ABSOLUTE RATE CONSTANTS, REACTIVE CROSS-SECTIONS AND ISOTOPIC BRANCHING RATIO FOR THE REACTION OF O(D-1) 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(D-1)+ HD were measured under single-collision conditions, O(D-1) 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 cr have been determined: k = (1.3 +/- 0.3) X 10(-10) cm(3)s(-1) molec(-1) and sigma(R)(0.14 eV)=(4.0 +/- 0.9) Angstrom(2) for the reaction channel O(D-1) + HD --> OD + H, and k = (1.0 +/- 0.3) X 10(-10) cm(3) s(-1) molec(-1) and sigma(R)(0.14 eV) = (3.0 +/- 0.7) Angstrom(2) for the reaction channel 0(1D) + HD --> OH + D. The isotopic branching ratio for the reaction O(1D) + HD was measured directly to be Gamma(H/D) = 1.35 +/- 0.20. In addition, from the measured H and D atom Doppler profiles the fraction f(T) of the available energy released as translational energy was determined for the individual product channels to be f(T)(OD + H) = 0.41 + 0.07 and f(T)(OH + D) = 0.32 + 0.05.