Nuclear quadrupole interactions in solids: A survey

Abstract

AbstractNuclear quadrupole interactions have been measured in solids for nearly forty years; with recent improvements in techniques and sensitivity, they are finding much application in the study of electronic structure and molecular motion. The most complete information on the quadrupole coupling tensor comes from investigations of single crystals as in recent 35Cl quadrupole resonance studies in low magnetic fields of 1,2‐dichloro‐3‐nitrobenzene and (CH3)3C.CO2SbCl4 and in high magnetic fields of 17O magnetic resonance in benzophenone. High‐field studies of quadrupole splitting in the nuclear magnetic resonance spectra of powders are becoming increasingly used, particularly 27Al interactions in minerals and zeolites and 2H splittings and their relation to structure and motion in polymers. The sensitivity of radiofrequency techniques can be considerably increased by the use of double resonance methods, illustrated by recent work on 17O quadrupole interactions in O — H…O hydrogen bonds, 7Li of defects in lithium metal, and 14N in the detection of disorder in p‐nitrobenzoic acid crystals. Nuclear methods have an important part to play because of their remarkable sensitivity; the use of Mössbauer spectroscopy in the study of Fe(0) clusters and perturbed angular distribution techniques to measure 19F quadrupole interactions by means of an excited nuclear state of spin 5/2 provide interesting examples. Finally, recent theoretical and experimental work has been attempting to resolve the important question of the extent of charge transfer in ionic solids, illustrated by recent 57mFe studies of α‐Fe2O3 and 7Li, 14N in the superionic conductor Li3N.