1
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Nötzold M, Wild R, Lochmann C, Rahim T, Melath SP, Dulitz K, Mant B, Franz J, Gianturco FA, Wester R. Vibrational Quenching of Optically Pumped Carbon Dimer Anions. PHYSICAL REVIEW LETTERS 2023; 131:183002. [PMID: 37977634 DOI: 10.1103/physrevlett.131.183002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 08/08/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023]
Abstract
Careful control of quantum states is a gateway to research in many areas of science such as quantum information, quantum-controlled chemistry, and astrophysical processes. Precise optical control of molecular ions remains a challenge due to the scarcity of suitable level schemes, and direct laser cooling has not yet been achieved for either positive or negative molecular ions. Using a cryogenic wire trap, we show how the internal quantum states of C_{2}^{-} anions can be manipulated using optical pumping and inelastic quenching collisions with H_{2} gas. We obtained optical pumping efficiencies of about 96% into the first vibrational level of C_{2}^{-} and determined the absolute inelastic rate coefficient from v=1 to 0 to be k_{q}=(3.2±0.2_{stat}±1.3_{sys})×10^{-13} cm^{3}/s at 20(3) K, over 3 orders of magnitude smaller than the capture limit. Reduced-dimensional quantum scattering calculations yield a small rate coefficient as well, but significantly larger than the experimental value. Using optical pumping and inelastic collisions, we also realized fluorescence imaging of negative molecular ions. Our work demonstrates high control of a cold ensemble of C_{2}^{-}, providing a solid foundation for future work on laser cooling of molecular ions.
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Affiliation(s)
- Markus Nötzold
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Robert Wild
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Christine Lochmann
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tanja Rahim
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Sruthi Purushu Melath
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Katrin Dulitz
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Barry Mant
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Jan Franz
- Faculty of Applied Physics and Mathematics and Advanced Materials Center, Gdańsk University of Technology, 80-233 Gdańsk, Poland
| | - Francesco A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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2
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Ladjimi H, Zrafi W, Farjallah M, Bejaoui M, Berriche H. Electronic structure, cold ion-atom elastic collision properties and possibility of laser cooling of BeCs + molecular ion. Phys Chem Chem Phys 2022; 24:18511-18522. [PMID: 35894602 DOI: 10.1039/d2cp00808d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The BeCs+ system represents a possible future candidate for the realization of samples of cold or ultra-cold molecular ion species that have not yet been investigated experimentally or theoretically. With the aim of highlighting the spectroscopic and electronic structure of the cesium and beryllium cation BeCs+, we theoretically investigate ground and low lying excited states of 1,3Σ+, 1,3Π and 1,3Δ symmetries below the first nine asymptotic limits dissociating into Be+(2s) + Cs(6s, 6p, 5d) and Be(2s2, 2s2p, 2s3s, 2p2) + Cs+. We used a quantum chemistry approach based on a semi-empirical pseudo potential for Be2+ and Cs+ cores, core polarization potentials (CPP), large Gaussian basis sets and full configuration interaction (FCI) method for the valence electrons. Additional calculations have been performed for the ground state using CCSD(T)/CI methods with different basis sets. Adiabatic potential energy curves, spectroscopic constants, vibrational levels, and permanent and transition dipole moments are reported in this work. Furthermore, the elastic scattering properties at low energy for both ground 11Σ+ and second excited states 31Σ+, of BeCs+ are theoretically investigated, and isotopic effects on cold and ultra-cold energy collisions are also detected. Vibrational lifetimes of the ground state 11Σ+ are calculated taking into account both spontaneous and stimulated emissions and also the absorption induced by black body radiation at room temperature (T = 300 K). Vibrational radiative lifetimes for the first 21Σ+ and second 31Σ+ excited states are also calculated and extensively analyzed. We found that the radiative lifetimes of the lower vibrational levels of the 11Σ+ state have an order of magnitude of seconds (s), while those of 21Σ+ and 31Σ+ states have an order of nanoseconds (ns). The Franck-Condon factors are also calculated for transitions from the low lying excited 21Σ+, 31Σ+, 11Π states to the ground state 11Σ+. We found that the favourite vibrational transition to the 11Σ+(v = 0) ground state is obtained for 11Π (v''' = 0)-11Σ+(v = 0) with a diagonal structure and a large Franck-Condon factor value of 0.94. This Franck-Condon factor value is sufficiently large to make the BeCs+ system a favorable candidate for direct laser cooling.
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Affiliation(s)
- Hela Ladjimi
- Laboratory of Interfaces and Advanced Materials, Faculty of Science, University of Monastir, 5019 Monastir, Tunisia.
| | - Wissem Zrafi
- Laboratory of Interfaces and Advanced Materials, Faculty of Science, University of Monastir, 5019 Monastir, Tunisia.
| | - Mohamed Farjallah
- Laboratory of Interfaces and Advanced Materials, Faculty of Science, University of Monastir, 5019 Monastir, Tunisia.
| | - Mohamed Bejaoui
- Laboratory of Interfaces and Advanced Materials, Faculty of Science, University of Monastir, 5019 Monastir, Tunisia.
| | - Hamid Berriche
- Laboratory of Interfaces and Advanced Materials, Faculty of Science, University of Monastir, 5019 Monastir, Tunisia. .,Department of Mathematics and Natural Sciences, School of Arts and Sciences, American University of Ras Al Khaimah, RAK, P.O. Box 10021, United Arab Emirates.
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Miossec C, Hejduk M, Pandey R, Coughlan NJA, Heazlewood BR. Design and characterization of a cryogenic linear Paul ion trap for ion-neutral reaction studies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:033201. [PMID: 35364974 DOI: 10.1063/5.0080458] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Ultra-high vacuum conditions are ideal for the study of trapped ions. They offer an almost perturbation-free environment, where ions confined in traps can be studied for extended periods of time-facilitating precision measurements and allowing infrequent events to be observed. However, if one wishes to study processes involving molecular ions, it is important to consider the effect of blackbody radiation (BBR). The vast majority of molecular ions interact with BBR. At 300 K, state selection in trapped molecular ions can be rapidly lost (in a matter of seconds). To address this issue, and to maintain state selectivity in trapped molecular ions, a cryogenic ion trap chamber has been constructed and characterized. At the center of the apparatus is a linear Paul ion trap, where Coulomb crystals can be formed for ion-neutral reaction studies. Optical access is provided, for lasers and for imaging of the crystals, alongside ion optics and a flight tube for recording time-of-flight mass spectra. The ion trap region, encased within two nested temperature stages, reaches temperatures below 9 K. To avoid vibrations from the cryocooler impeding laser cooling or imaging of the ions, vibration-damping elements are explicitly included. These components successfully inhibit the coupling of vibrations from the cold head to the ion trap-confirmed by accelerometer measurements and by the resolution of images recorded at the trap center (at 9 and 295 K). These results confirm that the cryogenic ion trap apparatus meets all requirements for studying ion-neutral reactions under cold, controlled conditions.
