Knowledge Bank

The microwave spectrum of trimethylene sulfide $(CH2CH2CH2S)$ has been analyzed by Harris, Harrington and Gwinn. Coupling between the two lowest states of the out-of-plane bending vibration causes large deviations from rigid rotor approximations. A potential function describing the out-of-plane bending vibration has been determined by Harris from analysis of the microwave spectrum of the molecule. The determination of this potential function can be facilitated from a knowledge of the energy level spacings of the out-of-plane bending mode. The energy separations of this type of vibration are often below $100cm-1$ and can be obtained from far-infrared or microwave intensity data. The intensity coefficients of the ground state rotational transitions and several vibrational satellites of trimethylene sulfide have been measured and the energy separations of the out-of-plane bending vibrational states have been calculated. These results will be discussed.