Resonant enhancement of an X-ray laser electric field inside an atom

In the frame of a time-dependent oscillator model, the field induced by the coupling between the atomic electric dipole and an external X-ray laser field is investigated. The aim of the paper is to asses if in the resonant case (the frequency of the incoming field matches the frequency of the atom's collective dipole oscillation) the damped collective oscillation induced by the external time-varying electric field can produce a significant amplification of the total electric field at the nucleus position.