Multiple Coulomb Excitation ofSm152,Er166, andYb172,174,176

Abstract

Multiple Coulomb excitation of the ground-state rotational band of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$, ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$, and ${}_{}{}^{172,174,176}{}_{}{}^{}\mathrm{Yb}$ was measured in order to test the predicted ratios of the $B\left(\mathrm{E}2\right)$ values for a rotational sequence of states. The deexcitation $\gamma$ rays from the rotational levels were observed in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-$\gamma$ and $\alpha -\gamma$ conicidence spectra with a Ge(Li) detector. Experimental excitation probabilities are compared to the probabilities calculated with the de Boer-Winther Coulomb-excitation computer program. The $B(E2, 2\to 4)$ and $B(E2, 4\to 6)$ values were determined to accuracies of 6-10%. The $B(E2, 6\to 8)$ values were determined to accuracies of 15-25%. For the poor-rotor ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$, the results indicate some increase in the $B\left(\mathrm{E}2\right)$ values over the rigid-rotor predictions for the higher transitions. The observed increase is less than that predicted by "centrifugal stretching" based on the level positions. However, the results for the four good-rotor nuclei show smaller $B\left(E2\mathrm{}\right)\mathrm{}$ values between higher rotational states than those given by the rigid-rotor values, rather than the larger values predicted by centrifugal stretching.