Refractive Index Correction Research Articles

Highly Photoluminescent Multilayer QD−Glass Films Prepared by LbL Self-Assembly

A novel and facile preparation method for layer-by-layer (LbL) self-assembled films incorporating quantum dots (QDs) and having intense photoluminescence (PL) from blue to red is presented. Functional sol-gel-derived glass layers prepared by the hydrolysis of 3-aminopropyltrimethoxysilane (APS) or 3-mercaptopropyltrimethoxysilane (MPS) have been used as a linkage between QD layers. Absorption, PL spectroscopy, transmission electron microscopy, and atomic force microscopy were employed for characterization, which revealed that the QDs in the prepared films had a nearly close-packed coverage and were not aggregated. The PL efficiencies of the QDs (CdTe or ZnSe, both are thioglycolic acid-stabilized) dispersed in the films were roughly half that of the initial colloidal solutions but reached 24% before a refractive index correction. The thickness of the red-emitting film with 10 CdTe QD layers was approximately 50 nm. The concentration of QDs in the film derived from the first absorption peak was approximately 0.01 M. Because the PL starts to show a red shift, the obtained concentration is practically the ultimate one in the glass matrix. The mercapto, amino, and carboxyl groups play important roles in LbL self-assembling processes.

A Hybrid Film Thickness Evaluation Scheme Based on Multi-Channel Interferometry and Contact Mechanics

A hybrid evaluation scheme for EHL film thickness determination is proposed and discussed. The film thickness profile in the contact region is measured using interferograms produced with a novel multi channel interferometry method. Since the refractive index distribution in the contact is pressure-dependent, and the initial film thickness profile will be evaluated assuming atmospheric pressure, a refractive index correction scheme is employed. The correction scheme is based on the Lorenz-Lorentz equation and a pressure-density relation together with a numerical pressure solver taking the initial film thickness measurement as input. The film thickness determination scheme is applied to an interesting phenomenon that can be observed at sliding conditions when the discrepancy occurred in the form of a deep and large dimple in the conjunction. Such a dimple appeared instead of the conventional plateau. The phenomenon was studied under different degrees of sliding. The detailed film thickness maps and pressure distributions for highly loaded EHL conjunctions at high degrees of sliding are produced using a hybrid evaluation scheme. The results are analyzed and discussed. [S0742-4787(00)00301-5]

The true refractive index correction to the fluorescence intensity in the commercial fluorescence spectrophotometer

The procedure was proposed to determine the true refractive index correction to the fluorescence intensity while measuring with a commercial fluorescence spectrophotometer. According to this procedure, the instrumental readings taken with common rectangular detecting geometry are to be compared to those obtained from an “ideal spectral instrument”. The procedure being applied to the analysis-oriented Hitachi Model F-4010 fluorescence spectrophotometer, the correction factor proved to obey n 2 law within the limits of experimental error.

Simple refractive index correction for the optical particle counter PCS 2000 by Palas

Simple refractive index correction for the optical particle counter PCS 2000 by Palas

Systematic corrections in Bragg x-ray diffraction of flat and curved crystals

Measurements of spectral wavelengths in Bragg diffraction from crystals often require refractive index corrections to allow a detailed comparison of experiment with theory. These corrections are typically 100–300 ppm in the x-ray regime, and simple estimates may sometimes be accurate to 5% or better. The inadequacies of these estimates are discussed. Even with a possibly improved index of refraction estimate, this correction is insufficient since additional systematics in the diffraction process occur at or above this level. For example, asymmetries of diffraction profiles with π-polarized radiation or due to three-beam diffraction can approach the magnitude of refractive index corrections for flat or curved crystals. The depth of penetration of the x-ray field inside curved crystals, the shift of the mean angle to the diffracting planes, and lateral shifts around the crystal surface are rarely considered but can dominate over refractive index corrections, particularly for high-order diffraction or medium-energy x rays. Shifts and nonlinearities arise when diffracting surfaces lie off the Rowland circle, and exhibit strong and rapidly varying angular dependencies. Johann geometries with the source located on the Rowland circle should be avoided to minimize profile truncation shifts from crystal ranges or minimum grazing angles, and to avoid extreme scaling corrections. Other significant shifts are identified and illustrated, with functional relations provided to allow an estimation of related magnitudes. The central concerns of this paper are the effects on flat crystal diffraction and curved crystal diffraction in the Johann geometry, with a source and crystal of variable dimensions and location. Experiments often interpolate or extrapolate from calibration lines, so dependencies upon the diffracting angle are as important as the magnitude of the corrections. These dependencies are presented in formulas and graphs.

