Refractive Spectra Research Articles

Antifungal Activity of Some New Binuclear Complexes

Three complexes of copper(II) and iron(II) with mixed ligands acetylacetonebis(thio-semicarbazone)- ABTSH2 and benzaldazine- BA have been prepared and characterized using different physico-chemical techniques including the determination of metal contents, mole-cular weight, measurement of molar conductivity, magnetic moment, molar refraction, infrared and electronic spectra. Accordingly, octahedral complexes having general formulaes [Cu2(ABTSH2)2(BA)2Cl2]Cl2 and [M2(ABTSH2)2(BA)2(SO4)2] {M= Cu(II) or (Fe(II)} have been proposed. The resulted complexes screened for antifungal activity in vitro against the citrus pathogen Aspergillus niger and Fusarium sp. which caused root rot of sugar and the beans pathogen Alternaria sp. All the complexes exhibited significant antifungal activities against these pathogens. The antifungal activity of these complexes were comparable with the standard fungicides in ethanol. The complex [Cu2(ABTSH2)2(BA)2Cl2]Cl2 had the best antifungal activity against Alternaria sp.

Preparation and Characterization of Cr(III) & Cu(II) Complexes With Mixed Ligand Containing Isatinazine and Semicarbazones

chromium(III) and copper(II) complexes with mixed ligands isatinazine-IAH2 and semicarbazone ligands {including benzoinsemicarbazone- B'SCH2 or isatinsemicarba- zone- ISCH2 or isatinbis(semicarbazone) -ISCH3} have been prepared in neutral (or slightly acidic) and basic medium.The resulted complexes have been characterized using elemental analysis by atomic absorption spectroscopy and by precipitation methods, relative molecular weight deter mination, molar conductance measurements, molar refraction, magnetic susceptibilities, infrared and electronic spectra. Accordingly, The study suggested that the above ligands form positive ionic complexes having general formula [M(IAH2)(LH2,3)(NO3)m](NO3)n-m or [Cr(IAH2)(B'SCH2)](NO3)3 in neutral (or slightly acidic) medium, whereas neural or negative ionic complexes of the general formula [M(IAH2-y΄)(LH2,3-y˝)] or Na[Cr(IA)(B'SC)] have been resulted in basic medium (where M= Cr+3 or Cu+2; y´=1 or 2; y˝=1 or 2; n=2 or 3; m=1; LH2,3= the ligands B'SCH2 or ISCH2 or ISCH3). The ligands acted as neutral or anionic (-1) in neutral (or slightly acidic) or basic medium, respectively. Hexacoordinated mononuclear complexes have been investigated by this study and having octahedral geometries.

Terahertz spectroscopy of biological molecules

We study experimentally the absorption and refraction spectra for a number of amino acids, proteins and nucleic acids in the frequency range 0.1–3.5 THz. The characteristic absorption lines are revealed. The spectroscopy of water solutions of proteins and nucleic acids is carried out under conditions of total internal refraction. This method can be used for studies of the functional properties of biomolecules and the dynamics of their interaction.

Analytical Dielectric Spectrum Formula Based on Representative Frequencies

According to experimental data available for the complex refractive index of particular dielectrics, a dielectric spectrum formula is proposed by the least square fitting technique combined with selected natural frequencies. From the dielectric spectrum formula, the spectra of optical and dielectric constants can be obtained in the whole frequency region. Three dielectrics, water, ethanol, and toluene, are taken as examples. In the region where the experimental data are available, the spectra of the optical constants calculated by the formula are in good agreement with the real refractive spectrum obtained by KramersKronig (KK) transform and the experimental imaginary refractive spectrum. In the region where no experimental data are available, the extrapolation of our formula can make predictions. The merits of the present treatment are that we are able to get the uniform spectrum formula, without splitting into different frequency sections, and the analytical form of the dielectric spectra will be useful in the theoretical description of solvation dynamics.

Separation and Characterization of Group Composition of Hydro-treated Naphthenic Lube Base Oil

In this article, a liquid chromatographic separation scheme was developed to separate hydro-treated lube base oil into six different fractions according to their polarity, i.e., saturates, light aromatics, middle aromatics, heavy aromatics, nitrogen-containing compounds, and oxygen-containing compounds. Each individual fraction and subfraction acquired was analyzed by a series of instrument technology such as refractive index method, infrared spectroscopy, ultraviolet spectrum (UV), and X-ray photoelectron spectra in detail. These analytic data not only demonstrated the effectiveness of separation into narrow compound classes but also characterized their chemical group composition in detail. This research result indicated that a suit of methods to separation and characterization of group composition aimed at hydro-treated lube base oil was relatively and successfully developed, at the same time. X-ray photoelectron spectra shows great potential for characterization of polar subfractions.

