Showing papers on "Ion published in 1974"

Site-binding model of the electrical double layer at the oxide/water interface

Abstract: A site-binding model of the oxide/aqueous electrolyte interface is introduced, in which it is proposed that the adsorbed counter ions form interfacial ion pairs with discrete charged surface groups. This model is used to calculate theoretical surface charge densities of the potential-determining (H+/OH–) ions and the potential at the Outer Helmholtz Plane, which are shown to be consistent with experimental data for oxides. An explanation is provided for the difference between silica and most other oxides in terms of the dissociation constants of the surface hydroxyl groups.

Thermodynamics of electrolytes. IV. Activity and osmotic coefficients for mixed electrolytes

Abstract: An equation has been developed with the guidance of recent statistical theories of electrolytes which is designed for convenient and accurate representation and prediction of the thermodynamic properties of aqueous electrolytes including mixtures with any number of components. The three previous papers have given the theoretical background and the evaluation of parameters for pure electrolytes of various charge types. The equation is here applied to a wide variety of mixed aqueous electrolytes at room temperature and at ionic strengths up to 6 M in many cases and occasionally even higher. The first objective is the prediction of properties of mixed electrolytes using only the parameters for pure electrolytes; on this basis standard deviations in ln ..gamma.. or phi for 69 sets of mixtures are less than 0.01 in 36 cases and above 0.05 in only seven cases all involving Cs/sup +/ or OH/sup -/. A second objective is the determination of parameters giving the differences in short-range interaction of ions of the same sign where these differ significantly from zero. As expected, these difference terms, while always small, are relatively most important for singly charged ions (and especially for OH/sup -/ and Cs/sup +/) and less important for ions ofmore » higher charge. The equations, including difference terms where known from binary mixtures with a common ion, were finally tested on 17 sets of mixtures involvingfour or more ions without any further adjustment of parameters. The standard deviation is less than 0.01 in all cases and is 0.003 or less in 11 cases. Thus these equations appear to yield accurate predictions of properties of mixed aqueous electrolytes. 5 tables.« less

Calculation of multiplet structure of core p -vacancy levels. II

Abstract: The multiplet splittings of core $p$-vacancy levels have recently been observed in various transition-metal complexes and in some rare-earth as well as actinide complexes. This paper presents the calculation of the multiplet structure of core $p$-vacancy levels in the Hartree-Fock free-ion approximation. The spin-orbit and crystal-field effects have been included. The cases studied are ${\mathrm{Mn}}^{2+}$ in Mn${\mathrm{F}}_{2}$ and the free ion ${\mathrm{Fe}}^{3+}$. For $3p$ vacancies these effects appear to be unimportant from the point of view of photoelectron spectroscopy owing to the limited resolution of the technique. For $2p$ vacancies the spin-orbit interaction is comparable to the electrostatic interaction between the electrons and both the interactions must be considered simultaneously. The conclusion is that the x-ray photoelectron spectra of inner-core electrons are more suitable for chemical analysis than those of outer electrons which, in addition, contain large correlation and many-body effects.

PVC matrix membrane ion-selective electrodes. Construction and laboratory experiments

Abstract: The experiments designed here are meant to introduce students to the methodology associated with their construction, evaluation and usage.

The effect of silver ions on the respiratory chain of Escherichia coli.

Abstract: Silver ions inhibited the oxidation of glucose, glycerol, fumarate, succinate, D- and L-lactate, and endogenous substrates by intact cell suspensions of Escherichia coli. Silver ions reacted with t...

The crystal structure of the 1:1 radical cation–radical anion salt of 2,2'-bis-l,3-dithiole (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ)

Abstract: The salt of the radical cation of 2,2'-bis-l,3-dithiole (TTF) and the radical anion of 7,7,8,8-tetracyanoquinodimethane (TCNQ), C18HaN4S4, crystallizes in the monoclinic system, space group P2~/c, with cell constants: a= 12.298 (6), b=3\"819 (2), c= 18\"468 (8) /~, fl= 104\"46 (4) °, Z=2, Dm= 1\"62 (1) and Dc=1\"615 g cm -3. Intensities for 1373 independent reflections were collected on an automated diffractometer. The structure was solved by standard heavy-atom methods and has been refined by fullmatrix least-squares calculations to an R value of 0\"044. The TTF radical cations and the TCNQ radical anions form homologous columnar stacks with interplanar spacings of 3.47 and 3.17 A, respectively. The dihedral angle between the least-squares planes of the cations and the anions is 58.5 ° and is approximately bisected by [010].

