Thermal and vibrational-state selected rates of the CH4+Cl↔HCl+CH3 reaction

Duncan, Wendell T.; Truong, Thanh N.

doi:10.1063/1.470731

Cited by 160 publications

(108 citation statements)

References 48 publications

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“…3, red bars) show significantly larger ratios, in support of this interpretation. In conjunction with the strong curvature couplings of both (stretching and umbrella-excited) active modes to the reaction coordinate (19)(20)(21)(22), a cascading energy flow could lead to a higher population in the ground-state pair (0, 0 0 ) s than the (0, 2 i ) s pairs, which is exactly shown in Fig. 3.…”

Section: As the CL Atom Abstracts The Stretch-excited H Atommentioning

confidence: 61%

“…These issues are at the heart of polyatomic reactivity and have been actively pursued both experimentally (10,28,(34)(35)(36)(37) and theoretically (19)(20)(21)(22) in recent years. We have reported a strong mode specificity in terms of pair-correlated distributions for two different modes of excitation: the C-H stretch and umbrella bend of the Cl ϩ CHD 3 3 HCl ϩ CD 3 reaction (10).…”

Section: Mode-specific and Bond-selective Reactivitymentioning

confidence: 99%

“…Theory predicted that as the Cl atom approaches the H end of CHD 3 , the chemical interaction induces a static curvature coupling (i.e., coupling of a vibrational mode to the reaction coordinate induced by the curvature of the reaction path) between the C-H stretching (v 1 ) motion and the reaction coordinate, resulting in a significant decrease of its frequency in the transition-state region (19)(20)(21)(22) and allowing energy flow between this mode and the reaction coordinate. Similar behavior was found for the CD 3 umbrella mode (v 3 ), yet other modes show little variation in frequencies.…”

Section: Visualizing the Cooperative Atomic Motions While A Chemical mentioning

confidence: 99%

“…By using the reaction path Hamiltonian approach (26), previous ab initio calculations of isotopically analogous reactions mapped out the minimum energy path and the evolution of the vibrational frequencies of various modes along the reaction path (19)(20)(21)(22). By adding the theoretically calculated vibration frequencies (with isotope corrections) to the minimum energy path, we connected the vibrational energy levels according to their symmetries, employing the rule that energy levels for vibration of the same symmetry do not cross (26).…”

Section: Visualizing the Cooperative Atomic Motions While A Chemical mentioning

confidence: 99%

“…The notation of 2 i refers to the vibrational mode 2 (the umbrella-bend) with i-quantum excitation.) Pair-correlated state and angular distributions were then exploited, in light of available ab initio theory (19)(20)(21)(22), to unveil the microscopic reaction pathways. We further sharpened the comparison with the result of a ground-state reaction at either the same initial translation energy (E c ) or the higher E c with an equivalent amount of total energy (vibration ϩ translation).…”

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confidence: 99%

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Tracking the energy flow along the reaction path

Yan

Liu

2008

Proc. Natl. Acad. Sci. U.S.A.

117

128

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We report a comprehensive study of the quantum-state correlation property of product pairs from reactions of chlorine atoms with both the ground-state and the CH stretch-excited CHD 3. In light of available ab initio theoretical results, this set of experimental data provides a conceptual framework to visualize the energy-flow pattern along the reaction path, to classify the activity of different vibrational modes in a reactive encounter, to gain deeper insight into the concept of vibrational adiabaticity, and to elucidate the intermode coupling in the transition-state region. This exploratory approach not only opens up an avenue to understand polyatomic reaction dynamics, even for motions at the molecular level in the fleeting transition-state region, but it also leads to a generalization of Polanyi's rules to reactions involving a polyatomic molecule. Over the past decades, there has been tremendous progress in experimental characterization of the structure of the transition state, notably by using the spectroscopic probes (2-4). Transition-state spectroscopy experiments performed to date are essentially the half-collision type in which the transition state is directly accessed either through photodetachment of negative ion precursor in a frequency-resolved experiment (3) or by the femtosecond pump-probe, time-resolved approach (4). As elegant and informative as those experiments are, half-collision results, in general, do not depict a full picture of how the reactants transform into the products. One way to think of this is as follows. The basic idea of a typical half-collision experiment is to initiate the reaction at transition state by a photoexcitation process. By virtue of photoabsorption, the total angular momentum, that is, the partial wave or the impact parameter, of the reactive system is then well specified and often limited to the lowest few quantum numbers in a restricted geometry of the Franck-Condon region. Consequently, the half-collision results are greatly simplified and more amenable to theoretical tests. In contrast, a chemical reaction inevitably constitutes the contribution from collisions with a full range of impact parameters and orientations. The resultant wave-interference patterns, arising from the coherent sum of scattering amplitudes of many partial waves, are manifested in the full-collision attribute such as product angular distribution (5, 6), which cannot be readily accounted for by the few-partial-wave, half-collision approach. On the horns of a dilemma, a full-collision experiment usually deals with asymptotic properties of the reaction, thereby rendering direct probes of the fleeting transition state difficult.Here, we propose an approach to delineate the dynamical aspects of the transition state in a full-collision experiment by tracking the energy flow along the reaction path. We previously introduced an experimental method to unfold the state-specific correlation of coincident product pairs in polyatomic reactions (7-9). More recently, we exploited the product pair-correl...

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Section: As the CL Atom Abstracts The Stretch-excited H Atommentioning

confidence: 61%

Section: Mode-specific and Bond-selective Reactivitymentioning

confidence: 99%

Section: Visualizing the Cooperative Atomic Motions While A Chemical mentioning

confidence: 99%

Section: Visualizing the Cooperative Atomic Motions While A Chemical mentioning

confidence: 99%

mentioning

confidence: 99%

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Tracking the energy flow along the reaction path

Yan

Liu

2008

Proc. Natl. Acad. Sci. U.S.A.

117

128

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TheRate: Program forab initio direct dynamics calculations of thermal and vibrational-state-selected rate constants

1998

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We introduce TheRate (THEoretical RATEs), a complete application program with a graphical user interface (GUI) for calculating rate constants from first principles. It is based on canonical variational transition‐state theory (CVT) augmented by multidimensional semiclassical zero and small curvature tunneling approximations. Conventional transition‐state theory (TST) with one‐dimensional Wigner or Eckart tunneling corrections is also available. Potential energy information needed for the rate calculations are obtained from ab initio molecular orbital and/or density functional electronic structure theory. Vibrational‐state‐selected rate constants may be calculated using a diabetic model. TheRate also introduces several technical advancements, namely the focusing technique and energy interpolation procedure. The focusing technique minimizes the number of Hessian calculations required by distributing more Hessian grid points in regions that are critical to the CVT and tunneling calculations and fewer Hessian grid points elsewhere. The energy interpolation procedure allows the use of a computationally less demanding electronic structure theory such as DFT to calculate the Hessians and geometries, while the energetics can be improved by performing a small number of single‐point energy calculations along the MEP at a more accurate level of theory. The CH4+H↔CH3+H2 reaction is used as a model to demonstrate usage of the program, and the convergence of the rate constants with respect to the number of electronic structure calculations. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1039–1052, 1998

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Reactive Scattering of Polyatomic Molecules

Clary

1998

Encyclopedia of Computational Chemistry

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Thermal and vibrational-state selected rates of the CH4+Cl↔HCl+CH3 reaction

Cited by 160 publications

References 48 publications

Tracking the energy flow along the reaction path

Tracking the energy flow along the reaction path

TheRate: Program forab initio direct dynamics calculations of thermal and vibrational-state-selected rate constants

Reactive Scattering of Polyatomic Molecules

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