Communication: Rigorous quantum dynamics of O + O2 exchange reactions on an <i>ab initio</i> potential energy surface substantiate the negative temperature dependence of rate coefficients

Li, Yaqin; Sun, Zhigang; Jiang, Bin; Xie, Daiqian; Dawes, Richard; Guo, Hua

doi:10.1063/1.4894069

Cited by 38 publications

(56 citation statements)

References 45 publications

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“…[46][47][48] It has a flat shoulder in the channels region, instead of a reef. This surface already allowed to improve temperature dependence of the atom-exchange rates in O 2 + O collisions [43][44][45] and may help to resolve some of the issues discussed above.…”

Section: Discussionmentioning

confidence: 99%

“…This effect was discussed in detail in our recent paper 30 and is also consistent with recent work on atom-exchange process in O 2 + O collisions, where significant isotope effects were observed and attributed to scattering resonances in O 3 alone, without any bath gas involved. [42][43][44][45] However, for rigorous description of this effect in symmetric and asymmetric isotopomers of both singly and doubly substituted isotopologues, the dimensionally reduced 2D model of O 3 is insufficient. It appears to be too rough.…”

Section: Discussionmentioning

confidence: 99%

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On stabilization of scattering resonances in recombination reaction that forms ozone

Ivanov

Babikov

2016

The Journal of Chemical Physics

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Calculations of energy transfer in the recombination reaction that forms ozone are carried out within the framework of the mixed quantum/classical theory and using the dimensionally reduced 2D-model of ozone molecule, with bending motion neglected. Recombination rate coefficients are obtained at room temperature for symmetric and asymmetric isotopomers of singly and doubly substituted isotopologues. The processes of resonance formation, spontaneous decay, collisional dissociation, and stabilization by bath gas (Ar) are all characterized and taken into account within the steady-state approximation for kinetics. The focus is on stabilization step, where the mysterious isotopic η-effect was thought to originate from. Our results indicate no difference in cross sections for stabilization of scattering resonances in symmetric and asymmetric isotopomers. As practical results, the general and simple analytic models for stabilization and dissociation cross sections are presented, which can be applied to resonances in any ozone molecule, symmetric or asymmetric, singly or doubly substituted. Present calculations show some isotope effect that looks similar to the experimentally observed η-effect, and the origin of this phenomenon is in the rates of formation/decay of scattering resonances, determined by their widths, that are somewhat larger in asymmetric isotopomers than in their symmetric analogues. However, the approximate two-dimensional model used here is insufficient for consistent and reliable description of all features of the isotopic effect in ozone. Calculations using an accurate 3D model are still needed. Published by AIP Publishing. [http://dx

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

On stabilization of scattering resonances in recombination reaction that forms ozone

Ivanov

Babikov

2016

The Journal of Chemical Physics

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“…Currently triatomic systems can be handled routinely 1 even when the reactants form a long-lived complex. 2,3,4 There are techniques that allow complete description of four-atomic systems 5,6,7 . The most complex system for which fully quantum mechanical state-to-state reaction probabilities have been obtained so far is the six-atomic CH4 + H → CH3 + H2 (R1) reaction, 8,9,10 but even there the total angular momentum is restricted to 0.…”

Section: Introductionmentioning

confidence: 99%

Testing the Palma–Clary Reduced Dimensionality Model Using Classical Mechanics on the CH₄ + H → CH₃ + H₂ Reaction

2016

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KEYWORDS Reduced dimensionality quantum scattering, Palma-Clary Hamiltonian, reaction cross section, quasiclassical trajectory method, one-period averaging method.ABSTRACT Application of exact quantum scattering methods in theoretical reaction dynamics of bimolecular reactions is limited by the complexity of the equations of nuclear motion to be solved.Simplification is often achieved by reducing the number of degrees of freedom to be explicitly handled by freezing the less important spectator ones. The reaction cross sections obtained in reduced-dimensionality (RD) quantum scattering methods can be used in the calculation of rate coefficients, but their physical meaning is limited. The accurate test of the performance of a reduced-dimensionality method would be a comparison of the RD cross sections with those obtained in accurate full-dimensional (FD) calculations, which is not feasible due to the lack of complete full-dimensional results. However, classical mechanics allows one to perform reaction dynamics calculations using both the RD and the FD model. In this paper an RD vs. FD comparison is made for the 8-dimensional Palma-Clary model on the example of four isotopologs of the CH4 + H → CH3 + H2 reaction, which has 12 internal dimensions. In the Palma-Clary model the only restriction is that the methyl group is confined to maintain C3v symmetry. Both RD and FD 2 opacity and excitation functions as well as differential cross sections were calculated using the quasiclassical trajectory method. The initial reactant separation has been handled according to our one-period averaging, 1PA method [Nagy, T.;Vikár, A.; Lendvay, G. J. Chem. Phys. 2016, 144, 014104]. The RD and FD excitation functions were found to be close to each other for some isotopologs but in general, the RD reactivity parameters are lower than the FD ones beyond statistical error and for one of the isotopologs the deviation is significant. This indicates that the goodness of RD cross sections cannot be taken for granted.

