Cross Sections For Single Ionization Research Articles

Electron impact single ionization cross-section and Maxwellian rate-coefficients of L-shell of tungsten ions W64+-W71+

The cross-sections and Maxwellian rate coefficients of electron impact single ionization is theoretically investigated for tungsten ions (W64+ to W71+) for fine structure levels of configurations containing n = 2 orbitals. To check the accuracy of calculated cross-sections and rate-coefficients, detailed comparison between result from different approximations, binary encounter dipole (BED), distorted wave (DW) and coulomb born exchange (CBE) is presented. The calculations for electron impact ionization cross-sections of ground state are carried out for energy range 20 keV–1000 keV of final electron and Maxwellian rate coefficients for ground state are evaluated at the temperature range 20 keV–300 keV. We have also provided cross-sections at five different energies and rate-coefficients at five different temperatures. The present study of tungsten ions may be useful in fusion plasma modelling and in future comparison.

Theoretical investigations on electron-impact single-ionization cross section of Sn 11+

The total cross-section of electron-impact single ionization for the ground configuration 3d 104s 24p 64d 3 and excited configuration 3d 104s 24p 64d 24f of Sn 11+ is determined from the ionization threshold to 1000 eV. The contributions of direct ionization, excitation auto-ionization, and resonant excitation double auto-ionization to the total electron-impact single ionization cross-section are systematically demonstrated. The cross-section of direct ionization and excited auto-ionization are determined using the level-to-level method, while the cross-section of partially resonant excited double auto-ionization are determined through the configuration averaged method. To obtain convergence, excitation channels with the maximum principal quantum number up to n = 25 are considered. A comparison of the present results with the experimental data [Borovik et al. J. Phys. B 46, 175 201 (2013)] reveal considerably improved agreement when including the resonant excitation double auto-ionization in the calculation.

Electron and positron impact differential cross sections for the (e,2e) process on water molecule

We present a theoretical study for electron and positron-impact ionization of water molecule by using the three-body formalism of distorted-wave approximation. In this approximation, the final state contains one-Coulomb, two-Coulomb, and three-Coulomb distortion due to pairwise Coulombic interactions, respectively. In the entrance channel, the initial state is a product of two wavefunctions: the first one for the incident electron/positron described by a Coulomb wave and the second one for the ten bound electrons. The molecular wavefunction for these bound electrons of H2O are described by the linear combination of atomic orbitals. We investigate the angular distribution of the triple differential cross section (TDCS) for single ionization of the outer orbitals 1b1,3a1,1b2, and 2a1. The structure with two peaks around the binary and recoil region are clearly observed for 1b1, 3a1, and 1b2 orbitals. At the same time, a single peak in the binary region with no recoil peak is found for the 2a1 orbital. The present TDCS results are compared with available experimental and theoretical findings. Fair agreement regarding the structure of angular profile of the TDCS is observed for all orbitals except 2a1. Finally, an enhanced TDCS have been found for positron impact compared to the electron impact.

Theoretical investigation of electron-impact ionization of W<sup>6+</sup> ion

Due to its unique characteristics, metal tungsten has been selected as the wall material for the tokamak magnetic confinement fusion device. The wall material directly interacts with the plasma for a long time, causing tungsten atoms and ions to be sputtered and ionized into different charge states, which then enter the tokamak device as plasma impurities. To ensure stable plasma combustion conditions, highly complex modeling is currently being conducted to evaluate the behavior of tungsten impurities and their impact on the tokamak plasma. This requires various high-precision atomic data for tungsten atoms and different ionized states of tungsten ions. Electron collision ionization, as a fundamental atomic physical process, is widely encountered in laboratory and astrophysical plasma environments. The parameters such as electron collision ionization cross-sections and rate coefficients are crucial for plasma radiation transport simulations and state diagnostics.Electron-impact single-ionization (EISI) cross sections of the ground state and metastable state for W<sup>6+</sup> ions have been calculated using the level-to-level distorted-wave (LLDW) method. The contribution of direct ionization (DI) and excited autoionization (EA) cross sections to the total EISI cross section has been primarily considered.Comparison of our calculated results with the experimental data from Stenke et al. reveals that the EISI cross section considering only the ground state is significantly smaller than the experimental findings. Therefore, it is imperative to take into account the contribution from the metastable state. To determine the fraction of ions in long-lived energy levels within the parent ion beam, three models have been employed.Our results, which include the contribution of metastable states, agree well with the experimental spectrum of Stenke et al. Comparing with the theoretical calculations of Pindzola et al. our calculaiton provides a more comprehensive understanding of the electron-impact single-ionization processes for W<sup>6+</sup> ions. The comparison is illustrated in Figure.Fig. Comparison of our W<sup>6+</sup> ions fitting EISI with experiment<sup>[24]</sup>. Red、green and blue solid line respresent the results of the model 1、model 2 and model 3, respectively. The black solid line is the EISI cross section of ground state 4<i>f</i><sup>14</sup>5<i>p</i><sup>6</sup>.

