Optically Forbidden Excitations of 3s Electron of Argon by Fast Electron Impact

The electron energy loss spectrum of argon in the energy region of 24.5—30.5 eV was measured at 2.5 ke V impact energy. The line profile parameters of the optically forbidden excitations of 3s^-1 ns (n = 4-6) and 3s^-1 nd (n = 3-7) of argon, i.e., Er,Г,q and μ were determined.     

Magneto-optical imaging of polycrystalline FeTe1−xSex prepared at various conditions

We have prepared high-quality polycrystalline FeTe_1?xSe_x by sintering at different temperatures and characterized their structural and magnetic properties with X-ray diffraction, magnetization measurements, and magneto-optical imaging. The intragranular J_c was estimated to be 5 × 10⁴ A/cm², which is smaller than the single crystal, but still in the range for practical applications.     

Microwave Absorption by Charge Density Waves in La2–xSrxCuO4

The results of studying the La_2–xSr_xCuO₄ (x = 0.077−0.195) crystals with the microwave absorption, direct current resistance and magnetic susceptibility measurements are presented. The doping-temperature phase diagram with the boundaries of the areas with charge density waves, superconducting fluctuation and the bulk superconductivity state is plotted. The doping range of the charge density wave existence is found to be broader than that obtained from the X-Ray Diffraction study. It spreads at least down to x = 0.077.

     

Phase diagram and oxygen annealing effect of FeTe1−xSex iron-based superconductor

Phase diagrams of as-grown and O₂-annealed FeTe_1?xSe_x determined from magnetic susceptibility measurement were obtained. For as-grown samples, the antiferromagnetic order was fully suppressed in the range region x≥0.15, and weak superconductivity appeared when x≥0.1. Beginning at x=0.5, weak superconductivity was found to evolve into bulk superconductivity. Interestingly, for O₂-annealed samples, complete suppression of magnetic order and the occurrence of bulk superconductivity were observed when x≥0.1. We found that O₂-annealing induces bulk superconductivity for FeTe_1?xSe_x. Oxygen probably plays a key role in the suppression of the magnetic order and the appearance of bulk superconductivity.     

Electron Spin Pairing and Excitations in High—Tc Superconductors

Effective spin coupling between conduction electrons mediated by local Cu moments in the doped CuO2 plane may induce the instability of the normal states of conduction electrons and pairing at Cu stes,where the superexchange interaction between local moments influenced by hole doping has been found to be Ising-like in recent experiments.By a mean field approach,we show that spin pairing and strong pair-pair interaction in the doped antiferromagnetic ordered Ising-like CuO2 plane gives rise to high-temperature superfluid condensation and the exceptional features of quasi-particle excitation in cuprates such as spin gap,pseudogap,and the linear temperature dependence of resistivity ρab in the normal states.     

Anomaly of Microwave Absorption of Ice near –45°C under Plastic Deformation

Technical Physics - The microwave absorption of fresh ice subjected to plastic deformation when changing temperature from 0 to –60°C has been measured. A decrease in the losses of...     

Microwave Absorption Properties of Nickel–Zinc Ferrites Synthesized by Different Means

Ferromagnetic resonance (FMR) characteristics are investigated for Ni_xZn_{1 ? x}Fe₂O₄ ferrites (where x = 0.25, 0.5) synthesized using different organic complexation agents. The microstructure of the synthesized ferrites is studied, and the effect complexation agents have on their microstructure and FMR characteristics is determined.     

Straight‐Chain Segment Length Distribution in Oriented Polyethylene as Revealed by LAM-Raman Spectroscopy

With the help of low-frequency Raman spectroscopy, the peculiarity of structural organization of oriented PE produced by multistage zone drawing of melt-crystallized films was studied. The draw ratios varied from DR=6 to 21 for PEI with M_η=8·10⁴ and from 3.5 to 5.7 for PEII with M_η≈10⁶.

