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Schatz GC, Wodtke AM, Yang X. Spiers Memorial Lecture: New directions in molecular scattering. Faraday Discuss 2024; 251:9-62. [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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2
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Pan H, Liu K, Caracciolo A, Casavecchia P. Crossed beam polyatomic reaction dynamics: recent advances and new insights. Chem Soc Rev 2017; 46:7517-7547. [DOI: 10.1039/c7cs00601b] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review summarizes the developments in polyatomic reaction dynamics, focusing on reactions of unsaturated hydrocarbons with O-atoms and methane with atoms/radicals.
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Affiliation(s)
- Huilin Pan
- Institute of Atomic and Molecular Sciences (IAMS)
- Academia Sinica
- Taipei
- Taiwan
| | - Kopin Liu
- Institute of Atomic and Molecular Sciences (IAMS)
- Academia Sinica
- Taipei
- Taiwan
- Department of Physics
| | - Adriana Caracciolo
- Dipartimento di Chimica
- Biologia e Biotecnologie
- Università degli Studi di Perugia
- 06123 Perugia
- Italy
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica
- Biologia e Biotecnologie
- Università degli Studi di Perugia
- 06123 Perugia
- Italy
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3
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Constantinidis P, Hirsch F, Fischer I, Dey A, Rijs AM. Products of the Propargyl Self-Reaction at High Temperatures Investigated by IR/UV Ion Dip Spectroscopy. J Phys Chem A 2016; 121:181-191. [DOI: 10.1021/acs.jpca.6b08750] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- P. Constantinidis
- Institute
of Physical and Theoretical Chemistry, University of Würzburg, Am
Hubland, D-97074 Würzburg, Germany
| | - F. Hirsch
- Institute
of Physical and Theoretical Chemistry, University of Würzburg, Am
Hubland, D-97074 Würzburg, Germany
| | - I. Fischer
- Institute
of Physical and Theoretical Chemistry, University of Würzburg, Am
Hubland, D-97074 Würzburg, Germany
| | - A. Dey
- Radboud University, Institute for Molecules and
Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - A. M. Rijs
- Radboud University, Institute for Molecules and
Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
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4
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Sun YL, Huang WJ, Lee SH. Formation of C3H2, C5H2, C7H2, and C9H2 from reactions of CH, C3H, C5H, and C7H radicals with C2H2. Phys Chem Chem Phys 2016; 18:2120-9. [DOI: 10.1039/c5cp06072a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A three-dimensional velocity distribution contour of C2n+1H2 produced from the reaction of C2n−1H (n = 1–4) with C2H2 in crossed molecular beams.
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Affiliation(s)
- Yi-Lun Sun
- National Synchrotron Radiation Research Center (NSRRC)
- Hsinchu 30076
- Taiwan
| | - Wen-Jian Huang
- National Synchrotron Radiation Research Center (NSRRC)
- Hsinchu 30076
- Taiwan
| | - Shih-Huang Lee
- National Synchrotron Radiation Research Center (NSRRC)
- Hsinchu 30076
- Taiwan
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5
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Casavecchia P, Leonori F, Balucani N. Reaction dynamics of oxygen atoms with unsaturated hydrocarbons from crossed molecular beam studies: primary products, branching ratios and role of intersystem crossing. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1039293] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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6
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Polino D, Klippenstein SJ, Harding LB, Georgievskii Y. Predictive Theory for the Addition and Insertion Kinetics of 1CH2 Reacting with Unsaturated Hydrocarbons. J Phys Chem A 2013; 117:12677-92. [DOI: 10.1021/jp406246y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniela Polino
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Dipartimento
di Chimica, Materiali e Ingegneria chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Lawrence B. Harding
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Yuri Georgievskii
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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7
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Albert DR, Davis HF. Studies of bimolecular reaction dynamics using pulsed high-intensity vacuum-ultraviolet lasers for photoionization detection. Phys Chem Chem Phys 2013; 15:14566-80. [DOI: 10.1039/c3cp51930a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Chin CH, Chen WK, Huang WJ, Lin YC, Lee SH. Exploring the Dynamics of Reaction C(3P) + C2H4 with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations. J Phys Chem A 2012; 116:7615-22. [DOI: 10.1021/jp304756t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chih-Hao Chin
