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J Phys Chem Lett. 2014 Jul 3;5(13):2241-6. doi: 10.1021/jz5008559. Epub 2014 Jun 16.

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

Author information

1
†JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, 440 UCB, Boulder, Colorado 80309, United States.
2
‡Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States.
3
§Arthur Amos Noyes Laboratory of Chemical Physics, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States.

Abstract

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-d1, 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.

KEYWORDS:

HOCO radicals; chemical kinetics; frequency combs; mid-infrared spectroscopy; time-resolved spectroscopy

PMID:
26279541
DOI:
10.1021/jz5008559

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