Augmented collisional ionization via excited states in XUV cluster interactions

TL;DR

This paper investigates how atomic excited states influence ionization in XUV laser-cluster interactions, revealing a two-step ionization process that enhances high charge state formation and energy dissemination.

Contribution

It introduces a detailed model demonstrating the significant role of excited states in XUV-induced ionization, supported by simulations of argon cluster experiments.

Findings

Excited states enable a two-step ionization process.

The process contributes to high charge state creation.

Implications for X-ray single molecule imaging.

Abstract

The impact of atomic excited states is investigated via a detailed model of laser-cluster interactions, which is applied to rare gas clusters in intense femtosecond pulses in the extreme ultraviolet (XUV). This demonstrates the potential for a two-step ionization process in laser-cluster interactions, with the resulting intermediate excited states allowing for the creation of high charge states and the rapid dissemination of laser pulse energy. The consequences of this excitation mechanism are demonstrated through simulations of recent experiments in argon clusters interacting with XUV radiation, in which this two-step process is shown to play a primary role; this is consistent with our hypothesis that XUV-cluster interactions provide a unique window into the role of excited atomic states due to the relative lack of photoionization and laser field-driven phenomena. Our analysis suggests that atomic excited states may play an important role in interactions of intense radiation with materials in a variety of wavelength regimes, including potential implications for proposed studies of single molecule imaging with intense X-rays.