Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ULTRAVIOLET SPECTRA”

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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Hydrogen peroxide on the surface of Europa

Spatially resolved infrared and ultraviolet wavelength spectra of Europa's leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide. Comparisons with laboratory measurements indicate surface hydrogen peroxide concentrations of about 0.13 percent, by number, relative to water ice. The inferred abundance is consistent with radiolytic production of hydrogen peroxide by intense energetic particle bombardment and demonstrates that Europa's surface chemistry is dominated by radiolysis.

Non-programmatic↗
DOE OSTI2021

Probing the Capability of Future Direct-imaging Missions to Spectrally Constrain the Frequency of Earth-like Planets

A critical question in astrobiology is whether exo-Earth candidates (EECs) are Earth-like, in that they originate life that progressively oxygenates their atmospheres similarly to Earth. We propose answering this question statistically by searching for O{sub 2} and O{sub 3} on EECs with missions such as HabEx or LUVOIR. We explore the ability of these missions to constrain the fraction, f {sub E}, of EECs that are Earth-like in the event of a null detection of O{sub 2} or O{sub 3} on all observed EECs. We use the Planetary Spectrum Generator to simulate observations of EECs with O{sub 2} and O{sub 3} levels based on Earth’s history. We consider four instrument designs—LUVOIR-A (15 m), LUVOIR-B (8 m), HabEx with a starshade (4 m, “HabEx/SS”), and HabEx without a starshade (4 m, “HabEx/no-SS”)—as well as three estimates of the occurrence rate of EECs (η {sub earth}): 24%, 5%, and 0.5%. In the case of a null detection, we find that for η {sub earth} = 24%, LUVOIR-A, LUVOIR-B, and HabEx/SS would constrain f {sub E} to ≤0.094, ≤0.18, and ≤0.56, respectively. This also indicates that if f {sub E} is greater than these upper limits, we are likely to detect O{sub 3} on at least one EEC. Conversely, we find that HabEx/no-SS cannot constrain f {sub E}, due to the lack of a coronagraph ultraviolet channel. For η {sub earth} = 5%, only LUVOIR-A and LUVOIR-B would be able to constrain f {sub E}, to ≤0.45 and ≤0.85, respectively. For η {sub earth} = 0.5%, none of the missions would allow us to constrain f {sub E}, due to the low number of detectable EECs. We conclude that the ability to constrain f {sub E} is more robust to uncertainties in η {sub earth} for missions with larger aperture mirrors. However, all missions are susceptible to an inconclusive null detection if η {sub earth} is sufficiently low.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Diffuse Bands 9577 and 9633: Relations to Other Interstellar Features

We study, for the first time, the relations of two strong diffuse bands (DIBs) at 9633 and 9577 Å, commonly attributed to C{sub 60}{sup +}, to other interstellar features seen in optical and UV spectra including H i, Ca i, Fe ii, Na i, Ti ii, CN, CH, CH{sup +}, and C{sub 2} and DIBs 5780, 5797, 6196, 6269, 6284, and 6614. We analyzed 62 lines of sight where the stellar contamination by Mg ii was corrected or found negligible for DIB 9633. Equivalent widths of DIB 9577 were measured in 62 lines of sight. Poor mutual correlation between the strengths of the above features and the major diffuse bands (5780 and 5797) as well as with other DIBs (with some exceptions) were revealed. The considered DIBs are also poorly correlated with the features of neutral hydrogen, molecular carbon, and those of simple interstellar radicals. Perhaps this phenomenon can be explained if the diffuse band 9577 is an unresolved blend of two or more interstellar features. There are indications that 9633 and 9577 diffuse bands are stronger in σ-type clouds, i.e., these features resemble the behavior of reasonably broad DIBs, which are strong in the lines of sight where the UV flux from the very hot nearby stars plays an important role.

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

Optical design and efficiency measurement of an extreme ultraviolet high-resolution spectrometer for unresolved transition array research

Understanding the structures of the unresolved transition array (UTA) observed in extreme ultraviolet (EUV) spectra from many-electron atoms is crucial for various applications, including fusion science and nanolithography. Here, to measure the fine structure of the UTA from tungsten and tin at around 5 and 13.5 nm at the Tokyo electron beam ion trap, we developed a high-resolution EUV spectrometer. The designed spectrometer achieves a resolving power of λ/dλ > 5000 at 5 and 13.5 nm. The fabricated large-area grating was experimentally examined at beamline BL5B of the UVSOR synchrotron facility to evaluate the diffraction efficiencies and their variation across the ruled area. The measured diffraction efficiencies are 0.65% ± 0.07% at 5 nm (second order) and 7.9% ± 0.2% at 13.5 nm (first order). The variation in the diffraction efficiency across the ruled area is 2.2%, 13.6%, and 10.0% in zeroth, first, and second order diffractions, respectively. The discrepancies in diffraction efficiencies between the experiments and the calculations were 5.2%, 29%, and 35% for the zeroth, first, and second diffraction orders, respectively.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Analysis of Coronado State Historic Site artifacts using X‐rays

