THE RADIOACTIVITY OF SOME RUTHENIUM
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
By
BASANT LAL SHARMA, B. Sc., M. Sc.
The Ohio State University 1959
Approved by:
" - y n - L . t o J Z ------x a s i s e r ------^ ------Department of Physics and Astronomy Acknowledgm ent
I take this opportunity to express my sincere appreciation to Professor M. L. Pool for his interest, suggestions, and encouragement throughout this work. Table of Contents
Page
General Introduction ...... 1
Instrumentation ......
PART I
RADIOACTIVE DECAY OF Ru106 AND THE ESTIMATION OF THE THERMAL NEUTRON ACTIVATION CROSS SECTION OF Ru105
Introduction...... 8
Experimental D ata...... 11
Calculation of the Thermal Neutron Activation Cross Section of R u ^ ^...... 23
Results and Discussion...... 28
Bibliography ...... 30
PART II
RADIOACTIVE DECAY OF Rh101
Introduction...... 31
Experimental D a ta ...... 33
R esults ...... 49
Discussion and Conclusions ...... 51
Bibliography ...... 55 Table of Contents (continued)
Page
PART in
RADIOACTIVE DECAY OF Er171 AND A SEARCH FOR RADIOACTIVE DECAY OF Er172
Introduction...... 56
Experimental D a ta ...... 58
Results and Conclusion...... 75
Bibliography ...... 78
Autobiography...... 79
iv List of Tables
Page
Table I Isotopic Composition of Natural Ruthenium and the Purity of the Sample labeled Ru - 104 ...... 11
Table II Isotopic Composition of Natural Ruthenium and the Composition of the Enriched ...... 3 3
Table III Isotopic Composition of Natural Erbium as Compared with that of Enriched Er170 ...... 58
Table IV Spectrographic Analysis of Enriched Er170 ...... 5 9
v List of Figures
“ge
Nal (Tl) Well Type Crystal Arrangement 4
100-Channel Pulse Height Analyzer . . . 6
_ 106 106 Decay Scheme of Ru - Rh ...... 10 103 Decay of the Gamma Ray due to Ru . . 1 3
Gamma Ray Spectrum of Sample N-809, 19 Days after Irradiation . . . . . 14
Comparison of the Gamma Ray Spectrum of the
Sample N-809 with that of: 27127 0 Day-Ag^® • • 15
106 Gamma Ray Spectrum of Rh 19
1 O A Gamma-Gamma Coincidence Spectrum of Rh 21
Gamma-Gamma Coincidence Spectrum of Sample N-100 9 (Ru106 - Rh1 °6) ...... 22
Gamma Ray Spectrum of Sample N-1119 .... 35
Gamma Ray Spectrum of Ru^^ + p (N-1119) . . 37
545 kev Gamma Decay of Rh^ ^ ...... 38
Gamma Ray Spectra of Rh^^ (Sample N-1124) . 39
310 kev Gamma Decay of Rh^-^ ...... 41
Copper and Lead Absroption Measurements . . 42
Gamma-Gamma Coincidence Spectrum of Rh"*"^ 44
Comparison of the Gamma Ray Spectrum of Ru ^ + p (N-l 119) with that of Ru + d (N-791) 46
vi List of Figures (continued)
F igure Page
18. Gamma-Gamma Coincidence Spectrum of Sample N-791 (Ru + d ) ...... 48
19. Proposed Decay Scheme of ...... 54 170 20. Gamma Ray Spectra of Er + n (N-1031) . . . 6 0
2 1 . 308 kev Gamma Decay of (N-1031) .... 62
22. Gamma Ray Spectrum of Sample N-1031...... 63
23. Gamma-Gamma Coincidence Spectrum of Er171 (Sample N-1031)...... 65
24. Gamma Ray Spectrum of Yb Fraction...... 67
25. Well Crystal Measurements of E r^^ (N-1090) . 69
26. Gamma Ray Spectra of Sc^^, La^^, and Yb^7~* Impurities in Sample N-1096 71
27. Gamma Ray Spectra of Tm^ 7^ (Test Tube No. 20) t Tm169 + n (N-1091), and Er170 + n (N-1096) ...... 73
28. Copper Absorption Gamma Ray Spectra of Er170 4 n ...... 74
1 71 29. Decay of Scheme of Tm ...... 76 General Introduction
Gamma ray scintillation spectrometry has developed greatly in recent years. The reasons for its development are manifold, but the most important one is that the detailed analysis of nuclear radia tion yields information about the properties of nuclear levels, which are of basic importance for our understanding of nuclear matter and for the development of nuclear theories, such as the theory of nuclear shell structure.
Scintillation counting offers three primary advantages for the detection of gamma rays. First, resolving times of the order of millimicroseconds allow high speed counting with no resolving time corrections. Second, the output pulse height generated by the
scintillation detector is proportional to the amount of energy dissi pated in the scintillator by the incident gamma ray. Third, the fact
that the sensitive volume is usually a solid results in approximately a hundredfold increase in efficiency over gas counters.
The availability of enriched isotopes, various types of bom
barding particles, higher neutron flux, and other improved modern
techniques have made it possible to study nuclear reactions in greater
detail and thus obtaining new information together with confirming
previous data. It is true that the modern techniques are capable of
analyzing complex spectra, but at the same time in some cases the spectra have become more complicated because of them. For
example, on one hand, the availability of higher thermal neutron flux has made it possible to study the decay of radioactive isotopes formed by double thermal neutron capture or decay of radioactive isotopes having very low capture cross sections; on the other hand, it has been
able to superimpose the spectra of impurities which are present in
very small quantities but have relatively higher thermal neutron cross
sections. However, the importance of the above mentioned techniques
cannot be challenged.
The study of the neutron capture cross sections of stable and
radioactive isotopes is also of great importance because an extensive
knowledge of them may show further interesting regularities and may
assist in accounting for the abundances of elements.
Keeping these basic points in mind, the following investiga
tions were undertaken. The dissertation is divided into three parts.
The first part concerns the study of radioactive decay of Ru^^ from
which it was possible to calculate the thermal neutron activation
cross section of Ru^^, The second part deals with the detailed study
of the decay of Rh^^. In the third part of this dissertation radio-
171 active decay of Er together with a search for radioactive decay of
£.r172 hag been studied. In all the above investigations, the en
riched isotopes obtained from Oak Ridge were used. Instrumentation
The choice of detector and the source-detector configuration largely depend on the activity of the isotope under examination, and will be discussed later for each of the isotopes separately.
The following is a brief description of the various types of
instruments and techniques which were used.
Scintillation Detectors
The detector, known as flat crystal in this laboratory, was
composed of a 1- 3/4- x 2" cylindrical Nal (Tl ) crystal, a DuMont
6292 photomultiplier tube, and a white cathode follower designed
at Oak Ridge National Laboratory. The pulses from this detector
were fed into a 100-channel analyzer.
Another type of scintillation detector used was the well type
crystal, which is shown in Fig. 1. This detector consisted of a
3" x 3" cylindrical Nal (Tl ) crystal with a 3/8" hole which extended
along the longitudinal axis to the center of the crystal, a DuMont
6 3 94 (5 inches) photomultiplier tube and a preamplifier. Es
sentially a 4ir geometry was obtained by placing the sample inside
the well of the crystal. For studying the effects of geometry vari
ation a source holder was provided outside the crystal. In order to
reduce the background radiation the whole assembly was placed in
a lead and iron shield. The above mentioned arrangement has 4
Be -Cu Si;rii
Re fie ctoi Sprayed
well Cup 0. 032 " tl.iek Alun iii iu.i\ i
Spun Body 0. 040 " tiiiek Type 1100-0 A Luii i k .u t n. *«
Reflector Packed Ai O. 0. 062 " t:.Ick
Optical Window 3-S 0. 12 5 " Glass
Crystal
FIG. 1. Nal (TL) vV Id LB TYPE CRYSTAL ARR AN GEMENT. many advantages; compton distribution accompanying the peak is greatly reduced, the sum peaks and self coincidences can be studied, the efficiency can be determined more accurately^.
Hundred Channel Pulse Height Analyzer
The RIDJL Model 3300, pulse height analyzer manufactured by the Radiation Instrument Development Laboratory was used, which was designed to scan simultaneously random voltage pulses having various amplitudes and waveforms and to sort them on an amplitude basis . This analyzer contained a simple magnetic core memory- type digital computer which was modified to obtain a capacity of slightly over one million counts per channel. The photograph of the
100-channel pulse height analyzer is shown in Fig. 2.
Gamma-gamma coincidences were also made with this instrument in an attempt to establish and verify the decay schemes of each isotope. The coincidence circuit used in this connection was
an integral part of the 100-channel analyzer. During the coincidence
runs a high random coincidence count, which resulted from a rather
long ( 1 p- sec ) resolving time of the circuit, were compensated for
^Beta and Gamma-ray Spectroscopy, K. Siegbahn, p. 155.
^Instruction Manual for Model 3300 Pulse Height Analyzer, Radiation Instrument Development Laboratory, p. 1-0-1. 100-CHANNEL PULSE HEIGHT ANALYZER by a delay line (6|^sec ) circuit which, automatically subtracted the random coincidence counts from the gross coincidence counts.
Geiger-Muller Counter
A TGC-3NA G-M tube was used for absorption measure ments. This tube had a 1.7 mg/cm2 mica window which permitted the detection of low energy electromagnetic radiation and also beta particles of energy greater than 30 kev. A standard high voltage power supply and a scaling unit were used in conjunction with the
G-M tube.. The tube and the sample rack, provided with a number of slots for holding samples and absorbers, were enclosed in a
cast iron shield to cut down the background radiation. PART I
RADIOACTIVE DECAY OF Ru1 06 AND THE ESTIMATION
OF THE THERMAL NEUTRON ACTIVATION CROSS SECTION
OF Ru1 05
8a Introduction
The gamma radiation from a 30-sec beta activity'*' which is generally used in an equilibrium condition with 1 year Ru* ^ ,
1 0 has been studied extensively during the past few years. Ru decays to Rh*"^k ky emitting a 39-kev. beta particle^. The first complex decay scheme of Rh*’^ was proposed^ by Peacock in 1947, and the first experimental evidence for greater complexity of the Rh***^ decay
scheme was obtained by Goldhabar and der Mateo si an^ in 1950, who
discovered that this activity could produce photoneutrons in Be and
d 2o .
