SEARCH · Search NASA

Results for “Atomic Resolution”

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.

SourceResearch connectionFrom yearThrough year

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

At least 271 records · Page 15

All sources NASA NTRS DOE OSTI

DOE OSTI2026

On the Prospect of Chemically Transferable Coarse-Grained Electronic Models for Soft Materials

Electronic coarse-graining (ECG) methods predict quantum-mechanical electronic properties directly from coarse-grained (CG) molecular configurations, enabling electronic predictions at mesoscale length scales. Here, we present a diagnostic assessment of the feasibility of chemically transferable ECG models across a broad polymer-relevant chemical space using all-atom, united-atom, and Martini-scale representations. While high-resolution ECG models achieve near-quantitative accuracy, we show that chemically transferable ECG at the Martini resolution fails because the CG force field does not sample the same configurational distribution of local molecular structure as that underlying the DFT-parameterized ECG model. We demonstrate that our proposed Element-Count-Label (ECL) representation, which augments Martini beads with explicit stoichiometric data, significantly improves chemical generalization across diverse polymer chemistries. However, we find that even with improved chemical resolution, the model cannot recover electronic property distributions that are absent from the configurational space sampled by the CG force field. These results demonstrate that chemically transferable ECG requires future Martini-like force fields to explicitly preserve quantum chemistry–compatible local molecular structure in addition to thermodynamic and structural fidelity.

Kidder, Katherine M [Department of Chemistry; Univ↗

NASA NTRS1987

The azimuthal and radial distributions of HI and H2 in NGC 6946

A study was completed of the atomic and molecular components of the ISM in NGC 6946. The distribution of molecular clouds was determined from a fully sampled CO map of the inner disk using the 14-meter telescope of the FCRAO. The distribution of atomic gas was derived from VLA observations at 40" resolution in the D configuration. When comparing the global CO and HI properties with other components of the galaxy, it was found that the azimuthally averaged radial distributions of CO, H-alpha, radio continuum and blue light all exhibit similar roughly exponential falloffs, while the azimuthally averaged HI surface densities vary by only a factor of 2 out to R = 16 kpc. This indicates that while the H-alpha/CO ratio is approximately constant with radius, the CO/HI ratio decreases by a factor of 30 from the center of the galaxy to R = 10 kpc.

Tacconi-Garman, Linda J.↗

NASA NTRS1989

Optical Interferometric Micrometrology

Resolutions in angstrom and subangstrom range sought for atomic-scale surface probes. Experimental optical micrometrological system built to demonstrate calibration of piezoelectric transducer to displacement sensitivity of few angstroms. Objective to develop relatively simple system producing and measuring translation, across surface of specimen, of stylus in atomic-force or scanning tunneling microscope. Laser interferometer used to calibrate piezoelectric transducer used in atomic-force microscope. Electronic portion of calibration system made of commercially available components.

Abel, Phillip B.↗

DOE OSTI2026

Controllable Formation of Threefold-Coordinated Oxygen in Graphene by Low-Energy Ion Implantation

The atomically precise engineering of impurities in graphene and the understanding of their structural and carrier-dependent electronic properties at the nanoscale are crucial for advancing graphene-based nanoelectronics, catalysis, and energy technologies. Here, we demonstrate controllable incorporation of the elusive 3-fold-coordinated O substitutions into graphene using low-energy O + ion implantation under ultrahigh-vacuum conditions. By combining high-resolution scanning tunneling microscopy and spectroscopy (STM/S), bond-resolved noncontact atomic force microscopy techniques, and density functional theory (DFT) calculations, we resolve both the structural and electronic properties of the O-related defects. The STM/S measurements, corroborated by DFT calculations, uncover a characteristic impurity state that is energetically pinned to the Dirac point across different charge-carrier doping regimes. Molecular dynamics simulations further reveal the distribution of implantation-induced configurations and identify the formation of 3-fold-coordinated O dopants. Furthermore, this work provides a viable route to incorporate 3-fold-coordinated O dopants and opens new opportunities for controlled defect engineering in graphene.

