溶胶CdS毫微晶的双光子吸收及其量子尺寸效应

本文利用单光束透过率法研究了溶胶CdS毫微晶的双光子吸收。对于毫微晶尺寸为5.5～11.0nm的样品,测得其在波长510.6nm时的双光子吸收系数为1.31～5.24/GW,并由此得到相应的x~(3)为2.8×10~(-12)～1.1×10~(-11)esu。文中还从理论上分析了CdS溶胶的双光子吸收与毫微晶尺寸的关系,理论计算与实验结果基本符合。     

纳米尺寸CdS半导体微晶的光致发光线宽宽化研究

测量了各种温度下玻璃中掺杂纳米尺寸CdS半导体微晶的光致发光光谱,研究了其光致发光带的峰值能量和线宽对温度的依赖关系.考虑CdS微晶的LO声子的相互作用,拟合了其带隙发光带的线宽随温度的变化曲线,获得样品的非均匀线宽.CdS微晶的非均匀线宽主要是由于微晶的尺寸分布引起的.     

纳米CdS-磺化聚苯胺（SPAn）多层复合膜的光学特性研究

研究了利用层-层自组织生长法制备的磺化聚苯胺-CdS纳米晶体复合膜的光学特性.研究发现，随样品中CdS 纳米晶体尺寸的减小，量子尺寸效应明显增强；在紫外吸收谱中表现为吸收边出现了明显蓝移；在光致发光谱中，不仅激子直接复合产生的带边发射产生了蓝移，而且陷阱态复合产生的宽带发射也发生了蓝移.还发现样品经低温退火处理后，激子复合产生的带边发射显著增强，发射带宽随纳米尺寸的减小而变窄.这说明退火后CdS 纳米晶粒的有序性和均匀度显著增加. 关键词： CdS 纳米晶体 SPAn 吸收 发光     

低强度飞秒激光激发下CdTe和CdTe/CdS核壳量子点的荧光上转换研究

利用400 nm和800 nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800 nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400 nm激发下的荧光峰相比蓝移最多达15 nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdT 关键词： CdTe量子点 CdTe/CdS核壳量子点 时间分辨荧光 上转换荧光     

CdS纳米带和纳米锯的热蒸发法的合成和光学性质研究

利用氢气辅助的一步热蒸发法,在镀有金膜的硅片上制备出大量的CdS纳米结构. CdS纳米结构由纤锌矿结构的CdS纳米带和纳米锯组成. 研究表明沉积温度对CdS纳米结构的形貌和尺寸具有重要影响. 用气-液-固和气-固复合生长机理解释了CdS纳米结构的形成过程.光致发光测试表明CdS纳米带和纳米锯均发射出波长为512 nm的很强的绿色发光峰,对应于CdS的带-带跃迁. 同时对CdS纳米结构的光波导性质也进行了观察和讨论.     

玻璃中CdSeS纳米晶体的室温光致发光谱

对掺有过饱和的镉、硒和少量硫的玻璃在500～800℃分别退火4h,生长了不同尺寸的CdSe_1-xS_x纳米晶体。测量了纳米晶体的室温吸收光谱和光致发光(PL)光谱,550℃生长的样品在300～800nm的范围没有观察到吸收和发光峰,表明温度低于550℃玻璃中不能形成纳米晶体。生长温度在600～650℃,纳米晶体的PL光谱主要为两个宽的发光带,即带边激子发光带和通过表面态复合的发光带。随着生长温度的升高,带边复合发光的蓝移减小,通过表面态的发光逐渐消失,并出现了叠加于宽发光带上的一系列明显的弱发射峰。不同温度生长的样品中,叠加峰的能量相同。同一样品中叠加峰的能量不随激发光波长的变化而变化。     

CdS,ZnS毫微晶的光学吸收与尺寸效应

本文用高阶Mie散射理论研究了CdS、ZnS毫微晶的吸收(消光)光谱及其随微晶尺寸的变化,提出了在CdS、ZnS毫微晶半径大于～10nm时,吸收峰及吸收边的蓝移主要由经典尺寸效应所引起;在毫微晶半径小于～10nm时,吸收的蓝移主要是量子尺寸效应的贡献.     

CdSe纳米晶带隙随温度变化的研究

根据带隙与吸收光谱的第一吸收峰峰位之间存在的关系,测量了粒子尺寸分别为4.0 nm和2.5 nm的CdSe纳米晶在不同温度下的吸收光谱,找出了吸收光谱第一吸收峰峰位随温度的变化关系,总结出了CdSe纳米晶的带隙随温度的变化关系.结果表明：CdSe纳米晶材料的发光器件的发光颜色取决于它的带隙.     