The Rh***^ decay and the energy levels for the excited states
i n A 5 a of Pd have been suggested by Hayward and Alburger . Later
gamma radiations of 30-second Rh"*®^ have been examined by Kahn
f-j and Lyon by using a Nal (Tl ) gamma ray spectrometer and the de-
■*L. ID. Glendenin and E. P. Steinberg, National Nuclear Energy Series, Plutonium Project Record 9, 793 (1951).
^H. M. Agnew, Phys. Rev. 77, 655 (1950).
^W. C. Peacock, Phys. Rev. 72, 1049 (1947).
^M. Goldhabar and der Mateosian, Brookhaven National Laboratory Report BNL 51, (S-5) (1950).
^R. H. Hayward, Phys. Rev. 85, 760 (1952).
6D. E. Alburger, Phys. Rev. ji8, 339 (1952).
^B. Kahn and W. S. Lyon, Phys. Rev. 92, 902 (1953). cay scheme proposed by them is essentially in agreement with the one proposed by Alburger except for an additional level in Pd^^ at Z.Z8
Mev. However, for the purpose of determining further details of the
Pd1 level structure Alburger and Toppel^ have reinvestigated
Rh^^, and have examined the internal conversion and gamma ray spectra of Ag*^. Ru separated from fission products was used as a 106 source for the measurement of the decay of Rh in all the above mentioned investigations.
In the present investigation an attempt was made to identify 1 06 the gamma radiations from Rh from a completely different angle.
106 The enriched isotope of Ru was used to investigate Ru and consequently Rh^^, which can be formed from Ru^^ by two con- Q secutive neutron captures. The decay scheme proposed by Alburger
shown in Fig. 3, and a Ru^^ - Rh^^ source obtained from Oak
Ridge National Laboratory, were used as standards for identifying and
comparing the activity due to Rh^^. After identifying this activity
an attempt was made to estimate the thermal neutron activation cross
section of Ru^^.
g D. E. Alburger and B. J. Toppel, Phys. Rev. 100, 1357 (1955),
^D. Strominger, J. M. Hollander, and G. T« Seaborg, Table of Isotopes, University of California, Radiation Laboratory Report (1958). 10
106 Ru 0+
106 Rh 1 +
6 %
3%
11% Me v
2. 40
68
1. 56
1. 134 1. 12
2+ 0. 513
106 Pd 0+
106 106 FIG. 3 . DECAY SCHEME OF Ru - Rh ( Taken from the Table of Isotopes, D. Strominger, et al., 1958.) Experimental Data
Fifteen milligrams of ruthenium enriched in isotope 104 was obtained in elemental form from the S table Isotopes Sales Division of
Oak Ridge National Laboratory. The natural abundances^ of the isotopes in ruthenium metal as well as the isotopic and spectro- graphic analyses^ of the electromagnetically enriched Ru^ ^ isotope are given in the following table.
Table I Isotopic Composition of Natural Ruthenium and the Purity of the Sample labeled Ru-104
Isotope Percent of Isotopic Analysis Spectr ographic Isotopein Atomic Percent Anal y si s Natural Ru Element Perc ent
R u-96 5. 47 Trace + Ag T Ru-98 1 . 84 Trace + - Cu <0.05T Ru-99 12. 77 0.1 + 0. 05 Mg <0. 02T Ru-100 12. 56 0.1 + 0. 05 Pb <0. IT Ru-1 01 17. 10 0.3 + 0. 05 Pt <0. 1FT Ru-102 31 . 70 1.3 + 0. 1 Si <0. 05T Ru-104 18. 56 98. 2 + 0. 1
The sample for irradiation was prepared by sealing 15 milli
grams of the enriched material in a small quartz vial which was
subsequently exposed to a thermal neutron flux of 1. 2 x 101 4- neutrons
■^J. R. Sites, Electr omagnetically Enriched Isotopes and Mass Spectrometry, p. 152, Academic Press, N. Y. (1956).
2 From Oak Ridge Report supplied with the sample.
11 1 2 cm ^sec."^ for 176.8 hours at the Materials Testing Reactor of the
Phillips Petroleum Company", Idaho. In addition to this vial, an empty vial was also irradiated. The purpose of this was to check the radiation emitted by the quartz vial. After irradiation, the quartz vial, containing radioactive ruthenium, was placed inside a cardboard pill box and was labeled as N-809.
At the beginning of the measurements the activity of the
103 sample (N-809) was very high and was mainly due to 39.7-d Ru
The decay of 498 kev gamma ray was followed on a single channel pulse height analyzer for a period of 55 days. The decay curve of
the 498 kev photo-peak due to and the typical gamma ray
spectrum of the sample (N-809) in the early part of the measurements
10 3 are shown in Fig. 4 and Fig. 5 respectively. Because of the Ru
activity, which was formed in sufficient amount to mask any activity i of 1 year-Ru , the sample was allowed to decay for a period of
400 days. After this period, it was observed that the activity of
1 year-Ru^^ was still masked by the activity of some impurity.
However, after comparing the gamma ray spectrum of the sample
(N-809) with that of 270 d-Ag^ ^ ^, as shown in Fig. 6, it was found
that this sample contained, as an impurity, the greatest amount of
a HO Ag
The chemical separation of the radioactive silver from this
sample was done as follows. Because of the difficulties encountered 3 x 10
103 Decay of the 498-kev photopeak of Ru
Single Channel Analyzer Detector: 1-3/4" x 2" Nal crystal Sample No. N-809
•H
40 days
3 x 10
Days after irradiation
FIG. 4 . DECAY OF THE GAMMA RAY DUE TO Ru103. Single Channel Analyzer Detector: 1-3/4" x 2" Nal crystal
100
•H
Bias voltage in volts FIG. 5 . GAMMA RAY SPECTRUM OF SAMPLE N - 809, 19 DAYS AFTER IRRADIATION. 657 kev Gamma ray spectrum of sample N-809 (Live tim e - 10 m in )
-o Gamma ray spectrum of Ag^^samplc (Live tim e - 20 m in )
Reference: pp. 1695-1697
N et count
1 0 10 :o 30 40 70 90 Channel Number rlG. u. COMPARISON OP TilC GAMMA RAY SPfcXTRUM OF TIL! SAMPLK N-809
WITH THAT O F 270 D A 7 - A,-,U ° .
Ui in dissolving ruthenium and the chances of losing it completely, the quartz vial was opened and approximately one-half of the total sample was used for this purpose. In order to dissolve ruthenium without spattering, it was sealed together with a fixed amount of concentrated nitric and Hcl acids in a glass tube and was heated in a furnace at constant temperature. After it was dissolved, the silver fraction, with the addition of silver carrier, was precipitated by the standard procedure used for the precipitation of silver. The method for the precipitation of silver was used again and again for a number of
times in order to remove the radioactive silver (Ag^®) completely.
The flow chart is shown below. 1 7
Solution. (417 counts/s ec)
Ag precipitate Solution (231 counts/ sec) after 1st precipitation
Ag precipitate Solution (111 counts/ sec) after 2nd precipitation
I Ag precipitate Solution (42 counts/ sec) after 3rd precipitation
Ag precipitate Solution (4. 6 counts/ sec) after 4th precipitation
1------Ag precipitate Solution (0.75 counts/ sec) after 5th precipitation
(9.4 counts/sec) (Sample N-100 5)
The counting rate values for the 656-kev gamma ray of Ag^^*,
mentioned in the above flow chart, were measured by placing the
sources at 13 cms from the crystal.
Although cobalt and europium were not listed as impurities in
the spectrographic data supplied by Oak Ridge National Laboratory,
the activities due to them were predominant in the sample (N-1005)
after the silver impurity was removed completely. Because of con
siderable difficulty encountered in separating cobalt activity from the
ruthenium sample, it was considered desirable to subtract the
gamma ray spectrum due to Co^® from that of the sample under 18 investigation as shown in Fig. 7. The net spectrum was compared with that of sample (N-1009) obtained from Oak Ridge,
From this comparision it was concluded that the photo-peaks of energy-
513 kev and 621 kev were due to activity present in the sample
(N-l 005) .
In order to identify more conclusively the origin of 513- and
621- kev photo-peaks, coincidence measurements were made with the
sample (N-1005). These coincidence results were compared with
those obtained from standard Ru^^1 - Rh^^ source (N-1009).
The gamma - gamma coincidences were observed by placing
the sample (N-1005) between two scintillation heads , each containing
a 1-3/4" x 2" Nal ( T1 ) crystal. These scintillation heads were
mounted horizontally with their axes oriented at 180° with respect to
each other. In order to get high coincidence yields and to minimize
the effects of anisotropic distribution of gamma rays, the crystal
faces were placed as close as possible to the radioactive source. In
the above mentioned arrangement, the single channel analyzer was
gated to accept the pulses corresponding only to 513 kev gamma ray
while the hundred channel pulse height analyzer with a fixed window
width 1% viewed the entire spectral region. In this way a pulse was
stored in the proper channel of the hundred channel analyzer memory
unit whenever a coinciding gate pulse was present. The 400 minutes 1 x 10'
Gamma ray spectrum of sample N-1005 (Live time- 30 min ) • Gamma ray spectrum of Co o—«—a Net spectrum after the subtraction of Co spectrum
Geometry. 7 cm from the crystal Reference: pp. 2312-2315 17 Mev Detector: 1-3/4" x 2" Nal crystal Net counts 1. 33 Mev
1 x 10
106 513
106
V. 2x 10' _L 10 20 40 5030 60 70 Channel Number 106 FIG. 7 . GAMMA RAY SPECTRUM OF Rh coincidence gamma ray spectrum of sample N-1005, obtained by fix ing the gate on the 513 kev photo-peak of Rh^^, is shown in Fig. 8.
