Microscopic calculations of C2 and C4 form factors in sd-shell nuclei

Abstract

Inelastic electron scattering to 2 + and 4 + states for the even–even N= Z sd-shell nuclei ( 20 Ne, 24 Mg, 28 Si and 32 S) are discussed taking into account higher energy configurations outside the sd-shell. Higher energy configurations, which are called core polarization effects, are included through a microscopic theory that includes excitations from the core 1 s and 1 p orbits and also from 2 s–1 d shell to the higher allowed orbits with 2ℏ ω excitations. The predictions of C2 and C4 Coulomb form factors are compared with the available experimental data. The calculations based on the Wildenthal interaction for the sd-shell model space and on the modified surface delta interaction for the core-polarization effects. The effect of higher excited configurations is found essential in both the transition strength and momentum transfer dependence of form factors, and gives a remarkably good agreement with the measured data.