular

processes involved in depositions of amorphous silicon

hydride films.

5. Geophysical measurement methods . The programs here are in

laser ranging, crustal movement, plate tectonics, portable

gravimeter, and a gravity gradiometer. Other NBS programs

in JILA, but managed by a member of Div. 524, involve a three wave geodimeter and gravity tiltmeters.

Before discussing the various programs in more detail, it is appropriate to elaborate a bit more on JILA as an institute, since it is difficult to discuss the Quantim Physics Division out of context with JILA.

Currently, there are 148 total staff in JILA distributed according

to Fig. 1. This figure fluctuates substanTTal ly Dver a year's time,

since there is an annual scientific turnover of 40 to 50 persons.

The permanent Ph.D. Staff or "Fellows of JILA" of which there are

26 form a collegial governing body which sets policy subject to review

by the Director of NBS and President of CU. A Chairman of the Fellows

is elected bi-ennially as the principal officer of the Institute, and is

responsible for operating the Institute within the limits of policy set

forth by the Fellows. An Executive Committee assists the Chairman with

policy matters of shorter duration or lesser moment that would command

attention of the Fellows, and the Executive Officer deals with most administrative matters as delegated by the Chairman. Of the 26 Fellows,

11 are CU full-time faculty from the Departments of Physics, Chemistry,

and Astro-Geophysics, 14 are NBS employees in the QPD, and 1 is an NBS

employee in the Time and Frequency Division. NBS Fellows hold adjoint

appointments in one of the three academic departments. While sharing

responsibility for the success of the Institute, the NBS and the University of Colorado each has full operational responsibility for its own employees who are physically located in and hold positions as Fellows or Members of JILA. Thus, these parent bodies apply exactly the same personnel review and reassignment procedures to each staff member in JILA

as would be applied to the same staff member were that person rostered

in another administrative unit and location, without consideration of

152
JILA STAFFING

1980-81

(148 Total)

PERMANENT PH.D. STAFF

Figure 1.

153
any special privileges or liabilities deriving from participation in

JILA or from designation as a Fellow.

One notes from the figure that of the 114 research scientists in

JILA, that 71 (or 62%) are postdoctoral s and students. There is thus a high level of youthful vitality and turnover in the scientific staff.

Of the 39 graduate students, 22 are supervised in their research by NBS

scientists through their adjoint appointments. Of the 32 postdoctoral

research associates, 18 work on research supervised by NBS scientists.

There is thus a tremendous amplification of the efforts or "leverage" of

the NBS scientists, achieving at once both University and NBS goals.

The Visiting Fellows program is perhaps one of the main components

of "glue" that holds this unique partnership together. This program is

funded by NBS by a contract with CU, and provides for the order of 10

senior level scientists to spend from 6 months to 1 year in the Institute. The participants are chosen competitively from a large number of

applicants, and the program which has operated for 17 years now has been

a spectacular success. Scientific productivity of this group who come

with no duties has been very high. For example, of the 324 publications

listed in this year's and last year's annual reports by QPD staff and

Visiting Fellows, approximately 42% were by Visiting Fellows. This program again provided tremendous amplification of NBS staff. Visiting

Fellows for 1979-80 and for 1980-81 are listed in Sec. III.

Goals

The five-year plan for the Center for Absolute Physical Quantities,

including the five-year plan for the Quantum Physics Division and the

Time and Frequency Division, are in the document by that title. However, it is useful to discuss these goals in a somewhat generic sense,

commenting both on the scientific goals and on institutional goals. One

of JILA's greatest strengths lies in the expertise it has developed in

laser physics. A new era in measurement has been ushered in by the

"laser revolution," accompanied by other technological advances. The

development and investigation of lasers, and other new technologies for

purposes of measurement is a high NBS priority as new orders of accuracy

not envisioned before now become possible, exposing new frontiers in

scientific investigation. These new techniques make it possible to attack major measurement problems associated with national programs in

energy, space, environment, national defense, and earthquake hazard prevention. As the laser is refined as a measurement tool, fundamental

postulates of physics become open for new and more refined examination

and testing. JILA has played a major role in starting this measurement

revolution which is still in its infancy.

Possibilities ahead excite the imagination. The laser revolution

will closely parallel the great revolution initiated by digital electronics. Indeed, these two great developments go hand-in-hand, promising a far-reaching "measurement" revolution through the concurrent

functions of sensing (with lasers) and recording-processing-controll ing

154
(with digital electronics), finis process will pervade technology. JILA

will continue to be an active player pushing the frontiers of laser

physics and laser measurement ahead.

Many projects in progress already are exciting both from the scientific and from the application points of view. Thus, we will continue

to work on the exciting new technique we have recently developed for

using lasers to excite and measure chain reactions occurring in combustion processes. Laser methods applied in the gravimeter and geodimeter

being developed at JILA will help push measurements of earth movement,

plate motion, earthquake prediction, etc., into a brand new arena. With

the next generation of highly stable lasers being developed at JILA, it

may be possible to detect and measure gravitational waves using satellites in stationary orbits. Such an experiment, which would provide the

first observation of gravitational waves, is in the design stage at

JILA. This new generation of lasers will also make possible new tests

on the dilation of time and the isotropy of space.

Growth and technological sophistication of national programs in alternative energy sources, laser development, environmental protection,

space activities, defense, and civilian product development have strained

the limits of our fundamental understanding of the behavior of atoms and

molecules. Needs that have grown out of these programs have highlighted

many fundamental processes which it is critical that we understand, but

for which no adequate measurement techniques have been developed, and

for which theoretical methods and models are not developed or advanced.

In many of these areas JILA has unique expertise which is being used to

develop measurement methods and make measurements to further the understanding of such processes and to develop theory and make calculations

for complementary advances. Such is the case particularly in the areas

of electron scattering, energy transfer, molecular photolysis, ion physics, and chemical reaction dynamics. As the above national programs are foreseen to be of high national priority for some time, JILA will continue to have parallel priorities so it can contribute in its unique way to

these efforts. An area of rich promise for the future which is closely

related to the current expertise in particle collisions and laser physics

is that of laser induced collisions. It is an extremely exciting and

rapidly blossoming scientific problem today and there are a number of

projected applications which may or may not materialize as our understanding of the basic processes increases. One attractive possibility,

for example, lies in some day being able to redirect and control chemical reactions at will by the use of lasers.

An area which is new in JILA, but which holds a place in the future, impinges the solar energy and semiconductor fields. Hydrogenated

amorphous silicon films are emerging as exciting candidates for inexpensive photovoltaic cells. These amorphous films are poorly understood

compared to crystalline cells, but rapid progress is being made in an increasing number of solid state laboratories. In fact, a worldwide

competition between industrial laboratories for marketable and patentable cells appears to be under way. Hie amorphous silicon hydride is

produced in discharges of silane. One of the difficulties encountered

155
in trying to understand these films is a lack of comparability between

films produced in different laboratories and at different times in the

same laboratory. This problem, as well as the inability to systematically control the film properties, is related to poor understanding and

control of the discharge. Atomic and molecular collision processes and

plasma behavior are important parts of this discharge problem. Members

of the Quantum Physics Division at JILA have expertise in these areas,

and a new research effort has been launched to understand the detailed

atomic and molecular processes involved in formation of these films. It

is anticipated that this will be an exciting area for the next few years.

The nation continues to recognize the importance of space exploration and astrophysics. Thus, in the next few years, the space shuttle

and important measurement satellites will be launched and used. Most

of the astrophysical effort in JILA comes through the CU side of the Institute; however, NBS continues to maintain a "window on astrophysics"

through 2 1/2 persons' efforts in JILA. JILA/NBS scientists serve on science commissioning teams for space shuttle experiments. They are active participants in satellite and projected shuttle experiments, and

heavily impact measurements made with these instruments. Since the

shuttle is just at the stage of coming to realization, these efforts

will continue into the future.

Institutionally, JILA recognizes the need to maintain health and

viability. With the Visiting Fellows Program, the large postdoctoral

program, and graduate students, the turnover in the Institute is about

50 scientists each year. This great flowthrough helps to insure an upto-date outlook and provide a vitality and excitement for which JILA has

come to be known. It is essential that these programs be kept healthy.

The most recent addition to JILA's permanent staff on the CU side was a brilliant young scientist, who is only 28 years old. Similarly, the

last addition to the NBS permanent staff, which occurred three years

ago, was an outstanding young man of similar age. JILA will continue to

build with young scientists of the highest qualifications as vacancies

are created. Our goal, to insure the continuing health of JILA, is to

add such a person every two or three years. Since growth is not needed,

it is hoped this can be accomplished mainly within the framework of normal turnover. The focus of JILA's science has in the past evolved to

keep abreast of national priorities. It will continue to be the case

that NBS research in JILA will be cognizant of national needs in a way

that optimum contribution to these needs can be made.

156
II. TECHNICAL ACTIVITIES

This section contains brief narrative descriptions of research programs currently underway or recently completed. An alternative insight

to these activities can be gained by reference to Sec. Ill where tables

are found of publications, invited talks. Visiting Fellows, and seminars

and colloquia, academic activities of NBS personnel, consulting, and

technical and professional committee participation and leadership.

Fundamental precision measurements

Progress was made during the year by Faller and Bender on studies

of whether future laser experiments in space can detect gravitational

waves with enough sensitivity to see signals from known rotating binary

stars, as well as probably signals from other sources. A search for

better spacecraft orbits for such experiments has been started, and preliminary papers discussing earlier ideas have been presented at two con- ferences. Path lengths of the order of one million kilometers are being

considered at present. B. Bertotti, who is a Visiting Fellow, is heavily involved in plans to search for possible gravitational waves from

stronger sources using microwave Doppler measurements during the International Solar Polar Mission. Measurements with sensitivity approaching

10“ 15 at 1000 second period and requiring hydrogen maser frequency standards at the Deep Space Network tracking stations are planned during the

interval when the spacecraft are out near the orbit of Jupiter.

This year J. Faller, M. Keiser, and P. Keyser obtained the first

significant results using the fluid (surrogate) fiber Etttvtis apparatus.

The value obtained for the fractional difference in the ratio of gravitational to inertial mass for copper and tungsten was n

= 0.6+4 x 10“ u , where

<Wcu - <VMI>W

n =

1 /zUm

6/Hj)Cu - (Ms/M l)wj

•

Study of non-thermal noise sources have indicated mechanical (geometrical) instability of the float and sensor were most probably the reason

that the observed float performance was 10x the kT limit. Attempts to

improve on the geometrical limitations are now underway. A new 50" diam

float which as a result of being 5x larger (diameter) should provide 55x

more sensitivity for the same integrating (observation) time is in the

final stages of machining. Futher initial contacts have been made with

potential suppliers of the needed ~1000 kg of mass material — most

probably Pb and Zn.

Super Spring

This past year, Faller and Rinker devised and built a shake table

(providing a truly vertical sinusoidal motion from dc to approximately

40 Hz) in order to experimentally test and verify the super spring performance. The results of this testing are extremely gratifying: the

spring provides outstanding isolation (for example >50 db at 1 Hz!) over

157
the frequency ranqe they are able to test which extends from dc ud to

about 20 Hz. Use of this spring to isolate (suspend) the cube corner in

the reference arm in our absolute qravity aooaratus reduces our droD-todrop scatter in "g" by a factor of more than 20. Further, the design

and mechanical fabrication has been completed on two new suDer sprinqs

(in which simplicity in construction as well as ease of assembly and

disassembly has been emphasized). These two (identical) new units are now in the assembly state. Figure 2 shows an isolation curve where the

period has been made abnormally short (12 sec) in order to show up the

natural resonance on the curve.

A significant part of the efforts this year of F. Kowalski and

J. Hall have been invested in preparing the new laser wavelengthUetermining interferometer ("Lambdameter") for use at the sub-MegaHertz

level (<10“ 9 ). Several optical improvements have led to a more precise

alignment technique for the reference and unknown laser beams. A clever

computer averaging algorithm, suggested by J. Snyder of Div. 520, should

reduce the random measurement noise of the Lambdameter by a significant

factor and thus make the systematic effects more conspicuous. Considering the near-term availability of JILA's new frequency-stabilized ring

dye lasers, it was decided to delay final tests and the high accuracy

wavelength measurements since the Dresent commercial stabilized dye la- ser is not really suitable for use at the target accuracy level. The new JILA ring dye laser system developed by J. Goldsmith , L. Hollberq

and J. Hall is giving very qood performance (20% power conversion and

stabilized line width <100 kHz). We plan to build 4 such systems for

experiments underway within JILA.

Visiting Fellow, H. Robinson and J. Hall have been study inq the

laser stabilization technique suqqested by ft. Drever (Cal Tech) in con- nection with interferometric qravity wave detection. Some technical

improvements, especially in the electro-optic modulator subsystem, Dromise locking to an accuracy of about 10" 3 transfer-cavity line widths

(~1 kHz). Improved calculations by Visitinq Fellow, W. Wing (and J.

Farley at Arizona), of the theoretical Rydberq atom level shifts due to

their coupling with the 300 K thermal fields give much smaller shifts

than our previous estimates. Wing finds an asymptotic value of 2.4 kHz

with a T2 dependence from explicit integration of the light shift formula over the blackbody spectrum. Because of the 10- fold decrease in

the theoretical estimate, before attempting the experiment, it seemed

valuable to refine the analysis of some two-photon Ramsey fringe data

taken earlier by S. A. Lee, J. Helmcke and J. Hall. The Ramsey profile

theory was extended further to contain the light shifts produced by the

measurement laser fields. A very effective integration technique was developed (J . Shirley [consultant] and C. Kunasz) which made it possible

to use the theoretical profile in an interactive way to least-squares

fit the data. Excellent fits were obtained. We note that the sharp

Ramsey fringe arises from absorbers that evolve most of their phase in

the darkness, giving a "dilution" of their light shift. Thus it was possible to use the shift of the background resonance (~10 kHz) to estimate the residual shift of the fringe itself (~1 kHz). The conclusion

is that the centers of the optical resonances can be determined to well

158
1

WORLD

Figure

2.

Super

Spring

Isolation.

Period

set

at

12

seconds

--

shorter

than

usual

in

order

that

the

spring's

resonance

(at

1/12

Hz)

shows

up

within

the

resolution

of

our

measurement

system.
within 100 Hz, limited mainly by si qnal /noise considerations. Thus, we

still expect to be able to observe and measure the shift of the absolute

position of rubidium Rydberg energy levels due to their coupling with

the background thermal radiation, and this is being pursued by Hall and

Robinson.

A new concept for measuring the relativistic time dilation to high

accuracy was developed by Hall as an extension of our program to measure

the helium Rydberg energy level s in a fast atomic beam. Basically the

idea is to use a longitudinal interaction geometry with two-photon absorption techniques in an ootical standi nq wave to pump He atoms from

Z

1 S to 5^ and 5*0 and from 2

3 S to n

3 S and n

3 D. Detection will be via

fluorescence for the lower states, and state-sensitive colli si onal charqe

transfer for the upper states. The excitation spectrum will show three

main two-photon peaks. The central "Doppler free" peak will have only

the second-order Doppler shift (time dilation). It will be flanked by

two Doppl er- shifted peaks. The displacement of some 3D A by the firstorder Doppler effect will give very precise knowledge of the actual beam

velocity. If a sufficiently stable reference line can be found, these

first-order-shifted peaks will also allow a very sensitive search for a possible P (cos q) anisotropy in the speed of light. Finally, it

should be recalled that a fundamental by-product of this entire project

is a precise knowledge of the absolute energy levels of He I. Our optical intervals and series limit information, taken with the finestructure

and intersystem microwave intervals measured by Wing and Farley, will

lead to a definitive knowledge of the excited states of He, with ex- pected accuracy no worse than 5 MHz.

D. G. Hummer has found exact analytic solutions to a class of

severely non-linear integral equations derived by JILA Visiting Fellow

J. Katriel in 1978-79, from a generalized Bose operator treatment of

optical harmonic generation. These operators are used to linearize the

relevant equations of motion in various wavs, some of which reproduce

results obtained by other workers, while others yield new approximations. The integral equations obtained in this way describe the number

of photons in the relevant modes and are of the qeneral tyoe (for fourwave mixing)

n(t) = a sin2

(e /

t {[b-n( t' )1[c-n(t' )1}^ dt '

)

0

where a, b, c, and e are parameters of the system. The solutions are expressed in terms of Jacobian Elliptic functions. This work is described in a paper submitted for publication to the Journal of Physics

A. Hummer has subsequently solved substantial generalizations of the

prototype equation.

J. Jeffries, S. Barlow and G. Dunn have observed the onset and

quenching of collective behavior of a sample of molecular ions confined

in a Penning configuration ion trap. A sample of ions in a Penning trap

forms a unique single component plasma. When the sample is produced,

the spatial extent of the ion cloud is very small compared to the Debye

length. As the ion cloud evolves, the Debye length becomes about the

160
same as the spatial extent of the ion cloud (Fig. 3a). When this happens, the onset of collective behavior is observed. This is seen as a rise of a bump in the observed noise power (Fig. 3b). The ion cloud

evolution time in the Penning trap is sufficiently long that the details

of the changes in the coherence of the ion sample can be monitored by

observing the z frequency noise power line width (Fig. 3c). The line

width of the z frequency noise power has the same time evolution as the

Debye length. The onset of collective behavior is characteristic of the

ion sample cooling mechanisms, which reduce the Debye length and are dominated near equilibrium by ion-neutral binary collisions. As the ion

sample continues to evolve, the collective behavior is quenched as the

Debye length grows again. The radial transport of ions across the magnetic field lowers the ion density, hence the Debye length increases.

This is monitored by the growth of the noise power line width (Fig. 3c)

and the decay of the coherent bump in the noise power temporal evolution

(Fig. 3b). This ability to observe collective behavior evolve makes the

ion plasma in the Penning trap unique. The observations appear to be

the clearest yet of an example of self-organization of a non-equil ibri urn system.

