Accuracy of the equilibrium structure of sulphur dioxide

Abstract

The ground state rotational spectra of 12 different isotopologues of sulphur dioxide have been refitted in a consistent way and an accurate experimental cubic force field has been determined. The experimental, semi-experimental and ab initio equilibrium structures have been calculated and found in good agreement across themselves. Different approximations limiting the accuracy are discussed. In particular, the influence of centrifugal distortion is analysed. A method is proposed to estimate the higher-order rovibrational corrections (γ-constants). Although an accurate semi-experimental structure was obtained for 19 isotopologues, it was not possible to determine and account for the breakdown of the Born–Oppenheimer approximation. Finally, it was shown that the ab initio CCSDTQ level of theory was required to obtain a good agreement with the experimental structure.

GRAPHICAL ABSTRACT

Acknowledgements

The authors are grateful to Jean-Marie Flaud for a critical reading of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

J.L. thanks the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) under grant number 2.5020.11 and by the Walloon Region, for computational ressources.