Time domain analysis: an alternative way to interpret PGSE experiment

We report a theoretical development which aims at interpreting Pulsed Gradi ent Spin Echo data for diffusing fluids in saturated porous media. It consi sts in analyzing the time dependence of PGSE amplitudes for each single gra dient strength, and introduces a new diffusion coefficient D((q) over right arrow) as being continuously dependent on the length scale in the material . Both experimental measurements on water saturated bead packings and simul ated experiments in 2D and 3D model systems are interpreted with this appro ach. D((q) over right arrow) is shown to give a new insight in the micro-ma cro transition. Its evolution vs. the length scale is non trivial, and can be sensitive to local slow kinetic effects. (C) 2001 Elsevier Science Inc. All rights reserved.