Energy dependence of 1+ spin excitations in Si28

Forward-angle cross sections and analyzing powers for the main 1+ T = 1 and 1+ T = 0 states in Si-28 have been measured by proton inelastic scattering at 200, 400, and 600 MeV bombarding energy. The results are compared with microscopic distorted-wave impulse approximation (DWIA) calculations. The sensitivity to the optical potentials is pointed out. Two DWIA methods give compatible results for the DELTA-T = 1 transition at 200 and 400 MeV, but differ strongly for the DELTA-T = 0 transition at 200 MeV. For both the DELTA-T = 0 and the DELTA-T = 1 transitions no clear dependence on the incident energy can be ascertained for the ratio of the experimental to the theoretical cross section.