Elastic scattering of 60-MeV alpha particles by the even nickel isotopes

An optical-model analysis of the scattering of 60-MeV α particles by ⁵⁸Ni, ⁶⁰Ni, ⁶²Ni, and ⁶⁴Ni has been performed with particular emphasis placed on (1) the significance of the backward-angle data with respect to removal of potential ambiguities and (2) the extent to which α elastic scattering at this energy is sensitive to the interior detail of the potential. In the ⁵⁸Ni case, six equivalent potentials are found to fit the diffraction scattering region (θ<70^∘), but only two of these simultaneously provide acceptable fits in the backward-angle region. It is shown that the detailed form of the real potential significantly affects the scattering only at distances beyond ~4 fm. The 60-MeV α probe is not sensitive to the detail of the total potential inside of ~3 fm in any way that affects the elastic cross section. [NUCLEAR REACTIONS ^58,60,62,64Ni(α,α), E=60 MeV; ⁶⁰Ni(α,α), E=75 MeV; measured σ(θ) θ=12-160^∘, enriched targets. Optical-model analysis.]