Rate Determination of the CO2* Chemiluminescence Reaction CO plus O plus M (sic) CO2* + M
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ABSTRACTElectronically excited carbon dioxide (CO2*) is known for its broadband emission, and its detection can lead to valuable information; however, owing to its broadband characteristics, CO2* is difficult to isolate experimentally, and its chemical kinetics are not well known. Although numerous works have monitored CO2* chemiluminescence, a full kinetic scheme for the excited species has yet to be developed. To this end, a series of shocktube experiments was performed in H2N2OCO mixtures highly diluted in argon at conditions where emission from CO2* could be isolated and monitored. These results were used to evaluate the kinetics of CO2*, in particular the main CO2* formation reaction CO + O + M CO2* + M (R1). Based on collision theory, the quenching chemistry of CO2* was estimated for 11 collision partners. The final mechanism developed for CO2* consists of 14 reactions and 13 species. The rate for (R1) was determined to within about 60% using lowpressure experiments performed in five different (H2)N2OCOAr mixtures, as follows: urn:x-wiley:05388066:media:kin20892:kin20892-math-0003 where R is the universal gas constant in cal/molK and T is the temperature in K. Final mechanism predictions were compared with experiments at low and high pressures, with good agreement at both conditions for the temperature dependence of the peak CO2* and the CO2* species time histories. Comparisons were also made with previous experiments in methaneoxygen mixtures, where there was slight overprediction of CO2* experimental trends, but with the results otherwise showing a dramatic improvement over an earlier mechanism. Experimental results and model predictions were also compared with past literature rates for CO2*, with good agreement for peak CO2* trends and slight discrepancies in CO2* species time histories. Overall, the ability of the CO2* mechanism developed in this work to reproduce a range of experimental trends represents an important improvement over the existing knowledge base on chemiluminescence chemistry.
