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Title:Spectral line shapes in the 2ν3 Q branch of 12CH4
Author(s):Devi, V. Malathy
Contributor(s):Boudon, Vincent; Mantz, Arlan; Ismail, Syed; Smith, Mary Ann H.; Yu, Shanshan; Crawford, Timothy J.; Brown, Linda R.; Sung, Keeyoon; Benner, D. Chris
Subject(s):Small molecules
Abstract:We will present the first experimental measurements of spectral line shapes (self- and air-broadened half width, pressure shift, and line mixing (via off-diagonal relaxation matrix element) coefficients and their temperature dependences, where appropriate, for transitions in the 2$\nu_3$ Q branch manifolds of $^{12}$CH$_4$ in the 1.6 $\mu m$ region. Employing a multispectrum nonlinear least squares technique\footnote{D.C. Benner, C.P. Rinsland, V. Malathy Devi, M.A. H. Smith, and D. Atkins. JQSRT 53 (1995) 705-721}, we simultaneously fitted 23 high-resolution spectra of $^{12}$CH$_4$ and mixtures of $^{12}$CH$_4$ in air, recorded at different pressure-temperature combinations between 130 and 296 K. These data were recorded using the Bruker IFS 125 HR Fourier transform spectrometer at the Jet Propulsion Laboratory together with two coolable sample cells\footnote{K. Sung, A.W. Mantz, M.A.H. Smith, L.R. Brown, T.J. Crawford, V.M. Devi, D.C. Benner. J.Mol. Spectrosc. 162 (2010)124-134.}$^{,}$\footnote{A.W. Mantz, K. Sung, T.J. Crawford, L.R. Brown, M.A.H. Smith, V.M. Devi, D.C. Benner, J. Mol. Spectrosc. 304 (2014) 12-24.}. By applying a set of constraints to the parameters of severely blended transitions, a self-consistent set of broadening, shift and line mixing parameters for CH$_4$-CH$_4$ and CH$_4$-air collisions were retrieved. A quadratic speed dependence parameter common for all transitions in each Q(J) manifold was determined. In addition to line shape parameters, line positions and line intensities were also measured for over 100 transitions in the whole Q branch region (5996.5 - 6007.7 cm$^{-1}$). Comparisons of present results with values in HITRAN2012 will be provided\footnote{Research described in this paper are performed at the College of William and Mary, Jet Propulsion Laboratory, California Institute of Technology, Connecticut College, and NASA Langley Research Center under contracts and cooperative agreements with the National Aeronautics and Space Administration.}
Issue Date:2016-06-22
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper/Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2017-01-26

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