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\ensuremath{\rightarrow}\ensuremath{\infty}, where n is the excited ${\mathrm{He}}^{+}$ principal quantum number, an estimate of the double-ionization cross sections is obtained. Comparison with other calculations is made.