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Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitudes and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such an underestimation. One way to do this is to test and validate the existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average or typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from the EISCAT (European Incoherent Scatter scientific radar system) radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from the Polar Operational Environmental Satellite (POES) as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

The synthesis of Nb4S3, a previously undiscovered binary sulfide, was achieved using Nb3Br7S as a precursor. Its structure is composed of Nb6S triangular prisms arranged in a polar (Imm2) configuration, with sulfur atoms lying in channels along the a axis. Electrical resistivity measurements and density functional theory calculations were used to determine that Nb4S3 is metallic and therefore a polar metal, with metallic bands occupied by electrons with primarily niobium character. The electrons near the Fermi level are so closely associated with the niobium sublattice that the sulfur atoms have positive Born effective charges, indicating that the electrostatic interactions between sulfur atoms are unscreened. Calculations of the dependence of the electron density on the sulfur atomic positions confirm that the metallic electrons do not screen the dipole-dipole interactions between sulfur atoms, which allows polarity and metallicity to coexist in Nb4S3. These findings suggest that applied electric fields might be able to reverse the polarity of thin films of Nb4S3.

Transient tuning of material properties by light usually requires intense laser fields in the nonlinear excitation regime. Here, we report ultrafast ferroelectric ordering on the surface of a paraelectric topological semimetal 1T'-MoTe2 in the linear excitation regime, with the order parameter directly proportional to the excitation intensity. The ferroelectric ordering, driven by a transient electric field created by electrons trapped angstroms away from the surface in the image potential state (IPS), is evidenced in two-photon photoemission spectroscopy showing the energy relaxation rate proportional to IPS electron density, but with negligible change in the free-electron-like parallel dispersion. First-principles calculations reveal an improper ferroelectric ordering associated with an anharmonic interlayer shearing mode. Our findings demonstrate an ultrafast charge-based pathway for creating transient polarization orders.

This work reports a 2-D full kinetic particle-in-cell plus Monte Carlo collision (PIC/MCC) model for an ion thruster discharge chamber. The model focuses on the influences of the magnetic field strength, the magnetic field topography, and the number of magnetic rings on discharge characteristics. The dependence of plasma behavior and discharge parameters on different magnetic field configurations is analyzed in detail. The simulation results suggest that the enhancement of the magnetic field strength aggravates the confinement of the primary electrons, resulting in higher electron density, ionization rate, and ion density. The primary electrons near the axis undergo numerous inelastic collisions and lose energy, which behaves that the energy of the primary electrons decreases with the increase in the magnetic field strength. Meanwhile, the stronger magnetic field reduces the discharge loss and advances the fraction of the ions extracted into the beam, which reflects favorable discharge efficiency. Furthermore, the improvement of magnetic field topography by adding additional magnetic rings promotes the off-axis of primary electrons and presents a better plasma uniformity. This effort provides insights for understanding plasma confinement and optimizing magnetic field design.

During the last decade a new probe design for active plasma resonance spectroscopy, the multipole resonance probe (MRP), was proposed, analyzed, developed, and characterized in two different designs: the spherical MRP (sMRP) and the planar MRP (pMRP). The advantage of the latter is that it can be integrated into the chamber wall and can minimize the perturbation of the plasma. Both designs can be applied for monitoring and control purposes of plasma processes for industrial applications. As usual for this measurement technique, a mathematical model is required to determine plasma parameter (electron density, electron temperature, and collision frequency of electrons with neutral atoms) from the measured resonances. Based on the cold plasma model a simple relationship between the resonance frequency and the electron density can be derived and leads to excellent measurement results. However, a simultaneous measurement of the electron temperature in low-pressure plasmas requires a kinetic model, because the half-width of the resonance peak is broadened by kinetic effects. Such a model has been derived and first results show the broadening of the spectra as expected. Deriving a relation between the half-width and the electron temperature will allow the simultaneous measurement and an improvement of monitoring and control concepts.

This article re-examines the Brillouin flow solutions in crossed-field diodes, with applications to magnetrons, magnetically insulated line oscillators (MILOs), and magnetically insulated transmission lines (MITLs). The Brillouin flow solutions are constructed for various geometries, including planar magnetrons, MILOs, and MITLs, cylindrical magnetrons with electrons flowing in the azimuthal direction, cylindrical MITLs and MILOs with electrons flowing in the axial direction, and radial MITLs and MILOs with electrons flowing in the radial direction. A common theme of this analysis is that two main external parameters are used to characterize the Brillouin flow: the anode–cathode voltage ( $V_{a}$ ) and the total magnetic flux within the crossed-field diodes ( $A_{a}$ ). These two parameters are equivalent to the gap voltage and a specification of the degree of magnetic insulation, which is approximately equal to the ratio of the magnetic field to the Hull cutoff (HC) magnetic field. The magnetic flux may be provided externally by a magnet (as in a magnetron) or by the wall currents without an external magnet (as in a MILO or MITL), or by some combination of the two, as in the intermediate case of a magnetron–MILO hybrid. Once these two parameters are specified, the electron flow speed at the top of the Brillouin hub is uniquely determined. This immediately yields the Buneman–Hartree (BH) condition according to the Brillouin flow model, whether it be a planar magnetron or a cylindrical MILO. In so doing, we have obtained, for the first time using the Brillouin flow model, the BH condition for a cylindrical MILO, and we show that the same condition is obtained from the single-particle orbit model. We also found that, in general, the electron current within the Brillouin hub contributes only to a very small fraction of the magnetic flux $A_{a}$ , regardless of the gap voltage $V_{a}$ , thereby correcting an erroneous notion that the electron flow within the crossed-field gap could be responsible for the magnetic insulation. Another counter-intuitive finding is that, for a given degree of magnetic insulation, the Brillouin hub height decreases as the gap voltage $V_{a}$ increases. These conclusions, and other results, were based on the simple, explicit analytic expressions that we have obtained for the Brillouin flow profiles, including the velocity, electron density, as well as the self-magnetic field and the self-electric field profiles due to the Brillouin hub electrons. From these analytical expressions, we deduce useful scaling laws that are applicable to the prevailing cases where the magnetic field exceeds 1.5 times the HC magnetic field, and they are valid in both relativistic and non-relativistic regimes. Thus, these scaling laws show the contrast between magnetrons and MILOs, and a ready assessment of the viability of building a moderate-current MILO, a low-voltage MILO, and a magnetron–MILO hybrid which might combine the advantages of a magnetron and a MILO. The Brillouin flow profiles in a radial MITL are explicitly calculated. Additional issues are addressed.

This article presents a compact quantum threshold voltage ( ${V}_{\text {th}}$ ) shift model for a junctionless (JL) quadruple-gate (QG) FET in subthreshold region. Starting from our previous compact model for JL QG FET, the potential and the classical electron density are calculated. Considering 2-D quantum confinement, four types of quantum systems are modeled as a combination of quantum harmonic oscillator (QHO) and quantum well with bottom perturbation potential, depending on the device dimensions. Electron subband energy level for each quantum system is analytically derived to get quantum electron density. The quantum ${V}_{\text {th}}$ shift model is obtained by the ratio of quantum and classical electron line density. The modeling results are validated by 3-D numerical device simulation. It is shown that the proposed model can accurately capture the quantum ${V}_{\text {th}}$ shift in JL QG FET where both fin width and height are 3 nm. Therefore, the proposed ${V}_{\text {th}}$ shift model can be used for quantum corrections for circuit simulation of JL QG FETs.

Using the integral form of governing equation in terms of pseudopotential, the effect of higher-order nonlinear and dispersive effects on the dressed solitons (DS) and double layers (DL) of ion-acoustic waves has been theoretically studied in an ultra-relativistic degenerate (URD) plasma consisting of cold inertial ions, degenerate two-temperature electrons and negatively charged dust particles. The solution of DS in such plasma is obtained up to second-order approximation. The profiles of DS are drawn and discussed for different values of density and temperature of this plasma. The DS is compressive in the plasma for different values of density and temperature of degenerate electrons, and its amplitude is much larger than that of the first-order (KdV) solitons. The DS is compressive with wave-like structure for some value of the temperature of degenerate electrons, and its amplitude is lower than that of the KdV solitons. Moreover, the solution for the DS near-critical state is obtained and discussed graphically. Near-critical state, the temperatures of URD electrons have important roles in the DS. The solution of DL in the plasma has also been obtained and graphically discussed. Both compressive and rarefactive DL will be excited in URD two-temperature-electron plasma for different values of the electron density. But, only rarefactive DL would be excited in this plasma for different values of the electron temperature. The results are new and these would be applicable in space plasma.

The molecular orbitals (MOs) of diformohydrazide have been determined from the electron density measured by X-ray diffraction. The experimental and refinement procedures are explained in detail and the validity of the obtained MOs is assessed from the crystallographic point of view. The X-ray structure factors were measured at 100 K by a four-circle diffractometer avoiding multiple diffraction, the effect of which on the structure factors is comparable to two-centre structure factors. There remained no significant peaks on the residual density map and the R factors reduced significantly. Among the 788 MO coefficients, 731 converged, of which 694 were statistically significant. The C—H and N—H bond distances are 1.032 (2) and 1.033 (3) Å, respectively. The electron densities of theoretical and experimental MOs and the differences between them are illustrated. The overall features of the electron density obtained by X-ray molecular orbital (XMO) analysis are in good agreement with the canonical orbitals calculated by the restricted Hartree Fock (RHF) method. The bonding-electron distribution around the middle of each bond is well represented and the relative phase relationships of the π orbitals are reflected clearly in the electron densities on the plane perpendicular to the molecular plane. However, differences are noticeable around the O atom on the molecular plane. The orbital energies obtained by XMO analysis are about 0.3 a.u. higher than the corresponding canonical orbitals, except for MO10 to MO14 which are about 0.7 a.u. higher. These exceptions are attributed to the N—H...O′′ intermolecular hydrogen bond, which is neglected in the MO models of the present study. The hydrogen bond is supported by significant electron densities at the saddle points between the H(N) and O′′ atoms in MO7, 8, 14 and 17, and by that of O′′-p extended over H(N) in MO21 and 22, while no peaks were found in MO10, 11, 13 and 15. The electron density of each MO clearly exhibits its role in the molecule. Consequently, the MOs obtained by XMO analysis give a fundamental quantum mechanical insight into the real properties of molecules.

This study employed the high-energy neutral-beam ion injection technique in orde to support the power of the magnetically confined plasmas in a tokamak reactor. Beside its potential role as a plasma fuelling mechanism, this technique would offer a considerable increase in the fusion power density, which is the result of the direct involvement of the injected ions with the fusion processes. In this way, the calculation and evaluation of these parameters affecting the energy multiplication factor become very important for D-6Li two-energy-component plasma. The results of this study indicate that the suitable injection energy of deuteron beam for doing this reaction is about 5 MeV. Moreover, the fusion energy multiplication factor $\psi _{{^{\textrm {D}{}^{6}\textrm {Li}}} } $ for $E_{0} > 5$ MeV decreases with the increase in the deuteron initial energy $E_{0}$ . This factor is enhanced with an increase in the electron temperature at constant $E_{0}$ and the $\psi _{{^{\textrm {D}{ }^{6}\textrm {Li}}}} $ increases slowly with the ion temperature. In order to produce effective electricity, $\psi _{{^{\textrm {D}{}^{6}\textrm {Li}}}} \simeq 12$ is also necessary. Besides, the life-time $\tau _{f}$ of the fast ions should be more than the energy confinement time $\tau _{E}$ , in order to obtain the full $\psi _{{^{\textrm {D}{}^{6}\textrm {Li}}}} $ . The contribution of the high-energy part of the dispersion is also more important than the contribution of the low-energy part at energies that are lower than the peak in the $\psi _{{^{\textrm {D}{}^{6}\textrm {Li}}}}$ -value. Furthermore, by using the “energy-clamping” methods, the amount of $\psi _{{^{\textrm {D}{ }^{6}\textrm {Li}}}} $ is increased by about 10% per decade of electron density and is also being improved for the same $T_{e}$ . In sum, this factor is decreased because of the existence of the impurity ions, the charge exchange, and the trapped electron losses under normal conditions.

