Nuclear quadrupole resonance

About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.

The NQR and NMR studies of icosahedral borides

Abstract: Boron NMR and NQR studies have been performed on three icosahedral borides: - and -rhombohedral boron and boron carbide (B12C3). Two 11B NMR peaks, separated by significant chemical shifts in the range from 130 ppm to 280 ppm, were clearly observed for all of the icosahedral borides that were not enriched in the 10B isotope. A single peak, however, was found for the 10B enriched boron carbide powder (90.6 at.% enrichment.) Moreover, the peak separation in the 11B NMR spectrum for the unenriched -boron was reduced when the sample was crushed into a fine powder. In addition to NMR responses, four strong NQR responses were observed for boron carbides from different manufacturers. Two resonance signals, observed at 513 kHz and 2769 kHz, correspond to one of the icosahedral boron sites and the boron in the CBC chain, respectively. The other two NQR responses, having frequencies of 361 and 380 kHz, are either 10B responses for the chain site or 11B responses for the other boron sites in the icosahedra. The NQR responses are not only consistent with the previous NMR studies performed independently by Silver and Bray (1959 J. Chem. Phys. 31 247) and by Hynes and Alexander (1971 J. Chem. Phys. 54 5296, 1972 J. Chem. Phys. Erratum 56), but also provide much higher accuracy for the values of the quadrupolar parameters.

35Cl NMR studies of the domain structure of tetramethylammonium cadmium chloride (TMCC) at lower temperatures

Abstract: Quadrupolar perturbed 35Cl NMR and 35Cl NQR investigations are performed on single crystals of tetramethylammonium cadmium chloride, (CH3)4NCdCl3 (TMCC), in order to study the formation of ferroelastic domains in the ferroelastic phase II below 118 K in which the hexagonal symmetry of the high temperature phase I is lost. The experimental results cannot simply be explained in terms of the well known monoclinic domain structure but additionally a twin domain structure is found to exist in phase II: six orientational domains are verified from the NMR rotational pattern at 113 K in contrast to the expected number of three for a classical 6/mF2/m transition. The rotational angle Θ between the epitaxially grown twins is calculated from the strain tensors of the three orientation states, applying an algebraic approach. The theoretical value Θ = 3.5° is in very good correspondence with the experimental result from the 35Cl NMR studies (~4°). Similar results were also derived in recent x-ray studies in phase II. In the low temperature phase III below 104 K the number of non-equivalent Cl positions is consistent with both the space group of phase III and the sixfold enlarged size of the unit cell in phase III with respect to that in phase I as observed in XRD studies.