Long-lasting XUV activation of helium nanodroplets for avalanche ionization

Abstract

We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times $\sim 200$~fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable `snowball' structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems.

References in corpus (9)

• Ionization of clusters in intense laser pulses through collective electron dynamics
• Highly charged droplets of superfluid helium
• Ionization and charge migration through strong internal fields in clusters exposed to intense X-ray pulses
• Harmonic Generation from Laser-Irradiated Clusters
• Laser-driven nanoplasmas in doped helium droplets: Local ignition and anisotropic expansion
• A Multipurpose End-Station for Atomic, Molecular and Optical Sciences and Coherent Diffractive Imaging at ELI Beamlines
• Relaxation dynamics in excited helium nanodroplets probed with high resolution, time-resolved photoelectron spectroscopy
• Dopant-induced ignition of helium nanoplasmas -- a mechanistic study
• Ignition of a helium nanoplasma by x-ray multiple ionization of a heavy rare-gas core

Cited by in corpus (2)

• Bright continuously-tunable VUV source for ultrafast spectroscopy
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