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Wild R, Nötzold M, Simpson M, Tran TD, Wester R. Tunnelling measured in a very slow ion-molecule reaction. Nature 2023; 615:425-429. [PMID: 36859549 DOI: 10.1038/s41586-023-05727-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 01/12/2023] [Indexed: 03/03/2023]
Abstract
Quantum tunnelling reactions play an important role in chemistry when classical pathways are energetically forbidden1, be it in gas-phase reactions, surface diffusion or liquid-phase chemistry. In general, such tunnelling reactions are challenging to calculate theoretically, given the high dimensionality of the quantum dynamics, and also very difficult to identify experimentally2-4. Hydrogenic systems, however, allow for accurate first-principles calculations. In this way the rate of the gas-phase proton-transfer tunnelling reaction of hydrogen molecules with deuterium anions, H2 + D- → H- + HD, has been calculated5, but has so far lacked experimental verification. Here we present high-sensitivity measurements of the reaction rate carried out in a cryogenic 22-pole ion trap. We observe an extremely low rate constant of (5.2 ± 1.6) × 10-20 cm3 s-1. This measured value agrees with quantum tunnelling calculations, serving as a benchmark for molecular theory and advancing the understanding of fundamental collision processes. A deviation of the reaction rate from linear scaling, which is observed at high H2 densities, can be traced back to previously unobserved heating dynamics in radiofrequency ion traps.
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Affiliation(s)
- Robert Wild
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Markus Nötzold
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Malcolm Simpson
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Thuy Dung Tran
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Optics, Palacký University, Olomouc, Czech Republic
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria.
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2
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Okada K, Sakimoto K, Schuessler HA. Rotational Cooling Effect on the Rate Constant in the CH 3F + Ca + Reaction at Low Collision Energies. J Phys Chem A 2022; 126:4881-4890. [PMID: 35857026 DOI: 10.1021/acs.jpca.2c01063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rotational cooling effect on the reaction rate constant of the gas-phase ion-polar-molecule reaction CH3F + Ca+ → CH3 + CaF+ was experimentally studied at low collision energies. Fluoromethane molecules showed higher reactivity as the rotational temperature decreased. The experimental rate constants were compared with the capture rate constants which were obtained by the Perturbed Rotational State (PRS) theory assuming the rotational level distribution corresponding to the experimental conditions. The PRS result shows a strong dependence of the capture rate constants on the rotational level distribution in accordance with the experimental findings. However, the PRS capture rate constants deviate from the measurement values as the average collision energy increases especially when the fluoromethane molecules are rotationally cooled far below room temperature. The present paper suggests that the rotational state distribution significantly affects the rate constants of ion-polar-molecule reactions and is one of the important issues to be considered in the study of molecular synthesis in the interstellar medium, where the thermal equilibrium is not necessarily established.
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Affiliation(s)
- Kunihiro Okada
- Department of Materials and Life Sciences, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554, Japan
| | - Kazuhiro Sakimoto
- Department of Materials and Life Sciences, 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, United States
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3
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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: 5] [Impact Index Per Article: 1.3] [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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4
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High-resolution rovibrational spectroscopy of c- C3H2+: The ν7 C–H antisymmetric stretching band. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2020.128023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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5
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Álvarez-Barcia S, Russ MS, Meisner J, Kästner J. Atom tunnelling in the reaction NH 3+ + H 2 → NH 4+ + H and its astrochemical relevance. Faraday Discuss 2018; 195:69-80. [PMID: 27711847 PMCID: PMC5317219 DOI: 10.1039/c6fd00096g] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The title reaction is involved in the formation of ammonia in the interstellar medium. We have calculated thermal rates including atom tunnelling using different rate theories. Canonical variational theory with microcanonically optimised multidimensional tunnelling was used for bimolecular rates, modelling the gas-phase reaction and also a surface-catalysed reaction of the Eley-Rideal type. Instanton theory provided unimolecular rates, which model the Langmuir-Hinshelwood type surface reaction. The potential energy was calculated on the CCSD(T)-F12 level of theory on the fly. We report thermal rates and H/D kinetic isotope effects. The latter have implications for observed H/D fractionation in molecular clouds. Tunnelling causes rate constants to be sufficient for the reaction to play a role in interstellar chemistry even at cryogenic temperature. We also discuss intricacies and limitations of the different tunnelling approximations to treat this reaction, including its pre-reactive minimum.
