纳米晶Y_2SiO_5∶Eu的浓度猝灭研究

报道了分别用溶胶－凝胶法合成的Ｙ２ＳｉＯ５∶Ｅｕ纳米晶和用高温固相法合成常规尺度的Ｙ２ＳｉＯ５∶Ｅｕ材料的光致发光光谱和猝灭浓度的实验研究．结果表明：纳米Ｙ２－ｘＥｕｘＳｉＯ５比常规尺度的Ｙ２－ｘＥｕｘＳｉＯ５有更高的猝灭浓度和更高的发光亮度．理论分析认为这是由于在纳米材料中能量共振传递被阻断和猝灭中心在各个纳米晶内分布的涨落造成的．这个结果为高亮度的Ｙ２ＳｉＯ５∶Ｅｕ纳米材料的实际开发应用展示了广阔前景．     

化学位移各向导性对半整数自旋四极核的2D NMR章动的影响

考察了化学位移各向异性对半整数自旋四极核2D NMR章动的影响.用数值方法对2D NMR章动实验的演化期的Hamiltonian矩阵进行对角化,然后用帐篷法进行粉末平均,获得了自旋为I=3/2、5/2、7/2和9/2的四极核在不同化学位移各向异性下的2D NMR章动谱.实验结果与理论计算符合较好.     

Effect of entanglement embedded in environment on quantum non-Markovianity based on collision model

By means of collision models(CMs) where the environment is simulated by a collection of ancillas consisting of two entangled qubits, we investigate the effects of entanglement in the environment on the non-Markovianity of an open quantum system. Two CMs are considered in this study, in the first one the open quantum system S directly collides with the environment,while in the second one the system interacts with two intermediate qubits which, in turn, are coupled to the environment. We show that it is possible to enhance the non-Markovianity by environment entanglement in both models. In particular, in the second model, we show that the initial state of the auxiliary qubits can also affect the non-Markovianity of the system and there exists the optimal combination of the initial environmental state and the initial state of auxiliary qubits. In this case, the non-Markovianity can be greatly enhanced.     

关于随机线性算子的G0-半群

首先对几乎处处有界的随机线性算子的Co-半群{B（t）：t≥0）利用L^0-范数的转化技巧给出一个特殊的性质．然后,基于这一性质,对与{B（t）：t≥0}的随机无穷小生成元相关的一些重要的性质进行了研究,并改进了近期文献中一些已知的结果。     

Structural and electrical properties of Au/Pt/Ti ohmic contacts to degenerated doped n-GaAs

The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical measurement showed a minimum ohmic contact resistance of 3×10^-4 Ω cm². The dominant current mechanism was found to be thermionic emission with a barrier height of Φ_b, of 0.09 V by comparing the experimental data with different theoretical models. Received: 14 December 2001 / Accepted: 4 April 2002 / Published online: 22 November 2002 RID="*" ID="*"Corresponding author. Fax: +86-21/6226-4397, E-mail: zhoujian999@163.net     

多峰场负氢离子源磁体布局对等离子体特性影响的数值模拟研究

负氢离子源的研究对于响应国家散裂中子源建设和国际热核聚变实验堆计划的开展都具有十分重要的意义. 由于离子源本身的物理特性导致数值模拟成为不可或缺的研究手段, 基于此, 首先对自主研发的全三维粒子模拟/蒙特卡罗碰撞算法进行阐述, 然后对负氢离子体积过程进行描述, 并在此基础上对中国原子能研究中心的多峰质子源进行了系统仿真, 在引出磁体极性相同和相反两种情形下, 分别对多峰质子源放电特性进行了讨论和分析. 结果显示: 在相反极性下, 两引出磁体附近的磁漂移方向相同且数值较大, 即磁漂移剧烈, 导致电子总数较大且高能电子在特定区域活跃, 进而负氢离子体积产率较高, 即负氢离子在空间呈现Y漂移; 反之, 在相同极性下, 电子约束效果相对较差且负氢离子体积产率较低, 但其空间分布均匀.     

Transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon: a nonresonant case

Under the nonresonant case where the carrier frequency of a Gaussian beam deviates from the resonant frequency of a Fabry–Perot etalon, the transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon has been investigated. The results show that under the nonresonant case, variations of the peak intensity, the position of the peak intensity and the spot size of the transmitted beam with the input angle behave differently and even with a reversed tendency compared with those obtained under the resonant case.     

理论研究F2BN3多聚体的结构特色和热力学稳定性

在密度泛函理论（DFT）B3LYP/6-311+G*水平上计算研究了叠氮二氟硼多聚体(F2BN3)n (n=1-4),获得了它们的结构和热力学性质,讨论了几何参数随聚合度的变化趋势。多聚体(F2BN3)2-4的优化构型均为由不同子体系的叠氮基α−N和B原子相连形成的环状结构。三聚体的船扭式构象比椅式构象的结合能低10.54 kJ•mol-1;四个新获得的四聚体的结合能差异较大,大小为3.1~45.65 kJ•mol-1。由焓变可知,单体形成二聚体在热力学上是不利的,而形成三聚体和四聚体在高达1200 K的温度下是有利的,同时分析比较了后续反应的热力学参数。     

两模腔场谱间的量子干涉

研究了高Q腔中单个二能级原子与两模二项式光场依赖强度耦合相互作用系统的腔场谱,给出了弱初始场条件下的数值结果,讨论了两模光场之间的量子干涉对腔场谱结构的影响. 发现当两模光场的频率差Δ>g（g为原子与腔场间的耦合常数）时,两模光场间的干涉效应对谱结构没有影响,系统的腔肠谱只是两模腔肠谱的简单叠加;当Δ≤g时两模腔场谱间的干涉比较明显. 在强初始场条件下,量子干涉效应可忽略. 关键词： 腔场谱 量子干涉 两模二项式光场     

实验并“快乐”着——让学生在物理实验选修课中感受快乐

高中实行新课程改革的目标就是要对学生实施素质教育,让学生按照自己的爱好特长和将来的发展方向,挑选自己感兴趣的课程,有选择地进行学习.