Measurements of the kinetics of the OH-initiated oxidation of α-pinene: Radical propagation in the OH+α-pinene+O2+NO reaction system

The mechanism of the OH-initiated oxidation of α-pinene in the presence of NO has been investigated using a discharge-flow system at 5 Torr and 300 K. The OH concentration was monitored as a function of reaction time by laser-induced fluorescence (LIF). The rate constant for the OH+α-pinene was measured to be (6.09±0.30)×10−11 cm3 molecule−1 s−1. OH radical regeneration was observed after addition of O2 and NO, and the measured OH concentration profiles were compared to simulations based on both the Master Chemical Mechanism and the Regional Atmospheric Chemistry Mechanism for α-pinene oxidation in order to determine the ability of these mechanisms to describe the observed efficiency of radical propagation. Both models are able to reproduce the observed OH concentrations profiles to within 30%. However, expanding the MCM to include isomerization of the β-hydroxy alkoxy radicals improves the agreement with the experimental observations.