DeepCSNet: a deep learning method for predicting electron-impact doubly differential ionization cross sections

Absolute electron impact ionization cross sections for highly charged ions: Scaling law for hydrogen-like ions

Currently there are no reliable theoretical approaches for calculating fully differential cross sections (FDCSs) for low-energy electron-impact ionization of large molecules. We have recently proposed the orientation-averaged molecular orbital (OAMO) for calculating cross sections averaged over molecular orientations. In this paper, we use the OAMO to calculate distorted wave Born approximation (DWBA) and molecular three-body distorted wave (M3DW) Born approximation FDCS for electron-impact ionization of the nitrogen molecule. Both coplanar symmetric and asymmetric FDCSs are investigated in the energy range of 35.6-400 eV. By comparing with the experimental data, we found that the M3DW is reasonably accurate in this energy range. We also found that the postcollision interaction plays a sufficiently important role and that the DWBA is not reliable.

The applicability of the geometrical model (GM) proposed in [14, 15] to calculate the ionization probability and cross section of atoms and ions during collisions with ions, including structural ions, was studied at high velocities of partners. The GM represents a version of the classical impulse approximation. It was shown that the GM in all cases under consideration allows estimation of the ionization probability and total corss section of an atom or an ion during collisions with ions with deviations of no more than 50% from the results of the classical Monte Carlo method. GM calculations are rather simple in computation respect and limit the ionization probability by unity at arbitrary impact parameters.

The BBK model is modified by the introduction of effective Sommerfeld parameters for both symmetric and asymmetric geometries on an empirical basis, while still maintaining the philosophy that all three Coulomb interactions are included on an equal footing. The triple differential cross sections for electron-impact ionization of atomic helium at an incident energy of 40 eV in an asymmetric geometry are calculated. Results of this approach are compared with the absolute measurements and the only existing theoretical results of the convergent close-coupling method.

Metasurface-based carpet cloaks although are very thin and have a good performance, are very sensitive to the incident angles and work only for a very narrow range of incident angles. In this paper, we have addressed this issue using PSO algorithm in combination with a deep neural network. A passive single-layer metasurface capable of making objects under it invisible for a wide range of incident angles, 0 to 70 degrees, is designed and optimized using PSO algorithm in combination with a deep neural network. The cloak has been designed and evaluated using full-wave numerical simulations, and the results show a good performance in the mentioned incident angle band.

The zero-coverage probability of dissociative chemisorption of O2 on Ir(110)-(1×2) has been measured using molecular-beam techniques for a wide range of incident kinetic energies, incident angles, and surface temperatures. The data indicate that a trapping-mediated mechanism is responsible for dissociative chemisorption at low energies, whereas at high energies a direct mechanism accounts for dissociative adsorption. Total energy scaling approximately describes the dissociative dynamics on the very corrugated Ir(110)-(1×2) surface.

