Pesce, G.Volpe, G.Volpe, G.Sasso, A.2016-02-082016-02-0820142470-0045http://hdl.handle.net/11693/25181We experimentally measure the effects of fluid inertia on the diffusion of a Brownian particle at very long time scales. In previous experiments, the use of standard optical tweezers introduced a cutoff in the free diffusion of the particle, which limited the measurement of these effects to times comparable with the relaxation time of the fluid inertia, i.e., a few milliseconds. Here, by using blinking optical tweezers, we detect these inertial effects on time scales several orders longer up to a few seconds. The measured mean square displacement of a freely diffusing Brownian particle in a liquid shows a deviation from the Einstein-Smoluchowsky theory that diverges with time. These results are consistent with a generalized theory that takes into account not only the particle inertia but also the inertia of the surrounding fluid. © 2014 American Physical Society.EnglishBrownian particlesInfluence of fluid07.10.Pz47.15.G−Article10.1103/PhysRevE.90.042309