Knight Shift and Zero-Field Splitting in Rhenium Determined by Nuclear Acoustic Resonance

Nuclear acoustic resonance signals have been observed in a single crystal of rhenium metal. From measurements of the resonance fields at different frequencies, values for the Knight shift and zero-field splitting at 4.2°K are obtained. The Knight shift, referred to aqueous NaRe${\mathrm{O}}_4$, is found to be (1.02 ± 0.06)%. The zero-field splitting, $\frac{3e^2\mathrm{qQ}}{20h}$, is found to be 40.6 ± 0.35 MHz for ${\mathrm{Re}}^{185}$ and 38.35 ± 0.2 MHz for ${\mathrm{Re}}^{187}$.