Cross-sectional Electron Research Articles

Electron scattering cross-sections for particle transport modeling in a weakly ionized air plasma

Data on processes of electron scattering on ions and neutral atoms are required in fundamental studies and in applied research in such fields as astro- and laser physics, low density plasma simulations, kinetic modeling etc. Experimental and computational data on elastic and inelastic electron scattering in a wide range of electron energies is available mostly for the electron interaction with neutral atoms, but are very limited for the scattering on ions, notably for elastic processes. In present work the calculational approaches for the cross-section computation of electron elastic and inelastic scattering on neutral atoms and ions are considered. The atomic and ion properties obtained in quantum-statistical Hartree-Fock-Slater model are used in the direct computation of electron elastic scattering and ionization cross-sections by a partial waves method, semiclassical and distorted-wave approximations. Calculated cross-sections for elastic scattering on nitrogen and oxygen atoms and ions, and electron ionisation cross-sections are compared with the available experimental data and widely used approximations and propose consistent results. Considering applicability of Hartree-Fock-Slater model in wide scope of temperatures and densities, such approach to the cross-section calculation can be used in a broad range of energies and ion charges.

Electron induced elastic and inelastic processes for perfluoroketone (PFK) molecules

We report the results of calculations of elastic and inelastic (ionization and excitation) cross sections for electron scattering from perfluoroketone molecules, C x F2x O (x = 1–6) over a wide energy range, from ∼the ionization potential to 5 keV. These molecules have been determined to have extremely low global warming potentials and therefore may have applications in next generation gas discharges and plasma reactors. The results are derived using the complex scattering potential-ionization contribution method to investigate ionization cross sections Q ION and are found to be in good agreement with the available data. The spherical complex optical potential formalism is used to evaluate elastic (Q EL), inelastic (Q INEL) and total cross sections (Q T). This study is a maiden effort to report summed total excitation cross section (∑Q EXC), Q ION and Q INEL for CF2O and C2F4O, and Q EL and Q T for C x F2x O (x = 1–6). The study includes various correlation analyses and a prediction of the dipole polarizability.

Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Ytterbium

We have applied the full-relativistic Dirac B-Spline R-matrix method to obtain cross sections for electron scattering from ytterbium atoms. The results are compared with those obtained from a semi-relativistic (Breit-Pauli) model-potential approach and the few available experimental data.

Measurement Mass Attenuation Coefficient of Palmitic Acid by Using Sources of Gamma Ray

The purpose of this paper is to determine the mass attenuation coefficient (μ/ρ), of a sample. In this work used (C16H32O2) fatty acid, exposed to gamma rays (γ), emitted from various sources 57Co, 133Ba, 22Na, 137Cs, 54Mn, and sCo with energies from 0.122 to 1.330 MeV. It exposes the compound to gamma rays and discloses the radiation force that passes through the sample, the rest of the gamma radiation attenuated. A NaI fluorescence detector (Tl) with an accuracy of 8.2% (at 662 kV) was used for the gamma ray detector beam. An advantage of using (μ/ρ) coefficient data can be obtained effective atomic numbers, atomic cross-section and effective electron densities.

Electron emission from fluorene (C13H10) upon 3.5 MeV/u Si8+ ion impact: double differential distributions

We have studied the electron emission from one of the polycyclic aromatic hydrocarbon (PAH) molecules namely, fluorene (C13H10), upon 3.5 MeV/u Si8+ ion impact. The experimentally measured absolute double differential cross sections (DDCS) are compared with the continuum distorted wave-eikonal initial state (CDW-EIS) model and the first Born approximation including correct boundary conditions (CB1). The measurements are carried out in the ejected e−-energy range of 1 eV–400 eV and in the angular range of 20°–160°. We have obtained the single differential and the total cross sections (TCSs) of e−-emission as well. The CB1 calculation largely underestimates the data. The CDW-EIS model, which is applied for the PAH molecule for the first time, provides an overall better agreement with the double differential, single differential and TCS data. The DDCS data for fluorene has also been compared with that for CH4 molecule, at a few angles. The forward–backward angular asymmetry shows a relatively flatter distribution compared to the theoretical predictions. The contribution due to the giant plasmon resonance could not be clearly observed except a mild indication in the asymmetry parameter. The angular distribution of the carbon KLL Auger electron cross section shows certain variations. The study of the KLL hyper-satellite component indicates the double K-ionization cross section is about 8.6% of the single K-ionization one.

(e,2e) ionization cross-sections for C4H4O, C4H8O and C6H8O

Secondary electron energy dependent differential cross-sections at incident electron energies 100 and 200 eV for (e, 2e) processes for the C4H4O, C4H8O and C6H8O molecules are evaluated by employing the Jain-Khare semi-empirical approach. The total electron ionization cross sections in the incident electron energy range ionization threshold to 5 keV are derived from energy dependent cross sections. The ionization rate coefficients for molecules are also calculated using the total ionization cross sections and the Boltzmann distribution of electron energies. The present results for ionization cross sections corresponding to (e, 2e) processes for these molecules are found in good agreement with available experimental and theoretical results.

