The dynamics of the reaction: O( 1D 2) + H 2S → OH(ν′) + HS

Abstract

The initial OH vibrational energy distribution from the reaction between O( 1D 2) and H 2S was determined by combining low-pressure IR chemiluminescence techniques with fast time-resolved Fourier transform spectroscopy (FTRFTS). This technique allowed us to observe the product energy distribution at a time corresponding to approximately two gas kinetic collisions after the reaction. The result, P(ν′ = 1:2:3:4:5 = 0.11:0.13:0.18:0.30:0.28), shows that the initial product vibrational energy distribution is strongly inverted. Laser induced fluorescence (LIF) measurements performed elsewhere show that the OH(ν′ = 0) population is larger than the OH(ν′ = 1) population, and hence the overall vibrational distribution is bimodal. This strongly bimodal product vibrational distribution implies the existence of two dynamically different reaction channels. The existing data do not permit an unequivocal identification of these channels. The potential energy surface permits both a direct hydrogen atom abstraction, which would create vibrationally excited OH, and an insertion (forming a long-lived HSOH or H 2SO intermediate), which would not produce much product vibrational excitation. It is likely that these channels produce the observed bimodal vibrational distribution; the direct abstraction predominantly populates OH(ν′ ≥1) and the insertion-elimination populates OH(ν′ ≤1).