Simulations of the Electron Spectrum of Quantum Wires in <i>n</i>-Si of Arbitrarily Doping Profile by Thomas-Fermi Method

Electron spectrum in doped n-Si quantum wires is calculated by the Thomas-Fermi (TF) method under finite temperatures. The many-body exchange corrections are taken into account. The doping profile is arbitrary. At the first stage, the electron potential energy is calculated from a simple two-dimensional equation. The effective iteration scheme is proposed there that is valid for multidimensional problems. Then the energy levels and wave functions of this quantum well are simulated from the Schr&#246;dinger equations. The expansion by the full set of eigenfunctions of the linear harmonic oscillator is used. The quantum mechanical perturbation theory can be utilized to compute the energy levels. Generally, the perturbation theory for degenerate energy levels should be used.

Resonance and Antiresonance in Electronic Transport Process Through a T-Shaped Quantum Waveguide

By means of the transfer matrix approach, the linear conductance spectrum for electronic transport through a T-shaped quantum waveguide is calculated. The resonant peaks and the antiresonant dips in the conductance spectrum are mainly focused. The previous prediction about their positions by other theoretical approaches is checked. In addition, a function of spin filtering is suggested based on the interplay of the resonance and antiresonance in this T-shaped quantum waveguide.

M_(αβ) X-ray production cross sections of Pb and B iby 9–40 keV electron impact

The experimental data of Mαβ X-ray production cross sections for Pb and Bi by 9–40 keV electron impact have been given. Thin films with thick carbon substrates are used in the experiment. The effects of target structure on the Mαβ X-ray production cross sections are corrected by using the Monte Carlo method. The corrected experimental data are compared with calculated cross sections in terms of the distorted-wave Born approximation(DWBA) theory. The measured Mαβ X-ray production cross sections for Pb and Bi are lower than the DWBA calculations. The atomic relaxation parameters used in comparing the DWBA values with experimental results affect the degree of difference.

Electron Momentum Density and X-ray Structure Factors of Fcc-Copper

In this paper, we report the ground state properties i.e. electron momentum density and X-ray structure factors of fcc-copper are presented. The Am241 Compton spectrometer, which uses 59.54 keV gamma-rays, has been used for the Compton profile measurement. To compare the experimental data, the Compton profiles within the framework of linear combination of atomic orbitals (LCAO) method using Hartree–Fock (HF), density functional (DF) and hybrid B3PW schemes embodied in the CRYSTAL06 code have been computed. Among the various theoretical calculations, it is found that the present experimental data is in very good agreement with the hybrid B3PW scheme. A real-space analysis of the experimental Compton profile shows the metal-like behavior of copper The structure factors for copper are computed using hybrid B3PW scheme and compared with available experimental and theoretical data.

Integral cross sections for electron impact excitations of argon and carbon dioxide

Electron-impact excitation integral cross sections play an important role in understanding the energy transfer processes in many applied physics. Practical applications require integral cross sections in a wide collision energy range from the excitation threshold to several ke V. The recently developed BE-scaling method is able to meet the demands of integral cross sections for dipole-allowed transitions while the prerequisite relies on the accurate generalized oscillator strengths. Fast electron and x-ray scatterings are the conventional experimental techniques to approach the generalized oscillator strengths,and the joint study by both methods can provide credible cross-checks. The validated generalized oscillator strengths can then be used to extrapolate optical oscillator strengths by fitting the data with the Lassettre formula. The fitted curve also enables the integration of generalized oscillator strengths over the whole momentum transfer region to obtain the BE-scaled integral excitation cross sections. Here, experimental measurements by both fast electron and x-ray scattering of argon and carbon dioxide are reviewed. The integral cross sections for some low-lying states are derived from the cross-checked generalized oscillator strengths for the first time. The integral cross sections presented in this paper are openly available at https://doi.org/10.11922/sciencedb.01466.

