1
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Jambrina PG, Croft JFE, Balakrishnan N, Guo H, Aoiz FJ. Determination of collision mechanisms at low energies using four-vector correlations. Faraday Discuss 2024. [PMID: 38836438 DOI: 10.1039/d3fd00173c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
In molecular dynamics, a fundamental question is how the outcome of a collision depends on the relative orientation of the collision partners before their interaction begins (the stereodynamics of the process). The preference for a particular orientation of the reactant complex is intimately related to the idea of a collision mechanism and the possibility of control, as revealed in recent experiments. Indeed, this preference holds not only for chemical reactions involving complex polyatomic molecules, but also for the simplest inelastic atom-diatom collisions at cold collision energies. In this work, we report how the outcome of rotationally inelastic collisions between two D2 molecules can be controlled by changing the alignment of their internuclear axes under the same or different polarization vectors. Our results demonstrate that a higher degree of control can be achieved when two internuclear axes are aligned, especially when both molecules are relaxed in the collision. The possibility of control extends to very low energies, even to the ultracold regime, when no control could be achieved just by the alignment of the internuclear axis of one of the colliding partners.
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Affiliation(s)
- P G Jambrina
- Departamento de Química Física, Universidad de Salamanca, Salamanca 37008, Spain.
| | - J F E Croft
- Department of Chemistry, Durham University, Durham, DH1 3LE, UK.
| | - N Balakrishnan
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, Nevada 89154, USA.
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
| | - F J Aoiz
- Departamento de Química Física, Universidad Complutense, Madrid 28040, Spain.
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2
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Le Duc V, Zou J, Osterwalder A. Alignment of ND3 molecules in dc-electric fields. J Chem Phys 2024; 160:204305. [PMID: 38804496 DOI: 10.1063/5.0210431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 05/08/2024] [Indexed: 05/29/2024] Open
Abstract
The control of movement and orientation of gas-phase molecules has become the focus of many research areas in molecular physics. Here, ND3 molecules are polarized in a segmented, curved electrostatic guide and adiabatically aligned inside a rotatable mass spectrometer (MS). Alignment is probed by photoionization using a linearly polarized laser. Rotation of the polarization at fixed MS orientation has the same effect as the rotation of the MS at fixed polarization, proving that the molecular alignment adiabatically follows the MS axis. Polarization-dependent ion signals reveal state-specific populations and allow for a quantification of the aligned sample in the space-fixed reference frame.
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Affiliation(s)
- Viet Le Duc
- Institute for Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Junwen Zou
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Andreas Osterwalder
- Institute for Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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3
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Mishra A, Kim J, Kim SK, Willitsch S. Isomeric and rotational effects in the chemi-ionisation of 1,2-dibromoethene with metastable neon atoms. Faraday Discuss 2024. [PMID: 38805255 DOI: 10.1039/d3fd00172e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
The specific geometry of a molecule can have a pronounced influence on its chemical reactivity. However, experimental data on reactions of individual molecular isomers are still sparse because they are often difficult to separate and frequently interconvert into one another under ambient conditions. Here, we employ a novel crossed-beam experiment featuring an electrostatically controlled molecular beam combined with a source for radicals and metastables to spatially separate the cis and trans stereoisomers as well as individual rotational states of 1,2-dibromoethene and study their specific reactivities in the chemi-ionisation reaction with excited neon atoms. The experiments reveal pronounced isomeric and rotational specificities in the rates and product branching ratios of the reaction. The present study underlines the importance and combined role of molecular geometry and of rotational motion in the dynamics of chemi-ionisation reactions.
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Affiliation(s)
- Amit Mishra
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
| | - Junggil Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea.
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea.
| | - Stefan Willitsch
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
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4
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Schatz GC, Wodtke AM, Yang X. Spiers Memorial Lecture: New directions in molecular scattering. Faraday Discuss 2024. [PMID: 38764350 DOI: 10.1039/d4fd00015c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2024]
Abstract
The field of molecular scattering is reviewed as it pertains to gas-gas as well as gas-surface chemical reaction dynamics. We emphasize the importance of collaboration of experiment and theory, from which new directions of research are being pursued on increasingly complex problems. We review both experimental and theoretical advances that provide the modern toolbox available to molecular-scattering studies. We distinguish between two classes of work. The first involves simple systems and uses experiment to validate theory so that from the validated theory, one may learn far more than could ever be measured in the laboratory. The second class involves problems of great complexity that would be difficult or impossible to understand without a partnership of experiment and theory. Key topics covered in this review include crossed-beams reactive scattering and scattering at extremely low energies, where quantum effects dominate. They also include scattering from surfaces, reactive scattering and kinetics at surfaces, and scattering work done at liquid surfaces. The review closes with thoughts on future promising directions of research.
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Affiliation(s)
- George C Schatz
- Dept of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Alec M Wodtke
- Institute for Physical Chemistry, Georg August University, Goettingen, Germany
- Max Planck Institute for Multidisciplinary Natural Sciences, Goettingen, Germany.
- International Center for the Advanced Studies of Energy Conversion, Georg August University, Goettingen, Germany
| | - Xueming Yang
- Dalian Institute for Chemical Physics, Chinese Academy of Sciences, Dalian, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen, China
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5
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Plomp V, Wang XD, Kłos J, Dagdigian PJ, Lique F, Onvlee J, van de Meerakker SY. Imaging Resonance Effects in C + H 2 Collisions Using a Zeeman Decelerator. J Phys Chem Lett 2024; 15:4602-4611. [PMID: 38640083 PMCID: PMC11071073 DOI: 10.1021/acs.jpclett.3c03379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 04/05/2024] [Accepted: 04/05/2024] [Indexed: 04/21/2024]
Abstract
An intriguing phenomenon in molecular collisions is the occurrence of scattering resonances, which originate from bound and quasi-bound states supported by the interaction potential at low collision energies. The resonance effects in the scattering behavior are extraordinarily sensitive to the interaction potential, and their observation provides one of the most stringent tests for theoretical models. We present high-resolution measurements of state-resolved angular scattering distributions for inelastic collisions between Zeeman-decelerated C(3P1) atoms and para-H2 molecules at collision energies ranging from 77 cm-1 down to 0.5 cm-1. Rapid variations in the angular distributions were observed, which can be attributed to the consecutive reduction of contributing partial waves and effects of scattering resonances. The measurements showed excellent agreement with distributions predicted by ab initio quantum scattering calculations. However, discrepancies were found at specific collision energies, which most likely originate from an incorrectly predicted quasi-bound state. These observations provide exciting prospects for further high-precision and low-energy investigations of scattering processes that involve paramagnetic species.
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Affiliation(s)
- Vikram Plomp
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Xu-Dong Wang
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jacek Kłos
- University
of Maryland, Department of Physics,
Joint Quantum Institute, College
Park, Maryland 20742, United States of America
| | - Paul J. Dagdigian
- Johns
Hopkins University, Department of Chemistry, Baltimore, Maryland 21218, United States
of America
| | - François Lique
- Université
de Rennes, Institut de Physique
de Rennes, 263 avenue
du Général Leclerc, Rennes CEDEX 35042, France
| | - Jolijn Onvlee
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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6
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Chen XY, Biswas S, Eppelt S, Schindewolf A, Deng F, Shi T, Yi S, Hilker TA, Bloch I, Luo XY. Ultracold field-linked tetratomic molecules. Nature 2024; 626:283-287. [PMID: 38297128 PMCID: PMC10849947 DOI: 10.1038/s41586-023-06986-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 12/15/2023] [Indexed: 02/02/2024]
Abstract
Ultracold polyatomic molecules offer opportunities1 in cold chemistry2,3, precision measurements4 and quantum information processing5,6, because of their rich internal structure. However, their increased complexity compared with diatomic molecules presents a challenge in using conventional cooling techniques. Here we demonstrate an approach to create weakly bound ultracold polyatomic molecules by electroassociation7 (F.D. et al., manuscript in preparation) in a degenerate Fermi gas of microwave-dressed polar molecules through a field-linked resonance8-11. Starting from ground-state NaK molecules, we create around 1.1 × 103 weakly bound tetratomic (NaK)2 molecules, with a phase space density of 0.040(3) at a temperature of 134(3) nK, more than 3,000 times colder than previously realized tetratomic molecules12. We observe a maximum tetramer lifetime of 8(2) ms in free space without a notable change in the presence of an optical dipole trap, indicating that these tetramers are collisionally stable. Moreover, we directly image the dissociated tetramers through microwave-field modulation to probe the anisotropy of their wavefunction in momentum space. Our result demonstrates a universal tool for assembling weakly bound ultracold polyatomic molecules from smaller polar molecules, which is a crucial step towards Bose-Einstein condensation of polyatomic molecules and towards a new crossover from a dipolar Bardeen-Cooper-Schrieffer superfluid13-15 to a Bose-Einstein condensation of tetramers. Moreover, the long-lived field-linked state provides an ideal starting point for deterministic optical transfer to deeply bound tetramer states16-18.
