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

Communications Physics

Long-term trapping of Stark-decelerated molecules

Dominik Haas, Claudio von Planta, Thomas Kierspel, Dongdong Zhang, Stefan Willitsch

Published Aug 29, 2019• 15 citations
Publisher

Abstract

Abstract Trapped cold molecules represent attractive systems for precision-spectroscopic studies and for investigations of cold collisions and chemical reactions. However, achieving their confinement for sufficiently long timescales remains a challenge. Here, we report the long-term trapping of Stark-decelerated OH radicals in their X2Π3/2 (ν = 0, J = 3/2, MJ = 3/2, f) state in a permanent magnetic trap. The trap environment is cryogenically cooled to a temperature of 17 K to suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetime. The cold molecules are thus confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared with room temperature experiments, at translational temperatures of ∼25 mK. The present results pave the way for new experiments using trapped cold molecules in precision spectroscopy, in studies of slow chemical processes at low energies and in the quantum technologies.

DOI
10.1038/s42005-019-0199-4

Related papers

A Cryogenic Molecular Ion-Neutral Hybrid Trap

Claudio von Planta

A hybrid trap was developed to confine neutral molecules and molecular ions. We demonstrated the long-term trapping of Stark-decelerated OH radicals in the X 2Pi3/2 (v = 0, J = 3/2, MJ = 3/2, f) state in a permanent magnetic trap. The trap environment was cryogenically cooled to a temperature of 17 K in order to efficiently suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetimes. The cold molecules were kept confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared to room-temperature experiments, at translational temperatures on the order of 25 mK. A cryogenic ion trap was built and laser cooled Ca+ ions were confined. This ion trap can be used to confine sympathetically cooled molecular ions such as N+2or H2O+. Furthermore, a mechanism to superimpose both trap centers by moving the permanent magnets from the magnetic trap over the ion trap was developed. Both traps were characterized and their functionality was proven. The challenges of lasercooling in the strong magnetic field gradients were discussed. The present results pave the way for investigations of cold collisions and reactions with very small reaction rates between molecular ions and neutral molecules, for new avenues for the production of ultracold molecules via sympathetic cooling and for the realization of new forms of hybrid matter with co-trapped atoms or ions.

•Jan 1, 2020•0 citations

Cold Polar Molecules for Novel Collision Experiments at Low Energies

Brian C. Sawyer

Research in the field of cold polar molecules is progressing rapidly. An array of interesting\ntopics is being developed including precision measurement and fundamental tests, quantum phase transitions, and ultracold chemistry. In particular, dipolar molecules in well-defined quantum states enable exquisite control of their interactions via applied electric fields. The long-range, anisotropic interaction between dipolar molecules leads to new collision dynamics that could be used for novel collective effects, quantum state engineering, and information processing. The focus of this Thesis is the production of cold samples of neutral OH molecules via Stark deceleration and magnetic trapping for novel collision experiments. This novelty results from our combination of cold external beams and trapped target molecules which facilitates observation of dipolar effects as well as low temperature collision resonances. The large permanent electric dipole moment of OH allows us to precisely tune the lab-frame velocity of the molecular packets from ∼ 500 m/s to rest. We have magnetically trapped OH packets at the terminus of our Stark decelerator at a temperature of 70 mK and density of 106 cm−3. With improved understanding of Stark deceleration, we optimize the decelerator efficiency and its coupling to the magnetic trap. Our latest trap design uses permanent ring magnets to create a three-dimensional magnetic quadrupole field. Use of magnetically trapped OH molecules for collision experiments with external beams allow us the unique opportunity of observing both elastic and inelastic collisions. In addition, the trap confinement yields sensitivity to differential elastic cross sections at low collision energies. This open magnetic trap has allowed measurement of collision cross sections between trapped OH and external supersonic beams of He and D2, the latter of which is of astrophysical interest due to the role of H2-OH collisions in pumping interstellar OH megamasers. The combination of trapped OH molecules and temperature tuned beams of He and D2 has facilitated measurement of the lowest-energy D2-OH collision cross sections yet reported. More recently, we report the first observation of electric-field dependent cross sections between two different species of cold polar molecules - OH and ND3 - thereby demonstrating control over molecular scattering in the cold regime. By combining for the first time the production techniques of Stark deceleration and buffer gas cooling, we increase the molecular interaction time by∼ 105 over traditional crossed-beam experiments to gain enhanced sensitivity at the characteristic densities of cold molecule production.

