Single crystal nuclear magnetic resonance in spinning powders

Andrew J. Pell 1 Guido Pintacuda 1 Lyndon Emsley 1
1 Centre de RMN à très hauts champs
ISA - Institut des Sciences Analytiques
Abstract : We present a method for selectively exciting nuclear magnetic resonances (NMRs) from well-defined subsets of crystallites from a powdered sample under magic angle spinning. Magic angle spinning induces a time dependence in the anisotropic interactions, which results in a time variation of the resonance frequencies which is different for different crystallite orientations. The proposed method exploits this by applying selective pulses, which we refer to as XS (for crystallite-selective) pulses, that follow the resonance frequencies of nuclear species within particular crystallites, resulting in the induced flip angle being orientation dependent. By selecting the radiofrequency field to deliver a 180 degrees pulse for the target orientation and employing a train of such pulses combined with cogwheel phase cycling, we obtain a high degree of orientational selectivity with the resulting spectrum containing only contributions from orientations close to the target. Typically, this leads to the selection of between 0.1% and 10% of the crystallites, and in extreme cases to the excitation of a single orientation resulting in single crystal spectra of spinning powders. Two formulations of this method are described and demonstrated with experimental examples on [1 -(13) C]-alanine and the paramagnetic compound Sm(2)Sn(2)O(7). (C) 2011 American Institute of Physics.
Type de document :
Article dans une revue
Journal of Chemical Physics, American Institute of Physics, 2011, 135 (14), pp.144201. 〈10.1063/1.3640418〉
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Soumis le : mardi 22 mai 2012 - 16:43:36
Dernière modification le : jeudi 8 février 2018 - 11:10:18

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Andrew J. Pell, Guido Pintacuda, Lyndon Emsley. Single crystal nuclear magnetic resonance in spinning powders. Journal of Chemical Physics, American Institute of Physics, 2011, 135 (14), pp.144201. 〈10.1063/1.3640418〉. 〈hal-00700337〉

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