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

Research output: Chapter in Book/Report/Conference proceedingPaper in conference proceeding


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 μm. The infrared laser pulses were produced through difference frequency generation in a LiNbO<sub>3</sub> 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 × 10<sup>13</sup> molecules/cm<sup>3</sup> (10 ppm in 70 mbar gas mixture) of C<sub>2</sub>H<sub>2</sub> were achieved using the P(11) line of the (010(11)<sup>0</sup>)-(0000<sup>0</sup>0<sup>0</sup>) band. The dependence of the IRPS signal on the pump laser fluence, acetylene mole fraction, and buffer gas pressure of Ar, N<sub>2</sub>, H<sub>2</sub>, and CO<sub>2</sub> 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. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics


  • Hydrocarbon detection, Combustion intermediates, Soot formation precursor, Combustion diagnostics, Polarization spectroscopy in the mid-infrared
Original languageEnglish
Title of host publicationProceedings of the Combustion Institute
Volume31 I
Publication statusPublished - 2007
Publication categoryResearch
Event31st International Symposium on Combustion - Heidelberg, Germany
Duration: 2006 Aug 52006 Aug 11

Publication series

Volume31 I
ISSN (Print)1540-7489
ISSN (Electronic)1873-2704


Conference31st International Symposium on Combustion