A Large-scale Approach to Modelling Molecular Biosignatures: The Diatomics. (arXiv:2106.07647v1 [physics.chem-ph])
<a href="http://arxiv.org/find/physics/1/au:+Cross_T/0/1/0/all/0/1">Thomas M. Cross</a>, <a href="http://arxiv.org/find/physics/1/au:+Benoit_D/0/1/0/all/0/1">David M. Benoit</a>, <a href="http://arxiv.org/find/physics/1/au:+Pignatari_M/0/1/0/all/0/1">Marco Pignatari</a>, <a href="http://arxiv.org/find/physics/1/au:+Gibson_B/0/1/0/all/0/1">Brad K. Gibson</a>
This work presents the first steps to modelling synthetic rovibrational
spectra for all molecules of astrophysical interest using the new code
Prometheus. 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 on
molecules identified as signatures of life in planetary atmospheres
(biosignatures). As a starting point, in this work we evaluate the accuracy of
our method by studying the diatomics molecules H$_2$, O$_2$, N$_2$ 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
$nu=0 rightarrow nu=1$ band, along with thermal profile modeling for the
rotational transitions. We present a novel new application of the TOSH theory
with regards to rotational constants. Our results show that this method can
achieve results that are a better approximation than the ones produced through
the basic harmonic method. We discuss the current limitations of our method. In
particular, we compare our results with high-resolution HITRAN spectral data.
We find that modelling accuracy tends to diminish for rovibrational transition
away from the band origin, thus highlighting the need for the theory to be
further adapted.
This work presents the first steps to modelling synthetic rovibrational
spectra for all molecules of astrophysical interest using the new code
Prometheus. 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 on
molecules identified as signatures of life in planetary atmospheres
(biosignatures). As a starting point, in this work we evaluate the accuracy of
our method by studying the diatomics molecules H$_2$, O$_2$, N$_2$ 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
$nu=0 rightarrow nu=1$ band, along with thermal profile modeling for the
rotational transitions. We present a novel new application of the TOSH theory
with regards to rotational constants. Our results show that this method can
achieve results that are a better approximation than the ones produced through
the basic harmonic method. We discuss the current limitations of our method. In
particular, we compare our results with high-resolution HITRAN spectral data.
We find that modelling accuracy tends to diminish for rovibrational transition
away from the band origin, thus highlighting the need for the theory to be
further adapted.
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