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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Plasma channel produced by femtosecond laser pulses as a medium for amplifying electromagnetic radiation of the subterahertz frequency range

The electron energy distribution function in the plasma channel produced by a femtosecond laser pulse with a wavelength of 248 nm in atmospheric-pressure gases was considered. Conditions were determined whereby this channel may be employed for amplifying electromagnetic waves up to the terahertz frequency range over the energy spectrum relaxation time ∼10{sup -7} s. Gains were calculated as functions of time and radiation frequency. The effect of electron – electron collisions on the rate of relaxation processes in the plasma and on its ability to amplify the electromagnetic radiation was investigated. (interaction of laser radiation with matter)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Understanding the nature of mean-field semiclassical light-matter dynamics: An investigation of energy transfer, electron-electron correlations, external driving, and long-time detailed balance

Semiclassical electrodynamics (with quantum matter plus classical electrodynamics fields) is an appealing approach for studying light-matter interactions, especially for realistic molecular systems. However, there is no unique semiclassical scheme. On the one hand, intermolecular interactions can be described instantaneously by static two-body interactions connecting two different molecules, while a classical transverse E field acts as a spectator at short distance; we will call this Hamiltonian no. I. On the other hand, intermolecular interactions can also be described as effects that are mediated exclusively through a classical one-body Ε field without any quantum effects at all (assuming we ignore electronic exchange); we will call this Hamiltonian no. II. Moreover, one can also mix these two different Hamiltonians into a third, hybrid Hamiltonian, which preserves quantum electron-electron correlations for lower excitations but describes higher excitations in a mean-field way. To investigate which semiclassical scheme is most reliable for practical use, here we study the real-time dynamics of a minimalistic many-site model—a pair of identical two-level systems (TLSs)—undergoing either resonance energy transfer (RET) or collectively driven dynamics. While both approaches (no. 1 and no. 2) perform reasonably well when there is no strong external excitation, we find that no single approach is perfect for all conditions (and all methods fail when a strong external field is applied). Each method has its own distinct problems: Hamiltonian no. I performs best for RET but behaves in a complicated manner for driven dynamics; Hamiltonian no. II is always stable, but obviously fails for RET at short distances. One key finding is that, for externally driven dynamics, a full configuration-interaction description of Hamiltonian no. I strongly overestimates the long-time electronic energy, highlighting the not obvious fact that, if one plans to merge quantum molecules with classical light, a full, exact treatment of electron-electron correlations can actually lead to worse results than a simple mean-field electronic structure treatment. Future work will need to investigate (i) how these algorithms behave in the context of more than a pair of TLSs and (ii) whether or not these algorithms can be improved in general by including crucial aspects of spontaneous emission.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Reaching high laser intensity by a radiating electron

The question of whether an electron radiating its energy away during the interaction with a laser can reach the region of highest intensity with energy high enough to make a number of different phenomena observable is one of the most studied and most important in strong field quantum electrodynamics. Here a simple analytical estimate for an average electron energy evolution is proposed and benchmarked against particle-in-cell simulations. Here, these results are used to estimate the electron and laser pulse properties required to make vacuum Cherenkov emission observable.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Information Carried by Electromagnetic Radiation Launched from Accelerated Polarization Currents

We show experimentally that a continuous, linear, dielectric antenna in which a superluminal polarization-current distribution accelerates can be used to transmit a broadband signal that is reproduced in a comprehensible form at a chosen target distance and angle. The requirement for this exact correspondence between broadcast and received signals is that each moving point in the polarization-current distribution approaches the target at the speed of light at all times during its transit along the antenna. This results in a one-to-one correspondence between the time at which each point on the moving polarization current enters the antenna and the time at which all of the radiation emitted by this particular point during its transit through the antenna arrives simultaneously at the target. This has the effect of reproducing the desired time dependence of the original broadcast signal. For other observer-detector positions, the time dependence of the signal is scrambled, due to the nontrivial relationship between emission (retarded) time and reception time. This technique represents a contrast to conventional radio transmission methods; in most examples of the latter, signals are broadcast with little or no directivity, selectivity of reception being achieved through the use of narrow frequency bands. In place of this, the current paper uses a spread of frequencies to transmit information to a particular location; the signal is weaker and has a scrambled time dependence elsewhere. Here, we point out the possible relevance of this mechanism to 5G neighborhood networks and pulsar astronomy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Exclusive dimuon production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with ATLAS

Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, PbPb(γγ) → μ + μ - (Pb (*) Pb (*) ), is studied using $\mathcal{L}$ int = 0.48 nb -1 of $\sqrt{s_{NN}}$ = 5.02 TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region p T,μ >4 GeV, |η μ |<2.4, invariant mass m μμ >10 GeV, and p T,μμ <2 GeV. The primary background from single-dissociative processes is extracted from the data using a template fitting technique. Differential cross sections are presented as a function of m μμ , absolute pair rapidity (|y μμ |), scattering angle in the dimuon rest frame (| cos $\mathscr{O}$$^{*}_{μμ}$|), and the colliding photon energies. The total cross section of the UPC γγ → μ + μ - process in the fiducial volume is measured to be $σ^{μμ}_{fid}$ = 34.1 ± 0.3(stat.) ± 0.7(syst.) μb. Generally good agreement is found with calculations from STARlight, which incorporate the leading-order Breit-Wheeler process with no final-state effects, albeit differences between the measurements and theoretical expectations are observed. In particular, the measured cross sections at larger |y μμ | are found to be about 10–20% larger in data than in the calculations, suggesting the presence of larger fluxes of photons in the initial state. Modification of the dimuon cross sections in the presence of forward and/or backward neutron production is also studied and is found to be associated with a harder incoming photon spectrum, consistent with expectations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Bunch Shaping in Electron Linear Accelerators

Modern electron linear accelerators are often designed to produce smooth bunch distributions characterized by their macroscopic ensemble-average moments. However, an increasing number of accelerator applications call for finer control over the beam distribution, such as by requiring specific shapes for its projection along one coordinate. Ultimately, the control of the beam distribution at the single-particle level could enable new opportunities in accelerator science. This review discusses the recent progress toward controlling electron beam distributions on the “mesoscopic” scale with an emphasis on shaping the beam or introducing complex correlations required for some applications. This review emphasizes experimental and theoretical developments of electron-bunch shaping methods based on bounded external electromagnetic fields or via interactions with the self-generated velocity and radiation fields.

Ha, G.↗
DOE OSTI2026

Exact solution of the DeWitt-Brehme-Hobbs equation in copropagating electromagetic and gravitational waves

An accelerated charge interacts with its own electromagnetic field, a phenomenon known as electromagnetic radiation reaction. The DeWitt-Brehme-Hobbs (DWBH) equation describes the motion of a charged mass in the presence of combined electromagnetic and gravitational fields, taking into account electromagnetic radiation-reaction effects. Here, we find the first exact analytical solution of the DWBH equation in the case of a charged mass in the presence of copropagating and otherwise arbitrary electromagnetic and gravitational plane waves. As a consequence of the Penrose limit, the scenario considered here can be seen as a local limit around ultrarelativistic trajectories in a general curved spacetime. Finally, the paradigmatic example of an electromagnetic wave in the presence of a constant-amplitude gravitational wave is worked out explicitly and it is shown how the presence of the gravitational wave can qualitatively change electromagnetic radiation-reaction effects.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Photonic Crystal-Based High-Power Backward Wave Oscillator

An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. In conclusion, the operating frequency and growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.

42 ENGINEERING↗
DOE OSTI2018

Laser Acceleration of Nuclei for Synthesis of Superheavy Elements in the Stability Island of the Periodic Table

Within a three-dimensionalmodel of interaction of a powerful electromagnetic fieldwith plasma of solid-state density, the effect of acceleration of calcium nuclei ({sub 20}{sup 48}Ca) to high energies that are likely to be sufficient for the synthesis of superheavy elements within the “stability island” of the periodic table of elements is obtained by numerically solving the Vlasov–Maxwell equations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

On the problems of relativistic laboratory astrophysics and fundamental physics with super powerful lasers

The ways toward modeling of astrophysical processes and extreme field regimes with super-power lasers are discussed. The main attention is paid to the problem of limited similarity in using the dimensionless parameters characterizing the processes in the laser and astrophysical plasmas. As the most typical examples, we address the magnetic reconnection and collisionless shock waves relevant to the problem of ultrarelativistic particle acceleration. In the extreme field limits we consider the regimes of dominant radiation reaction, changing the electromagnetic wave-matter interaction. In these regimes it, in particular, results in a new powerful source of ultra high-brightness gamma-rays and will make possible electron-positron pair creation in vacuum in a multiphoton processes. This will allow modeling under terrestrial laboratory conditions the processes in astrophysical objects and paves the way to experimental verifications using ultra intense lasers as they are currently developed within the ELI project.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Two-Dimensional Triplet Magnetoexcitons and a Magnetofermionic Condensate in the GaAs/AlGaAs Heterostructures

A fundamentally new collective state, namely, the magnetofermionic condensate, is discovered during photoexcitation of a sufficiently dense gas of long-lived triplet cyclotron magnetoexcitons in a twodimensional Hall insulator with a high electron mobility, a filling factor of ν = 2, and temperatures of T < 1 K. The condensed phase coherently interacts with an external electromagnetic field, exhibits superradiant properties in the recombination of correlated condensate electrons with heavy holes in the valence band, and spreads nondissipatively in the layer of a two-dimensional electron gas to macroscopical large distances, transferring an integer spin. The observed effects are explained in terms of a coherent condensate in a nonequilibrium system of two-dimensional fermions with a fully quantized energy spectrum, in which a degenerate ensemble of long-lived triplet magnetoexcitons obeying the Bose statistics is present.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

