ULTRASONIC MEASUREMENT OF THE VIBRATIONAL-RELAXATION IN LIQUID SO2

Measurements of the absorption and velocity of ultrasound in liquid sulfur dioxide have been made over a wide range of temperatures, greatly extending the temperature range of the measurements of Bass and Lamb on the same system. The data are complete now from 203 to 323 K in the frequency range from 6 to 90 MHz. All the data have been fit satisfactorily to a single-relaxation description, and give a temperature-independent relaxation frequency of 22.5±1 MHz. The relaxation amplitude has a strong temperature dependence of the Arrhenius type, with an energy of activation of ∼3 kcal/mole, the temperature behavior of which can be satisfactorily calculated on the basis of reported vibrational frequencies of the SO2 molecule. The velocity of sound, as measured, is a linear function of the temperature. Measurements are also reported for dilute mixtures of cyclohexane in SO2 where no shift in the measured relaxation frequency is observed, contrary to the usual situation for vibrational relaxations. © 1979 American Institute of Physics.