11-MeV Proton Optical-Model Analysis

An optical-model analysis of elastic scattering of 11-MeV protons from 24 nuclei in the mass range ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ to ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ is presented. The data analyzed include 18 angular distributions which we have measured and the previously published 10.5-MeV elastic-polarization data. An average set of geometrical parameters is determined for the data, and the real radius parameter of this potential is substantially larger than normally used at higher energies. The analysis performed with a fixed geometry, but allowing the well depths to be readjusted independently for each nucleus, reveals a very smooth dependence of the real-well depth as a function of mass number. However, the real-well depths fail to follow the expected isospin dependence of the optical potential.