外加磁场下抛物型量子线中的带电激子

在一维等效模型下采用有效差分法对抛物型量子阱线中带电激子的束缚能进行了计算,分析了约束势以及磁场对带电激子束缚能的影响,并对带正电激子(X⁺)和带负电激子(X^-)的情况进行了比较.结果表明:电子和空穴的振子强度对带电激子的稳定性有重要影响,X⁺的束缚能不总是比X^-的大,随着空穴振子强度的增加束缚能的函数曲线将会出现交叉,这同实验得到的结果符合;磁场的存在会增加粒子间的束缚,并且磁场对束缚能的影响同振子强度大小有关. 关键词： 带电激子 量子线 束缚能 磁场     

谱导数法在光谱研究GaInAs/InP和GaInP/AlGaInP多量子阱中的应用

在简要讨论谱导数法物理机理的基础上, 给出了其在光吸收谱和光反射谱方法研究张应变GaInAs/InP和GaInP/AlGaInP多量子阱中的成功应用实例. 比较了不同阶谱导数对测定激子跃 迁能量的影响，论及了其与双调制谱方法、曲线拟合方法的区别. 指出了谱导数法在光谱研 究GaInAs/InP和GaInP/AlGaInP多量子阱中的重要性和易行性. 关键词： 谱导数法 吸收谱 反射谱 多量子阱 激子     

变藻蓝蛋白发色团之间激子相互作用

本文尝试性地建立了APC(αβ)₃内内层部分具有C₃群对称特性的三个β发色团之间的“三聚体”激子相互作用的模型,依据“三聚体”激子相互作用的光谱表征,通过对APC(αβ)₃的吸收光谱和CD谱的解叠,分析和计算得到APC(αβ)₃内β发色团之间的距离,以及在坐标中的相对位置,估算了激发能在三个激子态之间的去局域时间.     

一维反铁磁体二水CsMnCl3中激子的振动猝灭和黄昆-Rhys因子

在一维反铁磁体CsMnCl₃·2H₂O中,用D₂O代替其中的结晶水之后,对于⁴T₁→⁶A₁激子跃迁,观察到三种明显的效应:激子线红移18cm^-1;激子讯号增强近一个数量级;激子寿命由0.58ms变为9.2ms,增加15倍。这后一种效应在文献中尚未见报道,它说明这种同位素替代使振动猝灭受到很大的减弱。利用多声子辐射和无辐射跃迁理论,讨 关键词：     

电子关联对C60激子极化子的影响

本文采用扩展的Ｈｕｂｂａｒｄ模型，在电子－晶格耦合的紧束缚近似下，研究了光激发下的Ｃ₆₀，分子的激子态和极化子态。我们发现，电子关联效应相当敏感地影响到单态和三态激子的束缚能。同时，Ｃ₆₀分子动力学晶格弛豫使激子极化子得以形成。光激发下的Ｃ₆₀分子，在电子相互作用Ｕ～５．０ｅＶ，Ｖ～２．０ｅＶ时，能够定性地解释荧光发射谱。 关键词：     

圆柱状量子点量子导线复合系统的激子能量和电子概率分布

建立了圆柱状量子点量子导线复合系统中激子满足的方程，用微扰论求出激子能量.以CdS/HgS/CdS/HgS/CdS圆柱状量子点量子导线复合系统为例，研究了系统中电子的概率分布和系统线度对激子能量的影响.结果表明：系统中电子、空穴以及激子的能量均随量子点高度h₀的增大而减小，电子-空穴相互作用对基态激子能量的影响要大于激发态；电子沿径向方向的概率分布呈起伏状，在轴线和表面附近的概率趋于零，而在R/2附近概率最大；在量子点附近电子沿轴向方向的概率分布呈振荡特征 关键词： 量子点 量子导线 激子 能量     

VN分子R线系跃迁结构的研究与分析

本文借助孙卫国课题组建立的能精确计算双原子分子R线系发射谱线的物理公式,利用实验上获得的低振动态跃迁谱线数据研究了电极材料VN分子电子态f¹Φ–a¹Δ以及电子态d¹∑⁺–X³Δ₁等跃迁体系的（0,0）跃迁带的R线系发射谱线. 从理论上预言了实验上难以获得的该跃迁带R线系高振转激发态的跃迁结构,为急需VN分子内部结构的其他研究领域提供了重要的结构信息. 从这些公式出发,我们定义了表征实验测定谱线对新谱线的贡献度C（contribution）参数,进一步分析了高激发振转跃迁谱线的相互依赖关系,结果表明该物理公式不仅很好地复现了已知的实验数据,正确地预言了实验未能测定的高激发振转跃迁谱线,而且还能了解不同实验谱线对新谱线的贡献程度,基于这些贡献度,实验学家可以将有限的资源更好地进行分配,重点研究那些贡献度大的振转跃迁谱线. 关键词： 双原子分子 跃迁谱线 贡献度 VN     

