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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Crossover from hydrogen to chemical bonding

Hydrogen bonds (H-bonds) can be interpreted as a classical electrostatic interaction or as a covalent chemical bond if the interaction is strong enough. As a result, short strong H-bonds exist at an intersection between qualitatively different bonding descriptions, with few experimental methods to understand this dichotomy. The [F-H-F] − ion represents a bare short H-bond, whose distinctive vibrational potential in water is revealed with femtosecond two-dimensional infrared spectroscopy. It shows the superharmonic behavior of the proton motion, which is strongly coupled to the donor-acceptor stretching and disappears on H-bond bending. In combination with high-level quantum-chemical calculations, we demonstrate a distinct crossover in spectroscopic properties from conventional to short strong H-bonds, which identify where hydrogen bonding ends and chemical bonding begins.

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

Yb:Lu 2 O 3 single-crystal fiber: spectroscopy, amplification, and lasing

For the first time, to our knowledge, a lutetium oxide (Lu 2 O 3 ) single-crystal fiber (SCF) laser is demonstrated. The laser heated pedestal growth (LHPG) technique was used to pull Yb-doped Lu 2 O 3 SCFs between 10 and 50 mm long and with diameters between 150 and 225 μm. Spectroscopic properties are first reported in detail, as the two-site nature of the host demands careful attention. Short 10 mm long, unclad fibers were used as amplifier media in a single pass copropagating configuration. Then, a 50 mm long 0.1%Yb:Lu 2 O 3 SCF with a 180 μm diameter was configured to lase by butt-coupling mirrors on the ends and pumping at 976 nm. Lasing occurred at the 1033 nm peak of Yb, and a maximum output of around 300 mW is reported. Finally, the results indicate there is no, at least obvious, fundamental reason that should deter future interest in Lu 2 O 3 as a SCF platform, which has been considered to have high potential for power scaling based on its beneficial intrinsic properties.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Quantum Chemical Treatment of Strongly Correlated Magnetic Systems Based on Heavy Elements. Final Report

The objective of this project over the years has been to develop novel quantum chemical methods and employ them to study the chemistry of systems containing actinides, and transactinides. We have focused on their electronic and spectroscopic properties, their reactivity and utilization as single molecule magnets. We have developed wave-function based methods that are optimal to treat strongly correlated systems, namely systems with many electronic configurations that are all important and should be treated on an equal foot. Moreover, relativistic effects have to be included in the model, with special focus on spin-orbit coupling. We have derived our theories and developed our codes and made them available to the community as parts of open source packages. We have modelled systems in collaboration with experimentalists in the program, so that we could address some of the questions that are relevant to this community. We have also worked in collaboration with people at Lawrence Livermore National Laboratories on a project on super-heavy atoms. We hope that our theoretical predictions will inspire novel experiments. We have trained about 10 students/postdocs during this period, which are now faculty, researchers at national laboratories and in companies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Precision Synthesis of Conjugated Polymer Films by Surface-Confined Stepwise Sonogashira Cross-Coupling

Thin films of poly(arylene ethynylene)-conjugated polymers, including low-energy-gap donor–acceptor polymers, can be prepared via stepwise polymerization utilizing surface-confined Sonogashira cross-coupling. This robust and efficient polymerization protocol yields conjugated polymers with a precise molecular structure and with nanometer-level control of the organization and the uniform alignment of the macromolecular chains in the densely packed film. In addition to high stability and predictable and well-defined molecular organization and morphology, the surface-confined conjugated polymer chains experience significant interchain electronic interactions, resulting in dominating intermolecular π-electron delocalization which is primarily responsible for the electronic and spectroscopic properties of polymer films. The fluorescent films demonstrate remarkable performance in chemosensing applications, showing a turn-off fluorescent response on the sub-ppt (part per trillion) level of nitroaromatic explosives in water. This unique sensitivity is likely related to the enhanced exciton mobility in the uniformly aligned and structurally monodisperse polymer films.

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

Two Young Planetary Systems around Field Stars with Ages between 20 and 320 Myr from TESS

Planets around young stars trace the early evolution of planetary systems. We report the discovery and validation of two planetary systems with ages ≲300 Myr from observations by the Transiting Exoplanet Survey Satellite (TESS). The 40--320 Myr old G star TOI-251 hosts a 2.74{sub −0.18}{sup +0.18} R{sub ⊕} mini-Neptune with a 4.94 day period. The 20--160 Myr old K star TOI-942 hosts a system of inflated Neptune-sized planets, with TOI-942b orbiting in a period of 4.32 days with a radius of 4.81{sub −0.20}{sup +0.20} R{sub ⊕} and TOI-942c orbiting in a period of 10.16 days with a radius of 5.79{sub −0.18}{sup +0.19} R{sub ⊕}. Though we cannot place either host star into a known stellar association or cluster, we can estimate their ages via their photometric and spectroscopic properties. Both stars exhibit significant photometric variability due to spot modulation, with measured rotation periods of ∼3.5 days. These stars also exhibit significant chromospheric activity, with age estimates from the chromospheric calcium emission lines and X-ray fluxes matching that estimated from gyrochronology. Both stars also exhibit significant lithium absorption, similar in equivalent width to well-characterized young cluster members. TESS has the potential to deliver a population of young planet-bearing field stars, contributing significantly to tracing the properties of planets as a function of their age.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Hot Stars with Kepler Planets Have High Obliquities

