Search NASA⌕ Search

SEARCH · Search NASA

Results for “ELECTRON SPECTRA”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

High Resolution UV Spectroscopy for Solar System Exploration

A new generation of high resolution UV imaging spacecraft (Polar, Galileo, HST) are studying the airglow and aurora of the Earth and the jovian planets. To keep pace with these technological improvements we have developed a laboratory program to provide electron collision cross sections of the major molecular planetary gasses. Molecular spectra under optically thin conditions have been measured with a high resolution UV spectrometer in tandem with an electron impact collision chamber. The results of various studies are reported in this paper.

spectrometry UV imaging electron cross sections mo↗
NASA NTRS1981

High resolution X-ray spectra of solar flares. V - Interpretation of inner-shell transitions in Fe XX-Fe XXIII

The paper examines high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee (1976), electron temperatures as a function of time for two large class X flares are derived. These temperatures are deduced from intensities of lines of Fe XXII, Fe XXIII, and Fe XXIV. The determination of the differential emission measure between about 12-million and 20-million K using these temperatures is considered. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed.

Doschek, G. A.↗
NASA NTRS1985

Observation of adsorbate-induced surface states by elastic electron tunneling spectroscopy

Electronic structure induced by adsorbates at the interface of Al/AlOx/Au tunnel junctions has been observed by elastic electron tunneling spectroscopy. Strong structures appearing in the tunneling spectra above approximately 1 eV after exposure to I, Hg, Bi, and organohalides, have been interpreted in terms of adsorbate-induced surface states. The spectroscopic capabilities of elastic electron tunneling spectroscopy may be useful in the area of chemical detection. In the broader sense, the observation of adsorbate-induced unoccupied electronic states below the vacuum energy, makes elastic electron tunneling spectroscopy a potentially useful technique for the study of surfaces.

Leduc, H. G.↗
NASA NTRS1976

Observations of energetic Jovian electrons and protons

The Goddard/University of New Hampshire experiment aboard Pioneers 10 and 11 used high and low energy telescopes to measure the nucleon and electron components of the Jupiter magnetosphere. Proton energy spectra are of the form E to the -4th in the outer region and become more complex in the inner region. Particle absorption by several of Jupiter's satellites is an important effect which clearly establishes that radial diffusion is the dominant acceleration process in this region. Observed electron bursts or increases were typically several hundred times the normal quiet-time electron flux, resulting in the quasi-continuous presence of these electrons in interplanetary space. It is suggested that Jupiter could be the source of most of the ambient low energy electrons in the heliosphere.

Mcdonald, F. B.↗
NASA NTRS1992

Observations of plasma waves in the solar wind interaction region of Comet Giacobini-Zinner at high time resolution

High-time-resolution spectra of plasma wave emissions detected in the interaction region of Comet Giacobini-Zinner with the solar wind reveal a wave phenomenology much more complicated than first reported. Spectra often exhibit three or more independent peaks, which become more prominent the deeper into the interaction region the spacecraft traversed. The main peaks correspond to whistler emissions below the electron cyclotron frequency, a midfrequency peak near the maximum Doppler shift frequency for waves with k lambda(D) = 1, a high-frequency peak above the Doppler shift maximum frequency, and electron plasma oscillations at the plasma frequency. Similar multipeaked spectra are also observed downstream from weak shocks at Earth, which suggests that the plasma wave generation mechanisms responsible need not require particle populations created by photoionization.

Moses, S. L.↗
NASA NTRS1990

On the dependence of solar flare X-ray spectral line intensity ratios of highly ionized sulfur, calcium, and iron on electron temperature, differential emission measure, and atomic physics

This paper focuses on what can be learned about the emission measure distribution and certain atomic physics parameters from spectral lines of highly ionized ions of sulfur, calcium, and iron that appear in solar flare spectra. The particular lines chosen for analysis allow the electron temperature to be determined independently of the assumption of ionization equilibrium. An attempt is made to find emission measure models based on selected functional dependences of emission measure on temperature that reproduce the observed temperatures deduced from spectral line ratios as well as the relative intensities of resonance lines of different elements.

Doschek, G. A.↗
NASA NTRS1975

Interpretation of recent positron-electron measurements between 20 and 800 MeV

Recently measured positron and negatron spectra are discussed with regard to the problem of solar modulation. At energies above 180 MeV, the spherically symmetric Fokker-Planck equation with a diffusion coefficient proportional to particle rigidity provides reasonable fits to both the positron and total electron data. At energies below 180 MeV, the data are consistent with a continuation of the same diffusion coefficient and a local source of negatrons or with a change in the diffusion coefficient to a constant value.

Pellerin, C. J.↗
NASA NTRS1973

The retarding-potential analyzer on Atmosphere Explorer.

A planar retarding-potential analyzer will be included in each of the Atmosphere Explorer (AE) payloads. The primary functions of the instrument are to supply ion-temperature and ion-concentration data, which it will do at least once every 40 km of flight path in the region of interest with an expected accuracy of better than 2%. In addition, the instrument will determine ion-drift velocities and energy spectra of both the thermal and suprathermal electrons. During eclipse, negative-ion concentrations greater than 0.3/cu cm can be detected, though the normal positive-ion sensitivity is approximately 1.5 ions per cu cm. Changes in the ion concentration along the flight path greater than 0.1% can be monitored with a spatial resolution of less than 40 m.

