Formation and reaction mechanisms of Criegee intermediates in the atmosphere

Criegee intermediates (CIs) can be generated by the ozonolysis of alkenes, and few amounts can come from radical-radical reactions. CIs are found to be the important oxidants, and can react with many gases in the atmosphere. The reaction rate of CIs with HCOOH is about 10^-10 cm³molcule^-1s^-1, and the reaction rate of SO₂ with CIs is much faster than with OH radical. A Matrix-isolate Vacuum FTIR method was constructed to capture CIs during the reaction of O₃ with alkenes. Different kinds of Primary ozonides (POZs), CIs, and Secondary ozonides (SOZs) were detected, and the reaction processes were deduced. Combining of the experimental and quantum chemistry methods, the reactivity of different structure CIs were investigated. The contribution of these CIs to the formation of OH radicals and SOA were further discussed. Fundamental understanding on the structures and reactivity of CIs is crucial to deepen the understanding of Criegee chemistry and its impact on the atmospheric chemistry.