By means of quasielastic neutron scattering we have shown that the dynamics of the α relaxation on three different polymeric glasses shows a clear non-Debye behavior on a mesoscopic time scale. The spectral shape is found to be independent of temperature and momentum transfer (Q). The characteristic relaxation time follows a power-law Q dependence, τ(Q)∝${\mathit{Q}}^{\mathrm{-}\mathit{n}}$ (n>2), n beong dependent on the system. We found that the Q behavior and the non-Debye behavior are directly correlated. These results have important implications concerning the physical mechanisms behind the dynamics of the α relaxation.

• Received 11 November 1991

DOI:https://doi.org/10.1103/PhysRevLett.69.478