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The ionization potentials and total ionization cross sections of glucose and ribose monosaccharide molecules were measured by electron impact at energies up to 70 eV. Using two methods, Hartree–Fock (HF) and density functional theory (DFT), the structure of d- and l-forms of glucose and ribose molecules were calculated using Gaussian. The energy characteristics of the molecular orbitals (MOs) were used to calculate the summarized single ionization cross sections (CS) based on the MOs by the Binary–Encounter–Bethe (BEB) and Gryzinsky (Gryz) models. By normalizing to Gryz-DFT cross sections at thresholds, at 11 eV (Glucose) and 12.65 eV (Ribose), the absolute values of the measured total ionization cross sections of these molecules were obtained. The ionization potentials of glucose and ribose molecules were evaluated from binding HOMO MOs energies and compared with the measured values: 12.25 ± 0.25 eV (Glucose) and 10.46 ± 0.25 eV (Ribose). The contributions of the higher orbitals HOMO, HOMO-1, HOMO-2 to the Gryz-DFT cross section were evaluated. [ABSTRACT FROM AUTHOR]

The single-center convergent close coupling (CCC) method has been applied to positron scattering from the oxygen atom. Cross sections have been calculated for total, elastic, momentum transfer, total ionization, inelastic, and excitation scattering processes from threshold to 5000 eV. Due to their relevance in transport studies, we also present stopping power and mean excitation energy results. Low-energy studies have been conducted to calculate scattering length, the hidden Ramsauer–Townsend minimum, and the energy of the positron virtual state. CCC-scaled complex optical potential calculations are utilized to calculate positronium-formation, direct ionization, and values between the positronium-formation and ionization thresholds. Good agreement is generally observed at high energies with past theory, electron-atomic oxygen experiment, and halved electron/positron O 2 experiment. Large discrepancies, however, have been found between current and previous calculations for positronium-formation cross section and for low-energy elastic scattering cross section. [ABSTRACT FROM AUTHOR]

State-selective non-dissociative electron capture and ionisation cross sections are calculated for collisions between bare helium-ions and molecular hydrogen. The two-centre wave-packet convergent close-coupling approach is used and the hydrogen molecule is represented as an effective one-electron target. For the electron-capture cross section, our results are in good agreement with experimental measurements at energies above 100 keV/u. However, near the peak of the cross section, they are larger than the experimental data. The total ionisation cross section is also in good agreement with experiment, particularly at low and high energies. The results for the state-selective electron-capture cross section are generally in good agreement with the limited experimental measurements. However, we find that our results appear to consistently overestimate the experimental data for electron capture into the s states at intermediate energies. The present results are the first calculations capable of producing electron capture and ionisation cross sections over a wide incident energy range within a single unified theoretical framework. [ABSTRACT FROM AUTHOR]

The relative performance of three- and four-body perturbation methods is evaluated for one-electron transfer in proton–helium collisions in a large interval of impact energies from 10 to 11000 keV. The four-body boundary-corrected continuum intermediate state (BCIS-4B) method and the three-body continuum distorted wave (CDW-3B) method are used to compute the state-selective and state-summed total cross sections for the first four principal quantum number levels of the formed atomic hydrogen. Detailed comparisons of the obtained results with the corresponding experimental data are exploited to establish the lowest energy limit of applicability of the perturbation theories. As is well known, the CDW-3B method strongly departs from the experimental data below about 80 keV. On the other hand, the BCIS-4B method is presently found to successfully describe the measured cross sections at 20–10500 keV. Moreover, in sharp contrast to the CDW-3B method, in all the considered cases, the BCIS-4B method systematically predicts the experimentally observed Massey peaks at the expected positions of matching of the incident velocity and the electron orbital velocity. [ABSTRACT FROM AUTHOR]

The absolute densities of O and O 3 in the effluent of a kINPen, an atmospheric pressure plasma jet, are determined by molecular beam mass spectrometry. A nitrogen gas curtain surrounding the effluent provides a stable environment and prevents interactions with the ambient air. Both He and Ar were used as feed gas with admixtures of O 2 up to 1%. Measurements are performed at discharge voltages from 1600 to 3000 V pp and at distances from 5.5 to 10.5 mm from the nozzle of the gas shielding device to the orifice of the mass spectrometer. The measured O atom densities are in the order of 1 × 10 14 cm - 3 to 2 × 10 15 cm - 3 , whereas the O 3 molecule densities are in the order of 1 × 10 14 cm - 3 to 5 × 10 14 cm - 3 , respectively, when operated in argon the plasma generates higher densities of reactive species. Additionally, a novel molecular beam chopper design with linear movement has been successfully tested in the mass spectromerty setup as an alternative to a rotating chopper. [ABSTRACT FROM AUTHOR]

