1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
2Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
3Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
4School of Chemical and Biomolecular Engineering and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
5Aerodyne Research, Inc., Billerica, MA, USA
6Air Pollution Research Center, Department of Environmental Sciences, and Environmental Toxicology Graduate Program, University of California, Riverside, CA, USA
Abstract. Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high- and low-NOx conditions, in which alkyl peroxy radicals (RO2) react primarily with NO and HO2, respectively, for multiple initial alkane concentrations. Experiments were run until 95–100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases. SOA yield differed by 2 orders of magnitude between the two limiting cases, but the same trends among alkane precursors were observed for both limiting cases. Vapor-phase wall losses were addressed through a modeling study and increased SOA yield uncertainty by approximately 30%. SOA yields were highest from cyclododecane under both NOx conditions. Under high-NOx conditions, SOA yields increased from 2-methylundecane < dodecane ~ hexylcyclohexane < cyclododecane, consistent with previous studies. Under low-NOx conditions, SOA yields increased from 2-methylundecane ~ dodecane < hexylcyclohexane < cyclododecane. The presence of cyclization in the parent alkane structure increased SOA yields, whereas the presence of branch points decreased SOA yields due to increased vapor-phase fragmentation. Vapor-phase fragmentation was found to be more prevalent under high-NOx conditions than under low-NOx conditions. For different initial concentrations of the same alkane and same NOx conditions, SOA yield did not correlate with SOA mass throughout SOA growth, suggesting kinetically limited SOA growth for these systems.