Far-Infrared Spectra of Trimethylene Sulfide and Cyclobutanone

Abstract

The far‐infrared spectra of trimethylene sulfide and cyclobutanone have been investigated. The positions of the trimethylene sulfide bands observed are well fitted by the potential function derived from the microwave studies of Harris et al. However, some of the band shapes cannot be explained in detail although the anomalies are probably due to Coriolis terms in the Hamiltonian. The positions of the lower frequency bands of cyclobutanone can be fit approximately by a quartic—quadratic potential with a small barrier. Although this potential function fits the rotational constants measured by Sharpen et al., it does not predict the positions of the higher frequency bands correctly. Furthermore the band shapes cannot be explained on the basis of the simple potential function, and it is suggested that the low‐frequency out‐of‐plane vibration of cyclobutanone is perturbed by a higher frequency vibration.