Diffusion waves formed the basis of several measurement technologies in materials science as well as in biological systems. They are, however, so heavily damped that their observation was a real challenge to the experimentalist. It was shown that accurate information about the refraction-like and reflection-like behavior of diffusion waves could be obtained by studying diffusion fronts. For this, H in a metal was used as a model system and its 2D migration was visualized with an optical indicator. The similarities between classical optics and diffusion, in particular, the applicability of Snell's law to diffusive systems, were discussed. The measurements were in good agreement with numerical simulations.

Refraction and Reflection of Diffusion Fronts. A.Remhof, R.J.Wijngaarden, R.Griessen: Physical Review Letters, 2003, 90[14], 145502 (4pp)