Fusion of 60Ni + 100Mo near and below the Coulomb barrier

The fusion excitation function of Ni-60 + Mo-100 has been measured from above the Coulomb barrier down to a cross section around 2 mu b, looking for coupling and hindrance effects in this soft mediummass system with positive Q-values for several neutron transfer channels. A comparison is made with previous results for Ni-64 + Mo-100 where no Q > 0 transfer channels exist and the hindrance effect is quite clear. The two excitation functions are very similar, as well as the corresponding logarithmic derivatives showing analogous saturations below the barrier. It appears that transfer couplings to Q > 0 channels seem to play a marginal role near and below the barrier for Ni-60 + Mo-100, even if measurements of cross sections lower than 1 mu b would be needed also for this system. Coupled-channels calculations confirm these observations and indicate that multi-phonon excitations dominate the fusion dynamics in the whole measured energy range.