Strong influence of the entrance channel on the formation of compound nuclei 216,222Th* and their evaporation residues

The dynamical effects of the entrance channel on the formation of the evaporation residues are studied by analyzing the 40Ar+176Hf, 86Kr+130,136Xe, 124Sn+92Zr, and 48Ca+174Yb reactions leading to the 216Th* and 222Th* compound nuclei. We find that the difference between the evaporation residue cross sections for the reactions leading to the same compound nucleus is caused by the different angular momentum distributions of the partial fusion cross sections σfusl(Ec.m.). The strong dependence of the fusion angular momentum distribution on the mass (charge) asymmetry and shell structure of reactants is demonstrated. The effect of the A/Z ratio for the 86Kr+130,136Xe reactions is discussed. The dynamical conditions of capture affect the competition between complete fusion and quasifission and, consequently, the shape of the angular momentum distribution of the compound nucleus. By this way the peculiarities of the entrance channel also affect the fission-evaporation competition of the excited intermediate nuclei along the deexcitation cascade of the compound nucleus and, consequently, the evaporation residue formation