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Electron-impact single-ionization (EISI) cross sections for W q+ (q = 9, 10) ions have been calculated by using the level-to-level distorted-wave (LLDW) method with emphasis on the contribution of metastable states to the total ionization cross sections. Contributions from direct-ionization (DI) and excitation-autoionization (EA) processes are taken into account. The calculated cross sections include the contributions from both the ground configuration and the long-lived metastable states with lifetimes exceeding 10−6 s. Calculated cross sections are in good agreement with experimental measurements when the influence of metastable states on the total ionization cross section are well considered.

Ab initio calculations of electrostatic potentials of C60 and C80 have been performed at the B3LYP/6-31G(d) level. Comparisons of the present calculations with phenomenological models and other ab initio results demonstrate that the new proposed electrostatic potentials give a better description of the confining effect than square potential well models. The present calculated electrostatic potentials are fitted with the Lorentz function. The electrostatic potentials obtained are expected to be useful for modelling atomic dynamic processes, such as photoionization and elastic scattering of endohedral fullerenes, and simulation of the interaction between energetic ions and fullerenes.

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 paper a projectile ions-recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22–6.35 MeV Cq+ (q = 1 – 4) ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization (or the single capture) of argon associated with single electron loss (or single electron capture) by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.

L-shell x-ray yields of molybdenum bombarded by highly charged Arq+ ions (q = 11-16) are measured. The x-ray production cross-sections are extracted from the yields data. The energy of the incident Ar ions ranges from 200 to 350 keV. After the binding energy correction, experimental data are explained in the framework of binary-encounter-approximation (BEA). The direct ionization is treated in the united atom (UA) limit (Lapicki and Lichten 1985 Phys. Rev. A 31 1354), not in the separate atom (SA) limit. The calculation results of BEA (Gacia and Fortner 1973 Rev. Mod. Phys. 45 111) are much lower than the experimental results, while the results of binding energy modified BEA are basically in agreement with the experimental results.

There is no available theoretical description of electron transfer from negative projectiles at a velocity below 0.1 a.u. during grazing scattering on insulating surfaces. In this low-velocity range, electron-capture and electron-loss processes coexist. For electron capture, the Demkov model has been successfully used to explain the velocity dependence of the negative-ion fraction formed from fast atoms during grazing scattering on insulating surfaces. For electron loss, we consider that an electron may be transferred from the formed ionic diabatic quasi-molecular state to the formed covalent diabatic quasi-molecular state by the crossing of the potential curves of negative projectiles approaching the surface cations, which can be described by the Landau-Zener two-energy-level crossing model. Combining these two models, we obtain good agreement between the experimental and calculated data for the F--LiF(001) collision system, which is briefly discussed.

New measurement of the ratio of the double ionization cross section to that of the single ionization of helium induced by 2.0-7.5 MeV partially stripped Oq+ ion (q = 1,2,3,4) is presented. Combining the measured data with the Olson-Schlachter scaling, the double ionization cross section of helium by partially stripped oxygen ion is obtained. It is found that the v/qeff dependence of the obtained double ionization cross section agrees well with the (v/qeff)-4 law.

For Li+ and Na+ ions scattered from high work function metal surfaces, efficient neutralization is observed, and it cannot be explained by the conventional free electron model. In order to explain these experimental data, we investigate the velocity-dependent neutral fraction with the modified Brako-Newns (BN) model. The calculated results are in agreement with the experimental data. We find that the parallel velocity effect plays an important role in neutralizing the Li+ and Na+ ions for large angle scattering. The nonmonotonic velocity behavior of neutral fraction is strongly related to the distance-dependent coupling strength between the atomic level and metal states.

