Detection of nitrogen atoms in flames using two-photon laser-induced fluorescence and investigations of photochemical effects.

Nitrogen atoms, in a flame or produced by photodissociation of nitrogen-containing molecules, were excited through a two-photon absorption process at 211 nm, and the near IR fluorescence was detected. Both in flame and in photodissociation experiments of cold gases, fluorescence, which was resonantly enhanced at the atomic nitrogen wavelength but which originated from excited oxygen atoms, was also identified. This phenomenon, the photochemical effects and those of molecular absorption, stimulated emission, and the mixing of gases are discussed in connection with the detection of atomic nitrogen in flames.