Single- and multiple-quantum cross-polarization in NMR of quadrupolar nuclei in static samples

被引:38
作者
Ashbrook, SE [1 ]
Wimperis, S [1 ]
机构
[1] Univ Oxford, Phys Chem Lab, Oxford OX1 3QZ, England
关键词
D O I
10.1080/00268970009483265
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Cross-polarization from a spin I = 1/2 nucleus (e.g., H-1) to a spin S = 3/2 nucleus (e.g., Na-23) or a spin S = 5/2 nucleus (e.g., Al-27 or O-17) 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 radiofrequency 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 crosspolarization to quadrupolar nuclei under MAS conditions and the application of these techniques to the MQMAS NMR experiment.
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页码:1 / 26
页数:26
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