Directional correlation of γ rays in 31 yr ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}_{}^{\mathit{m}}{}_{}{}^{}$ decay

Directional correlations of γ rays observed in the decay of the ${16}^{+}$ isomeric state in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$ were measured with a multidetector system. Multipole mixing ratios for four γ transitions in the rotational band based on the $8^{\mathrm{-}}$ two-quasiparticle isomeric state in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$ are derived, and the structure of this band is discussed.