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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electric dipole moments, new forces and dark matter

New sources of CP violation beyond the Standard Model are crucial to explain the baryon asymmetry in the Universe. We discuss the impact of new CP violating interactions in theories where a dark matter candidate is predicted by the cancellation of gauge anomalies. In these theories, the constraint on the dark matter relic density implies an upper bound on the new symmetry breaking scale from which all new states acquire their masses. We investigate in detail the predictions for electric dipole moments and show that if the relevant CP-violating phase is large, experiments such as the ACME collaboration will be able to fully probe the theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Infrared freeze-in of magnetic dipole dark matter

We propose a novel mechanism for the cosmological production of keV–GeV mass dark matter that interacts with the Standard Model through a small effective magnetic dipole moment. Such an interaction can be radiatively generated if dark matter couples to heavier charged particles. Previous studies have focused on the case where these charged states are much heavier than the reheat temperature, such that freeze-in production of dark matter is sensitive to the ultraviolet details of reheating. Here, we instead consider the possibility that these heavy states have masses comparable to the dark matter mass and are charged under a new kinetically-mixed U (1)$^{′}$. As a result, dark matter production is dominated by the infrared freeze-in of the heavy charged states that subsequently thermalize the rest of the dark sector to a temperature much below that of the visible bath. We delineate regions of parameter space consistent with cosmological and astrophysical constraints and identify benchmark scenarios that can guide the next generation of direct detection experiments searching for spin-dependent scattering of sub-GeV dark matter.

Berlin, Asher [Fermilab] (ORCID:0000000211561482)↗
DOE OSTI2014

Electroweak baryogenesis, electric dipole moments, and Higgs diphoton decays

Here, we study the viability of electroweak baryogenesis in a two Higgs doublet model scenario augmented by vector-like, electroweakly interacting fermions. Considering a limited, but illustrative region of the model parameter space, we obtain the observed cosmic baryon asymmetry while satisfying present constraints from the non-observation of the permanent electric dipole moment (EDM) of the electron and the combined ATLAS and CMS result for the Higgs boson diphoton decay rate. The observation of a non-zero electron EDM in a next generation experiment and/or the observation of an excess (over the Standard Model) of Higgs to diphoton events with the 14 TeV LHC run or a future e + e – collider would be consistent with generation of the observed baryon asymmetry in this scenario.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Fluorescent Benzocoumarin-π-Extended Styryl Hybrids: Solvatochromism, Excess Dipole Moment, NLO Properties and DFT Study

Four benzo[h]chromen-3-yl)ethylidene) malononitrilestyryl hybrid dyes are presented for their potential non-linear optical properties using solvatochromism and density functional theory. The dyes are characterized by {sup 1}H and {sup 13}C NMR and elemental analysis. They have different donor and same acceptor as dicyanovinyl coumarin. Absorption and emission properties are highly dependent on substituents and environment. Dyes 3a and 3c show absorption solvatochromism while 3b and 3d show emission solvatochromism. Solvatochromism is used for the evaluation of excited state dipole moment and nonlinear optical properties which are comparable with the computed values. Limits of hyperpolarizability are close to the experimental and calculated values. Results shows that these dyes having strong intramolecular charge transfer characters proposing their potential nonlinear optical character.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Giant dipole resonance parameters of ground-state photoabsorption: Experimental values with uncertainties

Updated values and corresponding uncertainties of Isovector Giant Dipole Resonance (GDR) parameters which are obtained by the least-squares fitting of theoretical photoabsorption cross sections to experimental data are presented. The theoretical photoabsorption cross sections are taken as a sum of the components corresponding to the excitation of the GDR and quasideuteron photodisintegration. The current compilation is an extension and improvement of the earlier compilations of Lorentzian parameters for ground-state photoneutron and photoabsorption cross sections and covers experimental data made available up to June 2017.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

A solvable problem in statistical mechanics: The dipole-type Hamiltonian mean field model

The present study documents a type of mean field approximation inspired by the dipole interaction model, which is analytically solved in the canonical and microcanonical ensembles. The current calculations were derived from the Hamiltonian mean field model developments. After describing the canonical partition function, the free and internal energies, magnetization, and specific heat are derived and graphically depicted. In the microcanonical ensemble, the entropy is calculated as well as other thermodynamic properties. The system shows a second-order phase transition emphasizing that both methods coincide, which is only valid only in equilibrium. In addition, the current model represents a nonsymmetric Hamiltonian mean field model that shows a phase transition.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Review of condensed matter laser cooling using electric-dipole-allowed transitions

