Fusion-evaporation competed against fusion-fragmentation and its isospin dependence

The competition between the fusion-evaporation (FE) and the fusion-fragmentation (FF) in the Ca + Ca reactions has been studied in the incident energy region from 10 to 35 MeV/nucleon. Using the isospin-dependent quantum molecular dynamics model, it is calculated the energy per nucleon E and density ρ of the projectile center (1 fm³ sphere) during the collision. The incident energy dependence and incompressibility dependence of the dynamics E–ρ trajectory are observed. It is indicated that the ending point of the E–ρ trajectory is closely related to the reactions mechanisms. Three type of reaction mechanisms, i.e. the binary-like, the fusion-evaporation and the fusion-fragmentation reactions, are distinguished using the kinematic global observable and the correlation between three largest fragments. The isospin dependence of the competition between fusion-evaporation and fusion-fragmentation is also studied. It is found that the symmetry energy provides the resistance in the compression phase, but promotes the expansion stage. The opposite effects of the symmetry energy on the compression and expansion phases weaken the isospin dependence of the fusion dynamics.