Fusion-fission dynamics in the superheavy nucleus production

The fusion-fission reaction mechanism leading to the massive nucleus format ion is studied. We investigate the superheavy nucleus formation in heavy-io n induced reactions by analysing the evaporation residue (ER) production in order to study the fusion dynamics and the decay properties of nuclei clos e to the stability island at Z = 114. We consider the Ni-64 + Pb-208, Ca-48 + U-238 and Ca-48 + Pu-244 reactions that lead to the Z = 110, 112 and 114 superheavy elements respectively. By using the dinuclear system (DNS) concept of the two interacting nuclei w e calculate the quasifission-fusion competition in the entrance channel and the fission-evaporation competition along the de-excitation cascade of the compound nucleus. The dynamics of the entrance channel allows us to determ ine the beam energy window which is favorable to the fusion, while the dyna mic evolution of the compound nucleus on the shell correction to the fissio n barrier and the dissipative effects influence the fission-evaporation com petition in order to obtain the residue nuclei from the superheavy nucleus formation. We also calculate the Gamma(n)/Gamma(tot) ratio at each step of the de-excitation cascade of the compound nucleus and we present a systemat ics of Gamma(n)/Gamma(tot) (at first step of the cascade) for many reaction s that lead to nuclei with Z = 102-114.