Direct Measurement of the Velocity Autocorrelation Function for a Brownian Test Particle

Abstract

The velocity autocorrelation function is measured directly for the first time for one Brownian test particle in nitrogen at two different densities. The persistence of the autocorrelation is more pronounced than predicted on the basis of the modified Langevin equation. The measured distribution for the Brownian displacement shows a considerable departure from the Gaussian distribution at both densities.