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Han S, Zhao B, Conte R, Malbon CL, Bowman JM, Yarkony DR, Guo H. Nonadiabatic Reactive Quenching of OH( A2Σ +) by H 2: Origin of High Vibrational Excitation in the H 2O Product. J Phys Chem A 2022; 126:6944-6952. [PMID: 36137233 DOI: 10.1021/acs.jpca.2c05704] [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
The nonadiabatic dynamics of the reactive quenching channel of the OH(A2Σ+) + H2/D2 collisions is investigated with a semiclassical surface hopping method, using a recently developed four-state diabatic potential energy matrix (DPEM). In agreement with experimental observations, the H2O/HOD products are found to have significant vibrational excitation. Using a Gaussian binning method, the H2O vibrational state distribution is determined. The preferential energy disposal into the product vibrational modes is rationalized by an extended Sudden Vector Projection model, in which the h and g vectors associated with the conical intersection are found to have large projections with the product normal modes. However, our calculations did not find significant insertion trajectories, suggesting the need for further improvement of the DPEM.
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Affiliation(s)
- Shanyu Han
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Bin Zhao
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Riccardo Conte
- Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, 20133 Milano, Italy
| | - Christopher L Malbon
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Joel M Bowman
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, United States
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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2
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Han S, de Oliveira-Filho AGS, Shu Y, Truhlar DG, Guo H. Semiclassical Trajectory Studies of Reactive and Nonreactive Scattering of OH(A 2S+) by H2 Based on an Improved Full-Dimensional Ab Initio Diabatic Potential Energy Matrix. Chemphyschem 2022; 23:e202200039. [PMID: 35179813 DOI: 10.1002/cphc.202200039] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/17/2022] [Indexed: 11/06/2022]
Abstract
We present a new full-dimensional diabatic potential energy matrix (DPEM) for electronically nonadiabatic collisions of OH( A 2 Σ + ) with H 2 , and we calculate the probabilities of electronically adiabatic inelastic collisions, nonreactive quenching, and reactive quenching to form H 2 O + H. The DPEM was fitted using a many-body expansion with permutationally invariant polynomials in bond-order functions to represent the many-body part. The dynamics calculations were carried out with the fewest-switches with time uncertainty and stochastic decoherence (FSTU/SD) semiclassical trajectory method. We present results both for head-on collisions (impact parameter b equal to zero) and for a full range of impact parameters. The results are compared to experiment and to earlier FSTU/SD and quantum dynamics calculations with a previously published DPEM. The various theoretical results all agree that nonreactive quenching dominates reactive quenching, but there are quantitative differences between the two DPEMs and between the b = 0 results and the all- b results, especially for the probability of reactive quenching.
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Affiliation(s)
- Shanyu Han
- University of New Mexico - Albuquerque: The University of New Mexico, Chemistry and Chemical Biology, UNITED STATES
| | | | - Yinan Shu
- University of Minnesota Twin Cities: University of Minnesota Twin Cities, Chemistry, UNITED STATES
| | - Donald G Truhlar
- University of Minnesota Twin Cities Campus: University of Minnesota Twin Cities, Chemistry, UNITED STATES
| | - Hua Guo
- University of New Mexico, Department of Chemistry, Clark Hall, 87131, Albuquerque, UNITED STATES
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3
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Guan Y, Xie C, Yarkony DR, Guo H. High-fidelity first principles nonadiabaticity: diabatization, analytic representation of global diabatic potential energy matrices, and quantum dynamics. Phys Chem Chem Phys 2021; 23:24962-24983. [PMID: 34473156 DOI: 10.1039/d1cp03008f] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nonadiabatic dynamics, which goes beyond the Born-Oppenheimer approximation, has increasingly been shown to play an important role in chemical processes, particularly those involving electronically excited states. Understanding multistate dynamics requires rigorous quantum characterization of both electronic and nuclear motion. However, such first principles treatments of multi-dimensional systems have so far been rather limited due to the lack of accurate coupled potential energy surfaces and difficulties associated with quantum dynamics. In this Perspective, we review recent advances in developing high-fidelity analytical diabatic potential energy matrices for quantum dynamical investigations of polyatomic uni- and bi-molecular nonadiabatic processes, by machine learning of high-level ab initio data. Special attention is paid to methods of diabatization, high fidelity construction of multi-state coupled potential energy surfaces and property surfaces, as well as quantum mechanical characterization of nonadiabatic nuclear dynamics. To illustrate the tremendous progress made by these new developments, several examples are discussed, in which direct comparison with quantum state resolved measurements led to either confirmation of the observation or sometimes reinterpretation of the experimental data. The insights gained in these prototypical systems greatly advance our understanding of nonadiabatic dynamics in chemical systems.
