Probing porous media with gas diffusion NMR

We show that gas diffusion nuclear magnetic resonance (GD-NMR) provides a p owerful technique for probing the structure of porous media. In random pack s of glass beads, using both laser-polarized and thermally polarized xenon gas, we find that GD-NMR can accurately measure the pore space surface-area -to-volume ratio, S/V-p, and the tortuosity, alpha (the latter quantity bei ng directly related to the system's transport properties). We also show tha t GD-NMR provides a good measure of the tortuosity of sandstone and complex carbonate rocks.