Yevheniy Ovcharenko
A5036613918- Advanced X-ray Imaging Techniques
- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Electron Microscopy Techniques and Applications
- Quantum, superfluid, helium dynamics
- Particle Accelerators and Free-Electron Lasers
- Laser-Plasma Interactions and Diagnostics
- Cold Atom Physics and Bose-Einstein Condensates
- Crystallography and Radiation Phenomena
- Atomic and Subatomic Physics Research
- Spectroscopy and Quantum Chemical Studies
- Ion-surface interactions and analysis
- Mass Spectrometry Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Laser-induced spectroscopy and plasma
- Photochemistry and Electron Transfer Studies
- Crystallography and molecular interactions
- Laser Design and Applications
- Medical Imaging Techniques and Applications
- Particle accelerators and beam dynamics
- Spectroscopy and Laser Applications
- Lattice Boltzmann Simulation Studies
- Boron Compounds in Chemistry
European X-Ray Free-Electron Laser
2016-2025
Technische Universität Berlin
2013-2022
Gazprom (Russia)
2020
Istituto di Metodologie Chimiche
2010-2012
Institute of Inorganic Methodologies and Plasmas
2011-2012
Institute of Electron Physics
2009-2011
AREA Science Park
2009
Elettra-Sincrotrone Trieste S.C.p.A.
2009
Institute of Structure of Matter
2009
Abstract Following structural dynamics in real time is a fundamental goal towards better understanding of chemical reactions. Recording snapshots individual molecules with ultrashort exposure times key ingredient this goal, as atoms move on femtosecond (10 −15 s) timescales. For condensed-phase samples, ultrafast, atomically resolved structure determination has been demonstrated using X-ray and electron diffraction. Pioneering experiments have also started addressing gaseous samples....
The idea of using ultrashort X-ray pulses to obtain images single proteins frozen in time has fascinated and inspired many. It was one the arguments for building free-electron lasers. According theory, extremely intense provide sufficient signal dispense with crystals as an amplifier, pulse duration permits capturing diffraction data before sample inevitably explodes. This first demonstrated on biological samples a decade ago giant mimivirus. Since then, large collaboration been pushing...
The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for study of atoms, molecules and clusters by means ion spectroscopies. Beams helium droplets as well metals can be produced three different pulsed valves. atomic molecular beams may seeded, pure, or doped with other atoms molecules. electrons ions ionization fragmentation samples intense light FERMI analysed available spectrometers, to give mass spectra energy angular...
Abstract Coherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet X-ray free-electron lasers, restricting this research field large-scale facilities. Here we demonstrate isolated helium nanodroplets using pulses from a femtosecond-laser-driven high harmonic source. We obtain...
The ionization dynamics of He nanodroplets irradiated with intense femtosecond extreme ultraviolet pulses up to 1013 W/cm2 power density have been investigated by photoelectron spectroscopy. Helium droplets were resonantly excited atomiclike 2p states a photon energy 21.4 eV, below the potential (Ip), and directly into continuum 42.8 eV photons. While electron emission following direct above Ip is well explained within model based on sequence events, resonant excitation provides evidence...
Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He^{+}(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of spectrum angular distribution electrons ejected from by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found vary strongly as function intensity. experimental data well described...
Ultrashort x-ray pulses from free-electron lasers can efficiently charge up and trigger the full fragmentation of molecules. By coincident detection to five ions resulting rapid Coulomb explosion highly charged iodomethane, we show that three-dimensional equilibrium geometry this prototypical polyatomic system be determined measured ion momenta with help a buildup model. Supported by simulations how would reflect specific changes in molecular bond lengths angles, demonstrate...
A velocity map imaging/ion time-of-flight spectrometer designed specifically for pump–probe experiments combining synchrotron and laser radiations is described. The in-house built delay line detector can be used in two modes: the high spatial resolution mode coincidence mode. In a kinetic energy of 6% has been achieved. to improve signal-to-noise ratio either by using gate count electrons only when present or recording coincidences with ion formed ionization process.
Free electron lasers (FELs) offer the unprecedented capability to study reaction dynamics and image structure of complex systems. When multiple photons are absorbed in systems, a plasma-like state is formed where many atoms ionized on femtosecond timescale. If multiphoton absorption resonantly-enhanced, system becomes electronically-excited prior plasma formation, with subsequent decay paths which have been scarcely investigated date. Here, we show using helium nanodroplets as an example...
A significant fraction of superfluid helium nanodroplets produced in a free-jet expansion has been observed to gain high angular momentum resulting large centrifugal deformation. We measured single-shot diffraction patterns individual rotating up scattering angles using intense extreme ultraviolet light pulses from the FERMI free-electron laser. Distinct asymmetric features wide-angle enable unique and systematic identification three-dimensional droplet shapes. The analysis data set allows...
