, Physique et Chimie du Milieu Interstellaire" (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES

S. Thomas, Hearne is warmly thanked for his careful reading of the manuscript

, Michaël Rey for stimulating helpful discussion regarding our recorded spectrum of methane

G. Tinetti, T. Encrenaz, and A. Coustenis, Spectroscopy of Planetary Atmospheres in Our Galaxy, Astron Astrophys Rev, vol.21, issue.1, 2013.
URL : https://hal.archives-ouvertes.fr/hal-02515925

M. R. Swain, G. Vasisht, and G. Tinetti, The Presence of Methane in the Atmosphere of an Extrasolar Planet, Nature, vol.452, issue.7185, pp.329-331, 2008.

P. F. Bernath, Molecular Opacities for Exoplanets, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, p.372, 2014.

M. Mayor, D. Queloz, and . Jupiter, Mass Companion to a Solar-Type Star, Nature, vol.378, issue.6555, pp.355-359, 1995.

M. R. Swain, G. Tinetti, G. Vasisht, P. Deroo, C. Griffith et al., Methane, and Carbon Dioxide Present in the Dayside Spectrum of the Exoplanet HD 209458b. Nippon rinsho, Japanese journal of clinical medicine, vol.704, issue.2, pp.1616-1621, 2009.

M. Ghysels, S. Vasilchenko, D. Mondelain, S. Béguier, S. Kassi et al., Laser Absorption Spectroscopy of Methane at 1000 K near 1.7 ?m: A Validation Test of the Spectroscopic Databases, Journal of Quantitative Spectroscopy and Radiative, vol.215, pp.59-70, 2018.
URL : https://hal.archives-ouvertes.fr/hal-01908297

E. Czinki, T. Furtenbacher, A. G. Császár, A. K. Eckhardt, G. Mellau et al., The 1943 K Emission Spectrum of H216O between 6600 and 7050 Cm ? 1, Journal of Quantitative Spectroscopy and Radiative, vol.206, pp.46-54, 2018.

J. D. Anderson, Gasdynamic Lasers: An Introduction

E. A. Michael, C. J. Keoshian, D. R. Wagner, S. K. Anderson, and R. J. Saykally, Infrared Water Recombination Lasers, Chemical Physics Letters, vol.338, issue.4-6, pp.253-259, 2001.

E. A. Michael, C. J. Keoshian, S. K. Anderson, and R. J. Saykally, Rotational Transitions in Excited Vibrational States of D2O, Journal of Molecular Spectroscopy, vol.208, issue.2, pp.219-223, 2001.

D. Zhao, K. D. Doney, and H. Linnartz, High-Resolution Infrared Spectra of Vibrationally Excited HC4H in a Supersonic Hydrocarbon Plasma Jet, Journal of Molecular Spectroscopy, vol.296, pp.1-8, 2014.

B. Courrèges-lacoste, G. Sprengers, J. P. Bulthuis, J. Stolte, S. Motylewski et al., Vibrationally Excited State Spectroscopy of Radicals in a Supersonic Plasma, Chemical Physics Letters, vol.335, issue.3-4, pp.17-20, 2001.

J. Oomens and J. Reuss, Hot Band Spectroscopy of Acetylene after Intermolecular Vibrational Energy Transfer from Ethylene, Journal of Molecular Spectroscopy, vol.173, issue.1, pp.14-24, 1995.

J. Dudek, K. Puczka, T. Urba?czyk, and J. Koperski, High-Temperature Continuous Molecular Beam Source for Aggressive Elements: An Example of Zinc, Review of Scientific Instruments, vol.90, issue.11, p.115109, 2019.

M. Louviot, N. Suas-david, V. Boudon, R. Georges, M. Rey et al., Strong Thermal Nonequilibrium in Hypersonic CO and CH4 Probed by CRDS, J. Chem. Phys, vol.2015, issue.21, p.214305
URL : https://hal.archives-ouvertes.fr/hal-01234231

M. Hepp, F. Herregodts, and M. Herman, Fourier Transform Infrared Jet Spectroscopy Using a Heated Slit Source, Chemical Physics Letters, vol.294, issue.6, pp.528-532, 1998.

D. K. Bronnikov, D. V. Kalinin, V. D. Rusanov, Y. G. Filimonov, Y. G. Selivanov et al., Journal of Quantitative Spectroscopy and Radiative Transfer, vol.60, issue.6, pp.210-210, 1998.

P. Wallraff, K. M. Yamada, and G. Winnewisser, Determination of the Vibrational Temperature of OCS in a Supersonic Free Jet, Journal of Molecular Spectroscopy, vol.126, issue.1, pp.90078-90084, 1987.

M. Rey, A. V. Nikitin, Y. L. Babikov, and V. G. Tyuterev, TheoReTS -An Information System for Theoretical Spectra Based on Variational Predictions from Molecular Potential Energy and Dipole Moment Surfaces, Journal of Molecular Spectroscopy, vol.327, pp.138-158, 2016.

