51
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Greaves SJ, Rose RA, Abou-Chahine F, Glowacki DR, Troya D, Orr-Ewing AJ. Quasi-classical trajectory study of the dynamics of the Cl + CH4→ HCl + CH3 reaction. Phys Chem Chem Phys 2011; 13:11438-45. [DOI: 10.1039/c0cp02694h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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52
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Estillore AD, Visger LM, Suits AG. Imaging the dynamics of chlorine atom reactions with alkenes. J Chem Phys 2010; 133:074306. [DOI: 10.1063/1.3473049] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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53
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Rose RA, Greaves SJ, Orr-Ewing AJ. Velocity map imaging the dynamics of the reactions of Cl atoms with neopentane and tetramethylsilane. J Chem Phys 2010; 132:244312. [DOI: 10.1063/1.3447378] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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54
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Greaves SJ, Rose RA, Orr-Ewing AJ. Velocity map imaging of the dynamics of bimolecular chemical reactions. Phys Chem Chem Phys 2010; 12:9129-43. [PMID: 20448868 DOI: 10.1039/c001233e] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The experimental technique of velocity map imaging (VMI) enables measurements to be made of the dynamics of chemical reactions that are providing unprecedented insights about reactive scattering. This perspective article illustrates how VMI, in combination with crossed-molecular beam, dual-beam or photo-initiated (Photoloc) methods, can reveal correlated information on the vibrational quantum states populated in the two products of a reaction, and the angular scattering of products (the differential cross section) formed in specific rotational and vibrational levels. Reactions studied by VMI techniques are being extended to those of polyatomic molecules or radicals, and of molecular ions. Subtle quantum-mechanical effects in bimolecular reactions can provide distinct signatures in the velocity map images, and are exemplified here by non-adiabatic dynamics on coupled potential energy surfaces, and by experimental evidence for scattering resonances.
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Affiliation(s)
- Stuart J Greaves
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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55
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Estillore AD, Visger LM, Suits AG. Crossed-beam dc slice imaging of chlorine atom reactions with pentane isomers. J Chem Phys 2010; 132:164313. [DOI: 10.1063/1.3414353] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
| | - Laura M. Visger
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Arthur G. Suits
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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56
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Rose RA, Greaves SJ, Orr-Ewing AJ. Velocity map imaging of the dynamics of the CH3+ HCl → CH4+ Cl reaction using a dual molecular beam method. Mol Phys 2010. [DOI: 10.1080/00268971003610234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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57
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Layfield JP, Troya D. Theoretical study of the dynamics of F+alkanethiol self-assembled monolayer hydrogen-abstraction reactions. J Chem Phys 2010; 132:134307. [DOI: 10.1063/1.3364858] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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58
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Hickson KM, Bergeat A, Costes M. A Low Temperature Study of the Reactions of Atomic Chlorine with Simple Alkanes. J Phys Chem A 2009; 114:3038-44. [DOI: 10.1021/jp9061253] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kevin M. Hickson
- Université de Bordeaux, Institut des Sciences Moléculaires, 351 Cours de la Libération, 33405 Talence Cedex, France, and CNRS UMR 5255, ISM, 33405 Talence Cedex, France
| | - Astrid Bergeat
- Université de Bordeaux, Institut des Sciences Moléculaires, 351 Cours de la Libération, 33405 Talence Cedex, France, and CNRS UMR 5255, ISM, 33405 Talence Cedex, France
| | - Michel Costes
- Université de Bordeaux, Institut des Sciences Moléculaires, 351 Cours de la Libération, 33405 Talence Cedex, France, and CNRS UMR 5255, ISM, 33405 Talence Cedex, France
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59
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Taylor MS, Ivanic SA, Wood GPF, Easton CJ, Bacskay GB, Radom L. Hydrogen Abstraction by Chlorine Atom from Small Organic Molecules Containing Amino Acid Functionalities: An Assessment of Theoretical Procedures. J Phys Chem A 2009; 113:11817-32. [DOI: 10.1021/jp9029437] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Mark S. Taylor
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Sandra A. Ivanic
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Geoffrey P. F. Wood
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Christopher J. Easton
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - George B. Bacskay
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Leo Radom
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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60
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Huang C, Li W, Estillore AD, Suits AG. Dynamics of CN+alkane reactions by crossed-beam dc slice imaging. J Chem Phys 2009; 129:074301. [PMID: 19044761 DOI: 10.1063/1.2968547] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogen atom abstraction reactions of CN (X (2)Sigma(+)) with alkanes have been studied using the crossed molecular beam technique with dc slice ion imaging at collision energies of 7.5 and 10.8 kcalmol. The product alkyl radical images were obtained via single photon ionization at 157 nm for the reactions of CN (X (2)Sigma(+)) with n-butane, n-pentane, n-hexane, and cyclohexane. From analysis of the images, we obtained the center-of-mass frame product angular distributions and translational energy distributions directly. The results indicate that the products are largely backscattered and that most of the available energy ( approximately 80%-85%) goes to the internal energy of the products. The reaction dynamics is discussed in light of recent kinetics data, theoretical calculations, and results for related halogen and oxygen atom reactions.
