How does fusion hindrance show up in medium-light systems? The case of 48Ca + 48Ca

Abstract The fusion excitation function of 48 Ca +  48 Ca has been measured above and well below the Coulomb barrier, thereby largely extending the energy range of a previous experiment down to very low cross sections. This system has a negative Q -value for compound nucleus formation. The fusion cross section decreases steadily below the barrier with no conspicuous change of slope below ≃ 300 μb . Coupled-channels calculations using a Woods–Saxon potential indicate that a large diffuseness parameter is needed to reproduce the sub-barrier cross sections. A close analogy with the case of 36 S +  48 Ca, with Q > 0 , is pointed out. The sign of the Q -value does not influence fusion cross sections down to the 300–600 nb level.