On the cooperativity of the β-relaxation:: A discussion based on dielectric relaxation and thermally stimulated depolarisation currents data

The idea recently spread in the literature that the beta -relaxation originates from cooperative motions in the glassy state is analysed. The results obtained by two different dielectric techniques, dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarisation currents (TSDC), are compared and, from this comparison, it is concluded that: 1, The beta -relaxation is distributed in energy, but not in entropy (i.e. in the pre-exponential factor). 2, It thus corresponds to local, non-cooperative molecular motional processes. 3, The results obtained by both dielectric techniques can be rendered compatible if we assume that the nature of the energy distribution associated with the beta -process is such that the most probable energy is temperature dependent.