电子与束缚激子的非弹性碰撞

在高激光密度J下,在ZnO上发现一条发光谱线,很可能对应于Hvam所报导的M线。这条线位于束缚激子线的低能边,它的特征是其极大有一个能量位移～J~(2/3),随着激发强度的增加谱线的形状从极不对称变成较为对称,同时谱线强度也按J~(1.8-1.6)而增加。与Hvam的结果相反,这条发光线原来是具有非本征性质的。我们提出了电子与束缚激子的非弹性碰撞作为一种可能的复合机理。对于这一过程,计算了     

掺AlZnO纳米线阵列的光致发光特性研究

采用化学气相沉积方法，以金做催化剂，在Si (100)衬底上制备了掺AlZnO纳米线阵列.扫描电子显微镜(SEM)表征发现ZnO纳米线的直径在30nm左右.X射线衍射(XRD)图谱上只存在ZnO的(002)衍射峰，说明ZnO纳米线沿c轴择优取向.掺AlZnO纳米线阵列的室温光致发光(PL)谱中出现了3个带边激子发射峰：373nm，375nm，389nm.运用激子理论推算出掺AlZnO纳米线的禁带宽度为3.343eV ，束缚激子结合能为0.156eV；纯ZnO纳米线阵列PL谱中3个带边激子发射 关键词： 光致发光 化学气相沉积(CVD) 激子 ZnO纳米线阵列     

CdSe/CdMnSe多量子阱的激子光学性质的研究

用分子束外延在GaAs衬底上生长了CdSe/CdMnSe多量子阱结构.利用X射线衍射(XRD)、变密度激发的PL光谱、变温度PL光谱和变密度激发的ps时间分辨光谱研究了CdSe/CdMnSe多量子阱结构和激子复合特性.讨论了随温度升高辐射线宽展宽和辐射复合效率降低的机理.发现不同激发密度下发光衰减时间不同,认为它的机理可能是无辐射复合引起的.在该材料中观测到激子激子散射发射峰,它被变密度激发和变温度PL光谱所证实. 关键词： CdSe/CdMnSe 量子阱 光学性质     

Frankel激子的有效质量与温度的关系

本文计及离子晶格的原子结构,用紧束缚方法导出了Frankel激子的有效质量与温度的关系。 关键词：     

光泵浦ZnCdSe／ZnSe单量子阱蓝绿受激发射的研究

报道了常压金属有机化学汽相淀积（ＭＯＣＶＤ）制备的Ｚｎ０．７Ｃｄ０．３Ｓｅ／ＺｎＳｅ单量子阱的光泵浦受激发射性质。在７７Ｋ下观测到了ｎ＝２的重空穴激子发光峰和ｎ＝１的重空穴激子吸收峰。在７７Ｋ脉冲激光泵浦下受激发射阈值功率密度为１１６ｋｗ／ｃｍ２。认为受激发射机理可能是激子局域态的空间填充。     

晶格振动对激子运动的影响

在本文中用Haga研究极化子时提出的微扰法讨论晶格振动对激子运动的影响。把作者过去的工作推广到电子和空穴质量不相等的普遍情形。在忽略反冲效应中不同波矢的声子之间的相互作用时,导出了激子的基态能量、有效质量、约化质量和内部势能。指出:激子的有效质量和电子、空穴与声子的相互作用有关;激子的约化质量不仅和电子、空穴与声子的相互作用有关,而且还和电子空穴质量比有关;激子形成自陷态的条件并非由电子、空穴与声子相互作用的大小,而是由电子、空穴质量比决定。形成激子自陷的条件是电子、空穴质量比0.261<μ_e/μ_h<3.83。在μ_e/μ_h<0.261或μ_e/μ_h>3.83的情形,激子极化晶体中并不形成自陷态。 关键词：     

Magnetic susceptibility and nuclear magnetic resonance of vanadium sulfides

Measurements of the magnetic susceptibility in the temperature range 4–1000°K are reported for the vanadium sulfides VS, V₃S₄-V₂S₃ and V₅S₈. At higher temperatures the susceptibility of all compounds approaches a constant, positive value, indicating a Pauli-paramagnetic contribution of itinerant electrons. At lower temperatures an increase of the susceptibility is observed. This effect is particularly pronounced in V₅S₈, and is taken as evidence for the presence of localized magnetic moments.Nuclear magnetic resonance spectra of V₅S₈ show two lines, one with a temperature-independent Knight shift, and one with a positive Knight shift which increases strongly at lower temperatures. The two lines are attributed to vanadium atoms with itinerant d electrons, and to vanadium atoms with localized d electrons, respectively. This interpretation is consistent with the magnetic susceptibility data. The difference in properties between two types of vanadium atoms in V₅S₈ can be understood by considering the crystal structure.     