Single-electron capture by fast protons from helium-like atomic targets is investigated at intermediate and high impact energies. The main purpose of the present study is a comprehensive analysis of the relative importance of the electron continuum intermediate state (ionization continua), with respect to direct transfer. To achieve this goal, first- and second-order theories are employed, and their results are thoroughly compared. The prior form of the boundary-corrected continuum intermediate state method (BCIS) is utilized, in both its three-body and four-body formulation, in addition to the four-body boundary-corrected first-Born approximation (CB1-4B), in both its prior and post form. BCIS methods belong to the class of second-order theories, while CB1 methods belong to the class of first-order theories. Relative importance of ionization continua is examined in the example of single-electron capture in collisions of fast protons with ground-state atomic helium. Both differential and total cross sections are analyzed, for single-electron capture into any final state of the projectile. The presented cross sections, aside from their fundamental importance, are relevant in various interdisciplinary applications, such as in astrophysics, thermonuclear fusion and plasma physics, and medical physics. [ABSTRACT FROM AUTHOR]

We have studied the electron emissions from the smallest hydrocarbon molecule, CH 4 , in collisions with 94 MeV Si 13 + -ions. The absolute double differential cross sections (DDCS) of electron emissions are measured in the energy range of 3–400 eV and in the angular range 20 ∘ to 160 ∘ The measured data have been compared with the continuum distorted wave-eikonal initial state (CDW-EIS) model. The CDW-EIS calculations performed with the complete neglect of differential overlap (CNDO) and the molecular orbital (MO) description of the target are presented. Calculations using both target descriptions show a reasonably good agreement with the measured data. However, the CDW-EIS (MO) shows better agreement with the measured cross sections as compared to the CDW-EIS (CNDO). The single differential cross section, total cross sections have also been deduced from the measured DDCS. The KLL Auger hypersatellite peak due to the double K-vacancy in C-atom has been observed. The ratio of double-to-single K-vacancy production cross section is found to be substantially large, i.e., 33%. The present data, obtained by using such highly charged ions, provides crucial input to the applicability of this MO-based CDW-EIS model for such collisions. [ABSTRACT FROM AUTHOR]

The two-centre wave-packet convergent close-coupling approach to ion–atom collisions is extended to study proton collisions with molecular hydrogen including electron-capture channels. We use a model potential to represent the molecular target as an effective one-electron spherically symmetric system. This greatly simplifies the target structure, allowing us to use already existing code developed for ion collisions with single-electron targets. Calculated total cross sections for electron capture, single ionisation, and excitation processes generally agree well with experimental data and other theoretical calculations where available. However, the total electron capture cross section is found to overestimate the experimental data at low energies, while the total ionisation cross section is slightly underestimated. Additionally, we present state-resolved cross sections for capture into the 1s, 2 ℓ , and 3 ℓ states of the projectile where deviation between various previous calculations is substantial. Our results lead to overall improvement over previous theoretical studies although discrepancies with experiment are observed for 3p and 3d capture. We conclude that treating molecular hydrogen as an effective one-electron system within the two-centre coupled-channel approach to one-electron targets can give reasonably accurate total cross sections at intermediate and high energies, without the need for a complex and computationally demanding two-electron target representation. [ABSTRACT FROM AUTHOR]

We propose a model potential for computing total ionization cross sections for atoms and molecules by electron impact. The potential is obtained by a fitting procedure using the Binary–Encounter–Bethe model cross sections as a starting point. We present total ionization cross section for hydrogen, carbon, nitrogen and oxygen atoms and for hydrogen, nitrogen, water, methane and benzene molecules. The results obtained with our model potential are compared with results obtained with the Binary–Encounter–Bethe model and with the first Born approximation, and agreement is quite good. Our results show that this potential could be used to account for the ionization channel in an electron–molecule collision calculation. [ABSTRACT FROM AUTHOR]

