NBS TECHNICAL NOTE 758

NBS Reactor:

Summary of Activities

October 1971 to September 1972

National

Bureau
NATIONAL BUREAU OF STANDARDS

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IIUUUIM. u-i

Library, E-01 Admin. Bldg. APR 2 3 1973

N/.T no NBS Reactor: CiVc

Summary of Activities

October 1971 to September 1972

Robert S. Carter, Editor

Reactor Radiation Division

Institute for Materials Research

National Bureau of Standards Washington, D.C. 20234

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of

transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

SfATES O* *

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued March 1973
National Bureau of Standards Technical Note 758

Nat. Bur. Stand. (U.S.), Tech. Note 758,140 pages (Mar. 1973) CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Price $2.10 domestic postpaid or $1.75 G P.O. Bookstore.
FOREWORD

The National Bureau of Standards Reactor was built not only to serve

the needs of the NBS but also those of the greater Washington Scientific

Community and other government agencies. The Reactor Radiation Division

was established to operate the reactor and to foster its scientific and

technological use. Toward this end, the Division has a small nucleus of

scientists experienced in the use of reactors for a wide range of scientific and technical problems. In addition to pursuing their own research

and developing sophisticated experimental facilities, they actively seek

out and encourage collaboration with other scientists, engaged in challenging programs, whose work can benefit from use of the reactor, but

who as yet do not have the reactor experience necessary to take full

advantage of the facilities available. The Division also provides

irradiation services to a wiqe variety of users as well as engineering

and other technical services.

The reactor operates at 10 MW and is designed to provide a broad

spectrum of facilities ranging from intense neutron beams to extensive

irradiation facilities, making it one of the most versatile high flux

research reactors in the country. Thus it is able to serve a large

number of scientists and engineers in a broad range of activities both

within and outside the NBS.

In previous years , this report was called "Reactor Radiation

Division: Annual Report". However, since the report attempts to summarize all the work done which is dependent on the reactor including a large number of programs outside the Division, it seemed appropriate to change to the current title, "NBS Reactor: Summary of Activities". The

first section summarizes those programs based primarily on Reactor Radiation Division (RRD) initiatives whereas the second and third sections

summarize collaborative programs between RRD scientists and other NBS or

iii
non-NBS scientists respectively. The fourth section summarizes NBS work

originating entirely outside of RRD which requires no collaboration with

RRD scientists. The section entitled, "Service Programs" covers those

programs originating outside NBS but for which RRD provides irradiation

services. The remaining sections are self-explanatory.

Robert S. Carter, Chief

Reactor Radiation Division
ABSTRACT

This report summarizes all those programs which depend on the NBS

reactor. It covers the period from October 1971 through September 1972.

The programs range from the use of neutron beams to study the structure

and dynamics of materials through nuclear physics and neutron standards

to sample irradiations for activation analysis, isotope production and

radiation effects studies.

Key Words : Activation analysis; crystal structure; diffraction; isotopes;

molecular dynamics; neutron; nuclear reactor; radiation

Cover photograph: National Bureau of Standards

Reactor Building, Gaithersburg, Maryland.
TABLE OF CONTENTS

Page

FOREWORD i

ABSTRACT lii

A, REACTOR RADIATION DIVISION PROGRAMS 1 Rotational Dynamics and Order-Disorder Transitions in Ionic and

Molecular Crystals 1

1. Hydrosulfide Salts 1

2. Sodium and Potassium Cyanide 6

3. Infrared and Raman Band Shape Analysis of Neopentane. ... 8 Neutron Scattering Studies of Hydrogen in Transition Metals ... 11

1. Tantalum Hydride 11

2. Palladium Hydride 14

Lattice Dynamics Studies 16

1. KCN and Alkali Hydrosulfides 16

2. Metal-Hydrogen Systems 16

Crystal Structure and Thermal Motion in Durene by Constrained

Least-squares Refinement - -, Use of Rigid Body Constraints in Least-squares Crystal Structure

Refinement 20

Derivative Lattices and Their Applications 20

Group Theoretical Selection Rules in Inelastic Neutron Scattering

Within the Rigid-molecule Model 26

Thermal Neutron Flux Measurements 28

Intercomparison of Neutron Dif fractometers 28

Time Reversal Violation in K° Meson Decays 28

Cold-Neutron Time-of-Flight Facility . ... 30

Cold-Neutron Source 30

B. RRD-NBS COLLABORATIVE PROGRAMS 32

The Structure of Ca(Ho P0.) o , 2 4 2 J/

The Crystal and Molecular Structure of Dinitratotetrathiazole

Copper (II), [Cu(C

3H

3NS)

4 ](N03

) 2 33

Neutron Diffraction Determination of the Liquid Helium Structure

Factor and Related Correlation Functions 37

Temperature Dependence of the Liquid Helium Structure Factor at Fixed Density 43

vi
TABLE OF CONTENTS

Page

Dispersion of Excitations in Liquid Helium at Fixed Density . . . 45

Three Atom Correlations in Liquid Neon 45

The "Rotator" Phase Transitions in N-Alkanes 48

C, INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS 50

The Lattice Dynamics of NaN0„ 50

Dynamics of Ammonium Perchlorate 51

Lattice Dynamics Studies of Complex Crystals Containing Linear

Tri-Atomic Groups 51

The Crystal Structure of Cyclotrimethylene-trinitramine 53

The Structure of Andalusite and Sillimanite 56

Distribution of Aluminum and Silicon Cations in a Feldspar

Mineral 58

The Crystal Structure of l,3,5,7,Tetraceto-l,3,5,7 ,TetrazacycloOctane 60

Magnetic Structures of Eu- _ Gd S 63

Phonon Dispersion in hcpBe 65

Soft-Phonon Mode Behavior in PbTe 67

Observation of an Amorphous Spin Distribution 69

Crystalline Ordering in Silica and Germania Glasses 71

Precision Measurement of the Thermal Neutron Scattering Amplitude

for Silicon 75

D, NON-RRD NBS PROGRAMS 78

Activation Analysis Section: Summary of Activities 78

1. Standard Reference Materials (SPM) 78

2. Cooperative and Service Analyses 79

3. Radiochemical Separations 79

4. 252 Californium Neutron Source 79

5. Nuclear Track Technique 80

6. Characterization of the NBSR 80

7. Conclusions 84

The Cavity Fission Neutron Source £4

Measurements with the NBS Double Fission Chambers 85

Extreme-Angle Emission of Long-Range Alpha particles in the

Thermal Neutron Fission of 235U .86 vii
TABLE OF CONTENTS

Page

A Search for Doubly Radiative N-P Capture 86

Parity Violation in Neutron-Capture y

-Rays 87

In-Core Fast-Neutron Measurements Using a

3 He Semiconductor

Spectrometer 88

Precision Measurement of the Compton Wavelength of the Electron. . 90

5 Co Gamma Ray Anisotropy Thermometry .91

Studies of Gasseous Fission Products 92

E, SUMMARY OF REACTOR OPERATIONS 93

F, SERVICE PROGRAMS 97

The Use of Neutron Activation Analysis in Scientific Crime

Detection 97

The Use of Activation Analysis in Scientific Crime Detection by

the Federal Bureau of Investigation 98

U. S. Postal Service Activation Analysis Program 99

Activation Analysis Program of the Food and Drug Administration

at the NBSR 100

1. Mercury in Foods 100

2. Instrumental Neutron Activation Analysis of Bromine in Pig

Tissue 100

3. Rapid Instrumental Analysis for Mercury in Biological

Materials by Neutron Activation 101

4. MTELMT: A Computer Language for the Reduction of Neutron

Activation Analysis Data 102

Development of Analytical Methods and Determination of

Constituents of Geological Samples . 104

Comparison and Preparation of 18 Fluorine and 99mTechnetium-tinphosphate Radiopharmaceuticals 105

Use of Neutron Activation Analysis in the Study of Copper in

wound Healing and Hepatic Diseases 109

Trace Elements in the Environment and Decay Scheme Studies. . . . HO

Sea and Atmosphere Pollution Studies HI

Neutron Activation Analysis Navy Oil Monitoring Program H2

Feasibility Investigations of a Fuel Bundle Motion Monitor. . . . H3

Studies of Magnetic Properties in Rare Earth Alloys at Cryogenic

Temperatures 114

Effect of Radiation on Magnetic Materials 116

viii
TABLE OF CONTENTS

Page

Mossbauer Spectrometry 116

Angular Correlation of Positron Annihilation Radiation in Metals. 117

Band Tailing in Indium Antimonide 118

Quality Assurance of Aluminum Ecapsulation Material 119

G, STAFF ROSTER 120

F, PUBLICATIONS 124

IX

A, Reactor Radiation Division Programs

ROTATIONAL DYNAMICS AND ORDER-DISORDER TRANSITIONS

IN IONIC AND mLECULAR CRYSTALS

Work has continued on detailed studies of phase transitions involving

orientational disorder of ionic groups or molecules in crystals. The

precise nature of the rotational disorder in the high-temperature cubic

phases of broad classes of inorganic and organic solids is not in general

well understood, nor is the microscopic basis of the changes in physical

and thermodynamic properties associated with these order-disorder transitions. During the past year we have obtained new information concerning

the dynamical and structural nature of such phase transitions in several

of prototype materials (ionic and organic) by combining the results of

neutron diffraction and inelastic scattering, infrared spectroscopy and

Raman scattering measurements.

1. Hydrosulfide Salts - J. J. Rush and R. C. Livingston

In the past year the analysis of our previous inelastic and quasielastic scattering experiments on sodium hydrosulfide (NaSH) has been

completed. In addition, samples of CsSF (whose high temperature phase has

a CsCl type cubic structure) and RbSH have been synthesized and neutron

spectra and neutron diffraction patterns have been measured for these

compounds over a wide range of temperature. Raman spectra have also been

measured for the three hydrosulfide salts at temperatures between 80 and

400K and will be discussed briefly in the next section on Lattice-Dynamics

studies

.

The results of our quasielastic and inelastic scattering measurements

on NaSH and CsSH are illustrated in Figs. 1 and 2. In Fig. 1 we show

corrected neutron spectra around the quasielastic scattering peaks (note

that 1 MeV = 1.52 ps

-1

) for the two hydrosulf ides in their cubic phases at scattering angles of 25 and 55°. It should be noted that the width of the

quasielastic peaks for both salts is considerably larger at the larger

scattering angle (momentum transfer) . The presence of this broadening

provides direct evidence for reorientation of the SH

_ ions on a time scale

1
REACTOR RADIATION DIVISION PROGRAMS

9.0 - -

xx - 80

NaSH

i 1 .

CsSH

-

70 * = 250° <t> = 25.0° T = I03°C X f T=98°C _ 60 f i n 3

. 50 - c V c: -

; i

- 4.0 -

\ \ :

i \

-

1 * 30 -

i \

• \ -

in - \ - t 2.0 _

f

* - z

r> - / *

- S i.o <

- J \

*.

-

K 0.0 , 1'-"'7^- ,.,.,, ,, ....••..•""

i "*"•**•<•.•.•- .....*. . 2

l±J s" - - ?

;£ NaSH

<t> = 55 ,1 x CsSH

«=55.0

en 2.0 T = I03°C

x X T=98°C

rr"-.

~

15

r •'. /' ' r \

r '• 1.0

•a" •*.. *

f

1

05 - rys 'W \

-

i i

... "'-'""'

'~'-r

- V'-.rfrr\ r\ "" i . v

5 -15 -10 FREQUENCY TRANSFER (ps

-1

)

Fig. 1. Examples of quasielastic incoherent scattering spectra S ((f), to) for

NaSH and CsSH in their cubic phases. The S(<f>,w)'s designated by

(x) represent values before correction for sodium incoherence.

Model calaulations with appropriate values of t (residence time) are indicated by dashed lines. The estimated inelastic scattering

contributions and instrumental resolution (solid lines) are also

shown.
REACTOR RADIATION DIVISION PROGRAMS

w

C/JWo

Tl . c CO

cfl CD

cn ts ca

C/l Xi

cfl (X S o

u H

o ^ 4-4 3

<_) •—

s

X 0) iC ,c ^s 4->

Of) C

•H

cnC £

3

•H O u M

3 cn rQ

•H <D H H

4-1 cd

cn H cn T) X)C

i>> cfl O ^3 d

0) c 3 o

cr •H

0) 4-1 n Cfl 4-1 U

rQ ~

•H

CI) iH >

•H CD

4-1 ,£ O 4-1 CD

4-1 ^ m iH w C

r O

60

•H

(siiNrraavM^.B
REACTOR RADIATION DIVISION PROGRAMS

of ^10" 12 sec. in the cubic phases of both compounds. No measurable broadening was observed in the elastic peak for NaSH in its trigonal phase. In

Fig. 2 we show "effective" phonon energy distributions calculated from the

inelastic neutron spectra for NaSH and CsSH, assuming one-phonon scattering

from a cubic crystal. In each case one observes a broad "librational"

band centered around an energy of 50 MeV, which clearly shows that the

SH~ ions are oscillating about an equilibrium position for some time

between reorientations. Moreover, the NaSH rotational bands above and

below the trigonal-cubic transition are very similar, which indicates that

the major dynamical change associated with the order-disorder transition

is a rapid increase in reorientation rate and not a change in the equilibrium oscillations of the SH~ ions.

The widths at half-maximum (AwV; 2

) of the experimental quasielastic

peaks for NaSH and CsSH have been measured as a function of temperature

and momentum transfer, 0. These widths have been compared with theoretical

calculations of quasielastic scattering behavior based on the assumption

of instantaneous jumps of the SH~ ions between a limited number of equilibrium orientations, namely the [100], [110] and [111] directions in the

cubic crystals. The results are shown in Fig. 3. It can be seen from the

figure that each of the jump reorientation models predicts an oscillatory

behavior for the observed line-widths, and such behavior is indeed observed

in the experimental results. Only for the lowest-temperature results,

however, is the fit for any of the model calculations close to satisfactory

over the entire range of Q. The observed line-widths at Q>3A_i are generally

larger than predicted from our simple jump diffusion models. This lack of

fit can be attributed to several factors, including the fact that the

reorientation jumps are not "instantaneous" as assumed in the theory but

in some cases have jump-times comparable to the residence times between

j ump s

In spite of the above uncertainties, however, our results lead us to the following conclusions concerning the disordered phases in NaSH and

CsSH. First it is clear from the oscillatory behavior of the experimental

widths and the observation of "librational" bands, that the disorder involves
REACTOR RADIATION DIVISION PROGRAMS

12

10

3<

3.0

2.5

2.0

1.5

NaSH

A I03°C

o I54°C

a 2I2°C

[joo] MODEL

[ill] MODEL

[lio] MODEL

I t

-A 6—

CsSH

A 23°C

o 98°C

a I40°C ,Uk--.

[JOO] MODEL —

[ill] MODEL —

[l"0] MODEL i/

•t=.90

t = .90

I.I t = 2.0

t=2.2

Q(A )

Fig. 3. Full widths at half-maximum AW]f/ 2 vs. Q of the experimental

S(cj),to)s for cubic NaSH and CsSTI at several temperatures. Also

shown are theoretical widths calculated for SH~ reorientations

assuming random jumps between 6[100], 12[110j or 8[111] crystal

directions. Residence times (t) between jumps are also indicated

for the theoretical curves.

5
REACTOR RADIATION DIVISION PROGRAMS

SH~ ion orientation among a finite number of quasiequilibrium sites. The

results thus rule out any kind of "static" disorder (on the neutron time

scale) or the existence of anything approaching free or isotropic reorientation. The residence times between jumps range from 0.4 to 0.2 for NaSH

in the temperature range 100 to 200°C and from 2.0 to 0.75 ps for CsSH in

the range from 23 to 140°C. Comparisons of the theoretical and experimental line-widths do not lead to a definite conclusion concerning equilibrium SH~ orientations, but they do suggest that the [100] and [111]

directions are least likely for NaSH and CsSH, respectively. It should be

noted here that we have recently measured quasielastic neutron spectra for

CsSH and RbSH at four times the instrumental resolution used in the experiments discussed here. These new measurements are in collaboration with

J. M. Rowe at Argonne National Laboratory and the results are currently

being analyzed in the hope of obtaining new information on the disordered

phases.

During the past year we have also measured neutron powder patterns for

NaSH, CsSH and RbSH at temperatures down to 80 K. These results combined

with our Raman scattering spectra discussed below have revealed the

existence of new crystal phases at low temperature for each hydrosulfide

salt, which involve further ordering of the SH~ ions.

2. Sodium and Potassium Cyanide - J. J. Rush

NaCN and KCN are members of a broad group of polymorphic compounds

W~XY~ (which includes the hydrosulf ides discussed above) whose crystal

phase below the melting point has a cubic structure requiring that the

linear XY~ ions assume effective spherical symmetry, either by rotation

or some kind of random orientation. Attempts to study the details of the

disorder in the cubic phases of the cyanides by x-ray and neutron powder

diffraction have been largely unsuccessful. To obtain more definitive

information on the structure of these phases, we have, in collaboration

with J. M. Rowe and D. L. Price of Argonne National Laboratory, measured

the neutron diffraction pattern of a single crystal of NaCN at 295K. The

data was collected on a 4-circle dif fractometer , using an incident wave-
REACTOR RADIATION DIVISION PROGRAMS

A [001]

y—-NaCN 295K

KCN I80K

KCN 295K

Fig. 4. Angular dependence in the [110] crystal plane of the density of

C and N atoms on a sphere of radius equal to one half the C = N bond length.
REACTOR RADIATION DIVISION PROGRAMS

o length of 1.232A. In our measurement 26 independent reflections were

accessible; measurable intensity was found for 19 of these.

The NaCN diffraction results and our earlier diffraction patterns for

KCN have been analyzed in terms of a model which expands the angular

orientation of the CN~ ions in a series of symmetry-adapted spherical

harmonics. This model enables us to obtain a fit to the observed diffraction intensities using as adjustable parameters a scale factor, an extinction correction, the C = N bond length, Debye-Waller factors for the

metal and cyanide ions, and the coefficients a; v

, of the expansion in

spherical harmonics. The results of these model fits to the several sets

of diffraction data can be summarized as follows: Weighted R- factors of

between 2-3% were obtained in each case. The derived cyanide angular

distributions indicate a monotonic trend in the series KCN(295K) through

KCN(180K) to NaCN(295K) involving a shift in preferential orientation from

the [111] toward the [100] direction in the crystal. A view of these

angular distributions is shown in Fig. 4. Unusually large translational

o ~ Debye-Waller factors (=0.06 - 0.07AZ

) have also been derived for NaCN and

KCN from the fitting procedure, in agreement with an earlier analysis of

o the KCN data. In addition, an average C = N bond distance of 1.18A was obtained from the three fits.

3. Infrared and Raman Band Shape Analysis of Neopentane -

R. C. Livingston and J. J. Rush

The correlation functions for the infrared and anisotropic Raman

bands of a spherical molecule such as neopentane are given by

<u(o)-u(t)> and l/2<3[u(o) -u(+)

2 -l>

where u(t) is a vector along one of the two-fold axes. These functions

are the Fourier transforms of infrared and depolarized Raman bands,

respectively. They yield detailed information on the time behavior of

rotational motion of a molecule. In addition both correlation functions

arise in a diffent way in the theory of neutron scattering so that a comparison of the optical results with those of neutron scattering can

in principle yield more information about the rotational behavior.
REACTOR RADIATION DIVISION PROGRAMS

24 -

•

i

INFRARED RAMAN

A

A

A 20

A

A 5 A (J 16 AA A 3 A/ * *

a"" A •

•

12

A

'

i

•

•

8

A

A A

A

•

•

•

t %

4

1

*

•

• •

1

•

•

•

1

1 I 100 150 200 250

T(K) 300

Fig. 5. Raman and infrared bandwidths (full widths at half maximum) of

the 924 cm

-1 rotation-vibration band of neopentane as a function

of temperature.

;o .y \ \

.8 \ \

.7 - \ A o

.6 - \ ^ o

.5 \ \ °

\ \ I72K / V, v

o

o .4

\ \

o

.3 \ °

.2

\ 295 K r *°

o

1 1 1 1 ot 1 A .6 .8 1.0 1.2 1.4 TIME (psec)

Fig. 6. Correlation functions of the 924 cm * Raman band of neopentane

The curves represent the free-rotor decay.

9
REACTOR RADIATION DIVISION PROGRAMS

Since the last reporting period, Raman spectra of the F„ vibration-

-1

rotation band (923 cm ) of neopentane have been measured at temperatures

in both the solid and liquid phases. Also, the previously reported

infrared measurements have been extended a wider range of temperatures.

These experiments are being done in collaboration with W.G. Rothschild of

the Ford Scientific Company. The full widths at half maximum for the

infrared and Raman bands from 140 K to 300 K are plotted in Fig. 1. In this region neopentane has two phase transitions: liquid-plastic at 253 K

and plastic-solid II at 140 K. As indicated in Fig. 1 there is no discontinuity at 253 K in either infrared or Raman bandwidths, which indicates

a large degree of molecular mobility in the plastic phase of neopentane.

At the plastic-solid II phase transitions both infrared and Raman bands

show an abrupt splitting into several (~6) unresolved peaks with a total

width of approximately the same magnitude as that at the lowest temperature in the plastic phase. This crystal field splitting strongly suggests

that the mobility exhibited in the liquid and plastic phases has disappeared. In Fig. 2 correlation functions calculated by Fourier transforming the infrared and Raman spectra at two temperatures are plotted along

with the behavior expected for a free rotor at the same two temperatures.

On comparing the experimental data with that of the free rotor, one sees

that both the Raman and infared data indicate that at room temperature

neopentane rotates freely for approximately .4 ps which corresponds to an angle of rotation before a "collision" of approximately 40 degrees. A

plot of the relaxation time (t=1/ttcAv) vs 1/T yields an activation energy

in the high temperature region of about 1.3 kcal/mol. This is in good

agreement with the activation energies determined by quasielastic neutron

scattering, NMR and entropy data. A full manuscript of this work will be

prepared and submitted as a publication.

10
REACTOR RADIATION DIVISION PROGRAMS

NEUTRON SCATTERING STUDIES OF HYDROGEN IN TRANSITION METALS

The behavior of hydrogen in metals is of considerable theoretical

and practical interest. Important aspects of metal-hydrogen systems

include the details of diffusion processes, the nature of the M-H bonds,

phase transitions, and the effects of hydriding on intermetallic forces

and on electrical, magnetic, and thermodynamic properties. In this

section we summarize the progress made over the past year in our continuing neutron scattering studies of the diffusion and vibration of

hydrogen in transition metals. Work completed during the past year,

including our first results in the investigation of hydrogen in metallic

single crystals, has yielded important information on the mechanism of

hydrogen diffusion in several systems.

