Resonant elastic X-ray scattering from 5<Emphasis Type="Italic">f</Emphasis> systems

The first REXS experiments on a uranium compound at the U M ₄ edge (3.728 keV) took place at BNL twenty years ago. An enormous enhancement of the scattering intensity was found. Since that time many other systems have been examined. This paper reviews some of the highlights of resonant scattering from actinide systems, and attempts to extrapolate what might be the future of this field.     

低气压长间隙介质阻挡放电的光谱诊断

设计了一种电极间隔为10 cm的介质阻挡放电装置,以氩气为工作气体,在低气压下产生等离子体。采用发射光谱法,研究了放电空腔内等离子体电子温度和电子密度随空间位置的变化规律。等离子体电子温度的变化通过使用Corona模型计算获得,等离子体电子密度的变化通过分析Ar原子750.4 nm谱线强度变化得到。实验发现空腔内不同位置的等离子体电子温度和电子密度是不同的。当测量位置从阴极向阳极移动时,电子温度先略上升而后迅速下降,再缓慢上升;电子密度先缓慢而后迅速地增大。     

类特异材料半导体复合结构中的电子Tamm态

通过选取具有特殊能带结构的半导体材料碲镉汞(Hg_1-xCd_xTe), 类比电磁体系得到了电子体系中的类单负材料、类双负材料等类特异材料, 然后将其组合成一维复合异质结构. 通过数值计算, 发现复合结构中存在新型电子Tamm态, 包括返向电子Tamm态和含类近零折射率材料复合结构中的电子Tamm态. 这些结果拓展了人们对电子Tamm态的认识.     

Study of the Optical Spectra of 4-Hydroxy-3-Methoxibenzoic Acid

Russian Physics Journal - Using electronic spectroscopy and quantum chemistry methods, the electronic spectra of vanillic acid in various solvents are interpreted. In the ground electronic state,...     

Opto-mechatronic configurations to maximize dynamic range and optimize resolution of optical instruments

We developed a new mechanical configuration which combines various optical techniques to maximize dynamic range and to optimize resolution in optical instruments. We assessed various optical configurations by looking at such variables as electronic signal processing and mechanical construction. Previous configurations developed over the last 10 years are discussed. In our new configuration, we adopted and integrated devices such as a microscopic, an interferometer, an electronic speckle pattern interferometer, and a photon tunneling microscope. We examined the impact of our new configuration on future opto-mechatronic systems design. Our new configuration can be an effective and versatile optical metrology tool for enhancing the performance of MEMS and NEMS devices.     

Review of ultrafast spectroscopy studies of valley carrier dynamics in two-dimensional semiconducting transition metal dichalcogenides

The two-dimensional layered transition metal dichalcogenides provide new opportunities in future valley-based information processing and also provide an ideal platform to study excitonic effects. At the center of various device physics toward their possible electronic and optoelectronic applications is understanding the dynamical evolution of various manyparticle electronic states, especially exciton which dominates the optoelectronic response of TMDs, under the novel context of valley degree of freedom. Here, we provide a brief review of experimental advances in using helicity-resolved ultrafast spectroscopy, especially ultrafast pump–probe spectroscopy, to study the dynamical evolution of valley-related many-particle electronic states in semiconducting monolayer transitional metal dichalcogenides.     

低速离子在固体中的电子阻止本领

本文介绍了低速离子在固体材料中电子阻止本领的理论发展情况。着重介绍了有效电荷理论和根据有效电荷理论,由氢离子在材料中的电子阻止截面标度各种重离子在同种材料中电子阻止截面的方法。 用电导理论导出了低速离子贯穿价电子气的阻止截面公式,并给出了一套有效电荷比的经验公式。利用这套公式求得的电子阻止截面Se的值,既符合实验上发现的Se随z_1或z_2振荡的规律,又符合Se随入射离子能量的变化关系。     

电极距离对分子器件电输运特性的影响

以4,4′_二巯基联苯分子为研究对象，利用从头计算方法和弹性散射格林函数理论，研究了两个电极之间的距离对分子几何结构和电子结构以及该分子结电输运性质的影响. 计算结果表明，电极距离的不同会改变分子的几何结构和电子结构，从而影响分子体系的电输运特性. 扩展分子的平衡状态不是电子输运的最佳状态，适当调整两个电极之间距离可以改善分子的电输运特性. 关键词： 电极距离 伏 安特性 分子电子学     

