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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Compounds and their Ions: Polycyclic Aromatic Nitrogen Heterocycles - 6

The matrix-isolation technique has been employed to measure the mid-infrared spectra of several polycyclic aromatic nitrogen heterocycles in both neutral and cationic forms. The species studied include: 7,8 benzoquinoline (C13H9N); 2-azapyrene (C15H9N); 1- and 2-azabenz(a)anthracene (C17H11N); and 1-, 2-, and 4-azachrysene (also C17H11N). The experimentally measured band frequencies and intensities for each molecule are tabulated and compared with their theoretically calculated values computed using density functional theory at the B3LYP/4-31G level. The overall agreement between experiment and theory is quite good, in keeping with previous investigations involving the parent aromatic hydrocarbons. Several interesting spectroscopic trends are found to accompany nitrogen substitution into the aromatic framework of these compounds. First, for the neutral species, the nitrogen atom produces a significant increase in the total integrated infrared intensity across the 1600 - 1100/cm region and plays an essential role in the molecular vibration that underlies an uncharacteristically intense, discrete feature that is observed near 1400/cm in the spectra of 7,8 benzoquinoline, 1-azabenz(a)anthracene, and 4-azachrysene. The origin of this enhanced infrared activity and the nature of the new 1400/cm vibrational mode are explored. Finally, in contrast to the parent hydrocarbon species, these aromatic nitrogen heterocycles possess a significant permanent dipole moment. Consequently, these dipole moments and the rotational constants are reported for these species in their neutral and ionized forms.

Mattioda, A. L.↗
NASA NTRS1991

Small Business Innovations (Fiber Optics)

Foster-Miller, Inc. Waltham, MA developed the In-Situ Fiber Optic Polymer Reaction Monitor which could lead to higher yields and lower costs in complex composite manufacturing. The monitor, developed under a Small Business Innovation Research (SBIR) contract with Langley Research Center, uses an infrared, fiber optic sensor to track the molecular vibrational characteristics of a composite part while it is being cured. It is the first analytical system capable of directly measuring the chemistry of advanced composite materials.

Source record↗
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 NTRS2003

A Study of Olivine Alteration to Iddingsite Using Raman Spectroscopy

A crucial task of Mars surface science is to determine past environmental conditions, especially aqueous environments and their nature. Identification of mineral alteration by water is one way to do this. Recent work interprets TES spectra as indicating altered basalt on Mars. Olivine, a primary basaltic mineral, is easily altered by aqueous solutions. Alteration assemblages of olivine may be specific to deuteric, hydrothermal, surface water, or metamorphic environments. Raman spectra are produced by molecular vibrations and provide direct means for studying and identifying alteration products. Here, we present a combined study of changes in the chemical composition and Raman spectra of an olivine as it alters to iddingsite. Iddingsite is found in some SNC meteorites and is presumably present on Mars. The term 'iddingsite' has been used as a catch-all term to describe reddish alteration products of olivine, although some authors ascribe a narrower definition: an angstrom-scale intergrowth of goethite and smectite (presumably saponite) formed in an oxidizing and fluid-rich environment. Alteration conserves Fe (albeit oxidized) but requires addition of Al and H2O and removal of Mg and Si. The smectite that forms may be removed by continued alteration. Dehydration of the goethite forms hematite. Our purpose is to study the mineral assemblage, determine the structural and chemical variability of the components with respect to the degree of alteration, and to find spectral indicators of alteration that will be useful during in-situ analyses on Mars.

Kuebler, K. E.↗
NASA NTRS2009

Nanowire Electron Scattering Spectroscopy

Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

Hunt, Brian↗
NASA NTRS2005

Simultaneous Conoscopic Holography and Raman Spectroscopy

A new instrument was developed for chemical characterization of surfaces that combines the analytical power of Raman spectroscopy with the three-dimensional topographic information provided by conoscopic holography. The figure schematically depicts the proposed hybrid instrument. The output of the conoscopic holographic portion of the instrument is a topographical map of the surface; the output of the Raman portion of the instrument is hyperspectral Raman data, from which the chemical and/or biological composition of the surface would be deduced. By virtue of the basic principles of design and operation of the instrument, the hyperspectral image data would be inherently spatially registered with the topographical data. In conoscopic holography, the object and reference beams of classical holography are replaced by the ordinary and extraordinary components generated by a single beam traveling through a birefringent, uniaxial crystal. In the basic conoscopic configuration, a laser light is projected onto a specimen and the resulting illuminated spot becomes a point source of diffuse light that propagates in every direction. The laser beam is rasterscanned in two dimensions (x and y) perpendicular to the beam axis (z), and at each x,y location, the pattern of interference between the ordinary and extraordinary rays is recorded. The recorded interferogram constitutes the conoscopic hologram. Of particular significance for the proposed instrument is that the conoscopic hologram contains information on the z coordinate (height) of the illuminated surface spot. Hence, a topographical map of the specimen is constructed point-by-point by rastering the laser beam in the x and y directions and correlating the x and y coordinates with the z information obtained from the interferograms. Conoscopic imaging is an established method, and conoscopic laboratory instruments for surface metrology are commercially available. In Raman spectroscopy of a surface, one measures the spectrum of laser light scattered inelastically from a laser-illuminated spot on the surface. The wavelengths of the inelastically scattered light differ from that of the incident laser beam by amounts that correspond to the energies of molecular vibrations. The resulting vibrational spectrum can be used to identify the molecules. Raman spectroscopy is a standard laboratory technique for identifying mineralogical, biological, and other specific chemical compositions.

