ULTRAFAST DIELECTRIC-RELAXATION RESPONSE OF POLAR LIQUIDS

In this paper we calculate the complex dielectric constant of polar li quids for microwave and far-infrared range of frequencies. We use the formalism of extended irreversible thermodynamics (EIT) to obtain the autocorrelation function of the polarization vector. To this end, we i ntroduce the local variation of the polarization flow as an independen t variable, which allows for the description of collective interacting effects into the formalism. The results obtained here are compared wi th previous work in tile so-called three-variable theory based on the Mori-Zwanzig projection operator technique. This comparison provides a n interpretation of EIT in terms of a microscopic theory from which th e role of the new independent variable can be established. Using the r esult of the complex dielectric constant presented here, we show that the fitting of experimental data in polar fluids can be improved in th e far infrared frequencies. (C) 1997 American Institute of Physics.