Heavy-ion fusion below the Coulomb barrier: The systems 28,30Si + 58,62,64Ni and 32,34,36S + 58,64Ni

Fusion cross-sections for the 12 systems 28,30Si + 58,62,64Ni and 32,34,36S + 58,64Ni were measured at many energies from well below up to about 1.5 times the Coluomb barriers. The data show large sub-barrier fusion probabilities with strong isotopic dependences. The results of coupled-channel calculations involving the lowest 2+ and 3− levels of both colliding nuclei and the 2-neutron transfer channel are compared with the measured excitation functions. Indications for the importance of the transfer channels are found. Signatures of system-dependent effects of the positive Q-value transfer channels are evidenced, also from a systematic intercomparison of the data.