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Affiliation(s)
- Cunshun Huang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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61
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Ziemkiewicz M, Nesbitt DJ. Nonadiabatic reactive scattering in atom+triatom systems: Nascent rovibronic distributions in F+H[sub 2]O→HF+OH. J Chem Phys 2009; 131:054309. [DOI: 10.1063/1.3194284] [Citation(s) in RCA: 30] [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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62
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Rudić S, Merritt JM, Miller RE. Study of the CH3⋯H2O radical complex stabilized in helium nanodroplets. Phys Chem Chem Phys 2009; 11:5345-52. [DOI: 10.1039/b817484a] [Citation(s) in RCA: 15] [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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63
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Greaves SJ, Orr-Ewing AJ, Troya D. Classical Trajectory Study of the Dynamics of the Reaction of Cl Atoms with Ethane. J Phys Chem A 2008; 112:9387-95. [DOI: 10.1021/jp802347v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | | | - Diego Troya
- Department of Chemistry, Virginia Tech, 107 Davidson Hall, Blacksburg, Virginia, 24061-0212
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64
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Retail B, Pearce JK, Greaves SJ, Rose RA, Orr-Ewing AJ. Adiabatic and nonadiabatic dynamics in the CH3(CD3)+HCl reaction. J Chem Phys 2008; 128:184303. [DOI: 10.1063/1.2913516] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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65
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66
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Retail B, Rose RA, Pearce JK, Greaves SJ, Orr-Ewing AJ. The dynamics of reaction of Cl atoms with tetramethylsilane. Phys Chem Chem Phys 2008; 10:1675-80. [DOI: 10.1039/b716512a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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67
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Nyman G, Zhou J, Zhang B, Liu K. Crossed-Beam and Quantum Dynamics Studies of the Reaction Cl + CHD3. Isr J Chem 2007. [DOI: 10.1560/ijc.47.1.1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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68
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Pearce JK, Retail B, Greaves SJ, Rose RA, Orr-Ewing AJ. Imaging the Dynamics of Reactions between Cl Atoms and the Cyclic Ethers Oxirane and Oxetane. J Phys Chem A 2007; 111:13296-304. [DOI: 10.1021/jp0773684] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Julie K. Pearce
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Bertrand Retail
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Stuart J. Greaves
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Rebecca A. Rose
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Andrew J. Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
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69
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Greaves SJ, Kim J, Orr-Ewing AJ, Troya D. Studying ‘chattering collisions’ in the Cl+ethane reaction with classical trajectories. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.05.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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70
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Küpper J, Merritt JM. Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nanodroplets. INT REV PHYS CHEM 2007. [DOI: 10.1080/01442350601087664] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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71
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72
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Huang C, Li W, Suits AG. Rotationally resolved reactive scattering: Imaging detailed Cl+C2H6 reaction dynamics. J Chem Phys 2006; 125:133107. [PMID: 17029433 DOI: 10.1063/1.2202827] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogen atom abstraction reaction of Cl (2P3/2) with ethane has been studied using the crossed molecular beam technique with dc slice imaging at collision energies from 3.2 to 10.4 kcal/mol. The products HCl (v,J) (v = 0, J = 0-5) were state-selectively detected using 2+1 resonance enhanced multiphoton ionization. The images were used to obtain the center-of-mass frame product angular distributions and translational energy release distributions. Two general features were found in all probed HCl quantum states at 6.7 kcal/mol collision energy, and these features have distinct translational energy release and angular distributions, as described for HCl (v = 0, J = 2) in a recent preliminary report [Li et al., J. Chem. Phys. 124, 011102 (2006)]. The results for HCl (v = 0, J = 2) at four collision energies were also compared to investigate the energy-dependent dynamics. We discuss the reaction in terms of a variety of models of polyatomic reaction dynamics. The dynamics of this well studied system are more complicated than can be accounted for by a single mechanism, and the results call for further theoretical and experimental investigations.
