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 is shown, that the dielectric function presented here obeys certain exact known properties such as sum rules. Using the dielectric function, the absorption coefficient for electro-magnetic wave interacting with dense targets is calculated. Regions for the applicability for simplified models are given. Implications for the diagnostics of laser-induced plasmas are pointed out.