Showing papers on "Ion published in 1971"
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378 citations
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367 citations
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TL;DR: In this paper, a simple collision model involving only the primary ion and a single isolated surface atom is proposed to identify surface impurity atoms, which can be used for characterizing thin films.
299 citations
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TL;DR: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: adsorption to the membranesolution interface; passage over an activation barrier to the opposite interface; and desorption into the aqueous solution.
Abstract: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: (1) adsorption to the membranesolution interface; (2) passage over an activation barrier to the opposite interface; and (3) desorption into the aqueous solution Support for this mechanism comes from a consideration of the potential energy of the ion, which has a minimum in the interface The formal analysis of the model shows that the rate constants of the individual transport steps can be determined from the relaxation of the electric current after a sudden change in the voltage Such relaxation experiments have been carried out with dipicrylamine and tetraphenylborate as permeable ions In both cases the rate-determining step is the jump from the adsorption site into the aqueous phase Furthermore, it has been found that with increasing ion concentration the membrane conductance goes through a maximum In accordance with the model recently developed by L J Bruner, this behavior is explained by a saturation of the interface, which leads to a blocking of the conductance at high concentrations
294 citations
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TL;DR: The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions as mentioned in this paper.
Abstract: The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions. The resistivity at 25°C was found to be 72 Ω‐cm, the lowest value reported for any ionically conducting oxide ceramic. The enthalpy of motion is 3.79 kcal/mole, and the transport of sodium ions takes place by an interstitialcy mechanism.
288 citations
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TL;DR: In this article, the electronic relaxation in solutions of solvated Fe3+, Mn2+ and Cr3+ is controlled by modulation of the quadratic zero field splitting interaction caused by collisions of the hydrated complex with bulk solvent molecules.
Abstract: Electronic relaxation in solutions of solvated Fe3+, Mn2+ (S=5/2) and Cr3+ (S=3/2) is controlled by modulation of the quadratic zero field splitting interaction. The modulation is caused by collisions of the hydrated complex with bulk solvent molecules. Theoretical expressions are derived for the electronic transversal and longitudinal relaxation times T 2e and T 1e and are used to interpret the E.S.R. data of these ions. The analysis yields results for the zero field splitting constants and for the mean lifetime between collisions. The latter are found to be in the range 4–9 × 10-12 s. The nuclear relaxation rate of the solvent nuclei are affected by the dipole-dipole and scalar interaction with the unpaired electrons of the paramagnetic ions. The usual equations for nuclear relaxation due to these interactions are modified to take into account the existence of several T 1e s and T 2e s. These equations are used to analyse proton relaxation data in aqueous solutions of Cr3+, Fe3+ and Mn2+. The E.S.R. and...
242 citations
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TL;DR: In this paper, the vibrational excitation of N2 molecules by resonance scattering of electrons of 2-3 eV is calculated with a compound state model, that is on the assumption that the mechanism is e+N2 to N2-to N2+e'.
Abstract: The vibrational excitation of N2 molecules by resonance scattering of electrons of 2-3 eV is calculated with a compound state model, that is on the assumption that the mechanism is e+N2 to N2- to N2+e'. The complex electronic energy of the N2- ion is treated parametrically, the essential new point being that Gamma /h(cross), the autoionization rate, varies with the separation of the nuclei. The variation comes from the dependence of the angular momentum barrier on the energy of the emitted electron. Good agreement is obtained with the experimental energy dependence of cross sections with reasonable values of the parameters. Calculations have also been done to illustrate the transition to the impulse limit as Gamma is increased, and to the compound molecule limit as Gamma is reduced.
218 citations
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TL;DR: In this paper, a model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline sample prepared by the combustion of Ti(iso-PrO)4.
Abstract: A model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline rutile sample prepared by the combustion of Ti(iso-PrO)4. It is suggested that the exterior surfaces of the rutile crystals correspond to three low index crystal planes—namely the (100), (101) and (110). Of these the first two are capable of adsorbing molecular water as ligand coordinated to Ti4+ surface ions, whereas the (110) crystal face adsorbs water dissociatively leading to the presence of equal quantities of two types of OH– ions. One of these types is associated with a surface Ti4+ ion which is five coordinate with respect to lattice oxide ions whereas the other type is bound to a surface Ti4+ ion which is only four fold oxide ion coordinate. It is possible to rationalize the observed thermal dehydroxylation and dehydration properties of the oxide and also account for its pyridine adsorption properties.
166 citations
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157 citations
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TL;DR: In this paper, the influence of a molecule's dipole moment on its ability to capture an electron into a stable bound state is examined, and it is proved that, in the fixed-nuclei approximation, a value greater than 1·625 Debye for the Dipole moment suffices to guarantee the existence of a discrete spectrum of negative ion states.
