表面极化声子的喇曼散射研究

本文主要研究表面极化声子的喇曼散射.在探测表面极化声子的衰减全反射方法以及喇曼散射方法的基础上,借鉴了Kretchmann配置的衰减全反射喇曼散射法,提出了Otto配置的衰减全反射喇曼散射法,并以CaF_2单晶体为样品做了一系列实验.同时,本文利用了能量守恒及平行于样品表面的能量守恒关系,利用了格林函数或响应函数所推出的表面极化声子的一般频散关系,理论上给出了CaF_2-空气表面极化声子的一个唯象的频散关系.实验上用特定设计制做的一个样品架对CaF_2样品测定了它与空气界面上的表面极化声子的频散关系,比较结果,理论与实验取得了比较令人满意的一致.     

极薄银膜光学常数的研究

本文利用衰减全反射(ATR)法对磁控溅射和热蒸发制备的极薄Ag膜的光学常数和光学特性进行了研究和比较,得到了光学常数和光吸收随膜厚的变化规律.     

可用于拓宽光波单向传输带宽的光子晶体异质结构界面

基于光波单向传输的全光二极管在集成光通信、全光网络和光信息处理中有重要应用.基于方向带隙失配设计的光子晶体异质结构可实现光波单向传输,但正向透射率较低,带宽较窄.基于对光子晶体异质界面倾斜角度的研究,根据界面全反射条件,利用可集成材料硅和二氧化硅设计了一种空气孔型二维光子晶体异质结构.异质结构界面两侧的光子晶体对1550 nm波长附近的TE模光波在Γ-X方向均呈导带,避免了方向带隙失配.研究发现当异质界面满足全反射条件时,由于光子晶体的自准直效应,较宽波段的正向光波得以高效传播,而反向光波在界面由于全反射而被禁止传播.光子晶体异质结构界面的全反射效应打破了方向带隙对光波单向传输的限制,使得反向光波在光子晶体中为导带时同样可实现近零透射率,从而拓宽了光波单向传输的波长范围.基于全反射界面的光子晶体异质结构经过优化后,其正向透射率达0.64,透射对比度为0.97,单向传输带宽可达553 nm.     

用双介质法测定金属薄膜的厚度和光学常数

用角度扫描衰减全反射方法(ATR),激励金属和两种介质界面处的表面等离子激元波(SPW)通过这些表面等离子激元波和介质折射率的关系同时确定了金属薄膜的厚度和光学常数.实验结果和理论分析相符.     

不同预淀积层银膜表面等离子激元波的辐射效率

测量了棱镜／ＬＢ膜／银膜／空气，棱镜／银膜／空气，棱镜／银膜／空气三种结构在衰减全反射条件下激发的表面等离子激元波由于银膜－空气界面粗糙度而散射以空气中的辐射效率，同时，由散射光强分布计算出表面度粗糙度参数随横向相关长度σ和表面波纹深度δ，再由σ和δ计算出理论辐射效率，理论与实验结果相符合。     

三层不对称人工电磁材料界面处表面等离子体激元的理论研究

从P和S偏振出发.研究了由常规材料/左手材料/负介电常数材料、及常规材料/左手材料/负磁导率材料这两种三层不对称结构界面上表面等离子体激元(Surface plasmon polaritons,SPPs)的存在区域、色散曲线及其激发.观察到表面等离子体激元的性质强烈地依赖于人工电磁材料的组成参量,例如介质板的厚度和等离子体的频率.最后,使用衰减全反射(Attenuated total reflection,ATR)技术,探究了激发和观察表面等离子体激元的可能性.并针对P和s偏振两种情况计算了衰减全反射光谱.     

“全反射”教学案例

1 教学目标 1.1 知识与技能 (1)知道什么是光疏介质和光密介质及相对性; (2)掌握临界角的概念和发生全反射的条件; (3)了解全反射现象的应用; (4)通过实验培养学生的观察能力,概括出发生全反射的条件,即培养学生的观察、概括能力.     

