Parity-Violating Asymmetry of the 501-keV Gamma Ray Emitted in the Decay ofHf180m

The parity-violating forward-backward asymmetry of the 501-keV $\gamma$ radiation emitted by ${}_{}{}^{180m}{}_{}{}^{}\mathrm{Hf}$ polarized at low temperatures is measured to be -(1.66±0.18)% at a polarization of 72%. From this asymmetry the magnitude of the irregular $\frac{\tilde{E}2}{M2\mathrm{}}$ mixing ratio is deduced to be 0.038±0.004, in good agreement with results of circular polarization measurements. The regular $\frac{E3\mathrm{}}{M2\mathrm{}}$ multipole mixing ratio of the 501-keV $\gamma$ ray is deduced to be 5.3±0.3, in agreement with results of directional-correlation measurements. The hyperfine splitting energy of ${}_{}{}^{180m}{}_{}{}^{}\mathrm{Hf}$ introduced as an impurity in Zr${\mathrm{Fe}}_2$ is deduced to be -(7.9±0.5) mK.