Gamma-ray angular distributions and parity tests in the decays of polarizedLu173andLum,g174

Abstract

Angular distributions of 18 $\gamma$ rays have been measured following the decays of ${}_{}{}^{173}{}_{}{}^{}\mathrm{Lu}$ and ${}_{}{}^{174}{}_{}{}^{}\mathrm{Lu}_{}^{m,g}{}_{}{}^{}$ polarized at low temperatures in the ferromagnetic cubic Laves-phase metal Zr${\mathrm{Fe}}_2$. The magnetic moments of the oriented parent states are deduced to be $\left|\mu \right({}_{}{}^{173}{}_{}{}^{}\mathrm{Lu}\left)\right|=(2.34\mathrm{}\pm 0.09){\mu }_N$, $\left|\mu \right({}_{}{}^{174}{}_{}{}^{}\mathrm{Lu}_{}^g{}_{}{}^{}\left)\right|=(1.94\mathrm{}\pm 0.28){\mu }_N$, and $\left|\mu \right({}_{}{}^{174}{}_{}{}^{}\mathrm{Lu}_{}^m{}_{}{}^{}\left)\right|=(2.34\mathrm{}\pm 0.33){\mu }_N$. The spin of the 1518-keV level of ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$ is shown unambiguously to be 6. Multipole mixing ratios are deduced for a number of ${}_{}{}^{173}{}_{}{}^{}\mathrm{Yb}$ and ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$ $\gamma$ rays, and several interband $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratios are compared with values deduced from a Coriolis mixing calculation. The 0°-180° asymmetries of the angular distributions of some of the strongly hindered ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$ transitions have been observed in a search for the presence of parity mixing effects; no such effects were seen. A possible empirical correlation between $\gamma$-ray hindrance and the magnitude of parity-violating effects is pointed out.