Proton NMR measurements in nearly dry Na bgr;alumina crystals display a Pake doublet due to H2O molecules. At 300 K the angular dependence of the Pake splitting shows the time average orientation of the water HH vectors is parallel to the crystalcaxis. Measurements at 133 K, where motional averaging is removed, demonstrate that HH is tilted from c by 5deg; to 13deg;. The frequency splitting of the doublet shows that the HH distance is between 1.65 and 1.71 Aring;, longer than in free H2O. Above 250 K, line narrowing indicates the H2O are translationally diffusing while maintaining their orientation. A model of this motion is suggested. The chemical shift anisotropy of the H2O is found to be in agreement with previous measurements of H2O in ice and gypsum.
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