Absolute rate constants, reactive cross-sections and isotopic branching ratio for the reaction of O(1D) with HD

Using the laser photolysis vacuum-UV laser-induced fluorescence ‘pump-and-probe’ technique, Doppler profiles of H and D atoms from the reaction O(1D) + HD were measured under single-collision conditions, O(1D) atoms were generated by laser photolysis of N2O at 193 nm. With a calibration method using HCl photolysis as a source of well defined H atom concentrations the following absolute rate constants k and absolute reactive cross-sections σR have been determined: k = (1.3 ± 0.3) × 10−10 cm3s−1 molec−1 and σR(0.14 eV) = 4.0 ± 0.9 Å2 for the reaction channel O(1D) + HD → OD + H, and k = (1.0 ± 0.3) × 10−10 cm3 s−1 molec−1 and σR(0.14 eV) = (3.0 ± 0.7) Å2 for the reaction channel O(1D) + HD → OH + D. The isotopic branching ratio for the reaction O(1D) + HD was measured directly to be ΓH/D = 1.35 ± 0.20. In addition, from the measured H and D atom Doppler profiles the fraction ƒT of the available energy released as translational energy was determined for the individual product channels to be ƒT(OD + H) = 0.41 ± 0.07 and ƒT(OH + D) = 0.32 ± 0.05.