用衰减全反射法研究极薄介质层的光学性质

本文介绍用衰减全反射方法,对银膜及银膜衬底上极薄介质层的衰减全反射谱(ATR谱)进行测量和拟合运算,利用衰减峰位移和增宽确定极薄介质层的光学常数,根据本文的实验条件,可测介质层的薄达5A。     

多元混合气体中非线性声衰减的数值模拟

采用直接模拟蒙特卡罗方法(DSMC)对多元混合气体中的非线性声衰减进行数值模拟,提出了一种不依赖于经验参数的声衰减的理论预测模型.通过DSMC数值模拟方法获得了包括氮气、氧气、二氧化碳、甲烷和水蒸气在内的多种多元混合气体的声衰减谱,研究的声波频率范围从8MHz到232MHz.与弛豫衰减的DL模型和经典衰减的Stokes-Kirchhoff公式的结果比较表明,该模犁的声衰减预测结果与之相符,其预测精度取决于对产生声衰减的分子碰撞过程的正确认识.另外数值模拟结果还表明,不同频率声波的声衰减对包含不同气体成分的混合气体特征不同,这将使得开发能够定量的检测不同环境和过程中的气体成分的智能声气体传感器成为可能.     

电介质膜对受抑全内反射结构中古斯-汉欣位移的增强

受抑全反射结构中,反射光束和透射光束的古斯汉欣(Goos-Hanchen)位移同时存在,对称双棱镜结构的受抑全反射古斯汉欣位移通常只有波长量级,在实验中很难测量。计算了在入射角大于棱镜与空气界面的临界角小于棱镜与薄膜界面临界角时,镀有电介质膜的对称双棱镜的受抑全反射过程中入射光束的反射系数和透射系数的复数表达式。利用稳态相位法计算得出透射光束和全反射光束的古斯汉欣位移。结果表明,反射光束和透射光束古斯汉欣位移量相同,与入射角大小、薄膜厚度以及空气层厚度有关。在入射角小于但接近棱镜与薄膜界面的临界角,薄膜厚度和空气层厚度一定时,古斯汉欣位移量共振增强达到波长的数百倍。     

Temporal effects in the growth of networks

We show that to explain the growth of the citation network by preferential attachment (PA), one has to accept that individual nodes exhibit heterogeneous fitness values that decay with time. While previous PA-based models assumed either heterogeneity or decay in isolation, we propose a simple analytically treatable model that combines these two factors. Depending on the input assumptions, the resulting degree distribution shows an exponential, log-normal or power-law decay, which makes the model an apt candidate for modeling a wide range of real systems.     

Final-state polarization in <Emphasis Type="Italic">B</Emphasis><Stack><Subscript><Emphasis Type="Italic">s</Emphasis></Subscript><Superscript>0</Superscript></Stack> decays

Certain B _s ⁰→V ₁ V ₂ decays (V _i is a vector meson) can be related by flavor SU(3) symmetry to corresponding B _d ⁰→V ₃ V ₄ decays. In this paper, we show that the final-state polarization can be predicted in the B _s ⁰ decay, assuming polarization measurements of the B _d ⁰ decay. This can be done within the scenario of penguin annihilation (PA), which has been suggested as an explanation of the unexpectedly large transverse polarization in B→φ K ^*. PA is used to estimate the breaking of flavor SU(3) symmetry in pairs of decays. Two of these for which PA makes a reasonably precise prediction of the size of SU(3) breaking are (B _s ⁰→φ φ,B _d ⁰→φ K ^0*) and ( ). The polarization measurement in the B _d ⁰ decay can be used to predict the transverse polarization in the B _s ⁰ decay and will allow for testing of PA as well as the other assumptions in the analysis.     

