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.