It has been known for a decade that hot stars with hot Jupiters tend to have high obliquities. Less is known about the degree of spin–orbit alignment for hot stars with other kinds of planets. Here, we reassess the obliquities of hot Kepler stars with transiting planets smaller than Neptune, based on spectroscopic measurements of their projected rotation velocities (vsin i). The basis of the method is that a lower obliquity—all other things being equal—causes sin i to be closer to unity and increases the value of vsin i. We sought evidence for this effect using a sample of 150 Kepler stars with effective temperatures between 5950 and 6550 K and a control sample of 101 stars with matching spectroscopic properties and random orientations. The planet hosts have systematically higher values of vsin i than the control stars, but not by enough to be compatible with perfect spin–orbit alignment. The mean value of sin i is 0.856 ± 0.036, which is 4σ away from unity (perfect alignment), and 2σ away from π/4 (random orientations). There is also evidence that the hottest stars have a broader obliquity distribution: when modeled separately, the stars cooler than 6250 K have 〈sin i〉=0.928±0.042 while the hotter stars are consistent with random orientations. This is similar to the pattern previously noted for stars with hot Jupiters. Based on these results, obliquity excitation for early-G and late-F stars appears to be a general outcome of star and planet formation, rather than being exclusively linked to hot Jupiter formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Search for Magnetic Accretion in SW Sextantis Systems

SW Sextantis systems are nova-like cataclysmic variables that have unusual spectroscopic properties, which are thought to be caused by an accretion geometry having part of the mass flux trajectory out of the orbital plane. Accretion onto a magnetic white dwarf is one of the proposed scenarios for these systems. To verify this possibility, we analyzed photometric and polarimetric time-series data for a sample of six SW Sex stars. We report possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with periods of 11.1, 41.2, and 25.7 minutes, respectively, and less significant periodicities for V380 Oph at 22 minutes and V442 Oph at 19.4 minutes. We confirm previous results that LS Peg shows variable circular polarization. However, we determine a period of 18.8 minutes, which is different from the earlier reported value. We interpret these periods as the spin periods of the white dwarfs. Our polarimetric results indicate that 15% of the SW Sex systems have direct evidence of magnetic accretion. We also discuss SW Sex objects within the perspective of being magnetic systems, considering the latest findings about the demography, formation, and evolution of cataclysmic variables.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

SDSS-IV MaNGA: pyPipe3D Analysis Release for 10,000 Galaxies

We present here the analysis performed using the pyPipe3D pipeline for the final MaNGA data set included in the Sloan Digital Sky Survey data release 17. This data set comprises more than 10,000 individual data cubes, being the integral field spectroscopic (IFS) galaxy survey with the largest number of galaxies. pyPipe3D processes the IFS data cubes to extract spatially resolved spectroscopic properties of both the stellar population and the ionized gas emission lines. A brief summary of the properties of the sample and the characteristics of the analyzed data are included. The article provides details of: (i) the analysis performed; (ii) a description of the pipeline; (iii) the adopted stellar population library; (iv) the morphological and photometric analysis; (v) the adopted data model for the spatially resolved properties derived; and (vi) the individual integrated and characteristic galaxy properties included in the final catalog. Comparisons with the results from a previous version of the pipeline for earlier data releases and from other tools using this data set are included. A practical example of how to use the full data set and the final catalog illustrates how to handle the delivered product. Our full analysis can be accessed and downloaded from our web page.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1971

Observations of O and Of stars.

Evaluation of spectrograms with a dispersion of 16.2 A/mm covering the spectral range from 3300 to 4900 A obtained for three early O stars and three early Of stars. Detailed line profiles of selected hydrogen and helium lines were obtained, and equivalent widths of nearly all visible lines were measured. Comparison of the spectroscopic properties between Of stars and O stars suggests that Of stars have lower surface gravities than do O stars. Comparison of their photometric properties confirms this suggestion. Hence present temperature scales for O5-O8 stars should not be applied to Of stars until the effect of gravity in determining spectral type has been determined. In addition, the spectra suggest that atmospheric models of Of stars should take into account spherical and hydrodynamic effects.

Heap, S. R.↗
NASA NTRS1976

Holographic Recording Materials Development

Organic photorefractive materials were evaluated for application in a reversible holographic memory system. Representative indigo and thioindigo derivatives and several stilbene derivatives were studied as well as 15, 16-dialkyldihydropyrene derivatives the following goals were achieved: (1) the successful writing of phase holograms in a thioindigo/polymer gel system, (2) the successful writing and erasing of phase holograms in a variety of indigo/polymer gel and indigo/solid polymer systems, and (3) the identification of indigoid dyes and 15, 16-dialkyldihydropyrene derivatives as materials potentially suitable for utilization in an operational system. Photochemical studies of the stilbene, indigo, thioindigo, and dialkyldihydropyrene derivatives in solution and in a variety of polymer matrix materials were conducted with the goal of optimizing the photorefractive behavior of the chemical system as a whole. The spectroscopic properties required of optimal photorefractive materials were identified, and it was shown that both the indigoid dyes and the dialkyldihydropyrenes closely match the required properties.

