Investigation of the role of the projectile-target orientation angles on the evaporation residue production

The measured yield of evaporation residues in reactions with massive nuclei have been well reproduced by using the partial fusion and quasifission cross sections obtained in the dinuclear-system model. The influence of the orientation angles of the projectile- and target-nucleus symmetry axes relative to the beam direction on the production of the evaporation residues is investigated for the 48Ca + 154Sm reaction as a function of the beam energy. At the low beam energies only the orientation angles close to αP = 30° (projectile) and αP = 0°-15° (target) can contribute to the formation of evaporation residues. At large beam energies (about Ec.m. = 140-180 MeV) the collisions at all values of orientation angles αP and αT of reactants can contribute to the evaporation residue cross section which ranges between 10-100 mb, while at Ec.m. > 185 MeV the evaporation residue cross section ranges between 0.1-1 mb because the fission barrier for the compound nucleus decreases by increasing its excitation energy and angular momentum.