Perturbed-Angular-Correlation Study of Electric-Quadrupole Interactions inYb172in Thulium Metal and Oxide Lattices

Electric-quadrupole hyperfine interactions at ytterbium ions in thulium metal and ${\mathrm{Tm}}_2$ ${\mathrm{O}}_3$ have been investigated at 296°K using time-differential perturbed angular correlation in $\gamma$-ray cascades in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}$. The ratio of the spectroscopic quadrupole moments of the 1174- and 79-keV states in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}$ was measured to be $\frac{Q\left(1174\right)\mathrm{}}{Q\left(79\right)\mathrm{}}=1.33\mathrm{}\pm 0.15$. Using this ratio and a value for $Q\left(79\right)\mathrm{}$ obtained from the Coulomb-excitation transition probability, the magnitudes of the electric-field-gradient (EFG) tensors are obtained. For ytterbium in thulium metal, the measured quadrupole interaction frequencies in the respective nuclear states are found to be ${\omega }_0\mathrm{}\left(1174\right)=(101\mathrm{}\pm 4)\times {10}^6$ rad/sec, ${\omega }_0\mathrm{}\left(79\right)=(190\mathrm{}\pm 19)\times {10}^6$ rad/sec, yielding for the magnitude of the largest component of the field gradient $V_{\mathrm{zz}}=(4.53\mathrm{}\pm 0.47)\times {10}^{17}$ V/${\mathrm{cm}}^2$ at 296°K, a value not significantly different from that found at thulium nuclei in thulium metal, indicating no significant ionic contribution to the EFG. In thulium sesquioxide, the corresponding values for the $C_2$ site are ${\omega }_0\mathrm{}\left(1174\right)=(374\mathrm{}\pm 30)\times {10}^6$ rad/sec and ${\omega }_0\mathrm{}\left(79\right)=(701\mathrm{}\pm 56)\times {10}^6$ rad/sec, from which $V_{\mathrm{zz}}=(1.67\mathrm{}\pm 0.20)\times {10}^{18}$ V/${\mathrm{cm}}^2$. The anisotropy $\eta$ expected from crystal-symmetry considerations is not observable within the experimental accuracy, and is probably small. The half-life of the 79-keV state in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}$ was measured to be 1.80±0.05 nsec. Within the time range of the experiment, no time-dependent attenuations or aftereffects of preceding decay events were found.