Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 33: Poster II

DY 33.43: Poster

Thursday, March 14, 2013, 17:00–19:00, Poster C

Characterization of diffusion processes with non-exponential dwell time distributions by the distribution of diffusivities — •Michael Bauer and Günter Radons — Chemnitz University of Technology, Germany

Many transport phenomena in physical and biological systems can be described by heterogeneous diffusion processes where the diffusive behavior changes during the motion. For instance, diffusion in ultra-thin liquid films is governed by layer-dependent diffusion coefficients and jumps between the liquid layers. Such processes are often characterized by observing individual tracers in single-particle tracking (SPT) experiments. To account for inhomogeneities, we suggested to investigate the distribution of diffusivities and its dependence on the time lag between snapshots [1]. We further studied the relation to ensemble-based measurements obtained from pulsed field gradient nuclear magnetic resonance (PFG NMR) and applied it to the two-compartment exchange (Kärger) model [2]. In our contribution, we extend the investigations to heterogeneous systems where the Kärger model is not applicable. In such systems the dwell time distribution does not decay exponentially but depends on the spatial potential related to, e.g., structured surfaces. We analyze such systems by the time-lag dependence of the distribution of diffusivities and its moments, which characterizes the diffusivity as a fluctuating quantity along a trajectory.

[1]  M. Bauer et al., Diffus. Fundam. 11, 104 (2009)

[2]  M. Bauer et al., J. Chem. Phys. 135, 144118 (2011)