EVIDENCE FOR SHORT-RANGE ORIENTATION EFFECTS IN PURE LIQUID SO2 FROM VIBRATIONAL RAMAN-SPECTROSCOPY

In the Raman spectrum of pure liquid SO2 a difference is observed between the wavenumbers of the isotropic and anisotropic components of the totally symmetric vibrations ν1 and ν2, the anisotropic component being at a higher frequency than the isotropic one. The separations are Δν1 = 5 cm−1, Δν2 ≃ 3.5 cm−1. This effect is approximately independent of temperature in the range −60 to +40°C. It disappears with dilution of SO2 in an inert solvent. The same shift is observed in solid SO2. Mirone and Fini2 and Josien3 have observed and interpreted such an effect in the case of larger molecules. They assume the liquid to be composed of clusters in which the molecules are partially ordered. In the case of SO2 our calculations based on such a model are in good agreement with the experimental results for ν2 but not for ν1. Copyright © 1979 Heyden & Son Ltd.