Photolysis by solar radiation is the primary mechanism of removal for a large fraction of atmospheric compounds. Many atmospheric organic compounds are sufficiently water-soluble and/or involatile to exist primarily in condensed phases, such as dilute aqueous solutions associated with cloud and fog droplets, concentrated aqueous solutions associated with aerosol particles, and highly-viscous environments in primary and secondary organic particles. The mechanisms of condensed-phase photolysis of atmospherically relevant organic compounds are poorly constrained. The long-term goal of our research is to assess the importance of condensed-phase photolysis of different classes of biogenic and anthropogenic organic compounds using a combination of photochemical experiments, atmospheric modeling, and semiempirical calculations. This presentation will discuss the following systems: (1) aqueous photolysis of methyl peroxide, the simplest organic peroxide; (2) aqueous and gas-phase photolysis of cis-pinonic acid, an important product of oxidation of monoterpenes; (3) photolysis of aliphatic aldehydes in liquid and solid organic phases representative of organic aerosols; (4) aqueous photolysis of organonitrates, common products of oxidation of hydrocarbons in urban air; (5) photolysis of nitrophenols trapped inside a viscous secondary organic aerosol material. In all of these cases, the on-the-fly semiempirical molecular dynamics methods used by the Gerber group have provided invaluable insights in the mechanistic interpretation of the experimental results by predicting the shapes of the absorption spectra for the molecules of interest, the dynamics of photodissociation, the distribution of the photolysis products, and the solvent effect on the photochemistry.

Combined experimental and theoretical studies of photolysis of atmospherically relevant organic compounds in various phases

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.