The vibrational distribution of the OH product from H2O photodissociation at 157 nm: Discrepancies between theory and experiment

Abstract

Photodissociation of H2O at 157 nm has been studied using the H atom Rydberg tagging time-of-flight technique. Vibrational state distribution has been measured for the OH product from H2O photodissociation. Comparisons with previous theoretical calculations and experimental results by laser-induced fluorescence (LIF) measurements have been made. The results in this work indicate that the relative populations for the high vibrationally excited OH(v≧2) products measured by the LIF technique 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 fairly good agreement with previous theoretical calculations, even though the calculated vibrational populations for the higher vibrational states of OH are still somewhat overestimated.