Importance of Large-Angle Data in Optical-Model Analysis of Helion Elastic Scattering

Abstract

Optical-model analyses which include data far into the backward hemisphere for elastic scattering of complex projectiles at intermediate energies are found to produce optical potentials with many of the common ambiguities removed. This paper reports differential cross-section data with an extensive optical-model analysis for 59.8-MeV helions elastically scattered from ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$. The data include scattering angles back to 166° for ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ and to 149° for ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$. Optical-model fits to these data are satisfactory only with a surface-peaked absorption term and with a spin-orbit term included in the potential. The discrete or family ambiguity in the potential is removed, and continuous ambiguities are notably suppressed.