Densitometric measurements of the rate of carbon dioxide dissociation in shock waves

Abstract

The dissociation of CO2 in mixtures with Kr has been studied behind incident shock waves over the temperature range 3600–6500°K. The rate of the primary dissociation reaction was determined using the initial rate, laser schlieren method of Breshears, Bird, and Kiefer [J. Chem. Phys. 55, 4017 (1971)]. These experiments showed no trace of the ``dip'' phenomenon observed in previous schlieren dissociation studies and an extrapolation procedure was used for the estimation of initial rate. Arrhenius parameters obtained for the second order rate coefficient of Kr–CO2 mixtures (CO2 has about twice the efficiency) are logA = 14.59 (A in cm3/mole · sec) and an activation energy Ea = 107.2±1 kcal/mole. Agreement of both the present dissociation rates and recent low-temperature measurements of recombination to either classical RRK or RRKM expressions is obtained with a threshold energy for dissociation of 130–132 kcal/mole.