Schramm, Harry F.↗
NASA NTRSDate not supplied

An exact solution of an augmented Burgers equation and amplitude-dependent acoustic propagation speed

Nonlinear sound propagation in the atmosphere is usually modeled using an augmented Burgers equation accounting for a weak nonlinearity and atmospheric absorption. Because the absorption includes the molecular vibrational relaxation, such a Burgers equation is more complex than the regular Burgers equation that only accounts for the thermoviscous dissipation in the absorption. Although an exact solution of the regular Burgers equation has long been derived using the Cole- Hopf transform, an exact solution of the augmented Burgers equation has not been derived previously. Thus, this paper presents an exact solution of the augmented Burgers equation. This novel solution is shown to be equivalent to the solution using the Cole-Hopf transform when the absorption only involves thermoviscous dissipation. It can also be reduced to the known solution of an N-wave when the absorption is ignored. The augmented Burgers equation is an approximation valid for weak nonlinearity. However, this assumption may not be accurate for acoustic signals propagating from the lower atmosphere and which are subsequently refracted downward from the upper atmosphere (e.g., stratosphere and thermosphere) due to the decreasing air density with increasing altitude [Lonzaga, et al., Geophysical Journal International, 200(3), pp.1347-1361]. Consequently, the current paper also discusses the effects of a strong nonlinearity that lead to an amplitude-dependent increase in signal propagation speed. For an impulsive signal such as a sonic boom, these effects cause a dispersion of the signal similar to the observed dispersion of acoustic signals from supersonic Concorde as well as from large explosions.

Joel B Lonzaga↗
NASA NTRSDate not supplied

Phase Change Materials for Photonics in NASA Science and Space Missions

Phase change materials (PCMs) such as Ge2Sb2Te5, Ge2Sb2Se4Te1, and Sb2S3have recently emerged as a promising platform to control light on-chip due to their fast, dramatic, and reversible change in refractive index. Significant technical progress in the field has been achieved in terms of improving optical transparency, controlling PCMs both optically and electrically, and integrating with complex photonic circuits, leading to exciting applications. When PCMs are mated with metasurfaces, devices are capable of controlling the phase and amplitude of propagating light with arrays of subwavelength structures. These enhance tunability and reconfigurability and continue to redefine the boundaries of optical sciences. PCM-based metasurface optics also help to accelerate the adoption of new architectures with reduced size, weight, and power (SWaP) for science and space mission platforms at NASA. In this talk, I will introduce two NASA-lead PCM photonic projects: 1. P-ACTIVE (PCM-based actively tunable filter) for broad imaging and sensing applications – from probing molecular vibrations in chemical species to detecting radiant thermal signatures of the space launch system. 2. PROWESS (Phase change reconfigurable optical wavefront synthesis system) as a beam steerer for both Earth and space LiDAR and free space optical communication applications. From this seminar, the attendees will be exposed not only to PCM-based photonic technologies but also NASA missions including the MISSE (Materials on the International Space Station Experiment) test campaign that was conducted to expose PCMs and PCM-based metasurfaces in space for 6 months in 2022.

phase change material↗
NASA NTRSDate not supplied

P-ACTIVE (PCM-Based Actively Tunable Filter) Project at NASA

Phase change material (PCM)-based actively tunable mid-wave IR filters have broad imaging and sensing applications—from probing molecular vibrations in chemical species to detecting radiant thermal signatures. We introduce the Phase-change actively tunable filter (P-ACTIVE) project lead by NASA Langley Research Center with collaborators MIT and the University of Cambridge. It covers background science, experimental and theoretical device performance, as well as recent results obtained from a MISSE-14 mission for space qualification of active metasurface optics and constituent PCM. We conclude with a prospective view of the technology and discuss the potential for these filters to serve multiple NASA missions.

phase change material↗
DOE OSTI2023

Probing Complex Chemical Processes at the Molecular Level with Vibrational Spectroscopy and X-ray Tools

