KINETICS OF THE REACTIONS OF N(S-4) ATOMS WITH O-2 AND CO2 OVER WIDE TEMPERATURES RANGES

Rate coefficients for the depletion of ground-state nitrogen atoms by O-2 have been measured using a high-temperature photochemistry reactor . The N atoms were generated by VUV flash photolysis of N2O, and the r elative concentrations were monitored by resonance fluorescence. The d ata are best fitted by the expression k(400-1220 K) = 2.0 x 10(-18)(T/ K)(2.15) exp(-2557 WT) cm(3) molecule(-1) s(-1) with 2 sigma precision limits varying from +/-7% to +/-20% depending upon temperature, and c orresponding 2 sigma accuracy limits of +/-23% to +/-30%. Good agreeme nt is found with earlier, electrical discharge initiated, rate coeffic ient measurements for the 280-910 K domain. Semiempirical theory-based calculations are presented that lead to a plot nearly indistinguishab le from those of the present results and the Baulch et al. recommendat ion for the 300-5000 K temperature range. These yield a classical barr ier E-0(double dagger) of 27.4 kJ mol(-1). No reaction with CO2 could be observed; upper Limit rate coefficients were obtained from 285 to 1 140 K. These upper limits indicate that the reverse reaction is insign ificant for models of nitrate ester and nitramine propellant dark zone s.