Chlorine-sulfur oxides in the Venusian atmosphere: Benchmark data from computational spectroscopy

Area of Science:

• Planetary Science
• Atmospheric Chemistry
• Computational Chemistry

Background:

• Chlorine-sulfur oxides (Cl2SOn, n=1-4) are vital intermediates in Venus's atmospheric sulfur and chlorine cycles.
• These compounds influence the formation of sulfuric acid (H2SO4) clouds on Venus.
• Higher oxidation state Cl2SOn species are largely uncharacterized, lacking structural and spectroscopic data.

Purpose of the Study:

• To computationally determine the equilibrium geometries, rotational constants, and vibrational frequencies for the Cl2SOn series.
• To provide accurate spectroscopic parameters for uncharacterized higher oxidation state chlorine-sulfur oxides.
• To aid in the identification of these reactive species in laboratory and planetary observations.

Main Methods:

• Employed explicitly correlated ab initio methods for high-accuracy electronic structure calculations.
• Utilized second-order vibrational perturbation theory to account for anharmonic vibrational effects.
• Calculated equilibrium geometries, rotational constants, and anharmonic vibrational frequencies for Cl2SOn (n=1-4).

Main Results:

• Generated a consistent dataset of spectroscopic parameters for the Cl2SOn series.
• Achieved high accuracy by balancing electron correlation and anharmonic effects, closely matching existing experimental data.
• Extended predictive accuracy to higher, previously uncharacterized, chlorine-sulfur oxide species.

Conclusions:

• The study provides the first comprehensive reference data for Cl2SOn species.
• Predicted spectroscopic features will aid in identifying these intermediates in Venus's atmosphere.
• Findings will support the interpretation of data from upcoming Venus missions like EnVision and VERITAS.