Sequential single-photon and direct two-photon absorption processes for Xe interacting with attosecond XUV pulses

TL;DR

This paper models the complex ionization pathways of xenon interacting with attosecond XUV pulses, highlighting the roles of single-photon, multi-photon, and direct two-photon processes in forming high charge states.

Contribution

It introduces a comprehensive theoretical framework that includes multiple ionization and decay processes to explain experimental ion yield results for xenon under attosecond XUV irradiation.

Findings

Sequential single-photon ionizations lead to double core-hole states.

Formation of Xe$^{5+}$ involves a direct two-photon absorption process.

Theoretical results agree with recent experimental data.

Abstract

We investigate the interaction of Xe with isolated attosecond XUV pulses. Specifically, we calculate the ion yields and determine the pathways leading to the formation of ionic charged states up to Xe$^{5+}$. To do so, in our formulation we account for single-photon absorption, sequential multi-photon absorption, direct two-photon absorption, single and double Auger decays, and shake-off. We compare our results for the ion yields and for ion yield ratios with recent experimental results obtained for 93 eV and 115 eV attosecond XUV pulses. In particular, we investigate the role that a sequence of two single-photon ionization processes plays in the formation of Xe$^{4+}$. We find that each one of these two processes ionizes a core electron and thus leads to the formation of a double core-hole state. Remarkably, we find that the formation of Xe$^{5+}$ involves a direct two-photon absorption process and the absorption of a total of three photons.