Raman qualitative interpretation

Changing electron-phonon couplings have been observed also for Cs2NaTmCl6. In this case the relative intensities of different Raman lines showed an anomalous behavior under pressure, which has been qualitatively interpreted as due to an electron-phonon coupling of the a/5 electronic state with the A + vs(t2g) vibronic state (Mak et al., 2002). 

Vibrational frequencies, so-called good group frequencies, are important in applying infrared and Raman spectroscopy to many chemical problems that require the qualitative interpretation of infrared spectra. A group frequency is that mode of vibration associated with a particular bond or sets of bonds. 

Through his studies on the aromatic character of the heterocyclic compounds, Bonino inevitably confronted the classical problem of the structure of benzene. [50] He completed his work on the Raman spectrum of aromatic compounds which included benzene, presenting his results in April 1934 at the 9th International Congress of Pure and Applied Chemistry in Madrid. At the Madrid Congress, Bonino recommended a new formula for benzene this formula, however, lacked a rigorous quantum mechanical grounding. Rather, it represented an attempt to summarize qualitatively some fundamental ideas in the wave-mechanical interpretation of benzene (Figure 4.4). 

Sample purity is a key concern. The NRVS experiment is a bulk technique sampling all Fe nuclei, and impurities that also contain the probe nucleus may confound quantitative data interpretation. Impurities may be introduced during sample preparation or may result from sample instability during measurement. Because of this, care must be taken to ensure purity and reproducibility as Judged by Mossbauer see Mossbauer Spectroscopy), singlecrystal X-ray diffraction, electronic absorption spectroscopy (see Electronic Spectroscopy), Raman spectroscopy or other qualitative techniques. 

Infrared spectroscopy provides a valuable qualitative indication of the degree of covalency of a given Pb-ligand interaction and also has been used (with much less success) to determine the coordination number of Pb(II). There have been limited studies of Pb(ll) complexes by IR (149, 151-162) and Raman (163-166) spectroscopies. The interpretation of these results is most successful when coupled with structural data from X-ray crystallography. X-ray absorption spectroscopy [extended X-ray absorption fine structure (EXAFS) or X-ray absorption near edge spectroscopy (XANES)], PES, or NMR spectroscopy (149, 154, 155, 157, 158, 160-162). 

The adsorption of nucleic acids at the electrodes used in electroanalyti-cal chemistry has been mostly investigated with the aid of a.c. polarog-raphy, linear sweep, differential or normal pulse voltammetry, ellipsometry and surface-enhanced Raman scattering spectroscopy. The results of these studies so far obtained have, however, rather qualitative character. Up to recently the samples of nucleic acids which would contain only identical and well defined molecules have not been available in the quantities sufficient for adsorption studies. The use of oligonucleotides or plasmid DNAs appears to be a way to interpret the adsorption analysis of nucleic acids more accurately. 

PA Tanner, K-H Leung. Spectral interpretation and qualitative analysis of organophosphorus pesticides using FT-Raman and FT infrared spectroscopy. Appl Spectrosc 50 565-571, 1996. 

The paper is divided into five sections. In section II, we review our basic electronic model of the RC and its qualitative experimental consequences. The new interpretation of vibronic coupling in the P band is discussed in section III, with special attention to the hole-burning and resonance Raman experiments. Subsequently, in section IV we present results based on a simplified model system to support our picture of the vibronic coupling in the P band. In the conclusion, section V, a plan for comprehensive future calculations for model refinement is presented. 

MCR provides straightforward information on the identity of the compounds in a sample through the pure responses contained in the matrix. These resolved profiles are particularly useful when they come from an instrumental technique with highly specific strucmral information, such as MS, or some spectroscopic techniques, such as Raman or Fourier transform infrared (FTIR). In these cases, the resolved profiles can be directly interpreted or matched with libraries of spectra. This is a common practice in the qualitative analysis of food products, the composition of which is relevant to understand final sensory properties, such as essential oils, spices or wines [21-25]. In general, the qualitative analysis of a food sample through the study of the resolved profiles in the matrix will always provide a deeper knowledge of the composition and the related nutritional or sensory properties of the sample or will inform on problems that could be linked to the contamination or adulteration by unexpected substances. 

While the present first volume contains much of the theoretical background, the emphasis in [1.35] is on experimental techniques, the interpretation of experimental results and the discussion of a number of phenomena which are directly related to phonons. Correspondingly, the second volume will contain a number of rather short chapters and its style will be somewhat different from this volume by exchanging depth for breadth in many places. It is planned to introduce the reader into the following topics Infrared, Raman and Bril-louin spectroscopy, interaction of X-rays with phonons, inelastic neutron scattering and some other techniques of interest. Phenomena such as piezoelectricity, ferroelectricity, melting and thermal conductivity will be given a qualitative discussion. The book will also contain some newer developments ... 

In contrast to Raman and IR spectroscopy, only few chemical functionalities (CH, OH, and NH) have a signature in the NIR spectra. Thus, the use of NIR spectra as stmctural interpretation tool is strongly limited. For raw material control or discrimination purposes, however, such as the sorting of polymer waste into a selected numher of commodities (e.g., polyethylene, polypropylene, polystyrene, poly(ethylene ter-ephthalate) (PET), and poly(vinyl chloride) (Figure 51), qualitative chemometric evaluation techniques (such as principal component analysis (PCA)) can he applied. ... 

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