A5019601988- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Dust and Plasma Wave Phenomena
- Scientific Measurement and Uncertainty Evaluation
- Advanced Thermodynamics and Statistical Mechanics
- Optical properties and cooling technologies in crystalline materials
- nanoparticles nucleation surface interactions
- Cold Atom Physics and Bose-Einstein Condensates
- X-ray Spectroscopy and Fluorescence Analysis
- Sports Science and Education
- Spectroscopy and Quantum Chemical Studies
- Quantum, superfluid, helium dynamics
- Advanced X-ray Imaging Techniques
- Phase Equilibria and Thermodynamics
- Pesticide Residue Analysis and Safety
- Plasma Diagnostics and Applications
- Physics and Engineering Research Articles
- Statistical Mechanics and Entropy
- Ion-surface interactions and analysis
- Particle Accelerators and Free-Electron Lasers
- Material Dynamics and Properties
University of Rostock
2010-2023
Universität Greifswald
1996-2015
University of Warwick
2010
University of Ottawa
2008
We present the first collective x-ray scattering measurements of plasmons in solid-density plasmas. The forward spectra a laser-produced narrow-band line from isochorically heated beryllium show that plasmon frequency is sensitive measure electron density. Dynamic structure calculations include collisions and detailed balance match measured spectrum indicating this technique will enable new applications to determine equation state compressibility dense matter.
A kinetic theory for quantum many-particle systems in time-dependent electromagnetic fields is developed based on a gauge-invariant formulation. The resulting equation generalizes previous results to and includes many-body effects. It is, particular, applicable the interaction of strong laser with dense correlated plasmas.
We report on the dynamics of ultrafast heating in cryogenic hydrogen initiated by a ≲300 fs, 92 eV free electron laser x-ray burst. The rise scattering amplitude from second pulse probes transition dense molecular to nearly uncorrelated plasmalike structure, indicating an electron-ion equilibration time ∼0.9 ps. agrees with radiation hydrodynamics simulations based conductivity model for partially ionized plasma that is validated two-temperature density-functional theory.
We investigate ultrafast (fs) electron dynamics in a liquid hydrogen sample, isochorically and volumetrically heated to moderately coupled plasma state. Thomson scattering measurements using 91.8 eV photons from the free-electron laser Hamburg (FLASH at DESY) show that has been driven nonthermal state with an temperature of 13 ion below 0.1 eV, while density is 2.8x10{20} cm{-3}. For dense plasmas, our experimental data strongly support nonequilibrium kinetics model uses impact ionization...
A quantum kinetic approach for the energy relaxation in strongly coupled plasmas with different electron and ion temperatures is presented. Based on density operator formalism, we derive a balance equation energies of electrons ions connecting kinetic, correlation, exchange quite general expression electron-ion energy-transfer rate. The latter given terms correlation function fluctuations which allows derivation increasingly realistic approximation schemes including coupled-mode expression....
Collective Thomson scattering with extreme ultraviolet light or x rays is shown to allow for a robust measurement of the free electron density in dense plasmas. excitations like plasmons appear as maxima signal. Their frequency position can directly be related density. The range applicability standard Gross-Bohm dispersion relation and an improved comparison calculations based on dielectric function random phase approximation investigated. More important, this well-established treatment...
Collisional absorption of dense, fully ionized plasmas in strong laser fields is investigated starting from a quantum kinetic equation with non-Markovian and field-dependent collision integrals dynamically screened Born approximation. This allows to find rather general balance equations for the energy current. For high-frequency fields, statistical expressions electrical current density cycle-averaged electron-ion frequency terms Lindhard dielectric function are derived. The valid arbitrary...
A kinetic approach is derived to take into account nonideality effects in the rate coefficients of plasmas. First results are given for a reacting hydrogen plasma.Received 30 November 1987DOI:https://doi.org/10.1103/PhysRevA.38.2174©1988 American Physical Society
Abstract We solve the Ornstein‐Zernike equation within hypernetted chain approximation for dense multi‐component plasmas using effective pair potentials. The method is used to study structural properties of plasmas, instance in order explain and predict X‐ray Thomson scattering spectra. Corresponding experiments are performed at free electron lasers such as FLASH Hamburg LCLS Stanford, or facilities energetic optical Omega Rochester Janus Livermore. Results distribution functions static...
