Effect of the Entrance Channel on the Fission of the Compound Nucleus

The effects of entrance channel with different projectile and target nuclei combinations on the fission of the 220 90 Th * , 254 102 No * and 256 104 Rf * compound nuclei are investigated. The dependence of the de-excitation of the compound nucleus on the dynamics of the entrance channel is analyzed for the first time. We find that the fission branching ratio Γ f / Γ tot of the compound nucleus formed in the two different reactions with massive nuclei is different due to the dynamical effects in the entrance channel even at the same excitation energy  E * . It is caused by the different partial fusion cross section σ l fus ( E ) for those reactions. Consequently, the excitation function of evaporation residues measured in such reactions is strongly related to the effect of the entrance channel. This phenomenon is explained by the dependence of the capture and fusion cross sections on the orbital angular momentum of collision.