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ORNL P
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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS - 1963
-
V
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-LEGAL NOTICE
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High Resolution Measurements of Gamma Rays from Thermal and Resonance Neutron
Capture in 127sn, 1185n and 12050*
J. A. HARITY and G. G. SLAUGHTER
Oak Ridge National Laboratory
Oak Ridge, Tennessee, USA
High resolution measurements of the gamma ray spectra from thermal and
resonance neutron capture in 'Sn, tºsn and 5°Sn have been made with a
lithium-drifted germanium detector. A beam of pure thermal neutrons was ob- .
tained by double reflection from inconel mirrors of a reactor beam from the
Oak Ridge Research Reactor. A cadmium filtered reactor beam served as the
source of resonance neutrons. Earlier measurements of the gamma rays from
the isotopes of tin with a NaI spectrometer had demonstrated the value of using
both thermal and resonance energy neutrons and the need for higher resolution
of the gamma rays. The lithium-drifted germanium crystal was 2.6 cm in area
by 7 mm thick and was furnished by R. J. Fox, ORNL. For high energy gamma rays
(> ~ 2000 keV) the pair production process with the subsequent escape of both
annihilation quanta is the predominant process. Above 4000 keV the resolution
was 10-15 keV for runs of several days duration and the energies of the lines
may be measured to I 10 keV absolute and £ 5 ke V relative. For low energy gamma
rays ( ~ 1500 keV) the energy resolution was 5-10 keV and the energies may
be measured to an absolute accuracy of 2 to 4 kev. The relative efficiency of
the detector vs gamma ray energy has been determined for both the double escape
peak and the full energy peak. In the energy range from 600 to 1600 keV de-
posited in the crystal, there 18 some ambiguity as to whether a weak peak 18
a full energy or a double escape peak.
The gamma ray spectra plotted against the energy in the crystal from
the capture of thermal and resonance energy neutrons in a 35-gram sample of
It isn are shown in Figure 1. The peaks are all double escape peaks and the
energies of the gamma rays are labelled above the peaks. Tables I and II
summarize the energies and intensities of the gamma rays from neutron capture
ARE ON EILE IN THE RECEYING SECTION,
THE PUBLIC IS APPROVED. PROCEDURES
PATENT CLEARANCE OBTAINED. RELEASE TU
11
in Sn. The intensities of the hic carey Dec rays were cüvairca by
riorralization to the intensity of the ground state transition which had bzen
measured previously with a la I spectrometor.-Ficmc 2 s..cis i.c energy
level diagram of 1-0 Sn deduced from the cards zay enerties listed in the
tables assuring the high energy transitions originated at the capturing state.
The excited state at 1225 is a 2* state cow the states at_1750, 2017, and 2480
KeV with spins of 0* 01 1° are knou fron (a,m) studies, [?] The stüies at
1675 and 2020 keV and at higher energies have not been reported previously.
Tre transition to the state ai 1750 keV was observed only from resonance capture
and the transition to the state ät 2020 keV only from thermal capture. Low
enerzy camma rays with energies 1224, 443, 531 and 812 keV from thermal capture
can be fitted to the level diazran as shown.
Tables I and II also surmarize the energies and intensities of the
gamma rays from neutron capture in a 160- 2 sample of thºsn and a 200-fram sample
of 12°Sn. Other observed weak lines (10 in -1°Sn and 8 in 12° Sn) are not listed
in the tables since there was an ambicuity as to whether they were rull enerey
or double escape peaks. main the intensit:es are relative to the intensity
of ground state and first excited state transitions previously determined from
measurements with a NaI spectrome tez.- Pibüre 3 shows the enerzy level
diagram of -Sn deduced from the moment energy cannra rays. The ground state
transition was not observed irom thermal neutron capture. The excited state
at 24 keV has spin 3/2" and the state at 1090 keV agrees with a level found in
(d,p) studies.bd Figure 4 shows how 5 of the low energy gamma rays can be
fitted to the level diagram of Sr. Excited states at 0.77, 0.921, 1.08 and i
1.34 MeV are known from (d,p)D] and Coulomb excitation studies.24) The fact
that the transitions from the 1090 and 1330 keV states are observed to only the
24 keV excited state and not to the ground state favors the 5/2* assignment
to these states.
From the 2 high enersy gamma rays observed from neutron capture in
- Sn, the first excited state in t-Sn is determined to be 61 keV. A state
at this excitation has not been observed previously. Since the capturing
state has spin 1/2*, strong transitions can reach final states of spins 1/2
or 3/2. Since the ground state has spin 3/2* (a dz/2 state) this 61-keV ex-
cited state must be the sy/2 state (1/2"). The higher excited states in - Sn
inferred from the other high energy camma rays listed in the tables show no
Egreement with states established from (d,p) studies.D.
.
-2-
.
·.
.
..
·
......
·
.
So117 to
..:: THERMAL:
Gommo Roy Speciro. :: .....9309 de
... . . .... . . . ... ... ..
............... .... iii.
.. . ... . . . . .,., . , .
-
...
COUNTS (3711 min)
TABLE II
Energies and Intensities of
Gamma Rays from Resonance
Neutron Capture
.
...
...ECA
CRYSTAL
VSTAL :::::
.
117sn
....
.
8094 do ...
ESONAI.CS:
Intensity
: ...ii . i . . . .
03220...
: :.....
:
COUNTS (3937 min)
.
.
.
...
..
...
... 19322 d
... ..
!
1.5
-
.
..:: --:E
CRYSTAL :: :::::....... ...;
.
.
-
-
-
TL 7500.
1
. 8000
... 8500
at
1:1620 Jessioni:;::!!!! !!! !!iii
..:........... THERMAL ::
... L: 1 GALA
ſkev)
9322 GS
8091
7637
7563
17277
7003 (?)
6835
6583
: 6124
...
1., 00
00
..
...........
..
...:
.
.
iiiii!..gande
it'.:.!;
17265 de 7292 do 1*; 7632 de
.
COUNTS (3711 min)

