Showing papers on "Ion published in 1995"

Selectivity coefficients for ion-selective electrodes: Recommended methods for reporting K A,B pot values (Technical Report)

Abstract: Chairman: 1989-91 R. A. Durst (USA); 1991-95 R. P. Buck (USA); Vice Chairman: 1989-91 M. Senda (Japan); Secretary: 1989-91 K. M. Kadish (USA); 1991-95 K. Tdth (Hungary); Titular Members: R. P. Buck (USA; 1989-91); M. Gross (France; 1987-91); K. Stulik (Czech Republic; 1989-95); K. Tdth (Hungary; 1987-91); M. L'Her (France: 1991-95); Y. Umezawa (Japan; 1991-95); S. Rondinini Cavallari (Italy; 1991-95); Associate Members: A. M. Bond (Australia; 1989-93); K. Cammann (FRG; 1989-95); M. Filomena Camoes (Portugal; 1987-95); A. G. Fogg (UK; 1987-95); W. Kutner (Poland; 1989-95); T. Kuwana (USA; 1989-91); W. R. Heinemann (USA; 1991-95); S. Kihara (Japan; 1991-95); W. F. Koch (USA; 1991-95); S. Rondinini Cavallari (Italy; 1987-91); G. Prabhakara Rao (India; 1989-93); H. P. van Leeuwen (Netherlands; 1985-93); J. Wang (USA; 1991-95); E. Wang (China; 1987-93); Y. Umezawa (Japan; 1987-91); M. L'Her (France; 1989-91); National Representatives: J.-M. Kauffmann (Belgium; 1992-95); H. B. Kristensen (Denmark; 1988-95); W. F. Koch (USA; 1989-91); G. E. Batley (Australia; 1985-91); B. Gilbert (Belgium; 1981-89); H.-Y. Chen (China; 1990-91); E. Lindner (Hungary; 1987-91); W. F. Smyth (Ireland; 1981-91); E. Grushka (Israel; 1981-91); T. Mussini (Italy; 1989-95); K. Izutsu (Japan; 1987-91); A. J. McQuillan (New Zealand; 1987-91); Z. Galus (Poland; 1979-91); J. Galvez (Spain; 1987-91); G. Johansson (Sweden; 1981-91); G. Somer (Turkey; 1987-91); A. K. Covington (UK; 1987-95); W. F. Koch (USA; 1989-91); 1. Piljac (Croatia; 1987-91).

Recombination line intensities for hydrogenic ions-IV. Total recombination coefficients and machine-readable tables for Z=1 to 8

Abstract: Line emissivities, effective recombination coefficients, opacity factors, departure coefficients and total recombination coefficients are calculated for hydrogenic ions with Z less-than-or-equal-to 8. Results are obtained for Cases A and B for n less-than-or-equal-to 50. Collisional transitions among individual n and l states are fully treated. Calculations were made for log N(e) = 2(1)14 for Case B and log N(e) = 2(1)10 for Case A. The electron temperature takes between nine and 12 values, lying within the range 500 to 100 000 K, depending on the ion. All results are available in the form of machine-readable files.Secondary files containing only effective emissivities for transitions for n less-than-or-equal-to 25 and total recombination coefficients are also available for use with an interactive data server. The server produces tables of relative intensities of any two specified transitions or emissivities for any transition at all temperatures and densities in the data set. Extensive facilities for two-dimensional interpolation of relative intensities, emissivities and total recombination coefficients are provided.

A three-dimensional plasma and energetic particle investigation for the wind spacecraft

Abstract: This instrument is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. The primary scientific goals are to explore the suprathermal particle population between the solar wind and low energy cosmic rays, to study particle accleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetosphere. Three arrays, each consisting of a pair of double-ended semi-conductor telescopes each with two or three closely sandwiched passivated ion implanted silicon detectors, measure electrons and ions above ∼20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV, while on the other side the incoming <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to ∼1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The telescopes provide energy resolution of ΔE/E≈0.3 and angular resolution of 22.5°×36°, and full 4π steradian coverage in one spin (3 s). Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons from ∼3 eV to 30 keV. All these analyzers have either 180° or 360° fields of view in a plane, ΔE/E≈0.2, and angular resolution varying from 5.6° (near the ecliptic) to 22.5°. Full 4π steradian coverage can be obtained in one-half or one spin. A large and a small geometric factor analyzer measure ions over the wide flux range from quiet-time suprathermal levels to intense solar wind fluxes. Similarly two analyzers are used to cover the wide range of electron fluxes. Moments of the electron and ion distributions are computed on board. In addition, a Fast Particle Correlator combines electron data from the high sensitivity electron analyzer with plasma wave data from the WAVE experiment (Bougeretet al., in this volume) to study wave-particle interactions on fast time scales. The large geometric factor electron analyzer has electrostatic deflectors to steer the field of view and follow the magnetic field to enhance the correlation measurements.

