Surface diffuseness of nuclear potential from heavy-ion fusion reactions

Fits to high precision fusion cross sections at above-barrier energies require values of ∼1 fm for the diffuseness parameter of the Woods-Saxon potential. This is large compared with the values deduced from elastic scattering. Double folding model calculations of the bare nucleus-nucleus potential have been carried out to predict the fusion barrier energies and nuclear potential diffusenesses. Both the calculated barrier energies, and equivalent potential diffusenesses at the barrier radii, are generally lower than those found experimentally. These discrepancies raise questions about both the determination of the bare nucleus-nucleus potential with the folding model, and the boundary of the effects of friction on the fusion process.