In order to describe heavy-ion fusion reactions around the Coulomb barrier with an actinide target nucleus, we propose a model which combines the coupled-channels approach and a fluctuation-dissipation model for dynamical calculations. This model takes into account couplings to the collective states of the interacting nuclei in the penetration of the Coulomb barrier and the subsequent dynamical evolution of a nuclear shape from the contact configuration. In the fluctuation-dissipation model with a Langevin equation, the effect of nuclear orientation at the initial impact on the prolately deformed target nucleus is considered. Fusion-fission, quasifission, and deep quasifission are separated as different Langevin trajectories on the potential energy surface. Using this model, we analyze the experimental data for the mass distribution of fission fragments (MDFF) in the reactions of 34 ,36S+238U and 30Si+238U at several incident energies around the Coulomb barrier. We find that the time scale in the quasifission as well as the deformation of fission fragments at the scission point are different between the 30Si+238U and 36S+238U systems, causing different mass asymmetries of the quasifission.
ASJC Scopus subject areas
- Nuclear and High Energy Physics