Phenomenological theory of thermally stimulated relaxation

A number of methods exist for deriving the activation energy E_A of properties of a system from the results of thermally stimulated relaxation processes, such as thermally stimulated currents and thermoluminescence. The standard analysis of such processes assumes that the isothermal relaxation of the system decays exponentially with time. An extension of this analysis, based on the use of the system's natural time, is presented for systems possessing an arbitrary time dependence of the isothermal relaxation, provided that this relaxation at different temperatures can be described by a suitably scaled master function. In particular, it is shown that for systems in which the isothermal relaxation decays with the time t as exp[-(t/τ)^α], the parameter determined by most of the methods is not the activation energy E_A of the scaling time but rather the product αE_A.