外电场作用下苯乙烯分子结构和电子光谱

采用密度泛函B3P86方法在6-311G基组水平上优化得到了在不同外电场(0—0.05a.u.)作用下,苯乙烯分子的基态电子状态、几何结构、电偶极矩和分子总能量.在优化构型下利用杂化CIS-DFT方法(CIS-B3P86)研究了同样外电场条件下对苯乙烯的激发能和振子强度的影响.计算结果表明,分子几何构型与电场大小呈现强烈的依赖关系,分子偶极矩随电场的增加而增大.分子总能量随着电场增加而降低.激发能随电场增加快速减小,表明在电场作用下,分子易于激发和解离. 关键词： 苯乙烯 电场 激发态 杂化CIS-DFT     

Measurement of Raman scattering in simple liquids under the influence of high quasi-static electric fields

The vibrational Raman bands of some simple liquids are investigated on the influence of an external electric dc field. Thereby the electric field strength is varied in the range of 0.1 to 1 MV/cm. The experiments demonstrate that Raman intensities and depolarization ratios increase with increasing field strength and — after passing a maximum — decrease with even higher field strengths. In mixtures the field dependence of Raman intensity takes a different course than in pure liquids.     

砷化镓半导体材料与器件中高频场分布研究的新方法——脉冲电光检测技术

介绍了砷化镓材料和器件中高频电场的分布测量的新方法——谐波混频脉冲电光检测:它的原理、实验装置以及在砷化镓共平面波导中微波驻波场分布测量中应用的结果.在频率高达20.10GHz及开路、短路和50Ω不同的负载条件下测得的结果与理论预计值符合很好.本文最后对方法的灵敏度和空间分辨率进行讨论.     

Forward scattering theory of electric-field-gradient-induced birefringence

We attempt to resolve the discrepancy between the Buckingham—Longuet-Higgins (BLH) and Imrie—Raab (IR) theories of linear birefringence induced in a gas of dipolar molecules by an electric field gradient. To this end we present a new calculation of the effect, based on forward scattering of a light beam incident on a thin lamina of gas molecules. We work to electric quadrupole—magnetic dipole order. The beam undergoes a time delay which is proportional to the thickness of the lamina and the electric field gradient, and can therefore be interpreted in terms of a contribution to the refractive index of the gas due to the field gradient. The birefringence is obtained by considering appropriate polarizations of the incident beam. To avoid the occurrence of a divergent quantity, such as appears in the BLH theory, it is essential to take account of the finite beam width. Calculations are performed using both primitive (traced) and traceless molecular quadrupole moments; as required on basic grounds, these results are equivalent. They are also identical to the BLH result. By contrast, the IR result is physically unacceptable because it is not invariant with respect to the use of traced and traceless moments. The source of error in the IR theory remains unclear.     

Formation of an effective electric field in track regions during the stopping of fast heavy charged particles in materials

A microscopic approach is used to study the formation of an electric field near the trajectories of fast heavy charged particles propagating in various materials. The analysis is based on determining the space—time distribution function of the fast δ-electrons generated when heavy ions are stopped in materials and the electric current produced by them. The spatial dependence of the electric field strength is determined at various times. The results are used to analyze the process of electric field energy transfer to the ionic subsystem. The spatial distribution of the energy acquired by the ionic subsystem from the electric field is determined over its characteristic lifetime. A mechanism is proposed to explain the formation of track regions both as a result of the higher local heating of the ionic subsystem and as a result of the possible irreversible displacement of the atoms from nodal points.     

用连续波电光检测技术进行LiNbO3定向耦合波导调制器的场分布测量

本文介绍一种新颖的无损伤检测技术——连续波电光检测技术(OWEOP)对LiNbO_3定向耦合波导调制器模拟样品内场分布进行各种测量所获得的实验结果。采取了背射和端射两种测量方式,测出了波导电极条下,电极间隙区以及电极中断区电场的分布,并对实验结果进行了讨论。     

Spin Hall effect in nonmagnetic conductors under the classical Hall conditions

The spin Hall effect—the excitation of a spin flux by an electric current normal to it—is considered in a paramagnetic sample in disregard of the spin-orbit coupling in the classical Hall effect case, when the Pauli spin polarization is induced by the magnetic field H ₀ normal to the electric current.     

