Multiple-quantum polarization-transfer coherence pathways in liquids

Polarization-transfer processes in liquid-state NMR are discussed in terms of a simplified operator formalism. The operator model is introduced and the various transformation rules are tabulated. The idea of a coherence pathway is also introduced and the various coherence pathways for the SPT, INEPT, and DEPT polarization-transfer experiments are discussed briefly. The bulk of the paper is devoted to the POMMIE family of pulse sequences and a detailed analysis is made of the extensive phase cycling possible with this pulse train. General expressions are derived for the signal acquired as the phase of the various pulses is changed. Subspectral editing using the POMMIE procedure is discussed in detail and it is shown to be superior to all other polarization-transfer techniques. Edited proton-decoupled carbon-13 spectra of cholesterol are generated using the POMMIE procedure.