Kohn anomalies in momentum dependence of magnetic susceptibility of some three-dimensional systems

We study a question of the presence of Kohn points, yielding at low temperatures nonanalytic momentum dependence of magnetic susceptibility near its maximum, in electronic spectra of some threedimensional systems. In particular, we consider a one-band model on face-centered cubic lattice with hopping between the nearest and next-nearest neighbors, which models some aspects of the dispersion of ZrZn₂, and the two-band model on body-centered cubic lattice, modeling the dispersion of chromium. For the former model, it is shown that Kohn points yielding maxima of susceptibility exist in a certain (sufficiently wide) region of electronic concentrations; the dependence of the wave vectors, corresponding to the maxima, on the chemical potential is investigated. For the two-band model, we show the existence of the lines of Kohn points, yielding maximum susceptibility, whose position agrees with the results of band structure calculations and experimental data on the wave vector of antiferromagnetism of chromium.     

Effects of applied magnetic field on the infrared transitions between hydrogenic states in a corrugated quantum well

The magnetic field induced transition energies between the ground and excited states of a donor impurity in a Ga_1-xAl_xAs /Ga_1-yAl_yAs corrugated quantum well is reported. The calculations are performed by the variational method based on a two-parametric trial wave function, in the framework of the single band effective mass approximation. The effect of nonparabolicity of the conduction band is considered through the energy dependent effective mass. The effect of magnetic field on the spin-orbit interaction on the electron magnetization and the magnetic susceptibility is discussed. The diamagnetic susceptibility using Hellmann-Feynman theorem is calculated for the ground and excited states of the donor. The transition lines lie in the optical range for a strong magnetic field. The results are compared with the other existing available literature.     

EuPtP: a new mixed valent europium-system

The europium valency in hexagonal EuPtP, as examined byL _III-x-ray absorption and Moessbauer experiments, is a function of temperature and changes from 2.16 at 295 K to 2.40 at 4 K. In the region of the strongest temperature dependence of the valency, the compound undergoes two first order phase transitions atT ₁=235 K andT ₂=190 K, characterized by discontinuities in the lattice constants and in the magnetic susceptibility. In the europium Moessbauer spectra, several temperature dependent absorption lines were found, indicating a complex europium valency behaviour. Furthermore, we observe antiferromagnetic order at 8.6 K.Supported by Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 125Supported by Deutsche Forschungsgemeinschaft     

Shock wave working of high-TC superconductors

Abstract

The results of investigating the processes of explosive compaction of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O powdered ceramic high temperature superconducting materials and the shock-induced variation of their properties are presented. The possibility for obtaining metal-ceramic cylinder and spiral-shaped articles is illustrated. The shock wave loading of sintered ceramics is shown to result in degrading its superconducting properties up on R(T), which are subsequently restored by low-temperature annealing. The loss of superconducting properties is demonstrated to correlate with the X-ray lines width. In case of Bi-4334 ceramic, we have observed the improving SP-properties on susceptibility just after shocking it. The effect of the compaction pressure, initial particle size, atmosphere (air, O₂, N₂), initial temperature on material properties is studied.     

Magnetic properties of TCNQ complex salts with polycations containing sulfur atoms in the main chain

The magnetic properties of TCNQ anion salts with polycations containing sulfur atoms in the main chain were investigated using ESR and magnetostatic methods. For the majority of these complex salts asymmetric ESR lines were recorded and characterized by g_⊥, g_∥, and ΔH_max values as well as by an asymmetry parameter δ′. An analysis of symmetrical ESR lines was carried out by the linear anamorphose technique. The temperature dependence of magnetic susceptibility χ_p was studied for the K_s [x, y] complex salts obtained. A correlation was found between the magnetic properties (ΔH_max, δ′, and χ_p) and the electrical properties ([sgrave]₂₅, E_a) studied in our previous works.     

Neutron diffraction and magnetic measurements of polycrystalline NH4MnCl3

Neutron diffraction and magnetic susceptibility measurements show NH₄MnCl₃ to be an antiferromagnet of type G with T_N ∼ 105°K. The low temperature patterns reveal a tetragonal splitting and superlattice lines which were accounted for by assuming the space group to be P bnm.