Isovector effects in proton-nucleus elastic scattering at medium energies are studied. The accuracy of the Kerman-McManus-Thaler isospin averaging procedure is found to be very good for nuclei larger than ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. Studies of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ suggest that the surface neutrons may be pulled in somewhat relative to the protons, although uncertainties in the detailed applicability of the present truncation of the multiple scattering treatment render firm conclusions premature.

• Received 17 December 1992

DOI:https://doi.org/10.1103/PhysRevC.47.2242