Systematic Studies of Asymmetric Mass Distributions in Proton-induced Fission of Actinides

Abstract

In order to clarify the relationship between a mass distribution and shell structure of the fission fragments in nuclear fission, the fragment mass and the kinetic energy distributions in the proton-induced fission of plutonium isotopes, ^{239, 242, 244}Pu, were precisely measured using a double time-of-flight system. It was found that the position of the light side of the heavy asymmetric mass distributions shifts to a larger fragment mass number according to the neutron-proton ratio, N_f/Z_f, of the fissioning nucleus. The result is qualitatively explained by the change of the most probable mass number of fission fragments for Z=50 proton shell.