Physical Review A

Cold collisions of Sr*−Sr in a magneto-optical trap

Timothy P. Dinneen, Kurt R. Vogel, E. Arimondo, J. L. Hall, Alan Gallagher

Published Feb 1, 1999• 110 citations

Abstract

We present measurements of cold collision processes in an alkaline-earth species. Collisions of ${}^{88}\mathrm{Sr}$ pairs in a magneto-optic trap are found to be dominated by very-long-range excitation to the nonradiating ${}^{1}{\ensuremath{\Pi}}_{g}$ state of ${\mathrm{Sr}}_{2}^{*}.$ We find good agreement between measured loss rate coefficients and a modified form of the semiclassical model that includes retardation effects that allow excitation to metastable molecular states.

DOI: 10.1103/physreva.59.1216

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Physical Review A

Cold collisions of Sr*−Sr in a magneto-optical trap

Timothy P. Dinneen, Kurt R. Vogel, E. Arimondo, J. L. Hall, Alan Gallagher

Published Feb 1, 1999• 110 citations

Publisher

Abstract

We present measurements of cold collision processes in an alkaline-earth species. Collisions of

{}^{88}\mathrm{Sr}

pairs in a magneto-optic trap are found to be dominated by very-long-range excitation to the nonradiating

{}^{1}{\ensuremath{\Pi}}_{g}

state of

{\mathrm{Sr}}_{2}^{*}.

We find good agreement between measured loss rate coefficients and a modified form of the semiclassical model that includes retardation effects that allow excitation to metastable molecular states.

DOI: 10.1103/physreva.59.1216

Related papers

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Reinaldo L. Cavasso-Filho, Artemio Scalabrin, D. Pereira +1 more

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Anderson R. L. Caires, Gustavo Deczka Telles, M. W. Mancini +4 more

We have measured the collisional loss rate for cold strontium atoms held in a magneto-optical trap as a function of light intensity in the regime of low intensity (2-6 mW/cm²). The results confirm our recently proposed model, where we showed that the sudden increase of loss rate at low intensities does not depend on hyperfine structure changing collision only. The model, which is based on radiative escape mechanism and a light intensity dependent escape velocity, is able to reproduce quite well the behavior of the experimental observations. The data here reported may be of importance for a recent proposed application for cold trapped 88Sr atoms, as well as other trappable alkaline earth metal atoms such as Ca.We have measured the collisional loss rate for cold strontium atoms held in a magneto-optical trap as a function of light intensity in the regime of low intensity (2-6 mW/cm²). The results confirm our recently proposed model, where we showed that the sudden increase of loss rate at low intensities does not depend on hyperfine structure changing collision only. The model, which is based on radiative escape mechanism and a light intensity dependent escape velocity, is able to reproduce quite well the behavior of the experimental observations. The data here reported may be of importance for a recent proposed application for cold trapped 88Sr atoms, as well as other trappable alkaline earth metal atoms such as Ca.

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Magnetic trapping of ytterbium and the alkaline-earth metals

Thomas H. Loftus, Jason R. Bochinski, THOMAS W. MOSSBERG

Atomic ytterbium (Yb), magnesium (Mg), calcium (Ca), and strontium (Sr) possess a simple yet versatile internal level structure and a diversity of naturally abundant fermionic and bosonic isotopes, making these systems ideal for studies of cold collisions and weakly interacting quantum degenerate gases. Unlike alkali-metal atoms, however, Yb, Mg, Ca, and Sr cannot be magnetically trapped in the ground state. We analyze a solution to this problem involving magnetic trapping in a low-lying metastable excited state and predict that significant magnetic trap populations can be obtained via continuous, in situ loading from Yb and Sr ${}^{1}{S}_{0}{\ensuremath{-}}^{1}{P}_{1}$ magneto-optical traps.Atomic ytterbium (Yb), magnesium (Mg), calcium (Ca), and strontium (Sr) possess a simple yet versatile internal level structure and a diversity of naturally abundant fermionic and bosonic isotopes, making these systems ideal for studies of cold collisions and weakly interacting quantum degenerate gases. Unlike alkali-metal atoms, however, Yb, Mg, Ca, and Sr cannot be magnetically trapped in the ground state. We analyze a solution to this problem involving magnetic trapping in a low-lying metastable excited state and predict that significant magnetic trap populations can be obtained via continuous, in situ loading from Yb and Sr ${}^{1}{S}_{0}{\ensuremath{-}}^{1}{P}_{1}$ magneto-optical traps.

Physical Review AJul 29, 200232 citations

We present measurements of cold collision processes in an alkaline-earth species. Collisions of

{}^{88}\mathrm{Sr}

pairs in a magneto-optic trap are found to be dominated by very-long-range excitation to the nonradiating

{}^{1}{\ensuremath{\Pi}}_{g}

state of

{\mathrm{Sr}}_{2}^{*}.

We find good agreement between measured loss rate coefficients and a modified form of the semiclassical model that includes retardation effects that allow excitation to metastable molecular states.

^{88}

-

_{2}

in a Magneto-Optical Trap (MOT). The measurement was carried out by monitoring the atom number loss rate as a function of background pressure of N

_{2}

and the cross section thus obtained was 8.1(4)

\times 10^{-18}

^{2}

. The measured collision cross section has been utilized for the determination of C

_{6}

coefficient of the ground state (

{^1S}_0

) of

^{88}

Sr atom, which can be useful to estimate the relative frequency shift in the clock transition. We also estimate the loss rate induced by the combined effect of the decay of atoms in the long-lived

{^3P}_0

state and temperature-induced atomic losses from the capture volume of the MOT. We find that the contribution due to the latter is dominant in comparison to the other atomic loss channels and must be included in the studies that rely on the total loss rate measurement.

We have investigated trap loss in a dual-species magneto-optical trap (MOT) comprised of

^{85}\mathrm{Rb}

and metastable

^{40}\mathrm{Ar}

. We measure the trap loss rate coefficients for each species due to the presence of the other as a function of trap light intensity. We clearly identify both Penning ionization of Rb by

{\mathrm{Ar}}^{*}

and associative ionization to form the molecular ion

\mathrm{Rb}{\mathrm{Ar}}^{+}

as two of the trap loss channels. We have also measured the trap loss rate coefficient for the

{\mathrm{Ar}}^{*}

MOT alone and observe production of

{\mathrm{Ar}}^{+}

and

\mathrm{Ar}_{2}{}^{+}

ions.

We study cold collisions between trapped ions and trapped atoms in the semiclassical (Langevin) regime. Using

{\mathrm{Yb}}^{+}

ions confined in a Paul trap and Yb atoms in a magneto-optical trap, we investigate charge-exchange collisions of several isotopes over three decades of collision energies down to $3\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$ (${k}_{B}\ifmmode\times\else\texttimes\fi{}35\text{ }\text{ }\mathrm{mK}$). The minimum measured rate coefficient of $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ is in good agreement with that derived from a Langevin model for an atomic polarizability of 143 a.u.