Photodissociation of D2O at 121.6 nm:: A state-to-state dynamical picture

The photodissociation dynamics of D2O at 121.6 nm have been studied using the D atom Rydberg tagging time-of-flight technique. Product kinetic energy distributions and angular distributions have been measured. From these distributions, rovibronic distributions of the OD radical product and the rotational state-resolved angular anisotropy parameters have been determined. The dissociation energy D-0(0) (D-OD) is determined to be 41912 +/- 20 cm(-1). Alternations of population in the OD (X, v=0) rotational distribution, similar to those in the H2O photodissociation [S. A. Harich , J. Chem. Phys. 113, 10 073 (2000)] have also been observed, and thus are also attributed to dynamical interference between two conical intersection pathways. Very highly vibrationally excited OD (X) products (at least up to v=9) have also been observed, which is in accord with recent theoretical studies of H2O photodissociation by van Hemert [J. Chem. Phys. 112, 5797 (2000)]. Evidence for the triple dissociation channel, O(P-3)+2D, is also shown in this work. Branching ratios for the different product channels have been determined through simulations. Overall, the energy disposal among the products of D2O photodissociation at 121.6 nm is qualitatively similar to that for H2O, although the mass change leads to changes in the branching ratios. (C) 2001 American Institute of Physics.