Atomic and Molecular Physics and Interactions

D. W. Norcross and D. G. Hummer have completed the first phase of a computational program designed to help satisfy the long-standing need

for an absolute calibration standard for electron scattering by atoms

and molecules. This involved elastic scattering by neutral helium, an

ideal candidate for such a standard that is already being used extensively for this purpose. Results for the position (19.365+0.004 eV)

,

width (10.7+0.1 meV), and background phase shift (1.792+0.02 rad) of the

oft-studied 2S resonance are in very good agreement with measured values

of 19.366+0-005 eV, 11.0+0.5 meV, and 1.813+0.015 rad, respectively.

These values are the results of the most accurate measurements ever made

for helium, indeed for any resonance in el ectron-atom scattering. The

latter two values were measured by A. Gallagher, R. Kennerly and R. Van

Brunt. The table below compares the calculated 2 S elastic scattering

phase shift with the results of another recent high precision calculation, illustrating both the kind of precision attained and the general

convergence of recent theoretical results.

Table 1. 2 S elastic scattering phase shifts for He, with

uncertainties in the last figure in parentheses

k

2

, Ryd 0.04 0.16 0.36 0.64 1.00

present

Nesbet

-0.2645(8)

-0.2655(6)

-0.537(2)

-0.539(1)

-0.793(1)

-0.793(1)

-1.014(2)

-1.015(2)

-1.201(3)

-1.206(4)

161
LBS

TIME (SEO

Figure 3. (a) Debye length, versus time, (b) Noise power versus time,

and (c) line width of noise power signal versus time for

ion cloud stored in a Penning trap. At about 1200 sec. where the Debye length is a minimum, the minimum in line

width and maximum in noise power show coherent motion of

the ions — an example of self-organization of a non- equilibrium system.

162
A. K. Pradhan, D. G. Hummer and D. W. Norcross have submitted the

first paper of several on cross sections and excitation rates for electron impact excitation of helium-like ions. Autoionizing resonances

were included through the use of correlation functions in the solution

of the scattering equations and through application of the powerful

techniques of Quantum Defect Theory. The resonances were found to make

a considerable contribution to the cross sections in many cases, and to

consequently enhance the excitation rates by significant factors. Illustrative results for the ion Be 2+ are shown in Figures 4 and 5. Computation of detailed and exhaustive rate coefficients for several ions

in this isoelectronic sequence is in progress, and they expect the re- sults to have very important consequences for practical application in

the analysis and modeling of a variety of laboratory (e.g. fusion) and

astrophysical (e.g. X-ray sources) plasmas.

D. W. Norcross and R. Christensen are engaged in a detailed computational study of electron impact excitation of the helium-like ion Li +

, the only atomic ion for which measurement of an excitation cross section

for anything other than a dipole-allowed transition have been accom- plished (by W. T. Rogers, J. 0. Olsen and G. H. Dunn). The transition

of greatest interest, the one measured, is the l

l

'S to 2

3 P transition,

that due to its optically forbidden nature is expected to be quite sen- sitive to the details of short-range correlation and exchange effects.

It has accordingly been the subject of numerous studies recently, as being prototypical of electron impact excitation of atomic ions so important in the fusion program. The experimental results, shown in

Figure 6, appear to be influenced by resonance effects, further stimulating the interest in these results. The results of two recent theoretical studies are also shown, along with those of their preliminary

work. None of these calculations include resonance effects, the subject

of their future work, but the improved wave functions used in their work

appear to yield the correct background trend.

N. T. Padial and D. W. Norcross are continuing to study aspects of

the theory of electron scattering by polar molecules. These are important constituents of a wide variety of plasma systems, e.g. the coalfired MHD power systems and the interstellar medium, and are known to

have very large cross sections for electron scattering and unusual properties with respect to electron attachment. Attention has been devoted

most recently to the molecule HCz, that is relatively weakly polar. In one recent publication (Norcross with L. A. Collins and R. J. W. Henry)

the importance of a careful treatment of exchange and polarization was demonstrated, with results that appear to have important implications

for vibrational excitation. They are also exploring the utility of approximations -to a complete treatment of the interaction potential in the

region of intermediate angular momentum, where the scattered particle

neither penetrates very deeply the molecular charge distribution nor is

the process amenable to the simplest perturbation-theoretic treatments.

Some of the results of this study are shown in Figure 7, that compares

transition matrix elements from a very elaborate calculation with those

from an essentially exact calculation for a point dipole, and from the

use of the Born approximation with the inclusion of quadrupole effects.

163
>»

cc

tn

<M

2C,

OJ sz

+J4-ocouc34-

(O

to

fO +

CM

a> CO

oo

co

CM • 00 OfH

-M •-< OO O

a; c > O T-

•r- -M

-M (O

•r~ r-* to 0) C SfOs_ +» -a

>>

a) cc si

+> c

•r- S~ ' O4- >>

CD -C s-

+-> aj CD c c cu

a;

$_ c

+> o

(O s_

+-> c o o <u

to a) rTM a; i— ai o s- O 4-

aj

s-3

CD

164
T ( K)

Figure 5. Rate parameter for the transition l^S - 2^S in Be +

as a function of electron temperature. Curve -o- is without

resonance contribution, curve includes it.

165
CROSS

SECTION

(10

cm

E (eV)

80

CM

Figure 6

E (Ryd)

3 .+ Cross section for excitation of the 2 P state of Li as a function of electron energy relative to the 1 S state.

Solid circles are the results of Rogers et al . , a and

those of other calculations, and x the present results.

166
Figure 7. Transition matrix elements for Z .symmetry scattering of

electrons by HC1 as a function of the angular momentum of

the electron. The circles are from close-coupling calculations for the full molecular potential, the crosses from an exact calculation for a point dipole, and the triangles and

boxes from the unitarized Born approximation with and without, respectively, inclusion of the quadrupole effects.

167
The importance of the latter, and the utility of the single Born approximation are manifest.

G. Steffani, R. Camilloni, A. Falk and G. Dunn used crossed beams

techniques to measure the electron impact ionization cross section of

B+

; and R. Phaneuf and D. Crandall at ORNL and A. Falk and G. Dunn measured the cross sections for C+2 and 0+2

. The B + and C+2 work along

with previous measurements by the ORML/JILA team on N+3 and 0

+<+ give a nice body of data on ionization of ions in the Be sequence. Similarly,

for the Li sequence Falk and Dunn recently completed measurements on Be +

, which together with the earlier work of the ORNl/JILA team on C

+3

, N , and 0+5 gives a satisfactory set of data for this sequence. For

the Li sequence, excitation-autoionization plays an increasing role with

increasing Z, being barely discernable for Be

+

, but playing a very prominent role for 0 5+

. Work has recently begun on ions of the Na sequence,

and A. Falk, G. Dunn, D. Crandall and R. Phaneuf recently completed measurements on ionization of A£+2

. Excitation-autoionization involving

the 2p 5 3s 2 and 2p 5 3s3d states plays a significant role in this ionization process. Work on Si 3+ will be done shortly, and work on K-like

Ti 3+ will also be undertaken.

J. Luine and G. Dunn have made a ma.ior breakthrouqh in measurement

techniques for ion-molecule reactions at low temperatures. It is believed such reactions play a maior role in the formation of the complicated molecules observed in interstellar space at 10-20 K. However,

other workers have not been able to make laboratory measurements below

about 80 K — and even this has only been achieved in recent months.

The Luine/Dunn method employs an ion trap operated at 4 K, and makes

measurements possible in a temperature regime never accessed before in

the laboratory for this type of study. Fiqure 8 shows preliminary re- sults for a key process in one of the modeling chains, and it is seen that at low temperatures a second process becomes operative in producing

the reaction. The points at 77 K and 200 K are not yet published, and

modelers had previously extrapolated the high temperature data — giving

essentially zero at 10-20 K. The measurement of a number of key processes will be pursued in the near future.

A. V. Phelps, in collaboration with K. Tachibana of Kyoto Technical

University, has succeeded in applying his electron drift tube technique

to the measurement of electron excitation coefficients for the lowest

metastable state of 0 , i.e., the a

x A

q

state. This metastable state is

particularly difficult to detect because it radiates in the infrared

(1.27 ym) and has a very long radiative lifetime (3900 sec). This metastable state is of particular interest because it can serve as an energy

source for the excitation of iodine atoms in the iodine laser.

. Thus far,

only chemically excited oxygen molecules have been used for this purpose.

These metastables are also of importance in ionized air because of the ease with which they cause electron detachment from negative ions.. In

collaboration with C. Yamabe this work will be extended to 0 -N

2

ITn

" x

" tures and to a search for previously unmeasured metastable states.

168
RATE

COEFFICIENT

(cm 5

sec*"

IO"12

IO" 13

IO

-'4

I IO IOO 1000

TEMPERATURE ( K

)

Figure 8 . Reaction rate coefficient (cm^ sec"*) versus temperature (K)

for the process NH3

+ + H2 + NH4+

+ H. Ion trap measurements

at low temperatures are the first ever for any ion at such

low temperatures. Higher temperature data are the flowing

afterglow (FA) data of the NOAA group and the selected

ion flow tube (SIFT) data of the Birmingham group <J> (unpublished)

.

t r

MEASUREMENTS

SIFT

/

and FA

MEASUREMENTS

I I

169
A. V. Phelps , in collaboration with L. C. Pitchford of the JILA

Information Center, has applied the techniques developed by Pitchford,

ONeil and Rumble for the solution of the Boltzmann equation for electrons in gases to the analysis of transport, excitation and ionization

coefficients in nitrogen. These calculations show that previous analyses of experimental data were in error by as much as 40 percent and that

corresponding adjustments must be made in the cross section sets derived

from transport data. Unfortunately this change causes a serious and, as yet, unresolved discrepancy between calculated and measured excitation

rate coefficients for the nitrogen A

3 e metastable state. In addition,

Monte Carlo techniques have been used to test the Boltzmann equation re- sults and to simulate the perturbing effects of electrodes used in the

experimental measurements. Because of the termination of other agency

funds, this work is being terminated.

A. V. Phelps has completed an extensive correlation of theoretical

• predictions of the rates of loss of electrons and ions from the positive

column of electrical discharges. This correlation covers a very wide

range of the discharge parameters of pressure, electron density and tube

radius. The results show good agreement with experimental data obtained

previously in collaboration with C. F. Muller.

A. V. Phelps plans to complete the development of simple models for

the calculation of the role of highly excited atoms in electrical discharges. This includes extension of models in which electron-excited

state collisions dominate to cases in which neutral atom-excited atom

collisions dominate.

T. Baer and J. Hall have undertaken a study of collisional damoinq

and dephasing of molecular dipoles using the technique of coherent optical transients. In these frequency-switchinq experiments, T. Baer has

observed a rather well-marked maximum in the dipole coll i si onal -damping

rate of HF near 1 millimeter laser mode size. Through the mode size/

solid angle duality, this value correlates reasonably well with the

*100 cm/sec nms velocity shift per collision typically found usinq a Kei 1 son-Storer collision kernel representation of the collision process.

They believe that these sub-Doppler techniques, coupled with their ability to select a different collisional angular sensitivity by manipulation

of the laser mode parameters, plus the well-defined dipole-dipole longrange force law should enable formulation of a rather detailed microscopic model of the collision process. For example, in the sub-Doppler re- gime, it seems clear that momentum transfer at large impact parameters

will be manifest as a central narrow notch in the collision kernel for

aV << AV^mg.

S. Geltman and S. Haan are continuing a theoretical study of the

time development of the resonant (3s-3p) ionization of Na by monochromatic radiation. The ejected electron energy distributions are being

studied as a function of time in the radiation pulse, and pulses with

sudden and ramp turn-ons are being used. Although the total ionization

probabilities are very low at these early times in the pulse, one sees a very rich structure in the ejected electron energy distribution due to

170
the real excitation of intermediate states by photons corresponding to

the Fourier transform of the pulse turn-on function. They are also

studying the frequency and intensity dependences of the transient ionization. This phenomenon is important as it will appear as an unavoidable source of background ionization in schemes to detect single atoms

by resonance ionization spectroscopy [Hurst et al., Rev. Mod. Phys. 51,

767 (1979)].

’

Geltman carried out a theoretical study of the two-photon ionization of Cs in the region of the interference minimim (near the 7p

x

# state) in conjunction with the recent successful Saclay measurement of

this [Morellec et al., Phys. Rev. Lett. 44, 1394 (1980)1. He used the

most accurate bound-bound dipole matrix 'elements available and quantum

defect theory for the bound-free matrix elements, and retained the intermediate states 6p, 7p, 8d, 9p (taking complete account of fine structure

effects). The results for the position of the minimum are seen to be

approaching the experimental result as additional intermediate np states

are included in the calculation, but the effects of the so far omitted

10p-«p plus continuum states are hard to estimate. The calculated cross

section magnitude at the minimum lies about an order of magnitude below

the measured value, and it is likely that this discrepancy is largely due

to a background of electric quadruoole transitions. These are presently

being studied. The calculation is being done for both linear and circular polarized radiation, and we find less pronounced differences for

these two cases than are reported by other theoretical workers.

The theory of laser-induced colli si onal ionization is being applied

by S. Geltman to the case of

Sr(5p 1 P) + Cs(7s 2

S) + + Sr(5s h) + Cs +

+ e , which has been studied experimentally by Brechniac et al., J. Phys. B 13,

L383 (1980). The laser which resonantly excites the Sr(bp : P) also provides the photons for the above process, and an asymmetric resonance profile is observed. He is using a quasi static molecular model for the collision in which the larger value for the van der Waals C for Sr(5p X P) + Cs(6s 2S) than for Sr(5s X S) + Cs(6s 2 S) explains the direction of the

asymmetry. The width of the profile is consistent with the Stark width

or Rabi frequency for the resonant excitation of Sr. He is setting up to

incorporate the above physical model into detailed calculations for the

ionization probabilities as a function of impact parameter. He will then

make detailed comparisons with the experimental results for the variation

of peak cross section, spectral width, and asymmetry as a function of

laser intensity (range of 1-15 MW/cm2 ).

A new project is being initiated in a collaboration between S.

Geltman and M. J. Conneely (visiting JILA from the University of Glalway,

Irel and) to calculate electron free-free transition cross sections that

are accompanied by changes in the state of the target atoms. This is

partially motivated by an experiment in progress by J. Zorn at Michigan

to look for the Is 2 X S ->• ls2s *S excitation in He by the joint action of

a monochromatic electron beam (of about 19.3 eV, near the ls2s2 2 S Schulz

171
Figure

9.

Doppler-averaged

excitation

functions

of

the

upper

level

asa

result

of

rectangular

pulses

(dashed

line)

and

triangular

pulses

of

various

lengths

(solid

lines)

of

the

multimode

radiation

described

in

the

text

acting

upon

the

Na

3s

-+

3p

transition.
resonance of He") and a laser beam of Hu = 1.5 eV. They will initially

confine themselves to electron-hydrogen and electron-helium systems and

use the IMPACT computer programs to obtain electron-atom scattering wave

functions. They will pay particular attention to scattering resonance

regions, where it is expected that the free- free processes will be

greatly enhanced over their nonresonant values. At very high energies

of electron impact it is expected that semi classical methods can be used

and the process becomes mainly coll i si on- induced absorption.

Geltman has been collaborating with an experimental group at Saclay

who have been carrying out measurements in the laser- induced ionization

of Na vapor. They use a pulsed dye laser which puts out a pulse of

about 1 psec and which contains about 350 modes with mode spacings of

about 200 MHz. The saturation conditions for the 3s-3p transition under

the influence of this type of radiation must be known for the interpretation of these measurements, and so Geltman studied the theory of the

response of a two-level system to multimode radiation. He found that an approximate expression for the average excitation of the upper state for

square pulses is

P

2 = V? [l - n

j Aj + flj

where Aj and flj are the detuning and Rabi frequency associated with the

power contained in- the mode. If the analysis is carried out for the

more realistic triangular pulses, P

£

becomes dependent on the pulse

lengths. The saturation characteristic we obtain for the Na 3s-3p transition and the Saclay laser is shown in Fig. 9, after averaging over the

expected Doppler distribution. This indicates that the transition can

be expected to be saturated for I > 10 3 W/cm2

, which covered the intensity range for the ionization measurements.

In experiments of R. Dang and A. Gallagher, an atomic beam of Na

is optically excited to the 3P state by laser radiation, and an electron

beam further excites these 3P atoms. The radiation from these higher

states is detected, so that total excitation cross sections are obtained.

The 3P atoms are also highly polarized, and polarization dependences of

the cross sections can be observed. In FY 1980 the apparatus has been

adapted and tested for this experiment and the laser put into service.

Cross-section measurements are planned for FY 1981, initially for the

3P ->• 4D and 3P - 5S excitations.

A relatively dense Na vapor is being stronqly excited by pulsed

laser radiation, and the time dependent intensities of fluorescence and

scattering from many excited states is beinq measured by J. Huennekins

and A. Gallagher. The processes of radiation scattering, radiation diffusion, and collision processes between excited atoms and with electrons

all occur in this situation. In order to isolate and understand these

many processes they are measuring the dependence of the Na excited-state

densities on Na density, laser power and laser pulse width. Considerable survey data have now been taken, raising a variety of mysteries

.

173
that require more systematic studies in the various density and power

regimes. Use of a cw dye laser as a probe of excited atom densities is

also planned for FY 81.

Colli si onal line shapes are a very powerful diagnostic for atomic

interactions, but it is very difficult to definitively test the lineshape theories due to incomplete knowledge of the atomic interactions.

The mixed alkali pairs are a very interesting system for such tests

since they have very lonq- range interactions that should be closely re- lated to the known transition moments of the separated atoms (e.g. the van der Waals coefficients are 10-100 times those for most atom pairs).

K. Niemax, L. Brillet, W. Kamke and A. Gallagher have thereby been

studying the line shapes of these colliding atoms. In FY 79 they measured the wing shapes of the Na resonance lines due to Rb perturbations,

and in FY 80 the broadening of the line cores by Cs. These experiments

are complicated by the high density of Na impurities in available Rb and

Cs, but they expect to complete these Rb and Cs broadening experiments

in FY 1981. In addition, the Li-Na system is now of considerable interest as theoretical interaction potentials have recently become available,

and the K-Rb system is of particular interest due to the exceptionally

long-range interactions. Colli si onal line shaoes have normally been applied only to non-reacting colliding atoms. They are starting a study

of the N

2 broadening of the Ma resonance lines, since this is a quasireactive system in which the Na electronic energy is transferred to N

2 vibrational energy. The broadening of the Na resonance line cores has

been measured, and measurements of the far winqs are under way.

