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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Accidentally Stable Dark Matter in a Parity Solution to the Strong CP Problem

Parity symmetry, with an extended gauge group $SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_X$, can solve the strong CP problem. In particular, the model where $SU(2)_R\times U(1)_X$ is broken by the Parity partner of the Standard Model Higgs solves the strong CP problem without the necessity of introducing extra symmetry. We discuss the possibility of accidentally stable dark matter in this framework and show that $SU(2)_L \times SU(2)_R$ bi-triplet fermions can be stable over cosmological timescales. We compute the relic abundance of the bi-triplet dark matter and derive constraints on the parameter space from collider, direct-detection, and indirect-detection experiments. The $SU(2)_R\times U(1)_X$ symmetry breaking scale is required to be below 150 TeV, and most of the parameter space can be probed by near-future indirect-detection experiments.

Baldwin, Matthew J. [Chicago U., EFI] (ORCID:00090↗
DOE OSTI2024

Theory of strong-field sequential double ionization of polyatomic molecules

Understanding of strong-field sequential double ionization (SDI) of molecules by a highly intense infrared laser pulse could be the key to observing electron motion in molecules in the attosecond to femtosecond timescale. Based on a novel density matrix approach for SDI (DM-SDI), a recent theoretical study has shown that SDI can be used as a probe to monitor the changes in vibronic coherence in homonuclear diatomic molecules. In this article, we extend the DM-SDI model to general molecules that could possess permanent dipole moments and arbitrary symmetry. We apply the model to SDI of a water molecule and identify the formation pathway of individual dication states. We further deduce that kinetic energy release spectra from two- and three-body fragments could carry the signature of vibronic coherence between the lowest two states of the water cation. Furthermore, our results suggest that observables from the SDI probe can be interpreted intuitively with only the knowledge of electronic structures of populated ionic states, making the SDI probe to be a highly desirable probing scheme for vibronic coherence in generic molecules.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Dissociation slowdown by collective optical response under strong coupling conditions

We consider an ensemble of diatomic molecules resonantly coupled to an optical cavity under strong coupling conditions at normal incidence. Photodissociation dynamics is examined via direct numerical integration of the coupled Maxwell–Schrödinger equations with molecular rovibrational degrees of freedom explicitly taken into account. It is shown that the dissociation is significantly affected (slowed down) when the system is driven at its polaritonic frequencies. The observed effect is demonstrated to be of transient nature and has no classical analog. An intuitive explanation of the dissociation slowdown at polaritonic frequencies is proposed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Nonadiabatic strong-field photoionization revisited: Detailed analysis

We develop a theoretical framework to interpret “bump-like” enhancements in the energy distribution of electrons emitted from cesium atoms subjected to intense infrared laser fields, as observed in a recent experiment. These emissions, detected at energies approaching twice the ponderomotive energy (2⁢𝑈 p ), indicate a mechanism where electrons are nonadiabatically ejected with substantial inward velocity following ionization. The bump-like features arise from returning trajectories that scatter off the residual ion. We interpret these experimental results classically using a periodically driven version of the Bohr model and quantum mechanically through Keldysh's adiabaticity parameter (𝛾 K ) and Reiss's continuum-state intensity parameter 𝒵 in a Coulomb-corrected version of the strong-field approximation (SFA) that incorporates “complex” electronic trajectories. Notably, our theoretical analysis shows that these emissions are independent of the specific short-range form of the atomic potential.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Strong Photon‐Magnon Coupling Using a Lithographically Defined Organic Ferrimagnet

Abstract A cavity‐magnonic system composed of a superconducting microwave resonator coupled to a magnon mode hosted by the organic‐based ferrimagnet vanadium tetracyanoethylene (V[TCNE] x ) is demonstrated. This work is motivated by the challenge of scalably integrating a low‐damping magnetic system with planar superconducting circuits. V[TCNE] x has ultra‐low intrinsic damping, can be grown at low processing temperatures on arbitrary substrates, and can be patterned via electron beam lithography. The devices operate in the strong coupling regime, with a cooperativity exceeding 1000 for coupling between the Kittel mode and the resonator mode at T≈0.4 K, suitable for scalable quantum circuit integration. Higher‐order magnon modes are also observed with much narrower linewidths than the Kittel mode. This work paves the way for high‐cooperativity hybrid quantum devices in which magnonic circuits can be designed and fabricated as easily as electrical wires.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

pH‐Mediated Strong Metal‐Support Interaction Construction Through Dynamic Fermi Level Tuning

