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Elastic scattering of electrons on a finite-temperature quantum screened potential is studied by using the partial wave decomposition of scattering wavefunction. The influence of plasma temperature on the total and l = 0, 1, and 2 partial wave cross sections is systematically analyzed in the present work. It is found that when the plasma density is fixed, the screened strength does not change monotonically with temperature, which leads to different conditions for forming shape resonance in the scattering cross sections for the different temperature domains. The scattering cross sections under the environments of low temperature limit are compared with those for zero-temperature quantum plasmas. [ABSTRACT FROM AUTHOR]

We theoretically study Ar8+-induced dissociation of C2H2 molecule at 1.2 MeV using the time-dependent density-functional theory non-adiabatically coupled to nuclear dynamics. We find that molecular dissociation depends strongly on the ionization at the initial stage and the collision configuration. A detailed analysis shows a correspondence between the charge state of [ C 2 H 2 ] q + and the final fragments. A remarkable impact parameter effect provides deep insights of bond breakup and electronic transport. We analyze two typical sequential dissociation channels reported in experiments by tracking structural and electronic dynamics in real time. Our results provide better understanding of experiments. Moreover, the comparison between various exchange-correlation functionals reveals that electrons' correlation and self-interaction do not significantly impact the initial ionization and fragment distribution in the present study. [ABSTRACT FROM AUTHOR]

The total, state-selective, and angular-differential cross sections for He2++H collision system in warm dense plasmas are studied by using the two-center atomic orbital close-coupling method in the energy range 0.1–300 keV/u. The calculations are performed for plasma density and temperature ranges ne ∼1018 to ∼1021 cm−3, Te = 0.3 eV–1.2 eV, typical for the H- and He-rich white dwarfs. The plasma environments are described by a unified screened potential involving electron degeneracy, finite-temperature gradient, and exchange-correlation effects. The results for H++H cases with the same plasma parameters are also presented for comparison to elucidate the discrepancies of plasma screening effects on the electron capture dynamics for collision systems with different nuclear symmetries. Moreover, classical Debye screening results are also given for comparison to clarify the effects of quantum correlations in warm dense plasmas on the electron capture dynamics. The present work is expected to provide theoretical and data support for the astrophysical plasmas. [ABSTRACT FROM AUTHOR]

Relativistic photoionization processes of an exemplary highly charged H-like ion Ar17+ for 1s1/2, 2lj (l = 0, 1), and 3lj (l = 1, 2) initial states are studied in plasmas with coulomb coupling parameter 0.007 < Γ < 0.202. Photoionization cross sections for both the strongly and weakly screened cases exhibit specific properties when their plasma densities and temperatures in the vicinities of the critical values at which nlj bound states enter the continuum. The electron degeneracy, finite-temperature gradient corrections, and quantum exchange-correlations effects have been included in the interaction between charged particles by the screened potential used in the present work. It is found that these effects for the plasmas with different coupled strength are reflected in the resonant regions of photoionization cross sections by comparing with Debye cases. The present work is expected to provide theoretical and data support for the fusion plasmas. [ABSTRACT FROM AUTHOR]

High resolution spectra of the B 2E-X 2A1 transitions of CaBH4 and SrBH4 have been recorded using laser excitation spectroscopy in a laser ablation/molecular jet source. Because of rotational cooling in the molecular jet and nuclear spin statistics, transitions arising from only the K′=1←K″=0, K′=2←K″=1, and K′=0←K″=1 subbands have been observed. For each molecule, an analysis of the data using 2E and 2A1 symmetric top Hamiltonians yielded rotational, spin-orbit, and spin-rotation parameters for the observed states. For both molecules the rotational constants compare well with those calculated for a tridentate borohydride structure. A large reduction in the spin-orbit splitting and in the metal-ligand separation for each molecule indicates an increase in the amount of d atomic orbital character in the first excited 2E states of the monoborohydrides as compared to the monomethyl derivatives. For each molecule no evidence of internal rotation of the BH4- ligand was found. A change in the magnitude and sign of the spin-rotation constant [variant_greek_epsilon]1 confirms an energy reordering of the first excited 2E and 2A1 states in both CaBH4 and SrBH4 as compared to CaCH3 and SrCH3. The data also suggest that the B 2E1/2 rotational energy levels of CaBH4 may be perturbed by a vibronic component of the à 2A1 state. [ABSTRACT FROM AUTHOR]

