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 Title: A New Strategy For Collection Of High-temperature Broad-band Absorption Spectra For Gas-phase Molecules In The Mid-infrared Author(s): Ding, Yiming Contributor(s): Hanson, Ronald K; Strand, Christopher L; Johnson, Sarah E Subject(s): Linelists Abstract: \begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.28]{Ethylene_nu_7_band_995K_2.3atm.eps} \end{wrapfigure} To address the notable lack of knowledge on high-temperature absorption cross sections of important molecular species in combustion and exoplanets, a new strategy is proposed and deployed to collect broad-band absorption spectra in shock-heated gases. The methodology utilizes a broad-scan, rapid-tuning external-cavity quantum cascade laser in conjunction with a shock tube and is capable of providing quantitative spectroscopic information across full vibrational bands spanning over 200 \wn within 6 ms ($>$ 30,000 \wn/s), with a spectral resolution between 0.3 – 0.6 \wn. This experimental approach is demonstrated with absorption spectra measurements on the \nub{7} vibrational band of ethylene (\chem{C_2H_4}) from 8.4 $\mu$m to 11.7 $\mu$m at temperature/pressure conditions between 800 – 1600 K, 1 – 5 atm. The measured spectra are compared against spectral simulations using existing spectroscopic databases, showing better agreement with the line list of Rey et al.\footnote{M. Rey, T. Delahaye, A. V. Nikitin, and V. G. Tyuterev, “First theoretical global line lists of ethylene ($^{12}$\chem{C_2H_4}) spectra for the temperature range 50-700 K in the far-infrared for quantification of absorption and emission in planetary atmospheres,” Astron. Astrophys., vol. 594, pp. 1–16, 2016.} than of HITRAN 2016\footnote{I. E. Gordon et al., “The HITRAN2016 molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transf., vol. 203, pp. 3–69, 2017.}. With the current set of instruments available, this methodology could be applied to numerous gas-phase molecules that have attractive absorption features in the spectral range of 3.6 – 11.7 $\mu$m and opens an efficient pathway towards improving knowledge on radiation absorption in the mid-infrared at high temperatures. Issue Date: 2021-06-22 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/111012 Date Available in IDEALS: 2021-09-24
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