Angular distributions have been measured for 25 gamma rays emitted in the decay of ${}_{}{}^{166}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$ oriented at low temperatures in paramagnetic neodymium ethyl sulfate and in ferromagnetic Ho metal. The hyperfine Hamiltonians are discussed and parameters describing the strength of the hyperfine interactions are deduced. The reduction of anisotropy in polycrystalline Ho metal is analyzed in detail, with reference to application to nuclear reaction studies using polarized nuclear targets. Spin assignments and multipole mixing ratios are deduced for the levels and transitions in ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$.

[RADIOACTIVITY ${}_{}{}^{166}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$ [from Ho ($n,\gamma$)]; measured $I_{\gamma }\left(\theta \right)$ from oriented nuclei. ${}_{}{}^{166}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$ deduced magnetic dipole moment, hyperfine interaction parameters; ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ deduced $J^{\pi }$, $\frac{E2\mathrm{}}{M1\mathrm{}}$ and $\frac{M2\mathrm{}}{E1\mathrm{}}$ mixing ratios.]

• Received 2 March 1981

DOI:https://doi.org/10.1103/PhysRevC.24.654