Magnetic relaxation in porous media

Abstract

Studies of a theoretical model suggest that nuclear magnetic relaxation measurements on porous media will yield only an average pore dimension. The model consists of a random walk on a site percolation lattice with absorbing sites. Over a broad range of porosities, diffusion coefficients, and surface relaxation rates, the model yields only a single relaxation time. Under conditions of fast diffusion the relaxation time is proportional to the volume-to-surface ratio of the system. Under conditions of slow diffusion the relaxation time appears to depend on a pore dimension. But this dimension cannot easily be related to the pore geometry.