First evidence of fusion hindrance for a small Q-value system

The excitation function for the fusion-evaporation reaction Si28+Ni64 has been measured down to a cross section of 25 nb. This is the first observation of fusion hindrance at extreme sub-barrier energies for a system with a small, negative Q-value (−1.78MeV). This result is further proof that heavy-ion fusion hindrance, reported earlier only for systems with large, negative Q-values, is a general phenomenon. The measured behavior can be reproduced by coupled-channels calculations with a modified ion-ion potential incorporating the effects of nuclear incompressibility.