A circuit modeling approach for self-sustained capacitively coupled microwave plasmas is introduced and validated in this article. The model solves the particle balance equation using a novel circuit optimization scheme to calculate the plasma parameters like electron density, sheath thickness, and electron temperature for a given input power, operating frequency, gas type, and pressure. While the existing models capture the ohmic loss in the bulk plasma region, the proposed model also takes into account power required to sustain plasma which proves to be considerable for higher electron densities. The model is rigorously validated using experimental results from two cases—one resonant and one non-resonant—both with self-sustained microwave plasma. As the post-processing results, other discharge parameters like sheath and plasma voltages as well as plasma reduced field are calculated. The proposed modeling approach can substantially simplify design and analysis of capacitively coupled microwave plasmas.

This work presents a systematic numerical investigation on the behaviors of electrons in the bullet in the Ar/O2 plasma jet in changing oxygen concentration and the applied voltage, based on a needle-plate discharge configuration and a 1-D particle-in-cell Monte-Carlo collision (PIC-MCC) method. The increase in oxygen concentration allows more electrons to be scattered toward the target, i.e., more electrons to most probably interact with the target, and induces a dramatic increase of reactive oxygen species (ROS), but leads to the decrease of the bullet velocity and average electron energy. In addition, there is a weak correlation between the electron density and ROS generation. When increasing the applied voltage, the electrons scattered toward the target decrease, however, the majority of these electrons, above 70%, are of energy higher than the threshold inducing a dissociative electron attachment (DEA) to water molecule, and meanwhile, there is an evident increase of high-energy electrons being able to excite water molecules. Also, there is a strong correlation between the electron density and ROS generation. The present results are also compared with those in the Ar/H2O plasma jets, indicating qualitative and quantitative differences.

The interaction between an argon plasma jet excited using microsecond duration voltage pulses and a liquid target was examined using Thomson scattering to quantify the temporal evolution of the electron density and temperature. The electrical resistance between a liquid target and the electrical ground was varied from 1 to $$680\, \text {k}\Omega $$ 680 k Ω to mimic different conductivity liquids while the influence of the varying electrical properties on the electron dynamics within the plasma were examined. It was demonstrated that the interaction between the plasma jet and a liquid target grounded via a high resistance resulted in typical dielectric barrier discharge behaviour, with two discharge events per applied voltage pulse. Under such conditions, the electron density and temperature reached a peak of $$1\cdot 10^{15}\, \text {cm}^{-3}$$ 1 · 10 15 cm - 3 and 3.4 eV, respectively; with both rapidly decaying over several hundreds of nanoseconds. For liquid targets grounded via a low resistance, the jet behaviour transitioned to a DC-like discharge, with a single breakdown event being observed and sustained throughout the duration of each applied voltage pulse. Under such conditions, electron densities of $$2{-}3 \cdot 10^{15}\, \text {cm}^{-3}$$ 2 - 3 · 10 15 cm - 3 were detected for several microseconds. The results demonstrate that the electron dynamics in a pulsed argon plasma jet are extremely sensitive to the electrical characteristics of the target, which in the case of water, can evolve during exposure to the plasma.

Atoms may repel or attract each other, but bound systems get virtually all of the attention in the classroom. To address the imbalance, instructors can explore the basis of repulsion in a few simple systems and highlight the important role played by the Pauli principle. A good example is the first triplet excited state of H2 wherein both electrons have the same spin. In light of the Hellmann–Feynman theorem, the net interaction is repulsive due to the low electron density that results in the region between the two nuclei. Analogous destabilization occurs in σ-bonding systems involving 3 electrons because two-thirds of the electrons have the same spin. Symmetrical systems like He2+ are exceptions and actually do form bonds because the minority spin is able to delocalize over both centers. In contrast, the ground state of the neutral He2 system entails 2 α and 2 β electrons and is strictly repulsive. Finally, the lowest energy triplet state of ethylene twists toward a D2d structure to avoid a destabilizing interaction akin to that identified in the triplet state of H2.

Electrostatic damped field characteristics in non-thermal fast positron and electron plasma having fluids of positive and negative pair ions have been discussed when collisional frequencies parameters are taken into account. The damped and forced form of Kadomtsev-Petviashvili (DKP) equations have been obtained. The plasma parameters effects of electron density ratio, the negative ionic density ratio, the pair ionic charge ratio, the density of positron ratio, the collisional frequencies, ion mass ratio and the fast non-thermality on the electrostatic damped and forced field formations, as observed in D-F -ionosphere and laboratory experiments have been investigated.

We report the results of studies of electron-electron relaxation processes in the system of strongly degenerated 2D-electrons with the fine structure of the energy spectrum and spatial distribution of the electron density. For a heavily doped heterojunction, when two subbands of size quantization are filled, the expressions for the time of the electron-electron intra- and inter-subband interactions are found, the matrix elements of the complete screening potential and polarization function are defined in the approximation far from the long-wavelength limit. It is shown that the oscillations of the temperature and concentration dependences of the electron-electron interaction time are associated with the excitation of plasma oscillations of 2D-electron system components.