The metal–support interface is central to governing catalytic transformations. While strong metal–support interaction (SMSI) is an established strategy to tailor the morphology and electronic properties of supported metal catalysts, the role of interfacial charge redistribution in SMSI formation remains poorly understood and rarely leveraged. Here, in this study, we report a dual-stimuli approach that combines pH modulation with ultrasonication to mediate SMSI construction in aqueous solution through dynamic Fermi level tuning. By leveraging in situ pH-driven charge redistribution at the metal–support interface, we achieve controllable SMSI encapsulation of metal nanoparticles, as verified by electrochemical analysis, work function measurements, and x-ray-based techniques. The resulting catalysts exhibit tunable SMSI features and deliver enhanced activity and selectivity in hydrogenation reactions. This work establishes a facile strategy to modulate catalyst structure and electronic properties by exploiting Fermi level variation as a driving force, thereby advancing rational SMSI design and catalytic performance across diverse environments.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Strong Lensing by Galaxies

Strong gravitational lensing at the galaxy scale is a valuable tool for various applications in astrophysics and cosmology. Some of the primary uses of galaxy-scale lensing are to study elliptical galaxies’ mass structure and evolution, constrain the stellar initial mass function, and measure cosmological parameters. Since the discovery of the first galaxy-scale lens in the 1980s, this field has made significant advancements in data quality and modeling techniques. In this review, we describe the most common methods for modeling lensing observables, especially imaging data, as they are the most accessible and informative source of lensing observables. We then summarize the primary findings from the literature on the astrophysical and cosmological applications of galaxy-scale lenses. We also discuss the current limitations of the data and methodologies and provide an outlook on the expected improvements in both areas in the near future.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

On the Strong Convergence of Forward-Backward Splitting in Reconstructing Jointly Sparse Signals

We consider the problem of reconstructing an infinite set of sparse, finite-dimensional vectors, that share a common sparsity pattern, from incomplete measurements. This is in contrast to the work (Daubechies et al., Pure Appl. Math. 57(11), 1413–1457, 2004), where the single vector signal can be infinite-dimensional, and (Fornasier and Rauhut, SIAM J. Numer. Anal. 46(2), 577613, 2008), which extends the aforementioned work to the joint sparse recovery of finite number of infinite-dimensional vectors. In our case, to take account of the joint sparsity and promote the coupling of nonvanishing components, we employ a convex relaxation approach with mixed norm penalty ℓ 2,1 . This paper discusses the computation of the solutions of linear inverse problems with such relaxation by a forward-backward splitting algorithm. However, since the solution matrix possesses infinitely many columns, the arguments of Daubechies et al. (Pure Appl. Math. 57(11), 1413–1457, 2004) no longer apply. As such, we establish new strong convergence results for the algorithm, in particular when the set of jointly sparse vectors is infinite.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Mutual information prediction for strongly correlated systems

We have trained a new machine-learning (ML) model which predicts mutual information (MI) for strongly correlated systems. This is a complex quantity, which is much more difficult to predict than one-site entropies, but carries important information about the correlation structure inside electronic systems. In this work, we replaced the expensive density matrix renormalization group (DMRG) calculations by newly trained ML model for prediction of the mutual information. We show the performance of the model on two important tasks: (a) to determine the correlation structure and (b) to determine ordering of orbitals for accurate DMRG calculations. In conclusion, the results are compared with the MI obtained from accurate DMRG calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Dependency of CO 2 methanation on the strong metal-support interaction for supported Ni/CeO 2 catalysts

