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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Hybrid theory calculation of electron-N2 scattering at 5 and 10 eV

Hybrid theory results pertaining to e-N2 scattering have been evaluated for differential elastic and first vibrational excitation cross sections at 5 and 10 eV. Comparison with the recent experiment of Chutjian, Srivastava, and Trajmar is good (1976), although there is an indication that the calculated nonresonant (adiabatic-nuclei) contribution is somewhat too small. A short discussion engendered by this point is given.

Chandra, N.↗
NASA NTRS1985

Theory and calculation of resonances and autoionization of two-electron atoms and ions

Techniques for calculating the electron scattering from one-electron hydrogen-like targets on the basis of the Feshback formalism, are discussed. The principal similarities between resonance parameters in the Feshbach formalism and the corresponding Breit-Wigner quantities, are described in detail. Special attention is devoted to a description of the Fano line shape parameter q, and a technique for formulating it in terms of a projector operator is proposed. The theoretical methods are illustrated by numerical calculations for 1S, 3P, and 1D states of H(-) below the first excited threshold of the target atom. Calculations of 1,3S 1,3P, 1,3D states for He are also presented.

Temkin, A.↗
NASA NTRS1988

Further study of a new dispersion relation for electron-atom scattering

A recently proposed dispersion relation (DR) is tested for e-He scattering; the results show that the new DR is not satisfied. Therefore, the analytic structure of the difference amplitude, previously assumed to be nonsingular, is investigated on the negative scattering energy axis. Even under severe approximations, the difference amplitude contains both poles and branch points. This suggests, however, a useful approximation of these contributions to the DR which gives very satisfactory agreement in both e-H and e-He scattering.

Bhatia, A. K.↗
NASA NTRS1995

Screening Effects on Nonrelativistic Bremsstrahlung in the Scattering of Electrons by Neutral Atoms

Atomic screening effects on nonrelativistic electron-atom bremsstrahlung radiation are investigated using a simple analytic solution of the Thomas-Fermi model for many-electron atoms. The Born approximation is assumed for the initial and final states of the projectile electron. The results show that the screening effect is important in the soft radiation region and is decreasing with increasing radiation. These results help provide correct information about the behavior of bound electrons in the target atom in bremsstrahlung processes.

Jung, Young-Dae↗
NASA NTRS1991

Synoptic maps constructed from brightness observations of Thomson scattering by heliospheric electrons

Observations of the Thomson scattering brightness by electrons in the inner heliosphere provide a means of probing the heliospheric electron distributions. An extensive data base of Thomson scattering observations, stretching over many years, is available from the zodiacal light photometers on board the two Helios spacecraft. A survey of these data is in progress, presenting these scattering intensities in the form of synoptic maps for successive Carrington rotations. The Thomson scattering maps reflect conditions at typically several tenths of an astronomical unit from the sun. Some representative examples from the survey in comparison with other solar/heliospheric data, such as in situ observations of the Helios plasma experiment and synoptic maps constructed from magnetic field, H alpha and K-coronameter data are presented. The comparison will provide some information about the extension of solar surface features into the inner heliosphere.

Hick, P.↗
NASA NTRS1979

Diffuse Jovian aurora influenced by plasma injection from Io

The paper demonstrates that the broad band of whistler-mode waves observed within the high density torus surrounding Io is consistent with electron cyclotron generation. Cyclotron resonant instability of Jovian energetic electrons is enhanced due to the lower resonant electron energy within the equatorial high density plasma torus surrounding the orbit of Io. The higher energy resonant electron scattering and the corresponding energetic electron lifetimes indicate that an efficient local acceleration process is required to replenish the precipitating relativistic electrons. Calculated energy deposition into the Jovian atmosphere should provide a dominant source of middle atmospheric ionization and excite a continuous band of diffuse auroral emission. It is suggested that the diffuse Jovian aurora should be influenced by the variable volcanic activity on Io which is thought to be an important source of plasma, since the cyclotron scattering process is strongly influenced by the ambient equatorial thermal plasma density.

Thorne, R. M.↗
NASA NTRS1992

Results of examination of silvered Teflon from the Long Duration Exposure Facility

A significant effort to determine the effects of low earth orbit (LEO) exposure on silver backed fluorinated ethylene-propylene (FEP) blankets from the Long Duration Exposure Facility (LDEF) was performed, and the results of this investigation are described. Extensive measurements of surface, optical, chemical, and mechanical properties were conducted. Effects of contamination and erosion rates of the FEP layer were determined. Specific results are reported on solar absorptance, thermal emittance, diffuse reflectance, cross sectional microphotography, secondary ion mass spectroscopy, electron scattering for chemical analysis, scanning electron microscopy, percent elongation, and tensile strength. These measurements show the effects of two distinctly different exposure environments, solar exposure, and simultaneous atomic oxygen (AO) and solar exposure.

Rousslang, Ken↗
NASA NTRS1980

Elastic scattering and vibrational excitation of CO2 by 4, 10, 20 and 50 eV electrons

Elastic and vibrationally inelastic differential, integral and momentum-transfer cross sections for electrons scattered by CO2 molecules are reported at 4, 10, 20 and 50 eV impact energies. The elastic cross sections are placed on an absolute scale by means of a relative flow technique. The inelastic cross sections are normalised to the elastic ones by using the inelastic to elastic intensity ratios. Data are reported for up to ten features in the 0.0 to 0.4 eV energy-loss region.

Register, D. F.↗