Small angle double quantum spectroscopy (SAQS NMR)

Abstract

A new experiment for recording double quantum spectra is introduced. The 2D DQ NMR experiment yields phase sensitive spectra with double quantum frequencies in F1. The appearance of remote peaks is vastly suppressed by using a small flip angle double quantum excitation and reconversion. Pulse sequences and phase sensitive processing are discussed. The complexity of the SQ antiphase magnetization given in larger proton spin networks could be reduced by using the option of band selective decoupling during the preparation period. In addition, an ACCORDION element is applied by incrementing the J evolution delay in concert with the t1 period. With this the excitation of double quantum coherence over a wider range of J values is achieved. A broadband homodecoupled version of the DQ experiment is proposed, where correlation peaks with singlet response at F2 chemical shifts and double quantum frequencies in F1 are obtained. We call this experiment Small Angle double Quantum Spectroscopy SAQS NMR.