Photoionization accompanied by excitation at intermediate photon energies

TL;DR

This paper investigates photoionization with excitation in helium and heliumlike ions at intermediate photon energies, including electron interactions, and analyzes mechanisms beyond high-energy approximations.

Contribution

It introduces a method to include electron interactions in photoionization calculations at intermediate energies, extending beyond high-energy limits.

Findings

Calculated photoionization-to-excitation ratios for helium and heliumlike ions.

Analyzed the influence of electron interactions and nonzero orbital momentum states.

Presented high energy limits as power expansions in inverse nuclear charge.

Abstract

We calculate the photoionization with excitation-to photoionization ratios for atomic helium and heliumlike ions at intermediate values of the photon energies. The final state interactions between the electrons are included in the lowest order of their Sommerfeld parameter. This enables us, in contrast to purely numerical calculations to investigate the roles of various mechanisms contributing beyond the high energy limit. The system of the two bound electrons is described by the functions obtained by the Correlation Function Hyperspherical Harmonic Method. For the case of heliumlike ions we present the high energy limits as power expansion in inverse charge of the nucleus. We analyse the role of excitation of states with the nonzero orbital momenta.