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Affiliation(s)
- Xing-Yan Chen
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
| | - Shrestha Biswas
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
| | - Sebastian Eppelt
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
| | - Andreas Schindewolf
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
| | - Fulin Deng
- School of Physics and Technology, Wuhan University, Wuhan, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
| | - Tao Shi
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China.
- AS Center for Excellence in Topological Quantum Computation & School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
| | - Su Yi
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
- AS Center for Excellence in Topological Quantum Computation & School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
- Peng Huanwu Collaborative Center for Research and Education, Beihang University, Beijing, China
| | - Timon A Hilker
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
| | - Immanuel Bloch
- Max-Planck-Institut für Quantenoptik, Garching, Germany
- Munich Center for Quantum Science and Technology, Munich, Germany
- Fakultät für Physik, Ludwig-Maximilians-Universität, Munich, Germany
| | - Xin-Yu Luo
- Max-Planck-Institut für Quantenoptik, Garching, Germany.
- Munich Center for Quantum Science and Technology, Munich, Germany.
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7
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Balakrishnan N, Jambrina PG, Croft JFE, Guo H, Aoiz FJ. Quantum stereodynamics of cold molecular collisions. Chem Commun (Camb) 2024; 60:1239-1256. [PMID: 38197484 DOI: 10.1039/d3cc04762h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Advances in quantum state preparations combined with molecular cooling and trapping technologies have enabled unprecedented control of molecular collision dynamics. This progress, achieved over the last two decades, has dramatically improved our understanding of molecular phenomena in the extreme quantum regime characterized by translational temperatures well below a kelvin. In this regime, collision outcomes are dominated by isolated partial waves, quantum threshold and quantum statistics effects, tiny energy splitting at the spin and hyperfine levels, and long-range forces. Collision outcomes are influenced not only by the quantum state preparation of the initial molecular states but also by the polarization of their rotational angular momentum, i.e., stereodynamics of molecular collisions. The Stark-induced adiabatic Raman passage technique developed in the last several years has become a versatile tool to study the stereodynamics of light molecular collisions in which alignment of the molecular bond axis relative to initial collision velocity can be fully controlled. Landmark experiments reported by Zare and coworkers have motivated new theoretical developments, including formalisms to describe four-vector correlations in molecular collisions that are revealed by the experiments. In this Feature article, we provide an overview of recent theoretical developments for the description of stereodynamics of cold molecular collisions and their implications to cold controlled chemistry.
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Affiliation(s)
- Naduvalath Balakrishnan
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, Nevada 89154, USA.
| | - Pablo G Jambrina
- Departamento de Química Física, Universidad de Salamanca, Salamanca 37008, Spain
| | - James F E Croft
- The Dodd Walls Centre for Photonic and Quantum Technologies, New Zealand and Department of Physics, University of Otago, Dunedin, New Zealand
| | - Hua Guo
- Department of Chemistry and Chemical Biology, Center for Computational Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - F Javier Aoiz
- Departamento de Química Física, Universidad Complutense, Madrid 28040, Spain
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8
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Song H, Guo H. Theoretical Insights into the Dynamics of Gas-Phase Bimolecular Reactions with Submerged Barriers. ACS PHYSICAL CHEMISTRY AU 2023; 3:406-418. [PMID: 37780541 PMCID: PMC10540288 DOI: 10.1021/acsphyschemau.3c00009] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/02/2023] [Accepted: 06/06/2023] [Indexed: 10/03/2023]
Abstract
Much attention has been paid to the dynamics of both activated gas-phase bimolecular reactions, which feature monotonically increasing integral cross sections and Arrhenius kinetics, and their barrierless capture counterparts, which manifest monotonically decreasing integral cross sections and negative temperature dependence of the rate coefficients. In this Perspective, we focus on the dynamics of gas-phase bimolecular reactions with submerged barriers, which often involve radicals or ions and are prevalent in combustion, atmospheric chemistry, astrochemistry, and plasma chemistry. The temperature dependence of the rate coefficients for such reactions is often non-Arrhenius and complex, and the corresponding dynamics may also be quite different from those with significant barriers or those completely dominated by capture. Recent experimental and theoretical studies of such reactions, particularly at relatively low temperatures or collision energies, have revealed interesting dynamical behaviors, which are discussed here. The new knowledge enriches our understanding of the dynamics of these unusual reactions.
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Affiliation(s)
- Hongwei Song
- State
Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Hua Guo
- Department
of Chemistry and Chemical Biology, University
of New Mexico, Albuquerque, New Mexico 87131, United States
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9
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Perera CA, Amarasinghe C, Guo H, Suits AG. Cold collisions of hot molecules. Phys Chem Chem Phys 2023; 25:22595-22606. [PMID: 37602475 DOI: 10.1039/d3cp02071a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2023]
Abstract
In this Perspective, we review our recent work on rotationally inelastic collisions of highly vibrationally excited NO molecules prepared in single rotational and parity levels at v = 10 using stimulated emission pumping (SEP). This state preparation is employed in a recently developed crossed molecular beam apparatus where two nearly copropagating molecular beams achieve an intersection angle of 4° at the interaction region. This near-copropagating beam geometry of the molecular beams permits very wide tuning of the collision energy, from far above room temperature down to 2 K where we test the theoretical treatment of the attractive part of the potentials and the difference potential for the first time. We have obtained differential cross sections for state-to-state collisions of NO (v = 10) with Ar and Ne in both spin-orbit manifolds using velocity map imaging. Overall good agreement of the experimental results was seen with quantum mechanical close-coupling calculations done on both coupled-cluster and multi-reference configuration interaction potential energy surfaces. Probing cold collisions of NO carrying ∼2 eV of vibrational excitation allows us to test state-of-the-art theory in this extreme nonequilibrium regime.
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Affiliation(s)
- Chatura A Perera
- Department of Chemistry, University of Missouri, Columbia, MO 65211, USA.
| | | | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Arthur G Suits
- Department of Chemistry, University of Missouri, Columbia, MO 65211, USA.
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10
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Plomp V, Onvlee J, Lique F, van de Meerakker SYT. Low-Energy Collisions of Zeeman-Decelerated NH Radicals with He Atoms. J Phys Chem A 2023; 127:2306-2313. [PMID: 36884215 PMCID: PMC10026067 DOI: 10.1021/acs.jpca.2c08712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
We report an experimental study of state-to-state inelastic scattering of NH (X 3Σ-, N = 0, j = 1) radicals with He atoms. Using a crossed molecular beam apparatus that combines a Zeeman decelerator and velocity map imaging, we study both integral and differential cross sections in the N = 0, j = 1 → N = 2, j = 3 inelastic channel. We developed various new REMPI schemes to state-selectively detect NH radicals, and tested their performance in terms of sensitivity and ion recoil velocity. We found a 1 + 2' + 1' REMPI scheme using the A 3Π ← X 3Σ- resonant transition, which yields acceptable recoil velocities and is more than an order of magnitude more sensitive than conventional one-color REMPI schemes to detect NH. We used this REMPI scheme to probe state-to-state integral and differential cross sections around the channel opening at 97.7 cm-1, as well as at higher energies where structure in the scattering images could be resolved. The experimental results are in excellent agreement with the predictions from quantum scattering calculations which are based on an ab initio NH-He potential energy surface.