Hydrogenated amorphous silicon films are potentially useful for

low-cost, thin film solar cells. H. Chatham, R. Robertson and A.

Gallagher have been constructing an apparatus (FY 1980) to study the

important processes and parameters involved in the electric discharge

production of these films. Measurements and interpretations of the

plasma parameters and the radiation and species emitted from the plasma

are planned for FY 1981. Their results will be integrated into an R & D

effort, sponsored by the Solar Energy Research Institute, that involves

a number of industrial and university laboratories.

A. V. Smith, J. E. M. Goldsmith, 0. E. Nitz and S. J. Smith have

used a new saturation method to measure absolute photoiom zation cross

sections of the 4D and 5S excited states of sodium. Two cw dye lasers

are used to stepwise excite a continuous, stable population of the 4D or

. 5S state in an atomic beam, and the number of ions generated by single

pulses from a Q- switched Nd:YAG laser is measured as a function of ionizing pulse energy (see Fiq. 10). The photoionization cross section is

then deduced from the energy at which the photoionization process saturates. This is an attractive method since the only calibration required

is that of the ionizing photon flux. The excited-atom density and the

absolute number of ions generated need not be known. Their cross-section

measurements are the first for excited states of the alkali metals other

than P states, and their results represent reliable, accurate excitedstate photoionization cross sections. They have been careful to specify

174
-1 I I L_

0.01 0.1 1.0 10

I (MW/cm 2

)

Figure 10. Dots are data points for single pulses of the Nd:YAG laser.

The solid line is best fit computed saturation curve in

which the cross section is the only free parameter. This

experiment was carried out with all laser beams circularly

polarized. This produces a definite alignment of the

excited atomic state and a well defined transition to the

continuum. Measured cross sections are converted to those

for unaligned atoms by use of angular momentum algebra.

175
the atomic alignment when necessary and to otherwise perform the measurement in a manner which leads to straightforward analysis. The quoted

error limits are conservative and include all systematic as well as statistical uncertainties. The measured cross sections for ionization

of unaligned atoms are 15.2+1.7 Mb for the 4D state and 1.49+0.13 Mb for

the 5S state, both in excellent agreement with calculated values.

D. Meschede and 5. J. Smith have developed an apparatus for observing super- fine rotational structure in symmetric molecules with the objective of searching for and measuring the clustering effects predicted

by W. E. Harter, former JILA Visiting Fellow. A stimulated Raman gain

method is based on the use of an intense diffraction limited tunable YAG

laser beam as a pump, and a He-Ne laser beam probe. The laser beams are

superposed and sent into an absorption cell containing a multipass optical system. After one hundred passes the beams are extracted, separated,

and the He-Ne comoonent directed into a red-sensitive multiplier. The

essential requirement is the complete isolation of the final He-Ne com- oonent from measurable contributions in the wings of the YAG beam.

Stimulated Raman emission at the He-Ne frequency is enhanced when the

difference frequency between the two lasers coincides with intervals

between components of the superfine rotational structure. They anticipate carrying out intensive studies of several symmetric molecules, initially CF

4

, during FY 81.

S. J. Smith and G. Leuchs are measuring and analyzing the angular

distributions of photoelectrons from atoms prepared in well -specified

spatially anisotropic states by means of step-wise resonant excitation

using polarized laser beams. The states of interest are excited states

with angular momentum quantum numbers a > 1 and with non-uniform populations of the magnetic sub-states m£

. The signatures of the magnetic

substates (z, m) are the spherical harmonics P

A m . The photoelectron

distributions exhibit these signatures. Of particular interest are the

signatures of the continuum states reached in the photoionization process, which are ordinarily restricted to those allowed by the dipole

orbital angular momentum selection rule aL = +1. Careful analysis of

the resulting distributions and identification of these signatures can lead to accurate information about the relative strengths of the aL = +1

and aL = -1 processes, as well as their relative phases. Such information is needed to test new calculations of processes involving excited

states in hot gaseous plasmas. For atoms such as barium and strontium,

which have autoionization structure in their electron conti nua, they

hope to develop the angular distribution technique as a device for identifying characteristics of such autoionizing states. Of fundamental interest is the ultimate possibility of studying angular distributions from

states sufficiently highly excited that the size of the atom (orbital

diameter) is no longer negligible compared to the wavelength of light.

This would be observed in the angular distribution as a breakdown of the

"dipole" selection rule aL = +1, a matter of some significance.

D. E. Nitz, A. V. Smith, M. 0. Levenson and S. J. Smith have been

conducting research to provide wel 1 -characteri zed guanti tati ve data for

the influence of field fluctuations on near-resonant absorption by atoms

176
in intense laser fields. The absorption characteristics obtained usinq

a carefully stabilized, very intense continuous wave laser field will be

compared with the characteristics when statistically well -characterized

fluctuations are imposed on the same laser beam, using acousto-optic and

electro-optic modulating devices. Techniques are being develooed to impose frequency fluctuations and amplitude fluctuations, to obtain data

in forms aoprooriate to test various theoretical models. Measurements

will be carried out using a beam of atomic sodium in hiqh vacuum, optically purnoed to a soecific substat'e so the absorbing 3S^ 2 > 3P

3 / 2 transition is completely defined, and Doppler effects are reduced. A SDecially developed cw ring laser, with a line width of <100 kHz obtained

by advanced stabilization techniques will provide the intense field.

Absorption will be studied by observing in fluorescence and also in

ionization by using an additional laser as a probe to excite 3 Pw2 -*D

transitions, which leads to ionization by the intense laser field. Of

interest in these studies are the effects of fluctuations on the shifting and splitting of atomic energy levels by the intense laser field,

effects which may have practical significance in technological applications of high power lasers. A representation of such splitting effects

is given in Fig. 11, showing plots of some data presently being analyzed.

In this work the carrier/frequency of the intense laser field was tuned

away from atomic resonance by about 2000 laser line widths. The traces

represent this limiting case for the effect of a "nearly monochromatic"

laser (below) and with the residual field fluctuations substantially

suppressed by a Fabry-Perot filter tuned to the laser frequency (above).

Following the suggestion of J. A. Rees, who found a serious inconsistency in elastic scattering in Ne, Visiting Fellow M. G. Menendez and

E. Beaty undertook measurements of the angular distribution of elastically scattered electrons from neon in the energy range 50 eV to 100 eV.

The differential cross section for elastic scattering shows a pronounced

minimum at angles near 100° for energies in this range. The energy at

which this minimum is deepest is the critical energy E c

, and its prediction is a sensitive test of theory. For energies close to E

c the electrons scattered at angles close to the critical angle will be highly

polarized. Previous measurements were in serious disagreement with

theory. The JILA results are in excellent agreement with calculated

values, and give E

c

= 64.0+1.0 eV at a critical angle of 102°.

Chemical Physics

It is difficult — and perhaps from some points of view artificial — to distinguish some of the programs in the above subsection (atomic

and molecular physics and interactions) from the programs noted here.

Nevertheless, it is important to point out that JILA has a very strong

chemical physics program with three Fellows rostered in the Chemistry

Department: W. C. Lineberger (CU), W. P. Reinhardt (CU), and S. R.

Leone (NBS). It is, of course, the work of Leone's group which is

l i sted here as part of the QPD program.

Low power laser pulses are used by D. J. Nesbitt and S. R. Leone to

initiate chain combustion reactions by specific dissociation of molecules

177

1
Ncr

SIGNAL

Na

+ SIGNAL vs PROBE LASER FREQUENCY

Figure 11. Comparison of ac Stark effect signals at a fixed detuning

of 40 GHz demonstrating explicitly the change in asymmetry

resulting from filtering the intense laser background light.

178
into atoms or radicals. The full time development of the chain reaction

is monitored by infrared chemiluminescence from vibrationally excited

products of the reactions. A complete mathematical formalism has been

developed and experimentally verified for a series of chain reactions

such as Cz

2 /H , (U /H

2S, Cz2/CH

3 SH, and Cji 2/butane. Experimental rate

constants can oe obtained for each of the propagation reactions and

termination steps. Chain reactions which proceed on exceedingly slow

time scales have been observed and can be sensitively detected and measured by this technique. More recently, it has been discovered that

specific product molecules, such as various chlorobutane derivatives,

can each be detected by their "fingerprint pattern" infrared emission

spectrum. The development of individual product molecules in a complex

mixture of combustible gases can be followed completely in time. Work

is proceeding to develop further capabilities for specific molecule detection in complex chain reaction systems and to study the kinetics of

oxygen-hydrocarbon chain systems at higher temperatures.

Infrared chemiluminescence is being used by T. S. Zwier, J. C.

Weisshaar, G. B. Ellison, V. M. Bierbaum, Z. Hermann and S. R. Leone to

study the dynamics of ion-molecule reactions in a device called a flowing afterglow. These are the first measurements of this kind. Recently

complete product vibrational state distributions have been obtained for

many of the simple proton abstraction reactions:

Cjf + HBr,HI + HCz(v) + Br“,l“

F" + HC£,HBr,HI * HF(v) + Cjf ,Br“,l"

and for the associative detachment reactions:

Cjf ,F~ + H -* HCji(v) , HF(v) + e" . An example of results for the F“ + HBr reaction is shown in Fig. 12.

These results provide some of the first detailed examinations of thermal

energy ion-molecule reaction dynamics through analysis of product states.

They already have had a significant impact on the theoretical description

of ion reactions. Certain ions play a prominent role in the chemistry of

the upper atmosphere and in interstellar molecule formation. Ions are also important infrared emitters, with consequences for sophisticated

military detection technology. In continuing studies, the methods developed here will be applied to ion reactions of atmospheric interest.

Experiments will be established to probe ion-molecule product states in

the collision-free regime and to increase the sensitivity of detection

by many orders of magnitude using laser-induced fluorescence detection.

A new technique has been developed by S. L. Baughcum, H. W. Hermann

and S. R. Leone to obtain complete infrared emission spectra of free

radical s produced by dissociation of polyatomic precursors. This method

was first applied to the CH

2

I radical. It was discovered that, in addition to the usual stretching and bending modes, the radical exhibits a broadband background emission due to the very dense number of states at

high levels of excitation. The technique has recently been applied to

the bending mode of the CH radical, which is excited from v = 1-10 upon

dissociation of CH I. It will be possible from this data to unravel the

179
180

Figure

12.

a)

Infrared

chemiluminescence

spectrum

from

the

v

=

1-4

levels

of

the

HF

product

in

the

reaction

F“

+

HBr

-*

HF(v)

+

Br~.

Relative

populations

into

the

various

vibrational

levels

are

obtained

from

a

computer

fit

(solid

line)

of

the

data

points

(x).

b)

Results

of

ion

experiments

obtained

are

compared

to

results

from

neutral

analog

experiments

of

Setser.
complex series of neqative anharmonic bands. Thus far this has only been

treated theoretically. These studies are being developed to provide new methods of detecting free radicals, to obtain information about their

spectroscopy, and to measure radical kinetic processes such as vibrational deactivation and reactivity.

Astrophysical Measurement

K. B. Gebbie and J. Toomre, in collaboration with L. J. November

and G. W. Simon ( SPO) have now completed the analysis of their observations of supergranul ar velocities obtained with the University of Colorado UV Spectrometer on the 0S0-8 satellite. Steady Doppler velocities

were determined from data obtained in a Si II spectral line and compared

with simultaneous ground-based measurements in Fe I and Mg I using the

SPO diode array instrument. The heights of formation of these spectral

lines span about 1400 km or nearly 11 density scale heights from the

photosphere to the middle chromosphere. The striking results of these

observations are that supergranul ar flows are able to penetrate into the

middle chromosphere, where regions of approaching and receding motion

correlate well with velocity fields observed in the photosphere. The

dynamic range of the steady Doppler velocities observed at radius vector

0.8 increases from 800 ms" 1 in the photosphere to over 3000 ms

-1 in the

middle chromosphere. Seen at disk center, the corresponding increase in

the vertical velocities is from 200 ms" 1 to again about 3000 ms" 1

. Here

the regions of downflow tend to correlate with the bright Ca II emission

network, those of upflow with the darker areas. Despite the increase

with height in the velocities, the vertical momentum associated with the

flow decreases by a factor of 10 3 owing the decrease in gas density.

From the three spectral lines studied, it appears that the scale height

for the decrease in this momentum component is about 135 km in the first

400 km above the photosphere, increasing to about 260 km in the subsequent 1000 km. Thus a distinct change apoears to occur in the flow

structure: in the low photosphere, the horizontal component of velocity

predominates, whereas higher in the atmosDhere, the motions apDear to

become increasingly isotropic.

K. B. Gebbie , J. Toomre and F. Hill, in collaboration with L. J.

November and G. W. Simon (SPO) have confirmed their detection of an intermediate scale of mesogranul ation, an intermediate scale of convective

motion in the solar photosphere and chromosphere. These mesogranul ar flows become evident only when the strong 5 minute oscillations are ac- curately filtered out by long time averages of the Doppler velocity.

Analysis of recent SPO diode array observations at disk center show that

these flows are space filling and cellular in structure, the same patterns of steady velocity being clearly identifiable for periods spanning

nearly two hours. The dynamic range in the amplitudes of these vertical

motions is about 200 ms ", compared with about 100 ms" 1 in the larger

scale supergranul ar flows. Spatial transforms suggest that the primary

power for mesogranul ation lies in the 5-8 Mn range of horizontal scales.

These results suggest that mesogranul ation may be the result of convective overshooting into the stable atmosphere. Such intermediate scales

of convective motions may be driven by the ionization of He at a depth

181
of about 7 Mm or they may simDly reflect hiqher spatial harmonics of the

primary superqranule cell.

The same research qrouo is carrying out an observational study of

steady flows in the upper chromosphere and transition region as a quest

investigator program on the Ultraviolet Spectrometer and Polarimeter ex- periment on the Solar Maximum Mission satellite. In collaboration with

the UVSP experiment team at Goddard, they have observed Doppler velocities in the quiet Sun and in active regions in Si II, Si IV, C II and

C IV spectral lines. Time averaged over one or more orbits, such data

yield the steady component of the velocity fields over a range of heights

in the atmosphere. Further, the time sampling in the observations is

sufficient to permit analysis of the Si II data for the chromospheric

mode in the five-minute oscillations. These SMM/UVSP observations have

been coordinated with simultaneous SPO diode array observations of the

photosphere and lower chromosphere.

D. G. Hummer, in collaboration with M. J. Barlow and J. C. Blades

of University College London, has analyzed spectra of the 0 VI type

Wolf-Rayet star Sand 3 obtained by Barlow and Blades, and has identified

recombination lines of 0 VII, 0 VIII and C V. These ions are among the

most highly stripped species seen in the optical spectra of stars, and

their presence in this star points to a very high energy source of excitation, probably through X-rays. The identification of the members of

the helium-like iso-electronic series was made quite difficult by the

fragmentary state of the relevant pages of Atomic Enerqy Levels, the

multi pi et tables and the periodical literature, a situation that emphasizes once again the importance to astrophysics of basic spectroscopic

measurements. This work is described in an Astrophysical Journal Letter

now in press. Ultraviolet spectra of this object have been obtained by

means of the International Ultraviolet Explorer (IUE) and analysis of

the extended spectra will start shortly. In the next year, a substantial effort will be made to construct models of this object, in the hope

of learning more of the elusive nature of the Wolf-Rayet stars through

this rather pathological case.

D. G. Hummer and G. B. Rybicki (SAO) have developed a generalization

of the escape- probabi 1 ity approximation for radiation transport in spectral lines that is valid for both static atmospheres and those with arbitrary flow speeds. This work bridges the gap between previously-obtained

approximations that were valid in only the static and high velocity limits, and makes it possible to establish a priori conditions for the va- lidity of the limiting-case approximations"! A further new feature of

this work is the exploration of the effect of line wings, arising from

collision damping, on the conditions for validity of the high-speed

limiting cases, which is much used; the presence of such line wings has

the effect of making these conditions much more difficult to satisfy.

Most of the work to date has been concerned with planar flows, although

the formal ati on for cases with spherical symmetry has been carried out

and preliminary results obtained. An account of this work is being

prepared for publication in the Astrophysical Journal . This work is

exceptionally timely, as the limiting forms of this approximation are

182
becoming very widely used because of their relative simplicity. In particular the study of stellar winds depends strongly on such approximations. This work has shown that much of the work for late- type stars

using this kind of treatment is invalid, and provides a basis for a more

accurate treatment. Further generalizations of this approach to include

the effects of partial frequency redi stribution and continuous absorption, are under way and will be developed in the cominq year. The approximate solutions obtained in this way will be compared with accurate

numerical solutions. The first application of these generalizations

will be to the interpretation of the Bowen cycle lines of 0 III and

N III formed in nebulae surrounding galactic X-ray sources, which should

provide useful diagnostics for the physical conditions, including the

state of motion, of this gas.

J. Linsky continues several stronq and multifaceted programs to

understand phenomena occurring in the outer atmospheres of the Sun and

related stars using satellites and ground-based telescopes and state-ofthe-art radiative transfer techniques in order to produce detailed atmosDheric models consistent with observations. In particular, he is

trying to understand stellar chromospheres, coronae, flares, winds, and

other manifestations of nonradiative heatinq in the atmospheres of stars

primarily by the detailed analysis of ultraviolet and visible spectra

and X-ray flux measurements. Two essential aspects of this work are the

development and testing of non-LTE radiative transfer techniques for optically thick transitions and of spectroscopic diagnostic techniques for

inferring density, temperature, departures from thermodynamic equilibrium, and other plasma parameters from the observed spectrum.

