Observation of constant loss in fast relaxation spectra of polymers

Observation of the constant loss contribution to the light scattering spectra in GHz frequency range is presented. The constant loss appears as a frequency-independent imaginary part of the susceptibility spectrum. It shows a strong temperature variation. Analysis of the spectra and literature data suggests that the constant loss can be general for many glass-forming systems but it is hidden in many cases by other relaxation contributions. The nature of the constant loss is not clear. The possible mechanisms are discussed.