Decay dynamics of H 2O( 1B 1): full characterization of OH product state distribution

Abstract

H 2O was excited to the lowest electronic excited state, 1B 1, at 157.6 nm and the OH product state distribution was completely analyzed by special laser-induced-fluorescence (LIF) experiments probing the fragment distribution by the transitions (υ′ = 0, 1←υ″). The OH rotational excitation is relatively low and can be described by a temperature parameter of ≈ 500 K independently of the OH vibrational excitation. This is in accordance with former measurements as well as with theoretical calculations. No selective population of the electronic fine-structure levels was observed which is in agreement with the expectations for a room-temperature experiment. The observed magnitude of the vibrational excitation ( P(υ″ = 0): P(υ″ = 1): P(υ″ = 2): P(υ″ = 3): P(υ″ = 4) = 59.2:33.1:6.1:1.4:0.2) is smaller than the one calculated. The calculations predicted the υ″ = 6 level to be populated, whereas in the experiment, transitions probing the υ″ = 5 state were not observed.