The cooling of solids via laser-excited anti-Stokes luminescence has reached the cryogenic regime and is now being considered for several applications that benefit from vibration-free cryogenic refrigeration. 4f-4f transitions in rare-earth-doped crystals with low phonon energies currently offer the best laser-cooling performance. These transitions, however, are electric-dipole (ED) forbidden and thus have low cross sections, limiting the minimum achievable temperatures in practical materials to the 50–100 K regime. In contrast, ED-allowed transitions may offer greater cross sections and potentially enable lower minimum temperatures or more compact devices. The search for laser cooling with ED-allowed transitions has been an active field of research over the past decades with a wide variety of materials having been studied. This paper reviews the fundamentals of solid-state laser cooling, provides a preliminary theoretical assessment showing that laser-cooling with ED-allowed transitions is in principle possible, and reviews the experimental results reported to date. While cooling with ED-allowed transitions has not yet been realized in the solid state, the existing experimental body of work along with the theoretical considerations presented here suggest that further research on this topic may be fruitful.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Finite element modeling of electropolishing of radio frequency dipole Nb crab cavity in hydrofluoric-sulfuric acid electrolyte

The superior performance of niobium superconducting radio frequency (SRF) cavities is achieved through meticulous surface treatment, notably via chemical electropolishing, ensuring exceptionally smooth surfaces. While this technique has been extensively employed for cylindrically symmetric structures, addressing more intricate geometries poses significant challenges in achieving uniform polishing and controlled material removal, especially when moving away from retractable cathodes. This presents a multifaceted electrochemical, thermal, and fluid dynamics conundrum. A prime example is the 197 MHz radio frequency dipole (RFD) crabbing cavity proposed for the Electron Ion Collider (EIC) project, exemplifying such complex structures. Our groundbreaking work integrates the localized oxide thickness variation, considering its impact on current distribution and Joule heating, within the framework of multi-physics modeling using the COMSOL® simulation suite. This approach was applied to a comprehensive model of the RFD cavity, allowing us to investigate optimal external cooling water flow conditions necessary for achieving desirable outcomes. In conclusion, this illustrates the increasing utility of such multi-physics codes to greatly aid in designing solutions to challenging processing requirements for increasingly complex accelerator cavities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Neutral-current neutrino cross section and expected supernova signals for 40 Ar from a three-fold increase in the magnetic dipole strength

In view of the great interest in liquid argon neutrino detectors, the 40 Ar(γ,γ') 40 Ar reaction was revisited to guide a calculation of the neutral current neutrino cross section at supernova energies. Using the nuclear resonance fluorescence technique with a monoenergetic, 99% linearly polarized photon beam, in this work we report a three-fold increase in magnetic dipole strength at around 10 MeV in 40 Ar. Based on shell-model calculations, and using the experimentally identified transitions, the neutral current neutrino cross sections for low-energy reactions on 40 Ar are calculated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Ultrahigh-Resolution Differential Ion Mobility Separations of Conformers for Proteins above 10 kDa: Onset of Dipole Alignment?

Biomacromolecules tend to assume numerous structures in solution or the gas phase. It has been possible to resolve disparate conformational families but not unique geometries within each, and drastic peak broadening has been the bane of protein analyses by chromatography, electrophoresis, and ion mobility spectrometry (IMS). The new differential IMS (FAIMS) approach using hydrogen-rich gases was recently found to separate conformers of a small protein ubiquitin with same peak width and resolving power up to ~400 as for peptides. Present work explores the reach of this approach for larger proteins, exemplified by cytochrome c and myoglobin. Resolution similar to that for ubiquitin was largely achieved with longer separations, while the onset of peak broadening and coalescence with shorter separations suggests the limitation of present technique to proteins under ~20 kDa. This capability may enable distinguishing whole proteins with differing residue sequences or localizations of posttranslational modifications. Small features at negative compensation voltages that markedly grow from cytochrome c to myoglobin indicate the dipole alignment of rare conformers in accord with theory, further supporting the concept of pendular macroions in FAIMS.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2020

