Absorption and velocity of ultrasonic waves in thiophene, o-, p-xylenes and their mixtures

The absorption in thiophene shows that all vibrational degrees of freedom take part in the observed relaxation, caused by the Kneser processes. This process can be described as a vibrational relaxation with one relaxation time. Absorption in the mixtures decreased when increasing the amount of xylenes, as predicted by theory of gases, thus suggesting that the absorption is probably due to the same phenomenon as in gases.