Quantitative Kinetics of the Reaction between CH₂OO and H₂O₂ in the Atmosphere

Criegee intermediates (CIs) are generated from the ozonolysis of unsaturated hydrocarbons in the atmosphere. They have an important role in determining the implications of atmospheric bimolecular reactions with other atmospheric species. The reaction between CH₂OO and H₂O₂ plays a crucial role in understanding how CIs impact the HO budget in the atmosphere. The reaction mechanism and kinetics are critical to atmospheric modeling, which is a prominent challenge in present-day climate change modeling. This is particularly true for bimolecular reactions that involve complex reaction sequences. Here, we report the mechanism and quantitative kinetics of the CH₂OO + H₂O₂ reaction by using a novel dual-level strategy that contains W3X-L//CCSD(T)-F12a/cc-pVTZ-F12 for the transition state theory and M11-L/MG3S functional method for direct dynamics calculations using canonical variational transition state theory with small-curvature tunneling to obtain both recrossing effects and tunneling. The present work shows that the CH₂OO + H₂O₂ reaction has a negative temperature dependency with the decrease in the rate constant of CH₂OO + H₂O₂ from 1.31 × 10^-13 cm³ molecule^-1 s^-1 to 3.80 × 10^-14 cm³ molecule^-1 s^-1 between 200 and 350 K. The calculated results also show that the CH₂OO + H₂O₂ reaction can have an impact on the H₂O₂ profile under certain atmospheric conditions. The present findings should have implications for the quantitative kinetics of Criegee intermediates with other hydroperoxides.