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Affiliation(s)
- Sonia Álvarez-Barcia
- Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
| | - Marie-Sophie Russ
- Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
| | - Jan Meisner
- Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
| | - Johannes Kästner
- Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
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6
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Potapov A, Canosa A, Jiménez E, Rowe B. Chemie mit Überschall: 30 Jahre astrochemische Forschung und künftige Herausforderungen. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201611240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Alexey Potapov
- Laborastrophysikgruppe des Max-Planck-Instituts für Astronomie am Institut für Festkörperphysik; Friedrich-Schiller-Universität Jena; Helmholtzweg 3 07743 Jena Deutschland
| | - André Canosa
- Département de Physique Moléculaire; Institut de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, Campus de Beaulieu; 263 Avenue du Général Leclerc 35042 Rennes Cedex Frankreich
| | - Elena Jiménez
- Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas; Universidad de Castilla-La Mancha; Avda. Camilo José Cela, 1B 13071 Ciudad Real Spanien
| | - Bertrand Rowe
- Rowe-consulting, 22 Chemin des Moines; 22750 Saint Jacut de la Mer Frankreich
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7
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Potapov A, Canosa A, Jiménez E, Rowe B. Uniform Supersonic Chemical Reactors: 30 Years of Astrochemical History and Future Challenges. Angew Chem Int Ed Engl 2017; 56:8618-8640. [DOI: 10.1002/anie.201611240] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 01/27/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Alexey Potapov
- Laborastrophysikgruppe des Max-Planck-Instituts für Astronomie am Institut für Festkörperphysik; Friedrich-Schiller-Universität Jena; Helmholtzweg 3 07743 Jena Germany
| | - André Canosa
- Département de Physique Moléculaire; Institut de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, Campus de Beaulieu; 263 Avenue du Général Leclerc 35042 Rennes Cedex France
| | - Elena Jiménez
- Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas; Universidad de Castilla-La Mancha; Avda. Camilo José Cela, 1B 13071 Ciudad Real Spain
| | - Bertrand Rowe
- Rowe-consulting, 22 Chemin des Moines; 22750 Saint Jacut de la Mer France
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8
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Meisner J, Kästner J. Atom Tunneling in Chemistry. Angew Chem Int Ed Engl 2016; 55:5400-13. [DOI: 10.1002/anie.201511028] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 01/08/2016] [Indexed: 01/01/2023]
Affiliation(s)
- Jan Meisner
- Institut für Theoretische Chemie Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Johannes Kästner
- Institut für Theoretische Chemie Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
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9
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Affiliation(s)
- Jan Meisner
- Institut für Theoretische Chemie Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Deutschland
| | - Johannes Kästner
- Institut für Theoretische Chemie Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Deutschland
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10
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Sleiman C, González S, Klippenstein SJ, Talbi D, El Dib G, Canosa A. Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation. Phys Chem Chem Phys 2016; 18:15118-32. [DOI: 10.1039/c6cp01982j] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally with a CRESU apparatus and a slow flow reactor as well as theoretically to explore the temperature and pressure dependence of its rate coefficient from 354 K down to 23 K.
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Affiliation(s)
- Chantal Sleiman
- Département de Physique Moléculaire
- Institut de Physique de Rennes
- UMR 6251 du CNRS - Université de Rennes 1
- Bat. 11C
- Campus de Beaulieu
| | - Sergio González
- Departamento de Química Física
- Facultad de Ciencias y Tecnologías Químicas
- Universidad de Castilla La Mancha
- Campus Universitario
- 13071 Ciudad Real
| | | | - Dahbia Talbi
- Laboratoire Univers et Particules de Montpellier – UMR 5299 du CNRS - Université de Montpellier
- Campus Triolet
- 34095 Montpellier Cedex 05
- France
| | - Gisèle El Dib
- Département de Physique Moléculaire
- Institut de Physique de Rennes
- UMR 6251 du CNRS - Université de Rennes 1
- Bat. 11C
- Campus de Beaulieu
| | - André Canosa
- Département de Physique Moléculaire
- Institut de Physique de Rennes
- UMR 6251 du CNRS - Université de Rennes 1
- Bat. 11C
- Campus de Beaulieu
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11
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Abstract
In this closing article, we first introduce the topics of dust and ice chemistry and their role in astrochemistry. We then discuss the invited contributions and discussions concerning these topics, dividing the papers into groupings by subject: (i) astronomical sources, (ii) basic properties of dust, (iii) processes on bare grains, (iv) processes on and in ice mantles, and (v) complex organic molecules. A sample of poster contributions is included in the text, when they complement the discussion. The article ends with some suggestions for future research.
