Coherent population transfer via a resonant intermediate state: The breakdown of adiabatic passage

We use the formalism of complex scaling to construct an energy-space treatment of resonances embedded in a continuum. We then use this formalism to study the nature of coherent population transfer through a resonant intermediate state. It is found that in the limit of rapid decay to the continuum, there is strong nonadiabatic coupling between the eigenstates of the matter-field Hamiltonian, which leads to imperfect population transfer.