The boundary-corrected continuum intermediate state (BCIS) method is used to compute total cross sections for electron capture by seven heavy nuclei ( Li 3 + , Be 4 + , B 5 + , C 6 + , N 7 + , O 8 + and F 9 + ) from atomic hydrogen H (1 s) at impact energies 20–3000 keV/amu. In all the cases, regarding the exit channel, we compute the cross sections Q if for the specific individual final bound states f = (n , l , m) of hydrogen-like ions, where throughout i = (1 , 0 , 0) = 1 s (the ground state of the target, H). The maximal value of the principal quantum number n has been taken to be n max = 4 , 5 and 6 for Li 3 + , Be 4 + and B 5 + , respectively, as well as n max = 7 for C 6 + , N 7 + , O 8 + and F 9 +. All the sub-levels (l, m) for every n are included in the computations. Further, the summed cross sections Q i , Σ = ∑ f Q if for all the final (f) states are reported. In Q i , Σ , the state-selective cross sections Q if contain the exact contributions from the final levels with n ≤ n max. The collective yield from the final states with n > n max is approximated by the Oppenheimer n - 3 scaling. To put the present results into perspective, comparisons are made with the boundary-corrected first Born (CB1) and the continuum distorted wave-eikonal final state (CDW-EFS) methods. Both the BCIS and CDW-EFS methods belong to the group of the second-order asymmetric methods for charge-exchange. Most importantly, the available experimental data are used to assess the relative performance of the BCIS method for total cross sections summed over all final states. This type of total cross section databases from our computations can find useful applications in several neighboring disciplines (plasma physics, astrophysics, new energy sources in fusion research) as well as in ion transport physics of relevance to, e.g., radiotherapy in medicine. [ABSTRACT FROM AUTHOR]

Electron-impact ionization cross sections are calculated for the ground configuration of the Pb atom. Time-dependent close-coupling cross sections for the direct ionization of the 6s and 6p subshells leading to single ionization are calculated with and without a polarization potential. Configuration-average distorted-wave cross sections for the direct ionization of the 6s and 6p subshells leading to single ionization are also calculated with and without a polarization potential. We find the time-dependent close-coupling cross sections using a polarization potential to be in good agreement with convergent-close-coupling cross sections using a polarization potential. The total direct ionization cross sections are compared to two sets of experimental measurements. The differences between the direct ionization cross sections and the experimental measurements are mainly due to indirect ionization cross sections coming from the 6 s 2 6 p 2 → 6 s 6 p 3 excitation followed by autoionization. [ABSTRACT FROM AUTHOR]

The processes of electron excitation, capture, and ionization were investigated in proton collisions with atomic hydrogen in the initial n = 1 and n = 2 states at impact energies from 1 to 300 keV. The theoretical analysis is based on the close-coupling two-center basis generator method in the semiclassical approximation. Calculated cross sections are compared with previous results which include data obtained from classical-trajectory Monte Carlo, convergent close-coupling, and other two-center atomic orbital expansion approaches. There is an overall good agreement in the capture and excitation cross sections while there are some discrepancies in the ionization results at certain impact energies. These discrepancies in the present results can be partially understood through the use of a 1/n3 scaling model in the description of electron-capture and target-excitation channels. [ABSTRACT FROM AUTHOR]

The effects of dense quantum plasma on 1 s → nlm charge transfer, for arbitrary n,l,m, in proton-hydrogen collisions have been studied by employing a distorted wave approximation. The interactions among the charged particles in the plasma have been represented by modified Debye-Huckel potentials. A detailed study has been made to explore the effects of background plasma environment on the differential and total cross sections for electron capture into different angular momentum states for the incident energy in the range 10-1000 keV. For the unscreened case, our results agree well with some of the most accurate results available in the literature. Graphical abstract: [ABSTRACT FROM AUTHOR]

The dynamics of the electron capture by He ions from H molecule has been investigated in the four-body first Born approximation. Cross sections differential in the scattering angle of the projectile ion have been calculated for various molecular orientations. The calculations account for the interference effects due to the coherent scattering of the particles from the two atomic centers. Total cross sections (integrated over the projectile's scattering angle and averaged over all the molecular orientations) have also been calculated by a three-body version of the classical trajectory Monte Carlo (CTMC) method based on use of a two-center molecular potential, as well as in a semi-classical quasi-molecular model. The obtained total cross sections are compared with the available experimental data and other theoretical calculations. For impact energies above 40 keV a reasonable agreement has been found between the present theoretical results and the experiment. Graphical abstract: [ABSTRACT FROM AUTHOR]

