NMR measurement of self-diffusion coefficients by slice selection

Most of the time, so-called inversion-recovery experiments concern longitudinal nuclear magnetization of the whole sample, the region of interest being limited by the transmitting-receiving coil. Here we address the question of what occurs if the region of interest is purposely limited to a thin slice selected by means of procedures employing magnetic field gradients. Gradients of both magnetic fields (B(0), the static magnetic field, and B(1), the radio-frequency magnetic field) can be used. In this study we resorted essentially to B(1) gradients and novel procedures, based on the natural inhomogeneity of the B(1) field delivered by a saddle coil, are described. It is obvious that molecules leaving and entering the slice during the evolution (recovery) period should influence the magnetization recovery. Molecular self-diffusion is responsible for such effects, experimentally visible and accounted for by an appropriate theory which has been approximated for by permitting an easy physical assessment. This approach should lead to alternative methods for measuring self-diffusion coefficients.