TY - JOUR A1 - Jurkovičová, Lucie A1 - Ben Ltaief, Ltaief A1 - Roos, Andreas Hult A1 - Hort, Ondřej A1 - Finke, Ondřej A1 - Albrecht, Martin A1 - Hoque, Ziaul A1 - Klimešová, Eva A1 - Sundaralingam, Akgash A1 - Antipenkov, Roman A1 - Grenfell, Annika A1 - Špaček, Alexandr A1 - Szuba, Wojciech A1 - Krikunova, Maria A1 - Mudrich, Marcel A1 - Nejdl, Jaroslav A1 - Andreasson, Jakob T1 - Bright continuously tunable vacuum ultraviolet source for ultrafast spectroscopy JF - Communications Physics N2 - Ultrafast electron dynamics drive phenomena such as photochemical reactions, catalysis, and light harvesting. To capture such dynamics in real-time, femtosecond to attosecond light sources are extensively used. However, an exact match between the excitation photon energy and a characteristic resonance is crucial. High-harmonic generation sources are advantageous in terms of pulse duration but limited in spectral tunability in the vacuum ultraviolet range. Here, we present a monochromatic femtosecond source continuously tunable around 21eV photon energy utilizing the second harmonic of an optical parametric chirped pulse amplification laser system to drive high-harmonic generation. The unique tunability of the source is verified in an experiment probing the interatomic Coulombic decay in doped He nanodroplets across the He absorption bands. Moreover, we achieved intensities sufficient for driving collective processes in multiply excited helium nanodroplets, which have been previously observed only at free electron lasers. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18462 SN - 2399-3650 VL - 7 PB - Nature Publishing Group ER - 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 - TY - JOUR A1 - Sishodia, Keshav A1 - Ben Ltaief, Ltaief A1 - Scheel, Niklas A1 - Földes, István B. A1 - Roos, Andreas Hult A1 - Albrecht, Martin A1 - Staněk, Matyáš A1 - Jurkovičová, Lucie A1 - Hort, Ondrej A1 - Nejdl, Jaroslav A1 - García-Alfonso, Ernesto A1 - Halberstadt, Nadine A1 - Andreasson, Jakob A1 - Klimešová, Eva A1 - Krikunova, Maria A1 - Krishnan, Sivarama A1 - Heidenreich, Andreas A1 - Mudrich, Marcel T1 - XUV fluorescence as a probe of interatomic coulombic decay of resonantly excited He nanodroplets JF - Scientific Reports N2 - Superfluid He nanodroplets resonantly excited by extreme ultraviolet (XUV) pulses can relax via interatomic coulombic decay (ICD), generally considered an ultrafast process. Here, we introduce a novel approach to probe the dynamics of ICD in He nanodroplets over timescales ranging from femtoseconds to nanoseconds. Our method relies on detecting XUV fluorescence emitted from the nanodroplets as they are driven into a nanoplasma by subsequent intense infrared pulses. Nanoplasma ignition is facilitated by tunnel ionization of XUV-excited He∗ atoms attached to the droplets; it thus serves as a sensitive probe of their relaxation dynamics. The observed nanosecond-scale decay is attributed to ICD between pairs of He∗ atoms undergoing roaming motion on the droplet surface, as supported by quantum-mechanical and classical model calculations. Y1 - 2026 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-21050 VL - 16 IS - 1 PB - Springer Nature ER -