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

Abstract

The dynamics of the H atom formation channel in the reaction of metastable oxygen atoms O( 1 D) 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( 1 D) atoms with an average collision energy of 37 kJ/mol in the O( 1 D)−CH 4 center-of-mass system were generated by laser photolysis of N 2 O at 193 nm. Nascent H atoms produced in reactive collisions of O( 1 D) with room-temperature CH 4 molecules were detected with sub-Doppler resolution via (2p 2 P ← 1s 2 S) laser-induced fluorescence. An absolute reaction cross section of σ H (37 kJ/mol) = 1.4 ± 0.5 Å 2 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.