Direct investigations of reactions of 2‐butoxy radicals using laser pulse initiated oxidation: Reaction with O2 and unimolecular decomposition at 293 K and 50 mbar

Reactions of 2‐butoxy radicals have been investigated using time‐resolved measurements of NO2 and OH concentration profiles in the flash initiated oxidation of 2‐bromobutane and subsequent numerical simulation. 2‐butoxy radicals were produced selectively by the excimer‐laser photolysis of 2‐bromobutane at 193 or 248 nm followed by the reaction of 2‐butyl radicals with O2 and NO. Whereas NO2 was detected by cw‐LIF, detection of OH was achieved by laser long‐path absorption at 308 nm. All experiments were performed at 293 K and a total pressure of 50 mbar. The rate coefficients of the O2 reaction (kO2) and of unimolecular decomposition (kdecomp) have been varied, using the FACSIMILE code, until best fits were obtained. The following rate coefficients were derived: kO2 = (6.5±2) × 10−15 cm3‐molecule−1·s−1 and kdecomp = (3.5±2) × 10−3 s−1.