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Double-quantum homonuclear correlations of spin I=5/2 nuclei
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Iuga, Dinu (2011) Double-quantum homonuclear correlations of spin I=5/2 nuclei. Journal of Magnetic Resonance, Vol.208 (No.2). pp. 225-234. doi:10.1016/j.jmr.2010.11.007 ISSN 1090-7807.
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Official URL: http://dx.doi.org/10.1016/j.jmr.2010.11.007
Abstract
The challenges associated with acquiring double-quantum homonuclear Nuclear Magnetic Resonance correlation spectra of half-integer quadrupolar nuclei are described. In these experiments the radio-frequency irradiation amplitude is necessarily weak in order to selectively excite the central transition. In this limit only one out of the 25 double-quantum coherences possible for two coupled spin I = 5/2 nuclei is excited. An investigation of all the 25 two spins double quantum transitions reveals interesting effects such as a compensation of the first-order quadrupolar interaction between the two single quantum transitions involved in the double quantum coherence. In this paper a full numerical study of a hypothetical two spin I = 5/2 system is used to show what happens when the RF amplitude during recoupling is increased. In principle this is advantageous, since the required double quantum coherence should build up faster, but in practice it also induces adiabatic passage transfer of population and coherence which impedes any build up. Finally an optimized rotary resonance recoupling (oR(3)) sequence is introduced in order to decrease these transfers. This sequence consists of a spin locking irradiation whose amplitude is reduced four times during one rotor period, and allows higher RF powers to be used during recoupling. The sequence is used to measure (27)Al DQ dipolar correlation spectra of Y(3)Al(5)O(12) (YAG) and gamma alumina (gamma Al(2)O(3)). The results prove that aluminium vacancies in gamma alumina mainly occur in the tetrahedral sites. (C) 2010 Elsevier Inc. All rights reserved.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | Journal of Magnetic Resonance | ||||
Publisher: | Academic Press | ||||
ISSN: | 1090-7807 | ||||
Official Date: | 2011 | ||||
Dates: |
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Volume: | Vol.208 | ||||
Number: | No.2 | ||||
Page Range: | pp. 225-234 | ||||
DOI: | 10.1016/j.jmr.2010.11.007 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Funder: | Engineering and Physical Sciences Research Council (EPSRC) , Biotechnology and Biological Sciences Research Council (BBSRC) , University of Warwick , Birmingham Science City Advanced Materials Project , European Regional Development Fund (ERDF) |
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