Physical Review A

Comparison of trap-loss collision spectra for Rb85 and Rb87

Paul Feng, Dominikus Hoffmann, Thad G Walker

Published May 1, 1993• 29 citations

Abstract

We present measurements of excited-state trap-loss collisions of optically trapped $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ atoms as a function of the frequency of the light used to excite the colliding atom pairs. For detunings outside the excited-state hyperfine structure, the trap-loss rates are found to be the same for the two isotopes. For detunings inside the excited-state hyperfine structure, $^{87}\mathrm{Rb}$ collisions occur at a substantially lower rate than those of $^{85}\mathrm{Rb}$. The spectra make it clear that the long-range dynamics of the collisions are strongly modified by the excited-state hyperfine structure, and that the dynamics are different for the two isotopes.

DOI: 10.1103/physreva.47.r3495

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Measurements of Rb trap-loss collision spectra

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The effects of hyperfine interactions on collisions between optically trapped atoms

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Excited-state collisions of trapped Rb85 atoms

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Jan 1, 19960 citations

Physical Review A

Comparison of trap-loss collision spectra for Rb85 and Rb87

Paul Feng, Dominikus Hoffmann, Thad G Walker

Published May 1, 1993• 29 citations

Publisher

Abstract

We present measurements of excited-state trap-loss collisions of optically trapped

^{85}\mathrm{Rb}

and

^{87}\mathrm{Rb}

atoms as a function of the frequency of the light used to excite the colliding atom pairs. For detunings outside the excited-state hyperfine structure, the trap-loss rates are found to be the same for the two isotopes. For detunings inside the excited-state hyperfine structure,

^{87}\mathrm{Rb}

collisions occur at a substantially lower rate than those of

^{85}\mathrm{Rb}

. The spectra make it clear that the long-range dynamics of the collisions are strongly modified by the excited-state hyperfine structure, and that the dynamics are different for the two isotopes.

DOI: 10.1103/physreva.47.r3495

Related papers

Measurements of Rb trap-loss collision spectra

D. Hofffmann, P. Feng, Thad G Walker

We describe studies of excited-state/ground-state collisions between optically trapped Rb atoms. Collision rates are deduced from the transients observed as atoms are loaded into a vapor-cell optical trap. The rates are measured as a function of the frequency of the light used to excite the atom pairs. A comparison of the results for 85Rb and 87Rb shows that excited-state hyperfine interactions play a vital role in the dynamics of the collisions. In addition, the absolute rates are smaller than those expected from recent models.We describe studies of excited-state/ground-state collisions between optically trapped Rb atoms. Collision rates are deduced from the transients observed as atoms are loaded into a vapor-cell optical trap. The rates are measured as a function of the frequency of the light used to excite the atom pairs. A comparison of the results for 85Rb and 87Rb shows that excited-state hyperfine interactions play a vital role in the dynamics of the collisions. In addition, the absolute rates are smaller than those expected from recent models.

Journal of the Optical Society of America BMay 1, 199444 citations

The effects of hyperfine interactions on collisions between optically trapped atoms

Thad G Walker, P.Y. Feng, Dominikus Hoffmann

The authors report measurements of excited state collision rates of optically trapped {sup 85}Rb and {sup 87}Rb. The collision rates have been measured in the vicinity of the P{sub 3/2} and P{sub 1/2} states of both isotopes. By studying the collision rates as a function of the frequency of light used to cause the collisions, they obtain collision spectra that reveal the importance of hyperfine interactions on the collision dynamics. In certain frequency ranges the collision rates for the two isotopes are nearly identical, while in others they find substantially reduced rates for {sup 87}Rb (large hyperfine interaction) as compared to {sup 85}Rb (small hyperfine interaction). For the P{sub 1/2} states, where hyperfine splittings are large compared to the characteristic frequency scales for these collisions, the shapes of the spectra more closely correspond to those expected from simple models that neglect hyperfine interactions.The authors report measurements of excited state collision rates of optically trapped {sup 85}Rb and {sup 87}Rb. The collision rates have been measured in the vicinity of the P{sub 3/2} and P{sub 1/2} states of both isotopes. By studying the collision rates as a function of the frequency of light used to cause the collisions, they obtain collision spectra that reveal the importance of hyperfine interactions on the collision dynamics. In certain frequency ranges the collision rates for the two isotopes are nearly identical, while in others they find substantially reduced rates for {sup 87}Rb (large hyperfine interaction) as compared to {sup 85}Rb (small hyperfine interaction). For the P{sub 1/2} states, where hyperfine splittings are large compared to the characteristic frequency scales for these collisions, the shapes of the spectra more closely correspond to those expected from simple models that neglect hyperfine interactions.

