Two-electron bound-free transitions in an intense laser field

The author presents a simple model of a two-electron bound state coupled to a continuum by a laser field. This model is a close relative of the Anderson model for impurity states in a metal. The author presents a solution for the model that is not based on the Hartree-Fock approximation. It displays the transition from correlated, high Coulomb repulsion, to independent electron behaviour as the bound-continuum coupling is increased. In this way the author shows some of the phenomena that may be observable in ultra-intense field photoionisation. Furthermore, one can see how the Hartree-Fock approximation may give absurd results for moderate fields.