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Affiliation(s)
- Cunshun Huang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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73
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Teslja A, Valentini JJ. State-to-state reaction dynamics: A selective review. J Chem Phys 2006; 125:132304. [PMID: 17029423 DOI: 10.1063/1.2354466] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A selective review of state-to-state reaction dynamics experiments is presented. The review focuses on three classes of reactions that exemplify the rich history and illustrate the current state of the art in such work. These three reactions are (1) the hydrogen exchange reaction, H+H2-->H2+H and its isotopomers; (2) the H+RH-->H2+R reactions, where RH is an alkane, beginning with H+CH4-->H2+CH3 and extending to much larger alkanes; and (3) the Cl+RH-->HCl+R reactions, principally Cl+CH4-->HCl+CH3. We describe the experiments, discuss their results, present comparisons with theory, and introduce heuristic models.
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Affiliation(s)
- Alexey Teslja
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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74
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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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75
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Holiday RJ, Kwon CH, Annesley CJ, Fleming Crim F. Mode- and bond-selective reaction of Cl(P3∕22) with CH3D: C–H stretch overtone excitation near 6000cm−1. J Chem Phys 2006; 125:133101. [PMID: 17029427 DOI: 10.1063/1.2352742] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Experiments explore the influence of different C-H stretching eigenstates of CH3D on the reaction of CH3D with Cl(2P3/2). We prepare the mid |110>|0>(A1,E), mid |200>|>0(E), and mid |100>|0> +nu3 +nu5 eigenstates by direct midinfrared absorption near 6000 cm(-1). The vibrationally excited molecules react with photolytic Cl atoms, and we monitor the vibrational states of the CH2D or CH3 radical products by 2+1 resonance enhanced multiphoton ionization. Initial excitation of the |200>|0>(E) state leads to a twofold increase in CH2D products in the vibrational ground state compared to|100>|0> +nu3 +nu5 excitation, indicating mode-selective chemistry in which the C-H stretch motion couples more effectively to the H-atom abstraction coordinate than bend motion. For two eigenstates that differ only in the symmetry of the vibrational wave function, |110>|0>(A1) and |110>|0>(E), the ratio of reaction cross sections is 1.00 +/- 0.05, showing that there is no difference in enhancement of the H-atom abstraction reaction. Molecules with excited local modes corresponding to one quantum of C-H stretch in each of two distinct oscillators react exclusively to form C-H stretch excited CH2D products. Conversely, eigenstates containing stretch excitation in a single C-H oscillator form predominantly ground vibrational state CH2D products. Analyzing the product state yields for reaction of the |110>|0>(A1) state of CH3D yields an enhancement of 20 +/- 4 over the thermal reaction. A local mode description of the vibrational motion along with a spectator model for the reactivity accounts for all of the observed dynamics.
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Affiliation(s)
- Robert J Holiday
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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76
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Castillo JF, Aoiz FJ, Bañares L. Quasiclassical trajectory study of the Cl+CH4 reaction dynamics on a quadratic configuration interaction with single and double excitation interpolated potential energy surface. J Chem Phys 2006; 125:124316. [PMID: 17014183 DOI: 10.1063/1.2357741] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An ab initio interpolated potential energy surface (PES) for the Cl+CH(4) reactive system has been constructed using the interpolation method of Collins and co-workers [J. Chem. Phys. 102, 5647 (1995); 108, 8302 (1998); 111, 816 (1999); Theor. Chem. Acc. 108, 313 (2002)]. The ab initio calculations have been performed using quadratic configuration interaction with single and double excitation theory to build the PES. A simple scaling all correlation technique has been used to obtain a PES which yields a barrier height and reaction energy in good agreement with high level ab initio calculations and experimental measurements. Using these interpolated PESs, a detailed quasiclassical trajectory study of integral and differential cross sections, product rovibrational populations, and internal energy distributions has been carried out for the Cl+CH(4) and Cl+CD(4) reactions, and the theoretical results have been compared with the available experimental data. It has been shown that the calculated total reaction cross sections versus collision energy for the Cl+CH(4) and Cl+CD(4) reactions is very sensitive to the barrier height. Besides, due to the zero-point energy (ZPE) leakage of the CH(4) molecule to the reaction coordinate in the quasiclassical trajectory (QCT) calculations, the reaction threshold falls below the barrier height of the PES. The ZPE leakage leads to CH(3) and HCl coproducts with internal energy below its corresponding ZPEs. We have shown that a Gaussian binning (GB) analysis of the trajectories yields excitation functions in somehow better agreement with the experimental determinations. The HCl(v'=0) and DCl(v'=0) rotational distributions are as well very sensitive to the ZPE problem. The GB correction narrows and shifts the rotational distributions to lower values of the rotational quantum numbers. However, the present QCT rotational distributions are still hotter than the experimental distributions. In both reactions the angular distributions shift from backward peaked to sideways peaked as collision energy increases, as seen in the experiments and other theoretical calculations.