Accelerated and Robust Generation of W State by Parametric Amplification and Inverse Hamiltonian Engineering

A scheme to realize the accelerated and robust generation of W state in a cavity quantum electrodynamics (QED) system by combining parametric amplification (PA) with inverse Hamiltonian engineering (IHE) is proposed. The atom-cavity coupling strength can be exponentially enhanced via parametrically squeezing the cavity mode, which facilitates the generation of W state. Moreover, the evolution of the system can be optimized with suppressing the populations of the intermediate states. Numerical simulations show that the scheme is fast and high-fidelity, immune to systematic parameter deviations, robust against spontaneous emission of atoms, and decay of cavities. Therefore, this scheme may provide some useful applications in entanglement generation.     

Experimental test of the Preisach–Arrhenius model with temperature

The magnetic aftereffect was measured for a magnetic particle tape over a temperature range of 10–380 K. Data were obtained for the saturation magnetization, the coercive field, and the remanent coercive field as a function of temperature. Switching field distributions and other Preisach parameters were also determined as a function of temperature. Based on these data, the Preisach–Arrhenius (PA) model predicts that the decay rate, S, should decrease monotonically as the temperature is reduced. It was found that, for the material studied, S is nearly proportional to temperature, T, for T between about 150 and 380 K, in good agreement with the PA model, but that there is considerable deviation for T<150 K and a temperature range exists over which S increases with decreasing temperature. A modification of the PA model is required to explain this low-temperature behavior is briefly noted.     

Non-equilibrium effects in copper vapor laser pumped Nd3+ doped PVA film: Photo-electon paramagnetic resonance and photoacoustic spectral investigations

Photo-EPR measurements carried out on Nd³⁺ -doped polyvinyl alcohol (PVA) films have shown that nearly 100% reduction occurs in the intensity of EPR of Nd³⁺ under in situ copper vapor laser (CVL) illumination (510.5 nm and 578.2 nm). The kinetics of decay and recovery were investigated. Photoacoustic (PA) spectra, observed under CVL pump condition had shown that the CVL induced changes were not due to photoinduced valence change, and that the CVL pumping creates highly favorable conditions for non-equilibrium population distribution in the excited electronic states. The complete disappearance of EPR under CVL pumping is attributed either to the possible equalization of population of |+〈 and |−〈 Zeeman components, through the decay of many excited states in the presence of magnetic field or configurational changes around Nd³⁺ shifting the resonance frequency. The former appears less probable in view of the relatively slower recovery of EPR signal.     

Thermoplastic Elastomer by Terpolymer Reactive Blending of Polyamide-6, Ethylene-1-Butene Rubber and Ethylene Ionomer

Reactive blending of polyamide-6 (PA6), maleic anhydride grafted ethylene-1-butene copolymer (EB-g-MAH) and ethylene-methacrylic acid ionomer partially neutralized by sodium ions (EMAA-Na) was performed to obtain a heat and oil resistant thermoplastic elastomer (TPE). The strain at break of the PA6/EB-g-MAH (40/60) was clearly higher than that of the PA6/EB (40/60). Addition of 2 wt% of EMAA-Na to the PA6/EB-g-MAH (38/60) blend induced an increase of the tensile modulus. TEM images confirmed that the PA6 was the matrix phase in the PA6/EB-g-MAH (40/60) blend, while the EB rubber phase was the matrix in the PA6/EB (40/60) blend. It was considered that the reaction between amino end groups of PA6 and maleic anhydride in EB-g-MAH induced the significant change of blend morphology. The PA6/EB-g-MAH/EMAA-Na blend showed similar morphology with the PA6/EB-g-MAH blend, and the EMAA-Na was expected to be located within the EB-g-MAH phase. It was found that ionic aggregates were formed in the EB-g-MAH phase by neutralization of the hydrated EB-g-MAH with sodium ions. The change of the mechanical properties by addition of EMAA-Na was due to the ionic aggregate formation which acted as physical crosslinks in the EB-g-MAH phase.     