Abstract Two historic‐period metal artifacts were provided by the New Mexico Historic Sites to Los Alamos National Laboratory for non‐destructive analysis. The artifacts were a crossbow quarrel (or bolthead) and a reliquary pendant recovered from Kuaua Pueblo (also known as the Coronado Historic Site) in Bernalillo, NM. The quarrel is a heavily patinated metal that had been flattened due to compressive forces. The pendant consisted of a metal casing that had previously surrounded two center gemstones on the front and rear face of the pendant. The gemstone in the rear setting had fractured and was displaced from the setting, leaving only a small, loose fragment within the pendant for study. The front gem appeared to be very dark, near‐black in color, and the fragment of the rear gem was a bright red color. The artifacts were analyzed to ascertain their composition and glean insight into their provenance using the following X‐ray techniques: X‐ray computed tomography, confocal micro X‐ray fluorescence, and X‐ray diffraction. Infrared spectroscopy and electron microscopy were used on selected areas. Ultraviolet Raman spectra were collected on the two gems and the pendant. The metal material of the artifacts was found to be primarily composed of copper. The gems in the pendant were composed of manganese (front gem) and calcium (side gem).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Cluster mediated conversion of amorphous Al(OH) 3 to γ-AlOOH

In this work, we report a synthetic pathway by which amorphous Al(OH) 3 is converted to γ-AlOOH through hydrothermal reaction in the presence of water at temperature T = 473 K. X-ray pair distribution function measurements reveal that the initially amorphous Al(OH) 3 possesses a locally γ-Al(OH) 3 -like structure, while nanocrystalline γ-AlOOH precipitates within 1 h of continuous hydrothermal exposure. Solid state nuclear magnetic resonance measurements show that resonant features associated with four- and five-member Al clusters persist through 20 min of hydrothermal treatment, and ultraviolet (UV) spectra mark the onset of UV-induced photoluminescent features characteristic to γ-AlOOH with 10 min of exposure, indicating a coexistence region of γ-Al(OH) 3 -like and γ-AlOOH-like amorphous species. Furthermore, powder x-ray diffraction measurements of desiccated powders reveal that the conversion process takes place in distinct, power law-defined stages with initial γ-AlOOH nucleation occurring within the first 20 min, followed by a ~ 1 h period of rapid grain coarsening and the subsequent onset of Lifshitz-Slyozov-Wagner-like coalescence.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Helical Organic and Inorganic Polymers

Despite being a staple of synthetic plastics and biomolecules, helical polymers are scarcely studied with Gaussian-basis-set ab initio electron-correlated methods on an equal footing with molecules. This article introduces an ab initio second-order many-body Green’s-function [MBGF(2)] method with nondiagonal, frequency-dependent Dyson self-energy for infinite helical polymers using screw-axis-symmetry-adapted Gaussian-spherical-harmonics basis functions. Together with the Gaussian-basis-set density-functional theory for energies, analytical atomic forces, translational-period force, and helical-angle force, it can compute correlated energy, quasiparticle energy bands, structures, and vibrational frequencies of an infinite helical polymer, which smoothly converge at the corresponding oligomer results. These methods can handle incommensurable structures, which have an infinite translational period and are hard to characterize by any other method, just as efficiently as commensurable structures. We apply them to polyethylene (2/1 helix), polyacetylene (Peierls’ system), and polytetrafluoroethylene (13/6 helix) to establish the quantitative accuracy of MBGF(2)/cc-pVDZ in simulating their (angle-resolved) ultraviolet photoelectron spectra, and of B3LYP/cc-pVDZ or 6-31G** in reproducing their structures, infrared and Raman band positions, phonon dispersions, and (coherent and incoherent) inelastic neutron scattering spectra. We then predict the same properties for infinitely catenated chains of nitrogen or oxygen and discuss their possible metastable existence under ambient conditions. They include planar zigzag polyazene (N2)x (Peierls’ system), 11/3-helical isotactic polyazane (NH)x, 9/4-helical isotactic polyfluoroazane (NF)x, and 7/2-helical polyoxane (O)x as potential high-energy-density materials.