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park,
Hsinchu 30076, Taiwan
| | - Wei-Kan Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park,
Hsinchu 30076, Taiwan
| | - Wen-Jian Huang
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park,
Hsinchu 30076, Taiwan
| | - Yi-Cheng Lin
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park,
Hsinchu 30076, Taiwan
| | - Shih-Huang Lee
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park,
Hsinchu 30076, Taiwan
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9
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Xu H, Jacovella U, Ruscic B, Pratt ST, Lucchese RR. Near-threshold shape resonance in the photoionization of 2-butyne. J Chem Phys 2012; 136:154303. [DOI: 10.1063/1.3701762] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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11
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Gannon KL, Blitz MA, Liang CH, Pilling MJ, Seakins PW, Glowacki DR. Temperature Dependent Kinetics (195−798 K) and H Atom Yields (298−498 K) from Reactions of 1CH2 with Acetylene, Ethene, and Propene. J Phys Chem A 2010; 114:9413-24. [DOI: 10.1021/jp102276j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- K. L. Gannon
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - M. A. Blitz
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - C. H. Liang
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - M. J. Pilling
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - P. W. Seakins
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - D. R. Glowacki
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, U.K., and School of Chemistry, Centre for Computational Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
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12
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Kaiser RI, Maksyutenko P, Ennis C, Zhang F, Gu X, Krishtal SP, Mebel AM, Kostko O, Ahmed M. Untangling the chemical evolution of Titan's atmosphere and surface–from homogeneous to heterogeneous chemistry. Faraday Discuss 2010; 147:429-78; discussion 527-52. [DOI: 10.1039/c003599h] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Naulin C, Daugey N, Hickson KM, Costes M. Dynamics of the Reactions of C(3PJ) Atoms with Ethylene, Allene, and Methylacetylene at Low Energy Revealed by Doppler−Fizeau Spectroscopy. J Phys Chem A 2009; 113:14447-57. [DOI: 10.1021/jp9038545] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christian Naulin
- Université de Bordeaux and CNRS UMR 5255, Institut des Sciences Moléculaires, 33405 Talence Cedex, France
| | - Nicolas Daugey
- Université de Bordeaux and CNRS UMR 5255, Institut des Sciences Moléculaires, 33405 Talence Cedex, France
| | - Kevin M. Hickson
- Université de Bordeaux and CNRS UMR 5255, Institut des Sciences Moléculaires, 33405 Talence Cedex, France
| | - Michel Costes
- Université de Bordeaux and CNRS UMR 5255, Institut des Sciences Moléculaires, 33405 Talence Cedex, France
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14
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Casavecchia P, Leonori F, Balucani N, Petrucci R, Capozza G, Segoloni E. Probing the dynamics of polyatomic multichannel elementary reactions by crossed molecular beam experiments with soft electron-ionization mass spectrometric detection. Phys Chem Chem Phys 2008; 11:46-65. [PMID: 19081908 DOI: 10.1039/b814709d] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this Perspective we highlight developments in the field of chemical reaction dynamics. Focus is on the advances recently made in the investigation of the dynamics of elementary multichannel radical-molecule and radical-radical reactions, as they have become possible using an improved crossed molecular beam scattering apparatus with universal electron-ionization mass spectrometric detection and time-of-flight analysis. These improvements consist in the implementation of (a) soft ionization detection by tunable low-energy electrons which has permitted us to reduce interfering signals originating from dissociative ionization processes, usually representing a major complication, (b) different beam crossing-angle set-ups which have permitted us to extend the range of collision energies over which a reaction can be studied, from very low (a few kJ mol(-1), as of interest in astrochemistry or planetary atmospheric chemistry) to quite high energies (several tens of kJ mol(-1), as of interest in high temperature combustion systems), and (c) continuous supersonic sources for producing a wide variety of atomic and molecular radical reactant beams. Exploiting these new features it has become possible to tackle the dynamics of a variety of polyatomic multichannel reactions, such as those occurring in many environments ranging from combustion and plasmas to terrestrial/planetary