1. Tantalum Hydride - J. J. Rush and R. C. Livingston

In collaboration with H. E. Flotow and J. M. Rowe of Argonne

National Laboratory, measurements have been completed on a study of

hydrogen dynamics in tantalum hydride, including the temperature and

concentration dependence of the hydrogen diffusion. This work represents

a natural extension of our previous studies on hydrogen in vanadium (another Group V-A metal) . Neutron spectra have been measured for both

TaH

1 _ and TaH at momentum transfers (for quasielastic scattering)

between = 0.5A and = 4.1A over a temperature range from 22 to 340°C,

These results, and a comparison with various theoretical model for hydrogen diffusion, lead us to the tentative conclusion that jumps between

tetrahedral sites are predominent in the diffusion process. In Fig. 1 we present the experimental full-widths at half-maximum (Aoj L_) in

ps (10" s ) derived from our measurements on TaH -,., plotted vs. Q

2

. Also shown are theoretical line-width curves calculated from models

assuming instantaneous near-neighbor jumps between octahedral and tetrahedral interstitial sites in the bcc metal lattice. The residence

times between jumps assumed in these calculations are listed in the fig- ure caption. The residence times obtained for TaH vary from 3.4 to

11
REACTOR RADIATION DIVISION PROGRAMS

2 °-2 Q (A2

)

Fig. 1. The measured widths of the quasielastic peaks for TaH„ .. compared with the predictions of several theoretical

models. Curves 1 and 2_; jumps between nearest-neighbor

octahedral sites; 1: t=1.8 ps; 2: t=2.5 ps; Curves _3 and k_ jumps between nearest neighbor tetrahedral sites; 3: t=2.3 ps,

4: t=3.4 ps.

12
REACTOR RADIATION DIVISION PROGRAMS

1.5 ps between 148 and 340°C while an activation energy off 10.5+1.7

kJ/mol is derived for hydrogen diffusion at this concentration. The

analysis of the TaH

n

,- data is not yet complete. However the results so far appear to confirm the predominence of tetrahedral jumps, and the

residence times are roughly double those for TaH

n

-i r at comparable temperatures. Hydrogen vibration spectra have also been obtained for

TaH and a detailed comparison with nmr results is being made.

Comparison of the tantalum hydride results with our previous results on VH also provides some additional insights on hydrogen diffusion in these systems. The VH results showed a significant increase in

quasielastic line width at Q>3A~ , whereas the jump diffusion theory

predicts little change in line-width in this region of Q. These results were attributed qualitatively to the influence of partial gas-like

behavior in the hydrogen diffusion due to the fact that the jump times

in the (bcc) phase of VH K at high temperatures (-0.1 ps) are not instanA eous but are comparable to the observed residence times (t) between jumps

(~0.5 to 1 ps) . The slower diffusion rates in TaH (t's between 1.3 and

4 ps) should minimize these effects, and offer an excellent chance to test this suggestion by examining the large Q behavior of the quasielastic

scattering in this system. The results in Fig. 1 show little increase in

the quasielastic line widths above 0=3 (except for TaH_ i r at the

highest temperature) and are thus quite consistent with our previous suggestions on the influence of "gas-like" behavior. It should also be noted

that the unusually high proton Debye-Waller factors which are observed for

VH are also absent in the tantalum hydride system.

We are in the process of extending these experiments to the measurement of quasielastic and inelastic scattering by hydrogen in a single

crystal of tantalum. This will enable us to examine in greater detail

the diffusion of hydrogen in various crystal directions and hopefully

will provide a more critical test of various diffusion models.

13
REACTOR RADIATION DIVISION PROGRAMS

2. Palladium Hydride - J. J. Rush and G. A. Ferguson (Naval Research

Laboratory)

In collaboration with J. M. Rowe of Argonne National Laboratory

we have continued our study of the diffusion of hydrogen in a single

crystal of palladium (3% H in Pd) by the quasielastic scattering of cold

neutrons. The use of a single crystal in these measurements eliminates

the averaging over crystallite orientations which complicates theoretical comparisons for experiments with polycrystal samples and enables

us to determine the neutron momentum transfer (Q) quite well with respect

to crystal direction. Measurements were obtained at T = 305°C at a series

of crystal orientations and over a range of 0.4 to 2. 5A . The linewidth results at every crystal orientation are in good agreement with a simple theory (Chudley-Elliott) which assumes that the migration of

individual hydrogens in the fee Pd lattice can be well described as instantaneous jumps between adjacent octahedral sites, with a residence

time of 2.8 ps at 350°C. In fact the results provide the best evidence

yet obtained for the applicability of a simple jump model of hydrogen

diffusion in a metal. The widths at half-maximum derived for diffusion

along the [110] crystal direction are shown in Fig. 3, along with theoretical widths calculated for jumps between near-neighbor octahedral

and tetrahedral sites. Our results confirm the conclusions of Skold and

Nelin concerning octahedral site occupations in PdH_

n

„, but the hydrogen Debye-Waller factors derived from our neutron intensities (p=0.05A

2 in the [110] direction and p=0.09A in the [100] direction are considerably lower than those obtained by these workers in their neutron spectral

measurements on palladium hydride powder.

Experiments on both single-crystal and powdered palladium hydride

samples are continuing. We will try to accurately measure the energy

and width of the local (hydrogen vibration) mode. We have also prepared

a single crystal sample of PdD_ _„,., so that isotope effects on the hydrogen dynamics can be investigated. Attempts are also being continued to prepare a single crystal sami

and lattice dynamics studies,

prepare a single crystal sample of 6-PdH . (above x = 0.6) for diffusion

14
REACTOR RADIATION DIVISION PROGRAMS

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15
kEaCTOR radiation division programs

LATTICE DYNAMICS STUDIES

1. KCN and Alkali Hydrosulf ides - J. J. Rush and R. C. Livingston

Preliminary neutron scattering measurements of the phonon dispersion

curves for acoustic branches in a single crystal of KCN have been obtained

in collaboration with J. M. Rowe and D. L. Price of Argonne National

Laboratory. The phonon branches measured thus far show no evidence of

unusually low frequencies which might be suggested by the unusually large

translational displacements derived from our diffraction data as discussed

above. This is an indication that the very large "Debye-Waller" factors

may reflect a random displacement of the ions from cubic lattice positions,

which is not directly related to lattice vibrational motions. Further

phonon measurements are planned during the coming year to obtain information about the dynamics and crystal forces in the cyanide cubic phases.

In collaboration with G. J. Rosasco of the Inorganic Materials

Division, the lattice vibrational modes (at q = o) of NaSH, RbSH and CsSH

have been investigated in three crystal phases, using the new Raman

scattering instrumentation in the IMR Central Laboratory. Dramatic changes

in the number, shape and frequency of the librational, translatory and S-H

stretching modes of the hydrosulfide crystals have been associated with

varying degrees of ordering of the SH~ ions. These results correlate

quite well with the neutron diffraction and inelastic scattering results

discussed above. A similar Raman study of the lattice modes of KCN and

NaCN at temperatures down to 30 K has also been completed in collaboration

with R. Khanna of the University of Maryland. Again very interesting

effects associated with order-disorder transitions are observed. The

spectroscopic results from both of these experiments are currently in the

final stage of analysis and a more complete report will be presented in the

next progress report.

2. Metal-Hydrogen Systems - J. J. Rush

Work has continued, in collaboration with J. M. Rowe and H. E. Flotow

at Argonne National Laboratory and G. L. Ferguson of NRL, on attempts to prepare large single crystal samples of 3~PdH(D) x , up to a concentration of

16
REACTOR RADIATION DIVISION PROGRAMS

x = 0.8. If and when they are prepared these crystals will be used in a study of the lattice dynamics and local modes of this system. As mentioned

above, single crystals of tantalum have also been obtained which will be

loaded with hydrogen to study the effects of interstitial hydrogen on the

lattice dynamics and intermetallic forces in transition metals.

CRYSTAL STRUCTURE AND THERMAL MOTION IN DURENE BY

CONSTRAINED LEAST"SOUARES REFINEMENT

E. Prince and J. J. Rush

and

L. W. Schroeder

The work on the crystal structure of durene (1,2,4,5-tetramethyl

benzene) described in the 1970 and 1971 progress reports has been

continued further during this year. Previous efforts to refine the

structure from diffraction data has produced a clear picture of overall

features of the structure, but the refined structure contained a number

of physically impossible details, particularly in the thermal parameters. The technique of refinement with constraints on the thermal

parameters described elsewhere in this report was applied to this

problem with satisfactory results. Figure 1 shows two views of the

molecule as determined from two different refinements, one with and one without constraints. The two pictures are very similar, but the

constrained one is preferable on physical grounds. The constrained

refinement leads to values for the meansquare amplitudes of the principal

librational modes of oscillation. Table 1 shows a comparison of the

frequencies inferred from these amplitudes with those determined by

Raman scattering and neutron inelastic scattering. The agreement

is qualitatively satisfactory, and in particular the order of the

frequencies of the various modes is in agreement.

17
REACTOR RADIATION DIVISION PROGRAMS

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18
REACTOR RADIATION DIVISION PROGRAMS

Fig. 1. Two views of the durene molecule resulting from a) the

unconstrained refinement and b) the constrained refinement,

19
REACTOR RADIATION DIVISION PROGRAMS

USE OF RIGID BODY CONSTRAINTS IN LEAST-SQUARES

CRYSTAL STRUCTURE REFINEMENT

E. Prince

and

L. W. Finger

(Carnegie Institution of Washington, Washington, D.C. 20008)

Recently G. S. Pawley, of the University of Edinburgh, and various

co-workers have drawn attention to the possibilities of using systems of

constraints, particularly on thermal parameters, as a way of utilizing

information in addition to diffraction information in the refinement of

crystal structures. Following this approach we have derived a set of

equations which relate the temperature factor coefficients for individual atoms in a molecule to rigid-body motion parameters of the molecule

as a whole, thereby making it possible to express the structure factor

formula in terms of the rigid-body parameters and to fit these parameters

to the data by means of least-squares refinement. The equations have

been further extended to allow for the attachment to the rigid molecule

of side groups which are free to librate around a single bond. The

results have been incorporated into a computer program and employed in a study of the crystal structure of durene.

DERIVATIVE LATTICES AND THEIR APPLICATIONS

A. Santoro

and

A. D. Mighell

(Inorganic Materials Division)

As part of a study of the geometrical properties of crystal lattices,

derivative lattices have been defined and methods for their calculation

have been found. 1 These lattices are not infrequently related to important properties of crystals and, therefore, find applications in

many fields of crystallography, for example in (1) the study of regular

20
REACTOR RADIATION DIVISION PROGRAMS

aggregates such as twins and epitaxis and syntaxic intergrowths; (2) the

study of the geometrical conditions controlling the mutual orientation1 of

crystals forming grain-boundaries in many materials of metallurgical

interest; (3) the study of some phase transitions, such as order-disorder

transformations; (4) the study of derivative structures; (5) the automatic

determination of the diffraction symmetry in single-crystals studies;

(6) the critical evaluation of Crystal Data. We will now summarize some

of the work in this area during the past year.

1. Theory

Let us consider a lattice A and let us describe it in terms of a triplet of non-cop lanar translations a^ (i = 1,2,3) defining a primitive

cell. Let us now perform the transformation

1 = s ±j £j

3

with |§| = 0. The translations t± can be regarded as the edges of a primitive cell defining a new lattice T which we have called "derivative

lattice". Derivative lattices have been classified on the basis of the

properties of the transformation matrix S. Specifically if the Sij's are integers and if |s|>l, r is a super lattice of A. If matrix T is the inverse

of S, and if the T

±

- ' s are integers and |t|>1, r is a sublattice of A. If

one or more of the T±i' s are fractional, T is a composite lattice of A.

It can be shown that all the possible superlattices associated with

a lattice A can be generated, without duplications, by using a restricted

class of matrices S, i.e. only those matrices whose coefficients are integers which satisfy the conditions, |s|>l; O-S-^-s <S-? -; for i< j ; S-jj = for i>j . It can also be shown that the unique sublattices can be generating superlattices. The matrices generating composite lattices can be

obtained by multiplying in any order and in any combination matrices

generating superlattices and sublattices.

The theoretical work on this subject has been completed and a paper

has been published in Acta Crystallographica.

21
REACTOR RADIATION DIVISION PROGRAMS

2. Applications

a. Heterotaxy

The term "heterotaxy" describes a regular aggregate of two or more

crystals of different crystalline species grown with a well-defined mutual

orientation. The formation of a regular aggregate is possible if the

lattices of the constituent crystals are related to each other in a simple manner (specifically, if they can be transformed into each other by

matrices with rational elements) . Heterotaxy can be two or three dimensional. In the first case the intergrowth is called "epitaxic", in the

second "syntaxic". The possibility of heterotaxy can be predicted on the

basis of derivative lattice theory. In fact, if two crystals are related

so that the lattice of one is a derivative of the other, then the geometrical conditions for syntaxic intergrowth are satisfied. For example,

the unit cell of the mineral Ewaldite can be transformed into the cell of

the mineral Mackelveyite by means of the transformation 110/210/00k with

k = 2/3. The lattice of Mackelveyite is a composite of the lattice of

Ewaldite and the relationship in the basal plane (00.1) is illustrated in

Fig. 1. The two minerals frequently form polycrystals in syntactic intergrowth. It is also worthwhile to note that Mackelveyite and Ewaldite have

the same chemical composition and that the first goes into the second by

an ordering phase transformation. If k were not a simple rational number, we would have had an epitaxic, rather than a syntaxic, intergrowth. Work

on this subject is now in progress,

b. Coincidence-Site Lattices

Field-ion and electron-microscopy studies have shown that in many

materials of metallurgical interest the two crystals forming a grainboundary are often mutually oriented so that they have a common superlattice which continues without disturbance from one crystal to the other.

This superlattice is called coincidence-site lattice and the two crystals

adjacent to the boundary are said to be in a coincidence-side relationship

or coincidence-site related. »' 5

The concept of coincidence-site lattice has been used in the study of

the "structure" of grain-boundaries and in connection with such subjects

22
REACTOR RADIATION DIVISION PROGRAMS

Fig. 1. Relationship between the lattices of Ewaldite and Mackelveryite

which frequently form syntactic intergrowths.

23
REACTOR RADIATION DIVISION PROGRAMS

©

/

A• \

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o o o / ©

/ \ /. ' \ / \ / * ' . \ / \ • / . ' N

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o / o o o o © „' ©

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' \ / /

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o o o o ©' o o o o/o o o o©

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Fig. 2. Two-dimensional example of coincidence-site related lattices.

The two lattices indicated by small circlets are identical and are mutually oriented so that they have in conversion the superlattice indicated by the large circlets.

24
REACTOR RADIATION DIVISION PROGRAMS

as grain-boundary migration in high purity materials and nucleation and

growth of boundary precipitates. >

'

The interpretation of experimental results in terms of the coincidencesite lattice model requires the knowledge of the geometrical conditions

under which two crystals are coincidence-site related. The characterization

of a coincidence-site lattice can be made by applying the theory of

derivative lattices because the original lattices are sublattices of the

coincidence-site lattice. An example of the geometry involved in

coincidence-site relationships is given in Fig. 2. Work on this subject

has been completed and a paper for Acta Crystallographica is in press.

c. Automatic Determination of Diffraction Symmetry

If three reflections from non-parallel planes are determined in a single-crystal diffraction experiment, we may calculate a set of provisional

lattice parameters from the settings necessary to bring the planes into

reflecting position. These parameters define the true lattice of the

crystal only if the reciprocal cell obtained from the three reflections

is primitive. If this is not the case, the provisional cell defines a sublattice of the true lattice, i.e. the reciprocal cell determined

experimentally is multiple primitive.

The true crystal lattice can be found by the following method based

on the results of derivative lattice theory. A powder pattern can be

obtained from the same crystal being used for intensity measurements (with

a Gandolfi's camera, for example). If the pattern cannot be indexed with

the provisional parameters, then we systematically generate the superlattices of the provisional lattice unitl the one which indexes the powder

pattern is found. This super lattice is the true crystal lattice.

The metric symmetry of the crystal can then be found by means of

known reduction procedures. The crystal symmetry, which is the same for

a subgroup of the metric symmetry, can then be determined from intensity

measurements of reflections supposed to be equivalent. Work on this

subject is still in progress.

25
REACTOR RADIATION DIVISION PROGRAMS

^antoro and Mighell, Acta Cryst. A28 , 284 (1972).

2 Donnay and Donnay, Tschermaks Min. Petr. Mitt. 15_, 201 (1971).

3 Ranganathan, Acta Cryst. 21, 197 (1966).

h Acton and Bevis, Acta Cryst. A]7 , 175 (1971).

5 Brandon, Acta Met. 14, 1479 (1966).

6 Aust and Rutter, Trans. A.I.M.E. 215 , 119 (1959).

7 Unwin and Nicholson, Acta Met. 17, 1379 (1969).

8 Busing and Levy, Acta Cryst. T2_, 457 (1967) . Mighell, Santoro and Donnay, Int. Table for X-ray Crystallography,

1, 530 (1969).

GROUP THEORETICAL SELECTION RULES IN INELASTIC NEUTRON

SCATTERING WITHIN THE RIGID-MOLECULE MODEL

R. C. Casella

and

S. F. Trevino

(Picatinny Arsenal, Dover, N. J.)

The general program for considering the effects of crystal symmetry

on the structure function for inelastic neutron scattering, the implementation of which was mentioned in the last Annual Progress Report, is

continuing. We have obtained extensive theoretical results for the

rigid-molecule model and work on applications has begun (See S. F. Trevino, H. Prask, and R. C. Casella in Interagency and University

Collaborative Programs, Sec. C) . A paper on the general theory has been

submitted for publication and an invited talk was presented at the AEC

Summer Institute on Neutron Spectroscopy at MIT in August 1972. A brief

discussion of this work follows:

The verification and exploitation of symmetries in nature permeates

modern physics. As applied to the phonon spectra of crystals inelastic

thermal neutron scattering plays a major role in elucidating these

symmetries

However, for sufficiently complex crystals with many atoms in the

26
REACTOR RADIATION DIVISION PROGRAMS

unit cell the number of phonon modes at a given wave vector q is so large

that the experimentalist's task of assigning symmetry types to the various phonon branches becomes increasingly difficult. The problem is com- pounded further by the fact that for such crystals the symmetry is generally lower than for simple crystals resulting in fewer symmetry types

(irreducible representations, IR) to which one must assign the phonon

modes. That is, the effects of symmetry tend to wash out. There are, nonetheless, situations where the symmetry effects remain

indelible even for complex crystals. When one deals with molecular units

whose internal vibrations lie at sufficiently high energies so as to decouple effectively from the intermolecular vibrations, one can greatly

reduce the number of potentially active modes via energy discrimination.

This simplification is embodied in the well known rigid-molecule approximation in which only translations of the molecular centers of mass (cm.)

and rotations about the cm. are allowed.

Another simplification in identifying lattice-mode symmetries was introduced several years ago by Elliott and Thorpe (ET) who devised a model-independent technique for assigning IR's to the phonon modes when

the atoms are allowed to vibrate without special constraints.

We have achieved a union of these two simplifications which we

believe permits handling considerably more complex crystals than was heretofore possible. The generalization of ET's work to apply to the

rigid-molecule model involves the resolution of several points of

principle. These have been resolved to yield simple and useful results.

(r) -* The ET structure function F (k) can be written as the sum of two non- negative terms

:

F

(r) (kWr) (£|R) +F(r) (k|e).

-y Here, k refers to the momentum transfer to the neutron, R denotes translations of the molecular cm. , 9 rotations about the cm. , and r labels

the IR. Closed expressions have been found for these quantities both in

the Brillouin-zone interior and at the boundary.

27
REACTOR RADIATION DIVISION PROGRAMS

THERMAL NEUTRON FLUX MEASUREMENTS

V. W. Myers and M. Ganoczy

A manganese sulfate bath is being used at a beamport for determining

the thermal neutron intensity of the beam. Cobalt glass beads activated

in the beam can then be used for calibrating a Nal well detector. An

unknown thermal flux can be measured by activating a cobalt glass bead in

the flux and then counting it in the calibrated well detector.

INTERCOMPARISON OF NEUTRON DIFFRACTOMETERS

V. W. Myers

Collaboration is continuing in a program of the International Union

of Crystallography for the comparison of neutron flux at various neutron

spectrometers. Gold foils are activated in the diffracted beam and sent

to one of the following laboratories for counting: Australian AEC;

Kjeller, Norway and NBS . Foils will be counted at NBS for irradiations

at spectrometers at the following reactors: Brookhaven HFBR, NBSR, Oak

Ridge HFIR, and Puerto Rico Nuclear Center. There may be irradiations

made at other facilities also and then counted at NBS. This study will

probably be completed by June 1973.

TIME REVERSAL VIOLATION IN K° MESON DECAYS

R. C. Casella

Since the discovery of CP violation in the decays of neutral kaons

into pions by Christenson, Cronin, Fitch, and Turlay in 1964, a convincing microscopic explanation which maintains contact with the rest of

physics has been lacking despite a highly successful phenomenological

framework due to Wu and Yang. Assuming CPT symmetry the CP violation

immediately implied T (time reversal) violation. In 1968-9, on the

basis of still quite crude data, Casella was able to show that T is

28
REACTOR RADIATION DIVISION PROGRAMS

violated independently of the assumption of CPT symmetry. Based upon

vastly improved data the violation of T and the validity of CPT (within

reasonable accuracy) are now independently established in kaonic decays

quite apart from any microscopic explanation.

In addition, the new data point increasingly towards the equality of

the Wu-Yang parameters r\ , and n characterizing the CP violation in the

_

°

r +- oo b

it tt and tt ir channels, an equality predicted much earlier by Wolfenstein

(1964) who assumed that CP is conserved in the weak interactions and that

the observed CP violation results from a mixing of the pure CP-even and

CP-odd states formed from the K and its antipartical, K . A new "superweak" interaction, essentially decoupled from the rest of physics, was postulated as the CP-violating mechanism inducing the mixing.

We are investigating the possibility that the experimentally acceptable "superweak" force which breaks time reversal invariance is not a new

one, but is instead related to the cosmic "time arrow" inherent in the

Hubble expansion of the universe. Earlier (1964) attempts at a global

explanation of T violation had focused attention on the diagonal elements

of the 2x2 mass matrix M describing the K -K complex, assuming (contrary to Einstein's equivalence principle) that the K and K interact

slightly differently with gravitational fields. Such theories predict

Lorentz-factor velocity dependences and CPT violation in disagreement

with experiment. It is now clear that the T violation must occur in the

off-diagonal elements of M where changes in the strong-interaction quantum number S (strangeness) also occur. This aspect and the smallness of

the Hubble expansion over a K lifetime present obstacles which must be

overcome if we are to obtain a theory along these lines which is consistent with (1) the equivalence principle, (2) CPT symmetry, and (3) other

aspects of the data.

29
REACTOR RADIATION DIVISION PROGRAMS

COLD-NEUTRON TIME-OF-FLIGHT FACILITY

R. S. Carter, A. A. Cinquepalma, D. H. Fravel,

and J. B. Sturrock

The cold neutron time-of-flight facility is designed for inelastic

neutron scattering studies of solids and liquids. A neutron beam from

the reactor is filtered through polycrystalline beryllium to eliminate

o neutrons with wavelengths shorter than 3.92A. The beam then passes

through a four rotor phased chopper systems which chops the beam into

short bursts of neutrons of selected energy. The sample to be studied is

placed immediately after the choppers and the scattered neutrons are detected in a large bank of detectors arranged along the arc of a circle

with a 2.4 meter radius. The detectors are located in a shielding room. The detector information is fed into a multi-channel analyzer and the

neutron energy determined from the flight time of the neutrons from the

sample to the detectors.

