HETERONUCLEAR DECOUPLING IN ROTATING SOLIDS

A simple two pulse phase modulation (TPPM) scheme greatly reduces the residual Linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments. Optimizati on of pulse lengths and phases-in the sequence produces substantial im provements in both the resolution and sensitivity of dilute spins (e.g ., C-13) over a broad range of spinning speeds at high magnetic field. The theoretical complications introduced by large homo- and heteronuc lear interactions among the spins, as well as the amplitude modulation imposed by MAS, are explored analytically and numerically. To our kno wledge, this method is the first phase-switched sequence to exhibit im provement over continuous-wave (cw) decoupling in a strongly coupled h omogeneous spin system undergoing sample spinning. (C) 1995 American I nstitute of Physics.