PHENOMENOLOGY OF PROTON ELASTIC-SCATTERING AND EVIDENCE FOR ANGULAR-MOMENTUM-DEPENDENT OPTICAL-MODEL POTENTIALS

An earlier suggestion of the authors (1976) that the proton optical-model potential has terms, both real and imaginary, which depend explicitly on angular momentum is hereby supported by a systematic study of proton scattering from 16O and 40Ca at a wide range of energies, as well as 58Ni and 56Fe. Not only are the fits to data improved (in some cases the improvement is very great), but the extracted parameters show certain striking regularities which were less apparent in l-independent fits. We also make some general remarks concerning the status of phenomenological fits and the interpretation of l dependence.