Acoustic relaxation in liquid methane and tetrafluoromethane

The absorption α and velocity u of sound are measured in liquid CH4 and CF4 along the saturation line at frequencies from 5 to 126 MHz and temperatures from 90 to 210°K. Dispersion of the quantity α/f2 is observed in CF4 over the entire investigated range of temperatures and frequencies, and slight dispersion of the velocity of sound is observed at low temperatures. Dispersion of α/f2 is observed in CH4 only for T > 140°K. Over the entire temperature range the absorption greatly exceeds the dissipative losses associated with the external thermal degrees of freedom. It is inferred from an analysis of the results that the effects observed in both substances are related to the excitation of intramolecular vibrational degrees of freedom. The resulting vibrational relaxation curves evince different kinetics for this process in the two liquids in connection with the different nature of the rotational motion of the particles.

Перевод пока недоступен