Optical reflectance spectroscopy

See, for example, Philpott, M. R. "Optical Reflection Spectroscopy of Organic Solids," Ann Rev. Phys. Chem. 1980, 31,... 

OP nickel complexes, 34 259 Optical reflectance spectroscopy, 34 277 Optical spectroscopy, 31 79-89, 259-261 Optical yields... 

The interaction of cupric ions with alumina supports has subsequently been studied more extensively as a function of the support surface area, metal loading, and calcination temperature (93,279) by means of EXAFS and X-ray absorption-edge shifts, in conjunction with XRD, EPR, XPS, and optical reflectance spectroscopy. These techniques, each sensitive to certain structural and electronic aspects, allow a unified picture of the phases present and the cation site location. Four Cu2 + ion sites are distinguished in the catalysts. In low concentrations (typically below about 4 wt. % Cu/100 m2/g support surface area) Cu2 + ions enter the defect spinel lattice of the A1203 support. The well-dispersed surface copper aluminate has Cu2+ ions predominantly occupying tetragonally (Jahn-Teller) distorted octahedral sites, although... 

VIII. Optical Reflectance Spectroscopy of Chromia-Alomina Catalysts. 289... 

Fibre optics reflectance spectroscopy (FORS) is a powerful and non-destructive method for the analysis of works of art [46]. 

For measuring the relative amount of the different species, physical methods play the most important role since they do not influence their ratio. The impressive colours of the catalysts recommend the use of optical (reflectance) spectroscopy. In the chromium case, for example, the characteristic absorptions (Fig. 18.3) allow a deconvolution and - with certain assump-... 

Lelekova (1998) Lelekova, O. Icon restoration and research in Russia The Art of Holy Russia Icons from Moscow 1400-1660 Royal Academy of Arts, London (1998) SI-92 Lemoine DU Manoir (1893) Lemoine, R. du Manoir, C. Les matieres premieres employees en peinture Rouen (1893) Leona Winter (2001) Leona, M. Winter, J. Fiber optics reflectance spectroscopy a unique tool for the investigation of Japanese paintings Studies in Conservation 46 3 (2001) 153-162... 

Among this palette of techniques, optical reflection spectroscopy in the mid- and near-IR range... 

Grafstrom, S. and Suter, D. (1996). Interaction of spin-polarized atoms with a surface studied by optical-reflection spectroscopy. 

While electron or ion beam techniques can only be applied under ultra-high vacuum, optical techniques have no specific requirements concerning sample environment and are generally easier to use. The surface information which can be obtained is, however, quite different and mostly does not contain direct chemical information. While with infra-red attenuated total reflection spectroscopy (IR-ATR) a deep surface area with a typical depth of some micrometers is investigated, other techniques like phase-measurement interference microscopy (PMIM) have, due to interference effects, a much better surface sensitivity. PMIM is a very quick technique for surface roughness and homogeneity inspection with subnanometer resolution. 

FIG. 3. Absolute atomic concentrations in units of 10 al./cm. determined by ERD. RBS, and optical reflection and transmission spectroscopy, of (a) hydrogen, (b) carbon, and (c) silicon as a function of the carbon fraction. v. Results are presented for the series ASTI (filled circles), AST2 (filled triangles), ATLl (open circles), and ATL2 (open triangles). (From R. A. C. M. M. van Swaaij. Ph.D. Thesis, Universiteit Utrecht. Utrecht, the Netherlands, 1994. with permission.)... 

Berendschot TTJM and van Norren D (2004), Objective determination of the macular pigment optical density using fundus reflectance spectroscopy, Arch. Biochem. Biophys. 430 149-155. 

Various optical detection methods have been used to measure pH in vivo. Fluorescence ratio imaging microscopy using an inverted microscope was used to determine intracellular pH in tumor cells [5], NMR spectroscopy was used to continuously monitor temperature-induced pH changes in fish to study the role of intracellular pH in the maintenance of protein function [27], Additionally, NMR spectroscopy was used to map in-vivo extracellular pH in rat brain gliomas [3], Electron spin resonance (ESR), which is operated at a lower resonance, has been adapted for in-vivo pH measurements because it provides a sufficient RF penetration for deep body organs [28], The non-destructive determination of tissue pH using near-infrared diffuse reflectance spectroscopy (NIRS) has been employed for pH measurements in the muscle during... 