Keeping the geometry and the amplifier gains of single and hundred channel analyzer same, another 400 minutes run was made with the
Ru^^ - Rh^^k sample (N-1009) obtained from Oak Ridge. The re
sult of this coincidence run, shown in Fig. 9,was found to be in close agreement with those of the previous one. 106, Gainma-gamma coincidence spectrum of sample N-1005 ( Rh 6 x 10 with gate set on 513 kev
Non-coincidence spectrum Geometry: (Live time- 5 min ) j Coincidence spectrum-. (Live time- 400 min ) -—V------‘Detecto rs Reference: pp. 1937-1944 1-3/4" x 2" Nal crystals
106 513 kev ( R1
1 x 10 Scale: N x l/c l
G ross counts 106,
10 20 30 50 60 70 ;,o Channel number ^ t-1 FIG. 8. GAMMA - GAMMA COINCIDENCE SPECTRUM OF Rh Gam, iia-;,aai.: ta coincidence spectrum of
sampleN-1009 ( Hu ^ - Rh ) with jate
Geometry: same as shown in £i
Non-coincidence spectrum {Liive t im e - 5 m in ) Coincidence spectrum (.Live tim e- 400 m in )
Reference: pp. 1947-1921
^-»Scale: N x 1/10
1, 05 M ev
0 10 20 30 40 5060 70 Channel number FIG. 9 . GAMMA - GAMMA COINCIDENCE SPECTRUM
OF SAMPLE N- 1009 ( R u'^'- Rh106) . Calculation of the Thermal Neutron Activation
Cross Section of Ru''^
To find the thermal neutron activation cross section for radioactive Ru^^ nuclide, the stable isotope Ru^^ is subjected to a thermal neutron irradiation. After two successive neutron captures
TD . , . Ru 106 is produced. 104 104 If we expose N „ atoms of Ru to a thermal neutron Ru flux
dN 1 0 6(t) 105 105 106 106 Ru = N (t) cr- 0 - X. N (t) (2) dt Ru Ru Ru Ru
105 106 where N (tl and N (t) are the number of radioactive Ru ' Ru w
r T, 105 , n 106 .. . , , atoms of Ru and Ru respectively at time t
(t ^ ti).
104 105 o~ and cr- are the thermal neutron activa- Ru Ru
104 105 tion cross section of Ru and Ru respectively.
and and are the decay constants of Ru^^ Ru Ru 23 24 and Ru 1 respectively. 105 106_ Knowing the initial conditions i.e. , at t = 0, N - N - 0 , Ku Kll the above equations (1) and ( 2) can be solved simultaneously for
105 106 ^ 05 N ^ (t) and N (t) . Hence the radioactive atoms of Ru and
10 6 Ru after the irradiation period t^ are given by
104 104 a~ N
= - --V.T 105 — (1 - = Ru 1 ) <3> Ru
104 105 104 ? 106 % °p Nr * - X ti N (t.) = Si------Ru------/ i _ e Ru \ R u ' 1' T05 10 5 1106 06 \ > X X Ru Ru
104 105 104 P 105 106 N r> * “ K Ru fcl ' KRu Ru Ru Ru v - e (4) T 05 To5 105 ( X VRu ^ Ru ” ^ Ru^ r e specti vely. 104 105 104 105 106 Thus knowing N , N (ti) ,tr" , 0 , X , X and 5 Ru Ru' 11 Ru Ru Ru
105 106 . 106 ti , one can evaluate o~ • However, Ru decays into Rh , 1 Ru and it is this activity of Rh^^ which is measured in actual practice.
Therefore, N4 ^ (t-i), the number of radioactive atoms of Ru^^ at tim Ru A ti is obtained in terms of N4^ (t) , the number of radioactive atoms 1 Rh V 1 25 of at any time t ^ tj_.
The rates of decay of radioactive atoms of and Rh'*"^^ at any time t ^ tj are given by
d N 106 (t) Ru .1 0 6 106 . dt R U Ru ^ ^ ^ and
, - t 106. . d N (t) Rh _ , 106 106.. 106 _106 dt = ' XRhN Rh W + X Ru N Ru 0) (6)
, ^106 J 106 wnere ^ D and N are the number of radioactive atoms -tv U- ±<.11
of Ru^ ^ and Rh^^ respectively at any time t ^ tj.
106 106 and X _ and X „, are the decay constants of Ru Rh _ 106 , 106 .. 1 Ru and Rh respectively. 106 Solving the above differential equations (5) and (6) for N (t)
and (t) and assuming that at t = t-i , ^ = 0 leads to Rh w 1 Rh
1 06 106 106 >>- (ti - t) N Ru « = N Ru (*l) * RU «
106 106 106 / ,\ \ ^ ^ ^ ^ 4-\ fq\ n106 . X Ku ” Ru fa) ^ Ru 1 _ e Kh(‘l-0 (8) Rh io6 - 106 7 A. \ Rh Ru
Thus measuring the total amount of the 27Od - Ag^ ^ 106 110 activity in the sample and the amounts of Rh and Ag activities no present in the fraction of the sample from which Ag was removed 106 completely, the total amount of Rh activity can be calculated. 106 106 . . Hence knowing N (t) at any time t > t]_ one can obtain N 105 and consequently one can evaluate •
105 The numerical values used in the calculation of cr^u are given below
104 1 a— = 0. 7 barn. Ru
p = 1. 2 x 10^4 neutrons cm ~^ sec"^
t]^ = 176. 8 hours
t = 62 0 days
105 T1/2 of Ru = 4.5 hours
Tf/2 of Ru'*' ^ =1.0 year
T1/2 of Rh^**^ = 30 seconds
M104 104 , Ru ’ ^‘*le nurnt>er of Ru atoms in 15 milligrams of Ru enriched in R u 104-. L Ql4 7L-^yg.L^ £f!) = 8.52 X 1019 atoms.
1 7 The crystal efficiency of 1-3/4” x 2” Nal crystal placed at 7. 5 cms
from the source, for 513 kev gamma ray = 0. 013. Knowing the crystal
^ W. H. Sullivan, Trilinear chart of Nuclides, AEC (Jan. 1957) ^E. A. Wolicki, etc. , "Calculated Efficiencies of Nal Crystal," NRL Report 4883, p. 32 (1956). N 4The calculated efficiency is defined as N 0 > where N is the total number of interactions in the crystal and No denotes the number of gamma/sec radiated by the source. 27 efficiency. N^n = \9* ^ 9 _ 7 7 4 counts/sec where 1 0 . 0 6 counts/sec is y Rh 0.013 the measured value of the total disintegration, per sec, which is obtained by multiplying the measured value of the net counting rate of
513 kev gamma ray of R h ^ 8 with the proper branching factor. The net counting rate was obtained after subtracting the cobalt and euro pium activities which were present in the sample N-1005
(Ref. pages 1854-1857).
Substituting these values in equation (3) yields
(7 74) x _ —-— V 9 9,2---- ) 106 v 1 v 30 365 x 24 x 3600 7 N R^l) = . 6 9 3 X 61 3 .6 9 3 X 613 X 24 X 360
/ Qo \ 365 " 30 % ( *693______) x e - e 365 x 24 x 3600
= 774 x 365 x 24 x 3600 9 30 x .3134 ------2‘6° X 10
K now ing (t^) and substituting the valu es of N* ^
104 105 .106 o“ r u , 9 , a. ^ ^ and ti m equation (4) we get
105 (2.60 x 1 0 9)______x Ru (.7 x 10-24) x (8. 52 x 1019) x (1. 44 x IQ28)
.693 x .693 3 600 x 3600 x 4. 5 x 122.7
= 2. 03 x 10-25 cm 2
Hence the calculated value of cr~ = 0.20 barn Ru Results and Discussions
104 106 The irradiation of Ru produced 1 year-Ru which decayed into 30 second-Rh 106 by emitting beta particles. After the silver impurity was removed, and the contributions from cobalt and europium impurities were subtracted, the 513- and 621-kev gamma rays of Rh^^ were verified to be in coincidence. The gamma energies and the coincidence results found in this research were consistent with the previously established results of this isotope.
105 The thermal neutron activation cross section of Ru was
calculated from the gamma ray intensity considerations. Using
513- kev gamma ray intensity, the thermal neutron activation cross
1 05 section of Ru was calculated to be 0. 2 0 barns. Whereas the
thermal neutron activation cross section of Ru^^, calculated from
621 kev gamma ray intensity consideration, was found to be 0.28
barns. Although the two calculated values of the thermal neutron
activation cross section are in close agreement with each other,
there would be some error present in them due to the activities
produced from impurities. It is true that a scintillation spectrome
ter and coincidence counting methods reduce the errors caused by
the activities produced from the impurities, but at the same time
they bring forward such problems as a quantitative knowledge of
28 the branching ratios or the intensity percentage values whenever more than one gamma rays are emitted. The question of impurities is very important because the successive neutron capture method is a second order process. Therefore, the very best chemical separation must be tried in such cases. Bibliography
Agnew, H. M. , Phys. Rev. Tl_, 655 (1950)
Alburger, D. E. , Phys. Rev. 88, 339 (1952)
Alburger, D. E. and Toppel, B. J., Phys. Rev. 100, 1357 (1955)
Glendenin, L. E. and Steinberg, E. P. , National Nuclear Energy Series, Plutonium Project Record, 9, 793 (1951)
Goldhabar , M. and der Mateosian, Brookhaven National Laboratory Report, BNLJ31, (S-5) (1950)
Hayward, R. H. , Phys. Rev. j55, 760 (1952)
Kahn, B. and Lyon, W. S. , Phys. Rev. 92 , 902 (1953)
Peacock, W. C. , Phys. Rev. 72, 1049 (1947)
Sites, J. R., Electr omagnetically Enriched Isotope s and Mass Spectrometry, p. 152, Academic Press, N. Y. (1956)
Strominger, D. , Hollander, J. M. and Seaborg, G. T. , Tables of Isotopes, University of California, Radiation Laboratory Report (1958)
Sullivan, W. H. , Trilinear Chart of Nuclides, AEC (1957)
Wolicki, E. A. and Jastrow, R. ,"Calculated Efficiencies of Nal Crystals," Naval Re search Laboratory Report 4883, 32 (1956)
30 PART II
RADIOACTIVE DECAY OF Rh101
31a Intr oduc tion
The activity of Rh^^ was first reported among others, by
Lindner and Perlman^ and by Eggen and Pool^. In 1951, Sullivan 3 101 et al. reported the half-life of Rh to be 5. 9 days. Later the radiations from Rh activity produced by the bombardment of pure Ru metal with protons were examined in a beta ray spectrometer by 4 Scoville, Fultz and Pool . According to them, the observed in ternal conversion peaks, decaying with a half life of 4. 5 days, were attributed to K and L conversion electrons from the 148 kev and 305
kev gamma rays ofr Rh , I 01 .
