Abstract

A quantum-chemistry and kinetics study of key chemical reactions involved in the ClCO radical cycle of the Venus atmosphere: Cl + CO + M → ClCO + M (1); ClCO + O₂ + M → ClC(O)OO + M (2) and ClC(O)OO + Cl → CO₂ + ClO + Cl (3) (M = CO₂), has been performed at 150–300 K. Unimolecular reaction rate theories on potential energy features derived at the G4//B3LYP/6-311+G(3df) ab initio composite level were employed. Limiting low pressure rate coefficients calculated for Reaction (1) are in good agreement with recommended experimental values. The present results validate rate coefficient values measured for Reaction (2) over relevant strato-mesosphere Venusian conditions. Rate coefficients calculated by the SACM/CT for Reaction (3) are given by k₃ = 2.5 × 10⁻¹¹ (T/300)^0.5 cm³ molecule^–1 s^–1. In the absence of experimental data, these values provide the first reliable prediction for k₃.