Raman effect applications

Inverse Raman spectroscopy The Inverse Raman effect is a form of Raman scattering, first noted by W.J. Jones and B.P. Stoicheff, wherein stokes scattering can exceed anti-Stokes scattering resulting in an absorption line (a dip in intensity) at the sum of irradiated monochromatic light and Raman frequency of the material. This phenomenon is referred to as the inverse Raman Effect, application of the phenomenon is referred to as inverse Raman spectroscopy, and a record of the continuum is referred to as an inverse Raman spectrum. 

A. Anderson (ed.) The Raman Effect, Principles, and The Raman Effect, Applications (Dekker, New York 1971 and 1973)... 

Before discussing specific examples of the application of Raman spectroscopy to studying adsorbate-adsorbent interactions, it will be necessary, at this juncture, to explain the nature of the Raman effect. 

The resonance Raman effect — review of the theory and of applications in inorganic chemistry. R. J. H. Clark and B. Stewart, Struct. Bonding (Berlin), 1979, 36, 1-80 (110). 

Raman spectroscopy is primarily useful as a diagnostic, inasmuch as the vibrational Raman spectrum is directly related to molecular structure and bonding. The major development since 1965 in spontaneous, c.w. Raman spectroscopy has been the observation and exploitation by chemists of the resonance Raman effect. This advance, pioneered in chemical applications by Long and Loehr (15a) and by Spiro and Strekas (15b), overcomes the inherently feeble nature of normal (nonresonant) Raman scattering and allows observation of Raman spectra of dilute chemical systems. Because the observation of the resonance effect requires selection of a laser wavelength at or near an electronic transition of the sample, developments in resonance Raman spectroscopy have closely paralleled the increasing availability of widely tunable and line-selectable lasers. 

With the available high-power lasers the nonlinear response of matter to incident radiation can be studied. We will briefly discuss as examples the stimulated Raman effect, which can be used to investigate induced vibrational and rotational Raman spectra in solids, liquids or gases, and the inverse Raman effect which allows rapid analysis of a total Raman spectrum. A review of the applications of these and other nonlinear effects to Raman spectroscopy has been given by Schrotter2i4)... 

The Raman effect has also been broadly applied to online and bench-top quantitative applications, such as determination of pharmaceutical materials and process monitoring [4-6], in vivo clinical measurements [7], biological materials [8, 9], to name only a few. Because the absolute Raman response is difficult to measure accurately (sample presentation and delivered laser power can vary), these measurements are almost always calculated as a percentage with respect to the response from an internal standard. This standard is typically part of the sample matrix in a drug product, the standard may be an excipient in a biological sample, it is commonly water. 

SERS and SERRS, in particular, are well positioned for applications in the area of highly sensitive and specific biological and chemical detection. This is due primarily to emerging advances in nanotechnology and the development of miniature laser sources and light detection techniques. Two recent reports clearly point to the feasibility of developing sensors based on the surface-enhanced Raman effect. 

First measurements for identifying optical activity in Raman scattering were undertaken soon after the Raman effect itself was discovered but proved unsuccessful [1,2]. The fact that the measurement of solutions of biomolecules is at present the most important application of ROA is remarkable in the face of the experimental difficulties which haunted these early attempts to observe it, even for pure, chiral liquids, the most favorable experimental situation. 

In the winter of 1932 Bonino visited the scientific laboratories of the Zeiss firm in Jena, where he became acquainted with Lowe and with the director of the spectroscopic department, Hansen. He and Hansen discussed technical details concerning the modern spectrograph that Zeiss had built for the institute in Bologna for utilizing the Raman effect. At Zeiss, Bonino could thus learn further technical aspects of the Raman spectrometer and its potential applications. Soon thereafter, he and his collaborators developed an intensive research program with this spectrograph in order to study the constitution of organic compounds. 

Application of Raman spectroscopy to a study of catalyst surfaces is increasing. Until recently, this technique had been limited to observing distortions in adsorbed organic molecules by the appearance of forbidden Raman bands and giant Raman effects of silver surfaces with chemisorbed species. However, the development of laser Raman instrumentation and modern computerization techniques for control and data reduction have expanded these applications to studies of acid sites and oxide structures. For example The oxidation-reduction cycle occurring in bismuth molybdate catalysts for oxidation of ammonia and propylene to acrylonitrile has been studied in situ by this technique. And new and valuable information on the interaction of oxides, such as tungsten oxide and cerium oxide, with the surface of an alumina support, has been obtained. 

J. H. Hibben, The Raman Effect and Its Chemical Application Reinhold Publishing Corp., New York, 1939. 

Utilizing Eqs. (4-2) and (4-3), V(P)/V(0) can be calculated at different pressures as seen in Table 4-11, and in Fig. 4-36. The compressibilities are obtained from the solid lines in Fig. 4-36 by using a simple polynomial fit of the lines. Values of 6.42 x lO GPa-1 for TbV04 and 6.07 x 10 3GPa 1 for DyV04 were calculated. This study demonstrates a unique application of the Raman effect. 

Iindustrial applications of the Raman effect have garnered intense interest since the introduction of FT-Raman instrumentation. Concurrent with FT-Raman instrumentation developments have been the fiber optics improvements and the advent of new detectors. These three factors have syner-gized and have led to the present interest in Raman spectroscopy. This has brought the Raman effect from the laboratory and into the plant, where in-situ measurements are now possible in a number of industrial environments. 

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