Probing orientation-specific charge-dipole interactions between hexafluoroisopropanol and halides: A joint photoelectron spectroscopy and theoretical study

The interactions between hexafluoroisopropanol (HFIP) and halogen anions X? (F?, Cl?, Br?, and I?) have been investigated by negative ion photoelectron spectroscopy (NIPES) and ab initio calculations. The measured NIPE spectrum of each [HFIP·X]? (X = Cl, Br, and I) complex shows the identical pattern to the corresponding X? by shifting to the high electron binding energy side, indicative of formation of [HFIP···X?] structure, in which X? interacts with HFIP via charge-dipole interactions. However, the spectrum of [HFIP·F]? appears completely different from that of F?, and is more similar to the spectrum of the deprotonated HFIP anion (HFIP?H?). The geometry and electron density calculations indicate that a neutral HF molecule is formed upon HFIP interacting with F? via proton transfer, rendering a stable structure of [HFIP?H···HF]?. Two conformers of [HFIP?H·HF]? with HFIP being in synperiplanar and antiperiplanar configurations, respectively, are observed, providing direct experimental evidences to show the distinctly different and orientation-specific interactions between HFIP and halide anions.

Wang, Lei↗
DOE OSTI2021

Probing the Dipole-Bound State in the 9-Phenanthrolate Anion by Photodetachment Spectroscopy, Resonant Two-Photon Photoelectron Imaging, and Resonant Photoelectron Spectroscopy

Valence-bound anions with a dipolar core can support dipole-bound states (DBSs) below the electron detachment threshold. The highly diffuse DBS observed is usually of σ symmetry with an s-like orbital. Recently, a π-type DBS was observed experimentally in the 9-anthrolate anion (9AT – ) and it was shown to be stabilized due to the large anisotropic polarizability of the 9AT core. To confirm the general existence of π-DBS and its structural dependence, here we report an investigation of the 9-phenanthrolate anion (9PT – ), which has a different structure and lower symmetry than 9AT – . Photodetachment spectroscopy revealed a DBS 257 cm -1 below the detachment threshold of 9PT – at 19,627 cm -1 (2.4334 eV). Resonant two-photon photoelectron imaging indeed showed a π symmetry for the DBS. Similar to that observed in 9AT – , the π-DBS in 9PT – is also stabilized by the anisotropic polarizability of the 9PT core and accessed via non-adiabatic population transfer from the initially populated σ-DBS. Photodetachment spectroscopy unveiled nine above-threshold vibrational resonances of the DBS, resulting in nine highly non-Franck-Condon resonant photoelectron spectra by tuning the detachment laser to the vibrational resonances. In conclusion, the combination of photodetachment spectroscopy and resonant photoelectron spectroscopy allowed frequencies for nine vibrational modes of the 9-phenathroxy radical to be measured, including the six lowest frequency bending modes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Vapor–Liquid Equilibrium and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-Spring versus Dipole Self-Consistent Field Approaches to Induced Polarization

Here we implemented the Gaussian charge-on-spring (GCOS) version of the original self-consistent field implementation of the Gaussian Charge Polarizable water model and test its accuracy to represent the polarization behavior of the original model involving smeared charges and induced dipole moments. Moreover, for that purpose we adapted the recently developed multiple-particle-move (MPM) within the Gibbs and isochoric-isothermal ensembles Monte Carlo methods for the efficient simulation of polarizable fluids. We also assessed the accuracy of the GCOS representation by a direct comparison of the resulting vapor-liquid phase envelope, microstructure, and relevant microscopic descriptors of water polarization along the orthobaric curve against the corresponding quantities from the actual GCP water model.

