21-MeV Alpha-Particle Scattering onA=58−64Targets

Abstract

Cross sections for 21-MeV $\alpha$ elastic and inelastic scattering to the first 2+ level were measured at 3° intervals between 30° and 166° for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$. Both the elastic and inelastic scattering data exhibit well-defined oscillations which obey the Blair phase rule throughout the angular range. Optical-model fits to the elastic scattering data were found at intervals corresponding to the half-wavelength rule for a wide range of real-well depth. Analysis of the data indicates that the scattering is concentrated in the nuclear surface but is also sensitive to the interior of the nuclear potential. Distorted-wave calculations of the inelastic angular distributions with parameters obtained from optical-model analysis of the inelastic scattering data gave good agreement with the data in the forward hemisphere, although good agreement was not generally obtained at large angles, where the inelastic scattering cross sections are comparable to the elastic scattering cross sections. Comparison of the inelastic data with distorted-wave calculations does not remove the ambiguity of the optical-model potential.