A5042039256- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Laser-Matter Interactions and Applications
- Advanced X-ray Imaging Techniques
- Laser Design and Applications
- Diamond and Carbon-based Materials Research
- X-ray Spectroscopy and Fluorescence Analysis
- Ion-surface interactions and analysis
- Laser Material Processing Techniques
- Particle Accelerators and Free-Electron Lasers
- Electron and X-Ray Spectroscopy Techniques
- Nuclear Physics and Applications
- Crystallography and Radiation Phenomena
- Advanced Electron Microscopy Techniques and Applications
- Advanced Chemical Physics Studies
- Atomic and Subatomic Physics Research
- Solid State Laser Technologies
- Metal and Thin Film Mechanics
- Cold Atom Physics and Bose-Einstein Condensates
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Spectroscopy and Laser Applications
- Terahertz technology and applications
University of California, Berkeley
2014-2024
Lawrence Berkeley National Laboratory
2013-2022
University of Colorado Boulder
2021
Berkeley College
1986-2020
SLAC National Accelerator Laboratory
2007-2016
University of Michigan
2007-2016
Princeton Plasma Physics Laboratory
2016
Sandia National Laboratories
2016
Deutsches Elektronen-Synchrotron DESY
2016
Los Alamos National Laboratory
2016
We examine the interaction of intense, femtosecond laser radiation with large (50--200 \AA{}) clusters produced in pulsed gas jets. Both experiment and simulation show that plasmas during these interactions exhibit electron temperatures far excess predicted by above-threshold ionization theory for a low-density gas. Efficient heating is followed rapid expansion long-lived x-ray emission from hot, decaying, underdense plasma. \textcopyright{} 1996 The American Physical Society.
Laser pulses with a power of ${10}^{12}$ W and duration ${10}^{\mathrm{\ensuremath{-}}13}$ s were focused onto both gas solid targets. Strong emission pulsed radiation at terahertz frequencies was observed from the resulting plasmas. The most intense detected density targets correlated MeV x rays electrons. Results indicate that radiative processes in such plasmas are driven by ponderomotively induced space charge fields excess ${10}^{8}$ V/cm. This work constitutes first direct observation...
A high-temperature plasma is created when an intense laser pulse focused onto the surface of a solid. An ultrafast x-ray radiation emitted from such length less than picosecond. high-speed streak camera detector was used to determine duration these pulses, and computer simulations plasmas agree with experimental results. Scaling laws predict that brighter more efficient sources will be obtained by use pulses. These can for time-resolved scattering studies development lasers.
Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high densities, the interatomic forces bind solids and determine many their properties substantially altered. Here, we present detailed mapping carrier densityâdependent potential bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques use high-brightness linear electron acceleratorâbased x-ray source...
We have used the Linac Coherent Light Source to generate solid-density aluminum plasmas at temperatures of up 180 eV. By varying photon energy x rays that both create and probe plasma, observing K-α fluorescence, we can directly measure position K edge highly charged ions within system. The results are found disagree with predictions extensively Stewart-Pyatt model, but consistent earlier model Ecker Kröll, which predicts significantly greater depression ionization potential.
Abstract The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery microscopic diamonds in remnants explosively driven graphite. Furthermore, shock synthesis lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected happen during violent meteor impacts. Here, we show unprecedented situ X-ray diffraction measurements formation on nanosecond timescales by compression pyrolytic as well...
Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well many technological applications including management nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, nanoparticle-mediated therapies. Thermal at the fundamentally different that macroscale determined by distribution carrier mean free paths dispersion material, length scales sources, distance over which...
Time-resolved x-ray diffraction with picosecond temporal resolution is used to observe scattering from impulsively generated coherent acoustic phonons in laser-excited InSb crystals. The observed frequencies and damping rates are agreement a model based on dynamical theory coupled analytic solutions for the laser-induced strain profile. results consistent 12 ps thermal electron-acoustic phonon coupling time together an instantaneous component deformation-potential interaction. Above critical...
We describe temporal and spectroscopic measurements of high-density plasmas produced by focusing intense, 160-fsec laser pulses on solids. Soft-x-ray emission with a duration 2\ifmmode\pm\else\textpm\fi{}2 psec is observed up to photon energies kilovolt. observe reduced from long-lived spectral lines, indicating the presence short-lived, plasma. Reflectivity indicate that absorption pulse occurs at surface solid before it expands.
