ARAS measurements on the thermal decomposition of CO2 behind shock waves

The dissociation rate coefficient of COi has been measured behind reflected shock waves in the temperature range 2400<T<4400 K at pressures 1.2<p <2.0 bar. By the use of the atomic resonance absorption spectroscopy, the formation of O atoms could directly be observed in the postshock reaction zone. The experiments have been performed in mixtures of CCh highly diluted in argon. The initial COi concentrations varied from 10 to 5000 ppm. The Arrhenius expression for the thermal decomposition of COz, CCh + M_^iCO + O + M was found to be k = 3.65 x 10 14exp(-52,525 K/T) cm3mol~1 s1. The effect of impurities was minimized by keeping background pressures in the shock tube below 5x 10 ~7 mbar.