A5090141980- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Mass Spectrometry Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Spectroscopy and Quantum Chemical Studies
- Ion-surface interactions and analysis
- Cold Atom Physics and Bose-Einstein Condensates
- Gold and Silver Nanoparticles Synthesis and Applications
- Laser Design and Applications
- Laser-induced spectroscopy and plasma
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Laser-Plasma Interactions and Diagnostics
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Electron Microscopy Techniques and Applications
- Advanced Materials Characterization Techniques
- Advanced Fiber Laser Technologies
- Nuclear physics research studies
- Fullerene Chemistry and Applications
- Spectroscopy and Laser Applications
- Photorefractive and Nonlinear Optics
- Quantum optics and atomic interactions
- Particle accelerators and beam dynamics
- Plasmonic and Surface Plasmon Research
Kansas State University
2016-2025
Max Planck Society
2007-2010
Max Planck Institute for Nuclear Physics
2008
University of Nebraska–Lincoln
2003
University of Freiburg
1988-2001
Center for Astrophysics Harvard & Smithsonian
2000
Stockholm University
1999
National Institute of Standards and Technology
1991-1993
Joint Institute for Laboratory Astrophysics
1991-1993
University of Colorado Boulder
1993
Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape the 3s3p⁶np ¹P Fano resonance series (26.6-29.2 eV) were modified intense few-cycle near infrared laser pulses, while delay between pulse changed a few femtoseconds. Numerical simulations revealed that observed splitting 3s3p⁶4p line is caused coupling two short-lived highly excited states in strong field.
Fully differential data for ${\mathrm{H}}_{2}$ dissociation in ultrashort (6 fs, 760 nm), linearly polarized, intense ($0.44\text{ }\text{ }\mathrm{PW}/{\mathrm{cm}}^{2}$) laser pulses with a stabilized carrier-envelope phase (CEP) were recorded reaction microscope. Depending on the CEP, molecular orientation, and kinetic energy release (KER), we find asymmetric proton emission at low KERs (0--3 eV), basically predicted by Roudnev Esry, much stronger than reported Kling et al. Wave packet...
Two-color (800 and 400 nm) short (45 fs) linearly polarized pulses are used to ionize dissociate D2 into a neutral deuterium atom deuteron. The yields energies of the ions measured left right along polarization vector. As relative phase two colors is varied, strong yield asymmetries found in ion-energy regions traditionally identified as bond softening, above-threshold dissociation rescattering. these quite different. A model based on dynamic coupling by laser field gerade ungerade states...
We demonstrate an experimental control of electron localization in deuterium molecular ions created and dissociated by the combined action attosecond pulse train a many-cycle infrared (IR) pulse. The is synthesized using both even odd high order harmonics driving IR frequency so that it can strobe field once per cycle. An asymmetric ejection oscillates with full period when APT-IR time-delay scanned. observed due to creation coherent superposition 1s sigma{g} 2p sigma{u} states via...
Experimentally, the bound and dissociative nuclear dynamics in small molecular ions can be resolved time by using intense ultrashort pump combination with delayed probe laser pulses. We discuss modelling of related pump–probe-delay-dependent fragment kinetic-energy-release (KER) spectra for laser-induced ionization selected diatomic molecules show how quantum-mechanical simulation measured KER spectra—in both domain as a function beat frequency between vibrational levels—reveals dissociation...
By combining carrier-envelope phase (CEP) stable light fields and the traditional method of optical pump-probe spectroscopy we study electron localization in dissociating H2(+) molecular ions. Localization localizability electrons is observed to strongly depend on time delay between two CEP-stable laser pulses with a characteristic periodicity corresponding oscillating wave packet. Variation allows us uncover underlying physical mechanism for localization, which are distinct sets interfering...
Photoionization by attosecond extreme ultraviolet (xuv) pulses into the laser-dressed continuum of ionized atom is commonly described in strong-field approximation, neglecting Coulomb interaction between emitted photoelectron (PE) and residual ion. By solving time-dependent Schr\"odinger equation, we identify a temporal shift $\ensuremath{\delta}\ensuremath{\tau}$ streaked PE spectra, which becomes significant at low energies. Within an eikonal trace this to combined action laser forces on...
We studied the nuclear dynamics in diatomic molecules (N${}_{2}$, ${\mathrm{O}}_{2}$, and CO) following their interaction with intense near-IR few-cycle laser pulses. Using Coulomb-explosion imaging combination pump-probe approach, we mapped dissociation pathways of those molecular ions. identified all symmetric asymmetric breakup channels for ions up to ${\mathrm{N}}_{2}^{5+}$, ${\mathrm{O}}_{2}^{4+}$, CO${}^{4+}$. For each measured kinetic energy release (KER) spectra as a function delay...
Significance Electron–electron interactions are among the fastest processes in materials that determine their fascinating properties, occurring on attosecond timescales up (1 as = 10 −18 s). The recent development of angle-resolved photoemission spectroscopy (atto-ARPES) using high harmonic generation has opened possibility probing electron–electron real time. In this paper, we distinguish screening and charge scattering time domain individual energy bands within a solid. These results open...
