We present calculations of two-photon matrix elements for two-photon two-colour ionization. We focus on ionization processes that use one infrared and one extreme-ultraviolet photon. The paper describes a novel algorithm used for the calculation of radial matrix elements, and also of radial phase shifts of continuum states.

J. Phys. B

Toma, E. S., & Muller, H. G. (2002). Calculation of matrix elements for mixed extreme-ultraviolet-infrared two-photon above-threshold ionization of argon. J. Phys. B: At., Mol. Opt. Phys., 35, 3435–3442.