Shock-Tube Study of the Recombination of O Atoms by Ar Catalysts at High Temperatures

Abstract

The three‐body recombination of O atoms by Ar catalysts was measured over a temperature range of 1340–2920°K in a shock‐tube experiment. The excess amount of O atoms was produced by shocking dilute O₃–Ar mixtures. Under the experimental conditions, the O atoms in excess of equilibrium produced by the reaction O₃+M→O+O₂+M had to recombine via the reaction O+O+M→O₂+M. The reaction O₃+O→2O₂ was ineffective due to the high temperature and high concentration of Ar. The O₂ formed by the recombination of the O atoms was monitored behind the shock wave by absorption of 1270‐Å radiation. The data scatter by about a factor of 2, but a slight negative temperature dependence is apparent. At 2000°K the recombination coefficient is about 0.7×10⁻³⁴ cm⁶/particle²‐sec. The experimental results are compared with calculated curves based on various authors' dissociation‐rate constants divided by the equilibrium constant. A dissociation‐rate constant given by k_d = 2.5×10¹⁶T^−½ exp (−D/RT) cc/mole‐sec, which is shown to fit dissociation data obtained in previous work and covering a temperature range of 5000–18 000°K, was found to fit best the present recombination data.