Barrier distributions fromS32+Zr90,96quasi-elastic scattering: Investigation of the role of neutron transfer in sub-barrier fusion reactions

Abstract

The differential cross sections of quasi-elastic scattering at backward angles were measured with high precision for 32 S+ 90,96 Zr around the Coulomb barrier, and barrier distributions were extracted from the measured excitation functions. The experimental barrier distribution of 32 S+ 90 Zr is well reproduced by the coupled-channels calculations including the low-lying quadruple and octupole vibrations in 32 S and 90 Zr. However, the model with the same coupling scheme fails to reproduce the experimental barrier distribution for 32 5+ 96 Zr. The coupled-channels calculation including the neutron transfer channels in the system 32 5 + 96 Zr gives an improved description of the experimental data. A comparison of the data on 40 Ca+ 90,96 Zr shows that the two systems 32 5, 40 Ca+ 90 Zr display barrier distributions that are similar to each other, whereas the barrier distributions of 32 S, 40Ca+ 96 Zr are both wider and flatter than the those of 40 Ca+ 90,96 Zr. The present results strongly indicate that neutron transfer plays an important role in the fusion processes.