A global pre-equilibrium analysis from 7 to 200 MeV based on the optical model potential

Abstract

We present a pre-equilibrium model for nucleons with incident energies from 7 to 200 MeV, for nuclides in the mass range A ⩾ 24 . This is accomplished by a new global approach for the two-component exciton model which, together with the complementary compound and direct reaction mechanisms, enables a description of continuum energy spectra over the whole outgoing energy range. We develop new forms for the internal transition rates with collision probabilities based on a recent optical model potential. To connect with conventional semi-classical analyses, we derive from this approach a new energy-dependent form for the average squared matrix element M 2 . Both implementations are shown to remove problems encountered when predicting measurements with older parameterizations that apply in more restricted energy ranges. Surface effects which depend on the type of projectile and the target mass are included. Another feature necessary for the large energy range of our analysis is the generalization of multiple pre-equilibrium processes up to any order of particle emission. To constrain our parameterization as much as possible and to assess the predictive power of our model, we have compared it with the complete experimental data collection of ( n , x n ) , ( n , x p ) , ( p , x n ) and ( p , x p ) spectra. As a result, remaining shortcomings of our model, as well as mutually inconsistent experimental data sets are identified.