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PhD intrumental molecular spectroscopy (M/F)

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General information

Reference : UMR5588-DIDMON-001
Date of publication : Tuesday, October 01, 2019
Scientific Responsible name : Didier MONDELAIN
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 January 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

This thesis is funded in the frame of the ANR project COMPLEAT (COntinuum Measurements for PLanEtary ATmospheres) coordinated by our laboratory and involving two teams of the Laboratoire de Météorologie dynamique (LMD).
The aim of our project is to characterize by experiment and theory the absorption continua of H2O-CO2, CH4-CO2 and H2-CO2 gas mixture in support of numerical climate simulations of CO2-enriched planetary atmospheres. At present, these continua are mostly unknown.
The thesis will consist in applying ultra-sensitive laser techniques, and particularly cavity ring down spectroscopy (CRDS), to the measurement of the weak absorption continua of H2O+CO2 and H2+CO2 in the CO2 transparency windows near 3.5 µm, 2.3 µm, 1.75 µm and 1.5 µm. This is challenging as it shows up as a small variation of the baseline spectra when the studied gas is injected in the absorption cell. Cavity enhanced absorption spectroscopy techniques are particularly well suited in this context. The same methodology as in our previous works on the measurement of water vapor continua will be applied. A thermalized high finesse absorption cell will also be developed to determine the temperature dependence of these continua.
The H2O-CO2 continuum measured during the thesis will be implemented at LMD in a 3D-Global Climate Model, to understand the role of meteoritic impact events in generating episodic precipitation in ancient Mars.
The H2-CO2 and CH4-CO2 continua measured at LIPhy will allow quantifying the amount of CH4 and H2 required to warm early Mars through greenhouse effect. The same continua will be used at LMD to investigate the evolution and observability of planets at the magma ocean stage and to prepare future observations of exo-planets' atmospheres.

Work Context

The Laboratoire Interdisciplinaire de Physique (LIPhy) is a research unit (UMR 5588) depending on CNRS and University of Grenoble Alpes. The LIPhy is located at the Saint Martin d'Hères' campus on the east side of Grenoble. The laboratory has approximately 150 members including 66 researchers and professors, 32 engineers, technicians and administrative staff and 39 PhD students. The lab is structured in seven teams of various sizes, with a broad scope of interests. These different teams address scientific questions mainly in the fields of Optics, Complex matter, and Living matter. Our group, named LAME (Lasers Molécules et Environnement), is particularly involved in the development of high-sensitivity/high precision laser-based absorption spectroscopy techniques for atmospheric and planetology applications as well as for detection of trace gases. In particular, since about 20 years we exploit high finesse optical cavities to increase the interaction of light with a (gaseous) sample to achieve effective absorption path lengths up to hundreds of km.

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