Estimates of Collisional Cooling and Quenching Rates for Atomic and Molecular Ion Collisions with Ultracold Atoms. WINTHROP SMITH, JAMES WELLS, University of Connecticut | Translational cross sections and rate

Collision cross sections and rate constants between two ground-state oxygen molecules are investigated theoretically at translational energies below $\ensuremath{\sim}1$ K and in zero magnetic field. We present calculations for elastic and spin-changing inelastic collision rates for different isotopic combinations of oxygen atoms as a prelude to understanding their collisional stability in ultracold magnetic traps. A numerical analysis has been made in the framework of a rigid-rotor model that accounts fully for the singlet, triplet, and quintet potential-energy surfaces in this system. The results offer insights into the effectiveness of evaporative cooling and the properties of molecular Bose-Einstein condensates, as well as estimates of collisional lifetimes in magnetic traps. Specifically, ${}^{17}{\mathrm{O}}_{2}$ looks like a good candidate for ultracold studies, while ${}^{16}{\mathrm{O}}_{2}$ is unlikely to survive evaporative cooling. Since ${}^{17}{\mathrm{O}}_{2}$ is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.Collision cross sections and rate constants between two ground-state oxygen molecules are investigated theoretically at translational energies below $\ensuremath{\sim}1$ K and in zero magnetic field. We present calculations for elastic and spin-changing inelastic collision rates for different isotopic combinations of oxygen atoms as a prelude to understanding their collisional stability in ultracold magnetic traps. A numerical analysis has been made in the framework of a rigid-rotor model that accounts fully for the singlet, triplet, and quintet potential-energy surfaces in this system. The results offer insights into the effectiveness of evaporative cooling and the properties of molecular Bose-Einstein condensates, as well as estimates of collisional lifetimes in magnetic traps. Specifically, ${}^{17}{\mathrm{O}}_{2}$ looks like a good candidate for ultracold studies, while ${}^{16}{\mathrm{O}}_{2}$ is unlikely to survive evaporative cooling. Since ${}^{17}{\mathrm{O}}_{2}$ is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.

arXiv:physics/0105085Physical Review AOct 2, 200166 citations

Model for collisions in ultracold-atom mixtures (9 pages)

D. Ciampini, Marco Anderlini

Physical Review AJan 1, 20050 citations

Radiative charge-transfer lifetime of the excited state of (NaCa)+

Oleg P. Makarov, Robin Côté, H. H. Michels +1 more

New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom--ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled ${\mathrm{Ca}}^{+}$ ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet $A{}^{1}{\ensuremath{\Sigma}}^{+}$ state of the $(\mathrm{NaCa}{)}^{+}$ molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and M\"oller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G $(3df).$ The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{sec},$ while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher $(1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{cm}}^{3}/\mathrm{sec}$ and $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}{\mathrm{cm}}^{3}/\mathrm{sec},$ respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer.New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom--ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled ${\mathrm{Ca}}^{+}$ ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet $A{}^{1}{\ensuremath{\Sigma}}^{+}$ state of the $(\mathrm{NaCa}{)}^{+}$ molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and M\"oller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G $(3df).$ The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{sec},$ while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher $(1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{cm}}^{3}/\mathrm{sec}$ and $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}{\mathrm{cm}}^{3}/\mathrm{sec},$ respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer.

arXiv:physics/0209077Physical Review AApr 11, 200392 citations

Universal reaction rates for ultracold molecular collisions

Paul S. Julienne, Zbigniew Idziaszek

Bulletin of the American Physical SocietyMay 27, 20100 citations

Reactive collisions of trapped anions with ultracold atoms

Johannes Deiglmayr, A. Göritz, Th. Best +2 more

We present a scheme to embed molecular anions in a gas of ultracold rubidium atoms as a route towards the preparation of cold molecular ions by collisional cooling with ultracold atoms. Associative detachment as an important loss process in collisions between OH${}^{\ensuremath{-}}$ molecules and rubidium atoms is studied. The density distribution of trapped negative ions in the multipole radio frequency trap is measured by photodetachment tomography, which allows us to derive absolute rate coefficients for the process. We define a regime where translational and internal cooling of molecular ions embedded into the ultracold atomic cloud can be achieved.We present a scheme to embed molecular anions in a gas of ultracold rubidium atoms as a route towards the preparation of cold molecular ions by collisional cooling with ultracold atoms. Associative detachment as an important loss process in collisions between OH${}^{\ensuremath{-}}$ molecules and rubidium atoms is studied. The density distribution of trapped negative ions in the multipole radio frequency trap is measured by photodetachment tomography, which allows us to derive absolute rate coefficients for the process. We define a regime where translational and internal cooling of molecular ions embedded into the ultracold atomic cloud can be achieved.

arXiv:1211.2436Physical Review AOct 31, 201258 citations

{}^{17}{\mathrm{O}}_{2}

looks like a good candidate for ultracold studies, while

{}^{16}{\mathrm{O}}_{2}

is unlikely to survive evaporative cooling. Since

{}^{17}{\mathrm{O}}_{2}

is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.

{\mathrm{Ca}}^{+}

ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet $A{}^{1}{\ensuremath{\Sigma}}^{+}$ state of the

(\mathrm{NaCa}{)}^{+}

molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and M\"oller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G

(3df).

The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{sec},$ while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher $(1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{cm}}^{3}/\mathrm{sec}$ and $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}{\mathrm{cm}}^{3}/\mathrm{sec},$ respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer.