Previous calculations [1] yielding the frequency spectrum of a one-mode radiation field interacting with a single atom are extended to the case of <I>M</I> atoms. Under the assumption <I>M</I> „<I>N</I> (<I>N</I> mean photon number) the total Hamiltonian is diagonalized, and the correlation function 〈&Ecircfr;(<I>t</I>₁ &Ecircfr;(<I>t</I>₂)〉 revealing the frequency spectrum of the interacting field calculated quite generally. The following special initial conditions are discussed in detail: a) Any atom is either in the upper or the lower state, and b) the electric dipole moment of the ensemble of atoms is oscillating in phase or with a phase difference of π with respect to the electric field strength. In case a) the initial monochromatic line is broadened, and in case b) a frequency shift appears.