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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Plasmon-Mediated Intramolecular Methyl Migration with Nanoscale Spatial Control

Plasmonic materials interact strongly with light to focus and enhance electromagnetic radiation down to nanoscale volumes. Due to this localized confinement, materials that support localized surface plasmon resonances are capable of driving energetically unfavorable chemical reactions. In certain cases, the plasmonic nanostructures are able to preferentially catalyze the formation of specific photoproducts, which offers an opportunity for the development of solar-driven chemical synthesis. Here, using plasmonic environments, we report inducing an intramolecular methyl migration reaction, forming 4-methylpyridine from N-methylpyridinium. Using both experimental and computational methods, we were able to confirm the identity of the N-methylpyridinium by making spectral comparisons against possible photoproducts. This reaction involves breaking a C–N bond and forming a new C–C bond, highlighting the ability of plasmonic materials to drive complex and selective reactions. Additionally, we observe that the product yield depends strongly on optical illumination conditions. This is likely due to steric hindrance in specific regions on the nanostructured plasmonic substrate, providing an optical handle for driving plasmonic catalysis with spatial specificity. Furthermore, this work adds yet another class of reactions accessible by surface plasmon excitation to the ever-growing library of plasmon-mediated chemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

First on-line detection of radioactive fission isotopes produced by laser-accelerated protons

Abstract The on-going developments in laser acceleration of protons and light ions, as well as the production of strong bursts of neutrons and multi- $$\hbox {MeV}$$ MeV photons by secondary processes now provide a basis for novel high-flux nuclear physics experiments. While the maximum energy of protons resulting from Target Normal Sheath Acceleration is presently still limited to around $$100 \, \hbox {MeV}$$ 100 MeV , the generated proton peak flux within the short laser-accelerated bunches can already today exceed the values achievable at the most advanced conventional accelerators by orders of magnitude. This paper consists of two parts covering the scientific motivation and relevance of such experiments and a first proof-of-principle demonstration. In the presented experiment pulses of $$200 \, \hbox {J}$$ 200 J at $$\approx \, 500 \, \hbox {fs}$$ ≈ 500 fs duration from the PHELIX laser produced more than $$10^{12}$$ 10 12 protons with energies above $$15 \, \hbox {MeV}$$ 15 MeV in a bunch of sub-nanosecond duration. They were used to induce fission in foil targets made of natural uranium. To make use of the nonpareil flux, these targets have to be very close to the laser acceleration source, since the particle density within the bunch is strongly affected by Coulomb explosion and the velocity differences between ions of different energy. The main challenge for nuclear detection with high-purity germanium detectors is given by the strong electromagnetic pulse caused by the laser-matter interaction close to the laser acceleration source. This was mitigated by utilizing fast transport of the fission products by a gas flow to a carbon filter, where the $$\upgamma$$ γ -rays were registered. The identified nuclides include those that have half-lives down to $$39 \, \hbox {s}$$ 39 s . These results demonstrate the capability to produce, extract, and detect short-lived reaction products under the demanding experimental condition imposed by the high-power laser interaction. The approach promotes research towards relevant nuclear astrophysical studies at conditions currently only accessible at nuclear high energy density laser facilities.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Pion electric polarizability from lattice QCD

Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Non-Hermitian wave packet approximation for coupled two-level systems in weak and intense fields

We introduce a non-Hermitian Schrödinger-type approximation of optical Bloch equations for two-level systems. This approximation provides a complete and accurate description of the coherence and decoherence dynamics in both weak and strong laser fields at the cost of losing accuracy in the description of populations. In this approach, it is sufficient to propagate the wave function of the quantum system instead of the density matrix, providing that relaxation and dephasing are taken into account via automatically adjusted time-dependent gain and decay rates. The developed formalism is applied to the problem of scattering and absorption of electromagnetic radiation by a thin layer comprised of interacting two-level emitters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