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

Electronic Configuration Assignments for UO from Electric Dipole Moment Measurements

Diatomic UO has more than 48 bound states within 10000 cm -1 of the ground state. This electronic state congestion has been attributed to interleaved states from the electronic configurations U 2+ ($5f^37s$)O 2- and U 2+ ($5f^27s^2$)O 2- , respectively. Ligand field theory predicts that each electronic configuration will exhibit states with distinguishable, characteristic vibrational and rotational constants. However, vibronic state mixing modifies the observed vibration–rotation constants, leading to uncertainty in the configurational assignments. The permanent electric dipole moment ($μ_e$) of an electronic state should also manifest a value that is characteristic of the parent electronic configuration. $μ_e$ and other electrostatic and magnetostatic properties should be less influenced by the vibronic state mixing, providing more robust indicators for configurational assignments. In the present study, we have measured the $μ_e$ values for four electronic states of UO. Here, the results clearly demonstrate that the ground state (X(1)4) and the first electronically excited state ((2)4) are derived from the U 2+ ($5f^37s$)O 2– and U 2+ ($5f^27s^2$)O 2– configurations, respectively.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Simple and Accurate One-Body Energy and Dipole Moment Surfaces for Water and Beyond

Water is often the testing ground for new, advanced force fields. While advanced functional forms for intermolecular interactions have been integral to the development of accurate water models, less attention has been paid to a transferable model for intramolecular valence terms. In this work, we present a one-body energy and dipole moment surface model, named 1B-UCB, that is simple yet accurate and can be feasibly adapted for both standard and advanced potentials. 1B-UCB for water is comparable in accuracy to those with much more complex functional forms, despite having drastically fewer parameters. The parametrization protocol has been implemented as part of the Q-Force automated workflow and requires only a quantum mechanical Hessian calculation as reference data, hence allowing it to be easily extended to a variety of molecular systems beyond water, which we demonstrate on a selection of small molecules with different symmetries.

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

Determining Orientations of Optical Transition Dipole Moments Using Ultrafast X-ray Scattering

Here, identification of the initially prepared, optically active state remains a challenging problem in many studies of ultrafast photoinduced processes. We show that the initially excited electronic state can be determined using the anisotropic component of ultrafast time-resolved X-ray scattering signals. The concept is demonstrated using the time-dependent X-ray scattering of N -methyl morpholine in the gas phase upon excitation by a 200 nm linearly polarized optical pulse. Analysis of the angular dependence of the scattering signal near time zero renders the orientation of the transition dipole moment in the molecular frame and identifies the initially excited state as the 3pz Rydberg state, thus bypassing the need for further experimental studies to determine the starting point of the photoinduced dynamics and clarifying inconsistent computational results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Resonant Two-Photon Photoelectron Imaging and Intersystem Crossing from Excited Dipole-Bound States of Cold Anions

In this work, we report the observation of a dipole-bound state (DBS) 659 cm –1 below the electron detachment threshold of cryogenically cooled deprotonated 4,4'-biphenol anion (bPh – ) and 19 of its lowest vibrational levels. Resonant two-photon photoelectron imaging (R2P-PEI) via the vibrational levels of the DBS displays a sharp peak with a constant binding energy. This observation indicates vertical detachment from the vibrational levels of the DBS to the corresponding neutral levels with the conservation of the vibrational energy, suggesting that the highly diffuse electron in the DBS has little effect on the neutral core. The R2P-PEI spectra also exhibit two features at lower binding energies, which come from intersystem crossings from the DBS to two lower-lying valence-bound triplet excited states of bPh – . The current study discloses the first R2P-PEI spectra from vibrational excited states of a DBS and direct spectroscopic evidence of transitions from a DBS to valence-bound states of anions.irect spectroscopic evidence of transitions from a DBS to valence-bound states of anions.

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

Polaritonic Probe of an Emergent 2D Dipole Interface

The use of work-function-mediated charge transfer has recently emerged as a reliable route toward nanoscale electrostatic control of individual atomic layers. Using α-RuCl 3 as a 2D electron acceptor, we are able to induce emergent nano-optical behavior in hexagonal boron nitride (hBN) that arises due to interlayer charge polarization. Using scattering-type scanning near-field optical microscopy (s-SNOM), we find that a thin layer of α-RuCl 3 adjacent to an hBN slab reduces the propagation length of hBN phonon polaritons (PhPs) in significant excess of what can be attributed to intrinsic optical losses. Concomitant nano-optical spectroscopy experiments reveal a novel resonance that aligns energetically with the region of excess PhP losses. These experimental observations are elucidated by first-principles density-functional theory and near-field model calculations, which show that the formation of a large interfacial dipole suppresses out-of-plane PhP propagation. Finally, our results demonstrate the potential utility of charge-transfer heterostructures for tailoring optoelectronic properties of 2D insulators.

36 MATERIALS SCIENCE↗