M/F PhD student to develop a chemical scheme to model the reactivity of heteroatomic gases (CHONS+P) at high temperatures, with application to exoplanet atmospheres
- Créteil, Val-de-Marne
- CDD
- Temps-plein
- The Laboratoire Réactions et Génie des Procédés (LRGP) is a joint research unit of the CNRS and the Université de Lorraine. It is located in Nancy, France's second-largest student city. It is mainly located in the city center, on the premises of the Ecole Nationale Supérieure des Industries Chimiques de Nancy (ENSIC). The research laboratory is one of the leading chemical and process engineering laboratories in France and worldwide. The PhD candidate will work in the radical kinetics group, which has internationally recognized expertise in combustion kinetics, both on the experimental and modeling side. Existing experimental setups to study these phenomena include shock tube, laminar flame and jet reactor experiments. Numerical tools include Gaussian16, Chemkin Pro, COSMO-RS and similar codes.- The Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) is a joint research unit of the CNRS, Université Paris-Est Créteil and Université de Paris. It is part of the Observatoire des Sciences de l'Univers EFLUVE and the Fédération de Recherche IPSL. It is located in Créteil, a major student city in the Paris region. The research laboratory is an international leader in atmospheric modeling. Its main mission is to improve our knowledge of the functioning of the Earth's and planetary atmospheres, in order to understand their past evolution and predict their future trajectories. The PhD candidate will join the Exobiology and Astrochemistry group, whose main objectives are the search for molecular structures and the study of the various physico-chemical processes governing the chemical evolution of various astrophysical objects (exoplanets, comets, Mars, Titan...). They are internationally recognized as world-class experts in the field of planetary atmospheres, both from a modeling and experimental point of view. They are heavily involved in the analysis of observational data from ground-based facilities and space missions.
This project will also be part of the ANR JCJC "EXACT" project led by Dr Olivia Venot and involving collaboration with the LRGP.
We offer: multidisciplinary training and training using state-of-the-art research equipment, participation in national and international schools, conferences and workshops. The doctoral student will also follow high-level training courses offered by the Doctoral School.Since the arrival of the first JWST data in summer 2022, the Astrophysics and Astronomy community has been able to make a huge leap forward in characterizing the atmospheres of exoplanets. For the first time, a sulfur species, sulfur dioxide (SO2), has been detected in the atmosphere of hot exoplanets (Tsai et al. Nature, 2023; Dyrek et al. Nature, 2023). Understanding this discovery was only possible through the use of atmospheric kinetic models to interpret observational data. Indeed, classical thermochemical equilibrium models do not predict the presence of SO2 under such temperature and pressure conditions. By contrast, "thermo-photochemical" (i.e. kinetic) models, which take into account chemical disequilibrium processes (photochemistry and transport), are able to reproduce the observed SO2 abundances: sulfur dioxide is produced through a reaction process initiated by photochemistry (dissociation of a species by stellar photons). To function, these kinetic models rely on chemical schemes (hundreds of reactions and associated velocities) to describe the chemical processes taking place in atmospheres. The reliability of these schemes is therefore crucial to our understanding of (exo-)planetary worlds.
In this context, a solid interdisciplinary collaboration, unique in the world, between Olivia Venot (LISA), expert in atmospheric modeling of exoplanets, and Baptiste Sirjean (LRGP), expert in combustion chemistry, has already enabled the development of CHON (Carbon, Hydrogen, Oxygen, Nitrogen) chemical schemes adapted to the extreme conditions found in hot exoplanets (Veillet, Venot, Sirjean et al. 2024). The schemes developed in this collaboration are extremely robust, thanks to an extensive experimental validation process (reproduction of combustion experiments). A scheme containing Sulfur (S) is currently being finalized within the framework of ANR EXACT (PI: Venot) and will be published by summer 2024.
After adding Sulfur, it is essential to add Phosphorus (P) to the chemical scheme. Phosphine (PH3) has been detected in some giant planets of the Solar System (Jupiter, Saturn) for over 30 years (Beer et al. 1979; Drossart et al. 1982; Fletcher et al. 2009), and studies (Wang et al. 2017; Baudino et al. 2017) have shown that this species could also be detectable in the atmospheres of hot exoplanets.
From the point of view of thermal processes, the extension of the CHONS scheme to phosphorus compounds is also of key importance in combustion applications. P-compounds are present in a large number of chemical products, and can be found as flame retardants in materials. The combustion of these compounds, whether during fire accidents or waste incineration, requires understanding and predicting the formation of the pollutants emitted. Today, the combustion pattern of phosphorus compounds remains poorly described in relation to CHON systems. Moreover, almost no work has been done on the chemical interactions between P and CHON compounds at high temperatures. Consequently, the development and validation of a CHONSP system for high-temperature combustion would have a major impact on the combustion community and industry.Objectives: During the first part of the thesis, the student will develop the CHONS+P scheme, starting from our most recent CHONS scheme (Veillet+in prep.). This will require both bibliographical work, in order to gather a database of experimental data on combustion kinetics on phosphorus species, and also for the missing reactions (S-P coupling, between radicals, ...) a major theoretical calculation work (ab-initio), of which the LRGP has the expertise. The kinetic model extended to P and including its coupling to the chemistry of S, N and C will be compared with the experimental database to ensure the validity of the scheme over a wide range of temperatures, compositions and pressures. During the second part of the PhD, the student will apply the newly developed scheme to the study of planetary atmospheres, using a kinetic model. The aim will be to model the molecular composition of atmospheres, taking into account chemical reactions, photodissociations, mixing and molecular diffusion. These model results will be compared with JWST data and used to prepare for observations by the Ariel telescope. This work will be carried out at LISA with experts in modeling (exo)planetary atmospheres. The PhD student will be co-supervised by Olivia Venot at LISA and Baptiste Sirjean at LRGP.Activities:
The main tasks of the thesis student will be as follows:
- Bibliographic work
- Lead the development and validation of CHONS+P kinetic models.
- Develop methods, using computational chemistry, for calculating and tabulating gas-phase rate constants.
- Adapt the existing chemical kinetics code to the newly developed scheme.
- Develop atmospheric models for various exoplanets and study their chemical composition.
- Evaluate the detectability of new P species on synthetic spectra.
- Write scientific articles and thesis manuscripts, and disseminate research results at conferences and seminars.Skills:
We are looking for a highly motivated student (M/W) who will be fully involved in a challenging interdisciplinary project linking the fields of combustion and astrophysics. The PhD candidate will have dual expertise in both chemical scheme development and atmospheric modeling. This unique training will guarantee an unprecedented interdisciplinary profile. Desired profile: i) Either a Master's or engineering degree in organic chemistry, chemical engineering, chemistry, physics or related fields with a strong interest in astrophysics, in particular exoplanets, or a Master's degree in astrophysics, with a solid background in chemistry, chemical engineering; ii) Good knowledge of English to work in an international environment; iii) Good programming skills.RequirementsResearch Field Astronomy Education Level Master Degree or equivalentResearch Field Astronomy Education Level Master Degree or equivalentResearch Field Astronomy Education Level Master Degree or equivalentLanguages FRENCH Level BasicResearch Field Astronomy Years of Research Experience NoneResearch Field Astronomy » Astrophysics Years of Research Experience NoneResearch Field Astronomy » Cosmology Years of Research Experience NoneAdditional InformationWebsite for additional job detailsWork Location(s)Number of offers available 1 Company/Institute Laboratoire inter-universitaire des systèmes atmosphèriques Country France City CRETEIL GeofieldWhere to apply WebsiteContact CityCRETEIL WebsiteSTATUS: EXPIRED
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