Centrifugal Distortion Analysis of a Near-Spherical Top, SO2F2: The First Determination of All Six Quartic Centrifugal Distortion Constants for an Asymmetric Top

Abstract

The rotational spectrum of the near-spherical top molecule SO2F2 (sulfuryl fluoride) has been investigated by microwave Fourier transform spectroscopy and by millimeter-wave spectroscopy. The ground state spectrum has been measured from 10 to 472 GHz. One of the reasons for studying this molecule is that it is a nearly spherical top and we wanted to verify our theoretical prediction that for such a molecule all six quartic centrifugal distortion constants (and nine sextic distortion constants) should be determinable, while for a standard asymmetric rotor, Watson has shown that only five quartic and seven sextic distortion constants are determinable. The analysis of the spectra confirmed our predictions, because all six quartic constants were well determinable. The results have been confirmed independently by ab initio calculations of the force field and quartic distortion constants. Because the molecule is relatively heavy, contributions of some sextic constants are too small and we have not been able to determine all nine sextic constants predicted by theory.