The properties of the cation vacancies in the cubic phase of the magnetic Fe3O4 oxide (magnetite) are calculated using the spin density functional theory with allowance for strong electron correlations (DFT+U method). The influence of the key model parameters (effective Hubbard correction value, supercell size, initial approximations to wavefunctions and electron density) on the description of the electronic structure of the cubic phase of magnetite is analyzed. A procedure is proposed to search for a solution with the lowest total energy, which solves the local minima problem peculiar to DFT+U. The found versions of the charge and orbital orderings of the ground state of the electronic system are characterized. The versions used to optimize the structures of cation vacancy models are described and the corresponding formation energies are determined.

Radio occultations are commonly used to determine vertical profiles of ionospheric electron density from measurements of frequency. “Frequency residuals” are important intermediate data products in radio occultation experiments. Frequency residuals are defined as the difference between observed and predicted values of the received frequency, where the predicted frequency includes all effects except refraction at the target object. However, relationships between properties of a vertical profile of ionospheric electron density and properties of time series of frequency residuals are not widely known by the broad community of scientists who may work with frequency residuals. Here we illustrate and explain how properties of a vertical profile of ionospheric electron density affect time series of frequency residuals. We also develop four quantitative relationships between electron density values and frequency residuals. These provide predictions for the topside plasma scale height, topside electron densities, peak altitude, and peak electron density that can be generated directly from a set of frequency residuals without the need to implement the full Abel transform analysis that is usually required to determine electron densities from frequency residuals. They can also be generated prior to the implementation of a high-quality baseline correction, to which the Abel transform analysis is sensitive. The development of these predictions assumed that the ionosphere has an exponential topside and a Chapman-like peak. These predictions are successfully tested on two-way radio occultation observations from the MAVEN Radio Occultation Science Experiment (ROSE) at Mars.

Polyynes (C2nH2) show the unusually strong πg + πu combination bands in the infrared absorption spectra. We calculated them as the first overtone of the local CCH bending; the strong intensities are interpreted as a consequence of the large-amplitude bending vibration of the acidic acetylenic hydrogen combined with the size-dependent π electron conjugation. Our theoretical calculations show that the absorption intensity increases steadily and their increase rate is gradually slowed down by increasing the number of acetylene units up to n = 9. However, the calculated vibrational wavenumber converges quickly in agreement with the experimental observation. The second-order electron density deformation caused by the local CCH bending was analyzed using the linear response functions, including the linear and nonlinear contributions, to explain the n dependence. The easily polarizable π electron density caused two kinds of deformation-dominant but dark δxx-yy type and minor but bright σ type. Both of them exhibit interesting zigzag sign alternations, consistent with the law of alternating polarity of Coulson and Longuet-Higgins. The electron density polarization in these intra- and interacetylene units induces a large axial component molecular dipole moment, contributing to the intensity that increases with n. The difference between the curvilinear and rectilinear bending coordinates is interpreted within the present theoretical scheme.

In radionuclide compounds undergoing electron capture (EC) decay, the electron density at the nucleus (ρ(0)) and half-life of the nucleus are inversely proportional. Thus, the decay can be accelerated by changing the chemical or physical conditions. A previous study reported a 1.1-1.5% reduction in the half-life of 7Be encapsulated in C60 compared with 7Be metal. However, 7Be was inserted into the fullerene using the rebound energy of the nuclear reaction, which may not be a practical method. This paper elucidates the mechanism of ρ(0) change in various Be compounds from density functional calculations and attempts to propose better systems that show faster EC decay (larger ρ(0)) and/or that are easier to generate than Be in C60. In typical Be compounds, ρ(0) decreases because Be donates electrons to other atoms through chemical bonds and, thus, is not effective. Among the various Be-encapsulated fullerenes (C20-C180), the largest increase in ρ(0) was obtained for C50 fullerene, but the magnitude was almost similar to that of C60. As new systems, we propose Be-encapsulated rare gas solids, which would be generated only by applying high pressure. An increase in ρ(0) from Be metal in the range 2-10%, which depends on the lattice constant, is obtained.

This work extends the orbital-free density functional theory to the field of quantum crystallography. The total electronic energy is decomposed into electrostatic, exchange, Weizsacker and Pauli components on the basis of physically grounded arguments. Then, the one-electron Euler equation is re-written through corresponding potentials, which have clear physical and chemical meaning. Partial electron densities related with these potentials by the Poisson equation are also defined. All these functions were analyzed from viewpoint of their physical content and limits of applicability. Then, they were expressed in terms of experimental electron density and its derivatives using the orbital-free density functional theory approximations, and applied to the study of chemical bonding in a heteromolecular crystal of ammonium hydrooxalate oxalic acid dihydrate. It is demonstrated that this approach allows the electron density to be decomposed into physically meaningful components associated with electrostatics, exchange, and spin-independent wave properties of electrons or with their combinations in a crystal. Therefore, the bonding information about a crystal that was previously unavailable for X-ray diffraction analysis can be now obtained.

It is shown that the intrinsic magnetization of transition metal dichalcogenide monolayers calculated within the two-band model depends significantly on the boundary conditions on the electron wavefunction even in a macroscopic sample. The saturation effect of the magnetization in a narrow ring made of a transition metal dichalcogenide monolayer is established: the magnetic moment per unit length of the ring circumference approaches a constant value with an unlimited increase in the linear electron density.

Electrides have been identified so far by two major routes: one is conversion of elemental metals and stoichiometric compounds by high pressure; the other is to search for electron-rich compounds, and this approach is more general. In contrast, few electron-deficient structures in existing databases have been revealed as potential electride candidates. In this work, we found an electron-deficient compound Ca5Pb3 could be transformed into electrides upon applying external pressure or strain along the c-axis, which induces the electron immigration from Pb to interstitial sites. Furthermore, the electron doping via Hf substitution of Ca atoms for Ca5Pb3 was found to be capable of tuning the interstitial electron density under ambient pressure, resulting in a new stable ternary electride Ca3Hf2Pb3, Hf-substituted Ca5Pb3. The electron-deficient electride discovered here is of novel type and can largely expand the research scope of electrides. Considering a recently reported neutral electride Na3N and the present finding, it is now clarified that electrides can be identified irrespective of stoichiometry (electron-rich, -neutral, or -poor) for compounds.

