Negative components in the representation d2(σE)dE2 of heavy-ion fusion cross sections

Negative components are observed in the representation d2(σE)/dE2 in heavy-ion fusions related to recent studies of noticeable oscillations in the high-energy region of the fusion excitation functions. A modified multi-Gaussian model has been developed, which includes contributions for both positive and negative components in the d2(σE)/dE2 representation. The model reproduces the heavy-ion fusion excitation functions very well, including oscillations. The property of these negative components in the d2(σE)/dE2 spectrum and the reaction mechanism of fusion at energies above the Coulomb barrier are investigated. The model also reproduces well light heavy-ion fusion reactions between C12 and O16 at high energy; results imply that the compound nucleus channel effect may have an important contribution at the high energy region for all fusion systems.