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Affiliation(s)
- Vikram Plomp
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jolijn Onvlee
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - François Lique
- Institut de Physique de Rennes, Université de Rennes 1, 263 avenue du Général Leclerc, 35042 Rennes CEDEX, France
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11
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Yang D, Chai S, Xie D, Guo H. ABC+D: A time-independent coupled-channel quantum dynamics program for elastic and ro-vibrational inelastic scattering between atoms and triatomic molecules in full dimensionality. J Chem Phys 2023; 158:054801. [PMID: 36754781 DOI: 10.1063/5.0137628] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We discuss the details of a time-independent quantum mechanical method and its implementation for full-dimensional non-reactive scattering between a closed-shell triatomic molecule and a closed-shell atom. By solving the time-independent Schrödinger equation within the coupled-channel framework using a log-derivative method, the state-to-state scattering matrix (S-matrix) can be determined for inelastic scattering involving both the rotational and vibrational modes of the molecule. Various approximations are also implemented. The ABC+D code provides an important platform for understanding an array of physical phenomena involving collisions between atoms and molecules.
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Affiliation(s)
- Dongzheng Yang
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Shijie Chai
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Daiqian Xie
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
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12
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Yang D, Guo H, Xie D. Recent advances in quantum theory on ro-vibrationally inelastic scattering. Phys Chem Chem Phys 2023; 25:3577-3594. [PMID: 36602236 DOI: 10.1039/d2cp05069b] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Molecular collisions are of fundamental importance in understanding intermolecular interaction and dynamics. Its importance is accentuated in cold and ultra-cold collisions because of the dominant quantum mechanical nature of the scattering. We review recent advances in the time-independent approach to quantum mechanical characterization of non-reactive scattering in tetratomic systems, which is ideally suited for large collisional de Broglie wavelengths characteristic in cold and ultracold conditions. We discuss quantum scattering algorithms between two diatoms and between a triatom and an atom and their implementation, as well as various approximate schemes. They not only enable the characterization of collision dynamics in realistic systems but also serve as benchmarks for developing more approximate methods.
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Affiliation(s)
- Dongzheng Yang
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
| | - Daiqian Xie
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China. .,Hefei National Laboratory, Hefei 230088, China
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13
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Mukherjee N. Quantum-Controlled Collisions of H 2 Molecules. J Phys Chem A 2023; 127:418-438. [PMID: 36602238 DOI: 10.1021/acs.jpca.2c06808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The amount of information that can be obtained from a scattering experiment depends upon the precision with which the quantum states are defined in the incoming channel. By precisely defining the incoming states and measuring the outgoing states in a scattering experiment, we set up the boundary condition for experimentally solving the Schrödinger equation. In this Perspective we discuss cold inelastic scattering experiments using the most theoretically tractable H2 and its isotopologues as the target. We prepare the target in a precisely defined rovibrational (v, j, m) quantum state using a special coherent optical technique called the Stark-induced adiabatic Raman passage (SARP). v and j represent the quantum numbers of the vibrational and rotational energy levels, and m refers to the projection of the rotational angular momentum vector j on a suitable quantization axis in the laboratory frame. Selection of the m quantum numbers defines the alignment of the molecular frame, which is necessary to probe the anisotropic interactions. For us to achieve the collision temperature in the range of a few degrees Kelvin, we co-expand the colliding partners in a mixed supersonic beam that is collimated to define a direction for the collision velocity. When the bond axis is aligned with respect to a well-defined collision velocity, SARP achieves stereodynamic control at the quantum scale. Through various examples of rotationally inelastic cold scattering experiments, we show how SARP coherently controls the dynamics of anisotropic interactions by preparing quantum superpositions of the orientational m states within a single rovibrational (v, j) energy state. A partial wave analysis, which has been developed for the cold scattering experiments, shows dominance of a resonant orbital that leaves its mark in the scattering angular distribution. These highly controlled cold collision experiments at the single partial wave limit allow the most direct comparison with the results of theoretical computations, necessary for accurate modeling of the molecular interaction potential.
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Affiliation(s)
- Nandini Mukherjee
- Department of Chemistry, Stanford University, Stanford, California94305, United States
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14
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Butcher TA, Coey JMD. Magnetic forces in paramagnetic fluids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 35:053002. [PMID: 36384048 DOI: 10.1088/1361-648x/aca37f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 11/16/2022] [Indexed: 06/16/2023]
Abstract
An overview of the effect of a magnetic field gradient on fluids with linear magnetic susceptibilities is given. It is shown that two commonly encountered expressions, the magnetic field gradient force and the concentration gradient force for paramagnetic species in solution are equivalent for incompressible fluids. The magnetic field gradient and concentration gradient forces are approximations of the Kelvin force and Korteweg-Helmholtz force densities, respectively. The criterion for the appearance of magnetically induced convection is derived. Experimental work in which magnetically induced convection plays a role is reviewed.
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Affiliation(s)
- Tim A Butcher
- School of Physics and CRANN, Trinity College, Dublin 2, Ireland
| | - J M D Coey
- School of Physics and CRANN, Trinity College, Dublin 2, Ireland
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15
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Onvlee J, Trippel S, Küpper J. Ultrafast light-induced dynamics in the microsolvated biomolecular indole chromophore with water. Nat Commun 2022; 13:7462. [PMID: 36460654 PMCID: PMC9718776 DOI: 10.1038/s41467-022-33901-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 10/04/2022] [Indexed: 12/05/2022] Open
Abstract
Interactions between proteins and their solvent environment can be studied in a bottom-up approach using hydrogen-bonded chromophore-solvent clusters. The ultrafast dynamics following UV-light-induced electronic excitation of the chromophores, potential radiation damage, and their dependence on solvation are important open questions. The microsolvation effect is challenging to study due to the inherent mix of the produced gas-phase aggregates. We use the electrostatic deflector to spatially separate different molecular species in combination with pump-probe velocity-map-imaging experiments. We demonstrate that this powerful experimental approach reveals intimate details of the UV-induced dynamics in the near-UV-absorbing prototypical biomolecular indole-water system. We determine the time-dependent appearance of the different reaction products and disentangle the occurring ultrafast processes. This approach ensures that the reactants are well-known and that detailed characteristics of the specific reaction products are accessible - paving the way for the complete chemical-reactivity experiment.
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Affiliation(s)
- Jolijn Onvlee
- grid.7683.a0000 0004 0492 0453Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany ,grid.9026.d0000 0001 2287 2617Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany ,grid.5590.90000000122931605Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Sebastian Trippel
- grid.7683.a0000 0004 0492 0453Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany ,grid.9026.d0000 0001 2287 2617Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Jochen Küpper
- grid.7683.a0000 0004 0492 0453Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany ,grid.9026.d0000 0001 2287 2617Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany ,grid.9026.d0000 0001 2287 2617Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
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16
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Perreault WE, Zhou H, Mukherjee N, Zare RN. Quantum Controlled Cold Scattering Challenges Theory. J Phys Chem Lett 2022; 13:10912-10917. [PMID: 36394562 DOI: 10.1021/acs.jpclett.2c03038] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Our previous rotationally inelastic cold scattering experiments between state prepared D2 (v = 2, j = 2, m = 0) and He disagreed with theory, raising serious concerns about either our understanding of the anisotropic potential or the accuracy of the measurement. To further interrogate interactions between molecular hydrogen and atomic helium, we study the Δj = 1and Δj = 2 rotational relaxation of HD (v = 2, j = 2, m = 0) by collision with He. The two rotational transitions probe different anisotropic components of the van der Waals potential. Our state resolved scattering study shows that these two transitions are mediated by two different shape resonances l = 1 for Δj = 1 and l = 2 for Δj = 2. The strong l = 1 resonance dominates the Δj = 1 scattering, agreeing with theory. However, the dominance of the weaker l = 2 resonance in the Δj = 2 transition, which matches our earlier D2-He result, contradicts theoretical calculations. The continued contradiction, when we expect one-to-one correspondence between our stereodynamically controlled scattering experiment and theoretical calculations, makes us question the accuracy of the weaker anisotropic part of the H2-He interaction potential.
