Collective dynamics of charge fluctuations in ionic conductors

The generalized hydrodynamic structure of the charge-charge response function has been derived for two-component ionic conductors. The effects of resistive processes and of couplings to mass and heat fluctuations have been singled out. The limiting case of a symmetric molten salt and the long wavelength limit have been examined in some detail. The charge-charge spectral function at k = 0 has been extracted from infra-red reflectivity data for molten LiF and shows a prominent peak due to optic-like collective excitations.