A. (Stellar Ultraviolet Astronomy) Linsky has a number of Guest

Observing programs under way to use the spectrographs on the International Ultraviolet Explorer (IUE) satellite to study the spectra of

stars with properties that may be similar to the Sun.

a) Stellar Surveys. One of these IUE observing programs was to

test whether the chromospheric radiative loss rates in a representative

sample of stars depends on stellar effective temperature and gravity in

a manner consistent with the acoustic wave theory of heatinq or is inconsistent with the theory. Using the Mg II resonance lines as indicators of chromospheric heatinq rates Linsky and G. S. Basri found that the

heating rates range over two orders of magnitude for stars of similar

effective temperature and qravity with little trend on stellar gravity.

This result is inconsistent with simple acoustic wave heating, but is

what one would expect if maqnetic fields (which presumably differ greatly

from star to star) play a critical role in the heating process, as for

example through magnetoacoustic waves.

One of the important early results from IUE was the discovery by

Linsky and B. M. Haisch that giant stars warmer than about 4400 ,K general ly show ultraviolet emission lines indicative of plasmas with

temperatures extending from 2 x 10 4 K to at least 2 x 10 5 K, atmospheric

layers called transition regions, whereas cooler giant stars (spectral

types K2 III and cooler) generally do not show any evidence for outer

183
layers any hotter than 1 x 10 4 K (extended chromospheres) . During the

last year Linsky and his col laborators observed a large sample of stars

which show that transition reqions probably do not exist in stars cooler

than their proposed dividing line, but the situation in the hotter stars

is more complex. During the last year Stencel and D. J. Mull an presented evidence for a Mg II asymmetry dividing line in the HertzsprungRussel Diagram (approximately vertical near spectral type K2 III) in

which the Mg II double emission features change from emission primarily

on the blue side or emission features of equal strenqth to emission primarily on the red side. They interpreted this chanqe of asymmetry as indicative of the onset of strong cool winds in stars cooler and more

luminous than spectral type K2 III.

Haisch, Li nsky and Basri have investigated the role that radiation

pressure in the Lyman alpha line might plan in initiating cool winds in

late- type stars. They found that this mechanism can indeed initiate

flows but some other mechanisms, such as A1 fven wave pressure, is needed

to continue the flow.

In another IUE observing program Linsky and N. C. Marstad observed

stars somewhat hotter than the Sun (spectral types A and F) to see if

chromospheres and transition regions do not occur in the hotter stars.

They concluded that the rapid increase in ultraviolet emission from the

photospheres of these stars with increasing effective temperature makes

it very difficult to see ultraviolet emission from the hotter layers,

and thus the question cannot be answered at this time.

Two other surveys using IUE have now been completed. T. R. Ayres,

Marstad and Linsky have correlated ultraviolet emission line strengths

and coronal X-ray emission in 28 stars observed by IUE and the Einstein

satellite. They found that the radiative loss rates from transition re- gions and coronae are proportional to the second or third power of the

corresponding chromospheric loss rates, suggesting that transition re- gions and coronae are heated by different processes than coronae. A

similar conclusion was reached by Linsky , P. L. Bornmann and collaborators at Ohio State, Arizona, and the Air Force in their survey of 3 dM

(nonemission line) and 7 dMe (emission line) stars. Thev found that

the radiative losses from chromospheres and transition regions are far

larger in dMe than dM stars, and that ratio of the heatinq rates of

transition regions to the rates for chromospheres increases rapidly

towards cooler stars.

b) Close Binary Systems. Stars in close binary systems can be very

interesting as tidal forces can produce synchronism of rotation and

revolution and thus rapid rotation. For stars with convective zones,

rapid rotation leads to enhanced dynamo processes, strong magnetic

fields, and more exaggerated phenomena like flares and coronal heating

than is seen in magnetic regions on the solar surface. T. Simon and

Linsky obtained IUE spectra of two spectroscopic binary systems of the

RS CVn-type, HR 1099 and UX Ari, and derived a model for the chromosphere and transition region of the more active stars in these systems

by matching fluxes of strong lines of Mg II, C II, Si II and Si III and

184
using density-dependent line ratios. They also observed UX Ari with IUE

during a major flare in which the chromospheric and transition region

lines were enhanced and the Mg II lines developed stronq emission in

their red wings. They proposed that the flare may be due to the annihilation of magnetic fields when loops from the two stars interact.

They also observed HR S 1 10 during a flare, but found no enhancement in

the emission lines compared to the nonflare state. They proposed that

this system is similar to Algol systems and the radio flare may be a consequence of mass exchange. Additional studies of RS CVn systems

with IUE are under way.

c) Stellar Model Chromospheres and Transition Regions . Over the

last few years Linsky and his col 1 aborators at JlLA pioneered the techniques for computing models for stellar chromospheres by matching com- puted and observed spectral features, in particular the resonance lines

of Ca II and Mg II. During the last year Basri and Linsky extended this

chromospheric modeling program to the supergiants e Gem and a Ori. This

task was particularly difficult because supergiants have very low chromospheric densities and thus the scattering of photons in the wings of

strong resonance lines is nearly coherent. As a part of this Ph.D.

thesis, Basri carefully considered the important role played by non-LTE

continuum transitions and the Doppler drifting of core photons to the

line wings with multiple scattering.

They have also extended their models to the hotter layers in a stellar atmosphere (up to 3 x lO 4 K) by analyzing IUE spectra of emission lines of C II, Si II, and Si III. Using these lines Basri and

Linsky computed a model for 3 Dra (G2 II), Simon, W. L. Kelch and Linsky

computed a model for e Eri (K2 V) , and Simon and Linsky computed amode)

for the active stars in the HR 1099 and UX Ari binary systems.

d) Future Programs . Li nsky and his collaborators at JILA will be

extending their studies of the chromospheres and transitions of stars

through new Guest Observer programs on IUE. The next generation ultraviolet spectrometer in space will be the High Resolution Spectrograph

(HRS) instrument on Space Telescope. Li nsky is a Co-Investigator on the

HRS Instrument Definition Team with responsibilities for defining the

late- type star observing program and analyzinq these observations, advising on absolute radiometric calibration. Another important effort

to be done over the next year is the incorporation into the radiative

transfer-statistical equilibrium equations for the coupled Lct-Lg-Ha

lines of hydrogen the new redistribution theory being developed by J.

Cooper and colleagues at JILA.

B. (Stellar X-Ray Astronomy.) Linsky also is pursuing a number

of Guest Observing Programs using the HtAO-1 (High Energy Astrophysical

Observatory) and HEAO-2 (Einstein) satellites to study X-ray emission

from analogues of the solar corona.

a) Stellar Surveys. With collaborators at U. California, Berkeley

and Cal Tech, Linsky searched the HEAO-1 all sky survey data for X-ray

emission from dwarfs and subgiants of spectral type F-K. They detected

185
6 definite and IS probable sources, and argued that the X-ray luminosity

from the most active single late- type stars is typically 10“* of the

stellar bolometric luminosity. The first survey of stellar X-ray

sources by the Einstein satellite was recently completed by a large

consortium of observers including Haisch and Linsky. As a result of

this survey, Li nsky has orooosed a broad scenario of coronal X-ray

emission in which remnant or dynamo-regenerated magnetic fields play

a predominant role in heating stellar coronae.

Ayres, Linsky and collaborators at the Harvard-Smithsonian Center

for Astrophysics have an observing program under way with Einstein to

determine whether solar-like coronae (T > 1 x 10 6 K) do not occur in

the cooler and more luminous stars. They measured only upper limits on stars cooler and more luminous than spectral type K2 III, suggesting

that hot coronae do not exist in these stars and the G-M suoergiants.

This important result is consistent with their results from IUE that

transition regions also do not exist in these stars but that strong cool

winds take their place.

b) Flare Stars . Haisch and Linsky presented Einstein X-ray flares

and IUE ultraviolet emission line fluxes for the flare star Proxima

Centauri (dM5e) during quiescent times. Haisch, Linsky and collaborators at the Center for Astrophysics also observed Proxima Centauri with

Einstein during a flare and estimated temperatures, luminosities, emission measures, and emitting volumes as a function of time during the

flare. X-ray emission during two very large flares each on the flare

stars AT Mic and AO Leo were observed with HEAO-1 and discussed by

Li nsky , Haisch and collaborators at Berkeley and NASA Goddard.

c) Future Work. The study of stellar coronae and flares by the

analysis of X-ray observations is continuing through several Einstein

Guest Observer programs and the analysis of this data.

Geophysical Measurement

P. Bender has collaborated with C. C. Goad and J. 0. Bossier of the

National Geodetic Survey on a theoretical study of the use of signals

from the NAVSTAR Global Positioning System (GPS) satellites for accurate

determination of geodetic baselines. They showed that a new approach

called the REconstructed CArrier Phase (RECAP) method is likely to give

as high accuracy as can be achieved by long baseline radio interferometry measurements for baseline lengths of up to hundreds of kilometers.

This conclusion also was reached independently by C. C. Counsel man and

I. I. Shapiro at MIT. The results of the two groups led to a decision

by the Defense Mapping Agency to fund the development of prototype GPS

receivers which will use the RECAP method. The National Geodetic Survey

and the U.S. Geological Survey also expect to procure GPS receivers

which use this method for establishing geodetic control in the many new areas where it is needed and also for detecting crustal movements.

More complete theoretical studies of the accuracy achievable with

the RECAP method have been carried out by D. Larden of the University of

186
Colorado and Bender , A "modified worst case" analysis was used, and gave

an expected accuracy of 1 cm for the horizontal coordinates and 2 cm for

the radial coordinate with only two hours of measurements at a given

site. This accuracy hopefully will be demonstrated in the next 18 months

by two groups in the U.S., even though only the first 6 of the 18 or 24

GPS satellites which are planned are now up. It also was shown that the

present 6 satellites are sufficient to permit measurements of the same accuracy to be obtained once per day in most of the major seismic zones of the world. Since the apparatus required is much simpler than for

VLBI measurements or laser ranging to satellites, it now is expected

that most of the mapping of crustal movements in seismic zones by space

techniques in the next decade will be done with GPS receivers.

Two review papers connected with improved measurement techniques

have been completed by Bender. One covered both ground and space techniques, and is in a book which is being published as part of the final

report of the International Geodynamics Project. The second is on the

expected contributions by space techniques to establishing suitable reference frames to which measurements of worldwide tectonic plate motions

and distortions within plates can be referred. It now appears likely

that geometric reference frames based on the new techniques will replace

the reference systems which long have been traditional in geodesy, where

the height above the geoid plus two horizontal coordinates were used.

J. Faller and Zumberge made substantial progress towards reaching

the 1981 goal of a portable and absolute (3 parts in 10 9

) gravimeter em- ploying the free falling laser interferometric method. At the present,

the precision obtained doing a 10 minute data run (150 drops) is 3 ygal

(3 in 10 9 ). With a 24 hour data run they are able to see (follow) the

earth tides (amplitude 1-2 parts in 10 7 ). A study of various possible

error sources is well under way. They expect shortly to incorporate the

Howard Layer developed I stabilized laser into the system. The wave- length stability of the present Lamb-dip stabilized laser is only 5-10

parts in 10 9

; the Layer-developed I 2 laser however provides more than the

stability required for our parts in 10 9 application. Initial contacts

have been established regarding possible cooperative scientific programs

with groups in West Germany and Canada involving both field testing and

the application of this portable absolute gravimeter to important geophysical problems.

Faller has pursued the possibility of using the Ebtvbs-developed

fluid-fiber technology for other purposes, and in particular its possible applications to the construction of an ultra-sensitive almost dc

gradiometer is being explored. It appears such a development would be

effective both for findinq tunnels (such as are being duq from North to

South Korea) as well as for intrusion detection in connection (for ex- ample) with nuclear stockpiles.

JILA Information Center

The activities of the JILA Information Center to survey the world

literature and produce comprehensive bibliographies on the subjects of

187
electron and photon collisions with atoms and molecules, heavy-particle

collisions and multi photon collisions with atoms and molecules are on- going. The following publications have resulted in FY 80:

"Bibliography of Low Energy Electron and Photon Cross Section

Data (1978) JILA Information Center Report No. 18, 150 pages

(January 1980), J. W. Gallagher and E. C. Beaty.

"A Bibliography of Electron Swarm Data," JILA Information

Center Report No. 20, 252 pages (December 1979), E. C. Beaty,

J. Dutton, and L. C. Pitchford.

"Energy Transfer Collisions of Atoms and Molecules," JILA

Information Center Newsletter, Number 11 (November 1979) and

Number 12 (January 1980), J. W. Gallagher.

Production of NBS Special Publication 593, "Data Index for Enerqy

Transfer Collisions of Atoms and Molecules - 1970-1979," J. W. Gallagher,

Janet Van Blerkom, E, C. Beaty, and J. R. Rumble, Jr., has been a significant effort of the Information Center this year. This publication

is currently in press at the Government Printing Office. Production of

this document combined with the enforced change of computing facilities

from the NOAA XDS 940 to an in-house computer combined with the NOAA

CDC 6600 has delayed production of the 1979 electron-photon and 1979

multi photon bibliographies. The latter two publications are currently

in production. The computer changeover has been time-consuming, but has

gone well. A system of indexing sources of data which is more comprehensive than that currently in use is in its planning stages.

Ongoing work to build and utilize a file of numerical data on electron collisions with atoms and molecules is exploiting the capabilities

of the Tektronix 4051 graphics system with dual disk drive. The work

this year has concentrated heavily on collection and analysis of differential cross sections for elastic scattering in collaboration with J. A.

Rees of the University of Liverpool, England. Dr. Rees has been in residence working with E. Beaty and the Center staff. The review and evaluation of these data are coming to an end. Rees has now left JILA and is

completing the manuscript in Liverpool. The Information Center is preparing figures and tables. A general and preliminary account of the

findings is given here. Aoproximately 1100 samples of data were found,

collected and examined. These represent data on many atoms at various

electron-impact energies. In no case has a "reliable" measurement been

made in the sense that a convincing analysis of possible errors has been

given with the result that uncertainty limits could be reasonably as- signed to the cross section values. In some cases the researchers did

not report enough detail of their procedures. Substantial errors have

probably arisen because the researchers assumed thinqs which seemed

credible but which were not true. An evaluation of these assumptions

requires firstly knowing what they are and secondly knowing enouqh about

the measurement situation to appraise (in the light of newer data) whether they are to be believed. In spite of the frequent lack of specific

information it has been possible to find some basis for making value

188
judgments. An interesting situation occurs in helium at enerqies less

than 20 eV. In this case a calculation done by Nesbet presumes to take

account of all Dossible computational inadequacies. We have not sought

to evaluate his procedures, but the report is in a class by itself in

addressing the problem of error. The most credible measurements agree

with Nesbet's calculations. Unfortunately the two most recently re- ported measurements disagree substantially, and the descriDtive material

included with the reports of these does not allow them to be counted as among the most credible. For other atoms the conclusions are even less

clear. It is widely recognized that normalization is a severe experimental problem, and in many cases it seems to have attracted all the experimentalist's efforts. The pattern of results indicates that in many cases

electron energies are reported incorrectly. A practice is developing of

using a phase shift analysis to supply a normalization. In appropriate

circumstances this works. However little consideration has been given

to the impact of angle-dependent errors. In neon we found little data

between 50 eV and 100 eV, and those available concerned the energy and

angle of a striking minimum near 60 eV. M. Menendez, a Visiting Fellow

at JILA, was able to fill this qap usinq our electron scattering apparatus. A striking observation was that the prior data reporting the minimum was in error by nearly 10 eV.

The Information Center has also been heavilv involved with a com- pilation of swarm data in collaboration with J. Dutton of the University

of Swansea, Wales. Some evaluation of these data with regard to reliability is being made. The Information Center is currently obtaining

microfilm output for this compilation using our new computer program

which produces publication-quality figures. Manuscripts for both the

elastic scattering review and the swarm compilation will be submitted to

the Journal of Physical and Chemical Reference Data.

Drs. Pitchford and Allis have been working on different aspects of

the relaxation of cross sections to swarm data. This program has led to

a substantial improvement in our ability to generate accurate numerical

solutions to the Boltzmann equation. Allis has been concerned with

analytic trends and limits. The general procedure can provide a test

of reliability of cross section data.

The Information Center has initiated discussions to expand its scope

to include a program on dielectric breakdown in gases. The data scope

includes sparking potentials and other quantitative information which is

related to, but more applied than, the swarm data. The proposed program

would include a retrospective and current literature search to identify

publications reporting the desired data, construction of a computer file

containing the numerical data and an evaluation of the data. This program has been proposed in collaboration with R. J. Van Brunt of NBS,

Gaithersburg, J. Dutton, J. A. Rees, and 0. Farrish of the University

of Strathclyde, Scotland.

189
III. PUBLICATIONS AND INTERACTIONS

Included in the following pages of this section are tables of

9 JILA Visiting Fellows for 1979-80 and 1980-81.

• Publications during the past year of NBS Fellows and

Visiting Fellows.

® Invited papers (talks) of NBS personnel of QPD.

• Technical and professional committee participation and

leadership of QPD personnel.

® Consulting by QPD personnel.

® Trips of QPD personnel sponsored by others.

• Conferences sponsored.

® Seminars and colloquiums.

190
PUBLICATIONS

AND

INTERACTIONS

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Arqonne,

IL

60439

techniques.
PUBLICATIONS

Quantum Physics Division (525)

* L. Armstrong, Jr., Bistability Effects in Coooerative Multi Dhoton

Ionization, J. Phys. B: Atom. Molec. Phys. 12 , L719-723 (1979).

* L. Armstrong, Jr. and (W. R. Fielder, Jr.), Photoionization Cross

Sections Using the Mul ti configuration Hartree-Fock and Its Extensions, in Nobel Symposium 45, Physica Scripta_21, 457-462 (19BO)

.

* L. Armstrong, Jr. and S. V. ONeil, Resonance Lineshape and Photoelectron Spectrum in Power Broadened Two-Photon Ionisation, J. Phys. B:

Atom. Molec. Phys. _U, 1125-1141 (1980).

* L. Armstrong, Jr. and J. H. Eberly, Coherence Versus Incoherence:

Laser Bandwidth Effect in Two-Channel Ionization, Phys. Rev. A

( submi tted)

.