Abstract: The influence of a molecule's dipole moment on its ability to capture an electron into a stable bound state is examined. It is proved that, in the fixednuclei approximation, a value greater than 1·625 Debye for the dipole moment suffices to guarantee the existence of a discrete spectrum of negative ion states. Implications for Hartree-Fock calculations of negative ions are discussed. The interaction of electronic, vibrational and rotational motions in negative dipolar ions is studied, and conclusions are drawn for real molecules.
145 citations
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TL;DR: In this article, the pulse-height vs energy response of a surface-barrier detector was measured for the ions He, C, O, Al, S, Ni, Cu, Ag, 31 MeV, and U, 26 MeV.
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TL;DR: In this paper, a fast and very sensitive technique has been developed to determine the extent of ionic contamination of oxides in MOS capacitors, based on the measurement of the displacement current response to a slow linear ramp voltage at elevated temperatures.
Abstract: A fast, simple and very sensitive technique has been developed to determine the extent of ionic contamination of oxides in MOS capacitors. The method is capable of detecting better than 109 mobile ions/cm2 and is based on the measurement of the displacement current response to a slow linear ramp voltage at elevated temperatures. This yields an ionic displacement current peak whose area is proportional to the total mobile ionic space charge. The method is expected to be very useful for routine process and quality control applications. This technique has been used to study positive mobile charge behavior in silicon dioxide. The voltage dependence of the ionic displacement current indicates that trapping of ions occurs at the metal‐oxide interface and that ionic transport from the metal to the silicon interface is controlled by trap emission. Ion transport from the silicon to the metal interface is characterized by a single, bulk‐limited transport mechanism below 300°C with an activation energy that appears concentration dependent. Above 300°C an additional transport mechanism is observed which is slow in comparison to the primary transport mechanism.
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TL;DR: Using an energy-resolved electron beam, ionization potentials for the following free radicals have been measured: vinyl 8.95 V, allyl 8.07 V, benzyl 7.27 V as mentioned in this paper.
Abstract: Using an energy-resolved electron beam, ionization potentials for the following free radicals have been measured: vinyl 8.95 V, allyl 8.07 V, benzyl 7.27 V. For vinyl and allyl ions new measurements of thresholds for dissociative ionization give ΔHf(C2H3+) = 266 kcal/mol and ΔHf(C3H5+) = 226 kcal/mol, leading to neutral radical heats of formation ΔHf(C2H3) = 59.6 kcal/mol and ΔHf(C3H5) = 40 kcal/mol. The data for benzyl radical and ion give ΔHf(benzyl cation) = 213 kcal/mol.
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NATO1
TL;DR: In this paper, the high resolution He I photoelectron spectrum of the (a12t25)2T2 < - (a 12t26)1A1 transition in methane has been recorded and analyzed and a value has been obtained for the adiabataic ionization potential.
Abstract: The high resolution He I photoelectron spectrum of the (a12t25)2T2 < - (a12t26)1A1 transition in methane has been recorded and analyzed and a value has been obtained for the adiabataic ionization potential. The electron spectrum resulting from ionization of a t2 electron is a composite of at least three overlapping electronic bands which are separated by several tenths of an eV. These bands are the split components of the 2T2 electronic state of the CH4+ ion which is distorted by strong Jahn-Teller forces. The symmetry of the molecule in these three electronic states is believed to be, in order of increasing energy, D2d
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TL;DR: In this paper, the first experimental determinations of orbital energy spectra of electrons in chemisorption bonds were presented, and a transition density function which is essentially the local density of states in the surface region of the solid was determined.
Abstract: This work presents the first experimental determinations of orbital energy spectra of electrons in chemisorption bonds. Our method, ion neutralization spectroscopy, determines a transition density function which is essentially the local density of states in the surface region of the solid. For the particular surface formed by chemisorption of the chalcogens in ordered, surface‐crystalline arrays on Ni(100), the local density of states includes a strong component from the orbital energy spectrum of the electrons in the bonds of the surface molecules formed from the adsorbate atom and Ni atoms presented by the substrate lattice. The orbital levels of electrons in the surface bonds are broadened resonances or virtual states in whose energy range local wavefunction magnitude and hence transition probability for ion neutralization are enhanced. These orbital energy spectra, coupled with measurement of work‐function change on adsorption, suggest, in many instances, plausible identifications of local bonding str...
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TL;DR: Growth rates for ion electromagnetic cyclotron (EMC) modes are calculated for several unconventional cases of magnetospheric importance, including total absence of cold plasma and presence of artificially injected heavy ion plasma as discussed by the authors.
