SUSCEPTIBILITY OF STRONGLY DRIVEN 2-LEVEL ATOMS - A NON-MARKOVIAN ANALYSIS

The absorptive part of the susceptibility of a system constituted by a strongly driven two-level atom (interacting with a reservoir) is anal yzed when probed by a weak field. Memory effects are taken into accoun t (the correlation time of the reservoir variables is finite) and we v erify that they lead to several distinct features for the absorption a nd stimulated emission of radiation, when compared with those obtained in the Markovian approximation. Moreover, we verify that memory effec ts lead to a signature, namely, the sensitive dependence of the maxima of the absorption lines on the Rabi frequency at off-resonance pumpin g. Other characteristics of the spectrum are enhanced, even in the pre sence of a small but non-null correlation time of the reservoir, for i nstance, the maxima of the dispersionlike absorption curves at on-reso nance pumping. In this work several situations are analyzed for differ ent values of the parameters of the problem: the off-resonance frequen cies of the driving field, the Rabi frequency, the memory time, and te mperature of the reservoir.