A5067934065- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Laser Material Processing Techniques
- Laser-induced spectroscopy and plasma
- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Diamond and Carbon-based Materials Research
- Laser-Ablation Synthesis of Nanoparticles
- Ion-surface interactions and analysis
- Spectroscopy and Quantum Chemical Studies
- nanoparticles nucleation surface interactions
- High-pressure geophysics and materials
- Carbon Nanotubes in Composites
- Molecular Junctions and Nanostructures
- Transition Metal Oxide Nanomaterials
- Advanced Fiber Laser Technologies
- Quantum Information and Cryptography
- Nonlinear Optical Materials Studies
- Force Microscopy Techniques and Applications
- Quantum and electron transport phenomena
- Silicon Nanostructures and Photoluminescence
- Advanced Electron Microscopy Techniques and Applications
- Mechanical and Optical Resonators
- Nonlinear Photonic Systems
- Electron and X-Ray Spectroscopy Techniques
University of Kassel
2015-2024
Fritz Haber Institute of the Max Planck Society
2017
Meta (United States)
2014
Pontificia Universidad Católica de Chile
2008
Freie Universität Berlin
1995-2004
Universitat de les Illes Balears
1998-2004
Institute for Scientific and Technological Research
2004
Fundació Universitat-Empresa de les Illes Balears
2004
Universität Greifswald
2002
Universidad de Valladolid
2000-2002
This review is devoted to the study of ultrafast laser ablation solids and liquids. The condensed matter under exposure subpicosecond pulses has a number peculiar properties which distinguish this process from induced by nanosecond longer pulses. includes light absorption electrons in skin layer, energy transfer layer target interior nonlinear electronic heat conduction, relaxation electron ion temperatures, melting, hydrodynamic expansion heated accompanied formation metastable states...
We employ grazing-incidence femtosecond x-ray diffraction to characterize the coherent, laser-induced lattice motion of a bismuth crystal as function depth from surface with temporal resolution 193+/-8 fs. The data show direct consequences on carrier diffusion and electron-hole interaction, allowing us estimate an effective rate D=2.3+/-0.3 cm(2)/s for highly excited carriers interaction time 260+/-20
The physical mechanisms for damage formation in graphite films induced by femtosecond laser pulses are analyzed using a microscopic electronic theory. We describe the nonequilibrium dynamics of electrons and lattice performing molecular simulations on time-dependent potential energy surfaces. show that has unique property exhibiting two distinct laser-induced structural instabilities. For high absorbed energies ( >3.3 eV/atom) we find melting followed fast evaporation. low intensities above...
A laser is a very sharp tool, so to speak, for carving materials at the nanoscale, but involves many poorly understood, nonequilibrium processes. The authors' investigation combines an advanced experimental technique, using UV realize much finer structures than possible visible beam, with atomistic-continuum computational method that allows direct comparison of simulations empirical results. This provides both tools and understanding needed develop nanotechnology diverse ends in e.g....
Most of the ongoing projects aimed at development specific therapies and vaccines against COVID-19 use SARS-CoV-2 spike (S) protein as main target [1-3]. The binding with ACE2 receptor (ACE2) host cell constitutes first key step for virus entry. During this process, domain (RBD) S plays an essential role, since it contains motif (RBM), responsible docking to receptor. So far, mostly biochemical methods are being tested in order prevent [4]. Here we show, help atomistic simulations, that...
We present a theoretical study of ultrafast phase transitions induced by femtosecond laser pulses arbitrary form. Molecular-dynamics simulations on time dependent potential-energy surfaces derived from microscopic Hamiltonian are performed. Applying this method to diamond, we show that nonequilibrium transition graphite takes place for wide range pulse durations and intensities. This $(\ensuremath{\sim}100 \mathrm{fs})$ is driven the suppression diamond minimum in surface excited system.
Using first principles, all-electron calculations and dynamical simulations we study the behavior of A_1g E_g coherent phonons induced in Bi by intense laser pulses. We determine potential landscapes heated material show that they exhibit phonon-softening, phonon-phonon coupling, anharmonicities. As a consequence mode modulates oscillations higher harmonics both modes appear, which explains recent isotropic reflectivity measurements. Our results offer unified description different...
What happens when an ultrashort high-intensity laser pulse heats up a silicon crystal? Accurate quantum-mechanical simulations of the motion atoms in crystal reveal synchronous atomic oscillations between two distinct types squeezed thermal-phonon modes.
Abstract In a bulk solid, optical control of atomic motion provides better understanding its physical properties and functionalities. Such studies would benefit from active visualization motions in arbitrary directions, yet, so far, mostly only one-dimensional has been shown. Here we demonstrate novel method to optically visualize two-dimensional solid. We use femtosecond laser pulse coherently superpose two orthogonal crystalline bismuth. The relative amplitudes those are manipulated by...
We present an atomistic-continuum model to simulate ultrashort-pulse laser melting processes in semiconductor solids on the example of silicon. The kinetics transient nonequilibrium phase transition mechanisms is addressed with a molecular dynamics method at atomic level, whereas light absorption, strong generated electron-phonon nonequilibrium, fast diffusion and heat conduction due photoexcited free carriers are accounted for continuum. give detailed description model, which then applied...
Time-resolved x-ray spectroscopy at the Si L edges is used to probe electronic structure of an amorphous foil as it melts following absorption ultrafast laser pulse. Picosecond temporal resolution allows observation transient liquid phase before vaporization and breaks up into droplets. The melting causes changes in spectrum that match predictions molecular dynamics ab initio codes.
We compute the potential energy surface of femtosecond-laser-excited InSb along directions in which crystal becomes soft. Using dynamical simulations time dependence atomic coordinates is obtained. find that at high excitation densities anharmonicity significant after approximately 100 fs. On basis our results we explain recent time-resolved x-ray diffraction experiments. point out an alternative model for ultrafast melting [A. M. Lindenberg, Science 308, 392 (2005)] inconsistent with calculations.
Microscopic processes leading to ultrafast laser-induced melting of silicon are investigated by large-scale ab initio molecular dynamics simulations. Before becoming a liquid, the atoms shown be fractionally diffusive, which is property that has so far been observed in crowded fluids consisting large molecules. Here, it found occur an elemental semiconductor.
We investigate the excitation of phonons in photoexcited antimony and demonstrate that entire electron-lattice interactions, particular coherent incoherent electron-phonon coupling, can be probed simultaneously. Using femtosecond electron diffraction (FED) with high temporal resolution, we observe fully symmetric \Ag\ optical phonon mode via shift minimum atomic potential energy surface. Ab initio molecular dynamics simulations on laser excited surfaces are performed to quantify change...
Markov state models (MSMs) have received an unabated increase in popularity recent years, as they are very well suited for the identification and analysis of metastable states related kinetics. However, state-of-the-art modeling methods tools enforce fulfillment a detailed balance condition, restricting their applicability to equilibrium MSMs. To date, unsuitable deal with general dominant data structures including cyclic processes, which essentially associated nonequilibrium systems....
To determine the size dependence of bonding in divalent-metal clusters we use a many-electron Hamiltonian describing interplay between van der Waals (vdW) and covalent interactions. Using saddle-point slave-boson method taking into account size-dependent screening charge fluctuations, obtain for ${\mathrm{Hg}}_{\mathit{n}}$ sharp transition with vdW to increasing n. We show also, by solving model exactly, that divalent metals coexist already dimers.
Intense ultrashort laser pulses can melt crystals in less than a picosecond but, spite of over thirty years active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations silicon on laser-excited potential-energy surface, exclusively revealing signatures laser-induced melting. From our simulated atomic trajectories, compute the decay five structure...