A ‘black hole theorem,’ and its implications

A general formulation of the basic conflict of the information problem is given, encapsulated in a 'black hole theorem.' This is framed in a more general context than the usual one of quantum field theory on a background, and is based on describing a black hole as a quantum subsystem of a larger system, including its environment. This sharpens the limited set of possible consistent options; as with the Coleman-Mandula theorem, the most important point is probably the loophole in the 'theorem,' and what this tells us about the fundamental structure of quantum gravity. This 'theorem' in particular involves the general question of how to define quantum subsystems in quantum gravity. If black holes do behave as quantum subsystems, at least to a good approximation, evolve unitarily, and do not leave remnants, the 'theorem' implies the presence of interactions between a black hole and its environment that go beyond a description based on local quantum fields. This provides further motivation for and connects to previous work giving a principled parameterization of these interactions, and investigating their possible observational signatures via electromagnetic or gravitational wave observations of black holes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Short-wavelength plasma turbulence and temperature anisotropy instabilities: Recent computational progress

Plasma turbulence consists of an ensemble of enhanced, broadband electromagnetic fluctuations, typically driven by multi-wave interactions which transfer energy in wavevector space via non- linear cascade processes. In addition, temperature anisotropy instabilities in collisionless plasmas are driven by quasi-linear wave–particle interactions which transfer particle kinetic energy to field fluctuation energy; the resulting enhanced fluctuations are typically narrowband in wavevector magnitude and direction. Whatever their sources, short-wavelength fluctuations are those at which charged particle kinetic, that is, velocity-space, properties are important; these are generally wavelengths of the order of or shorter than the ion inertial length or the thermal ion gyroradius. The purpose of this review is to summarize and interpret recent computational results concerning short-wavelength plasma turbulence, short-wavelength temperature anisotropy instabilities and relationships between the two phenomena.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Quantum Monte Carlo Calculations of Magnetic Form Factors in Light Nuclei

Here, we present Quantum Monte Carlo calculations of magnetic form factors in A = 6-10 nuclei, based on Norfolk two- and three-nucleon interactions, and associated one- and two-body electromagnetic currents. Agreement with the available experimental data for 6 Li, 7 Li, 9 Be and 10 B up to values of momentum transfer q ~ 3 fm -1 is achieved when two-nucleon currents are accounted for. We present a set of predictions for the magnetic form factors of 7 Be, 8 Li, 9 Li, and 9 C. In these systems, two body currents account for ~ 40-60% of the total magnetic strength. Measurements in any of these radioactive systems would provide valuable insights on the nuclear magnetic structure emerging from the underlying many-nucleon dynamics. A particularly interesting case is that of 7 Be, as it would enable investigations of the magnetic structure of mirror nuclei

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Physics of Correlated Systems, Final Project Report

The funding of this DOE project has enabled the P.I. and his collaborators to tackle a number of problems involving nonperturbatively coupled atomic systems, including their interactions with each other and/or with an external electromagnetic field of the type provided by either a continuous-wave or a femtosecond short-pulse laser. The progress includes a new, deeper understanding of an old and famous theory of autoionization lineshapes, developed initially by Ugo Fano in 1935 and later extended in a highly cited 1961 article; the new result specifically is that in a collaboration with the Heidelberg group we have been able to demonstrate an unexpectedly simple behavior in the time domain that is relevant for modern short-pulse lasers. This study also demonstrates a way to modify and even control the lineshapes of unstable atomic and molecular energy levels.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Texas A&M University in the JET Collaboration - Final Report

This final report summarizes the work done by PIs at Texas A&M University within the JET Topical Collaboration. The main focus of the group at Texas A&M has been the development and implementation of a hadronization model suitable to calculate hadronization of jet showers in heavy ion collisions event by event. The group successfully developed a hybrid model of parton recombination and remnant string fragmentation including recombination with thermal partons. A code realizing this model was developed and shared with other JET members. In addition, the group at Texas A&M worked on both open and hidden heavy flavor probes. In particular, they developed a description of heavy flavor hadronization based on recombination, and consistent with in-medium scattering rates of heavy quarks, and suggested the D s meson as a precise probe of the hadronization mechanism. Another noteworthy focus of their work was electromagnetic probes, in particular, dileptons and photons from interactions of jets with the medium. In the soft sector the group has made several contributions to modern topics, e.g. the splitting of elliptic flow between isospin partners and the role of the initial strong gluon fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Toward $\nu_{\mu}$CC $\eta$ Meson Cross Sections on Argon in SBND

