X-射线荧光分析散射幂函数法的原理及其应用Ⅱ.非相干散射

本文在较宽的基体原子序数变化范围内研究了非相干散射随基体吸收系数的变化规律,发现存在一种幂函数关系,而传统散射内标法所假定的反比关系仅在较窄的轻元素范围内存在.实验证实了这种理论规律的存在.提出了用康普顿散射幂函数法校正基体吸收效应的新方法.列举了幂函数法在地质样品中锶的测定实例,证明该法在宽的基体组成范围内比传统的散射内标法适应性强.     

X—射线荧光分析散函数法的原理及其应用：—Ⅲ.连续背景幂？…

本文在宽的基体变化范围内对波长为０．０８１ｎｍ的连续散射Ｘ－射线进行了研究,表明质量衰减系数与连续散射强度之间不再遵守传统散射内标法所假定的反比例关系,而是呈一种幂函数关系。理论证明和实验结果一致。提出了用０．０８１ｎｍ处的散射强度的函数校正基体效应的方法,用于地质样品中微量锶的测定,结果显示,在较大的基体变动范围内,本不与传统散射内标法相比准确度提高近４倍,克服了传统方法适应基体变化范围小的缺点     

X-射线荧光分析散射函数法的原理及其应用Ⅲ.连续背景幂函数法

本文在宽的基体变化范围内对波长为0.081 nm的连续散射X-射线进行了研究,表明质量衰减系数与连续散射强度之间不再遵守传统散射内标法所假定的反比例关系,而是呈一种幂函数关系.理论证明和实验结果一致.提出了用0.081 nm处的散射强度的函数校正基体效应的方法,并用于地质样品中微量锶的测定,结果显示,在较大的基体变动范围内,本法与传统散射内标法相比准确度提高近4倍,克服了传统方法适应基体变化范围小的缺点.     

X射线荧光光谱法测定铁矿石和岩石中的低微量元素时基体成分影响的研究

引言用X射线荧光光谱法测定试样中的主成分时,主要是用数学校正法来校正基体成分对分析结果的影响,然而用数学校正法来分析试样中的低微量元素是很困难的。大多数作者是采用散射内标法或加入内标法来校正基体效应。     

随机散射屏的原子力显微镜形貌分析及其光散射特性

用原子力显微镜对三种不同粗糙度的随机散射屏的表面形貌进行了测量分析,发现它们在短程范围内具有明显的分形特征.对于粗糙度较大和较小的散射屏,分形特征分别以无规则的 高度调制和无特征大小的小颗粒的形式存在.用自仿射分形表面模型对散射屏的统计特性进 行了描述和拟合.光散射测量发现,散射光强在远轴区域按负幂函数下降,理论分析证明这 源于表面的分形结构;在近轴区域有散射亮环存在,用自仿射分形表面模型尚不能给出理论解释. 关键词： 随机散射屏 光散射 自仿射分形表面     

X射线荧光散射内标法测定难熔合金中的锆、铪和钛

在X射线荧光分析中,基体影响,激发条件的漂移和样品物理特征的变化是重要的误差源。对于这类影响可以采用散射内标法加以补偿。这种方法是以如下假设为前提的:(1)分析元     

用氢作内标补偿ICP光谱分析中的基体效应

用ICP发射光谱法测定含有高量基体成份样品中的元素时,由于基体成份对雾化过程和等离子过程的影响,往往会导致发射信号降低,从而得出不正确的测定结果。内标法是补偿基体效应和校正这种误差的一种有效方法。但在内标法中,必不可少地要向校准溶液和试液中定量加入一外来元素作内标,而且内标元素在原试料中的含量必须低至可忽略不计的程度。本研究探讨用水中之氢作内标,以克服上述缺点。     

孔隙率对气凝胶热辐射特性的影响

本文研究了热辐射在气凝胶纳米微孔结构中的传递.应用离散偶极子方法对随机生成的纳米结构的散射进行了模拟.结果表明:孔隙率和微分散射截面、散射效率因子关系密切.孔隙率增加,微分散射截面和散射效率因子减小明显;微分散射截面、散射效率因子和材料的宏观密度之间存在幂函数关系.本文的研究结果有助于理解气凝胶的结构参数和热辐射特性之间的联系.     

