Optical-Model-Family Ambiguity Resolved forHe3Elastic Scattering fromNi60

Abstract

Optical-model fits with successive fixed values of real well depth $V$ to five angular distributions for ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$)${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ which include data to angles > 110° for projectile energies between 29.6 and 71.1 MeV yield ${\chi }^2$ vs $V$ plots with a deep minimum at $V\sim 130$ MeV for each data set. For the lower-energy data sets, other minima (parameter families) are observed at intervals above and below this value, but the higher-energy data sets (59.8 and 71.1 MeV) show only one unique family near $V=130\mathrm{}$ MeV. The absence of the family ambiguity for the higher-energy data sets demonstrates the importance of both large-angle and high-energy data for the removal of optical-potential ambiguities. The normalized volume integral of the real potential at $V\sim 130$ MeV is $J_R\sim 330$ MeV ${\mathrm{fm}}^3$ for each data set, and $J_R$ changes by ∼100 MeV ${\mathrm{fm}}^3$ for successive families. The unambigious value of $J_R\sim 330$ MeV ${\mathrm{fm}}^3$ for the higher-energy data sets and the near independence of $J_R$ on energy implies a similar unique value and corresponding unique family for the lower-energy data sets. This value of 330 MeV ${\mathrm{fm}}^3$ is somewhat lower than values of $J_R>400\mathrm{}$ MeV ${\mathrm{fm}}^3$ suggested by earlier studies.