We theoretically study the interaction of two time delayed, phase-locked, and nonresonant pulses with a two-level system in the strong field regime. The population transfer is shown to be extremely sensitive to the phase shift phi between the pulses, with efficient population transfer taking place only for phi close to pi. This effect is explained in terms of nonadiabatic jump and rapid adiabatic passage phenomena.
View online : Phys. Rev. A 79, 025401 (2009)