Ab initio molecular dynamics simulation of the solvation and transport of hydronium and hydroxyl ions in water

Abstract: Charge defects in water created by excess or missing protons appear in the form of solvated hydronium H3O+ and hydroxyl OH− ions. Using the method of ab initio molecular dynamics, we have investigated the structure and proton transfer dynamics of the solvation complexes, which embed the ions in the network of hydrogen bonds in the liquid. In our ab initio molecular dynamics approach, the interatomic forces are calculated each time step from the instantaneous electronic structure using density functional methods. All hydrogen atoms, including the excess proton, are treated as classical particles with the mass of a deuterium atom. For the H3O+ ion we find a dynamic solvation complex, which continuously fluctuates between a (H5O2)+ and a (H9O4)+ structure as a result of proton transfer. The OH− has a predominantly planar fourfold coordination forming a (H9O5)− complex. Occasionally this complex is transformed in a more open tetrahedral (H7O4)− structure. Proton transfer is observed only for the more waterlike (H7O4)− complex. Transport of the charge defects is a concerted dynamical process coupling proton transfer along hydrogen bonds and reorganization of the local environment. The simulation results strongly support the structural diffusion mechanism for charge transport. In this model, the entire structure—and not the constituent particles—of the charged complex migrates through the hydrogen bond network. For H3O+, we propose that transport of the excess proton is driven by coordination fluctuations in the first solvation shell (i.e., second solvation shell dynamics). The rate‐limiting step for OH− diffusion is the formation of the (H7O4)− structure, which is the solvation state showing proton transfer activity.

Metal Nanotubule Membranes with Electrochemically Switchable Ion-Transport Selectivity

Abstract: Membranes containing cylindrical metal nanotubules that span the complete thickness of the membrane are described. The inside radius of the nanotubules can be varied at will; nanotubule radii as small as 0.8 nanometer are reported. These membranes show selective ion transport analogous to that observed in ion-exchange polymers. Ion permselectivity occurs because excess charge density can be present on the inner walls of the metal tubules. The membranes reject ions with the same sign as the excess charge and transport ions of the opposite sign. Because the sign of the excess charge on the tubule can be changed potentiostatically, a metal nanotubule membrane can be either cation selective or anion selective, depending on the potential applied to the membrane.

Charge-resonance-enhanced ionization of diatomic molecular ions by intense lasers.

Abstract: We study the ionization of the ${\mathrm{H}}_{2}^{+}$ molecular ion in intense, short-pulse laser fields by numerically solving the three-dimensional time-dependent Schr\"odinger equation as a function of internuclear distance $R$. Anomalously high ionization for the molecular ion at large internuclear separations is observed for orientations parallel to the linearly polarized laser field. The ionization rate is found to exhibit maxima at large $R$, exceeding the atom limit by an order of magnitude. This is attributed to transitions between pairs of chargeresonant states which are strongly coupled by the field in diatomic molecular ions. The effect is shown to also occur in higher odd-charge diatomic molecular ions and can be attributed to field-induced nonadiabatic transitions between the charge-resonant states and electron tunneling suppression by the instantaneous Stark field of the laser.

Software for the Analysis of Emission Line Nebulae

Abstract: A set of software tools has been developed for the IRAF/STSDAS environment to derive the physical conditions in a low-density (nebular) gas given appropriate diagnostic emission line ratios; and lien emissivities given appropriate emission line fluxes, the electron temperature (Te) and density (Ne). The package is based on the five-level program developed by De Robertis, Dufour and Hunt (1987), but it includes diagnostics from a greater set of ions and emission lines, most particularly those in the satellite ultraviolet that are now observable. Two fo the applications make use of a 3-zone nebular model to derive Te and N3 simultaneously in separate zones of low-, and intermediate-, and high-ionization. These applications are useful for calculating nebular densities and temperatures directly from the traditional diagnostic line ratios, either to provide some reasonable input parameters for a more complicated physical model, or to calculate ionic abundances (or other quantities) within some simplifying assumptions. Examples of the utility of these diagnostics for real nebulae are presented.