In this article, the characteristics of the pseudospark (PS) discharge were studied through particle-in-cell simulations with the consideration of the external circuit. The different discharge stages, including the Townsend discharge, hollow cathode discharge, and super-dense glow, were characterized by the discharge voltage and current. The sources of electrons at different discharge stages were analyzed, with the electrons generated from the ionization of the background gas playing the dominant role. The electron densities at the Townsend discharge, hollow cathode discharge, and super-dense glow discharge stages were in the range of 1013, 1018, and 1020 m-3, respectively. The energy of the electron beam extracted at the anode aperture at different discharge phases was exported and postprocessed. The electron beams generated at the three stages have an energy spread of 10%, 20%, and 40%, respectively. The hollow cathode discharge phase has balanced parameters in beam energy, energy spread, and electron density in contrast to the Townsend discharge and super-dense glow discharge stages.

In this work we investigate the energy-loss straggling of low and medium energy protons on available simple materials (C, Al, Si, Ni, Cu, Zn, Ge, Se, Pd, Ag, Sb, Pt, Au, Pb) and demonstrate that the well-known Yang-O’Connor-Wang empirical formula for the energy-loss straggling of protons in matter has a clear physical interpretation. This formula predicts, on empirical grounds, energy-loss straggling values for protons that exceed the values of traditional straggling formulas (e.g., by Lindhard and Chu) at energies around 0.3 MeV/amu by a factor of 2–3. This excess is correlated to the bunching effect, which comes from the inhomogeneity feature of the electron density. Although this effect is specific to each element and can be calculated using e.g. the CasP and PASS programs, a single formula correlates better with overall experimental values. The Yang-O’Connor-Wang formula was refined accounting for subsequent experimental data.

The purpose of this article is to study the influence of different powers, pressures, frequencies, and gases on the electron density distribution in special structures. A simulation model is established, and the electronic density in a special capacitance coupled plasma (CCP) device is calculated over the power range of 0–10 kW, pressure range of 0–50 Pa, and frequency range of 13.56–300 MHz. The results show that the power is a logarithmic function of the electron density in helium and argon plasmas, and the peak value for the electron density occurs in the diffusion region. At a certain power, collisions between particles increase with increasing pressure, which leads to an increase in electron density. However, the high electron density region in the helium plasma is concentrated near the electrode, while the high density region in the argon plasma moves from the center of the device to the electrode with increasing gas pressure. At the same time, the increase in the power frequency increases the ionization rate, and energy is transferred to the electrons, which increases the electron density. However, the rate of increase in the electron density decreases with increasing power frequency at the same voltage and pressure. With increasing power frequency, the 2-D electron density distribution in the argon and helium plasmas is found to vary in a similar way to that found for increasing pressure.

The present investigation deals with the study of higher-order nonlinearity and dispersion to electron-acoustic waves in an unmagnetized and collisionless plasma system incorporating immobile ions, cool adiabatic electrons and nonthermal-Tsallis distributed hot electrons. Employing proper stretched coordinates and Reductive Perturbation Method (RPM), dispersion relation and Korteweg de-Vries (KdV) equation have been derived to the lower-order potential. An inhomogeneous KdV-type equation emerges to the next higher order that accounts for fifth-order dispersion. This study focuses on revealing the dependency of the behaviour of dressed electron-acoustic waves on nonthermal parameter (β), hot-to-cool electron density ratio (α), hot-to-cool electron temperature ratio (θ), Mach number ( $${{\Delta} M}$$ ) and nonextensive parameter (q). Only negative potential structures are reported for which the numerical results are interpreted in the form of two and three-dimensional profiles. The numerical results reflect the decrease in the amplitude of dressed solitary structures, thus obliging simulation of electron-acoustic solitary behaviour in the auroral regions and magnetosphere of Earth.

The main goal of the present study is to analyze and estimate the plasma screening effect on excitation energies O-like ions and photoionization process of F-like ions under the influence of strongly coupled plasma. We have employed an ion sphere model (ISM) in flexible atomic code (FAC) to study and analyze plasma effect in atomic structure of O-like ions and photoionization of F-like ions. We have presented shift in excitation energies of lowest 10 levels of Fe XIX, Co XX, Ni XXI, Cu XXII and Zn XXIII at electron densities ranges 1022–1024 cm−3 under plasma environment. We have also compared our transition wavelengths for Fe XIX with wavelengths observed in ENEA laser facility and calculated from Hebrew University Lawrence Livermore Atomic Code (HULLAC) code at electron density 1021 cm−3. The lowering in ionization potentials and effect on photoionization cross sections for ground and first excited states of Fe XVIII, Co XIX, Ni XX, Cu XXI and Zn XXII also studied at electron densities ranges 1022–1024 cm−3 at five photo-electron energies ranges 100–500 eV.

A single probe method is used to obtain the electron density and electron energy distribution function in a short discharge gap between a rectangular hollow cathode and a mesh anode. It is found that the electron distributions are non-Maxwellian and have an excess of high-energy electrons, the fraction of which decreases with distance from the cathode.

