Calculation of diffuse thermal x-ray scattering intensity in polycrystalline HCP metals

In this work we perform a calculation of the intensity of thermal diffuse scattering from polycrystalline samples with an hcp structure, an interesting physical problem, by calculating the dynamical matrix and its powers. This is a new approach for polycrystalline hep metals. M. V. Lomonosov State University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 3–6, December, 1998.     

Light intensity correlation measurements in the presence of multiple scattering

We discuss the results of a model calculation of the intensity correlation function for multiply scattered light and compare our analytic predictions with experiments.     

X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution

Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during the ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed and the buildup of these fluctuations is measured in real time. Small-angle scattering measurements reveal snapshots of the spontaneous nucleation of nanoscale voids within a metastable liquid and support theoretical predictions of the ablation process.     

A bubble detection technique based on light intensity and Mie scattering theory for spinning solution

A novel bubble detection technique based on light intensity and Mie scattering theory for spinning solution is presented theoretically and experimentally. With the light intensity in every direction, the particle or bubble size distribution can be calculated with the Mie scattering theory. The light intensity distribution in every direction, corresponding to the light intensity received by every assumed annulus of the detector has been calculated theoretically. According to the light intensity distribution, the size distribution of bubbles can be deduced. A series of standardized polystyrene micro-sphere (with 7 μm diameter) solution has been used not only as sample for experiments and calibration, but also as the bubbles in the glycerin. Theoretical and experimental results show that the technique can be used for bubble detection, in order to improve the traditional bubble detection scheme, and to lower production costs.     

Velocity measurement of the diffuse object based on time-differentiated speckle intensity fluctuations

This paper proposes a new velocity measuring method for a moving diffuse object on the basis of the autocorrelation of time-differentiated speckle intensity fluctuations. The theoretical background and experimental verification of this method are given. The correlation length of time-differentiated speckle intensity fluctuations is defined by the point at which the correlation becomes zero. By means of the correlation length the object velocity is found to be accurately measured.     

On field effect and diffuse surface scattering

An electric field effect mechanism by diffuse surface scattering is proposed. This new field effect mechanism is dominant at metal oxide interfaces and due to interfacial exchange between conduction electrons and trap states in the oxide.     

Absolute scattering cross-section measurements by a ratio technique

Calculations and measurements are presented which show that absolute scattering cross sections (“Rayleigh ratios”) can be determined by measuring the ratio of the depolarized intensity of doubly scattered light to the polarized intensity of singly scattered light. This technique should be useful in determining the susceptibilities of fluids and the molecular weights of macromolecules.     

Flow measurements based on Rayleigh scattering and Fabry-Perot interferometer

Flow diagnostics based on molecular Rayleigh scattering are discussed along with the results of a feasibility study to non-intrusively measure flow properties in a small supersonic wind tunnel. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow properties are determined. Each image is obtained with a single laser pulse, giving instantaneous measurements.     

基于双向反射分布函数实验测量的目标散射特性的分析

介绍了一种用双向反射分布函数(BRDF)测定仪进行目标双向反射分布函数测量的方法。以聚四氟乙烯(F4)粉压制板作为反射标准板,给出了F4标准板及所测样品在双向反射分布函数测定仪上的测量数据。被测样片的反射光强度经标定过的漫反射标准板传递,最终在较高分辨率的半球空间内分析计算出了样品在红外(1.06μm和0.86μm)波段的双向反射分布函数。实验结果表明,该方法是一种分析目标散射特性的可行性方法。     

Analyzing statistical errors for measurements of Brillouin scattering by the edge technique

The signal estimate and statistical uncertainty in the measurements of Brillouin shift by the edge technique are analyzed in detail. A signal to noise parameter factor is introduced and is used to discuss the statistical uncertainty in the measurements. The effect of signal averaging and the effect due to background noise are analyzed. Some helpful conclusions are predicted. PACS 42.68.Wt; 42.79.Qx; 78.35.+c     

Frequency-domain technique for optical property measurements in moderately scattering media

We demonstrate a reflection geometry frequency-domain technique that is suitable for measurement of the optical properties of a medium with moderate scatter and absorption (mu(s) and mu(a) ~ 1 m(-1)). Variations in absorption and scatter produce opposing tends in the amplitude signal and common trends in the phase signal, allowing unique determination of absorption and scattering coefficients for a given phase function. An analytical model based on single-scattering events gives good agreement with experimental measurements.     

