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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Far-infrared emission line spectroscopy of planetary nebulae from the KAO

The main focus of the overall project was to study the properties of planetary nebulae using far-infrared emission lines. The observations were conducted with the 'cooled grating spectrometer' or CGS, a moderate-resolution echelle spectrometer designed and built at the Ames Research Center. During the first few years of the program, the emphasis was on emission lines of doubly-ionized oxygen and nitrogen ((O III) 52 and 88 microns, (N III) 57 microns), which arise in the ionized regions of the nebulae. Starting around 1989, our emphasis shifted to observing fine-structure lines of neutral oxygen and singly-ionized carbon ((O I) 63 and 145 microns, (C II) 157 microns), which arise from predominantly neutral material outside the ionized regions. This program was typically assigned one or two observing flights per year. Because these studies required obtaining a substantial sample of objects in order to reach meaningful conclusions, publication of comprehensive papers summarizing all of the results is still pending. However, numerous interim reports based on the airborne results as well as on closely-related supporting observations have been published during the grant period. The bibliographic information for these reports is given in the publications section. An overall summary of the planetary nebula results was presented at the Airborne Astronomy Symposium (20th Anniversary of the KAO) on 8 July 1994; reprints will be provided when available. In parallel with the planetary nebula study, we also observed the (O III) and (N III) lines in several H II regions, and attempted (unsuccessfully) to detect these lines in several old nova remnants and the supernova remnant Cassiopeia A.

Dinerstein, Harriet L.↗
NASA NTRS1983

Nitrogen-, oxygen-, and air-broadened widths and relative intensities of N2O lines near 2450 per cm

Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for /m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20 percent with the values in this listing. Previously announced in STAR as N82-30201

Hawkins, R. L.↗
NASA NTRS2011

Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

We report on airborne measurements of atmospheric pressure using a fiber-laser based lidar operating in the oxygen A-band near 765 nm and the integrated path differential absorption measurement technique. Our lidar uses fiber optic technology and non-linear optics to generate tunable laser radiation at 765 nm, which overlaps an absorption line pair in the Oxygen A-band. We use a pulsed time resolved technique, which rapidly steps the laser wavelength across the absorption line pair, a 20 cm telescope and photon counting detector to measure Oxygen concentrations.

Riris, Haris↗
NASA NTRS2004

First Observation of Jupiter by XMM-Newton

We present the first X-ray observation of Jupiter by XMM-Newton. Images taken with the EPIC cameras show prominent emission, essentially all confined to the 0.2-2.0 keV band, from the planet s auroral spots; their spectra can be modelled with a combination of unresolved emission lines of highly ionised oxygen (OW and O W) , and a pseudo-continuum which may also be due to the superposition of many weak lines. A 2.8 enhancement in the RGS spectrum at 21-22 A (-0.57 keV) is consistent with an O W identification. Our spectral analysis supports the hypothesis that Jupiter s auroral emissions originate from the capture and acceleration of solar wind ions in the planet s magnetosphere, followed by X-ray production by charge exchange. The X-ray flux of the North spot is modulated at Jupiter s rotation period. We do not detect evidence for the -45 min X-ray oscillations observed by C W r u more than two years earlier. Emission from the equatorial regions of the planet s disk is also observed. Its spectrum is consistent with that of scattered solar X-rays.

Branduardi-Raymont, G.↗
DOE OSTI2019

Chemical abundances of Seyfert 2 AGNs – I. Comparing oxygen abundances from distinct methods using SDSS

ABSTRACT We compare the oxygen abundance (O/H) of the narrow-line regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass–metallicity relation of active galactic nuclei (AGNs) at low redshifts (z ≲ 0.4). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPAC Extragalactic Database (NED) to selected optical (3000 < λ(Å) < 7000) emission line intensities of 463 confirmed Seyfert 2 AGNs. The oxygen abundances of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the Bayesian H ii-Chi-mistry code and the Te-method. We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ∼0.8 dex, with the largest discrepancies in the low-metallicity regime ($\rm 12+\log (O/H) \: \lesssim \: 8.5$). We confirmed that the Te-method underestimates the oxygen abundance in NLRs, producing unreal subsolar values. We did not find any correlation between the stellar mass of the host galaxies and the metallicity of their AGNs. This result is independent of the method used to estimate Z.

