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Strong-coupling induced damping of spin-echo modulations in magic-angle-spinning NMR: Implications for J coupling measurements in disordered solids.

Authors
  • Guerry, Paul1
  • Brown, Steven P2
  • Smith, Mark E3
  • 1 Green Grow Scientific, 21 Montée de l'Observance, 69009 Lyon, France; Department of Physics, University of Warwick, Coventry CV4 7AL, UK. , (France)
  • 2 Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
  • 3 Department of Physics, University of Warwick, Coventry CV4 7AL, UK; Vice-Chancellor's Office, University House, Lancaster University, Lancaster LA1 4YW, UK; Department of Chemistry, Lancaster University, Lancaster LA1 4YB, UK. Electronic address: [email protected]
Type
Published Article
Journal
Journal of Magnetic Resonance
Publisher
Elsevier
Publication Date
Oct 01, 2017
Volume
283
Pages
22–32
Identifiers
DOI: 10.1016/j.jmr.2017.08.006
PMID: 28843058
Source
Medline
Keywords
License
Unknown

Abstract

In the context of improving J coupling measurements in disordered solids, strong coupling effects have been investigated in the spin-echo and refocused INADEQUATE spin-echo (REINE) modulations of three- and four-spin systems under magic-angle-spinning (MAS), using density matrix simulations and solid-state NMR experiments on a cadmium phosphate glass. Analytical models are developed for the different modulation regimes, which are shown to be distinguishable in practice using Akaike's information criterion. REINE modulations are shown to be free of the damping that occurs for spin-echo modulations when the observed spin has the same isotropic chemical shift as its neighbour. Damping also occurs when the observed spin is bonded to a strongly-coupled pair. For mid-chain units, the presence of both direct and relayed damping makes both REINE and spin-echo modulations impossible to interpret quantitatively. We nonetheless outline how a qualitative comparison of the modulation curves can provide valuable information on disordered networks, possibly also pertaining to dynamic effects therein.

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