| Quantum Dynamics of CH(X(2)Π)+H((2)S) Reactions on the CH(2)(X(2)A") Surface and Role of the Excited electronic States. | |
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MedLine Citation:
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PMID: 22817398 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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We present the Born-Oppenheimer quantum mechanical (QM) dynamics of the CH decay (d) CH(X(2)Π)+H((2)S)→C((3)P)+H(2)(X(1)Σ(g)(+)) and of the H exchange reaction (e) CH(X(2)Π) +H'((2)S)→CH'(X(2)Π)+H((2)S) on the CH(2)(X(2)A") PES of Harding et al. (J. Phys. Chem. 1993, 97, 5472). A thorough analysis of the correlation diagram of the four lowest CH(2) electronic states, as well as Renner-Teller and spin-orbit non-adiabatic test calculations on the X(3)A", a(1)A', and b(1)A" coupled PESs, validate the BO results, confirming that these reactions occur essentially on the uncoupled X(3)A" ground surface. We consider CH in the ground vibrational state and in the lowest four rotational states j(0). Thus we obtain initial-state resolved reaction probabilities, cross sections, and rate constants by propagating coupled-channel real wavepackets and performing flux analyses. If J is the total angular momentum quantum number and K is its projection along the body-fixed z axis, CH+H gives essentially the C+H(2) products via a barrierless K- inhibited insertion, CH(2) resonances at low J, and large cross sections near the threshold. These cross sections decrease strongly with the collision energy and depend slightly on j(0). On the other hand, the small cross sections obtained for the (e) channel are nearly independent on energy. From initial-state resolved rate constants and Boltzmann populations at temperature T, we obtain QM thermal rates from 100 to 400 K: at 300 K, k(d)=(9.57±0.96)×10(-11) and k(e)=(1.41±0.14)×10(-11) cm(3) s(-1) for (d) and (e) reactions, respectively. The k(d) value is in good agreement with previous quasi-classical trajectory (QCT) results on the same PES, but it is larger than that observed at 297 K by a factor of ~7. On the contrary, and in agreement with the small role of CH(2) excited electronic states, X(2)A" QCT and experimental rate constants agree at high temperatures. Thus, the discrepancy at room T between theory and experiment should be due to an experimental error or to some theoretical effects that we have not been considered in this work. At the present state of the art, an experimental error is more likely and suggests a new measurement of the rate constant. |
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Authors:
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Pablo Gamallo; Paolo Defazio; Sinan Akpinar; Carlo Petrongolo |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-7-20 |
Journal Detail:
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Title: The journal of physical chemistry. A Volume: - ISSN: 1520-5215 ISO Abbreviation: - Publication Date: 2012 Jul |
Date Detail:
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Created Date: 2012-7-23 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9890903 Medline TA: J Phys Chem A Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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