Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Colloid Dynamics
CPP 32.2: Vortrag
Donnerstag, 28. Februar 2008, 11:30–11:45, C 264
Persistent correlations of constrained colloidal motion — •Jonas A. Kraus1, Thomas Franosch1, Sylvia Jeney2, Branimir Lukić2, and László Forró2 — 1Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 München, Germany — 2Institut de Physique de la Matierère Complexe, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
The dynamic behavior of a single colloidal particle in water confined by an optical trap and a plane surface is investigated at time scales where the inertia of the surrounding fluid plays a significant role. First, we quantify the influence of the confinement created by the harmonic potential of the optical trap on the particle’s velocity autocorrelation (VACF). In particular, we observe a regime of anti-correlation which cannot be explained by the harmonic restoring force and the particle’s inertia alone. For intermediates times unconstrained bulk behavior is recovered and we give first direct experimental evidence for the celebrated power-law long-time tails.
Second, the particle is brought close to a surface and we observe how the subtle interplay of surface confinement and hydrodynamic backflow changes the decay of the particle’s VACF from a slow t−3/2 to a much faster power-law t−5/2. We compare our data to a recently developed theory by Felderhof [1] which we have extended by a harmonic trapping force.
[1] B.U. Felderhof, J. Phys. Chem. B 109, 21406 (2005).