Preparation of cluster states with trapped electrons on a liquid helium surface

We present a scheme for the preparation of one-dimensional (1D) and two-dimensional (2D) cluster states with electrons trapped on a liquid helium surface and driven by a classical laser beam. The two lowest levels of the vertical motion of the electron act as a two-level system, and the quantized vibration of the electron along one of the parallel directions (the x direction) serves as the bosonic mode. The degrees of freedom of the vertical and parallel motions of the trapped electron can be coupled together by a classical laser field. With the proper frequency of the laser field, the cluster states can be realized.     

The nature of the chemical bond in UO2

The nature of the chemical bond in UO₂ was analyzed taking into account the X-ray photoelectron spectroscopy (XPS) structure parameters of the valence and core electrons, as well as the relativistic discrete variation electronic structure calculation results for this oxide. The ionic/covalent nature of the chemical bond was determined for the UO₈ (D_4h) cluster, reflecting uranium's close environment in UO₂, and the U₁₃O₅₆ and U₆₃O₂₁₆ clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to ~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UO₂ single crystalline thin film. It was shown that unlike the crystal field theory results, the covalence effects in UO₂ are significant due to the strong overlap of the U 6p and U 5f atomic orbitals with the ligand orbitals, in addition to the U 6d atomic orbital (AO). A quantitative molecular orbital (MO) scheme for UO₂ was built. The contribution of the MO electrons to the chemical bond covalence component was evaluated on the basis of the bond population values. It was found that the electrons of inner valence molecular orbitals (IVMO) weaken the chemical bond formed by the electrons of outer valence molecular orbitals (OVMO) by 32% in UO₈ and by 25% in U₆₃O₂₁₆.     

光子与相对论麦克斯韦分布电子散射的能谱角度谱研究

光子与相对论麦克斯韦分布电子散射的描述及能谱角度谱计算非常复杂且费时.本文提出了一种光子与相对论麦克斯韦速度分布电子散射的蒙特卡罗(MC)模拟方法,该方法能够细致模拟高温等离子体中任意能量光子与任意温度电子的Compton和逆Compton散射问题.对于散射后光子的能谱和角度谱参数,可以根据电子温度抽样若干不同状态的电子,分别模拟其与光子发生散射,可以得到各次散射后的光子能量和偏转角度,取统计平均后的结果即可获得该光子与该温度电子散射的能谱和角度谱分布.根据该方法编写了光子与相对论电子散射MC模拟程序,开展了高温全电离等离子体中光子与相对论电子散射的能谱角度谱计算和分析,分析结果显示:热运动电子将展宽出射光子能谱,且低能光子与高温电子散射后的蓝移现象明显;出射光子的角度谱很复杂,其决定于入射光子能量、出射光子能量及电子温度.基于该方法计算并以数表形式给出的光子-相对论电子散射能谱角度谱数据,可以供辐射输运数值模拟程序使用.     

Dust ion‐acoustic solitons collision in weakly relativistic plasmas with superthermality‐distributed electrons and positrons: Higher‐order phase shifts

The higher‐order (H‐O) phase shift of dust ion‐acoustic solitons (DIASs) in a weakly relativistic plasma is examined considering the influence of both superthermality‐distributed electrons and positrons. Employing the extended Poincaré–Lighthill–Kuo method (EPLKM), the Korteweg–de Vries equations (KdVEs) and the deviation in trajectories of DIASs (i.e., phase shifts) are obtained after the collision. For obtaining H‐O phase shifts of DIASs, the fifth‐order dispersion terms are added into KdVEs. The effects of the relativistic factor for a weakly relativistic regime and the superthermality of both electrons and positrons on the H‐O phase shifts are discussed. Numerical analysis gives rise to important highlights on the excitation and the collision of DIASs in astrophysical situations such as a pulsar magnetosphere.     

Synthesis and Electrolytic Properties of Phases Based on Calcium Thiogadolinate as a Function of Method of the Precursor Synthesis

Differently treated phases based on CaGd₂S₄ are studied by electrochemical methods. The range of solid solutions, electrolytic temperature interval, and averaged transport numbers for ions and electrons are determined. Compositions with best electrolytic properties are established. The origin of conduction in a CaGd₂S₄-based solid electrolyte is investigated. The obtained data show the phases to be sulfide-conducting solid electrolytes with a small share of cationic conduction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 633–639.Original Russian Text Copyright © 2005 by Medvedeva, Kalinina, Metlin, Ushakova.     