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Affiliation(s)
- William E Perreault
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Haowen Zhou
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Nandini Mukherjee
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, California94305, United States
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17
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Miao L, Liu Z, Chen Z, Wang X, Zhou Z, Zhao J, Fang S, Yin G, Jia Z, Liu J, Moro R, deHeer WA, Ma L. Fourth generation cryogenic neutral cluster beam apparatus for studying fundamental properties of metallic clusters. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:113310. [PMID: 36461426 DOI: 10.1063/5.0087524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 10/13/2022] [Indexed: 06/17/2023]
Abstract
A cryogenic beam apparatus for studying neutral clusters has been built and tested. The lowest beam temperature reaches less than 9 K at a repetition rate of 20 Hz. Mechanical decoupling from the refrigerator avoids misalignment during temperature ramping. Adopting a permanent magnet based magnetic deflector eliminates the hysteresis and electric noise of the traditional electromagnet and offers excellent reproducibility of the applied magnetic field. The mass spectrometer can operate in either Mass Spectroscopy Time-Of-Flight mode or Position-Sensitive Time-Of-Flight mode with spatial resolution better than 7 μm. Its performance is demonstrated with niobium and cobalt clusters.
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Affiliation(s)
- Lin Miao
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Zhaojun Liu
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Zeyang Chen
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Xiaohan Wang
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Ziwen Zhou
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Jinbo Zhao
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Shaozheng Fang
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Guangjia Yin
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Zezhao Jia
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Jin Liu
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Ramiro Moro
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Walt A deHeer
- School of Physics, Georgia Institute of Technology, 837 North Ave. NW, Atlanta, Georgia 30332, USA
| | - Lei Ma
- Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
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18
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Herbers S, Caris YM, Kuijpers SEJ, Grabow JU, van de Meerakker SYT. Efficient transfer of inversion doublet populations in deuterated ammonia using adiabatic rapid passage. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2129105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/07/2022]
Affiliation(s)
- S. Herbers
- Institute for Molecules and Materials, Radboud Universiteit, Nijmegen, Netherlands
| | - Y. M. Caris
- Institute for Molecules and Materials, Radboud Universiteit, Nijmegen, Netherlands
| | - S. E. J. Kuijpers
- Institute for Molecules and Materials, Radboud Universiteit, Nijmegen, Netherlands
| | - J.-U. Grabow
- Institut für Physikalische Chemie und Elektrochemie, Gottfried Wilhelm Leibniz Universität, Hannover, Germany
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19
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Wang BB, Zhang M, Han YC. Ultracold state-to-state chemistry for three-body recombination in realistic 3He 2-alkaline-earth-metal systems. J Chem Phys 2022; 157:014305. [PMID: 35803812 DOI: 10.1063/5.0090243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ultracold state-to-state chemistry for three-body recombination (TBR) in realistic systems recently could be experimentally investigated with full quantum state resolution. However, many detected phenomena remain challenging to be explored and explained from the theoretical viewpoints because this generally requires computational powers beyond the state-of-the-art. Here, the product-state distributions after TBR of 3He2-alkaline-earth-metal systems, i.e. after the processes 3He+3He+X→3HeX+3He with X being 9Be, 24Mg, 40Ca, 88Sr, or 138Ba, in the zero-collision-energy limit are theoretically studied. Two propensity rules for the distribution of the products found in current experiments have been checked, and the mechanism underlying these product-state distributions is explored. Particularly, two main intriguing transition pathways are identified, which may be responsible for the nonlinear distribution of the products versus their rotational quantum number. In addition, the total TBR rates of these systems are also accounted for by the joint effects of major adiabatic potential energies and relevant nonadiabatic couplings.
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Affiliation(s)
- Bin-Bin Wang
- School of Physics and Astronomy, China West Normal University, China
| | | | - Yong-Chang Han
- Department of Physics, Dalian University of Technology, China
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20
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Perera CA, Zuo J, Guo H, Suits AG. Differential Cross Sections for Cold, State-to-State Spin-Orbit Changing Collisions of NO( v = 10) with Neon. J Phys Chem A 2022; 126:3338-3346. [PMID: 35605132 DOI: 10.1021/acs.jpca.2c02698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inelastic scattering processes have proven a powerful means of investigating molecular interactions, and much current effort is focused on the cold and ultracold regime where quantum phenomena are clearly manifested. Studies of collisions of the open shell nitric oxide (NO) molecule have been central in this effort since the pioneering work of Houston and co-workers in the early 1990s. State-to-state scattering of vibrationally excited molecules in the cold regime introduces challenges that test the suitability of current theoretical methods for ab initio determination of intermolecular potentials, and concomitant electronically nonadiabatic processes raise the bar further. Here we report measurements of differential cross sections for state-to-state spin-orbit changing collisions of NO (v = 10, Ω″ = 1.5, and j″ = 1.5) with neon from 2.3 to 3.5 cm-1 collision energy using our recently developed near-copropagating beam technique. The experimental results are compared with those obtained from quantum scattering calculations on a high-level set of coupled cluster potential energy surfaces and are shown to be in good agreement. The theoretical results suggest that distinct backscattering in the 2.3 cm-1 case arises from overlapping resonances.
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Affiliation(s)
- Chatura A Perera
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Junxiang Zuo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Arthur G Suits
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
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21
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Ritika, Dhilip Kumar T. Rotational quenching of C2 with 3He and 4He collisions at ultracold temperatures. Chem Phys Lett 2022. [DOI: 10.1016/j.cplett.2022.139623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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22
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Walter N, Doppelbauer M, Marx S, Seifert J, Liu X, Pérez-Ríos J, Sartakov BG, Truppe S, Meijer G. Spectroscopic characterization of the a 3Π state of aluminum monofluoride. J Chem Phys 2022; 156:124306. [DOI: 10.1063/5.0082601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong A1Π ← X1Σ+ transition around 227 nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden a3Π ← X1Σ+ transition around 367 nm, which has a recoil limit in the µK range. We here report on the spectroscopic characterization of the lowest rotational levels in the a3Π state of AlF for v = 0–8 using a jet-cooled, pulsed molecular beam. An accidental AC Stark shift is observed on the a3Π0, v = 4 ← X1Σ+, v = 4 band. By using time-delayed ionization for state-selective detection of the molecules in the metastable a3Π state at different points along the molecular beam, the radiative lifetime of the a3Π1, v = 0, J = 1 level is experimentally determined as τ = 1.89 ± 0.15 ms. A laser/radio frequency multiple resonance ionization scheme is employed to determine the hyperfine splittings in the a3Π1, v = 5 level. The experimentally derived hyperfine parameters are compared to the outcome of quantum chemistry calculations. A spectral line with a width of 1.27 kHz is recorded between hyperfine levels in the a3Π, v = 0 state. These measurements benchmark the electronic potential of the a3Π state and yield accurate values for the photon scattering rate and for the elements of the Franck–Condon matrix of the a3Π–X1Σ+ system.
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Affiliation(s)
- N. Walter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - M. Doppelbauer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - S. Marx
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - J. Seifert
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - X. Liu
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - J. Pérez-Ríos
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - B. G. Sartakov
- Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilovstreet 38, 119991 Moscow, Russia
| | - S. Truppe
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - G. Meijer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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23
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Glory scattering in deeply inelastic molecular collisions. Nat Chem 2022; 14:664-669. [DOI: 10.1038/s41557-022-00907-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 02/04/2022] [Indexed: 11/08/2022]
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24
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Mapping partial wave dynamics in scattering resonances by rotational de-excitation collisions. Nat Chem 2022; 14:538-544. [PMID: 35210587 DOI: 10.1038/s41557-022-00896-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 01/21/2022] [Indexed: 11/09/2022]
Abstract
One of the most important parameters in a collision is the 'miss distance' or impact parameter, which in quantum mechanics is described by quantized partial waves. Usually, the collision outcome is the result of unavoidable averaging over many partial waves. Here we present a study of low-energy NO-He collisions that enables us to probe how individual partial waves evolve during the collision. By tuning the collision energies to scattering resonances between 0.4 and 6 cm-1, the initial conditions are characterized by a limited set of partial waves. By preparing NO in a rotationally excited state before the collision and by studying rotational de-excitation collisions, we were able to add one quantum of angular momentum to the system and trace how it evolves. Distinct fingerprints in the differential cross-sections yield a comprehensive picture of the partial wave dynamics during the scattering process. Exploiting the principle of detailed balance, we show that rotational de-excitation collisions probe time-reversed excitation processes with superior energy and angular resolution.
