Search NASA⌕ Search

SEARCH · Search NASA

Results for “single particle spectroscopy”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Investigation into the crystal structure–dielectric property correlation in barium titanate nanocrystals of different sizes

For high capacitance multilayer ceramic capacitors, high dielectric constant and lead-free ceramic nanoparticles are highly desired. However, as the particle size decreases to a few tens of nanometers, their dielectric constant significantly decreases, and the underlying mechanism has yet to be fully elucidated. Herein, we report a systematic investigation into the crystal structure–dielectric property relationship of combustion-made BaTiO 3 (BTO) nanocrystals. When the nanocrystal size was 100 nm and below, a metastable paraelectric cubic phase was found in the as-received BTO (denoted as arBTO) nanocrystals based on an X-ray diffraction (XRD) study. A stable ferroelectric tetragonal phase was present when the nanocrystal size was above 200 nm. Notably, the cubic arBTO (particle size ≤100 nm) exhibited tetragonal fluctuations as revealed by Raman spectroscopy, whereas the tetragonal arBTO (particle size ≥200 nm) contained ~10% cubic fraction according to the Rietveld fitting of the XRD profiles. Thermal annealing of the multi-grain tetragonal arBTO at 950 °C yielded single crystals of annealed BTO (denoted as anBTO), whose dielectric constants were higher than those of arBTO. However, the single crystalline anBTO prevented the formation of 90° domains; therefore, they exhibited a low dielectric constant of ~300. Although X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy could not identify the exact structural defects, our study revealed that surface and bulk defects formed during synthesis affect the final crystal structures and thus the dielectric properties of BTO nanocrystals with different sizes. Finally, the understanding obtained from this study will help us design high dielectric constant perovskite nanocrystals for next-generation multilayer ceramic capacitor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Anomalous excitonic phase diagram in band-gap-tuned Ta2Ni(Se,S)5

Abstract During a band-gap-tuned semimetal-to-semiconductor transition, Coulomb attraction between electrons and holes can cause spontaneously formed excitons near the zero-band-gap point, or the Lifshitz transition point. This has become an important route to realize bulk excitonic insulators – an insulating ground state distinct from single-particle band insulators. How this route manifests from weak to strong coupling is not clear. In this work, using angle-resolved photoemission spectroscopy (ARPES) and high-resolution synchrotron x-ray diffraction (XRD), we investigate the broken symmetry state across the semimetal-to-semiconductor transition in a leading bulk excitonic insulator candidate system Ta 2 Ni(Se,S) 5 . A broken symmetry phase is found to be continuously suppressed from the semimetal side to the semiconductor side, contradicting the anticipated maximal excitonic instability around the Lifshitz transition. Bolstered by first-principles and model calculations, we find strong interband electron-phonon coupling to play a crucial role in the enhanced symmetry breaking on the semimetal side of the phase diagram. Our results not only provide insight into the longstanding debate of the nature of intertwined orders in Ta 2 NiSe 5 , but also establish a basis for exploring band-gap-tuned structural and electronic instabilities in strongly coupled systems.

36 MATERIALS SCIENCE↗
NASA NTRS2018

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48 cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

Raman Scattering↗
DOE OSTI2026

Probing Cellular Activity Via Charge‐Sensitive Quantum Nanoprobes

Nitrogen‐vacancy (NV) based quantum sensors hold great potential for real‐time single‐cell sensing with far‐reaching applications in fundamental biology and medical diagnostics. Although highly sensitive, the mapping of quantum measurements onto cellular physiological states has remained an exceptional challenge. Here, we introduce a novel quantum sensing modality capable of detecting changes in cellular activity. Our approach is based on the detection of environment‐induced charge depletion within an individual particle that, owing to a previously unaccounted transverse dipole term, induces systematic shifts in the zero‐field splitting (ZFS). Importantly, these charge‐induced shifts serve as a reliable indicator for lipopolysaccharide (LPS)‐mediated inflammatory response in macrophages. Furthermore, we demonstrate that surface modification of our diamond nanoprobes effectively suppresses these environment‐induced ZFS shifts, providing an important tool for differentiating electrostatic shifts caused by the environment from other unrelated effects, such as temperature variations. Notably, this surface modification also leads to significant reductions in particle‐induced toxicity and inflammation. Our findings shed light on systematic drifts and sensitivity limits of NV spectroscopy in a biological environment with ramifications for the critical discussion surrounding single‐cell thermogenesis. Notably, this work establishes the foundation for a novel sensing modality capable of probing complex cellular processes through straightforward physical measurements.