The only remaining item to be completed is the shielding room and

the installation of the detector bank. The shielding room is mounted on

a steel frame that floats on air pads to enable the whole room (^9' x 12'

x 14') to be moved to provide access to the choppers. The base and side

walls have been completed and assembled. The supporting framework for the

detectors has been installed. The top sections will be completed shortly.

Then the detectors will be mounted on the frame to complete the system.

COLD-NEUTRON SOURCE

R. S. Carter, E. M. Guglielmo, and F. J. Shorten

The NBS reactor includes a special port, 22" in diameter, which

penetrates the reflector up to the edge of the fuel elements. This large

opening was designed to provide space for the insertion of a cold neutron

source close to the core. By inserting a large, low temperature moderator it is possible to significantly increase the available intensity of

o very low energy neutrons (X >4A) which are very useful for many types of

30
REACTOR RADIATION DIVISION PROGRAMS

molecular dynamic studies.

The moderator will be a cylinder of D„0 ice 14" in diameter by 12"

long. A small amount of HO may be added to optimize the moderating

property of the source. The source will have a reentrant hole 4" deep by

8" in diameter for beam extraction. The hole will be filled with beryllium which has the property of reflecting the higher energy neutrons back

into the moderator while passing the lower energy neutrons. The moderator

will be maintained at 25 K by cold helium gas passing through tubing in

the moderator. The vacuum cryostat containing the moderator will be

constructed of thin-walled aluminum to minimize heating by capture gamma

rays. The cryostat will be mounted on a shielding plug and the whole

assembly will roll inside a second plug and shield assembly which itself

will roll into the special port of the NBSR. The shield mounted on the

second plug surrounds the cryostat and consists of about 4" of lead and

bismuth which greatly reduces the gamma ray heating of the moderator.

Two 6" and two 2" diameter beams can be extracted from the cold source

through the reactor shield. One of the 6" beams will be used for the

cold neutron time-of-flight facility while the others await future

development.

The helium for cooling is provided by an all helium regrigerator

using a turbine expansion engine developed by the NBS cryogenic laboratory

in Boulder. It has a one kilowatt capacity at 25 K which is sufficient

to handle the heat generated in the moderator at twice the current reactor

power.

The bismuth tip and cryostat are the only items which remain to be

installed. The cryostat has been received and extensive testing is

underway. The bismuth tip again failed to pass its acceptance tests and had to be rejected. The contract with the vendor has been terminated

since the damage to the cooling tubes done either during fabrication or during repair attempts is too extensive to be reliably repaired. A

completely new bismuth tip must now be fabricated.

31
B, RRD-NBS Collaborative Programs

THE STRUCTURE OF Ca(H2 P04

) 2

B. Dickens, L. W. Schroeder

(Polymers Division)

and

E. Prince

The work on the crystal structure of Ca(H PG,)2 described in the

2 4 1971 report has been completed this year. The neutron data suffered

serious extinction effects which were insufficiently accounted for by

a simple isotropic correction. A model which includes the effects of

anisotropic extinction gave more precise parameters. This model

suggests that extinction in Ca(H„P0,)

9 is dominated by the domain size

and anisotropy.

A successful refinement including anisotropic extinction allowed a more detailed analysis of the hydrogen positions and motions. The

variation of the mean-square-amplitudes of the nominally centered

hydrogens (H, and H,. of Fig, 1) with their displacement from the center

of symmetry along the 0...0 vector was studied. This showed that these

protons must be within .15 A of the center in order to fit the diffraction data with reasonable parameters. A consideration of these results

and the infrared spectrum of Ca(H„PO,)„ allows one to conclude that these

protons are in symmetric potential wells with zero-point energies greater

than any central barrier that may exist.

Figure 1 shows that the structure of Ca(H„PG\) exhibits complex and

unusual hydrogen bonding. The linking of PO, groups via symmetrical

hydrogen bonds (H,,H,-) to form chains is the most novel feature. These

I l chains are linked to form sheets which are separated by sheets of Ca

ions forming a layer structure. Another feature is the linking of

phosphate groups via hydrogen bonds (H„ , see lower left corner of Fig.

1) in a dimeric configurations which are further joined by hydrogen bonds

(H.. ,Ho) to the chains.

32
RRD-NBS COLLABORATIVE PROGRAMS

Fig. 1. Stereographic pair showing the atomic structure of Ca(H

2 PO^)

2

.

THE CRYSTAL AND MOLECULAR STRUCTURE OF DINITRATOTETRATHIAZOLE

COPPER (II), [Cu(C3H3 NS)4](N03)2

A. D. Mighell and C. W. Reimann

(Inorganic Materials Division)

and

A. Santoro

As a continuation of our study of compounds containing metal-organic

complex cations, the structure of dinitratotetrathiazole copper (II),

[Cu(C 3 H 3NS)i+ ] (N0 3 ) 2 , has been determined. The thiazole molecule, which

acts as ligand in this compound, has considerable biological interest, as

it is part of the molecule of thiamine (Vitamin B^) . The purpose of the

present study is to obtain accurate parameters of the thiazole ring and

of the N0 3 - anions, and to compare the packing of the [Cu(C3hT 3NS)[t ] 2+

cations with that of analogous complexes of imidazole and pyrazole whose

structures have been previously determined.

33
RRD-NBS COLLABORATIVE PROGRAMS

Fig. 1. Stereo view of the molecule [CuCC-H NS(, ] (NO ) ,

0(2) ,A^

120.6'

0(3)

120.1" v£

N(3)

1,0, o^

_ 2.011 .Cu N(|) ||L30

2.024 -&?

,C(3) >' 406

, C(2)

115.6"' 106.1

'^^113.4° 929c C ") N

,.685^

S( °

,N(2) v>"' N III.2'N^

? C<A)1 N c(6)

13.6° 114.0°,

1.6991K 11.373

I 91.4° 109.8°]

S(2) 1.690

C(5)

Fig. 2. Unique bond distances and angles in the molecule of

[Cu(C

3 H3NS)

4 ](N0

3

) 2

.

34
RRD-NBS COLLABORATIVE PROGRAMS

N(2')

N(2)

O(l')

Fig. 3. Coordination of the copper atom in the structure of [Cu(C»H~NS) ,

]

(N0»)„. The coordination polyhedron is a distorted octahedron.

35
RRD-NBS COLLABORATIVE PROGRAMS

Dinitratotetrathiazole Copper (II) is monoclinic, space group C2/c,

and lattice parameters a = 14.38A, b = 10.116A, c = 14.603A, 6 = 112.9°.

Single crystal x-ray intensities were measured with a counter dif fractometer

and the structure was solved by Patterson and Fourier methods. There are

four molecules of complex per unit cell. The complex is centrosymmetric

with the copper atom located at the center of symmetry of the space group.

All the other atoms occupy general positions. There are two thiazole

ligands and one nitrate ion in the structure which are crystallographically

independent. Figure 1 is a stereo view of the molecule of the complex.

Unique bond distances and angles are given in Figs. 2 and 3. The copper

atom sits at the center of a distorted octahedron and is coordinated by

four nitrogen atoms of the thiazole rings and by two oxygen atoms of the

nitrate groups. Preliminary calculations have shown that the thiazole

rings are planar.

The packing of this structure resembles that of Dichlorotetrapyra

zolenickel(ii) , [Ni(C3Hi+ N2)i+] CI2. 1 This analogy suggests that internal

hydrogen bonding may be present also in the structure of the copper complex.

Such bonding would involve hydrogen atoms bonded to carbon atoms.

(C-H...0) bonding has been observed in numerous structures? As the

positions of the hydrogen atoms have not been determined unambiguously

in the present analysis, we have no direct evidence to support the previous

hypothesis. Neutron diffraction work is contemplated, if crystals of the

appropriate dimensions can be grown.

^eimann, Mighell and Mauer, Acta Cvyst., 23_, 135 (1967)

2 See for example, Sutor, Nature, 195 (1962).

36
RRD-NBS COLLABORATIVE PROGRAMS

NEUTRON DIFFRACTION DETERMINATION OF THE LIOUID HELIUM

STRUCTURE FACTOR AND RELATED CORRELATION FUNCTIONS

B. Mozer

(Inorganic Materials Division)

and

B. LeNeindre

(CNRS, Bellevue, France)

and

L. A. deGraaf

(Interuniversitair Reactor Insituut, Delft, The Netherlands)

In a previous paper 1 we reported measurements of liquid neon structure

factors at fixed temperature and several densities. These measurements were performed to allow one to obtain an isothermal density derivative of

the liquid structure factor or the isothermal density derivative of the

radial distribution function which contains information about correlations

of three particles in the liquid. 2 There is sufficient interest in the

correlation of three helium atoms in liquid helium and some aspect of

this three-body correlation can also be obtained from an isothermal density

derivative of the liquid helium radial distribution function obtained

from neutron scattering measurements of the liquid helium structure factor.

Furthermore, there has been a suggestion that a measure of the condensate

fraction of liquid helium could be obtained from measurements of the

structure factor at several temperatures above and below the A transition

temperature. 3 Neutron diffraction measurements of high statistical accuracy have

been obtained for liquid helium at three densities, 0.1528, 0.1567, and

0.1628 g/cm 3

. These structure factors were measured at two temperatures,

one above the A transition at 2.86 Kelvin, and the other below the A transition in the neighborhood of 1.90 Kelvin. The measurements were performed

o using three different wavelength neutrons of 0.845, 1.063, and 2.428A to cover "momentum transfer" regions of K = ~— sin 9/2 of 3.5 to 7.0, 1.5 to

° —

i

4.6, and 0.2 to 2.2A l respectively. Statistical accuracy of the data

after background and other corrections was 0.4% using the shortest wave37
RRD-NBS COLLABORATIVE PROGRAMS

length neutrons and 0.1 to 0.2% in the other two wavelength measurements.

The data were corrected for the background contribution, multiple scattering, and inelastic neutron scattering. The resolution of the instrument as determined by the diffraction pattern of copper powder was AK = 0.1, 0.255 and 0.31A x for the (111) copper peak for the three wavelengths

of 2.428, 1.063, and 0.845A respectively. Instrumental resolution was

removed by a calculation using an iterative procedure in order to insure

proper joining of the data in the overlap regions in K. The result of

this calculation was to confirm our hypothesis that the joining of the

data can be accomplished by using the integrated intensity factors in the

overlap region.

The resultant structure factor is obtained by setting the corrected

o i data in the asymptotic region (K = 6. to 7. A

_i

) to unity and then working

toward the small kappa region by joining the data via integrated

intensities and unfolding the spectra for instrumental resolution. These

results for the structure factors show a linear region for small kappa,

the main peak at about 2.05A" 1 then two highly damped oscillations about

unity which eventually lead to a flat asymptotic behavior from about

5.5A and greater. These features can be seen in figures 1, 2, and 3. Changes in peak position with density are observed. One also notes that

the extrapolation of the linear region at small kappa agrees well with

calculated values of the structure factor at K = obtained from the bulk

compressibility and other known quantities. Also observed are significant

differences in the structure factor above or below the A for a given density.

The radial distribution function, g(r), for each density and each temperature has been obtained from a Fourier transform calculation of Dr. R. Mountain of the Heat Division. A representative radial distribution

function is shown in figure 4. What is observed is a pattern very

o similar to that for the structure factor. In the region to about 2A

where g(r) should be zero we see structure indicative of the noise in our spectrum for S (K) at large K. This structure can be reduced by a small

(0.2%) change in our asymptotic region but this is within our accuracy

in this region of 0.4%. The structure observed in the region

38
RRD-NBS COLLABORATIVE PROGRAMS

O

O

oo

CM

M-4o

4-1 •H

COn

0)

Q 3

sr H

l-H — " £1 o<t

-a

v: •H3

•H O >-) W

rO -J4-1 00 O

CN U

O cu

4-1 )-l o 3

nj 4-1

14-1 trt O !-< CM <u 0) u P. 3 £5

4-> <u a 4-1 3H T3

4-1 3

CO CO

00

•H

MS

39
EED-NBS COLLABORATIVE PROGRAMS

40
RKD-NBS COLLABORATIVE PROGRAMS

O

e

o

oO 00

CM

14-1 O

4-1 •H

COC

Q) 13

o e

<-t 3

•H

»'<r t-tdl * J3

T3H

O •H • ro H

H-l 00 O

CM U

o a)

4-1 n

o P

cfl 4-1 u U-i Cfl CVJ

CD

5-4 U a, 3 e

4-1 Q) U 4-1 3

S-l T3

4-1 C

to a)

60

O

41
RRD-NBS COLLABORATIVE PROGRAMS

-o

I.O

1.6 LIQUID HELIUM

1.4 p = 0.1567 g/cm3

T=2.86K

1.2 — o o

<£**%

1.0

£0.8

CM CP

go o o

o o o w

o

0.6

o

o

0.4

o

o

02 o

o

0.0

° o

o o o o

o5>

1 1 1 1 1 1 1 1 1 1 10 R(A)

12 14 16 18 20

Fig. 4. Radial destribution function, g 2 (R) , for liquid helium at a density of 0.1567 g/cm3 and a temperature 2.86K.

42
RRD-NBS COLLABORATIVE PROGRAMS

r>2 is very smooth with only a few characteristic excursions about unity

such as was noted for S(K). The smoothness of g(r) and the size of the

structure at small r yield support for the reliability and accuracy of the

structure factors.

A preliminary calculation of the three body correlations in liquid

helium has been obtained from our measurements of the structure factor.

These calculations indicate sizable three-body correlations in liquid

helium with significant differences above and below the X transition

temperature. Detailed results of the calculation of three-body correlations for liquid neon are given in a separate note in this report by

Raveche and Mountain and a corresponding study for liquid helium will be

reported later.

X L. A. de Graaf and Bernard Mozer, J. Chem. Phys. 55_, 4967 (1971).

2 H. J. Raveche and R. D. Mountain, J. Chem. Phys. 5_3, 3101 (1970).

3 G. J. Hylands, G. Rowlands, and F. W. Cummings, Phys. Letters, 31A,

465 (1970).

TEMPERATURE DEPENDENCE OF THE LIQUID HELIUM

STRUCTURE FACTOR AT FIXED DENSITY

B. Mozer

(Inorganic Materials Division)

and

B. LeNeindre

(CNRS, Bellevue, France)

It has been suggested that information about the condensate fraction

in liquid helium below the X transition temperature can be obtained from

measurements of the liquid helium structure factor. 1 We observed in our previous measurements on the liquid helium structure factor changes when

the temperature was above or below the X transition temperature at fixed

density. The temperature above the X transition was too high to critically

evaluate the suggestion offered in reference (!) . We therefore thought

43
RRD-NBS COLLABORATIVE PROGRAMS

it would be of value to have a careful scan of the structure factor at fixed density and several temperatures both above and below the A transition temperature. We obtained structure factors for liquid helium using

neutron diffraction at a fixed density of 0.1528 g/cm3 and at 6 temperatures, 1.86, 2.04, 2.33, 2.83 kelvin and just above and below the A transition temperature for this density, 2.132. The measurements were

o o performed using two different neutron wavelengths of 2.406A and 0.986A

° —

to cover the region of momentum transfer 0.2 to 3.5 and 1.5 to 7.0A . Resolution of the instrument was improved over the previous experiment by

using a Soller slit collimator in front of the neutron counter and

stopping down the monochromatic beam impinging on the specimen. The

resolution was determined from copper powder diffraction peaks and was

° — i less than 0.1A x for both wavelengths where the data overlaps. Statistical

accuracy of the measurements was maintained to better than 0.4% except at small values of the momentum transfer.

S(K) was determined from the raw data after correcting for background,

multiple scattering and inelastic scattering. The structure factor is

observed to decrease with temperature in the small momentum transfer region

corresponding to the decrease in the structure factor at zero momentum

t given by S (o) = pkgT\x wnere XT i- s the isothermal compressability as observed by Hallock in x-ray measurements. The most significant change

observed in the structure factor occurs at the main peak when one approaches the A transition. From our highest temperature to slightly

above the A transition we note a slight increase in the intensity of the

major peak. The intensity decreases slightly as the temperature goes

just below the A transition and then decreases more rapidly as the

temperature decreases. The change in the intensity from the lowest

temperature to the temperature at the A transition is 5% whereas the

intensity changes from slightly above the A transition to the highest

temperature is about 1%.

These results will be used to test the hypothesis of Cummings,

Hyland and Rowlands 1 about the relation of the condensate fraction to

44
RRD-NBS COLLABORATIVE PROGRAMS

the liquid structure factor in helium.

F. W. Cummings, G. J. Hyland, and G. Rowlands, Phys. kondens, Materie3 12, 90 (1970).

DISPERSION OF EXCITATIONS IN LIQUID HELIUM

AT FIXED DENSITY

B. Mozer

(Inorganic Materials Division)

and

B. LeNeindre

(CNRS, Bellevue, France)

Preliminary inelastic neutron scattering experiments on liquid

helium at the fixed density of 0.1528 g/cm3 have been performed in order

to provide both the structure factor and excitation spectrum for a critical evaluation of recent theories on liquid helium. We used the

time-of-f light system to observe excitations in kappa regions from 0.09

O-l to 2.56A x and at temperatures above the below the X transition temperature.

Our measurements cover the phonon region, rotor region and single particle

excitation region of the spectra.

Preliminary analysis of the data shows dispersion of the excitations

in agreement with other measurements. Temperature effects are quite

striking just below the A transition to just above.

THREE ATOM CORRELATIONS IN LIQUID NEON

H. J. Raveche

and

R. D. Mountain

(Heat Division)

De Graaf and Mozer have recently published' very accurate neutron

diffraction measurements in liquid neon. We have used these results to discuss the correlation of three atoms in liquid neon and to consider

several approximate forms for the triplet correlation function.

45
RRD-NBS COLLABORATIVE PROGRAMS

(The structure factor, S(k), was measured by De Graaf and Mozer for

three pressures, 21.4, 79.0 and 140.0 atm along the 35.05 K isotherm of

liquid neon; these pressures correspond to densities of 0.0317, 0.0334 and

0.0347 atom/A3 respectively. The experiment was designed to construct the

isothermal density derivative of the radial distribution function. The

quantity is a measure2 of both magnitude and range of the correlation

between three atoms and can be readily determined from the experimental

results by using the relation,

g 2 (r 12 ) = 1 + (2TT 2 pr 12 ) _1

JdK k sin k r 12 {S(ic)-l} (1)

From the isothermal density derivative, we computed 3 a measure of

three atom correlations through the functional

F < r 12 I S3) E

/ d r3g20i 3 )g2 (r 23 ){g 3 (r 12 ,r 13 ,r 23 )-l} , (2)

where g 3 (r 12 ,rj 3 ,r 2

) is the triplet correlation function. The results of

the diffraction data and two approximate representations of the triplet

correlation function are shown in Figure 1. The solid curve in the experimental result and the dashed-dotted curve were evaluated from the convolution approximation, C

h(r 12 )h(r 13 )h(r 23 ) + p Jdr^hCr 1

it )h(r2 i

f )h(r 3k ) g3(r i2>r 13 r 23 ) - l :

•—

:—

: ; (3)

§2(r 12)g2(ri3)g2(r23)

the dashed curve was computed from

h(r 12 )h(r 13 )h(r 23 ) g3( r 12> r 13> r 23) ~ 1 > W g 2 (r 12 )g 2 (r 13 )g2 (r 23 )+l

where h(r) = g 2 (r)-l. Several other approximations were also computed.

o The small structure of the solid curve, in the vicinity of 4 and 4.8A,

represents the uncertainty in the data. The results in Figure 1 show a substantial amplitude (solid curve) in F(r 12 jg 3

) for distances of nearly

two atomic diameters and, since the coefficients of g 3 (rj 2 ,r 1 3,r 2

) in

F ( r 12|g3) are positive, the oscillation of F(ri 2 |g 3

) about zero requires

the triplet function to oscillate about unity in value, as the distance

between three atoms vary.

46
RPJVSBS COLLABORATIVE PROGRAMS

2.577 3.804 4.786 5.768

o

rj 2

,A

7.363

Fig. 1. F(r 12 |g 3

) at T = 35.05, p = 0.0334 atoms/A3 as a function of

r 12 - The solid curve is the experimental result, the dasheddotted curve was computed from Eqn. (3) and the dashed curve

from Eqn. (4)

.

47
RRD-NBS COLLABORATIVE PROGRAMS

The relative agreement of the experimental results and those obtained

from the approximations (3) and (4) , are discussed in reference (3) in

terms of finding a representation for the triplet correlation function

which is accurate at liquid densities.

1 L. A. deGraaf and B. Mozer, J. Chem. Phys. 5_5, 4967 (1971).

2 H. J. Raveche and R. D. Mountain, J. Chem. Phys. 5_3, 3101 (1970).

3 H. J. Raveche and R. D. Mountain, to appear in J. Chem. Phys.,

Nov. 1, 1972.

THF "ROTATOR" PHASE TRANSITIONS IN N-ALKANES

John D. Barnes

(Polymers Division)

Analysis of our neutron inelastic scattering data from n-nonadecane

in terms of a circular random walk model has been completed and the

results submitted for publication. The circular random walk model

describes the kinematics of the alkane molecule as a series of rotational

jumps about the long axis of the molecule, represented by a random walk

among a number, N, of sites distributed at equal intervals on the circumference of a cube. The remaining parameters which describe the kinematics

of the molecule are the dipole relaxation time, t, and the radius, d, of

the circle. In Fig. 1 we show an example of the values of the half-width

at half-maximum derived from our theoretical scattering low calculations

for several values of the parameters defined above. A detailed comparison

of our theoretical and experimental scattering laws shows that the

following parameter set is consistent with our quasielastic scattering

results at T = 301K: 3.5 x 10_12

s <t<4.0 x 10_12

s, N^8

48
RRD-NBS COLLABORATIVE PROGRAMS

12

10-

8-

CJ

COo

4

2-

f=53

T=3.5ps,d=l.39&

N= 4

N= 6

N=8

-- N=I2

-1.2 -I.I -1.0 -0.9

CJf(radians/ps)

-0.8 -0.7

Fig. 1. Theoretical Contours of half-width at half-maximum of the

quasielastic scattering law calculated from the Circular Random

Walk Model. Note how the choice of different values for the

number of sites leads to differences in the shapes of the

contours

.

49
C. Interagency and University Collaborative Programs

THE LATTICE DYNAMICS OF NaNO

S. Trevino and H. Prask

(Picatinny Arsenal, Dover, N.J.)

and

R. C. Casella

Sodium nitrate crystallizes in a rhombohedral unit cell (R3C)

containing two formula units, and has been the subject of considerable

spectroscopic study, including some coherent neutron inelastic scattering

measurements

The room-temperature lattice dynamics of single-crystal NaNOg are now being examined using the Picatinny Arsenal-NBS three axis neutron

spectrometer recently made operational at the NBSR.