The half widths (Δν) of all observed LAM bands were larger than 10–20 cm^?1. This means that the bands comprise a continuum of the overlapped elementary bands with Δν≈3 cm^?1 because of the wide straight–chain segments (SCS) length distribution. The length (L) of straight segments calculated from LAM-spectra, following a routine procedure, lies in the range from 7–8 to 60 nm.

Weight fractions G_MW of the SCS, as functions of their length, have a bell-like shape. Comparison of the SCS lengths with the value of the long periods (D) inferred from SAXS data for the same samples indicates that the lengths do not exceed 2D. The structural interpretation of the data obtained is given on the basis of microfibrillar models of oriented polymers. The peculiarity of the microfibrillar structure in PEI and PEII samples such as crystallite sizes and shapes and concentrations of inter- and intrafibrillar tie molecules, manifest themselves as the shape of G_MW (L) functions obtained for PE samples of various M_w and DR.     

Absorption of Powerful Light by Free Electrons in Crystals: Intraband Electron–Phonon Rabi Oscillations

Optics and Spectroscopy - The absorption of high-power visible or near-IR laser radiation by free electrons is calculated using the modified resonance approximation. The probabilities Wexc of...     

Preparation of Diamond—Like carbon Films in methane by Electron Cyclotron Resonance Microwave Plasma Source Ion Implantation

Diamond-like carbon(DLC)films were prepared on Si(100) substrates by ion implantation from an electron cyclotron resonance microwave plasma source.During the implantation,650W microwave power was used to produce discharge plasma with methane as working gas,and-20KV voltage pulses were applied to the substrate holder to accelerate ions in the plasma.Confocal Raman spectra confirmed the DLC characteristics of the films.Fourier-transform infrared characterization indicates that the DLC films were composed of sp^3 and sp^2 carbonbonded hydrogen.The hardness of the films was evaluated with a Nano Indenter-XP System.The result shows that the highest hardness valus was 14.6 GPa.The surface rms roughness of the films was as low as 0.104nm measured with an atomic force microscope.The friction coeffcient of the films was checked using a ball-on-disk microtribometer.The average friction coefficient is approximately 0.122.     

New Microwave Diagnostic Theory for Measurement of Electron Density in Atmospheric Plasmas

We present the phase shift of an electromagnetic wave passing through an atmospheric plasma layer. In this kind of plasma, the phase shift depends not only on the line average electron density and layer width, but also on the electron-neutral collision frequency. Since the collision frequency is close to or even larger than the incident microwave frequency, a one-dimensional code for the numerical solution of the wave equation with full time and space variables is established to give the phase shift. When the width and the pressure (hence the electron-neutral collision frequency) are known, the measurement of phase shift will uniquely determine the line average electrons density in an atmospheric plasma.     

Measurement of Mg Content in Zn1-xMgxO Films by Electron Probe Microanalysis

Zn1-xMgxO films are grown on A-sapphire substrates by molecular beam epitaxy, and Mg content in the Zn1-xMgxO films is measured by electron probe microanalysis （EPMA） when the acceleration voltage, the emission current, and the magnification are set to be 1 k V, 30 μA and 1000, respectively. The dead time is controlled within 17%-20% during the measurement with the receive angle of characteristic x-ray of 45°. The Mg content of the ZnMgO film is calculated by the low energy calibration and the ZAF calibration. By comparing the measurement result with the theoretical analysis and the EPMA result with the inductively coupled plasma （ICP）, one can obtain that the measured value of Mg content of the samples is in good agreement with the theoretical analysis no matter whether the phase separation exists or not, and the correctness of ICP and EPMA is valid when Mg content in the samples is less than 0.5.     

Optimal Truncation in Ionization of hydrogen by Electron Impact

An analytic expression for the ionization amplitude of hydrogen by electron impact is found to contain a polyno-mial by an optimal truncation in an asymptotic series and a convergent series. The ionization amplitude, i.e., the transition matrix element on the energy shell, is decomposed into two parts: the structure-scattering factor and correlation factor, based on an approximation of the projectile plane wave in coplanar asymmetric geometries.The contribution of these factors to the triple differential cross section is evaluated using the method of optional truncation of asymptotic and convergent series.     

