Phenomenological and microscopic optical model analyses of the interaction of low-energy nucleons withNb93

The phenomenological optical model is parametrized in the energy range 10 keV—50 MeV so as to obtain a good agreement with all the available nucleon data. These include neutron and proton strength functions and elastic scattering data, as well as the neutron total cross sections and ($p$,$n$) isobaric analog state quasielastic scattering data. Comparison is made with the microscopic model of Jeukenne, Lejeune, and Mahaux including the new parametrization for nucleon energies less or near 10 MeV. From the analyses of sub-Coulomb proton experimental data the fundamental importance of the absorptive Coulomb correction term appears. The volume integral of this term is calculated and its energy dependence is exhibited.