Propagation of electromagnetic waves in Kolmogorov and non-Kolmogorov atmospheric turbulence: three-layer altitude model

Turbulence properties of communication links (optical and microwave) in terms of log-amplitude variance are studied on the basis of a three-layer model of refractive index fluctuation spectrum in the free atmosphere. We suggest a model of turbulence spectra (Kolmogorov and non-Kolmogorov) changing with altitude on the basis of obtained experimental and theoretical data for turbulence profile in the troposphere and lower stratosphere.

Retrieving parameters of the anisotropic refractive index fluctuations spectrum in the stratosphere from balloon-borne observations of stellar scintillation

Scintillation effects are not negligible in the stratosphere. We present a model based on a 3D model of anisotropic and isotropic refractive index fluctuations spectra that predicts scintillation rates within the so-called small perturbation approximation. Atmospheric observations of stellar scintillation made from the AMON-RA (AMON, Absorption par les Minoritaires Ozone et NO(x); RA, rapid) balloon-borne spectrometer allows us to remotely probe wave-turbulence characteristics in the stratosphere. Data reduction from these observations brings out values of the inner scale of the anisotropic spectrum. We find metric values of the inner scale that are compatible with space-based measurements. We find a major contribution of the anisotropic spectrum relative to the isotropic contribution. When the sight line plunges into the atmosphere, strong scintillation occurs as well as coupled chromatic refraction effects.

Synthesis and properties of AlBeB22 crystals

Platelike single crystals of aluminum boroberyllide (AlBeB22) with a tetragonal structure are produced from a solution in the Al melt. The crystal structure of the compound is determined, and the microhardness, refractive index dispersion, reflection spectrum, and photoconductivity are measured at 300 K.

Deposition of silicon oxynitride at room temperature by Inductively Coupled Plasma-CVD

Oxynitride thin films are used in important optical applications and as gate dielectric for MOS devices. Their traditional deposition processes have the drawbacks that high temperatures are needed, high mechanical stresses are induced and the deposition rate is low. Plasma assisted processes may alleviate these problems. In this study, oxynitride films were deposited at room temperature through the chemical reaction of silane, nitrogen and nitrous oxide (N 2O), in a conventional LPCVD furnace, which was modified into a high density Inductively Coupled Plasma (ICP) reactor. Deposition rates increased with applied coil power and were never lower than 10 nm/min, quite high for room temperature depositions. The films' refractive indexes and FTIR spectra indicate that for processes with low N 2O gas concentrations, when mixed together with N 2 and SiH 4, nitrogen was incorporated in the film. This incorporation increased the resistivity, which was up to 70 GΩ cm, increased the refractive index, from approximately 1.47 to approximately 1.50, and decreased the dielectric constant of these films, which varied in the 4–14 range. These characteristics are adequate for electric applications e.g. for TFT fabrication on glass or polymers which can not stand high temperature steps.

Optical polarized properties for the PbWO4 crystal containing lead vacancy

The electronic structure, dielectric functions, complex refractive indices and absorption spectra for the polarized light from the perfect PbWO4(PWO) crystal and the PWO crystal containing V2-Pb have been calcula ted using LAPW +LDA method with lattice structure optimized. The peaks of the absorpti on spectra corresponding to the electronic transitions have been studied. The op tical properties of PWO crystal containing V2-Pb are aniso trop ic. It may be caused by the anisotropy of lattice structure of the PWO crystal. Our calculated results indicate that the perfect PWO crystal does not have absor ption band in the visible and near_ultraviolet region, but the PWO crystal conta ining V2-Pb has absorption bands in visible and near_ultra viol et region. The absorption bands can be well decomposed into four Gaussian_shape bands peaking at about 350, 405, 550 and 670 nm. It predicates that these absor ption bands are related to the existence of the V2-Pb in t he PWO crystal.

