The generalized susceptibility function is calculated on the basis of
the autocorrelators of the velocity of nonideal plasma, obtained by us
earlier, and an analysis of fluctuations in the system is carried out
in accordance with the fluctuation-dissipation theorem. It is found t
hat local extrema of the calculated functions are indicative of the pr
esence of collective fluctuations frequencies close to the Langmuir fr
equency.