Atmospheric and Interfacial Reaction Dynamics

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Over the past funding period we have made significant progress in several areas related to heterogeneous atmospheric chemistry of aqueous, ice, dust and "urban grime" surfaces. We have used excitation and emission spectra of pH-sensitive fluorescent probes in conjunction with lancing-angle laser-induced fluorescence to determine pH at water and ice interfaces and used this measurement to track reactions there. We have optimized our glancing-angle Raman probes and used these to probe the propensity of nitrate anion to partition to the liquid and frozen water surface, and how the presence of halide anions affects this partitioning. We have continued to explore the influence of various monolayer organic coatings on chemical processes reactions at the air-water interface. We have demonstrated and explored photosensitized reactions occurring at water, dust, organic and "urban grime" surfaces. In most of these endeavours, we have been the first group to report the technique or its use in atmospheric chemistry.**During the next funding period we will continue to develop innovative ideas and techniques and will provide quantitative kinetic and photochemical parameters for use in atmospheric models. In particular, we will focus on understanding the basis for the very different reactivities observed at the air-ice and air-"grime" interfaces. We will continue to explore the role(s) which organic monolayer coatings play on influencing aqueous surface chemistry. We will push forward our ideas on how photochemistry at aqueous interfaces may be sensitively affected or "tuned" by tuning the chemical environment there. We will continue to study the roles of atmospheric mineral dust in influencing their local oxidation environment via photochemistry.**In these studies we will develop and utilize more new tools. In particular we will utilize acoustic levitation to study chemistry occurring in single droplets -a first in atmospheric studies - and will incorporate reflection-absorption IR spectroscopy into our suite of tools for surface interrogation.