Abstract: Growth rates for ion electromagnetic cyclotron (EMC) modes are calculated for several unconventional cases of magnetospheric importance, including total absence of cold plasma and presence of artificially injected heavy-ion plasma. Artificial injection of a very heavy ion such as barium or cesium is likely to suppress, rather than enhance, instability in the important ion-EMC mode, while injection of a light ion like lithium should be very effective in promoting instability in the ring current outside the plasmapause.
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TL;DR: In this article, a double sheath between two plasmas is presented in which reflected particles and the initial velocities of accelerated particles are considered, and it is shown that the ratio of the ion and electron current densities can depart significantly from Langmuir's (M/M)k.
Abstract: A model of a double sheath between two plasmas is presented in which reflected particles and the initial velocities of accelerated particles are considered. The model shows that, in addition to the voltage drop across the double sheath, the ions from the plasma sac acquire kinetic energy (comparable with the electron thermal energy) in a presheath region. The ratio of the ion and electron current densities can depart significantly from Langmuir's (M/M)k.
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TL;DR: The limiting quantum yield of hydrated electron formation is a linear function of quantum energy between 313 and 228 nm, reaching φe≃ 0.9 at 228 and 214 nm.
Abstract: Excitation of the Fe(CN)64− ion in aqueous solution into the 1T1u or 1T2g excited singlet state, below 313 nm, leads to hydrated electron formation in competition with internal conversion to the lowest excited singlet 1T1g state. The limiting quantum yield of hydrated electron formation is a linear function of quantum energy between 313 and 228 nm, reaching φe≃ 0.9 at 228 and 214 nm. Above 313 nm hydrated electron formation is not observed, but photoaquation is. Dependence of Φe on scavenger (N2O) concentration is observed. The involvement of CTTS character in the process, and the role of rapid solvent rearrangement in the dissociation of the excited state, are discussed.
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TL;DR: In this paper, a study of room-temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates was made.
Abstract: A study has been made of room‐temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates. Neutron activation combined with anodic oxidation and HF stripping techniques was used to determine the proflies of the implanted ions for Ga71 and Sb121. Electrical evaluation of the implanted layers by Hall effect and sheet resistivity measurements in conjunction with layer removal techniques yielded profiles of the net electrically active species and the depth variation of mobility after annealing for 30 min in the temperature range 600°–900°C. The ion species studied were B11 (60–200 keV), Al27 (200 keV), Ga69&71 (140 and 280 keV), P31 (100–280 keV), As75 (280 keV), Sb121&123 (120 and 260 keV), and Bi209 (240 keV). The epitaxial regrowth of the amorphous phase at 600°C causes most of the implanted ions within this region to become electrically active and uncompensated for the ion species B, P, As, Sb, and Bi even for peak ion concentrations in excess of 1020 cm−3. For Al and Ga implants, the number of carriers was less than the number of implanted ions. The profiles obtained for these implantations into amorphous Si were compared with predictions based on the theory of Lindhard, Scharff, and Schiott.
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TL;DR: In this paper, the reflected fraction of sodium, potassium, and krypton ions impinging on polycrystalline silver and gold and amorphous germanium targets have been made at medium keV energies.
Abstract: Measurements of the reflected fractions of sodium, potassium, and krypton ions impinging on polycrystalline silver and gold and amorphous germanium targets have been made at medium keV energies. The reflected fraction depends strongly on mass ratio and weakly on energy. Previous calculations of ion reflection (based on random slowing-down by elastic collisions in an infinite medium) have been extended. Corrections to the calculated values due to electronic stopping and surface effects have been estimated. Agreement between measurements and calculations is satisfactory.
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TL;DR: In this paper, the theory of transient fields acting on the nucleus of an energetic ion during slowing-down in magnetized materials is treated, and the enhancement of density at the ion nucleus, of atomic electrons scattered by the ion is χ ≈ 10 2 −10 3.
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TL;DR: In this article, the self-diffusion coefficients of sodium and cesium ions in Na 2 OCs 2 O SiO 2 glasses were measured at temperatures 350-550°C.
Abstract: As an approach to the mixed alkali effect in glass, the self-diffusion coefficients of sodium and cesium ions in Na 2 OCs 2 OSiO 2 glasses were measured at temperatures 350–550°C. Electrical conductivity of the glasses and the transport number for sodium ions were also measured. The substitution of the alkali ions in the glass by different alkali ions caused the mobility of each alkali ion to decrease pronouncedly and the activation energy for migration to increase rapidly. The increase of activation energy was attributed to an increase in alkali-oxygen bond strength resulting from the presence of two kinds of alkali ions. This is related to the expectation that the activity of the alkali ions decreases when two alkali ions are mixed.
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TL;DR: In this paper, the authors considered ion heating by a strong ion−ion two-stream instability perpendicular to a magnetic field in the presence of a relatively cold electron background (Te≪miVd2) is considered.
