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Abstract
Brillouin light and X-ray scattering have been used to investigate the dynamic structure factor of supercooled and glassy deuterated polybutadiene in the temperature range between 30 and 330 K. The temperature behaviour of velocity and absorption of longitudinal acoustic modes is reported, giving evidence of two relaxation processes: the structural relaxation and the fast secondary relaxation. A method is presented to obtain information on the shape of the relaxation functions and the activation energy of the fast process from velocity dispersion and absorption. The activation energy of the secondary process is close to that of the rotation around —CD2—CD= bonds of the polybutadiene backbone.