Reduced transition probabilities of vibrational states in /sup 156,158/Dy, /sup 162,164/Er, and /sup 168/Yb

The vibrational states of $^{156,158}\mathrm{Dy}$, $^{162,164}\mathrm{Er}$, and $^{168}\mathrm{Yb}$ have been studied via Coulomb excitation. Thin high purity targets were prepared in an isotope separator. The Coulomb excitation of these nuclei was studied by the scattering of 12-16 MeV $\ensuremath{\alpha}$ particles, which were detected in an Enge split-pole spectrograph. The reduced transition probabilities $B(E\ensuremath{\lambda};{0}_{\mathrm{g}.\mathrm{s}.}^{+}\ensuremath{\rightarrow}{I}^{\ensuremath{\pi}}K)$ were obtained for ${I}^{\ensuremath{\pi}}K={2}^{+}2, {2}^{+}0$, and ${I}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$ states in each nucleus. Limits on $B(E\ensuremath{\lambda})$ values and values extracted from published ($d, {d}^{\ensuremath{'}}$) cross sections are also presented. Trends in $B(E2)$ values and energy levels for the Dy, Er, and Yb nuclei show that the ${K}^{\ensuremath{\pi}}={2}^{+}$ levels are reasonably constant in energy for only Dy and Er. In all three nuclei $B(E2)$ values decrease with increasing neutron number. Except for the Dy isotopes, the lightest isotope has the largest $B(E2)$ value for the lowest lying ${I}^{\ensuremath{\pi}}K={2}^{+}0$ state. ${I}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$ states level energies and $B(E3)$ values are found to be in fair agreement with microscopic calculations. Values of $B(E2)$ for ${K}^{\ensuremath{\pi}}={2}^{+}$ states are in fair agreement with microscopic calculations when these exist.NUCLEAR REACTIONS $^{156,158}\mathrm{Dy}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}})$, $^{162,164}\mathrm{Er}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}})$, $^{168}\mathrm{Yb}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}})$, $E=12\ensuremath{-}16$ MeV; measured $\ensuremath{\sigma}$, deduced $B(E\ensuremath{\lambda})$. Enriched targets.