Proton Elastic Scattering Measurements at 9.8 MeV with Optical-Model Analysis

Differential-cross-section and polarization measurements are presented for the elastic scattering of 9.8-MeV protons by ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$. In general, the angular range 17-160° was covered with an accuracy of ±2% for the cross section and ±0.02 for the polarization measurements. The data are analyzed using an optical model in three ways: (1) using individual data sets for each element and either a seven- or a nineparameter model; (2) using all the data simultaneously and a "global" search routine; (3) using individual data sets and the folding version of G. W. Greenlees, G. J. Pyle, and Y. C. Tang. The analysis using procedure (1) suggests the model is overparameterized at 9.8 MeV. These difficulties are overcome to some extent using procedures (2) and (3).