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Accuracy of the equilibrium structure of sulphur dioxide*

par Demaison, Jean F.;Liévin, Jacques
Référence Molecular Physics, e1950857
Publication Publié, 2021-01-01

Article révisé par les pairs

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Résumé :

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.