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Affiliation(s)
- J F Castillo
- Departamento de Química Física I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain.
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77
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Rudić S, Merritt JM, Miller RE. Infrared laser spectroscopy of the CH3–HCN radical complex stabilized in helium nanodroplets. J Chem Phys 2006; 124:104305. [PMID: 16542077 DOI: 10.1063/1.2170087] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The CH3-HCN and CD3-HCN radical complexes have been formed in helium nanodroplets by sequential pickup of a CH3 (CD3) radical and a HCN molecule and have been studied by high-resolution infrared laser spectroscopy. The complexes have a hydrogen-bonded structure with C3v symmetry, as inferred from the analysis of their rotationally resolved nu = 1 <-- 0 H-CN vibrational bands. The A rotational constants of the complexes are found to change significantly upon vibrational excitation of the C-H stretch of HCN within the complex, DeltaA = A'-A" = -0.04 cm(-1) (for CH3-HCN), whereas the B rotational constants are found to be 2.9 times smaller than that predicted by theory. The reduction in B can be attributed to the effects of helium solvation, whereas the large DeltaA is found to be a sensitive probe of the vibrational averaging dynamics of such weakly bound systems. The complex has a permanent electric dipole moment of 3.1 +/- 0.2 D, as measured by Stark spectroscopy. A vibration-vibration resonance is observed to couple the excited C-H stretching vibration of HCN within the complex to the lower-frequency C-H stretches of the methyl radical. Deuteration of the methyl radical was used to detune these levels from resonance, increasing the lifetime of the complex by a factor of 2. Ab initio calculations for the energies and molecular parameters of the stationary points on the CN+CH4 --> HCN+CH3 potential-energy surface are also presented.
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Affiliation(s)
- S Rudić
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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78
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Merritt JM, Rudić S, Miller RE. Infrared laser spectroscopy of CH3⋯HF in helium nanodroplets: The exit-channel complex of the F+CH4 reaction. J Chem Phys 2006; 124:084301. [PMID: 16512710 DOI: 10.1063/1.2168450] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
High-resolution infrared laser spectroscopy is used to study the CH3...HF and CD3...HF radical complexes, corresponding to the exit-channel complex in the F + CH4 --> HF + CH3 reaction. The complexes are formed in helium nanodroplets by sequential pickup of a methyl radical and a HF molecule. The rotationally resolved spectra presented here correspond to the fundamental v = 1 <-- 0 H-F vibrational band, the analysis of which reveals a complex with C(3v) symmetry. The vibrational band origin for the CH3...HF complex (3797.00 cm(-1)) is significantly redshifted from that of the HF monomer (3959.19 cm(-1)), consistent with the hydrogen-bonded structure predicted by theory [E. Ya. Misochko et al., J. Am. Chem. Soc. 117, 11997 (1995)] and suggested by previous matrix isolation experiments [M. E. Jacox, Chem. Phys. 42, 133 (1979)]. The permanent electric dipole moment of this complex is experimentally determined by Stark spectroscopy to be 2.4+/-0.3 D. The wide amplitude zero-point bending motion of this complex is revealed by the vibrational dependence of the A rotational constant. A sixfold reduction in the line broadening associated with the H-F vibrational mode is observed in going from CH3...HF to CD3...HF. The results suggest that fast relaxation in the former case results from near-resonant intermolecular vibration-vibration (V-V) energy transfer. Ab initio calculations are also reported (at the MP2 level) for the various stationary points on the F + CH4 surface, including geometry optimizations and vibrational frequency calculations for CH3...HF.