Structure dependence of optical spectra of ferromagnetic Heusler alloy Ni–Mn–Ga

The influence of structural transformation on the optical properties of Heusler alloy Ni–Mn–Ga has been investigated by using Density Functional Theory code CASTEP. The calculated optical refractive and absorption spectra, the off-diagonal components of the dielectric function and the optical conductivity for L2 1 structure and the tetragonal phase show a noticeable structural dependence which were confirmed by the experiments (Y.V. Kudryavtsev et al., Phys. Rev. B 66 (2002) 115114).

Analysis of the efficacy, predictability, and safety of LASEK for myopia and myopic astigmatism using the Technolas 217 excimer laser

Purpose: To evaluate the efficacy, predictability, and safety of laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia and myopic astigmatism. Setting: Stanford University Eye Laser Center, Stanford, California, USA. Methods: This retrospective analysis comprised 102 eyes that had LASEK for myopia using the Bausch & Lomb Technolas® 217 excimer laser. Primary outcome variables including uncorrected visual acuity (UCVA), best spectacle- corrected visual acuity (BSCVA), manifest refraction, and complications were evaluated at 3, 6, and 12 months. Vector analysis was performed on eyes that received astigmatic correction. Results: The mean spherical equivalent was −7.03 diopters (D) ± 2.61 (SD) preoperatively, +0.19 ± 0.64 D at 3 months, +0.23 ± 0.82 D at 6 months, and +0.03 ± 0.63 D at 12 months ( P<.001). At 3, 6, and 12 months, the UCVA was 20/20 or better in 66%, 67%, and 83% of eyes, respectively, and 20/40 or better in 98%, 99%, and 100%; 74%, 70%, and 83%, respectively, were within ±0.5 D of emmetropia, and 89%, 86%, and 97%, respectively, were within ±1.0 D. No eye lost more than 2 lines of BSCVA. At 3, 6, and 12 months, 10.0%, 8.7%, and 0% of eyes, respectively, had trace corneal haze. Vector analysis found a success rate of approximately 78% to 80% in achieving the astigmatic surgical correction at the 3 postoperative visits. Conclusions: Laser-assisted subepithelial keratectomy was an effective, predictable, and safe procedure for the treatment of myopia and myopic astigmatism. Further studies are needed to determine the role of LASEK in the refractive surgery spectrum.

Morphology of poly( p-phenylenevinylene) thin films prepared directly on the surface of silicon wafers by the chemical vapor deposition polymerization

The chemical vapor deposition polymerization (CVDP) of α,α′-dichloro- p-xylene on the (0 0 1) plane of silicon wafer surface followed by thermal dehydrochlorination produced PPV nanofilms in which the polymer chains are found to be in highly ordered morphology. The same CVDP polymerization of α,α′-dichloro- p-xylene on the quartz surface, however, produced disordered polymer chains. The morphology and chain orientations were studied by X-ray diffractometry and polarized UV-Vis absorption and polarizesd photoluminescence spectroscopies. The angle dependence of IR refractive absorption spectra of the PPV films also were studied.

White-light continuum Z-scan technique for nonlinear materials characterization

We present a technique for rapid characterization of degenerate nonlinear absorption and refraction spectra using a femtosecond white-light continuum (WLC) pulse to perform Z-scans. The spectral components of the WLC source are temporally and spatially dispersed to minimize nondegenerate two-photon absorption (2PA) processes. We demonstrate the validity of the method by measuring the 2PA spectrum of a well-characterized semiconductor, ZnSe.

The temperature-dependent spectral properties of filter substrate materials in the far-infrared (6–40 μm)

This paper presents the experimental results on the low temperature absorption and dispersion properties for a variety of frequently used infrared filter substrate materials. Index of refraction ( n) and transmission spectra are presented for a range of temperatures 300–50 K for the Group IV materials silicon (Si) and germanium (Ge), and Group II–VI materials zinc selenide (ZnSe), zinc sulphide (ZnS) and cadmium telluride (CdTe).

Microstructure and Optical Functions of Transparent Conductors and their Impact on Collection in Amorphous Silicon Solar Cells

AbstractWe have developed new procedures for determining the microstructure as well as the index of refraction and extinction coefficient spectra {n(E),k(E)} for textured SnO2thin films on glass used as the top contact layers and superstrate for amorphous silicon (a-Si:H) p-i-n solar cells. These procedures combine (i) multichannel Mueller matrix spectroscopy using a dual rotating-compensator spectroscopic ellipsometer in reflection from the surface of the SnO2, a measurement that is most sensitive to microstructure andn(E), and (ii) transmission spectroscopy through a double-thick SnO2sandwich contacted with index-matching fluid, a measurement that is most sensitive tok(E). An important optical loss in a-Si:H p-i-n solar cells is reflection from the SnO2/p-layer interface. In this paper, we characterize this optical loss through modeling the solar cell optical quantum efficiency and demonstrate the extent to which microscopic roughness at this interface can serve as an anti-reflection layer for enhanced collection.

