无机材料BaFCl0.5Br0.5：Sm^2＋光子选通光谱烧孔

本文报道了无机材料的BaFCl_(0.5)Br_(0.5):Sm~(2+)的光子选通光谱烧孔.文中叙述了光子选通光谱烧孔的机制.在低温4.2K下进行多孔烧孔和探测.测量了孔的选通性和稳定性.实现了孔的可擦除和重复烧孔.测量结果表明,处于4.2K的BaFCl_(0.5)Br_(0.5):Sm~(2+)样品,在一个非均匀加宽轮廓内可实现1×10~3个以上数目的永久性光谱烧孔.     

波导适用型铝锗酸盐玻璃中铥离子上转换荧光光子输出与量子产率定量

制备了适用于钾钠离子交换波导的Tm~(3+)/Yb~(3+)掺杂铝锗酸盐玻璃,利用积分球配以光纤光谱仪在975nm激光泵浦下对玻璃的上转换荧光进行测试,解析出样品的绝对荧光特征参量。测试与计算结果显示,在380℃的KNO3熔盐中,Tm~(3+)/Yb~(3+)掺杂的铝锗酸盐玻璃的钾钠离子交换有效扩散系数为0.070μm~2/min,热离子交换过程易于控制。铝锗酸盐玻璃样品中,Tm~(3+)主要发出477 nm蓝光和806 nm近红外光,其中近红外光为支配性发射。绝对荧光参数和激发功率密度呈正相关,当功率密度达到1 482 W/cm2时,三光子上转换蓝光的绝对光谱功率、净发射光子数和量子产率分别为269μW、6.46×10~(14)/s和1.43×10~(-4),双光子近红外光上转换对应的3个参量分别为4 024μW、1.63×10~(16)/s和3.61×10~(-3)。基于波导适用型铝锗酸盐玻璃中Tm~(3+)上转换荧光的绝对化表征,为进一步研发光电子器件和激光材料提供了有益的数据参考。     

多波段相关光子光谱分布与时间相关性测量实验研究

基于相关光子的定标技术能够实现“无标准传递”绝对定标,研究相关光子的光谱辐射特性及时间相关特性对遥感器在宽波段的辐射定标具有重要意义。为满足光电探测器在宽谱段量子效率定标需求,基于相关光子的定标技术有必要从单一波段向更多波段扩展。根据自发参量下转换所满足的相位匹配条件,推导出相关光子在晶体内的非共线角计算公式,通过数值模拟相关光子光谱辐射角度分布规律,优化晶体相位匹配角,使得自发参量下转换产生的相关光子具有宽光谱分布,并且相关光子辐射角度与光谱波长能够一一对应。根据光谱分布数值模拟结果,建立了多波段相关光子的光谱分布和时间相关性测量实验系统,利用该系统测量了四对相关光子的光谱分布、符合计数、相关时间以及偏振特性。其中,测量的光谱分布范围为633~808 nm,最大光谱分布测量偏差为1.51 mm,光谱分布实验测量结果与数值模拟结果符合一致;测量了四对相关光子对的相关时间,最小相关时间为0.32 ns,并在实验中观察到了“符合三峰”现象;相关光子单光子计数及符合计数与泵浦光的偏振方向呈正弦函数关系。实验研究表明,相关光子对具有可见光~近红外宽波段分布、时间相关及偏振特性。论文研究结果在国内外尚属首次报道,该研究结果有望应用于光电探测器在多波段的辐射定标。     

I类自发参量下转换光谱圆环空间分布

理论模拟了I类自发参量下转换产生的相关光子光谱圆环的空间辐射角度及光强分布,搭建了相关光子圆环光强分布的实验测量装置,该装置利用355nm连续激光器泵浦BBO晶体产生I类自发参量下转换相关光子圆环,使用CMOS传感器作为相关光子圆环探测单元,通过2×2维点阵扫描方法探测了完整的相关光子圆环,测量的光谱分布为430~860nm.实验结果表明:测量的相关光子圆环直径与理论值符合较好;I类自发参量下转换过程产生的相关光子在空间呈同心圆环分布;相关光子光谱具有宽光谱分布特点.     

