The dynamics of the reactions H+H2O -> OH+H-2 and H+D2O -> OD+HD at 1.4 eV

OH(OD) quantum state populations, rovibrational quantum state-resolved cent er-of-mass angular scattering distributions, and H-2(HD) coproduct internal energy release distributions have been determined for the hot H atom react ions with H2O and D2O at mean collision energies close to 1.4 eV. The exper iments employ pulsed laser photolysis coupled with polarized Doppler-resolv ed laser induced fluorescence detection of the radical products. The OH((2) Pi (1/2),v'=0,N'=1,A') and OD((2)Pi (1/2),v(')=0,N-'=1,A(')) angular distri butions generated by the two isotopic reactions are quite distinct: that fo r the reaction with H2O shows intensity over a wide range of center-of-mass scattering angles, and peaks in the sideways direction, while the state-re solved angular distribution for the reaction with D2O displays more scatter ing in the backward hemisphere. For higher OH(OD) angular momentum states t he differences in the angular distributions for the two reactions are less marked, with both systems showing a slight preference for backward scatteri ng. The kinetic energy release distributions are insensitive to OH(OD) quan tum state and to isotopic substitution, and reveal that the H-2(HD) coprodu cts are born internally cold at 1.4 eV. OH(OD) quantum state averaged energ y disposals in the two reactions are also presented. The new experiments pr ovide detailed mechanistic information about the two reactions and clarify the dominant sources of product OH(OD) rotational excitation. Current theor etical understanding of the reaction is critically assessed. (C) 2001 Ameri can Institute of Physics.