A5059734733- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Laser-Matter Interactions and Applications
- Quantum Chromodynamics and Particle Interactions
- Laser Design and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Cold Atom Physics and Bose-Einstein Condensates
- High-pressure geophysics and materials
- Diamond and Carbon-based Materials Research
- Spectroscopy and Quantum Chemical Studies
- Magnetic confinement fusion research
- Mass Spectrometry Techniques and Applications
- Astrophysics and Cosmic Phenomena
- Advanced X-ray Imaging Techniques
- Nuclear Physics and Applications
- Gamma-ray bursts and supernovae
- Planetary Science and Exploration
- Nuclear Issues and Defense
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Inorganic Fluorides and Related Compounds
Lawrence Livermore National Laboratory
2010-2023
University of Alberta
2016-2017
General Atomics (United States)
2017
University of Michigan–Ann Arbor
2016
University of California, San Diego
2016
University of Rochester
2016
Energetics (United States)
2016
HUN-REN Wigner Research Centre for Physics
2015-2016
University of California, Davis
2016
California Polytechnic State University
1976
We report observations of amplified spontaneous emission at soft x-ray wavelengths. An optical laser ionized thin foils selenium to produce a population inversion the $2{p}^{5}3p$ and $2{p}^{5}3s$ levels neonlike ion. Using three time-resolved, spectroscopic measurements we demonstrated gain-length products up 6.5 gain coefficients 5.5\ifmmode\pm\else\textpm\fi{}1.0 ${\mathrm{cm}}^{\ensuremath{-}1}$ for $J=2 \mathrm{to} 1$ lines 206.3 209.6 \AA{}. also observed considerable amplification...
We have applied the stabilization method of calculating resonance energies to elastic scattering from a one-dimensional model potential containing barrier. For sufficiently large basis sets, yields good approximations inner part exact wave functions at equal eigenvalues truncated matrix Hamiltonian in both resonant and nonresonant energy regions. calculated phase shifts square-integrable produced by method. derived simple explain behavior as function size basis. The degree stability...
We describe a design for producing soft x-ray laser via $3p\ensuremath{-}3s$ transitions in Ne-like selenium (wavelength of about 200 \AA{}). A 0.53-\ensuremath{\mu} m laser, focused 1.2\ifmmode\times\else\texttimes\fi{}0.02-cm spot to \ensuremath{\sim} 5\ifmmode\times\else\texttimes\fi{}${10}^{13}$ W/${\mathrm{cm}}^{2}$, heats and burns through thin foil Se. Besides ionizing the Se state, explodes foil, creating region uniform electron density. This allows propagation x rays down 1-cm-long...
We report new experimental results obtained on three different laser facilities that show directed laser-driven relativistic electron-positron jets with up to 30 times larger yields than previously and a quadratic (∼E_{L}^{2}) dependence of the positron yield energy. This favorable scaling stems from combination higher energy electrons due increased intensity recirculation MeV in mm-thick target. Based this scaling, first principles simulations predict possibility using such jets, produced...
We clarify the computational procedure used in a stabilization calculation of resonance energy. propose new, variational method for width elastic scattering. The is based on minimum principle which holds ${L}^{2}$ trial functions satisfying certain assumptions. gives all parameters, including background phase shift, without requiring traditional scattering calculations.
Adiabatic-nuclei resonance theory has been applied to the study of dissociative attachement low-energy electrons ${\mathrm{F}}_{2}$. Stieltjes moment was used derive fixed-nuclei electronic parameters from large-scale configuration-interaction calculations on ${\mathrm{F}}_{2}$ and ${\mathrm{F}}_{2}^{\ensuremath{-}}$. Dissociative attachment cross sections for four lowest vibrational levels are reported compared with available experimental data.
In the recent successful demonstration of a soft-x-ray laser in neonlike selenium, 3p-3s, J=0-1 transition, which had been predicted to show very high gain, did not appear be amplified. Most previous calculations have assumed that dominant pumping mechanism is electron collisional excitation, and neglected effects ionization recombination on kinetics levels. this work, we studied three-body, radiative, dielectronic recombination, connecting three fluorinelike ground states lowest 89 levels...
The semiclassical impact-parameter method is extended to study the electronic excitation of molecules by electron impact. formalism describes molecular electrons quantum mechanically but treats collision classically using straight-line trajectories. expression for integrated cross section satisfies reciprocity. applicable spin-allowed transitions at intermediate and high impact energies where exchange negligible. Theoretical sections are presented...
The adiabatic-nuclei theory of electron-molecule scattering is extended to account for electronic excitation the target. approximate expressions wave function and amplitude are derived from a formally exact expansion in terms fixed-nuclei, electronic-scattering solutions. formalism treats molecular-bound continuum states on an equal footing. We also propose modified expression adiabatic-scattering which expected have increased range validity near thresholds.
