title: Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid-State NMR Spectroscopy.
abstract: Factors affecting the performance of1H heteronuclear decoupling sequences for magic-angle spinning (MAS) NMR spectroscopy of organic solids are explored, as observed by time constants for the decay of nuclear magnetisation under a spin-echo (T2' ). By using a common protocol over a wide range of experimental conditions, including very high magnetic fields and very high radio-frequency (RF) nutation rates, decoupling performance is observed to degrade consistently with increasing magnetic field. Inhomogeneity of the RF field is found to have a significant impact on T2' values, with differences of about 20 % observed between probes with different coil geometries. Increasing RF nutation rates dramatically improve robustness with respect to RF offset, but the performance of phase-modulated sequences degrades at the very high nutation rates achievable in microcoils as a result of RF transients. The insights gained provide better understanding of the factors limiting decoupling performance under different conditions, and the high values of T2' observed (which generally exceed previous literature values) provide reference points for experiments involving spin magnetisation refocussing, such as 2D correlation spectra and measuring small spin couplings.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, United Kingdom.
authors.forename: Ilya
authors.identifier: http://orcid.org/0000-0002-3589-6818
authors.initials: I
authors.lastname: Frantsuzov
authors.affiliation: Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 ED, Nijmegen, The Netherlands.
authors.forename: Suresh K
authors.initials: SK
authors.lastname: Vasa
authors.affiliation: Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland.
authors.forename: Matthias
authors.identifier: http://orcid.org/0000-0002-9538-6086
authors.initials: M
authors.lastname: Ernst
authors.affiliation: Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom.
authors.forename: Steven P
authors.identifier: http://orcid.org/0000-0003-2069-8496
authors.initials: SP
authors.lastname: Brown
authors.affiliation: Agilent Technologies (UK) Ltd., 6 Mead Road, Yarnton, Oxfordshire, OX5 1QU, United Kingdom.|Mestrelab Research, S.L Feliciano Barrera 9B-Bajo, 15706, Santiago de Compostela, Spain.
authors.forename: Vadim
authors.identifier: http://orcid.org/0000-0002-5572-0166
authors.initials: V
authors.lastname: Zorin
authors.affiliation: Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 ED, Nijmegen, The Netherlands.
authors.forename: Arno P M
authors.identifier: http://orcid.org/0000-0001-5893-4488
authors.initials: AP
authors.lastname: Kentgens
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, United Kingdom.
authors.forename: Paul
authors.identifier: http://orcid.org/0000-0003-0327-3349
authors.initials: P
authors.lastname: Hodgkinson
keywords: decoupling; magic-angle spinning; nutation; organic solids; solid-state NMR spectroscopy