Vertical transport and relaxation mechanisms in δ-doping superlattices

We report on electron transport in growth direction and relaxation mechanisms in δ-doped GaAs-superlattices. In order to investigate pure electron transport, n-type δ–n–i–p–i structures sandwiched between two n⁺-cladding layers have been investigated, with doping induced barrier heights ΔV smaller than the band gap energy E_g of the host material. An exponential increase of the current is expected with increasing bias due to tunneling through a decreasing barrier. At elevated temperatures, thermally activation over the barriers becomes possible. A simple WKB-model describes the experimental data reasonably well. Moreover, a current step appears in the I–V characteristics at a critical field which is clearly below the breakthrough value. Opto-electrical measurements confirm the existence of holes in the structure at fields larger than the critical field. A model is presented which explains the photocurrent and electroluminescence measurements consistently. The key mechanism is based on a few ballistically traveling electrons that can gain enough energy for interband avalanche multiplication.     

Effective spin susceptibility, electron mass and Landé factor in two-dimensional (2D) Si inversion layers

We have studied the silicon (Si) band-structure, electron–electron and electron-ionized donor interaction effects on our accurate and approximate results (AcR and ApR) for renormalized effective spin susceptibitity (RESS), electron mass (EEM), Landé factor and spin polarization in the impure 2D Si (electron system), showing that:(i) our ApR, being strongly deviated from our AcR, reproduces approximately all the data obtained recently by Pudalov et al. (Phys. Rev. Lett. 88 (2002) 196404) [in particular, RESS =4.7 at the critical value of Wigner–Seitz radius r_s: r_s=r_c≈8.5 at which occur the “apparent” metal–insulator transition (MIT)] and can also be compared with other ApRs found in the recent literature,(ii) both the RESS and EEM produce physical singularities at the same critical value: r_s=r_c11.05661 (weakly disordered samples) at which occurs the “true” MIT; the existence of such two “apparent and true” critical values in this impure system agrees with a recent discussion by Abrahams et al. (Rev. Mod. Phys. 73 (2001) 251), and(iii) at r_s=r_c=8.5, at which occurs the “apparent” MIT, our AcR for effective spin polarization and the corresponding result, obtained using a disordered Hubbard model and a determinant quantum Monte Carlo method by Denteneer and Scalettar (Phys. Rev. Lett. 90 (2003) 246401), both give the same result: ξ_eff.=ξ_c0.31 at B0.4 T, which is found to be lower than the critical parallel magnetic field for full spin polarization, B_c=1.29 T, supporting thus the existence of such an “apparent” MIT.     

Electron Transitions of Cadmium Oxide

The bands, densities of states, and spectrum of the permittivity ₂ of a CdO crystal have been calculated by the FP–LMTO method. The ₂, ₁, –Im ^–1, and Re ^–1 spectra for the CdO crystal in the range 1–30 eV have been obtained on the basis of the experimental spectrum of reflection. The spectra were decomposed into elementary components and their main parameters were calculated. The obtained spectrum of the transverse components was compared with the theoretical spectrum of ₂.     

新型具有两极性质的电致发光聚合物

合成了一种新型含有三苯胺和恶二唑基元的共聚物。聚合物在溶液中的紫外吸收光谱表明吸收是由电子的π－π^*跃迁引进的，在溶液和薄膜中发射蓝色的荧光，聚合物在溶液中的氧化还原性质证明其既具有电子传输性质又具有空穴传输性质，同时电化学方法得到的聚合物的禁带宽度与紫外吸收光谱的结果是一致的。     

Electron scattering from nonlinear molecules using multicentre wavefunction expansions

Summary The scattering of slow electrons by polyatomic molecules is studied within a full quantum formulation of the problem, and the wavefunctions of the target molecular bound electrons are obtained from a multicentre expansion (MCE) of Gaussian-type orbitals (GTOs) within the single-determinant Hartree-Fock (HF)-SCF scheme. It is shown that the scattering calculations require the solution of radial coupled equations where the interaction is obtained as a further multipolar expansion at the target centre of mass (c.o.m.), while the relevant numerical procedures are discussed for systems like SiH₄, GeH₄ and CF₄. The ensuing interaction coefficients are used to carry out convergence studies of the scattering cross-sections, over a broad range of energies, in the case of silane targets. The results are found to be rapidly converging for such a system, while the different behaviour expected for other targets is also analysed and explained.