A nonlocal optical model for neutron scattering from light 1p-shell nuclei

Abstract

Nonlocal effects result in complications when predicting scattering observables. This is usually seen when one analyses the data for nucleon scattering off light 1p-shell nuclei using local optical model potentials. In this work we employ the nonlocal optical model of Perey and Buck (1962) [10] to study the neutron-light nucleus scattering process. By fitting the individual elastic angular distributions we determine energy-dependent, target-specific potential parameters. Then, for each nucleus, a constant set of nonlocal parameters is obtained by simultaneously fitting the corresponding elastic angular distributions. The good quality of the fits prompted us to search for a global constant set of nonlocal parameters by simultaneously fitting a large number elastic angular distribution sets for neutron scattering off light nuclei from 6Li to 18O over the energy range 9 to 35 MeV. We also show that the implicit inclusion of nonlocality in the optical model does not fully remove the need for energy-dependent potential parameters. This is achieved by expressing the nonlocal imaginary volume and surface depths of the constant global set as linear functions of energy and the asymmetry term. The effectiveness of this set is tested by applying it to additional light nuclei and energies outside the fitted range. The predicted elastic angular distributions compared well with the measured data.