Nuclear Double Resonance Study of Na First-Order Quadrupole Splittings in a NaF-LiF Mixed Crystal

A nuclear magnetic double resonance experiment has been performed to measure the high-field first-order quadrupole splittings of ${\mathrm{Na}}^{23}$ nuclei located in the vicinity of ${\mathrm{Li}}^{+}$ substitutional impurities in a single crystal of NaF. The observed quadrupole-shifted frequency of those ${\mathrm{Na}}^{23}$ nuclei located at (1,0,1)-type sites [relative to the ${\mathrm{Li}}^{+}$ impurity at the (0,0,0) lattice site] was $\frac{e^2\mathrm{qQ}}{h}=\pm (544\mathrm{}\pm 10)$ kHz with an asymmetry parameter $\eta =0.65\mathrm{}\pm 0.05$. For those ${\mathrm{Na}}^{23}$ nuclei at (0,0,2)-type sites, $\frac{e^2\mathrm{qQ}}{h}=\pm (856\mathrm{}\pm 10)$ kHz with $\eta =0\mathrm{}$. The values of $\mathrm{eq}$ and $\eta$ thus obtained are compared with theoretical calculations. A mathematical analysis of the high-field double resonance process as it applies to rare, quadrupole-interacting nuclei is also presented.