Hanson, W. B.↗
NASA NTRS1976

Lyman-alpha emission from nonthermal proton beams

Nonthermal fast protons penetrating an atmosphere containing neutral hydrogen will produce some nonthermal fast neutrals which will radiate Doppler-shifted photons. The hydrogen line profiles observed from such an atmosphere will thus have nonthermal, partially polarized wings that contain information on the flux, energy spectrum, and direction of the incident proton beam. This paper develops the theory of this effect and applies it to proton beams from impulsive solar flares impacting on the sun's atmosphere. Calculations of the L-alpha profile from the region of impact have been made for the Vernazza-Avrett-Loeser solar atmosphere assuming proton energy fluxes and power-law spectra similar to those inferred for the electron beams believed responsible for hard X-ray bursts. The resulting profiles show that the effect should be detectable and that it could serve as a diagnostic for flare protons near their place of origin on the sun.

Orrall, F. Q.↗
NASA NTRS1980

Energetic particle penetrations into the inner magnetosphere

The nose structures observed on 90-deg pitch angle ion spectrograms characteristic of energetic particle injection into the ring current region of the inner magnetosphere in the afternoon to midnight sector are examined in detail on the basis of Explorer 45 data. A statistical analysis of the time dependence of nose structures yields a highest probability of occurrence at around 2000 MLT, and most events are found to occur on successive passes. The appearance of nose events is also related to an enhancement or change in configuration of the geoelectric field which alters magnetospheric convection patterns to drive an ion front close to the earth, where it can be observed by Explorer 45. The observed characteristics of nose structures are interpreted in terms of adiabatic charged particle motions in the magnetosphere in a Volland-Stern convection electric field model, which is also applied to explain the energy spectra and dispersion in penetration distances of electrons and ions observed in the postmidnight to morning sectors.

Ejiri, M.↗
NASA NTRS1980

Iodine monofluoride emission spectrum and formation kinetics in electron-beam-produced plasmas

The observation of intense blue-green spontaneous emission attributed to IF from electron-beam-excited Ar/CF3I/NF3 gas mixtures is reported. Intense emission from a structured band centered at a wavelength of 484 nm was observed when mixtures of 2000-4000 Torr AR (or He or Ne), 3 Torr CF3I and 1 Torr NF3 (or F2) were irradiated with a 3-nsec FWHM electron beam. Analysis of ICl and IBr spectra, which the present spectrum closely resembles, indicates that the 484-nm emission originates from the E to A 3 pi 1 transition of IF. Examination of the time dependence of metastable IF and I2 emission reveals that the IF (E) level is formed primarily by excitation transfer from metastable I(4P) states. The fluorescence efficiency of the E-A transition and the radiative lifetime of the metastable IF (E) state are estimated to be approximately 6% and 15 nsec, respectively, and it is suggested that metastable IF is an attractive candidate for a blue-green laser.

Hutchison, S. B.↗
NASA NTRS1980

Near-infrared spectral imaging Michelson interferometer for astronomical applications

The design and operation of an imaging Michelson interferometer-spectrometer used for near-infrared (0.8 micron to 2.5 microns) spectral imaging are reported. The system employs a rapid scan interferometer modified for stable low resolution (250/cm) performance and a 42 element PbS linear detector array. A microcomputer system is described which provides data acquisition, coadding, and Fourier transformation for near real-time presentation of the spectra of all 42 scene elements. The electronic and mechanical designs are discussed and telescope performance data presented.

Wells, C. W.↗
NASA NTRS1983

Accretion powered X-ray pulsars

The current theoretical understanding of the properties of X-ray pulsars is assessed through a comparison with unified descriptions of 14 such systems, extending over six orders of magnitude in luminosity, in whose phase averaged spectra the only notable trend is a less abrupt high energy cutoff in the lower luminosity systems. Detailed pulse phase spectroscopy is given for five of the systems. A reexamination of the pulse phase spectra of 4U 0115 + 63 has uncovered electron cyclotron lines at 11.5 and 23 keV that appear to be in absorption at pulse peak and in emission during an interpulse. Spectral hardening regions such as those from Her X-1 are a common feature in the low energy pulse of many pulsars, and may represent the passage of the magnetic axis through the observer's line of sight. Attention is given to the nature of the beaming from Her X-1, and it is concluded that a pencil beam configuration represents the simplest explanation of the overall properties of the pulse.

White, N. E.↗
NASA NTRS1984

Reduction and analysis of data from experiment CAI on the IMP-8 mission

The Caltech Electron/Isotope Spectrometer (EIS) on the Interplanetary Monitoring Platform 8 (IMP-8) has provided precise measurements of the energy spectra and time variations of low energy electrons (0.16 to 6 MeV), the isotopes of hydrogen and helium (approximately 2 to 40 MeV/nucleon), and the elements from lithium through oxygen (approximately 5 to 50 MeV/nucleon) in energetic particle fluxes of solar, galactic, interplanetary, and magnetospheric origin since 1973. The accomplishments that have resulted from EIS measurements during the period March 24, 1980 to December 31, 1984 are summarized.

Stone, E. C.↗