A5016748906- Laser-Matter Interactions and Applications
- Spectroscopy and Quantum Chemical Studies
- Mass Spectrometry Techniques and Applications
- Advanced Fiber Laser Technologies
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Laser Design and Applications
- Terahertz technology and applications
- Spectroscopy and Laser Applications
- Laser-Plasma Interactions and Diagnostics
- Advanced X-ray Imaging Techniques
- Laser-induced spectroscopy and plasma
- Advanced Electron Microscopy Techniques and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum optics and atomic interactions
- Nuclear Physics and Applications
- Photoreceptor and optogenetics research
- Nuclear physics research studies
- Photochemistry and Electron Transfer Studies
- Gyrotron and Vacuum Electronics Research
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Accelerators and Free-Electron Lasers
- Electron and X-Ray Spectroscopy Techniques
- Astro and Planetary Science
- Quantum chaos and dynamical systems
Louisiana State University
2016-2025
Baton Rouge Clinic
2013-2022
The Ohio State University
2019
University of Virginia
2019
SLAC National Accelerator Laboratory
2010-2016
University of Arizona
1987-2016
Stanford University
2011
Laser Zentrum Hannover
1998-2002
Ørsted (Denmark)
2002
University of Florida
1999
We present calculated optical harmonic spectra for atoms and ions in the high intensity regime to current short-pulse experiments. find that can produce harmonics comparable strength those obtained from neutrals, emission extends much higher order. Simple scaling laws of maximum observable are suggested. These results imply photoemission observed recent experiments helium neon contains contributions as well neutrals.
We present high sensitivity electron energy spectra for xenon in a strong 50 ps, 1.053 \ensuremath{\mu}m laser field. The above threshold ionization distribution is smoothly decreasing over the entire kinetic range (0--30 eV), with no abrupt changes slope. This direct contrast to sharp cutoff observed optical harmonic generation spectra. Calculations using single active approximation show excellent agreement distributions. These results directly address unresolved relationship between and...
The production of ${\mathrm{He}}^{+}$ and ${\mathrm{He}}^{2+}$ by a 160 fs, 780 nm laser has been measured over an unprecedented 12 orders magnitude in counting range. Enhanced double electron emission, called nonsequential (NS) ionization, was observed intensity range where the single ionization dynamics is evolving from multiphoton to pure tunneling. NS yield found scale with ac-tunneling rate for neutral, even when tunneling not dominant pathway. A rescattering mechanism fails predict...
The intefererence pattern produced by photoelectrons provides holographic snapshots of the photoionization process.
We use a nonperturbative method to solve the time-dependent Schr\"odinger equation for an electronic state of atom subject very intense (>${10}^{13}$ W/${\mathrm{cm}}^{2}$) laser. The oscillating, dipole induced by laser serves as source photoemission. Calculations single-atom photospectra reveal peaks at odd harmonics incident field superimposed on broad continuous background. discuss series calculations hydrogen and short-range Yukawa potential containing variable number bound states....
We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into gas cell containing argon atoms. The emitted then goes through hard aperture thin aluminum filter that selects 30-eV bandwidth around photon energy synchronizes all components, thereby enabling formation train almost...
The authors present theoretical studies of high-order harmonic generation in a rare-gas medium. experimental results obtained at Saclay with 1064 nm Nd-YAG laser the 1013 W cm-2 intensity range are summarized. emission strengths, first decrease rather steeply for orders, then form long plateau up to 21st xenon, or 33rd argon, before decreasing again abruptly. description these experiments consists calculation photoemission spectra emitted by single atom. numerically integrating time...
Attosecond pulses are generated by a macroscopic number of ionizing atoms interacting with focused laser pulse, via the process high harmonic generation. The physics their generation consists an interplay between microscopic laser–atom interaction and effects due to ionization phase matching in nonlinear medium. In this review, we focus on complete understanding way which attosecond arrive at target where they can be characterized used experiment. We discuss results from calculations pulse...
We study the generation of high-harmonic radiation by Bloch electrons in a model transparent solid driven strong midinfrared laser field. solve single-electron time-dependent Schr\"odinger equation (TDSE) using velocity-gauge method [M. Korbman et al., New J. Phys. 15, 013006 (2013)] that is numerically stable as intensity and number energy bands are increased. The resulting harmonic spectrum exhibits primary plateau due to coupling valence band first conduction band, with cutoff scales...