Integral cross sections for ion—molecule reactions. I. The guided beam technique

Abstract: A technique is described, that allows the measurement of integral cross sections for ion-molecule reactions and electron-transfer processes in the energy range from typically 0.1 to 20 eV (lab). Basically similar to the tandem mass spectrometer method, it uses inhomogeneous oscillatory electric fields for the storage and guidance of the primary ions and for the collection of the secondary ions. By these means a reduction of the number of excited ions in the primary beam and a good definition of the kinetic energy are obtained, together with a collection and detection probability for the secondary ions, that approaches unity for all scattering angles in a broad energy band. Tire ion beam intensity (10 5 to 10 7 ions per second) is only weakly dependent on the kinetic energy down to typically 0.15 eV (lab). The distribution of the collision energies is mainly determined by the thermal motion of the reactant gas in the scattering chamber (T ≈ 300 K). Measurements are reported for the reactions Ar + + D 2 → ArD + + D and Ne + + CO → C + Ne+O.

Energy density and time constant of heavy‐ion‐induced elastic‐collision spikes in solids

Abstract: Spike effects may influence sputtering and disordering of ion‐bombarded solids in the case of a high density of energy deposition and long lifetime. We estimate both quantities and find very pronounced variations with the atomic numbers of the projectile ion and target and the bombarding energy. The predicted energy range where sputtering should be affected is consistent with observed anomalies in the measured yield.

Spur reaction model of positronium formation

Abstract: A new model of positronium (Ps) formation is proposed. Positronium is assumed to be formed by a reaction between a positron and an electron in the positron spur. Ps formation must compete with electron‐ion recombination and electron or positron reactions with solvent molecules and scavenger impurities. It is also influenced by electron and positron solvation. The model correlates the measured Ps formation probabilities with the spur electron properties determined in radiation chemistry. The predictions of the model are shown to be in good agreement with experimental results for liquids and solids.

The anomalous rectification and cation selectivity of the membrane of a starfish egg cell.

Abstract: The cation selectivity and its relation to the inward-going rectification of the immature egg cell membrane of a starfish,Nordora punctiformis, were studied and the following results were obtained. (1) When the external saline contains usual ion species the cell membrane at rest is predominantly permeable to K ions. The K chord conductanceg k depends on the electrochemical potential of K ions, ΔV=V−E K′ and the external K concentration [K+] o by $$g_4 = A\left[ {1 + \exp \left( {\frac{{\Delta V - \Delta V_h }}{\upsilon }} \right)} \right]^{ - 1} ([K^ + ]_0 )^{\tfrac{1}{2}} $$ $$(\Delta V_h \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } - 15mV,\upsilon \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } 7mV)$$ . (2) The permeability sequence of monovalent cations and the permeability ratiosP x/PK of the cell membrane at rest obtained with membrane tpotential measurements are, T1 (1.5)>K(1.0)>Rb(0.3 to 0.4)>NH4(0.03 to 0.04)>Na, Cs. (3) Current-voltage relations obtained when the external solution contains Rb+, Cs+ or T1+ in addition to K+ show: (a) Rb+ and Cs+ decrease the K conductance and the rate of decrease becomes greater with an increasing hyperpolarization, thereby the inward-going rectification is reduced; (b) the membrane conductance shows an ‘anomalous mole fraction dependence’ in Tl-K media, i.e., the conductance becomes minimum at a certain mole fraction; and (c) the current-voltage relation often shows a transitiontype behavior suggesting that the membrane undergoes metastable states during an ncrease of hyperpolarization.

Sputtering of chemisorbed gas (nitrogen on tungsten) by low-energy ions

Abstract: Flash filament techniques and mass spectrometry have been used to measure sputtering yields for nitrogen chemisorbed on tungsten and bombarded with noble‐gas ions in the energy range up to 500 eV. The experimental results show that primarily nitrogen atoms rather than molecules are sputtered. Despite a high binding energy (∼6.7 eV/atom), we find high sputtering yields and low threshold energies. The results are found to be in reasonable agreement with simple theoretical estimates. It is sugguested that, in the investigated energy range, adsorbed nitrogen atoms are sputtered primarily as a consequence of direct knock‐on collisions with impinging and/or reflected noble‐gas ions. Estimates are also given for the yield of nitrogen atoms knocked off by sputtered tungsten atoms. This latter process is expected to dominate at much higher energies.