•Jan 1, 2010•2 citations

Production, Deceleration, and Detection of OH Radicals

Travis Briles

Samples of cold and ultracold polar molecules have the potential to revolutionize physical chemistry, precision measurement, and few-body quantum physics. This thesis describes experimental results for the production of cold samples of OH radicals by Stark deceleration of a supersonic beam. Since Stark deceleration cannot increase the phase space density of the sample, the initial production stage of the OH molecule is critical. The first set of experiments describes a general methodology for the production of OH beams with maximal phase space density, as well as the subsequent coupling to a Stark decelerator. Additionally, we describe the redesign of our electrostatic trap, optimized for future collision experiments of OH with co-trapped ultracold Rb atoms. The new design resulted in a 15-fold increase in total number of trapped molecules over the previous design when tested with ND3 molecules. The second set of experiments focuses on laser-based detection of OH molecules at the exit of the decelerator based on laser induced fluorescence (LIF) and resonance enhanced multiphoton ionizaton (REMPI). The latter method uses vacuum-ultraviolet light at 118nm produced by third-harmonic generation in Xe/Ar gas mixtures as the ionizing step. The sensitivity of this latter technique is limited by the attainable photon flux of the ionizing radiation at 118nm. We present detailed measurements of the conversion efficiencies as well as absolute photon fluxes. Strategies to overcome these limitations as well as prospects for detection of OH molecules in a trap are discussed.

•Jan 1, 2015•0 citations

Magnetic Trapping of Cold Methyl Radicals

Yang Liu, Manish Vashishta, Pavle Djuricanin +5 more

We have demonstrated that a supersonic beam of methyl radicals (CH_{3}) in the ground rotational state of both para and ortho species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for >1 s. The trapped CH_{3} radicals have a mean translational temperature of about 200 mK with an estimated density of >5.0×10^{7} cm^{-3}. The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.

arXiv:1609.07735•Physical Review Letters•Feb 27, 2017•63 citations

Molecular Beam Collisions with a Magnetically Trapped Target

Brian C. Sawyer, Benjamin Stuhl, Dajun Wang +2 more

Cold, neutral hydroxyl radicals are Stark decelerated and efficiently loaded into a permanent magnetic trap. The OH molecules are trapped in the rovibrational ground state at a density of $\ensuremath{\sim}{10}^{6}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$ and temperature of 70 mK. Collision studies between the trapped OH sample and supersonic beams of atomic He and molecular ${\mathrm{D}}_{2}$ determine absolute collision cross sections. The He-OH and ${\mathrm{D}}_{2}\mathrm{\text{\ensuremath{-}}}\mathrm{OH}$ center-of-mass collision energies are tuned from $60\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ to $230\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ and $145\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ to $510\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$, respectively, yielding evidence of quantum threshold scattering and resonant energy transfer between colliding particles.

arXiv:0806.2624•Physical Review Letters•Nov 14, 2008•113 citations

OH Trapped by Magnets

Confining atoms with a combination of optical and magnetic fields has led to the formation of new states of matter and provided a tunable test bed to explore many-body atomic and electronic interactions; however, its extension to molecules has been slow. Ultracold molecules (milikelvin temperatures and below) are of interest for a number of additional applications, including studies of quantum phase transitions and precision spectroscopy. One approach to confining polar molecules has relied on inhomogeneous electric fields. Sawyer et al. present an alternative method that traps molecules magnetically. They demonstrate the technique on hydroxyl (OH) radicals, which have appreciable magnetic as well as electric dipole moments. Lifetimes in the magnetoelectrostatic trap ranged from 20 to 500 ms, depending on the background pressure. The technique allows the additional degree of freedom of an electrical field to be superimposed onto the trapped molecules and should facilitate further studies in the direction of controlled molecular collisions and chemical reactions. — ISO