A generalized strong-field approximation is formulated to describe atoms interacting with intense laser fields. We apply it determine angular distributions of electrons in above-threshold ionization (ATI). The theory treats the effects an electron rescattering from its parent ion core a systematic perturbation series. Probability amplitudes for are interpreted terms quasiclassical trajectories. demonstrate that contributions direct tunneling processes absence not sufficient observed ATI...
We investigate the spectral and temporal structure of high harmonic emission from argon exposed to an infrared laser field its second harmonic. For a wide range generating conditions, trains attosecond pulses with only one pulse per cycle are generated. The synchronization necessary for producing such ensures that they have stable pulse-to-pulse carrier envelope phase, unlike generated color fields, which two pi phase shift between consecutive pulses. Our experiment extends generation...
Angular distributions of high energy photoelectrons from Xe and Kr, excited by a 50 ps, 1.05 \ensuremath{\mu}m laser, are presented. In Xe, strong, narrow rings \ensuremath{\sim}45 \ifmmode^\circ\else\textdegree\fi{} off the polarization axis appear in limited range centered around 9${\mathit{U}}_{\mathit{p}}$, where ${\mathit{U}}_{\mathit{p}}$ is ponderomotive energy. This effect much weaker Kr. Single active electron calculations agree well with these observations. We conclude that result...
The ionization dynamics of small rare-gas clusters in intense, ultrafast laser fields are studied via classical trajectory Monte Carlo simulations. Our results indicate that for similar pulses the charge states reached by atoms a cluster can be significantly higher than those gas phase. enhancement is strongly dependent on density and exhibits rapid increase state once intensity has threshold single ionization. This 'ionization ignition model' driven combination field strong from ionized...
We present calculations of ionization rates, trapping probabilities, and electron densities for a three-dimensional hydrogen atom in an intense, high-frequency, pulsed laser field. Under certain conditions, we find that has significant probability surviving the ramp field to intensities at which is strongly suppressed. examine dynamics this process discuss method observe it experimentally.
Using an ultrafast pump pulse affects the spectral and temporal characteristics of high order harmonics in unexpected fortuitous way. Calculations spectra for rare gases using 10--100 fs, 800 nm pulses show that as length decreases highest become correspondingly shorter while their conversion efficiencies increase dramatically. Especially significant is we find these have phase allow possibility compression to subfemtosecond time scales.
We perform detailed calculations of harmonic conversion in a 15-Torr jet xenon into which 1064-nm-wavelength 36-ps-pulse-width laser has been tightly focused, so that the peak intensity ranges from 5\ifmmode\times\else\texttimes\fi{}${10}^{12}$ to 5\ifmmode\times\else\texttimes\fi{}${10}^{13}$ W ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. The single-atom emission rates are obtained by integrating time-dependent Schr\"odinger equation. employ an improved atomic model includes excitation and...
We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as reference to measure bound WP. demonstrate our method by exciting helium atoms using pulse (AP) with bandwidth centered near ionization threshold, thus creating both and simultaneously. After variable delay, is ionized few-cycle infrared laser precisely synchronized original AP. By measuring delay-dependent photoelectron spectrum we obtain interferogram...
We present a spatiotemporal analysis of high harmonic generation, showing evidence for the presence several quantum path contributions to atomic dipole moment. show that radiation can largely be described as sum two fields having phase proportional intensity generating field. compare our results recent experimental demonstrating this separation [M. Bellini et al., Phys. Rev. Lett. 81, 297 (1998)]. how temporal and spatial coherence properties are influenced by effect, discuss it could used...
We present calculations of ionization rates, angular distributions, and above-threshold-ionization spectra for a hydrogen atom in strong, two-color laser field. The two lasers are first- second-harmonic fields with the same intensity constant relative phase difference between them. At longer wavelengths (1064 nm) higher intensities (>${10}^{13}$ W/${\mathrm{cm}}^{2}$), there is clear evidence dependence rates that takes place primarily through tunneling. Even though total rate this regime...