The C(3P) + O2(3 g-) CO2 CO(1 +)+ O(1D)/O(3P) Reaction: Thermal and Vibrational Relaxation Rates from 15 K to 20000 K
Abstract
Thermal rates for the C(3P) + O2(3 g-) CO(1 +)+ O(1D)/O(3P) reaction are investigated over a wide temperature range based on quasi classical trajectory (QCT) simulations on 3-dimensional, reactive potential energy surfaces (PESs) for the 1A', (2)1A', 1A'', 3A' and 3A'' states. The forward rate matches measurements at 15 K to 295 K whereas the equilibrium constant determined from the forward and reverse rates are consistent with those derived from statistical mechanics at high temperature. Vibrational relaxation, O+CO(=1, 2) → O+CO(=0), is found to involve both, non-reactive and reactive processes. The contact time required for vibrational relaxation to take place is τ ≥ 150 fs for non-reacting and τ ≥ 330 fs for reacting (oxygen atom exchange) trajectories and the two processes are shown to probe different parts of the global potential energy surface. In agreement with experiments, low collision energy reactions for the C(3P) + O2(3 g-, v=0) → CO(1 +)+ O(1D) lead to CO(1+, v'=17) with an onset at E c 0.15 eV, dominated by the 1A' surface with contributions from the 3A' surface. Finally, the barrier for the CO A(1+) + O B(3P) → CO B(1+) + O A(3P) atom exchange reaction on the 3A' PES yields a barrier of 7 kcal/mol (0.300 eV), consistent with an experimentally reported value of 6.9 kcal/mol (0.299 eV).
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