American Chemical Society, Journal of Physical Chemistry Letters, 13(5), p. 2241-2246, 2014
DOI: 10.1021/jz5008559
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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.