Dr. Susanne Ullrich will be hosting Dr. Geoff Smith of the University of Georgia Department of Chemistry this week. His talk is entitled, " "Super Cool" Reactions in Metastable Aerosol Particles."

Aerosol particles play important roles in the Earth's climate as they can both scatter and absorb solar radiation, act as cloud condensation nuclei and facilitate chemical reactions. These particles typically comprise a vast array of organic species derived from both anthropogenic and natural sources that can influence the physical and chemical characteristics of the aerosol. However, very little is understood about how these organic species react with gas-phase oxidants such as O3, OH and NO3 in the atmosphere. In an effort to understand such reactions better, we have studied the reaction of O3 with model organic aerosols containing oleic acid, a fatty acid that is often found in particles originating from meat cooking. We find that the presence of other, non-reactive species leads to drastic changes in the reactivity of oleic acid through changes in the particle morphology. A case study involving particles containing both oleic acid and n-docosane (a straight-chain alkane) will be presented highlighting the roles of supercooled liquids, metastable solid phases and an ordered surface frozen monolayer in determining the reactivity of these particles.