Effect of ion polarization on longitudinal excitations in ionic melts

A simplified model for a collective dynamics in ionic melts is proposed for the description of optic-like excitations. Within a polarization model of ionic melt, the analytical expressions for optic and relaxation dipole modes are obtained. The considered model allows one to describe a softening of frequency and an increase of damping of optic modes caused by polarization processes in comparison with the rigid-ion model. The contributions related with ion polarization to time correlation functions are calculated.