Quadrupole Splitting of the 6.2-keVγRays ofTa181in Rhenium Metal

Recoilless nuclear resonance absorption of the 6.2-keV $\gamma$ rays of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ was used to study the hyperfine interaction of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ in Re metal. From the completely resolved Mössbauer spectra measured at room temperature parallel and perpendicular to the [0001] axis of the single-crystalline ${}_{}{}^{181}{}_{}{}^{}\mathrm{W}\mathrm{}\left(\mathrm{Re}\right)\mathrm{}$ sources, we derived the sign and magnitude of the nuclear quadrupole interaction, $e^{2}qQ\left(\frac{7}{2}\right)=-(2.15\mathrm{}\pm 0.02)\times {10}^{-6\mathrm{}}$ eV, the quadrupole-moment ratio $\frac{Q\left(\frac{9}{2}\right)}{Q\left(\frac{7}{2}\right)}=1.133\mathrm{}\pm 0.010$, and the isomer shift of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}\mathrm{}\left(\mathrm{Re}\right)\mathrm{}$ relative to Ta metal, - 14.00±0.10 mm/sec.