Dipolar Recoupling of Heteronuclear Spin Pairs by Rotational-Echo, Double-Resonance Nuclear Magnetic Resonance
Nuclear Magnetic Resonance and Electron Spin Resonance Spectroscopy
Published Online: 15 JUN 2010
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Gullion, T. 2010. Dipolar Recoupling of Heteronuclear Spin Pairs by Rotational-Echo, Double-Resonance Nuclear Magnetic Resonance. Encyclopedia of Analytical Chemistry.
- Published Online: 15 JUN 2010
Nuclear magnetic resonance (NMR)-active nuclear spins interact through the dipolar interaction, an important source of structural information because of the r−3 dependence of this interaction on the internuclear distance. Fast random molecular reorientation averages the dipolar interaction to zero in solutions, and there is no direct evidence of the dipolar interaction in solution-state NMR spectra under typical laboratory conditions. In static solids with no significant molecular motion, measuring the dipolar coupling provides an important source of structural information. In high-resolution spectra of solids obtained through magic-angle spinning (MAS), however, the dipolar interaction is coherently averaged to zero, with concomitant loss of the information inherent to this interaction. Dipolar-recoupling experiments measure the dipolar coupling in MAS NMR. They are designed to produce a nonzero average effect of the dipolar interaction. Measured dipolar couplings obtained by dipolar-recoupling experiments can be used to determine the distance between coupled pairs of spins. One such dipolar-recoupling experiment is rotational-echo, double-resonance (REDOR) NMR, a commonly used technique to measure dipolar couplings between heteronuclear spin pairs. This article describes the REDOR experiment.
- magic-angle spinning;
- solid-state NMR;
- rotational-echo, double-resonance NMR;
- dipolar recoupling