Measurement of quasi-elastic back-scattering of {sup 64}Ni+{sup 118}Sn and {sup 58}Ni+{sup 124}Sn

Two systems of {sup 64}Ni+{sup 118}Sn and {sup 58}Ni+{sup 124}Sn produce the same compound nucleus {sup 182}Pt in the fusion reaction and they show the similar fusion cross sections below and near the Coulomb barriers, although only the system of {sup 58}Ni+{sup 124}Sn has positive Q-value multi-neutron transfer channels of 1-11 neutron(s). In order to investigate the possible effect of positive Q-value multi-neutron transfer channels on the capture cross sections, the quasi-elastic back-scattering for the two systems were measured below and near the Coulomb barriers at the backward angles of 162 deg. and 172 deg. The beam energies were altered in the energy range and the quasi-elastic back-scattering excitation functions were obtained. They were compared with the coupled-channel calculations of collective excitations and a two-neutron transfer channel, indicating no evidence of a significant effect of the positive Q-value multi-neutron transfer channels on the capture cross sections for the system of {sup 58}Ni+{sup 124}Sn.