Gan Z, Ernst R R
Laboratorium für Physikalische Chemie, Eidgenössische Technische Hochschule, Zürich, Switzerland.
Solid State Nucl Magn Reson. 1997 May;8(3):153-9. doi: 10.1016/s0926-2040(96)01294-5.
The mechanism of heteronuclear dipolar decoupling by the TPPM sequences, proposed by Bennett et al. (J. Chem. Phys. 103 (1995) 6951) is investigated by comparison with a modified pulse sequence, called TPFM, that uses frequency instead of phase modulation. By combining frequency and phase modulations, circularly modulated sequences are designed. The fact that only the left-handed modulation sequence FMPML leads to improved proton decoupling, while the right-handed modulation sequence FMPMR is ineffective, proves that the efficient decoupling is caused by a secondary resonance effect.
