Space-charge distribution in a neutral plasma
Space charge distribution of electrons and ions in neutral plasma
ION DISTRIBUTION↗
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Electron-beam-charged dielectrics: Internal charge distribution
Theoretical calculations of an electron transport model of the charging of dielectrics due to electron bombardment are compared to measurements of internal charge distributions. The emphasis is on the distribution of Teflon. The position of the charge centroid as a function of time is not monotonic. It first moves deeper into the material and then moves back near to the surface. In most time regimes of interest, the charge distribution is not unimodal, but instead has two peaks. The location of the centroid near saturation is a function of the incident current density. While the qualitative comparison of theory and experiment are reasonable, quantitative comparison shows discrepancies of as much as a factor of two.
Beers, B. L.↗
Multipole correction of atomic monopole models of molecular charge distribution. I. Peptides
The defects in atomic monopole models of molecular charge distribution have been analyzed for several model-blocked peptides and compared with accurate quantum chemical values. The results indicate that the angular characteristics of the molecular electrostatic potential around functional groups capable of forming hydrogen bonds can be considerably distorted within various models relying upon isotropic atomic charges only. It is shown that these defects can be corrected by augmenting the atomic point charge models by cumulative atomic multipole moments (CAMMs). Alternatively, sets of off-center atomic point charges could be automatically derived from respective multipoles, providing approximately equivalent corrections. For the first time, correlated atomic multipoles have been calculated for N-acetyl, N'-methylamide-blocked derivatives of glycine, alanine, cysteine, threonine, leucine, lysine, and serine using the MP2 method. The role of the correlation effects in the peptide molecular charge distribution are discussed.
NASA Discipline Exobiology↗
Electrostatic charge distribution on ultrahigh vacuum cleaved silicates.
Electrostatic charge distribution on ultrahigh vacuum cleaved silicates including instrumentation, UV irradiation, half life, Paschen relation, etc
Grossman, J. J.↗
A computer program for calculating the charge distribution about a space vehicle
Computer program for charge distribution around ionospheric space vehicle
SPACE VEHICLE↗
Direct determination of the ionic charge distribution of heavy ions in Fe-rich solar energetic particle events
The first direct determination of the iron charge distribution in the energy range 0.3-1.0 MeV/nucleon during Fe-rich and He-3-rich solar energetic particle events is reported. The deterimination was made on the basis of ISEE-3 data for the event from August 1978 to October 1979. The enrichment of He-3 iron relative to oxygen was found to be directly correlated with the enrichment of He-3 to He-4. Average ion charge distributions were computed for: (1) He-3-rich periods which were also Fe-rich and had a He-3/He-4 ratio of 0.1 and (2) periods with a He-3/He-4 ratio of less than 0.1. It is found that the mean iron charge state for He-3-rich periods was in the range 19.5 (+ or - 1.5) and only 14 (+ or - 1) for the time periods with He-3/He-4 less than ratio of 0.1. The reduced data are found to be in good agreement with the theoretical predictions of Fisk (1978), suggesting a temperature in the source region above 5 million degrees K for Fe-rich and He-3-rich solar energetic particle events.
Klecker, B.↗
Charge distributions near metal-dielectric interfaces before and after dielectric surface flashover
A technique was developed for measuring surface charge distribution near interfaces without placing any measuring apparatus near the face of the samples. The results of measurements which were made on FEP Teflon and Kapton dielectrics, before and after are given flashover, with various types of interfaces. Also given are data showing mean time between flashovers for various configurations exposed to a variety of environmental conditions. Several charge transfer mechanisms are considered as a means by which stable charge distributions may be maintained near interfaces.
Robinson, J. W.↗
Muonic X-ray spectra and charge distribution in deformed nuclei plus
Muon-meson X-ray spectra and charge distribution in deformed nuclei
QUANTUM MECHANICS↗
Computer programs calculate potential and charge distributions in a plasma
Computer program determines the potential and charge distributions between two electrodes in a plasma. Solutions of the Vlasov equations for plane, cylindrical, and spherical geometries are determined and density distributions are found for each of these configurations over a range of conditions.
Jefferies, N. P.↗
Charge distribution and response time for a modulation-doped extrinsic infrared detector
The electric charge distribution and response time of a modulation-doped extrinsic infrared detector are determined. First, it is demonstrated theoretically that the photoconductive layer is effectively depleted of ionized majority-impurity charges so that scattering is small and mobility is high for photogenerated carriers. Then, using parameters appropriate to an actual detector, the predicted response time is 10 to the -8th to about 10 to the -9th s, which is much faster than comparable conventional detectors. Thus, the modulation-doped detector design would be valuable for heterodyne applications.
Hadek, Victor↗
Ionic charge distributions of energetic particles from solar flares
The effects which solar flare X-rays have on the charge states of solar cosmic rays is determined quantitatively. Rather than to characterize the charge distribution by temperature alone, it is proposed that the X-ray flux at the acceleration site also is used. The effects of flare X-rays are modeled mathematically.
Mullan, D. J.↗
Direct determination of the ionic charge distribution of helium and iron in He-3-rich solar energetic particle events
The first direct measurement of the ionic charge distribution of the helium isotopes and of iron in (He-3)-Fe-rich solar energetic particle events is reported. No significant contribution of singly ionized helium to the events is found. The two-sigma upper limits for the He-3(+)/He-3(2+) and He-4(+)/He-4(2+) ratios are 0.02 and 0.03, respectively. The mean charge state of iron found by averaging five (He-3)-Fe-rich solar energetic particle events is 19 + or -2, significantly larger than the iron charge state for energetic solar particles in normal composition events. These results appear to favor the resonant heating model proposed by Fisk (1978). It is concluded that temperatures in the source region exceed 5 million K in the events under study.