A study of dosimetric parameters of new born tissue and adult tissue of some organs

We have calculated the radiological parameters such as computerized tomography (CT) numbers effective atomic number (Zeff) and electron density (Nel) of newborn tissue and adult tissue of lung, kidney, heart and brain. Effective atomic number is computed by calculating the molecular, atomic and electronic cross section in the wide energy range of 1 keV–100 keV using WinXCOM. The new born tissue and adult tissue a very similar, but their atomic number, CT number and electron densities differs. This fact helps in the radiography and radiotherapy.

Elastic Scattering of Electron and Positron by Radium and Radon Atoms

The Differential Cross Sections (DCS's), Total Cross Sections (TCS's) and Momentum Transfer Cross Sections (MTCS's) of electron and positron scattering by radium and radon atoms were calculated in the range of energy (5–500) eV using a total potential consisting of combining the static, exchange and polarization potentials at long distances. In addition, the correlation potential of Perdew–Zunger at short distances for electrons was used, as well as the correlation potential of Jain for positrons. The exchange potential for positrons was neglected. In this study, a good agreement with other experimental values and theoretical values of many investigators was found.

Electron collisions with molecular nitrogen in its ground and electronically excited states using the R-matrix method

A comprehensive study of electron collisions with the X 1Σg + ground state as well as the metastable A 3Σu + and a 1Πg excited states of the N2 molecule is reported using the fixed-nucleus R-matrix method. Integral elastic scattering and electronic excitation cross sections from the X 1Σg + ground state to the eight lowest electronic states, A 3Σu +, B 3Πg, W 3Δu, B′ 3Σu −, a 1Πg, a′ 1Σu −, w 1Δu and C 3Πu, overall agree well with the available experimental and theoretical results although updates of some recommended values are suggested. Accurate electron impact electronic transition cross sections starting from the A 3Σu + and a 1Πg metastable excited states are reported. The total summed electronic transition cross sections from the a 1Πg state is dominant: an order of magnitude higher than those of the X 1Σg + ground state. The de-excitation cross sections generally show a downward trend with increasing incident electron energy, which is different from the elastic and electronic excitation cross sections which generally increase with collision energy. There is a prominent 2Πu symmetry resonance peak at 2.8 eV for electronic de-excitation scattering of a 1Πg → B 3Πg, which significantly contributes to the total summed cross sections from the a 1Πg excited state. The present results provide a new insight which will aid understanding of electron spectra in the atmosphere of the Earth and Titan.

Klein–Nishina formula and Monte Carlo method for evaluating the gamma attenuation properties of Zn, Ba, Te and Bi elements

Abstract In this work, the Klein–Nishina (K–N) approach was used to evaluate the electronic, atomic, and energy-transfer cross sections of four elements, namely, zinc (Zn), tellurium (Te), barium (Ba), and bismuth (Bi), for different photon energies (0.662 MeV, 0.835 MeV, 1.170 MeV, 1.330 MeV, and 1.600 MeV). The obtained results were compared with the Monte Carlo method (Geant4 simulation) in terms of mass attenuation and mass energy-transfer coefficients. The results show that the K–N approach and Geant4 simulations are in good agreement for the entire energy range considered. As the photon energy increased from 0.662 MeV to 1.600 MeV, the values of the energy-transfer cross sections decreased from 81.135 cm2 to 69.184 cm2 in the case of Bi, from 50.832 cm2 to 43.344 cm2 for Te, from 54.742 cm2 to 46.678 cm2 for Ba, and from 29.326 cm2 to 25.006 cm2 for Zn. The obtained results and the detailed information of the attenuation properties for the studied elements would be helpful in developing a new generation of shielding materials against gamma rays.

Analytical approximation of cross sections of collisions of electrons with atoms of inert gases

The paper presents an analysis of data on the cross sections of elastic and inelastic collisions of electronswith noble gas atoms. The transport (diffusion) cross section, the excitation and ionization cross sectionsare considered. The bibliography on the cross sections of electron-atomic collisions includes manythousands of works. But the critical analysis of the results of experimental data in the review work is verydifficult due to the fact that the necessary initial data can only be available to the authors of the work. Theerrors of the order of 1-3% given in the original works are contrasted with each other, sometimesdiffering by 50%. Comparisons of the electron cross sections sets in noble gases was made. For theselected sets of experimental and theoretical data, optimal analytical formulas are found andapproximation coefficients are selected for them. The obtained semi-empirical formulas allow us toreproduce the cross-section values for them in a wide range of collision energies from 0.001 to 10000 eVwith an accuracy of several percent. Key words: electron atomic collisions, transport cross section, excitation cross section, ionization crosssection, approximation of cross sections, noble gases.