The present study deals with the calculation of elastic [integrated and differential cross section (DCS)], momentum-transfer, excitation, and ionization cross sections for electron impact on S${}_{2}$ molecules using the R-matrix method. The target states are represented by including correlations via a configuration-interaction technique. We used a double zeta plus polarization Gaussian basis set contracted as (12,8,1)/(6,4,1) for S atoms. The results of the static exchange, correlated one-state, and 20-state close-coupling approximations are presented. We have detected a stable anionic bound state ${}^{2}{\ensuremath{\Pi}}_{g}$ of S${}_{2}$${}^{\ensuremath{-}}$ having the configuration $1{\ensuremath{\sigma}}_{g}^{2}\ensuremath{\cdots}$$5{\ensuremath{\sigma}}_{g}^{2}$ $1{\ensuremath{\sigma}}_{u}^{2}\ensuremath{\cdots}4{\ensuremath{\sigma}}_{u}^{2}$ $1{\ensuremath{\pi}}_{u}^{4}$ $1{\ensuremath{\pi}}_{g}^{4}$ $2{\ensuremath{\pi}}_{u}^{4}$ $2{\ensuremath{\pi}}_{g}^{3}$. The vertical electron affinity value is 1.42 eV, which is comparable with the experimental value of $1.67\ifmmode\pm\else\textpm\fi{}0.015$ eV. We detected two shape resonances, both of ${}^{2}{\ensuremath{\Pi}}_{u}$ symmetry in the excitation cross sections of the ${}^{1}{\ensuremath{\Delta}}_{g}$ and ${}^{1}{\ensuremath{\Sigma}}_{g}^{+}$ excited states. The dissociative nature of these resonances is explored by performing scattering calculations in which the S-S bond is stretched. These resonances support dissociative attachment, yielding S and S${}^{\ensuremath{-}}$. We have also predicted six resonances of various symmetries (${}^{2}{A}_{u}$, ${}^{2}{B}_{1g}$,${}^{4}{A}_{u}$, ${}^{4}{B}_{1g}$) in the $X{\phantom{\rule{0.16em}{0ex}}}^{3}{{\ensuremath{\Sigma}}_{g}}^{\ensuremath{-}}$ $\ensuremath{\rightarrow}$ $B{\phantom{\rule{0.16em}{0ex}}}^{3}{{\ensuremath{\Sigma}}_{u}}^{\ensuremath{-}}$ transition. We have calculated the DCS, in a correlated one-state model, by using the polydcs program of Sanna and Gianturco. The data from the momentum-transfer cross section, generated from DCS, are used to compute effective collision frequencies over a wide electron temperature range (200--30 000 K). The ionization cross sections are calculated in the binary-encounter Bethe model in which Hartree-Fock molecular orbitals at a self-consistent level are used to calculate kinetic and binding energies of the occupied molecular orbitals. We have included up to $g$-partial wave ($l=4$) in the scattering calculations. For this molecule we have used a Born-closure top-up procedure to account for the higher partial waves for the convergence of the cross section for the dipole-allowed excitation from the ground state. We have also evaluated the scattering length of the S${}_{2}$ molecule, which is equal to 2.615${a}_{0}$.

Compact and inexpensive solar concentrators can be designed by using transmission gratings that diffract incident sunlight into a light guide. To this end a grating should have a small period and maintain a high diffraction efficiency over a wide range of incident angles. We numerically study the angular dependence of the diffraction efficiency of surface-relief gratings using Rigorous Coupled-Wave Analysis. It is shown how one can control the angular acceptance of gratings by tuning the refractive index or the grating topology. Gratings with a high refractive index maintain a high diffraction efficiency over a wide range of incident angles. By adjusting the topological symmetry one can design a grating with a high diffraction efficiency over a narrow range of incident angles, or a grating with a more homogenous distribution of the diffraction efficiency.

Deuteron-stripping reactions at high energy: George W. Barry. The Enrico Fermi Institute and the Department of Physics, The University of Chicago, Chicago, Illinois

Large volume of the experimental data on the ionization cross sections of atoms and molecules by electron impact obtained by various authors using different methods is analyzed. The dependence of the ionization cross section Q on the energy of the incident electron E is described by a curve with a maximum. For E ≤ I, where I is the ionization potential, the cross section naturally vanishes. For E > I, it first increases fast, passes through a high maximum, and then monotonically decreases with increasing E. For comparatively large energies E > 100 I, the Bethe formula describes the experimental data almost exactly, but in the region of maximum I < E < 10 I, it deviates significantly from the measurement data. In the present paper it has been established that the experimental dependence Q(E) in the region of maximum is well described by a resonant curve similar to Lorentz distribution. It is assumed that the main contribution to the atomic ionization by a slow electron comes from the resonant excitation and the decay of the Fermi electron-hole system. An empirical formula for the cross section of atom ionization by electron impact Q(E) is suggested which takes into account resonance for incident electrons of small energies and is transformed into the Bethe formula for large E. The parameters of the formula for the ionization cross section are calculated by the least-squares method for H, He, Ne, Ar, C, N, O, Li, Na, H2, N2, O2, K-shells of C, N, Ne, Ar, K, Ca, Rb, and Sr atoms and molecules. A comparison of the experimental dependences of the ionization cross section on the energy of the incident electron with the Bethe theoretical formula and empirical formulas suggested by Lotz, Alkhazov, Kim and Rudd, and Povyshev et al. demonstrates that the formula suggested in the present paper describes the available experimental data better than others.

