Measurements of motionally averaged heteronuclear dipolar couplings in MAS NMR using R-type recoupling

• A novel MAS NMR approach is presented for the determination of heteronuclear dipolar couplings in unoriented materials. The technique is based on the proton-detected local field (PDLF) protocol, and achieves dipolar recoupling by R-type radio-frequency irradiation. The experiment, which is called R-PDLF spectroscopy, is demonstrated on solid and liquid-crystalline systems. For mobile systems, it is shown that the R-PDLF scheme provides better dipolar resolution as compared to techniques combining conventional separated local field (SLF) spectroscopy with R-type recoupling.

Nyckelord

heteronuclear recoupling

magic-angle spinning

SLF

PDLF

R-type sequences

solid-state nmr

polarization transfer

liquid-crystals

cross-polarization

hexaoctyloxy-rufigallol

spinning conditions

rotating solids

columnar phases

pulse sequences

spectroscopy

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