Vibration, Excitation, and Molecular Dissociation of Gaseous Oxygen and Carbon Dioxide in a Shock Wave

Abstract

Absorption spectroscopy techniques were employed for a shock tube study of the kinetics of the nonequilibrium processes at high temperatures. Ultraviolet absorption intensity as a function of time was investigated behind the shock front. Pure carbon dioxide, oxygen and mixtures of oxygen with nitrogen, argon, xenon, helium, nitrogen dioxide, water vapour and C2H5OH were studied.The experimental value of the vibrational relaxation time of oxygen at T = 1200–7000°K was in accordance with the results of Landau-Teller theory; at T<2000°K, a significant difference was observed between our data and Blackman's well-known results.Dissociation of O2 and CO2 molecules occurs as a bimolecular reaction and dissociation rate constants are approximated by the following expressions: kd(O2, O2)= 4·6×109(T)1/2(D/RT)4exp(−D/RT) cm3/mol.sec (T = 2600–7000°K, D = 119 kcal⧸mol.); kd(CO2, CO2) =3×107(T)1/2(D/RT)6exp (−D/RT) cm3/mol.sec (T = 3000–5500°K, D =126 kcal/mol).