atmospheres and interstellar clouds. By measuring product angular and velocity distributions, after having suppressed or mitigated, when needed, the problem of dissociative ionization of interfering species (reactants, products, background gases) by soft ionization detection, essentially all primary reaction products can be identified, the dynamics of each reaction channel characterized, and the branching ratios determined as a function of collision energy. In general this information, besides being of fundamental relevance, is required for a predictive description of the chemistry of these environments via computer models. Examples are taken from recent on-going work (partly published) on the reactions of atomic oxygen with acetylene, ethylene and allyl radical, of great importance in combustion. A reaction of relevance in interstellar chemistry, as that of atomic carbon with acetylene, is also discussed briefly. Comparison with theoretical results is made wherever possible, both at the level of electronic structure calculations of the potential energy surfaces and dynamical computations. Recent complementary CMB work as well as kinetic work exploiting soft photo-ionization with synchrotron radiation are noted. The examples illustrated in this article demonstrate that the type of dynamical results now obtainable on polyatomic multichannel radical-molecule and radical-radical reactions might well complement reaction kinetics experiments and hence contribute to bridging the gap between microscopic reaction dynamics and thermal reaction kinetics, enhancing significantly our basic knowledge of chemical reactivity and understanding of the elementary reactions which occur in real-world environments.
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15
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Larrégaray P, Bonnet L, Rayez JC. Mean potential phase space theory of chemical reactions. J Chem Phys 2007; 127:084308. [PMID: 17764249 DOI: 10.1063/1.2768959] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A nonconventional application of phase space theory to the insertion reactions A+H(2), with A=C((1)D) and S((1)D), is presented. Instead of approximating the potential energies of interaction between separated fragments by their isotropic long-range contributions, as in the original theory, the latter are replaced by the accurate potential energies averaged with respect to Jacobi angles. The integral and differential cross sections obtained from this mean potential phase space theory (MPPST) turn out to be in very satisfying agreement with the benchmark predictions of the time-independent and time-dependent statistical quantum methods. The formal and numerical simplicity of MPPST with respect to any approach combining statistical assumptions and dynamical calculations makes it a promising tool for studying indirect polyatomic reactions.
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Affiliation(s)
- P Larrégaray
- Institut des Sciences Moléculaires, Université Bordeaux 1, 351 Cours de la Libération, 33405 Talence Cedex, France
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16
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Guo Y, Gu X, Zhang F, Mebel AM, Kaiser RI. A crossed molecular beam study on the formation of hexenediynyl radicals (H2CCCCCCH; C6H3(X2A′)) via reactions of tricarbon molecules, C3(X1Σg+), with allene (H2CCCH2; X1A1) and methylacetylene (CH3CCH; X1A1). Phys Chem Chem Phys 2007; 9:1972-9. [PMID: 17431525 DOI: 10.1039/b618179a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crossed molecular beams experiments have been utilized to investigate the reaction dynamics between two closed shell species, i.e. the reactions of tricarbon molecules, C(3)(X(1)Sigma(g)(+)), with allene (H(2)CCCH(2); X(1)A(1)), and with methylacetylene (CH(3)CCH; X(1)A(1)). Our investigations indicated that both these reactions featured characteristic threshold energies of 40-50 kJ mol(-1). The reaction dynamics are indirect and suggested the reactions proceeded via an initial addition of the tricarbon molecule to the unsaturated hydrocarbon molecules forming initially cyclic reaction intermediates of the generic formula C(6)H(4). The cyclic intermediates isomerize to yield eventually the acyclic isomers CH(3)CCCCCH (methylacetylene reaction) and H(2)CCCCCCH(2) (allene reaction). Both structures decompose via atomic hydrogen elimination to form the 1-hexene-3,4-diynyl-2 radical (C(6)H(3); H(2)CCCCCCH). Future flame studies utilizing the Advanced Light Source should therefore investigate the existence of 1-hexene-3,4-diynyl-2 radicals in high temperature methylacetylene and allene flames. Since the corresponding C(3)H(3), C(4)H(3), and C(5)H(3) radicals have been identified via their ionization potentials in combustion flames, the existence of the C(6)H(3) isomer 1-hexene-3,4-diynyl-2 can be predicted as well.