.
....
..
6418
E
CRYSTAL
...,.
iT 15500: ill.i..
60001
.:.:.6500
i11i
: 6062
-
5214
1227
· 6418 do! Iliri!! !
---!... RESONANCE
:1:1:
- 11
6583 de 1:
:1 1 : 7: 6835 de :.;:.1*;Tiiiii
Kij i ! :111:11:1; 7003 de? 707277 00:17
ll
" : { "ssia Yss at:
.:1:
COUNTS (3937 min)

118 sn
7-11lt-
With
CRYSTAL T:9 Tomate:1999:9;!Tr777
6493 GS
6466
500
176000 1100.6500MLILI
:5405
CHANNEL NUMOER
120 sn
Fig. 1
6164 GS
6102
.
.-.
.
.
.
.
REFERENCES
I] J. A. Harvey, G. G. Slaughter, J. R. Bird, and G. T. Champman, Phys.
Ann. Rept., Dec. 3, 1963, ORNL-3582, page 62.
[2] L. R. Norris and C. F. Moore, Phys. Rev. 136, B40 (1964);
B. I. Cohen and R. E. Price, Phys. Rev. 118, 1582 (1960).
] B. L. Cohen and R. E. Price, Phys. Rev. 121, 1441 (1961).
4) P. H. Stelson, F. K. McGowan, R. L. Robinson and J. L.. C. Ford, Jr.,
Bull. Am. Phy. Scc. 2, 484 (1964);
R. L. Robinson and P. H. Stelson, Bull. Am. Phy. Soc. 10, 245 (1965).
.
Research sponsored by the U. S. Atomic Energy Commission under contract with
the Union Carbide Corporation.
CABLE I
Energies and Intensities of Gemma Raye from Therma. Neutron Capture
CRNI - AC - OFFICIA
117sn
11891
120 sn

Intensity
20%)
Intensity
($)
Intensity
(%)
(keV
(keV)
(keV)
_
9309 GS
8090
7632
6485 GS
6456
6014
60.1
0.6
0.5
6164 GS
6104
4254
4192
4084
3916
3661
382
7292
0.4
7265
6994
6826
6642
5386
4498
3800
3759
1.6
ööjoririciri ciri ori
3604
sóriooooooirioodirició
12
..
3457
3273
..
..
Rel. Int.
100
1295
1175
1067
3506
3444
3422
3317
3075
2654
.
~2
27
Rel. int.
100
2.5
898
in conne
1414
3700
0.7
1.8
Rel. Iat.
100
1103
310
86€
850
308
1224
1177
1099
812
531
.32928
448
361
che con unojoooo
340
254
245
233
210
..
-.
noni AC no neciring
OANL - AEC - OFFICIAL
THERMAL
EXCITATION
ENERGY (kov)
9310 18
RESONANCE
10,
+ 38,8 ev

INTENSITIES
(PERCENTI

I
Kr.
.
2480
2040
10.110
10.01
10.11
HEFFIT
anal..
812aas.
1750-
1675
1225
229
1227
Sn"?
Neutron Coplure Gommo Roys
Fig. 2
THERMAL
RESONANCE
EXCITATICIV
ENERGY (kov)
EXCITATION
ENERGY
(hov)
1330

6485
y
at 45.8 av

.
-
1090
1.6
0.4
INTENSITIES
( PERCENT)
921

0.1
0.a
770
-3280
-3030
-2720
-2680
1295
1087
-1985
898
-1090
763
-4701?)
24
Sn 118+
Neutron Capture Gomma Rays.
Sn 118
Thermal Neutron Capture Gommo Roys.
Fig. 3
Fig. 4

END
DATE FILMED
8/ 27/65





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