Sub-barrier Fusion and Neutron Transfer with Positive Q-value

Fusion excitation functions of O-16+Ge-76 and O-18+Ge-74 have been measured with high precision at energies near and below the Coulomb barrier. Coupled-channels calculations including inelastic excitations well reproduce the experimental fusion excitation functions and the corresponding barrier distributions. There is no evidence that the two-neutron transfer with positive Q-value plays a role in the O-18+Ge-74 fusion. A systematic investigation on O-18 induced fusions has been performed to understand the roles of two-neutron transfers with positive Q-values, but the effects are inconsistent. No definitive conclusion can be made at present and further studies are strongly desired.