Photoionization of a charged exciton in a GaAs/GaAlAs corrugated quantum well

Binding energies of a charged exciton as a function of well width of a GaAs/GaAlAs corrugated quantum well are investigated. The calculations have been performed by the variational method based on a two parametric trial wave function within a single band effective mass approximation. We have also included the effect of nonparabolicity of the conduction band of GaAs. We study the spectral dependence of the charged exciton in a GaAs/GaAlAs corrugated quantum well as a function of well width. The photoionization cross section for the charged exciton placed at the center of the quantum well is computed as a function of normalized photon energy. The cross-section behavior as a function of incident energy is entirely different in the two cases of radiation being x-direction (along the growth direction) or z-direction. The interband emission energy as a function of well width is calculated and the dependence of the photoionization cross section on photon energy is carried out for the charged excitons. The resulting spectra are brought out for light polarized along and perpendicular to the growth direction. The results show that the charged exciton binding energy, interband emission energy and the photoionization cross section depend strongly on the well width. Our results are compared with the other existing literature available.     

Electron–phonon effect on the ground-state binding energy of hydrogenic impurity in quantum-well wire in presence of an electric field

The hydrogenic impurity binding energy in rectangular quantum well wire including both barriers of finite height and an applied electric field are studied. The polaron effects on the ground-state binding energy in electric field are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied electric field and the position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions.     

井中动电信号的实验测量与分析*

动电效应测井是一种具有潜在应用价值的油气勘探方法。本文针对小尺寸的砂岩模型井,在实验室内建立了动电测井的实验探头和实验测量系统,进行了声波测井和动电测井的实验测量研究工作。记录了单极源在井中激发的声波信号以及声波传播时诱导的动电转换信号,分析了井中动电信号的传播特性。此外,在实验模型的基础上进行了声波/动电测井的数值模拟研究,并将模拟结果和实验测量结果进行了对比,两者吻合很好。本文研究验证了动电测井理论模拟和实验测量结果的正确性,以及动电测井方法的可行性。     

Quantum chromodynamics results from HERA and JLAB

Recent QCD results from electron?Cproton interactions at HERA and JLAB are presented. Inclusive cross-section measurements as well as studies of the hadronic final state like jet production or the production of heavy quarks are discussed. The results are compared with perturbative QCD predictions and their impact on the determination of the parton density functions of the proton as well as of the strong coupling ?? _s is discussed.     

Confined-acoustic-phonon-assisted cyclotron resonance via multi-photon absorption process in GaAs quantum well structure

Phonon-assisted cyclotron resonance (PACR) in GaAs quantum well (QW) structure is investigated via multi-photon absorption process when electrons interact with the confined acoustic phonon through deformation potential. The additional peaks in the absorption spectrum due to transitions between Landau levels accompanied with the emission and absorption of phonons are indicated. The dependence of absorption power on the temperature, magnetic field and well width is presented. Using profile method, we obtain PACR-linewidth as profiles of the curves. The temperature, magnetic field and well width dependences of the PACR-linewidth are investigated. The results are compared with those in the case of mono-photon absorption process, as well as in the electron-bulk acoustic phonon interaction. The results show that the multi-photon absorption process is strong enough to be detected in PACR.     

The role of acoustic phonons for Rabi oscillations in semiconductor quantum dots

The damping of Rabi oscillations in quantum dots as well as the renormalization of the carrier-light coupling, due to the interaction with longitudinal acoustic phonons are studied as a function of temperature and laser pulse parameters. Numerical results are obtained by using a correlation expansion within the density matrix theory. The observed features like a non-monotonous dependence of the damping on the pulse duration are characteristic for the strongly non-Markovian nature of the phonon coupling in these systems. The results can be well interpreted on the level of a perturbation expansion in the carrier-phonon interaction. PACS 78.67.Hc; 63.20.Kr; 03.65.Yz     

