Influence of chemical and morphological properties on the mid-infrared refractive indices of Titan aerosol analogs
Abstract
The intrinsic properties of aerosols in Titan's atmosphere are one of the main sources of uncertainty when interpreting and understanding observations of its surface and atmosphere. The optical properties of the solid material have been recovered for both of Titan's aerosols using remote-sensing observations and laboratory analogs. Significant differences are observed in the refractive indices reported in the literature. For laboratory-generated solid analogs, these discrepancies in the refractive indices can originate from the different experimental factors influencing the morphological and chemical properties of solid samples, for example the energy distribution, gas flow rate, and/or gas temperature. In this study, we report new refractive indices, n and k, in the mid-infrared spectral range (2-20 µm) determined on Titan aerosol analogs with different morphological and chemical properties. We compare in detail the differences in optical properties of thin films, commonly used for refractive index measurements, and compressed pellets of quasispherical powders. Using transmission spectroscopy and reflection Mueller ellipsometry, we find that compressed powders are more absorbent than their film equivalent, with increased signature strengths of (hetero-)aromatic and amine features in agreement with a higher nitrogen-to-carbon ratio compared to the film analogs. Finally, we observe that the reflective power of these pellet analogs is not only affected by the refractive index (n) but also significantly by the inter-grain porosity.
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BibTeX
@article{perrin2026influence,
title = {{Influence of chemical and morphological properties on the mid-infrared refractive indices of Titan aerosol analogs}},
author = {Zoé Perrin and Thomas Drant and Enrique Garcia Caurel and Jean‐blaise Brubach and Nathalie Ruscassier and Thomas Gautier and Ella Sciamma-O’brien and Ludovic Vettier and Audrey Chatain and Olivier Guaitella and Nathalie Carrasco},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202554328},
url = {https://hal.science/hal-05769527v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Influence of chemical and morphological properties on the mid-infrared refractive indices of Titan aerosol analogs
AU - Zoé Perrin
AU - Thomas Drant
AU - Enrique Garcia Caurel
AU - Jean‐blaise Brubach
AU - Nathalie Ruscassier
AU - Thomas Gautier
AU - Ella Sciamma-O’brien
AU - Ludovic Vettier
AU - Audrey Chatain
AU - Olivier Guaitella
AU - Nathalie Carrasco
PY - 2026
DA - 2026/09/29
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202554328
UR - https://hal.science/hal-05769527v1
AB - The intrinsic properties of aerosols in Titan's atmosphere are one of the main sources of uncertainty when interpreting and understanding observations of its surface and atmosphere. The optical properties of the solid material have been recovered for both of Titan's aerosols using remote-sensing observations and laboratory analogs. Significant differences are observed in the refractive indices reported in the literature. For laboratory-generated solid analogs, these discrepancies in the refractive indices can originate from the different experimental factors influencing the morphological and chemical properties of solid samples, for example the energy distribution, gas flow rate, and/or gas temperature. In this study, we report new refractive indices, n and k, in the mid-infrared spectral range (2-20 µm) determined on Titan aerosol analogs with different morphological and chemical properties. We compare in detail the differences in optical properties of thin films, commonly used for refractive index measurements, and compressed pellets of quasispherical powders. Using transmission spectroscopy and reflection Mueller ellipsometry, we find that compressed powders are more absorbent than their film equivalent, with increased signature strengths of (hetero-)aromatic and amine features in agreement with a higher nitrogen-to-carbon ratio compared to the film analogs. Finally, we observe that the reflective power of these pellet analogs is not only affected by the refractive index (n) but also significantly by the inter-grain porosity.
SN - 0004-6361
SN - 1432-0746
ER -