Electron impact single ionization TDCS of H2O at 81 eV for coplanar asymmetric emission of electrons

We report the results of triple differential cross section (TDCS) for the electron impact single ionization of water molecules at incident electron energy 81 eV for coplanar asymmetric emission of electrons. The TDCS results have been obtained in distorted wave second Born approximation using orientation averaged molecular orbital (OAMO) approximation. The TDCS results have been calculated for the ionization of 1b1 and 3a1 molecular orbital of water molecules for the coplanar asymmetric emission of electrons. The obtained theoretical TDCSs are compared with the available measurements as well as with the first Born results. The second Born results are found to be significant by improving agreement with the measurements particularly in the binary peak region.

Theoretical investigation of electron-impact ionization of W8+ ion

The electron-impact single ionization cross section for W8+ ion has been calculated using flexible atomic code, employing the level-to-level distorted-wave approximation. This calculations takes into account contributions form both direct ionization (DI) and excitation autoionization (EA). However, the theoretical predictions, based solely on the ground state, tends to underestimate the experimental values. This discrepancy can be mitigated by incorporation contributions from excited states. We extended the theoretical analysis, including the contributions from the long-lived metastable states with lifetimes exceeding 1.5 × 10−5 s. We employed two statistical models to predict the fraction of ground state ions in the parent ion beam. Assuming a 79% fraction of parent ions in ground configuration, the experiment measurements align with the predictions. Furthermore we derived the theoretical cross-section for the ground state as correlated plasma rate coefficients, and compared it with existing data. Despite the uncertainty in our calculations, our results are still acceptable.

On the electron impact cross-section maxima for dissociative and non-dissociative single ionization of molecules and radicals

Determining absolute electron impact ionization cross-sections for atoms and molecules, whether through experimental or theoretical means, poses a formidable challenge and is typically limited to a narrow selection of species. In this paper, by using measured cross-sections and polarizability data, it was obtained empirical scaling laws for total single ionization and non-dissociative single ionization cross-section maximum of neutral molecules by collisions with electrons. It is found that the total single ionization cross-sections scale linearly with the target electric static polarizability, while the non-dissociate cross-sections exhibit a saturation effect for large target polarizabilities. This saturation effect is interpreted as the increasing role of fragmentation with polarizability.

Ionization and electron capture in O6+ + He collisions at 0.86, 1.5, 1.94 a.u. velocities

Using the projectile-ion-recoil-ion coincidence method, relative cross sections for single-electron capture, single ionization, double-electron capture, transfer ionization and double ionization in collisions of multiply charged O6+ ions with helium atoms have been measured at 0.86, 1.5, 1.94 a.u. velocities. Calculations based on the semi-classical over-barrier model in the framework of independent electron approximation is employed to discuss various competing reaction mechanisms. These results are also compared with other experimental and theoretical results available in the velocity range considered.

Triple differential cross sections for single ionization of an atom by bare ion impact

We present triple differential cross sections (TDCSs) for single ionization of atoms by proton and highly charged bare ions impact by means of the three-body formalism of the first Born, two-Coulomb wave and three-Coulomb (3C) wave (3CW) methods, respectively. The TDCS has been calculated both in the scattering and perpendicular planes. The purpose of this work is to investigate the validity of different methods as well as the role of interaction between projectile and residual-target-ion in the final state for weak perturbation strength with low electron emission energy at several momentum transfers. By comparing our calculations with experimental data, overall, the 3CW predicts better agreement with experiments than other calculations in the scattering plane. In the perpendicular plane, all calculations deviate from experimental data with increasing transverse momentum transfer for p − He collision. At low momentum transfer, the location of binary peak obtained by the first Born approximation calculation is well established with the experiment for proton impact. On the other hand, the 3CW model is in much better agreement with experiments, both in absolute values and peak position for highly charged impact. Finally, the strong influence of the internuclear Coulomb distortion on TDCS has been observed at low and intermediate momentum transfer.