Abstract: Ion heating by a strong ion‐ion two‐stream instability perpendicular to a magnetic field in the presence of a relatively cold electron background (Te≪miVd2) is considered. The magnetic field strength is such that the ion trajectories are straight, whereas the electrons are bound to the field lines (krLe≪1≪krLi). Theory is presented for both quasilinear and nonlinear stages of the evolution of the system for the case that the instability is electrostatic [(B2/8π) (1+β) >nmiVd2/8] and is compared with a series of computer simulation experiments. It is found that the quasilinear theory gives a fairly accurate description of spatially averaged plasma properties until the ion beams have been sufficiently modulated for ions to be trapped by the waves. In the subsequent nonlinear stage, stabilization occurs when the ion trapping period is equal to the reciprocal growth rate associated with the instability. The directed ion beam energy is mainly converted into random ion energy. The possible role of this instabil...
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TL;DR: In this paper, Sayer et al. used first-order quantal perturbation theory and the multipole Coulomb-excitation program of De Boer arid Winther as augmented by Sayer was used in analyzing the 16O ion data.
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TL;DR: In this paper, it is shown how marked effects on the state of disorder due to changes in the mass of the bombarding ion, in the flux of the impinging beam, or in the temperature an...
Abstract: Nucleation of damage centres in single crystal silicon held at room temperature and bombarded in a “random” direction with light ions is not at all times heterogeneous, as has sometimes been assumed. Homogeneous nucleation of interstitial clusters occurs at low ion fluences and this is characterized, for an extremely short period, by a linear dependence of the state of disorder on ion fluence, followed by a longer period during which disorder a (fluence)1/2. During these periods of ‘nucleation’ and ‘primary growth’ small interstitial clusters behave as unsaturable traps. For higher fluences there is a smooth transfer to a form of damage increase which is not of displacement cascade origin. In this period of ‘secondary growth’ the state of disorder varies linearly with ion fluence, and interstitial clusters behave as nucleation traps. It is shown how marked effects on the state of disorder due to changes in the mass of the bombarding ion, in the flux of the impinging beam, or in the temperature an...
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TL;DR: In this article, the metastable O+ 2D 2D ions were determined using the observation that O+(2D)+N2 has a small cross-section for forming NO+, while the ion energy dependence for both reactions has been measured within the energy range 1.0-500 eV.
Abstract: Laboratory measurements indicate that the metastable ions of O+ in reaction with N2 in the low‐energy range (14 eV) react to form principally N2+, while the ion—molecule reaction to form NO+ has a very small probability. The ground‐state O+ ion reacts mainly to form NO+. The abundance of metastable O+ 2D ions was determined using the observation that O+(2D)+N2 has a small cross section for forming NO+. The ion energy dependence for both reactions has been measured within the energy range 1.0–500 eV.
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TL;DR: In this article, the effect of thermal energy on the shape of photoionization-efficiency curves is analyzed and several methods for determining thresholds for dethermalized ionization−efficiency curves are presented.
Abstract: The effect of thermal energy on the shape of photoionization‐efficiency curves is analyzed. Several methods for determining thresholds for dethermalized ionization‐efficiency curves are presented. The assumptions and approximations used are explicitly stated for each method. The effect of thermal energy on the photoionization‐efficiency curves of some alkanes is analyzed and the results are in fair agreement with the hypothesis that thermal energy is fully effective in the dissociation of the parent ions.
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TL;DR: In this article, the branching ratio of atom pairs/ion pairs is interpreted in terms of the effective width of the adiabatic dissociation channel, compared with the spacing of the vibrational levels of the diabatic bound state.
Abstract: The primary dissociation step for alkali halide diatomics in argon has been studied in order to determine whether collisional dissociation produces ions, atoms, or a mixture of both types of products. The method is based on time‐resolved absorption spectroscopy of shock‐heated vapors. Results show that the cesium halides, and the rubidium and potassium halides, with the exception of the two iodides, dissociate essentially completely to ions; that the lithium salts and NaI and NaBr dissociate essentially completely to atoms; and that the other alkali halides (KI, RbI, NaCl, and probably NaF) dissociate to mixtures of atoms and ions, at least under some conditions. The branching ratio of atom pairs/ion pairs is interpreted in terms of the effective width of the adiabatic dissociation channel, compared with the spacing of the vibrational levels of the diabatic bound state.
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TL;DR: In this article, the photodetachment cross section of the negative ion of fluorine has been measured in the wavelength region between 2100 and 3600 \AA{}. Results were found to be in reasonable agreement with the calculated values of Robinson and Geltman.
Abstract: The absorption spectrum of the negative ion of fluorine has been observed in shock-heated vapors of CsF. The photodetachment cross section of the fluorine ion has been measured in the wavelength region between 2100 and 3600 \AA{}. Results are found to be in reasonable agreement with the calculated values of Robinson and Geltman.