Optical and mathematical corrections of micropipette measurements of red blood cell geometry during anisotonic perifusion

Accurate knowledge of red blood cell (RBC) membrane surface area and cellular volume is critical to understanding the geometric factors that affect RBC deformability. A useful method to determine RBC geometry is via micropipette aspiration in which the cell partially enters the tip of a glass pipette with a diameter of about 2 microns. Measurement of the cell while in the pipette allows calculation of cell geometry, but such measurements are subject to several artifacts. Herein, we analyze the effects of three artifacts on calculated RBC geometry during experimental osmotic manipulation. 1) The pipette internal diameter, as measured optically, requires correction for refractive index and focusing errors; 2) the pipette barrel is tapered rather than cylindrical; 3) the observed RBC outline is affected by a diffraction phenomenon. These optical and mathematical errors were all found to influence the calculated RBC geometry; both absolute values and relative changes during osmotic manipulation were affected. For RBC in isotonic medium, use of the above corrections significantly (p < 0.001) reduced the calculated area by 3.7%, the volume by 7.0%, and the minimum cylindrical diameter by 3.9%. The calculated membrane area dilation for cells exposed to hypotonic media was also significantly reduced; at 200 mOsm, the dilation was 2.8% +/- 0.2% without correction vs. 1.5% +/- 0.2% when all corrections were employed (p < 0.01). We therefore suggest that micropipette aspiration of RBC requires use of these correction techniques to obtain accurate values for RBC geometry and that such correction methods are of particular importance when RBC of different sizes are compared.

Experimental determination of a refractive-index correction in measurements of quantum luminescence yield

Experimental determination of a refractive-index correction in measurements of quantum luminescence yield

Benzene ring orientation in uniaxialplanar poly(ethylene terephthalate) films

A study is presented of the benzene ring orientation in a series of eight films of poly(ethylene terephthalate) drawn at constant width under constant force above the glass transition temperature. For each sample, seven orientation moment averages, P r lmn , for the overall benzene ring distribution were determined from a combination of Raman and infrared spectroscopic measurements. Comparison of orientation moment averages calculated with and without the assumption of a uniaxial Raman tensor, and with and without a refractive index correction to the Raman intensities, leads to the conclusion that the seven P r lmn are given, to a good approximation, by the simplest calculation assuming a uniaxial Raman tensor and neglecting the refractive index correction. The seven P r lmn were used to calculate the ‘most probable’ distribution function and the isometric projections of this distribution have been produced. The results indicate that the C 1–C 4 axis shows an approximately uniaxial overall distribution with a slight tendency to be more oriented out of the plane of the film and that the benzene rings tend to lie in the plane of the film. From a combination of these results with those of earlier X-ray measurements, the amorphous and crystalline contributions to the overall molecular orientation were obtained. The results show that the benzene ring planes are preferentially oriented towards the plane of the film only in the crystalline phase and have an almost uniaxial distribution around the draw direction in the amorphous phase. It has been shown that, in the amorphous phase as well as in the crystalline phase, the benzene rings tend to lie in the plane defined by the draw direction and the C 1–C 4 axis.

Asymmetric Diffraction with Parallel-Beam Synchrotron Radiation

AbstractIn this paper, the advantages and disadvantages of using the asymmetric 2θ scanning technique with a fixed incident angle α are described. Vertical-scan powder diffractometers with long horizontal parallel slits with an aperture of 0.05° and parallel-beam synchrotron radiation with λ = 1.54 Å and α = 10°, 2°, and 1° were used to collect α-Al2O3, silver behenate CH3(CH2)20COOAg, and Si powder diffraction patterns. The synchrotron radiation data were analyzed by profile fitting, and the results were compared with those obtained by the conventional θ-2θ scanning technique. As expected, significantly higher intensities were obtained from the asymmetric diffraction data with α = 10°. At smaller α = 2° and 1°, however, the intensities were reduced because of a smaller effective beam height. The peak positions remained practically unchanged for the data obtained with α = 10°, but displaced toward higher 2θ angles for α = 2° or lower, and, consequently a refractive-index correction was needed. Profile shape was slightly broadened and became more Lorentzian in asymmetric diffraction with highly oblique incidence of the beam. The change in shape was, however, negligibly small. The results showed that intensive and reliable powder diffraction data can be obtained from asymmetric diffraction by fixing the incident beam at a sufficiently large angle to fully illuminate the available sample surface.

Geometrical principles of the monolithic X-ray magnifier

The principles of the monolithic X-ray magnifier based on two successive asymmetric non-coplanar diffractions from the same crystal are analyzed from the geometrical point of view. The conditions of the distortion-free two-dimensional pattern magnification are formulated by means of matrix formalism. The general solution of the problem of determination of the crystal surface planes satisfying the conditions of distortion-free magnification is derived in the closed form. The calculation is performed on the basis of the kinematical theory of diffraction. It is shown that the number of solutions is infinite for any given pair of diffraction vectors and magnification. General properties of the solution are illustrated by some examples. The effect of the refraction of X-rays on the pattern distortion is estimated. The results suggest that the refractive index correction has a negligible influence on the distortion of the magnified pattern. The results presented enable us to prepare monolithic X-ray magnifiers or demagnifiers that can be used in various fields of X-ray optics, especially in X-ray topography and X-ray lithography.