3-fold-coordinated oxygen↗

NASA NTRS1981

Solar observations and atomic data for the 3s2 1s0-3s3p 3P1 transition in S v

High resolution solar observations of the S v intersystem line at 1199.18 A are available from Skylab. This line is potentially useful as a density diagnostic for high density plasmas expected in solar flares. S v lines are also prominent in solar spectra at wavelengths below 1000 A. Collision strengths and radiative decay rates are calculated for levels of the configurations 3 s2, 3s3p, 3p2, and 3s3d. Level populations for the five lowest energy levels have been calculated as a function of electron density. These calculations are carried out assuming the temperature at which S v is most abundant in solar plasmas. The calculated population of the 3s3p 3P1 level reaches a pseudo-Boltzmann equilibrium at a density which is about five times higher than is derived from solar spectra and previous density determinations. It is believed that the discrepancy is due to a significant contribution from resonances to the 3s2-3s3p 3P excitation rate coefficient. It is suggested that the contribution of the resonances to the S v excitation rate coefficient can be estimated from a comparison of the experimental results and the theoretical calculations.

Feldman, U.↗

NASA NTRS1994

Abundances, planetary nebulae, and stellar evolution

Among Henry Norris Russell's many achievements were his contributions to solar and stellar spectroscopy, in particular, to an analysis of the chemical composition of the solar atmosphere. The question of composition differences between stars was hotly debated; some distinguished astronomers argued that all stars had the solar composition. Some early challenges to this doctrine are described. Determinations of chemical compositions of gaseous nebulae were much more difficult. If we observe the lines of a given chemical element in one ionization stage in a stellar spectrum, we can deduce readily the abundance of that element. No such luxury is available for a planetary or diffuse gaseous nebula. We must measure lines of as many ionization stages as we can. Furthermore, a nebula is an extended object. Often detailed spectroscopy is at hand only for narrow pencil columns taken through the image. Different observers use a variety of apertures. Fortunately it is possible to calculate theoretical spectra for any arbitrary cross section taken through a symmetrical model, so UV, optical, and IR observations all can be compared properly with a prediction. The value of high-resolution spectra obtained with instruments such as the Hamilton Echelle Spectrograph at Lick Observatory is emphasized. Improved fluxes for weak but important transitions are found. Close blends of lines of different ions can be resolved, and checks can be made on predictions of atomic parameters such as Einstein A-values and collision strengths. High spectral resolution data have been obtained and reduced for 22 planetary nebulae of varying size, structure, stellar population membership, dustiness, level of excitation, evolutionary status, and chemical compositions. The promise seems justified that with such extensive, high quality data, additional insights on nebular genesis and late states of stellar evolution can be found. The present survey is confined to nebulae of high surface brightness, but among these are found some engaging objects such as NGC 7027, IC 4997, and NGC 6572.

Aller, Lawrence H.↗

DOE OSTI2025

Monolayer TiS 2 Nanosheets on Au(111)–Structural Characterization and Effect of Edge Stability for Shape Control

Transition metal dichalcogenides are promising alternatives to noble metal catalysts, e.g., for (photo-)activation of greenhouse gases or hydrogenations. Herein, a direct synthetic route for 2D TiS 2 nanosheets on Au(111) by titanium deposition in the presence of a mild, organic, non-oxidizing sulfur source is presented. High-resolution scanning tunneling microscopy (STM) is used to gain atomic-level insights into the TiS 2 nanosheet morphology. In contrast to the literature, this protocol gains mostly hexagonal and truncated triangular nanosheets with an increased edge contrast in STM, analog to metallic edge states in MoS 2 . Synchrotron-based photoelectron spectroscopy allows insights into compositional details, specifically to distinguish different S sites on the TiS 2 sheets and other S species on the sample. Further, a minimum size is identified (9 S atoms side length), which underlines the importance of moiré reconstructions for stress relief. The TiS 2 sheets coexist with [Au]Ti 1 S 3 clusters, in which a single gold atom is alloyed into the surface and capped by three S atoms. Together with the finding of a critical sheet size, this points toward on-surface Ostwald ripening as a relevant process in the sheet formation. Ab-initio calculations (density functional theory) underscore that the chemical potential of S is an essential descriptor to maintain shape control.