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12
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Hama T, Watanabe N. Surface Processes on Interstellar Amorphous Solid Water: Adsorption, Diffusion, Tunneling Reactions, and Nuclear-Spin Conversion. Chem Rev 2013; 113:8783-839. [DOI: 10.1021/cr4000978] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tetsuya Hama
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
| | - Naoki Watanabe
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
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13
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Rist C, Faure A, Hily-Blant P, Le Gal R. Nuclear-Spin Selection Rules in the Chemistry of Interstellar Nitrogen Hydrides. J Phys Chem A 2013; 117:9800-6. [DOI: 10.1021/jp312640a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Claire Rist
- IPAG, Observatoire
de Grenoble, Université Joseph Fourier, CNRS UMR5571, B.P. 53, 38041 Grenoble
Cedex 09, France
| | - Alexandre Faure
- IPAG, Observatoire
de Grenoble, Université Joseph Fourier, CNRS UMR5571, B.P. 53, 38041 Grenoble
Cedex 09, France
| | - Pierre Hily-Blant
- IPAG, Observatoire
de Grenoble, Université Joseph Fourier, CNRS UMR5571, B.P. 53, 38041 Grenoble
Cedex 09, France
| | - Romane Le Gal
- IPAG, Observatoire
de Grenoble, Université Joseph Fourier, CNRS UMR5571, B.P. 53, 38041 Grenoble
Cedex 09, France
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14
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Neill JL, Steber AL, Muckle MT, Zaleski DP, Lattanzi V, Spezzano S, McCarthy MC, Remijan AJ, Friedel DN, Widicus Weaver SL, Pate BH. Spatial Distributions and Interstellar Reaction Processes. J Phys Chem A 2011; 115:6472-80. [DOI: 10.1021/jp200539b] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Justin L. Neill
- Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Amanda L. Steber
- Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Matt T. Muckle
- Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Daniel P. Zaleski
- Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Valerio Lattanzi
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, United States
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Silvia Spezzano
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, United States
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Michael C. McCarthy
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, United States
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Anthony J. Remijan
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903, United States
| | - Douglas N. Friedel
- Department of Astronomy, University of Illinois, Urbana, Illinois 61801, United States
| | | | - Brooks H. Pate
- Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
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15
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Faure A, Vuitton V, Thissen R, Wiesenfeld L, Dutuit O. Fast ion–molecule reactions in planetary atmospheres: a semiempirical capture approach. Faraday Discuss 2010; 147:337-48; discussion 379-403. [DOI: 10.1039/c003908j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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16
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Jacox ME, ThompsonGuest researcher, National WE. Infrared spectrum of the NH4-dn+ cation trapped in solid neon. Phys Chem Chem Phys 2005; 7:768-75. [DOI: 10.1039/b414641g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Asvany O, Savić I, Schlemmer S, Gerlich D. Variable temperature ion trap studies of CH4++H2, HD and D2: negative temperature dependence and significant isotope effect. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2003.11.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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18
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Coutinho-Neto M, Deumens E, Öhrn Y. Abstraction and exchange mechanisms for the D2+NH3+ reaction at hyperthermal collision energies. J Chem Phys 2002. [DOI: 10.1063/1.1434991] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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19
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Baba T, Waki I. Chemical reaction of sympathetically laser-cooled molecular ions. J Chem Phys 2002. [DOI: 10.1063/1.1431273] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Ratkiewicz A, Niedzielski J, Turulski J. Effect of nuclear spin of a homonuclear molecule on the rate of ion capture. Chem Phys 2001. [DOI: 10.1016/s0301-0104(00)00341-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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21
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Aguillon F, Sizun M. Reduced dimensionality wave packet study of the NH3++H2, D2 reaction. J Chem Phys 2000. [DOI: 10.1063/1.481659] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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22
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Ion-molecule chemistry in interstellar clouds. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1071-9687(98)80003-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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23
