State-to-State Rate Constants for the O(³<i>P</i>)H₂(<i>v</i>) System: Quasiclassical Trajectory Calculations

Abstract

The rate constants of elementary processes in the atom–diatom system O(3P)+H2(v), including the processes of vibrational relaxation and dissociation, were studied using the quasiclassical trajectory method. All calculations were carried out along the ground potential energy surface (PES) 3A″ that was approximated by a neural network. Approximation data were obtained using ab initio quantum chemistry methods at the extended multi-configuration quasi-degenerate second-order perturbation theory XMCQDPT2 in a basis set limit. The calculated cross-sections of the reaction channels are in good agreement with the literature data. A complete set of state-to-state rate constants was obtained for the metathesis reaction, the dissociation and relaxation of the H2 molecule upon collision with an O atom. According to these data, Arrhenius approximations over a wide temperature range were obtained for the thermal rate constants of considered processes. Data obtained on the dissociation constants and VT relaxation of vibrationally excited H2 molecules can be used in constructing kinetic models describing the oxidation of hydrogen at high temperatures or highly nonequilibrium conditions.

Keywords

• quasiclassical trajectory (QCT) method
• state-resolved rate constants
• hydrogen
• atom-molecule collisions
• dissociation
• vibrational energy relaxation