THE DYNAMICS OF THE OH-PHASE REACTION - ABSOLUTE REACTION CROSS-SECTION AND H(HD GAS)D ATOM PRODUCT BRANCHING RATIO/

The dynamics of the OH + HD reaction were studied in the gas-phase usi ng the laser photolysis/vacuum-UV laser-induced fluorescence ''pump-an d-probe'' technique. Translationally energetic OH((II)-I-2) radicals w ith an average reagent translational energy of E-c.m.=0.24 eV in the ( OH-HD)-center-of-mass system were generated by the laser photolysis of H2O2 at 248 nm. Doppler profiles of nascent D and H atoms produced in reactive collisions of OH with room-temperature KD molecules were det ected under single-collision conditions by VUV-LIF at the Lyman-alpha transition. For the OH + HD reaction an absolute reaction cross sectio n of sigma(R)(0.24 eV) = (0.14 +/- 0.05) Angstrom(2) was determined by means of a calibration method using OH + D-2 as a reference reaction. The branching ratio for the OH + HD --> H + HOD(D + H2O) product chan nels was measured to be Gamma(H/D) = (1.2 +/- 0.2). (C) 1997 Elsevier Science B.V.