Physical Review A

Collisional losses in a K-Rb cold mixture

Luís Gustavo Marcassa, Gustavo Deczka Telles, Sérgio Ricardo Muniz, Vanderlei Salvador Bagnato

Published Dec 13, 2000• 45 citations

Abstract

We have observed a heteronuclear trap loss rate for a mixture of trapped ${}^{39}\mathrm{K}$ and ${}^{85}\mathrm{Rb}$ atoms. Our results indicate that hyperfine changing collision and radiative escape dominate in the low and high intensity regimes, respectively. They are also consistent with radiative escape taking place with the participation of the doubly excited state potential $({\mathrm{K}}^{*}\ensuremath{-}{\mathrm{Rb}}^{*}).$ A Gallagher-Pritchard model taking into account the doubly excited channel was implemented, reproducing the experimental results well qualitatively. The values obtained for the cross species trap loss indicate possibilities of future experiments with this mixture.

DOI: 10.1103/physreva.63.013413

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Physical Review A

Collisional losses in a K-Rb cold mixture

Luís Gustavo Marcassa, Gustavo Deczka Telles, Sérgio Ricardo Muniz, Vanderlei Salvador Bagnato

Published Dec 13, 2000• 45 citations

Publisher

Abstract

We have observed a heteronuclear trap loss rate for a mixture of trapped

{}^{39}\mathrm{K}

and

{}^{85}\mathrm{Rb}

atoms. Our results indicate that hyperfine changing collision and radiative escape dominate in the low and high intensity regimes, respectively. They are also consistent with radiative escape taking place with the participation of the doubly excited state potential

({\mathrm{K}}^{*}\ensuremath{-}{\mathrm{Rb}}^{*}).

A Gallagher-Pritchard model taking into account the doubly excited channel was implemented, reproducing the experimental results well qualitatively. The values obtained for the cross species trap loss indicate possibilities of future experiments with this mixture.

DOI: 10.1103/physreva.63.013413

Related papers

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Summary form only given. We present a set of experimental results of trap loss rate for the following mixtures: Na-Rb, K-Rb, Na-K, Rb-Cs and Cs-K. The analysis of our data set allows us to conclude that radiative escape is the main loss mechanism and we observed the significant contribution of the double-excited potential (both atoms excited) for the losses on the studied species. We also have applied an adapted Gallagher-Pritchard model to understand the importance of the reduced mass and the trap depth.Summary form only given. We present a set of experimental results of trap loss rate for the following mixtures: Na-Rb, K-Rb, Na-K, Rb-Cs and Cs-K. The analysis of our data set allows us to conclude that radiative escape is the main loss mechanism and we observed the significant contribution of the double-excited potential (both atoms excited) for the losses on the studied species. We also have applied an adapted Gallagher-Pritchard model to understand the importance of the reduced mass and the trap depth.

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Hyperfine structure modifications of collisional losses from light-force atom traps

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Inelastic atomic collisions constitute loss mechanisms for neutral atom traps, and the study of trap-loss rates may provide detailed information on the long-range interaction between atoms and on the dynamics of very slow collisions. Gallagher and Pritchard (1989) have given a simple two-state model for such collisions which includes a radiative transition or a single curve crossing at short range representing, for example, fine-structure-changing collisions. In order to better describe the more complicated case found in alkali metals, we have extended this model to include several excited hyperfine structure levels with curve crossings at long range. We find that collisions in a laser field that are capable of expelling atoms from the trap can be suppressed in some laser frequency regions and enhanced in others, in comparison with the predictions of the simple two-state model. Using this model to represent radiative escape via the 2 u potential of alkali dimer molecules we are able to greatly improve agreement between theory and experiment, including new measurements on 85 Rb reported here.Inelastic atomic collisions constitute loss mechanisms for neutral atom traps, and the study of trap-loss rates may provide detailed information on the long-range interaction between atoms and on the dynamics of very slow collisions. Gallagher and Pritchard (1989) have given a simple two-state model for such collisions which includes a radiative transition or a single curve crossing at short range representing, for example, fine-structure-changing collisions. In order to better describe the more complicated case found in alkali metals, we have extended this model to include several excited hyperfine structure levels with curve crossings at long range. We find that collisions in a laser field that are capable of expelling atoms from the trap can be suppressed in some laser frequency regions and enhanced in others, in comparison with the predictions of the simple two-state model. Using this model to represent radiative escape via the 2 u potential of alkali dimer molecules we are able to greatly improve agreement between theory and experiment, including new measurements on 85 Rb reported here.

