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The one-step model calculation is presented as an
ab-initio scheme on an APW basis for the initial bound states as well as for the final outgoing states. Furthermore a simplified
one-step model scheme is described.
The available modern light sources with high photon intensities ask for an extension of the code towards nonlinear field effects. Corrections have to be applied to the photoemission vertex in view of higher orders. The same holds also if strong correlation is considered. Using the language of Green function theory offers a systematic approach, though it may not represent the best access at present stage because of the complexity. |