DETERMINATION OF N-ATOM CONCENTRATIONS IN LOW-PRESSURE PREMIXED H-2/O2/N2 FLAMES DOPED WITH NH3, HCN AND (CN)2

Spatially resolved N-atom concentration and temperature profiles were measured in several stoichiometric, flat, premixed, low-pressure H-2/O2/N2 flames doped with small amounts of N-containing fuels. Temperature was obtained from OH (A 2-SIGMA+ -X 2-PI, 1-0) excitation spectra. N atoms were detected by two-photon laser-induced fluorescence, exciting the 3p 4D-degrees-7/2 state near 211 nm and monitoring the (3p 4D-degrees-3s 4P ) transition near 870 nm. N-atom concentrations were determined with the acid of a calibration technique using known atom concentrations in a discharge flow reactor and previously determined quenching coefficients. In the flames, peak N-atom mole fractions ranged from about 3 to 90 ppm.