We study theoretically the double ionization of helium by 6 MeV proton impact. For such fast projectiles, when considering the projectile-target interaction to first order, the four-body Schrödinger equation reduces to solving a three-body driven equation. We solve it with a generalized Sturmian functions approach and, without evaluating a transition matrix element, we extract the transition amplitude directly from the asymptotic limit of the first order scattering solution. Fivefold differential cross sections (FDCS) are calculated for the double ionization process for a number of coplanar kinematical situations. We present a detailed theory-experiment comparison for intermediate momentum transfers (from 0.8 to 1.2 a.u. and from 1.4 to 2.0 a.u.). In spite of some experimental restrictions (energy and momentum ranges) and the low count rates, we found that our theoretical description provides a very satisfactory reproduction of the measured data on relative scale. We then explore how the binary, recoil and back-to-back structures change with increasing momentum transfers (0.853 to 1.656, to 3.0 a.u.). Within the impulsive regime, with a momentum transfer of 3.0 a.u., we also analyze the FDCS for different excess energies. Finally, in analogy to an experimentalist gathering electrons with different excess energies to obtain enough counts, we provide a collective FDCS prediction that hopefully will stimulate further measurements. Graphical abstract: [ABSTRACT FROM AUTHOR]

The four body Born distorted wave (BDW-4B) approximation with correct boundary condition is used for single electron transfer in He-He collision. The post and prior total cross sections are obtained in the energy range 10-1000 keV/amu and the post-prior discrepancy is estimated. The sensitivity of the results with respect to the choice of the final helium-like ground state wave function is evaluated through two different wave functions. The importance of the dynamic electron correlations is tested as a function of impact energy. Additional experimental data at higher impact energies is needed for a better assessment of the validity of the present theory. Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper addresses two aspects of the electron-impact ionization of hydrogen and the alkali atoms Li, Na, K, and Cs. First, we show that the earlier observation that the detailed treatment of the 2 electrons in the final state of the hydrogen ionization process results in a cross section shape that is in excellent agreement with the cross section shape obtained from the semi-empirical Deutsch-Märk (DM) formalism can be extended to the 'quasi one-electron' atoms Li, Na, K, and Cs. Second, we discuss specific aspects of the calculated hydrogen ionization spin asymmetry in light of some recent experimental observations. [ABSTRACT FROM AUTHOR]

Cross sections of total single electron loss (SL), single electron loss with single ionization (SLSI) for Li + H, He collisions and cross sections of single electron loss with double ionization (SLDI) for Li + He collisions in the low- to intermediate-energy range have been calculated using a simple method based on the Bohr-Lindhard (B-L) model. The distributions of both the projectile and target electrons are considered. The calculated results are compared with the available experimental data. [ABSTRACT FROM AUTHOR]

The application of a classical approach to various quantum problems - the secular perturbation approach to quantization of a hydrogen atom in external fields and a helium atom, the adiabatic switching method for calculation of a semiclassical spectrum of a hydrogen atom in crossed electric and magnetic fields, a spontaneous decay of excited states of a hydrogen atom, Gutzwiller's approach to Stark problem, long-lived excited states of a helium atom discovered with the help of Poincaré section, inelastic transitions in slow and fast electron-atom and ion-atom collisions - is reviewed. Further, a classical representation in quantum theory is discussed. In this representation the quantum states are treated as an ensemble of classical states. This approach opens the way to an accurate description of the initial and final states in classical trajectory Monte Carlo (CTMC) method and a purely classical explanation of tunneling phenomenon. The general aspects of the structure of the semiclassical series such as renormgroup symmetry, criterion of accuracy and so on are reviewed as well. [ABSTRACT FROM AUTHOR]

A simple and straightforward calculating scheme is proposed for electron-impact single and multiple ionization of atoms. The method is based on the application of the Hulthén-Kohn dynamical variational principle. An effective charge seen by the scattered electron is determined for a certain type of trial wave functions mathematically in a rigorous way excluding any empirical assumptions. Validity of the elaborated approach is assessed by calculating triply differential cross section (TDCS) for electron-impact ionization of hydrogen. It is shown that, inclusion of the effective charge into the calculation reduces height of a 'binary peak' in comparison with the first Born approximation result. The height of a 'recoil peak' depends on the sign of the effective charge. The calculated TDCS are compared with the available experimental data and with the results of sophisticated theories and agreement is found. [ABSTRACT FROM AUTHOR]

