title: Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals.
abstract: The immense complexity inherent in the formation of secondary organic aerosol (SOA)-due primarily to the large number of oxidation steps and reaction pathways involved-has limited the detailed understanding of its underlying chemistry. As a means of simplifying such complexity, here we demonstrate the formation of SOA through the photolysis of gas-phase alkyl iodides, which generates organic peroxy radicals of known structure. In contrast to standard OH-initiated oxidation experiments, photolytically initiated oxidation forms a limited number of products via a single reactive step. As is typical for SOA, the yields of aerosol generated from the photolysis of alkyl iodides depend on aerosol loading, indicating the semivolatile nature of the particulate species. However, the aerosol was observed to be higher in volatility and less oxidized than in previous multigenerational studies of alkane oxidation, suggesting that additional oxidative steps are necessary to produce oxidized semivolatile material in the atmosphere. Despite the relative simplicity of this chemical system, the SOA mass spectra are still quite complex, underscoring the wide range of products present in SOA.
authors: Sean H
authors: SH
authors: Kessler
authors: ‡Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley California 94720, United States.|§Department of Chemistry, University of California, Berkeley, California 94720, United States.
authors: Theodora
authors: T
authors: Nah
authors: Anthony J
authors: AJ
authors: Carrasquillo
authors: #Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors: John T
authors: JT
authors: Jayne
authors: #Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors: Douglas R
authors: DR
authors: Worsnop
authors: ‡Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley California 94720, United States.
authors: Kevin R
authors: KR
authors: Wilson
authors: Jesse H
authors: JH
authors: Kroll
keywords: SOA; organic aerosol; oxidation; photolysis