Electron Temperature Measurement of Radiation-Heated CH Foam on Shenguang Ⅱ Laser Facility

A spectroscopic diagnostic method, to measure electron temperature of radiationheated CH foam on Shenguang Ⅱ laser facility, is described. A tracer layer of aluminum was embedded in the middle of the CH foam and a point-projection method used in the opacity experiment was induced to measure the transmission spectrum of the embedded Al foil. The electron temperature, of about 80 eV, was deduced through a comparison of the experimental absorption spectrum with the calculated one with a detailed level accounting opacity code. The results of hydrodynamic simulation show that it＇s reasonable to determine the CH foam temperature by measuring the embedded Al absorption spectrum. Thus, the electron temperature of radiationheated CH foam was obtained.

Application of Electron Microscopic on the Sources of PM_(10) in the Atmosphere

[ Objective] The aim was to study the application of scanning electron microscopy（SEM） on the physical property and ideological distri- bution of partials. [ Method] By dint of scanning electron microscopy, the morphological property of each source and main elements were analyzed. Compared with morphological property of sampling point, the source of particles was determined. [ Result] The results were consistent with the analysis of CMB8.2 chemical mass balance receptor model. Taking the four detection stations in Longyan Normal Training College, Minxi Vocational ＆ Technical College, Longyan University, and Longyan Environment Monitoring Station as examples, the major air pollutants respectively were soil sand, dust of burning coal, second fugitive dust; soil sand, second fugitive dust, vehicle exhausts; second fugitive dust, soil; and second fugitive dust, vehicle exhausts, dust of burning coal. [ Conclusion] The study result had certain guiding significance to the analysis of sources of particles in the atmosphere and atmosphere environment treatment.

Structural and Piezoelectric Properties of Sr_(0.6)Ba_(0.4)Nb_2O_6 Micro-rods Synthesized by Molten-Salt Method

Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragonal tungsten bronze structure.The measurement of X-ray diffraction indicates that the Sr0.6 Ba0.4 Nb2 O6 micro-rods synthesized at 1 300℃are anisotropic.The morphology of the powers is examined by transmission electron microscope.It reveals that the length-diameter ratio of Sr0.6 Ba0.4 Nb2 O6 micro-rods increases with increasing annealing temperature from 900℃to 1 300℃.At 1 300℃,the rod possesses a large length-diameter ratio of 8∶1.Moreover,the analysis of the piezoelectric properties of single micro-rods using apiezo-response force microscope indicates that the domains of the material are arranged along its radial direction.

A theoretical method based on Fourier spectrum analysis for the focusing performances of the X-ray compound refractive lenses

It is important to predict the intensity distribution in focusing plane for designing the X-ray compound refractive lenses. On the basis of analyzing the structure of X-ray compound lenses and comparing it with Praunhofer diffraction system, it is concluded that the X-ray focusing system can be regarded as a kind of Praunhofer diffraction system. Therefore, a method based on Fourier spectrum analysis is presented to predict the intensity distribution in the focusing plane for the X-ray lenses. A brief analysis on the relationship between the parameters of X-ray lenses and their focusing performance is also given in this paper.

电子产品野外环境下温循加速载荷谱编制方法

目的将电子产品在野外环境下日变化波动与季节差异明显的温度载荷编制成温循载荷谱和转换为加速载荷谱。方法通过四点雨流计数法提取原谱中的载荷循环信息,对提取的循环信息进行分布拟合、相关性检验等统计分析,进而构建循环均值与范围值的联合概率密度函数,再运用概率密度法,编制出8×8二维环境载荷谱。在二维载荷谱基础上,编制出温循载荷谱,使用针对电子部件参数修正的加速方程转化为加速载荷谱。结果利用野外作业现场1个作业周期内的气温纪录,提供了一套编制温循载荷谱和转换加速载荷谱的合理化流程和解决方案。结论该制谱方法可以利用原始环境谱中绝大部分有效信息,较好地还原电子部件野外作业阶段经历的温度变化过程,为电子产品的加速寿命试验和使用寿命预测奠定基础。

Theoretical study on S_1(~1B_(3u)) state electronic structure and absorption spectrum of pyrazine

Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S0(1Ag)) and the first (S1(1B3u)) excited state of pyrazine are investigated, and the electronic structures of the two states are characterized. In the present study, the conventional quantum mechanical method, taking account of the Born-Oppenheimer adiabatic approximation, is adopted to simulate the absorp-tion spectrum of S1(1B3u) state of pyrazine. The assignment of main vibronic transitions is made for S1(1B3u) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode ν6a. For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S1(1B3u) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S1(1B3u) absorption spectra. The distortion effect due to the so-called quadratic coupling is demonstrated to be unimportant for the absorption spectrum, except the coupling mode ν10a. The calculated S1(1B3u) ab-sorption spectrum is in reasonable agreement with the experimental spectra.

二正丁基二硫代氨基甲酸锌配合物的量子化学研究

The geometric configurations of binuclear Zinc( complex Zn2[(n-Bu)2NCSS]4 and the ligand Na[(n-Bu)2 NCSS] have been optimized by B3LYP quantum chemical method. The electronic structures have been performed by density functional theory at B3LYP/6-31G* level. The electronic spectrums of the complex and ligand were calculated by ZINDO/S-CIS method. It is indicated from the calculation that: (1) The coordination effect of bridging ligand is bigger than that of chelating one, and the bridging ligands also translate more charge to Zn than the chelating one. (2) The calculated results about electronic spectrums are similarly to experimental measurement, and farther explain that absorption band at λ=267 nm of complex is assigned to two n → π* transitions :one arising from the bridging ligands and the another mainly arising from the chelating ligands;but absorption band at λ=236 nm of complex is assigned to π → π* transition which the electron mainly translates from the bridging ligands to the chelating ligands. (3) By consideration of delocalization and polar effects in coordination, the charge transfer from ligand to metal decreases the π-π and p-π conjugation effects in the chromophore group NCS2 and to increase the energy needed for the π → π* and n → π* transitions, and results in the absorption bands shifting towards the short wavelength direction.

几种芳香胺类有机EL材料性质的量子化学研究(英文)

几种芳香胺类化合物E－12、E－13、E－14和E－15均为性能良好的有机电致发光（EL）和光致发光（PL）材料。采用量子化学计算方法，用RHF／AM1方法优化其构型，用RHF／CIS方法计算其电子光谱，计算结果与实验值基本吻合。

DNA碱基与电极的耦合强度对横向电输运的影响

采用基于密度泛函理论的非平衡格林函数方法,研究了以Au(111)面为电极、DNA的单个碱基(包括主链上的糖基和磷酸基)置于其间的两电极体系的电输运特性.在电极距离固定的情况下,通过改变碱基与电极的接触距离,分别计算了零偏压下DNA碱基处于不同耦合强度时的横向电导和传输谱.结果表明碱基的横向电输运性质受耦合强度的影响较大;除了鸟嘌呤G的氢键靠近电极时电导比腺嘌呤A小之外,碱基的电导排序符合G>A>C>T.

共轭杂环对席夫碱体系结构和非线性光学性质影响的量子化学研究

采用量子化学半经验FF/AM1,FF/PM 3,ZINDO -SOS方法 ,讨论了杂环取代对水杨醛缩苯胺结构、电子光谱、非线性光学系数的影响 ,得到这类化合物的特征吸收峰位于 2 94～ 30 3nm ,符合非线性光学材料对透明性的要求 ,且给电性杂环的引入可改善体系的非线性光学性质 。

二氰基二硫纶和4,4-二甲基2,2-联吡啶镍(Ⅱ)配合物的光谱和理论研究

报道了标题配合物Ni(mnt)(dmbpy)溶液的电子光谱、粉末样品部分IR光谱及量子化学理论研究结果.PM3方法的几何优化表明,该配合物分子为平面结构,其对称性属于C_(2v)点群,基态为自旋三重态.结合ZINDO方法的CI计算,解释了实测电子光谱,发现该配合物在可见区450～550nm存在本质上属于配体dmbpy到配体mnt^(2-)的荷移跃迁(LL′CT).建立了解析复杂分子振动光谱的一种新方法:根据理论计算所得三维动态图象,对于每一个正则模,先给出固定不动的点,再给出关键性的振动类型.在本方法中,用符号η(X)定义了一种新的沿给定方向起伏或跳动式的振动类型。