Using density functional theory, we investigate the structure of the double water bilayer with or without coadsorption of CO on Pt(111). The double water bilayer consists of two bilayers. Each bilayer is buckled with every second water molecule being closer to the surface than every other water molecule. CO is found to adsorb most strongly when substituting in the first bilayer, the water molecule closest to the surface. Dissociation of H2O in the water bilayer (with or without CO) is further considered. A great number of pathways for the dissociation are studied. These include homolytic pathways where both dissociation products end up adsorbed on the Pt surface and heterolytic pathways where only the OH is adsorbed, while a proton is transferred to the water adlayers. We find that the heterolytic dissociation pathways are energetically more favorable than the homolytic ones, yet they are all rather endothermic. The most favorable pathways found have reaction energies of 0.60 and 0.52 eV without and with CO present. The corresponding activation energies are 0.99 and 0.53 eV, respectively. [ABSTRACT FROM AUTHOR]

High-resolution laser excitation spectroscopy has been used to record the à 2E-X 2A1 electronic transition of SrCH3 in a laser ablation/molecular jet source. Transitions arising from the K′=1←K″=0, K′=0←K″=1, and K′=2←K″=1 subbands have been observed and assigned. The data were modeled with 2E and 2A1 symmetric top Hamiltonian matrices in a Hund’s case (a) basis, using a least squares fitting program. Rotational and fine structure parameters for the à 2E state were determined. A comparison of the spin-orbit energy separation in the à 2E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the à 2E state were calculated using the pure precession model and were found to be in good agreement with the experimentally determined parameters. These calculations suggest that the à 2E state of SrCH3 is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH3 in the à 2E state. The strontium-carbon bond length was found to decrease by ∼0.006 Å, and the hydrogen-carbon-hydrogen bond angle opened by ∼0.8° compared to the X 2A1 state, similar to the geometry changes observed for CaCH3. [ABSTRACT FROM AUTHOR]

Elastic scattering of electrons and positrons on a Friedel potential is studied in quantum plasmas with electron densities in the range of 1022–1027 cm−3 and particle collision energies in the range of 10−6–102 a.u. by using the partial wave decomposition of the scattering wavefunction. The total and partial-wave cross sections for electron and positron impact show distinct differences in their magnitudes and energy behavior. The structure of total and l = 0, 1, 2 partial wave cross sections is analyzed in terms of the scattering phase shifts. [ABSTRACT FROM AUTHOR]

Deals with a study which verified the smooth-approximation theory for a space-charge dominated beam in an axisymmetric periodic focusing channel. Review of the smooth-approximation theory for an axisymmetric focusing channel; Analysis of the image signals; Significance of the spherical aberration effect in solenoidal focusing system.

The photoionization process of the C5+ ion in warm, dense plasmas is studied using the relativistic approximation. Cross section calculations are performed for plasma density and temperature ranges of ne ∼ 1023–1026 cm−3 and Te = 150–300 eV, respectively. The used static screened potential includes the effects of plasma degeneracy, finite-temperature gradient corrections to the kinetic energy, and quantum exchange-correlation. The dependencies of the photoionization cross section on plasma density (for fixed temperature) and temperature (for fixed density) are investigated. [ABSTRACT FROM AUTHOR]

Electron capture and excitation processes in H+-H collisions imbedded in warm dense quantum plasmas are studied by the two-center atomic orbital close-coupling (TC-AOCC) method in the energy range 1-200 keV. The screened potential which is used to describe the interaction between charged particles incorporates the quantum electron degeneracy, exchange-correlation and finite-temperature gradient correlation effects. The total and state-selective electron capture and excitation cross-sections for this collision system with this potential are calculated in a wide range of plasma densities and temperatures. It is demonstrated that the screening of Coulomb interactions affects the collision dynamics and the magnitude and energy behavior of the excitation and electron capture cross-sections. The results at very low and high temperatures are also compared with those obtained for zero-temperature quantum plasmas and Debye plasmas, respectively. [ABSTRACT FROM AUTHOR]

The photoionization of hydrogen-like ions in n ⩽ 3 bound states, embedded in cold, dense quantum plasmas, is investigated in detail. The electron energies and wave functions for the bound and continuum states are determined by numerically solving the scaled Schrödinger equation by the fourth-order symplectic integration scheme. The monotonic behavior of the photoionization cross section for a pure Coulomb potential is dramatically changed due to the plasma screening effects described by the cosine-Debye-Hückel potential. In the region of low photoelectron energies, the photoionization cross section, besides the usual Wigner-law threshold behavior, exhibits a rich structure of shape and virtual-state resonances when the plasma screening parameter takes values around the critical screening parameter for which a bound state enters the continuum. It is observed that a shape resonance is followed by a Cooper minimum in the photoionization cross section when the principal quantum number of continuum quasi-bound state is equal to the one of the initial bound states. [ABSTRACT FROM AUTHOR]

