  A dielectric function including collisional correlations is derived by
linearizing the self consistent Vlasov equation with a Fokker-Planck collision
integral. The calculation yields the same type of dielectric function as in the
standard-theory of Schottky-noise in storage rings. This dielectric function is
compared with the Mermin-dielectric function derived from a kinetic equation
with relaxation time approximation. We observe that these functions are
identical, however the Mermin-DF is computationally advantageous. The limits of
both dielectric functions are given and the sum rules are proven. We apply
these dielectric functions for typical storage ring plasmas and calculate the
stopping power and the plasmon excitation spectrum.
