Capture and dissociation in the complex-forming CH+H2 → CH2+H, CH+H2 reactionsElectronic supplementary information (ESI) available: Numerical values of the capture, abstraction and exchange rate coefficients reported in the paper, and figures showing the dependence of the logarithm of the rate coefficients on temperature. For abstraction an exchange, the figures include the results obtained from all treatments of the ZPE leakage problem analyzed. See DOI: 10.1039/c0cp01188f

• Main Authors: González, Miguel, Saracibar, Amaia, Garcia, Ernesto
• Format: Journal Article
• Language: English
• Published: 08.02.2011
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c0cp01188f

The rate coefficients for the capture process CH+H 2 → CH 3 and the reactions CH+H 2 → CH 2 +H (abstraction), CH+H 2 (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH 3 collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems. Quasiclassical trajectory calculations with a proposed treatment of the zero point energy leakage problem can reproduce experimental capture and abstraction rate coefficients.