Zeeman-perturbed NQR

Key Words Chlorine-35, Chorine-37, Bromine-79, Bromine-81, Iodine-127, Quadrupolar nuclei, Zeeman-perturbed NQR, Solid-state NMR, Electric field gradient, Magnetic shielding tensor, Chemical shift tensor, Quantum chemical calculations, Ab initio calculations. 

TABLE 16 Bromine-79/81 solid-state NMR data for molecular systems (mainly from Zeeman-perturbed NQR measurements)... 

Subsequently, K. Rao and Murty measured the Br Zeeman-perturbed NQR spectrum, but could not resolve the three sites and assigned all three sites i q = 0.12 0.03. ... 

Zeeman-perturbed NQR on a single crystal. Temperature dependence also studied. 

Although this review is aimed at coverirtg high-field NMR experimertts on diamagnetic solids, a great number of studies have been published which serve to highlight the complimentary nature between Zeeman-perturbed NQR and... 

The first reports of Zeeman-perturbed bromine NQR, both using single crystals of NaBrQa, confirmed prior measurements of the Br magnetic dipole moment ° and also highlighted the fact that Kriiger s ° Zeeman-perturbed NQR theory was valid for both bromine isotopes. ... 

Subsequent Zeeman-perturbed NQR experiments were generally used to determine tjq (which is not possible using a pure NQR spectrum of an 7 = 3/2 nucleus), the orientation of the EEG tensor in the crystal frame, and could also be used to determine the bond character for the atoms directly bound to the bromine... 

Doane and Flultsch used a single crystal of NaBrOa to demonstrate the interesting possibility of using the Zeeman-perturbed NQR transitions to modify the signal intensity associated with the Br Zeeman transitions by irradiating the sample at NQR transition frequencies while in a weak magnetic field.This information was subsequently used to determine quadrupolar relaxation transition probabilities. ... 

Zeeman-perturbed NQR was applied by Kehrer et al. to determine the EFG tensor in glycyl-L-alanine hydroiodide monohydrate. Although this is not a typical solid-state NMR study, it is interesting to quote the quadrupolar parameters, Cq( I) = 74.04 MHz and rjQ = 0.776 (at 274.5 K) since the corresponding hydrobromide salt is isomorphous and could be of interest for further study. 

Zeeman-perturbed NQR spin-lattice relaxation measurements have been made for Cu nuclei in Sri4Cu2404i, at field intensities from 40 G to 9.4 T. Relaxation of Cu(2) nuclei in the ladder was dominated at low T by very low frequency dynamics, possibly related to slowing down of the spin fluctuations... 

Application of a weak magnetic field Zeeman perturbed NQR... 

The only chlorate which has been significantly studied using chlorine SSNMR is sodium chlorate. Many early Zeeman-perturbed chlorine NQR studies feature analyses of this salt. It is not surprising therefore, that one of the early chlortne-35 SSNMR studies was on this material, carried out by Kawamori and in 1963. The authors studied a single crystal and reported the resonance frequency for multiple orientations. Bain and co-workers ° re-examined a single crystal of NaClOa recently to confirm the validity of their theoretical approach for the exact calculation of combined Zeeman and quadrupolar interactions. 

Ba), via Zeeman-perturbed Ba NQR spectroscopy. No evidence was found for orbital currents (additional local fields) at the Ba site. Any static or dynamic fields must be less than 0.07 and 0.7 mT respectively (the detection limits of the method). 

Of the NMR-active nuclei around tluee-quarters have / > 1 so that the quadnipole interaction can affect their spectra. The quadnipole inter action can be significant relative to the Zeeman splitting. The splitting of the energy levels by the quadnipole interaction alone gives rise to pure nuclear quadnipole resonance (NQR) spectroscopy. This chapter will only deal with the case when the quadnipole interaction can be regarded as simply a perturbation of the Zeeman levels. 

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