The rovibronic spectra in UV absorption of S₂

¹ Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
² Department of Chemistry and Nanomaterials Science, Bohdan Khmelnytsky National University, Cherkasy, Ukraine
³ Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden

^★ Corresponding authors: bfmin43@ukr.net; yanbing@jlu.edu.cn

Received: 22 November 2024
Accepted: 25 August 2025

Abstract

Comprehensive rovibronic spectra for six electronic states of S₂ − X³ Σ_g⁻, B^′3Π_u, B³ Σ_u⁻, b¹Σg⁺, a¹Δ_g, and f¹Δ_u – are presented. The potential energy curves, electric dipole transition moments, orbital electronic angular momentum coupling, and spin-orbit coupling matrix elements were calculated using the multi-reference configuration interaction method. In addition, potential energy curves were refined via fitting to empirical energy levels. These data were used to estimate the intensities for rovibronic transitions. A set of molecular parameters for S₂, including partition functions, lifetimes, cross sections, and spectral data, is established. The rovibronic transitions cover wavenumbers up to 70 000 cm⁻¹ (λ >142 nm). Many observed experimental spectral bands were theoretically simulated. We expect that the spectra presented here will assist in characterizing exoplanetary atmospheres for future observational missions.