Assignment of spectral features

Electrochemical impedance spectroscopy (EIS) provides indirect information about the surface phenomena of all kinds of electrodes [32]. The high-frequency part of impedance spectra of electrodes is usually attributed to surface phenomena such as Li-ion migration through surface films, surface film capacitance, and interfacial charge transfer [33]. However, it should be noted that EES provides very ambiguous information. A special skill, as well as experience, is needed for a reliable assignment of spectral features to the time constants of a complicated electrochentical system such as that of composite electrodes [34]. 

Hall et al. [151] have demonstrated the feasibility of using NIRS to measure additive levels in PP pellets obtained from two process streams. Analysis was performed directly on the polymer pellets with no sample preparation. In a rugged spectroscopic model, variations in the polymer pellet size or shape, and sample and packing density, which will affect the effective path length of the NIR radiation in the sample, should be accounted for. Even when the chemical identity of the additive is unknown, the availability of a NIR spectrum permits assignability of spectral features (i.e. at 2172 nm) within the matrix that can be used for quantitative purposes. 

Tetrahydropyranylation of Alcohols. Protection of alcohol functionality as the THP ether is an often-utilized tool in organic synthesis. It must be noted that the reaction of a chiral alcohol with dihydropyran introduces an additional asymmetric center and hence a diastereomeric mixture is obtained (eq 1). This can lead to difficulties with purification, assignment of spectral features, etc., but does not prevent successful implementation. ... 

Raman spectroscopy, while typically used as a micro-analytical tool, can be conducted remotely. Performance of remote Raman analysis have been recently explored and reahzed for experiments on the surface of Mars (Sharma et al. 2001 Sharma et al. 2003). Raman spectroscopy is a powerful technique for mineralogical analysis, where the sharpness of spectral features of minerals allows for much less ambiguous detection, especially in the presence of mixtures. Visible, near-infrared, thermal, reflectance and in many cases emission spectroscopy of minerals all suffer from broad overlapping spectral features, which complicates interpretation of their spectra. On the other hand, Raman spectra of minerals exhibit sharp and largely non-overlapping features that are much more easily identified and assigned to various mineral species. 

The 8- and 4.5-nm particles are at most weakly emissive and the polarizations of spectral features assigned to these particles are determined by polarized bleach measurements. The bleach anisotropy was determined using femtosecond pulses, with the probe delayed a few picoseconds from the pump. This delay ensures electronic and vibrational relaxation as well as relaxation of optical Kerr effects induced in tire solvent. As a control, transient absorption experiments were performed with excitation at 475 nm and detection at 550 nm. This detection wavelengtli is to the red of the wavelengths at which a bleach would be observed and provides a measure of the transient absorption intensity in this general spectral... 

Different species of composition C2H2 have been variously proposed to be di-derived from ethylidyne), 1,1,1,2 tetra-corrugated surfaces Pt(210) and Pt(l 10), di-structural assignments take into account the arrangements of surface metal atoms (assuming no surface relaxation) as well as the positions and intensities of spectral features. The spectrum attributed to di-generated from ethyne (acetylene) 141). 

Table 1. Wave number ranges and vibrational mode assignments for spectral features commonly observed (650-3100 cm-1) in the infrared absorption spectra of explosives...

The present compilation of IR spectra of Figure 13-3 provides a unique example of spectral features for a consistent series of isolated tautomers of the same molecule. This assignment was very recently proposed independently by Mons et al. [21] from pure spectroscopic grounds and by Marian [24] from her quantum chemistry calculations. It is consistent with the IR spectra of related compounds, like 9MG, 7MG, IMG and 6MG, carried out using the R2PI technique [11-22], Indeed in all these methylated species, counterparts of the A-D UV band systems can be... 

In this experiment proton NMR spectroscopy is nsed in evalnating the equilibrium composition of various keto-enol mixtures. Chemical shifts and spin-spin splitting patterns are employed to assign the spectral features to specific protons, and the integrated intensities are used to yield a quantitative measure of the relative amounts of the keto and enol forms. Solvent effects on the chemical shifts and on the equilibrium constant are investigated for one or more j8-diketones and j8-ketoesters. 

Assign all spectral features using Table 1 and other NMR reference sources. Tabulate your results and use your integrated intensities to calculate the percentage enol present in solutions 1 to 3. If possible, use the total integral corresponding to the sum of methyl (or ethyl), methylene, methyne, and enol protons. If this proves difficult because of overlap with solvent bands, indicate clearly how you used the intensities to calculate the percentage enol. 

Polarization information provides a direct determination of selection rules and allows for rigorous assignments based on group theory allows correlation of spectral features with geometric structure providing detailed insight into electronic structure of metal ion active site... 

Recently the infrared spectrum of C2H7 in the range 2500-4000 cmhas been obtained using laser excitation of trapped ions in a tandem mass spectrometer. Two sets of spectral features were observed and have been assigned to isomers 4 and 5. For... 

Infrared spectra from NASA s Galileo mission show distinct absorptions on Jupiter s moon Europa that have been attributed to one or more sulfuric acid hydrates. Sulfuric acid in solution with water causes significant freezing-point depression of water s melting point, down to 210 K, and this would make more likely the existence of liquid solutions beneath Europa s icy crust.The interpretation of the spectra is somewhat controversial. Some planetary scientists prefer to assign the spectral features to the sulfate ion, perhaps as part of one or more minerals on Europa s surface. 

It is possible to identify particular spectral features in the modulated reflectivity spectra to band structure features. For example, in a direct band gap the joint density of states must resemble that of critical point. One of the first applications of the empirical pseudopotential method was to calculate reflectivity spectra for a given energy band. Differences between the calculated and measured reflectivity spectra could be assigned to errors in the energy band... 

Figure 7.10 shows the 60-MHz spectra of poly (methyl methacrylate) prepared with different catalysts so that predominately isotactic, syndiotactic, and atactic products are formed. The three spectra in Fig. 7.10 are identified in terms of this predominant character. It is apparent that the spectra are quite different, especially in the range of 5 values between about 1 and 2 ppm. Since the atactic polymer has the least regular structure, we concentrate on the other two to make the assignment of the spectral features to the various protons. 

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