Theoretical investigation of orbital alignment of x-ray-ionized atoms in exotic electronic configurations

TL;DR

This paper provides a theoretical analysis of orbital alignment in x-ray-ionized atoms, using improved electronic-structure calculations to understand how linearly polarized x rays influence transient ions and their subsequent decay processes.

Contribution

It introduces an enhanced theoretical framework combining first-order many-body perturbation theory with Hartree-Fock-Slater calculations to accurately predict orbital alignment in exotic electronic configurations.

Findings

Improved transition energy calculations with first-order corrections.

Quantitative analysis of orbital alignment parameters for argon.

Insights into the evolution of orbital alignment during Auger-Meitner decay.

Abstract

We theoretically study orbital alignment in x-ray-ionized atoms and ions, based on improved electronic-structure calculations starting from the Hartree-Fock-Slater model. We employ first-order many-body perturbation theory to improve the Hartree-Fock-Slater calculations and show that the use of first-order-corrected energies yields significantly better transition energies than originally obtained. The improved electronic-structure calculations enable us also to compute individual state-to-state cross sections and transition rates and, thus, to investigate orbital alignment induced by linearly polarized x rays. To explore the orbital alignment of transiently formed ions after photoionization, we discuss alignment parameters and ratios of individual state-resolved photoionization cross sections for initially neutral argon and two exotic electronic configurations that may be formed during x-ray multiphoton ionization dynamics induced by x-ray free-electron lasers. We also present how the orbital alignment is affected by Auger-Meitner decay and demonstrate how it evolves during a sequence of one photoionization and one Auger-Meitner decay. Our present work establishes a step toward investigation of orbital alignment in atomic ionization driven by high-intensity x rays.