The strong metal-support interaction (SMSI) for supported Ni/CeO 2 catalysts with different CeO 2 nanomorphologies was systematically explored. The degree of encapsulation of Ni particles originating from the SMSI effect was found to follow the trend of Ni/CeO 2 -(1 1 1) > Ni/CeO 2 -(1 0 0) > Ni/CeO 2 -(110 + 100), which parallels the CO 2 hydrogenation activity. Quasi in situ XPS reveals the presence of Ce 3+ sites in accordance with the formation of an amorphous surface CeOx layer encapsulating the Ni nanoparticles. In situ DRIFTS indicates the reaction pathway and rate-determining step are dependent on the degree of the SMSI effect, leading to distinct selectivities towards CH 4 , especially at a high weight hourly space velocity (WHSV). Finally, these findings present a fundamental strategy about tailoring catalytic performance through support facet dependent susceptibility of SMSI phenomena.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Determination of the strong coupling and its running from measurements of inclusive jet production

The value of the strong coupling α S is determined in a comprehensive analysis at next-to-next-to-leading order accuracy in quantum chromodynamics. The analysis uses double-differential cross section measurements from the CMS Collaboration at the CERN LHC of inclusive jet production in proton-proton collisions at centre-of-mass energies of 2.76, 7, 8, and 13 TeV, combined with inclusive deep-inelastic data from HERA. The value α S (m z ) = 0.1176 $^{+0.0014}_{-0.0016}$ is obtained at the scale of the Z boson mass. By using the measurements in different intervals of jet transverse momentum, the running of α S is probed for energies between 100 and 1600 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

A Bayesian framework to investigate radiation reaction in strong fields

Recent experiments aiming to measure phenomena predicted by strong-field quantum electrodynamics (SFQED) have done so by colliding relativistic electron beams and high-power lasers. In such experiments, measurements of collision parameters are not always feasible. However, precise knowledge of these parameters is required to accurately test SFQED. Here, we present a novel Bayesian inference procedure that infers collision parameters that could not be measured on-shot. This procedure is applicable to all-optical non-linear Compton scattering experiments investigating radiation reaction. The framework allows multiple diagnostics to be combined self-consistently and facilitates the inclusion of known information pertaining to the collision parameters. Using this Bayesian analysis, the relative validity of the classical, quantum-continuous and quantum-stochastic models of radiation reaction was compared for several test cases, which demonstrates the accuracy and model selection capability of the framework and highlight its robustness if the experimental values of fixed parameters differ from their values in the models.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Strongly Coupled Exciton–Surface Lattice Resonances Engineer Long-Range Energy Propagation

Achieving propagation lengths in hybrid plasmonic systems beyond typical values of tens of micrometers is important for quantum plasmonics applications. Iin this paper, we report long-range optical energy propagation due to excitons in semiconductor quantum dots (SQDs) being strongly coupled to surface lattice resonance (SLRs) in silver nanoparticle arrays. Photoluminescence (PL) measurements provide evidence of an exciton-SLR (ESLR) mode extending at least 600 mu m from the excitation region. We also observe additional energy propagation with range well beyond the ESLR mode and with dependency on the coupling strength, g, between SQDs and SLR. Cavity quantum electrodynamics calculations capture the nature of the PL spectra for consistent g values, while coupled dipole calculations show a SQD number-dependent electric field decay profile consistent with the experimental spatial PL profile. Our results suggest an exciting direction wherein SLRs mediate long-range interactions between SQDs, having possible applications in optoelectronics, sensing, and quantum information science.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Strong Coupling in Semiconductor Hyperbolic Metamaterials

Semiconductor-based layered hyperbolic metamaterials (HMMs) house high-wavevector volume plasmon polariton (VPP) modes in the infrared spectral range. VPP modes have successfully been exploited in the weak-coupling regime through the enhanced Purcell effect. In this paper, we experimentally demonstrate strong coupling between the VPP modes in a semiconductor HMM and the intersubband transition of epitaxially embedded quantum wells. We observe clear anticrossings in the dispersion curves for the zeroth-, first-, second-, and third-order VPP modes, resulting in upper and lower polariton branches for each mode. This demonstration sets the stage for the creation of novel infrared optoelectronic structures combining HMMs with embedded epitaxial emitter or detector structures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Strong Electronic Coupling of Graphene Nanoribbons onto Basal Plane of a Glassy Carbon Electrode

The grafting of molecular motifs to the conductive carbon represents a promising approach toward improved hybrid materials for electrocatalytic applications. Here, we investigate the electrochemical behavior of graphene nanoribbons (GNR) deposited onto a glassy carbon electrode using pi - pi stacking interactions. Using the bipyrimidine moiety on the nanoribbon edges as a reporter of the proton-coupled electron transfer chemistry, we illustrate that the simple electrochemical treatment of as-deposited nanoribbon generates a hybrid material that is in strong electronic communication with the conductive support. Overall, this work shows a strategy for modifying the basal plane of carbon materials and provides a potential platform for the incorporation of catalytic metal sites via coordination through the N-functionalities of GNR.

