Coherence selection in gradient-enhanced, heteronuclear correlation spectroscopy

The gradient-enhanced, heteronuclear, chemical-shift correlation experiment, which provides F quadrature detection in a single acquisition, is analyzed in terms of product operators. Spectral distortions due to eddy-current effects can be avoided by judicial placement of gradient episodes with respect to the incremented evolution period as illustrated by an alternative gradient sequence. The analysis demonstrates the gradient selection of coherences and shows that the relative value of the gradients for N-type or P-type selection now depends upon the value of the ratio of gyromagnetic ratios, rather than on its sign. The new sequence is experimentally demonstrated by the acquisition of a 2D heteronuclear HC correlation spectrum of strychnine