Spatially encoded ultrafast high-resolution 2D homonuclear correlation spectroscopy in inhomogeneous fields

Two-dimensional (2D) NMR spectroscopy shows strong vitality and unsubstitutable significance among NMR techniques. In many cases, however, it is virtually impossible to obtain high-resolution 2D spectra in inhomogeneous fields. Furthermore, conventional 2D NMR spectroscopy suffers from long acquisition time. In this paper, two new pulse sequences tracking the differences of the precession frequencies of two coupled spins are proposed to ultrafast achieve high-resolution 2D correlation spectroscopy (COSY and TOCSY) in inhomogeneous fields in a single scan. The spectral width of the indirect dimension can be reduced to improve the spectral resolution without loss of the correlative information for reconstructing the COSY and TOCSY spectra with mathematical manipulations. The theoretical analysis was given and experiments were performed to verify theoretical predictions. The results show that the proposed sequences can give correct 2D COSY and TOCSY spectra if the field inhomogeneity is linear along the orientation of encoding and decoding gradients.