Rapid Brillouin scattering measurement of the fast relaxation process in a glass-forming intermediate liquid

The rapid Brillouin scattering method was applied to the giga Hertz dynamics of the deuterated ethylene glycol-d4 by the combination of a highly sensitive charge coupled device(CCD) detector and an angular dispersion type Fabry-Perot interferometer. The temperature variation :vas measured on cooling ai a constant rats of 1 K/min. The obtained relaxation frequency was found to obey the Arrhenius law with the activation energy similar to 4.5 kcal/mol, which corresponds to the potential barrier for the rotational motion of an alkyl group which interacts with the surrounding molecules. This microscopic picture was discussed in relation with the cage effect predicted by the mode coupling theory.