Regensburg 2010 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 6: Poster Session I

DY 6.23: Poster

Monday, March 22, 2010, 16:00–18:00, Poster B2

Characterization of heterogeneous single molecule diffusion in ultra-thin liquid films from the probability density of scaled squared displacements — •Michael Bauer and Günter Radons — Chemnitz University of Technology, 09107 Chemnitz, Germany

Our objective is to characterize the behavior of heterogeneous diffusion processes observed from single molecule trajectories. Such processes arise in many physical and biological applications, for instance in ultra-thin liquid films. A change of diffusion properties between different liquid layers and a projection of the particle’s trajectory onto the two-dimensional plane lead to dynamic heterogeneities in the observed motion of the molecules [1]. Due to averaging, conventional methods like mean square displacement calculations conceal the effects originating from these inhomogeneities. Consequently, interesting parameters like distinct diffusion coefficients cannot be determined from averaged data. Hence, investigations based on the probability density of scaled squared displacements offer a promising approach to identify and characterize properties of the observed inhomogeneous diffusion process. We consider moments of the probability density and calculate time-dependent diffusion coefficients along with their fluctuations. Furthermore, our analysis is extended to static heterogeneities originating from modified compartments near the substrate. A map of probability densities enables the distinction between static and dynamic heterogeneities.

[1]  M. Bauer et al., Diffusion Fundamentals 11(70):1–2, 2009.