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Affiliation(s)
- J M Merritt
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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79
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Troya D, Weiss PJE. Ab initio and direct quasiclassical-trajectory study of the Cl+CH4→HCl+CH3 reaction. J Chem Phys 2006; 124:74313. [PMID: 16497042 DOI: 10.1063/1.2171689] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present an electronic structure and dynamics study of the Cl + CH(4)--> HCl + CH(3) reaction. We have characterized the stationary points of the ground-state potential-energy surface using various electronic structure methods and basis sets. Our best calculations, CCSD(T) extrapolated to the complete basis-set limit based on geometries and harmonic frequencies obtained at the CCSD(T)/aug-cc-pvtz level, are in agreement with the experimental reaction energy and indirect measurements of the barrier height. Using ab initio information, we have reparametrized a semiempirical Hamiltonian so that the predictions of the improved Hamiltonian agree with the higher-level calculations in various regions of the potential-energy surface. This improved semiempirical Hamiltonian is then used to propagate quasiclassical trajectories and characterize the reaction dynamics. The good agreement of the calculated HCl rotational and angular distributions with the experiment indicates that reparametrizing semiempirical Hamiltonians is a promising approach to derive accurate potential-energy surfaces for polyatomic reactions. However, excessive energy leakage from the initial vibrational energy of the CH(4) molecule to the reaction coordinate in the trajectory calculations calls into question the suitability of the standard quasiclassical-trajectory method to describe energy partitioning in polyatomic reactions.
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Affiliation(s)
- Diego Troya
- Department of Chemistry, Virginia Tech, 107 Davidson Hall, Blacksburg, 24061-0212, USA.
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80
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Camden JP, Bechtel HA, Ankeny Brown DJ, Zare RN. Comparing reactions of H and Cl with C–H stretch-excited CHD3. J Chem Phys 2006; 124:034311. [PMID: 16438587 DOI: 10.1063/1.2155434] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the methyl radical product state distributions for the reactions of H and Cl with CHD3(nu1 = 1,2) at collision energies of 1.53 and 0.18 eV, respectively. Both reactions demonstrate mode selectivity. The resulting state distributions from the H+CHD3(nu1 = 1,2) reactions are well described by a spectator model. The reactions Cl + CHD3(nu1 = 1,2) exhibit similar behavior, but in some aspects the spectator model breaks down. We attribute this breakdown to enhanced intramolecular vibrational redistribution in the Cl + CHD3(nu1 = 1,2) reactions compared to the H + CHD3(nu1 = 1,2) reactions, caused by the interaction of the slower Cl atom with the vibrationally excited CHD3, which is promoted either by its longer collision duration, its stronger coupling, or both.
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Affiliation(s)
- Jon P Camden
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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81
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Zhou J, Lau KC, Hassanein E, Xu H, Tian SX, Jones B, Ng CY. A photodissociation study of CH2BrCl in the A-band using the time-sliced ion velocity imaging method. J Chem Phys 2006; 124:034309. [PMID: 16438585 DOI: 10.1063/1.2158999] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Employing a high-resolution (velocity resolution deltanu/nu<1.5%) time-sliced ion velocity imaging apparatus, we have examined the photodissociation of CH2BrCl in the photon energy range of 448.6-618.5 kJ/mol (193.3-266.6 nm). Precise translational and angular distributions for the dominant Br(2P32) and Br(2P12) channels have been determined from the ion images observed for Br(2P32) and Br(2P12). In confirmation with the previous studies, the kinetic-energy distributions for the Br(2P12) channel are found to fit well with one Gaussian function, whereas the kinetic- energy distributions for the Br(2P32) channel exhibit bimodal structures and can be decomposed into a slow and a fast Gaussian component. The observed kinetic-energy distributions are consistent with the conclusion that the formation of the Br(2P32) and Br(2P12) channels takes place on a repulsive potential-energy surface, resulting in a significant fraction (0.40-0.47) of available energy to appear as translational energy for the photo fragments. On the basis of the detailed kinetic-energy distributions and anisotropy parameters obtained in the present study, together with the specific features and relative absorption cross sections of the excited 2A', 1A", 3A', 4A', and 2A" states estimated in previous studies, we have rationalized the dissociation pathways of CH2BrCl in the A-band, leading to the formation of the Br(2P32) and Br(2P12) channels. The analysis of the ion images observed at 235 nm for Cl(2P(32,12)) provides strong evidence that the formation of Cl mainly arises from the secondary photodissociation process CH2Cl + hnu --> CH2 + Cl.
