Role of the orientation angles of reacting nuclei in evaporation residue production

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 (ERs) is investigated for the 48Ca+154Sm reaction as a function of the beam energy. The measured yields of ERs by massive nuclei reactions have been well reproduced by using the partial fusion and quasi-fission cross-sections obtained in the dinuclear system model. At lower beam energies, only the orientation angles close to αP=30° (projectile) to αP=0°–15°(target) can contribute to the ER formation. At large beam energies (about E c.m.=140–180 MeV), all αP−αT configurations of reactants can contribute to the ER cross-section, which ranges between 10 and 100 mb, while at E c.m.>185 MeV, the ER cross-section ranges between 1 and 0.1 mb because the fission barrier for the compound nucleus decreases by increasing its excitation energy and angular momentum.

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