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25
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Sobczuk J, Urbańczyk T, Koperski J. Optical–optical double resonance process in free-jet supersonic expansion of van der Waals molecules: characteristics of the expansion, number of excited molecules and emitted photons. Mol Phys 2022. [DOI: 10.1080/00268976.2021.2024614] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Joanna Sobczuk
- Marian Smoluchowski Institute of Physics, Jagiellonian University Kraków, Poland
| | - Tomasz Urbańczyk
- Marian Smoluchowski Institute of Physics, Jagiellonian University Kraków, Poland
| | - Jarosław Koperski
- Marian Smoluchowski Institute of Physics, Jagiellonian University Kraków, Poland
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26
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Narevicius J, Narevicius E. Multichannel high peak power tunable duration pulse generation for the moving magnetic trap decelerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:013202. [PMID: 35104939 DOI: 10.1063/5.0077604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 12/31/2021] [Indexed: 06/14/2023]
Abstract
We present a multichannel setup capable of generating high peak power tunable duration pulses. Our architecture is based on a configurable RLC circuit and allows generation of 1120 current pulses, with the variable duration spanning 14-212 µs with 1 µs resolution and the peak current reaching 500 A. We use silicon controlled rectifier based multiplexing to deliver current pulses to dedicated inductors that generate 0.8 T strong magnetic fields that create a moving magnetic trap for paramagnetic particles in a supersonic beam.
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Affiliation(s)
- Julia Narevicius
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Edvardas Narevicius
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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27
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Plomp V, Wang XD, Lique F, Kłos J, Onvlee J, van de Meerakker SYT. High-Resolution Imaging of C + He Collisions using Zeeman Deceleration and Vacuum-Ultraviolet Detection. J Phys Chem Lett 2021; 12:12210-12217. [PMID: 34928163 PMCID: PMC8724800 DOI: 10.1021/acs.jpclett.1c03643] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/13/2021] [Indexed: 05/25/2023]
Abstract
High-resolution measurements of angular scattering distributions provide a sensitive test for theoretical descriptions of collision processes. Crossed beam experiments employing a decelerator and velocity map imaging have proven successful to probe collision cross sections with extraordinary resolution. However, a prerequisite to exploit these possibilities is the availability of a near-threshold state-selective ionization scheme to detect the collision products, which for many species is either absent or inefficient. We present the first implementation of recoil-free vacuum ultraviolet (VUV) based detection in scattering experiments involving a decelerator and velocity map imaging. This allowed for high-resolution measurements of state-resolved angular scattering distributions for inelastic collisions between Zeeman-decelerated carbon C(3P1) atoms and helium atoms. We fully resolved diffraction oscillations in the angular distributions, which showed excellent agreement with the distributions predicted by quantum scattering calculations. Our approach offers exciting prospects to investigate a large range of scattering processes with unprecedented precision.
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Affiliation(s)
- Vikram Plomp
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Xu-Dong Wang
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - François Lique
- Université
de Rennes, Institut de Physique de Rennes, 263 avenue du Général
Leclerc, Rennes 35042 CEDEX, France
| | - Jacek Kłos
- University
of Maryland, Department of Physics, Joint
Quantum Institute, College Park, Maryland 20742, United States of America
| | - Jolijn Onvlee
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
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28
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Guardado JL, Hood DJ, Luong K, Kidwell NM, Petit AS. Stereodynamic Control of Collision-Induced Nonadiabatic Dynamics of NO ( A2Σ +) with H 2, N 2, and CO: Intermolecular Interactions Drive Collision Outcomes. J Phys Chem A 2021; 125:8803-8815. [PMID: 34606268 DOI: 10.1021/acs.jpca.1c05653] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intermolecular interactions, stereodynamics, and coupled potential energy surfaces (PESs) all play a significant role in determining the outcomes of molecular collisions. A detailed knowledge of such processes is often essential for a proper interpretation of spectroscopic observations. For example, nitric oxide (NO), an important radical in combustion and atmospheric chemistry, is commonly quantified using laser-induced fluorescence on the A2Σ+ ← X2Π transition band. However, the electronic quenching of NO (A2Σ+) with other molecular species provides alternative nonradiative pathways that compete with fluorescence. While the cross sections and rate constants of NO (A2Σ+) electronic quenching have been experimentally measured for a number of important molecular collision partners, the underlying photochemical mechanisms responsible for the electronic quenching are not well understood. In this paper, we describe the development of high-quality PESs that provide new physical insights into the intermolecular interactions and conical intersections that facilitate the branching between the electronic quenching and scattering of NO (A2Σ+) with H2, N2, and CO. The PESs are calculated at the EOM-EA-CCSD/d-aug-cc-pVTZ//EOM-EA-CCSD/aug-cc-pVDZ level of theory, an approach that ensures a balanced treatment of the valence and Rydberg electronic states and an accurate description of the open-shell character of NO. Our PESs show that H2 is incapable of electronically quenching NO (A2Σ+) at low collision energies; instead, the two molecules will likely undergo scattering. The PESs of NO (A2Σ+) with N2 and CO are highly anisotropic and demonstrate evidence of electron transfer from NO (A2Σ+) into the lowest unoccupied molecular orbital of the collision partner, that is, the harpoon mechanism. In the case of ON + CO, the PES becomes strongly attractive at longer intermolecular distances and funnels population to a conical intersection between NO (A2Σ+) + CO and NO (X2Π) + CO. In contrast, for ON + N2, the conical intersection is preceded by an ∼0.40 eV barrier. Overall, our work shines new light into the impact of coupled PESs on the nonadiabatic dynamics of open-shell systems.
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Affiliation(s)
- José L Guardado
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - David J Hood
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
| | - Kate Luong
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - Nathanael M Kidwell
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
| | - Andrew S Petit
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
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29
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Zhelyazkova V, Martins FBV, Agner JA, Schmutz H, Merkt F. Multipole-moment effects in ion-molecule reactions at low temperatures: part I - ion-dipole enhancement of the rate coefficients of the He + + NH 3 and He + + ND 3 reactions at collisional energies Ecoll/ kB near 0 K. Phys Chem Chem Phys 2021; 23:21606-21622. [PMID: 34569565 PMCID: PMC8494273 DOI: 10.1039/d1cp03116c] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/02/2021] [Indexed: 11/29/2022]
Abstract
The energy dependence of the rates of the reactions between He+ and ammonia (NY3, Y = {H,D}), forming NY2+, Y and He as well as NY+, Y2 and He, and the corresponding product branching ratios have been measured at low collision energies Ecoll between 0 and kB·40 K using a recently developed merged-beam technique [Allmendinger et al., ChemPhysChem, 2016, 17, 3596]. To avoid heating of the ions by stray electric fields, the reactions are observed within the large orbit of a highly excited Rydberg electron. A beam of He Rydberg atoms was merged with a supersonic beam of ammonia using a curved surface-electrode Rydberg-Stark deflector, which is also used for adjusting the final velocity of the He Rydberg atoms, and thus the collision energy. A collision-energy resolution of about 200 mK was reached at the lowest Ecoll values. The reaction rate coefficients exhibit a sharp increase at collision energies below ∼kB·5 K and pronounced deviations from Langevin-capture behaviour. The experimental results are interpreted in terms of an adiabatic capture model describing the rotational-state-dependent orientation of the ammonia molecules by the electric field of the He+ atom. The model faithfully describes the experimental observations and enables the identification of three classes of |JKMp〉 rotational states of the ammonia molecules showing different low-energy capture behaviour: (A) high-field-seeking states with |KM| ≥ 1 correlating to the lower component of the umbrella-motion tunnelling doublet at low fields. These states undergo a negative linear Stark shift, which leads to strongly enhanced rate coefficients; (B) high-field-seeking states subject to a quadratic Stark shift at low fields and which exhibit only weak rate enhancements; and (C) low-field-seeking states with |KM| ≥ 1. These states exhibit a positive Stark shift at low fields, which completely suppresses the reactions at low collision energies. Marked differences in the low-energy reactivity of NH3 and ND3-the rate enhancements in ND3 are more pronounced than in NH3-are quantitatively explained by the model. They result from the reduced magnitudes of the tunnelling splitting and rotational intervals in ND3 and the different occupations of the rotational levels in the supersonic beam caused by the different nuclear-spin statistical weights. Thermal capture rate constants are derived from the model for the temperature range between 0 and 10 K relevant for astrochemistry. Comparison of the calculated thermal capture rate coefficients with the absolute reaction rates measured above 27 K by Marquette et al. (Chem. Phys. Lett., 1985, 122, 431) suggests that only 40% of the close collisions are reactive.