band bending↗
NASA NTRS2018

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

Wernet, Mark P.↗
NASA NTRS2018

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

Turbulence Modeling↗
DOE OSTI2022

Spectroscopy signatures of electron correlations in a trilayer graphene/hBN moiré superlattice

ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. Here, we report spectroscopy measurements of dual-gated TLG/hBN using Fourier transform infrared photocurrent spectroscopy. We observed a strong optical transition between moiré minibands that narrows continuously as a bandgap is opened by gating, indicating a reduction of the single-particle bandwidth. At half-filling of the valence flat band, a broad absorption peak emerges at ~18 milli–electron volts, indicating direct optical excitation across an emerging Mott gap. Similar photocurrent spectra are observed in two other correlated insulating states at quarter- and half-filling of the first conduction band. Our findings provide key parameters of the Hubbard model for the understanding of electron correlation in TLG/hBN.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Energetics of Ag Adsorption on and Adhesion to Rutile TiO 2 (100) Studied by Microcalorimetry

The adsorption and adhesion energies of vapor-deposited Ag on rutile TiO 2 (100) films have been measured using single crystal adsorption calorimetry (SCAC) and He + low energy ion scattering spectroscopy (LEIS). Ag grows as three-dimensional (3D) nanoparticles at 300 and 100 K. The saturation particle density is 8 × 10 16 particles/m 2 at 300 K and 2.5 × 10 17 particles/m 2 at 100 K. The differential heat of adsorption starts low, increases with Ag coverage, and finally approaches the sublimation enthalpy of Ag at both 300 and 100 K. At 300 K, the differential heat of adsorption starts from 208 kJ/mol and rises rapidly to 265 kJ/mol by 1 ML. At 100 K, Ag grows nanoparticles with smaller particle size on the terraces, while at 300 K, the Ag nanoparticles have bigger particle size and grow on step edges with stronger binding strength to the nanoparticles. Thus, the heat of Ag adsorption at 100 K starts at 141 kJ/mol (near the monomer size limit on terrace sites) and remains lower than that at 300 K until 1.5 ML. Here, the adhesion energy of Ag(solid) to rutile TiO 2 (100) is found to be large (~2.44 J/m 2 ), supporting a trend of decreasing adhesion energy with the enthalpy of oxide reduction.

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

Total absorption spectroscopy measurement on neutron-rich 74,75 Cu isotopes

This paper reports on the first β-decay study of 74,75 Cu isotopes using the technique of total absorption spectroscopy (TAS). The experiment was performed at the National Superconducting Cyclotron Laboratory at Michigan State University using the Summing NaI(Tl) (SuN) detector. The Cu isotopes are good candidates to probe the single-particle structure in the region because they have one proton outside the Z = 28 shell. Comparing the β-decay intensity distributions in the daughter Zn isotopes to the theoretical predictions provides a stringent test of the calculations. The nuclei in this region are also identified as playing an important role in the astrophysical r-process. Furthermore, the measured β-decay intensity distributions provide essential nuclear physics inputs required to better understand heavy element nucleosynthesis.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Iridium-Doped Nanosized Zn–Al Layered Double Hydroxides as Efficient Water Oxidation Catalysts

