Photodissociation of H2O and D2O below 132 nm

A complete determination of the rotational and vibrational distributions in the OH/OD(A (2)Sigma(+)) fragments which result from the VUV photodissocia tion of H2O/D2O as a function of excitation energy is presented. VUV excita tion was performed at eight different wavelengths (eleven for D2O) in the r ange between 132 and 124 nm. The vibrational branching ratios show a relati vely fast rise of the vibrational excitation at threshold followed by a pla teau. The general trend of the experimental results is well reproduced by a phase space theory calculation and by ab initio calculations reported by v an Hemert and van Harrevelt. Rotational distributions seem to depend only o n the available excess energy and, for a given excess energy appear to be s imilar for all vibrational levels in OH and OD. (C) 2000 American Institute of Physics. [S0021-9606(00)01413-6].