用硅离子注入方法制备的纳米硅的拉曼散射研究

在直角散射配置下测量了纳米硅样品的拉曼散射谱及其退火温度的关系。结果表明,在８００℃以下退火的样品只观察到单晶硅衬底的光学声子模,在９００℃以上退火,才观察到纳米硅的特征拉曼散射峰。在１２００℃下退火后,纳米硅的特征拉曼散射峰消失,观察到类似于非晶硅的光学声子特征峰,可能表示纳米硅不能承受这样的高温热退火。这些结果进一步证实了光致发光谱的结果。     

高阶相干喇曼散射光谱研究

本文报道了利用YAG激光系统CARS装置研究方解石的高阶相干喇曼散射(CRS)的实验结果,观察到1—6阶相干反斯托克斯喇曼散射谱(CARS)和1—2阶的相干斯托克斯喇曼散射谱(CSRS),讨论了影响高阶CRS产生的因素及有关的问题。 关键词：     

KDP晶体受激拉曼散射特性

详细比较了磷酸二氢钾(KDP)晶体的自发拉曼散射和受激拉曼散射光谱,在受激拉曼散射(SRS)中观察到了自发拉曼散射中最强的振动模的三阶Stokes光(559.43,589.74,623.50nm),由于其他振动模的受激拉曼散射增益系数较小,其SRS光谱未观察到。另外,比较了传统生长的未退火和退火后的KDP晶体及快速生长的锥区和柱区KDP晶体的受激拉曼散射增益系数,结果表明生长方法和热退火对KDP晶体的受激拉曼散射增益系数无明显影响。     

应变液晶散射偏光片的试制

介绍了聚合物分散液晶(PDLC)和应变液晶(SLC)以及散射偏光片的概念,实验制备了应变液晶散射偏光片样品,样品由两张胶片夹层聚合物分散液晶膜在紫外光固化过程中施加剪切应力所形成。给出了样品偏光显微镜照片和可见光分光光度计偏光特性光谱分析。实验结果表明,应变液晶散射偏光片样品外观半透明,在正交偏光场中转动样品有颜色变化,通过样品观察液晶显示器屏幕,在不同角度下有透射和散射作用,在偏光显微镜中观察样品有衬垫料被拉动的痕迹,光谱分析显示样品在绿光550nm波长处最大透光率T∥≈50%,最小透光率T⊥≈5%,偏振度P≈82%。实验结果对于研制实用的拉伸液晶散射偏光片具有参考意义。     

光通过纳米颗粒随机散射体透射光强的计算及分析

光通过随机散射体后透射光强的估算,对于提取散射体内部无法直接测量或者无法直接观察的信息至关重要。在分析平行光束通过纳米圆形颗粒随机散射体出射面上光强组成的基础上推导了透射光强的计算公式,并指出多重散射理论、一阶多重散射理论和朗伯-比尔定律在一定近似程度上可以相对精确地估算透射光强。这三种方法的估算结果之间会出现四种相对关系。根据这些相对关系,分析了光在散射体内部传输时散射过程的特征以及各种散射过程对出射面光强的贡献大小。     

一种描述散射体系中散射颗粒消光能力的新方法

提出了一种新的衡量散射体系中散射颗粒消光能力、散射能力和吸收能力的方法并与传统方法进行了比较。在此基础上 ,讨论了散射颗粒折射率和颗粒大小对其散射能力的影响。运用此方法可以为各种散射体系 ,尤其是强散射体系选择恰当的散射颗粒 ,其结果优于用传统方法所得的结果     

低能π介子—核子散射

本文应用向前方向附近的定角色散关系推出了π介子-核子散射的s波和p波振幅的积分方程。方程中包含湮没过程的贡献,其中主要贡献来自二π介子中间态,为了检验ππ作用在π介子-核子散射过程中的效应,将散射相移观察值代入方程中作了数值计算。利用了核子电磁结构形式因子的实验知識,取共振能量平方t_r=20,得到了I=J=1ππ散射共振宽度参数r≌0.1。此结果可同时符合三个低角动量分波振幅的实验材料,但共振宽度要比观察值小。     

