Evaporation residue cross sections for the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{58}$Ni and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{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 ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{58}$Ni.

• Received 14 April 1992

DOI:https://doi.org/10.1103/PhysRevC.46.2360