SPONTANEOUS EMISSION OF NONDISPERSIVE RYDBERG WAVE-PACKETS

Nondispersive electronic Rydberg wave packets may be created in atoms illuminated by a microwave field of circular polarization. We discuss the spontaneous emission from such states, and show that the elastic i ncoherent component (occurring at the frequency of the driving field) dominates the spectrum in the semiclassical limit. contrary to earlier predictions. We calculate the frequencies of single-photon emissions and the associated rates in the ''harmonic approximation,'' i.e., when the wave packet has approximately a Gaussian shape. The results agree well with exact quantum-mechanical calculations, which validates the analytical approach.