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Non-LTE spectroscopy of methane in hypersonic flow for the characterisation of hot Jupiters

Abstract : A state-of-art experimental system, SMAUG has been developed to produce unprecedented infrared spectroscopic reference data that will help planetologists to detect new molecules and reconstruct the vertical structure of the atmosphere of exoplanets. A specially designed small dimension Laval nozzle connected to a compact high enthalpy source equipped with cavity ringdown spectroscopy (CRDS) is used to produce high-resolution infrared spectra of polyatomic molecules in the 1.67 μm region. The experimental setup can operate according to two complementary working regimes to interpret the complex pattern of highly-excited vibrational states. The hypersonic jet delivers a strong out-ofequilibrium state, in which vibrationally hot and rotationally cold high-resolution infrared spectra was recorded. The obtained non-Local Thermodynamic Equilibrium (LTE) spectrum of methane provides accurate positions of the upper energy levels to refine the potential energy surface on which ab initio variational theoretical models are based. A post-shock CRDS technique results in conditions close to LTE which allow the analysis of a more complex rotational structure and complete information on the excited hot vibrational energy levels. Parallelly, through a collaboration, a transformed Pocket Rocket plasma source was developed and implanted into SMAUG to investigate an alternative heating system with more elevated vibrational energy levels. This work was done in the frame of the e-PYTHEAS project that focuses on hightemperature spectroscopy of small hydrocarbons.
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https://tel.archives-ouvertes.fr/tel-03341145
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Submitted on : Friday, September 10, 2021 - 3:11:09 PM
Last modification on : Sunday, September 12, 2021 - 3:10:29 AM

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  • HAL Id : tel-03341145, version 1

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Eszter Dudás. Non-LTE spectroscopy of methane in hypersonic flow for the characterisation of hot Jupiters. Physics [physics]. Université Rennes 1, 2021. English. ⟨NNT : 2021REN1S015⟩. ⟨tel-03341145⟩

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