Single- and multiple-quantum cross-polarization in NMR of quadrupolar nuclei in static samples
作者:
SHARONE. ASHBROOK,
STEPHEN WIMPERIS,
期刊:
Molecular Physics
(Taylor Available online 2000)
卷期:
Volume 98,
issue 1
页码: 1-26
ISSN:0026-8976
年代: 2000
DOI:10.1080/00268970009483265
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Cross-polarization from a spinI=1/2 nucleus (e.g.,1H) to a spinS= 3/2 nucleus (e.g.,23Na) or a spinS= 5/2 nucleus (e.g.,27A1 ornO) in static powder samples is investigated. The results of conventional (single-quantum), three-quantum, and five-quantum cross-polarization experiments are presented and discussed. Based on a generalization of an existing theory of cross-polarization to quadrupolar nuclei, computer simulations are used to model the intensity and lineshape variations observed in cross-polarized NMR spectra as a function of the radio-frequency field strengths of the two simultaneous spin-locking pulses. These intensity and lineshape variations can also be understood in terms of the spin S = 3/2 or 5/2 nutation rates determined from experimental quadrupolar nutation spectra. The results of this study are intended as a preliminary step towards understanding single- and multiple-quantum cross-polarization to quadrupolar nuclei under MAS conditions and the application of these techniques to the MQMAS NMR experiment.
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