Sub-barrier fusion hindrance in medium-light systems

The fusion excitation functions of 48Ca + 48Ca and 36S + 64Ni have been measured down to very low energies, where the phenomenon known as fusion “hindrance” should show up, extending previous measurements which were limited to rather large near-barrier cross sections. Both systems show a steady decrease of the sub-barrier fusion cross sections with no pronounced change of slope. The logarithmic slopes of the two fusion excitation functions have a steep rise in the barrier region with decreasing energy and then level off in both cases. A close analogy with the case of 36S + 48Ca, a system with a positive Q-value for fusion (Qfus), that was measured recently, is pointed out.