(LWFA) with a charge of 620 pC and a maximum energy up to 0.6 GeV by irradiating 80 TW laser pulses at a 3 mm Helium gas jet. The charge of injected electrons is much larger than the normal scaling laws of LWFA in bubble regime. We also got a quasi-monoenergetic electron beam with energy peaked at 249 MeV and a charge of 68 pC with the similar laser conditions but lower plasma density. As confirmed by 2D particle-in-cell simulations, the boosted bunch charge is due to the continuous injection caused by the self-steepening and self-compression of a laser pulse. During the nonlinear evolution of the laser pulse, the bubble structure broadens and stretches, leading to a longer dephasing length and larger beam charge. [ABSTRACT FROM AUTHOR]

We simulate the evolution of ultracold neutral plasmas using molecular dynamics calculations with open boundary conditions. The calculations use 6000 ions and 6000 electrons, respectively, with a quasi-real ion-electron mass ratio of mi=me = 1000. The simulated plasmas have both Gaussian and ordered initial distributions. While disorder-induced heating is absent in the initially ordered distributions, the ions are heated significantly by electron-ion collisions. We show that the value of the strong coupling parameter typically falls below 10 for realistic plasma densities. [ABSTRACT FROM AUTHOR]

Presents a study that prepared superconducting fibers and wires through spray pyrolysis of metal nitrate precursors on a commercial carbon fiber substrate, followed by heating in air and annealing in oxygen [sub2]. Details on approaches such as x-ray diffraction and scanning electron microscopy used to characterize the fibers; Use of carbon as the substrate for spray pyrolysis; Advantages offered by carbon substrates.

The properties of bound-bound transitions in hydrogen-like ions in dense quantum plasmas, characterized by a cosine-Debye-Huckel interaction between charged particles, are studied in detail. The transition frequencies, oscillator strengths, and radiative transition probabilities of Lyman and Balmer series are calculated for a wide range of screening strengths of the interaction up to the n = 5 shell. For An = 0 transitions, all these quantities exhibit a significant decrease with increasing screening strength, while for the An = 0 transitions and for the radiative lifetimes, the opposite is true. The present results are compared with those available from the literature. They are also compared with the results for the pure Debye-Huckel potential with the same screening strength. [ABSTRACT FROM AUTHOR]

By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble. [ABSTRACT FROM AUTHOR]

The relativistic effects in the photoionization of hydrogen-like ion with screened Coulomb interaction of Yukawa type are studied for a broad range of screening lengths and photoelectron energies. The bound and continuum wave functions have been determined by solving the Dirac equation. The study is focused on the relativistic effects manifested in the characteristic features of photoionization cross section for electric dipole nl → ε,l±1 transitions: shape resonances, Cooper minima and cross section enhancements due to near-zero-energy states. It is shown that the main source of relativistic effects in these cross section features is the fine-structure splitting of bound state energy levels. The relativistic effects are studied in the photoionization of Fe25+ ion, as an example. [ABSTRACT FROM AUTHOR]

The two-center atomic orbital close-coupling method is employed to study electron capture and excitation reactions in collisions of Liq+ (q=1-3) ions with ground state atomic hydrogen in the ion energy range from 0.1 keV/u to 300 keV/u, where u is the atomic mass unit. The interaction of the active electron with the projectile ions (Li+, Li2+) is represented by a model potential. Total and state-selective cross sections for charge transfer and excitation processes are calculated and compared with data from other sources when available. [ABSTRACT FROM AUTHOR]

To research the dynamic course of multipactor suppression on the periodically patterned surface, tens of electron collision processes are tracked by numerical calculation. The influences of microwave frequency, amplitude of RF electric field, slope angle, the local field enhancement, and the tilted incident electric field on the multipactor suppression are studied by tracking multi-generation electrons' trajectories, hopping and flight time, collision energy, and secondary emission yield. Meanwhile, the dynamic processes of secondary electrons on the periodic surface are analyzed by particle-in-cell (PIC) simulation. The PIC results are consistent with the analytical results in which the electrons fly reciprocatingly between the slopes and impact on the slopes; the methods of increasing the slope angle, enlarging the RF field, and lowering the frequency in a certain range are helpful to enhance the multipactor suppression steadily and persistently. [ABSTRACT FROM AUTHOR]