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Affiliation(s)
- Chloé Miossec
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
| | - Michal Hejduk
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Rahul Pandey
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
| | - Neville J A Coughlan
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Brianna R Heazlewood
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
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Interactions of Ions and Ultracold Neutral Atom Ensembles in Composite Optical Dipole Traps: Developments and Perspectives. ATOMS 2021. [DOI: 10.3390/atoms9030039] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Ion–atom interactions are a comparatively recent field of research that has drawn considerable attention due to its applications in areas including quantum chemistry and quantum simulations. In first experiments, atomic ions and neutral atoms have been successfully overlapped by devising hybrid apparatuses combining established trapping methods, Paul traps for ions and optical or magneto-optical traps for neutral atoms, respectively. Since then, the field has seen considerable progress, but the inherent presence of radiofrequency (rf) fields in such hybrid traps was found to have a limiting impact on the achievable collision energies. Recently, it was shown that suitable combinations of optical dipole traps (ODTs) can be used for trapping both atoms and atomic ions alike, allowing to carry out experiments in absence of any rf fields. Here, we show that the expected cooling in such bichromatic traps is highly sensitive to relative position fluctuations between the two optical trapping beams, suggesting that this is the dominant mechanism limiting the currently observed cooling performance. We discuss strategies for mitigating these effects by using optimized setups featuring adapted ODT configurations. This includes proposed schemes that may mitigate three-body losses expected at very low temperatures, allowing to access the quantum dominated regime of interaction.
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Kłos J, Guan Q, Li H, Li M, Tiesinga E, Kotochigova S. Roaming pathways and survival probability in real-time collisional dynamics of cold and controlled bialkali molecules. Sci Rep 2021; 11:10598. [PMID: 34011983 PMCID: PMC8134521 DOI: 10.1038/s41598-021-90004-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 04/30/2021] [Indexed: 11/25/2022] Open
Abstract
Perfectly controlled molecules are at the forefront of the quest to explore chemical reactivity at ultra low temperatures. Here, we investigate for the first time the formation of the long-lived intermediates in the time-dependent scattering of cold bialkali \documentclass[12pt]{minimal}
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\begin{document}$$^{23}\hbox {Na}^{87}$$\end{document}23Na87Rb molecules with and without the presence of infrared trapping light. During the nearly 50 nanoseconds mean collision time of the intermediate complex, we observe unconventional roaming when for a few tens of picoseconds either NaRb or \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Na}_2$$\end{document}Na2 and \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Rb}_2$$\end{document}Rb2 molecules with large relative separation are formed before returning to the four-atom complex. We also determine the likelihood of molecular loss when the trapping laser is present during the collision. We find that at a wavelength of 1064 nm the \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Na}_2\hbox {Rb}_2$$\end{document}Na2Rb2 complex is quickly destroyed and thus that the \documentclass[12pt]{minimal}
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\begin{document}$$^{23}\hbox {Na}^{87}$$\end{document}23Na87Rb molecules are rapidly lost.
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Affiliation(s)
- Jacek Kłos
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA.,Joint Quantum Institute, University of Maryland, College Park, MD, 20742, USA
| | - Qingze Guan
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Hui Li
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Ming Li
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Eite Tiesinga
- Joint Quantum Institute, University of Maryland, College Park, MD, 20742, USA.,National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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Mant B, Yurtsever E, González-Sánchez L, Wester R, Gianturco FA. Vibrational quenching of CN - in collisions with He and Ar. J Chem Phys 2021; 154:084305. [PMID: 33639742 DOI: 10.1063/5.0039854] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The vibrational quenching cross sections and corresponding low-temperature rate constants for the ν = 1 and ν = 2 states of CN-(1Σ+) colliding with He and Ar atoms have been computed ab initio using new three-dimensional potential energy surfaces. Little work has been carried out so far on low-energy vibrationally inelastic collisions for anions with neutral atoms. The cross sections and rates calculated at energies and temperatures relevant for both ion traps and astrochemical modeling are found by the present calculations to be even smaller than those of the similar C2 -/He and C2 -/Ar systems, which are in turn of the order of those existing for the collisions involving neutral diatom-atom systems. The implications of our finding in the present case mainly focus on the possible role of small computed rate constants in the dynamics of molecular cooling and the evolution of astrochemical modeling networks.
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Affiliation(s)
- Barry Mant
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
| | - Ersin Yurtsever
- Department of Chemistry, Koç University, Rumelifeneri yolu, Sariyer, TR-34450 Istanbul, Turkey
| | - Lola González-Sánchez
- Departamento de Química Física, University of Salamanca, Plaza de los Caídos sn, 37008 Salamanca, Spain
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
| | - Franco A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
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7
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Blackburn L, Keller M. The effect of the electric trapping field on state-selective loading of molecules into rf ion traps. Sci Rep 2020; 10:18449. [PMID: 33116215 PMCID: PMC7595205 DOI: 10.1038/s41598-020-74759-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 10/06/2020] [Indexed: 11/13/2022] Open
Abstract
Trapped molecular ions in pure rovibronic states are desirable in experiments ranging from cold chemistry to searches for physics beyond the Standard Model. Resonance-enhanced multiphoton ionisation (REMPI) can be used to prepare molecular ions in specific internal states with high fidelities. However, in the presence of electric fields, ionisation spectra exhibit frequency shifts and the ionisation thresholds are broadened. For this reason, REMPI studies are normally conducted in low and highly homogeneous electric fields, whereas the operating principle of rf ion traps requires electric fields that vary in space and time. In order to investigate the impact of this on the state-selectivity of REMPI in ion traps, we have simulated the expected broadening of the ionisation threshold under various operating conditions of a typical linear Paul trap. In many cases, the width of the ionisation threshold exceeds the separation between rotational energy levels, preventing state-selective ionisation. Careful choice of the trapping and laser parameters during loading can reduce this broadening, enabling state-selective ionisation in some instances. Where this strategy is not sufficient, the broadening can be reduced further by rapidly switching the trapping voltages off and on again during loading. This has been demonstrated experimentally for a Coulomb crystal of \documentclass[12pt]{minimal}
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\begin{document}$$^{40}\hbox {Ca}^+$$\end{document}40Ca+ ions without descrystallising it.
