Peroxy Radical Processes and Product Formation in the OH Radical-Initiated Oxidation of α-Pinene for Near-Atmospheric Conditions.

α-Pinene, CH, represents one of the most important biogenic emissions into the atmosphere. The formation of RO radicals HO-CHO, = 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) × 10 molecules cm. Main closed-shell products are substances with the composition CHO and CHO, most likely carbonyls, obtained with molar yields in the range 0.42-0.45 and 0.17-0.19, respectively, for NO concentrations >5 × 10 molecules cm. 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 [Formula: see text]. 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 RO radical processes of the OH + α-pinene reaction for atmospheric conditions and give an overview about the first-generation products.