Paramètres collisionnels de raies d'absorption infrarouge d'hydrocarbures : des basses jusqu'aux hautes températures.

Abstract

The aim of this work was the study of collisional parameters of hydrocarbon lines such as ethane, allene and methane, from low to high temperatures. The determination and the study require the precise knowledge of the spectral parameters of absorption lines, in particular the collisional broadening coefficients, on a wide range of temperature. In this context, we studied different gas mixture presenting an interest for the study of our atmosphere as well as that of Titan. First, to measure these parameters for temperature up to room temperature, we have conceived, developed and realized the set up of an “high temperature” absorption cell allowing spectroscopic studies of line profiles and collisional parameters of gaseous molecules between 300 and 750 K. With the help of this device and of low-temperature absorption cells developed previously in the Laboratory Lasers and Spectroscopies of the University of Namur, we measured the collisional broadening coefficients of infrared absorption lines of hydrocarbons as well as their temperature dependences. Nine gas mixtures have been studied : ethane (C2H6−O2, C2H6−air), allene (C3H4−C3H4, C3H4−N2, C3H4−O2, C3H4−air) and methane (CH4−N2, CH4−O2 et CH4−air). The spectra have been recorded in the Laboratory Lasers and Spectroscopies of the University of Namur, with the help of a diode-laser spectrometer and, in the Center of Microsystems and Photonics of the University of Strathclyde of Glasgow, with the help of a difference frequency generation (DFG) spectrometer. The spectral parameters have been deduced from individual fits of theoretical lineshape models on the experimental profiles of each line at each pressure and at each temperatures. Various theoretical models were used taking into account Doppler and collisional broadenings, but also fine effects as the Dicke narrowing and the speed dependence effect. A lot of these results are totally originals. However, as soon as it was possible we compared our results with the previous works.

Date of Award	21 Feb 2013
Original language	French
Awarding Institution	University of Namur
Supervisor	Muriel Lepere (Supervisor), Ghislain Blanquet (Jury), Stephane Lucas (President), D. Bermejo (Jury), Pierre Defrance (Jury) & Robert Gamache (Jury)