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Affiliation(s)
- Jingang Zhou
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA
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82
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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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83
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Choi MY, Douberly GE, Falconer TM, Lewis WK, Lindsay CM, Merritt JM, Stiles PL, Miller RE. Infrared spectroscopy of helium nanodroplets: novel methods for physics and chemistry. INT REV PHYS CHEM 2006. [DOI: 10.1080/01442350600625092] [Citation(s) in RCA: 327] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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84
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Ziemkiewicz M, Wojcik M, Nesbitt DJ. Direct evidence for nonadiabatic dynamics in atom+polyatom reactions: Crossed-jet laser studies of F+D2O→DF+OD. J Chem Phys 2005; 123:224307. [PMID: 16375476 DOI: 10.1063/1.2098648] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Quantum-state-resolved reactive-scattering dynamics of F+D(2)O-->DF+OD have been studied at E(c.m.)=5(1) kcal/mol in low-density crossed supersonic jets, exploiting pulsed discharge sources of F atom and laser-induced fluorescence to detect the nascent OD product under single-collision conditions. The product OD is formed exclusively in the v(OD)=0 state with only modest rotational excitation (<E(rot)> =0.50(1) kcal/mol), consistent with the relatively weak coupling of the 18.1(1) kcal/mol reaction exothermicity into "spectator" bond degrees of freedom. The majority of OD products [68(1)%] are found in the ground ((2)Pi(32) (+/-)) spin-orbit state, which adiabatically correlates with reaction over the lowest and only energetically accessible barrier (DeltaE( not equal) approximately 4 kcal/mol). However, 32(1)% of molecules are produced in the excited spin-orbit state ((2)Pi(12) (+/-)), although from a purely adiabatic perspective, this requires passage over a DeltaE( not equal) approximately 25 kcal/mol barrier energetically inaccessible at these collision energies. This provides unambiguous evidence for nonadiabatic surface hopping in F+D(2)O atom abstraction reactions, indicating that reactive-scattering dynamics even in simple atom+polyatom systems is not always isolated on the ground electronic surface. Additionally, the nascent OD rotational states are well fitted by a two-temperature Boltzmann distribution, suggesting correlated branching of the reaction products into the DF(v=2,3) vibrational manifold.
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Affiliation(s)
- Michael Ziemkiewicz
- Joint Institute for Laboratory Astrophysics (JILA), National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0040, USA
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85
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Murray C, Pearce JK, Rudić S, Retail B, Orr-Ewing AJ. Stereodynamics of Chlorine Atom Reactions with Organic Molecules. J Phys Chem A 2005; 109:11093-102. [PMID: 16331891 DOI: 10.1021/jp054627l] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of recent experimental and computational studies has explored how the dynamics of hydrogen abstraction from organic molecules are affected by the presence of functional groups in the molecule and by basic structural motifs such as strained ring systems. Comparisons drawn between reactions of Cl atoms with alkanes such as ethane, Cl + CH3CH3--> HCl + CH3CH2, which serve as benchmark systems, and with functionalized molecules such as alcohols, amines, and alkyl halides, Cl + CH3X --> HCl + CH2X (X = OH, NH2, halogen, etc.) expose a wealth of mechanistic detail. Although the scattering dynamics, as revealed from measured angular distributions of the velocities of the HCl with quantum-state resolution, show many similarities, much-enhanced rotational excitation of the HCl products is observed from reactions of the functionalized molecules. The degree of rotational excitation of the HCl correlates with the dipole moment of the CH2X radical and is thus attributed, at least in part, to post-transition-state dipole-dipole interactions between the separating, polar reaction products. This interpretation is supported by direct dynamics trajectories computed on-the-fly, and the HCl rotation is thus argued to serve as an in situ probe of the angular anisotropy of the reaction potential energy surface in the post-transition-state region. Comparisons between the dynamics of reactions of dimethyl ether and the three- and four-membered-ring compounds oxirane (c-C2H4O) and oxetane (c-C3H6O) raise questions about the role of reorientation of the reaction products on a time scale commensurate with their separation. The shapes and structures of polyatomic molecules are thus demonstrated to have important consequences for the stereodynamics of these direct abstraction reactions.
