Pair transfer and the sub-barrier fusion of sup 18 O+ sup 58 Ni

Evaporation residue cross sections for the {sup 18}O+{sup 58}Ni and {sup 16}O+{sup 60}Ni fusion reactions have been measured in the energy range from 3 below to 20 MeV above the Coulomb barrier. The low-energy fusion enhancements found in the two systems are very different. A comparative analysis suggests that collective pair transfer modes play an important role in the sub-barrier fusion of {sup 18}O+{sup 58}Ni.