ATOMIC-EMISSION SPECTRUM INCLUDING VIRTUAL PHOTON TRANSITIONS IN A CAVITY

We investigate the effect of virtual photon processes (due to the anti rotating terms in the Hamiltonian) on the time-dependent physical spec trum emitted by a two-level atom interacting with a single-mode quanti zed field in a perfect cavity. By means of a Heisenberg operator pertu rbative technique, a generalized emission spectrum is obtained which i ncludes a contribution from the phase-dependent quantum interference b etween the real and virtual photons. The spectrum is phase sensitive, The effects of different statistics of the initial cavity mode are rep orted. For the cavity mode in a coherent state, one of the sidebands i n the atomic emission spectrum can be reduced whilst the other can be enhanced due to the virtual photon transitions. The effect can be sign ificant, and may be detected using a highly excited Rydberg atom in a microwave cavity with a high quality factor.