The fragmentation of the ${\mathrm{H}}_{2}^{+}$ molecular ion in 25-fs, 800-nm laser pulses intensity range 0.05--0.5 P ${\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}$ is investigated by means wave-packet propagation calculations. We use a collinear reduced-dimensionality model that represents both nuclear and electronic motion one degree freedom including non-Born-Oppenheimer couplings. In order to reproduce accurately properties ``real'' three-dimensional molecule, we introduce modified...
We show that the electronic dynamics in a molecule driven by strong field is complex and potentially even counterintuitive. As prototype example, we simulate interaction of dissociating H2+ with an intense infrared laser pulse. Depending on intensity, direction electron's motion between two nuclei found to follow or oppose classical laser-electric force. explain sensitive dependence correlated electronic-nuclear terms diffracting momentum distribution two-center system. The dynamically...
Reaction Microscope-based, complete, and time-resolved Coulomb explosion imaging of vibrating dissociating D(2)(+) molecules with femtosecond time-resolution allowed us to perform an internuclear distance (R-)dependent Fourier analysis the corresponding wave packets. Calculations demonstrate that obtained two-dimensional R-dependent frequency spectra enable complete characterization packet dynamics directly visualize field-modified molecular potential curves in intense, ultrashort laser pulses.
Recent attosecond-streaking spectroscopy experiments [A. L. Cavalieri, Nature (London) 449, 1029 (2007)10.1038/nature06229] using copropagating extreme ultraviolet (XUV) and infrared (IR) pulses of variable relative delay have measured a approximately 100 attoseconds between photoelectrons emitted by single XUV photon from localized core states delocalized conduction-band tungsten surface. We analyze the underlying XUV-photoemission-IR-streaking mechanism combining perturbative description...
Streaked photoemission metrology allows the observation of an apparent relative time delay between detection photoelectrons from different initial electronic states. This is obtained by recording photoelectron yield as a function ionizing ultrashort extended ultraviolet pulse and streaking infrared (IR) pulse. Theoretically, delays can be defined based on (i) phase shift wave accumulates during release propagation (``Wigner delay'') and, alternatively, (ii) trace in calculated spectrum...
We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization H2 by strong laser fields. The absorbed photon is shared ejected a correlated fashion, resulting multiple diagonal lines their joint spectrum governed conservation all fragment particles.
We study the evolution of nuclear wave packets launched in molecular nitrogen, oxygen, and carbon monoxide by intense 8-fs infrared pulses. use velocity map imaging to measure momentum ion fragments when these are interrogated a second such pulse after variable time delay. Both quasibound dissociative observed. For former, measurements bound-state oscillations used identify participating states and, some cases, extract properties relevant potential-energy surfaces. Vibrational structure is...
High-order harmonic generation (HHG) from crystals is emerging as a new ultrashort source of coherent extreme ultraviolet (XUV) light. Doping the crystal structure can offer way to control properties. Here, we present study HHG enhancement in XUV spectral region an ionic crystal, using dopant-induced vacancy defects, driven by laser centered at wavelength 1.55 μm. Our numerical simulations based on solutions semiconductor Bloch equations and density-functional theory are supported our...
In strong-field ionization of molecules, intense light pulses are thought to have a negligible direct influence on atomic nuclei. Molecular dissociation is thus expected be determined by the geometrical configuration molecular ion at instant. Contrary this picture, we observe counterintuitive electron-proton angular correlation and formation proton vortices following <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi...
We present a new method to extract momentum distributions from time-dependent wavepacket calculations. In contrast established Fourier transformation of the spatial at fixed time, proposed 'virtual detector' examines time dependence position. first applications ionization model atoms and dissociation H2+, we find significant reduction computing are able reliable fragment by using comparatively small numerical grid for wavefunction.
We have extended the classical over-barrier model to simulate neutralization dynamics of highly charged ions interacting under grazing incidence with conducting and insulating surfaces. Our calculations are based on simple rates for resonant Auger transitions. include effects caused by dielectric response target and, insulators, localized surface charges. Characteristic deviations regarding charge-transfer processes from targets ion discussed. find good agreement previously published...
We discuss the extent to which measured time-dependent fragment kinetic energy release (KER) spectra and calculated nuclear probability densities can reveal (1) transition frequencies between stationary vibrational states, (2) nodal structure of (3) ground-state adiabatic electronic potential curve molecular ion, (4) progression decoherence induced by random interactions with environment. illustrate our discussion numerical simulations for motion wave packets in $\text{D}_{2}{}^{+}$ ion...
We compute spectrograms and relative time delays for laser-assisted photoemission by single attosecond extreme ultraviolet pulses from valence band (VB) 2p core levels (CLs) of a Mg(0001) surface within quantum-mechanical model. Comparing the time-dependent dispersion photoelectron (PE) wave packets VB CL emission, we find striking differences in their dependence on (i) electron mean free path (MFP) solid, (ii) screening streaking laser field, (iii) chirp pulse. The delay between PEs is...