Optical-Model Analysis ofp−O16Elastic Scattering from 23-53 MeV

Differential cross section and polarization angular distributions for $p-{\mathrm{O}}^{16}$ elastic scattering together with total-reaction cross section data in the energy range 23-53 MeV were analyzed using the eleven-parameter optical-model search code SEEK. The optical potential contains a surface-absorption term of Gaussian form rather than the usual Woods-Saxon derivative form. Emphasis was placed upon finding the energy dependence of the strengths of the potentials. Consequently, an averaged set of geometrical parameters was first defined, and then a search was made for the strengths of the real central, the volume and surface parts of the imaginary central, and the real spin-orbit potentials. The energy dependence of the real central potential for ${\mathrm{O}}^{16}$ in the energy range 23-53 MeV can be represented by $\frac{\mathrm{dV}}{\mathrm{dE}}\cong -0.29\mathrm{}$. The fits to the large-angle data are in general unsatisfactory. Difficulties were encountered in fitting the three sets of data below 30 MeV. This is consistent with what is expected from the nonmonotonic energy behavior of the differential cross sections and polarizations in this energy region.