光敏热显成像材料显影过程含银中间体的合成与表征

光敏热显成像(photothermographic material, 简称PTG)材料是近十多年来国际感光界关注的热点。采用液相沉淀法合成了PTG材料热显成像过程的含银中间体邻苯二甲酸二银(Ag₂PA),并进一步使其与酞嗪(PHZ)络合形成了Ag₂PHZ₂PA·H₂O配合物,通过元素分析、电感耦合等离子体原子发射光谱分析(ICP-AES)对Ag₂PA与Ag₂PHZ₂PA·H₂O配合物的元素组成进行了确定,采用X射线粉末衍射分析(XRD)、傅里叶变换红外光谱分析(FTIR)以及热分析(TG与DSC)等方法对Ag₂PA与Ag₂PHZ₂PA·H₂O进行了表征,实现了对PTG材料热显成像过程含银中间体的定性分析。     

Flowability and Mechanical and Thermal Properties of Nylon 6/Ethylene bis-Stearamide/Carboxylic Silica Composites

Nylon 6 (PA 6)/ethylene bis-stearamide (EBS)/SiO₂- carboxylic acid-functionalized silica nanoparticles (COOH) composites were prepared by in-situ polymerization of caprolactam. SiO₂-COOH was used to enhance the compatibility between SiO₂ and PA 6 matrix. For comparison, pure PA 6 and PA 6/EBS composites were also prepared via the same method. The PA 6/EBS/SiO₂-COOH composites with low content of EBS and SiO₂-COOH had greater melt-flow index (MFI) (the value of MFI increased by 50%–80%) than the pure PA 6. The results of mechanical properties showed almost no decrease in the tensile strength of PA 6/EBS/SiO₂-COOH composites, with the bending strength decreasing by 17%–21%. However, the Izod impact strength of the PA 6/EBS/SiO₂-COOH composites was greatly improved compared with pure PA 6, which indicated that the toughness of PA 6/EBS/SiO₂-COOH had been greatly improved. The morphology of Izod impacted fractured surfaces of PA 6/EBS/SiO₂-COOH was observed by scanning electron microscopy. The results revealed that the PA 6/EBS/SiO₂-COOH composites presented a typical ductile fracture behavior with large amounts of long and large strip-like cracks. When the content of SiO₂-COOH was 0.2 wt%, the SiO₂-COOH particles were uniformly dispersed over the entire body of the PA 6 matrix. The results from differential scanning calorimetry indicated that the melting point (T_m), degree of crystallinity (X_c), and crystallization temperatures (T_c) of PA 6/EBS/SiO₂-COOH composites were lower than the pure PA 6.     

稀土配合物中重叠峰分离的相分辨光声光谱研究

首次利用相分辨光声光谱法对稀土配合物中不同吸收中心的重叠谱峰进行了分离。在Nd(Trp) 3 Cl3 ·H2 O固态配合物中 (Trp :色氨酸 ) ,30 0～ 4 0 0nm这一波段内由于色氨酸配体强的π π 跃迁吸收 ,Nd3 +的光声峰被掩盖。通过光声谱同相和交相信号可以计算配体光声吸收的位相为 10 6° ,位相改变 90°后就得到仅与Nd3 +相关的光声光谱。相分辨光声光谱法用于谱峰分离时有它独特的优点 ,它不受谱峰形状和重叠程度的限制 ,而仅与不同吸收峰对应的光声位相有关     

Morphology and Crystallization in Polystyrene/polyamide 6 Blends: Influence of a Reactive Compatibilizer and Nano-TiO2

A polystyrene (PS)/polyamide 6 (PA6) (70/30, weight ratio) blend in the presence of terminal malic anhydride functionalized PS (FPS) and nano-TiO₂ were prepared using a meltmixing technique. The morphology of the blend was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallization behavior of the PA6 phase in the blend was studied using DSC techniques. The results showed that by adding 7.5 phr nano-TiO₂, the size of the dispersed PA6 domains was dramatically decreased; An additional 1.5 phr FPS to the PS/PA6/TiO₂ blend, for reactive blending, caused the size of the dispersed PA6 domain to become even smaller and more uniform, and a weak, broad crystallization exotherm of PA6 was observed. However, the degree of crystallinity of PA6 in PS/PA6/TiO₂/FPS blend was sharply increased.