The modeling of resonant neutrino interactions on argon is critical for achieving precision neutrino oscillation measurements and searching for physics beyond the Standard Model with both DUNE and the Short-Baseline Neutrino Program. Higher mass resonances beyond the $\Delta$(1232) baryon are particularly poorly constrained experimentally, and yet contribute a significant rate in multi-GeV interactions. The measurement of $\eta$(548) meson production from the decay of these resonances provides a unique probe, as well as the opportunity to measure observables sensitive to final state interactions with the nucleus. This poster will present progress towards the measurement of meson production with the Short-Baseline Near Detector (SBND) at Fermilab, leveraging the clean $\eta \rightarrow \gamma \gamma$ decay channel. The large statistics of the SBND dataset will provide high-precision measurements of this channel capable of constraining uncertainties in the modeling of higher order resonant interactions. This analysis further provides important handles on electromagnetic shower reconstruction performance through evaluation of the 548 MeV $\eta$ invariant mass peak.

Antonakis, Alexander [UC, Santa Barbara]↗
DOE OSTI2015

RHIC electron lenses upgrades

In the Relativistic Heavy Ion Collider (RHIC) 100 GeV polarized proton run in 2015, two electron lenses were used to partially compensate for the head-on beam-beam effect for the first time. Here, we describe the design of the current electron lens, detailing the hardware modifications made after the 2014 commissioning run with heavy ions. A new electron gun with 15-mm diameter cathode is characterized. The electron beam transverse profile was measured using a YAG screen and fitted with a Gaussian distribution. During operation, the overlap of the electron and proton beams was achieved using the electron backscattering detector in conjunction with an automated orbit control program.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

$\nu_e$ CC Event Identification Based on Shower Energy Profiles in LArTPCs

• Neutrino oscillations → Neutrinos have mass. Insight into physics beyond the Standard Model. • Liquid Argon Time Projection Chamber (LArTPC): - Distinguish between $e^-$ and $\gamma$ electromagnetic showers. - Exceptional calorimetry and tracking capabilities. • Weak interaction: - Neutral current (NC): $\nu_e \eta \to \nu_e \eta$ - Charged current (CC): $\nu_e \eta \to e^- p$ • Goal: Identify and select $e^-$ showers to do $\nu_e$ CC analysis.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

Quantifying the relationship between electric field enhancement and plasmon-driven electron transfer

Plasmonic materials interact strongly with light to create localized, out-of-equilibrium environments with intense electromagnetic fields known as hotspots. After forming, hotspots dissipate energy into their surroundings and can transfer energy and charge carriers to nearby molecules, giving plasmonic materials the potential to drive reactions with sunlight. However, the field needs a better mechanistic understanding of plasmon–molecule interactions and how the local plasmon environment, specifically the electromagnetic field enhancement and spatial distribution of hotspots, impacts the reaction yield. Here, in this work, we mapped plasmon-driven charge transfer across ordered plasmonic substrates using diffraction-limited surface-enhanced Raman spectroscopy (SERS) microscopy to understand the relationship between the average local electric field enhancement and charge transfer reaction yield. We tracked the plasmon-induced electron transfer to buckminsterfullerene (C 60 ) and found that areas with the greatest SERS intensity were not the areas with the greatest ensemble-averaged reduction of C 60 , suggesting that areas with higher electric field enhancement—or “hotter,” more enhancing hotspots—do not improve the charge transfer reaction yield. This work shows that efforts to improve plasmon-driven charge transfer should not merely focus on creating substrates with extremely enhancing regions but also consider how other factors could optimize photoreduction yields.

