We report a solid-state 17 O (I = 5/2) NMR study of the nitrite ion dynamics in crystalline NaNO 2 . Variable temperature (VT) 17 O NMR spectra were recorded at 3 magnetic fields, 11.7, 14.1, and 21.1 T. The VT 17 O NMR data suggest that the NO À 2 ion in the ferroelectric phase of NaNO 2 undergoes 2-fold flip motion about the crystallographic b axis and the corresponding rotational barrier is 68 AE 5 kJ mol À1 . We also obtained a 2D 17 O EXSY spectrum for a stationary sample of NaNO 2 at 250 K, which, in combination with 1D 17 O NMR spectral analyses, allowed precise determination of the relative orientation between the 17 O quadrupolar coupling and chemical shift tensors in the molecular frame of reference. The experimentally determined 17 O NMR tensors for NaNO 2 were in agreement with quantum chemical calculations produced by a periodic DFT code BAND.
K E Y W O R D Smolecular motion, oxygen-17, sodium nitrite, solid-state NMR