A SHOCK-TUBE STUDY OF REACTIONS OF C ATOMS WITH H-2 AND O2 USING EXCIMER PHOTOLYSIS OF C3O2 AND C ATOM ATOMIC RESONANCE-ABSORPTION SPECTROSCOPY

The reactions of C(3P) with H-2 and O2 were studied at high temperature in reflected shock wave experiments. C atoms were detected at 156.1 nm by atomic resonance absorption spectroscopy (ARAS). Controlled levels of C atoms for calibrating the ARAS diagnostic were made by high-temperature pyrolysis of highly dilute CH4/Ar mixtures. For kinetics experiments, C atoms were formed by pyrolysis of C3O2 above 2300 K and by ArF excimer photolysis of C3O2 below 2050 K. Formation of C atoms in the presence of excess H-2 or O2 permitted first-order rate coefficient determinations of the reactions C(3P) + H-2 --> CH + H (1) and C(3P) + O2 --> CO + O (2), yielding k1 = 4.0 X 10(14) exp(-11700 K/T) (+/- 50%) cm3 mol-1 s-1, over the temperature range 1525-2540 K and pressure range 0.5-1.2 atm, and k2 = 1.2 X 10(14) exp(-2010 K/T) (+/- 50%) cm3 mol-1 s-1, over the temperature range 1500-4200 K. The rate coefficient of the reverse (exothermic) reaction, k-1, is 1.1 X 10(14) cm3 mol-1 s-1, constant with temperature. A rate coefficient for the reaction C + C3O2 --> products (6) of k6 = 2.4 X 10(19)T-1.75 cm3 mol-1 s-1, over the temperature range 1450-1900 K, was determined from photolysis experiments. High-temperature absorption coefficient data for C3O2 at 156 and 193 nm (1500-1800 K) are also presented.