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“…Examples include surfaces for isomerization reactions of small polyatomic molecules, 1-3 for molecule-molecule interactions, 4,5 and very accurate surfaces for several triatomic and tetra-atomic molecules. 2,6 One example is a new and rather accurate potential energy surface (PES) of O 3 that has already been used recently to improve our understanding of the O atom exchange processes O + O 2 → O 2 + O, [7][8][9][10] and of the ozone forming recombination reaction 11 O + O 2 ⇔ O 3 * +bath gas − −−−−−− → O 3 .…”

Section: Introductionmentioning

confidence: 99%

Efficient method for calculations of ro-vibrational states in triatomic molecules near dissociation threshold: Application to ozone

Teplukhin

Babikov

2016

The Journal of Chemical Physics

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A method for calculations of rotational-vibrational states of triatomic molecules up to dissociation threshold (and scattering resonances above it) is devised, that combines hyper-spherical coordinates, sequential diagonalization-truncation procedure, optimized grid DVR, and complex absorbing potential. Efficiency and accuracy of the method and new code are tested by computing the spectrum of ozone up to dissociation threshold, using two different potential energy surfaces. In both cases good agreement with results of previous studies is obtained for the lower energy states localized in the deep (∼10 000 cm −1 ) covalent well. Upper part of the bound state spectrum, within 600 cm −1 below dissociation threshold, is also computed and is analyzed in detail. It is found that long progressions of symmetric-stretching and bending states (up to 8 and 11 quanta, respectively) survive up to dissociation threshold and even above it, whereas excitations of the asymmetric-stretching overtones couple to the local vibration modes, making assignments difficult. Within 140 cm −1 below dissociation threshold, large-amplitude vibrational states of a floppy complex O· · · O 2 are formed over the shallow van der Waals plateau. These are assigned using two local modes: the rocking-motion and the dissociative-motion progressions, up to 6 quanta in each, both with frequency ∼20 cm −1 . Many of these plateau states are mixed with states of the covalent well. Interestingly, excitation of the rocking-motion helps keeping these states localized within the plateau region, by raising the effective barrier. Published by AIP Publishing. [http://dx

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Communication: Rigorous quantum dynamics of O + O2 exchange reactions on an ab initio potential energy surface substantiate the negative temperature dependence of rate coefficients

Abstract: State-to-state reaction dynamics of 18 O+ 32 O 2 studied by a time-dependent quantum wavepacket method

Cited by 38 publications

References 45 publications

On stabilization of scattering resonances in recombination reaction that forms ozone

On stabilization of scattering resonances in recombination reaction that forms ozone

Testing the Palma–Clary Reduced Dimensionality Model Using Classical Mechanics on the CH₄ + H → CH₃ + H₂ Reaction

Efficient method for calculations of ro-vibrational states in triatomic molecules near dissociation threshold: Application to ozone

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Communication: Rigorous quantum dynamics of O + O2 exchange reactions on an ab initio potential energy surface substantiate the negative temperature dependence of rate coefficients

Abstract: State-to-state reaction dynamics of 18 O+ 32 O 2 studied by a time-dependent quantum wavepacket method

Cited by 38 publications

References 45 publications

On stabilization of scattering resonances in recombination reaction that forms ozone

On stabilization of scattering resonances in recombination reaction that forms ozone

Testing the Palma–Clary Reduced Dimensionality Model Using Classical Mechanics on the CH4 + H → CH3 + H2 Reaction

Efficient method for calculations of ro-vibrational states in triatomic molecules near dissociation threshold: Application to ozone

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Testing the Palma–Clary Reduced Dimensionality Model Using Classical Mechanics on the CH₄ + H → CH₃ + H₂ Reaction