Absolute Reactive Cross Section for H Atom Formation in the Reaction of Translationally Energetic O(1D) Atoms with Methane

The dynamics of the H atom formation channel in the reaction of metastable oxygen atoms O(1D) with methane were studied in the gas phase using the pulsed laser photolysis/vacuum-UV laser-induced fluorescence “pump-and-probe” technique. Translationally energetic O(1D) atoms with an average collision energy of 37 kJ/mol in the O(1D)−CH4 center-of-mass system were generated by laser photolysis of N2O at 193 nm. Nascent H atoms produced in reactive collisions of O(1D) with room-temperature CH4 molecules were detected with sub-Doppler resolution via (2p2P ← 1s2S) laser-induced fluorescence. An absolute reaction cross section of σH(37 kJ/mol) = 1.4 ± 0.5 Å2 was determined for the H atom formation channel by means of a calibration method. From the H atom Doppler profiles measured under single-collision conditions the product translational energy release was determined.