2D nanomaterials↗

NASA NTRS1982

Formation of the O I resonance triplet and intercombination doublet in the solar chromosphere

Spectrum synthesis calculations are presented for the O I resonance triplet at 1304 A and the intercombination doublet at 1358 A for the solar atmosphere and several variants, allowing for triplet fluorescence by the Ly-beta emission of H I. Profiles, synthesized from a seven-level plus continuum O I atom are compared to observations taken with the high-resolution spectrometer on OSO 8. It is found that the O I triplet emission is dominated by the Ly-beta fluorescence and that the agreement between observations and profiles computed with current chromospheric models is much improved over earlier studies.

Skelton, D. L.↗

NASA NTRS1993

Long-slit ultraviolet spectroscopy of Comet Austin (1990 V)

The spatial distributions of the brightest features in the far-UV spectrum of Comet Austin were measured, and it is found that they are generally similar to those found for Comet Halley during two rocket observations in 1986. As in Halley, the CO profile can be fit to a radial outflow profile for a source whose size is smaller than the instrumental spatial resolution. Neither the shape nor the magnitude of the extended atomic carbon profiles, however, can be satisfactorily explained by the photodissociation of CO. No evidence is found for an extended source of CO in the coma; thus, suggestions that the additional carbon can come directly from grains are difficult to accept since Austin is a low-dust comet. The presence of the O I 1356 A feature implies that there is a photoelectron excitation source in the coma. The measured O I 1304 A distribution is consistent with H2O being the dominant source of oxygen in the coma. The atomic sulfur profile matches that expected for a daughter product of relatively short-lived parents.

Sahnow, David J.↗

NASA NTRS1995

Airborne Astronomy with a 150 microns - 400 microns Heterodyne Spectrometer

This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 micron fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6) thereby allowing accurate line shapes and Doppler velocities to be measured.

Betz, A. L.↗

NASA NTRS1995

Airborne Astronomy with a 150 micron - 400 micron Heterodyne Spectrometer

This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 microns fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6), thereby allowing accurate line shapes and Doppler velocities to be measured.

Betz, A. L.↗

NASA NTRS2002

Charge Sharing and Charge Loss in a Cadmium-Zinc-Telluride Fine-Pixel Detector Array

Because of its high atomic number, room temperature operation, low noise, and high spatial resolution a Cadmium-Zinc-Telluride (CZT) multi-pixel detector is ideal for hard x-ray astrophysical observation. As part of on-going research at MSFC (Marshall Space Flight Center) to develop multi-pixel CdZnTe detectors for this purpose, we have measured charge sharing and charge loss for a 4x4 (750micron pitch), lmm thick pixel array and modeled these results using a Monte-Carlo simulation. This model was then used to predict the amount of charge sharing for a much finer pixel array (with a 300micron pitch). Future work will enable us to compare the simulated results for the finer array to measured values.

Gaskin, J. A.↗

NASA NTRS1999

Crystallization and preliminary X-ray diffraction analysis of restriction endonuclease EcoRII

Crystals of the restriction endonuclease EcoRII have been obtained by the vapor-diffusion technique in the presence of ammonium sulfate or polyethylene glycol. The best crystals were grown with ammonium sulfate as a precipitant. Crystals with dimensions of up to 0.6 x 0. 6 x 0.6 mm have been observed. The crystals diffract to about 4.0 A resolution at a cryo-temperature of 100 K using a rotating-anode X-ray source and a Rigaku R-AXIS IV imaging-plate detector. The space group has been determined to be either I23 or I2(1)3, with unit-cell parameters a = b = c = 160.3 A, alpha = beta = gamma = 90 degrees. The crystal asymmetric unit contains two protein molecules, and self-rotation function analysis shows a pseudo-twofold symmetry relating the two monomers. Attempts to improve the resolution of crystal diffraction and to search for heavy-atom derivatives are under way.

Deoxyribonucleases, Type II Site-Specific/chemistr↗

NASA NTRS1985

Detection of atomic oxygen and further line assignments in the far-infrared stratospheric spectrum

Recent progress in high-resolution measurement of sub-millimeter and far-infrared emission in the stratosphere is reviewed. Attention is given to the results of recent balloon measurements of the minor stratospheric constituents in the spectral range 40-190 per cm. Emission spectra are presented for HCl; HF; and OH. Emission spectra were also obtained for atomic oxygen; hydrobromic acid; and hydroperoxyl radical. The possibility of detecting HO2 and H2O2 in the far-infrared is also briefly discussed.

