A5043251304- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Spectroscopy and Quantum Chemical Studies
- Advanced Fiber Laser Technologies
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum, superfluid, helium dynamics
- Laser-Plasma Interactions and Diagnostics
- Ion-surface interactions and analysis
- Quantum optics and atomic interactions
- Terahertz technology and applications
- X-ray Spectroscopy and Fluorescence Analysis
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Real-time simulation and control systems
- Advanced Optical Sensing Technologies
- Quantum chaos and dynamical systems
- Fusion materials and technologies
- Photorefractive and Nonlinear Optics
- Hydraulic and Pneumatic Systems
- Diamond and Carbon-based Materials Research
- Fullerene Chemistry and Applications
- Black Holes and Theoretical Physics
- Fluid Dynamics and Turbulent Flows
TU Wien
2011-2021
ELI-HU Research and Development Non-Profit
2017
HUN-REN Institute for Nuclear Research
2017
Hungarian Academy of Sciences
2017
The University of Tokyo
2016
Los Alamos National Laboratory
2011
Photoemission from atoms is assumed to occur instantly in response incident radiation and provides the basis for setting zero of time clocking atomic-scale electron motion. We used attosecond metrology reveal a delay 21 +/- 5 attoseconds emission electrons liberated 2p orbitals neon with respect those released 2s orbital by same 100-electron volt light pulse. Small differences timing photoemission different quantum states provide probe modeling many-electron dynamics. Theoretical models...
Recent advances in ultrafast laser spectroscopy have made it possible to study the electron dynamics for physical and chemical processes at atomic level real time. This article reviews concepts techniques that are necessary understand interpret these experiments with focus on time-resolved photoemission.
We present accurate time-dependent ab initio calculations on fully differential and total integrated (generalized) cross sections for the nonsequential two-photon double ionization of helium at photon energies from 40 to 54 eV. Our computational method is based solution Schr\"odinger equation subsequent projection wave function onto Coulomb waves. compare our results with other recent discuss emerging similarities differences. investigate role electronic correlation in representation...
Attosecond streaking of atomic photoemission holds the promise to provide unprecedented information on release time photoelectron. We show that attosecond phase shifts indeed contain timing (or spectral phase) associated with Eisenbud-Wigner-Smith delay matrix quantum scattering. However, this is only accessible if influence infrared (IR) field emission process properly accounted for. The IR probe can strongly modify observed shift. part shift ("time shift") due interaction between outgoing...
Watching as helium goes topsy-turvy Theorists have long pondered the underpinnings of Fano resonance, a spectral feature that resembles adjacent rightside-up and upside-down peaks. An especially well-studied instance this appears in electronic spectrum transient state undergoes delayed ionization. Two studies now traced dynamics real time. Gruson et al. used photoelectron spectroscopy to extract amplitude phase electron wave packet after inducing its interference with reference packets tuned...
We present fully ab initio simulations of attosecond streaking for ionization helium accompanied by shakeup the second electron. This process represents a prototypical case strongly correlated electron dynamics on time scale. show that spectroscopy can provide detailed information Eisenbud-Wigner-Smith delay as well infrared-field dressing both bound and continuum states. find novel contribution to stems from interplay electron-electron interactions in exit channel. quantify all...
The interaction of laser pulses sub-femtosecond duration with matter opened up the opportunity to explore electronic processes on their natural time scale. One central conceptual question posed by observation photoemission in real is whether ejection photoelectron wavepacket occurs instantaneously, or response photoabsorption finite leading a delay photoemission. Recent experimental progress exploring attosecond streaking and RABBIT techniques find relative delays between from different...
Recent experimental developments of high-intensity, short-pulse extreme ultraviolet light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations investigate the so-called ``sequential'' regime ($\ensuremath{\hbar}\ensuremath{\omega}>54.4\text{ }\text{ }\mathrm{eV}$) in two-photon double ionization helium. show that attosecond pulses allow us not only probe but also induce angular and energy correlations emitted electrons. The final...
We revisit the time-resolved photoemission in neon atoms as probed by attosecond streaking. calculate streaking time shifts for emission of $2p$ and $2s$ electrons compare relative delay measured a recent experiment Schultze et al. [Science 328, 1658 (2010)]. The $B$-spline $R$-matrix method is employed to accurate Eisenbud-Wigner-Smith delays from multielectron dipole transition matrix elements photoionization. additional laser field-induced exit channel are obtained separate,...
We present the numerical implementation of time-dependent complete-active-space self-consistent-field (TD-CASSCF) method [Phys. Rev. A, 88, 023402 (2013)] for atoms driven by a strong linearly polarized laser pulse. The treats problem in its full dimensionality and introduces gauge-invariant frozen-core approximation, an efficient evaluation Coulomb mean field scaling with number basis functions, split-operator specifically designed stable propagation stiff spatial derivative operators....
We theoretically investigate time-resolved photoemission originating from two different shells ($1s$ and $2p$) of a fully correlated atomic two-electron model system ionized by an extreme-ultraviolet attosecond light pulse. The parameters the are tuned such that ionization potentials $1s$ $2p$ electrons have values close to those $2s$ levels in neon atom, for which relative time delay has been measured recent streaking experiment Schultze et al. [Science 328, 1658 (2010)]. Up now theoretical...
