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EXOMOL photodissociation cross sections I: HCl and HF

Pezzella, Marco; Tennyson, Jonathan; Yurchenko, Sergei N; (2022) EXOMOL photodissociation cross sections I: HCl and HF. Monthly Notices of the Royal Astronomical Society 10.1093/mnras/stac1634. (In press). Green open access

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Photon initiated chemistry, i.e. the interaction of light with chemical species, is a key factor in the evolution of the atmosphere of exoplanets. For planets orbiting stars in UV-rich environments, photodissociation induced by high energy photons dominates the atmosphere composition and dynamics. The rate of photodissociation can be highly dependent on atmospheric temperature, as increased temperature leads to increased population of vibrational excited states and the consequent lowering of the photodissociation threshold. This paper inaugurates a new series of papers presenting computed temperature-dependent photodissociation cross sections with rates generated for different stellar fields. Cross sections calculations are performed by solving the time-independent Schrödinger equation for each electronic state involved in the process. Here photodissociation cross sections for hydrogen chloride and hydrogen fluoride are computed for a grid of 34 temperatures between 0 and 10 000 K. Use of different radiation fields shows that for the Sun and cooler stars the photodissociation rate can increase exponentially for molecular temperatures above 1000 K; conversely the photodissociation rates in UV rich fields instead are almost insensitive to the temperature of the molecule. Furthermore, these rates show extreme sensitivity to the radiation model used for cool stars, suggesting that further work on these may be required. The provision of an ExoMol database of cross sections is discussed.

Type: Article
Title: EXOMOL photodissociation cross sections I: HCl and HF
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stac1634
Publisher version: https://doi.org/10.1093/mnras/stac1634
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
UCL > Provost and Vice Provost Offices > UCL BEAMS
URI: https://discovery.ucl.ac.uk/id/eprint/10150651
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