As protective apparatus, electromagnetic windows (EMWs) are usually realized utilizing dielectric materials with higher permittivity or larger thickness to perform good mechanical properties. However, due to impedance mismatch, higher insertion loss is inevitably created, especially at large incident angles. It is now still a great challenge to engineer EMWs with stable operating bands and a wide range of incident angles for both transverse electric (TE)-and transverse magnetic (TM)-polarizations. In this article, we propose a method to achieve such EMWs by the synergy of multimechanism resonances, which enables broadband transmissions of both TM-and TE-polarized waves in an ultrawide range of incident angles. Fano resonance is first introduced to expand the bandwidth for TE-polarization on the basis of thickness resonance. Drude resonances are then introduced to suppress adverse influences of the parasitic Lorentz resonance for TM-polarization, to maximize the shared transmission band for TM-and TE-polarizations. The ultrawide-angle broadband functionalities of this EMW are validated by experiments, which agree well with numerical simulations. This work provides an efficient route to realize practical high-performance EMWs, under sufficient consideration of available materials, structures, and fabrication techniques, which may find wide applications in radar, communication, and imaging systems.

Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122 degrees, while for the crystalline lens effect, the incident angle was varied from 60 to 90 degrees. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of x22.5 was found at an incident angle of 104 degrees which compares well with previous results. The average intensity gain at this angle was x7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at x8.6 at 84 degrees with average intensity gain of x2.3. The area of UVA exposure peaked at 4.7 mm2 at 70 degrees. A relatively wide range (30 degrees ) of incident angles produced peak PLF gains of x3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.

An analytical expression based on the binary-encounter-Bethe model for energy differential cross sections in the low binding energy regime is presented. Both the binary-encounter-Bethe model and its modified counterpart are extended to shells with very low binding energy by removing the constraints in the interference term of the Mott cross section, originally introduced by Kim et al. The influence of the ionic factor is also studied for such targets. All the binary-encounter-Bethe based models presented here are checked against experimental results of low binding energy targets, such as the total ionization cross sections of alkali metals. The energy differential cross sections for H and He, at several incident energies, are also compared to available experimental and theoretical values.

We have employed the R-matrix method to compute elastic (integrated and differential), momentum-transfer, excitation, and ionization cross sections for electron impact on the NH radical. The target states are represented by including correlations via a configuration interaction technique. The results of the static exchange, correlated one-state configuration interaction, and 19-state close-coupling approximation are presented. We have detected a stable anionic bound state {sup 2{Pi}} of NH{sup -} having the configuration 1{sigma}{sup 2}2{sigma}{sup 2}3{sigma}{sup 2}1{pi}{sup 3}. The data of the momentum-transfer cross section, generated from the differential cross section, is used to compute effective collision frequencies over a wide electron temperature range (200-30 000 K). The ionization cross sections are calculated in the binary-encounter Bethe model in which Hartree-Fock molecular orbitals at self-consistent levels are used to calculate kinetic and binding energies of the occupied molecular orbitals. We have included up to the g partial wave (l=4) in the scattering calculations. For this dipolar molecule we have used a Born-closure top-up procedure to account for the higher partial waves for the convergence of the cross section.

Multiphoton ionization of atoms is a typical example of one of the new fields of investigation in atomic physics that lasers have opened up. The different aspects of the multiphoton ionization of one-electron atoms have been well understood these last few years. They can be correctly described by rigorous theoretical models in the framework of perturbation theory when only one electron is assumed to be involved in the ionization [1–5]. Alkaline atoms which have only one valence electron, and of course atomic hydrogen, are the examples that best satisfy this condition. For example the different aspects of multiphoton ionization of cesium atoms now form a well developed field. Accurate measurements of absolute values of the two and four-photon ionization cross sections of cesium atoms are in good agreement with calculated values, and clearly emphasize the validity of perturbation theory [6]. In the same way, there is also a good agreement between theoretical and experimental results on resonance effects in multiphoton ionization of cesium atoms in the moderate laser intensity range, 107–109 W.cm-2 [7]. Resonance effects emphasize the important role played by laser-induced atomic level shifts. Destructive interference effects, which give rise to minima in the multiphoton ionization cross sections of atoms, have been investigated with a high degree of accuracy in the two-photon ionization of Cs atoms [8].