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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

(abstract) Electron Excitation of the H 2 (...) Continuum in the Vacuum Ultraviolet

Planetary exploration has pointed out the need for accurate electron impact excitation cross sections for H 2 . The quantum yield in the threshold energy region between vacuum ultraviolet (VUV) emission production by the band systems of the singlet and triplet states and dissociative production of fast H(1s) atoms by the triplet states is essential for energy budget modeling in planetary atmospheres and astronomy.

electron↗
NASA NTRS1974

Vacuum ultraviolet holography

The authors report the first demonstration of holographic techniques in the vacuum ultraviolet spectral region. Holograms were produced with coherent 1182 A radiation. The holograms were recorded in polymethyl methacrylate and read out with an electron microscope. A holographic grating with a fringe spacing of 836 A was produced and far-field Fraunhofer holograms of sub-micron particles were recorded.

Bjorklund, G. C.↗
NASA NTRS1995

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3x10(exp 17) and 9x10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Meyer, Scott Andrew↗
NASA NTRS1995

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Meyer, Scott Andrew↗
NASA NTRS1995

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Meyer, Scott Andrew↗
NASA NTRS1981

Absorption spectra of typical space materials in the vacuum ultraviolet

In order to develop a data base for potential optical degradation of space vacuum ultraviolet instruments, the collected volatile condensed material (CVCM) transmittance was measured in the wavelength region from 115 nm to 300 nm. The parent outgassing materials included: the adhesives, Ablebond 36-2, Trabond BB-2116, EA-9309, and Scotchweld 2216; the paints, Chemglaze Z-306, Z-306 over 9922 primer, Z-306 over AP-131 primer, Cat-A-Lac 463-3-8, 463-3-8 over primer, 3M Nextel 401-C10, and 401-C10 over 901-P1 primer; the resins, Fiberite 934, Solithane 113/C113-300 Formulation no. 1, and 113/C113-300 Formulation no. 8; the lubricants, Lube-Lok 4306 and RT/Duroid 5813; and the double-sided adhesive tape 3M-415. The effect of thermal vacuum conditioning of selected materials was also studied. The transmittance measurements were used to calculate the absorption coefficient for each of 28 different source materials versus wavelength.

Muscari, J. A.↗
NASA NTRS1966

Ion chambers simplify absolute intensity measurements in the vacuum ultraviolet

Single or double ion chamber technique measures absolute radiation intensities in the extreme vacuum ultraviolet region of the spectrum. The ion chambers use rare gases as the ion carrier. Photon absorbed by the gas creates one ion pair so a measure of these is a measure of the number of incident photons.

Sampson, J. A. R.↗
NASA NTRS2006

Solar CIV Vacuum-Ultraviolet Fabry-Perot Interferometers

Aims: A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (PPI) is designed for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155 nm). Methods: The integral part of the CIV narrow passband filter package (with a 2-10 pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157 nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The static interferometer of the filter is envisioned as being hudt using a set of fixed MgF2 plates. The four-mirror prefilter is designed to have dielectric multilayer n-stacks employing the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2 pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Results. Spectro-polarimetry observations of the transition region CIV emission can be performed to increase the understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where most of the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Designs of multiple VUV FPIs can be developed for integration into future orbiting solar observatories to obtain rapid cadence, spectral imaging of the transition region.

Gary, G. Allen↗
NASA NTRS2009

CIV Polarization Measurements using a Vacuum Ultraviolet Fabry-Perot Interferometer

Marshall Space Flight Center's (MSFC) is developing a Vacuum Ultraviolet (VUV) Fabry-P rot Interferometer that will be launched on a sounding rocket for high throughput, high-cadence, extended field of view CIV (155nm) measurements. These measurements will provide (i) Dopplergrams for studies of waves, oscillations, explosive events, and mass motions through the transition region, and, (ii), polarization measurements to study the magnetic field in the transition region. This paper will describe the scientific goals of the instrument, a brief description of the optics and the polarization characteristics of the VUV Fabry P rot.

West, Edward↗
NASA NTRS1988

Fluorescence yields from photodissociative excitation of HCOOH, HCOOCH3, and CH3COOH in the vacuum-ultraviolet region

The photoexcitation processes of HCOOH, HCOOCH3, and CH3COOH were studied in the vacuum-ultraviolet region by using synchroton radiation and a pulsed discharge lamp as light sources. The absorption and fluorescence cross sections of these molecules were measured in the 106-250-nm region. Fluorescences were detected from photoexcitation of HCOOH and HCOOCH3, but not from CH3COOH. Fluorescence produced at 123.9 nm was dispersed and identified as the excited OH and HCOO radicals. Fluorescence quantum yields of HCOOH and HCOOCH3 increase with decreasing excitation wavelengths with maxima of 5 and 0.3 percent at 106 nm, respectively.

Suto, Masako↗
NASA NTRS2005

Outgassing Measurements for Three Materials, Combined with Vacuum Ultraviolet Radiation Illumination of the Volatile Condensable Materials

The photolysis of three organic materials, by vacuum ultraviolet (VUV) radiation, has been quantified using 15-MHz temperature-controlled quartz microbalances (TQCM's). The rate at which molecular species, released from the individual samples, condensed on two TQCM s was measured for periods of up to 139.9-hours. The individual samples were heated in an effusion cell and the emitted molecular species collected on a pair of TQCM's which were maintained at -40 degrees Celsius. At several points during the deposition measurement, the deposition surface of one TQCM was illuminated by a 30 Watt deuterium lamp, and the loss of material from that surface was observed. V W illumination of the TQCM, concurrent with condensation, reduced the rate that material was lost from the deposition surface. These measurements present a contrasting picture of molecular deposition, in the presence of VUV, to that presented by other investigators who observed an enhanced rate of molecular deposition, when the deposition surface was illuminated by VUV.

Albyn, Keith↗
NASA NTRS2000

Steady State Vacuum Ultraviolet Exposure Facility With Automated Calibration Capability

NASA Glenn Research Center at Lewis Field designed and developed a steady state vacuum ultraviolet automated (SSVUVa) facility with in situ VUV intensity calibration capability. The automated feature enables a constant accelerated VUV radiation exposure over long periods of testing without breaking vacuum. This test facility is designed to simultaneously accommodate four isolated radiation exposure tests within the SSVUVa vacuum chamber. Computer-control of the facility for long, term continuous operation also provides control and recording of thermocouple temperatures, periodic recording of VUV lamp intensity, and monitoring of vacuum facility status. This paper discusses the design and capabilities of the SSVUVa facility.

Stueber, Thomas J.↗
NASA NTRS1972

Vacuum-ultraviolet spectrum of neutral boron /B I/.

Use of a hollow-cathode light source to produce the vacuum-ultraviolet spectrum of B I. One transition is resolved, and four transitions have been remeasured to a higher accuracy than previously because of the sharper lines emitted by the hollow-cathode light source. A revised value for one transition term results from these measurements.-

Goorvitch, D.↗