Self-exchange of oxygen behind reflected shock waves

Abstract

The rate of isotopic exchange of equimolar mixtures of 3202 + 3602 dilute in Ne-1% Ar was studied over the temperature range 2625-3700 K. The reacting gas was analyzed from the reflected shock zone at 20-ps intervals with a time-of-flight mass spectrometer. Each experimental product profile obtained was compared to the corresponding computer-simulated profile calculated from an atomic mechanism by using previously published rate constants. It was observed that the growth of the exchange product exceeded that predicted by the atomic mechanism at the lower temperatures of this study. However, these differences diminished as the temperature increased. Static analysis of the gas mixtures investigated revealed that H2 or D2 if present were at a level of less than 2,5 ppm. Computer simulation of product profiles demonstrated that this impurity level was insufficient to affect the observed rate of product formation. It is proposed that contributions from molecular channels are operative at the lower temperatures while atomic pathways dominate at the higher temperatures.