Adiabatic population transfer in multiphoton processes

Coherent transfer of population from one quantum state to another can be achieved in a controlled manner with the technique of adiabatic transfer. The essence of this technique is that the two states are not interacting resonantly for the whole duration of the interaction, but that the interaction is swept through resonance after which complete transfer of population from one state to the other can be obtained. Several experiments involving multiphoton transitions in atoms, which show the relevance of this process, are discussed.