Complete fusion cross sections from fission fragment angular distribution analysis and study of internuclear potentials

Abstract

A different approach to the determination of heavy-ion fusion cross sections is described which requires data on fission fragment angular distributions alone, without going to more difficult absolute measurements of the fission and evaporation residue cross sections. The present method involves a direct determination of lcr (maximum l-wave for which fusion is possible) from the statistical theory analysis of fragment angular distributions corresponding to the fission events with full momentum transfer, taking into consideration the contribution to fission from different stages of deexcitation. The published data on fission fragment angular distributions in the fission of ¹⁹⁷Au and ²⁰⁹Bi by B, C, N and O ions in the bombarding energy range of 60 MeV to 120 MeV were analysed to illustrate this method. For a few cases, where data on the direct measurement of σ_fu were available, these values were found to be in good agreement with those obtained by this method. The energy dependence of l_cr (or fusion cross sections) thus. determined, were also analysed to obtain internuclear potentials in a friction-free analysis and were compared with the proximity potential function. The energy variations of l_cr ² calculated on the basis of the proximity potential with and without the inclusion of one-body proximity friction are also compared with the experimental values. It was seen that satisfactory fits to the data can be achieved with the inclusion of one-body friction.