The present work is aimed at completing the characterization of the

external lattice modes with particular emphasis on the high-symmetry

C-axis direction. The dispersion curves of all of the relatively lowenergy modes (nw~18 MeV) have been measured and characterized in the

C-direction. Assignment of symmetry species at q = o from the neutron

scattering selection rules of Casella and Trevino, discussed elsewhere in

this report, agree with assignments inferred from optical spectroscopic

data for optically-active modes.

On completion of the room-temperature studies, the external mode

lattice dynamics will be examined above and below the specific heat

anomaly at 275 °C.

l K. W. Logan, S. F. Trevino, R. C. Casella, W. M. Shaw, L. D. Muhlestein

and R. D. Mical, in "Phonons", ed. M. A. Nusimovici, Flammarion Sciences

Press (Paris) 1971, p. 104.

50
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

DYNAMICS OF AMMONIUM PERCHLORATE

H. Prask and S. Trevino

(Picatinny Arsenal, Dover, N. J.)

and

J. J. Rush

As part of a planned detailed study of the dynamics, structure and

rotational behavior of ammonium perchlorate, we have measured preliminary

neutron inelastic scattering spectra for NH^CIO^ powder at 5, 78 and 295K.

Spectra were measured at scattering angles of 18.5, 71.5 and 107°, so that

the Q dependence of the "quasielastic" and inelastic scattering could be

surveyed. The results are presently being analyzed to assess their

implications concerning the possible quasifree rotation of the NH^"*" ions

in this crystal. Future neutron scattering and diffraction measurements

are planned on both powder and single crystal samples. Low temperature

Raman spectra will also be measured to complement the neutron scattering

experiments

.

LATTICE DYNAMICS STUDIES OF COMPLEX CRYSTALS

CONTAINING LINEAR TRI-ATOMIC GROUPS

R. S. Singh, S. F. Trevino and H. J. Prask

(Picatinny Arsenal, Dover, New Jersey)

Metal azide salts are materials which exhibit a broad range of

crystal stabilities and are thus of a considerable interest for explosive

applications. In the monovalent-metal azide salts, the azide ion (N3) is

linear and symmetric, whereas in the divalent-metal salts the azide

groups tend to be asymmetric and nonlinear; it is the latter type which

are considerably less stable.

The present program is aimed toward gaining an understanding of the

interatomic forces in metal azide salts in order to correlate differences

in bonding and stability. Earlier results have included lattice-dynamical

calculations and preliminary neutron-scattering studies of NaN3 1 and

KN3. 2 Reasonably complete infra-red reflection spectra for NaN3 (D^)

51
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

A2u Eu Crystals

TO LO TO LO TO LO

NaN3 195* 175*

173 243

KN3 138

140*

196 130

130*

154 166 192

RbN3 91

93*

109 123

127*

163

C SN3 85

91*

107 123

126*

163

*IR thin film transmission

TABLE I. kM3 TO and LO phonons of Na- , K-, Rb- and C SN3

. Polarized

reflectivity spectra of single crystals of KN 3 and unpolarized spectra of the pressed pellets of the others were

obtained. Thin film transmission measurements are also

included. Resolution was 2 cm~l with all quantities in cm

- -1".

and KN3 , RbN3 and CsN 3 (all D^) have now also been obtained at room

temperature, and are presented in Table I. Infrared reflection data

have been obtained and are being analyzed for Na and K bifluoride salts,

which are isomorphous to the corresponding metal-azide salts. High

resolution neutron scattering studies are also planned (with J. J. Rush,

NBS) for these salts.

1 H. A. Rafizadeh, S. Yip and H. Prask, J. Chem. Phys. 56, 5377 (1972).

2 K. R. Rao, S. F. Trevino, H. J. Prask and R. D. Mical, Phys. Rev. 4B,

4551 (1971).

52
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

THE CRYSTAL STRUCTURE OF CYCLOTRIMETHYLENE-TRINITRAMINE

C. S. Choi

(Picatinny Arsenal, Dover, N.J.)

and

E. Prince

The compound cyclotrimethylene-trinitramine, commonly known as RDX,

is a well-known explosive. The crystal structure of RDX has been investigated previously by other people using x-ray photographic data. The

present neutron diffraction study was undertaken to complete the crystal

structure by determining the hydrogen positions and refining overall

structural details. A total of 836 reflection data points were collected

within the limiting sphere of 100° in the 26 angle. The structure was refined with anisotropic temperature factors for all atoms to the final

R index, wR = 0.21 and R = 0.039. The final least squares parameters are given in Table 1. The compound crystallizes in orthorhombic space group Pbca, a =

o 13. 182 (2) A, with eight molecules per unit cell. The molecule consists of

alternate CH„ and N-N0o groups in a puckered ring (Fig. 1), the environment of the carbon atoms is essentially tetrahedral, and the N-N0„ groups

are planar. The molecule possesses a plane of approximate mirror symmetry

perpendicular to the plane defined by the three carbon atoms of the C-N

ring. It is interesting to compare the crystal structure of RDX to those

of both a- and 3-HMX (cyclotetramethylene-tetranitramine) , in view of the

close similarity in chemical composition and explosive nature. The bond

lengths and angles of RDX agree well with those of a- and g-HMX, except

for the C-N-C angles, which are approximately 8° smaller in RDX than in HMX. In both compounds, the N-N0„ group planes are bound tightly to the

molecular ring by strong 0. . .H as i^ell as 0...C interactions. Very short

intermolecular distances including weak hydrogen bonds of the type C-H...0

occur in both compounds. The thermal motions of both compounds may be described by rigid body motion of the ring and separate rigid body motion of

the nitro groups.

53
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

m -D

4-1 CO c CM

OJ pa

•H CM

C) •H +

U-J

y-i »<

01 J3 o *

CJ r) •K

(i) 01 .c co

9 +

WH

IH £2 tn Ocm (II •K J3

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54
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Fig. i. A perspective view of RDX molecule.

55
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

THE STRUCTURE OF ANDALUSITE AND SILLIFANITE

L. W. Finger

(Carnegie Institution of Washington, Washington, D.C.)

and

E. Prince

Anadusite and sillimanite are alunimum silicate minerals both of

which have the nominal composition Al„SiO . Nuclear magnetic resonance measurements of the electric field gradients at the aluminum nuclear

positions were in significant disagreement with values computed from the

crystal structures previously determined by x-ray diffraction. The neutron diffraction study was undertaken to see if more accurate values for

oxygen positions in the structures would resolve the discrepancies. A

highly accurate data set was obtained for andalusite and refined to a weighted R index of .026. Because of unavoidable characteristics of the

sample the sillimanite data were less accurate, and the final weighted R

was .045. In both cases there were small shifts in atomic coordinates

which resulted in better fits to the nmr data. A notable feature of the

results was that M-0 interatomic distances for the neutron structures were almost invariably shorter by significant amounts, than the corresponding distances in the x-ray structure. This can be seen in Table 1,

which compares the corresponding distances in andalusite. This result

suggests that there may be a systematic displacement of the electron

clouds around the oxygen atoms so as to make their centers further away

from the cations. It is hoped that a careful x-ray study on andalusite

will allow an accurate determination of the electron density distribution.

56
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

TABLE 1 Andalusite Interatomic Distances - Interatomic distances in

andalusite, as determined from x-ray and neutron diffraction.

Neutron Value, A X-Ray Value, A A(N - X)

Si tetrahedron

?1.TM0{b) 1.635(2)*

Si-O(c) 1.609(2)

Si-O(d) (2x) 1.623(1)

Mean Si-0 1.623

0(b)-0(c) 2.525(2)

0(b)-0(d) (2x) 2.690(2)

0(c)-0(d) (2x) 2.659(1)

0(d)- 2.663(2)

Mean 0-0 2.648

Al octahedron

Ali -0(a) (2x) 1.817(2)

Ali -0(b) (2x) 1.885(2)

Ali -0(d) (2x) 2.079(1)

Mean Ali-0 1.927

0(a)-0(a) 2.445(3)

0(a)-0(b) (2x) 2.780(1)

0(a)-0(d) (2x) 2.770(2)

0(a)-0(d) (2x) 2.739(2)

0(b)-0(d) (2x) 2.835(2)

0(b)-0(d) (2x) 2.791(2)

0(b)-0(b) 2.445(3)

Mean 0-0 2.727

Five-coordinated aluminum

Al -0(a) 1.800(3)

Al -0(c) 1.871(3)

Al -0(c) 1.833(3)

Al -0(d) (2x) 1.814(2)

Mean Al -0 1.826

0(a)-0(c) 2 483(2)

0(a) -0(d) (2x) 2.748(1)

0(c)-0(c) 2.233(3)

0(c)-0(d) (2x) 2.668(2)

0(c)-0(d) (2x) 3.253(2)

0(d)-0(d) 2.896(2)

Mean 0-0 2.772

1.635(5) 0.000

1.615(6) -0.006

1.631(4) -0.008

1.628 -0.005

2.514(7) +0.011

2.704(5) -0.006

2.681(6) -0.022

2.658(4) 0.005

2.657 -0.009

1.829(4) -0.012

1.892(4) -0.007

2.085(3) -0.006

1.935 -0.008

2.476(7) -0.031

2.780(1) 0.000

2.793(6) -0.023

2.738 0.001

2.854 -0.019

2.794(6) -0.003

2.469(7) -0.024

2.739 -0.012

1.816(6) -0.016

1.886(6) -0.015

1.843(5) -0.010

1.818(3) -0.004

1.836 -0.010

2 515(7) -0.032

2.761(5) -0.013

2.247(7) -C.014

2.677(5) -0.009

3.265 -0.012

2.901(4) -0.005

2.785 -0.013

*The estimated standard deviation of the final digit is given in parentheses.

57
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

DISTRIBUTION OF ALUMINUM AND SILICON CATIONS IN A FELDSPAR MINERAL

E. Prince

and

G. Donnay and R. F. Martin

(McGill University, Montreal, P.Q., Canada)

In the 1971 Progress Report we described a structure refinement

carried out on a crystal of the feldspar mineral orthoclase. The distribution of aluminum and silicon between two sites with slightly different, tetrahedral, oxygen environments is commonly used by geologists

as a means of studying the thermal history of the rocks in which the mineral crystals are found. Because of the similarity of their atomic

scattering factors for x-rays, the distribution of Si and Al cations cannot be determined directly from x-ray diffraction data, and mean M-0

distances in the tetrahedron have commonly been used as an indirect measure of this distribution. Our values for these distances, together

with the commonly accepted curve, implied an Al content for the site

designated T(2) of about 0.09. However it came to our attention that

Brown and co-workers of SUNY, Stony Brook, working at Brookhaven, had

successfully determined the distribution directly, in a similar mineral,

by neutron diffraction. We therefore tried a direct refinement with our

data, constraining the total Al and SI contents for the two sites to conform to the overall chemical analysis. This refinement resulted in a small but highly significant reduction in the weighted R index, and gave

an essentially zero value for the Al content in the T(2) site. Figure 1 shows a plot of the mean M-0 distances against Al content for the two sites

in our crystal and the two sites in the Brown et al study, which all lie,

perhaps fortuitously, on a straight line. The dashed line is the one previously used by the feldspar geologists. This result suggests that

the mean M-0 distance is not sufficient information to determine the

cation distribution.

58
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

<

Li 1.68 /

1-

< £f JO

<2 1.66 / ^— O

Q

s'

s£^

1>£F

i As

H 1.64

z hfln

< ^S^S

LLi ^^ / 2

1.62

/

/

i i • i i .2 .3 .4 .5

AI/(AI + Si)

Fig. 1. Mean metal-oxygen distances as a function of Aluminum content

in the tetrahedral sites, for two feldspar studies. The dashed

line has been used by geologists to relate the mean M-0 distance

to the cation distribution.

59
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

THE CRYSTAL STRUCTURE OF

1,3,5 ,7 ,TETRACETO-l ,3 ,5 ,7 ,TETRAZACYCLO-OCTANE

C. S. Choi

(Picatinny Arsenal, Dover, N. J.)

and

B. Dickens

(Polymer Division)

The compound 1 ,3 ,5 ,7 ,tetraceto-l,3 ,5 ,7 , tetrazacyclo-octane (TAT) is

a key intermediate in the production of HMX (cyclotetramethylenetetranitramine) , and commonly labeled as TAT. Preliminary investigation

by precession photographs with MoKa radiation revealed that the crystal

belongs to tetragonal space group P4 2 2 (enantiomorphous to P4„2 2) with

four molecules per unit cell. An automated 4-circle x-ray dif fractometer

equipped with a graphite monochromator to reflect MoKa radiation was used

for the measurement of reflection intensities and for precise determinao tion of the unit cell dimensions, i.e. a = b = 10. 540(2) A and C =

o 12. 137(2) A. The structure was solved by direct methods and refined to a final R-index wR = 0.037 and R = 0.039 for 1244 observed reflections.

The molecule consists of alternate CH and N-CO-CH groups in a puckered

C-N ring, having boat-shape configuration with a two fold rotation axis

through the center of the C-N ring (see Fig. 1). The heavy atoms of

each acetyl group are essentially coplanar with the neighboring nitrogen

atom. The TAT molecule is very similar to a-HMx which also has a boatshape configuration. The bond lengths and angles found here for the C-N

ring generally agree with those of a- and g-HMX. The rigid body thermal

motion analysis by using the aniostropic temperature factors indicate

that the molecular thermal motion is represented by three motions, i.e. a libration about the two-fold rotation axis and two intramolecular

bending motions about the diagonal of the C-N ring.

60
1-1 r*i p. CJ

CM H +

INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

r-t CM CM CO rH <r

CO CO <r <f CM CO rH CO CO CM <r rH o CO i

o r-{ CM

<r CO in tH vO

CO --r <f CM

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vO rH CO

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jH ^ ^cocmcoco-^cmcmcm

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v£) cm cm <r H

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0) CM

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a.CM £"* rHC^rHrHCMCMrHrH-Hr-^

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0) ,C

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61
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

C(6)

0(2)

0(1) C(3)

C(2)

C6 >4^ w2^^6

Fig. 1. The TAT molecule viewed from side and top of the molecule.

62
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

MAGNETIC STRUCTURES OF EUl Gd S 1-x X

S. Pickart and H. A. Alperin

(Naval Ordnance Laboratory, White Oak, Md.)

The rare-earth chalcogenide EuS is a ferromagnetic insulator, while

GdS is a metallic antiferromagnet . Mixtures of these two materials therefore offer an opportunity to study magnetic behavior of a system showing a complete range of transport properties. Furthermore, the system has a simple face-centered cubic lattice with both rare earth atoms having

identical spin-only magnetic moments (in a half-filled 4-f shell) , thus

encouraging theoretical analysis.

Our previous neutron diffraction measurements 1 showed that GdS has

the second type of antif erromagnetic order, with both first and second

neighbor interactions negative. This is presumably because of the

s-electron polarization (RDDY exchange) , while the ferromagnetic alignment in EuS is believed to result from localized (Heisenberg) exchange

forces. Magnetic measurements 2 on the mixed system Eu^_xGdxS showed

drastic changes for small x in the ordering temperature, but the saturation

magnetization behaved as though the Gd moment were not contributing, i.e. as simple dilution.

To understand this effect we investigated the magnetic alignment by

means of neutron diffraction in samples with x = 0.1, 0.2, 0.3, 0.6 and

0.8. The results, some of which are plotted in Fig. 1, show three ranges

of different behavior: only ferromagnetic alignment for x = 0.1 - 0.3,

only antif erromagnetic (GdS type) for x = 0.8, and negligible long-range

order of any type for x = 0.6. Small angle scattering, due to short-range

order, was observed in all samples. Consequently, we must conclude that

the magnetic structures in this mixed system are inhomogeneous, probably

forming clusters of Gd spins that are locally anti-parallel (and thus do

not contribute to the net moment) , but with the clusters not correlated on

a long-range basis.

1 1. McGuire, R. Gambino, S. Pickart and H. Alperin, J. Appl. Phys. 40,

1009 (1969).

2 T. McGuire and F. Holtzber, AIP Conf. Proa. 5_, 855 (1972).

63
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Eu,_ x Gd x S

I4K _ I?7K

(III) (200)

I I

1000

'^^ .'; V- *••>.

'—.

X=0.2

COz

o

tr

yUJ

1000

2000

1000

(1/2 1/2 1/2)

I

X=0.6

(3/2 1/2 1/2) (3/2 3/2 1/2)

I I

X=0.8

10 15 20

20 (DEG)

25 30

Fig. 1. Magnetic intensity (data at 77K subtracted from data at 4K)

for three samples in the Eu 1 _x

Gdx

S system. Reflections with

integral Miller indices are due to ferromagnetism, those with

half-integral indices to antiferromagnetism of the type found

in pure GdS.

64
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

PHONON DISPERSION IN hcpBe

H. Alperin, S. Pickart and J. Rhyne

(Naval Ordnance Laboratory, White Oak, Md.)

Be metal has a very high strength-to-weight ratio and heat capacity"

it is therefore useful in aerospace applications, and would be even more

so were it not so brittle. The ductility of polycrystal Be is known to go through a marked maximum at 440°C, and this has recently been correlated

with an anomaly in the lattice expansion1 in a single crystal. In order

to search for the microscopic origin of these phenomena, we have begun a study of the temperature dependence of the phonon spectra in single crystal

Be using neutron inelastic scattering. Correlation of interatomic force

constant changes with ductility might conceivably suggest methods of

enhancing the desirable properties of Be. Room temperature measurements have been completed for two propagation

directions, along the c-axis (shown in Fig. 1) and in the [1120] direction

in the basal plane. These data are much more accurate than previous

measurements2 and show no evidence of the Kohn anamolies predicted by a recent pseudopotential calculation3 (in contrast to the tensor force

constant model, which predicts smooth curves) . High temperature measurements are now in progress

.

1 F. Wang (private communication)

.

2 C. Thaper et al. , Proa. Intl. Conf. in Rennes, 1971; R. Schmunk,

Phys. Rev. 149 , 450 (1966).

3W. King and P. Cutler, S. S. Comm. 7_, 295 (1969).

65
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

>Q>

UJ

3U

80 ° C^-<x L0

70

60

| TO cS

50

40 /LA y^

30 / /

TA

20

/ / Be

1 // [0001]

.2 .3 q q max

.5

Fig. 1 Energy transfer (E) vs. reduced wavevector for longitudinal and

transverse acoustic and optic phonons propogating along the

c-direction in hep/Be.

66
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

SOFT-PHONON MODE BEHAVIOR IN PbTe

H, Alperin, S. Pickart and J. Rhyne

(Naval Ordnance Laboratory, White Oak, Md.)

and

V. Minkiewicz

(University of Maryland, College Park, Md.)

In recent years, a controversy has arisen as to whether or not

the compound semiconductor PbTe exhibits paraelectric behavior, i.e., a Curie-Law temperature dependence of the dielectric constant. This

characteristic, which might ultimately lead to a ferroelectric transition,

would be important for potential dielectric-constant related applications.

Cochran's theory of ferroelectricity relates the spontaneous polarization

acquired in the ferroelectric state to the tendency for certain types of

lattice vibrations to lower their energy or become "soft" as the temperature is lowered, ultimately becoming "frozen in" at the transition.

Since inelastic neutron scattering is the only direct method of observing

these effects, we have carried out a study of the PbTe vibrational

spectrum over an extended temperature range (300 to 4.2 K) , using this

technique.

Our results, summarized for the [111] propagation direction in Fig.

1, reveal that the longitudinal optical mode vibration is essentially

temperature independent, while the corresponding transverse optical

mode decreases strongly as the temperature is lowered. The latter does

not reach zero, however, so that the PbTe behavior is paraelectric, but

not ferroelectric. These measurements confirm the temperature dependence

of the static dielectric constant in PbTe which had been implied by an earlier experiment, and they explain how carrier mobilities in PbTe can reach such unusually high values at cryogenic temperatures.

67
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

J=

CJC

• ca

to u

01 ^

u3 CJ

4-> •H

cd 4-1 u ft

0) o

fte .H

0) cd

4-> C

•H O T) £ 3

J-l 4-1 •H u M

cd Co

0) H-l H

& •—

fin Xi c

•H ,co

CO c

01 cd > u n ,£> ao o

•H c 4-1 o ft

•H O

enn QJ

a) CO ft ^J CO Q) •H >

T3 COC

a cd o u

e H

-n ^N

Pj cd

60

•H

CD CD (A9UJ) 3

68
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

OBSERVATION OF AN AMORPHOUS SPIN DISTRIBUTION

J. Rhyne, S. Pickart and H. Alperin

(Naval Ordnance Laboratory, White Oak, Md.)

Neutron diffraction measurements made on a sputtered sample of

composition TbFe2 have provided the first direct evidence for an amorphous

spin distribution, i.e. a magnetically polarized state formed from atomic

spins with no spatial periodicity.

Previous classes of materials believed to be amorphous magnets are transition metal-loaded phosphorus glasses 1 and ternary Fe-Pd-C alloys 2

prepared by a variation of splat cooling. Neutron diffraction measurements made on the first class were either inconclusive or showed microcrystalline phases; the ternary alloys can be prepared only in thin foils

of micrometer thicknesses and are not suitable for the neutron scattering

technique (which is unique in that it measures the spin distribution

directly by the interaction of the neutron spin with the atomic moments)

.

Magnetic measurements on the sputtered TbFe2 sample show a welldefined Curie point at 388K and a saturation moment at OK of 2.8 yg per

molecule, both substantially lower than the values for the crystalline

TbFe2 phase. Neutron data were taken at 423K, in the paramagnetic region,

and at 4K, where maximum polarization is attained, both patterns showing

a broad diffuse maximum characteristic of amorphous materials but shifted

significantly at lower temperatures. The difference between these two patterns, seen in Fig. 1, is due to the magnetic scattering alone.

These data show unequivocally that the spatial distribution of the

magnetization in this material is amorphous or liquid-like. Without

further involved analysis, not much can be said about its exact nature,

other than that it is not simply ferromagnetic (each atom having the same average moment) or f errimagnetic (rare earth and iron moments antiparallel)

,

as in the crystalline phase.

Of particular interest is the small angle scattering in Fig. 1, which

is not observed in the data taken above the Curie point. It indicates an inhomogeneity or clustering in the magnetic structure which is not related

to any inhomogeneity in the atomic structure, perhaps intrinsic to the

69
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

magnetic amorphous state. Further measurements with applied magnetic

fields are in progress, and attempts will also be made to observe critical

scattering and spin-wave scattering to get information concerning the

dynamics in amorphous magnets.

TbFe2 (Sputtered) MAGNETIC INTENSITY 4K-423K

3.4 . . 4.4

K(A"')

Fig. 1. Magnetic vs. scattering vector (low temperature data minus

high) in sputtered TbFe„ . Arrows show the location of the

principal peaks in the crystalline TbFe„ phase.

l T. Egann et al., J. Fhys. C: Solid State 5_ (to be published).

-T. Sharon and C. Tsuei, Phys. Rev. B5_, 1047 (1972).

70
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

CRYSTALLINE ORDERING IN SILICA AND GERMAN I A GLASSES

J. H. Konnert, J. Karle, and G. A. Ferguson

(Naval Research Laboratory, Washington, D.C.)

