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

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Author

Summary, in English

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.

Department/s

Publishing year

2007

Language

English

Pages

817-824

Publication/Series

Proceedings of the Combustion Institute

Volume

31 I

Document type

Conference paper

Publisher

Elsevier

Topic

  • Atom and Molecular Physics and Optics

Keywords

  • Hydrocarbon detection
  • Combustion intermediates
  • Soot formation precursor
  • Combustion diagnostics
  • Polarization spectroscopy in the mid-infrared

Conference name

31st International Symposium on Combustion

Conference date

2006-08-05 - 2006-08-11

Conference place

Heidelberg, Germany

Status

Published

ISBN/ISSN/Other

  • ISSN: 1873-2704
  • ISSN: 1540-7489
  • CODEN: SYMCAQ