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Results for “Solid-state spectroscopy”

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At least 19 records

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NASA NTRS1987

International Conference on Vacuum Ultraviolet Radiation Physics, 8th, Lunds Universitet, Sweden, Aug. 4-8, 1986, Proceedings

The interactions of VUV radiation with solids are explored in reviews and reports of recent theoretical and experimental investigations from the fields of atomic and molecular physics, solid-state physics, and VUV instrumentation. Topics examined include photoabsorption and photoionization, multiphoton processes, plasma physics, VUV lasers, time-resolved spectroscopy, synchrotron radiation centers, solid-state spectroscopy, and dynamical processes involving localized levels. Consideration is given to the fundamental principles of photoemission, spin-polarized photoemission, inverse photoemission, semiconductors, organic materials, and adsorbates.

Nilsson, Per-Olof↗

NASA NTRS1986

Solid-state radio frequency oscillator for optogalvanic spectroscopy - Detection of nitric oxide using the 2-0 overtone transition

A compact, solid-state radio-frequency oscillator of low-power consumption is described, which allows quantitative measurement of the optogalvanic effect in low-pressure gas discharges. The oscillator has been used to record a portion of the 2-0 overtone band of nitric oxide at a pressure of about 1 Torr using a tunable color-center laser operating at 2.65 microns.

May, R. D.↗

NASA NTRS1984

Lasers, their development, and applications at M.I.T. Lincoln Laboratory

A historical account of the work on lasers at MIT Lincoln Laboratory is presented. Highlighted are the efforts that led to the coinvention of the semiconductor laser and the Laboratory's later role in establishing the feasibility of GaInAsP/InP semiconductor lasers for use in fiber telecommunications at 1.3-1.5 micron wavelengths. Descriptions of other important developments include tunable lead-salt semiconductor and solid-state lasers for spectroscopy and LIDAR applications, respectively, as well as ultrastable CO2 lasers for coherent infrared radar.

Rediker, R. H.↗

NASA NTRS1988

Mid-infrared solid-state lasers and laser materials

An account is given of NASA-Langley's objectives for the development of advanced lasers and laser materials systems applicable to remote sensing in the mid-IR range. Prominent among current concerns are fiber-optic spectroscopy, eye-safe solid-state lasers for both Doppler sensing and mid-IR wavelength-generation laser pumping, and nonlinear optics generating tunable mid-IR radiation. Ho:YAG lasers are noted to exhibit intrinsic advantages for the desired applications, and are pumpable by GaAlAs laser diodes with a quantum efficiency approaching 2.

Barnes, Norman P.↗

NASA NTRS1983

Physical aging and its influence on the reliability of network epoxies and epoxy-matrix composites

The matrix-dominated physical and mechanical properties of a carbon fiber reinforced epoxy composite and a neat epoxy resin were found to be affected by sub-Tg annealing in nitrogen and dark atmosphere. Postcured specimens of Thornel 300 carbon-fiber/Fiberite 934 epoxy as well as Fiberite 934 epoxy resin were quenched from above Tg and given annealing at 140 C, 110 C, or 80 C, for time up to one-hundred thousand minutes. No weight loss was observed during annealing at these temperatures. Significant variations were found in density, modulus, hardness, damping, moisture absorption ability, thermal expansivity. Moisture-epoxy interactious were also studied. The kinetics of aging as well as the molecular aggregation during this densification process were monitored by differential scanning calorimetry, dynamic mechanical analysis, density gradient column, microhardness tester, Instron, and solid-state nuclear magnetic resonance spectroscopy.

Heinemann, K.↗

NASA NTRS1983

Fire- and heat-resistant laminating resins based on maleimido-substituted aromatic cyclotriphosphazenes

A novel class of flame- and heat-resistant polymers has been synthesized by the thermal polymerization of maleimido-substituted aromatic cyclotriphosphazenes. The polymer obtained from tris-(aminophenoxy)tris(maleimidophenoxy)cyclotriphosphazene has good thermal stability and is noteworthy for its high char yield, viz., 82 percent at 800 C in nitrogen and 81 percent at 700 C in air. Graphite-fabric laminates prepared with this polymer did not burn in pure oxygen, even at 300 C, and were tested for mechanical properties. Hexakis(4-maleimidophenoxy)cyclotriphosphazene and some fluorine-containing monomers have also been synthesized. The structures of these cyclic phosphazene precursors and polymers were characterized by FT IR spectrophotometry, H-1 NMR, F-19 NMR, and P-31 solid-state magic angle spinning NMR spectroscopy, and mass spectrometry. The curing behavior of the polymer precursors and the thermal stabilities of the polymers were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA).