氮化铝单晶的布里渊散射几何研究

在对称散射和180°背散射两种散射几何设置下获得了单晶透明氮化铝布里渊散射谱图。分析了谱峰出现的原因及其对应的声波模式,分析了对称散射几何设置下谱图的偏振态。实验观察到对称散射谱图中准纵波峰和背散射谱图中的纯纵模峰,分析了它们出现的原因。文章根据实验谱图求得了样品材料的全部弹性常数信息。     

修正反射系数的Kirchhoff近似方法计算高斯起伏冰面三维声散射

针对随机起伏冰面的声散射计算问题,利用修正反射系数的Kirchhoff近似方法计算了高斯起伏冰面的三维声散射。在计算模型中引入了冰面局部统计平均反射系数的概念,将二维高斯起伏冰面的散射分为相干散射和非相干散射,分别得到两类散射成分的散射系数公式,计算了高斯起伏冰面三维声散射的散射强度。分析了散射强度与随机起伏冰面的均方根高度、声波入射角度及频率的关系。通过实验室水池中高斯起伏冰面的散射强度测量实验,对理论模型的计算结果进行了验证。将实验结果分别与采用冰面局部统计平均反射系数的模型计算结果和文献中采用平整冰面镜反射系数的模型计算结果进行了对比,采用冰面局部统计平均反射系数的模型计算结果与实验测量值吻合较好。      

Franz波波速计算及实验测量

本文给出了计算水中无限长刚性圆柱对垂直入射平面声波散射所产生的Franz波的相速的理论公式。用Schlieren方法,观察到圆柱影区散射声场的稳定图象,并由此推算出Franz波的传播速度。理论分析与实验结果基本相符。     

Induced Scattering of Plasma Electrons by Upper Hybrid Solitons

Induced scattering of plasma electrons by spontaneously created soliton is studied experimentally with the method of coincident analysis. The scattering model and the scattering time rate (STR) are obtained theoretically. From the comparison of experimental and theoretical results, experimental evidence of induced scattering and electron heating by the soliton is obtained.     

X-ray scattering from freely suspended smectic-A films

This work is devoted to a theoretical analysis of specular reflection and diffuse scattering of x-rays from a freely suspended smectic-A film, taking into account its spatial inhomogeneity and deviations of orientational and position ordering in smectic layers from ideal ordering. The results of the calculations are compared with the experimental data on small-angle scattering of x-rays from freely suspended films of 7 AB liquid crystals. It is found that the theoretical results agree with the experimental data.     

Size dependent optical characterization of semiconductor particle: CdS embedded in polymer matrix

We report the optical investigation and analysis of both nano-sized and micrometer size Cadmium Sulphide particles which is embedded in a transparent polyvinyl alcohol (PVOH) dielectric host material. A designed and fabricated laser based light scattering system using a He-Ne laser of wavelength 632.8nm was used for the measurement and study of the scattering properties of the particles as a function of the scattering angle at this wavelength. An attempt was made to experimentally determine the most significant elements of the Mueller scattering matrix using combinations of randomly and linearly polarized incident laser beam and subsequent analyzers in corresponding orientations. The analysis of the experimental data was done by the method of comparison with theoretically generated data. Novel computational technique, involving single scattering for spherical particles using Mie-theory, was developed and applied. The theoretical data was found to be in good agreement with the experimental data within an acceptable margin of error. The results have proved that the combination of the experimental setup and associated computational method is a highly efficient and reliable in-situ system for monitoring size growth of semiconductor particles in the laboratory.     

Discrimination of surface and bulk scattering of arbitrary level based on angle-resolved ellipsometry: Theoretical analysis

An experimental procedure, which was found to be valid for both low-level and high-level scattering of random media, was recently shown to directly discriminate between surface and bulk scattering origin [O. Gilbert, C. Deumie, C. Amra, Angle-resolved ellipsometry of scattering patterns from arbitrary surfaces and bulk materials, Opt. Express 13 (2005) 2403]. The method is based on the ellipsometric measurement of the scattered field over the scattering angle and the analysis of the obtained relative phase shift between s and p polarizations. In the case of low-level scattering, the results were already known and have been explained by first order electromagnetic theories. However, information detailing high-level scattering is scarce. Using rigorous electromagnetic theory, we examined high-level scattering. The differential method enabled us to validate the experimental observations of Gilbert et al. (2005) and explore the limits of validity of the discrimination technique.     

