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UCRL- 6252
2
Radiochemical Studies of Neutron-Induced Fission of U 35
and y738 and the Two-Mode Fission Hypothesis
H. B. Levy, H. G. Hicks,
*
W. E. Nervik, P. C. Stevenson,
J. B. Niday, and J. C. Armstrong,
Jr.
Lawrence Radiation Laboratory, University of California
Livermore,
March 3,
California
1961
ABSTRACT
It has been suggested that the effect of changing excitation energy on the
shape of the fission product mass-yield curve from fission of a single nuclear
species is due to the change in the relative amounts of two energy-independent
modes of fission, each giving rise to its own characteristic mass-yield curve.
It is shown here that this hypothesis predicts a linear relationship between
the fission yields of any pair of fission products measured ata set of excitation energies.
Linear relationships are also predicted between pairs of fission
yields measured relative to the yield of some reference fission product.
Fission product yields relative to the fission yield of Mo’
were measured
for fission of u*?? and of p38 with neutron beams of mean energies ranging
from 2 to 10 Mev.
cases.
The predicted linear relationships were observed in all
However, results for fission yields from u~?> with thermal neutrons
do notfall on the corresponding observed lines.
The two-mode fission hy-
pothesis is a possible explanation for the linear relationships observed,
but
does not explain all of the data.
*
This work was performed under the auspices of the U.S. Atomic Energy
Commission.
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