ICP-MS测定血中镁、铜、铅浓度时的基体效应单一内标校正方法研究

ICP-MS测定模拟全血基体中不同质量段的Mg, Cu, Pb元素,考察基体效应对测定值的影响,分别采用传统内标法和单一内标CAIS方法(common analyte internal standardization)对其进行校正和比较。结果表明CAIS方法适用于不同浓度血液基体中多种元素的同时校正,且效果良好,其相对平均误差仅为3.05%,明显低于传统内标法的12.39%和校正前的23.91%;CAIS方法不受内标元素和被测元素质量数差异、测定强度差异以及电极电位差异的限制;使用全血和血清标准物质对CAIS方法可靠性进行验证,测定值全部落在标准值范围内。     

X射线荧光光谱法测定橄榄岩主次痕量元素

本文采用熔融玻璃片和粉末压片法制样，用理论ａ系数和散射线内标法校正元素间的效应，     

Free-carrier absorption in a parabolic quantum well with consideration of scattering on ionized impurities

Intra-subband transitions caused by light absorption in a parabolic quantum well is considered taking into account the scattering by ionized impurity centers. To calculate the scattering matrix element, the Born approximation is used and the interaction with the impurity is described by the Coulomb potential. An analytical expression for the absorption coefficient of processes with the initial absorption of photon and further scattering by an ionized impurity center is obtained. For absorption coefficient the frequency characteristics and dependence on the width of quantum well are examined.     

Photothermal diffuse reflectance: a new tool for spectroscopic investigation of scattering samples

A new method named photothermal diffuse reflectance (PTDR) is presented. This method combines the diffuse reflectance spectroscopy with the photothermal technique and is particularly suited for the investigation of strongly scattering samples. This method takes advantage of the high spectral selectivity and absorption of the mid-infrared region with the larger scattering cross section and high detector sensitivity available in the near-infrared. A model describing the PTDR method is proposed and supported with experimental results. The potential of the PTDR technique is illustrated by experimental signals obtained from various scattering media like polymers, liquids and powders.     

Approximate solution for describing polarization characteristics of radiation in a Rayleigh scattering medium

An approximate analytical solution for the 4 × 4 Green’s matrix of the problem of polarized radiation transfer in a plane-parallel layer of an absorptive Rayleigh scattering medium is proposed. It permits one to perform fast estimates of angular distributions of the Stokes parameters that are created by an incident beam with an arbitrary polarization state at different levels in a layer when the layer thickness, absorption magnitude, and albedo of the underlying surface are varied. The developed solution is compared with data obtained by the numerical doubling method. The value of the scattering coefficient for a circularly polarized radiation is shown to be somewhat smaller than that for linearly polarized radiation.     

Structure and dynamics of water confined in silica hydrogels: X-ray scattering and dielectric spectroscopy studies

We have used a sol-gel technique to obtain optically transparent hydrogels in which water is confined within a 3D silica matrix. In this work we report X-ray scattering and dielectric spectroscopy measurements on samples having different aging times and compare them with previously obtained results with near-infrared (NIR) absorption spectroscopy. X-ray scattering at room temperature enables to characterize the structure and size of the matrix pores and the non-uniform distribution of water inside the hydrogel. Broad band dielectric spectroscopy in the temperature range 130-280 K enables to study water dynamics. In aged hydrogels two relaxations are clearly evident and show characteristic temperature dependence. The faster relaxation has an Arrhenius behavior in the whole temperature range investigated with an activation enthalpy of approximately 50 kJ/mol; it is attributed to water molecules strongly interacting with the silica matrix. The slower relaxation has a markedly non-Arrhenius behavior which can be fitted with a Vogel-Fulcher-Tamman (VFT) relation with critical temperature of approximately 100 K and activation enthalpies of 35 and 95 kJ/mol at 300 and 170 K respectively; it is attributed to water molecules within the pores that do not interact strongly with the matrix and behave collectively. The VFT temperature dependence of the dielectric relaxation time suggests that this water does not crystallize, in agreement with previous results from NIR spectroscopy.     