Here, we report on simulating the steady-state j–V characteristics of dye-sensitized solar cells (DSSCs). First, a set of differential equations describing the kinetic processes involving the charge carriers – electron, iodide, triiodide, and dye cation – are derived. We consider non-linearity both in transport and in the recombination of electrons. Also, we consider that the charge transport occurs only by diffusion. Moreover, Boltzmann statistics relate electron density and Fermi level in TiO2, a quasi-static equilibrium holds between free and total electrons, and traps in the semiconductor fit to an exponential distribution of energies. Most importantly, we assume that electron transport occurs according to the multiple-trapping model. The numerical solution provides j–V characteristics of the photoelectrode. To establish a relationship between the photovoltaic performance of the photoelectrode and that of the overall DSSCs, we consider the potential drops due to series-resistive elements according to the device physics of DSSCs. Finally, the model is applied to simulate the photovoltaic performance of real DSSCs with varying TiO2 film thickness and electrolyte composition. The critical parameters of the model were extracted from electrochemical impedance spectroscopy (EIS) data of the DSSCs. The model successfully reproduced the j–V curves of the DSSCs.

Electrides are an unusual class of compounds where electrons are localized in space distinct from atomic positions and behave like anions. This type of localization makes electron density very “fle...

Exploring nonlinear optical (NLO) functional motifs (FM, the structural origin of NLO efficiency) is vital for the rational design of NLO materials. Normal spectrum techniques applied in studying photon exciting materials are invalid for NLO materials, in which electrons are not excited substantially but only distorted under laser. A general strategy of determining NLO FM is proposed by comparative studies of experimental electron density (ED) without and under the laser. The in situ experimental ED and wavefunction of typical NLO material LiB3 O5 (LBO) under dark and 360 and 1064 nm lasers are investigated. Compared with the initial state under dark, the ED of [B3 O5 ]- unit at functional states under laser irradiation exhibits remarkable changes of topological atomic and bond properties, confirming the NLO FM being [B3 O5 ]- . The work extracts for the first time the FM of a NLO material experimentally and highlights the crucial role of in situ ED analysis in studying NLO mechanisms.

The formation of the gigantic dust-acoustic rouge waves (DARWs) in an electron depleted unmagnetized opposite polarity dusty plasma system is theoretically observed for the first time. The nonlinear Schr\"{o}dinger equation (derived by utilizing the reductive perturbation method) has been analytically as well as numerically analyzed to identify the basic features (viz., height, thickness, and modulational instability, etc.) of DARWs. The results obtained form this investigation should be useful in understanding the basic properties of these rouge waves which can predict to be formed in electron depleted unmagnetized opposite polarity dusty plasma systems like mesosphere, F-rings of Saturn, and cometary atmosphere, etc., Comment: 5 pages; 4 figures

This article presents a systematic investigation on the behavior of electrons in the bullet in the Ar/H2O plasma jet in increasing the applied voltage and water vapor concentration based on a needle-plate discharge configuration and a 1-D particle-in-cell Monte Carlo method. The scattering angle of the electron in the bullet is described using the angle between the electron scattering direction and the bullet propagation direction. The following results are obtained. The evolution characteristic of the angle spectrum of electrons in the bullet in increasing the applied voltage is the same as that in increasing water vapor concentration, namely, the electrons scattered toward the target get increasingly less. When increasing the applied voltage, the OH density, the electron density, and the average electron energy $E_{\mathrm {ave}}$ increase. However, the increase in water vapor concentration leads to an evidently increasing OH density and a decrease in both the electron density and $E_{\mathrm {ave}}$ . In the range of electron scattering angles below 90° in the bullet, the percentage of electrons with energy above 3.27 eV (the threshold of inducing dissociative electron attachment to water molecule) increases with increasing applied voltage but presents a slight decrease in increasing water vapor concentration. The majority of electrons to most probably interact with the target are of energies higher than 3.27 eV. Finally, a notable effect of H2O admixture is that it gives rise to the decrease in not only $E_{\mathrm {ave}}$ but also the electron density in the bullet, especially the latter decreases evidently.

The electron energy distribution functions that form in the plasma heating region were recovered from data on the soft X-ray spectra in the energy range of 2−20 keV. The spectra were measured at the L-2M stellarator in the regime of electron cyclotron resonance (ECR) heating in two experiments: on the axial ECR heating (the heating power was PECRH = 250 kW, the electron density was ne = 1.9 × 1019 m–3, and the electron temperature was Te = 0.74 keV) and the off-axial ECR heating (PECRH = 350 kW, ne = 2.5 × 1019 m–3, and Te = 0.7 keV). It was shown that in both experiments the electron energy distribution functions are not Maxwellian and that considerable ensembles of suprathermal electrons form in the heating regions.

Spontaneous processes triggered in a sample by free electrons are commonly regarded as incoherent, and therefore unable to interfere with external light sources. Here, we challenge this concept by showing through first-principles theory that light and free-electron pulses can interfere when interacting with a nanostructure, giving rise to a modulation in the spectral distribution of the cathodoluminescence light emission that is strongly dependent on the electron wave function. Specifically, for a temporally focused electron, cathodoluminescence can be cancelled upon illumination with a spectrally modulated dimmed laser that is phase-locked relative to the electron density profile. We illustrate this idea with realistic simulations under attainable conditions in currently available ultrafast electron microscopes. We further argue that the interference between excitations produced by light and free electrons opens a new window to manipulate the ultrafast materials response by combining the spectral and temporal selectivity of the light with the atomic resolution of electron beams., 26 pages, 7 figures, 87 references

The local electron density of an atom is one key factor that determines its chemical properties. Regulating electron density can promote the atom's reactivity and so reduce the reaction activation energy, which is highly desired in many chemical applications. Herein, we report an intra-crystalline electron lever strategy, which can regulate the electron density of reaction centre atoms via manipulating ambient lattice states, for Fenton activity improvement. Typically, with the assistance of ultrasound, the Mn4+ -O-Fe3+ bond in BiFe0.97 Mn0.03 O3 perovskite nanocrystals can drive valence electrons and free electrons to accumulate on Fe atoms by a polarization electric field originated from the designed lattice strain. The increase of electron density significantly improves the catalytic activity of Fe, decreasing the activation energy of BiFe0.97 Mn0.03 O3 -mediated Fenton reaction by 52.55 %, and increasing the . OH yield by 9.21-fold. This study provides a new way to understand the sono-Fenton chemistry, and the increased . OH production enables a highly effective chemodynamic therapy.