Four-body formalism of boundary corrected continuum intermediate state (BCCIS-4B) approximation have been applied to calculate the single-electron capture cross sections by fast protons through some helium-like ions in a large energy range from 30-1000 keV. In this model, distortion has been taken into account in the entrance channel. In the final channel, the passive electron plays the role of screening of the target ion. However, continuum states of the projectile and the electron in the field of the residual target ion are included. The comparison of the results is made with those of other theoretical investigations and experimental findings. The present calculated results are found to be in good agreement with the available experimental findings. [ABSTRACT FROM AUTHOR]

H impact single and He impact single and double electron capture cross sections of magnesium atoms have been calculated in the modified binary encounter approximation (BEA). The accurate expressions of ion impact $\sigma _{\Delta {E}}$ (cross section for energy transfer $\Delta E$) and Hartree-Fock momentum distributions of the target electrons have been used throughout the calculations. On the basis of the present work it is concluded that inner shell captures by H and He ions incident on magnesium atoms contribute partly to single electron capture and partly to transfer ionization cross sections. The calculated He impact double electron capture cross sections of magnesium are in reasonably good agreement with the experimental observations. This indicates the success of the present theoretical approach in study of charge transfer cross sections of atoms as indirect mechanisms do not interfere with double electron capture processes in this case. [ABSTRACT FROM AUTHOR]

In this article, we report calculations of total ionization cross sections, Q ion, for simple atoms (C, N, O, F) and molecules (NO and NH $_{3})$ of atmospheric interest on electron impact at energies from threshold to 2000 eV. We have employed the complex scattering potential – ionization contribution (CSP-ic) method for the present study. Attempt has been made to improve the method by computing the parameter that involves the ratio of sum of the total excitation cross sections ( Σ Q exc) and total inelastic cross section ( Q inel) at the peak of the inelastic cross section. The present study not only provided a better estimation of the parameter involved in the CSP-ic method but also provided better agreement with the available experimental and theoretical data on the ionization cross sections of the simple atomic and molecular targets studied here. [ABSTRACT FROM AUTHOR]

A simple user-friendly semiempirical model is proposed to calculate electron impact double ionization cross sections of He, Li, Li+, B+, C+, C3+, O, O2+, O3+, Ne, Ne+, Ne2+, Na, Mg, Al3+, S, and Arq+ (q=0–7) targets for the incident electron energies from threshold to 106 eV. The contributions in the total double ionization cross sections from the direct double ionization and inner-shell ionization processes are taken into account on the basis of experimental data considered. The results of the present analysis are compared with the available experimental data and theoretical calculations. The model is found successful for the description of experimental cross sections. Since, this model may be a prudent selection to meet the demand level in plasma modeling due to its simple inherent structure. [ABSTRACT FROM AUTHOR]

The total cross sections for charge transfer in Li2+-H and He+-He+ collisions have been calculated, using the four body first Born approximation with correct boundary conditions (CB1-4B) and four body continuum distorted wave method (CDW-4B) in the energy range 10–5000 keV/amu. The role of dynamic electron correlations is examined as a function of the impact energy. The present results call for additional experimental data at higher impact energies than presently available. [ABSTRACT FROM AUTHOR]

Determinations of radical density are essential to investigate the physical-chemical processes in plasmas and setup the related theoretical models. This paper presents the experimental measurement of atomic hydrogen near grounded electrode in dielectric barrier discharge medium-pressure hydrogen plasma via threshold ionisation-molecular beam mass spectrometry. After investigating the possible influences from parent molecules in excited states, background component and space-charge, evolution of atomic hydrogen density as functions of discharge parameters are investigated utilising the signal of H2 molecule beam as the reference. At fixed gas pressure of 6.0 torr and a discharge voltage of 24 kV, atomic hydrogen density increases monotonously from 1.1×1014 to 2.0×1015 cm-3 as the discharge frequency increases from 9 to 26 kHz. Similarly the rising discharge voltage also lead to enhancement of atomic hydrogen density. [ABSTRACT FROM AUTHOR]