Electron scattering cross sections for the ground and excited states of tin

A comprehensive set of cross sections for electron scattering from the ground and first four excited states of tin has been calculated using the Relativistic Convergent Close-Coupling method. Elastic scattering, momentum transfer, total scattering, and total-inelastic scattering cross sections have been produced for the 5p23P0,1,2, 1D2 and 1S0 states of atomic tin over a projectile energy range of 0.1 eV to 1000 eV. Over the same projectile energy range, state-resolved cross sections for excitations to the 5p2, 5p6s, 5p5d and 5p6p manifolds from the ground and first four excited states of tin are presented. Total single-ionisation cross sections have been calculated which account for the direct ionisation of electrons in the valence 5p and closed 5s shells, as well as indirect contributions from excitation auto-ionisation. These ionisation cross sections are presented for projectile energies up to 1000 eV. Maxwellian rate coefficients have been calculated for all studied transitions over electron temperatures ranging from 0.5 eV to 200 eV and fitted with simple formulas. The fit coefficients are tabulated for use in modelling applications.

Charge transfer and ionization cross-sections in collisions of singly charged lithium ions with helium and nitrogen atoms

We present a non-perturbative classical treatment of the charge transfer and ionization processes in collisions between singly charged lithium ions with helium and nitrogen atomic targets. Single capture and single ionization total cross sections are calculated using a three-body classical trajectory Monte Carlo (CTMC) method in which the interaction between the collision partners is described by a Garvey-type model potential. The cross sections are evaluated for collision energies between 20 keV and 100 MeV. In particular, we found excellent agreement between our results and the available experimental data for the case of the single capture of He(1s) by Li+ ions. In addition, our CTMC results are in a reasonable agreement with the experimental results for collision energies higher than 200 keV for single capture of N(2p) atoms by Li+. Furthermore, we present single ionization cross sections for both collision systems.

Investigation the fully differential cross section of helium atom single ionization by fast protons impact with three and four-body formalism

In the present work, the fully differential cross section of atomic helium ionization by protons impact at high energy ranges is calculated. The calculations of the fully differential cross section have been performed by using the three-body formalism in the first order Born-Faddeev approximation with an active electron model and four body formalism with the first Born approximation. In order to investigate the collision dynamics accurately, the first order Born-Faddeev approximation has been performed by using the single parameter and Hartree Fock as single-electron wave functions and in the first order Born approximation, the two-electron wave functions of Hylleraas and Silverman are used with considering the electron correlation. The fully differential cross sections at different ejected electron energies and momentum transfers are compared with the available experiment and theoretical results. The results show that the effects of electronic correlation are considerable at high impact energy range and ionization process.‎

Asymmetry parameters in single ionization of He, Ne by XUV pulses

Fully differential cross-sections of single ionization of He and Ne atoms are studied by linearly polarized extreme ultraviolet (XUV) photons in the energy range of 22.1 eV–43.7 eV, using a reaction microscope. Photoelectron angular distributions and the β asymmetry parameters for He 1s2 electrons prove the reliability of our experiment, and the β asymmetry parameters extracted from the angular distributions of Ne 2p6 electrons are obtained. By comparing with different theoretical calculations, it is found that the contribution of the electron correlation effect in Ne 2p6 single ionization becomes increasingly important as the incident photon energy increases, while the relativistic effect is relatively low in the whole incident energy range. Our experimental β asymmetry parameters may serve as a significant reference to test the most elaborated theories in the field. The datasets presented in this paper, including the photoelectron angular distributions and β asymmetry parameters, are openly available at https://doi.org/10.57760/sciencedb.j00113.00073.

Electron-impact ionization of W9+ and W10+

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.