Verber, C. M.↗
NASA NTRS1979

Correlated ground based observations in support of the HEAO-1 X-ray observatory

Using X-ray and optical photometry of UBVRI fluxes, energetic compact extragalactic sources were studied, such as BL Lacerta (Lac) and BL Lac objects-Markarian (Mrk) 421, Mrk 501, and B2 1308+32. BL Lac and BL Lac objects were found to have predominantly nonthermal spectrums. Photometric and spectroscopic properties of X Persei, an unusual Be star associated with an intrinsically weak X-ray source, were also studied. Both its X-ray and optical emission show complex variability on many different time scales.

Mufson, S.↗
NASA NTRS1979

A spectroscopic study of the optical counterparts of three X-ray bursters

One of the major puzzles in galactic X-ray astronomy is the nature of the galactic bulge sources in general and the X-ray burst sources in particular. The answer to this puzzle is likely to come from studies of the faint blue optical counterparts which have been identified with several of these sources. As part of such a study, some results of a detailed investigation of the spectroscopic properties of the optical counterparts to three X-ray bursters - 4U 1735-44, 4U 1636-53, and MXB 1659-29.

Canizares, C. R.↗
NASA NTRS1980

Surface texture of Vesta from optical polarimetry

Polarimetric, photometric, and reflective spectroscopic properties of asteroid 4 Vesta are simulated in the laboratory by a preparation of eucrite Bereba consisting of a broad mixture of particle sizes (mainly greater than 50-micron) mixed and partially coated with particles of size 10 microns and less. Coarse grains are necessary for producing the same albedo and a very fine dust coating is necessary for producing the same polarization inversion angle as observed for Vesta. There are less small grains and fine dust in this sample than in lunar soils. Photometrically, if coating a sphere, this sample shows a constant brightness on the sunward half of the observed hemisphere, the brightness being given on the other half by the Minnaert reciprocity principle. With such a photometric behavior, the global geometric albedo and the sub-earth point geometric albedo differ by no more than 5%. The microscopic phase coefficient is 0.021 magnitude per degree for the sample; the larger value, 0.025, observed telescopically for Vesta, indicates that large-scale roughness is present on this asteroid.

Le Bertre, T.↗
NASA NTRS1980

X-ray spectra of galactic X-ray sources

The spectroscopic properties of the various classes of Galactic X-ray sources are discussed, with particular emphasis on binary sources containing an accreting compact object, where post-emission scattering in an accretion disk often prevents the initially produced X-radiation from being observed directly. Theoretical interpretations and X-ray observations are considered for the cataclysmic variables, binary systems with a white dwarf as the compact object and which suffer relatively less from Thomson scattering, and the similar phenomenological spectral characteristics of the bulge sources, including soft transients, bursters and steady X-ray sources with thermal spectra, thought to represent an accreting neutron star, are pointed out. The spectral characteristics of X-ray pulsars in accreting binary systems (rather than the Crab pulsar, which is losing rotational kinetic energy with time) are then presented and interpreted in terms of accretion in the polar regions, and mechanisms for the newly discovered X-ray emission from late-type RS CVn stars are considered.

Holt, S. S.↗
NASA NTRS1981

The interhalogens IF and ICI as visible oscillators or amplifiers

The kinetic and spectroscopic properties of the interhalogens are reviewed, with emphasis on the iodine-monochloride (ICl) and iodine-monofluoride (IF) systems; the latter having produced 140 kW, 30 nsec FWHM pulses at 491 and 485 nm and may be scaled to the tens of millijoules per pulse level. Gain in excess of 1.0%/cm was observed across the entire IF blue-green band, demonstrating potentially wide tunability. Although ICl has not yet lased, its peak small-signal gain of 1.3%/cm and negligible background absorption in discharge plasmas make it an attractive candidate for a violet amplifier. The formation kinetics of IF- and ICl-excimer lasers in electron beam or discharge-produced plasmas, and the potential and limitations of these molecules as visible lasers or amplifiers are also discussed.

Eden, J. G.↗
NASA NTRS1981

Comet nucleus - Some characteristics and a hypothesis on origin and structure

The spectroscopic properties of comets are discussed, and consideration is given to the problems of the cosmic ray irradiation and the origin and structure of cometary nuclei. The classification of cometary spectra as continuum dominant, molecular emissions dominant and CO(+) dominant is examined, and changes in spectral characteristics with heliocentric distance although not with cometary age are pointed out. Spectral evidence for a variety of organic compounds in the cometary nucleus is noted, and a scenario is presented whereby these complex molecules may form as a result of cosmic ray irradiation of cometary ices in the Oort cloud. Finally, a model is proposed for the accumulation of small icy grains to form a cometary nucleus composed of cometesimals of size distribution following a -5th power dependence on mass.

Donn, B.↗