AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Computational Chemistry of Condensing and Clustering Vapors
Theo Kurten, NEIL DONAHUE, Ditte Linde Thomsen, Henrik Kjaergaard, Joseph Lane, Solvejg Jørgensen, Hanna Vehkamäki, University of Helsinki
Abstract Number: 82 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract According to current best knowledge, the formation and growth of atmospheric aerosols involves both oxidized sulfur compounds (mainly sulfuric acid), reduced nitrogen and nitrogen-carbon compounds (mainly ammonia and amines), and carbon compounds of varying oxidation states. Aerosol processes thus couple together the atmospheric parts of the biogeochemical sulfur, nitrogen and carbon cycles. Though much new information has been gained during the past years about the clustering processes responsible for the first steps of atmospheric new-particle formation, several important questions about the chemical sources and sinks of the participating condensing vapors still remain unanswered. Computational chemistry is a useful tool for answering these questions.
For example, our recent quantum chemical calculations, later verified by experiments, have shown that the reaction of Criegee Intermediates (carbonyl oxides) with sulfur dioxide is likely a major (and hitherto unaccounted for) source of gas-phase sulfuric acid. Carbonyl oxides may also play a role in the oxidation of central nitrogen compounds such as amines, though this reaction has not yet been studied much. Quantum chemical modeling is also improving our understanding of the alkene ozonolysis reactions responsible (among other things) for the formation of carbonyl oxides. However, many of the intermediates of the ozonolysis reaction chain have quite complicated electronic structures, and care must be taken in choosing computational methods appropriate to the task.
All these reactions may further be affected by clustering e.g. with water molecules, though our recent calculations indicate that water catalysis in the atmosphere may be less prevalent and important than suggested by some studies.