Homonuclear J-couplings and rotationally induced sideband enhancements in NMR spectra of rotating solids

We demonstrate direct detection of ¹³C-¹³C J-couplings in magic angle sample spinning NMR spectra despite the presence of the much larger homogeneous broadening caused by the homonuclear dipolar couplings. Carbon-carbon J-couplings were observed in doubly ¹³C-enriched samples of sodium acetate, glycine and glucose. The resolved J-coupling permits carbon-carbon connectivities to be established with standard two-dimensional techniques. Interesting spectral features are observed when the rotational sidebands of the coupled spins overlap: when a sideband from a dipolar-coupled pair approaches the centerband of its partner, a significant enhancement in sideband intensity is observed as well as small shifts in the resonance frequency.