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Affiliation(s)
- Laura Blackburn
- Department of Physics and Astronomy, University of Sussex, Falmer, BN1 9QH, UK.
| | - Matthias Keller
- Department of Physics and Astronomy, University of Sussex, Falmer, BN1 9QH, UK
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8
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Stollenwerk PR, Antonov IO, Venkataramanababu S, Lin YW, Odom BC. Cooling of a Zero-Nuclear-Spin Molecular Ion to a Selected Rotational State. PHYSICAL REVIEW LETTERS 2020; 125:113201. [PMID: 32975973 DOI: 10.1103/physrevlett.125.113201] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate rotational cooling of the silicon monoxide cation via optical pumping by a spectrally filtered broadband laser. Compared with diatomic hydrides, SiO^{+} is more challenging to cool because of its smaller rotational interval. However, the rotational level spacing and the large dipole moment of SiO^{+} allows for direct manipulation by microwaves, and the absence of hyperfine structure in its dominant isotopologue greatly reduces demands for pure quantum state preparation. These features make ^{28}Si^{16}O^{+} a good candidate for future applications such as quantum information processing. Cooling to the ground rotational state is achieved on a 100 ms timescale and attains a population of 94(3)%, with an equivalent temperature T=0.53(6) K. We also describe a novel spectral-filtering approach to cool into arbitrary rotational states and use it to demonstrate a narrow rotational population distribution (N±1) around a selected state.
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Affiliation(s)
| | - Ivan O Antonov
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | | | - Yen-Wei Lin
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Brian C Odom
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
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9
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Li M, Kłos J, Petrov A, Li H, Kotochigova S. Effects of conical intersections on hyperfine quenching of hydroxyl OH in collision with an ultracold Sr atom. Sci Rep 2020; 10:14130. [PMID: 32839529 PMCID: PMC7445183 DOI: 10.1038/s41598-020-71068-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/04/2020] [Indexed: 11/09/2022] Open
Abstract
The effect of conical intersections (CIs) on electronic relaxation, transitions from excited states to ground states, is well studied, but their influence on hyperfine quenching in a reactant molecule is not known. Here, we report on ultracold collision dynamics of the hydroxyl free-radical OH with Sr atoms leading to quenching of OH hyperfine states. Our quantum-mechanical calculations of this process reveal that quenching is efficient due to anomalous molecular dynamics in the vicinity of the conical intersection at collinear geometry. We observe wide scattering resonance features in both elastic and inelastic rate coefficients at collision energies below \documentclass[12pt]{minimal}
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\begin{document}$$k_{\text {B}}\times 10 \, \hbox {mK}$$\end{document}kB×10mK. They are identified as either p- or d-wave shape resonances. We also describe the electronic potentials relevant for these non-reactive collisions, their diabatization procedure, as well as the non-adiabatic coupling between the diabatic potentials near the CIs.
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Affiliation(s)
- Ming Li
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Jacek Kłos
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA.,Department of Physics, Joint Quantum Institute, University of Maryland, College Park, MD, 20742, USA
| | - Alexander Petrov
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA.,NRC, Kurchatov Institute PNPI, Gatchina, Russia, 188300.,Division of Quantum Mechanics, Saint Petersburg State University, St. Petersburg, Russia, 199034
| | - Hui Li
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
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10
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Li H, Jyothi S, Li M, Kłos J, Petrov A, Brown KR, Kotochigova S. Photon-mediated charge exchange reactions between 39K atoms and 40Ca + ions in a hybrid trap. Phys Chem Chem Phys 2020; 22:10870-10881. [PMID: 32367082 DOI: 10.1039/d0cp01131b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present experimental evidence of charge exchange between laser-cooled potassium 39K atoms and calcium 40Ca+ ions in a hybrid atom-ion trap and give quantitative theoretical explanations for the observations. The 39K atoms and 40Ca+ ions are held in a magneto-optical (MOT) and a linear Paul trap, respectively. Fluorescence detection and high resolution time of flight mass spectra for both species are used to determine the remaining number of 40Ca+ ions, the increasing number of 39K+ ions, and 39K number density as functions of time. Simultaneous trap operation is guaranteed by alternating periods of MOT and 40Ca+ cooling lights, thus avoiding direct ionization of 39K by the 40Ca+ cooling light. We show that the K-Ca+ charge-exchange rate coefficient increases linearly from zero with 39K number density and the fraction of 40Ca+ ions in the 4p 2P1/2 electronically-excited state. Combined with our theoretical analysis, we conclude that these data can only be explained by a process that starts with a potassium atom in its electronic ground state and a calcium ion in its excited 4p 2P1/2 state producing ground-state 39K+ ions and metastable, neutral Ca (3d4p 3P1) atoms, releasing only 150 cm-1 equivalent relative kinetic energy. Charge-exchange between either ground- or excited-state 39K and ground-state 40Ca+ is negligibly small as no energetically-favorable product states are available. Our experimental and theoretical rate coefficients are in agreement given the uncertainty budgets.
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Affiliation(s)
- Hui Li
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA.
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12
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Courageux T, Cournol A, Comparat D, Viaris de Lesegno B, Lignier H. Determining a vibrational distribution with a broadband optical source. Phys Chem Chem Phys 2020; 22:19864-19869. [DOI: 10.1039/d0cp03583a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
This work presents an experimental protocol conceived to determine the vibrational distribution of barium monofluoride molecules seeded in a supersonic beam of argon.
