Effects of autoionization in electron loss from helium-like highly charged ions in collisions with photons and fast atomic particles

TL;DR

This theoretical study examines how autoionization affects electron loss and emission patterns in helium-like highly charged ions during collisions with photons and fast particles, highlighting the impact of autoionization at different atomic numbers.

Contribution

It provides a detailed analysis of autoionization effects on electron loss and emission spectra in helium-like ions, considering different initial states and collision energies, which was not previously explored in depth.

Findings

Autoionization influences emission spectra shape up to Z ≈ 35-40 for the $1s^2$ state.

Autoionization significantly alters emission patterns and increases cross sections for the $(1s2s)_{J=0}$ state.

Autoionization effects depend strongly on the atomic number and initial state of the ion.

Abstract

We study theoretically single electron loss from helium-like highly charged ions involving excitation and decay of autoionizing states of the ion. Electron loss is caused by either photo absorption or the interaction with a fast atomic particle (a bare nucleus, a neutral atom, an electron). The interactions with the photon field and the fast particles are taken into account in the first order of perturbation theory. Two initial states of the ion are considered: $1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emission pattern depends on the atomic number $Z_{I}$ of the ion discussing, in particular, the inter-relation between electron loss via photo absorption and due to the impact of atomic particles in collisions at modest relativistic and extreme relativistic energies. According to our results, in electron loss from the $1s^2$ state autoionization may substantially influence the shape of the emission spectra only up to $Z_{I} \approx 35-40$. A much more prominent role is played by autoionization in electron loss from $(1s2s)_{J=0}$ where it not only strongly affect the shape of the emission pattern but also may substantially increase the total loss cross section.