Stuttgart 2012 – scientific programme
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A: Fachverband Atomphysik
A 42: Ultra-cold atoms, ions and BEC IV
A 42.5: Talk
Friday, March 16, 2012, 11:45–12:00, V57.03
Laser cooling of dense gases by collisional redistribution of radiation — •Anne Saß1, Ulrich Vogl2, and Martin Weitz1 — 1Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn — 2Joint Quantum Institute, University of Maryland in College Park, USA
We study laser cooling of atomic gases by collisional redistribution of fluorescence, a technique applicable to ultradense atomic ensembles of alkali atoms and a few hundred bar of buffer gas pressure. The cooled gas has a density of more than ten orders of magnitude above the typical values in Doppler cooling experiments of dilute atomic gases.
In frequent collisions with noble gas atoms in the dense gas system, the energy levels of the alkali atoms are shifted, and absorption of far red detuned incident radiation becomes feasible. The subsequent spontaneous decay occurs close to the unperturbed resonance frequency, leading to a redistribution of the fluorescence. The emitted photons have a higher energy than the incident ones, and the dense atomic ensemble is cooled. We here describe recent experiments on the redistribution laser cooling of atomic gases carried out using an industrial high power diode laser, with which cooling of a rubidium argon gas mixture from an initial temperature of 390°C down to room temperature is observed. With radiation from a Ti:sapphire laser, cooling to -120°C has been measured.
For the future, we expect that redistribution laser cooling might also be applied to molecular gas samples, where cooling can start directly from room temperature.