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Mid-Infrared Time-Resolved Frequency Comb Spectroscopy of Transient Free Radicals

Fleisher, Adam J. and Bjork, Bryce J. and Bui, Thinh Q. and Cossel, Kevin C. and Okumura, Mitchio and Ye, Jun (2014) Mid-Infrared Time-Resolved Frequency Comb Spectroscopy of Transient Free Radicals. Journal of Physical Chemistry Letters, 5 (13). pp. 2241-2246. ISSN 1948-7185 .

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We demonstrate time-resolved frequency comb spectroscopy (TRFCS), a new broadband absorption spectroscopy technique for the study of trace free radicals on the microsecond timescale. We apply TRFCS to study the time-resolved, mid-infrared absorption of the deuterated hydroxyformyl radical trans-DOCO, an important short-lived intermediate along the OD + CO reaction path. Directly after photolysis of the chemical precursor acrylic acid-d_1, we measure absolute trans-DOCO product concentrations with a sensitivity of 5 × 10^(10) cm^(–3) and observe its subsequent loss with a time resolution of 25 μs. The multiplexed nature of TRFCS allows us to detect simultaneously the time-dependent concentration of several other photoproducts and thus unravel primary and secondary chemical reaction pathways.

Item Type:Article
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URLURL TypeDescription Information
Bui, Thinh Q.0000-0001-6090-0930
Okumura, Mitchio0000-0001-6874-1137
Additional Information:© 2014 American Chemical Society. Received: April 30, 2014. Accepted: June 10, 2014. Publication Date (Web): June 10, 2014. We thank Keeyoon Sung of the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) for providing a list of D_2O mid-IR line positions and intensities measured by Robert A. Toth of JPL. We are grateful to Scott A. Diddams of the National Institute of Standards and Technology (NIST) and Tim Dinneen of Precision Photonics for providing the mid-IR VIPA etalon used in this work. We also thank Brad Baxley for artistic contributions to Figure 1 and acknowledge financial support from NIST, NSF, NASA, AFOSR, and DTRA. Adam J. Fleisher was supported by a National Research Council postdoctoral fellowship and Thinh Bui by a NASA Earth and Space Science Fellowship.
Funding AgencyGrant Number
National Institute of Standards and Technology (NIST)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Defense Threat Reduction Agency (DTRA)UNSPECIFIED
National Research Council of CanadaUNSPECIFIED
Subject Keywords:frequency combs; time-resolved spectroscopy; mid-infrared spectroscopy; HOCO radicals; chemical kinetics
Record Number:CaltechAUTHORS:20140815-145924440
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Official Citation:Mid-Infrared Time-Resolved Frequency Comb Spectroscopy of Transient Free Radicals Adam J. Fleisher, Bryce J. Bjork, Thinh Q. Bui, Kevin C. Cossel, Mitchio Okumura, and Jun Ye The Journal of Physical Chemistry Letters 2014 5 (13), 2241-2246
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48632
Deposited By: Ruth Sustaita
Deposited On:15 Aug 2014 22:35
Last Modified:27 Mar 2017 15:25

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