Population transfer in a three-level atom

We discuss population transfer from the ground to the excited state of a three-level atom or molecule in a Raman configuration exposed to pump and Stokes lasers. The middle level is exactly eliminated by means of a unitary transformation of the Hamiltonian. The dynamics is assumed to obey the conditions of adiabatic passage. We find two distinct ways in which the transfer of population can be carried out. (C) 1998 Elsevier Science B.V. All rights reserved