Particle Formation from Photooxidation of αpinene, Limonene, and Myrcene.

We present measurements of the effect of first-generation secondary organic aerosol (SOA) material on the growth of ∼10 nanometer diameter seed particles composed of sulfuric acid and water. Experiments were performed in an atmospheric pressure, vertically aligned flow reactor where OH was produced from HONO photolysis in the presence of either SO or a monoterpene. For typical conditions, organic compounds at ∼300 ppbv are exposed to photooxidation for a time of ∼80 s at a [OH] of about 6 × 10 cm: thus, oxidation products have minimal OH exposure.