Raman spectroscopy applications, generally

The last 4 years have seen a tremendous increase in the use of Raman spectroscopy in general and there is nowhere where this is more noticeable than in the area of process analysis. In comparison to the other optical spectroscopic techniques available, Raman spectroscopy offers a unique combination of well-resolved features and the ability to perform the analysis remotely by interfacing the spectrometer to the sample via standard silica fiber optics. Adar et al. [1] and Lipp and Leugers [2] have both reviewed the development of Raman spectroscopy for process applications in terms of necessary instrumentation and illustrated this with a discussion of several successful applications. Developments in fiber-optic probe design for Raman spectroscopy, up to mid-1996, have been thoroughly reviewed by Lewis and Griffiths [3] and more recently by Lewis and Lewis [4]. 

In addition to the many applications of SERS, Raman spectroscopy is, in general, a usefiil analytical tool having many applications in surface science. One interesting example is that of carbon surfaces which do not support SERS. Raman spectroscopy of carbon surfaces provides insight into two important aspects. First, Raman spectral features correlate with the electrochemical reactivity of carbon surfaces this allows one to study surface oxidation [155]. Second, Raman spectroscopy can probe species at carbon surfaces which may account for the highly variable behaviour of carbon materials [155]. Another application to surfaces is the use... 

Vibrational spectroscopy, in the form of mid-IR, NIR and Raman spectroscopy has been featured extensively in industrial analyses, both quality control (QC), process monitoring applications and held-portable applications [1-6]. The latter has been aided by the need for advanced instrumentation for homeland security and related HazMat applications. Next to chromatography, it is the most widely purchased classihcation of instrumentation for these measurements and analyses. Spectroscopic methods in general are favored because they are relatively straightforward to apply and to implement, are rapid in terms of providing results, and are often more economical in terms of service, support and maintenance. Furthermore, a single spectrometer or spectral analyzer, in a near-line application, may serve many functions, whereas chromatographs (gas and liquid) tend to be dedicated to only a few methods at best. 

Infrared and Raman spectroscopy are in current use fo r elucidating the molecular structures of nucleic acids. The application of infrared spectroscopy to studies of the structure of nucleic acids has been reviewed,135 as well as of Raman spectroscopy.136 It was noted that the assignments are generally based on isotopic substitution, or on comparison of the spectrum of simple molecules that are considered to form a part of the polynucleotide chain to that of the nucleic acid. The vibrational spectra are generally believed to be a good complementary technique in the study of chemical reactions, as in the study76 of carbohydrate complexation with boric acid. In this study, the i.r. data demonstrated that only ribose forms a solid complex with undissociated H3B03, and that the complexes are polymeric. 

The slow-scan CCD, also called the scientific CCD, or in the spectroscopy literature simply CCD, is the detector of choice for most applications of Raman spectroscopy. A well-designed CCD has essentially zero dark current, very low readout noise, and high quantum efficiency (peak 45—70% near 700 nm) in the visible region of the spectrum. However, the response drops quickly above 800 nm and there is no photon response above 1.05 J m. For routine spectroscopy or process control, thermoelectrically cooled (to about —40° C) CCDs are adequate. Although these detectors are somewhat noisier than detectors operated at —100° C or lower, the former do not require liquid nitrogen cooling. The general properties and spectroscopic applications of the CCD have been reviewed (22). 

It is too early to say whether surface enhanced Raman spectroscopy will become a widely applicable technique because, in spite of several theoretical investigations, no general theory of... 

This review does not deal with the general characterization of catalysts by Raman spectroscopy but is focused instead on the application to catalysts in reactive environments. Such experiments are often described as in situ," a term that is minimally used in this volume. The term "in situ, Latin for "on site," implies that the sample is analyzed at the location where it has been treated or is being treated. Several levels of such experiments are described here ... 

This section discusses applications of IR and Raman spectroscopy to materials with reasonable or even very high conductivity. These systems generally present special problems in addition to those described in earlier sections. Incident radiation interacts not only with the vibrational excitations of the material but also with the free carriers and with its electronic structure. These interactions may create phenomena such as free carrier absorption, excitation across the energy gap, exciton transitions, or light scattering by free electrons. Excitations are very often in the IR spectral range, particularly in the... 

After a short outline of the early history of infrared and Raman spectroscopy (Section 1), a general survey is given of different aspects of vibrational spectroscopy (Section 2). This survey is sufficient for readers who intend to get an impression of the fundamentals of vibrational spectroscopy. It serves as a common basis for subsequent chapters, which de.scribe special experimental features, the theory, and applicational details Section 3, Tools for infrared and Raman Spectroscopy Section 4, Vibrational spectroscopy of different classes and states of compounds Section 5, Evaluation procedures, and Section 6, Special techniques and applications. 

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