Analysis of neutron multiplicity and fission fragment mass distribution within the asymmetric two-center shell model

Abstract

The fission fragment mass distribution followed by neutron emission is studied for the 238U(18O,f) reaction using the asymmetric two-center shell model. Within the thermodynamic approach, excitation energy carried by the compound nucleus is dissipated in the emission of a pair of neutrons in several consecutive steps. Therefore, we have considered 2–12 (in step of 2) neutron emission channels in our formalism. The mass distribution corresponding to 8-neutron emission channel compares reasonably well with the experimental data. The observed fine structure dips corresponding to shell closure (Z = 50 and N = 82 of individual fission fragment arise mainly due to shell structure in the mass parameters. However, an exact location and magnitude of the dip at A = 124 in the mass distribution depends on how the temperature modifies masses and, also, on the precise information of pre- and post-neutron emission data. This suggests a possible importance of extending these calculations to get new insight into an understanding of the dynamical behaviour of fragment formation in the fission process.