Criegee + HONO reaction: a bimolecular sink of Criegee, and the missing non-photolytic source of OH ^•

Abstract. One of the most important puzzles in atmospheric chemistry is a mismatch between observed and modelled concentrations of OH•/HO2• in the presence of high concentration of volatile organic compounds. It is now well established that to fulfill this gap, one needs a reaction that is not only capable of producing OH• but also able to act as a sink of HO2•. In the present work, we are proposing the Criegee + HONO reaction as a possible solution of this puzzle. Our quantum chemical and kinetic calculations clearly suggest that this reaction can not only be an important source of OH radical but can also act as a sink of HO2 radical. Our study also suggests that HONO has the potential to act as a bimolecular sink of Criegee intermediates, and for some Criegee intermediates under certain atmospheric condition it can even surpass the traditionally known bimolecular sinks such as SO2 and water dimer, even in high humid conditions.