Characterization of CdS1−xSex thin films by chemical bath deposition technique

The cadmium sulfo selenide CdS_1?xSe_x thin films were chemical bath deposited in aqueous media onto coated glass substrates. As-deposited CdS_1?xSe_x thin films were annealed at 350 °C in air for 30 min. The structural, morphological, compositional and optical properties of deposited CdS_1?xSe_x thin films were studied using X-ray diffractometer (XRD), scanning electron microscopy (SEM), Energy dispersive analysis by X-ray (EDAX), and UV-Vis-NIR spectrophotometer respectively. X-ray diffraction patterns of CdS_1?xSe_x thin films reveal the polycrystalline nature and hexagonal structure. The microstructural parameters such as crystallite size (D), micro strain (?), and dislocation density were calculated and found to depend on compositions. The surface morphology and grain size are found to be influenced with the annealing temperature. The presence of Cd, S and Se of the CdS_1?xSe_x thin films and the composition of CdS_1?xSe_x thin film are estimated by EDAX analysis. The optical transmittance and absorption spectra were recorded in the range 400–2500 nm. The band gap of the CdS_1?xSe_x thin films is found to decrease from 2.5 eV to 1.75 eV.     

Electron Correlation in the Final Continuum of Ionization Hydrogen by 150-eV Electron Impact

Electron correlation in triple differential cross sections for ionization of atomic hydrogen by electron impact is analysed for the case of coplanar asymmetric geometry within the framework of the two-potential formulae. Based on the approximations of projectile and faster-electron plane wave, the transition matrix element is analytically expressed to be a product of two factors: the correlation factor of two electrons in the final channel and the structure-scattering factor. The contribution of both the factors to the angular distribution of the triple differential cross section is calculated. The present results are compared with the experimental data and the other theoretical calculations for the incident energy of 150eV.     

Superconductivity in LiTi2O4 Prepared by Hybrid Microwave Method

The well-known superconducting oxide LiTi2 04 has a structural phase transition from spinel to ramsdellite around 900℃. We have successfully obtained the superconducting spinel phase and the non-superconducting ramsdellitephase of LiTi2O4 using a hybrid microwave method. The samples are characterized by x-ray powder diffraction, scanning electron microscopy, and measurements of resistivity and magnetic susceptibility. The results show thatthe low-temperature spinel phase is a superconductor with Tc=13K, while the high-temperature ramsdellite phase is a semiconductor. By comparison between the crystal structures of the spinel and the ramsdellite phases, it is suggested that the geometrical frustration plays an important role in the superconductivity of the spinel LiTi2O4.     

Electron Transport in Ga-Rich InxGa1-xN Alloys

Resistivity and Hall effect measurements on n-type undoped Ga-rich InxGa1-xN （0.06 ≤ x ≤ 0.135） alloys grown by metal-organic vapour phase epitaxy （MOVPE） technique are carried out as a function of temperature （15-350 K）. Within the experimental error, the electron concentration in Inx Ga1-x N alloys is independent of temperature while the resistivity decreases as the temperature increases. Therefore, Inx Ga1-xN （0.06 ≤ x ≤0.135） alloys are considered in the metallic phase near the Mort transition. It has been shown that the temperaturedependent metallic conductivity can be well explained by the Mort model that takes into account electron-electron interactions and weak localization effects.     

Localized Excitations in a Sixth-Order （1＋1）-Dimensional Nonlinear Evolution Equation

In this letter, by means of the Lax pair, Darboux transformation, and variable separation approach, a new exact solution of a sixth-order （1＋1）-dimensional nonlinear evolution equation, which includes some arbitrary functions, is obtained. Abundant new localized excitations can be found by selecting appropriate functions and they are illustrated both analytically and graphically.