GC-MS在电子束辐照降解甲苯中的应用

用甲苯作为挥发性有机化合物的代表物质，建立了活性炭吸附-二硫化碳解吸气相色谱-质谱分析方法，对电子束辐照甲苯的静态实验和动态实验进行了定性、定量分析。实验结果表明：电子束辐照能有效地降解甲笨，其降解率随吸收剂量的增加而增大；同时，甲苯降解过程中也会生成部分有毒有害物质。该分析方法的检出限为0．02mg／L，工作曲线的线性范围为10～1000mg／L，相关系数为0．9998，活性炭吸附、解吸甲苯的加标回收率大于90％。

3种含氮芳烃化合物材料性质的量子化学研究

采用量子化学半经验方法RHF/AM1,对 3种含氮芳烃化合物电致发光材料 (EL)的性质进行了理论研究 .对 3种化合物优化后的构型作振动分析 ,均未出现虚频率 .在此基础上 ,采用RHF/CIS方法计算了电子光谱 ,计算结果与实验值基本吻合 .

医用加速器8MV X射线在水模体中的一阶散射X射线能谱的蒙特卡罗计算

目的:分析医用电子直线加速器的高能X射线与水模体相互作用过程中所产生的一次散射光子的能谱角分布和光子强度角分布。方法:利用蒙特卡罗粒子输运程序Geant4,模拟粒子输运过程,计算加速器8 MeV高能X射线能谱,并根据在水模体中实际测量的PDD吸收曲线为依据,修正蒙特卡洛计算的能谱;并以此能谱为虚拟源能谱,通过对X射线与水模体相互作用后的光子-电子联合输运过程进行蒙特卡罗模拟的方法获取有关散射X线能谱数据。结果:用蒙特卡洛方法得到加速器8 MV初始X射线与水模体作用产生的一次散射光子的散射光子强度和散射光子能量随散射角度变化的规律。结论:根据ICRP85出版物、ICRU44报告给出的数据,可以用组织平均原子序数作为组织等效原子序数;因此,组织密度变化在物理上反映了组织的原子密度的变化,当入射光子注量改变,模体密度变化时,仅引起相互作用的总截面相对于原子微分截面的线性变化,并不影响一阶散射X射线的散射光子的相对强度角分布和散射光子能量角分布,而散射光子发射的绝对量与初始X射线强度、组织的原子密度成正比。因此,一次散射光子的注量角分布、平均能量角分布结果可形成可调用的数据库,对快速蒙特卡洛计算很有意义。

5-[2′-氟-4′-溴-苯甲亚胺]-8-羟基喹啉铝的量子化学研究

应用密度泛函PBE0方法优化5-[2′-氟-4′-溴-苯甲亚胺]-8-羟基喹啉铝(AlA3)及5-[2′-氟-4′-溴-苯甲亚胺]-8-羟基喹啉(HA)的几何构型,用TDDFT法计算其电子光谱,对电荷转移及金属原子与配体的结合能进行了讨论.计算结果表明:(1)AlA3配合物较稳定,但结合能略低于8-羟基喹啉铝(AlQ3).与AlQ3相比,AlA3的轨道作用较强,静电作用较弱,两者之和相近,但AlA3排斥能较大.(2)计算AlA3的两个电子吸收峰与实验结果相符.AlA3中的电荷由羟基喹啉基团通过Al原子在不同配体间转移呈现出最大吸收峰,属于AlQ3类衍生物的特征吸收峰.因为体系的共轭程度增大使LUMO轨道能降低,电子跃迁需要的能量减少,故吸收峰比AlQ3红移;(3)290 nm吸收峰是电荷由C N基团向羟基喹啉基团转移产生的.在喹啉环接上5-[2′-氟-4′-溴-苯甲亚胺]基团可望制备出波长更长的发光材料,且增加了一个较强的吸收峰.