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.

Chlorine-nuclear-quadrupole-resonance study of the neutral-to-ionic transition in tetrathiafulvalene-chloranil.

Abstract: The temperature dependence of the chlorine-35 nuclear-quadrupole-resonance (NQR) parameters has been studied in the mixed-stack charge-transfer complex tetrathiafulvalene-chloranil and discussed with reference to spectroscopic and neutron-diffraction results. The NQR spectrum changes conspicuously at the neutral-to-ionic transition temperature, ${\mathit{T}}_{\mathit{N}\mathrm{\ensuremath{-}}\mathit{I}}$=79.2 K. The changes have been analyzed in terms of the symmetry breaking occurring at the transition. Below, coexistence of the neutral and ionic phases has been observed down to the limit of metastability of the neutral phase (${\mathit{T}}_{\mathit{c}}$\ensuremath{\sim}69 K). Spin-lattice relaxation rates reveal the existence of highly anisotropic critical fluctuations with a predominantly one-dimensional character.

Tautomerism and Possible Polymorphism in Solid Hydroxypyridines and Pyridones Studied by 14N NQR

Abstract: 14N nuclear quadrupole resonance frequencies have been measured in solid 2-pyridone, 3-hydroxypyridine, and 4-pyridone by 1H–14N nuclear quadrupole double resonance. Two slightly nonequivalent nitr...

Spectroscopic Studies of Proton Transfer Equilibria In Hydrogen Bonded Complexes

Abstract: Recent studies on proton transfer equilibria for many hydrogen bonded complexes are discussed. These studies employ various spectroscopic techniques as infrared, ultraviolet, 1H NMR, 13C NMR, 15N NMR and nuclear quadrupole resonance (NQR) spectroscopy. Special attention has been paid to Fourier transform infrared (FTIR), and it forms the main focus of this review, in particular for the study of proton transfer equilibria in proton sponges hydrogen bonded complexes. The influence of proton transfer equilibria on the physical, chemical and biological properties of hydrogen bonded complexes is shown. Some applications of proton transfer equilibria are also discussed. *Dedicated to Prof. Samir A. Abou-Ali, in appreciation for his efforts in modernizing our department.

Authentication of medicines using nuclear quadrupole resonance spectroscopy

Abstract: The production and sale of counterfeit and substandard pharmaceutical products, such as essential medicines, is an important global public health problem. We describe a chemometric passport-based approach to improve the security of the pharmaceutical supply chain. Our method is based on applying nuclear quadrupole resonance (NQR) spectroscopy to authenticate the contents of medicine packets. NQR is a non-invasive, non-destructive, and quantitative radio frequency (RF) spectroscopic technique. It is sensitive to subtle features of the solid-state chemical environment and thus generates unique chemical fingerprints that are intrinsically difficult to replicate. We describe several advanced NQR techniques, including two-dimensional measurements, polarization enhancement, and spin density imaging, that further improve the security of our authentication approach. We also present experimental results that confirm the specificity and sensitivity of NQR and its ability to detect counterfeit medicines.