(e,3e) processes on two-electron atoms: Cusp conditions and scaling law

Abstract

We study the double ionization by electron impact of the ground state of heliumlike atoms and propose a scaling law for fully differential (e,3e) cross sections. Within the first Born approximation, cross sections are calculated with a three-body Coulomb (3C) double-continuum wave function and initial states represented by highly accurate wave functions, which satisfy all two-body Kato cusp conditions. We first consider the helium atom in the kinematical and geometrical conditions of the only absolute, high incident energy, experimental data available: our calculations confirm unambiguously that satisfying or not Kato cusp conditions is not a relevant feature of the ground state. Other heliumlike atoms are then considered. Under similar conditions, cross sections for H- are much larger than for helium while the reverse is true for positive ions; a comparison with the rare other theoretical calculations is performed. Finally, within our theoretical framework, we propose an approximate scaling law for (e,3e) cross sections for heliumlike positive ions, and confirm it by calculations. © 2008 The American Physical Society.