Ionization avalanching in clusters ignited by extreme-ultraviolet driven seed electrons

TL;DR

This study demonstrates that ultrashort XUV pulses can precisely seed ionization avalanching in argon clusters under NIR laser exposure, enabling controlled ionization and heating with potential applications in laser-matter interactions.

Contribution

It introduces a method to control ionization avalanching in clusters using XUV seed electrons, supported by molecular dynamics simulations.

Findings

Highly charged ions up to Ar$^{8+}$ can be generated with minimal seed electrons.

XUV seed electrons enable switch-like control of ionization.

Simulations confirm the role of inverse bremsstrahlung and nanoplasma heating.

Abstract

We study the ionization dynamics of Ar clusters exposed to ultrashort near-infrared (NIR) laser pulses for intensities well below the threshold at which tunnel ionization ignites nanoplasma formation. We find that the emission of highly charged ions up to Ar$^{8+}$ can be switched on with unit contrast by generating only a few seed electrons with an ultrashort extreme ultraviolet (XUV) pulse prior to the NIR field. Molecular dynamics simulations can explain the experimental observations and predict a generic scenario where efficient heating via inverse bremsstrahlung and NIR avalanching are followed by resonant collective nanoplasma heating. The temporally and spatially well-controlled injection of the XUV seed electrons opens new routes for controlling avalanching and heating phenomena in nanostructures and solids, with implications for both fundamental and applied laser-matter science.