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Affiliation(s)
- T. Courageux
- Université Paris-Saclay
- CNRS
- Laboratoire Aimé Cotton
- Orsay
- France
| | - A. Cournol
- Université Paris-Saclay
- CNRS
- Laboratoire Aimé Cotton
- Orsay
- France
| | - D. Comparat
- Université Paris-Saclay
- CNRS
- Laboratoire Aimé Cotton
- Orsay
- France
| | | | - H. Lignier
- Université Paris-Saclay
- CNRS
- Laboratoire Aimé Cotton
- Orsay
- France
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13
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Toscano J, Lewandowski HJ, Heazlewood BR. Cold and controlled chemical reaction dynamics. Phys Chem Chem Phys 2020; 22:9180-9194. [DOI: 10.1039/d0cp00931h] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
State-to-state chemical reaction dynamics, with complete control over the reaction parameters, offers unparalleled insight into fundamental reactivity.
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Affiliation(s)
- Jutta Toscano
- JILA and the Department of Physics
- University of Colorado
- Boulder
- USA
| | | | - Brianna R. Heazlewood
- Physical and Theoretical Chemistry Laboratory (PTCL)
- Department of Chemistry
- University of Oxford
- Oxford
- UK
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14
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Dörfler AD, Eberle P, Koner D, Tomza M, Meuwly M, Willitsch S. Long-range versus short-range effects in cold molecular ion-neutral collisions. Nat Commun 2019; 10:5429. [PMID: 31780657 PMCID: PMC6882903 DOI: 10.1038/s41467-019-13218-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 10/28/2019] [Indexed: 12/27/2022] Open
Abstract
The investigation of cold interactions between ions and neutrals has recently emerged as a new scientific frontier at the interface of physics and chemistry. Here, we report a study of charge-transfer (CT) collisions of Rb atoms with N\documentclass[12pt]{minimal}
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\begin{document}$${}_{2}^{+}$$\end{document}2+ and O\documentclass[12pt]{minimal}
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\begin{document}$${}_{2}^{+}$$\end{document}2+ ions in the mK regime using a dynamic ion-neutral hybrid trapping experiment. We observe markedly different CT kinetics and dynamics for the different systems and reaction channels studied. While the kinetics in some channels are consistent with classical capture theory, others show distinct non-universal dynamics. The experimental results are interpreted with the help of classical-capture, quasiclassical-trajectory and quantum-scattering calculations using ab-initio potentials for the highly excited molecular states involved. The theoretical analysis reveals an intricate interplay between short- and long-range effects in the different reaction channels which ultimately determines the CT dynamics and rates. Our results illustrate salient mechanisms that determine the efficiency of cold molecular CT reactions. Studies on reactions between cold molecular ions and neutral atoms provide insights into intermolecular interactions. Here the authors explore the kinetics and dynamics of charge-transfer collisions between the cold N\documentclass[12pt]{minimal}
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\begin{document}$${}_{2}^{+}$$\end{document}2+ and O\documentclass[12pt]{minimal}
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\begin{document}$${}_{2}^{+}$$\end{document}2+ ions and neutral Rb atoms and discuss the role of long- and short-range effects.
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Affiliation(s)
- Alexander D Dörfler
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland
| | - Pascal Eberle
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland
| | - Debasish Koner
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland
| | - Michał Tomza
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
| | - Stefan Willitsch
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
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15
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Cerchiari G, Yzombard P, Kellerbauer A. Laser-Assisted Evaporative Cooling of Anions. PHYSICAL REVIEW LETTERS 2019; 123:103201. [PMID: 31573306 DOI: 10.1103/physrevlett.123.103201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Indexed: 06/10/2023]
Abstract
We report the first cooling of atomic anions by laser radiation. O^{-} ions confined in a linear Paul trap were cooled by selectively photodetaching the hottest particles. For this purpose, anions with the highest total energy were illuminated with a 532 nm laser at their maximal radial excursion. Using laser-particle interaction, we realized a both colder and denser ion cloud, achieving a more than threefold temperature reduction from 1.15 to 0.33 eV. Compared with the interaction with a dilute buffer gas, the energy-selective addressing and removal of anions resulted in lower final temperatures, yet acted 10 times faster and preserved twice as large a fraction of ions in the final state. An ensemble of cold negative ions affords the ability to sympathetically cool any other negative ion species, enabling or facilitating a broad range of fundamental studies from interstellar chemistry to antimatter gravity. The technique can be extended to any negative ion species that can be neutralized via photodetachment.
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Affiliation(s)
- G Cerchiari
- Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - P Yzombard
- Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - A Kellerbauer
- Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany
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16
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Mills M, Puri P, Li M, Schowalter SJ, Dunning A, Schneider C, Kotochigova S, Hudson ER. Engineering Excited-State Interactions at Ultracold Temperatures. PHYSICAL REVIEW LETTERS 2019; 122:233401. [PMID: 31298913 DOI: 10.1103/physrevlett.122.233401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Indexed: 06/10/2023]
Abstract
Using a recently developed method for precisely controlling collision energy, we observe a dramatic suppression of inelastic collisions between an atom and ion (Ca+Yb^{+}) at low collision energy. This suppression, which is expected to be a universal phenomenon, arises when the spontaneous emission lifetime of the excited state is comparable to or shorter than the collision complex lifetime. We develop a technique to remove this suppression and engineer excited-state interactions. By dressing the system with a strong catalyst laser, a significant fraction of the collision complexes can be excited at a specified atom-ion separation. This technique allows excited-state collisions to be studied, even at ultracold temperature, and provides a general method for engineering ultracold excited-state interactions.
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Affiliation(s)
- Michael Mills
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Prateek Puri
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Ming Li
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Steven J Schowalter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Alexander Dunning
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Christian Schneider
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | | | - Eric R Hudson
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
- Center for Quantum Science and Engineering, University of California, Los Angeles, California 90095, USA
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17
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Reaction blockading in a reaction between an excited atom and a charged molecule at low collision energy. Nat Chem 2019; 11:615-621. [DOI: 10.1038/s41557-019-0264-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 03/25/2019] [Indexed: 12/15/2022]
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18
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Affiliation(s)
- Brianna R. Heazlewood
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, United Kingdom
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19
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Abstract
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.
