Effects of multichance fission on isotope dependence of fission fragment mass distributions at high energies

Abstract

Fission fragment mass distributions of $^{234\text{--}240}\mathrm{U}$, $^{236\text{--}242}\mathrm{Np}$, and $^{238\text{--}244}\mathrm{Pu}$ are studied using the Langevin approach in the wide excitation energy range as ${E}^{*}=15\text{--}55\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. In the present calculation, neutron emission before fission, so-called multichance fission, was introduced. The calculated results well demonstrated the experimental data, which shows the double-peak structure up to the highest excitation energies and the clear dependence on the initial fissioning nuclides. The trend is nicely correlated with the neutron binding energy of the compound nucleus that dominates the neutron emission probability before fission.