Klecker, B.↗
Critical review of electrical conductivity measurements and charge distribution analysis of magnesium oxide
The electrical conductivity sigma of MgO single crystals shows a sharp increase at 500-800 C, in particular of sigma surface, generally attributed to surface contamination. Charge Distribution Analysis (CDA), a new technique providing information on fundamental properties that was previously unavailable, allows for the determination of surface charges, their sign and associated internal electric field. Data on 99.99% purity, arc-fusion grown MgO crystals show that mobile charge carriers start to appear in the bulk of the MgO crystals between 200 and 400 C when sigma (measured by conventional techniques) is in t he 10(exp -14) to 10(exp -16) /omega/cm range. Above 500 C, as sigma increases to 10(exp -6) to 10(exp -7)/omega/cm, more charges appear giving rise to a strong positive surface charge supported by a strong internal field. This indicates that charges are generated in the bulk and diffuse to the surface by an internally controlled process. On the basis of their positive sign they are identified as holes (defect electrons). Because of the low cation content of these very pure MgO crystals, theses holes cannnot be associated with transition metal impurties. Instead, they are associated with the O(2-) sublattice, e.g. consist of O(-) states or positive holes. This conclusion is supported by magnetic susceptibility data showing the appearance of 1000 +/- 500 ppm paramagnetic species between 200-500 C. The magnetic data are consistent with strongly coupled, diamagnetic O(-) pairs below 200-500 C, chemically equivalent to peroxy anions, O2(2-), and probably associated with cation vacancies in the MgO matrix. The formation of O2(2-) in arc-fusion grown MgO crystals is very unexpected because of the highly reducing growth conditions. Their presence implies an internal redox reaction involving dissolved 'water' by which OH(-) pairs convert to O2(2-) plus H2 molecules. This redox conversion is supported by mass spectroscopic measurements of the H2 release from highly OH(-)-doped, finely divided MgO and by wet-chemical analysis of its oxidant concentration.
Freund, Friedemann↗
Iron Charge Distribution as an Identifier of Interplanetary Coronal Mass Ejections
We present solar wind Fe charge state data measured on the Advanced Composition Explorer (ACE) from early 1998 to the middle of 2000. Average Fe charge states in the solar wind are typically around 9 to 11. However, deviations from these average charge states occur, including intervals with a large fraction of Fe(sup greater or = 16+) which are consistently associated with interplanetary coronal mass ejections (ICMEs). By studying the Fe charge state distribution we are able to extract coronal electron temperatures often exceeding 2 x 10(exp 6) kelvins. We also discuss the temporal trends of these events, indicating the more frequent appearance of periods with high Fe charge states as solar activity increases.
Lepri, S. T.↗
Space-charge distribution in a neutral plasma.
Spatial distribution of electrons and ions in neutral plasma, considering charge density
SPACE CHARGE↗
The nuclear and ionic charge distribution particle experiments on the ISEE-1 and ISEE-C spacecraft
The ISEE-1 and ISEE-C instruments are designed to measure the elemental abundances, charge state composition, energy spectra, and angular distributions of energetic ions in the energy range 2 keV/charge to 80 MeV/nucleon and electrons between 75 and 1300 keV. The instrument consists of three sensor systems: (1) ULECA which is an electrostatic deflection system with rectangular solid-state detectors for the 3-560 keV/charge range; (2) ULEWATT which is a double dE/dX vs E thin-window flowthrough proportional counter/solid-state detector telescope for the 0.2-80 MeV/nucleon (Fe) range; and (3) ULEZEQ which is a combination of an electrostatic deflection analyzer and a thin-window dE/dX vs E system with thin-window proportional counter and position-sensitive solid-state detector. The applications of the instruments to solar and interplanetary phenomena and to magnetospheric acceleration and trapped particles are discussed.
Hovestadt, D.↗
Determination and representation of electric charge distributions associated with adverse weather conditions
Algorithms are presented for determining the size and location of electric charges which model storm systems and lightning strikes. The analysis utilizes readings from a grid of ground level field mills and geometric constraints on parameters to arrive at a representative set of charges. This set is used to generate three dimensional graphical depictions of the set as well as contour maps of the ground level electrical environment over the grid. The composite, analytic and graphic package is demonstrated and evaluated using controlled input data and archived data from a storm system. The results demonstrate the packages utility as: an operational tool in appraising adverse weather conditions; a research tool in studies of topics such as storm structure, storm dynamics, and lightning; and a tool in designing and evaluating grid systems.
Rompala, John T.↗
Energy and charge distribution of energetic helium ions in the outer radiation belt of the earth
The first direct measurement of the charge states of helium at energies greater than 0.5 MeV/nucleon in the outer radiation belt, obtained aboard the ISEE-1 spacecraft in 1977, is reported. High abundances of singly ionized helium, with He(+)/He(2+) = 0.4 + or - 0.1 at L = 3.3 was found during one perigee pass, with a sudden decrease of that ratio by a factor of about 10 between L = 3.3 and 3.7. It is shown that nonstationary and/or nonadiabatic processes may play an important role for the distribution of helium ions in the outer radiation belt.
Klecker, B.↗