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A Large-scale Approach to Modeling Molecular Biosignatures: The Diatomics

Cross, Thomas M.; Benoit, David M.; Pignatari, Marco; Gibson, Brad K.


Thomas M. Cross

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Dr David Benoit
Senior Lecturer in Molecular Physics and Astrochemistry

Marco Pignatari

Brad K. Gibson


This work presents the first steps to modeling synthetic rovibrational spectra for all molecules of astrophysical interest using a new approach implemented in the Prometheus code. The goal is to create a new comprehensive source of first-principles molecular spectra, thus bridging the gap for missing data to help drive future high-resolution studies. Our primary application domain is for molecules identified as signatures of life in planetary atmospheres (biosignatures), but our approach is general and can be applied to other systems. In this work we evaluate the accuracy of our method by studying four diatomic molecules, H2, O2, N2, and CO, all of which have well-known spectra. Prometheus uses the transition-optimised shifted Hermite (TOSH) theory to account for anharmonicity for the fundamental ν = 0 → ν = 1 band, along with thermal-profile modeling for the rotational transitions. To this end, we expand TOSH theory to enable the modeling of rotational constants. We show that our simple model achieves results that are a better approximation of the real spectra than those produced through an harmonic approach. We compare our results with high-resolution HITRAN and ExoMol spectral data. We find that modeling accuracy tends to diminish for rovibrational transition away from the band origin, thus highlighting the need for the theory to be further adapted.


Cross, T. M., Benoit, D. M., Pignatari, M., & Gibson, B. K. (2022). A Large-scale Approach to Modeling Molecular Biosignatures: The Diatomics. The Astrophysical journal, 925(1), Article 57.

Journal Article Type Article
Acceptance Date Nov 11, 2021
Online Publication Date Jan 25, 2022
Publication Date Jan 20, 2022
Deposit Date Jan 5, 2022
Publicly Available Date Jan 31, 2022
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 925
Issue 1
Article Number 57
Keywords Biosignatures; Astrochemistry
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Published article (897 Kb)

Copyright Statement
© 2022. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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