Polarized electron scattering on spin zero and polarized spin-1/2 targets: Deep inelastic scattering,elastic electron-muon scattering,and elastic electron-nucleon scattering

A covariant formulation is developed and used to derive cross sections for the analysis of experiments in which polarized electrons (muons) are scattered from spin-zero and from polarized spin-1/2 targets. The analysis is based upon the single virtual photon representation of the electromagnetic interaction, initially, neither high-energy nor low-energy approximations are made so that one may derive results in which the orientation of the polarization vectors of the interacting particles changes as a result of the scattering. The general formulation is valid for all polarization configurations for the electron and nucleon in deep inelastic scattering, and for all polarization configurations for the initial and final state particles in elastic scattering. From the general covariant results, specific cross sections are derived for deep inelastic scattering as well as elastic scattering of electrons on muons, nucleons, and spin zero targets. In the latter case, the actual polarization vector for the scattered electron is determined. In the other cases discussed, this vector may be obtained from the cross sections. In addition, a method is presented for defining covariant cross sections, and this method is used to obtain results in the center-of-mass system as well as the laboratory system. Furthermore, explicit cross sections for virtual photon absorption are derived. Finally, in the appendices, an alternative method for the evaluation of traces is given as well as a discussion of the relativistic limit.     

Measurement of the absorption coefficient of scattering liquid media by the calorimetric method

Using the example of a number of hydrosols (gold nanorods and nanoshells, silver nanoshells, zinc phthalocyanine nanoparticles), we show that the absorption coefficient of a scattering liquid medium can be measured from its heating by a short-time laser irradiation. The degree of heating was determined from expansion of the liquid in an ampoule with a capillary (the principle of liquid thermometer). Irradiation was performed at a wavelength of 671 or 1069 nm. From the transmission of samples of hydrosols at these wave-lengths, the sum of the absorption and scattering coefficients has been determined. To measure the absorption spectra of scattering liquids by this method, a laser with a tunable radiation wavelength is required. In the case of monodisperse colloidal solutions, the method ensures the measurement of the absorption and scattering cross-section ratio of particles.     

Time-independent polarized radiation in radiators with scattering media

The necessary condition of stationarity in radiators with scattering media is deduced. It is obtained from the fact that all primary emitted radiation disappears with probability unity when radiation is time-independent. The disappearance due to the absorption by matter and to escape from radiator is taken into account. The condition of stationarity includes the characteristics of radiation polarization, the coefficients of medium absorption, and the elements of the Green's function matrix. The relations between intensity components of radiation are derived from the condition. The results may be used in investigations of various radiators with scattering media.     

烟尘簇团粒子光学截面和散射矩阵的数值计算

用离散偶极子近似方法，计算了单个烟尘簇团粒子的光学特性，得到了簇团粒子的散射截面、吸收截面及不对称因子随入射角的变化关系，为研究波在烟尘粒子中的传输特性提供了有效的计算方法；给出了不同入射角情况下烟尘簇团粒子散射矩阵元素的角分布，为研究散射体的散射特性、极化特性以及散射体结构特性提供了一种理论方法. 关键词： 烟尘簇团粒子 散射矩阵 光学截面 DDA     

多重散射方法研究轴对称空腔覆盖层的声学特性

发展了一种多重散射方法研究声学覆盖层的半数值半解析模型,分析了影响轴对称空腔结构声学性能的主要能量耗散机制。在球坐标条件下推导出轴对称空腔结构的位移和应力场基函数,通过对空腔表面基函数的数值积分,得到散射波和入射波之间的传输矩阵方程,结合分层介质声传播理论计算了周期性空腔结构覆盖层的反射、透射和吸声性能。研究结果表明;空腔共振是低频能量耗散的主要形式,边界条件对材料空腔结构的谐振特性影响很大,利用双空腔耦合共振可以拓宽材料的低频吸声频带;背衬对材料的高频吸声影响较小,材料的高频能量损耗取决于空腔的散射和波型转换特性。