Ionization and charge migration through strong internal fields in clusters exposed to intense X-ray pulses

TL;DR

This paper explores how intense X-ray pulses cause ionization and charge migration in clusters, leading to a core-shell structure that can be exploited to reduce radiation damage in imaging.

Contribution

It provides a microscopic model confirming the role of internal field ionization and demonstrates how sacrificial layers improve imaging quality.

Findings

Internal fields induce rapid core-shell formation

Substituting shell ions reduces radiation damage

Model aligns with experimental X-ray cluster data

Abstract

A general scenario for electronic charge migration in finite samples illuminated by an intense laser pulse is given. Microscopic calculations for neon clusters under strong short pulses as produced by X-ray free-electron laser sources confirm this scenario and point to the prominent role of field ionization by strong internal fields. The latter leads to the fast formation of a core-shell system with an almost static core of screened ions while the outer shell explodes. Substituting the shell ions with a different material such as helium as a sacrificial layer leads to a substantial improvement of the diffraction image for the embedded cluster thus reducing the consequences of radiation damage for coherent diffractive imaging.