All the members of the $h_{\frac{11}{2}}$ rotational structure have been observed in ${}_{69}{}^{159}{}_{}{}^{}\mathrm{Tm}$ up to spin ${\frac{49}{2}}^{+}$. The alignments of these bands relative to the core nuclei ${}_{68}{}^{158}{}_{}{}^{}\mathrm{Er}_{90}^{}{}_{}{}^{}$ and ${}_{70}{}^{160}{}_{}{}^{}\mathrm{Yb}_{90}^{}{}_{}{}^{}$ are presented. These data provide additional evidence that the second backbend of the yrast structure of the core results from an ${\left(h_{\frac{11}{2}}\right)}^2$ proton alignment.

NUCLEAR REACTIONS ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$,$3n$)${}_{}{}^{159}{}_{}{}^{}\mathrm{Tm}$, $E=68\mathrm{}$ MeV; measured $\gamma -\gamma$ coin, $\gamma \left(\theta \right)$. ${}_{}{}^{159}{}_{}{}^{}\mathrm{Tm}$ deduced levels.

• Received 21 May 1981

DOI:https://doi.org/10.1103/PhysRevC.24.2367