Differential cross sections and analyzing powers for scattering of 180 MeV protons by ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured for all narrow states below 12.1 MeV of excitation. Medium modifications to the effective interaction for normal-parity isoscalar transitions were studied using transition densities determined by electron scattering to minimize nuclear structure uncertainties. An empirical effective interaction, guided by nuclear matter theory, was fitted to inelastic scattering data for six states simultaneously. Distorted waves were generated from self-consistent optical potentials computed from the same effective interaction. The isoscalar effective interaction determined by this procedure provides a good global fit to the inelastic scattering data and is consistent with elastic scattering data that were not included in the fit. The results are consistent with earlier results for 135 MeV and show that the effective interaction is suppressed at low density but is less density dependent than predicted by nuclear matter theory and the local density approximation. These comparisons suggest effects in finite nuclei beyond the local density approximation. Finally, we compare data for $0^{\mathrm{-}}$ and $2^{\mathrm{-}}$ states at both 135 and 180 MeV with representative calculations.

• Received 27 November 1989

DOI:https://doi.org/10.1103/PhysRevC.41.2504