Initial population of large-l Rydberg states for the radiative deexcitation in the beam-foil geometry

Abstract

In the recent beam-foil experiment, resonances have been observed in decay of the beam-foil excited 2p and 2s states of H-like Fe ions at very large times. Qualitatively, the resonances were explained as a consequence of cascading down from the Rydberg states (n ≫ 1, l = n - 1) to 2p state. Full explanation requires the theoretical values of the population probabilities P n,l of the large-l Rydberg states of multiply charged ions of core charges Z ≫ 1 a.u. escaping the solid surfaces at velocities v≫1 a.u. The resonances observed in the time dependent photon intensity indicate the existence of resonances (pronounced maxima at several n = n res) in the P n,l distributions. Considering the population process within the framework of the time-symmetrized two-state vector model, with dynamically generalized interaction Hamiltonian, we found that the nonresonant electron pick up from the foil conduction band into the field of ionic core when the ion leaves the surface represents an important population mechanism. The obtained population distributions have the resonance-like structure like the ones simulated from the experimental signal, and the overlap shape and magnitude in accordance with the wake field model estimations. © 2013 Elsevier Ltd.