Model of competition between fusion and quasifission in reactions with heavy nuclei

The fusion process is studied by a model as the time evolution of a dinuclear system due to the diffusion in the mass asymmetry degree of freedom. The diffusion process in the relative distance between the centers of the interacting nuclei is responsible for the quasifission. The important point in the evolution of the dinuclear system to the compound nucleus is the appearance of a fusion barrier along the mass asymmetry degree of freedom. The model has the advantage that it treats the competition between the processes of complete fusion and quasifission in the asymmetric dinuclear system. A multidimensional Fokker-Planck equation and a Kramers-type expression are used to calculate the fusion rate. Due to the competition between the processes of complete fusion and quasifission, the fusion probability strongly decreases with decreasing mass asymmetry in the entrance channel of the reaction which is in agreement with experimental data.