Rate Determination of the CO2* Chemiluminescence Reaction CO + O + M ⇄ CO2* + M
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© 2014 Wiley Periodicals, Inc. Electronically 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 shock-tube experiments was performed in H2-N2O-CO 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 low-pressure experiments performed in five different (H2-)N2O-CO-Ar mixtures, as follows: k1 = 4.0 × 1014 exp(-2384/RT)cm6/mol2 - s where R is the universal gas constant in cal/mol-K 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 methane-oxygen 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.
author list (cited authors)
Kopp, M. M., Mathieu, O., & Petersen, E. L.