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Title: Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins

Abstract

In this experimental study we investigate the role of atmospheric CO{sub 2} on the optical properties of organic photochemical aerosols. To this end, we add CO{sub 2} to a N{sub 2}:CH{sub 4} gas mixture used in a plasma typically used for Titan studies. We produce organic thin films (tholins) in plasmas where the CO{sub 2}/CH{sub 4} ratio is increased from 0 to 4. We measure these films via spectrometric ellipsometry and apply a Tauc–Lorentz model, used for optically transparent materials, to obtain the thickness of the thin film, its optical band gap, and the refractive indices in the UV–visible (270–600 nm). All samples present a significant absorption band in the UV. According to the Tauc–Lorentz model, as the CO{sub 2}/CH{sub 4} ratio is quadrupled, the position of the UV band is shifted from ∼177 nm to 264 nm while its strength is quadrupled. Consequently, we infer that oxidized organic aerosols absorb more efficiently at longer UV wavelengths than reduced aerosols. Our laboratory wavelength-tabulated UV–vis refractive indices provide new constraints to atmospheric models of the early Earth and Earth-like exoplanets including photochemical hazes formed under increasingly oxidizing conditions.

Authors:
; ;  [1];  [2];  [3]
  1. LATMOS, Université Versailles St Quentin, UPMC Université Paris 06, CNRS, 11 blvd d’Alembert, F-78280 Guyancourt (France)
  2. LCP-A2MC, Institut Jean Barriol, Université de Lorraine, Metz (France)
  3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
Publication Date:
OSTI Identifier:
22654375
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 848; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; AEROSOLS; CARBON DIOXIDE; CONCENTRATION RATIO; ELLIPSOMETRY; METHANE; PHOTOCHEMISTRY; PLANETS; PLASMA; REFRACTIVE INDEX; SATELLITE ATMOSPHERES; SATELLITES; THIN FILMS; WAVELENGTHS

Citation Formats

Gavilan, Lisseth, Carrasco, Nathalie, Vettier, Ludovic, Broch, Laurent, and Fleury, Benjamin, E-mail: lisseth.gavilan@latmos.ipsl.fr. Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA8CC4.
Gavilan, Lisseth, Carrasco, Nathalie, Vettier, Ludovic, Broch, Laurent, & Fleury, Benjamin, E-mail: lisseth.gavilan@latmos.ipsl.fr. Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins. United States. doi:10.3847/2041-8213/AA8CC4.
Gavilan, Lisseth, Carrasco, Nathalie, Vettier, Ludovic, Broch, Laurent, and Fleury, Benjamin, E-mail: lisseth.gavilan@latmos.ipsl.fr. Tue . "Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins". United States. doi:10.3847/2041-8213/AA8CC4.
@article{osti_22654375,
title = {Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins},
author = {Gavilan, Lisseth and Carrasco, Nathalie and Vettier, Ludovic and Broch, Laurent and Fleury, Benjamin, E-mail: lisseth.gavilan@latmos.ipsl.fr},
abstractNote = {In this experimental study we investigate the role of atmospheric CO{sub 2} on the optical properties of organic photochemical aerosols. To this end, we add CO{sub 2} to a N{sub 2}:CH{sub 4} gas mixture used in a plasma typically used for Titan studies. We produce organic thin films (tholins) in plasmas where the CO{sub 2}/CH{sub 4} ratio is increased from 0 to 4. We measure these films via spectrometric ellipsometry and apply a Tauc–Lorentz model, used for optically transparent materials, to obtain the thickness of the thin film, its optical band gap, and the refractive indices in the UV–visible (270–600 nm). All samples present a significant absorption band in the UV. According to the Tauc–Lorentz model, as the CO{sub 2}/CH{sub 4} ratio is quadrupled, the position of the UV band is shifted from ∼177 nm to 264 nm while its strength is quadrupled. Consequently, we infer that oxidized organic aerosols absorb more efficiently at longer UV wavelengths than reduced aerosols. Our laboratory wavelength-tabulated UV–vis refractive indices provide new constraints to atmospheric models of the early Earth and Earth-like exoplanets including photochemical hazes formed under increasingly oxidizing conditions.},
doi = {10.3847/2041-8213/AA8CC4},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 848,
place = {United States},
year = {Tue Oct 10 00:00:00 EDT 2017},
month = {Tue Oct 10 00:00:00 EDT 2017}
}