A new technique for spatially resolved thermal lensing measurements

A new method is presented for spatially resolved thermal lensing measurements using multiple narrow probe beams and a two-dimensional array detector. The method is applied to an Er, Tm, Ho: YAG laser rod. No significant deviation from a parabolic temperature profile has been found although there is extraordinarily strong thermal lensing in the crystal. Thermo-optical constants of the material are reported.     

Investigation of atmospheric aerosols based on polarization measurements and scattering simulations

For an ongoing project involving ocean color and temperature scanner and polarization and directionary of the earth’s reflectance onboard the advanced earth observing satellite, the radiance and degree of polarization of atmospheric aerosols were measured with a portable photopolarimeter (FPR2000) at wavelengths of 0.559, 0.760 and 0.811 μm. The observations were undertaken over the ocean around Shikoku Island of Japan on clear days with few clouds in July, 1995. The measurements were compared with simulations of polarization fields. This work also describes retrieval algorithms for aerosols. It is shown that: (1) the radiance decreases with wavelength, (2) oceanic type aerosols are available to evaluate the degree of polarization over the Pacific Ocean, and (3) polarization data in the Seto Inland Sea are explained by a water-soluble aerosol model.     

Huang diffuse scattering of neutrons

Huang diffuse neutron scattering was measured for the first time on niobium with interstitially dissolved deuterium as well as on MgO after neutron irradiation and Li⁷F after-irradiation. With Huang diffuse scattering the strength and symmetry of the distortion field around lattice defects can be determined. Our results clearly demonstrate that this method is feasible with neutrons.The present results are compared with X-ray experiments and the advantages of using neutrons is discussed in some detail.     

Measurement of the differential and integral distribution of diffuse x-ray scattering intensity from defects in thin strained layers

Double-and triple-crystal diffractometry have been used to study structural perfection of a ∼1 μm-thick Ga_1−x In_xSb_1−y As_y epitaxial film (x=0.9, y=0.8) on GaSb. It is shown that scattering from samples of this system can be divided into coherent and diffuse. The arrangement of reciprocal-lattice points of the film and substrate in the two-dimensional intensity distribution for asymmetrical reflections argues for the absence of elastic-strain relaxation. No dislocation networks are formed, and the diffuse scattering is produced by Coulomb-type defects. Localization of diffuse scattering in reciprocal space suggests that these defects reside in the epitaxial film. The diffuse-scattering distribution in asymmetrical reflections is shown to be anomalous; namely, it extends in a direction parallel to the surface and is split into two maxima. Schemes have been proposed and realized for measuring integral distributions of diffracted intensity along the surface and perpendicular to it, and their potential for studying diffuse scattering from defects is explored. Fiz. Tverd. Tela (St. Petersburg) 39, 1188–1193 (July 1997)     

Optical scattering measurements and implications on thermal noise in Gravitational Wave detectors test-mass coatings

Photographs of the LIGO Gravitational Wave detector mirrors illuminated by the standing beam were analyzed with an astronomical software tool designed to identify stars within images, which extracted hundreds of thousands of point-like scatterers uniformly distributed across the mirror surface, likely distributed through the depth of the coating layers. The sheer number of the observed scatterers implies a fundamental, thermodynamic origin during deposition or processing. These scatterers are a possible source of the mirror dissipation and thermal noise foreseen by V. Braginsky and Y. Levin, which limits the sensitivity of observatories to Gravitational Waves. This study may point the way towards the production of mirrors with reduced thermal noise and an increased detection range.     

Molecular ruler based on concurrent measurements of enhanced Raman scattering and fluorescence

We report a way to assess the separation between a molecule and a metal surface on account of both Raman scattering and fluorescence intensities measured simultaneously. This approach has no need for an accurate quantity of molecules and bears 1 nm resolution. Its distance sensitivity is experimentally demonstrated in the case of dye molecules lying on a gold surface with a polymer spacer layer in between and is compared with theoretical prediction.