Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2210.02112 · Physical Review A

Number-resolved detection of dark ions in Coulomb crystals

Fabian Schmid, Johannes Weitenberg, Jorge Moreno, Theodor W. Hänsch, Thomas Udem, Akira Ozawa

Published Oct 4, 2022• 6 citations
arXivHTMLPDF

Abstract

Trapped ions without a suitable transition for laser cooling can be sympathetically cooled by embedding them in a Coulomb crystal of laser-cooled ions of another species. The authors demonstrate a method for identifying and counting such embedded ions in real time, which can be used for precision spectroscopy and for the study of ion-neutral chemical reactions.

DOI
10.1103/physreva.106.l041101

Related papers

Chemical applications of laser- and sympathetically-cooled ions in ion traps

Stefan Willitsch, Martin T. Bell, Alexander D. Gingell +1 more

Ensembles of cold atomic and molecular ions in ion traps prepared at millikelvin temperatures by laser and sympathetic cooling have recently found considerable interest in both physics and chemistry. At very low temperatures the ions form ordered structures in the trap also known as "Coulomb crystals". Ion Coulomb crystals exhibit a range of intriguing properties which render them attractive systems for novel experiments in chemical dynamics, ultrahigh-resolution spectroscopy and quantum-information processing. In this article we review the methods used to prepare atomic and molecular ion Coulomb crystals and discuss some recent studies in mass spectrometry, low-temperature chemistry and precision spectroscopy to illustrate their scientific potential for chemical applications. Finally, we conclude with an outlook on outstanding challenges and prospective further developments in the field.

Physical Chemistry Chemical Physics•Jan 1, 2008•146 citations

Spectroscopy of Molecular Ions in Coulomb Crystals

Aaron T. Calvin, Kenneth R. Brown

In this Perspective, we examine the use of laser-cooled atomic ions and sympathetically cooled molecular ions in Coulomb crystals for molecular spectroscopy. Coulomb crystals are well-isolated environments that provide localization and long storage times for sensitive measurements of weak signals and cold temperatures for precise spectroscopy. Coulomb crystals of molecular and atomic ions enable the detection of single-photon molecular ion transitions at a range of wavelengths by a change in atomic ion fluorescence at visible wavelengths. We give an overview of the state of the art from action spectroscopy to quantum logic spectroscopy for a wide range of molecular transitions from rotational sublevels separated by 10 –7 cm –1 to rovibronic transitions at 25 000 cm –1 . We emphasize how this system allows for unparalleled control of the molecular ion state for precision spectroscopy with applications in astrochemistry and fundamental physics. We conclude with an outlook of the use of this control in cold molecular ion reactions.

The Journal of Physical Chemistry Letters•Sep 13, 2018•19 citations

Sympathetic cooling and detection of a hot trapped ion by a cold one

M Guggemos, D. Heinrich, O. A. Herrera-Sancho +2 more

We investigate the dynamics of an ion sympathetically cooled by another laser-cooled ion or small ion crystal. To this end, we develop simple models of the cooling dynamics in the limit of weak Coulomb interactions. Experimentally, we create a two-ion crystal of Ca + and Al + by photo-ionization of neutral atoms produced by laser ablation. We characterize the velocity distribution of the laser-ablated atoms crossing the trap by time-resolved fluorescence spectroscopy. We observe neutral atom velocities much higher than the ones of thermally heated samples and find as a consequence long sympathethic cooling times before crystallization occurs. Our key result is a new technique for detecting the loading of an initially hot ion with energy in the eV range by monitoring the motional state of a Doppler-cooled ion already present in the trap. This technique not only detects the ion but also provides information about the dynamics of the sympathetic cooling process.

arXiv:1507.07761•New Journal of Physics•Sep 30, 2015•40 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.

Faraday Discussions•Jan 1, 2009•76 citations

Quantum memory for light based on ion coulomb crystals

Peter F. Herskind, A. Mortensen, E.S. Nielsen +2 more

The authors report on the stored light in an ion Coulomb crystal coupled to a relatively low finesse optical resonator. A two-species ion Coulomb crystal is employed in a linear Paul trap, where the laser cooled heavier ion-component sympathetically cools the lighter ion-component.

