The Infrared Absorption Spectrum of the Deuterium Sulfides

The spectra of HDS and D2S have been investigated under high dispersion using a grating spectrometer. An absorption band at 9.0μ in HDS has been identified as ν2 and has an average spacing of the rotation lines of about 6.85 cm—1. In D2S bands were located at 3.75μ, 5.0μ and 10.7μ which have line spacings of 4.8 cm—1, 5.0 cm—1, 5.0 cm—1 and may be identified as ν1+ν2, ν3 corresponding to a similar identification in H2S. As in H2S, ν2 appears to have a Q branch while ν3 does not. If this is actually so, ν2 must arise from a vibration of the electric moment parallel with the axis of least moment of inertia and ν3 from a vibration along the middle axis. Since ν2 is a vibration parallel with the symmetry axis of the triangle then this axis must be identified with the axis of least moment of inertia. This argument supports the acute angled model suggested by Sprague and Nielsen, and the evidence is interpreted to favor a vertex angle of 85° instead of the 110° angle of Bailey, Thompson and Hale.