title: Global analysis of the high temperature infrared emission spectrum of (12)CH4 in the dyad (ν2/ν4) region.
abstract: We report new assignments of vibration-rotation line positions of methane ((12)CH4) in the so-called dyad (ν2/ν4) region (1100-1500 cm(-1)), and the resulting update of the vibration-rotation effective model of methane, previously reported by Nikitin et al. [Phys. Chem. Chem. Phys. 15, 10071 (2013)], up to and including the tetradecad. High resolution (0.01 cm(-1)) emission spectra of methane have been recorded up to about 1400 K using the high-enthalpy source developed at Institut de Physique de Rennes associated with the Fourier transform spectrometer of the SOLEIL synchrotron facility (AILES beamline). Analysis of these spectra allowed extending rotational assignments in the well-known cold band (dyad-ground state (GS)) and related hot bands in the pentad-dyad system (3000 cm(-1)) up to Jmax = 30 and 29, respectively. In addition, 8512 new transitions belonging to the octad-pentad (up to J = 28) and tetradecad-octad (up to J = 21) hot band systems were successfully identified. As a result, the MeCaSDa database of methane was significantly improved. The line positions assigned in this work, together with the information available in the literature, were fitted using 1096 effective parameters with a dimensionless standard deviation σ = 2.09. The root mean square deviations dRMS are 3.60 × 10(-3) cm(-1) for dyad-GS cold band, 4.47 ×10(-3) cm(-1) for the pentad-dyad, 5.43 × 10(-3) cm(-1) for the octad-pentad, and 4.70 × 10(-3) cm(-1) for the tetradecad-octad hot bands. The resulting new line list will contribute to improve opacity and radiative transfer models for hot atmospheres, such as those of hot-Jupiter type exoplanets.
authors.affiliation: Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne Franche-Comté, 9 Avenue A. Savary, BP 47870, 21078 Dijon Cedex, France.
authors.forename: Badr
authors.initials: B
authors.lastname: Amyay
authors.affiliation: Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne Franche-Comté, 9 Avenue A. Savary, BP 47870, 21078 Dijon Cedex, France.
authors.forename: Maud
authors.initials: M
authors.lastname: Louviot
authors.affiliation: Ligne AILES, Synchrotron SOLEIL, L'Orme des Merisiers, F-91192 Gif-sur-Yvette, France and Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Pirali
authors.affiliation: Institut de Physique de Rennes, UMR 6251, Campus de Beaulieu, Université de Rennes 1/CNRS, F-35042 Rennes Cedex, France.
authors.forename: Robert
authors.initials: R
authors.lastname: Georges
authors.affiliation: Service de Chimie Quantique et Photophysique, C.P. 160/09, Université Libre de Bruxelles, 50 Avenue F. D. Roosevelt, B-1050 Brussels, Belgium.
authors.forename: Jean
authors.initials: J
authors.lastname: Vander Auwera
authors.affiliation: Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne Franche-Comté, 9 Avenue A. Savary, BP 47870, 21078 Dijon Cedex, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Boudon