The electronic spectra of 2- chlorothiophene and 3-chlorothiophene in the vacuum ultraviolet photoabsorption energy region (3.9–10.8 eV). (February 2023)

• Record Type: Journal Article
• Authors: Oliveira, F.V.S.; Barbosa, A. Souza; Jones, N.C.; Hoffmann, S.V.; Limão-Vieira, P.
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 296(2023)
• Publication Date: 2023-02
• Subjects: 2-chlorothiophene -- 3-chlorothiophene -- Photoabsorption -- VUV -- Cross section -- Rydberg states; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2022.108443
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: The absolute photoabsorption cross-sections for 2-chlorothiophene (2-Cl-Th) and 3-chlorothiophene (3-Cl-Th), in the 3.9–10.8 eV energy range, were recorded for the first-time using synchrotron radiation. Novel ab initio theoretical calculations performed at the time-dependent density functional theory (TD-DFT) level were used to help interpret the photoabsorption spectra. The nature of the excited states has been assigned to valence, mixed valence-Rydberg and Rydberg transitions. Photolysis lifetimes in the Earth^{\prime}s upper atmosphere for both chemical compounds have been estimated from the absolute photoabsorption cross-sections. Potential energy curves calculated with TD-DFT methods lend strong support to the rather efficient dissociative character of the lowest-lying electronic states of 3-Cl-Th relative to 2-Cl-Th. Abstract: The absolute photoabsorption cross-sections for 2-chlorothiophene (2-Cl-Th) and 3-chlorothiophene (3-Cl-Th), in the 3.9–10.8 eV energy range, were recorded for the first-time using synchrotron radiation. New ab initio theoretical calculations performed at the time-dependent density functional theory (TD-DFT) level were used to help interpret the photoabsorption spectra. These have provided important information on the nature of the excited states which have been assigned to valence, mixed valence-Rydberg and Rydberg transitions. The combination of high-resolution vacuum ultra-violet synchrotron radiation with TD-DFT, represents the most comprehensive and self-consistent assignment of the chlorothiophenes electronic excitation to date. Photolysis lifetimes in the Earth^{\prime}s upper atmosphere for both chemical compounds have been estimated from the absolute photoabsorption cross-sections. Potential energy curves have been obtained at the TD-DFT level of theory, showing that the dissociative character of the lowest-lying electronic states is more efficient in 3-Cl-Th. Graphical abstract: Image, graphical abstract