Surface-Delta-Interaction Model for Nuclear Structure Analyzed by Proton Inelastic Scattering

Abstract

Differential cross sections and polarizations for 17.8-MeV protons scattered by nickel isotopes have been calculated by solving the coupled equations. The nuclear states were described in terms of their microscopic composition in the two-quasiparticle approximation. Two such model calculations were used. The effect of the presence of pure "two-phonon" states was investigated by generating them from the collective operator for the $2_1^{}{}_{}{}^{+}$ state. The effects of the spin-flip term in the direct interaction were included. Comparison of the results with experiments suggests that, except for the collective $2_1^{}{}_{}{}^{+}$ state, the two-quasiparticle method is inadequate for treating nuclear states. The vibrational treatment also fails. A much more elaborate structure calculation which treats the mixing between the two-quasiparticle and the "two-phonon" configurations is suggested.