  Results of a previous article with the same title are retrieved by a
different method. A one-component plasma is bounded by a plane surface. The
plasma is fully coupled to the electromagnetic field, therefore the charge
correlations are retarded. The quantum correlation function of the surface
charge densities, at times different by $t$, at asymptotical large distances
$R$, at inverse temperature $\beta$, decays as $-1/(8\pi^2\beta R^3)$, a
surprisingly simple result: the decay is independent of Planck's constant
$\hbar$ and of the time difference $t$. The present paper is based on the
analysis of the collective vibration modes of the system.
