Wave-packet propagation based calculation of above-threshold ionization in the x-ray regime

TL;DR

This paper presents a wave-packet propagation method to calculate above-threshold ionization in light elements under hard x-ray radiation, providing theoretical predictions and analyzing the process's dependence on intensity.

Contribution

It introduces a wave-packet propagation approach for above-threshold ionization in the x-ray regime and compares computational methods to validate the mean-field potential approximation.

Findings

Two-photon above-threshold ionization cross sections predicted for H, C, N, O.

At high intensities, two-photon ionization of K-shell electrons in carbon is as probable as one-photon L-shell ionization.

The mean-field potential approach is justified through comparison with configuration-interaction calculations.

Abstract

We investigate the multi-photon process of above-threshold ionization for the light elements hydrogen, carbon, nitrogen and oxygen in the hard x-ray regime. Numerical challenges are discussed and by comparing Hartree-Fock-Slater calculations to configuration-interaction-singles results we justify the mean-field potential approach in this regime. We present a theoretical prediction of two-photon above-threshold-ionization cross sections for the mentioned elements. Moreover, we study how the importance of above-threshold ionization varies with intensity. We find that for carbon, at x-ray intensities around $10^{23}{\rm Wcm}^{-2}$, two-photon above-threshold ionization of the K-shell electrons is as probable as one-photon ionization of the L-shell electrons.