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Affiliation(s)
- Craig Murray
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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86
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Bass MJ, Brouard M, Cireasa R, Clark AP, Vallance C. Imaging photon-initiated reactions: A study of the Cl(P3∕22)+CH4→HCl+CH3 reaction. J Chem Phys 2005; 123:94301. [PMID: 16164339 DOI: 10.1063/1.2009737] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogen or deuterium atom abstraction reactions between Cl((2)P(3/2)) and methane, or its deuterated analogues CD(4) and CH(2)D(2), have been studied at mean collision energies around 0.34 eV. The experiments were performed in a coexpansion of molecular chlorine and methane in helium, with the atomic Cl reactants generated by polarized laser photodissociation of Cl(2) at 308 nm. The Cl-atom reactants and the methyl radical products were detected using (2+1) resonantly enhanced multiphoton ionization, coupled with velocity-map ion imaging. Analysis of the ion images reveals that in single-beam experiments of this type, careful consideration must be given to the spread of reagent velocities and collision energies. Using the reactions of Cl with CH(4), CD(4), and CH(2)D(2), as examples, it is shown that the data can be fitted well if the reagent motion is correctly described, and the angular scattering distributions can be obtained with confidence. New evidence is also provided that the CD(3) radicals from the Cl+CD(4) reaction possess significant rotational alignment under the conditions of the present study. The results are compared with previous experimental and theoretical works, where these are available.
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Affiliation(s)
- M J Bass
- The Physical and Theoretical Chemistry Laboratory, The Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
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87
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Shuman NS, Mihok M, Fistik M, Valentini JJ. Quasiclassical trajectory calculations to evaluate a kinematic constraint on internal energy in suprathreshold collision energy abstraction reactions. J Chem Phys 2005; 123:074312. [PMID: 16229575 DOI: 10.1063/1.1990122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Experimentally observed product quantum state distributions across a wide range of abstraction reactions at suprathreshold collision energies have shown a strong bias against product internal energy. Only a fraction, sometimes quite a small fraction, of the energetically accessible product quantum states are populated. Picconatto et al. [J. Chem. Phys. 114, 1663 (2001)] noted a simple mathematical relationship between the highest-energy rovibrational states observed and the kinematics of the reaction system. They proposed a reaction model based on reaction kinematics that quantitatively explains this behavior. The model is in excellent agreement with measured quantum state distributions. The assumptions of the model invoke detailed characteristics of reactive trajectories at suprathreshold collision energies. Here we test those assumptions using quasiclassical trajectory calculations for the abstraction reactions H+HCl-->H2+Cl, D+HCl-->HD+Cl, and H+DCl-->HD+Cl. Trajectories were run on a potential-energy surface calculated with a London-Eyring-Polyani-Sato function with a localized 3-center term (LEPS-3C) previously shown to accurately reproduce experimentally observed product state distributions for the H+HCl abstraction reaction. The trajectories sample collision energies near threshold and also substantially above it. Although the trajectories demonstrate some aspects of the model, they show that it is not valid. However, the inadequacy of the proposed model does not invalidate the apparent kinematic basis of the observed energy constraint. The present results show that there must be some other molecular behavior rooted in the reaction kinematics that is the explanation and the source of the constraint.
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Affiliation(s)
- Nicholas S Shuman
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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Retail B, Pearce JK, Murray C, Orr-Ewing AJ. Nonadiabatic dynamics in the CH3+HCl→CH4+Cl(PJ2) reaction. J Chem Phys 2005; 122:101101. [PMID: 15836300 DOI: 10.1063/1.1869497] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nonadiabatic dynamics in the title reaction have been investigated by 2+1 REMPI detection of the Cl(2P(3/2)) and Cl*(2P(1/2)) products. Reaction was initiated by photodissociation of CH(3)I at 266 nm within a single expansion of a dilute mixture of CH(3)I and HCl in argon, giving a mean collision energy of 7800 cm(-1) in the center-of-mass frame. Significant production of Cl* was observed, with careful checks made to ensure that no additional photochemical or inelastic scattering sources of Cl* perturbed the measurements. The fraction of the total yield of Cl(2P(J)) atoms formed in the J=1/2 level at this collision energy was 0.150+/-0.024, and must arise from nonadiabatic dynamics because the ground potential energy surface correlates to CH(4)+Cl(2P(3/2)) products.
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Affiliation(s)
- Bertrand Retail
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
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