A class of cobalt oxide magnetoresistance materials discovered with combinatorial synthesis

Abstract: The recent development of methods for generating libraries of solid-state compounds has made it possible to apply combinatorial approaches to the discovery of materials. A library of 128 members containing different compositions and stoichiometries of Ln x M y CoO δ , where Ln = Y or La and M = Pb, Ca, Sr, or Ba, was synthesized by a combination of thin-film deposition and physical masking techniques. Large magnetoresistance has been found in La x (Ba,Sr,Ca) y -CoO δ samples, whereas Y-based samples exhibit much smaller magnetoresistive effects. The magnetoresistance of the Co-containing compounds increases as the size of the alkaline earth ion increases, in sharp contrast to Mn-containing compounds, in which the magnetoresistance effect increases as the size of the alkaline earth ion decreases.

Global model of Ar, O2, Cl2, and Ar/O2 high‐density plasma discharges

Abstract: We develop a global (volume averaged) model of high‐density plasma discharges in molecular gases. For a specified discharge length and diameter, absorbed power, pressure, and feed gas composition, as well as the appropriate reaction rate coefficients and surface recombination constants, we solve the energy and particle balance equations to determine all species densities and the electron temperature. We use an expression for charged particle diffusive loss that is valid for low and high pressures and for electropositive and electronegative plasmas. We apply the model to Ar, O2, Cl2, and Ar/O2 discharges and compare with available experimental data. In Ar, we find that the ion density increases monotonically with increasing pressure, while for O2 and Cl2, the total positive ion density increases initially, then decreases as pressure is further increased. For a pure Cl2 discharge, we find that surface recombination processes are important in affecting the degree of dissociation and the negative‐ion density of the system. For mixtures of Ar and O2, we find that at a fixed ratio of Ar to O2 flowrates, the dominant ionic species changes from Ar+ to O+ as pressure is increased. When a small amount of Ar is added to a pure O2 discharge, the overall positive‐ion density increases, whereas the ratio of negative ion to electron density decreases.

Ion-acoustic solitons in electron-positron-ion plasmas

Abstract: The ion‐acoustic solitons are investigated in three‐component plasmas, whose constituents are electrons, positrons, and singly charged ions. It is found that the presence of the positron component in such a multispecies plasma can result in reduction of the ion‐acoustic soliton amplitudes.

Dynamic scaling of ion-sputtered surfaces.

Abstract: We derive a stochastic nonlinear equation to describe the evolution and scaling properties of surfaces eroded by ion bombardment. The coefficients appearing in the equation can be calculated explicitly in terms of the physical parameters characterizing the sputtering process. We find that transitions may take place between various scaling behaviors when experimental parameters, such as the angle of incidence of the incoming ions or their average penetration depth, are varied.

Gating of the voltage-dependent chloride channel CIC-0 by the permeant anion

Abstract: Chloride channels of the ClC family are important for the control of membrane excitability, cell volume regulation, and possibly transepithelial transport. Although lacking the typical voltage-sensor found in cation channels, gating of ClC channels is clearly voltage-dependent. For the prototype Torpedo channel ClC-0 (refs 11-15) we now show that channel opening is strongly facilitated by external chloride. Other less permeable anions can substitute for chloride with less efficiency. ClC-0 conductance shows an anomalous mole fraction behaviour with Cl-/NO3- mixtures, suggesting a multi-ion pore. Gating shows a similar anomalous behaviour, tightly linking permeation to gating. Eliminating a positive charge at the cytoplasmic end of domain D12 changes kinetics, concentration dependence and halide selectivity of gating, and alters pore properties such as ion selectivity, single-channel conductance and rectification. Taken together, our results strongly suggest that in these channels voltage-dependent gating is conferred by the permeating ion itself, acting as the gating charge.

Conformation of macromolecules in the gas phase: use of matrix-assisted laser desorption methods in ion chromatography.

Abstract: Conformational data for macromolecules in the gas phase have been obtained by the coupling of a matrix-assisted laser desorption ion source to an ion chromatograph. A series of polyethylene glycol (PEG) polymers "cationized" (converted to a cation) by sodium ions (Na+PEG9 to Na+PEG19) and a protonated neurotransmitter protein, bradykinin, were studied. Mobilities of Na+PEG9 to Na+PEG19 are reported. Detailed modeling of Na+PEG9 with molecular mechanics methods indicates that the lowest energy structure has the Na+ ion "solvated" by the polymer chain with seven oxygen atoms as nearest neighbors. The agreement between the model and experiment is within 1 percent for Na+PEG9, Na+PEG13, and Na+PEG17, giving strong support to both the method and the deduced structures. Similar agreement was obtained in initial studies that modeled experimental data for arginine-protonated bradykinin.

