Electric moments and charge deformation parameters inSm152,154,Gd156, andEr166

Abstract

Coulomb excitation experiments with $\ensuremath{\alpha}$ particles were performed on the four rare-earth nuclei $^{152,154}\mathrm{Sm}$, $^{156}\mathrm{Gd}$, and $^{166}\mathrm{Er}$. $E2$ and $E4$ transition matrix elements of low-lying levels in the rotational ground-state bands were obtained. Model dependent charge deformation parameters ${\ensuremath{\beta}}_{2}^{c}$ and ${\ensuremath{\beta}}_{4}^{c}$ were extracted assuming a deformed Fermi distribution with diffuse surface. The possible difference between charge and nuclear hexadecapole deformation observed in $^{154}\mathrm{Sm}$ does not show up in the isotone $^{156}\mathrm{Gd}$.