Showing papers on "Ion published in 1978"

Prediction of Flatband Potentials at Semiconductor‐Electrolyte Interfaces from Atomic Electronegativities

Abstract: The electron affinities of several metal oxide semiconductors that have been used as anodes in photoelectrochemical cells are calculated using the atomic electronegativities of the constituent atoms. These electron affinities are quantitatively related to the measured flatband potentials by considering the effects of specific adsorption of potential‐determining ions (for metal oxides used in photoelectrolysis, these are usually OH− and H+). Methods are discussed for determining the pH at which net adsorbed surface charge and thus potential across the Helmholtz layer is zero (point of zero zeta potential, pzzp). This pH value is shown to correlate with the electronegativity of the metal oxides. The application of these ideas to other semiconductor‐electrolyte systems is discussed.

Potassium channels as multi-ion single-file pores.

Abstract: A literature review reveals many lines of evidence that both delayed rectifier and inward rectifier potassium channels are multi-ion pores. These include unidirectional flux ratios given by the 2--2.5 power of the electrochemical activity ratio, very steeply voltage-dependent block with monovalent blocking ions, relief of block by permeant ions added to the side opposite from the blocking ion, rectification depending on E--EK, and a minimum in the reversal potential or conductance as external K+ ions are replaced by an equivalent concentration of T1+ ions. We consider a channel with a linear sequence of energy barriers and binding sites. The channel can be occupied by more than one ion at a time, and ions hop in single file into vacant sites with rate constants that depend on barrier heights, membrane potential, and interionic repulsion. Such multi-ion models reproduce qualitatively the special flux properties of potassium channels when the barriers for hopping out of the pore are larger than for hopping between sites within the pore and when there is repulsion between ions. These conditions also produce multiple maxima in the conductance-ion activity relationship. In agreement with Armstrong's hypothesis (1969. J. Gen. Physiol. 54:553--575), inward rectification may be understood in terms of block by an internal blocking cation. Potassium channels must have at least three sites and often contain at least two ions at a time.

"Optical-sideband Cooling of Visible Atom Cloud Confined in Parabolic Well"

Abstract: An assemblage of 50 ${\mathrm{Ba}}^{+}$ ions, contained in a parabolic well, has been visually observed and cooled by means of near-resonant laser irradiation.

Progress in atomic spectroscopy

Abstract: This book presents reviews by leading experts in the field covering areas of research at the forefront of atomic spectroscopy. Topics considered include the k ordering of atomic structure, multiconfiguration Hartree-Fock calculations for complex atoms, new methods in high-resolution laser spectroscopy, resonance ionization spectroscopy (inert atom detection), trapped ion spectroscopy, high-magnetic-field atomic physics, the effects of magnetic and electric fields on highly excited atoms, x rays from superheavy collision systems, recoil ion spectroscopy with heavy ions, investigations of superheavy quasi-atoms via spectroscopy of electron rays and positrons, impact ionization by fast projectiles, and amplitudes and state parameters from ion- and atom-atom excitation processes.

Nucleation and growth of porous anodic films on aluminium

Abstract: POROUS anodic films on aluminium are of considerable interest, not only because of their important practical uses in architecture and industry but also because of their novel regular morphology. The simple explanation involving field-assisted dissolution1,2 has now been extended and an additional mechanism involving direct loss of Al3+ ions to solution has been proposed3. Ultramicrotomy4 and ion beam thinning5 of films, together with transmission electron microscopy and secondary ion mass spectrometry, have provided greater information on the film morphology and composition. Here we outline some of the more significant findings relating to the large-featured, regular films formed in phosphoric acid.