套管井超声导波成像系统开发与工程应用研究

针对现有套管井检测与评价技术存在的缺陷,开展了进一步的导波成像方法与技术开发研究。对套管壁A0导波模式频散与泄漏衰减特性,以及泄漏衰减特性与管外粘结材料特性阻抗的关系进行了分析。在此基础上进行了不同粘结载荷钢板模型A0模泄漏衰减等特性以及脉冲回波厚度共振波特性的实验测试。结果显示,结合A0模式的衰减与管外粘结材料特性阻抗的测试结果,可有效定征管外粘结材料特性,进一步确定和成像管外环形空间水力联通特性。以此为基础,开发了耐温和耐压宽带超声换能器,以及检测与成像系统。通过模型井和实际井的测试,获得良好效果。     

Modeling hot, dense hydrogen with a classical spin dependent hamiltonian

Hot, dense hydrogen is studied with a classical model in which the interaction energy between atoms depends on their internal spins as well as their separation distance. The spins are treated as classical variables. This model is used in Monte Carlo simulations to calculate internal energies, pressures, and pair correlation functions, as well as the Hugoniot for shocked liquid deuterium. The results clearly show the transition of hot, dense hydrogen from a molecular to an atomic fluid. Our results are in reasonable agreement with far more elaborate quantum mechanical simulations.     

原子-腔-光纤复合系统中的纠缠特性

采用Negativity熵来描述两子系统间的纠缠,研究了由两个二能级原子与光纤联接的单模腔构成的系统的纠缠特性.利用数值计算方法讨论了原子与腔场的耦合强度和原子选择性测量对纠缠特性的影响.研究结果表明:对一个原子的选择性测量,可增强原子间与腔场间和腔场与腔场间的纠缠.     

Assessing the effect of the matrix in resonant infrared MAPLE

The ablation yield of polyethylene glycol is measured as a function of laser pulse energy and polymer molecular weight for both free running and Q-switched Er:YAG lasers. The results show that the deposition rate is dependent on the absorption coefficient in a way that is consistent with the blow-off ablation model but that the linear dependence of the efficiency on laser pulse energy is also consistent with a steady-state ablation model. The results for both lasers are remarkably similar given that the pulse durations are 350 μs and 85 ns, respectively. Furthermore, polystyrene thin films are deposited as well and it is found that the morphology depends on the THF/MeOH ratios in the matrices. The significance of these results is discussed as well as future directions for this research.     

TiO2电子结构与其双折射性、各向异性 关联的理论研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法对锐钛矿相TiO₂的晶体结构、能带结构、态密度等电子结构进行了理论分析, 在此基础上对介电函数、能量损失函数、光电导率等光学性质进行系统的理论计算, 分析了TiO₂双折射现象、各向异性与电子结构之间的关联, 其结果与文献报道的相关实验结果相符合, 从理论上探讨了TiO₂电子结构和其双折射现象、各向异性的特征.     

Domain wall dynamics in ferromagnets

The main results of studying the linear and nonlinear dynamics of a domain wall in ferromagnets are presented beginning with the first publications. The experimental data obtained on polycrystals, single crystals, and films differing in terms of their anisotropy, as well as on magnetic nanostructures, are compared with theoretical results obtained by various methods.     

原子-腔-光纤复合系统中的纠缠特性

采用Negativity熵来描述两子系统间的纠缠,研究了由两个二能级原子与光纤联接的单模腔构成的系统的纠缠特性.利用数值计算方法讨论了原子与腔场的耦合强度和原子选择性测量对纠缠特性的影响.研究结果表明:对一个原子的选择性测量,可增强原子间与腔场间和腔场与腔场间的纠缠.     

Some characteristics of high multiplicity (≧45) proton-AgBr interactions at 800 GeV

Experimental results on some characteristics of high multiplicity (≧45) proton-AgBr interactions at 800 GeV are presented. The results are compared with those in lower multiplicity regions as well as for CNO target. The various parameters investigated here are pseudorapidity distribution, mean normalised multiplicity, mean number of intranuclear collisions and normalised pseudorapidity.     

External electric field and hydrostatic pressure effects on the binding energy and self-polarization of an off-center hydrogenic impurity confined in a GaAs/AlGaAs square quantum well wire

Based on the effective-mass approximation within a variational scheme, binding energy and self-polarization of hydrogenic impurity confined in a finite confining potential square quantum well wire, under the action of external electric field and hydrostatic pressure, are investigated. The binding energy and self-polarization are computed as functions of the well width, impurity position, electric field, and hydrostatic pressure. Our results show that the external electric field and hydrostatic pressure as well as the well width and impurity position have a great influence on the binding energy and self-polarization.     