Science•Jul 12, 2007•0 citations
Abstract Trapped cold molecules represent attractive systems for precision-spectroscopic studies and for investigations of cold collisions and chemical reactions. However, achieving their confinement for sufficiently long timescales remains a challenge. Here, we report the long-term trapping of Stark-decelerated OH radicals in their X2Π3/2 (ν = 0, J = 3/2, MJ = 3/2, f) state in a permanent magnetic trap. The trap environment is cryogenically cooled to a temperature of 17 K to suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetime. The cold molecules are thus confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared with room temperature experiments, at translational temperatures of ∼25 mK. The present results pave the way for new experiments using trapped cold molecules in precision spectroscopy, in studies of slow chemical processes at low energies and in the quantum technologies.
A hybrid trap was developed to confine neutral molecules and molecular ions. We demonstrated the long-term trapping of Stark-decelerated OH radicals in the X 2Pi3/2 (v = 0, J = 3/2, MJ = 3/2, f) state in a permanent magnetic trap. The trap environment was cryogenically cooled to a temperature of 17 K in order to efficiently suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetimes. The cold molecules were kept confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared to room-temperature experiments, at translational temperatures on the order of 25 mK. A cryogenic ion trap was built and laser cooled Ca+ ions were confined. This ion trap can be used to confine sympathetically cooled molecular ions such as N+2or H2O+. Furthermore, a mechanism to superimpose both trap centers by moving the permanent magnets from the magnetic trap over the ion trap was developed. Both traps were characterized and their functionality was proven. The challenges of lasercooling in the strong magnetic field gradients were discussed. The present results pave the way for investigations of cold collisions and reactions with very small reaction rates between molecular ions and neutral molecules, for new avenues for the production of ultracold molecules via sympathetic cooling and for the realization of new forms of hybrid matter with co-trapped atoms or ions.
Research in the field of cold polar molecules is progressing rapidly. An array of interesting\ntopics is being developed including precision measurement and fundamental tests, quantum phase transitions, and ultracold chemistry. In particular, dipolar molecules in well-defined quantum states enable exquisite control of their interactions via applied electric fields. The long-range, anisotropic interaction between dipolar molecules leads to new collision dynamics that could be used for novel collective effects, quantum state engineering, and information processing. The focus of this Thesis is the production of cold samples of neutral OH molecules via Stark deceleration and magnetic trapping for novel collision experiments. This novelty results from our combination of cold external beams and trapped target molecules which facilitates observation of dipolar effects as well as low temperature collision resonances. The large permanent electric dipole moment of OH allows us to precisely tune the lab-frame velocity of the molecular packets from ∼ 500 m/s to rest. We have magnetically trapped OH packets at the terminus of our Stark decelerator at a temperature of 70 mK and density of 106 cm−3. With improved understanding of Stark deceleration, we optimize the decelerator efficiency and its coupling to the magnetic trap. Our latest trap design uses permanent ring magnets to create a three-dimensional magnetic quadrupole field. Use of magnetically trapped OH molecules for collision experiments with external beams allow us the unique opportunity of observing both elastic and inelastic collisions. In addition, the trap confinement yields sensitivity to differential elastic cross sections at low collision energies. This open magnetic trap has allowed measurement of collision cross sections between trapped OH and external supersonic beams of He and D2, the latter of which is of astrophysical interest due to the role of H2-OH collisions in pumping interstellar OH megamasers. The combination of trapped OH molecules and temperature tuned beams of He and D2 has facilitated measurement of the lowest-energy D2-OH collision cross sections yet reported. More recently, we report the first observation of electric-field dependent cross sections between two different species of cold polar molecules - OH and ND3 - thereby demonstrating control over molecular scattering in the cold regime. By combining for the first time the production techniques of Stark deceleration and buffer gas cooling, we increase the molecular interaction time by∼ 105 over traditional crossed-beam experiments to gain enhanced sensitivity at the characteristic densities of cold molecule production.
Samples of cold and ultracold polar molecules have the potential to revolutionize physical chemistry, precision measurement, and few-body quantum physics. This thesis describes experimental results for the production of cold samples of OH radicals by Stark deceleration of a supersonic beam. Since Stark deceleration cannot increase the phase space density of the sample, the initial production stage of the OH molecule is critical. The first set of experiments describes a general methodology for the production of OH beams with maximal phase space density, as well as the subsequent coupling to a Stark decelerator. Additionally, we describe the redesign of our electrostatic trap, optimized for future collision experiments of OH with co-trapped ultracold Rb atoms. The new design resulted in a 15-fold increase in total number of trapped molecules over the previous design when tested with ND3 molecules. The second set of experiments focuses on laser-based detection of OH molecules at the exit of the decelerator based on laser induced fluorescence (LIF) and resonance enhanced multiphoton ionizaton (REMPI). The latter method uses vacuum-ultraviolet light at 118nm produced by third-harmonic generation in Xe/Ar gas mixtures as the ionizing step. The sensitivity of this latter technique is limited by the attainable photon flux of the ionizing radiation at 118nm. We present detailed measurements of the conversion efficiencies as well as absolute photon fluxes. Strategies to overcome these limitations as well as prospects for detection of OH molecules in a trap are discussed.
We have demonstrated that a supersonic beam of methyl radicals (CH_{3}) in the ground rotational state of both para and ortho species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for >1 s. The trapped CH_{3} radicals have a mean translational temperature of about 200 mK with an estimated density of >5.0×10^{7} cm^{-3}. The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.
Cold, neutral hydroxyl radicals are Stark decelerated and efficiently loaded into a permanent magnetic trap. The OH molecules are trapped in the rovibrational ground state at a density of $\ensuremath{\sim}{10}^{6}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$ and temperature of 70 mK. Collision studies between the trapped OH sample and supersonic beams of atomic He and molecular D2{\mathrm{D}}_{2}D2​ determine absolute collision cross sections. The He-OH and ${\mathrm{D}}_{2}\mathrm{\text{\ensuremath{-}}}\mathrm{OH}$ center-of-mass collision energies are tuned from $60\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ to $230\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ and $145\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ to $510\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$, respectively, yielding evidence of quantum threshold scattering and resonant energy transfer between colliding particles.
Confining atoms with a combination of optical and magnetic fields has led to the formation of new states of matter and provided a tunable test bed to explore many-body atomic and electronic interactions; however, its extension to molecules has been slow. Ultracold molecules (milikelvin temperatures and below) are of interest for a number of additional applications, including studies of quantum phase transitions and precision spectroscopy. One approach to confining polar molecules has relied on inhomogeneous electric fields. Sawyer et al. present an alternative method that traps molecules magnetically. They demonstrate the technique on hydroxyl (OH) radicals, which have appreciable magnetic as well as electric dipole moments. Lifetimes in the magnetoelectrostatic trap ranged from 20 to 500 ms, depending on the background pressure. The technique allows the additional degree of freedom of an electrical field to be superimposed onto the trapped molecules and should facilitate further studies in the direction of controlled molecular collisions and chemical reactions. — ISO