High-level ab initio studies of the structure, vibrational spectra, and energetics of S3.

Observation of mass-dependent and non-mass-dependent sulfur isotope fractionations in elemental sulfur is providing new insight into the nature of the sulfur cycle in the atmosphere. Interpretation of the experimental isotope data requires estimation of the energetics for the reaction S+S₂→S₃ (isoelectronic with O+O₂→O₃). Key molecular properties of the S₃ potential-energy surface, such as vibrational frequencies and isotopic shifts, are presented that can be used to assess the mass-dependent fractionation effect. Ab initio results are compared to the available experimental results for S₂ to evaluate the reliability of the computational results for S₃. The S–S bond dissociation energy for S₃ is determined to be 60.9±1 kcal mol^-1. [ABSTRACT FROM AUTHOR]