High-field 23Na magnetic resonance studies in beta-alumina

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Abstract
A study of the 23Na magnetic resonance spectrum (1/2– −1/2 transition) at high magnetic field, 63.4 kG, in a single crystal of beta‐alumina is reported. A comparison of the high‐field rotation spectra obtained at room temperature with previous results obtained in lower magnetic fields allows the extraction of the 23Na chemical shift tensor, the first such tensor measured for an alkali atom. The three principal values for the sodium chemical shift tensor were equal within the experimental error of ±3 or 4 ppm. Linewidth measurements at the high field confirm the suggestions of lifetime broadening of room temperature lines and indicate that by 150 °K second‐order quadrupole broadening controls the linewidth. Measurements at low temperatures produce complex spectra which are interpreted to indicate that motional averaging of the sodium environments is still taking place at 77 °K.