We analyze the formation of low-energy structure (LES) in above-threshold ionization spectra strong-field by midinfrared laser pulses using both quasiclassical and quantum approaches. show this to be largely classical origin, resulting from a two-dimensional focusing energy--angular-momentum plane dynamics presence atomic potential. The latter is shown cause LES even absence long-range Coulomb tail. peak at low energy strongly correlated with high angular momenta photoelectrons. Quantum...
We investigate the photoionization spectrum of helium by attosecond XUV pulses both in spectral region doubly excited resonances as well above double ionization threshold. In order to probe for convergence, we compare three techniques extract photoelectron spectra from wave packet resulting integration time-dependent Schr\"odinger equation a finite-element discrete variable representation basis. These are projection on products hydrogenic bound and continuum states, onto multichannel...
Two-photon double ionization of He is studied at the Free Electron Laser in Hamburg (FLASH) by inspecting He2+ momentum () distributions 52 eV photon energy. We demonstrate that recoil ion can be used to infer information about highly correlated electron dynamics and find first experimental evidence for 'virtual sequential ionization'. The data are compared with results two calculations, both solving time-dependent Schrödinger equation. good overall agreement between experiment theory,...
We analyze two-photon double ionization of helium in both the nonsequential and sequential regime. show that energy spacing between two emitted electrons provides key parameter controls angular distribution reveals universal features present This universality, i.e., independence photon energy, is a manifestation continuity across threshold for ionization. For all energies, can be described by shape function contains only spectral temporal information entering second-order time-dependent...
We present a joint experimental and theoretical study of ionization argon atoms by linearly polarized two-color laser field (${\ensuremath{\lambda}}_{1}=800$ nm, ${\ensuremath{\lambda}}_{2}=400$ nm). Changing the relative phase $\ensuremath{\varphi}$ between two colors, forward-backward asymmetry doubly differential momentum distribution emitted electrons can be controlled. find excellent agreement measurements solution time-dependent Schr\"odinger equation in single-active electron...
We present a theoretical analysis of the atomic photoelectron emission spectra produced by linearly polarized sculpted laser pulse two colors with frequencies $\ensuremath{\omega}$ and $2\ensuremath{\omega}$. The spectrum ``direct'' electrons intermediate energies prominently features both intracycle intercycle interferences. derive simple analytic expression for this spectral range based on semiclassical approximation time-dependent distorted wave strong-field generalized to ionization...
We demonstrate the detection of high-lying Rydberg states produced in strong laser fields with coincidence spectroscopy. Electron emission after interaction pulses atoms and molecules is measured together parent ions measurements. These electrons originate from quantum numbers $n\ensuremath{\sim}20$ up to $n\ensuremath{\lesssim}120$ formed by frustrated field ionization. Ionization rates are retrieved ionization signal these states. Simulations show that both tunneling a weak dc...
We show that the correlation dynamics in coherently excited doubly resonances of helium can be followed real time by two-photon interferometry. This approach promises to map evolution two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. analyze interferometric signal terms a semianalytical model which is validated numerical solution time-dependent Schrödinger equation its full dimensionality.
The production of very-high-$n$ ($n\ensuremath{\sim}300$--500) strontium Rydberg atoms is explored using a crossed-laser-atom-beam geometry. $n$${}^{1}{S}_{0}$ and $n$${}^{1}{D}_{2}$ states are created by two-photon excitation via the $5s5p$ ${}^{1}{P}_{1}$ intermediate state radiation with wavelengths $\ensuremath{\sim}$461 $\ensuremath{\sim}$413 nm. atom densities as high $\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{5}$ cm${}^{\ensuremath{-}3}$ have been achieved, sufficient...
We present a numerical ab-initio simulation of the time delay in photoionization simplest diatomic molecule ${\mathrm{H}}_{2}^{+}$ as observed by attosecond streaking. show that strong variation Eisenbud-Wigner-Smith ${t}_{\mathrm{EWS}}$ function energy and emission angle becomes observable streaking shift ${t}_{\mathrm{S}}$ provided laser field induced components are accounted for. The strongly enhanced photoemission shifts traced to destructive Cohen-Fano (or two-center) interferences....
We investigate the role of electron correlation in two-photon double ionization helium for ultrashort pulses extreme ultraviolet (XUV) regime with durations ranging from a hundred attoseconds to few femtoseconds. perform time-dependent ab initio calculations mean frequencies so-called 'sequential' (ℏω > 54.4 eV). Electron induced by time between emission events manifests itself angular distribution ejected electrons, which strongly depends on energy sharing them. show that probabilities...
We investigate theoretically the single and double ionization of He atom by antiproton impact for projectile energies ranging from 3 keV up to 1000 keV. obtain accurate total cross sections directly solving fully correlated two-electron time-dependent Schr\"odinger equation. The are in excellent agreement with available experimental data. also present ab initio doubly differential data at 10 100 compare classical-trajectory Monte Carlo calculations. In these we identify binary-encounter peak...
We show that time ordering underlying time-dependent quantum dynamics is a physical observable accessible by attosecond streaking. demonstrate the extraction of for prototypical case time-resolved two-photon double ionization (TPDI) helium an XUV pulse. The Eisenbud-Wigner-Smith delay emission two-electron wavepacket and interval between subsequent events can be unambiguously determined two sensitively depends on energy, pulse duration, angular distribution emitted electron pair. Our...