Brillouin Scattering and Dispersion and Attenuation of Hypersonic Thermal Waves in Liquid Carbon Tetrachloride

Abstract

Brillouin spectra of liquid CCl4 (at 20.0°C) have been investigated 20 scattering angles, from 40° to 145°. The spectra were excited by 6328-Å radiation from a He-Ne laser and analyzed with a pressure-scanned Fabry-Perot spectrometer. The measured frequency shifts and linewidths of the Brillouin component were used to determine velocities and attenuations of thermal waves in the frequency range 1.6–4.7 Gc/sec. A large dispersion (>10%) and corresponding change in attenuation were found, characteristic of a thermal relaxation process in this region. A broad new component in the spectrum of isotropic scattering was observed, which is also characteristic of a relaxation process. Analyses of these data were carried out in two ways: one is based on a simple extension of acoustic equations to light scattering, and the other, on Mountain's theory of light scattering in the region of a thermal relaxation. It is shown that the observed spectra and derived data agree with Mountain's theory in all respects. Also, from these data it was possible to evaluate the total internal specific heat CI = 11.6±0.3 cal/mole°C. Within experimental error, this relaxes in a single relaxation time τ = (6.5±0.5) × 10−11 sec.

Vibrational Relaxation in Several Derivatives of Benzene

“…In these papers there was no explanation about the analysis of the spectra obtained in the region of relaxation of 2 GHz to 6 GHz and probably the data handling was done without taking into account the Rytov-Mountain line [16]. Its influence on the results obtained for CCl 4 was shown in many papers [17][18][19][20].…”

Brillouin-Streuung an dichten Fluiden/ On Brillouin Scattering in Dense Fluids

“…[1][2][3][4][5][6][7][8][9][10][11][12], wurde auf eine weitere Auswertung mit der MOUXI-Theorie verzichtet. Jedes experimentelle Spektrum wurde mit der Relaxationszeit als einzigen freien Parameter mit der MOUETA-und der TH-Theorie auf die vorhin beschriebene Weise ausgewertet.…”

“…Im Dichtebereich molekularer Flüssigkeiten fehlt jedoch ein quantitativer Vergleich der Theorien MOUETA und MOUXI mit der etwas neueren Theorie TH, da nur eine eher qualitative Überein-stimmung [12] aller drei Theorien mit entsprechenden Experimenten [10,11] festgestellt wurde.…”

Light Scattering from Binary Mixtures of Monatomic and Polyatomic Gases

“…In the case of molecular fluids, it is well known from light scattering experiments [10] that the conventional hydrodynamic equations do not correctly describe the spectrum of the scattered light. Modifications of the hydrodynamic equations [11][12][13][14] have usually been carried out to take into account the internal relaxation processes which occur in a molecular fluid.…”

“…A good quantitative agreement between experiment and the two-temperature predictions was not observed since the results presented by Johnson apply to mixtures of Maxwellian particles, for which thermal-diffusion effects are absent. The influence of thermal-diffusion effects on the Rayleigh-Brillouin light scattering spectra of binary mixtures of monatomic gases outside of the usual hydrodynamic regime was investigated recently [8] using the two-fluid hydrodynamic equations [9] for hard-sphere particles, Maxwellian particles and for particles that interact according to the Lennard-Jones (6)(7)(8)(9)(10)(11)(12) potential.…”