He2+ impact single ionization cross sections of Cu atom

Semi-classical binary encounter approximation has been used for theoretical calculations of single ionization cross sections of Cu atom at ground state by alpha particle impact in energy range varying from threshold 35 keV/amu to 425 keV/amu. An accurate expression of cross section for energy transfer ΔΕ (σΔΕ) as given by Vriens and quantum mechanical Hartree-Fock velocity distributions for target electrons have been used in the calculation. Major contribution to the total single ionization cross sections of Cu are from 4s and 3d subshells. The ionization cross sections decrease with the increase of impact energy same as experimental data reported. The theoretical and experimental results of single ionization cross sections have same trends against the increase of impact energy. The ratio factor falls within 2, varying from 1.26 to 1.86, for given energy range. Theoretical results are under valid range. About 50% of total theoretical results of single ionization cross sections have ratio factor (R) . Major contribution to total ionization cross section is from 3d and 4s subshells-electrons whose contributions varies from 62 to 71% and 41.7% to 23.8% respectively. The higher value of linear correlation coefficient (=0.9647) and lower value of standard deviation (=0.822) shows that results calculated are close to the experimental data in the intermediate and high energy range. BIBECHANA 19 (2022) 111-118

Electron-Impact Ionization of the Tungsten Ions: W38+ − W45+

In this manuscript, we present our calculations of detailed electron-impact single ionization cross-sections for tungsten ions, spanning charge states W38+− W45+. The level-to-level distorted-wave method implemented in the flexible atomic code (FAC) was used for calculation. Comparison between the present level-to-level distorted wave treatment and previous configuration-averaged calculations has been performed for the W45+ ion, and we explore the possible reason for the difference observed between two calculations. We demonstrate the importance of radiative damping on the total electron-impact ionization cross-section for the W43+ ion. Present calculations provide missing cross-sections for W38+− W45+. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community.

Collisions of proton or highly charged ion–atom in a strong magnetic field and dense quantum plasmas

Magneto inertial fusion driven by heavy ions beam (HIB) is a very attractive potential approach for the nuclear energy system. One of the key issues is to investigate the interaction process of the HIB-target considering the condition of plasma screening and strong magnetic field background. In this paper, the influence of the external magnetic field and the plasma screening was investigated by simplifying the process of beam bombarding into a two-body collision between the energetic ions and target atoms. The classical-trajectory Monte Carlo method was accommodated by modifying the Hamiltonian in the collision system, where the effects of plasma screening and the account for the strong magnetic field background were considered. The total cross sections of single electron ionization and charge transfer of the projectile (H+, He2+, Xe32+, Bi31+, U34+)–atom (H, He) collisions are computed. The results indicated that the magnetic field effect becomes more obvious in the low energy regime of the projectiles. With the increase in energy, the change of total cross sections and angular differential cross sections gradually disappears. In the dense quantum plasmas, plasma screening presents very different effects for protons and heavy ion projectiles. This work may pave the way for extending the study to other collision systems calculations.

Differential ionization cross-section of hydrogen bromide.

In this study, the relative single and double differential ionization cross-section of the hydrogen bromide molecule and their fragmented ions (HBr+, Br+, H+) have been theoretically evaluated. In the single differential ionization cross-sections, the loss of incident electron energies (W) at 100 eV, 200 eV, and 500 eV is calculated. The double differential ionization cross-section of the HBr molecule is determined for secondary electron energy (e) and different incident scattering angles (θ). The differential ionization cross-sections of the hydrogen bromide molecule were investigated for the first time.The derived results of the HBr molecule are not only important in spectrometry but may also be interesting for atmospheric sciences.

Post-collision and inter-nuclear effects on the fully differential cross sections of helium atom single ionization by heavy ion impact

Post-collision and inter-nuclear effects on the fully differential cross sections of helium atom single ionization by heavy ion impact

Contribution of the metastable states to electron-impact single ionization for W7+

In this paper, we present the electron-impact single ionization cross sections for W7+. The level-to-level distorted-wave method implemented in the flexible atomic code (FAC) was used for calculation. Contributions from direct ionization (DI) and excitation-autoionization (EA) processes are taken into account. Comparison between the results of previous experimental measurements and the present calculations show a prominent contribution from metastable states in the W7+ ion. We extended the theoretical analysis including level-to-level calculations from long-lived levels of the [Cd]4f135p6 ground configuration and excited, metastable [Cd]4f145p5, [Cd]4f135p55d and [Cd]4f145p45d configurations. Calculated results are in good agreement with experimental data when, within a statistical model, a 56% fraction of parent ions in the ground configuration is assumed.