Structural characterization, Raman

Raman spectroscopy is primarily a structural characterization tool. The spectrum is more sensitive to the lengths, streng ths, and arrangement of bonds in a material than it is to the chemical composition. The Raman spectmm of crystals likewise responds more to details of defects and disorder than to trace impurities and related chemical imperfections. 

This paper summarizes the results of our study of PE and APE waveguides in LiNb03 and EiTa03. We foeused on the optical and structural characterization of PE layers formed on Z-eut substrates. The reffaetive index ehange was measured and the propagation losses were estimated. Raman speetroseopy was used as a method providing direct information about the phonon spectrum. The latter was related to the structure and ehemieal bonds of a given erystalline phase. Sueh information may be useful for eorreet identification of both phase eomposition and the microscopic mechanisms responsible for the observed variation of the properties from phase to phase. 

Complexes of the [Ru(bpy)2L] " type in which L is a phen-based ligand are discussed next. Perchlorate salts of [Ru(bpy)2(phen)] + and [Ru(bpy)2(5-Mephen)] + have been prepared and structurally characterized. The steric strain within the coordination sphere is relieved in part by twisting of each bpy ligand. Time-resolved resonance Raman spectroscopy has been used to investigate the localization of the excited electron in the MLCT state of [Ru(bpy)2(4,7-Ph2-phen)] In neutral micelles, the electron is localized on the bpy ligands, but in the presence of DNA and anionic surfactants, it is localized on 4,7-Ph2phen when the complex is in aqueous... 

In 2007, in a very exhaustive paper, Paradies and coworkers carried out a comprehensive structural characterization of the colorless and yellow forms of Af-hydroxyphthalimide (NHPI) by means of single-crystal X-ray diffraction, FTIR and Raman spectroscopies and scanning electron microscopy. In the yellow form, the Af-hydroxyl group is significantly out of the plane (1.19°), but the Af-hydroxyl group in the colorless form is only 0.06° out of the plane. The irreversible conversion of the colorless crystalhne form to the yellow crystalhne form is more like a dynamic isomerism than a polymorphic transformation. 

The iron molybdenum oxide catalyst was structurally characterized by XRD and vibrational spectroscopy (IR and Raman). 

Thus each band in a Raman spectrum represents the interaction of the incident light with a certain atomic vibrations. Atomic vibrations, in turn, are controlled by the sizes, valences and masses of the atomic species of which the sample is composed, the bond forces between these atoms, and the symmetry of their arrangement in the crystal structure. These factors affect not only the frequencies of atomic vibrations and the observed Raman shifts, respectively, but also the number of observed Raman bands, their relative intensities, their widths and their polarization. Therefore, Raman spectra are highly specific for a certain type of sample and can be used for the identification and structural characterization of unknowns. 

In the geosciences Raman spectroscopy has traditionally been a laboratory tool for structural analysis of minerals. Recent developments in instrumentation make possible the use of Raman spectroscopy as a tool for routine identification of minerals in field situations. The following advantages characterize Raman analysis of minerals no sample preparation in situ real time measurement non-destructive and non-intrusive sampling samples may be transparent or opaque spectra are well resolved and with high information content. 

Structural characterization of the surface metal oxide species was obtained by laser Raman spectroscopy under ambient and dehydrated conditions. The laser Raman spectroscope consists of a Spectra Physics Ar" " laser producing 1-100 mW of power measured at the sample. The scattered radiation was focused into a Spex Triplemate spectrometer coupled to a Princeton Applied Research DMA III optical multichannel analyzer. About 100-200 mg of... 

Schrobilgen, Christe, and co-workers have recently carried out the first detailed structural characterization of the XF6+ cations (X = Cl, Br, I) as their SbjFj 1 salts.856 The XF6+ cations have octahedral geometries with average bond lengths of 1.550 A (Cl—F), 1.666 A (Br-F), and 1.779 A (I-F) measured at -130°C and -173°C. The cations have 13-16 interionic F—F contacts to the neighboring anions and six F—X contacts between the fluorine atoms of the anions and the central halogen atoms. Additional studies (NMR characterization of the central X atoms, Raman spectroscopy, and calculations) were also performed. 

Vibrational microspectroscopy provides a unique means for molecular level structure characterization of a variety of biological processes associated with skin. For the past several years, this laboratory has utilized Raman and IR spectroscopy, microscopy, and imaging to monitor the biophysics of the skin barrier, mechanisms of drug permeation and metabolism in intact tissue, and, more recently, the complex events that transpire during wound healing in an ex vivo skin model [1-6]. 

Another striking difference between normal and cultured skin is shown in Fig. 15.6. As discussed above (see Fig. 15.3c, factor 2), cholesterol-rich pockets containing highly ordered lipid chains are occasionally detected in human skin and are characterized by a Raman-active mode of cholesterol near 700 cm-1 and an intense lipid C-C stretch near 1130 cm-1 in Fig. 15.4a and b, respectively. The intensity of the cholesterol mode is normalized to a Phe vibration near 620 cm-1 and imaged in Fig. 15.6b. As is evident there are many such pockets in the cultured skin model, in contrast to human skin where they are only rarely observed (Fig. 15.3c, factor 2), and usually in the viable epidermis rather than in the SC (as in the cultured skin). These measurements illustrate the power of confocal Raman microscopy for combining spatial measurements with molecular structure characterization. 

Structural characterization LEED, HEED, RHEED, FIM, FEM, TED, XRD, HVEM, AEM, EXAFS, ISS, ion channeling, ESDIAD, UPS, electron channeling, SEXAFS, vibrational EELS, and Raman spectroscopy... 

Structurally Characterized Compounds Containing the Anions [X3E-EX3]2 (E = Ga, In) (E-E Bond Lengths in pm EE Stretching Vibrations vE-E from Raman Data in cm-1)... 

Hu S, Kincaid JR (1991) Resonance Raman structural characterization and the mechanism of formation of lactoperoxidase compound III. J Am Chem Soc 113 7189-7194... 

Structural Characterization of Operating Catalysts by Raman Spectroscopy... 

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