Proton NMR two-dimensional 2-D spectra of binary mixtures, obtained with the correlation spectroscopy revamped by asymmetric Z gradient echo detection pulse sequence, were employed to test various assumptions usually adopted to describe the role of diffusion in intermolecular double quantum coherences. When two molecular species, with significantly different diffusivities, are considered, the relative amplitudes of the peaks, and their widths, furnish a stringent test that unveils some inadequacies in standard approximations.
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