Fusion of 59Co with light projectiles at near barrier energies

Abstract

Fusion cross sections have been measured for the 14N, 16O+59Co systems at bombarding energies from 32 to 56 MeV. Total transfer cross sections to excited states were simultaneously measured for the stripping of one proton and stripping of one neutron channels in the 14N induced reactions, and their upper limits for other transfer channels could be estimated. The elastic-scattering angular distribution was measured at Elab = 40 MeV for the 16O+59Co system. The effects of collective properties of the nuclei, included in the Wong model or the alternative approach of coupling inelastic channels, were found to be too small to explain the large sub-barrier fusion cross section enhancement. In order to perform simplified coupled-channel calculations involving transfer channels, a semiclassical formalism was used to derive the transfer form factors. Within the uncertainties of the calculations, the behavior of the sub-barrier fusion could be understood in terms of the coupling of charged-particle transfer channels, particularly the stripping of multi-nucleons, which act as doorways to fusion. An alternative approach, the liquid drop model, which accounts for the neck formation, also leads to satisfactory and compatible results.