The CH+H reaction studied with quantum-mechanical and classical trajectory calculations

Abstract

The CH+H→C+H2 reaction is studied with quantum-mechanical wave packet calculations and quasiclassical trajectory calculations using a CH2 ground-state potential energy surface. Although quantum tunneling is important for direct hydrogen abstraction, the dominance of the complex formation mechanism ensures the reliability of quasiclassical calculations. Most collisions (≈80%) are nonreactive, because of a too-weak excitation of the CH vibration after a H–CH collision with H approaching CH with HCH angles larger than 60 deg. In this aspect the reaction differs from reactions such as the well-studied O(1D)+H2 reaction, where the H–H vibration in the triatomic complex is strongly excited. Also presented is the rate constant for a temperature range between 50 and 2000 K, obtained from quasiclassical cross-section results for collision energies between 0.0005 and 0.3 eV. The role of the excited triplet and singlet states of CH2 on the reaction dynamics is discussed.