A High Temperature Chemical Kinetics Study of the Reaction: OH+Ar = H+O+Ar by Atomic Resonance Absorption Spectrophotometry

Abstract

The OH radical dissociation has been studied behind shock waves in the temperature range of 2950-3700 K at total pressures of about 220-310 kPa by Atomic Resonance Absorption Spectroscopy using mixtures of H₂ and O₂ highly diluted in Ar. The OH decomposition was followed by monitoring the time dependent O concentration in the post shock reaction zone. In our experimental conditions this reaction is very sensitive to O-atom profiles. The rate constant k₋₂ of the termolecular recombination reaction between H, O and Ar as collision partner was calculated from OH dissociation rate constant k₂ measurements and the equilibrium constant. The results expressed in the simple Arrhenius form are:

with an uncertainty of ± 30 %, which are in good agreement with the estimate of Tsang and Hampson in 1986. No experimental results were reported by earlier investigators.

Keywords:

• shock tube
• chemical kinetics
• ARAS
• high temperature