TY - JOUR A1 - Medina, Cristian A1 - Lægdsmand, Asbjørn Ørnemark A1 - Ben Ltaief, Ltaief A1 - Hoque, Ziaul A1 - Roos, Andreas Hult A1 - Jurkovičová, Lucie A1 - Hort, Ondřej A1 - Finke, Ondřej A1 - Albrecht, Martin A1 - Nejdl, Jaroslav A1 - Stienkemeier, Frank A1 - Andreasson, Jakob A1 - Klimešová, Eva A1 - Krikunova, Maria A1 - Heidenreich, Andreas A1 - Mudrich, Marcel T1 - Long-lasting XUV activation of helium nanodroplets for avalanche ionization JF - New Journal of Physics N2 - 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. KW - nanoplasma KW - helium nanodroplet KW - pump–probe spectroscopy KW - avalanche ionization KW - high-harmonic generation KW - extreme ultraviolet Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-17701 VL - 25 PB - Institute of Physics (IOP) ER -