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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system

The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

Mukherjee, S. P.↗
NASA NTRS1983

Evidence for disequilibrium of ortho and para hydrogen on Jupiter from Voyager IRIS measurements

Preliminary results of an analysis of the ortho state/para state ratio (parallel/antiparallel) for molecular H2 in the Jovian atmosphere using Voyager IR spectrometer (IRIS) data are reported. The study was undertaken to expand the understanding of the thermodynamics of a predominantly H2 atmosphere, which takes about 100 million sec to reach equilibrium. IRIS data provided 4.3/cm resolution in the 300-700/cm spectral range dominated by H2 lines. Approximately 600 spectra were examined to detect any disequilibrium between the hydrogen species. The results indicate that the ortho-para ratio is not in an equilibrium state in the upper Jovian troposphere. A thorough mapping of the para-state molecules in the upper atmosphere could therefore aid in mapping the atmospheric flowfield.

Conrath, B. J.↗
NASA NTRS1984

Chemical and biological evolution in space

The formation of organic molecules in interstellar dust grains and the survival of bacterial spores in a space environment are examined, summarizing the results of experimental investigations and theoretical calculations. The interstellar medium is characterized; the production of organic yellow-stuff residues on the mantles of dust grains in molecular clouds by UV radiation is explained; an IR absorption spectrum toward a Galactic-center source is shown to confirm the presence of such residues; and the mass of such abiotically produced complex organic molecules in the Galaxy is estimated as at least 10 to the 7th solar mass, or 0.1 percent of the mass in the Galaxy. This finding is considered significant for the prebiotic chemistry of the earth, since comets containing large amounts of interstellar dust may have impacted the earth many times during comet showers in the early solar system. UV-irradiation experiments on bacterial spores show that initial exposures to solar UV, not interstellar survival, is the main factor rendering theries of panspermia questionable.

Greenberg, J. M.↗
NASA NTRS1994

Detection of absorption by H2 in molecular clouds: A direct measurement of the H2:CO ratio

Vibrational absorption by H2 and CO has been searched for toward infrared sources embedded in molecular clouds. H2 was detected toward NGC 2024 IRS 2 and possibly toward NGC 2264 (GL 989). CO was detected toward both sources. The results are consistent with the H2 ortho:para ratio being equilibrated at the cloud temperature. Toward NGC 2024, H2:CO = (3700(sub -2600)(sup +3100)) (2 sigma limits), and toward NGC 2264, H2:CO less than 6000. Approximately one-third of all carbon is in gas-phase CO.

Lacy, J. H.↗
NASA NTRS2002

Deuterated PAHs in Space

The cosmic deuterium to hydrogen (D/H) ratio is of key importance from a cosmological and stellar evolution perspective since deuterium originates from big-bang nucleosynthesis and is destroyed by stellar thermonuclear reactions. Further, from the interstellar perspective, the galactic distribution of deuterium and the D/H ratio among various molecular species also traces interstellar chemical evolution. Over the past few decades, radio observations have enabled the study of a handful of small, deuterated interstellar species. However, the number of deuterated species detected and environments probed are limited, raising issues of selection effects that hamper generalization and applications to other environments. Infrared spectroscopy of the interstellar medium offers a distinct advantage in this regard as the extent of deuteration of entire chemical families, rather than one species, can be probed. These observations require spaceborne telescopes because the molecular vibrations involving D which produce the strongest IR bands fall in spectral regions which are obscured by terrestrial CO2 absorption. Here we report the tentative detection of the C-D stretching vibration from deuterated interstellar polycyclic aromatic hydrocarbons in the Orion nebula. Since the PAH emission features are widespread and probe many different types of cosmic environments, follow up observations of deuterated PAHs will provide fundamental, far reaching new insight and perspective into galactic and extragalactic processes.

Peeters, Els↗
NASA NTRS2004

High Excitation Gas and ISM

An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic hydrocarbons and dust are summarized, their diagnostic capabilities illustrated and their implications highlighted.

Peeters, E.↗
NASA NTRS2002

Infrared Emission From Interstellar PAHs, New Probes of the Interstellar Medium

Tremendous strides have been made in the understanding of interstellar material over the past twenty years thanks to significant, parallel developments in two closely related areas: observational IR astronomy and laboratory astrophysics. Twenty years ago the composition of interstellar dust was largely unknown and the notion of abundant, gas phase, polycyclic aromatic hydrocarbons (PAHs) anywhere in the interstellar medium (ISM) considered impossible. Today the dust composition of the diffuse and dense ISM is reasonably well constrained and the spectroscopic case for interstellar PAHs, impossibly large molecules by early interstellar chemistry standards, is very strong. PAH spectral features are now being used as new probes of the ISM. PAH ionization states reflect the ionization balance of the medium while PAH size and structure reflect the energetic and chemical history of the medium. Aromatic carbon-rich materials ranging in size from PAHs and PAH nanoclusters, to sub-micron and micron-sized dust grains represent an important component of the ISM. These species: (1) dominate the heating and cooling of interstellar clouds via energetic photoelectron ejection and infrared (IR) emission; (2) moderate the ionization balance in photodissociation regions and molecular clouds; (3) moderate the composition of the gas phase and play an important role in determining the chemistry of the ISM; (4) contribute to the interstellar extinction in the near IR, visible, and UV spectral regions; and (5) convert UV, visible, and near-IR radiation to mid- and far-IR radiation in the ISM and, as such, are responsible for the well known, widespread family of mid-IR emission features with major components near 3.3, 6.2, 7.7, 8.6, and 11.3 microns.

