Emissions at 450 nm and 4.27 ~sm have been measured when a vaxiety of mixtures containing H 2, CO.
either 02 or NaO, and Ar were heated behind reflected shock waves to temperatures of 2000-2850 K and total concentrations near 5 x 101| molecule/era 3. These emissions were used to obtain absolute concentration-tbne data for both oxygen atoms and carbon dioxide. The data were then compared to the results of numerical integrations of the likely mechanisms. It was observed that quantitative agreement between calculations and observations were obtained for the Ha/CO/Oa/Ar system using recent high temperature literature rate constants. For the Ha/CO/NaO/Ar system, the rate constant for the reaction H * N20 = N 2 + OH was adjusted to fit the data. Here it was found that a good fit to both [OJ and [COal profiles could be achieved with k = 30 x 10 --~) exp (-113kJ/RT)cm 3 molecule -! s -1 Comparison to data at lower temperatures suggests that this might be another example of a "non-Arrhenius'" rate constant The implications of these results to studies of hydrocarbon oxidation are discussed * Supported by ProJect SQUID, Office of Naval Research convincingly demonstrated that many reactions of importance in combustion mechanisms exhibit markedly "'non-Arrhenius'" rate constants, in this light it appears to be most desirable to measure rate constants in the same high temperature regime where they will be used to test the combustion mechanisms. However, it is equally important that these data be obtained from relatively simple systems where assignment of the decired rate constant is not contingent upon proper assignment of a complex mechanism and the associated rate constants.
One such system results from the substitution of NaO for 0 2 in combustion studies. Recent work in this laboratory [ I I ] showed that N20 is a particularly useful source of oxygen atoms between 2000-3000 K. Thus a study of combustion systems where NaO replaced O a should provide useful information about rates of oxygen atom reactions at high temperatures. The primary advantage of NaO as an oxidant is that oxygen atom