Nuclear magnetic resonance studies of the glasses in the system Na2OB2O3SiO2

Abstract: The 11B NMR spectra have been used to study the structure of glasses in the system Na2OB2O3SiO2. The fraction of BO4 units, and the fraction of BO3 units with one or two nonbridging oxygens, are measured and analyzed according to a structural model. The results indicate that: (1) for a sodium oxide to boron oxide ratio of 0.5 or less, the Na+1 ions are attracted primarily by the borate network; therefore, the ternary glasses can be viewed as binary sodium borate glasses diluted by SiO2; (2) when the sodium oxide to boron oxide ratio exceeds 0.5, the additional Na2O results in the formation of [BSi4O10]−1 units at the expense of diborate and SiO4 units. In this process, Na+1 ions are still taken up only by the borate network. After all the available SiO4 units are consumed to form [BSi4O10]−1 units, additional Na+1 ions are proportionally shared between the borate and silicate networks.

The latitudinal, diurnal, and altitudinal distributions of upward flowing energetic ions of ionospheric origin

Abstract: Upward flowing fluxes of energetic (0.5-16 keV) H+ and O+ ions are frequently observed by the ion mass spectrometer on the polar-orbiting S3-3 satellite. Data obtained on the first ∼370 orbits have been used to derive the occurrence frequency of these fluxes. The upward acceleration of ionospheric ions to keV energies is a persistent phenomenon generally occurring in a zone closely associated with the statistical auroral oval. Upward flowing ion events with flux above ∼2 × 106 keV/(cm² sec ster keV) are observed in more than 60% of the orbits. A strong dawn-dusk asymmetry is found in the frequency of occurrence with the maximum in the dusk sector. The probability of observation increases with altitude up to apogee (8000 km) indicating that the main energization takes place preferentially at altitudes above ∼1 R E.

Stochastic Ion Heating by a Lower Hybrid Wave: II

Abstract: The motion of an ion in a coherent lower hybrid wave (characterized by ‖k∥‖<<‖k⊥‖ and ω≳≳Ωi) in a tokamak plasma is studied. For ions satisfying v⊥≳ω/k⊥, the Lorentz force law for the ions is reduced to a set of difference equations which give the Larmor radius and phase of an ion on one cyclotron orbit in terms of these quantities a cyclotron period earlier. These equations exhibit stochastic behavior when the wave amplitude exceeds a threshold. The stochasticity threshold is given a simple physical interpretation. In addition, the difference equations are used to derive a diffusion equation governing the heating of the ions above the stochasticity threshold. Far above the stochasticity threshold, ion Landau damping is recovered. By including the effects of collisions, the heating rate for the bulk ions is obtained.

A potential- and time-dependent blockade of inward rectification in frog skeletal muscle fibres by barium and strontium ions.

Abstract: 1. A three-electrode voltage clamp method was used to investigate the effects of Ba and Sr ions on the inwardly rectifying K conductance of resting frog sartorius muscle fibres. 2. When Ba2+ (0.01-5 mM) was added to the control (115 mM-K+) solution the inward currents recorded during hyperpolarizing voltage steps turned off exponentially with time as the blockade by Ba2+ developed. Outward currents showed no time-dependence. 3. Ba2+ ions reduced both the instantaneous and the steady-state values of currents recorded on hyperpolarization. The blockade was potential-dependent, steady-state currents being increasingly reduced with increasing hyperpolarization. 4. The concentration-effect relation for the blockade of instantaneous currents by Ba2+ could be fitted assuming 1:1 binding of Ba2+ to a receptor, with the block being proportional to the number of Ba2+-filled receptors. The apparent dissociation constant at the holding potential (-5 mV) was 0.65 mM. Concentration-effect relations were shifted along the concentration axis to lower concentrations by hyperpolarization. The apparent dissociation constant was reduced e-fold for a 16.8 mV change in potential. 5. Increasing the [Ba]o increased the rate of onset of the blockade at a given potential. 6. The rate of onset of the blockade had a high temperature dependence (Q10 = 3.15 +/- 0.08). 7. When [K]o was doubled to 230 mM, under conditions where [K]i was also doubled, [Ba]o had to be raised approximately fourfold to produce the same degree and rate of onset of blockade. Similarly, when [K]o was decreased, the degree and rate of onset of blockade were increased for a given [Ba]o. 8. The blockade could be readily removed by removal of Ba2+ from the bathing solution. In addition the blockade which develops on hyperpolarization is removed exponentially on return to the holding potential. 9. The blockade which exists at the holding potential may be removed by a depolarizing prepulse. 10. Sr causes a similar potential-dependent blockade to that by Ba2+, but is around 400 times less effective. 11. The results have been fitted with a model assuming that the permeability mechanism is an aqueous pore with a site which binds one Ba2+ ion or two K+ ions. The site must have affinity for Ba2+ and a low affinity for K+.