Ⅰ类自发参量下转换光谱圆环空间分布

理论模拟了I类自发参量下转换产生的相关光子光谱圆环的空间辐射角度及光强分布,搭建了相关光子圆环光强分布的实验测量装置,该装置利用355 nm连续激光器泵浦BBO晶体产生I类自发参量下转换相关光子圆环,使用CMOS传感器作为相关光子圆环探测单元,通过2×2维点阵扫描方法探测了完整的相关光子圆环,测量的光谱分布为430～860 nm.实验结果表明:测量的相关光子圆环直径与理论值符合较好;Ⅰ类自发参量下转换过程产生的相关光子在空间呈同心圆环分布;相关光子光谱具有宽光谱分布特点.     

窄带可调真空紫外激光——气相中的非线性过程

本文评述了气相中的非线性过程产生VUV激光的最新进展、在稀有气体和Hg蒸汽中,通过四波和六波混频过程,可产生可调范围为λ_(VUV)=60～200nm,光谱宽度为E=0.01～1cm,~(-1),光强为2×10~θ～ 3×10~(13)光子/脉冲的VUV激光、这一光源具有技术简单,使用方便等特点,对原子、分子的激光光谱以及激光化学等方面的深入研究起了重要作用。     

窄带可调真空紫外激光——气相中的非线性过程

本文评述了气相中的非线性过程产生VUV激光的最新进展、在稀有气体和Hg蒸汽中,通过四波和六波混频过程,可产生可调范围为λ_(VUV)=60～200nm,光谱宽度为E=0.01～1cm,~(-1),光强为2×10~θ～ 3×10~(13)光子/脉冲的VUV激光、这一光源具有技术简单,使用方便等特点,对原子、分子的激光光谱以及激光化学等方面的深入研究起了重要作用。     

利用光子相关光谱研究蛋白分子相互作用

利用光子相关光谱技术研究了人血清白蛋白分子在不同蛋白浓度和pH值条件下的扩散系数。结果表明库仑力对蛋白质的扩散起主要作用,在等电位点下(pH=5.2)库仑力的影响消失,蛋白质的扩散系数最小;等电点测量出扩散系数随浓度的增加而线性减小,主要原因是蛋白质间的库仑排斥力变小,引力得到相对增强,测得人血清白蛋白的半径为3.44±0.01nm。     

CO(A~1∏←X~1∑~+和e~3∑~-←X~1∑~+)双光子共振电离光谱的归属和双光子吸收截面的测量

我们得到了CO经过共振态A~1∏态和e~3∑~-态的转动分辨的紫外双光子共振四光子电离光谱,并测量了它们的双光子吸收截面,σ_(Xe)~(2)、σ_(A1)~(2)=1.4×10~(99)cm~8sec~(-1),σ_(A1)~(2)=2.6×10-~(50)cm~4see_(-1).用双色共振增强的方法明确地归属了受到扰动的CO A←X双光子吸收(0.0)带.     

溴乙烷分子的质量分辨阈值光谱

利用单色双光子(1C2P)技术得到了高精度的溴乙烷分子的质量分辨阈值(MATI)光谱，精确给出了溴乙烷分子的绝热电离势和离子振动频率.从中性基态到离子基态两个自旋-轨道分量X₁ ²E_1/2和X₂ ²E_1/2的绝热电离势分别为83097±3 cm^-1和85452±3 cm^-1，离子基态两个自旋-轨道分量的间隔为2355±6 cm^-1，这些值与文献报道值符合得较好，且精度更高.溴乙烷分子的单色双光子质量分辨阈值光谱展现出丰富的振动结构，这是在溴乙烷分子相继吸收两个光子的过程中波包在解离态势能面上演化的结果.以已有的离子振动谱标识为参考，以中性分子的振动频率为基础，标识了溴乙烷分子的质量分辨阈值光谱，发现观测到的振动模几乎都和溴乙烷分子的解离运动有关，其中还包括一些非全对称模. 关键词： 质量分辨阈值光谱 振动模 单色双光子零动能光谱技术 溴乙烷     