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Affiliation(s)
- Aaron T Calvin
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332-0400 , United States
| | - Kenneth R Brown
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332-0400 , United States
- Departments of Electrical and Computer Engineering, Chemistry, and Physics , Duke University , Durham , North Carolina 27708 , United States
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20
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Meir Z, Pinkas M, Sikorsky T, Ben-Shlomi R, Akerman N, Ozeri R. Direct Observation of Atom-Ion Nonequilibrium Sympathetic Cooling. PHYSICAL REVIEW LETTERS 2018; 121:053402. [PMID: 30118277 DOI: 10.1103/physrevlett.121.053402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Indexed: 06/08/2023]
Abstract
Sympathetic cooling is the process of energy exchange between a system and a colder bath. We investigate this fundamental process in an atom-ion experiment where the system is composed of a single ion trapped in a radio-frequency Paul trap and prepared in a classical oscillatory motion with total energy of ∼200 K, and the bath is an ultracold cloud of atoms at μK temperature. We directly observe the sympathetic cooling dynamics with single-shot energy measurements during one to several collisions in two distinct regimes. In one, collisions predominantly cool the system with very efficient momentum transfer leading to cooling in only a few collisions. In the other, collisions can both cool and heat the system due to nonequilibrium dynamics in the presence of the ion trap's oscillating electric fields. While the bulk of our observations agree well with a molecular-dynamics simulation of hard-sphere (Langevin) collisions, a measurement of the scattering angle distribution reveals forward-scattering (glancing) collisions which are beyond the Langevin model. This work paves the way for further nonequilibrium and collision dynamics studies using the well-controlled atom-ion system.
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Affiliation(s)
- Ziv Meir
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Meirav Pinkas
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Tomas Sikorsky
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ruti Ben-Shlomi
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Nitzan Akerman
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Roee Ozeri
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
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21
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Puri P, Mills M, West EP, Schneider C, Hudson ER. High-resolution collision energy control through ion position modulation in atom-ion hybrid systems. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:083112. [PMID: 30184618 DOI: 10.1063/1.5031145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/30/2018] [Indexed: 06/08/2023]
Abstract
We demonstrate an ion shuttling technique for high-resolution control of atom-ion collision energy by translating an ion held within a radio-frequency trap through a magneto-optical atom trap. The technique is demonstrated both experimentally and through numerical simulations, with the experimental results indicating control of ion kinetic energies from 0.05 to 1 K with a fractional resolution of ∼10 and the simulations demonstrating that kinetic energy control up to 120 K with a maximum predicted resolution of ∼100 is possible, offering order-of-magnitude improvements over most alternative techniques. Finally, we perform a proof-of-principle chemistry experiment using this technique and outline how the method may be refined in the future and applied to the study of molecular ion chemistry.
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Affiliation(s)
- Prateek Puri
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Michael Mills
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Elizabeth P West
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Christian Schneider
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Eric R Hudson
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
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22
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Haze S, Sasakawa M, Saito R, Nakai R, Mukaiyama T. Cooling Dynamics of a Single Trapped Ion via Elastic Collisions with Small-Mass Atoms. PHYSICAL REVIEW LETTERS 2018; 120:043401. [PMID: 29437432 DOI: 10.1103/physrevlett.120.043401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Indexed: 06/08/2023]
Abstract
We demonstrated sympathetic cooling of a single ion in a buffer gas of ultracold atoms with small mass. Efficient collisional cooling was realized by suppressing collision-induced heating. We attempt to explain the experimental results with a simple rate equation model and provide a quantitative discussion of the cooling efficiency per collision. The knowledge we obtained in this work is an important ingredient for advancing the technique of sympathetic cooling of ions with neutral atoms.
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Affiliation(s)
- Shinsuke Haze
- Institute for Laser Science, University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Mizuki Sasakawa
- Institute for Laser Science, University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Ryoichi Saito
- Institute for Laser Science, University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Ryosuke Nakai
- Institute for Laser Science, University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Takashi Mukaiyama
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
- PRESTO, Japan Science and Technology Agency, Honcho, Kawaguchi, Saitama 332-0012, Japan
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23
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Affiliation(s)
- Stefan Willitsch
- Department of Chemistry; University of Basel; Klingelbergstrasse 80, 4056 Basel Switzerland
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24
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Puri P, Mills M, Schneider C, Simbotin I, Montgomery JA, Côté R, Suits AG, Hudson ER. Synthesis of mixed hypermetallic oxide BaOCa+ from laser-cooled reagents in an atom-ion hybrid trap. Science 2017; 357:1370-1375. [DOI: 10.1126/science.aan4701] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 08/24/2017] [Indexed: 11/02/2022]
Abstract
Hypermetallic alkaline earth (M) oxides of formula MOM have been studied under plasma conditions that preclude insight into their formation mechanism. We present here the application of emerging techniques in ultracold physics to the synthesis of a mixed hypermetallic oxide, BaOCa+. These methods, augmented by high-level electronic structure calculations, permit detailed investigation of the bonding and structure as well as the mechanism of its formation via the barrierless reaction of Ca (3PJ) with BaOCH3+. Further investigations of the reaction kinetics as a function of collision energy over the range 0.005 kelvin (K) to 30 K and of individual Ca fine-structure levels compare favorably with calculations based on long-range capture theory.
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25
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Croft JFE, Makrides C, Li M, Petrov A, Kendrick BK, Balakrishnan N, Kotochigova S. Universality and chaoticity in ultracold K+KRb chemical reactions. Nat Commun 2017; 8:15897. [PMID: 28722014 PMCID: PMC5524979 DOI: 10.1038/ncomms15897] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 05/10/2017] [Indexed: 11/17/2022] Open
Abstract
A fundamental question in the study of chemical reactions is how reactions proceed at a collision energy close to absolute zero. This question is no longer hypothetical: quantum degenerate gases of atoms and molecules can now be created at temperatures lower than a few tens of nanokelvin. Here we consider the benchmark ultracold reaction between, the most-celebrated ultracold molecule, KRb and K. We map out an accurate ab initio ground-state potential energy surface of the K2Rb complex in full dimensionality and report numerically-exact quantum-mechanical reaction dynamics. The distribution of rotationally resolved rates is shown to be Poissonian. An analysis of the hyperspherical adiabatic potential curves explains this statistical character revealing a chaotic distribution for the short-range collision complex that plays a key role in governing the reaction outcome. Studying chemical reactions near zero temperature in detail is challenging both in theory and practice. Here the authors report an explicit quantum mechanical study of the benchmark ultracold reaction between a K atom and a KRb molecule, important for future controlled chemistry experiments.