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

No redshift evolution in the rest-frame ultraviolet emission line properties of quasars from z = 1.5 to z = 4.0

We analyse the rest-frame ultraviolet (UV) spectra of 2531 high-redshift (3.5 < z < 4.0) quasars from the Sloan Digital Sky Survey DR16Q catalogue. In combination with previous work, we study the redshift evolution of the rest-frame UV line properties across the entire redshift range, 1.5 < z < 4.0. We improve the systemic redshift estimates at z > 3.5 using a cross-correlation algorithm that employs high signal-to-noise template spectra spanning the full range in UV emission line properties. We then quantify the evolution of C iv and He ii emission line properties with redshift. The increase in C iv blueshifts with cosmological redshift can be fully explained by the higher luminosities of quasars observed at high redshifts. We recover broadly similar trends between the He ii equivalent width and C iv blueshift at both 1.5 < z < 2.65 and 3.5 < z < 4.0 suggesting that the blueshift depends systematically on the spectral energy density (SED) of the quasar and there is no evolution in the SED over the redshift range 1.5 < z < 4.0. C iv blueshifts are highest when L/L Edd ≥ 0.2 and M BH ≥ 10 9 M ⊙ for the entire 1.5 < z < 4.0 sample. We find that luminosity matching samples as a means to explore the evolution of their rest-frame UV emission line properties is only viable if the samples are also matched in the M BH –L/L Edd plane. Quasars at z ≥ 6 are on average less massive and have higher Eddington-scaled accretion rates than their luminosity-matched counterparts at 1.5 < z < 4.0, which could explain the observed evolution in their UV line properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Collection: TD-DFT and EOM-CCSD Calculations for the GDB-9-Ex Dataset

We present two datasets that contain quantum chemical electronic structure calculations for organic molecules from the GDB-9-Ex dataset. The “GDB-9-Ex_TD-DFT-PBE0” dataset contains calculations performed using the time-dependent density functional theory (TD-DFT) first principles method, and the “GDB-9-Ex_EOMCCSD” dataset contains calculations performed using the equation-of-motion coupled cluster (EOM-CCSD) method. Both types of calculations were performed using the ORCA software and provided ultraviolet-visible spectra with a high level of accuracy.

Mehta, Kshitij [Oak Ridge National Laboratory (ORN↗
DOE OSTI2023

Analysis of Coronado State Historic Site artifacts using X-rays

Two historic-period metal artifacts were provided by the New Mexico Historic Sites to Los Alamos National Laboratory for non-destructive analysis. The artifacts were a crossbow quarrel (or bolthead) and a reliquary pendant recovered from Kuaua Pueblo (also known as the Coronado Historic Site) in Bernalillo, NM. The quarrel is a heavily patinated metal that had been flattened due to compressive forces. The pendant consisted of a metal casing that had previously surrounded two center gemstones on the front and rear face of the pendant. The gemstone in the rear setting had fractured and was displaced from the setting, leaving only a small, loose fragment within the pendant for study. The front gem appeared to be very dark, near-black in color, and the fragment of the rear gem was a bright red color. The artifacts were analyzed to ascertain their composition and glean insight into their provenance using the following X-ray techniques: X-ray computed tomography, confocal micro X-ray fluorescence, and X-ray diffraction. Infrared spectroscopy and electron microscopy were used on selected areas. Ultraviolet Raman spectra were collected on the two gems and the pendant. The metal material of the artifacts was found to be primarily composed of copper. The gems in the pendant were composed of manganese (front gem) and calcium (side gem).

36 MATERIALS SCIENCE↗
DOE OSTI2026

The Emission and Suppression of Line Features in Luminous Transients

Featureless optical and ultraviolet (UV) spectra are a puzzling signature to emerge from recent observations of luminous fast blue optical transients (LFBOTs) and some tidal disruption events (TDEs). We describe the landscape of source and gas properties that are expected to form H, He I , and He II emission lines, and map spectral types to the parameter space of luminosity and system radius. Using one-dimensional radiative transfer calculations, we show that high source luminosities (L > 10 44 erg s −1 ) and compact ejecta radii (r < 10 14 cm) produce featureless spectra, due to the high temperature and ionization state of the emitting medium. Intermediate luminosities and moderately compact systems can generate He II -dominated spectra, while lower luminosities and more extended atmospheres result in conspicuous H and He I emission. Large expansion velocities (v ≥ 0.1c) can further broaden lines such that they blend into the continuum. Featureless UV spectra may require even more extreme ionization environments or velocities in order to suppress the many intrinsically strong metal lines at those wavelengths. Applying this framework to understand the absence of features observed in LFBOTs and featureless TDEs, we find that, under the optically thick, quasi-thermal conditions considered here, nonhomologous, compact outflows are likely necessary for featurelessness to persist in optical and UV spectra.

