E2Transition Densities and Proton Shell Structure inSr88,Y89, andZr90

Electron scattering data have been used to obtain transition charge densities for the low-lying $E2\mathrm{}$ transitions in ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. These charge densities show a characteristic shape indicative of their microscopic constituency, modified by core-polarization effects. A good description of transitions in the even-even nuclei is obtained by using the measured single-particle transitions in ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ as effective densities.