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 Title: Simultaneous Quantification Of Oh And Ho2 In Dimethyl Ether Oxidation Using Faraday Rotation Spectroscopy Author(s): Brumfield, Brian Contributor(s): Wysocki, Gerard; Ju, Yiguang; Lefkowitz, Joseph; Yang, Xueliang Subject(s): Analytical, Combustion, Plasma Abstract: \chem{OH} and \chem{HO_2} are key radical species that control the autoignition and flame chemistry of fuels. Quantification of these radicals in the low-temperature oxidation of fuels is challenging due to their low concentrations. Strong spectral interference from more abundant non-radical species can further complicate accurate quantification of \chem{OH} and \chem{HO_2}. Faraday Rotation Spectroscopy (FRS), a laser-based diagnostic that exploits magneto-optical properties of paramagnetic radical species, can overcome these technical challenges to provide sensitive and selective \textit{in situ} quantification of radicals. Previously we have been able to illustrate the strengths of FRS in quantification of \chem{HO_2} radicals in the low-temperature oxidation of dimethyl ether\footnote{B. Brumfield et al., \textit{J. Phys. Chem. Lett.}, \textbf{4}, 872 (2013).}$^{,}$\footnote{B. Brumfield et al., Dual Modulation Faraday Rotation Spectroscopy of \chem{HO_2} in a Flow Reactor’’ \textit{Accepted in Optics Letters} (2014).}$^{,}$\footnote{N. Kurimoto et al., Quantitative Measurements of \chem{HO_2} / \chem{H_2O_2} and Intermediate Species in Low and Intermediate Temperature Oxidation \\ \makebox[12pt]{} of Dimethyl Ether’’, \textit{Submitted to The 35th International Symposium on Combustion}.}. Recently we have constructed a dual-wavelength FRS system capable of simultaneous \textit{in situ} measurement of \chem{OH} and \chem{HO_2}. A DFB diode laser operating at 2.8 $\mu$m is used to target the Q(1.5e) and Q(1.5f) transitions in the fundamental vibrational band of the $^{2}\Pi_{3/2}$ ground electronic state of \chem{OH}. An EC-QCL operating at 7.1 $\mu$m is used to target a Q-branch spectral feature in the \nub{2} vibrational band of \chem{HO_2}. Concentrations of the target species are extracted from the measured spectra through fitting of an FRS spectral model. Based on preliminary retrievals, 3$\sigma$ detection limits of $<$1 ppmv for \chem{OH} and \chem{HO_2} have been estimated from the non-linear least-squares fitting results. In this talk I will discuss the application of dual-wavelength FRS for sensitive measurement of \chem{OH} and \chem{HO_2} radicals generated by oxidation of dimethyl ether in a flow reactor over a 520 K - 1050 K temperature range. Issue Date: 2014-06-16 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Brumfield, B.; Wysocki, G.; Ju, Y.; Lefkowitz, J.; Yang, X. SIMULTANEOUS QUANTIFICATION OF OH AND HO2 IN DIMETHYL ETHER OXIDATION USING FARADAY ROTATION SPECTROSCOPY. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.MJ10 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/50969 DOI: https://doi.org/10.15278/isms.2014.MJ10 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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