Rotational freezing in plastic crystals:: a model system for investigating the dynamics of the glass transition

The dynamics of the rotational freezing transition of the rotator phase (RP) crystal of ethanol into its orientational glass (OG) phase is monitored by measurements of molecular rotational components in the quasielastic neutron scattering spectrum. Such a transition is known to share several features in common with the canonical liquid --> glass transition (both taking place within the same temperature interval), and therefore some of the results from such a study should be of relevance for our understanding of the latter. We show that the basic features of the RP --> OG transition can be understood in terms of a hard-needle model by means of a mapping of the aspect ratio onto a temperature scale.