Notes on improvements and modifications to the automatic methods for determining dissolved micronutrients in seawater

Improvements made to established routine determinations of micronutrients in seawater include a universal baseline (wash) solution of 9,7 percent (v/v) ethanol in water, a copperized cadmium column, for reducing nitrate to nitrite, that has a longer life, more-stable reagents for determining ammonia-nitrogen (eliminating excessive baseline drift and frequent acid washes), and a refractive index correction which must be subtracted from the sample peaks, thus bringing the method in line with the manual method.

Investigation of ultrasonic transducers using optical techniques

Laser interferometry and laser-generated ultrasound have been applied to the calibration of contact transducers which are used to detect defects in solids by angled shear-waves. It was found that laser interferometry could readily be used to image the two-dimensional beam generated by each transducer, while laser-generated ultrasound could test its performance as an ultrasonic receiver. The ultrasonic waveforms were also recorded and analysed. The results of optical calibration were compared with traditional methods, i.e. calibration block and water tank. There was good overall agreement. It was confirmed that the refractive index correction which is applied to water tank beam plots is a valid method for predicting the beamin a solid such as aluminium. All the probes and shoes performed satisfactorily and radiated beams with well-defined profile even at the edge of the near-field. There was no evidence of significant side lobes or surface waves. There were small errors in the shoe beam angles as supplied. By using both the laser receiver and laser generator in turn, reciprocity was demonstrated for one probe.

The refractive-index correction in powder diffraction

Throughout the history of powder diffraction practice there has been uncertainty about whether or not a refractive-index correction should be made to Bragg's law. High-precision Bragg-angle measurements have been performed with synchrotron radiation on SRM- 640 silicon powders at glancing angles; it is found that little or no correction is necessary for the usual 2θ angle range.

Neon lineshift measurements in dense, laser-compressed plasmas

Measurement of shifts in the neon Lyman- alpha , - beta and - gamma lines and the He-like 1s2-1s2p line have been obtained in laser-compressed plasmas at ne approximately 3*1022 cm-3 and Te approximately 300 eV. Calibration of the neon line wavelengths was determined relative to the emission lines of higher Z elements present in the microballoon glass shell. A trend towards larger red shifts in the wavelengths of the lower neon Lyman series members was observed, and the neon He- alpha line was observed to be blue shifted. These trends are shown not to be the result of refractive index corrections to the dispersion of the crystal spectrometer used, and are unlikely to be the result of differential spatial or Doppler effects between the neon and the calibration lines. Assuming that the measured red shift of about 10 mAA for neon Lyman- alpha is an indication of the magnitude of the absolute shift, then the observed shift is an order of magnitude greater than predicted by current plasma polarisation shift theories at the plasma densities and temperatures obtained in the present experiment.

The experimental and theoretical expressions for the molecular electronic oscillator strength in solution

In this paper we propose the appropriate fundamental definition of the oscillator strength in solution and clearly show that both the experimental and theoretical expressions of the oscillator strength should contain refractive index correction factors of α and β, respectively. Therefore, in the discussion of the solvent effects on the oscillator strength the experimental and theoretical expressions containing the correction factors should be used instead of the usual expressions of α=1 and β=1.

The refractive-index correction to the radiative rate constant

It is widely accepted that the refractive-index correction factor for the radiative rate constant is n 2, where n is the refractive index of the solution. This letter points out that the factor varies between n and n 5, depending upon the shape of the solute molecule and the direction of the transition moment.

The refractive index correction to the radiative rate constant in fluorescence lifetime measurements

The dependence of fluorescence decay times upon the refractive index of the solvent has been measured in two types of system: (a) in a single solvent at different temperatures, (b) in different solvents. The results are consistent with an n 2 dependence of the radiative rate constant, as has been predicted theoretically.

Reply to the comment on the refractive index correction in luminescence spectroscopy

The need for a rigorous analysis in order to derive any correction factors required when measuring luminescence quantum yields is acknowledged, as is the defect in our previous method. An outline of our new full model is given and the preliminary results obtained compared with those of Ediger et al.

On the refractive index correction in luminescence spectroscopy

The derivation of the refractive index ( n) correction in luminescence spectroscopy is extended to cases with excitation beams. The accepted “l/ n 2 correction” is found to be valid for a large number of experimental arrangements in contrast to the analysis of a recent paper.

A chromatographic study of the oligomerization of butadiene

The parameters of MWD of oligobutadienes synthesized by the reaction of butadiene with 2-hexyl-lithium in a hydrocarbon medium have been determined by a combination of gel-permeation and gas-liquid chromatography methods. For calibration of the gel-chromatograph, oligomers with degrees of polymerization of 1 to 8 were used, which had been prepared by gas-liquid chromatography. For the treatment of the gel chromatograms, a refractive index correction was introduced. At various ratios of initiator to monomer (1·0: 0·5 to 1·0: 5), the reaction products contain a rather wide range of homologues, with polymerization degrees of 1 to 12.