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On the orientational dependence of resolution in 1 H solid‐state NMR, and its role in MAS, CRAMPS and delayed‐acquisition experiments
Author(s) -
Zorin Vadim E.,
Elena Benedicte,
Lesage Anne,
Emsley Lyndon,
Hodgkinson Paul
Publication year - 2007
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2108
Subject(s) - homonuclear molecule , dephasing , chemistry , solid state nuclear magnetic resonance , spins , magnetic dipole–dipole interaction , magic angle spinning , decoupling (probability) , nuclear magnetic resonance , dipole , magic angle , residual dipolar coupling , chemical physics , nuclear magnetic resonance spectroscopy , solid state , condensed matter physics , physics , molecule , stereochemistry , organic chemistry , control engineering , engineering
Numerical simulations and experiments are used to show that the spin dynamics of the dipolar‐coupled networks in solids is often strongly dependent on crystallite orientation. In particular, different rates of dephasing of the magnetisation mean that NMR signals obtained at longer dephasing times are dominated by orientations in which the local dipolar coupling strength is relatively weak. This often leads to a distinct improvement in spectral resolution as the dephasing time is increased. The effects are particularly noticeable under magic‐angle spinning (MAS), but are also observed when homonuclear decoupling is used to reduce the rate of dipolar dephasing. Numerical simulation is seen to be a powerful and easily used tool for understanding the behaviour of solid‐state NMR experiments involving dipolar‐coupled networks. The implications for solid‐state NMR spectra of abundant spins acquired under MAS and homonuclear decoupling are discussed, as well as insights provided into the performance of ‘delayed‐acquisition’ and ‘constant‐time’ experiments. Copyright © 2007 John Wiley & Sons, Ltd.