European Quantum Electronics Conference (EQEC)•Jan 18, 2006•0 citations

Chemistry Using Coulomb Crystals

Brianna R. Heazlewood, Heather J. Lewandowski

Laser cooling of atomic ions has long been used as a tool in physics to explore quantum entanglement for applications in quantum computing and information. More recently, laser-cooled atomic ions have been used as a platform for studying cold chemistry. Here, we describe an experimental system called a “Coulomb crystal,” where laser-cooled ions are confined in traps at sufficiently low translational energies that they form an ordered structure. We then present a range of experiments undertaken using this platform, from studies of reactions with an atomic species to reaction systems of increased complexity, involving molecular ions and neutral molecules. We also describe a few spectroscopic studies enabled by Coulomb crystals before discussing some possible future directions of the field. This is not meant to be a comprehensive review of the entire field, but rather a sampling of the types of experiments that can be performed and the knowledge gained from these studies.

ACS symposium series•Oct 27, 2021•8 citations
Trapped ions without a suitable transition for laser cooling can be sympathetically cooled by embedding them in a Coulomb crystal of laser-cooled ions of another species. The authors demonstrate a method for identifying and counting such embedded ions in real time, which can be used for precision spectroscopy and for the study of ion-neutral chemical reactions.
Ensembles of cold atomic and molecular ions in ion traps prepared at millikelvin temperatures by laser and sympathetic cooling have recently found considerable interest in both physics and chemistry. At very low temperatures the ions form ordered structures in the trap also known as "Coulomb crystals". Ion Coulomb crystals exhibit a range of intriguing properties which render them attractive systems for novel experiments in chemical dynamics, ultrahigh-resolution spectroscopy and quantum-information processing. In this article we review the methods used to prepare atomic and molecular ion Coulomb crystals and discuss some recent studies in mass spectrometry, low-temperature chemistry and precision spectroscopy to illustrate their scientific potential for chemical applications. Finally, we conclude with an outlook on outstanding challenges and prospective further developments in the field.
In this Perspective, we examine the use of laser-cooled atomic ions and sympathetically cooled molecular ions in Coulomb crystals for molecular spectroscopy. Coulomb crystals are well-isolated environments that provide localization and long storage times for sensitive measurements of weak signals and cold temperatures for precise spectroscopy. Coulomb crystals of molecular and atomic ions enable the detection of single-photon molecular ion transitions at a range of wavelengths by a change in atomic ion fluorescence at visible wavelengths. We give an overview of the state of the art from action spectroscopy to quantum logic spectroscopy for a wide range of molecular transitions from rotational sublevels separated by 10 –7 cm –1 to rovibronic transitions at 25 000 cm –1 . We emphasize how this system allows for unparalleled control of the molecular ion state for precision spectroscopy with applications in astrochemistry and fundamental physics. We conclude with an outlook of the use of this control in cold molecular ion reactions.
We investigate the dynamics of an ion sympathetically cooled by another laser-cooled ion or small ion crystal. To this end, we develop simple models of the cooling dynamics in the limit of weak Coulomb interactions. Experimentally, we create a two-ion crystal of Ca + and Al + by photo-ionization of neutral atoms produced by laser ablation. We characterize the velocity distribution of the laser-ablated atoms crossing the trap by time-resolved fluorescence spectroscopy. We observe neutral atom velocities much higher than the ones of thermally heated samples and find as a consequence long sympathethic cooling times before crystallization occurs. Our key result is a new technique for detecting the loading of an initially hot ion with energy in the eV range by monitoring the motional state of a Doppler-cooled ion already present in the trap. This technique not only detects the ion but also provides information about the dynamics of the sympathetic cooling process.
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.
Laser cooling of atomic ions has long been used as a tool in physics to explore quantum entanglement for applications in quantum computing and information. More recently, laser-cooled atomic ions have been used as a platform for studying cold chemistry. Here, we describe an experimental system called a “Coulomb crystal,” where laser-cooled ions are confined in traps at sufficiently low translational energies that they form an ordered structure. We then present a range of experiments undertaken using this platform, from studies of reactions with an atomic species to reaction systems of increased complexity, involving molecular ions and neutral molecules. We also describe a few spectroscopic studies enabled by Coulomb crystals before discussing some possible future directions of the field. This is not meant to be a comprehensive review of the entire field, but rather a sampling of the types of experiments that can be performed and the knowledge gained from these studies.