title: Lambert diffusion in porous media in the Knudsen regime: equivalence of self-diffusion and transport diffusion.
abstract: We study molecular diffusion in nanopores with different types of roughness under the exclusion of mutual molecular collisions, i.e., in the so-called Knudsen regime. We show that the diffusion problem can be mapped onto Levy walks and discuss the roughness dependence of the diffusion coefficients D(s) and D(t) of self- and transport diffusion, respectively. While diffusion is normal in d=3, diffusion is anomalous in d=2 with D(s) approximately ln t and D(t) approximately ln L, where t and L are time and system size, respectively. Both diffusion coefficients decrease significantly when the roughness is enhanced, in remarkable disagreement with earlier findings.
authors.affiliation: Institut für Theoretische Physik III, Justus-Liebig-Universität Giessen, D-35392 Giessen, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Russ
authors.forename: Stephan
authors.initials: S
authors.lastname: Zschiegner
authors.forename: Armin
authors.initials: A
authors.lastname: Bunde
authors.forename: Jörg
authors.initials: J
authors.lastname: Kärger