Quadrupole Moments ofTa181andLu175

The hyperfine structure of the spectrum of Ta i was studied by means of a hollow-cathode discharge tube and a Fabry-Pérot étalon, in order to determine the quadrupole moment of ${\mathrm{Ta}}^{181}$. The calculation was carried out for the quadrupole coupling constants of the levels ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$, ${}_{}{}^4{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$, ${}_{}{}^4{}_{}{}^{}F_{\frac{5}{2}}^{}{}_{}{}^{}$, ${}_{}{}^4{}_{}{}^{}F_{\frac{7}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}F_{\frac{9}{2}}^{}{}_{}{}^{}$ of the configuration $5d^{3}6s^2$, in which the three $5d$-electrons are combined by an intermediate coupling. This yielded the result that $Q\left({\mathrm{Ta}}^{181}\right)=(+4.3\mathrm{}\pm 0.4)\times {10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$, in which the polarization correction (due to Sternheimer) is taken into account. The value of $Q\left({\mathrm{Lu}}^{175}\right)$ was calculated from the data given in the literature, and was found to be (+5.7±0.3)×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$.