ZLI-1695 Liquid Crystal Anisotropy Characterization in the Near Infrared by Generalized Ellipsometry

One key point for an advantageous use of liquid crystals in optical devices for telecom applications is a proper design and simulation capability. For this purpose it is mandatory to know the optical behaviour of these materials at the wavelength of interest, i.e. the transparency windows of the optical fibers in the Near-IR region. To this aim, we have applied Generalized Ellipsometry, an extension of standard ellipsometry that allows optical characterizations of anisotropic thin films, for investigating liquid crystal samples. The optical anisotropy of the ZLI-1695 liquid crystal was measured as a function of the wavelength in the spectral range from 300 to 1700 nm. Comparing our experimental data with those reported by the manufacturer (Merck) at a single wavelength, we have also estimated the ordinary and extraordinary refractive indices spectra.

The PDF of intensity for Ocean WPRM—15 years later

Spatial intensity correlations for wave propagation in random media (WPRM) can be predicted in terms of the index of refraction space-time autocorrelation function, with scattering parameters Gamma (strength) and X (scaled range) in the iso-velocity case. In ocean WPRM the temporal intensity correlations are also well predicted from the modeled index of refraction spectrum for the lower path in sub-CZ propagation with a depth-dependent sound speed profile (Eastern Pacific). For both of these cases the intensity pdf’s have been shown [Ewart and Percival, 80, 1745–1753 (1986)] to be very well fit by generalized Gamma distributions. In that work quantile–quantile goodness of fit tests were used to test the generalized Gamma hypothesis. The upper path intensity correlations, in sub-CZ propagation, however, have not been predicted. The pdf’s of upper path data taken during MATE will be discussed. Several authors have proposed functional forms of intensity pdf’s, e.g., one distribution modulated by another. Quantile-quantile tests will be applied to see if such functions model ocean WPRM intensity pdf’s. [Work supported by ONR.]

Experimental demonstration of negative dispersion without absorption

We present the results of an experiment proving in principle that negative (anomalous) dispersive transparent media can be realized. The Ca-transition 4s 2 1S 0 → 4s4p 1P 1 at λ=423 nm was chosen to investigate the absorption and index of refraction spectra of a two-level system strongly driven at resonance. For the simultaneous high precision measurement of loss and phase shift imposed on a probe field during the interaction with a chopped Ca-atomic beam we used a novel spectrometer which is based on a phase modulated Mach–Zehnder interferometer. So far, a dispersion of ∂ ω n 0=−(3.1±1.0)×10 −10/MHz accompanied by residual absorption of α 0=(0.125±0.040)%/cm has been achieved. These values are compared to the requirements which have to be achieved for a certain application of negative dispersion without absorption, that is for a broadband high build-up cavity (white-light cavity).

Microstructure and optical properties of submicron porous silicon thin films grown at low current densities

The mechanism of porous silicon (PS) film growth remains a debate among researchers. This study investigates the effect of current density (J) and anodization time (t) on the film thickness, optical properties, and microstructure of films grown at low current densities. The samples reported herein were generated from polished and unpolished 〈100〉 single crystal wafers, with resistivities of 0.1 and 0.6 Ω cm, respectively. Current densities of 1–10 mA/cm2 and anodization times ranging from 3 to 900 s were used. This work shows that film growth is at first linear but beyond a given anodization time (dependent on J), the film produced is not continuous, but is best described as a finite number of stacked sublayers with each sublayer having a unique microstructure, porosity, and optical response. This article also shows that as the PS film grows, second and third order peaks appear in the reflectance spectra. This data, together with modulations in the index of refraction spectra and visual evidence from cross-sectional scanning electron microscopy (SEM) images demonstrate that submicron PS thin films grown at low current densities have a multilayer structure. Above a certain thickness, the modulation in the properties due to the sublayers phases out and the films appear as if they were single layered films. SEM is used to show the progression, from cross-sectional imaging, from a layered or stacked PS film structure to an apparently homogeneous film with depth. When using low current densities, single layer films are only obtained at very short times.