Nuclear orientation study of the decay ofLum177

Abstract

Angular distributions of 37 $\ensuremath{\gamma}$ rays were observed following the decays of 161-day $^{177}\mathrm{Lu}^{m}$ and 6.8-day $^{177}\mathrm{Lu}^{g}$ polarized at low temperatures in the ferromagnetic cubic Laves-phase compound ${\mathrm{ZrFe}}_{2}$. The magnetic moment of the $^{177}\mathrm{Lu}^{m}$ was deduced to be $|\ensuremath{\mu}|=(2.74\ifmmode\pm\else\textpm\fi{}.21){\ensuremath{\mu}}_{N}$, in excellent agreement with the value $\ensuremath{\mu}=+2.59{\ensuremath{\mu}}_{N}$ computed assuming the $^{177}\mathrm{Lu}^{m}$ to be the three-quasiparticle state ${\frac{7}{2}}^{+}{[404]}_{p},{\frac{9}{2}}^{+}{[624]}_{n},{\frac{7}{2}}^{\ensuremath{-}}{[514]}_{n}$. The magnetic hyperfine fields of Lu, Ta, Sc, and Co in ${\mathrm{ZrFe}}_{2}$ were deduced from the corresponding $\ensuremath{\gamma}$-ray anisotropies. Decays proceeding through the 1.1-sec $^{177}\mathrm{Hf}^{m}$ were observed to show characteristic relaxation times of ${T}_{1}\ensuremath{\approx}6.7$ sec. The $\frac{E2}{M1}$ mixing ratios of numerous intraband transitions in $^{177}\mathrm{Lu}$ and $^{177}\mathrm{Hf}$ were deduced, and the corresponding $\frac{({g}_{K}\ensuremath{-}{g}_{R})}{{Q}_{0}}$ values were computed. Several interband $\frac{M2}{E1}$ mixing ratios were deduced and were compared with calculations based on the Nilsson model including first-order Coriolis mixing. The 0-180\ifmmode^\circ\else\textdegree\fi{} asymmetries of several $^{177}\mathrm{Lu}$ transitions were observed in an effort to see if parity mixing effects might be present due to the particularly close-lying opposite parity states of $^{177}\mathrm{Lu}$; no effects were seen to the limit of 2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$.RADIOACTIVITY $^{177}\mathrm{Lu}^{m}$, $^{177}\mathrm{Lu}^{g}$; measured $\ensuremath{\gamma}(\ensuremath{\theta})$ from polarized nuclei; deduced magnetic moment $\ensuremath{\mu}$, hyperfine field $H$ of impurities in ${\mathrm{ZrFe}}_{2}$, relaxation time, $\ensuremath{\gamma}$-ray multipole mixing ratios, $\ensuremath{\delta}(\frac{E2}{M1})$, $\ensuremath{\delta}(\frac{M2}{E1})$, ${g}_{K}$, ${g}_{R}$, Coriolis mixing; deduced no observable parity violation.