Ab initio calculations on the X∼2B1 → X∼1A1 photoelectron spectrum of thioformaldehyde negative ion

Tian Guo; Jiangang Xu; Yannan Chen; Shuangxiong Ma; Yunguang Zhang

doi:10.1016/j.saa.2023.123390

Ab initio calculations on the X∼²B₁ → X∼¹A₁ photoelectron spectrum of thioformaldehyde negative ion

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Jan 5:304:123390. doi: 10.1016/j.saa.2023.123390. Epub 2023 Sep 9.

Authors

Tian Guo¹, Jiangang Xu¹, Yannan Chen¹, Shuangxiong Ma¹, Yunguang Zhang²

Affiliations

¹ School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710121, China.
² School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710121, China. Electronic address: zygsr@xupt.edu.cn.

PMID: 37708756
DOI: 10.1016/j.saa.2023.123390

Abstract

The equilibrium structures, multidimensional potential energy surfaces, and anharmonic vibrational frequencies of thioformaldehyde (H₂CS) and its ²B₁ radical anion were obtained at the (U)CCSD(T)-F12a/cc-pVTZ-F12 level; and the photoelectron spectrum of H₂CS^-X∼²B₁→ H₂CS X∼¹A₁ was simulated by calculating the Franck-Condon factors (FCFs). The additional electrons cause a significant change in the bond length of the C = S bond of H₂CS, which affects the potential energy surface and the C = S bond stretching mode, while the interaction between electrons turns the originally planar structure of H₂CS into a slightly out-of-plane umbrella structure, resulting in an unusual change in the vibrational frequency of the out-of-plane bending mode. Finally, a time-independent eigenstate-free Raman wave function approach (RWF) was used to calculate the photoelectron spectrum of H₂CS and to point out the changes in the band under the influence of different temperatures. These data provides a theoretical basis for interstellar observations and experimental studies.

Keywords: Franck-Condon factors; Photoelectron spectrum; Potential energy surface; Thioformaldehyde; Vibrational frequency.