Photoexcitation and -ionization in helium: Zero-kinetic-energy spectroscopy

Abstract

The cross sections for double and single photoexcitation and -ionization of helium are calculated in the acceleration gauge assuming a totally asymmetric energy and angular momentum partitioning between two electrons. The electron-electron correlation is taken, into account in the ground-state wave function. By extrapolating single-ionization differential oscillator strengths to n --> infinity, where n is the excited He+ principal quantum number, an estimate of the double-ionization cross sections is obtained. Comparison with other calculations is made.