Two limiting models have been proposed for glasses; in one model 1

the material is depicted as composed of small regions of crystalline-like

order bonded together in essentially random orientations and, alternatively,

another model of glass structure is described as a random network2 in

which the distribution of only the shortest interatomic distances corresponds throughout the material to those present in a crystalline phase.

Diffraction analyses performed on the glasses of silica 3-6 and germania 5 > 7

have been generally interpreted in terms of the random network model.

X-ray diffraction data were collected with MoKa radiation using fused

quartz and fused silica from vapor phase hydrolysis of pure silicon com- pounds ("infrasil" and "suprasil", respectively, prepared by Amersil Inc.).

All data sets produced nearly identical radial distribution functions

o (RDF's). Neutron diffraction data were collected at a wavelength of 0.84A.

The RDF's are illustrated in Fig. 1. Significant deviations from a uniform

o distribution of distances are present out to at least 20A.

Full details of the data reduction will be published elsewhere.

However, since this procedure has revealed previously undetected details

in the RDF's, the main points of the procedure will be mentioned. The

basic considerations concern the imposition of constraints on the RDF. 8 That portion of the total intensity function that contains interatomic

distance information, i(s), is isolated in a manner described for electron

diffraction. 9 The truncation problem is handled by recognizing that

in the usual experiments only the shortest distances are sufficiently

ordered to contribute to i(s) beyond the experimental limit of data

collection. These short distance (SD) contributions are removed from i(s)

by a least squares procedure that minimizes the spurious detail in the RDF

at small and large values of r. The equation employed is:

71
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

?ir f

SmaX V N-: •f i

f i exp(-^?.S 2 /2)

r

2 D(r)=4^r2 (p(r)-p ) = ^ s Ki(s)-L J J 3 sinsr

r J SD sr-rj f

2

, sinsrds

3r ii UC

+ SD contributions

where s = (4iTsin6)/A, A is the wavelength, 20 is the angle between the

incident and diffracted beam, K places the intensity on an absolute scale,

r^j is the distance between the ith and jth atoms, N-jj is the coordination

number, fcy is the disorder parameter, UC is the unit of composition (Si02 or Ge02) , smax is the experimental limit of data collection, the f's are

the atomic scattering factors, p is the density parameter, and 4-rrr 2

p (r)

is the probability weighted by the scattering factors of finding atoms in

the sample separated by the distance r. The short distances are reintroduced without associated truncation effects into the final RDF. RDF's were calculated for crystalline forms by broadening the Bragg

maxima in the powder patterns to correspond to an 11A particle size for

o 3/4 of the sample and a 20A size for 1/4. Such broadening reduces the

amplitudes of the RDF without altering the positions of the peaks, thus

affording a suitable approximation to the RDF corresponding to small

ordered regions. If the dimensions of these regions are less than the

unit cell dimensions, this corresponds to all configurations in the unit

cell being represented by different particles.

Atomic parameters obtained from crystal structure analyses were used

to calculate the diffraction patterns for quartz 1 ® and cristobalite. *

* Since tridymite forms highly twinned crystals with a variety of unit cells

o o o (all with a sub-cell of approximate dimensions a = 8.7A, b = 5.0A, c = 8.2A),

accurate atomic parameters are not available. The average structure has

been determined at 250°C and provides evidence for the bonding topology. 12 A powder diffraction pattern collected with a sample of tridymite from

Diamond Lake, Douglas Co., Oregon showed orthorhombic diffraction symmetry

o o ° with a = 81.97A, b = 9.94A, c = 17.23A. The approximate weight percent of

impurities, as indicated by electron probe analysis, are A1^2%, Na^l%, and

K^l%. Accurate atomic positions have not been determined for the crystalline polymorphs of germania. The neutron powder diffraction patterns for

72
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

quartz-like and cristobalite-like germania were calculated with the use

of the atomic coordinates of quartz and cristobalite and the appropriate

scattering factors for neutrons.

The r

3 D(r) curves are illustrated in Fig. 1. The x-ray RDF for

silica glass is quite similar to the RDF obtained from the powdered

tridymite, but quite different from the RDF's derived from cristobalite

and quartz. The positions of the maxima in the silica glass RDF's obtained

from neutron and x-ray diffraction data are nearly the same, indicating

that the distances tend to cluster similarly. The germania glass RDF

obtained from the neutron diffraction data is very similar to the silica

glass RDF obtained from the x-ray data. The Ge and atoms scatter neutrons

with approximately the same relative efficiency as Si and atoms scatter

x-rays, as illustrated by the similarity of the neutron diffraction RDF's

calculated for quartz-like and cristobalite-like germania to x-ray RDF's

of quartz and cristobalite. Thus the RDF's strongly suggest that silica

glass, germania glass, and tridymite posses the same short-range order.

The correspondence of the positions and magnitudes of the details in

the RDF's obtained for silica glass and tridymite-like particles indicates

that the data are consistent with a structure in which nearly all of the

atoms comprise parts of tridymite-like regions having dimensions ranging

o up to at least 20A. Details at large r suggest the possibility of a small

amount of cristobalite-like ordering. The relatively large details in the

outer portion of the RDF for silica glass from the neutron diffraction

data may arise from the oxygen atoms, the dominant neutron scatterers,

lying on the periphery of the ordered regions. However, the larger sample

used for the neutron diffraction experiment may, in fact, be more highly

ordered.

If the interpretation that nearly all atoms are part of ordered

regions is correct, it is required that these regions be efficiently

bonded together in a manner analogous to twinned crystals, but with a fairly large number of relative orientations and small distortions so that

isotropic properties would ensue. Differences in the inner regions of the

RDF's of silica glass and tridymite computed from the x-ray diffraction

73
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

5

SILICA GLASS

X-RAY

SILICA GLASS

NEUTRON

TRIDYMITE X-RAY

CRISTOBALITE

X-RAY

QUARTZ

X-RAY

GERMANIA

CRISTOBALITE

NEUTRON

"-tA"

15 20

Fig. 1. Radial distribution functions for silica and germania

glasses and comparision functions derived from the

broadened powder patterns of crystalline polymorphs.

74
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

data can be related to the junctures between the ordered regions. The

three shortest distances throughout the glass samples are nearly identical

to the corresponding distances in all of the crystalline modifications

where the silicon atoms are tetrahedrally bonded. The contribution to the

RDF from distances between atoms in different ordered regions would be

o progressively less as r increases, and after about 6A they would not

contribute any appreciable details.

While radial distribution functions of glasses do not alone provide

enough information for a unique structure determination, the comparisons

with the functions calculated from crystalline phases of nearly the same density as the glasses imply a great similarity between glasses and

crystals on the atomic level.

X N. Valenkov and E. Porai-Koshits, Z.Krist. 91, 195 (1936).

2W. H. Zachariasen, J. Am. Chem. Soo. 54, 3841 (1932).

3 C. Carraro, M. Domenici and T. Zucca, in Physics of Non-Crystalline

Solids, J. A. Prins, Ed. (North Holland Publ. Co., Amsterdam, 1965)

pp. 152-161

4 E. H. Henninger, R. C. Buschert and L. Heaten, J. Phys. Chem. Solids

28, 423 (1967).

5 E. Lorch, J. Phys. C 2, 229 (1969).

6 R. L. Mozzi and B. E. Warren, J. Appl. Cryst. 2, 164 (1969).

R. L. Mozzi, Ph.D. Thesis, Massachusetts Institute of Technology (1967).

7G. A. Ferguson and M. Hass, J. Am. Ceram. Soo. 53, 109 (1970).

8 I. L. Karle and J. Karle, J. Chem. Phys. 17, 1052 (1949); 18, 957,

963 (1950).

9 P. D'Antonio, C. George, A. H. Lowrey and J. Karle, J. Chem. Phys. 55_, 1071 (1971).

10 R. A. Young and Ben Post, Acta Cryst. 15, 337 (1962).

nW. A. Dollase, Zeit. Krist. 23, 617 (1967).

12W. A. Dollase, Acta Cryst. 23, 617 (1967).

13We thank Mr. L. Paollela for his aid in collecting the neutron diffraction

data. The research was supported in part by the Advanced Research Projects

Agency

.

75
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

PRECISION MEASUREMENT OF THE THERMAL NEUTRON

SCATTERING AMPLITUDE FOR SILICON

C. S. Schneider

(U. S. Naval Academy, Annapolis, Md.)

Measurements have been completed this year on the refractive shifts

of a nearly monochromatic (3.2A) neutron beam resulting from passage

through a right angled prism of silicon. This first result, b (Si) = 4.152(2) fm, is in good agreement with Shull's determination from the

Pendellosung effect in Bragg reflection from silicon and corrected for

the Foldy charge interaction: b

>T (Si) = 4. 1491 (10) fm.

The spectrometer has since been resuspended, by cables from above

replacing pneumatic tubes below, to improve the angular stability. The

o wavelength has also been increased to about 4.2A so that better advantage

may be taken of the full range of the torsion goniometer used in defection

measurements.

A precision (1/4 second arc) indexing goniometer head has replaced

the continuous sine-arm goniometer used for prism orientation and for

initial wavelength calibration; in this second mode the indexing head is

seated on a sine-arm which is driven by the computer-automated stepping

motor. With these improvements in the double crystal spectrometer, it seems quite feasible to obtain an accuracy of .001 fm in neutron scattering

amplitude determination. Since the prism determination includes only the

nuclear force contribution of the nucleus, due to the forward scattering

and unpolarized neutron spin, there are no corrections necessary for

other interactions possible when neutrons pass through matter. In particular, there is no Foldy charge contribution to the measured

amplitude so a comparison of this determination with Shull's uncorrected

value gives new experimental verification of the existence of the Foldy

interaction.

It is for later experiments to extend these comparisons to higher

accuracy leading to a possible clarification of the present discrepancy

between the recent Ringo-Krohn determination and the Foldy-predicted

amplitude of interaction between the neutron and electron.

76
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

TO DETECTOR

PERFECT Si(lll) MONOCHROMATOR

ASYMMETRICALLY

CUT.

PERFECT Si(lll) ANALYZER

ASYMMETRICALLY CUT.

SILICON- PRISM -I REFRACTIVf

SHIFT y

FROM REACTOR

Fig. 1. Schematic diagram of neutron optics in double perfect crystal

spectrometer.

ADJUSTABLE

SLIT/

Si (III > ANALYZER

INTERFEROMETER ' n TORSION p TT ^ rn

GONIOMETER

SILICON PRISM Si(lll) PRISM GONIOMETER MONOCHROMATOR

/

JX1

Fig. 2. Schematic diagram of control systems in double perfect

crystal spectrometer.

77
D. Non-RRD NBS Programs

ACTIVATION ANALYSIS SECTION: SLURRY OF ACTIVITIES

P. D. LaFleur

(Analytical Chemistry Division)

The Activation Analysis Section of the Analytical Chemistry Division

is physically located in the NBS Reactor Building. A complete description

of the Section's activities may be found in its annual progress report,

NBS Technical Note 588. Therefore, only a brief summary of some of the

work will be included here, with an emphasis on the NBSR characterization

work.

1. Standard Reference Materials (SRM)

Much of the section's efforts have been directed toward the development of high precision and high accuracy in neutron activation analysis,

with a primary aim being the analysis and certification of NBS Standard

Reference Materials.

a. Biological SRMS - The biological SRMs analyzed include Orchard

Leaves (SRM 1571) and Bovine Liver (SRM 1577) mentioned in last years T s report, and several new materials as well. These new biological materials

include Mercury in Tuna (SRM 1578), Tomato Leaves, as well as preliminary

work on a standard blood serum SRM.

b. Environmental SRMs - The environmental SRMs analyzed by neutron

activation analysis this year include Mercury in Coal (SRM 1630) , and preliminary analyses for trace elements in gasoline, residual fuel oil, coal

and fly ash.

c. Other SRMs - A wide variety of other types of SRMs were analyzed

by neutron activation analysis. A few of these materials include stainless steel, high purity iron, molybdenum concentrate, graphite, and

titanium. Some of the elements determined in one or more of the above

materials include gold, silver, rhenium, nickel, aluminum, iron, vanadium,

chromium, manganese, tantalum and titanium.

78
NON-RRD NBS PROGRAMS

2. Cooperative and Service Analyses

In addition to the analyses on SRMs, a large number of additional

analyses were made on non-SRM materials. These include cooperative

analyses, where the analysis is made on samples furnished by other

laboratories. In the past year such samples have included high purity

silicon, high purity iron, ion exchange resin, alveolar macrophages, and

single crystal magnesium oxide. A few of the elements determined include

gold, cobalt, iridium, manganese, scandium, zirconium, hafnium, tungsten,

and europium.

3. Radiochemical Separations

Many of the analytical determinations made by the section require a radiochemical separation to obtain the accuracy and precision necessary

for certification as standard material. To this end, there is always

research on radiochemical separations taking place, striving to improve

existing procedures or to develop new and better ones. Work this year

includes additional development of procedures using di(2-ethylhexyl)

phosphoric acid (HDEHP) as an extractant, and a new volatilization procedure in which a rapid quantitative separation of zinc, arsenic,

selenium, cadmium and mercury after neutron activation is performed.

Considerable work has been done in the application of reversed phase

chromatography using HDEHP on an inert base as the stationery phase, for

separations of the individual rare earth elements.

4. 25 Californium Neutron Source

Further studies on the applicability of 252 Cf sources to neutron

activation analysis include the evaluation of the 207mpb isotope (Ti/2=

0.8s) for the rapid screening of paint samples for lead content. This

procedure presently requires repetitive irradiation and counting cycles

252 for marginal results. However, with a considerably upgraded Cf sourc this analysis procedure may provide a very useful screening technique.

79
NON-RRD NBS PROGRAMS

5. Nuclear Track Technique

Further investigations into the applicability of the nuclear track

technique are in progress. Currently the elements which may be quantitatively determined using this technique include nitrogen, lithium, boron,

uranium, and thorium. During the past year analyses by this technique

included lithium and nitrogen in biological samples, boron in graphite,

and uranium and boron in lunar samples

6. Characterization of the NBSR

Since the initial startup of the NBSR in 1967, an extensive program

of reactor characterization has been in progress. This program has been

largely carried on through the efforts of the Activation Analysis Section,

primarily because of the striving of our group for the highest possible

precision and accuracy.

Many of the results shown here were published in part in the

Activation Analysis Section's previous progress report, NBS Technical

Notes 508 and 548, but have been recently updated or supplemented.

Figure 1 shows the results of the flux dropoff for each of the five

pneumatic tube facilities (rabbits) . Three of the rabbits have linear

flux dropoffs, with two non-linear. RT-4 shows the greatest dropoff, over 40% from end-to-end. Figure 2 shows the circumferential flux variation in each of the rabbit facilities. These results show very little

side-to-side variation for RT-1 through RT-3, with a slight variation

(< 4%) for RT-4. However, RT-T, the thermal column rabbit, has side-toside variation approaching 20%. Some preliminary results for the integral

fast neutron spectra for RT-1 through RT-4 are shown in Fig. 3. These

results, made using threshold foils, seem to indicate a curve shape very

similar to that of a pure fission spectrum. Further studies are in progress to elucidate the spectral shapes at neutron energies < 2MeV. The

flux distribution of the vertical thimble G-2 is shown in Fig. 4 with

copper-cadmium ratios [Cu(Cd)] shown for several locations. The circumferential flux distribution in G-2, while not shown was found to be less

than ± 3% outside of the core area (including core gap area) , but up to ±20% within the core area.

80
NON-RRD NBS PROGRAMS

2 3 4 5 6 7 DISTANCE FROM PROXIMAL END (CM)

Fig. 1. Axial neutron flux drop off

POSITION RT-1

102-

RT-4 POSITION

•

• • •

.98

1D2

1.00—a-*-#

-«-.-» —•-•-•-•-,-;

110- BOTTOM 1.00-

MIDDLE 1.00

.98

102

DISTAL 1.00

-,-«-•-

1.10- MIDDLE 1.00

~~ ^•^-T»^ a— -• top l.ooFig. 2. Relative circumferential flux distribution for NBSR pneumatic

tubes.

81
NON-RRD NBS PROGRAMS

234 567 89 10 II NEUTRON ENERGY (MEV)

12 13 14

Fig. 3. Integral fast neutron flux data as determined by preliminary

threshold foil measurements in the NBSR pneumatic tubes, com- pared to an unmoderated 235U fission spectrum.

82
NON-RRD NBS PROGBAMS

V

-/-

J\

\

CU(CD)

1830-

/

/

/

/

UPPER

CORE

CORE GAP 55-

LOWER

CORE 33-

84'

100 90 80 70 60 50 40 30 20 10

PERCENT OF MAXIMUM

FLUX

70

65

60

55

50

45

40

HEIGHT

35

(IN.)

30

25

20

H 15

Fig. 4. Neutron flux distribution in vertical thimble G-2

.

83
NON-RRD NBS PROGRAMS

7. Conclusion

The Activation Analysis Section of the Analytical Chemistry Division

has been involved with the analysis of a wide variety of sample types for

a large number of different elements. Work is continuing in most of these

areas, as well as on a number of fundamental studies in the field of

activation analysis.

THE CAVITY FISSION NEUTRON SOURCE

A. Fabry

(CEN-SCK Laboratory, Mol, Belgium)

and

J. A. Grundl

(Nuclear Radiation Division)

Extensive neutron transport computations of wall-return flux intensity and spectrum have been carried out by a visiting staff member from

the CEN-SCK Laboratory at Mol, Belgium. These computations, part of a joint effort to establish intense fluxes of pure fission neutrons, make

it possible now to estimate reliably the wall-return background at the

cavity Fission Neutron Source Facility. A paper presenting the results

of these computations will be presented in November at the Washington

Meeting of the American Nuclear Society. The following is an excerpt

from the published summary of this paper:

"Wall-Return Neutron Fluxes for High- and Intermediate-Energy

Cavity Neutron Sources." A. Fabry (CEN-SCK), D. J. Jenkins (ORNL)

Spherical cavities in graphite thermal columns of nuclear

reactors provide an ideal environment for the production of

comparatively intense, energy distributed neutron fields, i.e.,

either intended pure fission neutron spectrum sources or intermediate-energy standard neutron spectra. Cavities of 50 cm diameter are used in various laboratories; a 30 cm diameter

cavity is operated at NBS and a 1 meter diameter cavity has

recently been implemented at CEN-SCK.

84
NON-RRD NBS PROGRAMS

Numerical computations of graphite wall-return neutron

spectra have been performed by means of the discrete ordinates

multigroup method in one-dimensional spherical geometry. The

evaluated nuclear data files KEDAK, ENDF/B version 2, and ENDF/B

version 3 have been used and the convergence of the S multigroup multitable treatment has been established systematically.

Within the cavity, a good approximation of the wall-return

<j>w

(r,y, E;r

g

) = <j>w

(E) .

This relationship is correct to better than 2% for r, r - R/2

where R is the cavity radius and r

g the radius of a thin, fission

spectrum source shell. This fundamental property has led to the

development of an experimental method for determing wall-return

backgrounds. A comparison of such experiments with theory will

be discussed.

MEASUREMENTS WITH THE NBS DOUBLE FISSION CHAMBERS

J. A. Grundl

(Nuclear Radiation Division)

A number of fission rate measurements with the NBS double fission

chamber have been performed for both the NBS Neutron Standards Program

and for the AEC's Interlaboratory LMFBR Reactor Rate Program (ILRR)

.

Fission rate determinations with the chambers in the thermal beam at the

NBSR thermal column have been an essential support for all of these efforts.

The activities at the thermal column may be briefly summarized: (1) performance maximization and check-out of two chambers, one for absolute

fission rate measurements for the ILRR Program at the CFRMF reactor in

Idaho, and the second for intercomparison measurements in the IE Standard

Neutron Facility at the CEN-SCK Laboratory (Mol, Belgium); (2) thermal

239 235

neutron weighing of Pu, U, and normal-U fission foils; (3) intercomparison of the NBS double fission chamber with fission track detectors

developed at the Argonne National Laboratory.

85
NON-RRD NBS PROGRAMS

EXTREME-ANGLE EMISSION OF LONG-RANGE ALPHA PARTICLES IN THE

THERMAL NEUTRON FISSION OF

235

U

I. G. Schroder

(Nuclear Radiation Division)

An experiment has been performed in order to seek a correlation

between the kinetic energy of long-range alpha particles emitted at extreme angles (0°<0<30°, 180°f0fl50°) with respect to the line of emission of the light fission fragments and the kinetic energy of the fisson

fragments. An annular surface barrier detector (alpha detector) subtended

an angle of ±30° at the target ( 235U) with respect to a fission fragment

detector placed behind the annular detector. An annular aluminum foil was introduced between the alpha detector and the source. This let through

alpha particles ~ 6 MeV but stopped all fission fragments. A coincidence

circuit (15ns resolving time) demanded coincidence between the two detectors. The output from these was displayed on a 2-dimensional PHA. The results obtained show that extreme-angle alpha particles have higher

than average kinetic energies (>20 MeV) and rate of emission. Furthermore,

these alpha particles are associated with fission fragments in the region

of minimum kinetic energy between the light and heavy fission fragments.

A SEARCH FOR DOUBLY RADIATIVE N~P CAPTURE

R. G. Arnold and B. T. Chertok

(American University, Washington, D.C.)

and

I. G. Schroder

(Nuclear Radiation Division)

and

J. L. Alberi

(Harvard University, Cambridge, Mass.)

It has been suggested that the long-standing discrepancy of 24 mb

between the measured and the calculated thermal np capture cross sections

might be ascribed to captures leading to emission of two photons. An

86
NON-RRD NBS PROGRAMS

experiment has been performed. Gated prompt- and delayed-coincidence y spectra were obtained with two 2" x 2" NaI(T£) detectors using a H2O

target and a D2 target for background exposed to a beam of thermal

neutrons from the NBS reactor. The result is that no two photon captures

are observed at the 1 mb level, so the long-standing discrepancy still

remains. Analysis of data is in progress to reduce this upper limit in

order to test for the presence of an orthogonality breaking 3 S > 3 S + y transition. A calculation predicts an upper limit of 42ub for 3 S > 3 S +

2 Y .

! R. J. Adler, B. T. Chertok, and H. C. Miller, Phys. Rev. C23 69 (1970).

R. J. Adler (in press).

PARITY VIOLATION IN NEUTRON-CAPTURE Y-RAYS

J, L. Alberi and Richard Wilson

(Harvard University, Cambridge, Mass.)

and

I. G. Schroder

(Nuclear Radiation Division)

The program to study parity violation due to the weak interaction in

the overall nucleon-nucleon interaction (weak forces between nucleons) is

continuing in collaboration with Harvard University. The results obtained

with the reaction 113 Cd (n,y) 111+ Cd have been reportedWe have measured the circular polarization of y rays from thermal

neutron capture in 113 Cd and find a P = (6.0 ± 1.5) x 10 for the com- bined 8.51- and 9.04-MeV transitions. This value was measured using a transmission Compton polarimeter and pulse-counting technique. The value

confirms the existence of parity-nonconserving terms in the inter-nucleon

force. A search is being conducted for other nuclei which have neutron

capture states which are no longer eigenstates of parity and, therefore,

exhibit small parity impurities similar to those in cadmium.