An investigation is performed of the relaxation of plasma excitations in two-dimensional electron systems (2D-ESes) in GaAs/AlGaAs heterostructures. The effect radiational and incoherent collisional relaxation mechanisms have on the linewidth of cyclotron magnetoplasma resonance (CR) is studied. CR arises as a pure resonance that does not hybridize with dimensional magnetoplasma excitations. It is shown how magnetoplasma resonances form a CR’s fine structure due to the interaction between coherent radiative and incoherent collisional mechanisms of two-dimensional plasma relaxation. A comparative analysis is performed of the dependences of cyclotron and transport periods of relaxation on both the temperature and electron density of 2D-ESes. It is demonstrated that the period of cyclotron relaxation could exceed that of transport at low electron densities.

An accurate representation of bottomside, topside ionosphere, and plasmasphere electron content remains as one of the important issues for the development of realistic ionosphere and plasmasphere models. The reason is that the full altitude electron density profile specification is restricted by a simultaneous lack of adequate ground or space-based datasets. In this article, we present sensible assimilation of peak parameters in the topside profiles from the FormoSat-3/COSMIC ionospheric occultations with the auto-scaled bottomside profiles from 39 global Digisonde rather than peak to topside extrapolation. Under strict space-time collocation criteria, the integral electron content from the assimilated electron density profiles along with global positioning system derived total electron content demonstrates altitude dependent contributions. The corresponding estimations from the empirical ionospheric and plasmaspheric models (IRI-2016, NeQuick-2, and IRI-Plas 2017) are also assessed to realize their discrepancies with respect to the observed parameters. The statistical comparison metrics show relatively closer overall ionospheric electron content estimates from IRI with the assimilated results, followed by NeQuick and IRI-Plas models, with the last two models showing an opposite behavior between bottomside and topside electron content discrepancies. However, although the total electron content estimations reveal the relatively superior performance of IRI-Plas with successive proficiency of NeQuick and IRI models, the retrieved plasmaspheric electron content data does not evident any clear statistical metrics and dictates further investigation. Nevertheless, this assimilation work leads towards improving the altitudinal representation of ionospheric models, particularly in the context of real-time representation of topside, bottomside, and plasmaspheric electron content through a reconstruction of the complete electron density profile.

A multi-branch pre-breakdown streamer model for natural ester-based nanofluid is established in this paper to study the influence of electrons density fluctuation on the streamer branching and propagation during the pulsed discharge. The mechanism of electron density fluctuation on the streamer branching and propagation characteristics is further studied using the finite element software. Results show that the initial streamer branched more likely near the needle tip in the nanofluids than that in the pure oils, and the branching of the initial streamers in nanofluid significantly inhibit the streamer propagation. The fluctuation of carrier density and the low charge density regions caused by adsorption of electrons with nanoparticles near the needle tip are the leading causes for the initial streamer branching in the nanofluid. The repulsion of the charge with the same polarity between the streamer branches can change the propagation pattern of the streamer, resulting in the inhibition of the streamer propagation. Results provide a novel strategy for the inhibition of streamer propagation by electron density fluctuations-induced branched initial streamer in nanofluids.

This paper presents the analytical approximation of device physics of heterojunction based double gate (DG) Tunnel field effect transistors (TFETs) in terms of potential distribution, electron density and electron barrier tunneling. In order to improve the device performance with respect to ON current (ION), DG TFET with gate-drain overlap is developed. An asymmetric gate oxide is introduced in the gate - drain overlap region and is compared to DG TFET. The device physics and its performance characteristics are studied by using various materials, such as Si, SiGe, InAs and GaSb. The simulated results are validated against the model values. DG TFETs with gate-drain overlap offers higher tunneling probability compared to DG TFETs. Also GaSb/Si based DG TFETs with gate-drain overlap shows good performance improvement by offering higher tunneling probability which in turn offers a higher ION of 1.15 mA/μm.

The aim of this study is to calculate the experimental and theoretical the mass attenuation coefficient some Br compounds by using transmission method. Also using these values were determined the total electronic section, total atomic section, effective atomic number, effective electron density and Kerma. We performed the calculations of these values in attenuation by using direct excitation experimental geometry. The total attenuation cross sections of some halogene Br compounds were measured in a narrow beam good geometry using a high resolution Si(Li) detector in the energy with γ photons at 59.543 keV from Am-241 annular source. Theoretical mass attenuation coefficient values were computed from the XCOM data programme, based on mixture rule method. This study provide new insight into the literature since the values of effective atomic number, electron density and Kerma for some Br compounds have not been determined before. According to the results shown in mass attenuation coefficient, Zeff and Neff of Br compounds are closely associated with chemical structure. This research were undertaken to explore how Bromine compounds is gamma ray shielding material.