Chiroptical spectra of molecules with nearly degenerate electronic states

The influence of vibronic interactions on the chiroptical spectra associated with pairs of nearly degenerate electronic transitions in chiral systems is examined on a formal theoretical model. We consider the special case in which two nearly degenerate electronic states are coupled by a single non-totally symmetric vibrational mode. Formal expressions are developed for the rotatory strengths of individual vibronic transitions in this coupled system. Calculations based on these expressions are carried out for a large number of parameter sets appropriate for various energy spacings between the unperturbed electronic states, vibronic coupling strengths, oscillator (vibrational mode) frequencies, and electronic rotatory strengths. The calculated results demonstrate the profound influence of vibronic interactions on the sign patterns and intensity distributions within the rotatory strength spectrum associated with the two coupled electronic states. The implications of these results for interpretations of circular dichroism spectra are discussed.     

分子的位置取向对分子器件电输运特性的影响

以1,4-二硫酚(DTB)分子为研究对象，利用第一性原理计算方法和非平衡格林函数理论，研究了分子的位置取向对分子电子结构以及分子结电输运性质的影响.计算结果表明，分子位置取向的改变会影响分子的电子结构，从而影响分子体系的电输运特性，扩展分子的平衡态不是电子输运的最佳状态，适当调节分子的位置取向可以提高分子的电输运特性. 关键词： 位置取向 电子输运 分子电子学     

Analytical treatment for synchronizing chaos through unidirectional coupling and implementation of logic gates

The idea of synchronization can be explicitly demonstrated by both numerical and analytical means on a nonlinear electronic circuit. Also, we introduce a scheme to obtain various logic gate structures, using synchronization of chaotic systems. By a small change in the response parameter of unidirectionally coupled nonlinear systems, one is able to construct various logic behaviours by both numerical and analytical methods.     

Effect of heat treatment on electronic phase in underdoped La2-xSrxCuO4 single crystal

Superconducting La1.937Sr0.063CuO4 crystals grown by the travelling-solvent floating-zone technique were thermally treated under various temperatures and oxygen pressures for moderately adjusting the oxygen content. The response of intrinsic electronic property of the crystals to the change of hole density in La2-xSrxCuO4 in the vicinity of the magic doping of x= 1/16 （= 0.0625） is studied in detail by magnetic measurements under various fields up to 1 T. It is found that when the superconducting critical temperature （Tc） increases with the oxygen content, there appears also a new subtle electronic state that can be detected from the differential curves of diamagnetic susceptibility dx/dT of the crystal sample. In contrast with the intrinsic state, the new subtle electronic state is very fragile under the magnetic fields. Our results indicate that a moderate change in oxygen doping does not significantly modify the intrinsic electronic state originally existing at the magic doping level.     

Distorted magnetic orders and electronic structures for FeSe under pressure

We have studied various magnetic orders and electronic properties as well as pressure-induced effects on FeSe by using density functional theory with combination of Hubbard Model. We find that the Fe spins in striped antiferromagnetic orders with the broken symmetry are more stable in energy than the checkerboard antiferromagnetic ones with tetragonal symmetry. The electronic properties revealed that the enhanced metallic and the suppressed magnetism caused by quantum many-body effects would be the origin for the occurrence of pressure-induced superconductivity in FeSe system, which indicate that the superconductivity of FeSe system showed a closed relationship with the magnetism and its spin fluctuation. These results are useful in understanding the structural, magnetic and electronic properties of FeSe under pressure.     

Electronic structure of epitaxial interfaces

Metal-semiconductor (Schottky barrier) and semiconductor-semiconductor (heterojunction) interfaces show rectifying barrier heights and band offsets, which are two key quantities required to optimize the performance of a device. A large number of models and empirical theories have been put forward by various workers in the field during the last 50 years. But a proper understanding of the microscopic origin of these quantities is still missing. In this article, our focus is mainly to present a unified framework for first principles investigation of the electronic structure of epitaxial interfaces, in which one of the constituents is a semiconductor. LMTO method is now a well established tool for self-consistent electronic structure calculations of solids within LDA. Such calculations, when performed on supercell geometries, are quite successful in predicting a wide range of interface specific electronic properties accurately and efficiently. We describe here the basic formalism of this LMTO-supercell approach in its various levels of sophistication and apply it to investigate the electronic structure of A- and B-type NiSi₂/Si(111) interface as a prototype metal-semiconductor system, and CaF₂/Si(111) interface as a prototype insulator-semiconductor system. These are a few of the most ideal lattice matched epitaxial interfaces whose atomic and electronic structures have been extensively studied using a wide range of experimental probes. We give here a glimpse of these experimental results and discuss the success as well as limitations of LDA calculations to achieve accuracies useful for the device physicists.     

