A5062524741- Ion-surface interactions and analysis
- Integrated Circuits and Semiconductor Failure Analysis
- Electron and X-Ray Spectroscopy Techniques
- Advanced X-ray Imaging Techniques
- Laser Material Processing Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Laser-induced spectroscopy and plasma
- Diamond and Carbon-based Materials Research
- Laser-Plasma Interactions and Diagnostics
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor materials and devices
- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- High-pressure geophysics and materials
- Advanced Surface Polishing Techniques
- Nuclear Physics and Applications
- Particle Accelerators and Free-Electron Lasers
- Spectroscopy and Quantum Chemical Studies
- Nuclear materials and radiation effects
- nanoparticles nucleation surface interactions
- Advanced Semiconductor Detectors and Materials
- Mass Spectrometry Techniques and Applications
- Crystallography and Radiation Phenomena
- Force Microscopy Techniques and Applications
- Machine Learning in Materials Science
Czech Academy of Sciences, Institute of Plasma Physics
2016-2025
Czech Academy of Sciences
2016-2025
Czech Academy of Sciences, Institute of Physics
2016-2025
Centre of Plasma Physics - Institute for Plasma Research
2023
South Dakota State University
2021
John Wiley & Sons (United States)
2020
Hudson Institute
2020
Center for Free-Electron Laser Science
2011-2017
Deutsches Elektronen-Synchrotron DESY
2012-2017
Universität Hamburg
2011-2017
Electron-phonon coupling, being one of the most important parameters governing material evolution after ultrafast energy deposition, yet remains unexplored one. In this work, we applied dynamical coupling approach to calculate nonadiabatic electron-ion exchange in nonequilibrium solids with electronic temperature high above atomic It was implemented into tight-binding molecular dynamics code, and used study electron-phonon various elemental metals. The developed is a universal scheme...
As is known from visible-light experiments, silicon under femtosecond pulse irradiation can undergo so-called ``nonthermal melting'' if the density of electrons excited valence to conduction band overcomes a certain critical value. Such ultrafast transition induced by strong changes in atomic potential energy surface, which trigger relocation. However, heating material due electron-phonon coupling also lead phase transition, called ``thermal melting.'' This thermal melting occur even...
Since a few breakthroughs in the fundamental understanding of effects swift heavy ions (SHI) decelerating electronic stopping regime matter have been achieved last decade, it motivated us to review state-of-the-art approaches modeling SHI effects. The track kinetics occurs via several well-separated stages: from attoseconds ion-impact ionization depositing energy target, femtoseconds electron transport and hole cascades, picoseconds lattice excitation response, nanoseconds atomic relaxation,...
Experiments creating extreme states of matter almost invariably create non-equilibrium states. These are very interesting in their own right but need to be understood even if the ultimate goal is probe high-pressure or high-temperature equilibrium properties like equation state. Here, we report on capabilities newly developed imaginary time correlation function (ITCF) technique [1] detect and quantify pump-probe experiments fielding resolved x-ray scattering diagnostics. We find a high...
Ion tracks formed in amorphous Ge by swift heavy-ion irradiation have been identified with experiment and modeling to yield unambiguous evidence of an semiconductor. Their underdense core overdense shell result from quenched-in radially outward material flow. Following a solid-to-liquid phase transformation, the volume contraction necessary accommodate high-density molten produces voids, potentially precursors porosity, along ion direction. bow-tie shape, reproduced simulation, results...
The femtosecond dynamics of the electrons in aluminum after an intense extreme ultraviolet pulse is investigated by Monte Carlo simulations. Transient distributions conduction band show almost thermalized, low-energy part and a high-energy tail. Constructing emission spectra from these data, we find excellent agreement with measurements. radiative decay mainly reflects colder distribution, whereas highly excited dominate bremsstrahlung spectrum. For latter, also good between predicted...
In this paper, we present a novel theoretical approach, which allows the study of nonequilibrium dynamics both electrons and atoms/ions within free-electron laser excited semiconductors at femtosecond time scales. The approach consists Monte-Carlo method treating photoabsorption, high-energy-electron core-hole kinetics relaxation processes. Low-energy localized valence conduction bands target are treated with temperature equation, including source terms, defined by exchange energy particles...
FERMI is a novel class of free-electron laser that capable producing femtosecond pulses ultraviolet and x-ray light, essential to studying ultrafast processes in matter. A new investigation characterizes FERMI's pulse shape confirms it routinely generates Gaussian lasting few tens femtoseconds.
