The neutron capture cross section and f i s s i o n cross section far 2 3 3 ~ have been measured simultaneously in the neutron energy range from 0.4 t o 1000 eV. The data a r e presented i n graphical, tabular, and i n t e g r a l farm. Cornpaxisons w i t h previously published data, using similar and different methods, are given, *Work sponsored by the U, 5. Atomic Energy Commission under contracts w i t h Oa& Ri'dge National Labosatoq ( W-"/o? -eng-26) and Rensselaer Polytechnic Ins.titute [.AT( 30-3) -328 1, *Dep&rtment of' Nuclear Engineering and Science, Rensselaer Polytechnic I n s t i k t e . +Presen.t address: Los AIwos S c i e n t i f i c Laboratory.NOTICE This rlnrtfimertt rmtoin(i infmnntim atid was p r p p d primarily far internal use ot Laboratory. Ir i s subjec? tc revision or corre not tqxesent a final report. preliminary noturn Oak Ridge lrlotionul end therefare does DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government.
The neutron f i s s i o n and capture cross sections f o r 2 3 5~ have been measured simultaneously f o r incident neutron energies from 0.4 eV t o 3 keV. I n addition, t h e f i s s i o n cross section has been measured up t o a neutron energy of 20 keV.
843 so that q i and, finally, 3 M z =(M/j)(M z ) nlJT . (32) the form described in Appendix I, with the quantum numbers describing the subshell suppressed. Since only diagonal terms of the expectation value of the moment operator survive, M 2 =EkM| 2 [(^M(l),M,i^M(l)) + (^-M (2 ) >M22^/ 2-M (2 ))]. (34) APPENDIX II Let an arbitrary number of nucleons in the nljr subshell couple to a state with angular momentum / and Using Eq. (10) and realizing that an arbitrary number of nucleons from the n'Vj'r 1 subshell couple to a state with angular momentum /', Z|#M| 2 M=(J Z I), Y,\2 2 =Y,a M 2 -M (2), M (33) (34) yields, using the results of the previous Appendix: (35) where 1 and 2 refer to the coordinates of the nucleons in the respective subshells, and the CLM are the Clebsch-Gordon coefficients. The states M are of If/=/ / , then (/ 2 i)=(/ 22 )=l, giving the result (16).The "elastic" photoproduction of ir° mesons in helium has been measured as a function of center-of-mass angle for gamma-ray energies from 170 Mev to 340 Mev. The total cross section shows a maximum around 270-Mev excitation energy and the angular distribution at 300-Mev peaks around 65° in the center-of-mass system. An attempt has been made to interpret the results in terms of the differential cross section for photoproduction of TT° mesons in hydrogen, and to obtain (from the amount of interference of the waves emitted by the four nucleons) a value for the "mean radius" of the alpha particle and the relative phase of ir° emission from proton and neutron.The photodisintegration reaction 7+He 4 ->He 3 +w has also been investigated. The angular distribution of the He 3 recoil nuclei is found to be proportional to sin 2 0 for excitation energies between 40 Mev and 120 Mev.
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