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Title:Infrared identification of the criegee intermediate (CH3)2COO
Author(s):Lee, Yuan-Pern
Contributor(s):Wang, Yi-Ying
Abstract:The Criegee intermediates are carbonyl oxides that play critical roles in ozonolysis of alkenes in the atmosphere. We reported previously the mid-infrared spectra of the simplest Criegee intermediate \chem{CH_2OO}.\footnote { Y.-T. ~Su, Y.-H. ~Huang, H. A. ~Witek, Y.-P. ~Lee, \textit{Science} \underline{\textbf{340}}, 174 (2013).}$^{,}$ \footnote { Y.-H. ~Huang, J. ~Li, H. ~Guo, Y.-P. ~Lee, \textit{J. Chem. Phys.} \underline{\textbf{142}}, 214301 (2015).} and the methyl-substituted intermediate \chem{CH_3CHOO}.\footnote { H.-Y. ~Lin, Y.-H. ~Huang, X. ~Wang, J. M. ~Bowman, Y. ~Nishimura, H. A. ~Witek, Y.-P. ~Lee, \textit{Nat. Comm.} \underline{\textbf{6}}, 7012 (2015).} Here we report the transient infrared spectrum of \chem{(CH_3)_2COO}, produced on UV photolysis of a mixture of \chem{(CH_3)_2CI_2}, \chem{N_2}, and \chem{O_2} in a flow reactor, using a step-scan Fourier-transform spectrometer. Guided by results of quantum-chemical calculations, rotational contours of the four observed bands are simulated successfully and provide definitive identification of \chem{(CH_3)_2COO}. Although all observed bands of \chem{(CH_3)_2COO} contain hot bands from four vibrational modes of low energy, we were able to simulate the spectra satisfactorily. Observed bands with origins near 887, 1040, 1368, and 1422 cm$^{-1}$ agree satisfactorily with corresponding anharmonic vibrational wavenumbers at 903, 1061, 1364, and 1422 cm$^{-1}$ predicted with the B3LYP/aug-cc-pVTZ method. Furthermore, we could also estimate the rate coefficient of the self-reaction of \chem{(CH_3)_2COO}. The direct infrared detection of \chem{(CH_3)_2COO} should prove useful for future field measurements and laboratory investigations of this Criegee intermediate.
Issue Date:2016-06-23
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper/Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2016-08-22

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