Hudgins, D. M.↗
DOE OSTI2026

Peak2Patch: High-Fidelity Functional Group Identification through Attention-Based Fusion of Infrared and Mass Spectra

Identifying molecular structure based on spectroscopic readings is a key task in a variety of chemical and biological applications. Common spectroscopy techniques, such as Infrared (IR) Spectroscopy and Mass Spectrometry (MS), provide detailed information on the structure of molecular compounds but nonetheless require expert-level knowledge to decode. Machine learning has emerged as a potential solution for automating structure prediction from chemical spectra; however, current approaches generally focus on single sensor modalities, neglecting to leverage the complementary information contained within differing spectra. In this paper, we introduce Peak2Patch, a novel approach to fusion-enhanced prediction of functional groups from IR and mass spectra. First, we perform a detailed comparison of backbone networks for encoding both sparse mass spectra and dense IR spectra and demonstrate the superior performance of transformer neural networks over current state-of-the-art convolutional neural networks. Second, we evaluate three broad categories of fusion: early (raw feature), middle (deep feature), and late (decision) fusion, demonstrating the potential of a deep feature fusion-based approach. Lastly, we present Peak2Patch, our attention-based fusion scheme, which leverages cross-attention to mix features between encoded tokens of the two modalities. We validate our approach on a publicly available multimodal spectroscopic data set of 790k simulated molecules, demonstrating a large improvement in functional group prediction over both the previous state-of-the-art and our own strong single-modal baselines.

Jacobson, Philip [Sandia National Laboratories (SN↗
DOE OSTI2025

Paired Neural Network for Matching Experimental and Predicted Infrared Spectra

Here, we present a novel machine learning (ML)-based scoring technique for determining the similarity between experimental and predicted infrared (IR) spectra for identification purposes. IR spectroscopy is a powerful technique used to identify the molecular structure and composition of a sample by measuring the unique vibrational frequency pattern of the molecule’s functional groups. Molecular identifications are often made by comparing experimental and reference spectra. However, the limited number of reference spectra available in spectral libraries can confound the identification process. Alternative identification procedures rely on in silico techniques to simulate spectra for a wide range of molecules. However, scoring spectral similarity between an experimental query and computationally predicted reference remains a significant challenge. Our proposed ML-based scoring technique overcomes these barriers by accurately and efficiently determining spectral similarity.

Neural Network↗
DOE OSTI2021

Transparent window 2D IR spectroscopy of proteins

Proteins are complex, heterogeneous macromolecules that exist as ensembles of interconverting states on a complex energy landscape. A complete, molecular-level understanding of their function requires experimental tools to characterize them with high spatial and temporal precision. Infrared (IR) spectroscopy has an inherently fast time scale that can capture all states and their dynamics with, in principle, bond-specific spatial resolution. Two-dimensional (2D) IR methods that provide richer information are becoming more routine but remain challenging to apply to proteins. Spectral congestion typically prevents selective investigation of native vibrations; however, the problem can be overcome by site-specific introduction of amino acid side chains that have vibrational groups with frequencies in the “transparent window” of protein spectra. This Perspective provides an overview of the history and recent progress in the development of transparent window 2D IR of proteins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

The greenhouse of Titan.

Analysis of non-gray radiative equilibrium and gray convective equilibrium on Titan suggests that a massive molecular-hydrogen greenhouse effect may be responsible for the disagreement between the observed IR temperatures and the equilibrium temperature of an atmosphereless Titan. Calculations of convection indicate a probable minimum optical depth of 14 which corresponds to a molecular hydrogen shell of substantial thickness with total pressures of about 0.1 bar. It is suggested that there is an equilibrium between outgassing and blow-off on the one hand and accretion from the protons trapped in a hypothetical Saturnian magnetic field on the other, in the present atmosphere of Titan. It is believed that an outgassing equivalent to the volatilization of a few kilometers of subsurface ice is required to maintain the present blow-off rate without compensation for all geological time. The presence of an extensive hydrogen corona around Titan is postulated, with surface temperatures up to 200 K.

Sagan, C.↗
NASA NTRS1992

Near-infrared observations of the proto-planetary nebula AFGL 618

Near-IR images and spectroscopy of the bipolar protoplanetary nebula AFGL 618 are presented. Emission from molecular hydrogen is detected in the 0.90-1.34-micron spectrum. A visual extinction of 3.4 +4.0/-2.0 mag to the H2-emitting region is derived from molecular hydrogen line ratios. Models of collisionally excited and fluorescent H2 emission are compared with the data: the near-IR H2 spectrum is found to be dominated by emission from collisionally excited molecules at Tex of about 2000 K, but a component of fluorescent emission is also present. It is shown that this type of near-IR spectrum is an excellent tool for discriminating relatively low levels of fluorescent H2 emission from a strong collisionally excited component. Images in the H- and K-bandpasses are analyzed using models which assume single scattering of photons from the central objects. The models indicate that the bipolar axis is inclined to the plane of the sky by about 45 deg. The emission in the H- and K-bands is found to be consistent with single scattering of photons by dust with a distribution such that the dust density increases with increasing stellar latitude and is nearly zero at the poles.

