Elastic scattering of 50 MeV from Ni58, Ni60, and Ni64

Angular distributions have been measured for elastic scattering at 50 MeV from Ni58, Ni60, and Ni64. A target isospin dependence is observed in the + angular distributions in the region of the diffraction minimum, while the effect is less pronounced for -. The - angular distributions for these isotopes have a very deep minimum compared with those for +. The angular distributions are compared with predictions of the second-order Michigan State University potential. The potential describes the + data much better than the - data, though qualitative agreement was obtained for both. The discrepancy between the experimental and calculated cross sections is discussed. The Coulomb distortion of the nuclear amplitude is shown to be important in the region of the diffraction minimum. The +/- difference introduced by this distortion is responsible for the striking energy dependence of the cross sections near the diffraction minimum between 50 and 80 MeV and can account for the poorer agreement for -.