Peroxy Radical Processes and Product Formation in the OH Radical-Initiated Oxidation of α-Pinene for Near-Atmospheric Conditions
Torsten Berndt
Abstract
α-Pinene, C10H16, represents one of the most important biogenic emissions into the atmosphere. The formation of RO2 radicals HO–C10H16Ox, x = 2–6, and their closed-shell products from the OH + α-pinene reaction has been measured for close to atmospheric reaction conditions in the presence of NO with concentrations of (1.7–490) × 109 molecules cm–3. Main closed-shell products are substances with the composition C10H16O2 and C10H16O4, most likely carbonyls, obtained with molar yields in the range 0.42–0.45 and 0.17–0.19, respectively, for NO concentrations >5 × 1010 molecules cm–3. The corresponding total product yields amount to 0.75–0.81, indicating efficient product detection by the mass spectrometric method applied. All stated molar yields represent lower limit values affected with an uncertainty of . Kinetic and product analysis consistently revealed the suppression of the formation of highly oxygenated organic molecules (HOMs) by a factor of 2–2.2 for the highest NO concentration used. The findings of this study provide insights into the RO2 radical processes of the OH + α-pinene reaction for atmospheric conditions and give an overview about the first-generation products.