A tunable homonuclear dipolar decoupling scheme for high-resolution proton NMR of solids from slow to fast magic-angle spinning

A homonuclear dipolar decoupling scheme is introduced for obtaining proton high-resolution NMR spectra of solids under slow to fast magic-angle spinning (MAS). The basic unit is an extension of magic-echo sequence with its effective field tilted in the rotating frame, bracketed by two sandwich pulses. The angle of the tilt can be tuned for obtaining optimal spectral resolution according to the spinning frequency. Improved resolution has been obtained using this tunable sequence on a sample of glycine at 10 and 60 kHz of MAS compared with windowed phase-modulated Lee-Goldburg and magic-echo sandwich schemes.