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30
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Greenberg J, Krohn OA, Bossert JA, Shyur Y, Macaluso D, Fitch NJ, Lewandowski HJ. Velocity-tunable beam of continuously decelerated polar molecules for cold ion-molecule reaction studies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:103202. [PMID: 34717395 DOI: 10.1063/5.0057859] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
Producing high densities of molecules is a fundamental challenge for low-temperature, ion-molecule reaction studies. Traveling-wave Stark decelerators promise to deliver high density beams of cold, polar molecules but require non-trivial control of high-voltage potentials. We have overcome this experimental challenge and demonstrate continuous deceleration of ND3 from 385 to 10 m/s, while driving the decelerator electrodes with a 10 kV amplitude sinewave. In addition, we test an alternative slowing scheme, which increases the time delay between decelerated packets of ND3 and non-decelerated molecules, allowing for better energy resolution of subsequent reaction studies. We characterize this source of neutral, polar molecules suitable for energy-resolved reaction studies with trapped ions at cold translational temperatures. We also propose a combined apparatus consisting of the traveling-wave decelerator and a linear ion trap with a time-of-flight mass spectrometer and discuss to what extent it may achieve cold, energy-resolved, ion-neutral reactions.
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Affiliation(s)
- James Greenberg
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - O A Krohn
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Jason A Bossert
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Yomay Shyur
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - David Macaluso
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - N J Fitch
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - H J Lewandowski
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
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31
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Wang XD, Parker DH, van de Meerakker SYT, Groenenboom GC, Onvlee J. Laser ionisation detection of O(3Pj) atoms in the VUV; application to photodissociation of O2. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1979264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- X.-D. Wang
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - D. H. Parker
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | | | - G. C. Groenenboom
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - J. Onvlee
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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32
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Karra M, Schmidt B, Friedrich B. Quantum dynamics of a polar rotor acted upon by an electric rectangular pulse of variable duration. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1966111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Burkhard Schmidt
- Institut für Mathematik, Freie Universität Berlin, Berlin, Germany
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Liu S, Wang G, Li Y, Li X, Huang W, Feng E. Theoretical investigation of laser cooling for BN - anion by ab inito calculation. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 255:119670. [PMID: 33751960 DOI: 10.1016/j.saa.2021.119670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 01/25/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
A theoretical investigation for the feasibility of laser cooling BN-anion is presented. An ab initio calculation on the three low-lying states Χ2Σ+, Α2Π and Β2Σ+ are performed at the CASSCF/MRCI + Q level. The calculated spectroscopic constants are in good agreement with the available theoretical and experimental data. Radiative properties including Franck-Condon factor, Einstein coefficients and radiative lifetimes are determined. The calculation shows that the transition B2Σ+(v')↔X2Σ+(v'') has highly diagonal FCFs, especially f00 = 0.9898, and enough short radiative lifetimes. A cooling scheme by three laser beams is proposed, which requires one main pumping laser(λ00 = 474.67 nm) and two repumping lasers (λ01 = 514.64 nm, λ12= 514.90 nm). The population dynamics of cooling is investigated with the rate equation approach. The simulation demonstrates that the population does not remain trapped within the intermediate Α2Π state. The resultant scattered photons are about2.5×104, which is expected to stop BN-anion molecule in a cryogenic beam theoretically.
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Affiliation(s)
- ShuaiShuai Liu
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China
| | - Guangbao Wang
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China; Department of Media Engineering, Chuzhou Vocational and Technical College, Chuzhou 239000, People's Republic of China
| | - Ya Li
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China
| | - Xucheng Li
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China
| | - Wuyin Huang
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China
| | - Eryin Feng
- Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China.
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Auerbach DJ, Tully JC, Wodtke AM. Chemical dynamics from the gas‐phase to surfaces. ACTA ACUST UNITED AC 2021. [DOI: 10.1002/ntls.10005] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Daniel J. Auerbach
- Institut für physikalische Chemie Georg‐August Universität Göttingen Göttingen Germany
- Abteilung für Dynamik an Oberflächen Max‐Planck‐Institut für biophysikalische Chemie Göttingen Germany
| | - John C. Tully
- Department of Chemistry Yale University New Haven Connecticut USA
| | - Alec M. Wodtke
- Institut für physikalische Chemie Georg‐August Universität Göttingen Göttingen Germany
- Abteilung für Dynamik an Oberflächen Max‐Planck‐Institut für biophysikalische Chemie Göttingen Germany
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35
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Heazlewood BR. Quantum-State Control and Manipulation of Paramagnetic Molecules with Magnetic Fields. Annu Rev Phys Chem 2021; 72:353-373. [PMID: 33492979 DOI: 10.1146/annurev-physchem-090419-053842] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Since external magnetic fields were first employed to deflect paramagnetic atoms in 1921, a range of magnetic field-based methods have been introduced to state-selectively manipulate paramagnetic species. These methods include magnetic guides, which selectively filter paramagnetic species from all other components of a beam, and magnetic traps, where paramagnetic species can be spatially confined for extended periods of time. However, many of these techniques were developed for atomic-rather than molecular-paramagnetic species. It has proven challenging to apply some of these experimental methods developed for atoms to paramagnetic molecules. Thanks to the emergence of new experimental approaches and new combinations of existing techniques, the past decade has seen significant progress toward the manipulation and control of paramagnetic molecules. This review identifies the key methods that have been implemented for the state-selective manipulation of paramagnetic molecules-discussing the motivation, state of the art, and future prospects of the field. Key applications include the ability to control chemical interactions, undertake precise spectroscopic measurements, and challenge our understanding of chemical reactivity at a fundamental level.
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36
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Aggarwal P, Bethlem HL, Boeschoten A, Borschevsky A, Esajas K, Hao Y, Hoekstra S, Jungmann K, Marshall VR, Meijknecht TB, Mooij MC, Timmermans RGE, Touwen A, Ubachs W, Willmann L, Yin Y, Zapara A. A supersonic laser ablation beam source with narrow velocity spreads. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:033202. [PMID: 33819994 DOI: 10.1063/5.0035568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 02/06/2021] [Indexed: 06/12/2023]
Abstract
A supersonic beam source for SrF and BaF molecules is constructed by combining the expansion of carrier gas (a mixture of 2% SF6 and 98% argon) from an Even-Lavie valve with laser ablation of a barium/strontium metal target at a repetition rate of 10 Hz. Molecular beams with a narrow translational velocity spread are produced at relative values of Δv/v = 0.053(11) and 0.054(9) for SrF and BaF, respectively. The relative velocity spread of the beams produced in our source is lower in comparison with the results from other metal fluoride beams produced in supersonic laser ablation sources. The rotational temperature of BaF is measured to be 3.5 K. The source produces 6 × 108 and 107 molecules per steradian per pulse in the X2Σ+ (ν = 0, N = 1) state of BaF and SrF molecules, respectively, a state amenable to Stark deceleration and laser cooling.
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Affiliation(s)
- P Aggarwal
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - H L Bethlem
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - A Boeschoten
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - A Borschevsky
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - K Esajas
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - Y Hao
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - S Hoekstra
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - K Jungmann
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - V R Marshall
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - T B Meijknecht
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - M C Mooij
- Nikhef, National Institute for Subatomic Physics, Science Park 105, 1098 XG Amsterdam, The Netherlands
| | - R G E Timmermans
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - A Touwen
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - W Ubachs
- Department of Physics and Astronomy, and LaserLaB, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - L Willmann
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - Y Yin
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
| | - A Zapara
- Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Zernikelaan 25 9747AA, The Netherlands
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37
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Saribal C, Owens A, Yachmenev A, Küpper J. Detecting handedness of spatially oriented molecules by Coulomb explosion imaging. J Chem Phys 2021; 154:071101. [PMID: 33607914 DOI: 10.1063/5.0029792] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a new technique for detecting chirality in the gas phase: Chiral molecules are spatially aligned in three dimensions by a moderately strong elliptically polarized laser field. The momentum distributions of the charged fragments, produced by laser-induced Coulomb explosion, show distinct three-dimensional orientation of the enantiomers when the laser polarization ellipse is rotated by a non-right angle with respect to the norm vector of the detector plane. The resulting velocity-map-image asymmetry is directly connected to the enantiomeric excess and to the absolute handedness of molecules. We demonstrated our scheme computationally for camphor (C10H16O), with its methyl groups as marker fragments, using quantum-mechanical simulations geared toward experimentally feasible conditions. Computed sensitivity to enantiomeric excess is comparable to other modern chiroptical approaches. The present method can be readily optimized for any chiral molecule with an anisotropic polarizability tensor by adjusting the polarization state and intensity profile of the laser field.
