Quadrupole splitting of the 6.2-kev γ rays of 181Ta in rhenium metal

Recoilless nuclear resonance absorption of the 6.2-keV γ rays of ¹⁸¹Ta was used to study the hyperfine interaction of ¹⁸¹Ta in Re metal. From the completely resolved M\"ossbauer spectra measured at room temperature parallel and perpendicular to the [0001] axis of the single-crystalline ¹⁸¹W(Re) sources, we derived the sign and magnitude of the nuclear quadrupole interaction, e²qQ(7/2)=-(2.15±0.02)×10⁻⁶ eV, the quadrupole-moment ratio $\frac{Q\left(\frac{9}{2}\right)}{Q\left(\frac{7}{2}\right)}=1.133\pm 0.010$, and the isomer shift of ¹⁸¹Ta(Re) relative to Ta metal, - 14.00±0.10 mm/sec.