Real-time direct detection of Criegee intermediates from ozonolysis of alkenes in an atmospheric simulation chamber

Ozonolysis reactions are key oxidation mechanisms for unsaturated volatile organic compounds in the atmosphere, generating Criegee intermediates (CIs) that drive subsequent chemistry. Photolytic laboratory sources of certain CIs have demonstrated unexpectedly high CI reactivity but bypass the complex dynamics that occur in the atmosphere during ozonolysis, which affect yields and reactivity. Here, we report direct measurements of absolute concentrations of the CIs formaldehyde oxide (CH₂OO) and acetone oxide [(CH₃)₂COO] during ozonolysis reactions in an atmospheric simulation chamber made in real-time using UV cavity-enhanced absorption spectroscopy (CEAS). The measurements enable direct determination of stabilized CI yields and reaction kinetics under atmospheric conditions. The technique has the potential to reduce uncertainties associated with ozonolysis chemistry in atmospheric models.