神光Ⅲ原型上扩展X射线吸收精细结构谱实验研究

介绍了在大型激光装置上进行扩展X射线吸收精细结构(EXAFS)谱压缩物态参数测量的基本原理,以及为获得高质量EXAFS谱在神光Ⅲ原型装置上进行的实验研究。实验采用玻璃靶球、CH靶丸和金球作为EXAFS谱测量的背光源,通过多发次叠加、光子数累积的方法获得了信噪比良好的金属Ti在常温常压下的EXAFS谱,数据处理结果表明,实验测得的金属Ti EXAFS谱拟合结果与同步辐射实验拟合结果相吻合,表明实验设计的正确性与可靠性。对实验结果的分析表明,影响EXAFS谱质量的因素主要是光子计数、测量系统谱分辨率、噪声以及实验器件上的瑕疵。     

Effects of hydrostatic pressure on intrawell and interwell excitons in a strained GaAs/GaAlAs double quantum well system

Binding energies of intrawell and interwell excitons are investigated in a GaAs/GaAlAs double quantum well system in the presence of hydrostatic pressure applied in the z-direction. Calculations have been carried out with the variational technique within the single band effective mass approximations using a two parametric trial wave function. The interband emission energy as a function of well width is calculated in the influence of pressure. The pressure dependent photoionization cross section for a charged exciton placed at the center of the quantum well is computed as a function of normalized photon energy. The dependence of the photoionization cross section on photon energy is carried out for the charged excitons. The resulting spectra are brought out for light polarized along and perpendicular to the growth direction. The results show that the charged exciton binding energy, interband emission energy and the photoionization cross section depend strongly on the well width and the hydrostatic pressure. Our results are compared with the other existing literature available.     

MONTE CARLO STUDIES OF RADIATION DAMAGE INDUCED BY FUSION DYNAMIC SIMULATION OF SPUTTERING

In this paper, the sputtering caused by fusion of ⁴He particles in the first wall materials is investigated by using the dynamic Monte Carlo simulation, which is based on the binary collision approximation. The dependences of sputtering yields on the incident energy and angle, as well as the comparisons of results calculated using the Monte Carlo methed with results from experiments, are discussed. Energy spectrum and angular distributions of sputtered species, the depth of origin of the sputtered particles as well as range distributions of incident ions are given. From a comparison between the related experimental data and the calculated results with static and dynamic simulation it has been found that a better agreement is obtained for dynamic simulation.     

Laser field induced interband absorption in a strained GaAs/GaAlAs double quantum well system

Effect of laser field intensity on exciton binding energies is investigated in a GaAs/ GaAlAs double quantum well system. Calculations have been carried out with the variational technique within the single band effective mass approximations using a two parametric trial wave function. The interband emission energy as a function of well width is calculated in the influence of laser field. The laser field induced photoionization cross-section for the exciton placed at the centre of the quantum well is computed as a function of normalized photon energy. The dependence of the photoionization cross-section on photon energy is carried out for the excitons. The resulting spectra are brought out for light polarized along and perpendicular to the growth direction. The intense laser field dependence of interband absorption coefficient is investigated. The results show that the exciton binding energy, interband emission energy, the photoionization cross-section and the interband absorption coefficient depend strongly on the well width and the laser field intensity. Our results are compared with the other existing literature available.     

神光III原型上扩展X射线吸收精细结构谱实验研究

介绍了在大型激光装置上进行 扩展X射线吸收精细结构(EXAFS)谱压缩物态参数测量的基本原理,以及为获得高质量EXAFS谱在神光III原型装置上进行的实验研究。实验采用玻璃靶球、CH靶丸和金球作为EXAFS谱测量的背光源,通过多发次叠加、光子数累积的方法获得了信噪比良好的金属Ti在常温常压下的EXAFS谱,数据处理结果表明,实验测得的金属Ti EXAFS谱拟合结果与同步辐射实验拟合结果相吻合,表明实验设计的正确性与可靠性。对实验结果的分析表明,影响EXAFS谱质量的因素主要是光子计数、测量系统谱分辨率、噪声以及实验器件上的瑕疵。