Photodissociation dynamics of H2O and D2O via the (1A1) electronic state

Abstract

Photodissociation dynamics of H₂O and D₂O via the state by one-photon excitation have been investigated using the H/D atom Rydberg tagging time-of-flight technique. The TOF spectra of the H/D-atom product in both parallel and perpendicular polarizations have been measured. Product translational energy distributions and angular distributions have been derived from TOF spectra. By simulating these distributions, quantum state distributions of the OH/OD product as well as the state-resolved angular anisotropy parameters were determined. The most important pathway of H₂O/D₂O dissociation via the state leads to highly rotationally excited OH/OD(X, v = 0) products, while vibrationally excited OH/OD products with v ≥ 1 comprise only one third of the total OH/OD(X) population. The branching ratios of OH(A)/OH(X) and OD(A)/OD(X) have also been determined, 1.0/3.0 for H₂O at 122.12 nm and 1.0/2.2 for D₂O at 121.95 nm, which are reasonably consistent with the values predicted by the previous theory.