Goals:
Determine SOA yield of OH radical oxidation of the VOC

Summary:
Experiments were performed at ambient temperature (25 C) and pressure (84 kPa) in an 8 m^3 FEP Teflon environmental chamber. Purified air was supplied by AADCO clean air generators (< 5 ppb hydrocarbons, and < 1% RH). The chamber was first seeded with 200 ug/m^3 of either dioctyl sebacate (DOS) or dioctyl phthalate (DOP) polydisperse aerosol with peak particle diameter of 200 nm, which was added from an evaporation-condensation source. A measured mass of an alkyl nitrate was then added from a heated glass bulb using ultra-high purity (UHP) N2. Thermal decomposition was avoided by heating the bulb to only 65 C, well below the temperatures alkyl nitrates encounter during gas chromatographic analysis, and limiting the residence time in the gas phase to 1 s^-1 by flushing with 15 L/min of UHP N2. Glass bulbs containing a measured pressure of methyl nitrite or NO were prepared on a vacuum manifold and added to the chamber with UHP N2 in amounts sufficient to achieve concentrations of 5 ppm of each in the chamber. Reactions were initiated by turning on blacklights that are located on two sides of the chamber for 60 minutes at a light intensity corresponding to an NO2 photolysis rate constant of 0.37 min^-1. Under these conditions OH radicals were generated from the photolysis of methyl nitrite (Atkinson et al. 1981) with average concentrations of 3 x 107 molecules/cm^3, based on the amount of alkyl nitrate that reacted and an estimated rate constant for its reaction with OH radicals (Ziemann and Atkinson 2012).

Organization: Ziemann
Lab Affiliation: University of Colorado, Boulder, Boulder, CO, USA
Chamber: Janet (Chamber 1)

Experiment Category: Gas phase chemical reaction, Photolysis, any phase, Aerosol formation
Oxidant: Hydroxyl radical
Reactants: Methyl nitrite, Nitric oxide, 2-Decyl nitrate
Reaction Type: Photooxidation
Relative Humidity: 1
Temperature: 25
Seed Name: DOS
Pressure: 630