The study of chemical reactions between ions and neutral species at very low energies reveals precise informations about the dynamics of collisions and fine details of intermolecular interactions. Here, we report progress towards the development of next- generation experiments for the investigation of cold ion-neutral reactions. First, we present a new ''dynamic" hybrid ion-atom trap which enables the study of collisions with a superior energy resolution accessing a regime in which quantum scattering resonances may become observable. Second, we discuss and numerically characterize the concept and properties of a hybrid trap for cold neutral molecules and molecular ions which paves the way for the study of ion-molecule reactions in the millikelvin regime.The study of chemical reactions between ions and neutral species at very low energies reveals precise informations about the dynamics of collisions and fine details of intermolecular interactions. Here, we report progress towards the development of next- generation experiments for the investigation of cold ion-neutral reactions. First, we present a new ''dynamic" hybrid ion-atom trap which enables the study of collisions with a superior energy resolution accessing a regime in which quantum scattering resonances may become observable. Second, we discuss and numerically characterize the concept and properties of a hybrid trap for cold neutral molecules and molecular ions which paves the way for the study of ion-molecule reactions in the millikelvin regime.

Journal of Physics Conference SeriesSep 7, 201515 citations

Cold chemistry with trapped ions

C. D. Ahl, J.M. Hanson, M. Okane +4 more

Bulletin of the American Physical SocietyMay 30, 20180 citations

Ultracold atom-molecular ion systems: a photo-asisted spin-dependent polyatomic chemical reaction

I. Simbotin, John A. Jr. Montgomery, Robin C ot 'e

Bulletin of the American Physical SocietyJun 6, 20170 citations

Cold chemistry in high density atom-ion environments

Jesús Pérez‐Ríos, Artjom Krükow, Amir Mohamadi +4 more

Bulletin of the American Physical SocietyJun 11, 20150 citations

Chemical reactions between cold trapped Ba+ ions and neutral molecules in the gas phase

Bernhard Roth, David Offenberg, C. B. Zhang +1 more

Using a laser-cooled ion trapping apparatus, we have investigated laser-induced chemical reactions between cold trapped ${\mathrm{Ba}}^{+}$ ions and several neutral molecular gases at room temperature, ${\mathrm{O}}_{2}$ , $\mathrm{C}{\mathrm{O}}_{2}$ , and ${\mathrm{N}}_{2}\mathrm{O}$ , leading to the production of cold trapped $(\ensuremath{\approx}20\phantom{\rule{0.3em}{0ex}}\mathrm{mK})$ $\mathrm{Ba}{\mathrm{O}}^{+}$ ions. The $\mathrm{Ba}{\mathrm{O}}^{+}$ ions were converted back to ${\mathrm{Ba}}^{+}$ ions via reaction with room-temperature CO. Reaction rates were determined by employing molecular dynamics simulations. The cold mixed-species ion ensembles produced were used for studying the efficiency of sympathetic cooling, by variation of the ratio of laser-cooled to sympathetically cooled ion numbers. In one extreme case, 20 laser-cooled $^{138}\mathrm{Ba}^{+}$ ions were capable of maintaining the translational temperature of 120 sympathetically cooled barium isotopes $(^{135--137}\mathrm{Ba}^{+})$ and 430 $^{138}\mathrm{Ba}^{16}{\mathrm{O}}^{+}$ molecules at approximately $25\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ .Using a laser-cooled ion trapping apparatus, we have investigated laser-induced chemical reactions between cold trapped ${\mathrm{Ba}}^{+}$ ions and several neutral molecular gases at room temperature, ${\mathrm{O}}_{2}$, $\mathrm{C}{\mathrm{O}}_{2}$, and ${\mathrm{N}}_{2}\mathrm{O}$, leading to the production of cold trapped $(\ensuremath{\approx}20\phantom{\rule{0.3em}{0ex}}\mathrm{mK})$ $\mathrm{Ba}{\mathrm{O}}^{+}$ ions. The $\mathrm{Ba}{\mathrm{O}}^{+}$ ions were converted back to ${\mathrm{Ba}}^{+}$ ions via reaction with room-temperature CO. Reaction rates were determined by employing molecular dynamics simulations. The cold mixed-species ion ensembles produced were used for studying the efficiency of sympathetic cooling, by variation of the ratio of laser-cooled to sympathetically cooled ion numbers. In one extreme case, 20 laser-cooled $^{138}\mathrm{Ba}^{+}$ ions were capable of maintaining the translational temperature of 120 sympathetically cooled barium isotopes $(^{135--137}\mathrm{Ba}^{+})$ and 430 $^{138}\mathrm{Ba}^{16}{\mathrm{O}}^{+}$ molecules at approximately $25\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$.

