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Spectroscopic and Kinetic Studies of the ClSO Radical from Cl₂SO Photolysis

Chao, Wen and Jones, Gregory H. and Okumura, Mitchio and Percival, Carl J. and Winiberg, Frank A. F. (2022) Spectroscopic and Kinetic Studies of the ClSO Radical from Cl₂SO Photolysis. Journal of the American Chemical Society, 144 (44). pp. 20323-20331. ISSN 0002-7863. doi:10.1021/jacs.2c07912.

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Thionyl chloride (Cl₂SO) serves as a common Cl atom source in widespread applications of chlorine chemistry though little is known about the reactivity and spectroscopy of the ClSO radical after a Cl–S bond cleavage. We performed a Pulsed Laser Photolysis experiment to detect ClSO from Cl₂SO photolysis at 248 nm in a gas-flow reactor by time-resolved UV–vis transient absorption spectroscopy. A few chemical tests, using I₂ and NO₂, suggested the structured absorption band between 260 and 320 nm belonged to ClSO radical and that the termolecular ClSO + Cl + M → Cl₂SO association reaction occurred. From EOMIP-CCSD/ano-pVQZ calculations, the ClSO band was assigned to the 1²A″ ← X²A″ transition involving the π* ← π transition of the SO bond and the vibrational progression to the SO stretching mode of the 1²A″ state, with a maximum cross-section = (2.0 ± 0.5) × 10⁻¹⁸ cm² near 286 nm (1σ uncertainty) and an average spacing of vibrational structure of 658 cm⁻¹. The rapid decay of the ClSO signal monitored near 303 nm could be fit to a second-order kinetic model over 10–90 Torr, which yields an effective bimolecular rate coefficient k_(Cl+ClSO) = (1.48 ± 0.42) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 292 K and 90 Torr (1σ uncertainty). This fast recombination reaction suggests that Cl-containing SOx species might act as significant Cl atom reservoirs in sulfur oxide-rich environments such as Venus’ atmosphere. Moreover, the reported UV spectrum provides a new means for monitoring the ClSO radicals.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chao, Wen0000-0003-0602-1606
Jones, Gregory H.0000-0003-3275-1661
Okumura, Mitchio0000-0001-6874-1137
Percival, Carl J.0000-0003-2525-160X
Winiberg, Frank A. F.0000-0003-2801-5581
Additional Information:The experimental research herein was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA, 80NM0018D0004). Financial support was provided by the NASA Solar System Workings program and the J. Yang & Family Foundation. The authors thank Dr. S. Sander for discussion.
Funding AgencyGrant Number
J. Yang & Family FoundationUNSPECIFIED
Issue or Number:44
Record Number:CaltechAUTHORS:20230125-514949300.24
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118943
Deposited By: Research Services Depository
Deposited On:22 Feb 2023 19:40
Last Modified:22 Feb 2023 19:40

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