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Affiliation(s)
- J F E Croft
- Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154, USA
| | - C Makrides
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - M Li
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - A Petrov
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA.,NRC 'Kurchatov Institute' PNPI, Gatchina, Leningrad District 188300 Russia.,Division of Quantum Mechanics, St Petersburg State University, 7/9 Universitetskaya nab., St Petersburg 199034, Russia
| | - B K Kendrick
- Theoretical Division (T-1, MS B221), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - N Balakrishnan
- Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154, USA
| | - S Kotochigova
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
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26
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Preparation and coherent manipulation of pure quantum states of a single molecular ion. Nature 2017; 545:203-207. [DOI: 10.1038/nature22338] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 03/20/2017] [Indexed: 12/15/2022]
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27
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Atomic envoy enables molecular control. Nature 2017; 545:164-165. [DOI: 10.1038/545164a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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28
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Papp D, Sarka J, Szidarovszky T, Császár AG, Mátyus E, Hochlaf M, Stoecklin T. Complex rovibrational dynamics of the Ar·NO + complex. Phys Chem Chem Phys 2017; 19:8152-8160. [PMID: 28225106 DOI: 10.1039/c6cp07731e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Rotational-vibrational states of the Ar·NO+ cationic complex are computed, below, above, and well above the complex's first dissociation energy, using variational nuclear motion and close-coupling scattering computations. The HSLH potential energy surface used in this study (J. Chem. Phys., 2011, 135, 044312) is characterized by a first dissociation energy of D0 = 887.0 cm-1 and supports 200 bound vibrational states. The bound-state vibrational energies and the corresponding wave functions allow the interpretation of the scarcely available experimental results about the intermonomer vibrational motion of the complex. A very large number of long-lived quasibound combination states of the three vibrational modes, exhibiting a very similar energy-level structure as that of the bound states, are found embedded in the continuum. Additional short-lived resonance states are also identified and their properties are analyzed.
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Affiliation(s)
- Dóra Papp
- MTA-ELTE Complex Chemical Systems Research Group, P.O. Box 32, H-1518 Budapest 112, Hungary.
| | - János Sarka
- MTA-ELTE Complex Chemical Systems Research Group, P.O. Box 32, H-1518 Budapest 112, Hungary.
| | - Tamás Szidarovszky
- MTA-ELTE Complex Chemical Systems Research Group, P.O. Box 32, H-1518 Budapest 112, Hungary.
| | - Attila G Császár
- MTA-ELTE Complex Chemical Systems Research Group, P.O. Box 32, H-1518 Budapest 112, Hungary.
| | - Edit Mátyus
- Institute of Chemistry, Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
| | - Majdi Hochlaf
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, F-77454 Marne-la-Vallée, France
| | - Thierry Stoecklin
- Institut des Sciences Moléculaires, Université de Bordeaux, CNRS UMR 5255, 33405 Talence Cedex, France.
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29
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Tomza M. Cold interactions and chemical reactions of linear polyatomic anions with alkali-metal and alkaline-earth-metal atoms. Phys Chem Chem Phys 2017; 19:16512-16523. [DOI: 10.1039/c7cp02127e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cold interactions and channels of chemical reactions between linear polyatomic anions and atoms are investigated, opening the way for sympathetic cooling and controlled chemistry in these systems.
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Affiliation(s)
- Michał Tomza
- Centre of New Technologies
- University of Warsaw
- 02-097 Warsaw
- Poland
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30
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Hochlaf M. Advances in spectroscopy and dynamics of small and medium sized molecules and clusters. Phys Chem Chem Phys 2017; 19:21236-21261. [DOI: 10.1039/c7cp01980g] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Investigations of the spectroscopy and dynamics of small- and medium-sized molecules and clusters represent a hot topic in atmospheric chemistry, biology, physics, atto- and femto-chemistry and astrophysics.
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Affiliation(s)
- Majdi Hochlaf
- Université Paris-Est
- Laboratoire Modélisation et Simulation Multi Echelle
- MSME UMR 8208 CNRS
- 77454 Marne-la-Vallée
- France
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31
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Jyothi S, Ray T, Dutta S, Allouche AR, Vexiau R, Dulieu O, Rangwala SA. Photodissociation of Trapped Rb_{2}^{+}: Implications for Simultaneous Trapping of Atoms and Molecular Ions. PHYSICAL REVIEW LETTERS 2016; 117:213002. [PMID: 27911516 DOI: 10.1103/physrevlett.117.213002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Indexed: 06/06/2023]
Abstract
The direct photodissociation of trapped ^{85}Rb_{2}^{+} (rubidium) molecular ions by the cooling light for the ^{85}Rb magneto-optical trap (MOT) is studied, both experimentally and theoretically. Vibrationally excited Rb_{2}^{+} ions are created by photoionization of Rb_{2} molecules formed photoassociatively in the Rb MOT and are trapped in a modified spherical Paul trap. The decay rate of the trapped Rb_{2}^{+} ion signal in the presence of the MOT cooling light is measured and agreement with our calculated rates for molecular ion photodissociation is observed. The photodissociation mechanism due to the MOT light is expected to be active and therefore universal for all homonuclear diatomic alkali metal molecular ions.
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Affiliation(s)
- S Jyothi
- Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
| | - Tridib Ray
- Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
- Light-Matter Interactions Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-495, Japan
| | - Sourav Dutta
- Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
| | - A R Allouche
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France
| | - Romain Vexiau
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, Orsay Cedex 91405, France
| | - Olivier Dulieu
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, Orsay Cedex 91405, France
| | - S A Rangwala
- Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
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32
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Balakrishnan N. Perspective: Ultracold molecules and the dawn of cold controlled chemistry. J Chem Phys 2016; 145:150901. [DOI: 10.1063/1.4964096] [Citation(s) in RCA: 157] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- N. Balakrishnan
- Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154, USA
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33
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A novel molecular synchrotron for cold collision and EDM experiments. Sci Rep 2016; 6:32663. [PMID: 27600539 PMCID: PMC5013392 DOI: 10.1038/srep32663] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 08/11/2016] [Indexed: 11/09/2022] Open
Abstract
Limited by the construction demands, the state-of-the-art molecular synchrotrons consist of only 40 segments that hardly make a good circle. Imperfections in the circular structure will lead to the appearance of unstable velocity regions (i.e. stopbands), where molecules of certain forward velocity will be lost from the structure. In this paper, we propose a stopband-free molecular synchrotron. It contains 1570 ring electrodes, which nearly make a perfect circle, capable of confining both light and heavy polar molecules in the low-field-seeking states. Molecular packets can be conveniently manipulated with this synchrotron by various means, like acceleration, deceleration or even trapping. Trajectory calculations are carried out using a pulsed 88SrF molecular beam with a forward velocity of 50 m/s. The results show that the molecular beam can make more than 500 round trips inside the synchrotron with a 1/e lifetime of 6.2 s. The synchrotron can find potential applications in low-energy collision and reaction experiments or in the field of precision measurements, such as the searches for electric dipole moment of elementary particles.
