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A: Atomphysik

A 2: Multiphotonprozesse 1

A 2.1: Vortrag

Montag, 24. März 2003, 11:00–11:15, F128

Two–photon ionization of heavy, few–electron ions — •Peter Koval, Stephan Fritzsche, and Andrey Surzhykov — Universität Kassel, D–34132 Kassel, Germany

Multi–photon excitation and ionization processes have been widely explored during the last decades. Until now, however, these studies were restricted mainly to excitations from the valence shells due to the lack of proper VUV and x–ray laser sources. Owing to the development of free–electron lasers (XFEL’s), multi–photon experiments are likely to be extended soon to include also inner–shell phenomena.

To understand the behaviour of the two–photon ionization in medium and heavy elements, the non–resonant total cross sections are calculated by means of second–order perturbation theory, based on Dirac’s equation. In contrast to previous investigations, we apply a Green’s function approach to deal with the infinite summation over the complete spectrum of the atomic states. In this contribution, we will explain the construction of effective (one–particle) Green’s functions in a central–field potential and show, how the two–photon total ionization cross sections compare with each other for ions along the hydrogen and helium isoelectronic sequences.