Study of Reactor-Neutron-Induced Reactions. Double Neutron Capture Process and the Systematics of the (N, 2N) Reaction

摘要

Cross sections of the second neutron capture in the double-neutron-capture process were studied in the irradiation of exp 26 Mg, exp 64 Ni, exp 93 Nb, and exp 164 Dy with reactor neutrons. Weak radioactivities produced were determined with sufficient accuracy by taking advantage of high resolution Ge(Li) detectors. The neutron spectrum at the irradiating site was defined with Westcott's epithermal index determined by the use of the cadmium ratio method. The isomer cross-section ratio was obtained with the exp 94 Nb target. The statistical theory was found to be applicable to such an unstable or odd-odd nuclide as exp 94 Nb. Cross sections of isomers of exp 165 Dy were determined. The capture cross section of the ground state nuclei was found greater than that of the metastable state nuclei in this case. This differs from the other four isomers observed so far. Cross sections of exp 28 Al(n, p) exp 28 Mg and exp 58 Ni(n, 2n) exp 57 Ni reactions with fission neutrons were also measured. A simple formula was proposed for the systematics of (n,2n) reaction cross sections, which enabled prediction of the cross section more accurately than the previously proposed formulae. (Atomindex citation 12:594473)