Crossover from Debye to non-Debye dynamical behavior of the α relaxation observed by quasielastic neutron scattering in a glass-forming polymer

The dynamics of a very fragile glass-forming polymer is studied by time of flight neutron scattering in a time scale from 10^-13 to 10^-11 s. We observe a crossover from a Debye-like to a non-Debye behavior at a characteristic time which is effectively independent of temperature and momentum transfer Q. We also confirm the results previously obtained about the non-Debye {α} relaxation in a different time scale (10^-11 to 10^-8 s). The results here reported open a new outlook for understanding the fast dynamics of glass-forming systems.