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• A Kinetic Study of the Reaction NH2 with NO in the Temperature Range from 1400 to 2800 K

J. Deppe, G. Friedrichs, H.-J.-Römming, and H.Gg. Wagner
Phys. Chem. Chem. Phys. 1, 427-435 (1999)

 

The reaction (1) NH2+NO → products was investigated behind incident and reflected shock waves in the temperature range from 1400 to 2800 K and densities ranging from 1.4 to 20E-6 mol/cm3. The source of NH2 radicals was the thermal dissociation of hydrazine (N2H4). Time histories of NH2 (597.365 nm), NH (336.100 nm) and OH (308.417 nm) were detected by narrow linewidth laser absorption. The H and O atom formations were followed by means of atom resonance absorption spectroscopy (ARAS) at 121.5nm and 130.5nm. In addition, NH2 radicals were detected at very low concentrations using the very sensitive frequency modulated (FM) spectroscopy.
For the overall rate constant k1 in the temperature range from 1400 to 2200 K an Arrhenius expression of

k1 = 1.3E13·exp(-35 kJ/mol/RT) cm3/mols (±60%)

was determined. In connection with previous literature data a minimum of the overall rate constant was found around 1200 K. According to several other investigations, the reaction channel (1a) NH2+NO → N2+H2O clearly dominates the channel (1d) NH2+NO → N2+OH+H at temperatures lower than 1000 K. At room temperature a branching ration α(T) = k1d/(k1d+k1a) around 10% is reported. Our investigations of the products H and OH of the channel (1d) and the determination of the branching ratio shows that the contribution of channel (1d) increases from around 50% at 1500 K to >80% at 2800 K. The other reaction channels investigated (1c) leading to N2O+H2 and (1g) to HNO+NH are of minor importance.


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