Regensburg 2007 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 30: Poster II
DY 30.2: Poster
Donnerstag, 29. März 2007, 16:00–18:00, Poster D
Extending the Boltzmann equation to non-equilibrium: A novel method to determine external potentials. — •Valentin Blickle1, Thomas Speck2, Udo Seifert2, and Clemens Bechinger1 — 12. Physikalisches Institut, Universität Stuttgart — 2II. Institut für Theoretische Physik, Universität Stuttgart
In tilted potentials the motion of a colloidal particle is an interplay between thermal diffusion and drift. Due to this superimposed motion the diffusion coefficient and the average particle velocity become non trivial functions of the driving force f. In our experiment we drive a colloidal particle along a toroidal three-dimensional laser trap using scanning optical laser tweezers. We use an electrooptical modulator to additionally impose a static laser potential V along the torus. To characterize the laser potential we introduce a novel method, based on a steady state non-equilibrium measurement. The method uses a modified Boltzmann equation which additionally considers the stationary current. We show that this method is independent of the driving force f und thus allows to determine the static potential V. Being not restricted to equilibrium fluctuations we can characterize potential depths up to several 100 kBT.