Temperature Dependence Study of the Kinetics and Product Yields of the HO2 + CH3C(O)O2 Reaction by Direct Detection of OH and HO2 Radicals Using 2f-IR Wavelength Modulation Spectroscopy

The HO2 + CH3C(O)O2 reaction consists of three product channels: CH3C(O)OOH + O2 (R1a), CH3C(O)OH + O3 (R1b), and OH + CH3C(O)O + O2 (R1c). The overall rate constant (k1) and product yields (α1a, α1b, and α1c) were determined over the atmospherically relevant temperature range of 230–294 K at 100 Torr in N2. Time-resolved kinetics measurements were performed in a pulsed laser photolysis experiment in a slow flow cell by employing simultaneous infrared (IR) and ultraviolet (UV) absorption spectroscopy. HO2 and CH3C(O)O2 were formed by Cl-atom reactions with CH3OH and CH3CHO, respectively. Heterodyne near- and mid-infrared (NIR and MIR) wavelength modulation spectroscopy (WMS) was employed to selectively detect HO2 and OH radicals. Ultraviolet absorption at 225 and 250 nm was used to detect various peroxy radicals as well as ozone (O3). These experimental techniques enabled direct measurements of α1c and α1b via time-resolved spectroscopic detection in the MIR and the UV, respectively. At each temperature, ...