Laboratory studies of negative ion reactions with atmospheric trace constituents

Abstract: A flowing afterglow system has been used to measure 296°K reaction rate constants and equilibrium constants for a number of negative ion reactions with atmospheric constituents. Three‐body association reactions of O−, OH−, O2−, O3−, Cl−, CO3−, OH−(H2O), and O2−(H2O) with H2O have been measured and association rate constants for several ions with CO2 and SO2 have been measured. A number of binary reactions for these ions and their hydrates have been measured with H2O, CO2, SO2, NO2, O3, and NO. Some equilibrium constants for negative ion hydration and some equilibrium constants for solvent (H2O, CO2, and SO2) exchange to several negative ions are reported.

Clustering of water on hydrated protons in a supersonic free jet expansion

Abstract: This paper presents results concerning size distribution and growth in the gas phase of ions in the series H+(H2O)n. The measurements span a range of cluster sizes up to n =28, a domain not previously investigated quantitatively. The molecular beam sampling technique developed for this study promises to be a powerful tool in the study of ion nucleation phenomenon. Noteworthy observations include the unusual stability of the cluster with n =21 and the absence of trapped molecules of carrier gas within a cluster.

Applications of Ion Beams to Metals

Abstract: I. Implantation Modification of Superconductivity.- Superconductivity of Palladium and Pd-Alloys Charged with H or D by Ion Implantation at Helium Temperatures.- Ion Implantation in Superconducting Thin Films.- Ion Implantation in Superconducting Niobium Thin Films.- Superconducting Properties of the Dilute Magnetic Alloys Pb-Mn, Sn-Mn and Hg-Mn Obtained by Ion Implantation.- Ion Irradiation and Flux Pinning in Type II Superconductors.- II. Ion Induced Surface Reactions.- The Use of Ion Beams in Corrosion Science.- The Effects of Ion Bombardment on the Thin Film Oxidation Behavior of Zircaloy-4 and Zr-1.0 Nb.- Ion Implantation and Backscattering from Oxidized Single-Crystal Copper.- Movement of Ions During the Anodic Oxidation of Aluminum.- Friction and Wear of Ion Implanted Metals.- III. Thin Films and Interfaces.- Ion Beam Studies of Metal-Metal and Metal-Semiconductor Reactions.- Rutherford Scattering Studies of Diffusion in Thin Multilayer Metal Films.- Analysis of Compound Formation in Au-Al Thin Films.- Thin Film Interdiffusion of Chromium and Copper.- Ion Backscattering Study of WSi2 Layer Growth in Sputtered W Contacts on Silicon.- Reactions of Thin Metal Films with Si or SiO2 Substrates.- Ion Beam Induced Intermixing in the Pd/Si System.- IV. Alloying and Migration in High Fluence Implants.- Precipitation During Ion Bombardment of Metals.- Radiation Damage and Ion Behavior in Ion Implanted Vanadium and Nickel Single Crystals.- Sb-Implanted A? Studied by Ion Backscattering and Electron Microscopy.- The Changes in Electrical Properties of Tantalum Thin Films Following Ion Bombardment.- Implantation and Diffusion of Au in Be: Behavior During Annealing of a Low-Solubility Implant.- Anomalous Room Temperature Diffusion of Ion-Injected Ni in Zn Targets.- Study of Li-6 Implanted into Niobium.- V. Implanted Atom Location.- Lattice Location of Impurities Implanted into Metals.- High Substitutional Fractions in Cold Implantations of Xe and Te in Iron as Shown by Mossbauer Effect Measurements.- Valence Determination and Lattice Location via Mossbauer Spectroscopy of Gd151 Implanted into Iron.- Combined Lattice Location and Hyperfine Field Study of Yb Implanted into Fe.- Effect of Radiation Damage on Lattice Location and Hyperfine Interactions of Impurities Implanted in Iron.- Determination of Unique Site Population in Various In Implanted Non-Cubic Metals using Angular Correlations and the Nuclear Electric Quadrupole Interaction.- The Location of Displaced Manganese and Silver Atoms in Irradiated Aluminum Crystals by Backscattering.- Lattice Location Studies of 2D and 3He in W.- Location of He Atoms in a Metal Vacancy.- Simulation of Inert Gas Interstitial Atoms in Tungsten.- VI. Ion Lattice Damage.- Ion Damage Effects in Metals as Studied by Transmission Electron Microscopy.- Transmission Electron Microscopy Study of Implantation Induced Defects in Gold.- Transmission Electron Microscope Studies of Defect Clusters in Aluminium Irradiated with Gold Ions.- Dechanneling from Damage Clusters in Heavy Ion Irradiated Gold.- Heavy Ion Damage in Thin Metal Films.- Formation of Interstitial Agglomerates and Gas Bubbles in Cubic Metals Irradiated with 5 keV Argon Ions.- Observation of Ion Bombardment Damage in a Ni (100) Crystal by Helium Ion Injection.- VII. Ion Implanted Gas Buildup.- Helium Implantation Effects in Vanadium and Niobium.- Effect of He+ and D+ Ion Beam Flux on Blister Formation in Niobium and Vanadium.- Depth Distribution and Migration of Implanted Helium in Metal Foils using Proton Backscattering.- Blistering of Niobium due to Low Energy Helium Ion Bombardment Investigated by Rutherford Backscattering.- Radiation Damage and Gas Diffusion in Molybdenum Under Deuteron Bombardment.- Radiation Blistering After H+, D+ and He+ Ion Implantation into Surfaces of Stainless Steel, Mo, and Be.- VIII. Voids and Implantation Simulation of Neutron Damage.- A Review of Ion Simulation of High Temperature Neutron Damage and Void Formation.- Ion Radiation Damage.- 4 MeV Iron Atom Bombardment of Iron.- Flux (Dose Rate) Effects for 2.8 MeV 58Ni Irradiations of Pure Ni.- Heavy Ion-Induced Void Formation in Pure Nickel.- The Temperature Dependence of Irradiation Induced Void Swelling in 20% Cold Worked Type 316 Stainless Steel Irradiated with 5 MeV Nickel Ions.- Author Index.

