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Title:Exomolhd: Photodissociation Of Diatomic Molecules
Author(s):Pezzella, Marco
Contributor(s):Tennyson, Jonathan; Yurchenko, Sergei N.
Subject(s):Photodissociation and photochemistry
Abstract:\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.25,trim=0 0 0 2cm]{abstract.eps} \end{wrapfigure} The destruction of molecules by photodissociation influences the composition and dynamics of exoplanets, particularly in the presence of a UV-rich stellar environments, where molecules are hot. Current photodissociation calculations generally assume $T= 0$ K, appropriate for the cold interstellar medium but inadequate for hot (exo)planets and stars. We compute temperature-dependent photodissociation cross sections for molecules found in these atmospheres. The cross sections are calculated by solving the nuclear-motion Schrödinger equation as part of the ExoMol project using codes Duo and Exocross\footnote{Yurchenko \textit{et al} Comput Phys Commun 2016 \textbf{202} 262–275;Yurchenko \textit{et al} A\&A 2018 \textbf{614} A131 }, and averaging results obtained as discrete spectra. We benchmark our results for three systems. The general validity of the methodology is tested considering the A$^1\Pi \leftarrow$ X$^1\Sigma^+$ transition of HCl at low $T$. Our cross sections and rates agree with published results\footnote{Dishoeck \textit{et al} J. Chem. Phys. 1982 \textbf{77} 3693} (2.31*10$^{-10}$ s$^{-1}$ versus 2.10*10$^{-10}$ s$^{-1}$ respectively ). We also reproduce calculated photodissociation cross section of BeH$^+$ at T=1800 K.\footnote{Yang \textit{et al} J Quant Spectrosc Radiat Transf 2020 \textbf{254} 107203} We performed the simulations considering the three excited states, A$^1\Sigma^+$, B$^1\Pi$ and C$^1\Sigma^+$, see figure. The photodissociation spectrum of NaCl varies consistently with $T$: at $T=100$ K, there two peaks at 240 nm and 260 nm; while at $T=1500$ K the peaks merge.
Issue Date:2021-06-25
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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