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.

14N nuclear quadrupole resonance study of substituted anilines and prediction of in vitro activity of sulfanilamides

Abstract: 14N nuclear quadrupole resonance (NQR) spectra of 22 monosubstituted anilines are reported and analyzed in the framework of the Townes and Dailey theory. Satisfactory correlations of the NQR data with both the Hammett σ parameters and the in vitro biological activities of the corresponding sulfanilamides have been found. The results obtained suggest that the nitrogen lone-pair orbital is more sensitive than the nitrogen–carbon sigma orbital is to substituent effects.

The C–Cl bonds in trichloroethylidene trichlorolactic ester, Cl3CCHOCOCHOCCl3. A 35Cl–NQR single crystal study

Abstract: By single crystal 35Cl–NQR with a 4π Zeeman spectrometer, the six independent 35Cl‐nuclear quadrupole coupling tensors in trichloroethylidene trichlorolactic ester (chloralide) Cl3CCHOCOCHOCC13 have been studied at T=21 °C. The directions of the electric field gradient (EFG) tensor components have been determined. The main axes φzz are within ±0.5° parallel to the C–Cl bound directions. Very small asymmetry parameters in the range 0.005≤η≤0.053 are characteristic for the EFG tensors of Cl bond to carbon in aliphatic systems, and the six nuclear quadrupole coupling constants are found in the range 76.053≤e2qQh−1/MHz≤78.790. The orientations of the principal axes φxx and φyy is explained as due to intramolecular interactions likely of through space origin.

Temperature Dependence of Nuclear Quadrupole Resonance Frequencies of 121Sb, 123Sb and 35Cl in Solid Antimony Trichloride

Abstract: Nuclear quadrupole resonance frequencies of 121 Sb, 123 Sb, and 35 Cl in solid antimony trichloride were measured between 20°K and about 150°K to learn molecular motions and intermolecular forces in the solid. By use of a newly computed eigenvalue table, the quadrupole coupling constant and the asymmetry parameter of 121 Sb and 123 Sb were calculated. The asymmetry parameter decreases from 0.192 at 20°K to 0.180 at 140°K. The results were interpreted in terms of librational motion and weak intermolecular covalent bonds between Sb and Cl atoms.

Revealing dipolar coupling with NQR off-resonant pulsed spin locking

Abstract: Unexpectedly, we observe a strong Gaussian decay in the nuclear quadrupole resonance signal obtained from a powder sample of spin-1 nuclei under perturbation by off-resonant radio frequency pulses. Using a model composed of just pairs of nuclei, we theoretically determine that the decay is due to the homonuclear dipolar coupling being selectively unrefocused by the pulses. We find that the decay rate measures the dipolar coupling's strength and permits us to determine how much of the sample's linewidth is due to homonuclear dipolar coupling versus electric-field gradient inhomogeneity. Furthermore, knowing the strength, shape, frequency, and timing of the pulses that lead to this rapid decay is critical for the purposes of illicit substance detection since it reduces the signal and can lead to a false negative. We find that the experimental parameters that lead to this Gaussian decay are explained well by this simple model, which leads to a method for suppressing or revealing the decay. We confirm our theoretical understanding using two samples of sodium nitrite that vary in their broadening due to electric-field gradient inhomogeneity by as much as a factor of 3.

Use of two or more sensors in a nuclear quadrupole resonance detection system to improve signal-to-noise ratio

Abstract: The use of two or more sensors tuned to the same nuclear quadrupole resonance frequency and detecting the nuclear quadrupole resonance signal results in improved signal-to-noise ratio and therefore improved nuclear quadrupole resonance detection system performance.