Kinetics of the reaction between methyl radicals and oxygen atoms between 294 and 900 K

The kinetics of the reaction of methyl radicals with oxygen atoms has been investigated in a heatable tubular reactor coupled to a photoionization mass spectrometer. The reactants (CH/sub 3/ and O(/sup 3/P)) were generated homogeneously in the reactor by the simultaneous in situ photolysis of acetone and SO/sub 2/. Initial conditions were always chosen to yield (O)/(CH/sub 3/)/sub 0/ > 20. The decay of CH/sub 3/ was monitored as a function of (O) to yield rate constants for the reaction O + CH/sub 3/ ..-->.. H/sub 2/CO + H at five temperatures between 294 and 900 K. The rate constant was found to be independent of temperature, having a value 1.4 x 10/sup -10/ cm/sup 3/ molecule/sup -1/ s/sup -1/, and also independent of density in the range used in this study, (3-24) x 10/sup 16/ molecule cm/sup -3/. The mechanism was verified by direct observations of H/sub 2/CO production. The new experimental method, which can be used to investigate many reactions of oxygen atoms with free radicals, is described in detail.