Spectrum of light scattered coherently or incoherently by a collection of atoms

We discuss the spectrum of light scattered by N atomic dipoles. We present examples illustrating the nature of contributions proportional to N and N² in ``coherent'' and ``incoherent'' forward and side scattering. We use a detector-based formalism that differs in some respects from the formalism of Sundaram and Milonni [Phys. Rev. A 41, 6571 (1990)].