Accuracy of the equilibrium structure of sulphur dioxide

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