The far-infrared spectrum of OCCCS: high-resolution Fourier-transform measurements

Abstract

High-resolution far-infrared gas phase spectra of the linear cumulene-type molecule tricarbon oxide sulfide, OCCCS, have been measured between 50 and 660 cm −1 using a Bomem Fourier-transform spectrophotometer. Four band systems corresponding to the fundamental vibrations ν 4 , ν 5 , ν 6 , and ν 7 were observed. Analysis of the rotational structure of the two fundamental transitions [Formula: see text] and [Formula: see text] yielded the band origins and rotational constants ν 4 = 593.640 432 (270) cm −1 , ν 5 = 544.101 238 (210) cm −1 , B 4 = 1414.370 33 (36) MHz, and B 5 = 1415.186 10 (13) MHz. The very weak absorption of the bending vibration ν 6 was observed at lower resolution around 438 cm −1 . The band system due to the low-lying CCC bending mode ν 7 was found as a weak absorption near 80 cm −1 . Despite the high resolution of 0.004 cm −1 (apodized), the rotational structure of this band was not completely resolved. However, the band contour is in good agreement with the expected harmonic character of the bending potential. The ν 7 band systems of the three homologous molecules OCCCO, OCCCS, and SCCCS are compared in terms of their vibrational structure.