Aspegren, Olivia [University of California, Berkel↗
NASA NTRS1968

Mass Loss by Hot Stars

Mechanism explaining mass loss for luminous hot stars using ultraviolet line spectra of some ions

Lucy, L. B.↗
NASA NTRS1974

Balloon-borne ultraviolet stellar spectrometer: Acquisition, tracking and command systems

The NASA Balloon-borne Ultraviolet Stellar Spectrometer (BUSS) which is carried to an altitude of 40 km by a 15 million cubic foot balloon for night-time observations of ultraviolet stellar spectra is discussed. The BUSS optical system, comprising an 0.40 m aperture Cassegrain telescope and an Ebert-Fastie spectrometer, points at various selected stars and focuses a portion of their spectra on the photocathode of an image dissector tube. The spectral region between 2,775 Angstroms and 2,825 Angstroms is sampled by the detector at 0.25 Angstroms increments using photon counting techniques. The pointing system for the payload uses a pair of orthogonal magnetometers which sense the earth's magnetic field for an aximuth reference, and a platform potentiometer for an elevation reference. This pointing system places the target star within the 3x1 degree field of view of an outer optical star tracker. The outer star tracker is then used to point the entire instrument to within one arc minute of the target star.

Gibson, W. C.↗
NASA NTRS1974

Internal Ultraviolet Explorer (IUE) study program. Volume 1: Technology discussion

The results of a simulation study to predict the IUE imaging chain performance are presented, including simulation photographs and transparencies of ultraviolet echelle spectra. Errors in wavelength determination and radiometric measurements due to system degradation are indicated to be minor. Some order overlap is predicted at the bottom of the echelle format.

Turner, T. S., Jr.↗
NASA NTRS1976

Space stable thermal control coatings

The MOX method, i.e., the use of zinc and titanium oxalate precursors, has the distinct advantages of simple and rapid processing, and of controlled pigment particle size. The chemical identify of TiOX was determined. The Zn/Ti ratio effect on the reflectance spectra and ultraviolet irradiation stability in vacuum for Zn2TiO4 was examined. Optimized processing parameters are considered for reproducibly obtaining a pigment of the most desirable optical properties and behavior.

Harada, Y.↗
NASA NTRS1975

A search for molecular hydrogen fluorescence near 100 km

The fluorescence of H2 in the Lyman band system, excited by solar extreme ultraviolet radiation, provides a means for the optical detection of H2 in the upper atmosphere. In particular, the Ly beta line of hydrogen is nearly degenerate with the (6,0) P1 transition, and absorption in this line produces fluorescence in the v-prime = 6 progression, principally at 1265, 1366, 1462 and 1608 A. Absorption by O2 rapidly attenuates the Ly beta from an overhead sun below 100 km and also significantly attenuates the fluorescent radiation. Far-ultraviolet dayglow spectra from 1130 to 1510 A obtained from an Aerobee rocket experiment on 11 December 1972 give an upper limit for any H2 emission which is a factor of 5 higher than expected according to recent hydrogen models.

Feldman, P. D.↗
NASA NTRS1976

Scientific investigations on the Skylab satellite; Conference, Huntsville, Ala., October 30-November 1, 1974, Technical Papers

A Skylab overview is presented and the solar observation programs are examined, taking into account the operational aspects of Skylab, the XUV sun as observed by ATM S082, a classification of flares and flarelike events observed during the Skylab mission, a preliminary analysis of extreme ultraviolet and X-ray observations, and initial results from the EUV spectroheliometer on ATM. Attention is given to ultraviolet stellar spectra obtained with Skylab experiment S019, multicolor photometry of low-light level phenomena from Skylab, Skylab observations of comet Kohoutek, relativistic iron in space and its nuclear progeny, Skylab altimeter applications and scientific results, neutron and proton activation measurements from Skylab, Skylab D024 thermal control coatings and polymeric films experiment, the stability of liquid dispersions in low gravity, observations of the liquid/solid interface in low-gravity melting, and student experiments on Skylab. Individual items are announced in this issue and in issue 02, 1975.

Kent, M. I.↗