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Gas-phase Ion Structures of Molecules in Secondary Organic Aerosol: Infrared Photodissociation of Ions Across the Fingerprint Region
Corey Thrasher, Lemai Vo, Giel Berden, Jonathan Martens, Jos Oomens, RACHEL O'BRIEN, William & Mary
Abstract Number: 300
Working Group: Instrumentation and Methods
Abstract
Secondary organic aerosol (SOA) is a large fraction of the organic particulate matter in the atmosphere with impacts on climate, air quality, and human health. This fraction presents a challenge for modelers and experimentalists, given the trace sample masses and the complexity of the organic mixtures, with thousands of different molecules found in an aerosol sample. Mass spectrometry can provide insights into the molecular composition of organic aerosols, however, information on the chemical structure and functional groups can be limited. By combining infrared multi-photon dissociation (IRMPD) from the FELIX free electron laser with mass spectral analysis using an ion trap mass spectrometer, we demonstrate a new way to characterize the gas-phase ion structure of organics in complex mixtures. We use this technique to generate IR action spectra (IRMPD yield vs. wavenumber) for major components of α-pinene SOA as well as standards used as tracers for SOA sources. In combination with computational analysis, this method can provide insights into the lowest energy gas-phase conformations of the ions. By using different ion adducts (Cs+, I-, H+) we can investigate the influence of the charging species on the ion conformation. This work demonstrates a new platform to study the structures of organic molecules formed in the atmosphere with utility for both analytical characterizations as well as fundamental physical chemistry studies of formation products and pathways.