Exploring the Effects of Entrance Channel and Fissility on Pre-scission Neutron Multiplicity and Nuclear Dissipation

The pre-scission neutron multiplicity and dissipation strength are studied for a systematic understanding of the role of entrance-channel in fusion-fission dynamics using the statistical model formalism. The measured pre-scission neutron multiplicity is found to be higher for symmetric reactions as compared to the asymmetric ones for a given compound nucleus, with the exception of a few reaction channels, where the presence of quasi-fission affects the neutron yield. The calculated pre-scission neutron multiplicities are compared with the experimentally measured values and it is found that for the majority of reactions, the calculated values of pre-scission neutron multiplicities are under-estimated. The under-estimation of pre-scission neutron multiplicity indicates that dissipation is required in the fission channel to reproduce the experimental data. The systematic behaviour of pre-scission neutron multiplicity and dissipation strength as a function of fissility of the compound nucleus is also explored for the select energy ranges. It is found that the pre-scission neutron multiplicity shows nearly increasing behaviour as a function of fissility of the compound nucleus, whereas, dissipation does not seem to follow such an increasing trend for the studied reactions.