Heteronuclear decoupling in rotating solids: Improving the efficacy of symmetry-based tanh/tan adiabatic RF pulse schemes

Heteronuclear dipolar decoupling in MAS solid state NMR studies of biological systems has been investigated at moderate spinning speeds. It is shown that the efficacy of C N n ν symmetry-based decoupling schemes with tanh/tan adiabatic pulses can be significantly improved by optimising the amplitude and frequency modulation characteristics of the inversion pulses employed. The decoupling performance of the symmetry-based schemes is compared with that of the commonly used TPPM technique.