QUANTUM-THEORY OF THE MAZER .3. SPECTRUM

We calculate the spectrum of the micromaser with quantized motion of t he pump atoms [M. O. Scully, G. M. Meyer, and H. Walther, Phys. Rev. L ett. 76, 4144 (1996)] in different velocity regimes. We show that when the kinetic energy of the pump atoms is comparable to the atom-field interaction energy the spectrum of the cavity field is no longer cente red at the cavity frequency. In the case of very slow atoms huge broad enings and shifts occur in the vicinity of the mazer resonances. We pr esent approximate analytical results for the spectrum that allow a com parison with the exact numerical calculations. [S1050-2947(97)01611-9] .