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The experiment of 6.5-22.5 keV C-, O- and F- ions scattering on water covered Si(111) surface has been performed. It is found that the positive-ion fraction is very low and increases monotonically as a function of perpendicular exit velocity and exit angle. In particular, the negative-ion fraction increases monotonically with perpendicular exit velocity for specular scattering, and for a given incident energy the angle dependence of the fraction is nonmonotonic. We interpret the observed positive ions in terms of inelastic binary collision, and adopt a modified resonant charge transfer model to calculate the bell shaped negative-ion fraction. We find that the neutral yield at short ion-surface distance is nonzero and obeys well an exponential dependence. It strongly indicates that a dynamical equilibrium for negative ion formation is never achieved at short distances, and the band gap effect on charge transfer can be neglected to a large extent in this relatively high energy region. (C) 2016 Elsevier Ltd. All rights reserved.

Water–Cu(110) interaction is of particular importance during the routine use of graphene-based devices. In this work, water adsorption, dissociation, and desorption at elevated temperatures have been well studied using the time-of-flight ion scattering technique. It is found that water adsorption meets the first-order Langmuir adsorption model at room temperature. The variation of the ratio between residual O and H on the surface with temperature has been well determined, which profoundly reveals the dynamical process of surface composition. Furthermore, the change in the surface electronic properties has been probed by measuring negative-ion fractions as a function of the annealing temperature for fast ion scattering. It suggests that charge transfer is a very sensitive method for studying specific electronic processes in real time.

Water-Cu(110) interaction is of particular importance during the routine use of graphene-based devices. In this work, water adsorption, dissociation, and desorption at elevated temperatures have been well studied using the time-of-flight ion scattering technique. It is found that water adsorption meets the first-order Langmuir adsorption model at room temperature. The variation of the ratio between residual O and H on the surface with temperature has been well determined, which profoundly reveals the dynamical process of surface composition. Furthermore, the change in the surface electronic properties has been probed by measuring negative-ion fractions as a function of the annealing temperature for fast ion scattering. It suggests that charge transfer is a very sensitive method for studying specific electronic processes in real time.

This paper reports that the transmission of O6+ ions with energy of 150keV through capillaries in an uncoated Al2O3 membrane was measured, and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed. Due to using an uncoated capillary membrane, our c is larger than that using a gold-coated one with a smaller value of E-p/q, which suggests a larger equilibrium charge Q(infinity) in our experiment. The observed special width variation with time and a larger width than that using a smaller E-p/q were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation.

In this work, the efficient electron loss process was observed for the transmission of 10- to 18-keV Cu${}^{\ensuremath{-}}$ and Cl${}^{\ensuremath{-}}$ ions through Al${}_{2}$O${}_{3}$ nanocapillaries. The fractions of the scattered particles were simultaneously measured using a position-sensitive microchannel plate detector. The neutrals were guided through the capillary via multiple grazing scattering. In particular, the scattered Cl${}^{\ensuremath{-}}$ ions were observed in the transmission, whereas no Cu${}^{\ensuremath{-}}$ ion was formed. In contrast to highly charged ions, these results support strongly the fact that the scattering events dominate the transport of negative ions through the nanocapillaries and that there is no direct evidence for the formation of negative charge patches inside the capillaries which are able to repulse and guide negative ions efficiently.

We measured the double-to-single-ionization ratios $R$ of helium impacted by the intermediate velocity ${\mathrm{C}}^{4+}$ ion and found that $R$ decreases as 1/$v$. This type of velocity dependence is consistent with the data for very highly charged ions (N${}^{7+}$ \ensuremath{\sim} ${\mathrm{U}}^{92+}$). The charge state and velocity dependences of $R$ are interpreted well by the classical over-barrier-ionization (COBI) model. It is found that the ratio $R$ can be written in a manner of $R=0.28\sqrt{q}/v$ for very high-$q$ projectiles in the strong coupling (q/v g 1) regime. This theoretical prediction is in excellent agreement with extensive experimental data.

The transmission of 18-keV ${\text{O}}^{\ensuremath{-}}$ ions through ${\text{Al}}_{2}{\text{O}}_{3}$ nanocapillaries with 50 nm in diameter and $12\text{ }\ensuremath{\mu}\text{m}$ in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV ${\text{O}}^{\ensuremath{-}}$) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (${\text{O}}^{\ensuremath{-}}$, ${\text{O}}^{0}$, and ${\text{O}}^{+}$) decreased when the tilt angle increased. In transmitted particles, the fraction of ${\text{O}}^{\ensuremath{-}}$ declined but that of ${\text{O}}^{0}$ and ${\text{O}}^{+}$ ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.

The transmission of 10–18 keV O− ions through Al2O3 nano-capillaries has been investigated experimentally. From the angular distribution of the transmitted particles, O0 and O− and O+ ions can be distinguished in the mixed scattered beams. The fractions of the scattered ions increase with both the tilt angle and the incident energy, which indicates strongly that there is dynamical charge exchange in the scattering of negative ions on the insulator surface. Moreover, it is found that the scattered neutrals (O0) are only more or less guided along the capillary axis, which is greatly different from the case of the guiding effect of highly charged ions.

We investigate the angular distribution of the transmitted 18 keV negative ions Cl− through Al2O3 nanocapillaries of 50 nm in diameter and 10 μm in length. Elastic scattering ions and inelastic scattering ions are obtained simultaneously. The experimental result is partially consistent with the guiding effect. We can qualitatively explain our experimental result through a dynamic process.