Simulation of the off-resonance effect in one-dimensional heteronuclear multiple quantum coherence spectroscopy

When a heteronuclear multiple quantum coherence (HMQC) NMR experiment is pe rformed in one-dimensional mode, due to the wide range in chemical shift of the indirectly detected spin and the limited strength of the radio-frequen cy field, the off-resonance effect on the intensity of the observed signal can be serious. In this paper, the effect is studied using the spin-density -matrix formalism and simulations of the experimental results are presented . The bilinear rotation-decoupling sequence (BIRD), which is usually used i n HMQC experiments, is also discussed. It is shown that the BIRD sequence h as a negative effect by virtue of narrowing the excitation band.