Influence of nuclear structure on sub-barrier hindrance in Ni+Ni fusion

Fusion-evaporation cross sections for Ni-64+Ni-64 have been measured down to the 10 nb level. For fusion between two open-shell nuclei, this is the first observation of a maximum in the S-factor, which signals a strong sub-barrier hindrance. A comparison with the Ni-58+(NI)-N-58, Ni-58+Ni-60, and Ni-58+Ni-64 systems indicates a strong dependence of the energy where the hindrance occurs on the stiffness of the interacting nuclei.