Evaporation residue excitation functions from fusion of 63Cu with 65Cu

Abstract

Mass distributions of evaporation residues from the fusion of 63Cu + 65Cu have been measured at seven excitation energies from 55 to 105 MeV in a single irradiation experiment. They are interpreted as a mixture of residues produced by single nucleon evaporation cascades and cascades including α-particle evaporation. Compound nuclei with an average excitation energy of 55 MeV ( 51.5 ≦ E ∗ ≦ 59 MeV ) are still found to have a probability as high as 0.3 % for decaying by emission of a single nucleon. The low-energy behaviour of the excitation function can be interpreted as a fusion barrier effect. The parameters of this barrier are determined. The evaporation residue cross section at higher energies is shown to be limited by the fission of the compound nucleus.