More recently, Pd isotopes were prepared by oC particle
bombardment of Ru metal powder, and the radiations from these
isotopes and their Rh daughter were investigated with a scintillation
5 coincidence spectrometer by Katcoff and Abrash . After the decay of
Lindner and I. Perlman, Phys. Rev. 73, 1202 (1948).
^D. E. Eggen and M.L. Pool, Phys. Rev. 75, 1464 (1949).
^W. H. Sullivan, N. R. Sleight and E.M. Gladsow, NNES- PPR_9, 1949 (1951).
4 C. L. Scoville, S. C. Fultz and M.L. Pool, Phys. Rev. 85, 1046 (195 2).
^S. Katcoff and H. Abrash, Phys. Rev. 10 3, 966 (1956).
31 32 the shorter lived components in all the Rh and Pd samples, they observed that Rh^^ decayed by electron capture with a half life of 4. 7 days and the only gamma ray was at 310 kev.
Farmer^1 was the first to report that the 127- and 198- kev 7 gamma rays did not, as previously reported by Avingnon and others,
belong to Rh^^, but were due to a long-lived (half life 5+1 yr) isotope of Rh with A < 102. Since then several people have studied 8 the decay of long-lived isotopes of Rh. Hisatake et al. and Perrin
et al? , have assigned the 5 year-activity to Rh.^^.
Because of a considerable disagreement in the reported data
of half life and the number and energies of the gamma rays in the de
cay of Rh'*'^ , it was believed that a r einvestigation might be desirable.
Furthermore, a research on this isotope was also suggested by the
fact that the enriched Ru t formerly not available, could be
obtained from Oak Ridge. Hence the present investigation was under
taken with the view of obtaining a detailed information regarding the 10i decay of Rh
^D. J. Farmer, Phys. Rev. J?9, 659 A (1955).
^P. Avingnon, Compt. rend. 240, 176 (1955).
®K. Hisatake, J. T. Jones and J. D. Kurbatov, BulLAm. Phys. Soc., Series II, 271 (1956).
^N. Perrin, L. Dick, R. Foucher and H. Vartapetian, J. Phys. et. radium, 17, 539 (195 6). Experimental Data
The enriched R u ^ \ used in the present investigation, was obtained from Oak Ridge National Laboratory. The isotopic compo sition^ of natural ruthenium and the isotopic and spectrographic analyses^ of the electromagnetically enriched Ru^^ are given in the following table .
Table II Isotopic Composition of Natural Ruthenium and the Composition of the Enriched Ru
Isotope Percent of Isotopic Analysis Spectr ogr aphic Isotope in Atomic Percent Analysis Natural Ru Element Percent
Ru- 96 5. 47 0.1+ 0. 05 Cu <0. 05 T Ru- 98 1 . 84 0.1 + 0.05 K 0. 02 Ru-99 12. 77 0.4 + 0. 10 Ru-1 00 12. 56 2.3+ 0. 10 Ru-101 17. 10 91.1+ 0.20 Ru-1 02 31 . 70 5.7+ 0. 20 Ru-1 04 18. 56 0.4 + 0.10
In order to produce radioactive Rh^'*', the enriched Ru was bombarded with 6 Mev protons for 30 minutes at the Ohio State
University cyclotron. Shortly after the irradiation, a number of
^J. R. Sites, Electromagnetically Enriched Isotopes and Mass Spectrometry, p. 152, Academic Press, N. Y. (1956).
^From Oak Ridge Report supplied with the sample.
33 34 samples were prepared in order to perform all the different types of measurements simultaneously. The well crystal smaple N-1124 was made by pouring molten paraffin over a small portion of the original sample in the bottom of a l/4" x 2" glass test tube. Approximately two hours after the sample was removed from the cyclotron, measure ments with the 100-channel scintillation spectrometer were started.
These early measurements showed the presence of .310- , .442- ,
. 545- , .82 3- , 1.10- , 1.36- , 1. 56- , 1.93- , and 2.38- Mev gamma rays. All, except 310- and 545- kev gamma rays decayed with a half-life of 20 hours. This 20 hour-activity was attributed to
the decay of obtained by the proton bombardment of Ru^^
present in the enriched These gamma rays associated with 100 the 20-hour activity of Rh were compared with those reported by 3 Marquez and were found to be in close agreement with them. A
typical gamma ray spectrum of the flat crystal sample of + p
(N-1119), taken ten hours after the irradiation is shown in Fig. 10.
The decays of the 310- and 545- kev gamma rays, ob
served in the gamma ray spectrum of the Ru^^ + p sample (N-1119)*
were followed regularly over a period of20 days by means of a 100-
channel scintillation spectrometer employing a 1-3/4" x 2" Nal (TI )
"^L. Marquez, Phys. Rev. 92, 1511 (1953). 35
,310 kev
Gamma ray spectrum of the sample N-1119 ( Ru 10 hours after the bombardment.
Geometry: 4 cm from the crystal 545 k ev Detector: 1-3/4" x 2" Nal crystal Amplifier gain: F it 1/16 Reference: p. 6300
823 kev
1. 10 M ev
1. 36 M ev
1. 56 Mev
1. 93 M ev
2. 38 M ev
20 30 40 50 Channel Number FIG. 10 . GAMMA RAY SPECTRUM OF SAMPEE N-1119 . crystal. Throughout this period the source to crystal distance was kept constant at 4 centimeters. In each case the observed photo peak heights of this sample were normalized to the 661 and 360- kev photo 137 133 peaks of the long-lived Cs and Ba respectively. The gamma ray spectrum obtained, 5.7 days after the irradiation is shown in
Fig. 11. The logarithmic decay curve of the 310-kev gamma ray of this sample was linear for 4 half-lives with a half life of 4.4 + . 04 days. Although, the 545- kev photo peak was finally observed to de cay with a half life of 4.4 days, the relatively rapid initial decay of this gamma ray indicated the presence of a short-lived activity in the sample. After the analysis of the decay data, it was found that
the relatively rapid initial decay of the 545 kev photo peak was due to
the presence of the 535 kev gamma ray of 20 hr Rh^^* The loga
rithmic decay curve of the 545 kev gamma ray of the Ru^^ + p
sample (N-1119) is shown in Fig. 12. 101 In order to follow the decay of the Ru + p sample (N-1124)
more accurately, measurements using 3” x 3" well type crystal,
were made simultaneously. With the source placed in the well, the
+ p sample (N-1124) was observed to emit 75-, 310-, and 545-
kev gamma rays. The compton continuum accompanying the 310- kev
photo peak was much reduced in these observations. Some of the
gamma ray spectra obtained are shown in Fig. 13, As observed in 37
310 key
Gamma ray spectrum of s i :.b N-1119 (Ru10'+ p ), 5,7days alter the irradiation, Ge«..ctrr. 4 cm. from t:.c crystal Detector: 1-3/4’ x 2” Nal crystal
Geometry: 4cm irom the crystal Detector: 1-3/4" X 2" Nal (T I) crystal Reference: p. 0449
~L*k,i days
2 x 1 0 '
Channel number ^ FIG, 1 1 . GAMMA RAY SPECTRUM OF Ru f ( N - l l l f I 4 8 10 120 14 Days after irradiation FIG, 1 2 , 545 kev GAMMA DECAY OF R h '0 1 , lo‘‘ 10 10 3 2 Gross counts per 2 minutes 10 f , j HK -a ) x-ray HhK ( 5 v e k 75 20 I. i0 ( A PEE N-1124) 4 2 1 1 - N E E P SAM ( R li101 F O A R T C E P S Y A R A M M A G . 3 1 FIG. JO 40 l ber m u N el n n a h C 10 kev e k 0 31 50 70 54 5kev 1
(1
1 i r r 4
kev gamma rays were observed to decay with a 4. 4 day half-life. The
logarithmic decay curve of the 310 kev photo peak was linear for 5 half-lives with a half-life of 4.4 days, and is shown in Fig. 14.