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34
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Blue-sky bifurcation of ion energies and the limits of neutral-gas sympathetic cooling of trapped ions. Nat Commun 2016; 7:12448. [PMID: 27511602 PMCID: PMC4987526 DOI: 10.1038/ncomms12448] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 07/05/2016] [Indexed: 01/27/2023] Open
Abstract
Sympathetic cooling of trapped ions through collisions with neutral buffer gases is critical to a variety of modern scientific fields, including fundamental chemistry, mass spectrometry, nuclear and particle physics, and atomic and molecular physics. Despite its widespread use over four decades, there remain open questions regarding its fundamental limitations. To probe these limits, here we examine the steady-state evolution of up to 10 barium ions immersed in a gas of three-million laser-cooled calcium atoms. We observe and explain the emergence of nonequilibrium behaviour as evidenced by bifurcations in the ion steady-state temperature, parameterized by ion number. We show that this behaviour leads to the limitations in creating and maintaining translationally cold samples of trapped ions using neutral-gas sympathetic cooling. These results may provide a route to studying non-equilibrium thermodynamics at the atomic level.
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35
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Höltkemeier B, Weckesser P, López-Carrera H, Weidemüller M. Buffer-Gas Cooling of a Single Ion in a Multipole Radio Frequency Trap Beyond the Critical Mass Ratio. PHYSICAL REVIEW LETTERS 2016; 116:233003. [PMID: 27341228 DOI: 10.1103/physrevlett.116.233003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Indexed: 06/06/2023]
Abstract
We theoretically investigate the dynamics of a trapped ion immersed in a spatially localized buffer gas. For a homogeneous buffer gas, the ion's energy distribution reaches a stable equilibrium only if the mass of the buffer gas atoms is below a critical value. This limitation can be overcome by using multipole traps in combination with a spatially confined buffer gas. Using a generalized model for elastic collisions of the ion with the buffer-gas atoms, the ion's energy distribution is numerically determined for arbitrary buffer-gas distributions and trap parameters. Three regimes characterized by the respective analytic form of the ion's equilibrium energy distribution are found. Final ion temperatures down to the millikelvin regime can be achieved by adiabatically decreasing the spatial extension of the buffer gas and the effective ion trap depth (forced sympathetic cooling).
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Affiliation(s)
- Bastian Höltkemeier
- Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, INF 226, 69120 Heidelberg, Germany
| | - Pascal Weckesser
- Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, INF 226, 69120 Heidelberg, Germany
| | - Henry López-Carrera
- Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, INF 226, 69120 Heidelberg, Germany
| | - Matthias Weidemüller
- Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, INF 226, 69120 Heidelberg, Germany
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, and CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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36
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Stoecklin T, Halvick P, Gannouni MA, Hochlaf M, Kotochigova S, Hudson ER. Explanation of efficient quenching of molecular ion vibrational motion by ultracold atoms. Nat Commun 2016; 7:11234. [PMID: 27088647 PMCID: PMC4837476 DOI: 10.1038/ncomms11234] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 03/03/2016] [Indexed: 11/09/2022] Open
Abstract
Buffer gas cooling of molecules to cold and ultracold temperatures is a promising technique for realizing a host of scientific and technological opportunities. Unfortunately, experiments using cryogenic buffer gases have found that although the molecular motion and rotation are quickly cooled, the molecular vibration relaxes at impractically long timescales. Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl(+) by a laser-cooled Ca buffer gas. We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system. This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure.
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Affiliation(s)
- Thierry Stoecklin
- Université de Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, 33405 Talence, France
| | - Philippe Halvick
- Université de Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, 33405 Talence, France
| | - Mohamed Achref Gannouni
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France
| | - Majdi Hochlaf
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France
| | - Svetlana Kotochigova
- Department of Physics, Temple University, 1925 N 12th Street, Philadelphia, Pennsylvania 19122, USA
| | - Eric R. Hudson
- Department of Physics and Astronomy, University of California, 475 Portola Plaza, Los Angeles, California 90095, USA
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Wolf F, Wan Y, Heip JC, Gebert F, Shi C, Schmidt PO. Non-destructive state detection for quantum logic spectroscopy of molecular ions. Nature 2016; 530:457-60. [DOI: 10.1038/nature16513] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 11/27/2015] [Indexed: 01/11/2023]
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38
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Glöckner R, Prehn A, Englert BGU, Rempe G, Zeppenfeld M. Rotational Cooling of Trapped Polyatomic Molecules. PHYSICAL REVIEW LETTERS 2015; 115:233001. [PMID: 26684114 DOI: 10.1103/physrevlett.115.233001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 06/05/2023]
Abstract
Controlling the internal degrees of freedom is a key challenge for applications of cold and ultracold molecules. Here, we demonstrate rotational-state cooling of trapped methyl fluoride molecules (CH_{3}F) by optically pumping the population of 16 M sublevels in the rotational states J=3, 4, 5 and 6 into a single level. By combining rotational-state cooling with motional cooling, we increase the relative number of molecules in the state J=4, K=3, M=4 from a few percent to over 70%, thereby generating a translationally cold (≈30 mK) and nearly pure state ensemble of about 10^{6} molecules. Our scheme is extendable to larger sets of initial states, other final states, and a variety of molecule species, thus paving the way for internal-state control of ever-larger molecules.
