A5041616579- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Nuclear physics research studies
- Laser-Matter Interactions and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Spectroscopy and Quantum Chemical Studies
- Laser-induced spectroscopy and plasma
- X-ray Spectroscopy and Fluorescence Analysis
- Mass Spectrometry Techniques and Applications
- Particle accelerators and beam dynamics
- Molecular spectroscopy and chirality
- Muon and positron interactions and applications
- Scientific Measurement and Uncertainty Evaluation
- Electron and X-Ray Spectroscopy Techniques
- Advanced Frequency and Time Standards
- Crystallography and Radiation Phenomena
- Photochemistry and Electron Transfer Studies
- Quantum optics and atomic interactions
- Radioactive Decay and Measurement Techniques
- Quantum and Classical Electrodynamics
- Quantum Mechanics and Applications
- Geomagnetism and Paleomagnetism Studies
- Laser-Plasma Interactions and Diagnostics
- Geophysics and Gravity Measurements
- Astro and Planetary Science
University of Kassel
2016-2025
Institute of Applied Physics
2023
National Academy of Sciences of Ukraine
2023
Helmholtz Institute Jena
2011-2014
Peter the Great St. Petersburg Polytechnic University
2014
Heidelberg University
2009-2013
GSI Helmholtz Centre for Heavy Ion Research
2009-2013
Max Planck Society
1998-2010
St Petersburg University
1995-2007
Technische Universität Dresden
2003-2007
We perform ab initio QED calculations of energy levels for the $n=1$ and $n=2$ states He-like ions with nuclear charge in range $Z = 12$-100. The complete set two-electron corrections is evaluated to all orders parameter $\aZ$. Uncalculated contributions come through $\alpha^3 (\aZ)^2$, $\alpha^2 (\aZ)^7$, higher. calculation presented first treatment excited order (\aZ)^4$. A significant improvement accuracy theoretical predictions achieved, especially high-$Z$ region.
The relativistic nuclear recoil corrections to the energy levels of low-laying states hydrogen-like and high $Z$ lithium-like atoms in all orders $\alpha Z$ are calculated. calculations carried out using B-spline method for Dirac equation. For low results calculation good agreement with -expansion results. It is found that contribution, additional Salpeter's one, Lamb shift ($n=2$) hydrogen $-1.32(6)\,kHz$. total correction $(1s)^{2}2p_{\frac{1}{2}}-(1s)^{2}2s$ transition uranium constitutes...
The ground-state hyperfine splitting values of high-$Z$ hydrogenlike ions are calculated. relativistic, nuclear, and QED corrections taken into account. nuclear magnetization distribution correction (the Bohr-Weisskopf effect) is evaluated within the single-particle model with ${g}_{S}$ factor chosen to yield observed moment. An additional contribution caused by nuclear-spin-orbit interaction included in calculation effect. It found that theoretical value wavelength transition between...
Using a model methane-like chiral system, we theoretically demonstrate possibility to access photoelectron circular dichroism (PECD) by single experiment with two overlapping laser pulses of carrier frequencies $\omega$ and $2\omega$, which are linearly polarized in mutually-orthogonal directions. Depending on the relative phase, resulting electric field can be tailored have different rotational directions upper lower hemispheres along polarization $\omega$-pulse. We predict strong...
A possibility for investigations of quantum electrodynamics (QED) in experiments on the hyperfine splitting heavy ions is examined. It found that QED effects can be probed level a few percent specific difference values hydrogenlike and lithiumlike bismuth. This could provide test strongest electric field available at present experimental study.
We present ab initio calculations of the complete gauge invariant set self-energy screening diagrams for ${2p}_{1/2}\ensuremath{-}2s$ transition in Li-like ions. The calculation was performed extended nuclei range $Z=18--100.$ Various contributions to energy are collected. accuracy theoretical predictions is discussed.
The relativistic nuclear recoil, higher-order interelectronic-interaction, and screened QED corrections to the transition energies in Li-like ions are evaluated. calculation of recoil effect is performed all orders 1/Z. interelectronic-interaction correction beyond two-photon exchange level evaluated 1/Z within Breit approximation. evaluation carried out employing large-scale configuration-interaction Dirac-Fock-Sturm method. rigorous complete gauge invariant sets self-energy...
Absolute rate coefficients for dielectronic recombination (DR) of H-like ${\mathrm{U}}^{91+}$ ions have been measured. The electron-ion merged-beam technique at a heavy-ion storage ring was employed using stochastically cooled ion beam. Thereby, the previously accessible collision energies could be greatly extended to range 63--90 keV. High-resolution DR spectra were measured covering all $\mathit{KLL}$ and $\mathit{KLM}$ resonances. For resonance strengths, excellent agreement between...
We perform ab initio QED calculation of the $(1s{)}^{2}(2s{)}^{2}2{p}_{3/2}\mathrm{\text{\ensuremath{-}}}(1s{)}^{2}(2s{)}^{2}2{p}_{1/2}$ transition energy in five-electron ion argon. The is carried out by perturbation theory starting with an effective screening potential approximation. Four different types potentials are considered. rigorous calculations two lowest-order and electron-correlation effects combined approximate evaluations third- higher-order contributions. theoretical value for...