International audience; The independent gradient model (IGM) is a recent electron density-based computational method that enables to detect and quantify covalent and noncovalent interactions. When applied to large systems, the original version of the technique still relies on promolecular electron densities given by the sum of spherically averaged atomic electron distributions, which leads to approximate evaluations of the inter- and intramolecular interactions occurring in systems of biological interest. To overcome this drawback and perform IGM analyses based on quantum mechanically rigorous electron densities also for macromolecular systems, we coupled the IGM approach with the recently constructed libraries of extremely localized molecular orbitals (ELMOs) that allow fast and reliable reconstructions of polypeptide and protein electron densities. The validation tests performed on small polypeptides and peptide dimers have shown that the novel IGM-ELMO strategy provides results that are systematically closer to the fully quantum mechanical ones and outperforms the IGM method based on the crude promolecular approximation, but still keeping a quite low computational cost. The results of the test calculations carried out on proteins have also confirmed the trends observed for the IGM analyses conducted on small systems. This makes us envisage the future application of the novel IGM-ELMO approach to unravel complicated noncovalent interaction networks (e.g., in protein–protein contacts) or to rationally design new drugs through molecular docking calculations and virtual high-throughput screenings

For the first time, the effect of ions on complex conductivity and permittivity of dusty plasma at Polar Mesosphere Summer Echoes (PMSE) altitude is analyzed. Because of ions higher mass and smaller thermal velocity, generally, their effects are not considered in the study of electromagnetic properties of dusty plasmas. In this study, we modified the equations of conductivity and permittivity by adding the effect of ions. In the PMSE altitude region between 80 and 90 km, a local reduction in electron density (i.e., an electron bite-out), is produced by electron absorption onto dust particles. The bite-out condition contains high dust density and smaller electron density. From simulation results in comparatively strong bite-out conditions, we found that the ion effects on conductivity become significant with smaller dust size, lower electron temperature, and lower neutral density. For comparatively weak bite-out conditions, the ion effects on conductivity become significant with larger dust size, higher electron temperature, and higher neutral density. On the other hand, for different dust sizes, electron temperatures and neutral density, the ion effects on complex permittivity become significant only in very strong bite-out conditions. Based on these simulation results, we conclude that, in the absence of electron bite-out conditions, the effect of ions on complex conductivity and permittivity is not significant and can be ignored. However, during bite-out conditions, the effect of ions becomes significant and cannot be ignored because it significantly changes the conductivity and permittivity of dusty plasmas.

In this paper, a modified COMSOL Multiphysics model with artificial stability is adopted, and the boundary condition developed in the previous paper are applied to the calculation of the photoionization rate. The main processes involved in air discharge were simulated by 39 plasma chemical reactions composed of 12 kinds of particles. The characteristics of low-temperature sub-atmospheric pressure air discharge under unipolar square wave pulse voltage with 13kV applied amplitude, 25 kHz-50 kHz frequency and a duty cycle of 50%-75% are discussed. The results show that: When the duty cycle increases, the average density of electron, N2+, N4+, O2+, O4+, and N2O2+ show an increasing trend, and the average electron temperature changes little; When the frequency increases, the average electron density, the average density of N4+ and O4+ show a downward trend, the average density of N2+, O2+, N2O2+ change little; The average electron temperature shows an increasing trend, but the duration of high electron temperature becomes shorter. When discussing a single period, it is found that the potential difference between the electrode and the plasma determines the direction of the electric field in the space. For the photoionization reaction, even if its influence on the negative streamer is not important, it still needs to be considered in the simulation. The effect of temperature on discharge is also taken as the research emphasis, it includes the following aspects: Firstly, at low temperature, the collision reaction and attachment reaction rates are increased, while the recombination reaction rate is almost unaffected; Secondly, low temperature results in the decrease of secondary electron emission coefficient, which indirectly increases the electric field gradient and the peak value of electric field; Finally, at low temperature, the mobility of carriers, including electrons, positive and negative ions, is increased, but the streamer velocity is decreased.

The ditriel B⋯Al interaction has been characterised in Fδ−Bδ+⋯Alδ+Fδ− (δ > 0.6e) molecules using CCSD(T)/aug-cc-pVTZ calculations. It has a non-covalent character as evidenced by the topological analysis of electron density (AIM) and electron localisation function (ELF). The B⋯Al bonding is very weak (

Laser Wakefield is produced by ultra-high intensity laser pulse interacting with underdense plasma with special conditions for the laser wavelength and plasma density. In this mechanism, nonlinear forces appear due to the very high amplitudes of the electromagnetic wave and these forces evacuate plasma electrons from the path of the laser pulse leading to very high electron plasma density gradients. Due to the electrostatic forces which result from these density perturbations, the electrons move very fast in oscillatory manner to restore neutrality creating a wake of electron density perturbations behind the laser pulse. Detailed investigation has been dealt with the time-delay between the driver laser pulse and the probe pulse which can affect the production of high plasma gradients needed for photon acceleration process.

This work investigates the effect of the electron surface recombination coefficient ( K s ) on radio-frequency discharge characteristics. This investigation is performed by a fluid model with the drift–diffusion approximation. The simulation results show that when the electron recombination rate is larger, the plasma density is lower in the plasma bulk region. It is found that the cycle-averaged electron and ion fluxes decrease adjacent to the electrode, while the electric potential increases in the bulk plasma region as K s increases from 0.60 to 2.38. Moreover, the reduction in the electron density in the bulk region leads to decrease in the electron power dissipation in this region. The results also show that the electron ohmic heating and pressure heating, which play a crucial role in sustaining the discharge, can be both reduced in the sheath regions with increasing the electrons recombination rate. Finally, it is observed that the plasma characteristics can significantly be changed depending on the electrode surface properties.

The existence of various quasiparticles of polarons because of electron-boson couplings plays important roles in determining electron transport in titanium dioxide (TiO2), which affects a wealth of physical properties from catalysis to interfacial superconductivity. In addition to the well-defined Frohlich polarons whose electrons are dressed by the phonon clouds, it has been theoretically predicted that electrons can also couple to their own plasmonic oscillations, namely, the plasmonic polarons. Here we experimentally demonstrate the formation of plasmonic polarons in highly doped anatase TiO2 using angle-resolved photoemission spectroscopy. Our results show that the energy separation of plasmon-loss satellites follows a dependence on √n, where n is the electron density, manifesting the characteristic of plasmonic polarons. The spectral functions enable to quantitatively evaluate the strengths of electron-plasmon and electron-phonon couplings, respectively, providing an effective approach for characterizing the interplays among different bosonic modes in the complicate many-body interactions.