Asymmetric Superradiant Scattering Patterns from Bose--Einstein Condensates

The asymmetric patterns of superradiance from Bose-Einstein condensates are studied for the spatially inhomogeneous pump pulse with the semiclassical Maxwell-Schrodinger equations. The coupling dynamics between the optical field and condensate in the strong pulse and a faded wing in the weak coupling regime are discussed, which not only explain the spatial effects in the process of superradiance, but also supply a new method to control its patterns.     

Quantum Fluids of Self-Assembled Chains of Polar Molecules at Finite Temperature

The finite temperature properties of self-assembled dipole chains of polar molecules in strongly confined pancake traps are investigated. The single-chain vibrations at finite temperature, which become important for long chains in a strongly interacting regime, are found to lower the transition temperature and to shift the chain distribution by less than 10%. We also propose experimental parameters to observe such quantum phase transition.     

Characterizing localization properties of two spinless electrons in a one-dimensional Harper model with concurrence

By mapping the Fock space of many local fermionic modes isomorphically onto a many-qubit space and using the measure of concurrence, this paper studies numerically the mode entanglement of two spinless electrons with on-site interaction U moving in the one-dimensional Harper model. Generally speaking, for electrons in extended regimes （potential parameter λ 〈 2）, the spectrum-averaged concurrence N（C） first decreases slowly as A increases until its local minimum, then increases with λ until its peak at λ = 2, while for electrons in localized regimes （λ 〉 2）, N（C） decreases drastically as λ increases. The functions of N（C） versus λ are different for electrons in extended and localized regimes. The maximum of N（C） occurs at the point λ= 2, which is the critical value in the one-dimensional singleparticle Harper model. From these studies it can distinguish extended, localized and critical regimes for the two-particle system. It is also found for the same λ that the interaction U always induce the decreases of concurrence, i.e., the concurrence can reflect the localization effect due to the interaction. All these provide us a new quantity to understand the localization properties of eigenstates of two interacting particles.     

电场诱导空穴注入缓冲层PEDOT∶PSS取向对OLED发光性能的影响

实验中以PEDOT∶PSS在ITO基片上旋涂作为空穴传输层,并且在旋涂PEDOT∶PSS的过程中在与ITO玻璃平面垂直的方向施加一个诱导聚合物取向的高压电场,试验着重研究了所加电场强度对双层器件:ITO/PEDOT∶PSS/MEH-PPV/Al器件性能的影响。测试结果表明,旋涂时所加电场的大小对器件的发光强度和起亮电压都有明显的影响。随着所加电场的增大,器件发光强度明显增加,起亮电压减小。由此表明:在高电场作用下,聚合物分子链沿电场方向发生了取向,而且随着电场增强这种取向作用会表现得越明显,并且在PEDOT∶PSS膜表层会形成一个梯度变化的PSS聚集,使得从ITO到MEH-PPV的功函数逐渐上升,降低空穴注入势垒,增强了空穴的注入效率。     

CdS/PAMAM与氨基酸作用研究及其在潜在指印显现中的应用

提出了以硫化镉/聚酰胺-胺树形分子(CdS/PAMAM)纳米复合材料显现潜在指印的新方法。傅里叶变换光谱研究了PAMAM G4.5外部酯端基与氨基酸中胺基之间的胺解反应,选用相对峰高比H_{1 267/1 735}来监测不同条件下的反应进程,并发现温度对于胺解反应的影响很大,90 ℃时胺解反应可在4h内显著进行,120 ℃时胺解反应速率在3 h后发生递减。将CdS/PAMAM作为指印显现试剂,在同等条件下与现有常规指印显现液对比,发现前者的荧光强度约为后者的65倍,荧光性能优势明显。确定使用加热压显法显现不同客体表面潜在指印的条件为120 ℃下反应0.5～3 h。使用优化后的条件对多种载体表面潜在指印进行显现,可以获得理想的显现效果。该显现方法具有简便、快速、灵敏、安全、经济等特点。     

LIPS技术探测CH4/空气火焰中的OH自由基

论述了激光诱导偏振光谱技术的基本原理,实验方法及其对燃烧场的测量结果.利用光谱扫描方法获得了A2∑ -X2Ⅱ(0,0)跃迁带系列吸收谱线及P1(2)谱线的线型轮廓.测量了CH4/空气预混火焰不同化学配比、不同空间位置OH自由基的相对分布.实验中通过设计精密旋转调节装置有效提高了信噪比.     

密度泛函理论计算内掺氢分子富勒烯H2@C60及其二聚体的几何结构和电子结构

采用密度泛函理论中的广义梯度近似(generalized gradient approximation, 简称GGA),对内掺氢分子富勒烯H2@C60及其二聚体的几何结构和电子结构进行了计算研究.发现无论是在H2@C60单体,还是在其二聚体中,氢倾向以分子形式存在于碳笼中心处,且在室温下氢分子可以做自由旋转.电子结构分析表明,氢分子掺入到C60和C120中,仅对距离费米能级以下-8eV至-5eV能级处有一定的贡献,其他能级的分布和能隙几乎没有变化.     

具有前置公用工程的换热器网络的通用解法

本文在罗行等人提出的分级超结构换热器网络的通用解的基础上,提出一种将热冷公用工程放置于换热器网络每一级的冷热流体之前的带分流的分级超结构换热器网络数学模型,并根据这种新型的模型推导出换热器网络的出口温度和每一级流股节点的温度的计算公式,从而增强了分级超结构换热器网络模型的适用性.最后用实例证明所提出的数学模型的正确性.     

快离子导体AgxTiS2中Ag+离子-空位的二维基态结构与能量性质研究

根据Ag 离子-空位的二维有序结构建立了三维晶胞模型.采用局域密度近似下的平面波赝势方法,对有序Agx Tis2(x=0,1/4,1/3,1/2,2/3,3/4,1)系列进行了几何结构优化和总能量计算,并与Lix Tis2系列进行了对比研究.有序Agx Tis2系统的晶格参量增量△a0 和△c0随离子浓度单调增加,与实验结果符合得较好.有序Agx TiS2和Lix Tis2系统的总能量均随插层离子浓度增加线性下降,且前者下降较快.有序Agx TiS2(x=0,1/4,1/3,1/2,2/3,3/4,1)系统的形成能均小于零,表明其基态性质.具有3a0x3a0超结构的Ag1/3 Tis2系统的形成能最低.能量性质的对比显示,有序Agx TiS2系统的形成能较低,有序一无序相变温度较高,离子扩散活化能较高.根据计算结果对有关实验给出了合理解释.     

Enhanced Quantum Reflection of Ultracold Atoms with Strong Interatomic Interaction

We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result.