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MICROCOPY RESOLUTION TEST CHART
NATIONAL QUREAU OF STANDARDS -1963
LEGAL NOTICE
This report was prepared as an account of
Government sponsored work. Neither the
United States, nor the Commission, nor any
person acting on behalf of the Commission:
A, Makes any warranty or representa-
tion, expressed or implied, with respect to
the accuracy, completeness, or usefulness
of the information contained in this report,
or that the use of any information, appa-
ratus, method, or process disclosed in this
report may not infringe privately owned
rights; or
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to the use of, or for damages resulting from
the use of any information, apparatus,
method, or process disclosed in this repori.
As used in the above, "person acting on
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ployee or contractor of the Commission, or
employee of such contractor, to the extent
that such employee or contractor of the
Commission, or employee of such contractor
prepares, disseminates, or provides access
to, any information pursuant to his employ-
ment or contract with the Commission, or
his employment with such contractor.
ORNO
-35-2
ann
Oon E-650706-d
i i home on
JUN 24 1965
- LEGAL NOTICE -
TUI report no prepared nu account of Goronwat sponsored wort. Neither the Vallad
daw, sor the Commissa, nor way person acting on behall of the Coanlusion:
A. Makes uyuruly or rapormauulou, exproud or lopund, murorect to the accu-
rucy, complorar..., or wnstairs of the informuwon coatind u Wo roport, or lost in was
ol uy lalor nation, apparatus, molhad, or proces dixclound in de report may not latringe
prinuly owned rigauo; or
B. ASKURSS way liabilities will respect to the wool, or lor damarua reswung troma lhe
une ol uy Inforowalion, appunt, Bouhod, or procoos discloud ua de roport.
As word in the wor, "por O KON on behall of the Coanuku" wcludes way on-
ployee or courilor of the Commutaa, or saployms of such connector, to the extent that
such oployes or contractor of the Counloslon, or employs of much contractor preparos,
diin minalai, or proridne accu to, lay latoraaloo pumuat w No soployant or contract
will the Comalarla, or his employment with such contractor.
ORNI - Afi UINCIAL

i
nternational
with
'.
.,
.
.
.
Strong p-Wave Neutron Resonances in 12° sn, 110 Sn and 24sn*
J. A. KARVEY and TOYOJIRO FUKETA*
Oak Ridge National Laboratory
Oak Ridge, Tennessee, USA
In the study of the spectra of the gamma rays from neutron capture in
individual resonances of the isotopes of tin, several strong high energy
gama rays were observed to the ground and low-lying excited states which
jave iow spin and even parity. If these capturing states were formed by s-
wave neutrons, these transitions would most likely be M-1 transitions. If
they are M-l transitions, their strengths would be from mlo to 100 times that
expected from the summary by Bartholomew.LJ However, if the resonances were
p-wave resonances, these high energy gamma rays could be E-l transitions and
their strengths would be consistent with those summarized by Bartholomew.
Several of these resonances have sufficiently large neutron widths (al to
- 50% scattering) that it is possible to look for the interference between
resonance and potential scattering to determine whether the resonances are s
or p-wave resonances.
Neutron transmission measurements have been made with the ORR fast
chopper time-of-flight neutron spectrometer on 10-cm thick metal samples of
12°Sn (200 grams, 98%) and 110Sn (160 grams, 97%). Measurements were made
with BF, proportional counters at the 45-me ter flight station with a resolu-
tion of 60 nanoseconds/me cer and at the 180-meter station with a resolution
of 15 nanoseconds/meter. The open beam counting rate at the 45-meter flight
station was n 13 counts per 0.64 usecond channel per minute. The open beam
background was 13% and the sample-in background ni% of the oper beam rate.
UANL - AEC - OFFICIAL
inicio C!!!RANCE OSTAINED. RELEASE TO
TIT. 1.4T!!C IS APPROVED. PROCEDURES
::Titi lix illi: NG SECTION.
