Étude par spectroscopie diode-laser de paramètres collisionnels de raies d'absorption infrarouge du méthane aux basses et hautes températures

Abstract

This work is dedicated to the study of the collisional parameters of methane infrared absorption lines from the low to the high temperatures. A precise knowledge of the spectral parameters and their evolutions with the temperature is required to determine the vertical profile of methane concentration in an atmosphere. The gas mixtures under studied (methane-nitrogen, methane-oxygen and methane-dry air) are relevant for the remote sensing of the Earth’s atmosphere, as well as the one of Titan.

The measurements have been realized using a high resolution two beam tunable diode-laser spectrometer. This tool allows to determine the collisional shift and broadening of lines in the ν₃ band of methane for temperatures between 120K and 600K. The collisional parameters have been deduced from individual fit of theoretical lineshape models on the experimental profiles at each partial pressure and each considered temperature. The theoretical models used are the profiles of Voigt, Rautian-Sobel’man, Galatry and a hard collision speed dependent model.

The major part of the results obtained in this thesis are totally originals. Therefore, the comparisons with literature have been complicated. However, they give the opportunity to study the temperature dependence of the considered parameters. The wide range of temperatures allows to study the evolution of the collisional shift and broadening coefficients with a high precision. This is very interesting since the temperature dependence of the collisional line shift parameter is not clearly established in the literature. The measurements realized in this work give the opportunity to compare the different models used in the scientific community.

Date of Award	16 Nov 2016
Original language	French
Awarding Institution	University of Namur
Sponsors	Fund for Research Training in Industry and Agriculture (FRIA)
Supervisor	Muriel Lepere (Supervisor), Laurent Houssiau (President), Miguel Dhyne (Jury), Marie-Renée DE BACKER - BARILLY (Jury) & M. Herman (Jury)