We apply the diagrammatic formalism developed in Ref. to the study of several phenomena related to the electromagnetic vacuum of molecular dielectrics. Our approach is based on the linear response theory in the dipole approximation and exploits the fluctuation-dissipation theorem. The fundamental object which derives from it is an analytical formula for the polarization propagator in terms of the electrical susceptibility and the single-particle polarizability. That formula is used to compute the spectrum of dipole emission and the total vacuum energy density. In the former, we can distinguish the coherent emission from the total radiative emission. Regarding the latter, we show that the Lamb energy is only a part of it.
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