Kinetics, Energetics and OH Product Yield of the Reaction CH₃O + O(³P) → CH₃O^*₂ → Products

Abstract

Abstract The rate constant for the reaction (1) CH 3 O + O → products at 298 K has been determined using 248 nm laser co‐photolysis of CH 3 ONO/O 3 mixtures for the generation of CH 3 O radicals and O atoms combined with LTF for time resolved detection of CH 3 O and product OH. k 1 is found to be (2.5±0.7) 10 −11 cm 3 /s with a relative yield of OH of Φ = ‐Δ[OH]/Δ[CH 3 O] = 0.12 +0.08 −0.04 . The results are shown to be consistent with a primary capture mechanism on an electronically adiabatic surface forming highly vibrationally excited CH 3 O and followed by rapid subsequent decomposition or isomerization, viz. magnified image . From modelling of the OH yield using RRKM theory the isomerization barrier between CH 3 O 2 and CH 2 OOH is placed near 160 kJ/mol in good agreement with recent ab initio calculations. As a consequence the CH 3 + O 2 combustion reaction is predicted to proceed primarily via the low energy CH 2 O + OH channel, in contrast to most previous suggestions.