MIXING THE SOLAR WIND PROTON AND ELECTRON SCALES: EFFECTS OF ELECTRON TEMPERATURE ANISOTROPY ON THE OBLIQUE PROTON FIREHOSE INSTABILITY

The double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons, unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much faster and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma β and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Chip-based droplet sorting

A non-contact system for sorting monodisperse water-in-oil emulsion droplets in a microfluidic device based on the droplet's contents and their interaction with an applied electromagnetic field or by identification and sorting.

42 ENGINEERING↗
DOE OSTI2017

Chip-based droplet sorting

A non-contact system for sorting monodisperse water-in-oil emulsion droplets in a microfluidic device based on the droplet's contents and their interaction with an applied electromagnetic field or by identification and sorting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Electromagnetic field-assisted method for chemical conversion

Embodiments relate to methods for enhancing chemical conversions. One or more embodiments relate to a method for enhancing a multi-step chemical conversion reaction. The method includes providing a reactant mixture comprising one or more reacting specie(s); and providing a catalyst or sorbent comprising one or more support materials and one or more deposited catalytically active materials. The method further includes applying an electromagnetic field with a prescribed power, frequency, and pulsing strategy specific to interactions of reactant species and an electromagnetic field with at least one of the support materials, sorbent, and catalytically active materials in a particular chemical reaction.

Shekhawat, Dushyant↗
DOE OSTI2023

Multiscale Ecosystem for solving Maxwell-Schrodinger equations of open quantum systems (OpenMS)

Light-matter interactions play an important role in many branches of physics, chemistry, energy, and materials science. In the strong coupling regime, light-matter interactions are able to tune the materials properties via the formation of new quasiparticles, such as plasmons and polaritons. However, theoretical and numerical modeling of the light-matter interaction-mediated processes remain a big challenge because light-matter interactions are fundamentally multiscale and multiphysics problems involving multiple interactions between electrons, nuclei, and photons at different time/length scales. In the current community, light-matter interactions were treated at different levels of theoretical complexity in quantum chemistry and quantum optics. In quantum optics or quantum photonics, the matter is usually simplified as a few-level system, and the light is treated quantum-mechanically. On the other hand, quantum chemistry explores first-principles methods, including both single-particle and many-body-based techniques, to describe the electronic properties of matter in detail. However, light is usually prescribed as a classical electromagnetic field, and the light-matter interaction is taken into account as an external potential via classical approximations. This software is designed to fill current modeling shortcomings by delivering a first-ever scalable multiscale platform for simulating light-matter interactions in realistic electromagnetic environments. The software solves Maxwell and Schrodinger equations self-consistent on the heterogeneous platforms. It implements HF/DFT, TDDFT, and coupled-cluster counterparts for light-matter interactions and adopts modular programming to offload massively parallel algorithms on a large number of CPU/GPUs.

Zhang, Yu↗
DOE OSTI2025

Metasurfaces with Multipolar Resonances and Enhanced Light–Matter Interaction

Metasurfaces, composed of engineered nanoantennas, enable unprecedented control over electromagnetic waves by leveraging multipolar resonances to tailor light–matter interactions. This review explores key physical mechanisms that govern their optical properties, including the role of multipolar resonances in shaping metasurface responses, the emergence of bound states in the continuum (BICs) that support high-quality factor modes, and the Purcell effect, which enhances spontaneous emission rates at the nanoscale. These effects collectively underpin the design of advanced photonic devices with tailored spectral, angular, and polarization-dependent properties. This review discusses recent advances in metasurfaces and applications based on them, highlighting research that employs full-wave numerical simulations, analytical and semi-analytic techniques, multipolar decomposition, nanofabrication, and experimental characterization to explore the interplay of multipolar resonances, bound and quasi-bound states, and enhanced light–matter interactions. A particular focus is given to metasurface-enhanced photodetectors, where structured nanoantennas improve light absorption, spectral selectivity, and quantum efficiency. By integrating metasurfaces with conventional photodetector architectures, it is possible to enhance responsivity, engineer photocarrier generation rates, and even enable functionalities such as polarization-sensitive detection. The interplay between multipolar resonances, BICs, and emission control mechanisms provides a unified framework for designing next-generation optoelectronic devices. This review consolidates recent progress in these areas, emphasizing the potential of metasurface-based approaches for high-performance sensing, imaging, and energy-harvesting applications.

Kerker effect↗