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Affiliation(s)
- Ying Guo
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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Abstract
A critical overview of the recent progress in crossed-beam reactive scattering is presented. This review is not intended to be an exhaustive nor a comprehensive one, but rather a critical assessment of what we have been learning about bimolecular reaction dynamics using crossed molecular beams since year 2000. Particular emphasis is placed on the information content encoded in the product angular distribution-the trait of a typical molecular beam scattering experiment-and how the information can help in answering fundamental questions about chemical reactivity. We will start with simple reactions by highlighting a few benchmark three-atom reactions, and then move on progressively to the more complex chemical systems and with more sophisticated types of measurements. Understanding what cause the experimental observations is more than computationally simulating the results. The give and take between experiment and theory in unraveling the physical picture of the underlying dynamics is illustrated throughout this review.
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Affiliation(s)
- Kopin Liu
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, Taipei 10617, Taiwan.
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Fan H, Pratt ST. Near-threshold photoionization of hot isopropyl radicals. J Chem Phys 2006; 124:114312. [PMID: 16555893 DOI: 10.1063/1.2172611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A combination of ion imaging and vacuum ultraviolet, single-photon ionization is used to study the internal energy dependence of the photoionization cross section of isopropyl radicals produced by the 266 nm photodissociation of isopropyl iodide. The isopropyl radicals so produced have internal energies of approximately 0.3-2.0 eV. Images recorded for photoionization energies from just below the adiabatic ionization threshold at 7.37+/-0.02 and 8.04 eV are essentially identical both to each other and to that recorded at 9.67 eV. These results imply that the photoionization cross section is only weakly dependent on internal energy. Several factors contributing to this observation are discussed, as are the implications for the photoionization of other systems with significant internal excitation.
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Affiliation(s)
- H Fan
- Argonne National Laboratory, Argonne, Illinois 60439, USA
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20
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Abstract
In this article, we briefly review the recent experimental studies of the multiple channel dynamics of the O((1)D) reaction with alkane molecules using the significantly improved universal crossed molecular beam technique. In these reactions, the dominant reaction mechanism is found to be an O atom insertion into the C-H bond, while a direct abstraction mechanism is also present in the OH formation channel. While the reaction mechanism is similar for all of these reactions, the product channels are quite different because of the significantly different energetics of these reaction channels. In the O((1)D) reaction with methane, OH formation is the dominant process while H atom formation is also a significant process. In the O((1)D) reaction with ethane, however, the CH(3) + CH(2)OH is the most important process, OH formation is still significant and H atom formation is of minor importance. A new type of O atom insertion mechanism (insertion into a C-C bond) is also inferred from the O((1)D) reaction with cyclopropane. Through these comprehensive studies, complete dynamical pictures of many multiple channel chemical reactions could be obtained. Such detailed studies could provide a unique bridge between dynamics and kinetics research.
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Affiliation(s)
- Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, P. R. China
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Balucani N, Capozza G, Leonori F, Segoloni E, Casavecchia P. Crossed molecular beam reactive scattering: from simple triatomic to multichannel polyatomic reactions. INT REV PHYS CHEM 2006. [DOI: 10.1080/01442350600641305] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Abstract
Vibrationally hot CH(3) and CF(3) were produced by the 266 nm photodissociation of CH(3)I and CF(3)I, respectively, and probed by single-photon ionization at 118 nm. Comparison of the ion images of the CH(3) and CF(3) fragments with those of the complementary I atoms, and with previous measurements of the product branching fractions, allowed the determination of the relative photoion yields as a function of the vibrational energy of the molecular radical. Some general ideas about the internal-energy dependence of photoionization cross sections are also discussed.