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Fairley DA, Scott GB, Milligan DB, Maclagan RG, McEwan MJ. SIFDT study of the SO+2/H2 H-atom abstraction reaction. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s0168-1176(97)00242-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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24
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Matthews KK, Adams NG, Fisher ND. Isomeric Forms of the Products of the Collisional Associations of CH3+ with CH3OH and H3O+ with C2H4. J Phys Chem A 1997. [DOI: 10.1021/jp963293k] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kelly K. Matthews
- Department of Chemistry, University of Georgia, Athens, Georgia 30602
| | - Nigel G. Adams
- Department of Chemistry, University of Georgia, Athens, Georgia 30602
| | - Neyoka D. Fisher
- Department of Chemistry, University of Georgia, Athens, Georgia 30602
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25
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Herbst E, Woon DE. Why HOC+ is detectable in interstellar clouds: the rate of the reaction between HOC+ and H2. THE ASTROPHYSICAL JOURNAL 1996; 463:L113-L115. [PMID: 11541463 DOI: 10.1086/310059] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The recent confirmation by Ziurys and Apponi of the detection of HOC+ toward Sgr B2 (OH), and their identification of the ion in Orion-KL and several other sources show that HOC+ is far more abundant than predicted by previous ion-molecule models. In these models, the reaction HOC(+) + H2 --> HCO(+) + H2 is assumed to rapidly destroy HOC+, based on the results of a prior calculation. We have recalculated the rate of this reaction as a function of temperature using a new ab initio potential surface and a phase space approach to the dynamics which includes tunneling. The newly calculated rate is small (< or = 1 x 10(-10) cm3 s-1) at temperatures under 100 K.
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Affiliation(s)
- E Herbst
- Department of Physics, The Ohio State University, Columbus 43210-1106, USA.
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27
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Maluendes SA, McLean AD, Yamashita K, Herbst E. Calculations on the competition between association and reaction for C3H(+) + H2. J Chem Phys 1993; 99:2812-20. [PMID: 11539504 DOI: 10.1063/1.465190] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A potential energy surface has been calculated for the competing associative and reactive ion-molecule processes involving the reactants C3H(+) + H2. Our ab initio results show that the linear ion C3H+ and H2 can directly access the deep potential well of the propargyl ion H2CCCH+, which is calculated to lie 390 kJ mol-1 below the zero-point energy of the reactants. Isomerization between the propargyl ion and the lower energy, cyclic C3H3+ ion, calculated to lie 501 kJ mol-1 below the zero-point energy of reactants, can subsequently occur via two pathways. One of these pathways involves a transition state lying 22 kJ mol-1 below the energy of the reactants while the other, which occurs at much lower energies, involves two transition states and an intermediate. The dissociation of c-C3H3+ into c-C3H2(+) + H is calculated to occur directly, without any intermediate potential energy maximum, but the energy of the products lies 7.3 kJ mol-1 above the energy of the reactants. Using the minimum energy potential pathway and properties of the stationary point structures determined via ab initio methods, we have calculated both the association rate coefficient to produce C3H3+ as a function of density and the branching ratio between the propargyl and cyclic structures of the ion. Our results are in good agreement with some experimental results and in conflict with others. Specifically, we agree with the 1:1 branching ratio measured for the propargyl and cyclic isomers of C3H3+ at 80 and 300 K and we agree with the rate coefficient for radiative association measured at 80 K. We cannot reproduce reported measurements that the reactive channel (C3H2(+) + H) is the dominant channel at 80 K and at low gas densities, or that the association channel at high densities saturates at an effective rate coefficient well below the Langevin value -2x10(-11) cm3 s-1 at 300K and 1x10(-10) cm3 s-1 at 80K.
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Affiliation(s)
- S A Maluendes
- Molecular Research Institute, Palo Alto, California 94304, USA
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28
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Gerlich D. Experimental investigations of ion–molecule reactions relevant to interstellar chemistry. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/ft9938902199] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Yamashita K, Herbst E. Calculations on the rate of the ion–molecule reaction C2H+2+H2→C2H+3+H. J Chem Phys 1992. [DOI: 10.1063/1.462679] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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30
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Hawley M, Smith MA. The gas phase reaction of C2H+2 with H2 below 3 K: The reopening of the bimolecular C2H+3 channel at low energy. J Chem Phys 1992. [DOI: 10.1063/1.462198] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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