Mechanical response of supercooled ethylbenzene at ultrasonic frequencies

Measurements of acoustic attenuation at fixed ultrasonic frequency have been performed on ethylbenzene in the temperature range 100 - 300 K. A relaxation response can be observed in the temperature region below the melting temperature. The acoustic attenuation exhibits a peak featuring a remarkable asymmetric broadening in the low-temperature flank. The observed behaviour can be described as the superposition of two separate relaxational contributions. A main process, well described by a Vogel - Fulcher - Tamman temperature dependence, prevails in the high-temperature flank while a secondary process becomes relevant at decreasing temperatures, as the calorimetric glass transition region is approached.