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Affiliation(s)
- Cem Saribal
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Alec Owens
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Andrey Yachmenev
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Jochen Küpper
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
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38
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Abstract
The prospect of cooling matter down to temperatures that are close to absolute zero raises intriguing questions about how chemical reactivity changes under these extreme conditions. Although some types of chemical reaction still occur at 1 μK, they can no longer adhere to the conventional picture of reactants passing over an activation energy barrier to become products. Indeed, at ultracold temperatures, the system enters a fully quantum regime, and quantum mechanics replaces the classical picture of colliding particles. In this Review, we discuss recent experimental and theoretical developments that allow us to explore chemical reactions at temperatures that range from 100 K to 500 nK. Although the field is still in its infancy, exceptional control has already been demonstrated over reactivity at low temperatures.
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Zhelyazkova V, Martins FBV, Agner JA, Schmutz H, Merkt F. Ion-Molecule Reactions below 1 K: Strong Enhancement of the Reaction Rate of the Ion-Dipole Reaction He^{+}+CH_{3}F. PHYSICAL REVIEW LETTERS 2020; 125:263401. [PMID: 33449728 DOI: 10.1103/physrevlett.125.263401] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 10/14/2020] [Accepted: 11/04/2020] [Indexed: 06/12/2023]
Abstract
The reaction between He^{+} and CH_{3}F forming predominantly CH_{2}^{+} and CHF^{+} has been studied at collision energies E_{coll} between 0 and k_{B}·10 K in a merged-beam apparatus. To avoid heating of the ions by stray electric fields, the reaction was observed within the orbit of a highly excited Rydberg electron. Supersonic beams of CH_{3}F and He(n) Rydberg atoms with principal quantum number n=30 and 35 were merged and their relative velocity tuned using a Rydberg-Stark decelerator and deflector, allowing an energy resolution of 150 mK. A strong enhancement of the reaction rate was observed below E_{coll}/k_{B}=1 K. The experimental results are interpreted with an adiabatic capture model that accounts for the state-dependent orientation of the polar CH_{3}F molecules by the Stark effect as they approach the He^{+} ion. The enhancement of the reaction rate at low collision energies is primarily attributed to para-CH_{3}F molecules in the J=1, KM=1 high-field-seeking states, which represent about 8% of the population at the 6 K rotational temperature of the supersonic beam.
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Affiliation(s)
| | | | - Josef A Agner
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hansjürg Schmutz
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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40
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Santamaria L, Di Sarno V, Aiello R, De Rosa M, Ricciardi I, De Natale P, Maddaloni P. Infrared Comb Spectroscopy of Buffer-Gas-Cooled Molecules: Toward Absolute Frequency Metrology of Cold Acetylene. Int J Mol Sci 2020; 22:E250. [PMID: 33383699 PMCID: PMC7795711 DOI: 10.3390/ijms22010250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 12/18/2020] [Accepted: 12/24/2020] [Indexed: 11/20/2022] Open
Abstract
We review the recent developments in precision ro-vibrational spectroscopy of buffer-gas-cooled neutral molecules, obtained using infrared frequency combs either as direct probe sources or as ultra-accurate optical rulers. In particular, we show how coherent broadband spectroscopy of complex molecules especially benefits from drastic simplification of the spectra brought about by cooling of internal temperatures. Moreover, cooling the translational motion allows longer light-molecule interaction times and hence reduced transit-time broadening effects, crucial for high-precision spectroscopy on simple molecules. In this respect, we report on the progress of absolute frequency metrology experiments with buffer-gas-cooled molecules, focusing on the advanced technologies that led to record measurements with acetylene. Finally, we briefly discuss the prospects for further improving the ultimate accuracy of the spectroscopic frequency measurement.
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Affiliation(s)
- Luigi Santamaria
- Agenzia Spaziale Italiana, Contrada Terlecchia, 75100 Matera, Italy;
| | - Valentina Di Sarno
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; (V.D.S.); (R.A.); (M.D.R.); (I.R.)
- Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Roberto Aiello
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; (V.D.S.); (R.A.); (M.D.R.); (I.R.)
- Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Maurizio De Rosa
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; (V.D.S.); (R.A.); (M.D.R.); (I.R.)
- Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Iolanda Ricciardi
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; (V.D.S.); (R.A.); (M.D.R.); (I.R.)
- Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Paolo De Natale
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, Italy;
- Istituto Nazionale di Fisica Nucleare, Sez. di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
| | - Pasquale Maddaloni
- Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; (V.D.S.); (R.A.); (M.D.R.); (I.R.)
- Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy
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41
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Shuai Q, de Jongh T, Besemer M, van der Avoird A, Groenenboom GC, van de Meerakker SYT. Experimental and theoretical investigation of resonances in low-energy NO-H 2 collisions. J Chem Phys 2020; 153:244302. [PMID: 33380097 DOI: 10.1063/5.0033488] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The experimental characterization of scattering resonances in low energy collisions has proven to be a stringent test for quantum chemistry calculations. Previous measurements on the NO-H2 system at energies down to 10 cm-1 challenged the most sophisticated calculations of potential energy surfaces available. In this report, we continue these investigations by measuring the scattering behavior of the NO-H2 system in the previously unexplored 0.4 cm-1-10 cm-1 region for the parity changing de-excitation channel of NO. We study state-specific inelastic collisions with both para- and ortho-H2 in a crossed molecular beam experiment involving Stark deceleration and velocity map imaging. We are able to resolve resonance features in the measured integral and differential cross sections. Results are compared to predictions from two previously available potential energy surfaces, and we are able to clearly discriminate between the two potentials. We furthermore identify the partial wave contributions to these resonances and investigate the nature of the differences between collisions with para- and ortho-H2. Additionally, we tune the energy spreads in the experiment to our advantage to probe scattering behavior at energies beyond our mean experimental limit.
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Affiliation(s)
- Quan Shuai
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Tim de Jongh
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Matthieu Besemer
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ad van der Avoird
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Gerrit C Groenenboom
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Najafian K, Meir Z, Willitsch S. From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N 2. Phys Chem Chem Phys 2020; 22:23083-23098. [PMID: 33048077 DOI: 10.1039/d0cp03906c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent advances in quantum technologies have enabled the precise control of single trapped molecules on the quantum level. Exploring the scope of these new technologies, we studied theoretically the implementation of qubits and clock transitions in the spin, rotational, and vibrational degrees of freedom of molecular nitrogen ions including the effects of magnetic fields. The relevant spectroscopic transitions span six orders of magnitude in frequency, illustrating the versatility of the molecular spectrum for encoding quantum information. We identified two types of magnetically insensitive qubits with very low ("stretched"-state qubits) or even zero ("magic" magnetic-field qubits) linear Zeeman shifts. The corresponding spectroscopic transitions are predicted to shift by as little as a few mHz for an amplitude of magnetic-field fluctuations on the order of a few mG, translating into Zeeman-limited coherence times of tens of minutes encoded in the rotations and vibrations of the molecule. We also found that the Q(0) line of the fundamental vibrational transition is magnetic-dipole allowed by interaction with the first excited electronic state of the molecule. The Q(0) transitions, which benefit from small systematic shifts for clock operation and is thus well suited for testing a possible variation in the proton-to-electron mass ratio, were so far not considered in single-photon spectra. Finally, we explored possibilities to coherently control the nuclear-spin configuration of N2+ through the magnetically enhanced mixing of nuclear-spin states.