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Affiliation(s)
- Yafu Guan
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
| | - Changjian Xie
- Institute of Modern Physics, Northwest University, Xi'an, Shaanxi 710069, China.
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico, 87131, USA.
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4
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Zhao B, Han S, Malbon CL, Manthe U, Yarkony DR, Guo H. Full-dimensional quantum stereodynamics of the non-adiabatic quenching of OH(A 2Σ +) by H 2. Nat Chem 2021; 13:909-915. [PMID: 34373597 PMCID: PMC8440216 DOI: 10.1038/s41557-021-00730-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 05/11/2021] [Indexed: 11/16/2022]
Abstract
The Born–Oppenheimer approximation, assuming separable nuclear and electronic motion, is widely adopted for characterizing chemical reactions in a single electronic state. However, the breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry, and a detailed understanding of the non-adiabatic dynamics is still incomplete. Here we investigate the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 molecules using full-dimensional quantum dynamics calculations for zero total nuclear angular momentum using a high-quality diabatic-potential-energy matrix. Good agreement with experimental observations is found for the OH(X2Π) ro-vibrational distribution, and the non-adiabatic dynamics are shown to be controlled by stereodynamics, namely the relative orientation of the two reactants. The uncovering of a major (in)elastic channel, neglected in a previous analysis but confirmed by a recent experiment, resolves a long-standing experiment–theory disagreement concerning the branching ratio of the two electronic quenching channels. ![]()
The breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry and detailed understanding of non-adiabatic dynamics is still incomplete. Now, the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 has been investigated using full-dimensional quantum dynamics calculations and a high-quality diabatic-potential-energy matrix, providing insight into the branching ratio of the two electronic quenching channels.
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Affiliation(s)
- Bin Zhao
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA. .,Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Bielefeld, Germany.
| | - Shanyu Han
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA
| | | | - Uwe Manthe
- Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Bielefeld, Germany.
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, USA.
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA.
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5
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Malbon CL, Zhao B, Guo H, Yarkony DR. On the nonadiabatic collisional quenching of OH(A) by H2: a four coupled quasi-diabatic state description. Phys Chem Chem Phys 2020; 22:13516-13527. [DOI: 10.1039/d0cp01754j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
12A, 22A, and 32A electronic states of OH(A) + H2 where conical intersections facilitate the quenching of OH(A) by H2.
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Affiliation(s)
| | - Bin Zhao
- Department of Chemistry and Chemical Biology
- University of New Mexico
- Albuquerque
- USA
| | - Hua Guo
- Department of Chemistry and Chemical Biology
- University of New Mexico
- Albuquerque
- USA
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6
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Shu Y, Kryven J, Sampaio de Oliveira-Filho AG, Zhang L, Song GL, Li SL, Meana-Pañeda R, Fu B, Bowman JM, Truhlar DG. Direct diabatization and analytic representation of coupled potential energy surfaces and couplings for the reactive quenching of the excited 2Σ+ state of OH by molecular hydrogen. J Chem Phys 2019; 151:104311. [DOI: 10.1063/1.5111547] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Yinan Shu
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Joanna Kryven
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Antonio Gustavo Sampaio de Oliveira-Filho
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
- Departamento de Química, Laboratório Computacional de Espectroscopia e Cinética, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto-SP, Brazil
| | - Linyao Zhang
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Guo-Liang Song
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Shaohong L. Li
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Rubén Meana-Pañeda
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Bina Fu
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
- State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People’s Republic of China
| | - Joel M. Bowman
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
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7
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Brouard M, Lawlor J, McCrudden G, Perkins T, Seamons SA, Stevenson P, Chadwick H, Aoiz FJ. An experimental study of OH(A 2Σ +) + H 2: Electronic quenching, rotational energy transfer, and collisional depolarization. J Chem Phys 2017; 146:244313. [PMID: 28668067 DOI: 10.1063/1.4989567] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Zeeman quantum beat spectroscopy has been used to determine the thermal (300 K) rate constants for electronic quenching, rotational energy transfer, and collisional depolarization of OH(A2Σ+) by H2. Cross sections for both the collisional disorientation and collisional disalignment of the angular momentum in the OH(A2Σ+) radical are reported. The experimental results for OH(A2Σ+) + H2 are compared to previous work on the OH(A2Σ+) + He and Ar systems. Further comparisons are also made to the OH(A2Σ+) + Kr system, which has been shown to display significant non-adiabatic dynamics. The OH(A2Σ+) + H2 experimental data reveal that collisions that survive the electronic quenching process are highly depolarizing, reflecting the deep potential energy wells that exist on the excited electronic state surface.