1 Phys. Rev. Letters 29_, 518 (1972).

87
NON-RRD NBS PROGRAMS

IN-CORE FAST-NEUTRON MEASUREMENTS USING A

3HE SEMICONDUCTOR SPECTROMETER

J. C. Glynn

(U.S.A.E.C., Washington, D. C.)

and

F . J . Munno

(University of Maryland, College Park, Md.)

and

I. G. Schroder

(Nuclear Radiation Division)

The need to accurately determine reactor spectra (>0.5 MeV) has

become increasingly important with the advent of fast breeder reactors.

This need is particularly true in the study of fast fluence effects on structural materials and, in the calculation of spectral-dependent

parameters (Doppler coefficients). However, the inability of fast-neutron

spectrometers to operate in reactor environments (sensitivity to high

gamma fields) has made an accurate in-core determination of reactor spectra

unfeasible. To circumvent this problem a collimating system was designed

and built to scatter neutrons from the core of the NBS reactor and extract

a neutron beam which, in turn, could be related to the in-core spectrum.

A ^He semiconductor fast-neutron spectrometer was chosen to study the

emergent spectrum because of its high resolution, fast response, and wellcontrolled geometry. The incident beam was parallel to the surface of two semiconductor detectors and collimated such as not to strike either. This

minimized gamma sensitivity and fast-neutron damage. The sensitive volume

between the two detectors could only "see" a scatterer placed at the bottom

of the collimating assembly and adjacent to a fuel element. Three different

scatterers - carbon, aluminum, and lead - were chosen to maximize the

effect of the differential scattering cross section on the experimental

data. Figure 1 shows the data obtained for the carbon and lead scatterers

after corrections for background, detector efficiency, and resolution.

Calculations were made to determine both the scalar and vector fluxes.

By performing a series expansion of the vector flux, the expansion coefficients can be calculated, in principle, from the data obtained from each
N0N-RR3 NBS PROGRAMS

ENERGY, KeV

572 912 1252 1592

O CARBON SCATTERER PRESENT

A LOAD SCATTERER PRESENT

20 40

CHANNEL NUMBER

60 80

Fig. 1. Spectrometer response,

89
NON-RRD NBS PROGRAMS

scatterer. However, the errors in the known differential cross sections

and the experimental uncertainties masked the small differences obtained

in the data. To obtain the scalar flux, the assumption was made that

anisotropies in the flux were the same at all energies. » 2 With the

additional assumption that a negligible AE occurs for a neutron in an elastic collision with lead, an average angle of scatter was estimated

based on the difference between the low energy peaks in Fig. 1. The data

for carbon were then corrected for the neutron energy loss during scattering and the scalar flux calculated directly, as carbon is a highly

isotropic scatterer. These results indicate that an in-core flux can be

measured to an accuracy of 25%. To reduce this uncertainty, further

knowledge of both scattering cross sections and collimator characteristics

is needed. As a by-product of this study, an intense external reactor

beam has been obtained which can be of great value to study fast-neutron

spectrometers and can provide a facility where experimentalists can intercompare different instruments.

! R. J. Cerbone and K. D. Lathrop, "Sn Calculation of Highly Forward

Peaked Neutron Angular Fluxes Using Asymmetrical Quadrature Sets,"

Nucl. Sol. Eng. 3 35, 139 (1969).

2 D. R. Metcalf and P. F. Zweifel, "Solution of the Two-Group Neutron

Transport Equation - I, II," Nucl. Soi. Eng. ,33, 307 and 318 (1968).

PRECISION MEASUREMENT OF THE C0MPTON WAVELENGTH OF THE ELECTRON

W. C. Sauder, E. G. Kessler and R. D. Deslattes

(Quantum Metrology Division)

The purpose of this experiment is to determine the Compton wavelength by means of precision crystal diffraction spectroscopy of the

radiation emitted in two-photon annihilation of positronium. This will

yield a non-quantum electrodynamic determination of the fine structure

constant at the one ppm level.

Activity in the past year has consisted principally of assembling

the apparatus in the Reactor Building. A two-axis, Laue case trans90
NON-RRD NBS PROGRAMS

mission crystal diffraction spectrometer, perhaps the most critical

element in the experiment, is now in place in the experimental area. This instrument which was designed and fabricated at NBS is capable of

-4

Bragg angle sensitivities of better than 10 arc-sec. The spectrometer

rests upon an air-supported table in a temperature-controlled chamber

located in the NBS Reactor Building. This location for the experiment

was chosen in order to make (relatively) straight-forward the transfer

64 of the necessary 20 kilocurie Cu source from the reactor vessel to the

experimental area. The installation of the spectrometer and its peripheral equipment

(detector assembly, source positioning machinery, electronics, etc.) is

nearly completed, so that in the near future a preliminary measurement

198

of the 412 keV line from Au can be undertaken. Other nuclear gamma

lines also will be measured.

The source cryostat that will provide a 7 K annihilation environment

for positronium formed subsequent to the 3+ decay of the high intensity

copper source has been designed and presently is under construction.

The coming year should see the first of the annihilation data forthcoming from the experiment

.

60Co GAMMA RAY ANIS0TR0PY THERMOMETRY

H. Marshak, R. J. Soulen and D. B. Utton

(Heat Division)

Work is continuing on the comparison of a Josephson junction noise

thermometer to a Co y-ray anisotropy thermometer. In order to measure

the hyperfine splitting directly we are attempting a nuclear magnetic

59 resonance-oriented nuclei experiment. A very thin (3 mil) Co single

crystal disk shaped sample was irradiated in the NBS reactor to produce

the Co activity. Results of our first measurement were negative and

indicated that our sample was too thick. The experiment will be repeated

with a thinner sample.

91
NON-RRD NBS PROGRAMS

STUDIES OF GASSEOUS FISSION PRODUCTS

F. J. Schima and L. D. Miller

(Nuclear Radiation Division)

Early in 1972, the direction of the ARPA-supported program was reoriented along the lines of specific radioisotope standardization.

Several aspects of this prior reactor related research have been

successfully concluded and these were:

1. 81 Kr Decay Studies

A foil source of 81 Kr was prepared by means of the isotope separator

from the gas sample. This foil source has an activity level of about

100 dps. The K x-ray intensity was measured by comparison with standard

sources of 57 Co and 75 Se using the Si(Li) detector. The measured ratio

of the intensity of the 276 keV gamma to the K x-ray intensity was found

to be 6.8 ± .8% which implies a branching ratio of about 3.7%. The gamma

transition energy was measured as 275.99 + .01 keV. This is in excellent

agreement with recent energy measurements for the first excited state in

81 Br.

2. 129mXe Decay Studies

Considerable data have been obtained on the gamma decay of the

129mXe. The half-life has been measured as

T T = 8.92 ± .03 days

2

over a period of 4.2 half-lives. The two gamma transitions have been

measured as

E (isomeric) 196.38 + .11 keV

E (ground state) 39.50 ± .17 keV

92
E. Summary of Reactor Operations

During the period October 1, 1971 through September 30, 1972,

approximately 5100 hours of reactor time was provided to users. This is

equivalent to about 51,000 megawatt-hours of energy produced. Leaks in

the main heat exchanger and operations with minimum staffing reduced

reactor on-line time to 58% for this period which is the same as last

year but below previous years. Excellent fuel burnup of about 45% was

again achieved this year through utilization of heavier loaded elements.

A summary of operating statistics together with those of previous years

are presented in the following table:

NBSR Operating Summary

Nov. 1969 Oct. 1970 Oct. 1971

to to to Nov. 1970 Oct. 1971 Oct. 1972

78,213 123,761 175,161

59,186 51,175 51,400

6,000 5,440 5,200

247 213 214

67% 58% 58%

44 24 26

34% 48% 45%

11 6 6

3 10 11

1,500 3,000 4,000

4,000 4,000 3,400

Reactor Operations to date, MWh

Reactor Operations for year, MWh

Hours Reactor Critical

Number of Days at 10 MW

On-line time at 10 MW

Number of fuel elements used

Average U-235 Burnup

Number of Refueling Operations

Number of Unscheduled Shutdowns

Number of Irradiations

Number of Visitors

Over a period of 15 months, 11 heat exchanger leaks developed, nine

of which were during the last 10 months. These leaks resulted in a substantial loss of operating time and in a very costly degradation of

the heavy water in the primary system. A chronological history of the

leaks is presented in the following table.

93
CO

CD &

3H

T3 CM 0) O CJ> u • 3 O H

S Ph

SUMMARY OF REACTOR OPERATIONS

co co cm vd H O co *£>

CO

CD -OH

M

cw CI O -H

• CO O CD

O H H iH H

CO CO

rt *i 3 oi o CD -a h-1

4-1 3 H

-C cd

0/5. M

c H oi O X 4-1 t) o X

Cfl w

CD rt 4-1 CO m OJ o cn

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94
SUMMARY OF REACTOR OPERATIONS

Nine of the 11 leaks involved only a single tube, one involved two tubes and on one occasion the leak was so small that the leaky tube could

not be positively identified. To date 67 of 1285 tubes have been plugged.

Of these, 11 have definitely been identified as leakers. The remainder were plugged because they were suspect or thought to be potential leakers

based on eddy-current, helium, or freon testing or based on the pattern

that the location of the identified leaks followed. Of the 11 leaky

tubes that were found, seven were in the 14th row, two were in row 13, one in row 21, and one in row 35. There is a total of 60 rows of tubes.

In all 21 of 46 tubes were plugged in row 14, seven of which were leakers,

and six of 45 tubes were plugged in row 13, two of which were leakers.

In all cases where the leaks were identified the leaky tube was easily

found by ultrasonic testing.

Delivery of two new stainless steel heat exchangers (one to serve as

a backup) is scheduled for April 1973. Installation is presently planned

for the summer of 1973 in order to minimize the impact of the anticipated

two-month shutdown on the experimental program since the reactor is

operated on a curtailed schedule during the summer. The exact date will

depend on the condition of the present all aluminum heat exchanger.

During the repair of the leak of April 28, 1972, light water was inadvertently introduced into the primary heavy water system resulting

in degradation of the heavy water from its original purity of 99.5% to about 96 - 97%. Light water was being used to flush the heat exchanger,

which had been previously drained and isolated, in order to remove traces

of tritiated heavy water and permit access to the heat exchanger. The

diaphragm on the main isolation valve of the heat exchanger did not seat

properly permitting seepage of light water into the main heavy water

storage tank through an open drain line. Power operation could not be

sustained with the degraded water and the entire water content of the

primary system had to be replaced by reactor grade heavy water. It took

approximately 45 days to obtain the new heavy water resulting in a total

reactor shutdown of almost two months including the time used for repair

of the leak.

95
SUMMARY OF REACTOR OPERATIONS

A portion of the lost time was recovered through early performance

of required maintenance and surveillance tests thereby reducing scheduled

future shutdowns. Also because the new heavy water had very low tritium

activity, immediate access to the heat exchanger was possible. Leak

repair time was reduced to only two days resulting in a gain of several

days of operating time over that previously needed for the repair.

96
SUMMARY OF REACTOR OPERATIONS

F. SERVICE PROGRAMS

Service and irradiation programs have again shown substantial

increase over previous years. In all, approximately 4,000 irradiations

involving 40,000 samples were performed this year. These irradiations

covered a wide range of people-oriented projects, research and application

programs and radioisotopes production. Highlights of these programs are presented in following sections.

THE USE OF NEUTRON ACTIVATION ANALYSIS IN SCIENTIFIC CRIME DETECTION

Forensic Staff

(U. S. Treasury Department, Washington, D. C.)

The primary mission of the Forensic Laboratory is the examination

of physical evidence by scientific techniques. The evidence is related

in a large number of cases to activities of ATF agents who enforce the

1968 Gun Control Act and the Organized Crime Act of 1970. The Forensic

Laboratory also offers its services to State, Local and County agencies

in cases of mutual interest. Because of the increased services the

Forensic Laboratory has been called upon to provide, the Laboratory staff

has more than doubled in the past two years. The number of irradiations

at and use of the NBS reactor facilities has similarly significantly

increased.

The ATF Forensic Laboratory is equipped with atomic absorption, UV,

IR, x-ray diffraction and fluorescence, and an emission spectrograph

which are used to examine evidence in destructive device investigations.

Evidence connected with Arson/Firebomb cases are examined by gas-liquid

chromatography.

The ATF Laboratory examines hundreds of cases each year by NAA at the

NBS facility. The Laboratory is equipped with three 400 channel analyzers,

a 4096 ADC computer coupled data acquisition system with a 50 cm3 GeLi

97
SUMMARY OF REACTOR OPERATIONS

detector, and an off line computer system for the analysis of gunshot

residue data. A dual 4096 ADC Computer system will be acquired shortly.

In the past 12 months, the ATF Forensic Laboratory has examined 600

bomb /incendiary cases and analyzed 12,000 gunshot residue samples representing some 1500 cases. Neutron activation analysis was also used in several

hundred cases to examine a wide variety of evidentiary material including

drugs, hair, paint, soil and illicitly distilled spirits.

Court testimony has been given by Forensic Laboratory experts in

robbery, rape, homicide, and income tax fraud cases. Plans are being made to move a part of the Forensic Laboratory NAA

activities to the NBS reactor site in order to more fully utilize the

facility by measuring short lived radionuclides.

THE USE OF ACTIVATION ANALYSIS IN SCIENTIFIC CRIME DETECTION

BY THE FEDERAL BUREAU OF INVESTIGATION

Neutron Activation Analysis Unit

(Federal Bureau of Investigation, Washington, D.C.)

The FBI Laboratory uses neutron activation analysis (NAA) extensively

as a means of elemental analysis of metals, biological materials and

gunshot residue lifting mechanisms.

The capability of analyzing a specimen nondestructive!/ is very

important. Often the small metal fragments found on a tool or on a suspect's person are introduced as evidence at a trial. If a destructive

method of analysis was employed this is not possible and must be explained

to the court if necessary.

The sensitivity for many elements makes NAA ideal for analyzing the

minute metal fragments so often associated with cutting tools or pry bars

used in burglaries. For instance, a fragment of copper-colored metal

weighing 80 micrograms was removed from the jaws of a wire cutter. The

wire cutter was confiscated from a man accused of selling stolen wire to a junk dealer. The metal fragment was significantly different in com- position from the stolen wire submitted to the Laboratory. By neutron

98
SUMMARY OF REACTOR OPERATIONS

activation analysis it was possible to quantify selenium, gold, silver and

antimony in the copper fragment nondestructively.

The FBI Laboratory uses NAA in situations where classical chemical

methods of analysis are available but are time consuming and cumbersome.

For instance, the detection and quantifying of platinum and rhenium in an aluminum matrix was accomplished easily and quickly by NAA. The FBI Laboratory has purchased a low energy photon detector. Work

will be conducted on the detection and quantifying of some of the rare earths and other elements such as mercury which have isotopes which decay

with photon emissions less than 300 keV.

U. S. POSTAL SERVICE ACTIVATION ANALYSIS PROGRAM

G. R. Stangohr, J. Upton, and M. Beckman

(U. S. Postal Service, Washington, D. C.)

During the past year, the U. S. Postal Service Crime Laboratory in

Washington, D. C. , has continued to use the nuclear reactor facility at NBS for forensic neutron activation analysis. Items of evidence which

were irradiated at NBS included glass, hair, rope, paint, safe insultation,

and paper. Much of this evidence was derived from cases involving kidnapings , armed hold-ups, burglaries, mail bombs, and frauds.

One important case involving two separate kidnapings was successfully

resolved by using NAA to associate the rope used to tie each of the kidnaped victims with the rope recovered from the suspect's home. In another

case, utilization of NAA assisted in providing evidence to smash a burglary ring by matching paint particles found in a suitcase used to carry

burglary tools with paint from damaged safes from burglarized post offices

covering a wide geographic area.

99
SUMMARY OF REACTOR OPERATIONS

ACTIVATION ANALYSIS PROGRAM OF THE

FOOD AND DRUG ADMINISTRATION AT THE NBSR

J. T. Tanner and M. H. Friedman

(Food and Drug Administration, Washington, D.C.)

1. Mercury in Foods

A continuing program at FDA has been the analysis of mercury in

foods. Recently part of this study was published 1 which deals with

foods commonly eaten. The current part of this study involves a more

complex sampling of foods. In this case 77 different foods were

collected and divided into 12 different categories. Of these, 9 categories were analyzed for mercury: dairy products; fish, meat, and poultry;

cereals and grains; potatoes; leafy vegetables; legume vegetables; root

vegetables; garden fruits; and fruits. These foods were collected

throughout the country and should approximate the average mercury intake

by the USA consumer. These food samples were analyzed by neutron

activation analysis (NAA) at the National Bureau of Standards research

reactor at Washington, D.C, USA. Because the mercury content of these

samples was quite low, a chemical separation had to be used to enhance

the 279 keV y-ray of 203Hg with respect to the background. The procedure

consisted of anion-exchange chromatography and sulfide precipitation

previously described. No samples in this study were found to contain

more than 50 ppb Hg; in fact, most of the samples contained substantially

less than 20 ppb Hg. Thus, most foods consumed in the USA today appear to be relatively free from mercury.

2. Instrumental Neutron Activation Analysis of Bromine in Pig Tissue

Another continuing program of FDA is the analysis of bromine as an indicator of brominated vegetable oil (BVO) in pig tissue and organs.

Brominated vegetable oils are edible oils in which some or all of the

double bonds are saturated by bromine. They are used in the manufacture

of soft drinks to increase the specific gravity of the essential oil

components so that they remain in suspension which prevents the formation

100
SUMMARY OF REACTOR OPERATIONS

of rings of essential oil at the intersection of the surface of the

liquid and the bottle.

Recent studies in Canada have shown that prolonged use of high doses

of brominated vegetable oil causes physiological damage. The use of

brominated vegetable oil as a food additive has therefore been suspended

until studies are completed to determine what would be a safe limit.

The purpose of this study is to determine what amount of brominated

vegetable oil can be used safely as a food additive. To answer this

question pigs were fed brominated vegetable oil, the amount of bromine

present in different tissues was measured and correlated with observed

physiological changes. The physiological changes and the correlation

with the measured amount of bromine will be reported elsewhere.

Neutron activation has a number of advantages as a method of

quantitatively analyzing the samples for bromine. The analysis is done

completely instrumentally; no reagents are used and so this method of

analysis is completely free from reagent contamination. To the extent

that the sample does not appreciably attenuate the neutron flux or the

gamma rays leaving the sample the method is free of matrix effects. For

all biological materials and most other non-biological matrices these

conditions are easily satisfied.

3. Rapid Instrumental Analysis for Mercury in Biological Materials by

Neutron Activation

Most measurements of mercury in biological materials by neutron

activation analysis (NAA) rely on the 279 keV peak of 203Hg (t^/2 =

46.6 days) rather than on the x-rays that are produced when 197Hg(t 1 /2 =

64.1 hours) captures an orbital electron, thus decaying to 197Au. After

irradiation, however, the intensity of the K x-rays from the decay of

197Hg is much higher than that of the 279 keV 203Hg gamma ray and offers

the possibility of a more sensitive instrumental analysis. Measurements

of the 197Au Kq,., Ka

, Kg , Kg

2 x-rays (the respective energies are 66.99,

68.81, 77.9 and 80.1 keV) with the usual large volume Ge(Li) detector or

101
SUMMARY OF REACTOR OPERATIONS

Nal(Tl) crystal are hampered by a large Compton continuum in this region

and by inadequate resolution. The Compton background can be lowered with

a thin (5 mm) Ge(Li) detector which reduces the amount of material the

gamma radiation can interact with while the low-energy x rays, because of

their high photoelectric cross section, are detected with comparatively

high probability. The net effect is that with a thin Ge(Li) detector

one obtains an increase in the peak-to-background ratio in the x ray

region where a more sensitive instrumental analysis based on Hg is

possible.

This technique was used for a toxicological study undertaken to map

the distribution of mercury in the central nervous system of dogs fed

with MeHgCl. Three dogs were fed daily doses of 2.0-mg MeHgCl/(kg day)

for 15 days, at which point they became moribund; a fourth dog, given

10 doses of 2.0-mg MeHgCl/ (kg day), became moribund 26 days after the

dosage was discontinued. After the animals were sacrificed, their brains

were profused, the tissues dried, sealed in quartz vials, and irradiated

for 1 h in a flux of 6 x 10 13 n/(cm2 sec). Counting was done 3 days after

irradiation, with a sensitivity of 0.1 ppm. No effort was made to achieve

a more sensitive measurement since a sensitivity of 0.1 ppm was more than

adequate for the purpose of this work.

From these results we learn what mercury levels to expect in different

parts of the central nervous system, at the point of death, due to methyl

mercury poisoning. The concentration of mercury found in the central nervous system of the moribund dogs ranged from 2 ppm in the lumbar spinal

cord to 57 ppm in the prefrontal cortex. Thus, mercury was not found to be uniformly distributed in the central nervous system. Even though the

mercury concentration was high, the smallness of the sample, sensitivity,

ease of analysis, and specificity make neutron activation the method of

choice for these analyses.

4. MTELMT: A Computer Language for the Reduction of Neutron Activation

Analysis Data

102
SUMMARY OF REACTOR OPERATIONS

A computer reduction program is a fixed set of instructions for

doing some computation. However, because of the many variables inherent

in both acquiring and reducing neutron activation analysis data a single

set of instructions is not applicable to reducing all data sets. Typically

then, changes must be made in the program to get the required data reduction sequence or alternately the program is set up to do part of the

calculation but the final results are calculated manually. Neither

approach is entirely satisfactory: 1) changing a program written in

FORTRAN or ALGOL can involve so many details that it can only be done

convieniently by the person who wrote the program and even then it may

take a long time and 2) doing even part of a calculation manually can be

quite time-consuming if there are many samples to analyze. The MTELMT

language (mnemonic for multiple element) was developed to give the user a convienient way of communicating to the computer how to reduce any set of

neutron activation analysis data.

The language consists of a set of commands. A CDFRMT (card format) 2

command specifies the format of data to be read from IBM cards. Once the

card format has been specified, a spectrum consisting of any number of

channels (up to 4096) can be read in with the command CDDATA (card data)

.

A spectrum on tape can be read in with the command TPDATA if it is the

next spectrum on the tape or with the command SRCHTP if one must search

the tape for the proper spectrum. To skip over file marks on the tape,

the command FLSKIP (file skip) is used and the magnetic tape is rewound

with the command REWIND. To make a linear or semi-logarithmic CAL COMP

plot of any spectrum with up to 4096 channels the command GRAPH1 is used.

Options of the various commands are controlled by the command KNTROL.

The location of peaks and input parameters for drawing the background line

are input through the command INTPRM (integration parameters) . Pertinent

information which must be specified for each sample and standard (weight,

etc.) are input with the commands SAMPLE and STNDRD. The computation of

the ppm or micrograms or upper limit of the element specified by the

STNDRD command is initiated by the command ANLYZM (analyze in manual mode)

.

