Broadband, background-free methane absorption in the mid-infrared
Rotationally resolved, broadband absorption spectra of the fundamental vibrational transition of the asymmetric C–H stretch mode of methane are measured under single-laser-shot conditions using time-resolved optically gated absorption (TOGA). The TOGA approach exploits the difference in timescales b...
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Veröffentlicht in: | Optics express 2021-06, Vol.29 (13), p.21011-21019 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Rotationally resolved, broadband absorption spectra of the fundamental vibrational transition of the asymmetric C–H stretch mode of methane are measured under single-laser-shot conditions using time-resolved optically gated absorption (TOGA). The TOGA approach exploits the difference in timescales between a broadband, fs-duration excitation source and the ps-duration absorption features induced by molecular absorption to allow effective suppression of the broadband background spectrum, thereby allowing for sensitive detection of multi-transition molecular spectra. This work extends the TOGA approach into the mid-infrared (mid-IR) spectral regime, allowing access to fundamental vibrational transitions while providing broadband access to multiple mid-IR transitions spanning ∼150 cm −1 (∼160 nm) near 3.3 μm, thereby highlighting the robustness of this technique beyond previously demonstrated electronic spectroscopy. Measurements are conducted in a heated gas cell to determine the accuracy of the simultaneous temperature and species-concentration measurements afforded by this single-shot approach in a well-characterized environment. Application of this approach toward fuel-rich methane–nitrogen–oxygen flames is also demonstrated. |
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ISSN: | 1094-4087 1094-4087 |
DOI: | 10.1364/OE.430315 |