Heteronuclear decoupling in rotating solids via symmetry-based adiabatic RF pulse schemes

The performance of symmetry-based adiabatic RF pulse schemes for 1H decoupling at moderate magic angle spinning (MAS) frequencies has been evaluated via numerical simulations and experimentally compared with other decoupling techniques. Our studies reveal that in MAS solid state NMR studies of polycrystalline specimens, in contrast to symmetry-based RF pulse schemes involving rectangular RF pulses, adiabatic decoupling sequences can be effectively implemented to make use of all the available decoupling RF field strength and to eliminate the deleterious effects of H1 inhomogeneity and resonance offset. Symmetry-based adiabatic decoupling sequences lead to improved decoupling performance compared to a continuous train of adiabatic inversion pulses that are phase cycled as in solution state NMR studies.