J. R. Rumble, E. C. Beaty, and L. C. Pitchford, Unreliable Data—Its

Impact in Modeling MHD Power Generating Devices, in Proc., CODATA

Conference (B. Dreyfus, Ed., Pergamon, Oxford and New York, 1979),

pp. 243-246.

E. C. Beaty, Electron Bombardment of Atoms and Molecules, in Encyclopedia of Physics (American Institute of Physics).

J . W. Gallagher, J. R. Rumble, Jr., and E. C. Beaty, Bibliography of

Low Energy Electron and Photon Cross Section Data (January 1975

through December 1977), NBS Spec. Publ. 426, Suppl . 1 (U.S. Department of Commerce, Washington, DC, 1979).

E. C. Beaty, J. Dutton, and L. C. Pitchford, A Bibliography of Electron Swarm Data, JILA Information Center Report No. 20, December 1,

1979.

J. W. Gallagher and E. C. Beaty, Bibliography of Low Enerqy Electron

and Photon Cross Section Data (1978), JILA Information Center Report

No. 18, January 1, 1980.

E. C. Beaty, J. Dutton, and L. Pitchford, Electron Swarm Data Relevant to High-Voltage Insulation, in Proceedings, International Symposium on Gaseous Di electronics, Knoxville, Tenn., March 9-13, 1980.

J. W. Gallagher, Janet Van Blerkom, E. C. Beaty, and J. R. Rumble,

Jr., Data Index for Energy Transfer Collisions of Atoms and Molecules— 1970 - 1979, NBS Spec. Publ. 593 (in press).

* Entries with stars are those resulting from the work of JILA Visiting

Fellows.

NOTE: Names in parentheses are authors who are not connected with

JILA—NBS or CU.

194
PUBLICATIONS

Quantum Physics Division (525)

P. L. Bender and (C. C. Goad), Probable LAGEOS Contribution to a Worldwide Geodynamics Control Network, The Use of Artificial Satellites for Geodesy and Geodynamics, Vol . II (G. Vei s and E.

Livierators, eds.. National Technical University, Athens, 1979),

pp. 145-161.

E. B. Aronson, R. H. Ware, and P. L. Bender, Modelling of Solar Quiet

Magnetic Field Variations Near a Conductivity Anomaly, Geophys. J.

Roy. Astron. Soc. _59, 539-552 (1979).

P. L. Bender, Effects of Ground Motions on Amplitude Interferometry

,

in IAU Colloquium No. 50, High Angular Resolution Stellar Interferometry, (J . Davis and W. J. Tanqo, Eds., Univ. of Sydney, Australia,

1579), pp. 5-1 to 5-9.

(E. P. Fedorov, M. L. Smith), and P. L. Bender (Eds.), Nutation and

the Earth's Rotation, IAU Symposium No. 78 (Reidel, Dordrecht,

Boston, London, 1980)

.

* (Y. Rabin, M. Berman), and A. Ben-Reuven, Theory of Double Resonance

Raman Amplifier, J. Phys. B: Atom. Molec. Phys. _13, 2127-2136 (1980).

* (Y. Rabin) and A. Ben-Reuven, Resonance Fluorescence and Resonance

Raman Line Shapes in Strong Radiation Fields, J. Phys. B: Atom.

Molec. Phys. _13, 2011-2025 (1980).

* A. Ben-Reuven, Resonance Absorption and Scattering of Strong Coherent

Radiation in Thermally Relaxing Systems, in Lectures on Biological

and Chemical Physics: A Symposium in Honour of Shneior Li f son on His

65th Birthday (in press).

* A. Ben-Reuven, Theory of Two-Atom Coherence in Gases. I. Master Equations, Phys. Rev. A (in press).

* A. Ben-Reuven, Theory of Two-Atom Coherence in Gases. II. ContinuousWave Spectra, Phys. Rev. A (in press).

* A. Ben-Reuven, Recent Developments in Line Shape Theory, in Proceedings, 6th International Conference on Spectral Line Shaoes (in

press)

.

* G. Chanmuqam, Cyclotron Emission from Am Herculis, in The Second Year

of IUE: The Universe in Ultraviolet Wavelengths, NASA Goddard Space

Flight Center, Greenbelt, Mb, May 1980 (in press)

.

* G. Chanmuqam, Cyclotron Absorption in Accreting Maqnetic White

Dwarfs, Astrophys. J. (in press).

195
PUBLICATIONS

Quantum Physics Division (525)

G. Chanmuqam and (G. A. Dulk), Polarized Radiation from Hot Plasmas

and Applications to AM Herculis Binaries, Astrophys. J. (submitted).

(H. C. Bra.yman, D. R. Fi schell), and T. A. Cool, Soectroscopic

Studies of the Products of Reactions of Yttrium and Scandiun Atoms

with Halogen Molecules. I. The Oriqin of Chemiluminescence, J. Chem.

Phys. (in press).

(D. R. Fi schell, H. C. Brayman) , and T. A. Cool, Soectroscopic

Studies of the Products of Reactions of Yttrium and Scandium Atoms

with Halogen Molecules. II. Laser Induced Fluorescence from Yttrium

and Scandium Monohalides, J. Chem. Phys. (in press).

K. Davidson, Additional Upper Limits on a Lyman-Alpha Halo Around

PHL 957, Publ. Astron. Soc. Pacific 2^, 817-823 (1979).

K. Davidson and R. McCray, SS 433 as a Prototype of AstroDhysical

"Jets, " Astrophys. J. (in press).

G. H. Dunn, Electron-Ion Collisions: Experimental, in Proceedings of

the Nagoya Seminar on Atomic Processes in Fusion Plasmas ( I PP J -AM-13)

(Y. Itakawa and T. Kato, Eds., Institute of Plasma Physics, Nagoya,

Japan, 1979), pp. 57-65.

P. 0. Taylor, R. A. Phaneuf, and G. D. Dunn, Absolute Cross Sections

and Polarization for Electron-Impact Excitation of the Resonance

Multiplet of the Be

+ Ion, Phys. Rev. A 22, 435-444 (1980).

(B. Van Zyl), G. H. Dunn, (G. Chamberlain, and D. VI. 0. Heddle),

Benchmark Cross Sections for Electron Impact Excitation of n

x S Levels

of He, Phys. Rev. A 22_, #5 (1980).

(W. C. McColgin, A. P. Marchetti), and J. H. Eberly, The Nature of

Solution Spectra: Inhomogeneous Broadening and Phonon Effects in

Frozen Solutions, J. Am. Chem. Soc. 100, 5622 (1978).

(J. D. Stettler, C. M. Bowden, N. M. Witriol), and J. H. Eberly,

Population Trapping During Laser Induced Molecular Excitation and

Dissociation, Phys. Lett. 73A , 171-174 (1979).

J. H. Eberly, C. V. Kunasz, and (K. Wodkiewicz), Time-Dependent Spectrum of Resonance Fluorescence, J. Phys. B: Atom. Molec. Phys. 13,

217-239 (1980).

J. H. Eberly, Unified View of Spontaneous Emission in Several Theories of Radiation, in Proceedings of Symposium on the Foundations of

Radiation Theory and Quantum Electrodynamics, University of Colorado,

April 28-29, 1978 (A. 0. Barut, Ed., Plenum Press, 1980).
PUBLICATIONS

Quantum Physics Division (525)

G. M. Keiser and J. E. Fa Her, Etttvfts Experiment with a Fluid Fiber,

in Proceedings, Second Marcel Grossman Meeting on Recent Developments

of General Relativity, Miramare, Trieste, July 5-11, 1979 (in press).

J. E. Faller, R. L. Rinker, and M. A. Zumberqe, .Absolute Gravity as a Reconnaissance Tool for Vertical Heiqht Changes and for Studying Density Changes, Proceedings, 2nd International Symposium on Problems

Related to the Redefinition of North American Vertical Geodetic Networks, Ottawa, Canada, May 26-30, 1980.

J. E. Paller, P. L. Bender, (R. Decker, and J. L. Randall), Laser

Gravitational Wave Detector in Space, in Proceedings of SPIE Conference, April 1980, Washington, D.C.

L. Schumann, D. Wildman, and A. C. Gallagher, Electric Discharge

Excitation of T* in High Pressure Xe, J. Apol . Phys. 50, 7965-7990

(1979).

A. Zajonc and A. C. Gallagher, Electron Excitation of Li S and D

States, Phys. Rev. A 20 , 1393-1397 (1979).

R. Shuker, A. C. Gallagher, and A. V. Phelps, Models for High-Power

Discharges for Metal -Xe Excimer Lasers," J. Appl. Phys. J51_, 1306-1320

(1980).

D. Wildman, A. C. Gallagher, and L. Schumann, Na 3

2 D-3 2 P Line

Broadening by Ne, Ar, and Xe, J. Quant. Spectrosc. Radi at. Transfer

24_, 19-23 (1980).

L. Schumann, D. Wildman, and A. C. Gallagher, Emission of a Mg-Xe

Discharge and the MgXe Excimer Band, J. Chem. Phys. 72, 6081-6084

(1980)

.

R. H. Chatham, A. C. Gallagher, and E. L. Lewis, Broadening of the

Sodiun D Lines by Rare Gases, J. Phys. B: Atom. Molec. Phys. 13, L7-

11 (1980).

W-U L. Brillet and A. Gallagher, Inert Gas Collisional Broadeninq and

Shifts of Rb Rydberg States, Phys. Rev. A (in press).

(W. J. Sandle) and A. Gallagher, Dispersive and Absorptive Optical

Bistability by an Atomic Vapor, Phys. Rev. A (submitted).

(W. J. Sandle, R. J. Ballagh), and A. Gallagher, Optical Bistability

Experiments and Mean Field Theories, in Proceedings, International

Conference and Workshop on Optical Bistability (in press).

197
PUBLICATIONS

Quantum Physics Division (525)

R. E. Kennerly, R. J. Van Brunt, and A. C. Gallagher, High-Resolution

Measurement of the Helium (ls2s 2

) 2S Resonance Profile, Phys. Rev. A

( submi tted)

.

L. J. November, J. Toomre, K. B. Gebbie, and G. W. Simon, The Height

Variation of Supergranular Velocity Fields Determined from Simultaneous 0S0-8 Satellite and Ground-Based Observations, Astrophys. J.

227, 600-613 (1979).

J. Toomre, L. J. November, K. B. Gebbie, and G. W. Simon, Mesoqranulation — An Intermediate Scale of Motion on the Sun, B.A.A.S. 11,

640 (1979). ““

K. B. Gebbie, L. J. November, and J. Porter, Soectral Diagnostics of

a Solar Flare in the Helium Resonance Lines, B.A.A.S. _11_, 677 (1979).

L. J. November, J. Toomre, K. B. Gebbie, and G. W. Simon, The Detection of Mesogranul ation on the Sun, Astrophys. J. (Letters) (submi tted)

.

K. B. Gebbie, F. Hill, L. J. November, J. Toomre, and G. W. Simon,

Steady Velocity Fields in the Upper Chromosphere and Lower Transition

Region Determined from SMM/UVSP Observations, Astrophys. J. (Letters)

( submitted)

.

L. J. November, J. Toomre, K. B. Gebbie, and G. W. Simon, The Vertical Component of Supergranul ar Motions Observed in the Solar

Chromosphere, Astrophys. J. (submitted).

J. Porter, L. J. November, and K. B. Gebbie, The He I and He II Resonance Lines in the Solar Flare of 15 June 1973, Solar. Phys. (submitted) .

S. Geltman, Resonant Multiphoton Ionisation with Intense Monochromatic Lasers, J. Phys. B: Atom. Molec. Phys. JJ., 115-133 (1980).

S. Geltman, Approximate Response of a Two-Level System to Intense

Multimode Radiation, Phys. Lett, (submitted).

(F. Roussel, P. Breger, G. Spiess, C. Manus), and S. Geltman, Evidence of Superelastic Effects in Laser-Induced Ionization of Na

Vapor, J. Phys. B: Atom. Molec. Phys. (submitted).

S. A. Lee, J. Helmcke, and J. L. Hall, High Resolution Two-Photon

Spectroscopy of Rb Rydberg Levels, in Laser Spectroscopy IV (H.

Walther and K. W. Rothe, Eds., Springer-Verl ag. New York, Berlin,

Heidelberg, 1979), pp. 130-141.

198
PUBLICATIONS

Quantum Physics Division (525)

A. Brillet and J. L. Hall, An Improved Test of the Isotropy of Space

Using Laser Techniques, in Laser Spectroscopy IV (H. Walther and K.

W. Rothe, Eds., Springer-Verlaq, New York, Berlin, Heidelberg, 1979),

pp. 12-20.

T. Baer, F. V. Kowalski, and J. L. Hall, Frequency Stabilization of a 0.633 ym HeNe Longitudinal Zeeman Laser, Appl . Opt. (in press).

J. L. Hall, Tunable Laser Stabilization Techniques for Ultrahiqh

Resolution Spectroscopy, in Proceedings, International Conference on Lasers, Beijinq, China, June 1980 (in press).

D. G. Hummer and P. B. Kunasz, Energy Loss by Resonance Line Photons

in an Absorbing Medium, Astrophys. J. 236 , 609-618 (1980).

(M. J. Barlow, J. C. Blades), and D. G. Hummer, Optical Observations

of the Ul trahigh-Excitation Wolf-Rayet Star Sanduleak 3, Astrophys.

J. Lett, (in press).

A. K. Pradhan, D. W. Norcross, and D. G. Hummer, Cross Sections and

Excitation Rates for Electron Collisions with Helium-Like Ions, Phys.

Rev. A (in press).

J. Katriel and D. G. Hummer, Analytic Solutions for the Three- and

Four-Wave Mixing via Generalized Bose Operators, Optica Acta (submitted) .

* J. Katriel, Explicit Expressions for the Coefficients in Boson Series

Expansions of Arbitrary Spin Operators, Phys. Stat. Sol.(b) 93, K177-

179 (1979)

.

* (J. M. Peek) and J. Katriel, Hydrogen Molecular Ion in a High Magnetic Field, Phys. Rev. A 21_, 413-417 (1980).

* J. Katriel, Generalized Hiller-Sucher-Feinberg Identity, Phys. Rev. A

(Comments) 21_, 1067-1068 (1980).

J. Katriel and D. G. Hummer, Analytic Solutions for the Three- and

Four-Wave Mixing via Generalized Bose Operators, Optica Acta (submi tted)

.

* B. E. Kohler, Site Selection Soectroscopy, in Chemical and Biochemical Applications of Lasers (C. B. Moore, Ed., Academic, New

York, 1979), Vol. 4, ppTTPSTT

* (R. J. M. Anderson), B. E. Kohler, and (J. M. Stevenson), The Effects

of Strong Excitation-Phonon Coupling on Mixed Crystal Spectra: Diphenyl methyl ene in Benzophenone, J. Chem. Phys. 71, 1559-1563 (1979).

199
PUBLICATIONS

Quantum Physics Division (525)

* P. L. Jones, R. D. Mead, B. E. Kohler, D. R. Rosner, and W. C.

Lineberger, Photodetachment Spectroscopy of C

~ Autodetaching

Resonances, J. Chem. Phys. (submitted).

* H. J. G. L. M. Lamers, Mass Loss from 0 and B Stars, Astrophys. J.

(submitted)

.

W. H. Pence and S. R. Leone, New Atomic and Molecular Lasers and

Their Aopli cation .to the Study of Collision Physics, in El ectronic

and Atomic Collisions (N. Oda and K. Takayanaqi, Eds., North-Hoi 1 and,

Amsterdam, 1980), pp. 773-786.

D. J. Nesbitt and S. R. Leone, Laser-Initiated Chemical Chain Reactions, J. Chem. Phys. 72_, 1722-1732 (1980).

T. S. Zwier, V. M. Bierbaum, G. B. Ellison, and S. R. Leone, Vibrational Product State Distributions of Ion-Molecule Reactions by Infrared Chemiluminescence: CjT + HBr,HI + HCji(v) + Br“,I”, J. Chem.

Phys. 72, 5426-5436 (1980).

S. L. Baughcum and S. R. Leone, Photofragmentation Infrared Emission

Studies of Vibrational ly Excited Free Radicals CH and CH I, J. Chem.

Phys. 72_, 6531-6545 (1980).

T. S. Zwier, (M. M. Maricz), C.J.S.M. Simpson, V. M. Bierbaum,

G. B. Ellison, and S. R. Leone, Direct Detection of the Product

Vibrational -State Distribution in the Associative Detachment Reaction

CjT + H - HCji(v) + e, Phys. Rev. Lett. 44, 1050-1053 (1980).

D. J. Nesbitt and S. R. Leone, Observation of a Direct Reaction Between Br*(4 2P

1 / 2

) and H

2 (v=l), J. Chem. Phys. (submitted).

S. R. Leone, Photofragment Dynamics, in Dynamics of the Excited State

(K. Lawley, Ed., Advances in Chemical Physics Series).

* (G. L. Eesley), M. D. Levenson, D. E. Nitz, and A. V. Smith, Narrowband Pulsed Dye Laser System for Precision Nonlinear Spectroscooy

,

IEEE J. Quantum. Electron. QE-16 , 113-115 (1980).

J. L. Linsky, (S. P. Worden), W. McClintock, and (R. M. Robertson),

Stellar Model Chromospheres. X. Hiqh Resolution, Absolute Flux Profiles of the Ca II H and K Lines in Stars of Spectral Types F0-M2,

Astrophys. J. Supol . 41, 47-74 (1979).

J. L. Linsky, (D. M. Hunten, R. Sowell), D. L. Glackin, and W. L.

Kelch, Stellar Model Chromospheres. XI. A Survey of Ca II x8542 Line

Profiles in Late-Type Stars of Differing Chromospheric Activity,

Astrophys. J. Suppl . 41, 481-500 (1979).

200
PUBLICATIONS

Quantum Physics Division (525)

G. S. Basri and J. L. Linsky, Outer Atmospheres of Cool Stars. II.

Mg II Flux Profiles and Chromospheric Radiative Loss Rates,

Astrophys. J. 234, 1023-1035 (1079).

