The signature dependence of transition rates has been measured for the first time at and above the rotational frequency of the band crossing. The disappearance of an observed large signature dependence in both level energies and transition rates may be interpreted as a shape change. A large change in the transition rates in the band-crossing region and an apparent signature dependence of $\Delta I=1\mathrm{}$, $E2\mathrm{}$ transitions are difficult to understand within the available models.

NUCLEAR STRUCTURE ${}_{}{}^{157}{}_{}{}^{}\mathrm{Ho}$; measured $\gamma -\gamma$ coin, $I_{\gamma }\left(\theta \right)$; deduced levels, $J$, $\pi$, $\delta$, branching ratios, $g_K-g_R$.

• Received 1 March 1981

DOI:https://doi.org/10.1103/PhysRevC.25.3224