Relaxational dynamics in the glassy, supercooled liquid, and orientationally disordered crystal phases of a polymorphic molecular material

The relaxational dynamics of the ambient pressure phases of ethyl alcohol are studied by means of measurements of frequency dependent dielectric susceptibility. A comparison of the α relaxation in the supercooled liquid and in the rotator phase crystal indicates that the molecular rotational degrees of freedom are the dominant contribution to structural relaxation at temperatures near the glass transition, the flow processes having lesser importance. Below the glass transition a secondary β relaxation is resolved for the orientational and structural glasses. Computer molecular-dynamics results suggest that localized molecular librations, strongly coupled to the low-frequency internal molecular motions, are responsible for this secondary relaxation.