Ab initio calculations of dielectronic recombination rate coefficients of Ne-, Pd- and Ag-like tungsten have been performed. Energy levels, radiative transition probabilities and autoionization rates were calculated using the Flexible Atomic Code. The contributions from different channels to the total rate coefficients are discussed. The present calculated rate coefficients are compared with other calculations where available. Excellent agreement has been found for Ne-like W while a large discrepancy was found for Pd-like W, which implies that more ab initio calculations and experimental measurements are badly needed. Further calculations demonstrated that the influence of configuration interaction is small while nonresonant radiative stabilizing (NRS) contribution to doubly excited non-autoionizing states are vital. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community, which makes experimental verification even more essential.

The K-shell x-rays of Ti, V, Fe, Co, Ni, Cu, and Zn induced by 424-MeV/u C6+ ion impact are measured. It is found that the K x-ray shifts to the high energy side and the intensity ratio of K beta/K alpha is larger than the atomic data, owing to the L-shell multiple-ionization. The x-ray production cross sections are deduced from the experimental counts and compared with the binary encounter approximation (BEA), plane wave approximation (PWBA) and energy-loss Coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theoretical predictions. The BEA model with considering the multipleionization fluorescence yield is in better consistence with the experimental results. In addition, the cross section as a function of target atomic K-shell binding energy is presented.

The transfer ionization to single capture ratios for Arq+ ions on He, Ne and Ar atoms are measured by using position sensitive and time-of-flight techniques. It is found that the transfer ionization to single capture ratio increases as the charge state q increases for the isonuclear ion sequence at the energy studied. The measured results are compared with calculations of the molecular Coulomb over-barrier model including the statistical treatment of the transfer ionization. The discrepancy between the calculation and the experiment is discussed.

We measure the multiple ionization cross-section ratios Rk1 of Ar impacted by Cq+ (q = 1−3) ions in the energy range of 20–500 keV/u. The measured ratios Rk1 increase with the projectile energy at lower energies, and reach the maximum at energies of 50–150 keV/u, then decrease for higher energies. We also use the classical over barrier ionization model to calculate the ratios Rk1, and the calculation results are in good agreement with the data, which suggest that the multiple ionization process is described by the sequential over-barrier ionization process.

The values of cross-section ratio Rk1 of direct k-fold ionization cross section (σ k) to direct single ionization cross section (σ 1) of Ne impacted by Cq+ (q = 1–3) ions in an energy range of 10 keV/u–500 keV/u are measured in this work. The experimental data are compared with the results from our multi-electron classical over-barrier ionization (ME-COBI) model, showing that the model can give a good estimate to the experimental data.

We extend our previous work of a classical over-barrier ionization (COBI) model to calculate the single ionization cross sections of noble gases ranging from He to Xe at strong perturbative energies. The calculation results are in good agreement with extensive experimental data. The scaling law of single ion-atom impact ionization cross sections of noble gases on projectile charge q and energy E, also on target ionization energy I is drawn from the model.

The M x-rays of Th and U have been produced by alpha particle bombardment in the energy range of 2.5-4.5 MeV. N6,7 → M5(Mα), N6 → M4(Mβ), N5 → M3(Mγ), N4 → M2 and N2 → M1 lines were selected to deduce M-subshell x-ray production cross sections. The radiative transition rates and the Coster-Kronig yields and M-subshell fluorescence yields were used to convert the x-ray production cross sections into M-subshell ionization cross sections. The deduced M-subshell ionization cross sections were compared with the ECPSSR predictions. The discrepancies of our experimental results from the theoretical calculations are discussed.

We investigate the single-electron loss processes of light charged ions (Li-1+,Li-2 +, C-2+,C-3+,C-5+, and O-2+,O-3+) in collisions with helium. To better understand the experimental results, we propose a theoretical model to calculate the cross section of projectile electron loss. In this model, an ionization radius of the incident ion was defined under the classical over-barrier model, and we developed "strings" to explain the processes of projectile electron loss, which is similar with the molecular over-barrier model. Theoretical calculations are in good agreement with the experimental results for the cross section of single-electron loss and the ratio of double-to-single ionization of helium associated with one-electron loss.