牙齿组织光学穿透深度有限元仿真分析

利用有限元方法对光在二维牙齿双层有限尺寸模型中传输的扩散方程进行求解,获取了光能在组织体内部的分布情况,并对牙釉质和牙本质在不同光学参量模型下的光学穿透深度进行仿真分析.结果发现,穿透深度随牙釉质散射系数的增大而减小,随牙本质的散射系数增大而增大.但牙釉质的穿透深度随散射系数的变化率（βe=0.007 97）要远远大于牙本质（βd=0.000 828）.采用Monte Carlo随机统计方法验证了本文有限元求解扩散方程的正确性.     

Feasibility of glucose monitoring based on Brownian dynamics in time-domain optical coherence tomography

Our purpose is to investigate the feasibility of Brownian motion in time-domain optical coherence tomography (OCT) incorporated with wavelet power spectrum to monitor glucose concentration in Intralipid solution. The results show that the standard deviation (SD) of frequency in the superficial layer of single scattering region, linearly proportional to Brownian diffusion coefficient, is independent of the depth. Our preliminary results demonstrate that average SD of frequency in the single scattering region is inversely proportional to the glucose concentration in Intralipid solution, since the Brownian diffusion coefficient is a function of concentration. Thus the average SD of frequency in OCT signal is capable of differentiating the glucose concentration.     

电解质对浓悬浮液中胶体颗粒扩散特性的影响

本文利用相位调制光纤低相干动态光散射装置, 研究了不同物质量浓度下电解质 (NaCl及 BaCl₂) 对浓悬浮液中聚苯乙烯胶体颗粒扩散特性的影响. 实验结果表明, 当电解质浓度低于0.01 mol/L 时, 恒温条件下浓悬浮液中聚苯乙烯胶体颗粒扩散系数随电解质离子浓度以及离子化合价的增大而增大, 实验测量得到的扩散系数与Stern模型所得到的扩散系数符合较好. 关键词： 测量 电解质 浓悬浮液 低相干动态光散射     

牙齿组织自体荧光光场仿真分析

利用有限元数值方法对扩散方程进行求解,将激发光场作为荧光传输扩散方程的光源,获得了二维牙齿模型内部自体荧光光场的分布。讨论了牙釉质和牙本质不同散射系数时牙齿上表面的荧光能量分布。发现牙齿上表面荧光能量随牙釉质散射系数的增大而降低,随牙本质散射系数的增大而增大。并对牙釉质和牙本质的散射系数的改变量对荧光能量的影响进行了定量分析,结果表明βe=2.62,βd=0.0502,牙釉质散射系数的改变对荧光能量的影响远远大于牙本质。利用Monte Carlo随机统计方法对牙齿组织自体荧光进行仿真,发现与有限元结果吻合较好,验证了有限元求解组织体荧光光场分布的正确性。     

Effect of heavy-metal ions on dynamic characteristics of collagen molecules in solutions

Effect of heavy (Pb²⁺, Cs⁺) and light (Na⁺) metal ions on the molecular-dynamic characteristics of type-I collagen in aqueous solution was studied using the method of dynamic light scattering. It was found that the dependence of the translational diffusion coefficient D _t from pH solutions has a nonlinear form with a pronounced extremum close to the isoelectric point of the protein (pI 6.0). For pure aqueous solution of protein there is a maximum of D _t in isoelectric point. For collagen solutions with the addition of heavy-metal salts the minimum of D _t was observed near the isoelectric point. This fenomenon is connected with the formation of protein nanoclusters in solution. With concentration of heavy metal ions increasing translational diffusion coefficient Dt decreases, which shows on increasing of aggregation effect. The addition of sodium ions in aqueous solution of collagen containing heavy metal ions sharp decreasing of the translational diffusion of molecules is observed. That can be connected with the rise of scattering particles masses.     

