The environmental interface at play in tropospheric aerosols is a complex environment that mediates the chemical transformations of species trapped at the surface. This regime involves the interplay between ions in solution, surfactants at the surface, and reactive processing of key atmospheric molecules such as N2O5. Working with an interdisciplinary team, we are unraveling the chemical pathways that govern both photochemical degradation of organics as well as in the generation of reactive ClNO2 in the gas phase by surface collisions with N2O5. We will describe our role in this endeavor where we use composition- and temperature-controlled clusters to establish the microscopic, molecular level processes that drive bulk behavior. The basic theme of this approach is to study compositions that are simple enough to be amenable to accurate calculations, but are sufficiently complex to recover macroscopic properties. This presentation will focus on the vibrational signatures of free and metal-complexed surfactants and on the competition between ClNO2 generation and HNO3 formation in the surface-mediated chemistry of N2O5. We will also discuss recent results in which two-color, IR-IR double resonance methods are used to reveal the anharmonic vibrational mechanics that underlie the diffuse IR spectrum displayed by water molecules embedded at the air-water interface.

Understanding molecular aspects of aqueous interfacial chemistry with clusters

2019 Fall National Meeting

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