Intermediate-State Reorientation of Nuclei Aligned in Cerium Double Nitrate

Abstract

Radiation patterns and linear polarization of gamma rays from decay of ${\mathrm{Co}}^{57}$ and ${\mathrm{Ce}}^{141}$ aligned at low temperatures by Bleaney's method in cerium double nitrate were studied for evidence of intermediate-state reorientation in this crystal. Influence of spin-spin interactions should be negligible on theoretical grounds. Experimental results, expressed in terms of the mixing ratio $\ensuremath{\delta}=\ifmmode\pm\else\textpm\fi{}{(\frac{E2}{M1})}^{\frac{1}{2}}$ for the $M1+E2$ gamma transitions and of an attenuation coefficient ${Q}_{k}$ in the angular distribution $W(\ensuremath{\theta})=\ensuremath{\Sigma}{Q}_{k}{A}_{k}{P}_{k}(cos\ensuremath{\theta})$, are as follows: 123-keV gamma from ${\mathrm{Co}}^{57}$ in Ce-Zn nitrate $Y$ sites, $\ensuremath{\delta}=+0.148\ifmmode\pm\else\textpm\fi{}0.010$, ${Q}_{2}=0.81\ifmmode\pm\else\textpm\fi{}0.10$ at $\frac{1}{{T}^{*}}=157$; 145-keV gamma from ${\mathrm{Ce}}^{141}$ in Ce-Mg nitrate, $\ensuremath{\delta}=+0.085\ifmmode\pm\else\textpm\fi{}0.013$, ${Q}_{2}=1.08\ifmmode\pm\else\textpm\fi{}0.08$ at $\frac{1}{{T}^{*}}=150$. Comparisons are made with Steenberg's theory of intermediate-state reorientation by static, isotropic hfs coupling in the hard-core limit, and with results of other nuclear alignment experiments involving the same isotopes.