溶胶-凝胶法制备的GeO2-SiO2凝胶玻璃的红光发射

以3三氯锗丙酸和正硅酸乙酯为原料采用溶胶凝胶法制备了GeO2SiO2凝胶玻璃.室温下以532nm激光(Nd:YAG)激发GeO2SiO2凝胶玻璃有一强的发光峰,这种发光有两个发光带,其峰位分别在575nm和624nm.该发光现象是由镶嵌在GeO2SiO2凝胶玻璃中GeO2纳米颗粒产生的.利用吸收光谱和TEM对GeO2SiO2凝胶玻璃进行了表征,结果发现随着Ge含量的增加凝胶玻璃中GeO2纳米颗粒的尺寸越来越大,吸收边向低能边移动.X射线衍射和电子衍射确定GeO2SiO2凝胶玻璃中GeO2颗粒的结构为非晶结 关键词： GeO2-SiO2凝胶玻璃 溶胶-凝胶法 红光发射     

Tb~(3+)掺杂透明锗酸盐微晶玻璃：制备与面向X射线探测的增强发光（英文）

通过熔融淬火和后续热处理,成功制备了Tb~(3+)掺杂含LaF_3纳米晶透明锗酸盐微晶玻璃。详细研究了所制备的玻璃和微晶玻璃的发光性质。X射线衍射结果表明,玻璃基体中析出的晶相为纯LaF_3晶体,晶粒尺寸在16～21 nm之间。在377 nm紫外光和X射线激发下,Tb~(3+)掺杂含LaF_3纳米晶的微晶玻璃比Tb~(3+)掺杂的锗酸盐玻璃表现出更强的绿光发射,且绿光发射强度随热处理温度升高和时间的延长而增强。微晶玻璃在X射线激发下的最大积分发光强度约为商用闪烁晶体Bi_4Ge_3O_(12)的40.3%。本研究表明,掺Tb~(3+)含LaF_3纳米晶锗酸盐微晶玻璃在X射线探测中具有潜在的应用前景。     

Dissociative excitation of the cesium atom in e-CsCl collisions

The dissociative excitation of the cesium atom in collisions of slow electrons with cesium chloride molecules is studied by the method of extended crossed beams with detection of the optical signal from the crossing region. Forty-seven cross sections for the excitation of spectral lines of CsI in the spectral region 347–852 nm are measured at an electron energy of 100 eV, and 10 optical excitation functions (OEFs) are recorded. It is found that the dependence of the excitation cross sections on the principal quantum number of the upper level in the spectral series of Cs I corresponds to a power law. The characteristic values of the constants in the power law are determined for each of the investigated series. Zh. Tekh. Fiz. 69, 29–34 (January 1999)     

传递矩阵法预报时空随机激励下任意薄壳腔体内部噪声

利用结构有限元结合声有限元及边界元方法,建立了任意薄壳腔体弹性壳板振动与内外声场的耦合模型,并计算了激励力与壳板振动和内部声场之间的传递矩阵;湍流边界层脉动压力具有时空随机面激励特性,引入整体形状函数矩阵,进一步推导弹性壳板广义节点力功率谱密度函数矩阵与随机面分布激励力功率谱密度函数的关系,再利用声振耦合传递矩阵,得到弹性壳板振动和内部声场功率谱密度函数与广义节点力功率谱密度函数矩阵的关系,形成随机分布激励下任意薄壳腔体结构振动及内部声场的计算方法。以典型的内外均有声介质且一面为弹性矩形板的矩形腔声振耦合模型为例,计算了弹性壳板振动和内部声场功率谱密度函数,并与解析方法进行了比较,两者基本吻合,偏差分别为1 dB和2 dB左右。传递矩阵法不受腔体结构及其内部区域形状的制约,具有良好的适用性。      

Response of plates with unconstrained layer damping treatment to random acoustic excitation,part II: Response evaluation

Theoretical and experimental investigations on the response of a plate with unconstrained layer damping treatment to random acoustic excitation have been carried out. The theoretical response evaluation consisted of determining the power spectral density of the acceleration response of the layered plate by the use of generalized harmonic analysis under a specific random acoustic excitation, with use being made of modal frequencies and associated loss factors estimated as described in Part I. A study was made on the contribution of cross coupling terms of the acceleration response for the two boundary conditions investigated: namely, all edges simply supported and all edges clamped. In the experimental investigation, plates with different damping layer thicknesses were subjected to high intensity random acoustic excitation generated by an exponential horn driven by an electropneumatic transducer. The acceleration responses were recorded and later analyzed to yield the power spectral densities. Experimental and theoretical results are compared.     

Photodissociation effects on pulsed laser deposited silver oxide thin films: surface‐enhanced resonance Raman scattering

Temporal Raman scattering measurements with 488, 532 and 632 nm excitation wavelengths and normal Raman studies by varying the power (from 30 W/cm² to 2 MW/cm²) at 488 nm were performed on silver oxide thin films prepared by pulsed‐laser deposition. Initially, silver oxide Raman spectra were observed with all three excitation wavelengths. With further increase in time and power, silver oxide photodissociated into silver nanostructures. High‐intensity spectral lines were observed at 1336 ± 25 and 1596 ± 10 cm⁻¹ with 488 nm excitation. No spectral features were observed with 633 nm excitation. Surface‐enhanced resonance Raman scattering theory is used to explain the complex behavior in the intensity of the 1336/1596 cm⁻¹ lines with varying power of 488 nm excitation. Copyright © 2011 John Wiley & Sons, Ltd.     