Understanding the origins of structure and bonding at the molecular level in complex chemical systems spanning magnitudes in length and time is of paramount interest in physical chemistry. Here, we have coupled vibrational spectroscopy and X-ray based techniques with a series of microreactors and aerosol beams to tease out intricate and sometimes subtle interactions, such as hydrogen bonding, proton transfer, and noncovalent interactions. This allows for unraveling the self-assembly of arginine-oleic acid complexes in an aqueous solution and growth processes in a metal–organic framework. Terahertz and infrared spectroscopy provide an intimate view of the hydrogen-bond network and associated phase changes with temperature in neopentyl glycol. The hydrogen-bond network in aqueous glycerol aerosols and levels of protonation of nicotine in aqueous aerosols are visualized. Future directions in probing the hydrogen-bond networks in deep eutectic solvents and organic frameworks are described, and we suggest how X-ray scattering coupled to X-ray spectroscopy can offer insight into the reactivity of organic aerosols.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Rotationsal and vibrational spectra of molecular ions: Feasibility of laboratory and astrophysical observation

The rotational spectra of a number of small molecular ions should be detectable in the microwave or millimeter wave regions in laboratory experiments using currently available techniques. The dipole moments and absorption coefficients of polar diatomics CO(+) and NO(+) as well as asymmetric isotopically enriched species, like O-18O-16(+), NE-20NE-22(+), and OC-18 O-16(+) are calculated to be sufficiently large to allow observation of their spectra. In addition to the detailed molecular structure information which such spectral data would provide, precise knowledge of the transition frequencies would render likely the detection of certain of these ions in the interstellar sources or in planetary atmospheres. All of these ions also possess vibrational spectra which should be detectable in the infrared region in laboratory or astrophysical sources.

Woods, R. C.↗
NASA NTRS1982

Time-dependent calculations of Jupiter's ionosphere

Time-dependent calculations of the vertical distribution of protons in Jupiter's ionosphere show that the accumulation of protons in the topside ionosphere produced from solar ionizing radiation overwhelms the loss to vibrationally excited molecular hydrogen at vibrational temperatures as high at 1600 K. At 2500 K the ionization is decreased over the entire planet with little diurnal variation. For Voyager 1 then, unless the H2 vibrational temperature is as high as thousands of degrees and the topside density of H2 is asymmetric and larger by orders of magnitude, dynamical processes are more likely causes of the low electron densities seen in the nightside upper ionosphere. A calculation of the H3(+) density profile showed that the distribution above the turbopause is controlled by diffusion.

Chen, R. H.↗
NASA NTRS1992

Ab initio study of the molecular structure and vibrational spectrum of nitric acid and its protonated forms

The equilibrium structures, harmonic vibrational frequencies, IR intensities, and relative energetics of HNO3 and its protonated form H2NO3+ were investigated using double-zeta plus polarization and triple-zeta plus polarization basis sets in conjunction with high-level ab initio methods. The latter include second-order Moller-Plesset perturbation theory, the single and double excitation coupled cluster (CCSD) methods, a perturbational estimate of the effects of connected triple excitations (CCSD(T)), and the self-consistent field. To determine accurate energy differences CCSD(T) energies were computed using large atomic natural orbital basis sets. Four different isomers of H2NO3+ were considered. The lowest energy form of protonated nitric acid was found to correspond to a complex between H2O and NO2+, which is consistent with earlier theoretical and experimental studies.

Lee, Timothy J.↗
DOE OSTI2025

Infrared spectral signatures of interfacial water at TiO 2 –electrolyte interfaces from deep potential molecular dynamics

Vibrational spectroscopy is a powerful tool for probing water at oxide–electrolyte interfaces, but its molecular interpretation can be challenging. Here, we employ deep potential long-range molecular dynamics simulations with layer-resolved spectral analysis to investigate the microscopic origins of the infrared (IR) response of water at the interface with anatase TiO 2 (101), a prototypical oxide surface. The calculated interfacial spectra exhibit characteristic modifications compared to bulk water IR spectra, including enhanced intensities, a red shifted and broadened stretching band, and a higher-frequency shoulder, in qualitative agreement with experiments. Spectral decomposition shows that these signatures originate mainly from the first interfacial water layer, dominated by surface-bound H 2 O at Ti 5C sites, with secondary contributions from the second layer. A moderate salt concentration (0.4 M NaCl) leaves both the interfacial structure and the spectra essentially unchanged, while tuning the pH strongly modulates the spectral intensity. We establish a scaling relation linking the spectral intensity to the surface water dissociation fraction and the dipole moment, both governed by interfacial electric fields. These findings provide a microscopic framework for interpreting IR spectra of oxide–electrolyte interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