Dors, O. L.↗
DOE OSTI2020

Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G–K Dwarfs

It has been suggested that Fe abundances of K dwarfs derived from Fe i and Fe ii lines show considerable discrepancies, and oxygen abundances determined from high-excitation O i 7771–5 triplet lines are appreciably overestimated (the problem becoming more serious toward lower T {sub eff}), which, however, has not yet been widely confirmed. With the aim of clarifying this issue, we spectroscopically determined the atmospheric parameters of 148 G–K dwarfs (Hyades cluster stars and field stars) by assuming the classical Fe i/Fe ii ionization equilibrium as usual, and determined their oxygen abundances by applying the non-local thermal equilibrium spectrum fitting analysis to O i 7771–5 lines. It turned out that the resulting parameters did not show any significant inconsistency with those determined by other methods (for example, the mean differences in T {sub eff} and logg from the well-determined solutions of Hyades dwarfs are mostly ≲100 K and ≲0.1 dex). Likewise, the oxygen abundances of Hyades stars are around [O/H] ∼ +0.2 dex (consistent with the metallicity of this cluster) without exhibiting any systematic T {sub eff}-dependence. Accordingly, we conclude that parameters can be spectroscopically evaluated to a sufficient precision in the conventional manner (based on the Saha–Boltzmann equation for Fe i/Fe ii) and oxygen abundances can be reliably determined from the O i 7771–5 triplet for K dwarfs as far as stars of T {sub eff} ≳ 4500 K are concerned. We suspect that previously reported strongly T {sub eff}-dependent discrepancies may have stemmed mainly from overestimation of weak-line strengths and/or improper T {sub eff} scale.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2015

Laser Amplifier Development for the Remote Sensing of CO2 from Space

Accurate global measurements of tropospheric CO2 mixing ratios are needed to study CO2 emissions and CO2 exchange with the land and oceans. NASA Goddard Space Flight Center (GSFC) is developing a pulsed lidar approach for an integrated path differential absorption (IPDA) lidar to allow global measurements of atmospheric CO2 column densities from space. Our group has developed, and successfully flown, an airborne pulsed lidar instrument that uses two tunable pulsed laser transmitters allowing simultaneous measurement of a single CO2 absorption line in the 1570 nm band, absorption of an O2 line pair in the oxygen A-band (765 nm), range, and atmospheric backscatter profiles in the same path. Both lasers are pulsed at 10 kHz, and the two absorption line regions are sampled at typically a 300 Hz rate. A space-based version of this lidar must have a much larger lidar power-area product due to the approximately x40 longer range and faster along track velocity compared to airborne instrument. Initial link budget analysis indicated that for a 400 km orbit, a 1.5 m diameter telescope and a 10 second integration time, a approximately 2 mJ laser energy is required to attain the precision needed for each measurement. To meet this energy requirement, we have pursued parallel power scaling efforts to enable space-based lidar measurement of CO2 concentrations. These included a multiple aperture approach consists of multi-element large mode area fiber amplifiers and a single-aperture approach consists of a multi-pass Er:Yb:Phosphate glass based planar waveguide amplifier (PWA). In this paper we will present our laser amplifier design approaches and preliminary results.

Solid-State Laser Amplifier↗
NASA NTRS2016

High Energy, Narrow Linewidth 1572nm Eryb-Fiber Based MOPA for a Multi-Aperture CO2 Trace-Gas Laser Space Transmitter

Accurate global measurements of tropospheric CO2 mixing ratios are needed to study CO2 emissions and CO2 exchange with the land and oceans. NASA Goddard Space Flight Center (GSFC) is developing a pulsed lidar approach for an integrated path differential absorption (IPDA) lidar to allow global measurements of atmospheric CO2 column densities from space. Our group has developed, and successfully flown, an airborne pulsed lidar instrument that uses two tunable pulsed laser transmitters allowing simultaneous measurement of a single CO2 absorption line in the 1570 nm band, absorption of an O2 line pair in the oxygen A-band (765 nm), range, and atmospheric backscatter profiles in the same path. Both lasers are pulsed at 10 kHz, and the two absorption line regions are sampled at typically a 300 Hz rate. A space-based version of this lidar must have a much larger lidar power-area product due to the x40 longer range and faster along track velocity compared to airborne instrument. Initial link budget analysis indicated that for a 400 km orbit, a 1.5 m diameter telescope and a 10 second integration time, a 2 mJ laser energy is required to attain the precision needed for each measurement. To meet this energy requirement, we have pursued parallel power scaling efforts to enable space-based lidar measurement of CO2 concentrations. These included a multiple aperture approach consists of multi-element large mode area fiber amplifiers and a single-aperture approach consists of a multi-pass Er:Yb:Phosphate glass based planar waveguide amplifier (PWA). In this paper we will present our laser amplifier design approaches and preliminary results.

micropulse lidar↗
NASA NTRS1978

Auroral excitation of optical emissions of atomic and molecular oxygen

The O I 'green line' (1S-1D) at 5577 A and the O2 (0,0) atmosphere band at 7620 A were measured in a steady IBC II(plus) aurora simultaneously with N2 emissions and the auroral electron flux. An empirical model based on these rocket measurements shows that the principal excitation source of O2(b 1 Sigma g plus) is energy transfer from O(1D), with direct electron impact of O2 contributing less than 5 percent. While the altitude profile of the green line emission resembles that which would be produced by electron impact excitation of O2, a dissociative excitation cross section of 10 to the minus 16th power is required for this interpretation. None of the other known O(1S) excitation mechanisms are thought capable of producing the observed emission rate.

