Half-collision model for multiple ionization by photon impact

Abstract

We present a simple half-collision model that allows the approximate calculation of absolute cross sections for multiple ionization by breaking this process down into a primary ionization event followed by a half-scattering event in which additional electrons are ionized. As a critical test for the feasability of this approach, we consider the double ionization of two-electron systems, which we describe in terms of the single ionization of the ``primary'' electron followed by impact ionization of the slow ``secondary'' electron. For triple ionization of lithium, the model decomposes the three-electron breakup process into a double ionization of the two inner electrons followed by electron-electron half-scattering of the receding electrons at the residual ``spectator'' $2s$ electron. We find surprisingly good agreement with recent experimental data.