Resonances in Chemical Reactions in Faddeev Approach

The main features of resonance in scattering are described and resonances are determined on the basis of the theory of collisions in a two-body system, as well as resonances emerging as a result of collisions in a few-body system. Regularities in the emergence of such resonances and their characteristics are analyzed. The results of calculations of these resonant processes occurring during collisions of electrons with diatomic molecules, made on the basis of the quantum theory of scattering in a few-body system, based on Faddeev-Yakubovsky equations are discussed. The results of calculations of the resonant cross sections of electron and atom collisions with molecules are presented. Obtained results are compared with the available experimental data and with the results of calculations based on other approximations. In addition, some biological applications (e.g. properties biopolymer molecules) are presented.

Elastic electron scattering with formamide-(H2O) n complexes (n = 1, 2): Influence of microsolvation on the π * and σ * resonances* *Project supported by the National Natural Science Foundation of China (Grant Nos. U1504109 and 11604085) and the Program for Science and Technology Innovation Talents in the Universities of Henan Province, China (Grant No. 19HASTIT018).

We report elastic cross sections for low-energy electron scattering with formamide-(H2O) n complexes (n = 1, 2) in the energy region of 0.01–8 eV. The scattering calculations are performed using the R-matrix method in the static-exchange (SE) approximation. We consider three structures of formamide–H2O and six structures of formamide–(H2O)2 in the present work. Our purpose is to investigate effects of water molecules hydrogen-bonding to formamide. We focus on the influence of microsolvation on the π * and σ * resonances of formamide. The scattering result for complexes shows that the position of π * resonance appears at lower or higher energies in the cluster than in the isolated formamide depending on the complex structure and the water role in the hydrogen bonding. We explain this behavior according to the net charge of the solute. It is found that the microsolvation environment has a substantial effect on the width of π * resonance. Our results indicate that surrounding water molecules may affect the lifetime of the resonances, and hence the process is driven by the anion state, such as the dissociative electron attachment.

Changes in the chemical state of metallic Cr during deposition on a polyimide substrate: Full soft XPS and ToF-SIMS depth profiles

We demonstrate the effectiveness of the combination of depth profile analyses based on soft X-ray photoelectron spectroscopy (XPS) with Ar+ sputtering and time-of-flight secondary ion mass spectrometry (ToF–SIMS) with Cs+ sputtering, to determine the changes in the chemical states of Cr nanofilms during deposition on a polyimide (PI) substrate, with nanoscale-depth resolution. The XPS and ToF-SIMS depth profiles obtained show evidence of preferential oxygen sputtering during Ar+ and Cs+ bombardment. Therefore, detailed analyses of the depth profiles and spectra were performed with consideration of the results of cross-sectional electron energy loss spectroscopy and non-destructive hard XPS for the same sample. As a result, the depth profiles for Cr, Cr2O, Cr2O3, Cr(OH)3, and CrO3 in the Cr film were successfully differentiated with nanoscale resolution. At the deeper area, the ratio of Cr2O3, Cr(OH)3, and CrO3 decreases, while that of Cr metal and Cr2O increases, which was caused by Ar+ and Cs+ sputtering. The presence of the Cr2O phase in the Cr film was revealed, regardless of the preferential sputtering. These results are very useful for optimization of the Cr/PI bilayer fabrication process, which is one of the most important components in flexible electronics.

Overcoming incompatibility of donors and acceptors by constructing planar heterojunction organic solar cells

Nanoscale phase separation plays a critical role in achieving high photovoltaic performance in bulk-heterojunction organic solar cells, which is limited by solubility, crystallinity, and the compatibility of the donors and acceptors. However, these limits can be overcome by new applications of the traditional planar heterojunction structure. Herein, we demonstrate quasi-orthogonal solvents for a wide-band-gap donor (P2F-EHp) and a highly crystalline non-fullerene acceptor (M4–4F) to overcome the over-agglomeration and enabled the fabrication of a planar heterojunction device with a favorable power conversion efficiency of 14.2% (compared with 12.7% in bulk-heterojunction device), which is among one of the highest efficiencies of planar heterojunction devices to date. Detailed studies based on cross-sectional transmittance electron microscopy, grazing incidence wide-angle X-ray scattering at various incident angles, and resonance soft X-ray scattering measurements confirmed the formation of optimal nanoscale morphology. Further transient absorption measurements also proved that the exciton dissociation and free-carrier generation efficiency are not limited by the small mixed-phase area and large pure domains. These findings show insights into the intrinsic morphological changes and charge transfer process in bulk-heterojunction and planar heterojunction structures, providing a novel method for matching donors and acceptors with relatively poor compatibility. • Comparing absorption, morphology, and charge carrier dynamics of BHJ and PHJ devices. • Introducing an effective approach to construct OSCs using poorly compatible donors and acceptors. • Demonstrating the possibility of obviating the need for bulk-heterojunction structure.