Bulletin of the American Physical SocietyDec 1, 19930 citations

Excited-state collisions of trapped Rb85 atoms

Dominikus Hoffmann, P. Feng, R. S. Williamson +1 more

We descrbe a new method for measuring excited-state collisions between optically trapped atoms. With this method, trap-loss collision rates are deduced from the loading behavior of clouds of trapped atoms in the regime where radiation trapping limits the atom density. Our measurements indicate that $^{85}\mathrm{Rb}$ trap-loss collisions occur at significantly smaller rates than expected both from previous work on Cs and from recent models. In addition, the dependence of the trap-loss collisions on the frequency of the light used to excite the atom pairs is also different from that of Cs, suggesting that assumptions about the dynamics in these models need modification.We descrbe a new method for measuring excited-state collisions between optically trapped atoms. With this method, trap-loss collision rates are deduced from the loading behavior of clouds of trapped atoms in the regime where radiation trapping limits the atom density. Our measurements indicate that $^{85}\mathrm{Rb}$ trap-loss collisions occur at significantly smaller rates than expected both from previous work on Cs and from recent models. In addition, the dependence of the trap-loss collisions on the frequency of the light used to excite the atom pairs is also different from that of Cs, suggesting that assumptions about the dynamics in these models need modification.

Physical Review LettersAug 3, 199251 citations

Light-assisted collisional loss in a Rb85∕87 ultracold optical trap

Anthony Gorges, N. S. Bingham, Michael K. DeAngelo +2 more

We have studied heteronuclear and homonuclear excited-state--ground-state collisions by loading both $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ into a far off resonant trap (FORT). Because of the relatively weak confinement of the FORT, we expect the hyperfine structure of the different isotopes to play a crucial role in the collision rates. This dependence on hyperfine structure allows us to measure collisions associated with long-range interatomic potentials of different structures, such as long and short ranged; or such as purely attractive, purely repulsive, or mixed attractive and repulsive. We observe significantly different loss rates for different excited-state potentials. Additionally, we observe that some collisional channels' loss rates are saturated at our operating intensities $(15\phantom{\rule{0.3em}{0ex}}\mathrm{mW}∕{\mathrm{cm}}^{2})$ . These losses are important limitations in loading dual isotope optical traps.We have studied heteronuclear and homonuclear excited-state--ground-state collisions by loading both $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ into a far off resonant trap (FORT). Because of the relatively weak confinement of the FORT, we expect the hyperfine structure of the different isotopes to play a crucial role in the collision rates. This dependence on hyperfine structure allows us to measure collisions associated with long-range interatomic potentials of different structures, such as long and short ranged; or such as purely attractive, purely repulsive, or mixed attractive and repulsive. We observe significantly different loss rates for different excited-state potentials. Additionally, we observe that some collisional channels' loss rates are saturated at our operating intensities $(15\phantom{\rule{0.3em}{0ex}}\mathrm{mW}∕{\mathrm{cm}}^{2})$. These losses are important limitations in loading dual isotope optical traps.

