THE EFFECT OF FINITE DURATION OF GRADIENT PULSES ON THE PULSED-FIELD-GRADIENT NMR METHOD FOR STUDYING RESTRICTED DIFFUSION

The applicability of the Fourier relation between the averaged displacement profile and the experimental echo-attenuation curve for the PFG NMR method for studying restricted diffusion is discussed. Formally, this relation is valid only in the limit where the gradient pulse is given in the form of a delta function, the so-called short-gradient-pulse (SGP) limit. Experimentally, this condition can of course never be realized, and usually a block-shaped pulse of finite duration and amplitude is employed. This problem was investigated numerically and the results were compared with the analytic expression valid in the SGP limit. The results presented were calculated for the simplest restricted geometry: the diffusion between two plates. (C) 1994 Academic Press, Inc.