Elastic Scattering of 30.3-MeV Polarized Protons fromNi58,Sn120, andPb208

Results are presented for the elastic scattering of 30.3-MeV polarized protons from targets of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The angular region from 10 to 165° is covered with an absolute accuracy in the polarization measurements of about 0.01. The data, together with corresponding differential cross-section data previously reported, are analyzed using the optical model. Two forms of the model are used: (1) the standard version with independent geometries and ten parameters; and (2) the folding version of Greenlees, Pyle, and Tang with eight parameters. Good fits to the data are obtained, particularly for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Evidence is presented to support the suggestion that such models are most satisfactory for large nuclei (${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$), and that for smaller nuclei (${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$) second-order corrections ignored in the model are playing a nonnegligible role.