T. R. Ayres and J. L. Linsky, Outer Atmospheres of Cool Stars. III.

IUE Spectra and Transition Reqion Models for Aloha Centauri A and B,

Astrophys. J. 235, 76-84 (1980).

B. M. Haisch, J. L. Linsky, and G. S. Basri, Outer Atmospheres of

Cool Stars. IV. A Discussion of Cool Stellar Wind Models, Astrophvs.

J. 235 , 519-533 (1980) .

(S. M. Kahn), J. L. Linsky, (K. 0. Mason), B. M. Haisch, (C. S.

Bowyer, N. E. White, and S. H. Pravdo), HEAO-1 Observations of X-Ray

Emission from Flares on dMe Stars, Astrophys. J. (Letters) 234 , L107-

112 (1979).

J. L. Linsky, Accurate Measurement of Ultraviolet Light Intensity,

NBS Dimensions 63_, 10-13 (1979).

B. M. Haisch, J. L. Linsky, and K. A. van der Hucht, Lyman Alpha

Initiated Winds in Late-Type Stars, in The First Year of IUE, A

Symposium held at University College London, 4-6 April 1979 (A. J.

Willis, Ed., U. College London, 1979), pp. 383-393.

B. M. Haisch and J. L. Linsky, Observations of the Quiescent Corona,

Transition Region, and Chromosphere in the dMe Flare Star Proxima

Centauri, Astrophys. J. (Letters) 236 , L33-37 (1980).

(F. M. Walter), J. L. Linsky, (C. S. Bowyer, and G. Garmire), HEAO-1

Observations of Active Corona in Main-Sequence and Subqiant Stars,

Astrophys. J. (Letters) 236, L137-141 (1980).

T. Simon, W. L. Kelch, and J. L. Linsky, Outer Atmospheres of Cool

Stars. VI. Models for e Eridani Based on IUE Spectra of C II, Mq II,

Si II, and Si III, Astrophys. J. 237 , 72-81 (1980).

T. R. Ayres and J. L. Linsky, Outer Atmospheres of Cool Stars. V. IUE

Spectra and Transition Region Models for Capella A and B, Astrophys.

J. (in press)

.

J. L. Linsky, Stellar Chromospheres, in Turbulence in Stellar Atmospheres, Proceedings of IAU Colloquium No. 51 ( Springer-Verl ag) (Tn*

press)

.

(T. P. Snow, Jr.) and J. L. Linsky, Ultraviolet Spectroscopy of the

Outer Layers of Stars, Astrophys. Space Sci. 67, 285-307 (1980).

201
PUBLICATIONS

Quantum Physics Division (525)

(J . C. Brandt, A. Boqqess, S. R. Heao, S. P. Maran, A. M. Smith, E.

A. Beaver, M. Bottema, J. B. Hutchinqs, M. A. Jura), J. L. Linsky,

(B. D. Savage, L. M. Trafton, and R. J. Weyman) , Hiqh Resolution

Spectrograph for the Space Telescope, in Instrumentation in Astronomy

III (Society of Photo-Optical Enqineers, Bellingham, Wa, 1979 ), Vol.

T7T, pp. 254-263.

J. L. Linsky, Stellar Chromospheres, Ann. Rev. Astron. Astrophys. 18,

439-448 (1980). —

T. Simon, J. L. Linsky, and (F. H. Schiffer), IUE Spectra of a Flare

in the RS Canum Venati corum-Type System UX Arietis, Astrophys. J. (in

press)

.

J. L. Linsky, On the Differences at Chromospheric Levels Between

RS CVn-Type Binaries, Active and Quiet Chromosphere Single Stars,

and Active and Quiet Regions in the Sun, in Highlights of Astronomy

(in press).

R. E. Stencel , (D. J. Mullan), J. L. Linsky, (G. S. Basri, and S. P.

Worden), Outer Atmospheres of Cool Stars. VII. High Resolution, Absolute Flux Profiles of the Mq II h and k Lines in Stars of Spectral

Types F8 to M5, Astrophys. J. Suppl. (in press).

T. Simon and J. L. Linsky, IUE Ultraviolet Spectra and Chromospheric

Models of HR 1099 and UX Arietis, Astrophys. J. (in press).

B. M. Haisch, J. L. Linsky, (F. R. Harnden, R. Rosner, F. D. Seward,

and G. S. Vaiana), Einstein X-rav Observations of Proxima Centauri

and the Surrounding Reqion, Astrophys. J. (Letters) (in press).

J. L. Linsky, Theory of Stellar Coronae: An Interpretation of X-ray

Emission from Non-Degenerate Stellar Sources, in X-ray Astronomy , Proceedings of the HEAD/AAS January 1980 Cambridge, MA USA Meeting

( Reidel , in press)

.

T. Simon, J. L. Linsky, and (F. H. Schiffer III), IUE Spectra of a Flare in HR 5110: A Flaring RS CVn or ALGOL System? in Proceedings of

The Second Year of IUE: The Universe in Ultraviolet Wavelengths (in

press)

.

R. E. Stencel, (D. J. Mullan, G. S. Basri), and J. L. Linsky, High

Resolution Absolute Flux Profiles of the Mg II h and k Lines in

Evolved F8 to M5 Stars, in Proceedings of The Second Year of IUE:

The Universe in Ultraviolet Wavelengths (in press).

202
PUBLICATIONS

Quantum Physics Division (525)

J. L. Linsky and N. C. Marstad, IUE Spectra of F and Late A Stars, in

Proceedings of The Second Year of IUE: The Universe in Ultraviolet

Wavelengths ( i n press)

.

G. S. Basri and J. L. Linsky', Outer Atmospheres of Cool Stars. VIII.

IUE Observations and Chromospheric Models for the Supergiant Stars

3 Draconis (G2 II), e Geminorum (G8 lb) , and a Orionis (M2 lb)

,

Astrophys. J. (submitted).

E. Mosburg, The Effect of Ion Current in the Colli si on! ess Theory of

Floating ac Probe Measurements, Rev. Sci. Instrum, (submitted).

D. W. Norcross, Addendum to Photoabsorption by Cesium, Phys. Rev. A

20, 1285-1286 (1979).

L. A. Collins, W. D. Robb, and D. W. Norcross, Low-Energy Collisions

with Highly Polar Molecules: Orthogonal izati on and Model Exchange

Potentials, Phys. Rev. A 20, 1838-1840 (1979).

J. N. Bardsley and D. W. Norcross, Oscillator Strengths for Thallium

Calculated Using a Semiempirical Relativistic One-Electron CentralField Model Potential, J. Quant. Spectry. Radi at. Transfer 23, 575-

583 (1980) .

(L. A. Collins, R. J. W. Henry), and D. W. Norcross, Electron Collisions with Polar Molecules: Exchange and Polarization in Elastic

Scattering by HCjz

,

J. Phys. B: Atom. Molec. Phys. 13, 2299-2307

(1980).

G. B. Schmid, D. W. Norcross, and L. A. Collins, VLAM, A Program for

Computing the Electron- Molecule Static Interaction Potential from a Legendre Expansion of the Molecular Charge Density, Comp. Phys.

Commun. (in press).

A. K. Pradhan, D. W. Norcross, and D. G. Hummer, Cross Sections and

Excitation Rates for Electron Collisions with Helium-Like Ions, Phys.

Rev. A (in press).

N. T. Padial, D. W. Norcross, and L. A. Collins, Electron Collisions

with Polar Molecules: Treatment of Intermediate Values of Angular

Momentum, J. Phys. B: Atom. Molec. Phys. (submitted).

* (D. Bouloy) and A. Omont, Transitions in A-Doublets of Molecules

Induced by Collisions with Ions. II, Astron. Astrophys. Suppl . 38,

101-118 (1980).

203
PUBLICATIONS

Quantum Physics Division (525)

* (V. Bu.jarrabal, J. Guibert, N. Q. Rieu), and A. Omont, OH Pumping

by IR Line Overlap. Application of Circumstellar Masers, Astron.

Astrophys. 84, 311-316 (1980)

.

* S. J. Peale, (P. Cassen, and R. T. Reynolds), Tidal Dissipation,

Orbital Evolution and the Nature of Saturn's Inner Satellites, Icarus

(in press)

.

* (R. T. Reynolds), S. J. Peale, and (P. Cassen), Io: Enerqy Constraints and Plume Volcanism, Icarus (submitted).

A. V. Phelps, AddIi* cations and Needs, in Electron-Molecule Scatterinq

(S. C. Brown, Ed., Wiley, New York, 1979) , do. 81-106.

A. V. Phelos, The Determination of Electron Collision Cross Sections

from Swarm Data, in Proceedings, International Seminar on Swarm Experiments in Atomic Collision Research, September 6-7, 1979, Rikkyo

University, Tokyo (Rikkyo University, Tokyo, Japan, 1980), pp. 23-32.

K. Tachibana and A. V. Phelps, Excitation of the C

3 nu State of N by

Low Energy Electrons, J. Chem. Phys. 71_, 3544-3546 (1979).

R. Shuker, A. Gallagher, and A. V. Phelps, Models of the High-Power

Discharges for Metal-Xe Excimer Lasers, J. Appl. Phys. 51, 1306-1320

(1980). —

C. H. Muller and A. V. Phelps, Low Current ELectric Discharges in

H

2

-He Mixtures, J. Appl. Phys. (in press).

* (K. Niemax, M. Movre) , and G. Pichler, Near-Wing Asymmetries of the

Sel f- Broadened First Rb and Cs Resonance Lines, J. Phys. B: Atom.

Molec. Phys. _12_, 3503-3509 (1979).

* L. Rosenberg, Sum Rule and Classical Limit for Scattering in a LowFrequency Laser Field, Phys. Rev. A 20, 1352-1358 (1979).

* L. Rosenberg, Infrared Radiation in Potential Scattering, Phys. Rev.

A _21_, 157-162 (1980).

* P. L. Jones, R. D. Mead, B. E. Kohler, D. R. Rosner, and W. C.

Lineberger, Photodetachment Spectroscopy of C

2 ~ Autodetaching

Resonances, J. Chem. Phys. (submitted).

* (D. W. Fahey), L. D. Schearer, and (W. F. Parks), Alignment of Ions

in Penning Collisions, Phys. Rev. A _20_, 1372-1375 (1979).

* (M. Contini, B. Z. Kozlovsky), and G. Shaviv, The Calculation of the

Optical Spectra of the Cygnus Loop, Astron. Astrophys. (in press).

204
PUBLICATIONS

Quantum Physics Division (525)

* (M. Livio, 0. Regev) , and G. Shaviv, Kel vin-Helmhol tz Instability in

Clusters of Galaxies, Astrophys. J. (in press).

* (M. M. Shara, D. Prialnik), and G. Shaviv, What Determines the Speed

Class of Novae? Astrophys. J. (in press).

* (M. Livio) and G. Shaviv, The Stability of Accretion Disks to Short

Wavelength Perturbations, Astrophys. J. (in press).

* (M. Conti ni) and G. Shaviv, The Calculation of the UV Spectra of the

Cygnus Loop, AstroDhys. J. (submitted).

* (N. Brosch) and G. Shaviv, Mul tiaperture Photometry of Isolated

Galaxies, Astrophys. J. (submitted).

* (0. Regev) and G. Shaviv, Formation of Protostars in Collapsinq

Rotating Turbulent Clouds, Astrophys. J. (submitted).

* (W. P. Blair), R. E. Stencel , G. Shaviv, and (W. A. Feibelman),

HM Sagittae: Symbiotic Cousin of the RS CVn Stars? Astron. Astrophys.

( submitted) .

* (D. Prialnik), G. Shaviv, and (A. Kovetz) , The Effect of Diffusion on Asymptotic Branching Evolution, Astrophys. J. (submitted).

S. J. Smith and P. B. Hogan, Laser Bandwidth and Intensity Effects

in Multiphoton Ionization of Sodium, in Laser Spectroscopy IV , Proceedings 4th International Conference, Rottach-Egern, Germany, 1979

(H. Walther and K. W. Rothe, Eds., Springer-Verl ag. New York, Berlin,

Heidelberg, 1979), pD. 360-367.

(G. Leuchs) , S. J. Smith, and (H. Walther), High Resolution Spectroscopy of Rydberg States, in Laser Spectroscopy IV , Proceedings 4th

International Conference, Rottach-Egern, Germany, 1979 (H. Walther

and K. W. Rothe, Eds., Springer-Verl ag. New York, Berlin, Heidelberg,

1979), pp. 255-263.

S. J. Smith, (G. Leuchs, E. Khawaja, and H. Walther), Quantum Beats

Observed in Photoionization, Opt. Commun. 31 , 313-316 ( 1979 ).

(T. Hellmuth, G. Leuchs), S. J. Smith, and (H. Walther), Anqular Distribution of Photoelectrons in Multi photon Ionization, in Proceedings

of the 2nd International Conference on MultiDhoton Processes,

Budapest, Hungary, 14-18 April 1980 (in press).

A. V. Smith, J. E. M. Goldsmith, D. E. Nitz, and S. J. Smith, Absolute Photoionization Cross-Section Measurements of the Excited 4D and

5S States of Sodium, Phys. Rev. A 22, 577-81 (1980).

205
PUBLICATIONS

Quantum Physics Division (525)

(G. Leuchs, T. Hellmuth), S. J. Smith, and (H. Walther), Angular Distribution of Photoelectrons in Two-Step Photoionization--Influence of

the Hyperfine Structure, in Digest of 11th International Quantum

Electronics Conference, Boston, June 23-26, 1980.

* G. A. Victor and (E. R. Constantinides) , Double Photoinization and

Doubly Charged Ions in the Thermosphere, Geophys. Res. Letters 6,

519-522 (1979). “

* (C. Laughlin) and G. A. Victor, Intercombination Line Oscillator

Strengths for the Mg I Isoelectronic Sequence, Astrophys. J. 234,

407-410 (1979). "

* (H. Harris, E. W. Olszewski), and G. Wallerstein, The Binary Cepheid

AU Peg, Astron. J. 84, 1598-1602 (1979).

* G. Wallerstein, The Behavior of H« in Delta Cephei, Pub. Astron. Soc.

Pacific 9l_, 772-774 (1979).

* G. Wallerstein and (E. W. Brugel), The Absolute Magnitude of the

Field Population II Cepheid XX Virginia, Astron. J. 84, 1840-1845

(1979).

* G. Wallerstein and (W. M. Fawley), Additional Radial Velocities of

Maser Stars and Related M Supergiants, Pub. Astron. Soc. Pacific 92,

183-187 (1980).

* G. Wallerstein and (J. L. Greenstein), The Spectrum of the Nebulosity

Around the Symbiotic Long Period Variable R. Aquarii, Pub. Astron.

Soc. Pacific _92, 275-283 (1980).

* D. F. Walls, (P. D. Drummond, and K. J. McNeil), Bistable Systems in

Nonlinear Optics, Proceedings, International Conference and Workshop

on Optical Bistability (in press).

* D. F. Walls, (P. Zoller, and M. L. S. Ross), Optical Bistability from

Three Level Atoms, IEEE Journal of Quantum Electronics, Special Issue

on Optical Bistability (in press).

* J. C. Wheeler, Stars with Anomalous Mass: Is There Funny Business on the Main Sequence, Comments on Astrophysics 8_, 133-147 (1979).

* J. C. Wheeler, Blue Stragglers as Long-Lived Stars, Astrophys. J.

234, 569-578 (1979).

206
PUBLICATIONS

Quantum Physics Division (525)

* (D. S. King), J. C. Wheeler, J. P. Cox, (A. N. Cox, and S. W.

Hodson), Pulsation of High Luminosity Helium Stars, in Nonradial and

Non! i near Stellar Pul sation (H. A. Hill and W. A. Dziembowski , Eds.

,

Springer-Verl ag, New York, Berlin, Heidelberg, 1980), p. 161.

* J. C. Wheeler, Supernovae in Molecular Clouds, Astrophys. J. 237 , 781-792 (1980).

* (D. E. Tolliver, G. A. Kyrala), and W. H. Wing, Observation of the

Infrared Spectrum of the Helium Hydride Molecular Ion 1+HeH

+

, Phys.

Rev. Letters 43, 1719-1722 (1979).

* W. H. Wing, Electrostatic Trapping of Neutral Atomic Particles, Phys.

Rev. Letters (submitted).

* (J. T. Shy, J. W. Farley), and W. H. Wing, Observation of the Infrared Spectrum of the Tri atomic Deuterium Molecular Ion D

3 +

, Phys. Rev.

Letters (submitted).

207
INVITED TALKS

Quantum Physics Division (525)

P. L. Bender, "Instrumental Networks Tor Monitoring Short Period Tectonic Motions in Seismic Zones," IUGG Symoosium No. 9 on Recent Crustal

Movements, Canberra, Australia, December 14, 1979.

P. L. Bender, "Establishment of Terrestrial Reference Frames by New

Observational Techniques," IAU Colloq. No. 56 - Reference Coordinate

Systems for Earth Dynamics, Warsaw, Poland, September 8, 1980.

G. H. Dunn, "Electron-Ion Collisions," X Symposium on Physics of Ionized

Gases (SPIG), Dubrovnik, Yugoslavia, August 25, 1980.

G. H. Dunn, "The Technical Difficulties and Future of Electron-Ion Experiments," U.S. -Japan Workshop on Atomic Collision Data for Fusion,"

JILA, October 28, 1980.

J. E. Faller, "Some Gravitational Experiments at JILA," Department of

Physics, Princeton University, Princeton, New Jersey, February 7, 1980.

S. Geltman, "Model Calculations of Atom Ionization by Strong Static and

Oscillating Electric Fields," DEAP Session of American Physical Society

Annual Meeting, Chicago, Illinois, January 23, 1980.

J. L. Hall, "High Resolution Spectroscopy Using Stabilized Dye Lasers,"

presented at:

University of Waterloo, Waterloo, Canada, November 28, 1979,

IBM, San Jose, California, December 14, 1979,

University of British Columbia, Vancouver, British Columbia, Canada,

March 20, 1980.

