Asymmetry of the quadrupole satellites of 23Na in NaNO 2

Abstract

The second moment, third moment, and asymmetry of the satellite resonances in the quadrupole-split spectrum of 23Na in NaNO 2 have been studied at various crystal orientations. The lineshapes are governed mainly by inhomogeneous quadrupole broadening caused by local variations in both the magnitude of the quadrupole coupling constant (qcc) and the orientation of the twofold symmetry axis. The former broadening was found to be symmetric and the latter quite asymmetric. Such asymmetry is inconsistent with the symmetry of the crystal. Both the broadening and the asymmetry were similar in the two crystals examined, indicating that these may be intrinsic properties of NaNO 2. The underlying asymmetry of the magnetic dipole broadening was deduced from the orientation dependence of the observed asymmetry. From this, the qcc was found to be negative, in agreement with an earlier determination by Kanashiro and co-workers. Qualitative comparison of the orientation dependence of the observed asymmetry with that of the magnetic dipolar third moment allowed determination of the sign of the qcc, even when the asymmetry of the quadrupole broadening was an order of magnitude larger than the asymmetry associated with the dipolar broadening alone.