Layered double hydroxides (LDHs) are an ideal platform to host catalytic metal centers for water oxidation (WO) owing to the high accessibility of water to the interlayer region, which makes all centers potentially reachable and activated. In this paper, we report the syntheses of three iridium-doped zinc–aluminum LDHs (Ir-LDHs) nanomaterials (1–3, with about 80 nm of planar size and a thickness of 8 nm as derived by field emission scanning electron microscopy and powder X-ray diffraction studies, respectively), carried out in the confined aqueous environment of reverse micelles, through a very simple and versatile procedure. These materials exhibit excellent catalytic performances in WO driven by NaIO 4 at neutral pH and 25 °C, with an iridium content as low as 0.5 mol % (~0.8 wt %), leading to quantitative oxygen yields (based on utilized NaIO 4 , turnover number up to ~10,000). Nanomaterials 1–3 display the highest ever reported turnover frequency values (up to 402 min –1 ) for any heterogeneous and heterogenized catalyst, comparable only to those of the most efficient molecular iridium catalysts, tested under similar reaction conditions. The boost in activity can be traced to the increased surface area and pore volume (>5 times and 1 order of magnitude, respectively, higher than those of micrometric materials of size 0.3–1 μm) estimated for the nanosized particles, which guarantee higher noble metal accessibility. X-ray absorption spectroscopy (XAS) studies suggest that 1–3 nanomaterials, as-prepared and after catalysis, contain a mixture of isolated, single octahedral Ir(III) sites, with no evidence of Ir–Ir scattering from second-nearest neighbors, excluding the presence of IrO 2 nanoparticles. The combination of the results obtained from XAS, elemental analysis, and ionic chromatography strongly suggests that iridium is embedded in the brucite-like structure of LDHs, having four hydroxyls and two chlorides as first neighbors. These results demonstrate that nanometric LDHs can be successfully exploited to engineer efficient WOCs, minimizing the amount of iridium used, consistent with the principle of the noble-metal atom economy.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Impact of pellet preparation on reflectance measurements of ammonium sulfate by single-angle reflectance spectroscopy

The optical constants, n and k, are required to model the reflection, refraction and transmission of light at the first surface interface of a material, as well as its propagation through the material; here n corresponds to the real component and k the imaginary component of the refractive index. Several different spectroscopic methods have been used to determine the n and k values for different materials, including single angle reflectance spectroscopy and ellipsometry. The single-angle reflectance method quantitatively records the specular reflectance R(v) from a plane parallel face of the material and uses the Kramers-Kronig transform to extract the n and k values. For most compounds, however, it is difficult to obtain a single crystal or high-quality window of sufficient planarity and of the appropriate dimensions (several mm) to make the measurement. For this reason, we further investigate the use of pressed pellets of neat powdered substances to measure optical constants of these substances using the single-angle reflectance method. We have found that surface roughness can significantly influence the measured quantitative reflectance spectrum R(v) and, consequently, the derived n and k parameters. A collaborative study between Defence Research and Development Canada (DRDC) - Valcartier Research Center and Pacific Northwest National Laboratory (PNNL) has been carried out using different pellets of neat ammonium sulfate [(NH4)2SO4] to show how parameters such as the relative fraction of particle sizes for the component powder along with the grinding process of the pure compound all can affect the reflectance spectrum used to derive the optical constants. All pressed pellets were characterized by single-angle reflectance spectroscopy.

Diaz, Emmanuela↗
DOE OSTI2024

Energetics of Cu Adsorption on and Adhesion to Rutile-TiO 2 (100) Studied by Cu Vapor Adsorption Calorimetry

The heat of adsorption of Cu vapor versus coverage was measured on rutile-TiO 2 (100) at 300 and 100 K using single-crystal adsorption calorimetry. At these conditions, Cu nanoparticles nucleate and then grow larger. The average Cu particle size versus Cu coverage was measured using He + low-energy ion scattering spectroscopy. These data were analyzed with the recently introduced spherical cap model (SCM) to provide the heat of Cu adsorption and Cu chemical potential versus Cu particle size, as well as the contact angle (67°) and adhesion energy (2.50 J/m 2 ) at the Cu particle/rutile-TiO 2 (100) interface. The hemispherical cap model (HCM) was used to model the data first, and then those HCM results were converted to the more accurate SCM results using a recently published mathematical approximation whose high accuracy was validated here. Furthermore, the adhesion energy of Cu on rutile-TiO 2 (100) measured here is compared to prior values for Ag and Au on rutile-TiO 2 (100), showing a nearly proportional increase in adhesion energy with metal oxophilicity (per unit area).