J. L. Hall, "An Improved Test of the Isotropy of Space Using Laser Techniques," presented at:

University of Toronto, Toronto, Canada, November 29, 1979,

Colorado School of Mines, Golden, Colorado, December 11, 1979.

J. L. Hall, "Precision Laser Spectroscopy from Atoms to Improved Tests

of Relativity," Department of Physics, Harvard University, Cambridge,

Massachusetts, April 7, 1980.

J. L. Hall, "Tunable Laser Stabilization Techniques for Ultra High

Resolution Spectroscopy," presented at:

Conference on Precision Electromagnetic Measurements, Braunschweig,

West Germany, June 24, 1980,

International Conference on Lasers, Shanghai PRC, May 21, 1980.

208
INVITED TALKS

Quantum Physics Division (525)

J. L. Hall, "Usinq Stabilized Lasers to Test Fundamental Physical

Postulates," International Conference on Atomic Physics, Cambridge,

Massachusetts, August 8-12, 1980.

S. R. Leone, "Infrared Emission Studies of Laser Photofragmentation,"

American Chemical Society Meeting Symposium on Laser Dynamics and Spectroscopy of Excited Species, Syracuse, New York, October 4, 1979.

S. R. Leone, "State- Selected Kinetics of Laser Excited Species,"

Department of Chemistry Colloquium, Cornell University, Ithaca, New

York, October 1979.

S. R. Leone, "Laser State- Selected Kinetics," Physical Chemistry

Seminar, Northwestern University, Evanston, Illinois, November 1979.

S. R. Leone, "New Laser Techniques in Chemical Kinetics," US-France

Seminar on Lasers in Chemistry, NSF-CRNS sponsored workshop for collaborative scientific efforts, Philadelphia, Pennsylvania, November 1979.

S. R. Leone, "State-Selected Kinetics of Laser Excited Species," Department of Chemistry Colloquium, Indiana University, Bloomington, Indiana,

December 1979.

S. R. Leone, "Laser Studies of Chemical Chain Reactions and Free

Radicals," Argonne National Laboratory, Argonne, Illinois, March 1980.

S. R. Leone, "Laser State-Selected Near Resonant Collision Processes,"

Symposium on Inelastic Molecular Collisions, American Physical Society

Meeting, New York, New York, March 25, 1980.

S. R. Leone, "Infrared Emission Studies of Photofragment Dynamics," 14th

Informal Conference on Photochemistry, Newport Beach, California, April

2, 1980.

S. R. Leone, "Infrared Chemiluminescence Studies of Reactive Dynamics,"

presented at:

Chemistry Department Seminar, University of California at Berkeley,

Berkeley, California, April 7, 1980,

Departmental Seminar at the University of Toronto, Toronto, Ontario,

Canada, May 1980.

S. R. Leone, "Electronic and Ionic Processes Related to Atomic and

Molecular Lasers," Gordon Conference on Atomic and Molecular Interactions, Wolfeboro, New Hampshire, July 1980.

209
INVITED TALKS

Quantum Physics Division (525)

J. L. Linsky, "Theoretical Interpretation of X-ray Emission from Nondegenerate Stellar Sources," Invited review paper presented at the High

Energy Astrophysics Division of the American Astronomical Society,

Cambridge, Massachusetts, January 28, 1980.

J. L. Linsky, "Stellar Coronae and Winds in Late and Middle-Type Stars:

Observations and Theory," Invited review paper presented at the Santa Fe

Meeting on Solar Astronomy of Kitt Peak National Observatory, Sacramento

Peak Observatory, and the High Altitude Observatory, Santa Fe, New

Mexico, May 21, 1980.

J. L. Linsky, "Evidence for Chromospheres and Coronae in Stars," Invited

review paper presented at the NATO Advanced Study Institute on Solar

Phenomena in Stars and Stellar Systems, Chateau de Bonnas, France,

August 27, 1980.

J. L. Linsky, "Chromospheres of Late-Type Stars," Invited review paper

presented at the Workshop on Physical Processes in Red Giants, Brice,

Italy, September 8, 1980.

J. L. Linsky, "Winds from Late-Type Stars: Mechanisms of Mass Outflow,"

Invited review paper presented at International Astronomical Union

Colloquium No. 59 (Effects of Mass-Loss on Stellar Evolution), Trieste,

Italy, September 16, 1980.

J. L. Linsky, "Stellar Chromospheres: Are Recent Observations and

Theoretical Calculations Beginning to Answer the Basic Question,"

presented at:

Physics Department Seminar, Gettysburg College, Gettysburg,

Pennsylvania, October 29, 1980.

Center Science Colloquium, NASA Goddard Space Flight Center, October

31, 1980.

D. W. Norcross, Member of a panel on "Electron Atom and Ion Scattering,"

at the Fourth Johns Hopkins Workshop on Current Problems in Physics,"

March 28-29, 1980.

S. J. Smith, "Photoionization of Excited States of Atomic Sodium,"

Department of Physics, University of Missouri, Roll a, Missouri, May 1,

1980.

210
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

P. L. Bender, Member, Committee on Earth Sciences of the Space Science

Board, National Academy of Sciences and National Research Council.

P. L. Bender, Member, Ad Hoc Committee on Gravitational Physics of the

Space Science Board, National Research Council.

P. L. Bender, Member, SDace Science Board, National Academy of Science

and National Research Council.

P. L. Bender, Member, Panel on Crustal Movement Measurement, Committee

on Geodesy, National Academy of Science and National Research Council.

P. L. Bender, Chairman, Working Group on Instruments and Methods,

Commission on Recent Crustal Movements, International Association of

Geodesy.

P. L. Bender, Member, Laser Geodynamics Satellite (LAGEOS) Working

Group, NASA.

P. L. Bender, Member, Physics Department Advisory Council, Princeton

University.

G. H. Dunn, Chairman, Organizing Committee, Conference on Atomic

Processes in High Temperature Plasmas. To be held in Baton Rouge,

Louisiana, February 1081. A Topical Conference of the American

Physical Society.

G. H. Dunn, Member, Graduate Committee, Department of Physics and

Astrophysics, University of Colorado.

G. H. Dunn, Member, Program Committee, Division of Electron and Atomic

Physics, American Physical Society.

G. H. Dunn, Member, Fellowship Committee, DEAP, American Physical

Society.

J. E. Faller, Member, SDecial Study Group 3.37 "Special Technigues of

Gravity Measurements," of the International Gravity Commission.

J. E. Faller, Member, Plans Committee of the Geodesy Section of the AGU.

A. C. Gallagher, Member, ICPEAC Organizing Committee.

K. B. Gebbie, Member, Search Committee for Faculty Appointment in Solar

Physics, Department of Astro-Geophysics, University of Colorado.

K. B. Gebbie, Vice Chairman, Colorado Passenger Tramway Safety Board.

211
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

K. B. Gebbie, Member, Electorate Nominating Committee, Section D,

American Association for the Advancement of Science.

K. B. Gebbie, Member, Search Committee for Director of Coooerative Institute for Research in Environmental Sciences (CIRES), Enviromental

Research Laboratories of NOAA and University of Colorado.

K. B. Gebbie, Member, The Billings Award Committee, Department of AstroGeophysics, University of Colorado.

K. B. Gebbie, Member, Examinations Committee, Department of AstroGeophysics, University of Colorado.

S. Geltman, Member, International Orqanizino Committee, Second International Conference on Multiphoton Processes, Budapest, Hungary, ADril

14-18, 1980.

S. Geltman, Member, Graduate Committee, Department of Physics,

University of Colorado.

J. L. Hall, Member, National Research Committee on Fundamental Constants, National Research Council /National Academy of Sciences, July 1,

1976 - June 30, 1979, extended to June 30, 1982.

J. L. Hall, Delegate, Consultative Committee for the Definition of the

Meter (BIPM), Sevres, France, 1970 - present.

J. L. Hall, Member, International Steering Committee for Conferences on Laser Spectroscopy.

J. L. Hall, Member, NBS Committee for NBS Precision Measurement Grants.

J. L. Hall, Director-at-Large, Optical Society of America.

D. G. Hummer, Member, Computer Policy Committee, University of Colorado.

D. G. Hummer, Member, Editorial Board, Computer Physics Communications.

S. R. Leone, Associate Editor, Ootics Letters.

J. L. Linsky, Member, IUE (International Ultraviolet Explorer) Astronomy

Working Group, NASA.

J. L. Linsky, Member, Solar Physics Working Grouo of the Astronomy Survey

Committee, National Academy of Sciences and National Research Council.

J. L. Linsky, Co-Investiqator, ST (Space Telescope) High Resolution

Spectrograph Experiment.

212
TECHNICAL AND PROFESSIONAL COMMITTEE PARTICIPATION AND LEADERSHIP

Quantum Physics Division (525)

J. L. Linsky, Member, Committee to Evaluate the Future of the Cloudcraft

48-inch Telescope of Sacramento Peak Observatory, AURA (Association of

Universities for Research in Astronomy).

J. L. Linsky, Member, Committee on Space Astronomy and Astrophysics of

the Space Science Board, National Academy of Sciences and National

Research Council.

J. L. Linsky, Member, Solar Terrestrial Theory Program (STTP) Evaluation

Committee, NASA, January 2 - February 6, 1980.

J. L. Linsky, Member, Panel on Ultraviolet, Optical, and Infrared

Astronomy of the Astronomy Survey Committee, National Academy of

Sciences and National Research Council.

D. W. Norcross, Member, Data Center Advisory Committee.

A. V. Phelps, Research Advisory Committee of NBS.

A. V. Phelps, Member, The 1979 Earle K. Plyler Prize Committee (American

Physical Society).

A. V. Phelps, Steering Committee for DARPA Charged Particle Beam Theory

Review, June 1980.

S. J. Smith, Member, Committee on Atomic and Molecular Sciences,

National Academy of Sciences.

S. J. Smith, Member, Organizing Committee, Seventh International Conference on Atomic Physics, August 4-8, 1980, Cambridge, Massachusetts.

S. J. Smith, Chairman, Local Committee for Annual Meeting of Division of

Electron and Atomic Physics, Boulder, Colorado, 1982.

S. J. Smith, Co-Chairman, NAS-NRC Survey of Atomic and Molecular

Science.

S. J. Smith, Member, Organizing Committee, Eighth International Conference on Atomic Physics, Gtttteburg, Sweden, 1982.

S. J. Smith, Chairman, Nominating Committee, Division of Electron and

Atomic Physics of The American Physical Society, 1980.

213
CONSULTING

Quantum Physics Division (525)

J. L. Hall

Dr. Hall is consulting with the Theoretical Astrophysics Group

at Cal Tech in the area of laser techniques for gravity wave

detection.

D. W. Norcross

Dr. Norcross is consulting with the Theoretical Atomic and

Molecular Physics Group at Livermore Labs on problems related to

laser modeling and is a Visiting Scientist (consultant) to Division

T-4 of the Los Alamos Laboratories on problems related to electron

collisions with atoms, ions, and molecules.

A. V. Phelps

Dr. Phelps does informal consulting and advisinq with DoD and DoE

laboratories and their industrial and University contractors in the

area of atomic and molecular processes in high power lasers and

charged particle beam devices.

214
TRIPS SPONSORED BY OTHERS

E. C. Beaty

P. L. Bender

Quantum Physics Division (525)

May 16-25, 1080 - Paris, France.

Attended the Technical Committee Meeting of the

International Atomic Energy Agency (IAEA) and the Data

Center Network Consultants Meeting.

Sponsor: International Atomic Energy Agency.

October 10-13, 1979 - Washington, D.C.

Attended the meeting of the Panel on Crustal Movement

Measurements, National Academy of Sciences.

Sponsor: National Research Council.

October 22-25, 1979 - Washington, D.C.

Attended the meeting of the Committee on Earth Sciences

of the Space Science Board, National Academy of

Sciences.

Sponsor: National Research Council.

October 31 - November 2, 1979 - Washington, D.C.

Attended the meeting of the Space Science Board,

National Academy of Sciences.

Sponsor: National Research Council

.

January 28-31, 1980 - Los Angeles, California.

Attended the meeting of the Committee on Earth Sciences

of the Space Science Board, National Academy of

Sciences.

Sponsor: National Research Council.

February 5-9, 1980 - San Francisco, California.

Attended the meeting of Space Science Board, National

Academy of Sciences.

Sponsor: National Research Council.

April 10-13, 1980 - Scottsdale, Arizona.

Attended the meeting of Proposal Review Panel for the

Office of Earthquake Studies of the U.S. Geological

Survey.

Sponsor: U.S. Geological Survey.

April 20-24, 1980 - Cambridge, Massachusetts.

Attended the meeting of the Committee on Earth Sciences

of the Space Science Board, National Academy of

Sciences.

Sponsor: National Research Council.

215
TRIPS SPONSORED BY OTHERS

P. L. Bender

G. H. Dunn

J. E. Faller

K. B. Gebbie

S. Geltman

J. L. Hall

Quantum Physics Division (525)

June 2-7, 1080 - Menlo Park, California.

Attended the meeting to review the Earthquake Prediction Research Proqram of the U.S. Geoloqical Survey.

Sponsor: U.S. Geological Survey.

July 28 - August 2, 1980 - Woods Hole, Massachusetts.

Attended the meeting of the Committee on Earth Sciences

of the Space Science Board, National Academy of

Sciences.

Sponsor: National Research Council

.

August 23-30, 1980 - Dubrovnik, Yugoslavia.

Attended the X Summer School & Symposium of Ionized

Gases (SPIG '80) and gave an invited lecture at the

Summer School on "Electron-Ion Collisions."

Sponsor: The Organizing Committee of the X Summer

School and Symposium on the Physics of Ionized Gases.

November 12-13, 1979 - Washington, D.C.

Met with the National Science Foundation & other

members of the Physics Community to discuss the

Foundation's Fiscal Year 1980 budqet for the Physics

Divi sion.

SDonsor: National Science Foundation.

June 2, 1980 - July 11, 1980 - Greenbelt, Maryland.

Worked at NASA Goddard Soace Fliqht Center as a Guest

Investigator on the SMM/UVSP Experiment.

Sponsor: NASA.

March 31 - June 1, 1980 - Paris (Gif-sur-Yvette)

,

France.

Work visit to Service de Physique Atomique, Centre

D' Etudes Nucleaires de Saclay at the invitation of Dr.

Claude Manus, the head of the Service de Physique

Atomique at Saclay.

Sponsor: Centre D' Etudes Nucleaires de Saclay.

November 29, 1979 - Toronto, Canada.

Presented all-University lecture on "Improved Test of

the Isotropy of Space Using Laser Techniques," at the

University of Toronto and visited the research group of

Prof. B. P. Stoicheff and discussed collaborative

effort on Rydberg atom spectroscopy.

Sponsor: University of Toronto.

216
TRIPS SPONSORED BY OTHERS

J. L. Hall

D. G. Hummer

Quantum Physics Division (525)

December 13-14, 1979 - San Jose, California.

Presented invited lecture at IBM on "Hiqh Resolution

Spectroscopy Using Stabilized Dye Lasers."

Sponsor: IBM.

February 19-21, 1980 - Ann Arbor, Michigan.

Presented an invited colloquium lecture in the Department of Physics, University of Michiqan and discussed

the feasibility of several advanced experiments to test

the postulates of special theory of relativity with

Prof. A. Rich.

Sponsor: University of Michigan.

March 20-21, 1980 - Vancouver, British Columbia.

Presented an invited lecture at the University of

British Columbia entitled, "High Resolution Dye Laser

Spectroscopy."

Sponsor: University of British Columbia.

April 6-8, 1980 - Boston, Massachusetts.

Presented an invited lecture, "Precision Laser Spectroscopy from Atoms to Improved Tests of Relativity,"

and visited MIT laser labs to discuss scientific

problems of mutual interest with Profs. M. Feld, S.

Ezekial, D. Pritchard, and R. Fields.

Sponsor: Harvard Department of Physics.

June 22-26, 1980 - Braunschweig, Germany.

Presented an invited paper at the Conference on Precision Electromagnetic Measurements and attended the

Conference, "Tunable Laser Stabilization Techniques for

Ultra High Resolution Spectroscopy."

Sponsor: Conference on Precision Electromagnetic

Measurements

.

January 20 - December 8, 1979 - London, England.

Conducted research at University College London

with Dr. Mike Seaton. Research involved applying

relativistic effects to electron-ion collisions and

in extending the theory of radiation transport.

Sponsor: University College London.

March 19 - April 1, 1980 - Boston, Massachusetts.

Collaborated with Dr. G. B. Rybicki on completing two

papers on the escape-probability method in radiative

transfer.

Sponsor: Smithsonian As trophy si cal Observatory.

217
S. R. Leone

J. L. Linsky

TRIPS SPONSORED BY OTHERS

Quantum Physics Division (525)

October 4-5, 1979 - Ithaca, New York.

Gave a Chemistry Department Seminar at Cornell

University on "State Selected Kinetics of Laser

Excited Species," and visited Cornell University.

Sponsor: Cornell University.

November 25-28, 1979 - Philadelphia, Pennsylvania.

Attended the National Science Foundation-CRNS Workshoo

on lasers in chemistry and presented a review paper,

"New Laser Techniques in Chemical Kinetics."

Sponsor: The National Science Foundation.

December 4-6, 1979 - Bloomington, Indiana.

Visited Indiana University and presented Departmental

Seminar on, "State Selected Kinetics of Laser Excited

Species."

Sponsor: Indiana University.

March 28 - April 3, 1980 - Newport Beach, California.

Attended the 14th Informal Conference on Photochemistry

and presented an invited lecture on "Infrared Emission

Studies of Photofragment Dynamics."

Sponsor: Conference on Photochemistry.

April 7-9, 1980 - Berkeley, California.

Presented a talk on "Infrared Chemiluminescence Studies

of Reactive Dynamics," at a Chemistry Department

Seminar, and visited the University of California at

Berkel ey

.

Sponsor: University of California at Berkeley.

April 24-27, 1980 - Toronto, Ontario, Canada.

Visited the University of Toronto and presented a Departmental Seminar on "Infrared Chemiluminescence

Studies of Reactive Dynamics."

Sponsor: University of Toronto.

November 2-3, 1979 - Chicago, Illinois.

