Comprehensive quantum chemical analysis of the (ro)vibrational spectrum of thiirane and its deuterated isotopologue

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2023-12, Vol.302, p.123083, Article 123083
• Main Authors: De Vos, John, Schröder, Benjamin, Rauhut, Guntram
• Format: Article
• Language: English
• Subjects: Rovibrational calculations; Spectroscopic constants; Thiirane; Vibrational configuration interaction theory
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2023.123083

The (ro)vibrational spectra of thiirane, c-C2H4S, and its fully deuterated isotopologue, c-C2D4S, have been studied by means of vibrational configuration interaction theory, VCI, its incremental variant, iVCI, and subsequent variational rovibrational calculations, RVCI, which rely on multidimensional potential energy surfaces of coupled-cluster quality including up to four-mode coupling terms. Accurate geometrical parameters, fundamental vibrational transitions and first overtones, rovibrational spectra and rotational spectroscopic constants have been determined from these calculations and were compared with experimental results whenever available. A number of tentative misassignments in the vibrational spectra could be resolved and most results for the deuterated thiirane are high-level predictions, which may guide experiments to come. Besides this, a new implementation of infrared intensities within the iVCI framework has been tested for the transitions of the title compounds and are compared with results obtained from standard VCI calculations. [Display omitted] •Coupled cluster based PES with up to 4D terms for c-C2H4S and c-C2D4S.•VCI vibrational frequencies show excellent agreement with experiment.•A new implementation of IR intensities within iVCI is presented and validated.•Rovibrational spectra obtained from RVCI are compared to experimental results.•Spectroscopic constants are obtained through vibrational perturbation theory.