Nucleon-nucleus optical model potential: (III). The spin-orbit component

Abstract

As an extension of our earlier work, we calculate the spin-orbit part of the nucleon-nucleus optical potential ( V s.o. + W s.o.) starting from the Hamada-Johnston internucleon potential. We find that the radial shape of V s.o. is essentially energy independent and peaks in the nuclear surface while its strength varies only slowly with energy. The energy dependence of W s.o. is much greater. For 20 MeV nucleons we find that W s.o peaks appreciably further from the nuclear centre than V s.o. and that the ratio of the potential depths is W s.o./ V s.o. ≈ − 0.05. For 200 MeV nucleons W s.o. and V s.o. have the same shape and W s.o./ V s.o. ≈ −0.2. These predictions are not readily comparable with most phenomenological analyses because the earlier give a wide divergency of results. As a preliminary test of our theory we have used our calculated spin-orbit potential to obtain polarizations and cross sections for the scattering of 30.3 MeV protons from 40Ca. We obtain good agreement with the experimental data without any parameter fitting.