15min:

V. BOUDON, T. GABARD, Institut Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France; O. PIRALI, P. ROY, J.-B. BRUBACH, Ligne AILES -- Synchrotron SOLEIL, L'Orme des Merisiers, F-91192 Gif-sur-Yvette, France; L. MANCERON, Laboratoire de Dynamique, Interactions et Réactivité, UMR 7075 -- Université Pierre et Marie Curie -- CNRS, Case 49, 4 Place Jussieu, F-75252, Paris Cedex, France; J. VANDER AUWERA, Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles, CP 160/09, 50 avenue F.D. Roosevelt, B-1050 Brussels, Belgium.

Recently, we recorded the THz centrifugal distortion-induced spectrum of methane using synchrotron radiation at the SOLEIL facility. Intensities of pure rotation lines of CH₄ were precisely measured, from which the induced dipole moment of this weak spectrum, of great interest for planetology, was accurately inferred. This study should in particular help to measure methane concentrations in Titan's atmosphere.\footnoteA. Coustenis, R. K. Achterberg, B. J. Conrath et al.\/ , Icarus\/ 189, 35--62 (2007).

Here, we continue the work by presenting spectra of CH₄/N₂ mixtures, again recorded with a 150 m optical path in a White cell and a Bruker IFS 125 HR FTIR spectrometer at the AILES beamline of SOLEIL. More precisely, the spectra were recorded with 5 % of CH₄ in N₂ at various total pressures ( ca.\/ 100, 200, 400, 600 and 800 mbar). These spectra will allow to measure collisional broadening and shift coefficients, as well as line-mixing parameters, with N₂ as a perturber (like in Titan's atmosphere).