Ab initio potential energy surface and vibration-rotation energy levels of sulfur dioxide

An accurate potential energy surface of sulfur dioxide, SO2, in its ground electronic state X approximate to 1A1 has been determined from ab initio calculations using the coupled-cluster approach in conjunction with the correlation-consistent basis sets up to septuple-zeta quality. The results obtained with the conventional and explicitly correlated coupled-cluster methods are compared. The role of the core-electron correlation, higher-order valence-electron correlation, scalar relativistic, and adiabatic effects in determining the structure and dynamics of the SO2 molecule is discussed. The vibration-rotation energy levels of the (SO2)-S-32 and (SO2)-S-34 isotopologues were predicted using a variational approach. It was shown that the inclusion of the aforementioned effects was mandatory to attain the spectroscopic accuracy. (c) 2017 Wiley Periodicals, Inc.