The event-by-event Monte Carlo model, TREKIS, was developed to describe the excitation of electron subsystems various solids by a penetrating swift heavy ion (SHI), spatial spreading generated fast electrons, and secondary hole cascades. Complex dielectric function formalism is used obtain relevant cross sections. This allows recognition fundamental effects resulting from collective response subsystem target for that not possible within binary collision approximation these sections, e.g....
We review the results of our research on damage mechanisms in materials irradiated with femtosecond free-electron-laser (FEL) pulses. They were obtained using hybrid approach, X-ray-induced thermal and non-thermal transitions (XTANT). Various are discussed respect to pulse fluence material properties examples diamond, amorphous carbon, C 60 crystal, silicon. indicate following conditions: those producing melting targets as a result electron-ion energy exchange; phase due modification...
Response of dielectric crystals: MgO, Al2O3 and Y3Al5O12 (YAG) to irradiation with 167 MeV Xe ions decelerating in the electronic stopping regime is studied. Comprehensive simulations demonstrated that despite similar ion energy losses initial excitation kinetics systems lattices, significant differences occur among final structures tracks these materials, supported by experiments. No appeared whereas discontinuous distorted crystalline ~2 nm diameter were observed continuous amorphous...
We studied experimentally and theoretically the structural transition of diamond under an irradiation with intense femtosecond extreme ultraviolet laser (XUV) pulse 24--275 eV photon energy provided by free-electron lasers. Experimental results obtained show that irradiated undergoes a solid-to-solid phase to graphite, not amorphous state. Our theoretical findings suggest nature this is nonthermal, stimulated change interatomic potential triggered excitation valence electrons. Ultrashort...
Ultrafast changes of charge density distribution in diamond after irradiation with an intense x-ray pulse (photon energy, 7.8 keV; duration, 6 fs; intensity, $3\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$) have been visualized the pump--x-ray probe technique. The measurement reveals that covalent bonds are broken and electron around each atom becomes almost isotropic within $\ensuremath{\sim}5\text{ }\mathrm{fs}$ intensity maximum pump pulse. 15 fs...
The energy dissipation after irradiation of dielectrics with swift heavy ions is studied applying a combination the Monte Carlo (MC) method and two-temperature model (TTM). Within MC calculation transient dynamics electrons in excited dielectric described: primary excitation relaxation target as well creation secondary electrons. From data, it was observed that electron system can be considered thermalized time $t\ensuremath{\approx}100$ fs ion impact. Then TTM applied to calculate spatial...
In the present work, a theoretical study of electron-phonon (electron-ion) coupling rates in semiconductors driven out equilibrium is performed. Transient change optical coefficients reflects band gap shrinkage covalently bonded materials, and thus, heating atomic lattice. Utilizing this dependence, we test various models electron-ion coupling. The simulation technique based on tight-binding molecular dynamics. Our simulations with dedicated hybrid approach (XTANT) indicate that widely used...
Ultrafast proton migration and isomerization are key processes for acetylene its ions. However, the mechanism ultrafast of [HCCH]2+ to vinylidene [H2CC]2+ dication remains nebulous. Theoretical studies show a large potential barrier ( > 2 eV) on low-lying dicationic states, implying picosecond or longer timescales. recent experiment at femtosecond X-ray free-electron laser suggests sub-100 fs isomerization. Here we address this contradiction with complete theoretical study dynamics produced...
Ultrafast laser irradiation of metals can often be described theoretically with the two-temperature model. The energy exchange between excited electronic system and atomic one is governed by electron-phonon coupling parameter. depends on both, temperature. We analyze effect dependence parameter temperature in ruthenium, gold, palladium. It shown that induces nonlinear behavior, which a higher initial leads to faster equilibration. Analysis experimental measurements transient...
We present a concurrent Monte Carlo (MC) - molecular dynamics (MD) approach to modeling of matter response excitation its electronic system. The two methods are combined on-the-fly at each time step in one code, TREKIS-4. MC model describes arrival irradiation, which the current implementation can consist photon, an electron, or fast ion. It also traces induced cascades secondary particles, electrons and holes, their energy exchange with atoms due scattering. excited atomic system is...
Atomic heating in a solid takes place after an impact of swift heavy ion within time electronic cooling there, i.e., ∼100 fs. This implies extremely fast electron–ion energy exchange (“electron–phonon coupling”) necessary for the production detected tracks. In contrast, laser irradiation experiments and calculations show too slow electron–phonon to cause structural changes tracks solids. We demonstrate that this contradiction can be resolved by taking into account coupling is not sole...