Mid-infrared pumped laser-induced thermal grating spectroscopy for detection of acetylene in the visible spectral range

Research output: Contribution to journalArticle

Abstract

We present mid-infrared laser-induced thermal grating spectroscopy (IR-LITGS) using excitation radiation around 3 μm generated by a simple broadband optical parametric oscillator (OPO). Acetylene as a typical small hydrocarbon molecule is used as an example target species. A mid-infrared broadband OPO pumped by the fundamental output of a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used to generate the pump beams, with pulse energies of 6-10 mJ depending on the wavelength. The line width of the OPO idler beam was ∼5 cm-1, which is large enough to cover up to six adjacent acetylene lines. The probe beam was the radiation of a 532 nm cw solid state laser with 190 mW output power. Signals were generated in atmospheric pressure gas flows of N2, air, CO2 and Ar with small admixtures of C2H2. A detection limit of less than 300 ppm was found for a point measurement of C2H2 diluted in N2. As expected, the oscillation frequency of the IR-LITGS signal was found to have a large dependency on the buffer gas, which allows determination of the speed of sound. Moreover, the results reveal a very strong collisional energy exchange between C2H2 and CO2 compared to the other gases. This manifests as significant local heating. In summary, the MIR-LITGS technique enables spectroscopy of fundamental vibrational transitions in the infrared via detection in the visible spectral range.

Details

Authors
Organisations
External organisations
  • Friedrich-Alexander University Erlangen-Nürnberg
  • University of Bremen
  • University of Aberdeen
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics

Keywords

  • acetylene, Hydrocarbon detection, laser-induced gratings, LITGS, nonlinear optical spectroscopy, quenching
Original languageEnglish
Pages (from-to)1034-1043
Number of pages10
JournalApplied Spectroscopy
Volume70
Issue number6
Publication statusPublished - 2016 Jun 1
Publication categoryResearch
Peer-reviewedYes