The high frequency dynamics of Indomethacin and Celecoxib glasses has been investigated by inelastic x-ray scattering, accessing a momentum-energy region still unexplored in amorphous pharmaceuticals. We find evidence of phonon-like acoustic dynamics
, and determine the THz behavior of sound velocity and acoustic attenuation. Connections with ordinary sound propagation are discussed, along with the relation between fast and slow degrees of freedom as represented by non-ergodicity factor and kinetic fragility, respectively.
Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid Sulphur around $T_lambda$, i.e. in the temperature range where an abrupt increase in viscosity by four orders of magnitude is obs
erved upon heating within few degrees. This allowed us - overcoming photo-induced and absorption effects at visible wavelengths - to reveal a chain relaxation process with characteristic time in the ms range. These results do rehabilitate the validity of the Maxwell relation in Sulphur from an apparent failure, allowing rationalizing the mechanical and thermodynamic behavior of this system within a viscoelastic scenario.