Anisotropic effects induced by magnetic field in zero-gap semiconductors

The magnetic sub-band structure in zero-gap semiconductors α—Sn and HgTe is calculated and shown to depend strongly on the field orientation. This effect is discussed in connection with high-field transport and optical phenomena. It is demonstrated that a transverse electric field acts to increase the magnetically induced gap in α—Sn and to decrease it in HgTe.     

Imaginary-time method in quantum mechanics and field theory

An imaginary-time method was developed for calculating the probability of particle transmission through smooth barriers variable with time. Within the imaginary-time method, the tunneling process is described by using classical equations of motion written in terms of an imaginary time (t → it), while the probability of tunneling is determined by the imaginary part of the action functional, this imaginary part being calculated along the subbarrier particle trajectory. The fundamentals of the imaginary-time method are surveyed, and its applications in the theory of atomic-state ionization under the effect of constant electric and magnetic fields that have various configurations, in the field of intense monochromatic laser radiation and of an ultrashort electromagnetic pulse, in the process of Lorentz ionization of atoms and ions during their motion in a strong magnetic field, etc., are outlined. The applications of the imaginary-time method in relativistic cases—for example, in the theory of ionization of levels of multiply charged ions whose binding energy is commensurate with the electron rest energy—and in quantum field theory (Schwinger effect, which consists in the production of electron-positron pairs from a vacuum by a superstrong external field) are briefly described. Particular attention is given to methodological issues and details of the imaginary-time method that are of importance in solving specific physics problems, but which are usually skipped in original publications.     

Modell einer Schraubenversetzung in piezoelektrischen Kristallen. II Elektrisches Feld und Ladungsverteilung für eine Versetzung in einem Eigenhalbleiter im thermischen Gleichgewicht

The electric potential field occurring on dislocations in piezoelectric intrinsic semiconductors due to the piezoelectric effect is described, in the case of thermal equilibrium, by a quasi-linear partial elliptic differential equation. In most cases, already the linearized form of this differential equation yields solutions of sufficient accuracy. Closed expressions for the electric field and for the density? of free charge carriers are derived from this potential. As in part I explicit solutions are given and discussed in detail for a 〈001〉-screw dislocation in cubic crystals. — For ZnS and GaAs the proper numerical values are calculated.     

雷暴电场对宇宙射线次级粒子μ 子的影响研究

西藏羊八井宇宙射线观测站的中子监测器主要探测宇宙射线次级粒子中能量在500 MeV—20 GeV的核子成分和少量的负μ子成分. 本文分析了2008—2010年观测站附近发生的62次雷暴期间中子监测器和大气平均电场仪的同步观测资料, 发现27次雷暴期间中子监测器计数率发生明显变化, 显著性S>5σ, 其中13次变化显著, 显著性S>10σ . 显著性S>10σ的13次个例信号变化百分比与地面电场场强幅值之间存在大体一致的变化趋势, 而显著性在5σ <S<10σ之间的14次个例信号变化百分比与地面电场场强幅值之间不存在相似的变化趋势. 较强雷暴当顶时中子监测器计数率变化一般不明显, 而中子监测器计数率变化明显的个例则多发生于雷暴云不当顶, 但探测器仍处于雷暴云下部正电荷层的控制范围之内时, 或者当顶雷暴处于形成或消散阶段. Dorman等把雷暴期间中子监测器计数率的变化归因于雷暴云内电场对宇宙射线次级粒子μ子的作用, 并建立了雷暴期间中子监测器计数率变化与雷暴地面电场相关联的理论. 本文分析发现雷暴期间羊八井中子监测器计数率变化与地面电场场强之间相关性较小或者没有相关性, 不支持Dorman的理论.     

Electromechanical-induced antiferroelectricben ferroelectric phase transition in PbLa(Zr,Sn,Ti)O3 ceramic

Antiferroelectric—ferroelectric (AFE—FE) phase transition in ceramic Pb_0.97La_0.02(Zr_0.75Sn_0.136Ti_0.114)O₃ (PLZST) was studied by dielectric spectroscopy as functions of frequency (10²—10⁵ Hz) and pressure (0—500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were measured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant undergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE—AFE and AFE—FE.     

