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Physical Review A

Evidence of a two-color trap-loss channel

Gustavo Deczka Telles, L. S. Aguiar, Luís Gustavo Marcassa, Vanderlei Salvador Bagnato

Published Aug 27, 2002• 7 citations
Publisher

Abstract

We have previously reported experimental results on the trap-loss rate for a mixed species magneto-optical trap involving a pair of Na and Rb atoms [Phys. Rev. A 59, R23 (1999)]. The predicted dependence for the heteronuclear trap-loss rate as a function of laser detuning assuming a colliding pair of ground-state--excited-state atoms fails to explain the experimental results. Further investigation has shown that our observations are consistent if one assumes a loss channel involving an excited state--excited-state colliding pair of atoms. Here we present the model and discuss the physical interpretation applied to our previous experimental results. The present interpretation opens up other ways to understand the trap-loss mechanisms.

DOI
10.1103/physreva.66.025403

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Bulletin of the American Physical Society•May 1, 1993•0 citations
We have previously reported experimental results on the trap-loss rate for a mixed species magneto-optical trap involving a pair of Na and Rb atoms [Phys. Rev. A 59, R23 (1999)]. The predicted dependence for the heteronuclear trap-loss rate as a function of laser detuning assuming a colliding pair of ground-state--excited-state atoms fails to explain the experimental results. Further investigation has shown that our observations are consistent if one assumes a loss channel involving an excited state--excited-state colliding pair of atoms. Here we present the model and discuss the physical interpretation applied to our previous experimental results. The present interpretation opens up other ways to understand the trap-loss mechanisms.
Trap-loss rates due to hyperfine--structure-changing collisions involving cold Na and K atoms in a mixed species magneto-optical trap have been measured. The investigations were performed in the low intensity regime, where hyperfine--structure-changing collision are believed to be the dominant mechanism for atomic losses. Comparison between homonuclear (Na-Na) and heteronuclear (Na-K) collision rate coefficients reveals a higher loss rate in the case of heteronuclear collisions. Results obtained in the regime of low trap laser intensity are compared with existent loss rates for several alkali metals, showing themselves to be in good agreement with those expected.
We present a detailed analysis of the cold collision measurements performed in a high-gradient magneto-optical trap with a few trapped Cs atoms first presented in Ueberholz et al ( J. Phys. B: At. Mol. Opt. Phys. 33 (2000) L135 ). The ability to observe individual loss events allows us to identify two-body collisions that lead to the escape of only one of the colliding atoms (up to 10% of all collisional losses). Possible origins of these events are discussed here. We also observed strong modifications of the total loss rate with variations in the repumping laser intensity. This is explained by a simple semiclassical model based on optical suppression of hyperfine-changing collisions between ground-state atoms.
Collisions between ultra-cold (T << 1K) atoms confined in a magneto- optical trap (MOT) may result in the ejection of atoms from the trap. These collisional loss processes, which involve ground state/excited state collisions, fundamentally limit the density attainable in MOT traps. Although accurate calculations of collision rates between ultra-cold atoms require precise knowledge of the molecular potentials over a long range, the loss rate for Li was recently predicted to be significantly less than for the other alkali metals. Motivated by this result, we are measuring the collisional loss rate of Li in a vapor-cell MOT using a red-detuned laser beam to catalyze the collisions, similar to recent experiments using Rb and Cs. We will report our progress to measure the trap loss rate for {sup 6}Li and {sup 7}Li, which will be compared to investigate an isotopic dependence, as was recently observed for Rb.