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

Mechanochemistry-Induced Strong Metal–Support Interactions Construction toward Enhanced Hydrogenation

The construction of strong metal–support interactions (SMSIs) represented an attractive approach to producing supported noble metal nanocatalysts possessing enhanced stability by overlayer encapsulation. The development of facile approaches capable of achieving efficient, controllable, and extensive SMSI overlayer formation, particularly under neat and ambient conditions, is a long-standing challenge. In this work, a mechanochemistry-driven pathway was deployed for efficient and controllable SMSI construction under neat and ambient conditions to customize the capsulation degree and overlayer structures toward enhanced catalysis. The reducibility of the additives and the high interaction efficiency provided by the mechanochemical treatment could afford abundant active intermediates (e.g., Ti 3+ species and oxygen defects) within a short time to induce and tune the overlayer encapsulation. This facile approach could be extensively deployed to TiO2-derived nanocatalysts with diverse phases, diverse reducible metal oxides-involved systems, and different supported noble metal nanoparticles. Enhanced hydrogenation activity was achieved by the as-afforded nanocatalysts upon SMSI construction and further tuned by the encapsulation degree.

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

Tuning Strong Metal–Support Interactions via Synergistic Alloying

The encapsulation phenomenon associated with strong metal-support interaction (SMSI) has been largely restricted to catalyst systems consisting of group VIII metals with high surface energy and reducible transition metal oxide supports with low surface energy. Here, we demonstrate an encapsulation phenomenon that, while sharing morphological similarities with conventional SMSI, follows a distinctive pathway. This is shown by the encapsulation of CuAu nanoparticles (NPs) supported on highly ordered pyrolytic graphite (HOPG). Through dynamic monitoring of Cu, Au, and Cu 50 Au 50 NPs in an oxidizing atmosphere using ambient-pressure X-ray photoelectron spectroscopy, we show that this spontaneous encapsulation is achieved through the synergistic effect of the alloying elements. Specifically, the surface segregation of Cu promotes dissociative O 2 adsorption, leading to the formation of atomic O species, while the subsurface enrichment of Au hinders O incorporation into the bulk of CuAu NPs. Consequently, O spillover onto the graphite support occurs, resulting in the oxidation of the HOPG surface into graphitic oxide species. The higher affinity of the graphitic oxide species toward the Cu-segregated surface prompts their migration from the HOPG support to encapsulate the CuAu NPs. Finally, these results transcend the conventional SMSI and bear practical implications for the design and development of heterogeneous catalysts, particularly in carbon-supported alloy systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The effect of strong metal–support interaction (SMSI) on Pt–Ti/SiO 2 and Pt–Nb/SiO 2 catalysts for propane dehydrogenation

In this study, we show how strong metal–support interaction (SMSI) oxides in Pt–Nb/SiO 2 and Pt–Ti/SiO 2 affect the electronic, geometric and catalytic properties for propane dehydrogenation. Transmission electron microscopy (TEM), CO chemisorption, and decrease in the catalytic rates per gram Pt confirm that the Pt nanoparticles were partially covered by the SMSI oxides. X-ray absorption near edge structure (XANES), in situ X-ray photoelectron spectroscopy (XPS), and resonant inelastic X-ray scattering (RIXS) showed little change in the energy of Pt valence orbitals upon interaction with SMSI oxides. The catalytic activity per mol of Pt for ethylene hydrogenation and propane dehydrogenation was lower due to fewer exposed Pt sites, while turnover rates were similar. The SMSI oxides, however, significantly increase the propylene selectivity for the latter reaction compared to Pt/SiO 2 . In the SMSI catalysts, the higher olefin selectivity is suggested to be due to the smaller exposed Pt ensemble sites, which result in suppression of the alkane hydrogenolysis reaction; while the exposed atoms remain active for dehydrogenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