Double ionization of a helium-like atom or ion by a high energy photon

T. Suri^*, K. Pisk^* and R. H. Pratt $^{\dagger}$

^*Rugjer Bokovi Institute, P. O. Box 1016, Zagreb, Croatia
$^{\dagger}$Department of Physics and Astronomy, University of Pittsburgh,
Pittsburgh, PA 15260, USA

Abstract:

We review recent progress in calculations of the ratio of double to single photoionization of helium-like atoms and ions at high energies. The importance of relativistic effects is discussed, with particular emphasis on recent relativistic calculations of double ionization of helium-like atoms and ions by Compton scattering. These calculations, based on the sudden approximation or the impulse approximation, show that, for low Z elements, relativistic effects do not alter the high energy limit of the Compton double to single ratio R_C, even though they do affect single and double ionization Compton scattering separately.