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Affiliation(s)
- M Brouard
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - J Lawlor
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - G McCrudden
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - T Perkins
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - S A Seamons
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - P Stevenson
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - H Chadwick
- Chemistry Research Laboratory, The Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - F J Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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8
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Abstract
This review focuses on experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A2Σ+ radicals by molecular partners. The experimental observables include the branching between reactive and nonreactive decay channels, kinetic energy release, and quantum state distributions of the products. Complementary theoretical investigations reveal regions of strong nonadiabatic coupling, known as conical intersections, which facilitate the quenching process. The dynamical outcomes observed experimentally are connected to the local forces and geometric properties of the nuclei in the conical intersection region. Dynamical calculations for the benchmark OH-H2 system are in good accord with experimental observations, demonstrating that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.
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Affiliation(s)
- Julia H. Lehman
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Marsha I. Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
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9
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Dillon J, Yarkony DR. On the mechanism for the nonadiabatic reactive quenching of OH(A2Σ+) by H2(1Σg+): The role of the 22A state. J Chem Phys 2013; 139:064314. [DOI: 10.1063/1.4816768] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Joseph Dillon
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - David R. Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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10
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Conte R, Fu B, Kamarchik E, Bowman JM. A novel Gaussian Binning (1GB) analysis of vibrational state distributions in highly excited H2O from reactive quenching of OH* by H2. J Chem Phys 2013; 139:044104. [DOI: 10.1063/1.4816277] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Dillon J, Yarkony DR. Seams of Conical Intersections Relevant to the Quenching of OH(A2Σ+) by Collisions with H2. J Phys Chem A 2013; 117:7344-55. [DOI: 10.1021/jp401205c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joseph Dillon
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David R. Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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12
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Lehman JH, Lester MI, Yarkony DR. Reactive quenching of OH A 2Σ+ by O2 and CO: Experimental and nonadiabatic theoretical studies of H- and O-atom product channels. J Chem Phys 2012; 137:094312. [DOI: 10.1063/1.4748376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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13
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Collins MA, Godsi O, Liu S, Zhang DH. An ab initio quasi-diabatic potential energy matrix for OH(2Σ) + H2. J Chem Phys 2011; 135:234307. [DOI: 10.1063/1.3664759] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Lehman JH, Bertrand JL, Stephenson TA, Lester MI. Reactive quenching of OD A 2Σ+ by H2: Translational energy distributions for H- and D-atom product channels. J Chem Phys 2011; 135:144303. [DOI: 10.1063/1.3644763] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Bowman JM, Czakó G, Fu B. High-dimensional ab initio potential energy surfaces for reaction dynamics calculations. Phys Chem Chem Phys 2011; 13:8094-111. [DOI: 10.1039/c0cp02722g] [Citation(s) in RCA: 230] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Lehman JH, Dempsey LP, Lester MI, Fu B, Kamarchik E, Bowman JM. Collisional quenching of OD AΣ2+ by H2: Experimental and theoretical studies of the state-resolved OD XΠ2 product distribution and branching fraction. J Chem Phys 2010; 133:164307. [DOI: 10.1063/1.3487734] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Fu B, Kamarchik E, Bowman JM. Quasiclassical trajectory study of the postquenching dynamics of OH AΣ2+ by H2/D2 on a global potential energy surface. J Chem Phys 2010; 133:164306. [DOI: 10.1063/1.3488167] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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18
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Kamarchik E, Fu B, Bowman JM. Communications: Classical trajectory study of the postquenching dynamics of OH A ∑2+ by H2 initiated at conical intersections. J Chem Phys 2010; 132:091102. [DOI: 10.1063/1.3336402] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Dempsey LP, Sechler TD, Murray C, Lester MI. Quantum State Distribution of the OH X2Π Products from Collisional Quenching of OH A2Σ+ by O2 and CO2. J Phys Chem A 2009; 113:6851-8. [DOI: 10.1021/jp902935c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Logan P. Dempsey
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Timothy D. Sechler
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Craig Murray
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Marsha I. Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
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Dempsey LP, Sechler TD, Murray C, Lester MI, Matsika S. State-resolved distribution of OH X Π2 products arising from electronic quenching of OH A Σ2+ by N2. J Chem Phys 2009; 130:104307. [DOI: 10.1063/1.3077027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Hancock G, Saunders M. Vibrational distribution in NO(X2Pi) formed by self quenching of NO A 2Sigma+ (v=0). Phys Chem Chem Phys 2008; 10:2014-9. [PMID: 18688353 DOI: 10.1039/b719065d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Time-resolved FTIR has been used to study the emission from the NO X 2Pi (v) products formed both by fluorescence and by collisional self quenching of the NO A 2Sigma+ (v=0) state. Vibrational excitation has been observed in ground state NO with populations up to at least v=20. Under conditions where fluorescence is the dominant removal process the nascent distribution in ground state NO(v) was found to be determined by the relative magnitude of the emission coefficients. Collisional quenching by ground state NO populates higher vibrational levels in NO(v) than fluorescence. By comparing distributions acquired at different pressures and by using a surprisal analysis, a nascent distribution of NO(v=0-20) is estimated for collisional relaxation of NO A 2Sigma+ (v=0) by NO. This distribution was found to be slightly hotter than statistical (prior) and showed evidence of oscillations at specific vibrational levels. This work is one of the first to be published concerning the vibrational ground state products of the quenching of electronically excited molecules and the first to report emission over such a large number of vibrational levels.
