Measurement of the instantaneous velocity of Brownian motion of suspended particles in liquid probes the microscopic foundations of statistical mechanics in soft condensed matter. However, instantaneous velocity has eluded experimental observation for more than a century since Einstein's prediction of the small length and time scales involved. We report shot-noise–limited, high-bandwidth measurements of Brownian motion of micrometer-sized beads suspended in water and acetone by an optical tweezer. We observe the hydrodynamic instantaneous velocity of Brownian motion in a liquid, which follows a modified energy equipartition theorem that accounts for the kinetic energy of the fluid displaced by the moving bead. We also observe an anticorrelated thermal force, which is conventionally assumed to be uncorrelated.
Feed: Science: Current Issue
Posted on: Friday, 28 March 2014 11:00 AM
Author: Simon Kheifets
Subject: [Report] Observation of Brownian Motion in Liquids at Short Times: Instantaneous Velocity and Memory Loss
The motions of Brownian particles are tracked and evaluated on short time scales where solvent effects play a role. Authors: Simon Kheifets, Akarsh Simha, Kevin Melin, Tongcang Li, Mark G. Raizen
View article...<http://www.sciencemag.org/content/343/6178/1493.summary?rss=1>
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