Clustering of water on hydrated protons in a supersonic free jet expansion

Abstract: This paper presents results concerning size distribution and growth in the gas phase of ions in the series H+(H2O)n. The measurements span a range of cluster sizes up to n =28, a domain not previously investigated quantitatively. The molecular beam sampling technique developed for this study promises to be a powerful tool in the study of ion nucleation phenomenon. Noteworthy observations include the unusual stability of the cluster with n =21 and the absence of trapped molecules of carrier gas within a cluster.

Measurement of total cross sections for electron recombination with NO+ and O2 + using ion storage techniques

Abstract: The total cross section as a function of electron energy for recombination of electrons with room temperature NO+ has been measured with a trapped ion technique. Measurements were made in the electron energy range 0.045–4 eV with an energy resolution between 0.045 and 0.120 eV, and the cross sections, which showed some structure, ranged from 1.25 × 10−14 cm² at the lowest energy to 1.7 × 10−16cm² at the highest energy. Similar measurements were made on O2+, the species used to calibrate the apparatus geometry. A Maxwellian distribution of electron velocities was used with the measured cross sections to calculate rate constants, giving values extending to electron temperatures as high as 40,000°K. Comparison with previously measured rate coefficients at lower temperatures is quite satisfactory.

Nonlinear effects in heavy-ion sputtering

Abstract: To test the suggestion that an enhancement of sputtering occurs in very dense collision cascades, the sputtering yield per atom was compared for atomic and molecular ions. In all cases tested, the yield per atom was higher for the molecular ions. This effect is the more pronounced the heavier the projectile and the target. In the molecular cases the overlapping cascades have higher energy densities than those initiated by the atomic ions; our results, therefore, support the suggestion of a sputtering enhancement in dense cascades.