A VME-based experiment system for n-γ discrimination using the charge comparison method was established. A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of LabVIEW. The two-dimensional (2D) scatter plots of the charge in the slow component vs. the total charge from 241Am-Be and 252Cf neutron sources are presented. The 2D scatter plots of the energy vs. the ratio of the charge in the slow component to the total charge of the pulses are also presented. The quality of n-γ discrimination was checked by the figure-of-merit, and the results showed good performance of n-γ discrimination at the low energy range. Neutrons and γ-rays were separated above 50 keVee (electron-equivalent energy). The quality of n-γ discrimination has been improved compared with others' results at five energies (150, 250, 350, 450, 550 keVee).

A prototype laser ion source that could demonstrate the possibility of producing intense pulsed high charge state ion beams has been established with a commercial Nd:YAG laser (Emax=3 J, 1064 nm, 8–10 ns) to produce laser plasma for the research of Laser Ion Source (LIS). At the laser ion source test bench, high purity (99.998%) aluminum and lead targets have been tested for laser plasma experiment. An Electrostatic Ion Analyzer (EIA) and Electron Multiply Tube (EMT) detector were used to analyze the charge state and energy distribution of the ions produced by the laser ion source. The maximum charge states of Al12+ and Pb7+ were achieved. The results will be presented and discussed in this paper.

We have investigated the dependence of electron capture to the continuum (ECC) on the longitudinal momentum of recoil ions in the transfer ionization of 120 and 300 keV He2+ on argon collisions. Compared with theoretical lines predicted by the kinematical relationship between longitudinal momentum of recoil ions and ECC electrons, it is shown that the electron is mainly transferred to the first excited state of He+ ions. The experimental data also show that the electron capture to the ground state of He+ is accompanied by target excitation, where the target excitation results from direct excitation in the transfer ionization processes.

The transmission of Xe10+ ions, with incident kinetic energies of 200?500?keV, through polycarbonate capillaries, with a diameter of 150?nm and a length of 30??m, has been studied using a one-dimensional position sensitive detector. The transmitted ion yields were measured as a function of the tilt angle. The results are used to evaluate the guiding angle, which is a measure of the guiding power specifying the capability of insulating capillaries to guide ions at equilibrium. Following the semi-empirical scaling law, the potential in the entrance region in this work is nearly an order of magnitude larger than that proposed by low energy data.

A VME-based experiment system for n-{\gamma} discrimination using the charge comparison method was established. A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of LabVIEW. The two-dimensional (2D) scatter plots of the charge in the slow component vs. the total charge of recorded pulses from Am-Be and Cf neutron sources were presented. The 2D scatter plots of the energy vs. the ratio of the charge in the slow component to the total charge of the pulses were presented at the meantime. The quality of n-{\gamma} discrimination was checked by the figure-of-merit, and the results showed good performance of n-{\gamma} discrimination at low energy range. Neutrons and {\gamma}-rays were separated above 50 keVee (electron-equivalent energy). The quality of n-{\gamma} discrimination have been improved compared with others' results at 5 energies (150, 250, 350, 450, 550 keVee).

Our previous work on the classical over-barrier ionization model for helium double ionization is extended to the complex multi-electron system of Ne. The total and q-fold ionization cross sections are calculated at energies ranging from a few tens to several hundred keV/u. The calculation results are in good agreement with the experimental data, and the energy dependence of the cross sections suggests that the multi-ionization of a strong perturbated complex atom is probably the sequential over-barrier ionization process.

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.

Electron Capture and transfer ionization by Ar(8–12)+ in collisions with argon atoms were studied by using the position sensitive and time-of-flight techniques. Some of the measured projectile charge changing cross sections (σq,q−k) and phenomenological cross sections (σrq,q−k) are reported in this paper. The measured cross sections are compared with the predictions of the molecular Coulombic overbarrier model by considering the autoionization decay and electron evaporation of multiply excited states in projectiles and recoil ions respectively.