Improving resolution in proton solid-state NMR by removing nitrogen-14 residual dipolar broadening

Residual dipolar coupling between quadrupolar and other nuclei under MAS has not usually been thought to be important in high field NMR spectroscopy. We show that coupling to 14N broadens 1H lineshapes significantly even at 11.7 T, and that we can decouple 14N from 1H during 1H homonuclear decoupling to successfully improve 1H resolution. The method used for decoupling is the application of evenly spaced pulses to the quadrupolar nucleus.