纳米银对表面吸附甲基橙分子的光谱学性质的影响

甲基橙溶液中引入纳米银胶,甲基橙分子的π-π*和n-π*电子跃迁吸收蓝移。随着纳米银胶浓度增加,S2-S0跃迁荧光发射强度不断下降,发射峰红移,而S1-S0跃迁荧光发射强度不断增加。纳米银对pH=2.1的甲基橙溶液的S1-S0跃迁荧光发射强度增强高于pH=6的甲基橙溶液。采用透射电子显微镜、紫外-可见吸收分光光度计和荧光分光光度计等手段从局域场增强、分子间的相互作用和能量传输等方面初步探讨了纳米银胶对表面吸附甲基橙分子光谱学性质影响机制。     

Chaotic Control of Network Traffic

A method of chaotic control on network traffic is presented. By this method, the chaotic network traffic can be controlled to a pre-assigned equilibrium point according to chaotic prediction and the largest Lyapunov exponent of
the traffic on congested link is reduced, thereby the probability of traffic burst and network congestion can be reduced. Numerical examples show that this method is effective.     

MWECR CVD等离子体系统梯度磁场对沉积a-Si:H薄膜特性研究

分别研究了磁场线圈电流为115.2和137.7A以及137.7A并在加热台下加放SmCo永磁体的方法,来改变单磁场线圈分散场MWECR CVD系统等离子体室及沉积室磁场形貌.用洛伦兹拟合定量地得到了三种磁场形貌的磁场梯度.研究了磁场梯度对沉积a-Si:H薄膜性能的影响.研究表明：在衬底附近,高的磁场梯度可以获得高的沉积速率;在温度不很高时,高的磁场梯度可得到光敏性较好的a-Si:H薄膜.关键词：梯度磁场洛伦兹拟合a-Si:H薄膜MWECR CVD系统     

977nm抽运下掺铒碲酸盐基氧卤玻璃的光谱特性

研究了掺铒TeO2-ZnO-PbCl2碲酸盐基氧卤玻璃在977nm激光二极管抽运下的发光和上转换发光特性,结果发现除红外153μm4I13/2→４I15/2发光外（荧光半高宽高达69nm）,该玻璃还存在很强的２Ｈ11/2→４I15/2（527nm）,４Ｓ3/2→４I15/2（549nm）和４Ｆ９／２→４Ｉ１５／２（666nm）可见上转换发光.应用Judd-Ofelt理论计算得到玻璃强度参数Ωt（t=2,4,6）分别为Ω2=587×10-20cm2,Ω4=208×10-20cm2,Ω6=116×10-20cm2,计算了铒离子跃迁振子强度、自发辐射概率、荧光分支比、荧光寿命等光谱参量.应用McCumber理论计算得153μm处的玻璃受激发射截面可达875×10-21cm2实验结果表明,与硅酸盐玻璃、磷酸盐玻璃、氟化物玻璃等比较,掺铒碲酸盐基氧卤玻璃在宽带掺铒光纤放大器和上转换激光器中有着极大的研究和应用潜力.关键词：掺Er3+碲酸盐玻璃氧卤玻璃Judd-Ofelt理论光谱性质     

两步式放电改善反向开关晶体管开通特性研究

针对大功率半导体开关反向开关晶体管(RSD)由于预充不足造成的非均匀开通缺陷, 在直接预充放电工作电路的基础上, 设计了一种两步式放电工作电路. 根据RSD结构特点理论分析了正常开通所需条件, 并对器件元胞结构进行建模分析, 模型仿真结果表明RSD在窄脉宽预充电流作用下具有更佳的开通性能, 降低了预充阶段基区载流子复合. 两步式放电实验发现第一步放电电流幅值、脉宽对于两步式放电电路的正常工作起决定作用, 而反向预充电流主要作用于RSD第一步放电的正常开通, 降低了预充电路设计难度. 仿真及实验结果均表明两步式放电电路较直接式预充放电电路提高了RSD的均匀开通性能, 这是由于两步式放电显著提高了基区等离子体积累.     

Yb3+/Er3+共掺锗碲酸盐玻璃上转换发光增强机理的研究

玻璃的最大声子能量决定稀土离子的上转换发光强度,但本研究发现：Yb³⁺/Er ³⁺共掺锗碲酸盐玻璃在980nm LD抽运下,上转换荧光强度随着Bi₂O ₃对PbO的取代和碱 金属离子半径的增大而明显增强.而Raman光谱显示基质玻璃的最大声子能量并不随Bi ₂O₃对PbO的取代和碱金属离子半径的增大而变化,但玻璃的最大声子密 度随着Bi₂O₃对PbO 取代和碱金属离子半径的增大而降低.从玻璃无辐射跃迁概率的角度,通过分析表明,最大 声子密度的降低是玻璃上转换发光强度增强的主要原因.     

TeO2-ZnO-Na2O-K2O玻璃中Er3+离子掺杂浓度对其发光及荧光寿命的影响

测量了不同掺杂浓度下Er3+离子在碲酸盐玻璃中的吸收光谱、发射光谱和Er3+离子的荧光寿命,计算了Er3+离子的发射截面σe,分析了Er3+离子掺杂浓度对其发光强度和荧光寿命的影响.结果表明,Er3+离子掺杂浓度较低时,对其荧光强度和荧光寿命没有显著的影响;掺杂浓度高时,出现了浓度猝灭效应,使Er3+离子荧光光强度降低,荧光寿命下降.实验确定了掺杂浓度最优值,同时对浓度猝灭机制进行了分析.     

Further Study of A-Related Quantum Interference of H-State Diatomic on Collision-Induced Rotational Energy Transfer

In our previous theoretical studies [Meng-Tao Sun, Yong-Qing Lee, and Feng-Cai Ma, Chem. Phys.Left. 371 （2003） 342], we have reported the quantum interference on collision-induced rotational energy transfer on CO （A ^1 Π,v = 3） with inert gases, which originates from the difference between the two A-related collision potential energy surfaces. The interference angle, which measures the degree of coherence, is presented in this paper. Based on the time-dependent first order Born approximation, taking into account the anisotropic Lennard-Jones interaction potentials, the relation of the interference angle with the factors, including experimental temperature, partner, and rotational quantum number, are obtained. The changing tendencies with them are discussed. This theoretical model is important to understanding and performing this kind of experiment.     

稳定分散的纳米银溶胶的制备及其表征

Stable aqueous dispersive colloidal Ag nanoparticles were prepared by reducing silver nitrate with sodium borohydride in the presence of 3-mercaptopropionic acid. The formation process of the Ag nanoparticles was investigated by UV-Visible spectroscopy and transmission electron microscopy. The results show that the spherical and rodlike particles and aggregates are formed in the initial stage of the reaction, then the rodlike particles and aggregates are gradually decomposed into small spherical particles, and the final obtained Ag nanoparticles with an average size of 8 nm are in uniform shapes and narrow size distribution, and the colloid remains stable for more than one month, which makes it convenient for use in practice. The presence of capping agent plays an extra role over nanoparticles stabilization and morphology. The presence of capping agent on the surface of Ag nanoparticle is confirmed by the X-ray photoelectron spectroscopy. It is found that Ag nanoparticles are negatively charged in alkaline condition, whereas they are positively charged in acid condition. Electrosteric effect is responsible for their long-term stability.