In order to investigate the origin of the 75 kev photo peak,
the lead and copper absorption measurements were made with a
scintillation spectrometer on each of the observed photo peaks. In
the well crystal absorption measurements, the Ru^^ + p sample
(N-1124) was placed inside the 1.6 and 1.5 mm thick copper and lead
tubes, which in turn were placed in the well. A comparison of the
copper and lead absorption gamma ray spectra to the no absorption
101 gamma ray spectra of the Ru + p sample (N-1124) is shown in
Fig. 15. Two interesting points were observed during the course of
the above mentioned absorption measurements which strongly
suggested that the 75 kev photo peak was actually due to Pb x ray,
produced by the photoelectric absorption of 310 kev gamma ray in
the lead shield around the crystal. Firstly, the 75 kev photo peak,
in the lead absorption gamma ray spectrum of + p, was found 4x 10 4x 10 1x 10 1x
Counts per m inut 0 2 4 I. 4 30kv AM DCY F Rh OF DECAY GAMMA 310kev . 14 FIG. 6 8 as fe irdain . . . irradiation after Days eetr 3 x " a eltp crystal type well Nal 3" x 3" Detector: emty I h well the In Geometry; Decay of the 310-kev gamma ray of R h ^ * (sample N-1124 ) N-1124 (sample * ^ h R of ray gamma 310-kev the of Decay 10 12 14 16 18 20 10 10 Gross counts per 2 minutes 10 ' ' P K-x-ra (Pb 5 ev k 75 I 1 . N LAD AS PI AUE ENTS EASUREM M N RPTIO ABSO D LEA AND R E P P O C . 15 . FIG *
_L 0 0 0 0 0 60 50 40 30 20 10 JL 1 kev 310 pe ad ea or i f h mma r s y ra a m am g Rh of n tio rp so b a ad le and opper C anl er b m u n hannel C er p. 31 6343 - 6341 pp. : e c n re fe e R D e te c to r: 3" x 3" N al w ell-ty p e c ry s ta l l ta s ry c e p ell-ty w al N 3" x 3" r: to c te e D omer I ie ell w tile In : etry m eo G mpe N-14 p ) p + -1124 N ple: am S Pb ber 1 5 hi ed tb ) tube lead k ic th m m 5 tube) 1. er ( p p co r e k rb ic o s th b a m m b 6 ,P 1. ( r e rb o s b a ,Cu o ber e rb o s b a No 4 kev 545 101 42 to be more intense than that in the no absorption gamma ray spectrum of the same sample. Secondly, in the case of copper absorption measurement the 7 5 kev photo peak was observed to follow the absorption coefficient of 310 kev gamma ray instead of 75 kev gamma ray. Therefore, it was concluded that the 75 kev peak, observed in the Ru^^ + p gamma ray spectrum was merely a satellite of the 310 kev gamma ray. It was also observed that the back scattering peak of the 310 kev gamma ray was more intense in the copper absorption gamma ray spectrum of Ru^^ + p than in the no absorption gamma ray spectrum of the same sample. This could be explained due to the compton absorption in the copper absorber. Similar absorption measurements were also made by using the 1-3/4” x 2” Nal crystal.
The gamma-gamma coincidence measurements were
carried out in order to determine the decay scheme of this isotope.
Coincidences between successive gamma transitions in the Ru^^ + p
sample (N-1119) were observed by placing the sample between the two
scintillation heads, each containing a 1-3/4” x 2” Nal (T.l ) crystal. In
the first gamma-gamma coincidence measurements, the single channel
analyzer was gated to accept the pulses corresponding only to 310 kev
gamma ray, while the hundred channel analyzer viewed the entire
spectral region up to 1 Mev. This measurement, as shown in Fig. 16,
revealed that a weak 2 35 kev gamma ray was in coincidence with the 0 1 Total counts " 0 I 1 . AM - AM CICDNE PCR F . h R OF M SPECTRU COINCIDENCE GAMMA - GAMMA . 1C . FIG 10 20 anl u ber num hannel C 1 kev 310 G am m a - g am m a coin cid ence sp e c tru m of Rh Rh of m tru c e sp ence cid coin a m am g - a m am G smpl N12) t gt s o 30 kev. 310 on t se gate ith w N-1123) le p (sam 040 30 Nt oncdec s r m tru c e sp ence cid coin •Net m tru c e sp ence cid coin ss • ro G c ni nc s r m tru c e sp ce en incid -co n o N ee e p. 6466-6470 pp. ce: feren e R o etry: eom G Lv tme 5 n ) in m 5 - e tim (Live Lv tme- 20 n ) in m 200 - e tim (Live Lv tme- 20 n ) in m 200 - e tim (Live 3/ 2 Na cr al ta s ry c al N 2" x " /4 -3 1 55 kev ,545 ^ D e te c to rs rs to c te e D ^ o o cut=sal 10} x le sca counts= of (No. Smpe -1123 N ple rSam 50 * 60 44 101 45
310 kev gamma ray. However, the latter was not in coincidence with
545 kev gamma ray. Similar measurement was also made by setting the single channel analyzer on the peak arising from the 545 kev g gamma ray. It was observed that the 545 kev gamma ray was not in coincidence with 235- and 310- kev gamma rays. Although the 235 kev gamma ray was not observed in the non-coincidence spectrum of
the Ru^^ + p sample, the single channel analyzer was set on the
calibrated position of the 235 kev photo peak in order to observe the
gamma coincidences with this peak. The results, obtained in this
case were found to be in agreement with the above mentioned co
incidence results.
After the decay of 4.4 day activity, gamma rays of 127-,
1 98-, 325-, 475- and 620- kev were observed, and were found to
have a very long half-life. A sample of Ru + d (N-7 91), which was
allowed to decay for 13 years, strongly showed these above
mentioned radiations. A comparison of the gamma ray spectrum
of Ru + p (N-1119), taken 42 days after the irradiation, with the
gamma ray spectrum of a 13 year old sample of Ru + d (N-791) is
shown in Fig. 17. It was suspected that 325 kev photo peak was
actually a sum peak of 127- and 198- kev gamma rays. In order to
investigate this possibility, the gamma ray spectra of Ru^ ^ -f p(
obtained by placing the source inside and outside the well, were 10 ' Gross counts I. 17 FIG. oprsn fte am a pcrmo + N11) tkn4 as after days 42 ,taken (N-1119) p + (N-791). sample +dRu old 13year of spectrum ray gamma the with of Irradiation, the spectrum ray gamma the of Comparison COMPARISON 127ke F H GMA A SPECTRUM GAMMA RAY THE OF IH HT F u+d N71 . ) N-791 ( d+ Ru OF THATWITH hne Number Channel 40 ( ^3 lOkev^3 ( f 4. 325kei 4 d 4 Scale = N x 1/2 1/2 = N x Scale (Ru101N-1119 + p) sample of spectrum ray Gamma Geometry. Outside the well well the Outside Geometry. Live time- 6 minutes 6 time- Live N-1119 (RulOl + p) + (RulOl N-1119 sample of spectrum ray Gamma emty I h well the In Geometry: Live time - 6 minute 6 si time - Live sGanuna ray spectrum of spectrum ray sGanuna u+d ape (N-791) sample +Ru d Sc ale = N well the In Geometry eeec: pp. 6800-6805 Reference: 2minutes time- Live Detector: 3" x 3" Nal crystal Nal 3" x 3" Detector: OF u0 + ( l1 ) -ll19 N ( p Ru101 + xl C "
5 475 *2l0d-Rh ) kev 46 102 compared. The results are shown in Fig. 17. With the source placed outside the well, it was observed that the intensities of 127- and 198- kev photo peaks were relatively increased, whereas the 325 kev photo peak was greatly reduced. Therefore, it was evident that
325 kev photo peak was nothing but a sum peak of 127- and 198- kev gamma rays. This fact was further verified by coincidence measure ments. A number of coincidence measurements were made by pla
cing the Ru + d sample (N-7 91) between the two scintillation heads.
The single channel analyzer was set on various photo peaks. Figure
18 shows the gamma - gamma coincidence spectrum of the Ru + d
sample with gate set on 198 kev photo peak. The 127- and 198- kev
gamma rays were found to be in coincidence with each other. This
result confirmed the well crystal measurements, which* suggested
that 127- and 198- kev gamma rays were in cascade. The 47 5 kev
gamma ray was also found to be in coincidence with 62 0 kev and 1.1
Mev gamma rays. 4 8
127 kev 198 kev
Gamma- gamma coincidence spectrum of Ru + d (Sample N-791) with gate set on 198 kev.
- Non-coincidence spectrum (Live time- 5 min ) -• Gross coincidence spectrum (Live time- 150 min ) 325 kev Reference: pp. 5978-5980
475 kev
620 kev
Geometry: ^Sample N-791
'Detectors 1-3/4" x 2" Nal crystals
0 10 20 30 40 50 60 Channel number FIG. 18 . GAMMA - GAMMA COINCIDENCE SPECTRUM OF SAMPLE N-791 (Ru + d) . Results
Enriched bombarded with 6 Mev protons was observed to emit 75- , 310- , and 545- kev gamma rays each decaying on a 4. 4 day half-life. However, the lead and copper absorption measurements strongly indicated that the 75 kev photo peak, observed in the well crystal measurements, was actually due to Pb K x-rays, produced by the photo electric absorp tion of 310 kev gamma ray in the lead shield around the crystal.
Coincidence measurements showed that a weak 235 kev gamma ray was in coincidence with the main 310 kev gamma ray previously assigned to the decay of Rh^^^ by electron capture.
The 310 kev gamma ray was not observed to be in coincidence with 545 kev gamma ray. The lead and copper absorption
measurements also proved beyond doubt that 545 kev was not a
sum peak of 235- and 310-kev gamma rays.
After the decay of 4.4 day activity, gamma rays of 127-
and 198- kev energies were observed in a very long half-life
period and were found to be in coincidence with each other. The
325 kev sum peak of these two gamma rays were also observed
in the well crystal measurements. A sample of ruthenium bom
barded with deutrons, which was allowed to decay for 13 years,
4 9 50 strongly showed the long-lived 127- and 198- kev gamma rays. Due
4to. the presence of ^ Ru 100 andA nRu 102 isotopes m n theenriched . . , „Ru 101 , the 20 hour-Rh ^ and 210 day-Rh activities were also observed and were found to be in agreement with previously reported results
of those isotopes. Discussion and Conclusions
1 101 According to Katcoff et al. , Rh was observed to decay by electron capture with a half-life of 4. 7 days. No positions were observed and the only gamma ray found was at 310 kev. However,
the present investigations showed that, in addition to 3 1 0 kev gamma
ray, there were two other gamma rays of energies 235- and 545-
kev. Although the 2 35 kev gamma ray was observed only in the coin
cidence measurements, it was found to be in coincidence with 310
kev gamma ray. The 310- and 545- kev gamma rays were observed
to decay with a half-life of 4.4 day s. Ther efor e , the 235-, 310-,
and 545- kev gamma rays were associated with the 4.4 day activity
of Rh101 .
