O 2 Dissociation Rates O2-Ar Mixtures

Abstract

Experimental measurements of the O2 dissociation rate in shock-heated oxygen-argon mixtures were obtained with the ultraviolet light absorption technique described in the preceding article. The dissociation rate constant kAr for the reaction O2+Ar→O+O+Ar can be fit over the temperature range from 3400 °K to 7500 °K by the theoretical formula kAr = C(D/RT)n−12 exp(−D/RT), where C = 6.0×101±20% cc/mole-sec and n = 1.5±0.2. 0 = 5.116 ev is the oxygen dissociation energy; R is the gas constant; and T is the temperature. This result is compared with the classical collision theory and the theories of Wigner and Keck. The rates for the dissociation of O2 by O and O2 were also determined; compared to the argon rate constant kO≈25kAr, kO2⪅3kAr Our experimental results are compared with those of Byron and Matthews. The relaxation times for dissociation and vibration are observed to be comparable at about 8000 °K. The experimental data indicate that the dissociation rate above 8000 °K is at least a factor of two less than the expected rate when the vibration is not in equilibrium (the vibrational temperature being less than the translational temperature) during dissociation.