Optical model analysis of quasielastic (p, n) reactions at 22.8 Mev

Abstract

Quasielastic (p, n) differential cross sections have been measured for 29 nuclei ranging from 9Be to 208Pb at an energy of 22.8 MeV in approximately 7.5° steps from 10° to 152°. The results have been analysed with a distorted-wave Born approximation in terms of the generalized optical model due to Lane. Starting with a complex isospin interaction form factor, U 1, deduced from the Becchetti-Greenlees global set of proton optical parameters, the shape of the surface-peaked, imaginary part of U 1 was varied until good fits to the data were obtained. The shape of the real part of U 1 and the ratio of the real to imaginary well depths were kept fixed at the Becchetti-Greenlees values. The resulting best-fit form factors had overall strengths 20–30 % less than the Becchetti-Greenlees value. Further, the resulting imaginary part of U 1 was found to peak at a decreasing radius relative to the real part of U 1 with an increasing width as A increased. A smoothed parameterization of the best-fit U 1 is given for all nuclei with A > 40. The individual best-fit U 1 is used to generate self-consistent neutron optical potentials from the Becchetti-Greenlees proton optical potentials as prescribed by the Lane model. Neutron elastic scattering angular distributions and reaction cross sections predicted by these self-consistent potentials are in good agreement with observed neutron scattering data.