arXiv:0805.3708Physical Review ASep 18, 200813 citations

Trap-loss collisions of 85 Rb and 87 Rb : Dependence on trap parameters

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

Effects of laser light on ultracold atom collisions

V. Sánchez-Villicaña

Measurements of the temperature dependence of trap loss collisions of laser-cooled rubidium atoms are presented. A significant suppression of the rate of collisions between ground- and excited-state atoms is observed for temperatures below $\\sim$70 $\\mu$ K. In such inelastic collisions, the atomic excitation takes place at long range and must survive against spontaneous decay to short range. Our results are consistent with recent predictions for the low temperature suppression of these collisions due to reduced survival of atomic excitation at low collision velocities.^ We report on measurements of trap loss collisions between ultracold Rb atoms which are confined in a magneto-optical trap. Both isotopes $\\sp{85}$ Rb and $\\sp{87}$ Rb have been studied over wide range of trap laser intensities and detunings. The trap loss collision rates exhibit variations over 3 orders of magnitude. We observe significant differences between the isotopes. At large detunings the ability of the trap to recapture products of the hyperfine-changing collisions 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.^ Using laser light tuned to a repulsive molecular potential, we have been able to suppress inelastic ground-state hyperfine changing collisions between ultracold $\\sp{87}$ Rb atoms. Adiabatic excitation to the repulsive curve alters the atomic trajectories and prevents the atoms from approaching close enough for the hyperfine change to occur. Experimental results show suppressions up to $\\sim$50% and are in reasonable agreement with a simple Landau-Zener model.^ Finally, we have observed a significant cooperative effect in ultracold trap loss collisions induced by two separate lasers. One laser, tuned close to the atomic resonance, excites the atom pair to an attractive potential at long range. The resulting acceleration and deflection give rise to an enhancement in the collisional flux of ground-state atoms reaching short range, as probed by a second laser. Enhancements up to a factor of $\\sim$3 have been observed. ^Measurements of the temperature dependence of trap loss collisions of laser-cooled rubidium atoms are presented. A significant suppression of the rate of collisions between ground- and excited-state atoms is observed for temperatures below $\\sim$70 $\\mu$K. In such inelastic collisions, the atomic excitation takes place at long range and must survive against spontaneous decay to short range. Our results are consistent with recent predictions for the low temperature suppression of these collisions due to reduced survival of atomic excitation at low collision velocities.^ We report on measurements of trap loss collisions between ultracold Rb atoms which are confined in a magneto-optical trap. Both isotopes $\\sp{85}$Rb and $\\sp{87}$Rb have been studied over wide range of trap laser intensities and detunings. The trap loss collision rates exhibit variations over 3 orders of magnitude. We observe significant differences between the isotopes. At large detunings the ability of the trap to recapture products of the hyperfine-changing collisions 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.^ Using laser light tuned to a repulsive molecular potential, we have been able to suppress inelastic ground-state hyperfine changing collisions between ultracold $\\sp{87}$Rb atoms. Adiabatic excitation to the repulsive curve alters the atomic trajectories and prevents the atoms from approaching close enough for the hyperfine change to occur. Experimental results show suppressions up to $\\sim$50% and are in reasonable agreement with a simple Landau-Zener model.^ Finally, we have observed a significant cooperative effect in ultracold trap loss collisions induced by two separate lasers. One laser, tuned close to the atomic resonance, excites the atom pair to an attractive potential at long range. The resulting acceleration and deflection give rise to an enhancement in the collisional flux of ground-state atoms reaching short range, as probed by a second laser. Enhancements up to a factor of $\\sim$3 have been observed. ^

Jan 1, 19960 citations

We present measurements of excited-state trap-loss collisions of optically trapped

^{85}\mathrm{Rb}

and

^{87}\mathrm{Rb}

^{87}\mathrm{Rb}

collisions occur at a substantially lower rate than those of

^{85}\mathrm{Rb}

. The spectra make it clear that the long-range dynamics of the collisions are strongly modified by the excited-state hyperfine structure, and that the dynamics are different for the two isotopes.

^{85}\mathrm{Rb}

trap-loss collisions occur at significantly smaller rates than expected both from previous work on Cs and from recent models. In addition, the dependence of the trap-loss collisions on the frequency of the light used to excite the atom pairs is also different from that of Cs, suggesting that assumptions about the dynamics in these models need modification.

We have studied heteronuclear and homonuclear excited-state--ground-state collisions by loading both

^{85}\mathrm{Rb}

and

^{87}\mathrm{Rb}

into a far off resonant trap (FORT). Because of the relatively weak confinement of the FORT, we expect the hyperfine structure of the different isotopes to play a crucial role in the collision rates. This dependence on hyperfine structure allows us to measure collisions associated with long-range interatomic potentials of different structures, such as long and short ranged; or such as purely attractive, purely repulsive, or mixed attractive and repulsive. We observe significantly different loss rates for different excited-state potentials. Additionally, we observe that some collisional channels' loss rates are saturated at our operating intensities

(15\phantom{\rule{0.3em}{0ex}}\mathrm{mW}∕{\mathrm{cm}}^{2})

. These losses are important limitations in loading dual isotope optical traps.

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.

\\mu

K. In such inelastic collisions, the atomic excitation takes place at long range and must survive against spontaneous decay to short range. Our results are consistent with recent predictions for the low temperature suppression of these collisions due to reduced survival of atomic excitation at low collision velocities.^ We report on measurements of trap loss collisions between ultracold Rb atoms which are confined in a magneto-optical trap. Both isotopes

\\sp{85}

Rb and

\\sp{87}

Rb have been studied over wide range of trap laser intensities and detunings. The trap loss collision rates exhibit variations over 3 orders of magnitude. We observe significant differences between the isotopes. At large detunings the ability of the trap to recapture products of the hyperfine-changing collisions 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.^ Using laser light tuned to a repulsive molecular potential, we have been able to suppress inelastic ground-state hyperfine changing collisions between ultracold

\\sp{87}

Rb atoms. Adiabatic excitation to the repulsive curve alters the atomic trajectories and prevents the atoms from approaching close enough for the hyperfine change to occur. Experimental results show suppressions up to $\\sim$50% and are in reasonable agreement with a simple Landau-Zener model.^ Finally, we have observed a significant cooperative effect in ultracold trap loss collisions induced by two separate lasers. One laser, tuned close to the atomic resonance, excites the atom pair to an attractive potential at long range. The resulting acceleration and deflection give rise to an enhancement in the collisional flux of ground-state atoms reaching short range, as probed by a second laser. Enhancements up to a factor of $\\sim$3 have been observed. ^