A systematic QED treatment of electron correlation is presented for ions along the lithium isoelectronic sequence. We start with zeroth-order approximation that accounts a part electron-electron interaction by local model potential introduced into Dirac equation. The residual treated perturbation theory. Rigorous evaluation first two terms perturbative expansion; third-order contribution calculated within many-body report accurate numerical results electronic-structure ionization n=2 states...
We have performed ab initio QED calculations of the ${(1s)}^{2}{(2s)}^{2}2{p}_{3/2}\ensuremath{-}{(1s)}^{2}{(2s)}^{2}2{p}_{1/2}$ fine-structure splitting along boron isoelectronic sequence for all ions with $17\ensuremath{\le}Z\ensuremath{\le}100$. This level was evaluated within extended Furry picture and by making use four different screening potentials in order to estimate effects interelectronic correlations. The accuracy predicted transition energies has been improved significantly when...
A theoretical method to study the angle-resolved multiphoton ionization of polyatomic molecules is developed. It based on time-dependent formulation Single Center (TDSC) and consists in propagation single-active-electron wave packets effective molecular potentials presence intense laser pulses. For this purpose, Schrödinger equation for one electron, moving a field interacting with an arbitrary pulse, solved spherical coordinates by efficient numerical approach. As test, applied one-...
We present ab initio calculations of the complete gauge invariant set two-photon exchange graphs for ${2p}_{1/2}\ensuremath{-}2s$ transition energy in Li-like high-$Z$ ions. The evaluation is carried out to all orders $Z\ensuremath{\alpha}$ range $Z=20--100.$ Results are compared with based on relativistic many-body perturbation theory. All presently available contributions collected. resulting theoretical predictions experimental data.
The relativistic recoil effect has been the object of experimental investigations using highly charged ions at Heidelberg electron beam ion trap. Its scaling with nuclear charge $Z$ boosts its contribution to a measurable level in magnetic-dipole ($M1$) transitions B- and Be-like Ar ions. isotope shifts $^{36}\mathrm{A}\mathrm{r}$ versus $^{40}\mathrm{A}\mathrm{r}$ have detected sub-ppm accuracy, was extracted from $1{s}^{2}2{s}^{2}2p$ $^{2}P_{1/2}\ensuremath{-}^{2}P_{3/2}$ transition...
We consider a two-step process that may occur in relativistic ion-atom collisions. In this process, within single collision, an atomic electron is captured by the ion via radiative and/or nonradiative capture channels, while colliding nuclei of atom and simultaneously produce electron-positron pair with created bound state ion. As result, picks up two electrons positron emitted. calculate total cross section for collisions incident $1--4\text{ }\text{GeV}/\text{u}$ ${\text{U}}^{92+}$...
Cross sections and angular distribution parameters for the single-photon ionization of all electron orbitals Li2-8 are systematically computed in a broad interval photoelectron kinetic energies energetically most stable geometry each cluster. Calculations partial continuum waves clusters carried out by single center method within Hartree-Fock approximation. We study photoionization cross per one analyze some details general trends inner outer shells with respect to size The present...
The direct ionization of the helium atom by intense coherent high-frequency short laser pulses is investigated theoretically from first principles. To this end, we solve numerically time-dependent Schr\"odinger equation for two-electron wave packet and its interaction with linearly polarized pulse efficient restricted-active-space configuration-interaction method (TD-RASCI). In particular, consider photon energies which are nearly resonant $1s\ensuremath{\rightarrow}2p$ excitation in...
Photoelectron circular dichroism (PECD) in the ionization of chiral molecules by circularly polarized radiation is a well-established tool for recognition gas phase. The effect consists forward-backward asymmetry angular emission distributions photoelectrons with respect to light propagation direction, which survives averaging over molecular orientations. Its magnitude governed ability outgoing photoelectron probe an ionic potential multiple scattering effects, and it can be significantly...
Spin polarization in the multiphoton ionization of HI molecule with intense 395 nm, circularly polarized laser pulses is investigated theoretically. To this end, we numerically solve time-dependent Schrödinger equation basis spherical spinors employing single-center method. We investigate influence ionizing-pulse parameters, such as peak intensity, time envelope, and duration, well molecular orientation space on computed spin photoelectrons emitted by HOMO, HOMO-1, HOMO-2 states molecule....
The recoil correction to the ground state energy of hydrogenlike atoms is calculated all orders in \alpha Z range = 1-110. nuclear size corrections effect are partially taken into account. In case hydrogen, relativistic beyond Salpeter contribution and nonrelativistic effect, amounts -7.2(2) kHz. total uranium (^{238}U^{91+}) constitutes 0.46 eV.
Calculations of the vacuum-polarization corrections to low-lying energy levels Li-like highly charged ions are presented. The calculations carried out for extended nuclei in range $Z=20\ensuremath{-}100.$
A rigorous QED calculation of the two-photon exchange corrections to 2p(1/2)- 2s transition energy in Li-like high- Z ions is presented. The contribution due an by more than two photons evaluated within Breit approximation. resulting theoretical value uranium found be 280.44(20) eV.
The relativistic nuclear recoil corrections to the energy of 2p3/2 state hydrogen-like and (1s)22p3/2 high-Z lithium-like atoms in all orders alpha Z are calculated. calculations carried out using B-spline method for Dirac equation. For low results calculation good agreement with Z-expansion results. It is found that total contribution (1s)22p3/2-(1s)22s transition uranium constitutes -0.09 eV.