Shock-Tube Study of Carbon Dioxide Dissociation Rate

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Abstract
The homogeneous dissociation rate of carbon dioxide, diluted with large amounts of argon, was measured in a shock tube by two independent methods: (a) by the single‐pulse technique, in which the gas reacts behind a reflected shock, is quenched by a rarefaction wave, and is later analyzed chemically; and (b) by measurements of light intensity in the blue continuum due to CO2(3Π)→CO2(1Σ)+hν. The results of the two experiments agree. The rate is given by d[CO]/dt=k[CO2][M], with k=3×1011T½ exp (—86 000/RT) cm3 moles—1 sec—1. Dissociation evidently does not proceed directly from ground‐state CO2 to ground‐state CO and O. The mechanism probably involves the intermediate electronically excited state CO2(3Π), the rate‐controlling process being associated with its formation.