Experimental and theoretical investigation of the product channels of the O + CH{sub 3} reaction

The product channels of the O({sup 3}P)+CH{sub 3} reaction was investigated. In the experimental part, the branching fraction for formaldehyde production (O+CH{sub 3}{r_arrow}H{sub 2}CO+H) was measured at room temperature in a tubular flow reactor coupled to a photoionization mass spectrometer. The reactants (CH{sub 3} and O) were generated homogeneously in the reactor by simultaneous {ital in}{ital situ} 193-nm photolysis of acetone and SO{sub 2}. Formaldehyde yield relative to the methyl radicals consumed (branching fraction) was determined to be 1.0{+-}0.15. In the theoretical part, calculations of the energetics of possible decomposition pathways of the energy-rich methoxy radical initially formed in the O+CH{sub 3} reaction indicate that the dominant channel for decomposition is C-H bond cleavage leading to atomic hydrogen and formaldehyde. A possible, minor, secondary channel is hydrogen migration, followed by O-H bond cleavage, leading to the same final products. No energetically competitive pathways leading to H{sub 2}, HCO, HOC, or CO could be found