Diffusion coefficient depends on time, not on absorption

The recent controversy over whether the photon diffusion coefficient depends on absorption is addressed by use of the analytical solution of the photon transport equation in an infinite homogeneous scattering medium. The diffusion coefficient is found to be independent of absorption but temporally dependent. After a long period of time, the photon diffusion coefficient approaches D=1/3mu(s)(?) , which supports a claim made by Furutsu and Yamada [Phys. Rev. E 50, 3634 (1994)]. At early times, the diffusion coefficient is smaller than D=1/3mu(s)(?) , but this reduction cannot be expressed as D=1/3(mu(s)(?)+mu(a)) , since the time-dependent diffusion coefficient is found to be unrelated to absorption.     

Bounded diffusion in solid solution electrode powder compacts. Part I. The interfacial impedance of a solid solution electrode (MxSSE) in contact with a m+-ion conducting electrolyte

The transient and ac electrical response of electrochemical systems containing a solid solution electrode is derived using Laplace transform methods. First, the operational impedance of the electrolyte/solid solution electrode interface is derived, for both asymmetrical and symmetrical cell systems. From the operational impedance the current, voltage and ac impedance response is calculated. By combination of semi-infinite and bounded diffusive behaviour, both the chemical diffusion coefficient of the inserted ions and the thermodynamic factor (? ln a/? ln c) can be obtained from kinetic data only.     

辐射传输方程的三阶球谐展开(P3)近似的有限元法求解

从辐射传输方程出发,应用球谐函数方法对辐射率进行多项式展开,并利用球谐函数的正交性和递推性,在二维笛卡儿坐标下,导出了三阶展开的球谐函数微分方程组（P3近似）,改进了以往成像文献中忽略各项异性因子的P3近似,并用有限元方法对二维圆域均匀和非均匀两种情况做了数值模拟.与漫射近似模型相比较,P3近似能更准确地描述光源附近及吸收较强情况下边界的光辐射分布情况.     

Unusual thermal diffusion in polymer solutions

Thermal diffusion forced Rayleigh scattering results on thermal diffusion of poly(ethylene oxide) (PEO) in ethanol/water mixtures are presented. In water-rich solvent mixtures, PEO is found to migrate towards regions of lower temperature. This is typical for polymer solutions and corresponds to a positive Soret coefficient of PEO. In solvent mixtures with low water content, however, the polymer is found to migrate towards higher temperatures, corresponding to a negative Soret coefficient of PEO in ethanol-rich solutions. To our knowledge, this is the first observed sign change of the Soret coefficient of a polymer in solution. We also present a simple lattice model for the polymer solvent system and calculate Soret coefficients with statistical mechanics methods. The calculated values agree qualitatively with the experimental results.     

Influence of the degree of crystal perfection and deviation from the stoichiometric composition on the diffusion processes in samarium sulfide

The processes of diffusion of samarium and europium in nonstoichiometric samarium sulfide (SmS) at temperatures in the range 950–1600°C have been investigated by the radioactive isotope method and the method of weight loss upon evaporation of excess samarium. It has been found that there is a correlation between the diffusion coefficient D and the size of coherent X-ray scattering regions in SmS samples, as well as between the diffusion coefficient and the degree of deviation from the stoichiometric composition: the diffusion coefficient of impurities decreases as the size of coherent X-ray scattering regions increases and the stoichiometric composition is approached. The calculation of the diffusion coefficient of electrons in samarium sulfide at T = 77–300 K has demonstrated that the value of D increases with increasing temperature and increasing size of coherent scattering regions.