Spectroscopic Characterization of S3O Isomers: Potential Contributor to the Unknown UV Absorber in Venus’s Atmosphere

A long-standing question about Venus’s atmosphere concerns the origin and distribution of the mysterious ultraviolet (UV) absorber, which is responsible for the absorption band observed in the near-UV and blue regions of Venus’s spectrum. In this work, we investigate the electronic structure of S3O isomers, their excited states, and their photoabsorption cross sections using quantum chemistry methods. Our results demonstrate that the cis- and trans-S3O isomers exhibit strong absorption in the 300–500 nm range, making them plausible candidates for the unknown near-UV absorber. The electronic spectrum of ring-S3O is featureless, whereas planar-S3O exhibits absorption around 300 nm. Additionally, spectroscopic data were generated using vibrational configuration interaction (VCI) for the most stable isomer and its isotopes to aid in their detection in the laboratory or the interstellar medium. This study provides valuable insights into the photochemistry of S3O isomers and the complex sulfur chemistry within Venus’s atmosphere.

金星大气领域长期存在的一个未解问题，聚焦于神秘紫外（UV）吸收体的起源与分布——该吸收体正是金星光谱近紫外与蓝光波段观测到的吸收带的成因。本研究采用量子化学方法，探究了S₃O同分异构体的电子结构、激发态以及光吸收截面。研究结果表明，顺式（cis）与反式（trans）S₃O同分异构体在300~500纳米波段呈现强吸收特性，使其成为未知近紫外吸收体的可信候选物。环状（ring）S₃O同分异构体的电子光谱无明显特征，而平面型（planar）S₃O则在约300纳米处存在吸收。此外，本研究针对最稳定的同分异构体及其同位素，采用振动组态相互作用（vibrational configuration interaction，VCI）方法生成了光谱数据，以助力其在实验室环境或星际介质中的探测。本研究为S₃O同分异构体的光化学过程以及金星大气中复杂的硫化学体系提供了极具价值的科学见解。