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Abstract
Laboratory spectroscopic data is essential for the modeling of hot exoplanet atmospheres, since molecules such as methane, a major component of hot-Jupiter-type exoplanet atmospheres, have a complex vibrational energy structure that makes computational predictions difficult at high temperatures for ro-vibrational transitions involving highly excited vibrational sates. To better inform line lists used in radiative transfer modeling, the ro-vibrational spectrum of methane has been recorded in the tetradecad region between 1.7 and 1.65 μm (5880–6060 cm−1) through non-local thermodynamic equilibrium (non-LTE) cavity ringdown spectroscopy (CRDS). Non-LTE conditions, characterized by a low rotational temperature (~39 K) and a high vibrational temperature (up to 1130 K), have been obtained by hypersonic expansion of a pre-heated mixture of argon and methane in a contoured Laval nozzle. The high vibrational temperature increases the intensity of new hot bands, while the very low rotational temperature greatly simplifies their rotational structure, thus facilitating their identification. A close comparison of the recorded CRDS data to the TheoReTS database reveals both inefficient vibrational relaxation between polyads and efficient vibrational relaxation between vibrational states forming a polyad. These effects result in an overpopulation of the lowest vibrational energy level of each polyad, an effect not widely currently incorporated in non-LTE radiative transfer models. A series of new hot band transitions originating from the pentad and octad polyads were assigned and are provided as a line list for use in future databases.
Original language | English |
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Article number | 115421 |
Pages (from-to) | 115421 |
Journal | Icarus |
Volume | 394 |
DOIs | |
Publication status | Published - Apr 2023 |
Keywords
- High-temperature database
- Hot jupiters
- Hypersonic flow
- Infrared spectroscopy of methane
- Non-LTE spectroscopy
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Dive into the research topics of 'Non-LTE spectroscopy of the tetradecad region of methane recorded in a hypersonic flow'. Together they form a unique fingerprint.Projects
- 1 Finished
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Experimental and theoretical study of line shape parameters and their temperature dependence for infrared absorption lines of molecules with atmospheric interest
Vispoel, B. (PI) & Lepere, M. (Supervisor)
1/10/21 → 30/09/24
Project: Research