ON THE MOMENTUM DEPENDENCE OF THE NUCLEON-NUCLEUS OPTICAL-POTENTIAL

The momentum dependence of the mean-field contribution to the real part of the optical-model potential is investigated employing realistic nucleon-nucleon interactions. Within a non-relativistic approach a momentum dependence originates from the non-locality of the Fock exchange term. Deducing the real part of the optical model from a relativistic Dirac-Brueckner-Hartree-Fock approximation for the self-energy of the nucleons yields an additional momentum dependence originating from the non-relativistic reduction of the self-energy. It is demonstrated that large Fock terms are required in the non-relativistic approach to simulate these relativistic features. A comparison is made between a local-density approximation for the optical model and a direct evaluation in finite nuclei.