Latter, William B.↗
NASA NTRS2013

Absorption and Scattering by Molecules and Particles

The Earth's atmosphere absorbs, scatters, and emits electromagnetic radiation. Although air molecules are the primary actors in these processes, aerosol particles are also present ubiquitously and modify the radiation field. In fact, this modification constitutes the very physical basis of aerosol remote sensing. Whenever clouds are present, they have a much larger influence on radiation which largely overshadows the aerosol impact. Therefore, in aerosol remote sensing, one often has to limit observations to cloudless conditions and screen cloudy pixels. In the solar part of the spectrum, molecular absorption is mostly limited to ultraviolet (UV; ozone) and near-infrared (near-IR; carbon dioxide, water vapor) wavelengths and is characterized by strong and narrow oxygen bands. A brief description of atmospheric molecular absorption is presented in Section 2.2. Shortwave aerosol remote sensing is usually performed outside the absorption bands, but some instruments also have channels capturing absorption bands with the objective of quantifying gaseous components.

remote sensing↗
NASA NTRS1984

High-resolution far-infrared observations of the extended W51 complex

A far-IR map with 1 arcmin resolution was obtained of the W51 H II region molecular cloud complex. The 40-120 microns survey was performed to study embedded sources which excite the H II gas. The far-IR emission distribution overlapped radio emissions from the region, implying that the extended dust clouds were heated by the same sources as the H II regions. Four compact sources were characterized and associated with concentrations of luminosities that suggested a scarcity of low-mass stars. The brightest source, labeled W51-I, has a luminosity/mass ratio of 150, high enough to indicate a burst of massive O star formation. No triggering mechanism was identified for the burst of star formation.

Rengarajan, T. N.↗
NASA NTRS2003

Low threshold interband cascade lasers operating above room temperature

Mid-IR type-II interband cascade lasers were demonstrated in pulsed mode at temperatures up to 325 K and in continuous mode up to 200 K. At 80 K, the threshold current density was 8.9 A/cm2 and a cw outpout power of ~140 mW/facet was obtained.

interband cascade lasers GaSb molecular beam epita↗
DOE OSTI2023

Facile design of renewable lignin copolymers by photoinitiated RAFT polymerization as Pickering emulsion stabilizers

As the richest aromatic renewable resource, lignin has attracted significant attention for fabricating various materials. However, due to lignin's structural complexity, an effective and facile structural modification strategy remains a substantial challenge. Herein, we have successfully applied photoinitiated reversible addition–fragmentation chain transfer (RAFT) as a versatile tool to synthesize amphiphilic lignin copolymers with lignin derivatives as the macroinitiator. The experimental and density functional theory analysis systematically investigated the photopolymerization kinetics, proving excellent control over molecular weights. Additionally, 1 H NMR and FT-IR analyses confirmed the well-designed structures. Moreover, the structures of copolymers were tunable by simple variations of monomer structures. Finally, the self-assembly of the synthesized copolymers into nanoparticles was explored, together with the potential applications as Pickering emulsion stabilizers. Finally, we believe that this work will offer a facile and green approach to synthesize lignin-based novel copolymers and further expand its applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1985

Star formation in the inner Galaxy - A far-infrared and radio study of two H II regions

Far-infrared and radio continuum maps have been made of two inner-Galaxy H II region complexes, G30.8-0.0 and G25.4-0.2, along with radio and molecular line measurements at selected positions. The far-IR emission from each region is dominated by two sources. For both G25.4 and G30.8, the distribution of the emission is similar to that of the radio emission, indicating that OB stars provide most of the heating. There is evidence that extinction plays an important role in G30.8, even in the far-IR. A near-IR point source has been detected in G30.8 at the position of peak far-IR color temperature. This source may be the ionizing star for the core of G30.8. Measurement of forbidden S III 9532 A from G25.4SE indicates that the extinction toward this source is very low, which is difficult to reconcile with previously determined distance measurements to this source.

Lester, D. F.↗
NASA NTRS1987

Warm dense gas in luminous protostellar regions - A submillimeter and far-infrared CO line study

Spectroscopic measurements of the CO J = 7-6 and J = 16-15 sub-mm/far-IR rotational lines are combined for a study of the molecular gas in four massive star formation regions: W51 IRS 2, W51 Main, G34.3+0.1, and W49. CO emission over a wide velocity range is found in three of the four regions. Mass outflows from newly formed stars in the two W51 sources carry an order-of-magnitude-greater mass and momentum than in the Orion/KL flow; it is concluded that mass outflow rates scale with source luminosity up to the most luminous galactic star formation regions.

Jaffe, D. T.↗