A laboratory study of the reactions of N+, N2+, N3+, N4+, O+, O2+, and NO+ ions with several molecules at 300 K

Abstract: A study has been made of the rate coefficients and product ion distributions for the reactions at 300 K of the ions N+, N2+, N3+, N4+, O+, O2+, and NO+ with CH3NH2, NH3, H2S, CH3OH, H2CO, COS, O2, H2O, CH4, CO2, CO, H2, and N2 molecules listed in increasing order of their ionization energies. These measurements are intended as a contribution to stratospheric chemistry. In the binary reactions of the ions of large recombination energy with molecules of low ionization energy, multiple ion products generally result and the rate coefficients are close to gas kinetic. Conversely, the low recombination energy ions NO+ and O2+ generally undergo ternary association reactions with the large ionization energy molecules. The reactions of N2+ and N4+ are very similar, the most common mechanism apparently being direct charge transfer usually followed by fragmentation, the nitrogen–nitrogen bonds in the reacting ions remaining intact. The N+ and N3+ reactions differ from the N2+ and N4+ reactions in that they show a gr...

Ion-irradiation studies of the damage function of copper and silver

Abstract: A systematic study of the damage function of both Ag and Cu has been performed by measuring resistivity increments induced by irradiation of thin-foil specimens at 6 K with several species of ions. Beam energies were selected such that the projectiles were stopped within the target. Results were compared with theoretical calculations based on a modified Kinchin-Pease damage function. The damage efficiency (ratio of experimental-to-theoretical values) is roughly unity for irradiations with H, but decreases rapidly as the projectile mass increases, which results in harder recoil spectra. For projectiles heavier than Ne, the efficiency becomes relatively constant (0.4 for Ag and 0.35 for Cu). These results indicate that deviations from the modified Kinchin-Pease model begin to occur at energies not far above the displacement threshold energy and the efficiency becomes roughly constant for recoil energies greater than a few keV. Comparison is made with damage-rate studies for other types of irradiation.

Crystalline to amorphous transformation in ion-implanted silicon: a composite model

Abstract: The transformation of silicon to the amorphous state by implanted ions was studied both experimentally and theoretically. Experimentally, the amount of transformed silicon and the critical ion dose necessary to amorphize the entire implanted layer were determined by ESR. How the critical dose varies with ion mass (Li, N, Ne, Ar, and Kr), ion energy (20–180 keV), and implant temperature (77–475 K) was determined. Theoretically, several phenomenological models were used to analyze these data. The overlap‐damage model was used to determine the critical dose from the data, the size of the amorphous region around the ion track, and the degree of overlap damage required for amorphization. For all implants, the first ion created only predamage, while the second or third ion into the same region caused the amorphous transformation. The critical‐energy‐density model was in good agreement with the measured critical doses. This model assumed that a region would become amorphous if the energy density deposited into atomic processes by the ions exceeded the critical energy density of 6×1023 eV/cm3. For high‐temperature implantations, out‐diffusion models can explain the temperature dependence of the critical dose. Although the analysis is not completely definitive, the critical‐energy‐density model may also be valid at high temperature if diffusion of the damage energy is taken into account. This out‐diffusion of energy from around the ion track occurs via a thermally activated process. Probably, the energy moves with the out‐diffusion of the vacancies from the ion track.