Attended a meeting of the UVOIR (Ultraviolet, Optical,

and Infrared) Panel of the Astronomy Survey Committee

of the National Acadeny of Sciences.

Sponsor: National Academy of Sciences.

November 30 - December 2, 1979 - Tucson, Arizona.

Attended a meeting of the UVOIR (Ultraviolet, Optical,

and Infrared) Panel of the Astronomy Survey Committee

of the National Academy of Sciences.

Sponsor: National Academy of Sciences.

218
TRIPS SPONSORED BY OTHERS

J. L. Linsky

Quantum Physics Division (525)

January 17-18, 1080 - San Francisco, California.

Attended a meeting of the UVOIR (Ultraviolet, Optical,

and Infrared) Panel of the Astronomy Survey Committee

of the National Academy of Sciences.

Sponsor: National Academy of Sciences.

January 24-26, 1980 - Sunspot, New Mexico.

Attended the meeting to evaluate the future of the

Cloudcraft 48-inch telescope of Sacramento Peak

Observatory as a member of the committee appointed

by AURA (Association of Universities for Research in

Astronomy)

.

Sponsor: Association of Universities for Research in

Astronomy, Inc.

February 3-6, 1980, Greenbelt, Maryland.

Attended meeting of the Sol ar-Terrestrial Theory

Program Evaluation Committee at Goddard Space Flight

Center.

Sponsor: NASA.

February 13-17, 1980 - Washington, D.C. and Greenbelt,

Maryland.

Attended the meeting of the Committee on Space

Astronomy and Astrophysics at the National Academy of

Sciences Building in Washington, D.C., and attended a meeting of the UVOIR Panel of the Astronomy Space

Committee of the National Academy of Sciences.

Sponsor: National Academy of Sciences.

February 24-29, 1980 - Santa Cruz, California.

Attended the meeting of the UVOIR Panel of the

Astronomy Survey Committee of the National Academy of

Sciences.

Sponsor: National Academy of Sciences.

March 12-13, 1980 - Huntsville, Alabama.

Attended meeting of the Space Telescope Data and

Operations Team.

Sponsor: NASA.

April 14-15, 1980 - Greenbelt, Maryland.

Attended the meeting of the Management Operations

Working Group for the NASA Astronomy Program at Goddard

Space Flight Center.

Sponsor: National Academy of Sciences.

219
TRIPS SPONSORED BY OTHERS

J. L. Linsky

D. W. Norcross

Quantum Physics Division (525)

April 30 - May 2, 1980 - Greenbelt, Maryland.

Attended Critical Design Review of the Space Telescope

(ST) High Resolution Spectrograph.

Sponsor: NASA.

May 7-9, 1980 - Greenbelt, Maryland.

Attended Conference on the Universe at Ultraviolet

Wavelengths and present 3 contributed papers.

Sponsor: NASA.

May 19-20, 1980 - Austin, Texas.

Attended the meeting of the Committee on Space

Astronomy and Astronomy Physics.

Sponsor: National Academy of Sciences.

August 8, 1980 - Tucson, Arizona.

As a member of the Thesis Committee of Mark Giampapa,

as astronomy Ph.D. candidate at the University of

Arizona, attended his defense on August 8.

Sponsor: University of Arizona.

August 23 - September 18, 1980 - Toulouse, France.

Trapini, Italy, and Trieste, Italy.

Presented an invited review paper and lectures at the

NATA Advanced Study Institute on "Solar Phenomena in

Stars and Stellar Systems," in Toulouse, France.

Sponsor: NATO.

Presented an invited review paper and lectures at the

Erice Workshop on "Physical Processes in Red Giants,"

in Erice, Italy.

Sponsor: Erice Workshop.

Presented invited review paper at the IAU Colloquium

No. 59 on "Effects of Mass Loss on Stellar Evolution,"

in Trieste, Italy.

Sponsor: IAU.

September 1980 - September 1981 - Extended travel

to Smithsonian Center for Astrophysics, Cambridge,

Massachusetts.

220
TRIPS SPONSORED BY OTHERS

A. V. Phelps

S. J. Smith

Quantum Physics Division (525)

December 5-9, 1979 - Menlo Park, California and

Livermore, California.

Discussed physics of propagation of electron beams

in the atmosphere with Dr. Simon Yu at the Lawrence

Livermore Laboratory and presented a seminar to Dr.

W. L. Morgan's laser group on the role of excited atoms

in high pressure discharges in metal vapor rare gas

mixtures.

Sponsor: Lawrence Livermore Laboratory.

April 30 - May 2, 1980 - Ft. Collins, Colorado.

Participated in a Research Review Panel for the

Department of Physics of Colorado State University.

Sponsor: Colorado State University.

June 15-22, 1980 - La Jolla, California.

Attended a comprehensive review of all the theoretical

efforts currently supported by the Charged Particle Beam

Program of the Defense Advanced Research Projects

Agency (DARPA).

Sponsor: Naval Surface Weapons Center.

May 1, 1980 - Roll a, Missouri.

Gave an invited colloquium at the Department of

Physics, University of Missouri.

Sponsor: University of Missouri.

221
SPONSORED CONFERENCES

Quantum Physics Division (525)

A JILA Workshop on photoionization of excited atomic states, includinq

cross-sections, angular distributions, spin polarization and wavelength

dependence is planned for early March 1081. S. J. Smith and G. Leuchs

are co-organizers.

222
SEMINARS AND COLLOQUIUMS

Quantum Physics Division (525)

Laboratory Reports Seminars

Name/Affil iation/Titl e/Date

F. Kowalski (JILA Postdoctorate) - A proposed new measurement of electromagnetic momentum in a (gaseous) dielectric using the techniques of

high resolution laser spectroscopy, October 11, 1979.

J. Levine (JILA Fellow) - Laboratory Minicomputers in JILA—One person's

view of how we got where we are, what we (cooperative) are trying to do,

and what the future may hold, November 15, 1979.

L. Pendrill (JILAL Postdoctorate) - Laser Spectroscopy of Caesium Atoms.

I. Rydberg Radius 100 A, November 29, 1979.

L. Pendrill (JILA Postdoctorate) - Laser Spectroscopy of Caesium Atoms.

II. Rydberg Radius 1, December 6, 1979.

A. Smith (JILA Postdoctorate) - Photoionization of Excited States of Na,

January 31, 1980.

L. Pendrill (JILA Postdoctorate) /K. Niemax (JILA Visiting Fellow) - Isotope Shifts of Rydberg Atoms, February 20, 1980.

R. Dang (JILA Postdoctorate) - Electron Impact Excitation of Sodium Atom

in the 3

2 P

3 / 2 State, February 21, 1980.

P. Schulz (JILA Postdoctorate) - Photodetachment of OH", March 5, 1980.

T. Baer (JILA Postdoctorate) - A Cheap Frequency Standard: Stabilized

Zeeman HeNe Laser, March 20, 1980.

J. Jeffries (JILA Graduate Research Student) - Ion Trappology: What Do

We Really Understand?, April 3, 1980.

D. Van Baak (NBS-NRC Postdoctorate) - Rydberg States of Rubidium and

What They're Good For, April 10, 1980.

J. Goldsmith (NBS-NRC Postdoctorate) /L. Hollberg (JILA Graduate Research

Student) - A Few of the Things You Might Have Wanted to Know About Ring

Lasers, But Never Bothered to Ask, April 17, 1980.

T. Zwier (JILA Graduate Research Student) - Vibrational Product- State

Distribution in the C i~ + H Associative Detachment Reaction, April 24,

1980.

B. Rinker (JILA Graduate Research Student) - Isolation Characteristics

of Super Spring, May 22, 1980.

223
SEMINARS AND COLLOQUIUMS

Quantum Physics Division (525)

Informal Seminars on Atomic and Radiation Theory

Name/Affil iation/Ti tle/Date

N. Radial (JILA Postdoctorate) - Spin-Orbit Effect in Electron-Photon

Coincidence Experiments, October 16, 1979.

A. Maquet (JILA Senior Research Member) - Pad# Approximants in Physics

for Pedestrians, October 30, 1979.

A. Ben-Reuven (JILA Visiting Fellow) - Resonance Absorption and Scattering of Strong Coherent Radiation, November 6, 1979.

R. Christensen (JILA Postdoctorate) - Charge Exchange Between Hydrogen

and Multiply-Charged Ions, November 13, 1979.

P. Thomann (JILA Postdoctorate) - Two-State Atoms in a Strong Monochromatic Field: A Non-Perturbative Approach, November 20, 1979.

A. Pradhan (JILA Postdoctorate) - Electron Impact Excitation of He-Like

Ions, November 27, 1979.

A. Barut (Professor, Physics and Astrophysics, University of Colorado) - Narrow Resonances as an Eigenvalue Problem: An Exactly Soluble Model,

December 4, 1979.

G. Petite (Saclay and MIT) - Resonant Multiphoton Ionization of Atoms:

Theory and Experiment for Cesium, January 15, 1980.

W. Wing (JILA Visiting Fellow) - Electrostatic Trapping of Neutral

Atoms, January 29, 1980.

J. Pascal e (Saclay and SRI) - Theoretical Model for Collisions of High

Rydberg Atoms with Neutrals, February 12, 1980.

L. Spruch (New York University) - Thomas-Fermi Theory and Some of its

Ramifications —A Pedagogical Talk, June 27, 1980.

D. Walls (JILA Visiting Fellow) - Proposed Schemes for Optical Bistability, July 22, 1980.

M. Gavrila (FOM, Amsterdam) - Higher Born Approximations, July 29, 1980.

J. Gazeau (Univ. P. et M. Curie, Paris) - Sturmian Technique for the

Discrete Spectrum of the Schrbdinger Equation, August 27, 1980.

224
SEMINARS AMD COLLOQUIUMS

Quantum Physics Division (525)

Chemical Physics Seminars

Name/Affil iation/Titl e/Date

N. Adams (University of Birmingham, England) - Laboratory Studies of

Natural Plasmas Using Flow Tube Techniques, September 7, 1979.

T. Cool (JILA Visiting Fellow) - Spectroscopy of Yttrium Halides,

September 21, 1979.

H. Strauss (University of California, Berkeley) - Vibrations and Structures of Strained Systems: Cyclohexane Cvclooctane and Cuhane, September

28, 1979.

R. Zare (Stanford University) - Recent Studies of Multi Dhoton Processes,

October 5, 1979.

G. Atkinson (University of Syracuse) - Time Resolved Laser Detection of

Reactive Intermediates, October 12, 1979.

J. Hall (JILA Fellow) - Precision Laser Spectroscopy, Optical Frequency

Standards--And All That Jazz, October 19, 1979.

C. Lineberger (JILA Fellow) - The Saga of Methylene, October 26, 1979.

C. De Puy (University of Colorado) - What Can Organic Chemistry Contribute to Studies of Gas Phase Ion-Molecule Reactions?, November 2, 1979.

D. Kley (NOAA) - How Dry is the Sky?, November 9, 1979.

J. Levine (JILA Fellow) - How Great is the Gulf Between Physics and

Chemistry?, November 16, 1979.

A. Gallagher (JILA Fellow) - Molecular Continuum Radiation, November 30,

1979.

F. Fehsenfeld (NOAA) - Recent Flow Tube Studies of Ion-Molecule

Reactions and Their Application to Interstellar and Atmospheric Ion

Chemistry, December 7, 1979.

W. Reinhardt (JILA Fellow) - What Do We Know About the Relationship

Between Classical Mechanics and Quantum Mechanics and Why Are We Interested?, February 1, 1980.

E. Grant (Cornell University) - On the Dynamics of Infrared Multi photon

Excitation: Some Simple Results of Experiment and Theory, February 8,

1980.

225
SEMINARS AND COLLOQUIUMS

Quantum Physics Division (525)

Chemical Physics Seminars (continued)

Name/Affil iati on/Ti tl e/Date

D. Spence (Argonne National Laboratory) - Negative Ions, Autoionizing

States, Post-Collision Interactions and Confusion in Atomic Spectroscopy, February 15, 1980.

B. Kohler (Wesleyan University) - Polyene Photophysics— Isomerization at

Absolute Zero, February 22, 1980.

Z. Herman (J . Heyrovsky Institute of Physical Chemistry & Electrochemistry, Prague) - Beam Studies of Ion-Molecule Reaction Dynamics,

February 29, 1980.

U. Fano (University of Chicago) - The Physics of Dissociation, March 14,

1980.

N. Carlson (Stanford University) - Two-Step Polarization Labeling of

Rydberg States in Na

2

, March 21, 1980.

A. Nozik (Solar Energy Research Institute) - Aspects of Photoelectrochemical Energy Conversion, April 11, 1980.

3. Ladanyi (Colorado State University) - Light Scattering from Flexible

Molecules, April 18, 1980.

A. Carrington (University of Southampton, England) - Spectra of Molecular Ion Beams, April 25, 1980.

E. Mason (Brown University) - Determination of Ion-Molecule Forces From

Transport Measurements, May 9, 1980.

L. Allamandola (University of Leiden) - The Laboratory Simulation,

Photochemistry, and Spectroscopy of Low Temperature Interstellar Dust

Grain Molecular Mantles and Their Role in Interstellar Chemistry, June

16, 1980.

226
SEMINARS AND COLLOQUIUMS

Quantum Physics Division (525)

JILA Colloquium Speakers

Name/Affil iation/Titl e/Date

B. Edldn (Fysiska Institutionen, Lunda Universitet) - The Low Configurations in 3- to 9-Electron Ions, SeDtember 18, 1979.

*J. Bokor (University of Illinois) - Multiphoton Ultraviolet Excitation

of Atoms and Molecules, September 25, 1979.

I. Smith (University of Cambridge, England) - Laser Studies of Gas

Phase Energy Transfer, October 2, 1979.

J. Farley (University of Arizona) - Studies of Rydberg States of

Helium, October 3, 1979.

S. Werner (University of Missouri) - Gravity and Inertia in Quantum

Mechanics, October 9, 1979.

S. Rice (University of Chicago - James Franck Inst.) - Collision

Induced Vibrational Redistribution in Electronically Excited Molecules,

October 16, 1979.

R. Miller (University of Chicago) - Collisions Between Galaxies,

October 23, 1979.

S. Holt (NASA-Goddard) - Spectra of Cosmic X-Ray Sources, October 30,

1979.

S. Bobashev (Acad, of Sci. of the USSR, Leningrad - JILA Visiting

Fellow) - Two-Step Photoionization of Helium Via the 4P 1P

X State,

November 6, 1979.

V. McKoy (California Institute of Technology) - The Applications of

Schwinger Variational Principle to Electron-Molecule Scattering,

November 13, 1979.

*W. Fowler (California Institute of Technology) - Experiment and Theory

Relevant to Nucleosynthesis in Supernovae, November 15, 1979.

*J. Harrison (University of Colorado) - New Ideas on Earth Tides,

November 21, 1979.

A. Georges (University of Toronto) - Resonant Multi photon Processes in

Fluctuating Laser Fields, January 8, 1980.

*Joint JILA/Physics Colloquium.

227
SEMINARS AND COLLOQUIUMS

Quantum Physics Division (525)

JILA Colloquium Speakers (continued)

T. Gallagher (Stanford Research Institute) - Interaction of Black Body

Radiation with Rydberg Atoms, January 20, 1980.

M. Aaronson (Steward Observatory) - A New Determination of the Hubble

Expansion Rate, February 5, 1980.

*J. Lawler (Stanford) - Doppler- free Optogalvanic Spectroscopy, February

6, 1980.

J. Polanyi (University of Toronto) - Recent Studies of Reaction

Dynamics by Laser Spectroscopy, February 12, 1980.

D. Crandall (Oak Ridge National Lab.) - Atomic Collisions with Multicharged Ions —Basic Physics and Aoplications in Fusion and Astrophysics, February 19, 1980.

E. Lee (University of California) - Photochemistry and Spectroscooy of

Small Molecules and Dimers, February 26, 1980.

*A. Ferguson (Oxford University) - Picosecond Liqht Pulse Spectroscooy,

February 27, 1980.

*P. Koch (Yale University) - Hiqhly Excited Hydrogen Atoms: An Atomic

Cornucopia, March 3, 1980.

*B. Lutz (Lowell Observatory) - Laboratory Astrophysics and Planetary

Atmospheres: It's All Done With Mirrors, March 4, 1980.

*T. Baer (JILA Postdoctorate) - Photon Echoes, Free Induction Decay and

Other Coherent Transient Probes of Atomic and Molecular Collisions,

March 7, 1980.

S. Moody (Mathematical Sciences Northwest) - HG 2

: Something That

Doesn't Laser and Why It Doesn't, March 11, 1980.

J. Moseley (University of Oregon) - Photodissociation and Photofragment

Spectroscopy of Molecular Ions, March 18, 1980.

J. Steinfeld (MIT) - Chemistry, Physics, and Applications of Multiple

Infrared Photon Excitation in Molecules, April 15, 1980.

M. Levenson (IBM, San Jose) - Laser Spectroscopy and Non-Linear Optics

in the More-or-Less Real World, July 1, 1980.

228
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Consultant

MBS-114A 'REV. 2-80

U.S. DEPT. OP COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

'2. Performing Organ. Report No. 3. Publication Data NBSIR 80-2165 October 1980

4. TITLE AND SUBTITLE

Annual Report of Technical Activities of the Center for Absolute Physical

Quantities

5. AUTHOR(S)

Karl G. Kessler

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE * WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Reports Period Covered"

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

NBS

10. SUPPLEMENTARY NOTES ~ .

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) _ . •

•

This report sunmarizes research projects, measurement method development, calibration and data evaluation activities carried during Fiscal Year 1980 in the NBS

Center for Absolute Physical Quantities. These activities fall in the areas of:

quantum metrology; measurements and standards for the electrical units, temperature

and pressure, length and mass, time and frequency; and quantum physics. *"

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Electrical measurements and standards; length and mass measurements and standards,

temperature and pressure measurements and standards; time and frequency; quantum

metrology; quantum physics. —

13. AVAILABILITY

f X| Unlimited

I I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20-402.

[X] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

15. Price
iTi

J