2-PHOTON INDUCED POLARIZATION SPECTROSCOPY APPLIED TO THE DETECTION OF NH3 AND CO MOLECULES IN COLD FLOWS AND FLAMES

Two-photon induced polarization spectroscopy, TIPS, is demonstrated fo r the detection of NH3 and CO molecules. Measurements were performed i n flow as well as in flame environments. The signal dependence on the laser pulse intensity and on the pump beam polarization was investigat ed. Two-dimensional signal intensity maps were formed from one-dimensi onal signal distribution measurements at different heights in flames. With a proper choice of the laser wavelength two-photon polarization s pectroscopy signals from NH, and one-photon polarization spectroscopy signals from OH could be measured simultaneously. The spectrum of the Q branch of the X(1) Sigma-B-1 Sigma(+) (0,0) band of the CO molecule at different temperatures and the dependence of the two-photon polariz ation signal on the number density of CO molecules in the presence of N-2 and He molecules were also measured. A comparison between the TIPS and two-photon DFWM techniques for flame studies is briefly discussed .