Treating hair with quaternized polymers

Abstract: A quaternized polymer having recurring units of the formula ##STR1## wherein X.sup.⊖ represents an anion derived from an organic or mineral acid; R' 2 is an aliphatic radical having a maximum of 20 carbon atoms; R' 1 is an aliphatic, alicyclic or arylaliphatic radical containing a minimum of 2 carbon atoms and a maximum of 20 carbon atoms, or R' 1 and R' 2 together with the nitrogen atom to which they are attached form a ring capable of containing a second heteroatom other than said nitrogen; A represents a divalent group of the formula ##STR2## wherein x, y and t are whole numbers ranging from 0 to 11 and being such that the sum (x+y+t) is greater than or equal to 0 and less than 18, and E and K represent hydrogen or an aliphatic radical having less than 18 carbon atoms; B represents a divalent group of the formula ##STR3## wherein D and G represent hydrogen or an aliphatic radical having less than 18 carbon atoms and v, z, and u are whole numbers ranging from 0 to 11, two of them being able to be simultaneously equal to 0 such that the sum (v+z+u) is greater than or equal to 1 and lower than 18, and such that the sum (v+z+u) is greater than 1 when the sum (x+y+t) is equal to 0, and n is a whole number equal to 2 or 3. The polymers are usefully employed in cosmetic compositions for application to the hair or skin.

Discrete Variational Xα Cluster Calculations. II. Application to the Surface Electronic Structure of MgO

Abstract: Discrete variational (DV) Xα cluster method is extended to ionic crystals with inclusion of the long-ranged Coulomb potential of the ions outside the cluster. As a typical example of partially ionic crystals, the surface and the bulk electronic structures of MgO crystal are calculated. The strong electric field, the reduction in the Madelung potential and the charge redistribution on the surface are found to be important factors for the formation of the surface state. Various features of the DV-Xα cluster method, such as the size and the shape dependence of the cluster, the effect of the exterior potential and so on are investigated.

Theory of Rayleigh-Taylor bubbles in the equatorial ionosphere

Abstract: We present a theory of rising bubbles (or sharp density depletions) in the equatorial ionosphere. Both ion inertia and ion-neutral collisions are included. In the collision-dominated case the bubble velocity is independent of its size, while in the collisionless case it is proportional to the square root of the bubble size.

Mechanism of the SIMS matrix effect

Abstract: Quantization of ion microprobe mass spectrometric analyses has been complicated by the variation in the ion yield of an element contained in different matrices. This work demonstrates that, for O− and Cs+ bombardment, these ion‐yield variations are solely attributable to variations in the matrix sputtering yield. It is argued that the matrix sputtering yield determines the near‐surface concentration of the ion‐yield‐enhancing species O and Cs.

Nickel in plants: I. Uptake kinetics using intact soybean seedlings.

Abstract: The absorption of Ni(2+) by 21-day-old soybean plants (Glycine max cv. Williams) was investigated with respect to its concentration dependence, transport kinetics, and interactions with various nutrient cations. Nickel absorption, measured as a function of concentration (0.02 to 100 mum), demonstrated the presence of multiple absorption isotherms. Each of the three isotherms conforms to Michaelis-Menten kinetics; kinetic constants are reported for uptake by the intact plant and for transfer from root to shoot tissues. The absorption of Ni(2+) by the intact plant and its transfer from root to shoot were inhibited by the presence of Cu(2+), Zn(2+), Fe(2+), and Co(2+). Competition kinetic studies showed Cu(2+) and Zn(2+) to inhibit Ni(2+) absorption competitively, suggesting that Ni(2+), Cu(2+), and Zn(2+) are absorbed using the same carrier site. Calculated K(m) and K(i) constants for Ni(2+) in the presence and absence of Cu(2+) were 6.1 and 9.2 mum, respectively, whereas K(m) and K(i) constants were calculated to be 6.7 and 24.4 mum, respectively, for Ni(2+) in the presence and absence of Zn(2+). The mechanism of inhibition of Ni(2+) in the presence of Fe(2+) and Co(2+) was not resolved by classical kinetic relationships.

