Mid-infrared polarization spectroscopy of C2H2: Non-intrusive spatial-resolved measurements of polyatomic hydrocarbon molecules for combustion diagnostics

Z.S. Li, M. Linvin, J. Zetterberg, Johannes Kiefer, M. Aldén

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Polarization spectroscopy in the mid-infrared (IRPS) has been applied to the detection of acetylene molecules making use of the asymmetric C-H stretching vibration at around 3 mu m. The infrared laser pulses were produced through difference frequency generation in a LiNbO3 crystal pumped by a Nd:YAG and dye laser system. By directly probing the ro-vibrational transitions with IRPS, sensitive detection of molecules with otherwise inaccessible electronic states was realized with high temporal and spatial resolution by using a pulsed laser and a cross-beam geometry. Detection sensitivities of 2 x 10(13) molecules/cm(3) (10 ppm in 70 mbar gas mixture) of C2H2 were achieved using the P(11) line of the (010(11)(0))-(0000(0)0(0)) band. The dependence of the IRPS signal on the pump laser fluence, acetylene mole fraction, and buffer gas pressure of Ar, N-2, H-2, and CO2 has been studied experimentally. The investigation demonstrates the quantitative nature of IRPS for sensitive detection of polyatomic IR active molecules. In order to fully demonstrate the technique for combustion applications, nascent acetylene molecules were measured in a low pressure methane/oxygen flame.
Original languageEnglish
Pages (from-to)817-824
Number of pages8
JournalProceedings of the Combustion Institute
Issue number1
Early online date18 Sep 2006
Publication statusPublished - Jan 2007



  • IRPS
  • C2H2
  • soot formation precursor
  • combustion intermediates
  • hydrocarbon detection

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