Vol. 10, issue 04-05, article # 4

Abstract:

Within the framework of the perturbation theory developed on the basis of the Floquet–Lyapunov theorem the evolution operator of a two-level quantum system in a nonresonance monochromatic field is determined without the use of the rotating wave approximation. It is shown that matrix elements of the evolution operator which are linear combinations of the quasi-energy state wave functions make it possible to follow up the connections with the initial level populations of the system unperturbed by the field, in contrast to quasi-energy wave functions. Using the evolution operator obtained the problem of a stationary absorption spectrum of a weak monochromatic field resonance to a two-level atom has been solved. It is shown that, as a result of the action of a nonresonance perturbing field, the probe field absorption line strength decreases, and when recording the time-averaged signal at low frequencies of perturbing field the line profile contains narrow dips and peaks observable at microwave transitions.