Rate constants for the reactions of CH3O2 with HO2, NO and NO2 using molecular modulation spectrometry

Abstract

Molecular modulation spectrometry has been employed to obtain new measurements of the rate constants for three reactions of the CH₃O₂ radical in the gas phase. CH₃O₂ was produced by photolysis of Cl₂ in the presence of CH₄ and O₂ and was measured in absorption at 250 nm. With added H₂, HO₂ was also produced and kinetic data were obtained under pseudo second-order conditions for the reaction: CH₃O₂+ HO₂= CH₃O₂H + O₂(4), k₄=(7.7^+18.4_–5.4)× 10^–14 exp[(1296 ± 364)/T] cm³ molecule^–1 s^–1 over the range 275–338 K. The reactions of CH₃O₂ with NO and NO₂ were studied under pseudo first-order conditions and the following rate constants obtained; CH₃O₂+ NO = CH₃O + NO₂(2), k₂=(6.5 ± 2.0)× 10^–12 cm³ molecule^–1 s^–1 at 298 K and 540 Torr; CH₃O₂+ NO₂= CH₃O₂NO₂(3), 10¹²k₃= 1.6 ± 0.3 and 1.2 ± 0.3 cm³ molecule^–1 s^–1 at 540 Torr N₂ and 50 Torr Ar + CH₄, respectively.