Coherent excitation of a three-level system

An analytic expression is derived for the quasienergies and quasienergy states of a three-level system in a resonant field, which is valid over the whole frequency range. Oscillations of the populations are investigated when the field is applied instantaneously. It is demonstrated that the Autler–Townes effect may be observed using a single radiation source. It is found that in the course of adiabatic frequency scanning over the resonance region, the system is transferred to the maximum energy state. This effect is also found for an n-level system.