Spin echo diffraction in disordered media with single length scales

The spin echo diffraction observed in a pulsed field gradient NMR experiment is studied by simulation in computer generated two-dimensional disordered porous media characterized by a single length scale such as their mean pore diameter. In the propagator formulation of the pulsed field gradient experiments carried out in fluids confined inside porous media one expects to see a diffraction pattern characterizing the above length scale. We have explored the possibility of using this echo diffraction technique as a practical noninvasive tool to extract information about the pore geometries. It turns out that even for a disordered medium, the echo-diffraction pattern picks up the dominant length scale.