NUCLEAR-SURFACE LOCALIZATION OF PREEQUILIBRIUM REACTIONS AT LOW ENERGIES

Average quantities related to the characteristics of the nucleon-nucle on (NN) interaction along the trajectory of the projectile in preequil ibrium reactions are calculated by using the semiclassical method to f ollow the incoming particle's path in the nuclear target. The radial d ependences of the nucleon's mean free path and the probability for the first NN collision have pointed out the surface character of the firs t NN interaction in multistep reactions even at low energies. In the l ocal density approximation an average Fermi energy and an average stre ngth of the effective NN interaction (V) over bar(0) along the traject ory of the incident nucleon are obtained with respect to both the nucl ear density and the first NN-collision probability. Good agreement is found between the average strengths obtained with the Hartree-Fock pot ential plus the dispersive component and by using the parametrization based on the Brueckner-Hartree-Fock nuclear matter calculations. It is also shown that the nuclear-density dependence of the effective NN in teraction may account for the low-energy phenomenological V-0 values w hich are much more increased in comparison with any prediction.