Angular correlations in the two--photon decay of helium--like heavy ions

TL;DR

This paper investigates the angular correlations in the two-photon decay of heavy helium-like ions using relativistic quantum theory, focusing on how the decay's angular distribution depends on atomic structure and non-dipole effects.

Contribution

It provides detailed relativistic calculations of angular correlations in two-photon decay for specific heavy helium-like ions, including non-dipole contributions and shell structure effects.

Findings

Angular correlations depend on the initial and final state shell structure.

Non-dipole effects significantly influence the angular emission patterns.

Results are provided for xenon, gold, and uranium ions.

Abstract

The two-photon decay of heavy, helium-like ions is investigated based on second-order perturbation theory and Dirac's relativistic equation. Special attention has been paid to the angular emission of the two photons, i.e., how the angular correlation function depends on the shell structure of the ions in their initial and final states. Moreover, the effects from the (electric and magnetic) non-dipole terms in the expansion of the electron-photon interaction are discussed. Detailed calculations have been carried out for the two-photon decay of the $1s2s \, ^1S_0$, $1s2s \, ^3S_1$ and $1s2p \, ^3P_0$ states of helium-like xenon Xe$^{52+}$, gold Au$^{77+}$ and uranium U$^{90+}$ ions.