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Affiliation(s)
- Kaveh Najafian
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland.
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43
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Li J, Zhao B, Xie D, Guo H. Advances and New Challenges to Bimolecular Reaction Dynamics Theory. J Phys Chem Lett 2020; 11:8844-8860. [PMID: 32970441 DOI: 10.1021/acs.jpclett.0c02501] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Dynamics of bimolecular reactions in the gas phase are of foundational importance in combustion, atmospheric chemistry, interstellar chemistry, and plasma chemistry. These collision-induced chemical transformations are a sensitive probe of the underlying potential energy surface(s). Despite tremendous progress in past decades, our understanding is still not complete. In this Perspective, we survey the recent advances in theoretical characterization of bimolecular reaction dynamics, stimulated by new experimental observations, and identify key new challenges.
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Affiliation(s)
- Jun Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China
| | - Bin Zhao
- Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Daiqian Xie
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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44
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Zuo J, Guo H. Time-independent quantum theory on vibrational inelastic scattering between atoms and open-shell diatomic molecules: Applications to NO + Ar and NO + H scattering. J Chem Phys 2020; 153:144306. [PMID: 33086802 DOI: 10.1063/5.0026637] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A full-dimensional rigorous quantum mechanical treatment of non-reactive inelastic scattering of an open-shell diatom [e.g., NO(2Π)] with a structureless and spinless atom is presented within the time-independent close-coupling framework. The inclusion of the diatomic vibrational degree of freedom allows the investigation of transitions between different vibrational manifolds, in addition to those between different rotational, spin-orbit, and Λ-doublet states. This method is applied to the scattering of vibrationally excited NO(2Π) with Ar and H (with its spin ignored). The former has negligible vibrational inelasticity, thanks to the weak interaction between the two collisional partners. This conclusion justifies the commonly used two-dimensional approximation in treating NO scattering with rare gas atoms. The latter, on the other hand, is shown to undergo significant vibrational relaxation, even in the ultra-cold regime, owing to a chemically bonded (HNO) complex on the lowest-lying singlet potential energy surfaces.
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Affiliation(s)
- Junxiang Zuo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
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45
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Jansen P, Merkt F. Manipulating beams of paramagnetic atoms and molecules using inhomogeneous magnetic fields. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 120-121:118-148. [PMID: 33198967 DOI: 10.1016/j.pnmrs.2020.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/07/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
We review methods to manipulate the motion of pulsed supersonic atomic and molecular beams using time-independent and -dependent inhomogeneous magnetic fields. In addition, we discuss current and possible future applications and research directions.
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Affiliation(s)
- Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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46
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Okada K, Sakimoto K, Takada Y, Schuessler HA. A study of the translational temperature dependence of the reaction rate constant between CH 3CN and Ne + at low temperatures. J Chem Phys 2020; 153:124305. [PMID: 33003759 DOI: 10.1063/5.0013807] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have measured the translational temperature dependence of the reaction rate constant for CH3CN + Ne+ → products at low temperatures. A cold Ne+ ensemble was embedded in Ca+ Coulomb crystals by a sympathetic laser cooling technique, while cold acetonitrile (CH3CN) molecules were produced by two types of Stark velocity filters to widely change the translational temperatures. The measured reaction rate constant gradually increases with the decrease in the translational temperature of the velocity-selected CH3CN molecules from 60 K down to 2 K, and thereby, a steep increase was observed at temperatures lower than 5 K. A comparison between experimental rate constants and the ion-dipole capture rate constants by the Perturbed Rotational State (PRS) theory was performed. The PRS capture rate constant reproduces well the reaction rate constant at a few kelvin but not for temperatures higher than 5 K. The result indicates that the reaction probability is small compared to typical ion-polar molecule reactions at temperatures above 5 K.
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Affiliation(s)
- Kunihiro Okada
- Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554, Japan
| | - Kazuhiro Sakimoto
- Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554, Japan
| | - Yusuke Takada
- Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554, Japan
| | - Hans A Schuessler
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA
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Plomp V, Gao Z, van de Meerakker SYT. A velocity map imaging apparatus optimised for high-resolution crossed molecular beam experiments. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1814437] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Vikram Plomp
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Zhi Gao
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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48
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Zou J, Osterwalder A. Investigation of the low-energy stereodynamics in the Ne( 3P 2) + N 2, CO reactions. J Chem Phys 2020; 153:104306. [PMID: 32933296 DOI: 10.1063/5.0022053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
We report on an experimental investigation of the low-energy stereodynamics of the energy transfer reactions Ne(3P2) + X, producing Ne(1S) + X+ and [Ne-X]+ (X = N2 or CO). Collision energies in the range 0.2 K-700 K are obtained by using the merged beam technique. Two kinds of product ions are generated by Penning and associative ionization, respectively. The intermediate product [Ne-X]+ in vibrationally excited states can predissociate into bare ions (X+). The experimental ratio of the NeX+ and X+ product ion yields is similar for both molecules at high collision energies but diverge at collision energies below 100 K. This difference is explained by the first excited electronic state of the product ions, which is accessible in the case of CO but lies too high in energy in the case of N2.
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Affiliation(s)
- Junwen Zou
- Institute for Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Andreas Osterwalder
- Institute for Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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49
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Tang G, Besemer M, de Jongh T, Shuai Q, van der Avoird A, Groenenboom GC, van de Meerakker SYT. Correlations in rotational energy transfer for NO-D 2 inelastic collisions. J Chem Phys 2020; 153:064301. [PMID: 35287454 DOI: 10.1063/5.0019472] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X 2Π1/2, j = 1/2, f) radicals and D2 (j = 0, 1, 2, 3) molecules at collision energies of 100 cm-1 and 750 cm-1. Using the combination of Stark deceleration and velocity map imaging, we fully resolve pair-correlated excitations in the scattered molecules. Both spin-orbit conserving and spin-orbit changing transitions in the NO radical are measured, while the coincident rotational excitation (j = 0 → j = 2) and rotational de-excitation (j = 2 → j = 0 and j = 3 → j = 1) in D2 are observed. De-excitation of D2 shows a strong dependence on the spin-orbit excitation of NO. We observe translation-to-rotation energy transfer as well as direct rotation-to-rotation energy transfer at the lowest collision energy probed. The experimental results are in good agreement with cross sections obtained from quantum coupled-channels calculations based on recent NO-D2 potential energy surfaces. The observed trends in the correlated scattering cross sections are understood in terms of the NO-D2 quadrupole-quadrupole interaction.
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Affiliation(s)
- Guoqiang Tang
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Matthieu Besemer
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Tim de Jongh
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Quan Shuai
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ad van der Avoird
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Gerrit C Groenenboom
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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50
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Sun ZF, van Hemert MC, Loreau J, van der Avoird A, Suits AG, Parker DH. Molecular square dancing in CO-CO collisions. Science 2020; 369:307-309. [PMID: 32675372 DOI: 10.1126/science.aan2729] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 05/22/2020] [Indexed: 11/02/2022]
Abstract
Knowledge of rotational energy transfer (RET) involving carbon monoxide (CO) molecules is crucial for the interpretation of astrophysical data. As of now, our nearly perfect understanding of atom-molecule scattering shows that RET usually occurs by only a simple "bump" between partners. To advance molecular dynamics to the next step in complexity, we studied molecule-molecule scattering in great detail for collision between two CO molecules. Using advanced imaging methods and quasi-classical and fully quantum theory, we found that a synchronous movement can occur during CO-CO collisions, whereby a bump is followed by a move similar to a "do-si-do" in square dancing. This resulted in little angular deflection but high RET to both partners, a very unusual combination. The associated conditions suggest that this process can occur in other molecule-molecule systems.
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Affiliation(s)
- Zhong-Fa Sun
- Department of Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands.,Anhui Province Key Laboratory of Optoelectric Materials Science and Technology, Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Marc C van Hemert
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Einsteinweg 55, 2333 CC Leiden, Netherlands
| | - Jérôme Loreau
- Department of Chemistry, KU Leuven, B-3001 Leuven, Belgium
| | - Ad van der Avoird
- Theoretical Chemistry, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
| | - Arthur G Suits
- Department of Chemistry, University of Missouri, Columbia, MO 65211, USA
| | - David H Parker
- Department of Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands.
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