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Quadrupolar and Chemical Shift Tensors Characterized by 2D Multiple-Quantum NMR Spectroscopy

✍ Scribed by Ales Medek; Lucio Frydman

Publisher: Elsevier Science
Year: 1999
Tongue: English
Weight: 165 KB
Volume: 138
Category: Article
ISSN: 1090-7807
DOI: 10.1006/jmre.1999.1750

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✦ Synopsis

The present work discusses a new 2D NMR method for characterizing the principal values and relative orientations of the electric field gradient and the chemical shift tensors of half-integer quadrupolar sites. The technique exploits the different contributions that quadrupolar and shielding interactions impart on the evolution of multiple-quantum and of single-quantum coherences, in order to obtain 2D powder lineshapes that are highly sensitive to these nuclear spin coupling parameters. Different spinning variants of this experiment were assayed, but it was concluded that a static version can yield the highest sensitivity to the values of the principal components and to the relative geometries of the local coupling tensors. It was found that correlating the central transition evolution with the highest available order of the spin coherence was also helpful for maximizing this spectral information. Good agreement between data obtained on 87 Rb (S ‫؍‬ 3 2 ) and 59 Co (S ‫؍‬ 7

2 ) samples and ideal theoretical lineshape predictions of this experiment was obtained, provided that heterogeneities in the multiple-quantum excitation and conversion processes were suitably accounted by procedures similar to those described in the spin-1 2 multiple-quantum NMR literature.

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