Plasma effects on the high-energy electron-impact ionization process from 2p orbital of Hydrogen-like ions embedded in weakly coupled plasmas are investigated in the first Born approximation. The plasma screening of the Coulomb interaction between charged particles is represented by the Debye Hückel model. The screening of Coulomb interactions decreases the ionization energies and varies the wave functions for not only the bound orbital but also the continuum; the number of the summation for the angular-momentum states in the generalized oscillator strength densities is reduced with the plasma screening stronger when the ratio of [variant_greek_epsilon]/I2p (I2p is the ionization energy of 2p state and [variant_greek_epsilon] is the energy of the continuum electron) is kept, and then the contribution from the lower-angular-momentum states dominates the generalized oscillator strength densities, so the threshold phenomenon in the generalized oscillator strength densities and the double differential cross sections are remarkable: The accessional minima, the outstanding enhancement, and the resonance peaks emerge a certain energy region, whose energy position and width are related to the vicinity between δ and the critical value δnlc, corresponding to the special plasma condition when the bound state |nl just enters the continuum; the multiple virtual-state enhancement and the multiple shape resonances in a certain energy domain also appear in the single differential cross section whenever the plasma screening parameter passes through a critical value δnlc, which is similar to the photo-ionization process but different from it, where the dipole transition only happens, but multi-pole transition will occur in the electron-impact ionization process, so its multiple virtual-state enhancements and the multiple shape resonances appear more frequently than the photo-ionization process. [ABSTRACT FROM AUTHOR]

Chronic wounds are a major burden for worldwide health care systems, and patients suffer pain and discomfort from this type of wound. Recently gas plasmas have been shown to safely speed chronic wounds healing. In this paper, we develop a deterministic mathematical model formulated by eight-species reaction-diffusion equations, and use it to analyze the plasma treatment process. The model follows spatial and temporal concentration within the wound of oxygen, chemoattractants, capillary sprouts, blood vessels, fibroblasts, extracellular matrix material, nitric oxide (NO), and inflammatory cell. Two effects of plasma, increasing NO concentration and reducing bacteria load, are considered in this model. The plasma treatment decreases the complete healing time from 25 days (normal wound healing) to 17 days, and the contributions of increasing NO concentration and reducing bacteria load are about 1/4 and 3/4, respectively. Increasing plasma treatment frequency from twice to three times per day accelerates healing process. Finally, the response of chronic wounds of different etiologies to treatment with gas plasmas is analyzed. [ABSTRACT FROM AUTHOR]

Two kinds of floating electrode, floating dielectric barrier covered electrode (FDBCE) and floating pin electrode (FPE), which can enhance the performance of plasma jet are reported. The intense discharge between the floating electrode and power electrode decreased the voltage to trigger the plasma jet substantially. The transition of plasma bullet from ring shape to disk shape in the high helium concentration region happened when the floating electrode was totally inside the powered ring electrode. The enhanced electric field between propagating plasma bullet and ground electrode is the reason for this transition. The double plasma bullets happened when part of the FDBCE was outside the powered ring electrode, which is attributed to the structure and surface charge of FDBCE. As part of the FPE was outside the powered ring electrode, the return stroke resulted in a single intensified plasma channel between FPE and ground electrode. [ABSTRACT FROM AUTHOR]

The intensities of charge exchange recombination spectroscopy (CXRS) of α particles colliding with the hydrogen atoms in the neutral beam injection (NBI) are calculated by solving the rate equations including electron collision processes in the quasi-static state approximation. The effects of electron collision processes on the CXRS signals for He+(n=4→3) at λ=468.6nm in various plasma conditions are discussed, and it is found that these effects can increase the CXRS signals by 50% for electron density ne≥1015cm-3. However, their importance decreases with the increasing of NBI energy. For the short pulse of NBI, the influences of electron collision processes can be neglected for ne≤1014cm-3. Furthermore, the spectra of He+(n→n') are present for the plasma conditions of HT-7 tokamak. [ABSTRACT FROM AUTHOR]

The photoionization cross sections in the photoelectron energy below 2 Ry are calculated for the ground and n≤4 excited states of Li embedded in plasma environments and the radiative-recombination (RR) rate coefficients for Li+ were presented for temperature T=100–32 000 K in a wide range of plasma parameters. The plasma screening interaction is described by the Debye–Hückel model and the energy levels and wave functions including both the bound and continuum states are calculated by solving the Schrödinger equation numerically in a symplectic integration scheme. The screening of Coulomb interactions remarkably changes the photoionization cross sections near the ionization threshold, and especially for the ns states, the Cooper minimum is uncovered and shifted to the higher energy as the screening interaction increases. The RR rate coefficients at low temperature have a complex variation on the Debye lengths; whereas at higher temperature the RR rate coefficients decrease with the increasing of screening effects. Comparison of present results with those of other authors when available is made. [ABSTRACT FROM AUTHOR]