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Affiliation(s)
- Rosa Glöckner
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany
| | - Alexander Prehn
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany
| | - Barbara G U Englert
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany
| | - Gerhard Rempe
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany
| | - Martin Zeppenfeld
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany
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Eberle P, Dörfler AD, von Planta C, Ravi K, Haas D, Zhang D, van de Meerakker SYT, Willitsch S. Ion-Atom and Ion-Molecule Hybrid Systems: Ion-Neutral Chemistry at Ultralow Energies. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/1742-6596/635/1/012012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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González-Sánchez L, Carelli F, Gianturco F, Wester R. Collisional state-changing of OH− rotations by interaction with Rb atoms in cold traps. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2015.05.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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41
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Dunning A, Petrov A, Schowalter SJ, Puri P, Kotochigova S, Hudson ER. Photodissociation spectroscopy of the dysprosium monochloride molecular ion. J Chem Phys 2015; 143:124309. [DOI: 10.1063/1.4931817] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alexander Dunning
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Alexander Petrov
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Steven J. Schowalter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Prateek Puri
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | | | - Eric R. Hudson
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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42
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Khanyile NB, Shu G, Brown KR. Observation of vibrational overtones by single-molecule resonant photodissociation. Nat Commun 2015. [PMID: 26197787 PMCID: PMC4525170 DOI: 10.1038/ncomms8825] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Molecular ions can be held in a chain of laser-cooled atomic ions by sympathetic cooling. This system is ideal for performing high-precision molecular spectroscopy with applications in astrochemistry and fundamental physics. Here we show that this same system can be coupled with a broadband laser to discover new molecular transitions. We use three-ion chains of Ca+ and CaH+ to observe vibrational transitions via resonance-enhanced multiphoton dissociation detected by Ca+ fluorescence. On the basis of theoretical calculations, we assign the observed peaks to the transition from the ground vibrational state, ν=0 to ν=9 and 10. Our method allows us to track single-molecular events, and it can be extended to work with any molecule by using normal mode frequency shifts to detect the dissociation. This survey spectroscopy serves as a bridge to the precision spectroscopy required for molecular ion control. Studying the spectra of molecules typically requires large samples, which can be difficult to achieve for hard-to-generate ions. Here, the authors obtain spectra from single CaH+ molecules in a three-ion Columbic crystal, observing new molecular transitions.
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Affiliation(s)
- Ncamiso B Khanyile
- Schools of Chemistry and Biochemistry, Computational Science and Engineering, and Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
| | - Gang Shu
- Schools of Chemistry and Biochemistry, Computational Science and Engineering, and Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
| | - Kenneth R Brown
- Schools of Chemistry and Biochemistry, Computational Science and Engineering, and Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
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Abstract
Coulomb crystals-as a source of translationally cold, highly localized ions-are being increasingly utilized in the investigation of ion-molecule reaction dynamics in the cold regime. To develop a fundamental understanding of ion-molecule reactions, and to challenge existing models that describe the rates, product branching ratios, and temperature dependence of such processes, investigators need to exercise full control over the experimental reaction parameters. This requires not only state selection of the reactants, but also control over the collision process (e.g., the collisional energy and angular momentum) and state-selective product detection. The combination of Coulomb crystals in ion traps with cold neutral-molecule sources is enabling the measurement of state-selective reaction rates in a diverse range of systems. With the development of appropriate product detection techniques, we are moving toward the ultimate goal of examining low-energy, state-to-state ion-molecule reaction dynamics.
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44
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Puri P, Schowalter SJ, Kotochigova S, Petrov A, Hudson ER. Action spectroscopy of SrCl+ using an integrated ion trap time-of-flight mass spectrometer. J Chem Phys 2014; 141:014309. [DOI: 10.1063/1.4885363] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Prateek Puri
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Steven J. Schowalter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | | | - Alexander Petrov
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Eric R. Hudson
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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45
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Chen K, Sullivan ST, Hudson ER. Neutral gas sympathetic cooling of an ion in a Paul trap. PHYSICAL REVIEW LETTERS 2014; 112:143009. [PMID: 24765957 DOI: 10.1103/physrevlett.112.143009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Indexed: 06/03/2023]
Abstract
A single ion immersed in a neutral buffer gas is studied. An analytical model is developed that gives a complete description of the dynamics and steady-state properties of the ions. An extension of this model, using techniques employed in the mathematics of economics and finance, is used to explain the recent observation of non-Maxwellian statistics for these systems. Taken together, these results offer an explanation of the long-standing issues associated with sympathetic cooling of an ion by a neutral buffer gas.
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Affiliation(s)
- Kuang Chen
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Scott T Sullivan
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Eric R Hudson
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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46
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Hansen AK, Versolato OO, Kłosowski Ł, Kristensen SB, Gingell A, Schwarz M, Windberger A, Ullrich J, López-Urrutia JRC, Drewsen M. Efficient rotational cooling of Coulomb-crystallized molecular ions by a helium buffer gas. Nature 2014; 508:76-9. [DOI: 10.1038/nature12996] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 12/19/2013] [Indexed: 01/06/2023]
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47
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Abstract
Over the past decade, and particularly the past five years, a quiet revolution has been building at the border between atomic physics and experimental quantum chemistry. The rapid development of techniques for producing cold and even ultracold molecules without a perturbing rare-gas cluster shell is now enabling the study of chemical reactions and scattering at the quantum scattering limit with only a few partial waves contributing to the incident channel. Moreover, the ability to perform these experiments with nonthermal distributions comprising one or a few specific states enables the observation and even full control of state-to-state collision rates in this computation-friendly regime: This is perhaps the most elementary study possible of scattering and reaction dynamics.
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Affiliation(s)
- Benjamin K Stuhl
- Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899
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48
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Loh H, Cossel KC, Grau MC, Ni KK, Meyer ER, Bohn JL, Ye J, Cornell EA. Precision spectroscopy of polarized molecules in an ion trap. Science 2013; 342:1220-2. [PMID: 24311686 DOI: 10.1126/science.1243683] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Polar molecules are desirable systems for quantum simulations and cold chemistry. Molecular ions are easily trapped, but a bias electric field applied to polarize them tends to accelerate them out of the trap. We present a general solution to this issue by rotating the bias field slowly enough for the molecular polarization axis to follow but rapidly enough for the ions to stay trapped. We demonstrate Ramsey spectroscopy between Stark-Zeeman sublevels in (180)Hf(19)F(+) with a coherence time of 100 milliseconds. Frequency shifts arising from well-controlled topological (Berry) phases are used to determine magnetic g factors. The rotating-bias-field technique may enable using trapped polar molecules for precision measurement and quantum information science, including the search for an electron electric dipole moment.
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Affiliation(s)
- H Loh
- JILA, National Institute of Standards and Technology (NIST), and University of Colorado, and Department of Physics, University of Colorado, Boulder, CO 80309-0440, USA
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