Microscopic Mechanisms of N₂O₅ Hydrolysis on the Surface of Water Droplets

Reactions of N₂O₅, in particular heterogeneous hydrolysis, play a vital role in determining the chemistry of the atmosphere. The N₂O₅ heterogeneous hydrolysis reaction has been the subject of extensive research for decades, yet the physicochemical details of the mechanism have not been established. In this study, we show that this reaction can occur on the surface of a pure water droplet. We compute a relevant transition state for a nano-size model system and follow its evolution in time by means of ab initio molecular dynamics. This transition state, where N₂O₅ has a strong ion-pair character, leads directly to HNO₃. Both electrophilic and nucleophilic mechanisms take place. It is suggested that corresponding simulations for hydrolysis in the bulk are desirable.