Plasma screening effects on the high-energy electron-impact excitation of hydrogenlike ions are investigated under the first Born approximation. The screening interactions are described by the Debye–Hückel model, and the wave functions are calculated numerically in a symplectic scheme. The generalized oscillator strengths (GOS) for transitions between the principal quantum number n≲3 bound states are presented, and as an example, the scaled differential cross sections and total cross sections for 1s→2s and 2p and 2s→2p transitions are also given. It is found that the plasma screening interactions reduce the GOS for transitions between the states with different n and increase the GOS between the states with same n. The differential and total cross sections are decreased as the screening interactions increase. [ABSTRACT FROM AUTHOR]

The processes of charge exchange and ionization in collisions of ground state hydrogen atom with fully stripped ions in a weakly coupled plasma are studied by the classical trajectory Monte Carlo method in the collision energy range 10–900 keV/amu. The interparticle interactions are described by the Debye-Hückel model with inclusion of dynamical effects associated with the projectile velocity. The microcanonical distribution of initial state electronic coordinates and momenta has been determined by inclusion of plasma screening effects. The cross section dependencies on plasma parameters and ion charge and velocity are investigated. It is shown that plasma effects on charge exchange and ionization cross sections are significant and particularly pronounced at low collision velocities. The results of systematic cross section calculations for different values of Debye screening length (in the range 1–50a0) and ion charges (in the range 1–14) are presented. [ABSTRACT FROM AUTHOR]

The longitudinal instability of space-charge dominated beams in transport channels with complex wall impedances is studied. The dispersion equation, derived from the one-dimensional Vlasov equation, characterizes the instability with all the relevant parameters including the space charge, the beam energy spread, the real and imaginary parts of the complex wail impedances. For a beam without energy spread, the growth rates of the instability in the different parameter ranges are discussed. The application of the theory to a resistive-wall channel and to a channel with induction gaps is presented. For a beam with energy spread, Lorentzian and Gaussian distributions are treated and the results presented illustrate the dependence of the stable regions on the beam perveance, the energy spread and the wall properties. [ABSTRACT FROM AUTHOR]

A new method for the diagnostics of charged particle beams by employing localized space-charge waves is presented. The propagation of space-charge waves in the form of localized perturbations can be measured easily and accurately in experiments. The results carry valuable information about many beam parameters such as the wave speed, the geometry factor g for the longitudinal space-charge field, the beam radius, the beam impedance under longitudinal perturbations, etc. The principle of this technique and an experimental example are given in this article. [ABSTRACT FROM AUTHOR]

The mechanical heterogeneity is quantified based on the spatial nanohardness distributions in three bulk metallic glasses with different plasticities. It is found that the metallic glass with high mechanical heterogeneity is more plastic. We propose that the appropriate mechanical heterogeneity makes the metallic glasses meliorate their plasticity by increasing inelastic strained area and promoting energy dissipation. [ABSTRACT FROM AUTHOR]

The tensile stress induced by the metal TiN film in the atomic layer deposited HfO2/TiN stacks has been found from the crystallite coalescence mechanism of the Volmer–Weber-type growth mode at the early stage of the TiN film formation. The higher tensile stress induced by 3 nm TiN film than that by the 20 nm TiN film resulted from the smaller grain size and the [200] orientation of the TiN layer. Electron energy loss spectrum profile shows that there is no significant elemental interdiffusion between HfO2 and TiN, which could contribute to stress relaxation. [ABSTRACT FROM AUTHOR]

Three spin-on dielectric (SOD) shallow trench isolation (STI) structures were studied: nitride liner, nitride liner with anisotropic amorphous silicon (a-Si) bottom fill, and nitride liner with thin conformal a-Si. All samples received the same SOD material conditions and final thermal oxidation. Convergent beam electron diffraction determined the induced STI strain and has been shown to accurately measure strain on 60 nm active areas. The results revealed effects that the liners have in balancing stress induced by volume shrinkage of the SOD. The conformal a-Si liner decreased the shear force that causes dislocations that form at the bottom corners of STI structures. [ABSTRACT FROM AUTHOR]

A correction to the article "Density functional theory study of water dissociation in a double water bilayer with or without coadsorption of CO on Pt(111)," is presented.