R. Ferrer, A. Barzakh, B. Bastin, R. Beerwerth, M. Block et al., Towards High-Resolution Laser Ionization Spectroscopy of the Heaviest Elements in Supersonic Gas Jet Expansion, Nature Commun, vol.8, 2017.
URL : https://hal.archives-ouvertes.fr/hal-01554412

R. Georges, J. Thiévin, A. Benidar, S. Carles, B. Amyay et al., High Enthalpy Source Dedicated to Quantitative Infrared Emission Spectroscopy of Gas Flows at Elevated Temperatures, Review of Scientific Instruments, vol.90, issue.9, p.93103, 2019.
URL : https://hal.archives-ouvertes.fr/hal-02309943

J. Thiévin, R. Georges, S. Carles, A. Benidar, B. Rowe et al., High-Temperature Emission Spectroscopy of Methane, Journal of Quantitative Spectroscopy and Radiative Transfer, vol.109, issue.11, pp.2027-2036, 2008.

N. Suas-david, V. Kulkarni, A. Benidar, S. Kassi, and R. Georges, Line Shape in a Free-Jet Hypersonic Expansion Investigated by Cavity Ring-down Spectroscopy and Computational Fluid Dynamics, Chemical Physics Letters, vol.659, pp.209-215, 2016.
URL : https://hal.archives-ouvertes.fr/hal-01358139

A. H. Shapiro, . Compressible, and . Flow, , p.663

H. Pauly, Atom, Molecule, and Cluster Beams I: Basic Theory, Production and Detection of Thermal Energy Beams

, Springer Series on Atomic, Optical, and Plasma Physics, Atom, Molecule, and Cluster Beams, 2000.

A. V. Nikitin, V. Boudon, C. Wenger, S. Albert, L. R. Brown et al., High Resolution Spectroscopy and the First Global Analysis of the Tetradecad Region of Methane 12CH4, Phys. Chem. Chem. Phys, vol.2013, issue.25, p.10071

M. Rey, A. V. Nikitin, B. Bézard, P. Rannou, A. Coustenis et al., New Accurate Theoretical Line Lists of 12CH4 and 13CH4 in the 0-13400 Cm?1 Range: Application to the Modeling of Methane Absorption in Titan's Atmosphere, Icarus, vol.303, pp.114-130, 2018.
URL : https://hal.archives-ouvertes.fr/hal-01918917

M. Rey, A. V. Nikitin, V. G. Tyuterev, . Theoretical, . Methane et al., ApJ, vol.789, issue.1, 2000.

M. Rey, A. V. Nikitin, Y. L. Babikov, and V. G. Tyuterev, TheoReTS -An Information System for Theoretical Spectra Based on Variational Predictions from Molecular Potential Energy and Dipole Moment Surfaces, Journal of Molecular Spectroscopy, vol.327, pp.138-158, 2016.

S. N. Yurchenko and J. Tennyson, ExoMol Line Lists -IV. The Rotation-Vibration Spectrum of Methane up to 1500 K, Mon Not R Astron Soc, vol.440, issue.2, pp.1649-1661, 2014.

J. Tennyson, S. N. Yurchenko, A. F. Al-refaie, E. J. Barton, K. L. Chubb et al., The ExoMol Database: Molecular Line Lists for Exoplanet and Other Hot Atmospheres, Journal of Molecular Spectroscopy, vol.327, pp.73-94, 2016.

L. S. Rothman, I. E. Gordon, R. J. Barber, H. Dothe, R. R. Gamache et al., HITEMP, the High-Temperature Molecular Spectroscopic Database, Journal of Quantitative Spectroscopy and Radiative Transfer, issue.15, pp.2139-2150, 2010.

Y. A. Ba, C. Wenger, R. Surleau, V. Boudon, M. Rotger et al., MeCaSDa and ECaSDa: Methane and Ethene Calculated Spectroscopic Databases for the Virtual Atomic and Molecular Data Centre, Journal of Quantitative Spectroscopy and Radiative Transfer, vol.130, pp.62-68, 2013.

S. Kassi, B. Gao, D. Romanini, and A. Campargue, The Near-Infrared (1.30-1.70 ?m) Absorption Spectrum of Methane down to 77 K, Physical Chemistry Chemical Physics, vol.10, issue.30, p.4410, 2008.
URL : https://hal.archives-ouvertes.fr/hal-01096835

A. L. Laraia, R. R. Gamache, J. Lamouroux, I. E. Gordon, and L. S. Rothman, Total Internal Partition Sums to Support Planetary Remote Sensing, Icarus, vol.215, issue.1, pp.391-400, 2011.

L. S. Rothman, I. E. Gordon, Y. Babikov, A. Barbe, D. Benner et al., The HITRAN2012 Molecular Spectroscopic Database, Journal of Quantitative Spectroscopy and Radiative Transfer, vol.130, pp.4-50, 2013.
URL : https://hal.archives-ouvertes.fr/hal-01005779

J. C. Hilico, G. S. Baronov, D. K. Bronnikov, S. A. Gavrikov, I. I. Nikolaev et al., High-Resolution Spectroscopy of (Pentad-Dyad) and (Octad-Pentad) Hot Bands of Methane in a Supersonic Jet, Journal of Molecular Spectroscopy, vol.161, issue.2, pp.435-444, 1993.