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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Diffusion and Dynamics

CPP 25.1: Vortrag

Mittwoch, 25. März 2009, 15:30–15:45, ZEU 160

Hot Brownian Motion — •Daniel Rings¹, Romy Radünz², Frank Cichos², and Klaus Kroy¹ — ¹ITP, Uni Leipzig, Germany — ²EXP1, Uni Leipzig, Germany

Brownian motion is abundant throughout the microscopic and mesoscopic world. Since Einstein’s seminal work, there is a good understanding of this process under conditions of thermal equilibrium. Brownian motion of particles in media with inhomogeneous temperature distributions poses several new questions. One way – already introduced by Maxwell – to cope with temperature gradients is to modify the boundary conditions at the particle’s surface and allow slip in order to account for effects of thermal gradients. This approach is purely phenomenological, however, and does not take into account the temperature-dependence of the solvent viscosity, which is pronounced in water and e. g. hence most relevant for biological systems.

Here, we present a simple theoretical model for a suspension of heated Brownian particles. We determine the Stokes’ flow around a spherical particle for radially varying viscosity and thus obtain effective quantities η, T. With these, we formulate a generalized Stokes-Einstein relation 6πη RD=k_BT, which has been justified by a novel experimental technique called Photothermal Correlation Spectroscopy (PhoCS) presented by Romy Radünz also at this conference.