Temperature dependent kinetics of the formation and self-reactions of FC(O)O2 and FC(O)O radicals

Abstract

This paper presents the ultraviolet (UV) absorption spectrum of FC(O)O2 and the temperature dependent rate constants for its formation via the addition of O2 to FCO, its self-reaction to form FC(O)O, and for the subsequent dimerization of FC(O)O. The UV spectrum of FC(O)O2 shows two absorption bands in the 190–300 nm range. The lower energy band has a peak cross section of (3.0±0.3)×10−18 cm2 at 232 nm. A higher energy band begins at ∼210 nm and reaches an absorption cross section of 4.3×10−18 cm2 at 190 nm. The FC(O)O2 self-reaction exhibits a negative temperature dependence with k2(T)=(2.5±0.4)×10−12 e(286±40)/T cm3 s−1 over the 213–358 K temperature range. The oxygen addition to FCO has a rate constant of k1=(8.0±0.8)×10−13 cm3 s−1 and the FC(O)O dimerization rate constant is in the range k3a=(2.3–6.5)×10−12 cm3 s−1, at 293 K and 300 Torr total pressure. Both of these rate constants show little variation over the 213–358 K temperature range.