Anisotropic Scattering in BaTiO_3: Ce Single Crystal

InPastdecadesseveralformsoflight-inducedscatteringhavebeenobservedfromBaTiossinglecrystali1luminatedbyalinear,polarizedlaserbeam[1~7j.Ingeneral,thescattteringPatterncanbeisotropicoranisotropicdependingonthepropagationdirectionofthelightbomrelativetothecrystallographicaxesandthebeampolarization,itiscom-monlyacceptedthatthephysicaloriginofthisphenomenonistherandomrecordingofParasiticgratingswrittenbyanincidentbeamanditsscatteredbeamfromcrystalinhomo-geneities[1J.Recently,anewtyPeofnonlinearopt…     

Singular value distribution of the propagation matrix in random scattering media

The distribution of singular values of the propagation operator in a random medium is investigated, in a backscattering configuration. Experiments are carried out with pulsed ultrasonic waves around 3 MHz, using an array of 64 programmable transducers placed in front of a random scattering medium. The impulse responses between each pair of transducers are measured and form the response matrix. The evolution of its singular values with time and frequency is computed by means of a short-time Fourier analysis. The mean distribution of singular values exhibits a very different behaviour in the single and multiple scattering regimes. The results are compared with random matrix theory. Once the experimental matrix coefficients are renormalized, experimental results and theoretical predictions are found to be in a very good agreement. Two kinds of random media have been investigated: a highly scattering medium in which multiple scattering predominates and a weakly scattering medium. In both cases, residual correlations that may exist between matrix elements are shown to be a key parameter. Finally, the possibility of detecting a target embedded in a random scattering medium based on the statistical properties of the strongest singular value is discussed.     

Semiclassical treatment of heavy ion elastic scattering

A generalized semiclassical treatment for the elastic scattering of heavy ions is developed in the presence of a complex optical potential. The scattering phase shift and its derivatives with respect to the impact parameter are calculated after extending the JWKBL approximation. The results are compared with experimental data for the elastic scattering of¹⁶O from medium and heavy target nuclei and relation between the present treatment and that of the optical model and Regge pole analysis is established     

Phonon-Resonanzstreuung und Wärmeleitung in einer Silizium-Korngrenze

The thermal conductivity of a grain-boundary in silicon bicrystals has been measured in the temperature range from 12°K to 150°K using a newly developed method. The analysis of the experimental results shows that the thermal conductivity is governed by two scattering processes: the acoustical mismatch of both crystal halves and the resonant scattering of the phonons by impurity atoms of the grain boundary. A new method is thereby presented for the direct observation of phonon resonant scattering.     

XANES analysis of spectral properties and structures of arsenate adsorption on TiO2 surfaces

X‐ray absorption near‐edge structure (XANES) of arsenate adsorption on TiO₂ surfaces was calculated using self‐consistent multiple‐scattering methods, allowing a structural analysis of experimental spectra. A quantitative analysis of the effect of disorder revealed that the broadening and weakening of the characteristic absorption in experimental XANES was due to the structural disorder of the arsenate–TiO₂ adsorption system. The success with calculating the scattering amplitude of a specific set of paths using the path expansion approach enables the scattering contributions of different coordination shells to the XANES to be sorted out. The results showed that the scattering resonances from high‐level shells inherently overlapped onto the first‐shell scattering amplitudes, and formed the fine structures in the XANES region. A variation in one oscillatory feature could be due to several structural changes affecting specific single/multiple‐scattering amplitudes. Therefore, direct assignments of spectral features with structural elements should be based on adequate theoretical analysis.     

State-to-state dynamics of high-n Rydberg H-atom scattering with D2

Full quantum-state resolved scattering of a highly excited Rydberg H atom with D2 has been carried out using the Rydberg H-atom time-of-flight method. A detailed analysis of the experimental results shows that both inelastic and reactive scatterings are significant in the Hn-D2 collisions, and nuclear spin is conserved in the inelastic scattering process. The differential cross sections for the Hn-D2 reaction measured in this work are then compared with the results for the H+ reaction with D2 in an ion beam scattering experiment. The remarkable agreement between the two experiments suggests that the Fermi independent-collider model is valid even at the full quantum state-to-state scattering level, providing a promising tool for investigating the state-to-state dynamics of certain elementary ion-molecule reactions.