Infrared Spectra of Crystalline and Matrix-Isolated Carbonyl Sulfide

Abstract

The infrared spectrum of carbonyl sulfide has been examined as a polycrystalline film at 80°K and also in matrix‐isolated form, using argon, nitrogen, and CS₂ as the matrix materials. Particular attention has been given to the ν₃ vibration, which appears as an abnormally broad and asymmetric band in solid OCS. The asymmetry of ν₃ does not appear to be the result of any significant reflection effects nor is it due to disorder in the crystal. A study of the concentration dependence of the ν₃ frequency in isotopic mixtures shows that a good part of the asymmetry can be attributed to the ν₃ absorption of molecules containing ³³S and ³⁴S. Spectra of dilute mixtures of OCS in argon matrices display absorption by both isolated molecules and molecular pairs. The features of the spectrum are qualitatively accounted for in terms of a simple model of pairs interacting through transition‐dipole coupling. In both N₂ and CS₂ matrices, the evidence suggests two different sites for the OCS molecule in the host lattice.