Nonlocal Optical Model for Nucleon-Nuclear Interactions

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Abstract
An attempt is made to achieve a unified potential description of the gross structure of the nucleon-nuclear interactions in bound states and in states of scattering. A model is employed with a nonlocal complex diffuse potential with spin-orbit coupling and surface absorption. This represents a relatively simple nonlocal generalization of the usual static models which might reasonably be expected to describe the nucleon-nuclear interaction in the low-energy range (say from -25 Mev to 25 Mev). Choosing the range of the nonlocal forces as suggested by considerations of the properties of infinite nuclear matter, the real parameters are fixed largely on the basis of neutron and proton separation energies. Two absorption parameters are then adjusted to provide agreement with total reaction and differential elastic cross-section data for neutrons. It is found that the successes of local optical models with energy-dependent parameters are largely preserved. Contrary to expectations, it is found that nonlocality tends to accentuate rather than wash out diffraction patterns. Although a diverse variety of experimental phenomena are treated, a range of parameter choices remains. Because of theoretical uncertainties as to the size of the "rearrangement energy," an effort is made to establish limits as to its magnitude on phenomenological grounds. The influence of several choices upon the physical phenomena used in adjusting the parameters of this model are shown. It would appear that this study does allow for a rearrangement energy but that it is rather small (