Square-well generalized optical model

Abstract

The interaction of neutrons with « collective » even-even nuclei is discussed on the basis of the generalized optical model. The spin-orbit coupling and both the surface and volume absorbtion terms are taken into account. By assuming a square-well radial interaction and by introducing the elastic-channel logarithmic derivative, the effects of virtual and real excitation of the first 2+ level on the cross-sections are deeply analysed. Particular interest is devoted to the behaviour of the cross-sections in the zero-energy limit, in threshold and in the limit of very weak coupling. In particular the analysis of the last point allows us to derive some general and interesting properties of the intermediate structures, by considering the growing up of the collective spectrum over the single-particle background, as far as the coupling with the 2+ level is gradually switched on.