Resonance absorption measurements of N, O, and H atoms in shock heated HCN/O 2/Ar mixtures

Abstract

Atomic resonance absorption spectroscopy (ARAS) was used to measure the concentrations of N, O, and H atoms behind reflected shock waves in HCN O 2 mixtures highly diluted in Ar. For the temperature range 2195 ≤ T ≤ 3390K at pressures of about 1.5–1.9 bar, the concentrations of the initial reactants varied between 25 and 200 ppm for HCN, and 50 and 1000 ppm for O 2. Nearly 80 experiments were performed and compared with computer simulations based on a reaction model of 33 elementary reactions and selected rate coefficients. The rate coefficient of the reaction CN + O 2 → NCO + O (R3) was varied to match the measured and calculated concentration profiles. The determined rate coefficient of reaction R3 is found to be in good agreement with the result reported by Louge and Hanson in Int. J. Chem. Kin. 16: k 3 = 4.9 × 10 12 cm 3 mol -1 s -1 Using the rate coefficient data reported in the literature for the other reactions of the kinetic model, a percentage standard deviation of about ± 15 % was obtained from the experimental scatter observed for k 3. However, a detailed uncertainty analysis conducted for two experiments led to error bars of about + 150% and −50% for the individual results of k 3.