Broadband homonuclear chemical shift correlation at high MAS frequencies: a study of tanh/tan adiabatic RF pulse schemes without 1H decoupling during mixing.

At high magic angle spinning (MAS) frequencies the potential of tanh/tan adiabatic RF pulse schemes for 13C chemical shift correlation without 1H decoupling during mixing has been evaluated. It is shown via numerical simulations that a continuous train of adiabatic 13C inversion pulses applied at high RF field strengths leads to efficient broadband heteronuclear decoupling. It is demonstrated that this can be exploited effectively for generating through-bond and through-space, including double-quantum, correlation spectra of biological systems at high magnetic fields and spinning speeds with no 1H decoupling applied during the mixing period. Experiments carried out on a polycrystalline sample of histidine clearly suggest that an improved signal to noise ratio can be realised by eliminating 1H decoupling during mixing.