Energy Dependence of the Optical Model forHe3Scattering fromNi60

An optical-model analysis of measured angular distributions for elastic scattering of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ from ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ at five different energies (29.6, 35.1, 49.7, 59,8, and 71.1 MeV) produced satisfactory fits to all five of the data sets with an optical potential having all parameters common. This energy independent potential gave a ${\chi }^2$ minimum with $V=126\mathrm{}$ MeV, $r_R=r_s=1.12\mathrm{}$ fm, $a_R=a_s=0.84\mathrm{}$ fm, $W_D=20.4\mathrm{}$ MeV, $r_I=1.26\mathrm{}$ fm, $a_I=0.84\mathrm{}$ fm, and $V_s=2.85\mathrm{}$ MeV. Another parameter family with $V=170\mathrm{}$ MeV also gave an equally good minimum in ${\chi }^2$. These two parameter families were used to predict scattering cross sections at 180° over the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ energy range from 21 to 32 MeV, and corresponding laboratory data were found to be in better agreement with the predictions of the above listed family with $V=126\mathrm{}$ MeV. Slightly improved fits to the five data sets were obtained in a search with the real and imaginary well depths dependent on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ energy and with the rest of the parameters common. In this case $V$ and $W_D$ were found to have a weak but approximately linear dependence on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ energy $E$, with $V=133.9-0.14E$ MeV and $W_D=22.4-0.04E$ MeV.