The strong field approximation within a Faddeev-like formalism for   laser-matter interactions
  We consider the interaction of atomic hydrogen with an intense laser field within the strong-field approximation. By using a Faddeev-like formalism, we introduce a new perturbative series in the binding potential of the atom. As a first test of this new approach, we calculate the electron energy spectrum in the very simple case of a photon energy higher than the ionisation potential. We show that by contrast to the standard perturbative series in the binding potential obtained within the strong field approximation, the first terms of the new series converge rapidly towards the results we get by solving the corresponding time-dependent Schroedinger equation. 
Yu. Popov, A. Galstyan, F. Mota-Furtado, P.F. O'Mahony and B. Piraux
physics.atom-ph