Hannover 2010 – wissenschaftliches Programm
Q 2.8: Vortrag
Montag, 8. März 2010, 15:45–16:00, A 320
Laser cooling of atoms by collisional redistribution of radiation — •Anne Sass, Ulrich Vogl, and Martin Weitz — Institut für Angewandte Physik der Universität Bonn, Wegelerstraße 8, D-53115 Bonn
The general idea that optical radiation may cool matter was put forward by Pringsheim already in 1929. Doppler cooling of dilute atomic gases is an extremely successful application of this concept, and more recently anti-Stokes fluorescence cooling in multilevel systems has been explored. We experimentally demonstrate cooling of an atomic gas by collisional redistribution of fluorescence, a technique based on the atomic two level system, using rubidium atoms subject to 200 bar of argon gas pressure. The frequent collisions in the ultradense gas transiently shift a far red detuned laser beam into resonance, while spontaneous decay occurs close to the unperturbed atomic resonance frequency. During each excitation cycle, a kinetic energy of order of the thermal energy kBT is extracted from the dense atomic sample. We presently achieve cooling in a heated gas from an initial temperature of 410 ∘C down to −120 ∘C temperature in the laser beam focus. The cooled gas has a density of more than 10 orders of magnitude above the typical values in Doppler cooling experiments. Future prospects of the demonstrated technique can include cryocoolers and the study of homogeneous nucleation in saturated vapour.