Products of Criegee intermediate reactions with NO 2 : experimental measurements and tropospheric implications.

The reactions of Criegee intermediates with NO ₂ have been proposed as a potentially significant source of the important nighttime oxidant NO ₃ , particularly in urban environments where concentrations of ozone, alkenes and NO _x are high. However, previous efforts to characterize the yield of NO ₃ from these reactions have been inconclusive, with many studies failing to detect NO ₃ . In the present work, the reactions of formaldehyde oxide (CH ₂ OO) and acetaldehyde oxide (CH ₃ CHOO) with NO ₂ are revisited to further explore the product formation over a pressure range of 4-40 Torr. NO ₃ is not observed; however, temporally resolved and [NO ₂ ]-dependent signal is observed at the mass of the Criegee-NO ₂ adduct for both formaldehyde- and acetaldehyde-oxide systems, and the structure of this adduct is explored through ab initio calculations. The atmospheric implications of the title reaction are investigated through global modelling.