Knowledge Bank

The microwave spectra of the $\nu 2,2\nu 2,3\nu 2,\nu 1,\nu 3,\nu 1+\nu 2$ and $\nu 2+\nu 3$ vibrational excited states of sulfur dioxide have been recorded. A careful analysis of the $\nu 1,\nu 2,\nu 3,$ and $2\nu 2$ states yielded the equilibrium distortion constants, from which the harmonic force field has been calculated. A few lines, which are slightly shifted from their calculated positions, cannot be explained without considering a weak resonance. In connection with that point, the frequency of the origin of the $2\nu 2$ vibration rotation band will be discussed.