Sympathetic cooling of molecular ions with ultracold atoms

Abstract

Sympathetic cooling of molecular ions with ultracold gases is enabling a new era of research in chemistry and physics. There has been much progress in this new field in the last several years and many unanticipated challenges have been overcome. The aim of the present manuscript is to provide a concise review of this work and discuss the way forward for the field.

Engineering Excited-State Interactions at Ultracold Temperatures

“…Finally, the reaction blockading effect observed and controlled here is extremely important for the growing field of hybrid atom-ion trapping, where sympathetic cooling of ions with laser-cooled atoms is being pursued [21,35]. The existence of this reaction blockading effect means that detrimental chemical reactions from excited atomic states, which are energetically unavoidable, will not occur during the sympathetic cooling process.…”

Studying fundamental physics using quantum enabled technologies with trapped molecular ions

“…Using an astute selective photo-ionization scheme combined with sympathetic cooling it has been possible to produce samples of rotationally and vibrationally state-selected, translationally cold molecular ions (64 ). We also note that alternative strategies are promising: the reader will find a recent review of sympathetic cooling of molecular ions by ultra-cold neutral atoms in (65 ). 12 Precise spectroscopic measurements with molecules have indeed increasingly been used in the last decade to test fundamental symmetries (parity (66 , 67 ), or parity and time-reversal, a signature of which would be the existence of a non-zero electron EDM, see note 1 ) and postulates of quantum mechanics (68 ), to measure either absolute values of fundamental constants (such as the Boltzmann constant k B (69 , 70 ), or the protonto-electron mass ratio µ, with recently the first determination of µ from a molecular system (71 )), or their variation in time (fine structure constant α (72 ), proton-to-electron mass ratio µ, see note 2 ) 13 Over the last few years, several techniques for the production of molecular ions have emerged and are reviewed in (65 ).…”

“…We also note that alternative strategies are promising: the reader will find a recent review of sympathetic cooling of molecular ions by ultra-cold neutral atoms in (65 ). 12 Precise spectroscopic measurements with molecules have indeed increasingly been used in the last decade to test fundamental symmetries (parity (66 , 67 ), or parity and time-reversal, a signature of which would be the existence of a non-zero electron EDM, see note 1 ) and postulates of quantum mechanics (68 ), to measure either absolute values of fundamental constants (such as the Boltzmann constant k B (69 , 70 ), or the protonto-electron mass ratio µ, with recently the first determination of µ from a molecular system (71 )), or their variation in time (fine structure constant α (72 ), proton-to-electron mass ratio µ, see note 2 ) 13 Over the last few years, several techniques for the production of molecular ions have emerged and are reviewed in (65 ). The technique pioneered by the Drewsen group consists in first trapping an atomic ion of interest, usually produced by ionization of a neutral atomic gas, and then leaking in neutral molecular gas to react with the atomic ions and produce the desired molecular ions (22 ).…”

A hybrid ion-atom trap with integrated high resolution mass spectrometer

“…Ion-atom hybrid traps are also proposed to attain the rovibrational ground state of molecular ions 20 . The rich internal structure of molecules makes them well suited for precision experiments such as time variation of fundamental constants 21 , precise measurement of the electron's electric dipole moment 22 and study of parity violation 23 .…”

“…One can expect more efficient rotational cooling using interactions with laser cooled atoms. This technique is independent of the molecular ion species as it does not involve any resonance phenomena 20 . One of the goals of our ion-atom hybrid trap presented in this manuscript involves realizing CaH + molecular ions in their internal and external ground state.…”