Dresden 2006 – scientific programme

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AKB: Biologische Physik

AKB 24: Brownian Motion and Fluctuation Theorems

AKB 24.1: Talk

Thursday, March 30, 2006, 17:15–17:30, ZEU 255

Observation of nondiffusive Brownian motion of an isolated particle — •Sylvia Jeney¹, Branimir Lukic¹, Christian Tischer², Andrzej Kulik¹, Laszlo Forro¹, and Ernst-Ludwig Florin³ — ¹Institut de Physique de la Matière Complexe, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland — ²European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany — ³Center for Nonlinear Dynamics, University of Texas, Austin, Texas 78712, USA

The thermal position fluctuations of a single micron-sized sphere immersed in a fluid were recorded by optical trapping interferometry with nanometer spatial and microsecond temporal resolution. We find, in accord with the theory of Brownian motion including hydrodynamic memory effects, that the transition from the ballistic to the diffusive motion is delayed to significantly longer times than predicted by the standard Langevin equation. This delay is a consequence of the inertia of the fluid. On the shortest time scales investigated, the sphere*s inertia has a small, but measurable, effect. Furthermore, our study gives insight on the particle’s behavior, when confined in a harmonic potential. Surprisingly the hydrodynamic memory effects coming from the inertia of the fluid and the harmonic potential act at the same time scale for the studied system.