Using a simple classical model, we calculate the distribution of final states resulting from autoionization Σg1(2pσu2) state H2(D2) to 2Σg(1sσg) H2+(D2+). The population vibrational levels differs markedly that predicted by Franck-Condon principle for direct ionization. calculated kinetic energy distributions H+ and D+ have maxima at threshold (Ekin=0). probability forming dissociated products is smaller D2 than H2.
In previous work, the stabilization method of calculating resonance parameters was applied to potential scattering and elastic from a target. The is here extended compound-state resonances in inelastic its application model problem for target with three bound states examined. eigenfunctions associated eigenvalues ${\ensuremath{\epsilon}}_{j}$ obtained diagonalization exact Hamiltonian appropriately chosen sets square-integrable basis functions are good approximations, inner region,...
We report on the detection of time-dependent B-field amplitude and topology in a laser-driven solenoid. The inferred from both proton deflectometry Faraday rotation ramps up linearly time reaching 210 ± 35 T at end 0.75-ns laser drive with 1 TW 351 nm. A lumped-element circuit model agrees well linear rise suggests that blow-off plasma screens field between plates leading to an increased plate capacitance converts laser-generated hot-electron current into voltage source drives through ALE3D...
Superponderomotive-energy electrons are observed experimentally from the interaction of an intense laser pulse with a relativistically transparent target. For target, kinetic modeling shows that generation energetic is dominated by energy transfer within main, classically overdense, plasma volume. The produces narrowing, funnel-like channel inside volume generates field structure responsible for electron heating. combines slowly evolving azimuthal magnetic field, generated strong...
The energy and width of the $^{1}\ensuremath{\sigma}_{u}^{2}^{1}\ensuremath{\Sigma}_{g}^{+}$ state ${\mathrm{H}}_{2}$ are calculated using Feshbach projection operators Stieltjes moment method. results compared with an analysis double minima in potential-energy curves $^{1}\ensuremath{\Sigma}_{g}^{+}$ Rydberg states. doubly excited $^{1}\ensuremath{\sigma}_{u}^{2}$ configuration is unstable respect to autoionization for $R<2.65{a}_{0}$, rate sensitive both value internuclear separation...
In a previous paper, the stabilization method of calculating resonance parameters was applied to one-dimensional model problem potential scattering. The is here extended compound-state resonances in elastic scattering, and its application for target with two bound states examined. are calculated by methods which use information obtained diagonalization exact Hamiltonian appropriately chosen sets square-integrable basis functions: One presented first time here; other similar procedure used...
This paper presents experimental scalings of the electrons and positrons produced by intense laser-target interactions at relativistic laser intensities (1018–1020 W cm−2). The data were acquired from three short-pulse facilities with energies ranging 80 to 1500 J. We found a non-linear (≈EL2) scaling positron yield [Chen et al., Phys. Rev. Lett. 114, 215001 (2015)] linear electron energy. These are explained theoretical numerical analyses. Positron acceleration target sheath field is...
Using ab initio molecular dynamics, we have investigated liquid deuterium under pressure, in a range of densities relevant to recent laser shock experiments. Our results show that between four- and sixfold compression, temperatures 5000 10 000 K, the goes continuously from dissociation/recombination regime, where substantial proportion atoms form D${}_{2}$ complexes, scattering mostly are present. At about K find is poor metal. simulations point at compression along Hugoniot larger than...
Compares the available theoretical predictions for energy of 1 Pi u(1 sigma u2 pi g) autoionizing state H2. The present results cast serious doubt on previous assignment this by Bottcher (1974) as responsible 4 eV protons which are observed in dissociative ionization H2 electron impact.
In this paper we present a description of atomic and molecular Rydberg states using an effective Hamiltonian in the one-electron Hartree—Fock approximation. A pseudopotential is introduced to ensure orthogonality orbitals core. The core represented by ground-state wavefunction corresponding positive ion. order incorporate formalism states, original theory extended case where valence are eigenfunctions different operators. applied triplet S helium beryllium atoms results numerical...
We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using frequency-doubled Titan short pulse laser system Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate generation pure proton beam with maximum energy 2 MeV. Furthermore, record quasi-monoenergetic peak 1.1 MeV in spectrum emitted forward direction suggesting an alternative acceleration mechanism. solid-density mixed hydrogen-deuterium target,...
Fixed-nuclei, static-exchange calculations have been performed to study the vibrational-rotational excitation of HF by electrons from threshold 5 eV. Our calculated, $R$-dependent $K$-matrix elements in $^{2}\ensuremath{\Sigma}^{+}$, $^{2}\ensuremath{\Pi}$, and $^{2}\ensuremath{\Delta}$ symmetry are combined with exact point-dipole laboratory-frame first-Born-approximation results for higher symmetries obtain converged, integrated cross sections. The show strong peaks which related...