Ultrasonic and hypersonic investigations of vibrational relaxation in liquid thiophene

The measurements of hypersonic wave propagation velocity in the fre-quency range 2-7 GHz and ultrasonic wave absorption coefficient in the fre-quency range 10-60 MHz in thiophene have revealed the existence of two relaxation regions associated with vibrational specific heat: the first one asso-ciated with the first mode (v1) of molecule vibrations and the second, associated with the remaining modes excluding the first one. It follows from the experi¬mental values of hypersonic wave absorption coefficient that the bulk viscosity coefficient in this frequency range ny,o exceeds by a factor 2.5 the laminar viscosity coefficient ns.