Ionic conductivity of lanthanoid silicates, Ln10(SiO4)6O3(Ln = La, Nd, Sm, Gd, Dy, Y, Ho, Er and Yb)

Abstract: Ionic conductivities have been investigated for lanthanoid silicates of the Ln10(SiO4)6O3 solid solution series and related compounds. The activation energy and conductivity at 500 °C were estimated to be 69 kJ mol–1 and 1.8 × 10–4 S cm–1 for La10(SiO4)6O3 and 71 kJ mol–1 and 1.5 × 10–4 S cm–1 for Nd10(SiO4)6O3. The a and c lattice constants of the hexagonal phase decreased with decreasing radius of the Ln3+ ion for Ln10(SiO4)6O3(Ln = La, Nd, Sm, Gd and Dy). The activation energy increased and the conductivity decreased when Ln3+ ions with smaller ionic radii were used. The sole carrier in these materials is the O2– ion.

Demonstration of a 10-hz femtosecond-pulse-driven xuv laser at 41.8 nm in xe ix

Abstract: We report the observation of a gain of approximately $\mathrm{exp}\left(11\right)$ at 41.8 nm in 8-times-ionized xenon. This extreme ultraviolet (XUV) laser is driven by a 10-Hz, 70-mJ circularly polarized femtosecond laser pulse. The laser is focused into Xe at pressures ranging from 5 to 12 torr. The laser is collisionally excited, with both the ions and electrons produced by field induced tunneling.

Atomic and molecular processes in fusion edge plasmas

Abstract: Basic Properties of Fusion Edge Plasmas and Role of Atomic and Molecular Processes (R.K. Janev). Spectroscopic Processes and Data for Fusion Edge Plasmas (W.L. Wiese). Elastic and Excitation Electron Collisions with Atoms (S. Trajmar, I. Kanik). Electron Impact Ionization of Plasma Edge Atoms (T. Mark). Electron-Ion Recombination Processes in Plasmas (Y. Hahn). Excitation of Atomic Ions by Electron Impact (S.S. Tayal et al.). Ionization of Atomic Ions by Electron Impact (D. Defrance et al.). The Dependence of Electron Impact Excitation and Ionization Cross Sections of H2 and D2 Molecules on Vibrational Quantum Number (M. Capitelli, R. Celiberto). Electronmolecular Ion Collision Processes (J.B.A. Mitchell). Energy and Angular Distributions of Secondary Electrons Produced by Electronimpact Ionization (Y.K. Kim). Elastic and Related Cross Sections for Low Energy Collisions among Hydrogen and Helium Ions, Neutrals, and Isotopes (D.R. Schultz et al.). Rearrangement Processes Involving Hydrogen and Helium Atoms and Ions (F. Brouillard, X. Urbain). Reactive Ionmolecule Collisions Involving Hydrogen and Helium (F. Linder et al.). 3 additional articles. Index.

Damage threshold for ion‐beam induced graphitization of diamond

Abstract: The critical dose for graphitization of diamond as a result of ion implantation induced damage (boron and arsenic) and subsequent thermal annealing is determined by combining secondary ion mass spectroscopy measurements, chemical etching of the graphitized layer, and TRIM simulations. Li ions are implanted as a deep marker to accurately determine the position of the graphite/diamond interface. The damage density threshold, beyond which graphitization occurs upon annealing, is found to be 1022 vacancies/cm3. This value is checked against published data and is shown to be of general nature, independent of ion species or implantation energy.

CELIAS — Charge, Element and Isotope Analysis System for SOHO

Abstract: The CELIAS experiment on SOHO is designed to measure the mass, ionic charge and energy of the low and high speed solar wind, of suprathermal ions, and of low energy flare particles. Through analysis of the elemental and isotopic abundances, the ionic charge state, and the velocity distributions of ions originating in the solar atmosphere, the investigation focuses on the plasma processes on various temporal and spatial scales in the solar chromosphere, transition zone, and corona. CELIAS includes 3 mass- and charge-discriminating sensors based on the time-of-flight technique: CTOF for the elemental, charge and velocity distribution of the solar wind, MTOF for the elemental and isotopic composition of the solar wind, and STOF for the mass, charge and energy distribution of suprathermal ions. The instrument will provide detailed in situ diagnostics of the solar wind and of accelerated particles, which will complement the optical and spectroscopic investigations of the solar atmosphere on SOHO. CELIAS also contains a Solar Extreme Ultraviolet Monitor, SEM, which continously measures the EUV flux in a wide band of 17 – 70 nm, and a narrow band around the 30.4 nm He II line.