Second-order recoupling of chemical-shielding and dipolar-coupling tensors under spin decoupling in solid-state NMR

TitleSecond-order recoupling of chemical-shielding and dipolar-coupling tensors under spin decoupling in solid-state NMR
Publication TypeJournal Article
Year of Publication1996
AuthorsErnst M., Bush S., Kolbert A.C, Pines A
JournalJournal of Chemical Physics
Volume105
Issue9
Pagination3387-3397
Date PublishedSep 1
ISBN Number0021-9606
Accession NumberWOS:A1996VD76800005
Keywordswaltz-16
Abstract

The source of the residual line broadening in continuous-wave (cw) decoupled spectra under magic-angle sample spinning conditions is reexamined. It is shown that an important contribution to the line broadening comes from a second-order recoupling of the heteronuclear dipolar-coupling tensor and the chemical-shielding tensor of the irradiated spin. Such an interference between the two tensors leads to a sum of a zeroth-rank, a second-rank, and a fourth-rank tensor component in the Hamiltonian. The zeroth-rank and the fourth-rank tensor components are not averaged out under magic-angle sample spinning (MAS) conditions, requiring the use of higher-order averaging such as double rotation (DOR) for obtaining narrow lines. This broadening is distinctly different from off-resonance decoupling effects which transform as a second-rank tensor and can be averaged out by MAS. The properties of this second-order recoupling as a source of structural information are explored, and the conditions for removing the broadening in systems with weak homonuclear dipolar-coupling networks are discussed. (C) 1996 American Institute of Physics.

URL<Go to ISI>://WOS:A1996VD76800005
DOI10.1063/1.472224
Short TitleSecond-order recoupling of chemical-shielding and dipolar-coupling tensors under spin decoupling in solid-state NMR
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