The Low Density Matter (LDM) beamline has been built as part of the FERMI free-electron laser (FEL) facility to serve atomic, molecular and cluster physics community. After commissioning phase, it received first external users at end 2012. design characterization LDM photon transport system is described, detailing optical components beamline.
A central motivation for the development of x-ray free-electron lasers has been prospect time-resolved single-molecule imaging with atomic resolution. Here, we show that photoelectron diffraction—where a emitted after absorption illuminates molecular structure from within—can be used to image increase internuclear distance during x-ray-induced fragmentation an O2 molecule. By measuring molecular-frame emission patterns two-photon sequential K-shell ionization in coincidence fragment ions,...
Finding the lowest energy configuration of N unit charges on a sphere, known as Thomson's problem, is long-standing query which has only been studied via numerical simulations. We present its physical realization using multiply charged He nanodroplets. The charge positions are determined by x-ray coherent diffractive imaging with Xe contrast agent. In neutral droplets, filaments resulting from atoms condensing quantum vortices observed. Unique to however, clusters that condense distributed...
The nonlinear interaction of x rays with matter is at the heart understanding and controlling ultrafast molecular dynamics from an atom-specific viewpoint, providing new scientific analytical opportunities to explore structure small quantum systems. At increasingly high x-ray intensity, sensitivity ultrashort pulses specific electronic states emerging short-lived transient intermediates particular relevance for our fundamental multiphoton absorption processes. In this work, intense...
Abstract The photochemistry of heterocyclic molecules plays a decisive role for processes and applications like DNA photo-protection from UV damage organic photocatalysis. photochemical reactivity heterocycles is determined by the redistribution photoenergy into electronic nuclear degrees freedom, initially involving ultrafast internal conversion. Most are planar in their ground state conversion requires symmetry breaking. To lower symmetry, molecule must undergo an out-of-plane motion,...
Highly charged ions are formed in the center of composite clusters by strong free-electron laser pulses and they emit fluorescence on a femtosecond time scale before competing recombination leads to neutralization nanoplasma core. In contrast mass spectrometry that detects remnants interaction, extreme ultraviolet spectral range provides fingerprints transient states high energy density matter. Spectra from consisting xenon core surrounding argon shell show small fraction signal comes...
The relaxation of photoexcited nanosystems is a fundamental process light-matter interaction. Depending on the couplings internal degrees freedom, can be ultrafast, converting electronic energy in few fs, or slow, if trapped metastable state that decouples from its environment. Here, helium nanodroplets are resonantly excited by femtosecond extreme-ultraviolet (XUV) pulses seeded free-electron laser. Despite their superfluid nature, we find lowest electronically states undergo ultrafast...
The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated molecules to short x-ray pulse from free-electron laser and detected momenta all produced ions coincidence. By combining experimental results theoretical modeling, we can image dissociation individual unprecedented detail. reveal significant molecular H2O2+, such as asymmetric deformation bond-angle opening, leading two-body or three-body...
The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain rate of ICD, resulting yield Ne_{2}^{+} ions was recorded as a function delay between pump and UV probe pulses. extracted lifetimes long-lived states, 390(-130/+450)...
Intense short-wavelength pulses from free-electron lasers and high-harmonic-generation sources enable diffractive imaging of individual nanosized objects with a single x-ray laser shot. The enormous data sets up to several million diffraction patterns present severe problem for analysis because the high dimensionality data. Feature recognition selection is crucial step reduce dimensionality. Usually, custom-made algorithms are developed at considerable effort approximate particular features...
We report on a multiparticle coincidence experiment performed at the European X-ray Free-Electron Laser Small Quantum Systems instrument using COLTRIMS reaction microscope. By measuring two ions and electrons in coincidence, we investigate double core-hole generation O_{2} molecules gas phase. Single-site two-site core holes have been identified their molecular-frame electron angular distributions obtained for breakup of oxygen molecule into doubly charged ions. The measured are compared to...
Nonlinear x-ray spectroscopy The extension of nonlinear optics to the spectral domain is a promising direction in development spectroscopy. Although theoretical concepts were developed decades ago, scientists still struggle implement them because elusive nature effects. Eichmann et al. now present atomic momentum (AMS), which based on detection scattered atom after transfer from photons (see Perspective by Pfeifer). authors show how AMS can observe stimulated Raman scattering signals at neon...
The inner shell excitation of pyrimidine and some halogenated pyrimidines near the C N K-edges has been investigated experimentally by edge x-ray absorption fine structure spectroscopy theoretically density functional theory calculations. selected targets, 5-Br-pyrimidine, 2-Br-pyrimidine, 2-Cl-pyrimidine, 5-Br-2-Cl-pyrimidine, allow effects functionalization ring to be studied either as a function different halogen atoms bound same molecular site or atom sites. results show that individual...