arXiv:1608.07043 · Physical Review A

Characterization of charge-exchange collisions between ultracold Li6 atoms and Ca40+ ions

Ryoichi Saito, Shinsuke Haze, Mizuki Sasakawa, R. Nakai, Maurice Raoult, Humberto da Silva, Olivier Dulieu, Takashi Mukaiyama

Published Mar 31, 2017• 48 citations

arXiv HTML PDF

Abstract

We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of $^{6}\mathrm{Li}$ atoms and ${^{40}\mathrm{Ca}}^{+}$ ions. Deliberately excited ion micromotion is used to control collision energy of atoms and ions. The energy dependence of the charge-exchange collision cross section obeys the Langevin model in the temperature range of the current experiment, and the measured magnitude of the cross section is correlated to the internal state of the ${^{40}\mathrm{Ca}}^{+}$ ions. Revealing the relationship between the charge-exchange collision cross sections and the interaction potentials is an important step toward the realization of the full quantum control of the chemical reactions at an ultralow-temperature regime.

DOI: 10.1103/physreva.95.032709

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arXiv:1608.07043 · Physical Review A

Characterization of charge-exchange collisions between ultracold Li6 atoms and Ca40+ ions

Ryoichi Saito, Shinsuke Haze, Mizuki Sasakawa, R. Nakai, Maurice Raoult, Humberto da Silva, Olivier Dulieu, Takashi Mukaiyama

Published Mar 31, 2017• 48 citations

arXiv HTML PDF

Abstract

We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of

^{6}\mathrm{Li}

atoms and

{^{40}\mathrm{Ca}}^{+}

ions. Deliberately excited ion micromotion is used to control collision energy of atoms and ions. The energy dependence of the charge-exchange collision cross section obeys the Langevin model in the temperature range of the current experiment, and the measured magnitude of the cross section is correlated to the internal state of the

{^{40}\mathrm{Ca}}^{+}

ions. Revealing the relationship between the charge-exchange collision cross sections and the interaction potentials is an important step toward the realization of the full quantum control of the chemical reactions at an ultralow-temperature regime.

DOI: 10.1103/physreva.95.032709

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We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of

^{6}\mathrm{Li}

atoms and

{^{40}\mathrm{Ca}}^{+}

{^{40}\mathrm{Ca}}^{+}

Charge-exchange collisions between ultracold fermionic

^{6}\mathrm{Li}

atoms and

^{40}\mathrm{Ca}^{+}

ions are observed in the millikelvin temperature range. The reaction product of the charge-exchange collision is identified via mass spectrometry during which the motion of the ions is excited parametrically. The cross sections of the charge-exchange collisions between

^{6}\mathrm{Li}

atoms in the ground state and

^{40}\mathrm{Ca}^{+}

ions in the ground and metastable excited states are determined. Investigation of the inelastic collision characteristics in the atom-ion mixture is an important step toward ultracold chemistry based on ultracold atoms and ions.

Studies of charge transfer and total cross sections in elastic collisions of atom-ion alkali metals at ultralow temperatures are reported. Calculations for

\mathrm{Na}+{\mathrm{Na}}^{+}

have been carried out with the best available ${}^{2}{\ensuremath{\Sigma}}_{g}^{+}$ and ${}^{2}{\ensuremath{\Sigma}}_{u}^{+}$ potential curves. As functions of energy, the cross sections show considerable structure and are large in the limit of low temperature. The scattering lengths were also computed, and the effective range expansion verified. For higher temperatures, we compare quantal and semiclassical results, and investigate the range of applicability of the Langevin formula. Even at temperatures of a few degrees kelvin, the charge-transfer cross sections are large, and could provide an efficient way to produce cold ions.

\\text{Na}-\\text{Ca}^+

system, including measurements of sympathetic cooling and charge-exchange rates which change as a function of energy and molecular state. The quantum-state distributions of Na in our magneto-optical trap is also explored, as well as its agreement and subsequent deviation based on a predictive model. The measurements of reaction rate reveal that there are reaction-energy thresholds in two separate reaction pathways, which can be attributed to either an endothermic reaction pathway or an activation barrier due to quantum-mechanical interactions.