Electron scattering at 180° from the "single-hole" states inN15

Abstract

Results are presented for the scattering of electrons through 180° from the ${\mathrm{½}}^{-}$ ground state and the ${\frac{3}{2}}^{-}$ excited state at 6.32 MeV in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$. The range of the momentum transfer $q$ is from 0.70 to 3.25 ${\mathrm{fm}}^{-1\mathrm{}}$. Comparisons are made with the predictions of the $0_{\mathrm{p}}$-shell proton-hole model, a large basis $2\hslash \omega$ shell model calculation, and core polarization models. In general, it was found that the theoretical description of the data improved markedly as the model space was expanded, but the predicted cross sections were consistently below the data for $q>\mathrm{}2.4\mathrm{}$ ${\mathrm{fm}}^{-1\mathrm{}}$. The present data rule out the low value of the Migdal parameter $g^{\prime }$ needed to describe the (e,e′) data for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, and do not support the previous suggestion that pion-condensation effects are important in finite nuclear systems.