Product spin-orbit state resolved dynamics of the H+H₂O and H+D₂O abstraction reactions

The product state-resolved dynamics of the reactions H-H ₂O/D₂O→OH/OD(²II _ω:v′,N′,f) + H₂/HD have been explored at center-of-mass collision energies around 1.2, 1.4. and 2.5 eV. The experiments employ pulsed laser photolysis coupled with polarized Doppler-resolved laser induced fluorescence detection of the OH/OD radical products. The populations in the OH spin-orbit states at a collision energy of 1.2 eV have been determined for the H + H₂O reaction, and for low rotational levels they are shown to deviate from the statistical limit. For the H + D₂O reaction at the highest collision energy studied the OD( ²II_3/2,v′ = 0.N′ = 1.A′) angular distributions show scattering over a wide range of angles with a preference towards the forward direction. The kinetic energy release distributions obtained at 2.5 eV also indicate that the HD coproducts are born with significantly more internal excitation than at 1.4 eV. The OD( ²II_3/2,v′ = 0.N′ = 1.A′) angular and kinetic energy release distributions are almost identical to those of their spin-orbit excited OD(²II_1/2,v′ = 0.N′ = 1.A′) counterpart. The data are compared with previous experimental measurements at similar collision energies, and with the results of previously published quasiclassical trajectory and quantum mechanical calculations employing the most recently developed potential energy surface. Product OH/OD spin-orbit effects in the reaction are discussed with reference to simple models.