TY - JOUR A1 - Roos, Andreas Hult A1 - Hoque, Ziaul A1 - Klimešová, Eva A1 - Ben Ltaief, Ltaief A1 - Medina, Cristian A1 - Jurkovič, Matej A1 - Albrecht, Martin A1 - Finke, Ondřej A1 - Hort, Ondřej A1 - Nejdl, Jaroslav A1 - Mudrich, Marcel A1 - Andreasson, Jakob A1 - Krikunova, Maria T1 - Electron correlation dynamics in atomic Kr excited by XUV pulses and controlled by NIR laser pulses of variable intensity JF - New Journal of Physics N2 - We have investigated the possibility to track and control correlation dynamics of valence electrons in krypton (Kr) initiated by the absorption of one extreme ultraviolet (XUV) photon. In this investigation, pump-probe experiments have been performed where monochromatized single high-harmonics at photon energies 29.6, 32.8, and 35.9 eV have been used as pump to populate different intermediate excited states. A temporally delayed near-infrared (NIR) pulse probes the population of various decay channels via the detection of Kr²⁺ ion yields and its transient profiles. We observe that by varying the NIR pulse intensity within a range from 0.3 x 10¹³ to 2.6 x 10¹³ W cm⁻², the shape of the Kr²+ transient profile changes significantly. We show that by varying the intensity of the NIR pulse, it is possible—(i) to control the ratio between sequential and non-sequential double ionization of Kr; (ii) to selectively probe quantum beating oscillations between Kr+* satellite states that are coherently excited within the bandwidth of the XUV pulse; and (iii) to specifically probe the relaxation dynamics of doubly excited (Kr**) decay channels. Our studies show that the contribution of different ionization and decay channels (i)–(iii) can be altered by the NIR pulse intensity, thus demonstrating an efficient way to control the ionization dynamics in rare gas atoms. KW - electron correlation KW - control ionization dynamics KW - krypton satellite states KW - XUV/NIR pump-probe KW - HHG KW - quantum beating oscillation KW - doubly excited states Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16987 VL - 25 PB - Institute of Physics Publishing (IOP) ER - 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 - Klimesová, Eva A1 - Roos, Andreas Hult A1 - Hoque, Ziaul A1 - Smijesh, N. A1 - Squibb, R.J. A1 - Coudert-Alteirac, H. A1 - Feifel, R. A1 - Andreasson, Jakob A1 - Krikunova, Maria T1 - Update on MAC End-Station at ELI Beamlines Facility JF - Acta Physica Polonica A N2 - The MAC end-station at the ELI Beamlines facility is a multipurpose user's station for atomic, molecular, and optical sciences and coherent diffractive imaging. The technical design of the station, the available instruments, and an overview of the whole beamline have been published in Eur. Phys. J. Spec. Top. 230, 4183 (2021). Here, we address ongoing upgrades of the MAC end-station that will provide users with advanced capabilities for beam manipulation and electron/ion detection. The upgrades include (i) the installation of a beam preparation chamber in front of the MAC chamber, (ii) a magnetic bottle electron spectrometer with high collection and detection efficiency and high energy resolution, and (iii) an event-driven TPX3CAM detector for velocity map imaging spectrometer, which provides both spatial and temporal information for each pixel. We present results from the first commissioning measurements with these instruments, confirming their performance for state-of-the-art experiments in atomic, molecular, and optical sciences. KW - atomic and molecular sciences KW - laser KW - electron and ion spectroscopy Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18840 UR - http://appol.ifpan.edu.pl/index.php/appa/article/view/145_118 N1 - Konferenz: Zakopane School of Physics "Breaking Frontiers: Submicron Structures in Physics and Biology", 23.-27.05.2023, Zakopane, Poland. VL - 145 IS - 2 SP - 118 EP - 122 PB - Institute of Physics (IOP) and Polish Physical Society ER - TY - JOUR A1 - Klimesova, Eva A1 - Kulyk, Olena A1 - Martin, Lucas Janos A1 - Schütte, Bernd A1 - Frühling, Ulrike A1 - Drescher, Markus A1 - Pan, Rui A1 - Stojanovic, Nikola A1 - Bermudez Macias, Ivette J. A1 - Düsterer, Stefan A1 - Andreasson, Jakob A1 - Wieland, Marek A1 - Krikunova, Maria T1 - Electron thermalization and ion acceleration in XUV-produced plasma from nanoparticles in He gas environment JF - New Journal of Physics N2 - We use intense femtosecond extreme ultraviolet (XUV) pulses with a photon energy of 92 eV from the FLASH free electron laser to irradiate substrate-free CsCl nanoparticles surrounded by a He gas with a number density of around 1015 cm−3. By simultaneously detecting electrons and energetic ions from the laser-irradiated micron-size target we study the acceleration mechanism of light ions at the microplasma-vacuum boundary as well as at the layer close to the nanoparticle surface. When the XUV pulse interacts with the gas alone, helium ions are accelerated to energies exceeding 100 eV. In the presence of the nanoparticle, light ions gain additional energy in the electric field around the ionized nanoparticle and their energy spectrum changes considerably. We present an electrostatic model to explain the ion acceleration mechanisms both with and without the nanoparticle and discuss the role of the gas environment in experiments. KW - light–matter interaction KW - free electron laser KW - nanoparticle injection KW - electron and ion spectroscopy Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-19818 VL - 27 PB - Institute of Physics Publishing (IOP); Deutsche Physikalische Gesellschaft ER - TY - INPR A1 - Ševaev, Dmitrij A1 - Nomerotski, Andrei A1 - Švihra, Peter A1 - Sishodia, Keshav A1 - Roos, Andreas Hult A1 - Albrecht, Martin A1 - Andreasson, Jakob A1 - Krikunova, Maria A1 - Klimešová, Eva T1 - Studies of ultrafast dynamics in substrate-free nanoparticles at ELI using Timepix3 optical camera T2 - arXiv.org N2 - We present a novel application of the Timepix3 optical camera (Tpx3Cam) for investigating ultrafast dynamics in substrate-free nanoparticles at the Extreme Light Infrastructure European Research Infrastructure Consortium (ELI ERIC). The camera, integrated into an ion imaging system based on a micro-channel plate (MCP) and a fast P47 scintillator, enables individual time-stamping of incoming ions with nanosecond timing precision and high spatial resolution. The detector successfully captured laser-induced ion events originating from free nanoparticles disintegrated by intense laser pulses. Owing to the broad size distribution of the nanoparticles (10-500 nm) and the variation in laser intensities within the interaction volume, the detected events range in occupancy from near-zero to extremely high, approaching the readout limits of the detector. By combining time-of-flight and velocity map imaging (VMI) techniques, detailed post-processing and analysis were performed. The results presented here focus on the performance of Tpx3Cam under high-occupancy conditions, which are of particular relevance to this study. These conditions approach the limitations imposed by the camera readout capabilities and challenge the effectiveness of standard post-processing algorithms. We investigated these limitations and associated trade-offs, and we present improved methods and algorithms designed to extract the most informative features from the data. KW - VMI KW - Timepix3 KW - Tpx3Cam Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-20875 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 -