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Affiliation(s)
- Gus Hancock
- Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, UK OX1 3QZ.
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22
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Dempsey LP, Murray C, Cleary PA, Lester MI. Electronic quenching of OH A 2Σ+radicals in single collision events with H2and D2: a comprehensive quantum state distribution of the OH X 2Π products. Phys Chem Chem Phys 2008; 10:1424-32. [DOI: 10.1039/b715611a] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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23
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Dempsey LP, Murray C, Lester MI. Product branching between reactive and nonreactive pathways in the collisional quenching of OH AΣ+2 radicals by H2. J Chem Phys 2007; 127:151101. [DOI: 10.1063/1.2800316] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Cleary PA, Dempsey LP, Murray C, Lester MI, Kłos J, Alexander MH. Electronic quenching of OH AΣ+2 radicals in single collision events with molecular hydrogen: Quantum state distribution of the OH XΠ2 products. J Chem Phys 2007; 126:204316. [PMID: 17552771 DOI: 10.1063/1.2730505] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We report a combined experimental and theoretical investigation of the nonreactive quenching channel resulting from electronic quenching of OH A 2Sigma+ by molecular hydrogen. The experiments utilize a pump-probe scheme to determine the OH X 2Pi population distribution following collisional quenching in a pulsed supersonic expansion. The pump laser excites OH A 2Sigma+ (nu'=0, N'=0), which has a significantly reduced fluorescence lifetime due to quenching by H2. The probe laser monitors the OH X 2Pi (nu", N") population via laser-induced fluorescence on various A-X transitions under single collision conditions. The experiments reveal a high degree of rotational excitation (N") of the quenched OH X 2Pi products observed in nu"=1 and 2 as well as a pronounced propensity for quenching into the Pi(A') Lambda-doublet level. These experiments have been supplemented by extensive multireference, configuration-interaction calculations aimed at exploring the topology of the relevant potential energy surfaces. Electronic quenching of OH A 2Sigma+ by H2 proceeds through conical intersections between two potentials of A' reflection symmetry (in planar geometry) that correlate with the electronically excited A 2Sigma+ and ground X 2Pi states of OH. The conical intersections occur in high-symmetry geometries, in which the O side of OH points toward H2. Corroborating and extending earlier work of Hoffman and Yarkony [J. Chem. Phys. 113, 10091 (2000)], these calculations reveal a steep gradient away from the OH-H2 conical intersection as a function of both the OH orientation and interfragment distance. The former will give rise to a high degree of OH rotational excitation, as observed for the quenched OH X 2Pi products.
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Affiliation(s)
- Patricia A Cleary
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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25
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Ortiz-Suárez M, Witinski MF, Davis HF. Reactive quenching of OH(AΣ+2) by D2 studied using crossed molecular beams. J Chem Phys 2006; 124:201106. [PMID: 16774309 DOI: 10.1063/1.2206779] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Reactive quenching of OH(A 2Sigma+,v=0) by D2 forming HOD+D was studied in crossed molecular beams. The D atom products are primarily forward scattered relative to the incident D2. The dominant mechanism involves a direct reaction from relatively large impact parameters with approximately 88% of the available energy appearing in HOD internal excitation.
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Affiliation(s)
- Mariví Ortiz-Suárez
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
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26
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Pollack IB, Lei Y, Stephenson TA, Lester MI. Electronic quenching of OH A2Σ+ radicals in collisions with molecular hydrogen. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.01.083] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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27
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Lewandowski H, Hudson ER, Bochinski J, Ye J. A pulsed, low-temperature beam of supersonically cooled free radical OH molecules. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.07.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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