Dissociation dynamics of the water molecule on the (A)over-tilde 1B1 electronic surface

Photodissociation of H2O, D2O, and HOD on the (A) over tilde B-1(1)' surface through 157.6 nm excitation has been studied using the H(D) atom Rydberg tagging time-of-flight technique. Vibrational state distribution has been measured for the OH/OD product from the photodissociation of the H2O, D2O, and HOD molecules. Comparisons of our results with previous theoretical calculations and experimental results obtained using the laser induced fluorescence (LIF) technique have been made. Experimental results in this work indicate that the relative populations for vibrationally excited OH(v greater than or equal to2) products measured using LIF are significantly underestimated, suggesting that LIF as a technique to quantitatively measure vibrational distributions of reaction product OH is seriously flawed. The experimental results presented here are in rather good agreement with previous theoretical calculations. However, our results indicate that the calculated vibrational populations for the higher vibrational states of OH are still somewhat overestimated. Relative branching ratio of H and D productions from HOD has also been estimated. This complete set of data for the photodissociation of H2O should provide an excellent testing ground for improving the theoretical potential energy surface of the first electronically excited state of the water molecule. (C) 2000 American Institute of Physics. [S0021-9606(00)01220-4].