Pore opening effects and transport diffusion in the Knudsen regime in comparison to self- (or tracer-) diffusion

¹  Universität Giessen, Institut für Theoretische Physik III - Giessen, Germany
²  Universität Leipzig, Fakultät für Physik und Geowissenschaften - Leipzig, Germany

Received: 13 December 2006
Accepted: 23 February 2007

Abstract

We study molecular diffusion in linear nanopores with different types of roughness in the so-called Knudsen regime. Knudsen diffusion represents the limiting case of molecular diffusion in pores, where mutual encounters of the molecules within the free pore space may be neglected and the time of flight between subsequent collisions with the pore walls significantly exceeds the interaction time between the pore wall and the molecules. We present an extension of a commonly used procedure to calculate transport diffusion coefficients. Our results show that using this extension, the coefficients of self- and transport diffusion in the Knudsen regime are equal for all regarded systems, which improves previous literature data.