Furthermore, in order to help identify this 4.4 day activity,
assumed to be due to its gamma ray spectrum was compared
with that of Since both of these nuclides decay to stable Ru^\
it was expected that some of the gamma rays might be identical from
both. As expected, the energies of the gamma rays, observed to
decay with a 4.4 day half-life, were identical, within the experimental
uncertainty, with the energies of the three of the gamma rays^.
■*■3. Katcoff and H. Abrash, Fhys. Rev. 103, 966 (1956).
2G. D. O'Kelley, Q. V. Larson and G. E. Boyd, Bull. Am. Fhys. Soc. Ser. H, 2, 24 (1957).
51 52
101 j • As the nuclear energy states of Ru have been studied in a number of reactions and processes, the de-excitation gamma ray spectrum, 101 obtained by Coulomb excitation of Ru , has been studied by Temmer
3 and Heydenburg . 127-, 180-, 307-, and 520- kev gamma rays were 4 observed by them. However, McGowan et al. observed a number of 101 additional transitions in Ru , most of them only by coincidence
detection. They also had evidence that the 307 kev state was really
a doublet, one member of which decayed direct by ground state
transition and the other only by cascade via 127 kev state.
After the decay of 4.4 day Rh^^ activity, gamma rays of
127- and 198- kev were observed in a very long half-life period and
were found to be in coincidence with each other. The 127 kev
radiation was identified with Rh^^ from the reported coulomb exci
tation of Ru^^ and the decay of Tc^^. Among others, Goldberg^
has also assigned this long-lived (half-life 5 + 1 yr) activity to R h ^ \
The results of the present investigations, together with the
gamma rays reported from the Coulomb excitation of Ru101 and the
decay of Tc^^ suggest a possible decay scheme of Rh^^ . The
^G. M. Temmer and N. P. Heydenburg, Phys. Rev. 104, 967 (1956) .
^F. K. McGowan and P. H. Stelson, Footnote (G. M. Temmer and N. P. Heydenburg, Phys. Rev. 104, 968 (1956) ).
^N. Goldberg, Bull. Am. Phys. Soc. Ser. II 2, 230(1957). proposed decay scheme of Rh. is shown in Fig. 19. The spin of the ground state of has been previously measured^ as 5/2. The other spin assignments are tentative, and are based on the theory of nuclear shell structure. An attempt was made to observe the gamma
ray associated with the internal transition between 4.4 day- and 5 101 year- levels of Rh . However, it was not observed in the present
inve stigations.
^*J. H. E. Griffiths and J. Owen, Proc. Phys. Soc. (London) 65A, 951 (1952). Bibliography
54
Avingnon, P ., Compt rend, 240, 176 (1955)
Eggen, D, E. and Pool. M. L . , Phys, Re?. 75, 1464 (1949)
Farmer, D .J,, Phys. Rev. 99, 659A (1955)
Goldberg, N ., Bull. Am. Phys, Soc, Ser.II 2, 230 (1957) H o H A Griffiths, J. H, E ., and Owen, J ., Proc. Phys, Soc. (London) Hi 65A, 951 (1952) h 0 Hisatake, K ., Jones, J. T. and Kurbatov, J. D ., Bull, Am, W Phys, Soc, Ser, II 1, 271 (1956) t Ul3 Katcoff, S, and A brash, H ., Phys. Rev, .103, 966 (1956) u 10 Lindner, M. and Perlman, I., Phys. Rev. 73, 1202 (1948)
u H Marquez, L ,, Phys. Rev. 92, 1511 (1953) 0 N H (0 M Q McGowan, F. K ., and Stelson, P. H ., Footnote (G. M. Temmer hi andN , P . Heydenburg, Phys, Rev, K)4, 968 (1956) M 0 ft O'Kelley, G, D., Larson, Q, V, and Boyd, G, E., Bull. Am, Phys, 0 A Soc. S er. II, 2, 24 (1957) ft Perrin, N ., Dick, L ., Foucher, R, and Vartapetian, H., J. Phys, et, radium, 17, 593 (1956)
Scoville, C, L „ Fultz, S. C. and Pool, M. L., Phys. Rev. 85, 1046(1952)
Sites, J, R ., Electromagnetically Enriched Isotopes and Mass Spectrometry, p. 152, Academic Press, N. Y, (1956)
Sullivan, W, H ., Sleight, N. R. andGladrow, E, M ., NNES-PPR 9,1949 (1951)
\N T em m er, G, M. and Heydenburg, N. P ., Phys. Rev. j_04, 967 H \ (1956)
55
fi; :■ \ ? i % i ■■^ ■■ PA R T in
RADIOACTIVE DECAY OF Er1?1AND A 172 SEARCH FOR RADIOACTIVE DECAY OF Er
56a« Introduction
The 7.5 hour neutron induced activity in erbium was first
171 1 observed and identified with Er by Ketelle and Peacock . Ac-
171 cording to them, Er decayed by negatron emission to energy
171 levels of the odd-proton nuclide Tm . Since then several studies
2-4 6 have been reported , the most recent being that of Cranston et al.
On the basis of coincidence studies, intensity data, internal con version coefficients, and the measured transition energies, Cranston
171 e t al. proposed a consistent decay scheme of Er . The ground
171 state of Tm is a beta unstable ~ ^ ^ yr) » anc^ the beta decay of Tm^^ has been studied, among others, by Smith et al.^ Ac cording to them, two beta groups with end point energies of 96. 5 kev and ~ 30 kev were observed. A 67 kev transition was also o b s e r v e d
171 by them. In all the above studies, however, the Er was produced by thermal neutron bombardment of E^Og of natural isotopic
^ B. H. Ketelle and W. C . Peacock, Phys. Rev. 7 3, 1269 A (1948). 2H.B.Keller and J. M. Cork, Phys. Rev. _84, 1079 (1951).
•^S.A. E. Johansson, Phys. Rev. 105, 189 (1957).
^E.N. Hatch and F. Boehm, Phys. Rev. 108, 113 (1957).
5 FJP. Cranston, Jr. , M. E. Bunker and J.W. Starner, Phys. Rev. 110, 1427 (1958).
^W. G. Smith, R. L. Robinson, J. H. Hamilton and L. M. Eanger Phys. Rev. 107, 1314 (1957)
56 abundance.
171 The present investigation of radioactive Er , produced by
170 thermal neutron bombardment of enriched Er isotope, was under
taken with the view of comparing the gamma radiations with those
observed by others. Because of the discrepancies in the previously
reported data, an attempt was also made to reinvestigate the beta
171 decay of Tm . During the course of this work, a search for the
activities of two newisotopes, E r^^ of half-life 49.8 hr. , and Tm"^ 7 of half-life 63.8 hr, reported by Nethaway et al. , were made. How
ever, the activities associated with these two isotopes were not
observed in the present investigation.
^D. R. Nethaway, M. C. Michel and W. E. Nervik, Phys. Rev. 103, 147 (1958). Experimental Data
Erbium enriched in isotope Er was obtained in the form of E^O^ from the Stable Isotopes Sales Division of Oak Ridge Nation al Laboratory. The natural abundances^ of the isotopes in erbium and the isotopic composition of the electromagnetically enriched
170 Er are given in Table III.
Table in Isotopic Composition of Natural Erbium as Compared with that of Enriched Erl^O
Isotope Percent of Isotope Isotopic Analysis in Natural Erbium of Enriched Er 170 Atomic Percent
Er-162 0. 136 <0.05 Er -1 64 1. 56 <0.05 Er-1 66 33. 41 1 . 68 + 0. 05 Er -1 67 22. 94 2.1 +0.1 Er-1 68 27. 07 9.0 +0.1 Er-170 14.88 87.3 +0.2
2 Table IV shows the spectrographic analysis of the
170 electromagnetic ally enriched Er . Twenty milligrams of
1 1A enriched Er was sealed in a quartz vial, and was subsequently irradiated at the Battelle Memorial Institute Research Reactor for
^R. J. Hayden, D. C. Hess, Jr., and M. G. Ingrham, Phys. Rev. TJ_, 299 (1950).
2. From Oak Ridge report supplied with the sample.
58 59 a period of 6 days at a thermal neutron flux of 10^^ neutrons cm-^
sec."^ In addition to this quartz vial, similar quartz vials containing
16 7 168 20 milligrams of enriched Er and Er were also irradiated. The
purpose of these irradiations were to compare the radiations from
1 70 them with those emitted from the irradiated sample of Er
Table IV 170 Sp ectrographic Analysis of Enriched Er
Rare Earth Percent General Percent General Perc ent Element Element Element
Y <0.015 Al <0. 05 Na <0.01 La <0.04 Ba <0. 02 Ni <0.05 Ge <0.2 Be <0. 005 Pb <0. 1 Fr <0.2 Ga <0. Q2T Si <0.0 5 Nd <0.2 Gb <0. 1 Sn <0.05 Sm <0.2 Co <0. 05 T1 <0. 02 Eu <0. 02 Cr <0. 05 V <0.02 Gd <0. 02 Gu <0. 05 Zr <0. 1 Tb <0. 1 Fe <0. 05 Dy <0. 1 K <0. 01 Ho <0. 04 Li <0. 01 Tm 0. 008 Mg <0. 05 Yb 0.01 Mn <0. 02 Lu <0. 04 Mo <0. 02
170 The quartz vial containing Er + n was placed inside
of a cardboard pill box and was labeled as N-1031. Approximately
six hours after the irradiation, the measurements with the 100-
channel scintillation spectrometer were started. The observed
170 gamma ray spectra of Er + n sample (N-1031) are shown in Fig.
