By Dr. Björn Lindman, Professor Sture Forsén (auth.)
The expanding curiosity in NMR spectroscopy of what in a few confer ences during this box is often termed "other nuclei" is unmistakable. Chemists and biologists who hire NMR spectroscopy to review their difficulties have, even if, been a little reluctant to review nuclei with electrical quadrupole moments. those nuclei often supply upward push to huge NMR signs, occasionally too extensive to be detectable with traditional excessive solution NMR spectrometers. Spectrometers that may do something about huge NMR signs of low depth, "wide-line" spectrometers, were to be had because the mid 1950:s however it seems to be that the majority of those tools ended up in actual laboratories the place the study was once basically directed in the direction of good kingdom difficulties. The learn of quadrupolar nuclei grants specific and extremely priceless info on various physico-chemical and organic platforms. For something the comfort of quadrupolar nuclei is in lots of methods more straightforward to interpret than the comfort of non-quadrupolar nuclei, because the former is in lots of situations because of only intramolecular interactions modulated via the molecular movement. reviews of quadrupolar rest have for this reason offered vital information regarding molec ular reorientation and organization in beverages and feature performed - and may definitely play for a few years - a huge position in trying out new theoretical types of molecular movement in liquids.
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Additional info for Chlorine, Bromine and Iodine NMR: Physico-Chemical and Biological Applications
From Ref. 5, difficulties in observing the halogen NMR signal are often appreciable and for many cases special techniques are required. Thus the first observations [5-7,12,17] of chlorine, bromine and iodine NMR were achieved for the ions in solution and early attempts with covalent compounds were unsuccessful. The failure to observe the bromine NMR of liquid Br 2 and CHBr 3 was correctly interpreted by Pound  in terms of an extremely rapid quadrupole relaxation, and a consequently low signal amplitude, resulting from large field gradients in the covalent bonds.
F d 35Cl relaxation rates were the same for CHCl 3 and CDCl 3 within experimental error. e Calculated assuming v = 80 MHz. c Inconsistent data given in original report. b Also 37Cl NMR investigated. Relaxation time obtained from shape of 19F NMR pattern. 19F CW Sn sc etc. indicate that chlorine relaxation times were calculated from the relaxation time of another nucleus, which is relaxed by scalar interactions. exch 119 Meiboom-Gill modification of the Carr-Purcell pulse method. Relaxation time obtained from NMR exchange experiments.
For spin-3/2 nuclei, n must be obtained from studies on single crystals, whereas for 1271 with I = 5/2 both the quadrupole coupling constant and the asymmetry parameter may be obtained from the spectrum of a polycrystalline powder. For gases the most important method for obtaining quadrupole coupling constants is micro-wave spectroscopy. However, only a small number of halogen quadrupole coupling constants are known for the gaseous state . With a knowledge of the quadrupole relaxation rate and the quadrupole coupling constant for a molecule it is, as follows from the above discussion, possible to evaluate information on the correlation time for the reorientation of the field gradients.