Using the dielectric function for diagnostics of laser-induced plasmas

We present an approach to the dielectric function of dense plasma based on a generalized linear response theory. The relation of this approach to the Drude model as well as to the random phase approximation is discussed. It i s shown, that the dielectric function presented here obeys certain exact kn own properties such as sum rules. Using the dielectric function, the absorp tion coefficient for electro-magnetic wave interacting with dense targets i s calculated. Regions for the applicability for simplified models are given , implications for the diagnostics of laser-induced plasmas are pointed out .