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.

Spectroscopic Measurements in the Shock Relaxation Region of a Hypervelocity Mach Reflection

“…However, non-Boltzmann distributions are modeled for NO produced by the second Zeldovich reaction. 34 The thermochemical model was validated by comparision with experimentally obtained data for rate constants, 35,36 vibrational relaxation times, 37, 38 dissociation rates 39,40 and VV transfer probabilities. 41 Using the master equation approach of Park, 23 a total of 37, 48, and 40 vibrational levels for O 2 , N 2 , and NO respectively are obtained in addition to monatomic O, N, and Ar, resulting in a 128 species mixture.…”

NO and OH Spectroscopic Vibrational Temperature Measurements in a Post-Shock Relaxation Region

“…Using the master equation approach of Park [33], a total of 37, 48, and 40 vibrational levels for O 2 , N 2 , and NO, respectively, are obtained in addition to monatomic O, N, and Ar, resulting in a 128-species mixture. The extended thermochemical model has been previously validated by comparision with experimentally obtained data for rate constants [46,47], vibrational relaxation times [48,49], dissociation rates [50,51], and vibration-vibration transfer probabilities [52]. Initial inflow conditions for the calculations (static pressure, static temperature, and test gas Mach number) are obtained from inviscid, perfect-gas calculations of expansion tube operation.…”

A SHOCK TUBE STUDY OF THE COUPLING OF THE 02-Ar RATES OF DISSOCIATION AND VIBRATIONAL RELAXATION

“…Lin has measured the shock front curvature as a -4- -1/2 6 (mm) = 1. 75 P 1 (mm of Hg) (4) At the lowest initial pressures used in these experiments (1/4 mm), the shock front curvature would amount to 3.5 mm. The optical slits used for all the experiments were 1 mm wide, hence,, a shock front curvature of 3.…”