ORNI-KEC - OFFICIAL
The transmission of the 10-cm saxaple was only 0.15 and runs of several days
duration were required to obtain transmission points with statistical accuracies
of n 2%. The open beam counting rate at 180 meters was nl.5 counts per 0.64 .
usecond channel per minute. The open beam background was u 13% and the sample-
in background n 10% of the open beam rate. Runs of several days duration were
required to obtain transmission points with statistical accuracies of w6%.
The_resonances have been analyzed with the area and shape analysis
programs which include Doppler and resolution broadening. The resonance in
SaSn at 922 eV with 50% scattering shows considerable interference between
resonance and potential scattering and is definitely an 8-wave resonance. The
resonances au 427 and 1720 eV with n 20% and ~ 70% scattering respectively do
not exhibit the asymmetry computed for s-wave resonances. Hence, both ttese
resonances must be p-wave resonances. Strong gamma ray transitionstid had
been observed from neutron capture in this 427-eV resonance to the ground
state and low-lying excited states.
The large resonances in 0sn at 359, 770, 1580, 2960, 3450 and 7400
eV are obviously s-wave resonances from the interference observed. Several of
these resonances were already known to be s-wave resonances from the earlier
transmission measurements of Fuketa et al._*d using a 2.5 cm thick sample.
The resonance at 45.8-eV is probably a p-wave resonance; however, it is diffic
to make a definite assignment_since for this resonance 18 only 40.6%.
Strong garama ray transitions+J had been observed from neutron capture in this
45.8-eV resonance to the 1/2* ground state and/or the 3/2* excited state at
25 keV, and the 3/2 or 512" state at 1090 keV. If the 45.8-eV resonance were
·an s-wave resonance these high energy gamma transitions would have M-l strengths
450 times the average valueded for M-l transitions for other nuclides in this
mass region.
From the transmission measurements in with a 2.5 cm thick sample of
124 sn (35 grams, 93%), it was determined that the 62.0-eV resonance with 10%
scattering was definitely a p-wave resonance. Figure 1 shows the comparison
of a theoretical curve including Doppler and resolution broadening to the
experimental transmission points for l = 0 and l ko. Strong gamma ray trans-
itions_+J had also been observed from neutron capture in this resonance to the
low-lying 3/27 and 1/2* excited states.
Assuming a p-wave strength function of 4 x 10, a nuclear radius of
0.62 x 10°12 cm and that the level spacing does not depend on parity, the 62.0
-2-
1!10U
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1838.
vocniddi
me*
,
-
-
-
-
-
"
."
eV resonance in *-*Sn is n 80 times stronger than expected for an average p-
wave resonance. The p-wave resonances at 427 and 1720-eV in basn and at 45.8-
eV in --°Sn are m 20 times stronger than expected for average p-wave resonances
in these nuclides. These strong p-wave resonances have reduced neutron widths
which are comparable to those of the 3 quasi-particle 1/2.states computed by
Shakinbd. These strong p-wavz resonances are suggestive of p-wave "doorway"
states.
ORNI - AEC - OFFICIAL
.;,,
REFERENCES
* Research sponsored by the V. S. Atomic Energy Commission under contract with
the Union Carbide Corporation.
**
Permanent address: Japan Atomic Energy Research Institute, Tokai-mura,
Naka-gun, Ibaraki-ken, Japan.
......
.
[1] J. A. Harvey, G. G. Slaughter, J. R. Bird and G. T. Chapman, Payz. Div.
Ann. Progr. Rept., Dec. 31, 1963, ORNL-3582, page 62.
[] G. A. Bartholomew, Ann. Rev. Nucl. Sci. 11, 259 (1961). .
•37 S. E. Atta and J. A. Harvey, ORNL 3205 (1961), and Addendua: Phys. Div.
Ann. Progr. Rept., Jan. 31, 1963, ORNL-3425, page 46.
.....
inner.
.vj.
.
.
......
[4]
T. Fuketa, F. A. Khan and J. A. Harvey, Phys. Div. Ann. Progr. Rept.,
Jan. 31, 1963, ORNL-3425, page 36.
C. Shakin, Annals of Physics 22, 373 (1963).
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END
DATE FILMED
9 / 16 / 65