The plane wave Born approximation is used to calculate total electron impact ionization cross section of silver and copper. Wavefunctions of the target and residual ions were modeled by non orthogonal Hartree-Fock and Dirac-Fock orbitals. The wave functions of the atom and residual ion are calculated with allowance for relaxation effects. The one-electron wavefunction of the continuous spectrum for the ejected electron is obtained using single-configuration Hartree-Fock and Dirac-Fock method. The orthogonalization of the ejected electron wave functions to all occupied orbitals of the target atom is performed. Results of calculations are compared to available experimental measurements and theoretical calculations performed by non relativistic one-electron PWBA, where the ejected electrons is modeled by the hydrogenic Coulomb wave function. [ABSTRACT FROM AUTHOR]

A one channel distorted wave approximation has been used to calculate the ionization cross section for the 3s electron of Na atom by alpha particle impact. For a consistency check we have also run the standard CDW-EIS code of McSherry et al. [Comput. Phys. Commun. 155, 144 (2003)] and found reasonable agreement in the high energy region among the present results, the CDW-EIS results and the classical trajectory Monte Carlo (CTMC) calculations. It is also found that the present results tend to agree qualitatively with the low energy measurement of Knoop et al. [J. Phys. B 38, 1987 (2005)] at as low as 10 keV amu-1, although the present theoretical approach is expected to be suitable in the high energy area. This qualitative agreement in the low energy region is attributed to the partially correlated ground state wave function used in the present calculation. [ABSTRACT FROM AUTHOR]

A simple empirical formula is proposed for the rapid calculation of electron impact total ionization cross sections both for the open- and closed-shell neutral atoms considered in the range 1≤ Z≤92 and the incident electron energies from threshold to about 104 eV. The results of the present analysis are compared with the available experimental and theoretical data. The proposed model provides a fast method for calculating fairly accurate electron impact total ionization cross sections of atoms. This model may be a prudent choice, for the practitioners in the field of applied sciences e.g. in plasma modeling, due to its simple inherent structure. [ABSTRACT FROM AUTHOR]

Classical Trajectory Monte Carlo method (CTMC) with the modal interaction potential [1] has been used to simulate the differential, total and partial capture cross sections in proton-oxygen atom collisions in the energy range of 0.5–200 keV. An interesting feature of the calculated differential cross sections (DCS) curve below the scattering angle 0.1○ is the presence of oscillations showing asymmetry in angular positions. The oscillations in the partial cross sections are explained in terms of swapping effect. The DCS and total cross sections are found to be in good agreement with the experimental as well as other theoretical results. [ABSTRACT FROM AUTHOR]

The recently modified Kolbenstvedt (MKLV) model [Eur. Phys. J. D 37, 361 (2006)], developed for electron impact ionization (EII) of the K-shell atomic targets, has been extended to generalize its two parameters in terms of the electronic orbitals nl. The generalized MKLV (GKLV) with two sets of the species independent parameters for the same nl, one set for the ionization of inner orbits and another for the outermost orbit, is found profoundly successful in accounting for the EII cross section data of the K, L and M-shell neutral atoms with atomic numbers Z = 1-92 for the incident energies up to 1000 MeV in a consistent manner. [ABSTRACT FROM AUTHOR]

The Classical Trajectory Monte Carlo (CTMC) Method has been used to calculate the differential, partial and total single electron capture cross sections for the collision of H+/D+ with Ca and Mg atoms in the energy range of 1–100 keV. The differential cross sections at angles near the diffraction limit (<0.1○) in both systems show a forward peak followed by an asymptotic fall at higher angles. Total and partial capture cross sections are found to be in good agreement with the experimental observations. Oscillations in the partial capture cross sections have been explained due to the swapping of the field electron. Isotope effect in the electron transfer is reported to be negligible. [ABSTRACT FROM AUTHOR]

Electron impact single and double ionization cross-sections for argon have been calculated in the binary encounter approximation (BEA) in the energy regions ranging from respective near thresholds to 5300 eV. The accurate expression for σΔE (cross-section for energy transfer ΔE) including exchange and interference as given by Vriens and Hartee-Fock velocity distributions for the target electrons have been used throughout the calculations. It is observed that consideration of ionization of 3p and 3s shells explains overall satisfactory agreement of single ionization cross-sections with the experimental data. It is also concluded that the present method gives reasonable values of direct double ionization cross-sections. Inclusion of contributions of Auger effect due to vacancy in 2p shell brings the theoretical results of double ionization cross-sections in reasonably good agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

