Quantitative measurement of molecular diffusion coefficients by NMR spectroscopy

An offset-independent adiabatic inversion pulse is used in the diffusion experiment to uniformly excite a sample region that is sufficiently long to ignore the ending effects, yet is short enough to have a homogeneous RF field and to represent the pulsed field gradient with a linear approximation. Under these conditions, the diffusion decay of the peak intensity appears to be Gaussian as a function of the effective gradient field ge as if all the molecules inside the selected region experienced the same ge. Quantitative measurement of molecular diffusion coefficients is therefore made possible.