The vibrational states of ${}_{}{}^{154,156,158,160}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{176,178,180}{}_{}{}^{}\mathrm{Hf}$ have been studied via Coulomb excitation. Thin high-purity targets were prepared in an isotope separator. Coulomb excitation of these nuclei was studied by the scattering of 11-17 MeV $\alpha$ particles. The particles were detected in an Enge split-pole spectrograph. The reduced transition probabilities $B(E\lambda ; 0_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}\to I^{\pi }K)$, were obtained for $I^{\pi }K=2^{+}2$ states in each nucleus, and for $I^{\pi }K=2^{+}0$ and $I^{\pi }=3^{-}$ states in several nuclei. The $K^{\pi }=2^{+}$ levels are reasonably constant in energy and $B\left(E2\mathrm{}\right)\mathrm{}$ strength while the $K^{\pi }=0^{+}$ states change rapidly in energy and excitation strength with neutron number. In both the softly deformed Gd nuclei and the more strongly deformed Hf nuclei, the lightest nucleus has the lowest energy and largest $B\left(E2\mathrm{}\right)\mathrm{}$ for an $I^{\pi }K=2^{+}0$ state, despite the difference in the sizes of the deformations at these lightest masses.

NUCLEAR REACTIONS ${}_{}{}^{154-160}{}_{}{}^{}\mathrm{Gd}(\alpha , {\alpha }^{\prime })$, ${}_{}{}^{176-180}{}_{}{}^{}\mathrm{Hf}(\alpha , {\alpha }^{\prime })$, $E=11-17\mathrm{}$ MeV; measured $\sigma$, deduced $B\left(E\lambda \right)$ and $M\left(E\lambda \right)$. Enriched targets.

• Received 13 January 1977

DOI:https://doi.org/10.1103/PhysRevC.15.1671