N-ATOM MEASUREMENTS IN HIGH-TEMPERATURE C2N2 NO/AR REACTION SYSTEMS/

N-atom concentration profiles were measured in highly diluted C2N2/NO/ Ar reaction systems behind reflected shock waves at temperatures betwe en 3050 K and 4430 K by applying atomic resonance absorption spectrosc opy (ARAS). C2N2 served as a thermal source for CN radical which react with both, NO and the subsequently formed N atoms. Computer simulatio ns based on a simplified reaction mechanism revealed strong sensitivit y of the measured N atoms to the elementary reactions: (R5) CN+NOk(5) reversible arrow NCO+N (R9) CN+Nk(9) reversible arrow C+N-2 A fitting procedure of all experiments allowed determination of individual value s of the rate coefficients: (1) K-5=9.6x10(13) exp(-21200 K/T) cm(3) m ol(-1) s(-1) (2) k(9)=1.9...6.0x10(13) cm(3) mol(-1) s(-1) The present results enlarge the temperature range of the recommended Arrhenius ex pression of k(5) [1] and confirm recent measurements of the backward r eaction of (R-9) [2,3]. (C) 1997 John Wiley & Sons, Inc.