OCS₂ Isomers in the Venusian Atmospheric Chemistry: Spectroscopic Characterization and Photochemistry

Abstract The atmosphere of Venus exhibits absorption in the 300–500 nm wavelength range, which is driven by unknown chemical processes. In our study, we explore electronic transitions in molecules that may exist in the Venusian atmosphere, specifically focusing on the photoabsorption cross sections and the lowest singlet and triplet electronic states of the OCS 2 , SSCO, and OSCS isomers using highly accurate ab initio methods. Our analysis suggests that the SSCO isomer is a strong candidate for explaining the unknown UV absorption. Furthermore, these isomers may serve as significant astrochemical reservoirs in the atmosphere of Venus, where photodissociation could produce atomic sulfur in both its ground and excited states along with OCS and CS 2 , offering a plausible mechanism for the sulfur cycle dynamics and the formation of S x species. This study provides valuable insights into the complex sulfur chemistry within the atmosphere of Venus.