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Title:Gas-phase molecular structure of nopinone and its water complexes studied by microwave fourier transform spectroscopy and quantum chemical calculations
Author(s):Neeman, Elias M.
Contributor(s):Huet, T. R.; Aviles Moreno, Juan-Ramon
Abstract:Several monoterpenes and terpenoids are biogenic volatile organic compounds which are emitted in the atmosphere, where they react with OH, O$_3$ and NO$_x$ etc. to give rise to several oxidation and degradation products.\footnote{A. Calogirou, B.R. Larsen, and D. Kotzias, \textit{ Atmospheric Environment}, \textbf{33}, 1423-1439, (1999).} Their decomposition products are a major source of secondray organic aerosol (SOA).\footnote{P. Paasonen et al., \textit{Nat. Geosci.}, \textbf{6}, 438-442 (2013)} Spectroscopic information on these atmospheric species is still very scarce. The rotational spectrum of nopinone (C$_9$H$_{14}$O) one of the major oxidation products of $\beta$-pinene,\footnote{D. Zhang and R. Zhang \textit{The Journal of Chemical Physics}, \textbf{122}, 114308, (2005).} \footnote{R. Winterhalter et al. \textit{ Journal of Atmospheric Chemistry}, \textbf{35}, 165-197, (2000).} and of its water complexes were recorded in a supersonic jet expansion with a Fourier transform microwave spectrometer over the range 2-20 GHz. The structure of the unique stable conformer of the nopinone was optimized using density functional theory and \textit{ab initio} calculations. Signals from the parent species and from the $^{13}C$ and $^{18}O$ isotopomers were observed in natural abundance. A magnetic hyperfine structure associated with the pairs of hydrogen nuclei in the methylene groups was observed and modeled. \\ The structures of several conformers of the nopinone-water complexes with up to three molecules of water were optimized using density functional theory and \textit{ab initio} calculations. The energetically most stable of calculated conformers were observed and anlyzed. The rotational and centrifugal distortion parameters were fitted to a Watson’s Hamiltonian in the A-reduction. The present work provides the first spectroscopic characterization of nopinone and its water complexes in the gas phase.\\
Issue Date:2016-06-21
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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