The concept of Diffusive Representation is used in this paper for modeling purposes in the field of electrical engineering, namely when some non-rational dynamics are involved [2]. Diffusive formulations are convenient for analysis and cheap numerical approximations. We study the problem of time-domain identification of the so-called diffusive symbol η(ξ) associated to the permittivity ε(p) of dielectric material. The so-obtained state-space models allow simple and precise time-domain simulation of such dynamical components.