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Affiliation(s)
- F Aguirre
- Argonne National Laboratory, Argonne, Illinois 60439, USA
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Maeda S, Ohno K. Global Mapping of Equilibrium and Transition Structures on Potential Energy Surfaces by the Scaled Hypersphere Search Method: Applications to ab Initio Surfaces of Formaldehyde and Propyne Molecules. J Phys Chem A 2005; 109:5742-53. [PMID: 16833907 DOI: 10.1021/jp0513162] [Citation(s) in RCA: 263] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Technical details of a new global mapping technique for finding equilibrium (EQ) and transition structures (TS) on potential energy surfaces (PES), the scaled hypersphere search (SHS) method (Ohno, K.; Maeda, S. Chem. Phys. Lett. 2004, 384, 277), are presented. On the basis of a simple principle that reaction pathways are found as anharmonic downward distortions of PES around an EQ point, the reaction pathways can be obtained as energy minima on the scaled hypersphere surface, which would have a constant energy when the potentials are harmonic. Connections of SHS paths between each EQ are very similar to corresponding intrinsic reaction coordinate (IRC) connections. The energy maximum along the SHS path reaches a region in close proximity to the TS of the reaction pathway, and the subsequent geometry optimization from the SHS maximum structure easily converges to the TS. The SHS method, using the one-after-another algorithm connecting EQ and TS, considerably reduces the multidimensional space to be searched to certain limited regions around the pathways connecting each EQ with the neighboring TS. Applications of the SHS method have been made to ab initio surfaces of formaldehyde and propyne molecules to obtain systematically five EQ and nine TS for formaldehyde and seven EQ and 32 TS for propyne.
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Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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Yu HG, Muckerman JT. Ab Initio and Direct Dynamics Studies of the Reaction of Singlet Methylene with Acetylene and the Lifetime of the Cyclopropene Complex. J Phys Chem A 2005; 109:1890-6. [PMID: 16833521 DOI: 10.1021/jp045049w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The energetics of the (1)CH(2) + C(2)H(2) --> H + C(3)H(3) reaction are accurately calculated using an extrapolated coupled-cluster/complete basis set (CBS) method based on the cc-pVDZ, cc-pVTZ, and cc-pVQZ basis sets. The reaction enthalpy (0 K) is predicted to be -20.33 kcal/mol. This reaction has no classical barrier in either the entrance or exit channel. However, there are several stable intermediates-cyclopropene (c-C(3)H(4)), allene (CH(2)CCH(2)), and propyne (CH(3)CCH)-along the minimum energy path. These intermediates with zero-point energy corrections lie below the reactants by 87.11 (c-C(3)H(4)), 109.69 (CH(2)CCH(2)), and 110.78 kcal/mol (CH(3)CCH). The vibrationally adiabatic ground-state (VAG) barrier height for c-C(3)H(4) isomerization to allene is obtained as 45.2 kcal/mol, and to propyne as 37.2 kcal/mol. In addition, the (1)CH(2) + C(2)H(2) reaction is investigated utilizing the dual-level "scaling all correlation" (SAC) ab initio method of Truhlar et al., i.e., the UCCSD(SAC)/cc-pVDZ theory. Results show that the reaction occurs via long-lived complexes. The lifetime of the cyclopropene intermediate is obtained as 3.2 +/- 0.4 ps. It is found that the intermediate propyne can be formed directly from reactants through the insertion of (1)CH(2) into a C-H bond of C(2)H(2). However, compared to the major mechanism in which the propyne is produced through a ring-opening of the cyclopropene complex, this reaction pathway is much less favorable. Finally, the theoretical thermal rate constant exhibits a negative temperature dependence, which is in excellent agreement with the previous results. The temperature dependence is consistent with the earlier RRKM results but weaker than the experimental observations at high temperatures.
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Affiliation(s)
- Hua-Gen Yu
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
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