Wave packet quantum dynamics of \begin{document}${\bf{C}}{(^3}{\bf{P}}) + {{\bf{H}}_2}({{\bf{X}}^1} \Sigma _{\bf{g}}^ + ) $\end{document} \begin{document}$ \to {\bf{H}}{(^2}{\bf{S}}) + {\bf{CH}}{(^2} \Pi ) $\end{document} reaction based on new CH2(\begin{document}${\tilde {\bf X}{}^3}\bf A''$\end{document}) surface

Abstract

The C(³P) + H₂→ CH+H reaction in a collision energy range of 1.0–2.0 eV with the initial state <inline-formula><tex-math id="M6">\begin{document}$\nu = 0{\rm{ }},j = 0$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20200132_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20200132_M6.png"/></alternatives></inline-formula> is investigated based on the new potential energy surface (PES) by using the Chebyshev wave packet method. All partial wave contributions up to <i>J</i> = 60 are calculated explicitly by the coupled state (CS) approximation method and the Coriolis coupling (CC) effect. Dynamic properties such as reaction probabilities, integral cross sections, and state specific rate constants are calculated. The calculated probabilities and integral reaction cross sections display an increasing trend with the increase of the collision energy and an oscillatory structure due to the CH₂ well on the reaction path. The thermal rate constants of the endoergic reaction with a temperature ranging from 1000 K to 2000 K are obtained also. The calculated rate constants increase in the entire temperature range, showing a sharp <i>T</i> dependence in a range of 1400–2000 K. The rate constants are sensitive to the temperature due to the high threshold of the title reaction. In addition, the results of the exact calculations including CC effect are compared with those from the CS approximation. For smaller <i>J</i>, the CS probabilities are larger than the CC results, while for larger <i>J</i>, they are smaller than the CC ones. For reaction cross sections and rate constants, the CS results and the CC ones are in good agreement with each other at lower energy. However, they turn different at higher energy. The comparison between the CC and CS results indicates that neglecting the Coriolis coupling leads the cross sections and the rate constants to be underestimated due to the formation of a CH₂ complex supported by stationary point of CH₂(<inline-formula><tex-math id="M7">\begin{document}${\tilde{\rm X}}{}^3 \rm A''$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20200132_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20200132_M7.png"/></alternatives></inline-formula>) PES. It is suggested that the CH₂ complex plays an important role in the process of the title reaction. However, it seems to overestimate the CS and CC rate constants because the barrier recrossing is neglected. Unfortunately, the results obtained in the present work have no corresponding theoretical or experimental data to be compared with, therefore these results provide simply a certain reference significance to the follow-up study of the title reaction.