Electrons in disordered systems. Scaling near the mobility edge

Renormalization group arguments are applied to an ensemble of disordered electronic systems (without electron-electron interaction). The renormalization group procedure consists of a sequence of transformations of the length and the energy scales, and of orthogonal transformations of the electronic states. Homogeneity and power laws are obtained for various one and two-particle correlations and for the low-temperature conductivity in the vicinity of the mobility edge. Two types of fixed point ensembles are proposed, a homogeneous ensemble which is roughly approximated by a cell model, and an inhomogeneous ensemble.     

Electrical parameters retrieval of carbon nanoparticle-based metal semiconductor metal structure by standard methods and beta-ray-induced charge

Semiconducting carbon nanoparticles (CNPs) represent various applications in sensing systems with exceptional electronic properties. The extraction of electronic parameters of a sensor is very important to interpret the sensing characteristics of the electronic devices. This work is concerned with the extraction of electronic parameters such as the ideality factor, the barrier height, the series resistance, and some other diode parameters of a CNP-based metal semiconductor metal structure. The parameters are determined from the experimental data and physical model using the standard current–voltage (I–V) analysis in the frame of the thermionic emission theory, impedance spectroscopy, and other methods. The mobility-lifetime products (μτ) for electrons and holes in CNP micro-wire were determined by beta-ray-induced charge with Schottky contacts.     

Near-surface structural study of transition metal oxides to understand their electronic properties

The atomic arrangement in a solid contains a great amount of information, and observation of its structure is essential for understanding the electronic and magnetic properties of transition metal oxides at a microscopic level. Increasing interest in the surfaces and interfaces of oxide systems, which is partly driven by the anticipation of device applications, enhances the importance of structural studies of the near-surface region. We review various types of structural studies with x-ray scattering on the near-surface region of metal oxides-from thick films to surfaces-in order to clarify the structural effects on their electronic properties.     

A theoretical study of potential energy curves and spectroscopic constants of VC

Potential energy curves for the various low-lying electronic states of VC have been studied using complete active space multi-configuration self-consistent field (CASMCSCF) followed by first-order and multireference singles and doubles configuration interaction (FOCI, MRSDCI) calculations. The MRSDCI calculations included up to 6 million configurations. Two very low-lying electronic states are found as candidates for the ground state of VC, namely a high spin state ⁴Δ and a low-spin ²Δ state, which is favoured at higher levels. A number of low-lying excited electronic states of VC are predicted, which are yet to be observed. The low-lying electronic states of VC are found to be ionic as inferred from the dipole moments and the charge density calculations. Electron donation and the back-donation process are suggested to be operative in the V-C bond formation.     

Microscopic aspects of Si-Ge heterojunction formation

We present the results of an investigation of the electronic structure of heterojunctions formed by deposition of Germanium on Si (lll) surfaces. Energy Loss Spectra for various Ge coverages have been taken and compared with theoretical calculations. The results indicate that the interface is abrupt and at low coverages Ge is deposited uniformly on the substrate. Above 2 monolayers coverage modifications in the electronic structure appear probably caused by the growth mechanism.     

First principles hybrid functional study of small polarons in doped SrCeO<Subscript>3</Subscript> perovskite: towards computation design of materials with tailored polaron

SrCeO₃ perovskites are promising materials for hydrogen separation membranes. High hydrogen flux in SrCeO₃ is achieved by various elemental doping to increase protonic and electronic conductivity. While the effect of B-site dopants on protonic conductivity is established, the polaronic mechanism induced by B-site cations, which is essential for electronic transport, has been less understood. Using first principles hybrid functional calculations, we investigated the polaron formation and migration in SrCeO₃ perovskites doped with different elements. Our computation results revealed distinctive behaviors of different dopant elements in localizing polarons and explained previous literature results of doping SrCeO₃ for increasing electronic conductivity and hydrogen flux. In addition, new promising dopants are predicted to increase electronic conductivity. The computation approach demonstrated in this study provides a general scheme to design materials with tailored polaron formation and enhanced functional properties.