Nonlocality and the Real Surface Terms in the Velocity-Dependent Optical Potential for Elastic Scattering of Neutrons from Carbon Isotopes

The velocity-dependent optical potential used in this work leads to a local energy-dependent potential that consists of real surface terms that are proportional to the derivatives of the nuclear matter density. Such term—in other works—has been accounted for nonlocality due to the surface deformation in the light nuclei. In the present work, we have examined the ability of the velocity-dependent potential, which contains real surface-peaked terms, to account for nonlocality. This is achieved by inspecting the case of fitting the angular distribution data for the neutron that elastically scattered from a light nucleus, carbon isotopes (¹⁰C, ¹²C, and ¹⁴C) in the energy range of 12–20 MeV, by using two potential models: the modified velocity optical potential (which conations real surface-term) and the conventional optical potential. A comparison between the two models has been made. Furthermore, the total elastic cross sections and the analyzing power are calculated using both models and compared to the experimental data. The volume integrals per nucleon of the real central potential and the imaginary surface potential in the modified velocity optical potential have also been determined and the results are in good agreement with the corresponding values calculated using other models. It is shown that a significant improvement in angular distributions was observed when the velocity-dependent potential was applied, specifically in the large angle scattering region and in certain energy ranges.