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 ν4, ν5, ν6, and ν7 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 ν4 = 593.640 432 (270) cm−1, ν5 = 544.101 238 (210) cm−1, B4 = 1414.370 33 (36) MHz, and B5 = 1415.186 10 (13) MHz. The very weak absorption of the bending vibration ν6 was observed at lower resolution around 438 cm−1. The band system due to the low-lying CCC bending mode ν7 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 ν7 band systems of the three homologous molecules OCCCO, OCCCS, and SCCCS are compared in terms of their vibrational structure.