Koble, MaKenna M. [Univ. of Minnesota, Minneapolis↗
DOE OSTI2021

Substrate-enhanced photothermal nano-imaging of surface polaritons in monolayer graphene

Surface polaritons comprise a wealth of light–matter interactions with deep sub-wavelength scale confinement of electromagnetic modes. However, their nanoscale localized dissipation and thermalization processes are not readily accessible experimentally. Here, we introduce photothermal force microscopy to image surface plasmon polaritons (SPPs) in monolayer graphene through their non-radiative SiO2 substrate dissipation. We demonstrate the real-space SPP imaging via photo-induced atomic force detection, and from comparison with scattering-type scanning near-field optical microscopy imaging attribute the force response to substrate dissipation-enhanced thermal expansion. This work illustrates that nano-optical tip–sample induced dissipative forces facilitate a direct mechanical detection of surface polariton interactions with monolayer sensitivity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Mapping the electromagnetic fields of heavy-ion collisions with the Breit-Wheeler process

Ultra-relativistic heavy-ion collisions are expected to produce the strongest electromagnetic fields in the known Universe. These highly-Lorentz contracted fields can manifest themselves as linearly polarized quasi-real photons that can interact via the Breit-Wheeler process to produce lepton anti-lepton pairs. Furthermore, the energy and momentum distribution of the produced dileptons carry information about the strength and spatial distribution of the colliding fields. Recently it has been demonstrated that photons from these fields can interact even in heavy-ion collisions with hadronic overlap, providing a purely electromagnetic probe of the produced medium. In this review we discuss the recent theoretical progress and experimental advances for mapping the ultra-strong electromagnetic fields produced in heavy-ion collisions via measurement of the Breit-Wheeler process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Transport signatures of Majorana quantum criticality realized by dissipative resonant tunneling

We consider theoretically the transport properties of a spinless resonant electronic level coupled to strongly dissipative leads, in the regime of circuit impedance near the resistance quantum. Using the Luttinger liquid analogy, one obtains an effective Hamiltonian expressed in terms of interacting Majorana fermions, in which all environmental degrees of freedom (leads and electromagnetic modes) are encapsulated in a single fermionic bath. General transport equations for this system are then derived in terms of the Majorana T-matrix. Perturbative treatment of the Majorana interaction term yields the appearance of a marginal, linear dependence of the conductance on temperature when the system is tuned to its quantum critical point, in agreement with recent experimental observations. Here, we investigate in detail the different crossovers involved in the problem, and analyze the role of the interaction terms in the transport scaling functions. In particular, we show that single barrier scaling applies when the system is slightly tuned away from its Majorana critical point, strengthening the general picture of dynamical Coulomb blockade.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Current density partitioning in time-dependent current density functional theory

We adapt time-dependent current density functional theory to allow for a fragment-based solution of the many-electron problem of molecules in the presence of time-dependent electric and magnetic fields. Regarding a molecule as a set of non-interacting subsystems that individually evolve under the influence of an auxiliary external electromagnetic vector-scalar potential pair, the partition 4-potential, we show that there are one-to-one mappings between this auxiliary potential, a sharply-defined set of fragment current densities, and the total current density of the system. The partition electromagnetic (EM) 4-potential is expressed in terms of the real EM 4-potential of the system and a gluing EM 4-potential that accounts for exchange-correlation effects and mutual interaction forces between fragments that are required to yield the correct electron dynamics. We prove the zero-force theorem for the fragmented system, establish a variational formulation in terms of action functionals, and provide a simple illustration for a charged particle in a ring.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Computing the dipole polarizability of Ca 48 with increased precision

Here, we compute the electric dipole polarizability of 48 Ca with an increased precision by including more correlations than in previous studies. Employing the coupled-cluster method we go beyond single and double excitations and include leading-order three-particle-three-hole (3p-3h) excitations for the ground state, excited states, and the similarity-transformed operator. We study electromagnetic sum rules, such as the bremsstrahlung sum rule m 0 and the polarizability sum rule αD using interactions from chiral effective field theory. To gauge the quality of our coupled-cluster approximations we perform several benchmarks with the effective interaction hyperspherical harmonics approach in 4 He and with self consistent Green's function in 16 O. We compute the dipole polarizability of 48 Ca employing the chiral interaction N 2 LO sat and the 1.8/2.0 (EM). We find that the effect of 3p-3h excitations in the ground state is small for 1.8/2.0 (EM) but non-negligible for N 2 LO sat . The addition of these new correlations allows us to improve the precision of our 48 Ca calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined αD from proton inelastic scattering in 48 Ca. For the computation of electromagnetic and polarizability sum rules, the inclusion of leading-order 3p-3h excitations in the ground state is important, while it is less so for the excited states and the similarity-transformed dipole operator.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