Double folding nucleus-nucleus potential applied to heavy-ion fusion reactions

Double folding model calculations to obtain the bare nucleus-nucleus potential have been carried out with the Reid and Paris M3Y effective nucleon-nucleon (NN) interactions. The exchange part of the interaction was taken to be of finite range and the density dependence of the NN interaction was accounted for. The calculated fusion barrier energies are generally lower than those expected taking into account potential renormalization due to coupling to collective states at high excitation energies. Fitting the potentials at the barrier radii with a Woods-Saxon form results in effective potential diffuseness of ∼0.65-0.70 fm, smaller than the values of ∼ 1 fm generally found from fitting fusion cross sections at above-barrier energies. These discrepancies raise questions about both the determination of the bare nucleus-nucleus potential with the folding model, and the boundary of the effect of friction on the fusion process.