The feature which makes this program so powerful is that it defines

103
SUMMARY OF REACTOR OPERATIONS

a language and the words of the language can be put together in many

different ways to accomplish different tasks. Between the CDDATA, TPDATA

and SRCHTP commands data can be read in from cards and tape in any sequence

that is desired. Because of the CDFRMT command the program can accomodate

spectra on cards in any format. The result is an extremely flexible, yet

simple to use, input/output capability. With the use of the REWIND command,

for data which is on the magnetic tape, in a single computer run one can analyze the data again in a different way. Between the STNDRD and the

INTPRM command the pertinent information for any element can be readily

input to the computer. Thus, this program can analyze for any element

for which the x ray or gamma ray peaks are resolved.

The MTELMT language is on the drum of the UNIVAC 1108 computer at NBS.

1 Science 177, 1102 (September 22, 1972).

The mnemonic appears in parenthesis following the command.

DEVELOPMENT OF ANALYTICAL METHODS AND DETERMINATION OF

CONSTITUENTS OF GEOLOGICAL SAMPLES

J . J . Rowe

(U.S. Geological Survey, Washington, D. C.)

The U. S. Geological Survey has been utilizing the reactor facilities of the National Bureau of Standards for the development and application of neutron activation analysis and isotope dilution techniques

for the determination of trace constituents in geological materials.

The reactor has been used for the preparation of As for use in

the isotopic dilution determination of arsenic in soils as part of a study of environmental pollution. The method has been applied to the

analysis of more than 5,000 samples of soils and rocks from various

areas

Instrumental neutron activation analysis has been applied to the

determination of tantalum and hafnium in lunar rocks and soils. Various

104
SUMMARY OF REACTOR OPERATIONS

terrestrial materials have been analyzed for thorium, chromium, scandium,

hafnium, tantalum, caesium, rubidium, antimony, lanthanum and the rare earths for geochemical studies.

Activation analysis with post-irradiation radiochemistry has been

applied to the determination of gold in many rocks and minerals ; selenium

in sulfide minerals and tungsten in rocks and minerals.

Trace concentrations of platinum and palladium in rocks have been

determined using a fire assay preconcentration and post-irradiation radiochemistry. A method has been developed for the determination of ruthenium

and is being applied to the analysis of chromites and rocks. The collection of ruthenium on a plastic film before irradiation overcomes fission

product interferences and permits the instrumental determination for

samples containing as little as 10 ppb of ruthenium.

Epithermal irradiations have been used for the determination of gold

in native silver and copper. It is planned to extend the application of

epithermal irradiations to the determination of rare earths in phosphate

rocks

.

COMPARISON AND PREPARATION OF FLUORINE AND

9 9m

TECHNET I UM-T I N"PH0SPHATE RAD 1 OPMRTACEUTI CALS

Major George Dunson

(Armed Forces Radiobiology Research Institute, Bethesda, Md.)

Fazle Ho sain

(Johns Hopkins Medical Institutions, Baltimore, Md.)

John Harbert

(Georgetown University Hospital, Washington, D.C.)

and

Ira Godwin

(Northern Virginia Pathology Laboratories, Fairfax, Va.)

18 During 1970 and 1971 F produced in the NBS reactor was used for

bone lesion imaging in patients in the Bethesda Naval Hospital, Fairfax

Hospital, Georgetoxjn University Hospital, Johns Hopkins University

105
SUMMARY OF REACTOR OPERATIONS

Hospital, Northern Virginia Pathology Laboratories, Walter Reed General

Hospital, Washington Hospital Center and Washington Veterans Administration Hospital. The methods of producing the radiochemical and preparing it as a radiopharmaceutical were published in the NBS Technical

Note 714, March, 1972. x » 2

In 1971 Dr. Subrumanian of the Upstate Medical Center, Syracuse,

99m,, N. Y. published articles on the use of Tc polyphosphate as a bone

lesion imaging radiopharmaceutical. ' This innovation created a need

for a study to compare " T^c polyphosphate with F and other bone

imaging radio-pharmaceuticals and to develop a method of compounding

xc polyphosphate that could be used by technicians in the various

nuclear medicine clinics to prepare the radiopharmaceutical as needed.

The study was carried out in two phases during 1971 and 1972 in approximately 300 patients in the medical facilities listed above.

T .„. ,, . . - 18_ 67_ 85_ 87m_ , 99HU Initially comparisons were made of F, Ga, Sr, Sr and T^c

polyphosphate and reported at the March, 1972, meeting of the Mid-Eastern

1 8 Society of Nuclear Medicine. 5 ' 6 This report indicated that both F and

tc polyphosphate were superior to the other bone lesion imaging radiopharmaceuticals and that each had advantages and disadvantages. It was

also reported that the published materials and methods for compounding

99m„

Tc polyphosphate gave intermittently successful and unsuccessful

results and required individual preparation by an experienced radiopharmacist

18F advantages were that physicians were sufficiently experienced

with the radiopharmaceutical to easily interpret the nuclear images,

technicians were familiar with dosing and instrumentation techniques and

18

the radiopharmaceutical was always of high quality. F disadvantages

were due to its nuclear properties. It is made by nuclear bombardment of

a stable parent and decays with a 2 hour half-life. Therefore, it must

be prepared for patients on a scheduled basis, quickly processed and

transported to using institutions. F is a positron emitter which gives

off 511 keV gamma rays upon annihilation. This energy is poorly collimated

and suitable only for rectilinear imaging.

106
SUMMARY OF REACTOR OPERATIONS

18 Fig. 1A. F rectilinear image

; mam m

am i < < mm

Fig. IB. "Vc-tin-phosphate

rectilinear image

99 Fig. 2. Tc-tin-phosphate gamma camera composite image

107
SUMMARY OF REACTOR OPERATIONS

99^c polyphosphate advantages were due to the nuclear properties of

its " Tc component. Tc is a decay product of 2.7 day half-life

99molybdenum. It is easily obtained as a sterile, pyrogen free, eluate

of a commercial generator system that is stocked by most nuclear medicine

clinics. Tc decays with a 6 hour half-life and gives off 140 keV

gamma rays. This energy is ideally suited for both rectilinear and gamma

18 99m camera imaging. Comparison of F and Tc polyphosphate rectilinear

images of the pelvic area are shown in Fig. 1A and IB. Both images

demonstrate sacroiliac abnormalities and urinary bladder accumulation.

99m

Tc polyphosphate disadvantages were due to the chemical nature of Tc

99m and the Tc polyphosphate complex and lack of experience with Tc and a bone lesion imaging agent.

1

In the second phase of the study F was used as a standard for

patient imaging and interpretation while physicians and technicians

developed interpretation, dosing and instrumentation techniques using a

99itlTc-tin-phosphate kit radiopharmaceutical developed by the group

radiopharmacist. This kit eliminated the chemical disadvantages of

Tc polyphosphate because it gives a high quality successful radiopharmaceutical every time, can be stored indefinitely and can be prepared by technicians within 5 minutes when needed. Fig. 2 shows typical

gamma camera images of a pig dosed with Tc-tin-phosphate using a kit

prepared at the Armed Forces Radiobiology Research Institute (AFRRI)

Patient images are of equal quality. This study led to the gradual disuse

18

of F by participating medical institutions as physicians and technicians

gained experience in Tc bone imaging.

1 G. Dunson, I. Godwin, J. Harbert et al, "Fluorine-18 radiopharmaceutical

for Bond Lesion Localization, NBS Tech. Bulletin 714:70-7$ (1972).

2 G. Dunson, W. Crofford and J. Ring, : Fluorine-18 Production in the NBS

Reactor, NBS Tech. Bulletin 714: 75 (1972).

3 G. Subrumanian and J. G. McAfee, "A New Complex of Tc-99m for skeletal

Imaging," Radiology 99: 192 (1971).

108
SUMMARY OF REACTOR OPERATIONS

G. Subrumanian et al, "Tc-99m Polyphosphate PP46 : A New Radiopharmaceutical for Skeletal Imaging," J. Nual. Med. 12: 399 (1971).

5 G. Dunson, J. Harbert and F. Curl, "Comparison of Bone Lesion Visualization Using Tc Polyphosphate, Ga-67 Citrate and Sr-85 Nitrate, MidEastern," Soo. of Nual. Med, March 1972.

6 F. Hosain, P. Dugal, G. Dunson et al, "Pediatric Bone Scanning and

Relative Merits of Fluorine-18, Sr-87m Citrate and Tc-99m Polyphosphate,'

Mid-Eastern Soo. of Nual. Med. , March, 1972.

USE OF NEUTRON ACTIVATION ANALYSIS IN THE STUDY OF COPPER

IN WOUND HEALING AND HEPATIC DISEASES

G. C. Battistone

(U.S. Army Inst, of Dental Research, Washington, D.C.)

Studies on the role of copper in wound healing have continued during

the past year. Although some success has been achieved in accelerating

bone healing with certain copper chelates , the overall effect of the

copper chelates used has been toxic in the experimental animals used.

Thus far no totally acceptable copper chelate complex has been found.

When non-toxic dose levels of the copper complexes were used, no observable effect was seen on the healing process.

In collaboration with the Hepatic Disease Research Branch of the

Armed Forces Institute of Pathology, a study was begun during the past

year to determine copper levels in various hepatic diseases in order to obtain a better understanding of the role of copper in these diseases.

Data are being collected as biopsy and autopsy material becomes available,

It is hoped from an accumulation of such data that copper determinations

will provide greater diagnostic as well as etiological information.

109
SUMMARY OF REACTOR OPERATIONS

TRACE ELEMENTS IN THE ENVIRONMENT AND DECAY

SCHEME STUDIES

W. H. Zoller, G. E. Gordon and W. B. Walters

(University of Maryland, College Park, Md.)

During the past year our work has centered on the analysis of trace

elements on atmospheric particulate material and pollution-source materials,

We have used the facilities of the NBS reactor to irradiate a large

number of samples followed by y-ray spectroscopy using Ge(Li) detectors.

Atmospheric particulate material from Boston, Massachusetts, Friendship

Airport (near Baltimore, Maryland), College Park, Maryland and the general

Washington, D.C. area have been analyzed. These studies are related to the atmospheric chemistry program at the University of Maryland. The

samples were collected on filters such as Millipore, Nucleopore, Whatman

and Delbag which can be pressed into pellets prior to irradiation using

a Nickel-Nylon die system to eliminate contamination of the samples.

Other samples were collected by cascade impactors which separate the

particles into size fractions on polyethylene. The polyethylene with the

collected material can then be irradiated directly and counted.

The analysis of a set of air samples collected in Antarctica during

the last two years has nearly been completed. The results of these

experiments have shown that the concentration of trace elements in this

very clean location is nearly a factor of 10,000 less than in the rural

United States. This project will continue, as more samples will be

collected this year. Mr. John Ondov of the University of Maryland will go

to the South Pole station to set up equipment and bring back samples which

have been collected there during the past winter.

Our analyses of hydrocarbon fuels by INAA has yielded results on fractions down to the boiling point of iso-octane. These lighter fractions

are sealed in quartz under vacuum prior to irradiation. We find these

lighter fractions to be much lower in trace elements than heavier fractions

as the distillation process leaves them behind.

Most impurities are from additives put into the fuels by the producers.

Nearly twenty automobile lubricating oils have also been analyzed under

110
SUMMARY OF REACTOR OPERATIONS

this project as we need to know their compositions for our studies on automobile emissions to the atmosphere.

Experiments on different types of monitors for activation analysis

have been initiated. In this project we are comparing liquid monitors

with weighted solids and evaporated solutions on certain matrices. We

have obtained excellent results by making monitor solutions from ultrapure weighable (i.e. non-hydrated) compounds of the elements and

evaporating known quantities of the solutions to dryness on hydrophyllic

filter paper. The filter material is then pressed to form pellets having

the same dimensions as the pellets containing atmospheric particulates.

Some separated isotopes Fe, Cd, Gd, and Ru have been irradiated to produce isotopes whose decay schemes need to be studied in greater detail.

This work will continue beyond this year and others will be added in the

future. Some of these isotopes are used for tracer work on chemical

separation currently being studied at the University of Maryland.

SEA AND ATMOSPHERE POLLUTION STUDIES

D. J. Bressan

(Naval Research Laboratory, Washington, D.C.)

During the year, laboratory experiments and chemical analyses have

been carried out in connection with studies on sea water and atmospheric

aerosol chemistry, transport and fractionation of chemicals from the sea

surface to the atmosphere, and the transport and distribution of pollutants in the ocean and the atmosphere. These studies require the analysis

of Hg, Pb, Ag, Fe, Mn, Sc, Na, K, S, Ca, Sr, Br, CI and I. The NBS reactor has been used to analyze samples of sea water, rain,

fog condensate, atmospheric aerosols and atmospheric dust for microgram

amounts of the above named elements. Radioactive tracers for some elements were made at the NBS facility and used in laboratory experiments

at NRL. These experiments are to determine transport mechanisms, distribution and partitioning of man-made pollutants and naturally occurring

elements in the natural systems under study.

Ill
SUMMARY OF REACTOR OPERATIONS

This program is continuing with significant results expected for

publication next year.

NEUTRON ACTIVATION ANALYSIS NAVY OIL MONITORING PROGRAM

D. A. Kubose

(Naval Ordnance Laboratory, White Oak, Md.)

The Naval Ordnance Laboratory is presently involved in a project to investigate the use of neutron activation as an analytical method in its

oil monitoring program.

The Navy's oil monitoring program has been in operation for the past

fifteen years. The ultimate goal of the program is the development of a method which can precisely predict and pinpoint sources of engine and

transmission failures by analysis of trace components in the oil used to lubricate these parts.

The premise upon which the program is based is that excessive wear

in the engine and transmission will be reflected in increased levels of

trace elements in their lubricating oils. Systematic analysis of these

oils should indicate when and possibly where this excessive wear is occurring. Engines and transmissions can be overhauled and/or otherwise fixed

before catastrophic failure results.

The Navy is presently utilizing emission spectrometry in its oil

monitoring systems. While the present method has been successful in

detecting accelerated wear in engines and transmissions, it has not been

able to pinpoint where this wear is occurring. This may be due in part

to the inherent limitations (in terms of instrument sensitivity and versatility) of the system.

Neutron activation analysis is an extremely sensitive method which

is capable of simultaneous multielement determination on a purely instrumental basis. Because of its extreme sensitivity, one can obtain detailed

qualitative/quantitative trace element patterms which may allow the tracing of wear metals in the lubrication oil to its ultimate source in the

112
SUMMARY OF REACTOR OPERATIONS

engine or transmission component. The primary objective of the NOL research

will be directed toward that achievement.

FEASIBILITY INVESTIGATIONS OF A FUEL BUNDLE MOTION MONITOR

J. P. Boright and R. E. Patrick

(U.S. Arms Control and Disarmament Agency, Washington, D.C.)

and

0. E. Frizzell

This program reported in the Annual Progress Report for the period

ending October 31, 1972 was continued and concluded in this reporting

period.

The work was expanded to include the radiation effects on the

sensitivity of the solid state electronics employed in the monitor. The

amplifier utilized was a radiation hardened solid state D.C. amplifier.

Tests were conducted in high energy gamma fluxes up to 10 20 R without

degradation of the amplifier sensitivity or calibration.

A part of this program has been the mapping of the high energy

gamma fields from the spent fuel elements. The reported values of energies

by various investigators on this type of element is in the 0.8 to 1.6 MeV

range. The element intensity does drop off with time but this does not

present a serious obstacle since the average energy remains relatively

constant and the radiation intensity can be measured and converted to dosage values. The intensity of the element drops about a decade in a 120-day period. The spent elements are renewed with fresh spent elements

from reactor on a 90- to 120-day cycle.

This experiment necessitated the development of a means of measuring

the intensity of the elements at different distances and locations from

the element or elements. A high range gamma chamber (lOroR to 10 R/h)

and an electrometer were utilized for this purpose. An absolute calibration was not conducted since reproducibility was the experimental

requirement

.

113
SUMMARY OF REACTOR OPERATIONS

A method of optical sighting was also developed in conjunction with

the experiment to locate the target within ±1/4 in. on the X and Y axis

under 20 ft. of water.

The experiment was concluded by a test of the completely assembled

collimator, ion chambers and electronics. Spent fuel bundles were moved

past the system through various background fields of gamma radiation to determine the limits of sensitivity. Various geometrical configurations

of shielding material were inserted between the spent fuel bundle and

detectors to determine the limits of sensitivity.

As a part of the same program demonstrations were conducted of the

TV surveillance system developed at NBS 1 under similar environmental

conditions under which it will be installed.

Measurement Engineering Division (446.03), IAT,

STUDIES OF MAGNETIC PROPERTIES IN RARE EARTH ALLOYS

AT CRYOGENIC TEMPERATURES

R. Segnan and D. M. Sweger

(American University, Washington, D.C.)

"

l fi l A Mossbauer effect source of Dy has been prepared in a matrix of

Gd203 for use in magnetic rare earth alloys studies of cryogenic temperatures. A high velocity drive (±25 cm/s ) has been assembled for use in

measuring resonant absorption in 151 Dy.

Magnetic rare earth alloys offer promise of possible use as materials

suitable for high energy density electromagnetic applications. Particularly

promising are Dy-Gd and Dy-Y alloys, since these tend to have quite

attractive magnetic properties (for example, dysprosium has a saturation

magnetization of approximately 34 kilogauss at 4.2 K)

n The alloy system Gd-Dy can be investigated by Mossbauer spectroscopy

by using a suitable radioisotope of either Gd or Dy. An analysis of the

properties and availability of possible radioactive sources led to the

selection of a

161Dy isotope. The y-ray used in this case comes from

114
SUMMARY OF REACTOR OPERATIONS

the decay of the 25.6 keV excited state to the ground state in Dy.

The excited state of 16 *Dv can be populated by thermal neutron irradiation

of 160Gd.

Gadolinium oxide, Gd 2 03, enriched to 96% Gd ^n tne f°rm °f a fine powder is the source material. The source is activated in the RT-4

pneumatic facility of the National Bureau of Standards Reactor in a thermal neutron flux of 1.3 x 10 13 neutrons/cm2 s . Such a flux will

yield a source strength of about 3 millicuries/h gram of enriched Gd203.

The splitting of the saturation hyper fine field in 161 Dy is 43.7 cm/s and thus the drive must be capable of peak velocities of

about ±25 cm/s . Velocities such as these are at least an order of

ti magnitude larger than are required for most other Mossbauer isotopes. In addition, as for all drive systems, the velocity must be linear to within

1%. A modified version of the NBS Mossbauer drive was used to achieve the

high velocities required for the 161 Dy resonance. Measurements have been taken on four Dy-Gd alloys from 4.2K to their

neel (curie) temperatures. A saturation magnetic hyper fine splitting of

43.7 ± .1 cm/s is obtained for 1.0 ± .2 cm/s. The data for HINT (T) are composed to existing molecular field and spin-wave series, and it is

found that spin-wave theory, when an anisotropy energy gap on the order of

24K is included in the spin wave spectrum, is in reasonably good agreement

with the HjNT (T) data below 0.5 TN

(TC

) . The temperature dependence of

the data for quadrupole coupling is in good agreement with a theory by

Callen and Callen 1 and indicates that the dominant contribution to Vzz is

the single ion magnetocrystalline antisotrophy

.

%. D. Callen and E. Callen, J. Phys. Chem. Solids, 27_, 1271-1285 (1966)

115
SUMMARY OF REACTOR OPERATIONS

EFFECT OF RADIATION ON MAGNETIC MATERIALS

R. S. Sery and D. I. Gordon

(Naval Ordnance Laboratory, White Oak, Md.)

The Naval Ordnance Laboratory is a primary research and development

activity of the Naval Material Command. Its mission includes research,

design, development, testing, evaluation, fleet engineering support in

weapons systems, etc., and investigations in related fields of science

and technology.

One of the current projects of interest is that of determining

radiation resistance of magnetic materials and devices including bubble

memory materials for potential military applications.

The main purpose of this investigation is to determine whether or not

they are invulnerable and if vulnerable how the materials and devices may

be amenable to "radiation hardening."

Extensive sample irradiations have been performed to date at the

NBS reactor facilities. The results thus far are preliminary and require

further evaluation plus additional irradiation experiments in order to determine threshold values of doses, below which no radiation induced

changes can be detected, and to give adequate statistical weight to (either confirming or contradicting) the findings obtained to date.

MOSSBAUER SPECTROMETRY

D. A. Kubose

(Naval Ordnance Laboratory, While Oak, Md.)

The program being carried out at NOL which requires the use of the

neutron irradiation facility at NBS concerns work in Mossbauer Spectrometry,

The NBS facility has been used to produce radioactive Mossbauer sources.

In Mossbauer spectrometry, an absorber, which contains atoms of a particular nuclide, is interposed between a radioactive source and a detector. The radioactive source contains radionuclides that decay to the same nuclide that is in the absorber. Count rates are observed from

the detector as a function of the relative velocity of the source as it

116
SUMMARY OF REACTOR OPERATIONS

is moved with respect to the absorber. The resultant velocity (energy)

spectrum shows dips which are the result of resonant absorption of the

gamma rays in the absorber. The system is extremely sensitive to small

changes in gamma-ray energy that are caused by variations in the density

of the valence electrons surrounding the atomic nucleus. The technique

thus should find wide application as a sensitive analytical method for the

determination of the chemical species of specific elements in samples,

whether such elements be present in macro or tracer concentrations.

Once Mossbauer spectrometry has been successfully demonstrated, a suitable platform will be assembled such that coulomb excitation of a sample can be performed in conjunction with the NOL Van de Graaf accelerator. Upon completion of this assembly, it will be possible to use Mb'ss- bauer spectrometry as an analytical tool for the determination of the

chemical species of many elements in any sample matrix. Applications will

be made to the study of the chemical species of elements in seawater and

in atmospheric particles.

ANGULAR CORRELATION OF POSITRON ANNIHILATION

RADIATION IN METALS

A. C. Ehrlich

(Naval Research Laboratory, Washington, D.C.)

The electronic structure of the conduction electrons in alloys at any temperature and pure metals at all but the lowest temperatures cannot

be studied by the experimental techniques that have been so successfully

employed in studies of pure metals at low temperatures. These techniques

require that the electrons have very long mean free paths and this occurs

only in the purest metals at temperatures near absolute zero. Among the very limited number of direct ways of studying the electronic structure of alloys (and pure metals at all but the lowest

temperatures) is the angular correlation of positron annihilation radiation. In this method, one makes use of the fact that the small deviations from 180° made by the direction of travel of the two y

_ rays which

117
SUMMARY OF REACTOR OPERATIONS

are emitted when a positron annihilates with an electron is a direct measure of the momentum of the annihilated electron. Thus, measurement

of the number of coincident y-xaj pairs as a function of the angle

between them provides direct information of the momentum spectrum of the

electrons in a metal.

In order to provide useful information, however, the angles that

must be resolved are very small (£ 10 radians) , whereas to minimize

statistical uncertainties the total number of counts must be large. To

reconcile these opposing conditions, previous experimental setups have

resolved only one component of momentum (one angle) . To obtain more

precise information, we have constructed an apparatus designed around

two components of momentum while still achieving a satisfactorily high

count rate. The technique requires that the specimen under study be

rendered a highly radioactive positron emitter. This is most conven- iently achieved by studying copper based alloys which, when irradiated in

a neutron flux, become strong positron emitters. At the same time, minimizing crystallographic damage suggests the use of a thermalized (rather

than a high energy) neutron flux. The RT-4 facility at the NBS nuclear

reactor seems well suited to this purpose. Sufficent preliminary data

has already been collected to determine that the experiment is feasible

and should provide information on the electronic structure of alloys of

a precision heretofore unobtainable.

