Ultrasonic relaxation and the vibrational specific heat of liquid sulphur dioxide

Measurements have been made of the absorption of ultrasonic waves in liquid sulphur dioxide over the range of frequency from 3 to 45 Mc/s and at temperatures of 0, 25 and 50°C. A pronounced relaxation is found, centred about a frequency of approximately 23 Mc/s; this is associated with the time delay in deactivation of two of the three vibrational modes. The mode which does not participate is that of lowest wave-number which is presumed to be responsible for a relaxation at higher frequencies (of the order of 1500 Mc/s). The results are discussed with reference to dispersion measurements in the gas phase.