Until quite recently the very initial stages of metal deposition were difficult to characterize in detail by structure- and morphology-sensitive techniques. As a consequence and for practical purposes - multilayers were more useful for applications than monolayers - the main interest was focussed onto thick deposits. Optical and electron microscopy, ellipsometry and specular or diffuse reflectance spectroscopy were the classic tools, by which the emerging shape of the deposit was monitored [4-7],... 

With development of ultrashort pulsed lasers, coherently generated lattice dynamics was found, first as the periodic modulation in the transient grating signal from perylene in 1985 by De Silvestri and coworkers [1], Shortly later, similar modulation was observed in the reflectivity of Bi and Sb [2] and of GaAs [3], as well as in the transmissivity of YBCO [4] by different groups. Since then, the coherent optical phonon spectroscopy has been a simple and powerful tool to probe femtosecond lattice dynamics in a wide range of solid... 

In ideal situations, optical spectroscopy as a function of temperature for single crystals is employed to obtain the electronic spectrum of a SCO compound. Knowledge of positions and intensities of optical transitions is desirable and sometimes essential for LIESST experiments, particularly if optical measurements are applied to obtain relaxation kinetics (see Chap. 17). In many instances, however, it has been demonstrated that measurement of optical reflectivity suffices to study photo-excitation and relaxation of LIESST states in polycrystalline SCO compounds (cf. Chap. 18). 

Many compounds exhibit near-IR and mid-IR absorption. By using IR transparent optical fibers, detection of an absorption band in the IR region is possible for optical sensing. Both direct sensing using the absorption property of the analyte or indicator sensing are widely exploited. Most mid-IR sensing schemes are based on the principles of internal reflection spectroscopy, or the attenuated total reflection (ATR) [3,14-21],... 

This method is commonly nsed on spectral data to correct for multiplicative variations between spectra. In spectroscopy, snch variations often originate from nnintended or uncontrolled differences in sample path length (or effective path length, in the case of reflectance spectroscopy), caused by variations in sample physical properties (particle size, thickness), sample preparation, sample presentation, and perhaps even variations in spectrometer optics. Snch variations can be particularly problematic because they are confounded with mnltiplicative effects from changes in component concentrations, which often constitute the signal in qnantitative applications. It is important to note that multiplicative variations cannot be removed by derivatives, mean-centering or variable-wise scaling. 

M. Blanco, J. Coello, H. Iturriaga, S. Maspoch, C. Pezuela and E. Russo, Control analysis of a pharmaceutical preparation by near-infrared reflectance spectroscopy a comparative study of a spinning module and fibre optic probe, Anal. Chim. Acta, 298, 183-191 (1994). 

Reeves, J.B. Ill and McCarty, G.W. (2001) Quantitative analysis of agricultural soils using near infrared reflectance spectroscopy and a fibre-optic probe. Journal of Near Infrared Spectroscopy 9, 25-34. 

A good review article on optical constants and their measurement is that by Bell (1967). Determination of optical constants from reflectance measurements is treated by Wendlandt and Hecht (1966) and from internal reflection spectroscopy by Harrick (1967). Ellipsometric techniques are discussed at length by Azzam and Bashara (1977). 

The thicknesses of free soap films and liquid films adsorbed on surfaces (Figs. 1.26d and 1.26e), which can be measured using optical techniques such as reflected intensity, total internal reflection spectroscopy, or ellipsometry as functions of salt concentration or vapor pressure, can provide information on the long-range repulsive forces stabilizing thick wetting films. We see an example of this in Chapter 11. 

In internal reflection spectroscopy (IRS), the spectrum is obtained with the sample in optical contact with another material (e.g. a prism) and the beam is passed through the prism onto the sample. The prism is optically denser than the sample, the incoming light forms a standing wave pattern at the interface within the dense prism medium whereas in the sample (with the lower refractive index), the amplitude of the electric field falls off exponentially with the distance from the phase boundary. When the sample exhibits absorbance, the reflectance measured is given by ... 

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