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Q: Quantenoptik

Q 411: Fallen und Kühlung I

Q 411.2: Vortrag

Donnerstag, 7. März 2002, 14:15–14:30, HS 22/B01

RF-induced Sisyphus cooling in an optical dipole trap — •Stephan Dürr, Kurt W. Miller, and Carl E. Wieman — JILA, NIST, and University of Colorado, Boulder, CO, 80309-0440, USA

We store 87Rb atoms in a circularly polarized far-off-resonance trap (FORT). The circular polarization of the trapping laser light induces a splitting of the Zeeman states of the trapped atoms. Detuning the FORT light a few nanometers from the atomic resonance, the residual scattering of the FORT photons optically pumps almost all the atoms to a stretched Zeeman state [1]. We cool the atoms by forcing them to undergo so-called Sisyphus cycles. Such a cycle starts with a radio-frequency (RF) induced transition to other Zeeman states. Unlike a magnetic trap, a FORT is able to trap all Zeeman states. Therefore atoms transferred by the RF are not ejected from the trap. Instead, they lose energy by rolling uphill in the other trapping potentials. Eventually, the FORT photon scattering repumps the atoms into the stretched state, thus closing a Sisyphus cooling cycle. We have obtained substantial cooling and increase in phase space density. Ref.[1] K. Corwin et al., Phys. Rev. Lett. 83, 1311 (1999).