Ramsauer\u2013Townsend minimum in electron scattering from CF_4: modified effective range analysis

Elastic cross sections for electron scattering on tetrafluoromethane (CF_4) from 0 up to 5 eV energy are analyzed using semi-analytical approach to the modified effective range theory (MERT). It is shown that energy and angular variations of differential, integral and momentum transfer cross sections can be parameterized accurately by six MERT coefficients up to the energy region of the resonant scattering. In particular, the model is used to determine the depth and the position of the Ramsauer–Townsend minimum as well as the s-wave scattering length. Moreover, we investigate the influence of the dipole polarizability value on the predictions of present model. To further validate our approach, the elastic data are combined with the Born-dipole cross sections for vibrational excitations as the input data for Monte Carlo simulation of electron swarm coefficients.Graphic

Characterization of as-deposited cold sprayed Cr-coating on Optimized ZIRLO™ claddings

As-produced Cr-coated Optimized ZIRLO™ cladding material fabricated with the cold-spray (CS) deposition process is studied. Cross-sectional electron microscopy, nano-hardness profiling, transmission electron microscopy, transmission Kikuchi diffraction, and atom probe tomography (APT) were performed to investigate the nature of the CS Cr-coating/Optimized ZIRLO™ interface, the microstructure of the coating, and the effects of the deposition on the Zr-substrate microstructure. The former surface of the Zr-substrate was found to have a highly deformed nano-crystalline microstructure, the formation of which was attributed to dynamic recrystallization occurring during coating deposition. This microstructural change, evaluated with electron backscattered diffraction and nano-hardness profiling, appeared to be confined to a depth of a few microns. Through APT analysis, a 10–20 nm thick intermixed bonding region was observed at the interface between coating and substrate. The chemical composition of this region suggests that this layer originated from a highly localized shearing and heating of a thin volume of the outermost former surface of the substrate. The study of the intermixed bonding region's crystalline structure was performed with high resolution transmission electron microscopy and revealed a distorted hexagonal close-packed structure.

Ion irradiation-induced localized stress relaxation in W thin film revealed by cross-sectional X-ray nanodiffraction

The influence of ion irradiation on residual stress and microstructure of thin films is not fully understood. Here, 5 MeV Si2+ ions were used to irradiate a 7 µm thick tungsten film prepared by magnetron sputtering. Cross-sectional X-ray nanodiffraction and electron microscopy analyses revealed a depth-localized relaxation of in-plane compressive residual stresses from −2.5 to −0.75 GPa after the irradiation, which is correlated with the calculated displacements per atom within a ~2 µm thick film region. The relaxation can be explained by the irradiation-induced removal of point defects from the crystal lattice, resulting in a reduction of strains of the 3rd order, manifested by a decrease of X-ray diffraction peak broadening, an increase of peak intensities and a decrease of lattice parameter. The results indicate that ion irradiation enables control over the residual stress state at distinct depths in the material.

Recommended Cross Sections for Electron–Indium Scattering

We report, over an extended energy range, recommended angle-integrated cross sections for elastic scattering, discrete inelastic scattering processes, and the total ionization cross section for electron scattering from atomic indium. In addition, from those angle-integrated cross sections, a grand total cross section is subsequently derived. To construct those recommended cross-section databases, results from original B-spline R-matrix, relativistic convergent close-coupling, and relativistic optical-potential computations are also presented here. Electron transport coefficients are subsequently calculated, using our recommended database, for reduced electric fields ranging from 0.01 Td to 10 000 Td using a multiterm solution of Boltzmann’s equation. To facilitate those simulations, a recommended elastic momentum transfer cross-section set is also constructed and presented here.

Electron transport in DNA bases: An extension of the Geant4-DNA Monte Carlo toolkit

The Geant4-DNA Monte Carlo toolkit is extended to include electron interactions with the four DNA bases using cross sections implemented in Geant-DNA CPA100 models. Electron cross sections for elastic scattering, ionisation, and excitation are calculated in the four DNA bases (adenine, thymine, guanine and cytosine) with relativistic energy range. These are implemented within the “option6” physics constructor to extend its capability of tracking electrons in DNA material in addition to liquid water. Differential and integrated cross sections calculations are in good agreement with the literature for all DNA bases. Stopping power, range and inelastic mean free path calculations in the four bases agree well with other studies, especially for high energy electrons with some deviations at low energies. Differences from water simulations emphasize the need to include DNA bases cross sections in track structure codes for better estimation of radiation effects on biological material.