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S. D. Gensemer, V. Sánchez-Villicaña, K. Y. N. Tan +2 more

We report on measurements of trap-loss collisions between ultracold Rb atoms that are confined in a magneto-optical trap. Both isotopes, ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb},$ have been studied over a wide range of trap laser intensities and detunings. The trap-loss collisional rate constant exhibits variations over three orders of magnitude. At low intensities and/or large detunings, the trap loss is dominated by ground-state hyperfine-changing collisions, while at high intensities and small detunings, collisions involving excited atoms are more important. We see significant differences between the isotopes in both regimes. At large detunings, the ability of the trap to recapture products of a hyperfine-changing collision is significantly diminished. This finding is supported by our numerical simulations of the recapture process. The trap loss rates due to collisions with room-temperature background gas have also been measured. A surprisingly large increase in this rate is seen when the confining power of the trap is reduced.We report on measurements of trap-loss collisions between ultracold Rb atoms that are confined in a magneto-optical trap. Both isotopes, ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb},$ have been studied over a wide range of trap laser intensities and detunings. The trap-loss collisional rate constant exhibits variations over three orders of magnitude. At low intensities and/or large detunings, the trap loss is dominated by ground-state hyperfine-changing collisions, while at high intensities and small detunings, collisions involving excited atoms are more important. We see significant differences between the isotopes in both regimes. At large detunings, the ability of the trap to recapture products of a hyperfine-changing collision is significantly diminished. This finding is supported by our numerical simulations of the recapture process. The trap loss rates due to collisions with room-temperature background gas have also been measured. A surprisingly large increase in this rate is seen when the confining power of the trap is reduced.

Physical Review ANov 1, 199757 citations

We have observed a heteronuclear trap loss rate for a mixture of trapped

{}^{39}\mathrm{K}

and

{}^{85}\mathrm{Rb}

({\mathrm{K}}^{*}\ensuremath{-}{\mathrm{Rb}}^{*}).

We have realized a two-species mirror-magneto-optical trap containing a mixture of

^{87}\mathrm{Rb}\phantom{\rule{0.3em}{0ex}}(^{85}\mathrm{Rb})

and

^{133}\mathrm{Cs}

atoms. Using this trap, we have measured the heteronuclear collisional loss rate ${\ensuremath{\beta}}_{\mathrm{Rb-Cs}}^{\ensuremath{'}}$ due to intraspecies cold collisions. We find a distinct difference in the magnitude and intensity dependence of ${\ensuremath{\beta}}_{\text{Rb-Cs}}^{\ensuremath{'}}$ for the two isotopes

^{87}\mathrm{Rb}

and

^{85}\mathrm{Rb}

which we attribute to the different ground-state hyperfine splitting energies of the two isotopes.

We report on measurements of trap-loss collisions between ultracold Rb atoms that are confined in a magneto-optical trap. Both isotopes,

{}^{85}\mathrm{Rb}

and

{}^{87}\mathrm{Rb},

have been studied over a wide range of trap laser intensities and detunings. The trap-loss collisional rate constant exhibits variations over three orders of magnitude. At low intensities and/or large detunings, the trap loss is dominated by ground-state hyperfine-changing collisions, while at high intensities and small detunings, collisions involving excited atoms are more important. We see significant differences between the isotopes in both regimes. At large detunings, the ability of the trap to recapture products of a hyperfine-changing collision is significantly diminished. This finding is supported by our numerical simulations of the recapture process. The trap loss rates due to collisions with room-temperature background gas have also been measured. A surprisingly large increase in this rate is seen when the confining power of the trap is reduced.