Computational study of PAH adsorption at the ice-vapor interface with implications for PAH photochemistry in ice and snow

Organic pollutants such as polycyclic aromatic hydrocarbons (PAH) undergo photochemical reactions on the snow and ice surfaces. The air-ice interface is a specific environment in which water molecules behave neither like a liquid nor like a solid. In this disordered interfacial region (the so-called quasi-liquid layer, QLL), the unique solute-solute and solute-solvent interactions result in the photoemission/absorption spectra of many species being distinctly different compared to their behavior in bulk water or at the air-water interface. In this work we present a combined molecular dynamics/ab initio computational approach to obtain information about the structural and energetic aspects of adsorption, the solute-solute interaction and the absorption and emission spectra of several PAH species (naphthalene, methylnaphthalene and dibenzylketone) in the ice-QLL. These results will help to improve the understanding of important atmospherically relevant chemical processes occurring at the air-ice interface in particular in the polar area.