Feldman, P. D.↗
NASA NTRS1989

Flammability and sensitivity of materials in oxygen-enriched atmospheres; Proceedings of the Fourth International Symposium, Las Cruces, NM, Apr. 11-13, 1989. Volume 4

The present volume discusses the ignition of nonmetallic materials by the impact of high-pressure oxygen, the promoted combustion of nine structural metals in high-pressure gaseous oxygen, the oxygen sensitivity/compatibility ranking of several materials by different test methods, the ignition behavior of silicon greases in oxygen atmospheres, fire spread rates along cylindrical metal rods in high-pressure oxygen, and the design of an ignition-resistant, high pressure/temperature oxygen valve. Also discussed are the promoted ignition of oxygen regulators, the ignition of PTFE-lined flexible hoses by rapid pressurization with oxygen, evolving nonswelling elastomers for high-pressure oxygen environments, the evaluation of systems for oxygen service through the use of the quantitative fault-tree analysis, and oxygen-enriched fires during surgery of the head and neck.

Stoltzfus, Joel M.↗
NASA NTRS1980

X-ray line emission from the Cygnus Loop

The HEAO 1 satellite has observed the X-ray spectrum of the Cygnus Loop in the 0.1-2.0 keV band. The observed count-rate spectrum is deconvolved by the Kahn and Blissett technique to demonstrate conclusively the presence of oxygen- and iron-line emission between 0.6 and 0.9 keV. The spectrum has been fitted with single- and two-component Raymond-Smith plasma emission models. The best-fit dominant X-ray temperature is approximately 3,200,000 K, and the best-fit interstellar column density is approximately a few times 10 to the 20th/sq cm.

Kahn, S. M.↗
DOE OSTI2025

Plasma-free hydrogenation of oxygen-terminated polycrystalline diamond as determined by circular transmission line measurements (CTLM)

Here, we developed a process to fully hydrogen-terminate diamond by annealing in forming gas. The surface was characterized using circular transmission line measurements (CTLMs) to evaluate the onset and degree of hydrogen termination. No hydrogenation occurred at temperatures at or below 500 °C. Hydrogenation occurs after annealing for 5 min at temperatures between 600 and 1000 °C, with complete hydrogenation achieved at 1000 °C, which showed the same sheet resistance as diamond terminated in a hydrogen plasma. Annealing at temperatures lower than 1000 °C resulted in only partial hydrogenation but can be compensated by increasing the anneal time. At temperatures exceeding 1100 °C, the sheet resistance suddenly and drastically increases, indicating instability of a hydrogen-terminated diamond surface at elevated temperatures under forming gas. The activation energy was determined to be 1.20eV. SEM inspection showed that annealing in hydrogen produced significantly reduced surface roughness compared to diamond surfaces hydrogenated in a H 2 plasma.

36 MATERIALS SCIENCE↗
NASA NTRS1953

The Condensation Line of Air and the Heats of Vaporization of Oxygen and Nitrogen

The condensation pressure of air was determined over the range of temperature from 60 to 85 K. The experimental results were slightly higher than the calculated values based on the ideal solution law. Heat of vaporization of oxygen was determined at four temperatures ranging from about 68 to 91 K and of nitrogen similarly at four temperatures ranging from 62 to 78 K.

GASES, THERMODYNAMIC - PROPERTIES↗
NASA NTRS1996

Atomic Resonance Radiation Energetics Investigation as a Diagnostic Method for Non-Equilibrium Hypervelocity Flows

Absorption measurements with a tunable vacuum ultraviolet light source have been proposed as a concentration diagnostic for atomic oxygen, and the viability of this technique is assessed in light of recent measurements. The instrumentation, as well as initial calibration measurements, have been reported previously. We report here additional calibration measurements performed to study the resonance broadening line shape for atomic oxygen. The application of this diagnostic is evaluated by considering the range of suitable test conditions and requirements, and by identifying issues that remain to be addressed.

Meyer, Scott A.↗
NASA NTRS1993

Nonintrusive fast response oxygen monitoring system for high temperature flows

A new technique has been developed for nonintrusive in situ measurement of oxygen concentration, gas temperature, and flow velocity of the test media in hypersonic wind tunnels. It is based on absorption of near-infrared radiation from inexpensive GaAlAs laser diodes used in optoelectronics industry. It is designed for simultaneous measurements along multiple lines of sight accessed by fiber optics. Molecular oxygen concentration is measured from the magnitude of absorption signals; rotational gas temperature is measured from the intensity ratio of two oxygen absorption lines; and the flow velocity is measured from the Doppler shift of the absorption line positions. This report describes the results of an extensive series of tests of the prototype instrument in laboratory flames emphasizing assessment of the instruments capabilities for quantitative measurement of O2 concentration (mole fraction) and gas temperature.

Oh, Daniel B.↗
NASA NTRS1989

Auger electron intensity variations in oxygen-exposed large grain polycrystalline silver

Auger electron spectroscopic studies of the grains in oxygen-charged polycrystal-line silver show significant intensity variations as a function of crystallographic orientation. These intensity variations were observed by studies of the Auger images and line scans of the different grains (randomly selected) for each silver transition energy. The results can be attributed to the diffraction of the ejected Auger electrons and interpreted by corresponding changes in the electron mean-free path for inelastic scattering and by oxygen atom accumulation in the subsurface. The subsurface (second layer) octahedral sites increased in size because of surface relaxation and serve as a stable reservoir for the dissolved oxygen.

Lee, W. S.↗