Above-threshold ionization of atoms by coherent x-rays

We investigate how the strong-field limit of ionization manifests in situations where rare gas atoms are exposed to intense attosecond x-ray pulses. We focus our theoretical study on above threshold ionization where electrons liberated by a single x-ray photon may absorb additional photons while in the continuum. Models involving perturbation theory and a Coulomb-corrected version of the strong-field approximation are applied to describe the angular and energy resolved ejection of electrons from a target comprised of helium atoms.