Carli, B.↗

NASA NTRS2023

Advancing Solar and Heliospheric Science Through the Ongoing Development and Support of Atomic and Laboratory Plasma Physics

This paper outlines the necessity for the availability, accessibility, and expansion of atomic physics data and analysis tools for the meaningful interpretation of spectroscopic and polarimetric observations. As we move towards observing the Sun at higher spatio-temporal resolutions, and near-continuously at a range of wavelengths, it becomes critical to develop the appropriate atomic data and physics tools to facilitate scientific progress. We recommend the continued improvement and expansion of current databases to support the development of optically-thick/radiative transfer models, evaluate non-thermal and non-equilibrium ionization effects, and quantify uncertainties in atomic and molecular values. A critical longterm goal will require extending and strengthening collaborations across the atomic, solar/heliospheric, and laboratory plasma physics communities through the participation and training of early career scientists. We also recommend establishing funding for a centralized atomic physics resource made up of a comprehensive and user-oriented atomic database and modeling framework.

Y J Rivera↗

DOE OSTI2026

Nanometer Scale Imaging to Develop Quantitative Descriptors of Bipolar Membrane Junction Structure

Swings in pH can be achieved by electrically polarizing a bipolar membrane (BPM) to drive water dissociation at the BPM junction for electrochemical conversion and separation processes. BPM junction design is critical to tailor performance for specific applications; however, characterization techniques capable of resolving the nanometer scale physical structure of the junction are limited. We present sample preparation, imaging, and analysis workflows that are adaptable to a variety of BPM junction architectures. Atomic force microscopy produces BPM junction images with nanometer scale lateral resolution for samples with and without a graphene oxide water dissociation catalyst in the junction. Subsequent image segmentation and analysis quantify line edge roughness and catalyst layer thickness as descriptors of junction structure. Comparison of pre- and post-electrodialysis junctions suggests electric field-induced alignment of catalyst particles during electrodialysis. This characterization workflow can inform manufacturing protocols, computational modeling, and failure mode analysis for next-generation BPMs.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1980

Atomic data for S IV and solar observations of the 3x/2/3p /2/P-3s3p/2/ /4/P multiplet

High resolution observations of intersystem lines of S IV near 1400 A are available from Skylab. These lines are potentially useful as density diagnostics for the solar atmosphere. Energy levels, transition probabilities and collision strengths have, therefore, been calculated for S IV, including the configurations 3x(2)3p, 3s3p(2), and 3s(2)3d. Line intensities and level populations have been calculated as a function of electron density. The calculated population of the 3s3p(2) (4)P(5/2) level is found to reach a pseudo-Boltzmann equilibrium at a density which is four times higher than is inferred from solar spectra and level population calculations of lighter ions such as O IV.

Bhatia, A. K.↗

NASA NTRS1982

Ultraviolet absorption by highly ionized atoms in the Orion Nebula

The International Ultraviolet Explorer was used to obtain high-resolution, far-UV spectra of theta 1 A, theta 1 C, theta 1 D, and theta 2 A Orionis. The interstellar absorption lines in these spectra are discussed with an emphasis on the high-ionization lines of C IV and Si IV. Theta 2 A Ori has interstellar C IV and Si IV absorption of moderate strength at the velocity found for normal H II region ions. Theta 1 C Ori has very strong interstellar C IV and Si IV absorption at velocities blueshifted by about 25 km/s from that found for the normal H II region ions. The possible origin of the high-ionization lines by three processes is considered: X-ray ionization, collisional ionization, and UV photoionization. It is concluded that the C IV and Si IV ions toward theta 2 A and theta 1 C Ori are likely produced by UV photoionization of surrounding nebular gas. In the case of theta 1 C Ori, the velocity shift of the high-ionization lines may be produced through the acceleration of high-density globules in the core of the nebula by the stellar wind of theta 1 C Ori.

Franco, J.↗