The spectrum of x-ray Thomson scattering is proportional to the dynamic structure factor. An important contribution ion feature which describes elastic x rays off electrons. We apply an ab initio method for calculation form factor bound electrons, slope screening cloud free and ion-ion in warm dense beryllium. With presented we can calculate from first principles. These results will facilitate a better understanding matter accurate measurement temperatures would allow determining...
A quantum kinetic theory for correlated charged-particle systems in strong time-dependent electromagnetic fields is developed. Our approach based on a systematic gauge-invariant nonequilibrium Green's functions formulation. Extending our previous analysis (Kremp et al., Phys. Rev. E vol. 60, p. 4725 (1999) we concentrate the selfconsistent treatment of dynamical screening and which applicable to arbitrary situations. The resulting equation generalizes results plasmas with full includes...
In the framework of real-time Green's functions, general kinetic equations are investigated in a first-order gradient expansion. Within this approximation, problem reconstruction two-time correlation functions from one-time Wigner function was solved. For function, cluster expansion is found terms quasiparticle distribution function. equilibrium, leads to well-known generalized Beth-Uhlenbeck expression second virial coefficient. As special case, T-matrix approximation for self-energy...
The introduction of brilliant free-electron lasers enables new pump-probe experiments to characterize warm dense matter states. For instance, a short-pulse optical laser irradiates liquid hydrogen jet that is subsequently probed with soft x-ray radiation. strongly inhomogeneous plasma prepared by the characterized particle-in-cell simulations. interaction probe radiation for different time delays between pump and also taken into account via radiative hydrodynamic We calculate respective...
We investigate subpicosecond dynamics of warm dense hydrogen at the XUV free-electron laser facility (FLASH) DESY (Hamburg). Ultrafast impulsive electron heating is initiated by a ≤300-fs short x-ray burst 92-eV photon energy. A second pulse probes sample via scattering jitter-free variable time delay. show that initial molecular structure dissociates within (0.9±0.2) ps, allowing us to infer energy transfer rate between electrons and ions. evaluate Saha Thomas-Fermi ionization models in...
Collisional absorption of dense fully ionized plasmas in strong laser fields is investigated using quantum statistical methods as well molecular dynamics simulations. For high-frequency fields, expressions for the electrical current density and electron-ion collision frequency are presented. Strong correlations taken into account their influence on rate discussed. The valid arbitrary field strength assuming nonrelativistic case. In addition, simulations were performed to calculate heating...
We have performed HNC calculations for dense beryllium plasma as studied experimentally using x-ray Thomson scattering, recently. treated non-equilibrium situations with different electron and ion temperatures which are relevant in pump-probe experiments on ultra-short time scales. To consider quantum effects adequately, we used effective pair potentials to describe the interactions. Results compared classical well corrected Debye model calculations.
X-ray scattering using highly brilliant x-ray free-electron laser (FEL) radiation provides new access to probe density, temperature and ionization in near-solid density plasmas. First experiments at the soft FEL FLASH DESY, Hamburg, show capabilities of this technique. The ultrashort pulses particular can equilibration phenomena occurring after excitation plasma optical pumping. We have investigated liquid hydrogen find that interaction very intense alone heats sample volume. As establishes,...
Inverse bremsstrahlung (IB) heating, an important process in the laser–matter interaction, involves two different kinds of interaction—the interaction electrons with external laser field and electron–ion interaction. This makes analytical approaches very difficult. In a quantum perturbative approach to IB heating rate strong fields, usually first Born approximation respect potential is considered, whereas influence electric taken exactly Volkov wave functions. this paper, treatment presented...
Optimal control techniques combined with femtosecond laser pulse shaping are applied to steer and enhance the strong-field induced emission of highly charged atomic ions from silver clusters embedded in helium nanodroplets. With light fields shaped amplitude phase we observe a substantial increase ${\mathrm{Ag}}^{q+}$ yield for $q>10$ when compared bandwidth-limited optimally stretched pulses. A remarkably simple double-pulse structure, containing low-intensity prepulse stronger main...
The interaction of intense laser fields with silver and argon clusters is investigated theoretically using a modified nanoplasma model. Single pulse double excitations are considered. influence the dense cluster environment on inner ionization processes studied including lowering energies. There considerable changes in dynamics laser-cluster interaction. Especially, for clusters, energies leads to increased yields highly charged ions.