Post form of “boundary corrected continuum intermediate state (BCIS)” approximation has been employed to study charge transfer cross-sections in collision of Cq+, Nq+ and Oq+ (q=1–5) with ground state atomic hydrogen in the energy range of 50–200 keV/amu. In this formalism we have adopted model potential for the interaction of the active electron with the projectile ion. Calculated results for total charge transfer cross-sections have significant improvement over other existing theoretical results in their comparison to the available experimental findings except for singly charge ions. Sub-shell distribution for total charge transfer cross-section has also been reported in graphical form. Predictions suggested by Olson in connection with the sub-shell distribution of total charge transfer cross-section has been reaffirmed. However, an oscillatory structure of charge state dependence of the total charge transfer cross-sections has not been found in the present investigation. [ABSTRACT FROM AUTHOR]

The positive water and hydronium ions are of interest in a variety of chemical and biological applications. Here we study the steric effect in charge transfer collisions, i.e. the spatial dependence of single electron capture, in collisions mediated by these ions. In particular, the steric effect is demonstrated in the O+(2D)/H2 and H+/H2O charge transfer collisions in the energy range of 100 eV/amu to 10 keV/amu. [ABSTRACT FROM AUTHOR]

A modification of the Kolbensvedt model, MKLV, in terms of ionic, correlation (between the incident and target electrons) and relativistic corrections, is proposed to calculate the K-shell electron impact ionization cross-sections of neutral and ionic targets. The modified model, with a single set of parameters, is found to reproduce satisfactorily the experimental data for the neutral H, Al, Ar, Mn, Ge, Mo, Ag, Sn, Au, Bi and U and ionic Li+, B4+ and O7+ targets better than the existing empirical models from threshold energies to as high as 104 MeV. For the Ag target, the calculations from MKLV follow closely the results of Scofield, and for Au, those of Scofield, and Ndefru and Malik, both done in the relativistic Born approximation with the Møller interaction, at energies higher than the peak region. [ABSTRACT FROM AUTHOR]

In the present work, the total cross-sections for single- and double-electron-capture by low-energy highly-charged Neq+ (q =2-6) recoil ions from He atomic gas have been measured in the energy range 600–1000 eV/q. These measurements are compared with other available experimental results. The charge state dependence of the single-electron-capture cross-sections for Neq+ (q = 2-6) recoil ions incident on He at energy of 1000 eV/q is compared with the theoretical predictions of the absorbing sphere model and the classical model. [ABSTRACT FROM AUTHOR]

We investigate the problem of the double charge transfer cross-section of a helium atom by bare ions of helium and lithium at energies ranging from 60 to 200 keV/amu. The boundary corrected continuum intermediate state approximation (BCCIS) is used to calculate the capture cross-section in the ground state. The continuum state of each electron has been accounted for in the formalism. The present results are compared with existing theoretical and experimental results. [ABSTRACT FROM AUTHOR]

The article reports that absolute cross-section for electron impact single and multiple ionization of atoms or ions are of considerable interest in many fields of research ranging from controlled nuclear fusion to astrophysics. In context of applications, ionization processes are important in moderate and high temperature plasmas and in all gaseous environments with an abundance of energetic electrons. Triple and higher multiple ionization processes start at increasing higher energies and the corresponding cross-sections are much smaller in magnitude compared to double ionization cross-sections.

The coupled-channel method is used to calculate excitation, single- and double-ionization cross-sections for helium collisions with heavy ions. The wave functions of the channels are helium wave functions constructed with Slater functions and Coulomb wave packets. Results of calculations with various projectiles and incident energies are compared with experimental data and other theoretical cross-sections. [ABSTRACT FROM AUTHOR]

Abstract: In this work, two classical models which have been proposed to describe He atoms in collision processes by charged particle impact are revisited and analyzed. These are the Heisenberg-core and the energy-bounded classical trajectory Monte Carlo methods. These models avoid the classical autoionization by introducing in the Hamiltonian momentum-dependent terms. The physical implication of different choices of the involved parameters are analyzed as well as their influence at the total cross section level. Graphical abstract: [ABSTRACT FROM AUTHOR]