Physical Review AOct 24, 200828 citations

Ion-molecule chemistry at very low temperatures: cold chemical reactions between Coulomb-crystallized ions and velocity-selected neutral molecules

Martin T. Bell, Alexander D. Gingell, James M. Oldham +2 more

The recent development of a range of techniques for producing cold atoms and molecules at very low translational temperatures T < or = 1 K has provided the opportunity to investigate collisional processes in a new physical regime. We have recently presented a new experimental method to study low-temperature reactive collisions between translationally cold ions and neutral molecules (S. Willitsch et al., Phys. Rev. Lett. 2008, 100, 043203). Our technique relies on the combination of a quadrupole-guide velocity selector for the generation of translationally cold neutral molecules with a facility to produce ordered structures of cold ions (Coulomb crystals) by laser cooling in a linear quadrupole ion trap. The strong localisation of the ions in the trap in combination with the high sensitivity of laser-induced-fluorescence detection enabled us to study chemical reactions on the single-particle level, down to temperatures of T approximately 1 K. In the current paper, we present a detailed characterisation of the scope and limitations of this method based on our study of the reaction between laser-cooled Ca+ ions and velocity-selected CH3F molecules. The properties of our cold-neutrals source and the dependence of the measured rate constant on the shape of the Coulomb crystals, trapping and laser-cooling parameters are discussed. An extension of our technique for the study of low-temperature reactions with sympathetically cooled molecular ions (translational temperature T > 10 mK) is presented and first results on the charge-transfer reaction between OCS+ and ND3 are discussed. Finally, perspectives for further developments of our method are explored.The recent development of a range of techniques for producing cold atoms and molecules at very low translational temperatures T < or = 1 K has provided the opportunity to investigate collisional processes in a new physical regime. We have recently presented a new experimental method to study low-temperature reactive collisions between translationally cold ions and neutral molecules (S. Willitsch et al., Phys. Rev. Lett. 2008, 100, 043203). Our technique relies on the combination of a quadrupole-guide velocity selector for the generation of translationally cold neutral molecules with a facility to produce ordered structures of cold ions (Coulomb crystals) by laser cooling in a linear quadrupole ion trap. The strong localisation of the ions in the trap in combination with the high sensitivity of laser-induced-fluorescence detection enabled us to study chemical reactions on the single-particle level, down to temperatures of T approximately 1 K. In the current paper, we present a detailed characterisation of the scope and limitations of this method based on our study of the reaction between laser-cooled Ca+ ions and velocity-selected CH3F molecules. The properties of our cold-neutrals source and the dependence of the measured rate constant on the shape of the Coulomb crystals, trapping and laser-cooling parameters are discussed. An extension of our technique for the study of low-temperature reactions with sympathetically cooled molecular ions (translational temperature T > 10 mK) is presented and first results on the charge-transfer reaction between OCS+ and ND3 are discussed. Finally, perspectives for further developments of our method are explored.

Faraday DiscussionsJan 1, 200976 citations

Using a laser-cooled ion trapping apparatus, we have investigated laser-induced chemical reactions between cold trapped

{\mathrm{Ba}}^{+}

ions and several neutral molecular gases at room temperature,

{\mathrm{O}}_{2}

\mathrm{C}{\mathrm{O}}_{2}

, and

{\mathrm{N}}_{2}\mathrm{O}

, leading to the production of cold trapped $(\ensuremath{\approx}20\phantom{\rule{0.3em}{0ex}}\mathrm{mK})$

\mathrm{Ba}{\mathrm{O}}^{+}

ions. The

\mathrm{Ba}{\mathrm{O}}^{+}

ions were converted back to

{\mathrm{Ba}}^{+}

ions via reaction with room-temperature CO. Reaction rates were determined by employing molecular dynamics simulations. The cold mixed-species ion ensembles produced were used for studying the efficiency of sympathetic cooling, by variation of the ratio of laser-cooled to sympathetically cooled ion numbers. In one extreme case, 20 laser-cooled

^{138}\mathrm{Ba}^{+}

ions were capable of maintaining the translational temperature of 120 sympathetically cooled barium isotopes

(^{135--137}\mathrm{Ba}^{+})

and 430

^{138}\mathrm{Ba}^{16}{\mathrm{O}}^{+}

molecules at approximately

25\phantom{\rule{0.3em}{0ex}}\mathrm{mK}