Probing entrance channel effects in fusion-fission dynamics through neutron multiplicity measurement of Rn-208

The pre- and post-scission neutron multiplicities are measured for the fission of Rn-208, populated with Si-30+Hf-178 and the reactions Ti-48 + Gd-160 in the excitation energy range of 54.5 - 80.8 MeV. We found significant differences in the pre-scission neutron multiplicities of these two systems. Also, both the reactions exhibit an enhancement in the pre-scission multiplicity with respect to the existing data for the O-16+Pt-194 reaction populating Rn-210. The measured multiplicities are compared with the theoretical predictions obtained from the Langevin dynamical model for fission. Dynamical simulations are also performed to estimate the capture cross-sections. Contribution of the neutrons, emitted during the fusion process, is shown to be crucial in determining the neutron multiplicities for the present systems. Moreover, in case of the Ti-48+Gd-160 reaction, rapid quasi-fission dynamics prevents neutron emission from the thermalized target-projectile composite. The present measurement helps us to understand the relative importance of fusion and quasi-fission processes and their timescales depending on the entrance channel mass asymmetry. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The neutron multiplicities before and after scission were measured for the fission of Rn-208 induced by Si-30+Hf-178 and Ti-48+Gd-160 reactions. Significant differences were found in the pre-scission neutron multiplicities of these two systems. The study emphasizes the crucial contribution of neutrons emitted during the fusion process in determining the neutron multiplicities for the present systems.