X 67 20. Except for intensity, the gamma ray spectra of Er + n and 60
170 Gamma ray spectra of sample N>1031 (Er
51 kev 308 kev 113 kev
Detector: 1-3/4" x 2" Nal crystal Reference: pp. 2461,2581 and 2602
23. 8 hours after the irradiation o
37. 7 hours after the irradiation
52. 8 hours after the irradiation
0 10 20 30 40 50 60 70 Channel number , FIG. 20 . GAMMA RAY SPECTRA OF Er + n ( N-1031) Er + n samples were found to be identical in every respect with
170 the gamma ray spectrum of the Er + n sample. Apart from the
308- and 11 3- kev photo peaks, the thulium K x-ray peak was also
171 observed. The half life of Er was measured by observing the decay of the 113- and 308- kev photo peaks with the 100-channel scintillation spectrometer. These data indicated that the half-life of
Er^^ was 7.5 hr. The decay of 308 kev photo peak is shown in
Fig. 21. The logarithmic decay curves of 113- and 308- kev gamma rays were observed to be linear for 8 half-lives. Because of the high intensities of the emitted radiations, it was impossible to per form the well crystal measurements just after the irradiation. How
ever, three days after the ir radiation, the well crystal measure ments were started by placing the sample (N-1031) on the top of
thewell crystal. These measurements revealed the presence of
additional photo peaks at energies of approximately 0.210, 0. 397,
0.490, 0.82, 0.89, 1.12 and 1. 60 Mev. However, they were ob
served to decay on very different half-lives. The high energy
portion of the gamma ray spectrum, taken three days after the
irradiation is shown in Fig. 22. In order to determine the gamma
rays as sociated with Er and their coincidence relationships, the
gamma-gamma coincidence measurements were carried out by
setting the single channel analyzer at various photo peaks. The x 3 1 1 X 1 x x Net counts per 3 minutes ht f 0 e photopcak. kev 308 of that Tin K x -ra y peak (-51 kev) and 113 kev photopeak photopeak kev 113 and kev) (-51 peak y -ra x K Tin w ere observed to decay with the sam e half-life as as half-life e sam the with decay to observed ere w 2 1 . . 1 2 30Hkev Time after irradiation in o ur|.,j ur|.,j o in irradiation after Time tco: 3/ x " a (l cr t l sta ry c (Tl) Nal 2" x N-1031) " /4 -3 ple 1 (sam etector: ^ D r E of y ra a m gam 308-kev the of Decay GAMMA GAMMA , hours 5 7, CY f O .CAY V r ( ,l-1 . ) f,-lt-31 ( ‘ .r 103 103 Net counts per 6 rninutes 1 2 3 4 fo c 0 0 VO 80 70 6c f;o 40 30 20 10 0 ______I ______113 l«cv I ______G. n A SPECTRUM OF -01 . N-1031 E k P M A S F O M U R T C E P S RAY A M M nA . 2 2 . IG F 9 kev 397 1 ______i. i> via. Source: N-lOJl (no che.uiatry) G eom etry: On the top of the well crystal crystal well the of top the On etry: eom G eeec; . Reference; irraiLiatiun. t. f aftrr 3 days Detector: 3 >• 3" Nai well -ty p e cryst.il cryst.il e p -ty well >• Nai 3" 3 Detector: 1 ______i « l a uetun f sai of upectru.n ray Gluumol num ber ber num Gluumol Ili O l 1 ______• 2 kev 820 1 ______1 ______1 VO .2 Mcv 1.12 I ------63 - ( 100 coincidence spectrum obtained when the gate interval was centered on the 308 kev photo peak is shown in Fig. 2 3. The 308 kev photo peak was observed to be strongly in coincidence with 113 kev photo peak and the Tm K x-ray peak. It was evident from the coincidence measurements that the prominent thulium K x-ray peak resulted primarily from K conversion of the transitions which contribute to the 113 kev photo peak.
In order to study the high energy portion of the gamma
170 ray spectrum, shown in Fig .2 2, the quartz vial containing the Er
+ n sample (N-1031) was reirradiated at the B.M.I. Research
Reactor for a period of three days. After this irradiation, the quartz vial was opened and a portion of the sample was used for pre paring a well crystal sample. Few hours after the bombardment, the
chemical separation, using an ion-exchange column, was carried
17 0 out on a small amount of the Er + n sample. The ion-exchange
column was 13 centimeters long and 0.4 centimeter in diameter,
and was made of ammonium form Dowex-50 resin, having settling
time of about 5-20 min/5 cm. The sample was eluted with 0. 25 M
lactic acid of pH 3. 0. The flow rate was adjusted to approximately
one drop every three minutes. The drops were collected in test
tubes, which changed every ten minutes by means of an automatic
test tube changer. The activity of the test tubes was then 10 10 10 4 3
2 Net counts 0 1 e ( Kx-ra K (T m kev 51 10 113 kev 113 I. 3 GMA GMA ON1EC. SPECTRUM .2 COINC1DENC GAMMA - GAMMA . 23 FIG. 20 smpe -01 wt gt st n 0 kev. 308 on set Lr of gate with spectrum N-1031) ple (sam coincidence rna a-gam m am G OF OF Er1'1 Channel num ber ber num Channel ncicdne pcrm spectrum on-coincidence N e cicdne pcrm spectrum coincidence Net frne p. 2551-2558 pp. eference: R ) in m 5 - e tim (Live Lv tme-0 min) -100 e tim (Live Geometry: SML N13 ) N-1031 SAMPLE ( 40 1-3/4 etectors D 30 kev 8 5030 a crystals Nal cl: x /G ) l/lG x N Scale: ape eil le - N Sample 171 65 7 66 measured by means of the 100-channel scintillation spectrometer employing a 1-3/4" x 2" Nal (T 1 ) crystal. From the ion-exchange separation three different elements were obtained, which were later identified as Yb, Tm and Er.
The gamma ray spectrum of the Yb fraction, obtained
17 0 by ion- exchange column separation of Er + n, is shown in Fig.
24. Yb fraction was observed to emit gamma rays of energies
1 1 0-, 1 98-, 280-and 397-kev. The 397 kev photo peak was observed to decay with a half-life of 4. 2 days, whereas 198 kev gamma ray was observed to decay with a half-life of 30 days. The decay of these photo peaks, followed regularly over a period of 25 days,
showed that the activity of the Yb fraction was mainly due to 4.2
day-Yb^^ and 30 day-Yb*^. The activity of the Tm fraction was
17 0 mainly due to Tm impurity (a 129-day electron emitter with an
17 0 84- kev transition in the daughter) in the Er + n sample. Be-
171 cause of a weak transition in Tm , this activity was not observed
in this Tm fraction. The only observed radiation from the erbium
X 71 1 ^ ^ fraction other than Er was the 0.33 Mev beta group of Er
(9.4 day). The high energy photo peaks associated with 7.5 hr
E r^^, previously reported by Cranston et al. were not observed
170 in this Er fraction. The remaining of the Er + n sample was
used for two other similar ion-exchange column separations, which 67
Gamma ray spectrum of Yb fraction obtained by 170 ion-exchange column separation of Er + n.
Geometry. As close to the crystal as possible
Detector: 1-3/4" x 2" Nal crystal Sample: Test tube no. 11 10 Reference: Page 3447
■110 kev
198 kev( 30 d-Yb169) 10 280 kev
397 kev , (4. 2d-Yb
10
10 20 30 40 50 Channel number
FIG. 24 . GAMMA RAY SPECTRUM OF Yb FRACTION. 68 were made at an interval o£ few days. The results of these chemical separations were found to be in agreement with the one mentioned above.
1 70 In order to compare the activity of Tm , present as an
170 170 impurity in the Er + n sample, with that of Tm produced by the
170 thermal neutron bombardment of Tir^C^, the enriched Er and high- purity Trrt 2C>3 were irradiated at Battelle Research Reactor for a
period of one day. After the irradiation, the quartz vials were opened
and the radioactive contents were used for preparing several well
crystal samples of varying strengths. Typical gamma ray spectra of
17 0 the Er + n sample (N-1090), inside and outside the well, are shown
in Fig. 25. It was obvious from the well crystal measurements that
the previously reported 360- and 420- kev peaks were the results of
coincidence summing of Tm K x-ray and 308 kev gamma ray and of
113- and 308- kev gamma ray groups respectively. These results
were found to be in close agreement with the coincidence measure
ments.
Besides the observed gamma radiations, due to the
170 presence of Yb and Tm impurities in the Er + n sample, a
number of photo peaks were observed to decay on different half-
lives. In order to determine the origin of these radiations, the well
crystal and coincidence measurements were carried out. A series of unai ;a ray spectra of E r* ’*'1 + n (N-1090 )
------In the well (Livi. haic- 5 nii-i) •—-• ------• Outside the well (Live tii.ie- 5 mil.)
Detector: 3" .. 3'' Nal well -type crystal Reference: p p . 3-1 iO -5*1C 2 ✓ 300 Lev
ev
0 10 20 30 50 / 70 C’-.iiuu-l eu.uher j
ilu. 2'.. WELL CK'.S'.’Ai, MEASUREMENTS OE Er ‘ ( N-1090 70 gamma-gamma coincidence studies showed that 0.8 9- and 1.12-
Mev transitions and 0.490- and 1.60- Mev transitions were in coin cidence. 1.60 Mev photo peak was also observed to be in coinci dence with 0.82 Mev photo peak. These coincidence results were also confirmed by observing the sum peaks at 2.01- and 2.42- Mev, when the sample (N-1096) was placed inside the well of the crystal.
The high-energy portions of the gamma ray spectra, with the source placed inside and outside the spectrometer, are shown in Fig, 26.