Three-dimensional phase diagram of a ferroelectric

On the basis of the molecular-dynamic theory, by phenomenologically generalizing the expression for the energy of a ferroelectric, an equation of state is derived here for a ferroelectric in electric field intensity as well as temperature and mechanical stress. The σ(mechanical stress) — T(temperature) phase diagram is analyzed, whereupon ths spinodal, the critical point, and the supercritical line extending into the low-temperature range are plotted. A superposition of this diagram with the E (electric field intensity) — T(temperature) diagram yields a three-dimensional phase diagram in all three state variables. Its elements are the spinodal surface, the critical line, and the supercritical surface bordering on the critical line.     

Thermoelectronic mechanism of quenching the photoluminescence of ZnS — Cl phosphors by an electric field

Results are presented of an investigation of the quenching of the photoluminescence of ZnS — Cl by an electric field as a function of the specimen temperature, the intensity of the exciting radiation, and the electric-field intensity. The experimental data are explained on the basis of a thermoelectronic quenching mechanism.     

Two identical conducting spheres with same potential in a uniform electric field

Interaction, polarization, and charges or electric field distribution of conducting spheres in applied electric field are in many fields including electrorheological fluids, electrophoresis, and electrical engineering. A system with two equipotential conducting spheres in an applied uniform electric field is analyzed by image method. A new method is put forward to calculate the image charges distribution when using image method, which ensures the validity of image method to analyze equipotential cases. An apparatus is constructed to measure the force experimentally as well. Results show that the distribution of electric field and electric interaction are different with the case not equipotential.     

外电场作用下Si_2O分子的激发特性

主要对2种Si2O分子异构体的激发特性进行研究,由计算结果可知,外电场对Si2O分子的激发能,振子强度,跃迁偶极矩及吸收光谱有着显著的影响.无外电场时三角型Si2O(C2v,1A1)分子在可见光区无吸收谱,外电场作用下其在可见光区(407.18—526.93nm)有比较弱的吸收谱.直线型Si-Si-O(C∞v,3Σ-)分子在有无外电场作用时在蓝光和紫光区均有一定的吸收谱,其中比较难得的是在蓝色光区(478.88—488.59nm)呈现较强的吸收谱.     

实现全反射镜功能的光子晶体禁带特性

用传输矩阵法研究一维光子晶体G(AB)mC(AB)mH的能带特性及电场分布,结果发现:随着m的增大,在830—883nm波长范围内,光子晶体G(AB)mC(AB)mH禁带中的导带透射率逐渐趋于零,即光被禁止通过,实现全反射镜功能,且随着入射角的增大,光子晶体的禁带逐渐向短波方向移动。随着介质层G、H的折射率增大,光子晶体在833.6—879.1nm波长范围内出现大的禁带,亦实现全反射镜功能。光子晶体G(AB)5C(AB)5H内部存在很强的局域电场,即在光子晶体内传输的光,被强烈局域在禁带范围内,并在缺陷层C处达到极大值,而且随着m的增大,局域强度增强。这些光学传输特性,为研究、设计新型光学器件全反射镜、滤波器等提供指导。     

In-medium two-nucleon properties in high electric fields

The quantum mechanical two — particle problem is considered in hot dense nuclear matter under the influence of a strong electric field such as the field of the residual nucleus in heavy — ion reactions. A generalized Galitskii-Bethe-Salpeter equation is derived and solved which includes retardation and field effects. Compared with the in-medium properties in the zero-field case, bound states are turned into resonances and the scattering phase shifts are modified. Four effects are observed due to the applied field: (i) A suppression of the Pauli-blocking below nuclear matter densities, (ii) the onset of pairing occurs already at higher temperatures due to the field, (iii) a field dependent finite lifetime of deuterons and (iv) the imaginary part of the quasiparticle self-energy changes its sign for special values of density and temperatures indicating a phase instability. The latter effect may influence the fragmentation processes. The lifetime of deuterons in a strong Coulomb field is given explicitly.