BAND TAILING IN INDIUM ANTIMONIDE

John Stannard

(Naval Research Laboratory, Washington, D.C.)

Irradiation of the semiconductor indium antimonide with thermal

neutrons transmutes indium into tin. Careful control of the neutron

fluence allows the concentration of tin donor atoms and therefore the

electrical properties of the irradiated crystals to be controlled. This

has allowed the fabrication of surface active millimeter wave detectors

whose impedance and physical strength are much improved over that of the

118
SUMMARY OF REACTOR OPERATIONS

state-of-the-art Rollin detector. The detectivity of these devices

appears at present to approach that of the Rollin detector.

QUALITY ASSURANCE OF ALUMINUM ECAPSULATION MATERIAL

L. S. Kellogg and W. N. McElroy

(Hanford Engineering Development Laboratory, Richland, Wash.)

High Purity Aluminum for encapsulation of fission foils to be used

in the Liquid Metal Fast Broader Reactor program were analyzed by the

Hanford Engineering Development Laboratory. As part of the Quality

Assurance program, a set of six foils was prepared and irradiated for a total of 16 hours (total fluence ^8 x 10 ) in the NBS reactor RT-4 position (highly thermalized) . These foils indicated a number of contaminating gamma activities. Those now identified are Sc, Ta, and Co with Sc the major contributor to the gamma spectra. Gamma energies of

peaks noted but not identified at this time (in MceV) are: 54, 65, 99,

147, 316, 606, 324, 486, 135, and 1101. Preliminary calculations

assuming Sc(N,y) Sc indicate an initial concentration of Sc of M3.1

46

ppm. The variation in impurity content (homogeneity) utilizing Sc for

the measurements was found to be <3% relative.

119
G. Staff Roster

RRD ORGANIZATION CHART

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120
STAFF ROSTER

-RRD NBS STAFF LOCATED AT REACTOR

Division 310.08

D. A. Becker

B. S. Carpenter

W. A. Cassatt

T. Gills

P. D. LaFleur

G. J. Lutz

L. T. McClendon

E. Orvini (U. of PaVia, Italy)

G. M. Reimer

H. L. Rook

R. W. Shideler

J. E. Suddueth

R. M. Young

H. P. Yule

Division 313.00

B. Mozer

B. LeNeindre (CNRS-Bellevue, France)

Division 240.01

P. R. Cassidy

H. E. DeSpain

E. J. Embree

J. J. Shubiak

Division 242.01

R. A. Dallatore

J. A. Grundl

I. G. Schroder

A. Fabry (Cen-Sek, Belgium)

GUEST WORKERS AND COLLABORATORS

Division 221.03

H. Marshak

R. J. Soulen, Jr.

D. B. Utton

Division 221.05

R. D. Mountain

H. J. Raveche

Division 232.06

R. D. Deslattes

W. C. Sauder

E. G. Kessler

Division 242.02

L. D. Miller

F. J. Schima

Division 311.03

J. D. Barnes

Division 311.05

B. Dickens

L. W. Schroeder

Division 313.01

C. W. Reimann

Division 313.06

A. D. Mighell

Argonne National Laboratory

H. Flotow

D. C. Price

J . M . Rowe

121
STAFF ROSTER

Armed Forces Radiobiology Res. Inst. Maj . G. Dunson

Federal Bureau of Investigation

D. B. Davies

J. W. Kilty

J. M. Little

G

P

Mahoney

J, P. Riley

Food and Drug Administration

M. Friedman*

R. E. Simpson

J. T. Tanner*

Harry Diamond Laboratory

D. McGarry

Northern Virginia Pathology Lab

Ira Godwin

Naval Ordnance Laboratory

H. Alperin*

D. I. Gordon

D. A. Kubose

S. J. Pickart*

J. J. Rhyne*

R. S. Sery

R. H. Williams*

Naval Research Laboratory

D. J. Bresson

A. C. Ehrlich

G. A. Ferguson

J. Karle

J. H. Konnert

L. F. Paolella*

J. Stannard

P. E. Wilkniss

Picatinny Arsenal

C. S. Choi*

H. J. Prask*

R. S. Singh*

S. F. Trevino*

U.S. ACDA

J. D. Boright

R. E. Patrick

U.S. Army Inst, of Dental Res.

G. C. Battistone

U.S. Atomic Energy Commission

J. C. Glynn

U.S. Geological Survey

F. W. Brown

R. Finkelman

L. P. Greenland

J . J . Rowe

G. Sellers

F. 0. Simon

U.S. Postal Service

M. Beckman

G. R. Stangohr

J. Upton

U.S. Treasury Department

R. L. Brunelle

P. C. Buscemi

C. M. Hoffman

F. A. Lundgren

M. J. Pro

Hanford Engineering Devel. Lab,

L. S. Kellogg

W. N. McElroy

The Ford Motor Company

W. G. Rothschild

American University

R. G. Arnold

B. T. Chertok

R. A. Segnan

R. Simon

D. M. Sweger

122
STAFF ROSTER

Carnegie Institution of Washington

L. W. Finger

Harvard University

J. L. Alperi*

R. Wilson

Interuniversitair Reactor Instituut

L. A. de Graaf

McGill University

G. Donnay

J. D. H. Donnay

R. F. Martin

Temple University

M. Green

V. R. Warkulwiz*

U.S. Naval Academy

C. S. Schneider

University of Maryland

J. Barker

p. Buhl

R. A. Cahill

T. J. Conry

E. Gladney

C. Glinka

G. E. Gordon

J. Graber

S. Harrison

A. Jones

R. Khanna

V. J. Minkiewicz

F. J . Munno

J. Ondov

L. Raber

J. Reednick

W. B. Walters

W. H. Zoller

Georgetown University Hospital

J. Harbert

Northern Va. Pathology Lab.

Ira Godwin

Johns Hopkins Medical Inst

.

F. Hosain

Located full-time at NBS Reactor

123
H. Publications

COLLABORATIVE PROGRAMS

ALPERIN, H. A., S. J. PICKART, J. J. RHYNE AND V. J. MINKIEWICZ, Softening

of the Transverse Optic Mode in PbTe," Phys. Letters 40A, 295 (1972).

BARNES, J. D., "Neutron Inelastic Scattering Study of the 'Rotator' Phase

Transition in N-Alkanes," Proa. Intern. Symposium on Inelastic

Scattering of Neutrons, Grenoble, France (March 1972)

CASELLA, R. C. , "Possible Failure of the Pomeranchuk Theorem Shrinkage of

the Forward Elastic Peak and Oscillations," Elementary Processes at

High Energy (Academic Press, New York, 1971), p. 578.

CHOI, C. S., AND E. PRINCE, "The Crystal Structure of Cyclo-trimethylenetrinitramine," Acta Cryst. B28_, 2857 (1972).

CHOI, C. S., J. E. MAPES, AND E. PRINCE, "The Structure of Ammonium Nitrate

(IV)," Acta Cryst. B28 , 1357 (1972).

CHOI, C. S., AND J. E. ABEL, "The Crystal Structure of 1,3,5-Trinitrobenzene by Neutron Diffraction," Acta Cryst. B28 , 193 (1972).

CLARK, A. E., H. S. BELSON, J. J. RHYNE, S. J. PICKART AND E. R. CALLEN,

"Magnetostriction and Magnetic Anisotropy of TbFe2," Phys. Rev.

Letters (to be published)

DEGRAAF, L. A., J. J. RUSH, R. C. LIVINGSTON, H. E. FLOTOW AND J. M. ROWE,

"Study of Hydrogen Diffusion in Vanadium and Tantalum Hydride by

Quasielastic Thermal Neutron Scattering," Proc. Intern. Meeting on Hydrogen in Metals, JUL-Conf-6 (Vol. I) (March 1972), p. 301.

DEGRAAF, L. A., J. J. RUSH AND R. C. LIVINGSTON, "Neutron Scattering

Study of the Rotational Motions and Phase Transitions in Sodium and

Cesium Hydrosulf ides," Proc. 5th IAEA Symposium on Inelastic Scattering of Neutrons, Grenoble, France (March 1972).

DEGRAAF, L. A. AND B. MOZER, "Structure Study of Neutron Diffraction by

Liquid Neon," J. Chem. Phys. 55_, 4967 (1971).

DEGRAAF, L. A., J. J. RUSH, H. E. FLOTOW AND J. M. ROWE, "Quasielastic

Thermal Neutron Scattering by Hydrogen in a-Vanadium Hydride," J. Chem. Phys. 56, 4574 (1972).

KONNERT, J., J. KARLE AND G. A. FERGUSON, "Structure of Vitreous Silica

and Germania by Neutron and X-ray Diffraction," Science (to be

published)

124
PUBLICATIONS

LEUNG, P. S., J. J. RUSH AND T. I. TAYLOR, "Study of Hindered Rotation in

Crystals by Neutron Transmission Measurements: Comparison of Calculated

and Measured Scattering Cross Sections," J. Chem. Phys. 57_, 1?5 (1972).

LOGAN, D. W., S. F. TREVINO, R. C. CASELLA, W. M. SHAW, L. D. MUHLESTEIN

AND R. D. MICAL, Phonons, (Flammarion Science Press, Paris, 1971),

p. 104.

MIGHELL, A.D., AND A. SANTORO, "The Crystal and Molecular Structure of

Hexakis (imidazole)cadmium(II) nitrate, [Cd(C„H,N„) ,] (NO )„ and

Hexakis (imidazole) cadmium (II) hydroxide nitrate tetrahydrate,

[Cd(C

3H

4 N2

) 6 ](OH)(N0

3 )-4H

2 0", Acta Cryst . B27 , 2089 (1971).

MIGHELL, A. D., C. W. REIMANN, AND A. SANTORO, "The Crystal and Molecular

Structure of the 2:1 Dimer Dibromobis (Pyridine N-oxide) Copper (II)

[Pyridine N-oxide) -CuB^k," Acta Cryst. B28 , 126 (1972).

MYERS, V. W., "Klein-Gordon Equation for Charged Particle Interacting

with an Electromagnetic Wave," J. Franklin Institute (to be published) .

PRICE, D. L., J. M. ROWE, J. J. RUSH, D. PRINCE, D. G. HINKS AND S. SUSMAN,

"Single Crystal Neutron Diffraction Study of Potassium Cyanide," J. Chem. Phys. 56, 3697 (1972)

PRASK , H., S. TREVINO, J. GAULT AND K. W. LOGAN, "Ice I-Lattice Dynamics

and Incoherent Neutron Scattering," J. Chem. Phys. 56_, 3217 (1972).

PRINCE, E., "The Configuration of the Water Molecule in Cupric Fluoride

Dihydrate at 928°K," J. Chem. Phys. 56, 4352 (1972).

PRINCE, E., L. W. SCHROEDER, AND J. J. RUSH, "A Constrained Refinement of

the Structure of Durene," Acta Cryst. (to be published).

PRINCE, E., A. D. MIGHELL, C. W. REIMANN, AND A. SANTORO, "Hexakis (Imidazole) Cobalt (II)

(to be published)

zole) Cobalt(II) Nitrate [Co(C

3H4N2

) 6

] (NO^," Crystal. Struct. Comm.

PRINCE, E., G. DONNAY AND R. F. MARTIN, "Neutron Diffraction Refinement

of an Ordered Orthoclase Structure," Am. Mineralogist (to be published) .

PRINCE, E., AND L. W. FINGER, "Use of Constraints on Thermal Motion in

Structure Refinement of Molecules vzith Librating Side Groups," Acta

Cryst. (to be published)

.

RAFIZADEH, H. A., S YIP AND H. PRASK, "Lattice Dynamics of Rhombohedral

Sodium Azide," J. Chem. Phys. 56_, 5377 (1972).

125
PUBLICATIONS

RAO, K. R., S. F. TREVINO, H. J. PRASK AND R. D. MICAL, "The Lattice

Dynamics of KN

3 ," Phys. Rev. 4B, 4551 (1971).

REIMANN, C. W.,- M. ZOCCHI, A. D. MIGHELL AND A. SANTORO, "Crystal and

Molecular Structure of Nitrotobis-(2,2 '-dipyridyl) cobalt (III) Hydroxide Nitrate Tetrahydrate [XCo(C H N ) (NO ) ] (NO ) (OH) -4H 0," Acta

Cryst. B27_, 2211 (1971).

RHYNE, J. J., S. J. PICKART, AND H. A. ALPERIN, "Direct Observation of an Amorphous Spin Polarization Distribution," Phys. Rev. Letters (to be

published)

ROWE, J. M. , J. J. RUSH, L. A. DEGRAAF AND G. A. FERGUSON, "Neutron Quasielastic Scattering Study of Hydrogen Diffusion in a Single Crystal

of Palladium," Phys. Rev. Letters (to be published).

RUSH, J. J., L. W. SCHROEDER AND A. J. MELVEGER, "The Dynamics of Sodium

and Potassium Bifluoride," J. Chem. Phys. 56_, 2793 (1972).

RUSH, J. J., L. A. DEGRAAF AND R. C. LIVINGSTON, "Neutron Scattering

Investigation of the Rotational Dynamics and Phase Transitions in

Sodium and Cesium Hydrosulfides," J. Chem. Phys. (to be published).

SANTORO, A., AND A. D. MIGHELL, "Coincidence-Site Lattices," Acta Cryst.

(to be published)

SANTORO, A., AND A. D. MIGHELL, "Properties of Crystal Lattices: The

Derivative Lattices and Their Determination," Acta Cryst. (to be

published)

SAVAGE, H. T., AND J. J. RHYNE, "Magnetic Characteristics of Gd Doped

SnTe and PbTe," A. I. P. Conf. Proc. 5, 879 (1972).

SCHROEDER, L. W. , L. A. DEGRAAF, AND J. J. RUSH, "Neutron Diffraction

Study of the Trigonal and Cubic Phases of NaSH," J. Chem. Phys. 55_, 5363 (1971).

WANG, F. E., S. J. PICKART, AND H. A. ALPERIN, "Mechanism of the TiNi

Martensitic Transformation and the Crystal Structures of TiNi-II and

TiNi-III Phases," J. Appl. Phys. 43, No. 1 (1972).

INDEPENDENT PROGRAMS

ALBERI, J. L., R. WILSON, AND I. G. SCHRODER, "Parity Violations in

Neutron Captive Gamma Rays," Phys. Rev. Letters (to be published).

126
PUBLICATIONS

BECKER, D. A., AND P. D. LAFLEUR, "Neutron Activation Analysis: Applications to Trace Element Analysis in Biological and Environmental

Materials," Proc, Conf. on Trace Substances in Environmental

Health, Columbia, MO, June, 1971 (1972) pp. 447-453.

BECKER, D. A., AND P. D. LAFLEUR, "Determination of Trace Quantities of

Uranium in Biological Materials by Neutron Activation Analysis Using

a Rapid Radiochemical Separation," Anal. Chem. 44, 1508 (1972).

BECKER, D. A. "Trace Analysis for Platinum in Glasses by Neutron Activation

Analysis," Anal. Chim. Acta 61_ (1972).

CARPENTER, B. S., "The Use of the Nuclear Track Technique for Boron and

Uranium Analyses in Botanical Material," Proc. Am. Nucl. Soc. Meeting,

Boston, June 1971 (1971), pp. 130-131.

CARPENTER, B. S., "Determination of Trace Concentrations of Boron and

Uranium in Glass by the Nuclear Track Technique," Anal. Chem. 44_, 600 (1972).

CARPENTER, B. S., AND P. D. LAFLEUR, "Observing Proton Tracks in Cellulose

Nitrate," Intern. J. Appl. Radiation and Isotopes 2_3, 157 (1972).

CARPENTER, B. S., "Quantitative Applications of the Nuclear Track Technique," The Microscope 20_, 175 (1972).

CARPENTER, B. S., AND P. D. LAFLEUR, "Nitrogen Determination in Biological

Samples Using thex Nuclear Track Technique," Proc. Am. Nucl. Soc.

Meeting, June, 1972 to be published)

.

DUCE, R. A., W. H. ZOLLER, and A. G. JONES, "Atmosphere Particulate and

Gas Sampling at McMurdo and South Pole Stations," Antartic J. of

U.S. ) (1971), 133.

FABRY, A., and J. D. JENKINS, "Calculations of the E£ Facility with ENDF/BVersions II and III and Comparison with Experiment," Proc. Am. Nucl.

Soc, Washington, November, 1972 (1972), p. 940.

FABRY, A., AND J. D. JENKINS, "Wall Return Neutron Fluxes for High- and

Intermediate-Energy Cavity Neutron Sources," Proc. Am. Nucl. Soc,

Washington, November, 1972 (1972), p. 975.

FRIEDMAN, M. H. , J. T. TANNER AND E. MILLER, "Rapid Instrumental Analysis

for Mercury in Biological Materials by Neutron Activation," Transactions of the Am. Nucl. Soc. 15, 150-151 (1972).

GLADNEY, E. S., W. H. ZOLLER, R. A. DUCE, AND A. G. JONES, "Vanadium,

Aluminum and Manganese in Atmosphere Particulate from McMurdo and

South Pole Stations," Antartic J. of U.S. (1972).

127
PUBLICATIONS

GLYNN, J. C, F. J. MUNNO, AND I. G. SCHRODER, "In-core Fast-Neutron

Measurements Using a He Semiconductor Spectrometer," Trans. Am. Nucl.

Soc. 15, 537 (1972).

GOTTFRIED, D., J. J. ROWE, AND R. I. TILLING, "Distribution of Gold in

Igneous Rocks," Geological Survey Professional Paper 727 (1972).

GRUNDL, J. A., V. SPIEGEL, JR., AND C. EISENHAUER, "Measurement of 235U

and 238U Fission Cross Sections for 252 Cf Spontaneous Fission Neutrons," Proa. Am. Nual. Soc, Washington, November, 1972 (1972),

p. 945.

JONES, A. E., N. CHAED, G. L. DUNSON, AND F. HOSAIN, "Clinical Evaluation

of Orally Administered Fluorine-18 for Bone Scanning," J. Radiology

(to be published)

LAFLEUR, P. E., "Retention of Mercury When Freeze-Drying Biological

Materials," Anal. Chem. (to be published).

LINCOLN, D. N., M. H. FRIEDMAN, AND J. T. TANNER, "Application of Neutron

Activation Analysis to the Determination of Mercury in Food Products:

A Bibliography," F.D.A. By-Lines 2, No. 2., 88-89 (1971).

LUTZ, G. J., "Determination of Lead in Environmental Samples by Photon

Activation Analysis," Proa. Am. Nual. Soc. Topical Meeting, Aug.

1971 (1972), pp. 144-149.

LUTZ, G. J., R. J. BORENI, R. S. MADDOCK, AND J. WING, "Activation Analysis: A Bibliography through 1971," NBS Techn. Note 467 (1972).

MARGOSIS, M., AND J. T. TANNER, "Neutron Activation Analysis: Logistics

and Economics," F.D.A. By-Lines 2, No. 5, 215-224 (1972).

MARSHAK, H., AND R. J. SOULEN, JR., "The Temperature Scale Defined by

60 Co y-ray Anisotropy and Noise Thermometry," Proc. of LT-lZ,

Boulder, Colorado (to be published)

MASTERS, L. W. , AND G. J. LUTZ, "Determination of Thallium by Photon

Activation Analysis," Anal. Chim. Acta 5_6, 365 (1971).

ROOK, H. L., P. D. LAFLEUR AND T. E. GILLS, "Mercury in Coal: A New

Standard Reference Material," Environ. Letters 2_, 195 (1972).

ROOK, H. L., T. E. GILLS, AND P. D. LAFLEUR, "Method for Determination of

Mercury in Biological Materials in Biological Materials by Neutron

Activation Analysis," Anal. Chem. 44, 1114 (1972).

128
PUBLICATIONS

ROOK, H. L., "Rapid, Quantitative Separation for the Determination of

Selenium Using Neutron Activation Analysis," Anal. Chem. 44 , 1276

(1972).

SCHRODER, I. G., "Emission of Long-Range Alpha Particles in the Sub-Thermal, Thermal, and Resonance-Neutron Fission of Pu ," Nual. Phys.

(to be published)

.

SEITZ, M. G., R. M. WALKER AND B. S. CARPENTER, "Improved Methods for

Measurement of Thermal Neutron Dose by the Fission Track Technique,"

J. Appl. Phys. (to be published)

.

SOULEN, R. J. JR., AND H. MARSHAK, "The Use of Josephson Junctions for

Noise Thermometry Below 1 Kelvin," Proo. Applied Conductivity Conf.

,

Annapolis3 Md. (May 1972)

.

TANNER, J. T., M. H. FRIEDMAN, AND D. N. LINCOLN, "Mercury Content of

Common Foods Determined by Neutron Activation Analysis," Science

177 , 1102-1103 (1972).

THOMPSON, B. A., AND E. C. MILLER, "Determination of Trace Elements in

Ruby Laser Crystals by Neutron Activation Analysis," J. of Research,

NBS--A. Physics and Chemistry 15k, 429 (1971).

THOMPSON, B. A., AND G. J. LUTZ , "Characterization of Ancient Bronze

Artifacts by Neutron and Photon Activation Analysis.," Radiochem and

Radioanal. Letters 9_, 343 (1972).

THOMPSON, B. A., AND P. D. LAFLEUR, "Gamma Ray Spectroscopy," Encyclopedia

of Chemistryj Third Edition (to be published)

.

YULE, H. P., "Study of Gamma-Ray Spectrum Distortion by Mathematical

Smoothing," Anal. Chem. 44, 1245 (1972).

YULE, H. P., "A Conversational Text Editor for a Laboratory Minicomputer, 1

' Anal. Chem. (to be published).

ZOLLER, W. H., G. E. GORDON, E. S. GLADNEY, AND A. G. JONES, "The Sources

and Distribution of Vanadium in the Atmosphere," Advances in Chemistry (to be published)

.

•U. S. GOVERNMENT PRINTING OFFICE :1973 —511-324 (204)

129
FORM NBS-H4A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-7582. Gov't Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE NBS REACTOR: SUMMARY OF ACTIVITIES OCTOBER 1971 TO SEPTEMBER

1972

5. Publication Date March 1973

6. Performing Organization Code

7. AUTHOR(S)

Robert S. Carter

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/Work Unit No. NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address Reactor Radiation Division

National Bureau of Standards

Washington, D„C„ 20234

13. Type of Report & Period Covered 10/1/71 - 10/1/72

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. 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 summarizes all those programs which depend on the NBS reactor. It covers the period from October 1971 through September 1972. The programs range from the use of neutron beams to study the structure and dynamics of materials through nuclear

physics and neutron standards to sample irradiations for activation analysis, isotope

production and radiation effects studies.

17. KEY WORDS (Alphabetical order, separated by semicolons) Activation analysis; crystal structure; diffraction; isotopes; molecular dynamics;

neutron; nuclear reactor; radiation

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21. NO. OF PAGES

14

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