Concentration effects on absolute depolarized Rayleigh ratios and effective polarizability derivatives of CS₂ in liquid mixtures with CCl₄

Abstract

Experimental results are reported from polarized and depolarized Raman intensity measurements in combination with absolute depolarized Rayleigh ratios of liquid CS₂ in CCl₄ mixtures at 25°C. Using a calibrated Raman spectrometer it was possible to determine the concentration dependence of g ₂ · γ² _eff of CS₂. Intensity measurements of the polarized and depolarized Raman spectra of the symmetric stretching vibration of CS₂ under the same conditions allowed the determination of the effective values of α₀₁ and γ₀₁ respectively to the normal mode Σ⁺ _g in the liquid phase. In the neat liquid, α₀₁ = 0·19 ų and γ₀₁ = 0·22 ų. In mixtures with CCl₄ the values of α₀₁ decrease at lower CS₂ concentration whereas the values of γ₀₁ increase. These results indicate that the isotropic induced dipole field is increasingly cancelled as the environment becomes more isotropic while the anisotropic part is amplified in CCl₄. A report is also given of an anomalous concentration behaviour of the intensity of the combination mode v ₁ + v ₂-v ₂ on the low frequency side of the v ₁ transition which is amplified relative to the intensity of the v ₁ mode as the CCl₄ concentration increases.