Theoretical derivation of 1/f noise in quantum chaos

It was recently conjectured that 1/f noise is a fundamental characteristic of spectral fluctuations in chaotic quantum systems. This conjecture is based on the power spectrum behavior of the excitation energy fluctuations, which is different for chaotic and integrable systems. Using random matrix theory, we derive theoretical expressions that explain without free parameters the universal behavior of the excitation energy fluctuations power spectrum. The theory gives excellent agreement with numerical calculations and reproduces to a good approximation the 1/f (1/f(2)) power law characteristic of chaotic (integrable) systems. Moreover, the theoretical results are valid for semiclassical systems as well.     

Independence of Maximum Single Molecule Fluorescence Count Rate on the Temporal and Spectral Laser Pulse Width in Two-Photon FCS

We investigate the fluorescence emission characteristics of standard dye tetramethylrhodamine (TMR) in two-photon fluorescence correlation spectroscopy for different temporal and spectral properties of the femtosecond excitation pulses. After determining the second-order dispersion of our setup, including the microscope objective, a pulse stretcher was employed to control the temporal width at the location of the specimen. As expected, the fluorescence per molecule and therefore the signal-to-noise ratio of an FCS-measurement can be improved at constant average excitation power by altering either the temporal or spectral width of the excitation pulses. We found however, that the maximum achievable molecular brightness is largely independent of the temporal and spectral width in the regime analyzed. This observation confirms the current working hypothesis for two-photon fluorescence correlation spectroscopy that bleaching and saturation, and thus, the inherent properties of the dye system, are the dominant effects limiting the quality of measurements. As a practical consequence, elaborate optimization of temporal and spectral laser pulse width, e.g. by introducing pulse stretchers in the beam path, is less critical than previously expected.     

微型计算机在微弱光谱测试系统中的应用

本文报道了在我们研制的微弱光谱测试系统中微计算机的应用,介绍了数据采集、双机间的DMA传送数据、二维光栅扫描控制、应用微机改善信噪比、应用软件和图形显示等问题。着重讨论如何通过我们所做的研制工作,使性能较低的EG3003微计算机达到OMA系统所要求的水平。     

Laser-excited spectra of Lu2SiO5:Ce scintillator

The emission spectra of Lu₂SiO₅:Ce single crystal under the excitation of 266 nm laser were investigated. The emission spectra of LSO single crystal show no temperature quenching from 20 to 300 K, under the excitation of 266 nm laser with 2 mJ pulse energy. With rising temperature, the Ce1 emission is slightly decreased, while the Ce2 emission is slightly increased. These results show the emissions of Ce1 and Ce2 is not only dependent on the concentration ratio but also influenced by the possible energy transfer processes, including Ce1 to Ce2, intrinsic STHs to Ce2 and the phonon-assisted transfer processes. The spectral thermal broadening and the spectral overlap become evident at high temperature, leading to the enhancement of energy transfer. When the excitation power lowers, the ratio of Ce1 and Ce2 emission increases, and is close to the Xe lamp ultraviolet (UV) excitation, suggesting that the energy transfer from Ce1 center to Ce2 center may be also dependent on the excitation power.     

Emission of organic dyes in the case of nonlinear absorption upon excitation by the XeCl* laser

Spectral luminescent properties of eight organic dyes are studied upon excitation by focused radiation from the XeCl* laser at the pump power up to 200 MW/cm². The transmission of pump radiation by dyes is investigated as a function of the pump power. It is shown that variations in the energy, spectral, and temporal parameters of radiation of organic dyes upon high-power excitation are explained by the development of superluminescence (amplified spontaneous emission).     

Eu(DBM)_3Phen掺杂聚甲基丙烯酸甲酯静电纺丝荧光纤维

通过静电纺丝技术获得直径约为700 nm,均匀且随机取向的亚微米级Eu(DBM)3Phen/PMMA纤维。在紫外光辐射下,亚微米级荧光纤维发出明亮的红色荧光。其激发光谱表明,荧光纤维有效激发波长范围为200~400 nm。利用积分球配以CCD探测器,在367 nm长波紫外LED激发下对荧光纤维开展绝对光谱功率测试。当LED泵浦功率为535.76#W时,厚度80#m的Eu(DBM)3Phen/PMMA纤维薄层对紫外辐射的吸收率高达89%,350~850 nm范围内发射的总绝对光谱功率、总光子数和总荧光量子产率分别为36.56#W、11.46×10~(13)cps和12.94%。亚微米级Eu(DBM)_3Phen/PMMA纤维薄层中,Eu~(3+)较高的跃迁发射几率及较大的发射截面使得纤维可以高效吸收紫外辐射并转变为可见光,在提高太阳能电池光电转换效率方面具有潜在应用价值。