Mass dependence of theHe3optical potential at 40 MeV

The elastic scattering of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ions has been studied at 39.7 MeV from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{105}{}_{}{}^{}\mathrm{Pd}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at angles between 4° and 108°. The data are analyzed in terms of the optical model. A standard geometry is used to study the mass dependence of the real and imaginary well depths obtained from analysis of our data and that of others. The utility of a spin-orbit term is discussed. Continuous ambiguities of the geometrical parameters are examined. Improvements in the standard geometry are considered.