Frequency broadening caused by fluctuations in orientations of anisotropically polarizable molecules in liquid carbon disulfide and in liquid mixtures of carbon disulfide and carbon tetrachloride has been investigated by observing scattered light from an ${\mathrm{Ar}}^{+}$ laser at 4880 Å. This scattering has been found to be a broad line with a maximum intensity at zero frequency shift. Intensities and half-widths of the scattered radiation were measured in carbon disulfide from 161 to 313°K; half-widths range from about 0.1 ${\mathrm{cm}}^{-1\mathrm{}}$ near the triple-point to 6 ${\mathrm{cm}}^{-1\mathrm{}}$ near the boiling point. Addition of C${\mathrm{Cl}}_4$ to C${\mathrm{S}}_2$ at room temperature causes the line to narrow. These measurements show that the half-widths of the scattered radiation are approximately proportional to the temperature divided by the viscosity of the liquid, in agreement with Debye's simple picture for orientation scattering in an electromagnetic field. The line shape close to 4880 Å in C${\mathrm{S}}_2$ is found to be nearly Lorentzian, but details in the structure of the scattered-light spectrum show that there are other scattering processes. Line-shape measurements and polarization measurements are in agreement with theoretical predictions. The total scattering intensity in C${\mathrm{S}}_2$ is constant over the range of temperatures investigated. Measurement of the half-widths of the scattered radiation from anisotropic molecules appears to provide a way to obtain viscosities of liquids and the volume of interaction of molecular scatters.

• Received 19 September 1966

DOI:https://doi.org/10.1103/PhysRev.154.129