The persistent correlation effects in double ionization of helium-like atoms or ions which are probed with high energy photons

R. H. Pratt
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA

T. Suri and K. Pisk
Rugjer Bokovi Institute,
P. O. Box 1016, Zagreb, Croatia

Abstract:

We analyze the correlation effects in two electron atoms and ions which can be probed in double ionization with high energy photons. We consider total cross sections and differential cross sections for double ionization by photoabsorption and Compton scattering and discuss the shake and non-shake mechanisms which may contribute to these observables. The total cross section for photoabsorption (at high energies) is determined by two mechanisms, the shake-off mechanism and a quasi-equal-energy sharing mechanism, while for Compton scattering it is determined by the shake-off mechanism. In general the shake-off mechanism probes different distances in the two processes, so that the shake-off ratios are different. Analyzing differential cross sections, we are able to distinguish the shake from the non-shake contributions in photoabsorption, or the variation of shake-off result with distance probed in Compton scattering. We discuss the utilization of the double ionization Compton profile (as distinguished from the ordinary Compton profile) for studying the correlation effects in Helium.