Kumar, D.↗

NASA NTRS1990

Identification of lunar rock types and search for polar ice by gamma ray spectroscopy

This paper examines the possibility of mapping the surface composition of the moon from an orbiting spin-stabilized spacecraft, using gamma ray spectroscopy and a cooled germanium solid-state device as a detector. A design for accommodating the germanium detector gamma ray spectrometer was devised, and the detection sensitivity was applied to typical lunar-rock compositions. For sets comprising nine highland and 16 mare types, the most useful elements were found to be Mg, Al, K, Ti, Fe, U, and Th. An analysis of the expected instrument response to the gamma ray and neutron fluxes of water ice indicated that a neutron mode added to the spectrometer will be more sensitive than the gamma ray mode to the possible presence of polar ice. It was calculated that, with a pair of selected neutron absorbers and a model which provides that 2.5 percent of the area above 75-deg latitude is occupied by trapping sites, the instrument will provide a 1-yr mission detection limit of 0.056 percent H2O by weight for each polar region.

Metzger, Albert E.↗

NASA NTRS1992

Tm,Ho:YAG laser with tunable range of 2.08-2.12 microns and its applications to spectroscopy

In recent advanced lasers, 2 micron solid-state lasers such as Tm:YAG and Ho:YAG lasers are very attractive for laser radar remote sensing technologies because of eye safety, realizations of all solid-state laser pumped by diode laser and smaller dimension, tunability of lasing wavelength, possibility of coherent detection, etc. Featuring these advantages, 2 micron lasers have been candidated as laser transmitters for use in water vapor Differential Absorption Lidar (DIAL), laser altimeter, Doppler wind sensor, Mie lidar, etc. Characterization of a tunable Cr, Tm, Ho:YAG laser and its applications to spectroscopy concerning absorption and reflectance are reported.

Asai, Kazuhiro↗

NASA NTRS1983

Physical aging in graphite/epoxy composites

Sub-Tg annealing has been found to affect the properties of graphite/epoxy composites. The network epoxy studied was based on the chemistry of tetraglycidyl 4,4'-diamino-diphenyl methane (TGDDM) crosslinked by 4,4'-diamino-diphenyl sulfone (DDS). Differential scanning calorimetry, thermal mechanical analysis, and solid-state cross-polarized magic-angle-spinning nuclear magnetic resonance spectroscopy have been utilized in order to characterize this process of recovery towards thermodynamic equilibrium. The volume and enthalpy recovery as well as the 'thermoreversibility' aspects of the physical aging are discussed. This nonequilibrium and time-dependent behavior of network epoxies are considered in view of the increasingly wide applications of TGDDM-DDS epoxies as matrix materials of structural composites in the aerospace industry.

Kong, E. S. W.↗

NASA NTRS1980

X-ray and ultraviolet spectroscopy of Cygnus X-1 = HDE 226868

Observations of Cygnus X-1 with the solid-state spectrometer on the Einstein Observatory are presented. The X-ray spectra of two intensity dips viewed near superior conjunction did not exhibit increased photoelectric absorption. Rather, the data support a model in which an increase in the electron-scattering optical depth modifies both the observed spectrum and the intensity. The characteristic temperature of the intervening material is greater than about 50 million K. These measurements were in part simultaneous with observations by IUE. The ultraviolet spectrum and intensity remained relatively constant during an X-ray intensity dip.

Pravdo, S. H.↗

NASA NTRS1981

Multispectral mapper - Imaging spectroscopy as applied to the mapping of earth resources

An instrument concept that uses solid-state array imaging has been developed for a future land observing system. The design concept is responsive to a variety of use needs and provides improved capabilities over the planned Landsat Thematic Mapper. A comparison of the differing approaches to the instrument design was made, resulting in the selection of a concept which uses a spectrograph coupled to a line-array imager to provide simultaneous spatial and spectral resolution. The design provides an inherent solution to the problem of achieving precise registration among the spectral bands. Data processing on the focal plane is used to select the spectral bands and their band widths. Onboard capabilities include radiometric correction, selection of instantaneous field-of-view and swath width, and data compression.

Wellman, J. B.↗

NASA NTRS1980

X-ray and UV spectroscopy of Cygnus X-1 = HDE226868

Observations are presented of Cygnus X-1 with the solid-state spectrometer on the Einstein Observatory. The X-ray spectra of two intensity dips viewed near superior conjunction did not exhibit increased photoelectric absorption. Rather the data support a model in which an increase in the electron scattering optical depth modifies both the observed spectrum and the intensity. The characteristic temperature of the intervening material is greater than 5 x 10 to the 7th power K. These measurements were in part simultaneous with observations by IUE. The ultra violet spectrum and intensity remained relatively constant during an X-ray intensity dip.