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

Multiscale and multidimensional modeling of particle acceleration and transport in solar flares

Multi-messenger, multi-viewpoint, and time-resolved observations of solar flares are now providing unprecedented constraints on particle acceleration sites, energy conversion, and energy transport. The interpretation of current observations, including microwave imaging spectroscopy from EOVSA, hard x-ray (HXR) imaging from Solar Orbiter/STIX, gamma-ray diagnostics from Fermi, and in situ measurements from Parker Solar Probe and Solar Orbiter, collectively demands modeling frameworks that go beyond traditional spatially unresolved, one-zone models or single-mechanism descriptions. This review surveys multiscale and multidimensional modeling approaches, including kinetic, magnetohydrodynamic (MHD), and macroscopic particle models, that are being developed to meet the need. Kinetic simulations reveal that three-dimensional (3D) effects, including field-line chaos and self-generated turbulence, are essential for sustained power-law particle acceleration. MHD simulations now capture flux-rope eruptions, plasmoid-unstable current sheets, and turbulent flare regions in realistic magnetic topologies. Macroscopic models coupling MHD with energetic-particle models produce spatially resolved electron distributions and synthetic HXR and microwave emissions for direct comparison with observations. Despite these advances, outstanding challenges remain in bridging kinetic and global scales, improving MHD simulations and macroscopic particle models, and achieving quantitative model-observation closure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Precision spectroscopy of nuclear decays using quantum optomechanical sensors

This project developed and demonstrated a fundamentally new way to detect individual nuclear decays: rather than capturing the energy that decay products deposit in a detector, we measure the tiny mechanical recoil of the entire micron- or nanometer-sized particle in which the decaying nucleus is embedded. Because momentum is conserved, this approach is sensitive even to neutral, weakly interacting particles, including neutrinos, that escape conventional detectors. During the award, the Yale group reported the first-ever mechanical detection of single nuclear decays, a result featured widely in the scientific press, and pushed the sensitivity of smaller levitated nanoparticles into the quantum measurement regime, reaching an impulse resolution within a factor of five of the fundamental Standard Quantum Limit (SQL), good enough in principle to detect the momentum kicked to the particle by a single emitted neutrino. In parallel, the LBNL group developed the theory of quantum-enhanced (sub-SQL) readout tailored to this experiment, showing how squeezed light can push the sensitivity below the SQL. Together these results establish levitated optomechanical sensors as a new tool for precision nuclear decay spectroscopy, with further applications in neutrino physics, quantum metrology, and nuclear forensics and safeguards.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1986

Meteoritic ablation and fusion spherules in Antarctic ice

In the course of two Antarctic expeditions in 1980/1981 and 1982/1983 approximately 4 metric tons of documented ice samples were collected from the Atka Bay Ice Shelf, Antarctica, and subsequently shipped for cosmic dust studies. After filtration of the melt water, approximately 700 Antarctic spherules (AAS) in the size range of 5 to 500 microns were handpicked from the filter residue under optical microscopes. For the chemical investigation of single dust grains the following techniques were applied: scanning electron microscopy (SEM), X-ray analysis (EDAX), instrumental neutron activation analysis (INAA), laser microprobe mass analysis (LAMMA), and accelerator mass spectroscopy (AMS). For more than 95% of the total mass the bulk and trace elements were determined in single grain analyses using EDAX, INAA, and LAMMA. The element pattern of the dust particles was compared with that of typical terrestrial material and meteoritic matter. The majority of the spherules exhibited elemental compositions compatible with meteoritic element patterns.

Thiel, K.↗