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 Title: AB INITIO STUDY OF GROUND-STATE CS PHOTODISSOCIATION VIA HIGHLY EXCITED ELECTRONIC STATES Author(s): Xu, Zhongxing Contributor(s): Crabtree, Kyle N.; Wang, Lee-Ping ; Federman, Steven ; Ng, Cheuk-Yiu ; Jackson, William M.; Luo, Nan Subject(s): Electronic structure, potential energy surfaces Abstract: Wavelength-dependent photodissociation cross sections are key data required by modern astrochemical models to simulate the evolution of chemical species in photon-dominated regions. Although photodissociation is considered as the dominant destruction pathway for carbon monosulfide (CS) in these enviroments, the photodissociation rate pf CS is essentially unknown due to a lack of vacuum ultraviolet (VUV) laboratory measurements and accurate theoretical calculations. Here we present a high-level \textit{ab initio} study of CS photodissociation, including for the first time a detailed investigation of its predissociation via the $B\,^1\Sigma^+$ and $C\,^1\Sigma^+$ states. Potential energy curves of CS electronic states were calculated at the MRCI+Q/aug-cc-pV(5+C)Z level and photodissociation cross sections from the vibrational and electronic ground state were calculated by solving the coupled-channel Schr\"{o}dinger equation. We found that the $C-X$ $(0-0)$ transition followed by spin-orbit coupling into several triplet states is responsible for 73\% of the overall photodissociation of CS under the standard interstellar radiation field (ISRF), giving rise to the main atomic products C ($^3P$) and S ($^1D$). Our new calculations of the photodissociation rate are a factor of 2.4 larger than the value currently adopted by the Leiden database, suggesting that this value may be revised for improving the accuracy of astrochemical models. Issue Date: 2019-06-19 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104381 DOI: 10.15278/isms.2019.WD04 Rights Information: Copyright 2019 Zhongxing Xu Date Available in IDEALS: 2019-07-152020-01-25
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