Pravdo, S. H.↗

NASA NTRS1980

Spectroscopy of compact extragalactic X-ray sources

The X-ray spectra of compact extragalactic sources obtained from the HEAO-1 A-2 experiment and the solid-state spectrometer onboard HEAO-2 (the Einstein Observatory) are reviewed. Seyfert spectra are remarkably consistent with characteristic power-law spectra of energy index alpha = 0.7 + .1 over a dynamic range of almost 100 in both luminosity for the whole sample, and energy for individual members. Radio-quiet quasars have similar spectra, perhaps slightly steeper, for the limited sample available. New solid-state spectrometer results for NGC 4151 yield a consistent picture for the geometry of the broad-line clouds in both these related radio-quiet classes of galactic nuclei. Radio-loud objects, especially BL Lacs, are considerably more variable in spectrum as well as luminosity. Direct synchrotron and synchrotron-self-Compton components are consistent with what we observe from these objects. Finally, the role of spectroscopy in addressing the extent to which compact extragalactic nuclei might contribute to the diffuse X-ray background is discussed.

Holt, S. S.↗

NASA NTRS1989

BIN Diode For Submillimeter Wavelengths

Diode formed by selective doping during epitaxial growth, starting with semi-insulating substrate. Use of high-mobility semiconductors like GaAs extends cutoff frequency. Either molecular-beam epitaxy (MBE) or organometallic chemical-vapor deposition used to form layers of diode. Planar growth process permits subsequent fabrication of arrays of diodes by standard photolithographic techniques, to achieve quasi-optical coupling of submillimeter radiation. Useful for generation of harmonics or heterodyne mixing in receivers for atmospheric and space spectroscopy operating at millimeter and submillimeter wavelengths. Used as frequency doublers or triplers, diodes of new type extend frequency range of present solid-state oscillators.

Maserjian, J.↗

NASA NTRS1985

Thin-film chemical sensors based on electron tunneling

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

Khanna, S. K.↗

NASA NTRS1991

Determination of lunar ilmenite abundances from remotely sensed data

The mineral ilmenite (FeTiO3) was found in abundance in lunar mare soils returned during the Apollo project. Lunar ilmenite often contains greater than 50 weight-percent titanium dioxide (TiO2), and is a primary potential resource for oxygen and other raw materials to supply future lunar bases. Chemical and spectroscopic analysis of the returned lunar soils produced an empirical function that relates the spectral reflectance ratio at 400 and 560 nm to the weight percent abundance of TiO2. This allowed mapping of the lunar TiO2 distribution using telescopic vidicon multispectral imaging from the ground; however, the time variant photometric response of the vidicon detectors produced abundance uncertainties of at least 2 to 5 percent. Since that time, solid-state charge-coupled device (CCD) detector technology capable of much improved photometric response has become available. An investigation of the lunar TiO2 distribution was carried out utilizing groundbased telescopic CCD multispectral imagery and spectroscopy. The work was approached in phases to develop optimum technique based upon initial results. The goal is to achieve the best possible TiO2 abundance maps from the ground as a precursor to lunar orbiter and robotic sample return missions, and to produce a better idea of the peak abundances of TiO2 for benefaction studies. These phases and the results are summarized.

Larson, Stephen M.↗

NASA NTRS1988

Imaging spectroscopy II; Proceedings of the Meeting, San Diego, CA, Aug. 20, 21, 1987

The conference presents papers on airborne imaging spectrometers, imaging spectrometry analysis, and spaceborne imaging spectrometers. Consideration is given to an imaging spectrometer for ocean and land remote sensing, an advanced solid-state array spectroradiometer, airborne visible/infrared imaging spectrometer design and performance, and a signal chain for the airborne visible/infrared imaging spectrometer. Other topics include imaging spectrometry as a tool for botanical mapping, the estimation of forest canopy characteristics and nitrogen cycling using lasing spectrometry, and a continuous readout photon counting imaging detector.

Vane, Gregg↗

NASA NTRS1983

Inelastic electron tunneling spectroscopy

Inelastic electron tunneling spectroscopy is a useful technique for the study of vibrational modes of molecules adsorbed on the surface of oxide layers in a metal-insulator-metal tunnel junction. The technique involves studying the effects of adsorbed molecules on the tunneling spectrum of such junctions. The data give useful information about the structure, bonding, and orientation of adsorbed molecules. One of the major advantages of inelastic electron tunneling spectroscopy is its sensitivity. It is capable of detecting on the order of 10 to the 10th molecules (a fraction of a monolayer) on a 1 sq mm junction. It has been successfully used in studies of catalysis, biology, trace impurity detection, and electronic excitations. Because of its high sensitivity, this technique shows great promise in the area of solid-state electronic chemical sensing.

Khanna, S. K.↗