Experimental and Computational Vibrational Sum Frequency Spectroscopy Studies of Atmospheric Organics and Their Surface-Active Hydration and Oligomer Products at the Air-Water Interface

Abstract

Organics at aerosol interfaces greatly affect aerosol properties in turn affecting the climate. However, many aspects about the formation and atmospheric processing of aerosols, in particular secondary organic aerosol (SOA), remain poorly understood. The traditional mechanism of SOA formation does not adequately predict experimental observations in the atmosphere. It is increasingly being recognized that aqueous phase processing of atmospheric organics is another important pathway to SOA formation. A better picture of the surface behavior of these organics and their reaction products will aid in further understanding the role these organics play in the formation potential of aqueous secondary organic aerosol. The work within details studies on the adsorption, orientation, and hydration state of select atmospheric carbonyls (glyoxal, hydroxyacetone, methylglyoxal, and pyruvic acid) and their aqueous reaction products at the air-water interface. Data are gathered using a combination of experimental and theoretical techniques, including vibrational sum frequency (VSF) spectroscopy, surface tensiometry measurements, classical molecular dynamics (MD) simulations, and density functional theory (DFT) calculations.