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Conference on Lasers and Electro-Optics

Observation of Collisional Narrowing in an Ensemble of Cold Atoms

Yoav Sagi, Ido Almog, Nir Davidson

Published Jan 1, 2010• 0 citations
Publisher

Abstract

We study the coherence dynamics of optically trapped 87Rb atoms. We observe a decrease of the dephasing rate for an increasing elastic collision rate, and show that it depends only on the phase space density.
DOI
10.1364/qels.2010.qfe1

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We study the spectral narrowing induced by collisions in a dense cold atomic ensemble. We report on experiments showing a prolongation of the coherence time of optically trapped 87Rb atoms as the density increases, a phenomenon we call collisional narrowing in analogy to the motional narrowing effect in NMR. We derive an expression for the new dephasing time scale in terms of the collision rate and the inhomogeneous decay time. Remarkably, this time scale universally depends only on the atomic phase space density.
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We have explored experimentally a novel possibility to study exoergic cold atomic collisions. Trapping of small countable atom numbers in a shallow magneto-optical trap and monitoring of their temporal dynamics allows us to directly observe isolated two-body atomic collisions and provides detailed information on loss statistics. A substantial fraction of such cold collisional events has been found to result in the loss of one atom only. We have also observed for the first time a strong optical suppression of ground-state hyperfine-changing collisions in the trap by its repump laser field.