We report the generation of short-wavelength, high-order harmonics intense laser radiation from atom clusters. Clusters containing about 1${0}^{3}$ atoms are produced in a high-pressure gas jet. show them to be unique nonlinear medium. Compared with monomer gases they yield higher appearance intensity for given harmonic order, stronger dependence signal on intensity, higher-order harmonics, and reduced saturation at high intensity.
The interaction between high-intensity, ultrashort laser pulses and plasmas leads to the emission of coherent, short-pulse radiation at terahertz frequencies. In this work we discuss a model for effect its experimental realization. Our measurements constitute direct observation laser-induced wake fields. From gas-density targets, resonant enhancement is observed if plasma frequency close inverse pulse length exciting pulse. At higher densities, subpicosecond, unipolar electromagnetic...
The interaction of an intense laser pulse with large $(\ensuremath{\sim}100\AA{})$ clusters present in pulsed gas jets is shown to produce novel plasmas electron temperatures far excess that predicted by above-threshold ionization theory. enhanced absorption the light dense results production high ion charge states via collisional resulting strong x-ray emission from hot plasma.
Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of duration are hampered by inability precisely synchronize an external laser accelerator. At Sub-Picosecond Pulse Source Stanford Linear-Accelerator Center we solved this problem measuring arrival time each high energy electron bunch with electro-optic sampling. This measurement indirectly determined...
Electron mobility within iron (oxyhydr)oxides enables charge transfer between widely separated surface sites. There is increasing evidence that this internal conduction influences the rates of interfacial reactions and outcomes redox-driven phase transformations environmental interest. To determine links crystal structure charge-transport efficiency, we used pump-probe spectroscopy to study dynamics electrons introduced into iron(III) (oxyhydr)oxide nanoparticles via ultrafast electron...
Spectrally resolved scattering of ultrafast K-α x-rays has provided experimental validation the modeling compression and heating shocked matter. The elastic component characterized evolution coalescence two shocks launched by a nanosecond laser pulse into lithium hydride with an unprecedented temporal resolution 10 picoseconds. At shock coalescence, we observed rapid to temperatures 25,000 kelvin when spectra show collective plasmon oscillations that indicate transition dense metallic plasma...
X-ray free-electron lasers (FELs) produce femtosecond x-ray pulses with unprecedented intensities that are uniquely suited for studying many phenomena in atomic, molecular, and optical (AMO) physics. A compilation of the current developments at Linac Coherent Light Source (LCLS) future plans LCLS-II Next Generation (NGLS) outlined. The AMO instrumentation LCLS its performance parameters summarized. few selected experiments representing rapidly developing field ultra-fast peak intensity...
We present the first x-ray scattering measurements of state compression and heating in laser irradiated solid beryllium. The scattered spectra at two different angles show Compton plasmon features indicating a dense Fermi-degenerate plasma with Fermi energy above 30 eV temperatures range 10--15 eV. These indicate by factor 3 agreement Hugoniot data detailed radiation-hydrodynamic modeling.
We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states warm dense copper that is produced isochorically through an ultrafast optical pulse. The temperature superheated electron-hole plasma, which ranges from 4000 10 000 K, was determined by comparing measured spectrum with a simulation. structure adequately described high state calculated functional theory. dynamics electron consistent two-temperature model, while temperature-dependent...
Detailed measurements of the electron densities, temperatures, and ionization states compressed CH shells approaching pressures 50 Mbar are achieved with spectrally resolved x-ray scattering. Laser-produced 9 keV x-rays probe plasma during transient state three-shock coalescence. High signal-to-noise scattering spectra show direct evidence continuum depression in highly degenerate warm dense matter densities ne>1024 cm-3. The measured temperatures agree well radiation-hydrodynamic modeling...
Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation a coherent acoustic pulse generated by ultrafast laser excitation. The surface bulk components strain could be simultaneously measured due large penetration depth. Comparison experimental data with dynamical simulations suggests that conventional model for impulsively underestimates partitioning energy into modes.