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 Na²³ nuclei located in the vicinity of Li⁺ substitutional impurities in a single crystal of NaF. The observed quadrupole-shifted frequency of those Na²³ nuclei located at (1,0,1)-type sites [relative to the Li⁺ impurity at the (0,0,0) lattice site] was e²qQh=±(544±10) kHz with an asymmetry parameter η=0.65±0.05. For those Na²³ nuclei at (0,0,2)-type sites, e²qQh=±(856±10) kHz with η=0. The values of eq and η 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.