Ultrasonic and Light-Scattering Studies of Carbon Tetrachloride

Abstract

A detailed examination of laser light‐scattering data in CCl₄ at 25°C was undertaken to determine which of reported relaxation times, determined from velocity‐dispersion data in the gigahertz region, is consistent with both ultrasonic and hypersonic data. Assuming total relaxation of the vibrational specific heat, two relaxation times are shown to be consistent with ultrasonic absorption data: ${\text{τ″\hspace{0.17em}=\hspace{0.17em}5.4\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−11}}\sec$ with the bulk viscosity ${\eta }_{\upsilon }\mathrm{\hspace{0.17em}=\hspace{0.17em}}\frac{4}{3}{\eta }_s$ , the shear viscosity, and ${\text{τ″\hspace{0.17em}=\hspace{0.17em}3.7\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−11}}\sec$ with ${\eta }_{\upsilon }\text{\hspace{0.17em}=\hspace{0.17em}10(}\frac{4}{3}{\eta }_s)$ . For both cases, velocities were calculated from the dispersion equation for temporally damped waves and were adjusted for instrumental effects and the presence of the second unshifted and antisymmetric Brillouin components. Spectra were also calculated on a digital computer by convoluting the exact expression for the light‐scattering spectrum of a singly relaxing fluid with an appropriate instrumental function. It is concluded, by comparison of the theoretical results with experimental velocities and spectra, that if there is just one relaxing specific heat, then its relaxation time ${\text{τ″\hspace{0.17em}≈\hspace{0.17em}5.4\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−11}}\sec$ and ${\eta }_{\upsilon }{\mathrm{\hspace{0.17em}\approx \hspace{0.17em}\eta }}_s$ .