Restricted molecular diffusion in the vicinity of a reflective wall as probed by NMR measurements using radio-frequency field gradients

Abstract

Radiofrequency field gradients ( B 1 gradients) are known to be insensitive to the background static field gradients ( B 0 gradients) which arise from zones of different magnetic susceptibility within the object under investigation. This feature is exploited here in order to detect restricted diffusion at the edge of a standard cylindrical glass tube containing water. A simple method based on B 1 gradients has been devised for producing a spatially resolved map in which translational diffusion coefficients are displayed along the third dimension. A decrease of the apparent self-diffusion coefficient at the liquid–glass boundary is indeed observed and explained by a simple theory used previously in the case of very rapidly diffusing systems [Y.Q. Song, B.M. Goodson, B. Sheridan, T.M. de Swiet, A. Pines, J. Chem. Phys. 108 (1998) 6233].