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 Title: Time-resolved Frequency Comb Spectroscopy Of Transient Free Radicals In The Mid-infrared Spectral Region Author(s): Bjork, Bryce J Contributor(s): Ye, Jun; Okumura, Mitchio; Cossel, Kevin; Bui, Thinh Quoc; Changala, Bryan; Fleisher, Adam J. Subject(s): Mini-symposium: Spectroscopy in Kinetics and Dynamics Abstract: The chemical kinetics of transient free radicals, such as HOCO and Criegee intermediates, play important roles in combustion and atmospheric processes. Establishing accurate kinetics models for these complex systems require knowledge of the reaction rates and lifetimes of all molecules along a particular reaction pathway. However, standard spectroscopic techniques lack a combination of sensitivity, frequency resolution, and adequate temporal resolution to survey these reactions on the $\mu$s timescale. To answer this challenge, we have developed time-resolved frequency comb spectroscopy (TRFCS). This novel technique allows for the detection of transient intermediates with high time-resolution and sensitivity while also permitting the direct determination of rotational state distributions of all relevant molecules. We demonstrate this technique in the mid-infrared spectral region, at 3.7 $\mu$m, by studying the photolysis of deuterated acrylic acid. We simultaneously observe the time-dependent concentrations of photoproducts trans-DOCO, HOD, and D$_2$O, identified through their unique rovibrational structure, with $5 \times 10^{10}$ molecules cm$^{-3}$ sensitivity, and with a time resolution of 25 $\mu$s. We aim to apply this technique to detect directly the formation of the DOCO intermediate in the OD + CO chemical reaction at atmospherically relevant pressures, in order to validate statistical rate models of this reaction. Issue Date: 2014-06-16 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Bjork, B.J.; Ye, J.; Okumura, M.; Cossel, K.; Bui, T.Q.; Changala, B.; Fleisher, A.J. TIME-RESOLVED FREQUENCY COMB SPECTROSCOPY OF TRANSIENT FREE RADICALS IN THE MID-INFRARED SPECTRAL REGION. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.MH08 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/51209 DOI: 10.15278/isms.2014.MH08 Rights Information: Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/ Date Available in IDEALS: 2014-09-172015-04-14
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