Exchange Interaction of Manganese 3d5 States with Band Electrons in Cd1−xMnxTe

Abstract: The influence of a system of magnetic-field-aligned paramagnetic ions on the conduction and valence band electron states is studied. A model applicable to large-gap semiconductors is presented, in which the direct influence of a magnetic field on the band electron states is neglected. This assumption allows to calculate the E(k) dependence in the presence of a magnetic field. The calculations are performed in the Kohn-Luttinger model producing a strongly anisotropic and nonparabolic structure. As an illustration of the obtained results measurements of the exciton reflection structure in a magnetic field are presented on the ternary semiconductor CdMnTe. The ratio of the exchange integrals of conduction band electrons and valence band electrons to manganese ions is estimated to α/β = −0.25. Es wird der Einflus eines Systems von im Magnetfeld ausgerichteten paramagnetischen Ionen auf die Leitungs- und Valenzbandelektronenzustande untersucht. Vorgeschlagen wird ein auf breitbandige Halbleiter anwendbares Modell, in dem der direkte Einflus des Magnetfeldes auf die Bandelektronenzustande vernachlassigt wird. Diese Voraussetzung ermoglicht die Berechnung der E(k)-Abhangigkeit bei Vorhandensein eines Magnetfeldes. Die Bcrechnungen werden ausgefuhrt im Kohn-Luttinger-Modell, welches eine stark anisotrope und nichtparobolische Struktur ergibt. Zur Illustration der erhaltenen Ergebnisse werden Messungen der Exzitonen-Reflexions-struktur im Magnetfeld fur CdMnTe-Halbleiter angefuhrt. Das Verhaltnis der Austauschintegrale von Leitungsbandelektronen und Valenzbandelektronen mit Mangan-Ionen wird zu α/β = −0,25 geschatzt.

X-ray spectroscopy of multiply-charged ions from laser plasmas.

Abstract: Original results are reported on the observation and identification of spectra of multiply-charged ions in the range of λ ≈ 1.5–15 A, which corresponds to transitions with a range of principal quantum number n. The main part of the review consists of tables with about a thousand spectral lines, which have been mainly observed in laser-plasma radiation, as well as in the solar corona and other laboratory sources at an electron temperature Te≈107°K. The accuracy for the wavelengths (Δλ) is the following: Δλ is equal to ≈ 0.0005 A for λ ≈ 2.5 A and it is equal to ≈ 0.003 A for λ ≈ 15 A. The spectral lines are considered for the following transitions: 1-n type for [H]-like ions (Z = 11–16)and [He]-like ions (Z = 11–26); 2-n type for [Li]-like ions (Z = 19–26), [Be]-like ions (Z = 22–34) and [Ne]-like ions (Z = 26–42); 3-n type [Co]- and [Ni]-like ions (Z = 73). The line-list contains about four hundred wavelengths for multiply-charged iron L-ions (Fe(XVII)-Fe(XXIV)) and is presented with identification of some of the transitions. The wavelengths and intensities of satellites of the [H]-like ions and [He]-like ions, which are caused by transitions from the doubly-excited autoionization states 2l2l′ and 1s2l2L′ of [He]-like ions (Z = 11–16) and [Li]-like ions (Z = 11–26), respectively, are also considered.

Signal modeling for ion cyclotron resonance

Abstract: A new signal model, called the rotating electric monopole signal model, is developed for ion cyclotron resonance (ICR) experiments. Unlike prior signal models, the model is applicable to all forms of ICR spectroscopy which use radio‐frequency detection methods. The signal model consists of a rotating electric monopole which is shown to be equivalent for signal generation purposes to a rotating electric dipole and for a macroscopic number of ions to a rotating electric polarization. The rotating polarization induces an alternating charge in the plates of the ICR cell and an alternating current between and an alternating voltage across the plates of the ICR cell. A noise analysis is performed, and if amplifier noise is neglected, the ICR sensitivity according to the model is found to be inversely proportional to the ion mass. This is the same sensitivity dependence as is found with conventional ICR power absorption experiments. The ICR voltage signal strength is inversely proportional to ion mass if the monitoring circuit is predominantly resistive and is independent of ion mass if the circuit is predominantly capacitive. The model clearly illustrates the parallelism between signal generation in ICR spectroscopy and signal generation in other coherent radiation spectroscopies such as NMR and microwave spectroscopy.