Steplike intensity threshold behavior of extreme ionization in laser-driven Xe clusters

TL;DR

This study observes a sharp intensity threshold for extreme ionization in laser-driven Xe clusters, revealing a rapid saturation of high charge states and elucidating the underlying mechanisms through molecular dynamics simulations.

Contribution

It uncovers a steplike intensity threshold behavior for ionization in Xe clusters and explains it with molecular dynamics analysis, a novel insight into laser-cluster interactions.

Findings

High charge Xe ions up to q=24 are produced at low threshold intensity.

Ion charge spectrum saturates quickly above threshold.

Molecular dynamics simulations match experimental results.

Abstract

The generation of highly charged Xe$^{q+}$ ions up to {$q=24$} is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses ($\lambda$=800 nm). Laser intensity resolved measurements show that the high-$q$ ion generation starts at an unexpectedly low threshold intensity of about {10$^{14}$ W/cm$^{2}$}. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.