Mainz 2017 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 30: Ultracold atoms and BEC - III (with A)
Q 30.5: Talk
Tuesday, March 7, 2017, 15:30–15:45, N 1
Observation of individual tracer atoms in an ultracold dilute gas — •Felix Schmidt1,2, Daniel Mayer1,2, Tobias Lausch1, Daniel Adam1, Steve Haupt1, Michael Hohmann1, Farina Kindermann1, Nicolas Spethmann1, and Artur Widera1,2 — 1Department of Physics and Research Center OPTIMAS, University of Kaiserslautern — 2Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, 67663 Kaiserslautern
Diffusion of particles in fluids and gases is an essential and omnipresent transport phenomenon in nature. While diffusion is well understood in the limit of a heavy particle in a dense gas (known as Brownian motion), much less is known, both theoretically and experimentally, about light particles diffusing in a dilute gas.
Here, we report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the nonequilibrium relaxation of the initial nonthermal state of Cs and detect the effect of a of single collision, i.e. the fundamental building block of diffusion. We show that the diffusive motion of the single Cs atom in the Rb cloud is well described by a generalized Langevin equation with a velocity-dependent friction coefficient, an unfamiliar feature of the Langevin equation emerging for light particles.