Products of Criegee intermediate reactions with NO₂: experimental measurements and tropospheric implications

Abstract

The reactions of Criegee intermediates with NO₂ have been proposed as a potentially significant source of the important nighttime oxidant NO₃, particularly in urban environments where concentrations of ozone, alkenes and NO_x are high. However, previous efforts to characterize the yield of NO₃ from these reactions have been inconclusive, with many studies failing to detect NO₃. In the present work, the reactions of formaldehyde oxide (CH₂OO) and acetaldehyde oxide (CH₃CHOO) with NO₂ are revisited to further explore the product formation over a pressure range of 4-40 Torr. NO₃ is not observed; however, temporally resolved and [NO₂]-dependent signal is observed at the mass of the Criegee-NO₂ 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.