Half-life measurements were carried out by observing the decay of various photo peaks. The coincidence measurements together with the half-life measurements suggested that 0.89- Mev gamma ray was in cascade with the 1.12- Mev gamma ray and were due to the presence of Sc^ (Tj^ = 84 days) impurity in the Er^^ + n sample
These two photo peaks were also observed in Er^^ + n and Er^^+n samples. However, the 0.49-, 0. 82-,and 1.60 Mev photo peaks were observed to decay with a half-life of about 40 hours and were attributed to the presence of La^^ as impurity in the Er^^ + n sample.
171 170 The Tm was produced by slow neutron capture by Er
171 171 and subsequent beta decay of 7. 5 Er to Tm . ln order to study the beta decay of 1.9 yr Tm*7*, the Er fraction, showing strong 7.5- hr activity, was allowed to decay for few weeks. After the decay Net counts per 10 n iin . e N-1096 ( '+ n; + ' ' r E ( 6 9 0 1 - N le p m a s f o m u r t c e p s y a r a m m a G ■ sampi Er n + r E ( 6 9 0 1 - N ic p m a s f o m u r t c e p s y a r a m m a G » after t decay of 7. hour activity t i v i t c a r u o h 5 . 7 f o y a c e d l e l e th w r e e t th f a In , : ) y tr y e r t m s o i e G m e h c o n ry: Out de t well e w e th e id ts u O : y tr e m o e G o he decay of 5 activity. y t i v i t c a r u o h 5 . s 7 e t f u o in y m a c e 10 d - e e th im r t e t f e a f ) iv L y r t s i m e h c no ve time- 1 mi s e t u in m 10 - e m i t e iv L ZC GAMMA RAY SPECTRA OF Sc S F O A R T C E P S Y A R A M M A G . 37 v e k 397 •
8 c ) Sc - d 84 ( v e M 89 0.
La , nd Yb es in s ie t i r u p m i b Y d an , a L , c S f o a r t c e p s y a r a m m a G - j- 6 4 mi l e n n a h C 8 d ) c S - d 84 ( . Mev e M 1 2 1. n e ( . ) 6 9 0 1 - N ( le p m a s n + . ----- 50 -
46 10 5 7 1 140 6 4 _ , ( 2 - La I a L - r h 2 . 0 4 ( r 1 6 , v e M 60 1. - 5560 - 5 4 6 55 - 0 6 5 5 . p p : e c n e r e f e R " 3 Nal -type crystal a t s y r c e p y t l- l e w l a N 3" X 3" : r o t c e t e D TI N -10'.h N E L P M A S IN S IE IT R U P M I
0. 9 1 1 1. + v e M 69 . 0 ( Z, 0 1 Mev 0, . '+. i v ) ev M fiO ('v+l. ?.M H , 0 ( i Z Z . 4 4 . ) v e M 2 ev M
71 of 7. 5 hour activity, the well crystal sample was made out of this Er fraction. The well crystal measurements of the radiation from this
sample were made by placing this sample on the top of the crystal.
The energy of the most intense peak in this sapnple was calibrated
with the help of known Eu, Tb, Gd, and Dy x-rays, and was found to 3 be 52.4 kev. Comparing this value with the recently reported values
of the rare earth x-rays, this peak was found to be due to Yb K «
x-rays. The comparison of this gamma ray spectrum with the 170 . gamma ray spectra of Er + n sample (N-1096) and Tm + n
sample (N-1091) is shown in Fig. 27. The small bumps on the right
hand side of the intense 52.4 kev peak were attributed to the Yb
x-ray ( ~ 60 Kev) and a highly internally converted photo peak at 67
kev. The copper absorption measurements, by placing the samples
inside a copper tube and then placing the latter inside the well, are
shown in Fig. 28. From these above measurements, the identity
of the highly internally converted at 67 kev photo peak was certain.
3E. L. Chupp, J. W. M. DuMond, F. J. Gordon, R. C. Jopson and Hans Mark, Phys. Rev. 112, 1183 (1958). 73
10
>cale= No. of counts x 1/10
10 10 20 30 50 6040 70 80 Channel number 171 FIG, 27 . GAMMA RAY SPECTRA OF Tm { TEST TUBE No. 20 ) , Tm169 + n ( N-1091 ) . AND E r170 + n ( N-1096 ). 74
10' 52. 4 kev Yb K x-ray ) -*Gannna ray spectrum of - Gamma ray spectrum of Er fraction sample (Test o 170 tube no. 20), after the Er + n ( N- 1096 decay of 7. 5 hr. activity chemistry ) Geometry: In the well Geometry: In the well No absorber Cu absorber (1,6 nun thick Cu tube) Gamma ray spectrum of Liive time- 100 ruin. I *70 o Er + n ( N-1096 ) Detector: 3" X 3" Nal well Geometry: In the well type crystal. Cu absorber ( 1. 6 mm Amplifier gain: 3/4 X 1/4 tliick Cu tube) Reference: pp. 5776-577 84 kei ( Iodine escape peak ( Tm /
10
v 2
10 A 4 5 5 5 Channel number FIG. 28 . COPPER ABSORPTION GAMMA RAY SPECTRA OF Er + n. Results and Conclusions
171 The half-life of Er was determined to be 7.5 hour by
CL following"*the decay of the various gamma rays with a scintillation o- e> spectrometer. The 113- and 308- kev gamma ray groups were ob served to be in coincidence, and were found to be in agreement with the previously reported results. - It was evident from the well crystal measurements that the previously reported 360- and 420- kev peaks were sum peaks of Tm K x-ray and 308 key gamma ray and of 113- and 308- kev gamma ray groups respectively, The only observed radiation from isotopes of erbium other than Er171 was the 0.33-
169 Mev beta group of Er (9.4 day). In the present investigations,
the gamma rays, emitted because of the presence of Yb, Tm,Sc,and
17 0 La impurities in the Er + n sample, were observed to decay on
different half-lives.
170 An examination of the radiation emitted by various Er
+ n samples revealed no activity which could be assigned to the
*177 17 2 previously reported 49.8 hr-Er and 63.8 hr-Tm activities.
170 . . . Although the double neutron capture of Er is possible in princi-
12 -2 -1 pie, a thermal neutron flux higher than 10 neutrons cm ° sec ,
used in the present investigations, would be required to produce a
172 detectable amount of Er - - . 171 ,, * In order to study the beta decay of 1 . 9 year Tm , the
75 Er fraction, showing strong 7. 5 hour activity, was allowed to decay ior a considerable long time. The well crystal measurements of the O tx ss radiation from this sample were then made by placing the sample in- v a side and outside the*well. Apart from the Yb K»x-rays and their
escape peaks, above measurements showed the presence °of a highly
internally converted photo peak of 67 kev. The proposed decay schem
171 of Tm , based on the results of the present investigation together
with the- pr eviously reported beta spectrum and conver sion line
measurements, is shown below.
1/ 2 + Tm (1.9 yr)
kev
3/2- 0. 067
1/2 Yb
Fig. 2 9. “Decay Scheme of Tm^^
The spin assignments of various states are based on the
following considerations. 77
Mottelson and Nilsson's'*' level calculations indicate that the ground state spin arid parity of is l/Z + or 7/2- . The spin of has been determined to be l/2, therefore the l/2 + assignment seems reasonable for Tm^"^. The ground state spin and parity of Yb^^ is
/ 2 also 1/2- . According to the unified model of Bohr and Mottelson > © * • <3 which permits the prediction that the spin of the first excited state, with ground siate spin = l/2, will be 3/2 with the same parity as the ° o ground state in this region, the spin and parity of the first excited state of Yb^*'are taken to be 3/2- .
^Mottelson, B. R. , and Nilsson, S. G. , Phys. Rev. 99, 1615 (1955).
^Bohr, A., and Mottelson, B. R. , Kgl. Danske Videnskab. Selskab, Mat. - fys. Medd. 27, No. 16 (1953). Bibliography
Bohr, A. and Mottelson, B. R. , Kgl. Danske Videnskab. Selskab, Mat. - fys. Medd. 27, No. 16 (1953)
Chupp,*E. E. , DuMond, J. W. M. , Gordon, F. J., Jopson, R. G. and Mark, H. , Phys. Rev. 112, 1183 (1958)
Cranston, Jr. , F. P. , Bunker, M. E. and Starner, J. W. , Phys. Rev. 110, 1427 (1958)
Hatch, E. N. and Boehm, F. , Phys. Rev. 108 , 113 (1957)
Hayden, R. J. , Hess, Jr. , D. C. and Ingrham, M. G. , Phys. Rev. T7, 2 99 (1950)
Johansson, S. A. E. Phys. Rev. 105, 189 (1957)
Keller, H. B. , and Cork, P. M. , Phys. Rev. _84, 1079 (1951)
Ketelle, B. H. , and Peacock, W. C. , Phys. Rev. J73, 1269A (1948)
Mottelson, B. R. , and Nilsson, S. G. , Phys. Rev. _99, 1615 (1955)
Nethaway, D.® R. ,® Michel, M. C. , and^Nervilsi, W . E. , Phys. Rev. 103, 147 (1958)
Smith, W* G. , Robinson, R." E. ", Hamilton , J. H. and Langer, E. M. , Phys. Rev. 107, 1314 (1957)
78 Autobiography
I, Basant Lai Sharma, . as born in Dhanbad, Bihar, n India, February 12, 1932. I matriculated from S. M. J. E. C. O High School, Khurja in 1947. I received my undergraduate training at Benares Hindu University, which granted me the Intermediate in
Science degree in 1949 and the Bachelor of Science degree in 1951.
From the University of Lucknow, I received my Master of Science degree in 1953. I worked as demonstrator in the Department of O Physics and Mathematics, JLndian School of Mines and Applied
Geology, Dhanbad, from July 1953 to June 1954. After being appointed as Teaching Assistant in the Department of Physics and O O Astronomy, I came to study nuclear physics at The Ohio State o University. During my stay here, I have worked as Research^
O Q Assistant in the Department of Physics and Astronomy as well as
Research Assistant in the Department of Mathematics. I was awarded
a University Fellowship for° the year 1958-5 9, which I held while
completing the requirements for the degree Doctor of Philosophy.
79