Optical-Model Analysis of Nucleon Scattering from1p-Shell Nuclei between 10 and 50 MeV

Abstract

Differential cross sections for protons scattered from ${\mathrm{B}}^{10}$ were measured and, combined with published differential cross sections and polarizations for protons elastically scattered from ${\mathrm{Li}}^6$, ${\mathrm{Li}}^7$, ${\mathrm{Be}}^9$, ${\mathrm{B}}^{10}$, ${\mathrm{B}}^{11}$, ${\mathrm{C}}^{12}$, ${\mathrm{C}}^{13}$, ${\mathrm{N}}^{14}$, and ${\mathrm{O}}^{16}$ at bombarding energies between 10 and 50 MeV, are analyzed in terms of the optical model. An investigation of the systematic effects observed in applying the optical model to light nuclei reveals two peculiarities. First, an examination of the effects of a nonlocal potential indicates that the radius parameter of the real central potential is energy-dependent. Second, the Thomas form usually used for the spin-orbit potential is shown to lose its surface-peaked character in the case of light nuclei; but a proposed slight modification avoids this defect. The set of parameters found to give a good description of the data over a range of incident nucleon energy and target mass was shown to be similar to the sets of parameters found to describe the nucleon scattering from heavy nuclei. Using the prescriptions for the parameters of the present study but reversing the signs of the $\frac{\mathrm{}(N-Z)\mathrm{}}{A}$ terms leads to fits of comparable quality to the differential cross sections for 14-MeV neutrons scattered from ${\mathrm{Li}}^7$, ${\mathrm{Be}}^9$, ${\mathrm{B}}^{11}$, and ${\mathrm{N}}^{14}$.