Compaction of ion‐implanted fused silica

Abstract: Ion‐bombardment‐induced compaction of fused silica is measured using a cantilever plate technique for H, He, O, Ne, and A ions with a variety of ion energies. A phenomenological theory is developed which is based on the superposition of two independent compaction mechanisms, one proportional to the density of energy deposited into atomic collisions and the other dependent on the density of energy deposited into electronic excitations. All the present experimental data can be fit to within experimental error with the model using only three adjustable parameters and ion‐energy partitioning calculations. Further substantiation of the present energy partitioning calculations and model are provided by showing the proportionality between the density of energy deposited into atomic collisions and other workers' published results for ion‐bombardment‐induced index‐of‐refraction changes in quartz and fused silica. It is concluded that the atomic‐collision‐induced‐compaction and index‐of‐refraction changes are ion independent. Finally, a dose‐rate dependence of the ionization‐induced compaction is noted for the first time.

Covalent bonding of Mn2+ ions in octahedral and tetrahedral coordination

Abstract: This paper is divided into four parts: The first part (Sec. I) contains a brief review of different assumptions made by several authors for the numerical values of the free Mn2+ ion parameters. It is shown that if only the Racah parameters B and C are taken into account, then the Orgel‐Griffith choice B=960 cm−1, C=3325 cm−1 seems to be the best one. Tanabe and Sugano's figures lead to errors as high as 3800 cm−1. Adding only the Racah‐Trees correction α does not seriously improve the fitting of levels 4G, 4D, and 4F because a singular set of equations is then obtained. An exact experimental agreement can be obtained for all quartet levels by simultaneously using the Racah‐Trees correction α and the seniority correction β. The best fit values of the adjustable parameters relevant to the Mn2+ ion are given; it is found that α and β do not differ very much from Shadni's values. Section II deals with the well‐known use of the two normalization parameters Nt, Ne for describing covalent bonding. A routine meth...

Near thermal energy charge transfer reactions of rare gas ions with diatomic and simple polyatomic molecules: The importance of Franck-Condon factors and energy resonance on the magnitude of the rate constants

Abstract: Charge transfer rate constants for reactions of He+, Ne+, Ar+, Kr+, and Xe+ with N2, O2, CO, NO, CO2, N2O, and CH4 were measured using an ion cyclotron resonance spectrometer. The absolute values of the rate constants were within the upper limit predicted from the Gioumousis‐Stevenson orbiting theory for ion‐molecule reactions. The magnitudes for the charge transfer rate constants are discussed with respect to (1) the availability of an energy level of the molecular ion resonant with the recombination energy of the rare gas ion, and (2) the value of the Franck‐Condon factor connecting this energy level of the molecular ion with the molecular neutral.

Temperature dependence of some ionospheric ion-neutral reactions from 300°–900°K

Abstract: A flowing afterglow system that operates from 300° to 900°K has been used to measure the temperature dependence of a number of aeronomically important reaction rate constants over this temperature range. This extends previous measurements in an earlier system that operated up to 600°K. The reactions measured include O+ with N2, O2, and CO2; N+, N2+, and CO2+ with O2; O2+ with NO; and He+ and He2+ with N2. The measurements are compared with the previous measurements that exist and with measurements of rate constants as a function of ion kinetic energy alone.

Study of the structure of molecular complexes. VIII. Small clusters of water molecules surrounding Li+, Na+, K+, F−, and Cl− ions

Abstract: The two‐body Hartree‐Fock potential for the ion‐water interaction and the two‐body Hartree‐Fock potential for the water‐water interaction have been used in the pairwise additivity approximation to study the Li+(H2O)n, the Na+(H2O)n, the K+(H2O)n, the F−(H2O)n, and the Cl−(H2O)n complexes, where n =2,3,4, ⋯ ,10. The complex configurations have been constrained to have either symmetrical geometries around the central ion or to be free to assume the lowest energy configuration. For n smaller than 5 (depending on the specific ion in consideration), the symmetrical configuration is the lowest energy configuration. For higher values of n, some of the water molecules tend to form a second shell of solvated water around the ion. The configurational optimalization was carried out only at T =0°K; but for a small cluster containing only four molecules of water, calculations have been performed at T =298°K. From the study at 298°K we have computed the correlation functions gI–O, gI–H, gO–O, gO–H, and gH–H (where the ...

A powerful injector of neutrals with a surface-plasma source of negative ions

Abstract: The operation of surface plasma sources for negative ion beams is described. A diagram shows the dependence of the H/sup -/ current density inside the emission slit on the discharge current under optimized conditions with a plasma layer thickness of 0.5 mm. Various parameters of the source are discussed. (MOW)