Characterization Of The H2o+co2 Continuum Absorption Within The Infrared Transparency Windows For Planetary Applications

Fleurbaey, Helene

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https://hdl.handle.net/2142/116713 Copy

Description

Title

Characterization Of The H2o+co2 Continuum Absorption Within The Infrared Transparency Windows For Planetary Applications

Author(s)

Fleurbaey, Helene

Contributor(s)

• Campargue, Alain
• Fakhardji, Wissam
• Hartmann, Jean-Michel
• Mondelain, Didier

Issue Date

2022-06-24

Keyword(s)

Lineshapes, collisional effects

Abstract

Accurate knowledge of the absorption by a gas mixture of \chem{CO_2} and water is crucial for planetary sciences, as it allows for better modeling the atmospheres of rocky planets, e.g. improving our understanding of the early climate of Mars or why Venus and the Earth have evolved so differently. In addition to local monomer lines proportional to the density of each species, the absorption spectrum of such a gas mixture includes binary absorption features varying smoothly with frequency: self-continuum absorption proportional to the squared density, and ``crossed'' absorption involving both species and scaling as the density product $\rho_{CO_{2}}\rho_{H_{2}O}$. We used highly sensitive spectroscopy techniques (CRDS and OFCEAS) to measure the absorption by H$_{2}$O+CO$_{2}$ gas mixtures in several spectral regions situated in transparency windows where the monomer absorption of both species is weak (1.5-1.53 $\mu$m, 1.68-1.75 $\mu$m, 2.06 $\mu$m, 2.2-2.35 $\mu$m, 3.5 $\mu$m). For both water and \chem{CO_2}, the monomer lines, modeled using HITRAN parameters, and the self-continuum absorption, calculated from literature values or measured in dedicated experiments, were subtracted from the measured absorption. The obtained ``crossed absorption'' coefficients are compared to the only available empirical model based on far wings of line shape profiles scaled by $\chi$-factors.\footnote{Fleurbaey H, Campargue A, Carreira Mendès Da Silva Y, Grilli R, Kassi S, Mondelain D. J Quant Spectrosc Radiat Transf 108119 (2022)} An additional absorption peak centered at about 6000 \wn was attributed to a collision-induced simultaneous transition of \chem{H_2O} and \chem{CO_2} through the \nub{1} and \nub{3} modes, respectively. The assignment was confirmed using humidified \chem{^{13}CO_2}, where a similar band was observed about 68 \wn away corresponding to the isotopic spectral shift of the \nub{3} band of \chem{CO_2}. Classical molecular dynamics simulations (CMDS) of the considered collision-induced absorption were conducted and are found in good agreement with the experiment.\footnote{Fleurbaey H, Mondelain D, Fakhardji W, Hartmann J-M, Campargue A. Submitted to J Quant Spectrosc Radiat Transf}

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116713

DOI

https://doi.org/10.15278/isms.2022.FE06

Copyright and License Information

Copyright 2022 held by the authors

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